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ANATOMY 


DESCRIPTIVE  AND  APPLIED 


BY 

HENRY  GRAY,  F.R.S. 

FELLOW    OF   THE    HOYAL    COLLEGE   OF   SURGEONS;   LECTUREB   ON  ANATOMY  AT   ST.    GEORGE's 
HOSPITAL  MEDICAL   SCHOOL,    LONDON 


A  NEW  AMERICAN  EDITION 

THOROUGHLY  REVISED  AND  RE-EDITED 
WITH   THE   ORDINARY   TERMINOLOGY 


FOLLOA\'E»    BY    THE 


BASLE  ANATOMICAL  NOMENCLATURE  IN  LATIN 


BY 

EDWARD  ANTHONY  SPITZKA,  M.D. 

DIRECTOR  OF  THE  DANIEL.  BAUGH  INSTITUTE  OF  ANATOMY  AND  PROFESSOR    OF  GENERAL    ANATOMY  IN  ' 
JEFFERSON  MEDICAL  COLLEGE,  PHILADELPHIA 


HUustratet)  witb  1225  lEnaravinos 


LEA   &  FEBIGER 

PHILADELPHIA    AND    NEW    YORK 


Entered  according  to  the  Act  of  Congress,  in  the  year  1913,  by 

LEA   &   FEBIGER 
to  the  OfiB.ce  of  the  Librarian  of  Congress.     All  rights  reserved. 


THE   FIRST   EDITION    OP   THIS   WORK 
WAS    DEDICATED   TO 

SIB  BENJAMIN  COLLINS  BRODIE,  Bart.,  F.R.S.,  D.C.L. 

IN    ADMIRATION    OF 

HIS   GREAT   TALENTS 

AND    IN    REMEMBRANCE    OF 

MANY    ACTS    OF    KINDNESS    SHOWN    TO    THE    ORIGINAL 

AUTHOR    OF    THE    BOOK 

FROM    AN 

EARLY    PERIOD    OF    HIS    PROFESSIONAL    CAREER 


PREFACE. 


As  a  thoroughly  practical  treatise  on  the  subject  for  the  medical  student, 
Gray's  Anatomy,  both  in  the  original  and  its  many  succeeding  editions,  has  long 
been  held  in  the  highest  esteem.  In  this  as  in  previous  revisions  the  Editor  has 
endeavored  to  adhere  to  the  plan  as  much  as  possible,  supplying  such  facts  and 
views  as  the  advances  in  the  science  of  anatomy  rendered  it  necessary  to  in- 
corporate. Descriptions  of  undue  length  have  been  curtailed,  and  any  difficult 
passages  in  the  text  have  been  clarified;  so  that  the  essentials  are  here  embodied 
into  a  fairly  complete  account  of  the  structures  of  the  human  body  and  their 
development.  It  has  also  been  the  Editor's  aim  to  achieve  the  utmost  degree  of 
uniformity  in  the  mode  of  treatment  throughout  the  work. 

Under  the  heading  of  Applied  Anatomy  many  important  medical  and  surgical 
considerations  are  discussed.  In  the  use  of  descriptive  terms,  concerning  which 
widely  different  opinions  prevail,  the  Editor  has  sought  to  take  a  middle  course, 
employing  such  designations  as  seem  sanctioned  by  their  usage  in  current  medi- 
cal literature.  The  Basle  Nomina  A7iatomica  Nomenclature,  in  italics,  has  been 
added  in  parentheses,  except  where  the  two  nomenclatures  are  identical,  and  the 
terms  are  listed  in  the  General  Index.  Here,  also,  they  have  been  italicized,  and 
thus  distinguished  they  afford  a  working  glossary  of  the  BNA  system.  Other 
synonyms  are  printed  in  Roman  type. 

Illustrations  have  been  added  from  original  drawings  and  preparations,  and 
some  from  standard  works,  wherever  it  seemed  that  any  important  point  could 
be  made  more  clear. 

The  Editor  is  greatly  indebted  to  his  assistants.  Dr.  Howard  Dehoney,  Demon- 
strator of  Anatomy,  and  Dr.  Henry  E.  Radasch,  Assistant  Professor  of  Histology 
and  Embryology  in  the  Jefferson  Medical  College,  for  valuable  aid  in  the  prepara- 
tion of  this  revision.  The  Editor  also  wishes  to  thank  Mr.  William  A.  Hassett,  of 
Lea  &  Febiger,  for  indexing  the  book,  for  seeing  it  through  the  press,  and  for  the 

valuable  aid  he  has  ungrudgingly  given. 

E.  A.  S. 
Philadelphia,  1913. 


fv) 


PUBLISHERS'  NOTE. 


Books,  like  men,  have  characters  that  can  be  analyzed-  to  a  certain  point, 
but  beyond  or  below  lies  a  quality,  subtle  as  life,  and  incapable  of  analysis  or 
imitation,  which  is  called  personality.  The  greater  the  author,  and  the  more 
intense  his  mental  action  in  creating  his  book,  the  more  it  partakes  of  this  ele- 
ment. This  principle,  so  clear  as  to  be  almost  axiomatic,  is  illustrated  to  the 
fullest  extent  in  the  work  in  hand.  Henry  Gray  combined  two  faculties,  either 
one  sufficient  to  make  his  name  famous.  He  was  a  great  anatomist  and  a  great 
teacher.  He  possessed  a  thorough  knowledge  of  anatomy  and  an  equal  insight 
into  the  best  methods  of  imparting  it  to  other  minds.  His  text  was  unequalled 
in  clearness,  and  he  united  with  it  a  series  of  incomparable  illustrations.  He 
devised  the  method  of  engraving  the  names  of  the  parts  directly  upon  them, 
thereby  exliibiting  at  a  glance  not  only  their  nomenclature,  but  also  their  posi- 
tion, extent,  and  relations.  His  work,  still  unique  in  this  respect,  was  also  the 
first  to  employ  colors.  Summing  all,  it  is  hardly  to  be  wondered  at  that  students 
and  teachers  alike  find  their  labors  reduced  and  the  permanence  of  knowledge 
increased  by  the  use  of  such  a  book. 

On  its  original  appearance,  half  a  century  ago,  it  immediately  took  the 
leading  place,  and  it  has  not  only  maintained  its  position  in  its  own  subject, 
but  has  also  become  the  best-known  work  in  all  medical  literature  in  the 
English  language.  It  is  incomparably  the  greatest  text-book  in  medicine, 
measured  by  the  numbers  of  students  who  have  used  it,  and  it  is  unique  also 
in  being  the  one  work  which  is  certain  to  be  carried  from  college  to  afi'ord 
guidance  in  the  basic  questions  underlying  practice. 

The  consequent  demand  is  evidenced  in  the  number  of  editions,  which 
collectively  represent  the  labors  of  many  of  the  leading  anatomists  since  the 
early  death  of  its  talented  author.  In  this  new  revision  every  line  has  been 
carefully  considered,  any  possible  obscurity  has  been  clarified,  the  latest  acces- 
sions to  anatomical  knowledge  have  been  introduced,  and  much  has  been 
rewritten.  Care  has  been  exercised  to  make  the  text  a  homogeneous,  sequen- 
tial, and  complete  presentation  of  the  subject,  sufficing  for  every  need  of  the 
student,  physician,  or  surgeon. 

As  ample  directions  are  given  for  dissecting,  this  volume  will  serve  every 
requirement  of  the  student  throughout  his  course.  The  new  nomenclature  and 
that  still  in  common  use  have  been  introduced  in  a  manner  rendering  the  work 
universal  in  the  prime  essential  of  terminology.  The  Table  of  Contents  is  so 
arranged  as  to  give  a  complete  conspectus  of  anatomy,  a  feature  of  ob^'ious 
value.  The  whole  book  is  thoroughly  organized  in  its  headings  and  the 
sequence  of  subjects,  so  that  the  student  receives  his  knowledge  of  the  parts  in 
their  anatomical  dependence. 

As  a  teaching  instrument  the  new  Gray's  Anatomy  embodies  all  that  careful 
thought  and  unstinted  expenditure  can  combine  in  book  form. 

(vii) 


CONTENTS. 
DESCRIPTIVE  AND  APPLIED  ANATOMY. 


OSTEOLOGY. 


Introduction 33 

General  Anatomy  of  the  Skeleton 

The  Skeleton 35 

Number  of  the  Bones 35 

Form  of  Bones 35 

Long  Bones 35 

Short  Bones 36 

Flat  Bones 36 

Irregular  Bones 36 

Surface  of  Bones 36 

Structure  of  Bone 38 

Bloodvessels  of  Bone 40 

Chemical  Composition  of  Bone 41 

Ossification  and  Growth  of  Bone 42 

Applied  Anatomy  of  the  Bones 46 

SPECLA.L  Anatomy  of  the  Skeleton. 

The  Vertebhal  oh  Spinal  Column  or  the  Spine. 

General  Characters  of  a  Vertebra. 

The  Cervical  VertebriB 49 

Atlas 50 

Axis : 52 

Seventh  Cervical 53 

The  Thoracic  VertebrEe 53 

Peculiar  Thoracic  Vertebrce 54 

The  Lumbar  Vertebrae :  ■  . .  56 

The  Sacral  and  Coccygeal  Vertebrae 58 

Sacrum 58 

The  Sacral  Canal 61 

Differences  in  the  Sacrum  of  the 

Male  and  Female 61 

Coccyx 61 

Structure  of  the  VertebrEe 62 

Development  of  the  Vertebrae 63 

Development  of  the  Atlas 63 

Development  of  the  Axis 64 

Development  of  the  Seventh  Cervical ,  64 

Development  of  the  Lumbar  Vertebrae ....  64 

The  Vertebral  Column  as  a  Whole 66 

Surface  Form  of  the  Vertebral  Column ....  67 

Applied  Anatomy  of  the  Vertebral  Column.  fi8 

The  Skull. 

The  Cerebral  Cranium. 

The  Occipital  Bone 70 

The  Parietal  Bone 74 

The  Frontal  Bone 76 

Vertical  Portion  of  the  Frontal  Bone.  76 
Horizontal   or   Orbital   Portion   of   the 

Frontal  Bone 79 

The  Temporal  Bone 80 

The  Squamous  Portion 80 

The  Petromastoid  Portion 81 

The  Mastoid  Portion 82 

The  Petrous  Portion 83 

The  Tympanic  Portion 87 


The  Sphenoid  Bone 89 

The  Body  of  the  Sphenoid  Bone 90 

The  Greater  or  Temporal  Wings 92 

The  Lesser  or  Orbital  Wings 93 

The  Pterygoid  Processes 94 

The  Sphenoidal  Turbinated  Processes. .  95 

The  Ethmoid  Bone 96 

The  Horizontal  Lamina  or  Cribriform 

Plate 96 

The  Vertical  Plate 97 

The  Lateral  Mass  or  Labyrinth 97 

The  Bones  of  the  Face. 

The  Nasal  Bones 99 

The  Maxillae 100 

Changes  Produced  in  the  Upper  Jaw  by  Age .  106 

The  Lacrimal  Bone 106 

The  Malar  Bone 107 

The  Palate  Bone 109 

The  Turbinated  Bone 113 

The  Vomer 114 

The  Mandible  or  Lower  Jaw 115 

Changes  Produced  in  the  Mandible  by 

Age 119 

Side  Views  of  the  Mandible  at  Different 

Periods  of  Life 119 

The  Sutures 121 


The  Skull 


Whole. 


The  Vertex  of  the  Skull 123 

The  Base  of  the  Skull 123 

The  Lateral  Region  of  the  Skull 132 

The  Temporal  Fossa 132 

The  Mastoid  Portion 133 

The  Zygomatic  Fossa 133 

The  Sphenomaxillary  Fossa 134 

The  Anterior  Region  of  the  Skull 134 

The  Orbits 136 

The  Nasal  Cavity 138 

Development  of  the  Skull 141 

Differences  in  the  Skull  Due  to  Age 143 

Obliteration  of  the  Sutures 144 

Differences  in  the  Skull  Due  to  Sex 144 

Supernumerary,  Wormian,  Sutural  or  Epac- 

tal  Bones 144 

Craniology 144 

Surface  Form  of  the  Skull 147 

Applied  Anatomy  of  the  Skull 149 


The  Hyoid  or  Lingual  Bone. 
The  Thorax. 


153 


Boundaries  of  the  Thorax 154 

The  Cavity  of  the  Thorax 1^7 

The  Sternum  or  Breast  Bone 157 

The  Ribs 161 

Peculiar  Ribs 163 

The  Costal  Cartilages 16o 

Surface  Form  of  Thorax 166 

Applied  Anatomy  of  Thorax 167 

(ix) 


CONTENTS 


The  Upper  Extremity. 

The  Shoulder  Girdle. 

The  Clavicle 169 

Surface  Form  of  the  Clavicle 171 

Applied  Anatomy  of  the  Clavicie 172 

The  Scapula  or  Shoulder  Blade 172 

Surface  Form  of  the  Scapula 177 

Applied  Anatomy  of  the  Scapula 17S 


The  Humerus  or  Arm  Bone 178 

Surface  Form  of  the  Humerus 184 

Api^lied  Anatomy  of  the  Humerus 184 


The  Forearm. 

The  Ulna  or  Elbow  Bone 185 

Surface  Form  of  the  Ulna .  190 

The  Radius 190 

Surface  Form  of  the  Radius 192 

Applied  Anatomy  of  the   Radius  and 

Ulna 192 

The  Hand. 

The  Carpus 195 

Bones  of  the  Upper  Row 196 

The  Scaphoid  or  Navicular  Bone..  196 

The  Semilunar  Bone 197 

The  Cuneiform  Bone 197 

The  Pisiform  Bone 198 

Bones  of  the  Lower  Row 198 

The  Trapezium 198 

The  Trapezoid 199 

The  Os  Magnum 199 

The  Unciform 200 

The  Metacarpus 201 

Peculiar  Characters  of  the  Metacarpal 

Bones 202 

The  Phalanges  of  the  Hand 204 

Surface  Form  of  the  Bones  of  the  Hand ....  205 

Applied  Anatomy  of  the  Bones  of  the  Hand  205 

Development  of  the  Bones  of  the  Hand ....  206 


The  Lower  Extremity. 

The  Os  Innominatum 207 

The  Ilium 207 

The  Ischium 210 

The  Pubis 212 

The  Cotyloid  Cavity  or  Acetabulum..  .  213 

The  Obturator  or  Thyroid  Foramen .  .  .  213 

The  Pelvis 215 

Position  of  the  Pelvis 217 

Axes  of  the  Pelvis 218 

Differences     between    the     Male     and 

Female  Pelvis 218 

Surface  Form  of  the  Pelvis 219 

Applied  Anatomy  of  the  Pelvis 220 

The  Thigh. 

The  Femur  or  Thigh  Bone 221 

Surface  Form  of  the  Femur 228 

Applied  Anatomy  of  the  Femur 229 

The  Leg. 

The  Patella  or  Knee  Cap 230 

Surface  Form  of  the  Patella 231 

Applied  Anatomy  of  the  Patella 231 

The  Tibia  or  Shin  Bone 231 

Surface  Form  of  the  Tibia 236 

The  Fibula  or  Calf  Bone 236 

Surface  Form  of  the  Fibula 238 

Applied  Anatomy  of  the  Bones  of  the  Leg.  .  239 

The  Foot: 

The  Tarsus 239 

The  Calcaneus 239 

The  Astragalus  or  Ankle  Bone 244 

The  Cuboid 245 

The  Scaphoid  or  Navicular  Bone 246 

The  Cuneiform  or  Wedge  Bones 247 

The  Metatarsal  Bones 249 

Peculiar  Characters  of  the  Metatarsal 

Bones 250' 

The  Phalanges  of  the  Foot 252 

Development  of  the  Foot 254 

Construction  of  the  Foot  as  a  Whole 254 

Surface  Form  of  the  Foot 255 

Applied  Anatomy  of  the  Foot 256 

Sesamoid  Bones 257 


THE  AETICULATIONS  OR  JOINTS. 


structures  Composing  the  Joints 259 

Bone 259 

Cartilage 259 

Ligaments 261 

Synovial  Membrane 261 

Forms  of  Articulation : 

Synarthrosis  (Immovable  Articulation)  263 

Amphiarthrosis  (Mixed  Articulation)  . .  264 

Diarthrosis  (Movable  Articulation) ....  264 

Kinds  of  Movement  Admitted  in  Joints. . . .  266 

Ligamentous  Action  of  Muscles 267 

Articulations  of  the  Trunk. 

Articulations  of  the  Vertebral  Column 268 

The  Ligaments  of  the  Vertebral  Bodies 

or  Centra 268 

The  Ligaments  Connecting  the  Laminae  271 
The  Ligaments  Connecting  the  Articu- 
lar Processes 271 

The  Ligaments  Connecting  the  Spinous 

Processes 272 

The  Ligaments  Connecting  the  Trans- 
verse Processes 272 

Articulations  of  the  Atlas  with  Axis 273 

Articulations  of  the  Vertebral  Column  with  Cranium-. 

Articulation  of  Atlas  with  Occipital  Bone.  .  275 

Articulation  of  Axis  with  Occipital  Bone .  .  .  277 
Applied   Anatomy   of  Articulations   of   the 

Vertebral  Column 278 


The  Temporomandibular  Articulation 279 

Surface  Form 281 

Applied  Anatomy 281 

Articulations  of  the  Ribs  with  the  Vertebral 

or  the  Costovertebral  Articulations .  .  282 

The  Costocentral  Articulations 282 

The  Costotransverse  Articulations 284 

The  Costosternal  Articulations 286 

Articulations  of  the  Cartilages  of  the 

Ribs  with  Each  Other 288 

Articulations    of   the    Ribs    with    their 

Cartilages 288 

Articulations  of  the  Sternum 288 

Articulation  of  the  Vertebral  Column  with 

the  Pelvis ■  289 

Articulations  of  the  Pelvis 290 

Articulation  of  the  Sacrum  and  Ilium .  .  290 
Ligaments  Passing  between  the  Sacrum 

and  Ischium 291 

Articulation   of   the  Sacrum   and   Coc- 
cyx    292 

Articulation  of  the  Pubic  Bones 294 

Articulations  of  the  Upper  Extremity. 

Sternocla-vdcular  Articulation 295 

Surface  Form , 297 

Applied  Anatomy 297 

Acromioclavicular  Articulation  or  Scapulo- 
clavicular Articulation 297 

Surface  Form 299 

Applied  Anatomy 299 


CONTENTS 


XI 


Proper  Ligaments  of  the  Scapula 299 

The  Shoulder-joint 301 

Surface  Form 304 

Applied  Anatomy 304 

The  Elbow-joint 306 

Surface  Form 309 

Applied  Anatomy 309 

Radio-ulnar  Articulation 310 

Superior  Artirulation 310 

Surf:H-r  I-(,nii 311 

AiU'lii''!  Anatomy 311 

Middle  Kadio-ulnar  Ligaments 311 

Inferior  Articulation 312 

Surface  Form 314 

The  Radiocarpal  or  Wrist-joint 314 

Surface  Form 315 

Applied  Anatomy 315 

Articulations  of  the  Carpus 315 

Articulations  of  the  First  Row  of  Carpal 

Bones 315 

Articulations   of    the    Second    Row    of 

Carpal  Bones '.  .  316 

Articulations    of    the    Two    Rows    of 

Carpal  Bones  with  Each  Other 316 

Carpometacarpal  Articulations 317 

Articulation   of   the   Metacarpal   Bone 

of  the  Thumb  with  the  Trapezium.  .  317 
Articulations  of  the  Metacarpal  Bones 
of  the  Four  Inner  Fingers  with  the 

Carpus 318 

Articulations  of  the  Metacarpal  Bones 

with  Each  Other 319 

Metacarpophalangeal  Articulations 320 

Surface  Form. 321 

Articulations  of  the  Phalanges 321 

Articulations  of  the  Lower  Extremity. 

The  Hip-joint 322 

Surface  Form 329 


The  Hip-joint — 

Applied  Anatomy 329 

The  Knee-joint 331 

Surface  Form 33y 

Applied  Anatomy 338 

Tibiofibular  Articulation 340 

Superior  Tibiofibular  Articulation 340 

Middle  Tibiofibular  Ligament  or  Inter- 
osseous Membrane 341 

Inferior  Tibiofibular  Articulation 341 

The  Tibiotarsal  Articulation  or  Ankle-joint  342 

Surface  Form  of  Ankle-joint 346 

Applied  Anatomy  of  Ankle-joint 346 

Articulations  of  the  Tarsus 347 

Articulation     of     the    Calcaneus    and 

Astragalus 347 

Articulation  of  the  Calcaneus  with  the 

Cuboid 347 

The    Ligaments    Conneoting   the    Cal- 
caneus and  Scaphoid 348 

Applied  Anatomy 349 

Articulation    of    the    Astragalus    with 

the  Scaphoid  Bone 349 

The  Articulation  of  the  Scaphoid  with 

the  Cuneiform  Bones 349 

The  Articulation  of  the  Scaphoid  with 

the  Cuboid 350 

The  Articulations  of  the  Cuneiform 
Bones  with  Each  Other  or  the  Inter- 
cuneiform Articulations 350 

The     Articulation     of     the     External 

Cuneiform  Bone  with  the  Cuboid  351 

Applied  Anatomy •. 351 

Tarsometatarsal  Articulations 351 

Articulations     of     the     Metatarsal     Bones 

with  Each  Other 352 

Metatarsophalangeal  Articulations 353 

Articulations  of  the  Phalanges 354 

Surface  Form 354 

Applied  Anatomy 364 


THE  MUSCLES  AND  FASCIA. 


General  Description  of  Muscles 355 

Form  and  Attachment  of  Muscles 357 

Applied  Anatomy  of  Muscles 359 

General  Description  of  Tendons 360 

General  Description  of  Aponeurosis 360 

General  Description  of  Fasciae 360 

Development  of  Skeletal  Musculature 361 

Muscles  and  Fascia  of  the  Cranium  and  Face. 

Subdivision  in  Groups 362 

The  Cranial  Region 362 

The  Skin  of  the  Scalp 363 

Superficial  Fascia 363 

The  Occipitofrontalis 36.3 

Applied  Anatomy 365 

The  Auricular  Region '. 365 

Attrahens  Aurem 366 

Attolens  Aurem 366 

Retrahens  Aurem 366 

The  Palpebral  Region 366 

Orbicularis  Palpebrarum 366 

Corrugator  Supercilii 367 

Tensor  Tarsi  or  Horner's  Muscle 367 

Tlie  Orbital  Region 368 

Orbital  Septum 368 

Levator  Palpebrae  Superioris 369 

Recti 370 

Superior  Oblique 370 

Inferior  Oblique 370 

Fasciae  of  the  Orbit 371 

Applied  Anatomy 371 

The  Nasal  Region 372 

Py ramidalis  Nasi 372 

Levator  Labii  Superioris  Alaeque  Nasi .  372 

Dilator  Naris  Posterior 372 

Dilator  Naris  Anterior 372 

Compressor  Naris 372 

Compressor  Narium  Minor 372 

Depressor  Alae  Nasi 372 


The  Maxillary  Region 373 

Levator  Labii  Superioris 373 

Levator  Anguli  Oris 373 

Zygomaticus   Major 373 

Zygomaticus  Minor 373 

The  Mandibular  Region 374 

Levator  Menti 374 

Depressor    Labii    Inferioris    or    Quad- 

ratus  Menti 374 

Depressor  Anguli  Oris 374 

The  Buccal  Region 374 

Orbicularis  Oris 374 

Buccinator 375 

Risorius 377 

The  Temporomandibular  Region 377 

Masseteric  Fascia 377 

Masseter  Muscle 377 

Temporal  Fascia 378 

Temporal  Muscle 378 

The  Pterygomandibular  Region 379 

External  Pterygoid  Muscle 379 

Internal  Pterygoid  Muscle 380 

Surface  Form  of  Muscles  of  Head  and  Face.  381 

Muscles  and  Fascia  of  the  Neck. 

Subdivisions  into  Groups 381 

The  Superficial  Cer\'ical  Region 381 

Superficial  Cervical  Fascia 381 

Platysma 381 

Deep  Cervical  Fascia 382 

Applied  Anatomy 384 

Sternomastoid 385 

Triangles  of  the  Neck 386 

Applied  Anatomy 386 

The  Infrahyoid  Region 386 

Sternohyoid 386 

Sternothyroid 387 

Thyrohyoid 387 

Omohyoid 3SS 


CONTENTS 


The  Suprahyoid  Region 388 

Digastric 388 

Stylohyoid 389 

Mylohyoid 389 

Geniohyoid 390 

The  Lingual  Region 391 

Geniohyoglossus 391 

Hyoglossus 391 

Chondroglossus 392 

Styloglossus 392 

The  Muscle  Substance  of  the  Tongue. .  393 

Applied  Anatomy 394 

The  Pharyngeal  Region 394 

Inferior  Constrictor 394 

Middle  Constrictor 395 

Superior  Constrictor 395 

Stylopharyngeus 396 

The  Palatal  Region 397 

Levator  Palati 397 

Tensor  Palati 397 

Palatal  Aponeurosis 397 

Azygos  Uvulae 398 

Palatoglossus 398 

Palatopharyngeus 398 

Salpingopharyngeus 399 

Applied  Anatomy 399 

The  Anterior  Vertebral  Region 400 

Rectus  Capitis  Anticus  Major 400 

Rectus  Capitis  Anticus  Minor 400 

Rectus  Capitis  Lateralis 400 

Longus  Colli 401 

The  Lateral  Vertebral  Region 401 

Scalenus  Anticus 401 

Scalenus  Medius 401 

Scalenus  Posticus 402 

Surface  Form  of  Muscles  of  Neck 402 

Muscles  and  Fascia  of  the  Trtjnk. 

Subdivision  into  Groups 403 

Muscles  of  the  Back. 

Subdivision  into  Groups 403 

The  First  Layer 404 

Superficial  Fascia 404 

Deep  Fascia 404 

Trapezius 404 

Ligamentum  Nuchae 406 

Latissimus  Dorsi 406 

The  Second  Layer 407 

Levator  Anguli  Scapulae 407 

Rhomboideus  Minor 407 

Rhomboideus  Major 407 

The  Third  Layer 408 

Serratus  Posticus  Superior 408 

Serratus  Posticus  Inferior 408 

Vertebral  Aponeurosis 408 

Splenius  Capitis 409 

Splenius  Colli 409 

The  Fourth  Layer 410 

Erector  Spinae 410 

Iliocostalis 410 

Musculus  Accessorius 410 

Cervicalis  Ascendens 412 

Longissimus  Dorsi 412 

Trans versalis  Cervicis 412 

Trachelomastoid 412 

Spinalis  Dorsi ."  412 

Spinalis  Colli 412 

Complexus 412 

The  Fifth  Layer 413 

Semispinalis  Dorsi 413 

Semispinalis  Colli 413 

Multifidus  Spinae 413 

Rotatores  Spinae 413 

Supraspinales 414 

Interspinales 414 

Extensor  Coccygis 414 

Intertransversales 414 

Rectus  Capitis  Posticus  Major 414 

Rectus  Capitis  Posticus  Minor 414 

Obliquus  Inferior 415 

Obliquus  Superior 415 

Suboccipital  Triangle 415 

Applied  Anatomy 416 


Muscles  and  Fascice  of  the  Thorax. 

Intercostal  Fascia 417 

Intercostal  Muscles 417 

External  Intercostals 417 

Internal  Intercostals 417 

Infracostales 417 

Triangularis  Sterni 417 

Levatores  Costarum 417 

Diaphragm 418 

Muscles  of  the  Abdomen. 

Antero-lateral  Muscles   of  the  Abdomen  .  .  .  423 

Superficial  Fascia 424 

Deep  Fascia 424 

External  or  Descending  Oblique 424 

Aponeurosis      of      the      External 

Oblique 425 

External  Abdominal  Ring 426 

Applied  Anatomy 427 

Poupart's  Ligament 427 

Gimbernat's  Ligament 428 

Triangular  Fascia 428 

Ligament  of  Cooper 428 

Internal  or  Ascending  Oblique 428 

Cremaster  Muscle 430 

Transversalis 432 

Rectus  Abdominis 433 

Pyramidalis 435 

Linea  Alba 435 

Linea  Semilunares 436 

Fascia  Transversalis 436 

Internal  or  Deep  Abdominal  Ring  437 

Inguinal  or  Spermatic  Canal 437 

Surface  Form 439 

Posterior  Muscles  of  the  Abdomen 439 

The    Fascia    Covering    the    Quadratus 

Lumborum 439 

Quadratus  Lumborum 439 

Muscles  and  Fascice  of  the  Pelvic  Outlet 

The     Central     Tendinous     Point     of     the 

Perineum 442 

The  Muscles  of  the  Perineum  in  the  Male.  .  442 

Superficial  Transverse  Perineal 442 

Accelerator  Urinae 443 

Erector  Penis 444 

The  Muscles  of  the  Perineum  in  the  Female  445 

Superficial  Transverse  Perineal.. .......  445 

Sphincter  Vaginae 445 

Erector  Clitoridis 446 

The  Triangular  Ligament  in  the  Male  and  in 

the  Female 446 

Compressor  or  Constrictor  Urethrae.  .  .  448 

The  Pelvic  Fascia 448 

Levator  Ani 450 

Coccygeus 453 

Muscles  of  the  Ischiorectal  Region 453 

Corrugator  Cutis  Ani 453 

External  Sphincter  Ani 453 

Internal  Sphincter  Ani 454 

Ischiorectal  Fossa 454 


Muscles  and  Fascia  of  the  Upper  Extremity. 

Subdivision  into  Groups 455 

Dissection  of  Pectoral  Region  and  Axilla .  .  .  455 

Muscles  and  Fascice  of  the  Thoracic  Region. 

The  Anterior  Thoracic  Region 455 

Superficial  Fascia 455 

Deep  Fascia 456 

Pectoralis  Major 456 

Costocoracoid  Membrane  or  the  Clavi- 

pectoral  Fascia 459 

Pectoralis  Minor 460 

Subclavius 460 

The  Lateral  Thoracic  Region 461 

Serratus  Magnus 461 

Applied  Anatomy 461 


CONTENTS 


Muscles  and  Fascim  of  the  Shoulder  and  Arm. 

The  Acromial  Region 462 

Deltoid 462 

Applied  Anatomy 463 

The  Anterior  Scapular  Region 463 

Subscapularis 464 

The  Posterior  Scapular  Region 464 

Supraspinatus 464 

Infraspinatus 465 

Teres  Minor 466 

Teres  Major 466 

Muscles  and  Fascice  of  the  Arm, 

The  Anterior  Humeral  Region 467 

Deep  Fascia 467 

Coracobrachialis 468 

Biceps  or  Biceps  Flexor  Cubiti 469 

Brachialis  Anticus 469 

The  Posterior  Humeral  Region 470 

Triceps  or  Triceps  Extensor  Cubiti ....  470 

Subanconeus 471 

Muscles  and  Fascice  of  the  Forearm. 

Deep  Fascia 471 

The  Anterior  Radioulnar  Region 472 

Superficial  Layer 472 

Pronator  Teres 472 

Applied  Anatomy . . . '. 473 

Flexor  Carpi  Radialis 473 

Palmaris  Longus 474 

Flexor  Carpi  Ulnaris 474 

Flexor  Sublimis  Digitorum 475 

Deep  Layer 476 

Flexor  Profundus  Digitorum 476 

Flexor  Longus  PoUicis 476 

Pronator  Quadratus 478 

Applied  Anatomy 478 

The  Radial  Region 479 

Brachioradialis 479 

Extensor  Carpi  RadiaUs  Longior 479 

Extensor  Carpi  Radialis  Brevior 479 

The  Posterior  Radioulnar  Region 480 

Superficial  Layer 480 

Extensor  Communis  Digitorum .  .  .  480 

Extensor  Minimi  Digiti 481 

Extensor  Carpi  Ulnaris 482 

Anconeus 482 

Supinator  (Brevis) 482 

Extensor  Ossis  Metacarpi  PoUicis.  482 

Extensor  Brevis  PoUicis 483 

Extensor  Longus  PoUicis 484 

Extensor  Indicis 484 

Applied  Anatomy 485 

Muscles  and  Fascice  of  the  Hand. 

Anterior  Annular  Ligament 486 

The    Synovial    Membranes    of    the    Flexor 

Tendons  at  Wrist 486 

Applied  Anatomy 487 

Bursae  about  the  Hand  and  Wrist 487 

Posterior  Annular  Ligament 487 

Superficial  Transverse  Ligament  of  Fingers .  489 

The  Radial  Region 489 

Abductor  PoUicis 489 

Opponens  PoUicis 490 

Flexor  Brevis  PoUicis ,.  .  .  .  490 

Adductor  Obliquus  PoUicis 490 

Adductor  Transversus  PoUicis 492 

The  Ulnar  Region 492 

Palmaris  Brevis 492 

Abductor  Minimi  Digiti 492 

Flexor  Brevis  Minimi  Digiti 493 

Opponens  Minimi  Digiti 493 

The  Middle  Palmar  Region 493 

Lumbricales 493 

Interossei 493 

Dorsal  Interossei 494 

First  Dorsal  Interossei  Muscle  or 

Abductor  Indicis 494 

Palmar  Interossei 494 


Surface  Form  of  Muscles  of  the  Upper  Ex- 
tremity      495 

Applied  Anatomy  of  Muscles  of  the  Upper 
Extremity 497 


Muscles  and  Fasci/E  of  the  Lower  Extremity. 

Subdivision  into  Groups 501 

Muscles  and  Fascice  of  the  Iliac  Region. 

lUac  Fascia 502 

Psoas  Magnus 504 

Psoas  Parvus 504 

Iliacus 504 

Applied  Anatomy 505 

Muscles  and  Fasciw  of  the  Thigh. 

The  Anterior  Femoral  Region 505 

Superficial  Fascia 506 

Deep  Fascia  or  Fascia  Lata 506 

Applied  Anatomy 508 

Tensor  Fasciae  Femoris 508 

Sartorius 508 

Quadriceps  Extensor 509 

Rectus  Femoris 510 

Vastus  Externus 510 

Vastus  Internus 510 

Crureus 511 

Subcrureus 512 

AppUed  Anatomy 512 

The  Internal  Femoral  Region 512 

Gracilis 512 

Pectineus 513 

Adductor  Longus 513 

Adductor  Brevis 514 

Adductor  Magnus 514 

Hunter's  Canal 515 

Applied  Anatomy 515 

The  Muscles  and  Fascice  of  the  Hip. 

The  Gluteal  Region 515 

Gluteus  Maximus 515 

Gluteus  Medius 516 

Gluteus  Minimus 517 

Pyriformis 517 

Obturator  Membrane 517 

Obturator  Internus 518 

GemelU 520 

Quadratus  Femoris 520 

Obturator  Externus 521 

The  Posterior  Femoral  Region 522 

Biceps  Femoris 522 

Semitendinous 524 

Semimembranous 524 

Applied  Anatomy 525 

Muscles  and  Fascice  of  the  Leg. 

The  Anterior  Tibiofibular  Region 525 

Deep  Fascia  of  the  Leg 525 

Tibialis  Anticus 526 

Extensor  Proprius  Hallucis 527 

Extensor  Longus  Digitorum 527 

Peroneus  Tertius 527 

The  Posterior  Tibiofibular  Region 528 

Superficial  Layer 528 

Gastrocnemius 528 

Soleus 529 

Tendo  Achillis 530 

Plantaris 530 

Deep  Layer 531 

Deep  Transverse  Fascia 531 

Popliteus 531 

Flexor  Longus  Hallucis 532 

Flexor  Longus  Digitorum 533 

Tibialis  Posticus 533 

The  Fibular  Region 534 

Peroneus  Longus 534 

Peroneus  Brevis 535 

Applied  Anatomy 535 


CONTENTS 


Muscles  and  Fascice  of  the  Foot. 

Anterior  Annular  Ligament 536 

Internal  Annular  Ligament 536 

External  Annular  Ligament 537 

The  Dorsal  Region 537 

Fascia  of  the  Dorsal  Region 537 

Extensor  Brevis  Digitorum 537 

The  Plantar  Region 537 

Plantar  Fascia 537 

The  First  Layer 538 

Abductor  Hallucis 538 

Flexor  Brevis  Digitorum 538 

Fibrous  Sheaths  of  Flexor  Tendons  539 

Abductor  Minimi  Digiti 539 


The  Plantar  Region — 

The  Second  Layer 539 

Flexor  Accessorius 539 

Lumbricales 540 

The  Third  Layer 541 

Flexor  Brevis  Hallucis 541 

Adductor  Obliquus  Hallucis 541 

Adductor  Transversus  Hallucis  .  .  .  541 

Flexor  Brevis  Minimi  Digiti 541 

The  Fourth  Layer 541 

Interossei  Muscles 541 

Surface    Form    of    Muscles    of    the    Lower 

Extremity. 543 

Applied  Anatomy  of  Muscles  of  the  Lower 

Extremity 544 


THE  VASCULAR  SYSTEMS. 


The  Heart  and  Bloodvessels. 
The  Circulation  of  the  Blood 


The  Pericardium. 

Structure  of  the  Pericardium 

Vestigial  Fold  of  the  Pericardium 

Applied  Anatomy  of  the  Pericardium. 

The  Heart. 

Position  of  the  Heart 

Component  Parts  of  the  Heart 

The  Cavities  of  the  Heart 

Right  Auricle ".  .  .  . 

Right  Ventricle 

Left  Auricle . 


548 
550 
550 


551 
553 
553 
554 
557 
559 


The  Cavities  of  the  Heart — 

Left  Ventricle 560 

Capacity  of  the  Cavities  of  the  Heart 561 

Size  and  Weight  of  the  Heart 562 

Structure  of  the  Heart 562 

Endocardium 562 

Myocardium 562 

Fibres  of  Auricles 562 

Fibres  of  Ventricles 563 

The  Cardiac  Cycle  and  the  Action  of  the 

Valves 565 

Surface  Form  of  the  Heart 567 

Applied  Anatomy  of  the  Heart 568 

Peculiarities  of  the  Vascular  System  in  the 

Fetus 568 

Fetal  Circulation 570 

Changes  in  the  Vascular  System  at  Birth .  .  571 


THE    ARTEEIES. 


The  Distribution  of  the  Arteries 572 

Anastomosis  of  the  Arteries 572 

Histology  of  Arteries  and  Capillaries 573 

Bloodvessels  of  the  Bloodvessel  Wall 573 

Lymphatics  of  the  Arteries 574 

Nerves  of  the  Arteries 574 

Arterial  Sheath 574 

Applied  Anatomy  of  the  Arteries 574 

The  Pulmonary  Artery. 

Right  Branch  of  the  Pulmonary  Artery.  .  .  .  575 

Left  Branch  of  the  Pulmonary  Artery 575 

Applied  Anatomy  of  the  Pulmonary  Artery  575 

The  Aorta. 

The  Ascending  Aorta. 

Relations  of  the  Ascending  Aorta 576 

Branches  of  the  Ascending  Aorta 578 

The  Coronary  Arteries 578 

Applied  Anatomy  of  the  Coronary 

Arteries 578 


The  Arch  of  the  Aorta. 

Relations  of  the  Arch  of  the  Aorta 

Peculiarities  of  the  Arch  of  the  Aorta 

AppHed  Anatomy  of  the  Arch  of  the  Aorta . 

Branches  of  the  Arch  of  the  Aorta 

The  Innominate  Artery 

Relations 

Branches 

Thyroidea  Ima 

Applied  Anatomy 

Peculiarities 


579 
580 
580 
581 
582 
582 
582 
582 
582 
583 


The  Arteries  of  the  Head  and  Neck. 

The  Common  Carotid  Artery. 

Relations  of  the  Common  Carotid  Artery.  .     583 

Peculiarities  of  the  Common  Carotid  Artery     586 

Surface  Marking  of  the  Common  Carotid 

Artery 586 

Applied  Anatomy  of  the  Common  Carotid 

Artery 586 


The  External  Carotid  Artery 

Relations 

Surface  Marking 

Applied  Anatomy 

Branches 

Superior  Thyroid  Artery 

Applied  Anatomy 

Lingual  Artery 

Applied  Anatomy 

Facial  Artery 

Applied  Anatomy 

Occipital  Artery 

Posterior  Auricular  Artery 

Ascending  Pharyngeal  Artery. . . . 

Applied  Anatomy 

Superficial  Temporal  Artery 

Applied  Anatomy 

Internal  Maxillary  Artery 

Applied  Anatomy 

The  Triangles  of  the  Neck 

Anterior  Triangle  of  the  Neck 

Posterior  Triangle  of  the  Neck 

The  Internal  Carotid  Artery 

Cervical  Portion . 

Petrous  Portion 

Cavernous  Portion 

Cerebral  Portion 

Peculiarities 

Applied  Anatomy 

Branches 

Tympanic 

Vidian 

Arteriae  Receptaculi 

Anterior  Meningeal 

Ophthalmic 

Anterior  Cerebral 

Middle  Cerebral 

Posterior  Communicating  Artery. 
Choroid  Artery 


The  Arteries  of  the  Brain. 

The  Central  GangUonic  System 

The  Cortical  Arterial  System 

The  Vertebral  Artery 

Applied  Anatomy 


588 
588 
588 
589 
589 
590 
590 
591 
592 
595 
595 
596 
597 
597 
597 
598 
598 
600 
602 
603 
605 
606 
607 
607 


609 
609 
609 
610 
614 
616 
617 
617 


618 
619 
619 
620 


CONTENTS 


The  Ahteries  of  the  Upper  Extremity. 

The  Subclavian  Artery. 

First  Part  of  the  Right  Subclavian  Artery .  .  623 

First  Part  of  the  Left  Subclavian  Artery .  .  .  625 
Second  and  Third  Parts  of  the  Subclavian 

Artery 625 

Peculiarities  of  the  Subclavian  Artery 626 

Surface  Marking  of  the  Subclavian  Artery .  .  626 

Applied  Anatomy  of  the  Subclavian  Artery .  627 

Branches 628 

Vertebral  Artery 628 

Thyroid  Axis 628 

Peculiarities 630 

Internal  Mammary  Artery 631 

Superior  Intercostal  Artery 633 

The  Axilla. 

Boundaries  of  the  Axilla 633 

Contents  of  the  Axilla 634 

Applied  Anatomy 634 

The  Axillary  Artery 635 

Surface  Marking 637 

Applied  Anatomy 637 

Branches 638 

Superior  Thoracic 638 

Acromiothoracic 638 

Long  Thoracic  or  External  Mam- 
mary   638 

Alar  Thoracic 639 

Subscapular 639 

Circumflex  Arteries 639 

The  Brachial  Artery. 

Relations  of  the  Brachial  Artery 640 

Anatomy  of  the  Bend  of  the  Elbow 641 

Peculiarities  of  the  Brachial  Artery 641 

Surface  Marking  of  the  Brachial  Artery. . .  .  641 

Applied  Anatomy  of  the  Brachial  Artery.  .  .  641 

Branches  of  the  Brachial  Artery 642 

Superior  Profunda  Artery 642 

Nutrient  Artery 643 

Inferior  Profunda  Artery 643 

Anastomotica  Magna 643 

Muscular  Branches 644 

The  Anastomosis  Around  the  Elbow- 
joint 644 

The  Radial  Artery 644 

The  Deep  Palmar  Arch 645 

Surface  Marking 646 

Applied  Anatomy 646 

Branches 646 

Radial  Recurrent 646 

Muscular  Branches 646 

Anterior  Radial  Carpal 647 

Superficialis  Volae 647 

Posterior  Radial  Carpal 647 

Dorsalis  Pollicis. 647 

Dorsalis  Indicis 647 

Princeps  Pollicis 647 

Radialis  Indicis ; 647 

Perforating  Arteries 648 

Palmar  Interosseous 648 

Palmar  Recurrent  Branches 648 

The  Ulnar  Artery 648 

Surface  Marking 649 

Applied  Anatomy 649 

Branches 650 

Anterior  Ulnar  Recurrent 650 

Posterior  Ulnar  Recurrent 650 

Interosseous  Artery 650 

Muscular  Branches 651 

Anterior  Ulnar  Carpal 651 

Posterior  Ulnar  Carpal 651 

Profunda  Branch 651 

Superficial  Palmar  Arch 652 

Surface  Marking 652 

Applied  Anatomy 652 

The  Arteries  of  the  Trunk. 
The  Descending  Aorta. 

The  Thoracic  Aorta 653 

Applied  Anatomy 654 

Branches 654 


The  Thoracic  Aorta — Branches — 

Bronchial  .VrtiTJfs 654 

CEso|.h:ii;(M!  ,\riiTies 654 

Peric;ir.li;il    \il-rirs 654 

MediiisliiKil  I'.iaiiches 654 

Intercostal  Arteries 655 

Applied  Anatomy 657 

The  Abdominal  Aorta 657 

Surface  Marking 657 

Applied  Anatomy 658 

Branches 658 

Inferior  Phrenic  Arteries 658 

The  Cceliac  Axis  or  Artery 659 

Applied  Anatomy 662 

The  Suprarenal  Artery 662 

The  Lumbar  Arteries 662 

The  Superior  Mesenteric  Artery...  663 

The  Renal  Arteries 665 

The  Spermatic  Arteries 665 

The  Ovarian  Arteries 665 

The  Inferior  Mesenteric  Artery .  .  .  666 

The  Cojntnon  Iliac  Arteries. 

Relations  of  the  Common  Iliac  Arteries. .  .  .  668 

Branches  of  the  Common  Iliac  Arteries  ....  668 

Peculiarities  of  the  Common  Iliac  Arteries  .  668. 

Surface  Marking 669 

Applied    Anatomy   of    the    Common    Iliac 

Arteries 669 

The  Internal  Iliac  Artery 669 

Applied  Anatomy 671 

Branches 671 

Superior  Vesical 671 

Middle  Vesical 672 

Inferior  Vesical 672 

Middle  Hemorrhoidal 672 

Uterine  Artery 672 

Vaginal  Artery 672 

Applied  Anatomy 673 

Obturator  Artery 673 

Internal  Pudic  Artery 674 

Sciatic  Artery 677 

Iliolumbar  Artery 678 

Lateral  Sacral  Arteries 678 

Gluteal  Artery 678 

Surface  Marking 679 

Applied  Anatomy 679 

The  External  Iliac  Artery 679 

Surface  Marking 680 

Applied  Anatomy 680 

Branches 680 

Deep  Epigastric  Artery 680 

Applied  Anatomy 681 

Deep  Circumflex  Iliac  Artery 682 

The  Arteries  of  the  Lower  Extremity. 

The  Femoral  Artery. 

The  Femoral  or  Crural  Sheath 683 

The  Femoral  or  Crural  Canal 684 

Scarpa's  Triangle 685 

Hunter's  Canal  or  the  Adductor  Canal 685 

Relations  of  the  Femoral  Artery 686 

PecuUarities  of  the  Femoral  Artery 687 

Surface  Marking  of  the  Femoral  Artery ....  687 

Applied  Anatomy  of  the  Femoral  Artery.  .  .  687 

Branches  of  the  Femoral  Artery 688 

Superficial  Epigastric ' 689 

Superficial  Circumflex  Iliac 689 

Superficial  External  Pudie.or  the  Supe- 
rior Superficial  External  Pudic 689 

Deep  External  Pudic 689 

Muscular  Branches 6S9 

Deep  Femoral  or  the  Profunda  Femoris  689 

The  Popliteal  Artery. 

The  Popliteal  Space 691 

Boundaries 692 

Contents 692 

Position  of  Contained  Parts 692 

Peculiarities 693 

Surface  Marking 693 

Applied  Anatomy 693 

Branches 694 


CONTENTS 


The  Popliteal  Space — Branches — 

Superior  Muscular  Branches 694 

Inferior       Muscular       or       Sural 

Branches 694 

Cutaneous  Branches 694 

Superior  Articular  Arteries 694 

Azygos  Articular  Artery 695 

Inferior  Articular  Arteries 695 

Circumpatellar  Anastomosis 696 

The  Anterior  Tibial  Artery 696 

Surface  Marking 697 

Applied  Anatomy 697 

Branches 697 

Posterior  Recurrent  Tibial 698 

Superior  Fibular 698 

Anterior  Recurrent  Tibial 698 

Muscular  Branches 698 

The  Dorsalis  Pedis  Artery 698 

Surface  Marking 699 

Applied  Anatomy 699 

Branches 699 


The  Dorsalis  Pedis  Artery — Branches — 

Cutaneous  Branches 699 

Tarsal  Artery 699 

Metatarsal  Artery 699 

Communicating  Artery 700 

The  Posterior  Tibial  Artery. 700 

Surface  Marking 701 

Applied  Anatomy 701 

Branches 701 

Peroneal  Artery 701 

Cutaneous  Branches 702 

Nutrient  Artery 702 

Muscular  Branches 703 

Communicating  Branch 703 

Malleolar  or  Internal  Malleolar.  .  .  703 

Internal  Calcaneal 703 

Internal  Plantar  Artery 703 

External  Plantar  Artery 703 

Surface  Marking 704 

Apphed  Anatomy 704 


THE  A^EINS. 


Subdivisions  of  the  Veins 705 

Histology  of  the  Veins 706 

Superficial  or  Cutaneous  Veins 707 

Deep  Veins 707 

Sinuses 707 

The  Pulmonary  Veins. 
Applied  Anatomy  of  the  Pulmonary  Veins . .     708 

The  Systemic  Veins. 
The  Cardiac  Veins. 
The  Coronary  Sinus 


708 


The  Veins  of  the  Head  and  Neck. 

Veins  of  the  Exterior  of  the  Head  and  Face  710 

Frontal  Vein 710 

Supraorbital  Vein 710 

Angular  Vein 710 

Facial  Vein 710 

Common  Facial  Vein 710 

Applied  Anatomy 711 

Superficial  Temporal  Vein 712 

Pterygoid  Plexus 712 

Internal  Maxillary  Vein 712 

Temporomaxillary  Vein 712 

Posterior  Auricular  Vein 712 

Occipital  Vein 713 

The  Veins  of  the  Neck 713 

External  Jugular  Vein 713 

Posterior  External  Jugular  Vein 713 

Anterior  Jugular  Vein 713 

Internal  Jugular  Vein 714 

Applied  Anatomy 717 

Vertebral  Vein 717 

The  Veins  of  the  Diploe 718 

Meningeal  or  Dural  Veins 719 

The  Cerebral  Veins _ V19 

Superficial  Cerebral  Veins 719 

Deep  Cerebral  Veins  or  Veins  of  Galen  720 

Superficial  Cerebellar  Veins 720 

Deep  Cerebellar  Veins 720 

Veins  of  the  Pons 720 

Veins  of  the  Medulla  Oblongata 721 

The  Sinuses  of  the  Dura.   Ophthalmic  Veins 

and  Emissary  Veins 721 

Superior  Sagittal  Sinus 721 

Inferior  Sagittal  Sinus 722 

Straight  or  Tentorial  Sinus 722 

Lateral  Sinuses 722 

Occipital  Sinus 723 

Cavernous  Sinus 724 

Applied  Anatomy 724 

Sphenoparietal  Sinuses 725 

Circular  Sinus 726 

Superior  Petrosal  Sinus 726 


The  Sinuses  of  the  Dura.     Ophthalmic  Veins 
and  Emissary  Veins — 

Inferior  Petrosal  Sinus 726 

Transverse  or  Basilar  Sinus 727 

Emissary  Veins 727 

Applied  Anatomy 727 


The  Veins  of  the  Upper  Extremity  and  Thorax. 

The    Superficial   Veins    of    the    Upper   Ex- 
tremity    728 

Superficial    Veins    of    the    Hand    and 

Fingers 728 

Anterior  Ulnar  Vein 729 

Posterior  Ulnar  Vein 729 

Common  Ulnar  Vein 729 

Radial  Vein 730 

Median  Vein 730 

BasUic  Vein 730 

Cephalic  Vein 730 

The  Deep  Veins  of  the  Upper  Extremity.  .  .  731 

Interosseous  Veins 731 

Deep  Palmar  Veins 731 

Brachial  Veins 731 

Axillary  Vein 731 

Applied  Anatomy 732 

Subclavian  Vein 732 

Innominate  or  Brachiocephalic  Veins .  .  733 

Internal  Mammary  Veins 734 

Vertebral  Vein 734 

Inferior  Thyroid  Veins 734 

Superior  Intercostal  Veins 735 

Superior  Vena  Cava 735 

Azygos  Veins 736 

Applied  Anatomy 737 

Bronchial  Veins 737 

The  Vertebral  Veins 737 

Extravertebral  Veins 737 

Intravertebral  Veins 738 

Veins  of  the  Bodies  of  the  Vertebrae  . .  .  738 

Veins  of  the  Spinal  Cord 739 


Veins  of  the  Lower  Extremity,  Abdomen,  and  j 

Superficial  Veins  of  the  Lower  Extremity ...  739 

Superficial  Veins  of  the  Foot 739 

Internal  or  Long  Saphenous  Vein 740 

External  or  Short  Saphenous  Vein 741 

Applied  Anatomy 741 

Deep  Veins  of  the  Lower  Extremity 741 

Deep  Veins  of  the  Foot 741 

Posterior  Tibial  Veins 742 

Anterior  Tibial  Veins 742 

Pophteal  Vein 742 

Femoral  Vein 742 

External  Iliac  Vein 742 

Deep  Epigastric  Vein 742 

Deep  Circumflex  Iliac  Vein 742 


CONTENTS 


XVII 


Deej)  Veins  of  the  Lower  Extremity — 

Pubic  Vein 743 

Internal  Iliac  Vein 743 

Hemorrhoidal  Plexus 745 

.  Vesicoprostatic  Plexus 745 

Vesical  Plexus 745 

Applied  Anatomy 745 

Dorsal  Veins  of  the  Penis 746 

Vaginal  Plexuses  and  Veins 747 

Uterine  Plexuses 747 

Common  Iliac  Veins 747 

Inferior  Vena  Cava 748 

Applied  Anatomy 748 

Lumbar  Veins 749 

Spermatic  Veins 750 

Applied  Anatomy 750 

Ovarian  Veins 751 


Deep  Veins  of  the  Lower  Extremity — 

Renal  Veins 751 

Suprarenal  Veins 751 

Inferior  Phrenic  Veins 751 

Hepatic  Veins 751 

The  Portal  System  of  Vkins. 

The  Portal  Vein 751 

The  Splenic  Vein 752 

The  Superior  Mesenteric  Vein 753 

The  Cysrie  Vein 754 

Paraumbilical  Veins 754 

Anastomosis  between  Portal  and  Systemic 

Veins 754 

Applied  Anatomy 754 

Development  of  the  Blood-vascular  System .  755 


THE   LYMPHATIC   SYSTEM. 


Subdi\asions  into  Superficial  and  Deep  Sets .  767 

Lymph  Nodes  or  Lymphatic  Glands 768 

Hemolymph  Nodes 768 

Structure  of  Lymphatics 769 

Origin  of  Lymphatics 769 

Termination  of  Lymphatics 769 

Development  of  Lymphatic  Vessels 769 

Applied  Anatomy 770 

The  Thoracic  Duct. 

Structure  of  the  Thoracic  Duct 773 

The  Right  Lymphatic  Duct 773 

Applied  Anatomy 774 

Lymphatics  of  the  Head,  Face,  and  Neck. 

The  Lymphatic  Nodes  of  the  Head  and  Face  774 

Occipital  Nodes 774 

Posterior  Auricular  or  Mastoid  Nodes..  774 

Parotid  Ljonph  Nodes 774 

Internal  Maxillary  Nodes 776 

Lingual  Nodes 776 

Retropharyngeal  Nodes 776 

Lymphatic  Vessels  of  the  Scalp 776 

Lymphatic  Vessels  of  the  Pinna  and  Exter- 
nal Auditory  Meatus 777 

Lymphatic  Vessels  of  the  Face 777 

Lymphatic  Vessels  of  the  Nasal  Fossae 777 

Lymphatic  Vessels  of  the  Mouth ■ . .  777 

Lymphatic  Vessels  of  the  Tongue 777 

Lymph  Nodes  of  the  Neck 777 

Superficial  Cervical  Nodes 777 

Submaxillary  Nodes 778 

Submental  or  Suprahyoid  Nodes 779 

Retropharyngeal  Nodes 779 

Deep  Cervical  Nodes 779 

Lymphatic  Vessels  of  the  Skin  and  Muscles 

of  the  Neck 780 

Applied  Anatomy 780 

The  Lymph.atics  of  the  Upper  Extremity. 

The  Lymph  Nodes  of  the  Upper  Extremity .  781 

Superficial  Lymph  Nodes 781 

Deep   Lymph    Nodes   or   the   Axillary 

Nodes 782 

Lymphatic  Vessels  of  the  Upper  Extremity  783 

Superficial  Lymphatic  Vessels 783 

Deep  Lymphatic  Vessels 784 

Applied  Anatomy 784 

The  Lymphatics  of  the  Lower  Extremity. 

The  Lymph  Nodes  of  the  Lower  Extremity  784 

Anterior  Tibial  Node 784 

Popliteal  Nodes 784 

Inguinal  Nodes 785 

Superficial  Inguinal  Nodes 785 

Deep  Inguinal  Nodes 786 

Applied  Anatomy 786 

The  Lymphatic  Vessels  of  the   Lower  Ex- 
tremity    786 

Superficial  Vessels 786 

Deep  Vessels 787 


The  Lymph.atics  of  the  Pelvis  .and 
Abdomen. 

The  Parietal  Nodes 787 

External  Iliac  Nodes 787 

Internal  IKac  or  Hypogastric  Nodes.  . .  787 

Common  Iliac  Nodes 788 

Lumbar  Nodes 788 

Lateral  Aortic  Nodes 788 

Lymphatic    Vessels    of   the   Abdomen    and 

Pelvis 789 

Superficial  Vessels 789 

Deep  Vessels 790 

Lymphatic  Vessels  of  the  Perineum  and 

External  Genitals 790 

The  Visceral. Nodes 790 

The  Superior  Mesenteric  Nodes 790 

Mesenteric  Nodes 790 

Applied  Anatomy 791 

Ileocolic  Nodes 791 

Mesocolic  Nodes 791 

Inferior  Mesenteric  Nodes 791 

Lymphatic    Vessels   of   the    Abdomen    and 

Pelvic  Viscera 792 

Lymphatic  Vessels  of  the  Stomach 792 

Applied  Anatomy 793 

Lymphatic  Vessels  of  the  Duodenum  . .  .  793 
Lymphatic   Vessels   of   the    Small    In- 
testine    793 

Lymphatic  Vessels  of  the  Large  Intes- 
tine   794 

Lymphatic   Vessels   of   the   Anus    and 

Rectum 794 

Lymphatic  Vessels  of  the  Liver 794 

Lymphatic  Vessels  of  the  Gall-bladder.  795 

Lymphatic  Vessels  of  the  Pancreas ....  796 

Lymphatic  Vessels  of  the  Spleen 796 

Lymphatic   Vessels   of  the ,  Suprarenal 

Glands 796 

Lymphatic     Vessels     of     the     Urinary 

Organs 796 

Lymphatic  Vessels  of  the  Kidney.  796 

Lymphatic  Vessels  of  the  Ureter. .  796 

Ljonphatic  Vessels  of  the  Bladder.  796 

Lymphatic  Vessels  of  the  Prostate  796 

Ljonphatic  Vessels  of  the  Urethra.  796 
Lymphatic  Vessels  of  the  Reproductive 

Organs 796 

Lymphatic  Vessels  of  the  Testes  .  .  796 
Lymphatic    Vessels    of    the    Vas 

Deferens 797 

Lymphatic  Vessels  of  the  Ovarj' .  .  797 
Lymphatic  Vessels  of  the  Fallopian 

Tube 797 

Lymphatic  Vessels  of  the  Uterus . .  797 

Lymphatic  Vessels  of  the  Vagina. .  797 

The  Lymphatics  of  the  Thorax. 

The  Parietal  Lymph  Nodes 798 

Internal  Mammary  Nodes 798 

Intercostal  Nodes 798 

Diaphragmatic  Nodes 798 


CONTENTS 


Superficial  Lymphatic  Vessels  of  the  Tho- 

racic  Wall ■• 'J* 

Lymphatic   Vessels   of   the   Mammary 

'Gland .■•^;n    ■  ■•  Vtm 

Deep  Lymphatics  of  the  Thoracic  Wall.  ...  799 

Lymphatic  Vessels  of  the  Diaphragm .  .  799 

Applied  Anatomy '^ 

The  Visceral  Lymph  Nodes «UU 

Anterior  Mediastinal  Nodes »uu 

Posterior  Mediastinal  Nodes »uu 


The  Visceral  Lymph  Nodes— 

Tracheobronchial  Nodes hUU 

Applied  Anatomy ■  •  • °0- 

Lymphatic  Vessels  of  the  Thoracic  Viscera  .  802 

Lymphatic  Vessels  of  the  Heart 802 

Lymphatic  Vessels  of  the  Lungs 802 

Lymphatic  Vessels  of  the  Pleura 802 

Lymphatic    Vessels    of    the    Thymus 

Gland ■^■■■- 802 

Lymphatic  Vessels  of  the  (Esophagus.  802 


THE  NERVE  SYSTEM. 


The    Spinal   Cord   and   Brain,    with   their 
Meninges. 

Fundamental  Facts  Regarding  the  Develop-  | 

ment  of  the  Nerve  System 804 

Development  of  Nerve  Tissue »OD 

Structure  of  the  Nerve  System |U ' 

The  Neurone ^  °Xn 

The  Dendrites =Yn 

The  Axone o^V 

The  Collaterals ^^^ 

Nerve  Cell  Nidi  or  Nuclei 812 

"Nerve  Fibres"  and  Nerves. 

Origin  and  Termination  of  Nerves.  ■••■■■■•  81* 
The    Supporting    Tissue    Elements    of    the 

.       Nerve  System »{° 

The  NeurogUa °J° 

Chemical  Composition  of  Nerves oia 

The  Central  Nerve  System. 

Preliminary  Considerations 819 

The  Spinal  Cord. 

External  Morphology  of  the  Spinal  Cord. . .  822 

The  Enlargements  of  the  Spinal  Cord  .  .      .  »jA 

Fissures  and  Grooves  of  the  Spinal  Cord ...  82o 

Columns  of  the  Spinal  Cord      . 82b 

Development  of  the  Spinal  Cord. 82^ 

Internal  Structure  of  the  Spinal  Cord 8-9 

Gray  Substance  of  the  Cord 829 

White  Substance  of  the  Cord 8dd 

Tracts  of  the  Spinal  Cord  .•■■•■• gg* 

Ground  Bundle  of  the  Dorsal  Column  .  837 

Ground  Bundle  of  the  Lateral  Column  839 

Ground  Bundle  of  the  Ventral  Column  840 

Myelinization  of  the  Axones  of  the  Cord  840 

Applied  Anatomy  of  the  Spinal  Cord 842 

The  Membranes  of  the  Cord. 

The  Spinal  Dura |43 

The  Arachnoid °** 

The  Pia  of  the  Cord ■  ■  ■  ■      o4& 

Applied  Anatomy  of  the  Membranes  oi  the 
Cord 


S46 


847 


The  Brain  or  Encephalon. 
General  Appearance  and  Topography  of  the 

Brain 

Dimensions  of  the  Bram 849 

Weight  of  the  Brain .•  •  ■  ■  j'  V  tt  '  '  'i 

The  Development  of  the  Bram  and  the  Usual 

Classifioations  of  its  Subdivisions 850 

Brief  Consideration  of  the  Phases  of  Devel- 
opment of  the  Brain  Tube 852 

Forebrain °52 

Midbrain °°^ 

Hindbrain °°g 

Flexures  of  the  Brain  Tube :••;.■•,     °°^ 

Dorsal  and  Ventral  Laminai  or  Longitudinal 
Zones  of  the  Brain ood 

Descriptive  Anatomy  of  the  Adult  Human  Brain. 
Parts  Derived  from  the  Hindbrain  (Rhom- 
bencephalon)        861 

The  Medulla  Oblongata 8bl 


Parts  Derived  from  the  Hindbrain— 

The  Pons.. =64 

Fourth  Ventricle  of  the  Brain 8o4 

Internal  Structure  of  the  Medulla 

Oblongata 867 

Internal  Structure  of  the  Pons  and  Pars 

Dorsalis  Pontis /,'  '   ■■  i 

Central    Connections    of    the    Cranial  

Nerves  to  the  Hindbrain 8/  / 

The  Cerebellum ;  >; '  '  V  „  ■  '  '  '  §So 

Internal  Structure  of  Cerebellum. .  888 

The  Cerebellar  Peduncles 889 

Weight  of  the  Cerebellum 893 

The  Midbrain 893 

External  Morphology 894 

Corpora  Quadrigemina 894 

Superior  Brachium 895 

Internal  Geniculate  Body 895 

Crura  Cerebri 895 

Taenia  Pontis 895 

Tractus  Peduncularis  Transversus  895 

Internal  Structure  of  Midbrain 896 

The  Aqueduct  and  Central  Aque- 
duct Gray 897 

Substantia  Nigra  or  Intercalatum .  897 

Corpora  Quadrigemina 897 

Tegmentum 897 

Red  Nucleus  or  Rubrum 898 

Fountain  Decussation 900 

Crusta  or  Pes ■  •  900 

Summary  of   the  Gray  Masses   m   the 

Midbrain ;■.■.•  ^ 

Deep  Origin  of  Cranial  Nerves  Arising 

in  the  Midbrain 900 

Parts  Derived  from  the  Forebrain 902 

External  Morphology 9U2 

TheThalami 902 

The  Pineal  Body 9Ub 

Third  Ventricle ■■■■_■  90/ 

External     Morphology    of    the    Optic 

Portion  of  the  Hypothalamus .  .  908 

Tuber  Cinereum 90S 

Pituitary  Body  or  Hypophysis 909 

Lamina  Terminahs  or  Terma 909 

Optic  Tract  and  its  Central  Con- 
nections    909 

Optic  Chiasm 910 

The  Cerebral  Hemispheres 91- 

External  Morphology ■  ■  .  ■.■  ■'!'' 

Configuration  of  Each  Cerebral  Hemi- 

Cerebral  Fissures  and  Gyres 915 

Cerebral  Lobes  and  Fissures 91b 

The  Interlobar  Fissures 916 

Frontal  Lobe 919 

Parietal  Lobe 922 

Occipital  Lobe 924 

Temporal  Lobe 924 

The  Island  of  Reil 925 

The  Rhinencephalon  or  Olfactory 

Lobe ■■■;  ^^^ 

Internal  Configuration  of  the  Cerebral 

Hemispheres 931 

The  Cortex 932 

The  Corpus  Callosum 933 

The  Lateral  Ventricles 93b 

The  Choroid  Fissure  or  Rima 940 

The  Choroid  Plexus  of  the  Lateral 

Ventricles  and  Velum  Interposi-      

turn 940 


CONTENTS 


The  Cerebral   Hemispheres — Internal  Con- 
figuration of —    ■ 

The  Hippocampus  and  Fornix  ....  942 

The  Septum  Lucidum 945 

The  Anterior  Commissure 946 

Gray  Masses  in  the  Cerebral  Hemi- 
sphere    946 

Intimate  Structure  of  the  Cerebral 
Cortex  and  its  Special  Types  in  Dif- 
ferent Regions 951 

Summary  of  the  Cerebral  Fibre  System  954 

The  Olfactory  Pathways 958 

Cortical  Localization  of  Function. 

Motor  Area ,  959 

Sensory  Area 960 

Language  Area 960 

Association  Areas 961 

Craniocerebral  Typography 962 

The  Meninges  or  Meningeal  Membranes  of  the 
Brain. 

The  Dura  of  the  Brain 964 

Processes  of  the  Dura 966 

The  Arachnoid  of  the  Brain 968 

Subarachnoid  Space 969 

The  Arachnoid  Villi  or  Pacchionian  Bodies  970 

The  Pia  of  the  Brain 971 

Velum  Interpositum  or  the  Tela  Chor- 

oidea  Superior 971 


The  Cranial  Nerves. 

The  First  or  Olfactory  Nerves. 

Applied  Anatomy , 974 

The  Second  or  Optic  Nerve. 

■Optic  Chiasm 974 

Applied  Anatomy 975 

The  Third  or  Oculomotor  Nerve. 

Applied  Anatomy 977 

The  Fourth  or  Trochlear  Nerve. 

Applied  Anatomy 978 

The  Fifth,   Trigeminal,  or  Trifacial  Nerve. 

Gasserian  or  Semilunar  Ganglion 978 

Ophthalmic  Nerve 979 

The  Superior  Maxillary  Nerve 982 

The  Inferior  Maxillary  or  Mandibular  Nerve  987 

Surface  Marking 990 

Apphed  Anatomy 991 

The  Sixth  or  Abducent  Nerve. 

Applied  Anatomy 994 

The  Seventh  or  Facial  Nerve. 

Applied  Anatomy 999 

The  Eighth  or  Acoustic  Nerve. 

The  Cochlear  Nerve 1000 

The  Vestibular  Nerve 1000 

Applied  Anatomy 1001 

The  Ninth  or  Glossopharyngeal  Nerve. 

The  Superior  or  Jugular  Ganglion 1002 

The  Inferior  or  Petrous  Ganglion 1002 

The  Gustatory  Path 1003 

Applied  Anatomy 1003 


The  Tenth,   Vagus,  or  Pneumogastric  Nerve. 

The  Ganglion  of  the  Root  or  the  Jugular 
Ganglion 1005 

The  Ganglion  of  the  Trunk  or  the  Inferior 
Ganglion 1005 

Applied  Anatomy 1008 

The  Eleventh  or  Spinal  Accessory  Nerve. 

The  Bulbar  or  Vagal  Accessory  Part 1009 

The  Spinal  Portion 1009 

Applied  Anatomy 1009 

The   Twelfth  or  Hypoglossal  Nerve. 
Applied  Anatomy 1012 


The  Spinal  Neeve.s. 

The  Anterior  or  Ventral  Root 

The  Posterior  or  Dorsal  Root 

Spinal  Ganglia 

Points  of  Emergence  of  Spinal  Nerves. 
Divisions  of  Spinal  Nerves 


1013 
1013 
1013 
1014 
1014 


The  Cervical  Plexus. 

The   Superficial   Branches   of   the   Cervical 

The  Deep  Branches  of  the  Cervical  Plexus, 

Internal  Series 

Applied  Anatomy 

The  Deep  Branches  of  the  Cervical  Plexus, 

External  Series 

Applied  Anatomy 


The  Brachial  Plexus. 

Applied  Anatomy 

The  Anterior  or  Ventral  Divisions  of  Thor- 
acic Nerves 

Applied  Anatomy 

The  Lumbosacral  Plexus. 

The  Anterior  or  Ventral  Di-visions  of  the 
Lumbar  Nerves 

The  Lumbar  Plexus 

The  Anterior  or  Ventral  Divisions  of  the 
Sacral  and  Coccygeal  Nerves 

The  Sacral  Plexus. 
Relations 

The  Pudendal  Plexus. 

Applied  Anatomy 


1023 
1025 


1025 
1026 


1040 
1043 


1044 
1044 

1051 
1053 

1062 


The  Sympathetic  Nerve  System. 

Structure  of  the  Sympathetic  System 1063 

The  Gangliated  Cord. 

Cervicocephalic  Portion  of  the  Gangliated 

Cord 1066 

The  Superior  Cervical  Ganglion 1066 

The  Middle  Cervical  Ganglion 1069 

The  Inferior  Cer^dcal  Ganglion 1069 

Applied  Anatomy 1069 

Thoracic  Portion  of  the  Gangliated  Cord  1070 

Lumbar  Portion  of  the  Gangliated  Cord  . . .  1071 

Pelvic  Portion  of  the  Gangliated  Cord .....  1072 

The  Great  Plexuses  of  the  Sympathetic  System. 

The  Cardiac  Plexus 1072 

The  CceUac  or  Solar  Plexus 10/3 

The  Hypogastric  Plexus 1077 

The  Pelvic  Plexuses 1077 


CONTENTS 


THE  OEGANS  OF  SPECIAL  SENSE. 


The  Nose. 

The  Outer  Nose. 
Structure 1079 

The  Nasal  Fossae. 

The  Anterior  Nares 1081 

The  Posterior  Nares 1081 

The  Outer  Wall 1082 

The  Inner  Wall lOhS 

The  Mucous  Membrane 1083 

AppUed  Anatomy  of  the  Nose 1085 

The  Eye. 

The  Capsule  of  Tenon 1086 

The  Tunics  of  the  Bye. 

The  Solera  and  Cornea 1089 

The  Sclera 1090 

The  Cornea 1090 

The  Choroid,  Ciliary  Body,  and  Iris 1092 

The  Choroid 109.3 

The  Ciliary  Body 1094 

The  Iris 1096 

Membrana  Pupillaris 1100 

The  Retina  or  Tunica  Interna 1 100 

The  Refracting  Media. 

The  Aqueous  Humor 1105 

The  Vitreous  Body 1105 

The  Crystalline  Lens 1106 

Applied  Anatomy  of  the  Eye 1109 

The  Appendages  of  the  Eye. 

The  Eyebrows 1112 

The  EveHds 1112 

The  Eyelashes 1113 

The  Meibomian  or  Tarsal  Glands 1114 

The  Conjunctiva 1114 

The  Lacrimal  Apparatus 1115 

The  Lacrimal  Gland 1115 

The  Lacrimal  Canals 1116 

The  Lacrimal  Sac 1116 


The  Lacrimal  Apparatus — 

The  Nasal  Duct 1117' 

Surface  Form HIT" 

Applied  Anatomy 1118 

The  Ear. 

The  External  Ear. 

The  Pinna  or  Auricula 1119 

The  Auditory  Canal  or  Meatus 1122 

Applied  Anatomy 1124 

The  Middle  Ear,  Drum  or  Tympanum. 

The  Tympanic  Cavity 1125' 

The  Membrana  Tympani 1128 

The  Ossicles  of  the  Tympanum 1131 

The  Malleus 1131 

The  Incus 1132 

The  Stapes 1133 

Applied  Anatomy •■ 1135 

The  Internal  Ear  or  Labyrinth. 

The  Osseous  Labsointh 1136 

The  Vestibule 1136 

The  Bony  Semicircular  Canals 1137 

The  Modiolus 1138 

The  Membranous  LabjTinth 1140 

The  Utricle 1140 

The  Saccule 1141 

The  Membranous  Semicircular  Canals.  1142 

Structure 1142 

The  OHGAN.S  of  T.aste 1148 

The  Skin. 

The  Cuticle,  Scarf  Skin,  or  Epidermis 1151 

I  The  Corium,   Cutis  Vera,   Derma,   or  True 

Skin llo3 

I  The  Appendages  of  the  Skin. 

The  Nails.. 1156 

The  Hairs llg?- 

I  The  Sebaceous  Glands 1161 

The  Sudoriferous  or  Sweat  Glands 1161 


THE  OEGANS  OF  VOICE  AND  EESPIRATION. 


The  Larynx. 

The  Cartilages  of  the  Larynx 1163 

The  Ligaments  of  the  Larynx 1167 

Interior  of  the  Larj'nx 1169 

Muscles  of  the  Larynx 1172 

The  Trachea  .and  Bronchi. 

The  Risht  Bronchus 1176 

The  Left  Bronchus 1177 

Surface  Form }}on 

Applied  Anatomy 1180 

The  PLETjHa:. 

The  Mediastinum  or  Interpleural  Space. 

The  Superior  Mediastinum 1186 


The  Anterior  Mediastinum 1186 

The  Middle  Mediastinum 1186 

The  Posterior  Mediastinum 1187 

Applied  Anatomy 1188 

The  Lungs. 

The  Apex  of  the  Lung 1188 

The  Base  of  the  Lung 11|8 

Surfaces  of  the  Lung 1189 

Borders  of  the  Lung 1190 

Fissures  and  Lobes  of  the  Lung 1190 

:  The  Root  of  the  Lung 1193 

Di«sions  of  the  Bronchi 1194 

Surface  Form ll™ 

Applied  Anatomy 1197 


THE  ORGANS  OF  DIGESTION. 

The  Mouth,  Oral  or  Buccal  Cavity.    '     I  The  CaHty  of  the  Mouth  Proper 

Floor  of  the  Mouth 

The  Lips  1200    The  Palate 

The  Vestibule  of  the  Mouth 1200    The  Teeth ^  •  ,-  ■  ,  ■  ,u  ■  ,,  • 

The  Mucous  Membrane 1200  Temporary.  Deciduous,  or  Milk  Teeth, 

The  rVippks  ; .  .    1200  Permanent  1  eeth .  .^.  .....  . 

The  Buccal  Glands'.  ■.■.■.■.;::: 1200  .  Chemical  Compo^tion  o    the  Teeth  .  . . 

The  Gums 1200  i  Development  of  the  Teeth 


1201 
1201 
1202 
1204 
1205 
1206 
1210 
1212 


CONTENTS 


XXI 


The  Tongue. 

The  Body  of  the  Tongue 1217 

The  Base  or  Root  of  the  Tongue 1217 

The  Apex  or  Tip  of  the  Tongue 1217 

The  Dorsum  of  the  Tongue 1217 

The  Margin  of  the  Tongue 1217 

The  Under  or  Inferior  Surface  of  the  Tongue  1217 

Development  of  the  Tongue 1221 

Applied  Anatomy 1222 

The  Salivary  Glands. 

The  Parotid  Gland 1223 

The  Submaxillary  Gland 1225 

The  Sublingual  Gland 1226 

Development  of  the  Salivary  Glands 1227 

Surface  Form 1227 

Applied  Anatomy 1229 

The  Pharynx. 

The  Nasal  Part  or  Nasopharynx 1229 

The  Oral  Part 1230 

The  Tonsils 1230 

Development 1232 

Applied  Anatomy 1233 

The  Laryngeal  Part 1233 

Development  of  the  Pharynx 1234 

Applied  Anatomy  of  the  Pharynx 1235 

The  (Esophagus. 

Applied  Anatomy 1239 

The  Abdomen. 

Boundaries  of  the  Abdomen 1241 

Regions  of  the  Abdomen 1242 

The  Peritoneum. 
Development      of     the     Peritoneum      and 

Alimentary  Tract 1245 

Retroperitoneal  Fossas 1265 

Applied  Anatomy 1268 

The  Stomach. 

Openings  of  the  Stomach 1271 

Curvatures  of  the  Stomach 1271 

Surfaces  of  the  Stomach 1271 

■Component  Parts  of  the  Stomach 1272 


Interior  of  the  Stomach 1273 

Movement  and  Innervation  of  the  Stomach .  127!) 

Surface  Form 1280 

Applied  Anatomy '  12)50 

The  Small  Intestine. 

The  Duodenum 1282 

Interior  of  the  Duodenum 1286 

Applied  Anatomy 1287 

The  Jejunum  and  Ileum 1287 

Meckel's  Diverticulum 1288 

Structure  of  the  Villi 1291 

Applied  Anatomy  of  the  Small  Intestine.  .  .  1295 

The  Large  Intestine. 

The  Cecum 1296 

The  Vermiform  Appendix 1298 

The  Ileocecal  Valve 1301 

Applied  Anatomy 1,302 

The  Colon 1,303 

Apphed  Anatomy 1.306 

The  Rectum 1306 

The  Anal  Canal 1.309 

The  Anal  Orifice  or  Anus 1309 

Movements  and  Innervations  of  the  Intes- 
tines   1312 

Surface  Form  of  the  Intestines 1313 

Applied  Anatomy  of  the  Intestines 1314 

The  Liver. 

Surfaces  of  the  Liver 1320 

Fissures  of  the  Liver 1322 

Lobes  of  the  Liver 1323 

Ligaments  of  the  Liver 1324 

Support  and  Movability  of  the  Liver 1325 

Abnormalities  of  the  Liver 1326 

The  Excretory  Apparatus  of  the  Liver 1331 

The  Hepatic  Duct 1332 

The  Gall-bladder 1332 

The  Cystic  Duct 1333 

The  Common  Bile  Duct 1333 

Surface  Relations  of  the  Liver 1334 

Applied  Anatomy  of  the  Liver 1335 

The  Pancreas. 

Pancreatic  Juice 1341 

Surface  Form  of  the  Pancreas 1341 

Applied  Anatomy  of  the  Pancreas 1341 


THE  UEINOGENITAL  ORGANS. 


The  Urinary  Organs. 
The  Kidneys. 

Relations  of  the  Kidneys 1343 

Anterior  Surface  of  Right  Kidney 1343 

Anterior  Surface  of  Left  Kidney 1343 

Posterior  Surface  of  the  Kidney 1345 

Borders  of  the  Kidney 1347 

Extremities  of  the  Kidney 1348 

Fixation  of  the  Kidney 1348 

Minute  Anatomy  of  the  Kidney 1350 

Variations  and  Abnormalities  of  the  Kidney  1354 

Surface  Form  of  the  Kidney ".  1354 

Applied  Anatomy  of  the  Kidney 1355 

The   Ureters. 

Applied  Anatomy  of  the  Ureters 1358 

The  Urinary  Bladder. 

Surfaces  of  the  Bladder 1359 

The  Fundus  or  Base 1361 

The  Summit  or  Apex 1361 

The  Urachus  or  Middle  Umbilical  Ligament  1361 

The  Ligaments  of  the  Bladder 1361 

The  Interior  of  the  Bladder 1364 

Surface  Form  of  the  Bladder 1365 

Applied  Anatomy  of  the  Bladder 1366 

The  Male   Urethra. 

The  Prostatic  Portion 1366 

The  Membranous  Portion 1367 


The  Penile  or  Spongy  Portion 1368 

Apphed  Anatomy 1369 

The  Female  Urethra 1370 

The  Male  Reproductive  Organs. 

The  Testicles. 

The  Scrotum 1372 

The  Intercolumnar  or  External  Spermatic 

Fascia _ 1374 

The  Cremasteric  Fascia 1374 

The  Infundibuliform  Fascia 1374 

The  Tunica  Vaginalis 1374 

The  Inguinal  or  Spermatic  Canal 1375 

The  Spermatic  Cord 1375 

The  Testes 1377 

The  Epididymis 1378 

The  Tunics  of  the  Testicle 1379 

The  Semen 1381 

Applied  Anatomy  of  the  Testicle 1382 

The  Vas  Deferens. 

Organ  of  Giraldfe 1384 

The  Seminal  Vesicles. 

Applied  Anatomy  of  the  Seminal  Vesicles. .  1385 

The  Ejttculatory  Duels 13S6 


xxu 


CONTENTS 


The  Penis. 

The  Root  of  the  Penis 1388 

The  Body  of  the  Penis 1388 

AppUed  Anatomy  of  the  Penis 1390 

The  Prostate  Gland. 

Applied  Anatomy  of  the  Prostate  Gland  .  . .  1395 

Cowper's  Glands 1397 

The  Female  Repboductive  Organs. 

The  Ovaries. 

The  Ovary  at  Different  Ages 1399 

Applied  Anatomy  of  the  Ovaries 1401 

The  Fallopian  Tube  or  Oviduct. 

Applied  Anatomy  of  the  Fallopian  Tube  . .  .  1402 

The  Uterus  or  Womb.  q'he  Mammary  Gland. 

The  Fundus  of  the  Uterus 1404    The  Nipple 1428 

The  Body  of  the  Uterus 1404    Variations  in  Mammte 1429 

The  Neck  or  Cervix  Uteri 1405    Applied  Anatomy 1432 

Folds  and  Ligaments  of  the  Uterus 1406    The  Male  Breast 1433 

The  Uterus  at  Different  Ages 1408  Applied  Anatomy 1433 


Abnormalities  of  the  Uterus 1408- 

Changes  at  a  Menstrual  Period 1408 

Changes  Induced  by  Pregnancy 1409 

AppUed  Anatomy  of  the  Uterus 1411 

The  Vagina. 

Relations  of  the  Vagina 1414 

The  External  Organs. 

The  Mods  Veneris 1415 

The  Labia  Majora 1415 

The  Labia  Minora  or  Nymphse 1416 

The  Vestibule  of  the  Vagina 1416 

The  Clitoris 1418 

The  Vaginal  Bulb 1420 

The  Glands  of  Bartholin 1420 

Development  of  the  Urinary  and  Generative 

1420 


THE  DUCTLESS  GLANDS. 


The  Thyhoid  Gland  oh  Body. 

Accessory  Thyroids 1436 

Apphed  Anatomy 1438 

The  Parathyroid  Gland. 

Embryology. . .  .  r?T"^-r.._^.^j^^ 1440 

Applied  Anatomy ^TT^  :  rr^-r^^ 1440 

The  Thymus  Gland. 

Applied  Anatomy 1442 

The  Spleen. 
Relations  of  the  Spleen 1444 


Surface  Form  of  the  Spleen 1446 

Applied  Anatomy 1447 

The  Suprabenal  Gland  ob  Adbenal  Capsule. 

Accessory  Suprarenal  Glands 1448 

The  Carotid  Glands  or  Carotid  Bodies. 

Applied  Anatomy 1450 

The  Coccygeal  Gland  ob  Body,  or  Luschka's 
Gland. 

Structure  of  the  Coccygeal  Gland 1450 

The  Parasympathetic  Bodies.  .  .    1450 


DESCRIPTIVE  AND  APPLIED  ANATOMY. 


INTRODUCTION. 


ANATOMY  (dva,  apart,  and  re/iwco,  I  cut)  is  the  name  given  to  that  division 
of  natural  science  which  deals  with  the  structure  or  organization  of  living 
things.  Human  anatomy  is  that  division  of  general  anatomy  which  applies  to  the 
structure  of  man,  bearing  in  mind  the  fact  that  man  is  distinguished  as  a  sepa- 
rate genus  among  primate  mammals,  an  order  of  vertebrates. 

Man,  as  a  vertebrate,  possesses  an  internal  skeleton  with  a  median  longitudinal 
axis,  which  is  divided  transversely  into  segments  called  vertebrse.  This  vertebral 
axis  (spinal  column)  in  the  habitually  erect  position  of  the  human  body  is  sup- 
ported by  the  pelvic  limbs,  and  is  surmounted  by  the  skull.  The  pelvic  limbs 
serve  the  purposes  of  progression,  while  the  pectoral  limbs  are  adapted  as  organs 
of  prehension;  a  distinction  common  to  nearly  all  primates  is  the  possession  of 
an  opposable  first  digit  or  thumb.  The  possession  of  milk  glands,  rudimentary 
in  the  male,  but  well  developed  and  important  in  the  female,  relegates  the  human 
species  to  the  class  of  mammals. 

The  present  work  is  an  account  of  the  various  parts  and  organs  of  the  human 
body,  being  descriptive  of  their  characteristics  as  revealed  by  dissection,  and, 
with  a  view  toward  practical  application,  certain  parts  or  regions  of  the  body 
are  examined  in  their  entirety.  These  two  methods  of  studying  anatomy  are 
conventionally  termed  descriptive  anatomy  and  applied  or  topographic  anatomy. 
Embryology  deals  with  the  origin  and  development  of  the  body  and  its  organs. 
Histology  deals  with  the  minute  structure  of  the  tissues  and  organs  as  revealed 
by  the  microscope.  In  the  present  work  only  brief  accounts  of  the  embryology 
and  histology  of  the  organs  are  interpolated  in  their  proper  places;  the  minute 
details  must  be  sought  for  in  special  works  upon  these  subjects. 

The  systematic  consideration  of  the  parts  of  the  human  body  requires  a  foreword 
as  to  the  descriptive  terms,  nomenclature,  and  classification  employed  in  anatomy. 

The  descriptive  terms  are  names  indicative  of  position  and  direction.  Despite 
the  structural  homologies  discernible  among  vertebrates  in  general,  there  are 
wide  differences  regarding  the  natural  attitude  or  position  habitually  assumed,  so 
that  whatever  is  situated  "  in  front"  in  the  erect  man  is  "  below"  in  the  quadrupedal 
animal.  The  use  of  terms  like  anterior,  posterior,  superior,  inferior,  in  front  of, 
beneath,  has  given  rise  to  great  ambiguity  and  confusion  whenever  applied  at  one 
and  the  same  time  to  homologous  parts  in  man  and  other  vertebrates. 

It  is  essential  that  the  names  used  in  designating  structural  parts  shall  be  so 
definite  that  each  of  the  terms  shall  have  but  one  signification.  The  study  of 
anatomy  has  been  made  unnecessarily  difficult  by  a  multiplicity  of  synonyms  and 
compound  names,  when  single  words  would  answer  all  requirements.  Further- 
more, many  of  the  terms  even  now  in  general  use  are  not  equally  applicable  to 
lower  animals  and  man,  a  condition  which  constitutes  a  great  hindrance  to  ana- 
tomic progress.  Various  reforms  have  been  proposed,  chief  of  which  has  been 
that  of  a  commission  of  the  German  Anatomic  Society,  which,  in  1895,  formulated 
a  list  of  terms,  the  Basle  Nomina  Anatomica  (BNA),  which  is  unfortunately 

3  (33) 


34  DESCRIPTIVE  AND  APPLIED  ANATOMY 

replete  with  serious  imperfections  and  inconsistencies.  Thus  while  one  of  the 
branches  of  the  radial  nerve  is  called  the  N.  cutaneus  brachii  posterior,  the  nominal 
suffix  of  two  other  branches  of  the  same  nerve  is  dorsalis.  It  cannot  be  said 
that  the  BNA  has  as  yet  completely  displaced  some  of  the  designations  in 
common  use  to  that  degree  which  its  enthusiastic  advocates  would  wish.  The 
ambiguous,  confusing,  and  vague  terms  will  gradually  fall  into  disuse  as  time 
shows  their  inutility  and  better  expressions  achieve  universal  adoption. 

For  descriptive  purposes  the  liuman  body  is  supposed  to  be  in  the  erect  position, 
the  arms  hanging  by  the  sides  and  the  palms  of  the  hands  directed  forward. 
The  body,  as  a  whole,  as  with  most  vertebrates,  consists  of  two  general  divisions, 
axial  and  appendicular;  the  former  is  the  body  proper  (soma),  the  latter  comprises 
the  limbs  (membra).  The  middle  plane  of  the  body  is  called  the  meson,  from  the 
Greek  to  ftiffou,  the  middle;  while  mesal  and  mesad  (ad  being  the  Latin  ecjuiva- 
lent  of  the  English  -ward)  are  adjectival  and  adverbial  inflections.  The  mesal 
plane  is  also  the  dorsoventral  plane  which  passes  approximately  through  the 
sagittal  suture  of  the  skull,  and  hence  any  plane  parallel  to  it  is  termed  a  sagittal 
plane.  A  vertical  plane  at  right  angles  to  the  mesal  plane  passes,  roughly  speaking, 
through  the  central  part  of  the  coronal  suture  or  through  a  line  parallel  to  it; 
such  a  plane  is  therefore  called  a  coronal  plane  or  frontal  plane.  A  plane  at  right 
angles  to  both  the  mesal  and  coronal  planes  is  termed  a  transverse  plane.  The 
terms  anterior  and  posterior  have  been  employed  to  indicate  the  relation  of  parts 
to  the  front  or  back  of  the  body,  and  the  terms  superior  and  inferior  to  signify  the 
relative  levels  of  different  structures;  but  the  growing  use  of  data  derived  from  com- 
parative anatomy  and  embryology  in  the  elucidation  of  the  human  structure  makes 
it  desirable  that  terms  should  be  employed  which  may  without  ambiguity  indicate 
relative  position  in  both  man  and  animals.  Thus,  ventral  and  dorsal,  cephalic  and 
caudal  (together  with  their  adverbial  derivatives  ending  in  -ad),  are  preferable  and 
are  thus  sometimes  used  in  this  edition.  Lateral  and  laterad  are  general  terms  per- 
taining to  the  sides  of  the  body,  while  dextral  and  sinistral  are  specific  terms  for 
right  and  left  respectively.  The  terms  central  (centrad)  and  peripheral  (periph- 
erad)  are  in  general  use,  though  specially  applicable  to  the  bloodvessels  and  the 
nerve  system.  The  common  terms  "inner"  and  "outer,"  "deep"  and  "superfi- 
cial," "beneath,"  "under,"  and  so  on,  are  too  frequently  ambiguous.  The  use  of 
the  words  ental  and  ectal,  derived  respectively  from  ivzo:;  (inward)  and  iy.ro; 
(outward),  and  their  inflections  entad  and  ectad  often  serve  to  avoid  such  ambi- 
guity. Wherever  a  series  of  organs  embraces  several  similar  parts,  bearing  like 
names,  the  general  terms  are  combined  with  distinctive  prefixes,  as,  for  instance, 
sitpraspinatus  and  m/raspinatus.  The  terms  proximal  and  distal  refer  to  the 
attached  and  free  ends  of  the  limbs  and  their  parts,  being  preferable  to  the  less 
precise  and  sometimes  confusing  designations  of  upper  and  lower.  The  other 
aspects  (borders  or  sides)  of  each  limb  are  variously  designated  by  the  terms 
ulnar,  radial,  anconal,  and  thenar;  tibial,  fibidar,  patellar,  and  popliteal.  It  is 
often  convenient  to  speak  of  the  flexor  and  extensor  aspects  of  the  limb  divisions 
and  their  bones.  The  designation  of  parts  in  the  limbs  by  anterior  and  posterior  is 
still  largely  employed,  though  the  demands  of  consistency  and  logic  will  probably 
compel  the  adoption  of  substitutes  more  in  accord  with  the  nomenclature  of  com- 
parative anatomy.    The  classification  which  is  used  in  the  present  work  is  as  follows  : 

Osteology,  or  description  of  the  bones. 

Syndesmology,  or  description  of  the  joints  and  ligaments. 

Myology,  or  description  of  the  muscles  and  fasciae. 

Angiology,  or  description  of  the  heart  and  the  bloodvessels  and  lymph  vessels. 

Neiirology,  or  description  of  the  nerve  system  and  organs  of  special  sense. 

Splanchnology,  or  description  of  the  viscera,  comprising  the  organs  of  respira- 
tion and  phonation,  digestion,  reproduction,  excretion,  and  internal  secretion. 


OSTEOLOGY. 


GENEEAL  ANATOMY  OF  THE  SKELETON. 

THE  general  framework  of  the  body  is  built  up  mainly  of  a  series  of  bones, 
supplemented,  however,  in  certain  regions  by  pieces  of  cartilage;  the  bony 
part  of  the  framework  constitutes  the  skeleton. 

In  comparative  anatomy  the  term  skeleton  has  a  wider  application,  as  in  some 
of  the  lower  animals  hard,  protective,  and  supporting  structures  are  more  exten- 
sively distributed,  being  developed  in  association  with  the  integumentary  system. 
In  such  animals  the  skeleton  may  be  described  as  consisting  of  an  internal  or 
deep  skeleton,  the  endoskeleton,  and  an  external  or  superficial,  the  exoskeleton. 
In  the  human  subject  the  exoskeleton  is  extremely  rudimentary,  its  only  important 
representatives  being  the  teeth  and  nails.  The  term  skeleton  is,  therefore, 
confined  to  the  endoskeleton,  and  this  is  divisible  into  an  axial  part,  which  includes 
that  of  the  head  and  trunk,  and  an  appendicular  part,  which  comprises  that  of 
the  limbs. 

In  the  skeleton  of  the  adult  there  are  206  distinct  bones,  as  follows: 

f  Vertebral  column 26 

Axial      J  Skull 22 

Skeleton    j  Hyoid  bone 1 


iRil; 


libs  and  sternum 25 

—  74 
Appendicular  f  Upper  limbs 64 

Skeleton       \  Lower  limbs 62 

—  126 
Auditory  ossicles 6 

Total 206 

The  patellae  are  included  in  this  enumeration,  but  the  smaller  sesamoid  bones 
are  not  reckoned. 

Bones  are  divisible,  according  to  their  shape,  into  four  classes — long,  short, 
flat,  and  irrecjular. 

Long  Bones. — The  long  bones  are  found  in  the  limbs,  where  they  form  a 
system  of  levers,  which  sustain  the  weight  of  the  trunk  and  confer  the  power  of 
locomotion  and  prehension.  A  long  bone  consists  of  a  shaft  and  two  extremities. 
The  shaft,  or  diaphysis,  is  a  hollow  cylinder,  the  central  cavity  being  termed  the 
medullary  canal;  the  wall  consists  of  dense,  compact  tissue  of  considerable  thickness 
in  the  middle  part  of  the  shaft,  but  becoming  thinner  toward  the  extremities; 
the  cancellous  tissue  is  scanty.  The  extremities,  or  epiphyses,  are  generally  ex- 
panded, for  the  purposes  of  articulation  and  to  aiTord  broad  surfaces  for  muscle 
attachment.  They  are  usually  developed  from  separate  centres  of  ossification 
termed  epiphyses,  and  consist  of  cancellous  tissue  surrounded  by  a  thin  layer  of 
compact  bone.  The  long  bones  are  not  straight,  but  curved,  the  curve  generally 
taking  place  in  two  planes,  thus  affording  greater  strength  to  the  bone.     The 

(35) 


36 


GENERAL  ANATOMY  OF  THE  SKELETON 


bones  belonging  to  this  class  are  the  clavicle,  humerus,  radius,  uhia,  femur,  tibia, 
fibula,  metacarpal  and  metatarsal  bones,  and  the  phalanges. 

Short  Bones. — Where  a  part  of  the  skeleton  is  intended  for  strength  and 
compactness,  and  its  motion  is  at  the  same  time  slight  and  limited,  it  is  divided 
into  a  number  of  small  bones  united  by  ligaments,  and  the  separate  bones  are 

short  and  compressed,  such  as  the  bones  of 
the  carpus  and  tarsus.  These  consist  of  can- 
cellous tissue  covered  by  a  thin  crust  of  com- 
pact substance.  The  patellae  also,  together 
with  the  other  sesamoid  bones,  are  by  some 
regarded  as  short  bones. 

Flat  Bones. — Where  the  principal  re- 
Cjuirement  is  either  extensive  protection  or 
the  provision  of  broad  surfaces  for  the  at- 
tachment of  muscles,  we  find  the  osseous 
structure  expanded  into  broad,  flat  plates, 
as  is  seen  in  the  bones  of  the  skull  and  the 
scapulae.  Flat  bones  are  composed  of  two 
thin  layers  of  compact  tissue  enclosing  be- 
tween them  a  variable  quantity  of  cancellous 
tissue.  In  the  cranial  bones  these  layers  of 
compact  tissue  are  familiarly  known  as  the 
tables  of  the  skull;  the  outer  table  is  thick 
and  tough;  the  inner  table  is  thinner,  denser, 
and  more  brittle,  and  hence  is  termed  the 
vitreous  table.  The  intervening  cancellous 
tissue  is  called  the  diploe.  The  flat  bones 
are:  the  occipital,  parietal,  frontal,  nasal,  lacri- 
mal, vomer,  scapula,  os  innominatum,  sternum, 
ribs,  and,  according  to  some,  the  patella. 

Irregular  Bones. — The  irregular  or  mixed 
liones  are  such  as,  from  their  peculiar  form, 
cannot  be  grouped  under  either  of  the  pre- 
ceding heads.  Their  structure  is  similar  to 
that  of  other  bones,  consisting  of  a  layer  of 
compact  tissue  externally  and  of  spongy, 
cancellous  tissue  within.  The  irregular 
bones  are:  the  vertebrae,  sacrum,  coccyx, 
temporal,  sphenoid,  ethmoid,  malar,  maxilla, 
mandible,  palate,  turbinated,  and  hyoid. 

Surfaces  of  Bones. — If  the  surface  of 
any  bone  is  examined,  certain  eminences 
and  depressions  are  seen,  to  which  descrip- 
tive anatomists  have  given  the  following 
names. 

These  eminences  and  depressions  are  of 
two  kinds:  articular  and  nonarticular.  Well- 
marked  examples  of  articular  eminences  are 
found  in  the  heads  of  the  humerus  and  femur,  and  of  articular  depressions  in  the 
glenoid  cavity  of  the  scapula  and  the  acetabulum.  Nonarticular  eminences  are 
designated  according  to  their  form.  Thus  a  broad,  rough,  uneven  elevation  is 
called  a  tuberosity;  a  small,  rough  prominence,  a  tubercle;  a  sharp,  slender,  pointed 
eminence,  a  spine;  a  narrow,  rough  elevation,  running  some  way  along  the  surface, 
a  ridge,  line,  or  crest. 


Fig.  1, — General 


of  the  human  skeleton. 


SURFACES  OF  BONES 


37 


The  nonarticular  depressions  are  also  of  very  variable  form,  and  are  descril)eil 
as  fossae,  grooves,  furrows,  fissures,  notches,  sulci,  etc.  These  nonarticular  emi- 
nences and  depressions  serve  to  increase  the  extent  of  surface  for  the  attachment 
of  ligaments  and  muscles,  and  are  usually  well  marked  in  proportion  to  the 
muscularity  of  the  subject;  the  grooves,  fissures,  and  notches  often  transmit 
vessels  and  nerves. 


FtG.  2. — Diagram  of  the  structure  of  compact  bone.  A  small  part  of  a  transverse  section  of  the  shaft  of  a  long 
bone  is  shown.  At  the  uppermost  part  is  the  periosteum  covering  the  outside  of  the  bone;  at  the  lowermost 
part  is  the  endosteum  lining  the  marrow  cavity.  Between  these  is  the  compact  tissue,  consisting  largely  of  a 
series  of  Haversian  systems,  each  being  circular  in  outline  and  perforated  by  a  central  canal.  In  the  first  one 
is  shown  only  the  area  occupied  by  a  system;  in  the  second  is  seen  the  concentric  arrangement  of  the  lamellae; 
and  in  the  others,  respectively,  canaliculi;  lacuna?;  lacunee  and  canaliculi;  the  contents  of  the  canal,  artery, 
vein,  lymphatic  and  areolar  tissue;  lamellae,  lacunse,  and  canaliculi;  and,  finally,  all  of  the  structures  composing 
a  complete  system.  Between  the  systems  are  circumferential  and  intermediate  lamellfe,  only  a  few  of  which  are 
represented  as  lodging  lacunse,  though  it  is  to  be  understood  that  the  lacunie  are  in  all  parts.  The  periosteum 
is  seen  to  be  made  up  of  a  fibrous  layer  and  a  vascular  layer,  and  to  have  upon  its  attached  surface  a  stratum  of 
cells.     From  the  fibrous  layer  project  inward  the  rivet-like  fibres  of  Sharpey.     (F.  H.  Gerrish.) 

A  prominent  process  projecting  from  the  surface  of  a  bone  which  it  has  never 
been  separate  from  or  movable  upon  is  termed  an  apophysis  (from  anotlnjae:;, 
an  excrescence);  but  if  such  process  is  developed  as  a  separate  piece  from  the 
rest  of  the  bone,  to  which  it  is  afterward  joined,  it  is  termed  an  epiphysis  (from 
i7Tl(}n)acz,  an  accretion).  The  main  part  of  the  bone,  or  sliaft,  which  is  formed 
from  the  primary  centre  of  ossification,  is  termed  the  diaphysis,  and  is  separated, 
during  growth,  from  the  epiphysis  by  a  layer  of  cartilage,  at  which  growth  in 
length  of  the  bone  takes  place.     Some  bones  are  hollow  and  contain  sinuses, 


38 


GENERAL  ANATOMY  OF  THE  SKELETON 


which  are  spaces  for  air.     Canals,  or  foramina,  are  channels  or  openings  in  bone 
through  which  nerves  or  vessels  pass. 

Structure  of  Bone. — Bone  is  a  highly  speciaHzed  form  cf  connective  tissue.  In  reality,  it  is 
white  filjrous  tissue,  calcified  and  structurally  modified  until  it  becomes  osseous  tissue.  Bone 
is  not  simply  a  crude  mass  resulting  from  the  calcification  of  cartilage  or  fibrous  tissue;  it  is  a 
distinct  tissue,  of  a  definite  structure,  the  constituent  parts  of  which  are  arranged  symmetrically. 
There  are  two  varieties  of  bone:  dense  or  compact  bone  {substantia  compacta),  and  can- 
cellous, loose,  or  spongy  bone  (substantia  spongiosa). 

Compact  bone  is  dense,  and  is  always  found  upon  the  exterior  of  the  bony  tissue.  Even  this 
apparently  compact  tissue  is  porous;  it  differs  from  cancellous  bone  in  its  greater  densitv  and  in 
the  arrangement  of  its  osseous  substance  into  lamellae.  It 
forms  practically  the  entire  shafts  of  the  long  bones  and 
constitutes  the  outer  portion  of  their  extremities  and  of  the 
short,  flat,  and  irregular  bones.  With  the  exception  of 
enamel  and  dentin  it  represents  the  hardest  substance  of  the 
body,  is  tough  and  elastic,  and  much  force  is  required  to 
break  it.  Compact  bone  consists  of  an  outer  membrane, 
the  periosteum,  internal  to  which  is  seen  the  osseous 
tissue. 

The  periosteum  (Fig.  2)  is  a  fibrous  membrane  adhering 
to  the  surface  of  the  bone  in  nearly  every  part  except  at  the 
cartilage-covered  extremities.  When  strong  tendons  or 
ligaments  are  attached  to  the  bone,  the  periosteum  is  incor- 
porated with  them.  By  means  of  the  periosteum  many 
vessels  reach  and  enter  the  hard  bone  through  Volkmann's 
canals.  This  is  shown  by  stripping  the  periosteum  from 
the  surface  of  living  bone,  when  small  bleeding  points  are 
seen,  each  of  which  marks  the  entrance  of  a  vessel  from 

Yia.  3. Fibres  of  Sharpey  from  the     the  periosteum.     It  thus  becomes  obvious  that  the  loosen- 

p.irietal  bone  (adult  man)  isolated  by     Jng  of  the  periosteum,  bv  depriving  a  portion  of  the  bone 
dissociation.     (After  KoUiker.)  r. -.  ■  ,  ^   _.       '       j         „  ■         t^i,     ._   ._u 

01  Its  nourishment,  may  produce  necrosis,     ine  membrane 

is  firmly  attached  to  the  bone  by  trabeculfe  of  fibrous  tissue, 
Sharpey's  fibres  (Fig.  3),  which  penetrate  the  bone  at  right  angles  to  its  surface,  and  carry 
bloodvessels.  They  do  not  directly  enter  the  Haversian  systems,  but  only  the  circumferential 
and  intermediate  lamellje — parts  that  are  formed  by  periosteal  action.  Prolongations  from  some 
of  these  vessels  reach  the  Haversian  canals,  and  even  the  bone  marrow.     In  the  extremities  of 


Fig.  4. — Transverse  section  of  compact  tissue  of  bone.     Magnified  about  150  diameters.      (Sharpey.) 


a  long  bone,  vessels  from  the  periosteum  penetrate  the  layer  of  compact  bone  and  reach  the 
cancellous  tissue.  In  the  newborn  and  in  the  young  the  periosteum  is  composed  of  three 
layers:  an  outer  or  fibrous  layer,  containing  some  bloodvessels,  and  composed  of  bundles  of 
white  fibrous  tissue;  a  middle  or  flbroelastic  layer,  containing  some  bloodvessels,  fibrous 
tissue,  and  much  elastic  tissue;  and  an  inner  or  osteogenetic  layer,  which  is  very  vascular  and 
contains  numerous  cells,  which  are  converted  into  osteoblasts  or  bone-forming  cells. 


TRANSVERSE  SECTION  OF  COMPACT  BONE  39 

Transverse  Section  of  Compact  Bone  (Fio;.  4). — The  osseous  tissue  consists  of  cells, 
osteoblasts,  and  intercellular  substance  anun^iod  in  lamellae.  In  the  osseous  tissue  are 
found  Haversian  systems,  lacunae,  canaliculi,  and  osteoblasts.  In  the  middle  of  long  bones 
is  a  space,  the  medullary  or  marrow  cavity,  containing  the  marrow. 

There  are  four  varieties  of  lamella?:  (1)  The  periosteal,  peripheral,  circumferential,  or 
external;  (2)  the  Haversian,  or  concentric;  (3)  the  interstitial,  ground,  or  intermediate; 
and  (4)  the  perimeduUary,  or  internal.  The  ]5eriosteal  lamellfe  are  sometimes  called  primary, 
as  they  are  the  first  to  appear,  and  are  formed  by  the  direct  transformation  of  the  inner  layer 
of  the  periosteum  into  bone.  In  the  shaft  of  a  long  bone  there  are  several  layers  of  periosteal 
lamellfe,  but  no  one  layer  is  extensive  enough  to  surround  the  bone  completely.  Lacunje  and 
canaliculi  are  present.  _  _ 

In  the  outer  surface  of  the  layer  of  periosteal  lamellaj  depressions  exist  that  are  known  as 
Howship's  foveolae,  or  lacunae.  These  depressions  a,re  made  by  large  cells,  called  osteoclasts, 
which  destroy  bone.  There  are  no  Haversian  canals  in  this  outer  layer,  but  there  are  some 
larce  channels,  Volkmann's  canals,  that  convey  bloodvessels  into  the  bone  and  run  at  right 
angles  to  the  periosteal  surface.  Many  small  arteries  from  the  periosteum  enter  the  periphery 
bodi  of  the  shaft  and  of  the  epiphyses. 

The  Haversian  or  concentric  lamellae 
are  circular  layers  arranged  around  a 
central  space,  or  canal,  known  as  the 
Haversian  canal.  There  is  no  fixed 
number  of  these  layers,  there  being 
usually  from  five  to  ten.  The  layers  of 
each  system  are  parallel  to  one  another. 


Fig.  5. — Nucleated  bone  cells  (osteoblasts)  and 
their  processes,  contained  in  the  bone  lacuna  and 
their  canaliculi  respectively.  From  a  section 
through  the  vertebra  of  an  adult  mouse.  (Klein 
and  Noble  Smith.) 


Fig.  6. — Combined  transverse  and  longitudinal  section  of 
compact  bone.  CH.  Longitudinal  Haversian  canal  and 
anastomosing  canals,  o.  Communicating  with  medullary 
cavity.  Si.  Intermediate  systems.  Spe.  Circumferential 
lamella?.  Spi.  PerimeduUary  lamelte.  os.  Osteoblasts. 
(Poirier  and  Charpy.) 


but  the  layers  of  different  systems  cross  at  va  rious  angles.  Between  these  layers  are  small,  irreg- 
ular spaces  called  lacunae;  and  extending  radially  nut  from  the  lacunte  and  piercing  the  various 
lamellas  are  delicate  canals  known  as  canaliculi,  which  connect  the  lacuna?.  The  lacuna  nearest 
to  the  Haversian  canal  communicates  with  it  by  means  of  canaliculi;  and  canaliculi  also  com- 
municate with  other  Haversian  systems.  The  Haversian  canal  contains  bloodvessels— an  artery 
or  a  vein,  or  both — and  a  nerve.  The  vessel  in  the  canal  is  covered  with  endothelial  cells,  and  the 
canal  itself  is  lined  with  them.  The  space  thus  formed  is  a  lymph  channel,  and  into  these  chan- 
nels the  canahculi  empty.  Beneath  the  periosteum  and  at  the  periphery  of  the  medullary  cavity 
there  are  lymph  spaces  that  are  in  direct  communication  with  the  canaliculi  of  the  Haversian 
systems.  In  each  lacuna  is  a  bone  cell — a  corpuscle  that  almost  fills  the  space,  and  sends  arms, 
or  processes,  out  into  the  canaliculi  (Fig.  .5).     This  bone  cell  is  an  osteoblast. 

The  interstitial  or  intermediate  lamellae  occupy  the  spaces  between  the  Haversian  systems. 
They  represent  the  remains  cf  p.  riiihcral  lamell*. '  They  are  usually  short  and  very  irregular, 
but  possess  lacunae  and  canaliculi,  which  are  arranged  as  in  the  Haversian  systems. 

The  perimeduUary  lamellae  are  irregular  and  few  in  number.  They  surround  the  marrow 
cavity,  and  in  areas  mav  be  interrupted.     Lacunse,  canaliculi,  and  osteoblasts  are  present. 

Lining  the  marrow  cavity  surface  of  the  bone  is  a  membrane,  the  endosteum,  that  resembles 
the  periosteum  in  structure,  but  is  not  cjuite  so  prominent. 

The  osteoblasts  are  irregular,  flattened,  stellate  masses  of  protoplasm,  possessing  a  number 
of  processes.     The  protoplasm  is  granular,  and  each  cell  contains  a  large  and  distinct  nucleus. 


40 


GENERAL  ANATOMY  OF  THE  SKELETON 


Osteoblasts  are  met  with  in  the  deeper  layer  of  the  periosteum,  in  the  endosteum,  and  in  the 
lacunae. 

Longitudinal  Section  of  Compact  Bone  (Figs.  6  and  8). — We  do  not  see  concentric  rings, 
as  in  a  transverse  section,  but  rows  of  lacuna;  parallel  to  the  course  of  the  Haversian  canals — and 
these  canals  appear  like  half  tubes  instead  of  circular  spaces.  The  tubes  are  seen  to  branch 
and  communicate,  so  that  each  separate  Haversian  canal  runs  only  a  short  distance.  In  other 
respects  the  structure  closely  resembles  that  of  a  transverse  section. 

Cancellous  bone  is  found  in  the  interior  of  flat  and  irregular  bones  and  forming  the  bulk 
of  the  extremities  of  the  long  bones.  It  consists  of  anastomosing  spicules  of  bone  forming  a 
meshwork  for  the  red  marrow.  The  spicules  have  a  fibrillar  structure,  and  contain  lacunae  and 
canaliculi,  but  no  Haversian  systems. 

In  the  epiphyses  the  spicules  are  placed,  as  a  rule,  at  right  angles  to  the  planes  of  the  articular 
surface  (the  lines  of  greatest  pressure) ;  these  are  bound  together  by  other  spicules  that  correspond 
in  direction  to  the  planes  of  the  articulation  (the  lines  of  greatest  tension).  Those  spicules 
nearer  the  marrow  cavity  are  usually  heavier  and  stronger  (Fig.  181). 


-Cells  of  red  marrow  of  the  gu 
i-t.  Erythroblasts 


Marrow. — There  are  three  varieties:  red,  yellow,  and  mucoid. 

Red  marrow  {medulla  ossium  rubra)  is  found  in  the  diploe  of  the  cranial  bones,  in  the  cancellous 
tissue  of  the  vertebrse,  ribs,  and  sternum,  and  in  the  extremities  of  the  long  bones.  Red  marrow 
contains  much  less  fat  and  is  less  solid  than  yellow  marrow.  It  consists  of  a  delicate  net- 
work of  retiform  connective  tissue,  supporting  a  dense  capillary  plexus;  some  fat;  and  numer- 
ous cellular  elements.  Surrounding  the  marrow  is  the  endosteum.  The  cellular  elements 
of  red  marrow  (Figs.  7  and  12)  comprise  four  main  groups:  (1)  Marrow  cells,  or  myelocytes, 
which  are  granular  protoplasmic  masses,  capable  of  ameboid  movements,  and  containing  large 
nuclei.  They  are  not  found  in  normal  blood,  but  are  abundant  in  leukemia.  (2)  Small 
nucleated,  reddish  cells  called  erythroblasts  are  found;  they  resemble  the  nucleated  red  cells 
of  the  blood  of  the  embryo;  eventually  by  the  loss  of  their  nuclei  they  become  normal  red 
blood  corpuscles.  (3)  Nonnucleated  red  blood  corpuscles;  and  (4)  giant  cells,  containing  one 
or  more  nuclei — the  osteoclasts — complete  the  cellular  elements.  In  addition  there  are  a  large 
number  of  leukocytes,  or  white  blood  cells,  i.  e.,  polynuclear  cells,  eosinophiles,  and  basophiles. 

Yellow  marrow  is  found  in  the  shafts  of  long  bones  of  adults,  and  differs  from  the  preceding 
in  the  presence  of  a  great  quantity  of  fat  and  a  corresponding  decrease  in  the  number  of  cellular 
elements. 

Gelatinous  or  mucoid  marrow  is  formed  by  the  absorption  of  the  fat  and  the  cellular 
elements  of  yellow  marrow,  and  by  the  serous  infiltration  of  the  intercellular  substance.  It  is 
produced  by  starvation,  old  age,  and  certain  pathological  conditions.  Neither  yellow  nor 
mucciid  marrow  are  blood-cell  forming  in  function. 

Bloodvessels  of  Bone. — Small  arteries  derived  from  the  periosteum  enter  Volkmann's  canals 
and  pass  to  the  Haversian  canals  and  ultimately  to  the  marrow.  The  cancellous  tissue  is  sup- 
plied by  fewer  but  larger  vessels,  which  are  derived  from  the  periosteum,  and  which  often  pene- 
trate the  covering  of  the  compact  bone  and  ramify  in  the  cavities  of  the  spongy  tissue. 

The  marrow  is  supplied  by  a  large  artery  (sometimes  more  than  one)  called  the  nutrient 
artery.  It  enters  the  bone  by  the  nutrient  foramen,  which  is  usually  near  the  centre  of  the 
shaft,  runs  in  an  oblique  canal   through  the  compact  substance,  giving  off  branches  to  this 


CHEMICAL   COMPOSITION  OF  BONE 


41 


structure,  and  entering  the  medullary  cavity,  sends  branches  toward  the  extremities,  thus 
forming  capillary  plexuses  in  the  marrow.  These  branches  communicate  with  branches  from 
the  periosteal  vessels  The  walls  of  the  \essels  are  ^erv  thin,  the  venous  blood  enters  the 
spaces  of  the  led  marrow  and  the  current  becomes  extremely  slow.  Small  \eins  collect  the 
venous  blood  and  emii^c    tiom  the  bone 


_.     _       „iuuii  lluiifeitudmal  seLtioii  thiouth  tliL  diapln  Is  ut  tliL  hu 

with  pigment    which  la  here  black      Ha\  ersian  canalb  aie  cut  longitudin \Uj 


\11  ctnals  are  filled 
90       (tozymonowicz  ) 


Veins  emerge  from  the  long  bones  in  three  places:  (1)  One  or  two  large  veins  accompany 
the  nutrient  artery.  (2)  Numerous  veins  emerge  at  the  articular  extremities.  (3)  Many  small 
veins  arise  in  and  emerge  from  compact  substance.  The  latter  two  classes  do  not  accompany 
arteries.  The  veins  in  the  marrow  and  in  the  bone  are  devoid  of  valves;  but  immediately  after 
emerging  from  the  bone  they  have  numerous  valves.  In  the  flat  cranial  bones  the  veins  are 
numerous  and  large. 

The  lymphatics  are  chiefly  periosteal;  but  some  have  been  demonstrated  as  entering  the  bone, 
nlong  with  the  vessels,  and  running  in  the  Haversian  canals. 

Nerves,  meduUated  {myelinic)  and  nonmeduUated  (amyelinic) ,  are  found  in  bone.  They  are 
distributed  freely  to  the  periosteum,  and  some  of  the  fibres  terminate  in  this  structure  as  Pacinian 
corpuscles.  Nerves  accompany  the  nutrient  arteries  into  the  interior  of  the  bone,  and  also  reach 
the  marrow  from  the  periosteum  by  w^ay  of  Volkmann's  canals  and  the  Haversian  canals.  They 
certainly  supply  the  arterial  coats  and  possibly  ramify  about  the  osteoblasts.  Nerves  are  most 
numerous  in  the  articular  extremities  of  the  long  bones,  in  the  vertebrae,  and  the  large  flat  bones. 

Chemical  Composition  of  Bone. — Bone  consists  of  about  36  per  cent,  of  animal  {organic) 
and  about  64  per  cent,  of  earthy  {inorganic)  substance  intimately  combined. 

The  animal  part  may  be  obtained  by  immersing  the  bone  for  a  considerable  time  in  dilute 
mineral  acid,  after  which  process  the  bone  comes  out  exactly  the  same  shape  as  before,  but  per- 
fectly flexible,  so  that  a  long  bone  (one  of  the  ribs,  for  example)  can  easily  be  tied  into  a  knot, 
if  now  a  transverse  section  is  made,  the  same  general  arrangement  of  the  Ha\'ersian  canals, 


42 


GENERAL  ANATOMY  OF  THE  SKELETON 


lamelliE.  lacunte,  and  canaliculi  is  seen,  though  not  so  plainly  as  in  the  ordinary  section.  The 
animal  basis  is  lararely  composed  of  ossein,  or  fat  collagen.  When  boiled  with  water,  especially 
under  pressure,  fat  collagen  is  almost  entirely  resolved  into  gelatin. 

The  earthy  part  may  be  obtained  by  calcination,  in  which  process  the  animal  matter  is  com- 
pletely burned  out.  The  bone  will  still  retain  its  original  form,  but  it  will  be  white  and  brittle, 
will  have  lost  about  one-third  of  its  original  weight,  and  will  crumble  upon  the  slightest  pressure. 
The  earthy  matter  confers  on  bone  its  hardness  and  rigidity,  and  the  animal  matter  its  tenacity. 
The  mineral  matter  consists  chiefly  of  calcium  phosphate,  forming  about  two-thirds  of  the 
weight  of  bone. 

Ossification  and  Growth  of  Bone. — For  the  early  development  of  the  skeleton  the 
reader  is  referred  to  text-books  on  embryology.     Embryonic  connective-tissue  cells  of  the  meso- 

blast  develop  membrane.  Membrane  may  become 
bone  directly  or  cartilage  may  be  deposited,  which 
cartilage  by  the  process  of  ossification  is  changed  into 
bone.  The  tissue  which  is  eventually  to  become  bone 
contains  cellular  elements  which  evolve  into  osteo- 
blasts, or  bone-forming  cells.  Osteoblasts  exist  in  the 
connective  tissues  which  become  bone  by  intramem- 
branous  ossification,  and  in  the  deeper  layers  of  the 
tissue  called  perichondrium  which  invests  cartilage 
and  which  becomes  the  osteogenetic  layer  of  the  peri- 
osteum. In  view  of  the  fact  that  in  the  fetal  skeleton 
some  bones  are  preceded  by  membrane  (parietal  bones, 
frontal  bone,  upper  part  of  tabular  portion  of  occipital 
bone,  most  of  the  bones  of  the  face),  and  others  are  pre- 
ceded by  rods  of  cartilage  (the  long  bones),  two  kinds 
of  ossification  are  described — viz.,  the  intramembra- 
nous  and  the  intracartilaginous. 

Intramembranous  Ossification. — In  the  case  of 
bones  which  are  developed  in  membrane  no  cartilagi- 
nous mould  precedes  the  appearance  of  the  bone  tissue. 
The  membrane,  which  occupies  the  place  of  the  future 
bone,  consists  of  white,  fibrous  connective  tissue,  and 
ultimately  forms  the  periosteum.  At  this  stage  it  is  seen 
to  be  composed  of  fibres  and  granular  cells  in  a  matrix. 
The  outer  portion  is  more  fibrous,  while  internally  the  cells  or  osteoblasts  predominate;  the  whole 
tissue  is  quite  vascular.  At  the  outset  of  the  process  of  bone  formation  a  little  network  of  bony 
spicules  is  first  noticed  radiating  from  the  point  or  centre  of  ossification.     When  these  rays  of 


Fig.  9. — Schematic  diagram,  showing  epi- 
physis and  diaphysis  and  line  of  ossification, 
Ev.  Epiphysis  of  endochondral  bone.  zpt. 
Zone  of  proliferation.  7C.  Zone  of  calcifica- 
tion,    ca.  Cartilage.     (Poirier  and  Charpy.) 


Union  q 

adjacent 


Fig.  10, — Part  of  the  grow 


V  Bony 

^^^iT^  "      spicules. 

ng  edge  of  the  developing  parietal  bone  of  a  fetal  cat,     (After  J.  Lawr 


growing  bone  are  examined  with  a  microscope  they  are  found  to  consist  at  their  growing  point 
of  a  network  of  fine,  clear  fibres  and  granular  corpuscles,  with  an  intervening  ground  substance 
(Pig.  10).     The  fibres  are  termed  osteogenetic  fibres,  and  are  made  up  of  fine  fibrils  differing 


INTJRAMEMBBANO  US  OSSIFXCA  TION 


43 


little  from  from  those  of  white  fibrous  tissue.  Like  them,  they  are  probably  deposited  in  the  matrix 
through  the  influence  of  the  cells — in  this  case  the  osteoblasts.  The  osteogenetic  fibres  soon 
assume  a  dark  and  granular  appearance  from  the  deposition  of  calcareous  granules  in  the  fibres 
and  in  the  intervening  matrix,  and  as  they  calcify  they  are  found  to  enclose  some  of  the  granular 


C'o^ 


Fig.  11. — Longitudinal  section  tlirnuch  tlie  second  phalanx  of  tlie  fincer  of  a  seven  months'  human  embryo. 
Stained  in  hematoxylin  and  eosin.  X  104.  A.  Periosteum.  B.  Primary  areola.  C.  Periosteal  bone.  D.  Sec- 
ondary areola  and  marrow.     E,  Calcareous  material.     F^  Endochondral  bone.      (Szymonowicz.) 

corpuscles,  or  osteoblasts.  By  the  fusion  of  the  calcareous  granules  the  bony  tissue  again  assumes 
a  more  transparent  appearance,  but  the  fibres  are  no  longer  so  distinctly  seen.  The  involved 
osteoblasts  form  the  corpu.scles  of  the  future  bone,  the  spaces  in  which  they  are  enclosed  con- 
stituting the  lacuniE.  As  the  osteogenetic  fibres  grow  out  to  the  periphery  they  continue  to 
ossify  and  give  rise  to  fresh  bone  spicules.      Thus,  a  network  of  bone  is  formed,  the  meshes  of 


Fig.   12. — Section  through  the  red  bone 
B.  Eosinophiles.     C.  Nucleated  red  blood 


__  a  rabbit.       Biondi's  stain.       X  640.       .4.  Jlyelocytes. 
puscles.     D.  Giant  cells.     E.  Myelocyte.     (Szymonowicz.) 


which  contain  the  bloodvessels  and  a  delicate  connective  tissue  crowded  with  osteoblasts.  The 
bony  trabecule  thicken  by  the  addition  of  fresh  layers  of  bone  formed  by  the  osteoblasts  on  their 
surface,  and  the  meshes  are  correspondingly  encroached  upon.  Subsequently  successive  layers 
of  bony  tissue  are  deposited  under  the  periosteum  and  around  the  larger  vascular  channels. 


44 


GENERAL  ANATOMY  OF  THE  SKELETON 


which  become  the  Haversian  canals,  so  that  the  bone  increases  much  in  thickness.  The  process 
spreads  laterally  to  the  region  of  the  future  suture,  and  here  between  the  various  bones  a  layer 
of  fibrous  tissue,  the  cambium  layer,  is  maintained  until  the  full  size  of  the  bone  is  reached. 
The  cambium  layer  then  ossifies  and  the  bone  ceases  to  grow  at  its  edges. 

Intracartilaginous  Ossification. — .Just  before  ossification  begins  the  bone  is  entirely  carti- 
laginous, and  in  the  long  bone,  which  may  be  taken  as  an  example,  the  process  commences  in 
the  centre  and  proceeds  toward  the  extremities,  which  for  some  time  remain  cartilaginous. 
Subsequently  a  similar  process  commences  in  one  or  more  places  in  those  extremities  and 
gradually  ossifies  them.  The  extremities  do  not,  however,  become  joined  to  the  shaft  by  bony 
tissue  until  growth  has  ceased,  but  are  attached  to  it  by  a  layer  of  cartilaginous  tissue  termed  the 
epiphyseal  cartilage. 

The  first  step  {proliferation)  in  the  ossification  of  the  cartilage  is  that  the  cartilage  cells,  at  the 
point  where  ossification  is  commencing  and  which  is  termed  a  centre  of  ossification,  multiply, 
enlarge,  and  arrange  themselves  in  rows  (Fig.  11).     The  matrix  in  which  they  are  embedded 


■>^^ 


\-^ 


/ 


Fig.  13. — Cross-section  of  a  developing  bone  of  a  human  fetus  of  four  montlis,  a.  Periosteum,  h.  Boundary 
between  endochondral  and  periosteal  bone.  c.  Perichondral  bone.  d.  Remains  of  area  of  e&lcification. 
c.  Endochondral  bone,  f,  f.  Bloodvessels,  g.  g'.  Developing  Haversian  spaces.  A.  Marrow,  i.  Bloodvessel. 
(Radasch,  after  Stohr's  Histology.) 

increases  in  quantity,  so  that  the  cells  become  further  separated  from  each  other.  A  deposit 
of  calcareous  material  (calcification)  now  takes  place  in  this  matrix,  between  the  rows  of  cells, 
so  that  they  become  separated  from  each  other  by  longitudinal  coliunns  of  calcified  matrix. 
These  columns  are  connected  to  one  another  by  transverse  bars  of  calcareous  substance,  and 
present  a  granular  and  opaque  appearance.  In  the  calcareous  areas  the  cartilage  cells  repro- 
duce so  rapidly  that  a  number  of  cells  are  seen  in  each  large  lacuna,  or  space,  which  is  called  a 
primary  areola.  This  process  is  succeeded  by  destruction  of  some  of  the  columns  between  the 
smaller  spaces,  forming  thus  a  fewer  number  of  larger  spaces,  the  secondary  areolae.  Some  of 
the  cells  within  the  areolse  disappear,  others  become  osteoblasts,  which  appty  themselves  to  the 
columns  and  secrete  a  thin  veneer  of  osseous  tissue  upon  the  calcareous  matter;  still  others 
of  these  cells  become  osteoclasts. 

At  the  same  time  that  this  process  is  going  on  in  the  centre  of  the  solid  bar  of  cartilage  of 
which  the  fetal  bone  consists,  certain  changes  are  taking  place  on  its  surface.  This  is  covered 
by  a  very  vascular  membrane,  the  perichondrium,  entirely  similar  to  the  embryonic  connective 
tissue  already  described  as  constituting  the  basis  of  membrane  bone,  on  the  inner  or  cartilage 


INTRA  CA  R  TIL  A  GINO  US  OSSIFICA  TION 


45 


siirface  of  which  the  cells  become  osteoblasts,  or  bone-forming  cells.  By  the  agency  of  these 
cells  a  thin  layer  of  bony  tissue  is  being  formed  between  the  outer  membrane,  now  the  periosteum, 
and  the  cartilage  by  the  intramembraiious  mode  of  ossification  just  described;  this  constiiuics 
the  first  periosteal  lamella.  These  two  processes  go  on  simultaneously.  The  second  stan-e 
i vascularization)  consists  in  the  prolongation  into  the  cartilage  of  processes  of  the  deeper  or 
osteogenetic  layer  of  the  periosteum,  these  processes  consisting  of  bloodvessels  and  cells — 
osteoblasts,  or  bone  formers,  and  osteoclasts,  or  bone  destroyers.  The  latter  are  similar  to 
the  giant  cells  (myeloplaques)  found  in  marrow,  and  they  excavate  passages  through  the  new- 
formed  bony  layer  by  absorption,  and  ]3ass  through  it  into  the  areolae.  Wherever  these  processes 
come  in  contact  with  the  calcified  walls  of  the  primary  areolse  they  absorb  it,  and  thus  cau.se  a 
fusion  of  the  original  cavities  and  assist  in  the  formation  of  larger  spaces,  which  are  termed  the 
secondary  areolae  (Sharpey),  or  medullary  spaces.  These  secondary  spaces  become  filled  with 
enibryoni:'  marrow,  consisting  of  ostenlilasts,  vessels,  a  few  leukocytes,  and  a  few  myelocytes. 

Tiie  first  periosteal  lamella  is  rapiiily  followed  by  the  formation  of  others  of  the  same  nature, 
the  osteoblasts  secreting  the  lamellre  remaining  between  the  successive  layers  with  their  pro- 
cesses passing  from  one  to  the  other.  The  spaces  occupied  by  these  cells  are  the  lacunae  and  the 
small  channels  occupied  by  the  processes  are  the  canaliculi.  A  periosteal  lamella  is  not  smooth 
and  regular  and  does  not  extend  completely  around  the  developing  bone,  but  meets  others 
that  aid  in  completing  the  circle.  The  irregularities  are  due  to  projecting  processes  of  bone  that 
meet  others  and  enclose  small,  irregu- 
lar, longitudinal  canals,  which  contain 
vessels  and  primitive  marrow,  and 
are  the  primitive  Haversian  canals. 
These  are  also  seen  at  the  junctions 
of  the  lamellae  (Fig.  13).  The  osteo- 
clasts of  the  primitive  marrow  apply 
themselves  to  the  walls  of  the  canals 
and  absorb  the  osseous  tissue  until  a 
comparatively  large  and  regular 
canal  is  formed,  and  within  this  canal 
the  osteoblasts  secrete  successive 
concentric  layers  of  bone  until  a 
small  central  canal  alone  remains 
which  contains  a  little  marrow  and 
the  vessels.  This  canal  is  the  true 
Haversian  canal.  The  concentric 
lamelke  are  the  Haversian  lamellae, 
between  which  the  osteoblasts  remain 
in  their  lacunae  and  radiating  can- 
aliculi. The  remains  of  the  peri- 
osteal lamellae  between  the  Haversian 
systems  constitute  the  interstitial 
lamellae  (Fig.  6).  Within  the  centre 
of  the  rod  of  devebping  bone  the  osteoclasts  meanwhile  destroy  the  trabeculae  of  calcific 
material  covered  by  osseous  tissue,  and  thus  is  formed  one  common  cavity — the  beyinning 
of  ilie  medullar!/  cavity.  The  marrow  then  forms  one  common  mass  in  the  centre  of  the  bone, 
and  the  surrounding  fibrous  tissue  becomes  a  second  periosteum,  or  endosteum,  which  sur- 
rounds the  marrow  and  secretes  incomplete  lamellae,  thus  bounding  the  marrow  cavity  as  the 
perimedullary  lamellae.  All  of  the  above  osseous  tissue  is  merely  temporary  in  the  growth  of 
the  bone  thickness.  As  can  now  be  readily  seen,  the  long  bones  increase  evenly  in  thickness  by 
the  periosteal  method,  while  increase  in  length  is  due  entirely  to  the  intracartilaginous  method. 

.Such  are  the  changes  which  may  be  observed  at  one  particular  point,  the  centre  of  ossification. 
While  they  have  been  going  on  here  a  similar  process  has  been  set  up  in  the  surrounding  parts 
and  has  been  gradually  proceeding  toward  the  ends  of  the  shaft,  so  that  in  the  ossifying  bone 
all  the  changes  described  above  may  be  seen  in  different  parts,  from  the  true  bone  in  the  centre 
of  the  shaft  to  the  hyaline  cartilage  at  the  extremities.  The  bone  thus  formed  differs  from  the 
bone  of  the  adult  in  being  more  spongy  and  less  regularly  lamellated. 

As  more  and  more  bone  is  removed  by  this  process  of  absorption  from  the  interior  of  the  bone 
to  form  the  medullary  canal,  so  more  and  more  bone  is  deposited  on  the  e.xterior  by  the  peri- 
osteum, until  at  length  the  bone  has  attained  the  shape  and  size  which  it  is  destined  to  retain 
during  adult  hfe.  As  the  ossification  of  the  cartilaginous  shaft  extends  toward  the  articular 
ends  it  carries  with  it,  as  it  were,  a  layer  of  cartilage,  or  the  cartilage  grows  as  it  ossifies,  and  thus 
the  bone  is  increased  in  length.  During  this  period  of  growth  the  articular  end,  or  cpiphyxis, 
remains  for  some  time  entirelv  cartilaginous;  then  a  bony  centre  appears  in  it,  and  it  undergoes 
the  same  process  of  intracartilaginous  ossification;  the  cancellous  bone  of  the  extremities  of  the 
processes  of  the  bones  is  never  completely  removed  to  form  a  single  marrow  cavity,  but  the 


Fig.  14. — Osteoblasts  from  the  parietal  bone  of  a  human  eflfcryo 
thirteen  weeks  old.  a.  Bony  septa  with  the  cells  of  the  lacunae. 
h.  Layers  of  osteoblasts,  c.  The  latter  in  transition  to  bone  cor- 
puscles.     (-\fter  Gegenbaur.) 


46  GENERAL  ANATOMY  OF  THE  SKELETON 

spaces  become  somewhat  enlarged  as  the  bones  grow.  The  epiphyses  remain  separated  from  the 
shaft  by  a  narrow  cartilaginous  {cambium)  layer  for  a  definite  time  (Fig.  9).  This  layer  ulti- 
mately ossifies,  the  distinction  between  shaft  and  epiphysis  is  obliterated,  and  the  bone  assumes 
its  completed  form  and  shape.  The  same  remarks  also  apply  to  the  processes  of  bone  which  are 
separately  ossified,  such  as  the  trochanters  of  the  femur.  The  bones,  having  been  formed,  con- 
tinue to  grow  until  the  body  has  acquired  its  full  stature. 

The  number  of  ossific  centres  varies  in  different  bones.  In  most  of  the  short  bones  ossification 
commences  at  a  single  point  in  the  centre,  and  proceeds  toward  the  circumference.  In  the  long 
bones  there  is  a  central  point  of  ossification  for  the  shaft  or  diaphysis;  and  one  or  more  for  each 
extremity,  the  epiphysis.  That  for  the  shaft  is  the  first  to  appear.  The  union  of  the  epiphyses 
with  the  shaft  takes  place  in  the  reverse  order  to  that  in  which  their  ossification  began,  with 
the  exception  of  the  fibula,  and  appears  to  be  regulated  by  the  direction  of  the  nutrient  artery 
of  the  bone.  Thus,  the  nutrient  arteries  of  the  bones  of  the  arm  and  forearm  are  directed  toward 
the  elbow,  and  the  epiphyses  of  the  bones  forming  this  joint  become  united  to  the  shaft  before 
those  at  the  shoulder  and  wrist.  In  the  lower  limb,  on  the  other  hand,  the  nutrient  arteries 
pass  in  a  direction  from  the  knee;  that  is,  upward  in  the  femur,  downward  in  the  tibia  and  fibula; 
and  in  them  it  is  observed  that  the  upper  epiphysis  of  the  femur  and  the  lower  epiphysis  of  the 
tibia  and  fibula  become  first  united  to  the  shaft. 

Where  there  is  only  one  epiphysis,  the  nutrient  arter}'  is  directed  toward  that  end  of  the  bone 
where  there  is  no  additional  centre,  as  toward  the  acromial  end  of  the  clavicle,  toward  the  distal 
end  of  the  metacarpal  bone  of  the  thumb  and  great  toe,  and  toward  the  proximal  end  of  the  other 
metacarpal  and  metatarsal  bones. 

Besides  these  epiphyses  for  the  articular  ends,  there  are  others  for  projecting  parts  or  processes, 
which  are  formed  separately  from  the  bulk  of  the  bone.  For  an  account  of  these  the  reader 
is  referred  to  the  description  of  the  individual  bones  in  the  sequel. 

A  knowledge  of  the  exact  periods  when  the  epiphyses  become  joined  to  the  shaft  is  often 
of  great  importance  in  medicolegal  inquiries.  It  also  aids  the  surgeon  in  the  diagnosis  of 
many  of  the  injuries  to  which  the  joints  are  liable;  for  it  not  infrequently  happens  that  on  the 
application  of  severe  force  to  a  joint  the  epiphysis  becomes  separated  from  the  shaft,  and  such 
an  injur}'  may  be  mistaken  for  a  fracture  or  dislocation. 

Applied  Anatomy. — It  has  been  stated  above  that  the  bones  increase  first  in  length  by  ossi- 
fication continuing  to  extend  in  the  epiphyseal  cartilage,  which  goes  on  growing  in  advance  of 
the  ossifying  process;  and  secondly  in  circumference  by  deposition  of  new  bone  from  the  deeper 
layer  of  the  periosteum.  A  thorough  realization  of  these  facts  is  essential  to  the  student,  when 
he  comes  to  consider  the  various  pathological  changes  which  affect  bone.  Anything  which  inter- 
feres with  the  growth  at  the  epiphyseal  line  will  lead  to  a  diminution  in  the  length  which  the  bone 
should  attain  in  adult  life,  and  similarly  anything  which  interferes  with  the  growth  from  the 
deeper  layer  of  the  periosteum  will  result  in  a  disproportion  in  the  thickness  of  the  bone.  Thus, 
separation  of  the  epiphyses,  septic  or  tuberculous  disease  about  the  epiphyseal  line,  and  excisions 
involving  the  epiphyseal  line,  will  result  in  varying  amounts  of  shortening  of  the  bone,  as  com- 
pared with  that  of  the  opposite  side;  whereas  separation  or  imperfect  nutrition  of  the  periosteum 
results  in  defective  growth  in  circumference. 

It  is  thus  obvious  that  a  careful  study  of  osseous  development  is  of  the  very  greatest  utility 
in  the  proper  understanding  of  bone  disease;  and,  moreover,  that  an  accurate  knowledge  of 
the  blood  supply  of  a  long  bone  has  many  important  bearings.  The  outer  portion  of  the  compact 
tissue  being  supplied  by  periosteal  vessels,  which  reach  the  bone  through  muscle  attachments, 
it  follows  that  where  the  muscles  or  muscle  attachments  are  well  developed,  and  therefore  amply 
supplied  with  blood,  the  periosteum  will  ako  be  well  nourished  and  the  bones  proportionately 
well  developed  in  girth;  this  is  well  seen  L.  strong,  muscular  men  with  well-marked  ridges  on 
the  bones.  Conversely,  if  the  muscle  development  be  poor,  the  bones  are  correspondingly 
thin  and  light,  and  if  from  any  cause  a  limb  has  been  paralyzed  from  early  childhood,  all  of  the 
bones  of  that  extremity  are  remarkable  for  their  extreme  thinness — that  is  to  say,  the  periosteal 
blood  supply  has  been  insufficient  to  nourish  that  membrane,  and  consequently  very  little  new 
osseous  tissue  has  been  added  to  the  bones  from  the  outside. 

The  best  example  of  this  condition  is  seen  in  connection  with  the  disease  known  £(s  infantile 
paralysis,  where  a  limb  becomes  paralyzed  at  a  very  early  period  of  childhood,  where  the  muscles 
become  flaccid  and  atonic,  and  where  the  blood  supph'  is  in  consequence  very  greatly  diminished. 
In  such  cases,  although  the  limb  does  continue  to  grow  in  length  from  the  epiphyseal  lines,  its 
length  is  considerably  less  than  on  the  normal  side,  as  a  result  of  the  imperfect  nutrition;  but  the 
most  striking  feature  about  all  the  long  bones  of  the  limb  is  their  remarkable  tenuity,  little  or 
no  addition  having  been  made  to  their  diameters. 

In  cases  where  the  periosteum  has  been  separated  from  the  compact  tissue  by  extensive 
injury  or  inflammatory  exudation,  necrosis  or  death  of  the  underlying  portion  of  bone  takes 
place,  due  to  interference  with  the  blood  supply,  and  the  dead  portion  or  sequestrum  has  to  be 
subsequently  separated  and  cast  off. 

Cases,  however,  occur  in  which  the  inflammatory  process  affects  the  whole  oi  a  great  portion 


APPLIED  ANATOMY 


47 


of  the  diaphysis  of  a  long  bone,  and  here  extensive  necrosis  of  the  affected  portion  takes  place, 
and  the  condition  goes  by  the  name  of  acute  infective  periostitis.  Where  this  occurs  the  shaft  of 
the  bone  dies  very  rapidly,  especially  if  the  singly  nutrient  artery  be  thrombosed  at  the  same  time. 
The  pus  which  has  formed  beneath  the  periosteum  is  set  free  by  timely  excision,  or  burrows  to 
the  surface;  the  periosteum  then  falls  back  on  the  necrosed  diaphysis  and  rapidly  forms  a  layer 
of  new  periosteal  bone,  surrounding  the  sequestrum.  This  layer  is  called  the  involiicrum, 
and  the  openings  in  it  through  which  the  pus  escapes  the  cloacw.  When  the  inflammatory 
process  affects  mainly  the  medullary  canal,  the  condition  is  spoken  of  as  osteomyelitis,  and  the 
two  conditions  very  frequently  co-exist,  and  then  go  by  the  name  of  acute  infective  necrosis  of 
hone  or  acute  diaphysitis.  When  the  medullary  cavity  is  filled  with  pus,  septic  thrombosis  of 
the  veins  in  the  Haversian  canals  takes  place,  and  there  is  a  very  great  danger  of  septic  emboli 
being  separated  and  carried  into  the  general  circulation,  thus  setting  up  a  fatal  pyemia.  In 
fact,  pyemia  is  more  frequently  due  to  septic  bone  conditions  than  to  any  other  cause. 

In  the  preantiseptic  days  pyemia  frequently  resulted  from  amputations,  when  the  medullary 
canal  of  a  long  bone  was  opened  by  the  saw  cut.  Osteomyelitis  ensued,  and  if  the  patient  sur- 
vived, a  tubular  sequestrum  of  the  divided  shaft  subsequently  separated. 

A  proper  understanding  of  the  epiphyses  is  of  the  utmost  possible  importance  to  the  student, 
and  greatly  simplifies  many  of  the  problems  in  the  pathology  of  bone  disease. 

Speaking  generally,  the  long  bones  have  at  either  end  an  epiphysis  from  the  cartilage  of  which 
growth  occurs,  and  hence  the  shaft  of  the  bone  increases  in  length  at  both  ends.  In  every  case, 
however,  one  epiphysis  is  the  more  active,  and  also  continues  in  its  activity  for  a  longer  time. 
This  actively  growing  epiphysis  is  always  the  one  from  which  the  nutrient  foramen  in  the  diaphy- 
sis is  directed,  and  it  unites  to  the  shaft  at  a  later  date.  It  follows,  therefore,  that  the  increase 
in  length  of  a  long  bolie  is  largely  dependent  on  the  epiphysis,  and  hence  anything  which  inter- 
feres with  the  growth  from  this  epiphyseal  line  at  any  time  prior  to  the  union  of  the  epiphysis 
with  the  shaft  must  result  in  a  cessation  of  growth  in  length  of  that  bone.  Thus,  when  dealing 
with  disease  in  the  neighborhood  of  this  actively  growing  epiphysis  very  great  care  should  be 
taken  not  to  excise  or  destroy  its  line  of  union  with  the  shaft.  These  epiphyses  are  particularly 
prone  to  become  the  seat  of  tuberculous  disease,  which  especially  tends  to  attack  the  soft,  highly 
vascular  cancellous  tissue. 

Again,  the  actively  growing  epiphyseal  line  is  the  portion  of  a  long  bone  which  is  in  the  vast 
majority  of  cases  affected  by  tumor  growth  in  bone,  whether  it  be  innocent  or  malignant,  the 
former  (viz.,  osteoma)  usually  appearing  about  puberty,  and  the  latter  (viz.,  sarcoma)  usually 
toward  the  end  of  the  active  period  of  epiphyseal  growth. 

Epiphyseal  growth,  moreover,  has  to  be  considered  by  the  surgeon  when  he  is  about  to  ampu- 
tate in  a  child.  If  tlie  amputation  is  being  performed  through  a  bone,  the  actively  growing 
epiphysis  of  which  is  at  the  upper  end,  and  which  will  continue  to  grow  for  many  years  (i.  e., 
humerus  and  tibia),  it  will  be  necessary  to  make  allowance  for  this  and  to  cut  the  flaps  long;  as 
otherwise,  owing  to  continued  growth,  the  sawed  end  of  the  bone  will  ultimately  project  through 
the  stump,  and  a  condition  known  as  "conical  stump"  will  result.  This  requires  removal  of  a 
further  portion  of  the  bone. 

An  inflammatory  condition  termed  acute  epiphysitis  also  occurs,  although  it  is  not  so  frequent 
as  the  acute  infective  conditions  of  the  diaphysis,  owing  to  the  freer  blood  supply  of  the  epiphysis; 
in  late  years  it  has  been  shown  that  acute  epiphysitis  in  children  is  very  frequently  the  result  of 
a  pneumococcal  infection,  and  it  may  pass  on  to  complete  separation  of  the  epiphysis.  In  this 
connection  it  is  worthy  of  note  that  some  of  the  epiphyseal  lines  lie  entirely  within  the  capsules 
of  their  corresijonding  joints,  in  other  cases  entirely  without  the  capsules;  and  it  must  follow 
that  in  the  former  case  epiphyseal  disease,  acute  or  chronic,  becomes,  ipso  facto,  practically 
synonymous  with  disease  of  that  joint.  The  best  examples  of  intracapsular  epiphyses  are  those 
of  the  head  of  the  femur  and  the  head  of  the  humerus,  and  the  vast  majority  of  all  cases  of 
tuberculous  disease  of  the  hip  starts  as  a  tuberculous  epiphysitis  about  the  intracapsular 
epiphyseal  line  of  the  femur;  again,  cases  of  acute  septic  arthritis  of  the  shoulder-  or  hip-joint 
generally  have  their  origins  in  these  intracapsular  epiphyseal  lines,  and  often  result  in  separa- 
tion of  the  affected  epiphysis.  The  other  class,  or  extracapsular  epiphysitis,  when  diseased,  do 
not  tend  to  involve  the  neighboring  joint  so  readily;  and  it  should  be  the  surgeon's  duty  to  keep 
the  disease  from  involving  the  joint.  For  example,  the  trochanteric  epiphysis  of  the  femur  is 
extracapsular  as  regards  the  hip-joint,  and  the  epiphyseal  line  of  the  head  of  the  tibia  is  well 
below  the  level  of  the  knee-joint,  and  should  a  chronic  tuberculous  abscess  form  in  the  latter 
situation,  it  should  be  attacked  from  the  outside  before  it  has  time  to  spread  up  and  involve  the 
cartilage  of  the  head  of  the  tibia.  It  is,  therefore,  of  great  surgical  interest  to  note  in  every  case 
the  relations  which  the  various  epiphyseal  lines  bear  to  their  respective  joint  capsules. 


48  SPECIAL  ANATOMY  OF  THE  SKELETON 

SPECIAL  ANATOMY  OF  THE  SKELETON. 

THE  VERTEBRAL  OR  SPINAL  COLUMN,  OR  THE  SPINE 
(COLUMNA  VERTEBRALIS). 

The  vertebral  column  is  a  flexuous  and  flexible  column  formed  of  a  series  of 
bones  called  vertebrae. 

The  vertebrse  are  thirty-three  in  number,  and  have  received  the  names  cervical, 
thoracic,  lumbar,  sacral,  and  coccygeal,  according  to  the  position  which  they  occupy; 
seven  are  found  in  the  cervical  region,  twelve  in  the  thoracic,  five  in  the  lumbar, 
five  in  the  sacral,  and  foui-  in  the  coccygeaTf" 

This  number  is  sometimes  increased  by  an  additional  vertebra  in  one  region,  or 
the  number  may  be  diminished  in  one  region,  the  deficiency  being  supplied  by 
an  additional  vertebra  in  another.  These  observations  do  not  apply  to  the  cervical 
portion  of  the  vertebral  column,  as  the  number  of  bones  forming  it  is  rarely 
increased  or  diminished. 

The  vertebrse  in  the  upper  three  regions  of  the  spine  remain  separate  through- 
out life,  and  are  known  as  true  or  movable  vertebra;  but  those  found  in  the  sacral 
and  coccygeal  regions  are  firmly  united  in  the  adult,  so  as  to  form  two  bones — 
five  entering  into  the  formation  of  the  upper  bone  or  sacrum,  and  four  into  the 
terminal  bone  of  the  spine  or  cocc3rx.  The  fused  vertebra  are  known  as  false 
or  immovable  vertebrae. 

With  the  exception  of  the  first  and  second  cervical,  the  true  or  movable  verte- 
brae present  certain  common  characteristics  which  are  best  studied  by  examining 
one  from  the  middle  of  the  thoracic  region. 

GENERAL  CHARACTERS  OF  A  VERTEBRA. 

A  typic  vertebra  consists  of  two  essential  parts — an  anterior  solid  segment,  the 
body,  and  a  posterior  segment,  the  arch  (arcus  vertebrae),  or  the  neural  arch.  The 
arch  is  formed  of  two  pedicles  &ad  two  laminae,  supporting  seven  processes — viz., 
four  articular,  two  transverse,  and  one  spinous. 

The  bodies  of  the  vertebrse  are  placed  one  upon  the  other,  forming  a  strong 
pillar  for  the  support  of  the  skull  and  trunk;  the  arches  forming  a  hollow 
cylinder  behind  the  bodies  for  the  protection  of  the  spinal  cord.  The  different 
vertebrae  are  connected  by  means  of  the  articular  processes  and  the  intervertebral 
fibrocartilages;  while  the  transverse  and  spinous  processes  serve  as  levers  for  the 
attachment  of  muscles  which  move  the  different  parts  of  the  vertebral  column. 
Lastly,  between  each  pair  of  vertebrte  apertures  (foramina  intervertehralia)  exist 
through  which  the  spinal  nerves  pass. 

The  Body  (corpus  vertebrae)  is  the  largest  part  of  a  vertebra.  Its  tipper 
and  lower  surfaces  are  flattened  and  rough  for  the  attachment  of  the  intervertebral 
fibrocartilages,  and  each  presents  a  rim  around  its  circumference.  In  front  it 
is  convex  from  side  to  side,  concave  from  above  downward.  Behind  it  is  flat 
from  above  downward  and  slightly  concave  from  side  to  side.  Its  anterior 
surface  is  perforated  by  a  few  small  apertures,  for  the  passage  of  nutrient  vessels; 
while  on  the  posterior  surface  is  a  single  large,  irregular  aperture,  or  occasionally 
more  than  one,  for  the  exit  of  veins,  the  venae  basis  vertebrae,  from  the  body  of 
the  vertebra. 

Pedicles  (radix  arcus  vertebrae). — The  pedicles  are  two  short,  thick  pieces 
of  bone,  which  project  backward,  one  on  each  side,  from  the  upper  part  of  the 


THE  CERVICAL    VERTEBRA  49 

body  of  the  vertebra,  at  the  line  of  junction  of  its  posterior  and  lateral  surfaces 
and  form  the  root  of  the  vertebral  arch.  The  concavities  above  and  below 
the  pedicles  are  the  superior  and  inferior  intervertebral  notches  [iucisura  vertebralis 
superior  et  inferior);  they  are  four  in  number,  two  on  each  side,  the  inferior  onps 
being  generalTj^Jhe-deeper.  When  the  vertebrae  are  articulated  the  notches  of 
each  contiguous  pair  of  bones  form  the  intervertebral  foramina  (foramina  inter- 
vertebralia),  which  communicate  with  the  vertebral  canal  and  transmit  the  spinal 
nerves  and  bloodvessels. 

Laminae. — ^The  laminae  are  two  broad  plates  of  bone  which  complete  the 
neural  arch  by  fusing  together  in  the  middle  line  behind.  They  enclose  a  foramen, 
the  spinal  or  vertebral  foramen  {foramen  vertehrale),  which  serves  for  the  protection 
of  the  spinal  cord.  AVhen  the  vertebrte  are  joined  they  form,  with  their  ligaments, 
the  vertebral  canal  (canalis  vertebralis).  The  laminae  are  connected  to  the  body 
by  means  of  the  pedicles.  Their  upper  and  lower  borders  are  rough,  for  the 
attachment  of  the  ligamenta  subfiava. 

Processes.  Spinous  Process  (processus  spinosvs). — The  spinous  process  is 
a  rather  long,  three-sided  mass  of  bone  which  projects  backward  from  the 
junction  of  the  two  laminae  and  may  terminate  in  a  tubercle,  and  serves  for  the 
attachment  of  muscles  and  ligaments. 

Articular  Processes. — The  articular  processes  (zygapophyses),  four  in  number, 
two  on  each  side,  spring  from  the  junction  of  the  pedicles  with  the  laminae.  Each 
superior  process  (processus  articularis  superior)  projects  upward,  its  articular  sur- 
face (fades  articularis  superior)  being  directed  more  or  less  backward;  each 
inferior  process  (processus  articularis  inferior)  projects  downward,  its  articular 
surface  (fades  articularis  inferior)  looking  more_i>z_l£ss-4©Fward.' 

Transverse  Processes  (processus  transversa) . — The  transverse  processes,  two  in 
number,  project  one  at  each  side  from  the  point  where  the  lamina  joins  the 
pedicle,  between  the  superior  and  inferior  articular  processes.  They  serve  for 
the  attachment  of  muscles  and  ligaments. 

The  Cervical  Vertebrae  (Vertebrae  Cervicales)  (Fig.  15). 

The  cervical  vertebrte  are  smaller  than  those  in  any  other  region  of  the  spine, 
and  may  be  readily  distinguished  by  the  foramen  in  the  transverse  process,  which 
does  not  exist  in  the  transverse  process  of  either  a  thoracic  or  lumbar  vertebra. 

Body. — The  body  is  small,  comparatively  dense,  and  broader  from  side  to 
side  than  from  before  backward.  The  anterior  and  posterior  surfaces  are  flattened 
and  of  equal  depth;  the  former  is  placed  on  a  lower  level  than  the  latter,  and  its 
inferior  border  is  prolonged  downward,  so  as  to  overlap  the  upper  and  fore  part 
of  the  vertebra  below.  Its  upper  surface  is  concave  transversely,  and  presents 
a  projecting  lip  on  each  side;  its  lower  surface  is  convex  from  side  to  side,  concave 
from  before  backward,  and  presents  laterally  a  shallow  concavity  which  receives 
the  corresponding  projecting  lip  of  the  adjacent  vertebra. 

Pedicles. — The  pedicles  are  directed  outward  and  backward,  and  are  attached 
to  the  body  midway  between  the  upper  and  lower  borders;  so  that  the  superior 
intervertebral  notch  is  as  deep  as  the  inferior,  but  it  is,  at  the  same  time,  narrower. 

Laminae. — The  laminae  are  narrow,  long,  thinner  above  than  below,  and 
overlap  each  other,. enclosing  the  vertebral  foramen,  which  is  very  large,  and  of 
a  triangular  form. 

Processes.  Spinous  Process. — The  spinous  process  is  short,  and  bifid  at  the 
extremity,  to  afi'ord  greater  extent  of  surface  for  the  attachment  of  muscles,  the 

'  It  may,  perhaps,  be  as  well  to  remind  the  reader  that  the  direction  of  a  surface  is  determined  by  that  of  l 
line  drawn  at  right  angles  to  it. 


50 


SPECIAL  ANATOMY  OF  THE  SKELETON 


two  divisions  being  often  of  unequal  size.  They  increase  in  length  from  the  fourth 
to  the  seventh  vertebra. 

Articular  Processes. — ^The  articular  processes  are  flat,  oblique,  and  of  an  oval 
form ;  the  -superior  are  directed  backward  and  upward,  the  inferior  forward  and 
downward. 

Transverse  Processes. — ^The  transverse  processes  are  short,  directed  down- 
ward, outward,  and  forward,  bifid  at  their  extremity,  and  marked  by  a  groove 
along  the  upper  surface,  which  runs  downward  and  outward  from  the  superior 
intervertebral  notch  and  serves  for  the  transmission  of  one  of  the  cervical  nerves. 
They  are  situated  in  front  of  the  articular  processes  and  on  the  outer  side  of  the 
pedicles.  The  transverse  processes  are  pierced  at  their  bases  by  a  foramen, 
for  the  transmission  of  the  vertebral  artery,  vein,  and  a  plexus  of  sympathetic 
nerves.  This  foramen  is  known  as  the  transverse  foramen,  the  costotransverse 
foramen,  and  the  vertebrarterial  foramen  (J'oramen  iransversarium).  Each  process 
is  formed  by  two  roots — the  anterior  root,  sometimes  called  the  costal  process, 
arising  from  the  side  of  the  body,  and  the  homologue.of  the  rib  in  the  thoracic 
region  of  the  column ;  the  posterior  root  springs  from  the  junction  of  the  pedicle 
with  the  lamina,  and  corresponds  to  the  transverse  process  in  the  thoracic  region. 


Antenor  tubercle  of  t)  ajis- 
verse  pi  oces!> 

Costotransverse  foramen  for 
vertebral  artery  and  vein  and' 
sympathetic  plexu 
Posterior  tubercle  of 
transverse  process 


Costal  process 


Ti  anil  eise  process. 

1 


^-^npei  lor  articular 
pi  ocess. 
Infeiior  articular  pro 


Fig.  15. — Ce^^'ical  vertebra. 


It  is  by  the  junction  of  the  two  that  the  foramen  for  the  vertebral  vessels  is  formed. 
The  extremity  of  each  of  these  roots  form  the  anterior  and  posterior  tubercles 
of  the  transverse  processes. 

The  peculiar  vertebrae  in  the  cervical  regions  are  the  first,  or  atlas;  the  second, 
or  axis;  and  the  seventh,  or  vertebra  promlnens.  The  great  modifications  in  the 
form  of  the  atlas  and  axis  are  designed  to  admit  of  the  nodding  and  rotatory 
movements  of  the  head. 

Atlas. — ^The  atlas  (Fig.  16)  is  so  named  because  it  supports  the  globe  of  the 
head.  The  chief  peculiarities  of  this  bone  are  that  it  has  neither  body  nor  spinous 
process.  The  body  is  detached  from  the  rest  of  the  bone,  and  forms  the  odontoid 
process  of  the  second  vertebra;  while  the  parts  corresponding  to  the  pedicles 
join  in  front  to  form  the  anterior  arch.  The  atlas  is  ring-like,  and  consists  of 
an  anterior  arch,  a  posterior  arch,  and  two  lateral  masses.  The  anterior  arch 
(arcus  anterior)  forms  about  one-fifth  of  the  ring;  its  anterior  surface  is  convex, 
and  presents  about  its  centre  a  tubercle  (tuberculum  anterius) ,  for  the  attachment 
of  the  Longus  colli  muscle;  posteriorly  it  is  concave,  and  marked  by  a  smooth, 
oval  facet  {fovea  dentis),  covered  with  cartilage,  for  articulation  with  the  odontoid 
process  of  the  axis.  The  upper  and  lower  borders  give  attachment  to  the  anterior 
occipito-atlantal  and  the  anterior  atlanto-axial  ligaments,  which  connect  it  with 


THE  CERVICAL    VERTEBRAE 


51 


the  occipital  bone  above  and  the  axis  below.  The  posterior  arch  {arcuH  posterior) 
forms  about  two-fifths  of  the  circumference  of  the  bone;  it  terminates  behind 
in  a  tubercle  (iuberculum  postenvs) ,  which  is  the  rudiment  of  a  spinous  process, 
and  gives  origin  to  the  Rectus  capitis  px^.st.ini.s  minor.  The  diminutive  size  of 
this  process  prevents  any  interference  in  the  movements  between  the  atlas  and  the 
cranium.  The  posterior  part  of  the  arch  presents  above  and  behind  a  rounded 
edge  for  the  attachment  of  the  posterior  occipitoatlantal  ligament,  while  in  front 
immediately  behind  each  superior  articular  process,  is  a  groove  {sidcvs  arteriae 
■vertebralis)  (Fig.  16),  sometimes  converted  into  a  foramen  by  a  delicate  bony 
spiculum,  which  arches  backward  from  the  posterior  extremity  of  the  superior 
articular  process.  These  grooves  represent  the  superior  intervertebral  notches, 
and  are  peculiar  in  that  they  are  situated  behind  the  articular  processes,  instead 
of  in  front  of  them,  as  in  the  other  vertebra;.  They  serve  for  the  transmission  of 
the  vertebral  artery,  which,  ascending  through  the  foramen  in  the  transverse 
process,  winds  around  the  lateral  mass  in  a  backward  and  inward  direction. 
They  also  transmit  the  suboccipital  (first  spinal)  nerve.  On  the  under  surface  of 
the  posterior  arch,  in  the  same  situation,  are  two  other  grooves,  placed  behind 
the  lateral, masses,  and  representing  the  inferior  intervertebral  notches  of  other 
vertebrae.     They  are  much  less  marked  than  the  superior.     The  lower  border 

*"  Dtaqram  of  section  of  odontoid, 

pt  oce^s 

Diaqi  am  of  section  of 
t)ansieise  hgamenL 

Foramen  for 
vertebral  artery. 


Groove  for  vertebral  artery 
and  1st  cermcal  nerve. 


Endhnentary  spinous  process. 

Fig.  16. — First  cervical  vertebra, 


i\,_J,^\    CoJ^^'"^    j^aWti'-"-^  Vv^C^ftv 


also  gives  attachment  to  the  posterior  atlanto-axial  ligament,  which  connects  it 
with  the  axis.  The  lateral  masses  {massae  laterales)  are  the  most  bulky  and  solid 
parts  of  the  atlas,  in  order  to  support  the  weight  of  the  head;  they  present  two 
articulating  surfaces  above  and  two  below.  Each  represents  one-fifth  of  the  ring. 
The  superior  articular  surface  {fovea  articularis  superior)  of  each  is  of  large  size,  oval, 
concave,  and  approaches  its  companion  in  front,  but  diverges  from  it  behind ;  it 
is  directed  upward,  inward,  and  a  little  backward,  forming  a  kind  of  cup  for  the 
corresponding  condyle  of  the  occipital  bone.  The  two  processes  are  admirably 
adapted  to  the  nodding  movements  of  the  head.  Not  infrequently  they  are  par- 
tially subdivided  by  a  more  or  less  deep  indentation,  which  encroaches  upon 
each  lateral  margin.  Each  inferior  articular  process  (fades  articularis  inferior)  is 
circular  in  form,  flattened  or  slightly  concave,  and  directed  downward  and  inward, 
articulating  with  the  axis.  The  inferior  processes  permit  the  rotatory  movements. 
Just  below  the  inner  margin  of  each  superior  articular  surface  is  a  small  tubercle, 
for  the  attachment  of  the  transverse  ligament,  which,  stretching  across  the  ring 
of  the  atlas,  divides  it  into  two  unequal  parts  or  arches;  the  anterior  or  smaller 
segment  receiving  the  odontoid  process  of  the  axis,  the  posterior  allowing  the 
transmission  of  the  spinal  cord  and  its  membranes.  This  part  of  the  vertebral 
canal  is  of  considerable  size,  to  aft'ord  space  for  the  spinal  cord;  and  hence  lateral 


52  SPECIAL  ANATOMY  OF  THE  SKELETON 

displacement  of  the  atlas  may  occur  without  compression  of  this  structure.  The 
transverse  processes  are  of  large  size,  project  directly  outward  and  downward 
from  the  lateral  masses,  and  serve  for  the  attachment  of  special  muscles  which 
assist  in  rotating  the  head.  They  are  long,  not  bifid,  and  perforated  at  their 
bases  by  a  canal  for  the  vertebral  artery,  which  is  directed  from  below,  upward, 
and  backward. 

Axis. — The  axis  (epistropheus)  (Fig.  17)  is  the  pivot  upon  which  the  first 
vertebra,  carrying  the  head,  rotates.  The  most  distinctive  character  of  this  bone 
is  the  strong,  prominent  process,  tooth-like  in  form,  which  rises  perpendicularly 
from  the  upper  surface  of  the  body.  The  body  is  deeper  in  front  than  behind, 
and  prolonged  downward  anteriorly  so  as  to  overlap  the  upper  and  fore  part  of 
the  next  vertebra.  It  presents  in  front  a  median  longitudinal  ridge,  separating 
two  lateral  depressions,  for  the  attachment  of  the  Longus  colli  muscles  of  either 
side.  The  odontoid  process  presents  two  articulating  surfaces  covered  with 
cartilage;  one  in  front,  of  an  oval  form,  for  articulation  with  the  atlas  (fades 
articularis  anterior) ;  another  behind  (fades  articularis  posterior) ,  for  the  transverse 

Odontoidjprocess, 

Bough  surface  for  checTc  ligaments. —      ,^i^, 

■■^i^s  it.,^    1     j^Yfii^niar  surface  for 
atlas. 
Articular  surf  ace  for  ti  ansierse  ligament ^^i  X\    i 


Spinous  process.-^^i^  'W'MW  iJ  ■/ 

I  Transtiei  »e  process. 
Inferior  articular  process. 
Fig.  17. — Second  c-ervical  vertebra,  or  a.xis. 

ligament — the  latter  frequently  encroaching  on  the  sides  of  the  process.  The 
apex  is  pointed,  and  gives  attachment  to  the  middle  odontoid  ligament.  Below 
the  apex  the  process  is  somewhat  enlarged,  and  presents  on  either  side  a  rough 
impression  for  the  attachment  of  the  lateral  fasciculi  of  the  odontoid  or  check 
ligaments,  which  connect  it  to  the  occipital  bone;  the  base  of  the  process,  wliere 
it  is  attached  to  the  body,  is  constricted,  so  as  to  prevent  displacement  from  the 
transverse  ligament,  which  binds  it  in  this  situation  to  the  anterior  arch  of  the 
atlas.  The  pedicles  are  broad  and  strong,  especially  their  anterior  extremities, 
which  coalesce  with  the  sides  of  the  body  and  the  root  of  the  odontoid  process. 
The  laminas  are  thick  and  strong,  and  the  spinal  foramen  large,  but  smaller 
than  that  of  the  atlas.  The  transverse  processes  are  very  small,  not  l^ifid,  and  each 
is  perforated  by  the  foramen  for  the  vertebral  artery,  wErdi  is  directed  obliquely 
upward  and  outward.  The  superior  articular  siu-faces  (fades  articulares  superiores) 
are  circular,  slightly  convex,  directed  upward  and  outward,  and  are  peculiar 
in  being  supported  on  the  body,  pedicles,  and  transverse  processes.  The  inferior 
articular  surfaces  (fades  articulares  inferiores)  have  the  same  direction  as  those 
of  the  other  cervical  vertebree.  The  superior  intervertebral  notches  are  very 
shallow,  and  lie  behind  the  articular  processes;  the  inferior  in  front  of  them, 
as  in  the  other  cervical  vertebrae.  The  spinous  process  is  of  large  size,  very  strong, 
deeply  channelled  on  its  under  surface,  and  presents  a  bifid,  tubercular  extremity' 
for  the  attachment  of  muscles  which  serve  to  rotate  the  headTipon  the  spine. 


THE  THORACIC   VEllTEBRjE 


53 


Seventh  Cervical  (Fig.  18).— The  most  distinctive  character  of  this  vcrtel)ra 
is  the  existence  of  a  very  long  and  prominent  spinous  process,  hence  the  name, 
vertebra  prominens.  This  pro- 
cess is  thick,  nearly  horizontal 
in  direction,  not  bifurcated,  and 
gives  attachment  to  the  lower 
end  of  the  ligamentum  nuchae. 
The  transverse  process  is  usually 
of  large  size,  its  posterior  tuber- 
cles are  large  and  prominent, 
while  the  anterior  are  small  and 
faintly  marked;  its  upper  surface 
has  usually  a  shallow  groove,  and 
it  seldom  presents  more  than  a 
trace  of__bifurcation  at  its  ex- 
tremity. The  foramen  in  the 
transverse  process  is  sometimes 
as  large  as  in  the  other  cervical 
vertebras,  but  is  usually  smaller 
on  one  or  both  sides,  and  is 
sometimes  absent.  Usually  the 
vertebral  artery  and  vein  pass  in 
front  of  the  transverse  process, 
but  occasionally  it  is  traversed  on  both  sides  by  these  vessels,  or  the  left  one 
alone  may  give  passage  to  them.  Occasionally  the  anterior  root  of  the  trans- 
verse process  exists  as  a  separate  bone,  and  attains  a  large  size.  It  is  then 
called' a  cervical  rib. 


The  Thoracic  Vertebrae  (Vertebrae  Thoracales). 

The  thoracic  vertebrae  are  intermediate  in  size  between  those  in  the  cervical  and 
those  in  the  lumbar  region,  and  increase  in  size  from  above  downward,  the  upper 
vertebrse  in  this  segment  of  the  column  being  much  smaller  than  those  in  the 
lower  part.  A  thoracic  vertebra  may  be  at  once  recognized  by  the  presence  on 
each  side  of  the  body  of  one  or  more  facets  or  half-facets  for  the  heads  of  the  ribs. 

Bodies. — The  bodies  of  the  thoracic  vertebrae  resemble  those  in  the  cervical 
and  lumbar  regions  at  the  respective  ends  of  this  portion  of  the  vertebral  column, 
but  in  the  middle  of  the  thoracic  region  their  form  is  very  characteristic,  being 
heart-shaped,  and  as  broad  in  the  antero-posterior  as  in  the  lateral  direction. 
They  are  thicker  behind  than  in  front,  flat  above  and  below,  convex  and  prominent 
in  front,  deeply  concave  behind,  slightly  constricted  in  front  and  at  the  sides, 
and  marked  on  each  side,  near  the  root  of  the  pedicle,  by  two  demi-facets,  one 
above,  the  other  below  (fovea  costalis  superior  et  inferior).  These  are  covered  by 
cartilage  in  the  recent  state,  and,  when  articulated  with  the  adjoining  vertebrse, 
form,  with  the  intervening  fibrocartilage,  oval  surfaces  for  the  reception  of  the 
heads  of  the  corresponding  ribs. 

Pedicles. — The  pedicles  are  directed  backward,  and  the  inferior  intervertebral 
notches  are  of  large  size,  and  deeper  than  in  any  other  region  of  the  spine. 

Laminae. — The  laminae  are  broad,  thick,  and  imbricated — that  is  to  say, 
overlapping  one  another  like  tiles  on  a  roof.  The  vertebral  foramen  is  small, 
and  of  a  circidar  form. 

Processes. — Spinous  Processes. — Each  spinous  process  is  long,  triangular  on 
transverse  section,  directed  obliquely  downward,  and  terminates  in  a  tubercular 


54 


SPECIAL  ANATOMY  OF  THE  SKELETON 


extremity.     They  overlap  one  another  from  the  fifth  to  the  eighth  vertebra,  but 
are  less  oblique  in  direction  above  and  below. 

Articular  Processes. — The  articular  processes  are  flat,  nearly  vertical  in  direction, 
and  project  from  the  upper  and  lower  part  of  the  pedicles;  the  superior  being 
directed  backward  and  slightly  outward  and  upward,  the  inferior  forward  and  a 
little  inward  and  downward. 


Superior  articulai  pt  ocesi 


Facet  for  tubercle  of 


F-.o.  19.— A  th 


Transverse  Processes. — The  transverse  processes  arise  from  the  same  parts 
of  the  arch  as  the  posterior  roots  of  the  transverse  processes  in  the  neck,  and 
are  situated  behind  the  articular  processes  and  pedicles;  they  are  thick,  strong, 
and  of  great  length,  directed  obliquely  backward  and  outward,  presenting  a 
clubbed  extremity,  and  having  on  its  anterior  part  near  its  tip  a  small  concave 
surface,  for  articulation  with  the  tubercle  of  a  rib  (fovea  costalis  transversalis). 
Besides  the  articular  facet  for  the  rib,  three  indistinct  tubercles  may  be  seen 
arising  from  the  transverse  processes — one  at  the  upper  border,  one  at  the  lower 
border,  and  one  externally.  In  man  they  are  of  comparatively  small  size,  and 
serve  only  for  the  attachment  of  muscles.  But  in  some  animals  they  attain  con- 
siderable magnitude,  either  for  the  purpose  of  more  closely  connecting  the  segments 
of  this  portion  of  the  vertebral  column  or  for  muscular  and  ligamentous  attachment. 

The  peculiar  thoracic  vertebrse  are  the  first,  ninth,  tenth,  eleventh,  and  twelfth 
(Fig.  20). 

First  Thoracic  Vertebra. — The  first  thoracic  vertebra  presents,  on  each  side 
of  the  body,  a  sin^e^ntire  articular  facet  for  the  head  of  the  first  rib  and  a  demi- 
facet  for  the  upper  half  of  the  second.  The  body  is  like  that  of  a  cervical  vertebra, 
being  broad  transversely,  its  upper  surface  is  concave,  and  lipped,  pneach  side. 
The  articular  surfaces  are  oblique,"and  the  spinous  process  thick,  long,  and  almost 
horizontal. 

Ninth  Thoracic  Vertebra. — ^The  ninth  thoracic  vertebra  has  no  demi-facet 
below.  In  some  subjects,  however,  the  ninth  has  two  demi-facets  on  eacTi  side; 
when  this  occurs  the  tenth  has  only  a  demi-facet  at  the  upper  part. 

Tenth  Thoracic  Vertebra. — The  tenth  thoracic  vertebra  has  (except  in  the 
case  just  mentioned)  an  entire  articular  facet  on  each  side,  above,  which  is  partly 


THE  THORACIC  VERTEBRAE 

placed  on  the  outer  jurface-of-the-pedicle.     It  has  no  demi-facet  below, 
times  it  has  no  facet  on  its  transverse  process.  


55 

Some- 


(  An  entire  facet  above; 
\     a  demi-facet  below. 


—A  demi-facet  atiove. 


One  entire  facet. 


entire  facet. 


J.  No  facet  on  rudimentary 
(_      transverse  process. 


entire  facet. 
No  facet  on  trans- 
verse process. 
Inferior    articidat 


Fig.  20.— Peculi; 


Eleventh  Thoracic  Vertebra. — The  body  of  this  vertebra  approaches  in  its 
form  and  size  that  of  the  lumbar  vertebra.  The  articular  facets  for  the  heads 
of  the  ribs,  one  on  each  side,  are  of  large  size,  and  placed  chiefly  on  the  pedicles, 
which^are'thicker  and  stronger  in  this  and  the  next  vertebra  than  in  any  other 
part  of  the  thoracic  region.  The  spinous  process  is  short,  and  nearly  horizpntal 
in  direction.  The  transverse  processes  are  very  short,  Tubercular  at  their  extrem- 
ities, and  have  no  articiilar  facets  for  the  tubercles  o?  tbe  ribs. 

Twelfth  Thoracic  Vertetra. — The  twelfth  thoracic  vertebra  has  the  same 
general  characters  as  the  eleventh,  but  may  be  distinguished  from  it  by  the  in- 


56 


SPECIAL  ANATOMY  OF  THE  SKELETON 


ferior  articular  processes  being  convex  and  turned  outward,  like  those  of  the 
lumbar  vertebrae;  and  by  the  fact  that  this  vertebra  resembles  the  lumbar  vertebrae 
in  the  general  form  of  the  body,  laminae,  and  spinous  process;  and  by  the  trans- 
verse processes  being  shorter,  and  marked  by  three  elevations,  the  superior, 
inferior,  and  external  tubercles,  which  correspond  to  the  mammillary,  accessory, 
and  transverse  processes  of  the  lumbar  vertebrae.  There  is  no  facet  on  its 
transverse  process  for  the  twelfth  rib. 


The  Lumbar  Vertebrae  (Vertebrae  Lumbales)  (Fig.  21). 

The  lumbar  vertebrae  are  the  largest  segments  of  the  vertebral  column,  and  can 
at  once  be  distinguished  by  the  absence  of  the  foramen  in  the  transverse  process, 
the  characteristic  point  of  the  cervical  vertebrae,  and  by  the  absence  of  any  articu- 
lating facet  on  the  side  of  the  body,  the  distinguishing  mark  of  the  thoracic 
vertebrae. 


Superioi  a)ticula>  pi  ocas 


Fig.  21. — Lumbar  vertebra. 

Body. — ^The  body  is  large,  and  has  a  greater  diameter  from  side  to  side  than 
from  before  backward,  slightly  thicker  in  front  than  behind,  flattened  or  slightly 
concave  above  and  below,  concave  behind,  and  deeply  constricted  in  front  and  at 
the  sides,  presenting  prominent  margins,  which  afford  a  broad  surface  for  the 
support  of  the  superincumbent  weight. 

Pedicles. — The  pedicles  are  very  strong,  directed  backward  from  the  upper 
part  of  the  bodies;  consequently,  the  inferior  intervertebral  notches  are  of  con- 
siderable depth. 

Laminaj.-  The  laminae  are  broad,  short,  and  strong,  and  the  vertebral  foramen 
triangular,  larger  than  in  the  thoracic,  smaller  than  in  the  cervical,  region. 

Processes.  Spinous  Processes. — The  spinous  processes  are  thick  and  broad, 
somewhat  quadrilateral,  horizontal  in  direction,  thicker  below  than  above,  and 
terminating  in  a  rough,  uneven  border. 

Articular  Processes. — The  superior  articular  processes  are  concave,  and  look 
backward  and  inward;  the  inferior  are  convex,  and  look  forward  and  outward; 
the  former  are  separated  by  a  much  wider  interval  than  the  latter,  embracing 
the  lower  articulating  processes  of  the  vertebra  above. 

Transverse  Processes. — The  transverse  processes  are  long,  slender,  directed 
transversely  outward  in  the  upper  three  lumbar  vertebrae,  slanting  a  little  upward 
in  the  lower  two.  They  are  situated  in  front  of  the  articular  processes,  instead 
of  behind  them,  as  in  the  thoracic  vertebrae,  and  are  homologous  with  the  ribs.  Of 
the  three  tubercles  noticed  in  connection  with  the  transverse  processes  of  the 


THE  LUuMBAB    VERTEBRA 


57 


twelfth  thoracic  vertebra,  the  superior  one  on  each  side  becomes  connected  in  tliis 
region  witli  the  back  part  of  the  superior  articular  process,  and  has  received  tiie 
name  of  mammillary  process  {processus  mamillaris) ;  the  inferior  is  represented 
by  a  small  process  pointing  downward,  situated  at  the  back  part  of  the  base  of 
the  transverse  process,  and  called  the  accessory  process  (processus  accessorius); 
these  are  the  true  transverse  processes,  which  are  rudimentary  in  this  region  of 
the  spine.  The  external  one,  the  so-called  transverse  process,  is  the  homoloo-ue 
of  the  rib,  and  constitutes  the  costal  process  (processus  costarius)  (Fig.  22). 
Although  in  man  the  costal  processes  are  comparatively  small,  in  some  animals 
they  attain  considerable  size,  and  serve  to  lock  the  vertebrte  more  closely  together. 


Inferior  articulaT 
process 


Transverse  process 


Superior  articular 
process 


StNf^              /«*V^P           a            Mammillary  process 
\\\/       MvA.j^    S^^W.///Z^^  ^ ^  Accessory  process- 


Fig.  22. — Lumbar  vertebra,  viewed  obliquely. 


i'ifth  Lumbar  Vertebra. — The  fifth  lumbar  vertebra  is  characterized  by 
haing  the  body  much  thicker  in  front  than  behind,  which  accords  with  the  promi- 
nence of  the  sacrovertebral  articulation;  by  the  smaller  size  of  its  spinous  process; 
by  t\e  wide  interval  between  the  inferior  articulating  processes ;  and  by  the  greater 
size  \nd  thickness  of  its  transverse  processes,  which  spring  from  the  body  as  well 
as  fr^  the  pedicles. 

Attahment  of  Muscles. — To  the  Atlas  are  attached  nine  pairs:  the  Longus  colli,  Rectus 
capitis  ntieus  minor,  Rectus  lateralis,  Obliquus  capitis  superior  and  inferior,  Splenius  colli, 
Levator\nguli  scapulae.  First  Intertransverse,  and  Rectus  capitis  posticus  minor. 

To  th*  Axis  are  attached  eleven  pairs:  the  Longus  colli.  Levator  anguli  scapulae,  Splenius 
colli,  Scajnus  medius,  Transversalis  colli,  Intertransversales,  Obliquus  capitis  inferior.  Rectus 
capitis  poiicus  major,  Semispinalis  colli,  Multifidus  spinae,  Interspinales. 

To  the  -emaining  vertebrae,  generally,  are  attached  thirty-five  pairs  and  a  single  muscle: 
anteriorly,  he  Rectus  capitis  anticus  major,  Longus  colli.  Scalenus  anticus,  medius,  and  posticus. 
Psoas  magiis  and  parvus,  Quadratus  lumborum,  Diaphragm,  Obliquus  abdominis  internus, 
and  Trans\rsalis  abdominis;  posteriorly,  the  Trapezius,  Latissimus  dorsi.  Levator  anguli 
scapulae,  Rtimboideus  major  and  minor,  Serratus  posticus  superior  and  inferior,  Splenius, 
Erector  spirip,  Iliocostalis,  Longissimus  dorsi.  Spinalis  dorsi,  Cervicalis  ascendens,  Trans- 
versalis colli,Trachelomastoid,  Complexus,  Biventer  cervicis,  Semispinalis  dorsi  and  colli, 
Multifidus  spine,  Rotatores  spinae,  Interspinales,  Supraspinales,  Intertransversales,  Levatores 
costarum.         \ 


58 


SPECIAL  ANATOMY  OF  THE  SKELETON 


The  Sacral  and  Coccygeal  Vertebrae. 

The  sacral  and  coccygeal  vertebrae  consist,  at  an  early  period  of  life,  of  nine 
separate  pieces,  which  are  united  in  the  adult  so  as  to  form  two  bones,  five  enter- 
ing into  the  formation  of  the  sacrum,  four  into  that  of  the  coccyx.  Occasionally, 
the  coccyx  consists  of  five  bones. ^ 

Sacrum  (os  sacrum). — The  sacrum  is  a  large,  triangular  bone  (Fig.  23), 
situated  at  the  lower  part  of  the  vertebral  column,  and  at  the  upper  and  back 
part  of  the  pelvic  cavity,  where  it  is  inserted  like  a  wedge  between  the  two  in- 
nominate bones;  its  upper  part  or  base  articulating  with  the  last  lumbar  vertebra. 


Fig.  23. — Sacrum,  anterior  surface. 


its  apex  with  the  coccyx.  It  is  composed  of  five  segments  of  bone.  The  acrum 
is  curved  upon  itself,  and  placed  very  obliquely,  its  upper  extremity  prqecting 
forward,  and  forming,  with  the  last  lumbar  vertebra,  a  very  prominent  angle, 
called  the  promontory  (promontorium),  or  sacrovertebral  angle;  while  its  central 
part  is  directed  backward,  so  as  to  give  increased  capacity  to  the  pelvi  cavity. 
It  presents  for  examination  an  anterior  and  posterior  surface,  two  lateraburfaces, 
a  base,  an  apex,  and  a  central  Canal. 

Surfaces.  Anterior  or  Pelvic  Surface  (fades  pelvina). — The  antervr  surface 
is  concave  from  above  downward,  and  slightly  so  from  side  to  sid-  In  the 
middle  are  seen  four  transverse  ridges  (Imeae  transversae) ,  indicating  fle  original 
division  of  the  bone  into  five  separate  pieces.     The  portions  of  bonentervening 


^  Sir  George  Humphry  describes  this 


ual  composition  of  the  coccyx.     "  On  the  Slie'fo 


THE  SACRAL  AND  COCCTGEAL   VERTEBRA 


59 


between  the  ridges  correspoiui  to  the  bodies  of  the  vertebrae.  The  body  of  the  first 
segment  is  of  large  size,  and  in  form  resembles  that  of  a  luml)ar  vertebra;  the 
succeeding  ones  diminish  in  size  from  above  downward,  are  flattened  from  before 
backward,  and  curved  so  as  to  accommodate  themselves  to  the  form  of  the  sacrum 
being  concave  in  front,  convex  behind.  At  each  end  of  the  ridges  above  men- 
tioned are  seen  the  anterior  sacral  foramina  (foramina  sacralia  anteriora),  analoo-ous  • 
to  the  intervertebral  foramina,  four  in  number  on  each  side,  somewhat  circular 
in  form,  diminishing  in  size  from  above  downward,  and  directed  outward  and 
forward;  they  transmit  the  anterior  branches  of  the  sacral  nerves  and  the  lateral 
sacral  arteries.  External  to  these  fora- 
mina is  the  lateral  mass  (pars  lateralis), 
consisting  at  an  early  period  of  life  of 
separate  segments ;  these  become  blended, 
in  the  adult,  vi^ith  the  bodies,  with  each 
other,  and  with  the  posterior  transverse 
processes.  Each  lateral  mass  is  traversed 
by  four  broad,  shallow  grooves,  which 
lodge  the  anterior  divisions  of  the  sacral 
nerves  as  they  pass  outward,  the  grooves 
being  separated  by  prominent  ridges  of 
bone,  which  give  attachment  to  the  slips 
of  the  Pyriformis  muscle. 

If  a  vertical  section  is  made  through 
the  centre  of  the  sacrum  (Fig.  24),  the 
bodies  are  seen  to  be  united  at  their  cir- 
cumference by  bone,  a  wide  interval  being 
left  centrally,  which,  in  the  recent  state, 
is  filled  by  intervertebral  substance. 
In  some  bones  this  union  is  more  com- 
plete between  the  lower  segments  than 
between  the  upper  ones. 

Posterior  or  Dorsal  Suriace  (fades  dor- 
salis). — The  posterior  suriace  (Fig.  25) 
is  convex  and  much  narrower  than  the 
anterior.  In  the  middle  line  are  three 
or  four  tubercles,  which  represent  the  rudi- 
mentary spinous  processes  of  the  sacral 
vertebrae.  Of  these  tubercles,  the  first 
is  usually  prominent,  and  perfectly  dis- 
tinct from  the  rest;  the  second  and 
third  are  either  separate  or  united  into  a 
tubercular  ridge  (crista  sacralis  media),  which  diminishes  in  size  from  above 
downward;  the  fourth  usually,  and  the  fifth  always,  remaining  undeveloped; 
being  undeveloped,  in  this  situation  the  lower  end  of  the  sacral  canal  is  exposed. 
The  gap  is  called  the  hiatus  sacralis.  External  to  the  spinous  processes  on  each 
side  are  the  laminje,  broad  and  well  marked  in  the  first  three  pieces;  sometimes 
the  fourth,  and  generally  the  fifth.  External  to  the  laminae  is  a  linear  series  of 
indistinct  tubercles  representing  the  articular  processes  (crisfac  sacrales  artiat- 
lares);  the  upper  pair  are  large,  well  developed,  and  correspond  in  shape  and 
direction  to  the  superior  articulating  processes  of  a  lumbar  vertebra;  the  second 
and  third  are  small;  the  fourth  and  fifth  (usually  blended  together)  are  situated 
on  each  side  of  the  exposed  part  of  the  sacral  canal  and  form  downward  project- 
ing processes^  the  sacral  cornua,  and  are  connected  to  the  cornua  of  the  coccyx. 


-Vertical  section  of  the  sacrum. 


60 


SPECIAL  ANATOMY  OF  THE  SKELETON 


External  to  the  articular  processes  are  the  four  posterior  sacral  foramina  {foram- 
ina sacralia  posteriora) ;  they  are  smaller  in  size  and  less  regular  in  form  than  the 
anterior,  and  transmit  the  posterior  branches  of  the  sacral  nerves.  On  the  outer 
side  of  the  posterior  sacral  foramina  is  a  series  of  tubercles,  the  rudimentary 
transverse  processes  of  the  sacral  vertebrse  (cristae  sacrales  laterales).  The 
first  pair  of  transverse  tubercles  are  large,  very  distinct,  and  correspond  with 
each  superior  angle  of  the  bone;  they,  together  with  the  second  pair,  which  are 
of  small  size,  give  attachment  to  the  horizontal  part  of  the  posterior  sacro- 
iliac ligament;  the  third  gives  attachment  to  the  oblique  fasciculi  of  the  pos- 
terior sacroiliac  ligaments;  and  the  fourth  and  fifth  to  the  great  sacrosciatic 
ligaments.  The  interspace  between  the  spinous  and  transverse  processes  on 
the  back  of  the  sacrum  presents  a  wide,  shallow  concavity,  called  the  sacral 


Erector  spinse. 


|H— ia^iSSiOTua  dorsl. 


] — •  Erector  spinas. 


Upper  half  of  fifth 
lor  sacral  foramen. 


Fig.  25. — Sacrum,  dorsolateral  view. 


groove;  it  is  continuous  above  with  the  vertebral  groove,  and  lodges  the  origin 
of  the  Multifidus  spinae. 

Lateral  Surface. — ^The  lateral  surface,  broad  above,  becomes  narrowed  into  a 
thin  edge  below.  Its  upper  half  presents  in  front  a  broad,  ear-shaped  surface  for 
articulation  with  the  ilium.  This  is  called  the  auricular  surface  [fades  auricularii), 
and  in  the  fresh  state  is  coated  with  fibrocartilage.  It  is  bounded  posteriorly 
by  deep  and  uneven  impressions,  for  the  attachment  of  the  posterior  sacroiliac 
ligaments.  The  chief  prominence  is  called  the  tuberosity  {tuberositas  sacralis). 
The  lower  half  is  thin  and  sharp,  and  terminates  in  a  projection  called  the  inferior 
lateral  angle;  below  this  angle  is  a  notch,  which  is  converted  into  a  foramen  by 
articulation  with  the  transverse  process  of  the  upper  piece  of  the  coccyx,  and 


THE  SACRAL  AND   COCCYGEAL   VERTEBRA  01 

transmits  the  anterior  division  of  the  fifth  sacral  nerve.  This  lower,  sharp  border 
gives  attachment  to  the  greater  and  lesser  sacrosciatic  ligaments,  and  to  some 
fibres  of  the  Gluteus  maximus  posteriorly,  and  to  the  Coccygeus  in  front. 

Base  (basis  oss.  sacri). — The  base  of  the  sacrum,  which  is  broad  and  expanded, 
is  directed  upward  and  forward.  In  the  middle  is  seen  a  large  oval  articular 
surface,  which  is  connected  with  the  under  surface  of  the  body  of  the  last  lumbar 
vertebra  by  a  fibrocartilaginous  disk.  It  is  bounded  behind  by  the  large,  tri- 
angular orifice  of  the  sacral  canal.  The  orifice  is  formed  behind  by  the  laminae 
and  spinous  process  of  the  first  sacral  vertebra:  the  superior  articular  processes 
project  from  it  on  each  side;  they  are  oval,  concave,  directed  backward  and  inward, 
like  the  superior  articular  processes  of  a  lumbar  vertebra;  and  in  front  of  each 
articular  process  is  an  intervertebral  notch,  which  forms  the  lower  part  of  the 
foramen  between  the  last  lumbar  and  first  sacral  vertebra.  Lastly,  on  each  side 
of  the  large  oval  articular  plate  is  a  broad  and  flat  triangular  surface  of  bone, 
which  extends  outward,  supports  the  Psoas  magnus  muscle  and  lumbosacral 
cord,  and  is  continuous  on  each  side  with  the  iliac  fossa.  This  is  called  the  ala  of 
the  sacrum  (ala  sacralis),  and  gives  attachment  to  a  few  of  the  fibres  of  the  Iliacus 
muscle.  The  posterior  part  of  the  ala  represents  the  transverse  process  of  the 
first  sacral  segment. 

Apex  (apex  OSS.  sacri). — The  apex,  directed  downward  and  slightly  forward, 
presents  a  small,  oval,  concave  surface  for  articulation  with  the  coccyx.  ^ 

The  Sacral  Canal  (canalis  sacralis)  runs  throughout  the  greater  part  of 
the  bone;  it  is  large  and  triangular  in  form  above,  small  and  flattened,  from 
before  backward,  below.  In  this  situation  its  posterior  wall  is  incomplete,  from 
the  non-development  of  the  laminae  and  spinous  processes  (hiafus  sacralis). 
It  lodges  the  sacral  nerves,  and  is  perforated  by  the  anterior  and  posterior  sacral 
foramina,  through  which  these  pass  out.  I^  constitutes  the  sacral  continuation 
of  the  vertebral  canal  (Fig.  24). 

Diflerences  in  the  Sacrum  of  the  Male  and  Female.— The  sacrum  in  the  female 
is  shorter  and  wider  than  in  the  male;  the  lower  half  forms  a  greater  angle  with  the  upper,  the 
upper  half  of  the  bone  being  nearly  straight,  the  lower  half  presenting  the  greatest  amount 
of  curvature.  The  bone  is  also  directed  more  obliquely  backward,  which  increases  the  size 
of  the  pelvic  cavity;  but  the  sacrovertebral  angle  projects  less.  In  the  male  the  curvature  is 
more  evenly  distributed  over  the  whole  length  of  the  bone,  and  is  altogether  greater  than  in  the 
female. 

Variations. — This  bone,  in  some  cases,  consists  of  six  pieces;  occasionally  the  number  is 
reduced  to  four.  Sometimes  the  bodies  of  the  first  and  second  segments  are  not  joined  or  the 
laminse  and  spinous  processes  have  not  coalesced.  Occasionally  the  upper  pair  of  transverse 
tubercles  are  not  joined  to  the  rest  of  the  bone  on  one  or  both  sides;  and,  lastly,  the  sacral  canal 
may  be  open  for  nearly  the  lower  half  of  the  bone,  in  consequence  of  the  imperfect  development 
of  the  laminae  and  spinous  processes.  The  sacrum,  also,  varies  considerably  with  respect  to 
its  degree  of  curvature. 

Articulations. — With /our  bones:  the  last  hmibar  vertebra,  coccyx,  and  the  two  innominate 
bones. 

Attachment  of  Muscles. — To  eight  pairs:  in  front,  the  Pyriformis  and  Coccygeus,  and  a 
portion  of  the  Iliacus  to  the  base  of  the  bone;  behind,  the  Gluteus  maximus,  Latissimus  dorsi, 
Multifidus  spinae,  and  Erector  spinae,  and  sometimes  the  Extensor  coccygis. 

Coccyx  (os  coccygis). — ^The  coccyx  (Fig.  26)  is  usually  formed  of  four  small 
segments  of  bone,  the  most  rudimentary  parts  of  the  vertebral  column  (vertebrae 
coccygeae).  In  each  of  the  first  three  segments  may  be  traced  a  rudimentary 
body,  articular  and  transverse  processes;  the  last  piece  (sometimes  the  third) 
is  a  mere  nodule  of  bone,  without  distinct  processes.  All  the  segments  are  desti- 
tute of  pedicles,  laminae,  and  spinous  processes,  and  consequently  of  interverte- 
bral foramina  and  vertebral  canal.  The  first  segment  is  the  largest;  it  resembles 
the  lowermost  sacral  vertebra,  and  often  exists  as  a  separate  piece;  the  last  three, 


62 


SPECIAL  ANATOMY  OF  THE  SKELETON 


diminishing  in  size  from  above  downward,  are  usually  blended  to  form  a  single 
bone.  The  gradual  diminution  in  the  size  of  the  pieces  gives  this  bone  a  tri- 
angular form,  the  base  of  the  triangle  joining  the  apex  of  the  sacrum.  It  presents 
for  examination  an  anterior  and  posterior  surface,  two  borders,  a  base,  and  an 
apex. 


■'Tor  ►" 

Antunor  surface. 


Posterior  surface. 


Fig.  26. — Coccyx, 


Surfaces.  Anterior  Surface. — The  anterior  surface  is  slightly  concave  and 
marked  with  three  transverse  grooves,  indicating  the  points  of  junction  of  the  differ- 
ent pieces.  It  has  attached  to  it  the  anterior  sacrococcygeal  ligament  and  Levator 
ani  muscle,  and  supports  the  lower  end  of  the  rectum. 

Posterior  Surface. — The  posterior  surface  is  convex,  marked  by  transverse 
grooves  similar  to  those  on  the  anterior  surface;  and  presents  on  each  side  a  lineal 
row  of  tubercles,  the  rudimentary  articular  processes  of  the  coccygeal  vertebrse. 
Of  these,  the  superior  pair  are  large,  and  are  called  the  cornua  of  the  coccjrx  (cornua 
coccygea) ;  they  project  upward,  and  articulate  with  the  cornua  of  the  sacrum,  the 
junction  between  these  two  bones  completing  the  fifth  posterior  sacral  foramen  for 
the  transmission  of  the  posterior  division  of  the  fifth  sacral  nerve. 

Borders. — The  lateral  borders  are  thin,  and  present  a  series  of  small  emi- 
nences, which  represent  the  transverse  processes  of  the  coccygeal  vertebrae.  Of 
these,  the  first  on  each  side  is  the  largest,  flattened  from  before  backward,  and  often 
ascends  to  join  the  lower  part  of  the  thin  lateral  edge  of  the  sacrum,  thus  completing 
the  fifth  anterior  sacral  foramen  for  the  transmission  of  the  anterior  division 
of  the  fifth  sacral  nerve;  the  others  diminish  in  size  from  above  downward,  and 
are  often  wanting.  The  borders  of  the  coccyx  are  narrow,  and  give  attachment  on 
each  side  to  the  sacrosciatic  ligaments,  to  the  Coccygeus  muscles  in  front  of  the 
ligaments,  and  to  the  Gluteus  maximus  behind  them. 

Base. — The  base  presents  an  oval  surface  for  articulation  with  the  sacrum. 

Apex. — ^The  apex  is  rounded,  and  has  attached  to  it  the  tendon  of  the  external 
Sphincter  muscle.  It  is  occasionally  bifid,  and  sometimes  deflected  to  one  or 
the  other  side. 


Articulation.— With  the  sacrum. 

Attachment  of  Muscles. — To  four  pairs  and  one  single  muscle:  on  either  side,  the  Coccygeus; 
behind,  the  Gluteus  maximus  and  Extensor  coccygis,  when  present;  at  the  apex,  the  Sphincter 
ani;  and  in  front,  the  Levator  ani. 

Structure  of  the  Vertebrae. — The  body  is  composed  of  light,  spongy,  cancellous  tissue, 
having  a  thin  coating  of  compact  tissue  on  its  external  surface  perforated  by  numerous  orifices 
of  various  sizes  for  the  passage  of  vessels;  its  interior  is  traversed  by  one  or  two  large  canals 
(for  the  transmission  of  veins) ,  which  converge  toward  a  single  large,  irregular  aperture  or  several 
small  apertures  at  the  posterior  part  of  the  body  of  each  bone.     The  arch  and  processes  pro- 


THE  SACRAL  AND   COCCYGEAL    VERTELU^K  63 

jecting  from  it  have,  on  the  contrary,  an  exceedingly  thick  covering  of  compact  tissue  (Fig 
27). 

The  sacrum  and  coccyx  consist  mainly  of  spongy  bone  covered  by  a  thin  layer  of  compact 
bone. 


Fig.  27. — Bony  structure  of  a  lumbar  vertebra.     (Poirier  and  Charpy.) 

Development. — Each  vertebra  is  formed  of  four  primary  centres  of  ossification  (Fig.  28), 
one  for  each  lamina  and  its  processes,  and  two  for  the  body.'  Ossification  commences  in  the 
laminae  about  the  sixth  week  of  fetal  life,  in  the  situation  where  the  transverse  processes  afterw  ard 
project,  the  ossific  granules  spreading  backward  to  the  spine,  forward  into  the  pedicles,  and  out- 
ward into  the  transverse  and  articular  processes.  Ossification  in  the  body  commences  in.  the 
middle  of  the  cartilage  about  the  eighth  week  by  two  closely  approximated  centres,  which  speedily 
coalesce  to  form  one  central  ossific  point.  According  to  some  authors,  ossification  commences 
in  the  laminie  only  in  the  upper  vertebrs;  — i.  e.,  in  the  cervical  and  upper  thoracic.  The  first 
ossific  points  in  the  lower  vertebrae  are  those  which  are  to  form  the  body,  the  osseous  centres 
for  the  laminse  appearing  at  a  subsequent  period.  At  birth  these  three  pieces  are  entirely  sepa- 
rate. During  the  first  year  the  laminae  become  united  behind,  the  union  taking  place  first  in 
the  lumbar  vertebrae  and  then  extending  upward  through  the  thoracic  and  lower  cervical  verte- 
bras. About  the  third  year  the  body  is  joined  to  the  arch  on  each  side  in  such  a  manner  that  the 
body  is  formed  from  the  three  original  centres  of  ossification,  the  amount  contributed  by  the 
pedicles  increasing  in  extent  from  below  upward.  Thus,  the  bodies  of  the  sacral  vertebra  are 
formed  almost  entirely  from  the  central  nuclei;  the  bodies  of  the  lumbar  are  formed  laterally 
and  behind  by  the  pedicles;  in  the  thoracic  region  the  pedicles  advance  as  far  forward  as  the 
articular  depressions  for  the  head  of  the  ribs,  forming  these  cavities  of  reception ;  and  in  the  neck 
the  lateral  portions  of  the  bodies  are  formed  entirely  by  the  advance  of  the  pedicles.  The  line 
along  which  union  takes  place  between  the  body  and  the  neural  arch  is  named  neurocentral 
suture.  Before  puberty  no  other  changes  occur,  excepting  a  gradual  increase  in  the  gro\\th  - 
of  these  primary  centres;  the  upper  and  under  surfaces  of  the  bodies  and  the  ends  of  the  transverse 
and  spinous  processes  being  tipped  with  cartilage,  in  which  ossific  granules  are  not  as  yet  de- 
posited. At  sixteen  years  (Fig.  30)  three  secondary  centres  appear,  one  for  the  tip  of  each  trans- 
verse process,  and  one  for  the  extremity  of  the  spinous  process.  In  some  of  the  lumbar  vertebrae, 
especially  the  first,  second,  and  third,  a  second  ossifying  centre  appears  at  the  base  of  the  spinous 
process.  At  twenty-one  years  (Fig.  29)  a  thin,  circular,  epiphyseal  plate  of  bone  is  formed 
in  the  layer  of  cartilage  situated  on  the  upper  and  under  surfaces  of  the  body,  the  former  being 
the  thicker  of  the  two.  These  represent  two  additional  secondary  centres  of  ossification.  \\\ 
these  become  joined,  and  the  bone  is  completely  formed  between  the  twenty-fifth  and  thirtieth 
year  of  life. 

Exceptions  to  this  mode  of  development  occur  in  the  first,  second,  and  seventh  cervical,  and 
in  the  vertebrae  of  the  lumbar  region. 

Atlas  (Fig.  31).— The  number  of  centres  of  ossification  of  the  atlas  is  quite  variable.  It 
may  be  developed  from  iwo,  three,  four,  or  five  centres.  The  most  frequent  method  is  from 
three  centres.  Two  of  these  are  destined  for  the  two  lateral  or  neural  masses,  the  ossification 
of  which  commences  about  the  seventh  week  near  the  articular  processes,  and  extends  backward; 
these  portions  of  bone  are  separated  from  one  another  behind,  at  birth,  by  a  narrow  interval 
filled  in  with  cartilage.  Between  the  third  and  fourth  vears  they  unite  either  directly  or  through 
the  medium  of  a  separate  centre  developed  in  the  cartilage  in  the  median  line.     The  anterior 

>  By  many  observers  it  is  asserted  that  the  bodies  of  the  vertebra  are  developed  from  a  single  centre  which 
speedily  becomes  bilobed,  so  as  to  give  the  appearance  of  two  nuclei;  but  that  there  are  two  centres,  at  all  eienta 
sometimes,  is  evidenced  by  the  facts  that  the  t-s-o  h.alves  of  the  body  of  the  vertebra  may  remam  distmct 
throughout  life,  and  be  separated  by  a  fissure  through  which  a  protrusion  of  the  spinal  membrane  may  take 
place,  constituting  an  anterior  spina  bijida. 


64 


SPECIAL  ANATOMY  OF  THE  SKELETON 


arch,  at  birth,  is  altogether  cartilaginous,  and  in  this  a  separate  nucleus  appears  about  the  end 
of  the  first  year  after  birth,  and,  extending  laterally,  joins  the  neural  processes  in  front  of  the  pedi- 
cles.    Sometimes  there  are  two  centres  developed  in  the  cartilage,  one  on  either  side  of  the  median 

line,  which  join  to  form  a  single  mass. 


By  If  primary  centres. 

1  fui  hud;/  (Sih  week). 


1  for  each  lamina  (6th  weeh). 
Fig.  28. — Development  of  a  vertebra. 


I  plates. 


1  for  upper  surface  "i 
of  body, 


■  21  year^ 


,1  for  nn.der  surface 
of  body. 


By  4  secondary  centres. 


1  for  each  trans- 
verse process, 
16  years. 


2  (sometimes  1)  for  spinous  process  (16  years). 
Fig.  30 


By  S  ccnir 


anterior  arch  (1st  year), 

not  c/mstant. 


before  birth. 


6th  month. 

1  for  each  lateral  mass. 

1  for  body  (4fh  month). 
1  'for  under  surface  of 

body. 
Axis. 


jnr  tubeicles  on  supenoi  aiticulai  process. 
Fig.  33. — Lumbar  vertebra. 


And  occasionally  there  is  no  separate 
centre,  but  the  anterior  arch  is  formed 
by  the  gradual  extension  forward  and 
ultimate  junction  of  the  two  neural  pro- 
cesses. 

Axis. — The  axis  (Fig.  32)  is  developed 
by  seven  centres,  five  primarij  and  tico 
secondary.  The  body  and  arch  of  this 
bone  are  formed  in  the  same  manner  as 
the  corresponding  parts  in  the  other 
vertebrae:  one  centre  (or  two,  which 
speedily  coalesce)  for  the  lower  part  of 
the  body,  and  one  for  each  lamina. 
The  centres  for  the  laminre  appear 
about  the  seventh  or  eighth  week,  that 
for  the  body  about  the  fourth  month. 
The  odontoid  process  consists  originally 
of  an  extension  upward  of  the  cartilagi- 
nous mass  in  which  the  lower  part  of  the 
body  is  formed.  At  about  the  sixth 
month  of  fetal  life  two  centres  make 
their  appearance  in  the  base  of  this  pro- 
cess; they  are  placed  laterally,  and  join 
before  birth  to  form  a  conical  bilobed 
mass  deeply  cleft  above;  the  interval  be- 
tween the  cleft  and  the  summit  of  the 
process  is  formed  by  a  wedge-shaped 
piece  of  cartilage,  the  base  of  the  process 
being  separated  from  the  body  by  a  car- 
tilaginous interval,  which  gradually  be- 
comes ossified  at  its  circumference,  but 
remains  cartilaginous  in  its  centre  until 
advanced  age.  Finally,  the  apex  of  the 
odontoid  process  has  a  separate  (second- 
ary) centre,  which  appears  in  the  second 
year  and  joins  about  the  twelfth  year. 
In  addition  to  these  there  is  a  secondary 
centre  for  a  thin  epiphyseal  plate  on  the 
under  surface  of  the  body  of  the  bone. 

Seventh  Cervical. — The  anterior  or 
costal  part  of  the  transverse  process  of  the 
seventh  cervical  is  developed  from  a 
separate  osseous  centre  at  about  the 
sixth  month  of  fetal  life,  and  joijis  the 
body  and  posterior  division  of  the  trans- 
verse process  between  the  fifth  and  sixth 
years..  In  rare  instances  this  process 
continues  as  a  separate  piece,  and,  be- 
coming lengthened  outward,  constitutes 
what  is  known  as  a  cervical  rib.  This 
separate  ossific  centre  for  the  costal 
process  has  also  been  found  in  the  fourth, 
fifth,  and  sixth  cervical  vertebras. 

Lumbar  Vertebree.  —  The  hmibai- 
vertebrre  (Fig.  33)  have  two  additional 
centres  (besides  those  peculiar  to  the 
vertebrae  generally)  for  the  mamraillary 
tubercles,  which  project  from  the  back 
part  of  the  superior  articular  processes. 
The  transverse  process  of  the  first 
lumbar  is  sometimes  developed  as  a 
separate  piece,  which  ma}'  remain  per- 


THE  SACRAL  AND   COCCYGEAL    VETlTEBRjE 


60 


manently  unconnected  with  the  remaining  portion  of  the  bone,  thus  forming  a  himhar  rib a 

peculiarity. 

The  sacrum,  formed  by  the  union  of  five  vertebrae,  has  thirty-five  centres  of  ossification. 

The  bodies  of  the  sacral  vertebrae  have  each  three  ossific  centres — one  for  the  central  part 
and  one  for  the  epiphyseal  plates  on  its  upper  and  under  surface.  Occasionally  the  iirimary 
centres  for  the  bodies  of  the  first  and  second  piece  of  the  sacrum  are  double.  The  arch  of  each 
sacral  vertebra  is  developed  from  two  centres,  one  for  each  lamina.  These  unite  with  each  other 
behind,  and  subsequently  join  the  body. 

The  lateral  masses  have  six  additional  centres,  two  for  each  of  the  first  three  vertebrte.  These 
centres,  representing  costal  elements,  make  their  appearance  above  and  to  the  outer  side  of 
the  anterior  sacral  foramina  (Fio;.  34),  and  are  developed  into  separate  segments  (Fig.  3.5); 
they  are  subsequently  blended  with  each  other,  and  with  the  bodies  and  transverse  processes 
to  form  the  lateral  mass. 

Lastly,  each  lateral  surface  of  the  sacrum  is  developed  from  two  epiphyseal  plates  (Fig.  36) — 
one  for  the  auricular  surface,  and  one  for  the  remaining  part  of  the  thin  lateral  edge  of  the  bone. 


Additional  cetitte^ 
for  the  /i)s(  time  piei 


Two  epiphysial  lamines 
for  each  lateral  surface/'^ 


Fig.  34. — Development  of  the  sacrum. 


Period  of  Development.— At  about  the  eighth  or  ninth  week  of  fetal  life  ossification  of  the 
central  part  of  the  bodies  of  the  first  three  vertebrae  commences,  and  between  the  fifth  and 
eighth  months  in  the  last  two.  Between  the  si.xth  and  eighth  months  ossification  of  the  lamina 
takes  place;  and  at  about  the  same  period  the  centres  for  the  lateral  masses  for  the  first  three  sacral 
vertebrfe  make  their  appearance.  The  period  at  which  the  arch  becomes  completed  by  the  junc- 
tion of  the  laminae  with  the  bodies  in 
front  and  with  each  other  behind  varies 
in  different  segments.  The  junction 
between  the  laminae  and  the  bodies  takes 
place  first  in  the  lower  vertebrae  as  early 
as  the  second  year,  but  is  not  effected  in 
the  uppermost  until  the  fifth  or  sixth  year. 
About  the  sixteenth  year  the  epiphyses 
for  the  upper  and  under  surfaces  of  the 
bodies  are  formed,  and  between  the 
eighteenth  and  twentieth  years  those  for 
each  lateral  surface  of  the  sacrum  make 
their  appearance.  The  bodies  of  the 
sacral   vertebrae    are,  during   early  life, 

separated  from  each  other  by  intervertebral  disks.  At  about  the  eighteenth  year  the  two 
lowest  segments  become  joined  by  ossification  extending  through  the  disk.  This  process 
gradually  extends  upward  until  all  the  segments  become  united,  and  the  bone  is  completely 
formed  from  the  twenty-fifth  to  the  thirtieth  year  of  life. 

The  coccyx  is  developed  from  four  centres,  one  for  each  piece.  Occasionally  one  of  the  first 
three  pieces  of  this  bone  is  developed  from  two  centres,  placed  side  by  side.  The  ossific  nuclei 
make  their  appearance  in  the  following  order:  In  the  first  segment,  between  the  first  and  fourth 
years;  in  the  second  piece,  at  from  five  to  ten  years;  in  the  third,  from  ten  to  fifteen  years;  inthe 
fourth  from  fourteen  to  twenty  years.  As  age  advances  these  various  segments  become^  united 
with  each  other  from  below  upward,  the  union  between  the  first  and  second  segments  being  fre- 
quently delayed  until  after  the  age  of  twenty-five  or  thirty.  At  a  late  period  of  life,  especially  in 
females,  the  coccyx  often  becomes  ankylosed  to  the  end  of  the  sacrum. 


'arly  stage. 


66 


SPECIAL  ANATOMY  OF  THE  SKELETON 


Coccyx. 
Fig,  38. — Lateral  view  of  the  vertebral  column. 


The  Vertebral  Column  as  a  Whole. 

The  vertebral  column  (columna  verte- 
bralis),  formed  by  the  interarticulatioii  of 
the  vertebrae,  is  situated  in  the  median  line, 
in  the  posterior  part  of  the  trunk;  its  average 
length  is  about  two  feet  two  or  three  inches 
(65  to  67.5  cm.),  measuring  along  the  curved 
anterior  surface  of  the  column.  Of  this 
length,  the  cervical  part  measures  about 
five,  the  thoracic  about  eleven,  the  lumbar 
about  seven  inches,  and  the  sacrum  and 
coccyx  the  remainder.  The  female  column 
is  about  one  inch  less  than  that  of  the  male. 

Viewed  laterally  (Fig.  38),  the  spinal 
column  presents  several  curves  which  cor- 
respond to  the  different  regions  of  the 
column,  and  are  called  cervical,  thoracic, 
lumbar,  and  pelvic.  The  cervical  curve 
commences  at  the  apex  of  the  odontoid 
process,  and  terminates  at  the  middle  of 
the  second  thoracic  vertebra;  it  is  convex 
in  front,  and  is  the  least  marked  of  all 
the  curves.  The  thoracic  curve,  which  is 
concave  forward,  commences  at  the  middle 
of  the  second,  and  terminates  at  the  middle 
of  the  twelfth  thoracic  vertebra.  Its  most 
prominent  point  behind  corresponds  to  the 
spine  of  the  seventh  thoracic  vertebra.  The 
lumbar  curve  commences  at  the  middle  of 
the  last  thoracic  vertebra,  and  terminates 
at  the  sacrovertebral  angle.  It  is  convex 
anteriorly;  the  convexity  of  the  lower  three 
vertebrae  being  much  greater  than  that  of 
the  upper  two.  The  pelvic  curve  com- 
mences at  the  sacrovertebral  articulation 
and  terminates  at  the  point  of  the  coccj^x. 
It  is  concave  anteriorly.  The  thoracic  and 
pelvic  curves  are  the  primary  curves,  and 
begin-  to  be  formed  at  an  early  period  of 
fetal  life,  and  are  due  to  the  shape  of  the 
bodies  of  the  vertebrae.  The  cervical  and 
lumbar  curves  are  compensatory  or  sec- 
ondary, and  are  developed  after  birth  in 
order  to  maintain  the  erect  position.  They 
are  due  mainly  to  the  shape  of  the  in- 
tervertebral disks.  Not  uncommonly  the 
thoracic  portion  of  the  vertebral  column — 
even  in  healthy  persons — deviates  toward 
the  right.  This  is  due  to  the  position  of 
the  heart  and  of  the  arch  of  the  aorta. 

The  movable  part  of  the  vertebral  column 
presents  for  examination  an  anterior,  a  pos- 
terior, and  two  lateral  surfaces;  a  base,  a 
summit,  and  the  vertebral  canal. 


THE   VERTEBBAL   COLUMN  AS  A    WHOLE  67 

Surfaces. — The  anterior  or  ventral  surface  presents  the  bodies  of  the  vertebra; 
separated  in  the  recent  state  by  the  intervertebral  disks.  The  bodies  are  broad 
in  the  cervical  region,  narrow  in  the  upper  part  of  the  thoracic,  and  broadest  in 
the  himbar  region.  The  whole  of  this  surface  is  convex  transversely,  concave 
from  above  downward  in  the  thoracic  region,  and  convex  in  the  same  direction 
in  the  cervical  and  lumbar  regions. 

The  posterior  or  dorsal  surface  presents  in  the  median  line  the  spinous  pro- 
cesses. These  are  short,  horizontal,  with  bifid  extremities,  in  the  cervical  region. 
In  the  thoracic  region  they  are  directed  obliquely  above,  assume  almost  a  vertical 
direction  in  the  middle,  and  are  horizontal  below,  as  are  also  the  spines  of  the 
lumbar  vertebrae.  They  are  separated  by  considerable  intervals  in  the  loins, 
by  narrower  intervals  in  the  neck,  and  are  closely  approximated  in  the  middle 
of  the  thoracic  region.  On  either  side  of  the  spinous  processes,  extending  the 
whole  length  of  the  column,  is  the  vertebral  groove  formed  by  the  laminse  in  the 
cervical  and  lumbar  regions,  where  it  is  shallow,  and  by  the  laminae  and  transverse 
processes  in  the  thoracic  region,  where  it  is  deep  and  broad.  In  the  recent  state 
these  grooves  lodge  the  deep  muscles  of  the  back.  External  to  each  vertebral 
groove  are  the  articular  processes,  and  still  more  externally  are  the  transverse 
processes.  In  the  thoracic  region  the  latter  processes  stand  backward,  on  a  plane 
considerably  posterior  to  that  of  like  processes  in  the  cervical  and  lumbar  regions. 
In  the  cervical  region  the  transverse  processes  are  placed  in  front  of  the  articular 
processes,  and  on  the  outer  side  of  the  pedicles,  between  the  intervertebral 
foramina.  In  the  thoracic  region  they  are  posterior  to  the  pedicles,  inter- 
vertebral foramina,  and  articular  processes.  In  the  lumbar  region  they  are  placed 
in  front  of  the  articular  processes,  but  behind  the  intervertebral  foramina. 

The  lateral  surfaces  are  separated  from  the  dorsal  surface  by  the  articular 
processes  in  the  cervical  and  lumbar  regions,  and  by  the  transverse  processes 
in  the  thoracic  region.  These  surfaces  present  in  front  the  sides  of  the  bodies  of 
the  vertebrse,  marked  in  the  thoracic  region  by  the  facets  for  articulation  with 
the  heads  of  the  ribs.  More  posteriorly  are  the  intervertebral  foramina,  formed 
by  the  juxtaposition  of  the  intervertebral  notches,  oval  in  shape,  smallest  in  the 
cervical  and  upper  part  of  the  thoracic  regions,  and  gradually  increasing  in  size  to 
the'  last  lumbar  vertebra.  They  are  situated  between  the  transverse  processes  in  the 
neck,  and  in  front  of  them  in  the  back  and  loins,  and  transmit  the  spinal  nerves. 

Base. — The  base  of  that  portion  of  the  vertebral  column  formed  by  the 
twenty-four  movable  vertebrae  is  formed  by  the  under  surface  of  the  body  of  the 
fifth  lumbar  vertebra;  and  the  summit  by  the  upper  surface  of  the  atlas. 

Vertebral  Canal. — ^The  vertebral  canal  follows  the  different  curves  of  the  verte- 
bral column;  it  is  largest  in  those  regions  in  which  the  vertebral  column  enjoys 
the  greatest  freedom  of  movement,  as  in  the  neck  and  loins,  where  it  is  wide  and 
triangular;  and  is  narrow  and  cylindrical  in  the  back,  where  motion  is  more  limited. 

Surface  Form.— The  only  parts  of  the  vertebral  column  -svhich  lie  closely  under  the  skin,  and 
so  directly  influence  surface  form,  are  the  apices  of  the  spinous  processes.  These  are  always 
distinguishable  at  the  bottom  of  a  median  furrow,  which,  more  or  less  evident,  runs  down  the 
mesal  line  of  the  back  from  the  external  occipital  protuberance  above  to  the  middle  of  the  sacrum 
below.  Occasionally  one  of  these  processes  deviates  a  little  from  the  median  line — a  fact  to  be 
remembered  in  practice,  as  irregularities  of  this  kind  are  attendant  also  on  fracture  or  displace- 
ments of  the  vertebral  column.  In  the  cervical  region  the  furrow  is  between  the  Trapezii 
muscles;  in  the  back  and  loins  it  is  between  the  Erector  spinae  muscles.  In  the  neck  the  furrow 
is  broad,  and  terminates  in  a  conspicuous  projection,  which  is  caused  by  the  spinous  process  of 
the  seventh  cervical  vertebra  {vertebra  promincns).  Above  this  the  spinous  process  of  the  sLxth 
cervical  vertebra  may  sometimes  be  seen  projecting;  the  other  cervical  spines  are  sunken,  and 
are  not  visible,  though  the  spine  of  the  axis  can  be  felt,  and  generally  also  the  spines  of  the  third, 
fourth,  and  fifth  cervical  vertebra;.  In  the  thoracic  region  the  furrow  is  shallow,  and  durmg 
stooping  disappears,  and  then  the  spinous  processes  become  more  or  less  visible.  The  markmgs 
produced  by  these  spines  are  small  and  close  together.  In  the  lumbar  region  the  fm-row  is 
deep,  and  the  situation  of  the  lumbar  spines  is  frequently  indicated  by  little  pits,  or  depressions, 


68  SPECIAL  ANATOMY  OF  THE  SKELETON 

especially  if  the  muscles  in  the  loins  are  well  developed  and  the  process  incurved.  They  are  much 
larger  and  farther  apart  than  in  the  thoracic  region.  In  the  sacral  region  the  furrow  is  shallower, 
presenting  a  flattened  area  which  terminates  below  at  the  most  prominent  part  of  the  posterior 
surface  of  the  sacrum,  formed  by  the  spinous  processes  of  the  third  sacral  vertebra.  At  the  bottom 
of  the  furrow  may  be  felt  the  irregular  posterior  surface  of  the  bone.  Below  this,  in  the  deep 
groove  leading  to  the  anus,  the  coccyx  may  be  felt.  The  only  other  portions  of  the  vertebral 
column  which  can  be  felt  from  the  surface  are  the  transverse  processes  of  three  of  the  cervical 
vertebrae,  viz.,  the  first,  the  sLxth,  and  the  seventh.  The  transverse  process  of  the  atlas  can  be 
felt  as  a  rounded  nodule  of  bone  just  below  and  in  front  of  the  apex  of  the  mastoid  process, 
along  the  anterior  border  of  the  Sternomastoid.  The  transverse  process  of  the  sixth  cervical 
vertebra  is  of  surgical  importance.  If  deep  pressure  be  made  in  the  neck  in  the  course  of  the 
carotid  artery,  opposite  the  cricoid  cartilage,  the  prominent  anterior  tubercle  of  the  transverse 
process  of  the  sixth  cervical  vertebra  can  be  felt.  This  has  been  named  Chassaignac's  tubercle, 
and  against  it  the  carotid  artery  may  be  most  conveniently  compressed  by  the  finger.  The 
transverse  process  of  the  seventh  cervical  vertebra  can  also  often  be  felt.  Occasionally  the  ante- 
rior root,  or  costal  process,  is  large  and  separate,  forming  a  cervical  rib. 

Applied  Anatomy. — It  is  frequently  necessary  to  locate  certain  vertebr».  Several  of  them 
can  be  easily  found  and  identified.  The  seventh  cervical  spine  is  conspicuously  prominent,  and 
when  the  skin  over  it  has  been  marked  with  a  blue  pencil  the  spine  of  the  sixth  cervical  above  and 
of  the  first  thoracic  below  may  be  located.  The  spine  of  the  third  thoracic  vertebra  is  on  a  level 
with  the  root  of  the  spine  of  the  scapula.  The  spine  of  the  fourth  lumbar  vertebra  is  on  a  level 
with  the  highest  point  of  the  iliac  crest.  When  one  or  two  vertebrae  have  been  definitely  recog- 
nized the  other  ones  can  be  found  by  counting  the  spines  from  a  fixed  point  or  from  fixed  points. 
Over  the  fifth  lumbar  spine  there  is  no  prominence,  but  a  depression.  The  third  sacral  spine 
is  on  a  level  with  the  posterior  superior  spines  of  the  ilium.  The  level  at  which  the  spinal  cord 
terminates  should  be  known  to  the  surgeon  if  he  proposes  to  tap  the  spinal  theca  {lumbar  punc- 
ture) for  diagnostic  or  therapeutic  purposes  or  for  spinal  anesthesia.  In  an  adult  the  cord  terminates 
at  the  lower  border  of  the  first  lumbar  vertebra,  and  the  theca  terminates  opposite  the  body  of  the 
third  sacral  vertebra.  In  a  young  child  the  cord  terminates  opposite  the  body  of  the  third  lumbar 
vertebra,  and  the  theca  ends  at  about  the  same  level  as  in  an  adult.  Hence,  in  either  a  child 
or  an  adult,  a  puncture  below  the  level  of  the  fourth  lumbar  vertebra  will  infiict  no  injury  upon 
the  cord.  In  children  the  puncture  is  made  just  beneath  the  spinous  process,  and  in  adults 
about  one-half  an  inch  to  either  side  of  the  spinous  process,  although  the  needle  should  be  made 
to  enter  the  dura  in  the  median  line.  In  either  case  the  needle  is  directed  upward  and  forward. 
As  previously  pointed  out,  the  surgical  anatomy  of  an  infant's  spine  is  not  identical  with  the  sur- 
gical anatomy  of  an  adult's  spine.  The  umbilicus  of  an  infant  is  opposite  the  body  of  the  fourth 
lumbar  vertebra;  in  an  adult  it  is  opposite  the  spinous  process  of  the  third  lumbar  vertebra. 
In  an  infant  the  base  of  the  sternum  is  on  a  level  with  the  top  of  the  seventh  cervical  spine,  and 
in  an  adult  of  the  second  thoracic  spine  (A.  H.  Tubby).  The  vertebral  column  may  be  the  seat 
of  tuberculosis,  which  may  destroy  the  bodies  of  the  vertebrae;  in  such  cases  a  deflection  of  the 
column  may  be  directed  either  forward  or  backward.  This  deflection  is  produced  by  the  great 
weight  of  the  trunk  on  the  diseased  bone.  If  the  deflection  is  directed  forward,  it  is  called 
lordosis;  if  backward,  kyphosis.  Scoliosis  (lateral  deviation  of  the  vertebral  column)  is  usually 
due  to  a  faulty  attitude  of  children  while  standing  or  while  sitting  at  school  desks. 

Occasionally  the  coalescence  of  the  laminfe  is  not  completed,  and  consequently  a  cleft  is  left 
in  the  arches  of  the  vertebrae,  through  which  a  protrusion  of  the  spinal  membranes  (dura  mater 
and  arachnoid),  and  sometimes  of  the  spinal  cord  itself,  takes  place,  constituting  a  malformation 
known  as  spina  bifida  or  hydrorhacliitis.  This  condition  is  most  common  in  the  lumbosacral 
region ;  but  it.  may  occur  in  the  thoracic  or  cervical  region,  or  the  arches  throughout  the  whole 
length  of  the  canal  may  remain  unapproximated.  In  some  rare  cases,  in  consequence  of  the 
noncoalescence  of  the  two  primary  centres  from  which  the  body  is  formed,  a  similar  condition 
may  occur  in  front  of  the  canal,  the  bodies  of  the  vertebrae  being  found  cleft  and  the  tumor 
projecting  into  the  thorax,  abdomen,  or  pelvis,  between  the  lateral  halves  of  the  bodies  aft'ected. 

The  construction  of  the  spinal  column  of  a  number  of  pieces,  securely  connected  together 
and  enjoying  only  a  slight  degree  of  movement  between  any  two  individuals  pieces,  though 
permitting  of  a  very  considerable  range  of  movement,  as  a  whole,  allows  a  sufficient  degree  of 
mobility  without  any  material  diminution  of  strength.  The  main  joints  of  which  the  spine  is 
composed,  together  with  the  very  varied  movements  to  which  it  is  subjected,  render  it  liable  to 
sprains,  which  may  complicate  other  injuries  or  may  exist  alone;  but  so  closely  are  the  individual 
vertebrae  articulated  that  these  sprains  are  seldom  severe,  and  an  amount  of  violence  sufficiently 
great  to  produce  tearing  of  the  ligaments  would  tend  to  cause  a  dislocation  or  fracture.  The 
further  safety  of  the  column  and  its  less  liability  to  injury  is  provided  for  by  its  disposition  in 
curves  instead  of  in  one  straight  line.  For  it  is  an  elastic  column,  and  must  first  bend  before 
it  breaks;  under  these  circumstances,  being  made  up  of  three  curves,  it  represents  three  columns, 
and  greater  force  is  required  to  produce  bending  of  a  short  column  than  of  a  longer  one  that  is 
equal  to  it  in  breadth  and  material.  Again,  the  safety  of  the  column  is  provided  for  by  the  inter- 
position of  the  intervertebral  disks  between  the  bodies  of  the  vertebrae,  which  act  as  admirable 


THE  SKULL 


69 


buffers  in  counteracting  the  effects  of  violent  jars  or  shocks.  Fracture  didncation  of  the  verteliral 
column  may  be  caused  by  direct  or  indirect  violence,  or  by  a  combination  of  the  two,  as  when 
a  person  falling  from  a  height  strikes  against  some  prominence  and  is  doubled  over  it.  The 
fractures  from  indirect  violence  are  the  more  common,  and  here  the  bodies  of  the  vertebrte  are 
compressed,  while  the  arches  are  torn  asunder;  while  in  fractures  from  direct  violence  the  arches 
are  compressed  and  the  bodies  of  the  vertebrae  separated  from  each  other.  It  will  therefore  be 
seen  that  in  both  classes  of  injury  the  spinal  cord  is  the  part  least  likely  to  be  injured,  and  may 
escape  damage  even  when  there  has  been  considerable  lesion  of  the  bony  framework.  For,  as 
Mr.  Jacobson  states,  "being  lodged  in  the  centre  of  the  column,  it  occupies  neutral  ground  in 
•respect  to  forces  which  might  cause  fracture.  For  it  is  a  law  in  mechanics  that'  when  a  beam, 
as  of  timber,  is  exposed  to  breakage  and  the  force  does  not  exceed  the  limits  of  the  strength  of 
the  material,  one  division  resists  compression,  another  laceration  of  the  particles,  while  the  third, 
between  the  two,  is  in  a  negative  condition."'  Applying  this  principle  to  the  vertebral  column, 
it  will  be  seen  that,  whether  the  fracture  dislocation  be  produced  by  direct  violence  or  by  indirect 
force,  one  segment,  either  the  anterior  or  posterior,  will  be  exposed  to  compression,  the  other  to 
laceration,  and  the  intermediate  part,  where  the  cord  is  situated,  will  be  in  a  neutral  state.  When 
a  fracture  dislocation  is  produced  by  indirect  violence  the  displacement  is  almost  always  the  same, 
the  upper  segment  being  driven  forward  on  the  lower,  so  that  the  cord  is  compressed  between  the 
body  of  the  .vertebra  below' and  the  arch  of  the  vertebra  above. 

The  parts  of  the  vertebral  column  most  liable  to  be  injured  are  (1)  the  thoracolumbar  region, 
for  this  part  is  near  the  middle  of  the  column,  and  there  is  therefore  a  greater  amount  of  leverage, 
and,  moreover,  the  portion  above  is  comparatively  fixed,  and  the  vertebrae  which  form  it,  though 
much  smaller,  have  nevertheless  to  bear  almost  as  great  a  weight  as  those  below;  (2)  the  cervico- 
thoracic  region,  because  here  the  flexible  cervical  portion  of  the  vertebral  column  joins  the  more 
fixed  thoracic  region;  and  (3)  the  atlantoaxial  region,  because  it  enjoys  an  extensive  range  of 
movement,  and,  being  near  the  skull,  is  influenced  by  violence  applied  to  the  head.  In  fracture 
dislocation,  spinous  processes  and  portions  of  the  laminae  may  be  removed  {laminectomy)  in  order 
to  free  the  spinal  cord  from  pressure,  and  to  permit  the  surgeon  to  explore,  to  arrest  hemorrhage, 
to  remove  bone  fragments,  or  to  apply  sutures.  Laminectomy  is  also  resorted  to  in  some  cases 
of  paraplegia  due  to  Pott's  disease  of  the  spine. 

THE  SKULL. 

The  Skull,  or  superior  expansion  of  the  vertebral  cohimn,  has  been  described 
as  if  composed  of  four  vertebrae,  the  elementary  parts  of  which  are  specially 
modified  in  form  and  size,  and  almost  immovably  connected,  for  the  reception 
of  the  brain  and  special  organs  of  the  senses.  These  vertebrae  are  the  occipital 
parietal,  frontal,  and  nasal.  Descriptive  anatomists,  however,  divide  the  skull 
into  two  parts,  the  Cranium  and  the  Face.  The  Cranium  is  composed  of  eight 
bones,  viz.,  the  occipital,  two  parietals,  frontal,  two  temporals,  sphenoid,  and  ethmoid. 
The  Face  is  composed  of  fourteen  bones,  viz.,  the  two  nasals,  two  maxillce,  two 
lacrimals,  two  malars,  two  palates,  two  turbinates,  vomer,  and  mandible.  The  ossic- 
uli  auditus,  the  teeth,  and  Wormian  hones  are  not  included  in  this  enumeration. 

Occipital. 


Skull,  22  bones 


Two  parietals. 
Cranium,  8  bones   .       ^    Twftemporals. 


Sphenoid. 
L  Ethmoid. 
f  Two  nasals. 

Two  maxillae. 

Two  lacrimals. 

r,        ,  .  J  I    Two  malars. 

Face,  14  bones  .      .       <   ^^^,^  ^.^^^^^^ 

Two  turbinates. 
I    Vomer. 
L  Mandible. 

The  Hyoid  Bone,  situated  at  the  root  of  the  tongue  and  attached  to  the  base 
of  the  skull  by  ligaments,  has  also  to  be  considered  in  this  section. 

'  Holmes'  System  of  Surgery,  1883,  vol.  i,  p.  529. 


70 


SPECIAL  ANATOMY  OF  THE  SKELETON 


THE    CEREBRAL    CRANIUM    (CRANIUM    CEREBRALE) 
The  Occipital  Bone  (Os  Occipitale). 

The  occipital  bone  is  situated  at  the  back  part  and  base  of  the  cranium,  is  curved 
on  itself,  and  is  trapezoidal  in  shape.  The  bone  presents  for  examination  two 
surfaces,  four  borders,  and  four  angles. 

Surfaces. — The  external  surface  is  convex.  Midway  between  the  summit 
of  the  bone  and  the  posterior  margin  of  the  foramen  magnum — a  large  oval 
opening  for  transmission  of  the  spinal  cord — is  a  prominent  tubercle,  the  external 
occipital  protuberance  { protuberantia  occipitalis  externa),  and,  descending  from  it 


Lmea 
sup) 


as  far  as  the  foramen,  a  vertical  ridge,  the  external  occipital  crest  (crista  occipitalis 
externa).  This  protuberance  and  crest  give  attachment  to  the  ligamentum  nuchae 
and  Trapezius,  and  vary  in  prominence  in  different  skulls.  Passing  outward  from 
the  occipital  protuberance  is  a  semicircular  ridge  on  each  side,  the  superior  curved 
line  (linea  niiclme  superior).  Above  this  line  there  is  often  a  second  less  distinctly 
marked  ridge,  called  the  highest  curved  line  (linea  nuchae  suprema);  to  it  tlie 
epicranial  aponeurosis  is  attached.  The  bone  between  these  two  lines  is  smoother 
and  denser  than  the  rest  of  the  surface.  Running  parallel  with  these  from  the 
middle  of  the  crest  is  another  semicircular  ridge,  on  each  side,  the  inferior  curved 
line  (linea  nuchae  inferior).  The  surface  of  the  bone  above  the  linea  suprema  is 
rough  and  porous,  and  in  the  recent  state  is  covered  by  the  Occipitofrontalis 
muscle.  The  superior  and  inferior  curved  lines,  together  with  the  surfaces  of 
bone  between  and  below  them,  serve  for  the  attachment  of  several  muscles. 


THE  OCCIPITAL  BONE 


71 


The  superior  curved  line  gives  attachment  internally  to  the  Trapezius,  externally 
to  the  muscular  origin  of  the  Occipitofrontalis,  and  to  the  Sternomastoid  to  the 
extent  shown  in  Fig.  39;  the  depressions  between  the  curved  lines  to  the  Com- 
plexus  internally,  the  Splenius  capitis  and  Obliquus  capitis  superior  externally. 
The  inferior  curved  line  and  the  depressions  below  it  afford  insertion  to  the  Rectus 
capitis  posticus,  major  and  minor. 

The  foramen  magnum  {foramen  occipitale  magnum)  is  a  large,  oval  apertiu'e, 
its  long  diameter  extending  from  before  backward.  It  transmits  the  lower  por- 
tion of  the  medulla  oblongata  and  its  membranes,  the  spinal  part  of  the  spinal 
accessory  nerves,  the  vertebral  arteries,  the  anterior  and  posterior  spinal  arteries, 
and  the  occipitoaxial  ligaments.  Its  back  part  is  wide  for  the  transmission  of 
the  medulla  oblongata,  and  the  corresponding  margin  rough  for  the  attachment 
of  the  dura  enclosing  it;  the  fore  part  is  narrower,  being  encroached  upon  by  the 
condyles;  it  has  projecting  toward  it,  from  below,  the  odontoid  process,  and  its 
margins  are  smooth  and  bevelled  internally  to  support  the  meclulla  oblongata. 
On  each  side  of  the  foramen  magnum  are  the  condyles  for  articulation  with  the 
atlas.  Each  condyle  (condylus  occipitalis)  is  convex,  oval,  or  reniform  in  shape, 
and  directed  downward  and  outward.  The  condyles  converge  in  front,  and 
encroach  slightly  upon  the  anterior  segment  of  the  foramen.  On  the  inner  border 
of  each  condyle  is  a  rough  tubercle  for  the  attachment  of  the  ligaments  (check) 
which  connect  this  bone  with  the  odontoid  process  of  the  axis;  while  external  to 
tliem  is  a  rough  tubercular  prominence,  the  transverse  or  jugular  process  (processus 
jugularis),  channelled  in  front  by  a  deep  notch  (incisura  jugularis),  which  forms, 
part  of  the  jugular  foramen  (foramen  lacerum  posterius).  The  under  surface  of 
this  process  presents  an  eminence  (processus  intrajugularis) ,  which  represents  the 
paramastoid  process  of  some  mammals.  The  eminence  is  occasionally  large,  and 
extends  as  low  as  the  transverse  process  of  the  atlas.  This  surface  affords  attach- 
ment to  the  Rectus  capitis  lateralis  muscle  and  to  the  lateral  occipitoatlantal 
ligament;  its  upper  or  cerebral  surface  presents  a  deep  groove,  which  lodges  part 
of  the  lateral  sinus,  while  its  external  surface  is  marked  by  a  quadrilateral  rough 
facet,  covered  with  cartilage  in  the  fresh  state,  and  articulating  with  a  similar 
surface  on  the  petrous  portion  of  the  temporal  bone.  On  the  outer  side  of  each 
condyle,  near  its  fore  part,  is  a  foramen,  the  anterior  condylar  foramen  (canalis 
hypoglossi);  it  is  directed  downward,  outward,  and  forward,  and  transmits  the 
hypoglossal  nerve,  and  occasionally  a  meningeal  branch  of  the  ascending  pharyn- 
geal artery.  This  foramen  is  sometimes  double.  Behind  each  condyle  is  a 
fossa^  (fossa  condyloideus),  sometimes  perforated  at  the  bottom  by  a  foramen, 
the  posterior  condylar  foramen  (canalis  condyloideus),  for  the  transmission  of  a 
vein  to  the  lateral  sinus.  The  basilar  process  (pars  basilaris)  is  a  strong  quadri- 
lateral plate  of  bone,  which  is  wider  behind  than  in  front,  and  is  situated  in  front 
of  the  foramen  magnum.  Its  under  surface  is  rough,  presents  in  the  median  line 
a  tubercular  ridge,  the  pharyngeal  spine  {tuherculuni  pharyngeum),  for  the  attach- 
ment of  the  tendinous  raph^and  Superior  constrictor  of  the  pharynx,  and  on  each 
side  of  it  rough  depressions  for  the  attachment  of  the  Rectus  capitis  anticus, 
major  and  minor. 

The  internal  surface  (Fig.  40)  is  deeply  concave.  The  posterior  part  is  divided 
by  a  crucial  ridge  into  four  fossa?.  The  two  superior  fossa;  receive  the  occipital 
lobes  of  the  cerebrum,  and  present  slight  eminences  and  depressions  corresponding 
to  their  convolutions.  The  two  inferior,  which  receive  the  hemispheres  of  the 
cerebellum,  are  larger  than  the  former,  and  comparatively  smooth ;  both  are  marked 
by  slight  grooves  for  the  lodgement  of  arteries.     At  the  point  of  meeting  of  the  four 

>  This  fossa  presents  many  variations  in  size.  It  is  usually  shallow,  and  the  foramen  small;  occasionally 
wanting  on  one  or  both  sides.  Sometimes  both  fossa  and  foramen  are  large,  but  confined  to  one  side  only;  more 
rarely,  the  fossa  and  foramenare  very  large  on  both  sides. 


72 


SPECIAL  ANATOMY  OF  THE  SKELETON 


divisions  of  the  crucial  ridge  is  an  eminence,  the  intemal  occipital  protuberance  {yro- 
tuberantia  occipitalis  interna).  It  nearly  corresponds  to  that  on  the  outer  surface, 
though  it  is  often  on  a  slightly  higher  level,  and  is  perforated  by  one  or  more 
large  vascular  foramina.  From  this  eminence  the  superior  division  of  the  crucial 
ridge  runs  upward  to  the  superior  angle  of  the  bone;  it  presents  a  deep  groove, 
.the  sagittal  sulcus  (sulcus  sagittalis),  for  the  superior  saggittal  sinus.  The 
margins  of  the  groove  give  attachment  to  the  falx  cerebri.  The  inferior  division, 
the  intemal  occipital  crest  (crista  occipitalis  interna),  runs  to  the  posterior  margin 
of  the  foramen  magnum,  on  the  edge  of  which  it  becomes  gradually  lost;  this 


Superior 


Inferior  angle. 
Fig.  40, — Occipital  bone.     Inner  surface. 

ridge,  which  is  bifurcated  below,  serves  for  the  attachment  of  the  falx  cerebelli. 
It  is  usually  marked  by  a  single  groove,  which  commences  at  the  back  part  of 
the  foramen  magnum  and  lodges  the  occipital  sinus.  Occasionally  the  groove 
is  double  where  two  sinuses  exist.  A  transverse  groove  (sulcus  transversus)  passes 
outward  on  each  side  to  the  lateral  angle.  The  grooves  are  deep  channels  for 
the  lodgement  of  the  lateral  sinuses,  their  prominent  margins  affording  attachment 
to  the  tentorium.^  At  the  point  of  meeting  of  these  grooves  is  a  depression, 
the  torcular^  (confluens  sinuum),  placed  a  little  to  one  or  the  other  side  of  the  internal 

1  Usually  one  of  the  transverse  grooves  is  deeper  and  broader  than  the  other;  occasionally,  both  grooves  are 
of  equal  depth  and  breadth,  or  both  equally  indistinct.     The  broader  of  the  two  transverse  grooves  is  nearly 

•always  continuous  with  the  vertical  groove  for  the  superior  sagittal  sinus, 

2  The  columns  of  blood  coming  in  different  directions  were  supposed  to  be  pressed  together  at  this  point 
iiorcular,  a  wine  press). 


THE  OCCIPITAL  BONE  73 

occipital  protuberance.  More  anteriorly  is  the  foramen  magnum,  and  on  each 
side  of  it,  but  nearer  its  anterior  than  its  posterior  part,  the  internal  openinn's 
of  the  anterior  condylar  foramen.  On  the  superior  aspect  of  the  lateral  portion 
of  the  bone  the  jugular  tubercle  (tuherculum  jugulare)  is  seen.  This  corresponds 
to  the  portion  of  bone  which  roofs  in  the  anterior  condylar  foramen.  The 
internal  openings  of  the  posterior  condylar  foramina  are  a  little  external  and 
posterio  ■  to  the  openings  of  the  anterior  condylar  foramina,  protected  by  a  small 
arch  of  bone.  At  this  part  of  the  internal  surface  there  is  a  very  deep  groove  in 
which  the  posterior  condylar  foramen,  when  it  exists,  has  its  termination.  This 
groove  is  continuous,  in  the  complete  skull,  with  the  transverse  groove  on  the 
posterior  part  of  the  bone,  and  lodges  the  end  of  the  lateral  sinus.  In  front 
of  the  foramen  magnum  is  the  basilar  process,  presenting  a  shallow  depression, 
the  basilar  groove  (clivus),  which  slopes  from  behind,  upward  and  forward,  and 
supports  the  medulla  oblongata  and  part  of  the  pons  (Varolii),  and  on  each  side 
of  the  basilar  process  is  a  narrow  channel,  which,  when  united  with  a  similar 
channel  on  the  petrous  portion  of  the  temporal  bone,  forms  a  groove  (sulcus 
peiros'us  inferior),  which  lodges  the  inferior  petrosal  sinus. 

Borders. — The  superior  border  (viargo  lambdoideus).  extends  on  each  side 
from  the  superior  to  the  lateral  angle,  is  deeply  serrated  for  articulation  with  the 
parietal  bone,  and  forms,  by  this  union,  the  lambdoid  suture. 

The  inferior  border  extends  from  the  lateral  to  the  inferior  angle;  its  upper  half 
(marcjo  mastoideus)  is  rough,  and  articulates  with  the  mastoid  portion  of  the  tem- 
poral, forming  the  masto-occipital  suture;  the  inferior  half  articulates  with  the 
petrous  portion  of  the  temporal,  forming  the  petro-occipital  suture ;  these  two  por- 
tions are  separated  from  each  other  by  the  jugular  process.  In  front  of  this 
process  is  a  deep  notch,  which  with  a  similar  one  on  the  petrous  portion  of  the 
temporal  forms  the  jugular  foramen  (foramen,  lacerum  posterius).  This  notch 
is  occasionally  subdivided  into  two  parts  by  a  small  process  of  bone  (processus 
intrajugularis) ,  and  it  generally  presents  an  aperture  at  its  upper  part,  the  internal 
opening  of  the  posterior  condylar  foramen. 

Angles.. — The  superior  angle  is  received  into  the  interval  between  the  posterior 
superior  angles  of  the  two  parietal  bones;  it  corresponds  with  that  part  of  the 
skull  in  the  fetus  which  is  called  the  posterior  fontanelle. 

The  inferior  angle  is  represented  by  the  square-shaped  surface  of  the  basilar 
process.  At  an  early  period  of  life  a  layer  of  cartilage  separates  this  part  of 
the  bone  from  the  sphenoid,  but  in  the  adult  the  union  between  them  is  osseous. 

The  lateral  angles  correspond  to  the  outer  ends  of  the  transverse  grooves,  and 
are  received  into  the  interval  between  the  posterior  inferior  angles  of  the  parietal 
and  the  mastoid  portion  of  the  temporal. 

Structure. — The  occipital  bone  consists 
of  two  compact  laminse,  called  the  outer 
and  inner  tables,  having  between  them 
the  diploic  tissue;  this  bone  is  especially 
thick  at  the  ridges,  protuberances,  con- 
dyles, and  anterior  part  of  the  basilar 
process;  while  at  the  bottom  of  the  fossae, 
especially  the  inferior,  it  is  thin,  semitrans- 
parent,  and  destitute  of  diploe. 

Development  (Fig.  41).— At  birth  the 
bone  consists  of  four  distinct  parts — a 
tabular    or    squamous     portion,    which  \&f^ -1  for  basilar  portion.    ,. 

lies   behind    the    foramen    magnum;  two       ^      ,,      x,      ,    ^^"^  j.    r       ■  •»  i  v,  -r =o„o„ 

,    ,.  ,  ■  I      P  P       ■  ,  ,.        Fig.  41. — Development  of  occipital  bone.     From  seven 

condylic  parts,  which   form  the  sides  01  centres, 

the  foramen;   and  a  basilar  part,  which 

lies  in  front  of  the  foramen.  The  tabular  portion  is  usually  developed  from  four  centres,  though 
the  number  may  vary  from  one  to  eight;  two  centres  appear  near  the  median  line  of  the  bone 


74  SPECIAL  ANA  TOMY  OF  THE  SKELETON 

during  the  second  month,  and  two  more  a  little  lateral  to  the  preceding  during  the  third  month. 
These  parts  tend  to  unite,  but  complete  union  does  not  occur  until  about  the  fourth  month  after 
birth.  That  part  of  the  tabular  portion  above  the  highest  curved  line  is  developed  by  the 
iidramembranous  method,  and  may  exist  in  the  adult  as  a  separate  element,  the  interparietal 
bone,  or  os  incae,  because  of  its  frequent  occurrence  in  Peruvian  skulls.  The  remainder  of 
the  tabular  portion  and  the  basilar  and  two  condyloid  parts  are  developed  from  cartilage. 
Usually  two  centres  appear  in  the  basilar  portion  during  the  sixth  fetal  week,  and  by  rapid 
coalescence  give  the  appearance  of  a  single  centre.  Each  condylic  portion  develops  from  a 
single  centre  that  appears  at  about  the  end  of  the  eighth  fetal  week.  At  about  the  fourth 
year  the  tabular  and  the  two  condyloid  pieces  unite,  and  about  the  sixth  year  the  bone 
consists  of  a  single  piece.  Between  the  eighteenth  and  twenty-fifth  years  the  occipital  and 
sphenoid  become  united,  forming  a  single  bone. 

Articulations. — With  six  bones — two  parietal,  two  temporal,  sphenoid,  and  atks. 

Attachment  of  Muscles. — To  twelve  pairs — to  the  superior  curved  line  are  attached  the 
Occipitofrontalis,  Trapezius,  and  Sternomastoid.  To  the  space  between  the  curved  lines,  the 
Complexus,^  Splenius  capitis,  and  Obliquus  capitis  superior;  to  the  inferior  curved  line,  and 
the  space  between  it  and  the  foramen  magnum,  the  Rectus  capitis  posticus,  major  and  minor; 
to  the  transverse  process,  the  Rectus  capitis  lateralis;  and  to  the  basilar  process,  the  Rectus 
capitis  anticus,  major  and  minor,  and  Superior  constrictor  of  the  pharynx. 


The  Parietal  Bone  (Os  Parietale). 

The  parietal  bones  are  paired  bones,  and  form,  by  their  union,  the  sides  and 
roof  of  the  cranium  proper.  Each  bone  is  of  an  irregular  quadrilateral  form, 
and  presents  for  examination  two  surfaces,  four  borders,  and  four  angles. 

Surfaces. — The  external  surface  (fades  parietalis)  (Fig.  42)  is  convex,  smooth,  and 
marked  about  its  centre  by  an  eminence  called  the  parietal  eminence  {tuber  parietale), 
which  indicates  the  point  where  ossification  commenced.  Crossing  the  middle 
of  the  bone  in  an  antero-posterior  direction  are  two  well-marked  curved  ridges, 
the  upper  and  lower  temporal  ridges  (linea  temporalis  superior  et  inferior-) ;  the  former 
gives  attachment  to  the  temporal  fascia,  while  the  latter  indicates  the  upper  limit 
of  the  origin  of  the  Temporal  muscle.  These  lines  form  the  temporal  crest. 
Above  these  ridges  the  surface  of  the  bone  is  covered  by  the  aponeurosis  of  the 
Occipitofrontalis;  below  them  the  bone  forms  part  of  the  temporal  fossa,  and 
affords  attachment  to  the  temporal  muscle.  At  the  back  part, of  the  superior 
border,  close  to  the  sagittal  suture,  which  separates  the  two  parietal  bones,  is  a 
small  foramen  (foramen  parietale),  which  transmits  the  emissary  vein  of  Santorini 
to  the  scalp  from  the  superior  sagittal  sinus.  It  sometimes  also  transmits  a 
small  branch  of  the  occipital  artery.  Its  existence  is  not  constant,  and  its  size 
varies  considerably. 

The  internal  or  cerebral  surface  (fades  cerebralis')  (Fig.  43)  is  concave,  presents 
depressions  for  the  lodgement  of  the  convolutions  of  the  cerebrum,  and  numerous 
furrows  for  the  branches  of  the  middle  meningeal  artery;  the  latter  runs  upward 
and  backward  from  the  anterior  inferior  angle  and  from  the  central  and  posterior 
part  of  the  lower  border  of  the  bone.  Sometimes  a  distinct  canal  exists  for  the 
artery,  but  it  never  remains  a  canal  for  a  long  distance.  Along  the  upper  .margin 
of  the  bone  is  part  of  a  shallow  groove,  which,  when  joined  to  the  opposite  parietal, 
forms  a  channel  for  the  superior  sagittal  sinus.  The  elevated  edges  of  the  groove 
afford  attachment  to  the  falx  cerebri.  Near  the  groove  are  seen  several  depres- 
sions. Pacchionian  depressions  (foveolae  granulares  [Pacchioni]).  They  are  most 
frequently  foimd  in  the  skulls  of  old  persons,  and  lodge  the  arachnoid  villi  (Pacchi- 
onian bodies).  The  interna!  opening  of  the  parietal  foramen  is  also  seen  when 
that  aperture  exists.  On  the  inner  surface  of  the  posterior  inferior  portion  of 
the  bone  is  a  portion  of  the  groove  for  the  lodgement  of  the  lateral  sinus. 

*  To  these  the  Biventer  cervicis  should  be  added,  if  it  is  regarded  as  a  separate  muscle. 


THE  PARIETAL  BONE 


75 


occipital  bone. 


of  te-Ki-V 
Fig.  42. — Left  parietal  bone.     External  surface. 


Fig.  43. — Left  parietal  bone.      Internal  surface. 


76  SPECIAL  ANATOMY  OF  THE  SKELETON 

Borders. — The  superior  border  (margo  sagiUalis),  the  longest  and  thickest, 
is  dentated  to  articulate  with  its  fellow  of  the  opposite  side,  forming  the  sagittal 
suture. 

The  inferior  border  (niargo  squamosus)  is  divided  into  three  parts;  of  these, 
the  anterior  is  thin  and  pointed,  bevelled  at  the  expense  of  the  outer  surface,  and 
overlapped  by  the  tip  of  the  greater  wing  of  the  sphenoid;  the  middle  portion  is 
arched,  bevelled  at  the  expense  of  the  outer  surface,  and  overlapped  by  the 
squamous  portion  of  the  temporal;  the  posterior  portion  is  thick  and  serrated  for 
articulation  with  the  mastoid  portion  of  the  temporal. 

The  anterior  border  [margo  frontalis),  deeply  serrated,  is  bevelled  at  the  expense 
of  the  outer  surface  above  and  of  the  inner  below;  it  articulates  with  the  frontal 
bone,  forming  the  coronal  suture. 

The  posterior  border  (margo  occipitalis),  deeply  denticulated,  articulates  with 
the  occipital,  forming  the  lambdoid  suture. 

Angles. — The  anterior  superior  angle  (angulus  frontalis),  thin  and  pointed, 
corresponds  with  that  portion  of  the  skull  which  in  the  fetus  is  membranous,  and 
is  called  the  anterior  fontanelle  {bregma). 

The  anterior  inferior  angle  (angulus  sphenoidalis)  is  thin  and  lengthened,  being 
received  in  the  interval  between  the  greater  wing  of  the  sphenoid  and  the  frontal. 
Its  inner  surface  is  marked  by  a  deep  groove,  sometimes  a  canal,  for  the  anterior 
branch  of  the  middle  meningeal  artery.  At  the  anterior  inferior  angle  the  parietal 
and  frontal  bones  and  the  greater  wing  of  the  sphenoid  bone  meet.  This  spot  is 
called  the  pterion. 

The  posterior  superior  angle  (angulus  occipitalis)  corresponds  with  the  junction 
of  the  sagittal  and  lambdoid  sutures.  In  the  fetus  this  part  of  the  skull  is  mem- 
branous, and  is  called  the  posterior  fontanelle  (lambda). 

The  posterior  inferior  angle  (angulus  mastoideus)  articulates  with  the  mastoid 
portion  of  the  temporal  bone,  and  generally  presents  on  its  inner  surface  a  broad, 
shallow  groove  for  the  lodgement  of  part  of  the  lateral  sinus. 

Development. — The  parietal  bone  is  formed  in  membrane,  being  developed  from  one  centre, 
which  corresponds  with  the  parietal  eminence,  and  makes  its  first  appearance  about  the  seventh 
or  eighth  week  of  fetal  life.  Ossification  gradually  extends  from  the  centre  to  the  circumference 
of  the  bone;  the  angles  are  consequently  the  parts  last  formed,  and  it  is  in  their  situation  that  the 
fontanelles  exist  previous  to  the  completion  of  the  growth  of  the  bone.  Occasionally  the  parietal 
bone  is  divided  into  two  parts,  upper  and  lower,  by  an  antero-posterior  suture. 

Articulations. — With  five  bones — the  opposite  parietal,  the  occipital,  frontal,  temporal,  and 
sphenoid. 

Attachment  of  Muscles.— 0»e  only,  the  Temporal.  ^ 


The  Frontal  Bone  (Os  Frontale). 

The  frontal  bone  consists  of  two  portions — a  vertical  or  frontal  portion,  situated 
at  the  anterior  part  of  the  cranium  proper,  forming  the  forehead;  and  a  horizontal 
or  orbital  portion,  which  enters  into  the  formation  of  the  roof  of  the  orbits  and 
nasal  fossae. 

Vertical  Portion.  Surfaces. — External  Surface  (fades  frontalis)  (Fig.  44). — In 
the  median  line,  traversing  the  bone  from  the  upper  to  the  lower  part,  is  occasionally 
seen  a  slightly  elevated  ridge,  and  in  young  subjects  a  suture  (frontal  or  metopic 
suture)  which  represents  the  line  of  union  of  the  two  lateral  halves  of  which  the  bone 
consists  at  an  early  period  of  life;  in  the  adult  this  suture  is  usually  obliterated  and 
the  bone  forms  one  piece.  On  either  side  of  this  ridge,  a  little  below  the  centre  of 
the  bone,  is  a  rounded  prominence,  the  frontal  eminence  (tuber  frontale).  These 
eminences  vary  in  size  in  different  individuals,  and  are  occasionally  unsymmetrica! 


THE  FRONTAL  BONE 


77 


in  the  same  subject.  The  whole  surface  of  the  bone  above  this  part  is  sinootli, 
and  covered  by  the  aponeurosis  of  the  Occipitofrontalis  muscle.  Below  the  frontal 
eminence  and  separated  from  it  by  a  slight  groove  is  the  superciliary  ridge  (arcus 
super ciliar is),  broad  internally,  where  it  is  continuous  with  the  nasal  eminence, 
but  less  distinct  as  it  arches  outward.  These  ridges  are  caused  by  the  projection 
outward  of  the  frontal  air  sinuses/  and  give  attachment  to  the  Orbicularis 
palpebrarum  and  Corrugator  supercilii.  Between  the  two  superciliary  ridges 
is  a  smooth,  flat  surface,  the  glabella.  Beneath  the  superciliary  ridge  is  the 
supraorbital  arch  (margo  supraorbitalis),  a  curved  and  prominent  margin,  which 
forms  the  upper  boundary  of  the  orbit  and  separates  the  vertical  fi-om  the  hori- 
zontal portion  of  the  bone.  The  outer  part  of  the  arch  is  sharp  and  prominent, 
affording  to  the  eye,   in   that  sititation,   considerable  protection   from    injury; 


the  inner  part  is  less  prominent.  At  the  junction  of  the  internal  and  middle 
third  of  this  arch  is  a  notch,  sometimes  converted  into  a  foramen,  and  called  the 
supraorbital  notch  {incistira  supraorbitalis).  It  transmits  the  supraorbital  artery, 
vein,  and  nerve.  A  small  aperture  is  seen  in  the  upper  part  of  the  notch,  which 
transmits  a  vein  from  the  diploe  to  join  the  supraorbital  vein.  To  the  median 
side  of  the  supraorbital  notch  there  is  often  a  notch  (incisura  frontalis)  for  the 
passage  of  the  frontal  artery  and  nerve.  The  supraorbital  arch  terminates 
externally  in  the  external  angular  process  and  internally  in  the  internal  angular 


1  Some  confusion  is  occasioned  to  students  commencing  the  study  of  anatomy  by  the  name  '  'sinuses  ha\ing 
bsen  given  to  two  perfectly  different  kinds  of  spaces  connected  with  the  sliull.  It  miiy  be  .is  well,  therefore,  to 
state  here,  at  the  outset,  that  the  "sinuses"  in  tne  interior  of  the  cranium  which  produce  the  grooves  on  the  in"cr 
surface  of  the  bones  are  venous  channels  along  which  the  blood  runs  in  its  passage  back  from  the  brain,  while 
the  "sinuses"  external  to  the  cranial  cavity  (the  frontal  sphenoidal,  ethmoidal,  and  maxillary)  are  hollow 
spaces  in  the  bones  themselves  which  communicate  with  the  nostrils,  and  contaiil  air. 


78 


SPECIAL  ANATOMY  OF  THE  SKELETON 


process.  The  external  angular  process  is  strong,  prominent,  and  articulates 
with  the  malar  bone;  running  upward  and  backward  from  it  are  two  well-marked 
lines,  which,  starting  together  from  the  external  angular  process  as  the  temporal 
crest,  soon  diverge  from  each  other  and  run  in  a  curved  direction  across  the  ])one. 
These  are  the  upper  and  lower  temporal  ridges ;  the  upper  gives  attachment  to  the 
temporal  fascia,  the  lower  to  the  Temporal  muscle.  Beneath  them  is  a  slight 
concavity  that  forms  the  anterior  part  of  the  temporal  fossa  and  gives  origin  to 
the  Temporal  muscle.  The  internal  angular  process  is  less  marked  than  the 
external,  articulates  with  the  lacrimal  bones,  and  gives  attachment  to  the 
Orbicularis  palpebrarum. 


With  maxilla 

With  nasal  ii  ,     ,  ^         j-  7 

I  !  nthi  sm  face  of  nasal  pi  ocess, 

With  perpendicular  plate  of  ethmoid    '  foiming  pait  of  loof  of  nose 
Fig.  45. — Frontal  "bone.      Inner  surface. 


Internal  Surface  (cerebral  surface,  fades  cerehralis)  (Fig.  45). — Along  the  median 
line  is  a  vertical  groove,  the  sulcus  sagittalis,  the  edges  of  which  unite  below  to 
form  a  ridge,  the  frontal  crest  {crista  frontalis');  the  groove  lodges  the  superior 
sagittal  sinus,  while  its  margins  afford  attachment  to  the  falx  cerebri.  The 
crest  terminates  below  at  a  small  notch  which  is  converted  into  a  foramen  by 
articulation  with  the  ethmoid.  It  is  called  the  foramen  cecum,  and  varies  in 
size  in  different  subjects;  it  is  sometimes  partially  or  completely  impervious, 
lodges  a  process  of  the  falx,  and  when  open  transmits  a  vein  from  the  mucous 
membrane  of  the  nose  to  the  superior  sagittal  sinus.  On  either  side  of  the  groove 
the  bone  is  deeply  concave,  presenting  depressions  for  the  convolutions  of  the 
brain,  and  numerous  small  furrows  for  the  ramifications  of  the  anterior  branches 
of  the  middle  meningeal  arteries.  Several  small,  irregular  fossse  are  seen  also  on 
either  side  of  the  groove,  for  the  reception  of  the  arachnoid  villi. 

The  border  of  the  vertical  portion  is  thick,  deepl}'  serrated,  bevelled  at  the 


THE  FRONTAL  BONE 


79 


expense  of  the  internal  table  above,  where  it  rests  upon  the  parietal  iKjnes,  and 
at  the  expense  of  the  external  table  at  each  side,  where  it  receives  the  lateral 
pressure  of  those  bones;  this  border  is  continued  below  into  a  triangular  rough 
surface  which  articulates  with  the  greater  wing  of  the  sphenoid. 

Horizontal  or  Orbital  Portion. — ^This  portion  of  the  bone  consists  of  two  thin 
plates,  the  orbital  plates,  wiiich  form  the  vault  of  the  orbit,  separated  from  one 
another  by  a  median  gap,  the  ethmoidal  notch. 

Surfaces.  Orbital  Surface. — The  surface  of  each  orbital  plate  {fades  orhitali.s) 
consists  of  a  smooth,  concave,  triangular  lamina  of  bone,  marked  at  its  front 
and  external  part  ( immediately  beneath  the  external  angular  process)  by  a  shallow 
depression,  the  lacrimal  fossa  {fossa  cilandulae  lacrimalis),  occupied  by  the  lacrimal 
gland;  and  at  its  anterior  and  internal  part  by  a  depression  (sometimes  a  small 
tubercle),  the  trochlear  fossa  {fovea  trochlearis),  for  the  attachment  of  the  carti- 
laginous pulley  of  the  Superior  oblique  muscle  of  the  eye.  These  plates  are  united 
in  front  by  a  roughened  uneven  surface  called  the  nasal  process,  which  articulates 
in  front  with  the  nasal  bones,  laterally  with  the  nasal  process  of  each  maxilla. 
From  the  middle  of  the  nasal  process  a  thin  lamina  of  bone  (the  nasal  spine) 
projects  downward  and  forward;  on  either  side  of  this  is  a  shallow  groove,  which 
enters  into  the  formation  of  the  nasal  fossa.  The  nasal  spine  articulates  in  front 
with  the  nasal  bones  and  behind  with  the  perpendicular  plate  of  the  ethmoid, 
and  by  so  doing  assists  in  forming  the  septum  of  the  nose.  The  ethmoidal  notch 
(incisura  ethvioidalis)  separates  the  two  orbital  plates;  it  is  quadrilateral,  and 
occupied,  when  the  bones  are  united,  by  the  cribriform  plate  of  the  ethmoid. 
The  margins  of  this  notch  present  several  half  cells,  which,  when  united  with 
corresponding  half  cells  on  the  upper  surface  of  the  ethmoid,  complete  the  eth- 
moidal cells;  two  grooves  are  also  seen  crossing  these  edges  obliquely;  they  are 
con\erted  into  canals  by  articulation  with  the  ethmoid,  and  are  called  the  anterior 
and  posterior  ethmoidal  canals  {foramen  ethmoidale  anterius  and  foramen  ethvioidale 
posterius) ;  they  open  on  the  inner  wall  of  the  orbit.  The  anterior  one  transmits 
the  nasal  nerve  and  anterior  ethmoidal  vessels;  the  posterior  one,  the  posterior 
ethmoidal  vessels.  In  front  of  the  ethmoidal  notch,  on  each  side  of  the  nasal 
process,  is  the  opening  of  the  frontal  air  sinus  {sinus  frontalis).  These  are  two 
irregular  cavities,  which  extend  upward  and  outward,  a  variable  distance,  between 
the  two  tables  of  the  skull,  and  are  separated  from  each  other  by  a  thin  bony 
septum  {septum  simnim  frontalium) ,  which  is  often  displaced  to  one  side.  Within 
the  sinuses  imperfect  trabecule  of  bone  often  exist.  The  sinuses  are  beneath 
and  gi\e  rise  to  the  prominences  above  the  supraorbital  arches  called  the  super- 
ciliary ridges  {arciis  snperciliares).  The  frontal  air  sinuses  are  absent  at  birth, 
become  apparent  about  the  seventh  year  of  life,  and  from  this  period  until  the 
age  of  twenty  gradually  increase  in  size.  Sometimes,  however,  the  sinuses  remain 
very  small  or  never  develop  at  all — or  one  side  may  be  large  and  the  other  small — 
or  one  may  exist  on  one  side  and  be  absent  on  the  other.  The  right  sinus  is  usually 
the  larger.  These  cavities  are  larger  in  men  than  in  women.  The  floor  of  each 
sinus  is  very  thin  and  is  over  the  orbit  and  the  upper  border  of  the  lateral  mass 
■of  the  ethmoid.  The  thinnest  portion  of  the  floor  is  at  the  upper  and  inner 
angle  of  the  orbit.  The  frontal  sinuses  are  lined  by  mucous  membrane,  and 
each  sinus  communicates  with  the  middle  meatus  of  the  nose  by  the  infundi- 
bulum.  In  some  cases  the  sinuses  communicate  with  each  other  by  means  of 
an  aperture  in  the  septum  and  occasionally  join  the  sinus  in  the  crista  galli  of 
the  ethmoid. 

The  internal  surface  {cerebral  surface,  fades  cercbralis)  of  the  horizontal  portion 
presents  the  convex  upper  surfaces  of  the  orbital  plates,  separated  from  each  other 
in  the  median  line  by  the  ethmoidal  notch,  and  marked  by  eminences  and  de- 
pressions for  the  convolutions  of  the  frontal  lobes  of  the  cerebrum. 


80  SPECIAL  ANATOMY  OF  THE  SKELETON 

The  border  of  the  horizontal  portion  is  thin,  serrated,  and  articulates  with 
the  lesser  wing  of  the  sphenoid. 

Structure. — The  frontal  portion  and  external  angular  processes  consist  of  diploic  tissue  sur- 
rounded by  compact  bone.  In  the  frontal  sinus  region  the  cancellous  tissue  is  wanting.  The 
horizontal  portion  is  thin,  translucent,  and  composed  entirely  of  compact  tissue. 

Development  (Fig.  46). — The  frontal  bone  is 
formed  in  membrane,  being  developed  from  two 
primary  centres,  one  for  each  lateral  half,  which 
make  their  appearance  about  the  seventh  or 
eighth  week,  above  the  orbital  arches.  From 
this  point  ossification  extends,  in  a  radiating 
manner,  upward  into  the  forehead  and  backward 
over  the  orbit.  The  nasal  spine  is  developed 
from  two  secondary  centres,  while  additional  cen- 
tres appear  in  the  regions  of  the  internal  and 
external  angular  processes.  Sometimes  a  centre 
appears  on  either  side  at  the  lower  end  of  the 
coronal  suture.  This  latter  centre  sometimes  re- 
mains ununited,  and  is  known  as  the  pterion. 
,  ossicle,  or  it  may  join  with  the  parietal,  sphenoid, 

;.         °  °       or  temporal   bone.     At   birth   the  bone  consists 

of  two  pieces,  which  afterward  become  united, 
along  the  median  line,  by  a  suture  (metopic)  which  runs  from  the  vertex  to  the  root  of  the  nose. 
This  suture  usually  becomes  obliterated  within  a  few  years  after  birth,  but  it  occasionally  remains 
throughout  life. 

Articulations. — With  twelve  bones — two  parietal,  the  sphenoid,  the  ethmoid,  two  nasal,  two 
maxillse,  two  lacrimal,  and  two  malar. 

Attachment  of  Muscles. — To  three  pairs — the  Corrugator  supercilii,  Orbicularis  palpe- 
brarum, and  Temporal,  on  each  side. 


The  Temporal  Bone  (Os  Temporale). 

The  temporal  bone  consists  of  three  parts — (a)  the  squamous,  (6)  the  petro- 
mastoid,  and  (c)  the  tympanic  portions — which,  though  separate  in  early  life, 
become  united  in  the  adult.  The  three  parts  meet  and  form  a  part  of  the 
outer  wall  and  a  part  of  the  base  of  the  skull  and  the  external  auditory  meatus. 

The  Squamous  Portion  {pars  squamosa  temporalis). — The  squamous  portion, 
the  anterior  and  upper  part  of  the  bone,  is  scale-like  in  form,  and  is  thin  and 
translucent  (Fig.  47).  Its  external  surface  is  smooth,  convex,  and  grooved  at 
its  back  part  for  the  deep  temporal  arteries;  it  affords  attachment  to  the  Tem- 
poral muscle  and  forms  part  of  the  temporal  fossa.  At  its  back  part  may  be 
seen  a  curved  ridge  (part  of  the  temporal  ridge),  which  serves  for  the  attachment 
of  the  temporal  fascia,  limits  the  origin  of  the  Temporal  muscle,  and  marks 
the  boundary  between  the  squamous  and  mastoid  portions  of  the  bone.  Pro- 
jecting from  the  lower  part  of  the  squamous  portion  is  a  long,  arched  process 
of  bone,  the  zygoma,  or  zygomatic  process.  This  process  is  at  first  directed  out- 
ward, its  two  surfaces  looking  upward  and  downward;  it  then  appears  as  if 
twisted  upon  itself,  and  runs  forward,  its  surfaces  now  looking  inward  and  out- 
ward. The  superior  border  of  the  process  is  long,  thin,  and  sharp,  and  serves 
for  the  attachment  of  the  temporal  fascia.  The  inferior,  short,  thick,  and  arched, 
has  attached  to  it  some  fibres  of  the  Masseter  muscle.  Its  outer  surface  is  convex 
and  subcutaneous;  its  inner  is  concave,  and  also  affords  attachment  to  the  Masse- 
ter. The  extremity,  broad  and  deeply  serrated,  articulates  with  the  malar  bone. 
The  zygomatic  process  is  connected  to  the  temporal  bone  by  three  divisions, 
called  its  roots — an  anterior,  middle,  and  posterior.  The  anterior,  which  is  short, 
but  broad  and  strong,  is  directed  inward,  to  terminate  in  a  rounded  eminence. 


THE  TEMl^ORAL  BONE 


SI 


the  emiiientia  arti.cularis.  This  eminence  forms  the  front  boundary  of  tlie 
glenoid  fossa,  and  in  the  recent  state  is  covered  with  cartilage.  The  middle 
root  (posfglenoid  process)  forms  the  posterior  boundary  of  the  mandibular  portion 
of  the  glenoid  fossa;  while  the  posterior  root,  which  is  strongly  marked,  runs  from 
the  upper  border  of  the  zygoma,  in  an  arched  direction,  upward  and  backward, 
forming  the  posterior  part  of  the  temporal  ridge  (s2ipramastoid  crest).  At  the 
junction  of  the  anterior  root  with  the  zygoma  is  a  projection,  called  the  tubercle, 
for  the  attachment  of  the  external  lateral  ligament  of  the  mandible;  and  between 


Groove  for  middle 
temporal  artery 


Incisura  parietalis 

/       Supramental 
\  Uwn,,lc 

^'-'^^  OCCIPITO- 


Zygomatic    proc 

Lnunentta 
articulans- 
Postglenoid  pi  ocess 

Glenoid  cavity 


Glaserian  fissure 

Tympavic  plate 


STYLOGLOSSU 


Occipital  groove 


External  auditory  process 
stvlohyoi'd 

Styloid  process 


Fig.  47.— Left  tempoiLiI  bo 


Lateral  surface. 


the  anterior  and  middle  roots  is  an  oval  depression,  forming  part  (mandibular) 
of  the  glenoid  fossa,  for  the  reception  of  the  condyle  of  the  mandible.  Between 
the  posterior  wall  of  the  external  auditory  meatus  and  the  posterior  root  of  the 
zygoma  is  the  area  called  the  suprameatal  triangle  (Macewen),  often  marked  by 
a  spinous  process  (spine  of  Henle). 

The  internal  surface  of  the  squamous  portion  (Fig.  48)  is  concave,  presents 
numerous  eminences  and  depressions  for  the  convolutions  of  the  cerebrum,  and 
two  well-marked  grooves  for  the  branches  of  the  middle  meningeal  artery. 

Borders. — The  superior  border  is  thin,  bevelled  at  the  expense  of  the  internal 
surface,  so  as  to  overlap  the  lower  border  of  the  parietal  bone,  forming  the 
squamous  suture.  The  anterior  inferior  border  is  thick,  serrated,  and  bevelled, 
alternately  at  the  expense  of  the  inner  and  outer  surfaces,  for  articulation  with 
the  greater  wing  of  the  sphenoid. 

The  Petromastoid  Portion  {partes  petrosa  ct  mastoidea). — The  petromastoid 
portion  consists  of  (a)  a  mastoid  portion,  the  thick  conical  posterior  part  behind 


82 


SPECIAL  ANATOMY  OF  THE  SKELETON 


the  external  auditory  meatus,  and  (6)  a  pyramidal   portion  named  the  petrous 
portion,  which  contains  the  internal  ear  and  forms  part  of  the  floor  of  the  cranial 

cavity- 


^to-l   bone 


ETmnentia 
arcuata. 


Foramen  Tnastoidev/m  I 

Aquaeductus  vestihuli 

AqiULeductus  cockleie 

Meatus  acusticus  intemus 

Fig.  48. — Left  temporal  bone.     Inner  surface. 


The  Mastoid  Portion  {pars  mastoidea). — The  mastoid  portion  is  situated  at 
the  posterior  part  of  the  bone  (Figs.  47  and  49). 

Surfaces.  Outer  Surface. — ^The  outer  surface  of  the  mastoid  is  rough,  and 
gives  attachment  to  the  Occipitofrontalis  and  Retrahens  aurem  muscles.  It  is 
perforated  by  numerous  foramina;  one  of  these,  of  large  size,  situated  at  the 
posterior  border  of  the  bone,  is  termed  the  mastoid  foramen  {foramen  mastoidemii)  ; 
it  transmits  a  vein  from  the  lateral  sinus  and  a  small  artery  from  the  occipital 
to  supply  the  dura.  The  position  and  size  of  this  foramen  are  very  variable. 
It  is  not  always  present;  sometimes  it  is  situated  in  the  occipital  bone  or  in  the 
suture  between  the  temporal  and  the  occipital.  The  mastoid  portion  is  con- 
tinued below  into  a  conical  projection,  the  mastoid  process  {processus  niastoidevs), 
the  size  and  form  of  which  vary  somewhat.  This  process  serves  for  the  attach- 
ment of  the  Sternomastoid,  Splenius  capitis,  and  the  Trachelomastoid.  On  the 
inner  side  of  the  mastoid  process  is  a  deep  groove,  the  digastric  fossa  {incisura 
mastoidea),  for  the  attachment  of  the  Digastric  muscle;  and,  running  parallel 
with  it,  but  more  internal,  the  occipital  groove  {sulcus  a.  occipitalis),  which  lodges 
the  occipital  artery  {fossa  mastoidea). 

Internal  Surface. — The  internal  surface  of  the  mastoid  portion  presents  a  deep, 
cu^^'ed  groove,  the  sigmoid  fossa,  which  lodges  part  of  the  lateral  sinus;  and  into 


THE  TEMPORAL  BONE 


83 


it  may  be  seen  opening  the  mastoid  foramen,  which  transmits  an  emissary  vein 
from  the  lateral'  sinus  to  the  posterior  auricular  or  occipital  vein  and  a  small 
artery,  the  mastoid  branch  of  the  occipital  artery.  A  section  of  the  mastoid 
process  (Figs.  49  and  50)  shows  it  to  contain  a  number  of  cellular  spaces,  com- 
municating with  one  another,  called  the  mastoid  cells  (cellulae  mastoideae),  which 
exhibit  the  greatest  possible  variety  as  to  their  size  and  number.  At  the  upper 
and  front  part  of  the  bone  these  cells  are  large  and  irregular,  and  contain  air. 
They  diminish  in  size  toward  the  lower  part  of  the  bone;  those  situated  at  the 
apex  of  the  mastoid  process  are  quite  small,  representing  spaces  of  cancellous 
bone,  and  usually  containing  marrow.     Occasionally  they  are  entirely  absent,  and 


Mastoid  antrum 


Tegmen  tympani 

Prominence  of  extl.  semicircular  canal 
Prominence  of  facial  canal 
Fenestra  ovalis 
Bristle  in  canal  for  Tensor  tympani 
Processus  cocldeariformis 
Bnstle  in  hiaivs  Fallopii 


Mastoid  cells 


Carotid  canal 
Bony  pa}  t  of  Eustachian  tube 
Promontory 
Bristle  in  pyramid 
Fenestra  rotunda 
Sulcus  tympanicus 
Bristle  in  stylomastoid  foramen. 


Fig.  49. — Section  through  the  petrous  and  mastoid  portions  of  the  temporal  bone,  showing   the  communication 
of  the  cavity  of  the  tympanum  wiith  the  mastoid  antrum. 

the  mastoid  is  solid  throughout.  In  addition  to  these  pneumatic  cells  may  be 
seen  a  large,  irregular  cavity,  the  mastoid  antrum  (Figs.  49  and  50),  situated  at 
the  upper  and  front  part  of  the  section.  This  must  be  distinguished  from  the 
mastoid  cells,  though  it  communicates  with  them.  The  mastoid  cells  are  not 
developed  until  after  puberty,  but  the  mastoid  antrum  is  almost  as  large  at  birth 
as  it  is  in  the  adult  bone.  The  antrum  and  cells  are  filled  with  air,  and  are  lined 
with  a  prolongation  of  the  mucous  membrane  of  the  tympanum,  which  extends 
into  them  through  an  opening,  by  which  they  communicate  with  the  cavity  of 
the  tympanum. 


In  consequence  of  the  communication  which  exists  between  the  tympanum  and  mastoid  cells, 
inflammation  of  the  hning  membrane  of  the  former  cavity  may  easily  travel  backward  to  that 
of  the  antrum,  leading  to  caries  and  necrosis  of  their  walls  and  the  risk  of  transference  of  the 
inflammation  to  the  lateral  sinus  or  encephalon. 

The  Petrous  Portion  {pars  petrosa  [pyramid])  (Fig.  48). — The  petrous  portion 
is  a  pyramidal  process  of  bone  wedged  in  at  the  base  of  the  skull  between  the 


84 


SPECIAL  ANAT03IY  OF  THE  SKELETON 


sphenoid  and  occipital  bones.  Its  direction  from  without  is  inward,  forward, 
and  a  little  downward.  It  presents  for  examination  an  apex,  four  surfaces,  and 
four  borders,  and  contains  in  its  interior  the  essential  parts  of  the  organ  of  hearing. 

Apex  {apex  pyramidis) . — The  apex  of  the  petrous  portion,  rough  and  uneven, 
is  recei^'ed  into  the  angular  interval  between  the  posterior  border  of  the  greater 
wing  of  the  sphenoid  and  the  basilar  process  of  the  occipital ;  it  presents  the  ante- 
rior or  internal  orifice  of  the  carotid  canal  (foramen  caroticum  internum),  and 
forms  the  posterior  and  external  boundary  of  the  foramen  lacerum  medium. 

Surfaces. — The  superior  surface  of  the  petrous  portion  (Fig.  48)  forms  the 
posterior  part  of  the  middle  fossa  of  the  skull;  it  looks  upward  and  forward. 
This  surface  is  continuous  with  the  squamous  portion,  to  which  it  is  united  by 


PANIC  CANfl 


Fig.  50. — Right  temporal  bone  cut  open  to  show  the  anterior  surface  of  the  petrous  portion.     X  2.     (Spalteholz.) 


a  suture,  the  petrosquamous  suture,  the  remains  of  which  are  distinct  even  at  a 
late  period  of  life. 

The  superior  surface  presents  five  points  for  examination:  (1)  An  eminence 
(eminentia  arcuata)  near  the  centre,  which  indicates  the  situation  of  the  superior 
semicircular  canal.  (2)  In  front  and  a  little  to  the  outer  side  of  this  eminence  a 
depression  indicating  the  position  of  the  tympanum;  here  the  layer  of  bone  which 
separates  the  tympanum  from  the  cranial  cavity  is  extremely  thin,  and  is  known 
as  the  tegmen  tympani.  The  tliin  inferior  extremity  of  this  plate  drops  downward 
and  presents  itself  at  the  inner  extremity  of  the  Glaserian  fissure,  there  making 
the  fissure  double;  the  anterior  slit  is  called  the  canal  of  Huguier,  and  it  transmits 
the  chorda  tympani  nerve.  (3)  A  shallow  groove,  sometimes  double,  leading 
outward  and  backward  to  an  oblique  opening,  the  hiatus  Fallopii  (liiatus  caualis 
facialis),  for  the  passage  of  the  greater  petrosal  nerve  and  the  petrosal  branch  of 
the  middle  meningeal  artery.  (4)  A  smaller  opening  (apertura  superior  canaliculi 
tympanici),  occasionally  seen  external  to  the  latter,  for  the  passage  of  the  smaller 
petrosal  nerve.     (5)  A  shallow  depression,  the  trigeminal  depression  {impressio 


THE  TEMPORAL  BONE 


85 


trigemini),  for  the  reception  of  the  Gasserian  ganghon,  is  placed  at  the  inner 
extremity  of  this  surface. 

The  anterior  or  tympanic  surface  (Fig.  50)  is  mostly  hidden  by  the  tympanic  por- 
tion of  the  bone,  and  is  best  studied  either  in  very  young  skulls  or  in  bones  which 
have  been  cut  behind  the  tympanic  membrane.  This  surface  forms  the  postero- 
internal wall  of  the  tympanum  and  presents  an  oval  foramen  (fenestra  ve.stibiili) , 
into  which  the  base  of  the  stapes  is  fitted.  Just  above  and  external  to  the  fenestra 
ovalis  is  the  mastoid  antrum,  leading  from  the  tympanum  to  the  mastoid  cells. 
The  antrum  is  roofed  by  the  tegmen  tym- 

pani.     Below  and  internal  to  the  fenestra  2  3 

ovalis  is  a  rounded  eminence,  the  promon- 
tory, formed  by  the  first  turn  of  the  cochlea. 
Below  the  promontory  is  situated  the  fe- 
nestra rotunda,  which  is  closed  in  the  recent 
state  by  a  membrane. 

Internal  to  the  fenestra  ovalis  is  the 
orifice  of  the  canal  which  transmits  the 
Tensor  tympani;  below  this  is  the  Eusta- 
chian canal  for  the  passage  of  air  from 
the  pharynx  to  the  tympanum.  The  two 
canals  are  separated  by  the  processus  coch- 
leariformis.  On  this  surface,  just  above, 
then  external  to  the  oval  foramen,  be- 
tween it  and  the  antrum,  is  the  facial 
canal  {canalis  facialis).  This  canal  is 
traversed  by  the  facial  nerve  on  its  way  to 
the  stylomastoid  foramen.  The  portion 
of  the  anterior  surface  not  covered  by  the 
tympanic  plate  is  occupied  by  the  termina- 
tion of  the  carotid  canal  (foramin  caroti- 
cum  internum),  the  wall  of  w'hich  is  defi- 
cient in  front. 

The  posterior  surface  forms  the  front  part 
of  the  posterior  fossa  of  the  skull,  and  is  continuous  with  the  inner  surface  of  the 
mastoid  portion  of  the  bone.  It  presents  three  points  for  examination:  (1) 
About  its  centre  a  large  orifice,  the  meatus  auditorius  internus  {meatus  acusticus 
internus),  through  which  pass  the  facial,  auditory  and  intermediate  nerves, 
and  the  auditory  artery.  The  size  of  this  meatus  varies  considerably;  its  margins 
are  smooth  and  rounded,  and  it  leads  into  a  short  canal,  about  one-third  inch  in 
length,  which  runs  directly  outward  and  is  closed  by  a  vertical  plate,  the  lamina 
cribrosa,  which  is  divided  by  a  horizontal  crest,  the  falciform  crest  {crista  transversa), 
into  two  unequal  portions  (Fig.  51).  Each  portion  is  subdivided  by  a  small 
vertical  crest  into  two  parts,  named,  respectively,  anterior  and  posterior. 
The  lower  portion  presents  three  sets  of  foramina :  one  group  just  below  the  pos- 
terior part  of  the  crest,  the  area  cribrosa  media,  consisting  of  a  number  of  small 
openings  for  the  nerves  of  the  saccule;  below  and  posterior  to  this,  the  foramen 
singulare,  or  opening  for  the  nerve  of  the  posterior  semicircular  canal;  in  front 
and  below  the  first,  the  tractus  spiralis  foraminosus,  consisting  of  a  number  of  small, 
spirally  arranged  openings  which  terminate  in  the  canalis  centralis  cochleae  and 
transmit  the  nerve  of  the  cochlea;  the  upper  portion,  that  above  the  crista,  pre- 
sents behind  a  series  of  small  openings,  the  area  cribrosa  superior,  for  the  passage 
of  filaments  of  the  utricle  and  superior  and  external  semicircular  canal,  and,  in 
front,  one  large  opening,  the  commencement  of  the  aquaeductus  Fallopii  {canalis 
facialis),  for  the  passage  of  the  facial  nerve.     (2)  External  and  below  the  meatus 


Fig.  5i. — Diagrammatic  view  of  the  fundus  ol 
the  internal  auditory  meatus:  1,  Falciform  crest, 
2,  Anterior  superior  cribriform  area,  2',  Internal 
opening  of  the  aquaeductus  Fallopii,  3,  Vertical 
crest  which  ssparates  the  anterior  and  posterior 
superior  cribriform  areas,  4.  Posterior  superior 
cribriform  area,  with  (4')  openings  for  nerve 
filaments.  5.  Anterior  inferior  cribriform  area, 
5'.  Spirally  arranged,  sieve-like  openings  for  the 
nerves  to  the  cochlea.  5".  Opening  of  the  cen- 
tral canal  of  the  cochlea.  6,  Crest  which  sepa- 
rates t':c  anterior  and  posterior  inferior  cribriform 
areas.  7.  Posterior  inferior  cribriform  area.  7'. 
Orifices  for  the  branches  of  the  nerve  to  the 
saccule.  8.  Foramen  singulare  of  Morgagni, 
with  the  anterior  portion  of  the  canal  which  gives 
passage  to  the  nerve  to  the  posterior  semicircular 
canal.     (Testut.) 


86  SPECIAL  ANATOMY  OF  THE  SKELETON 

auditorius  is  a  small  slit  (apertura  externa  aquaedudus  vestibuli),  almost  hidden 
by  a  thin  plate  of  bone,  leading  to  a  canal,  the  aquaeductus  vestibuli,  which  trans- 
mits the  ductus  endolymphaticus,  together  with  a  small  artery  and  vein.  (3)  In 
the  interval  between  these  two  openings,  but  above  them,  is  an  angular  depression 
{fossa  subarcuata.) ,  which  lodges  a  process  of  the  dura,  and  transmits  a  small  vein 
into  the  cancellous  tissue  of  the  bone.  In  the  child  this  depression  is  represented 
by  a  large  fossa,  the  floccular  fossa,  which  extends  backward  as  a  blind  tunnel 
under  the  superior  semicircular  canal. 

The  inferior  or  basilar  surface  (Fig.  52)  is  rough  and  irregular,  and  forms  part 
of  the  base  of  the  skull.  Passing  from  the  apex  to  the  base,  this  surface  presents 
the  following  points  for  examination:  (1)  A  rough  surface,  quadrilateral  in  form, 
which  serves  partly  for  the  attachment  of  the  Levator  palati  and  Tensor  tympani 


STYLOPHARYNGEUS 


Sough  quadrilateral  surface.  _ 

External  opening  0/"*'%^ 

carotid  canal.  -^ 

Canal  for  Jacobson^s  nerve. 

Aquaeductus  cochleae. 

Canal  for  Arnold' a  nerve. 

Jugular  fossa. 

Vaginal  process. 

Styloid  process. 
Stylomastoid  foramen. 
Jugular  surface. 
Auricular  fissure. 


Fig.  52. — Petrous  portion  of  the  left  temporal  bone.     Inferior  surface. 

muscles.  (2)  The  large  circular  aperture  of  the  carotid  canal,  the  external  carotid 
opening  (foramen  caroticum  externum) ;  the  canal  ascends  at  first  vertically,  and 
then,  making  a  bend,  runs  horizontally  forward  and  inward;  it  transmits  the 
internal  carotid  artery  and  the  carotid  sympathetic  plexus.  Within  the  carotid 
canal  are  several  openings  {canaliculi  caroticotympanici) ,  which  transmit  tympanic 
branches  of  the  internal  carotid  artery  and  of  the  carotid  sympathetic  plexus. 
(3)  The  opening  of  the  aquaeductus  cochleae  {apertura  externa  canaliculi  cochleae), 
a  small,  triangular  opening,  lying  on  the  inner  side  of  the  latter,  close  to  the  pos- 
terior border  of  the  petrous  portion;  it  transmits  a  vein  from  the  cochlea,  which 
joins  the  internal  jugular.  (4)  External  to  these  openings  a  deep  depression,  the 
jugular  fossa  {fossa  jugularis) ,  which  varies  in  depth  and  size  in  different  skulls ; 
it  lodges  the  lateral  sinus,  and,  with  a  similar  depression  on  the  margin  of  the 
jugular  process  of  the  occipital  bone,  forms  the  foramen  lacerum  posterius  or 


THE  TEMPORAL  BONE  87 

jugular  foramen.  (5)  A  foramen  which  is  the  opening  of  a  small  canal  (canaliai- 
lu^  tympanicus)  for  the  passage  of  Jacobson's  nerve  (the  tympanic  branch  of  the 
glossopharyngeal) ;  this  foramen  is  seen  in  front  of  the  bony  ridge  dividing  the 
carotid  canal  from  the  jugular  fossa.  (6)  A  small  foramen  on  the  wall  of  the 
jugular  fossa,  for  the  passage  of  the  auricular  branch  of  the  vagus  {Arnold's) 
nerve.  (7)  Behind  the  jugular  fossa  a  smooth,  square-shaped  facet,  the  jugular 
surface;  it  is  covered  with  cartilage  in  the  recent  state,  and  articulates  with  the 
jugular  process  of  the  occipital  bone.  (S)  The  stylomastoid  foramen  {joravien 
stylomastoidevm) ,  a  rather  large  orifice,  placed  between  the  styloid  and  mastoid 
processes;  it  is  the  termination  of  the  facial  canal,  and  transmits  the  facial  nerve 
and  stylomastoid  artery. 

Borders. — The  posterosuperior  border  {angulus  superior  pyramidis),  the  longest, 
is  grooved  for  the  superior  petrosal  sinus,  and  has  attached  to  it  the  tentorium 
cerebelli ;  at  its  inner  extremity  is  a  semilunar  notch,  upon  which  the  fifth  nerve 
lies. 

The  postero-inferior  border  is  intermediate  in  length  between  the  postero- 
superior and  antero-inferior.  Its  inner  half  is  marked  by  a  groove,  which,  when 
completed  by  its  articulation  with  the  occipital,  forms  the  channel  for  the  infe- 
rior petrosal  sinus.  Its  outer  half  presents  a  deep  excavation,  the  jugular  fossa 
{fossa  jugularis),  which,  with  a  similar  notch  on  the  occipital,  forms  the  foramen 
lacerum  posterius.  A  projecting  eminence  of  bone  occasionally  stands  out  from 
the  centre  of  the  notch,  and  divides  the  foramen  into  two  parts. 

The  anterosuperior  border  is  divided  into  two  parts — an  outer,  joined  to  the 
squamous  portion  by  a  suture,  the  remains  of  which  are  distinct;  an  inner,  free, 
articulating  with  the  spinous  process  of  the  sphenoid.  At  the  angle  of  junction 
of  the  petrous  and  squamous  portions  is  seen  the  opening  of  the  canalis  viuscvlo- 
tuharius. 

The  antero-inferior  border  is  also  divided  into  two  parts — the  outer  portion  is 
hidden  from  view  by  the  tympanic  plate.  The  inner  part  is  free  and  forms  the 
inferior  lip  of  the  carotid  canal  and  gives  attachment  to  the  Tensor  tympani  and 
Levator  palati  muscles. 

The  Tympanic  Portion  {pars  tympanica). — The  tympanic  portion  is  placed  in 
front  of  the  anterior  surface  of  the  petrous  portion;  its  most  internal  part  is 
narrow  and  forms  the  anterior  wall  of  the  Eustachian  canal.  Externally  it 
broadens  out  and  has  an  antero-inferior  and  a  posterosuperior  surface,  an 
anterosuperior,  an  antero-inferior,  and  an  external  border.  The  antero-inferior 
surface  looks  forward  and  downward  and  forms  the  posterior  part  of  the  glenoid 
fossa.  The  posterosuperior  surface  forms  the  anterior  wall  of  the  external  audi- 
tory canal.  From  this  surface  there  continues  on  to  the  anterior  part  of  the 
mastoid  portion  a  U-shaped  process,  with  its  concavity  upward;  this  process 
shares  in  forming  the  inferior  and  posterior  wall  of  the  external  auditory  canal. 
Between  the  upturned  part  of  the  U-shaped  process  and  the  mastoid  is  a  foramen 
(fissura  tympanoviastoidea)  transmitting  the  tympanic  (auricular  nerve  of  Arnold) 
branch  of  the  vagus.  In  the  concavity  of  this  U-shaped  process  is  a  furrow 
{sidcus  tympanicus),  in  which  is  placed  the  tympanic  membrane  {membrana 
tympani),  like  a  mirror  in  its  frame.  The  anterosuperior  border  fuses  with  the 
middle  zygomatic  root.  Internally,  this  border  is  continuous  with  the  upper 
border  of  the  narrow  part  of  the  bone,  and  is  separated  from  the  squamous 
portion  of  the  bone  by  the  Glaserian  fissure  and  a  small  part  of  the  tegmen 
tympani.  The  antero-inferior  border  is  thin  internally;  externally  it  divides  into 
two  laminse  and  ensheaths  the  root  of  the  styloid  process — hence  the  name 
vaginal  process  given  to  this  border.  The  external  border  is  free  and  rough,  and 
has  attached  to  it  the  cartilaginous  part  of  the  ear. 

The  glenoid  fossa  {fossa  mandibular  is)  is  a  considerable  hollow  formed  in  front 


SPECIAL  ANATOMY  OF  THE  SKELETON 


by  the  squamous  part  of  the  temporal,  and  behind  by  the  tympanic  bone.  The 
part  of  the  fossa  formed  by  the  squamous  portion  is  covered  with  cartilage  and 
articulates  with  the  condyle  of  the  mandible.  The  posterior  part  of  the  fossa  lodges 
part  of  the  parotid  gland,  and  is  formed  by  the  antero-inferior  surface  of  the  tym- 
panic portion.  The  fossa  is  crossed  by  an  oblique  fissure,  the  petrotympanic  fissure 
(Glaserian  fissure),  which  leads  into  the  tympanum,  lodges  the  processus  gracilis 
of  the  malleus,  and  transmits  the  tympanic  branch  of  the  internal  maxillary 
artery.  This  fissure  is  closed  externally;  at  its  inner  extremity  it  is  separated 
from  the  squamous  portion  by  the  downgrowth  of  a  process  of  bone  from  the 
tegmen  tympani  {^processus  inferior  tegmini  tympani)  of  the  petrous  portion 
between  the  squamous  and  tympanic  plates,  making  the  fissure  at  its  internal 
extremity  a  double  one.  The  anterior  limb  is  known  as  the  canal  of  Huguier 
{canaliculus  chordae  tympani),  and  transmits  the  chorda  tympani  nerve. 

The  external  auditory  meatus  is  bounded  in  front,  below,  and  behind  by  the 
tympanic  portion.  The  roof  and  the  upper  part  of  the  posterior  wall  are  formed 
by  the  squamous  portion.  The  canal  is  about  three-quarters  of  an  inch  (18  mm.) 
in  length,  and  is  directed  inward  and  forward.  In  vertical  section  it  is  of  oval 
outline,  the  long  axis  of  the  oval  being  vertical  in  the  outer  segment  and  oblique 
in  the  inner  segment. 

The  styloid  process  is  a  sharp  spine  of  varying  length.  It  projects  downward 
and  forward  from  the  vaginal  process  of  the  tympanic  part,  and  gives  origin 
to  the  stylohyoid  and  stylomandibular  ligaments,  and  to  the  Styloglossus,  Stylo- 
pharyngeus,  and  Stylohyoid  muscles. 

Structure. — The  squamous  portion  is  like  that  of  the  other  cranial  bones;  the  mastoid  portion, 
cellular;  and  the  petrous  portion,  dense  and  hard. 

Development  (Fig.  53). — The  temporal  bone  is  developed  from  ten  centres,  exclusive  of  those 
for  the  internal  ear  and  the  ossicles — viz.,  one  for  the  squamous  portion,  including  the  zygoma, 

one  for  the  tympanic  plate,  six  for  the  petrous 
and  mastoid  parts,  and  two  for  the  styloid 
process.  Just  before  the  close  of  fetal  life 
the  temporal  bone  consists  of  four  parts: 
(1)  The  squamozygomatic  part,  ossified  in 
membrane  from  a  single  nucleus,  'n'hich 
appears  at  its  lower  part  about  the  second 
month.  (2)  The  tympanic  plate,  an  imper- 
fect ring,  in  the  concavity  of  which  is  a 
groove,  the  sulcus  tympanicus,  for  the  at- 
tachment of  the  circumference  of  tlie  tym- 
panic membrane.  This  is  also  ossified  from 
a  single  centre,  which  appears  in  membrane 
about  the  third  month.  (3)  The  petromas- 
toid  part,  which  is  developed  from  six  centres, 
appearing  in  the  cartilaginous  ear  capsule 
about  the  fifth  or  sixth  month.  Four  of  these 
are  for  the  petrous  portion  and  are  placed 
around  the  labyrinth,  and  two  are  for  the 
mastoid  (Vrolik).  According  to  Huxley,  the 
centres  are  more  numerous  and  are  disposed 
so  as  to  form  three  portions:  The  first  por- 
tion includes  most  of  the  labyrinth  (part  of 
the  cochlea,  vestibule,  superior  semicircular 
canals,  and  the  inner  wall  of  the  tympanic 
cavity)  and  a  part  of  the  petrous  and  mastoid. 
This  portion  he  has  named  the  pro-otic.  The  second  portion — the  opisthotic — consists  of  the  rest 
of  the  petrous,  and  is  thus  made  up:  the  floor  of  the  tympanum  and  vestibule  surrounds  the  caro- 
tid canal  and  the  outer  and  lower  portions  of  the  cochlea  and  spread  inward  below  the  internal 
auditory  meatus.  The  third  portion — the  pteriotic — roofs  the  antrum  and  tympanic  cavity. 
The  fourth  portion — the  epiotic — includes  the  remainder  of  the  mastoid.  The  petromastoid 
is  ossified  in  cartilage.  (4)  The  styloid  process  is  also  ossified  in  cartilage  from  two  centres — 
one  for  the  base,  which  appears  before  birth,  and  is  termed  the  tympanohyal ;  the  other,  comprising 


JS' 


6  for  petrous 

and  mastoid 

portioiis. 


2' for  styloid  p 
Fio.  53. — Developmi 


THE  SPHENOID  BONE 


89 


the  rest  of  the  process,  is  named  the  stylohyal,  and  does  not  appear  until  after  birth.  Shortly 
before  birth  the  tympanic  plate  unites  with  the  squamous.  Tlie  petrous  and  mastoid  unite  at 
puberty,  and  in  some  slculls  never  becomes  united.  The  subsequent  changes  in  this  bone  are, 
that  the  tympanic  plate  e.\tends  outward  and  backward,  so  as  to  form  the  meattis  auditorius. 
(1)  The  extension  of  the  tympanic  plate,  however,  does  not  take  place  at  an  equal  rate  all  around 
the  circumference  of  the  ring,  but  occurs  most  rapidly  on  its  anterior  and  posterior  portions, 
and  these  outgrowths  meet  and  blend,  and  thus,  for  a  time,  there  exists  in  the  floor  of  the  meatus 
a  foramen,  the  foramen  of  Huschke;  this  foramen,  usually  closed  by  the  fifth  year,  may  persist 
throughout  life.  (2)  The  glenoid  cavity  is  at  first  extremely  shallow,  and  looks  outward  as 
well  as  downward;  it  becomes  deeper  and  is  ultimately  directed  downward.  Its  change  in  direc- 
tion is  accounted  for  as  follows:  the  part  of  the  squamous  temporal  which  supports  it  lies  at  first 
hclmc  the  level  of  the  zygoma.  As,  however,  the  base  of  the  skull  increases  in  width,  this  lower 
part  of  the  squama  is  directed  horizontally  inward  to  contribute  to  the  middle  fossa  of  the  skull, 
and  its  surfaces  therefore  come  to  look  upward'and  downward.  (3)  The  mastoid  portion  is 
at  first  quite  flat,  and  the  stylomastoid  foramen  and  rudimentary  styloid  process  lie  immediately 
behind  the  tympanic  ring.  With  the  development  of  the  air  cells  the  outer  part  of  the  mastoid 
portion  grows  downward  and  forward  to  form  the  mastoid  process,  and  the  styloid  process 
and  stylomastoid  foramen  now  come  to  lie  on  the  under  surface.  The  descent  of  the  foramen 
is  necessarily  accompanied    by  a  corresponding  lengthening  of  the  aqueduct  of    Fallopius. 


Squamozis  portion 


Petrosqua7nous 
sutute 


Squamous  portion 

Peirosquonnous  suture 
Eimneniia  arcuata, 


Fig.  54. — Temporal  bone  at  birth.     Outer  aspect. 


Fossa  subarcuaia 
Meatus  acusticus  internus 
Fig.  55. — Temporal  bone  at  birth.     Inner  aspect. 


(4)  The  downward  and  forward  growth  of  the  mastoid  process  also  pushes  forward  the  tympanic 
plate,  so  that  the  portion  of  it  which  formed  the  original  floor  of  the  meatus  and  containing 
the  foramen  of  Huschke  is  ultimately  found  in  the  anterior  wall.  (5)  With  the  gradual  increase 
in  size  of  the  petrous  portion  the  floccular  fossa  or  tunnel  under  the  superior  semicircular  canal 
becomes  filled 'up  and  almost  obliterated. 

Articulations. — With  Jive  bones — occipital,  parietal,  sphenoid,  mandible,  and  malar. 

Attachment  of  Muscles.— To  fifteeen—to  the  squamous  portion,  the  Temporal;  to  the 
zygoma,  the  Masseter;  to  the  mastoid  portion,  the  Occipitofrontalis,  Sternomastoid,  Splenius 
<;apitis,  Trachelomastoid,  Digastric,  and  Posterior  auricular;  to  the  styloid  process,  the  Stylo- 
pharyngeus,  Stylohyoid,  and  Styloglossus;  and  to  the  petrous  portion,  the  Levator  palati,  Tensor 
tympani.  Tensor  palati,  and  Stapedius. 


The  Sphenoid  Bone  (Os  Sphenoidale). 


The  sphenoid  bone  is  situated  at  the  anterior  part  of  the  base  of  the  skull, 
articulating  with  all  the  other  cerebral  cranial  bones,  which  it  binds  firmly  and 
solidly  together.  In  its  form  it  somewhat  resembles  a  bat  with  its  wings  extended ; 
and  is  divided  into  a  central  portion  or  body,  two  greater  and  two  lesser  wir.gs 


90 


SPECIAL  ANATOMY  OF  THE  SKELETON 


extending  outward  on  each  side  of  the  body,  and  two  processes — the  pterygoid 
processes — which  project  from  the  lower  part  of  this  body. 

The  Body  {corpus). — The  body  is  of  large  size  and  hollowed  out  in  its  interior 
so  as  to  form  a  mere  shell  of  bone.  It  presents  for  examination  four  surfaces — 
a  superior,  an  inferior,  an  anterior,  and  a  posterior. 

Surfaces. — The  superior  surface  (Fig.  56)  presents  in  front  a  prominent  spine, 
the  ethmoidal  spine,  for  articulation  with  the  cribriform  plate  of  the  ethmoid; 
behind  this  is  a  smooth  surface  having  in  the  median  line  a  slight  longitudi- 
nal eminence,  with  a  depression  on  each  side  for  the  lodgment  of  the  olfac- 
tory lobes.  This  surface  is  bounded  behind  by  a  ridge,  which  forms  the  ante- 
rior border  of  a  narrow,  trans^'erse  groove,  the  optic  groove  {sulnis  chiasmatis) ; 
behind  the  ridge  lies  the  optic  chiasm ;  the  groove  is  continuous  on  each  side  with 
the  optic  foramen  (foramen  opticum)  ,ioT  the  passage  of  the  optic  nerve  and  ophthal- 
mic artery.     Behind  the  optic  groove  is  a  small  eminence,  olive-like  in  shape,  the 


Middle  chnoid  process. 
Posterior  dinoid  process. 


Ethmoidal 


Optic  foramen. 

Sphenoidal  fissure 

Foramen  rotundum. 

Foramen  Vesalii: 

Foramen  oval^: 

Foramen  spinosum. 


Fig.  56 — Sphenoid   bone.     Superior   surface. 


olivary  eminence  (tuberculum  sellae) ;  and  still  more  posteriorly  a  deep  depression, 
the  sella  turcica  (fossa  hypophyseos) ,  which  lodges  the  circular  sinus  and  the 
hypophysis.  This  fossa  is  perforated  by  numerous  foramina,  for  the  transmission 
of  nutrient  vessels  into  the  substance  of  the  bone.  It  is  bounded  in  front  by  the 
olivary  eminence,  and  also  by  two  small  processes,  one  on  either  side,  called  the 
middle  clinoid  processes  (processus  clinoidei  medii),  which  are  sometimes  connected 
by  a  spiculum  of  bone  to  the  anterior  clinoid  processes.  It  is  bounded  behind  by 
a  square-shaped  plate  of  bone,  the  dorsum  sellae,  terminating  at  each  superior 
angle  in  a  tubercle,  the  posterior  clinoid  process  (processus  clinoideus  posterior'). 
The  size  and  form  of  these  processes  vary  considerably  in  different  individuals. 
They  deepen  the  sella  turcica,  and  serve  for  the  attachment  of  prolongations 
from  the  tentorium  cerebelli.  The  sides  of  the  dorsum  sellae  are  notched  for 
the  passage  of  the  abducent  nerves,  and  below  present  a  sharp  process,  the 
petrosal  process,  which  is  joined  to  the  apex  of  the  petrous  portion  of  the  temporal 
bone,  forming  the  inner  boundary  of  the  middle  lacerated  foramen.  Behind 
this  plate  the  bone  presents  a  shallow  depression,  which  slopes  obliquely  backward, 
and  is  continuous  with  the  basilar  groove  of  the  occipital  bone;  it  is  called  the 
clivus,  and  supports  the  upper  part  of  the  pons.     On  either  side  of  the  body  is 


THE  SPHENOID  BONE 


91 


a  broad,  /-shaped  groove,  which  lodges  the  internal  carotid  artery  and  the 
cavernous  sinus.  (See  page  724  for  other  structures  in  the  sinus.)  It  is  called 
the  cavernous  groove  {sulcus  caroiicus).  Along  the  outer  margin  of  this  groo\'e, 
at  its  posterior  part,  is  a  ridge  of  bone  in  the  angle  between  the  body  and  greater 
wing,  called  the  lingula  (lingula  sphenoidalis). 

The  posterior  surface,  quadrilateral  in  form,  is  joined  to  the  basilar  process 
of  the  occipital  bone.  During  childhood  these  bones  are  separated  by  a  layer 
of  cartilage;  but  later  (between  the  eighteenth  and  twenty-fifth  years)  this  becomes 
ossified  from  above  downward,  and  the  two  bones  then  form  one  piece. 

The  anterior  surface  (Fig.  57)  presents,  in  the  median  line,  a  vertical  ridge  of 
bone,  the  ethmoidal  crest  {crista  sphenoidalis),  which  articulates  in  front  with  the 
perpendicular  plate  of  the  ethmoid,  forming  part  of  the  septum  of  the  nose  (Fig. 
57).  On  either  side  of  it  are  irregular  openings  leading  into  the  sphenoidal  sinuses 
(sinus  sphenoidales),  which  are  two  large,  irregular  cavities  of  the  hollowed  out 
interior  of  the  body  of  the  sphenoid  bone,  and  separated  more  or  less  completely 
from  each  other  by  a  perpendicular  bony  septum  {septum  sinuuvi  sphenoidalium). 
Occasionally  they  extend  into  the  basilar  process  of  the  occipital  nearly  as  far 
as  the  foramen  magnum.     Their  form  and  size  vary  considerably;  they  are  seldom 


Flerygoid  ridge 


Jiiternal  pterygoid  plate. 
Hamv.lar  process. 


symmetrical,  and  are  often  partially  subdivided  by  irregular,  osseous  laminae. 
One  or  both  sinuses  may  be  absent.  The  septum  is  seldom  quite  vertical,  being 
commonly  bent  to  one  or  the  other  side.  These  sinuses  do  not  exist  in  very 
young  children,  but  appear,  according  to  Laurent,  in  the  seventh  year.  After 
once  appearing  they  increase  in  size  as  age  advances.  They  are  partially  closed, 
in  front  and  below,  by  two  thin,  curved  plates  of  bone,  the  sphenoidal  turbinated 
processes  {conchae  sphenoidales).  At  the  upper  part  of  each  is  a  round  opening 
{aperttira  sinus  sphenoidalis),  by  which  the  sinus  communicates  with  the  upper 
and  back  part  of  the  nose,  and  occasionally  with  the  posterior  ethmoidal  cells 
or  sinuses.  The  lateral  margins  of  the  surface  present  a  serrated  edge,  which 
articulates  with  the  os  planum  of  the  ethmoid,  completing  the  posterior  ethmoidal 
cells;  the  lower  margin,  also  rough  and  serrated,  articulates  with'  the  orbital 
process  of  the  palate  bone. 

The  inferior  surface  presents,  in  the  middle  line,  a  triangular  spine,  the  rostrum 


92  SPECIAL  ANA  TOMV  OF  THE  SKELETON 

(rostrum  sphenoidalis),  which  is  continuous  with  the  sphenoidal  crest  on  the 
anterior  surface,  and  is  received  into  a  deep  fissure  between  the  altie  of  the  vomer. 
On  each  side  may  be  seen  a  projecting  lamina  of  bone,  the  vaginal  process  (pro- 
cessus vaginalis),  which  runs  horizontally  inward  from  near  the  base  of  the  ptery- 
goid process  and  articulates  with  the  edges  of  the  vomer.  Close  to  the  root  of 
the  pterygoid  process  is  a  groove  (sulcus  plerygopalatinus),  formed  into  a  com- 
plete canal  when  articulated  with  the  sphenoidal  process  of  the  palate  bone;  it 
is  called  the  pterygopalatine  canal,  and  transmits  the  pterygopalatine  vessels 
and  a  pharyngeal  branch  of  the  sphenopalatine  ganglion. 

The  Greater  or  Temporal  Wings  {alae  magna) . — The  greater  wings  are  two 
strong  processes  of  bone  which  arise  from  the  sides  of  the  body,  and  are  curved 
in  a  direction  upward,  outward,  and  backward,  each  being  prolonged  behind 
into  a  sharp-pointed  extremity,  the  alar,  or  sphenoidal  spine  (spina  angidaris). 
Each  wing  presents  three  surfaces  and  a  circumference. 

Surfaces. — The  superior  surface  (fades  cerebralis)  (Fig.  56)  forms  part  of 
the  middle  fossa  of  the  skull;  it  is  deeply  concave,  and  presents  eminences  and 
depressions  for  the  convolutions  of  the  cerebrum.  At  its  anterior  and  internal 
part  is  seen  a  circular  aperture,  the  foramen  rotundum,  for  the  transmission  of 
the  second  division  of  the  trigeminal  nerve.  Behind  and  external  to  this  is  a 
large  oval  foramen,  the  foramen  ovale,  for  the  transmission  of  the  third  division 
of  the  trigeminal  nerve,  the  small  meningeal  artery,  and  sometimes  the  small 
petrosal  nerve.  At  the  inner  side  of  the  foramen  ovale  a  small  aperture  may 
occasionally  be  seen  opposite  the  root  of  the  pterygoid  process;  it  is  the  foramen 
Vesalii,  transmitting  a  small  vein.  In  the  posterior  angle,  near  to  the  spine  of 
the  sphenoid,  is  a  short  canal,  sometimes  double,  the  foramen  spinosum,  which 
transmits  the  middle  meningeal  artery  and  the  meningeal  branch  of  the  superior 
maxillary  nerve.  Just  to  the  inner  side  of  the  foramen  spinosum  a  minute  fora- 
men (canaliculus  innominatum)  is  occasionally  found,  for  the  passage  of  the  small 
petrosal  nerve. 

The  external  surface  (Fig.  57)  is  convex  and  divided  by  a  transverse  ridge, 
the  pterygoid  ridge  (crista  infratemporalis),  into  two  portions.  The  superior 
or  larger,  convex  from  above  downward,  concave  from  before  backward,  enters 
into  the  formation  of  the  temporal  fossa,  and  gives  attachment  to  part  of  the 
Temporal  muscle.  The  inferior  portion,  smaller  in  size  and  concave,  enters 
into  the  formation  of  the  zygomatic  fossa,  and  affords  attachment  to  the  External 
pterygoid  muscle.  It  presents,  at  its  posterior  part,  a  sharp-pointed  eminence 
of  bone,  the  spine,  to  which  are  connected  the  internal  lateral  ligament  of  the 
mandible  and  the  Tensor  palati  muscle.  At  its  inner  and  anterior  extremity  is 
a  triangular  spine  of  bone,  which  serves  to  increase  the  extent  of  origin  of  the 
External  pterygoid  muscle. 

The  anterior  surface  is  divided  into  two  parts,  the  orbital  surface  above  and  the 
sphenomaxillary  below.  The  orbital  surface  is  quadrilateral  in  form;  it  looks 
inward  and  forward,  and  assists  in  forming  the  outer  wall  of  the  orbit.  It 
is  bounded  above  by  a  serrated  edge  for  articulation  with  the  frontal  bone. 
Internally  this  edge  is  sharp  and  free  and  forms  the  lower  boundary  of  the 
sphenoidal  fissure.  At  about  the  centre  of  the  free  part  of  this  border  a  little 
tubercle  projects,  giving  origin  to  one  head  of  the  External  rectus  muscle  of  the 
eyeball.  At  its  outer  part  is  a  notch  for  the  transmission  of  a  recurrent  branch 
of  the  lacrimal  artery.  The  outer  border  is  serrated  for  articulation  with  the 
malar  bone.  The  lower  border  is  rounded  and  enters  into  the  formation  of  the 
sphenomaxillary  fissure.  This  border  separates  the  orbital  surface  above  from 
the  sphenomaxillary  portion  below.  This  latter  portion  is  situated  just  above 
the  pterygoid  process  and  helps  to  form  the  posterior  wall  of  the  sphenomaxillary 


THE  SPHENOID  BONE 


93 


fossa  in  the  articulated  skull  and  exhibits  the  anterior  extremity  of  the  foramen 
rotundum. 

Circumference  (Fig.  56). — Commencing  from  behind,  that  portion  of  the  circum- 
ference of  the  body  of  the  sphenoid  to  the  spine  is  serrated  and  articulates  by  its 
outer  half  with  the  inner  part  of  the  antero-superior  border  of  the  petrous  portion 
of  the  temporal  bone,  while  the  inner  half  forms  the  anterior  boundary-  of  the  mid- 
dle lacerated  formaen,  and  presents  the  posterior  aperture  of  the  Vidian  canal 
{canalis  pterygoideus) ,  for  the  passage  of  the  Vidian  nerve  and  artery.  In  front 
of  the  spine,  the  circumference  of  the  greater  wing  presents  a  serrated  edge, 
bevelled  at  the  expense  of  the  inner  table  below  and  of  the  external  above,  which 
articulates  with  the  squamous  portion  of  the  temporal  bone.  At  the  tip  of  the 
greater  wing  a  triangular  portion  is  seen,  bevelled  at  the  expense  of  the  internal 
surface,  for  articulation  with  the  anterior  inferior  angle  of  the  parietal  bone. 
Internal  to  this  is  a  triangular,  serrated  surface,  for  articulation  with  the  frontal 


Posterior  view. 


bone ;  this  surface  is  continuous  internally  with  the  sharp  inner  edge  of  the  orbital 
plate,  which  assists  in  the  formation  of  the  sphenoidal  fissure,  and  externally 
with  the  serrated  margin  for  articulation  with  the  malar  bone. 

The  Lesser  or  Orbital  Wings  {alae  parvae). — The  lesser  wings  are  two  thin 
triangular  plates  of  bone  which  arise,  one  on  each  side,  from  the  upper  part  of  the 
lateral  surface  of  the  body  of  the  sphenoid,  and,  projecting  transversely  outward, 
terminate  in  a  sharp  point  (Fig.  56).  The  superior  surface  of  each  forms  part  of 
the  anterior  fossa  of  the  skull,  is  smooth,  flat,  broader  internally  than  externally, 
and  supports  part  of  the  frontal  lobe  of  the  cerebrum.  The  inferior  surface 
forms  the  back  part  of  the  roof  of  the  orbit  and  the  upper  boundary  of  the  sphenoi- 
dal fissure,  or  foramen  lacerum  anterius.  This  fissure  is  of  a  triangular  form,  and 
leads  from  the  cavity  of  the  cranium  into  the  orbit.  It  transmits  the  third,  the 
fourth,  the  three  branches  of  the  ophthalmic  di^■ision  of  the  trigeminal,  the 
abducent  nerve,  some  filaments  from  the  cavernous  plexus  of  the  sympathetic,  the 
orbital  branch  of  the  middle  meningeal  artery,  a  recurrent  branch  from  the  lacri- 
mal artery  to  the  dura  and  the  ophthalmic  vein.     The  anterior  border  of  the  lesser 


94 


SPECIAL  ANATOMY  OF  THE  SKELETON 


wing  is  serrated  for  articulation  with  the  frontal  bone ;  the  posterior  border,  smooth 
and  rounded,  is  received  into  the  sylvian  fissure  of  the  cerebrum.  The  inner 
extremity  of  this  border  forms  the  anterior  clinoid  process  {processus  dinoideus 
anterior).  The  lesser  wing  is  connected  to  the  side  of  the  body  by  two  roots,  the 
upper  thin  and  flat,  the  lower  thicker,  obliquely  directed,  and  presenting  on  its 
outer  side,  near  its  junction  with  the  body,  a  small  tubercle,  for  the  attachment 
of  the  common  tendon  of  origin  of  three  of  the  Extrinsic  muscles  of  the  eye.  Be- 
tween the  two  roots  is  the  optic  foramen,  for  the  transmission  of  the  optic  nerve 
and  ophthalmic  artery. 

The  Pterygoid  Processes  {-processus  pterygoidei). — ^The  pterygoid  processes, 
one  on  each  side,  descend  perpendicularly  from  the  place  where  the  body  and 
greater  wing  unite  (Fig.  59).  Each  process  consists  of  an  external  and  an  in- 
ternal plate,  which  are  joined  together  by  their  anterior  borders  above,  but 
are  separated  below,  leaving  an  angular  cleft,  the  pterygoid  notch,  in  which  the 
pterygoid  tuberosity  of  the  palate  bone  is  received.  The  two  plates  diverge 
from  each  other  from  their  line  of  connection  in  front,  so  as  to  form  in  conjunc- 
tion with  the  tuberosity  of  the  palate  bone  a  V-shaped  fossa,  the  pterygoid  fossa. 
The  external  pterygoid  plate  {laviina  lateralis  processus  pterygoidei)  is  broad  and 


Fig.  59. — Sphenoid  bone.     Posterior  surface. 


thin,  turned  a  little  outward,  and,  by  its  outer  surface,  forms  part  of  the  inner  wall 
of  the  zygomatic  fossa,  giving  attachment  to  the  External  pterygoid;  its  inner  sur- 
face forms  part  of  the  pterygoid  fossa,  and  gives  attachment  to  the  Internal 
pterygoid.  The  posterior  border  of  this  plate  frequently  has  one  or  more  rough 
projections,  to  one  of  which  is  attached  the  pterygospinous  ligament,  when  this  is 
present.  The  internal  pterygoid  plate  {lamina  medialis  processus  pterygoidei)  is 
much  narrower  and  longer,  curving  outward,  at  its  extremity,  into  a  hook-like 
process  of  bone,  the  hamular  process  {haviulii-s  pterygoideus) ,  around  which  turns 
the  tendon  of  the  Tensor  palati  muscle.  The  outer  surface  of  this  plate  forms 
part  of  the  pterygoid  fossa,  the  inner  surface  forming  the  outer  boundary  of  the 
posterior  aperture  of  the  nares.  The  posterior  border  of  this  plate  gives  attach- 
ment to  the  phar.yngeal  aponeurosis  throughout  its  entire  length.  The  Superior 
constrictor  muscle  of  the  pharynx  arises  from  its  lower  half.  Projecting  back- 
ward from  the  middle  of  this  border  is  a  spine  {processus  tuharius),  which  supports 
the  pharyngeal  end  of  the  Eustachian  tube.  Above  this  the  border  divides  into 
two  lips;  the  space  between  is  the  scaphoid  fossa  ( fossa  scaphoidea).  In  this  fossa 
arises  the  Tensor  palati  muscle.  The  anterior  margin  articulates  with  the  poste- 
rior border  of  the  perpendicular  plate  of  the  palate  bone. 

Superiorly,  the  internal  pterygoid  plate  has  a  thin  lamina  of  bone,  the  vaginal 


THE  SPHENOID  BOXE 


95 


process  {processus  vagiiialis),  which  runs  inward  on  the  under  surface  of  the  body  of 
the  sphenoid  nearly  to  tlie  rostrum.  In  the  groove  between  the  two  in  the  articu- 
lated skull  are  seen  the  alae  of  the  vomer.  On  the  under  surface  of  the  vaginal 
process  is  a  groove  (svlciis  pterygopalatimos),  which  in  the  articulated  skull  is  con- 
verted into  the  pterygopalatal  canal  by  union  with  the  sphenoidal  process  of  the 
palate  bone.  At  the  junction  of  the  vaginal  process  and  the  inner  plate  is  the 
pterygoid  tubercle,  just  above  which  is  the  posterior  opening  of  the  Mdian  canal. 
The  anterior  surface  of  the  pterygoid  process  is  quite  broad  at  its  base,  and  forms 
the  chief  part  of  the  posterior  wall  of  the  sphenomaxillary  fossa. 

The  Sphenoidal  Turbinated  Processes  (conchae  sphenoidales). — The  sphe- 
noidal turbinated  processes  are  two  thin  curved  plates  of  bone,  which  exist  as 
separate  pieces  until  puberty,  and  occasionally  are  not  joined  to  the  sphenoid 
in  the  adult.  They  are  situated  at  the  anterior  part  of  the  body  of  the  sphe- 
noid, an  aperture  (aperiura  sinus  sjjhcnoidalis)  of  \ariable  size  being  left  in 
the  anterior  wall  of  each,  through  which  the  sphenoidal  sinuses  open  into  the 
nasal  fossse.  They  are  irregular  in  form  and  taper  to  a  point  behind,  being 
broader  and  thinner  in  front.  Their  upper  surface,  which  looks  toward  the 
cavity  of  the  sinus,  is  concave;  their  under  surface  convex.  Each  bone  articulates 
in  front  with  the  ethmoid,  externally  with  the  palate;  its  pointed  posterior 
extremity  is  placed  above  the  vomer,  and  is  received  between  the  root  of 
the  pterygoid  process  on  the  outer  side  and  the  rostrum  of  the  sphenoid  on  the 
inner.' 

Development. — Up  to  about  the  eighth  month  of  fetal  life  the  sphenoid  bone  consists  of  two 
distinct  parts — a  posterior  or  postsphenoid  part,  which  comprises  the  sella  turcica,  the  greater 
wings,  and  the  pterygoid  processes;  and  an  anterior  or  presphenoid  part,  to  which  the  anterior 
part  of  the  body  and  lesser  wings  belong.  It  is  developed  (ram  fourteen  centres — eight  for  the 
postsphenoid  division  and  six  for  the  presphenoid.  All  parts  except  the  internal  pterygoid 
plates  have  an  intracartilaginous  origin. 

Postsphenoid  Division. — The  first  nuclei  to  appear  are  those  for  the  greater  wings  (alt- 
sphenoids).  They  make  their  appearance  between  the  foramen  rotundum  and  foramen  ovale 
about  the  eighth  week,  and  from  them  the  external  pterygoid  plates  are  also  formed.  Soon  after, 
the  nuclei  for  the  posterior  part  of  the  body  appear,  one  on  either  side  of  the  sella  turcica,  and 
become  blended  together  aljout  the  middle  of  fetal  life.  About  the  ninth  or  tenth  week  the 
centre  for  the  internal  pterygoid  plate  appears,  followed  by  the  centre  for  the  hamiilar  process; 
the  centre  for  the  lingula  appears  during  the  fourth  month,  and  soon  joins  the  rest  of  the  body. 
The  internal  and  external  pterygoid  plates  become  joined  at  about  the  sixth  month. 

one  for  each     two  for  anterior 
lesser  wing,    part  of  body. 


one  for  each  tntemat  - 
pterygoid  plate 

one  for  /»'  «««''  hngula  v 

each  greater  wing  and  external  ptery- 
[_goid  plate, 
one/or  each  Sphenoidal  turbinated  process. 


Fig.  61. — Sphenoid  bone  at  birth.     Posterior  aspect. 


Presphenoid  Division. — The  first  nuclei  to  appear  are  those  for  the  lesser  wings  (orbito- 
phenoids).     They  make  their  appearance  about  the  ninth  week,  at  the  outer  borders  of  the  optic 


*  -A.  small  portion  of  the  sphenoidal  turbinated  process  sometimes  enters  into  the  formation  of  the  inner 
wall  of  the  orbit,  between  the  os  planum  of  the  ethmoid  in  front,  the  orbital  plate  of  the  palate  below,  and 
the  frontal  above. — Cleland,  Roy.  Soo.  Trans.,  1862. 


96 


SPECIAL  ANATOMY  OF  THE  SKELETON 


foramina.  A  second  pair  of  nuclei  appears  on  the  inner  side  of  the  foramina  shortly  after,  and, 
becoming  united,  form  the  front  part  of  the  body  of  the  bone.  The  remaining  two  centres  for 
the  sphenoidal  turbinated  processes  make  their  appearance  about  the  fifth  month.  At  birth  they 
consist  of  small  triangular  laminse,  and  it  is  not  until  the  third  year  that  they  become  hollowed  out 
and  cone-shaped.  About  the  fourth  j-ear  they  become  fused  with  the  lateral  masses  of  the 
ethmoid,  and  between  the  ninth  and  twelfth  years  they  unite  with  the  sphenoid  bone. 

The  presphenoid  is  united  to  the  body  of  the  postsphenoid  about  the  eighth  month,  so  that  at 
birth  the  bone  consists  of  three  pieces — viz.,  the  body  in  the  centre,  and  on  each  side  the  great 
wings  with  the  pterygoid  processes.  The  lesser  wings  become  joined  to  the  body  at  about  the 
time  of  birth.  During  the  first  year  after  birth  the  greater  wings  and  l:>ody  are  united.  From 
the  ninth  to  the  twelfth  year  the  turbinated  processes  are  partially  united  to  the  sphenoid,  their 
junction  being  complete  by  the  twentieth  year.  Lastly,  the  sphenoid  joins  the  occipital  from  the 
eighteenth  to  the  twenty-fifth  year. 

Articulations. — The  sphenoid  articulates  with  all  the  bones  of  the  cerebral  cranium,  and 
five  pf  the  face — the  two  malar,  the  two  palate,  and  vomer;  the  exact  extent  of  articulation  with 
each  bone  is  shown  in  the  accompanying  figures.' 

Attachment  of  Muscles. — To  elemn  pairs — the  Temporal,  External  pterygoid,  Internal 
pterygoid,  Superior  constrictor,  Tensor  palati,  Levator  palpebrae,  Superior  oblique,  Superior 
rectus.  Internal  rectus,  Inferior  rectus.  External  rectus. 

The  Ethmoid  Bone  (Os  Ethmoidale) . 

The  ethmoid  is  an  exceedingly  light,  spongy  bone,  of  a  cubical  form,  situated 
at  the  anterior  part  of  the  base  of  the  cranium  proper,  between  the  two  orbits 
at  the  root  of  the  nose,  and  contributing  to  the  formation  of  each  of  these  cavi- 
ties. It  consists  of  four  parts — a  horizontal  plate,  which  forms  part  of  the  base 
of  the  cranium  proper;  a  perpendicular  plate,  which  forms  part  of  the  septum  of 
the  nose;  and  two  lateral  masses,  containing  a  number  of  spaces. 


Slit  for  nasal  nerv& 

Anterior  ethmoidal  cells 


Vertical  plate 
{lamina  perpendicularis) 


Unciform  process 


Fig.  62. — Ethmoid  bone.     Outer  surface  of  right  lateral  mass.     (Enlarged.) 

The  Horizontal  Lamina,  or  Cribriform  Plate  {lamina  cribrosa)  (Fig.  62),  forms 
part  of  the  anterior  fossa  of  the  base  of  the  skull,  and  is  received  into  the  eth- 
moid notch  of  the  frontal  bone  between  the  two  orbital  plates.  Projecting  up- 
ward from  the  middle  line  of  this  plate  is  a  thick,  smooth,  triangular  process  of 
bone,  the  crista  galli.  Its  base  joins  the  cribriform  plate.  Its  posterior  border, 
long,  thin,  and  slightly  curved,  serves  for  the  attachment  of  the  falx  cerebri.  Its 
anterior  border,  short  and  thick,  articulates  with  the  frontal  bone,  and  presents 
two  small  projecting  alse  {'processus  alares),  which  are  received  into  corresponding 
depressions  in  the  frontal,  completing  the  foramen  cecum  behind.  Its  sides  are 
smooth  and  sometimes  bulging,  in  which  case  it  is  found  to  enclose  a  small  sinus. 
On  each  side  of  the  crista  galli  the  cribriform  plate  is  narrow  and  deeply  grooved, 
to  support  the  bulb  of  the  olfactory  tract,  and  is  perforated  by  foramina  for  the 
passage  of  the  olfactory  nerves.  These  foramina  are  arranged  in  three  rows: 
The  innermost,  which  are  the  largest  and  least  numerous,  are  lost  in  grooves  on  the 

lit  also  sometimes  articulates  with  the  tuberosity  of  the  maxilla. 


THE  ETHMOID  BONE 


97 


upper  part  of  the  septum ;  the  foramina  of  the  outer  row  are  continued  on  to  the 
surface  of  the  superior  turbinated  process.  The  foramina  of  the  middle  row 
are  the  smallest;  they  perforate  the  bone  and  transmit  nerves  to  the  roof  of  the 
nose.  At  the  front  part  of  the  cribriform  plate,  on  each  side  of  the  crista  galli,  is 
a  small  fissure,  which  transmits  the  nasal  branch  of  the  ophthalmic  nerve;  and 
at  its  posterior  part  a  triangular  notch,  which  receives  the  ethmoidal  spine  of  the 
sphenoid. 


Cnsta  galh 


Lamina  crihrosa 


Lateral  7ii.ass 


Superior  turhina  ted 

process 
Superior  meatus 

Piocessus  uncinaius 


Biferior  turbinated  process 
Perpendicular  plate 


Fig.  63. — Ethmoid  bone  from  behind. 


Fig.  64. — Ethmoid  bo 


(Spalteholz.) 


icitli  EtlimoKfa/ 


The  Vertical  Plate  {lamina  perpendicular  is)  (Fig.  65)  is  a  thin,  flattened, 
lamella  of  bone,  which  descends  from  the  under  surface  of  the  cribriform  plate, 
and  assists  in  forming  the  septum  of  the  nose.  It  is  much  thinner  in  the  middle 
than  at  the  circumference, 
and  is  generally  deflected 
a  little  to  one  side.  Its 
anterior  border  articulates 
with  the  nasal  spine  of  the 
frontal  bone  and  crest  of 
the  nasal  bones.  Its  pos- 
terior border,  divided  into 
two  parts,  articulates  by 
its  upper  half  with  the 
sphenoidal  crest  of  the 
sphenoid,  by  its  lower 
half  with  the  vomer.  The 
inferior  border  serves  for 
the  attachment  of  the 
triangular  cartilage  of  the 
nose.  On  each  side  of 
the  perpendicular  plate 
numerous  grooves  are  seen, 

leading  from  the  foramina  on  the  cribriform  plate;  they  lodge  filaments  of  the 
olfactory  nerves. 

The  Lateral  Mass,  or  Labyrinth  (labyrinthus  ethmoidalis),  of  the  ethmoid 
consists  of  a  number  of  thin-walled  cellular  cavities,  the  ethmoidal  cells  (celhdae 
ethvioidales),  interposed  between  two  vertical  plates  of  bone,  the  outer  one  of  which 
forms  part  of  the  orbit,  and  the  inner  one  part  of  the  outer  wall  of  the  nasal  fossa 


Fig.  65. — Perpendicula 


■  plate  of  ethmoid  (enlarged) ,  showr 
the  right  lateral  mass. 


98 


SPECIAL  ANA  TO  MY  OF  THE  SKELETON 


Fig.  66. — Ethmoid  bone.     Inner  surface  of  right  lateral 


of  the  corresponding  side.  There  are  two  lateral  masses,  one  on  each  side.  The 
ethmoidal  cells  are  not  present  at  birth,  but  appear  during  the  fifth  year.  In  the 
disarticulated  bone  many  of  these  cells  appear  to  be  broken ;  but  when  the  bones  are 
articulated  they  are  closed  in  at  every  part,  except  where  they  open  into  the  nasal 
fossae.  The  upper  surface  of  each  lateral  mass  presents  a  number  of  apparently 
half-broken  cellular  spaces;  these  are  closed  in,  when  articulated,  by  the  edges  of 
the  ethmoidal  notch  of  the  frontal  bone.  Crossing  this  surface  are  two  grooves 
on  each  side,  converted  into  canals  by  articulation  with  the  frontal;  they  are  the 
anterior  and  posterior  ethmoidal  canals  (canalis  ethmoidale  anterius  et  posterius), 
and  open  on  the  inner  wall  of  the  orbit.  The  anterior  transmits  the  nasal  nerve 
and  the  anterior  ethmoidal  vessels;  the  posterior  transmits  the  posterior  ethmoidal 
A'essels. .  The  posterior  surface  also  presents  large  irregular  cellular  cavities,  which 
are  closed  in  by  articulation  with  the  sphenoidal  turbinated  processes  and  the  orbi- 
tal process  of  the  palate.  The  cells  at 
the  anterior  surface  are  completed  by 
the  lacrimal  bone  and  nasal  process  of 
the  maxilla,  and  those  below  also  by 
the  maxilla.  The  outer  surface  of  each 
lateral  mass  consists  chiefly  of  a  thin, 
smooth,  oblong  plate  of  bone,  called 
the  OS  planum  (lamina  papyracea);  it 
forms  part  of  the  inner  wall  of  the  orbit, 
and  articulates,  above,  with  the  orbital 
plate  of  the  frontal;  helow,  with  the 
maxilla;  in  front,  with  the  lacrimal; 
and  behind,  with  the  sphenoid  .and 
orbital  process  of  the  palate.  In 
front  of  the  os  planum  are  found  the  anterior  ethmoidal  cells,  which  are  completed 
by  the  lacrimal  bone  and  the  nasal  process  of  the  maxilla. 

From  the  inferior  part  of  each  lateral  mass,  immediately  beneath  the  os 
planum,  there  projects  downward  and  back'ward  an  irregular  hook-like  lamina 
of  bone,  called  the  unciform  process  (processus  uncinatus);  it  serves  to  close  in 
the  upper  part  of  the  orifice  of  the  antrum  (Fig.  71),  and  articulates  with  the 
ethmoidal  process  of  the  turbinated  bone.  It  is  often  broken  in  disarticulating 
the  bones. 

The  inner  surface  of  each  lateral  mass  forms  part  of  the  outer  wall  of  the  nasal 
fossa  of  the  corresponding  side.  It  is  formed  of  a  thin  lamella  of  bone,  which 
descends  from  the  under  surface  of  the  cribriform  plate,  and  terminates  below  in 
a  free,  convoluted  margin,  the  middle  turbinated  process  (concha  nasalis  media). 
The  whole  of  this  surface  is  rough  and  marked  above  by  numerous  grooves,  which 
run  nearly  vertically  downward  from  the  cribriform  plate;  they  lodge  branches 
of  the  olfactory  nerve,  which  are  distributed  on  the  mucous  membrane  covering 
the  bone.  The  back  part  of  this  surface  is  subdivided  by  a  narrow  oblique  fissure, 
the  superior  meatus  of  the  nose,  bounded  above  by  a  thin,  curved  plate  of  bone, 
the  superior  turbinated  process  (concha  nasalis  superior).  By  means  of  an  orifice 
at  the  upper  part  of  this  fissure  the  posterior  ethmoidal  cells  open  into  the  superior 
meatus.  Below,  and  in  front  of  the  superior  meatus,  is  seen  the  convex  surface 
of  the  middle  turbinated  process.  It  extends  along  the  whole  length  of  the  inner 
surface  of  each  lateral  mass.  The  middle  of  its  lower  margin  is  free  and  thick. 
The  anterior  portion  articulates  with  the  superior  turbinated  crest  of  the  nasal 
process  of  the  maxilla,  and  the  posterior  portion  articulates  with  the  superior  tur- 
binated crest  of  the  maxilla  and  palate  bone.  Its  concavity,  directed  outward, 
assists  in  forming  the  middle  meatus.     It  is  by  a  large  orifice  at  the  upper  and 


THE  NASAL  BONES  99 

front  part  of  the  middle  meatus  that  the  anterior  ethmoidal  cells,  and  through 
them  the  frontal  sinuses,  communicate  with  the  nose  by  means  of  a  funnel- 
shaped  canal,  the  infundibulum  {infundihulum  ethnoidale)  (Fig.  62).  The  cell- 
ular cavities  of  each  lateral  mass,  thus  walled  in  by  the  os  planum  in  the  outer 
side  and  by  the  other  bones  already  mentioned,  are  divided  by  a  thin  trans- 
verse bony  partition  into  two  sets,  which  do  not  communicate  with  each  other; 
they  are  termed  the  anterior  and  posterior  ethmoidal  sinuses.  The  former,  more 
numerous,  communicate  with  the  frontal  sinuses  above  and  the  middle  meatus; 
below  by  means  of  the  infundibulum;  the  posterior,  less  numerous,  open  into 
the  superior  meatus  and  communicate  (occasionally)  with  the  sphenoidal  sinuses. 
In  some  cases  the  ethmoidal  sinuses  communicate  with  the  maxillary  sinus. 
In  some  cases  the  os  planum  never  develops,  and  the  ethmoidal  sinuses  are 
separated  from  the  orbit  merely  by  membrane. 

Development. — The  ethmoid  is  developed  in  cartilage  from  three  centres — one  for  the  per- 
pendicular lamella,  and  one  for  each  lateral  mass.  The  lateral  masses  are  first  developed, 
ossific  granules  making  their  appearance  in  the  os  planum  between  the  fourth  and  fifth  months 
of  fetal  life,  and  extending  into  the  turbinated  processes.  At  birth  the  bone  consists  of  the  two 
lateral  masses,  which  are  small  and  poorly  developed.  During  the  first  year  after  birth  the 
perpendicular  plate  and  crista  galli  begin  to  ossify,  from  a  single  centre,  and  become  joined  to  the 
lateral  masses  about  the  beginning  of  the  second  year.  The  cribriform  plate  is  ossified  partly 
from  the  perpendicular  plate  and  partly  from  the  lateral  masses.  The  formation  of  the  ethmoidal 
cells,  which  completes  the  bone,  does  not  commence  until  the  end  of  the  fourth  year. 

Articulations. — With  thirteen  bones — the  sphenoid,  the  frontal,  and  eleven  of  the  face,  the 
two  nasal,  two  palate,  two  maxillse,  two  lacrimal,  two  turbinated,  and  the  vomer.  No  muscles 
are  attached  to  this  bone. 

THE  BONES  OF  THE  FACE   (OSSA  FACIEI). 

The  facial  bones  are  fourteen  in  number — viz.,  the 

Two  nasal.  Two  palate. 

Two  maxillse.  Two  turbinated. 

Two  lacrimal.  Vomer. 

Two  malar.  Mandible. 


The  Nasal  Bones  (Ossa  Nasalia). 

The  nasal  bones  are  two  small  oblong  bones,  varying  in  size  and  form  in  dif- 
ferent individuals;  they  are  placed  side  by  side  at  the  middle  and  upper  part  of 
the  face,  forming  by  their  junction  "the  bridge"  of  the  nose  (Fig.  67).  Each 
bone  presents  for  examination  two  surfaces  and  four  borders. 

Surfaces. — The  outer  surface  is  concave  from  abo\'e  downward,  convex  from 
side  to  side;  it  is  covered  by  the  Pyramidalis  and  Compressor  nasi  muscles.  It 
is  marked  by  numerous  small  arterial  furrows,  and  perforated  about  its  centre 
by  a  foramen  {foramen  nasale),  sometimes  double,  for  the  transmission  of  a 
sinall  vein. 

The  inner  sm'face  is  concave  from  side  to  side,  convex  from  above  downward, 
in  which  direction  it  is  traversed  by  a  longitudinal  groove  (sometimes  a  canal), 
for  the  passage  of  a  branch  of  the  nasal  nerve. 

Borders. — The  superior  border  is  narrow,  thick,  and  serrated,  for  articulation 
with  the  nasal  notch  of  the  frontal  bone. 

The  inferior  border  is  broad,  thin,  sharp,  inclined  obliquely  downward,  out- 
ward, and  backward,  and  serves  for  the  attachment  of  the  lateral  cartilage  of 
the  nose.     This  border  presents,  about  its  middle,  a  notch,  through  which  passes 


100 


SPECIAL  ANATOMY  OF  THE  SKELETON 


the  branch  of  the  nasal  nerve  above  referred  to,  and  is  prolonged  at  its  inner 
extremity  into  a  sharp  spine,  which,  when  articulated  with  the  opposite  bone, 
forms  the  nasal  angle. 

The  external  border  is  serrated,  bevelled  at  the  expense  of  the  internal  surface 
above  and  of  the  external  below,  to  articulate  with  the  nasal  process  of  the 
maxilla. 


Mic.  with  malar. 


Groove  for 
nasal  nerve 


Inner  Surface. 

Fig.  69.— Left  nasal  bone 


The  internal  border,  thicker 
above  than  below,  articulates 
with  its  fellow  of  the  opposite 
side,  and  is  prolonged  behind 
into  a  vertical  crest,  which 
forms  part  of  the  septum  of  the 
nose;  this  crest  articulates  from 
above  downward  with  the  nasal 
spine  of  the  frontal,  the  per- 
pendicular plate  of  the  eth- 
moid, and  the  triangular  septal 
cartilage  of  the  nose. 


Development. — Of  intramembranous  origin  and  from  one  centre  for  each  bone,  which 
appears  about  the  eighth  week. 

Articulations. — With  four  bones — two  of  the  cerebral  cranium,  the  frontal  and  ethmoid, 
and  two  of  the  face,  the  opposite  nasal  and  the  maxilla. 

The  nasal  bone  has  no  muscles  attached  to  it. 


The  Maxillae  (Upper  Jaw). 

The  maxillae  are  the  largest  bones  of  the  face,  excepting  the  mandible,  and 
form,  by  their  union,  the  whole  of  the  upper  jaw.  Each  maxilla  assists  in  the 
formation  of  the  walls  of  three  cavities,  the  roof  of  the  mouth,  the  floor  and 
outer  wall  of  the  nasal  fossae,  and  the  floor  of  the  orbit,  and  also  enters  into  the 


THE  MAXILLA 


101 


formation  of  two  fossae,  the  zygomatic  and  sphenomaxillary,  and  two  fissures, 
the  sphenomaxillary  and  pterygomaxillary.  The  bone  presents  for  examination 
a  body  and  four  processes — malar,  nasal,  alveolar,  and  palatal. 

The  Body  (corpus  maxillae). — The  body  is  somewhat  cuboid  and  is  hollowed 
out  in  its  interior  to  form  a  large  cavity,  the  antrum  of  Highmore  {sinus  maxillaris). 
Its  surfaces  are  four — an  external  or  facial,  a  posterior  or  zygomatic,  a  superior 
or  orbital,  and  an  internal  or  nasal. 

Surfaces. — The  facial  surface  (fades  anterior)  (Fig.  70)  is  directed  forward  and 
outward.  It  presents  at  its  lower  part  a  series  of  eminences  corresponding  to  the 
position  of  the  anterior  five  teeth.  Just  above  those  for  the  incisor  teeth  is  a 
depression,  the  incisive  fossa,  which  gives  origin  to  the  Depressor  alae  nasi ;  and 
below  it  to  the  alveolar  border  is  attached  a  slip  of  the  Orbicularis  oris.  Above 
and  a  little  external  to  it  the  Compressor  naris  arises.  More  external  is  another 
depression,  the  canine  fossa  (fossa  canina),  larger  and  deeper  than  the  incisive  fossa, 
from  which  it  is  separated  by  a  vertical  ridge,  the  canine  eminence,  corresponding  to 
the  socket  of  the  canine  tooth.  The  canine  fossa  gives  origin  to  the  Levator  anguli 
oris.     Above  the  canine  fossa  is  the  infraorbital  foramen  {foramen  infraorbiiale), 

Outer  Surface. 


Incisive  fossa. 


Posterior  dental 
canals. 


Maxillary  tuberosity. 


Fig.  70. — Left  maxilla.     Outer  surface. 


the  termination  of  the  infraorbital  canal;  it  transmits  the  infraorbital  vessels  and 
nerve.  Sometimes  the  infraorbital  canal  opens  by  two,  very  rarely  by  three, 
orifices  on  the  face.  Above  the  infraorbital  foramen  is  the  margin  of  the  orbit 
{margo  infraorhitalis),  which  affords  partial  attachment  to  the  Levator  labii 
superioris.  To  the  sharp  margin  of  bone  which  bounds  this  surface  in  front 
and  separates  it  from  the  internal  surface  is  attached  the  Dilatator  naris  posterior. 
The  posterior  (fades  infratem-poralis)  or  zygomatic  surface  is  convex,  directed 
backward  and  outward,  and  forms  part  of  the  zygomatic  fossa.  It  is  sepa- 
rated from  the  facial  surface  by  a  strong  ridge  of  bone,  the  malar  process,  which 
extends  upward  from  the  socket  of  the  second  molar  tooth.  It  presents  about 
its   centre   several   apertures   leading  to  canals   in   the  substance  of  the  bone; 


102  SPECIAL  ANATOMY  OF  THE  SKELETON 

they  are  termed  the  posterior  dental  canals  {foramina  aheolaria),  and  transmit 
the  posterior  dental  vessels  and  nerves.  At  the  lower  part  of  this  surface  is  a 
rounded  eminence,  the  maxillary  tuberosity  {tuber  maxillare),  especially  prominent 
after  the  growth  of  the  wisdom  tooth,  rough  on  its  inner  side  for  articulation  with 
the  tuberosity  of  the  palate  bone,  and  sometimes  with  the  external  pterygoid 
plate.  It  gives  attachment  to  a  few  fibres  of  origin  of  the  Internal  pterygoid 
muscle.  Immediately  above  this  is  a  smooth  surface,  which  forms  the  anterior 
boundary  of  the  sphenomaxillary  fossa;  it  presents  a  groove  which,  running  ob- 
liquely downward,  is  converted  into  a  canal  by  articulation  with  the  palate  bone, 
forming  the  posterior  palatine  or  palatomaxillary  canal  for  the  descending  palatine 
artery  and  great  palatine  nerve.  The  posterior  border  forms  the  anterior  bound- 
ary of  the  pterygomaxillary  fissure. 

The  superior  or  orbital  siu-face  {fades  orbitalis)  is  thin,  smooth,  triangular, 
and  forms  part  of  the  floor  of  the  orbit.  It  is  bounded  internally  by  an  irregular 
margin,  which  in  front  presents  a  notch,  the  lacrimal  notch  {incisura  lacrimalis), 
which  receives  the  lacrimal  bone;  in  the  middle  it  articulates  with  the  os  planum  of 
the  ethmoid,  and  behind  with  the  orbital  process  of  the  palate  bone;  bounded  ex- 
ternally by  a  smooth,  rounded  edge  which  enters  into  the  formation  of  the  spheno- 
maxillary fissure,  and  which  sometimes  articulates  at  its  anterior  extremity  with 
the  orbital  plate  of  the  sphenoid;  bounded  in  front  by  part  of  the  circumference  of 
the  orbit,  which  is  continuous  on  the  inner  side  with  the  nasal,  on  the  outer  side 
with  the  malar  process.  Along  the  middle  line  of  the  orbital  surface  is  a  deep 
groove,  the  infraorbital  groove  {sidcus  infraorbitalis) ,  for  the  passage  of  the  infra- 
orbital vessels  and  nerve.  The  groove  commences  at  the  middle  of  the  outer 
border  of  this  surface,  and,  passing  forward,  terminates  in  a  canal,  which  subdi- 
vides into  two  branches.  One  of  the  canals,  the  infraorbital  canal,  opens  just  below 
the  margin  of  the  orbit;  the  other,  which  is  smaller,  runs  downward  in  the  sub- 
stance of  the  anterior  wall  of  the  antrum;  it  is  called  the  anterior  dental  canal,  and 
transmits  the  anterior  dental  vessels  and  nerve  to  the  front  teeth  of  the  maxilla. 
From  the  back  part  of  the  infraorbital  canal  a  second  small  canal  is  sometimes 
given  off,  which  runs  downward  in  the  outer  wall  of  the  antrum,  and  conveys  the 
middle  dental  nerve  to  the  biscupid  teeth.  Occasionally  this  canal  is  a  branch  of 
the  anterior  dental  canal. 

At  the  inner  and  fore  part  of  the  orbital  surface,  just  external  to  the  lacrimal 
groove  for  the  nasal  duct,  is  a  depression  which  gives  origin  to  the  Inferior  oblique 
muscle  of  the  eye. 

The  internal  surface  (Fig.  71)  is  unequally  divided  into  two  parts  by  a  horizontal 
projection  of  bone,  the  palatal  process  {processus  palatinus);  the  portion  above 
the  palatal  process  is  known  as  the  nasal  surface  {fades  nasalis).  It  forms  part 
of  the  outer  wall  of  the  nasal  fossa.  Below  the  palate  process  is  the  cavity  of 
the  mouth.  The  superior  division  of  the  nasal  surface  presents  a  large,  irregu- 
lar opening  {hiatus  maxillaris),  leading  into  the  maxillary  sinus.  At  the  upper 
border  of  this  aperture  are  numerous  broken  cellular  cavities,  which  in  the  articu- 
lated skull  are  closed  by  the  ethmoid  and  lacrimal  bones.  Below  the  aperture 
is  a  smooth  concavity  which  forms  part  of  the  inferior  meatus  of  the  nasal  fossa, 
and  behind  it  is  a  rough  surface  which  articulates  with  the  perpendicular  plate  of 
the  palate  bone,  traversed  by  a  groove  which,  commencing  near  the  middle  of  the 
posterior  border,  runs  obliquely  downward  and  forward,  and  forms,  when  com- 
pleted by  its  articulation  with  the  palate  bone,  the  posterior  palatine  or  palato- 
maxillary canal.  In  front  of  the  opening  of  the  antrum  is  a  deep  groove,  con- 
verted into  a  canal  {canalis  nasolacrimalis)  by  the  lacrimal  and  turbinated  bones. 
The  groove  is  called  the  lacrimal  groove  {sulcus  lacrimalis),  and  lodges  the  nasal 
duct.  More  anteriorly  is  a  well-marked  rough  ridge,  the  inferior  turbinated  crest 
{crista  conchalis),  for  articulation  with  the  turbinated  bone.     The  shallow  con- 


THE  MAXILLJE 


103 


cavity  above  this  ridge  forms  part  of  the  middle  meatus  of  the  nose,  while  that 
below  it  forms  part  of  the  inferior  meatus.  The  portion  of  this  surface  below 
the  palatal  process  is  concave,  rough,  and  uneven,  and  perforated  by  numerous 
small  foramina  for  the  passage  of  nutrient  vessels.  It  enters  into  the  formation 
of  the  roof  of  the  mouth. 

The  antrum  of  Highmore  (sinus  maxillaris)  is  a  pyramidal  cavity  hollowed 
out  of  the  body  of  the  maxilla.  It  varies  much  in  size.  It  is  in  most  cases  a 
large  cavity,  but  in  some  is  very  small.  The  apex  of  the  antrum,  directed  outward, 
is  formed  by  the  malar  process ;  its  base  by  the  outer  wall  of  the  nose.  Its  walls 
are  everywhere  exceedingly  thin,  and  correspond  to  the  orbital,  facial,  and  zygo- 
matic surfaces  of  the  body  of  the  bone.  The  floor  is  formed  by  the  alveolar  process 
of  the  maxilla.  The  roof  corresponds  to  the  orbital  plate.  Its  inner  wall,  or  base, 
presents,  in  the  disarticulated  bone,  a  large,  irregular  aperture  (hiatus  maxil- 
laris), which  communicates  with  the  nasal  fossa.  The  margins  of  this  aperture 
are  thin  and  ragged,  and  the  aperture  itself  in  the  articulated  skull  is  much  con- 


■^jSi-/''-o^ 


£on^  partially  closinff  orifice  of  antrum 
marked  in  outline 


Ethmoid. 

Turbinated. 

Palate. 


Anterior  nasal  spine. 


Bristle  passed 
through  anterior 
palatine  candl. 


^"-^W^iwV^. 


Fig.  71. — Left  maxilla.     Internal  surface. 

tracted  by  its  articulation  with  the  ethmoid  above,  the  turbinated  bone  below, 
and  the  palate  bone  behind.^  In  the  articulated  skull  this  cavity  communicates 
with  the  middle  meatus  of  the  nasal  cavity,  generally  by  two  small  apertures 
left  between  the  above-mentioned  bones.  In  the  recent  state  usually  only  one 
small  opening  exists,  near  the  upper  part  of  the  cavity,  sufficiently  large  to 
admit  the  end  of  a  probe,  the  other  being  closed  by  the  lining  membrane  of 
the  sinus. 

Crossing  the  cavity  of  the  antrum  are  often  seen  several  projecting  laminse  of 
bone,  similar  to  those  seen  in  the  sinuses  of  the  cranium;  on  its  posterior  wall  are 
the  posterior  dental  canals,  transmitting  the  posterior  dental  vessels  and  nerves  to 
the  teeth.     Projecting  into  the  floor  are  several  conical  processes,  corresponding 


'  In  some  cases,  at  any  rate,  the  lacrimal  bone  encroacfies  'slightly  on  the  anterior  superior  portion  of  the 
opening,  and  assists  in  forming  the  inner  wall  of  the  antrum. 


104  SPECIAL  ANA  TOMY  OF  THE  SKELETON 

to  the  roots  of  the  first  and  second  molar  teeth;  in  some  cases  the  floor  is  per- 
forated by  the  teeth  in  this  situation;  projecting  into  the  antrum  from  the  roof 
is  a  ridge  corresponding  to  the  infraorbital  canal. 

The  Processes. — The  malar  process  (^processus  zygomaticus)  is  a  rough,  trian- 
gular eminence,  situated  at  the  angle  of  separation  of  the  facial  from  the  zygo- 
matic surface.  In  front  it  is  concave,  forming  part  of  the  facial  surface;  behind  it 
is  also  concave,  and  forms  part  of  the  zygomatic  fossa;  above  it  is  rough  and 
serrated  for  articulation  with  the  malar  bone;  while  below  a  prominent  ridge 
marks  the  division  between  the  facial  and  zygomatic  surfaces.  A  small  part  of 
the  Masseter  muscle  arises  from  this  process. 

The  nasal  process  (processus  frontalis)  is  a  strong,  triangular  plate  of  bone,  which 
projects  upward,  inward,  and  backward  by  the  side  of  the  nose,  forming  part 
of  its  lateral  boundary.  Its  external  surface  is  concave,  smooth,  perforated  by 
numerous  foramina, andgivesattachment  totheLevatorlabiisuperiorisalaecjue  nasi, 
the  Orbicularis  palpebrarum,  and  the  Tendo  oculi.  Its  infernal  surface  forms  part 
of  the  outer  wall  of  the  nasal  fossa;  at  its  upper  part  it  presents  a  rough,  uneven 
surface,  which  articulates  with  the  ethmoid  bone,  closing  in  the  anterior  ethmoidal 
cells;  below  this  is  a  transverse  ridge,  the  superior  turbinated  crest  (crista  ethmoi- 
dalis),  for  articulation  with  the  middle  turbinated  process  of  the  ethmoid;  below 
the  crest  is  a  shallow,  smooth  concavity  which  forms  part  of  the  middle  meatus; 
below  this  again  is  the  inferior  turbinated  crest  (already  described),  where  the  pro- 
cess joins  the  body  of  the  bone.  Its  upper  border  articulates  with  the  nasal  notch 
of  the  frontal  bone.  The  anterior  border  of  the  nasal  process  is  thin,  directed 
obliquely  downward  and  forward,  and  presents  a  serrated  edge  for  articulation  with 
the  nasal  bone;  its  posterior  border  is  thick,  and  hollowed  into  a  groove,  the  lacrimal 
groove,  for  the  nasal  duct;  of  the  two  margins  of  this  groove,  the  inner  one  articu- 
lates with  the  lacrimal  bone,  the  outer  one  forms  part  of  the  circumference  of  the 
orbit.  Just  where  the  latter  joins  the  orbital  surface  is  a  small  tubercle,  the 
lacrimal  tubercle,  which  articulates  with  the  hamular  process  of  the  lacrimal  bone. 
The  lacrimal  groove  in  the  articulated  skull  is  converted  into  a  canal  {canalis 
lacrimalis)  by  the  lacrimal  bone  and  lacrimal  process  of  the  turbinated  bene;  it 
is  directed  downward,  and  a  little  backward  and  outward,  is  about  the  diameter 
of  a  goose-quill,  slightly  narrower  in  the  middle  than  at  either  extremity,  and 
terminates  below  in  the  inferior  meatus.     It  lodges  the  nasal  duct. 

The  alveolar  process  (^processus  alveolaris)  is  the  thickest  and  most  spongy 
part  of  the  bone,  broader  behind  than  in  front,  and  excavated  into  deep  cavities 
for  the  reception  of  the  teeth  (alveoli  dentales).  These  cavities  are  eight  in  number, 
and  vary  in  size  and  depth  according  to  the  teeth  they  contain.  That  for  the 
canine  tooth  is  the  deepest;  those  for  the  molars  are  the  widest,  and  subdivided 
into  minor  cavities  by  septa;  those  for  the  incisors  are  single,  but  deep  and  narrow. 
The  Buccinator  muscle  arises  from  the  outer  surface  of  this  process  as  far  forward 
as  the  first  molar  tooth.  After  the  loss  of  the  prominent  teeth  at  any  time,  but 
especially  in  old  age,  this  process,  like  that  of  the  mandible,  is  absorbed. 

The  palatal  process  (processus  palatinus),  thick  and  strong,  projects  horizon- 
tally inward  from  the  inner  surface  of  the  body.  It  is  much  thicker  in  front  than 
behind,  and  forms  a  considerable  part  of  the  floor  of  the  nostril  and  the  roof  of 
the  mouth.  Its  inferior  surface  (Fig.  72)  is  concave,  rough  and  uneven,  contains 
numerous  little  cavities  for  the  glands  of  the  mucous  membrane,  and  forms  part 
of  the  roof  of  the  mouth.  This  surface  is  perforated  by  numerous  foramina  for 
the  passage  of  the  nutrient  vessels,  channelled  at  the  back  part  of  its  alveolar  border 
by  a  longitudinal  groove,  sometimes  a  canal,  for  the  transmission  of  the  posterior 
palatine  vessels,  and  the  great  posterior  palatine  ner^'e  from  Meckel's  ganglion, 
and  presents  little  depressions  for  the  lodgement  of  the  palatine  glands.  When 
the   two    maxillae  are  articulated,   a   large   fossa   may   be   seen    in   the   middle 


THE  MAXILLJE 


105 


Anterior  palatine  canat. 


Foramina  ofStens 


^^-^^Fo)  amen  of  Scarpa, 


Palate  proceis  uj 

maxilla        K^  V 

1     /- 


line,  immediately  behind  the  incisor  teeth.  This  is  the  anterior  palatine  fossa. 
On  examining  the  bottom  of  this  fossa  four  canals  are  seen:  two  branch  off 
laterally  to  the  right  and  left  nasal  fossae,  and  two — one  in  front  and  one  behind 
— lie  in  the  middle  line.  Tlie  former  pair  of  these  openings  are  named  the 
incisor  foramina,  or  foramina  of  Stenson;  they  are  the  openings  of  the  forking  incisor 
canal,  through  which  pass  the  anterior  or  terminal  branches  of  the  descending 
or  posterior  palatine  arteries,  which  ascend  from  the  mouth  to  the  nasal  fossa?, 
and  they  contain  the  remains  of  Jacobson's  organ.  The  canals  in  the  middle  line 
are  termed  the  foramina 
of  Scarpa,  and  transmit 
the  nasopalatine  nerves, 
the  left  passing  through 
the  anterior,  and  the  right 
through  the  posterior, 
canal.  Occasionally  in 
adults'  skulls,  often  in 
children's  skulls,  on  the 
palatal  surface  of  the 
process  a  delicate  linear 
suture  may  sometimes  be 
seen  extending  from  the 
anterior  palatine  fossa  to 
the  interval  between  the 
lateral  incisor  and  the 
canine  tooth.  This  marks 
out  the  premaxillary  bones 
(o.s  incisivwn)  on  each 
side,  and  includes  the 
whole  thickness  of  the 
alveolus,  the  correspond- 
ing part  of  the  floor  of 
the  nose,  and  the  anterior 
nasal  spine,  and  contains 
the  sockets  of  the  incisor  teeth;  in  some  animals  it  exists  as  a  separate  bone.  The 
upper  surface  of  the  palatal  process  is  concave  from  side  to  side,  smooth,  and 
forms  part  of  the  floor  of  the  nose.  It  presents  the  upper  orifices  of  the  foramina 
of  Stenson  and  Scarpa,  the  former  being  on  each  side  of  the  middle  line,  the 
latter  being  situated  in  the  intermaxillary  suture,  and  therefore  not  visible  unless 
the  two  bones  are  placed  in  apposition.  The  otder  border  of  the  palatal  process 
is  incorporated  with  the  rest  of  the  bone.  The  inner  border  is  thicker  in  front 
than  behind,  and  is  raised  above  into  a  ridge,  the  nasal  crest  {crista  uasalis), 
which,  with  the  corresponding  ridge  in  the  opposite  bone,  forms  a  groove  for 
the  reception  of  the  vomer.  In  front  this  crest  rises  to  a  considerable  height,  and 
this  portion  is  named  the  incisor  crest.  The  anterior  margin  is  bounded  by  the 
thin,  concave  border  of  the  opening  of  the  nose,  prolonged  forward  internally  into 
a  sharp  process,  forming,  with  a  similar  process  of  the  opposite  bone,  the  anterior 
nasal  spine  {spina  nasalis  anterior).  The  posterior  border  is  serrated  for  articu- 
lation with  the  horizontal  plate  of  the  palate  bone. 


palatine  canals. 


Accessory  palatine  foramina. 

Fig.  72. — The  palate  and  alveolar  arch. 


Development.— This  bone  commences  to  ossify  at  a  very  early  period,  and  ossification 
proceeds  in  it  with  great  rapidity,  so  that  it  is  difficult  to  ascertain  with  certainty  ks  precise 
number  of  centres.  It  appears,  however,  ]:)robable  that  it  is  ossified  from  six  centres, 
which  develop  in  membrane:  (1)  One,  the  ocit/oHn.raZ,  which  forms  that  portion  of  the  body 
of  the  bone  which  lies  internal  to  the  infraorbital  canal,  including  the  floor  of  the  orbit,  the 
outer  wall  of  the  nasal  fossa,  and  the  nasal  process.     (2)  A  malar,  which  gives  origin  to  that 


106 


SPECIAL  ANATOMY  OF  THE  SKELETON 


Anterior  Surjace. 


portion  of  the  bone  which  has  external  to  the  infraorbital  canal  and  the  malar  process.  (3) 
A  palatal,  from  which  is  developed  the  palatal  process  posterior  to  Stenson's  canal  and  the 
adjoining  part  of  the  nasal  wall.  4.  A  premaxiUary,  for  the  front  part  of  the  alveolus,  which  carries 
the  incisor  teeth  and  corresponds  to  the  premaxillary  bone  of  the  lower  animals.  (5)  A  nasal, 
that  gives  rise  to  the  nasal  process  and  the  portion  above  the  canine  tooth.  (6)  An  infravomerine, 
that  lies  beneath  the  vomer  and  between  the  palatal  and  premaxillary  centres.  The  premaxillary 
centre  is  in  close  association  with  the  development  of  the  perpendicular  plate  of  the  ethmoid  and 
the  vomer.  According  to  Albrecht  it  develops  from  two  centres  of  ossification,  each  having  an 
incisive  tooth.  The  one  possessing  the  mesal  segment  he  calls  the 
endogiiatldon.  The  lateral  segment  he  calls  the  mesognathion, 
while  to  the  maxilla  he  gives  the  name  exognathion.  These  seg- 
ments are  separated  by  five  sutures.  The  failure  of  union  of  any 
of  these  segments  will  lead  to  the  various  forms  of  cleft  palate. 
These  centres  appear  about  the  eighth  week,  and  by  the  tenth 
week  have  become  fused  together  so  that  the  bone  consists  of  two 
portions,  one  the  maxilla  proper,  and  the  other  the  premaxillary 
portion.  The  suture  between  these  two  portions  on  the  palate 
persists  until  middle  life,  but  is  not  to  be  seen  on  the  facial  surface. 
This  is  believed  by  Callender  to  be  due  to  the  fact  that  the  front 
wall  of  the  sockets  of  the  incisive  teeth  is  not  formed  by  the  pre- 
maxillary bone,  but  by  an  outgrowth  from  the  facial  part  of  the 
maxilla.  The  antrum  appears  as  a  shallow  groove  on  the  inner 
surface  of  the  bone  at  an  earlier  period  than  any  of  the  other  nasal 
sinuses,  its  development  commencing  about  the  fourth  month  of 
fetal  life,  and  reaches  its  full  size  after  the  second  dentition.  The 
sockets  for  the  teeth  are  formed  by  the  growing  downward  of 
two  plates  from  the  dental  groove,  which  subsequently  becomes 
divided  by  partitions  jutting  across  from  the  one  to  the  other.  If 
the  two  palatal  processes  fail  to  unite  partially  or  completely,  a 
partial  or  complete  cleft  palate  results. 

Articulations. — With  nine  bones,  two  of  the  cerebral  cranium, 
the  frontal  and  ethmoid,  and  seven  of  the  face — viz.,  the  nasal, 
malar,  lacrimal,  turbinated,  palate,  vomer,  and  its  fellow  of  the 
opposite  side.     Sometimes  it  articulates  with  the  orbital  plate  of 
the  sphenoid,  and  sometimes  with  its  external  pterygoid  plate. 
Attachment  of  Muscles. — To  twelve — the  Orbicularis  palpebrarum,  Obliquus  oculi  infe- 
rior, Levator  labii  superioris  alaeque  nasi.  Levator  labii  superioris,  Levator  anguli  oris,  Com- 
pressor naris.  Depressor  alae  nasi.  Dilatator  naris  posterior,  Masseter,  Buccinator,  Internal 
pterygoid,  and  Orbicularis  oris. 

Applied  Anatomy. — It  is  from  the  extreme  thinness  of  the  walls  of  the  antrum  that  we  are 
enabled  to  explain  how  a  tumor  growing  from  the  antrum  encroaches  upon  the  adjacent  parts, 
pushing  up  the  floor  of  the  orbit  and  displacing  the  eyeball,  projecting  inward  into  the  nose, 
protruding  forward  on  to  the  cheek,  and  making  its  way  backward  into  the  zygomatic  fossa 
and  downward  into  the  mouth. 


Inferior  Surface. 


CHANGES  PRODUCED  IN  THE  UPPER  JAW  BY  AGE. 

At  birth  and  during  infancy  the  diameter  of  the  bone  is  greater  in  an  antero-posterior  than 
in  a  vertical  direction.  Its  nasal  process  is  long,  its  orbital  surface  large,  and  its  tuberosity 
well  marked.  In  the  adult  the  vertical  diameter  is  the  greater,  owing  to  the  development  of 
the  alveolar  process  and  the  increase  in  size  of  the  antrum.  In  old  age  the  bone  approaches 
again  in  character  to  the  infantile  condition;  its  height  is  diminished,  and  after  the  loss  of  the 
teeth  the  alveolar  process  is  absorbed,  and  the  lower  part  of  the  bone  contracted  and  diminished 
in  thickness. 


The  Lacrimal  Bone  (Os  Lacrimale). 


The  lacrimal  (lacrima,  a,  tear)  is  the  smallest  and  most  fragile  bone  of  the  face. 
There  are  two  lacrimal  bones.  They  are  situated  at  the  front  part  of  the  inner 
wall  of  the  orbit  (Fig.  67),  and  resemble  somewhat  in  form,  thinness,  and  size  a 
finger  nail ;  hence,  they  are  termed  the  ossa  un^is.  Each  bone  presents  for  exami- 
nation two  surfaces  and  four  borders. 


THE  MALAB  BONE  '       107 

Surfaces. — The  external  or  orbital  surface  (Fig.  74)  is  divided  by  a  vertical 
ridge,  the  lacrimal  crest  {crista  lacrimalis  posterior),  into  two  parts.  The  portion 
of  bone  in  front  of  this  ridge  presents  a  smooth,  concave,  longitudinal  groove 
(sulcus  lacrimalis),  the  free  margin  of  which  unites  with  the  nasal  process  of  the 
maxilla,  completing  the  lacrimal  canal.  The  upper  part  of  this  groove  {fossa 
sacci  lacrimalis)  lodges  the  lacrimal  sac;  the  lower  part  lodges  the  nasal  duct. 
The  portion  of  bone  behind  the  ridge  is  smooth,  slightly  concave,  and  forms 
part  of  the  inner  wall  of  the  orbit.  The  ridge,  with  a  part  of  the  orbital  surface 
immediately  behind  it,  affords  origin  to  the  Tensor  tarsi 
muscle ;  it  terminates  below  in  a  small  hook-like  projection,  wuhfrmtai. 

the  hamular  process  {hamulus  lacrimalis),  which  articulates 
with  the  lacrimal  tubercle  of  the  maxilla  and  completes  the 
upper  orifice  of  the  lacrimal  canal.  It  sometimes  exists  as  a 
separate  piece,  which  is  then  called  the  lesser  lacrimal  bone. 

The  internal  or  nasal  surface  presents  a  depressed  furrow, 
corresponding  to  the  ridge  on  its  outer  surface.  The  sur- 
face of  bone  in  front  of  this  forms  part  of  the  middle 
meatus,  and  that  behind  it  articulates  with  the  ethmoid 
bone,  closing  in  the  anterior  ethmoidal  cells. 

Borders. — Of  the  four  borders,  the  anterior  is  the  long- 
est, and  articulates  with  the  nasal  process  of  the  maxilla.     ,^  fig.  74,— Left  lacrimal 

f^^,  ,  .  ,  .       ,  -11  bone.      iivXternal      surface. 

ihe  postenor,  thm  and  uneven,  articulates  with  the  os  (Siightiy  enlarged.) 
planum  of  the  ethmoid.  The  superior,  the  shortest  and 
thickest,  articulates  with  the  internal  angular  process  of  the  frontal  bone.  The 
inferior  is  divided  by  the  lower  edge  of  the  vertical  crest  into  two  parts;  the 
posterior  part  articulates  with  the  orbital  plate  of  the  maxilla;  the  anterior 
portion  is  prolonged  downward  into  a  pointed  process,  which  articulates  with 
the  lacrimal  process  of  the  turbinated  bone  and  assists  in  the  formation  of  the 
lacrimal  canal. 

Development. — From  a  single  centre,  which  makes  its  appearance  in  membrane  at  about 
the  eighth  or  ninth  week. 

Articulations. — With  four  bones — two  of  the  cerebral  cranium,  the  frontal  and  ethmoid, 
and  two  of  the  face,  the  maxilla  and  the  turbinated. 

Attachment  of  Muscles. — To  one  muscle,  the  Tensor  tarsi. 


The  Malar  Bone  (Os  Zygomaticum). 

The  malar  bone  is  a  quadrangular  bone,  situated  at  the  upper  and  outer  part  of 
the  face.  It  forms  the  prominence  of  the  cheek,  part  of  the  outer  wall  and  floor 
of  the  orbit,  and  part  of  the  temporal  and  zygomatic  fossae  (Fig.  7.5).  Each  bone 
presents  for  examination  an  external  and  an  internal  surface;  three  processes,  the 
frontal,  orbital,  and  zygomatic  processes;  and  four  borders. 

Surfaces.— The  external  surface  {fades  malaris)  (Fig.  76)  is  smooth,  convex, 
perforated  near  its  centre  by  a  small  aperture,  the  malar  foramen,  for  the  passage 
of  nerves  and  vessels  from  the  orbit.  The  malar  surface  is  co-\-ered  by  the  Orbicu- 
laris palpebrarum  muscle,  and  affords  attachment  to  the  Zygomaticus  major  and 
minor  muscles. 

The  internal  surface  {fades  temporalis)  (Fig.  77),  directed  backward  and  inward, 
is  conca-\'e,  presenting  anteriorly  a  rough,  triangular  surface,  for  articulation  with 
the  maxilla ;  and  behind,  a  smooth  concave  surface,  which  above  forms  the  anterior 
boundary  of  the  temporal  fossa,  and  below,  where  it  is  wider,  forms  part  of  the 
zygomatic  fossa.     This  surface  presents,  a  little  above  its  centre,  the  aperture  of 


108 


SPECIAL  ANATOMY  OF  THE  SKELETON 


a  malar  canal   {foramen  zygomaticotemporale) ,  and  affords  attachment  at  its 
lower  part  to  a  portion  of  the  Masseter  muscle. 

Processes. — ^The  frontal  process  (^processus  frontosphenoidalis)  is  thick  and 
serrated,  and  articulates  with  the  external  angular  process  of  the  frontal  bone.  To 
its  orbital  margin  is  attached  the  external  tarsal  ligament. 


Frontal  pi  Oct  s'i    Ert   angular  pi  ocess 


Ki^ht  inilir  bone  m  s%tu 


The  orbital  process  is  a  thick  and  strong  plate,  which  projects  backward  from  the 
orbital  margin  of  the  bone.  Its  supero-infernal  surface  (fades  orbitalis),  smooth 
and  concave,  forms,  by  its  junction  with  the  orbital  surface  of  the  maxilla  and  with 
the  greater  wing  of  the  sphenoid,  part  of  the  floor  and  outer  wall  of  the  orbit.  Its 
temporal  surface,  smooth  and  concave,  forms  part  of  the  zygomatic  and  temporal 


yfiih  froittal. 


Si-istl^s  passed        / 
through  iempoi  o-      ^  e 
malar  canals.       ,  ^  &.) 


fossfe.  Its  anterior  viargin  is  smooth  and  rounded,  forming  part  of  the  circum- 
ference of  the  orbit.  Its  superior  margin,  rough  and  directed  horizontally,  artic- 
ulates with  the  frontal  bone  behind  the  external  angular  process.     Its  posterior 


THE  PALATE  BONE  109 

inargin  is  rough  and  serrated  for  articulation  with  the  sphenoid ;  wtpniaUy  it  is 
also  serrated  for  articulation  with  the  orbital  surface  of  the  maxilla.  At  the 
angle  of  junction  of  the  sphenoidal  and  maxillary  portions  a  short,  rounded,  non- 
articular  margin  is  generally  seen;  this  forms  the  anterior  boundary  of  the  spheno- 
maxillary fissure;  occasionally  no  such  nonarticular  margin  exists,  the  fissure 
being  completed  by  the  direct  junction  of  the  maxilla  and  sphenoid  bones  or  by 
the  interposition  of  a  small  Wormian  bone  in  the  angular  interval  between  them. 
On  the  supero-internal  surface  of  the  orbital  process  is  seen  the  orifice  of  one  of  the 
temporomalar  canals.  This  canal  may  be  bifurcated,  or  there  may  be  two  canals 
from  the  beginning;  one  of  these  usually  opens  on  the  temporal  surface,  the 
other  (occasionally  two)  on  the  facial  surface;  they  transmit  filaments  of  the 
orbital  branch  of  the  superior  maxillary  nerve. 

The  zygomatic  process  {processus  temporalis),  long,  narrow,  and  serrated,  articu- 
lates with  the  zygomatic  process  of  the  temporal  bone. 

Borders. — The  antero-superior  {orbital  border)  is  smooth,  arched,  and  forms 
a  considerable  part  of  the  circumference  of  the  orbit.  The  antero-inferior  (maxil- 
lary border)  is  rough,  and  bevelled  at  the  expense  of  its  inner  table,  to  articulate 
with  the  maxilla,  affording  attachment  by  its  margin  to  the  Levator  labii  superioris, 
just  at  its  point  of  junction  with  the  maxilla.  The  postero-superior  (temporal 
border)  curved  like  an  italic  letter/,  is  continuous  above,  with  the  commencement 
of  the  temporal  ridge;  below,  with  the  upper  border  of  the  zygomatic  arch;  it 
affords  attachment  to  the  temporal  fascia.  The  postero-inferior  (masseteric 
border)  is  continuous  with  the  lower  border  of  the  zygomatic  arch,  affording 
attachment  by  its  rough  edge  to  the  Masseter  muscle. 

Development. — The  malar  bone  ossifies  generally  from  three  centres,  which  appear  about  the 
eighth  week — one  for  the  zygomatic  and  two  for  the  orbital  portion — and  which  fuse  about  the 
fifth  month  of  fetal  life.  The  bone  is  sometimes,  after  birth,  seen  to  be  divided  by  a  horizontal 
suture  into  an  upper  and  larger  and  a  lower  and  smaller  division.  In  some  primates  the  malar 
bone  consists  of  two  parts,  an  orbital  and  a  malar. 

Articulations. — With  four  bones — three  of  the  cranium,  frontal,  sphenoid,  and  temporal;  and 
one  of  the  face,  the  maxilla. 

Attachment  of  Muscles. — To  four — the  Levator  labii  superioris  proprius,  Zygomaticus 
major  and  minor,  and  Masseter. 


The  Palate  Bone  (Os  Palatinum). 

The  palatal  bones'  are  situated  at  the  back  part  of  the  nasal  fossre ;  they  are  wedged 
in  between  the  maxilla  and  the  pterygoid  processes  of  the  sphenoid  (Fig.  78). 
Each  bone  assists  in  the  formation  of  three  cavities — the  floor  and  outer  wall  of  the 
nose,  the  roof  of  the  mouth,  and  the  floor  of  the  orbit — and  enters  into  the  formation 
of  two  fossae,  the  sphenomaxillary  and  pterygoid  fossae;  and  one  fissure,  the  sphe- 
nomaxillary fissure.  In  form  the  palate  bone  somewhat  resembles  the  letter  L, 
and  may  be  divided  into  an  inferior  or  horizontal  plate  and  a  superior  or  vertical 
plate. 

The  Horizontal  Plate  (pars  liorizontaUs)  (Figs.  79  and  80)  is  of  a  quadrilateral 
form,  and  presents  two  surfaces  and  four  borders. 

Surfaces. — The  superior  or  nasal  surface  (fades  nasalis^,  concave  from  side  to 
side,  forms  the  back  part  of  the  floor  of  the  nasal  cavity. 

The  inferior  or  palatine  surface  (fades  palatina),  slightly  concave  and  rough,  forms 
the  back  part  of  the  hard  palate.  At  its  posterior  part  may  be  seen  a  transverse 
ridge,  more  or  less  marked,  for  the  attachment  of  part  of  the  aponeurosis  of  the 

'  The  word  palate  is  frequently  \ised  as  an  adjective.  Palatal  is  the  correct  form  (froni  palatum,  the  palate), 
but  usage  sanctions  palatine  in  certain  compounds,  despite  the  fact  that  palatine  is  derived  from  palatium,  ix 
palace.  This  is  another  example  of  what  is  charitably  called  a  "late  Latin"  form,  akin  to  hallux  and  hallucis. 
— [Editor.] 


110 


SPECIAL  ANATOMY  OF  THE  SKELETON 


Tensor  palati  muscle.  At  the  outer  extremity  of  this  ridge  is  a  deep  groove,  the 
pterygopalatine  groove  (sulcus  pterygopalatinus) ,  converted  into  a  canal  by  its 
articulation  with  the  tuberosity  of  the  maxilla,  and  forming  the  lower  end  of  the 
posterior  palatine  canal  {canalis  ijterycjojjalatiniis) .  Near  this  groove  the  orifices 
of  one  or  two  small  canals,  accessory  posterior  palatine  canals  (canales  iKilatim), 
may  be  seen  for  the  passage  of  the  middle  and  posterior  palatine  nerves  from  the 
sphenopalatine  (Meckel's)  ganglion.  Through  the  posterior  palatine  canal 
emerge  the  descending  palatine  artery  and  the  great  posterior  palatine  nerve. 

Borders. — ^The  anterior  is  serrated,  bevelled  at  the  expense  of  its  inferior  sur- 
face, and  articulates  with  the  palatal  process  of  the  maxilla.  The  posterior 
is  concave,  free,  and  serves  for  the  attachment  of  the  soft  palate.  Its  inner 
extremity  is  sharp  and  pointed,  and  when  united  with  the  opposite  bone  forms  a 


Sphenopalatine  notch. 


Sup.  turbinated  crest,     n^? 

N-,    MIDQ 


Inf.  turbinated  crest. 


Sup  turbinated  crest. 


Inf  turbinated  crest. 


Ant.  nasal  spiiie. 


projecting  process,  the  palatine  spine  (.'.■piua  nasalis  fostcrior),  for  the  attachment 
of  the  Azygos  uvulae  muscle.  The  external  is  united  with  the  lower  part  of  the 
perpendicular  plate  almost  at  right  angles.  The  internal,  the  thickest,  is  serrated 
for  articulation  with  its  fellow  of  the  opposite  side;  its  superior  edge  is  raised  into 
a  ridge,  which,  united  with  the  opposite  bone,  forms  a  crest  (crista  nasalis),  into 
which  the  vomer  is  received. 

The  Vertical  or  Perpendicular  Plate  (pars  perpend icidaris)  (Figs.  79  and  80) 
forms  the  back  part  of  the  outer  wall  of  the  nasal  fossa,  is  thin,  of  an  oblong  form, 
and  directed  upward  and  a  little  inward.  It  presents  two  surfaces,  an  external 
and  an  internal,  and  three  borders. 

Surfaces. — The  internal,  medial,  or  nasal  surface  (fades  nascdis)  presents  at  its 
lower  part  a  broad,  shallow  depression,  which  forms  part  of  the  inferior  meatus 
of  the  nose.  Immediately  above  this  is  a  well-marked  ridge,  the  inferior  turbin- 
ated crest  (crista  conchali.s),  for  articulation  with  the  turbinated  bone;  above  this 
a  second  broad,  shallow  depression,  which  forms  part  of  the  middle  meatus,  sur- 
mounted above  by  a  horizontal  ridge  less  prominent  than  the  inferior,  the  superior 
turbinated  crest  (crista  ethmoidalis) ,  for  articulation  with  the  middle  turbinated 


THE  PALATE  BONE 


111 


process.     Above  the  superior  turbinated  crest  is  a  narrow,  horizontal  groove, 
which  forms  part  of  the  superior  meatus. 

The  external  or  lateral  surface  (J'aclesmaxillaris)  is  rough  and  irregular  throughout 
the  greater  part  of  its  extent,  for  articulation  with  the  inner  surface  of  the  maxilla, 
its  upper  and  back  part  being  smooth  where  it  enters  into  the  formation  of  the 
sphenomaxillary  fossa;  it  is  also  smooth  in  front,  where  it  covers  the  orifice  of  the 
antrum.      Toward  the  back 

Orbital  process. 

Orbilal  surface. 


Superior  meatus 
Sphenopalatine  /c 


Maxillary  surface. 


Maxillary 
*  process. 


Fig.  79. 


Horizontal  Plate. 

-Left  palate  bone.     Internal 


(Enlarged.) 


part  of  this  surface  is  a  deep 
groove,  the  pterygopalatine 
groove,  converted  into  a  canal, 
the  posterior  palatine  canal, 
by  its  articulation  with  the 
maxilla.  It  transmits  the 
posterior  or  descending  pala- 
tine vessels  and  the  great  or 
anterior  palatine  nerve  from 
Meckel's  ganglion. 

Borders.  ■ —  The  anterior 
border  (Fig.  79)  is  thin,  irreg- 
ular, and  presents  opposite 
the  inferior  turbinated  crest 
a  pointed,  projecting  lamina, 
the  maxillary  process  (processiis 
maxillaris),  which  is  directed 
forward,  and  closes  in  the 
lower  and  back  part  of  the 
opening  of  the  antrum. 

The  posterior  border  (Fig.  80)  presents  a  deep  groove,  the  edges  of  which  are 
serrated  for  articulation  with  the  pterygoid  process  of  the  sphenoid.  At  the 
lower  part  of  this  border  is  seen  a  pyramidal  process  of  bone,  the  tuberosity  of  the 
palate  {processus  pyramidalis),  which  is  received  into  the  angular  interval  between 

the  two  pterygoid  plates  of  the  sphenoid 
at  their  inferior  extremity.  This  process 
presents  at  its  back  part  a  median  groove 
and  two  lateral  surfaces.  The  groove  is 
smooth,  and  forms  part  of  the  pterygoid 
fossa,  affording  attachment  to  the  Internal 
pterygoid  muscle;  while  the  lateral  surfaces 
are  rough  and  uneven,  for  articulation 
with  the  anterior  border  of  each  pterygoid 
plate.  A  few  fibres  of  the  Superior  con- 
strictor of  the  pharynx  arise  from  the 
tuberosity  of  the  palate  bone.  The  base 
of  this  process,  continuous  with  the  hori- 
zontal portion  of  the  bone,  presents  the 
apertures  of  the  accessory  posterior  pala- 
tine canals,  through  which  pass  the  two 
smaller  descending  branches  of  Meckel's 
ganglion;  while  its  outer  surface  is  rough 
for  articulation  with  the  inner  surface  of 
the  body  of  the  maxilla. 

The  superior  border  of  the  vertical  plate 
presents  two  well-marked  processes  separated  by  an  intervening  notch.  The  ante- 
rior, or  larger,  is  called  the  orbital  pi-ocess ;  the  posterior,  the  sphenoidal  process. 


Orbital  process. 

^^^^^sw  tcce 


^Sphenopalatine 
foramen, 

,  Sphenoidal  process. 
~  Articular  portion. 
J^on-artictdar  portion. 


Fig.  80. — Left  palate  bone.     Posterior 
(Enlarged.) 


112  SPECIAL  ANATOMY  OF  THE  SKELETON 

Processes. — The  orbital  process  {processus  orhitalis) ,  directed  upward  and  out- 
ward, is  placed  on  a  higher  level  than  the  sphenoidal.  It  presents  five  surfaces, 
which  enclose  a  hollow  cellular  cavity,  and  is  connected  with  the  perpendicular 
plate  by  a  narrow,  constricted  neck.  Of  these  five  surfaces,  three  are  articular, 
two  nonarticular  or  free  surfaces.  The  three  articular  are  the  anterior  or  maxillary 
surface,  which  is  directed  forward,  outward,  and  downward,  is  of  an  oblong  forni, 
and  rough  for  articulation  with  the  maxilla.  The  posterior  or  sphenoidal  surface  is 
directed  backward,  upward,  and  inward.  It  ordinarily  presents  a  small,  open  cell, 
the  orbital  sinus,  which  communicates  with  the  sphenoidal  cells,  and  the  mar- 
gins of  which  are  serrated  for  articulation  with  the  vertical  part  of  the  sphe- 
noidal turbinated  process.  The  internal  or  ethmoidal  surface  is  directed  inward, 
upward,  and  forward,  and  articulates  with  the  lateral  mass  of  the  ethmoid  bone. 
In  some  cases  the  cellular  cavity  opens  on  the  internal  surface  of  the  bone ;  it  then 
communicates  with  the  posterior  ethmoidal  cells.  More  rarely  it  opens  on  both 
surfaces,  and  then  communicates  with  both  the  posterior  ethmoidal  and  the 
sphenoidal  cells.  The  nonarticular  or  free  surfaces  are  the  superior  or  orbital 
surface,  directed  upward  and  outward,  of  triangular  form,  concave,  smooth,  and 
forming  the  back  part  of  the  floor  of  the  orbit;  and  the  external  or  zygomatic 
surface,  directed  outward,  backward,  and  downward,  of  an  oblong  form,  smooth, 
lying  in  the  sphenomaxillary  fossa,  and  looking  into  the  zygomatic  fossa.  The 
latter  surface  is  separated  from  the  orbital  by  a  smooth,  rounded  border,  which 
enters  into  the  formation  of  the  sphenomaxillary  fissure. 

The  sphenoidal  process  (processus  sphenoidalis)  of  the  palate  bone  is  a  thin,  com- 
pressed plate,  much  smaller  than  the  orbital,  and  directed  upward  and  inward. 
It  presents  three  surfaces  and  two  borders.  The  superior  surface,  the  smallest 
of  the  three,  articulates  with  the  under  surface  of  the  sphenoidal  turbinated  pro- 
cess; it  presents  a  groove,  which  contributes  to  the  formation  of  the  pterygopala- 
tine canal.  The  internal  surface  is  concave,  and  forms  part  of  the  outer  wall  of 
the  nasal  fossa.  The  external  surface  is  divided  into  an  articular  and  a  nonartic- 
ular portion;  the  former  is  rough,  for  articulation  with  the  inner  surface  of  the 
internal  pterygoid  plate  of  the  sphenoid;  the  latter  is  smooth,  and  forms  part  of 
the  sphenomaxillary  fossa.  The  anterior  border  forms  the  posterior  boundary  of 
the  sphenopalatine  notch.  The  posterior  border,  serrated  at  the  expense  of  the 
outer  table,  articulates  with  the  inner  surface  of  the  internal  pterygoid  plate. 

The  orbital  and  sphenoidal  processes  are  separated  from  each  other  by  a  deep 
notch,  the  sphenopalatine  notch  ( incisura  sphenopalatina),  which  is  converted  into 
a  foramen,  the  sphenopalatine  foramen  (foramen  sphenopalatinum) ,  by  articulation 
with  the  under  surface  of  the  body  of  the  sphenoid  bone.  Sometimes  the  two  pro- 
cesses are  united  above,  and  form  between  them  a  complete  foramen  (Figs.  79 
and  80),  or  the  notch  is  crossed  by  one  or  more  spiculse  of  bone,  so  as  to  form 
two  or  more  foramina.  In  the  articulated  skull  this  foramen  is  seen  to  pass  from 
the  sphenomaxillary  fossa  into  the  back  part  of  the  superior  meatus.  It  trans- 
mits the  sphenopalatine  vessels  and  the  superior  nasal  and  nasopalatine  nerves. 

Development. — From  a  single  centre,  which  makes  its  appearance  in  membrane  about  the 
second  month  at  the  angle  of  junction  of  the  two  plates  of  the  bone.  From  this  point  ossification 
spreads  inward  to  the  horizontal  plate,  downward  into  the  tuberosity,  and  upward  into  the  vertical 
plate.  In  the  fetus  the  horizontal  plate  is  much  larger  than  the  vertical,  and  even  after  it  is 
fully  ossified  the  whole  bone  is  remarkable  for  its  shortness. 

Articulations. — With  six  bones — the  sphenoid,  ethmoid,  maxilla,  turbinated,  vomer,  and 
opposite  palate. 

Attachment  of  Muscles. — To  four — the  Tensor  palati,  Azygos  uvulae,  Internal  pterygoid, 
and  Superior  constrictor  of  the  pharynx. 


THE  TURBINATED  BONE 


\VA 


The  Turbinated  Bone  (Concha  Nasalis  Inferior), 

The  turbinated  bones  are  situated  one  on  each  side  of  the  outer  wall  of  each 
nasal  fossa.  Each  consists  of  a  layer  of  thin,  spongy  bone,  curled  upon  itself  like  a 
scroll — hence  its  name  "turbinated" — and  extends  horizontally  along  the  outer 
wall  of  the  nasal  fossa,  immediately  below  the  orifice  of  the  antrum  (Fig.  SI). 
Each  bone  presents  two  surfaces,  two  borders,  and  two  extremities. 


Fig.  81.~N;isal  cavity,  right  lateral  wall,  from  the  left.     (Spalteholz.) 


Surfaces. — ^The  internal  surface  (Fig.  82)  is  convex,  perforated  by  numerous 
apertures,  and  traversed  by  longitudinal  grooves  and  canals  for  the  lodgement 
of  arteries  and  veins.  In  the  recent  state  it  is  covered  by  the  lining  membrane  of 
the  nose.  The  external  surface  is  concave  (Fig.  83),  and  forms  part  of  the  inferior 
meatus. 


-Right  turbinated  bo 


Internal  surface.  Fic.  S3. — Right  turbinated  bone.     External  surface. 


Borders. — Its  upper  border  is  thin,  irregular,  and  connected  to  various  bones 
along  the  outer  wall  of  the  nose.  It  may  be  divided  into  three  portions;  of  these, 
tlie  anterior  articulates  with  the  inferior  turbinated  crest  of  the  maxilla ;  the  poste- 
rior with  the  inferior  turbinated  crest  of  the  palate  bone;  the  middle  portion  of  the 


114  SPECIAL  ANATOMY  OF  THE  SKELETON 

superior  border  presents  three  well-marked  processes,  which  vary  much  in  their 
size  and  form.  Of  these,  the  anterior  and  smallest  is  situated  at  the  junction  of 
the  anterior  fourth  with  the  posterior  three-fourths  of  the  bone;  it  is  small  and 
pointed,  and  is  called  the  lacrimal  process  {-processus  lacrimal  is);  it  articulates  by 
its  apex  with  the  anterior  inferior  angle  of  the  lacrimal  bone,  and  by  its  margins 
with  the  groove  on  the  back  of  the  nasal  process  of  the  maxilla,  and  thus  assists 
in  forming  the  canal  for  the  nasal  duct.  At  the  junction  of  the  two  middle  fourths 
of  the  bone,  but  encroaching  on  its  posterior  fourth,  a  broad,  thin  plate,  the  eth- 
moidal process  (processus  ethmoidalis),  ascends  to  join  the  unciform  process  of  the 
ethmoid;  from  the  lower  border  of  this  process  a  thin  lamina  of  bone  curves  down- 
ward and  outward,  hooking  over  the  lower  edge  of  the  orifice  of  the  antrum,  which 
it  narrows  below;  it  is  called  the  maxillary  process  (processus  maxillaris),  and  fixes 
the  bone  firmly  to  the  outer  wall  of  the  nasal  fossa.  The  inferior  border  is  free  and 
thick,  more  especially  in  the  middle  of  the  bone.  Both  extremities  are  more  or 
less  narrow  and  pointed,  the  posterior  being  the  more  tapering.  If  the  bone  is 
held  so  that  its  outer  concave  surface  is  directed  backward  (i.  e.,  toward  the  holder), 
and  its  superior  border,  from  which  the  lacrimal  and  ethmoidal  processes  project, 
upward,  the  lacrimal  process  will  be  directed  to  the  side  to  which  the  bone  belongs.' 

Development. — From  a  mngle  centre,  which  makes  its  appearance  about  the  middle  of  fetal 
life  in  the  outer  wall  of  the  cartilaginous  nasal  septum. 

Articulations. — With  four  bones — one  of  the  cerebral  cranium,  the  ethmoid,  and  three  of 
the  face,  the  maxilla,  lacrimal,  and  palate. 

No  muscles  are  attached  to  this  bone. 


The  Vomer. 

The  vomer  is  a  single  bone,  situated  vertically  at  the  back  part  of  the  nasal 
fossae,  forming  part  of  the  septum  of  the  nose  (Fig  84).  It  is  thin,  somewhat  like  a 
ploughshare  in  form;  but  varies  in  different  individuals,  being  frequently  bent  to 
one  or  the  other  side ;  it  presents  for  examination  two  surfaces  and  four  borders. 

Surfaces. — ^The  lateral  surfaces  are  smooth,  marked  by  small  furrows  for  the 
lodgement  of  bloodvessels,  and  by  a  groove  on  each  side,  sometimes  a  canal, 
the  nasopalatine  groove,  or  canal,  which  runs  obliquely  downward  and  forward  to 
the  intermaxillary  suture;  it  transmits  the  nasopalatine  nerve. 

Borders. — ^The  superior  border,  the  thickest,  presents  a  deep  groove,  bounded 
on  each  side  by  a  horizontal  projecting  leaf  of  bone;  these  leaves  are  the  alse  (alae 
vomeris).  The  groove  formed  by  the  alae  receives  the  rostrum  of  the  sphenoid, 
while  the  alse  are  overlapped  and  retained  by  the  vaginal  processes,  which  pro- 
ject on  the  under  surface  of  the  body  of  the  sphenoid  at  the  base  of  the  pterygoid 
processes.  At  the  front  of  the  groove  a  fissure  is  left  for  the  transmission  of  blood- 
vessels to  the  substance  of  the  bone.  The  inferior  border,  the  longest,  is  broad  and 
uneven  in  front,  where  it  articulates  with  the  crests  of  the  two  maxillae ;  thin  and 
sharp  behind,  where  it  joins  with  the  palate  bones.  The  upper  half  of  the  anterior 
border  usually  consists  of  two  laminse  of  bone,  in  the  groove  between  which  is 
received  the  perpendicular  plate  of  the  ethmoid ;  the  lower  half,  also  separated  into 
two  lamellse,  receives  between  them  the  lower  margin  of  the  septal  cartilage  of  the 
nose.  The  posterior  border  is  free,  concave,  and  separates  the  nasal  fossee  behind. 
It  is  thick  and  bifid  above,  thin  below. 

The  surfaces  of  the  vomer  are  covered  by  mucous  membrane,  which  is  inti- 
mately connected  with  the  periosteum,  with  the  intervention  of  very  little,  if  any, 
submucous  connective  tissue. 

1  If  the  lacrimal  process  is  broken  off,  as  is  often  the  case,  the  side  to  which  the  bone  belongs  may  be  known 
by  recollecting  that  the  maxillary  process  is  nearer  the  back  than  the  front  of  the  bone. 


THE  MANDIBLE,   OR  LOWER  JAW 


115 


Space  for  fnavqida) 
cartilage  of  septum      '*^^^PI||| 


Lo'.ti  urn  of  sphenoid. 


Fig.  S4. — Vomer  ; 

Development.— The  vomer  at  an 
early  period  consists  of  two  laminse, 
separated  by  a  very  considerable  in- 
terval, and  enclosing  between  them  a 
plate  of  cartilage,  the  vomerine  car- 
tilage, which  is  prolonged  forward 
to  form  the  remainder  of  the  septum. 
Ossification  commences,  about  the 
eighth  week,  in  the  membrane  at  the 
postero-inferior  part  of  this  cartilage 
from  two  centres,  one  on  each  side  of 
the  middle  line,  which  extend  to  form 
the  two  laminse.  The  intervening 
cartilaginous  plate  is  absorbed.  They 
begin  to  coalesce  at  the  lower  part, 
but  their  union  is  not  complete  until 
after  puberty. 

Articulations. — With  nx  bones — two  of  the  cerebral  cranium,  the  sphenoid  and  ethmoid, 
and  four  of  the  face,  the  maxillse  and  the  two  palate  bones;  and  with  the  cartilage  of  the  septum. 

The  vomer  has  no  muscles  attached  to  it. 


With  maxillae  and  palate. 

Fig.  85, — The  vomer. 


The  Mandible,  or  Lower  Jaw  (Mandibula). 


The  mandible,  the  largest  and  strongest  bone  of  the  face,  serves  for  the  reception 
of  the  lower  teeth.  It  consists  of  a  curved,  horizontal  portion,  the  body,  and  two 
perpendicular  portions,  the  rami,  which  join  the  back  part  of  the  body  nearly  at 
right  angles. 

The  Body  (corpus  mandibulae)  (Fig.  86). — The  body  is  convex  in  its  general 
outline,  and  curved  somewhat  like  a  horseshoe.  It  presents  for  examination 
two  surfaces  and  two  borders.  , 

Surfaces. — ^The  external  surface  is  convex  from  side  to  side,  concave  from  above 
downward.     In  the  median  line  is  a  vertical  ridge,  the  symphysis,  which  extends 


116 


SPECIAL  ANATOMY  OF  THE  SKELETON 


from  the  upper  to  the  lower  border  of  the  bone,  and  indicates  the  point  of  junction 
of  the  two  pieces  of  which  the  bone  is  composed  at  an  early  period  of  life.  The 
lower  part  of  the  ridge  terminates  in  a  prominent  triangular  eminence,  the  mental 
process  (protuberantia  mentalis).     This  eminence  is  rounded  below,  and  often 


Coronoid  process. 


Condyle 


Groove  for  faaal  aitery 
-The  mandible.     Outer  surface. 


presents  a  median  depression  separating  two  processes,  the  mental  tubercles  (iubercula 
mentalia).  It  forms  the  chin,  a  feature  peculiar  to  the  human  skull.  On  either 
side  of  the  symphysis,  just  below  the  cavities  for  the  incisor  teeth,  is  a  depression, 
the  incisor  fossa,  for  the  attachment  of  the  Levator  menti;  more  externally  is 


>  ^''". 


Fig.  87. — The  mandible.     Inner  surface.     Side  view. 


attached  a  portion  of  the  Orbicularis  oris,  and  still  more  externally,  a  foramen, 
the  mental  foramen  (foramen  meiitale),  for  the  pas'sage  of  the  mental  vessels  and 
nerve.  This  foramen  is  placed  just  below  the  interval  between  the  two  bicuspid 
teeth.     Running  outward  from  the  base  of  the  mental  process  on  each  side  is  a 


THE  MANDIBLE,   OB  LOWER  JAW  II7 

ridge,  the  external  oblique  line  (linea  obliqua).  The  ridge  is  at  first  nearly  hori- 
zontal, but  afterward  inclines  upward  and  backward,  and  is  continuous  with  the 
anterior  border  of  tire  ramus;  it  aii'ords  attachment  to  the  Depressor  labii  inferioris 
and  Depressor  anguH  oris;  below  it  the  Platysma  is  attached. 

The  Internal  surface  (Fig.  87)  is  concave  from  side  to  side,  convex  from  above 
downward.  In  the  middle  line  is  an  indistinct  linear  depression,  corresponding 
to  the  symphysis  externally;  on  either  side  of  this  depression,  just  below  its 
centre,  are  two  prominent  tubercles,  one  above  and  one  below,  the  genial 
tubercles  {spinae  mentales) ,  which  afford  attachment,  the  upper  pair  to  the  Genio- 
hyoglossi,  the  lower  pair  to  the  Geniohyoidei,  muscles.  Sometimes  the  tubercles 
on  each  side  are  blended  into  one;  at  others  they  all  unite  into  an  irregular 
eminence;  or,  again,  nothing  but  an  irregularity  may  be  seen  on  the  surface  of 
the  bone  at  this  part.  On  either  side  of  the  genial  tubercles  is  an  oval  depression, 
the  sublingual  fossa  (fovea  sublingualis),  for  the  lodgement  of  the  sublingual  gland; 
and  beneath  the  fossa  a  rough  depression,  tlie  digastric  fossa  (fossa  digastrica),  on 
each  side,  wliich  gives  attachment  to  the  anterior  belly  of  the  Digastric  muscle. 

At  the  back  part  of  the  sublingual  fossa  the  internal  oblique  line,  or  mylohyoid 
ridge  (linea  mylohyoidea),  commences;  it  is  at  first  faintly  marked,  but  becomes 
more  distinct  as  it  passes  upward  and  outward,  and  is  especially  prominent 
opposite  the  last  two  molar  teeth;  it  affords  attachment  throughout  its  whole 
extent  to  the  Mylohyoid  muscle;  the  Superior  constrictor  of  the  pharynx  with 
the  pterygomandibular  ligament  being  attached  above  its  posterior  extremity,  near 
the  alveolar  margin.  The  portion  of  the  bone  above  this  ridge  is  smooth  and 
covered  by  the  mucous  membrane  of  the  mouth;  the  portion  below  presents  an 
oblong  depression,  the  submaxillary  fossa  (fovea  submaxillaris) ,  wider  behind  than 
in  front,  for  the  lodgment  of  the  submaxillary  gland.  The  external  and  internal 
oblique  lines  divide  the  body  of  the  bone  into  a  superior  or  alveolar  and  an  infe- 
rior or  basilar  portion. 

Borders. — ^The  superior  or  alveolar  portion  of  the  body  (pars  alveolaris)  has 
above  a  narrow  border  which  is  wider  and  the  margins  of  which  are  thicker 
behind  than  in  front.  It  is  hollowed  into  numerous  cavities  (alveoli  dentales),  for 
the  reception  of  the  teeth ;  these  cavities  are  sixteen  in  number,  and  vary  in  depth 
and  size  according  to  the  teeth  which  they  contain.  To  the  outer  side  of  the  alveo- 
lar border  the  Buccinator  muscle  is  attached  as  far  forward  as  the  first  molar  tooth. 
The  inferior  or  basilar  portion  (basis  mandibulae)  is  rounded,  longer  than  the  superior 
and  thicker  in  front  tlian  behind;  it  presents  a  shallow  groove,  just  where  the  body 
joins  the  ramus,  over  wliich  the  facial  artery  turns. 

The  Perpendicular  Portions  or  Rami  (rami  mandibulae). — ^The  perpendicular 
portions  or  rami  are  of  a  quadrilateral  form.  Each  presents  for  examination  two 
surfaces,  four  borders,  and  two  processes. 

Surfaces. — The  external  surface  is  flat,  marked  with  ridges,  and  gives  attachment 
throughout  nearly  the  whole  of  its  extent  to  the  Masseter  muscle. 

The  internal  surface  presents  about  its  centre  an  oblique  foramen  (foramen  man- 
dibulare),  the  beginning  of  the  inferior  dental  canal,  which  transmits  the  inferior 
dental  vessels  and  nerve.  The  margin  of  this  opening  is  irregular;  it  presents 
in  front  a  prominent  ridge,  surmounted  by  a  sharp  spine,  the  lingula  (lingula 
mandibidae),  which  gives  attachment  to  the  internal  lateral  ligament  of  the 
mandible,  and  at  its  lower  and  back  part  a  notch  leading  to  a  groove,  the  mylo- 
hyoidean  groove  (sulcus  mylohyoideus) ,  which  runs  obliquely  downward  to  the  back 
part  of  the  submaxillary  fossa,  and  lodges  the  mylohyoid  vessels  and  nerve.  Be- 
hind the  groove  is  a  rough  surface,  for  the  insertion  of  the  Internal  pterygoid 
muscle.  The  inferior  dental  canal  (canalis  mandibulae)  runs  obliquely  downward 
and  forward  in  the  substance  of  the  ramus,  and  then  horizontally  forward  in  the 
body;  it  is  here  placed  under  the  alveoli,  with  which  it  communicates  by  small 


118  SPECIAL  ANATOMY  OF  THE  SKELETON 

openings.  On  arriving  at  the  incisor  teeth,  it  turns  back  to  communicate  with  the 
mental  foramen,  giving  off  two  small  canals,  which  run  forward,  to  be  lost  in  the 
cancellous  tissue  of  the  bone  beneath  the  incisor  teeth.  This  canal,  in  the  poste- 
rior two-thirds  of  the  bone,  is  situated  nearer  the  internal  surface  of  the  jaw ;  and 
in  the  anterior  third,  nearer  its  external  surface.  Its  walls  are  composed  of  com- 
pact tissue  at  either  extremity,  and  of  cancellous  in  the  centre.  It  contains  the 
inferior  dental  vessels  and  nerve,  from  which  branches  are  distributed  to  the  teeth 
through  small  apertures  at  the  bases  of  the  alveoli. 

Borders. — ^The  lower  border  of  the  ramus  is  thick,  straight,  and  continuous  with 
the  body  of  the  bone.  At  its  junction  with  the  posterior  border  is  the  angle  of  the 
jaw  (angiilus  mandihulae).  The  angle  is  either  inverted  or  everted,  and  marked 
by  rough,  oblique  ridges  on  each  side,  for  the  attachment  of  the  Masseter  externally 
and  the  Internal  pterygoid  internally;  the  stylomaxillary  ligament  is  attached  to 
the  angle  between  these  muscles.  The  anterior  border  is  thin  above,  thicker  below, 
and  continuous  with  the  external  oblique  line.  The  posterior  border  is  thick, 
smooth,  rounded,  and  covered  by  the  parotid  gland.  The  upper  border  of  the 
ramus  is  thin,  and  presents  two  processes,  separated  by  a  deep  concavity,  the 
sigmoid  notch.  Of  these  processes,  the  anterior  is  the  coronoid,  the  posterior, 
the  condyloid. 

The  coronoid  process  (processus  coronoideus)  is  a  thin,  flat,  triangular  eminence, 
which  varies  in  shape  and  size.  Its  anterior  border  is  convex,  and  is  continuous 
below  with  the  anterior  border  of  the  ramus;  its  posterior  border  is  concave,  and 
forms  the  anterior  boundary  of  the  sigmoid  notch.  Its  external  surface  is  smooth, 
and  affords  attachment  to  the  Temporal  and  Masseter  muscles.  Its  internal 
surface  gives  insertion  to  the  Temporal  muscle,  and  presents  a  ridge  which  begins 
near  the  apex  of  the  process  and  runs  downward  and  forward  to  the  inner  side  of 
the  last  molar  tooth.  Between  this  ridge  and  the  anterior  border  is  a  grooved 
triangular  area,  the  upper  part  of  which  gives  attachment  to  the  Temporal,  the 
lower  part  to  some  fibres  of  the  Buccinator. 

The  condyloid  process  (^processus  condyloideus),  shorter  but  thicker  than  the 
coronoid,  consists  of  two  portions,  the  condyle  (capitulum  mandihulae),  and  the 
constricted  portion  which  supports  the  condyle,  the  neck  [collum  mandihulae). 
The  condyle  is  of  an  oblong  form,  its  long  axis  being  transverse,  and  set  obliquely 
on  the  neck  in  such  a  manner  that  its  outer  end  is  a  little  more  forward  and  a  little 
higher  than  its  inner.  It  is  convex  from  before  backward  and  from  side  to  side, 
the  articular  surface  extending  farther  on  the  posterior  than  on  the  anterior  aspect. 
At  its  outer  extremity  is  a  small  tubercle  for  the  attachment  of  the  external  lateral 
ligament  of  the  temporomandibular  joint.  The  neck  of  the  condyle  is  flattened 
from  before  backward,  and  strengthened  by  ridges  which  descend  from  the  fore 
part  and  sides  of  the  condyle.  Its  lateral  margins  are  narrow,  the  external  one 
giving  attachment  to  part  of  the  external  lateral  ligament.  Its  posterior  surface 
is  convex;  its  anterior  is  hollowed  out  on  its  inner  side  by  a  depression,  the  ptery- 
goid depression  (fovea  pterygoidea),  for  the  attachment  of  the  External  pterygoid 
muscle. 

The  sigmoid  notch  (incisura  inandihulae),  separating  the  two  processes,  is  a 
deep  semilunar  depression,  crossed  by  the  masseteric  vessels  and  nerve. 

Development. — The  mandible  is  ossified  in  the  fibrous  membrane  covering  the  outer  surfaces 
of  Meckel's  cartilages.  These  cartilages,  one  on  either  side,  form  the  cartilaginous  bar  of  the 
mandibular  arch,  being  joined  at  the  symphysis  by  mesodermal  tissue.  The  proximal  end  of 
each  cartilage  is  connected  with  the  periotic  capsule,  and  here  serves  to  form  the  malleus  and 
incus.  The  next  succeeding  portion  as  far  as  the  lingula  is  replaced  by  fibrous  tissue  to  form 
the  sphenomandibular  ligament.  Between  the  lingula  and  the  canine  tooth  the  cartilage  disap- 
pears, while  the  portion  near  the  symphysis  becomes  ossified  and  incorporated  with  the  incisor 
division  of  the  mandible.  This  ossific  centre  appears  in  about  the  sixth  week  of  fetal  life — i.  e., 
earlier  than  in  any  other  bone  except  the  clavicle;  ossification  is  practically  complete  by  the  tenth 


THE  MANDIBLE,   OR  LO  WEB  JA  W  \  19 

week.  Accessory  nuclei  develop  to  form  the  condyle  and  the  coronoid  process,  in  the  front  part 
of  both  alveolar  walls  and  along  the  front  of  the  lower  border  of  the  bone. 

These  accessory  nuclei  possess  no  separate  ossific  centres,  but  ossification  extends  into  them 
from  the  adjacent  membrane  bone  and  they  undergo  absorption.  The  inner  alveolar  border, 
usually  described  as  arising  from  a  separate  ossific  centre  {splenial  centre),  is  formed  in  the  human 
mandible  by  an  ingrowth  from  the  main  mass  of  the  bone.  At  birth  the  bone  consists  of  two 
halves,  united  by  a  fibrous  symjihysis,  in  which  ossification  takes  place  during  the  first  year. 

Articulation. — With  the  glenoid  fossse  of  the  two  temporal  bones. 

Attachment  of  Muscles. — To  fifteen  -pairs — to  its  external  surface,  commencing  at  the  sym- 
physis, and  proceeding  backward:  Levator  menti,  Depressor  labii  inferioris,  Depressor  anguli 
oris,  Platysma,  Buccinator,  Masseter;  a  portion  of  the  Orbicularis  oris  is  also  attached  to  this 
surface.  To  its  internal  surface,  commencing  at  the  same  point:  Geniohyoglossus,  Geniohyoirl, 
Mylohyoid,  Digastric,  Superior  constrictor,  Temporal,  Internal  pterygoid,  External  pterygoid. 


Meckel's  cartilage 


Fic.  SS. — Scheme  showing  ossification  of  the  mandible,  inner  side  (Low).  The  membrane  bone  is  colored 
red.  The  greater  part  of  Meckel's  cartilage  is  colored  blue.  The  upturned,  stippled  portion  near  the  symphysis 
represents  the  part  of  Meckel's  cartilage,  which  is  surrounded  and  invaded  by  the  membrane  bone.  The  accessory 
nuclei  of  cartilage  in  the  condyle,  coronoid  process,  alveolar  border,  and  body  are  indicated  by  stippled  areas. 


Fig.  89. — Scheme  showing  ossification  of  mandible  from  the  outer  side  (Low).     Membrane  bone  colored  red. 
Accessory  nuclei  of  cartilage  stippled. 

CHANGES  PRODUCED  IN  THE  MANDIBLE  BY  AGE. 

The  changes  which  the  mandible  undergoes  after  birth  relate  (1)  to  the  alterations  effected 
in  the  body  of  the  bone  by  the  first  and  second  dentitions,  the  loss  of  the  teeth  in  the  aged,  and 
the  subsequent  absorption  of  the  alveoli;  (2)  to  the  size  and  situation  of  the  dental  canal;  and 
(3)  to  the  angle  at  which  the  ramus  joins  with  the  body. 

At  birth  (Fig.  90)  the  bone  consists  of  lateral  halves,  united  by  fibrous  tissue.  The  body  is 
a  mere  shell  of  bone,  containing  the  sockets  of  the  two  incisor,  the  canine,  and  the  two  tem- 
porary molar  teeth,  imperfectly  partitioned  from  one  another.  The  dental  canal  is  of  large  size, 
and  runs  near  the  lower  border  of  the  bone,  the  mental  foramen  opening  beneath  the  socket  of 
the  first  molar.  The  angle  is  obtuse  (17.5  degrees),  and  the  condyloid  portion  nearly  in  the 
same  horizontal  line  with  the  body;  the  neck  of  the  condyle  is  short,  and  bent  backward.  The 
coronoid  process  is  of  comparatively  large  size,  and  situated  at  right  angles  with  the  rest  of 
the  bone. 

SIDE  VIEW  OF  THE  MANDIBLE  AT  DIFFERENT  PERIODS  OF  LIFE. 

After  birth  (Fig.  91)  the  two  segments  of  the  bone  become  joined  at  the  symphysis,  from 
below  upward,  in  the  first  year;  but  a  trace  of  separation  may  be  visible  in  the  beginning  of  the 
second  year  near  the  alveolar  margin.  The  body  becomes  elongated  in  its  whole  length,  but 
more  especially  behind  the  mental  foramen,  to  provide  space  for  the  three  additional  teeth 
developed  in  this  part.  The  depth  of  the  body  becomes  greater,  owing  to  increased  growth  of 
the  alveolar  part,  to  afford  room  for  the  fangs  of  the  teeth,  and  by  thickening  of  the  subdental 
portion,  which  enables  the  jaw  to  withstand  the  powerful  action  of  the  masticatory  muscles;  but 
the  alveolar  portion  is  the  deeper  of  the  two,  and,  consequently,  the  chief  part  of  the  body  lies 
above  the  oblique  line.  The  dental  canal  after  the  second  dentition  is  situated  just  above  the 
level  of  the  mylohyoid  ridge,  and  the  mental  foramen  occupies  the  position  usual  to  it  in  the 
adult.  The  angle  becomes  less  obtuse,  owing  to  the  separation  of  the  jaws  by  the  teeth.  (About 
the  fourth  year  it  is  140  degrees.) 


120 


SPECIAL  ANA  TOMY  OF  THE  SKELETON 


Fig.  90. — Mandible  in  newborn. 


Fig.  91. — In  child  six  to  seven  years  of  age. 


Fig.  92. — In  the  adult. 


Fig.  93.— In  old  age.     (Spalteholz.) 


THE  SUTURES  121 

In  the  adult  (Fig.  92)  the  alveolar  and  basilar  portions  of  the  body  are  usually  of  equal  dejjth. 
The  mental  foramen  opens  midway  between  the  upper  and  lower  border  of  the  bone,  and  the 
dental  canal  runs  nearly  parallel  with  the  mylohyoid  line.  The  ramus  is  almost  vertical  in 
direction,  and  joins  the  body  nearly  at  right  angles. 

In  old  age  (Fig.  93)  the  bone  becomes  greatly  reduced  in  size;  for  with  the  loss  of  the  teeth 
the  alveolar  process  is  absorbed,  and  the  basilar  part  of  the  bone  alone  remains,  conseciuently, 
the  chief  part  of  the  bone  is  heloiv  the  oblique  line.  The  dental  canal,  with  the  mental  foramen 
opening  from  it,  is  close  to  the  alveolar  liorder.  The  rami  are  oblique  in  direction,  the  angle 
obtuse,  and  the  neck  of  the  condyle  more  or  less  bent  backward. 


The  Sutures. 

The  bones  of  the  cerebral  cranium  and  face  are  connected  to  each  other  by  means 
of  sutures.  That  is,  the  articulating  surfaces  or  edges  of  the  bones  are  more  or 
less  roughened  or  uneven,  and  are  closely  adapted  to  each  other,  a  small  amount 
of  intervening  fibrous  tissue,  the  sutiual  ligament,  fastening  them  together.  The 
cranial  sutures  may  be  divided  into  three  sets:  (1)  Those  at  the  vertex  of  the  skull. 
(2)  Those  at  the  side  of  the  skull.     (3)  Those  at  the  base. 

The  sutures  at  the  vertex  of  the  skull  are  four — the  metopic,  the  sagittal,  the 
coronal,  and  the  lambdoid. 

The  metopic  or  frontal  suture  (sutiira  frontalis)  (Fig.  44)  is  usually  noted  in 
adults  as  a  trivial  fissure,  just  above  the  glabella.  At  birth  the  two  halves  of  the 
frontal  bone  are  separated  by  the  suture.  This  suture  is,  as  a  rule,  almost  com- 
pletely or  completely  closed  during  the  fifth  or  sixth  year,  but  occasionally  it 
persists  throughout  life. 

The  interparietal  or  sagittal  suture  {sutura  sagittalis)  is  formed  by  the  junction 
of  the  two  parietal  bones,  and  extends  from  the  middle  of  the  frontal  bone  back- 
ward to  the  superior  angle  of  the  occipital.  This  suture  is  sometimes  perforated, 
near  its  posterior  extremity,  by  the  parietal  foramen;  and  in  front,  where  it  joins 
the  coronal  suture,  a  space  is  occasionally  left  which  encloses  a  large  Wormian 
bone. 

The  frontoparietal  or  coronal  suture  (sutura  coronalis)  (Fig.  99)  extends  trans- 
versely across  the  vertex  of  the  skull,  and  connects  the  frontal  with  the  parietal 
bones.  It  commences  at  the  extremity  of  the  greater  wing  of  the  sphenoid  on  one 
side,  and  terminates  at  the  same  point  on  the  opposite  side.  The  dentations  of  the 
suture  are  more  marked  at  the  sides  than  at  the  summit,  and  are  so  constructed 
that  the  frontal  rests  on  the  parietal  above,  while  laterally  the  frontal  supports 
the  parietal. 

The  occipitoparietal  or  lambdoid  suture  (sutura  lamhdoidea)  (Fig.  99),  so  called 
from  its  resemblance  to  the  Greek  letter  A,  connects  the  occipital  with  the  parietal 
bones.  It  commences  on  each  side  at  the  mastoid  portion  of  the  temporal  bone, 
and  inclines  upward  to  the  end  of  the  sagittal  suture.  The  dentations  of  this 
suture  are  very  deep  and  distinct,  and  are  often  interrupted  by  several  small 
Wormian  bones. 

The  lateral  sutures  (Fig.  99)  extend  from  the  external  angular  process  of  the 
frontal  bone  to  the  lower  end  of  the  lambdoid  suture  behind.  The  anterior 
fortion  is  formed  between  the  lateral  part  of  the  frontal  bone  above  and  the 
malar  and  greater  wing  of  the  sphenoid  below,  forming  the  frontomalar  suture 
(sutura  zygomaticofrontalis)  and  frontosphenoidal  suture  (sutura  sphenofrontal  is). 
These  sutures  can  also  be  seen  in  the  orbit,  and  form  part  of  the  so-called 
transverse  facial  suture.  The  posterior  portion  is  formed  between  the  parietal 
bone  above  and  the  greater  wing  of  the  sphenoid,  the  squamous  and  mastoid 
portions  of  the  temporal  bone  below,  forming  the  sphenoparietal,  squamoparietal, 
and  mastoparietal  sutures. 


122  SPECIAL  ANA  TOMY  OF  THE  SKELETON 

The  sphenoparietal  (sutura  sphenopariefalis)  is  very  short;  it  is  formed  by  the 
tip  of  the  greater  wing  of  the  sphenoid,  which  overlaps  the  anterior  inferior  angle 
of  the  parietal  bone. 

The  squamoparietal  (sutura  squamosa)  is  arched,  and  is  formed  by  the  squamous 
portion  of  the  temporal  bone  overlapping  the  middle  division  of  the  lower  border 
of  the  parietal. 

The  mastoparietal  (sutura  parietmnastoidea),  a  short  suture,  deeply  dentated, 
is  formed  by  the  posterior  inferior  angle  of  the  parietal  and  the  superior  border  of 
the  mastoid  portion  of  the  temporal. 

The  sutures  at  the  base  of  the  ^kull  (Fig.  98)  are  the  basilar  in  the  centre,  and  on 
each  side  the  petro-occipital,  the  masto-occipital,  the  petrosphenoidal,  and  the 
squamosphenoidal. 

The  basilar  suture  (Jissura  spheiwoccipitalis)  is  formed  by  the  junction  of  the 
basilar  surface  of  the  occipital  bone  with  the  posterior  surface  of  the  body  of 
the  sphenoid.  At  an  early  period  of  life  a  thin  plate  of  cartilage  exists  between 
these  bones,  but  in  the  adult  they  become  fused  into  one  (synchondrosis  spheno- 
occipitalis).  Between  the  outer  extremity  of  the  basilar  suture  and  the  termina- 
tion of  the  lambdoid  an  irregular  suture  exists,  which  is  subdivided  into  two  por- 
tions. The  inner  portion,  formed  by  the  union  of  the  petrous  part  of  the  temporal 
with  the  occipital  bone,  is  termed  the  petro-occipital  fissure  (fissiira  petrooccipitalis). 
The  outer  portion,  formed  by  the  junction  of  the  mastoid  part  of  the  temporal 
with  the  occipital,  is  called  the  masto-occipital  suture  (sutura  occipitomastoidea) . 
Between  the  bones  forming  the  petro-occipital  suture  a  thin  plate  of  cartilage  exists; 
in  the  masto-occipital  is  occasionally  found  the  opening  of  the  mastoid  foramen. 
Between  the  outer  extremity  of  the  basilar  suture  and  the  sphenoparietal  an  irregu- 
lar suture  may  be  seen,  formed  by  the  union  of  the  sphenoid  with  the  temporal 
bone.  The  inner  and  smaller  portion  of  this  suture  is  termed  the  petrosphenoidal 
fissure  (fissura  sphenopetrosal;  it  is  formed  between  the  petrous  portion  of  the 
temporal  and  the  greater  wing  of  the  sphenoid;  the  outer  portion,  of  greater 
length  and  arched,  is  formed  between  the  squamous  portion  of  the  temporal  and 
the  greater  wing  of  the  sphenoid;  it  is  called  the  squamosphenoidal  suture  (sutura 
sphenosquamosa). 

The  bones  of  the  cerebral  cranium  are  connected  with  those  of  the  face,  and  the 
facial  bones  with  each  other,  by  numerous  sutures,  which,  though  distinctly 
marked,  have  received  no  special  names.  The  only  remaining  suture  deserving 
especial  consideration  is  the  transverse  suture.  This  extends  across  the  upper  part 
of  the  face,  and  is  formed  by  the  junction  of  the  frontal  with  the  facial  bones;  it 
extends  from  the  external  angular  process  of  one  side  to  the  same  point  on  the 
opposite  side,  and  connects  the  frontal  with  the  malar,  the  sphenoid,  the  ethmoid, 
the  lacrimal,  the  maxillae,  and  the  nasal  bones  on  each  side  (suiura  zygomatico- 
jrontalis;  the  orbital  portion  of  the  sutura  sphenofrontalis,  sutura  frontoethmoidalis, 
sutura  frontolacrimalis,  sutura  frontomaxillaris,  sutura  nasofrontalis) . 

The  sutures  remain  separate  for  a  considerable  period  after  the  complete  for- 
mation of  the  skull.  It  is  probable  that  they  serve  the  purpose  of  permitting  the 
growth  of  the  bones  at  their  margins,  while  their  peculiar  formation,  together 
with  the  interposition  of  the  sutural  ligament  between  the  bones  forming  them, 
prevents  the  dispersion  of  blows  or  jars  received  upon  the  skull.  Humphry 
remarks,  "that,  as  a  general  rule,  the  sutures  are  first  obliterated  at  the  parts  in 
which  the  ossification  of  the  skull  was  last  completed — viz.,  in  the  neighborhood 
of  the  fontanelles;  and  the  cranial  bones  seem  in  this  respect  to  observe  a  similar 
law  to  that  which  regulates  the  union  of  the  epiphyses  to  the  shafts  of  the  long 
bones."  The  same  author  remarks  that  the  time  of  their  disappearance  is 
extremely  variable;  they  are  sometimes  found  well  marked  in  skulls  edentulous 
with  age,  while  in  others  which  have  only  just  reached  maturity  they  can  hardly 


THE  SKULL  AS  A    WHOLE  \  23 

be  traced.     The  obliteration  of  the  sutures  takes  place  sooner  on  the  inner  ihun 
"on  the  outer  surface  of  the  skull.     The  sagittal  and  coronal  sutures  are,  as  a  rule, 
the  first  to  become  ossified — the  process  starting  near  the  posterior  extremity  of 
the  former  and  the  lower  ends  of  the  latter. 


THE  SKULL  AS  A  WHOLE. 

The  skull,  formed  by  the  union  of  the  several  cranial  and  facial  bones  already 
described,  when  considered  as  a  whole  is  divisible  into  five  regions — a  superior 
region  or  vertex,  an  inferior  region  or  base,  two  lateral  regions,  and  an  anterior 
region,  the  face. 

The  Vertex  of  the  Skull. — The  superior  region,  or  vertex,  presents  two  sur- 
faces, an  external  and  an  internal. 

Surfaces. — The  external  surface  {norma  verticalis)  is  bounded,  in  front,  by  the 
glabella  and  superciliary  ridges;  behind,  by  the  occipital  protuberance  and  superior 
curved  lines  of  the  occipital  bone;  laterally,  by  an  imaginary  line  extending  from 
the  outer  end  of  the  superior  curved  line,  along  the  temporal  ridge,  to  the  external 
angular  process  of  the  frontal  bone.  This  surface  includes  the  greater  part  of 
the  vertical  portion  of  the  frontal,  the  greater  part  of  the  parietal,  and  the  superior 
third  of  the  occipital  bone;  it  is  smooth,  convex,  of  an  elongated  oval  form,  crossed 
transversely  by  the  coronal  suture,  and  from  before  backward  by  the  sagittal, 
which  terminates  behind  in  the  lambdoid.  The  point  of  junction  of  the  coronal 
and  sagittal  sutures  is  named  the  bregma.  The  point  of  junction  of  the  sagittal 
and  lambdoid  sutures  is  called  the  lambda,  and  is  about  2f  inches  (7  cm.)  above 
the  external  occipital  protuberance.  From  before  backward  may  be  seen  the 
frontal  eminences  and  remains  of  the  suture  connecting  the  two  lateral  halves  of 
the  frontal  bone;  on  each  side  of  the  sagittal  suture  are  the  parietal  foramen  and 
parietal  eminence,  and  still  more  posteriorly  the  convex  surface  of  the  occipital 
bone.  In  the  neighborhood  of  the  parietal  foramen  the  skull  is  often  flattened, 
and  the  name  of  obelion  is  sometimes  given  to  that  point  of  the  sagittal  suture 
which  lies  exactly  opposite  to  the  parietal  foramen. 

The  internal  or  cerebral  surface  is  concave,  presents  depressions  for  the  convolu- 
tions of  the  cerebrum,  and  numerous  furrows  for  the  lodgement  of  branches  of  the 
meningeal  arteries.  Along  the  middle  line  of  this  surface  is  a  longitudinal  groove, 
narrow  in  front,  where  it  commences  at  the  frontal  crest,  but  broader  behind, 
where  it  lodges  the  superior  longitudinal  sinus,  and  by  its  margin  affords  attachment 
'  to  the  falx  cerebri.  On  either  side  of  it  are  several  depressions  for  the  arachnoid 
villi,  and  at  its  back  part  the  internal  openings  of  the  parietal  foramina.  This 
surface  is  crossed,  in  front,  by  the  coronal  suture;  from  before  backward  by  the 
sagittal;  behind,  by  the  lambdoid. 

The  Base  of  the  Skull  (the  Skull  being  without  the  Mandible).— The 
inferior  region,  or  base  of  the  skull,  presents  two  surfaces — an  internal  or  cerebral, 
and  an  external  or  basilar. 

Siu'faces.— The  internal  or  cerebral  surface  (Fig.  94)  presents  three  fossa:",  called 
the  anterior,  middle,  and  posterior  fossw  of  the  cranium. 

The  anterior  fossa  (fossa  cranii  aiiterior)  (Fig.  94)  is  formed  by  the  orliital  plates 
of  the  frontal,  the  cribriform  plate  of  the  ethmoid,  the  anterior  third  of  the  superior 
surface  of  the  body,  and  the  upper  surface  of  the  lesser  wings  of  the  sphenoid  bone, 
and  is  situated  at  a  higher  level  than  the  other  fosste.  It  is  the  most  elevated  of  the 
three  fosste,  convex  externally  where  it  corresponds  to  the  roof  of  the  orbit,  con- 
cave in  the  median  line  in  the  situation  of  the  cribriform  plate  of  the  ethmoid. 
It  is  traversed  on  either  side  by  three  sutures,  the  ethmofrontal,  ethmosphenoidal, 
and  frontosphenoidal,  and  lodges  the  frontal  lobes  of  the  cerebrum.     It  presents. 


124  SPECIAL  ANATOMY  OF  THE  SKELETON 

in  the  median  line,  from  before  backward,  the  commencement  of  the  groove  for 
the  superior  sagittal  sinus  and  the  frontal  crest  for  the  attachment  of  the  falx  cerebri; 


Groove  for  superior  sagittal  sinus. 

Gi'OOves  for  anterior  meningeal  artery. 

Foramen  csecum. 

Crista  galli. 

Slit  for  nasal  nerve. 

Groove  for  nasal  nerve. 

Anterior  ethmoidal  foramen. 

Orifices  for  olfactory  nerves. 

Posterior  ethmoidal  foramen. 

Ethmoidal  spine. 


Olfactory  grooves. 

Optic  foramen.. 

Optic  groove. 

Olivary  process. 

Anterior  clinoid  process. 

Middle  clinoid  process. 

PosteHor  clinoid  process. 

Groove  for  6th  nerve. 

Foramen  lacerum  medinm. 

OHfiee  of  carotid  canal. 

ion  for  Gasserian  ganglion. 


Deprei 


Meatus  auditorius  inter 

Floccular  fossa. 

Superior  petrosal  groove. 

Foramen  lacerum  posterius. 

Anterior  condylar  forarnen. 

Aquxducius  vesiUndi. 

Posterior  condylar  foramen. 


i  foramen. 
Posterior  meningeal  grooves. 


Fig.  94. — Base  of  the  skull.     Inner  or  cerebral  surface. 


the  foramen  cecum,  an  aperture  formed  between  the  frontal  bone  and  the  crista 
gaUi  of  the  ethmoid,  which,  if  pervious,  transmits  a  small  vein  from  the  nose  to 
the  sagittal  sinus;  behind  tlae  foramen  cecum,  the  crista  galli,  the  posterior  mar- 


THE  SKULL  AS  A    WHOLE 


125 


gin  of  which  affords  attachment  to  the  falx  cerebri;  on  either  side  of  the  crista 
gaili,  the  cribriform  plate,  which  supports  the  olfactory  bulb,  and  presents  three 
rows  of  foramina  for  the  transmission  of  its  nerve  filaments,  and  in  front  a  slit- 
like opening  {nasal  slit)  for  the  nasal  branch  of  the  ophthalmic  division  of  the 
trigeminal  nerve.  On  the  outer  side  of  each  olfactory  groove  are  the  internal 
openings  of  the  anterior  and  posterior  ethmoidal  foramina,  the  former  situated  about 
the  middle  of  the  outer  margin  of  the  olfactory  groove.  The  anterior  ethmoidal 
foramen  transmits  the  anterior  ethmoidal  vessels  and  the  nasal  nerve,  which  latter 
runs  in  a  depression  along  the  surface  of  the  ethmoid  to  the  slit-like  opening 
above  mentioned ;  while  the  posterior  ethmoidal  foramen  opens  at  tlie  })ack  part 
of  this  margin  under  cover  of  the  projecting  lamina  of  the  sphenoid,  and  trans- 
mits the  posterior  ethmoidal  vessels.  Farther  back  in  the  middle  line  is  the  eth- 
moidal spine,  bounded  behind  by  a  slight  elevation,  separating  two  shallow  longi- 


FiG.  95. — Base  of  the  skull.     Interior  view. 


tudinal  grooves  which  support  the  olfactory  lobes.  Behind  this  is  a  transverse 
sharp  ridge,  running  outward  on  either  side  to  the  anterior  margin  of  the  optic 
foramen,  and  separating  the  anterior  from  the  middle  fossa  of  the  base  of  the  skull. 
The  anterior  fossa  presents,  laterally,  depressions  for  the  convolutions  of  the  cere- 
brum and  grooves  for  the  lodgement  of  the  anterior  meningeal  arteries. 

The  middle  fossa  (fossa  cranii  media)  (Fig.  94),  deeper  than  the  preceding,  is 
narrow  in  the  middle  line,  but  becomes  wider  at  the  side  of  the  skull.  It  is  bounded  in 
front  by  the  posterior  margin  of  the  lesser  wings  of  the  sphenoid,  the  anterior  clinoid 
processes,  and  the  ridge  forming  the  anterior  margin  of  the  optic  groove;  behind, 
by  the  superior  border  and  anterior  surface  of  the  petrous  portions  of  the  temporal 
and  the  dorsum  sellse;  externally,  by  the  squamous  portions  of  the  temporal  and 
the  anterior  inferior  angle  of  the  parietal  bones  and  greater  wings  of  the  sphenoid. 
On  each  side  it  is  traversed  by  four  sutures,  the  squamoparietal,  sphenoparietal, 


126 


SPECIAL  ANATOMY  OF  THE  SKELETON 


squamosphenoidal,  and  petrosphenoidal.  In  the  middle  line,  from  before  back- 
ward, is  the  optic  groove,  which  supports  the  optic  commissure;  the  groove  terminates 
on  each  side  in  the  optic  foramen,  for  the  passage  of  the  optic  nerve  and  ophthal- 
mic artery;  behind  the  optic  groove  is  the  olivary  process  and  laterally  the  anterior 
clinoid  processes,  to  which  are  attached  processes  of  the  tentorium  cerebelli. 
Farther  back  is  the  sella  turcica,  a  deep  depression  which  lodges  the  hypophysis 
and  circular  sinus,  bounded  in  front  by  a  small  eminence  on  either  side,  the  middle 
clinoid  process,  and  behind  by  a  broad,  square  plate  of  bone,  the  dorsum  sellae, 
surmounted  at  each  superior  angle  by  a  tubercle,  the  posterior  clinoid  process; 
beneath  the  latter  process  is  a  notch,  for  the  abducent  nerve.  On  each  side  of 
the  sella  turcica  is  the  carotid  groove;  it  is  broad,  shallow,  and  curved  somewhat 
like  the  italic  letter  /,•  it  commences  behind  at  the  foramen  lacerum  medium,  and 


Fig.  96. — Median  sagittal  section  of  tlie  skull. 


terminates  on  the  inner  side  of  the  anterior  clinoid  process,  and  presents  along  its 
outer  margin  a  ridge  of  bone,  the  lingula.  This  groove  lodges  the  cavernous 
sinus,  the  internal  carotid  artery,  and  the  nerves  which  enter  the  orbit.  The 
sides  of  the  middle  fossa  are  of  considerable  depth;  they  present  depressions  for 
the  convolutions  of  the  cerebrum  and  grooves  for  the  branches  of  the  middle  men- 
ingeal artery;  the  latter  commence  on  the  outer  side  of  the  foramen  spinosum,  and 
consist  of  two  large  branches,  an  anterior  and  a  posterior;  the  former  passing 
upward  and  forward  to  the  anterior  inferior  angle  of  the  parietal  bone,  the  latter 
passing  upward  and  backward.  The  following  foramina  may  also  be  seen  on 
either  side  from  before  backward.  Most  anteriorly  is  seen  the  sphenoidal  fissure 
{foramen  lacerum  ajiterius),  formed  above  by  the  lesser  wing  of  the  sphenoid; 
below^  by  the  greater  wing;  internally,  by  the  body  of  the  sphenoid;  and  some- 


THE  SKULL  AS  A    WHOLE  127 

times  completed  externally  by  the  orbital  plate  of  the  frontal  bone.  It  trans- 
mits the  third,  the  fourth,  the  three  branches  of  the  ophthalmic  division  of 
the  trigeminal,  the  abducent  nerve,  some  filaments  from  the  cavernous  plexus 
of  the  sympathetics,  the  orbital  branch  of  the  middle  meningeal  artery,  a  recurrent 
branch  from  the  lacrimal  artery  to  the  dura,  and  the  ophthalmic  vein.  Behind 
the  inner  extremity  of  the  sphenoidal  fissure  is  the  foramen  rotundum,  for  the  passage 
of  the  second  division  of  the  trigeminal  nerve ;  still  more  posteriorly  is  seen  a  small 
orifice,  the  foramen  Vesalii,  an  opening  situated  between  the  foramen  rotundum 
and  the  foramen  ovale,  a  little  internal  to  both;  it  varies  in  size  in  dift'erent  indi- 
viduals, and  is  often  absent;  when  present  it  transmits  a  small  vein  and  opens  below 
into  the  outer  side  of  the  scaphoid  fossa.  Behind  and  external  to  the  latter  open- 
ing is  the  foramen  ovale,  which  transmits  the  third  division  of  the  trigeminal  nerve, 
the  small  meningeal  artery,  and  sometimes  the  small  petrosal  nerve.  On  the 
outer  side  of  the  foramen  ovale  is  the  foramen  spinosum,  for  the  passage  of  the  middle 
meningeal  artery;  occasionally  a  small  foramen  (canaliculus  innominatus)  for  the 
transmission  of  the  small  superficial  petrosal  nerve  is  seen  internal  to  the  fora- 
men spinosum.  On  the  inner  side  of  the  foramen  ovale  is  the  foramen  lacerum 
medium  ( foramen  lacerum) ;  the  lower  part  of  this  aperture  is  filled  in  the  recent 
state  with  cartilage  which  is  pierced  by  the  Vidian  nerve  and  a  meningeal  branch 
from  the  ascending  pharyngeal  artery.  On  the  anterior  surface  of  the  petrous 
portion  of  the  temporal  bone  is  seen,  from  without  inward,  the  eminence  caused 
by  the  projection  of  the  superior  semicircular  canal ;  in  front  of  and  a  little  outside 
this  is  a  depression,  the  tegmen  tympani,  corresponding  to  the  roof  of  the  tympa- 
num; the  groove  leading  to  the  hiatus  Fallopii,  for  the  transmission  of  the  greater 
petrosal  nerve  and  the  petrosal  branch  of  the  middle  meningeal  artery;  beneath 
it,  a  smaller  groove,  for  the  passage  of  the  lesser  petrosal  nerve;  and,  near  the  apex 
of  the  bone,  the  depression  for  the  Gasserian  ganglion;  and  the  internal  orifice 
of  the  carotid  canal,  for  the  passage  of  the  internal  carotid  artery  and  carotid 
plexus  of  nerves. 

The  posterior  fossa  ( fossa  cranii  posterior) ,  deeply  concave,  is  the  largest  of  the 
three,  and  situated  on  a  lower  level  than  either  of  the  preceding.  It  is  formed  by 
the  posterior  third  of  the  superior  surface  of  the  body  of  the  sphenoid,  by  the 
occipital,  the  posterior  surface  of  the  petrous  and  the  mastoid  portions  of  the  tem- 
poral, and  the  posterior  inferior  angle  of  the  parietal  bones;  it  is  crossed  on  either 
side  by  four  sutures,  the  petro-occipital,  the  masto-occipital,  the  mastoparietal, 
and  the  basilar;  and  lodges  the  cerebellum,  pons,  and  medulla  oblongata.  It  is 
separated  from  the  middle  fossa  in  the  median  line  by  the  dorsum  sellee,  and  on 
each  side  by  the  superior  border  of  the  petrous  portion  of  the  temporal  bone.  This 
border  serves  for  the  attachment  of  the  tentorium  cerebelli,  is  grooved  for  the  supe- 
rior petrosal  sinus,  and  at  its  inner  extremity  presents  a  notch,  in  which  rests  the 
trigeminal  nerve.  The  circumference  of  the  fossa  is  bounded  posteriorly  by  the 
grooves  for  the  lateral  (transverse)  sinuses.  In  the  centre  of  this  fossa  is  the  fora- 
men magnum,  bounded  on  either  side  by  a  rough  tubercle,  which  gives  attachment 
to  the  odontoid  or  cheek  ligaments;  and  a  little  above  these  are  seen  the  internal 
openings  of  the  anterior  condylar  foramina,through  which  pass  the  hypoglossal  ner\'e 
and  meningeal  branches  from  the  ascending  pharyngeal  arteries.  In  front  of  the 
foramen  magnum  is  a  grooved  surface,  formed  by  the  basilar  process  of  the  occipi- 
tal bone  and  by  the  posterior  third  of  the  superior  surface  of  the  body  of  the  sphe- 
noid, which  supports  the  medulla  oblongata  and  pons;  and  articulates  on  each  side 
with  the  petrous  portion  of  the  temporal  bone,  forming  the  petro-occipital  suture, 
the  anterior  half  of  which  is  grooved  for  the  inferior  petrosal  sinus,  the  posterior 
half  being  encroached  upon  by  the  foramen  lacerum  posterius  {foramen  jugulare). 
This  foramen  presents  three  compartments — through  the  anterior  passes  the  infe- 
rior petrosal  sinus;  through  the  posterior,  the  lateral  sinus  and  some  meningeal 


128  SPECIAL  ANATOMY  OF  THE  SKELETON 

branches  from  the  occipital  and  ascending  pharyngeal  arteries;  and  through  the 
middle,  the  glossopharyngeal,  vagus,  and  spinal  accessory  nerves.  Above  the  jugu- 
lar foramen  is  the  internal  auditory  meatus,  for  the  facial  and  auditory  nerves  and 
auditory  artery;  behind  and  external  to  this  is  the  slit-like  opening  leading  into  the 
aquaeductus  vestibuli,  which  lodges  the  ductus  endolymphaticus;  while  between 
the  two  latter,  and  near  the  superior  border  of  the  petrous  portion,  is  a  small,  tri- 
angular depression,  the  remains  of  the  floccular  fossa,  which  lodges  a  process  of  the 
dura  and  occasionally  transmits  a  small  vein  from  the  substance  of  the  bone.  Be- 
hind the  foramen  magnum  are  the  inferior  occipital  fossae,  which  lodge  the  hemi- 
spheres of  the  cerebellum,  separated  from  each  other  by  the  internal  occipital 
crest,  which  serves  for  the  attachment  of  the  falx  cerebelli  and  lodges  the 
occipital  sinus.  The  posterior  fossae  are  limited  above  by  the  deep  transverse 
grooves  for  the  lodgment  of  the  lateral  sinuses,  which  diverge  forward  on  each 
side  from  a  depression  in  the  mesal  plate,  the  torcular.  These  channels,  in  their 
passage  outward,  groove  the  occipital  bone,  the  posterior  inferior  angles  of  the 
parietals,  the  mastoid  portions  of  the  temporals,  and  the  jugular  processes  of 
the  occipital,  and  terminate  at  the  back  part  of  the  jugular  foramen.  Where  the 
lateral  sinus  grooves  the  mastoid  portion  of  the  temporal  bone  (sigmoid  fossa) 
the  orifice  of  the  mastoid  foramen  may  be  seen.  Just  previous  to  the  termination 
of  the  groove  the  posterior  condylar  foramen  opens  into  it.  Neither  foramen  is 
constant. 

The  basilar  surface  (norma  basalis)  (Fig.  97)  of  the  skull  is  extremely  irregular. 
It  is  bounded  in  front  by  the  incisor  teeth  in  the  maxillae;  behind  by  the  inion  and 
the  superior  curved  lines  of  the  occipital  bone;  and  laterally  by  the  alveolar  arch, 
the  lower  border  of  the  malar  bones,  the  zygoma,  and  an  imaginary  line  extending 
from  the  zygoma  to  the  mastoid  process  and  extremity  of  the  superior  curved  line 
of  the  occiput.  It  is  formed  by  the  palatal  processes  of  the  maxillae  and  palate 
bones,  the  vomer,  the  pterygoid  processes,  under  surface  of  the  greater  wings, 
spinous  processes  and  part  of  the  body  of  the  sphenoid,  the  under  surface  of  the 
squamous,  mastoid,  and  petrous  portions  of  the  tempoi'als,  and  the  under  surface  of 
the  occipital  bone.  The  anterior  part  of  the  base  of  the  skull  is  raised  above  the 
le\el  of  the  rest  of  this  surface  (when  the  skull  is  turned  over  for  the  purpose  of 
examination),  is  surrounded  by  the  alveolar  process,  which  is  thicker  behind  than 
in  front,  and  excavated  by  sixteen  depressions  for  the  lodgement  of  the  teeth  of 
the  maxillae,  the  cavities  varying  in  depth  and  size  according  to  the  teeth  they  con- 
tain. Immediately  behind  the  incisor  teeth  is  the  anterior  palatine  fossa.  At  the 
bottom  of  this  fossa  may  usually  be  seen  four  apertures,  two  placed  laterally,  the 
foramina  of  Stenson,  which  open  above,  one  in  the  floor  of  each  nostril,  and  trans- 
mit the  anterior  branch  of  the  posterior  palatine  vessels,  and  two  in  the  median 
line  in  the  intermaxillary  suture,  the  foramina  of  Scarpa,  one  in  front  of  the  other, 
the  anterior  transmitting  the  left,  and  the  posterior  (the  larger)  the  right,  naso- 
palatine nerve.  These  two  lateral  canals  are  sometimes  wanting,  or  they  may 
join  to  form  a  single  one,  or  one  of  them  may  open  into  one  of  the  lateral  canals 
above  referred  to.  The  palatine  vault  is  concave,  uneven,  perforated  by  numerous 
foramina,  marked  by  depressions  for  the  palatine  glands,  and  crossed  by  a  crucial 
suture,  formed  by  the  junction  of  the  four  bones  of  which  it  is  composed.  At  the 
front  part  of  this  surface  a  delicate  linear  suture  may  frequently  be  seen,  passing 
outward  and  forward  from  the  anterior  palatine  fossa  to  the  interval  between  the 
lateral  incisor  and  canine  teeth,  and  marking  off  the  premaxillary  portion  of  the 
bone.  At  each  posterior  angle  of  the  hard  palate  is. the  posterior  palatine  foramen, 
for  the  transmission  of  the  posterior  palatine  vessels  and  great  descending  palatine 
nerve;  and  running  forward  and  inward  from  it  a  groove,  for  the  same  vessels  and 
nerve.  Behind  the  posterior  palatine  foramen  is  the  tuberosity  of  the  palate  bone, 
perforated  by  one  or  more  accessory  posterior  palatine  canals,  giving  passage  to  the 


THE  SKULL  AS  A    WHOLE 


129 


middle  and  posterior  palatine  nerves  from  the  sphenopalatine  (Meckel's)  ganglion, 
and  marked  by  the  commencement  of  a  ridge  which  runs  transversely  inward, 


Anterior  palatine  fossa. 

Transmits  left  nasopalatine  nerve. 
Transmits  anterior  palatine  vessel. 
Transmits  right  nasopalatine  nerve. 


Accessory  palatine  foramina. 


■Sphenoid  process  of  palate. 
Pterygopalatine  canal. 


Fig.  97. — Base  of  the  skuU.     E.xternal  surface. 
9 


130 


SPECIAL  ANATOMY  OF  THE  SKELETON 


and  serves  for  the  attachment  of  the  tendinous  expansion  of  the  Tensor  palati 
muscle.  Projecting  backward  from  the  centre  of  the  posterior  border  of  the  hard 
palate  is  the  posterior  nasal  spine,  for  the  attachment  of  the  Azygos  uvulae  muscle. 
Behind  and  above  the  hard  palate  is  the  posterior  aperture  of  the  nasal  fossae 
(choanse),  divided  into  two  parts  by  the  vomer,  bounded  above  by  the  body  of 
the  sphenoid,  below  by  the  horizontal  plate  of  the  palate  bone,  and  laterally 
by  the  internal  pterygoid  plate  of  the  sphenoid.  Each  aperture  measures  about 
an  inch  in  the  vertical  and  about  half  an  inch  in  the  transverse  direction.  At  the 
base  of  the  vomer  may  be  seen  the  expanded  alse  of  this  bone,  receiving  between 
them  the  rostrum  of  the  sphenoid.  Near  the  lateral  margins  of  the  vomer,  at  the 
root  of  the  pterygoid  processes,  are  the  pterygopalatine  canals,  which  transmit  the 
pterygopalatine  vessels  and  the  pharyngeal  nerve  from  the  sphenopalatine 
(Meckel's)  ganglion.  The  pterygoid  process,  which  bounds  the  posterior  nares 
on  each  side,  presents  near  its  base  the  pterygoid  or  Vidian  canal,  for  the  Vidian 
nerve  and  artery.  Each  process  consists  of  two  plates,  which  bifurcate  at  the 
extremity  to  receive  the  tuberosity  of  the  palate  bone,  and  are  separated  behind 
by  the  pterygoid  fossa,  which  lodges  the  Internal  pterygoid  muscle.    The  internal 


Fig.  98.— Base  of  the  skull.     External  surface. 


plate  is  long  and  narrow,  presenting  on  the  border  of  its  base  the  scaphoid  fossa, 
for  the  origin  of  the  Tensor  palati  muscle,  and  at  its  extremity  the  hamular  process, 
around  which  the  tendon  of  this  muscle  turns.  The  external  pterygoid  plate  is 
broad,  forms  the  inner  boundary  of  the  zygomatic  fossa,  and  affords  attachment  by 
its  outer  surface  to  the  External  pterygoid  muscle. 

Behind  the  nasal  fossse  in  the  middle  line  is  the  basilar  surface  of  the  occipital 


THE  SKULL  AS  A    WHOLE  131 

bone,  presenting  in  its  centre  the  pharyngeal  spine,  for  the  attachment  of  the 
Superior  constrictor  muscle  of  the  pharynx,  with  depressions  on  each  sifle  for 
the  insertion  of  the  Rectus  capitis  anticus  major  and  minor.  At  the  base  of  the 
external  pterygoid  plate  is  the  foramen  ovale,  for  the  transmission  of  the  third  divi- 
sion of  the  trigeminal  nerve,  the  small  meningeal  artery,  and  sometimes  the  small 
petrosal  nerve;  behind  this,  the  foramen  spinosum,  which  transmits  the  middle 
meningeal  artery,  and  the  prominent  spinous  process  of  the  sphenoid,  which  gi\es 
attachment  to  the  internal  lateral  ligament  of  the  mandible  and  the  Tensor  palati 
muscle.  External  to  the  spinous  process  is  the  glenoid  fossa,  divided  into  two  parts 
by  the  Glaserian  fissure  (page  88),  the  anterior  portion  concave,  smooth,  bounded 
in  front  by  the  eminentia  articularis,  and  serving  for  the  articulation  of  the  condyle 
of  the  mandible;  the  posterior  portion  rough,  bounded  behind  by  the  tympanic 
plate,  and  serving  for  the  reception  of  part  of  the  parotid  gland.  Emerging  from 
between  the  laminae  of  the  vaginal  process  of  the  tympanic  plate  is  the  styloid 
process,  and  at  the  base  of  this  process  is  the  stylomastoid  foramen,  for  the  exit  of 
the  facial  nerve  and  entrance  of  the  stylomastoid  artery.  External  to  the  stylo- 
mastoid foramen  is  the  auricular  fissure,  for  the  exit  of  the  auricular  branch  of  the 
vagus,  bounded  behind  by  the  mastoid  process.  Upon  the  inner  side  of  the  mas- 
toid process  is  a  deep  groove,  the  digastric  fossa;  and  a  little  more  internally  the 
occipital  groove,  for  the  occipital  artery.  At  the  base  of  the  internal  pterygoid  plate 
is  a  large  and  somewhat  triangular  aperture,  the  foramen  lacerum  medium,  bounded 
in  front  by  the  greater  wing  of  the  sphenoid,  behind  by  the  apex  of  the  petrous  por- 
tion of  the  temporal  bone,  and  internally  by  the  body  of  the  sphenoid  and  basilar 
process  of  the  occipital  bone;  it  presents  in  front  the  posterior  orifice  of  the  Vidian 
canal;  behind,  the  aperture  of  the  carotid  canal.  The  basilar  surface  of  this  open- 
ing is  filled  in  the  recent  state  by  fibrocartilaginous  substance,  which  is  pierced 
by  the  Vidian  nerve  and  a  meningeal  branch  of  the  ascending  pharyngeal  artery; 
across  its  upper  or  cerebral  aspect  passes  the  internal  carotid  artery.  External  to 
this  aperture  the  petrosphenoidal  suture  is  observed,  at  the  outer  termination  of 
which  is  seen  the  orifice  of  the  canal  for  the  Eustachian  tube  and  that  for  the  Ten- 
sor tympani  muscle.  Behind  this  suture  is  seen  the  under  surface  of  the  petrous 
portion  of  the  temporal  bone,  presenting  from  within  outward,  the  quadrilateral, 
rough  surface,  part  of  which  affords  attachment  to  the  Levator  palati  and  Tensor 
tympani  muscles;  posterior  to  this  surface  is  the  orifice  of  the  carotid  canal  and  the 
orifice  of  the  aquaeductus  cochleae,  the  former  transmitting  the  internal  carotid 
artery  and  the  ascending  branches  of  the  superior  cervical  ganglion  of  the  sympa- 
thetic, the  latter  serving  for  the  passage  of  a  small  artery  to  and  a  small  vein  from 
the  cochlea.  Behind  the  carotid  canal  is  a  large  aperture,  the  jugular  foramen, 
formed  in  front  by  the  petrous  portion  of  the  temporal,  and  behind  by  the  occipital; 
it  is  generally  larger  on  the  right  than  on  the  left  side,  and  is  divided  into  three 
compartments  by  processes  of  dura.  The  anterior  is  for  the  passage  of  the  inferior 
petrosal  sinus;  the  posterior,  for  the  lateral  sinus  and  some  meningeal  branches  from 
the  occipital  and  ascending  pharyngeal  arteries;  the  central  one,  for  the  glosso- 
pharyngeal, vagus,  and  spinal  accessory  nerves.  On  the  ridge  of  the  bone  dividing 
the  carotid  canal  from  the  jugular  foramen  is  the  small  foramen  for  the  transmis- 
sion of  Jacobson's  nerve  (tympanic  branch  of  the  glossopharyngeal) ;  and  on  the 
wall  of  the  jugular  foramen,  near  the  root  of  the  styloid  process,  is  the  small  aper- 
ture for  the  transmission  of  the  auricular  branch  of  the  vagus  nerve  (Arnold's 
nerve) .  Behind  the  basilar  surface  of  the  occipital  bone  is  the  foramen  magnum, 
bounded  on  each  side  by  the  condyles,  rough  internally  for  the  attachment  of  the 
check  ligaments,  and  presenting  externally  a  rough  surface,  the  jugular  process, 
which  serves  for  the  attachment  of  the  Rectus  capitis  lateralis  muscle  and  the  lat- 
eral occipito-atlantal  ligament.  The  middle  of  the  anterior  margin  of  the  foramen 
magnum  is  called  the  basion.     The  mid-point  of  the  posterior  margin  is  called  the 


132 


SPECIAL  ANATOMY  OF  THE  SKELETON 


opisthion.  On  either  side  of  each  condyle  anteriorly  is  the  anterior  condylar  fossa, 
continued  as  the  anterior  condylar  foramen,  for  the  passage  of  the  hypoglossal 
nerve  and  often  a  meningeal  branch  of  the  ascending  pharyngeal  artery.  Behind 
each  condyle  is  the  posterior  condylar  fossa,  continued  as  the  posterior  condylar 
foramen,  for  the  transmission  of  a  vein  to  the  lateral  sinus.  Behind  the  foramen 
magnum  is  the  external  occipital  crest,  terminating  above  at  the  external  occipital 
protuberance,  while  on  each  side  are  seen  the  superior  and  inferior  curved  lines; 
these,  as  well  as  the  surfaces  of  bone  between  them,  are  rough  for  the  attachment 
of  the  muscles,  which  are  enumerated  on  pages  70  and  71. 

The  Lateral  Region  of  the  Skull. — The  norma  lateralis  is  of  a  somewhat 
triangular  form,  the  base  of  the  triangle  being  formed  by  a  line  extending  from  the 
external  angular  process  of  the  frontal  bone  along  the  temporal  ridge  backward  to 
the  outer  extremity  of  the  superior  curved  line  of  the  occiput;  and  the  sides  by 
two  lines,  the  one  drawn  downward  and  backward  from  the  external  angular 
process  of  the  frontal  bone  to  the  angle  of  the  mandible,  the  other  from  the  angle 
of  the  mandible  upward  and  backward  to  the  outer  extremity  of  the  superior 
curved  line.  This  region  is  divisible  into  three  portions — temporal  fossa,  mastoid 
portion,  and  zygomatic  or  infratemporal  fossa. 


Fig.  99. — Lateral  aspect  of  the  skull. 


The  Temporal  Fossa  (fossa  temporalis). — The  temporal  fossa  is  bounded  above 
and  behind  by  the  temporal  ridges,  which  extend  from  the  extei-nal  angular  process 
of  the  frontal  upward  and  backward  across  the  frontal  and  parietal  bones,  curving 
downward  behind  to  terminate  in  the  posterior  root  of  the  zygomatic  process.  In 
front  it  is  bounded  by  the  frontal,  malar,  and  greater  wing  of  the  sphenoid ;  externally 
by  the  zygomatic  arch  formed  conjointly  by  the  malar  and  temporal  bones;  heloiD, 
it  is  separated  from  the  zygomatic  fossa  by  the  pterygoid  ridge,  seen  on  the  outer 


THE  SKULL  AS  A    WHOLE 


1.3:3 


surface  of  the  greater  wing  of  the  sphenoid.  This  fossa  is  formed  by  five  bones, 
part  of  the  frontal,  greater  wing  of  the  sphenoid,  parietal,  squamous  portion  of  the 
temporal  and  malar  bones,  and  is  traversed  by  six  sutures,  part  of  the  frontomalar, 
sphenomalar,  coronal,  sphenoparietal,  squamoparietal,  and  squamosphenoidal. 
The  point  where  the  coronal  suture  crosses  the  superior  temporal  ridge  is  named 
the  stephanion;  and  the  region  where  the  four  bones,  the  parietal,  the  frontal, 
the  squamous  portion  of  the  temporal,  and  the  greater  wing  of  the  sphenoid, 
meet,  at  the  anterior  inferior  angle  of  the  parietal  bone,  is  named  the  pterion. 
This  point  is  about  on  a  level  with  the  external  angular  process  of  the  froii(<d 
bone  and  about  one  and  a  half  inches  (-3.75  cm.)  behind  it.  This  fossa  is  deeply 
concave  in  front,  convex  behind,  traversed  by  grooves  which  lodge  branches  of 
the  deep  temporal  arteries,  and  filled  by  the  Temporal  muscle. 

The  Mastoid  Portion. — The  mastoid  portion  of  the  side  of  the  skull  is  bounded 
in  front  by  the  anterior  root  of  the  zygoma;  above,  by  a  line  which  runs  from  the 
posterior  root  of  the  zygoma  to  the  end  of  the  mastoparietal  suture;  behind  and 
below  by  the  masto-occipital  suture.  It  is  formed  by  the  mastoid  and  part  of  the 
squamous  and  petrous  portions  of  the  temporal  bone;  its  surface  is  convex  and 
rough  for  the  attachment  of  muscles,  and  presents,  from  behind  forward,  the 
mastoid  foramen,  the  mastoid  process,  the  external  auditory  meatus  surrounded  by 


External  auditory  meatus 
Tympanicplate 


Spheno-inii.ciUary  fissure 

Infra- temporal  crest 
Pterygo-inaxillary  fissure 

Hamidar  process 


Styloid  process 
Glenoid  cavity 

Zygomatic  process  (cut) 


External  pterygoid  plate 
Fig.  100. — Left  zygomatic  fossa. 

the  tympanic  plate,  and,  most  anteriorly,  the  temporomandibular  articulation.  The 
point  where  the  posterior  inferior  angle  of  the  parietal  meets  the  occipital  and 
mastoid  portion  of  the  temporal  is  named  the  asterion. 

The  Zygomatic  Fossa  {fossa  infratemporaUs). — The  zygomatic  fossa  is  an  irregu- 
larly shaped  cavity,  situated  below  and  on  the  inner  side  of  the  zygoma ;  bounded  in 
front  by  the  zygomatic  surface  of  the  maxilla  and  the  ridge  which  descends  from  its 


134  SPECIAL  ANATOjMY  OF  THE  SKELETON 

malar  process;  behind,  by  the  posterior  border  of  the  external  pterygoid  plate  and 
the  emiiientia  articularis;  above,  by  the  pterygoid  ridge  on  the  outer  surface  of  the 
greater  wing  of  the  sphenoid  and  the  under  part  of  the  squamous  portion  of  the 
temporal ;  below,  by  the  alveolar  border  of  the  maxilla ;  internally,  by  the  external 
pterygoid  plate;  and  externally,  by  the  zygomatic  arch  and  ramus  of  the  mandible 
(Fig.  100).  It  contains  the  lower  part  of  the  Temporal,  the  External  and  Internal 
pterygoid  muscles,  the  internal  maxillary  artery  and  vein,  and  inferior  maxillary 
nerve  and  their  branches.  In  its  roof  are  seen  the  foramen  ovale  and  the  foramen 
spinosum;  on  its  anterior  wall  open  the  posterior  dental  canals.  At  its  upper  and 
inner  part  may  be  observed  the  sphenomaxillary  and  pterygomaxillary  fissures. 

The  sphenomaxillary  fissure  {fissura  orbitalis  inferior),  horizontal  in  direction, 
opens  into  the  outer  and  back  part  of  the  orbit.  It  is  formed  above  bj'  the  lower 
border  of  the  orbital  surface  of  the  greater  wing  of  the  sphenoid;  below,  by  the 
external  border  of  the  orbital  surface  of  the  maxilla  and  a  small  part  of  the  palate 
bone;  externally,  by  a  small  part  of  the  malar  bone;^  internally,  it  joins  at  right 
angles  with  the  pterygomaxillary  fissure.  This  fissure  permits  the  orbit  to  com- 
municate with  three  fossae — the  temporal,  zygomatic,  and  sphenomaxillary  fossae; 
it  transmits  the  superior  maxillary  nerve  and  its  orbital  branch,  the  infraorbital 
vessels,  and  ascending  branches  from  the  sphenopalatine  or  Meckel's  ganglion. 

The  pterygomaxillary  fissure  is  vertical,  and  descends  at  right  angles  from  the 
inner  extremity  of  the  preceding;  it  is  a  V-shaped  interval  formed  by  the  diver- 
gence of  the  maxilla  from  the  pterygoid  process  of  the  sphenoid.  It  serves 
to  connect  the  sphenomaxillary  fossa  with  the  zygomatic  fossa,  and  transmits 
the  internal  maxillary  artery. 

The  Sphenomaxillary  Fossa  (fossa  pterygopalatina). — ^The  sphenomaxillary  fossa 
is  a  small,  triangular  space  situated  at  the  angle  of  junction  of  the  sphenomaxillary 
and  pterygomaxillary  fissures,  and  placed  beneath  the  apex  of  the  orbit.  It  is  formed 
above  by  the  under  surface  of  the  body  of  the  sphenoid  and  by  the  orbital  process  of 
the  palate  bone;  in  front,  by  the  maxilla;  behind,  by  the  anterior  surface  of  the  base 
of  the  pterygoid  process  and  lower  part  of  the  anterior  surface  of  the  greater  wing  of 
the  sphenoid ;  internally,  by  the  vertical  plate  of  the  palate.  This  fossa  has  three 
fissures  terminating  in  it — the  sphenoidal,  sphenomaxillary,  and  pterygomaxillary; 
it  communicates  with  the  orbit  by  the  sphenomaxillary  fissure;  with  the  nasal 
fossae  by  the  sphenopalatine  foramen,  and  with  the  zygomatic  fossa  by  the  pterygo- 
maxillary fissure.  It  also  communicates  with  the  cavity  of  the  cranium,  and  has 
opening  into  it  five  foramina.  Of  these,  there  are  three  on  the  posterior  wall — 
the  foramen  rotimdum  above;  below  and  internal  to  this,  the  Vidian  canal;  and 
still  more  inferiorly  and  internally,  the  pterygopalatine  canal.  On  the  inner  wall 
is  the  sphenopalatine  foramen,  by  which  the  sphenomaxillary  communicates  with 
the  nasal  fossa;  and  below  is  the  superior  orifice  of  the  posterior  palatine  canal, 
besides  occasionally  the  orifices  of  the  accessory  posterior  palatine  canals.  The 
fossa  contains  the  superior  maxillary  nerve  and  Meckel's  ganglion,  and  the  termi- 
nation of  the  internal  maxillary  artery. 

The  Anterior  Region  of  the  Skull  (norma  frontalis). — The  norma  frontalis 
forms  the  face,  is  of  an  oval  fo*'m,  presents  an  irregular  surface,  and  is  excavated 
for  the  reception  of  two  of  the  organs  of  sense,  the  eyes  and  the  nose.  It  is  bounded 
above  by  the  glabella  and  margins  of  the  orbit;  below,  by  the  prominence  of  the 
chin;  on  each  side  by  the  malar  bone  and  interior  margin  of  the  ramus  of  the  man- 
dible. In  the  median  line  are  seen  from  above  downward  the  glabella,  and  diverg- 
ing from  it  are  the  superciliary  ridges,  which  indicate  the  situation  of  the  frontal 
sinuses  and  support  the  eyebrow.  Below  the  glabella  is  the  frontonasal  suture, 
the  mid-point  of  which  is  termed  the  nasion,  and  below  this  is  the  arch  of  the  nose, 

1  Occasionally  the  maxilla  and  the  sphenoid  articulate  with  each  other  at  the  anterior  extremity  of  this  fissure: 
the  malar  is  then  excluded  from  entering  into  its  formation. 


THE  SKULL  AS  A    WHOLE 


135 


formed  by  the  nasal  bones,  and  the  nasal  processes  of  the  maxillae.  The  nasal 
arch  is  convex  from  side  to  side,  concave  from  above  downward,  presenting  in  the 
median  line  the  intemasal  suture  (sutura  inter nasalis),  formed  between  the  nasai 
bones,  laterally,  on  either  side,  the  nasomaxillary  suture  {sutura  nasomaxillaris), 
formed  between  the  nasal  bone  and  the  nasal  process  of  the  maxilla.  Below  the 
nose  is  seen  the  opening  of  the  apertura  pyriformis,  which  is  heart-shaped,  with 
the  narrow  end  upward,  and  presents  laterally  the  thin,  sharp  margins  serving 
for  the  attachment  of  the  lateral  cartilages  of  the  nose,  and  in  the  middle  line 
below  a  prominent  process,  the  anterior  nasal  spine,  bounded  by  two  deep  notches. 
Below  this  is  the  intermaxillary  suture  {sutura  intermaxillaris),  and  on  each  side 
of  it  the  incisive  fossa.  Beneath  this  fossa  are  the  alveolar  processes  of  the  maxilla 
and  mandible,  containing  the  incisor  teeth,  and  at  the  lower  part  of  the  median 
line  the  symphysis  of  the  chin,  the  mental  process,  with  its  two  mental  tubercles, 
separated  by  a  median  groove,  and  the  incisive  fossa  of  the  mandible. 

On  each  side,  proceeding  from  above  downward,  is  the  supraorbital  ridge, 
terminating  externally  in  the  external  angular  process  at  its  junction  with  the  malar, 
and  internally  in  the  internal  angular  process;  toward  the  inner  third  of  this  ridge 
is  the  supraorbital  notch  or  foramen,  for  the  passage  of  the  supraorbital  vessels 


Fig.  101. — Anterior  aspect  of  the  skull. 


and  nerve.  Beneath  the  supraorbital  ridge  is  the  opening  of  the  orbit,  bounded 
externally  by  the  orbital  ridge  of  the  malar  bone;  below,  by  the  orbital  ridge 
formed  by  the  malar  and  maxilla;  internally,  by  the  nasal  process  of  the  maxilla 


136 


SPECIAL  ANATOMY  OF  THE  SKELETON 


and  the  internal  angular  process  of  the  frontal  bone.  On  the  outer  side  of  the 
orbit  is  the  quadrilateral  outer  surfact;  of  the  malar  bone,  perforated  by  one  or 
two  small  malar  foramina.  Below  the  inferior  margin  of  the  orbit  is  the  infra- 
orbital foramen,  the  termination  of  the  infraorbital  canal,  and  beneath  this  the 
canine  fossa,  which  gives  attachment  to  the  Levator  anguli  oris ;  still  lower  are  the 
alveolar  processes,  containing  the  teeth  of  the  upper  and  lower  jaws.  Beneath  the 
alveolar  arch  of  the  mandible  is  the  mental  foramen,  for  the  passage  of  the  mental 


\Groove  for 
facial  artery 


Fig.  102. — Anterolateral  region  of  the  skull. 


vessels  and  nerve,  the  external  oblique  line,  and  at  the  lower  border  of  the  bone, 
at  the  point  of  junction  of  the  body  with  the  ramus,  a  shallow  groove  for  the 
passage  of  the  facial  artery. 

The  Orbits. — The  orbits  (Fig.  102)  are  two  quadrilateral  pyramidal  cavities,  situ- 
ated at  the  upper  and  anterior  part  of  the  face,  their  bases  being  directed  forward 
and  outward,  and  their  apices  backward  and  inward,  so  that  the  axes  of  the  two,  if 
continued  backward,  would  meet  over  the  body  of  the  sphenoid  bone.  Each  orbit 
(orbita)  is  formed  of  seven  bones — the  frontal,  sphenoid,  ethmoid,  maxilla,  malar, 
lacrimal,  and  palate;  but  three  of  these,  the  frontal,  ethmoid,  and  sphenoid, 
enter  into  the  formation  of  both  orbits,  so  that  the  two  cavities  are  formed  of 
eleven  bones  only.  Each  cavity  presents  for  examination  a  roof,  a  floor,  an  inner 
and  an  outer  wall,  four  angles,  a  base,  and  an  apex. 


THE  SKULL  AS  A    WHOLE  137 

The  roof  {paries  superior)  is  concave,  directed  downward  and  slightly  forward, 
and  formed  m  front  by  the  orbital  plate  of  the  frontal;  behind,  by  the  lesser  wing 
of  the  sphenoid.  This  surface  presents  internally  the  depression  for  the  carti- 
laginous pulley  of  the  Superior  oblique  muscle;  externally,  the  depression  for  the 
lacrimal  gland;  and  posteriorly,  the  suture  connecting  the  frontal  and  lesser  wing 
of  the  sphenoid. 

The  floor  (paries  inferior)  is  directed  upward  and  outward,  and  is  of  less  extent 
than  the  roof;  it  is  formed  chiefly  by  the  orbital  surface  of  the  maxilla;  in  front,  to 
a  small  extent,  by  the  orbital  process  of  the  malar,  and  behind,  by  the  superior 
surface  of  the  orbital  process  of  the  palate.  This  surface  presents  at  its  anterior 
and  internal  part,  just  external  to  the  lacrimal  groove,  a  depression  for  the  attach- 
ment of  the  Inferior  oblique  muscle;  externally,  the  suture  between  the  malar 
and  the  maxilla;  near  its  middle,  the  infraorbital  groove;  and  posteriorly,  the  suture 
between  the  maxilla  and  palate  bone. 

The  inner  or  medial  wall  (paries  medialis)  is  flattened,  nearly  vertical,  and  formed 
from  before  backward  by  the  nasal  process  of  the  maxilla,  the  lacrimal,  os  planum 
of  the  ethmoid,  and  a  small  part  of  the  body  of  the  sphenoid.  This  surface  pre- 
sents the  lacrimal  groove  and  crests  of  the  lacrimal  bone,  and  the  sutures  connect- 
ing the  lacrimal  with  the  maxilla,  the  ethmoid  with  the  lacrimal  in  front,  and  the 
ethmoid  with  the  sphenoid  behind. 

The  outer  or  lateral  wall  (paries  lateralis)  is  directed  forward  and  inward,  and 
is  formed  m  front  by  the  orbital  process  of  the  malar  bone;  behind,  bv  the  orljital 
surface  of  the  greater  wing  of  the  sphenoid.  On  it  are  seen  the  orifices  of  one  or 
two  malar  canals,  and  the  suttn-e  connecting  the  sphenoid  and  malar  bones. 

Of  the  angles,  the  superior  external  is  formed  by  the  junction  of  the  upper 
and  outer  walls;  it  presents  from  before  backward,  the  suture  connecting  the 
frontal  with  the  malar  in  front  and  with  the  greater  wing  of  the  sphenoid  behind; 
quite  posteriorly  is  the  foramen  lacerum  anterius,  or  sphenoidal  fissure,  which 
transmits  the  third,  the  fourth,  the  three  branches  of  the  ophthalmic  division  of  the 
trigeminal,  the  abducent  nerve,  some  filaments  from  the  cavernous  plexus  of  the 
sympathetics,  the  orbital  branch  of  the  middle  meningeal  artery,  a  recurrent 
branch  from  the  lacrimal  artery  to  the  dura,  and  the  ophthalmic  vein.  The 
superior  internal  is  formed  by  the  junction  of  the  upper  and  inner  wall,  and  pre- 
sents the  suture  connecting  the  frontal  bone  with  the  lacrimal  in  front  and  with 
the  ethmoid  behind.  The  point  of  junction  of  the  anterior  border  of  the  lacri- 
mal with  the  frontal  has  been  named  the  dacryon.  This  angle  presents  two  fora- 
mina, the  anterior  and  posterior  ethmoidal  foramina,  the  former  transmitting  the 
anterior  ethmoidal  vessels  and  nasal  nerve,  the  latter  the  posterior  ethmoidal  vessels. 
The  inferior  external,  formed  by  the  junction  of  the  outer  wall  and  floor,  pre- 
sents the  sphenomaxillary  fissure,  which  transmits  the  superior  maxillary  nerve  and 
its  orbital  branches,  the  infraorbital  vessels,  and  the  ascending  branches  from  the 
sphenopalatine  or  Meckel's  ganglion.  The  inferior  internal  is  formed  by  the 
union  of  the  lacrimal  bone  and  the  os  planum  of  the  ethmoid  with  the  maxilla 
and  palate  bone. 

The  circumference  or  base  of  the  orbit,  quadrilateral  in  form,  is  bounded  above 
(margo  supraorbitalis)  by  the  supraorbital  ridge;  below  (margo  infraorbital  is), 
by  the  anterior  border  of  the  orbital  plate  of  the  malar  and  maxilla;  externally, 
by  the  external  angular  process  of  the  frontal  and  malar  bones ;  internally,  by  the 
internal  angular  process  of  the  frontal  and  the  nasal  process  of  the  maxilla.  The 
circumference  is  marked  by  three  sutures,  the  frontomaxillary  internally,  the 
frontomalar  externally,  and  the  malomaxillary  below;  it  contributes  to  the  forma- 
tion of  the  lacrimal  groove,  and  presents,  above,  the  supraorbital  notch  (or  fora- 
men), for  the  passage  of  the  supraorbital  vessels  and  nerve. 


138  SPECIAL  ANA  TOMY  OF  THE  SKELETON 

The  apex  is  situated  at  the  back  of  the  orbit  and  corresponds  to  the  optic 
foramen,'  a  short  circular  canal  which  transmits  the  optic  nerve  and  ophthalmic 
artery.  It  will  thus  be  seen  that  there  are  nme  openings  communicating  with 
each  orbit — viz.,  the  optic  foramen,  sphenoidal  fissure,  sphenomaxillary  fissure, 
supraorbital  foramen,  infraorbital  canal,  anterior  and  posterior  ethmoidal  for- 
amina, malar  foramina,  and  the  canal  for  the  nasal  duct. 

The  Nasal  Cavity. — The  nasal  cavities  {camim  nasi),  or  nasal  fossae  (Figs.  81  and 
103),  are  two  large,  irregular  cavities  situated  on  either  side  of  the  middle  line 
of  the  face,  extending  from  the  base  of  the  cranium  to  the  roof  of  the  mouth, 
and  separated  from  each  other  by  a  thin  vertical  septum,  the  septum  of  the  nose, 
formed  by  the  perpendicular  plate  of  the  ethmoid  and  by  the  vomer.  Each 
cavity  communicates  by  a  large  aperture,  the  anterior  nasal  aperture  {apertura 
pyriformis),^  with  the  front  of  the  face,  and  by  the  two  posterior  nares  (choance) 


LACRIMAL  CANAL  PALATE  BONE 

Fig.  103.— Nasal  cavity,  right  lateral  wall,  from  the  left.     (Spalteholz.) 


with  the  nasopharynx  behind.  These  fosste  are  much  narrower  above  than 
below,  and  in  the  middle  than  at  the  anterior  or  posterior  openings;  their  depth, 
which  is  considerable,  is  much  greater  in  the  middle  than  at  either  extremity. 
The  nasal  fossse  are  surrounded  by  four  other  fossae — above  is  the  cranial  fossa; 
laterally,  the  orbital  fossae;  and  below,  the  cavity  of  the  mouth.  Each  nasal  fossa 
communicates  with  four  sinuses — the  frontal  above,  the  sphenoidal  behind,  and 
the  maxillary  and  ethmoidal  on  the  outer  wall.  Each  fossa  also  communicates 
with  four  cavities — with  the  orbit  by  the  lacrimal  groove,  with  the  mouth  by  the 
anterior  palatine  canal,  with  the  cranium  by  the  olfactory  foramina,  and  with  the 
sphenomaxillary  fossa  by  the  sphenopalatine   foramen;   and  they  occasionally 


iQuain,  Testut,  and  others  give  the  apex  of  the  orbit  aa  corresponding  with  the  inner  end  of  the  sphenoidal 
fiaaure.  It  seems  better,  however,  to  adopt  the  statement  in  the  text,  since  the  muscles  of  the  eyeball  take  origin 
around  the  optic  foramen,  and  diverge  from  it  to  the  globe  of  the  eye. 

2  In  the  skull  freed  of  soft  parts  the  anterior  nasal  cavities  open  in  front  by  the  apertura  pyriformis.  In  the 
skull  with  the  soft  parts  in  place  they  open  by  the  anterior  nares. 


THE  SKULL  AS  A    WHOLE  139 

communicate  with  each  other  by  an  aperture  in  the  septum.  The  bones  entering 
into  their  formation  are  fourteen  in  number — three  of  the  cerebral  cranium,  the 
frontal  sphenoid,  and  ethmoid,  and  ail  the  bones  of  the  face,  excepting  the  malar 
and  mandible.  Each  cavity  is  bounded  by  a  roof,  a  floor,  an  inner  and  an  outer 
wall. 

The  upper  wall,  or  roof,  is  long,  narrow,  and  horizontal  in  its  centre,  but  slopes 
downward  at  its  anterior  and  posterior  extremities ;  it  is  formed  in  front  by  the 
nasal  bones  and  nasal  spine  of  the  frontal,  which  are  directed  downward  and 
forward;  in  the  middle,  by  the  cribriform  plate  of  the  ethmoid,  which  is  hori- 
zontal ;  and  behind,  by  the  anterior  and  under  surface  of  the  body  of  the  sphenoid 
and  sphenoidal  turbinated  process,  the  ala  of  the  vomer  and  the  sphenoidal  process 
of  the  palate  bone,  which  are  directed  downward  and  backward.  This  surface 
presents,  from  before  backward,  the  internal  aspect  of  the  nasal  bones ;  on  their  outer 
side,  the  suture  formed  between  the  nasal  bone  and  the  nasal  process  of  the  maxilla; 
on  their  inner  side,  the  elevated  crest  which  receives  the  nasal  spine  of  the  frontal 
and  the  perpendicular  plate  of  the  ethmoid,  and  articulates  with  its  fellow  of  the 
opposite  side;  while  the  surface  of  the  bones  is  perforated  by  a  few  small  vascular 
apertin-es,  and  presents  the  longitudinal  groove  for  the  nasal  nerve;  farther  back 
is  the  transverse  suture,  connecting  the  frontal  with  the  nasal  in  front,  and  the 
ethmoid  behind,  the  olfactory  foramina  and  nasal  slit  on  the  under  surface  of  the 
criiiriform  plate,  and  the  suture  lietween  it  and  the  sphenoid  behind;  quite  pos- 
teriorly are  seen  the  sphenoidal  turbinated  process,  the  orifice  of  the  sphenoidal 
sinus,  and  the  articulation  of  the  ala  of  the  vomer  with  the  under  surface  of  the 
body  of  the  sphenoid. 

The  floor  (Fig.  103)  is  flattened  from  before  backward,  concave  from  side  to 
side,  and  wider  in  the  middle  than  at  either  extremity.  It  is  formed  in  front 
by  the  palatal  process  of  the  maxilla ;  behind,  by  the  horizontal  plate  of  the  palate 
bone.  This  surface  presents,  from  before  backward,  the  anterior  nasal  spine; 
behind  this,  the  upper  orifices  of  the  anterior  palatine  canal;  the  elevated  crest 
which  articulates  with  the  vomer;  and  behind,  the  suture  between  the  palate 
and  maxilla,  and  the  posterior  nasal  spine. 

The  inner  or  medial  wall,  or  septum  (septum  nasi  osseum)  (Fig.  105),  is  a  thin 
vertical  partition  which  separates  the  nasal  fossse  from  each  other.  It  is  formed, 
in  front,  by  the  crest  of  the  nasal  bones  and  nasal  spine  of  the  frontal ;  in  the 
middle,  by  the  perpendicular  plate  of  the  ethmoid  and  ethmoidal  crest  of  the 
sphenoid;  behind,  by  the  vomer  and  rostrum  of  the  sphenoid;  below,  by  the  crests 
of  the  maxillae  and  palate  bones.  It  presents,  in  front,  a  large,  triangular  notch, 
which  receives  the  septal  cartilage  of  the  nose;  and  behind,  the  grooved  edge  of  the 
vomer.  Its  surface  is  marked  by  numerous  canals  for  vessels  and  nerves,  and 
the  groove  for  the  nasopalatine  nerve,  and  is  traversed  by  sutures  connecting 
the  bones  of  which  it  is  formed. 

The  outer  or  lateral  wall  (Figs.  81  and  103)  is  formed,  in  front,  by  the  nasal 
process  of  the  maxilla  and  lacrimal  bones ;  in  the  middle,  by  the  ethmoid  and  inner 
surface  of  the  body  of  the  maxilla  and  turbinated  bone;  behind,  by  the  vertical 
plate  of  the  palate  bone;  and  the  internal  pterygoid  plate  of  the  sphenoid.  Upon 
this  outer  wall  are  two  marked  projections  of  bone  (Fig.  81).  One  is  known 
as  the  turbinated  bone  and  the  other  as  the  middle  turbinated  process.  The  supe- 
rior turbinated  process  appears  as  a  less  distinct  bony  projection.  This  surface 
presents  three  irregular  longitudinal  passages,  termed  the  superior,  middle,  and 
inferior  meatuses  of  the  nose  (Fig.  104).  The  superior  meatus,  the  smallest  of 
the  three,  is  situated  at  the  upper  and  back  part  of  each  nasal  fossa,  occupying 
the  posterior.third  of  the  outer  wall.  It  is  situated  between  the  superior  and  mid- 
dle turbinated  processes,  and  has  opening  into  it  two  foramina,  the  sphenopalatine 
foramen  at  the  back  of  its  outer  wall,  and  the  posterior  ethmoidal  cells  at  the  front 


140 


SPECIAL  ANATOMY  OF  THE  SKELETON 


part  of  the  outer  wall.  The  sphenoidal  sinus  opens  into  a  recess  (recesstw  spheno- 
ethmoidalis) ,  which  is  situated  above  and  behind  the  superior  turbinated  process. 
The  middle  meatus  is  situated  external  to  the  middle  turbinated  process,  between 


TRUM  OF-iJ 


STLE   PASSED  THRG 
NDIBULUM   FROM 
TAL  SINUS  TO 
LE  MEATUS 


OBE    PASSED 
THROUGH   LACRI- 
L  CANAL 


NTAL  CANAL 


ASAL  CANAL 


Fig.  104. — Coronal  section  through  the  frontal  sinus  and  nasal  fossa.      (Poirier  and  Charpy.) 


Crest  of  nasal  bone. 

Nasal  spine  of 
frontal  boi 


Space  for  triangula) 
cartilage  of  ieptiini 


»   .  "   Ci  est  of  palate  bone. 
Crest  of  maxilla. 


Fig.  105. — Inner  wall  of  nasal  fossEe,  or  septum  of  i 


THE  SKULL  AS  A    WHOLE 


141 


it  and  the  turbinated  bone,  and  extends  from  the  anterior  end  of  the  turbinated 
to  the  sphenopalatine  foramen  of  the  outer  wall  of  the  nasal  fossa.  Anteriorly 
it  terminates  in  a  depression,  the  atrium  of  the  nasal  meatus  {atrium  meatiw  medii). 
The  middle  meatus  presents  in  front  the  orifice  of  the  infundibulimi,  by  which 
the  middle  meatus  communicates  with  the  anterior  ethmoidal  cells,  and  through 
these  with  the  frontal  sinuses.  The  posterior  ethmoidal  cells  also  open  into 
this  meatus,  while  at  the  centre  of  the  outer  wall  is  the  orifice  of  the  maxillary 
antrum  which  varies  somewhat  as  to  its  exact  position  in  different  skulls.  The 
inferior  meatus,  the  largest  of  the  three,  is  the  space  between  the  turbinated  bone 
and  the  floor  of  the  nasal  fossa.  It  extends  along  the  entire  length  of  the  outer 
wall  of  the  nose,  is  broader  in  front  than  behind,  and  presents  anteriorly  the  lower 
orifice  of  the  canal  for  the  nasal  duct. 


Pituitary 
fossa 


Mesoderm  of  base 
of  skull 


Development  of  the  Skull. — Up  to  a  cei-tain  stage  the  development  of  the  skull  corresponds 
with  that  of  the  vertebral  column;  but  it  is  modified  later  in  association  with  the  expansion  of 
the  brain  vesicles,  the  formation  of  the  organs  of  smell,  sight,  and  hearing,  and  the  development 
of  the  mouth  and  pharynx. 

The  notochord  extends  as  far  forward  in  the 
base  of  the  future  skull  as  the  anterior  end  of  the 
mid-brain,  and  becomes  partly  surrounded  by 
mesoderm  (Fig.  106).  The  posterior  part  of  this 
mesodermal  investment  corresponds  with  the 
future  basiocciput,  and  shows  a  subdivision  into 
four  segments,  which  are  separated  by  the  roots 
of  the  hypoglossal  nerve.  The  mesoderm  then 
extends  over  the  brain  vesicles,  and  thus  the  entire 
brain  is  enclosed  by  a  mesodermal  investment, 
which  is  termed  the  membranous  primordial  cra- 
nium. From  the  inner  layer  of  this  the  bones  of 
the  skull  and  the  membranes  of  the  brain  are  de- 
veloped; from  the  outer  layer  the  muscles,  blood- 
vessels, true  skin,  and  subcutaneous  tissues  of  the 
scalp.  In  the  shark  and  dog-fish  this  ineinbnin- 
ous  cranium  undergoes  complete  chondrifi(  ation, 
and  forms  the  cartilaginous  skull,  or  rliondro- 
cranium,  of  these  animals.  In  mammals,  on  the 
other  hand,  the  process  of  chondrification  is 
limited  to  the  base  of  the  skull — the  roof  and 
sides  being  covered  in  by  membrane.  Thus, 
the  bones  of  the  base  of  the  skull  are  preceded 

by  cartilage,  those  of  the  roof  and  sides  by  membrane.  The  posterior  part  of  the  base  of  the 
skull  is  developed  around  the  notochord,  and  exhibits  a  segmented  condition  analogous  to 
that  of  the  vertebral  column,  while  the  anterior  part  arises  in  front  of  the  notochord  and  shows 
no  regular  segmentation.  The  base  of  the  skull  may  therefore  be  divided  into  (a)  o  chordal  or 
vertebral,  and  (6)  a  prechordal  or  prevertebral  portion. 

In  the  lower  vertebrates  two  pairs  of  cartilages  are  developed,  viz.,  a  pair  of  parachordal 
cartilages,  one  on  either  side  of  the  notochord;  and  a  pair  of  prechordal  cartilages,  the  trabeculae 
cranii,  in  front  of  the  notochord  (Figs.  107  and  108).  The  parachordal  cartilages  (Fig.  108)  unite 
to  form  a  cartilaginous  plate,  from  which  the  cartilaginous  part  of  the  occipital  bone  and  the  basi- 
sphenoid  are  developed.  On  the  lateral  aspect  of  the  parachordal  cartilages  the  otic  or  auditory 
■vesicles  are  situated,  and  the  mesoderm  enclosing  them  is  soon  converted  into  cartilage,  forming 
the  cartilaginous  ear  capsules.  These  cartilaginous  ear  capsules,  which  are  of  an  oval  shape, 
fuse  with  the  lateral  aspects  of  the  basilar  plate,  and  from  them  arise  the  petromastoid  portions 
of  the  temporal  bones.  The  trabeculae  cranii  (Fig.  107)  are  two  curved  bars  of  cartilage  which 
embrace  the  pituitary  body;  their  posterior  ends  soon  unite  with  the  basilar  plate,  while  their 
anterior  ends  join  to  form  the  ethmoidal  plate,  which  extends  forward  between  the  forebrain  and 
the  olfactory  pits.  Later,  the  trabecula;  meet  and  fuse  below  the  pituitary  body,  forming  the 
floor  of  the  pituitary  fossa,  and  so  cutting  off  the  anterior  lobe  of  the  pituitary  body  from  the  stoma- 
todeum.  The  mesal  part  of  the  ethmoidal  plate  forms  the  bony  and  cartilaginous  parts  of  the 
nasal  septum.  From  the  lateral  margins  of  the  trabeculae  cranii  three  processes  grow  out  on 
either  side.  The  anterior  forms  the  lateral  mass  of  the  ethmoid  and  the  alar  cartilages  of  the 
nose;  the  middle  gives  rise  to  the  lesser  wing  of  the  sphenoid,  while  from  the  posterior  the  greater 
wing  and  external  pterygoid  plate  of  the  sphenoid  are  developed  (Figs.  109  and  110).     The  bones 


Anterior  arch  of  atlas 

Notochord 

Body  of  axis 

Third  cervical 
vertebra 

Fig,  106. — Sagittal  section  of  cephalic  end  of 
notochord.      (Furness). 


142 


SPECIAL  ANATOMY  OF  THE  SKELETON 


of  the  vault  are  of  membranous  formation,  and  are  termed  dermal  or  covering  hones.  They  are 
partly  developed  from  the  mesoderm  of  the  primordial  cranium,  and  partly  from  that  which 
lies  outside  the  entoderm  of  the  foregut.  They  comprise  the  upper  part  of  the  tabular  por- 
tion of  the  occipital  (interparietal),  the  squamous  temporals  and  tympanic  plates,  the  panetals, 


Situation  of  olfactory  pit      Ethmoid  plate 

and  nasal      Olfactory  organ 
K         sp.ptu 


Pituitary  fossa 


Extension  around 
olfactory  organ 
Foramina  for 
olfactory  nerves 

—  Eyehall 
--  Pituitary  fossa 


Figs.  107  and  108. — Diagrams  of  the  cartilaginous  cranium.     (Wiedersheim.) 


Meckel's  cartilage 
Malleus 
Incus 

Int.  aud.  meat 
JugutXar  f '>*>■'  >*'''  ■ 

Fossa  sub'    « ' 


^--^^&rya 


Optic  foramen. 
^         r^!& Greater  wing  of 


Eor.  hypi 


Foramen  magnum. 

Fig.  I09.-Model  of  the  chondrocranium  of  .a^human  embryo.  8'^f„., The  membrane  bones  are  not 
represented.     (From  Hertwig's  Handbuch  der  Entwickelungslehre.) 

the  frontal   the  vomer,  the  internal  pterygoid  plates,  and  the  bones  of  the  face.     Some  of  them 

remain  diiinct  throughout  life  (..  i  parietal  and  frontal),  while  others  30m  w>th  the  bones  of 

thrchondrocrani^m  (..  q..  interparietal,  squamous  temporals,  arid  internal  pterygoid  plate  ). 

Recent  Ob  ervations  have  shown  that,  in  mammals,  the  basicranial  cartilage,  both  m  the 


THE  SKULL  AS  A    WHOLE 


143 


chordal  and  prechordal  regions  of  the  base  of  the  skull,  is  developed  as  a  single  plate,  which 
extends  from  behind  forward.  In  man,  however,  its  posterior  part  shows  an  indication  of  its 
being  developed  from  two  chondrifying  centres  which  fuse  rapidly  in  front  and  below.  The 
relation  of  this  cartilaginous  plate  to  the  notochord  differs  in  different  animals.  In  the  ral  embryo 
it  lies  vcntrad  of  the  notochord  (Robinson);  in  the  sheep,  pig,  calf,  and  ferret  the  cranial  |i;irl  of 
the  notochord  is  enclosed  within  it;  in  man,  the  anterior  and  posterior  thirds  of  (he  carlilage 
surround  the  notochord,  but  its  middle  third  lies  on  the  dorsal  aspect  of  the  notochord,  which  in 
this  region  is  placed  between  the  cartilage  and  the  wall  of  the  pharynx. 


Optic  foramen 


g  of  sphenoid 


Nasal  capsule 


Nasal  septu: 


Maxilla. 

Vomer 


Meckel  s  cartilage   f^  ^^       /       j      \  i>tt/hid  process 

Thyroid  carlilagc'-^^^^^fj^lf^lJ    Fen.  cocldeae. 
Cricoid  cartilage.       ^^  For.  h'jpogl. 

Fig.  110. — The  same  model  as  shown  in  Fig.  109  from  the  left  side.     Certain  of  the  membrane  bones  of  the 
right  side  are  represented  in  yellow. 

Differences  in  the  Skull  Due  to  Age. — At  birth  the  skull  as  a  whole  is  large  in  pro- 
portion to  the  other  parts  of  the  skeleton,  but  its  facial  portion  is  small,  and  equals  only  about 
one-eighth  of  the  bulk  of  the  cranium  as  compared  with  one-half  in  the  adult.  The  frontal  and 
parietal  eminences  are  prominent,  and  the  greatest  width  of  the  skull  is  at  the  level  of  the  latter; 
on  the  other  hand,  the  glabella,  superciliary  ridges,  and  mastoid  processes  are  not  developed. 
Ossification  of  the  skull  bones  is  not  completed,  and  many  of  them — e.  g.,  the  occipital, 
temporals,  sphenoid,  frontal,   and  mandible — consist  of  more  than  one  piece.      Unossified 


^     .  ,  Fig    112, — The  lateral  fontanelles. 

Fig.  hi, — Skull  at  birth,  showing  the  anterior 
and  posterior  fontanelles. 

membranous  intervals,  termed /o.ta.Wfes-,  are  seen  at  ^e  angles  of  the  parietal  bones;  th^ 

"The  a,aerior  or  hreg.naiic  fonianelle  (Fig.  Ill)  is  the  largest,  an  A  is  ^^^ j^Z 
of  the  sagittal,  coronal,  and  interfrontal  sutures;  U  ,s  '-^"g^-^J.^^'^^^'^i^J^^X  V-  -■"•"^ 
inch  and  a  half  in  its  antero-posterior  and  an  mch  in  its  transNerse  diametei,  / 


144  SPECIAL  ANATOMY  OF  THE  SKELETON 

fontanelle  is  triangular  in  form  and  is  situated  at  the  junction  of  the  sagittal  and  lambdoid  sutures. 
The  \?ittT?A  fontanelles  (Fig.  112)  are  small,  irregular  in  shape,  and  correspond  respectively  with 
the  antero-inferior  and  postero-inferior  angles  of  the  parietal  bones.  An  additional  fontanelle 
is  sometimes  seen  in  the  sagittal  suture  at  the  region  of  the  obelion.  The  fontanelles  are  usually 
closed  by  the  growth  and  extension  of  the  bones  which  surround  them,  but  sometimes  they  are 
the  sites  of  separate  ossific  centres  which  develop  into  Wormian  bones.  The  posterior  and 
lateral  fontanelles  are  obliterated  within  a  month  or  two  after  birth,  but  the  anterior  is  not  com- 
pletely closed  until  the  first  half  of  the  second  year;  sometimes  it  remains  open  beyond  the  second 
year,  a  condition  which  is  usually  seen  in  rhachitis,  and  is  due  to  malnutrition.  A  knowledge  of 
the  shape  and  position  of  the  fontanelles  is  of  service  to  the  accoucheur  in  enabling  him  to  deter- 
mine which  part  of  the  fetal  head  is  presenting  during  parturition. 

The  small  size  of  the  face  at  birth  is  mainly  accounted  for  by  the  rudimentary  condition  of  the 
ja\\»s,  the  noneruption  of  the  teeth,  and  the  small  size  of  the  maxillary  air  sinuses  and  nasal 
cavities.  At  birth  the  nasal  cavities  lie  almost  entirely  between  the  orbits,  and  the  lower  border 
of  the  anterior  nasal  aperture  is  only  a  little  below  the  level  of  the  orbital  floor.  With  the  eru]3- 
tion  of  the  milk  teeth  there  is  an  enlargement  of  the  face  and  jaws,  and  these  changes  are  still 
more  marked  after  the  second  dentition. 

The  skull  grows  rapidly  from  birth  to  the  seventh  year,  by  which  time  the  foramen  magnum 
and  petrous  parts  of  the  temporals  have  reached  their  full  size  and  the  orbital  cavities  are  only 
a  little  smaller  than  those  of  the  adult.  Growth  is  slow  from  the  seventh  year  until  the  approach 
of  puberty,  when  a  second  period  of  activity  takes  place;  this  consists  of  an  increase  in  all  direc- 
tions, but  it  is  especially  marked  in  the  frontal  and  facial  regions,  where  it  is  associated  with  the 
development  of  the  air  sinuses. 

Obliteration  of  the  Sutures.. — Obliteration  of  the  sutures  of  the  vault  takes  place  as  age 
advances,  usually  beginning  during  the  fourth  decade  of  life  and  first  becoming  manifest  on  the 
inner  surface,  appearing  externally  about  ten  years  later;  the  posterior  part  of  the  sagittal  suture 
is  usually  the  first  to  become  obliterated,  next  the  coronal,  and  then  the  lambdoid.  The  most 
striking  feature  of  an  old  skull  is  the  marked  diminution  in  the  size  of  the  jaws  consequent  on 
the  loss  of  the  teeth  and  the  absorption  of  the  alveolar  processes,  thus  reducing  the  facial  height 
and  altering  the  mandibular  angles. 

Differences  in  the  Skull  Due  to  Sex. — Until  the  age  of  puberty  little  difference  exists  be- 
tween the  male  and  the  female  skull.  The  skull  of  an  adult  female  is,  as  a  rule,  lighter  and 
smaller.  While  the  cranial  capacity  of  white  males  averages  1560  c.c,  that  of  females  is  nearly 
200  c.c.  less.  The  female  skull  has  thinner  walls,  its  ridges  for  muscle  attachment  are  less 
strongly  marked,  the  superciliary  ridges,  glabella,  and  mastoid  processes  are  less  prominent,  and 
the  corresponding  air  sinuses  are  smaller.  The  upper  margin  of  the  orbit  is  sharper,  the  frontal 
and  parietal  eminences  are  more  prominent,  and  the  vault  is  somewhat  flattened  as  compared 
with  the  male  skull.  The  contour  of  the  face  is  more  rounded,  the  facial  bones  are  smoother, 
and  the  jaws  and  teeth  are  smaller. 

No  single  structural  characteristic,  however,  serves  to  determine  the  sex,  and  the  features 
enumerated  above  can  guide  in  the  examination  only  when  they  are  sufficiently  pronounced  to 
justify  a  probable  diagnosis.' 

Supernumerary,  Wormian,-  Sutural,  or  Epactal  Bones  (Ossa  Triquetra). 

In  addition  to  the  constant  centres  of  ossification  of  the  skull,  additional  ones  are  occasion- 
ally found  in  the  course  of  the  sutures.  These  form  irregular,  isolated  bones,  interposed  between 
the  cranial  bones,  and  have  been  termed  Wormian  bones,  or  ossa  triquetra.  They  are  most 
frecjuently  found  in  the  course  of  the  lambdoid  suture,  but  occasionally  also  occupy  the  situation 
of  the  fontanelles,  especially  the  posterior  and,  more  rarely,  the  anterior.  Frequently  one  is 
found  between  the  anterior  inferior  angle  of  the  parietal  bone  and  the  greater  wing  of  the  sphe- 
noid, the  epipteric  bone,  or  the  pterion  ossicle  (Fig.  113).  They  have  a  great  tendency  to  be 
symmetrical  on  the  two  sides  of  the  skull,  and  they  vary  much  in  size,  being  in  some  cases  not 
larger  than  a  pin's  head,  and  confined  to  the  outer  table;  in  other  cases  so  large  that  one  pair  of 
these  bones  maj'  form  the  whole  of  the  occipital  bone  above  the  superior  cmwed  lines. 

Craniology. 

Skulls  vary  in  shape  and  size,  and  the  term  craniology  is  applied  to  the  comparative  study 
of  these  variations.  By  means  of  exact  measurements  and  their  correlation,  skulls  may  be 
classified  in  various  w-ays. 

'  See  P.  J.  Mobius:  Ueber  die  Verschiedenheit  mannlicher  und  weiblicher  Schiidel.  Archiv  fur  Anthiopologie, 
1907,  N.  F.,  vol.  vi. 

2  Wormiu3,  a  physician  of  Copenhagen,  is  said  to  have  given  the  first  detailed  description  of  these  bones. 


THE  SKULL  AS  A    WHOLE 


145 


I.  According  to  capacity,  measured  by  means  of  shot,  mustard  seed,  etc. 

1    Microcephalic,  with  a  capacity  of  less  than  1350  c.c.  (e.  g.,  Australians,  Andamanese). 

2.  Mesocephalic,  with  a  capacity  of  from  1350  to  1450  c.c.  (e   g.,  Negroes,  Chinese). 

3.  Megacephalic,  with  a  capacity  of  over  1450  c.c.  (e.  g.,  Europeans,  Japanese,  and  Eskimos). 


F:g.  113. — Wormian  bones. 


Fig.  114. — Brachycephalic  cranium.     (Poirier 
and  Charpy.) 


Fig.  115. — Dolichocephalic  cranium     (Poirier 
and  Charpy.) 


Fig.  116. — Brachycephalic 

and  Charpy.) 


FiG.  1)7 — Dolichocephalic  cranium.     (Poirier 
and  Charpy.) 


146  SPECIAL  ANATOMY  OF  THE  SKELETON 

II. — To  facilitate  regional  description  and  to  compare  the  normae  of  one  skull  with  those  of 
another,  the  skull  is  placed  in  such  a  way  that  a  plane  passing  through  the  inferior  margin  of  the 
orbit  and  the  superior  margin  of  the  external  auditory  meatus  shall  be  horizontal  (the  horizontal 
line  of  the  Frankfort  agreement).  Various  linear  and  arc  measurements  are  made  between 
definite  and  easily  localized  points  on  the  surface  of  the  skull,  and,  although  previously  men- 
tioned, are  here  tabulated  for  convenience  of  reference.  They  are  divided  into  two  groups; 
(1)  those  in  the  mesal  plane,  and  (2)  those  on  either  side  of  it.      - 

The  Points  in  the  Mesal  Plane  are: 

Mental  Point. — The  most  prominent  point  of  the  chin. 

Alveolar  Point,  or  Prosthion. — The  central  point  of  the  anterior  margin  of  the  upper  alveolar 
arch. 

Subnasal  Point. — The  middle  of  the  lower  border  of  the  anterior  nasal  aperture,  at  the  base  of 
the  nasal  spine. 

Nasion. — The  central  point  of  the  frontonasal  suture. 

Glabella. — The  point  in  the  middle  line  at  the  level  of  the  superciliary  ridges. 

Ophryon. — The  point  in  the  middle  line  at  the  level  where  the  temporal  lines  most  nearly 
approach  each  other. 

Bregma. — The  meeting  point  of  the  coronal  and  sagittal  sutures. 

Obelion. — A  point  in  the  sagittal  suture  on  a  level  with  the  parietal  foramina. 

Lambda. — The  point  of  junction  of  the  sagittal  and  lambdoid  sutures. 

Occipital  Point. — The  point  in  the  middle  line  of  the  occipital  bone  farthest  from  the  glabella. 

Inion. — The  external  occipital  protuberance. 

Opisthion. — The  mid-point  of  the  posterior  margin  of  the  foramen  magnum. 

Basion. — The  mid-point  of  the  anterior  margin  of  the  foramen  magnum. 

The  Points  on  Either  Side  of  the  Mesal  Plane  are: 

Gonion. — The  outer  margin  of  the  angle  of  the  mandible. 

Dacryon. — The  point  of  union  of  the  antero-superior  angle  of  the  lacrimal  with  the  frontal 
bone  and  the  frontal  process  of  the  maxilla. 

Stephanion. — The  point  where  the  temporal  line  intersects  the  coronal  suture. 

Pterion. — The  point  where  the  greater  wing  of  the  sphenoid  joins  the  antero-inferior  angle 
of  the  parietal. 

Auricular  Point. — The  centre  of  the  orifice  of  the  external  auditory  meatus. 

Asterion. — The  point  of  meeting  of  the  lambdoid,  masto-occipital,  and  mastoparietal  sutures. 

The  horizontal  circumference  of  the  cranium  is  measured  in  a  plane  passing  through  the 
glabella  (Turner)  or  the  ophryon  (Flower)  in  front,  and  the  occipital  point  behind;  it  averages 
about  twenty  inches  (50  cm.)  in  the  female  and  twenty-one  inches  (52.5  cm.)  in  the  male. 

The  occipitofrontal  or  longitudinal  arc  is  measured  from  the  nasion  over  the  middle  line  of  the 
vertex  to  the  opisthion;  while  the  basinasal  length  is  the  distance  between  the  basion  and  the 
nasion.  These  two  measurements,  plus  the  antero-posterior  diameter  of  the  foramen  magnum, 
represent  the  vertical  circumference  of  the  cranium. 

The  length  is  measured  from  the  glabella  to  the  occipital  point,  while  the  breadth,  or  greatest 

transverse  diameter,  is  usually  found  near  the  external  auditory  meatus.     The  proportion  of 

,        ,,        ,        ,   (breadth  X 100)  .  ,   ,  ,    ,.    .    , 

breadth  to  length -. -r is  termed  the  cephalic  index,  or  index  of  breadth. 

The  hei-ght  is  usually  measured  from  the  basion  to  the  bregma,  and  the  proportion  of  height 
,        ,    (height  X  100) 
to  length  j TT constitutes  the  vertical  or  height  index. 

In  studying  the  face  the  principal  points  to  be  noticed  are  the  proportion  of  its  length  and 
breadth,  the  shape  of  the  orbits  and  of  the  anterior  nasal  aperture,  and  the  degree  of  projection 
of  the  jaws. 

The  length  of  the  face  may  be  measured  from  the  ophryon  or  nasion  to  the  chin,  or,  if  the  man- 
dible be  wanting,  to  the  alveolar  point;  while  its  ividth  is  represented  by  the  distance  between  the 
zygomatic  arches.  By  comparing  the  length  with  the  width  of  the  face,  skulls  may  be  divided 
into  two  groups — dolichofacial,  or  leptoprosope  (long-faced),  and  brachyfadal,  or  chemoprosnpe 
(short-faced). 

The  orbital  index  signifies  the  proportion  which  the  orbital  height  bears  to  the  orbital  width, 
thus: 

orbital  height  X  100 
orbital  width 

The  na-sal  index  expresses  the  proportion  which  the  width  of  the  anterior  nasal  aperture  bears 
to  the  height  of  the  nose,  the  latter  being  measured  from  the  nasion  to  the  lower  margin  of  the 
nasal  aperture,  thus: 

nasal  width  X  100 
nasal  height 


THE  SKULL  Afi  A    WHOLE 


147 


The  degree  of  projection  of  the  jaws  is  determined  by  the  fjiiathic  or  alveolar  index,  which 
represents  the  proportion  between  the  basialveolar  and  basinasal  lengths,  thus: 

basialveolar  length  X  100 
basinasal  length 

The  following  table,  modified  from  that  given  by  Duckworth,   illustrates  how  these  different 
indices  may  be  utilized  in  the  classification  of  skulls. 


Index. 

Classification. 

Nomenclature. 

Examples. 

1.  Cephalic     . 

Below  75 

Between  75  and  SO 

Above  80 

Dolichocephalic 
Mesaticephalic 
Brachycephalic 

Kaffirs  and  Native  Australians 
Europeans  and  Chinese 
MongoUans  and  Andamans 

2.  Orbital       .      . 

Below  84 

Between  84  and  89 

Above  89 

Microseme 
Mesoseme 
Megaseme 

Tasmanians  and  Nati\'e  Australians 

Europeans 

Chinese  and  Polynesians 

3.  Nasal  .      .      . 

Below  48 

Between  48  and  53 

Above  53 

Leptorhine 
Mesorhine 
Platyrhine 

Europeans 

Chinese  and  Japanese 

Negroes  and  Native  Australians 

4.  Gnathic     . 

Below  98 

Between  98  and  103 

Above  103 

Orthognathous 
Mesognathous 
Prognathous 

Europeans 

Chinese  and  Japanese 

Native  Australians 

Surface  Form. — The  various  bony  prominences  or  landmarks  which  can  be  easily  felt  and 
recognized  in  the  head  and  face,  and  which  afford  the  means  of  mapping  out  the  important  struc- 
tures comprised  in  this  region,  are  as  follows: 


1.  Supraorbital  arch. 

2.  Internal  angular  process. 

3.  E.xternal  angular  process. 

4.  Zygomatic  arch. 

5.  Mastoid  process. 

6.  External  occipital  protuberance. 

7.  Superior  curved  line  of  occipital  bone. 


8.  Parietal  eminences. 

9.  Temporal  ridge. 

10.  Frontal  eminences. 

1 1 .  Superciliary  ridges. 

12.  Nasal  bones. 

13.  Lower  margin  of  orbit. 

14.  Mandible. 


(1)  The  supraorbital  arches  are  to  be  felt  throughout  their  entire  extent,  covered  by  the  eye- 
brows. They  form  the  upper  boundary  of  the  circumference  or  base  of  the  orbits,  and  separate 
the  face  from  the  forehead.  They  are  strong  and  arched,  and  terminate  internally  on  each  side 
of  the  root  of  the  nose  in  the  internal  angular  process,  which  articulates  with  the  lacrimal  bone. 
Externally  they  terminate  in  the  external  angular  process,  which  articulates  with  the  malar  bone. 
This  arched  ridge  is  sharper  and  more  defined  in  its  outer  than  in  its  inner  half,  and  forms  an 
overhanging  process  which  protects  and  shields  the  lacrimal  gland.  It  thus  protects  the  eye  in 
its  most  exposed  situation  and  in  the  direction  from  which  blows  are  most  likely  to  descend.  '  The 
supraorbital  arch  varies  in  prominence  in  different  individuals.  It  is  more  marked  in  the  male 
than  in  the  female,  and  in  some  races  of  mankind  than  others.  In  the  less  civilized  races,  as  the 
forehead  recedes  backward,  the  supraorbital  arch  becomes  more  prominent,  and  approaches 
more  to  the  characters  of  the  monkey  tribe,  in  which  the  supraorbital  arches  are  very  largely  devel- 
oped, and  acquire  additional  prominence  from  the  oblique  direction  of  the  frontal  bone.  (2)  The 
internal  angular  process  is  scarcely  to  be  felt.  Its  position  is  indicated  by  the  angle  formed 
by  the  supraorbital  arch  with  the  nasal  process  of  the  maxilla  and  the  lacrimal  bone  at  the  inner 
side  of  the  orbit.  Between  the  internal  angular  processes  of  the  two  sides  is  a  broad  surface 
which  as.sists  in  furiiiiiig  the  root  of  the  nose,  and  immediately  above  this  a  broad,  smooth, 
somewhat  ti-iaiiguhir  suifiicc,  the  glabella,  situated  between  the  superciliary  ridges.  (3)  The 
external  angular  process  is  much  more  strongly  marked  than  the  internal,  and  is  plainly  to  be 
felt.  It  is  formed  by  the  junction  or  confluence  of  the  supraorbital  and  temporal  ridges,  and, 
articulating  with  the  malar  bone,  it  serves  to  a  very  considerable  extent  to  support  the  bones  of 
the  face.  In  carnivorous  animals  the  external  angular  process  does  not  articulate  with  the  malar, 
and  therefore  this  lateral  support  to  the  bones  of  the  face  is  not  present.  (4)  The  zygomatic 
arch  is  plainly  to  be  felt  throughout  its  entire  length,  being  situated  almost  immediately  under 
tne  skin.  It  is  formed  by  the  malar  bone  and  the  zygomatic  process  of  the  temporal  bone.  At 
its  anterior  extremity,  where  it  is  formed  by  the  malar  bone,  it  is  broad  arjfl  forms  the  prominence 


148  SPECIAL  ANATOMY  OF  THE  SKELETON 

of  the  cheek;  the  posterior  part  is  narrower,  and  terminates  just  in  front  and  a  little  above  the 
tragus  of  the  external  ear.  "I'he  lower  border  is  more  plainly  to  be  felt  than  the  upper,  in  conse- 
quence of  the  dense  temporal  fascia  being  attached  to  the  latter,  which  somewhat  obscures  its 
outline.  Its  shape  differs  very  much  in  individuals  and  in  different  races  of  mankind.  In  the 
skulls  of  savages — as,  for  instance,  in  the  skull  of  the  negro  of  the  Guinea  Coast — the  malar  bones 
project  forward  and  not  outward,  and  the  zygoma  at  its  posterior  extremity  extends  farther 
outward  before  it  is  twisted  on  itself  to  be  prolonged  forward.  This  makes  the  zygomatic  arch 
stand  out  in  bold  relief,  and  affords  greater  space  for  the  Temporal  muscle.  In  skulls  which 
have  a  more  pyramidal  shape,  as  in  the  Eskimos  or  Greenlanders,  the  malar  bones  do  not  pro- 
ject forward  and  downward  under  the  eyes,  as  in  the  preceding  form,  but  take  a  direction  out- 
ward, forming  with  the  zygoma  a  large,  rounded  sweep  or  segment  of  a  circle.  Thus  it  happens 
that  if  two  lines  are  drawn  from  the  zygomatic  arches,  touching  the  temporal  ridges,  they  meet 
above  the  top  of  the  head,  instead  of  being  parallel,  or  nearly  so,  as  in  the  European  skull,  in 
which  the  zygomatic  arches  are  not  nearly  so  prominent.  This  gives  to  the  face  a  more  or  less 
oval  type.  (5)  Behind  the  ear  is  the  mastoid  portion  of  the  temporal  bone,  plainly  to  be  felt, 
and  terminating  below  in  a  nipple-shaped  process.  Its  anterior  border  can  be  traced  immediately 
behind  the  concha,  and  its  apex  is  on  about  a  level  with  the  lobule  of  the  ear.  It  is  rudimentary 
in  infancy,  but  gradually  develops  in  childhood,  and  is  more  marked  in  the  negro  than  in  the 
European.  (6)  The  external  occipital  protuberance  (inion)  is  always  plainly  to  be  felt  just 
at  the  level  where  the  skin  of  the  neck  joins  that  of  the  head.  At  this  point  the  skull  is  thick  for 
the  purposes  of  safety,  while  radiating  from  it  are  numerous  curved  arches  or  buttresses  of  bone 
which  give  to  this  portion  of  the  skull  further  security.  (7)  Running  outward  on  either  side  from 
the  external  occipital  protuberance  is  an  arched  ridge  of  bone,  which  can  be  more  or  less  plainly 
perceived.  This  is  the  superior  curved  line  of  the  occipital  bone,  and  gives  attachment  to 
some  of  the  muscles  which  keep  the  head  erect  on  the  vertebral  column;  accordingly,  we  find  it 
more  developed  in  the  negro  tribes,  in  whom  the  jaws  are  much  more  massive,  and  therefore 
require  stronger  muscles  to  prevent  their  extra  weight  carrying  the  head  forward.  Below  this 
line  the  surface  of  bone  at  the  back  of  the  head  is  obscured  by  the  overlying  muscles.  Above  it 
the  vault  of  the  cranium  is  thinly  covered  with  soft  structures,  so  that  the  form  of  this  part  of  the 
head  is  almost  exactly  that  of  the  upper  portion  of  the  occipital,  the  parietal,  and  the  frontal 
bones  themselves;  and  in  bald  persons,  even  the  lines  of  junction  of  the  bones,  especially  the 
junction  of  the  occipital  and  parietal  at  the  lambdoid  suture,  may  be  defined  as  a  slight  depression 
caused  by  the  thickening  of  the  borders  of  the  bones  in  this  situation.  (8)  In  the  line  of  the 
greatest  transverse  diameter  of  the  head,  on  each  side  of  the  middle  line,  are  generally  to  be  found 
the  parietal  eminences,  one  on  each  side  of  the  middle  line,  though  sometimes  these  eminences 
are  not  situated  at  the  point  of  the  greatest  transverse  diameter,  which  is  at  some  other  prominent 
part  of  the  parietal  region.  They  denote  the  point  where  ossification  of  the  parietal  bone  began. 
They  are  much  more  prominent  and  well  marked  in  early  life,  in  consequence  of  the  sharper 
curve  of  the  bone  at  this  period,  so  that  it  describes  the  segment  of  a  smaller  circle.  Later  in  life, 
as  the  bone  grows,  the  curve  spreads  out  and  forms  the  segment  of  a  larger  circle,  so  that  the 
eminence  becomes  less  distinguishable.  In  consequence  of  this  sharp  curve  of  the  bone  in  early 
life,  the  whole  of  the  vault  of  the  skull  has  a  squarer  shape  than  it  has  in  later  life,  and  this  appear- 
ance may  persist  in  those  suffering  from  rhachitis.  The  eminence  is  more  apparent  in  the  negro's 
skull  than  in  that  of  the  European.  This  is  due  to  greater  flattening  of  the  temporal  fossa  in  the 
former  skull  to  accommodate  the  larger  Temporal  muscle  which  exists  in  these  races.  The 
parietal  eminence  is  particularly  exposed  to  injury  from  blows  or  falls  on  the  head,  but  fracture 
is  to  a  certain  extent  prevented  by  the  shape  of  the  bone,  which  forms  an  arch,  so  that  the  force 
of  the  blow  is  diffused  over  the  bone  in  every  direction.  (9)  At  the  side  of  the  head  may  be  felt 
the  temporal  ridge.  Commencing  at  the  external  angular  process,  it  may  be  felt  as  a  curved 
ridge,  passing  upward  and  then  curving  backward,  on  the  frontal  bone,  separating  the  forehead 
from  the  temporal  fossa.  It  may  then  be  traced  passing  backward  in  a  curved  direction,  over 
the  parietal  bone,  and,  though  less  marked,  still  generally  to  be  recognized.  Finally,  the  ridge 
curves  downward,  and  terminates  in  the  posterior  root  of  the  zygoma,  which  separates  the 
squamous  from  the  subcutaneous  mastoid  portion  of  the  temporal  bone.  (10)  The  frontal 
eminences  vary  a  good  deal  in  different  individuals,  being  considerably  more  prominent  in  some 
than  in  others,  and  they  are  often  not  symmetrical  on  the  two  sides  of  the  bodj',  the  one  being 
much  more  pronounced  than  the  other.  This  is  often  especially  noticeable  in  the  skull  of  the 
young  child  or  infant,  and  becomes  less  marked  as  age  advances.  The  prominence  of  the 
frontal  eminences  depends  more  upon  the  general  shape  of  the  whole  bone  than  upon  the  size 
of  the  protuberances  themselves.  As  the  skull  is  more  highly  developed  in  consequence  of  in- 
creased intellectual  capacity,  so  the  frontal  bone  becomes  more  upright  and  the  frontal  eminences 
stand  out  in  bolder  relief.  Thus  they  may  be  considered  as  affording,  to  a  certain  extent,  an 
indication  of  the  development  of  the  hemispheres  of  the  cerebrum  beneath,  and  of  the  mental 
powers  of  the  individual.  They  are  not  so  much  exposed  to  injury  as  the  parietal  eminences. 
In  falls  forward  the  upper  extremities  are  involuntarily  thrown  out,  and  break  the  force  of  the 
fall,  and  tlius  shield  the  frontal  bone  from  injury.     (11)  Below  the  frontal  eminences  on  the  fore- 


THE  8KULL  AS  A    WHOLE  149 

head  are  the  superciliary  ridges,  which  denote  the  position  of  the  frontal  sinuses,  and  vary 
according  to  the  size  of  the  sinuses  in  different  individuals,  being,  as  a  rule,  small  in  the  female, 
absent  in  children,  and  sometimes  unusually  prominent  in  the  male,  when  the  frontal  sinuses  are 
largely  developed.  They  commence  on  either  side  of  the  glabella,  and  a(  first  present  a  rounded 
form,  which  gradually  fades  away  at  their  outer  ends.  (12)  The  nasal  bones  form  the  promi- 
nence of  the  nose.  They  vary  much  in  size  and  shape,  and  to  them  arc  due  the  variations  in 
contour  of  this  organ  and  much  of  the  character  of  the  face.  Thus,  in  the  Mongolian  or  Ethio- 
pian they  are  flat,  broad,  and  thick  at  their  base,  giving  to  these  races  the  flattened  nose  by  which 
they  are  characterized,  and  differing  very  decidedly  from  the  Caucasian,  in  whom  the  nose,  owing 
to  the  shape  of  the  nasal  bones,  is  narrow,  elevated  at  the  bridge,  and  elongated  downward. 
Below,  the  nasal  bones  are  thin  and  connected  with  .the  cartilages  of  the  nose,  and  the  angle  or 
arch  formed  by  their  union  serves  to  throw  out  the  bridge  of  the  nose,  and  is  nuuh  more  marked 
in  some  individuals  than  others.  (13)  The  lower  margin  of  the  orbit,  formed  by  the  maxilla 
and  the  malar  bone,  is  plainly  to  be  felt  throughout  its  entire  length.  It  is  continuous  inter- 
nally with  the  nasal  process  of  the  maxilla,  which  forms  the  inner  boundary  of  the  orbit.  At  the 
point  of  junction  of  the  lower  margin  of  the  orbit  with  the  nasal  process  is  to  be  felt  a  little  tubercle 
of  bone,  which  can  be  plainly  perceived  by  running  the  finger  along  the  bone  in  this  situation. 
This  tubercle  serves  as  a  guide  to  the  position  of  the  lacrimal  sac,  which  is  situated  above  and 
behind  it.  (14)  The  outline  of  the  mandible  may  be  felt  throughout  its  entire  length.  Just  in 
front  of  the  tragus  of  the  external  ear,  and  below  the  zygomatic  arch,  the  condyle  can  be  made 
out.  When  the  mouth  is  opened  this  prominence  of  bone  can  be  perceived  advancing  out  of  the 
glenoid  fossa  on  to  the  eminentia  articularis,  and  receding  again  when  the  mouth  is  closed. 
From  the  condyle  the  posterior  border  of  the  ramus  can  be  felt  extending  down  to  the  angle. 
A  line  drawn  from  the  condyle  to  the  angle  would  indicate  the  exact  position  of  this  border.  From 
the  angle  to  the  symphysis  of  the  chin  the  lower,  rounded  border  of  the  body  of  the  bone  may  be 
plainly  felt.  At  the  point  of  junction  of  the  two  halves  of  the  bone  is  a  well-marked  triangular 
eminence,  the  mental  process,  which  forms  the  prominence  of  the  chin. 

Applied  Anatomy. — The  thickness  of  the  skull  varies  greatly  in  different  regions  of  the  same 
•  skull  and  in  different  individuals.  The  average  thickness  of  the  skullcap  is  about  one-fifth 
of  an  inch  (-5  mm.).  The  thickest  portions  are  the  occipital  protuberance,  the  inferior  portion  of 
the  frontal  bone,  and  the  mastoid  process.  The  thinnest  portions  are  the  occipital  fossse,  the 
squamous  portion  of  the  temporal  bone,  and  over  certain  sinuses  and  arteries.  An  arrest  in  the 
ossifying  process  may  give  rise  to  deficiencies  or  gaps,  or  to  fissures,  which  are  of  importance  in 
a  medicolegal  point  of  view,  as  they  are  liable  to  be  mistaken  for  fractures.  The  fissures  gener- 
ally extend  from  the  margin  toward  the  centre  of  the  bone,  but  gaps  may  be  found  in  the  middle 
as  well  as  at  the  edges.  In  course  of  time  they  may  become  covered  with  a  thin  lamina  of  bone. 
Occasionally  a  protrusion  of  the  brain  or  its  membranes  may  take  place  through  one  of  these 
gaps  in  an  imperfectly  developed  skull.  When  the  protrusion  consists  of  membranes  only,  and 
is  filled  with  cerebrospinal  fluid,  it  is  called  a  meningocele;  when  the  protrusion  consists  of 
brain  as  well  as  membranes,  it  is  termed  an  encephalocele;  and  when  the  protruded  brain  is  a 
prolongation  from  one  of  the  ventricles,  and  is  distended  by  a  collection  of  fluid  from  an  accu- 
mulation in  the  ventricle,  it  is  termed  a  hydrencephalocele.  This  latter  condition  is  some- 
times found  at  the  root  of  the  nose,  where  a  protrusion  of  the  anterior  horn  of  the  lateral  ventricle 
takes  place  through  a  deficiency  of  the  frontonasal  suture.  These  malformations  are  usually 
found  in  the  middle  line,  and  most  frequently  at  the  back  of  the  head,  the  protrusion  taking  place 
through  the  fissures  which  separate  the  four  centres  of  ossification  from  which  the  tabular  portion 
of  the  occipital  bone  is  originally  developed  (see  page  73).  They  most  frequently  occur  through 
the  upper  part  of  the  vertical  fissure,  which  is  the  last  to  ossify,  but  not  uncommonly  through  the 
lower  part,  when  the  foramen  magnum  may  be  incomplete.  More  rarely  these  protrusions  have 
been  met  with  in  other  situations  than  those  above  mentioned,  both  through  normal  fissures,  as 
the  sagittal,  lambdoid,  and  other  sutures,  and  also  through  abnormal  gaps  and  deficiencies  at 
the  sides,  and  even  at  the  base  of  the  skull.  Force  may  be  responsible  in  a  young  person  for 
separating  a  suture.  This  accident,  seldom  met  with  even  in  the  young,  is  only  occasionally 
encountered  in  older  persons. 

Fractures  of  the  skull  may  be  divided  into  those  of  the  vault  and  those  of  the  5a.se.  Frac- 
tures of  the  vault  are  usually  produced  by  direct  violence.  This  portion  of  the  skull  varies  in 
thickness  and  strength  in  different  individuals,  but,  as  a  rule,  is  sufficiently  strong  to  resist  a  very 
considerable  amount  of  violence  without  being  fractured.  This  is  due  to  several  causes — the 
rounded  shape  of  the  head  and  its  construction  of  a  number  of  secondary  elastic  arches,  each 
made  up  of  a  single  bone;  the  fact  that  it  consists  of  a  number  of  bones,  united  at  all  events  in 
early  life  by  a  sutural  ligament,  which  acts  as  a  sort  of  buffer  and  interrupts  the  continuity  of 
any  violence  applied  to  the  skull;  the  presence  of  arches  or  ridges,  both  on  the  inside  and  outside 
of  the  skull,  which  materially  strengthen  it;  and  the  mobility  of  the  head  upon  the  vertebral 
column,  which  further  enables  it  to  withstand  violence.  The  elasticity  of  the  bones  of  the  head 
is  especially  marked  in  the  skull  of  the  child,  and  this  fact,  together  with  the  wide  separation  of 


150  SPECIAL  ANATOMY  OF  THE  SKELETON 

the  individual  bones  from  each  other,  and  the  interposition  between  them  of  other  and  softer 
structures  render  fracture  of  the  bones  of  the  head  a  very  uncommon  event  in  infants  and  quite 
young  children;  as  age  advances  and  the  bones  become  joined,  fracture  is  more  common,  though 
still  less  liable  to  occur  than  in  the  adult.  Fractures  of  the  vault  may,  and  generally  do,  involve 
the  whole  thickness  of  the  bone;  but  sometimes  one  table  may  be  fractured  without  any  corre- 
sponding injury  to  the  other.  Thus,  the  outer  table  of  the  skull  may  be  splintered  and  driven  into 
the  diploe,  or  in  the  frontal  or  mastoid  regions  into  the  frontal  or  mastoid  cells,  without  any  injury 
to  the  internal  table.  And  on  the  other  hand,  the  internal  table  has  been  fractured,  and  por- 
tions of  it  depressed  and  driven  inward,  without  any  fracture  of  the  outer  table.  As  a  rule,  in 
fractures  of  the  skull  the  inner  table  is  more  splintered  and  comminuted  than  the  outer,  and 
this  is  due  to  several  causes.  It  is  thinner  and  more  brittle;  the  force  of  the  violence  as  it  passes 
inward  becomes  broken  up,  and  is  more  diffused  by  the  time  it  reaches  the  inner  table;  the 
bone,  being  in  the  form  of  an  arch,  bends  as  a  whole  and  spreads  out,  and  thus  presses  the  par- 
ticles together  on  the  convex  surface  of  the  arch — i.  e.,  the  outer  table — and  forces  them  asunder 
on  the  concave  surface  or  inner  table;  and  lastly,  there  is  nothing  firm  under  the  inner  table  to 
support  it  and  oppose  the  force.  Fractures  of  the  vault  may  be  simple  fissures  or  starred  and 
comminuted  fractures,  and  these  may  be  depressed  or  elevated.  These  latter  cases  of  fracture 
with  elevation  of  the  fractured  portion  are  uncommon,  and  can  only  be  produced  by  direct 
wound.  In  comminuted  fracture  a  portion  of  the  skull  is  broken  into  several  pieces,  the  lines 
of  fracture  radiating  from  a  centre  where  the  chief  impact  of  the  blow  was  felt;  if  depressed,  a 
fissure  circumscribes  the  radiating  line,  enclosing  a  portion  of  skull.  If  this  area  is  circular,  it 
is  termed  a  pond  fracture,  and  would  in  all  probability  have  been  caused  by  a  round  instru- 
ment, as  a  blackjack  or  hammer;  if  elliptical  in  shape,  it  is  termed  a  gutter  fracture,  and 
would  owe  its  shape  to  the  instrument  which  had  produced  it,  as  a  poker.  A  fracture  may  take 
place  along  the  line  of  an  ossified  or  partly  ossified  suture.  When  a  surgeon  explores  the  vault 
of  the  skull  through  a  wound  he  must  not  mistake  a  Wormian  bone  for  a  fragment  produced  by 
a  fractiu'e.  A  Wormian  bone  which  may  lead  to  mistake  is  encountered  at  the  anterior  inferior 
angle  of  the  parietal  bone. 

Fractures  of  the  base  are  most  frequently  produced  by  the  extension  of  a  fissure  from  the 
vault,  as  in  falls  on  the  head,  where  the  fissure  starts  from  the  part  of  the  vault  which  first  struck 
the  ground.  Sometimes,  however,  they  are  caused  by  direct  violence,  when  foreign  bodies  have 
been  forced  through  the  thin  roof  of  the  orbit,  through  the  cribriform  plate  of  the  ethmoid  from 
being  thrust  up  the  nose,  or  through  the  roof  of  the  pharynx.  Other  cases  of  fracture  of  the  base 
occur  from  indirect  violence,  as  in  fracture  of  the  occipital  bone  from  impaction  of  the  spinal 
column  against  its  condyles  in  falls  on  the  buttocks,  knees,  or  feet,  or  in  cases  where  the  glenoid 
cavity  has  been  fractured  by  the  violent  impact  of  the  condyle  of  the  mandible  against  it  from 
blows  on  the  chin. 

The  most  common  place  for  fracture  of  the  base  to  occur  is  through  the  middle  fossa,  and 
here  the  fissure  usually  takes  a  fairly  definite  course.  Starting  from  the  point  struck,  which  is 
generally  somewhere  in  the  neighborhood  of  the  parietal  eminence,  it  runs  downward  through  the 
parietal  bone  and  the  squamous  portion  of  the  temporal  bone  and  across  the  petrous  portion  of 
this  bone,  frequently  traversing  and  implicating  the  internal  auditory  meatus,  to  the  middle 
lacerated  foramen.  From  this  it  may  pass  across  the  body  of  the  sphenoid,  through  the  pituitary 
fossa  to  the  middle  lacerated  foramen  of  the  other  side,  and  may  indeed  travel  round  the  whole 
cranium,  so  as  completely  to  separate  the  anterior  from  the  posterior  part.  The  course  of  the 
fracture  should  be  borne  in  mind,  as  it  explains  the  symptoms  to  which  fracture  in  this  region  may 
give  rise;  thus,  if  the  fissure  pass  across  the  internal  auditory  meatus,  injury  to  the  facial  and 
auditory  nerves  may  result,  with  consequent  facial  paralysis  and  deafness;  or  the  tubular  pro- 
longation of  the  arachnoid  around  these  nerves  in  the  meatus  may  be  torn,  and  thus  permit  of 
the  escape  of  the  cerebrospinal  fluid  should  there  be  a  communication  between  the  internal  ear 
and  the  typanum  and  the  membrana  tympani  be  ruptured,  as  is  frequently  the  case;  again,  if 
the  fissure  passes  across  the  pituitary  fossa  and  the  mucoperiosteum  covering  the  under  surface 
of  the  body  of  the  sphenoid  is  torn,  blood  will  find  its  way  into  the  pharynx  and  be  swallowed, 
and  after  a  time  vomiting  of  blood  will  result.  Fractures  of  the  anterior  fossa,  involving  the  bones 
forming  the  roof  of  the  orbit  and  nasal  fossa,  are  generally  the  results  of  blows  on  the  forehead; 
but  fracture  of  the  cribriform  plate  of  the  ethmoid  may  be  a  complication  of  fracture  of  the  nasal 
bone.  When  the  fracture  implicates  the  roof  of  the  orbit,  the  blood  finds  its  way  into  this  cavity, 
and,  travelling  forward,  appears  as  a  subconjunctival  ecchymosis.  Subconjunctival  ecchymosis 
can  also  be  caused  by  fracture  of  the  malar  bone.  If  the  roof  of  the  nasal  fossa  be  fractured, 
the  blood  escapes  from  the  nose.  In  rare  cases  there  may  be  also  escape  of  cerebrospinal  fluid 
from  the  nose  where  the  dura  and  arachnoid  have  been  torn.  In  fractures  of  the  posterior  fossa 
extravasation  of  blood  takes  place  beneath  the  deep  fascia,  and  discoloration  of  the  skin  is  soon 
observed  in  the  course  of  the  posterior  auricular  artery,  the  discoloration  first  appearing  in  the 
skin  over  the  tip  of  the  mastoid  process  of  the  temporal  bone  (Battle's  sign).  Some  of  the 
blood  which  was  extra vasated  beneath  the  deep  fascia  approaches  the  surface  through  the  open- 
ings in  the  deep  fascia  for  the  passage  of  vessels  and  nerves. 


THE  SKULL  AS  A    WHOLE 


151 


The  bones  of  the  skull  are  frequently  the  seat  of  nodes,  and  not  uncommonly  necrosis 
results  from  this  cause,  also  from  injury.  Necrosis  may  involve  the  entire  thickness  of  the 
skull,  but  is  usually  confined  to  the  external  table.  Necrosis  of  the  internal  table  alone  is 
rarely  met  with.     The  bones  of  the  skull  are  also  sometimes  the  seat  of  sarcomatous  tumors. 

The  skull  in  rachitis  is  peculiar — the  forehead  is  high,  square,  and  projecting,  and  the  antero- 
posterior diameter  of  the  skull  is  long  in  relation  to  the  transverse  diameter.  The  bones  of  the 
face  are  small  and  ill-developed,  and  this  gives  the  appearance  of  a  larger  head  than  actually 
exists.  The  bones  of  the  head  are  often  thick,  expecially  in  the  neighborhood  of  the  sutures, 
and  the  anterior  fontanelle  is  late  in  closing,  sometimes  remaining  unclosed  until  the  fourth 
year.  The  condition  of  craniotabes  has  by  some  been  also  believed  to  be  the  result  of  rachitis, 
by  others  is  believed  to  be  due  to  inherited  syphilis.  In  all  probability  it  is  due  to  both.  In 
these  cases  the  bone  undergoes  atrophic  changes  in  patches,  so  that  it  becomes  greatly  thinned 
in  places,  generally  where  there  is  pressure,  as  from  the  pillow  or  nurse's  arm.  It  is,  therefore, 
usually  met  with  in  the  parietal  bone  and  vertical  plate  of  the  occipital  bone. 

In  congenital  syphilis  deposits  of  porous  bone  are  often  found  at  the  angles  of  the  parietal  bones 
and  two  halves  of  the  frontal  bone  which  bound  the  anterior  fontanelle.  These  deposits  are 
separated  by  the  coronal  and  sagittal  sutures,  and  give  to  the  skull  the  appearance  of  a  hot  cross 
bun.     They  are  known  as  Parrot's  nodes,  and  such  a  skull  has  received  the  name  of  natifonn, 


Fia.  118. — Division  of  the  aiastoid  prottss  into  four  tquil  parts  An  opening  in  the  upper  anterior  quadrant 
reaches  the  mastoid  antrum  into  the  upper  posterior  quadrant  reaches  the  lateral  sinus  the  lower  anterior  quad- 
rant into  mastoid  cells;  a  superficial  opening  into  the  lower  posterior  quadrant  reaches  mastoid  cells;  a  deep  open- 
ing reaches  the  descending  limb  of  the  lateral  sinus.     (A.  E.  bchmitt.) 


from  its  fancied  resemblance  to  the  buttocks.  The  cells  of  the  mastoid  are  sometimes  the  seat 
of  suppuration  as  the  result  of  infection  extending  backward  from  the  tympanic  cavity.  In 
such  cases  the  antrum  of  the  mastoid  must  be  opened  in  order  that  the  pus  escape.  This  is 
done  by  applying  the  gouge  between  the  posterior  wall  of  the  external  auditory  meatus  and  the 
posterior  root  of  the  zygoma.     This  space  is  called  the  siiprameatal^  triangle  of  Macewen. 

In  connection  with  the  bones  of  the  face  a  common  malformation  is  cleft  palate,  o^ying  to 
the  nonunion  of  the  palatal  processes  of  the  maxillary  or  preoral  arch.  This  cleft  may  involve 
the  whole  or  only  a  portion  of  the  hard  palate,  and  usually  involves  the  soft  palate  also.  The 
cleft  is  in  the  middle  line,  except  it  involves  the  alveolus  in  front,  when  it  follows  the  suture 
between  the  main  portion  of  the  bone  and  the  premaxillary  bone.  Sometimes  the  cleft  runs 
on  either  side  of  the  premaxillary  bone,  so  that  this  bone  is  quite  isolated  from  the  maxillary 
bones  and  hangs  from  the  end  of  the  vomer.  In  such  a  case  the  premaxillary  bone  usually 
contains  the  germs  of  the  central  incisors  only.  In  some  cases  there  is  no  premaxillary  bone 
and  the  great  gap  in  the  lip  is  in  the  median  line.  Cleft  palate  (page  106)  is  usually  associated 
with  harelip,  which,  when  single,  is  almost  always  on  one  side,  corresponding  to  the  position 
of  the  suture  between  the  lateral  incisor  and  canine  tooth.  Some  few  cases  of  median  harelip 
have  been  described.     In  double  harelip  there  is  a  cleft  on  each  side  of  the  middle  line. 

The  outlines  and  the  height  of  the  arch  of  the  palate  vary  greatly  in  different  persons.  A 
narrow  palate  with  a  high  arch  is  common  in  idiots  and  certain  degenerates. 

The  bones  of  the  face  are  sometimes  fractured  as  the  result  of  direct  violence.    The  two 


152  SPECIAL  ANATOMY  OF  THE  SKELETON 

most  commonly  broken  are  the  nasal  bone  and  the  mandible,  and  of  these,  the  latter  is  by  far  the 
most  frequently  fractured  of  all  the  bones  of  the  face.  Fracture  of  the  nasal  bone  is  for  the  most 
part  transverse,  and  takes  place  about  half  an  inch  from  the  free  margin.  The  broken  portion 
may  be  displaced  backward  or  more  generally  to  one  side  by  the  force  which  produced  the  lesion, 
as  there  are  no  muscles  here  which  can  cause  displacement.  The  malar  bone  is  probably  never 
broken  alone;  that  is  to  say,  unconnected  with  a  fracture  of  the  other  bones  of  the  face.  The 
zygomatic  arch  is  occasionally  fractured,  and  when  this  occurs  from  direct  violence,  as  is  usually 
the  case,  the  fragments  may  be  displaced  inward.  This  lesion  is  often  attended  with  great  diffi- 
culty or  even  inability  to  open  and  shut  the  mouth,  and  this  has  been  stated  to  be  due  to  the 
depressed  fragments  perforating  the  temporal  muscle,  but  would  appear  rather  to  be  caused  by 
the  injury  done  to  the  bony  origin  of  the  Masseter  muscle.  Fractures  of  the  maxilla  may  vary 
much  in  degree,  from  the  chipping  off  of  a  portion  of  the  alveolar  arch,  to  an  extensive  comminu- 
tion of  the  whole  bone  from  severe  violence,  as  the  kick  of  a  horse.  The  most  common  situa- 
tion for  a.  fracture  of  the  mandible  is  in  the  neighborhood  of  the  canine  tooth,  as  at  this  spot  the 
jaw  is  weakened  by  the  deep  socket  for  the  fang  of  this  tooth;  it  is  next  most  frequently  fractured 
at  the  angle;  then  at  the  symphysis,  and  finally  the  neck  of  the  condyle  or  the  coronoid  process 
may  be  broken.  Occasionally  a  double  fracture  may  occur,  one  in  either  half  of  the  bone. 
The  fractiu-es  are  usually  compound,  from  laceration  of  the  mucous  membrane  covering  the 
gums.  The  displacement  is  mainly  the  result  of  the  same  violence  as  produced  the  injury,  but 
may  be  fiu-ther  increased  by  the  action  of  the  muscles  passing  from  the  neighborhood  of  the  sym- 
physis to  the  hyoid  bone. 

The  maxilla  and  mandible  are  both  of  them  frequently  the  seat  of  necrosis,  though  the  disease 
affects  the  latter  much  more  frequently  than  the  former.  It  may  be  the  result  of  periostitis, 
from  tooth  irritation,  injury,  or  the  action  of  some  specific  poison,  as  syphilis,  or  from  salivation 
by  mercury;  it  not  infrequently  occurs  in  children  after  attacks  of  the  exanthematous  fevers,  and 
a  special  form  occurs  from  the  action  of  the  fumes  of  phosphorus  in  persons  engaged  in  the 
manufacture  of  matches. 

Tumors  attack  the  jaw  bones  not  infrequently,  and  these  may  be  either  innocent  or  malig- 
nant; in  the  upper  jaw  cysts  may  occur  in  the  antrum,  constituting  the  so-called  dropsy  of  the 
antrum ;  or,  again,  cysts  may  form  in  either  jaw  in  connection  with  the  teeth — either  cysts  con- 
nected with  the  roots  of  fully  developed  teeth,  the  "dental  cyst;"  or  cysts  connected  with  imper- 
fectly developed  teeth,  the  "dentigerous  cyst."  Solid  innocent  tumors  include  the  fibroma, 
the  chondroma,  and  the  osteoma.  Of  malignant  tumors  there  are  the  endotheliomata,  the 
sarcomata,  and  the  epitheliomata.  The  sarcomata  are  of  various  kinds,  the  spindle-celled, 
the  round-celled,  which  are  of  a  very  malignant  character,  and  the  myeloid  sarcomata,  prin- 
cipally affecting  the  alveolar  margin  of  the  bone.  Of  the  epitheliomata  we  find  the  squamous 
variety  spreading  to  the  bone  from  the  palate  or  gum,  and  the  cylindrical  epithelioma  origi- 
nating in  the  antrum  or  nasal  fossEe. 

Both  mandible  and  maxilla  occasionally  recjuire  excision  for  tumors  and  in  some  other  condi- 
tions. The  maxilla  is  removed  by  an  incision  from  the  inner  canthus  of  the  eye,  along  the  side 
of  the  nose,  around  the  ala,  and  down  the  middle  line  of  the  upper  lip.  A  second  incision  is 
carried  outward  from  the  inner  canthus  of  the  line  along  the  lower  margin  of  the  orbit  as  far  as 
the  prominence  of  the  malar  bone.  The  flap  thus  formed  is  reflected  outward  and  the  surface  of 
the  bone  exposed,  and  the  central  incisor  of  the  diseased  side  is  removed.  The  connections 
of  the  bone  to  the  other  bones  of  the  face  are  then  divided  with  a  narrow  saw  and  bone-cutting 
forceps.  They  are  (1 )  the  junction  with  the  malar  bone,  passing  into  the  sphenomaxillary  fissure; 
(2)  the  nasal  process;  a  small  portion  of  its  upper  extremity,  connected  with  the  nasal  bone  in 
front,  the  lacrimal  bone  behind,  and  the  frontal  bone  above,  being  left;  (3)  the  connection  with 
the  bone  on  the  opposite  side  and  the  palate  in  the  roof  of  the  mouth.  The  bone  is  now  firmly 
grasped  with  lion-jaw  forceps,  and  by  means  of  a  rocking  movement  upward  and  downward  the 
remaining  attachments  of  the  orbital  plate  with  the  ethmoid  and  the  back  of  the  bone  with  the 
palate,  broken  through.  The  soft  palate  is  first  separated  from  the  hard  with  a  scalpel,  and  is  not 
removed.  Occasionally  in  removing  the  maxilla  it  will  be  found  that  the  orbital  plate  can  be 
spared,  and  this  should  always  be  done  if  possible.  A  horizontal  saw-cut  is  to  be  made  just 
below  the  infraorbital  foramen  and  the  bone  cut  through  with  a  chisel  and  mallet.  Lockwood 
has  pointed  out  that  in  removing  the  maxilla  the  surgeon  must  be  careful  in  dividing  the  nasal 
process  of  the  maxilla  to  preserve  the  internal  orbital  or  palpebral  ligament  (Tendo  oculi), 
because  this  ligament  arises  from  the  palpebral  fascia,  and  if  it  is  interfered  with  the  eye  will 
inevitably  drop  downward.  Removal  of  one-half  of  the  mandible  is  sometimes  required.  If 
possible,  the  section  of  the  bone  should  be  made  to  one  side  of  the  symphysis,  so  as  to  save  the 
genial  tubercles  and  the  origin  of  the  Geniohyoglossus  muscle,  as  otherwise  the  tongue  tends  to 
fall  backward  and  may  produce  sufl^ocation.  Having  extracted  the  central  or  preferably  the 
lateral  incisor  tooth,  a  vertical  incision  is  made  down  to  the  bone,  commencing  at  the  free  margin 
of  the  lip,  and  carried  to  the  lower  border  of  the  bone;  it  is  then  carried  along  its  lower  border  to 
the  angle  and  up  the  posterior  margin  of  the  ramus  to  a  level  with  the  lobule  of  the  ear.     The  flap 


THE  II VOID   OB  LINGUAL  BONE 


153 


thus  formed  is  raised  by  separating;  all  the  structures  attached  to  the  outer  surface  of  the  l)one. 
The  jaw  is  now  sawed  through  at  the  point  where  the  tooth  has  been  extracted,  and  the  knife 
passed  along  the  inner  side  of  the  mandible,  separating  the  structures  attached  to  this  surface. 
The  mandible  is  then  grasped  by  the  surgeon  and  strongly  depressed,  so  as  to  bring  down  the 
coronoid  process  and  enable  the  operator  to  sever  the  tendon  of  the  Temporal  muscle.  The 
mandible  can  be  now  further  depressed,  care  being  taken  to  not  evert  it  nor  rotate  it  outward, 
which  would  endanger  the  internal  maxillary  artery,  and  the  External  pterygoid  muscle  is  torn 
through  or  divided.  The  capsular  ligament  is  now  opened  in  front  and  the  lateral  ligaments 
divided,  and  the  mandible  removed  with  a  few  final  touches  of  the  knife. 

The  antrum  of  Highmore  occasionally  requires  tapping  for  suppuration.  This  may  be  done 
through  the  socket  of  a  tooth,  preferably  the  first  molar,  the  fangs  of  which  are  most  intimately 
connected  with  the  antrum,  or  through  the  facial  aspect  of  the  bone  above  the  alveolar  pro- 
cess. This  latter  method  does  not  perhaps  afford  such  efficient  drainage,  but  there  is  less 
chance  of  food  finding  its  way  into  the  cavity.  The  operation  may  be  performed  by  incising  the 
mucous  membrane  above  the  second  molar  tooth,  and  driving  a  trocar  or  any  sharp-pointed 
instrument  into  the  cavity. 


THE  HYOID  OR  LINGUAL  BONE  (OS  HYOIDEUM). 

The  hyoid  bone  (Fig.  119)  is  a  bony  arch,  shaped  like  a  horseshoe,  and  consist- 
ing of  five  segments — a  body,  two  greater  cornua,  and  two  lesser  cornua.  It 
is  suspended  from  the  tips  of  the  styloid  processes  of  the  temporal  bones  by 
ligamentous  bands,  the  stylohyoid  ligaments. 

The  Body,  or  basihyal  {corpus  ossei  hyoidei),  forms  the  central  part  of  the 
bone,  and  is  of  a  quadrilateral  form. 

Surfaces. — Its  anterior  surface  (Fig.  119),  convex,  directed  forward  and  upward, 
is  divided  into  two  parts  by  a  vertical  ridge  which  descends  along  the  median 


Fia.  H9. — Hyoid  bone.     Anterior 


line  and  is  crossed  at  right  angles  by  a  horizontal  ridge,  so  that  this  surface 
is  divided  into  four  spaces  or  depressions.  At  the  point  of  meeting  of  these  two 
lines  is  a  prominent  elevation,  the  tubercle.  The  anterior  surface  gives  attach- 
ment to  the  Geniohyoid  in  the  greater  part  of  its  extent;  above,  to  the  Genio- 
hyoglossus;  belotv,  to  the  Mylohyoid,  Stylohyoid,  and  the  aponeurosis  of  the 
Digastric  (suprahyoid  aponeurosis);  and  between  these  to  part  of  the  Hyo- 
glossus.  The  posterior  surface  is  smooth,  concave,  directed  backward  and 
downward,  and  separated  from  the  epiglottis  by  the  thyrohyoid  membrane 
and  by  a  quantity  of  loose  areolar  tissue.  The  lateral  surfaces  are  joined  to  the 
greater  cornua.  In  early  life  they  are  connected  with  the  cornua  by  cartilaginous 
surfaces,  and  held  together  by  ligaments,  and  occasionally  a  synovial  membrane 
is  found  between  them. 


154  SPECIAL  ANATOMY  OF  THE  SKELETON 

Borders. — The  superior  border  is  rounded,  and  gives  attachment  to  the  thyro- 
hyoid membrane,  part  of  the  Geniohyoglossi  and  Chondroglossi  muscles.  The 
inferior  border  gives  attachment,  in  front,  to  the  Sternohyoid;  behind,  to  the  Omo- 
hyoid and  to  the  part  of  the  Thyrohyoid  at  its  junction  with  the  great  cornua. 
It  also  gives  attachment  to  the  Levator  glandulae  thyroideae  when  this  muscle 
is  present. 

The  Greater  Cornua  (cornua  viajora),  or  thyrohyals,  project  backward  from 
the  lateral  surfaces  of  the  body;  they  are  flattened  from  above  downward, 
diminish  in  size  from  before  backward,  and  terminate  posteriorly  in  a  tubercle 
for  the  attachment  of  the  lateral  thyrohyoid  ligament.  The  outer  surface  gives 
attachment  to  the  Hyoglossus,  their  upper  border  to  the  Middle  constrictor  of 
the  pharynx,  their  lower  border  to  part  of  the  Thyrohyoid  muscle. 

The  Lesser  Cornua  (cornua  minora),  or  ceratohyals,  are  two  small,  conical- 
shaped  eminences  attached  by  their  bases  to  the  angles  of  junction  between  the 
body  and  greater  cornua,  and  giving  attachment  by  their  apices  to  the  stylohyoid 
ligaments.'  The  smaller  cornua  are  connected  to  the  body  of  the  bone  by  a 
distinct  diarthrodial  joint,  which  usually  persists  throughout  life,  but  occasion- 
ally becomes  ankylosed. 

Development. — From  six  centres — two  (sometimes  one)  for  the  body,  and  one  for  each 
cornu.  Ossification  commences  in  the  body  about  the  eighth  month,  and  in  the  greater  cornua 
toward  the  end  of  fetal  Ufe.  Ossification  of  the  lesser  cornua  commences  in  the  first  or  second 
year  after  birth. 

Attachment  of  Muscles. — Sternohyoid,  Thyrohyoid,  Omohyoid,  aponeurosis  of  the 
Digastric,  Stylohyoid,  Mylohyoid,  Geniohyoid,  Geniohyoglossus,  Chondroglossus,  Hyoglossus, 
Middle  constrictor  of  the  pharynx,  and  occasionally  a  few  fibres  of  the  Inferior  lingualis.  It 
also  gives  attachment  to  the  thyrohyoidean  membrane  and  the  stylohyoid,  thyrohyoid,  and 
hyoepiglottic  ligaments. 

Surface  Form. — The  hyoid  bone  can  be  felt  in  the  receding  angle  below  the  chin,  and  the 
finger  can  be  carried  along  the  whole  length  of  the  bone  to  the  greater  cornu,  which  is  situated 
just  below  the  angle  of  the  mandible.  This  process  of  bone  is  best  perceived  by  making  pressure 
on  one  cornu,  and  so  pushing  the  bone  over  to  the  opposite  side,  when  the  cornu  of  this  side  will 
be  distinctly  felt  immediately  beneath  the  skin.  This  process  of  bone  is  an  important  landmark 
in  ligation  of  the  lingual  artery. 

Applied  Anatomy. — The  hyoid  bone  is  occasionally  fractured,  generally  from  direct  vio- 
lence, as  in  the  act  of  garroting  or  throttling.  It  is  frequently  found  broken  in  those  who  have 
been  hanged.  The  greater  cornu  is  the  part  of  the  bone  most  frequently  broken,  but  sometimes 
the  fracture  takes  place  through  the  body  of  the  bone.  In  consequence  of  the  muscles  of  the 
tongue  having  important  connections  with  this  bone,  there  is  great  pain  upon  any  attempt  being 
made  to  move  the  tongue,  as  in  speaking  or  swallowing. 


THE  THORAX. 

The  thorax,  or  chest,  is  an  osseocartilaginous  cage,  the  cavity  of  which  (cavum 
thoracis)  contains  and  protects  the  principal  organs  of  respiration  and  circula- 
tion. It  is  conical  in  shape,  being  narrow  above  and  broad  below,  flattened 
from  before  backward,  and  longer  behind  than  in  front.  It  is  somewhat  reni- 
form  on  transverse  section. 

Boundaries. — The  posterior  surface  is  formed  by  the  twelve  thoracic  vertebrae 
and  the  posterior  part  of  the  ribs.  It  is  concave  from  above  downward,  and  pre- 
sents on  each  side  of  the  middle  line  a  deep  groove,  the  vertebral  groove,  in  conse- 
quence of  the  direction  backward  and  outward  which  the  ribs  take  from  their 
vertebral  extremities  to  their  angles.  The  anterior  surface  is  flattened  or  slightly 
convex,  and  inclined  forward  from  above  downward.     It  is  formed  by  the  sternum 

1  These  ligaments  in  many  animals  are  distinct  bones,  and  in  man  are  occasionally  ossified  to  a  certain  extent. 


THE  THORAX 


155 


and  costal  cartilages.  The  lateral  sxirfaces  are  convex;  they  are  formed  by  the 
ribs,  separated  from  each  other  by  spaces.  Each  space  is  called  an  intercostal 
space  (sfatiwm  inter costale).  These  are  eleven  in  number,  and  are  occupied  by 
the  intercostal  muscles. 


Fir'it  thoracic 


Fig.  120.— The  thor: 


The  superior  or  upper  aperture  of  the  thorax,  the  inlet  (apertura  thoracis  supe- 
rior), is  reniform  in  shape,  being  broader  from  side  to  side  than  from  before  back- 
ward. It  is  formed  by  fhe  first  thoracic  vertebra  behind,  the  upper  margin 
of  the  sternum  in  front,  and  the  first  rib  on  each  side.  It  slopes  downward 
and  forward,  so  that  the  anterior  boundary  is  on  a  lower  level  than  the  posterior. 
The  antero-posterior  diameter  is  about  two  inches  (5  cm.),  and  the  transverse 
about  Jour  (10  cm.).  The  parts  which  pass  through  the  upper  opening  of  the 
thorax  are,  froiri' tefore  backward  in  or  near  the  middle  line,  the  Sternohyoid 
and  Sternothyroid  muscles,  the  remains  of  the  thymus  gland,  the  trachea, 
oesophagus,  thoracic  duct,  the  inferior  thyroid  veins,  and  the  Longus  colli  muscle 
of  each  side;  at  the  sides,  the  innominate  artery,  the  left  common  carotid,  and 


156 


SPECIAL  ANATOMY  OF  THE  SKELETON 


left  subclavian  arteries,  the  internal  mammary  and  superior  intercostal  arteries, 
the  right  and  left  innominate  veins,  the  vagus,  cardiac,  phrenic,  and  sympathetic 
nerves,  the  anterior  branch  of  the  first  thoracic  nerve,  and  the  recurrent  laryngeal 
nerve  of  the  left  side.  The  apex  of  each  lung,  covered  by  the  pleura,  also  projects 
through  this  aperture,  a  little  above  the  margin  of  the  first  rib. 


Fig.  121. — The  thorax.     Dorsal  view.      (Spaltcholz.) 


The  inferior  or  lower  opening  (apertura  thoracis  inferior)  is  formed  by  the 
twelfth  thoracic  vertebra  behind,  by  the  twelfth  ribs  at  the  sides,  and  in  front 
by  the  eleventh,  tenth,  ninth,  eighth,  and  seventh  costal  cartilages,  which  ascend 
on  either  side  and  form  an  angle,  the  subcostal  angle  (angulus  infrasternalis), 
from  the  apex  of  which  the  ensiform  cartilage  projects.  It  is  wider  transversely 
than  from  before  backward.  It  slopes  oblicjuely  downward  and  backward,  so 
that  the  cavity  of  the  thorax  is  much  deeper  behind  than  in  front.  The 
Diaphragm  closes  in  the  opening  forming  the  floor  of  the  thorax. 


THE  STEBNU3I,   OB  BREAST  BONE  I57 

The  Cavity  of  the  Thorax  (caviim  thoracis). — The  capacity  of  the  cavity  of  the 
thorax  does  not  correspond  with  its  apparent  size  externally,  because  (1)  the  space 
enclosed  by  the  lower  ribs  is  occupied  by  some  of  the  abdominal  viscera;  and  (2) 
the  cavity  extends  above  the  first  rib  into  the  neck.  The  size  of  the  cavity  of  the 
thorax  is  constantly  varying  during  life,  with  the  movements  of  the  ribs  and 
Diaphragm,  and  with  the  degree  of  distention  of  the  abdominal  viscera.  From 
the  collapsed  state  of  the  lungs,  as  seen  when  the  thorax  is  opened,  in  the  dead 
body,  it  would  appear  as  if  the  viscera  only  partly  filled  the  cavity  of  the  thorax, 
but  during  life  there  is  no  vacant  space,  that  which  is  seen  after  death  being 
filled  up  during  life  by  the  expanded  lungs. 

In  the  female  the  thorax  differs  as  follows  from  the  male:  (1)  Its  general  capacity  is  less.  (2) 
The  sternum  is  shorter.  (3)  The  upper  margin  of  the  sternum  is  on  a  level  with  the  lower  part 
•of  the  body  of  the  third  thoracic  vertebra,  whereas  in  the  male  it  is  on  a  level  with  the  lower 
part  of  the  body  of  the  second  thoracic  vertebra.  (4)  The  upper  ribs  are  more  movable,  and 
so  allow  a  greater  enlargement  of  the  upper  part  of  the  thorax  than  in  the  male. 


The  Sternum,  or  Breast  Bone. 

The  sternum,  or  breast  bone  (Figs.  122  and  123),  is  a  flat,  narrow  bone,  situated 
in  the  median  line  of  the  front  of  the  chest,  and  consisting,  in  the  adult,  of  three 
portions.  It  has  been  likened  to  an  ancient  sword;  the  upper  piece,  representing 
the  handle,  is  termed  the  manubrium  sterni  (presternum) ;  the  middle  and  largest 
piece,  which  represents  the  chief  part  of  the  blade,  is  termed  the  gladiolus 
(corpus  sterni  or  mesosternum) ;  and  the  inferior  piece,  which  is  hkened  to  the  point 
of  the  sword,  is  termed  the  ensiform  appendix  {processus  xiphoideus  or  meta- 
sternum).  In  its  natural  position  its  inclination  is  oblique  from  above  down- 
ward and  forward.  It  is  slightly  convex  in  front,  concave  behind,  broad  above, 
becoming  narrowed  at  the  point  where  the  first  and  second  pieces  are  connected, 
after  which  it  again  widens  a  little,  and  is  pointed  at  its  extremity.  Its  average 
length  in  the  adult  is  abouL,§£.ven  inches  (17.5  cm.),  being  rather  longer  IiTthe 
male  than  in  the  female.  At  the  junction  of  the  manubrium  and  gladiolus  is  a 
distinct  angle  {angulus  Ludovici),  the  gladiolus  looking  forward,  the  manubrium 
also  looking  forward,  but  to  a  less  degree.  This  angle  is  on  a  level  with  the 
second  rib,  and  is  produced  by  retraction  of  the  upper  portion  of  the  thorax. 

First  Piece. — The  manubrium  sterni  is  of  a  somewhat  triangular  form,  broad  and 
thick  above,  narrow  below  at  its  junction  with  the  middle  piece. 

Surfaces. — Its  anterior  surface,  convex  from  side  to  side,  concave  from  above 
downward,  is  smooth,  and  affords  attachment  on  each  side  to  the  Pectoralis 
major  and  sternal  origin  of  the  Sternomastoid  muscle.  In  well-marked  bones 
the  ridges  limiting  the  attachment  of  these  muscles  are  very  distinct.  Its  posterior 
surface,  concave  and  smooth,  affords  attachment  on  each  side  of  the  Sternohyoid 
and  Sternothyroid  muscles. 

Borders. — The  superior  border,  the  thickest,  presents  at  its  centre  the  prestemal 
notch  (i)icisura  jiigularis),  and  on  each  side  an  oval  articular  surface,  the 
clavicular  facet  (incisura  clavicidaris),  directed  upward,  backward,  and  outward, 
for  articulation  with  the  sternal  end  of  the~clavicle.  The  inferior  border  presents 
an  oval,  rough  surface,  covered  in  the  recent  state  with  a  thin  layer  of  cartilage, 
for  articulation  with  the  second  portion  of  the  bone  (synchondrosis  sternalis). 
The  junction  of  the  manubrium  with  the  gladiolus  is  marked  by  a  transverse 
ridge,  which  corresponds  to  the  attachment  on  each  side  of  the  cartilage  of 
the  second  rib.  The  lateral  borders  are  marked  above  by  a  depression  (iiicisura 
cosfalis  I)  for  the  first  costal  cartilage,  and  below  by  a  small  facet,  which,  with  a 


158 


SPECIAL  ANATOMY  OF  THE  SKELETON 


i\G.  122.— Anterior  (ventral)  surface  of  sternum  and  Fig.  123.— Posterior  (dorsal)  surface  of  sternum, 

costal  cartilages. 


THE  STERNUM,   OB  BREAST  BONE  159 

similar  facet  on  the  upper  angle  of  the  middle  portion  of  the  bone,  forms  a  notch 
{incisura  costalis  II)  for  the  reception  of  the  costal  cartilage  of  the  second  rib. 
These  articular  surfaces  are  separated  by  a  narrow,  curved  edge,  which  slopes 
from  abo\'e  downward  and  inward. 

Second  Piece. — The  gladiolus,  considerably  longer,  narrower,  and  thinner  than 
the  first  piece,  is  broader  below  than  above. 

Surfaces. — Its  anterior  surface  (planum  sternale)  is  nearly  flat,  directed  upward 
and  forward,  and  marked  by  three  transverse  lines  which  cross  the  bone  opposite 
the  third,  fourth,  and  fifth  articular  depressions.  These  lines  are  produced  by  the 
union  of  the  four  separate  pieces  of  which  this  part  of  the  bone  consists  at  an  early 
period  of  life.  At  the  junction  of  the  third  and  fourth  pieces  is  occasionally  seen 
an  orifice,  the  sternal  foramen;  it  varies  in  size  and  form  in  different  individuals 
and  pierces  the  bone  from  before  backward.  This  surface  affords  attachment 
on  each  side  to  the  sternal  origin  of  the  Fectoralis  major.  The  posterior  surface, 
slightly  concave,  is  also  marked  by  three  transverse  lines,  but  they  are  less  dis- 
tinct than  those  in  front;  this  surface  affords  attachment  below,  on  each  side, 
to  the  Triaogularis  sterni  muscle,  and  occasionally  presents  the  posterior  opening 
of  the  sternal  foramen. 

Borders. — The  superior  border  presents  an  oval  surface  for  articulation  with  the 
manubrium.  The  inferior  border  is  narrow,  and  articulates  with  the  ensiform 
appendix.  Each  lateral  border  presents,  at  each  superior  angle,  a  small  facet, 
which,  with  a  similar  facet  on  the  manubrium,  forms  a  cavity  for  the  cartilage  of 
the  second  rib;  the  four  succeeding  angular  depressions  receive  the  cartilages  of 
the  third,  fourth,  fifth,  and  sixth  ribs;  while  each  inferior  angle  presents  a  small 
facet,  which,  with  a  corresponding  one  on  the  ensiform  appendix,  forms  a  notch 
for  the  cartilage  of  the  se\'enth  rib.  They  are  separated  by  a  series  of  curved 
interarticular  intervals,  which  diminish  in  length  from  above  downward,  and 
correspond  to  the  intercostal  spaces.  Most  of  the  cartilages  belonging  to  the  true 
ribs,  as  will  be  seen  from  the  foregoing  description,  articulate  with  the  sternum 
at  the  line  of  junction  of  two  of  its  primitive  component  segments.  This  is 
well  seen  in  many  of  the  lower  animals,  where  the  separate  parts  of  the  bone 
remain  ununited  longer  than  in  man.  In  this  respect  a  striking  analogy  exists 
between  the  mode  of  connection  of  the  ribs  with  the  vertebral  column  and  the 
connection  of  the  costal  cartilages  with  the  sternum. 

Third  Piece. — The  ensiform  or  xiphoid  appendix  is  the  smallest  of  the  three ;  it 
is  thin  and  elongated  in  form,  cartilaginous  in  structure  in  youth,  but  more  or 
less  ossified  at  the  upper  part  in  the  adult. 

Surfaces. — Its  anterior  surface  affords  attachment  to  the  chondroxiphoid  liga- 
ment; its  posterior  surface,  to  .some  of  the  fibres  of  the  Diap^liragm  and  Triangii^ 
laris  sterni  muscles;  its  lateral  borders,  to  the  aponeurosis  of  the  abdominal  muscles. 
Above  Tf  articulates  with  the  lower  end  of  the  gladiolus,  and  at  each  superior 
angle  presents  a  facet  (incisura  costalis  VII),  for  the  lower  half  of  the  cartilage 
of  the  seventh  rib;  below,  by  its  pointed  extremity,  it  gives  attachment  to  the  linea 
alJDa.  This  portion  of  the  sternum  varies  much  in  appearance,  being  some- 
times pointed,  broad,  and  thin,  sometimes  bifid  or  perforated  by  a  circular  open- 
ing, occasionally  curved  or  deflected  considerably  to  one  or  the  other  side. 

Structure. — The  bone  is  composed  of  delicate  cancellous  structure,  covered  by  a  thin 
layer  of  compact  tissue,  which  is  thickest  in  the  manubrium  between  the  articular  facets  for 
the  clavicles. 

Development. — The  cartilaginous  sternum  originally  consists  of  two  bars,  situated  one  on 
either  side  of  the  mesal  plane  and  connected  with  the  rib  cartilages  of  its  own  side.  It  is  usual 
for  the  eighth  cartilage  to  lose  its  attachment  to  the  sternum  and  become  attached  to  the  seventh 
cartilage.     The  sternal  end  of  the  ninth  cartilage  divides  longitudinally,  the  mesal  part  remains 


160 


SPECIAL  ANATOMY  OF  THE  SKELETON 


attached  to  the  sternum  and  becomes  the  ensiform  process.  The  remaining  part  acquires 
attachment  to  the  eighth  cartilage.  These  two  bars  fuse  with  each  other  along  the  middle  line, 
and  the  bone,  including  the  ensiform  appendix,  is  usually  developed  from  six  centres,  one  for 

the  first  piece  or  manubrium,  four  for  the  second 
piece  or  gladiolus,  and  one  for  the  ensiform  appendix. 
Up  to  the  middle  of  fetal  life  the  sternum  is  entirely 
cartilaginous,  and  when  ossification  takes  place  the 
ossific  granules  are  deposited  in  the  middle  of  the 
intervals  between  the  articular  depressions  for  the 
costal  cartilages,  iu  the  following  order  (Fig.  125):  In 
the  manubrium  and  first  piece  of  the  gladiolus,  during 
the  sixth  month;  in  the  second  and  third  pieces  of  the 
gladiolus  between  the  seventh  and  ninth  months; 
the  fourth  piece  of  the  gladiolus  ossifies  toward  the 
latter  part  of  the  first  year;  the  ensiform  process 
ossifies  Vjetween  the  fifth  and  eighteenth  years.  The 
centres  appear  in  the  upper  part  of  each  segment  and 
proceed  gradually  downward.  To  these  may  be  added 
the  occasional  existence,  as  described  by  Breschet,  of 
two  episternal  centres,  which  make  their  appearance 
one  on  each  side  of  the  presternal  notch.  They 
are  probably  vestiges  of  the  episternal  bone  of  the 
monotremata  and  lizards.  It  occasionally  happens 
that  some  of  the  segments  are  formed  from  more  than 
one  centre,  the  number  and  position  of  which  vary  (Fig.  127).  Thus,  the  first  piece  may  have 
two,  three,  or  even  six  centres.  When  two  are  present,  they  are  generally  situated  one  above 
the  other,  the  upper  one  being  the  larger;' the  second  piece  has  seldom  more  than  one;  the 


Fig.  124. — Showing  ventral  ends  of  the 
upper  seven  (cartilaginous)  ribs  fused  to 
form    a   pair    of    longitudinal    sternal    bars. 


1  for  mannbriiim 


4  for  gladiobisJ^       \  7th  month 

5     1st  year  after  birth 


'^z::^r\'''^'' ''"''""- 


[  Barely  unite, 

Sijrii'"  ■  '^  1     except  in  old  age. 


Between  puberty 
and  the  25th  year. 


Soon  after  puberty. 


Partly  cartilaginous  to 
advanced  life. 


Fig.  126. — Time  of  unioa  of 


for  first  piece,  two  or  more  centres. 

12^  V""^  f<^^'  second  piece,  usually  one. 

%T~  for  third    1 
'0    u  tO  for  fourth  \  2,  placed  laterally. 
f^^   K)  for  fifth     J 


Arrest  of  development 
of  lateral  pieces,  producing 


Sternal  fissure,  and 
Sternal  foramen. 


Fig,  127. — Peculiarities  in  number  of  centres  of  sternum.       Fig.  128. — Peculiarities  in  mode  of  union  of  sternum. 
^  Sir  George  Humphry  states  that  this  is  "probably  the  more  complete  condition." 


THE  RIBS  101 

Non-articular  pari  of  tubercle 
Angle  I 

I  1^         Articular  part  of  lulerclc 


third,  fourth,  and  fifth  pieces  are  often  formed  from  two 
centres  placed  laterally,  the  irregular  union  of  which  will 
serve  to  explain  the  occasional  occurrence  of  the  sternal  fora- 
men (Fig.  126),  or  of  the  vertical  sternal  fissure,  which  occa- 
sionally intersects  this  part  of  the  bone  (Fig.  126),  and 
which  is  further  explained  by  the  manner  in  which  the 
cartilaginous  matrix,  in  which  ossification  takes  place,  is 
formed.  Union  of  the  various  centres  of  the  gladiolus  com- 
mences about  puberty,  from  below,  and  proceeds  upward, 
so  that  by  the  age  of  twenty-five  they  are  all  united,  and 
this  portion  of  bone  consists  of  one  piece.  The  ensiform 
cartilage  becomes  joined  to  the  gladiolus  about  forty.  The 
manubrium  is  occasionally  but  seldom  joined  to  the  gladiolus 
in  advanced  life  by  bone.  When  this  union  takes  place, 
however,  it  is  generally  only  superficial,  a  portion  of  the 
centre  of  the  sutural  cartilage  remaining  unossified. 

Articulations. — With  the  clavicles  and  seven  costal  carti- 
lages on  each  side. 

Attachment  of  Muscles.— To  nine  pairs  and  one  single 

muscle — the  Pectoralis  major,  Sternomastoid,  Sternohyoid, 

Sternothyroid,    Triangularis     sterni,     aponeuroses    of    the 

■Shaft  Obliquus  externus  abdominis,  Obliquus  internus  abdominis, 

Transversalis,  Rectus  abdominis  muscles,  and  Diaphragm. 


The  Ribs  (Costae). 

Tlie  ribs  are  elastic  arches  of  bone,  which  form 

the  chief  part  of  the  thoracic  wails.     They  are  twelve 

in  number  on  each  side;  but    this  number  may  be 

increased  by  the  development  of  a  cervical  or  lumbar 

rib,  or  may  be  diminished  to  eleven.     The  first^ .seven 

are  connected  behind  with  the  spine  and  in  front 

with  the  sternum,  through   the   intervention  of  the 

costal  cartilages;  they  are  called  true  (vertebrosternal) 

ribs   (costae  verae)}     The  remaining  five  are  false 

ribs  {costae  spuriae);   of  these,  the  first  three  have 

'<,\  their  cartilages  attached  to  the  cartilage  of  the  rib 

\\       ^  above,  the  vertebrochondral  ribs;  the  last  two  are  free 

V\  ^     \  ^'  '^heir  anterior  extremities,  the  floating  or  vertebral 

\ \  \     \        ribs.     The  ribs  vary  in  their  direction,  the  upper  ones 

•d    l^<?'"g  I^ss  oblique  than  the  lower.     The  extent  of 

'"X   ~f/    oblic{uity  reaches  its  maximum  at  the  ninth  ril),  and 

'^•^^        gradualty7recTeases~from  that  rib  to  the  twelfth.     The 

ribs   are   situated   one  below   the  other   in    such  a 

^'^-^fdeT^rferioraipeJt.*"'""    manner  that  spaces  are  left  between  them.     Each 

'  Sometimes  the  eighth  rib  cartilage  articulates  with  the  sternum;  this  condition  occurs  more  frequently  on  the 
■ight  than  on  the  left  side. 

11 


162 


SPECIAL  ANATOMY  OF  THE  SKELETON 


space  is  called  an  intercostal  space  (spatium  intercostale).  The  length  of  these 
spaces  corresponds  to  the  length  of  the  ribs  and  their  cartilages;  their  breadth 
is  greater  in  front  than  behind,  and  between  the  upper  than  between  the  lower 
ribs.  The  ribs  increase  in  length  from  the  first  to  the  seventh,  when  they  again 
diminish  to  the  twelfth.  In  breadth  they  decrease  from  above  downward;  in  the 
upper  ten  the  greatest  breadth  is  at  the  sternal  extremity. 

Common  Characters  of  the  Ribs. — A  rib  from  the  middle  of  the  series 
should  be  taken  in  order  to  study  the  common  characters  of  the  ril)s  (Figs.  129 
and  130).  Each  rib  presents  two  extremities,  a  posterior  or  vertebral,  an  anterior 
or  sternal,  and  an  intervening  portion — the  body  or  shaft. 

Posterior  Extremity. — The  posterior  or  vertebral  extremity  presents  for  examina- 
tion a  head,  neck,  and  tuberosity. 

The  head  (capituhim  costae)  (Fig.  130)  is  marked  by  a  kidney-shaped  artic- 
ular surface,  divided  by  a  horizontal  ridge  (crista  capituli)  into  two  facets  for 


Demifacet  for  vertebra 


Interariicular  crest 


',C^^''%J>i|/  ^Demifacet  for  vertebra. 


Subcostal  groove 


Fig.  130. — A  central  rib  of  the  left  side,  viewed  from  bebind. 


articulation  with  the  costal  cavity  formed  by  the  junction  of  the  bodies  of  two 
contiguous  thoracic  vertebras;  the  upper  facet  is  small,  the  inferior  one  of  larger 
size;  the  ridge  separating  them  serves  for  the  attachment  of  the  interarticular 
ligament. 

The  neck  (collum  costae)  is  that  flattened  portion  of  the  rib  which  extends  out- 
ward from  the  head;  it  is  about  an  inch  long,  and  is  placedLjnJi'ont  of  thejracs- 
verse  process  of  the  lower  of  the  two  vertebrae  with  which  the  head  articulates. 
Its  anterior  surface  is  flat  and  smooth,  its  posterior  surface  is  rough  for  the  attach- 
ment of  the  middle  costotransverse  ligament,^^JKt  is  perforated  by  nimierous 
foramina,  the  direction  of  which  is  less  constant  than  those  found  on  the  inner 
surface  of  the  shaft.  Of  its  two  borders,  the  superior  border  presents  a  rough 
crest  (crista  colli  costae)  for  the  attachment  of  the  anterior  costotransverse  liga- 
ment; its  inferior  border  is  rounded.  On  the  posterior  surface  of  the  neck,  just 
where  it  joins  the  shaft,  and  nearer  the  lower  than  the  upper  border,  is  an  eminence 
— the  tuberosity,  or  tubercle. 

The  tuberosity  (tuhrrciilnm  costae)  consists  of  an  articular  and  a  nonanicular 
portion.  The  articular  portion  (fades  articularis  tubercidi  costae),  the  more  in- 
ternal and  inferior  of  the  two,  presents  a  small,  oval  surface  or  articulation  with 
the  extremity  of  the  transverse  process  of  the  lower  of  the  two  vertebrse  to  which 
the   head   is  connected.       The  nonarticular  portion  is  a  rough   elevation,   which 


THE  RIBS  153 

affords  attachment  to  the   posterior  costotransverse  ligament.     The   tiihercle  is 
much  more  prominent  in  the  upper  than  in  tlie  lower  ril)s. 

Anterior  Extremity. — The  anterior  or  sternal  extremity  is  flattened,  and  presents 
a  porous,  oval,  concave  depression,  into  which  the  costal  cartilage  is  received. 

The  shaft  (cor-pus  costae)  is  thin  and  flat,  so  as  to  present  two  surfaces,  an 
external  and  an  internal,  and  two  borders,  a  superior  and  an  inferior. 

The  external  surface  is  convex,  smooth,  and  marked  at  its  back  part,  a  little 
in  front  of  the  tuberosity,  by  a  prominent  line,  directed  obliquely  from  above 
downward  and  outward;  this  gives  attachment  to  a  tendon  of  the  Iliocostalis_ 
muscle  or  of  one  of  its  accessory  portions,  and  is  called  the  angle  (anc/ulus  costae). 
At  this  point  the  rib  is  bent  in  two  directions.  If  the  rib  is  laid  upon  its  lower 
border,  it  will  be  seen  that  the  portion  of  the  shaft  in  front  of  the  angle  rests  upon 
this  border,  while  the  portion  of  the  shaft  behind  the  angle  is  bent  inward  and  at 
the  same  time  tilted  upward.  The  interval  between  the  angle  and  the  tuberosity 
increases  gradually  from  the  second  to  the  tenth  rib.  The  portion  of  bone  between 
these  two  parts  is  rounded,  rough,  and  irregular,  and  serves  for  the  attachment  of 
the  Longissimus  dorsimuscle.  The  portion  of  bone  between  the  tubercle  and 
sternal  extremity  is  also  slightly  twisted  upon  its  own  axis,  the  external  surface 
looking  downward  behind  the  angle,  a  little  upward  in  front  of  it.  This  surface 
presents  toward  its  sternal  extremity  an  oblique  line,  the  anterior  angle. 

The  internal  surface  is  concave,  smooth,  directed  a  little  upward  behind  the  angle, 
a  little  downward  in  front  of  it.  This  surface  is  marked  by  a  ridge  which  com- 
mences at  the  lower  extremity  of  the  head;  it  is  strongly  marked  as  far  as  the 
inner  side  of  the  angle,  and  gradually  becomes  lost  at  the  junction  of  the  anterior 
with  the  middle  third  of  the  bone.  The  interval  between  it  and  the  inferior  border 
presents  a  groove,  subcostal  groove  {sulcus  costae),  for  the  intercostal  vessels  and 
nerve.  At  the  back  part  of  the  bone  this  groove  belongs  to  the  inferior  border, 
but  just  in  front  of  the  angle,  where  it  is  deepest  and  broadest,  it  corresponds  to 
the  internal  surface.  The  superior  edge  of  the  groove  is  rounded;  it  serves  for 
the  attachment  of  the  Internal  intercostal  muscle.  The  inferior  edge  corresponds 
to  the  lower  margin  of  the  rib  and  gives  attachment  to  the  External  intercostal 
muscle.  Within  the  groove  are  seen  the  orifices  of  numerous  small  foramina 
which  traverse  the  wall  of  the  shaft  obliquely  from  before  backward. 

The  superior  border,  thick  and  rounded,  is  marked  by  an  external  and  an  inter- 
nal lip,  more  distinct  behind  than  in  front;  they  serve  for  the  attachment  of  the 
External  and  Internal  intercostal  muscles. 

The  inferior  border,  thin  and  sharp,  has  attached  to  it  the  External  intercostal 
muscle. 

Peculiar  Ribs. — The  ribs  which  require  especial  consideration  are  five  in 
number,  viz.,  the  first,  second,  tenth,  eleventh,  and  twelfth. 

First  Rib. — The  first  rib  (Fig.  131)  is  the  shortest  and  the  most  curved  of  all 
the  ribs;  it  is  broad  and  flat,  its  surfaces  looking  upward  and  downward,  and 
its  borders  inward  and  outward.  The  head  is  of  small  size,  rounded,  and  presents 
only  a  single  articular  facet  for  articulation  with  the  body  of  the  first  thoracic  ver- 
tebra. The  neck  is  narrow  and  rounded.  The  tuberosity,  thick  and  prominent, 
rests  on  the  outer  border.  There  is  no  angle,  but  in  this  situation  the  rib  is  slightly 
bent,  with  the  convexity  of  the  bend  upward,  so  that  the  head  of  the  bone  is 
directed  downward.  The  upper  surface  of  the  shaft  is  marked  by  two  shallow 
depressions,  separated  by  a  small  rough  surface  (tuberculum  scaleni)  for  the  attach- 
ment of  the  Scalenus  anticus  muscle — the  shallow  groove  in  front  of  it  trans- 
mitting the  subclavian  vein,  the  deeper  groove  behind  it  (sulcus  subclaviae^ 
the  subclavian  artery.  Between  the  groove  for  the  subclavian  artery  and  the 
tuberosity  is  a  rough  surface,  for  the  attachment  of  the  Scalenus  medius  muscle. 
The  under  surface  is  smooth,  and  destitute  of  the  groove  observed  on  the  other 


164  SPECIAL  ANATOMY  OF  THE  SKELETON 

ribs  The  outer  border  is  convex,  thick,  and  rounded,  and  at  its  posterior  part 
gives  attachment  to  the  first  serration  of  the  Serratus  magnus;  the  inner  is  con- 
cave   thin    and  sharp,  and  marked  about  its  centre  by  the  commencement  ot 


Bm^i^^^^'''' 


Single  articular  facet  — 


SinjZe  arftCM/rtr/ncrf.—  ^^^^      Tuberosity  11 


Single  articular  facet. 


Figs.  131  to  135.— Pecul 


the  rough  surface  for  the  Scalenus  anticus.     The  anterior  extremity  is  larger  and 
thicker  than  any  of  the  other  ribs. 

Second  Rib.— The  second  rib  (Fig.  132)  is  much  longer  than  the  first,  but  bears 
a  very  considerable  resemblance  to  it  in  the  direction  of  its  curvature.     The  non- 


THE  COSTAL  CARTILAGES  165 

articular  portion  of  the  tuberosity  is  occasionally  only  slightly  marked.  The  angle 
is  slight  and  situated  close  to  the  tuberosity,  and  the  shaft  is  not  twisted,  so  tliat 
both  ends  touch  any  plane  surface  upon  which  it  may  be  laid;  but  there  is  a  similar 
though  slighter  bend,  with  its  convexity  upward,  to  that  found  in  the  first  rib.  The 
shaft  is  not  horizontal,  like  that  of  the  first  rib,  its  outer  surface,  which  is  convex, 
looking  upward  and  a  little  outward.  It  presents,  near  the  middle,  a  rough  emi- 
nence {tuberositas  costae  II),  for  the  attachment  of  part  of  the  first  and  all  of  the 
second  digitations  of  the  Serratus  magnus;  behind  and  above  which  is  attached 
the  Scalenus  posticus.  The  inner  surface,  smooth  and  concave,  is  directed  down- 
ward and  a  little  inward;  it  presents  a  short  groove  tow^ard  its  posterior  part. 

Tenth  Rib. — The  tenth  rib  (Fig  133)  has  only  a  single  articular  facet  on  its  head. 

Eleventh  and  Twelfth  Ribs.— The  eleventh  and  twelfth  ribs  (Figs.  134  and 
135)  have  each  a  single  articular  facet  on  the  head,  which  is  of  rather  large  size; 
they  have  no  neck  or  tuberosity,  and  are  pointed  at  the  extremity.  The  eleventh 
has  a  slight  angle  and  a  shallow  groove  on  the  lower  border.  The  twelfth  has 
neither,  and  is  much  shorter  than  the  eleventh,  and  the  head  has  a  slight  inclina- 
tion downward.     Sometimes  the  twelfth  rib  is  even  shorter  than  the  first. 

Structure. — The  ribs  consist  of  cancellous  tissue  enclosed  in  a  thin  layer  of  compact  bone. 

Development. — Each  rib,  with  the  exception  of  the  last  two,  is  developed  from  three  centres, 
one  for  the  shaft  near  the  angle,  one  for  the  head,  and  one  for  the  tubercle.  The  last  two  ribs 
have  only  two  centres,  that  for  the  tubercle  being  wanting.  Ossification  commences  in  the 
shaft  of  the  ribs  between  the  ninth  and  eleventh  weeks  before  its  appearance  in  the  vertebrje. 
The  epiphysis  of  the  head,  which  is  of  slightly  angular  shape,  and  that  for  the  tubercle,  of  a 
lenticular  form,  make  their  appearance  between  the  sixteenth  and  twentieth  years,  and  are  not 
united  to  the  rest  of  the  bone  until  about  the  twenty -fifth  year. 

Attachment  of  Muscles. — To  nineteen — the  Intercostales  externi  et  interni,  Scalenus 
anticus,  Scalenus  uicdius,  Sc^ilenus  posticus,  Pectoralis  minor,  Serratus  magnus,  Obliquus 
externus  ulidominis,  (^uadratus  lumborum.  Diaphragm,  Latissimus  dorsi,  Serratus  posticus 
superior,  Serratus  posticus  inferior,  Iliocostalis,  Musculus  accessorius  ad  iliocostalem,  Lon- 
gissimus  dorsi,  Cervicalis  ascendens,  Levatores  costarum,  and  Infracostales. 

The  Costal  Cartilages. 

The  costal  cartilage  (cartilago  costalis)  (Fig.  122)  is  white,  hyaline  cartilage.  The 
cartilages  serve  to  prolong  the  ribs  forward  to  the  front  of  the  thorax,  and  they 
contribute  very  materially  to  the  elasticity  of  its  walls.  The  first  seven  are  con- 
nected with  the  sternum,  the  next  three  with  the  lower  border  of  the  cartilage  of 
the  preceding  rib.  The  cartilages  of  the  last  two  ribs  have  pointed  extremities, 
W'hich  terminate  in  free  ends  in  the  walls  of  the  abdomen.  Like  the  ribs,  the 
costal  cartilages  vary  in  their  length,  breadth,  and  direction.  They  increase  in 
length  from  the  first  to  the  seventh,  then  gradually  diminish  to  the  last.  They 
diminish  in  breadth,  as  well  as  the  intervals  between  them,  from  the  first  to  the 
last.  They  are  broad  at  their  attachment  to  the  ribs,  and  taper  toward  their  sternal 
extremities,  excepting  the  first  two,  which  are  of  the  same  breadth  throughout, 
and  the  sixth,  seventh,  and  eighth,  which  are  enlarged  where  their  margins  are 
in  contact.  In  direction  they  also  vary;  the  first  descends  a  little,  the  second  is 
horizontal,  the  third  ascends  slightly,  while  all  the  rest  follow  the  course  of  the 
ribs  for  a  short  extent,  and  then  ascend  to  the  sternum  or  preceding  cartilage. 
Each  costal  cartilage  presents  two  surfaces,  two  borders,  and  two  extremities. 

Surfaces. — The  anterior  surface  is  convex,  and  looks  forward  and  upward;  that 
of  the  first  gives  attachment  to  the  costoclavicular  ligament  and  the  Subclavius 
muscle;  that  of  the  second,  third,  fourth,  fifth,  and  sixth,  at  their  sternal  ends, 
to  the  Pectoralis  major.'  The  others  are  covered  by,  and  give  partial  attachment 
to,  some  of  the  great  flat  muscles  of  the  abdomen.     The  posterior  surface  is  con- 

1  The  first  and  seventh  also,  occasionally,  give  origin  to  the  same  muscle. 


166  SPECIAL  ANATOMY  OF  THE  SKELETON 

cave,  and  directed  backward  and  downward,  the  first  giving  attachment  to  the 
Sternothyroid,  the  third  to  the  sixth  inclusive  to  the  Triangularis  sterni,  and 
the  six  or  seven  inferior  ones  to  the  Transversalis  muscle  and  the  Diaphragm. 

Borders. — Of  the  two  borders,  the  superior  border  is  concave,  the  inferior  con- 
vex; they  afford  attachment  to  the  Internal  intercostal  muscles,  the  upper  border 
of  the  sixth  giving  attachment  to  the  Pectoralis  major  muscle.  The  contiguous 
borders  of  the  sixth,  seventh,  and  eighth,  and  sometimes  the  ninth  and  tenth, 
costal  cartilages  present  small,  smooth,  oblong-shaped  facets  at  the  points  where 
they, articulate. 

Extremities. — Of  the  two  extremities,  the  outer  extremity  is  continuous  with 
the  osseous  tissue  of  the  rib  to  which  it  belongs.  The  inner  extremity  of  the  first 
is  continuous  with  the  sternum;  the  six  succeeding  ones  have  rounded  extremities, 
which  are  received  into  shallow  concavities  on  the  lateral  margins  of  the  sternum. 
The  inner  extremities  of  the  eighth,  ninth,  and  tenth  costal  cartilages  are  pointed, 
and  are  connected  with  the  cartilage  above.  Those  of  the  eleventh  and  twelfth 
are  free  and  pointed. 

The  costal  cartilages  are  most  elastic  in  youth,  those  of  the  false  ribs  being  more  so  than  the 
true.    In  old  age  they  become  of  a  deep  yellow  color,  and  are  prone  to  calcify. 

Attachment  of  Muscles. — To  nine — the  Subclavius,  Sternothyroid,  Pectoralis  major, 
Internal  oblique,  Transversalis,  Rectus  abdominis.  Diaphragm,  Triangularis  sterni,  and 
Internal  intercostals. 

Surface  Form. — The  bones  of  the  thorax  are  to  a  very  considerable  extent  covered  by  mus- 
cles, so  that  in  the  strongly  developed  muscular  subject  they  are  for  the  most  part  concealed. 
In  the  emaciated  subject,  on  the  other  hand,  the  ribs,  especially  in  the  lower  and  lateral  region, 
stand  out  as  prominent  ridges  with  the  sunken,  intercostal  spaces  between  them. 

In  the  median  line,  in  front,  the  superficial  surface  of  the  sternum  is  to  be  felt  throughout  its 
entire  length,  at  the  bottom  of  a  deep  median  furrow-  (the  sternal  furrow)  situated  between 
the  two  great  pectoral  muscles.  These  muscles  overlap  the  anterior  surface  somewhat,  so 
that  the  whole  of  the  sternum  in  its  entire  width  is  not  subcutaneous;  and  this  overlapping  is 
greater  opposite  the  centre  of  the  bone  than  above  and  below,  so  that  the  furrow  is  wider  at  its 
upper  and  lower  parts,  but  narrower  in  the  middle.  The  centre  of  the  upper  border  of  the  ster- 
num is  visible,  constituting  the  prestemal  notch,  but  the  lateral  parts  of  this  border  are 
obscured  by  the  tendinous  origins  of  the  Sternomastoid  muscles,  which  present  themselves 
as  oblique  tendinous  cords,  which  narrow  and  deepen  the  notch.  Lower  down  on  the  sub- 
cutaneous surface,  a  well-defined  transverse  ridge,  the  angulus  Ludovici,  is  always  to  be  felt. 
This  denotes  the  line  of  junction  of  the  manubrium  and  the  body  of  the  bone,  and  is  a  useful 
guide  to  the  second  costal  cartilage,  and  thus  to  the  identity  of  any  given  rib.  The  second  rib 
being  found  through  its  costal  cartilage,  it  is  easy  to  count  downward  and  find  any  other.  From 
the  middle  of  the  sternum  the  furrow  spreads  out,  and,  exposing  more  of  the  surface  of  the 
body  of  the  bone,  terminates  below  in  a  sudden  depression,  the  infrastemal  depression,  or 
pit  of  the  stomach  {scrohiculus  cordis),  which  corresponds  to  the  ensiform  cartilage.  This 
depression  lies  between  the  cartilages  of  the  seventh  ribs,  and  in  it  the  ensiform  cartilage  may 
be  felt.  The  sternum  in  its  vertical  diameter  presents  a  general  convexity  forward,  the  most 
prominent  point  of  which  is  at  the  joint  between  the  manubrium  and  gladiolus. 

On  each  side  of  the  sternum  the  costal  cartilages  and  ribs  on  the  front  of  the  thorax  are  par- 
tially obscured  by  the  great  jiectoral  muscles,  through  which,  however,  they  are  to  be  felt  as 
ridges,  with  yielding  intervals  between  them,  corresponding  to  the  intercostal  spaces.  Of  these 
spaces,  the  one  between  the  second  and  third  ribs  is  the  widest,  the  next  two  somewhat  nar- 
rower, and  the  remainder,  with  the  exception  of  the  last  two,  comparatively  narrow. 

The  lower  border  of  the  Pectoralis  major  muscle  corresponds  to  the  sixth  rib,  and  below 
this,  on  the  front  of  the  thorax,  the  broad,  flat  outline  of  the  ribs  as  they  begin  to  ascend,  and 
the  more  rounded  outline  of  the  costal  cartilages,  are  often  visible.  The  lower  boundary  of 
the  front  of  the  thorax,  the  abdominothoracic  arch,  which  is  most  plainly  seen  by  arching 
the  body  backward,  is  formed  by  the  ensiform  cartilage  and  the  cartilages  of  the  seventh,  eighth, 
ninth,  and  tenth  ribs,  and  the  extremities  of  the  eleventh  and  twelfth  ribs  or  their  cartilages. 

On  each  side  of  the  thorax,  from  the  axilla  downward,  the  flattened  external  surfaces  of  the 
ribs  may  be  defined  in  the  form  of  oblique  ridges,  separated  by  depressions  corresponding  to  the 
intercostal  spaces.  They  are,  however,  covered  by  muscles,  which  obscure  their  outline  to  a 
certain  extent  in  the  strongly  developed.  Nevertheless,  the  ribs,  with  the  exception  of  the  first, 
can  generally  be  followed  over  the  front  and  sides  of  the  thorax  without  difficulty.  The  first  rib, 
being  almost  completely  covered  by  the  clavicle  and  scapula,  can  only  be  distinguished  in  a 


THE  COSTAL  CARTILAGES  107 

small  portion  of  its  extent.  At  the  back  the  angles  of  the  ribs  form  a  slightly  marked  oblique 
line  on  each  side  of  and  some  distance  from  the  vertebral  spines.  This  line  diverges  some- 
what as  it  descends,  and  external  to  it  is  a  broad,  convex  surface  caused  by  the  projection  of 
the  ribs  beyond  their  angles.  Over  this  surface,  except  where  covered  by  the  scapula,  the 
individual  ribs  can  be  distinguished. 

Applied  Anatomy. — Malformations  of  the  sternum  present  nothing  of  surgical  importance 
beyond  the  fact  that  abscesses  of  the  mediastinum  may  sometimes  escape  through  the  sternal 
foramen.  Fractures  of  the  sternum  are  by  no  means  common,  due,  no  doubt,  to  the  elasticity 
of  the  ribs  and  their  cartilages,  which  support  it  like  so  many  springs.  When  broken  it  is  fre- 
quently associated  with  fracture  of  the  vertebral  column,  and  may  be  caused  by  forcibly  bending 
the  body  either  backward  or  forward  until  the  chin  becomes  impacted  against  the  top  of  the 
sternum.  It  may  also  be  fractured  by  direct  violence  or  by  muscular  action.  The  fracture 
usually  occurs  in  the  upper  half  of  the  body  of  the  bone.  Dislocation  of  the  gladiolus  from  the 
manubrium  also  takes  place,  and  is  sometimes  described  as  a  fracture. 

The  bone,  cancellous  in  structure  and  being  subcutaneous,  is  frequently  the  seat  of  (jiimma- 
tous  tumors,  and  not  uncommonly  is  affected  with  caries.  Occasionally  the  bone,  and  especially 
its  ensiform  appendix,  becomes  altered  in  shape  and  driven  inward,  in  workmen,  by  the 
pressure  of  tools  against  the  chest. 

The  rihs  are  frequently  broken,  though  from  their  connections  and  shape  they  are  able  to 
withstand  great  force,  yielding  under  the  injury  and  recovering  themselves  like  a  spring.  The 
middle  of  the  series  are  the  ones  most  liable  to  fracture.  The  first,  and  to  a  less  extent  the 
second,  being  protected  by  the  clavicle,  are  rarely  fractured;  and  the  eleventh  and  twelfth,  on 
account  of  their  loose  and  floating  condition,  enjoy  a  like  immunity.  The  fracture  generally 
occurs  from  indirect  violence,  from  forcible  compression  of  the  thoracic  wall,  and  the  bone  then 
gives  way  at  its  weakest  part — i.  e.,  just  in  front  of  the  angle.  But  the  ribs  may  also  be  broken 
by  direct  violence,  when  the  bone  gives  way  and  is  driven  inward  at  the  point  struck,  or  they 
may  be  broken  by  muscular  action.  It  seems  probable,  however,  that  in  the  latter  case  the 
bone  has  undergone  some  atrophic  changes.  Fracture  of  the  ribs  is  frequently  complicated  by 
some  injury  to  the  viscera  contained  within  the  thorax  or  upper  part  of  the  abdominal  cavity, 
and  this  is  most  likely  to  occur  in  fractures  from  direct  violence.  Occasionally  supernumerary 
ribs  exist.  They  may  come  from  the  lumbar  vertebrse  or  from  the  cervical  vertebrse.  A  cervical 
rib  is  due  to  excessive  development  of  the  costal  element  of  the  seventh  cervical  vertebra. 
In  nearly  two-thirds  of  the  reported  cases  the  condition  is  bilateral.  It  rarely  produces  symp- 
toms until  after  the  twentieth  year.  The  symptoms  are  a  superficial  pulsation  of  the  sub- 
clavian artery,  a  prominence  which  can  be  felt,  and  evidences  of  pressure  in  the  brachial  plexus 
(Carl  Beck).  Beck  divides  the  different  types  of  the  condition  as  follows:  (a)  Slight  degree: 
The  cervical  rib  reaches  beyond  the  transverse  process.  (6)  More  advanced :  The  cervical  rib 
reaches  beyond  the  transverse  process,  either  with  a  free  end  or  touching  the  first  rib.  (c) 
Almost  complete:  The  connection  between  the  cartilage  of  the  first  rib  is  formed  either  by 
means  of  a  distinct  band  or  by  the  end  of  its  long  body,  {d)  Complete:  It  has  become  a  true 
rib  and  possesses  a  true  cartilage  which  unites  with  the  cartilage  of  the  first  rib.'  A  very  rare 
condition  is  a  rib  from  the  sixth  cervical  vertebra.  The  diagnosis  is  confirmed  by  the  .r-rays. 
The  treatment  of  cervical  rib  is  excision. 

Fracture  of  the  costal  cartilages  may  also  take  place,  though  it  is  a  comparatively  rare  injury. 

The  thorax  is  frequently  found  "to  be  altered  in  shape  in  certain  diseases.  The  shape 
of  the  thorax  in  those  suffering  from  rhachitis  is  produced  chiefly  by  atmospheric  pressure. 
The  balance  between  the  air  on  the  inside  of  the  thorax  and  the  air  on  the  outside  during 
some  stage  of  respiration  is  not  equal,  the  preponderance  being  in  favor  of  the  air  outside; 
and  this,  acting  on  the  softened  ribs,  causes  them  to  be  forced  in  at  the  junction  of  the  carti- 
lages with  the  bones,  which  is  the  weakest  part.  In  consequence  of  this  the  sternum  projects 
forward  with  a  deep  depression  on  either  side  caused  by  the  sinking  in  of  the  softened  ribs. 
The  depression  is  less  on  the  left  side,  on  account  of  the  rijas  being  supported  by  the  heart.  The 
condition  is  known  as  pigeon-h-east.  The  lower  ribs,  however,  are  not  involved  in  this  deform- 
ity, as  they  are  prevented  from  falling  in  by  the  presence  of  the  stomach,  liver,  and  spleen.  And 
when  the  liver  and  spleen  are  enlarged,  as  they  sometimes  are  in  rhachitis,  the  lower  ribs  may  be 
pushed  outward;  this  causes  a  transverse  constriction  just  above  the  costal  arch.  The  anterior 
extremities  of  the  ribs  are  usually  enlarged  in  rhachitis,  giving  rise  to  what  has  been  termed  the 
rhachitio  rosary.  The  phthisical  chest  is  often  long  and  narrow,  flattened  from  before  backward, 
and  with  great  obliquity  of  the  ribs  and  projection  of  the  scapute.  In  pulmonary  emphysrma 
the  thorax  is  enlarged  in  all  its  diameters,  and  presents  on  section  an  almost  circular  outline.  It 
has  received  the  name  of  the  barrel-shaped  chest.  In  severe  cases  of  lateral  curvature  of  the 
spine  the  thorax  becomes  much  distorted.  In  consequence  of  the  rotation  of  the  bodies  of  the 
vertebrre  which  takes  place  in  this  disease  the  ribs  opposite  the  convexity  of  the  thoracic  curve 
become  extremely  convex  behind,  being  thrown  out  and  bulging,  and  at  the  same  time  flattened 

'  Jour.  .\mer.  Med.  Assoc,  June  17,  1905. 


168  SPECIAL  ANATOMY  OF  THE  SKELETON 

in  front,  so  that  the  two  bends  of  the  same  rib  are  almost  parallel.  Coincident  with  this,  the 
ribs  on  the  opposite  side,  on  the  concavity  of  the  curve,  are  sunken  and  depressed  behind  and 
bulging  and  convex  in  front.  In  addition  to  this  the  ribs  become  occasionally  welded  together 
by  bony  material. 

The  ribs  are  frequently  the  seat  of  caries  leading  to  abscesses  and  sinuses,  which  may  burrow- 
to  a  considerable  extent  over  the  wall  of  the  thorax.  The  only  special  anatomical  point  in  con- 
nection with  abscesses  and  sinuses  is  that  care  must  be  taken  in  dealing  with  them  that  the 
intercostal  space  is  not  punctured  and  the  pleural  cavity  opened  or  the  intercostal  vessels 
wounded,  as  the  necrosed  portion  of  bone  is  generally  situated  on  the  internal  surface  of  the  rib. 

In  cases  of  empyema  the  thorax  requires  opening  to  evacuate  the  pus.  There  is  considerable 
difference  of  opinion  as  to  the  best  position  to  do  this.  Probably  the  best  place  for  intercostal 
drainage  is  between  the  fifth  and  sixth  ribs,  in  or  a  little  in  front  of  the  mid-axillary  line.  This 
is  the  last  part  of  the  cavity  to  be  closed  by  the  expansion  of  the  lung;  it  is  not  thickly  covered 
by  soft  parts;  the  space  between  the  two  ribs  is  sufficiently  great  to  allow  of  the  introduction  of 
a  fair-sized  drainage  tube,  and  when  the  patient  is  confined  to  bed  he  does  not  lie  upon  the 
drainage  tube  as  he  does  when  the  opening  is  posterior.  Better  than  intercostal  drainage  in  the 
vast  majority  of  cases  is  rib  resection  and  drainage.  A  portion  of  the  fifth  or  sixth  rib  should 
be  removed  in  the  mid-axillaiy  line.  In  chronic  empyema  the  lung  becomes  shrunken  and  ad- 
herent, and  simple  drainage  will  not  bring  about  a  cure.  It  is  necessary  in  such  cases  to  do  an 
operation  that  will  permit  of  collapse  of  the  chest  wall.  Estlander  s  operation  consists  in  resect- 
ing a  portion  of  every  rib  which  overlies  the  cavity  of  the  empyema.  Schede's  operation  consists 
in  removing  ribs  from  the  second  rib  down  over  the  empyema  cavity.  The  ribs  are  removed 
from  cartilages  to  angles,  and  intercostal  muscles  and  the  parietal  layer  of  the  pleura  are  also 
taken  away.  Fowler  and  de  Lorme  not  only  practise  extensive  rib  resection  and  remove  the 
parietal  layer  of  the  pleura,  but  also  remove  pulmonary  pleura  (total  pleurectomy  or  pulmonary 
decortication). 

THE   EXTREMITIES. 

The  extremities,  or  limbs,  are  those  long,  jointed  appendages  of  the  body 
which  are  connected  to  the  trunk  by  one  end  and  free  in  the  rest  of  their  extent. 
They  are  four  in  number:  an  upper  or  thoracic  pair,  connected  with  the  thorax 
through  the  intervention  of  the  shoulder  and  subservient  mainly  to  prehension; 
and  a  lower  or  pelvic  pair,  connected  with  the  pelvis,  intended  for  support  and 
locomotion.  Both  pairs  of  limbs  are  constructed  after  one  common  type,  so  that 
they  present  numerous  analogies,  while  at  the  same  time  certain  differences  are 
observed  between  the  upper  and  lower  pair,  dependent  on  the  peculiar  offices 
they  have  to  perform. 

The  bones  by  which  the  upper  and  lower  limbs  are  attached  to  the  trunk  are 
named,  respectively,  the  shoulder  and  pelvic  girdles,  and  they  are  constructed  on  the 
same  general  type,  though  presenting  certain  modifications  relating  to  the  diflerent 
uses  to  which  the  upper  and  lower  limbs  are  respectively  applied.  The  shoulder 
girdle  is  formed  by  the  scapula  and  clavicles,  and  is  imperfect  in  front  and  behind. 
In  front,  however,  the  girdle  is  completed  by  the  upper  end  of  the  sternum,  with 
which  the  inner  extremities  of  the  clavicle  articulate.  Behind,  the  girdle  is  widely 
imperfect  and  the  scapula  is  connected  to  the  trunk  by  muscles  only.  The  pelvic 
girdle  is  formed  by  the  innominate  bones,  and  is  completed  in  front  through  the 
symphysis  pubis,  at  which  the  two  innominate  bones  articulate  with  each  other. 
It  is  imperfect  behind,  but  the  intervening  gap  is  filled  in  by  the  upper  part  of 
tlie  sacrum.  The  pelvic  girdle,  therefore,  presents,  with  the  sacrum,  a  complete 
ring,  massive  and  comparatively  rigid,  in  marked  contrast  to  the  lightness  and 
mobility  of  the  shoulder  girdle. 

THE  UPPER  EXTREMITY. 

The  bones  of  the  upper  extremity  consist  of  the  clavicle  and  scapula  (pectoral 
girdle),  the  humerus  (arm),  the  radius  and  ulna  (forearm),  the  carpal  bones 
(wrist),  the  metacarpal  bones  (palm),  and  the  phalanges  (digits). 


THE  CLA  VICLE,   OB  COLLAR  BONE  ](J9 

THE  SHOULDER  GIRDLE. 

The  shoulder  girdle  consists  of  the  clavicle  and  the  scapula. 

The  Clavicle,  or  Collar  Bone  (Clavicula). 

The  clavicle  forms  the  anterior  portion  of  the  shoulder  girdle.  It  is  a  long 
bone,  curved  somewhat  like  the  italic  letter  /,  and  placed  nearly  horizontally  at 
the  upper  and  anterior  part  of  the  thorax,  immediately  over  the  first  rib.  It 
articulates  by  its  inner  extremity  with  the  upper  border  of  the  sternum,  and  by 
its  outer  extremity  with  the  acromion  process  of  the  scapula,  serving  to  sustain 
the  upper  extremity  in  the  various  positions  which  it  assumes,  while  at  the  same 
time  it  allows  of  great  latitude  of  motion  in  the  arm.'  It  presents  a  double  curva- 
ture when  looked  at  in  front,  the  convexity  being  forward  at  the  sternal  end  and 
the  concavity  at  the  scapular  end.  Its  outer  third  is  flattened  from  above  downward, 
and  extends,  in  the  natural  position  of  the  bone,  from  a  point  opposite  the  cora- 
coid  process  to  the  acromion.  Its  inner  two-thirds  are  of  a  prismatic  form, 
and  extend  from  the  sternum  to  a  point  opposite  the  coracoid  process  of  the  scapula. 

Outer  or  Flattened  Portion. — The  outer  third  is  flattened  from  above  down- 
ward, so  as  to  present  two  surfaces,  an  upper  and  a  lower;  and  two  borders,  an 
anterior  and  a  posterior. 

Surfaces. — The  upper  surface  is  flat,  rough,  marked  by  impressions  for  the 
attachment  of  the  Deltoid  in  front  and  the  Trapezius  behind;  between  these  two 
impressions  a  small  portion  of  the  bone  is  subcutaneous.  The  under  surface  is 
flattened.  At  its  posterior  border,  a  little  external  to  the  point  where  the  pris- 
matic joins  with  the  flattened  portion,  is  a  rough  eminence,  the  conoid  tubercle 
(tuberositas  coracoidea) ;  this,  in  the  natural  position  of  the  bone,  surmoimts  the 
coracoid  process  of  the  scapula  and  gives  attachment  to  the  conoid  ligament. 
From'  this  tubercle  an  oblique  line,  occasionally  a  depression,  passes  forward 
and  outward  to  near  the  outer  end  of  the  anterior  border;  it  is  called  the  oblique 
line  or  trapezoid  ridge,  and  aflfords  attachment  to  the  trapezoid  ligament. 

Borders. — The  anterior  border  is  concave,  thin,  and  rough,  and  gives  attachment 
to  the  Deltoid;  it  occasionally  presents,  at  its  inner  end,  at  the  commencement  of 
the  deltoid  impression,  a  tubercle,  the  deltoid  tubercle.  The  posterior  border  is 
convex,  rough,  broader  than  the  anterior,  and  gives  attachment  to  the  Trapezius. 

Inner  or  Prismatic  Portion. — The  prismatic  portion  forms  the  inner  two- 
thirds  of  the  bone.  It  is  curved  so  as  to  be  convex  in  front,  concave  behind,  and 
is  marked  by  three  borders,  separating  three  surfaces. 

Borders. — The  anterior  border  is  continuous  with  the  anterior  margin  of  the  flat 
portion,  and  separates  the  anterior  surface  from  the  inferior;  at  the  inner  half 
of  the  clavicle  it  forms  the  lower  boundary  of  an  elliptical  space  for  the  attach- 
ment of  the  clavicular  portion  of  the  Pectoralis  major,  and  approaches  the  pos- 
terior border  of  the  bone;  it  coincides  with  the  anterior  margin  of  the  subclavian 
groove.  The  superior  border  is  continuous  with  the  posterior  margin  of  the  flat 
portion,  and  separates  the  anterior  from  the  posterior  surface.  At  its  commence- 
ment it  is  smooth  and  rounded,  becomes  rough  toward  the  inner  third  for  tlie 
attachment  of  the  Sternomastoid  muscle,  and  terminates  at  the  upper  angle  of 
the  sternal  extremity.     The  posterior  or  subclavian  border  separates  the  posterior 

>  The  clavicle  acts  especially  as  a  fulcrum  to  enable  the  muscles  to  give  lateral  motion  to  the  arm.  It  is 
accordingly  absent  in  those  animals  in  which  the  fore  limbs  are  used  only  for  progression,  but  is  present  for  the 
most  part  in  those  animals  in  which  the  anterior  extremities  are  clawed  and  used  for  prehension,  though  m  some 
of  them— as,  for  instance,  in  a  large  number  of  the  carnivora— it  is  merely  a  rudimentary  bone  suspended  among 
the  muscles,  and  not  articulating  with  the  scapula  or  sternum. 


170 


SPECIAL  ANA  TOMY  OF  THE  SKELETON 


from  the  inferior  surface,  and  extends  from  the  conoid  tubercle  to  the  rhomboid 
impression.  It  forms  the  posterior  boundary  of  the  groove  for  the  Subclavius 
muscle,  and  gives  attachment  to  a  layer  of  cervical  fascia  covering  the  Omohyoid 
muscle. 

Surfaces. — The  anterior  surface  is  included  betw^een  the  superior  and  anterior 
borders.  It  is  directed  forward  and  a  little  upward  at  the  sternal  end,  outward 
and  still  more  upward  at  the  acromial  extremity,  where  it  becomes  continuous 
with  the  upper  surface  of  the  flat  portion.  Externally,  it  is  smooth,  convex, 
nearly  subcutaneous,  being  covered  only  by  the  Platysma;  but,  corresponding 
to  the  inner  half  of  the  bone,  it  is  divided  by  a  more  or  less  prominent  line  into 
two  parts — a  lower  portion,  elliptical  in  form,  rough,  and  slightly  convex,  for  the 
attachment  of  the  Pectoralis  major;  and  an  upper  part,  which  is  rough,  for 
the  attachment  of  the  Sternomastoid.     Between  the  two  muscular  impressions 


Aaonual  exfremiti/. 


Sternal  extremity. 


Fig.  136. — Left  clavicle.     Superior  surface. 


Capsidar 
ligament 


Fig.  137. — Left  clavicle.     Inferior  surface. 


is  a  small  subcutaneous  interval.  The  posterior  or  cervical  surface  is  smooth, 
flat,  and  looks  backward  toward  the  root  of  the  neck.  It  is  limited,  above,  by  the 
superior  border;  below,  by  the  posterior  border;  internally,  by  the  margin  of  the 
sternal  extremity;  externally,  it  is  continuous  with  the  posterior  border  of  the  flat 
portion.  It  is  concave  from  within  outward,  and  is  in  relation,  by  its  lower  part, 
with  the  suprascapular  vessels.  This  surface,  at  about  the  junction  of  the  inner 
and  outer  curves,  is  also  in  close  relation  with  the  brachial  plexus  and  subclavian 
vessels.  It  gives  attachment,  near  the  sternal  extremity,  to  part  of  the  Sternohyoid 
muscle;  and  presents,  at  or  near  the  middle,  a  nutrient  foramen.  It  opens  into 
a  nutrient  canal,  which  is  directed  obliquely  outward  and  transmits  the  chief 
nutrient  artery  of  the  bone.  Sometimes  there  are  two  foramina  on  the  poste- 
rior surface,  or  one  on  the  posterior  and  one  on  the  inferior  surface.  The  infe- 
rior or  subclavian  surface  is  bounded,  in  front,  by  the  anterior  border;  behind, 


THE  CLAVICLE,    OR   COLLAR  BONE  171 

by  the  posterior  border.  It  is  narrow  internally,  but  gradually  increases  in 
width  externally,  and  is  continuous  with  the  under  surface  of  the  flat  portion. 
Commencing  at  the  sternal  extremity  may  be  seen  a  small  facet,  the  costal  facet, 
for  articulation  with  the  cartilage  of  the  first  rib.  This  is  continuous  with  the 
articular  surface  at  the  sternal  end  of  the  bone.  External  to  this  is  a  broad,  rough 
surface,  the  rhomboid  impression  (tuberositas  costalis),  rather  more  than  an  inch 
in  length,  for  the  attachment  of  the  costoclavicular  (rhomboidj  ligament.  The 
remaining  part  of  this  surface  is  occupied  by  a  longitudinal  groove,  the  subclavian 
groove,  broad  and  smooth  externally,  narrow  and  more  uneven  internally;  it  gives 
attachment  to  the  Subclavius  muscle,  and  by  its  margins  to  the  costocoracoid 
membrane,  which  splits  to  enclose  the  muscle.  Not  infrequently  this  groove  is 
subdivided  into  two  parts  by  a  longitudinal  line,  which  gives  attachment  to  the 
intermuscular  septum  of  the  Subclavius  muscle. 

Internal  or  Sternal  Extremity  (extremitas  sternalis). — The  internal  or  sternal 
extremity  of  the  clavicle  is  triangular  in  form,  directed  inward  and  a  little  down- 
ward and  forward;  and  presents  an  articular  facet  (fades  articularis  sternalis), 
concave  from  before  backward,  convex  from  above  downward,  which  articulates 
with  the  sternum  through  the  intervention  of  an  intra-articular  fibrocartilage; 
the  circumference  of  the  articular  surface  is  rough,  for  the  attachment  of  numer- 
ous ligaments.  The  posterior  border  of  this  surface  is  prolonged  backward,  so 
as  to  increase  the  size  of  the  articular  facet;  the  upper  border  gives  attachment 
to  the  intra-articular  fibrocartilage,  and  the  lower  border  is  continuous  with  the 
costal  facet  on  the  inner  end  of  the  inferior  surface,  which  articulates  with  the 
cartilage  of  the  first  rib. 

Outer  or  Acromial  Extremity  (extremitas  acromialis). — The  outer  or  acromial 
extremity,  directed  outward  and  forward,  presents  a  small,  flattened,  oval  facet, 
acromial  surface  (fades  articularis  acromialis),  which  looks  obliquely  downward, 
and  which  articulates  with  the  acromion  process  of  the  scapula.  The  circum- 
ference of  the  articular  facet  is  rough,  especially  above,  for  the  attachment  of 
the  acromioclavicular  ligaments. 

Peculiarities  of  the  Bone  in  the  Sexes  and  in  Individuals.— In  the  female  the  clavicle 
is  generally  shorter,  thinner,  less  curved,  and  .siiioolhei-  than  in  the  male;  in  the  female  it  is 
placed  almost,  if  not  quite,  horizontal,  while  in  the  male  it  inclines  slightly  downward  and  inward. 
In  those  persons  who  perform  considerable  manual  labor,  which  brings  into  constant  action  the 
muscles  connected  with  this  bone,  it  becomes  thicker  and  more  curved,  its  ridges  for  muscle 
attachment  become  prominently  marked.  The  right  clavicle  is  generally  longer,  thicker,  and 
rougher  than  the  left. 

Structure. — The  shaft,  as  well  as  the  extremities,  consists  of  cancellous  tissue,  invested  by  a 
coni|ia(t  layer  much  thicker  in  the  middle  than  at  either  end.    It  has  no  true  medullary  cavity. 

Development. — From  two  centres,  one  for  the  shaft  and  outer  extremity  and  one  for  the 
st<Tnal  cxtreraity.  The  primary  centre  for  the  shaft  appears  very  early,  before  that  of  any 
other  bone,  at  about  the  fifth  or  sixth  week  of  fetal  life.  The  secondary  centre  for  the  sternal 
end  makes  its  appearance  about  the  fifteenth  to  the  twentieth  year,  and  unites  with  the  rest  of 
the  bone  about  the  twenty-fifth  year. 

Articulations. — With  the  sternum,  scapula,  by  intra-articular  fibrocartilaginous  disks,  and 
with  tiie  cartilage  of  the  first  rib. 

Attachment  of  Muscles. — To  six — the  Sternomastoid,  Trapezius,  Pectoralis  major, 
Deltoid,  Subclavius,  and  Sternohyoid. 

Surface  Form. — The  clavicle  can  be  felt  throughout  its  entire  length,  even  in  persons  who 
are  very  fat.  Commencing  at  the  inner  end,  the  enlarged  sternal  extremity,  where  the  bone 
projects  above  the  upper  margin  of  the  sternum,  can  be  felt,  forming  with  the  sternum  and  the 
rounded  tendon  of  the  Sternomastoid  a  V-shaped  notch,  the  presternal  notch.  Passing  out- 
ward, the  shaft  of  the  bone  can  be  felt  immediately  under  the  skin,  with  its  convexity  forward 
in  the  inner  two-thirds,  the  surface  partially  obscured  above  and  below^  by  the  attachments  of 
the  Sternomastoid  and  Pectoralis  major  muscles.  In  the  outer  third  it  forms  a  gentle  curve 
backward,  and  terminates  at  the  outer  end  in  a  somewhat  enlarged  extremity  which  articulates 
with  the  acromial  process  of  the  scapula.  The  direction  of  the  clavicle  is  almost,  if  not  quite, 
horizontal  when  the  arm  is  lying  quietly  by  the  side,  though  in  well-developed  subjects  it  may 


172  SPECIAL  ANATOMY  OF  THE  SKELETON 

incline  a  little  upward  at  its  outer  end.    Its  direction  is,  however,  very  changeable,  altering  with 
the  varying  movements  of  the  shoulder-joint. 

Applied  Anatomy. — The  clavicle  is  the  most  he(\\iexit\y  fractured  of  any  single  bone  in  the 
body.  This  is  due  to  the  fact  that  it  is  much  exposed  to  violence,  and  is  the  only  bony  connec- 
tion between  the  upper  limb  and  the  trunk.  The  bone,  moreover,  is  slender,  and  is  very  super- 
ficial. The  bone  may  be  broken  by  direct  or  indirect  violence  or  by  muscular  action.  The  most 
common  cause  is,  however,  from  indirect  violence,  and  the  bone  then  gives  way  at  the  junction 
of  the  fi.xed  outer  one-third  with  the  movable  inner  two-thirds  of  the  bone.  This  is  the  weakest 
and  most  slender  part  of  the  bone.  The  fracture  is  generally  oblique,  and  the  displacement 
of  the  outer  fragments  is  inward,  away  from  the  surface  of  the  body;  hence,  compound  fracture 
of  the  clavicle  is  of  rare  occurrence.  The  inner  fragment,  as  a  rule,  is  little  displaced.  Beneath 
the  bone  the  main  vessels  of  the  upper  limb  and  the  great  nerve  cords  of  the  brachial  plexus 
lie  on  the  first  rib,  and  are  liable  to  be  wounded  in  fracture,  especially  in  fracture  from  direct 
violence,  when  the  force  of  the  blow  drives  the  broken  ends  inward.  Fortunately,  the  Subclavius 
muscle  is  interposed  between  these  structures  and  the  clavicle,  and  this  often  protects  them 
from  injury. 

The  clavicle  is  not  uncommonly  the  seat  of  sarcomatous  tumors,  rendering  the  operation 
of  excision  of  the  entire  bone  necessary.  This  operation  is  best  performed  by  exposing  the 
bone  freely,  disarticulating  at  the  acromial  end,  and  turning  it  inward.  The  removal  of 
the  outer  part  is  comparatively  easy,  but  resection  of  the  inner  part  is  fraught  with  difficulty, 
the  main  danger  being  the  risk  of  wounding  the  great  veins  which  are  in  relation  with  its  • 
under  surface. 

The  Scapula,  or  Shoulder  Blade. 

The  scapula  forms  the  back  part  of  the  shoulder  girdle.  It  is  a  large  flat  bone, 
triangular  in  shape,  situated  at  the  posterior  aspect  and  side  of  the  thorax,  between 
the  second  and  seventh  or  sometimes  the  eighth  rib,  its  internal  border  or  base 
being  about  an  inch  from  and  nearly  but  not  quite  parallel  with  the  spinous  pro- 
cesses of  the  vertebrse,  so  that  it  is  rather  closer  to  them  above  than  below.  It 
presents  for  examination  two  surfaces,  three  borders,  and  three  angles. 

Surfaces. — The  anterior  or  ventral  surface  (fades  costalis)  (Fig.  138)  presents 
a  broad  concavity,  the  subscapular  fossa  (fossa  subscapular  is).  It  is  marked,  in 
the  inner  two-thirds,  by  several  oblique  ridges  (lineae  musculares),  which  pass 
outward  and  upward;  the  outer  third  is  smooth.  The  oblique  ridges  give  origin 
to  the  tendinous  intersections,  and  the  surfaces  between  them  to  the  fleshy  fibres, 
of  the  Subscapularis  muscle.  The  outer  third  of  the  fossa  is  smooth,  is  covered 
by,  but  does  not  afford  attachment  to,  the  fibres  of  this  muscle.  This  surface  is 
separated  from  the  internal  border  by  a  smooth,  triangular  margin  at  the  supe- 
rior and  inferior  angles,  and  in  the  interval  between  these  by  a  narrow  edge  which 
is  often  deficient.  This  marginal  surface  aft'ords  attachment  throughout  its  entire 
extent  to  the  Serratus  magnus  muscle.  The  subscapular  fossa  presents  a  trans- 
verse depression  at  its  upper  part,  where  the  bone  appears  to  be  bent  on  itself, 
forming  a  considerable  angle,  called  the  subscapular  angle,  thus  giving  greater 
strength  to  the  body  of  the  bone  from  its  arched  form,  while  the  summit  of  the 
arch  serves  to  support  the  spine  and  acromion  process.  It  is  in  this  situation 
that  the  fossa  is  deepest,  so  that  the  thickest  part  of  the  Subscapularis  muscle 
lies  in  a  line  perpendicular  to  the  plane  of  the  glenoid  cavity,  and  must  conse- 
quently operate  most  effectively  on  the  head  of  the  humerus,  which  is  contained 
in  that  cavity. 

The  posterior  or  dorsal  surface  (fades  dorsal  is)  (Fig.  139)  is  arched  from  above 
downward,  alternately  concave  and  convex  from  side  to  side.  It  is  subdivided 
unequally  into  two  parts  by  the  spine;  the  portion  above  the  spine  is  called  the 
supraspinous  fossa,  and  that  below  it  the  infraspinous  fossa. 

The  supraspinous  fossa  (fossa  supraspinata),  the  smaller  of  the  two,  is  concave, 
smooth,  and  broader  at  the  vertebral  than  at  the  humeral  extremity.  It  affords 
attachment  by  its  inner  two-thirds  to  the  Supraspinatus  muscle. 

The  infraspinous  fossa  (fossa  infraspinata)  is  much  larger  than  the  preceding; 


THE  SCAPULA,'  OR  SHOULDER  BLADE 


173 


toward  its  vertebral  margin  a  shallow  concavity  is  seen  at  its  upper  part;  its  centre 
presents  a  prominent  convexity,  while  toward  the  axillary  border  is  a  deep  groove 
which  runs  from  the  upper  toward  the  lower  part.  The  inner  two-thirds  of  this 
surface  affords  origin  to  the  Infraspinatus  muscle;  the  outer  third  is  only  covered 
by  it,  without  giving  attachment  to  its  fibres.  This  surface  is  separated"  from  the 
axillary  border  by  an  elevated  ridge,  which  runs  from  the  lower  margin  of  the  glenoid 


Coraco-aCTora  ial 
ligament 


Fig.  138. — Left  scapula.     Anterior  surface  or  venter. 

cavity  downward  and  backward  to  the  internal  border,  about  an  inch  above  the 
inferior  angle.  The  ridge  serves  for  the  attachment  of  a  strong  aponeurosis  which 
separates  the  Infraspinatus  from  the  two  Teres  muscles.  The  surface  of  bone 
between  this  line  and  the  axillary  border  is  narrow  in  the  upper  two-thirds  of  its 
extent,  and  traversed  near  its  centre  by  a  groove  for  the  passage  of  the  dorsalis 
scapulae  vessels;  it  affords  origin  to  the  Teres  minor  muscle.      Its  lower  third 


174 


SPECIAL  ANATOMY  OF  THE  SKELETON 


presents  a  broader,  somewhat  triangular  surface,  which  gives  origin  to  the  Teres 
major,  and  over  which  the  I>atissimus  dorsi  glides;  sometimes  the  latter  muscle 
takes  origin  by  a  few  fibres  from  this  part.  The  broad  and  narrow  portions  of 
bone  above  alluded  to  are  separated  by  an  oblique  line  which  runs  from  the  axillary 
border,  downward  and  backward,  to  meet  the  elevated  ridge;  to  it  is  attached  the 
aponeurosis  separating  the  two  Teres  muscles  from  each  other. 


Coracohumeral 
ligament 


Coracoacromial  ligament 
Trapezoid  ligament 
Conoid  ligament 


Fig.  139.— Left  scapula 


Posterior  surface  or  dorsum. 


The  spine  (spina  scapulae)  is  a  prominent  plate  of  bone  which  crosses  obliquely 
the  inner  four-fifths  of  the  dorsum  of  the  scapula  at  its  upper  part,  and  separates 
the  supra-  from  the  infraspinous  fossa;  it  commences  at  the  vertebral  border  by  a 
smooth,  triangular  surface,  over  which  the  Trapezius  glides,  and;  gradually  be- 
coming more  elevated  as  it  passes  outward,  terminates  in  the  acromion  process 
which  overhangs  the  shoulder-joint-     The  spine  is  triangular  and  flattened  from 


THE  SCAPULA,    OB  SHOULDER  BLADE  175 

above  downward,  its  apex  corresponding  to  the  vertebral  border,  its  base  (which 
is  directed  outward)  to  the  neck  of  the  scapula.  It  presents  two  surfaces  and  three 
borders.  Its  superior  surface  is  concave,  assists  in  forming  tiie  supraspinous 
fossa,  and  affords  attachment  to  part  of  the  Supraspinatus  muscle.  Its  inferior 
surface  forms  part  of  the  infraspinous  fossa,  gives  origin  to  part  of  the  Infraspi- 
natus muscle,  and  presents  near  its  centre  the  orifice  of  a  nutrient  canal.  Of  the 
three  borders,  the  anterior  is  attached  to  the  dorsum  of  the  bone;  the  posterior, 
or  crest  of  the  spine,  is  broad,  and  presents  two  lips  and  an  intervening  rough 
interval.  To  the  superior  lip  is  attached  the  Trapezius  to  the  extent  shown  in 
Fig.  139.  A  rough  tubercle  is  generally  seen  occupying  that  portion  of  the  spine 
which  receives  the  insertion  of  the  middle  and  inferior  fibres  of  this  muscle.  From 
the  inferior  Up,  throughout  its  whole  length,  arises  the  Deltoid.  The  interval 
between  the  lips  is  also  partly  covered  by  the  tendinous  fibres  of  these  muscles. 
The  external  border,  or  base,  the  shortest  of  the  three,  is  slightly  concave,  its  edge 
thick  and  round,  continuous  above  with  the  under  surface  of  the  acromion  process, 
below  with  the  neck  of  the  scapula.  The  narrow  portion  of  bone  external  to  this 
border,  and  separating  it  from  the  glenoid  cavity,  is  called  the  great  scapular  notch, 
and  serves  to  connect  the  supra-  and  infraspinous  fosste. 

The  acromion  process  (acromion)  is  a  large  and  somewhat  triangular  or  oblong 
process,  flattened  from  behind  forward,  directed  at  first  a  little  outward,  and  then 
curving  forward  and  upward,  so  as  to  overhang  the  glenoid  cavity.  Its  upper 
surface,  directed  upward,  backward,  and  outward,  is  convex,  rough,  and  gives 
origin  to  some  fibres  of  the  Deltoid,  and  in  the  rest  of  its  extent  it  is  subcutaneous. 
Its  under  surface  is  smooth  and  concave.  Its  outer  border  is  thick  and  irregular, 
and  presents  three  or  four  tubercles  for  the  tendinous  origins  of  the  Deltoid 
muscle.  Its  inner  margin,  shorter  than  the  outer,  is  concave,  gives  attachment 
to  a  portion  of  the  Trapezius  muscle,  and  presents  about  its  centre  a  small  oval 
surface  for  articulation  with  the  acromial  end  of  the  clavicle.  Its  apex,  which 
corresponds  to  the  point  of  meeting  of  these  two  borders  in  front,  is  thin,  and  has 
attached  to  it  the  coracoacromial  ligament. 

Margins,  or  Borders  of  the  Scapula. — The  superior  border  (margo  superior)  is 
the  shortest  and  thinnest  of  the  three  borders;  it  is  concave  and  extends  from  the 
internal  ang'e  to  the  coracoid  process.  At  its  outer  part  is  a  deep,  semicircular 
notch,  the  suprascapular  notch  (i.ncisura  scapxdae),  formed  partly  by  the  base 
of  the  coracoid  process.  The  notch  is  converted  into  a  foramen  by  the  supra- 
scapular ligament,  and  serves  for  the  passage  of  the  suprascapular  nerve.  Some- 
times this  foramen  is  entirely  surrounded  by  bone.  The  adjacent  margin  of  the 
superior  border  affords  attachment  to  the  Omohyoid  muscle. 

The  external  or  axillary  border  (margo  axillaris)  is  the  thickest  of  the  three.  It 
commences  above  at  the  lower  margin  of  the  glenoid  cavity,  and  inclines  obliquely 
downward  and  backward  to  the  inferior  angle.  Immediately  below  the  glenoid 
cavity  is  a  rough  impression,  the  infraglenoid  tubercle  {tuberositas  itifraglenoidalis), 
about  an  inch  in  length,  which  affords  origin  to  the  long  head  of  the  Triceps  muscle; 
in  front  of  this  is  a  longitudinal  groove,  which  extends  as  far  as  the  lower  third 
of  the  external  border  and  afl^ords  origin  to  part  of  the  Subscapularis  muscle. 
The  inferior  third  of  this  border,  which  is  thin  and  sharp,  serves  for  the  origin 
of  a  few  fibres  of  the  Teres  major  behind  and  the  Subscapularis  in  front. 

The  internal  or  vertebral  border  (margo  vertebralis)  is  the  longest  of  the  three, 
and  extends  from  the  internal  to  the  inferior  angle  of  the  bone.  It  is  arched,  is 
intermediate  in  thickness  between  the  superior  and  the  external  borders,  and  the 
portion  of  it  above  the  spine  is  bent  considerably  outward,  so  as  to  form  an  obtuse 
angle  with  the  lower  part.  The  internal  border  presents  an  anterior  lip,  a  posterior 
lip,  and  an  intermediate  space.  The  anterior  lip  affords  attachment  to  the  Serratus 
magnus;  the  posterior  lip,  an  origin  to  the  Supraspinatus  above  the  spine,  the 


176  SPECIAL  ANATOMY  OF  THE  SKELETON 

Infraspinatus  below;  to  the  interval  between  the  two  lips,  the  Levator  anguli 
scapulae  is  inserted;  above  the  triangular  surface  at  the  commencement  of  the  spine, 
the  Rhomboideus  minor  to  the  edge  of  that  surface;  the  Rhomboideus  major 
is  attached  by  means  of  a  fibrous  arch  connected  above  to  the  lower  part  of 
the  triangular  surface  at  the  base  of  the  spine,  and  below  to  the  lower  part  of  the 
posterior  border. 

Angles.— The  internal  angle  (angulus  medialis),  formed  by  the  junction  of  the 
superior  and  internal  borders,  is  thin,  smooth,  rounded,  somewhat  inclined 
outward,  and  gives  attachment  to  a  few  fibres  of  the  Levator  anguli  scapulae 
muscle. 

The  inferior  angle  (angulus  inferior),  thick  and  rough,  is  formed  by  the  union 
of  the  vertebral  and  axillary  borders,  its  posterior  surface  affording  origin  to  the 
Teres  major  and  frequently  to  a  few  fibres  of  the  Latissimus  dorsi. 

The  external  angle  {angulus  lateralis)  is  the  thickest  part  of  the  bone,  and  forms 
what  is  called  the  head  of  the  scapula.  The  head  presents  a  shallow,  pyriform, 
articular  surface,  the  glenoid  surface  (cavitas  glenoi'dalis) ,  the  longest  diameter 
of  which  is  from  above  downward,  and  its  direction  outward  and  forward.  It 
is  broader  below  than  above.  Just  above  it  is  a  rough  surface,  the  supra- 
glenoid  tubercle  {tuberositas  supraglenoidalis) ,  from  which  arises  the  long 
tendon  of  the  Biceps  muscle.  The  glenoid  cavity  is  covered  with  cartilage  in 
the  recent  state;  and  its  margins  are  slightly  raised  and  give  attachment  to  a 
fibrocartilaginous  structure,  the  glenoid  ligament,  by  which  its  cavity  is  deepened. 
The  neck  of  the  scapula  {collum  scapulae)  is  the  slightly  depressed  surface  which 
surrounds  the  head;  it  is  more  distinct  on  the  posterior  than  on  the  anterior  surface, 
and  below  than  above.  In  the  latter  situation  it  has  arising  from  it  a  thick  promi- 
nence, the  coracoid  process. 

The  coracoid  process  {processus  coracoideus)  is  a  thick,  curved  process  of  bone 
which  arises  by  a  broad  base  from  the  upper  part  of  the  neck  of  the  scapula;  it 
is  directed  at  first  upward  and  inward,  then,  becoming  smaller,  it  changes  its 
direction  and  passes  forward  and  outward.  The  ascending  portion,  flattened  from 
before  backward,  presents  in  front  a  smooth,  concave  surface  over  which  passes 
the  Subscapularis  muscle.  The  horizontal  portion  is  flattened  from  above 
downward,  its  upper  surface  is  convex  and  irregular;  its  under  surface  is  smooth; 
its  inner  border  is  rough,  and  gives  attachment  to  the  Pectoralis  minor;  its  outer 
border  is  also  rough  for  the  coracoacromial  ligament,  while  the  apex  is  embraced 
by  the  conjoined  tendon  of  origin  of  the  short  head  of  the  Biceps  and  of  the 
Coracobrachialis  and  gives  attachment  to  the  costocoracoid  ligament.  At  the 
inner  side  of  the  root  of  the  coracoid  process  is  a  rough  impression  for  the  attach- 
ment of  the  conoid  ligament;  and  running  from  it  obliquely  forward  and  outward 
on  the  upper  surface  of  the  horizontal  portion,  an  elevated  ridge  for  the  attachment 
of  the  trapezoid  ligament. 

Structure. — In  the  head,  processes,  and  all  the  thickened  parts  of  the  bone  the  scapula  is 
composed  of  cancellous  tissue  covered  by  compact  bone,  while  in  the  rest  of  its  extent  it  is  com- 
posed of  a  thin  layer  of  dense,  compact  tissue.  The  central  part  of  the  supraspinous  fossa  and 
the  upper  part  of  the  infraspinous  fossa,  but  especially  the  former,  are  usually  so  thin  as  to 
be  semitransparent;  occasionally  the  bone  is  found  wanting  in  this  situation,  and  the  adjacent 
muscles  come  into  contact. 

Development  (Fig.  140). — From  seven,  or  more  centres — one  for  the  body,  two  for  the 
coracoid  process,  two  for  the  acromion,  one  for  the  vertebral  border,  and  one  for  the  inferior 
angle.  Ossification  of  the  body  of  the  scapula  commences  about  the  second  month  of  fetal  life 
by  the  formation  of  an  irregular  quadrilateral  plate  of  bone  immediately  behind  the  glenoid 
cavity.  This  plate  extends  itself  so  as  to  form  the  chief  part  of  the  bone,  the  spine  growing 
up  from  its  posterior  surface  about  the  third  month.  At  birth  a  large  part  of  the  scapula  is 
osseous,  but  the  glenoid  cavity,  coracoid  and  acromion  processes,  the  posterior  border,  and 
inferior  angle  are  cartilaginous.      From  the  fifteenth  to  the  eighteenth  month  after  birth 


THE  SCAPULA,   OB  SHOULDER  BLADE 


177 


ossification  takes  place  in  the  middle  of  the  coracoid  process,  which  usually  becomes  joined  wilii 
the  rest  of  the  bone  at  the  time  when  the  other  centres  make  their  appearance.  Between  the 
fourteenth  and  twentieth  years  ossification  of  the  remaining  centres  takes  place  in  quick 
succession,  and  in  the  following  oviei-:  fir.-it,  in  the  root  of  the  coracoid  process,  in  the  form  of 
a  broad  scale;  second,  near  the  base  of  the  acromion  process;  third,  in  the  inferior  ande  and 
contiguous  part  of  the  posterior  hor Aev;  fourth,  near  the  extremity  of  the  acromion;  fifth, 
in  the  posterior  border.  The  acromion  process,  besides  being  formed  of  two  separate  nuclei, 
has  its  base  formed  by  an  extension  into  it  of  the  centre  of  ossification  which  belongs  to  the 
spine,  the  extent  of  which  varies  in  different  cases.  The  two  separate  nuclei  unite  and  then 
join  with  the  extension  from  the  spine.  These  various  epiphyses  become  joined  to  the  bone 
between  the  ages  of  twenty-two  and 
twenty-five  years.  Sometimes  fail- 
ure of  union  between  the  acromion 
process  and  spine  occurs,  the  junc- 
tion being  effected  by  fibrous  tissue 
or  by  an  imperfect  articulation;  in 
some  cases  of  supposed  fracture 
of  the  acromion  with  ligamentous 
union  it  is  probable  that  the  de- 
tached segment  was  never  united  to 
the  rest  of  the  bone.  The  upper 
third  of  the  glenoid  cavity  is  usually 
ossified  from  a  separate  centre  {suh- 
coracoid)  which  makes  its  appearance 
between  the  tenth  and  eleventh 
years.  Very  often,  in  addition,  an 
epiphysis  appears  for  the  lower  part 
of  the  glenoid  cavity. 

Articulations.  — With  the  hu- 
merus and  clavicle. 

Attachment  of  Muscles. — To 
seventeen — to  the  anterior  surface, 
theSubscapularis;  posterior  surface, 
Supraspinatus,  Infraspinatus;  spine. 
Trapezius,  Deltoid;  superior  border. 
Omohyoid;  vertebral  border,  Serra- 
tus  magnus.  Levator  anguli  scapulae, 
Rhomboideus,  minor  and  major; 
axillary  border.  Triceps,  Teres 
minor,  Teres  major;  apex  of  glen- 
oid cavity,  long  head  of  the  Biceps; 
coracoid  process,  short  head  of  the 
Biceps,  Coracobrachialis,  Pectoralis 
minor;  and  to  the  inferior  angle  oc- 
casionally a  few  fibres  of  the  Latissi- 
mus  dorsi. 

Surface  Form.— The  only  parts 
of  the  scapula  which  are  truly  sub- 
cutaneous are  the  spine  and  acro- 
mion process,  but,  in  addition  to  these,  the  coracoid  process,  the  internal  or  vertebral  border 
and  inferior  angle,  and,  to  a  less  extent,  the  axillary  border,  may  be  defined.  The  acro- 
mion process  and  spine  of  the  scapula  are  easily  felt  throughout  their  entire  length,  forming, 
with  the  clavicle,  the  arch  of  the  shoulder.  The  acromion  can  be  ascertained  to  be  connected 
to  the  clavicle  at  the  acromioclavicular  joint  by  running  the  finger  along  it,  its  position  being 
often  indicated  by  an  irregularity  or  bony  outgrowth  from  the  clavicle  close  to  the  joint.  The 
acromion  can  be  felt  forming  the  point  of  the  shoulder,  and  from  this  can  be  traced  backward  to 
join  the  spine  of  the  scapula.  The  place  of  junction  is  usually  denoted  by  a  prominence,  which 
is  sometimes  called  the  acromial  angle.  From  here  the  spine  of  the  scapula  can  be  felt  as  a 
prominent  ridge  of  bone,  marked  on  the  surface  as  an  oblique  depression,  which  becomes  less 
and  less  distinct,  and  terminates  a  little  external  to  the  spinous  processes  of  the  vertebra?.  Its 
termination  is  usually  indicated  by  a  slight  dimple  in  the  skin  on  a  level  with  the  interval  be- 
tween the  third  and  fourth  thoracic  spines.  Below  this  point  the  vertebral  border  of  the  scapula 
may  be  traced,  running  downward  and  outward,  and  thus  diverging  from  the  vertebral  spines, 
to  the  inferior  angle  of  the  bone,  which  can  be  recognized,  although  covered  by  the  Latissimus 
dorsi  muscle.  From  this  angle  the  axillary  border  can  usually  be  traced  through  this  thick 
muscular  covering,  forming,  with  the  muscles,  the  posterior  fold  of  the  axilla.    The  coracoid 


ifenof 


Fig.  140. — Plan  of  the  development  of  the  scapula.  From 
seven  centres.  The  epiphyses  (except  one  for  the  coracoid  pro- 
cess) appear  from  fifteen  to  seventeen  years,  and  unite  between 
twenty-two  and  twenty-five  years  of  age. 


178  SPECIAL  ANA  TOMY  OF  THE  SKELETON 

process  may  be  felt  about  an  inch  below  the  junction  of  the  middle  and  outer  thirds  of  the 
clavicle.  Here  it  is  covered  by  the  anterior  border  of  the  Deltoid  and  lies  a  little  to  the  outer 
side  of  a  slight  depression  which  corresponds  to  the  interval  between  the  Pectoralis  major 
and  Deltoid  muscles.  When  the  arms  are  hanging  by  the  side,  the  upper  angle  of  the  scapula 
corresponds  to  the  upper  border  of  the  second  rib  or  the  interval  between  the  first  and  second 
thoracic  spines,  the  inferior  angle  to  the  upper  border  of  the  eighth  rib  or  the  interval  between 
the  seventh  and  eighth  thoracic  spines. 

Applied  Anatomy. — Fractures  of  the  body  of  the  scapula  are  rare,  owing  to  the  mobility  of 
the  bone,  the  thick  layer  of  muscles  \>y  which  it  is  encased  on  both  surfaces,  and  the  elasticity  of 
the  ribs  on  which  it  rests.  Fracture  of  the  neck  of  the  bone  is  also  uncommon.  The  most  fre- 
quent course  of  a  line  of  fracture  of  the  neck  is  from  the  suprascapular  notch  to  the  infraglenoid 
tubercle  (surgical  neck),  and  it  derives  its  principal  interest  from  its  simulation  to  a  subglenoid 
dislocation  of  the  humerus.  The  diagnosis  can  be  made  by  noting  the  alteration  in  the  position 
of  the  coracoid  process.  A  fracture 'of  the  neck  external  to,  and  not  including,  the  coracoid 
process  (anatomical  neck)  is  said  to  occur,  but  it  is  exceedingly  doubtful  whether  such  an 
accident  ever  takes  place.  The  acromion  process  is  more  frequently  broken  than  any  other 
part  of  the  bone,  and  there  is  sometimes,  in  young  subjects,  a  separation  of  the  epiphysis.  It 
is  believed  that  many  of  the  cases  of  supposed  fracture  of  the  acromion,  with  fibrous  union, 
which  have  been  found  on  postmortem  examination  are  really  cases  of  imperfectly  united 
epiphysis.  Sir  Astley  Cooper  believed  that  most  fractures  of  this  bone  are  united  by  fibrous 
tissue,  and  the  cause  of  this  mode  of  union  is  the  difficulty  that  arises  in  keeping  the  fractured 
ends  in  constant  apposition.  The  coracoid  process  is  occasionally  broken  oft',  either  by  direct 
violence  or  perhaps,  rarely,  by  muscular  action. 

Tumors  of  various  kinds  grow  from  the  scapula.  Of  the  innocent  form  of  tumors,  probably 
the  osteomata  are  the  most  common. '  When  an  osteoma  grows  from  the  anterior  surface  of  the 
scapula,  as  it  sometimes  does,  it  is  of  the  compact  variety,  such  as  usually  grows  from  mem- 
brane-formed bones,  as  the  bones  of  the  skull.  This  would  appear  to  afford  evidence  that  this 
portion  of  the  bone  is  formed  from  membrane,  and  not,  like  the  rest  of  the  bone,  from  cartilage. 
Sarcomatous  tumors  sometimes  grow  from  the  scapula,  and  may  necessitate  removal  of  the  bone, 
with  or  without  amputation  of  the  upper  limb.  Removal  of  the  upper  limb  with  the  scapula  and 
the  outer  two-thirds  of  the  clavicle  is  known  as  the  mterscaqndothoracic  amputafion.  The  scapula 
may  be  partially  resected  or  completely  excised.  There  are  several  methods  of  complete  excision. 
The  bone  may  be  excised  by  a  T-shaped  incision,  and,  the  flaps  being  reflected,  the  removal  is 
commenced  from  the  vertebral  border,  so  that  the  subscapular  vessels  which  lie  along  the  axillary 
border  are  among  the  last  structures  divided,  and  can  be  at  once  secured. 


THE    ARM. 

The  arm  is  that  portion  of  the  upper  extremity  which  is  situated  between  the 
shoulder  and  the  elljow.     Its  skeleton  consists  of  a  single  bone,  the  humerus. 

The  Humerus,  or  Arm  Bone  (Figs.  141,  142). 

The  humerus  is  the  longest  and  largest  bone  of  the  upper  extremity;  it  presents 
for  examination  a  shaft  and  two  extremities. 

Upper  or  Proximal  Extremity. — The  upper  extremity  presents  a  large, 
rounded  head,  joined  to  tlie  shaft  by  a  constricted  portion,  called  the  neck,  and 
two  other  eminences,  the  greater  and  lesser  tuberosities. 

The  Head  (caput  humeri). — ^The  head,  nearly  hemispherical  in  form,^  is  dii'ected 
upward,  inward,  and  slightly  backward,  and  articulates  with  the  glenoid  surface 
of  the  scapula;  its  surface  is  smooth  and  coated  with  cartilage  in  the  recent  state. 
The  circumference  of  its  articular  surface  is  slightly  constricted,  and  is  termed 
the  anatomical  neck,  in  contradistinction  to  the  constriction  which  exists  below  the 
tuberosities.  The  latter  is  called  the  surgical  neck  (collum  chirurgicuvi) ,  as  it  is 
often  the  seat  of  fracture. 

The  anatomical  neck  (collum  anatomicum)  is  obliquely  directed,  forming  an 

1  Though  the  head  is  nearly  hemispherical  in  form,  its  margin,  as  Sir  G.  Humphry  has  shown,  is  by  no  means 
a  true  circle.  Its  greatest  measurement  is  from  the  top  of  the  bicipital  groove  in  a  direction  downward,  inward, 
and  backward.  Hence,  it  follows  that  the  greatest  elevation  of  the  arm  can  be  obtained  by  rolling  the  articular 
surface  in  this  direction — that  is  to  say,  obliquely  upward,  outward,  and  forward. 


THE  HUMERUS,   OB  ABM  BONE 


179 


Capsular  ligament 


[brevis]. 


Fig.  141. — Left  humerus.     Anterior  view. 


ISO  SPECIAL  ANATOMY  OF  THE  SKELETON 

obtuse  angle  with  the  shaft.  It  is  more  distinctly  marked  in  the  lower  half  of 
its  circumference  than  in  the  upper  half,  where  it  presents  a  narrow  groove, 
separating  tlie  head  from  the  tuberosities.  Its  circumference  affords  attachment 
to  the  capsular  ligament  and  is  perforated  by  numerous  vascular  foramina. 

The  Greater  Tuberosity  (tubercuhim  majus). — The  greater  tuberosity  is  situated 
on  the  outer  side  of  the  head  and  lesser  tuberosity.  Its  upper  surface  is  rounded 
and  marked  by  three  flat  facets,  separated  by  two  slight  ridges;  the  highest  facet 
gives  attachment  to  the  tendon  of  the  Supraspinatus;  the  middle  one,  to  the  Infra- 
spinatus ;  the  inferior  facet  and  the  shaft  of  the  bone  below  it,  to  the  Teres  minor. 
The  outer  surface  of  the  greater  tuberosity  is  convex,  rough,  and  continuous  \\ath 
the  outer  side  of  the  shaft. 

The  Lesser  Tuberosity  (t'uberculum  minus). — The  lesser  tuberosity  is  more 
prominent,  although  smaller  than  the  greater;  it  is  situated  in  front  of  the  head, 
and  is  directed  inward  and  forward.  Its  summit  presents  a  prominent  facet 
for  the  insertion  of  the  tendon  of  the  Subscapularis  muscle.  The  tuberosities 
are  separated  from  each  other  by  a  deep  groove,  the  bicipital  groove  (sulcus  inter- 
iuhercularis).  This  groove  lodges  the  long  tendon  of  the  Biceps  muscle,  accom- 
panied by  a  branch  of  the  anterior  circumflex  artery.  It  commences  above  be- 
tween the  two  tuberosities,  passes  obliquely  downward  and  a  little  inwai'd,  and 
terminates  at  the  junction  of  the  upper  with  the  middle  third  of  the  bone.  It  is 
deep  and  narrow  at  the  commencement,  and  becomes  shallow  and  a  little  broader 
as  it  descends.  In  the  recent  state  it  is  covered  with  a  thin  layer  of  cartilage, 
lined  by  a  prolongation  of  the  synovial  membrane  of  the  shoulder-joint,  and 
receives  the  tendon  of  insertion  of  the  Latissimus  dorsi  muscle. 

The  Shaft  (corpus  humeri). — The  shaft  of  the  humerus  is  almost  cylindrical 
in  the  upper  half  of  its  extent,  prismatic  and  flattened  below,  and  presents  three 
borders  and  three  surfaces  for  examination. 

The  anterior  border  runs  from  the  front  of  the  greater  tuberosity  above  to  the 
coronoid  depression  below,  separating  the  internal  from  the  external  surface. 
Its  upper  part  is  very  prominent  and  rough,  forms  the  outer  Up  of  the  bicipital 
groove,  and  serves  for  the  attachment  of  the  tendon  of  the  Pectoralis  major. 
About  its  centre  it  forms  the  anterior  boundary  of  the  rough  deltoid  impression  j 
below,  it  is  smooth  and  rounded,  affording  attachment  to  the  Brachialis  anticus. 
muscle. 

The  external  border  (iiiargo  lateralis)  runs  from  the  back  part  of  the  greater 
tuberosity  to  the  external  condyle,  and  separates  the  external  from  the  posterior 
surface.  It  is  rounded  and  indistinctly  marked  in  its  upper  half,  serving  for  the 
attachment  of  the  lower  part  of  the  insertion  of  the  Teres  minor  muscle,  and  below 
this  of  the  external  head  of  the  Triceps  muscle;  its  centre  is  traversed  by  a  broad, 
but  shallow,  oblique  depression,  the  musculospiral  groove  (sulcus  nervi  radialis); 
its  lower  part  is  marked  by  a  prominent,  rough  margin,  a  little  curved  from 
behind  forward,  the  external  supracondylar  ridge,  which  presents  an  anterior  lip 
for  the  attachment  of  the  Brachioradialis  above  and  Extensor  carpi  radialis 
longior  below,  a  posterior  lip  for  the  Triceps,  and  an  intermediate  space  for  the 
attachment  of  the  external  intermuscular  septum. 

The  internal  border  {margo  medialis)  extends  from  the  lesser  tuberosity  to  the 
internal  condyle.  Its  upper  third  is  marked  by  a  prominent  ridge,  forming 
the  internal  lip  of  the  bicipital  groove,  and  gives  attachment  to  the  tendon  of  the 
Teres  major.  About  its  centre  is  an  impression  for  the  attachment  of  the  Coraco- 
brachialis,  and  just  below  this  is  seen  the  entrance  of  the  nutrient  canal,  directed 
downward.  Sometimes  there  is  a  second  canal  situated  at  the  commencement 
of  the  musculospiral  groove,  for  a  nutrient  artery  derived  from  the  superior  pro- 
funda branch  of  tlie  brachial  artery.  The  inferior  third  of  this  border  is  raised 
into  a  slight  ridge,  the  internal  supracondylar  ridge,  which  becomes  very  prominent 


THE  HUMERUS,    OR  ARM  BONE 


181 


below;  it  presents  an  anterior  lip  for  the 
attachment  of  the  Brachialis  anticus  muscle, 
a  posterior  lip  for  the  internal  head  of  the 
Triceps  muscle,  and  an  intermediate  space 
for  the  attachment  of  the  internal  intermus- 
cular septum. 

The  external  surface  (fades  anterior  later- 
alis) is  directed  outward  above,  where  it  is 
smooth,  rounded,  and  covered  by  the  Del- 
toid muscle;  forward  and  outward  below, 
where  it  is  slightly  concave  from  above 
downward,  and  gives  origin  to  part  of  the 
Brachialis  anticus  muscle.  About  the  mid- 
dle of  this  surface  is  seen  a  rough,  triangular 
impression  for  the  insertion  of  the  Deltoid 
muscle,  deltoid  impression  {tuberositas  deltoi- 
dea),  a.nd  below  this  the  musculospiral  groove, 
directed  obliquely  from  behind  forward  and 
downward,  and  transmitting  the  musculo- 
spiral nerve  and  superior  profunda  artery. 

The  internal  surface  (fades  anterior  medi- 
alis),  less  extensive  than  the  external,  is 
directed  inward  above,  forward  and  inward 
below ;  at  its  upper  part  it  is  narrow  and 
forms  the  floor  of  the  bicipital  groove;  to 
it  is  attached  the  Latissimus  dorsi.  The 
middle  part  of  this  surface  is  slightly 
roughened  for  the  attachment  of  some  of 
the  fibres  of  the  tendon  of  insertion  of  the 
Coracobrachialis;  its  lower  part  is  smooth, 
concave  from  above  downward,  and  gives 
attachment  to  the  Brachialis  anticus  mus- 
cle.^ A  little  below  the  middle  of  the  shaft 
is  the  nutrient  foramen.  This  leads  into  a 
nutrient  canal,  which  is  directed  toward  the 
elbow-joint. 

The  posterior  surface  (fades  posterior) 
(Fig.  142)  appears  somewhat  twisted,  so 
that  its  upper  part  is  directed  a  little  inward, 
its  lower  part  backward  and  a  little  outward. 
Nearly  the  whole  of  this  surface  is  covered 
by  the  external  and  internal  heads  of  the 


•  A  sm;ill  hook-shaped  process  of  bone,  the  supracondylar 
process,  varying  from  i/io  to  3/4  of  an  inch  in  length,  is  not  in- 
frequently found  projecting  from  the  inner  surface  of  the 
shaft  of  the  humerus  two  inches  above  the  internal  condyle. 
It  is  curved  downward,  forward,  and  inward,  and  its 
pointed  extremity  is  connected  to  the  internal  border,  just 
above  the  inner  condyle,  by  a  ligament  or  fibrous  band, 
which  gives  origin  to  a  portion  of  the  Pronator  teres;  through 
the  arch  completed  by  this  fibrous  band  the  median  nerve 
and  brachial  artery  pass  when  these  structures  deviate 
from  their  usual  course.  Sometimes  the  nerve  alone  is 
transmitted  through  it,  or  the  nerve  may  be  accompanied  by 
the  ulnar  artery  in  cases  of  high  division  of  the  brachial.  A 
well-marked  groove  is  usually  found  behind  the  process  in 
which  the  nerve  and  artery  are  lodged.  This  space  is  anal- 
ogous to  the  supracondyloid  foramen  in  many  animals,  and 
probably  serves  in  them  to  protect  the  nerve  and  artery 
from  compression  during  the  contraction  of  the  muscles  in 
this  region. 


Fig.  142. — Left  humerus.     Posterior  surface. 


182  SPECIAL  ANATOMY  OF  THE  SKELETON 

Triceps,  the  former  of  which  is  attached  to  its  upper  and  outer  part,  the  latter  to 
its  inner  and  back  part,  the  two  being  separated  by  the  musculospiral  groove. 
The  Lower  or  Distal  Extremity  is  flattened  from  before  backward,  and  curved 
sHghtly  forward;  it  terminates  below  in  a  broad,  articular  surface  which  is  divided 
into  two  parts  by  a  slight  ridge.  Projecting  on  either  side  are  the  external  and 
internal  condyles.  By  some  anatomists  the  external  condyle  is  called  the  external 
epicondyle  and  the  internal  condyle  is  called  the  internal  epicondyle.  The  articular 
surface  extends  a  little  lower  than  the  condyles,  and  is  curved  slightly  forward,  so 
as  to  occupy  the  more  anterior  part  of  the  bone;  its  greatest  breadth  is  in  the 
transverse  diameter,  and  it  is  obliquely  directed,  so  that  its  inner  extremity  occupies 
a  lower  level  than  the  outer.  The  outer  portion  of  the  articular  surface  presents 
a  smooth,  rounded  eminence,  which  has  received  the  name  of  the  capitellum,  or 
radial  head  of  the  humerus  (capitulum  humeri) ;  it  articulates  with  the  cup-shaped 
depression  on  the  head  of  the  radius,  and  is  limited  to  the  front  and  lower  part  of 
the  bone,  not  extending  as  far  back  as  the  other  portion  of  the  articular  surface. 
On  the  inner  side  of  this  eminence  is  a  shallow  groove,  in  which  is  received  the 
inner  margin  of  the  head  of  the  radius.  Above  the  front  part  of  the  capitellum 
is  a  slight  depression,  the  radial  fossa  (fossa  radialis),  which  receives  the  anterior 
border  of  the  head  of  the  radius  when  the  forearm  is  flexed.  The  inner  portion 
of  the  articular  surface,  the  trochlea  (trochlea  humeri),  presents  a  deep  depression 
between  two  well-marked  borders.  This  surface  is  convex  from  before  backward, 
concave  from  side  to  side,  and  occupies  the  anterior,  lower,  and  posterior  parts 
of  the  bone.  The  external  border,  less  prominent  than  the  internal,  corresponds 
to  the  interval  between  the  radius  and  the  ulna.  The  internal  border  is  thicker, 
more  prominent,  and  consequently  of  greater  length,  than  the  external.  The 
grooved  portion  of  the  articular  surface  fits  accurately  within  the  greater  sigmoid 
cavity  of  the  ulna;  it  is  broader  and  deeper  on  the  posterior  than  on  the  anterior 
aspect  of  the  bone,  and  is  inclined  obliquely  from  behind  forward  and  from  without 
inward.  Above  the  front  part  of  the  trochlear  surface  is  seen  a  smaller  depression, 
the  coronoid  fossa  (J'ossa  coronoidea),  which  receives  the  coronoid  process  of  the 
ulna  during  flexion  of  the  forearm.  Above  the  back  part  of  the  trochlear  surface 
is  a  deep,  triangular  depression,  the  olecranon  fossa  (J'ossa  olecrani),  in  which 
is  received  the  summit  of  the  olecranon  process  in  extension  of  the  forearm. 
These  fossae  are  separated  from  one  another  by  a  thin,  transparent  lamina  of  bone, 
which  is  sometimes  perforated  by  a  foramen,  the  supratrochlear  foramen;  their 
upper  margins  afi'ord  attachment  to  the  anterior  and  posterior  ligaments  of  the 
elbow-joint,  and  they  are  lined,  in  the  recent  state,  by  the  synovial  membrane 
of  this  articulation.  The  articular  surfaces,  in  the  recent  state,  are  covered  with 
a  thin  layer  of  hyaline  cartilage.  The  external  condyle  (epicondi/his  lateralis) 
is  a  small,  tubercular  eminence,  less  prominent  than  the  internal,  curved  a  little 
forward,  and  giving  attachment  to  the  external  lateral  ligament  of  the  elbow- 
joint,  and  to  a  tendon  common  to  the  origin  of  some  of  the  Extensor  and  Supinator 
muscles.  The  internal  condyle  (epifrochlea  or  epicondyhis  medialis),  larger  and 
more  prominent,  is  directed  a  little  backward;  it  gives  attachment  to  the  internal 
lateral  ligament,  to  the  Pronator  teres,  and  to  a  tendon  common  to  the  origin  of 
some  of  the  Flexor  muscles  of  the  forearm.  The  ulnar  nerve  runs  in  a  groove, 
the  ulnar  groove  (sulcus  nervi  ulnaris),  at  the  back  of  the  internal  condyle,  or 
between  It  and  the  olecranon  process.  These  condyles  are  directly  continuous 
above  with  the  external  and  internal  supracondylar  ridges. 

Structure. — The  extremities  consist  of  cancellous  tissue,  covered  with  a  thin  compact  layer; 
the  shaft  is  composed  of  a  cylinder  of  compact  tissue,  thicker  at  the  centre  than  at  the  extremities, 
and  hollowed  out  by  a  large  medullary  canal,  which  extends  along  its  whole  length.  In  the 
head  of  the  humerus  the  plates  of  the  cancellous  tissue  are  arranged  in  curves  (Fig.  143), 
known  as  pressure  curves.     Most  of  the  bone  plates  are  at  right  angles  to  the  plane  of  the 


THE  HUMERUS,    OR  ARM  BONE 


]S3 


articular  surface  (the  lines  of  greatest  pressure),  and  they  are  bound  togetlier  l)y  other  bone 
fibres,  which  usually  correspond  to  the  plane  of  the  articulation  (the  lines  of  greatest  tension). 
This  arch-like  arrangement  strengthens  the  head  of  the  bone,  and  it  is  further  strengthened  by 
the  binding  fibres. 

Development. — From  eiyht  centres  (Fig.  144),  one  for  each  of  the  following  parts:  The 
shaft,  head,  each  tuberosity,  the  radial  head,  the  trochlear  portion  of  the  articular  surface,  and 
each  condyle.  The  nucleus  for  the  shaft  appears  near  the  centre  of  the  bone  in  the  eighth 
week,  and  soon  extends  toward  the  extremities.  At  birth  the  humerus  is  ossified  ncarjv  in  its 
whole  length,  the  extremities  remaining  cartilaginous.  During  the  first  year,  sometimes  even 
before  birth,  ossification  commences  in  the  head  of  the  bone,  and  during  the  third  year  the  centre 
for  the  greater  tuberosity  makes  its  appearance,  that  for  the  lesser  being  small  and  not  appearing 
until  tlie  fifth  year.  By  the  sixth  year  the  centres  for  the  head  and  tuberosities  have  increased  in 
size  and  become  joined,  so  as  to  form  a  single  large  epiphysis. 


Epiphyseal  line. 


_  >  of  head  and 
tuberosities  blend  at 
Bth  year,  and  unite 
with  shaft    at   20th 


Fig.  144. — Plan  of  the  development  of  the 
humerus  from  eight  centres. 


The  lower  end  of  the  humerus  is  developed  in  the  following  manner:  At  the  end  of  the  second 
year  ossification  commences  in  the  capitellum,  and  from  this  point  extends  inward,  so  as  to  form 
the  chief  part  of  the  articular  end  of  the  bone,  the  centre  for  the  inner  part  of  the  trochlea  not 
appearing  until  about  the  age  of  twelve.  Ossification  commences  in  the  internal  condyle  about 
the  fifth  year,  and  in  the  external  one  not  until  about  the  thirteenth  or  fourteenth  year.  About 
the  sixteenth  or  seventeenth  year  the  outer  condyle  and  both  portions  of  the  articulating  surface 
(which  have  already  joined)  unite  with  the  shafi ;  M  \\\r  rit^hieenth  year  the  inner  condyle  l)ecomes 
joined;  while  the  upper  epiphysis,  although  the  Hr.s(  formed,  is  not  united  until  about  the  twen- 
tieth year. 

Articulations. — With  the  glenoid  cavity  of  the  scapula  and  with  the  ulna  and  radius. 

Attachment  of  Muscles. — To  twenty-four — to  the  greater  tuberosity,  the  Supraspinafus, 
Infraspinatus,  and  Teres  minor;  to  the  lesser  tuberosity,  the  Subscapularis;  to  the  externa! 
bicipital  ridge,  the  Pectoralis  major;  to  the  internal  bicipital  ridge,  the  Teres  major;  to  the  bicip- 
ital groove,  the  Latissimus  dorsi;  to  the  shaft,  the  Deltoid,  Coracobrachialis,  Brachialis  anticus, 
external  and  internal  heads  of  the  Triceps;  to  the  internal  condyle,  the  Pronator  teres,  and  com- 
mon tendon  of  the  Fle.xor  carpi  radialis,  Palmaris  longus.  Flexor  sublimis  digitorum,  and  Flexor 
carpi  ulnaris;  to  the  external,  supracondylar  ridge,  the  Brachioradialis  and  Extensor  carpi  radi- 


184  SPECIAL  ANATOMY  OF  THE  SKELETON 

alls  longior;  to  the  external  condyle,  the  common  tendon  of  the  Extensor  carpi  radialis  brevior, 
Extensor  communis  digitorum,  Extensor  minimi  digiti,  Extensor  carpi  ulnaris,  and  Supinator 
[brevis];  to  the  back  of  the  external  condyle,  the  Anconeus. 

Surface  Form. — The  humerus  is  almost  entirely  clothed  by  the  muscles  which  surround  it, 
and  the  only  parts  of  this  bone  which  are  strictly  subcutaneous  are  small  portions  of  the  inter- 
nal and  external  condyles.  In  addition  to  these,  the  tuberosities  and  a  part  of  the  head  of  the 
bone  can  be  felt  under  the  skin  and  muscles  by  which  they  are  covered.  Of  these,  the  greater 
tuberosity'  forms  the  most  prominent  bony  point  of  the  shoulder,  extending  beyond  the  acromion 
process  and  covered  by  the  Deltoid  muscle.  It  influences  materially  the  surface  form  of  the 
shoulder.  It  is  best  felt  while  the  arm  is  lying  loosely  by  the  side;  if  the  arm  be  raised,  it  recedes 
from  under  the  finger.  The  lesser  tuberosity,  directed  forward  and  inward,  is  to  be  felt  to  the 
inner  side  of  the  greater  tuberosity,  just  below  the  acromioclavicular  joint.  Between  the  two 
tuberosities  lies  the  bicipital  groove.  This  can  be  defined  by  placing  the  finger  and  making 
firm  pressure  just  internal  to  the  greater  tuberosity;  then,  by  rotating  the  humerus,  the  groove 
will  be  felt  to  pass  under  the  finger  as  the  bone  is  rotated.  With  the  arm  abducted  from  the 
side,  by  pressing  deeply  in  the  axilla  the  lower  part  of  the  head  of  the  bone  is  to  be  felt.  On 
each  side  of  the  elbow-joint,  and  just  above  it,  the  internal  and  external  condyles  of  the  bone 
may  be  felt.  Of  these,  the  internal  is  the  more  prominent,  but  the  ridge  passing  upward  from 
it,  the  internal  supracondylar  ridge,  is  much  less  marked  than  the  external,  and,  as  a  rule,  is 
not  to  be  felt.  Occasionally,  however,  we  find  along  this  border  the  hook-shaped  process  men- 
tioned in  the  foot-note  on  page  181.  The  external  condyle  is  most  plainly  to  be  seen  diu-ing 
semiflexion  of  the  forearm,  and  its  position  is  indicated  by  a  depression  between  the  attachment 
of  the  adjacent  muscles.  From  it  is  to  be  felt  a  strong  bony  ridge  running  up  the  outer  border 
of  the  shaft  of  the  bone.  This  is  the  external  supracondylar  ridge;  it  is  concave  forward,  and 
corresponds  with  the  curved  direction  of  the  lower  extremity  of  the  humerus. 

Applied  Anatomy. — There  are  several  points  of  surgical  interest  connected  with  the  humerus. 
First,  as  regards  its  development.  The  upper  end,  though  the  first  to  ossify,  is  the  last  to 
join  the  shaft,  and  the  length  of  the  bone  is  mainly  due  to  growth  from  this  upper  epiphysis. 
Hence,  in  cases  of  amputation  of  the  arm  in  young  subjects  the  humerus  continues  to  grow  con- 
siderably, and  the  end  of  the  bone,  which  immediately  after  the  operation  was  covered  with  a 
thick  cushion  of  soft  tissue,  begins  to  project,  thinning  the  soft  parts  and  rendering  the  stump 
conical.  This  may  necessitate  another  operation,  which  consists  in  the  removal  of  a  couple  of 
inches  or  so  of  the  bone,  and  even  after  this  operation  a  recurrence  of  the  conical  stump  may 
take  place. 

There  are  several  points  of  surgical  interest  in  connection  with  fractures.  First,  as  regards 
their  causation,  the  bone  may  be  broken  by  direct  or  indirect  violence  like  the  other  long  bones, 
but,  in  addition  to  this,  it  is  probably  more  frecjuently  fractm-ed  by  muscular  action  than  any 
other  of  this  class  of  bone  in  the  body.  It  is  usually  the  shaft,  just  below  the  insertion  of  the 
Deltoid,  which  is  thus  broken.  Fractures  of  the  upper  end  may  take  place  through  the 
anatomical  neck,  through  the  surgical  neck,  or  separation  of  the  greater  tuberosity  may  occur. 
Fracture  of  the  anatomical  neck  is  a  very  rare  accident ;  in  fact,  it  is  doubted  by  some  whether  it 
ever  occurs.  These  fractures  are  usually  considered  to  be  intracapsular,  but  they  are  probably 
partly  within  and  partly  without  the  capsule,  as  the  lower  part  of  the  capsule  is  inserted  some 
little  distance  below  the  anatomical  neck,  while  the  upper  part  is  attached  to  it.  They  may  be 
impacted  or  nonimpacfed.  In  most  cases  there  is  little  or  no  displacement  on  account  of  the 
capsule,  in  whole  or  in  part,  remaining  attached  to  the  lower  fragment.  Separation  of  the  upper 
epiphysis  of  the  humerus  sometimes  occurs  in  the  young  subject,  and  is  marked  by  a  character- 
istic deformity  by  which  the  lesion  may  be  at  once  recognized.  This  consists  in  the  presence 
of  an  abrupt  projection  at  the  front  of  the  joint  a  short  distance  below  the  coracoid  process, 
caused  by  the  upper  end  of  the  lower  fragment.  In  fractures  of  the  shaft  of  the  huvterus  the 
lesion  may  take  place  at  any  point,  but  appears  to  be  more  common  in  the  lower  than  in  the 
upper  part  of  the  bone.  The  points  of  interest  in  connection  with  these  fractures  are:  (1)  That 
the  musculospiral  nerve  may  be  injured  as  it  lies  in  the  groove  on  the  bone,  or  may  become 
involved  in  the  callus  which  is  subsequently  thrown  out;  and  (2)  the  frequency  of  nonunion. 
This  is  believed  to  be  more  common  in  the  humerus  than  in  any  other  bone,  and  various  causes 
have  been  assigned  for  it.  It  would  seem  most  probably  to  be  due  to  the  difiiculty  that  there 
is  in  fixing  the  shoulder-joint  and  the  upper  fragment,  and  possibly  the  elbow-joint  and  lower 
fragment  also.  Other  causes  which  have  been  assigned  for  the  nonunion  are:  (1)  That  in  attempt- 
ing passive  motion  of  the  elbow-joint  to  overcome  any  rigidity  which  may  exist,  the  movement 
does  not  take  place  at  the  articulation,  but  at  the  seat  of  fracture;  or  that  the  patient,  in  con- 
sequence of  the  rigidity  of  the  elbow,  in  attempting  to  flex  or  extend  the  forearm  moves  the 
fragment  and  not  the  joint.  (2)  The  presence  of  small  portions  of  muscle  tissue  between  the 
broken  ends.  (3)  Want  of  support  to  the  elbow,  so  that  the  weight  of  the  arm  tends  to  drag  the 
lower  fragment  away  from  the  upper.  An  important  distinction  to  make  in  fractures  of  the 
loiver  end  of  the  humerus  is  between  those  that  involve  the  elbow-joint  and  those  which  do  not; 
the  former  are  always  serious,  as  they  may  lead  to  stiffness  of  the  joint  and  impairment  of  the 


THE  ULNA,   Oli  ELBOW  BONE  185 

utility  of  the  limb.  They  include  the  T-shaped  fracture  and  oblique  fractures  which  involve 
the  articular  surface.  The  fractures  which  do  not  involve  the  joint  are  the  transverse  above 
the  condyles  and  the  so-called  epitrochlear  fracture,  in  which  the  tip  of  the  internal  condyle 
is  broken  off,  genei-ally  by  direct  violence. 

Under  the  head  of  i-eparation  of  the  lower  epiphysis  two  separate  injuries  have  been  described: 
(1)  Where  the  whole  of  the  four  ossific  centres  which  form  the  lower  extremity  of  the  bone 
are  separated  from  the  shaft;  and  (2)  where  the  articular  portion  is  alone  separated,  the  two 
condyles  remaining  attached  to  the  shaft  of -the  bone.  The  epiphyseal  line  between  the  shaft 
and  lower  end  runs  across  the  bone  just  above  the  tips  of  the  condyles,  a  point  to  be  borne  in 
mind  in  performing  the  operation  of  excision.    Shortening  may  follow  epiphysitis. 

Tumors  originating  from  the  humerus  are  of  frequent  occurrence.  A  not  uncommon  place 
for  a  chondroma  to  grow  from  is  the  shaft  of  the  bone  somewhere  in  the  neighborhood  of  the 
insertion  of  the  deltoid.    Sarcomata  frequently  grow  from  this  bone. 


THE   FOREARM. 

The  forearm  is  that  portion  of  the  upper  extremity  which  is  situated  between 
tlie  elbow  and  the  wrist.  Its  skeleton  is  composed  of  two  bones,  the  ulna  and 
radius. 

The  Ulna,  or  Elbow  Bone  (Figs.  14-5,  147). 

The  ulna  is  a  long  bone,  prismatic  in  form,  placed  at  the  inner  side. of  the 
forearm,  parallel  with  the  radius.  It  is  the  larger  and  longer  of  the  two  bones. 
Its  upper  extremity,  of  great  thickness  and  strength,  forms  a  large  part  of  the 
articulation  of  the  elbow-joint;  it  diminishes  in  size  from  above  downward,  its 
lower  extremity  being  very  small,  and  excluded  from  the  wrist-joint  by  the  inter- 
position of  an  intra-articular  fibrocartilage.  It  is  divisible  into  a  shaft  and  two 
extremities. 

The  Upper  or  Proximal  Extremity,  the  strongest  part  of  the  bone,  presents 
for  examination  two  large,  curved  processes,  the  olecranon  process  and  the 
coronoid  process;  and  two  concave,  articular  cavities,  the  greater  and  lesser 
sigmoid  cavities. 

The  olecranon  process  {i •lecranon)  is  a  large,  thick,  curved  eminence  situated 
at  the  upper  and  back  part  of  the  ulna.  It  is  curved  forward  at  the  summit 
so  as  to  present  a  prominent  tip  which  is  received  into  the  olecranon  fossa  of  the 
humerus  in  extension  of  the  forearm,  its  base  being  contracted  where  it  joins  the 
shaft.  This  is  the  narrowest  part  of  the  upper  end  of  the  ulna.  The  posterior 
surface  of  the  olecranon,  directed  backward,  is  triangular,  smooth,  subcutaneous, 
and  covered  by  a  bursa.  Its  zipper  surface  is  of  a  quadrilateral  form,  marked 
behind  by  a  rough  impression  for  the  attachment  of  the  Triceps  muscle;  and  in 
front,  near  the  margin,  by  a  slight  transverse  groove  for  the  attachment  of  part 
of  the  posterior  ligament  of  the  elbow-joint.  Its  anterior  surface  is  smooth, 
concave,  covered  with  cartilage  in  the  recent  state,  and  forms  the  upper  and 
back  part  of  the  greater  sigmoid  cavity.  The  lateral  borders  present  a  continuation 
'  of  the  same  groove  that  was  seen  on  the  margin  of  the  superior  surface ;  they  serve 
for  the  attachment  of  ligaments — viz.,  the  back  part  of  the  internal  lateral  ligament 
internally,  the  posterior  ligament  externally.  To  the  inner  border  is  also  attached 
a  part  of  the  Flexor  carpi  ulnaris,  while  to  the  outer  border  is  attached  the  Anconeus 
muscle. 

The  coronoid  process  {processus  coronoideus)  is  a  triangular  eminence  of  bone 
which  projects  horizontally  forward  from  the  upper  and  front  part  of  the  ulna. 
Its  base  is  continuous  with  the  shaft,  and  of  considerable  strength;  so  much  so 
that  fracture  of  it  is  an  accident  of  rare  occurrence.  Its  apex  is  pointed,  slightly 
curved  upward,  and  is  received  into  the  coronoid  depression  of  the  hiuneriis  in 


186 


SPECIAL  ANATOMY  OF  THE  SKELETON 

Ulna. 


,  cr  a>i 


'C^imiiar  ligamtnt. 
Radius. 


PRONATOR  TERES 


Occasional  ongm  of   y. .  .   ^r 

rUEXOR  tONQUS    POLL  CIS     *'     /      \       \ 

V  1  \  I 


Radial  origin  of  flexor 

DIGITORUM 


Oapstdar 


Styloid  pi  ocess 


Styloid  process. 
Fig.  145, — Bones  of  the  left  forearm,     Antei'ior  view. 


THE  ULNA,   OB  ELBOW  BONE 


187 


Olecranon  process 

\ 


flexion  of  the  forearm.  Its  upper  surface  is  smooth,  concave,  and  forms  the  lower 
part  of  the  greater  sigmoid  cavity.  The  under  siirface  is  concave;  and  marked  by 
an  impression  internally  for  the  insertion  of  the  Brachialis  anticus.  At  the  junc- 
tion of  this  surface  with  the  shaft  is  a  rough  eminence,  the  tubercle  of  the  ulna 
(tuberositas  ulnae),  for  the  attachment  of  the  oblique  ligament  of  the  middle 
radio-ulnar  articulation.  Its  outer  surface  presents'  a  narrow,  oblong,  articular 
depression,  the  lesser  sigmoid  cavity.  The  inner  surface,  by  its  prominent 
free  margin,  serves  for  the  attachment  of  part  of  the  internal  lateral  ligament. 
At  the  front  part  of  this  surface  is  a  small,  rounded  eminence  for  the  attach- 
ment of  one  head  of  the  Flexor  sublimis  digitorum;  behind  the  eminence,  a 
depression  for  part  of  the  origin  of  the  Flexor  profundus  digitorum;  and,  descend- 
ing from  the  eminence,  a  ridge  which  gives  attachment  to  one  head  of  the  Pro- 
nator teres.  Generally,  the  Flexor  longus  pollicis  has  an  origin  from  the  lower 
part  of  the  coronoid  process  by  a  rounded  bundle  of  muscle  fibres. 

The  greater  sigmoid  cavity  (incisura  semilunaris)  is  a  semilunar  depression 
of  large  size,  formed  by  the  olecranon  and  coronoid  processes,  and  serving  for 
articulation  with  the  trochlear  surface  of  the 
humerus.  About  the  middle  of  either  lateral 
border  of  this  cavity  is  a  notch  which  con- 
tracts it  somewhat,  and  serves  to  indicate 
the  junction  of  the  two  processes  of  which 
it  is  formed.  The  cavity  is  concave  from 
above  downward,  and  divided  into  two 
lateral  parts  by  a  smooth,  elevated  ridge 
which  runs  from  the  summit  of  the  olecranon 
to  the  tip  of  the  coronoid  process.  Of  these 
two  portions,  the  internal  is  the  larger,  and 
is  slightly  concave  transversely;  the  external 
portion  is  convex  above,  slightly  concave  be- 
low. The  articular  surface,  in  the  recent 
state,  is  covered  with  a  thin  layer  of  hyaline 
cartilage. 

The  lesser  sigmoid  cavity  {incisura  radi- 
alis)  is  a  narrow,  oblong,  articular  depres- 
sion, placed  on  the  outer  side  of  the  coronoid 
process,  and  receives  the  lateral  articular  sur- 
face of  the  head  of  the  radius.  It  is  concave 
from  before  backward,  and  its  extremities, 
which  are  prominent,  serve  for  the  attach- 
ment of  the  orbicular  ligament.  In  the  recent  state  it  is  covered  with  a  thin  layer 
of  hyaline  cartilage. 

The  Shaft  (corpus  ulnae),  at  its  upper  part,  is  prismatic  in  form,  and  curved 
from  behind  forward  and  from  without  inward,  so  as  to  be  convex  behind  and 
externally;  its  central  part  is  quite  straight;  its  lower  part  rounded,  smooth,  and 
bent  a  little  outward;  it  tapers  gradually  from  above  downward,  and  presents 
for  examination  three  borders  and  three  surfaces. 

The  anterior  or  palmar  border  (marcjo  volaris)  commences  above  at  the  prominent 
inner  angle  of  the  coronoid  process,  and  terminates  below  in  front  of  the  styloid 
process.  It  is  well  marked  above,  smooth  and  rounded  in  the  middle  of  its  extent,' 
and  affords  origin  to  the  Flexor  profundus  digitorum;  its  lower  fourth,  marked 
off  from  the  rest  of  the  border  by  the  commencement  of  an  oblique  ridge  on  the 
anterior  surface,  serves  for  the  origin  of  the  Pronator  quadratus.  It  separates 
the  anterior  from  the  internal  surface. 

The  posterior  or  dorsal  border  (margo  dorsalis)  commences  above  at  the  apex 
of  the  triangular  subcutaneous  surface  at  the  back  part  of  the  olecranon,  and 


188 


SPECIAL  ANATOMY  OF  THE  SKELETON 

Ulna. 


Capsular  ligament 


LIMIS     DIGITORUM, 


■Capsular  ligament 


Fig.  147. — Bones  of  the  left  forearm.     Posterior  view. 


THE  ULNA,   OR  ELBO  W  BONE  1,S9 

terminates  below  at  the  back  part  of  the  styloid  process;  it  is  well  marked  in  the 
upper  three-fourths,  and  gives  origin  to  the  aponeurosis  common  to  the  Flexor 
carpi  ulnaris,  the  Extensor  carpi  ulnaris,  and  the  Flexor  profundus  digitonim 
muscles;  its  lower  fourth  is  smooth  and  rounded.  This  border  separates  the 
internal  from  the  posterior  surface. 

The  external  or  interosseous  border  (crista  interossea)  commences  above  by  the 
union  of  two  lines,  which  converge  one  from  each  extremity  of  the  lesser  sigmoid 
cavity,  enclosing  between  them  a  triangular  space  for  the  origin  of  part  of  the 
Supinator  [brevis],  and  terminates  below  at  the  middle  of  the. lower  extremity. 
Its  two  middle  fourths  are  very  prominent;  its  lower  fourth  is  smooth  and  rounded. 
This  border  gives  attachment  to  the  interosseous  membrane,  and  .separates  the 
anterior  from  the  posterior  surface. 

The  anterior  or  palmar  surface  {fades  volaris')  lies  between  the  anterior  and 
external  borders,  is  much  broader  above  than  below,  is  concave  in  the  upper  three- 
fourths  of  its  extent,  and  affords  origin  to  the  Plexor  profundus  digitorum;  its 
lower  fourth,  also  concave,  is  covered  by  the  Pronator  quadratus.  The  lower 
fourth  is  separated  from  the  remaining  portion  of  the  bone  by  a  prominent 
ridge  (pronator  ridge)  directed  obliquely  from  above  downward  and  inward; 
this  ridge  marks  the  extent  of  attachment  of  the  Pronator  quadratus.  At  the 
junction  of  the  upper  with  the  middle  third  of  the  bone  is  the  nutrient  foramen. 
It  opens  into  the  nutrient  canal,  which  is  directed  obliquely  inward  and  upward 
(proximally). 

The  posterior  or  extensor  surface  (fades  dorsalis)  is  bounded  externally 
by  the  interosseous  border,  internally  by  the  posterior  border,  and  is  directed 
backward  and  outward;  it  is  broad  and  concave  above,  somewhat  narrower  and 
convex  in  the  middle  of  its  course,  narrow,  smooth,  and  rounded  below.  It  pre- 
sents, above,  an  oblique  ridge,  which  runs  from  the  posterior  extremity  of  the 
lesser  sigmoid  cavity,  downward  to  the  posterior  border;  the  triangular  surface 
above  this  ridge  receives  the  insertion  of  the  Anconeus  muscle,  while  the  upper 
part  of  the  ridge  itself  aiYords  origin  to  the  Supinator.  The  surface  of  bone 
below  this  is  subdivided  by  a  longitudinal  ridge  into  two  parts;  the  internal  part 
is  smooth,  and  covered  by  the  Extensor  carpi  ulnaris;  the  external  portion,  wider 
and  rougher,  gives  origin  from  above  downward  to  part  of  the  Supinator,  the 
Extensor  ossis  metacarpi  pollicis,  the  Extensor  longus  pollicis,  and  the  Extensor 
indicis  muscles. 

The  internal  surface  (Jades  medialis)  is  broad  and  concave  above,  narrow  and 
convex  below.  It  gives  origin  by  its  upper  three-fourths  to  the  Flexor  profundus 
digitorum  muscle;  its  lower  fourth  is  subcutaneous.  The  anterior  and  the  inner 
surfaces  constitute  the  flexor  surface. 

The  Distal  or  Lower  Extremity  is  of  small  size,  and  excluded  from  the 
articulation  of  the  wrist-joint.  It  presents  for  examination  two  eminences,  tlie 
outer  and  larger  of  which  is  a  rounded,  articular  eminence,  termed  the  head 
(capitulum  ulnae),  the  inner,  narrower  and  more  projecting,  is  a  nonarticular 
eminence,  the  styloid  process  (processus  sti/loideus).  The  head  presents  an 
articular  facet,  part  of  which,  of  an  oval  form,  is  directed  downward,  and  plays 
on  the  upper  surface  of  the  triangular  fibrocartilage  which  separates  it  from  the 
wrist-joint;  the  remaining  portion,  directed  outward,  is  narrow,  convex,  and 
received  into  the  sigmoid  cavity  of  the  radius.  The  styloid  process  projects  from 
the  inner  and  back  part  of  the  bone,  and  descends  a  little  lower  than  the  head, 
terminating  in  a  rounded  summit,  which  affords  attachment  to  the  internal  lateral 
ligament  of  the  wrist.  The  head  is  separated  from  the  styloid  process  by  a 
depression  for  the  attachment  of  the  triangular  intra-articular  fibrocartilage;  and 
behind,  by  a  shallow  groove  for  the  passage  of  the  tendon  of  the  Extensor  carpi 
ulnaris. 


190 


SPECIAL  ANATOMY  OF  THE  SKELETON 


Appears  at^^ 
10th  year. 


Olecranon. 


-Joins  shaft  a 
16th  year. 


Stracture. — Similar  to  tliat  of  the  other  long  bones. 

Development. — From  thrive  centres — one  for  the  shaft,  one  for  the  inferior  extremity,  and 
one  for  the  olecranon  (Fig.  148).  Ossification  commences  near  the  middle  of  the  shaft  about 
the  eighth  week,  and  soon  extends  through  the  greater  part  of  the  bone.  At  birth  the  ends  are 
cartilaginous.  About  the  fourth  year  a  separate  osseous  nucleus  appears  in  the  middle  of  the 
head,  which  soon  extends  into  the  styloid  process.  About  the  tenth  year  ossific  material  appears 
in  the  olecranon  near  its  extremity,  the  chief  part  of  this  process  being  formed  from  an  extension 
of  the  shaft  of  the  bone  into  it.  At  about  the  sixteenth  year  the  upper  epiphysis  becomes  joined 
to  the  shaft,  and  at  about  the  twentieth  year  the  lower  one. 
Articulations. — With  the  humerus  and  radius. 

Attachment  of  Muscles. — To  sixteen:  To  the  olecranon,  the  Triceps,  Anconeus,  and  one 
head  of  the  Flexor  carpi  ulnaris.  To  the  coronoid  process,  the  Brachialis  anticus.  Pronator  teres. 
Flexor  sublimis  digitorum,  and  Flexor  profundus  digitorum; 
generally  also  the  Flexor  longus  pollicis.  To  the  shaft,  the 
Flexor  profundus  digitorum,  Pronator  quadratus,  Flexor  carpi 
ulnaris.  Extensor  carpi  ulnaris.  Anconeus,  Supinator  [brevis], 
Extensor  ossis  metacarpi  pollicis.  Extensor  longus  pollicis,  and 
Extensor  indicis. 

Surface  Form. — The  most  prominent  part  of  the  ulna  on 
the  surface  of  the  body  is  the  olecranon  process,  which  can 
always  be  felt  at  the  back  of  the  elbow-joint.  When  the  fore- 
arm is  flexed,  the  upper  quadrilateral  surface  can  be  felt, 
directed  backward;  during  extension  it  recedes  into  the  olec- 
ranon fossa,  and  the  contracting  fibres  of  the  triceps  prevent 
its  being  perceived.  At  the  back  of  the  olecranon  is  the 
smooth,  triangular,  subcutaneous  surface,  which  below  is 
continuous  with  the  posterior  border  of  the  shaft  of  the  bone, 
and  felt  in  every  position  of  the  forearm.  During  extension 
the  upper  border  of  the  olecranon  is  slightly  above  the  level 
of  the  internal  condyle,  and  the  process  itself  is  nearer  to  this 
condyle  than  the  outer  one.  Running  down  the  back  of  the 
forearm,  from  the  apex  of  the  triangular  surface  which  forms 
the  posterior  surface  of  the  olecranon,  is  a  prominent  ridge  of 
bone,  the  posterior  border  of  the  ulna.  This  may  be  felt 
throughout  the  entire  length  of  the  shaft  of  the  bone,  from  the 
olecranon  above  to  the  styloid  process  below.  As  it  passes 
down  the  forearm  it  pursues  a  sinuous  course  and  inclines  to 
the  inner  side,  so  that,  though  it  is  situated  in  the  middle  of 
the  back  of  the  limb  above,  it  is  on  the  inner  side  of  the  wrist 
at  its  termination.  It  becomes  rounded  off  in  its  lower  third, 
and  may  be  traced  below  to  the  small,  subcutaneous  surface  of 
the  st3'loid  process.  Internal  to  this  border  the  lower  fourth 
of  the  inner  surface  ma)'  be  felt.  The  styloid  process  may  be 
felt  as  a  prominent  tubercle  of  bone,  continuous  above  with  the  posterior  subcutaneous  border 
of  the  ulna,  and  terminating  below  in  a  blunt  apex,  which  lies  a  little  internal  and  behind,  but 
on  a  level  with,  the  wrist-joint.  The  styloid  process  is  best  felt  when  the  hand  is  in  the  same 
line  as  the  bones  of  the  forearm,  and  in  a  position  midway  between  supination  and  pronation. 
If  the  forearm  is  pronated  while  the  finger  is  placed  on  the  process,  it  will  be  felt  to  recede,  and 
another  prominence  of  bone  will  appear  just  behind  and  above  it.  This  is  the  head  of  the  ulna, 
which  articulates  with  thejower  end  of  the  radius  and  the  triangular  intra-articular  fibrocarti- 
lage,  and  now  projects  between  the  tendons  of  the  Extensor  carpi  ulnaris  and  the  Extensor 
minimi  dij;iti  muscles. 


8th' ^ 


Appears  aij 
Jfth  year. 


^Joins  shaft  at 
Both  year. 


Inferior  extremity. 

Fig,  148. — Plan  of  the  development 
of  the  ulna.     From  three  centres. 


The  Radius. 

The  radius  is  situated  on  the  outer  side  of  the  forearm,  lying  side  by  side  with  the 
ulna,  which  exceeds  it  in  length  and  size  (Fig.  145).  Its  upper  end  is  small,  and 
forms  only  a  small  part  of  the  elbow-joint;  but  its  lower  end  is  large,  and  forms 
the  chief  part  of  the  wrist.  It  is  one  of  the  long  bones,  prismatic  in  form,  slightly 
curved  longitudinally,  and,  like  other  long  bones,  has  a  shaft  and  two  extremities. 

The  Proximal  or  Upper  Extremity  presents  a  head,  neck,  and  tuberosity. 

The  head  (capituluni  radii)  is  of  a  cylindrical  form,  depressed  on  its  upper 
surface  into  a  shallow  cup  (fovea  capituli  radii),  which  articulates  with  the  capitel- 
lum  or  radial  head  of  the  humerus.     In  the  recent  state  it  is  covered  with  a  layer 


THE  RADIUS  191 

of  hyaline  cartilage  which  is  thinnest  at  its  centre.  Around  the  circumference  of 
the  head  is  a  smooth,  articular  surface  {circumferentia  articularis) ,  broad  internally, 
where  it  articulates  with  the  lesser  sigmoid  cavity  of  the  ulna;  narrow  in  the  rest 
of  its  circumference,  where  it  rotates  within  the  orbicular  ligament.  It  is  coated 
with  hyaline  cartilage  in  the  recent  state.  The  head  is  supported  on  a  round, 
smooth,  and  constricted  portion  of  bone,  called  the  neck  (collum  radii),  which 
presents,  behind,  a  slight  ridge,  for  the  attachment  of  part  of  the  Supinator 
[brevis].  Beneath  the  neck,  at  the  inner  and  front  aspect  of  the  bone,  is  a  rough 
eminence,  the  bicipital  tuberosity  {tuberositas  radii).  Its  surface  is  divided  into 
two  parts  by  a  vertical  line — a  posterior,  rough  portion,  for  the  insertion  of  the 
tendon  of  the  Biceps  muscle;  and  an  anterior,  smooth  portion,  on  which  a  bursa 
is  interposed  between  the  tendon  and  the  bone. 

The  Shaft  {corpus  radii)  is  prismoid  in  form,  narrower  above  than  below,  and 
slightly  curved,  so  as  to  be  convex  outward.  It  presents  three  surfaces,  separated 
by  three  borders. 

The  anterior  border  {marcjo  volaris)  extends  from  the  lower  part  of  the  tuber- 
osity above  to  the  anterior  part  of  the  base  of  the  styloid  process  below.  It 
separates  the  anterior  from  the  external  surface.  Its  upper  third  is  very  promi- 
nent; and  from  its  oblique  direction,  downward  and  outward,  has  received  the 
name  of  the  oblique  line  of  the  radius.  It  gives  insertion  externally  at  the 
Supinator  [brevis]  internally,  it  limits  the  origin  of  the  Flexor  longus  pollicis,  and 
between  these,  arising  from  it,  is  the  radial  origin  of  the  Flexor  sublimis  digitorum. 
The  middle  third  of  the  anterior  border  is  indistinct  and  rounded.  Its  lower 
fourth  is  sharp,  prominent,  affords  attachment  to  the  Pronator  quadratus  and  to  the 
posterior  annular  ligament  of  the  wrist,  and  terminates  in  a  small  tubercle  at  the 
base  of  the  styloid  process,  into  which  is  inserted  the  tendon  of  the  Brachioradialis. 

The  posterior  border  {margo  dorsalis)  commences  above  at  the  back  part  of 
the  neck  of  the  radius,  and  terminates  below  at  the  posterior  part  of  the  base  of 
the  styloid  process;  it  separates  the  posterior  from  the  external  surface.  It  is 
indistinct  above  and  below,  but  well  marked  in  the  middle  third  of  the  bone. 

The  internal  border  {crista  interossea)  commences  above  at  the  back  part  of 
the  tuberosity,  where  it  is  rounded  and  indistinct,  becomes  sharp  and  prominent 
as  it  descends,  and  at  its  lower  part  divides  into  two  ridges,  which  descend  to 
the  anterior  and  posterior  margins  of  the  sigmoid  cavity.  This  border  separates 
the  anterior  from  the  posterior  surface,  and  has  the  interosseous  membrane 
attached  to  it  throughout  the  greater  part  of  its  extent. 

The  anterior  or  flexor  surface  {fades  volaris)  is  concave  for  its  upper  three- 
fourths,  and  gives  origin  to  the  Flexor  longus  pollicis  muscle;  it  is  broad  and  flat 
for  its  lower  fourth,  and  gives  attachment  to  the  Pronator  quadratus.  A  promi- 
Bent  ridge  limits  the  attachment  of  the  Pronator  quadratus  below,  and  between 
this  and  the  inferior  border  is  a  triangular  rough  surface  for  the  attachment  of 
the  anterior  ligament  of  the  wrist-joint.  At  the  junction  of  the  upper  and  middle 
third  of  this  surface  is  the  nutrient  foramen,  the  opening  of  the  nutrient  canal, 
which  is  directed  obliquely  upward  (proximally). 

The  posterior  or  extensor  surface  {fades  dorsalis)  is  rounded,  convex,  and 
smooth  in  the  upper  third  of  its  extent,  and  covered  by  the  Supinator  [brevis] 
muscle.  Its  middle  third  is  broad,  slightly  concave,  and  gives  origin  to  the 
Extensor  ossis  metacarpi  pollicis  above,  the  Extensor  brevis  pollicis  below.  Its 
lower  third  is  broad,  convex,  and  covered  by  the  tendons  of  the  muscles,  which 
subsequently  run  in  the  grooves  on  the  lower  end  of  the  bone. 

The  external  surface  {fades  lateralis)  is  rounded  and  convex  throughout  its 
entire  extent.  Its  upper  third  gives  attachment  to  the  Supinator  [brevis]  muscle. 
About  its  centre  is  seen  a  rough  ridge,  for  the  insertion  of  the  Pronator  teres 
muscle.  Its  lower  part  is  narrow,  and  covered  by  the  tendons  of  the  Extensor 
ossis  metacarpi  pollicis  and  Extensor  brevis  pollicis  muscles. 


192  SPECIAL  ANATOMY  OF  THE  SKELETON 

The  Lower  Extremity  is  large,  of. quadrilateral  form,  and  provided  with  two 
articular  surfaces — one  at  the  extremity,  for  articulation  with  the  carpus,  and  one 
at  the  inner  side  of  the  bone,  for  articulation  with  the  ulna.  The  carpal  articular 
surface  (fades  articularis  carpea)  is  of  triangular  form,  concave,  smooth,  and  divided 
by  a  slight  antero-posterior  ridge  into  two  parts.  Of  these,  the  external  is  of  a  tri- 
angular form,  and  articulates  with  the  scaphoid  bone;  the  inner  is  quadrilateral 
and  articulates  with  the  semilunar  bone.  The  articular  surface  for  the  head  of  the 
ulna  is  called  the  sigmoid  cavity  of  the  radius  (incisura  ulnaris) ;  it  is  narrow,  con- 
cave, smooth,  and  articulates  with  the  head  of  the  ulna.  The  circumference  of  this 
end  of  the  bone  presents  three  surfaces — an  anterior,  external,  and  posterior.  The 
anterior  surface,  rough  and  irregular,  affords  attachment  to  the  anterior  ligament  of 
the  wrist-joint.  The  external  surface  is  prolonged  obliquely  downward  into  a  strong 
conical  projection,  the  styloid  process  (processus  styloideus),  which  gives  attachment 
by  its  base  to  the  tendon  of  the  Brachioradialis,  and  by  its  apex  to  the  external 
lateral  ligament  of  the  wrist-joint.  The  outer  surface  of  this  process  is  marked 
by  a  flat  gi-oove,  which  runs  obliquely  downward  and  forward,  and  gives  passage 
to  the  tendons  of  the  Extensor  ossis  metacarpi  pollicis  and  the  Extensor  brevis 
pollicis.  The  posterior  surface  is  convex,  affords  attachment  to  the  posterior 
ligament  of  the  wrist,  and  is  marked  by  three  grooves.  Proceeding  from  without 
inward,  the  first  groove  is  broad  but  shallow,  and  subdivided  into  two  by  a  slightly 
elevated  ridge;  the  outer  of  these  two  transmits  the  tendon  of  the  Extensor  carpi 
radial  is  longior,  the  inner  the  tendon  of  the  Extensor  carpi  radialis  brevior.  The 
second,  which  is  near  the  centre  of  the  bone,  is  a  deep  but  narrow  groove,  bounded 
on  its  outer  side  by  a  sharply  defined  ridge;  it  is  directed  obliquely  from  above, 
downward  and  outward,  and  transmits  the  tendon  of  the  Extensor  longus  pollicis. 
The  third,  lying  most  internally,  is  a  broad  groove,  for  the  passage  of  the  tendons 
of  the  Extensor  indicis  and  Extensor  communis  digitorum. 

Structure. — Similar  to  that  of  the  other  long  bones. 

Development  (Fig.  149). — From  three  centres,  one  for  the  shaft  and  07ie  for  each  extremity. 
That  for  the  shaft  makes  its  appearance  near  the  centre  of  the  bone,  about  the  eighth  week  of 
fetal  life.  About  the  end  of  the  second  year  ossification  commences  in  the  lower  epiphysis,  and 
about  the  fifth  year  in  the  upper  end.  At  the  age  of  seventeen  or  eighteen  the  upper  epiphysis 
becomes  joined  to  the  shaft,  the  lower  epiphysis  becoming  united  about  the  twentieth  year.  Some- 
times an  additional  centre  appears  about  the  fourteenth  year  in  the  bicipital  tuberosity. 

Articulation. — With  four  bones — the  humerus,  idna,  scaphoid,  and  semilunar. 

Attachment  of  Muscles. — To  nitie:  To  the  tuberosity,  the  Biceps;  to  the  oblique  ridge,  the 
Supinator  [brevis],  Flexor  sublimis  digitorum,  and  Flexor  longus  pollicis;  to  the  shaft  (its  anterior 
surface),  the  Flexor  longus  pollicis  and  Pronator  quadratus;  (its  posterior  surface),  the  Extensor 
ossis  metacarpi  pollicis  and  Extensor  brevis  pollicis;  (its  outer  surface),  the  Pronator  teres;  and 
to  the  styloid  process,  the  Brachioradialis. 

Surface  Form. — Just  below  and  a  little  in  front  of  the  posterior  surface  of  the  external  con- 
dyle a  part  of  the  head  of  the  radius  may  be  felt,  covered  by  the  orbicular  and  external  lateral 
ligaments.  There  is  in  this  situation  a  little  dimple  in  the  skin,  which  is  most  visible  when  the 
arm  is  extended,  and  which  marks  the  position  of  the  head  of  the  bone.  If  the  finger  is  placed 
on  this  dimple  and  the  forearm  pronated  and  supinated,  the  head  of  the  bone  will  he  distinctly 
perceived  rotating  in  the  lesser  sigmoid  cavity.  The  upper  half  of  the  shaft  of  the  radius  can- 
not be  felt,  as  it  is  sturounded  by  the  fleshy  muscles  arising  from  the  external  condyle.  The 
lower  half  of  the  shaft  can  be  readily  examined,  although  covered  by  tendons  and  muscles  and 
not  strictly  subcutaneous.  If  traced  downward,  the  shaft  will  be  felt  to  terminate  in  a  lozenge- 
shaped,  convex  surface  on  the  outer  side  of  the  base  of  the  styloid  process.  This  is  the  only 
subcutaneous  part  of  the  bone,  and  from  its  lower  extremity  the  apex  of  the  styloid  process 
will  be  felt  bending  inward  toward  the  wrist.  About  the  middle  of  the  posterior  aspect  of  the 
lower  extremity  of  the  bone  is  a  well-marked  ridge,  best  perceived  when  the  hand  is  slightly 
flexed  on  the  A\Tist.  It  forms  the  outer  boundary  of  the  oblique  groove  on  the  posterior  surface 
of  the  bone,  through  which  the  tendon  of  the  Extensor  longus  pollicis  runs,  and  serves  to  keep 
that  tendon  in  place. 

Applied  Anatomy  of  the  Radius  and  Ulna. — The  two  bones  of  the  forearm  are  more  often 
broken  together  than  is  either  the  radius  or  ulna  separately.  It  is,  therefore,  convenient  to  consider 
fractures  of  both  bones  in  the  first  instance,  and  subsequently  to  mention  the  principal  fractures 


THE  RADIUS 


193 


Apyears  a 
5th  year. 


Unites  with  shaft 
-  about    18th     or 
20th  year. 


which  take  place  in  each  bone  individually.  These  fractures  may  be  produced  bv  either  direct 
or  indirect  violence,  though  more  commonly  by  direct  violence.  When  indirect  force  i.s  ap|)lied 
to  the  forearm  the  radius  generally  alone  gives  way,  though  both  bones  may  suffer.  The  fracture 
from  indirect  force  generally  takes  place  somewhere  about  the  middle  of  the  bones;  fracture 
from  direct  violence  may  occur  at  any  part,  more  often,  however,  in  the  lower  half  of  the  bone. 
The  fracture  is  usually  transverse,  but  may  be  more  or  less  oblique.  A  point  of  interest  in  con- 
nection with  these  fi-actures  is  the  tendency  that  there  is  for  the  two  bones  to  unite  across  the 
interosseous  membrane;  the  limb  should  therefore  be  put  up  in  a  position  midway  between  supi- 
nation and  pronation,  which  is  not  only  the  most  comfortable  position,  but  also  separates  the  bone-s 
most  widely  from  each  other,  and  therefore  diminishes 
the  risk  of  the  bones  becoming  united  across  the  inter- 
osseous membrane.  The  splints,  anterior  and  posterior, 
which  are  applied  in  these  cases  should  be  rather  wider 
than  the  limb,  so  as  to  prevent  any  lateral  pressure  on 
the  bones.  In  these  cases  there  is  a  greater  liability  to 
gangrene  from  the  pressure  of  the  splints  than  in  other 
parts  of  the  body.  This  is  no  doubt  due  princijially  to 
two  causes:  (1)  The  flexion  of  the  forearm  compressing 
to  a  certain  extent  the  brachial  artery  and  retarding 
the  flow  of  blood  to  the  limb;  and  (2)  the  superficial 
position  of  the  two  main  arteries  of  the  forearm  in  a 
part  of  their  course,  and  their  liability  to  be  compressed 
by  the  splints.    The  special  fractures  of  the  ulna  are: 

(1)  Fracture  of  the  olecranon.  This  may  be  caused  by 
direct  violence,  falls  on  the  elbow  with  .the  forearm 
flexed,  or  by  muscular  action  by  the  sudden  contraction 
of  the  triceps.  The  most  common  place  for  the  frac- 
ture to  occur  is  at  the  constricted  portion  where  the 
olecranon  joins  the  shaft  of  the  bone,  and  the  fracture 
may  be  either  transverse  or  oblique;  but  any  part  may 
be  broken,  even  a  thin  shell  may  be  torn  off.  Fractures 
from  direct  violence  are  occasionally  comminuted.  The 
displacement  is  sometimes  very  slight,  owing  to  the 
fibrous  structures  around  the  process  not   being  torn. 

(2)  Fracture  of  the  coronoid  process  sometimes  occurs 
as  a  complication  of  dislocation  backward  of  the  bones 
of  the  forearm,  but  it  is  doubtful  if  it  ever  occurs  as  an 
xmcomplicated  injury.  (3)  Fractures  of  the  shaft  of  the 
ulna  may  occur  at  any  part,  but  usually  takes  place  at  the 
middle  of  the  bone  or  a  little  below  it.  They  are  usually 
the  result  of  direct  violence.  (4)  The  styloid  process  may  be  knocked  off  by  direct  violence. 
Fractures  of  the  radius  consist  of:  (1)  Fracture  of  the  head  of  the  bone;  this  generally  occurs 
in  conjunction  with  some  other  lesion,  but  may  occur  as  an  uncomplicated  injury.  (2)  Fracture 
of  the  neck  may  also  take  place,  but  is  generally  complicated  with  other  injury.  (3)  Fractures  of 
the  shaft  of  the  radius  are  very  common,  and  may  take  place  at  any  part  of  the  bone.  They 
may  take  place  from  either  direct  or  indirect  violence.  In  fractures  of  the  upper  third  of  the 
shaft  of  the  bone,  that  is  to  say,  above  the  insertion  of  the  Pronator  teres,  the  displacement  is 
very  great.  The  upper  fragment  is  strongly  supinated  by  the  Biceps  and  Supinator,  and  flexed 
by  the  Biceps,  while  the  lower  fragment  is  pronated  and  drawn  toward  the  ulna  by  the  two 
pronators.  If  such  a  fracture  is  put  up  in  the  ordinary  position,  midway  between  supination 
and  pronation,  the  fracture  will  unite  with  the  upper  fragment  in  a  position  of  supination,  and 
the  lower  one  in  the  mid-position,  and  thus  considerable  impairment  of  the  movements  of  the 
hand  will  result.  The  limb  should  be  put  up  with  the  forearm  supinated.  (4)  The  most  impor- 
tant fracture  of  the  radius  is  that  of  the  lower  end  (Colles'  fracture).  The  fracture  is  transverse, 
and  generally  takes  place  about  an  inch  from  the  lower  extremity.  It  is  caused  by  falls  on  the 
]5alm  of  the  hand,  and  is  an  injury  of  advanced  life,  occurring  more  frequently  in  the  female 
than  the  male.  In  consequence  of  the  manner  in  which  the  fracture  is  caused,  the  upper  frag- 
ment becomes  driven  into  the  lower,  and  impaction  is  the  result;  or  else  the  lower  fragment 
becomes  split  up  into  two  or  more  pieces,  so  that  no  fixation  occurs.  Separation  of  the  lower 
epiphysis  of  the  radius  may  take  place  in  the  young.  This  injury  and  Colles'  fracture  may  be 
distinguished  from  other  injuries  in  this  neighborhood — especially  dislocation,  with  W'hich  it  is 
liable  to  be  confounded — by  observing  the  relative  positions  of  the  styloid  processes  of  the  ulna 
and  radius.  In  the  natural  condition  of  parts,  with  the  arm  hanging  by  the  side,  the  styloid 
process  of  the  radius  is  on  a  lower  level  than  that  of  the  ulna;  that  is  to  say,  nearer  the  groiuid. 
After  fracture  or  separation  of  the  epiphysis  this  process  is  on  the  same  or  a  higher  level  than  that 
of  the  ulna,  whereas  it  would  be  unaltered  in  position  in  dislocation. 

13 


.ippeari 
2d  yea  I 


Unites  with  shaft 
about  20th  year. 


Lowei  extiemity. 


194 


SPECIAL  ANATOMY  OF  THE  SKELETON 


THE  HAND, 

The  skeleton  of  the  hand  is  subdivided  into  three  segments — the  carpus,  or  wrist 
bones;  the  metacarpus,  or  bones  of  the  palm;  and  the  phalanges,  or  bones  of  the  digits. 


FLEXOR 

^      PROFUNDUS 
f  I       DIGITORUM 


Fio.   150. — Bones  of  the  left  hand.     Palmar  surface. 


THE  CARPUS 


195 


The  Carpus  (Ossa  Carpi)  (Figs.  150,  151). 

The  bones  of  the  carpus,  eight  in  number,  are  arranged  in  two  rows.     Those 
of  the  upper  row,  enumerated  from  the  radial  to  the  uhiar  side,  are  the  scaphoid. 


'-^Aj^a 


EXTENSOR  COMMUNIS 

DiGiTORUM  and 

EXTENSOR    INDICIS. 


Fig.   151.— Bonea  of  the  left  hand.     Dorsal  surface. 


196 


SPECIAL  ANATOMY  OF  THE  SKELETON 


semilunar,  cuneiform,  and  pisiform;  those  of  the  lower  row,  enumerated  in  the 
same  order,  are  the  trapezium,  trapezoid,  os  magnum,  and  unciform. 

Common  Characters  of  the  Carpal  Bones. — Each  bone  (excepting  the  pisi- 
form) presents  six  surfaces.  Of  these  the  anterior,  palmar,  or  volar,  and  the 
posterior  or  dorsal  are  rough  for  hgamentous  attachment,  the  dorsal  surface  being 
the  broader,  except  in  the  scaphoid  and  semilunar.  The  superior  or  proximal 
and  inferior  or  distal  are  articular,  the  superior  generally  convex,  the  inferior 
concave;  and  the  internal  and  external  are  also  articular  when  in  contact  with 
contiguous  bones,  otherwise  rough  and  tubercular.  The  structure  of  all  is  similar, 
consisting  of  cancellous  tissue  enclosed  in  a  layer  of  compact  bone. 


Vad'^'' 


With  1 
Fig.  152. —  Diagram  to  show  articulations 


Bones  of  the  Upper  Row. — The  scaphoid  or  navicular  bone  {os  naviculare 
manus)  (Fig.  1.5.3)  is  the  largest  bone  of  the  first  row.  It  is  situated  at  the  upper 
and  outer  part  of  the  carpus,  its  long  axis  being  from  above  downward,  outward, 
and  forward. 


For  radius 


For  semilunar 


Tuberosity 


For  trapesimn 


For  OS  magnum. 


tor  f)apezoid 

A  B 

Fig.  153. — The  left  scaphoid.     A,  seen  from  behind;  B,  seen  from  in  front. 

Surfaces. — The  superior  surface  is  convex,  smooth,  of  triangular  shape,  and 
articulates  with  the  lower  end  of  the  radius.  The  inferior  surface,  directed  down- 
ward, outward,  and  back\i'ard,  is  smooth,  convex,  also  triangular,  and  divided  by 
a  slight  ridge  into  two  parts,  the  external  of  which  articulates  with  the  trapezium, 
the  inner  with  the  trapezoid.  The  posterior  or  dorsal  surface  presents  a  narrow, 
rough  groove  which  runs  the  entire  length  of  tlie  bone  and  serves  for  the  attachment 
of  ligaments.  The  anterior  or  palmar  siu-face  is  concave  above,  and  elevated  at 
its  lower  and  outer  part  into  a  prominent  rounded  tuberosity  (tuberculum  ossis 
iiavicidaris),  which  projects  forward  from  the  front  of  the  carpus  and  gives  attach' 


THE  CARPUS 


197 


ment  to  the  anterior  annular  ligament  of  the  wrist  and  sometimes  a  few  fibres 
of  the  Abductor  poUicis.  The  external  surface  is  rough  and  narrow,  and  gives 
attachment  to  the  external  lateral  ligament  of  the  wrist.  The  internal  surface 
presents  two  articular  facets;  of  these,  the  superior  or  smaller  one  is  flattened, 
of  semilunar  form,  and  articulates  with  the  semilunar;  the  inferior  or  laro-er  is 
concave,  forming,  with  the  semilunar  bone,  a  concavity  for  the  head  of  the  os 
magnum. 

To  ascertain  to  which  side  the  bone  belongs,  hold  the  convex  radial  articular  surface  upward, 
and  the  dorsal  surface  backward;  the  prominent  tubercle  will  be  directed  to  the  side  to  which 
the  bone  belongs. 

Articulations. — With  five  bones — the  radius  above,  trapezium  and  trapezoid  l)elo\v,  os 
magnum  and  semilunar  internally. 

Attachment  of  Muscles. — Occasionally  a  few  fibres  of  the  Abductor  pollicis. 

The  semilunar  bone  (Fig.  154)  may  be  distinguished  by  its  deep  concavity  and 
crescentic  outline.  It  is  situated  in  the  centre  of  the  upper  row  of  the  carpus, 
between  the  scaphoid  and  cuneiform. 


For  cuneiform 


For  scaphoid 
For  unciform    For  os  magnum 

A  B 

Fig.  154. — The  left  semilunar.     A,  anterior  and  internal  surfaces;  B,  external  surface. 

Surfaces. — The  superior  surface,  convex,  smooth,  and  bounded  by  four  edges, 
articulates  with  the  radius.  The  inferior  surface  is  deeply  concave,  and  of  greater 
extent  from  before  backward  than  transver,sely ;  it  articulates  with  the  head  of  the 
OS  magnum  and  by  a  long,  narrow  facet  (separated  by  a  ridge  from  the  general 
surface)  with  the  unciform  bonc^^fhe  anterior  or  palmar  and  posterior  or  dorsal 
surfaces  are  rough,  for  the  attachment  of  ligaments,  the  former  being  the  broader 
and  of  a  somewhat  rounded  form.  The  external  surface  presertts  a  narrow,  flat- 
tened, semilunar  facet  for  articulation  with  the  scaphoid.  The  internal  surface 
js  marked  by  a  smooth,  quadrilateral  facet,  for  articulation  with  the  cuneiform. 

To  ascertain  to  which  hand  this  bone  belongs,  hold  it  with  the  dorsal  surface  upward,  and 
the  convex  articular  surface  backward;  the  quadrilateral  articular  facet  will  then  point  to  the 
side  to  which  the  bone  belongs. 

Articulations. — With  five  bones — the  radius  above,  os  magnum  and  unciform  below,  sca])hoid 
externally,  and  cuneiform  internally. 


For  pisifor 


The  cuneiform  (os  f.riquetrum)  (Fig.  155)  may  be 
distinguished  by  its  pyramidal  shape,  and  by  'its 
having  an  oval,  isolated  facet  for  articulation  with  the 
pisiform  bone.  It  is  situated  at  the  upper  and  inner 
side  of  the  carpus. 

Surfaces. — ^The  superior  surface  presents  an  internal, 
i'ough,  nonarticular  portion,  and  an  external  or 
articular  portion,  which  is  convex,  smooth,  and  articu- 
lates with  the  triangular  intra-articular  fibrocartilage 
of  the  wrist.  The  inferior  surface,  directed  outward,  is  concave,  sinuously  curved, 
and  smooth  for  articulation  with  the  unciform.     The  posterior  or  dorsal  surface  is 


For  unciform 
Fig.  155. — The  left   cuneiform. 


198  SPECIAL  ANATOMY  OF  THE  SKELETON 

rough,  for  the  attachment  of  ligaments.  The  anterior  or  palmar  surface  presents. 
at  its  inner  side,  an  oval  facet,  for  articulation  with  the  pisiform,  and  is  rough 
externally,  for  ligamentous  attachment.  The  external  surface,  the  base  of  the 
pyramid,  is  marked  by  a  flat,  quadrilateral,  smooth  facet,  for  articulation  with 
the  semilunar.  The  internal  surface,  the  summit  of  the  pyramid,  is  pointed  and 
roughened,  for  the  attachment  of  the  internal  lateral  ligament  of  the  wrist. 

To  ascertain  to  which  hand  this  bone  belongs,  hold  it  so  that  the  base  is  directed  backward, 
and  the  articular  facet  for  the  pisiform  bone  upward;  the  concave  articular  facet  will  point  to 
the  side  to  which  the  bone  belongs. 

Articulations. — With  three  bones — the  semilunar  externally,  the  pisiform  in  front,  the  unci- 
form below;  and  with  the  triangular,  interarticular  fibrocartilage  which  separates  it  from  the 
lower  end  of  the  ulna. 

The  pisiform  (os  pisiforme)  (Fig.  156)  may  be  known  by  its  small  size  and  by 

its  presenting  a  single  articular  facet.     It  is  situated  on  a  plane  anterior  to  the 

other  bones  of  the  carpus;  it  is  spheroidal  in  form,  with  its  long 

For  cuneiform  ,.  ,         ,.        ,     ,  j.-      n 

, '  diameter  directed  vertically. 

Surfaces. — Its   posterior  surface    is  a   smooth,  oval   facet,  for 

articulation  with  the  cuneiform.     This    facet   approaches    the 

superior,  but  not  the  inferior  border  of  the  bone.     The  anterior 

Fig.  156.— The  left     or  palmar  surface  is  rounded  and  rough,  and  gives  attachment  to 

posterior  and  lateral     the  anterior  annular  ligament  and  to  the  Flexor  carpi  ulnaris 

sur  aces.  ^^^  Origin  to  the  Abductor  minimi  digiti.     The  outer  and  inner 

surfaces  are  also  rough,  the  former  being  concave,  the  latter  usually  convex. 

To  ascertain  to  which  hand  this  bone  belongs,  hold  the  bone  with  its  posterior  or  articular 
facet  downward  and  the  nonarticular  portion  of  the  same  surface  backward;  the  inner  concave 
surface  will  point  to  the  side  to  which  it  belongs. 

Articulations. — With  one  bone,  the  cuneiform. 

Attachment  of  Muscles. — To  two — the  Flexor  carpi  ulnaris  and  Abductor  minimi  digiti; 
and  to  the  anterior  annular  ligament. 

Bones  of  the  Lower  Row. — The  trapezium  (os  multangtdum  majus)  (Fig. 
157)  is  of  very  irregular  form.  It  may  be  distinguished  by  a  deep  groove,  for 
the  tendon  of  the  Flexor  carpi  radialis  muscle.  It  is  situated  at  the  external  and 
inferior  part  of  the  carpus  between  the  scaphoid  and  first  metacarpal  bone. 

For  scaphoid 

For  trapezoid        ^,.r».    /  ,-5;:^^?>C  n     ±  -j 

■^      ,       . — -^"^Ss.  /  .^i^'--  «^  For  trapezoid 


For  2nd    Al-.M 
metacarpal   ^  '  '^ 


Bidge 


\ 
For  1st  metacarpal  F°^  ^'«^  metacarpal 

A  B 

Fig.  157. — The  left  trapezium.     A,  as  seen  from  in  front;  B,  from  above  and  mesal  side. 

Surfaces. — The  superior  surface,  concave  and  smooth,  is  directed  upward  and 
inward,  and  articulates  with  the  scaphoid.  The  inferior  surface,  directed  down- 
ward and  inward,  is  oval,  concave  from  side  to  side,  convex  from  before  backward, 
so  as  to  form  a  saddle-shaped  surface,  for  articulation  with  the  base  of  the  first 
metacarpal  bone.  The  anterior  or  palmar  surface  is  narrow  and  rough.  At  its 
upper  part  is  a  deep  groove  running  from  above  obliquely  downward  and  inward; 
it  transmits  the  tendon  of  the  Flexor  carpi  radialis,  and  is  bounded  externally 


THE  CARPUS  199 

by  a  prominent  ridge,  the  oblique  ridge  of  the  trapezium  {hiherruluni  ossis  mul- 
tanguli  majoris).  This  surface  gives  origin  to  the  Abductor  pollicis,  Opponens 
poUicis,  sometimes  to  a  portion  of  the  superficial  head  of  the  Flexor  bre\-is  pollicis 
muscles,  and  the  anterior  annular  ligament.  The  posterior  or  dorsal  surface 
is  rough.  The  external  surface  is  also  broad  and  rough,  for  the  attachment  of 
ligaments.  The  internal  surface  presents  two  articular  facets;  the  upper  one, 
large  and  concave,  articulates  with  the  trapezoid;  the  lower  one,  small  and  oval, 
with  the  base  of  the  second  metacarpal  bone. 

To  ascertain  to  which  hand  this  bone  belongs,  hold  it  with  the  grooved  palmar  surface  upward, 
and  the  external  broad,  nonarticular  surface  backward;  the  saddle-shaped  surface  will  then  be 
directed  to  the  side  to  w-hich  the  bone  belongs. 

Articulations. — With  four  bones — the  scaphoid  above,  the  trapezoid  and  second  metacarpal 
bones  internally,  the  first  metacarpal  below. 

Attachment  of  Muscles. — Abductor  pollicis,  Opponens  pollicis,  and  sometimes  the  superficial 
head  of  the  Flexor  brevis  pollicis. 

The  trapezoid  (os  multangidum  minus)  (Fig.  158)  is  the  smallest  bone  in  the 
second  row.  It  may  be  known  by  its  wedge-shaped  form,  the  broad  end  of  the 
wedge  forming  the  dorsal,  the  narrow  end  the  palmar,  surface,  and  by  its  having 
four  articular  surfaces 'touching  each  other  and  separated  by  sharp  edges. 

Palmar  For 

surface    trapesium 


Fig.  158. — The  left  trapezoid.     A,  as  seen  from  above,  inner  side  and  behind;  B,  from  in  front. 


Surfaces. — The  superior  surface,  quadrilateral  in  form,  smooth,  and  slightly  con- 
cave, articulates  with  tiie  .scaphoid.  The  inferior  surface  articulates  with  the  upper 
end  of  the  second  metacarpal  bone;  it  is  convex  from  side  to  side,  concave  from 
before  backward,  and  subdivided  by  an  elevated  ridge  into  two  unequal  lateral 
facets.  The  posterior  or  dorsal  and  anterior  or  palmar  surfaces  are  rough,  for  the 
attachment  of  ligaments,  the  former  being  the  larger  of  the  two.  The  external 
surface,  convex  and  smooth,  articulates  with  the  trapezium.  The  internal  surface 
is  concave  and  smooth  in  front,  for  articulation  with  the  os  magnum;  rough  behind, 
for  the  attachment  of  an  interosseous  ligament. 

To  ascertain  to  which  hand  this  bone  belongs,  let  the  broad  dorsal  surface  be  held  upward, 
and  the  inferior  concavo-convex  surface  forward;  the  internal  concave  surface  will  then  point 
to  the  side  to  which  the  bone  belongs 

Articulations. — With  four  bones — the  scaphoid  above,  second  metacarpal  bone  below,  trape- 
zium externally,  os  magnum  internally. 

The  OS  magnum  {os  capitatum)  (Fig.  159)  is  the  largest  bone  of  the  carpus, 
and  occupies  the  centre  of  the  wrist.  It  presents,  above,  a  rounded  portion  or 
head,  which  is  recei\"ed  into  the  conca^'ity  formed  by  the  scaphoid  and  semilunar 
bones;  a  constricted  portion  or  neck;  and,  below,  the  body. 

Surfaces. — The  superior  surface  is  rounded,  smooth,  and  articulates  with  the  semi- 
lunar. The  inferior  surface  is  divided  by  two  ridges  into  three  facets  for  articu- 
lation with  the  second,  third,  and  fourth  metacarpal  bones,  that  for  the  third  (the 
middle  facet)  being  the  largest  of  the  three.  The  posterior  or  dorsal  surface  is 
broad  and  rough;  the  anterior  or  palmar,  narrow,  rounded,  and  also  rough,  for  the 


200 


SPECIAL  ANATOMY  OF  THE  SKELETON 


attachment  of  ligaments,  and  it  gives  origin  to  a  part  of  the  Adductor  obHquus 
polHcis.  The  external  surface  articulates  with  the  trapezoid  by  a  small  facet 
at  its  anterior  inferior  angle,  behind  which  is  a  rough  depression  for  the  attach- 
ment of  an  interosseous  ligament.  Above  this  is  a  deep  and  rough  groove,  which 
forms  part  of  the  neck  and  serves  for  the  attachment  of  ligaments,  bounded  supe- 
riorly by  a  smooth,  convex  surface  for  articulation  with  the  scaphoid.     The 


For  scaphoid 


For  trapezoid 


For  semilunar 


For  3rd 
For  %nd     metacarpal 
metacarpal 


For  4th  metacarpal  Palmar  surface 


Fig.  159. — The  left  os  magnum.     A,  outer  side  seen  from  below;  B,  internal  posterior  surface. 

internal  surface  articulates  with  the  unciform  by  a  smooth,  concave,  oblong 
facet  which  occupies  its  posterior  and  superior  parts,  and  is  rough  in  front,  for 
the  attachment  of  an  interosseous  ligament. 

To  ascertain  to  which  hand  this  bone  belongs,  the  rounded  head  should  be  held  upward,  and 
the  broad  dorsal  surface  forward;  the  internal  concave  articular  surface  will  point  to  the  side  to 
which  the  bone  belongs. 

Articulations. — With  seven  bones — the  scaphoid  and  semilunar  above;  the  second,  third,  and 
fourth  metacarpal  below;  the  trapezoid  on  the  radial  side;  and  the  unciform  on  the  ulnar  side. 

Attachment  of  Muscles. — Part  of  the  Adductor  obliquus  pollicis. 

The  unciform  {os  hamahim)  (Fig.  160)  may  be  readily  distinguished  by  its 
wedge-shaped  form  and  the  hook-like  process  that  projects  from  its  palmar  surface. 
It  is  situated  at  the  inner  and  lower  angle  of  the  carpus,  with  its  base  downward, 
resting  on  the  two  inner  metacarpal  bones,  and  its  apex  directed  upward  and 
outward. 


For  semilunar 


For  cuneifor? 


For  OS  magnum — 


For  ith  metacarpal 

For  5th  metacarpal       Unciform  process  For  5th  metacarpal 

A  B 

Fig.  160. — The  left  unciform.     A,  internal  surface;  B,  outer  and  distal  surfaces. 

Surfaces. — The  superior  surface,  the  apex  of  the  wedge,  is  narrow,  convex, 
smooth,  and  articulates  with  the  semilunar.  The  inferior  surface  articulates  with 
the  fourth  and  fifth  metacarpal  bones,  the  concave  surface  for  each  being  sepa- 
rated by  a  ridge  which  runs  from  before  backward.  The  posterior  or  dorsal 
surface  is  triangular  and  rough,  for  ligamentous  attachment.  The  anterior  or 
palmar  surface  presents,  at  its  lower  and  inner  side,  a  curved,  hook-like  process  of 
bone,  the  imciform  process  (hamulus  ossis  hamati),  directed  from  the  palmar  sur- 
face forward  and  outward.     It  gives  attachment  by  its  apex  to  the  annular  liga- 


THE  METACARPUS  201 

ment  and  insertion  to  some  of  the  fibres  of  the  Flexor  carpi  uhiaris;  by  its  inner 
surface  it  gives  origin  to  the  Flexor  brevis  minimi  digiti  and  the  Opponens  niininii 
digiti;  and  is  grooved  on  its  outer  side,  for  the  passage  of  the  Flexor  tendons  into 
the  palm  of  the  hand.  This  is  one  of  the  four  eminences  on  the  front  of  the  carpus 
to  which  the  anterior  annular  ligament  is  attached,  the  others  being  the  pisiform 
internally,  the  oblique  ridge  of  the  trapezium  and  the  tuberosity  of  the  scaphoid 
externally.  The  internal  surface  articulates  with  the  cuneiform  by  an  oblong 
facet  cut  obliquely  from  above,  downward  and  inward.  The  external  surface 
articulates  with  the  os  magnum  by  its  upper  and  posterior  part,  the  remaining 
portion  being  rough,  for  the  attachment  of  ligaments. 

To  ascertain  to  which  hand  it  belongs,  hold  the  apex  of  the  bone  upward,  and  the  broad  dorsal 
surface  backward;  the  concavity  of  the  process  will  be  on  the  side  to  which  the  bone  belongs. 

Articulations. — With  five  bones — the  semilunar  above,  the  fourth  and  fifth  metacarpal 
below,  the  cuneiform  internally,  the  os  magnum  externally. 

Attachment  of  Muscles.  —To  three — the  Flexor  brevis  minimi  digiti,  the  Opponens 
minimi  digiti,  the  Flexor  cari)!  ulnaris. 


The  Metacarpus  (Ossa  Metacarpalia)  (Figs.  150,  151). 

The  metacarpal  bones  are  five  in  number,  and  they.are  numbered  from  1  to  5 
inclusive,  the  first  being  the  metacarpal  bone  of  the  thumb,  the  fifth  the  meta- 
carpal bone  of  the  little  finger.  They  are  long,  cylindrical  bones,  presenting  for 
examination  a  shaft  and  two  extremities. 

Common  Characters  of  the  Metacarpal  Bones. — The  shaft  (corpus)  is  pris- 
moid  in  form,  and  curved  longitudinally,  so  as  to  be  convex  in  the  longitudinal 
direction  behind,  concave  in  front.  It  presents  three  surfaces — two  lateral  and 
one  posterior.  The  two  lateral  surfaces  constitute  the  palmar  or  volar  aspect. 
The  lateral  surfaces  are  concave,  for  the  origin  of  the  Interossei  inuscles,  and 
separated  from  one  another  by  a  prominent  anterior  ridge.  The  posterior  or 
dorsal  surface  presents  in  its  distal  half  a  smooth,  triangular,  flattened  area  which 
is  covered,  in  the  recent  state,  by  the  tendons  of  the  Extensor  muscles.  This 
triangular  surface  is  bounded  by  two  lines,  which  commence  in  small  tubercles 
situated  on  the  dorsal  aspect  on  either  side  of  the  digital  extremity,  and,  running 
backward,  converge  to  meet  some  distance  behind  the  centre  of  the  bone  and 
form  a  ridge  which  runs  along  the  rest  of  the  dorsal  surface  to  the  carpal  ex- 
tremity. This  ridge  separates  two  lateral,  sloping  surfaces  for  the  origin  of  the 
Dorsal  interossei  muscles.'  To  the  tubercles  on  the  digital  extremities  are 
attached  the  lateral  ligaments  of  the  metacarpophalangeal  joints.  On  the  pal- 
mar surface  of  each  metacarpal  bone  is  a  nutrient  foramen,  which  opens  into  a 
nutrient  canal.  In  the  first  metacarpal  the  direction  of  this  foramen  is  toward  the 
phalanges  (distad).  In  each  of  the  other  metacarpals  it  is  from  the  phalanges 
(proximad). 

The  carpal  or  proximal  extremity  (bask)  is  of  a  cuboidal  form,  and  broader 
behind  than  in  front;  it  articulates  above  with  the  carpus,  and  on  each  side 
with  the  adjoining  metacarpal  bones;  its  dorsal  and  palmar  surfaces  are  rough, 
for  the  attachment  of  tendons  and  ligaments. 

The  distal  extremity  (capltulum)  presents  an  oblong  surface,  markedly  con- 
vex from  before  backward,  less  so  from  side  to  side,  and  flattened  laterally;  it 
articulates  with  the  proximal  phalanx;  it  is  broader  and  extends  farther  forward 
on  the  palmar  than  on  the  dorsal  aspect.  It  is  longer  in  the  antero-posterior  than 
in  the  transverse  diameter.     On  either  side  of  the  head  is  a  tubercle  for  the  attach- 

the  hand  mav  be  at  once  differentiated  from  the  metatarsal 


202 


SPECIAL  ANATOMY  OF  THE  SKELETON 


ment  of  the  lateral  ligament  of  the  metacarpophalangeal  joint.  The  posterior 
surface,  broad  and  flat,  supports  the  Extensor  tendons;  the  anterior  surface  is 
grooved  in  the  middle  line  for  the  passage  of  the  Flexor  tendons,  and  marked  on 
each  side  by  an  articular  eminence  continuous  with  the  terminal  articular  surface. 
The  metacarpal  spaces  (spatia  interossea  metacarpi) 
are  the  intervals  between  the  metacarpal  bones. 
They  are  occupied  by  the  Interossei  muscles.  The 
broadest  space  is  between  the  metacarpal  bones  of 
the  thumb  and  index  finger. 

Peculiar  Characters  of  the  Metacarpal  Bones. 
— The  metacarpal  bone  of  the  thumb  (o«  metacar- 
pale  I)  (Fig.  161)  is  shorter  and  wider  than  the 
rest,  diverges  to  a  greater  degree  from  the  carpus, 
and  its  palmar  surface  is  directed  inward  toward 
the  palm.  The  shaft  is  flattened  and  broad  on 
its  dorsal  aspect,  and  does  not  present  the  ridge 
which  is  found  on  the  other  metacarpal  bones;  it 
is  concave  from  above  downward,  on  its  palmar 
surface.  The  carpal  extremity,  or  base,  presents 
a  concavo-convex  surface,  for  articulation  with  the 
trapezium;  it  has  no  lateral  facets,  but  presents 
externally  a  tubercle  for  the  insertion  of  the  Extensor  ossis  metacarpi  poUicis. 
The  distal  extremity  is  less  convex  than  that  of  the  other  metacarpal  bones,  broader 
from  side  to  side  than  from  before  backward.  It  presents  on  its  palmar  aspect 
two  distinct  articular  eminences  for  the  two  sesamoid  bones  in  the  tendons  of 
the  Flexor  brevis  pollicis,  the  outer  one  being  the  larger  of  the  two. 


Tubercle 
Foi   ti  ape'sium.        For  trape: 

Fig.  161.— The  first  metacarpal.  (Left.) 


The  side  to  which  this  bone  belongs  may  be  known  by  holding  it  in  the  position  it  occupies 
in  the  hand,  with  the  carpal  extremity  upward  and  the  dorsal  surface  backward;  the  tubercle  for 
the  Extensor  ossis  metacarpi  pollicis  will  point  to  the  side  to  which  it  belongs. 

Attachment  of  Muscles. — To  four — the  Opponens  pollicis,  the  Extensor  ossis  metacarpi 
pollicis,  the  Flexor  brevis  pollicis,  and  the  First  dorsal  interosseous. 

The  metacarpal  bone  of  the  index  finger  (os  metacarpaJe  II)  (Fig.  162)  is  the 
longest  and  its  base  the  largest  of  the  other  fcfir.  Its  carpal  extremity  is  prolonged 
upward  and  inward,  forming  a  prominent  ridge.  The  dorsal  and  palmar  surfaces 
of  this  extremity  are  rough,  for  the  attachment  of  tendons  and  ligaments.  It  pre- 
sents four  articular  facets — three  on  the  upper  aspect  of  the  base;  the  middle 
one  of  the  three  is  the  largest,  concave  from  side  to  side,  convex  from  before  back- 
ward, for  articulation  with  the  trapezoid;  the  external  one  is  a  small,  flat,  oval 
facet,  for  articulation  with  the  trapezium;  the  internal  one  on  the  summit  of  the 
ridge  is  long  and  narrow,  for  articulation  with  the  os  magnum.  The  fourth  facet 
is  on  the  inner  or  the  ulnar  side  of  the  extremity  of  the  bone,  and  is  for  articulation 
with  the  third  metacarpal  bone. 

The  side  to  which  this  bone  belongs  is  indicated  by  the  absence  of  the  lateral  facet  on  the  outer 
(radial)  side  of  its  base,  so  that  if  the  bone  is  placed  with  the  base  toward  the  student  and  the 
palmar  surface  upward,  the  side  on  which  there  is  no  lateral  facet  will  be  that  to  which  it  belongs. 

Attachment  of  Muscles. — To  six — Flexor  carpi  radialis,  Extensor  carpi  radiahs  longior, 
the  deep  portion  of  the  Flexor  brevis  pollicis.  First  and  Second  dorsal  interosseous,  and  First 
palmar  interosseous. 


The  metacarpal  bone  of  the  middle  finger  (os  metacarpale  III)  (Fig.  163)  is  a 
little  smaller  than  the  preceding;  it  presents  a  pyramidal  eminence,  the  styloid 


THE  METACARPUS 


203 


process  {processus  styloideus),  on  the  radial  side  of  its  base  (dorsal  aspect),  wliicl) 
extends  upward  behind  the  os  magnum;  immediately  below  this,  on  the  dorsal 
aspect,  is  a  rough  surface  for  the  attachment  of  the  Extensor  carpi  radialis  brevior. 
The  carpal,  articular  facet  is  concave  behind,  flat  in  front,  and  articulates  with  the 
OS  magnum.  On  the  radial  side  is  a  smooth,  concave  facet,  for  articulation  with 
the  second  metacarpal  bone,  and  on  the  ulnar  side  two  small,  oval  facets,  for  articu- 
lation with  the  fourth  metacarpal. 

_  The  side  to  which  this  bone  belongs  is  easily  recognized  by  the  styloid  process  on  the  radial 
side  of  its  base.  With  the  palmar  surface  uppermost  and  the  base  toward  the  student,  this  process 
points  toward  the  side  to  which  the  bone  belongs. 

Attachment  of  Muscles.— To  s?.r~E\-tensor  carpi  radialis  brevior.  Flexor  carpi  radialis. 
Adductor  transversus  pollicis,  Adductor  obliquus  pollicis,  and  Second  and  Thu-d  dorsal  inter- 
osseous. 


.    For  third  metacarpal 
Sor  trapezoid.  For  os  magiiuvi. 

Fig.  162. — The  second  metacirp.il.     (Left.) 


For  fourlh 
metacarpal. 


SlyloiH  For  second 
process,  metacarpal. 

For  OS  magnum. 

Fig.  163.— The  third  metacarpal.     (Left.) 


The  metacarpal  bone  of  the  ring  finger  (os  metacarpale  IV)  (Fig.  164)  is  shorter 
and  smaller  than  the  preceding,  and  its  base  small  and  quadrilateral;  the  carpal 
surface  of  the  base  presenting  two  facets,  a  large  one  internally,  for  articulation 
with  the  unciform,  and  a  small  one  externally,  for  the  os  magnum.  On  the 
radial  side  are  two  oval  facets,  for  articulation  with  the  third  metacarpal  bone; 
and  on  the  ulnar  side  a  single  concave  facet,  for  the  fifth  metacarpal. 

If  this  bone  is  placed  with  the  base  toward  the  student  and  the  palmar  surface  upward,  the 
radial  side  of  the  base,  which  has  two  facets  for  articulation  with  the  third  metacarpal  bone,  wili 
be  on  the  side  to  which  it  belongs.  If,  as  sometimes  happens  in  badly  marked  bones,  one  of  these 
facets  is  indistinguishable,  the  side  may  be  known  by  selecting  the  surface  on  which  the  larger 
articular  facet  is  present.  This  facet  is  for  the  fifth  metacarpal  bone,  and  would  therefore  be 
situated  on  the  ulnar  side— that  is,  the  one  to  which  the  bone  does  not  belong. 

Attachment  of  Muscles.— To  three— the  Third  and  Fourth  dorsal  and  Second  palmar  inter- 


The  metacarpal  bone  of  the  little  finger  (os  meiacarfaJe  V)  (Fig.  165)  presents 
on  its  base  one  facet,  which  is  concavo-convex,  and  which  articulates  with  the 
unciform  bone,  and  one  lateral,  articular  facet,  which  articulates  with  the  fourth 
metacarpal  bone.     On  its  ulnar  side  is  a  prominent  tubercle,  for  the  insertion  of 


204 


SPECIAL  ANATOMY  OF  THE  SKELETON 


the  tendon  of  the  Extensor  carpi  ulnaris.  The  dorsal  surface  of  the  shaft  is  marived 
by  an  obhque  ridge  which  extends  from  near  the  ulnar  side  of  the  upper  extremity 
to  the  radial  side  of  the  lower.  The  outer  division  of  this  surface  serves  for 
the  attachment  of  the  Fourth  dorsal  interosseous  muscle;  the  inner  division  is 
smooth  and  covered  by  the  Extensor  tendons  of  the  little  finger. 


L-'^N 


For  third 
metacarpal.      For  os 
magnum. 


For  fift  h  meta- 
carpal 
For  unciform. 


Fig.   164.— The  fourth  metacarpal.     (Left.) 


For  unciform, 
metacarpal. 

Fig.    16S.— The  fifth   metacarpal.     (Left.) 


If  thi.s  Vione  is  placed  with  its  base  toward  the  student  and  its  pahnar  surface  upward,  the 
side  of  the  head  wiiich  has  a  lateral  facet  will  be  that  to  which  the  bone  belongs. 

Attachment  of  Muscles. — To  five — the  E.xtensor  carpi  ulnaris,  Fle.xor  carpi  ulnaris,  Oppo- 
nens  minimi  digiti.  Fourth  dorsal,  and  Third  palmar  interossei. 

Articulations. — Besides  the  phalangeal  articulations,  the  first  metacarpal  bone  articulates 
with  the  trapezium;  the  second  with  the  trapezium,  trapezoid,  os  magnum,  and  third  metacarpal 
bones;  the  third  with  the  os  magnum  and  second  and  fourth  metacarpal  bones;  the  fourth  with, 
the  OS  magnum,  unciform,  and  third  and  fifth  metacarpal  bones;  and  the  fifth  with  the  unciform 
and  fourth  metacarpal. 

Th.^  first  has  no  lateral  facets  on  its  carpal  extremity;  the  second  has  no  lateral  facet  on  its 
radial  side,  but  one  on  its  ulnar  side;  the  third  has  one  on  its  radial  and  two  on  its  ulnar  side; 
the  fourth  has  two  on  its  radial  and  one  on  its. ulnar  side;  and  the  fifth  has  only  one  on  its  radial 
side. 


The  Phalanges  of  the  Hand  (Phalanges  Digitorum  Manus). 

The  phalanges  (phalanges  digitorum  manus)  are  fourteen  in  number,  three  for 
each  finger,  and  two  for  the  thumb.  In  numbering  them  the  proximal  bone 
is  designated  as  the  first  phalanx  (phalan.v  I).  They  are  long  bones,  and  present 
for  examination  a  shaft  and  two  extremities.  The  shaft  (corpus  phaJangis) 
tapers  from  above  downward,  is  convex  posteriorly,  concave  in  front  from  above 
downward,  flat  from  side  to  side,  and  marked  laterally  by  rough  ridges,  which 
give  attachment  to  the  fibrous  sheaths  of  the  Flexor  tendons.  A  nutrient  foramen 
on  the  palmar  surface  leads  into  a  nutrient  canal  which  runs  toward  the  periphery 
(distad).  The  metacarpal  extremity,  or  base  (basis  plialangis),  of  each  phalanx 
in  the  first  row  presents  an  oval,  concave,  articular  surface,  broader  from  side 
to  side  than  from  before  backward;  and  the  same  extremity  in  the  other  two 
rows,  a  double  concavity,  separated  by  a  longitudinal  median  ridge,  extending 
from  before  backward.     The  distal  extremity  of  the  first  phalanx  of  the  thumb 


THE  PHALANGES  OF  THE  HAND  205 

and  of  the  first  and  second  phalanx  of  each  of  the  fingers  is  smaller  than  the 
base,  and  terminates  in  two  small,  lateral  condyles,  separated  by  a  slight  groove 
(trochlea  phahnqis);  the  articnlar  surface  being  prolonged  farther  forward  on 
the  palmar  than  on  the  dorsal  surface,  especially  in  the  first  row. 

The  ungual  phalanges  (distal)  are  convex  on  their  dorsal,  flat  on  their  palmar, 
surfaces;  they  are  recognized  by  their  small  size  and  by  a  roughened,  elevated 
surface  of  a  horseshoe  form  on  the  palmar  aspect  of  their  ungual  extremity  (tuber- 
ositas luujuicularis),  which  serves  to  support  the  sensitive  pulp  of  the  finger. 

Articulations. — The  first  row,  with  the  metacarpal  bones  and  the  second  row  of  phalanges; 
the  second  row,  with  the  first  and  third;  the  third,  with  the  second  ro^\'. 

Attachment  of  Muscles.— To  the  base  of  the  first  phalanx  of  the  thumb,  ^w  muscles— the 
Extensor  brevis  [joUicis,  Flexor  brevis  poliicis.  Abductor  pollicis,  Adductores  transversus  and 
Obliquus  pollicis.  To  the  second  phalanx,  two — the  Flexor  longus  pollicis  and  the  Extensor 
Jongus  pollicis.  To  the  base  of  the  first  phalanx  of  the  index  finger,  the  First  dorsal  and  the  First 
palmar  interosseous;  to  that  of  the  middle  finger,  the  Second  and  Third  dorsal  interosseous; 
to  that  of  the  ring  finger,  the  Fourth  dorsal  and  the  Second  palmar  interossei;  and  to 
that  of  the  little  finger,  the  Third  palmar  interosseous,  the  Flexor  brevis  minimi  digiti,  and 
Abductor  minimi  digiti.  To  the  second  phalanges,  the  Flexor  sublimis  digitorum.  Extensor 
communis  digitorum,  and,  in  addition,  the  Extensor  indicis  to  the  index  finger,  the  Extensor 
minimi  digiti  to  the  little  finger.  To  the  third  phalanges,  the  Flexor  profundus  digitorum  and 
Extensor   communis    digitorum. 

Surface  Form  of  Carpal  and  Metacarpal  Bones  and  of  the  Phalanges.— On  the 
front  of  tlie  wrist  are  two  subcutaneous  eminences,  one  on  the  radial  side,  the  larger  and 
flatter,  due  to  the  tuberosity  of  the  scaphoid  and  tlie  ridge  on  the  trapezium;  the  other,  on 
the  ulnar  side,  caused  by  the  pisiform  bone.  The  tubercle  of  the  scaphoid  may  be  felt  just 
below  and  in  front  of  the  apex  of  the  styloid  process  of  the  radius.  It  is  best  perceived  by 
■extending  the  hand  on  the  forearm.  Immediately  below  may  be  felt  another  prominence,  better 
marked  than  the  tubercle;  this  is  the  ridge  on  the  trapezium  which  gives  attachment  to  some  of 
the  short  muscles  of  the  thumb.  On  the  inner  side  of  the  front  of  the  wrist  the  pisiform  bone 
may  be  felt,  forming  a  small  but  prominent  projection  in  this  situation.  It  is  some  distance  below 
the  styloid  process  of  the  ulna,  and  may  be  said  to  be  just  below  the  level  of  the  styloid  process  of 
the  radius.  The  rest  of  the  front  of  the  carpus  is  covered  by  tendons  and  the  annular  ligament, 
and  entirely  concealed,  with  the  exception  of  the  hooked  process  of  the  unciform,  which  can  only 
be  made  out  with  difficulty.  The  back  of  the  carpus  is  convex  and  covered  by  the  Extensor  ten- 
dons, so  that  none  of  the  posterior  surfaces  of  the  bones  are  to  be  felt,  with  the  exception  of  the 
cuneiform  on  the  inner  side.  Below  the  carpus  the  dorsal  surfaces  of  the  metacarpal  bones, 
except  the  fifth,  are  covered  by  tendons,  and  are  scarcely  visible  e.xcept  in  very  thin  hands.  The 
dorsal  surface  of  the  fifth  is,  however,  subcutaneous  throughout  almost  its  whole  length,  and  may 
be  plainly  perceived  and  felt.  In  addition  to  this,  slightly  external  to  the  middle  line  of  the  hand, 
is  a  prominence,  frequently  well  marked,  but  occasionally  indistinct,  formed  by  the  base  of  the 
metacarpal  of  the  middle  finger.  The  heads  of  the  metacarpal  bones  may  be  plainly  felt  and  seen, 
rounded  in  contour  and  standing  out  in  bold  relief  under  the  skin,  when  the  fist  is  clenched.  It 
should  be  borne  in  mind  that  when  the  fingers  are  flexed  on  the  hand,  the  articular  surfaces  of 
the  first  phalanges  glide  off  the  heads  of  the  metacarpal  bones  on  to  their  anterior  surfaces,  so 
that  the  head  of  these  bones  form  the  prominence  of  the  knuckles  and  receive  the  force  of  any 
blow  which  may  be  given.  The  head  of  the  third  metacarpal  bone  is  the  most  prominent,  and 
receives  the  greater  part  of  the  shock  of  the  blow.  This  bone  articulates  with  the  os  magnum, 
so  that  the  concussion  is  carried  through  this  bone  to  the  scaphoid  and  semilunar,  with  which  the 
head  of  the  os  magnum  articulates,  and  by  these  bones  is  transferred  to  the  radius,  along  which 
it  may  be  carried  to  the  capitellum  of  the  humerus.  The  enlarged  extremities  of  the  phalanges 
may  be  plainly  felt;  they  form  the  joints  of  the  fingers.  When  the  digits  are  bent  the  proximal 
phalanges  of  the  joints  form  prominences,  which  in  the  joint  between  the  first  and  second  pha- 
langes is  slightly  hollowed,  in  accordance  with  the  grooved  shape  of  their  articular  surfaces, 
while  at  the  last  row  the  prominence  is  flattened  and  square-shaped.  In  the  palm  of  the  hand 
the  four  inner  metacarpal  bones  are  covered  by  muscles,  tendons,  and  the  palmar  fascia,  and  no 
part  of  them  but  their  heads  is  to  be  distinguished.  With  regard  to  the  thumb,  on  the  dorsal 
aspect  the  base  of  the  metacarpal  bone  forms  a  prominence  below  the  styloid  process  of  the  radius; 
the  shaft  is  to  be  felt,  covered  by  tendons,  terminating  at  its  head  in  a  flattened  pi'ominence,  in 
front  of  which  can  be  felt  the  sesamoid  bones. 

Applied  Anatomy. — The  carpal  bones  are  not  very  liable  to  fracture,  except  from  extreme 
violence,  when  the  parts  may  be  so  comminuted  as  to  necessitate  amputation.  Occasionally 
they  are  the  seat  of  tubemdous  disease.  The  metacarpal  bones  and  the  phalanges  are  not  infre- 
quently broken  by  direct  violence.     The  first  metacarpal  bone  is  the  one  most  commonly  frae- 


206 


SPECIAL  ANATOMY  OF  THE  SKELETON 


tured;  then  the  second,  the  fourth,  and  the  fifth,  the  third  being  the  one  least  frequently  broken. 
There  are  two  diseases  of  the  metacarpal  bones  and  phalanges  which  require  special  mention  on 
account  of  the  frequency  of  their  occurrence.  One  is  tuberculous  dactylitis,  consisting  in  a  deoosit 
of  tuberculous  material  in  the  medullary  canal,  expanding  the  bone,  with  subsequent  caseadon 
and  resulting  necrosis.  The  other  is  chondroma,  which  is  perhaps  more  frequently  found  in 
connection  with  the  metacarpal  bones  and  phalanges  than  with  any  other  bones.  When  chon- 
dromatous  growth  takes  place  there  are  usually  multiple  tumors,  and  they  may  spring  either 
from  the  medullary  canal  or  from  the  periosteum.  •  ■ 

Development  of  the  Bones  of  the  Hand. — The  carpal  bones  are  each  developed  from  a 
single  centre.  At  birth  they  are  all  cartilaginous.  Ossification  proceeds  in  the  following  order 
(Fig.  166):  In  the  os  magnum  and  unciform  an  ossific  point  appears  during  the  first  year,  the 
former  preceding  the  latter;  in  the  cuneiform,  at  the  third  year;  in  the  trapezium  and  semilunar, 
at  the -fifth  year,  the  latter  preceding  the  former;  in  the  scaphoid,  in  the  si.\th  to  the  eighth  year; 
in  the  trapezoid,  during  the  eighth  year;  and  in  the  pisiform,  about  the  twelfth  year. 


Appears  3rd  year. 

Unite  Wth  year. 
Appears  8th  week. 


Carpus. 

One  centre  for  each  bone 
Alt  cartilaginous  at  butti. 


Metacarpus. 

Two  centres  for  each  tone  • 
One  for  shaft, 
One  for  distal  extremity, 
except  first. 


Phalanges. 

Two  centres  for  eacli  bone   [IJ 
One  for  shaft, 
One  for  metacarpal 
extremity. 


^Appears  ttih-Sth  year. 
Unite  IStli-SOth  year. 
§,  ^l^i—Apnears  8th  week. 

Appears  Uh-Sth  year. 
Unite  ISth-SO  year. 
.^  I  [-^Appears  8th  week. 

Fig.  166. — Plan  of  the  development  of  the  bones  of  the  hand. 

Occasionally  an  additional  bone,  the  os  centrale,  is  found  in  the  carpus,  lying  between  the 
scaphoid,  trapezoid,  and  oS  magnum.  During  the  second  month  of  fetal  life  it  is  represented 
by  a  small  cartilaginous  nodule,  which,  however,  fuses  with  the  cartilaginous  scaphoid  about  the 
third  month.  Sometimes  the  styloid  process  of  the  third  metacarpal  is  detached  and  forms  an 
additional  os.sicle. 

The  metacarpal  bones  are  each  developed  from  ttvo  centres,  one  for  the  shaft  and  one  for 
the  distal  extremity  for  the  four  inner  metacarpal  bones;  one  for  the  shaft  and  one  for  the  base 
for  the  metacarpal  bone  of  the  thumb,  which  in  this  respect  resembles  the  phalanges.'  Ossi- 
fication commences  in  the  centre  of  the  shaft  about  the  eighth  or  ninth  week,  the  centre  for  the 
first  metacarpal  bone  being  the  last  to  appear;  ossification  gradually  proceeds  to  either  end  of 

'  Allan  Thomson  has  demonstrated  the  fact  that  the  first  metacarpal  bone  is  often  developed  from  three  centres; 
that  is  to  say,  there  is  separate  nucleus  for  the  distal  end,  forming  a  distinct  epiphysis,  visible  at  the  age  of  seven  or 
eight  years.  He  also  states  that  there  are  traces  of  a  proximal  epiphysis  in  the  second  metacarpal  bone. — Journal  of  . 
Anatomy  and  Physiology,  1S69. 


THE  OS  INNOMINA  TUM  207 

the  bone:  about  the  third  year  the  distal  extremities  of  the  four  inner  nietaoarpal  bones  and  the 
base  of  the  first  metacarpal  begin  to  ossify,  and  they  unite  with  the  shaft  about  the  twentieth  year. 

The  phalanges  are  each  developed  from  two  centres,  one  for  the  shaft  and  one  for  the  base. 
Ossification  commences  in  the  shaft,  in  all  three  rows,  at  about  the  eighth  week,  and  gradually 
involves  the  whole  bone  excepting  the  upper  extremity.  Ossification  of  the  base  commences  in 
the  first  row  between  the  third  and  fourth  years,  and  a  year  later  in  those  of  the  second  and  third 
rows.    The  two  centres  become  united,  in  each  row,  between  the  eighteentli  and  twentieth  years. 

In  the  ungual  phalanges  the  centre  for  the  shaft  appears  at  the  distal  extremity  of  the  phalanx, 
instead  of  at  the  middle  of  the  shaft,  as  is  the  case  with  the  other  phalanges.  The  ungual 
phalanges  are  the  first  boiies  of  the  hands  to  begin  to  ossify. 


THE  LOWER  EXTREMITY. 

The  lower  extremity  consists  of  the  following  bones:  Ossa  innominata  (with 
the  sacrum  and  coccyx  forming  the  pelvis),  the  femur  (thigh),  the  tibia  and 
fibula  (the  leg),  the  tarsus,  the  metatarsus  and  phalanges  {(ht  foot). 


THE  OS  INNOMINATUM,  CALLED  ALSO  OS  COXAE,  HIP  BONE  (Figs.  167,  168). 

The  OS  iimonunatlun  is  a  large,  irregularly  shaped,  flat  bone,  constricted  in  the 
centre  and  expanded  above  and  below.  With  its  fellow  of  the  opposite  side  it 
forms  the  sides  and  anterior  wall  of  the  pelvic  cavity.  In  young  subjects  it 
consists  of  three  separate  parts,  which  meet  and  form  the  large,  cup-like  cavity, 
the  acetabulum,  situated  near  the  middle  of  the  outer  surface  of  the  bone;  and, 
although  in  the  adult  these  have  become  united,  it  is  usual  to  describe  the  bone 
as  divisible  into  three  portions — the  ilium,  the  ischium,  and  the  pubis. 

The  ilium  is  the  superior,  broad,  and  expanded  portion  which  runs  upward 
from  the  acetabulum  and  forms  the  prominence  of  the  hip. 

The  ischium  is  the  inferior  and  strongest  portion  of  the  bone ;  it  proceeds  down- 
ward from  the  acetabulum,  expands  into  a  large  tuberosity,  and  then,  curving 
forward,  helps  to  bound,  with  the  descending  ramus  of  the  os  pubis,  a  large 
aperture,  the  obturator  foramen. 

The  OS  pubis  is  that  portion  which  extends  inward  and  downward  from  the 
acetabulum  to  articulate  in  the  middle  line  with  the  bone  of  the  opposite  side;  it 
forms  the  front  of  the  pelvis  and  supports  the  external  organs  of  generation. 

The  Ilium  (os  ilium)  presents  for  examination  two  surfaces,  an  external  and 
an  internal,  a  crest,  and  two  borders,  an  anterior  and  a  posterior. 

The  external  surface  (Fig.  167)  is  divided  into  two  parts — an  upper  or  gluteal 
and  a  lower  or  acetabular.  The  upper  portion — known  as  the  dorsum  ilii — is 
directed  backward  and  outward  behind,  and  downward  and  outward  in  front. 
It  is  smooth,  convex  in  front,  deeply  concave  behind;  bounded  above  by  the  crest, 
beloio  by  the  upper  border  of  the  acetabulum;  in  front  and  behind  by  the  anterior 
and  posterior  borders.  This  surface  is  crossed  in  an  arched  direction  by  three 
semicircular  lines — the  superior,  middle,  and  inferior  curved  lines.  The  superior 
curved  line  (linea  glutaea  posterior),  the  shortest  of  the  three,  commences  at  the 
crest,  about  two  inches  in  front  of  its  posterior  extremity;  it  is  at  ftrst  distinctly 
marked,  but  as  it  passes  downward  and  backward  to  the  upper  part  of  the  great 
sacrosciatic  notch,  where  it  terminates,  it  becomes  less  marked,  and  is  often  alto- 
gether lost.  Behind  this  line  is  a  narrow  semilunar  surface,  the  upper  part  of 
vyhich  is  rough  and  affords  origin  to  part  of  the  Gluteus  maximus;  the  lower  part 
is  smooth  and  has  no  muscle  fibres  attached  to  it.  The  middle  curved  line  (linea 
glutaea  anterior),  the  longest  of  the  three,  commences  at  the  crest,  about  an  inch 
behind  its  anterior  extremity,  and,  taking  a  curved  direction  downward  and 
backward,  terminates  at  the  upper  part  of  the  great  sacrosciatic  notch.     The 


208 


SPECIAL  ANATOMY  OF  THE  SKELETON 


space  Ijetween  the  superior  and  middle  curved  lines  and  the  crest  is  concave, 
and  affords  origin  to  the  Gluteus  medius  muscle.  Near  the  central  part  of  this 
line  may  often  be  observed  the  orifice  of  a  nutrient  foramen.     The  inferior  curved 


Anterior  superior 


CTOR  LONGUS 


GEMELLUS    INFERIOR 


Fig.  167. — Right  os  innominatum.     E.xternal  surface. 

line  {linea  glutaea  inferior),  the  least  distinct  of  the  three,  commences  in  front 
at  the  notch  on  the  anterior  border,  and,  taking  a  cun'ed  direction  backward 
and  downward,  terminates  at  the  middle  of  the  great  sacrosciatic  notch.  The 
surface  of  bone  included  between  the  middle  and  inferior  curved  lines  is  concave 
from  above  downward,  convex  from  before  backward,  and  affords  origin  to  the 
Gluteus  minimus  muscle.  Beneath  the  inferior  curved  line,  and  corresponding 
to  the  upper  part  of  the  acetabulum,  is  a  roughened  surface  (sometimes  a  depres- 
sion), from  which  arises  the  reflected  tendon  of  the  Rectus  femoris  muscle. 
The  lower  or  acetabular  part  of  the  external  surface  enters  into  the  formation 


THE  OS  INNOMINATUM 


209 


of  the  acetabulum,  of  which  it  forms  rather  less  than  two-fifths.  It  is  separated 
from  tlie  gluteal  portion  by  a  prominent  rim,  which  forms  part  of  the  margin 
of  the  acetabular  cavity. 


COMPRESSOR  L 

Cnts  penis/  erector  penje 

Fig.  168. — Right  os  innominatum.     Internal  surface. 

The  internal  surface  (Fig.  168)  is  bounded  above  by  the  crest;  belotv  it  is  con- 
tinuous with  the  pelvic  surface  of  the  os  pubis  and  ischium,  a  faint  line  only 
indicating  the  place  of  union;  and  before  and  behind  it  is  bounded  by  the 
anterior  and  posterior  borders.  It  presents  a  large,  smooth,  concave  surface, 
called  the  iliac  fossa  (fossa  iliaca),  which  lodges  the  Iliacus  muscle,  and  presents 
at  its  lower  part  the  orifice  of  a  nutrient  canal,  and  below  this  a  smooth,  rounded 
border,  the  iliopectineal  line  (linea  arcuata).  which  separates  the  iliac  fossa  from  that 
portion  of  the  internal  surface  which  enters  into  the  formation  of  the  true  pelvis, 
and  which  gives  origin  to  part  of  the  Obturator  internus  muscle.  Behind  the 
iliac  fossa  is  a  rough  surface  divided  into  two  portions,  an  anterior  and  a  posterior 

14 


210  SPECIAL  ANATOMY  OF  THE  SKELETON 

The  anterior  or  auricular  portion  { fades  aiiricidaris) ,  so  called  from  its  resemblance 
in  shape  to  the  ear,  is  coated  with  cartilage  in  the  recent  state,  and  articulates 
with  a  surface  of  similar  shape  on  the  side  of  the  sacrum.  The  posterior  portion 
(ivherositas  iliaca)  is  rough,  for  the  attachment  of  the  posterior  sacroiliac  ligaments 
an,d  for  a  part  of  the  origin  of  the  Erector  and  Multifidus  spinae. 

The  crest  of  the  ilium  (crista  iliaca)  is  convex  in  its  general  outline  and  sinuously 
curved,  being  concave  inward  in  front,  concave  outward  behind.  It  is  longer  in 
the  female  than  in  the  male,  very  thick  behind,  and  thinner  at  the  centre  than  at 
the  extremities.  It  terminates  at  either  end  in  a  prominent  eminence,  the  anterior 
superior  and  posterior  superior  spinous  process  {spina  iliaca  anterior  superior  el 
spina  iliaca  posterior  superior).  The  surface  of  the  crest  is  broad,  and  divided 
into  an  external  lip  (labium  externmn),  an  internal  lip  (labium  internum),  and- an 
intermediate  space  (linea  intermedia).  About  two  inches  behind  the  anterior 
superior  spinous  process  there  is  a  prominent  tubercle  on  the  outer  lip.  To  the 
external  lip  is  attached  the  Tensor  fasciae  femoris,  Obliquus  externus  abdominis, 
and  Latissimus  dorsi,  and  along  its  whole  length,  the  fascia  lata;  to  the  space 
between  the  lips,  the  Internal  oblique;  to  the  internal  lip,  the  Transversalis, 
Quadratus  lumborum,  and  Erector  spinae,  the  Iliacus,  and  the  iliac  fascia. 

The  anterior  border  of  the  ilium  is  concave.  It  presents  two  projections,  sepa- 
rated by  a  notch.  Of  these,  the  uppermost,  situated  at  the  junction  of  the  crest 
and  anterior  border,  is  called  the  anterior  superior  spinous  process  of  the  ilium, 
the  outer  border  of  which  gives  attachment  to  the  fascia  lata  and  the  origin  of 
the  Tensor  fasciae  femoris;  its  inner  border,  to  the  Iliacus;  while  its  extremity 
affords  attachment  to  Poupart's  ligament  and  the  origin  of  the  Sartorius.  Beneatli 
this  eminence  is  a  notch  which  gives  origin  to  the  Sartorius  muscle,  and  across 
which  passes  the  external  cutaneous  nerve.  Below  the  notch  is  the  anterior 
inferior  spinous  process  (spina  iliaca  anterior  inferior),  which  terminates  in  the 
upper  lip  of  the  acetabulum;  it  gives  origin  to  the  straight  tendon  of  the  Rectus 
femoris  muscle  and  the  iliofemoral  ligament.  On  the  inner  side  of  the  anterior 
inferior  spinous  process  is  a  broad,  shallow  groove,  over  which  passes  the  Ilio- 
psoas muscle.  This  groove  is  bounded  internally  by  an  eminence,  the  iliopectineal 
eminence  (eminentia  iliopectinea) ,  which  marks  the  point  of  union  of  the  ilium  and 
OS  pubis. 

The  posterior  border  of  the  ilium,  shorter  than  the  anterior,  also  presents  two 
projections  separated  by  a  notch,  the  posterior  superior  spinous  process  (spi7ia 
iliaca  posterior  superior)  and  the  posterior  inferior  spinous  process  (spina  iliaca 
posterior  inferior).  The  former  corresponds  \\ith  that  portion  of  the  inner 
surface  of  the  ilium  which  serves  for  the  attachment  of  the  oblique  portion  of  the 
sacroiliac  ligaments  and  the  Multifidus  spinae  muscle;  the  latter,  to  the  auricular 
portion  which  articulates  with  the  sacrum.  Below  the  posterior  inferior  spinous, 
process  the  posterior  border  forms  the  upper  part  of  a  deep  notch,  the  great 
sacrosciatic  notch. 

The  Ischium  (os  ischii)  forms  the  lower  and  back  part  of  the  os  innominatum. 
It  is  di^'isible  into  a  thick  and  solid  portion — the  body;  a  large,  rough  eminence, 
on  W'hich  the  trunk  rests  in  sitting — the  tuberosity;  and  a  thin  part  which  passes 
inward  and  slightly  upward — the  ramus. 

The  body  (corpus  ossis  ischii),  somewhat  triangular  in  form,  presents  three 
surfaces,  antero-external,  internal,  and  postero-external ;  and  three  borders,  ex- 
ternal, internal,  and  posterior.  The  antero-external  surface  corresponds  to  that 
portion  of  the  acetabulum  formed  by  the  ischium;  it  is  smooth  and  concave, 
and  forms  a  little  more  than  two-fifths  of  the  acetabular  cavity;  its  outer  margin 
is  bounded  by  a  prominent  rim  or  lip,  the  external  border,  to  which  the  cotyloid 
fibrocartilage  is  attached.  Below  the  acetabulum,  between  it  and  the  tuberosity, 
is  a  deep  groove,  along  w-hich  the  tendon  of  the  Obturator  externus  muscle  runs 


THE  OH  INNOMINATUM  211 

as  it  passes  outward  to  be  inserted  into  the  trochanteric  fossa  of  the  femur. 
The  internal  surface  is  smooth,  concave,  and  enters  into  the  formation  of  the  lateral 
boundary-  of  the  true  peh'ic  canity.  This  surface  is  perforated  by  two  or  three 
large,  vascular  foramina,  and  affords  origin  to  part  of  the  Obturator  internus 
muscle.  The  postero-external  surface  is  quadrilateral  in  form,  broad  and  smooth. 
Below,  where  it  joins  the  tuberosity,  it  presents  a  groove,  the  obturator  groove 
(sulcus  ohturatorius) ,  continuous  with  that  on  the  antero-external  surface;  in 
this  groo\'e  is  received  the  posterior  fleshy  part  of  the  Obturator  externus  muscle 
when  the  thigh  is  flexed.  The  lower  edge  of  this  groove  is  formed  by  the  tuberosity 
of  the  ischium,  and  affords  origin  to  the  Gemellus  inferior  muscle.  The  postero- 
external surface  is  limited,  externally,  by  the  margin  of  the  acetabulum;  behind, 
by  the  posterior  border;  it  supports  the  Pyriformis,  the  two  Gemelli,  and  the 
Obturator  internus  muscles  in  their  passage  to  the  great  trochanter.  The  ex- 
ternal border  separates  the  postero-external  from  the  antero-external  surface. 
The  internal  border  is  thin,  and  forms  the  outer  circumference  of  the  obturator 
foramen.  The  posterior  border  of  the  body  of  the  ischium  is  continuous  with 
the  posterior  border  of  the  ilium;  it  presents,  a  little  below  the  centre,  a  thin 
and  pointed  triangular  eminence,  the  spine  of  the  ischium  {spina  ischiadica), 
more  or  less  elongated  in  different  subjects;  its  external  surface  gives  origin 
to  the  Gemellus  superior,  its  internal  surface  to  the  Coccygeus  and  Levator 
ani;  while  to  the  pointed  extremity  is  connected  the  lesser  .sacrosciatic  ligament. 
Above  the  spine  is  a  notch  of  large  size,  the  great  sacrosciatic  notch,  converted  into 
a  foramen,  the  great  sacrosciatic  foramen  (foramen  ischiadicum  majus),  by  the 
lesser  and  greater  sacrosciatic  ligaments;  it  transmits  the  Pyriformis  muscle, 
the  gluteal  vessels,  and  superior  and  inferior  gluteal  nerves;  the  sciatic  vessels, 
the  greater  and  lesser  sciatic  nerves,  the  internal  pudic  vessels  and  nerve,  and  the 
nerves  to  the  Obturator  internus  and  Quadratus  femoris.  Of  these,  the  gluteal 
vessels  and  superior  gluteal  nerve  pass  out  above  the  Pyriformis  muscle,  the  other 
structures,  below  it.  Below  the  spine  is  a  smaller  notch,  the  lesser  sacrosciatic 
notch  (incisura  ischiadica  minor);  it  is  smooth,  coated  in  the  recent  state  with 
cartilage.  It  is  converted  into  a  foramen,  the  lesser  sacrosciatic  foramen  (foramen 
ischiadicum  minus),  by  the  sacrosciatic  ligaments,  and  transmits  the  tendon  of 
the  Obturator  internus,  the  nerve  which  supplies  that  muscle,  and  the  internal 
pudic  vessels  and  nerve. 

The  tuberosity  of  the  ischium  (tuber  ischiadicum)  is  the  portion  of  bone  between 
the  body  and  the  ramus.  The  tuberosity  presents  for  examination  three  sur- 
faces— external,  internal,  and  posterior.  The  external  surface  is  quadrilateral 
in  shape  and  rough,  for  the  attachment  of  muscles.  It  is  bounded  above  by 
the  groove  for  the  tendon  of  the  Obturator  externus;  in  front  it  is  limited  by 
the  posterior  margin  of  the  obturator  foramen,  and  below  it  is  continuous  with  the 
ramus  of  the  bone;  behind,  it  is  bounded  by  a  prominent  margin  which  separates 
it  from  tlie  posterior  surface.  In  front  of  this  margin  the  surface  gives  origin 
to  the  Quadratus  femoris,  and  anterior  to  this  some  of  the  fibres  of  origin  of  the 
Obturator  externus.  The  lower  part  of  the  surface  gives  origin  to  part  of  the 
Adductor  magnus.  The  internal  surface  forms  part  of  the  bony  wall  of  the  true 
^  pelvis.  In  front  it  is  limited  by  the  posterior  margin  of  the  obturator  foramen; 
behind,  it  is  bounded  by  a  sharp  ridge,  for  the  attachment  of  a  falciform  pro- 
longation of  the  great  sacrosciatic  ligament;  it  sometimes  presents  a  groove  on 
the  inner  side  of  this  ridge  for  the  lodgement  of  the  internal  pudic  vessels  and  nerve ; 
and,  more  anteriorly,  has  attached  the  Transversus  perinaei  and  Erector  penis  vel 
clitoridis  muscles.  The  posterior  surface  is  divided  into  two  portions — a  lower 
rough,  somewhat  triangular  part,  and  an  upper  smooth,  quadrilateral  portion. 
The  lower  portion  is  subdivided  by  a  prominent  y-ertical  ridge,  passing  from 
base  to  apex,  into  two  parts;  the  outer  one  gives  origin  to  the  Adductor  magnus; 


212  SPECIAL  ANAT03fY  OF  THE  SKELETON 

the  inner,  to  the  great  sacrosciatic  hgament.  The  upper  portion  is  subdivided 
into  two  facets  by  an  obUque  ridge  which  runs  downward  and  outward ;  from  the 
upper  and  outer  facet  arises  the  Semimembranosus;  from  the  lower  and  inner, 
the  Biceps  and  Semitendinosus. 

The  ramus  {raimis  inferior  ossis  ischii)  is  the  thin,  flattened  part  of  the  ischium 
which  ascends  from  the  tuberosity  upward  and  inward,  and  joins  the  descending 
ramus  of  the  os  pubis,  their  point  of  junction  being  indicated  in  the  adult  by  a 
rough  line.  The  outer  surface  of  the  ramus  is  rough,  for  the  origin  of  the  Obtura- 
tor externus  muscle,  and  also  some  fibres  of  the  Adductor  magnus;  its  inner  sur- 
face forms  part  of  the  anterior  wall  of  the  pelvis.  Its  inner  border  is  thick,  rough, 
slightly  everted,  forms  part  of  the  outlet  of  the  pelvis,  and  presents  two  ridges  and 
an  intervening  space.  The  ridges  are  continuous  with  similar  ones  on  the  de- 
scending ramus  of  the  os  pubis;  to  the  outer  one  is  attached  the  deep  layer  of 
the  superficial  perineal  fascia,  and  to  the  inner,  the  superficial  layer  of  the  tri- 
angular ligament  of  the  perineum.  If  these  two  ridges  are  traced  backward, 
they  will  be  found  to  join  with  each  other  just  behind  the  point  of  origin  of  the 
Transversus  perinei  muscle;  here  the  two  layers  of  fascia  are  continuous  behind 
the  posterior  border  of  the  muscle.  To  the  intervening  space,  just  in  front  of  the 
point  of  junction  of  the  ridges,  is  attached  the  Transversus  perinei  muscle,  and  in 
front  of  this  arises  a  portion  of  the  crus  penis  vel  clitoridis  and  the  Erector  penis 
vel  clitoridis  muscle.  Its  outer  border  is  thin  and  sharp,  and  forms  part  of  the 
inner  margin  of  the  obturator  foramen. 

The  Pubis  (os  pubis)  forms  the  anterior  part  of  the  os  innominatum,  and,  with  the 
bone  of  the  opposite  side,  forms  the  front  boundary  of  the  true  pelvic  cavity.  It  is 
divisible  into  a  body,  a  superior  or  ascending  and  an  inferior  or  descending  ramus. 

The  body  (corpus  ossis  pubis)  is  the  broad  portion  of  bone  formed  at  the  junc- 
tion of  the  two  rami.  It  is  somewhat  quadrilateral  in  shape,  and  presents  for  ex- 
amination two  surfaces  and  three  borders.  The  anterior  surface  is  rough,  directed 
downward  and  outward,  and  serves  for  the  attachment  of  various  muscles.  From 
the  upper  and  inner  angle,  immediately  below  the  upper  border,  arises  the  Adduc- 
tor longus;  lower  down,  from  without  inward,  arise  the  Obturator  externus,  the 
Adductor  brevis,  and  the  upper  part  of  the  Gracilis.  The  posterior  surface, 
convex  from  above  downward,  concave  from  side  to  side,  is  smooth,  and  forms 
part  of  the  anterior  wall  of  the  pelvis.  It  gives  origin  to  the  Levator  ani,  Obturator 
internus,  a  few  muscle  fibres  prolonged  from  the  bladder,  and  the  puboprostatic 
ligaments.  At  the  outer  part  of  the  upper  border  is  a  prominent  tubercle,  which 
projects  forward  and  is -called  the  spine  (tuberciduvi  ptibicimi);  to  it  is  attached 
Poupart's  ligament.  Passing  upward  and  outward  from  this  is  a  prominent 
ridge,  forming  part  of  the  iliopectineal  line  (linea  arcuata).  It  marks  the  brim  of 
the  true  pelvis;  to  it  are  attached  a  portion  of  the  conjoined  tendon  of  the  Internal 
oblique  and  Transversalis  muscles,  Gimbernat's  ligament,  and  the  triangular 
fascia.  Internal  to  the  spine  the  upper  border  is  called  the  crest,  which  ex- 
tends from  this  process  to  the  inner  extremity  of  the  bone.  It  affords  attach- 
ment to  the  conjoined  tendon  of  the  Internal  Oblique  and  Trans^"e^salis,  and 
to  the  Rectus  abdominis  and  Pyramidalis  muscles.  The  point  of  junction  of 
the  crest  with  the  inner  border  of  the  bone  is  called  the  angle ;  to  it,  as  well  as  to 
the  symphysis,  is  attached  the  internal  pillar  of  the  external  abdominal  ring. 
The  internal  border  is  articular;  it  is  oval,  covered  by  eight  or  nine  transverse 
ridges,  which  serve  for  the  attachment  of  a  thin  layer  of  cartilage.  This  surface 
is  united  to  its  fellow  of  the  opposite  side  in  the  whole  pelvis.  The  joint  is  called 
the  symphysis  pubis.  The  outer  border  presents  a  sharp  margin,  which  forms 
part  of  the  circumference  of  the  obturator  foramen  and  afi'ords  attachment  to 
the  obturator  membrane. 

The  ascending  ramus  (ramus  superior  ossis  pubis)  extends  from  the  body  to 


THE  OS  INNOMINATUM  213 

the  point  of  junction  of  the  os  pubis  with  the  ihum,  and  forms  the  upper  part 
of  the  circumference  of  the  obturator  foramen.  It  presents  for  examination 
a  superior,  inferior,  and  posterior  surface,  and  an  outer  extremity.  The  supe- 
rior surface  presents  a  continuation  of  the  iliopectineal  Hne,  already  mentioned  as 
commencing  at  the  pubic  spine.  In  front  of  this  ridge  the  surface  of  bone  is 
triangular  in  form,  wider  externally  than  internally,  smooth,  and  is  covered  by 
the  Pectineus  muscle.  The  surface  is  bounded  externally  by  a  rough  eminence, 
the  iliopectineal  eminence  {eminentia  iliopectinea),  which  serves  to  indicate  the 
point  of  junction  of  the  ilium  and  os  pubis,  and  gives  attachment  to  the  Psoas 
parvus,  when  this  muscle  is  present.  The  triangular  surface  is  bounded  ijelow 
by  a  prominent  ridge,  the  obturator  crest  (crista  obturatoria),  which  extends  from 
the  cotyloid  notch  to  the  spine  of  the  os  pubis.  The  inferior  surface  forms  the 
upper  boundary  of  the  obturator  foramen,  and  presents  externally  a  l)road  and 
deep  oblique  groove,  the  obturator  groove  (sulcus  obturaforius),  for  the  passage 
of  the  obturator  vessels  and  nerve;  and  internally  a  sharp  margin  which  forms 
part  of  the  circumference  of  the  obturator  foramen,  and  to  which  the  obturator 
membrane  is  attached.  The  posterior  surface  forms  part  of  the  anterior  boundary 
of  the  true  pelvis.  It  is  smooth,  convex  from  above  downward,  and  affords 
origin  to  some  fibres  of  the  Obturator  internus.  The  outer  extremity,  the  thickest 
part  of  the  ramus,  forms  one-hfth  of  the  cavity  of  the  aceta!)ulum. 

The  descending  ramus  (ramus  inferior  ossis  pubis)  is  thin  and  flattened.  It 
passes  outward  and  downward,  becoming  narrower  as  it  descends,  and  joins 
with  the  ramus  of  the  ischium.  Its  anterior  surface  is  rough,  for  the  origin  of 
muscles — the  Gracilis  along  its  inner  border;  a  portion  of  the  Obturator  externus 
where  the  ramus  enters  into  the  formation  of  the  obturator  foramen;  and  be- 
tween these  two  muscles  the  Adductores  brevis  and  magnus  from  within  out- 
ward. The  posterior  surface  is  smooth,  and  gives  origin  to  the  Obturator  internus, 
and,  close  to  the  inner  margin,  to  the  Compressor  urethrae.  The  inner  border  is 
thick,  rough,  and  everted,  especially  in  females.  It  presents  two  ridges,  separated 
by  an  intervening  space.  The  ridges  extend  downward,  and  are  continuous 
with  similar  ridges  on  the  ascending  ramus  of  the  ischium;  to  the  external  one 
is  attached  the  deep  layer  of  the  superficial  perineal  fascia,  and  to  the  internal 
one  the  superficial  layer  of  the  triangular  ligament  of  the  perineum.  The  outer 
border  is  thin  and  sharp,  forms  part  of  the  circumference  of  the  obturator  fora- 
men, and  gives  attachment  to  the  obturator  membrane. 

The  Cotyloid  Cavity,  or  Acetabulum,  is  a  deep,  cup-shaped,  hemispherical 
depression,  directed  downward,  outward,  and  forward;  formed  internally  by  the 
os  pubis,  above  by  the  ilium,  behind,  externally,  and  beloic  by  the  ischium,  a  little 
less  than  two-fifths  being  formed  by  the  ilium,  a  little  more  tlian  two-fifths  by  the 
ischium,  and  the  remaining  fifth  by  the  pubic  bone.  It  is  bounded  by  a  prominent 
uneven  rim,  which  is  thick  and  strong  above,  and  serves  for  the  attachment  of  the 
cotyloid  ligament,  which  contracts  its  orifice  and  deepens  the  surface  for  articula- 
tion. It  presents  below  and  internally  a  deep  notch,  the  cotyloid  notch  (incisura 
ucetabuli),  which  is  continuous  with  a  circular  depression,  the  fossa  of  the  ace- 
tabulum (fossa  acetabuli),  at  the  bottom  of  the  cavity;  this  depression  is  perforated 
by  numerous  apertures,  lodges  a  mass  of  fat,  and  its  margins,  as  well  as  those  of 
the  notch,  serve  for  the  attachment  of  the  ligamentum  teres.  The  fossa  acetabuli 
is  partly  surrounded  by  a  concave  rim  of  bone  (fades  lunata).  The  cotyloid  notch 
is  converted,  in  the  natural  state,  into  a  foramen  by  a  dense  ligamentous  band, 
the  transverse  ligament,  which  passes  across  it.  Through  this  foramen  the  nu- 
trient vessels  and  nerA'cs  of  the  joint  pass. 

The  Obturator,  or  Thyroid  Foramen  (foramen  obturatum),  is  a  large  aperture 
situated  between  the  ischium  and  os  pubis.  In  the  male  it  is  large,  of  an  oval 
form,  its  longest  diameter  being  obliquely  from  before  backward;  in  the  female 


214  SPECIAL  ANATOMY  OF  THE  SKELETON 

it  is  smaller  and  more  triangular.  It  is  bounded  by  a  thin,  uneven  margin,  to 
which  a  strong  membrane  is  attached,  and  presents,  anteriorly,  a  deep  groove, 
the  obturator  groove  (sulcus  obtiiratorius),  which  runs  from  the  pelvis  obliquely 
inward  and  downward.  This  groove  is  converted  into  a  foramen  by  a  ligamentous 
band,  a  specialized  part  of  the  obturator  membrane,  attached  to  two  tubercles, 
one  (tuberculum  obturatorium  posterkis)  on  the  internal  border  of  the  ischium,  just 
in  front  of  the  cotyloid  notch,  the  other  (tubercuhim  obturatorium  anterius)  on  the 
inferior  margin  of  the  posterior  surface  of  the  ascending  ramus  of  the  pubis,  and 
transmits  the  obturator  vessels  and  nerve. 

Structure. — This  bone  consists  of  much  cancellous  tissue,  especially  where  it  is  thick,  enclosed 
between  two  layers  of  dense,  compact  tissue.  In  the  thinner  parts  of  the  bone,  as  at  the  bottom 
of  the  acetabulum  and  centre  of  the  iliac  fossa,  it  is  usually  semitransparent,  and  composed 
entirely  of  compact  tissue. 

Development  (Fig.  169). — From  eight  centres — three  primary,  one  for  the  ilium,  one  for  the 
ischium,  and  one  for  the  os  pubis;  and  five  secondary,  one  for  the  crest  of  the  ilium,  one  for  the 
anterior  inferior  spinous  process  (said  to  occur  more  frequently  in  the  male  than  in  the  female), 
one  for  the  tuberosity  of  the  ischium,  one  for  the  symphysis  pubis  (more  frequent  in  the  female 
than  the  male),  and  one  or  more  for  the  Y-shaped  piece  at  the  bottom  of  the  acetabulum.    These 


„  ■  ,,       J       \  Three  primary  {Ilium,  Ischium,  and  Os  Pubis). 

F'-om  eight  centres  ip^^^^^^y^^ 


S.  Symphysis  pub/: 


The  three  primary  centres  unite  through  a  V-shaped  piece  about  puberty. 
Epiphyses  appear  about  puberty,  and  unite  about  the  twenty-Jifth  year. 

Fig.  169. — Plan  of  the  development  of  the  os  innominatum. 

various  centres  appear  in  the  following  order:  First,  in  the  ilium,  at  the  lower  part  of  the  bone, 
immediately  above  the  sciatic  notch,  at  about  the  eighth  or  ninth  week;  secondly,  in  the  body  of 
the  ischium,  at  about  the  third  month  of  fetal  life;  thirdly,  in  the  body  of  the  os  pubis,  between 
the  fourth  and  fifth  months.  At  birth  the  three  primary  centres  are  quite  separate,  the  crest,  the 
bottom  of  the  acetabulum,  the  ischial  tuberosity,  and  the  rami  of  the  ischium  and  pubes  being 
still  cartilaginous.  At  about  the  seventh  or  eighth  year  the  rami  of  the  os  pubis  and  ischium  are 
almost  completely  united  by  bone.  About  the  twelfth  year  the  three  divisions  of  the  bone  have 
extended  their  growth  into  the  bottom  of  the  acetabulum,  being  separated  from  each  other  by  a 
Y-shaped  portion  of  cartilage,  which  now  presents  traces  of  ossification,  often  by  two  or  more 
centres.  One  of  these,  the  os  acetahuli,  appears  about  the  age  of  twelve,  between  the  ilium  and  os 
pubis,  and  fuses  with  them  about  the  aeeof  eighteen.  It  forms  the  pubic  part  of  the  acetabulum. 
The  ilium  and  ischium  then  become  joined,  and  lasdy  the  os  pubis  to  the  ischium,  through  the 


THE  PELVIS  215 

intervention  of  this  Y-shaped  portion.  At  about  the  age  of  puberty  ossification,  takes  place 
in  each  of  the  remaining  portions,  and  they  become  joined  to  the  rest  of  the  bone  between  the 
twentieth  and  twenty-fifth  years.  Separate  centres  are  frequently  found  for  the  pubic  and  ischiiil 
.spines. 

Articulations. — ^Yith  its  fellow  of  the  opposite  side,  the  sacrum,  and  femur. 

Attachment  of  Muscles.— To  the  ilium,  sixteen.  To  the  outer  lip  of  the  crest,  the  Tensor 
vaginae  femoris,  Obliquus  externus  abdominis,  and  Latissimus  dorsi;  to  the  internal  lip,  the 
Iliacus,  Transversalis,  Quadratus  lumborum,  and  Erector  spinae;  to  the  intenspace  between  the 
lips,  the  Obliquus  internus.  To  the  outer  surface  of  the  ilium,  the  Gluteus  maximus.  Gluteus 
medius.  Gluteus  minimus,  reflected  tendon  of  the  Rectus  femoris;  to  the  upper  part  of  the  great 
sacrosciatic  notch,  a  portion  of  the  Pyriformis;  to  the  internal  surface,  the  Iliacus;  to  that  portion 
of  the  internal  surface  below  the  iliopectineal  line,  the  Obturator  internus  to  the  internal  surface 
of  the  posterior  superior  spine,  and  the  Multifidus  spinae;  to  the  anterior  border,  the  Sartoi'ius 
and  straight  tendon  of  the  Rectus  femoris.  To  the  ischium,  thirteen.  To  the  outer  surface  of 
the  ramus,  the  Obturator  e.xternus  and  Adductor  magnus;  to  the  internal  surface,  the  Obturator 
internus  and  Erector  penis.  To  the  spine,  the  Gemellus  superior,  Levator  ani,  and  Coccygeus. 
To  the  tuberosity,  the  Biceps,  Semitendinosus,  Semimembranosu.s,  Quadi'atus  femoris.  Adductor 
magnus,  Gemellus  inferior,  Transversus  perinei.  Erector  penis.  To  the  pubis,  sixteen:  Obliquus 
externus,  Obliquus  internus,  Transversalis,  Rectus  abdominis,  Pyramidalis,  Psoas  parvus, 
Pectineus,  Adductor  magnus,  Adductor  longus.  Adductor  brevis.  Gracilis,  Obturator  externus 
and  internus.  Levator  ani,  Compressor  urethrae,  and  occasionally  a  few  fibres  of  the  Accelerator 
urinae. 

THE   PELVIS    (Figs.  170,  171). 

The  pelvis  is  stronger  and  more  massively  constructed  than  either  the  cranial 
or  thoracic  cavity;  it  is  a  bony  ring,  interposed  between  the  lower  end  of  the  verte- 
bral column,  which  it  supports,  and  the  lower  extremities,  upon  which  it  rests. 
It  is  composed  of  four  bones — the  two  ossa  innominata,  which  boiuid  it  on  either 
side  and  in  front,  and  the  sacrum  and  cocc3rx,  which  complete  it  behind.  The 
pelvis  is  divided  by  an  oblique  plane  passing  through  the  prominence  of  the 
sacrum,  the  iliopectineal  line,  and  the  upper  margin  of  the  syinphysis  pubis 
into  the  false  and  true  pelvis. 

The  False  Pelvis  {pelvis  major)  is  the  expanded  portion  of  the  pelvic  cavity 
which  is  situated  above  this  plane.  It  is  bounded  on  each  side  by  the  ossa  ilii; 
in  front  it  is  incomplete,  presenting  a  wide  interval  between  the  spinous  proces.ses 
of  the  ilia  on  either  side,  which  is  filled  up  in  the  recent  state  by  the  parietes  of 
the  abdomen;  behind,  in  the  middle  line,  is  a  deep  notch.  This  broad,  shallow 
cavity  is  fitted  to  support  the  intestines  and  to  transmit  part  of  their  weight  to 
the  anterior  wall  of  the  abdomen,  and  is,  in  fact,  really  a  portion  of  the  abdominal 
cavity.  The  term  false  pelvis  is  incorrect,  and  this  space  ought  more  properly  to 
be  regarded  as  part  of  the  hypogastric  and  iliac  regions  of  the  abdomen. 

The  True  Pelvis  (pelvis  minor)  is  that  part  of  the  pelvic  cavity  which  is 
situated  below  the  iliopectineal  line.  It  is  smaller  than  the  false  pelvis,  but  its 
walls  are  more  perfect.  For  convenience  of  description  it  is  divided  into  a  superior 
circumference,  or  inlet,  an  inferior  circumference,  or  outlet,  and  a  cavity. 

Tiie  superior  circumference,  or  inlet  (apertura  pelvis  superior),  forms  the  brim 
of  the  pelvis,  the  included  space  being  called  the  inlet.  It  is  formed  by  the  ilio- 
pectineal line,  completed  in  front  by  the  crests  of  the  pubic  bones,  and  behind 
by  the  anterior  margin  of  the  base  of  the  sacrum  and  sacrovertebral  angle.  Tlie 
inlet  of  the  pelvis  is  somewhat  heart-shaped,  obtusely  pointed  in  front,  diverging 
on  either  side,  and  encroached  upon  behind  by  the  projection  forward  of  the 
promontory  of  the  sacrum.  It  has  three  principal  diameters — antero-posterior 
(sacropubic),  transverse,  and  oblique.  The  antero-posterior  or  conjugate  diameter 
(conjugata)  extends  from  the  sacrovertebral  angle  to  the  symphysis  pubis.  Its 
average  measurement  is  four  inches  in  the  male  and  four  and  three-fifths  inches 
in  the  female.  The  transverse  diameter  {diameter  transversa)  extends  across 
the  greatest  width  of  the  inlet,  from  the  middle  of  the  brim  on  one  side  to  the 


216  SPECIAL  ANATOMY  OF  THE  SKELETON 

same  point  on  the  opposite;  its  average  measurement  is  five  inches  in  the  male, 
five  and  one-fourth  inches  in  the  female.  The  oblique  diameter  (diameter  ohliqua) 
extends  from  the  margin  of  the  pelvis,  corresponding  to  the  iliopectineal  eminence 


170.— Male  pelvis  (adult). 


on  one  side,  to  the  sacroiliac  articulation  on  the  opposite  side;  its  average  measure- 
ment is  four  and  one-fourth  inches  in  the  male  and  five  in  the  female. 

The  cavity  of  the  true  pelvis  is  bounded  in  front  by  the  symphysis  pubis;  behind, 
by  the  concavity  of  the  sacrum  and  coccyx,  vt'hich,  curving  forward  above  and 


Fig.  171. — Female  pelvis  (adult). 


belovv^,  contracts  the  inlet  and  outlet  of  the  canal;  and  laterally  it  is  bounded  by 
a  broad,  smooth,  quadrangular  surface  of  bone,  corresponding  to  the  inner  surface 
of  the  body  of  the  ischium  and  that  part  of  the  ilium  which  is  below  the  ilio- 


THE  PEL  Vm  217 

pectineal  line.  The  cavity  is  sliallow  in  front,  measuring  at  the  symphysis  an 
inch  and  a  half  in  depth,  three  inches  and  a  half  in  the  middle,  and  four 
inches  and  a  half  posteriorly.  From  this  description  it  will  be  seen  that  the  cavity 
of  the  pelvis  is  a  short,  curved  canal,  considerably  deeper  on  its  posterior  thaii 
on  its  anterior  wall.  This  cavity  contains,  in  the  recent  subject,  the  rectum, 
bladder,  and  some  of  the  organs  of  generation.  The  rectum  is  placed  at  the  back 
of  the  pelvis,  and  corresponds  to  the  curve  of  the  sacrococcygeal  segment  of  the 
vertebral  column;  the  bladder  in  front,  behind  the  symphysis  pubis.  In  the  female 
the  uterus  and  vagina  occupy  the  interval  between  these  viscera. 

The  lower  circumference  is  very  irregular;  the  space  enclosed  by  it  is  called 
the  outlet  (apertura  pelvis  inferior).  It  is  bounded  by  three  prominent  emi- 
nences— one  posterior,  formed  by  the  point  of  the  coccyx;  and  one  on  each  side, 
the  tuberosities  of  the  ischia.  These  eminences  are  separated  by  three  notches; 
one  in  front,  the  pubic  arch  (arciis  pubis),  formed  by  the  convergence  of  the  rami 
of  the  ischia  and  pubic  bones  on  each  side.  The  other  notches,  one  on  each  side, 
are  formed  by  the  sacrum  and  coccyx  behind,  the  ischium  in  front,  and  the  ilium 
above ;  they  are  called  the  sacrosciatic  notches ;  in  the  natural  state  they  are  converted 
into  foramina  by  the  lesser  and  greater  sacrosciatic  ligaments.  In  the  recent 
state,  when  the  ligaments  are  in  situ,  the  oudet  of  the  pelvis  is  lozenge-shaped, 
bounded  in  front  by  the  subpubic  ligament  and  the  rami  of  theos  pubis  and  ischium; 
on  each  side  by  the  tuberosities  of  the  ischia;  and  behind  by  the  great  sacrosciatic 
ligaments  and  the  tip  of  the  coccyx. 

The  diameters  of  the  outlet  of  the  pelvis  are  two,  antero-posterior  and  trans- 
verse. The  antero-posterior  diameter  extends  from  the  tip  of  the  coccyx  to  the 
lower  part  of  the  symph}'sis  pubis;  its  average  measurement  is  three  and  three- 
quarter  inches  in  the  male  and  four  and  one-half  inches  in  the  female.  The 
antero-posterior  diameter  varies  with  the  length  of  the  coccyx,  and  is  capable 
of  increase  or  diminution  on  account  of  the  mobility  of  that  bone.  During  labor 
the  coccyx  may  be  bent  back  so  that  the  conjugate  is  increased  one  inch,  or  even 
one  and  one-fourth  inches.  The  transverse  diameter  extends  from  the  posterior 
part  of  one  ischiatic  tuberosity  to  the  same  point  on  the  opposite  side;  the  average 
measurement  is  three  and  one-half  inches  in  the  male  and  four  and  three-fourths 
in  the  female.' 

Position  of  the  Pelvis. — In  the  erect  posture  the  pelvis  is  placed  obliquely  with 
regard  to  the  trunk  of  the  body;  the  bony  ring,  which  forms  the  brim  of  the  true 
pelvis,  is  placed  so  as  to  form  an  angle  of  about  60  to  65  degrees  with  the  ground 
on  which  we  stand  (inclinatio  pelvis).  The  pelvic  surface  of  the  symphysis 
pubis  looks  upward  and  backward,  the  concavity  of  the  sacrum  and  coccyx  down- 
ward and  forward,  the  base  of  the  sacrum  in  well-formed  female  bodies  being 
nearly  four  inches  above  the  upper  border  of  the  symphysis  pubis,  and  the  apex 
of  the  coccyx  a  little  more  than  half  an  inch  above  its  lower  border.  In  conse- 
quence of  the  obliquity  of  the  pelvis  the  line  of  gravity  of  the  head,  which  passes 
through  the  middle  of  the  odontoid  process  of  the  axis  and  through  the  points 
of  junction  of  the  curves  of  the  vertebral  column  to  the  sacrovertebral  angle, 
descends  toward  the  front  of  the  cavity,  so  that  it  bisects  a  line  drawn  transversely 
through  the  middle  of  the  heads  of  the  thigh  bones.  And  thus  the  centre  of  gravity 
of  the  head  is  placed  immediately  over  the  heads  of  the  thigh  bones  on  which  the 
trunk  is  supported. 

'  The  measurements  of  the  pelvis  given  above  are,  I  believe,  fairly  accurate,  but  different  measurements  are 
given  by  various  authors,  no  doubt  due  in  a  great  measure  to  differences  in  the  physique  and  stature  of  the 
population  from  whom  the  measurements  have  been  taken.  The  accompanying  table  has  been  formulated  to 
show  the  measurements  of  the  pelvis  which  are  adopted  by  many  obstetricians. — [Editor.] 


Diameters  of  the  True  Pelvis  in  Woman. 
Antero-posterior.  Oblique.  Transrerse. 

Of  inlet      .      .     4';5  inches  (118  mm.)  5  inches  (127  mm.)  SVt  inches  (135  i 

Of  outlet.      .     4'/..,  inches  (115  mm.)  4»;i  inches  (120  i 


218 


SPECIAL  ANATOMY  OF  THE  SKELETON 


Axes  of  the  Pelvis  (Fig.  172). — The  plane  of  the  inlet  of  the  true  pelvis  will 
be  represented  by  a  line  drawn  from  the  base  of  the  sacrum  to  the  upper  margin 
of  the  symphysis  pubis.  A  line  carried  at  right  angles  with  this  at  its  middle 
would  correspond  at  one  extremity  with  the  umbilicus,  and  at  the  other  with  the 
middle  of  the  coccyx;  the  axis  of  the  inlet  is  therefore  directed  downward  and 
backward.     The  axis  of  the  outlet,  prolonged  upward,  would  touch  the  base  of 

the  sacrum,  and  is  therefore  directed  downward 
and  forward.  The  axis  of  the  cavity  is  curved 
like  the  cavity  itself;  this  curve  corresponds  to 
the  concavity  of  the  sacrum  and  coccyx,  the 
extremities  being  indicated  by  the  central  points 
of  the  inlet  and  outlet.  A  knowledge  of  the 
direction  of  these  axes  serves  to  explain  the 
course  of  the  fetus  in  the  passage  through  the 
pelvis  during  parturition. 

Differences     between    the    Male    and    Female 

Pelvis. — The  female  pelvis,  looked  at  as  a  whole, 

is   distinguished   from    the   male   by   the  bones 

being  more  delicate,  by  its  width  being  greater 

and  its  depth  smaller.     The  whole  pelvis  is  less 

massive,  and    its    bones  are    lighter   and    more 

slender,  and  its  muscular  impressions  are  slightly 

marked.     The  iliac  fossae  are  shallow,  and  the 

anterior  iliac  spines  widely  separated;  hence  the 

greater  prominence  of  the  hips.     The  inlet  in 

the  female  is  larger  than  in  the  male;  it  is  more 

nearly    circular,    and    the    sacrovertebral   angle 

projects  less  forward.     The  cavity  is  shallower  and  wider;  the  sacrum  is  shorter, 

wider,  and  less  curved;  the  obturator  foramina  are  triangular,  and  smaller  in  size 

than  in  the  male.     The  outlet  is  larger  and  the  coccyx  more  movable.     The 


Plane  0/ 


outlet. 


Fig.  172. — Vertical  section  of  the  pelvis, 
with  lines  indicating  the  axis  of  the  pelvis. 


Fig.  173. — Diameters  of  the  pelvic  inlet  in  the  female. 


spines  of  the  ischia  project  less  inward.  The  tuberosities  of  the  ischia  aud  the 
acetabula  are  wider  apart.  The  pubic  arch  is  wider  and  more  rounded  than  in 
the  male,  where  it  is  an  angle  rather  than  an  arch.     In  consequence  of  this  the 


THE  PELVIS 


219 


width  of  the  fore  part  of  the  pelvic  outlet  is  much  increased  and  the  passage 
of  the  fetal  head  facilitated. 

The  size  of  the  pelvis  varies  not  only  in  the  two  sexes,  but  also  in  different 
members  of  the  same  sex.  This  does  not  appear  to  be  influenced  in  any  way  by 
the  height  of  the  individual.  Women  of  short  stature,  as  a  rule,  have  broad 
pelves.  Occasionally  the  pelvis  is  equally  contracted  in  all  its  dimensions,  so 
much  so  that  all  its  diameters  measure  an  inch  less  than  the  average,  and  this 
even  in  women  of  average  height  and  otherwise  well  formed.  The  principal 
divergences,  however,  are  foimd  at  the  inlet,  and  affect  the  relation  of  the  antero- 
posterior to  the  transverse  diameter.  Thus  we  may  have  a  pelvis  the  inlet  of 
which  is  elliptical  either  in  a  transverse  or  antero-posterior  direction;  the  trans- 
verse diameter  in  the  former  and  the  antero-posterior  in  the  latter  greatly  exceeding 
the  other  diameters.  Again,  the  inlet  of  the  pelvis  in  some  instances  is  seen  to 
be  almost  circular.  The  same  differences  are  found  in  various  races.  European 
women  are  said  to  have  the  most  roomy  pelves.  That  of  the  negress  is  smaller, 
circular  in  shape,  and  with  a  narrow  pubic  arch.  The  Hottentots  and  Bushwomen 
possess  the  smallest  pelves. 


Fig.  174. — Diameters  of  the  pelvic  outlet  in  the  female. 

In  the  fetus  and  for  several  years  after  birth  the  pelvis  is  small  in  proportion 
to  that  of  the  adult.  The  cavity  is  deep  and  the  projection  of  the  sacrovertebral 
angle  less  marked.  The  generally  accepted  opinion  that  the  female  pelvis  does 
not  acquire  its  sexual  characters  until  after  puberty  has  been  shown  by  recent 
observations^  to  be  erroneous,  the  characteristic  differences  between  the  male  and 
female  pelvis  being  distinctly  indicated  as  early  as  the  fourth  month  of  fetal  life. 
At  birth  these  differences  are  distinct  (Romiti),  the  female  pelvis  possessing  less 
straight  ilia,  a  broader  subpubic  arch,  and  less  height  than  the  male. 

Surface  Form.— The  pelvic  bones  are  so  thickly  covered  with  muscles  that  it  is  only  at  cer- 
tain points  that  they  approach  the  surface  and  can  be  feU  through  the  skin.  In  front,  the  anterior 
superior  spinous  process  is  easily  recognized;  a  portion  of  it  is  subcutaneous,  and  in  thin  sub- 
jects may  be  seen  to  stand  out  as  a  prominence  at  the  outer  extremity  of  the  fold  of  the  groin, 
in  fat  subjects  its  position  is  marked  by  an  oblique  depression  among  the  surrounding  fat, 
at  the  bottom  of  which  the  bony  process  may  be  felt.  Proceeding  upward  and  outward  from 
this  process,  the  crest  of  the  ilium  may  be  traced  throughout  its  whole  length,  sinuously  curved. 
It  is  represented,  in  muscular  subjects,  on  the  surface,  by  a  groove  or  furrow,  the  iliac  furrow, 
caused  by  the  projection  of  fleshy  fibres  of  the  External  oblique  muscles  of  the  abdomen ;  the 

niik..  Band  ix  and  x;  and  Arthur  Thomson,  Journ.al  of  .Anatomy  and 


220  SPECIAL  ANATOMY  OF  THE  SKELETON 

iliac  furrow  lies  slightly  below  the  level  of  the  crest.  It  terminates  behind  in  the  posterior  supe- 
rior spinous  process,  the  position  of  which  is  indicated  by  a  slight  depression  on  a  level  with  the 
spinous  process  of  the  second  sacral  vertebra.  Between  the  two  posterior  superior  spinous 
processes,  but  at  a  lower  level,  is  to  be  felt  the  spinous  process  of  the  third  sacral  vertebra  (see 
page  68).  Another  part  of  the  bony  pelvis  easily  accessible  to  touch  is  the  tuberosity  of  the 
ischium,  situated  beneath  the  gluteal  fold,  and,  when  the  hip  is  flexed,  it  is  easily  felt,  as  it  is  then 
to  a  great  extent  uncovered  by  muscle.  Finally,  the  spine  of  the  os  pubis  can  always  be  readily 
felt,  and  constitutes  an  important  surgical  guide,  especially  in  connection  with  the  subject  of 
hernia.  It  is  nearly  in  the  same  horizontal  line  with  the  upper  edge  of  the  great  trochanter.  In 
thin  subjects  it  is  very  apparent,  but  in  the  obese  it  is  obscured  by  the  pubic  fat.  It  can,  however, 
be  detected  by  everting  the  thigh  and  following  up  the  tendon  of  origin  of  the  Adductor  longus 
muscle. 

Applied  Anatomy. — There  is  arrest  of  development  in  the  bones  of  the  pelvis  in  cases  of 
extroversion  of  the  bladder;  the  anterior  part  of  the  pelvic  girdle  being  deficient,  the  bodies  of  the 
pubic  bones  imperfectly  developed,  and  the  symphysis  absent.  The  pubic  bones  are  separated 
to  the  extent  of  from  two  to  four  inches,  the  superior  rami  shortened  and  directed  forward,  and 
the  obturator  foramen  diminished  in  size,  narrowed,  and  turned  outward.  The  iliac  bones  are 
straightened  out  more  than  normal.  The  sacrum  is  very  peculiar.  The  lateral  curve,  instead  of 
being  concave,  is  flattened  out  or  even  convex,  with  the  iliosacral  facets  turned  more  outward 
than  normal,  while  the  vertical  curve  is  straightened.' 

Fractures  of  the  pelvis  are  divided  into  fractures  of  the  false  pelvis  and  of  the  true  pelvis.  Frac- 
tures of  the  false  pelvis  vary  in  extent:  a  small  portion  of  the  iliac  crest  may  be  broken  or  one  of 
the  spinous  processes  may  be  torn  off,  and  this  may  be  the  result  of  muscular  action;  or  the 
bone  may  be  extensively  comminuted.  This  latter  accident  is  the  result  of  some  crushing  vio- 
lence, and  may  be  complicated  with  fracture  of  the  true  pelvis.  These  cases  may  be  accompanied 
by  injury  to  the  intestine  as  it  lies  in  the  hollow  of  the  bone,  or  to  the  iliac  vessels  as  they  course 
along  the  margin  of  the  true  pelvis.  Fractures  of  the  true  pelvis  generally  occur  through  the 
ascending  ramus  of  the  os  pubis  and  the  ramus  of  the  ischium,  as  this  is  the  weakest  part  of  the 
bony  ring,,  and  may  be  caused  either  by  crushing  violence  applied  in  an  antero-posterior  direction, 
when  the  fracture  occurs  from  direct  force,  or  by  compression  laterally,  when  the  acetabula  are 
pressed  together,  and  the  bone  gives  way  in  the  same  place  from  indirect  violence.  Occasionally 
the  injury  may  be  double,  a  break  occurring  on  both  sides  of  the  body.  In  fracture  of.  the  true 
pelvis  the  contained  viscera  are  liable  to  be  damaged;  the  small  intestines,  the  urethra,  the  bladder, 
the  rectum,  the  vagina,  and  even  the  uterus,  in  the  female,  have  all  been  lacerated  by  a  dis- 
placed fragment.  Fractures  of  the  acetabulum  are  occasionally  met  with;  either  a  portion  of 
the  rim  may  be  broken  off,  or  a  fracture  may  take  place  through  the  bottom  of  the  cavity,  and  the 
head  of  the  femur  may  be  driven  inward  and  project  into  the  pelvic  cavity.  Separation  of  the 
Y-shaped  cartilage  at  the  bottom  of  the  acetabulum  may  also  occur  in  the  young  subject, 
dispersing  the  bone  into  its  three  anatomical  portions. 

The  sacrum,  is  seldom  broken.  The  cause  is  direct  violence — i.  e.,  blows,  kicks,  or  falls  on  the 
part.  The  lesion  may  be  complicated  with  injury  to  the  nerves  of  the  sacral  plexus,  leading 
to  paralysis  and  loss  of  sensation  in  the  lower  extremity  or  to  incontinence  of  feces  from  paralysis 
of  the  Sphincter  ani. 

Fracture  of  the  coccyx  is  a  very  rare  injury,  but  does  occasionally  take  place.  Some  sup- 
posed dislocations  of  this  bone  have  been  fractures  and  so  have  some  of  the  cases  diagnosticated 
as  coccygodynia.    A  fracture  of  the  coccyx  is  due  to  direct  force. 

The  pelvic  bones  often  undergo  important  deformity  in  rhachiti-s,  the  effect  of  which  in  the 
adult  woman  may  interfere  seriously  with  childbearing.  The  deformity  is  due  mainly  to  the 
weight  of  the  spine  and  trunk,  which  presses  on  the  sacrovertebral  angle  and  greatly  increases 
it,  so  that  the  antero-posterior  diameter  of  the  pelvis  is  diminished.  But,  in  addition  to  this, 
the  weight  of  the  viscera  on  the  venter  ilii  causes  the  ilia  to  expand  and  the  tuberosities  of  the 
ischia  to  incurve.  In  osteomalacia  also  great  deformity  may  occur.  The  weight  of  the  trunk 
causes  an  increase  in  the  sacrovertebral  angle  and  a  lessening  of  the  antero-posterior  diameter 
of  the  inlet,  and  at  the  same  time  the  pressure  of  the  acetabula  on  the  heads  of  the  thigh  bones 
causes  these  cavities,  with  the  adjacent  bone,  to  be  pushed  upward  and  backward,  so  that  the 
oblique  diameters  of  the  pelvis  are  also  diminished,  and  the  cavity  of  the  pelvis  assumes  a  tri- 
radiate  shape,  with  the  symphysis  pubis  pushed  forward. 

THE  THIGH. 

The  thigh  is  that  portion  of  the  lower  extremity  which  is  situated  between  the 
pelvis  and  the  knee.     It  consists  in  the  skeleton  of  a  single  bone,  the  fenmr. 

1  Wood,  Heath's  Dictionary  of  Practical  Surgery,  i,  426. 


THE  FE31VB,    OR  THIGH  BONE 


221 


The  Femur,  or  Thigh  Bone 

(Figs.  175,  177). 

The  femur  (femur)  is  tiie  long- 
est,' largest,  and  strongest  bone 
in  the  skeleton,  and  almost  per- 
fectly cylindrical  throughout  the 
greater  part  of  its  extent.  In  the 
erect  posture  it  is  not  vertical, 
being  separated  from  its  fellow 
above  by  a  considerable  interval, 
which  corresponds  to  the  entire 
breadth  of  the  pelvis,  but  inclin- 
ing  gradually  downward  and  in- 
ward, so  as  to  approach  its  fellow 
toward  its  lower  part,  for  the 
purpose  of  bringing  the  knee-joint 
near  the  line  of  gravity  of  the 
body.  The  degree  of  this  incli- 
nation varies  in  different  persons, 
and  is  greater  In  the  female  than 
the  male,  on  account  of  the  greater 
breadth  of  the  pelvis.  The  femur, 
like  other  long  bones,  is  divisible 
into  a  shaft  and  two  extremities. 

The  Upper  or  Proximal  Ex- 
tremity presents  for  examination 
S  head,  a  neck,  and  a  greater  and 
a  lesser  trochanter. 

The  head  {caput  femor is)  ,v\\\ch. 
is  globulai^  and  forms  rather  more 
than  a  hemisphere,  is  directed  up- 
ward, inward,  and  a  little  forward, 
the  greater  part  of  its  convexity 
being  above  and  in  front.  Its 
surface  is  smooth,  coated  with 
hyaline  cartilage  in  the  recent 
state,  except  at  a  little  behind  and 
below  its  centre,  where  there  is 
an  ovoid  depression  {fovea  capitis 
femoris),  for  the  attachment  for 
the  ligamentum  teres. 

The  neck  {collum  femoris)  is 
a  flattened  pyramidal  process  of 
bone  which  connects  the  head 
with  the  shaft.  It  varies  in  length 
and  obliquity  at  various  periods  in 
life  and  under  different  circum- 
stances. The  angle  is  widest  in 
infancy,  and  becomes  lessened 
during  growfh,  so  that  at  puberty 
it  forms  a  gehtle  curve  from  the 


1  In  a  man  six  fee^  high  it  measures  eighteen 
inches — one-fourth  of  the  whole  body  stature. 


DepreMion  for 

LIGAMENTUM   TERES. 


'"■e/-  CoiliW 


"Ve. 
Fig.  175. — Right  femu 


Anterior  surfacei 


'222 


SPECIAL  ANATOMY  OF  THE  SKELETON 


axis  of  the  shaft.  In  the  adult  it  forms  an  angle  of  about  125  degrees  with  the 
shaft,  but  varies  in  inverse  proportion  to  the  development  of  the  pelvis  and  the 
stature.  In  consequence  of  the  prominence  of  the  hips  and  widening  of  the  pelvis 
in  the  female,  the  neck  of  the  thigh  bone  forms  more  nearly  a  right  angle  with  the 
shaft  than  it  does  in  the  male.  The  neck  is  flattened  from  before  backward, 
contracted  in  the  middle,  and  broader  at  its  outer  extremity,  where  it  is  connected 
with  the  shaft,  than  at  its  summit,  where  it  is  continuous  with  the  head.  The 
vertical  diameter  of  the  outer  half  is  increased  by  the  thickening  of  the  lower  edge, 
which  slopes  downward  to  join  the  shaft  at  the  lesser  trochanter;  as  a  result  of 
this  the  outer  half  of  the  neck  is  flattened  from  before  backward,  and  its  vertical 
diameter  measures  one-third  more  than  the  antero-posterior.  The  inner  half 
is  smaller  and  of  a  more  circular  shape.  The  anterior  surface  of  the  neck  is  per- 
forated by  numerous  vascular  foramina.  The  posterior  surface  is  smooth,  and  is 
broader  and  more  concave  than  the  anterior;  it  gives  attachment  to  the  posterior 
part  of  the  capsular  ligament  of  the  hip-joint,  about  half  an  inch  above  the 
posterior  intertrochanteric  line.  The  superior  border  is  short  and  thick,  and  ter- 
minates externally  at  the  great  trochanter;  its  surface  is  perforated  by  large 
foramina.  The  inferior  border,  long  and  narrow,  curves  a  little  backward,  to 
terminate  at  the  lesser  trochanter. 


Obturator  intemus  and  GemelU 
Pip  if 01  nns 

4'^^  Insertion  of  Obturator 
"  c^&^        extemus 


Greater  trochanter 


Fig.  176. — Upper  extremity  of  the  femur  \iewed  from  behind  and  abov 


The  trochanters  are  prominent  processes  of  bone  which  afford  leverage  to  the 
muscles  which  rotate  the  thigh  on  its  axis.  They  are  two  in  number,  the  greater 
and  the  lesser. 

The  greater  trochanter  (trochanter  major)  is  a  large,  irregular,  quadrilateral  emi- 
nence, situated  at  the  outer  side  of  the  neck,  at  its  junction  with  the  upper  part  of 
the  shaft.  It  is  directed  a  little  outward  and  backward,  and  in  the  adult  is  about 
three-quarters  of  an  inch  lower  than  the  head.  It  presents  for  examination 
two  surfaces  and  four  borders.  The  external  surface,  quadrilateral  in  form,  is 
broad,  rough,  convex,  and  marked  by  a  prominent  diagonal  impression,  which 
extends  from  the  posterior  superior  to  the  anterior  inferior  angle,  and  serves  for 
the  attachment  of  the  tendon  of  the  Gluteus  medius.  Above  the  impression  is 
a  triangular  surface,  sometimes  rough  for  part  of  the  tendon  of  the  same  muscle, 
sometimes  smooth  for  the  interposition  of  a  bursa  between  that  tendon  and  the 
bone.  Below  and  behind  the  diagonal  line  is  a  smooth,  triangular  surface, 
over  which  the  tendon  of  the  Gluteus  maximus  muscle  plays,  a  bursa  being  inter- 
posed.    The  internal  surface  is  of  much  less  extent  than  the  external,  and  presents 


THE  FEMUR,   OR  THIGH  BONE 


223 


at  its  base  a  deep  depression,  the 
digital  or  trochanteric  fossa  {fossa 
Irochauterica),  for  the  attachment 
of  the  tendon  of  the  Obturator 
externus  muscle;  above  and  in 
front  of  this  an  impression  for 
the  attachment  of  the  Obtura- 
tor internus  and  Gemelli.  The 
superior  border  is  free;  it  is  thick 
and  irregular,  and  marked  near 
the  centre  by  an  impression,  which 
extends  onto  the  internal  surface, 
for  the  attachment  of  the  Pyri- 
formis.  The  inferior  border  cor- 
responds to  the  point  of  junction 
of  the  base  of  the  trochanter  with 
the  outer  surface  of  the  shaft;  it 
is  marked  by  a  rough,  prominent, 
slightly  curved  ridge,  which  gives 
origin  to  the  upper  part  of  the 
Vastus  externus  muscle.  The 
anterior  border  is  prominent, 
somewhat  irregular,  as  well  as  the 
surface  of  bone  immediately  be- 
low it ;  it  affords  attachment  at  its 
outer  part  to  the  Gluteus  mini- 
mus. The  posterior  border  is  veiy 
prominent,  and  appears  as  a  free, 
rounded  edge,  which  forms  the 
back  part  of  the  digital  fossa. 

The  lesser  trochanter  (trochan- 
ter minor)  is  a  conical  eminence 
which  varies  in  size  in  different 
subjects;  it  projects  from  the  lower 
and  back  parts  of  the  base  of  the 
neck.  Its  base  is  triangular,  and 
connected  with  the  adjacent  parts 
of  the  bone  by  three  well-marked 
borders;  two  of  these  are  above 
— the  internal  border,  continuous 
with  the  lower  border  of  the  neck, 
the  external  border,  with  the  pos- 
terior intertrochanteric  line  — 
while  the  inferior  border  is  con- 
tinuous with  the  middle  division 
of  the  linea  aspera.  Its  summit, 
which  is  directed  inward  and 
backward,  is  rough  and  gives 
insertion  to  the  tendon  of  the 
Iliopsoas.  The  Iliacus  is  also 
inserted  into  the  shaft  below 
the  lesser  trochanter  between  the 
Vastus  internus  in  front  and  the 
Pectineus  behind. 


^  Groove  for  tendon  of 


Tic    177. — Eight  femur      Posterior  surface. 


224 


SPECIAL  ANATOMY  OF  THE  SKELETON 


A  well-marked  prominence  of  variable  size,  which  projects  from  the  upper  and 
front  part  of  the  neck  at  its  junction  with  the  great  trochanter,  is  called  the 
tubercle  of  the  femur;  it  is  the  point  of  meeting  of  five  muscles — the  Gluteus  mini- 
mus externally,  the  Vastus  externus  below,  and  the  tendon  of  the  Obturator  internus 
and  Gemelli  internally.  Running  obliquely  downward  and  inward  from  the 
tubercle  is  the  spiral  line  of  the  femur,  or  anterior  intertrochanteric  line  (linea  inter- 
Irochanierica);  it  winds  around  the  inner  side  of  the  shaft,  below  the  lesser  tro- 
chanter, and  terminates  about  two  inches  below  this  eminence  in  the  linea  aspera. 
Its  upper  half  is  rough,  and  affords  attachment  to  the  iliofemoral  ligament  of  the 
hip-joint;  its  lower  half  is  less  prominent,  and  gives  origin  to  the  upper  part  of  the 
Vastus  internus.  Running  obliquely  downward  and  inward  from  the  summit 
of  the  great  trochanter  on  the  posterior  surface  of  the  neck  is  a  very  prominent, 
well-marked  ridge,  the  posterior  intertrochanteric 
a,  .&  line  (crista  intertrochavf erica).      Its  upper  half 

forms  the  posterior  border  of  the  great  tro- 
chanter, and  its  lower  half  runs  down\\"ard  and 
inward  to  the  upper  and  back  part  of  the  lesser 
trochanter.  A  slight  ridge  sometimes  com- 
mences about  the  middle  of  the  posterior  intertro- 
chanteric line,  and  passes  vertically  downward 
for  about  two  inches  along  the  back  part  of  the 
shaft;  it  is  called  the  linea  quadrati,  and  gives 
attachment  to  the  Quadratus  femoris  and  a  few 
fibres  of  the  Adductor  magnus  muscles.' 

The  Shaft  (corpus  femoris). — The  shaft,  almost 
cylindrical  in  form,  is  a  little  broader  above  than 
in  the  centre,  and  somewhat  flattened  below,  from 
before  backward.  It  is  slightly  arched,  so  as  to 
be  convex  in  front  and  concave  behind,  where  it 
is  strengthened  by  a  prominent  longitudinal  ridge, 
the  linea  aspera.  It  presents  for  examination 
three  borders,  separating  three  surfaces.  Of 
the  three  borders,  one,  the  linea  aspera,  is  poste- 
rior; the  other  two  are  placed  laterally. 

The  linea  aspera  (Fig.  178)  is  a  prominent 
longitudinal  ridge  or  crest,  on  the  middle  third 
of  the  bone,  presenting  an  external  lip  (labium 
laterale),  an  internal  lip  (labium  mecliale),  and  a 
rough  intermediate  space.  Above,  this  crest  is 
prolonged  by  three  ridges.  The  most  external 
ridge  is  very  rough,  and  is  continued  almost 
vertically  upward  to  the  base  of  the  great  trochanter.  It  is  sometimes  termed 
the  gluteal  ridge  (tuberositas  glutaea),  and  gives  attachment  to  part  of  the  Gluteus 
maximus  muscle;  its  upper  part  is  sometimes  elongated  into  a  roughened 
crest,  on  which  is  a  more  or  less  well-marked,  rounded  tubercle,  a  rudimental 
third  trochanter  (trochanter  tertius).  The  middle  ridge  (linea  pectinea),  the  least 
distinct,  is  continued  to  the  base  of  the  lesser  trochanter,  and  the  internal  ridge  is 
lost  above  in  the  spiral  line  of  the  femur.  Below,  the  linea  aspera  is  prolonged 
by  two  ridges,  which  pass  to  the  condyles  and  enclose  between  them  a  triangular 
space,  the  popliteal  surface  (planum  popliteum),  upon  which  rests  the  popliteal 
artery.  Of  these  two  ridges,  the  outer  one  is  the  more  prominent,  and  descends 
to  the  summit  of  the  outer  condyle.     The  inner  one  is  less  marked,  especially  at 


ADDUCTOR 
TUBERCLE 

Fig.  178. — Diagram  of  linea  aspera  of  the 
right  femur,     {.\fter  Birmingham.) 


'  Generally  there  is  merely  a  slight  thickening  about  the  centre  of  the  intertrochanteric  line,  marking  the  point 
of  attachment  of  the  Quadratus  femoris.     This  is  termed  by  some  anatomists  the  tubercle  of  the  Quadratus. 


THE  FEMUR,   OR  THIGH  BONE  225 

its  upper  part,  where  it  is  crossed  by  the  femoral  artery.  It  terminates,  below, 
at  the  summit  of  the  internal  condyle,  in  a  small  tul^ercle,  the  adductor  tubercle, 
which  affords  attachment  to  the  tendon  of  the  Adductor  magnus.  To  the  inner 
lip  of  the  linea  aspera  and  its  inner  prolongation  above  and  below  arises  the 
Vastus  internus,  and  to  the  outer  lip  and  its  outer  prolongation  above  arises  the 
Vastus  externus.  The  Adductor  magnus  is  attached  to  the  linea  aspera,  to  its 
outer  prolongation  above  and  its  inner  prolongation  below.  Between  the  Vastus 
externus  and  the  Adductor  magnus  are  attached  two  muscles — viz.,  the  Gluteus 
maximus  above,  and  the  short  head  of  the  Biceps  femoris  below.  Between  the 
Adductor  magnus  and  the  Vastus  internus  four  muscles  are  attached — the  Iliacus 
and  Pectineus  above,  the  Adductor  brevis  and  Adductor  longus  below  (Fig.  178). 
A  little  below  the  centre  of  the  linea  aspera  is  the  nutrient  foramen,  the  orifice  of 
the  nutrient  canal,  which  is  directed  obliquely  upward  (proximally). 

The  two  lateral  borders  of  the  femur  are  only  slightly  marked,  the  outer  one  ex- 
tending from  the  anterior  inferior  angle  of  the  great  trochanter  to  the  anterior 
extremity  of  the  external  condyle;  the  inner  one  from  the  spiral  line  at  a  point 
opposite  the  lesser  trochanter,  to  the  anterior  extremity  of  the  internal  condyle. 
The  internal  border  marks  the  limit  of  origin  of  the  Crureus  muscle  internally. 

The  anterior  surface  includes  that  portion  of  the  shaft  which  is  situated  bet\\een 
the  two  lateral  borders.  It  is  smooth,  convex,  broader  above  and  below  than  in 
the  centre,  slightly  twisted,  so  that  its  upper  part  is  directed  forward  and  a  little 
outward,  its  lower  part  forward  and  a  little  inward.  From  the  upper  three-fourths 
of  this  surface  the  Crureus  takes  origin;  the  lower  fourth  is  separated  from  the 
muscle  by  the  intervention  of  the  synovial  membrane  of  the  knee-joint  and  a  bursa, 
and  affords  origin  to  the  Subcrureus  to  a  small  extent. 

The  external  surface  includes  the  portion  of  bone  between  the  external  border 
and  the  outer  lip  of  the  linea  aspera;  it  is  continuous  above  with  the  outer  surface 
of  the  great  trochanter,  below  with  the  outer  surface  of  the  external  condyle; 
from  its  upper  three  fourths  arises  the  outer  portion  of  the  Crureus  muscle. 

The  internal  surface  includes  the  portion  of  bone  between  the  internal  border 
and  the  inner  lip  of  the  linea  aspera;  it  is  continuous  above  with  the  lower  border 
of  the  neck,  below  with  the  inner  side  of  the  internal  condyle;  it  is  covered  by  the 
Vastus  internus  muscle. 

Lower  or  Distal  Extremity. — The  lower  extremity,  larger  than  the  upper, 
is  of  a  cuboidal  form,  flattened  from  before  backward,  and  divided  into  two  large 
eminences,  the  condyles,  by  an  interval  which  presents  a  smooth  depression  in 
front  called  the  trochlea  {fames  ■patellaris),  and  a  notch  of  consideraljle  size  behind — 
the  intercondyloid  notch  (fossa  intercondyloidea).  The  external  condyle  (condyles 
lateralis)  is  the  more  prominent  anteriorly,  and  is  the  broader  both  in  the  antero- 
posterior and  transverse  diameters.  The  internal  condyle  (condylus  medialis)  is 
the  longer,  and  more  prominent  inferiorly.  This  difference  in  the  length  of  the 
two  condyles  is  only  observed  when  the  bone  is  perpendicular  and  depends  upon 
the  obliquity  of  the  thigh  bones,  in  consequence  of  their  separation  above  at  the 
articulation  with  the  pelvis.  If  the  femur  is  held  obliquely,  the  surfaces  of  the 
two  condyles  will  be  seen  to  be  nearly  horizontal.  The  two  condyles  are  directly 
continuous  in  front,  and  form  a  smooth,  trochlear  surface,  tjie  trochlea.  The 
trochlea  and  the  inferior  surface  of  the  condyles  constitute  the  articular  surface 
of  the  lower  end  of  the  femur,  and  are  covered  by  hyaline  cartilage  in  the  recent 
state.  The  trochlea  articulates  with  the  patella.  It  presents  a  median  groove, 
which  extends  downward  and  backward  to  the  intercondyloid  notch;  and  two 
lateral  convexities,  of  which  the  external  is  the  broader,  more  prominent,  and  pro- 
longed farther  upward  upon  the  front  of  the  outer  condyle.  The  external  border 
of  this  articular  surface  is  also  more  prominent,  and  ascends  higher  than  the 
internal  one.    The  inferior  surfaces  of  the  condyles  are  convex  from  side  to  side 

15 


226  ^FECIAL  ANATOMY  OF  THE  SKELETON 

and  from  before  backward,  and  articulate  with  the  corresponding  surfaces  of 
the  tibia.  They  are  marked  off  from  the  trochlea  by  two  irregular  grooves. 
The  outer  groove  runs  obliquely  outward  and  forward  from  the  anterior  extremity 
of  the  intercondyloid  notch  to  the  outer  side  of  the  external  condyle.  The  inner 
is  less  well  marked  and  placed  farther  forward  than  the  one  on  the  external 
condyle;  it  extends  obliquely  inward  and  backward.  In  the  grooves  the  semilunar 
cartilages  fit  when  the  knee  is  extended.  The  opposed  surfaces  of  the  condyles 
form  the  lateral  walls  of  the  intercondyloid  notch. 


_  /        ■  groove. 


^       .Inner  tuberosity. 
»     ^Semilunar  area. 


Outer  tuberosity.  .     ,-     , 


y 


Fig.  179. — Lower  extremity  of  riglit  femur  viewed  from  below. 

The  outer  surface  of  the  external  condyle  presents,  a  little  behind  its  centre, 
an  eminence,  the  outer  tuberosity  (epico7idylus  lateralis);  it  is  less  prominent 
than  the  inner  tuberosity,  and  gives  attachment  to  the  external  lateral  ligaments 
of  the  knee.  Immediately  beneath  it  is  the  popliteal  groove,  which  commences 
at  a  depression  a  little  behind  the  centre  of  the  lower  border  of  this  surface; 
the  front  part  of  this  depression  gives  origin  to  the  Popliteus  muscle,  the  tendon 
of  which  is  lodged  in  the  groove  during  flexion  of  the  knee.  The  groove  is  smooth, 
covered  with  hyaline  cartilage  in  the  recent  state,  and  runs  upward  and  back- 
ward to  the  posterior  extremity  of  the  condyle.  The  posterior  extremity  is  con- 
vex and  smooth;  just  above  and  to  the  outer  side  of  the  articular  surface  is  a  de- 
pression for  the  tendon  of  the  outer  head  of  the  Gastrocnemius,  above  which  is 
the  origin  of  the  Plantaris. 

The  inner  surface  of  the  inner  condyle  presents  a  convex  eminence,  the  inner 
tuberosity  {epicondyliw  medialis) ,  rough,  for  the  attachment  of  the  internal  lateral 
ligament.  Just  above  the  articular  surface  of  this  condyle,  behind,  is  a  depres- 
sion for  the  tendon  of  origin  of  the  inner  head  of  the  Gastrocnemius. 

The  intercondyloid  notch  is  bounded  laterally  by  the  opposed  surfaces  of  the 
.condyles,  and  lodges  the  crucial  ligaments  of  the  knee-joints.  The  inner  wall 
of  the  notch  at  its  front  part  has  attached  to  it  the  posterior  crucial  ligament. 
The  external  wall  at  its  upper  and  back  part  affords  attachment  to  the  anterior 
crucial  ligament.  Above,  it  is  separated  from  the  popliteal  surface  by  a  ridge — 
the  linea  inter condyloidea. 

Structure. — ^The  shaft  of  the  femur  is  a  cylinder  of  compact  tissue,  hollowed  by  a  large  med- 
ullary canal.  The  cyhnder  is  of  great  thickness  and  density  in  the  middle  third  of  the  shaft, 
where  the  bone  is  narrowest  and  the  medullary  canal  well  formed;  but  above  and  below  this 
the  cavity  gradually  becomes  smaller,  owing  to  a  separation  of  the  layers  of  the  bone  into  cancelli, 
which  project  into  the  medullary  canal  and  finally  obliterate  it,  so  that  the  upper  and  lower 
ends  of  the  shaft,  and  the  articular  extremities  more  especially,  consist  of  cancellated  tissue 
invested  by  a  thin,  compact  layer. 

The  arrangement  of  the  cancelli  in  the  ends  of  the  femur  is  remarkable.  In  the  upper  end  they 
are  arranged  in  two  sets.     One,  starting  from  the  top  of  the  head,  the  upper  surface  of  the  neck. 


THE  FEMUR,    OR   THIGH  BONE 


227 


and  the  great  trochanter,  converge  to  the  inner  circumference  of  the  shaft  (Figs.  ISO  and  ISl); 
these  are  placed  in  the  direction  of  greatest  pressure,  and  serve  to  support  the  vertical  weight 
of  the  body.  The  second  set  are  planes  of  lamellae  intersecting  the  former  nearly  at  right  angles, 
and  are  situated  in  the  line  of  the  greatest  tension — 
that  is  to  say,  along  the  lines  in  which  the  muscles  and 
ligaments  exert  their  traction.  In  the  head  of  the 
bone  these  planes  are  arranged  in  a  cur\'ed  form,  in 
order  to  strengthen  the  bone  when  exposed  to  pressure 
in  all  directions.  In  the  midst  of  the  cancellous  tis- 
sue of  the  neck  is  a  vertical  plane  of  compact  bone, 
the  femoral  spur  (calcar  femorale),  which  commences 
at  the  point  where  the  neck  joins  the  shaft  just  exter- 
nal to  the  lesser  trochanter,  and  extends  in  the  direc- 
tion of  the  digital  fossa  (Fig.  1S2).  This  materially 
strengthens  this  portion  of  the  bone.  Another  point  in 
connection  with  the  structure  of  the  neck  of  the  femur 
requires  mention,  especially  on  accoimt  of  its  influence 
on  the  production  of  fracture  in  this  situation.  It  wdll 
be  noticed  that  a  considerable  portion  of  the  great 
trochanter  lies  behind  the  level  of  the  posterior  sur- 
face of  the  neck;  and  if  a  section  be  made  tlirough 
the  trochanter  at  this  level,  it  will  be  seen  that  the 
posterior  wall  of  the  neck  is  prolonged  into  the  tro- 
chanter. This  prolongation  is  termed  by  Bigelow  the  true  neck,'  and  forms  a  thin,  dense 
plate  of  bone,  which  passes  beneath  the  posterior  intertrochanteric  ridge  toward  the  outer  sur- 
face of  the  bone.     In  the  lower  end  the  cancelU  spring  on  all  sides  from  the  inner  surface  of  the 


Fig.  180. — Scheme  showing  disposition  of 
principal  cancellous  lamellEe  in  upper  extrem- 
ity of  femur. 


Epiphyseal  line. 


Fig.  ISl. — Longitudinal  section  of  head  and  necic  of  femur. 

cylinder,  and  descend  in  a  perpendicidar  direction  to  the  articular  surface,  the  cancelli  being 
strongest  and  ha\'ing  a  more  accurately  perpendicular  course  above  the  condyles.     In  addition 


the  Hip,  p.  121. 


228 


SPECIAL  ANATOMY  OF  THE  SKELETON 


to  this,  however,  horizontal  planes  of  cancellous  tissue  are  to  be  seen,  so  that  the  spongy  tissue  in 
this  situation  presents  an  appearance  of  being  mapped  out  into  a  series  of  rectangular  areas. 

Articulations. — With  tkree  bones — the  os  innominatum,  tibia,  and  patella. 

Development  (Fig.  1  S3). — The  femur  is  developed  from  five  centres — one  for  the  shaft,  one 
for  each  extremity,  and  one  for  each  trochanter.  Of  all  the  long  bones,  except  the  clavicle,  it  is 
the  first  to  show  traces  of  ossification;  this  commences  in  the  shaft,  at  about  the  seventh  week  of 
fetal  life,  the  centres  of  ossification  in  the  epiphyses  appearing  in  the  following  order:  First,  in 
the  lower  end  of  the  bone,  at  the  ninth  month  of  fetal  life'  (from  this  the  condyles  and  tuber- 
osities are  formed) ;  in  the  head  at  the  end  of  the  first  year  after  birth ;  in  the  great  trochanter, 
during  the  foiu'th  year;  and  in  the  lesser  trochanter,  between  the  thirteenth  and  fourteenth  years. 
The  order  in  which  the  epiphyses  are  joined  to  the  shaft  is  the  reverse  of  that  of  their  appearance; 
their  junction  does  not  commence  until  after  puberty,  the  lesser  trochanter  being  first  joined, 
then  the  great,  then  the  head,  and  lastly  the  inferior  extremity  (the  first  in  which  ossification 
commenced),  which  is  not  united  until  the  twentieth  year.  Because  of  this  late  union,  the  lower 
extremity  of  the  femur  has  been  called  the  "growing  end"  of  the  bone,  and  early  arrest  of  ossifi- 
cation here  results  in  more  or  less  marked  diminution  of  stature. 


Great  trochanter. 


^  Digital  fossa. 


Appears  at    Ifth 
year; joins  shaft  ^ 
ahout  18th  year.  i= 


'^  Joins  shaft  at  SOth 
9th  mon  '  i        ^J^      J^^     year. 
(fetaC).      \=f 

Lower  extremity. 


J^iG,  182. — Calcar  femorale. 


Attachment  of  Muscles.— To  tiventy-three.  To  the  great  trochanter:  the  Gluteus  medius, 
■Gluteus  minimus,  Pyriformis,  Obturator  internus.  Obturator  externus,  Gemellus  superior, 
and  Gemellus  inferior.  To  the  lesser  trochanter:  the  Psoas  magnus  and  the  Iliacus  below  it. 
To  the  shaft:  the  Quadratus  femoris,  Vastus  externus,  Gluteus  maximus,  short  head  of  the 
Biceps  femoris.  Vastus  internus.  Adductor  magnus,  Pectineus,  Adductor  brevis.  Adductor 
longus,  Crureus,  and  Subcrureus.  To  the  condyles:  the  Gastrocnemius,  Plantaris,  and 
Popliteus. 

Surface  Form. — The  femur  is  covered  with  muscles,  so  that  in  fairly  muscular  subjects  the 
shaft  is  not  to  be  detected  through  its  fleshly  covering,  and  the  only  parts  accessible  to  the  touch 
are  the  outer  surface  of  the  great  trochanter  and  the  lower  expanded  end  of  the  bone.  The 
external  surface  of  the  great  trochanter  may  be  felt,  especially  in  certain  positions  of  the  limb.  Its 
position  is  generally  indicated  by  a  depression,  owing  to  the  thickness  of  the  Gluteus  medius  and 


^  This  is  said  to  be  the  only  epiphysis  in  which  ossification  begins  before  birth;  though,  according  to 
observers,  the  centre  for  the  upper  epiphysis  of  the  tibia  also  appears  before  birth. 


THE  FEMUR,   OB  THIGH  BONE  229 

minimus,  which  project  above  it.  When,  however,  the  thigh  is  flexed,  and  espeeiully  if  crossed 
over  the  opposite  one,  the  trochanter  produces  a  blunt  eminence  on  the  surface.  The  upjjer 
border  is  about  on  a  hne  with  the  spine  of  the  os  pubis,  and  its  exact  level  is  indicated  by  a  line 
drawn  from  the  anterior  superior  spinous  process  of  the  ilium,  over  the  outer  side  of  the  liip, 
to  the  most  prominent  point  of  the  tuberosity  of  the  ischium.  This  is  known  as  N§laton's  line. 
The  outer  and  inner  condyles  of  the  lower  extremity  may  easily  be  felt.  The  outer  one  is 
more  subcutaneous  than  the  inner  one,  and  readily  felt.  The  tuberosity  on  it  is  comparatively 
little  developed,  but  can  be  more  or  less  easily  recognized.  The  inner  condyle  is  more  thickly 
covered,  and  this  gives  a  general  convex  outline  to  this  part,  especially  when  the  knee  is  flexed. 
The  tuberosity  on  it  is  easily  felt,  and  at  the  upper  part  of  the  condyle  the  sharp  tubercle  for  the 
insertion  of  the  tendon  of  the  Adductor  magnus  can  be  recognized  without  difficulty.  Occa- 
sionally, exostoses  develop  in  the  tendon  of  insertion  of  the  Adductor  magnus;  these  are  the 
"rider's  hones"  of  cavalry  soldiers  and  horsemen  (pp.  360,  515).  When  the  knee  is  flexed,  and 
the  patella  situated  in  the  interval  between  the  condyles  and  the  upper  end  of  the  tibia,  a  part 
of  the  trochlear  surface  of  the  femur  can  be  made  out  above  the  patella. 

Applied  Anatomy. — There  are  one  or  two  points  about  the  ossification  of  the  femur  bear- 
ing on  practice  to  which  allusion  must  be  made.  It  has  been  stated  above  that  the  lower  end 
of  the  femur  is  the  only  epiphysis  in  which  ossification  has  commenced  at  the  time  of  birth. 
The  presence  of  the  ossific  centre  in  newly  born  children  found  dead  is,  therefore,  a  proof  that 
the  child  has  arrived  at  the  full  period  of  uterogestation.  However,  according  to  Hartman, 
at  term  this  centre  is  absent  in  12  per  cent,  of  cases.  The  position  of  the  epiphyseal  line  should 
be  carefully  noted.  It  is  on  a  level  with  the  adductor  tubercle,  and  the  epiphysis  does  not, 
therefore,  form  the  whole  of  the  cartilage-clad  portion  of  the  lower  end  of  the  bone.  It  is  essen- 
tial to  bear  this  point  in  mind  in  performing  excision  of  the  knee,  since  growth  in  length  of  the 
femur  takes  place  chiefly  from  the  lower  epiphysis,  and  any  interference  with  the  epiphyseal 
cartilage  in  a  young  child  would  involve  such  ultimate  shortening  of  the  limb,  from  want  of 
growth,  as  to  render  it  almost  useless.  Separation  of  the  loiver  epiphysis  may  take  place  up  to 
the  age  of  twenty,  at  which  time  it  becomes  completely  joined  to  the  shaft  of  the  bone;  but,  as 
a  matter  of  fact,  few  cases  occur  after  the  age  of  sixteen  or  seventeen.  The  epiphysis  of  the  head 
of  the  femur  is  of  interest  principally  on  account  of  its  being  the  seat  of  origin  of  a  large  number 
of  cases  of  tiiberciilous  disease  of  the  hip-joint.  The  disease  commences  in  the  majority  of  cases 
in  the  highly  vascular  and  growing  tissue  in  the  neighborhood  of  the  epiphysis,  and  from  here 
extends  into  the  joint.  In  the  condition  known  as  coxa  tarn  the  head  of  the  femur  falls  to  a  lower 
level  than  normal.  The  angle  between  the  neck  and  shaft  is  greatly  diminished  and  may  become 
a  right  ^ngle,  or  the  head  may  actually  descend  to  a  lower  level  than  that  of  the  trochanter.  The 
neck  is  also  bent  with  a  convexity  forward ;  coxa  vara  is  due  to  rachitis. 

Fractures  of  the  femur  are  divided,  like  those  of  the  other  long  bones,  into  fractures  of  the 
upper  end,  of  the  shaft,  and  of  the  lower  end.  The  fractures  of  the  upper  end  may  be  classi- 
fied into  (1)  fracture  of  the  neck;  (2)  fracture  at  the  junction  of  the  neck  with  the  great  trochanter; 
(.3)  fracture  of  the  great  trochanter;  and  (4)  separation  of  the  epiphysis,  either  of  the  head  or 
the  great  trochanter.  The  first  of  these,  fracture  of  the  neck,  is  usually  termed  intracapsular 
fracture,  but  this  is  scarcely  a  correct  designation,  as,  owing  to  the  attachment  of  the  capsular 
ligament,  the  fracture  may  be  partly  within  and  partly  without  the  capsule,  when  the  fracture 
occurs  at  the  lower  part  of  the  neck.  It  generally  occurs  in  old  people,  principally  women,  and 
usually  from  a  very  slight  degree  of  indirect  violence.  Probably  the  main  cause  of  the  fracture 
taking"  place  in  old  people  is  in  consequence  of  the  degenerative  changes  which  the  bone  has 
undergone.  Merkel  believes  that  it  is  mainly  due  to  the  absorption  of  the  calcar  femorale. 
These  fractures  are  occasionally  impacted.  As  a  rule,  they  unite  by  fibrous  tissue,  and  frequently 
no  union  takes  place,  and  the  surfaces  of  the  fracture  become  smooth  and  eburnated.  The 
lack  of  reparative  power  in  intracapsular  fracture  is  due  to  lack  of  apposition  of  the  fragments  and 
diminution  in  the  amount  of  blood  sent  to  the  smaller  fragment.  The  head  of  the  bone  receives 
blood  from  the  neck  through  the  reflected  portions  of  the  capsule  and  through  the  ligamentum 
teres.    A  fracture  cuts  off  the  supply  by  the  neck  and  by  the  reflected  portions  of  the  capsule. 

Fractures  at  the  junction  of  the  rieck  with  the  great  trochanter  are  usually  termed  extracap- 
sular, but  this  designation  is  also  incorrect,  as  the  fracture  is  partly  within  the  capsule,  owing 
to  its  attachment  in  front  to  the  anterior  intertrochanteric  line,  which  is  situated  below  die  line 
of  fracture.  These  fractures  are  produced  by  direct  violence  to  the  great  trochanter,  as  from  a 
blow  or  fall  laterally  on  the  hip.  From  the  rnanner  in  which  the  accident  is  caused,  the  neck  of 
the  bone  is  driven  'into  the  trochanter,  where  it  may  remain  impacted  or  the  trochanter  may 
split  up  into  two  or  more  fragments,  and  thus  no  fixation  takes  place. 

Fractures  of  the  great  trochanter  may  be  either  "oblique  fracture  through  the  trochanter 
major,  without  implicating  the  neck  of  the  bone"  (Astley  Cooper),  or  separation  of  the  great 
trochanter.  Most  of  the  "recorded  cases  of  this  latter  injury  occurred  in  young  persons,  and 
were  probably  cases  of  separation  of  the  epiphysis  of  the  great  trochanter.  Sepai-ation  of_  the 
epiphysis  of  the  head  of  the  femur  has  been  said  to  occur,  but  has  probably  never  been  verified 
by  postmortem  examination. 


230  SPECIAL  ANATOMY  OF  THE  SKELETON 

Fracture  of  the  shaft  may  occur  at  any  part,  but  the  most  usual  situation  is  at  or  near  the 
centre  of  the  bone.  They  may  be  caused  by  direct  or  indirect  violence  or  by  muscular  action. 
Fractures  of  the  upper  third  of  the  shaft  are  almost  always  the  result  of  indirect  violence,  while 
those  of  the  lower  third  are  the  result,  for  the  most  part,  of  direct  violence.  In  the  middle  third 
fractures  occur  from  both  forms  of  injury  in  about  equal  proportions.  Fractures  of  the  shaft 
are  generally  oblique,  but  they  may  be  transverse,  longitudinal,  or  spiral.  The  transverse  frac- 
ture occurs  most  frequently  in  children.  The  fractures  of  the  lower  end  of  the  femur  include 
transverse  fracture  above  the  condyles,  the  most  common;  and  this  may  be  complicated  by  a 
vertical  fracture  between  the  condyles,  constituting  the  T-shaped  fracture.  In  these  cases  the 
popliteal  artery  is  in  danger  of  being  wounded.  Oblique  fracture,  separating  either  the  internal 
or  external  condyle,  and  a  longitudinal  incomplete  fracture  between  the  condyles,  may  also  take 
place. 

The  femur  and  also  the  bones  of  the  leg  are  frequently  the  seat  of  acute  osteomyelitis  in  young 
children.  This  is  no  doubt  due  to  their  greater  exposure  to  injury,  which  is  often  the  exciting 
cause  of  this  disease.  Tumors  not  infrequently  are  found  growing  from  the  femur,  the  most 
common  forms  being  sarcoma,  which  may  grow  either  from  the  periosteum  or  from  the  medullary 
tissue  within  the  interior  of  the  bone;  and  exostosis,  which  is  commonly  found  originating  in 
the  neighborhood  of  the  epiphyseal  cartilage  of  the  lower  end. 

Genu  varum  is  a  form  of  how-leg  in  which  the  tibia  and  femur  are  curved  outward,  the  knees 
being  widely  separated.  Both  extremities  are  usually  affected.  In  early  life  the  disease  is  due 
to  rhachitis.  In  elderly  people  it  may  be  due  to  arthritis  deformans.  Genu  valgum  (knock-knee) 
is  a  condition  in  which  the  knees  are  close  together,  the  feet  are  wide  apart,  and  the  internal 
lateral  ligament  of  the  knee-joint  is  stretched.  It  is  due  to  excessive  growth  of  the  inner  con- 
dyle of  the  femur,  the  shaft  of  the  femur  curving  inward.  It  may  be  due  to  rhachitis,  attitude  of 
an  occupation,  or  flat-foot,  and  one  or  both  knees  may  be  affected. 


THE  LEG. 

The  skeleton  of  the  leg  consists  of  three  bones — the  patella,  a  large  sesamoid 
bone,  placed  in  front  of  the  knee;  the  tibia;  and  the  fibula. 


The  Patella,  or  Kneecap  (Fig.  184). 

The  patella  is  a  flat,  triangular  bone,  situated  at  the  anterior  part  of  the  knee- 
joint.  It  is  usually  regarded  as  a  sesamoid  bone,  developed  in  the  tendon  of 
the  Quadriceps  extensor.  It  serves  to  protect  the  front  of  the  joint,  and  in- 
creases the  leverage  of  the 
Quadriceps  extensor  by  making 
it  act  at  a  greater  angle.  It 
presents  an  anterior  and  a  pos- 
terior surface,  three  borders, 
and  an  apex. 

Surfaces. — The  anterior  sur- 
face is  convex,  perforated  by 
small  apertures,  for  the  passage 
of  nutrient  vessels,  and  marked 
by  numerous  rough,  longitudi- 

FlQ.  184.— Right  patella.        A.  Anterior  surface.     B.  Posterior       yisI  StrisB        This  SUrfaCC  is  COV- 
surface.  i     •        'i 

ered,  ni  the  recent  state,  by  an 
expansion  from  the  tendon  of  the  Quadriceps  extensor,  which  is  continuous 
below  with  the  superficial  fibres  of  the  ligamentum  patellae.  It  is  separated 
from  the  integument  by  a  bursa. 

The  posterior  surface  presents  a  smooth,  oval-shaped,  articular  surface  {fades 
articidaris),  covered  with  hyaline  cartilage  in  the  recent  state,  and  divided  into  two 
facets  by  a  vertical  ridge,  which  descends  from  the  superior  border  toward  the 
inferior  angle  of  the  bone.     The  ridge  corresponds  to  the  groove  on  the  trochlear 


THJiJ  TIBIA,    OB.  SHIN  BONE  231 

surface  of  the  femur,  and  the  two  facets  to  the  articular  surfaces  of  the  two  con- 
dyles; the  outer  facet,  for  articulation  with  the  outer  condyle,  being  broader  and 
deeper.  This  character  serves  to  indicate  the  side  to  which  the  bone  belongs. 
Below  the  articular  surface  is  a  rough,  convex,  nonarticular  depression,  the  lower 
half  of  which  gives  attachment  to  the  ligamentum  patellae,  the  upper  half  being 
separated  from  the  head  of  the  tibia  by  adipose  tissue. 

Borders. — The  superior  border  (basis  patellae)  is  thick,  and  sloped  from  Ijehind, 
downward  and  forward;  it  gives  attachment  to  that  portion  of  the  Quadriceps 
extensor  which  is  derived  from  the  Rectus  femoris  and  Crureus  muscles. 

The  lateral  borders  are  thinner,  converging  below.  They  give  attachment 
to  that  portion  of  the  Quadriceps  extensor  derived  from  the  external  and  internal 
Vasti  muscles. 

The  apex  (ape.r  patellae)  is  pointed,  and  gives  attachment  to  the  ligamentum 
patellae. 

Structure. — This  bone  resembles  a  sesamoid  bone  (1)  in  being  developed  in  a  tendon;  (2)  in 
its  centre  of  ossification  presenting  a  knotty  or  tuberculated  outline;  (3)  in  its  structure  being 
composed  mainly  of  dense  cancellous  tissue.  It  consists  of  a  nearly  uniform,  dense  cancellous 
tissue  covered  by  a  thin  compact  lamina.  The  cancelli  immediately  beneath  the  anterior  surface 
are  arranged  parallel  with  it.  In  the  rest  of  the  bone  they  radiate  from  the  posterior  articular 
surface  toward  the  other  parts  of  the  bone. 

Development. — From  a  single  centre,  which  makes  its  appearance  in  the  second  or  third,  but 
may  not  ajjpear  until  the  sixth  year.  More  rarely,  the  bone  is  developed  by  two  centres,  placed 
side  by  side.    Ossification  is  completed  about  the  age  of  puberty. 

Articulations. — With  the  two  condyles  of  the  femur. 

Attachment  of  Muscles. — To  four — the  Rectus,  Crureus,  Vastus  internus,  and  Va.stus 
externus.     These  muscles,  joined  at  their  insertion,  constitute  the  Quadriceps  extensor  cruris. 

Surface  Form. — The  external  surface  of  the  patella  can  be  seen  and  felt  in  front  of  the  knee. 
In  the  extended  position  of  the  limb  the  internal  border  is  a  little  more  prominent  than  the 
outer,  and  if  the  Quadriceps  extensor  is  relaxed  the  bone  can  be  moved  from  side  to  side  and 
appears  to  be  loosely  fixed.  If  the  joint  is  flexed,  the  patella  recedes  into  the  hollow  between  the 
condyles  of  the  femur  and  the  upper  end  of  the  tibia,  and  becomes  firmly  fixed  against  the  femur. 

Applied  Anatomy. — The  main  surgical  interest  about  the  patella  is  in  connection  with  frac- 
tures, which  are  of  common  occurrence.  They  may  be  produced  by  muscular  action;  that  is 
to  say,  by  violent  contraction  of  the  Quadriceps  extensor  while  the  limb  is  in  a  position  of  semi- 
flexion, so  that  the  bone  is  snapped  across  the  condyles;  or  by  direct  violence,  such  as  falls  on 
the  knee.  Most  fractures  are  due  to  muscular  action;  in  fact,  the  patella  is  more  often  broken 
by  muscular  action  than  is  any  other  bone.  In  fractures  by  muscular  action  the  line  of  fracture 
is  transverse.  In  fractures  by  direct  force  the  line  of  fracture  may  be  oblique,  longitudinal, 
stellate,  or  the  bone  variously  comminuted.  The  principal  interest  in  these  cases  attaches  to 
their  treatment.  Owing  to  the  wide  separation  of  the  fragments,  and  the  difficulty  there  is  in 
maintaining  them  in  apposition,  union  takes  place  by  fibrous  tissue,  and  this  may  subsequently 
stretch,  producing  wide  separation  of  the  fragments  and  permanent  lameness.  Various  plans, 
including  opening  the  joint  and  suturing  the  fragments,  have  been  advocated  for  overcoming 
this  difficulty.  In  many  cases  a  portion  of  fascia  or  capsule  gets  between  the  fragments.  In 
such  a  condition  operation  is  necessary. 

In  the  larger  number  of  cases  of  fracture  of  the  patella  the  l>nee-joint  is  involved,  the  car- 
tilage which  covers  its  posterior  surface  being  torn,  the  s3'novial  membrane  lacerated,  the  lateral 
fibrous  expansions  ruptured,  and  the  patellar  bm-sa  torn  open.  In  cases  of  fracture  from  direct 
violence,  however,  this  need  not  necessarily  happen,  the  lesion  may  involve  only  the  superficial 
part  of  the  bone;  and,  as  Morris  has  pointed  out,  it  is  an  anatomical  possibility,  in  complete 
fracture,  if  the  lesion  involve  only  the  lower  and  nonarticular  part  of  the  bone,  for  it  to  take 
place  without  injury  to  the  synovial  membrane. 


The  Tibia,  or  Shin  Bone  (Figs.  185,  186). 

The  tibia  is  situated  at  the  front  and  inner  side  of  the  leg,  and,  excepting  the 
femur,  is  the  longest  and  largest  bone  in  the  skeleton.  It  is  prismoid  in  form, 
expanded  above,  where  it  enters  into  the  knee-joint,  more  slightly  enlarged  below. 


232  SPECIAL  ANATOMY   OF  THE  SKELETON 

Capsular  ligament 


Sti/loid  -y, 


External  malleohts. 


Capsular  ligament 


Fig.  1S5. — Bones  of  the  right  leg.     .interior  surface.     Fig.  186.— Bones  of  the  right  leg.     Posterior  surface. 


THE  TIBIA,    OR  SHIN  BONE 


233 


In  the  male  its  direction  is  vertical  and  parallel  with  the  bone  of  the  opposite 
side;  but  in  the  female  it  has  a  slightly  oblique  direction  downward  and  outward, 
to  compensate  for  the  oblique  direction  of  the  femur  inward.  It  presents  for 
examination  a  shaft  and  two  extremities. 

The  Proximal  or  Upper  Extremity.— The  upper  extremity,  or  head,  is 
large,  and  expanded  on  each  side  into  two  lateral  eminences,  the  internal  and 
external  tuberosities  (coiidijlus  medialis  and  condylus  lateralis).  Superiorly,  each 
tuberosity  presents  a  smooth,  concave  surface  {fades  articularis  superior),  which 
articulates  with  a  condyle  of  the  femur.  The  internal  articular  surface  is  oval  in 
shape  and  concave  from  side  to  side;  the  external  one  is  circular,  concave  from  side 
to  side,  but  slightly  convex  from  before  backward,  especially  at  its  posterior 
part,  where  it  is  prolonged  on  to  the  posterior  surface  for  a  short  distance;  the 
central  portions  of  these  surfaces  articulate  with  the  condyles,  while  the  peripheral 
portions  are  overlaid  by  the  semilunar  cartilages  of  the  knee.  Between  the  two 
articular  surfaces,  and  nearer  the  posterior  than  the  anterior  aspect  of  the  bone, 
is  an  eminence,  the  spine  of  the  tibia  (eminentia  intercondijloidea);  surmounted 
by  a  prominent  tubercle  on  each  side  (the  tuherculum  intercond.yloideum  mediale 
and  the  tuherculum  intercondyloideuni  laterale),  on  to  the  lateral  aspect  of  which 


External  semilunar 
cartilage. 


Po-iterior  crucial 
llqatntnt 


External  semilunar 
cartilage. 


Anterior  crucial 
ligament. 


Internal  scmiluruir 
cartilage. 


Internal  semilunar 
cartilage. 


Fig.  187. — Upper  surfaces  of  right  tibia,  showing  attachment  of  crucial  ligaments 
cartilages  have  been  partly  cut  away. 


nd  semilunar  cartilages.    The 


the  facets  just  described  are  prolonged;  in  front  and  behind  the  spinous  process 
is  a  rough  depression  (fossa  intercondyloidea  anterior  and  the  fossa  intercondy- 
loidea  posterior)  for  the  attachment  of  the  anterior  and  posterior  crucial  ligaments 
and  the  semilunar  fibrocartilages  (Fig.  187). 

The  anterior  surfaces  of  the  tuberosities  are  continuous  with  one  another,  form- 
ing a  single  large  surface,  which  is  somewhat  flattened;  it  is  triangular,  broad 
above,  and  perforated  by  large  vascular  foramina;  narrow  below,  where  it  ter- 
minates in  a  prominent  oblong  elevation  of  large  size,  the  tubercle  of  the  tibia 
{tuberositas  tibiae);  the  lower  half  of  this  tubercle  is  rough,  for  the  attachment  of 
the  ligamentura  patellae;  the  upper  half  presents  a  smooth  facet  supporting,  in 
the  recent  state,  a  bursa  which  separates  the  ligament  from  the  bone.  Poste- 
riorly the  tuberosities  are  separated  from  each  other  by  a  shallow  depression, 
the  popliteal  notch  {incisura  poplitea),  which  gives  attachment  to  part  of  the  pos- 
terior crucial  ligament  and  part  of  the  posterior  ligament  of  the  knee-joint.  The 
inner  tuberosity  presents  posteriorly  a  deep  transverse  groove,  for  the  insertion 
of  one  of  the  fasciculi  of  the  tendon  of  the  Semimembranosus  (Fig.  266) .  Its  lateral 
surface  is  convex,  rough,  and  prominent,  and  gives  attachment  to  the  internal 
lateral  ligament.  The  outer  tuberosity  presents  posteriorly  a  flat  articular  facet 
{fades  articidaris  fibidaris) ,  nearly  circular  in  form,  directed  downward,  backward. 


234  SPECIAL  ANATOMY  OF  THE  SKELETON 

and  outward,  for  articulation  with  the  fibula.  Its  lateral  surface  is  convex  and 
rough,  more  prominent  in  front  than  the  internal,  and  presents  a  prominent 
rough  eminence,  situated  on  a  level  with  the  upper  border  of  the  tubercle  of  the 
tibia  at  the  junction  of  its  anterior  and  outer  surfaces,  for  the  attachment  of  the 
iliotibial  band.  Just  below  this  the  Extensor  longus  digitorum  arises,  and  a  slip 
from  the  Biceps  femoris  cruris  is  attached.  x 

Shaft  of  the  Tibia  (corpus  tibiae). — The  shaft  of  the  tibia  is  of  a  triangular 
prismoid  form,  broad  above,  gradually  decreasing  in  size  to  its  most  slender  part, 
the  commencement  of  its  lower  fourth;  it  then  enlarges  again  toward  its  lower 
extremity.     It  presents  for  examination  three  borders  and  three  surfaces. 

The  anterior  border,  the  most  prominent,  is  called  the  crest  of  the  tibia  (crista 
anterior) ;  it  commences  above  at  the  tubercle,  and  terminates  below  at  the  anterior 
margin  of  the  inner  malleolus.  This  border  is  very  prominent  in  the  upper 
two-thirds  of  its  extent,  smooth  and  rounded  below.  It  presents  a  very  sinuous 
course,  being  usually  curved  outward  above  and  inward  below;  it  gives  attachment 
to  the  deep  fascia  of  the  leg. 

The  internal  border  (margo  medialis)  is  smooth  and  rounded  above  and  below, 
but  more  prominent  in  the  centre;  it  commences  at  the  back  part  of  the  inner  tuber- 
osity, and  terminates  at  the  posterior  border  of  the  internal  malleolus;  its  upper 
part  gives  attachment  to  the  internal  lateral  ligament  of  the  knee  to  the  extent 
of  about  two  inches,  and  to  some  fibres  of  the  Popliteus  muscle,  and  its  middle 
third  to  some  fibres  of  origin  of  the  Soleus  and  Flexor,  longus  digitorum  muscles.. 

The  external  border  (crista  interossea),  or  interosseous  ridge,  is  thin  and  prominent, 
especially  its  central  part,  and  gives  attachment  to  the  interosseous  membrane; 
it  commences  above  in  front  of  the  fibular  articular  facet,  and  bifurcates  below, 
to  form  the  boundaries  of  a  triangular  rough  surface,  for  the  attachilient  of  the 
interosseous  ligament  connecting  the  tibia  and  fibula. 

The  internal  surface  (fades  medialis)  is  smooth,  convex,  and  broader  above  than 
below;  its  upper  third,  directed  forward  and  inward,  is  covered  by  the  aponeurosis 
derived  from  the  tendon  of  the  Sartorius,  and  by  the  tendons  of  the  Gracilis  and 
Semitendinosus,  all  of  which  are  inserted  nearly  as  far  forward  as  the  anterior 
border;  in  the  rest  of  its  extent  it  is  subcutaneous. 

The  external  surface  (fades  lateralis)  is  narrower  than  the  internal;  its  upper 
two-thirds  presents  a  shallow  groove  for  the  origin  of  the  Tibialis  anticus  muscle; 
its  lower  third  is  smooth,  convex,  curves  gradually  forward  to  the  anterior  aspect 
of  the  bone,  and  is  covered  from  within  outward  by  the  tendons  of  the  following 
muscles:  Tibialis  anticus.  Extensor  proprius  hallucis.  Extensor  longus  digitorum. 

The  posterior  surface  (fades  posterior)  (Fig.  186)  presents,  at  its  upper  part,  a 
prominent  ridge,  the  oblique  line  of  the  tibia  (l.inea  poplitea),  which  extends  from 
the  back  part  of  the  articular  facet  for  the  fibula  obliquely  downward,  to  the  in- 
ternal border,  at  the  junction  of  its  upper  and  middle  thirds.  It  marks  the  lower 
limit  for  the  insertion  of  the  Popliteus  muscle,  and  serves  for  the  attachment  of 
the  popliteal  fascia  and  part  of  the  Soleus,  Flexor  longus  digitorum,  and  Tibialis 
posticus  muscles;  the  triangular  concave  surface,  above  and  to  the  inner  side  of 
this  line,  gives  attachment  to  the  Popliteus  muscle.  The  middle  third  of  the 
posterior  surface  is  divided  by  a  vertical  ridge  into  two  lateral  halves;  the  ridge 
is  well  marked  at  its  commencement  at  the  oblique  line,  but  becomes  gradually 
indistinct  below;  the  inner  and  broader  half  gives  origin  to  the  Flexor  longus 
digitorum,  the  outer  and  narrower  to  part  of  the  Tibialis  posticus.  The  remaining 
part  of  the  bone  presents  a  smooth  surface  covered  by  the  Tibialis  posticus. 
Flexor  longus  digitorum,  and  Flexor  longus  hallucis  muscles.  Immediately 
below  the  oblique  line  is  the  nutrient  foramen,  which  is  large  and  directed  obliquely 
downward.  It  is  the  opening  of  the  nutrient  canal,  which  is  directed  toward  the 
ankle. 


THE  TIBIA,   OB  SHIN  BONE 


235 


Upper  rxtmnity. 


The  Distal  or  Lower  Extremity.— The  lower  extremity,  much  smaller  than 
the  upper,  presents  five  surfaces;  it  is  prolonged  downward,  on  its  inner  side, 
to  a  strong  process,  tiie  internal  malleolus  (malleolus  medialis). 

The  inferior  surface  (Jacicn  cniiciilaris  inferior)  of  the  bone  is  cjuadrilateral, 
and  smooth  for  articulation  with  the  astragalus.  This  surface  is  concave  from 
before  backward,  and  broader  in  front  than  behind.  It  is  traversed  from 
before  backward  by  a  slight  elevation,  separating  two  lateral  depressions.  It  is 
narrow  internally,  where  the  articular  surface  becomes  continuous  with  that  on 
the  inner  malleolus. 

The  anterior  surface  of  the  lower  extremity  is  smooth  and  rounded  above,  and 
covered  by  the  tendons  of  the  Extensor  muscles  of  the  toes;  its  lower  margin 
presents  a  rough  transverse  depression,  for  the  attachment  of  the  anterior  ligament 
of  the  ankle-joint. 

The  posterior  surface  presents  a  superficial  groove  directed  obliquely  downward 
and  inward,  continuous  with  a  similar  groove  on  the  posterior  surface  of  the  as- 
tragalus, and  serving  for  the  passage  of  the  tendon  of  the  Flexor  longus  hallucis. 

The  external  surface  presents  a  triangular  rough  depression  for  the  attachment 
of  the  interior  interosseous  ligament,  connecting  it  with  the  fibula;  the  lower  part 
of  this  depression,  the  iiicisura  fibularis,  is  smooth,  covered  with  cartilage  in  the 
recent  state,  and  articulates  with  the  fibula.  This  surface  is  bounded  by  two 
prominent  borders,  continuous  above  with  the  interosseous  ridge;  they  afford 
attachment  to  the  anterior  inferior  and  posterior  inferior  tibiofibular  ligaments. 

The  internal  surface  of  the  lower  extremity  is  prolonged  downward  to  form  a 
strong  pyramidal  process,  flattened  from  without  inward — the  internal  malleolus 
(malleolus  medialis).  The  inner  surface  of  this  process  is  convex  and  subcu- 
taneous; its  outer  surface  is  smooth  and 
slightly  concave,  and  articulates  with  the 
astragalus;  its  anterior  border  is  rough, 
for  the  attachment  of  the  anterior  fibres 
of  the  internal  lateral  or  deltoid  ligament; 
its  posterior  border  presents  a  broad  and 
deep  groove  (sulcus  malleolar  is),  directed 
obliquely  downward  and  inward,  which 
is  occasionally  double;  this  groove  trans- 
mits the  tendons  of  the  Tibialis  posticus 
and  Flexor  longus  digitorum  muscles. 
The  apex  of  the  internal  malleolus  is 
marked  by  a  rough  depression  behind, 
for  the  attachment  of  the  internal  lateral 
ligaments  of  the  ankle-joint. 

Structure.— Like  that  of  the  other  long  bones. 
At  the  junction  of  the  middle  and  lower  third, 
where  the  bone  is  smallest,  the  wall  of  the  shaft 
is  thicker  than  in  other  parts,  in  order  to  com- 
pensate for  the  smallness  of  the  calibre  of  the 
bone. 

Development.  —  From  three  centres  (Fig. 
1 88),  one  for  the  shaft  and  one  for  each  extrem- 
ity. Ossification  commences  in  the  centre  of  the 
shaft  about  the  seventh  week,  and  gradually  ex- 
tends toward  either  extremity.  The  centre  for  the 
upper  epiphysis  appears  before  or  shortly  after 

birth;  it  is  flattened  in  form,  and  has  a  thin,  tongue-shaped  process  in  front  which  forms  the 
tubercle.  That  for  the  lower  epiphysis  appears  in  the  second  year.  The  lower  epiphysis 
joins  the  shaft  at  about  the  eighteenth,  and  the  upper  one  about  the  twentieth  year.  T\yo 
additional  centres  occasionally  exist — one  for  the  tongue-shaped  process  of  the  upper  epiphysis, 
which  forms  the  tubercle,  and  one  for  the  inner  malleolus. 


Appenrs  shorily 
after  birth. 


Appears  at  Snd_ 
year. 


Joins  shaft  ahout 
20th  year. 


_Joins  shaft  about 
ISlh  year. 


236  SPECIAL  ANATOMY  OF  THE  SKELETON 

Articulations. — With  three  bones — the  femur,  fibula,  and  astragalus. 

Attachment  of  Muscles. — To  twelve:  To  the  inner  tuberosity,  the  Semimembranosus;  to  the 
outer  tuberosity,  the  Tibialis  anticus  and  Extensor  longus  digitorum  and  Biceps  femoris,  to  the 
shaft,  its  internal  surface,  the  Sartorius,  Gracilis,  and  Semitendinosus;  to  its  external  surface, 
the  Tibialis  anticus;  to  its  posterior  surface,  the  Popliteus,  Soleus,  Flexor  longus  digitorum,  and 
Tibialis  posticus;  to  the  tubercle,  the  ligamentum  patellae,  by  which  the  Quadriceps  extensor 
muscle  is  inserted  into  the  tibia.  In  addition  to  these  muscles,  the  Tensor  fasciae  femoris  is 
inserted  indirectly  into  the  tibia,  through  the  iliotibial  band,  and  the  Peroneus  longus  occasionally 
derives  a  few  fibres  of  origin  from  the  outer  tuberosity. 

Surface  Form. — A  considerable  portion  of  the  tibia  is  subcutaneous  and  easily  felt.  At  the 
upper  extremity  the  tuberosities  are  to  be  recognized  just  below  the  knee.  The  internal  one  is 
broad  and  smooth,  and  merges  into  the  subcutaneous  surface  of  the  shaft  below.  The  external 
one  is  narrower  and  more  prominent,  and  on  it,  about  midway  between  the  apex  of  the  patella 
and  the  head  of  the  fibula,  may  be  felt  a  prominent  tubercle  for  the  insertion  of  the  iliotibial 
band.  In  front  of  the  upper  end  of  the  bone,  between  the  tuberosities,  is  the  tubercle  of  the 
tibia,  forming  an  oval  eminence  which  is  continuous  below  with  the  anterior  border  or  crest 
of  the  bone.  This  border  can  be  felt,  forming  the  prominence  of  the  shin,  in  the  upper  two- 
thirds  of  its  extent  as  a  sharp  and  sinuous  ridge,  curved  outward  above  and  inward  below.  In 
the  lower  third  of  the  leg  the  border  disappears,  and  the  bone  is  concealed  by  the  tendons  of  the 
muscles  on  the  front  of  the  leg.  Internal  to  the  anterior  border  is  to  be  felt  the  broad  internal 
surface  of  the  tibia,  slightly  encroached  upon  by  the  muscles  in  front  and  behind.  It  com- 
mences above  at  the  wide  expanded  inner  tuberosity,  and  terminates  below  at  the  internal  malle- 
olus. The  internal  malleolus  is  a  broad  prominence  situated  on  a  higher  level  and  somewhat 
farther  forward  than  the  external  malleolus.  It  overhangs  the  inner  border  of  the  arch  of  the 
foot.  Its  anterior  border  is  nearly  straight;  its  posterior  border  presents  a  sharp  edge  which 
forms  the  inner  margin  of  the  groove  for  the  tendon  of  the  Tibialis  posticus  muscle. 

The  Fibula,  or  Calf  Bone  (Figs.  185,  186). 

The  fibula  is  situated  at  the  outer  side  of  the  leg.  It  is  the  smaller  of  the  two 
bones,  and,  in  proportion  to  its  length,  the  most  slender  of  all  the  long  bones;  it 
is  placed  on  the  outer  side  of  the  tibia,  with  which  it  is  connected  above  and  below. 
Its  upper  extremity  is  small,  placed  toward  the  back  of  the  head  of  the  tibia  and 
below  the  level  of  the  knee-joint,  and  excluded»4i'om  its  formation;  the  lower 
extremity  inclines  a  little  forward,  so  as  to  be  on  a  plane  anterior  to  that  of  the 
upper  end,  projects  below  the  tibia,  and  forms  the  outer  ankle.  It  presents 
for  examination  a  shaft  and  two  extremities. 

The  Proximal  or  Upper  Extremity. — The  upper  extremity,  or  head  (capitu- 
limi  fibulae),  is  of  an  irregular  quadrate  form,  presenting  above  a  flattened  articular 
facet,  directed  upward,  forward,  and  inward,  for  articulation  with  a  corresponding 
facet  on  the  external  tuberosity  of  the  tibia.  On  the  outer  side  is  a  thick  and 
rough  prominence,  continued  behind  into  a  pointed  eminence,  the  styloid  process 
of  the  fibula  (apex  capituli  fibulae),  which  projects  upward  from  the  posterior 
part  of  the  head.  The  prominence  gives  attachment  to  the  tendon  of  the  Biceps 
femoris  muscle  and  to  the  long  external  lateral  ligament  of  the  knee,  the  ligament 
dividing  the  tendon  into  two  parts.  The  apex  of  the  styloid  process  gives  at- 
tachment to  the  short  external  lateral  ligament.  The  remaining  part  of  the 
circumference  of  the  head  is  rough,  for  the  attachment  of  muscles  and  ligaments. 
It  presents  in  front  a  tubercle  for  the  origin  of  the  upper  and  anterior  part  of  the 
Peroneus  longus,  and  the  adjacent  surface  gives  attachment  to  the  anterior 
superior  tibiofibular  ligament;  and  behind,  another  tubercle  for  the  attachment 
of  the  posterior  superior  tibiofibular  ligament  and  the  upper  fibres  of  origin  of 
the  Soleus  muscle. 

The  Shaft  (corpus  fibulae).^ — The  shaft  presents  four  borders — the  antero- 
external,  the  antero-internal,  the  postero-external,  and  the  postero-internal;  and 
four  surfaces — anterior,  posterior,  internal,  and  external. 

•  Authorities  differ  as  to  the  best  description  of  the  borders  and  surfaces  of  the  shaft  of  the  fibula.  The  editor  has 
followed  the  scheme  in  general  use  at  the  present  time.  A  more  appropriate  plan  might  be  afforded  by  the  consid- 
eration of  three  surfaces:   extensor,  peroneal,  and  flexor,  the  last  being  subdivided  by  the  oblique  ridge. — Editor. 


THE  FIBULA,   OR  CALF  BONE  237 

The  antero-external  border  (crista  anterior)  commences  above  in  front  of  the 
head,  runs  vertically  downward  to  a  little  below  the  middle  of  the  bone,  and  then, 
curving  somewhat  outward,  bifurcates  so  as  to  embrace  the  triangular  subcutane- 
ous surface  immediately  above  the  outer  surface  of  the  external  malleolus.  This 
border  gives  attachment  to  an  intermuscular  septum,  which  separates  the  Extensor 
muscles  on  the  anterior  surface  of  the  leg  from  the  Peroneus  longus  and  brevis 
muscles  on  the  outer  surface. 

The  antero-intemal  border  (crista  iuterossea),  or  interosseous  ridge,  is  situated 
close  to  the  inner  side  of  the  preceding,  and  runs  nearly  parallel  with  it  in  the  upper 
third  of  its  extent,  but  diverges  from  it  so  as  to  include  a  broader  space  in  the  lower 
two-thirds.  It  commences  above,  just  beneath  the  head  of  the  bone  (sometimes 
it  is  quite  indistinct  for  about  an  inch  below  the  head),  and  terminates  below  at 
the  apex  of  a  rough  triangular  surface  immediately  above  the  articular  facet  of 
the  external  malleolus.  It  serves  for  the  attachment  of  the  interosseous  membrane, 
which  separates  the  Extensor  muscles  in  front  from  the  Flexor  muscles  behind. 

The  postero-extemal  border  (crista  lateralis)  is  prominent;  it  commences  above 
at  the  base  of  the  styloid  process,  and  terminates  below  in  the  posterior  border 
of  the  outer  malleolus.  It  is  directed  outward,  above,  backward  in  the  middle 
of  its  course,  backward  and  a  little  inward  below,  and  gives  attachment  to  an 
aponeurosis  which  separates  the  Peronei  muscles  on  the  outer  surface  of  the  shaft 
from  the  Flexor  muscles  on  its  posterior  surface. 

The  postero-intemal  border  (crista  medialis)  sometimes  called  the  oblique  line, 
commences  above  at  the  inner  side  of  the  head,  and  terminates  by  becoming 
continuous  with  the  interosseous  ridge  at  the  lower  fourth  of  the  bone.  It  is 
well  marked  and  prominent  at  the  upper  and  middle  parts  of  the  bone.  It  gives 
attachment  to  an  aponeurosis  which  separates  the  Tibialis  posticus  from  the 
Soleus  above  and  the  Flexor  longus  hallucis  below. 

The  anterior  siirface  {Jacies  anterior)  is  the  interval  between  the  antero-external 
and  antero-internal  borders.  It  is  extremely  narrow  and  flat  in  the  upper  third 
of  its  extent,  broader  and  grooved  longitudinally  in  its  lower  third;  it  serves  for 
the  origin  of  three  muscles,  the  Extensor  longus  digitorum,  Peroneus  tertius, 
and  Extensor  proprius  hallucis. 

The  external  surface  Q'acies  lateralis)  is  the  space  between  the  antero-external 
and  postero-external  borders.  It  is  much  broader  than  the  preceding,  and  often 
deeply  grooved,  is  directed  outward  in  the  upper  two-thirds  of  its  course,  backward 
in  the  lower  third,  where  it  is  continuous  with  the  posterior  border  of  the  external 
malleolus.  This  surface  is  completely  occupied  by  the  Peroneus  longus  and  brevis 
muscles. 

The  internal  surface  (fades  medialis)  is  the  interval  included  between  the  antero- 
internal  and  the  postero-internal  borders.  It  is  directed  inward,  and  is  grooved 
for  the  origin  of  the  Tibialis  posticus  muscle. 

The  posterior  surface  (Jacies  posterior)  is  the  space  included  between  the  postero- 
external and  the  postero-internal  borders;  it  is  continuous  below  with  the  rough 
triangular  surface  above  the  articular  facet  of  the  outer  malleolus;  it  is  directed 
backward  above,  backward  and  inward  at  its  middle,  directly  inward  below. 
Its  upper  third  is  rough,  for  the  origin  of  the  Soleus  muscle;  its  lower  part  presents 
a  triangular  rough  surface,  connected  to  the  tibia  by  a  strong  interosseous  ligament, 
and  between  these  two  points  the  entire  surface  is  covered  by  the  fibres  of  origin 
of  the  Flexor  longus  hallucis  muscle.  At  about  the  middle  of  this  surface  is  the 
nutrient  foramen.     It  opens  into  the  nutrient  canal,  which  is  directed  downward. 

The  Distal  or  Lower  Extremity.— The  lower  extremity,  or  external  malleolus 
(malleolus  lateralis),  is  of  a  pyramidal  form,  somewhat  flattened  from  without  in- 
ward, and  is  longer,  and  descends  lower  than  the  internal  malleolus.  Its  external 
surface  is  convex,  subcutaneous,  and  continuous  with  the  triangular  (also  sub- 


238 


SPECIAL  ANATOMY  OF  THE  SKELETON 


cutaneous)  surface  on  the  outer  side  of  the  shaft.  The  internal  surface  presents 
in  front  a  smooth  triangular  facet  {fades  artlcularis  malleoli),  broader  above  than 
below,  and  convex  from  above  downward,  which  articulates  with  a  corresponding 
surface  on  the  outer  side  of  the  astragalus.  Behind  and  beneath  the  articular 
surface  is  a  rough  depression  which  gives  attachment  to  the  posterior  fasciculus 
of  the  external  lateral  ligament  of  the  ankle.  The  anterior  border  is  thick  and 
rough,  and  marked  below  by  a  depression  for  the  attachment  of  the  anterior 
fasciculus  of  the  external  lateral  ligament.  The  posterior  border  is  broad  and 
marked  by  a  shallow  groove  (sulcus  malleolaris),  for  the  passage  of  the  tendons 
of  the  Peroneus  longus  and  brevis  muscles.  The  ai:iex  is  rounded,  and  gives 
'attachment  to  the  middle  fasciculus  of  the  external  lateral  ligament. 


Interosseous 

I        "fi  border 


Upper  extremity. 


Appears  atout  ^ 
4th  year.     ^ 


.  Unites  about 
'  S5th  year. 


For  post,  fascic.  of 
extl.  lateral  ligt. 


Appeals  at  JSM  Unites  about 
Sndyea,    ~\W\  -Othyear. 

I.oirer  erfremify. 


-Lower  extremity  of  right  fibula. 
Internal  aspect. 


In  order  to  distinguish  ttie  side  to  wliich  the  bone  belongs,  hold  it  with  the  lower  extremit}^ 
downward  and  the  broad  groove  for  the  Peronei  tendons  backward — i.  e.,  toward  the  holder; 
the  triangular  subcutaneous  surface  will  then  be  directed  to  the  side  to  which  the  bone  belongs. 

Development. — From  three  centres  (Fig.  190) — one  for  the  shaft  and  one  for  each  extremity. 
Ossification  commences  in  the  shaft  about  the  eighth  week  of  fetal  life,  a  little  later  than  in  the 
tibia,  and  extends  gradually  toward  the  extremities.  At  birth  both  ends  are  cartilaginous.  Ossifi- 
cation commences  in  the  lower  end  in  the  second  year,  and  in  the  upper  one  about  the  fourth 
year.  The  lower  epiphysis,  the  first  in  which  ossification  commences,  becomes  united  to  the 
shaft  about  the  twentieth  year;  the  upper  epiphysis  joins  about  the  twenty-fifth  year.  Ossifi- 
cation appearing  first  in  the  lower  epiphysis  is  contrary  to  the  rule  which  prevails  with  regard 
to  the  commencement  of  ossification  in  epiphyses — viz.,  that  epiphysis  toward  which  the  nutrient 
artery  is  directed  commences  to  ossify  last;  but  it  follows  the  rule  which  prevails  with  regard  to 
the  union  of  epiphyses,  by  uniting  first. 

Articulations. — With  two  bones:  the  tibia  and  astragalus. 

Attachment  of  Muscles.— To  nine:  To  the  head,  the  Biceps  femoris,  Soleus,  and  Peroneus 
longus;  to  the  shaft,  its  anterior  surface,  the  Extensor  longus  digitorum,  Peroneus  tertius,  and 
Extensor  proprius  hallucis;  to  the  internal  surface,  the  Tibialis  posticus;  to  the  posterior  surface, 
the  Soleus  and  Flexor  longus  hallucis,  to  the  external  surface,  the  Peroneus  longus  and  brevis. 

Surface  Form. — The  only  parts  of  the  fibula  which  may  be  fe't  are  the  head  and  the  lower 
part  of  the  externa!  surface  of  the  shaft  and  the  external  malleolus.    The  head  may  be  seen 


THE  FOOT  239 

and  felt  behind  and  to  the  outer  side  of  the  outer  tuberosity  of  the  tibia.  It  presents  a  small, 
prominent  triangular  eminence  slightly  above  the  level  of  the  tubercle  of  the  tibia.  The  exter- 
nal malleolus  presents  a  narrow  elongated  prominence,  situated  on  a  plane  posterior  to  the 
internal  malleolus  and  reaching  to  a  lower  level.  From  it  may  be  traced  the  lower  third  or 
half  of  the  external  surface  of  the  shaft  of  the  bone  in  the  interval  between  the  Peroneus  tertius 
in  front  and  the  other  two  Peronei  tendons  behind. 

Applied  Anatomy. — In  fractures  of  the  bones  of  the  ley  both  bones  are  usually  fractured,  but 
either  bone  may  be  broken  separately,  the  fibula  more  frequently  than  the  tibia.  Fracture  of 
both  bones  may  be  caused  either  by  direct  or  indirect  violence.  When  it  occurs  from  indirect 
force  the  fracture  in  the  tibia  is  usually  at  the  junction  of  the  middle  and  lower  third  of  the  bone. 
Many  causes  conduce  to  render  this  the  weakest  part  of  the  bone.  The  fracture  of  the  fibula 
is  usually  at  rather  a  higher  level.  These  fractures  present  great  variety,  both  as  regards  their 
direction  and  condition.  They  may  be  oblique,  transverse,  longitudinal,  or  spiral.  When 
oblique,  they  are  usually  the  result  of  indirect  violence,  and  the  direction  of  the  fracture  is  from 
behind,  downward,  forward,  and  inward  in  many  cases,  but  may  be  downward  and  outward 
or  downward  and  backward.  When  transverse,  the  fracture  is  often  at  the  upper  part  of  the 
bone,  and  is  the  result  of  direct  violence.  The  spiral  fracture  usually  commences  as  a  vertical 
fissure,  involving  the  ankle-joint,  and  is  associated  with  fracture  of  the  fibula  higher  up.  It  is 
the  result  of  torsion,  from  twisting  of  the  body  while  the  foot  is  fixed. 

Fractures  of  the  tiliia  alone  are  almost  always  the  result  of  direct  violence,  except  where  the 
malleolus  is  broken  off  by  twists  of  the  foot.  Fractures  of  the  fibula  alone  may  arise  from  indi- 
rect or  direct  force,  those  of  the  lower  end  being  usually  the  result  of  the  former,  and  those  higher 
up  being  caused  by  a  direct  blow  on  the  part. 

The  tibia  and  fibula,  like  the  femur,  are  frequently  the  seat  of  acute  osteomyelitis.  Tuhemdoiis 
abscess  is  more  frequently  met  with  in  the  cancellous  tissue  of  the  head  and  lower  end  of  the 
tibia  than  in  any  other  bone  of  the  body.  The  abscess  is  of  small  size,  very  chronic,  and  prob- 
ably the  result  of  tuberculous  osteitis  in  the  highly  vascular  growing  tissue  at  the  end  of  the  shaft 
near  the  epiphyseal  cartilage  in  the  young  subject.  Such  an  abscess  in  bone  is  called  Brodie's 
abscess. 

The  tibia  is  the  bone  which  is  most  frequently  and  most  extensively  distorted  in  rhachitis.  It 
gives  way  at  the  junction  of  the  middle  and  lower  third,  its  weakest  part,  and  presents  a  curve 
forward  and  outward.  Boto-leg  is  due  to  outward  curvature  of  the  femur,  tibia,  and  fibula, 
the  bend  being  about  the  junction  of  the  shafts  and  lower  extremities. 


THE  FOOT  (Figs.  191,  192). 

The  skeleton  of  the  foot  consists  of  three  divisions — the  tarsus,  metatarsus,  and 
phalanges. 

The  Tarsus  (os.m  tarsi). — The  hones  of  the  tarsus  are  seven  in  number — 
viz.,  tlie  calcaneus,  or  os  calcis,  astragalus,  cuboid,  scaphoid,  internal,  middle,  and 
external  cvmeiform. 

The  Calcaneus  (os  calcis)  (Fig.  194). — The  heel  bone  is  the  largest  and  strongest 
of  the  tarsal  bones.  It  is  irregularly  cuboidal  in  form,  having  its  long  axis  directed 
forward  and  outv\ard.  It  is  situated  at  the  lower  and  back  part  of  the  foot, 
serving  to  transmit  the  weight  of  the  body  to  the  ground,  and  forming  a  strong 
lever  for  the  muscles  of  the  calf.  It  presents  for  examination  six  surfaces — 
superior,  inferior,  external,  internal,  anterior,  and  posterior. 

The  superior  surface  is  formed,  behind,  by  the  upper  aspect  of  that  part  of  the 
OS  calcis  which  projects  backward  to  form  the  heel.  It  varies  in  length  in  different 
individuals;  is  convex  from  side  to  side,  concave  from  before  backward,  and  cor- 
responds above  to  a  mass  of  adipose  substance  placed  in  front  of  the  tendo  Achillis. 
In  the  middle  of  the  superior  surface  are  two  (sometimes  three)  articular  facets, 
separated  by  a  broad  shallow  groove  (sulcus  calcanei),  which  is  directed  obliquely 
forward  and  outward,  and  is  rough  for  the  attachment  of  the  interosseous  ligament 
connecting  the  astragalus  and  os  calcis.  When  the  calcaneus  is  in  contact  with 
the  astragalus  this  groove  is  converted  into  a  canal  (sinus  tarsi).  Of  the  articular 
surfaces,  the  posterior  articular  siu-face  (fades  articularis  posterior)  is  th^  larger,  and 
is  situated  on  the  body  of  the  bone;  it  is  of  an  oblong  form,  wider  behind  than  in 


240 


SPECIAL  ANA  TOMY  OF  THE  SKELETON 


Fig.   191. — Bones  of  the  right  foot.     Dorsal  surface. 


THE  FOOT 


241 


AOOESSOniU&. 


,rLExcR  snevis  hallucis. 


Fig.  192. — Bones  of  the  right  foot.      Plantar  surface. 
16 


242 


SPECIAL  ANA  T03IY  OF  THE  SKELETON 


front,  and  convex;  it  articulates  with  the  posterior  articular  area  of  the  astragalus. 
The  anterior  articular  stirf ace  is  usually  divided  into  two  facets,  the  anterior  of  which 
(fades  articularis  anterior)  supports  the  head  of  the  astragalus.  The  more  pos- 
teriorly situated  facet  (fades  articularis  calcanea  media)  articulates  with  the  middle 
facet  on  the  under  surface  of  the  astragalus.  The  anterior  articular  surface  is 
supported  on  a  projecting  process  of  bone,  called  the  lesser  process  of  the  cal- 
caneus (sustentaculum  tali);  it  is  oblong,  concave  longitudinally,  and  sometimes 
subdivided  into  two  parts,  which  differ  in  size  and  shape.     IMore  anteriorly  is 

seen  the  upper  surface  of  the  greater 
process  of  the  calcaneus,  marked  bv  a 
rough  depression  for  the  attachment 
of  numerous  ligaments,  and  a  tubercle 
for  the  origin  of  the  Extensor  brevis 
digitorum  muscle. 

The  inferior  surface  is  narrow, 
rough,  uneven,  wider  behind  than  in 
front,  and  convex  from  side  to  side; 
it  is  bounded  posteriorly  by  two 
tubercles  separated  by  a  rough  de- 
pression; the  external  tubercle  (pro- 
cessus lateralis  tuberis  calcanei),  small, 
prominent,  and  rounded,  gives  origin 
to  part  of  the  Abductor  minimi 
digiti;  the  internal  tubercle  (processus 
medialis  tuberis  calcanei),  broader  and 
larger,  for  the  support  of  the  heel, 
gives  origin,  by  its  prominent  inner 
margin,  to  the  Abductor  hallucis,  and 
in  front  to  the  Flexor  brevis  digitorum 
muscle  and  plantar  fascia;  the  de- 
pression between  the  tubercles  gives 
origin  to  the  Abductor  minimi  digiti. 
The  rough  surface  in  front  of  the 
tubercles  gives  attachment  to  the  long 
plantar  ligament  and  origin  to  the 
outer  head  of  the  Flexor  accessorius 
muscle;  while  to  a  prominent  tubercle 
nearer  the  anterior  part  of  this  sur- 
face, as  well  as  to  a  transverse  groove 
in  front  of  it,  is  attached  the  short 
plantar  ligament. 
The  external  surface  is  broad,  flat,  and  almost  subcutaneous;  it  presents  near 
its  centre  a  tubercle,  for  the  attachment  of  the  middle  fasciculus  of  the  exter- 
nal lateral  ligament.  At  its  upper  and  anterior  part  this  surface  gives  attach- 
ment to  the  external  calcaneo-astragaloid  ligament;  and  in  front  of  the  tubercle 
it  presents  a  narrow  surface  marked  by  two  oblique  grooves;  separated  by  an 
elevated  ridge  which  varies  much  in  size  in  different  bones,  it  is  named  the  peroneal 
spine  {processus  trochlear  is),  and  gives  attachment  to  a  fibrous  process  from  the 
external  annular  ligament.  The  superior  groo-ve  transmits  the  tendon  of  the 
Peroneus  brevis;  the  inferior  groove  the  tendon  of  the  Peroneus  longus. 

The  internal  surface  is  deeply  concave;  it  is  directed  obliquely  downward  and 
forward,  and  serves  for  the  transmission  of  the  plantar  vessels  and  nerves  into  the 
sole  of  the  foot;  it  affords  origin  to  part  of  the  Flexor  accessorius  muscle.  At 
its  upper  and  fore  part  it  presents  an  eminence  of  bone,  the  sustentaculum  tali, 


Fig.  193, — Schematic  representation  of  the  articula- 
tions of  the  tarsus.     Occasional  articulations    shown  hy 


THE  FOOT 


243 


which  projects  horizontally  inward,  and  to  it  a  slip  of  the  tendon  of  the  Tibialis 
posticus  is  attached.  This  process  is  concave  above,  and  supports  the  anterior 
articular  surface  of  the  astragalus;  below,  it  is  grooved  for  the  tendon  of  the  Flexor 
longus  hallucis.  Its  free  margin  is  rough,  for  the  attachment  of  part  of  the 
internal  lateral  ligament  of  the  ankle-joint. 

The  anterior  surface  {fades  articularis  cuhoidea),  of  a  somewhat  triangular 
form,  articulates  with  the  cuboid.  It  is  concave  from  above  downward  and  out- 
ward, and  convex  in  the  opposite  direction.  Its  inner  border  gives  attachment 
to  the  inferior  calcaneoscaphoid  ligament. 


Groove  for  Peroneus  bre. 

A. 


Feroneal  tubercle 

Groove  for  Feroneus  longus 


tendo  AchiUia 


External-  tubercle 


B 


For  posterim-  facet  of  astragal:is 
For  middle  facet  of  astragalus 

For  ntitei  tor  facet  of  astragalus 


Internal  tubercle 
Groove  for  Flexor  longus  hallucis 

Sustentaculum  tali 

Groove  for  interosseous  ligament 

Fig.  194. — The  left  calcaneus.     A.  Postero-external  view.     B.  Antero-internal  view. 

The  posterior  surface  is  rough,  prominent,  convex,  and  wider  below  than  above. 
The  posterior  extremity  is  the  projection  of  the  heel.  It  is  called  the  tuberosity 
(tuber  calcanei).  Its  lower  part  is  rough,  for  the  attachment  of  the  tendo  Achillis 
and  the  tendon  of  the  Plantaris  muscle;  its  upper  part  is  smooth,  and  is  covered 
.by  a  bursa  which  separates  the  tendons  from  the  bone. 


244 


SPECIAL  ANA  TOMY  OF  THE  SKELETON 


Articulations. — With  two  bones — the  astragalus  and  cuboid. 

Attachment  of  Muscles. — To  eight,  part  of  the  TibiaHs  posticus,  the  tendo  Achilhs,  Plan- 
taris,  Abductor  hallucis,  Abductor  minimi  digiti,  Flexor  brevis  digitorum,  Flexor  accessorius, 
and  Extensor  brevis  digitorum. 


For  scaphoid  Neck  A  Sup.  surface,  for  tibia 

'  For  inferior  tibiofibular 

ligament 


For  ext.  malleolus 


For  int.  malleoUu 


Sup.  surface,  fur  tihia 


Groove  for  Flexor  longus         \ .  ^ 

hallucis 


For  inferior  calcaneo 
navicular  ligament 


Middle  calcaneal 
facet 


Posterior  calcaneal 
facet 


Groove  for  Flex, 
long,  hallucis 


For  scaphoid 


'For  scaphoid 
j{      ~~~^~i^ZW -interior  calcaneal  facet 


Groove  for  interosseous 
ligaynent 


Fig.  195. — The  left  astragalus.     A.  Supero-external 


C.  Inferior  view. 


The  Astragalus,  or  Ankle  Bone  {talus)  (Fig.  195).— The  astragaliLS  is  the  second 
largest  of  the  tarsal  bones.  It  occupies  the  middle  and  upper  part  of  the  tarsus, 
supporting  the  tibia  above,  articulating  with  the  malleoli  on  either  side,  resting 
below  upon  the  calcaneus,  and  joined  in  front  to  the  scaphoid.     This  bone  may 


THE  FOOT  245 

be  easily  recognized  by  its  large  rounded  head,  by  the  broad  articular  facet  on  its 
upper  convex  surface,  and  by  the  two  articular  facets  separated  by  a  deep  groove 
on  its  under  concave  surface.     It  presents  six  surfaces  for  examination. 

The  superior  surface  presents,  behind,  a  broad  smooth  trochlear  surface  {trochlea 
tali)  for  articulation  with  the  tibia.  The  trochlea  is  broader  in  front  than  behind, 
convex  from  before  backward,  slightly  concave  from  side  to  side;  in  front  of  it  is  the 
upper  surface  of  the  neck  of  the  astragalus,  rough  for  the  attachment  of  ligaments. 

The  inferior  surface  presents  two  articular  areas  separated  by  a  deep  groove 
{svlcits  tali).  The  groove  runs  obliquely  forward  and  outward,  becoming  gradu- 
ally broader  and  deeper  in  front;  it  corresponds  with  a  similar  groove  upon  the 
upper  surface  of  the  calcaneus,  and  forms,  when  articulated  with  that  bone,  a 
canal,  filled  up  in  the  recent  state  by  the  calcaneo-astragaloid  ligament.  Of 
the  two  articular  areas,  the  posterior  (fades  articularis  calcanea  posterior)  is  the 
larger,  of  an  oblong  form,  and  deeply  concave  from  side  to  side ;  it  rests  on  the 
posterior  articular  surface  of  the  os  calcis;  the  anterior  articular  area  is  shorter 
and  narrower,  of  an  elongated  oval  form,  convex  longitudinally,  and  most  often 
subdivided  into  two  facets  by  an  elevated  ridge;  of  these,  the  posterior  (fades 
articularis  calcanea  media)  articulates  with  the  hinder  portion  of  the  anterior 
articular  surfaces  of  the  calcaneus;  the  anterior  (fades  articularis  calcanea  anterior) 
rests  upon  the  anterior  portion  of  the  anterior  articular  surface  of  the  calcaneus 
just  mentioned. 

The  internal  surface  presents  at  its  upper  part  a  pear-shaped  articular  facet  (fades 
malleolaris  medialis)  for  the  inner  malleolus,  continuous  above  with  the  trochlear 
surface;  below  the  articular  surface  is  a  rough  depression,  for  the  attachment 
of  the  deep  portion  of  the  internal  lateral  ligajnent. 

The  external  surface  presents  a  large  triangular  facet  (fades  malleolaris  lateralis), 
concave  from  above  downward  for  articulation  with  the  external  malleolus; 
it  is  continuous  above  with  the  trochlear  surface;  and  in  front  of  it  is  a  rough 
depression  for  the  attachment  of  the  anterior  fasciculus  of  the  external  lateral 
ligament  of  the  ankle-joint. 

The  anterior  surface  (fades  articularis  navicularis)  forms  the  head  of  the  astrag- 
alus, is  convex  and  rounded,  smooth,  of  an  oval  form,  and  directed  obliquely 
inward  and  downward;  it  articulates  with  the  scaphoid.  On  its  under  and  inner 
surface  is  a  small  facet,  continuous  in  front  with  the  articular  surface  of  the  head, 
and  behind  with  the  anterior  articular  area  for  the  calcaneus.  This  rests  on  the 
inferior  calcaneoscaphoid  ligament,  being  separated  from  it  by  the  syno\ial  mem- 
brane. The  head  is  attached  to  the  rest  of  the  bone  by  a  constricted  portion,  the 
neck  of  the  astragalus  (collum  tali). 

The  posterior  surface  is  traversed  by  a  groove  (sidcus  m.  flexoris  hallucis  longi), 
which  runs  obliquely  downward  and  inward,  and  transmits  the  tendon  of  the 
Flexor  longus  hallucis,  external  to  which  is  the  prominent  external  tubercle  (pro- 
cessus posterior  tali),  to  which  the  posterior  fasciculus  of  the  external  lateral 
ligament  is  attached.  This  tubercle  is  sometimes  separated  from  the  rest  of  the 
astragalus,  and  is  then  known  as  the  os  trigonum. 

To  ascertain  to  which  foot  the  bone  belongs,  hold  it  with  the  broad  articular  surface  upward, 
and  the  rounded  head  forward;  the  lateral  triangular  articular  surface  for  the  external  malleolus 
will  then  point  to  the  side  to  which  the  bone  belongs. 

Articulations. — With  four  bones — tibia,  fibula,  calcaneus,  and  scaphoid. 

The  Cuboid  (os  cuboideum)  (Fig.  196). — The  cuboid  is  placed  on  the  outer 
side  of  the  foot,  in  front  of  the  calcaneus,  and  behind  the  fourth  and  fifth  meta- 
tarsal bones.  It  is  of  a  pyramidal  shape,  its  base  being  directed  inward,  its  apex 
outward.     It  may  be  distinguished  from  the  other  tarsal  bones  by  the  existence 


246  SPECIAL  ANATOMV  OF  THE  SKELETON 

of  a  deep  groove  on  its  under  surface,  for  the  tendon  of  the  Peroneus  longus  muscle. 
It  presents  for  examination  six  surfaces,  three  articular  and  three  nonarticular. 
The  nonarticular  surfaces  are  the  dorsal,  plantar,  and  external.  The  dorsal 
surface,  directed  upward  and  outward,  is  rough,  for  the  attachment  of  numerous 
ligaments.  The  plantar  surface  presents  in  front  a  deep  groove,  the  peroneal 
groove  (sulcus  m.  peroiiei  loncji),  which  runs  obliquely  from  without,  forward  and 
inward;  it  lodges  the  tendon  of  the  Peroneus  longus,  and  is  bounded  behind  by 
a  prominent  ridge,  to  which  is  attached  the  long  calcaneocuboid  ligament.  The 
ridge  terminates  externally  in  an  eminence  (tuberositas  ossi-s  cuboidei),  the  surface 
of  which  presents  a  convex  facet,  for  articulation  with  the  sesamoid  bone  of  the 
tendon  contained  in  the  groove.  The  surface  of  bone  behind  the  groove  is  rough, 
for  the  attachment  of  the  short  plantar  ligament,  a  few  fibres  of  origin  of  the 
Flexor  brevis  hallucis,  and  a  fasciculus  from  the  tendon  of  the  Tibialis  posticus. 
The  external  surface,  the  smallest  and  narrowest  of  the  three,  presents  a  deep 
notch  formed  by  the  commencement  of  the  peroneal  groove. 


For  ext.  cuneiform        For  4tk  -metatarsal 


Occasional  facet 
for  scaphoid 


Fui  5th 
tatarsal 


Groovefor     Tubeiositij     Foi   ralcaneni 
Peroneus 
longus  B 

Fig.  196. — The  left  cuboid.     .-1.  .\ntero-internaI  view.     B.  Postero-external  view. 

The  articular  surfaces  are  the  posterior,  anterior,  and  internal.  The  posterior 
surface  is  smooth,  triangular,  and  concavo-convex,  for  articulation  with  the 
anterior  surface  of  the  calcaneus.  The  anterior  surface,  of  smaller  size,  but  also 
irregularly  triangular,  is  divided  by  a  vertical  ridge  into  two  facets :  the  inner  one, 
quadrilateral  in  form,  articulates  with  the  fourth  metatarsal  bone;  the  outer  one, 
larger  and  more  triangular,  articulates  with  the  fifth  metatarsal.  The  internal 
surface  is  broad,  rough,  irregularly  quadrilateral,  presenting  at  its  middle  and 
upper  part  a  smooth  oval  facet,  for  articulation  with  the  external  cuneiform  bone; 
and  behind  this  (occasionally)  a  smaller  facet,  for  articulation  with  the  scaphoid; 
it  is  rough  in  the  rest  of  its  extent,  for  the  attachment  of  strong  interosseous  liga- 
ments. 

To  ascertain  to  which  foot  the  bone  belongs,  hold  it  so  that  its  under  surface,  marked  by  the 
peroneal  groove,  looks  downward,  and  the  large  concavo-convex  articular  surface  backward 
toward  the  holder:  the  narrow  nonarticular  surface,  marked  by  the  Commencement  of  the 
peroneal  groove,  will  point  to  the  side  to  which  the  bone  belongs. 

Articulations. — With  foiir  bones — the  calcaneus,  external  cuneiform,  and  the  fourth  and  fifth 
metatarsal  bones;  occasionally  with  the  scaphoid. 

Attachment  of  Muscles. — Part  of  the  Flexor  brevis  hallucis  and  a  slip  from  the  tendon  of 
the  Tibialis  posticus. 

Scaphoid  or  Navicular  Bone  (os  naviculare  pedis)  (Fig.  197). — The  scaphoid  is 
situated  at  the  inner  side  of  the  tarsus,  between  the  astragalus  behind  and  the 
three  cuneiform  bones  in  front.  It  may  be  distinguished  by  its  form,  being  con- 
cave behind,  convex  and  subdivided  into  three  facets  in  front. 

The  anterior  surface,  of  an  oblong  form,  is  convex  from  side  to  side,  and  sub- 
divided by  two  ridges  into  three  facets,  for  articulation  with  the  three  cuneiform 
bones.     The  posterior  surface  is  oval,  concave,  broader  externally  than  internally. 


THE  FOOT 


247 


and  articulates  with  the  rounded  head  of  the  astragalus.  The  dorsal  surface  is 
convex  from  side  to  side,  and  rough  for  the  attachment  of  ligaments.  The  plantar 
is  irregular,  and  also  rough  for  the  attachment  of  ligaments.  The  internal  surface 
presents  a  rounded  tubercular  eminence,  the  tuberosity  {tuberositas  ossis  navicu- 
laris),  the  lower  part  of  which  projects,  and  gives  attachment  to  part  of  the  tendon 
of  the  Tibialis  posticus.  The  external  surface  is  rough  and  irregular,  for  the 
attachment  of  ligamentous  fibres,  and  occasionally  presents  a  small  facet  for 
articulation  with  the  cuboid  bone. 


For  viid.  cuneiforin 


For  int.  cuneifoi  m 


Fig.  197  —The  left  scaphoid 


For  astragalus        Tubercle 


eternal  view.     B.  Postero-internal  view. 


For Znd  For 

For  1st  metatarsal  metatarsal       mid-cuneiform 


To  ascertain  to  which  foot  the  bone  belongs,  hold  it"  with  the  concave  articular  surface  back- 
ward, and  the  convex  dorsal  surface  upward;  the  external  surface — i.  e.,  the  surface  opposite 
the  tubercle — will  point  to  the  side  to  which  the  bone  belongs. 

Articulations. — With  four  bones — astragalus  and  three  cuneiform;  occasionally  also  with 
the  cuboid. 

Attachment  of  Muscles. — Part  of  the  Tibialis  posticus. 

Cuneiform  or  Wedge  Bones. — The  cuneiform  bones  have  received  their  name 
from  their  wedge-like  shape.  They  form,  with  the  cuboid,  the  distal  row  of 
the  tarsus,  being  placed  between  the  scaphoid  behind,  the  three  innermost  meta- 
tarsal bones  in  front,  and  the 
cuboid  externally.  They  are 
called  the  first,  second,  and 
third,  counting  from  the  inner 
to  the  outer  side  of  the  foot, 
and,  from  their  position,  in- 
ternal, middle,  and  external. 

Internal  or  First  Cuneiform 
{OS  cuneiforms  primum)  (Fig. 
198). — The  internal  cuneiform 
is  the  largest  of  the  three.  It 
is  situated  at  the  inner  side  of- 
the  foot,  between  the  scaphoid 
behind  and  the  base  of  the  first 
metatarsal  in  front.  It  may  be 
distinguished   from  the  other 

two  by  its  large  size,  and  by  its  not  presenting  such  a  distinct  wedge-like  form. 
Without  the  others  it  may  be  known  by  the  large,  kidney-shaped  anterior  articu- 
lating surface  and  by  the  prominence  on  the  inferior  or  plantar  surface  for  the 
attachment  of  the  Tibialis   posticus.     It  presents  for   examination  six  surfaces. 

The  internal  surface  is  subcutaneous,  and  forms  part  of  the  inner  border  of  the 
foot;  it  is  broad,  quadrilateral,  and  presents  at  its  anterior  inferior  angle  a  smooth 
oval  facet,  into  which  the  tendon  of  the  Tibialis  anticus  is  partially  inserted; 
in  the  rest  of  its  extent  it  is  rough,  for  the  attachment  of  ligaments.     The  external 


For  tendon  of 
Tibialis  anticus 


For  scapticrid 


Antero-internal  view. 


248  SPECIAL  ANATOMY  OF  THE  SKELETON 

surface  is  concave,  presenting,  along  its  superior  and  posterior  borders,  a  narrow, 
reversed,  I>-shaped  surface,  for  articulation  with  the  middle  cuaeiform  behind 
and  second  metatarsal  bone  in  front;  in  the  rest  of  its  extent  it  is  rough,  for  the 
attachment  of  ligaments,  and  part  of  the  tendon  of  the  Peroneus  longus.  The 
anterior  surface,  kidney-shaped,  much  larger  than  the  posterior,  articulates  with 
the  metatarsal  bone  of  the  great  toe.  The  posterior  surface  is  triangular,  concave, 
and  articulates  with  the  innermost  and  largest  of  the  three  facets  on  the  anterior 
surface  of  the  scaphoid.  The  plantar  surface  is  rough,  and  presents  a  prominent 
tuberosity  at  its  back  part  for  the  attachment  of  part  of  the  tendon  of  the  Tibialis 
posticus.  It  also  gives  attachment  in  front  to  part  of  the  tendon  of  the  Tibialis 
anticus.  The  dorsal  surface  is  the  narrow-pointed  end  of  the  wedge,  which  is 
directed  upward  and  outward;  it  is  rough  for  the  attachment  of  ligaments. 

To  ascertain  to  which  side  the  bone  belongs,  hold  it  so  that  its  dorsal  narrow  edge  looks 
upward,  and  the  long,  kidney-shaped,  articular  surface  forward;  the  external  surface,  marked 
by  its  vertical  and  horizontal  articular  facets,  will  point  to  the  side  to  which  it  belongs. 

Articulations. — With  four  bones:  scaphoid,  middle  cuneiform,  first  and  second  metatarsal 
bones. 

Attachment  of  Muscles. — To  three — the  Tibialis  anticus  and  posticus,  and  Peroneus  longus. 

Middle  or  Second  Cuneiform  (os  cuneiforme  secundum)  (Fig.  199). — The  middle 
cuneiform,  the  smallest  of  the  three,  is  of  very  regular  wedge-like  form,  the  broad 
extremity  being  placed  upward,  the  narrow  end  downward.     It  is  situated  between 

the  other  two  bones  of  the  same 
For  int.  cuneiform  p^^  scaphoid       "ame,   and    articulates    with    the 

scaphoid  behind  and  the  second 
metatarsal  in  front.  It  is  smaller 
than  the  external  cuneiform  bone, 
from  which  it  may  be  further  dis- 
tinguished by  the  L-shaped  artic- 
ular facet,  which  runs  around  the 
„    „    ,      \  ,  •    T.       .        .t^„  upper  and  back  part  of  its  inner 

.For  2nd  metatarsal        For  ext  cuneiform  ff  r 

surface. 

Fig.  199. — The  left  middle  cuneiform.     A.  Antero-mtern.il  rr^,  .  .  , 

view.    B.  Postero-externai  view.  i  he  anterior  surface,  triangular 

in  form  and  narrower  than  the 
posterior,  articulates  with  the  base  of  the  second  metatarsal  bone.  The  posterior 
surface,  also  triangular,  articulates  with  the  scaphoid.  The  internal  surface 
presents  an  L-shaped  articular  facet,  running  along  the  superior  and  posterior 
borders,  for  articulation  with  the  internal  cuneiform,  and  is  rough  in  the  rest  of  its 
extent,  for  the  attachment  of  ligaments.  The  external  surface  presents  posteriorly  a 
smooth  facet  for  articulation  with  the  external  cuneiform  bone.  The  dorsal 
surface  forms  the  base  of  the  wedge;  it  is  quadrilateral,  broader  behind  than  in 
front,  and  rough  for  the  attachment  of  ligaments.  The  plantar  surface,  pointed 
and  tubercular,  is  also  rough  for  ligamentous  attachment  and  for  the  insertion 
of  a  slip  from  the  tendon  of  the  Tibialis  posticus. 

To  ascertain  to  which  foot  the  bone  belongs,  hold  its  superior  or  dorsal  surface  upward,  the 
broadest  edge  being  toward  the  holder;  the  smooth  facet  (limited  to  the  posterior  border)  will 
then  point  to  the  side  to  which  it  belongs. 

Articulations. — With  four  bones — scaphoid,  internal  and  external  cuneiform,  and  second 
metatarsal  bone. 

Attachment  of  Muscles. — A  slip  from  the  tendon  of  the  Tibialis  posticus  is  attached  to 
this  bone. 

External  or  Third  Cuneiform  (os  cuneiforme  terfium)  (Fig.  200). — The  external 
cuneiform,  intermediate  in  size  between  the  two  preceding,  is  of  a  very  regular 
wedge-like  form,  the  broad  extremity  being  placed  upward,  the  narrow  end  down- 


TH1<J  FOOT 


249 


ward.  It  occupies  the  centre  of  the  front  row  of  the  tarsus,  between  the  middle 
cuneiform  internally,  the  cuboid  externally,  the  scaphoid  behind,  and  the  third 
metatarsal  in  front.  It  is  distinguished  from  the  internal  cuneiform  bone  by  its 
more  regular  wedge-like  shape  and  by  the  absence  of  the  kidney-shaped  articular 
surface;  from  the  middle  cuneiform,  by  the  absence  of  the  L-shaped  facet,  and 
by  the  two  articular  facets  which  are  present  on  both  its  inner  and  outer  surfaces. 
It  has  six  surfaces  for  examination. 

The  anterior  surface,  triangular  in  form,  articulates  with  the  third  metatarsal 
bone.  The  posterior  surface  articulates  with  the  most  external  facet  of  the  scaphoid, 
and  is  rough  below  for  the  attachment  of  ligamentous  fibres.  The  internal 
surface  presents  two  articular  facets,  separated  by  a  rough  depression;  the  anterior 
one,  sometimes  divided  into  two,  articulates  with  the  outer  side  of  the  base  of 
the  second  metatarsal  bone;  the  posterior  one  skirts  the  posterior  border  and  articu- 
lates with  the  middle  cuneiform;  the  rough  depression  between  the  two  gives 
attachment  to  an  interosseous  ligament.  The  external  surface  also  presents  two 
articular  facets,  separated  by  a  rough  nonarticular  surface;  the  anterior  facet, 
situated  at  the  superior  angle  of  the  bone,  is  small,  and  articulates  with  the  inner 
side  of  the  base  of  the  fourth  metatarsal ;  the  posterior  and  larger  one  articulates 
with  the  cuboid;   the  rough,  nonarticular  surface  serves  for  the  attachment  of 


For  scaphoid  For  tniddle-cuneiforin 


For  Uh 
metatarsal'  For  cuhoid 


Fig.  200. — The  left  external  cuneiform.     A.  Postero-internal 


Antero-external  view. 


an  interosseous  ligament.  The  three  facets  for  articulation  with  the  three  meta- 
tarsal bones  are  continuous  with  one  another,  and  covered  by  a  prolongation  of 
the  same  cartilage;  the  facets  for  articulation  with  the  middle  cuneiform  and 
scaphoid  are  also  continuous,  but  that  for  articulation  with  the  cuboid  is  usually 
separate.  The  dorsal  surface  is  of  an  oblong  square  form,  its  posterior  external 
angle  being  prolonged  backward.  The  plantar  surface  is  an  obtuse  rounded 
margin,  and  serves  for  the  attachment  of  ligaments  and  a  part  of  the  tendon  of 
the  Tibialis  posticus,  and  for  part  of  the  fibres  of  origin  of  the  Flexor  brevis  hallucis. 

To  ascertain  to  which  side  the  bone  belongs,  hold  it  with  the  broad  dorsal  surface  upward, 
the  prolonged  edge  backward;  the  separate  articular  facet  for  the  cuboid  will  point  to  the  proper 
side. 

Articulations. — With  dx  bones — the  scaphoid,  middle  cuneiform,  cuboid,  and  second,  third, 
and  fourth  metatarsal  bones. 

Attachment  of  Muscles. — To  two— ]>3,vt  of  the  Tibialis  posticus,  and  Flexor  brevis  hallucis. 

The  number  of  tarsal  bones  may  be  reduced  owing  to  congenital  ankylosis  which  may  occur 
between  the  os  calcis  and  cuboid,  the  os  calcis  and  scaphoid,  the  os  calcis  and  astragalus,  or  the 
astragalus  and  scaphoid. 


The  Metatarsal  Bones  (ossa  metatarsalia). — The  metatarsal  bones  are  five 
in  number,  and  are  numbered  one  to  five,  in  accordance  with  their  position  from 
within  outward;  they  are  long  bones,  and  present  for  examination  a  shaft  and  two 
extremities. 


250 


SPECIAL  ANATOMY  OF  THE  SKELETON 


Common  Characters. — The  shaft  (corpus)  is  prismoid  in  form,  tapers  gradually 
from  the  tarsal  to  the  phalangeal  extremity,  and  is  slightly  curved  longitudinally, 
so  as  to  be  concave  below,  slightly  convex  above.     On  the  plantar  surface  of  the 

shaft  of  each  bone  is  a  nutrient 
foramen  corresponding  to  the 
nutrient  foramen  in  each  meta- 
carpal bone.  The  proximal 
extremity,  or  base  (basis),  is 
wedge-shaped,  articulating  by 
its  terminal  surface  with  the 
tarsal  bones,  and  by  its  lateral 
surfaces  with  the  contiguous 
metatarsal  bones,  its  dorsal  and 
plantar  surfaces  being  rough  for 
the  attachment  of  ligaments. 
The  distal  extremity,  or  head 
(capitvlvvi) ,  presents  a  terminal 
rounded  articular  surface,  oblong 
from  above  downward,  and  ex- 
tending farther  backward  below 
than  above.  Its  sides  are  flat- 
tened and  present  a  depression, 
surmounted  by  a  tubercle,  for 
ligamentous  attachment.  Its 
under  surface  is  grooved  in  the  middle  line  for  the  passage  of  the  Flexor  tendon, 
and  marked  on  each  side  by  an  articular  eminence  continuous  with  the  terminal 
articular  surface. 


Occasional  Jati  t  joi 
second  metatarsal. 


For  internal  cuneiform, 

Fig.  201. — The  first  metatarsal.     (Left.) 


Occii'^iimnl 

I               /ai  et  for  first  „         ,         , 

I               metatarsal.  ^"'^  external 

For  middle  cuneiform.  cimeijorm. 


\  For  second  metatarsal. 
For  middle  cuneiform. 


For  fourth 
metatarsal. 


Fig.   202. — The  second  metatar.sal.      (Left.) 


Fig.   203. — The   third  metatarsal.      (Left.) 


Peculiar  Characters. — The  metatarsal  bone  of  the  great  toe  (os  metatarsale  I) 
(Fig.  201)  is  remarkable  for  its  great  thickness,  but  is  the  shortest  of  all  the 
metatarsal  bones.     The  shaft  is  strong  and  of  well-marked  prismoid  form.     The 


THE  FOOT  251 

proximal  extremity  presents,  as  a  rule,  no  lateral  articular  facet,  but  occasionally 
on  the  outer  side  there  is  an  oval  facet  by  which  it  articulates  with  the  second 
metatarsal  bones.  Its  proximal  articular  surface  is  of  large  size  and  kidney 
shaped;  it  corresponds  to  the  distal  extremity  of  the  internal  cuneiform;  its  cir- 
cumference is  grooved,  for  the  tarsometatarsal  ligaments,  and  internally  gives 
attachment  to  part  of  the  tendon  of  the  Tibialis  anticus  muscle;  its  inferior  angle 
presents  a  rough  oval  prominence,  the  tuberosity  {tuberositas  ossis  metatarsalis  I), 
for  the  insertion  of  the  tendon  of  the  Peroneus  longus.  The  head  is  of  large  size; 
on  its  plantar  surface  are  two  grooved  facets,  over  which  glide  sesamoid  bones; 
the  facets  are  separated  by  a  smooth  elevated  ridge. 

This  bone  is  known  by  the  single  kidney-shaped  articular  surface  on  its  base,  the  deeply 
grooved  appearance  of  the  plantar  surface  of  its  head,  and  its  great  thickness  relatively  to  its 
length.  When  it  is  placed  in  its  natural  position,  the  concave  border  of  the  kidney-shaped 
articular  surface  on  its  l)ase  points  to  the  side  to  which  the  bone  belongs. 

Attachment  of  Muscles. — To  three — part  of  the  Tibialis  anticus,  the  Peroneus  longus,  and 
the  First  dorsal  interosseous. 

The  second  metatarsal  (os  metaiarsale  II)  (Fig.  202)  is  the  longest  and  largest 
of  the  remaining  metatarsal  bones,  being  prolonged  backward  into  the  recess 
formed  between  the  three  cuneiform  bones.  Its  tarsal  extremity  is  broad  above, 
narrow  and  rough  below.  It  presents  four  articular  surfaces — one  behind,  of 
a  triangular  form,  for  articulation  with  the  middle  cuneiform;  one  at  the  upper 
part  of  its  internal  lateral  surface,  for  articulation  with  the  internal  cuneiform; 
and  two  on  its  external  lateral  surface — an  upper  and  a  lower,  separated  by 
a  rough  nonarticular  interval.  Each  of  these  articular  surfaces  is  divided  by  a 
vertical  ridge  into  two  facets,  thus  making  four  facets;  the  two  anterior  of  these 
articulate  with  the  third  metatarsal;  the  two  posterior  (sometimes  continuous) 
with  the  external  cuneiform.  In  addition  to  these  articular  surfaces  there  is 
occasionally  a  fifth  when  this  bone  articulates  with  the  first  metatarsal  bone. 
It  is  oval  in  shape,  and  is  situated  on  the  inner  side  of  the  shaft  near  the  base. 

The  facets  on  the  tarsal  extremity  of  the  second  metatarsal  bone  serve  at  once  to  distinguish  it 
from  the  rest,  and  to  indicate  the  foot  to  which  it  belongs;  there  being  one  facet  at  the  upper 
angle  of  the  internal  surface,  and  two  facets,  each  subdivided  into  two  parts,  on  the  external 
surface,  pointing  to  the  side  to  which  the  bone  belongs.  The  fact  that  the  two  posterior  subdi- 
visions of  these  external  facets  sometimes  run  into  one  should  not  be  forgotten. 

Attachment  of  Muscles.— To  /o((r— the  Adductor  obliquus  hallucis,  First  and  Second 
dorsal  interossei,  and  a  slip  from  the  tendon  of  the  Tibialis  posticus;  occasionally  also  a  slip 
from  the  Peroneus  longus. 

The  third  metatarsal  (os  metatarsale  III)  (Fig.  203)  articulates  proximally,  by 
means  of  a  triangular  smooth  surface,  with  the  external  cuneiform;  on  its  inner 
side,  by  two  facets,  with  the  second  metatarsal;  and  on  its  outer  side,  by  a  single 
facet,  with  the  fourth  metatarsal.  The  latter  facet  is  of  circular  form  and  situated 
at  the  upper  angle  of  the  base. 

The  third  metatarsal  is  known  by  possessing  at  its  tarsal  end  two  undivided  facets  on  the  inner 
side,  and  a  single  facet  on  the  outer.  This  distinguishes  it  from  the  second  metatarsal,  in  which 
the  two  facets,  found  on  one  side  of  its  tarsal  end,  are  each  subdivided  into  two.  The  single  facet 
(when  the  bone  is  put  in  its  natural  position)  is  on  the  side  to  which  the  bone  belongs. 

Attachment  of  Muscles.— To  five — Adductor  obliquus  hallucis,  Second  and  Third  dorsal 
and  First  plantar  interossei,  and  a  slip  from  the  tendon  of  the  Tibialis  posticus. 

The  fourth  metatarsal  {os  metatarsale  IV)  (Fig.  204)  is  smaller  in  size  than  the 
preceding;  its  tarsal  extremity  presents  a  terminal  quadrilateral  surface,  for  articu- 
lation with  the  cuboid;  a  smooth  facet  on  the  inner  side,  divided  by  a  ridge  into 
an  anterior  portion  for  articulation  with  the  third  metatarsal,  and  a  posterior 


252 


SPECIAL  ANATOMY  OF  THE  SKELETON 


portion  for  articulation  with  the  external  cuneiform;  on  the  outer  side  a  single 
facet,  for  articulation  with  the  fifth  metatarsal. 

The  fourth  metatarsal  is  known  by  its  having  a  single  facet  on  either  side  of  the  tarsal  extrem- 
xty,  that  on  the  inner  side  being  divided  into  two  parts.  If  this  subdivision  be  not  recognizable, 
the  fact  that  its  tarsal  end  is  bent  somewhat  outward  will  indicate  the  side  to  which  it  belongs. 

Attachment  of  Muscles.^To  five — Adductor  obliquus  hallucis.  Third  and  Fourth  dorsal, 
and  Second  plantar  interossei,  and  a  slip  from  the  tendon  of  the  Tibialis  posticus. 

The  fifth  metatarsal  bone,  or  the  metatarsal  bone  of  the  little  toe  {os  metatarsale  V) 
(Fig.  205),  is  recognized  by  the  tubercle  (tuberositas  ossis  metatarsalis  V)  on  the 
outer  side  of  its  base.  It  articulates  behind,  by  a  triangular  surface  cut  obliquely 
from  without  inward,  with  the  cuboid,  and  internally  with  the  fourth  metatarsal. 


For  cuboid* 
For  ext.  cuneiform. 

Fig.  204.— The  fourth  metatarsal.      (Left.) 


Tuberosity. 


For  fourth  \ 
vietatarsal. 

For  cuboid. 

Fig.  205. — The  fifth  metatarsal.     (Left.) 


The  projection  on  the  outer  side  of  this  bone  at  its  tarsal  end  at  once  distinguishes  it  from 
the  others,  and  points  to  the  side  to  which  it  belongs. 

Attachment  of  Muscles. — To  si.v — the  Peroneus  brevis,  Peroneus  tertius,  Flexor  brevis 
minimi  digiti,  Adductor  transversus  hallucis,  Fourth  dorsal,  and  Third  plantar  interossei. 

Articulations. — Each  bone  articulates  with  the  tarsal  bones  by  one  extremity  (proximal),  and 
by  the  other  (distal)  extremity  with  the  first  row  of  phalanges.  The  number  of  tarsal  bones 
with  which  each  metatarsal  articulates  is  one  for,  the  first,  three  for  the  second,  one  for  the  third, 
tw'o  for  the  fourth,  and  one  for  the  fifth. 


The  Phalanges  of  the  Foot  (Phalanges  Digitorum  Pedis). 

The  phalanges  of  the  foot,  both  in  number  and  general  arrangement,  resemble 
those  in  the  hand-;  there  being  two  in  the  great  toe  and  three  in  each  of  the  other 
toes.     The  nutritive  foramina  correspond  to  those  in  the  phalanges  of  the  hand. 

The  first  or  proximal  phalanx  (phalanx  prima)  resembles  closely  the  corre- 
sponding bone  of  the  hand.  The  shaft  also  is  compressed  from  side  to  side, 
convex  above,  concave  below.  The  proximal  extremity  is  concave;  and  the  distal 
extremity  presents  a  trochlear  surface,  for  articulation  with  the  second  phalanx. 


THE  FOOT 


253 


The  second  phalanx  (phalanx  secwida)  is  remarkably  small  and  short,  but 
rather  broader  than  the  first  phalanx. 

The  ungual  or  distal  phalanx  (phalanx  terfia)  in  form  resembles  the  bone  of  the 
corresponding  finger,  but  is  smaller,  flattened  from  above  downward,  presenting 
a  broad  base  for  articulation  with  the  second  phalanx,  and  an  expanded  extremity 
for  the  support  of  the  nail  and  end  of  the  toe. 


y  s  I  s. 


> Appears  10th  year ; 

imites  after  puberty. 


Tarsus. 

One  centre  for  each  toiie, 

except  calcaneus 


Two  centres  for  each  totie 
One  for  shaft, 
One  for  digital  cMtreit 
except  1st. 


Phalanges 
Two  centres  for  each  hone : 
One  for  shaft. 
One  for  proximal 
extremity. 


3d  year. 
Unite  ISth-SO  year. 

Appears  7th  week. 


Appeal  s  9th  week 

Unite  18th  20th  yeai 
Appears  Sth-Sth  year. 

Appears  M^i  year. 
Unite  17-18th  year.  | 
Appears  Snd-4th  month. 


Appears  6th-7lh  year. 


Unite  17th-18th  year.  ■, 

Appears  Snd-4th  month.~^-~J  fi  \  / 

Appears  6th  year.^       3  ^^ 

Unite  17th-18th  year.AW  S 
Appears  10th  week.—vj'^ 

Fig.  206. — Plan  of  the  development  of  the  foot. 


Articulation. — The  first  row,  with  the  metatarsal  bones  behind  and  second  phalanges  in 
front;  the  second  row  of  the  four  outer  toes,  with  the  first  and  third  phalanges;  of  the  great  toe, 
with  the  fir.st  plialanx;  tlie  third  row  of  the  four  outer  toes,  with  the  second  phalanges. 

Attachment  of  Muscles. — To  the  first  phalanges:  Great  toe,  five  muscles— innermost  tendon 
of  E.xteiisor  l)ievis  diijitorum,  Abductor  hallucis.  Adductor  obliquus  hallucis.  Flexor  brevis 
hallucis,  Adductor  transversus  hallucis.  Second  toe,  three  muscles — First  and  Second  dorsal 
interosseous  and  First  lumbrical.  Third  toe,  three  muscles — Third  dorsal  and  First  plantar  inter- 
osseous and  Second  lumbrical.  Fourth  toe,  three  muscles — Fourth  dorsal  and  Second  plantar 
interosseous  and  Third  lumbrical.  Fifth  toe,  four  muscles — Flexor  brevis  minimi  digiti,  Abduc- 
tor minimi  digiti,  and  Third  plantar  interosseous,  and  Fourth  lumbrical.  Second  phalanges: 
Great  toe — Extensor  longus  huUucis,  Flexor  longus  hallucis.  Other  toes — Flexor  brevis  digitorum, 
one  slip  of  the  common  tendon  of  the  Extensor  longus  and  brevis  digitorum.'  Third  phalanges: 
Two  slips  from  the  common  tendon  of  the  Extensor  longus  and  Extensor  brevis  digitorum,  and 
the  Flexor  longus  digitorum. 


Except  the  second  phalanx  of  the  fifth  toe,  which 


no  slip  from  the  Extensor  brevis  digitorum. 


254  SPECIAL  ANATOMY  OF  THE  SKELETON 


Development  of  the  Foot  (Fig.  206). 

The  tarsal  bones  are  each  developed  from  a  single  centre,  excepting  the  calcaneus,  which  has 
an  epiphysis  for  its  posterior  extremity.  The  centres  make  tlieir  appearance  in  the  following 
order:  calcaneus,  at  the  sixth  month  of  fetal  life;  astragalus,  about  the  seventh  month;  cuboid, 
at  the  ninth  month;  external  cuneiform,  during  the  first  year;  internal  cuneiform,  in  the  third 
year;  middle  cuneiform  and  scaphoid,  in  the  fourth  year.  The  epiphysis  for  the  posterior 
tuberosity  of  the  calcaneus  appears  at  the  tenth  year,  and  unites  with  the  rest  of  the  bone  soon 
after  puberty.     When  this  part  remains  as  a  separate  bone,  it  is  called  the  oa  trigonum. 

The  metatarsal  bones  are  each  developed  from  two  centres — one  for  the  shaft  and  one  for  the 
digital  extremity  in  the  four  outer  metatarsal;  one  for  the  shaft  and  one  for  the  base  in  the  metatar- 
sal bone  of  the  great  toe.^  Ossification  commences  in  the  centre  of  the  shaft  about  the  ninth  week, 
and  extends  toward  either  extremity.  The  centre  in  the  proximal  end  of  the  first  metatarsal 
bone  appears  about  the  third  year,  the  centre  in  the  distal  end  of  the  other  bones  between  the  fifth 
and  eighth  years;  they  unite  with  the  shaft  between  the  eighteenth  and  twentieth  years. 

The  phalanges  are  de\'eloped  from  two  centres  for  each  bone — one  for  the  shaft  and  one  for 
the  proximal  extremity.  The  centre  for  the  shaft  appears  about  the  tenth  week,  that  for  the 
epiphysis  between  the  fourth  and  tenth  years ;  they  join  the  shaft  about  the  eighteenth  year. 


Construction  of  the  Foot  as  a  Whole  (Figs.  207,  208). 

The  foot  is  constructed  on  the  same  principles  as  the  hand,  but  modified  to 
form  a  firm  Ijasis  of  support  for  the  rest  of  the  body  when  in  the  erect  position. 
It  is  more  solidly  constructed,  and  its  component  parts  are  less  movable  on  each 
other  than  in  the  hand.  This  is  especially  the  case  with  the  great  toe,  M'hich  has 
to  assist  in  supporting  the  body,  and  is  therefore  constructed  with  greater  solidity; 
it  lies  parallel  with  the  other  toes,  and  has  a  very  limited  degree  of  mobility, 
whereas  the  thumb,  which  is  occupied  in  numerous  and  varied  movements,  is 
constructed  in  such  a  manner  as  to  permit  of  great  mobility.  Its  metacarpal  bone 
is  directed  away  from  the  others,  so  as  to  form  an  acute  angle  with  the  second, 
and  it  enjoys  a  considerable  range  of  motion  at  its  articulation  with  the  carpus. 
The  foot  is  placed  at  right  angles  to  the  leg — a  position  which  is  almost  peculiar 
to  man,  and  has  relation  to  the  erect  position  which  he  maintains.  In  order  to 
allow  of  its  supporting  the  weight  of  the  whole  body  in  this  position  with  the 
least  expenditure  of  material,  it  is  constructed  in  the  form  of  an  arch.  This 
antero-posterior  or  longitudinal  arch  is  made  up  of  two  unequal  limbs.  The 
hinder  one,  which  is  made  up  of  the  calcaneus  and  the  posterior  part  of  the  astrag- 
alus, is  about  half  the  length  of  the  anterior  limb,  and  measures  about  three 
inches.  The  anterior  limb  consists  of  the  rest  of  the  tarsal  and  the  metatarsal 
bones,  and  measures  about  seven  inches.  It  may  be  said  to  consist  of  two  parts, 
an  inner  segment  made  up  of  the  head  of  the  astragalus,  the  scaphoid,  the  three 
cuneiform,  and  the  three  inner  metatarsal  bones;  and  an  outer  segment  composed 
of  the  calcaneus,  the  cuboid,  and  the  two  outer  metatarsal  bones.  The  summit  of 
the  arch  is  at  the  superior  articular  surface  of  the  astragalus;  and  its  two  extremi- 
ties— that  is  to  say,  the  two  piers  on  which  the  arch  rests  in  standing^are  the 
internal  tubercle  on  the  under  surface  of  the  calcaneus  posteriorly,  and  the  heads 
of  the  metatarsal  bones  anteriorly.  The  weakest  part  of  the  arch  is  the  joint 
between  the  astragalus  and  scaphoid;  and  here  it  is  more  liable  to  yield  in  those 
who  are  overweighted,  and  in  those  in  whom  the  ligaments  which  complete  and 
preserve  the  arch  are'  relaxed.  This  weak  point  in  the  arch  is  braced  on  its  con- 
cave surface  by  the  inferior  calcaneoscaphoid  ligament,  which  is  more  elastic 
than  most  other  ligaments,  and  thus  allows  the  arch  to  yield  from  jars  or  shocks 
applied  to  the  anterior  portion  of  the  foot  and  quickly  restores  it  to  its  pristine 

'  As  was  noted  in  the  first  metacarpal  bone,  so  in  the  first  metatarsal,  there  is  often  to  be  observed  a  tendency 
to  the  formation  of  a  second  epiphysis  in  the  distal  extremity. 


CONSTRUCTION  OF  THE  FOOT  AS  A    WHOLE 


255 


condition.  This  ligament  is  supported  internally  by  blending  with  the  deltoid 
ligament,  and  inferiorly  by  the  tendon  of  the  Tibialis  posticus  muscle,  which  is 
spread  out  into  a  fan-shaped  insertion,  and  prevents  undue  tension  of  the  liga- 
ment or  such  an  amount  of  stretching  as  would  permanently  elongate  it. 

In  addition  to  this  longitudinal  arch  the  foot  presents  a  transverse  arch,  at  the 
anterior  part  of  the  tarsus  and  hinder  part  of  the  metatarsus.  This,  however,  can 
scarcely  be  described  as  a  true  arch,  but  presents  more  the  character  of  a  half- 
dome.     The  inner  border  of  the  central  portion  of  the  longitudinal  arch  is  elevated 


Fig.  207. — Skeleton  of  the  foot,  internal  border.      (Poirier  and  Charpy.) 

from  the  ground,  and  from  this  point  the  bones  arch  over  to  the  outer  border, 
which  is  in  contact  with  the  ground,  and,  assisted  by  the  longitudinal  arch,  pro- 
duce a  sort  of  rounded  niche  on  the  inner  side  of  the  foot,  which  gives  the  appear- 
ance of  a  transverse  as  well  as  a  longitudinal  arch. 

The  line  of  the  foot,  from  the  point  of  the  heel  to  the  toes,  is  not  quite  straight, 
but  is  directed  a  little  outward,  so  that  the  inner  border  is  a  little  convex  and  the 
outer  border  concave.  This  disposition  of  the  bones  becomes  more  marked  when 
the  longitudinal  arch  of  the  foot  is  lost,  as  in  the  condition  known  under  the  name 
of  "flat-foot." 


OLE    CUNEIFORM 


ST    METATARSAL 


Fig.  20S. — Skeleton  of  the  foot,  external  border.      (Poirier  and  Charpy.) 


Surface  Form. — On  the  dorsum  of  the  foot  the  individual  bones  are  not  to  be  distinguished 
■with  the  e.x'ception  of  the  head  of  the  astragalus,  which  forms  a  rounded  projection  in  front  of 
the  ankle-joint  when  the  foot  is  forcibly  extended.  The  whole  surface  forms  a  smooth  convex 
outline,  the  summit  of  which  is  the  ridge  formed  by  the  head  of  the  astragalus,  the  scaphoid, 
the  middle  cuneiform,  and  the  second  metatarsal  bones;  from  this  it  gradually  inclines  outward 
and  more  rapidly  inward.  On  the  inner  side  of  the  foot,  the  internal  tubercle  of  the  calcaneus 
and  the  ridge  separating  the  inner  from  the  posterior  surface  of  the  bone  may  be  felt  most  pos- 
teriorly. In  front  of  this,  and  below  the  internal  malleolus,  may  be  felt  the  projection  of  the 
sustentaculum  tali.  Passing  forward  is  the  well-marked  tuberosity  of  the  scaphoid  bone,  situ- 
ated about  an  inch  or  an  inch  and  a  quarter  in  front  of  the  internal  malleolus.  Further  toward 
the  front,  the  ridge  formed  by  the  base  of  the  first  metatarsal  bone  can  be  obscurely  felt,  and 
from  this  the  shaft  of  the  bone  can  be  traced  to  the  expanded  head  articulating  with  the  base 


256  SPECIAL  ANATOMY  OF  THE  SKELETON 

of  the  first  phalanx  of  the  great  toe.  Immediately  beneath  the  base  of  this  phalanx,  the  internal 
sesamoid  bone  is  to  be  felt.  Lastly,  the  expanded  ends  of  the  bones  forming  the  last  joint  of 
the  great  toe  are  to  be  felt.  On  the  outer  side  of  the  foot  the  most  posterior  bony  point  is  the 
external  tubercle  of  the  calcaneus,  with  the  ridge  separating  the  posterior  from  the  outer  surface 
of  the  bone.  In  front  of  this  the  greater  part  of  the  external  siu^face  of  the  calcaneus  is  subcu- 
taneous; on  it,  below  and  in  front  of  the  external  malleolus,  may  be  felt  the  peroneal  spine  when 
this  is  present.  Farther  forward,  the  base  of  the  fifth  metatarsal  bone  forms  a  prominent  and 
well-defined  landmark,  and  in  front  of  this  the  shaft  of  the  bone,  with  its  expanded  head,  and 
the  base  of  the  first  phalanx  may  be  defined.  The  sole  of  the  foot  is  almost  entirely  covered 
by  soft  parts,  so  that  but  few  bony  parts  are  to  be  made  out,  and  these  somewhat  obscurely. 
The  hinder  part  of  the  under  surface  of  the  calcaneus  and  the  heads  of  the  metatarsal  bones, 
with  the  exception  of  the  first,  which  is  concealed  by  the  sesamoid  bones,  may  be  recognized. 

Applied  Anatomy. — Considering  the  injuries  to  which  the  foot  is  subjected,  it  is  surpris- 
ing how  seldom  the  tarsal  bones  are  fractured.  This  is  no  doubt  due  to  the  fact  that  the  tarsus 
is  composed  of  a  number  of  bones,  articulated  by  a  considerable  extent  of  surface  and  joined 
together  by  very  strong  ligaments,  which  serve  to  mitigate  the  intensity  of  violence  applied  to  this 
part  of  the  body.  When  fracture  does  occur,  these  bones,  being  composed  for  the  most  part 
of  a  soft  cancellous  structure,  covered  only  by  a  thin  shell  of  compact  tissue,  are  often  extensively 
comminuted,  especially  as  most  of  the  fractures  are  produced  by  direct  violence.  As  the  bones 
have  only  a  very  scanty  amount  of  soft  parts  over  them,  fractures  are  very  often  compound,  and 
amputation  is  frequently  necessary. 


CALCANEUS 


of  Chopart's  amputation.  Fig.  210. — Line  of  Lisfranc's  amputation, 

(Poirier.)  (Poirier.) 

When  fracture  occurs  in  the  anterior  group  of  tarsal  bones,  it  is  almost  invariably  the  result 
of  direct  violence,  but  fractures  of  the  posterior  group,  that  is,  of  the  calcaneus  and  astragalus, 
are  most  frequently  produced  by  falls  from  a  height  on  to  the  feet;  though  fracture  of  the  cal- 
caneus may  be  caused  by  direct  violence  or  by  muscular  action.  The  posterior  part  of  the  bone, 
that  is,  the  part  behind  flie  articular  surfaces,  is  almost  always  the  seat  of  the  fracture,  though 
some  few  cases  of  fracture  of  the  sustentaculum  tali  and  of  vertical  fracture  between  the  two 
articulating  facets  have  been  recorded.  The  neck  of  the  astragalus,  being  the  weakest  part  of 
the  bone,  is  most  frequently  fractured,  though  fractures  may  occur  in  any  part  and  almost  in 
any  direction,  either  associated  or  not  with  fracture  of  other  bones. 

In  cases  of  club-foot,  especially  in  congenital  cases,  the  bones  of  the  tarsus  become  altered 
in  shape  and  size,  and  displaced  from  their  proper  positions.  This  is  especially  the  case  in 
congenital  equinovarus,  in  which  the  astragalus,  particularly  about  the  head,  becomes  twisted  and 
atrophied,  and  a  similar  condition  may  be  present  in  the  other  bones,  more  especially  the 
scaphoid.  The  tarsal  bones  are  peculiarly  liable  to  become  the  seat  of  tuberculous  caries,  and  this 
condition  may  arise  after  comparatively  trivial  injuries.  There  are  several  reasons  to  account 
for  this.  They  are  composed  of  a  delicate  cancellated  structure,  surrounded  by  intricate  synovial 
membranes.  They  are  situated  at  the  farthest  point  from  the  central  organ  of  the  circulation 
and  exposed  to  vicissitudes  of  temperature;  and,  moreover,  on  their  dorsal  surface  are  thinly 
clad  with  soft  parts  which  have  but  a  scanty  blood-supply.  And  finally,  after  slight  injuries, 
they  are  not  maintained  in  a  condition  of  rest  to  the  same  extent  as  structures  suffering  from 
similar  injuries  in  some  other  parts  of  the  body.  Caries  of  the  calcaneus  or  astragalus  may 
remain  limited  to  the  one  bone  for  a  long  period,  but  when  one  of  the  other  bones  is  affected, 
the  remainder  frequently  become  involved,  in  consequence  of  the  disease  spreading  through 
the  large  and  complicated  synovial  membrane  which  is  more  or  less  common  to  these  bones. 

Amputation  of  the  whole  or  a  part  of  the  foot  is  frequently  required  either  for  injury  or  disease. 
The  principal  amputations  are  as  follows:  (1)  Syme's  amputation  at  the  ankle-joint  by  a  heel- 
flap,  with  the  removal  of  the  malleoli  and  a  thin  slice  from  the  lower  end  of  the  tibia.  (2) 
Pirogoff's  amputation:  removal  of  the  whole  of  the  tarsal  bones,  except  the  posterior  part  of  the 


SESAMOID  BONES 


257 


calcaneus.  A  thin  slice  is  sawed  from  the  tibia  and  fibula,  including  the  two  malleoli.  The  sawed 
surface  of  the  calcaneus  is  then  turned  up  and  united  to  the  similar  surface  of  the  tibia.  (.3) 
Subastragaloid  amputation:  removal  of  the  foot  below  the  astragalus  through  the  joint  between 
it  and  the  calcaneus. 

The  bones  of  the  tarsus  occasionally  recjuire  removal  individually.  This  is  especially  the 
case  with  the  astragalus  and  calcaneus  for  disease  limited  to  the  one  bone,  or  again  the 
astragalus  may  require  excision  in  cases  of  subastragaloid  dislocation.  In  cases  of  in\'eterate 
talipes  the  head  of  the  astragalus  and  greater  process  of  the  calcaneus  is  often  removed,  some- 
times the  scaphoid  is  also  taken  out.  Finally,  Mikulicz  and  Watson  have  devised  operations  for 
the  removal  of  more  extensive  portions  of  the  tarsus.  Mikulicz's  operation  consists  in  the  re- 
moval of  the  calcaneus  and  astragalus,  along  with  the  articular  surfaces  of  the  tibia  and  fibula, 
and  also  of  the  scaphoid  and  cuboid.  The  remaining  portion  of  the  tarsus  is  then  brought 
into  contact  with  the  sawed  surfaces  of  the  tibia  and  fibula,  and  fixed  there.  The  result  is  a 
position  of  the  shortened  foot  resembling  talipes  ecjiiinus.  Watson's  operation  is  adapted  to 
those  cases  where  the  disease  is  confined  to  the  anterior  tarsal  bones.  By  two  lateral  incisions 
he  saws  through  the  bases  of  the  metatarsal  bones  in  front  and  opens  up  the  joints  between  the 
scaphoid  and  astragalus,  and  the  cuboid  and  calcaneus,  and  removes  the  intervening  bones. 

Fractures  of  the  metatarsal  bones  and  phalanges  are  nearly  always  due  to  direct  violence,  and 
in  many  cases  the  injury  is  the  result  of  severe  crushing  accidents,  necessitating  amputation. 
The  metatarsal  bones,  and  especially  the  metatarsal  bone  of  the  great  toe  are  frequently  dis- 
eased, either  in  tuberculous  subjects  or  in  perforating  ulcer  of  the  foot. 


Sesamoid  Bones  (Ossa  Sesamoidea)  (Figs.  211,  212). 

These  are  small  rounded  masses,  cartilaginous  in  early  life,  osseous  in  the  adult, 
which  are  developed  in  those  tendons  which  exert  a  great  amount  of  pressure  upon 


Fig.  211  —Sesamoid  bones  of  the  hand.     (Poirier 
and    Charpy.) 

the  parts  over  which  they  glide.  It  is  said  that  they  are  more  commonly  found  in 
the  male  than  in  the  female,  and  in  persons  of  an  active  muscular  habit  than  in 
those  who  are  weak  and  debilitated.  They  are  invested  throughout  their  whole 
surface  by  the  fibrous  tissue  of  the  tendon  in  which  they  are  found,  excepting  upon 
that  side  which  lies  in  contact  with  the  part  over  which  they  play,  where  they 
present  a   Iree   articular   facet.      They  may  be  divided   into  two  kinds — those 


258  SPECIAL  ANATOMY  OF  THE  SKELETON 

which  glide  over  the  articular  surfaces  of  the  joints,  and  those  which  play  over 
the  cartilaginous  facets  found  on  the  surfaces  of  certain  bones. 

The  sesamoid  bones  of  the  joints  in  the  upper  extremity  are  two  on  the  palmar 
surface  of  the  metacarpophalangeal  joint  in  the  thumb,  developed  in  the  tendons 
of  the  Flexor  brevis  poUicis;  one  on  the  palmar  surface  of  the  interphalangeal 
joint  of  the  thumb;  occasionally  one  or  two  opposite  the  metacarpophalangeal 
articulations  of  the  fore  and  little  fingers;  and,  still  more  rarely,  one  opposite  the 
same  joints  of  the  third  and  fourth  fingers.  In  the  lower  extremity,  the  patella, 
which  is  developed  in  the  tendon  of  the  Quadriceps  extensor;  two  small  sesamoid 
bones,  found  in  the  tendons  of  the  Flexor  brevis  hallucis,  opposite  the  metatarso- 
phalangeal joint  of  the  great  toe;  one  sometimes  over  the  interphalangeal  joint 
of  the  great  toe;  and  occasionally  one  in  the  metatarsophalangeal  joint  of  the 
second  toe,  the  little  toe,  and,  still  more  rarely,  the  third  and  fourth  toes. 

Those  found  in  the  tendons  which  glide  over  certain  bones  occupy  the  following 
situations:  One  sometimes  found  in  the  tendon  of  the  Biceps  brachii,  opposite  the 
tuberosity  of  the  radius;  one  in  the  tendon  of  the  Peroneus  longus,  where  it  glides 
through  the  groove  in  the  cuboid  bone;  one  appears  late  in  life  in  the  tendon  of 
the  Tibialis  anticus,  opposite  the  smooth  facet  of  the  internal  cuneiform  bone; 
one  is  found  in  the  tendon  of  the  Tibialis  posticus,  opposite  the  inner  side  of  the 
head  of  the  astragalus;  one  in  the  outer  head  of  the  Gastrocnemius,  behind  the 
outer  condyle  of  the  femur;  and  one  in  the  conjoined  tendon  of  the  Psoas  and 
Iliacus,  where  it  glides  over  the  os  pubis.  Sesamoid  bones  are  found  occasionally 
in  the  tendon  of  the  Gluteus  maximus,  as  it  passes  over  the  great  trochanter,  and 
in  the  tendons  which  wind  around  the  inner  and  outer  malleolL 


THE  AETICULATIONS,  OE  JOINTS. 


THE  various  bones  of  which  the  skeleton  consists  are  connected  at  different 
parts  of  their  surfaces,  and  such  connections  are  designated  hv  the 
name  of  joints,  or  articulations.  Certain  joints  are  immovable,  as  all  those  between 
the  cranial  bones  excepting  the  temporomandibular  joint.  In  an  immovable  joint 
the  adjacent  margins  of  the  Ijones  are  applied  in  close  contact,  a  thin  layer  of 
fibrous  membrane,  the  sutural  ligament,  or,  as  at  the  base  of  the  skull,  in  certain 
situations,  a  thin  layer  of  cartilage,  being  interposed.  Where  slight  movement  is 
required,  combined  with  great  strength,  the  osseous  surfaces  are  united  by  tough 
and  elastic  fibrocartilages,  as  in  the  joints  between  the  vertebral  bodies  and 
in  the  interpubic  articulation;  but  in  the  movable  joints  the  bones  forming  the 
articulation  are  generally  expanded  for  greater  convenience  of  mutual  connection, 
covered  by  hyaline  cartilage,  held  together  by  strong  bands  or  capsules  of  fibrous 
tissue  called  ligaments,  and  partially  lined  by  a  membrane,  the  synovial  membrane, 
which  transudes  a  fluid  to  lubricate  the  various  parts  of  which  the  joint  is  formed; 
so  that  the  structures  which  enter  into  the  formation  of  a  joint  are  bone,  hyaline 
cartilage,  fibrocartilage,  ligament,  and  synovial  membrane 

Bone. — Bone  constitutes  the  fundamental  element  of  all  the  joints  In  the 
long  bones  the  extremities  are  the  parts  which  form  the  articulations;  they' are 
generally  somewhat  enlarged,  and  consist  of  spongy,  cancellous  tissue,  with  a  thin 
coating  of  compact  substance.  The  layer  of  compact  bone  which  forms  the 
articular  surface,  and  to  which  the  cartilage  is  attached,  is  called  the  articular 
lamella.  It  is  of  a  white  color,  extremely  dense,  and  varies  in  thickness.  Its 
structure  differs  from  ordinary  bone  tissue  in  this  respect,  that  it  contains  no 
Haversian  canals,  and  its  lacunae  are  much  larger  than  in  ordinary  bone  and 
have  no  canaliculi  The  vessels  of  the  cancellous  tissue,  as  they  approach  the 
articular  lamella,  turn  back  in  loops,  and  do  not  perforate  it;  this  layer  is  conse- 
quently more  dense  and  firmer  than  ordinary  bone,  and  is  evidently  designed  to 
form  a  firm  and  unyielding  support  for  the  articular  cartilage.  In  the  flat  bones 
the  articulations  usually  take  place  at  the  edges,  and,  in  the  short  bones,  at  various 
parts  of  their  surface. 

Cartilage. — There  are  three  varieties  of  cartilage — ^1,  hyaline;  B,  fibrocartilage; 
and  C,  yellow  elastic  cartilage;  of  these,  but  two,  hyaline  and  fibrocartilage  are 
utilized  in  the  structure  of  a  joint. 

In  general,  cartilage  consists  of  a  genetic  investing  membrane,  the  perichondrium,  surrounding 
the  cartilage  substance  proper.  The  latter  consists  of  the  cellular  elements,  or  chondroblasts, 
and  the  intercellular  substance,  or  matrix. 

The  perichondrium  is  composed  chiefly  of  white  fibrous  connecti^'e  tissue  ivith  a  few  added 
yellow  elastic  fibres  and  cellular  elements.  The  outer  part  contains  few  cells,  and  is  called  the 
fibrous  layer.  The  inner  part,  or  (jenetic  Inijer,  contains  the  bloodvessels,  and  is  rich  in  flat- 
tened, elongated,  or  spindle-shaped  cells,  the  chondroblasts. 

The  chondroblasts  vary  in  shape;  those  immediately  beneath  the  perichondrium  are  flat 
and  elongated,  while  those  farther  in  become  larger  and  o\'al  in  form.  Each  cell  contains  a 
prominent  nucleus  embedded  in  a  clear  protoplasm  that  may  contain  one  or  more  vacuoles. 
Each  cell  is  sharply  outlined,  and  lies  in  a  space  called  the  lacuna,  but  two  or  more  cells  may  be 
seen  to  occupy  the  same  lacuna.  The  matrix  immediately  surrounding  the  lacuna  is  somewhat 
differentiated  from  the  remaining  matrix,  and  is  called  the  capsule  of  the  lacuna. 

(259) 


260 


THE  ARTICULATIONS,    OR  JOINTS 


The  matrix  varies  in  the  different  varieties  of  cartilage.  In  hyaline  cartilage  it  is  bluish 
or  ]5early  in  appearance,  and  under  low  magnification  is  apparently  homogeneous;  in  the  fibro- 
cartilage  the  matrix  consists  mainly  of  white  fibrous  tissue  arranged  in  bundles  of  varying  size 
with  islands  of  hyaline  matrix  and  cartilage  cells  at  intervals;  the  matrix  of  elastic  cartilage 
is  mainly  yellinv  clastic  lis.sue  with  islands  of  hyaline  matrix  and  cartilage  cells. 

A.  Hyaline  cartilage  is  surrounded  by  its  perichondrium,  internal  to  which  is  found  the 
apparently  homogeneous  or  slightly  granular  matrix.  If  the  latter  be  examined  by  polarized 
light  or  be  first  treated  with  potassium  hydrate,  the  fundamental  fibrillse  are  discernible.  The 
fibrils  form  a  meshwork  that  contains  the  hyaline  substance  and  cells. 

In  joints  the  hyaline  cartilage  is  found  as  a  thin  layer  covering  the  articular  surfaces  of 
the  bones  concerned,  and  is  here  called  articular  cartilage.  In  this  form  the  peripheral  cells 
are  parallel  to  the  surface;  deeper  in  toward  the  bone  the  cells  become  arranged  in  rows  at 
right  angles  to  the  surface.  The  latter  condition  may  account  for  the  vertical  splitting  of  articular 
cartilage  that  occurs  in  certain  diseases. 

Hyaline  cartilage  is  also  found  in  the  costal,  tracheal,  bronchial,  and  most  of  the  larjmgeal 
cartilages.  It  tends  to  calcify  and  even  ossify  in  old  age,  and  upon  boiling  yields  a  substance 
called  chondrin. 

The  hyaline  cartilage  that  covers  the  joint  surfaces  of  the  bones,  by  its  elasticity  enables  it 
to  break  the  force  of  any  concussion,  while  its  smoothness  affords  ease  and  freedom  of  move- 
ment. It  varies  in  thickness  according  to  the  shape  of  the  articular  surface  on  which  it  lies; 
where  this  is  convex  the  cartilage  is  thickest  at  the  centre,  where  the  greatest  pressure  is  received; 
the  reverse  is  the  Case  on  the  concave  articular  surfaces. 


:  rr      \'>-'  __•==" 


g 


_.^ 


Fig.  213. — Sections  of  cartilage.  A.  Hyaline  cartilage,  a.  Fibrous  layer  of  perichondrium.  6.  Genetic 
layer  of  perichondrium,  c.  Youngest  chondroblasts.  d.  Older  chondroblasts.  e.  Capsule,  f.  cells,  g.  Lacuna. 
B.  Elastic  cartilage.     C.   Wnite  fibrocartilage.     (Radasch.) 


5.  Fibrocartilage  is  surrounded  by  a  perichondrium;  its  matrix  differs  from  that  of  the 
hyaline  variety  in  consisting  chiefly  of  white  fibrous  tissue  arranged  in  bundles  with  little  islands 
of  hyaline  substance  and  cells  scattered  here  and  there.  It  is  found  in  the  intra-articular  car- 
tilages, deepening  joint  cavities,  and  in  the  intervertebral  disks.  It  is  arranged  in  three 
groups — (1)  intra-articular,  (2)  connecting,  and  (.3)  circumferential. 

1.  The  articular  flbrocartilages,  or  articular  disks  (menisci  artindares),  are  flattened,  fibro- 
cartilaginous plates,  of  a  round,  oval,  triangular,  or  sickle-like  form,  interposed  between  the 
articular  cartilages  of  certain  joints.  They  are  free  on  both  surfaces,  thinner  toward  their 
centre  than  at  their  circumference,  and  held  in  position  b}'  the  attachment  of  their  margins 
and  extremities  to  the  surrounding  ligaments.  The  synovial  membrane  of  the  joint  is  prolonged 
over  them  a  short  distance  from  their  attached  margins.  They  are  found  in  the  temporo- 
mandibular, sternoclavicular,  acromioclavicular,  wrist-  and  knee-joints.     These  cartilages  are 


LIGAMENTS  261 

usually  found  in  those  joints  which  are  most  exposed  to  violent  concussion  and  subject  to  fre- 
quent movements.  Their  use  is  to  maintain  the  apposition  of  the  ojjposed  surfaces  in  their 
various  motions;  to  increase  the  depth  of  the  articular  surfaces  and  give  ease  to  the  gliding 
movement;  to  moderate  the  effects  of  great  pressure  and  deaden  the  intensity  of  the  shocks  to 
which  the  parts  may  be  subjected.  Iluraphry  has  pointed  out  that  these  intra-arlicular  fil)ro- 
cartilages  serve  an  important  purpose  in  increasing  the  variety  of  movements  in  a  joint.  Thus, 
in  the  knee-joint  there  are  two  kinds  of  motion — viz.,  angular  movement  and  rotation—  although 
it  is  a  hinge-joint,  in  which,  as  a  rule,  only  one  variety  of  motion  is  permitted;  the  former 
movement  takes  place  between  the  condyles  of  the  femur  and  the  articular  cartilages,  the 
latter  between  the  cartilages  and  the  head  of  the  tibia.  So,  also,  in  the  temporomandibular 
joint,  the  upward  and  downward  movement  of  opening  and  shutting  the  mouth  takes  place 
between  the  fibrocartilage  and  the  mandible,  the  grinding  movement  between  the  glenoid  cavity 
and  the  fibrocartilage,  the  latter  moving  with  the  mandible. 

Intra-articular  cartilages  may  divide  the  joint  into  two  distinct  cavities,  as  in  the  temporo- 
mandibular articulation.  The  periphery  of  an  articular  cartilage  is  attached  particularly  to 
the  capsule,  and  may  also  be  attached  to  the  nonarticular  portion  of  the  bone.  The  semilunar 
cartilages  of  the  knee  resemble  tendon  more  than  they  do  cartilage.  The  fibres  are  arranged 
in  dense,  more  or  less  parallel  bundles,  separated  by  small,  scattered  hyaline  cells,  and  the  disks 
are  attached  to  the  bone  by  thin  layers  of  hyaline  cartilage. 

2.  The  connecting  fibrocaitilages  are  interposed  between  the  bony  surfaces  of  those  joints 
which  admit  of  only  slight  moliility,  as  between  the  bodies  of  the  vertebras  and  between  the 
pubic  bones.  They  form  disks  which  adhere  closely  to  both  of  the  opposed  surfaces,  and  are 
composed  of  concentric  rings  of  fibrous  tissue,  with  cartilaginous  laminte  interposed,  the  former 
tissue  predominating  toward  the  circumference,  the  latter  toward  the  centre. 

3.  The  circumferential  fibrocartilages  consist  of  a  rim  of  fibrocartilage,  which  surrounds  the 
margin  of  sonu-  ol'  the  ariicular  caviiii-s,  as  the  cotyloid  cavity  of  the  hip  and  the  glenoid  cavity 
of  the  shoulder;  tliey  serve  (o  deepen  the  articular  surface,  and  to  protect  its  edges. 

Elastic  cartilage,  although  not  utilized  in  joints,  may  be  considered  here.  It  is  surrounded 
by  a  perichondrium,  and  its  matrix  differs  from  the  preceding  varieties  in  being  composed 
chiefly  of  yellow  elastic  tissue.  It  is  found  in  the  pinna  of  the  ear,  Eustachian  tube,  epiglottis, 
and  small  cartilages  of  the  larynx.     It  does  not  ossify  or  calcify. 

Cartilage,  in  the  adult,  is  an  avascular  tissue,  and  although  vessels  at  times  are  seen  in  the 
costal  cartilages,  they  do  not  nourish  it,  as  no  branches  are  given  off.  Nerves  are  likewise 
absent. 

Ligaments  consist  of  bands  of  various  forms,  serving  to  connect  the  articular 
extremities  of  bones,  and  are  composed  mainly  of  coarse  bundles  of  very 
dense,  white,  fibrous  tissue  placed  parallel  with,  or  closely  interlaced  with,  one 
another,  and  presenting  a  white,  shining,  silvery  aspect.  A  ligament  is  pliant 
and  flexible,  so  as  to  allow  of  the  most  perfect  freedom  of  movement,  but  it  is 
strong,  tough,  and  inextensile,  so  as  not  readily  to  yield  under  the  most  severely 
applied  force;  it  is  consequently  well  adapted  to  serve  as  the  connecting  medium 
between  the  bones.  Some  ligaments  consist  entirely  of  yellow  elastic  tissue,  as 
the  ligamenta  subflava,  which  connect  together  the  adjacent  arches  of  the  verte- 
brae in  man,  and  the  ligamentum  nuchae  in  the  lower  animals  are  composed  of 
yellow  elastic  tissue.  In  these  cases  it  will  be  observed  that  the  elasticity  of  the 
ligament  is  intended  to  act  as  a  substitute  for  muscular  power. 

Synovial  membrane  is  a  thin,  delicate,  serous  membrane,  arranged  in  its 
simplest  form  like  a  short,  wide  tube,  attached  by  its  open  ends  to  the  margins 
of  the  articular  cartilages  and  covering  the  inner  surfaces  of  the  various  ligaments 
which  connect  the  articulating  surfaces,  so  that,  along  with  cartilages,  it  completely 
encloses  the  joint-cavity.  Its  transudate  is  thick,  viscid,  and  glairy,  like  the 
white  of  an  egg,  hence  it  is  termed  synovia.  It  is  composed  of  a  single  layer  of 
endothelial  cells  resting  upon  a  thin  layer  of  fibroelastic  (subendothelial)  tissue. 
The  synovial  membranes  found  in  the  body  admit  of  subdivision  into  three  kinds — 
articular,  bursal,  and  vaginal. 

Articular  synovial  membrane  is  found  in  every  freely  movable  joint.  It  lines  the  capsule 
of  the  joint  and  is  reflected  upon  the  nonarticular  intracapsular  portion  of  the  bones  which 
enter  iiito  the  formation  of  the  joint.     In  the  fetus  this  membrane  is  said,  by  Toynbee,  to 


262 


THE  ARTICULATIONS,   OR  JOINTS 


be  continued  over  the  surface  of  the  cartilages ;  but  in  the  adult  it  merely  encroaches  for  a  short 
distance  upon  the  margins  of  the  cartilages,  to  which  it  is  firmly  attached;  it  then  invests  the 
inner  surface  of  the  capsular  or  other  ligaments  enclosing  the  joint,  and  is  reflected  over  the 
surface  of  any  tendons  passing  through  its  cavity,  as  the  tendons  of  the  Popliteus  in  (he  knee 
and  the  tendon  of  the  Sleeps  in  the  shoulder.  In  some  of  the  joints  the  synovial  membrane 
is  thrown  into  folds,  which  pass  across  the  cavity.  They  are  called  synovial  ligaments, 
and  are  especially  distinct  in  the  knee.  These  folds,  when  large,  frequently  contain  con- 
siderable quantities  of  fat,  which  acts  as  a  cushion  between  the  two  articular  surfaces  and 
serves  a  valuable  purpose  in  filling  up  gaps.  In  some  joints  there  are  flattened  folds,  sub- 
divided at  their  margins  into  fringe-like  processes  (sjoiovial  villi),  the  vessels  of  which  have 
a  convoluted  arrangement.  These  latter  generally  project  from  the  synovial  membrane  near 
the  margin  of  the  cartilage  and  lie  flat  upon  its  surface.  They  consist  of  fibroelastic  tissue 
covered  with  endothelium,  and  contain  fat-cells  in  variable  quantities,  and,  more  rarely,  isolated 
cartilage-cells.  Under  certain  diseased  conditions  similar  processes  are  found  covering  the 
entire  surface  of  the  synovial  membrane,  forming  a  mass  of  pedunculated  fibrofatty  growths 
which  project  into  the  joint.  Similar  structures  are  also  found  in  some  of  the  bursal  and  vaginal 
synovial  membranes. 

The  bursal  synovial  membranes  are  sacs  interposed  between  surfaces  w  hich  move  upon  each 
other,  producing  friction,  as  in  the  gliding  of  a  tendon  or  of  the  integument  o^er  projecting  bony 
surfaces.  There  are  two  groups  of  synovial  bursse  designated  according  to  situation:  (1)  Sub- 
cutaneous synovial  bursse  {btirsae  mucosae  suhndaneae)  (Fig.  214)  are  those  situated  between  the 
integument  and  a  prominent  process  of  bone.  Subcutaneous  bursge  are  found  between  the 
integument  and  the  front  of  the  patella,  over  the  olecranon,  the  malleoli,  and  other  prominent 
parts.  (2)  Subtendinous  synovial  bursas  (hursae  mucosae  subtendineae)  (Fig.  214)  are  those  situ- 
ated between  tendons  or  muscles  and  the  bony  or  cartilaginous  surfaces  over  which  the  tendons 
or  muscles  glide.     For  example,  a  bursa  is  placed  between  the  Glutei  muscles  and  the  surface 


Fig.  214. — Scheme  of  a  serous  bursa.     (Poirier  and  Charpj-.) 


of  the  great  trochanter.  Subtendinous  bursfe  are  found  often  about  joints  and  not  unusually  com- 
municate directly  with  the  cavity  of  the  joint  by  means  of  an  opening  in  the  joint  capsule,  the 
synovial  membrane  of  the  joint  being  continuous  with  the  synovial  membrane  of  the  bursa. 
For  instance,  the  bursa  between  the  tendon  of  the  Psoas  and  Iliacus  muscles  and  the  capsular 
ligament  of  the  hip  communicates  with  the  hip-joint;  and  the  bursa  between  the  under  surface 
of  the  Subscapularis  muscle  and  the  neck  of  the  scapula  communicates  with  the  shoulder-joint. 
Bursse  consist  of  a  thin  wall  of  connective  tissue,  lined  by  endothelial  cells,  and  contain  a  viscid 
fluid. 

The  vaginal  synovial  membrane  (Figs.  257  and  365),  which  is  the  synovial  sheath  or  the 
thecal  synovial  bursa  ( I'dt/tna  mucosa  tendinis),  serves  to  facilitate  the  gliding  of  a  tendon  in  the 
osseofibrous  canal  through  \\hich  it  passes.  The  membrane  is  here  arranged  in  the  form  of 
a  sheath,  one  layer  of  which  adheres  to  the  w  all  of  the  canal,  and  the  other  is  reflected  upon  the 
surface  of  the  contained  tendon,  the  space  between  the  two  surfaces  of  the  membrane  containing 
synovia.  These  sheaths  are  chiefly  found  surrounding  the  tendons  of  the  Flexor  and  Extensor 
rnuscles  of  the  fingers  and  toes  as  they  pass  through  the  osseofibrous  canals  in  the  hand  or  foot. 
A  vaginal  sheath  covers  the  long  head  of  the  Biceps  brachii  muscle  from  its  origin  to  the  surgical 
neck  of  the  humerus  (Fig.  247). 

Subjacent  to  the  synovial  membrane  of  certain  joints  are  found  pads  of  adipose  tissue,  the 
synovial  pads.  These  serve  to  fill  up  large  spaces,  and  by  adapting  themselves  to  changes  of 
position  maintain  the  form  of  the  joint  during  movement. 


SYNARTHROSIS 


2(53 


The  articulations  are  divided  into  tliree  classes — synarthrosis,  or  immovable; 
amphiarthrosis,  or  mixed;  and  diarthrosis,  or  movable  joints. 

Synarthrosis  (Immovable  Articulation). — Synarthrosis  includes  all  those  artic- 
ulations in  which  tlie  surfaces  of  the  bones  are  in  almost  direct  contact,  being 
fastened  together  by  an  intervening  mass  of  connective  tissue,  and  in  which  there 


Sutural  ligament 


Fig.  215, — Section  across  the  sagittal  suture. 


Cartilage 


Perichondrium 


-Section  through  the  occipitosphenoid 
synchondrosis  of  an  infant. 


is  no  joint  cavity  and  no  appreciable  motion.  Examples  of  synarthrosis  are  the 
joints  between  the  bones  of  the  cranium  and  of  the  face,  excepting  those  of  the 
mandible.  The  varieties  of  synarthrosis  are  four  in  number — sutura,  schindylesis, 
gomphosis,  and  synchondrosis. 


Lifjament 
Intervertehral  disk 
of  fibrocartUage 


Articular  cartilage  -rT^?||%(Spo 

Fig.  217. — Diagrammatic  section  of  a  symphysis. 


The  sutura  is  that  form  of  articulation  met  with  only  in  the  skull,  where  the 
contiguous  margins  of  flat  bones  are  apparently  but  not  really  in  immediate 
contact,  a  thin  layer  of  fibrous  tissue,  sutural  membrane,  being  interposed.  This 
membrane  is  continuous  externally  with  the  pericranium  and  internally  with  the 


Articular  cartilage 
Synovial  membrane 
Capsular  ligament 


Synovial  membrane 

Articular  cartilage 

Intra-articidar 
fibrocartUage 

Capsular  ligament 


Fig.  219. — Diagrammatic  section  of  a  diarthrodial 
joint,  with  an  intra-articular  fibrocartilage. 


dura.  In  some  of  the  sutures  the  sutural  membrane  gradually  disappears  as 
age  advances  and  the  two  bones  form  an  osseous  fusion.  Where  the  articulating 
surfaces  are  connected  by  a  series  of   processes  and    indentations  interlocked. 


264  THE  ARTICULATIONS,   OB  JOINTS 

it  is  termed  a  true  suture,  or  sutura  vera,  of  which  there  are  three  varieties — sutura 
dentata,  serrata,  and  limbosa.  The  sutura  dentata  is  so  called  from  the  tooth-liive 
form  of  the  projecting  articular  processes,  as  in  the  suture  between  the  parietal 
bones.  In  the  sutura  serrata  the  edges  of  the  two  bones  forming  the  articulation 
are  serrated  like  the  teeth  of  a  fine  saw,  as  between  the  two  portions  of  the  frontal 
bone.  In  the  sutura  limbosa  besides  the  dentated  processes,  there  is  a  certain 
degree  of  bevelling  of  the  articular  surfaces,  so  that  the  bones  overlap  each  other, 
as  in  the  suture  between  the  parietal  and  frontal  bones.  When  the  articulation 
is  formed  by  roughened  surfaces  placed  in  apposition  with  one  another,  it  is 
termed  the  false  suture,  of  which  there  are  two  kinds — the  sutura  squamosa,  formed 
by  the  overlapping  of  two  contiguous  bones  by  broad  bevelled  margins,  as  in  the 
squamoparietal  (squamous)  suture;  and  the  sutura  harmonia,  where  there  is  simple 
apposition  of  two  contiguous,  rough,  bony  surfaces,  as  in  the  articulation  between 
the  two  maxilla;  or  of  the  horizontal  plates  of  the  palate  bones. 

Schindylesis  is  that  form  of  articulation  in  which  a  thin  plate  of  bone  is 
received  into  a  cleft  or  fissure  formed  by  the  separation  of  two  laminse  in  another 
bone,  as  in  the  articulation  of  the  rostrum  of  the  sphenoid  and  perpendicular 
plate  of  the  ethmoid  mth  the  vomer,  or  in  the  reception  of  the  latter  in  the 
median  fissure  between  the  maxillse  and  palate  bones.  i 

A  gomphosis  is  an  articulation  formed  by  the  insertion  of  a  conical  process 
into  a  socket,  as  a  nail  is  driven  into  a  board;  this  is  not  illustrated  by  any  articu- 
lation between  bones,  properly  so  called,  but  is  seen  in  the  articulation  of  the  teeth 
with  the  alveoli  of  the  maxillae  and  mandible. 

A  synchondrosis  is  a  joint  in  which  the  connecting  medium  is  hyaline  cartilage. 
This  is  a  temporary  form  of  joint,  because  the  hyaline  cartilage  becomes  con- 
verted into  bone  before  adult  life.  Such  joints  are  found  between  the  epiphyses 
and  shafts  of  long  bones,  between  the  occipital  and  the  sphenoid  at,  and  for  some 
years  after  birth. 

Amphiarthrosis  (Mixed  Articulation). — In  this  form  of  articulation  the  con- 
tiguous osseous  surfaces  are  either  connected  by  broad  flattened  disks  of  fibro- 
cartilage  which  adhere  to  the  end  of  each  bone,  as  in  the  articulation  between  the 
bodies  of  the  vertebrae,  or  else  the  articular  surfaces  are  co^'ered  with  fibro- 
cartilage,  partially  lined  by  synovial  membrane,  and  connected  by  external  liga- 
ments, as  in  the  pubic  symphysis,  both  of  these  joints  being  capable  of  limited 
motion. 

The  articulation  between  the  bodies  of  the  vertebrae  resemble  the  synarthrodia! 
joints  in  the  continuity  of  their  surfaces  and  the  absence  of  a  synovial  sac;  the 
symphysis  pubis  resembles  the  diarthrodial  articulation. 

Diarthrosis  (Movable  Articulation). — This  form  of  articulation  includes  the 
greater  number  of  the  joints  in  the  body,  mobility  being  their  distinguishing 
character.  They  are  formed  by  the  approximation  of  two  contiguous  bony 
surfaces  covered  with  cartilage,  connected  by  ligaments  and  lined  with  synovial 
membrane.  The  varieties  of  joints  in  this  class  have  been  determined  by  the 
kind  of  motion  permitted  in  each.  There  are  two  varieties  in  which  the  move- 
ment is  uniaxial;  that  is  to  say,  all  movements  take  place  around  one  axis.  In 
one  form,  the  ginglymus,  or  hinge-joint,  this  axis  is,  practically  speaking,  trans- 
verse; in  the  other,  the  trochoid,  or  pivot-joint,  it  is  longitudinal.  There  are  two 
varieties  where  the  movement  is  biaxial  or  around  two  horizontal  axes  at  right 
angles  to  each  other  or  at  any  intervening  axis  between  the  two.  These  are  the 
condyloid  joint  and  the  saddle-joint.  There  is  one  form  of  joint  where  the  move- 
ment is  polyaxial,  the  enarthrosis,  or  ball-and-socket  joint.  And  finally  there  are 
the  arthrodia,  or  gliding  joints.  In  a  diarthrosis  there  is  always  a  joint  cavity 
lined  with  synovial  membrane — the  articular  surfaces  of  the  bones  are  covered 
with  hyaline  cartilage,  and  the  bones  are  held  in  contact  by  ligaments. 


S  VNA  B  TIIR  OSIS  265 

The  ginglymus,  or  hinge-joint,  is  that  form  of  joint  in  which  the  articular  surfaces 
are  moulded  to  eacii  other  in  such  a  manner  as  to  permit  motion  only  in  one  plane, 
forward  and  backward;  the  extent  of  motion  at  the  same  time  being  coi^siderahle. 
The  direction  which  the  distal  bone  takes  in  this  motion  is  never  in  the  same 
plane  as  that  of  the  axis  of  the  proximal  bone,  and  there  is  always  a  certain  amount 
of  alteration  from  the  straight  line  during  flexion.  The  articular  surfaces  are 
connected  together  by  strong  lateral  ligaments,  which  form  their  chief  bond  of 
union.     The  most  perfect  forms  of  ginglymus  are  the  interphalangeal  joints. 

A  trochoid,  or  pivot-joint  or  rotary  joint,  is  one  in  which  the  movement  is 
limited  to  rotation;  the  joint  is  formed  by  a  pivot-like  process  turning  within 
a  ring,  or  the  ring  on  the  pivot,  the  ring  being  formed  partly  of  bone,  partly  of 
ligament.  In  the  superior  radioulnar  articulation  the  ring  is  formed  partly  by 
the  lesser  sigmoid  cavity  of  the  ulna  and  in  the  rest  of  its  extent  by  the  orbicular 
ligament;  here  the  head  of  the  radius  rotates  within  the  ring.  In  the  articulation 
of  the  odontoid  process  of  the  axis  with  the  atlas  the  ring  is  formed  in  front  by 
the  anterior  arch  of  the  atlas;  behind,  by  the  transverse  ligament;  here  the  ring 
rotates  around  the  odontoid  process. 

Condyloid  or  biaxial  articulation  is  that  form  of  joint  in  which  an  ovoid  artic- 
ular head,  or  condyle,  is  received  into  an  elliptical  cavity  in  such  a  manner  as 
to  permit  of  flexion  and  extension,  adduction  and  abduction  and  circumduction, 
but  no  axial  rotation.  The  articular  surfaces  are  connected  together  by  anterior, 
posterior,  and  lateral  ligaments.  An  example  of  this  form  of  joint  is  found  in 
the  wrist. 

Articulation  by  reciprocal  reception,  or  saddle-joint,  is  that  variety  in  which  the 
articular  surfaces  are  concavo-convex;  that  is  to  say,  they  are  inversely  convex 
in  one  direction  and  concave  in  the  other.  The  movements  are  the  same  as  in 
the  preceding  form;  that  is  to  say,  there  is  flexion,  extension,  adduction,  abduction, 
and  circumduction,  but  no  axial  rotation.  The  articular  surfaces  are  connected 
by  a  capsular  ligament.  The  best  example  of  this  form  of  joint  is  the  carpo- 
metacarpal joint  of  the  thumb. 

An  enarthrosis,  or  ball-and-socket  joint,  is  that  form  of  joint  in  which  the  distal 
bone  is  capable  of  motion  around  an  indefinite  number  of  axes  which  have  one 
common  centre.  It  is  formed  by  the  reception  of  a  globular  head  into  a  deep 
cup-like  cavity,  the  parts  being  kept  in  apposition  by  a  capsular  ligament  strength- 
ened by  accessory  ligamentous  bands.  Examples  of  this  form  of  articulation  are 
found  in  the  hip-  and  shoulder-joints. 

Arthrodia. — Arthrodia  is  that  form  of  joint  which  admits  of  a  gliding  move- 
ment; it  is  formed  by  the  approximation  of  plane  surfaces  or  of  one  slightly  con- 
cave to  one  slightly  convex,  the  amount  of  motion  between  them  being  limited 
by  the  ligaments,  or  osseous  processes,  surrounding  the  articulation;  as  in  the 
articular  processes  of  the  vertebrte,  the  carpal  joints,  except  that  of  the  os  magnum 
with  the  scaphoid  and  semilunar  bones. 

Below,  in  tabular  form,  are  the  names,  distinctive  characters,  and  examples 
of  the  different  kinds  of  articulations: 


266 


IHE  ARTICULATIONS,   OR  JOINTS 


Synarthrosis,  or  Im- 
movable Joint.  Sur- 
faces separated  by 
fibrous  membrane  or 
by  a  line  of  cartilage, 
without  any  interven- 
ing synovial  cavity, 
and  immovably  con- 
nected 'with  each 
other. 

As  in  joints  of  cran- 
ium and  face  (except 
mandible). 


Amphiarthrosis, 
Mixed  Articulation. 


Suiura.  Articu- 
lation by  processes 
and  indentations '' 
interlocked. 


Diarthrosis, 
^Movable  Joint. 


f     Dentaia,    having    tooth- 
I  like  processes. 
I      As  in  interparietal  suture. 
Serrata,   having   serrated 
Sutura  vera  (true)  I  ^'^S^^   ^'^^   ^^   ^eeth  of   a 
articulate  bv  indent-  -1  ^^^''   ... 
ed  borders. "  "^  mtertrontal  suture. 

Limbosa,  having  bevelled 
margins  and  dentated  pro- 
cesses. 

As  in   frontoparietal   su- 
l  ture. 

I      Squamosa,     formed     by 
thin  bevelled  margins,  over- 
lapping each  other. 
Sutura  notha  ^J"^^  ''^     squamoparietal 

(false),  articulate  hy  {       tt    '        ■        „  ,     , 

UP  ■'  '      Harmonia,     formed     bv 

rough  surfaces.  ^,  .,.'        „  .    •■ 

"  the  apposition  of   contigu- 

ous rough  surfaces. 

As  in  intermaxillary    su- 
[  ture. 

Schindylesis. — Articulation  formed  by  the  reception  of  a  thin  plate 
of  one  bone  into  a  fissure  of  another. 

As  in  articulation  of  rostrum  of  sphenoid  with  vomer. 

Gomphosis. — Articulation  formed  by  the  insertion  of  a  conical  process 
into  a  socket — the  teeth. 

Synchondrosis — (1)  Surfaces  connected  by  fibrocartilage  and  not 
separated  by  synovial  membrane.  Has  limited  motion.  As  in  joints 
between  bodies  of  vertebrse. 

(2)  Surfaces  covered  by  fibrocartilage,  lined  by  partial  synovial 
membrane.     As  in  pubic  symphysis. 

Ginglymus. — Hinge-joint;  motion  limited  to  two  directions,  for- 
ward and  backward.  Articular  surfaces  fitted  together  so  as  to 
permit  of  movement  in  one  plane.  As  in  the  interphalangeal 
joints. 

Trochoid,  or  Pivoi-joint. — Articulation  by  a  pivot  process  turning 
within  a  ring  or  ring  around  a  pivot.  As  in  superior  radioulnar  articu- 
lation and  atlanto-axial  joint. 

Condyloid. — Ovoid  head  received  into  elliptical  cavity.  Movements 
in  every  direction  except  axial  rotation.    As  the  wrist-joint. 

Reciprocal  Reception  (saddle-joint). — Articular  surfaces  inversely  con- 
vex in  one  direction  and  concave  in  the  other.  Movement  in  e\"ery 
direction  except  axial  rotation.  As  in  the  carpometacarpal  joint  of  the 
thumb. 

Enart.hrosis. — Ball-and-socket  joint ;  capable  of  motion  in  all  directions. 
Articulations  by  a  globular  head  received  into  a  cup-like  cavity.  As  in 
hip-  and  shoulder-joints. 

Arthrodia. — Gliding  joint;  articulations  by  plane  surfaces,  which 
glide  upon  each  other.    As  in  carpal  and  tarsal  articulations. 


The  Einds  of  Movement  Admitted  in  Joints. 


The  movements  admissible  in  the  joints  may  be  divided  into  four  kinds — ghding, 
angular  movement,  circumduction,  and  rotation.  These  movements  are  often, 
however,  more  or  less  combined  in  the  various  joints,  so  as  to  produce  an  infinite 
variety,  and  it  is  .seldom  that  we  find  only  one  kind  of  motion  in  any  particular 
joint. 

Gliding  movement  is  the  most  simple  kind  of  motion  that  can  take  place  in  a 
joint,  one  surface  gliding  or  moving  over  another  without  any  angular  or  rotatory 
movement.  It  is  common  to  all  movable  joints,  but  in  some,  as  in  the  articu- 
lations of  the  carpus  and  tarsus,  it  is  the  only  motion  permitted.  This  movement 
is  not  confined  to  plane  surfaces,  but  may  exist  between  any  two  contiguous 


TliU  KINDS  OF  MO  VE3IENT  ADMITTED  IN  JOINTS  2G7 

surfaces,  of  whatever  form,  limited  by  the  ligaments  which  enclose  the  articu- 
lation. Gliding  over  a  wide  range,  as  is  seen  in  the  sliding  of  the  patella  over 
the  condyles  of  the  femur,  is  called  coaptation. 

Angular  movement  occurs  only  between  the  long  bones,  and  by  it  the  angle 
between  the  two  bones  is  increased  or  diminished.  It  may  take  place  in  four 
directions — forward  and  backward,  constituting  flexion  or  bending  and  extension 
or  straightening,  or  inward  toward  and  outward  from  the  medial  line  of  the  body, 
constituting  adduction  and  abduction.  Al)duction  of  a  limb  is  movement  away 
from  the  medial  line  of  the  body.  Adduction  of  a  limb  is  movement  toward  the 
medial  line  of  the  body.  In  the  fingers  and  toes  the  significance  of  the  terms  are 
different;  abduction  means  movement  of  the  fingers  away  from  the  middle  finger 
or  of  the  toe  away  from  the  second  toe;  adduction  means  movement  of  fingers 
toward  the  middle  finger  or  of  the  toes  toward  the  second  toe.  The  strictly  gingly- 
moid  or  hinge-joints  admit  of  flexion  and  extension  only.  Abduction  and  adduc- 
tion, combined  with  flexion  and  extension,  are  met  with  in  the  more  movable 
joints;  as  in  the  hip-,  shoulder-,  and  metacarpal-joint  of  the  thumb,  and  partially 
in  the  wrist.  When  two  anterior  surfaces  are  brought  nearer  together,  as  by 
bending  the  elbow  or  wrist,  we  speak  of  the  movement  as  anterior  or  ventral 
flexion.  Ventral  flexion  of  the  wrist  is  also  called  volar  or  palmar  flexion.  If 
two  posterior  surfaces  are  brought  nearer  together,  as  by  bending  the  knee  or 
extending  the  wrist,  we  speak  of  the  movement  as  posterior  or  dorsal  flexion. 

At  the  wrist-joint  the  bending  of  the  ulnar  margin  of  the  hand  toward  the 
ulnar  side  of  the  forearm  is  ulnar  flexion;  the  bending  of  the  radial  margin  of 
the  hand  toward  the  radial  side  of  the  forearm  is  radial  flexion. 

Circumduction  is  that  limited  degree  of  motion  which  takes  place  between  the 
head  of  the  bone  and  its  articular  cavity,  while  the  extremity  and  sides  of  the  limb 
are  made  to  circumscribe  a  conical  space,  the  base  of  which  corresponds  with  the 
inferior  extremity  of  the  limb,  the  apex  with  the  articular  cavity;  this  kind  of 
motion  is  best  seen  in  the  shoulder-  and  hip-joints. 

Rotation  is  the  movement  of  a  bone  upon  an  axis,  which  is  the  axis  of  the  pivot 
on  which  the  bone  turns,  as  in  the  articulation  between  the  atlas  and  axis,  when 
the  odontoid  process  serves  as  a  pivot  around  which  the  atlas  turns;  or  else  is  the 
axis  of  a  pivot-like  process  which  turns  within  a  ring,  as  in  the  rotation  of  the 
radius  upon  the  humerus. 

Ligamentous  Action  of  Muscles. — The  movements  of  the  different  joints  of  a  limb  are  com- 
bined by  means  of  the  long  muscles  which  pass  over  more  than  one  joint,  and  which,  when 
relaxed  and  stretched  to  their  greatest  extent,  act  as  elastic  ligaments  in  restraining  certain 
movements  of  one  joint,  except  when  combined  with  corresponding  movements  of  the  other,  these 
latter  movements  being  usually  in  the  opposite  direction.  Thus,  the  shortness  of  the  Hamstring 
muscles  prevents  complete  flexion  of  the  hip,  unless  the  knee-joint  is  also  flexed,  so  as  to  bring 
their  attachments  nearer  together.  The  uses  of  this  arrangement  are  threefold :  (1 )  It  coordinates 
the  kinds  of  movement  which  are  the  most  habitual  and  necessary,  and  enables  them  to  be  per- 
formed with  the  least  expenditure  of  power.  "Thus,  in  the  usual  gesture  of  the  arms,  whether 
in  grasping  or  rejecting,  the  shoulder  and  the  elbow  are  fiexed  simultaneously,  and  simultaneously 
extended,"  in  consequence  of  the  passage  of  the  Biceps  and  Triceps  brachii  over  both  joints. 
(2)  It  enables  the  short  muscles  which  pass  over  only  one  joint  to  act  upon  more  than  one.  "Thus, 
if  the  Rectus  femoris  remain  tonically  of  such  length  that,  when  stretched  over  the  extended  hip, 
it  compels  extension  of  the  knee,  theia  the  Gluteus  maximus  becomes  not  only  an  extensor  of  the 
hip,  but  an  extensor  of  the  knee  as  well."  (3)  It  provides  the  joints  with  ligaments  which,  while, 
they  are  of  very  great  power  in  resisting  movements  to  an  extent  incompatible  with  the  mechan- 
ism of  the  joint,  at  the  same  time  spontaneously  yield  when  necessary.  "Taxed  beyond  its 
strength,  a  ligament  will  be  ruptured,  whereas  a  contracted  muscle. is  easily  relaxed;  also,  if 
neighboring  joints  be  united  by  ligaments,  the  amount  of  flexion  or  extension  of  each  must  remain 
in  constant  proportion  to  that  of  the  other;  while,  if  the  union  be  by  muscles.the  seijaration  of 
the  points  of  attachment  of  those  muscles  may  vary  considerably  in  different  varieties  of  move- 
ment, the  muscles  adapting  themselves  tonically  to  the  length  required."'  Dr.  W.  W.  Keen 
points  out  how  important  it  is  "  that  the  stu-geon  should  remember  this  ligamentous  action  of 

'  Dr.  Cleland,  in  Journal  of  Anatomy  and  Physiology,  1S66,  No.  1,  p.  85. 


268  THE  ARTICULATIONS,   OR  JOINTS 

muscles  in  making  passive  motion — for  instance,  at  tlie  wrist  after  Colles'  fracture.  If  the 
fingers  be  extended,  tlie  wrist  can  be  fiexed  to  a  right  angle.  If,  however,  thev  be  first  flexed, 
as  in  'making  a  fist.'  flexion  at  the  wrist  is  stricti}'  limited  to  from  40  to  50  degrees  in  difTerent  per- 
sons, and  is  very  painful  beyond  that  point.  Hence,  passive  motion  here  should  be  made  with 
the  fingers  extended.  In  the  leg,  when  flexing  the  hip,  the  knee  should  be  flexed."  Dr.  Keen 
further  points  out  that  "a  beautiful  illustration  of  this  is  seen  in  the  perching  of  birds,  whose 
toes  are  forced  to  clasp  the  perch  by  just  such  a  passive  ligamentous  action  so  soon  as  they 
stoop.    Hence,  they  can  go  to  sleep  and  not  fall  off  the  perch." 

The  articulations  may  be  arranged  into  those  of  the  trunk,  those  of  the  upper 
extremity,  and  those  of  the  lower  extremity. 


ARTICULATIONS  OF  THE  TRUNK. 

These  may  be  divided  into  the  following  groups,  viz. : 


I.  Of  the  Vertebral  Column. 
II.  Of  the  Atlas  with  the  Axis. 

III.  Of    the   Atlas   with    the   Occipital 

Bone. 

IV.  Of  the  Axis  with  tiae  Occipital  Bone. 
V.  Of  the  Mandible. 

VI.  Of  the  Ribs  with  the  Vertebrae. 


VII.  Of  the  Cartilages  of  the  Ribs  with 
the    Sternum  and    with   Each 
Other. 
VIII.  Of  the  Sternum. 
IX.  Of  the  Vertebral  Column  with  the 

Pelvis. 
X.  Of  the  Pelvis. 


I.  Articulations  of  the  Vertebral  Column. 

The  different  segments  o*^  the  vertebral  column  are  connected  by  spinal  ligaments 
iQigamenta  coluninae  vertehralis),  which  may  be  divided  into  five  sets:  (1)  Those 
connecting  the  bodies  of  the  vertebrse.  (2)  Those  connecting  the  laminae.  (3) 
Those  connecting  the  articular  processes.  (4)  Those  connecting  the  spinous  processes. 
(5)  Those  of  the  transverse  processes  (the  last  four  kinds  being  known  as  interneural) . 

The  articulations  of  the  bodies  of  the  vertebrfe  with  each  other  form  a  series 
of  amphiarthrodial  joints;  those  between  the  articular  processes  form  a  series  of 
arthrodial  joints. 


1.  Ligaments  of  the  Vertebral  Bodies  or  Centra  (Intercentral 

Ligaments). 

Anterior  Common  Ligament. 
Posterior  Common  Ligament. 
Intervertebral  Substance. 

The  anterior  common  ligament  {Ugamentum  longitidinale  anterms)  (Figs. 
222,  225,  and  228)  is  a  broad  and  strong  band  of  longitudinal  fibres  which  extends 
along  the  anterior  (ventral)  surface  of  the  bodies  of  the  vertebrfe  from  the  axis 
to  the  sacrum.  It  is  broader  below  than  above,  thicker  in  the  thoracic  than  in 
the  cervical  or  lumbar  regions,  and  somewhat  thicker  opposite  the  front  of  the 
body  of  each  vertebra  than  opposite  the  intervertebral  substance.  It  is  attached, 
above,  to  the  body  of  the  axis  by  a  pointed  process,  where  it  is  continuous  with  the 
.anterior  atlanto-axial  ligament,  is  connected  with  the  tendon  of  insertion  of  the 
Longus  colli  muscle,  and  extends  down  as  far  as  the  upper  bone  of  the  sacrum. 
It  consists  of  dense  longitudinal  fibres,  which  are  intimately  adherent  to  the 
^intervertebral  substance  and  the  prominent  margins  of  the  vertebrfe,  but  less 


ARTICULATIONS  OF  THE   VERTEBRAL   COLUMN 


269 


closely  to  the  middle  of  the  bodies.  In  the  latter  situation  the  fibres  are  exceed- 
ingly thick,  and  serve  to  fill  up  (he  concavities  on  their  front  surface  and  to  make 
the  anterior  surface  of  the  vertebral  column  more  even.  This  ligament  is  com- 
posed of  several  layers  of  fibres,  which  vary  in  length,  but  are  closely  interlaced 
with  each  other.  The  most  superficial  or  longest  fibres  extend  between  four  or 
five  vertebrse.  A  second  subjacent  set  extends  between  two  or  three  vertebrte, 
while  a  third  set,  the  shortest  and  deepest,  extends  from  one  vertebra  to  the  next. 
At  the  side  of  the  bodies  the  ligament  consists  of  a  few  short  fibres,  which  pass 
from  one  vertebra  to  the  next,  separated  from  the  median  portion  by  large  oval 
apertures  for  the  passage  of  vessels. 

The  posterior  common  ligament  {ligamentum  lomjitudinale  posferius)  (Figs. 
227  and  228)  is  situated  within  the  vertebral  canal,  and  extends  along  the  posterior 
(dorsal)  surface  of  the  liodies  of  the  vertebrae  from  the  body  of  the  axis  above,  where 


nterverte- 
jral  fibro- 
:artilage 


LIGAMENT 

-Vertebral   bodies   with   ligaments 
behind.     (Spalteholz.) 


ith     the     adjacent. 
(Spalteholz.) 


it  is  continuous  with  the  posterior  occipito- 
axial  ligament,  to  the  sacrum  below.  It  is 
broader  above  than  below,  and  thicker  in 
the  thoracic  than  in  the  cervical  or  lumbar 
regions.  In  the  situation  of  the  interver- 
tebral substance  and  contiguous  margins 
of  the  vertebrfe,  where  the  ligament  is  more  intimately  adherent,  it  is  broad,  and 
presents  a  series  of  dentations  with  intervening  concave  margins;  but  it  is  narrow 
and  thick  over  the  centre  of  the  bodies,  from  which  it  is  separated  by  the  vente 
basis  vertebrte.  This  ligament  is  composed  of  smooth,  shining,  longitudinal 
fibres,  denser  and  more  compact  than  those  of  the  anterior  ligament,  and  formed 
of  a  superficial  layer  occupying  the  interval  between  three  or  four  vertebrre,  and 
of  a  deeper  layer  which  extends  between  one  vertebra  and  the  next  adjacent 
to  it.  It  is  separated  from  the  dura  of  the  spinal  cord  by  loose  connective  tissue. 
The  Intervertebral  Fibrocartilages  {fibrocartilagines  inienertebralcs)  (Figs. 
221  and  222). — Each  fibrocartilaginous  disk  is  of  lenticular  form  and  of  composite 
structure.  The  disks  are  interposed  between  the  adjacent  surfaces  of  the  bodies 
of  the  vertebrse  from  the  axis  to  the  sacrum,  and  form  the  chief  bonds  of  connec- 
tion between  those  bones.  In  young  children  intervertebral  substance  exists 
in  the  coccyx.  These  disks  vary  in  shape,  size,  and  thickness  in  dift'erent  parts 
of  the  vertebral  column.  In  shape  they  accurately  correspond  with  the  surfaces 
of  the  bodies  between  which  they  are  placed,  being  oval  in  the  cervical  and  lumbar 
regions,  and  circular  in  the  thoracic.     Their  size  is  greatest  in  the  lumbar  region. 


270  THE  ABTJCULATIONS,   OB  JOINTS 

In  thickness  they  vary  not  only  in  the  different  regions  of  the  vertebral  column, 
but  in  different  parts  of  the  same  disk;  thus,  they  are  thicker  in  front  than  behind 
in  the  cervical  and  lumbar  regions,  while  they  are  uniformly  thick  in  the  thoracic 
reo-ion.  The  intervertebral  disks  form  about  one-fourth  of  the  vertebral  column, 
exclusive  of  the  first  two  vertebrae;  they  are  not  equally  distributed,  however, 
between  the  various  bones;  the  thoracic  portion  of  the  vertebral  column  having, 
in  proportion  to  its  length,  a  much  smaller  quantity  than  in  the  cervical  and  lumbar 


right  half  of  sectic 


regions,  which  necessarily  gives  to  the  latter  parts  greater  pliancy  and  freedom 
of  movement.  The  intervertebral  disks  are  adherent,  by  their  surfaces,  to  a 
thin  layer  of  hyaline  cartilage  which  covers  the  upper  and  under  surfaces  of  the 
bodies  of  the  vertebrse,  and  in  which,  in  early  life,  the  epiphyseal  plates  develop, 
and  by  their  circumference  are  closely  connected  in  froat  to  the  anterior,  and 
behind  to  the  posterior  common  ligament;  while  in  the  thoracic  region  they 
are  connected  laterally,  by  means  of  the  interarticular  ligament,  to  the  heads  of 
those  ribs  which  articulate  with  two  vertebrae;  they,  consequently,  form  part  of 
the  articular  cavities  in  which  the  heads  of  these  bones  are  received. 

Structure  of  the  Intervertebral  Substance. — The  outer  portion  of  the  intervertebral  sub- 
stance is  composed  of  many  layers  of  fibrous  connective  tissue.  This  enveloping;  portion  is  called 
the  annulus  fibrosus.  The  central  portion  of  the  disk  is  composed  of  soft,  pulpy,  highly  elastic 
fibrocartilage,  containing  some  bands  of  connective  tissue.  It  is  called  the  nucleus  pulposus,  is  of 
a  yellowish  color,  and  rises  up  considerably  above  the  surrounding  level  when  the  ilisk  is  divided 
horizontally.  This  pulpy  substance,  which  is  especially  well  developed  in  the  lumliar  region, 
is  the  remains  of  the  notochord,  and,  according  to  Luschka,  contains  a  small  synovial  cavity  in  its 
centre.  The  outer  layers  of  the  disk  are  arranged  concentrically  one  within  the  other,  the  outer- 
most consisting  of  ordinary  fibrous  tissue,  but  the  others  and  more  numerous  consisting  of  white 
fibrocartilage.  These  plates  are  not  quite  vertical  in  their  direction,  those  near  the  circumference 
being  curved  outward  and  closely  approximated;  while  those  nearest  the  centre  curve  in  the 
opposite  direction,  and  are  somewhat  more  widely  separated.  The  fibres  of  which  each  plate  is 
composed  are  directed,  for  the  most  part,  obliquely  from  above  downward,  the  fibres  of  adjacent 
plates  passing  in  opposite  directions  and  varying  in  every  layer;  so  that  the  fibres  of  one  layer 
are  directed  across  those  of  another,  like  the  limbs  of  the  let'tei;  X.  This  laminar  arrangement 
belongs  to  about  the  outer  half  of  each  disk.  The  pulpy  substance  presents  no  concentric  arrange- 
ment, and  consists  of  a  fine  fibrous  matrix,  containing  angular  cells,  united  to  form  a  reticular 


ARTICULATIONS  OF  THE    VERTFAiBAL   COLUMN 


271 


structure.  J.  Bland  Sutton'  calls  attention  to  the  fact  that  in  the  human  fetus  a  transverse 
ligamentous  band  crosses  the  dorsal  aspect  of  the  intervertebral  disk  and  is  continuous  with  the 
interosseous  ligaments  of  the  heads  of  the  riljs;  and  also  that  a  fetal  ligamentous  band  exists  in 
the  ventral  surface  of  the  intervertelwal  disiv  which,  after  development,  becomes  the  middle 
fasciculus  of  the  stellate  ligament.  These  liands  are  named  by  Sutton  the  posterior  conjugal 
ligaments  and  the  anterior  conjugal  ligaments. 

Intemeural  articulations  inciiule  tiie  ligaments  of  the  laminse;  articular  pro- 
cesses, spinous  processes,  and  transverse  processes. 


2.  Ligaments  Connecting  the  Lamin.e. 


Ligamenta  Subflava. 

•The  ligamenta  subflava  {Ibjamenta  intercmralia)  (Figs.  222  and  223)  are  inter- 
posed between  the  lamina?  of  the  vertebrse,  from  the  axis  to  tlie  sacrum.  They 
are  most  distinct  wlien  seen  from  tlie  interior  of  tlie  vertebral  canal;  when  viewed 
from  the  outer  surface  they  ap- 
pear sliort,  being  overlapped  by 
the  laminae.  Each  ligamentum 
subfiavum  consists  of  two  lateral 
portions,  which  commence  on 
each  side  at  the  root  of  either 
articular  process,  and  pass  back- 
ward to  the  point  where  the 
laminfe  converge  to  form  the 
spinous  process,  where  their  mar- 
gins are  in  contact  and  to  a 
certain  extent  united;  slight  in- 
tervals being  left  for  the  passage 
of  small  vessels.  These  ligaments 
consist  of  yellow  elastic  tissue, 
the  fibres  of  which,  almost  per- 
pe:idicular  in  direction,  are  at- 
tached to  the  anterior  surface  of 
the  laminse  above,  some  distance 
from  its  inferior  margin,  and  to 
the  posterior  surface,  as  well  as 
to  the  margin  of  the  lamina 
below.  In  the  cervical  region 
they  are  thin  in  texture,  but  very 
broad  and  long;  they  become 
thicker  in  the  thoracic  region, 
and  in  the  lumbar  acquire  very 
considerable  thickness.  Their 
highly  elastic  property  serves  to 
preserve  the  upright  posture  and  to  assist  in  resuming  it  after  the  spine  has  been 
flexed.  These  ligaments  do  not  exist  between  the  occiput  and  atlas  or  between 
the  atlas  and  axis. 


3.  Ligaments  Connecting  the  Articular  Processes. 
Capsular  Ligaments. 

The  capsular  ligaments  {ca-psidae  articiikires)   (Fig.  225)  are  thin  and  loose 
ligamentous  sacs,  attached  to  the  contiguous  margins  of  the  articulating  processes 

•  Ligaments:  Their  Nature  and  Morphology,  1887. 


272 


THE  ARTICULATIONS,   OR  JOINTS 


of  each  vertebra  through  the  greater  part  of  their  circumference,  and  completed 
internally  by  the  ligamenta  subflava.  They  are  longer  and  looser  in  the  cervical 
than  in  the  thoracic  or  lumbar  regions.  The  capsular  ligaments  are  lined  on 
their  inner  surface  with  synovial  membrane. 

4.  Ligaments  Connecting  the  Spinous  Processes. 

Supraspinous  Ligament. 
Ligamentum  Nuchae. 
Interspinous  Ligaments. 

The  supraspinous  ligament  (ligamentum  sicprasfinale  (Fig.  222)  is  a  strong 
fibrous  cord,  which  connects  the  apices  of  the  spinous  processes  from  the  seventh 
cervical  to  the  spinous  processes  of  the  sacrum.  It  is  thicker  and  broader  in 
the  lumbar  than  in  the  thoracic  region,  and  intimately  blended,  in  both  situa- 
tions, with  the  neighboring  aponeurosis.  The  most  superficial  fibres  of  this 
ligament  connect  three  or  four  vertebrae;  those  deeper-seated  pass  between  two 
or  three  vertebrae;  while  the  deepest  connect  the  contiguous  extremities  of  neigh- 
boring vertebrae.  It  is  continued  upward  to  the  external  occipital  protuberance 
as  the  ligamentum  nuchae. 

The  ligamentum  nuchae  is  a  fibrous  membrane  which,  in  the  neck,  represents 
the  supraspinous  ligaments  of  the  lower  vertebrte.  It  extends  from  the  external 
occipital  protuberance  and  crest  to  the  spinous  process  of  the  seventh  cervical 
vertebra.  From  its  anterior  border  a  fibrous  lamina  is  given  off,  which  is  attached 
to  the  posterior  tubercle  of  the  atlas,  and  to  the  spinous  processes  of  all  the  cervical 
vertebrae,  so  as  to  form  a  septum  between  the  muscles  on  either  side  of  the  neck. 
In  man  it  is  merely  a  rudiment  of  an  important  elastic  band  which,  in  some  of 
the  lower  animals,  serves  to  sustain  the  weight  of  the  head. 

The  interspinous  ligaments  {ligamenta  interspinalia)  (Fig.  222),  thin  and 
membranous,  are  interposed  between  the  spinous  processes.  Each  ligament 
extends  from  the  root  to  the  summit  of  each  spinous  process  and  connects  their 
adjacent  margins.  They  meet  the  ligamenta  subflava  in  front  and  the  supraspin- 
ous ligament  behind.  They  are  narrow  and  elongated  in  the  thoracic  region; 
broader,  Cjuadrilateral  in  form,  and  thicker  in  the  lumbar  region;  and  only  slightly 
developed  in  the  neck. 

5.  Ligaments  Connecting  the  Transverse  Processes. 

Intertransverse  Ligaments. 

The  intertransverse  ligaments  {ligamenta  intertransversaria)  (Fig.  235)  consist 
of  bundles  of  fibres  interposed  between  the  transverse  processes.  In  the  cervical 
region  they  consist  of  a  few  irregular,  scattered  fibres;  in  the  thoracic,  they  are 
rounded  cords  intimately  connected  with  the  deep  muscles  of  the  back;  in  the 
lumbar  region  they  are  thin  and  membranous. 

Movements  of  the  Vertebral  Column. — The  movements  permitted  in  the  vertebra 
column  are  flexion,  exteiision,  lateral  movement,  circumduction,  and  rotation. 

In  flexion  (forward  flexion),  or  movement  of  the  vertebral  column  forward,  the  anterior 
common  ligament  is  rela.\ed,  and  the  intervertebral  substances  are  compressed  in  front,  while 
the  posterior  common  ligament,  the  ligamenta  subflava,  and  the  inter-  and  supraspinous  liga- 
ments are  stretched,  as  well  as  the  posterior  fibres  of  the  intervertebral  disks.  The  interspaces 
between  the  laminte  are  widened,  and  the  inferior  articular  processes  of  the  vertebrse  above 
glide  upward  upon  the  articular  processes  of  the  vertebrae  below.  Flexion  is  the  most  extensive 
of  all  the  movements  of  the  vertebral  column. 

In  extension  (backward  flexion),  or  movement  of  the  vertebral  column  backward,  an  exacdy 
opposite  disposition  of  the  parts  take  place.  This  movement  is  not  extensive,  being  limited 
by  the  anterior  common  ligament  and  by  the  approximation  of  the  spinous  processes. 


ARTICULATION  OF  THE  ATLAS  WITH  THE  AXIS 


273 


Flexion  and  extension  are  greatest  in  the  lower  part  of  the  lumbar  region  between  the  third 
and  fourth  and  fourth  and  fifth  lumbar  vertebroe;  above  the  third  they  are  much  diminished, 
and  reach  their  minimum  in  the  middle  and  upper  part  of  the  back.  They  increase  again  in  the 
neck,  the  capability  of  motion  backward  from  the  upright  position  being  in  this  region  greater 
than  that  of  the  motion  forward,  whereas  in  the  lumbar  region  the  reverse  is  the  case. 

In  lateral  flexion,  the  sides  of  the  interveitebral  disks  are  compressed,  the  extent  of  motion 
being  liiiiiicd  by  the  resistance  offered  by  the  surrounding  ligaments  and  by  the  approximation 
of  the  traiisxcrse  i)rocesses.  This  movement  may  take  place  in  any  part  of  the  vertebral  column, 
but  has  the  greatest  range  in  the  neck  and  loins. 

Circumduction  is  limited,  and  is  produced  merely  by  a  succession  of  the  preceding  movements. 

Rotation  is  produced  by  the  twisting  of  the  intervertebral  substances;  this,  although  only 
slight  between  any  two  vertebrre,  produces  a  considerable  extent  of  movement  when  it  takes 
place  in  the  whole  length  of  the  vertebral  column,  the  front  of  the  upper  part  of  the  column 
being  turned  to  one  or  the  other  side.  This  movement  takes  place  only  to  a  slight  extent  in  the 
neck,  but  is  more  .pronounced  in  the  upper  part  of  the  thoracic  region,  and  is  altogether  absent  in 
the  lumbar  region.  It  is  thus  seen  that  the  cervical  region  enjoys  the  greatest  extent  of  each 
variety  of  movement,  flexion  and  extension,  especially,  being  very  extensive.  In  the  thoracic 
region  the  three  movements  of  flexion,  extension,  and  circumduction  are  permitted  only  to  a 
slight  extent,  while  rotation  is  very  extensive  in  the  upper  part  and  ceases  below.  In  the  lumbar 
region  there  is  extensive  flexion,  extension,  and  lateral  movement,  but  no  rotation. 

The  movements  permitted  are  mainly  due  to  the  shape  and  position  of  the  articulating  pro- 
cesses. In  the  loins  the  inferior  articulating  processes  are  turned  outward  and  are  embraced  by 
the  superior;  this  renders  rotation  in  tliis  region  of  the  vertebral  column  impossible,  while  there  is 
nothing  to  prevent  a  sliding  upward  and  downward  of  the  surfaces  on  each  other,  so  as  to  allow 
of  flexion  and  extension.  In  the  thoracic  region,  on  the  other  hand,  the  articulating  processes,  by 
their  direction  and  mutual  adaptation,  especially  at  the  upper  part  of  the  series,  permit  of  rotation, 
but  prevent  extension  and  flexion,  while  in  the  cervical  region  the  greater  obliquity  and  lateral 
slant  of  the  articular  processes  allow  not  only  flexion  and  extension,  but  also  rotation. 

The  principal  muscles  which  produce  flexion  are  the  Sternomastoid,  Rectus  capitis  anticus 
major,  and  Longus  colli ;  the  Scaleni ;  the  abdominal  muscles  and  the  Psoas  magnus.  Extension 
is  produced  by  the  fourth  layer  of  the  muscles  of  the  back,  assisted  in  the  neck  by  the  Splenius, 
Semispinales  dorsi  et  colli,  and  the  Multifidus  spinae.  Lateral  motion  is  produced  by  the  fourth 
layer  of  the  muscles  of  the  back,  by  the  Splenius  and  the  Scaleni,  the  Quadratus  lumborum 
and  Psoas  magnus,  the  muscles  of  one  side  only  acting;  and  rotation  by  the  action  of  the  fol- 
lowing muscles  of  one  side  only — viz.,  the  Sternomastoid,  the  Rectus  capitis  anticus  major,  the 
Scaleni,  the  Multifidus  spinae,  the  Complexus,  and  the  abdominal  muscles. 

II.  Articulation  of  the  Atlas  with  the  Axis  (Articulatio  Atlantoepistrophica). 

The  articulation  of  the  atlas  with  the  axis  is  of  a  complicated  nature,  compris- 
ing no  fewer  than  four  distinct  joints.  There  is  a  pivot  articulation  between  the 
odontoid  process  of  the  axis  and  the  ring  formed  between  the  anterior  arch  of 


Fig.  224. — Articulation  between  odontoid  process  and  atlaa. 


the  atlas  and  the  transverse  ligament  (Fig.  224).     Here  there  are  two  joints — one 
in  front  between  the  posterior  surface  of  the  anterior  arch  of  the  atlas  and  the  front 

18 


274 


THE  ARTICULATIONS,   OR  JOINTS 


of  the  odontoid  process  (atlanto-odontoid  joint);  the  other  between  the  anterior 
surface  of  the  transverse  ligament  and  the  back  of  the  process  (syndosmo-odon- 
toid  joint).  Between  the  articular  processes  of  the  two  bones  there  is  a  double 
arthroidal  or  gliding  joint.     The  ligaments  which  connect  these  bones  are  the 


Anterior  Atlanto-axial. 
Posterior  Atlanto-axial. 


Transverse. 
Two  Capsular. 


The  anterior  atlanto-axial  ligament  (Figs.  225  and  228)  is  a  strong,  membranous 
layer,  attached,  above,  to  the  lower  border  of  the  anterior  arch  of  the  atlas;  below, 
to  the  base  of  the  odontoid  process  and  to  the  front  of  the  body  of  the  axis.  It  is  ■ 
strengthened  in  the  middle  line  by  a  rounded  cord,  which  is  attached,  above, 
to  the  tubercle  on  the  anterior  arch  of  the  atlas,  and  heloiv  to  the  body  of  the  axis, 
being  a  continuation  upward  of  the  anterior  common  ligament  of  the  vertebral 
column.     The  ligament  is  in  relation,  in  front,  with  the  Recti  antici  majores. 

The  posterior  atlanto-axial  ligament  (Figs.  225  and  228)  is  a  broad  and  thin 
membranous  layer,  attached,  above,  to  the  lower  border  of  the  posterior  arch 
of  the  atlas;  below,  to  the  upper  edge  of  the  laminte  of  the  axis.  This  ligament 
supplies  the  place  of  the  ligamenta  subflava,  and  is  in  relation,  behind,  with  the 
Inferior  oblique  muscles. 

The  transverse  ligament  of  the  atlas'  (ligamentum  transversum  atlantis)  (Figs. 
227  and  228)  is  a  thick,  strong  band,  which  arches  across  the  ring  of  the  atlas, 
and  serves  to  retain  the  odontoid  process  in  firm  connection  with  its  anterior 


«L  LIGAMENT        f  "^'^    rtl'Sj 


ANTERIOR    CONDYLAR 


Fig.  225. — Occipital  bone 


TRANSVERSE 

CESS  OF 
ATLAS 


JOIN- 

r  BETWEEI 

lODY  Of 

■VERT 

"EBR 

AND 

INTEI 

=tVER 

TEBHAL  F 

IBRO 

CARTI 

LAGI 

TRANSVERSE  PROCESS 
THrRD  CERVICAL 
HTEBRA 


ical  vertebra  with  ligaments,  from  in  front.     (Spalteholz.) 


arch.     This  ligament  is  flattened  from  before  backward,  broader  and  thicker  in 

st,',rw''^n,?r»!S^^t°''tr^t"f  •*"  describe  the  transverse  ligament  with  those  of  the  atlas  and  axis;  but  the 
?h^  ,forteb.,1  n^t^^"''''''  *''*,  'I  '5  ™''"^  ^  •i°''"°"  °f  'he  mechanism  by  which  the  movements  of  the  head  on 
«?;l'/^LTlire\trw;?nt£i1^tt^e°r*b^  "^<^  ^"^^  '^^  ^^^  --^^^  ^'^^^^  '<>  "-^  ^'^^^^ 


ARTICULATION  OF  THE  ATLAS  WITH  THE  OCCIPITAL  BONE     275 

the  middle  than  at  either  extremity,  and  firmly  attached  on  each  side  to  a  small 
tubercle  on  the  inner  surface  of  the  lateral  mass  of  the  atlas.  As  it  crosses  the 
odontoid  process,  a  small  fasciculus  is  derived  from  its  upper,  and  another  from 
its  lower  border;  the  former  passing  upward,  to  be  inserted  into  the  anterior  sur- 
face of  the  foramen  magnum  of  the  occipital  bone;  the  latter,  downward,  to  be 
attached  to  the  posterior  surface  of  the  body  of  the  axis;  hence,  the  whole  ligament 
has  received  the  name  of  cruciform  ligament  {Ugamentum  cnwiahim  atlantis). 
A  synovial  surface  is  interposed  between  the  odontoid  process  and  the  trans- 
verse ligament,  and  one  is  placed  between  the  anterior  surface  of  the  odontoid 
process  and  the  anterior  arch  of  the  atlas.  The  transverse  ligament  divides  the 
vertebral  foramen  of  the  atlas  into  two  unequal  compartments;  of  these,  the  pos- 
terior and  larger  serves  for  the  transmission  of  the  cord  and  its  membranes  and 
the  spinal  accessory  nerves;  the  anterior  and  smaller  contains  the  odontoid  pro- 
cess. Since  the  space  between  the  anterior  arch  of  the  atlas  and  the  transverse 
ligament  is  smaller  at  the  lower  part  than  the  upper  (because  the  transverse 
lio-ament  embraces  tightly  the  narrow  neck  of  the  odontoid  process),  this  process 
is  retained  in  firm  connection  with  the  adas  after  all  the  other  ligaments  have  been 
divided. 

The  capsular  ligaments  (capsulae  articulares)  (Figs.  226  and  227)  are  two  thin 
and  loose  capsules,  connecting  the  lateral  masses  of  the  adas  with  the  superior 
articular  surfaces  of  the  axis,  the  fibres  being  strengthened  at  the  posterior  and 
inner  part  of  each  articulation  by  an  accessory  ligament,  which  is  attached  below 
to  the  body  of  the  axis  near  the  base  of  the  odontoid  process. 

Synovial  Membranes  (Fig.  224). — There  are  four  sjoiovial  membranes  in  this  articulation — 
one  linhig;  the  inner  surface  of  each  of  the  capsular  Hgaments;  one  between  the  anterior  surface 
of  the  odontoid  process  and- the  anterior  arch  of  the  atlas;  and  one  between  the  posterior  surface 
of  the  odontoid  process  and  the  transverse  ligament.  The  latter  often  communicates  with 
those  between  the  condyles  of  the  occipital  bone  and  the  articular  surfaces  of  the  atlas. 

Movements. — This  joint  allows  the  rotation  of  the  atlas  (and,  with  it,  of  the  cranium)  upon 
the  axis,  the  extent  of  rotation  being  limited  by  the  odontoid  ligaments. 

The  principal  muscles  by  which  this  action  is  produced  are  the  Sternomastoid  and  Com- 
plexus  of  one  side,  acting  with  the  Rectus  capitis  anticus  major,  Splenius,  Trachelomastoid, 
Rectus  capitis  posticus  major,  and  Inferior  oblique  of  the  other  side. 


ARTICULATIONS  OF  THE  VERTEBRAL  COLUMN   WITH  THE  CRANIUM. 

The  ligaments  connecting  the  vertebral  column  with  the  cranium  may  be  divided 
into  two  sets — those  connecting  the  occipital  bone  with  the  atlas,  and  those  con- 
necting the  occipital  bone  with  the  axis. 

III.  Articulation  of  the  Atlas  with  the  Occipital  Bone  (Articulatio 
Atlanto-occipitalis) . 

This  articulation  is  a  double  condyloid  joint.     Its  ligaments  are  the 

Anterior  Occipito-atlantal.  Posterior  Occipito-atlantal. 

Two  Capsular. 

The  anterior  occipito-atlantal  ligament  (viembrana  atlanfooccipitalis  anterior) 
(Figs.  225  and  22S)  is  a  broad  membranous  layer,  composed  of  densely  woven 
fibres,  which  passes  between  the  anterior  margin  of  the  foramen  magnum  above, 
and  the  whole  length  of  the  upper  border  of  the  anterior  arch  of  the  atlas  below. 
Laterally,  it  is  continuous  with  the  capsular  ligaments.     In  the  middle  line  in 


276 


THE  ARTICULATIONS,   OB  JOINTS 


front  it  is  strengthened  by  a  strong,  narrow,  rounded  cord,  which  is  attached, 
above,  to  the  basilar  process  of  the  occiput,  and,  below,  to  the  tubercle  on  the 
anterior  arch  of  the  atlas,  and  which  is  a  continuation  of  the  anterior  common 
ligament.  This  ligament  is  in  relation,  in  front,  with  the  Recti  antici  minores; 
hehiyid,  with  the  odontoid  ligaments. 

The  posterior  occipito-atlantal  ligament  (membrana  atlanto-occipitalis  posterior, 
posterior  occipito-atloid  ligament)  (Figs.  226  and  228)  is  a  very  broad  but  thin 
membranous  lamina  intimately  blended  with  the  dura.  It  is  connected,  above, 
to  the  posterior  margin  of  the  foramen  magnum;  heloic,  to  the  upper  border  of 
the  posterior  arch  of  the  atlas.  This  ligament  is  incomplete  at  each  side,  and 
forms,  with  the  groove  in  the  upper  surface  of  the  posterior  arch,  an  opening  for 
the  vertebral  artery  and  suboccipital  nerve.  The  fibrous  band  which  arches  over 
the  artery  and  nerve  sometimes  becomes  ossified.  The  ligaments  are  in  relation, 
behind,  with  the  Recti  postici  minores  and  Obliqui  superiores;  in  front,  with  the 
dura  of  the  vertebral  canal,  to  which  they  are  intimately  adherent. 


POSTERIOR  OC 

CIPITO-ATLANTA 

LIGAMEN 


POSTERIOR  OC- 
CIPITO-ATLANTAL 
LIGAMENT 


TRANSVERSE 
PROCESS  OF 
ATLAS 


Fig.  226. — Occipital  bone,  first  and  second  cervical  vertebree  with  ligaments  from  behind.     (Spalteholz.) 

The  capsular  ligaments  (capsulae  articulares)  (Fig.  227)  surround  the  condyles 
of  the  occipital  bone,  and  connect  them  with  the  articular  processes  of  the  atlas; 
they  consist  of  thin  and  loose  capsules,  which  enclose  the  synovial  membranes 
of  the  articulations. 


Synovial  Membranes. — There  are  two  synovial  membranes  in  this  articulation,  one  lining  the 
inner  surface  of  each  of  the  capsular  ligaments.  These  occasional!)'  communicate  with  that 
between  the  posterior  surface  of  the  odontoid  process  and  the  transverse  ligament. 

Movements. — The  movements  permitted  in  this  joint  are  flexion  and  extension,  which  give 
rise  to  the  ordinary  forward  and  backward  nodding  of  the  head.  Slight  lateral  motion  to  one 
or  the  other  side  may  also  take  place.  When  either  of  these  actions  is  carried  beyond  a  slight 
extent,  the  whole  of  the  cervical  portion  of  the  spine  assists  in  its  production.  Flexion  \s  mainly 
produced  by  the  action  of  the  Rectus  capitis  anticus  major  et  minor  and  the  Sternomastoid 
muscles;  extension  by  the  Rectus  capitis  posticus  major  et  minor,  the  Obliquus  superior,  the 
Complexus,  Splenius,  and  upper  fibres  of  the  Trapezius.  The  Recti  laterales  are  concerned  in 
the  lateral  movement,  assisted  by  the  Trapezius,  Splenius,  Complexus,  and  the  Sternomastoid 
of  the  same  side,  all  acting  together.  According  to  Cruveilhier,  there  is  a  slight  amount  of 
rotation  in  this  joint. 


ARTICULATION  OF  THE  AXIS  WITH  THE  OCCIPITAL  BONE     277 

IV.  Articulation  of  the  Axis  with  the  Occipital  Bone. 

The  ligaments  of  this  articulation  are  the 


Occipito-axial. 


Three  Odontoid. 


To  expose  these  ligaments  the  vertebral  canal  should  be  laid  open  by  removing 
the  posterior  arch  of  the  atlas,  the  laminae  and  spinous  process  of  the  axis,  and 
the  portion  of  the  occipital  bone  behind  the  foramen  magnum,  as  seen  in  Fig.  227. 


Fig.  227. — Occipito-axial  and  atlanto-axial  ligaments.     Posterior  view,  obtained  by 
the  vert«bri3e  and  the  posterior  part  of  the  skull. 


^•ing  the  arches  of 


The  posterior  occipito-axial  ligament  (membrana  tectoria)  (Figs.  227  and  22^) 
is  situated  within  the  vertebral  canal.  It  is  a  broad,  strong  band,  which  covers 
the  odontoid  process  and  its  ligaments,  and  appears  to  be  a  prolongation  upward 
of,  or  a  membrane  due  to  fusion  with,  the  posterior  common  ligament  of  the  spine. 
It  is  attached,  below,  to  the  posterior  surface  of  the  body  of  the  axis,  and,  becom- 
ing expanded  as  it  ascends,  is  inserted  into  the  basilar  groove  of  the  occipital 
bone,  in  front  of  the  foramen  magnum,  where  it  becomes  blended  with  the  dura 
of  the  skull. 

Relations. — By  its  anterior  surface  with  the  transverse  Hgament;  by  its  'posterior  surface 
with  the  posterior  common  ligament. 

The  lateral  odontoid  ligaments  (ligamenta  alaria)  (Figs.  227  and  228)  are 
strong,  rounded,  fibrous  cords,  which  arise  one  on  either  side  of  the  upper  part  of 
the  odontoid  process,  and,  passing  obliquely  upward  and  outward,  are  inserted 
into  the  rough  depressions  on  the  inner  side  of  the  condyles  of  the  occipital  bone. 
In  the  triangular  interval  left  between  these  ligaments  another  strong  fibrous 


278 


THE  ARTICULATIONS,   OR  JOINTS 


cord,  the  middle  odontoid  ligament  (ligavientum  apicis  dentis),  may  be  seen,  which 
passes  ahnost  perpendicularly  from  the  apex  of  the  odontoid  process  to  the 
anterior  margin  of  the  foramen  magnum,  being  intimately  blended  with  the 
deep  portion  of  the  anterior  occipito-atlantal  ligament  and  upper  fasciculus  of 
the  transverse  ligament  of  the  atlas. 

Movements. — The  odontoid  ligaments  serve  to  limit  tlie  extent  to  which  rotation  of  the 
cranium  may  be  carried;  hence,  they  have  received  the  name  of  check  ligaments. 

In  addition  to  these  ligaments,  which  connect  the  atlas  and  axis  to  the  skull,  the  ligamentum 
nuchae  must  be  regarded  as  one  of  the  ligaments  by  which  the  vertebral  column  is  connected  with 
the  cranium.    It  is  described  on  page  272. 


L-VE-  OF  POSTERIOR  COMMON 
Lf  T      L  PARATED   FROM  THE 
LH   OH  OCCrPITO-AXIAL  LIGAMENT 


ANTERIOR  OCCIFITO    ■        Js     ^^Li 
ITLANTAL   LIGA^  ENT     '         (v^  V 


ANTERIOR  COM 


Fig.  228.— Median  sagittal  section  through  the  occipital  bone  and  first  three  cervical  vertebrae  with  ligaments. 

(Spalteholz). 

Applied  Anatomy.— The  ligaments  which  unite  the  component  parts  of  the  vertebrre  together 
are.so  strong,  and  these  bones  are  so  interlocked  by  the  arrangement  of  their  articulating  processes, 
that  dislocation  is  very  uncommon,  and,  indeed,  "unless  accompanied  hy  fracture,  seldom  occurs, 
except  in  the  upper  part  of  the  neck.  Dislocation  of  the  occiput  from  the  atlas  has  only  been 
recorded  m  one  or  two  cases;  but  dislocation  of  the  atlas  from  the  axis,  with  rupture  of  the  trans- 
verse ligament,  is  much  more  common;  it  is  the  mode  in  which  death  is  produced  in  some  cases 
ot  execution  by  hanging.  In  the  lower  part  of  the  neck— that  is,  below  the  third  cervical  vertebra 
—dislocation  unattended  by  fracture  occasionally  takes  place. 


TEMPOBOMANDIB ULAR  ARTICULATION 


279 


V.  Temporomandibular  Articiilation  (Articulatio  Mandibularis) . 

This  is  a  ginglymo-arthrodial  joint;  the  parts  entering  into  its  formation  on 
each  side  are,  above,  the  anterior  part  of  the  glenoid  cavity  of  the  temporal  bone 
and  the  eminentia  articularis;  and,  below,  the  condyle  of  the  mandible.  The 
ligaments  are  the  following: 


External  Lateral. 
Internal  Lateral. 


Articular  Disk 


Stylomandibular. 
Capsular. 


The  external  lateral  ligament  {ligamenium  temporomaitdibulare)  (Fig.  229) 
is  a  short,  thin,  and  narrow  fasciculus,  attached,  above,  to  the  outer  surface  of 
the  zygoma  and  to  the  tubercle  on  its  lower  border;  beloiv,  to  the  outer  border  of 
the  neck  and  to  the  tubercle  at  the  outer  extremity  of  the  condyle  of  the  mandible. 
It  is  broader  above  than  below;  its  fibres  are  placed  parallel  to  one  another, 


ss»m\    ^        ^^^^     Temporal    bone.     k\      ,    ,A 


Fig.  229. — Tempoi 


and  directed  obliquely  downward  and  backward.  Externally,  it  is  covered  by 
the  parotid  gland  and  by  the  integument.  Internally  it  is  in  relation  with  the 
capsular  ligament,  of  which  it  is  an  accessory  band,  and  from  which  it  is  not 
separable. 

The  internal  lateral  ligament  (licfamentum  sphenomandibulare)  (Fig.  230)  is 
.a  flat,  thin  band  which  is  attached  above  to  the  spine  of  the  sphenoid  bone,  and, 
becoming  broader  as  it  descends,  is  inserted  into  the  margin  of  the  dental  foramen 
and  the  portion  of  bone,  the  lingula,  which  overhangs  the  foramen  in  front. 
This  ligament  is  not  a  true  articular  ligament,  but  is  an  accessory  band,  contrib- 
uted to  the  capsule  by  the  deep  cervical  fascia.  Its  outer  surface  is  in  relation, 
above,  with  the  External  pterygoid  muscle;  lower  down  it  is  separated  from  the 
neck  of  the  condyle  by  the  internal  maxillary  artery;  and  still  more  inferiorly, 
the  inferior  dental  vessels  and  nerve  separate  it  from  the  ramus  of  the  mandible. 
The  inner  surface  is  in  relation  with  the  Internal  pterygoid. 


280 


THE  ARTICULATIONS,   OB  JOINTS 


Fig.  230. — Temporomandibular  articulation.      Internal 


The  stylomandibular  ligament  Qigamentum  stylomandibulare)  (Fig.  230)  is  a 
specialized  band  of  the  cervical  fascia,  which  extends  from  near  the  apex  of  the 
styloid  process  of  the  temporal  bone  to  the  angle  and  posterior  border  of  the 
ramus  of  the  mandible,  between  the  Masseter  and  Internal  pterygoid  muscles. 
This   ligament   separates   the   parotid   from   the   submaxillary   gland,   and    has 

attached  to  its  inner  side  part  of 
the  fibres  of  origin  of  the  Stylo- 
glossus muscle.  Although  usually 
classed  among  the  ligaments  of 
the  mandible,  it  can  be  considered 
only  as  an  accessory  to  the  articu- 
lation. 

The  capsular  ligament  {cap- 
sula  articularis)  (Figs.  229  and 
230)  forms  a  thin  and  loose  cap- 
sule, passing  from  the  circum- 
ference of  the  glenoid  cavity  and 
the  articular  surface  immediately 
in  front  to  the  upper  margin  of 
the  articular  disk,  and  from  the 
lower  margin  of  the  articular  disk 
to  the  neck  of  the  condyle  of  the 
mandible.  It  consists  of  very 
thin  fibres,  and  is  complete.  It 
forms  two  joint  cavities,  distinct 
from  each  other,  and  separated 
by  the  articular  disk.  So  thin  is 
it  that  it  is  hardly  to  be  considered  as  a  distinct  ligament;  it  is  thickest  at  the 
back  part,  and  thinnest  on  the  inner  side  of  the  articulation.' 

The  articular  meniscus  (discus  articularis)  (Fig.  231)  is  a  thin  plate  of  an  oval 
form,  placed  horizontally  between  the  condyle  of  the  mandible  and  the  glenoid 
cavity.  Its  upper  surface  is  con- 
cavo-convex from  before  backward, 
and  a  little  convex  transversely,  to 
accommodate  itself  to  the  form  of 
the  glenoid  cavity.  .  Its  under  sur- 
face, where  it  is  in  contact  with  the 
condyle,  is  concave.  Its  circumfer- 
ence is  connected  to  the  capsular 
ligament,  and  in  front  to  the  tendon 
of  the  External  pterygoid  muscle. 
It  is  thicker  at  its  circumference, 
especially  behind,  than  at  its  centre. 
The  fibres  of  which  it  is  composed 
have  a  concentric  arrangement,  more 
apparent  at  the  circumference  than 
at  the  centre.  Its  surfaces  are 
smooth.  It  divides  the  joint  into  two  cavities,  each  of  which  is  furnished  with  a 
separate  synovial  membrane  reflected  from  the  capsular  ligament. 

Synovial  Membranes  (Fig.  231). — The  synovial  membranes,  tivo  in  number,  are  placed, 
one  above,  and  the  other  below,  the  articular  disk.  The  upper  one,  the  larger  and  looser  of  the 
two,  is  continued  from  the  margin  of  the  cartilage  covering  the  glenoid  cavity  and  eminentia 

'  Sir  G.  Humphry  describes  the  internal  portion  of  the  capsular  ligament  separately  as  the  short  internal 
lateral  ligament;  and  it  certainly  seems  as  deserving  of  a  separate  description  as  is  the  external  lateral  ligament. 


THE  TEMPOROMANDIBULAR  ARTICULATION  281 

articularis  on  to  the  upper  surface  of  the  articular  disk.  The  lower  one  passes  from  the  under 
surface  of  the  articular  disk  to  the  neck  of  the  condyle  of  the  mandible,  being  prolonged  down- 
ward a  little  farther  behind  than  in  front.  The  articular  disk  is  sometimes  perforated  in  its 
centre;  the  two  synovial  sacs  then  communicate  with  each  other. 

The  nerves  of  this  joint  are  derived  from  the  auriculotemporal  and  masseteric  branches 
of  the  inferior  maxillary.  The  arteries  are  derived  from  the  temporal  branch  of  the  external 
carotid. 

Movements. — The  movements  possible  in  this  articulation  are  very  extensive.  Thus,  the 
mandible  may  be  depressed  or  elevated,  or  it  may  be  carried  forward  or  backward.  It  must  be 
borne  in  mind  that  there  are  two  distinct  joints  in  this  articulation — that  is  to  say,  one  between 
the  condyle  of  the  mandible  and  the  articular  disk,  and  another  between  the  disk  and  the  glenoid 
fossa;  when  the  mandible  is  depressed,  as  in  o])e'ning  the  mouth,  the  movements  which  take  place 
in  these  two  joints  are  not  the  same.  In  the  lower  compartment,  that  between  the  condyle  and 
the  articular  disk,  the  movement  is  of  a  ginglymoid  or  hinge-like  character,  the  condyle  rotating 
on  a  transverse  axis  on  the  articular  disk;  while  in  the  upper  compartment  the  movement  is  of 
a  gliding  character,  the  articular  disk,  together  with  the  condyle,  gliding  forward  on  to  the 
eminentia  articularis.  These  two  movements  take  place  simultaneously — the  condyle  and 
articular  disk  move  forward  on  the  eminence,  and  at  the  same  time  the  condyle  revolves  on 
the  articular  disk.  In  the  opposite  movement  of  shutting  the  mouth  the  reverse  action  takes 
place;  the  articular  disk  glides  back,  carrying  the  condyle  with  it,  and  this  at  the  same  time 
revolves  back  to  its  former  position.  When  the  mandible  is  carried  horizontally  forward,  as 
in  protruding  the  lower  incisors  in  front  of  the  upper,  the  movement  takes  place  principally 
in  the  upper  compartment  of  the  joint — the  articular  disk,  carrying  with  it  the  condj'le,  glides 
forward  on  the  glenoid  fossa.  This  is  because  this  movement  is  mainly  effected  by  the  External 
pterygoid  muscles,  which  are  inserted  into  both  condyle  and  articular  disk.  The  grinding  or 
chewing  movement  is  produced  by  the  alternate  movement  of  one  condyle,  with  its  disk,  for- 
,  ward  and  backward,  while  the  other  condyle  moves  simultaneously  in  the  opposite  direction; 
at  the  same  time  the  condyle  undergoes  a  vertical  rotation  on  its  own  axis  on  the  disk  in  the 
lower  compartment.  One  condyle  advances  and  rotates,  the  other  condyle  recedes  and  rotates, 
in  alternate  succession. 

The  mandible  is  depressed  by  its  own  weight,  assisted  by  the  Platysma,  the  Digastric,  the 
Mylohyoid,  and  the  Geniohyoid  muscles.  It  is  elevated  by  the  anterior  part  of  the  Temporal, 
Masseter,  and  Internal  pterygoid  muscles.  It  is  drawn  forward  by  the  simultaneous  action  of 
the  External  pterygoid  and  the  superficial  fibres  of  the  Masseter;  and  it  is  drawn  backward  by 
the  deep  fibres  of  the  Masseter  and  the  posterior  fibres  of  the  Temporal  muscles.  The  grinding 
movement  is  caused  by  the  alternate  action  of  the  two  External  pterygoids. 

Surface  Form. — The  temporomandibular  articulation  is  quite  superficial,  situated  below  the 
base  of  the  zygoma,  in  front  of  the  tragus  and  external  auditory  meatus,  and  behind  the  posterior 
border  of  the  upper  part  of  the  Masseter  muscle.  Its  exact  position  can  be  at  once  ascertained 
by  feeling  for  the  condyle  of  the  mandible,  the  working  of  which  can  be  distinctly  felt  in  the 
movements  of  the  mandilile  in  opening  and  shutting  the  mouth.  When  the  mouth  is  opened 
wide,  the  condyle  advances  out  of  the  glenoid  fossa  on  to  the  eminentia  articularis,  and  a  depres- 
sion is  felt  in  the  situation  of  the  joint. 

Applied  Anatomy. — Genuine  dislocation  of  the  mandible  is  almost  always  forward.  Croker, 
King,  and  Theim,  however,  have  reported  posterior  displacement.  Dislocation  is  caused  by  vio- 
lence or  muscular  action.  When  the  mouth  is  open,  the  condyle  is  situated  on  the  eminentia 
articularis,  and  any  sudden  violence,  or  even  a  sudden  muscular  spasm,  as  during  a  convulsive 
yawn,  may  displace  the  condyle  forward  into  the  zygomatic  fossa.  The  displacement  may  be 
unilateral  or  bilateral,  according  as  one  or  both  of  the  condyles  is  displaced.  The  latter  of  the 
two  is  the  more  common.  The  articular  disk  adheres  to  the  condyle  until  it  passes  over  the 
eminentia  articularis,  but  at  this  point  remains  behind. 

Sir  Astley  Cooper  described  a  condition  which  he  termed  "subluxation."  It  occurs  princi- 
pally in  delicate  women,  and  is  belived  by  some  to  be  due  to  the  relaxation  of  the  ligaments, 
permitting  too  free  movement  of  the  bone.  Others  believe  it  is  due  to  displacement  of  the  articular 
disk.  Still  others  attribute  the  symptoms  to  gouty  or  rheumatic  changes  in  the  joint.  In  close 
relation  to  the  condyle  of  the  mandible  is  the  external  auditory  meatus  and  the  tympanum; 
any  force,  therefore,  applied  to  the  bone  is  liable  to  be  attended  with  damage  to  these  parts,  or 
inflammation  in  the  joint  may  extend  to  the  ear,  or,  on  the  other  hand,  inflammation  of  the  middle 
ear  may  involve  the  articulation  and  cause  its  destruction,  thus  leading  to  ankylosis  of  the  joint. 
In  children,  arthritis  of  this  joint  may  follow  the  exanthemata,  and  in  adults  it  occurs  as  the 
result  of  some  constitutional  conditions,  as  rheumatism  or  gout.  The  temporomandibular 
joint  is  also  occasionally  the  seat  of  osteoarthritis,  leading  to  great  suffering  during  efforts  of  mas- 
tication. A  peculiar  affection  sometimes  attacks  the  neck  and  condyle  of  the  mandible,  consisting 
in  hypertrophy  and  elongation  of  these  parts  and  consequent  protrusion  of  the  chin  to  the  opposite 
side. 


282 


THE  ARTICULATIONS,   OR  JOINTS 


VI.  Articulations  of  the  Ribs  with  the  Vertebrae  or  the  Costovertebral 
Articulations  (Articulationes  Costovertebrales). 

The  articulations  of  the  ribs  with  the  vertebral  column  may  be  divided  into 
two  sets:  (1)  Those  which  connect  the  heads  of  the  ribs  with  the  bodies  of  the 
vertebrae — costocentral.  (2)  Those  which  connect  the  necks  and  tubercles  of  the 
ribs  with  the  transverse  processes — costotransverse. 


1.  Costocentral  Articulations  (Articulationes  Capitulorum) 
(Figs.  232  and  233). 

These  constitute  a  series  of  arthrodial  joints,  formed  by  the  articulation  of  the 
heads  of  the  ribs  with  the  cavities  on  the  contiguous  margins  of  the  bodies  of  the 


Fig.  232.— Vertebral  column 


(Spalteholz.) 


thoracic  vertebras  and  the  intervertebral  substance  between  them,  except  in  the 
case  of  the  first,  tenth,  eleventh,  and  twelfth  ribs,  where  the  cavity  is  formed 
by  a  single  vertebra.     The  bones  are  connected  by  the  following  ligaments: 

Anterior  Costovertebral  or  Stellate. 
Capsular.  Intra-articular 

The  anterior  costovertebral  or  stellate  ligament  (ligamentum  capituli  costae 
radiatum)  (Figs.  232  and  235)  connects  the  anterior  part  of  the  head  of  each 
rib  with  the  sides  of  the  bodies  of  two  vertebrae  and  the  intervertebral  disk 
between  them.  It  consists  of  three  flat  bundles  of  ligamentous  fibres,  which  are 
attached  to  the  anterior  part  of  the  head  of  the  rib,  just  beyond  the  articular 


ARTICULATIONS  OF  THE  BIBS  WITH  THE  VEBTEBBJE     283 

surface.  The  superior  fibres  pass  upward  to  be  connected  with  the  body  of 
the  vertebra  above;  the  inferior  one  descends  to  the  body  of  the  vertebra  below; 
and  the  middle  one,  the  smallest  and  least  distinct,  passes  horizontally  inward, 
to  be  attached  to  the  intervertebral  substance. 

On  the  first  rib,  which  articulates  with  a  single  vertebra,  this  ligament  does 
not  present  a  distinct  division  into  three  fasciculi;  its  fibres,  however,  radiate, 
and  are  attached  to  the  body  of  the  last  cervical  vertebra,  as  well  as  to  the  body 
of  the  vertebra  with  which  the  rib  articulates.  In  the  tenth,  eleventh,  and  twelfth 
ribs  also,  which  likewise  articulate  with  a  single  vertebra,  the  division  does  not 
exist;  but  the  fibres  of  the  ligament  in  each  case  radiate  and  are  connected  with 
the  vertebra  above,  as  well  as  that  with  which  the  ribs  articulate. 

Relations. — In  front,  with  the  thoracic  ganglia  of  the  sympathetic,  the  pleura,  and,  on  the 
right  side,  with  the  vena  azygos  major;  behind,  with  the  interarticular  ligament  and  synovial 
membranes. 


The  capsular  ligament  (capsula  articularis)  is  a  thin  and  loose  ligamentous 
bag,  which  surrounds  the  joint  between  the  head  of  the  rib  and  the  articular 
cavity  formed  by  the  inter- 
vertebral disk  and  the  ad- 
jacent vertebra.  It  is  very 
thin,  firmly  connected  with 
the  anterior  ligament,  and 
most  distinct  at  the  upper 
and  lower  parts  of  the 
articulation.  Behind,  some 
of  its  fibres  pass  through 
the  intervertebral  foramen 
to  the  back  of  the  inter- 
vertebral disk.  This  is  the 
}\om.o\ogueoH\\e.liga'mentum 
conjugale  of  some  mammals, 
which  unites  the  heads  of 
opposite  ribs  'across  the 
back  of  the  intervertebral 
disk. 

The  intra-articular  liga- 
ment (Jigamentum  capifidi 
costae  interarticidare)  (Figs. 
23.3  and  234)  is  situated  in 
the  interior  of  the  joint.  It 
consists  of  a  short  band  of 

fibres,  flattened  from  above  downward,  attached  by  one  extremity  to  the  sharp 
crest  which  separates  the  two  articular  facets  on  the  head  of  the  rib,  and  by  the 
other  to  the  intervertebral  disk.  It  divides  the  joint  into  two  cavities,  which 
have  no  communication  with  each  other.  For  the  first,  tenth,  eleventh,  and 
twelfth  ribs  the  intra-articular  ligament  does  not  exist;  consequently  there  is 
but  one  synovial  membrane. 

Synovial  Membranes  (Figs.  233  and  234). — There  are  two  syno\'iaI  membranes  in  each  of 
the  articulations  in  which  there  is  an  intra-articular  ligament,  one  on  each  side  of  this  structure. 


284 


THE  ARTICULATIONS,    OB  JOINTS 


2.  Costotransverse  Articulations  (Articulationes  Costotransversariae) 

(Fig.  234). 

The  articular  portion  of  the  tubercle  of  the  rib  and  adjacent  transverse  process 
form  an  arthrodial  joint. 

For  the  eleventh  and  twelfth  rihs  this  articulation  is  wanting. 
The  ligaments  connecting  these  parts  are  the 


Anterior  or  Superior  Costotransverse. 
Middle  Costotransverse  (Interosseous). 


Posterior  Costotransverse. 
Capsular. 


The  anterior  or  superior  ligament  (ligamentum  costotransversarium  anterius) 
(Figs.  234  and  235)  consists  of  two  sets  of  fibres;  the  one  (anterior)  is  attached 
below  to  the  sharp  crest  on  the  upper  border  of  the  neck  of  each  rib,  and  passes 


Fig.  234. — Costotransverse  articulation.     Seen  from  above. 

obliquely  upward  and  outward  to  the  lower  border  of  the  transverse  process 
immediately  above;  the  other  (posterior)  is  attached  below  to  the  neck  of  the  rib, 
and  passes  upward  and  inward  to  the  base  of  the  transverse  process  and  outer 
border  of  the  lower  articular  process  of  the  vertebra  above. 

The  first  rib  has  no  anterior  costotransverse  ligament.  For  the  twelfth  rib  the 
ligament  is  absent  or  is  a  mere  vestige. 

Relations. — This  ligament  is  in  relation,  in  front,  with  the  intercostal  vessels  and  nerves; 
behind,  with  the  Longissimus  dorsi  muscle.  Its  internal  border  is  thickened  and  free,  and  bounds 
an  aperture  through  which  pass  the  posterior  branches  of  the  intercostal  vessels  and  nerves.  Its 
external  border  is  continuous  with  a  thin  aponeurosis  which  covers  the  External  intercostal 
muscle. 

The  middle  costotransverse  or  interosseous  ligament  (ligamentum  colHcostae} 
(Fig.  234)  consists  of  short  but  strong  fibres  which  pass  between  the  rough  surface 
on  the  posterior  part  of  the  neck  of  each  rib  and  the  anterior  surface  of  the  ad- 
jacent transverse  process.     In  order  to  fully  expose  this  ligament,  a  horizontal 


VERSE   LIG 
INTER! 
VERSE   LIGAMENT 


ARTICULATIONS  OF  THE  BIBS   WITH  THE  VERTEBRA     285 

section  should  be  made  across  the  transverse  process  and  corresponding  part 
of  the  rib;  or  the  rib  may  be  forcibly  separated  from  the  transverse  process  and 
the  fibres  of  tlie  ligament  put  on  the  stretch. 

For  the  eleventh  and  twelfth  ribs  this  ligament  is  quite  rudimentary  or  wanting. 

The  posterior  costotransverse  ligament  (ligamentum  costotransversarmm  pos- 
ierius)  (Fig.  234)  is  a  short  but  thick  and  strong  fasciculus  which  passes  obliquely 
from  the  summit  of  the  transverse  process  to  the  rough  nonarticular  portion  of 
the  tubercle  of  the  rib. 

This  ligament  is  shorter  ^\o. 

and  more  oblique  in  the 
upper  than  in  the  lower 
ribs.  Those  correspon- 
ding to  the  superior  ribs 
ascend,  while  those  of 
the  inferior  ribs  descend 
slightly. 

For  the  eleventh  and 
twelfth  ribs  this  ligament 
is  M-anting. 

The  capsular  liga- 
ment (capsula  artic'ular- 
is)  is  a  thin,  membranous 
sac  attached  to  the  cir- 
cimiference  of  the  articu- 
lar surfaces,  and  enclos- 
inga  syno\-ial  membrane. 

For  the  eleventh  and 
twelfth  ribs  this  ligament 
is  absent. 

Movements.~The  heads 
of  the  ribs  are  so  closely 
connected  to  the  bodies  of 
the  vertebrae  by  the  stellate 
and  intra-articular  hgaments, 
and  the  necks  and  tubercles 

of  the  ribs   to  the  transverse       Fig.  235. — Ribs  and  corresponding  -vertebra;  with  ligaments, 

processes,  that  only  a  slight  ^^^  "sht.    (Spaltehoh.) 

gliding  movement  of  the  ar- 
ticular surfaces  on  each  other  can  take  place  in  these  articulations.  The  result  of  this  gliding 
movement  with  respect  to  the  six  upper  ribs  consists  in,  an  elevation  of  the  front  and  middle 
portion  of  the  rib  with  a  consequent  enlargement  of  the  antero-posterior  diameter  of  the  thorax, 
the  hinder  part  being  prevented  from  performing  any  upward  movement  by  its  close  connection 
with  the  vertebral  column.  In  this  gliding  movement  the  rib  rotates  on  an  axis  corresponding 
to  a  line  drawn  through  the  two  articulations,  costocentral  and  costotransverse,  which  the  rib 
forms  with  the  vertebral  column.  None  of  the  ribs  lie  in  a  truly  horizoiKal  plane;  they  are  all 
directed  more  or  less  obliquely,  so  that  their  anterior  extremities  lie  at  a  lower  level  than  their 
posterior;  this  obliquity  increases  from  the  first  to  the  seventh,  and  then  again  decreases.  If  we 
examine  any  one  rib — say  that  in  which  there  is  the  greatest  obliquity — we  shall  see  that  it  is 
obvious  that  as  its  sternal  extremity  is  carried  upward  it  must  also  be  thrown  forward;  so  that 
the  rib  may  be  regarded  as  a  radius  moving  on  the  vertebral  joint  as  a  centre,  and  causing  the 
.sternal  attachment  to  describe  an  arc  of  a  circle  in  the  vertical  plane  of  the  body.  Since  all  the 
ribs  are  oblique  and  connected  in  front  to  the  sternum  by  the  flexible  costal  cartilages,  they 
must  have  a  tendency  to  thrust  the  sternum  forward,  and  so  increase  the  antero-posterior  diameter 
of  the  thorax.  With  respect  to  the  seventh,  eighth,  ninth,  and  tenth  ribs,  each  one,  besides  rotating 
in  a  similar  manner  to  the  upper  six,  also  rotates  on  an  axis  corresponding  with  a  line  drawn  from 
the  head  of  the  rib  to  the  sternum.  By  this  movement  an  elevation  of  the  middle  portion  of  the 
rib  takes  place,  and  consequently  an  increase  in  the  transverse  diameter  of  the  thorax.  For  the 
ribs  not  only  slant  downward  and  forward  from  their  vertebral  attachment,  but  they  are  also 
oblique  in  relation  to  their  transverse  plane — that  is  to  say,  their  middle  is  at  a  lower  level  than 


INFERIOR  AHTIC 
ULAfl    PROCESS 


286 


THE  ARTICULATIONS,   OB  JOINTS 


either  their  vertebral  or  sternal  extremities.    It  results  from  this  that  when  the  ribs  are  raised,  the 
central  portion  is  thrust  outward,  somewhat  after  the  fashion  in  which  the  handle  of  a  bucket  is 

thrust  away  from  the  side  when  raised  to 
a  horizontal    position,   and  the   lateral 
I     ijl  diameter  of  the  thorax  is  increased  (see 

Fig.  236).  The  mobility  of  the  diflerent 
ribs  varies  greatly.  The  first  rib  is  more 
fixed  than  the  others,  on  account  of  the 
weight  of  the  upper  extremity  and  the 
strain  of  the  ribs  beneath;  but  on  the 
freshly  dissected  thorax  it  moves  as 
freely  as  the  others.  From  the  same 
causes  the  movement  of  the  second  rib  is 
also  not  very  extensive.  In  the  other 
ribs  this  mobility  increases  successively 
down  to  the  last  two,  which  are  very 
movable.  The  ribs  are  generally  more 
movable  in  the  female  than  in  the  male. 


VII.   Costosternal  Articulations 
(Articulationes  Sternocostales) 

(Fig.  237). 


^  Fig.  236. — I)i:im:njis  .showing  the  axis  of  rotation  of  the 
ribs  in  the  moveiiieiiU  ut  respiration.  The  one  axi.s  of  rota- 
tion corresponds  with  the  Une  drawn  through  the  two  articula- 
tions which  the  rib  forms  with  the  vertebral  column  (a,  6),  and 
the  other  with  a  line  drawn  from  the  head  of  the  rib  to  the 
sternum  (A,  B).     (From  Kirke's  Handbook  of  Physiology.) 


The  articulations  of  the  carti- 
lages of  the  true  ribs  with  the 
sternum  are  arthrodial  joints,  with 
the  exception  of  the  first,  in  which 
the  cartilage  is  almost  always 
directly  united  with  the  sternum, 
and  which  must  therefore  be  re- 
garded as  a  synarthrodial  articu- 
lation. Tlae  ligaments  connecting 
them  are  the 

Anterior  Chondrosternal. 

Capsular. 

Posterior  Chondrosternal. 

Intra-articular  Chondrosternal. 

Chondroxiphoid. 


The  anterior  chondrosternal  ligament  (liganientum  sternocostale  radiatum)  (Fig. 
237)  is  a  broad  and  thin  membranous  band  that  radiates  from  the  front  of  the  inner 
extremity  of  the  cartilages  of  the'  true  ribs  to  the  anterior  surface  of  the  sternum. 
It  is  composed  of  fasciculi  which  pass  in  different  directions.  The  superior 
fasciculi  ascend  obliquely,  the  inferior  fasciculi  pass  obliquely  downward,  and 
the  middle  fasciculi  pass  horizontally.  The  superficial  fibres  of  this  ligament 
are  the  longest;  they  intermingle  with  the  fibres  of  the  ligaments  above  and 
below  them,  with  those  of  the  opposite  side,  and  with  the  tendinous  fibres  of 
origin  of  the  Pectoralis  major,  forming  a  thick  fibrous  membrane  which  covers 
the  surface  of  the  sternum  (inembraiia  sterni).  This  is  more  distinct  at  the 
lower  than  at  the  upper  part. 

The  capsular  ligament  (capsida  articidaris)  surrounds  the  joint  formed  between 
the  cartilage  of  a  true  rib  and  the  sternum.  It  is  very  thin,  intimately  blended 
with  the  anterior  and  posterior  ligaments,  and  strengthened  at  the  upper  and 
lower  part  of  the  articulation  by  a  few  fibres  which  pass  from  the  cartilage  to 
the  side  of  the  sternum.     These  ligaments  protect  the  synovial  membranes. 

The  posterior  chondrosternal  or  sternocostal  ligament  (ligamentum  sterno- 
costale radiatum),  less  thick  and  distinct  than  the  anterior,  is  composed  of  fibres 


COSTOSTERNAL  ARTICULA  TI0N8 


287 


which  radiate  from  the  posterior  surface  of  the  sternal  end  of  the  cartilages  of 
the  true  ribs  to  the  posterior  surface  of  the  sternum,  becoming  blended  with  the 
periosteum. 

The  intra-articular  chondrosternal  ligament  {ligamentum  sternocostale  inier- 
articulare)  (Fig.  237)  is  found  between  the  second  costal  cartilage  and  the  sternum. 
The  cartilage  of  the  second  rib  is  connected  with  the  sternum  by  means  of  an 


Fig.  237. — Sternum  and  ribs  with  ligaments,  from  in  front.  In  the  right  half  of  the  figure  the  most  anterior 
layer  has  been  removed  and  the  joint  cavities  have  been  opened;  the  parts  are  separated  somewhat  from  one 
another  on  the  left  side.     (Spalteholz.) 

intra-articular  ligament  attached  by  one  extremity  to  the  cartilage  of  the  second 
rib,  and  by  the  other  extremity  to  the  cartilage  which  unites  the  first  and  second 
pieces  of  the  sternum.  This  articulation  is  provided  with  two  synovial  membranes. 
The  cartilage  of  the  third  rib  is  also  occasionally  connected  with  the  sternum 
by  means  of  an  intra-articular  ligament  which  is  attached  by  one  extremity  to 
the  cartilage  of  the  third  rib,  and  by  the  other  extremity  to  the  sternum.     This 


288  THE  ARTICULATIONS,   OB  JOINTS 

articulation  may  be  provided  with  two  synovial  membranes.  In  the  other  joints 
intra-articular  ligaments  may  exist,  but  they  rarely  completely  divide  the  joint 
into  two  cavities. 

The  anterior  chondroxiphoid  ligament  (ligamentum  costoxiphoideum  anterius) 
(Fig.  237)  is  a  band  of  ligamentous  fibres  which  connects  the  anterior  surface 
of  the  seventh  costal  cartilage,  and  occasionally  also  that  of  the  sixth,  to  the 
anterior  surface  of  the  ensiform  cartilage.  It  varies  in  length  and  breadth  in 
different  subjects.  A  similar  band  of  fibres  on  the  posterior  surface,  though 
less  thick  and  distinct,  may  be  demonstrated.  It  is  spoken  of  as  the  posterior 
chondroxiphoid  ligament. 

Synovial  Membranes  (Fig.  2.37). — There  is  no  synovial  membrane  between  the  first  costal 
cartilage  and  the  sternum,  as  this  cartilage  is  directly  continuous  with  the  manubrium.  There  are 
tioo  synovial  membranes,  both  in  the  articulation  of  the  second  and  third  costal  cartilages  to  the 
sternum.  There  is  generally  one  synovial  membrane  in  each  of  the  joints  between  the  fourth, 
fifth,  sixth,  and  seventh  costal  cartilages  to  the  sternum;  but  it  is  sometimes  absent  in  the  sixth 
and  seventh  chondrosternal  joints.  Thus,  there  are  usually  eiyht  synovial  cavities  on  each  side 
in  the  articulations  between  the  costal  cartilages  of  the  true  ribs  and  the  sternum.  After  middle 
life  the  articular  surfaces  lose  their  polish,  become  roughened,  and  the  synovial  membranes 
appear  to  be  wanting.  In  old  age  the  articulations  do  not  exist,  the  cartilages  of  most  of  the 
ribs  becoming  continuous  with  the  sternum. 

Movements. — The  movements  which  are  permitted  in  the  chondrosternal  articulations  are 
limited  to  elevation  and  depression,  and  these  only  to  a  slight  extent. 

Articulations  of  the  Cartilages  of  the  Ribs  with  Each  Other  {articulationes 
interchondrales)  (Fig.  237). — The  contiguous  borders  of  the  sixth,  seventh,  and 
eighth,  and  sometimes  the  ninth  and  tenth,  costal  cartilages  articulate  with  each 
other  by  small,  smooth,  oblong-shaped  facets.  Each  articulation  is  enclosed  in 
a  thin  capsular  ligament  lined  by  synovial  membrane,  and  strengthened  externally 
and  internally  by  ligamentous  fibres,  external  and  internal  interchondral  ligaments 
(ligamenta  intercostalia  externa  et  interna),  which  pass  from  one  cartilage  to  the 
other.  Sometimes  the  fifth  costal  cartilage,  more  rarely  that  of  the  ninth,  articu- 
lates, by  its  lower  border,  with  the  adjoining  cartilage  by  a  small  oval  facet; 
more  frequently  they  are  connected  by  a  few  ligamentous  fibres.  Occasionally 
the  articular  surfaces  above  mentioned  are  wanting. 

Articulations  of  the  Ribs  with  their  Cartilages  (Fig.  237).— The  outer 
extremity  of  each  costal  cartilage  is  received  into  a  depression  in  the  sternal 
ends  of  the  ribs,  and  the  two  are  held  together  by  the  periosteum.  There  is  no 
real  joint.  Occasionally  a  synovial  membrane  exists  between  the  first  rib  and 
the  corresponding  cartilage. 

VIII.  Articulations  of  the  Sternum  (Fig.  237) 

The  first  piece  of  the  sternum  is  united  to  the  second  either  by  an  amphi- 
arthrodial  joint — a  single  piece  of  true  fibrocartilage  uniting  the  segments — or  by 
a  diarthrodial  joint,  in  which  each  bone  is  clothed  with  a  distinct  lamina  of  hyaline 
cartilage,  adherent  on  one  side,  free  and  lined  with  synovial  membrane  on  the 
other.  In  the  latter  case  the  cartilage  covering  the  gladiolus  is  continued  without 
interruption  on  to  the  cartilages  of  the  second  ribs.  The  two  segments  are 
further  connected  by  an 

Anterior  Intersternal  I^igament.  Posterior  Intersternal  Ligament. 

The  anterior  intersternal  ligament  consists  of  a  lajer  of  fibres,  having  a  longi- 
tudinal direction ;  it  blends  with  the  fibres  of  the  anterior  chondrosternal  liga- 
ments on  both  sides,  and  with  the  tendinous  fibres  of  origin  of  the  Pectoralis 


ARTICULATION  OF  VERTEBRAL  COLUMN  WITH  THE  PELVIS    289 

major  muscle.     This  ligament  is  rough,  irregular,  and  much  thicker  below  than 
above. 

The  posterior  intersternal  ligament  is  disposed  in  a  somewhat  similar  manner 
on  the  posterior  surface  of  the  articulation. 


IX.  Articulation  of  the  Vertebral  Column  with  the  Pelvis. 

The  ligaments  connecting  the  last  lumbar  vertebra  with  the  sacrum  are  similar 
to  those  which  connect  the  segments  of  the  vertebral  column  with  each  other — viz. : 
(1)  The  continuation  downward  of  the  anterior  and  posterior  common  liga- 
ments. (2)  The  intervertebral  substance  connecting  the  flattened  oval  surfaces 
of  the  two  bones  and  forming  an  amphiarthrodial  joint.  (.3)  Ligamenta  subflava, 
connecting  the  arch  of  the  last  lumbar  vertebra  with  the  posterior  border  of  the 
sacral  canal.  (4)  Capsular  ligaments  connecting  the  articulating  processes  and 
forming  a  double  arthrodia.     (5)  Inter-  and  supraspinous  ligaments. 


Occasional  aperture  of 
communication  with 
Bursa  0/  psoas  and  iliacus. 


Femur. 

Fig.  238. — Articulations  of  the  pelvis  and  hip.     Anterior  ' 

The  two  proper  ligaments  connecting  the  pelvis  with  the  vertebral  column  are 
the  lumbosacral  and  iliolumbar. 

The  lumbosacral  ligament  (Fig.  2.38)  is  a  short,  thick,  triangular  fasciculus, 
which  is  connected  above  to  the  lower  and  front  part  of  the  transverse  process 
of  the  last  lumbar  vertebra;  it  passes  obliquely  outward  and  is  attached  below 
to  the  lateral  surface  of  the  base  of  the  sacrum.  It  is  closely  blended  with  the 
anterior  sacroiliac  and  the  iliolumbar  ligaments,  and  is  to  be  regarded  as  a  portion 
■  of  the  iliolumbar  ligament.  This  ligament  is  in  relation,  in  frojit,  with  the  Psoas 
muscle.  The  internal  border  of  the  lumbosacral  ligament  margins  the  foramen 
of  the  last  lumbar  nerve. 


290  THE  ARTICULATIONS,   OB  JOINTS 

The  iliolumbar  ligament  (Hgamentum  iliolumhale)  (Fig.  238)  passes  horizontally 
outward  from  the  apex  of  the  transverse  process  of  the  last  lumbar  vertebra  to 
the  crest  of  the  ilium  immediately  in  front  of  the  sacroiliac  articulation.  It 
is  of  a  triangular  form,  thick  and  narrovsf  internally,  broad  and  thinner  externally. 
It  is  in  relation,  in  front,  vi'ith  the  Psoas  muscle;  behind,  with  the  muscles  occupy- 
ing the  vertebral  groove;  above,  with  the  Quadratus  lumborum.  It  blends  in 
places  with  the  lumbosacral  ligament,  and  its  crescentic  inner  margin  marks 
the  limit  of  the  foramen  for  the  fourth  limibar  nerve.  These  ligaments  are  thick 
prolongations  from  the  anterior  layer  of  the  lumbar  fascia. 

X.  Articulations  of  the  Pelvis. 

The  ligaments  connecting  the  bones  of  the  pelvis  with  each  other  may  be 
divided  into  four  groups:  (1)  Those  connecting  the  sacrum  and  ilium.  (2)  Those 
passing  between  the  sacrum  and  ischium.  (3)  Those  connecting  the  sacrum  and 
coccyx.     (4)  Those  between  the  tv/o  pubic  bones. 

1.  Articulation  of  the  Sacrum  and  Ilium  (Articulatio  Sacroiliaca). 

The  sacroiliac  articulation  is  an  amphiarthrodial  joint,  formed  between  the 
lateral  surfaces  of  the  sacrum  and  ilium.  The  anterior  or  auricular  portion  of 
each  articular  surface  is  covered  with  a  thin  plate  of  hyaline  cartilage,  thicker 
on  the  sacrum  than  on  the  ilium.  These  ai'e  in  close  contact  with  each  other, 
and  to  a  certain  extent  united  together  by  irregular  patches  of  softer  fibro- 
cartilage,  and  at  their  upper  and  posterior  part  by  fine  fibres  of  interosseous 
fibrous  tissue.  Throughout  a  considerable  part  of  their  extent,  especially  in 
advanced  life,  they  are  not  connected  together,  but  are  separated  "by  a  space 
containing  a  synovial-like  fluid,  and  hence  the  joint  presents  the  characters  of 
a  diarthrosis. 

The  ligaments  connecting  these  surfaces  are  the 

Anterior  Sacroiliac.  Posterior  Sacroiliac. 

The  anterior  sacroiliac  ligament  (Ugamenta  sacroiliaca  anteriora)  (Fig.  238) 
consists  of  numerous  thin  bands  which  connect  the  anterior  surfaces  of  the 
sacrum  and  ilium. 

The  posterior  sacroiliac  ligament  Qigamentum  sacroUiacum  posterius)  (Fig.  239) 
is  a  strong  ligament,  situated  in  a  deep  depression  between  the  sacrum  and  ilium 
behind,  and  forming  the  "chief  bond  of  connection  between  those  bones.  It 
consists  of  numerous  strong  fasciculi  which  pass  between  the  bones  in  various 
directions.  The  upper  part  of  the  ligament,  the  short  sacroiliac  {Hgamentum 
sacroiliacuni  posterius  breve)  is  nearly  horizontal  in  direction  and  passes  from 
the  first  and  second  transverse  tubercles  on  the  posterior  surface  of  the  sacrum 
to  the  rough,  uneven  surface  at  the  posterior  part  of  the  inner  surface  of  the 
ilium.  The  lower  part  (Hgamentum  sacroUiacum  posterius  longum),  oblique  in 
direction,  is  attached  by  one  extremity  to  the  third  transverse  tubercle  on  the 
posterior  surface  of  the  sacrum,  and  by  the  other  to  the  posterior  superior  spine 
of  the  ilium;  it  is  sometimes  called  the  oblique  sacroiliac  ligament. 

Surface  Form. — The  position  of  the  sacroiliac  joint  is  indicated  by  the  posterior  superior 
spine  of  the  ilium.     This  process  is  immediately  behind  the  centre  of  the  articulation. 


ARTICULATIONS  OF  THE  PELVIS 


291 


2.  Ligaments  Passing  between  the  Sacrum  and  Ischium  (Fig.  239). 

The  Great  Sacrosciatic  (Posterior). 
The  Small  Sacrosciatic  (Anterior). 

The  great  or  posterior  sacrosciatic  ligament  {Ugamentum  sacroiuberosum)  (Figs. 
239  and  240)  is  situated  at  the  lower  and  back  part  of  the  pelvis.  It  is  flat,  and 
triangular  in  form;  narrower  in  the  middle  than  at  the  extremities;  attached 
by  its  broad  base  to  the  posterior  inferior  spine  of  the  ilium,  to  the  fourth  and 
fifth  transverse  tubercles  of  the  sacrum,  and  to  the  lower  part  of  the  lateral  margin 
of  that  bone  and  the  coccyx.     Passing  obliquely  downward,  outward,  and  for- 


^  Femm 

Fig.  239. — .Articulations  of  pelvis  and  hip.     Posterior  Mew 

ward,  it  becomes  narrow  and  thick,  and  at  its  insertion  into  the  inner  margin 
of  the  tuberosity  of  the  ischium  it  increases  in  breadth,  and  is  prolonged  forward 
along  the  inner  margin  of  the  ramus,  forming  what  is  known  as  the  falciform 
process  of  the  great  sacrosciatic  ligament  {processus  falciformis) .  The  free  concave 
edge  of  this  prolongation  has  attached  to  it  the  obturator  fascia,  with  which  it 
forms  a  kind  of  groove,  protecting  the  internal  pudic  vessels  and  nerve.  One 
of  its  surfaces  is  turned  toward  the  perineum,  the  other  toward  the  Obturator 
internus  muscle. 

Relations. — The  superficial  surface  of  this  ligament  gives  origin,  by  its  whole  extent,  to  fibres 
of  the  Gluteus  ma.xiraus  muscle.  Its  deep  surface  is  united  to  the  lesser  sacrosciatic  ligament. 
Its  external  border  forms,  above,  the  posterior  boundary  of  the  great  sacrosciatic  foramen,  and, 
below,  the  posterior  boundary  of  the  lesser  sacrosciatic  foramen.  Its  loioer  border  forms  part 
of  the  boundary  of  the  perineum.  It  is  pierced  by  the  coccygeal  branch  of  the  sciatic  artery 
and  the  coccygeal  nerve. 


292 


THE  ARTICULATIONS,   OB  JOINTS 


The  small  or  anterior  sacrosciatic  ligament  {ligamentum  sacrospinosuTri)  (Figs. 
239  and  240),  much  shorter  and  smaller  than  the  preceding,  is  thin,  triangular 
in  form,  attached  by  its  apex  to  the  spine  of  the  ischium,  and  internally,  by  its 
broad  base,  to  the  lateral  margin  of  the  sacrum  and  coccyx,  anterior  to  the  attacli- 
ment  of  the  great  sacrosciatic  ligament,  with  wliich  its  fibres  a're  intermingled. 


-ANT.    SACI 

aOILlAC 

LIGAMENT. 

-GREAT    SA 

CRO- 

SCIATIC 

LIGA- 

MENT. 

.SMALL  SA< 

CRO- 

SCIATIC 

LIGA- 

MENT. 

.GREAT   SA 

CRO- 

SCIATIC 

LIGA' 

MENT. 

Obtu. 
membrane. 


Fig.  240. — Side  view  of  pelvis,  showing  the  greater  and  lesser  sacrosciatic  ligaments. 


Relations. — Its  deep  surface  is  in  relation  with  the  Cotcygeus  muscle;  its  superficial  surface 
is  covered  by  the  great  sacrosciatic  ligament  and  crossed  by  the  internal  pudic  vessels  and 
nerve.  Its  superior  harder  forms  the  lower  boundary  of  the  great  sacrosciatic  foramen;  its 
inferior  border,  part  of  the  lesser  sacrosciatic  foramen. 

These  two  ligaments  convert  the  sacrosciatic  notches  into  foramina.  The  superior  or  great 
sacrosciatic  foramen  (foramen  ischiadicmn  majiis)  (Figs.  239  and  240)  is  bounded,  in  front  and 
above,  by  the  posterior  border  of  the  os  innominatum;fcp/«"?!fi,  by  the  great  sacrosciatic  ligament; 
and  below,  by  the  lesser  sacrosciatic  ligament.  It  is  partially  filled  in  the  recent  state  by  the 
Pyriformis  muscle,  which  passes  through  it.  Above  this  muscle  the  gluteal  vessels  and  superior 
gluteal  nerve  emerge  from  the  pelvis,  and,  below  it,  the  sciatic  vessels  and  nerves,  the  internal 
pudic  vessels  and  nerve,  the  inferior  gluteal  nerve,  and  the  nerves  to  the  Obturator  internus  and 
Quadratus  femoris.  The  inferior  or  lesser  sacrosciatic  foramen  (foramen  ischiadicum  minus) 
(Figs.  239  and  240)  is  bounded,  in  front,  by  the  tuber  ischii;  above,  by  the  spine  and  lesser  sacro- 
sciatic ligament;  behind,  by  the  greater  sacrosciatic  ligament.  It  transmits  the  tendon  of  the 
Obturator  internus  muscle,  its  nerve,  and  the  internal  pudic  vessels  and  nerve. 


3.  Articulation  of  the  Sacrum  and  Coccyx  (Symphysis  Sacrococcygea). 

This  articulation  is  an  amphiarthrodial  joint,  formed  between  the  oval  surface 
at  the  apex  of  the  sacrum  and  the  base  of  the  coccyx.  It  is  analogous  to  the 
joints  between  the  bodies  of  the  vertebrae.     The  ligaments  are  the 


Anterior  Sacrococcygeal. 
Posterior  Sacrococcygeal. 


Lateral  Sacrococcygeal. 
Interposed  Fibrocartilage. 


ABTICULATIONS  OF  THE  PELVIS 


293 


The  anterior  sacrococcygeal  ligament  {llgamentum  sacrococcygemn  anierius) 
consists  of  a  few  irre<j;ular  fibres  which  descend  from  the  anterior  surface  of  the 
sacrum  to  the  front  of  the  coccyx,  becoming  blended  with  the  periosteum.  It 
is  a  continuation  of  tiie  anterior  common  ligament. 

The  posterior  sacrococcygeal  ligament  [ligameufum  sacmcoccygeum  poaferim) 
(Fig.  241)  is  divided  into  two  portions,  tiie  deep  and  the  superficial.  Tlie  deep 
portion  (Ikjamcidum  sacrococcygcum  posterius  profuiidum),  which  is  a  continua- 
tion of  the  posterior  common  ligament,  is  a  flat  band  of  a  pearly  tint,  which  arises 
from  the  margin  of  the  lower  orifice  of  the  sacral  canal,  and  descends  to  be  inserted 
into  the  posterior  surface  of  the  coccyx.  This  ligament  completes  the  lower 
and  back  part  of  the  sacral  canal.  Its  superficial  fibres  are  much  longer  than 
the  more  deeply  seated.  This  ligament  is  in  relation,  behind,  with  the  Gluteus 
maximus.  The  superficial  portion  (ligamentum  sacrococcygeiivi  posferius  super- 
ficiale)  is  composed  of  longitudinal  fibrous  bands  which  extend  from  the  lower 
portion  of  the  middle  sacral  ridge  to  the  posterior  surface  of  the  coccyx  and 
closes  partly  the  sacral  hiatus,  and  of  fibrous  bands  which  extend  from  the  sacral 
cornua  to  the  coccygeal  cornua.  A  portion  of  this  ligament  corresponds  to  the 
ligamenta  subflava  and  the  balance  to  the  capsular  ligament. 


EX  OF  SACRUM 

LATERAL  SACBO- 

CCYGEAL    LIGAMENT 
PERFICIAL    PORTION  OF  POST 
CROCOCCYGEAL  LIGAMENT 
EF   PORTION   OF  POSTERIOR 

SACROCOCCYGEAL  LIGAMENT 


Fig.  241. — Ligaments  between  the 


and  the  coccyx.     (Spalteholz.) 


A  lateral  sacrococcygeal  or  intertransverse  ligament  (Fig.  241)  connects  the 
trans\'erse  process  of  the  coccyx  to  the  lower  lateral  angle  of  the  sacrum  on  each 
side. 

A  fibrocartilage  or  articular  disk  is  interposed  between  the  contiguous  surfaces 
of  the  sacrum  and  coccyx;  it  diti'ers  from  that  interposed  between  the  bodies  of 
the  vertebrae  in  being  thinner,  and  its  central  part  firmer  in  texture.  It  is  some- 
what thicker  in  front  and  behind  than  at  the  sides.  Occasionally,  a  synovial 
membrane  is  found  and  the  coccyx  is  freely  movable.  This  is  especially  the  case 
during  pregnancy. 

The  different  segments  of  the  coccjnc  are  connected  by  an  extension  downward 
of  the  anterior  and  posterior  sacrococcygeal  ligaments,  a  thin  annular  articular 
disk  being  interposed  between  each  of  the  bones.  In  the  adult  male  all  the 
pieces  become  ossified,  but  in  the  female  this  does  not  commonly  occur  until  a 
later  period  of  life.  The  separate  segments  of  the  coccyx  are  first  united,  and  at 
a  more  advanced  age  the  joint  between  the  sacrum  and  coccyx  is  obliterated. 


294 


THE  ARTICULATIONS,   OB  JOINTS 


Movements.— The  movements  which  take  place  between  the  sacrum  and  coccyx,  and  between 
the  different  pieces  of  the  latter  bone,  are  forward  and  backward,  and  are  very  limited.  Their 
extent  increases  during  pregnancy. 


Interpubic  dish 
Cavity  at  uppe 
and  back  pa}  t 


4   Articulation  of  the  Pubic  Bones  (Symphysis  Ossioi  Pubis) 
(Figs.  238,  242). 

The  articulation  between  the  pubic  bones  is  an  amphiarthrodial  joint,  formed 
by  the  apposition  of  the  two  oval  articular  surfaces  of  the  pubic  bones.  The 
ligaments  of  this  articulation  are  the 

Anterior  Pubic.  Superior  Pubic. 

Posterior  Pubic.  Inferior  Pubic. 

Interpubic  Disk. 

The  anterior  pubic  Ugament  (Fig.  238)  consists  of  several  superimposed  layers 
which  pass  across  the  front  of  the  articulation.     The  superficial  fibres  pass  ob- 
liquely from  one  bone  to  the  other. 
Hyaline  cartiiaiie  coveHnri  bone.  decussating  and  forming  an  interlace- 

ment with  the  fibres  of  the  aponeurosis 
of  the  External  oblique  and  the  tendon 
of  the  Rectus  abdominalis  muscles. 
The  deep  fibres  pass  transversely 
across  the  symphysis,  and  are  blended 
with  the  interpubic  disk. 

The  posterior  pubic  ligament  consists 
of  a  few  thin,  scattered  fibres  which 
unite  the  two  pubic  bones  posteriorly. 
The  superior  pubic  ligament  Qiga- 
mentum  pubicum  superhis)  (Fig.  238) 
is  a  band  of  fibres  which  connects 
the  two  pubic  bones  superiorly. 

The  inferior  pubic  or  subpubic 
ligament  Qigamentum  arciiatit  m  pubis) 
(Fig.  238)  is  a  thick,  triangular  arch 
of  ligamentous  fibres,  connecting  the 
two  pubic  bones  below  and  forming  the  upper  boundary  of  the  pubic  arch. 
Above,  it  is  blended  with  the  articular  disk;  laterally  it  is  united  with  the  descend- 
ing rami  of  the  pubis.  Its  fibres  are  closely  connected  and  have  an  arched 
direction.  Its  lower  margin  is  separated  from  the  triangular  ligament  of  the 
perineum  by  a  gap,  through  which  runs  the  dorsal  vein  of  the  penis. 

The  interpubic  disk  (lamina  fibrocartilaginea  interpubica)  (Fig.  242)  consists 
of  a  disk  of  fibrocartilage  connecting  the  surfaces  of  the  pubic  bones  in  front. 
Each  of  the  two  surfaces  is  covered  by  a  thin  layer  of  hyaline  cartilage  whicli  is 
firmly  connected  to  the  bone  by  a  series  of  nipple-like  processes  which  accurately 
fit  within  corresponding  depressions  on  the  osseous  surfaces.  These  apposed 
cartilaginous  surfaces  are  connected  by  an  intermediate  stratum  of  fibrous 
tissue  and  fibrocartilage  which  varies  in  thickness  in  different  subjects.  It 
often  contains  a  cavity  (cavwrn  articulare)  in  its  centre,  probably  formed  by 
the  softening  and  absorption  of  the  fibrocartilage,  since  it  rarely  appears  before 
the  tenth  year  of  life,  and  is  not  lined  by  synovial  membrane.  It  is  larger  in  the 
female  than  in  the  male.     It  is  most  frequently  limited  to  the  upper  and  back 


Fig.  242. — Vertical  section  of  the  symphysis  pubi> 
Made  near  its  posterior  surface. 


STERNOCLAVICULAR  ARTICULATION 


295 


part  of  the  joint,  but  it  occasionally  reaches  to  the  front,  and  may  extend  the 
entire  length  of  the  cartilage.  This  cavity  may  sometimes  be  demonstrated  by 
making  a  vertical  section  of  the  symphysis  pubis  near  its  posterior  surface 
(Fig.  242). 

The  obturator  ligament  is  more  properly  regarded  as  analogous  to  the  mus- 
cular fasciae,  with  which  it  will  be  described. 


ARTICULATIONS   OF   THE   UPPER  EXTREMITY. 


The  articulations  of  the  upper  extremity  may  be  arranged  in  the  following 
groups : 


I.  Sternoclavicular  Articulation. 
II.  Acromioclavicular  Articulation. 

III.  Ligaments  of  the  Scapula. 

IV.  Shoulder-joint. 
V.  Elbow-joint. 

VI.  Radioulnar  Articulations. 


VII.  Wrist-joint. 

VIII.  Articulations  of  the  Carpal  Bones. 
IX.  Carpometacarpal  Articulations. 
X.  Metacarpophalangeal       Articula- 
tions. 
XI.  Articulations  of  the  Phalanges. 


I.  Sternoclavicular  Articulation  (Articulatio  Stemoclavicularis)  (Fig.  243). 

The  sternoclavicular  is  an  arthrodial  joint.  The  parts  entering  into  its  forma- 
tion are  the  sternal  end  of  the  clavicle,  the  upper  and  lateral  part  of  the  first  piece 
of  the  sternum,  and  the  cartilage  of  the  first  rib.     The  articular  surface  of  the 


Fig.  243. — Sternoclavicular  articulation.     Anterior 


sternum  is  covered  with  hyaline  cartilage.  The  articular  surface  of  the  clavicle 
is  much  larger  than  that  of  the  sternum,  and  invested  with  a  layer  of  hyaline 
cartilage'  which  is  considerably  thicker  than  that  on  the  latter  bone.  The  liga- 
ments of  this  joint  are  the 


Capsular. 

Anterior  Sternoclavicular. 

Posterior  Sternoclavicular. 


Interclavicular. 
Costoclavicular. 
Articular  Disk. 


1  According  to  Bruch,  the  sternal 
cartilaginous  in  structure. 


nd   of  the  clavicle  is  covered  by  a  tissue  which  is  rather  fibrous  than 


296  THE  ARTICULATIONS,    OB  JOINTS 

The  capsular  ligament  {capsula  articularis)  completely  surrounds  the  articula- 
tion, consisting  of  fibres  of  varying  degrees  of  thickness  and  strength.  Those 
in  front  and  behind  are  of  considerable  thickness,  and  form  the  anterior  and 
posterior  sternoclavicular  ligaments;  but  those  above  and  below,  especially  in 
the  latter  situation,  are  thin  and  scanty. 

The  anterior  sternoclavicular  ligament  (Ikjamenium,  sternodavicnlare)  (Fig. 
243)  is  a  part  of  the  capsule.  It  is  a  broad  band  of  fibres  which  covers  the  anterior 
surface  of  the  articulation,  being  attached,  above,  to  the  upper  and  front  part 
of  the  inner  extremity  of  the  clavicle,  and,  passing  obliquely  downward  and 
inward,  is  attached,  below,  to  the  upper  and  front  part  of  the  first  piece  of  the 
sternum.  This  ligament  is  covered,  m  front,  by  the  sternal  portion  of  the  Sterno- 
mastoid  and  the  integument;  behind,  it  is  in  relation  with  the  articular  disk  and 
the  two  synovial  membranes. 

The  posterior  sternoclavicular  ligament,  also  a  part  of  the  capsule,  is  a  band 
of  fibres  which  covers  the  posterior  surface  of  the  articulation,  being  attached, 
above,  to  the  upper  and  back  part  of  the  inner  extremity  of  the  clavicle,  and. 
passing  obliquely  downward  and  inward,  is  attached,  below,  to  the  upper  and 
back  part  of  the  first  piece  of  the  sternum.  It  is  in  relation,  in  fro7it,  with  the 
articular  disk  and  synovial  membranes;  behind,  with  the  Sternohyoid  and 
Sternothyroid   muscles. 

The  interclavicular  ligament  (ligamentum  interdaviculare)  (Fig.  243)  is  a  flat- 
tened band  which  varies  considerably  in  form  and  size  in  different  individuals; 
it  passes  in  a  curved  direction  from  the  upper  part  of  the  inner  extremity  of  one 
clavicle  to  the  other,  and  is  also  attached  to  the  upper  margin  of  the  sternum. 
It  is  in  relation,  in  front,  with  the  integument;  behind,  with  the  Sternothyroid 
muscles. 

The  costoclavicular  or  rhomboid  ligament  Qicjamentum  costoclavicidare)  (Fig. 
243)  is  short,  flat,  and  strong;  it  is  of  a  rhomboid  form,  attached,  belotv,  to  the 
upper  and  inner  part  of  the  cartilage  of  the  first  rib;  it  ascends  obliquely  back- 
ward and  outward,  and  is  attached,  above,  to  the  rhomboid  depression  on  the 
under  surface  of  the  clavicle.  It  is  in  relation,  in  front,  with  the  tendon  of  origin 
of  the  Subciavius;  behind,  with  the  subclavian  vein. 

The  articular  disk  (discus  articularis)  (Fig.  243)  is  a  flat  and  nearly  circular 
meniscus,  interposed  between  the  articulating  surfaces  of  the  sternum  and  clavicle. 
It  is  attached,  above,  to  the  upper  and  posterior  border  of  the  articular  surface 
of  the  clavicle;  beloiv,  to  the  cartilage  of  the  first  rib,  at  its  junction  with  the 
sternum;  and  by  its  circumference,  to  the  anterior  and  posterior  sternoclavicular 
and  the  interclavicular  ligaments.  It  is  thicker  at  the  circumference,  especially 
its  upper  and  back  part,  than  at  its  centre  or  below.  It  divides  the  joint  into 
two  cavities,  each  of  which  is  furnished  with  a  separate  synovial  membrane. 

Synovial  Membrane. — Of  the  two  synovial  membranes  found  in  this  articulation,  one  is 
reflected  from  the  sternal  end  of  the  clavicle  over  the  adjacent  surface  of  the  articular  disk  and 
cartilage  of  the  first  rib;  the  other  is  placed  between  the  articular  surface  of  the  sternum  and 
adjacent  surface  of  the  articular  disk;  the  latter  is  the  larger  of  the  tT\-o. 

Movements. — This  articulation  is  the  centre  of  the  movements  of  the  shoulder,  and  admits 
of  a  limited  amount  of  motion  in  nearly  every  direction — upward,  downward,  backward,  for- 
ward— as  well  as  circumduction.  When  these  movements  take  place  in  the  joint,  the  clavicle 
in  its  motion  carries  the  scapula  with  it,  this  bone  gliding  on  the  outer  surface  of  the  thorax.  This 
joint  therefore  forms  the  centre  from  which  all  movements  of  the  supporting  arch  of  the  shoulder 
originate,  and  is  the  only  point  of  articulation  of  this  part  of  the  skeleton  with  the  trunk.  "The 
movements  attendant  on  elevation  and  depression  of  the  shoulder  take  place  between  the  clavicle 
and  the  articular  disk,  the  bone  rotating  upon  the  ligament  on  an  axis  drawn  from  before  back- 
ward through  its  own  articular  facet.  When  the  shoulder  is  moved  forward  and  backward,  the 
clavicle,  with  the  articular  disk,  rolls  to  and  fro  on  the  articular  surface  of  the  sternum,  revolving, 
■with  a  gliding  movement,  around  an  axis  drawn  nearly  vertically  through  the  sternum.  In  the 
circumduction  of  the  shoulder,  which  is  compounded  of  these  two  inovements,  the  clavicle  revolves 


ACROMIOCLAVICULAR  ARTICULATION  297 

upon  the  articular  disk,  and  the  latter,  with  the  clavicle,  rolls  upon  the  sternum."'  Elevation 
of  the  clavicle  is  principally  limited  by  the  costoclavicular  ligament;  depression  by  the  inter- 
clavicular. The  muscles  which  raise  the  clavicle,  as  in  shrugging  the  shoulder,  are  the  upper 
fibres  of  the  Trapezius,  the  Levator  anguli  scapulae,  the  clavicular  head  of  the  Sternomastoid, 
assisted  to  a  certain  extent  by  the  two  Rhomboids,  which  pull  the  vertebral  border  of  the  scapula 
backward  and  upward,  and  so  rai^c  (he  clavicle.  The  ilrjircssioii  iif  (lie  chivicle  is  principally 
effected  by  gravity,  assisted  liy  iln-  SuUclavius,  Pec'omlis  niiimi-,  ;iiiil  Idwcr  fibres  of  the  Trape- 
zius. It  is  drawn  backward  \i\  the  ifhomboids  and  the  middle  and  luwcr  liUrcs  of  the  Trapezius; 
smA  forward  by  theSerratus  magnus  and  Pectoralis  minor. 

Surface  Form. — The  position  of  the  sternoclavicular  joint  may  be  easily  ascertained  by  feeling 
the  enlarged  sternal  end  of  the  collar-bone  just  external  to  the  long,  cord-like,  sternal  origin 
of  the  Sternomastoid  muscle.  If  this  muscle  is  relaxed  by  bending  the  head  forward,  a  depres- 
sion just  internal  to  the  end  of  the  clavicle,  and  between  it  and  the  sternum,  can  be  felt,  indi- 
cating the  exact  position  of  the  joint,  which  is  subcutaneous.  When  the  arm  hangs  by  the  side, 
the  cavity  of  the  joint  is  V-shaped.  If  the  arm  is  raised,  the  bones  become  more  closely  approxi- 
mated, and  the  cavity  becomes  a  mere  slit. 

Applied  Anatomy. — The  strength  of  this  joint  mainly  depends  upon  its  ligaments,  and  it 
is  because  of  the  ligaments  and  because  the  force  of  a  blow  is  generally  transmitted  along  the 
long  axis  of  the  clavicle,  that  dislocation  so  rarely  occurs,  and  that  the  bone  is  generally  broken 
rather  than  displaced.  When  dislocation  does  occur,  the  course  which  the  displaced  bone  takes 
depends  more  upon  the  direction  in  which  the  violence  was  applied  than  upon  the  anatomical 
construction  of  the  joint;  it  may  be  either  forward,  backward,  or  upward.  A  complete  upward 
dislocation  is  also  inward.  A  complete  forward  or  backward  dislocation  is  also  inward  and 
downward.  The  chief  point  worthy  of  note,  as  regards  the  construction  of  the  joint,  in  regard  to 
dislocations,  is  the  fact  that,  owing  to  the  shape  of  the  articular  surfaces  being  so  little  adapted 
to  each  other,  and  that  the  strength  of  the  joint  mainly  depends  upon  the  ligaments,  the  dis- 
placement when  reduced  is  very  liable  to  recur,  and  hence  it  is  extremely  difficult  to  keep  the 
end  of  the  bone  in  its  proper  place,  and  it  may  be  necessary  to  incise  the  soft  parts  and  wire  the 
bone  in  place. 


II.  Acromioclavicular  or  Scapuloclavicular  Articulation  (Articulatio 
Acromioclavicularis)  (Fig.  244). 

The  acromioclavicular  is  an  arthrodial  joint  formed  between  the  outer  ex- 
tremity of  the  clavicle  and  the  inner  margin  of  the  acromion  process  of  the  scapula. 
The  ligaments  which  surround  the  joint  form  a  capsule.  The  ligaments  of  this 
articulation  are  the 

Superior  Acromioclavicular.  f  Trapezoid 

Inferior  Acromioclavicular.  Coracoclavicular  -!       and 

Articular  Disk.  [  Conoid. 

Tlie  superior  acromioclavicular  ligament  (Ugamentum  acromiodavindare)  (Figs 
244  and  245)  is  a  portion  of  the  joint  capsule.  It  is  a  quadrilateral  band  which 
covers  the  superior  part  of  the  articulation,  extending  between  the  upper  part  of 
the  outer  end  of  the  clavicle  and  the  adjoining  part  of  the  upper  surface  of  the 
acromion.  It  is  composed  of  parallel  fibres  which  interlace  with  the  aponeurosis 
of  the  Trapezius  and  Deltoid  muscles;  below,  it  is  in  contact  with  the  articular 
disk  (when  it  exists)  and  the  synovial  membranes. 

The  inferior  acromioclavicular  ligament,  somewhat  thinner  than  the  preceding, 
and,  like  it,  a  portion  of  the  capsule,  covers  the  under  part  of  the  articulation 
and  is  attached  to  the  adjoining  surfaces  of  the  two  bones.  It  is  in  relation, 
above,  with  the  synovial  membranes,  and  in  rare  cases  with  the  articular  disk; 
below,  with  the  tendon  of  the  Supraspinatus.  These  two  ligaments  are  con- 
tinuous with  each  other  in  front  and  behind,  and  form  a  complete  capsule  around 
the  joint. 

'  Humphry,  On  the  Human  Skeleton,  p.  402. 


298  THE  ARTICULATIONS,   OB  JOINTS 

The  articular  disk  {discus  articularis)  is  frequently  absent  in  this  articulation. 
When  the  meniscus  exists  it  is  generally  incomplete  and  only  partially  separates 
the  articular  surfaces,  and  occupies  the  upper  part  of  the  articulation.  More 
jarely  it  completely  separates  the  joint  into  two  cavities. 

The  Synovial  Membrane. — There  is  usually  only  one  synovial  membrane  in  this  articu- 
lation, but  when  a  complete  articular  disk  exists  there  are  two  synovial  membranes. 

The  coracoclavicular  ligament  (ligamentum  coracoclaviculare)  (Figs.  244  and 
245)  serves  to  connect  the  clavicle  with  the  coracoid  process  of  the  scapula.  It 
does  not  properly  belong  to  this  articulation,  but  as  it  forms  a  most  efficient  means 
in  retaining  the  clavicle  in  contact  with  the  acromial  process,  it  is  usually  described 
with  it.     It  consists  of  two  fasciculi,  called  the  trapezoid  and  conoid  ligaments. 


Fig.  244. — The  left  shoulder-joint,  scapuloclavicular  articulations,  and  proper  ligaments  of  the  scapula. 

The  trapezoid  ligament  (ligamentum  trapezoidcum),  the  anterior  and  external 
■fasciculus,  is  broad,  thin,  and  quadrilateral;  it  is  placed  obliquely  between  the 
coracoid  process  and  the  clavicle.  It  is  attached,  below,  to  the  upper  surface 
of  the  coracoid  process;  above,  to  the  oblique  line  on  the  under  surface  of  the 
clavicle.  Its  anterior  border  is  free;  its  posterior  border  is  joined  with  the  conoid 
ligament,  the  two  forming  by  their  junction  a  projecting  angle. 

The  conoid  ligament  (ligamentum  conoideum),  the  posterior  and  internal  fas- 
ciculus, is  a  dense  band  of  fibres,  conical  in  form,  the  base  being  directed  upward, 
the  summit  downward.  It  is  attached,  below,  by  its  apex  to  a  rough  impression  at 
the  base  of  the  coracoid  process,  internal  to  the  trapezoid  ligament ;  above,  by  its 
expanded  base,  to  the  conoid  tubercle  on  the  under  surface  of  the  clavicle,  and 
■  to  a  line  proceeding  internally  from  it  for  half  an  inch.     These  ligaments  are 


PBOPEB  LIGAMENTS  OF  THE  SCAPITLA  299 

in  relation,  in  front,  with  the  Subclavius  and  Deltoid;  behind,  with  the  Trapezius. 
They  serve  to  limit  rotation  of  the  scapula,  the  trapezoid  limiting  rotation  forward, 
and  the  conoid  backward. 

Movements. — The  movements  of  this  articulation  are  of  two  kinds:  (1  j  A  gliding  motion  of 
the  articular  end  of  the  clavicle  on  the  acromion.  (2)  Rotation  of  the  scapula  forward  and  back- 
ward upon  the  clavicle,  the  extent  of  this  rotation  being  limited  by  the  two  portions  of  the  coraco- 
■clavicular  ligament. 

The  acromioclavicular  joint  has  important  functions  in  the  movements  of  the  upper  extremity. 
It  has  been  well  pointed  out  by  Sir  George  Humphry  that  if  there  had  been  no  joint  between 
the  clavicle  and  scapula  the  circular  movement  of  the  scapula  on  the  ribs  (as  in  throwing  both 
shoulders  backward  or  forward)  would  have  been  attended  with  a  greater  alteration  in  the 
direction  of  the  shoulder  than  is  consistent  with  the  free  use  of  the  arm  in  such  position,  and 
it  would  have  been  impossible  to  give  a  blow  straight  forward  with  the  full  force  of  the  arm ;  that 
is  tisay,  with  the  combined  force  of  the  scapula,  arm,  and  forearm.  "This  joint,"  as  he  happily 
says^'is  so  adjusted  as  to  enable  either  bone  to  turn  in  a  hinge-like  manner  upon  a  vertical 
Axis  drawn  through  the  other,  and  it  permits  the  surfaces  of  the  scapula,  like  the  baskets  in  a 
roundabout  swing,  to  look  the  same  way  in  every  position,  or  nearly  so."  Again,  when  the  whole 
Arch  formed  by  the  clavicle  and  scapula  rises  and  falls  (in  elevation  or  depression  of  the  shoul- 
ders), the  joint  between  these  two  bones  enables  the  scapula  still  to  maintain  its  lower  part  in 
■contact  with  the  ribs. 

Surface  Form. — The  position  of  the  acromioclavicular  joint  can  generally  be  ascertained  by 
the  sli^tly  enlarged  extremity  of  the  outer  end  of  the  clavicle,  which  causes  it  to  project  above 
the  leva^f  the  acrDuiion  process  of  the  scapula.  Sometimes  this  enlargement  is  so  considerable 
as  to  form  a  mundcd  eminence,  which  is  easily  to  be  felt.  The  joint  lies  in  the  plane  of  a  vertical 
line  passing  u|)  the  middle  of  the  front  of  the  arm. 

Applied  Anatomy. — Owing  to  the  slanting  shape  of  the  articular  surfaces  of  this  joint,  the 
■commonest  didocation  is  the  passing  of  the  acromion  process  of  the  scapula  under  the  outer 
end  of  the  clavicle;  but  dislocations  in  the  opposite  direction  have  been  described.  The  first 
form  of  dislocation  is  produced  by  violent  force  applied  to  the  scapula  so  as  to  drive  the  shoulder 
forward.  The  displacement  in  acromioclavicular  dislocation  is  often  incomplete,  on  account 
of  the  strong  coracoclavicular  ligaments  which  remain  untorn.  The  same  difficulty  exists,  as  in 
the  sternoclavicular  dislocation,  in  maintaining  the  ends  of  the  bone  in  apposition  after  reduction, 
and  it  may  become  necessary  to  wire  them  in  place  after  incision  of  the  soft  parts. 


III.  Proper  Ligaments  of  the  Scapula  (Figs.  244,  245). 

The  proper  ligaments  of  the  scapula  pass  between  portions  of  that  bone,  but 
are  not  parts  of  an  articulation.     They  are  the 

Coracoacromial.  Superior   Transverse. 

Inferior  Transverse. 

The  coracoacromial  ligament  (ligamentum  coracoacromiale)  is  a  strong  triangular 
band,  extending  between  the  coracoid  and  acromial  processes.  It  is  attached, 
by  its  apex,  to  the  summit  of  the  acromion  just  in  front  of  the  articular  surface 
for  the  clavicle,  and  by  its  broad  base  to  the  whole  length  of  the  outer  border  of 
the  coracoid  process.  Its  posterior  fibres  are  directed  inward,  its  anterior  fibres 
forward  and  inward.  This  ligament  completes  the  vault  formed  by  the  coracoid 
and  acromion  processes  for  the  protection  of  the  head  of  the  humerus.  It  is  in 
relation,  above,  with  the  clavicle  and  under  surface  of  the  Deltoid  muscle;  below, 
with  the  tendon  of  the  Supraspinatus  muscle,  a  bursa  being  interposed.  Its 
■Older  border  is  continuous  with  a  dense  lamina  that  passes  beneath  the  Deltoid 
upon  the  tendons  of  the  Supra-  and  Infraspinatus  muscles.  This  ligament  is 
sometimes  described  as  consisting  of  two  marginal  bands  and  a  thinner  inter- 
vening portion,  the  two  bands  being  attached,  respectively,  to  the  apex  and  base 
of  the  coracoid  process,  and  joining  together  at  their  attachment  into  the  acromion 
process,     ^^^len  the  Pectoralis  minor  is  inserted,  as  sometimes  is  the  case,  into 


300 


THE  ARTICULATIONS,    OR  JOINTS 


the  capsule  of  the  shoulder-joint  instead  of  into  the  coracoid  process,  it  passes 
between  these  two  bands,  and  the  intervening  portion  is  then  deficient. 

The  superior  transverse  or  suprascapular  ligament  (lit/amentum  transversum 
scapulae  swperius)  (Figs.  245  and  246)  converts  the  suprascapular  notch  into  a 


Fig,  245. — Right  clavicle  and  scapula  with  ligament,  from  without  and  somewhat  from  in  front.     (Spalteholz.) 


ELTOID.      SUPHASPINATUS. 


TERES    MAJ 


TEBEs  MAJOR.       Circumflex  vessels. 
Fig.  246. — Vertical  sections  through  the  shoulder-joint,  the 


Circumflex  vessels. 
being  vertical  and  hor 


SCAPULARIS. 

ntal.     (.\fter  Henle.) 


foramen.  It  is  a  thin  and  flat  fasciculus,  narrower  at  the  middle  than  at  the 
extremities,  attached  by  one  end  to  the  base  of  the  coracoid  process,  and  by  the 
other  to  the  inner  extremity  of  the  scapular  notch.  The  suprascapular  nerve 
passes  through  the  foramen;  the  suprascapular  vessels  pass  over  the  ligament. 


SHO  ULDER-JOINT  30 1 

An  additional  ligament,  the  inferior  transverse  or  spinoglenoid  ligament  (Ji(j(i- 
mentum  traiisversum  scapulae  Inferius),  is  sometimes  found  on  the  scapula, 
stretching  from  the  outer  border  of  the  spine  to  the  margin  of  the  glenoid  cavity. 
When  present,  it  forms  an  arch  under  which  the  suprascapular  vessels  and  nerve 
pass  as  they  enter  the  infraspinous  fossa. 

Movements. — The  scapula  is  capable  of  being  moved  upward  and  downward,  forward  and 
backward,  or,  by  a  combination  of  these  movements,  circumducted  on  the  wall  of  the  thorax.  The 
muscles  which  raise  the  scapula  are  the  upper  fibres  of  the  Trapezius,  the  Levator  anguli  scapulae, 
and  the  two  Rhomboids;  those  which  depress  it  are  the  lower  fibres  of  the  Trapezius,  the  Pec- 
toralis  minor,  and,  through  the  clavicle,  the  Subclavius.  The  scapula  is  drawn  hackicard  by  the 
Rhomboids  and  the  middle  and  lower  fibres  of  the  Trapezius,  and  forward  by  the  Serratus 
magnus  and  Pectoralis  ininor,  assisted,  when  the  arm  is  fixed,  by  the  Pectoralis  major.  The 
mobility  of  the  scapula  is  very  considerable,  and  greatly  assists  the  movements  of  the  arm  at  the 
shoulder-joint.  Thus,  in  raising  the  arm  from  the  side  the  Deltoid  and  Supraspinatus  can  only 
lift  it  to  a  right  angle  with  the  trunk,  the  further  elevation  of  the  limb  being  effected  by  the  Trape- 
zius and  Serratus  magnus  moving  the  scapula  on  the  wall  of  the  thorax.  This  mobility  is  of 
special  importance  in  ankylosis  of  the  shoulder-joint,  the  movement  of  this  bone  compensating 
ito  a  very  great  extent  for  the  immobility  of  the  joint. 


IV.  Shoulder-Joint  (Articulatio  Humeri)  (Figs.  245,  246). 

The  shoulder-joint  is  an  enarthrodial  or  ball-and-socket  joint.  The  bones  enter- 
ing into  its  formation  are  the  large  globular  head  of  the  humerus,  which  is  received 
into  the  shallow  glenoid  cavity  of  the  scapula — an  arrangement  which  permits 
of  very  considerable  movement,  while  the  joint  itself  is  protected  against  dis- 
placement by  the  tendons  which  surround  it  and  by  atmospheric  pressure.  The 
ligaments  do  not  maintain  the  joint  surfaces  in  apposition,  because  when  they 
alone  remain  the  humerus  can  be  separated  to  a  considerable  extent  from  the 
glenoid  cavity;  their  use,  therefore,  is  to  limit  the  amount  of  movement.  Above, 
the  joint  is  protected  by  an  arched  vault,  formed  by  the  under  surfaces  of  the 
coracoid  and  acromion  processes,  and  the  coracoacromial  ligament.  The  articular 
surfaces  are  covered  by  a  layer  of  hyaline  cartilage;  that  on  the  head  of  the  humerus 
is  thicker  at  the  centre  than  at  the  circumference,  the  reverse  being  the  case  in 
the  glenoid  cavity.     The  ligaments  of  the  shoulder  are  the 

Capsular.  Transverse  Humeral. 

Coracohumeral.  Glenoid.' 

The  capsular  ligament  (capsula  articularis)  (Figs.  245  and  247)  completely 
encircles  the  articulation,  being  attached,  above,  to  the  circumference  of  the 
glenoid  cavity  beyond  the  glenoid  ligament,  below,  to  the  anatomical  neck  of  the 
humerus,  approaching  nearer  to  the  articular  cartilage  above  than- in  the  rest 
of  its  extent.  It  is  thicker  above  and  below  than  elsewhere,  and  is  remarkably 
loose  and  lax,  and  much  larger  and  longer  than  is  necessary  to  keep  the  bones 
in  contact,  allowing  them  to  be  separated  from  each  other  more  than  an  inch 
— an  evident  provision  for  that  extreme  freedom  of  movement  which  is  peculiar 
to  this  articulation.  Its  superficial  surface  is  strengthened,  above,  by  the  Supra- 
spinatus; below,  by  the  long  head  of  the  Triceps;  behind,  by  the  tendons  of  the 
Infraspinatus  and  Teres  minor;  and  in  front,  by  the  tendon  of  the  Subscapularis. 
The  capsular  ligament  usually  presents  three  openings:  One  anteriorly,  below 
the  coracoid  process,  establishes  a  communication  between  the  synovial  mem- 
brane of  the  joint  and  a  bursa  beneath  the  tendon  of  the  Subscapularis  muscle. 

1  The  long  tendon  of  origin  of  the  Biceps  brachii  muscle  also  acts  as  one  of  the  ligaments  of  this  joint.  See  the 
observations  on  p.  267  on  the  function  of  the  muscles  passing  over  more  than  one  joint. 


302 


THE  ARTICULATIONS,    OB  JOINTS 


The  second,  which  is  not  constant,  is  at  the  posterior  part,  where  a  communica- 
tion sometimes  exists  between  the  joint  and  a  bursal  sac  belonging  to  the  Infra- 
spinatus muscle.  The  third  is  seen  between  the  two  tuberosities,  for  the  passage 
of  tlie  long  tendon  of  the  Biceps  brachii  muscle.  It  transmits  a  sac-like  prolonga- 
tion of  the  synovial  membrane,  which  ends  as  a  blind  pouch  opposite  the  surgicaL 
neck  of  the  bone. 

The  coracohumeral  ligament  (ligamentum  coracohumerale)  (Fig.  244)  is  a  broad 
band  which  strengthens  the  upper  part  of  the  capsular  ligament.  It  arises  from 
the  outer  border  of  the  coracoid  process,  and  passes  obliquely  downward  and 
outward  to  the  front  of  the  gi'eat  tuberosity  of  the  humerus,  being  blended  with 
the  tendon  of  the  Supraspinatus  muscle.  This  ligament  is  intimately  united  tO' 
the  capsular  ligament  throughout  the  greater  part  of  its  extent. 


SUPERIOR 

TRANSVERSE 

LIGAMENT 


Fig.  247. — Right  shoulder-joint,  frontal  section,  from  behind.     (Spalteholz.) 


Supplemental  Bands  of  the  Capsular  Ligament. — In  addition  to  the  coracohumeral 
ligament,  the  capsular  ligament  is  strengthened  by  supplemental  bands  in  the 
interior  of  the  joint,  and  can  be  best  studied  by  opening  the  capsule  from  behind 
and  removing  the  head  of  the  humerus.  One  of  these  bands  (Flood's  ligament) 
passes  from  the  anterior  edge  of  the  glenoid  cavity  to  the  lower  part  of  the  lesser 
tuberosity  of  the  humerus.  It  is  supposed  to  correspond  with  the  ligamentum 
teres  of  the  hip-joint.  A  second  of  these  bands  (Schlemm's  ligament),  is  situated 
at  the  lower  part  of  the  joint,  and  passes  from  the  under  edge  of  the  glenoid  cavity 
to  the  under  part  of  the  neck  of  the  humerus.  A  third,  called  the  glenohumera.l 
ligament,  is  situated  at  the  upper  part  of  the  joint.  It  is  attached,  above,  to  the 
apex  of  the  glenoid  cavity,  close  to  the  root  of  the  coracoid  process,  and,  passing 
downward  along  the  inner  edge  of  the  tendon  of  the  Biceps  brachii,  is  attached, 
below,  above  the  lesser  tuberosity  of  the  humerus,  where  it  forms  the  inner  boundary 


SHOULDER-JOINT  303 

of  the  upper  part  of  the  bicipital  groove.  It  is  a  thin,  ribbon-like  band,  occasion- 
ally quite  free  from  the  capsule. 

The  transverse  humeral  ligament  is  a  prolongation  of  the  capsular  ligament. 
It  is  a  broad  hand  of  fibrous  tissue  passing  from  the  lesser  to  the  greater  tuber- 
osity of  the  humerus,  and  always  limited  to  that  portion  of  the  bone  which  lies 
above  the  epiphyseal  line.  It  converts  the  bicipital  groove  into  an  osseoaponeu- 
rotic  canal,  and  is  the  homologue  of  the  strong  process  of  bone  which  connects 
the  summits  of  the  two  tuberosities  in  the  musk  o.x. 

The  glenoid  ligament  {labrum  glenoidale)  (Figs.  245  and  247)  is  a  fibrocartilagi- 
nous rim,  attached  around  the  margin  of  the  glenoid  cavity.  It  is  triangular  on 
section,  the  thickest  portion  being  fixed  to  the  circumference  of  the  cavity,  the 
free  edge  being  thin  and  sharp.  It  is  continuous  above  with  the  long  tendon 
of  the  Biceps  muscle,  which  bifurcates  at  the  upper  part  of  the  cavity  into  two 
fasciculi,  and  becomes  continuous  with  the  fibrous  tissue  of  the  glenoid  ligament. 
This  ligament  deepens  the  cavity  for  articulation,  and  protects  the  edges  of  the 
bone. 

Synovial  Membrane  (Fig.  247). — The  synovial  membrane  is  reflected  from  the  margin  of 
the  glenoid  cavity  over  the  fibrocartilaginous  rim  surrounding  it;  it  is  then  reflected  over  the 
internal  surface  of  the  capsular  ligament,  covers  the  lower  part  and  sides  of  the  anatomical  neck 
of  the  humerus  as  far  as  the  cartilage  covering  the  head  of  the  bone.  The  long  tendon  of  the 
Biceps  brachii,  which  passes  through  the  capsular  ligament,  is  enclosed  in  a  tubular  sheath  of 
synovial  membrane  (vagina  mucosa  intertubercularis),  which  is  reflected  upon  it  at  the  point 
vvhere  it  perforates  the  capsule,  and  is  continued  around  it  as  far  as  the  level  of  the  surgical 
neck  of  the  humerus.  The  tendon  of  the  Biceps  is  thus  enabled  to  traverse  the  articulation,  but 
it  is  not  contained  in  the  interior  of  the  synovial  cavity. 

Bursse. — A  large  bursa,  the  subscapular  bursa,  exists  between  the  joint  capsule  and  the  ten- 
don of  the  Subscapularis  muscle.  I'liis  sa<'  communicates  with  the  shoulder-joint  by  means 
of  an  opening  at  the  inner  side  of  the  ciipsular  ligament.  Occasionally  another  and  smaller  bursa, 
the  infraspinatus  bursa,  exists  beneath  the  tendon  of  the  Infraspinatus.  It  communicates  with 
the  shoukier-joint  by  means  of  an  opening  in  the  outer  surface  of  the  capsule.  The  subdeltoid 
or  subacromial  bursa  is  placed  between  the  under  surface  of  the  Deltoid  muscle  and  the  outer 
surface  of  the  capsule.  It  does  not  communicate  with  the  joint.  The  subcutaneous  acromial 
bursa  is  between  the  surface  and  the  summit  of  the  acromion  process.  There  is  a  bursa  beneath 
the  Coracobrachialis  muscle,  one  beneath  the  Teres  major,  and  one  beneath  the  tendinous 
portion  of  the  Latissimus  dorsi.  There  is  also  a  bursa  between  the  tendon  of  insertion  of 
the  Pectoralis  major  muscle  and  the  long  head  of  the  Biceps. 

The  muscles  in  relation  with  the  joint  are,  above,  theSupraspinatus;  beloiv,  the  long  head  of 
the  Triceps;  mfronf,  the  Subscapularis;  behind,  the  Infraspinatus  and  Teres  minor;  wiihiii,  the 
long  tendon  of  the  Biceps.  The  Deltoid  is  placed  most  externally,  and  covers  the  articulation 
on  its  outer  side,  as  well  as  in  front  and  behind. 

The  arteries  supplying  the  joint  are  articular  branches  of  the  anterior  and  posterior  circum- 
flex, and  the  suprascapular. 

The  nerves  are  derived  from  the  circumflex  and  suprascapular. 

Movements. — The  shoulder-joint  is  capable  of  movement  in  every  direction,  forward,  back- 
ward, abduction,  adduction,  circumduction,  and  rotation.  The  humerus  is  drawn  fonvard  by 
the  Pectoralis  major,  anterior  fibres  of  the  Deltoid,  Coracobrachialis,  and  by  the  Biceps  when 
the  forearm  is  flexed;  backward,  by  the  Latissimus  dorsi.  Teres  major,  posterior  fibres  of  the  Del- 
toid, and  by  the  Triceps  when  the  forearm  is  extended;  it  is  abducted  (elevated)  by  the  Del- 
toid andSupraspinatus;  it  is  adducted  (depressed)  by  the  Subscapularis,  Pectoralis  major,  Latis- 
simus dorsi,  and  Teres  major;  it  is  rotated  outward  by  the  Infraspinatus  and  Teres  minor;  and 
it  is  rotated  inward  by  the  Subscapularis,  Latissimus  dorsi.  Teres  major,  and  Pectoralis  major. 

The  most  striking  peculiarities  in  this  joint  are:  (1 )  The  large  size  of  the  head  of  the  humerus 
in  comparison  with  the  depth  of  the  glenoid  cavity,  even  when  supplemented  by  the  glenoid 
ligament.  (2)  The  looseness  of  the  capsule  of  the  joint.  (3)  The  intimate  connection  of  the  cap- 
sule with  the  muscles  attached  to  the  head  of  the  humerus.  (4)  The  peculiar  relation  of  the 
Biceps  tendon  to  the  joint. 

It  is  in  consequence  of  the  relative  size  of  the  two  articular  surfaces  that  the  joint  enjoys  such 
free  movement  in  every  possible  direction.  When  these  movements  of  the  arm  are  arrested  in 
the  shoulder-joint  by  the  contact  of  the  bony  surfaces  and  by  the  tension  of  the  corresponding 
fibres  of  the  capsule,  together  with  that  of  the  muscles  acting  as  accessory  ligaments,  they  can 
be  carried  considerably  farther  by  the  movements  of  the  scapula,  involving,  of  course,  motion  at 


304  THE  ARTICULATIONS,   OR  JOINTS 

the  acromio-  and  sternoclavicular  joints.  These  joints  are  therefore  to  be  regarded  as  accessory 
structures  to  the  shoulder-joint.'  The  extent  of  these  movements  of  the  scapula  is  very  con- 
siderable, especially  in  extreme  elevation  of  the  arm,  which  movement  is  best  accomplished 
when  the  arm  is  thrown  somewhat  forward  and  outward,  because  the  margin  of  the  head  of  the 
humerus  is  by  no  means  a  true  circle;  its  greatest  diameter  is  from  the  bicipital  groove  downward, 
inward,  and  backward,  and  the  greatest  elevation  of  the  arm  can  be  obtained  by  rolling  its 
articular  surface  in  the  direction  of  this  measurement.  The  great  width  of  the  central  portion 
of  the  humeral  head  also  allows  of  very  free  horizontal  movement  when  the  arm  is  raised  to  a 
rifht  ancle,  in  which  movement  the  arch  formed  by  the  acromion,  the  coracoid  process,  and  the 
coracoacromial  ligament  constitutes  a  sort  of  supplemental  articular  cavity  for  the  head  of  the 
bone. 

The  looseness  of  the  capsule  is  so  great  that  the  arm  will  fall  about  an  inch  from  the  scapula 
when  the  muscles  are  dissected  from  the  capsular  ligament  and  an  opening  made  in  it  to  remove 
the  atmospheric  pressure.  The  movements  of  the  joint,  therefore,  are. not  regulated  by  the 
capsule  so  much  as  by  the  surrounding  muscles  and  by  the  pressure  of  the  atmosphere — an 
arrangement  which  "renders  the  movements  of  the  joint  much  more  easy  than  they  would 
otherwise  have  been,  and  permits  a  swinging,  pendulum-like  vibration  of  the  limb  when  the 
muscles  are  at  rest"  (Humphry).  The  fact,  also,  that  in  all  ordinary  positions  of  the  joint  the 
■capsule  is  not  put  on  the  stretch  enables  the  arm  to  move  freely  in  all  directions.  Extreme 
movements  are  checked  by  the  tension  of  appropriate  portions  of  the  capsule,  as  well  as  by  the 
interlocking  of  the  bones.  Thus  it  is  said  that  "abduction  is  checked  by  the  contact  of  the  great 
tuberosity  with  the  upper  edge  of  the  glenoid  cavity,  adduction  by  the  tension  of  the  coraco- 
humeral  ligament"  (Beaunis  et  Bouchard).  Cleland^  maintains  that  the  limitations  of  move- 
ment at  the  shoulder-joint  are  due  to  the  structure  of  the  joint  itself,  the  glenoid  ligament  fitting, 
in  different  positions  of  the  elevated  arm,  into  the  anatomical  neck  of  the  humerus. 

Cathcart^  has  pointed  out  that  in  abducting  the  arm  and  raising  it  above  the  head,  the  scapula 
TOtates  throughout  the  whole  movement  with  the  exception  of  a  short  space  at  the  beginning  and 
at  the  end;  that  the  humerus  moves  on  the  scapula  not  only  from  the  hanging  to  the  horizontal 
position,  but  also  in  passing  upward  as  it  approaches  the  vertical  above;  that  the  clavicle  moves 
not  only  during  the  second  half  of  the  movement  but  in  the  first  as  well,  though  to  a  less  extent — 
i.  p.,  the  scapula  and  clavicle  are  concerned  in  the  first  stage  as  well  as  in  the  second;  and  that 
the  humerus  is  partly  involved  in  the  second  as  well  as  chiefly  in  the  first. 

The  intimate  union  of  the  tendons  of  the  four  short  muscles  with  the  capsule  converts  these 
muscles  into  elastic  and  spontaneously  acting  ligaments  of  the  joint,  and  it  is  regarded  as  being 
also  intended  to  prevent  the  folds  into  which  all  portions  of  the  capsule  would  alternately  fall  in 
the  varying  positions  of  the  joint  from  being  driven  between  the  bones  by  the  pressure  of  the 
atmosphere. 

The  peculiar  relations  of  the  Biceps  tendon  to  the  shoulder-joint  appear  to  subserve  various 
purposes.  In  the  first  place,  by  its  connection  with  both  the  shoulder  and  elbow  the  muscle 
harmonizes  the  action  of  the  two  joints,  and  acts  as  an  elastic  ligament  in  all  positions,  in  the 
manner  previously  adverted  to.*  .\^ext,  it  strengthens  the  upper  part  of  the  articular  cavity,  and 
prevents  the  head  of  the  humerus  from  being  pressed  up  against  the  acromion  process,  when  the 
Deltoid  contracts,  instead  of  forming  the  centre  of  motion  in  the  glenoid  cavity.  By  its  passage 
.along  the  bicipital  groove  it  assists  in  rendering  the  head  of  the  humerus  steady  in  the  various 
movements  of  the  arm.  ^Vhen  the  arm  is  raised  from  the  side  it  assists  the  Supra-  and  Infra- 
spinatus in  rotating  the  head  of  the  humerus  in  the  glenoid  cavity.  It  also  holds  the  head  of  the 
bone  firmly  in  contact  with  the  glenoid  cavity,  and  prevents  its  slipping  over  its  lower  edge,  or 
lieincf  displaced  by  the  action  of  the  Latissimus  dorsi  and  Pectoralis  major,  as  in  climbing 
and  many  other  movements. 

Surface  Form. — The  direction  and  position  of  the  shoulder-joint  may  be  indicated  by  a  line 
•drawn  from  the  middle  of  the  coracoacromial  ligament,  in  a  curved  direction,  with  its  con- 
vexity inward,  to  the  innermost  part  of  that  portion  of  the  head  of  the  humerus  which  can  be 
-felt  in  the  axilla  when  the  arm  is  forcibly  abducted  from  the  side.  When  the  arm  hangs  by  the 
side,  not  more  than  one-third  of  the  head  of  the  bone  is  in  contact  with  the  glenoid  cavity,  and 
three-quarters  of  its  circumference  is  in  front  of  a  vertical  line  drawn  from  the  anterior  border 
•of  the  acromion  process. 

Applied  Anatomy. — Owing  to  the  construction  of  the  shoulder-joint  and  the  freedom  of 
movement  which  it  enjoys,  as  well  as  in  consequence  of  its  exposed  situation,  it  is  more  fre- 
■quently  dislocated  than  any  other  joint  in  the  body.  Dislocations  of  the  shoulder  contribute 
about  forty  per  cent,  of  the  cases  in  tables  of  dislocations.  Dislocation  occurs  when  the  arm 
is  thrown  into  extreme  abduction,  and  when,  therefore,  the  head  of  the  humerus  presses  against 
ithe  lower  and  front  part  of  the  capsule,  which  is  the  thinnest  and  least  supported  part  of  the  liga- 

i  See  p.  299.  ^  Journal  of  Anatomy  and  Physiology,  1884,  vol.  xviii. 

8Ibid.,voI.  xviii.  <  See  p.  267. 


SHOULDEE^  JOINT  305 

ment.  The  rent  in  the  capsule  ahnost  invarialily  takes  jilace  in  this  situation,  between  the 
tendon  of  the  Subscapularis  and  the  Triceps,  and  thn)ui:i;h  it  the  head  of  the  bone  escapes,  so 
that  the  dislocation  in  most  instances  is  primarily  subijlinoid.  The  head  of  the  bone  does  not 
usually  remain  in  this  situation,  but  generally  assumes  some  other  position,  which  varies  accord- 
ing to  the  direction  and  amount  of  force  producing  the  dislocation  and  the  relative  strength  of 
the  muscles  in  front  and  behind  the  joint.  In  consequence  of  the  muscles  at  the  back  being 
weaker  than  those  in  front,  and  especially  on  account  of  the  long  head  of  the  Triceps  preventing 
the  bone  passing  backward,  dislocation  forward  is  much  more  common  than  backward.  The 
most  frequent  position  which  the  head  of  the  humerus  ultimately  assumes  is  on  the  front  of  the 
neck  of  the  scapula,  beneath  the  coracoid  process,  and  hence  named  subcoracoid  dislocation. 
Occasionally,  in  consequence,  probably,  of  a  greater  amount  of  force  being  brought  to  bear  on 
the  limb,  the  head  is  driven  farther  inward,  and  rests  on  the  upper  part  of  the  front  of  the  thorax, 
beneath  the  clavicle  (subclamcular).  If  the  head  of  the  bone  passes  under  the  Subscapularis 
muscle  and  also  under  the  Teres  major  or  the  lower  border  of  the  Pectoralis  major,  the  arm 
remains  abducted,  or  even  with  the  elbow  raised  above  the  head  (luxatio  erecta).  Sometimes 
the  humerus  remains  in  the  position  in  which  it  was  primarily  displaced,  resting  on  the  axillary 
border  of  the  scapula  {subijlenoid),  and  rarely  it  passes  backward  and  remains  in  the  infra- 
spinous  fossa  beneath  the  spine  (subspinous).  If  dislocation  frequently  recurs  the  condition  may 
be  amended  in  some  cases  by  exposing  the  capsule  and  putting  tucks  in  it  by  means  of  sutures. 

An  old  unreduced  dislocation  is  sometimes  treated  by  incising  the  soft  parts  and  returning 
the  head  of  the  humerus  into  the  glenoid  cavity.  In  other  cases  the  head  of  the  humerus  is 
excised.  Dislocation  oi  the  long  tendon  of  the  Biceps  muscle  from  the  bicipital  groove  is  a  rare 
accident.  When  it  occurs  the  arm  is  rigid  in  abduction,  but  the  head  of  the  humerus  is  found 
to  be  in  the  glenoid  cavity.  It  is  reduced  by  flexion  of  the  elbow  and  rotation  of  the  arm.  Rup- 
ture of  the  long  tendon  of  the  Biceps  is  more  common  than  dislocation  of  the  tendon.  After  this 
injury  the  belly  of  the  muscle  is  relaxed  and  is  nearer  than  normal  to  the  elbow;  flexion  of 
the  forearm  is  much  weakened,  and  is  weaker  in  supination  than  it  is  in  pronation.  The  head 
of  the  humerus  passes  forward  and  inward,  and  the  condition  is  often  mistaken  for  dislocation 
of  the  bone. 

If  we  desire  to  aspirate  the  shoulder-joint,  place  the  arm  against  the  side,  flex  the  forearm  at 
a  right  angle  to  the  arm,  carry  the  forearm  across  the  front  of  the  thorax,  and  enter  the  trocar 
below  the  acromion  (De  Vos). 

The  shoulder-joint  is  sometimes  the  seat  of  all  those  inflammatory  affection,?,  both  acute  and 
chronic,  which  attack  joints,  though  perhaps  it  suffers  less  frequently  than  some  other  joints  of 
equal  size  and  importance.  Acute  synovitis  may  result  from  injury,  rheumatism,  or  pyemia,  or 
may  follow  secondarily  on  the  so-called  acute  epiphysitis  of  infants.  It  is  attended  with  effusion 
into  the  joint,  and  when  this  occurs  the  capsule  is  evenly  distended  and  the  contour  of  the  joint 
rounded.  Special  projections  may  occur  at  the  site  of  the  openings  in  the  capsular  ligament. 
Thus,  a  swelling  may  appear  just  in  front  of  the  joint,  internal  to  the  lesser  tuberosity,  from 
effusion  into  the  bursa  beneath  the  Subscapularis  muscle;  or,  again,  a  swelling  which  is  some- 
times bilobed  may  be  seen  in  the  interval  between  the  Deltoid  and  Pectoralis  major  muscles, 
from  effusion  into  the  diverticulum,  which  runs  down  the  bicipital  groove  with  the  tendon  of  the 
Biceps.  The  effusion  into  the  synovial  membrane  can  be  best  ascertained  by  examination  from 
the  axilla,  where  a  soft,  elastic,  fluctuating  swelling  can  usually  be  felt.  The  bursa  beneath  the 
Deltoid  is  sometimes  ruptured  by  violence,  and  sometimes  inflames,  suppurates,  or  becomes 
tuberculous. 

Tuberculous  arthritis  not  infrequently  attacks  the  shoulder-joint,  and  may  lead  to  total 
destruction  of  the  articulation,  when  ankylosis  may  result  or  long-protracted  suppuration  may 
necessitate  excision.  This  joint  is  also  one  of  those  which  is  most  liable  to  be  the  seat  of  osteo- 
arthritis, and  may  also  be  affected  in  gout  and  rheumatism;  or  in  locomotor  ataxia,  when  it 
occasionally  becomes  the  seat  of  Charcot's  disease. 

E.xdsion  of  the  shoulder-joint  may  be  required  in  cases  of  arthritis  (especially  the  tubercu- 
lous form)  which  have  gone  on  to  destruction  of  the  articulation;  in  compound  di^locaticms  and 
fractures,  particularly  those  arising  from  gunshot  injuries,  in  which  there  has  been  extensive 
injury  to  the  head  of  the  bone;  in  some  cases  of  old  unreduced  dislocation,  where  there  is  much 
pain;  and  possibly  in  some  few  cases  of  growth  connected  with  the  upper  end  of  the  bone.  The 
operation  is  best  performed  by  making  an  incision  from  the  middle  of  the  coracoacromial  liga- 
ment down  the  arm  for  about  three  inches;  this  will  expose  the- bicipital  groove  and  the  tendon 
of  the  Biceps,  which  may  be  either  divided  or  hooked  out  of  the  way,  according  as  to  whether  it 
is  implicated  in  the  disease  or  not.  The  capsule  is  then  freely  opened,  and  the  muscles  attached 
to  the  greater  and  lesser  tuberosities  of  the  humerus  divided.  The  head  of  the  bone  can  then 
be  thrust  out  of  the  wound  and  sawed  off,  or  divided  with  a  narrow  saw  in  situ  and  subsequently 
removed.  The  section  should  be  made,  if  possible,  just  below  the  articular  surface,  so  as  to 
leave  the  bone  as  long  as  possible.  The  glenoid  cavity  must  then  be  examined,  and  gouged 
if  carious. 

20 


306 


THE  ARTICULATIONS,   OB  JOINTS 


V.  Elbow-joint  (Articulatio  Cubiti)  (Figs.  248,  249). 

The  elbow  is  a  ginglymus  or  hinge-joint.  The  bones  entering  into  its  forma- 
tion are  the  trochlea  of  the  humerus,  which  is  received  into  the  greater  sigmoid 
cavity  of  the  ulna,  and  admits  of  the  movements  peculiar  to  such  a  joint — viz., 
flexion  and  extension;  while  the  capitellum  or  radial  head  of  the  humerus  articu- 
lates with  the  cup-shaped  depression  on  the  head  of  the  radius;  the  circum- 
ference of  the  head  of  the  radius  articulates  with  the  lesser  sigmoid  cavity  of 
the  ulna,  allowing  of  the  movement  of  rotation  of  the  radius  on  the  ulna,  the 
chief  action  of  the  superior  radioulnar  articulation.  The  articular  surfaces 
are  covered   by  a  thin  layer  of  hyaline  cartilage,  and  connected  by  a  capsular 


Fig.  248. — Left  elbow-joint,  showing  anterior 
and  internal  ligaments. 


Fig.  249. — Left  elbow-joint,  showing  posterior 
and  external  ligaments. 


ligament  (capsula  articulafis)  (Fig.  250)  of  unequal  thickness,  being  especially 
thickened  on  its  two  sides  and,  to  a  less  extent,  in  front  and  behind.  These 
thickened  portions  are  usually  described  as  distinct  ligaments  under  the  following 
names: 


Anterior. 
Posterior. 


Internal  Lateral. 
External  Lateral, 


ELBOW  JOINT 


307 


The  orbicular  ligament  of  the  upper  radio-ulnar  articulation  must  also  be 
reckoned  among  the  ligaments  of  the  elbow  (see  p.  310). 

The  anterior  ligament  (Fig.  248)  is  a  broad  and  thin  fibrous  layer  which  covers 
the  anterior  surface  of  the  joint.  It  is  attached,  above,  to  the  front  of  the  internal 
condyle  and  to  the  front  of  the  humerus  immediately  above  the  coronoid  and 
radial  fossae;  belotv,  to  the  anterior  surface  of  the  coronoid  process  of  the  ulna 
and  to  the  orbicular  ligament,  being  continuous  on  each  side  with  the  lateral 
ligaments.  Its  superficial  fibres  pass  obliquely  from  the  inner  condyle  of  the 
humerus  outward  to  the  orbicular  ligament.  The  middle  fibres,  vertical  in 
direction,  pass  from  the  upper  part  of  the  coronoid  depression  and  become  partly 
blended  with  the  preceding,  but  are  mainly  inserted  into  the  anterior  surface  of 
the  coronoid  process.  The 
deep  or  transverse  set  inter- 
sects these  at  right  angles. 
This  ligament  is  in  relation, 
in  front,  with  the  Brachialis 
anticus  muscle,  except  at  its 
outermost  part. 

The  posterior  ligament 
(Fig.  249)  is  a  thin  and  loose 
membranous  fold,  attached, 
above,  to  the  lower  end  of 
the  humerus,  above  and  at 
the  sides  of  the  olecranon 
fossa;  below,  to  the  groove 
on  the  upper  and  outer  sur- 
faces of  the  olecranon.  The 
superficial  or  transverse  fibres 
pass  between  the  adjacent 
margins  of  the  olecranon 
fossa.  The  deeper  portion 
consists  of  vertical  fibres, 
some  of  which,  thin  and 
weak,  pass  from  the  upper 
part  of  the  olecranon  fossa  to 
the  margin  of  the  olecranon; 
others,  thicker  and  stronger, 
pass  from  the  back  of  the 
capltellum  of  the  humerus  to 
the  posterior  border  of  the 
lesser  sigmoid  cavity  of  the 
ulna.  This  ligament  is  in 
relation,  behind,  with  the 
tendon  of  the  Triceps  muscle 
and  the  Anconeus  muscle. 

The  internal  lateral  ligament  (ligamentum  collaterale  ulnare)  (Fig.  248)  is 
a  thick  triangular  band  consisting  of  two  portions,  an  anterior  and  posterior, 
united  by  a  thinner  intermediate  portion.  The  anterior  portion,  directed  obliquely 
forward,  is  attached,  above,  by  its  apex,  to  the  front  part  of  the  internal  condyle 
of  the  humerus;  and,  below,  by  its  broad  base,  to  the  inner  margin  of  the  coronoid 
process.  The  posterior  portion,  also  of  triangular  form,  is  attached,  above,  by 
its  apex,  to  the  lower  and  back  part  of  the  internal  condyle;  below,  to  the  inner 
margin  of  the  olecranon.  Between  these  two  bands  a  few  intermediate  fibres 
descend  from  the  internal  condyle  to  blend  with  a  transverse  band  of  ligamentous 


50. — Right  elbow-joint,  cut   tlirough   at    right   angles  to  the 
of  the  trochlea  humeri,  from  the  ulnar  side.     (Spalteholz.) 


308 


THE  ARTICULATIONS,    OR  JOINTS 


tissue  which  bridges  across  the  notch  between  the  olecranon  and  coronoid  pro- 
cesses. This  ligament  is  in  relation,  internally,  with  the  Triceps  and  Flexor 
carpi  ulnaris  muscles  and  the  ulnar  nerve,  and  gives  origin  to  part  of  the  Flexor 
sublimis  digitorum  muscle. 

The  external  lateral  ligament  {ligamenhmi  collatemle  radiale)  (Fig.  249)  is  a 
short  and  narrow  fibrous  band  less  distinct  than  the  internal,  attached,  above, 
to  a  depression  below  the  external  condyle  of  the  humerus;  below,  to  the  orbicular 
ligament,  some  of  its  most  posterior  fibres  passing  over  that  ligament,  to  be 
inserted  into  the  outer  margin  of  the  ulna.  This  ligament  is  intimately  blended 
with  the  tendon  of  origin  of  the  Supinator  [brevis]  muscle. 


Synovial  Membrane  (Fig.  250). — The  synovial  itiembrane  is  very  extensive.  It  covers  the 
margin  of  the  articular  surface  of  the  humerus,  and  lines  the  coronoid  and  olecranon  fossae  on 
that  bone;  from  these  points  it  is  reflected  over  the  anterior,  posterior,  and  lateral  ligaments, 

and  forms  a  pouch  (recessus  sacciformis)  between 
the  lesser  sigmoid  cavity,  the  internal  surface  of 
the  orbicular  ligament,  and  the  circumference  of 
the  head  of  the  radius.  Projecting  into  the  cavity 
is  a  crescentic  fold  of  synovial  membrane,  between 
the  radius  and  ulna,  suggesting  the  division  of  the 
joint  into  two — one  the  humeroradial,  the  other  the 
humeroulnar. 

Between  the  capsular  ligament  and  the  synovial 
membrane  are  three  masses  of  fat — one,  the  largest, 
above  the  olecranon  fossa,  which  is  pressed  into 
the  fossa  by  the  Triceps  during  flexion;  a  second, 
over  the  coronoid  fossa;  and  a  third,  over  the 
radial  fossa.  The  two  last-named  pads  are  pressed 
into  their  respective  fossse  during  extension. 

The  muscles  (Fig.  251)  in  relation  with  the  joint 
are,  in  front,  the  Brachialis  anticus;  behind,  the 
Triceps  and  Anconeus;  externally,  the  Supinator 
[brevis]  and  the  common  tendon  of  origin  of  the 
Extensor  muscles;  internally,  the  common  tendon 
of  origin  of  the  Flexor  muscles,  and  the  Flexor 
carpi  ulnaris,  with  the  ulnar  nerve. 

The  arteries  supplying  the  joint  are  derived 
from  the  anastomosis  between  the  superior  pro- 
funda, inferior  profunda,  and  anastomotica  magna, 
branches  of  the  brachial,  with  the  anterior,  pos- 
terior, and  interosseous  recurrent  branches  of  the 
ulnar  and  the  recurrent  branch  of  the  radial. 
These  vessels  form  a  complete  chain  of  anasto- 
moses around  the  joint. 

The  nerves  are  derived  from  the  ulnar  as  it 
passes  between  the  internal  condyle  and  the  olec- 
ranon ;  a  filament  from  the  musculocutaneous,  and 
two  filaments  from  the  median. 
Bursse.^The  olecranon  hva&a,  {bursa  snbcnfanea  olecrani)  is  placed  between  the  olecranon 
process  and  the  cutaneous  surface.  A  bursa  exists  between  the  tendon  of  the  Biceps  brachii 
and  the  tubercle  of  the  radius  (bursa  bicipitoradialis);  another  between  the  Triceps  tendon  and 
the  olecranon  process  {bursa  subtendinea  olecrani) ;  a  third  between  the  cutaneous  surface  and  the 
external  condyle  {bursa  subcuianea  epicondyli  humeri  lateralis) ;  a  fourth  between  the  cutaneous 
surface  and  the  internt,!  condyle  {bursa  subcutanea  epicondyli  humeri  ?nedialis);  and  a  fifth 
internal  to  the  Triceps  ttndon  at  its  insertion  on  the  olecranon  {bursa  intratendi?iea  olecrani). 

Movements. — The  elbow-joint  comprises  three  different  portions — viz.,  the  joint  between 
the  ulna  and  humerus,  that  between  the  head  of  the  radius  and  the  humerus,  and  the  superior 
radioulnar  articulation,  described  below.  All  these  articular  surfaces  are  invested  by  a  common 
synovial  membrane,  and  the  movements  of  the  whole  joint  should  be  studied  together.  The  com- 
bination of  the  movements  of  flexion  and  extension  of  the  forearm  with  those  of  pronation  and 
supination  of  the  hand,  which  is  insured  by  the  two  being  performed  at  the  same  joint,  is  essential 
to  the  accuracy  of  the  various  minure  movements  of  the  hand. 

The  portion  of  the  joint  between  the  ulna  and  humerus  is  a  simple  hinge-joint,  and  allows 


Fig  2d1      ^      It   I  )  ,  I 

joint    taken  somewhat  obhquelj  d 
the  radial  aspect      (A.fter  Braune  ) 


ELBOW-JOINT  309 

of  movements  of  flexion  and  extension  only.  Owing  to  the  obliquity  of  the  trochlear  surface  of 
the  humerus,  this  movement  does  not  take  place  in  a  straight  line.  When  the  forearm  is  extended 
and  supinated  the  axis  of  the  arm  is  not  in  the  same  line  as  the  axis  of  the  forearm,  but  the  axis 
of  the  arm  forms  an  angle  with  the  axis  of  the  forearm,  and  the  hand,  with  the  forearm,  is 
directed  outward.  During  flexion,  on  the  other  hand,  the  forearm  and  the  hand  tend  to  approach 
the  middle  line  of  the  body,  and  thus  enable  the  hand  to  be  easily  carried  to  the  face.  The  shape 
of  the  articular  surface  of  the  humerus,  with  its  prominences  and  depressions  accurately  adapted 
to  the  opposing  surface  of  the  olecranon,  prevents  any  lateral  movement.  Flexion  is  produced 
by  the  action  of  the  Biceps  and  Brachialis  anticus,  assisted  by  the  muscles  arising  from  the  inter- 
nal condyle  of  the  humerus  and  by  the  Brachioradialis;  extension,  by  the  Triceps  and  Anconeus, 
assisted  by  the  Extensors  of  the  wrist  and  by  the  Extensor  communis  digitorum  and  Extensor 
minimi  digiti. 

The  joint  between  the  head  of  the  radius  and  the  capitellum  or  radial  head  of  the  humerus 
is  an  arthrodial  joint.  The  bony  surfaces  would  of  themselves  constitute  an  enarthrosis,  and 
allow-  of  the  movement  in  all  directions  were  it  not  for  the  orbicular  ligament  by  which  the  head 
of  the  radius  is  bound  down  firmly  to  the  lesser  sigmoid  cavity  of  the  ulna,  an  arrangement  which 
prevents  any  lateral  separation  of  the  two  bones.  It  is  to  the  same  ligament  that  the  head  of 
the  radius  owes  its  security  from  dislocation,  which  would  otherwise  constantly  occur  as  a  con- 
sequence of  the  shallowness  of  the  cup-like  surface  on  the  head  of  the  radius.  In  fact,  but  for 
this  ligament  the  tendon  of  the  Biceps  would  be  liable  to  pull  the  head  of  the  radius  out  of  joint.' 
In  complete  extension  the  head  of  the  radius  glides  so  far  back  on  the  outer  condyle  that  its 
edge  is  plainly  felt  at  the  back  of  the  articulation.  Flexion  and  extension  of  the  elbow-joint  are 
limited  by  the  tension  of  the  structures  on  the  front  and  back  of  the  joint,  the  limitation  of  flexion 
being  also  aided  by  the  soft  structures  of  the  arm  and  forearm  coming  in  contact. 

In  combination  with  any  position  of  flexion  or  extension  the  head  of  the  radius  can  be  rotated 
in  the  upper  radioulnar  joint,  carrying  the  hand  with  it.  The  hand  is  directly  articulated  to  the 
lower  surface  of  the  radius  only,  and  the  concave  or  sigmoid  surface  on  the  lower  end  of  the 
radius  travels  around  the  lower  end  of  the  ulna.  The  latter  bone  is  excluded  from  the  wrist-joint 
(as  will  be  seen  in  the  sequel)  by  the  articular  disk.  Thus,  rotation  of  the  head  of  the  radius 
around  an  axis  which  passes  through  the  centre  of  the  radial  head  of  the  humerus  imparts  circular 
movement  to  the  hand  through  a  very  considerable  arc. 

Surface  Form. — If  the  forearm  be  slightly  flexed  on  the  arm,  a  curved  crease  or  fold  with 
its  convexity  downward  may  be  seen  running  across  the  front  of  the  elbow,  extending  from  one 
condyle  to  the  other.  The  centre  of  this  fold  is  some  slight  distance  above  the  line  of  the  joint. 
The  position  of  the  radiohumeral  portion  of  the  joint  can  be  at  once  ascertained  by  feeling  for  a 
slight  groove  or  depression  between  the  head  of  the  radius  and  the  capitellum  of  the  humerus  at 
the  back  of  the  articulation. 

Applied  Anatomy. — From  the  great  breadth  of  the  joint,  and  the  manner  in  which  the  articular 
surfaces  are  interlocked,  and  also  on  account  of  the  strong  lateral  ligaments  and  the  support 
which  the  joint  derives  from  the  mass  of  muscles  attached  to  each  condyle  of  the  humerus, 
lateral  displacement  of  the  bones  is  very  uncommon,  whereas  antero-posterivr  dislocation,  on 
account  of  the  shortness  of  the  antero-posterior  diameter,  the  weakness  of  the  anterior  and 
posterior  ligaments,  and  the  want  of  support  of  muscles,  much  more  frequently  takes  place, 
dislocation  backward  taking  place  when  the  forearm  is  in  a  position  of  extension,  and  forward 
when  in  a  position  of  flexion.  For,  in  the  former  position,  that  of  extension,  the  coronoid  process 
is  not  interlocked  into  the  coronoid  fossa,  and  loses  its  grip  to  a  certain  extent,  whereas  the 
olecranon  process  is  in  the  olecranon  fossa,  and  entirely  prevents  displacement  forward.  On 
the  other  hand,  during  flexion,  the  coronoid  process  is  in  the  coronoid  fossa,  and  prevents  dis- 
location backward,  while  the  olecranon  loses  its  grip  and  is  not  so  efficient,  as  during  extension, 
in  preventing  a  forward  displacement.  When  lateral  dislocation  does  take  place,  it  is  generally 
incomplete. 

Dislocation  of  the  elbow-joint  is  of  common  occurrence  in  children,  far  more  common  than 
dislocation  of  any  other  articulation.  In  lesions  of  this  joint  there  is  often  very  great  difficultv  in 
ascertaining  the  exact  nature  of  the  injury.  Sprain  of  the  elbow  is  a  very  common  injury  in  child- 
hood. Injury  to  the  radiohumeral  joint  is  frequently  ]>roduced  by  lifting  a  child  by  the  hand, 
as  in  swinging  it  over  a  gutter.  The  Supinator  [brevis],  which  under  normal  circumstances  would 
retain  the  head  of  the  radius  against  the  capitellum  of  the  humerus,  is  unable  to  do  so,  the  radio- 
humeral articulation  receives  the  force  and  the  orbicular  ligament  undergoes  upward  displace- 
ment, is  caught  between  the  head  of  the  radius  and  the  capitellum,  and  jams  the  joint.  This 
injury  is  often  called  subluxation  of  the  head  of  the  radius. 

The  elbow-joint  is  occasionally  the  seat  of  acute  synovitis.  The  synovial  membrane  then 
becomes  distended  with  fluid,  the  bulging  showing  itself  principally  around  the  olecranon  process; 
that  is  to  say,  on  its  inner  and  outer  sides  and  above,  in  consequence  of  the  laxness  of  the 

'  Humphry,  op.  cit..  p.  419. 


310  THE  ARTICULATIONS,   OB  JOINTS 

posterior  ligament.  Occasionally,  a  weE-marked,  triangular  projection  may  be  seen  on  the  outer 
side  of  the  olecranon,  from  bulging  of  the  synovial  membrane  beneath  the  Anconeus  muscle. 
A^ain,  there  is  often  some  swelling  just  above  the  head  of  the  radius,  in  the  line  of  the  radio- 
humeral  joint.  There  is  generally  not  much  swelling  at  the  front  of  the  joint,  though  sometime'^ 
deep-seated  fulness  beneath  the  Brachialis  anticus  may  be  noted.  When  suppuration  occurs  rlifj 
abscess  usually  points  at  one  or  other  border  of  the  Triceps  muscle;  occasionally  the  pus  dis- 
charges itself  in  front,  near  the  insertion  of  the  Brachialis  anticus  muscle.  Chronic  synovitis, 
usually  of  tuberculous  origin,  is  of  common  occurrence  in  the  elbow-joint;  under  these  circum- 
stance's the  forearm  tends  to  assume  the  position  of  semiflexion,  which  is  that  of  greatest  ease 
and  relaxation  of  ligaments.  It  should  be  borne  in  mind  that  should  ankylosis  occur  in  this  or 
the  extended  position,  the  limb  will  not  be  nearly  so  useful  as  if  it  becomes  ankylosed  in  a  position 
of  rather  less  than  a  right  angle.  Loose  cartilages-  are  sometimes  met  with  in  the  elbow-joint, 
not  so  commonly,  however,  as  in  the  knee;  nor  do  they,  as  a  rule,  give  rise  to  such  urgent  symp- 
toms. They  rarely  require  operative  interference.  The  elbow-joint  is  also  sometimes  affected 
with  osteoarthritis,  but  this  affection  is  less  common  in  this  articulation  than  in  some  other 
of  the  larger  joints.  Bursitis  about  the  elbow,  generally  known  as  miners'  elboiv,  is  not 
uncommon. 

Excision  of  the  elbow  is  principally  required  for  one  of  three  conditions — viz.,  tuberculous 
arthritis,  injury  and  its  results,  and  ankylosis  in  a  positior.  which  greatly  impairs  the  useful- 
ness of  the  limb;  but  may  be  necessary  for  some  other  rarer  conditions,  such  as  disorganizing 
arthritis  after  pyemia,  unreduced  dislocation,  and  osteoarthritis.  The  results  of  the  operation 
are,  as  a  rule,  more  favorable  than  those  of  excision  of  any  other  joint,  and  it  is  one,  therefore, 
that  the  surgeon  should  never  hesitate  to  perform,  especially  in  the  first  three  of  the  conditions 
mentioned  above.  The  operation  is  best  performed  by  a  single  vertical  incision  down  the  back 
of  the  joint,  a  transverse  incision,  over  the  outer  condyle,  being  added  if  the  parts  are  much 
thickened  and  fixed.  A  straight  incision  is  made  about  four  inches  long,  the  mid-point  of  which 
is  on  a  level  with  and  a  little  to  the  inner  side  of  the  tip  of  the  olecranon.  This  incision  is  made 
down  to  the  bone,  through  the  substance  of  the  Triceps  muscle.  The  operator  with  the  point 
of  his  knife,  and  guarding  the  soft  parts  with  his  thumb-nail,  separates  them  from  the  bone. 
In  doing  this  there  are  two  structures  which  he  should  carefully  avoid — the  ulnar  nerve,  which 
lies  parallel  to  his  incision,  but  a  little  internal,  as  it  courses  down  between  the  internal  condyle 
and  the  olecranon  process,  and  the  prolongation  of  the  Triceps  into  the  deep  fascia  of  the  fore- 
arm over  the  Anconeus  muscle.  Having  cleared  the  bones  and  divided  the  lateral  and  posterior 
lio-aments,  the  forearm  is  strongly  flexed  and  the  ends  of  the  bone  turned  out  and  sawed  off.  The 
section  of  the  humerus  should  be  through  the  base  of  the  condyles,  that  of  the  ulna  and  radius 
should  be  just  below  the  level  of  the  lesser  sigmoid  cavity  of  the  ulna  and  the  neck  of  the  radius. 
In  this  operation  the  object  is  to  obtain  such  fibrous  union  as  shall  allow  free  motion  of  the 
bones  of  the  forearm:  and,  therefore,  passive  motion  must  be  commenced  early,  that  is  to  say, 
about  the  tenth  day. 

VT.  Radioulnar  Articulation  (Articulatio  Radioulnaris) . 

The  articulation  of  the  radius  with  the  ulna  is  effected  by  ligaments  which 
connect  both  extremities  as  well  as  the  shafts  of  these  bones.  It  may,  conse- 
quently, be  subdivided  into  three  articulations:  (1)  The  superior  radioulnar, 
which  is  a  portion  of  tlie  elbow-joint;  (2)  the  middle  radioulnar;  and  (3)  the 
inferior  radioulnar  articulations. 


1.  Superior  Articulation  (Articulatio  Radioulnaris  Proximalis). 

This  articulation  is  a  trochoid  or  pivot-joint.  The  bones  entering  into  its  forma- 
tion are  the  inner  side  of  the  circumference  of  the  head  of  the  radius  rotating 
within  tlie  lesser  sigmoid  cavity  of  the  ulna.  Its  only  ligament  is  the  annular 
or  orbicular. 

The  orbicular  or  annular  ligament  (Jigamenium  annulare  radii)  (Figs.  248, 249, 
and  2.52)  is  a  strong,  flat  band  of  ligamentous  fibres  which  surrounds  the  head  of 
the  radius  and  retains  it  in  firm  connection  with  tire  lesser  sigmoid  cavity  of  the 
ulna.  It  fonns  about  four-fifths  of  an  osseofibrous  ring,  attached  by  each  end  to 
tlie  extremities  of  the  lesser  sigmoid  cavity,  and  is  smaller  at  the  lower  part  of  its 


BA  DIO  ULNAR  A  R  TICULA  TION 


311 


ORBICULAR 


circumference  than  above,  by  which  means  the  head  of  the  radius  is  more  securely 
held  in  its  position.  Its  outer  surface  is  strengthened  by  the  external  lateral 
ligament  of  the  elbow,  and  affords 
origin  to  part  of  the  Supinator  [brevis] 
muscle.  Its  inner  surface  is  smooth, 
and  lined  with  synovial  membrane. 
The  synovial  mem  brane  is  continuous 
with  that  which  lines  the  elbow-joint. 

Movements. — The  movement  which  takes 
place  in  this  articulation  is  limited  to  rotation 
of  the  head  of  the  radius  within  the  orbicular 
ligament,  and  upon  the  lesser  sigmoid  cavity 
of  the  ulna;  the  axis  of  rotation  passes  through 
the  centre  of  the  capitellum  of  the  humerus. 
Rotation  forward  is  called  pronation;  rota- 
tion backward,  supinaiion.  Supination  is 
performed  by  the  Biceps  and  Supinator 
[brevis],  assisted  to  a  slight  extent  by  the  Ex- 
tensor muscles  of  the  thumb  and,  in  certain 
positions,  by  the  Brachioradialis.  Pronation 
is  effected  by  the  Pronator  teres  and  Pronator 
quadratus,  assisted,  in  some  positions,  by  the 
BrJichioradialis. 

Surface  Form. — The  position  of  the  su- 
perior radioulnar  joint  is  marked  on  the 
surface  of  the  body  by  the  little  dimple  on 
the  back  of  the  elbow,  which  indicates  the 
position  of  the  head  of  the  radius. 

Applied  Anatomy.— D;.?/oca(?o».  of  the 
head  of  the  radius  alone  is  not  an  uncommon 
accident,  and  occurs  most  frequently  in  young 
persons  from  falls  on  the  hand  when  the  fore- 
arm is  extended  and  supinated,  the  head  of 
the  bone  being  displaced  forward.  It  is  at- 
tended by  rupture  of  the  orbicular  ligament. 
Occasionally  a  peculiar  injury,  which  is  sup- 
posed to  be  a  subluxation,  occurs  in  young 
children  in  lifting  them  from  the  ground  by 
the  hand  or  forearm.  It  is  believed  that  the 
head  of  the  radius  is  displaced  downward  or 
the  orbicular  ligament  upward,  and  the  upper 
border  of  the  ligament  becomes  folded  over 
the  head  of  the  radius,  between  it  and  the 
capitellum  of  the  humerus. 


2.  Middle  R.\dioulnar  Lig.\ments.  ' 

The  interval  between   the  shafts  of 
the  radius  and  ulna  is  occupied  by  two 

ligaments. 


Oblique. 
Interosseous. 

The  oblique  ligament  (chorda  ohli-  ^'°- '""-^^eX  ^4lt\■s1LV'°Ts^™teh;lz^  *'"'  "'"" 
qua)  (Figs.  248  and  252)  is  a  small,  flat- 
tened fibrous  band  which  extends  obliquely  downward  and  outward  from  the 
tubercle  of  the  ulna  at  the  base  of  the  coronoid  process  to  the  radius  a  little  below 
the  bicipital  tuberosity.     Its  fibres  run  in  the  opposite  direction  to  those  of  the 


312 


THE  ARTICULATIONS,   OB  JOINTS 


interosseous  ligament,  and  it  appears  to  be  placed  as  a  substitute  for  it  in  the 
upper  part  of  the  interosseous  interval.  This  ligament  is  sometimes  wanting. 
The  interosseous  membrane  (membrana  interossea  antehrachii)  (Fig.  252)  is  a 
broad  and  thin  plane  of  fibrous  tissue  descending  obliquely  downward  and  inward, 
from  the  interosseous  ridge  on  the  radius  to  that  on  the  ulna.  It  is  deficient 
above,  commencing  about  an  inch  beneath  the  tubercle  of  the  radius;  is  broader 
in  the  middle  than  at  either  extremity;  and  presents  an  oval  aperture  just  above 
its  lower  margin  for  the  passage  of  the  anterior  interosseous  vessels  to  the  back  of 
the  forearm.  This  ligament  serves  to  connect  the  bones  and  to  increase  the  extent 
of  surface  for  the  attachment  of  the  deep  muscles.  Between  its  upper  border 
and  the  oblique  ligament  an  interval  exists  through  which  the  posterior  inter- 
osseous vessels  pass  to  the  dorsum  of  the  forearm.  Two  or  three  fibrous  bands 
are  occasionally  found  on  the  dorsal  surface  of  this  membrane  which  descend 
obliquely  from  the  ulna  toward  the  radius,  and  which  have  consequently  a  direc- 
tion contrary  to  that  of  the  other  fibres.  It  is  in  relation,  in  front,  by  its  upper 
three-fourths  with  the  Flexor  longus  pollicis  on  the  outer  side,  and  with  the 
Flexor  profundus  digitorum  on  the  inner,  lying  upon  the  interval  between  which 
are  the  anterior  interosseous  vessels  and  nerve;  by  its  lower  fourth,  with  the  Pro- 
nator quadratus;  behind,  with  the  Supinator  [brevis].  Extensor  ossis  metacarpi 
pollicis,  Extensor  brevis  pollicis.  Extensor  longus  pollicis.  Extensor  indicis;  and, 
near  the  wrist,  with  the  anterior  interosseous  artery  and  posterior  interosseous 


3.  Inferior  Articulation  (Articulatio  Radioulnaris  Distalis). 

This  is  a  pivot-joint,  formed  by  the  sigmoid  cavity  at  the  inner  side  of  the  lower 
end  of  the  radius  receiving  the  head  of  the  ulna.  The  articular  surfaces  are 
covered  by  a  thin  layer  of  hyaline  cartilage,  and  connected  by  a  capsule,  portions 
of  which  are  usually  described  as  distinct  ligaments.  The  ligaments  of  the 
articulation  are: 

Anterior  Radioulnar.  Posterior  Radioulnar. 

Triangular  Articular  Disk. 

The  anterior  radioulnar  ligament  (Fig.  253)  is  a  narrow  band  of  fibres 
extending  from  the  anterior  margin  of  the  sigmoid  cavity  of  the  radius  to  the 
anterior  surface  of  the  head  of  the  ulna. 

The  posterior  radioulnar  ligament  (Fig.  254)  extends  between  similar  points 
on  the  posterior  surface  of  the  articulation. 

The  triangular  articular  disk  (discus  articularis)  (Figs.  252  and  256)  is  triangular 
in  shape,  and  is  placed  transversely  beneath  the  head  of  the  ulna,  binding  the  lower 
end  of  this  bone  and  the  radius  firmly  together.  Its  periphery  is  thicker  than  its 
centre,  which  is  thin  and  occasionally  perforated.  It  is  attached  by  its  apex 
to  a  depression  which  separates  the  styloid  process  of  the  ulna  from  the  head  of 
that  bone;  and  by  its  base,  which  is  thin,  to  the  prominent  edge  of  the  radius, 
which  separates  the  sigmoid  cavity  from  the  carpal  articulating  surface.  Its 
margins  are  united  to  the  ligaments  of  the  wrist-joint.  Its  upper  surface,  smooth 
and  concave,  articulates  with  the  head  of  the  ulna,  forming  an  arthrodial  joint; 
its  under  surface,  also  concave  and  smooth,  forms  part  of  the  wrist-joint  and  articu- 
lates with  the  cuneiform  and  inner  part  of  the  semilunar  bone.  Both  surfaces 
are  covered  by  a  synovial  membrane — the  upper  surface  by  one  peculiar  to  the 
radioulnar  articulation;  the  under  surface,  by  the  synovial  membrane  of  the 
wrist. 


RADIOULNAR  ARTICULATION 


3l3 


Synovial  Membrane. — The  synovial  membrane  (Fig.  256)  of  this  articulation  has  been  called, 
from  its  extreme  looseness,  the  membrana  sacciformis.  It  projects  horizontally  inward  between 
the  head  of  the  ulna  and  the  articular  disk,  and  upward' between  the  radius  and  the  ulna,  forming 
a  very  loose  cul-de-sac  {reccssus  sacciformis).  The  quantity  of  synovia  which  it  contains  is  usually 
considerable.    The  inferior  radioulnar  joint  does  not  communicate  with  the  wrist-joint. 


radioulnar 
articulation. 


Carpometacarpal 
iculatimis. 


Fig.  253, — Ligaments  of  wrist  and  hand.     Anterior  viewv 


Inferior  radioulnar 

articulation 

Wrist-joint 


Carpal  articulations 


Carpometacarpal 

articulation 


Fig.  254. — Ligaments  of  wrist  and  hand.     Posterior  i 

Movements.— These  consist  of  a  movement  of  rotation  through  about  1 60  degrees  of  the  lower 
end  of  the  radius  around  an  axis  which  corresponds  to  the  centre  of  the  head  of  the  ulna.  When 
the  radius  rotates  forward,  pronation  of  the  forearm  and  hand  is  the  result;  and  when  backwaid, 
snpinaiion.  It  will  thus  be  seen  that  in  pronation  and  supination  of  the  forearm  and  hand 
the  radius  describes  a  segment  of  a  cone,  the  axis  of  which  extends  from  the  centre  of  the  head 


314  THE  ARTICULATIONS,   OR  JOINTS 

of  the  radius  to  the  middle  of  the  head  of  the  ulna.  In  this  movement,  however,  the  ulna  is 
not  quite  stationary,  but  rotates  a  little  in  the  opposite  direction.  So  that  it  also  describes  the 
segment  of  a  cone,  though  of  smaller  size  than  that  described  by  the  radius.  The  movement 
■n-hich  causes  this  alteration  in  the  position  of  the  head  of  the  ulna  takes  place  principally  at  the 
shoulder-joint  by  the  rotation  of  the  humerus,  but  possibly  also  to  a  slight  extent  at  the  elbow- 
joint.' 

Surface  Form. — The  position  of  the  inferior  radio-ulnar  joint  may  be  ascertained  by  feeling 
for  a  slight  groove  at  the  back  of  the  ^\Tist,  between  the  prominent  head  of  the  ulna  and  the 
lower  end  of  the  radius,  when  the  forearm  is  in  a  state  of  almost  complete  pronation. 

VII.  Radiocarpal  or  Wrist-joint  (Articulatio  Radiocarpea)   (Figs.  253,  254). 

The  wrist  is  a  condyloid  articulation.  The  parts  entering  into  its  formation 
are  the  lower  end  of  the  radius  and  under  surface  of  the  articular  disk,  which 
form  together  the  receiving  cavity,  and  the  scaphoid,  semilunar,  and  the  cunei- 
form bones,  which  form  the  condyle.  The  articular  surface  of  the  radius  and  the 
under  surface  of  the  articular  disk  are  the  receiving  cavity,  forming  together  a 
transversely  elliptical  concave  surface.  The  articular  surfaces  of  the  scaphoid, 
semilunar,  and  cuneiform  bones  form  together  a  smooth,  convex  surface,  the  con- 
dyle, which  is  received  into  the  concavity  above  mentioned.  All  the  bony  surfaces 
of  the  articulation  are  co\'ered  by  hyaline  cartilage,  and  are  connected  by  a  capsule, 
which  is  divided  into  the  following  ligaments: 

External  Lateral.  Anterior. 

Internal  Lateral.  Posterior. 

The  external  lateral  ligament  Qigamentum  collaterale  carpi  radiale)  (Fig.  253) 
extends  from  the  summit  of  the  styloid  process  of  the  radius  to  the  outer  side  of 
the  scaphoid,  some  of  its  fibres  being  prolonged  to  the  trapezium  and  annular 
ligament. 

The  internal  lateral  ligament  (llgamenttim  collaterale  carpi  ulnars)  (Fig.  253) 
is  a  rounded  cord,  attached,  above,  to  the  extremity  of  the  styloid  process  of  the 
ulna,  and  dividing,  below,  into  two  fasciculi,  which  are  attached,  one  to  the  inner 
side  of  the  cuneiform  bone,  the  other  to  the  pisiform  bone  and  annular  ligament. 

The  anterior  or  volar  ligament  (ligamentum,  radiocarpeum  volare)  (Fig.  253) 
is  a  broad,  membranous  band,  attached,  above,  to  the  anterior  margin  of  the 
lower  end  of  the  radius,  to  its  styloid  process,  and  to  the  ulna;  its  fibres  pass  down- 
ward and  inward  to  be  inserted  into  the  palmar  surface  of  the  scaphoid,  semilunar, 
and  cuneiform  bones.  Some  of  the  fibres  are'  continued  to  the  os  magnum.  In 
addition  to  this  broad  membrane  there  is  a  distinct  rounded  fasciculus,  superficial 
to  the  rest,  which  passes  from  the  base  of  the  styloid  process  of  the  ulna  to  the  semi- 
lunar and  cuneiform  bones.  This  ligament  is  perforated  by  numerous  apertures 
for  the  passage  of  vessels,  and  is  in  relation,  in  front,  with  the  tendons  of  the 
Flexor  profundus  digitorum  and  of  the  Flexor  longus  pollicis. 

The  posterior  or  dorsal  ligament  {ligamentum  radiocarpeum  dorsale)  (Fig.  254), 
thinner  and  weaker  than  the  anterior,  is  attached,  above,  to  the  posterior  border 
of  the  lower  end  of  the  radius ;  its  fibres  pass  obliquely  downward  and  inward,  to 
be  attached  to  the  dorsal  surface  of  the  scaphoid,  semilunar,  and  cuneiform  bones, 
and  are  continuous  with  those  of  the  dorsal  carpal  ligaments.  This  ligament 
is  in  relation,  behind,  with  the  Extensor  tendons  of  the  fingers. 

Synovial  Membrane.— The  synovial  membrane  (Fig.  255)  lines  the  inner  surface  of  the 
ligaments  above  described,  extending  from  the  lower  end  of  the  radius  and  articular  disk  above 

'  See  Hultkrantz,  Das  Ellenbogen  Gelenk  und  seine  Mechanik,  Jena,  1S97. 


ARTICULATIOJ^ti  OF  THE  CARPUS  315 

to  the  articular  surfaces  of  the  carpal  bones  below.  It  is  loose  and  lax,  and  presents  numerous 
fdlils,  cs])ccia]ly  behind. 

The  arteries  supplying  the  joint  are  the  anterior  and  posterior  carpal  branches  of  the  radial 
and  ulnar,  the  anterior  and  posterior  interosseous,  and  some  ascending  branches  from  the  deep 
palmar  arch. 

The  nerves  are  derived  from  the  ulnar  and  posterior  interosseous. 

Movements. — The  movements  permitted  in  this  joint  are  volar  flexion,  dorsi-flexion, 
abduction,  addudion,  and  circumduction.  Its  actions  will  be  further  studied  with  those  of  the 
carpus,  with  which  they  are  combined. 

Surface  Form. — The  line  of  the  radiocarpal  joint  is  on  a  level  with  the  apex  of  the  styloid 
process  of  the  ulna. 

Applied  Anatomy. — The  wrist-joint  is  rarely  dislocated,  its  strength  depending  mainly  upon 
the  numerous  strong  tendons  which  surround  the  articulation.  Its  security  is  further  pro- 
vided for  by  the  number  of  small  bones  of  which  the  carpus  is  made  up,  and  which  are  united 
by  very  strong  ligaments.  The  slight  movement  which  takes  place  between  the  several  bones 
serves  to  break  the  jars  that  result  from  falls  or  blows  on  the  hand.  Dislocation  backward, 
which  is  the  more  common  dislocation,  simulates  to  a  considerable  extent  CoUes'  fracture  of  the 
radius,  and  is  apt  to  be  mistaken  for  it.  The  diagnosis  can  be  easily  made  out  by  observing 
the  relative  position  of  the  styloid  processes  of  the  radius  and  ulna.  In  the  natural  condition 
the  styloid  process  of  the  radius  is  on  a  lower  level — i.  e.,  nearer  the  ground — when  the  arm  hangs 
by  the  side,  than  that  of  the  ulna,  and  the  same  would  be  the  case  in  dislocation.  In  Colles' 
fracture,  on  the  other  hand,  the  styloid  process  of  the  radius  is  on  the  same  or  even  a  higher 
level  than  that  of  the  ulna. 

The  wrist-joint  is  occasionally  the  seat  of  acute  synovitis,  the  result  of  traumatism  or  con- 
sequent upon  rheumatic  or  pyemic  conditions.  When  the  synovial  sac  is  distended  with  fluid, 
the  swelling  is  greatest  on  the  dorsal  aspect  of  the  wrist,  and  shows  a  general  fulness,  with  some 
bulging  between  the  tendons.  The  inflammation  is  prone  to  extend  to  the  intercarpal  joints  and 
to  attack  also  the  sheaths  of  the  tendons  in  the  neighborhood.  Chronic  inflammation  of  the  wrist 
is  generally  tuberculous,  and  often  leads  to  similar  disease  in  the  synovial  sheaths  of  adjacent 
tendons  and  of  the  intercarpal  joints.  The  disease,  therefore,  when  progressive,  frequently 
leads  to  necrosis  of  the  carpal  bones,  and  the  result  is  often  unsatisfactory. 


VIII.  Articulations  of  the  Carpus  (Articulatio  Intercarpea)  (Figs.  253,  254). 

These  articulations  may  be  subdivided  into  three  sets: 

1.  The  Articulations  of  the  First  Row  of  Carpal  Bones. 

2.  The  Articulations  of  the  Second  Row  of  Carpal  Bones. 

3.  The  Articulations  of  the  Two  Rows  with  each  other. 


1.  Articulations  of  the  First  Row  of  Carpal  Bones 

These  are  arthrodial  joints.  The  ligaments  connecting  the  scaphoid,  semi- 
lunar, and  cuneiform  hones  are: 

Dorsal.  Palmar. 

Two  Interosseous. 

The  dorsal  ligaments  (llgameida  intercarpea  dorsalia)  are  placed  transversely 
behind  the  bones  of  the  first  row;  they  connect  the  scaphoid  and  semilunar  and 
the  semihuiar  and  cimeiform. 

The  palmar  or  volar  ligaments  (Ugamenta  intercarpea  volaria)  connect  the 
scaphoid  and  semilunar  and  the  semilunar  and  cuneiform  bones;  they  are  weaker 
than  the  dorsal,  and  placed  very  deeply  below  the  anterior  ligament  of  the  wrist. 

The  interosseous  ligaments  (ligamenta  intercarpea  interossea^  (Fig.  255)  are  tvi'o 
narrow  bundles  of  fibrous  tissue  connecting  the  semilunar  bone  on  one  side  with 
the  scaphoid,  and  on  the  other  with  the  cuneiform.  They  are  on  a  level  with 
the  superior  surfaces  of   these   bones,  and   close  the   upper  part  of  the  spaces 


316  THE  ARTICULATIONS,   OB  JOINTS 

between  them.     Their  upper  surfaces  are  smooth,  and  form  with  the  bones  the 
convex  articular  surfaces  of  the  wrist-joint. 

The  hgaments  connecting  the  pisiform  bone  are: 

Capsular.  Two  Palmar  Ligaments. 

The  capsular  ligament  is  a  thin  membrane  which  connects  the  pisiform  bone 
to  the  cuneiform.     It  is  lined  by  a  separate  synovial  membrane. 

The  two  palmar  ligaments  are  two  strong  fibrous  bands  which  connect  the 
pisiform  to  the  unciform  {ligamentum  pisohamatum) ,  and  to  the  base  of  the  fifth 
metacarpal  bone  {ligainentum  pisometacarpeum). 


2.  Articulations  of  the  Second  Row  of  Carpal  Bones. 

These  are  also  arthrodial  joints.  The  articular  surfaces  are  covered  with 
hyaline  cartilage,  and  connected  by  the  following  ligaments: 

Dorsal.  Palmar. 

Three  Interosseous. 

The  dorsal  ligaments  {ligamenta  iniercarpea  dorsalia)  extend  transversely  from 
one  bone  to  another  on  the  dorsal  surface,  connecting  the  trapezium  with  the  trape- 
zoid, the  trapezoid  with  the  os  magnum,  and  the  os  magnum  with  the  unciform. 

The  palmar  ligaments  (^ligamenta  iniercarpea  volaria)  have  a  similar  arrange- 
ment on  the  palmar  surface. 

The  three  interosseous  ligaments  (ligamenta  intercarpea  inierossea)  (Fig.  255),. 
much  thicker  than  those  of  the  first  row,  are  placed  one  between  the  os  magnum 
and  the  unciform,  a  second  between  the  os  magnum  and  the  trapezoid,  and  a 
third  between  the  trapezium  and  trapezoid.  The  first  of  these  is  much  the 
strongest,  and  the  third  is  sometimes  wanting. 


3.  Articulations  of  the  Two  Rows  of  Carpal  Bones  with  Each  Other 
(Figs.  253,  254). 

The  joint  between  the  scaphoid,  semilunar,  and  cuneiform,  and  the  second 
row  of  the  carpus,  or  the  midcarpal  joint,  is  made  up  of  three  distinct  portions; 
in  the  centre  the  head  of  the  os  magnum  and  the  superior  surface  of  the  unciform 
articulate  with  the  deep,  cup-shaped  cavity  formed  by  the  scaphoid  and  semilunar 
bones,  and  constitute  a  sort  of  ball-and-socket  joint.  On  the  outer  side  the  trape- 
zium and  trapezoid  articulate  with  the  scaphoid,  and  on  the  inner  side  the  unci- 
form articulates  with  the  cuneiform,  forming  gliding  joints. 

Sometimes  a  small  ligament  joins  the  navicular  to  the  neck  of  the  os  magnum 
and  is  representative  of  the  os  centrale  (p.  206)  (Sutton). 

The  ligaments  are: 

Anterior.  External  Lateral. 

Posterior.  Internal  Lateral. 

The  anterior  or  palmar  ligaments  (ligamenta  intercarpea  volaria)  consist  of 
short  fibres,  which  pass,  for  the  most  part,  from  the  palmar  surface  of  the  bones 
of  the  first  row  to  the  front  of  the  os  magnum. 


CARPOMETACARPAL  ARTICULATIONS  317 

The  posterior  or  dorsal  ligaments  (ligmnenta  intercarpea  dorsalis)  consist  of 
short,  irregular  bundles  of  fibres  passing  between  the  bones  of  the  first  and  second 
row  on  the  dorsal  surface  of  the  carpus. 

The  lateral  ligaments  are  very  short;  they  are  placed,  one  on  the  radial,  the 
other  on  the  ulnar  side  of  the  carpus;  the  former,  the  stronger  and  more  distinct, 
■connecting  the  scaphoid  and  trapezium,  the  latter  the  cuneiform  and  unciform; 
they  are  continuous  with  the  lateral  ligaments  of  the  wrist-joint.  In  addition  to 
these  ligaments,  a  slender  interosseous  band  sometimes  connects  the  os  magnum 
and  the  scaphoid. 

Synovial  Membrane  (Fig.  255). — The  synovial  membrane  of  the  carpus  is  very  extensive; 
it  passes  from  under  the  surface  of  the  scaphoid,  semilunar,  and  cuneiform  bones  to  the  upper 
sm-face  of  the  bones  of  the  second  row,  sending  upward  two  prolongations — between  the  scaphoid 
and  semilunar  and  the  semilunar  and  cuneiform;  sending  downward  three  prolongations  between 
the  four  bones  of  the  second  row,  which  are  further  continued  onward  into  the  carpometacarpal 
joints  of  the  four  inner  metacarpal  bones,  and  also  for  a  short  distance  between  the  metacarpal 
bones.    There  is  a  separate  synovial  membrane  between  the  pisiform  and  the  cuneiform  bones. 

Movements. — The  articulation  of  the  hand  and  wrist,  considered  as  a  whole,  is  divided  into 
three  parts:  (1)  The  radius  and  the  articular  disk,  (2)  the  meniscus,'^  formed  by  the  scaphoid, 
semilunar,  and  cuneiform,  the  pisiform  bone  having  no  essential  part  in  the  movements  of  the 
hand;  (.3)  the  hand  proper,  the  metacarpal  bones  with  the  four  carpal  bones  on  which  they  are 
svipported — viz.,  the  trapezium,  trapezoid,  os  magnum,  and  unciform.  These  three  elements 
form  two  joints:  (1)  The  superior,  wrist-joint  proper,  between  the  meniscus  and  bones  of  the 
forearm;  (2)  the  inferior,  transverse  or  midcarpal  joint,  between  the  hand  and  nHiiiscus. 

1.  The  articulation  between  the  forearm  and  carpus  is  a  true  condyloid  articulation,  and 
therefore  all  movements  but  rotation  are  permitted.  Flexion  and  extension  are  the  most  exten- 
sive, and  of  these  a  greater  amount  of  extension  than  flexion  is  permitted  on  account  of  the 
articulating  surfaces  extending  farther  on  the  dorsal  than  on  the  palmar  aspect  of  the  carpal 
bones.  In  this  movement  the  carpal  bones  rotate  on  a  transverse  axis  drawn  between  the  tips 
of  the  styloid  processes  of  the  radius  and  ulna.  A  certain  amount  of  adduction  (or  ulnar  flexion) 
and  abduction  (or  radial  flexion)  is  also  permitted.  Of  these  movements,  the  former  is  consider- 
ably greater  in  extent  than  the  latter.  In  these  movements  the  carpus  revolves  upon  an  antero- 
posterior axis  drawn  through  the  centre  of  the  wrist.  Finally,  circumduction  is  permitted  by 
the  consecutive  movements  of  adduction,  extension,  abduction,  and  flexion,  with  intermediate 
movements  between  them.  There  is  no  rotation,  but  this  is  provided  for  by  the  supination  and 
pronation  of  the  radius  on  the  ulna.  The  movement  of  volar  flexion  is  performed  by  the 
Flexor  carpi  radialis,  the  Flexor  carpi  ulnaris,  and  by  the  Palmaris  longus;  dorsi-flexion,  by 
the  Extensor  carpi  radialis  longior  et  brevior  and  the  Extensor  carpi  ulnaris;  adduction  (ulnar 
flexion),  by  the  Flexor  carpi  ulnaris  and  the  Extensor  carpi  ulnaris;  and  abduction  (radial 
flexion),  by  the  Extensors  of  the  thumb  and  the  Extensores  carpi  radialis  longior  et  brevior 
and  the  Flexor  carpi  radialis. 

2.  The  chief  movements  permitted  in  the  transverse  or  midcarpal  joint  are  flexion,  extension, 
and  a  slight  amount  of  rotation.  In  flexion,  and  extension,  which  are  the  movements  most  freely 
enjoyed,  the  trapezium  and  trapezoid  on  the  radial  side  and  the  unciform  on  the  ulnar  side 
glide  forward  and  backward  on  the  scaphoid  and  cuneiform  respectively,  while  the  head  of  the 
OS  magnum  and  the  superior  surface  of  the  unciform  rotate  in  the  cup-shaped  cavity  of  the 
scaphoid  and  semilunar.  Flexion  at  this  joint  is  of  greater  range  than  extension.  A  very  trifling 
amount  of  rotation  is  also  permitted,  the  head  of  the  os  magnum  rotating  around  a  vertical  axis 
drawn  through  its  own  centre,  while  at  the  same  time  a  slight  gliding  movement  takes  place  in 
the  lateral  portions  of  the  joint. 

IX.  Carpometacarpal  Articulations  (Articulationes  Carpometacarpeae)  (Fig.  254). 

1.  Articulation   of   the   Metacarpal   Bone   of   the   Thumb   with   the 
Trapezium  (Articulatio  Carpometacarpea  Pollicis). 

This  is  a  joint  of  reciprocal  reception,  and  enjoys  great  freedom  of  movement, 
on  account  of  the  configuration  of  its  articular  surfaces,  which  are  saddle-shaped, 

'  Called  meniscus  because  the  bones  composing  it  serve  the  essential  purposes  of  an  articular  disk. 


318  THE  ARTICULA  TIONS,    OR  JOINTS 

so  that,  on  section,  each  bone  appears  to  be  received  into  a  cavity  in  the  other, 
according  to  the  direction  in  which  they  are  cut.  The  joint  is  surrounded  by  a 
capsular  ligament. 

The  capsular  ligament  is  thick  and  fibrous,  but  loose,  and  passes  from  the  cir- 
cumference of  the  upper  extremity  of  the  metacarpal  bones  to  the  rough  edge 
bounding  the  articular  surface  of  the  trapezium;  it  is  thickest  externally  and  behind, 
and  lined  with  a  separate  synovial  membrane. 

Movements. — In  the  articulation  of  the  metacarpal  bone  of  the  thumb  with  the  trapezium, 
the  movements  permitted  are  flexion,  extension,  adduction,  abduction,  and  circumduction.  When 
the  joint  is  flexed  the  metacarpal  bone  is  brought  in  front  of  the  palm  and  the  thumb  is  gradu- 
ally turned  to  the  fingers.  It  is  by  this  peculiar  moveaent  that  the  tip  of  the  thumb  is  opposed 
to  the  other  digits;  for  by  slightly  flexing  the  fiiif^ers  the  palmar  surface  oi  the  thumb  can  be 
brought  in  contact  with  their  palmar  surfaces. 


2.  Articulations  of  the  Metacarpal  Bones  of  the  Four  Inner  Fingers 
WITH  THE  Carpus  (Articulationes  Carpometacarpeae). 

The  joints  formed  between  the  carpus  and  four  inner  metacarpal  bones  are 
arthrodial  joints.     The  ligaments  are: 

Dorsal.  Palmar. 

Interosseous. 

The  dorsal  ligaments  (Jigamenta  carpometacarpea  dorsalis),  the  strongest  and 
most  distinct,  connect  the  carpal  and  metacarpal  bones  on  their  dorsal  surface. 
The  second  metacarpal  bone  receives  two  fasciculi — one  from  the  trapezium, 
the  other  from  the  trapezoid;  the  third  metacarpal  receives  two — one  from  the 
trapezoid  and  one  from  the  os  magnum;  the  fourth,  two — one  from  the  os  magnum 
and  one  from  the  unciform;  the  fifth  receives  a  single  fasciculus  from  the  unciform 
bone,  which  is  continuous  with  a  similar  ligament  on  the  palmar  surface,  thus 
forming  an  incomplete  capsule. 

The  palmar  ligaments  (Ugamenta  carpometacarpea  volaria)  have  a  somewhat 
similar  arrangement  on  the  palmar  surface,  with  the  exception  of  the  third  meta- 
carpal, which  has  three  ligaments — an  external  one  from  the  trapezium,  situated 
above  the  sheath  of  the  tendon  of  the  Flexor  carpi  radialis;  a  middle  one,  from 
the  OS  magnum;  and  an  internal  one,  from  the  unciform. 

The  interosseous  ligaments  consist  of  short,  thick  fibres,  which  are  limited  to 
one  part  of  the  carpometacarpal  articulation;  they  connect  the  contiguous  inferior 
angles  of  the  os  magnum  and  unciform  with  the  adjacent  surfaces  of  the  third 
and  fourth  metacarpal  bones. 

Synovial  Membrane. — The  synovial  membrane  is  a  continuation  of  that  between  the  two 
rows  of  carpal  bones.  Occasionally,  the  articulation  of  the  unciform  with  the  fourth  and  fifth 
metacarpal  bones  has  a  separate  synovial  membrane. 

The  synovial  membranes  of  the  wrist  and  carpus  (Fig.  255)  are  thus  seen  to  be  five  in  number. 
The  first,  the  membrana  saccifonnis  of  the  inferior  radioulnar  articulation,  passes  from  the 
lower  end  of  the  ulna  to  the  sigmoid  cavity  of  the  radius,  and  lines  the  upper  surface  of  the 
articular  disk.  The  second  passes  from  the  lower  end  of  the  radius  and  articular  disk  above 
to  the  bones  of  the  first  row  below.  The  third,  the  most  extensive,  passes  between  the  contig- 
uous margins  of  the  two  rows  of  carpal  bones — between  the  bones  of  the  second  row  to  the 
carpal  extremities  of  the  four  inner  metacarpal  bones.  The.  fourth  passes  from  the  margin  of 
the  trapezium  to  the  metacarpal  bone  of  the  thumb.  The  fifth  passes  between  the  adjacent 
margins  of  the  cuneiform  and  pisiform  bones. 


\ 


CA RPOMETA  CA RPA L  AR TICULA  T10N8 


31& 


Movements. — The  movement  permitted  in  the  carpometacarpal  articulations  of  the  four 
inner  fingers  is  limited  to  a  slight  gliding  of  the  articular  surfaces  upon  each  other,  the  extent 
of  which  varies  in  the  different  joints.  Thus,  the  articulation  of  the  metacarpal  bone  of  the 
little  finger  is  most  movable,  then  that  of  the  ring  linger.  The  metacarpal  bones  of  the  index 
and  middle  fingers  are  almost  immovable. 


MEMBRANA  SACCI- 

FORMIS  OF  INFERIOR 

RADIO-ULNAR 

ARTICULATION 


TRIANGULAR 

ARTICULAR  DISK 

STYLOID  PROCESS 

OF  ULNA 


ARTICULATION  OF 
TRAPEZIUM  AND 
METACARPAL  BONE 
OF  THUMB 


METACARPAL  BONES 

Fig.  255.— Joints  of  the  right  hand,  from  the  back  of  the  hand.     (Spalteholz.) 


3.  Articulations  of  the  Metacarpal  Bones  with  Each  Other  (Articu- 
LATioNES  Intermetacarpeae  (Figs.  254,  255). 


The  carpal  extremities  of  the  four  inner  metacarpal  bones  articulate  with  one 
another  at  each  side  by  small  surfaces  covered  with  cartilages,  and  connected 
by  dorsal,  palmar,  and  interosseous  ligaments. 

The  dorsal  ligaments  {ligamenta  hasium  oss.  metacarp.  dorsalia)  and  palmar 
ligaments  (liejamenta  hasium  oss.  vietacarp.  volaria)  pass  transversely  from  one 
bone  to  another  on  the  dorsal  and  palmar  surfaces. 

The  interosseous  ligaments  (lujamenta  hasium  oss.  metacarp.  interossea)  pass 
between  their  contiguous  surfaces,  just  beneath  their  lateral  articular  facets. 


320 


THE  ARTIGULA  TIONS,    OB  JOINTS 


S3movial  Membrane  (Fig.  255). — ^The  synovial  membrane  between  the  lateral  facets  is  a 
reflection  from  that  between  the  two  rows  of  carpal  bones. 


ANTERIOR 
>R  VAGINAL 
LIGAMENT 

TRANSVERS 
METACARPAL 
kiGAMENT 


SECOND 
PALMAR 
MTER05SE0US 
MUSCLE 


Fig.  256. — Metacarpal  bones  and  first  phalanges  of  the  second  to  the  fifth  finger  of  the  right  hand,  with 
ligaments,  from  the  volar  surface.     (Spaltebolz.) 


The  transverse  metacarpal  ligament  Qigamentum  capitidorum  oss.  metacar- 
■paliuvi  transversum)  (Fig.  256)  is  a  narrow,  fibrous  band  which  passes  trans- 
Tersely  across  the  anterior  surfaces  of  the  digital  extremities  of  the  four  inner 
metacarpal  bones,  connecting  them.  It  is  blended  anteriorly  with  the  palmar 
ligaments  of  the  metacarpophalangeal  articulations.  To  its  posterior  border  is 
connected  the  fascia  which  covers  the  Interossei  muscles.  Its  anterior  surface  is 
concave  where  the  Flexor  tendons  pass  over  it.  Behind  it  the  tendons  of  the 
Interossei  muscles  pass  to  their  insertion. 


X.  Metacarpophalangeal  Articulations  (ArticulationesMetacarpophalangeae) 

(Figs.  256,  257). 

These  articulations  are  of  the  condyloid  variety,  formed  by  the  reception  of 
the  rounded  head  of  the  metacarpal  bone  into  a  shallow  cavity  in  the  extremity 
of  the  first  phalanx.  The  expansion  of  the  Extensor  communis  digitorum  tendoii 
acts  as  a  dorsal  ligament.  There  is  a  capsular  ligament  which  at  certain  points 
has  strengthening  ligaments.     The  ligaments  are: 


Anterior. 


Two  Lateral. 


ARTICULATIONS  OF  THE  PHALANGES 


321 


The  palmar  or  vaginal  ligament  {li(/amentum  vagmale,  glenoid  ligament  of  Cru- 
veilhier)  is  a  thick,  dense,  fibrous  structure,  placed  on  the  palmar  surface  of  the 
joint  in  the  interval  between  the  lateral  liga- 
ments, to  which  it  is  connected;  it  is  loosely 
united  to  the  metacarpal  bone,  but  very  firmly 
to  the  base  of  the  first  phalanx.  Its  palmar 
surface  is  intimately  blended  with  the  transverse 
metacarpal  ligament,  and  presents  a  groove  for 
the  passage  of  the  Flexor  tendons,  the  sheath 
surrounding  which  is  connected  to  each  side  of 
the  groove.  By  its  deep  surface  it  forms  part  of 
the  articular  surface  for  the  head  of  the  meta- 
carpal bone,  and  is  lined  Ijy  a  synovial  mem- 
brane. 

The  lateral  ligaments  (Ucjamcnta  coUateralia) 
are  strong,  rounded  cords  placed  one  on  each  side 
of  the  joint,  each  being  attached  by  one  extremity 
to  the  posterior  tubercle  on  the  side  of  the  head 
of  the  metacarpal  bone,  and  by  the  other  to  the  ahticu 
contiguous  extremity  of  the  phalanx. 

Movements. — The  movements  which  occur  in  these 
joints  are  flexion,  extension,  adduction,  abduction,  and 
circumduction;  the  lateral  movements  are  very  extensive. 

Surface  Form. — The  prominences  of  the  knuckles  do 
not  correspond  to  the  position  of  the  joints  either  of  the 
metacarpophalangeal  or  interphalangeal  articulations. 
These  prominences  are  invariably  formed  by  the  distal 
ends  of  the  proximal  bone  of  each  joint,  and  the  line 
indicating  the  position  of  the  joint  must  be  sought  con- 
siderably in  front  of  the  middle  of  the  knuckle. 


ARTICULAR 
CAPSULE 


XI.  Articulations    of    the    Phalanges     (Articu- 
lationes  Digitorum  Manus)   (Fig.  257) 

These  are  ginglymus  joints.  Each  joint  has  a 
capsule,  and  certain  accentuated  portions  are  re- 
garded as  definite  ligaments.    These  ligaments 


Anterior  or  Palmar. 

Two  Lateral   {ligamenta  coUateralia). 

The  arrangement  of  these  ligaments  is  similar 
to  those  in  the  metacarpophalangeal  articula- 
tions; the  Extensor  tendon  supplies  the  place 
of  a  dorsal  ligament. 


Fig.  257. — Metacarpal  bones  and  first 
phalanges  of  the  third  finger  of  the  right 
nand.  with  ligaments,  from  the  radial  side, 
(Spalteholz.) 


Movements. — The  only  movements  permitted  in  the  phalangeal  joints  are  flexion  and 
extension;  these  movements  are  more  extensive  between  the  first  and  second  phalanges  than 
between  the  second  and  third.  The  movement  of  flexion  is  very  considerable,  but  extension 
is  limited  by  the  anterior  and  lateral  ligaments. 

•21 


322  THE  ARTICULATIONS,   OR  JOINTS 


ARTICULATIONS   OF  THE  LOWER  EXTREMITY. 

The  articulations  of  the  lower  extremity  comprise  the  following  groups: 


I.  The  Hip-joint. 
11.  The  Knee-joint. 
III.  The    Articulations    between    the 


VI.  The  Tarsometatarsal  Articulations, 

VII.  Articulations    of    the    Metatarsal 

Bones  with  each  other. 


Tibia  and  Fibula.  I  \^III.  The  Metatarsophalangeal  Articu- 

IV.  The  Ankle-joint.  i  lations. 

V.  The  Articulations  of  the  Tarsus,  j      IX.  TheArticulations  of  the  Phalanges. 


I.  The  Hip-joint  (Articulatio  Coxae)  (Figs.  258,  2.59). 

This  articulation  is  an  enarthrodial  or  ball-and-socket  joint,  formed  by  the 
reception  of  the  head  of  the  femur  into  the  cup-shaped  cavity  of  the  acetabulum. 
The  articulating  surfaces  are  covered  by  hyaline  cartilage,  that  on  the  head  of 
the  femur  being  thicker  at  the  centre  than  at  the  circumference,  and  covering 
the  entire  surface  with  the  exception  of  a  depression  just  below  its  centre  for  the 
attachment  of  the  ligamentum  teres;  that  covering  the  acetabulum  is  much  thinner 
at  the  centre  than  at  the  circumference.  This  cartilage  forms  an  incomplete 
ring  of  a  horseshoe  shape,  being  deficient  below,  where  there  is  a  circular  depres- 
sion, which  in  the  recent  state  is  occupied  by  a  mass  of  fat  covered  by  synovial 
membrane.     The  ligaments  of  the  joints  are  the 

Capsular.  Teres. 

Iliofemoral.  Cotyloid. 

Transverse. 

The  capsular  ligament  (capsula  articularis)  (Figs.  258  and  259)  is  a  strong,  dense, 
ligamentous  capsule,  embracing  the  margin  of  the  acetabulum  above  and  surround- 
ing the  neck  of  the  femur  below.  Its  upper  circumference  is  attached  to  the  acetab- 
ulum a  short  distance  above  and  behind  the  cotyloid  ligament,  but  in  frotit  it  is 
attached  to  the  outer  margin  of  the  ligament,  and  opposite  to  the  notch,  where 
the  margin  of  this  cavity  is  deficient,  it  is  connected  to  the  transverse  ligament, 
and  by  a  few  fibres  to  the  edge  of  the  obturator  foramen.  Its  loioer  circumference 
surrounds  the  neck  of  the  femur,  being  attached,  in  front,  to  the  spiral  or  anterior 
intertrochanteric  line;  above,  to  the  base  of  the  neck;  behind,  to  the  neck  of  the 
lione,  about  half  an  inch  above  the  posterior  intertrochanteric  line.  From  this 
insertion  the  fibres  are  reflected  upward  over  the  neck  of  the  femur,  forming  a 
sort  of  tubular  sheath,  the  cervical  reflection,  which  blends  with  the  periosteum 
and  can  be  traced  as  far  as  the  cartilage  which  covers  the  head  of  the  femur. 
On  the  surface  of  the  neck  of  the  femur  some  of  these  reflected  fibres  are  raised 
into  longitudinal  folds,  termed  retinacula.  It  is  much  thicker  at  the  upper  and 
fore  part  of  the  joint,  where  the  greatest  amount  of  resistance  is  required,  than 
below  and  internally,  where  it  is  thin,  loose,  and  longer  than  in  any  other  part. 
It  consists  of  two  sets  of  fibres,  circular  and  longitudinal.  The  circular  fibres, 
zona  orbicularis  (Fig.  261),  are  most  abundant  at  the  lower  and  back  part  of  the 
capsule,  and  form  a  sling  or  collar  around  the  neck  of  the  femur.  Anteriorly 
they  blend  with  the  deep  surface  of  the  iliofemoral  ligament,  and  through  this 
medium  reach  the  anterior  inferior  spine  of  the  ilium.  The  longitudinal  fibres 
are  greatest  in  amount  at  the  upper  and   front   part  of  the  capsule,  where 


THE  HIP-JOINT 


323 


they  form  distinct  bands  or  accessory  ligaments,  of  which  the  most  important 
is  the  iliofemoral.  Other  accessory  bands  are  iinown  as  the  pubofemoral  (Jiga- 
mentum  pubocapsidare),  passing  from  the  outer  portion  of  the  horizontal  pubic 
ramus,  the  iliopectineal  eminence,  the  obturator  crest  and  the  obturator  mem- 


M 


OFEMORAL 
1_  I  G  AM  E  ?MT 


ANTERIOR 

INTERTRO 

CHANTERIC    LINE 


Fig.  258. — Right  hip-joint,  from  in  front.     (Spalteholz.) 

brane,  to  the  front  of  the  capsule;  and  the  ischiocapsular  ligament  or  ligament 
of  Bertin  (ligamentum  ischiocapsulare),  which  passes  from  the  ischium,  just  laelow 
the  acetabulum,  to  blend  with  the  circular  fibres  at  the  lower  part  of  the  joint. 
The  external  surface  is  rough,  covered  by  numerous  muscles,  and  separated  in 
front  from  the  Psoas  and  Iliacus  muscles  by  a  synovial  bursa,  which  not  infre- 
quently communicates,  by  a  circular  aperture,  with  the  cavity  of  the  joint.  It 
differs  from  the  capsular  ligament  of  the  shoulder  in  being  much  less  loose  and 
lax,  and  in  not  being  perforated  for  the  passage  of  a  tendon. 

The  iliofemoral  (ligamentum  iliofemorale)  (Figs.  261  and  262)  is  an  accessory 
band  of  fibres  extending  obliquely  across  the  front  of  the  joint;  it  is  intimately 
connected  with  the  capsular  ligament,  and  serves  to  strengthen  it  in  this  situa- 


324 


THE  ARTICULATIONS,    OB  JOINTS 


tion.  It  is  attached,  above,  to  the  lower  part  of  the  anterior  inferior  spine  of  the 
ihum  and  the  adjacent  rim  of  the  acetabulum;  and,  diverging  below,  forms  two 
bands,  of  which  one  passes  downward  to  be  inserted  into  the  lower  part  of  the 
anterior  intertrochanteric  line;  the  other  passes  downward  and  outward  to  be 
inserted  into  the  upper  part  of  the  same  line  and  the  adjacent  part  of  the  neck 
of  the  femur.  Between  the  two  bands  is  a  thinner  part  of  the  capsule.  Some- 
times there  is  no  division,  but  the  ligament  spreads  out  into  a  flat,  triangular 


Fig.  259.— Right  hip-joint,  from  behind.      (The 


band,  which  is  attached  below  into  the  whole  length  of  the  anterior  intertrochan- 
teric line.  This  ligament  is  frequently  called  the  Y-shaped  ligament  of  Bigelow; 
and  the  outer  or  upper  of  the  two  bands  is  sometimes  described  as  a  separate 
ligament,  under  the  name  of  the  iliotrochanteric  ligament. 

The  ligamentiun  teres  {ligamentuin  teres  femoris)  (Figs.  261  and  262)  is  a  tri- 
angular band  implanted  by  its  apex  into  the  depression  a  little  behind  and  below 


THE  HIP  JOINT 


325 


the  centre  of  the  head  of  the  femur,  and  by  its  broad  base  into  the  margins  of  the 
cotyloid  notch,  where  it  blends  with  the  transverse  ligament.  It  is  formed  of 
white  fibrous  connective  tissue,  surrounded  by  a  tubular  sheath  of  synovial  mem- 
brane. Sometimes  only  the  synovial  fold  exists.  Very  rarely  it  is  absent.  The 
ligament  is  made  tense  when  the  hip  is  semiflexed,  and  the  limb  adducted  and 
rotated  outward;  it  is,  on  the  other  hand,  relaxed  when  the  limb  is  abducted. 
It  has,  however^  but  little  influence  as  a  ligament,  and  though  it  may  to  a  certain 
extent  limit  movement,  it  would  appear  to  be  merely  a  "vestigial  and  practically 
useless  ligament.'" 


Fig.  260. — Right  hip-joint  from  the  mesal  side.     (The  bottom  of  the  acetabulum  has  been  chiselled  away 
sufficiently  to  make  the  head  of  the  femur  visible.)     (Spalteholz.) 


The  cotyloid  ligament  {labruvi  glenoidale  (Fig.  263)  is  a  fibrocartilaginous  rim 
attached  to  the  margin  of  the  acetabulum,  the  cavity  of  which  it  deepens;  at  the 
same  time  it  protects  the  edges  of  the  bone  and  fills  up  the  inequalities  on  its  sur- 
face. It  bridges  over  the  notch  as  the  transverse  ligament  of  the  acetabulum,  and 
thus  forms  a  complete  circle,  which  closely  surrounds  the  head  of  the  femur, 
and  assists  in  holding  it  in  its  place.  It  is  prismoid  on  section,  its  base  being 
attached  to  the  margin  of  the  acetabulum  and  its  opposite  edge  being  free  and 
sharp.  Its  two  surfaces  are  invested  by  synovial  membrane,  the  external  one  being 
in  contact  with  the  capsular  ligament,  the  internal  one  being  inclined  inward,  so 
as  to  narrow  the  acetabulum  and  embrace  the  cartilaginous  surface  of  the  Tiead 
of  the  femur.  It  is  much  thicker  above  and  behind  than  below  and  in  front, 
and  consists  of  close,  compact  fibres,  which  arise  from  different  points  of  the 

1  J.  Bland  Sutton,  Ligaments:  Their  Nature  and  Morphology,  1887. 


326 


THE  ARTICULATIONS,   OR  JOINTS 


circumference  of  the  acetabulum  and  interlace  with  each  other  at  very  acute 
angles. 

The  transverse  ligament  of  the  acetabulum  Qigamentum  transversum  acetahidi) 
(Figs.  260  and  263)  is  in  reality  a  portion  of  the  cotyloid  hgament,  though  difFering 
from  it  in  having  no  cartilage  cells  among  its  fibres.  It  consists  of  strongs 
flattened  fibres,  which  cross  the  notch  at  the  lower  part  of  the  acetabulum  and 
convert  it  into  a  foramen.  Thus  an  interval  is  left  beneath  the  ligament  for  the 
passage  of  nutrient  vessels  to  the  joint. 


R  LIGAMENT 


CAPSULA 

FIBRO 

CAPSULA 

SYNOV 


OPER'S  LIGAMENT 
)F  PUBIS 


Fig.  261. — The  right  hip-joint,  seen  from  before.     (Toldt.) 


The  synovial  membrane  (Figs.  261  and  262)  is  very  extensive.  Commencing  at  the  margin 
of  the  cartilaginous  surface  of  the  head  of  the  femur,  it  covers  all  that  portion  of  the  neck  which 
is  contained  within  the  joint;  from  the  neck  it  is  reflected  on  the  internal  surface  of  the  capsular 
ligament;  it  covers  both  surfaces  of  the  cotyloid  ligament  and  the  mass  of  fat  contained  in  the 
depression  at  the  bottom  of  the  acetabulum,  and  it  is  prolonged  as  far  as  the  head  of  the  femur 
in  the  form  of  a  tubular  sheath  around  the  ligamentum  teres.  It  sometimes  communicates 
through  an  aperture  in  the  capsular  ligament  between  the  inner  band  of  the  Y-shaped  ligament 
and  the  pubofemoral  ligament  with  a  bursa  situated  on  the  under  surface  of  the  Iliopsoas 
muscle. 

The  muscles  in  relation  with  the  joint  (Fig.  263)  are,  in  front,  the  Psoas  and  Iliacus,  sepa- 
rated from  the  capsular  ligament  by  a  synovial  bursa;  above,  the  reflected  head  of  the  Rectus 
femoris  and  Gluteus  minimus,  the  latter  being  closely  adherentto  the  capsule;  internally,  the 


THE  HIP-JOINT 


•i21 


Obturator  externus  and  Pectineus;  behind,  the  Pyriformis,  Gemellus  superior,  Obturator 
internus,  Gemellus  inferior,  Obturator  externus,  and  Quadratus  femoris. 

The  arteries  supplying  the  joint  are  derived  from  the  obturator,  sciatic,  internal  circumflex, 
and  gluteal. 

The  nerves  are  articular  branches  from  the  sacral  plexus,  great  sciatic,  obturator,  accessory 
obturator,  and  a  filament  from  the  branch  of  the  femoral  (anterior  crural)  supplying  the 
Rectus  femoris. 

Bursas. — Numerous  bursse  exist  in  the  neighborhood  of  the  hip-joint.  Some  anatomists  have 
counted  twenty-one  (Synnestredt).  The  chief  ones  are:  (1)  The  iliopectineal  bursa  (bursa  ilio- 
pcctinea)  (Fig.  264),  between  the  Iliopsoas  tendon  and  the  capsule  of  the  joint.  This  bursa 
often  communicates  with  the  hip-joint.  (2)  The  subtendinous  iliac  bursa  (biirxa  iliaca  .lub- 
tendiiiea),  between  the  tendon  of  the  Psoas  and  Iliacus  and  the  lesser  trochanter.    (3)  The  ischio- 


FiG.  262.— Right  hip-joint.      Frontul  section.     Posterior  half,  viewed  from  in  front.     The  joint  surfaces 
hiive  been  somewhat  pulled  apart.      (Spalteholz.) 


gluteal  bursa  (bursa  ischiadica  m.  glutaei  maximi),  between  the  Gluteus  maximus  muscle  and 
the  tuberosity  of  the  ischium  (not  constant).  (4)  The  bursa  of  the  greater  trochanter  (bursa 
trochanierica  m.  glutaei  maximi),  between  the  greater  trochanter  and  the  Gluteus  maximus  muscle 
near  the  muscular  insertion.  (.5)  Two  or  three  gluteofemoral  bursae  (bursae  (/lufaiofimornles) 
below.  (6)  The  obturator  bursa  (bursa  m.  ohtiirattu-ii  iiilrnii),  between  the  margin  of  the  great 
sacrosciatic  notch  and  the  tendon  of  the  Obturatdv  internus  muscle.  (7)  The  subcutaneous 
trochanteric  bursa  (bursa  trochanterica  subcutanea),  between  the  cutaneous  surface  and  the  great 


328 


THE  ARTICULATIONS,    OB  JOINTS 


trochanter.  Besides  these  there  is  a  bursa  between  the  greater  trochanter  and  the  anterior  part 
of  the  Gluteus  medius;  between  the  greater  trochanter  and  the  posterior  part  of  the  Gluteus 
medius;  between  the  greater  trochanter  and  the  Gluteus  minimus;  beneath  the  PjTiformis 
muscle;  between  the  lesser  trochanter  and  the  Quadratus  femoris  muscle;  and  there  are  bursse 
beneath  the  Biceps  femoris  muscle. 

Movements. — The  movements  of  the  hip  are  very  extensive,  and  consist  of  flexion,  exten- 
s-ion,  adducfion,  abduction,  circumduction,  and  rotation. 

The  hip-joint  presents  a  very  striking  contrast  to  the  shoulder-joint  in  the  much  more  com- 
plete mechanical  arrangements  for  its  security  and  for  the  limitation  of  its  movements.  In  the 
shoulder,  as  we  have  seen,  the  head  of  the  humerus  is  not  adapted  at  all  in  size  to  the  glenoid 
cavity,  and  is  hardly  restrained  in  any  of  its  ordinary  movements  by  the  capsular  ligament.  In 
the  hip-joint,  on  the  contrary,  the  head  of  the  femur  is  closely  fitted  to  the  acetabulum  for  a 
distance  extending  over  nearly  half  a  sphere,  and  at  the  margin  of  the  bony  cup  it  is  still  more 
closely  embraced  by  the  cotyloid  ligament,  so  that  the  head  of  the  femur  is  held  in  its  place  by 
that  ligament  even  when  the  fibres  of  the  capsule  have  been  cjuite  divided  (Humphry).  The 
anterior  portion  of  the  capsule,  described  as  the  iliofemoral  ligament,  is  the  strongest  of  all 
the  ligaments  in  the  body,  and  is  put  on  the  stretch  by  any  attempt  to  extend  the  femur 
beyond  a  straight  line  with  the  trunk.  That  is  to  say,  this  ligament  is  the  chief  agent  in  main- 
taining   the  erect  position  without  muscular  fatigue;  for  a  vertical  line  passing  through  the 


Fig.  263. — Relation  oi    ii  i     U     t  ,  t  le  capsule  of  the  hip-joint.      (From  a  drawing  by  Mr.  F.  A.  Barton.) 

centre  of  gravity  of  the  trunk  falls  behind  the  centres  of  rotation  in  the  hip-joint,  and  therefore 
the  pelvis  tends  to  fall  backward,  but  is  prevented  by  the  tension  of  the  iliofemoral  and  capsular 
ligaments.  The  security  of  the  joint  may  be  also  provided  for  by  the  two  bones  being  directly 
united  through  the  ligamentum  teres;  but  it  is  doubtful  whether  this  so-called  ligament  can  have 
much  influence  upon  the  mechanism  of  the  joint.  Flexion  of  the  hip-joint  is  arrested  by  the 
soft  parts  of  the  thigh  and  abdomen  being  brought  into  contact  when  the  leg  is  flexed  on  the 
thigh ;  and  by  the  action  of  the  Hamstring  muscles  when  the  leg  is  extended.'  Extension  is 
arrested  by  the  tension  of  the  iliofemoral  ligament  and  the  front  of  the  capsule;  adduction, 
by  the  thighs  coming  into  contact;  adduction  loith  flexion,  by  the  outer  band  of  the  iliofemoral 
ligament,  and  the  outer  part  of  the  capsular  ligament;  abduction,  by  the  inner  band  of  the  ilio- 


•  The  hip-joint  cannot  be  completely  fieved,  in  most  persons,  without  at  the  same  time  flexing  the  knee,  on 
account  of  the  shortness  of  the  Hamstring  muscles. — Cleland,  Jour,  of  Anat.  and  Physiol,  No.  l.Old  Series,  p.  87. 


THE  HIP-JOINT 


329 


femoral  ligament  and  the  pubofemoral  band ;  rotation  outward,  by  the  outer  band  of  the  iliofemoral 
ligament;  and  rotation  inward,  by  the  isehiocapsular  ligament  and  the  hinder  part  of  the  cap- 
sule. The  muscles  which  flex  the  femur  on  the  pelvis  are  the  Psoas,  Iliacus,  Rectus  femoris, 
Sartorius,  Pectineus,  Adductor  longus  and  brevis,  and  the  anterior  fibres  of  the  Gluteus  medius 
and  minimus.  Extension  is  mainly  performed  by  the  Gluteus  maximus,  assisted  by  the  Ham- 
string muscles.  The  thigh  is  atlducted  by  the  Adductores  magnus,  longus,  and  brevis,  the 
Pectineus,  the  Gracilis,  and  the  lower  part  oi'  the  Gluteus  maximus,  and  abducted  by  the  Gluteus 
medius  and  minimus  and  the  upper  part  of  the  Gluteus  maximus.  The  muscles  which  rotate 
the  thio-h  inward  are  the  anterior  fibres  of  the  Gluteus  medius,  the  Gluteus  minimus,  and 
the  Tensor  fasciae  femoris;  while  those  which  rotate  it  outward  are  the  posterior  fibres  of  the 
<iluteus  medius,  the  Pyriformis,  Obturator  externus  and  internus,  Gemellus  superior  and  inferior, 
Quadratus  femoris,  Iliacus,  Gluteus  maximus,  the  three  Adductors,  the  Pectineus,  and  the 
Sartorius. 

Surface  Form. — A  line  drawn  from  the  anterior  superior  spinous  process  of  the  ilium  to 
the  most  prominent  part  of  the  tuberosity  of  the  ischium  (Nelaton's  line)  runs  through  the 
centre  of  the  acetabulum,  and  would,  therefore,  indicate  the  level  of  the  hip-joint;  or,  in  other 
words,  the  upper  border  of  the  great  trochanter,  which  lies  on  Nekton's  line,  is  on  a  level  with 
the  centre  of  the  hip-joint. 

Applied  Anatomy. — Inflammation  of  hursoB  about  the  hip-joint  gives  rise  to  confusing 
symptoms,  and  is  not  uncoriimonly  mistaken  for  hip-joint  disease. 


Great  sacrosciat 


Small  sacrosctatic 
ligament 


'  J  Anterior  superior 
spine 


.Great  trochanter 
of  femur. 


Fig.  264. — Nelaton's  line  and  Bryant's  triangle. 


In  dislocation  of  the  hip  "the  head  of  the  thigh  bone  may  rest  at  any  point  around  its  socket" 
(Bryant);  but  whatever  position  the  head  ultimately  assumes,  the  primary  displacement  is 
generally  downward  and  inward,  the  capsule  giving  way  at  its  weakest — that  is,  its  lower  and 
inner — part.  The  situation  that  the  head  of  the  bone  subsequently  assumes  is  determined 
by  the  degree  of  flexion  or  extension,  and  of  outward  ov  inward  rotation  of  the  thigh  at  the 
moment  of  luxation,  influenced,  no  doubt,  by  the  iliofemoral  ligament,  which  is  not  easily  rup- 
tured. When,  for  instance,  the  head  is  forced  backward,  this  ligament  forms  a  fixed  axis,  around 
which  the  head  of  the  bone  rotates,  and  the  head  is  thus  driven  on  to  the  dorsum  of  the  ilium. 
The  iliofemoral  ligament  also  influences  the  position  of  the  thigh  in  the  various  dislocations: 
in  the  dislocations  backward  it  is  tense,  and  produces  inversion  of  the  limb;  in  the  dislocation 
on  to  the  pubes  it  is  relaxed,  and  therefore  allows  the  External  rotators  to  evert  the  thigh;  while 
in  the  thyroid  dislocation  it  is  tense  and  produces  flexion. 


330  THE  ABTICULA  TIONS,   OB  JOINTS 

.  The  iliofemoral  ligament  is  rarely  torn  in  dislocations  of  the  hip,  and  this  fact  is  taken  advan- 
tao-e  of  by  the  surgeon  in  reducing  these  dislocations  by  manipulation.  It  is  made  to  act  as 
a  fulcrum  to  a  lever  of  which  the  long  arm  is  the  shaft  of  the  femur,  and  the  short  arm  the 
neck  of  the  bone. 

The  hip-joint  is  rarely  the  seat  of  acute  synovitis  from  injury,  on  account  of  its  deep  position 
and  its  thick  covering  of  soft  parts.  Acute  inflammation  may,  and  does,  frequently  occur  as 
the  result  of  constitutional  conditions,  as  rheumatism,  pyemia,  etc.  When,  in  these  cases, 
effusion  takes  place,  and  the  joint  becomes  distended  with  fluid,  the  swelling  is  not  very  easy 
to  detect  on  account  of  the  thickness  of  the  capsule  and  the  depth  of  the  articulation.  It  is 
principally  to  be  found  on  the  front  of  the  joint,  just  internal  to  the  iliofemoral  ligament;  or 
behind,  at  the  lower  and  back  part.  In  these  two  places  the  capsule  is  thinner  than  elsewhere. 
Disease  of  the  hip-joint  is  much  more  frequently  of  a  chronic  character  and  is  usually,  of  tuber- 
culous origin.  It  begins  either  in  the  bones  or  in  the  synovial  membrane,  more  frequently  in  the 
former,  and  probably,  in  most  cases,  in  the  growing,  highly  vascular  tissue  in  the  neighborhood 
of  the  epiphyseal  cartilage.  In  this  respect  it  differs  very  materially  from  the  tuberculous  arthritis 
of  the  knee,  where  the  disease  often  commences  in  the  synovial  membrane. 

In  chronic  hip  disease  the  affected  limb  assumes  an  altered  position,  the  cause  of  which  it 
is  important  to  understand.  In  the  early  stage  of  a  typical  case  the  limb  is  flexed,  abducted, 
and  rotated  outward.  In  this  position  all  the  ligaments  of  the  joint  are  relaxed — the  front  of 
the  capsule  by  flexion;  the  outer  band  of  the  iliofemoral  ligament  by  abduction;  and  the  inner 
band  of  this  ligament  and  the  back  of  the  capsule  by  rotation  outward.  It  is,  therefore,  the 
position  of  the  greatest  ease.  The  condition  is  not  quite  obvious  at  first  upon  examining  a 
patient.  If  the  patient  is  laid  in  the  supine  position,  the  affected  limb  will  be  found  to  be  ex- 
tended and  parallel  with  the  other.  But  it  will  be  found  that  the  pelvis  is  tilted  downward  on 
the  diseased  side  and  the  limb  apparently  longer  than  its  fellow,  and  that  the  lumbar  portion  of 
the  vertebral  column  is  arched  forward  (lordosis).  If  now  the  thigh  is  abducted  and  flexed,  the  tilt- 
ino-  downward  and  the  arching  forward  of  the  pelvis  disappears.  The  condition  is  thus  explained. 
A  limb  which  is  flexed  and  abducted  is  obviously  useless  for  progression,  and,  to  overcome  the 
difficulty,  the  patient  depresses  the  affected  side  of  his  pelvis  in  order  to  produce  parallelism 
of  his  limbs,  and  at  the  same  time  rotates  his  pelvis  on  its  transverse  horizontal  axis,  so  as  to 
direct  the  limb  downward  instead  of  forward.  In  the  latter  stages  of  the  disease  the  limb  becomes 
flexed,  adducted,  and  inverted.  The  position  probably  depends  upon  the  muscular  action, 
at  all  events  as  regards  the  adduction.  The  Adductor  muscles  are  supplied  by  the  obturator 
nerve,  which  also  largely  supplies  the  joint.  These  muscles  are  therefore  thrown  into  reflex 
a?tion  by  the  irritation  of  the  peripheral  terminations  of  this  nerve  in  the  inflamed  articulation. 
Osteoarthritis  is  not  uncommon  in  the  hip-joint,  and  it  is  said  to  be  more  common  in  the  male 
than  in  the  female,  in  whom  the  knee-joint  is  more  frequently  affected.  It  is  a  disease  of  middle 
age  or  more  advanced  period  of  life. 

Congenital  dislocation  is  more  commonly  met  with  in  the  hip-joint  than  in  any  other  articula- 
tion. The  displacement  usually  takes  place  on  to  the  dorsum  ilii.  It  gives  rise  to  extreme 
lordosis,  and  a  waddling  gait  is  noticed  as  soon  as  the  child  commences  to  walk. 

Excision  of  the  hip  may  be  required  for  disease  or  for  injury,  especially  for  gunshot  wound. 
It  may  be  performed  either  by  an  anterior  or  an  external  incision.  The  former  one  entails 
less  interference  with  important  structures,  especially  muscles,  than  the  posterior  one,  but . 
permits  of  less  efficient  drainage.  In  the  operation  in  front  the  surgeon  makes  an  incision 
three  or  four  inches  in  length,  starting  immediately  below  and  external  to  the  anterior  superior 
spinous  process  of  the  ilium,  downward  and  inward  between  the  Sartorius  and  Tensor  fasciae 
femoris,  to  the  neck  of  the  bone,  dividing  the  capsule  at  its  upper  part.  A  narrow-bladed  saw 
now  divides  the  neck  of  the  femur,  and  the  head  of  the  bone  is  extracted  with  sequestrum  forceps. 
All  diseased  tissue  is  carefully  removed  with  a  sharp  spoon  or  scissors,  and  the  cavity  thoroughly 
flushed  with  a  hot  aseptic  fluid. 

The  external  method  consists  in  making  an  incision  three  or  four  inches  long,  commencing 
midway  between  the  top  of  the  great  trochanter  and  the  anterior  superior  spine,  and  ending 
over  the  shaft,  just  below  the  trochanter.  The  muscles  are  detached  from  the  great  trochanter, 
and  the  capsule  opened  freely.  The  head  and  neck  are  freed  from  the  soft  parts  and  the  bone 
sawed  through  just  below  the  top  of  the  trochanter  with  a  narrow  saw.  The  head  of  the  bone  is 
then  levered  out  of  the  acetabulum.  In  both  operations,  if  the  acetabulum  is  eroded,  it  must  be 
freely  gouged. 


THE  KNEE-JOINT  331 


II.  The  Knee-joint  (Articulatio  Genu). 

The  knee-joint  was  formerly  described  as  a  ginglymus  or  hinge-joint,  but  is 
really  of  a  much  more  complicated  character.  It  must  be  regarded  as  consist- 
ing of  three  articulations  in  one — one  between  each  condyle  of  the  femur  and  the 
corresponding  tuberosity  of  the  tibia,  which  are  condyloid  joints,  and  one  between 
the  patella  and  the  femur,  which  is  partly  arthroidal,  but  not  completely  so,  since 
the  articular  surfaces  are  not  mutually  adapted  to  each  other,  so  that  the  movement 
is  not  a  simple  gliding  one.  This  view  of  the  construction  of  the  knee-joint 
receives  confirmation  from  the  study  of  the  articulation  in  some  of  the  lower 
mammals,  where  three  synovial  membranes  are  sometimes  found,  corresponding 
to  these  three  subdivisions,  either  entirely  distinct  or  only  connected  by  small 
communications.  This  view  is  further  rendered  probable  by  the  existence  of 
the  two  crucial  ligaments  within  the  joint,  which  must  be  regarded  as  the  external 
and  internal  lateral  ligaments  of  the  inner  and  outer  joints  respectively.  The 
existence  of  the  ligamentum  mucosum  would  further  indicate  a  tendency  to  sepa- 
ration of  the  synovial  cavity  into  two  minor  sacs,  one  corresponding  to  each  joint. 

The  bones  entering  into  the  formation  of  the  knee-joint  are  the  condyles  of  the 
femur  above,  the  head  of  the  tibia  beloiv,  and  the  patella  in  front.  The  bones  are 
connected  by  ligaments,  some  of  which  are  placed  on  the  exterior  of  the  joint, 
while  others  occupy  its  interior. 

External  Ligaments.  Interior  Ligaments. 

Capsular.  Anterior,  or  External  Crucial. 

Anterior,  or  Ligamentum  Patellae.  Posterior,  or  Internal  Crucial. 

Posterior.  Two  Semilunar  Fibrocartilages. 

Internal  Lateral.  Transverse. 

Two  External  Lateral.  Coronary. 

The  capsular  ligament  (capsula  articularis)  (Fig.  265)  consists  of  an  exceedingly 
thin,  but  strong,  fibrous  membrane,  which  is  strengthened  in  almost  its  entire 
extent  by  heavy  bands  which  are  inseparably  connected  with  it.  In  front  it  blends 
with  and  forms  part  of  the  lateral  patellar  ligaments  and  fills  in  the  interval 
between  the  anterior  and  lateral  ligaments  of  the  joints,  with  which  latter  structures 
it  is  closely  connected.  It  is  deficient  above  the  joint  and  beneath  the  tendon  of 
the  Quadriceps  extensor.  Behind,  it  is  formed  chiefly  of  vertical  fibres,  which 
arise  above  from  the  condyles  and  intercondyloid  notch  of  the  femur,  and  is  con- 
nected below  with  the  back  part  of  the  head  of  the  tibia,  being  closely  united 
with  the  origins  of  the  Gastrocnemius,  Plantaris,  and  Popliteus  muscles.  It 
passes  in  front  of,  but  is  inseparably  connected  with,  the  posterior  ligament. 

The  anterior  ligament,  or  ligamentimi  patellae  (Figs.  265, 269,  and  270),  is  the 
central  portion  of  the  common  tendon  of  the  Extensor  muscles  of  the  thigh,  which 
is  continued  from  the  patella  to  the  tubercle  of  the  tibia,  supplying  the  place  of 
an  anterior  ligament.  It  is  a  strong,  flat,  ligamentous  band  about  three  inches  in 
length,  attached,  above,  to  the  apex  of  the  patella  and  to  the  rough  depression  on 
its  posterior  surface;  below,  to  the  lower  part  of  the  tubercle  of  the  tibia,  its  super- 
ficial fibres  being  continuous  over  the  front  of  the  patella  with  those  of  the  tendon 
of  the  Quadriceps  extensor.  The  lateral  portions  of  the  tendon  of  the  Extensor 
muscles  in  conjunction  with  the  fascia  lata  pass  down  on  either  side  of  the  patella, 
and  are  attached  to  the  tibia  on  either  side  of  the  tubercle;  these  are  termed 
lateral  patellar  ligaments  (retinaculum  patellae  mediale  et  laterale),  and  merge 
into  the  capsule.     The  posterior  surface  of  the  ligamentum  patellae  is  separated. 


332 


THE  ARTICULATIONS,    OB,  JOINTS 


above,  from  the  synovial  membrane  by  a  fold  of  fat;  beloiv,  it  is  separated  from 
the  head  of  the  tibia  by  a  synovial  bursa. 

The  posterior  ligament  {ligamentum  popliteum  ohliquum)  (Fig.  266)  is  a  broad, 
flat,  fibrous  band,  formed  of  fasciculi  separated  from  one  another  by  apertures 
for  the  passage  of  vessels  and  nerves.  It  is  attached,  above,  to  the  upper  margin 
of  the  intercondyloid  notch  of  the  femur,  and,  below,  to  the  posterior  margin  of 
the  head  of  the  tibia.  Superficial  to  the  main  part  of  the  ligament  and  forming 
a  portion  of  it  is  a  strong  fasciculus  derived  from  the  tendon  of  the  Semimembra- 
nosus; it  passes  from  the  back  part  of  the  inner  tuberosity  of  the  tibia  obliquely 
upward  and  outward  to  the  back  part  of  the  outer  condyle  of  the  femur  and  blends 
with  the  posterior  ligament.     This  expansion  from  the  tendon  of  the  Semimem- 


FiG  265  — Right  knee  joint      Anterior 


Fig.  266. — Right  knee-joint.    Posterior  ■ 


branosus  muscle  is  called  the  posterior  ligament  of  Winslow.  The  posterior  liga- 
ment forms  part  of  the  floor  of  the  popliteal  space,  and  the  popliteal  artery  rests 
upon  it. 

The  internal  lateral  ligament  {ligamentum  collaterale  tibiale)  (Figs.  265  and 
266)  is  a  broad,  flat,  membranous  band,  thicker  behind  than  in  front,  and  situated 
nearer  to  the  back  than  the  front  of  the  joint.  It  is  attached,  above,  to  the  inner 
tuberosity  of  the  femur;  below,  to  the  inner  tuberosity  and  inner  surface  of  the 
shaft  of  the  tibia  to  the  extent  of  about  two  inches.  It  is  crossed,  at  its  lower 
part,  by  the  tendons  of  the  Sartorius,  Gracilis,  and  Semitendinosus  muscles,  a 
synovial  bursa  being  interposed.  Its  deef  surface  covers  the  anterior  portion  of 
the  tendon  of  the  Semimembranosus,  with  which  it  is  connected  by  a  few  fibres, 
and  the  inferior  internal  articular  vessels  and  nerve;  it  is  intimately  adherent 
to  the  internal  semilunar  fibrocartiiage. 


THE  KNEE-JOINT 


333 


Femur. 


The  external  lateral  or  long  external  lateral  ligament  (Ugamentum  collaierale 

fibidare)  (Figs.  266  and  270)  is  a  .strong,  rounded,  fibrous  cord  situated  nearer 

to  the  back  than  the  front  of  the  joint.     It  is  attached,  above,  to  the  back  part 

of  the  outer  tuberosity  of  the  femur;  below, 

to  the  outer  part  of  the  head  of  the  fibula. 

Its  outer  surface  is  covered  by   the  tendon 

of  the  Biceps  femoris,  which  divides  at  its 

insertion  into  two  parts,  separated   by  the 

ligament.  The  ligament  has,  passing  be- 
neath it,  the  tendon  of  the  Popliteus  muscle 

and   the  inferior  external    articular  vessels 

and  nerve. 
The    short   external   lateral    ligament 

(ligamentum    laterale    externum    breve    seu 

posticum)    (Fig.    266)    is    not    a    constant 

structure.      It    is    an    accessory    bundle    of 

fibres  placed  behind  and  parallel  with  the 

preceding,    attached,    above,   to    the    lower 

and  back  part  of  the  outer  tuberosity  of  the 

femur;  below,  to  the  summit  of  the  styloid 

process  of  the  fibula.  This  ligament  is  in- 
timately connected  with  the  capsular  liga- 
ment,   and    has,    passing    beneath    it,    the 

tendon  of    the  Popliteus    muscle    and    the 

inferior  external  articular  vessels  and  nerve. 
The  crucial    ligaments   (ligamenta   cru- 

ciata  genu)  (Figs.  267   and   268)   are    two 

interosseous     ligaments      of     considerable 

strength  situated  in  the  interior  of  the  joint, 

nearer  its  posterior  than   its  anterior  part. 

They  are  called  crucial  because  they  cross 

each  other  somewhat   like   the   lines  of  the 

letter  X;  and  have  received  the  names  anterior  crucial  and  posterior  crucial,  from 

the  position  of  their  attachment  to  the  tibia. 

The  anterior  or  external  crucial  ligament  {ligamentum  cruciatum  anterhis)  (Fig. 

267)  is  attached  to  the  depression  in  front  of  the  spine  of  the  tibia,  being  blended 

with  the  anterior  extremity 
of  the  external  semilunar 
fibrocartilage,  and,  passing 
obliquely  upward,  backward, 
and  outward,  is  inserted  into 
the  inner  and  back  part  of 
the  outer  condyle  of  the 
femur. 

The  posterior  or  internal 
crucial  ligament  {ligamen- 
tum cruciatum  posterius)  is 
stronger,  but  shorter  and 
less  oblique  in  its  direction 
than  the  anterior.  It  is  at- 
tached to  the  back  part  of 
the    depression    behind    the 

spine  of  the  tibia,  to  the  popliteal  notch,  and  to  the  posterior  extremity  of  the 

external  semilunar  fibrocartilage;  and  passes  upward,  forward,  and  inward,  to 


Showing   interior 


Fig.  268.— Head  of  tibi 


milunir  oirtil  iges 
Right  side. 


334 


THE  ARTICULATIONS,   OR  JOINTS 


be  inserted  into  the  outer  and  fore  part  of  the  Inner  condyle  of  the  femur.  It  is 
in  relation,  in  front,  with  the  anterior  crucial  ligament;  behind,  with  the  capsular 
ligament. 

The  semilunar  fibrocartilages  (menisci)  (Figs.  267  and  268)  are  two  crescentic 
lamellfe  which  serve  to  deepen  the  surface  of  the  head  of  the  tibia,  for  articula- 
tion with  the  condyles  of  the  femur.  The  circumference  of  each  cartilage  is  thick, 
convex,  and  attached  to  the  inside  of  the  capsule  of  the  knee;  the  inner  border 


PATELLAR  BURSA 


TUBEROSITY 


.t.-l'^'fiy"  "^,1.%*  J.'^tVtJ'HV''    1  O'' TIBIA 
^ .  '     v/   -'.  &*  *   V  *   -e  a  »  -^  V      S 


Fig.  269. — Right  knee-ioint  Sagittal  section  through  the  external  condyle  of  the  femur.  Mesal  half  oi 
section,  from  the  lateral  side.  The  knee  is  slightly  flexed;  the  joint  surfaces  have  been  pulled  a  little  apart. 
<Spalteholz.) 

is  thin,  concave,  and  free.  Their  upper  surfaces  are  concave,  and  in  relation 
with  the  condyles  of  the  femur;  their  lower  surfaces  are  flat,  and  rest  upon  the 
head  of  the  tibia.  Each  cartilage  covers  nearly  the  outer  two-thirds  of  the 
corresponding  articular  surface  of  the  tibia,  leaving  the  inner  third  uncovered; 
both  surfaces  are  smooth  and  invested  by  synovial  membrane. 

The  internal  semilunar  fibrocartilage  {tiieniscus  medialis)  is  nearly  semicir- 
cular in  form,  a  little  elongated  from  before  backward,  and  broader  behind  than 


THi:  KNEE-JOINT 


335 


in  front;  its  anterior  extremity,  thin  and  pointed,  is  attached  to  a  depression  on  the 
anterior  margin  of  the  head  of  the  tibia,  in  front  of  the  anterior  crucial  Hgament; 
its  posterior  extremity  is  attached  to  the  depression  behind  the  spine,  between 
the  attachments  of  the  external  cartilage  and  the  posterior  crucial  ligaments. 

The  external  semilunar  fibrocartilage  {meniscus  lateralis)  forms  nearly  an  entire 
circle,  covering  a  larger  portion  of  the  articular  surface  than  the  internal  one. 


J  OF  QUAD- 
RICEPS EXTENSOR 
FEMORIS 


13MG  EXTE 

LATERAL. 
LIGAMENT 


REPATELLAR 


TERNAL  SEMI- 
NAR FIBRO- 
RTiLAGE 


FiQ.  270.— Eight  knee-joint,  from  the  lateral  surface.     The  joint  cavity  and  several  bursffi  have  been  injectea 
with  a  stiffening  medium  and  then  dissected  out.     (Spalteholz.) 


It  is  grooved  on  its  outer  side  for  the  tendon  of  the  Popliteus  muscle.  Its  ex- 
tremities, at  their  insertion,  are  interposed  between  the  two  extremities  of  the 
internal  cartilage;  the  anterior  extremity  is  attached  in  front  of  the  spine  of  the 
tibia  to  the  outer  side  of,  and  behind,  the  anterior  crucial  ligament,  with  which 
it  blends;  the  posterior  extremity  is  attached  behind  the  spine  of  the  tibia,  in 
front  of  the  posterior  extremity  of  the  internal  cartilage.     Just  before  its  insertion 


336  THE  ARTICULATIONS,   OH  JOINTS 

posteriorly  it  gives  off  a  strong  fasciculus,  tlie  ligament  of  Wrisberg,  which  passes 
obliquely  upward  and  outward,  to  be  inserted  into  the  inner  condyle  of  the  femur, 
close  to  the  attachment  of  the  posterior  crucial  ligament.  Occasionally  a  small 
fasciculus  is  given  off  which  passes  forward  to  be  inserted  into  the  back  part 
of  the  anterior  crucial  ligament.  The  external  cartilage  gives  oft'  from  its  anterior 
convex  margin  a  fasciculus  which  forms  the  transverse  ligament. 

The  transverse  ligament  (ligamentum  transversum  genu)  (Fig.  268)  is  a 
band  of  fibres  which  passes  transversely  from  the  anterior  convex  margin  of  the 
external  cartilage  to  the  anterior  convex  margin  of  the  internal  cartilage;  its 
thickness  varies  considerably  in  different  subjects,  and  it  is  sometimes  absent 
altogether. 

The  coronary  ligaments  are  merely  portions  of  the  capsular  ligament,  which 
connect  the  circumference  of  each  of  the  semilunar  fibrocartilages  with  the  margin 
of  the  head  of  the  tibia. 

Ssmovial  Membrane  (Figs.  269  and  270). — The  synovial  membrane  encloses  the  articular 
cavity  {cavum  ariiculare)  of  the  knee-joint.  It  is  the  largest  and  most  extensive  synovial  mem- 
brane in  the  body.  Commencing  above  the  upper  border  of  the  patella,  it  forms,  on  the  lower 
part  of  the  front  of  the  shaft  of  the  femur,  a  short  cul-de-sac  beneath  the  Quadriceps  extensor 
tendon  of  the  thigh;  this  communicates,  by  an  orifice  of  variable  size,  with  a  synovial  bursa  inter- 
posed between  the  tendon  and  the  front  of  the  femur  (bursa  suprapateUaris).  On  each  side  of  the 
patella  the  synovial  membrane  extends  beneath  the  aponeurosis  of  the  Vasti  muscles,  and  more 
especially  beneath  that  of  the  Vastus  internus.  Below  the  patella  it  is  separated  from  the  anterior 
ligament  by  the  anterior  part  of  the  capsule  and  a  considerable  quantity  of  adipose  tissue,  known 
as  the  infrapatellar  pad  (Fig.  269),  In  this  situation  the  synovial  membrane  sends  off  a  tri- 
angular prolongation,  containing  a  few  ligamentous  fibres,  which  extends  from  the  anterior 
part  of  the  joint  below  the  patella  to  the  front  of  the  intercondyloid  notch.  This  fold  has  been 
termed  the  ligamentum  mucosmn  (plica  synovialis  patellaris).  It  also  sends  off  two  fringe- 
like folds,  called  the  ligamenta  alalia  (;plicae  alares)  (Fig.  269).  which  extend  from  the  sides  of 
the  ligamentum  mucosum,  upward  and  laterally  between  the  patella  and  femiir.  On  either 
side  of  the  joint  it  passes  downward  from  the  femur,  lining  the  capsule  to  its  point  of  attach- 
ment to  the  semilunar  cartilages;  it  may  then  be  traced  over  the  upper  surfaces  of  these 
cartilages  to  their  free  borders,  and  from  thence  along  their  under  surfaces  to  the  tibia. 
At  the  back  part  of  the  external  one  it  forms  a  cul-de-sac  between  the  groove  on  its  surface 
and  the  tendon  of  the  Popliteus;  it  surrounds  the  crucial  ligaments  and  lines  the  inner  surface 
of  the  ligaments  which  enclose  the  joint.  The  pouch  of  synovial  membrane  between  the  Quad- 
riceps extensor  tendon  and  the  front  of  the  femur  is  supported,  during  the  movements  of  the 
knee,  by  a  small  muscle,  the  Subcrureus,  which  is  inserted  into  the  upper  part  of  the  capsular 
ligament. 

The  folds  of  synovial  membrane  and  the  fatty  processes  contained  in  them  act,  as  it  seems, 
mainly  as  a  padding  to  fill  up  interspaces  and  obviate  concussions.  Sometimes  the  bursa  beneath 
the  Quadriceps  extensor  is  completely  shut  off  from  the  rest  of  the  synovial  cavity,  thus  forming 
a  closed  sac  between  the  Quadriceps  and  the  lower  part  of  the  front  of  the  femur;  sometimes  it 
communicates  with  the  synovial  cavity  by  a  minute  aperture;  usually  the  two  cavities  are  incom- 
pletely separated  by  a  synovial  fold. 

Bursae. — The  burste  about  the  knee-joint  are  the  following:  In  front  there  are  four  bursse;  one 
is  interposed  between  the  patella  and  the  skin.  It  is  known  as  the  prepatellar  bursa  (bursa 
praepaiellaris  subcutanea);  another,  of  small  size,  between  the  upper  part  of  the  tuberosity  of 
the  tibia  and  the  ligamentum  patellae  is  called  the  deep  infrapatellar  bursa  (bursa  infrapatellaris 
profunda);  and  a  third  between  the  lower  part  of  the  tuberosity  of  the  tibia  and  the  skin,  the 
subcutaneous  tibial  bursa  (bursa  subcutanea  tuberositatis  tibiae).  A  fourth  bursa  exists  in  front, 
the  suprapatellar  biu:sa  (bursa  suprapateUaris).  It  lies  between  the  anterior  surface  of  the 
lower  end  of  the  femur  and  the  posterior  surface  of  the  Quadriceps  femoris.  Spalteholz  says  that 
the  suprapatellar  bursa  is  closely  connected  with  the  Quadriceps  tendon  and  is  usually  incom- 
pletely shut  off  from  the  cavity  of  the  joint.^  Occasionally  there  is  a  bursa  between  the  ex- 
pansion of  the  fascia  lata  and  the  Quadriceps  and  the  patella  (bursa  praepafellaris  suhfascialis), 
and  sometimes  one  between  the  tendon  of  the  Quadriceps  and  the  anterior  surface  of  the  patella 
(bursa  praepatellaris  subtendinea) .  On  the  outer  side  there  are  four  bursEe:  (1 )  One  (which  some- 
times communicates  with  the  joint)  beneath  the  outer  head  of  the  Gastrocnemius;  (2)  one  above 
the  external  lateral  ligament  between  it  and  the  tendon  of  the  Biceps  femoris;  (3)  one  beneath  the 

1  Sualteholz's  Hand  .\tlas  of  Human  Anatomy.     Translated  by  Lewellys  F.  Barker. 


THE  KNEE  JOINT  337 

external  lateral  ligament  between  it  and  the  tendon  of  the  Popliteus  (this  is  sometimes  only  an 
(■xpansion  from  the  next  bursa);  (4)  one  beneath  the  tendon  of  the  Popliteus  {bursa  mu.icuK 
poplitri)  between  it  and  the  condyle  of  the  femur,  which  is  almost  always  an  extension  from  the 
synovial  membrane  of  the  joint.  On  the  inner  side  there  are  five  bursa- :  (1)  One  beneath  the 
inner  head  of  the  Gastrocnemius,  which  sends  a  prolongation  between  the  tendons  of  the  Gastroc- 
nemius and  Semimembranosus;  this  bursa  often  communicates  with  the  joint;  (2)  one  above 
the  internal  lateral  ligament  between  it  and  the  tendons  of  the  Sartorius,  Gracilis,  and  Semi- 
tendinosus;  (3)  one  beneath  the  internal  lateral  ligament  between  it  and  the  tendon  of  the 
Semimembranosus;  this  is  sometimes  only  an  expansion  from  the  next  bursa;  (4)  one  beneath 
the  tendon  of  the  Semimembranosus,  between  it  and  the  head  of  the  tibia;  (5)  sometimes  there 
is  a  bursa  between  the  tendons  of  the  Semimemltranosus  and  of  the  Semitendinosus. 

Structures  around  the  Joint.  —In  front  and  at  the  sides,  the  Quadriceps  extensor;  on  the 
oitier  sidr,  the  tendons  of  the  Biceps  fo-moris  and  (he  Popliteus  and  the  external  popliteal  nerve; 
on  the  inner  side,  the  Sartorius,  Gracilis,  Semitendinosus,  and  Semimembranosus;  behind,  an 
expansion  from  the  tendon  of  the  Semimembranosus,  the  popliteal  vessels,  and  the  internal 
popliteal  nerve,  the  Popliteus,  the  Plantaris,  and  the  inner  and  outer  heads  of  the  Gastrocnemius, 
some  lymph  nodes,  and  fat. 

The  arteries  supplying  the  joint  are  derived  from  the  anastomotica  magna  branch  of  the 
femoral,  articular  branches  of  the  (lopliteal,  anterior  and  posterior  recurrent  branches  of  the 
anterior  tibial,  and  a  descending  branch  fniin  (lie  external  circumflex  of  the  profunda. 

The  nerves  are  derived  from  the  oliturator,  femoral,  and  external  and  internal  pojiliteal. 

Movements. — The  knee-joint  permits  of  movements  of /?f.vion  and  extension,  and,  in  certain 
positions,  of  slicjht  rotation  inward  and  outward.  The  movement  of  flexion  and  extension  does 
not,  however,  take  place  in  a  simple,  finger-like  manner,  as  in  other  joints,  but  is  a  complicated 
movement,  consisting  of  a  certain  amount  of  gliding  and  rotation;  so  that  the  same  part  of  one 
articular  surface  is  not  always  applied  to  the  same  part  of  the  other  articular  surface,  and  the 
axis  of  motion  is  not  a  fixed  one.  If  the  joint  is  examined  while  in  a  condition  of  extreme  flexion, 
the  posterior  part  of  the  articular  surfaces  of  the  tibia  will  be  found  to  be  in  contact  with  the 
posterior  rounded  extremities  of  the  condyles  of  the  femur;  and  if  a  simple  hinge-like  movement 
•were  to  take  place,  the  axis,  around  which  the  revolving  movement  of  the  tibia  occurs,  would  be 
in  the  back  part  of  the  condyle.  If  the  leg  is  now  brought  forward  into  a  position  of  semiflexion, 
the  upper  surface  of  the  tibia  will  be  seen  to  glide  over  the  condyles  of  the  femur,  so  that  the  ' 
middle  part  of  the  articular  facets  are  in  contact,  and  the  axis  of 
rotation  must  therefore  have  shifted  forward  to  nearer  the  centre 
of  the  condyles.  If  the  leg  is  now  brought  into  the  extended  posi- 
tion, a  still  further  gliding  takes  place  and  a  further  shifting  for- 
ward of  the  axis  of  rotation.  This  is  not,  however,  a  simple 
movement,  but  is  accompanied  by  a  certain  amount  of  rotation 
outward  around  a  vertical  axis  drawn  through  the  centre  of  the 
head  of  the  tibia.  This  rotation  is  due  to  the  greater  length  of 
the  internal  condyle,  and  to  the  fact  that  the  anterior  portion 
of  its  articular  surface  is  inclined  obliquely  outward.  In  conse- 
■quence  of  this  it  will  be  seen  that  toward  the  close  of  the  move- 
ment of  extension — that  is  to  say,  just  before  complete  extension 
is  effected — the  tibia  glides  obliquely  upward  and  outward  over  •  ^'°' f '^  ~7lh^  °'^  hJ"' ''t'fl"" 
this  oblique  surface  on  the  inner  condvle,  and  the  leg  is  therefore  showing  diagrammatically  the 
■necessarily  rotated  outward.  In  flexion  of  the  joint  the  converse  fn'^"igere'S'''posTt'ions'''c/'''the 
of  these  movements  takes  place;  thetiViia  glides  back^vard  around  knee, 
the  end  of  the  femur,  and  at  the  commencement  of  the  move- 
ment the  tibia  is  directed  downward  and  inward  along  the  oblique  curve  of  the  inner  condyle, 
thus  causing  an  inward  rotation  to  the  leg. 

During  flexion  and  extension  the  patella  moves  on  the  lower  end  of  the  femur,  but  this 
movement  is  not  a  simple  gliding  one;  for  if  the  articular  surface  of  this  bone  is  examined,  it 
will  be  found  to  present  on  each  side  of  the  central  vertical  ridge  two  less  marked  transverse 
Tidges,  which  divide  the  surface,  except  a  small  portion  along  the  inner  border,  which  is  cut  off 
by  a  slight  vertical  ridge  into  six  facets  (Fig.  271),  and  therefore  does  not  present  a  uniform 
■curved  surface  as  would  be  the  case  if  a  simple  gliding  movement  took  place.  These  six  facets — 
three  on  each  side  of  the  median  vertical  ridge — correspond  to  and  denote  the  parts  of  the  bone, 
respectively,  in  contact  with  the- condvles  of  the  femur  during  flexion,  semiflexion,  and  extension. 
In  flexion  only  the  upper  facets  on  the  patella  are  in  contact  with  the  trochlea  of  the  femur;  the 
lower  two-thirds  of  the  bone  rests  upon  the  infrapatellar  pad  which  occupies  the  space  between 
the  femur  and  tibia.  In  the  semiflexed  position  of  the  joint  the  middle  facets  on  the  patella  rest 
upon  the  most  prominent  portion  of  the  trochlea,  and  thus  afford  greater  leverage  to  the  Quad- 
riceps by  increasing  its  distance  from  the  centre  of  motion.  In  complete  extension  the  patella 
is  drawn  up,  so  that  only  the  lower  facets  are  in  contact  with  the  trochlea.     The  narrow  strip 


338  THE  ARTICULATIONS,   OB  JOINTS 

along  the  inner  border  is  in  contact  with  the  outer  aspect  of  the  internal  condyle  when  the  leg 
is  fully  flexed  at  the  knee-joint.  As  in  the  elbow,  so  it  is  in  the  knee — the  axis  of  rotation  in 
flexion  and  extension  is  not  precisely  at  right  angles  to  the  axis  of  the  Vjone,  but  during  flexion 
there  is  a  certain  amount  of  alteration  of  plane;  so  that,  whereas  in  flexion  the  femur  and  tibia 
are  in  the  same  plane,  in  extension  the  one  bone  forms  an  angle  of  about  10  degrees  with  the 
other.  There  is,  however,  this  difference  between  the  two  extremities:  that  in  the  upper,  during 
extension,  the  humeri  are  parallel  and  the  bones  of  the  forearm  diverge;  in  the  lower,  the  femora 
converge  below  and  the  tibis  are  parallel. 

In  addition  to  the  slight  rotation  during  flexion  and  extension,  the  tibia  enjoys  an  independent 
rotation  on  the  condyles  of  the  femur  in  certain  positions  of  the  joint.  This  movement  takes 
place  between  the  articular  menisci  and  the  tibia,  whereas  the  movement  of  flexion  and  extension 
takes  place  between  the  articular  menisci  and  the  femur.  So  that  the  knee  may  be  said  to  consist 
of  two  joints,  separated  by  the  menisci — an  upper,  meniscofemoral,  in  which  flexion  and  extension 
take  place;  and  a  lower,  meniscotibial,  allowing  of  a  certain  amount  of  rotation.  This  latter 
movement  can  only  take  place  in  the  semiflexed  position  of  the  limb,  W'hen  all  the  ligaments  are 
relaxed. 

Durinu  iJexion  the  ligamentum  patellae  is  put  upon  the  stretch,  as  is  also  the  posterior  crucial 
lii'ament  in  extreme  flexion.  The  other  ligaments  are  all  relaxed  by  flexion  of  the  joint,  though 
the  relaxation  of  the  anterior  crucial  ligament  is  very  trifling.  During  life  flexion  is  checked 
by  the  contact  of  the  leg  with  the  thigh.  In  the  act  of  extending  the  leg  upon  the  thigh  the  liga- 
mentum patellae  is  tightened  by  the  Quadriceps  extensor;  but  when  the  leg  is  fully  extended,  as 
in  the  erect  posture,  the  ligament  becomes  relaxed,  so  as  to  allow  free  lateral  movement  to  the 
'latella,  which  then  rests  on  the  front  of  the  lower  end  of  the  femur.  The  other  ligaments,  with 
the  exception  of  the  posterior  crucial,  which  is  partly  relaxed,  are  all  on  the  stretch.  When  the 
limb  has  been  brought  into  a  straight  line,  extension  is  checked  mainly  by  the  tension  of  all  the 
ligaments  except  the  posterior  crucial  and  the  ligamentum  patellae.  The  movements  of  rotation 
of  which  the  knee  is  capable  are  permitted  in  the  semiflexed  condition  by  the  partial  relaxation 
of  both  crucial  ligaments,  as  well  as  of  the  lateral  hgaments.  Rotation  inward  appears  to  be 
limited  bv  the  tension  of  the  anterior  crucial  ligament,  and  by  the  interlocking  of  the  two  liga- 
ments; but  rotation  outward  does  not  appear  to  be  checked  by  either  crucial  ligament,  since 
they  uncross  during  the  execution  of  this  movement,  but  it  is  checked  by  the  lateral  ligaments, 
especially  the  internal.  The  main  function  of  the  crucial  ligaments  is  to  act  as  a  direct  bond 
of  union  between  the  tibia  and  femur,  preventing  the  former  bone  from  being  carried  too  far  back- 
ward or  forward.  Thus,  the  anterior  crucial  ligament  prevents  the  tibia  being  cari'ied  too  far 
forward  by  the  Extensor  tendons,  and  the  posterior  crucial  checks  too  great  movement  back- 
ward by  the  Flexors.  They  also  assist  the  lateral  ligaments  in  resisting  any  lateral  bending  of  the 
joint.  The  semilunar  cartilages  are  intended,  evidently,  to  adapt  to  a  certain  extent  the  surface 
of  the  tibia  to  the  shape  of  the  femur,  in  order  to  fill  intervals  which  would  otherwise  occur  in  the 
changing  of  joint  position  and  to  interrupt  jars  which  otherwise  would  be  so  frequently  trans- 
mitted up  the  limb  through  jumping  or  falling  on  the  feet.  These  cartilages  also  contribute  to 
the  varieties  of  motion — flexion,  extension,  and  rotation — as  explained  above.  The  patella  is  a 
treat  defence  to  the  knee-joint  from  any  injury  inflicted  in  front,  and  it  distributes  upon  a  large 
and  tolerably  even  surface  during  kneeling  the  pressure  which  would  otherwise  fall  upon  the 
prominent  ridges  of  the  condyles;  it  also  affords  leverage  to  the  Quadriceps  extensor  muscle  when 
it  acts  upon  the  tibia ;  and  Mr.  Ward  has  pointed  out'  how  this  leverage  varies  in  the  various 
positions  of  the  joint,  so  that  the  action  of  the  muscles  produces  velocity  at  the  expense  of  force 
in  the  commencement  of  extension,  and,  on  the  contrary,  at  the  close  of  extension  tends  to 
diminish  velocity,  and  therefore  the  shock  to  the  ligaments  at  the  moment  tension  of  the  struc- 
tures takes  place. 

Extension  of  the  leg  on  the  thigh  is  performed  by  the  Quadriceps  extensor;  /p.Tio»  by  the  Ham- 
string muscles,  assisted  by  the  Gracilis  and  Sartorius,  and,  indirectly,  by  the  Gastrocnemius, 
Popliteus,  and  Plantaris;  rotation  outward,  by  the  Biceps  femoris;  and  rotation  inward  by  the 
Popliteus,  Semitendinosus,  and,  to  a  slight  extent,  the  Semimembranosus,  the  Sartorius,  and  the 
Gracilis. 

Surface  Form. — The  interval  between  the  two  bones  enteriiig  into  the  formation  of  the  knee- 
joint  can  always  easily  be  felt.  If  the  limb  is  extended,  it  is  situated  on  a  slightly  higher  level 
than  the  apex  of  the  patella;  but  if  the  limb  is  slightly  flexed,  a  knife  carried  horizontally  back- 
ward immediately  below  the  apex  of  the  patella  would  pass  directly  into  the  joint.  When  the 
knee-joint  is  distended  with  fluid,  the  outline  of  the  synovial  membrane  at  the  front  of  the  knee 
may  be  fairly  well  mapped  out. 

Applied  Anatomy. — The  bursce  about  the  knee  are  frequently  the  seat  of  inflammation. 
Enlargement  of  the  prepatellar  bursa  constitutes  housemaid's  knee.    The  bursa  beneath  the 

1  Human  Osteology,  p.  40.=;. 


THE  KNEE-JOINT  339 

Semimembranosus  may  enlarge  greatly.  It  communicates  with  the  knee-joint  and  can  frequently 
be  made  to  disappear  by  pressure  when  the  knee  is  flexed.  Treves  points  out  that  enlargement 
of  the  bursa  between  the  Biceps  tendon  and  the  external  lateral  ligament  causes  great  pain 
because  the  peroneal  nerve  crosses  the  sac' 

From  a  consideration  of  the  construction  of  the  knee-joint  it  would  at  first  sight  appear  to  be 
one  of  the  least  secure  of  any  of  the  joints  in  the  body.  It  is  formed  between  the  two  longest 
liones,  and  therefore  the  amount  of  leverage  which  can  be  brought  to  bear  upon  it  is  very  con- 
siderable; the  articular  surfaces  are  but  ill  adapted  to  each  other,  and  the  range  and  varietv  of 
motion  which  it  enjoys  is  great.  All  these  circumstances  tend  to  render  the  articulation  very 
insecure;  but,  nevertheless,  on  account  of  the  very  powerful  ligaments  which  bind  the  bones 
together,  the  joint  is  one  of  the  strongest  in  the  body,  and  dislocation  from  traumatism  is  of  very 
rare  occurrence.  When,  on  the  other  hand,  the  ligaments  have  been  softened  or  destroyed 
by  disease,  partial  displacement  is  very  liable  to  occur,  and  is  frequently  brought  about  by  the 
mere  action  of  the  muscles  displacing  the  articular  surfaces  from  each  other.  The  tibia  may 
be  dislocated  in  any  direction  from  the  femur — forward,  backward,  im\'ard,  or  outward;  or  a 
combination  of  two  of  these  dislocations  may  occur — that  is,  the  tibia  may  be  dislocated  for- 
ward and  laterally,  or  backward  and  laterally,  and  any  of  these  dislocations  may  be  complete 
or  incomplete.  As  a  rule,  however,  the  antero-posterior  dislocations  are  complete,  the  lateral 
ones  incomplete. 

One  or  other  of  the  semilunar  cartilages  may  become  displaced  and  nipped  between  the  femur 
and  tibia.  The  accident  is  produced  by  a  twist  of  the  leg  when  the  knee  is  flexed,  and  is  accom- 
panied by  a  sudden  pain  and  fixation  of  the  knee  in  a  flexed  position.  The  cartilage  may  be 
displaced  either  inward  or  outward;  that  is  to  say,  either  inward  toward  the  tibial  spine,  so 
that  the  cartilage  becomes  lodged  in  the  intercondyloid  notch;  or  outward,  so  that  the  cartilage 
projects  beyond  the  margin  of  the  articular  surface.  Acute  synovitis,  the  result  of  traumatism 
or  exposure  to  cold,  is  very  common  in  the  knee,  on  account  of  its  superficial  position.  When 
distended  with  fluid,  the  swelling  shows  itself  above  and  at  the  sides  of  the  patella,  reaching 
about  an  inch  or  more  above  the  trochlear  surface  of  the  femur,  and  extending  a  little  higher 
under  the  Vastus  internus  than  the  Vastus  externus.  Occasionally  the  swelling  may  extend 
two  inches  or  more.  At  the  sides  of  the  patella  the  swelling  extends  lower  at  the  inner  side 
than  it  does  on  the  outer  side.  The  lower  level  of  the  synovial  membrane  is  just  above  the  level 
of  the  upper  part  of  the  head  of  the  fibula.  In  the  middle  line  it  covers  the  upper  third  of  the 
ligamentum  patellae,  being  separated  from  it,  however,  by  the  capsule  and  a  pad  of  fat.  Chronic 
si/n.ovitis  principally  shows  itself  in  the  form  of  pulpy  degeneration  of  the  synovial  membrane, 
the  result  of  tuberculous  arthritis.  The  reasons  why  tuberculous  disease  of  the  knee  so  often 
commences  in  the  synovial  membrane  appear  to  be  the  complex  and  extensive  nature  of  this 
sac;  the  extensive  vascular  supply  to  it;  and  the  fact  that  injuries  are  generally  dift'used  and 
applied  to  the  front  of  the  joint  rather  than  to  the  ends  of  the  bone.  Syphilis  not  infrequently 
attacks  the  knee-joint.  In  the  hereditary  form  of  the  disease  the  attack  is  usually  symmetrical — 
both  joints  are  involved.  They  become  filled  with  synovial  effusion  and  cure  is  very  difficult. 
In  acquired  syphilis  gummatous  infiltration  of  the  synovial  membrane  may  take  place.  The 
knee  is  one  of  the  joints  most  commonly  affected  with  osteoarthritis,  and  is  said  to  be  more 
frequently  the  seat  of  this  disease  in  women  than  in  men.  The  occurrence  of  the  so-called  loose 
cartilage  is  almost  confined  to  the  knee,  though  loose  cartilages  are  occasionally  met  with  in  the 
elbow,  and,  rarely,  in  some  other  joints.  Many  of  them  occur  in  cases  of  osteoarthritis,  in  which 
calcareous  or  cartilaginous  material  is  formed  in  one  of  the  synovial  fringes  and  constitutes  the 
foreign  body,  and  may  or  may  not  become  detached,  in  the  former  case  only  meriting  the  usual 
term,  "loose"  cartilage.  In  other  cases  they  have  their  origin  in  the  exudation  of  inflammatory 
lymph,  and  possibly,  in  some  rare  instances,  a  portion  of  the  articular  cartilage  or  one  of  the 
semilunar  cartilages  becomes  detached  and  constitutes  the  foreign  bodv. 

Genu  valgum,  or  knock-knee,  is  a  common  deformity  of  childhood,  in  which,  owing  to  changes 
in  and  about  the  joint,  the  angle  between  the  outer  border  of  the  tibia  and  femur  is  diminished, 
so  that  as  the  patient  stands  the  two  internal  condyles  of  the  femora  are  in  contact,  but  the  two 
internal  malleoli  of  the  tibiae  are  more  or  less  widely  separated  from  each  other.  When,  howe\'er, 
the  knees  are  flexed  to  a  right  angle,  the  two  legs  are  practically  parallel  with  each  other.  At 
the  commencement  of  the  disease  there  is  a  yielding  of  the  internal  lateral  ligainent  and  other 
fibrous  structures  on  the  inner  side  of  the  joint;  as  a  result  of  this  there  is  a  constant  undue 
pressure  of  the  outer  tuberosity  of  the  tibia  against  the  outer  condyle  of  the  femur.  This  extra 
pressure  causes  arrest  of  growth,  and,  possibly,  wasting  of  the  outer  condyle,  and  a  consequent 
tendency  for  the  tibia  to  become  separated  from  the  internal  condyle.  To  prevent  this  the 
internal  condyle  becomes  depressed;  probably,  as  was  first  pointed  out  bv  Mikulicz,  bv  an 
increased  growth  of  the  lower  end  of  the  diaphysis  on  its  inner  side,  so  that  the  line  of  the 
epiphysis  becomes  oblique  instead  of  transverse  to  the  axis  of  the  bone,  with  a  direction  down- 

1  .Applied  Anatomy. 


340 


THE  ARTICULATIONS,   OB  JOINTS 


ward  and  inward.    It  is  often  said  that  the  deformity  is  produced  by  undue  length  of  the  inner 
condyle,  but  in  reality  the  condyle  grows  as  the  deformity  progresses. 

Excision  of  the  knee-joint  is  most  frequently  required  for  tuberculous  disease  of  this  articulation, 
but  is  also  practised  in  cases  of  disorganization  of  the  knee  after  rheumatic  fever,  pyemia,  etc., 
in  osteoarthritis,  and  in  ankylosis.  It  is  also  occasionally  called  for  in  cases  of  injury,  gun- 
shot or  otherwise.  The  operation  is  best  performed  either  by  a  horseshoe  incision,  starting  from 
one  condyle,  descending  as  low  as  the  tubercle  of  the  tibia,  where  it  crosses  the  leg,  and  is  then 

carried  upward  to  the  other  condyle;  or  by 
a  transverse  incision  across  the  patella. 
In  this  latter  incision  the  patella  is  either 
removed  or  sawed  across,  and  the  halves 
subsequently  sutured  together.  The  bones 
having  been  cleared,  and  in  those  cases 
where  the  operation  is  performed  for 
tuberculous  disease  all  pulpy  tissue  hav- 
ing been  carefully  removed,  the  section 
of  the  femur  is  first  made.  This  should 
never  include,  in  children,  more  than,  at 
the  most,  two-thirds  of  the  articular  sur- 
face, otherwise  the  epiphyseal  cartilage 
will  be  involved,  with  disastrous  results 
as  regards  the  growth  of  the  limb.  After- 
ward a  thin  slice  should  be  removed  from 
the  upper  end  of  the  tibia,  not  more  than 
half  an  inch.  If  any  diseased  tissue  still 
appears  to  be  left  in  the  bones,  it  should 
be  removed  with  the  gouge  rather  than 
by  making  a  further  section  of  the  bones. 


III.  The  Tibiofibular  Articulation 
(Articulatio  Tibiofibularis) . 

The  articulations  between  the 
tibia  and  fibula  are  effected  by 
ligaments  which  connect  both  ex- 
tremities, as  well  as  the  shafts  of 
the  bones.  It  may,  consequently,  be 
subdivided  into  three  articulations: 
(1)  The  superior  tibiofibular  articu- 
lation. (2)  The  middle  tibiofibular 
ligament  or  interosseous  membrane. 
(3)  The  inferior  tibiofibular  articu- 
lation. 

1.  The  Superior  Tibiofibular- 

Articulation  (Articulatio 

Tibiofibularis). 

This  articulation  is  an  arthrodial 
joint.  The  contiguous  surfaces  of 
the  bones  present  two  flat,  oval 
facets  covered  with  cartilage,  and 
are  interconnected  by  the  following 
ligaments : 


272. — Ligaments  of  the  right  ieg,  from  i 
(Spalteholz.) 


Capsular. 

Anterior  Superior  Tibiofibular. 

Posterior  Superior  Tibiofibular. 


THE  TIBIOFIBULAR  ARTICULATION  341 

The  capsular  ligament  (capsula  ariicularis)  consists  of  a  membranous  bag 
which  surrounds  the  articulation,  being  attached  around  the  margins  of  the 
articular  facets  on  the  tibia  and  fibula,  and  is  much  thicker  in  front  than  behind. 

The  anterior  superior  ligament  (Fig.  272)  consists  of  two  or  three  broad  and 
fiat  bands  which  pass  obliquely  upward  and  inward  from  the  front  of  the  head 
of  the  fibula  to  the  front  of  the  outer  tuberosity  of  the  tibia. 

The  posterior  superior  ligament  ( Fig.  265)  is  a  single  thick  and  broad  band 
which  passes  upward  and  inward  from  the  back  part  of  the  head  of  the  fibula 
to  the  back  part  of  the  outer  tuberosity  of  the  tibia.  It  is  covered  by  the 
tendon  of  the  Popliteus  muscle. 

Synovial  Membrane. — A  synovial  membrane  lines  this  articulation,  which  at  its  upper  and 
back  part  is  occasionally  continuous  with  that  of  the  knee-joint. 


2.  The  Middle  Tibiofibular  Ligament  or  Interosseous  Membrane 
(Membrana  Interossea  Cruris)  (Fig.  272). 

An  interosseous  membrane  extends  between  the  contiguous  margins  of  the 
tibia  and  fibula  and  separates  the  muscles  on  the  front  from  those  on  the  back 
of  the  leg.  It  consists  of  a  thin,  aponeurotic  lamina  composed  of  oblique  fibres 
which  for  the  most  part  pass  downward  and  outward  between  the  interosseous 
ridges  on  the  two  bones;  some  few  fibres,  however,  pass  in  the  opposite  direction, 
downward  and  inward.  It  is  broader  above  than  below.  Its  upper  margin 
does  not  quite  reach  the  superior  tibiofibular  joint,  but  presents  a  free  concave 
border,  above  which  is  a  large,  oval  aperture  for  the  passage  of  the  anterior  tibial 
vessels  forward  to  the  anterior  aspect  of  the  leg.  At  its  lower  part  is  an  opening 
for  the  passage  of  the  anterior  peroneal  vessels.  It  is  continuous  below  with 
the  inferior  interosseous  ligament,  and  is  perforated  in  numerous  places  for  the 
passage  of  small  vessels.  It  is  in  relation,  in  front,  with  the  Tibialis  anticus. 
Extensor  longus  digitorum,  Extensor  proprius  halhicis,  Peroneus  tertius,  and 
the  anterior  tibial  vessels  and  nerve;  behind,  with  the  Tibialis  posticus  and 
Flexor  longus  hallucis. 


3.  The  Inferior  Tibiofibular  Articulation  (Syndesmosis  Tibiofibularis) 

(Figs.  274,  275). 

This  articulation  is  formed  by  the  rough,  convex  siu'face  of  the  inner  side  of 
the  lower  end  of  the  fibula,  connected  with  a  concave  rough  surface  on  the  outer 
side  of  the  tibia.  Below,  to  the  extent  of  about  one-sixth  of  an  inch,  these  sur- 
faces are  smooth,  and  covered  with  cartilage,  which  is  continuous  with  that  of 
the  ankle-joint.     The  ligaments  of  this  joint  are: 

Anterior  Inferior  Tibiofibular.  Transverse  or  Inferior. 

Posterior  Inferior  Tibiofibular.  Inferior  Interosseous. 

The  anterior  inferior  ligament  (Ugamentum  malleoli  lateralis  anierius)  (Figs. 
272  and  276)  is  a  flat,  triangular  band  of  fibres,  broader  below  than  above,  which 
extends  obliquely  downward  and  outward,  between  the  adjacent  margins  of  the 
tibia  and  fibula,  on  the  front  aspect  of  the  articulation.  It  is  in  relation,  in  front, 
with  the  Peroneus  tertius,  the  aponeurosis  of  the  leg,  and  the  integument,  behind, 
with  the  inferior  interosseous  ligament;  and  lies  in  contact  with  the  cartilage 
covering  the  astragalus. 


342 


THE  ARTICULATIONS,   OB  JOINTS 


The  posterior  inferior  ligament  (ligamentum  malleoli  lateralis  posterius)  (Fig. 
276),  smaller  than  the  preceding,  is  disposed  in  a  similar  manner  on  the  posterior 
surface  of  the  articulation. 

The  inferior  transverse  ligament  lies  under  cover  of  the  posterior  ligament, 
and  is  a  strong,  thick  band  of  yellowish  fibres  which  passes  transversely  across 
the  back  of  the  joint,  from  the  external  malleolus  to  the  posterior  border  of 
the  articular  surface  of  the  tibia,  almost  as  far  as  its  malleolar  process.  This 
ligament  projects  below  the  margin  of  the  bones,  and  forms  part  of  the  articulating 
surface  for  the  astragalus. 

The  inferior  interosseous  ligament  (Fig.  274)  consists  of  numerous  short,  strong, 
fibrous  bands  which  pass  between  the  contiguous  rough  surfaces  of  the  tibia  and 
fibula,  and  constitute  the  chief  bond  of  union  between  the  bones.  This  ligament 
is  continuous  above  with  the  interosseous  membrane. 

Synovial  Membrane. — The  synovial  membrane  lining  the  articular  surface  is  derived  from 
that  of  the  ankle-joint  (Fig.  274). 

Movements. — The  movement  permitted  in  these  articulations  is  limited  to  a  very  slight 
gliding  of  the  articular  surfaces  one  upon  another. 


IV.  The  Tibiotarsal  Articulation,  or  Ankle-joint  (Articulatio  Talocruralis) 

(Figs.  273,  274). 

The  ankle  is  a  ginglymus  or  hinge-joint.  The  bones  entering  into  its  forma- 
tion are  the  lower  extremity  of  the  tibia  and  its  malleolus  and  the  external  malleolus 
of  the  fibula,  which  forms  a  mortise  (Fig.  272)  to  receive  the  upper  convex  surface 


Tarsometatarsal 
articulations  X 


Tarsal  articulations. 


Fig.  273. — Ankle-joint:  tarsal  and  tarsometatarsal  articulations.     Internal  view.     Right 


of  the  astragalus  and  its  two  lateral  facets.  The  bony  surfaces  are  covered  by 
hyaline  cartilage  and  interconnected  by  a  capsule  (capsida  articularis),  which  in 
places  forms  thickened  bands  constituting  the  following  ligaments: 


Anterior. 
Posterior. 


Internal  I^ateral. 
External  Lateral. 


THE  TIBIOTAIU^AL  ARTICULATION 


343 


The  anterior  tibibtarsal  ligament  (ligameiiium  taloUbiale  anterius)  is  a  broad, 
thin,  niemhraiious  layer,  attaelied,  above,  to  the  anterior  margin  of  the  lower 
extremity  of  the  tibia;  beUnv,  to  the  margin  of  the  astragalus,  in  front  of  its 
articular  surface.  It  is  in  relation,  in  front,  with  the  Extensor  tendons  of  the 
toes,  with  the  tendons  of  the  Tibialis  anticus  and  Peroneus  tertius,  and  the 
anterior  tiliial  vessels  and  nerve;  behind,  it  lies  in  contact  with  the  synovial 
membrane. 

The  posterior  tibiotarsal  ligament  (ligamentum  talotihiale  posierius)  is  very 
thin,  and  consists  principally  of  transverse  fibres.  It  is  attached,  above,  to  the 
margin  of  the  articular  surface  of  the  tibia,  blending  with  the  inferior  transverse 
tibiofibular  ligament;  below,  to  the  astragalus,  behind  its  trochlear  surface, 
externally,  where  it  blends  with  the  inferior  transverse  tibiofibular  ligament,  it  is 
thickest. 

The  internal  lateral  or  deltoid  ligament  {liyamentitm  deltoidev7n)  (Figs.  274 
and  275)  consists  of  a  superficial  and  a  deep  set  of  fibres;  the  superficial  set  consti- 


ADIPOSE    PAD 


TER08SE0US  CAL- 
INEO-ASTRAGALOID 

LIGAMENT 

FLEXOR  LONGUS 

DIGITORUM 

FLEXOR  LONGUS 


TIBIAL  VESSELS 


Fig.  274. — Coronal  section  through  the  ankle-joint  and  the  calcaneo-aatragaloid  articulation.     (Poirier  and 

Charpy.) 


tute  a  strong,  flat,  triangular  band,  which  is  attached,  above,  to  the  apex  and  to 
the  anterior  and  posterior  borders  of  the  inner  malleolus.  The  most  anterior 
fibres  pass  forward  to  be  inserted  into  the  scaphoid  bone  {lig.  calcaneotibiale)  and 
the  inferior  calcaneoscaphoid  ligament  {lig.  tibionavicidare) ,  the  middle  descend 
almost  perpendicularlj'  to  be  inserted  into  the  sustentaculum  tali  of  the  calcaneus 
{lig.  calcaneotibiale) ;  and  the  posterior  fibres  pass  backward  and  outward  to  be 
attached  to  the  inner  side  of  the  astragalus  (Zigr.  taloiibiale  posteriiis).  The  deep 
set  is  attached,  above,  to  the  notch  of  the  inner  malleolus,  and,  below,  to  the 
inner  side  of  the  astragalus.  This  ligament  is  covered  by  the  tendons  of  the 
Tibialis  posticus  and  Flexor  longus  digitorum.  muscles. 

The  external  lateral  ligament  (Figs.  275  and  276)  consist  of  three  distinctly 
specialized  fasciculi  of  the  capsule,  taking  dift'erent  directions  and  separated 
by  distinct  intervals;  for  which  reason  it  is  divided  by  some  anatomists  into 
three  distinct  ligaments,  and  so  described.' 

^  Humphry,  On  the  Skeleton,  p.  559. 


344 


THE  ARTICULATIONS,   OR  JOINTS 


The  anterior  fasciculus  (ligamentum  talofihulare  anterius);  the  shortest  of  the 
three,  passes  from  the  anterior  margin  of  the  external  malleolus  forward  and 
inward  to  the  astragalus,  in  front  of  its  external  articular  facet. 


INTERNAL 

INTEROSSEOUS 

LIGAMENT 

TARSO- 
METATARSAL 
»HTICULATIONS 


ASTRAGALO- 

SCAPHOID 

ARTICULATION 


RLE-JOINT 

MIDDLE  EASCICULUS 
,OF  THE  EXTERNAL 
LATERAL  LIGAMENT 


Fig.  275. — Joints  of  the  right  foot,  from  the  back  of  the  foot.     (Spalteholz.) 

The  posterior  fasciculus  (ligamentum  talofibvlare  posterms),  the  most  deeply 
seated,  passes  inward  from  the  depression  at  the  inner  and  back  part  of  the 
external  malleolus  to  the  prominent  external  tubercle  on  the  posterior  surface  of 
the  astragalus.     Its  fibres  are  almost  horizontal  in  direction. 

The  middle  fasciculus  {ligamentum  calcaneofibulare)  (Figs.  275  and  276),  the 
longest  of  the  three,  is  a  narrow,  rounded  cord  passing  from  the  apex,  of  the 


THE   TIIilOTARSAL  ARTICULATION 


345 


external  malleolus  downward  and  slightly  backward  to  the  peroneal  spine  on  the 
outer  surface  of  the  calcaneus.  It  is  covered  by  the  tendons  of  the  Peroneus 
longus  and  brevis. 


Synovial  Membrane. — The  synovial  membrane  (Fig.  272)  invests  the  inner  surface  of  the 
ligaments,  and  sends  a  duplicature  upward  between  the  lower  extremities  of  the  tibia  and  fibula 
for  a  short  distance. 

Relations. — The  tendons,  vessels,  and  nerves  in  connection  with  the  joint  are,  in  front,  from 
within  outward,  the  Tibialis  anticus.  Extensor  proprius  hallucis,  anterior  tibial  vessels  and 
nerve,  Extensor  longus  digitorum,  and  Peroneus  tertius;  behind,  from  within  outward,  the 
Tibialis  posticus.  Flexor  longus  digitorum,  posterior  tibial  vessels  and  nerve,  Flexor  longus 
hallucis;  and  in  the  groove  behind  the  external  malleolus,  the  tendons  of  the  Peroneus  longus 
and  brevis. 

The  arteries  supplying  the  joint  are  derived  from  the  malleolar  branches  of  the  anterior 
tibial  and  the  peroneal. 

The  nerves  are  derived  from  the  anterior  and  posterior  tibial. 


Inferior  tibiofibular  articulation. 


Fig,  27G. — Ankle-joint:  tarsal  and  tarsometatarsal  articulations.     External  ■ 


Right  side. 


Movements. — The  movements  of  the  joint  are  those  of  flexion  and  extension.  Flexion  con- 
sists in  the  apjiroximation  of  the  dorsum  of  the  foot  to  the  front  of  the  leg,  while  in  extension 
the  heel  is  drawn  up  and  the  toes  pointed  downward.  The  malleoli  tightly  embrace  the  astragalus 
in  all  positions  of  the  joint,  so  that  any  slight  degree  of  lateral  movement  which  may  exist  is  • 
simply  due  to  stretching  of  the  inferior  tibiofibular  ligaments  and  slight  bending  of  the  shaft  of 
the  filDula.  Of  the  ligaments,  the  internal  is  of  very  great  strength — so  much  so  that  it  usually 
resists  a  force  which  fractures  the  process  of  bone  to  which  it  is  attached.  Its  middle  portion, 
together  with  the  middle  fasciculus  of  the  external  lateral  ligament,  binds  the  bones  of  the  leg 
firmly  to  the  foot  and  resists  displacement  in  every  direction.  Its  anterior  and  posterior  fibres 
limit  extension  and  flexion  of  the  foot,  respectively,  and  the  anterior  fibres  also  limit  abduction. 
The  posterior  portion  of  the  external  lateral  ligament,  assists  the  middle  portion  in  resisting  the 
displacement  of  the  foot  backward,  and  deepens  the  cavity  for  the  reception  of  the  astragalus.  The 
anterior  fasciculus  is  a  security  against  the  displacement  of  the  foot  forward,  and  limits  extension 
of  the  joint.  The  movements  of  inversion  and  eversion  of  the  foot,  together  with  the  minute 
changes  in  form  by  which  it  is  applied  to  the  ground  or  takes  hold  of  an  object  in  climbing,  etc., 
are  mainly  effected  in  the  tarsal  joints,  the  one  which  enjoys  the  greatest  amount  of  motion 
being  that  between  the  astragalus  and  ("ilcanciis  behind  and  the  scaphoid  and  cuboid  in  front. 
This  is  often  called  the  transverse  or  mediotarsal  joint,  and  it  can,  with  the  subordinate  joints 
of  the  tarsus,  replace  the  ankle-joint  in  a  great  measure  when  the  latter  has  become  anky- 
losed. 


346 


THE  ARTICULATIONS,   OB  JOINTS 


Extension  of  the  tarsal  bones  upon  the  tibia  and  fibula  is  produced  by  theGast;  ),?neinius 
Soleus,  Plantaris,  Tibialis  posticus,  Peroneus  longus  and  brevis,  Flexor  longus  digitcium,  and 
Flexor  longus  hallucis;  flexion,  by  the  Tibialis  anticus,  Peroneus  tertius.  Extensor  longus 
dio-itorum,  and  Extensor  proprius  hallucis'  (Fig.  268);  inversion,  in  the  extended  position,  is 
produced  by  the  Tibialis  anticus  and  posticus;  and  eversion  by  the  Peronei. 

Surface  Form. — The  line  of  the  ankle-joint  may  be  indicated  by  a  transverse  line  drawn 
across  the  front  of  the  lower  part  of  the  leg,  about  half  an  inch  above  the  level  of  the  tip  of  the 
internal  malleolus. 

Applied  Anatomy. — Displacement  of  the  trochlear  surface  of  the  astragalus  from  the  tibio- 
fibular mortise  is  not  of  common  occurrence,  as  the  ankle-joint  is  a  very  strong  and  powerful 
articulation,  and  great  force  is  required  to  produce  dislocation.  Nevertheless,  dislocation  does 
occasionallv  occur,  both  in  antero-posterior  and  a  lateral  direction.  In  the  latter,  which  is  the 
most  common,  fracture  is  a  necessary  accompaniment  of  the  injury.  The  dislocation  in  these 
cases  is  somewhat  peculiar,  and  is  not  a  displacement  in  a  horizontally  lateral  direction,  such  as 
usually  occurs  in  lateral  dislocations  of  ginglymoid  joints,  but  the  astragalus  undergoes  a  partial 
rotation  around  an  antero-posterior  axis  drawn  through  its  own  centre,  so  that  the  superior 
surface,  instead  of  being  directed  upward,  is  inclined  more  or  less  inward  or  outward  accordinji 
to  the  variety  of  the  displacement. 


Fig.  277. — Section  of  the  right  foot  near  its  inner  border,  dividing  the  tibia,  astragalas,  calcaneus,  scaphoid 
internal  cuneiform,  and  first  metatarsal  bone,  and  the  first  phalanx  of  the  great  toe.     (After  Braune.) 

The  ankle-joint  is  more  frequently  sprained  than  any  other  joint  in  the  body,  and  this  may- 
lead  to  acute  synovitis.  In  these  cases,  when  the  synovial  sac  is  distended  with  fluid,  the  bulging 
appears  principally  in  the  front  of  the  joint,  beneath  the  anterior  tendons,  and  on  either  side, 
between  the  Tibialis  anticus  and  the  internal  lateral  ligament  on  the  inner  side,  and  between  the 
Peroneus  tertius  and  the  external  lateral  ligament  on  the  outer  side.  In  addition  to  this,  bulging 
frequently  occurs  posteriorly,  and  a  fluctuating  swelling  may  be  detected  on  either  side  of  the 
tendo  Achillis. 

Chronic  synovitis  may  result  from  frequent  sprains,  and  when  once  this  joint  has  been  sprained 
it  is  more  liable  to  a  recurrence  of  the  injury  than  it  was  before;  chronic  synovitis  ma}'  be  tuber- 
culous in  its  origin,  the  disease  usually  commencing  in  the  astragalus  and  extending  to  the  joint, 
though  it  may  commence  as  a  synovitis,  the  result  probably  of  some  slight  strain  in  a  tuber- 
culous subject. 

Excision  of  the  ankle-joint  is  not  often  performed  for  two'  reasons.  In  the  first  place,  disease 
of  the  articulation,  for  which  this  operation  is  indicated,  is  frequently  associated  with  disease  of 
the  tarsal  bones,  which  prevents  its  performance;  and,  secondly,  the  foot  after  excision  is  fre- 
quently of  very  little  use;  far  less,  in  fact,  than  after  a  Syme's  amputation,  which  is  often,  there- 
fore, a  preferable  operation  in  these  cases. 


'The  student  must  bear  m  mmd  that  the  Extensor  Irngus  digitorum  and  Extensor  proprius  hallucis  are 
■extm^ors  of  the  toes,  but  flexors  of  the  ankle,  and  that  tne  Flexor  longus  digitorum  and  Flexor  longus  hallucis 
Jlre  flexors  of  the  toes,  but  extensors  of  the  ankle. 


THE  ARTICULATIONS  OF  THE  TAliNVS  347 

V.  The  Articulations  of  the  Tarsus  (Articulationes  Intertarseae) 

(Figs.  275,  276). 

1.  The  Articulu^tion  of  the   Calcaneus  and  Astragalus   (Articulatio 

Talocalcanea)  (Fig.  275). 

The  articulations  between  the  calcaneus  and  astragalus  are  two  in  number — 
anterior  and  posterior.  They  are  arthrodial  joints.  The  bones  are  connected 
by  a  capsule  (capsula  articularis) ,  which  is  at  certain  points  accentuated  into 
definite  ligaments.     There  are  five  ligaments  in  this  articulation: 

External  Calcaneo-astragaloid.  Anterior  Calcaneo-astragaloid. 

Internal  Calcaneo-astragaloid.  Posterior  Calcaneo-astragaloid. 

Interosseous. 

The  external  calcaneo-astragaloid  ligament  {ligamenhtm  talocalcaneiim  laterale) 
(Fig.  276)  is  a  short,  strong,  fasciculus  passing  from  the  outer  surface  of  the 
astragalus,  immediately  beneath  its  external  malleolar  facet,  to  the  outer  surface 
of  the  calcaneus.  It  is  placed  in  front  of  the  middle  fasciculus  of  the  external 
lateral  ligament  of  the  ankle-joint,  with  the  fibres  of  which  it  is  parallel. 

The  internal  calcaneo-astragaloid  ligament  (lir/amentmn  talocalcaneum  mediale) 
is  a  band  of  fibres  connecting  the  internal  tubercle  of  the  back  of  the  astragalus 
with  the  back  of  the  sustentaculum  tali.  Its  fibres  blend  with  those  of  the  inferior 
calcaneoscaphoid  ligament. 

The  anterior  calcaneo-astragaloid  ligament  (ligamenium  talocalcaneum.  an- 
terius)  passes  from  the  front  and  outer  surface  of  the  neck  of  the  astragalus  to 
the  superior  surface  of  the  calcaneus. 

The  posterior  calcaneo-astragaloid  ligament  {licjamentum.  talocalcaneum  jms- 
terius)  connects  the  external  tubercle  of  the  astragalus  with  the  upper  and  inner 
part  of  the  calcaneus;  it  is  a  short  band,  the  fibres  of  which  radiate  from  their 
narrow  attachment  to  the  astragalus. 

The  interosseus  ligament  {ligamentuvi  talocalcaneuvi  interosseuvi)  (Fig.  279) 
forms  the  chief  bond  of  union  between  the  bones.  It  consists  of  numerous 
vertical  and  oblique  fibres  attached  by  one  extremity  to  the  groove  between 
the  articulating  facets  on  the  under  surface  of  the  astragalus;  by  the  other  to 
a  corresponding  depression  on  the  upper  surface  of  the  calcaneus.  It  is  very 
thick  and  strong,  being  at  least  an  inch  in  breadth  from  side  to  side,  and  serves 
to  unite  the  calcaneus  and  astragalus  solidly  together. 

Sjmovial  Membrane. — The  synovial  membranes  (Fig.  279)  are  two  in  number,  one  for  the 
posterior  calcaneo-astragaloid  articulation,  a  second  for  the  anterior  calcaneo-astragaloid  joint. 
The  latter  synovial  membrane  is  continued  forward  between  the  contiguous  surfaces  of  the 
astragalus  and  scaphoid  bones. 

Movements. — ^The  movements  permitted  between  the  astragalus  and  calcaneus  are  limited  to 
a  gliding  of  the  one  bone  on  the  other  in  a  du-ection  from  before  backward,  and  from  side  to  side. 

2.  The  Articulation  of  the  Calcaneus  with  the  Cuboid   (Articulatio 

Calcaneocuboidea)  (Fig.  275). 

In  this  joint  the  articular  capsule  {capsula  articularis)  is  strengthened  at  certain 
points  by  definite  ligaments. 
The  ligaments  connecting  the  calcaneus  with  the  cuboid  are  four  in  number: 

Superior  Calcaneocuboid.  rj,  ,    pi     ,      f  Long  Calcaneocuboid. 

The  Internal  Calcaneocuboid.  ^°      ^^       \  Short  Calcaneocuboid. 


348  THE  ARTICULATIONS,   OR  JOINTS 

The  superior  calcaneocuboid  ligament  (ligamentum  cahaneocuhoideuvi  dorsale) 
(Fig.  276)  is  a  broad  portion  of  the  capsule  which  passes  between  the  contiguous 
surfaces  of  the  calcaneus  and  cuboid  on  the  dorsal  surface  of  the  joint. 

The  internal  calcaneocuboid  or  the  interosseous  ligament  (fjars  calcaneo- 
cuboidea  ligamenti  bifurcati)  is  a  short  but  thick  and  strong  band  of  fibres  arising 
from  the  calcaneus,  in  the  deep  hollow  which  intervenes  between  it  and  the  astrag- 
alus, and  closely  blended,  at  its  origin,  with  the  superior  calcaneoscaphoid  liga- 
ment. These  two  ligaments  are  often  regarded  as  a  single  bifurcated  ligament 
(ligamentum  bifurcatiim).  The  internal  calcaneocuboid  ligament  is  inserted  into 
the  inner  side  of  the  cuboid  bone.  This  ligament  forms  one  of  the  chief  bonds 
of  union  between  the  first  and  second  rows  of  the  tarsus. 

The  long  calcaneocuboid  or  long  plantar  or  superficial  long  plantar  ligament 
(ligamentum  plantare  longum)  (Fig.  278),  the  more  superficial  of  the  two  plantar 
ligaments,  is  the  longest  of  all  the  ligaments  of  the  tarsus;  it  is  attached  to  the 
under  surface  of  the  calcaneus,  from  near  the  tuberosities,  as  far  forward  as  the 
anterior  tubercle;  its  fibres  pass  forward  to  be  attached  to  the  ridge  on  the  under 
surface  of  the  cuboid  bone,  the  more  superficial  fibres  being  continued  onward 
to  the  bases  of  the  second,  third,  and  fourth  metatarsal  bones.  This  ligament 
crosses  the  groove  on  the  under  surface  of  the  cuboid  bone,  converting  it  into  a 
canal  for  the  passage  of  the  tendon  of  the  Peroneus  longus. 

The  short  calcaneocuboid  or  short  plantar  ligament  (ligamentum  calcaneo- 
cuhoideum  lolantare)  (Fig.  278)  lies  nearer  the  bones  than  the  preceding,  from  which 
it  is  separated  by  a  little  areolar  tissue.  It  is  exceedingly  broad,  about  an  inch 
in  length,  and  extends  from  the  tubercle  and  the  depression  in  front  of  it,  on  the 
fore  part  of  the  under  surface  of  the  calcaneus,  to  the  inferior  surface  of  the  cuboid 
bone  behind  the  peroneal  groove. 

Synovial  Membrane  (Fig.  279). — The  synovial  membrane  in  this  joint  is  distinct.  It  Hnes 
the  inner  surface  of  the  ligaments. 

Movements. — The  movements  permitted  between  the  calcaneus  and  cuboid  are  limited  to  a 
slight  gliding  upon  each  other. 

3.  The  Ligaments  Connecting  the  Calcaneus  ant)  Scaphoid. 

Though  these  two  bones  do  not,  as  a  rule,  directly  articulate,  they  are  con- 
nected by  two  ligaments: 

Superior  or  External  Calcaneoscaphoid. 
Inferior  or  Internal  Calcaneoscaphoid. 

The  superior  or  external  calcaneoscaphoid  ligament  (pars  calcaneonavicuhris 
ligamenti  bifurcati)  arises,  as  already  mentioned,  with  the  internal  calcaneocuboid 
in  the  deep  hollow  between  the  astragalus  and  calcaneus,  constituting  a  part  of 
the  ligamentum  bifurcatum;  it  passes  forward  from  the  upper  surface  of  the  ante- 
rior extremity  of  ]the  calcaneus  to  the  outer  side  of  the  scaphoid  bone.  These 
two  ligaments  resemble  the  letter  Y,  being  blended  together  behind,  but  separated 
in  front. 

The  inferior  or  internal  calcaneoscaphoid  ligament  (ligamentum  calca7ieonavicu- 
lare  plantare)  (Fig.  278)  is  by  far  the  larger  and  stronger  of  the  two  ligaments  be- 
tween these  bones;  it  is  a  broad  and  thick  band  of  fibres,  which  passes  forward 
and  inw^ard  from  the  anterior  margin  of  the  sustentaculum  tali  of  the  calcaneus 
to  the  under  surface  of  the  scaphoid  bone.  This  ligament  not  only  serves  to 
connect  the  calcaneus  and  scaphoid,  but  supports  the  head  of  the  astragalus, 
forming  part  of  the  articular  cavity  in  which  it  is  received.     The  upper  surface 


THE  ARTICULATIONS  OF  THE  TARSUS 


349 


presents  a  fibrocartilaginous  facet,  lined  with  the  synovial  membrane  continued 
from  the  anterior  calcaneo-astragaloid  articulation,  upon  which  a  portion  of  the 
head  of  the  astragalus  rests.  Its  under  surface  is  in  contact  with  the  tendon  of  the 
Tibialis  posticus  muscle,  its  inner  border  is  blended  with  the  fore  part  of  the  deltoid 
ligament,  thus  completing  the  socket  for  the  head  of  the  astragalus. 

Applied  Anatomy. — ^The  inferior  calcaneoscaphoid  ligament,  by  supporting  the  head  of  the 
astragakis,  is  principally  concerned  in  maintaining  the  arch  of  the  foot,  and  wlien  it  yields  the 
liead  of  the  astragalus  is  pressed  downward,  inward,  and  forward  by  the  weight  of  the  body,  and 
the  foot  become  flattened,  expanded,  and   turned 
outward,  constituting  the  condition  known  as  fiat- 
foot.   This  ligament  contains  a  considerable  amount 
of  elastic  tissue,  so  as  to  give  elasticity  to  the  arch 
and  spring  to  the  foot;  hence,  it  is  sometimes  called 
the  "  spring"  ligament.     It  is  supported,  on  its  under 
surface,  by  the  tendon  of  the  Tibialis  posticus,  which 
spreads  out  at  its  insertion  into  a  number  of  fascic- 
uli which  are  attached  to   most  of  the  tarsal  and 
metatarsal  bones;  this  prevents  undue  stretching  of 
the  ligament,  and  is  a  protection  against  the  occur- 
rence of  flat-foot. 

4.  The  Articulation  of  the  Astragalus 

WITH  the  Scaphoid  Bone  (  Articulatio 

Talonavicularis)  (Fig.  275). 

This  is  an  arthrodial  joint,  the  rounded 
head  of  the  astragalus  being  received  into 
the  concavity  formed  by  the  posterior  sur- 
face of  the  scaphoid,  the  anterior  articulating 
surface  of  the  calcaneus,  and  the  upper  sur- 
face of  the  inferior  calcaneoscaphoid  liga- 
ment, which  fills  up  the  triangular  interval 
between  these  bones.  The  only  ligament  of 
this  joint  is  the  superior  astragaloscaphoid 
Fig.  273).  It  is  a  broad  band,  which  passes 
obliquely  forward  from  the  neck  of  the 
astragalus  to  the  superior  surface  of  the 
scaphoid  bone.  It  is  thin,  and  weak  in 
texture,  and  covered  by  the  Extensor  ten- 
dons. The  inferior  calcaneoscaphoid  liga- 
ment supplies  the  place  of  an  inferior 
astragaloscaphoid  ligament. 

Synovial  Membrane  (Fig.  279), — The  synovial  membrane  which  lines  the  joint  is  continued 
forward  frc^m  the  anterior  calcaneo-astragaloid  articulation. 

Movements. — This  articulation  permits  of  considerable  mobility,  but  its  feebleness  is  such 
as  to  allow  occasionally  of  dislocation  of  the  otlu'i-  bones  of  the  tarsus  from  the  astragalus. 

The  transverse  tarsal  or  mediotarsal  joint  {(irlirn/iiiln  tarsi  transversa  [Choparti])  (Figs.  275 
and  280)  is  formed  by  the  articulation  of  the  os  calcis  with  the  cuboid,  and  by  the  articulation 
of  the  astragalus  with  the  scaphoid.  The  movement  which  takes  place  in  this  joint  is  more 
extensive  than  that  in  the  other  tarsal  joints,  and  consists  of  a  sort  of  rotation  by  means  of 
which  the  sole, of  the  foot  may  be  slightly  flexed  and  extended  or  carried  inward  (inverted)  and 
outward  (everted). 

5.  The  Articulation  of  the  Scaphoid  with  the  Cuneiform  Bones 
(Articulatio  Cuneonavicularis)  (Fig.  275). 

The  scaphoid  is  connected  to  the  three  cuneiform  bones  by 
Dorsal  and  Plantar  Ligaments. 


350  THE  ARTICULATIONS,   OR  JOINTS 

The  dorsal  ligaments  Qigamenta  navicidaricuneiformia  dorsalia)  (Figs.  273  and 
275)  are  small,  longitudinal  bands  of  fibrous  tissue  arranged  as  three  bundles, 
one  to  each  of  the  cuneiform  bones.  That  bundle  of  fibres  which  connects  the 
scaphoid  with  the  internal  cuneiform  is  continued  around  the  inner  side  of  the 
articulation  to  be  continuous  with  the  plantar  ligament  which  connects  these 
two  bones. 

The  plantar  ligaments  Qigamenta  Jiavicularicimeiformia  plantaria)  (Fig.  278) 
have  a  similar  arrangement  to  those  on  the  dorsum.  They  are  strengthened  by 
processes  given  off  from  the  tendon  of  the  Tibialis  posticus. 

Synovial  Membrane  (Fig.  279). — The  synovial  membrane  of  these  joints  is  part  of  the 
great  tarsal  synovial  membrane. 

Movements. — The  movements  permitted  between  the  scaphoid  and  cuneiform  bones  are 
limited  to  a  slight  gliding  upon  each  other. 

6.  The   Articulation  of  the  Scaphoid  with  the  Cuboid   (Articulatio 

cuboideonavicularis) . 

The  scaphoid  bone  is  connected  with  the  cuboid  by 

Dorsal,  Plantar,  and  Interosseous  Ligaments. 

The  dorsal  ligament  {ligamentum  cuhoideonaviculare  dorsale)  (Fig.  276)  con- 
sists of  a  band  of  fibrous  tissue  which  passes  obliquely  forward  and  outward 
from  the  scaphoid  to  the  cuboid  bone. 

The  plantar  ligament  {Jigamentum  cuhoideonaviculare  plantare)  consists  of  a 
band  of  fibrous  tissue  which  passes  nearly  transversely  between  these  two  bones. 

The  interosseous  ligament  (Figs.  275  and  279)  consists  of  strong  transverse 
fibres  which  pass  between  the  rough  nonarticular  portions  of  the  lateral  sur- 
faces of  these  two  bones. 

Synovial  Membrane  (Fig.  279). — The  synovial  membrane  of  this  joint  is  part  of  the  great 
tarsal  synovial  membrane. 

Movements. — The  movements  permitted  between  the  scaphoid  and  cuboid  bones  are 
limited  to  a  slight  gliding  upon  each  other. 

7.  The  Articulations  of  the  Cuneiform  Bones  with  Each  Other  or 

THE  Intercuneiform  Articul.a.tions  (Fig.  275). 

These  bones  are  connected  by 

Dorsal,  Plantar,  and  Interosseous  Ligaments. 

The  dorsal  ligaments  {ligamenta  intercuneiformia  dorsalia)  consist  of  two  bands 
of  fibrous  tissue  which  pass  transversely,  one  connecting  the  internal  with  the 
middle  cuneiform,  and  the  other  connecting  the  middle  with  the  external  cunei- 
form. 

The  plantar  ligaments  (Ugaynenta  intercuneiformia  plantaria)  have  a  similar 
arrangement  to  those  on  the  dorsum.  They  are  strengthened  by  the  processes 
given  off  from  the  tendon  of  the  Tibialis  posticus. 

The  interosseous  ligaments  {ligamenta  intercuneiformia  interossea)  consist  of 
strong  transverse  fibres  which  pass  between  the  rough  nonarticular  portions  of 
the  lateral  surfaces  of  the  first  and  second  and  the  second  and  third  cuneiform 
bones.  The  outer  portion  of  the  third  cunieiform  is  attached  to  the  cuboid  h^ 
the  ligamentum  cuneocuboideum  interosseum  (page  351). 


THE  TARSOMETATARSAL  ARTICULATIONS  351 

Synovial  Membrane  (Fig.  279). — The  synovial  membrane  of  these  joints  is  part  of  the  great 
tarsal  synovial  membrane. 

Movements. — The  movements  permitted  between  the  cuneiform  bones  are  limited  to  a  slight 
gliding  upon  each  other. 

8.  The  Articulation  of  the  External  Cuneiform  Bone  with  the 
Cuboid   (Fig.  275). 

These  bones  are  connected  by 

Dorsal,  Plantar,  and  Interosseous  Ligaments. 

The  dorsal  ligament  (llgamentum  cuneocuboideum  dorsale)  (Fig.  276)  consists 
of  a  band  of  fibrous  tissue  which  passes  transversely  between  these  two  bones. 

The  plantar  ligament  {ligamentum  cuneocuboideum  plantare)  has  a  similar 
arrangement.  It  is  strengthened  by  a  process  given  ofp  from  the  tendon  of  the 
Tibialis  posticus. 

The  interosseous  ligament  (ligamentum  cuneocuboideum  interosseum)  (Fig. 
275)  consists  of  strong  transverse  fibres  which  pass  between  the  rough  non- 
articular  portions  of  the  lateral  surfaces  of  the  adjacent  sides  of  these  two  bones. 

Synovial  Membrane  (Fig.  279). — The  synovial  membrane  of  this  joint  is  part  of  the  great 
tarsal  synovial  membrane. 

Movements. — The  movements  permitted  between  the  external  cuneiform  and  cuboid  are 
limited  to  a  slight  gliding  upon  each  other. 

Nerve  Supply. — All  the  joints  of  the  tarsus  are  supplied  by  the  anterior  tibial  nerve. 

Applied  Anatomy. — In  spite  of  the  great  strength  of  the  ligaments  which  hold  the  tarsal 
bones  together,  dislocation  at  some  of  the  tarsal  joints  occasionally  occurs;  these  bones,  on  account 
of  their  spongy  character,  are,  as  the  result  of  direct  violence,  more  frequently  broken  than  dis- 
located. When  dislocation  does  occur,  it  is  most  commonly  in  connection  with  the  astragalus; 
for  not  only  may  this. bone  be  dislocated  from  the  tibia  and  fibula  at  the  ankle-joint,  but  the 
other  bones  may  be  dislocated  from  it,  the  trochlear  surface  of  the  bone  remaining  in  situ  in  the 
tibiofibular  mortise.  This  constitutes  what  is  known  as  the  suhastragaloid  dislocation.  Or, 
again,  the  astragalus  may  be  dislocated  from  all  its  connections — from  the  tibia  and  fibula 
above,  the  os  calcis  below,  and  the  scaphoid  in  front — and  may  even  undergo  a  rotation,  either 
on  a  vertical  or  horizontal  axis.  In  the  former  case  the  long  axis  of  the  bone  becoming  directed 
across  the  joint,  so  that  the  head  faces  the  articular  surface  on  one  or  other  malleolus;  or,  in  the 
latter,  the  lateral  surfaces  becoming  directed  upward  and  downward,  so  that  the  trochlear  sur- 
face faces  to  one  or  the  other  side.  Finally,  dislocation  may  occur  at  the  mediotarsal  joint,  the 
anterior  tarsal  bones  being  luxated  from  the  astragalus  and  calcaneum.  The  other  tarsal  bones 
are  also,  occasionally,  though  rarely,  dislocated  from  their  connections. 

Pes  planus  or  flat-foot  is  a  condition  in  which  there  is  abduction,  eversion,  and  loss  of  both 
the  longitudinal  and  the  transverse  arch.  The  head  of  the  astragalus  passes  downward  and 
inward;  the  anterior  portion  of  the  foot  is  turned  outward  and  the  inner  side  of  the  foot  is 
lengthened  and  broadened.  Deformity  is  increased  when  standing.  In  severe  cases  the 
patient  walks  on  the  inner  side  of  the  foot.  The  condition  is  due  to  weakness  of  the  Tibialis 
posticus  muscle,  with  a  consequent  yielding  of  the  tarsal  ligaments.  Abduction  is  permitted 
by  yielding  of  the  internal  lateral  and  calcaneo-astragaloid  ligaments.  Yielding  of  the  inferior 
calcaneo-scaphoid  ligament  permits  the  head  of  the  astragalus  to  pass  downward  and  forward, 
and  the  entire  arch  falls. 

VI.  The  Tarsometatarsal  Articulations  (Articulationes  Tarsometatarseae) 

(Figs.  275,  276). 

These  are  arthrodial  joints.  The  bones  entering  into  their  formation  are  four 
tarsal  bones — viz.,  the  internal,  middle,  and  external  cuneiform  and  the  cuboid — 
which  articulate  with  the  metatarsal  bones  of  the  fi^'e  toes.  The  metatarsal 
bone  of  the  great  toe  articulates  with  the  internal  cuneiform;  that  of  the  second 
is  deeply  wedged  in  between  the  internal  and  external  cuneiform,  rests  against 
the  middle  cuneiform,  and  is  the  most  strongh'  articulated  of  all  the  metatarsal 


352  THE  ARTICULATIONS,   OB  JOINTS 

bones;  the  third  metatarsal  articulates  with  the  extremity  of  the  external  cunei- 
form; the  fourth,  with  the  cuboid  and  external  cuneiform;  and  the  fifth,  with 
the  cuboid.  The  articular  surfaces  are  covered  by  hyaline  cartilage,  lined  with 
syno^'ial  membrane,  and  interconnected  by  capsules  and  by  the  following  liga- 
ments : 

Dorsal.  Plantar.  Interosseous. 

The  dorsal  ligaments  (ligamenta.  tarsometatarsea  dorsalia)  consist  of  strong, 
flat,  fibrous  bands,  which  connect  the  tarsal  with  the  metatarsal  bones.  The 
first  metatarsal  is  connected  to  the  internal  cuneiform  by  a  single  broad,  thin, 
fibrous  band;  the  second  has  three  dorsal  ligaments,  one  from  each  cuneiform 
bone;  the  third  has  one  from  the  external  cuneiform;  the  fourth  has  two,  one 
from  the  external  cuneiform  and  one  from  the  cuboid;  and  the  fifth,  one  from 
the  cuboid. 

The  plantar  ligaments  {Ugavienta  tarsometatarsea  flantaria)  consist  of  longi- 
tudinal and  oblique  fibrous  laands  connecting  the  tarsal  and  metatarsal  bones, 
but  disposed  with  less  regularity  than  on  the  dorsal  surface.  Those  for  the  first 
and  second  metatarsal  are  the  most  strongly  marked;  the  second  and  third 
metatarsal  receive  strong  fibrous  bands  which  pass  obliquely  across  from  the 
internal  cuneiform;  the  plantar  ligaments  of  the  fourth  and  fifth  metatarsal 
consist  of  a  few  scanty  fibres  derived  from  the  cuboid. 

The  interosseous  ligaments  {ligamenta  cuneometatarsea  interossea)  are  three 
in  number— internal,  middle,  and  external.  The  internal  one  is  the  strongest 
of  the  three,  and  passes  from  the  outer  extremity  of  the  internal  cuneiform  to 
the  adjacent  angle  of  the  second  metatarsal.  The  middle  one,  less  strong  than 
the  preceding,  connects  the  external  cuneiform  with  the  adjacent  angle  of  the 
second  metatarsal.  The  external  interosseous  ligament  connects  the  outer  angle 
of  the  external  cuneiform  with  the  adjacent  side  of  the  third  metatarsal. 

Synovial  Membrane  (Fig.  279). — The  synovial  membrane  between  the  internal  cuneiform 
bone  and  the  first  metatarsal  bone  is  a  distinct  sac.  The  synovial  membrane  between  the  middle 
and  external  cuneiform  behind,  and  the  second  and  third  metatarsal  bones  in  front,  is  part  of  the 
great  tarsal  synovial  membrane.  Two  prolongations  are  sent  forward  from  it — one  between 
the  adjacent  sides  of  the  second  and  third  metatarsal  bones,  and  one  between  the  third  and 
fourth  metatarsal  bones.  The  synovial  membrane  between  the  cuboid  and  the  fourth  and 
fifth  metatarsal  bones  is  a  distinct  sac.  From  it  a  prolongation  is  sent  forward  between  the  fourth 
and  fifth  metatarsal  bones. 

Movements. — The  movements  permitted  between  the  tarsal  and  metatarsal  bones  are 
limited  to  a  slight  gliding  upon  each  other. 

VII.  The  Articulations  of  the  Metatarsal  Bones  with  Each  Other 

(Articulationes  Intermetatarseae)  (Figs.  275,  276). 

The  base  of  the  first  metatarsal  bone  is  not  connected  with  the  second  meta- 
tarsal bone  by  any  ligaments;  in  this  respect  it  resembles  the  thumb. 

The  bases  of  the  four  outer  metatarsal  bones  are  connected  by  dorsal,  plantar, 
and  interosseous  ligaments. 

The  dorsal  ligaments  (ligamenta  hasium  [oss.  mefatars.]  dorsalia)  consist  of 
bands  of  fibrous  tissue  which  pass  transversely  between  the  adjacent  metatarsal 
bones. 

The  plantar  ligaments  (ligamenta  basium  [oss.  metatars.]  plantaria)  have  a 
similar  arrangement  to  those  on  the  dorsum. 

The  interosseous  ligaments  (ligamenta  basium  [oss.  metatars.]  interossea)  con- 
sist of  strong  transverse  fibres  which  pass  between  the  rough  nonarticular  portions 
of  the  lateral  surfaces. 


THE  METATARSOPHALANGEAL  ABTLCTJLATIONS 


353 


Synovial  Membrane. — The  synovial  membrane  between  the  second  and  third  and  the  third 
and  fourth  metatarsal  bones  is  part  of  the  great  tarsal  synovial  membrane.  The  synovial  mem- 
brane between  the  fourth  and  fifth  metatarsal  bones  is  a  prolongation  of  the  synovial  membrane 
of  the  cubometatarsal  joint  (Fig.  279). 

Movements.-  -The  movement  permitted  in  the  tarsal  ends  of  the  metatarsal  bones  is  limited 
to  a  sliijht  i/liiliini  of  the  articular  surfaces  upon  one  another. 

The  Synovial  Membranes  in  the  Tarsal  and  Metatarsal  Joints. — The  synovial  mem- 
branes (Fig.  279)  found  in  the  articulations  of  the  tarsus  and  metatarsus  are  six  in  number — 
one  for  the  posterior  calcaneo-astragaloid  articulation;  a  second  for  the  anterior  calcaneo-astrag- 
aloid  and  astragaloscaphoid  articulations;  a  third  for  the  calcaneocuboid  articulation;  and  a 
fourth  for  the  articulations  of  the  scaphoid  with  the  three  cuneiform,  the  three  cuneiform 
with  each  other,  the  external  cuneiform  with  the  cuboid,  and  the  middle  and  external  cunei- 
form with  the  bases  of  the  second  and  third  metatarsal  bones,  and  the  lateral  surfaces  of  the 
Becond,  third,  and  fourth  metatarsal  bones  with  each  other.  The  Jiffh  synovial  membrane  is 
found  in  the  articulation  of  the  internal  cuneiform  with  the  metatarsal  bone  of  the  great  toe;  and 
tiere  is  a  sixth  for  the  articulation  of  the  cuboid  with  the  fourth  and  f5fth  metatarsal  bones.  A 
small  synovial  membrane  is  sometimes  found  between  the  contiguous  surfaces  of  the  scaphoid 
and  cuboid  bones. 

Nerve  Supply. — The  nerves  supplying  the  tarsometatarsal  joints  are  derived  from  the 
anterior  tibial. 


Fig.  279. — Oblique  section  of  the  articuhtions  of  tarsus  and  metatarsus      Showing  the  six  s\  no\  lal  membranes. 


The  digital  extremities  .'f  all  the  metatarsal  bones  are  connected  by  the  transverse 
metatarsal  ligament. 

The  transverse  metatarsal  ligament  is  a  narrow  fibrous  band  which  passes 
transversely  across  the  anterior  extremities  of  all  the  metatarsal  bones,  con- 
necting them.  It  is  blended  aiiieriorhj  with  the  plantar  (glenoid)  ligament  of 
each  metatarsophalangeal  articulation.  To  its  posterior  border  is  connected 
the  fascia  covering  the  Interossei  muscles.  Its  inferior  surface  is  concave  where 
the  Flexor  tendons  pass  over  it.  Above  it  the  tendons  of  the  Interossei  muscles 
pass  to  their  insertion.  It  differs  from  the  transverse  metacarpal  ligament  in 
that  it  connects  the  metatarsal  bone  of  the  great  toe  with  the  rest  of  the  meta- 
tarsal bones. 


Vin.  The  Metatarsophalangeal  Articulations  (Articulationes  Metatarso- 
phalangeae) . 

The  metatarsophalangeal  articulations  are  of  the  condyloid  variety,  formed  by 
the  reception  of  the  rounded  heads  of  the  metatarsal  bones  into  shallow  cavities 
in  the  extremities  of  the  first  phalanges.  Each  joint  has  a  capsule  and  certain 
other  ligaments.     These  ligaments  are : 


Plantar. 


Two  Lateral. 


354  THE  ARTICULATIONS,   OB  JOINTS 

The  plantar  ligaments  (ligamenta  accessoria  flantaria)  are  thick,  dense,  fibrous 
structures.  Eacii  is  placed  on  the  plantar  surface  of  the  joint  in  the  interval 
between  the  lateral  ligaments,  to  which  it  is  connected.  The  plantar  ligaments 
are  loosely  united  to  the  metatarsal  bones,  but  very  firmly  to  the  bases  of  the 
first  phalanges.  The  plantar  surface  of  each  is  intimately  blended  with  the 
transverse  metatarsal  ligament,  and,  except  in  the  great  toe,  presents  a  groove 
for  the  passage  of  the  Flexor  tendons,  the  sheath  surrounding  which  is  connected 
to  each  side  of  the  groove.  The  plantar  ligament  of  the  great  toe  contains  two 
large  sesamoid  bones.  By  their  deep  surface  they  form  part  of  the  articular  sur- 
face for  the  head  of  the  metatarsal  bone,  and  are  lined  with  synovial  membrane. 

The  lateral  ligaments  (ligamenta  collateralia)  are  strong,  rounded  cords,  placed 
one  on  each  side  of  the  joint,  each  being  attached,  by  one  extremity,  to  the  posterior 
tubercle  on  the  side  of  the  head  of  the  metatarsal  bone;  and,  by  the  other,  to 
the  contiguous  extremity  of  the  phalanx. 

The  place  of  a  dorsal  ligament  is  supplied  by  the  Extensor  tendon  over  the 
back  of  the  joint. 

Movements. — The  movements  permitted  in  the  metatarsophalangeal  articulations  are  flexion, 
•  extension,  abduction,  and  adduction. 

IX.  The  Articulations  of  the  Phalanges  (Articulationes  Digitorum  Pedis). 

The  articulations  of  the  phalanges  are  ginglymoid  joints.  Besides  the  cap- 
.  sular  the  ligaments  are : 

Plantar.  Two  Lateral  Qigamenta  collateralia). 

The  arrangement  of  these  ligaments  is  similar  to  those  in  the  metatarsophalan- 
geal articulations;  the  Extensor  tendon  supplies  the  place  of  a  dorsal  ligament. 

Movements. — The  only  movements  permitted  in  the  phalangeal  joints  are  flexion  and  exten- 
-sion;  these  movements  are  more  extensive  between  the  first  and  second  phalanges  than  between 
the  second  and  third.  The  movement  of  flexion  is  very  considerable,  but  extension  is  limited 
bv  the  pkntar  and  lateral  ligaments. 

Surface  Form. — The  principal  joints  which  it  is  necessary  to  distinguish,  with  regard  to  the 
surgery  of  the  foot,  are  the  intertarsal  and  the  tarsometatarsal.  The  joint  between  the  astragalus 
and  the  scaphoid  is  best  found  by  means  of  the  tubercle  of  the  scaphoid,  for  the  line  of  the  joint 
is  immediately  behind  this  process.  If  the  foot  is  grasped  and  forcibly  extended,  a  rounded 
prominence,  the  head  of  the  astragalus,  will  appear  on  the  inner  side  of  the  dorsum  in  front 
of  the  ankle-joint,  and  if  a  knife  is  carried  downward,  just  in  front  of  this  prominence  and  behind 
the  line  of  the  scaphoid  tubercle,  it  will  enter  the  astragaloscaphoid  joint.  The  calcaneocuboid 
joint  is  situated  midway  between  the  external  malleolus  and  the  prominent  end  of  the  fifth 
metatarsal  bone.  The  plane  of  the  joint  is  in  the  same  line  as  that  of  the  astragaloscaphoid. 
The  position  of  the  joint  between  the  fifth  metatarsal  bone  and  the  cuboid  is  easily  found  by 
the  projection  of  the  fifth  metatarsal  bone,  which  is  the  guide  to  it.  The  direction  of  the  line 
of  the  joint  is  very  oblique,  so  that,  if  continued  onward,  it  would  pass  through  the  head  of  the 
first  metatarsal  bone.  The  joint  between  the  fourth  metatarsal  bone  and  the  cuboid  and  external 
cuneiform  is  the  direct  continuation  inward  of  the  previous  joint,  but  its  plane  is  less  oblique;  it 
would  be  represented  by  a  line  drawn  from  the  outer  side  of  the  articulation  to  the  middle  of  the 
first  metatarsal  bone.  The  plane  of  the  joint  between  the  third  metatarsal  bone  and  the  external 
cuneiform  is  almost  transverse.  It  would  be  represented  by  a  line  drawn  from  the  outer  side 
of  the  joint  to  the  base  of  the  first  metatarsal  bone.  The  tarsometatarsal  articulation  of  the  great 
toe  corresponds  to  a  groove  which  can  be  felt  by  making  firm  pressure  on  the  inner  side  of  the 
foot  one  inch  in  front  of  the  tubercle  on  the  scaphoid  bone;  and  the  joint  between  the  second 
metatarsal  bone  and  the  middle  cuneiform  is  to  be  found  on  the  dorsum  of  the  foot,  half 
an  inch  behind  the  level  of  the  tarsometatarsal  joint  of  the  great  toe.  The  line  of  the  joints 
between  the  metatarsal  bones  and  the  first  phalanges  is  about  an  inch  behind  the  webs  of  the 
'  corresponding  toes. 

Applied  Anatomy.— This  is  considered  on  p.  256. 


THE  MUSCLES  AND  FASCM/ 


MYOLOGY  is  the  branch  of  anatomy  which  treats  of  the  muscles.  The 
muscles  are  formed  of  bundles  of  reddish  fibres,  endowed  notably  with  the 
property  of  contractility  in  the  direction  of  the  long  axes  of  the  muscle  cells. 
Contractions  of  muscle  fibres  induce  motion.  The  two  principal  kinds  of  muscle 
tissue  found  in  the  body  are  the  more  highly  differentiated,  or  voluntary,  and 
the  less  highly  differentiated,  or  involuntary.  The  former  of  these,  from  the  char- 
acteristic appearances  which  its  fibres  exhibit  under  the  microscope,  is  known  as 
striated,  or  striped  muscle.  As  most  striped  muscles  are  capable  of  being  put  into 
action  and  controlled  by  the  will,  they  are  generally  called  "voluntary"  muscles. 
The  fibres  of  involuntary  muscle  do  not  present  any  cross-striped  appearance,  and 
■are  not  under  the  control  of  the  will;  such  muscles  are  known  as  unstriated,  un- 
striped  or  vegetative.  The  muscle  fibres  of  the  heart  differ  in  certain  particulars 
from  both  these  groups,  and  they  are  therefore  separately  described  as  cardiac 
muscle  fibres. 

Thus,  it  will  be  seen  that  there  are  three  varieties  of  muscle  tissue:  (1)  Trans- 
versely striated  fibres,  which  are  for  the  most  part  voluntary  and  under  the  control 
■of  the  will.  This  variety  of  muscle  is  also  called  skeletal.  (2)  Transversely 
striated  muscle  fibres,  which  are  not  under  the  control  of  the  will — i.  e.,  the 
cardiac  muscles.  The  cardiac  muscle  occupies  a  mid-position  in  the  scale  be- 
tween the  cells  of  involuntary  and  the  striated  fibres  of  voluntary  muscle.  (3) 
Plain  or  unstriped  muscle  fibres,  which  are  involuntary,  and  are  controlled  by 
.a  different  part  of  the  nerve  system  from  that  which  controls  the  activity  of  the 
voluntary  muscles.  Such  are  the  muscular  walls  of  the  stomach  and  intestine, 
of  the  uterus  and  bladder,  of  the  bloodvessels,  of  certain  canals  and  ducts,  etc. 
The  statement  that  striated  muscle  is  always  voluntary,  and  that  nonstriated 
muscle  is  always  involuntary,  cannot  be  accepted  as  invariably  and  inevitably 
true.  There  are  animals  in  which  some  voluntary  muscle  is  free  from  distinct 
striation,  while  the  Diaphragm,  made  up  of  striated  muscle  fibres,  is  not  wholly 
under  the  control  of  the  will. 

Although  the  voluntary  striated  muscle  tissue  alone  is  concerned  in  the  skeletal 
musculature,  all  three  varieties  of  muscle  tissue  will  be  described  here.  The 
skeletal  muscles  act  upon  the  bones,  and  thus  produce  movement.  The  primitive 
contractile  elements  of  a  muscle  are  the  fibres.  Fibres  are  gathered  into  groups 
known  as  primary  bundles  or  fasciculi,  and  the  fasciculi  are  aggregated  into  masses 
called  secondary  bundles.  In  coarse  muscles  the  fasciculi  are  of  considerable 
size;  in  fine  muscles  they  are  of  trivial  size.  Fasciculi  may  be  long  or  short, 
.and  the  length  does  not  depend  on  the  length  of  the  muscle. 

Structure  of  Striated  Muscle. — Each  muscle  is  surrounded  by  a  sheath  of  fibrous  tissue 
called  the  epimysium;  this  sends  in  septa  which  surround  the  secondary  bundles;  these  in 
turn  send  in  the  perimysium  which  surrounds  each  muscle  fasciculus.     The  fibres  of  each 

*  The  Muscles  and  Fascite  are  described  conjointly,  in  order  that  the  student  may  consider  the  arrangement 
of  the  latter  in  his  dissection  of  the  former.  It  is  rare  for  the  student  of  anatomy  in  this  coiintry  to  dissect 
the  fasciiE  separately:  and  it  is  for  this  reason,  as  well  as  from  the  close  connection  that  exists  between  the 
muscles  and  their  investing  sheaths,  that  they  are  considered  together.  Some  general  observations  are  first 
made  on  the  histology  and  anatomy  of  the  nauscles  and  fasciie,  the  special  description  being  given  in  connection 
with  the  different  regions. 

(355) 


356 


THE  MUSCLES  AND  FASCIJE 


fasciculus  are  separated  by  a  delicate  meshwork  of  fibroelastic  tissue,  the  endcmysium,  which 
supports  the  small  vessels  and  nerves. 

Structure  of  the  Muscle  Fibre. — A  muscle  fibre  is  a  long  cylindrical  cell  varying  from 
less  than  one  to  fi\'e  inches  (2.5  to  12.5  cm.)  in  length.  It  is  surrounded  by  a  delicate  sheath 
called  the  sarcolemma,  within  which  lie  the  nuclei  and  muscle  substance.  The  muscle  sub- 
stance consists  of  two  elements — the  fibrillae,  or  contractile  portion  of  the  fibre,  and  the  sarco- 
plasm,  or  undifferentiated  portion.  The  fibrillae  are  arranged  parallel  to  one  another  and  are 
separated  by  the  sarcoplasm;  and  as  the  former  respond  well  to  the  protoplasmic  stains,  and  the 
latter  practically  not  at  all,  the  alternation  of  such  stained  and  unstained  stripes  produces  the 


\tropiC  Mjcr— ijHiiH  If  r(<ittJ(»*!/ 

fi  i"  fiiHiiivi!.;.' 


Primitive  jibril 


\Mxmi\i 


se  line  of  Briicke 


Fig.  280. — Two  human  muscle  fibres. 
X  .350.  In  the  one  the  bundle  of  fibrilte 
(6)  is  torn,  and  the  sarcolemma  (a)  is 
seen  as  an  empty  tube. 


;  (fiij  xitiuiiiii'X 
'.'tiiiifuiiiiiiitji; 

i  ii\  i  i  1  a  Hi  f /'lifiij 

;  (iiiiiiijj'^f'jtJj.'ifJ     y 

jMfiJtntTij'ifiin]'! — 

'  .(iiJtini  iiiijiji'i 
ituTiuTiJsii'}}'! 
fiisiKriHi''!!!?     r^        ,  , 

lljliiill i f HilljL-^'""'""^^  membrane 

^iliiiisjinjiyi'- ''  "^ 


Fig.  281, — A  bit  of  a  cross-striated  muscle  of  a  frog,  show- 
ing the  nucleus  and  the  ease  of  its  division  both  transversely 
and  longitudinally.      X  650.     (Szymonowicz  and  MacCallum.) 


longitudinal  striaiions  so  typical  of  the  appearance  of  a  longitudinal  section  of  muscle  under 
the  microscope.  •  In  a  cross-section  the  fibrillae  are  arranged  more  or  less  in  groups  called 
Cohnheim's  fields. 

The  fibrillar,  or  sarcostyle,  are  not  unbroken  threads,  but  all  are  interrupted  at  intervals  into 
short  segments  called  sarcous  elements.  As  a  result  of  this  segmentation  a  fibre  exhibits  alter- 
nating transverse  dark  and  light  bands  (cross-striations).  If  a  muscle  fibre  be  examined  under 
high  magnification,  a  light  line  is  seen  traversing  each 
dark  band  (anisotropic) ;  this  is  the  membrane  of  Hensen. 
The  light  band  (isotropic)  is  traversed  by  a  dark  line, 
Dobie's  line,  or  the  memjorane  of  Krause,  that  divides 
the  band  into  two  parts,  the  lateral  disks.  A  sarcomere 
is  that  part  of  a  fibril  between  two  membranes  of 
Krause,  and  consists  of  a  sarcous  element  and  a  lateral 
disk  at  each  end  of  the  sarcous  element. 

The  nuclei  are  numerous  and  are  situated  peripherally, 
i.  e.,  just  beneath  the  sarcolemma.  They  are  narrow 
and  elongated  in  form,  and  respond  readily  to  the  usual 
stains.  Branched  fibres  are  occasionally  seen  in  the 
tongue.  There  are  two  kinds  of  fibres,  red  and  wltite; 
the  former  are  rich  in  sarcoplasm  and  the  nuclei  are 
deeply  placed  and  are  intermediate  in  development  be- 
tween myoplasm  and  the  white  fibres.  The  w/iife  fibres  are  poor  in  sarcoplasm  and  predominate 
in  human  muscles.     The  Trapezius  muscle  contains  both  red  and  white  fibres. 

The  arteries  of  voluntary  muscles  are  numerous.     They  pierce  the  epimysium,  pass  along 
the  septa  from  the  epimysium,   and   divide   into   small   branches,  which  enter  between  the 


Fig.  2S2. — Section  of  a  muscle  fibre, 
showing  areas  of  Cohnheim.  Three  nuclei 
are  seen   lying  close   to   the   sarcolemma. 

(Schafer.) 


FOBBI  AND  ATTACHMENT  OF  MUSCLES 


357 


m 


fasciculi.  These  small  branches  pass  into  capillaries  which  run  parallel  to  the  fibres.  At 
intervals  dilatable  connections  {ampullce)  are  established  between  the  capillaries,  and  it  is  into 
these  that  during  contractions  of  the  muscle  the  blood  passes  to  relieve  the  tension  in  the  longi- 
tudinal capillaries. 

Veins  accompany  the  arteries,  and  even  the  smaller  ones  possess  valves  (Spalteholz) . 

The  nerve  endings  in  voluntary  nuiscle  comprise  both  motor  and  sen.sor  varieties.  A  motor 
nerve  iiirrccs  the  ciiiinysiuiri  and  breaks  up  into  numerous  branches  to  form  an  interfascicular 
plexus  in  I  lie  pciimysiuni.  From  this  ]ilexus  nerve  fibrils  arise,  and  usually  one  nerve  fibril  passes 
to  each  muscle  fibre.  The  nerve  fibril  pierces  the  sarcolemma,  the  neurilemma,  and  myelinic 
sheath  disappearing  before  the  nerve  fibril  reaches  the  muscle  fibre,  and  probably  being  lost 
by  fusing  with  the  sarcolemma.     The  naked  axone  beneath 

the  sarcolemma  of  a  fibre   continues  to  the  surface  of   the  mms:  ,  r,  - ,    ■  --,     .,_    ,.„„^ 

muscle  fibre  and  undergoes  arborization  to  form  an  end  organ. 
Ai-ound  the  end  organ  is  a  quantity  of  grantilar  saix  Jiilasm, 
which,  with  the  nerve  and  organ,  constitutes  a  sole  plate. 
A  sensor  nerve  takes  origin  from  a  muscle  spindle,  \\  Inch 
consists  of  a.  bundle  of  encapsulated  muscle  fibres  about  sensor 
nerve  twigs. 

Involuntary  striated  or  cardiac  muscle  is  found  in  the 
heart  and  is  not  under  the  control  of  the  will.  Each  fibre  is 
a  short  cylinder  varying  from  1 00 ,«  to  200  /i  in  length  and 
of  about  25  /j.  to  40  fi  in  diameter.  The  striations  are  both 
longitudinal  and  transverse,  but  the  latter  are  usually  not 
distinct.  Each  fibre  is  surrounded  by  a  delicate  membrane. 
The  cells  give  off  narrow  processes  of  branches  which  con- 
nect with  each  other,  thus  forming  "a  reticulum  of  muscle 
fibres.  The  meshes  of  this  reticulum  are  occupied  by  areolar 
tissue  in  which  the  vascular  and  nerve  supply  of  the  tissue 
is  situated." 

Usually  a  single,  large,  oval  nucleus  occupies  the  centre  of 
the  cell  and  is  surrounded  by  an  area  of  clear  and  undiffer- 
entiated protoplasm  in  which  fibrilloe  do  not  exist.  Pigment 
granules  are  seen  in  this  undifferentiated  protoplasm. 

Purkinje  fibres  are  peculiar  muscle  fibres  found  in  the 
heart,  and  will  be  described  with  that  organ. 

The  nerves  are  both  sympathetic  and  cerebrospinal. 

Involimtaiy  non-striated  or  smooth  muscle  is  not  under  the  control  of  the  will.  It  is  found 
in  the  alimentary  tract  from  the  middle  third  of  the  oesophagus  down,  in  gland  ducts,  trachea, 
bronchi,  bronchial  tubes,  in  the  urinogenital  system,  bloodvessels  and  lymph  vessels,  etc.  It  is 
found  arranged  in  layers  that  encircle  the  organs  longitudinally,  transversely,  and  sometimes 
in  an  interlaced  manner. 


-'J 


Fig.  283. ■ — Anastomosing  muscle 
fibres  of  the  heart,  seen  in  a  longitu- 
dinal section.  On  the  right  the  limits 
of  the  separate  cells  with  their  nuclei 
are  e.\hibited  somewhat  diagrammat- 
ically. 


Intercellular 
bridges' 


Fig.  284. — Longitudinal  section  in  the  smooth  muscle  of  a  dog's  large  intestine,  to  show  especially  intercellular 
bridges.     X  530.     (Szymonowicz  and  IMacCallum.) 

Each  fibre  is  short  and  spindle-shaped,  varying  from  25  /i  to  200  fi  in  length  and  from  5  /j. 
to  7  /i  in  diameter.  In  the  gravid  uterus  they  are  much  larger  in  both  dimensions.  Occa- 
sionally, longitudinal  striations  are  seen,  and  then  the  fibrillse  so  formed  are  coarse  and  periph- 
erally located.  Each  fibre  contains  a  single  slender  nucleus  which  is  centrally  located.  Branched 
fibres  are  occasionally  seen  in  the  aorta  and  in  the  bladder. 

The  bloodvessels  form  a  raeshwork  between  the  fibres. 

The  nerves  are  from  the  sympathetic  system,  though  Kuntz  has  recently  shown  that  in  some 
organs,  at  least,  the  nerves  are  originally  derived  from  the  vagus. 


Form  and  Attachment  of  Muscles. — The  muscles  are  connected  with  the  bones, 
cartilages,   liaaments,  and  skin,  either  directly  or  through  the  intervention  of 


358  THE  MUSCLES  AND  FASCIA 

fibrous  structures  called  tendons  or  aponeuroses.  Where  a  muscle  is  attached 
to  bone  or  cartilage,  the  fibres  terminate  in  blunt  extremities  upon  the  periosteum 
or  perichondrium,  and  do  not  come  into  direct  relation  with  the  osseous  or  carti- 
laginous tissue.  Where  muscles  are  connected  with  the  skin,  they  either  lie  as 
a  flattened  layer  beneath  it,  or  are  connected  with  its  areolar  tissue  by  larger  or 
smaller  bundles  of  fibres,  as  in  the  muscles  of  the  face.  The  origin  of  a  muscle 
is  its  head  (caput),  while  the  intermediate  portion  is  called  the  belly,  or  venter. 
The  muscles  vary  extremely  in  their  form.  In  the  limbs  they  are  of  consider- 
able length,  especially  the  more  superficial  ones,  the  deep  ones  being  generally 
broad;  they  surround  the  bones  and  form  an  important  protection  to  the  various 
joints.  In  the  trunk  they  are  broad,  flattened,  and  expanded,  forming  the  parietes^ 
of  the  cavities  which  they  enclose;  hence  the  reason  of  the  terms  lotig,  broad, 
short,  etc.,  used  in  the  description  of  a  muscle. 

There  is  a  considerable  variation  in  the  arrangement  of  the  fibres  of  certain 
muscles  with  reference  to  the  tendons  to  which  they  are  attached.  In  some,  the 
fibres  are  parallel  and  run  directly  from  their  origin  to  their  insertion;  these  are 
quadrilateral  muscles,  such  as  the  Thyrohyoid.  A  modification  of  these  is  found 
in  the  fusiform  muscles  in  which  the  muscle  tapers  at  each  end;  in  their  action, 
however,  they  resemble  the  quadrilateral  muscles. 
Secondly,  in  other  muscles  the  fibres  are  con- 
vergent; arising  by  a  broad  origin,  they  converge 
to  a  narrow  or  pointed  insertion.  This  arrange- 
ment of  fibres  is  found  in  the  triangular  muscles — 
e.  (J.,  the  Temporal.  In  some  muscles,  which 
otherwise  would  belong  to  the  quadrilateral  or 
triangular  type,  the  origin  and  insertion  are  not  in 
the  same  plane,  but  the  plane  of  the  line  of  origin 
intersects  that  of  their  insertion;  such  is  the  case 
in  the  Pectineus  muscle.  Thirdly,  in  some  muscles 
the  fibres  are  oblique  and  converge,  like  the 
plumes  of  a  pen,  to  one  side  of  a  tendon,  which 
runs  the  entire  length  of  the  muscle.  Such  a 
muscle  is  penniform  Qn.  unipennatus),  as  the 
„„„,,,.  ti,.    T^,    •■  Peronei.     A  modification  of  these  muscles  is  found 

Fig.  285.— Diagram    of  the    Deltoid,   an       .       ,  ,  t  t  m  i       i 

example  of  a  multipennate  muscle.  m  tllOSC  CaSCS  Wliere  obliqUC  nbrCS  COllVCrge  tO  DOth 

sides  of  a  central  tendon  which  runs  down  the 
middle  of  the  muscle ;  these  are  called  bipenniform  (??i.  bipennaius),  and  an  example  is 
afforded  in  the  Rectus  femoris.  Multipennate  muscles  are  those  in  which  the  muscle 
fibres  alternate  with  a  series  of  tendinous  bands,  as  in  the  Deltoid.  Biventral 
muscles  occur,  such  as  the  Digastric,  while  the  Rectus  abdominis  shows  subdivision 
into  four  or  more  sections  by  intervening  inscriptiones  tendineae.  Certain  muscles 
do  not  act  in  a  direct  manner,  for  they  or  their  tendons  pass  around  a  bony  pro- 
jection or  through  a  septal  pulley  (trochlea).  Finally,  we  have  muscles  in  which 
the  fibres  are  arranged  in  curved  bundles  in  one  or  more  planes,  as  in  an  orbicular 
muscle  and  in  that  variety  of  orbicular  muscle  called  a  sphincter  muscle.  The 
arrangement  of  the  muscle  fibres  is  of  considerable  importance  in  respect  to  their 
relative  strength  and  range  of  movement.  Those  muscles  in  which  the  fibres  are 
long  and  few  in  number  have  great  range,  but  diminished  strength;  where,  on 
the  other  hand,  the  fibres  are  short  and  more  numerous,  there  is  great  power,, 
but  lessened  range. 

Muscles  differ  much  in  size;  the  Gastrocnemius  forms  the  chief  bulk  of  the 
back  of  the  leg;  the  Sartorius  is  very  long;  the  Stapedius,  a  small  muscle  of  the 
internal  ear,  weighs  about  a  grain,  and  its  fibres  are  not  more  than  4  mm.  in 
length. 


FOBM  AND  ATTACHMENT  OF  MUSCLES  359 

The  names  applied  to  the  various  muscles  have  been  derived  (1)  from  their 
situation,  as  the  Tibialis,  Radialis,  Ulnaris,  Peroneus;  (2)  from  their  direction,  as 
the  Rectus  abdominis,  Obliquus  capitis.  Transversal  is;  (3)  from  their  uses,  as 
Flexors,  Extensors,  Abductors,  I^evators,  Compressors,  etc. ;  (4)  from  their  shape, 
as  the  Deltoid,  Trapezius,  Rhomboideus,  Digastric;  (5)  from  the  v.umber  of  their 
divisions,  as  the  Biceps,  the  Triceps;  (6)  from  their  points  of  attachment,  as  the 
Sternomastoid,  Sternohyoid,  Sternothyroid. 

In  the  description  of  a  muscle  the  term  origin  is  meant  to  imply  its  more  fixed 
or  central  attachment,  and  the  term  insertion,  the  movable  point  to  which  the 
force  of  the  muscle  is  directed;  but  the  origin  is  absolutely  fixed  in  only  a  very 
small  number  of  muscles,  such  as  those  of  the  face,  which  are  attached  by  one 
extremity  to  the  bone  and  by  the  movable  integument;  the  greater  number  of 
muscles  can  be  made  to  act  from  either  extremity. 

In  the  dissection  of  the  muscles,  the  student  should  pay  especial  attention  to 
the  exact  origin,  insertion,  and  actions  of  each,  and  its  more  important  relations 
with  surrounding  parts.  While  accurate  knowledge  of  the  points  of  attachment  of 
the  muscles  is  of  great  importance  in  the  determination  of  their  actions,  it  is  not  to 
be  regarded  as  conclusive.  The  action  of  a  muscle  deduced  from  its  attachments, 
or  even  by  pulling  on  it  in  the  dead  subject  is  not  necessarily  its  action  in  the 
living.  By  pulling,  for  example,  on  the  Brachioradialis  in  the  cadaver  the  hand 
may  be  slightly  supinated'  when  in  the  prone  position  and  slightly  pronated  when 
in  the  supine  position,  but  there  is  no  evidence  that  these  actions  are  performed 
by  the  muscle  during  life.  It  is  impossible  for  an  individual  to  throw  into  action 
any  one  muscle;  in  other  words,  movements,  not  muscles,  are  represented  in  the 
central  nerve  system.  To  carry  out  a  movement  a  definite  combination  of  muscle? 
is  called  into  play,  and  the  individual  has  no  power  either  to  leave  out  a  muscle 
from  this  combination,  or  to  add  one  to  it.  One  muscle  (or  more)  of  the  combina- 
tion is  the  chief  moving  force:  when  this  muscle  passes  over  more  than  one  joint 
other  muscles  (sjmergic  muscles)  come  into  play  to  inhibit  the  movements  not 
required;  a  third  set  of  muscles  (fixation  muscles)  fix  the  limb — /.  e.,  in  the  case 
of  the  limb  movements — and  also  prevent  disturbances  of  the  equilibrium  of 
the  body  generally.  As  an  example,  the  movement  of  the  closing  of  the  fist 
may  be  considered:  (11  The  prime  movers  are  the  Flexores  digitorum,  Flexor 
longus  pollicis,  and  the  small  muscles  of  the  thumb;  (2)  the  synergic  muscles  are 
the  Extensores  carpi,  which  prevent  flexion  of  the  wrist;  while  (3)  the  fixation 
muscles  are  the  Biceps  and  Triceps,  which  steady  the  elbow  and  shoulder.  A 
further  point  which  must  be  borne  in  mind  in  considering  the  actions  of  muscles 
is  that  in  certain  positions  a  movement  can  be  efl^ected  by  gravity,  and  in  such  a 
case  the  muscles  acting  are  the  antagonists  of  those  which  might  be  supposed 
to  be  in  action.  Thus,  in  flexing  the  trunk  when  no  resistance  is  interposed  the 
Erectores  spinae  contract  to  regulate  the  action  of  gravity,  and  the  Recti  abdominis 
are  relaxed.^ 

Applied  Anatomy. — By  a  consideration  of  the 'action  of  the  muscles  the  surgeon  is  able  to 
explain  the  causes  of  displacement  in  various  forms  of  fracture,  and  the  causes  \yhich  produce 
distortion  in  various  deformities,  and,  consequently,  to  adopt  appropriate  treatment  in  each 
case.  The  relations,  also,  of  some  of  the  muscles,  especially  those  in  immediate  apposition 
with  the  larger  bloodvessels,  and  the  surface-markings  they  produce,  should  be  carefully  remem- 
bered, as  they  form  useful  guides  in  the  application  of  ligatures  to  those  vessels. 

Degeneration  of  muscle  tissue  is  important  clinically,  and  is  met  with  in  two  main  conditions. 
In  one,  the  degeneration  is  myopathic,  or  primary  in  the  muscles  themselves;  in  the  other  it 
is  neuropathic,  or  secondary  to  some  lesion  of  the  nerve  system — a  hemorrhage  into  the  brain, 

1  Hence  the  old  name  Supinator  longus,  dow  supplanted  by  Brachioradialis. 

-  Consult  in  this  connection  the  Croonian  Lectures  (190.3)  on  "  Muscular  Movements  and  Their  Representation  in 
the  Central  Nervous  System,"  by  Charles  E.  Beevor,  M.D. 


360  THE  MUSCLES  AND  FASCIA 

for  example,  or  injury  or  inflammation  of  some  part  of  the  spinal  cord  or  peripheral  nerves. 
In  either  case  more  or  less  paralysis  and  atrophy  of  the  affected  muscles  result.  When  the 
degeneration  begins  primarily  in  the  muscles,  however,  it  often  happens  that  though  the  muscle 
fibres  waste  away,  their  place  is  taken  by  fibrous  and  fatty  tissue  to  such  an  extent  that  the 
affected  muscles  increase  in  volume,  and  actually  appear  to  hypertrophy. 

Ossification  of  muscle  tissue  as  a  result  of  repeated  strain  or  injury  is  not  infrequent.  It  is 
oftenest  found  about  the  tendon  of  the  Adductor  longus  and  Vastus  internus  in  horsemen,  or  in 
the  Pectoralis  major  and  Deltoid  of  soldiers.  It  may  take  the  form  of  exostoses  firmly  fixed  to 
the  bone — e.  g.^  "rider's  bones"  on  the  femm-  (pages  229  and  51.5) — or  of  layers  or  spicules  of 
bone  lying  in  the  muscles  of  their  fasciae  and  tendons.  Busse  states  that  these  bony  deposits 
are  preceded  by  a  hemorrhagic  myositis  due  to  injury,  the  effused  blood  organizing  and  being 
finally  converted  into  bone.  In  the  rarer  disease,  progressive  myositis  ossifi,cans,  there  is  an 
unexplained  tendency  for  practically  any  of  the  voluntary  muscles  to  become  converted  into 
solid  and  brittle  bony  masses  which  are  completely  rigid. 

Tendons  are  white,  glistening,  fibrous  cords,  varying  in  length  and  thickness, 
sometimes  round,  sometimes  flattened,  of  considerable  strength,  and  devoid  of 
elasticity.  They  consist  almost  entirely  of  dense,  white  fibrous  tissue,  the  fibrils 
of  which  run  in  an  undulating  parallel  course  and  are  firmly  united  together. 
They  are  very  sparingly  supplied  with  bloodvessels,  the  smaller  tendons  present- 
ing not  a  trace  of  them  in  their  interior.  Nerves  supplying  tendons  have  special 
modifications  of  their  terminals,  termed  neurotendinous  spindles  or  organs  of 
Golgi  (p.  817). 

Aponeuroses  are  fllattened  or  ribbon-shaped  tendons,  of  a  pearly-white  color, 
iridescent,  glistening,  and  similar  in  structure  to  the  tendons;  the  thicker  ones  are 
only  sparingly  supplied  with  bloodvessels. 

The  tendons  and  aponeuroses  are  connected,  on  the  one  hand,  with  the  muscles, 
and,  on  the  other  hand,  with  movable  structures,  as  the  bones,  cartilages,  liga- 
ments, fibrous  membranes  (for  instance,  the  sclera).  Where  the  muscle  fibres 
are  in  a  direct  line  with  those  of  the  tendon  or  aponeurosis,  the  two  are  directly 
continuous,  the  muscle  fibre  being  distinguishable  from  that  of  the  tendon  only 
by  its  striation  and  increase  of  muscle  nuclei.  But  where  the  muscle  fibres  join 
the  tendon  or  aponeurosis  at  an  oblicjue  angle  the  former  terminate,  according 
to  KoUiker,  in  rounded  extremities,  which  are  received  into  corresponding  de- 
pressions on  the  surface  of  the  latter,  the  connective  tissue  between  the  fibres 
being  continuous  with  that  of  the  tendon.  The  latter  mode  of  attachment  occurs 
in  all  the  penniform  and  bipenniform  muscles,  and  in  those  muscles  the  tendons 
of  which  commence  in  a  membranous  form,  as  the  Gastrocnemius  and  Soleus. 

The  fasciae  are  fibroareolar  or  aponeurotic  laminte  of  variable  thickness  and 
strength,  found  in  all  regions  of  the  body,  investing  the  softer  and  more  delicate 
organs.  The  fascise  have  been  subdivided,  from  the  situation  in  which  they  are 
found,  into  two  groups,  superficial  and  deep. 

The  superficial  fascia  (pannicidus  adiposus)  is  found  immediately  beneath  the 
integument  over  almost  the  entire  surface  of  the  body.  It  connects  the  skin 
with  the  deep  or  aponeurotic  fascia,  and  consists  of  fibroareolar  tissue,  containing 
in  its  meshes  pellicles  of  fat,  in  varying  quantity.  The  superficial  fascia  varies 
in  thickness  in  different  parts  of  the'  body :  in  the  groin  it  is  so  thick  as  to  be 
capable  of  being  subdivided  into  several  laminae.  Beneath  the  fatty  layer  of 
the  superficial  fascia,  which  is  immediately  subcutaneous,  there  is  generally 
another  layer  of  the  same  structure,  comparatively  devoid  of  adipose  tissue, 
in  which  the  trunks  of  the  subcutaneous  vessels  and  nerves  are  found,  as  the 
superficial  epigastric  vessels  in  the  abdominal  region,  the  radial  and  ulnar  veins 
in  the  forearm,  the  saphenous  veins  in  the  leg  and  thigh,  and  the  superficial 
lymph  nodes.  Certain  cutaneous  muscles  also  are  situated  in  the  superficial 
fascia,  as  the  Platysma  in  the  neck,  and  the  Orbicularis  palpebrarum  around 
the  eyelids.  This  fascia  is  most  distinct  at  the  lower  part  of  the  abdomen,  the 
scrotum,  perineum,  and  extremities;  it  is  very  thin  in  those  regions  where  mus- 


APONEUROSES'  361 

cle  fibres  are  inserted  into  the  integument,  as  on  the  side  of  the  neck,  the  face, 
and  around  the  margin  of  the  anus.  It  is  very  dense  in  the  scalp,  in  the  mammae, 
the  palms  of  the  hands  and  soles  of  the  feet,  forming  a  fibrofatty  layer  which 
binds  the  integument  firmly  to  the  subjacent  structure. 

The  superficial  fascia  connects  the  skin  to  the  subjacent  parts,  facilitates  the 
movement  of  the  skin,  serves  as  a  soft  medium  for  the  passage  of  vessels  and  nerves 
to  the  integument,  and  retains  the  warmth  of  the  body,  since  the  fat  contained  in 
its  areoliie  is  a  poor  conductor  of  heat. 

The  deep  or  aponeurotic  fascia,  is  a  dense,  inelastic,  unyielding  fibrous  mem- 
brane, forming  sheaths  for  the  muscles  and  afl^ording  them  broad  surfaces  for 
attachment.  It  consists  of  shining  tendinous  fibres,  placed  parallel  to  one 
another,  and  connected  by  other  fibres  disposed  in  a  rectilinear  manner.  It  is 
usually  exposed  on  the  removal  of  the  superficial  fascia,  forming  a  strong  in- 
vestment,which  not  only  binds  down  collectively  the  muscles  in  each  region,  but 
gives  a  separate  sheath  to  each,  as  well  as  to  the  vessels  and  nerves.  The  fascia 
are  thick  in  unprotected  situations,  as  on  the  outer  side  of  a  limb,  and  thinner  on 
the  inner  side.  The  deep  fascise  assist  the  muscles  in  their  action  by  the  degree 
of  tension  and  pressure  they  make  upon  their  surface;  and  in  certain  situations 
this  is  increased  and  regulated  by  muscular  action;  as,  for  instance,  by  the  Tensor 
fasciae  femoris  and  Gluteus  maximus  in  the  thigh,  by  the  Biceps  in  the  upper 
and  lower  extremities,  and  Palmaris  longus  in  the  hand.  In  the  limbs  the  fasciae 
not  only  invest  the  entire  limb,  but  give  off  septa  which  separate  the  various 
muscles,  and  are  deeply  attached  to  the  periosteum;  these  prolongations  of  fasciae 
are  usually  spoken  of  as  intermuscular  septa. 

Bevelopment  of  the  Skeletal  Musculature. — The  voluntary  muscles  are  developed  from 
the  myotomes  of  the  mesodermal  somites.  Portions  of  the  myotomes  retain  their  position  along 
the  body  axis  in  segmental  order,  such  as  the  short  muscles  of  the  vertebral  column.  Others 
migrate  into  the  body  wall,  where  again  they  may  retain  their  segmental  relation  (intercostal 
muscles),  or  may  fuse  with  adjacent  segments  to  form  Qat  muscles  such  as  those  in  the  abdom- 
inal wall.  In  the  limbs,  portions  of  myotomes  wander  into  the  limb  buds  and  there  undergo 
fusions  and  alterations  in  form  to  produce  the  limb  muscles,  thus  losing  their  segmental  char- 
acter, but  retaining  the  appropriate  segmental  nerve  supplies.  Some  of  the  limb  muscles  expand 
and  migrate  secondarily  toward  the  dorsimesal  line  (e.  g.,  Trapezius,  Latissimus)  or  toward 
the  ventromesal  line  (e.  g.,  Pectoralis  major).  Again,  muscles  may  migrate  cephalad  (e.  g., 
the  facial  muscles  derived  from  the  hyoid  arch)  or  caudad  (e.  g.,  Serratus  magnus).  In  all 
cases  the  muscles  carry  with  them  the  segmental  nerves  of  the  myotomes  from  which  they  were 
derived;  the  most  striking  example  is  the  Diaphragm  which  is  derived  from  the  third,  fourth, 
and  fifth  cervical  myotomes,  and  is  supplied  by  the  phrenic  nerves,  which  spring  from  the 
third,  fourth,  and  fifth  cervical  nerves.  Some  of  the  derivatives  of  the  myotomes  degenerate 
and  are  converted  into  ai^oneuroses  (e.  g.,  epicranial  aponeurosis)  or  into  ligaments  {c.  g.,  great 
sacrosciatic   ligament  and  external  lateral  ligament  of  the  knee). 

Various  disturbances  of  development  characterize  what  are  known  as  variable  or  anomalous 
muscles.  Such  muscles  may  be  wanting,  or  excessively  developed  in  the  way  of  accessory 
portions  or  with  atypic  attachments.  The  resemblance  which  such  muscles  in  the  human  subject 
bear  to  certain  muscles  in  lower  animals  has  been  regarded  by  some  anatomists  as  an  expression 
of  atavistic  reversion.' 

The  muscles  and  fasciae  may  be  arranged  according  to  the  general  division 
of  the  body,  into  those  of  the  cranium,  face,  and  neck;  those  of  the  trunk;  those  of 
the  upper  "extremity  or  pectoral  limb;  and  those  of  the  lower  extremity  or  pelvic 
limb. 

■  See.  however,  Huntington,  American  Journal  of  Anatomy,  1902-03,  vol.  ii,  p.  157. 


362 


THE  MUSCLES  AND  FASCIA 


MUSCLES  AND  FASCI-ffi  OF  THE  CRANIUM  AND  FACE. 

The  muscles  of  the  cranium  and  face  consist  of  ten  groups,  arranged  according 
to  the  region  in  which  they  are  situated: 

6.  Maxillary  Region. 

7.  Mandibular  Region. 

8.  Buccal  Region. 
9'.  Temporomandibular  Region. 

10.  Pterygomandibular  Region. 


1.  Cranial  Region. 


Auricular  Region. 
Palpebral  Region. 
Orbital  Region. 
Nasal  Region. 


The  muscles  contained  in  each  of  these  groups  are  the  following: 
1.  Cranial  Region.  6.  Maxillary  Region. 

Occipitofrontalis.  Levator  labii  superioris. 


2.  Auricular  Region. 

Attrahens  aurem. 
Attollens  aurem. 
Retrahens  aurem. 

3.  Palpebral  Region. 

Orbicularis  palpebrarum. 
Corrugator  supercilii. 
Tensor  tarsi. 


4.  Orbital  Region. 

Levator  palpebrae. 
Rectus  superior. 
Rectus  inferior. 
Rectus  internus. 
Rectus  externus. 
Obliquus  oculi  superior. 
Obliquus  oculi  inferior. 

5.  Nasal  Region. 

Pyramidalis  nasi. 

Levator  labii  superioris  alaeque 

nasi. 
Dilatator  naris  posterior. 
Dilatator  naris  anterior. 
Compressor  nasi. 
Compressor  narium  minor. 
.  Depressor  alae  nasi. 


Levator  anguli  oris. 
Zygomaticus  major. 
Zygomaticus  minor. 


7.  Mandibular  Region. 

Levator  menti. 
Depressor  labii  inferioris. 
Depressor  anguli  oris. 


8.  Buccal  Region. 

Buccinator. 
Risorius. 
Orbicularis  oris. 


9.  Temporomandibular  Region, 

Masseter. 
Temporal. 

10.  Pterygomandibular  Region. 

Pterygoideus  externus. 
Pterygoideus  internus. 


1.  The  Cranial  Region. 

Occipitofrontalis. 

Dissection  (Fig.  286).— The  head  being  shaved,  and  a  block  placed  beneath  the  back  of 
the  neck,  make  a  vertical  incision  through  the  skin,  commencing  at  the  root  of  the  nose  in  front, 


THE  CRANIAL  BEGION 


363 


and  terminating  behind  at  the  occipital  protuberance;  make  a  second  incision  in  a  horizontal 
direction  along  the  forehead  and  around  the  side  of  the  head,  from  the  anterior  to  the  posterior 
extremity  of  the  preceding.  Raise  the  skin  in  front,  from  the  subjacent  mus.?le,  from  below 
upward;  this  must  be  done  with  extreme  care,  removing  the  integument  from  the  outer  surface 
of  the  vessels  and  the  nerves  which  lie  immediately  beneath  the  skin. 

The  Skin  of  the  Scalp. — This  is  thicker  than  in  any  other  part  of  the  body.  It  is  intimately 
adherent  to  llii-  Nupcrficial  fascia,  which  attaches  it  firmly  to  the  underlying  aponeurosis  and 
muscle.  ^lovcnicuts  of  (lie  mascle  move  the  skin.  The  hair  follicles  are  very  closely  set  together, 
and  extend  throughout  the  whole  thickness  of  the  skin.  It  also  contains  a  number  of  sebaceous 
glands. 


Fig.  2SG. — Dissection  of  the  head,  face,  and  neck. 


The  superficial  fascia  in  the  cranial  region  is  a  firm,  dense,  fibrofatty  layer, 
intimately  adherent  to  the  integument,  and  to  the  Oceipitofrontalis  and  its  tendi- 
nous aponeurosis;  it  is  continuous,  behind,  with  the  superficial  fascia  at  the  back 
part  of  the  neck;  and,  laterally,  is  continued  over  the  temporal  fascia.  It  contains 
between  its  layers  the  superficial  vessels  and  nerved  and  much  fat. 

The  Oceipitofrontalis  {m.  epicranius)  (Fig.  287)  is  a  broad  musculofibrous 
layer,  which  covers  the  whole  of  one  side  of  the  vertex  of  the  skull,  from  the  occiput 
to  the  eyebrow.  It  consists  of  two  muscle  slips,  separated  by  an  intervening 
tendinous  aponeurosis.  The  occipital  portion  {m.  occipitalis)  is  thin,  quadri- 
lateral in  form,  and  about  an  inch  and  a  half  in  length;  it  arises  from  the  outer 
two-thirds  of  the  superior  curved  line  of  the  occipital  bone,  and  from  the  mastoid 
portion  of  the  temporal  bone.  Its  fibres  of  origin  are  tendinous,  but  they  are 
soon  succeeded  by  muscle  fibres,  and  ascend  in  a  parallel  direction  to  terminate 
in  a  tendinous  aponeurosis.  The  frontal  portion  {m.  frontalis)  is  thin,  of  a  quadri- 
lateral form,  and  intimately  adherent  to  the  superficial  fascia.  It  is  broader, 
its  fibres  are  longer,  and  their  structures  paler  than  the  occipital  portion.  It  has 
no  bony  attachments.  Its  medial  fibres  are  continuous  with  those  of  the 
Pyramidalis  nasi.  Its  middle  fibres  become  blended  with  the  Corrugator  super- 
cilii  and  Orbicularis  palpebrarum;  and  the  outer  fibres  are  also  blended  with  the 
latter  muscle  over  the  external  angular  process.  From  these  attachments  the 
fibres  are  directed  upward,  and  join  the  aponeurosis  in  front  of  the  coronal  suture. 
The  inner  margins  of  the  frontal  portions  of  the  two  muscles  are  joined  together 
for  some  distance  above  the  root  of  the  nose;  but  between  the  occipital  portions 
there  is  a  considerable,  though  variable,  interval,  which  is  occupied  by  the  apon- 
eurosis. 

The  epicranial  aponeurosis  (c/alea  aponeurotica)  covers  the  upper  part  of  the  vertex 
of  the  skull,  being  continuous  across  the  middle  line  with  the  aponeurosis  of  the 


364 


THE  MUSCLES  AND  FASCIjE 


opposite  muscle.  Behind,  it  is  attached,  in  the  interval  between  the  occipital 
origins,  to  the  occipital  protuberance  and  highest  curved  lines  of  the  occipital 
bone;  in  front,  it  forms  a  short  and  narrow  prolongation  between  the  frontal  por- 
tions'; and  on  each  side  it  gives  origin  to  the  Attollens  and  Attrahens  aurem  muscles. 
This  aponeurosis  is  closely  connected  to  the  integument  by  the  firm,  dense, 
fibrofatty  layer  which  forms  the  superficial  fascia;  it  is  connected  with  the  pen- 


Fig.  287. — Muscles  of  the  head,  face,  and  neck. 

cranium  (cranial  periosteum)  by  loose  cellular  tissue,  which  allows  of  a  consider- 
able degree  of  movement  of  the  integument.  It  is  continuous  with  the  temporal 
fascia  below  the  temporal  ridge,  and  it  is  in  reality  the  representative  of  the  deep 
fascia. 

Nerves. — The  frontal  portion  of  the  OccipitofrontaHs  is  supplied  by  the  temporal  branches 
of  the  facial  nerve;  its  occipital  portion  by  the  posterior  auricular  branch  of  the  facial. 


THE  A  URICULAB  BEG  ION 


365 


Actions. — The  frontal  portion  of  the  muscle  raises  the  eyebrows  and  the  skin  over  the  root  of 
the  nose,  and  at  the  same  time  draws  the  scalp  forward,  throwing  the  integument  of  the  forehead 
into  transverse  wrinkles.  The  posterior  portion  draws  the  scalp  backward.  By  bringing  alter- 
nately into  action  the  frontal  and  occipital  portions  the  entire  scalp  may  be  moved  forward  and 
backward.  In  the  ordinary  action  of  the  muscles,  the  eyebrows  are  elevated,  and  at  the  same 
time  the  aponeurosis  is  fixed  by  the  posterior  portion,  thus  giving  to  the  face  the  expression  of 
surprise;  if  the  action  is  more  exaggerated,  the  eyebrows  are  still  further  raised,  and  the  .skin 
of  the  forehead  thrown  into  transverse  wrinkles,  as  in  the  expression  of  fright  or  horror. 

Applied  Anatomy. — The  skull  is  covered  by  the  scalp  (Fig.  288).  This  consists,  from  without 
inward,  of  live  layers:  (1)  Skin;  (2)  subcutaneous  fat;  (3)  the  Occipitofrontalis  mu.scle  and  apo- 
neurosis; (4)  a  layer  of  connective  tissue  beneath  the  Occipitofrontalis  aponeurosis  (subaponeu- 
rotic tissue) ;  (.5)  the  pericranium.  The  subcutaneous  tissue  is  composed  of  bands  of  fibrous 
tissue  enclosing  spaces  filled  with  fat.  The  fibrous  character  of  this  tissue  greatly  limits  discolor- 
ation and  swelling  when  inflammation  occurs.  The  edges  of  a  wound  which  does  not  involve  the 
aponeurosis  or  muscle  do  not  retract,  hence  the  wound  does  not  gape.  The  bloodvessels  run  prac- 
tically in  the  skin,  and  as  they  lie  in  very  dense  tissue  and  are  adherent  to  it,  wounds  bleed  profusely, 
the  arteries  being  unable  freely  to  contract  and  retract.  It  is  very  difficult  or  impossible  to  pick 
up  with  forceps  a  vessel  in  the  skin  of  the  scalp,  and  bleeding  must  be  arrested  by  suture  liga- 
tures or  by  the  stitches  which  close  the  wound.  Sebaceous  glands  in  the  skin  of  the  scalp  may 
develop  into  sebaceous  cysts  (wens).  If  a  wound  involves  the  muscle  or  aponeurosis,  it  gapes 
widely,  the  greatest  amount  of  gaping  being  observed  in  transverse  wounds.     The  subaponeu- 


RICRANIUM 


Fig.  2SS. — The  scalp.    Sagittal  section.     (Schematic.)     (Poirier  and  Charpy.) 


rotic  tissue  space  between  the  aponeiu-osis  and  the  pericranium  is  called  by  Treves  the  danger- 
ous area  of  the  scalp.  It  contains  a  layer  of  connective  tissue,  and  suppuration  in  this  tissue 
spreads  widely.  An  abscess  in  the  dangerous  area  should  be  opened  above  the  superior  curved 
line  of  the  occipital  bone,  above  the  eyebrow  or  above  the  zygoma.  In  a  wound  or  contusion 
superficial  to  the  aponeurosis  but  little  blood  can  be  effused  in  the  tissue  because  its  fibrous 
structure  prevents  it,  and  abscesses  do  not  tend  to  spread  widely.  Between  the  aponeurosis 
and  the  pericranium  a  great  amount  of  blood  can  be  effused.  An  effusion  of  blood  beneath 
the  pericranium  is  called  a  cephalhematoma.  Such  a  condition  may  occur  from  pressure  during 
birth.  An  extravasation  beneath  the  pericranium  is  limited  to  the  surface  of  one  bone.  The 
pericranium  is  tightly  attached  to  the  sutures,  but  adheres  lightly  to  the  surface  of  the  bone, 
and  abscess  beneath  the  pericranium  is  restricted  to  the  surface  of  one  bone. 


2.  The  Auricular  Region  (Fig.  287). 


Attrahens  aiirem. 


Attollens  aurem. 


Retrahens  aurem. 


These  three  small  muscles  are  placed  immediately  beneath  the  skin,  around  the 
external  ear.     In  man,  in  whom  the  external  ear  is  almost  immovable,  they  are 


366  THE  MUSCLES  AND  FASCIA 

rudimentary.     They  are  the  homologues  of  large  and  important  muscles  in  some 
of  the  mammalia. 

Dissection. — This  requires  considerable  care,  and  should  be  performed  in  the  following 
manner:  To  expose  the  AttoUens  aurem,  draw  the  pinna,  or  broad  part  of  the  ear,  downward, 
when  a  tense  band  will  be  felt  beneath  the  skin,  passing  from  the  side  of  the  head  to  the  upper 
part  of  the  concha;  by  dividing  the  skin  over  this  band  in  a  direction  from  below  upward,  and 
then  reflecting  it  on  each  side,  the  muscle  is  exposed.  To  bring  into  view  the  Attrahens  aurem, 
draw  the  helix  backward  by  means  of  a  hook,  when  the  muscle  will  be  made  tense,  and  may  be 
exposed  in  a  similar  manner  to  the  preceding.  To  expose  the  Retrahens  aurem,  draw  the  pinna 
forward,  when  the  muscle,  being  made  tense,  may  be  felt  beneath  the  skin  at  its  insertion  into 
the  back  part  of  the  concha,  and  may  be  exposed  in  the  same  manner  as  the  other  muscles. 

The  Attrahens  aurem  {m.  auricularis  anterior),  the  smallest  of  the  three, 
is  thin,  fan-shaped,  and  its  fibres  pale  and  indistinct;  they  arise  from  the  lateral 
edge  of  the  aponeurosis  of  the  Occipitofrontalis,  and  converge  to  be  inserted 
into  a  projection  of  the  front  of  the  helix. 

The  AttoUens  aurem  (jn.  auricularis  superior),  the  largest  of  the  three,  is 
thin  and  fan-shaped;  its  fibres  arise  from  the  aponeurosis  of  the  Occipitofrontalis 
and  converge  to  be  inserted  by  a  thin,  flattened  tendon  into  the  upper  part  of  the 
cranial  surface  of  the  pinna. 

The  Retrahens  aurem  (m.  auricularis  posterior)  consists  of  two  or  three 
fleshv  fasciculi,  which  arise  from  the  mastoid  portion  of  the  temporal  bone  by 
short  aponeurotic  fibres.  They  are  inserted  into  the  lower  part  of  the  cranial 
surface  of  the  concha. 

Nerves. — The  Attrahens  and  AttoUens  aurem  are  supplied  by  the  temporal  branch  of  the 
facial ;  the  Retrahens  aurem  is  supplied  by  the  posterior  auricular  branch  of  the  same  nerve. 

Actions. — In  man,  these  muscles  possess  very  little  action:  the  Attrahens  aiu:em  draws  the 
pinna  forward  and  upward;  the  .^ttolens  aurem  slightly  raises  it;  and  the  Retrahens  aurem 
draws  it  backward. 

3.  The  Palpebral  Region  (Fig.  287). 

Orbicularis  palpebrarum.  Levator  palpebrae. 

Corrugator  supercilii.  Tensor  tarsi. 

Dissection  (Fig.  286). — In  order  to  expose  the  muscles  of  the  face,  continue  the  longitudinal 
incision  made  in  the  dissection  of  the  Occipitofrontalis  down  the  median  line  of  the  face  to  the 
tip  of  the  nose,  and  from  this  point  onward  to  the  upper  lip;  and  carry  another  incision  along  the 
margin  of  the  lip  to  the  angle  of  the  mouth,  and  transversely  across  the  face  to  the  angle  of  the 
mandible.  Then  make  an  incision  in  front  of  the  external  ear,  from  the  angle  of  the  mandible 
upward;  to  join  the  transverse  incision  made  in  exposing  the  Occipitofrontalis.  These  incisions 
include  a  square-shaped  flap,  which  =hould  be  removed  in  the  direction  marked  in  the  figure, 
with  care,  as  the  muscles  at  some  points  are  intimately  adherent  to  the  integument. 

The  Orbicularis  palpebrarum  (m.  orbicularis  oculi)  is  a  sphincter  muscle,  which 
surrounds  the  circumference  of  the  orbit  and  eyelids.  It  arises  from  the  internal 
angular  process  of  the  frontal  bone,  from  the  frontal  process  of  the  maxilla  in 
front  of  the  lacrimal  groove  for  the  nasal  duct,  and  from  the  anterior  surface 
and  borders  of  a  short  tendon,  the  tendo  oculi,  or  internal  tarsal  ligament,  placed 
at  the  inner  angle  of  the  orbit.  From  this  origin  the  fibres  are  directed  outward, 
forming  a  broad,  thin,  and  flat  layer,  which  covers  the  e}-elids,  surrounds  the 
circumference  of  the  orbit,  and  spreads  out  over  the  temple  and  downward  on  the 
cheek.  The  internal  or  palpebral  portion  (pars  palpebral  is)  of  the  Orbicularis  is 
thin  and  pale;  it  arises  from  the  bifurcation  of  the  tendo  oculi,  and  forms  a  series 
of  concentric  curves,  which  are  on  the  outer  side  of  the  eyelids  inserted  into 
the  external  tarsal  ligament.  The  external  or  orbital  portion  {^pars  orbitalis)  is 
thicker  and  of  a  reddish  color;  its  fibres  are  well  developed,  and  form  complete 


THE  PALPEBRAL  REGION  3G7 

ellipses.     The  upper  fibres  of  tiiis  portion  blend  with  the  Occipitofrontalis  and 
Corrugator  supercilij. 

Relations. — By  its  superficial  surface,  with  the  integument.  By  its  deep  surface,  above,  -with 
the  Occipitofrontalis  and  Corrugator  superciHi,  with  which  it  is  intimately  blended,  and  with 
the  supraorbital  vessels  and  nerve;  below,  it  covers  the  lacrimal  sac,  and  the  origin  of  the  Levator 
labii  superioris  alaeque  nasi,  the  Levator  labii  superioris,  and  the  Zygomaticus  minor  muscles. 
Internally,  it  is  occasionally  blended  with  the  Pyramidalis  nasi.  Externally,  it  lies  on  the  tem- 
poral fascia.  On  the  eyelids  it  is  separated  from  the  conjunctiva  by  the  Levator  paipebrae, 
the  tarsal  ligaments,  the  tarsal  plates,  and  the  Meibomian  glands. 

The  tendo  ocuii  or  internal  tarsal  ligament  {ligamentum  palpebrale  mediale)  is  a 
short  tendon,  about  one-si.\th  of  an  inch  in  length  and  half  as  much  in  breadth, 
attached  to  the  frontal  process  of  the  maxilla  in  front  of  the  lacrimal  groove. 
Crossing  the  lacrimal  sac,  it  divides  into  two  parts,  each  division  being  attached 
to  the  inner  extremity  of  the  corresponding  tarsal  plate.  As  the  tendon  crosses 
the  lacrimal  sac,  a  strong  aponeurotic  lamina  is  given  ofi"  from  the  posterior  surface, 
which  expands  over  the  sac,  and  is  attached  to  the  ridge  on  the  lacrimal  bone. 
This  is  the  reflected  aponeurosis  of  the  tendo  oculi. 

The  external  tarsal  ligament  (raphe  palpebralis  lateralis)  is  a  much  weaker  struc- 
ture than  the  tendo  oculi.  It  is  attached  to  the  margin  of  the  frontal  process  of 
the  malar  bone,  and  passes  inward  to  the  outer  commissure  of  the  eyelid,  where 
it  divides  into  two  slips,  which  are  attached  to  the  margins  of  the  two  tarsal  plates. 

Use  of  Tendo  Oculi. — Besides  giving  attachment  to  part  of  the  Orbicularis 
palpebrarum  and  to  the  tarsal  plates,  it  serves  to  suck  the  tears  into  the  lacrimal 
sac,  by  its  attachment  to  the  sac.  Thus,  each  time  the  eyelids  are  closed,  the 
tendo  oculi  becomes  tightened,  through  the  action  of  the  Orbicularis,  and  draws 
the  wall  of  the  lacrimal  sac  outward  and  forward,  so  that  the  tears  are  sucked  along 
the  lacrimal  canals  into  it. 

The  Corrugator  supercilii  (Figs.  287  and  289)  is  a  small,  narrow,  pyramidal 
muscle,  placed  at  the  inner  extremity  of  the  eyebrow,  beneath  the  Occipito- 
frontalis and  Orbicularis  palpebrarum  muscles.  It  arises  from  the  inner  extrem- 
ity of  the  superciliary  ridge,  from  whence  its  fibres  pass  upward  and  outward 
between  the  palpebral  and  orbital  portions  of  the  Orbicularis  palpebrarum, 
and  are  inserted  into  the  deep  surface  of  the  skin,  opposite  the  middle  of  the 
orbital  arch. 

Relations. — By  its  superficial  surface  with  the  Occipitofrontalis  and  Orbicularis  palpebrarum 
muscles;  by  its  deep  surface,  with  the  frontal  bone  and  supratrochlear  nerve. 

The  Tensor  tarsi  or  Horner's  muscle  (pars  lacrimalis  m.  orhindaris  ocidi) 
(Fig.  289)  is  a  small  thin  muscle  about  a  quarter  of  an  inch  in  breadth  and 
half  an  inch  in  length,  situated  at  the  inner  side  of  the  orbit,  behind  the  tendo 
oculi  and  lacrimal  sac.  It  arises  from  the  crest  and  adjacent  part  of  the  orbital 
surface  of  the  lacrimal  bone,  and,  passing  across  the  lacrimal  sac,  divides  into  two 
slips,  which  coverthe  lacrimal  canals  and  are  inserted  into  the  tarsal  plates  internal 
to  the  puncta  lacrimalia.  Its  fibres  appear  to  be  continuous  with  those  of  the 
palpebral  portion  of  the  Orbicularis  palpebrarum;  it  is  occasionally  very  indis- 
tinct. 

Nerves. — The  Orbicularis  palpebrarum,  Corrugator  supercilii,  and  Tensor  tarsi  are  supplied 
by  the  facial  nerve. 

Actions. — The  Orbicularis  palpebrarum  is  the  sphincter  muscle  of  the  eyelids.  The  palpebral 
portion  acts  involuntarily,  closing  the  lids  gently,  as  in  sleep,  or  in  blinking;  the  orbicular  por- 
tion is  subject  to  the  will,  ^^^len  the  entire  muscle  is  brought  into  action,  the  skin  of  the  fore- 
head, temple,  and  cheek  is  drawn  inward  toward  the  inner  angle  of  the  orbit,  and  the  eyelids 
are  firmly  closed  as  in  photophobia.  When  the  skin  of  the  forehead,  temple,  and  cheek  is  thus 
drawn  inward  by  the  action  of  the  muscle  it  is  thrown  into  folds,  especially  radiating  from  the 


368 


THE  MUSCLEiS  AND  FASCIA 


outer  ano-le  of  the  eyelids,  which  give  rise  in  old  age  to  the  so-called  "crow's  feet."  The  Levator 
palpebrae  is  the  dii-ect  antagonist  of  this  muscle;  it  raises  the  upper  eyelid  and  exposes  the  globe 
of  the  eye.  The  Corrugator  supercilii  draws  the  eyebrow  downward  and  inward,  producing  the 
vertical  wrinkles  of  the  forehead.  It  is  the  "frowning"  muscle,  and  may  be  regarded  as  the 
principal  agent  in  the  expression  of  suiTering.  The  Tensor  tarsi  draws  the  eyelids  inward  and 
compresses  the  eyelids  and  the  extremities  of  the  lacrimal  canals  against  the  surface  of  the  globe 
of  the  eye;  thus  placing  the  canals  in  the  most  favorable  situation  for  receiving  the  tears.  It 
serves,  also,  to  compress  the  lacrimal  sac. 


FRONTAL  SrNUS 


4f  TENSOR 


nighmore: 


ORBITAL  portion   OF 
ORBICULARIS  PALPEBRARUM 

Fig.  289. — The  three  portions  of  the  Orbicularis  palpebrarum  muscle,  and  the  relation  of  this  muscle  to  the 
Corrugator  supercilii  muscle,  seen  from  behind.     (Left  side.)     (Toldt.) 


4.  The  Orbital  Region  (Fig.  291). 

Levator  palpebrae  superioris.  Rectus  internus. 

Rectus  superior.  Rectus  externus. 

Rectus  inferior.  Obliquus  oculi  superior. 

Obliquus  oculi  inferior. 

Dissection. — To  open  the  cavity  of  the  orbit,  remove  the  skullcap  and  brain ;  then  saw  through 
the  frontal  bone  at  the  inner  extremity  of  the  supraorbital  ridge,  and  externally  at  its  junction 
with  the  malar.  Break  in  pieces  the  thin  roof  of  the  orbit  by  a  few  slight  blows  of  the  hammer, 
and  take  it  away;  drive  forward  the  superciliary  portion  of  the  frontal  bone  by  a  smart  stroke, 
but  do  not  remove  it,  as  that  would  destroy  the  pulley  of  the  Obliquus  superior.  When  the 
fragments  are  cleared  away,  the  periosteum  of  the  orbit  will  be  exposed;  this  being  removed, 
together  with  the  fat  which  fills  the  cavity  of  the  orbit,  the  several  muscles  of  this  region  can 
be  examined.  The  dissection  will  be  facilitated  by  distending  the  globe  of  the  eye.  In  order 
to  effect  this,  puncture  the  optic  nerve  near  the  eyeball  with  a  curved  needle,  and  push  the  needle 
onward  into  the  globe;  insert  the  point  of  a  blowpipe  through  this  aperture,  and  force  a  little 
air  into  the  cavity  of  the  eyeball;  then  apply  a  ligature  around  the  nerve  so  as  to  prevent  the  air 
escaping.    The  globe  being  now  drawn  forward,  the  muscles  will  be  put  upon  the  stretch. 


Orbital  Septum. — Subjacent  to  the  Orbicularis  palpebrarum  a  dense  fascial 
sheet  supports  the  tarsal  plates  and  serves  as  a  septum  (septum  orbitale),  which 
is  attached  to  the  orbital  margin.      It   is  perforated  by  the  small  vessels  and 


THE  ORBITAL  REGION 


369 


nerves  which  supply  the  integument  of  the  eyeUds.     The  tarsal  ligaments  pre- 
viously descrilied  are  reen forcing  bands  of  this  fascial  septum. 

The  Levator  palpebrae  superioris  is  thin,  flat,  and  triangular  in  shape.  It 
arises  from  the  under  surface  of  the  lesser  wing  of  the  sphenoid,  above  and  in 
front  of  the  optic  foramen,  from  which  it  is  separated  by  the  origin  of  the  Superior 


Tendon  of  Obliquus  siipt;}'i 
OrWal  plate  of  frontal  hone 
Let}alor  palpehrce  supu  torts 
Jiecli^s  sitpet  lot 


Optic  nerve 
Rectus  inferior 
Roof  of  antrum  of  High 

Obliquus  inferior 


Ot  hicularis  palpebrarum 
Superior  tarsal  plate 
Upper  eyelid 


Lower  eyelid 
Iitferior  tarsal  plate 
Orbicularis  palpebrarum 


Fig.  290. — Sagittal  section  of  left  orbital  cavity. 


rectus  (Fig.  292).  At  its  origin  it  is  narrow  and  tendinous,  but  soon  becomes 
broad  and  fleshy,  and  terminates  anteriorly  in  a  wide  aponeurosis,  which  splits 
into  three  lamellse.  The  superficial  lamella  blends  with  the  superior  palpebral 
ligament,  and  is  prolonged  forward  above  the  superior  tarsal  plate  to  the  palpebral 
part  of  the  Orbicularis  palpebrarum  and  to  the  deep  surface  of  the  skin  of  the 


of  the  right  orbit. 


upper  eyelid.  The  middle  lamella,  largely  made  up  of  unstriped  muscle  fibres 
(superior  tarsal  muscle),  is  inserted  into  the  upper  margin  of  the  superior  tarsal 
plate,  while  the  deepest  lamella  blends  with  an  expansion  from  the  sheath  of 
the  Superior  rectus  muscle  and  with  it  is  attached  to  the  superior  forni.x  of  the 
conjunctiva  (Fig.  290). 


370  THE  MUSCLES  AND  FASCIA 

Relations.— By  its  orbital  surface,  with  the  frontal  nerve  and  supraorbital  artery,  the  peri- 
osteum of  the  orbit  and  lacrimal  gland;  and,  in  the  lid,  with  the  inner  surface  of  the  tarsal  liga- 
ment; bv  its  ocular  surface,  with  the  Superior  rectus,  and,  in  the  lid,  with  the  conjunctiva.  A 
small  branch  of  the  oculomotor  nerve  enters  its  under  surface. 

The  four  Recti  (Fig.  292)  arise  from  a  fibrous  ring  {annulus  tendineus  comvninis) 
[Zinn]  which  surrounds  the  upper,  inner,  and  lower  margins  of  the  optic  foramen 
and  encircles  the  optic  nerve.  Two  specialized  parts  of  this  ring  may  be  made  out : 
(1)  A  lower,  ligament  of  Ziim,  which  gives  origin  to  the  Inferior  rectus,  part  of  the 
Internal  rectus,  and  the  lower  head  of  the  External  rectus;  and  (2)  an  ujjper, 
the  tendon  of  Lockwood,  which  gives  origin  to  the  Superior  rectus,  the  rest  of  the 
Internal  rectus,  and  the  upper  head  of  the  External  rectus. 

Each  of  the  four  Recti  passes  forward  in  the  position  implied  by  its  name,  to 
be  inserted  by  a  tendinous  expansion  into  the  sclera,  about  a  quarter  of  an  inch 
from  the  margin  of  the  cornea.     Between  the  two  heads  of  the  External  rectus 

is  a  narrow  interval,  through  which  pass  the 

two  divisions  of  the  oculomotor  nerve,  the  nasal 

Reciu,s,.p<Tior  brauch  of  the  ophthalmic  division  of  the  tri- 

^wsuperiorJ  j —  geminal   nerve,   the   abducent  nerve,  and  the 

Superior  oblique}  I '<s^*%s^^  ophthalmic    vein.       Of    the    four    Recti,   the 

Internal  rectus  is  the  broadest,  the  External 
the  longest,  and  the  Superior  the  thinnest  and 
narrowest.  Beyond  the  insertion  of  the  Inferior 
rectus  a  thin  layer  of  non-striated  muscle 
fibres  (inferior  tarsal  muscle)  continues  into 
the  lower  eyelid  to  be  inserted  into  the  inferior 
tarsal  plate. 

Fig.  292. — The  relative  position  and  attach-  rpi  £!„„,-_;„■«     ...l^K^iin     /  IT  T 

ment  of  the  muscles  o£  the  left  eyebaU.  i  he     bUpePlOr     ODliqUe     (?«..    obhquVS    OCUU 

superior)  is  a  fusiform  muscle  placed  at  the 
upper  and  inner  side  of  the  orbit,  internal  to  the  Levator  palpebrae.  It  arises  a 
little  above  the  inner  margin  of  the  optic  foramen  (Fig.  292),  and,  passing  forward 
to  the  inner  angle  of  the  orbit,  terminates  in  a  rounded  tendon,  which  plays  in  a 
fibrocartilaginous  ring  or  pulley,  the  trochlea,  attached  to  the  trochlear  fossa  near 
the  internal  angular  process  of  the  frontal  bone.  The  contiguous  surfaces  of  the 
tendon  and  ring  are  covered  with  a  delicate  synovial  membrane  and  are  enclosed 
in  a  thin  fibrous  investment.  The  tendon  is  reflected  backward,  outward,  and 
downward  beneath  the  Superior  rectus  to  the  outer  part  of  the  globe  of  the  eye, 
and  is  inserted  into  the  sclera,  behind  the  equator  of  the  eyeball,  the  insertion  of 
the  muscle  lying  between  the  Superior  and  External  recti. 

Relations. — By  its  orbital  surface,  with  the  periosteum  covering  the  roof  of  the  orbit  and  the 
trochlear  nerve;  the  tendon,  where  it  lies  on  the  globe  of  the  eye,  is  covered  by  the  Superior 
rectus;  by-its  ocular  surface,  with  the  nasal  nerve,  ethmoidal  arteries,  and  the  upper  border  of  the 
Internal  rectus. 

The  Inferior  oblique  (m.  ohliquus  ocuU  inferior)  is  a  thin,  narrow  muscle  placed 
near  the  anterior  margin  of  the  orbit.  It  arises  from  a  depression  on  the  orbital 
plate  of  the  maxilla,  external  to  the  lacrimal  groove  (Fig.  291).  Passing  outward, 
backward,  and  upward  between  the  Inferior  rectus  and  the  floor  of  the  orbit, 
and  then  between  the  eyeball  and  the  External  rectus,  it  is  inserted  into  the  outer 
part  of  the  sclera  between  the  Inferior  and  External  recti,  near  to,  but  somewhat 
behind,  the  tendon  of   insertion  of  the  Superior  oblique. 

Relations. — By  its  ocular  surface,  with  the  globe  of  the  eye  and  with  the  Inferior  rectus;  by 
its  orbital  surface,  with  the  periosteum  covering  the  floor  of  the  orbit,  and  with  the  External 
rectus.  Its  borders  look  forward  and  backward;  the  posterior  one  receives  a  branch  of  the 
oculomotor  nerve. 


THE  ORBITAL  REGION  371 

The  orbital  muscle,  or  Miiller's  muscle  (muscttlvs  orbitale),  which  spans  the 
sphenomaxillary  fissure  and  infraorbital  groove,  is  composed  of  nonstriated 
fibres,  and  is  a  rudimentary  structure  continuous  with  the  periosteum  of  the 
orbit.i 

Nerves. — The  Levator  palpebrae,  Inferior  oblique,  and  all  the  Recti  excepting  the  External 
are  supplied  by  the  oculomotor  nerve;  the  Superior  oblique,  by  the  trochlear;  the  External 
rectus,  by  the  abducent. 

Actions. — The  Levator  palpebrae  raises  the  upper  eyelid,  and  is  the  direct  antagonist  of  the 
Orbicularis  palpebrarum.  The  four  Recti  muscles  are  attached  in  such  a  manner  to  the  globe 
of  the  eye  that,  acting  singly,  they  will  turn  its  corneal  surface  either  upward,  downward,  inward, 
or  outward,  as  expressed  by  their  names.  The  movement  produced  by  the  Superior  or  Inferior 
rectus  is  not  quite  a  simple  one,  for,  inasmuch  as  they  pass  obliquely  outward  and  forward  to  the 
eyeball,  the  elevation  or  depression  of  the  cornea  must  be  accompanied  by  a  certain  deviation 
inward,  with  a  slight  amount  of  rotation.  These  latter  movements  are  corrected  by  the  Oblique 
muscles,  the  Inferior  oblique  correcting  the  deviation  inward  of  the  Superior  rectus,  and  the 
Superior  oblique  that  of  the  Inferior  rectus.  The  contraction  of  the  External  and  Internal 
recti,  on  the  other  hand,  produces  a  purely  horizontal  movement.  If  any  two  contiguous  Recti 
of  one  eye  act  together,  they  carry  the  globe  of  the  eye  in  the  diagonal  of  these  directions — 
viz.,  upward  and  inward,  upward  and  outward,  downward  and  inward,  or  downward  and  out- 
ward. The  movement  of  circumduction,  as  in  looking  around  a  room,  is  performed  by  the  alter- 
nate action  of  the  four  Recti.  The  Oblique  muscles  rotate  the  eyeball  on  its  antero-posterior  axis, 
this  kind  of  movement  being  required  for  the  correct  viewing  of  an  object  when  the  head  is  moved 
laterally,  as  from  shoulder  to  shoalder,  in  order  that  the  picture  may  fall  in  all  respects  on  the 
same  part  of  the  retina  of  either  eye.  Sometimes  the  corresponding  Recti  and  sometimes  the 
opposite  ones  of  the  two  eyes  act  together ;  for  instance,  the  two  Superior  and  Inferior  recti  carry 
both  ej'eballs  upward  and  downward,  respectively.  In  looking  toward  the  right,  the  right  Exter- 
nal and  left  Internal  recti  act  together,  the  reverse  being  the  case  in  looking  toward  the  left.  In 
turning  both  eyes  toward  the  middle  line,  as  in  directing  our  vision  toward  an  object  less  than 
twenty  feet  distant,  the  two  Internal  recti  act  together. 

Fascise  of  the  Orbit. — The  connective  tissue  of  the  orbit  is  in  various  places  condensed  into 
thin  membranous  layers,  which  may  be  conveniently  described  as  (1)  the  orbital  fascia;  (2)  the 
sheaths  of  the  muscles;  and  (3)  the  fascia  of  the  eyeball. 

1.  The  Orbital  Fascia. — This  forms  the  periosteum  of  the  orbit.  It  is  loosely  connected  to 
the  bones,  from  whirh  it  can  be  readily  separated.  Beliind,  it  is  connected  with  the  dura  by 
processes  which  pass  through  the  optic  foramen  and  sphenoidal  fissure,  and  with  the  sheath  of 
the  optic  nerve.  In  front  it  is  connected  with  the  periosteum  at  the  margin  of  the  orbit,  and 
sends  off  a  process  which  assists  in  forming  the  palpebral  fascia  or  orbital  septum.  From  its 
internal  surface  two  processes  are  given  off — one  to  enclose  the  lacrimal  gland,  the  other  to 
hold  the  pulley  of  the  Superior  oblique  muscle  in  position. 

2.  The  Sheaths  of  the  Muscles. — The  sheaths  of  the  muscles  give  off  expansions  to  the 
margins  of  the  orbit  which  limit  the  action  of  the  muscles. 

3.  The  Fascia  of  the  Eyeball. —  Tenon's  capsule — surrounds  the  posterior  two-thirds  of  the 
eyeball;  it  will  l>e  described  with  the  anatomy  of  the  eyeball. 

Applied.  Anatomy. — The  position  and  exact  point  of  insertion  of  the  tendons  of  the  Inter- 
nal and  External  recti  muscles  into  the  globe  should  be  carefully  examined  from  the  front  of 
the  eyeball,  as  the  surgeon  is  often  required  to  divide  the  one  or  the  other  muscle  for  the  cure 
of  strabismus  (squint).  In  convergent  strabismus,  which  is  the  more  common  form  of  the  disease, 
the  eye  is  turned  inward,  requiring  the  division  of  the  Internal  rectus.  In  the  divergent  form 
which  is  more  rare,  the  eye  is  turned  outward,  the  External  rectus  being  especially  implicated. 
The  deformity  produced  in  either  case  is  to  be  remedied  by  division  of  one  or  the  other  muscle. 
The  operation  is  thus  performed:  The  lids  are  to  be  well  separated;  the  eyeball  being  rotated 
outward  or  inward,  the  conjunctiva  should  be  raised  by  a  pair  of  forceps  and  divided  immedi- 
ately beneath  the  lower  border  of  the  tendon  of  the  muscle  to  be  divided,  a  littie  behind  its 
insertion  into  the  sclera;  the  submucous  areolar  tissue  is  then  divided,  and  into  the  small  aper- 
ture thus  made  a  blunt  hook  is  passed  upward  between  the  muscle  and  the  globe,  and  the 
tendon  of  the  muscle  and  conjunctiva  covering  it  divided  by  a  pair  of  blunt-pointed  scissors. 
Or  the  tendon  may  be  divided  by  a  subconjunctival  incision,  one  blade  of  the  scissors  being 
passed  upward  between  the  tendon  and  the  conjunctiva,  and  the  other  between  the  tendon  and 
the  sclera.  Inflammation  of  the  synovial  membrane  lining  the  trochlea  of  the  Superior  oblique 
may  lead  to  the  formation  of  a  cyst  of  considerable  size. 

1  See  F.  Groyer,  in  the  Vienna  Sitzungsberiohte  der  Kaiserliohen  Akademie  der  Wissenschaften,  1903,  Band 


372  THE  MUSCLES  AND  FASCIA 

In  performing  enucleation  of  the  eyeball  the  conjunctiva  is  clipped  with  scissors  near  the  cornea 
and  the  capsule  of  T6non  is  divided  with  it.  One  Rectus  muscle  after  another  is  caught  up 
on  a  blunt  hook  and  divided.  The  scissors  are  now  pushed  well  in  along  the  outer  orbital  wall 
and  the  optic  nerve  is  divided.  Finally,  the  Oblique  muscles,  the  ciliary  vessels  and  nerves,  and 
fragments  of  tissue  helping  to  retain  the  globe  are  cut  and  the  eyeball  is  enucleated. 

An  orbital  abscess  is  evacuated  by  making  an  incision  close  to  the  border  of  the  orbit,  above 
or  below  the  eyeball. 

Exophthalmos,  or  abnormal  protrusion  of  the  eyeball,  is  believed  to  be  due  to  hypersecretion 
of  the  thyroid  (as  in  goitre),  which,  through  the  cervicocephalic  division  of  the  sympathetic, 
stimulates  the  nonstriated  tarsal  muscles  to  sustained  contraction.  These  muscles  are  arranged 
like  a  cuff,  and  may  be  regarded  as  having  their  origin  in  the  orbital  septum  and  their  insertion 
at  the  equator  of  the  eyeball.  In  their  action  they  are  antagonists  of  the  Recti,  and  of  the 
Levator  palpebrae  superioriS;  and  open  wide  the  palpebral  fissure  and  draw  the  eyeball  forward. 
(Consult  J.  Landstrom,  Ueber  Morbus  Basedowii,  Thesis,  Stockholm,  1907.) 


5.  The  Nasal  Region  (Fig.  287). 

Pyramidalis  nasi.  Dilatator  naris  anterior. 

Levator  labii  superioris  alaeque  nasi.  Compressor  nasi. 

Dilatator  naris  posterior.  Compressor  narium  minor. 

Depressor  alae  nasi. 

The  Pyramidalis  nasi  (m.  frocerus)  is  a  small  pyramidal  slip  placed  over  the 
nasal  bone.  Its  origin  is  by  tendinous  fibres  from  the  fascia  covering  the  lower 
part  of  the  nasal  bone  and  upper  part  of  the  cartilage,  where  it  blends  with  the 
Compressor  nasi,  and  it  is  inserted  into  the  skin  over  the  lower  part  of  the  forehead 
between  the  two  eyebrows,  its  fibres  decussating  with  those  of  the  Occipitofron- 
talis  (see  page  364). 

The  Levator  labii  superioris  alaeque  nasi  is  a  thin  triangular  muscle  placed 
by  the  side  of  the  nose,  and  extending  between  the  inner  margin  of  the  orbit 
and  upper  lip.  It  arises  by  a  pointed  extremity  from  the  upper  part  of  the  nasal 
process  of  the  maxilla,  and,  passing  obliquely  downward  and  outward,  divides  into 
two  slips,  one  of  which  is  inserted  into  the  cartilage  of  the  ala  of  the  nose;  the 
other  is  prolonged  into  the  upper  lip,  becoming  attached  to  the  under  surface  of 
the  skin  and  blended  with  the  Orbicularis  oris  and  Levator  labii  superioris 
proprius. 

The  Dilatator  naris  posterior  is  a  small  muscle  which  is  placed  partly  beneath 
the  elevator  of  the  nose  and  lip.  It  arises  from  the  margin  of  the  nasal  notch 
of  the  maxilla  and  from  the  sesamoid  cartilages,  and  is  inserted  into  the  skin  near 
the  margin  of  the  nostril. 

The  Dilatator  naris  anterior  is  a  thin,  delicate  fasciculus  passing  from  the 
cartikge  of  the  ala  of  the  nose  to  the  integument  near  its  margin.  This  muscle  is 
situated  in  front  of  the  preceding. 

The  Compressor  naris  (m.  nasalis)  is  a  small,  thin,  triangular  muscle  arising 
by  its  apex  from  the  maxilla,  above  and  a  little  external  to  the  incisive  fossa; 
its  fibres  proceed  upward  and  inward,  expanding  into  a  thin  aponeurosis  which 
is  attached  to  the  fibrocartilage  of  the  nose  and  is  continuous  on  the  bridge  of 
the  nose  with  that  of  the  muscle  of  the  opposite  side  and  with  the  aponeurosis  of 
the  Pyramidalis  nasi. 

The  Compressor  narium  minor  is  a  small  muscle  attached  by  one  end  to  the 
alar  cartilage,  and  by  the  other  to  the  integument  at  the  end  of  the  nose. 

The  Depressor  alae  nasi  (m.  depressor  septi)  is  a  short  radiated  muscle  arising 
from  the  incisive  fossa  of  the  maxilla;  its  fibres  ascend  to  be  inserted,  into  the 
septum  and  back  part  of  the  ala  of  the  nose.  This  muscle  lies  between  the 
mucous  membrane  and  muscular  structure  of  the  lip. 


THE  MAXILLA  B I '  REGION  373 

Nerves. — All  of  the  muscles  of  this  group  are  supplied  by  the  facial  nerve. 

Actions.  -The  Pj'ramidalis  nasi  draws  down  the  inner  angle  of  the  eyebrows  and  produces 
transverse  wrinkles  over  the  bridge  of  the  nose.  The  Levator  labii  superioris  alaec|ue  nasi  draws 
upward  the  upper  lip  and  ala  of  the  nose;  its  most  important  action  is  upon  the  no.se,  which  it 
dilates  to  a  considerable  e.xtent.  The  action  of  this  muscle  produces  a  marked  influence  over 
the  countenance,  and  it  is  the  principal  agent  in  the  e.xpression  of  contempt  and  disdain.  The 
two  Dilatatores  nasi  enlarge  the  aperture  of  the  nose.  Their  action  in  ordinary  breathing  is 
to  resist  the  tendency  of  the  nostrils  to  close  from  atmospheric  pressure,  but  in  difficult  breath- 
ing they  may  be  noticed  to  be  in  violent  action,  as  well  as  in  some  emotions,  as  anger.  The 
Depressor  alae  nasi  is  a  direct  antagonist  of  the  other  muscles  of  the  nose,  drawing  the  ala  of  the 
nose  downward,  and  thereby  constricting  the  aperture  of  the  nares.  The  Compressor  naris 
depresses  the  cartilaginous  part  of  the  nose  and  compresses  the  alee  together. 


6.  The  Maxillary  Region  (Fig.  287). 

Levator  labii  superioris.  Zygomaticu.s  major. 

Levator  anguli  oris.  Zygomaticus  minor. 

In  the  BNA  term  musculus  quadratus  labii  superioris  tliree  muscles  are  in- 
cluded. The  caput  aiigulare  is  called  in  this  book  the  Levator  labii  superioris 
alaeque  nasi.  The  capiit  iiifraorbitale  is  called  the  Levator  labii  superioris.  The 
capiit  zi/c/omaticum  is  called  the  Zygomaticus  minor.' 

The  Levator  labii  superioris  is  a  thin  muscle  of  a  quadrilateral  form.  It 
arises  from  the  lower  margin  of  the  orbit  immediately  above  the  infraorbital 
foramen,  some  of  its  fibres  being  attached  to  the  maxilla,  others  to  the  malar 
bone;  its  fibres  converge  to  be  inserted  into  the  muscular  substance  of  the  upper 

The  Levator  anguli  oris  (m.  camnus)  arises  from  the  canine  fossa  immediately 
below  the  infraorbital  foramen;  its  fibres  incline  downward  and  a  little  outward,  to 
be  inserted  into  the  deep  surface  of  the  skin  and  into  the  subcutaneous  tissue 
near  the  angle  of  the  mouth  and  intermingles  with  the  fibres  of  the  Zygomaticus 
major,  the  Depressor  anguli  oris,  and  the  Orbicularis  oris. 

The  Zygomaticus  major  (m.  zygomaticus)  is  a  slender  fasciculus  which 
arises  from  the  malar  bone,  in  front  of  the  zygomatic  suture,  and,  descending 
obliquely  downward  and  inward,  is  inserted  into  the  deep  surface  of  the  skin  and 
subcutaneous  tissue  at  the  outer  portion  of  the  upper  lip  and  into  the  angle  of 
the  mouth,  where  it  blends  with  the  fibres  of  the  Levator  anguli  oris,  the  Orbicu- 
laris oris,  and  the  Depressor  anguli  oris. 

The  Zygomaticus  minor,  which  is  often  absent,  arises  from  the  malar  bone 
immediately  behind  the  maxillary  suture,  and,  passing  downward  and  inward, 
is  inserted  internal  to  the  angle  of  the  mouth  and  is  continuous  with  the  Orbicularis 
oris  at  the  outer  margin  of  the  Levator  labii  superioris.  It  lies  in  front  of  the 
Zygomaticus  major. 

Nerves. — This  group  of  muscles  is  supplied  by  the  facial  nerve. 

Actions, — The  Levator  labii  superioris  is  the  proper  elevator  of  the  upper  lip,  carrying  it 
at  the  same  time  a  little  forward.  It  assists  in  forming  the  nasolabial  ridge  which  passes  from 
the  side  of  the  nose  to  the  upper  lip  and  gives  to  the  face  an  expression  of  sadness.  The  Levator 
anguli  oris  raises  the  angle  of  the  mouth  and  draws  it  inward,  and  assists  the  Levator  labii  su- 
perioris in  producing  the  nasolabial  ridge.  The  Zygomaticus  major  draws  the  angle  of  the  mouth 
backward  and  upward,  as  in  laughing;  while  the  Zygomaticus  minor,  being  inserted  into  the 
outer  part  of  the  upper  lip  and  not  into  the  angle  of  the  mouth,  draws  it  backward,  upward, 
and  outward,  and  thus  gives  to  the  face  an  expression  of  sadness. 

I  That  this  grouping  is  quite  artificial  and  morphologically  unwarranted  has  been  shown  by  McMurrich 
American  Journal  of  Anatomy,  vol.  iii,  Proceedings,  p.  iii. 


374  THE  MUSCLES  AND  FASCIA 


7.  The  Mandibular  Region  (Fig.  287). 

Levator  menti.  Depressor  labii  inferioris. 

Depressor  anguli  oris. 

Dissection.  -  -Tlie  muscles  in  this  region  may  be  dissected  by  maliing  a  vertical  incision  tlirough 
the  integument  from  the  margin  of  the  lower  lip  to  the  chin;  a  second  incision  should  then  be 
carried  along  the  margin  of  the  mandible  as  far  as  the  angle,  and  the  integument  carefully 
removed  in  the  direction  shown  in  Fig.  286. 

The  Levator  menti  (m.  mentalis)  is  a  small  conical  fasciculus  placed  on  the 
side  of  the  frenum  of  the  lower  lip.  It  arises  from  the  mandibular  incisive  fossa, 
external  to  the  symphysis  of  the  mandible;  its  fibres  descend  to  be  inserted  into 
the  integument  of  the  chin. 

The  Depressor  labii  inferioris,  or  Quadratus  menti  (m.  quadrafus  labii 
inferioris)  (Fig.  294),  is  a  small  quadrilateral  muscle.  It  arises  from  the  external 
oblique  line  of  the  mandible,  between  the  symphysis  and  mental  foramen,  and 
passes  obliquely  upward  and  inward,  to  be  inserted  into  the  integument  of  the 
lower  lip,  its  fibres  blending  with  the  Orbicularis  oris  and  with  those  of  its  fellow 
of  the  opposite  side.  It  is  continuous  with  the  fibres  of  the  Platysma  at  its  origin. 
This  muscle  contains  much  fat  intermingled  with  its  fibres. 

The  Depressor  anguli  oris  (?re.  triangularis)  (Fig.  287)  is  triangular  in  shape, 
arising,  by  its  broad  base,  from  the  external  oblique  line  of  the  mandible,  from 
whence  its  fibres  pass  upward,  to  be  inserted,  by  a  narrow  fasciculus,  into  the 
angle  of  the  mouth.  It  is  continuous  with  the  Platysma  at  its  origin  and  with 
the  Orbicularis  oris  and  Risorius  at  its  insertion,  and  some  of  its  fibres  are  directly 
continuous  with  those  of  the  Levator  anguli  oris.^ 

Nerves. — This  group  of  muscles  is  supplied  by  the  facial  nerve. 

Actions. — The  Levator  menti  raises  the  lower  lip  and  protrudes  it  forward,  and  at  the  same 
time  wrinkles  the  integument  of  the  chin,  expressing  doubt  or  disdain.  The  Depressor  labii 
inferioris  draws  the  lower  lip  directly  downward  and  a  little  outward,  as  in  the  expression  of 
irony.  The  Depressor  anguli  oris  depresses  the  angle  of  the  mouth,  being  the  antagonist  to  the 
Levator  anguli  oris  and  Zygomaticus  major;  acting  with  the  Levator  anguli  oris,  it  will  draw 
the  angle  of  the  mouth  directly  inward. 


8.  The  Buccal  Region. 

Orbicularis  oris.  Buccinator.  Risorius. 

Dissection. — Tie  dissection  of  these  muscles  may  be  considerably  facilitated  by  filling  the 
cavity  of  the  mouth  with  tow,  so  as  to  distend  the  cheeks  and  lips;  the  mouth  should  then  be 
closed  by  a  few  stitches  and  the  integument  carefully  removed  from  the  surface. 

The  Orbicularis  oris  (Figs.  287  and  293)  is  not  a  simple  sphincter  muscle,  like 
the  Orbicularis  palpebrarum,  but  consists  of  numerous  strata  of  muscle  fibres, 
having  different  directions,  which  surround  the  orifice  of  the  mouth.  These 
fibres  are  partially  derived  from  the  other  facial  muscles  which  are  inserted  into 
the  lips,  and  are  partly  fibres  proper  to  the  lips  themselves.  Of  the  former, 
a  considerable  number  are  derived  from  the  Buccinator  and  form  the  deeper 
stratum  of  the  Orbicularis.  Some  of  the  Buccinator  fibres — namely,  those  near 
the  middle  of  the  muscle — decussate  at  the  angle  of  the  mouth,  those  arising 
from  the  maxilla  passing  to  the  lower  lip,  and  those  from  the  mandible  to  the 

'  Muscle  fibres  connecting  the  two  muscles  below  the  chin  are  occasionally  met  with;  they  constitute  the 
Husculus  transversus  menti  of  His  and  Waldeyer. 


THE  BUCCAL  It  EG  ION 


375 


upper  lip.  Other  fibres  of  the  muscle,  situated  at  its  upper  and  lower  part, 
pass  across  the  lips  from  side  to  side  without  decussation.  Superficial  to  this 
stratum  is  a  second,  formed  by  the  Levator  and  Depressor  anguli  oris,  which  cross 
each  other  at  the  angle  of  the  mouth,  those  from  the  Depressor  passing  to  the  upper 
lip,  and  those  from  the  Levator  to  the  lower  lip,  along  which  they  run  to  be  in- 
serted into  the  skin  near  the  median  line.  Li  addition  to  these  there  are  fibres  from 
the  other  muscles  inserted  into  the  lips — the  Levator  labii  superioris,  the  Levator 
labii  superioris  alaeque  nasi,  the  Zygomatici,  and  the  Depressor  labii  inferioris; 
these  intermingle  with  the  transverse  fibres  above  described,  and  have  principally 
an  oblique  direction.  The  proper  fibres  of  the  lips  are  oblique,  and  pass  from  the 
under  surface  of  the  skin  to  the  mucous  membrane  through  the  thickness  of  the 
lip.  In  addition  to  these  are  fibres  by  which  the  muscle  is  connected  directly 
with  the  maxilla  and  mandible  and  with  the  septum  of  the  nose.  Li  the  upper  lip 
these  consist  of  two  bands,  an  inner  and  an  older,  on  each  side  of  the  nasal  plane; 
the  outer  band  (m.  incisivus  superior)  arises  from  the  alveolar  border  of  the  maxilla, 
opposite  the  lateral  incisor  tooth,  and,  arching  outward  on  each  side,  is  continuous 


'•e:vatoh 


*ryBUCCINATOF» 


E.  A.  S. 


Fig.  293. — Plan  of  the  fibres  constituting  the  Orbicularis 


nuscle. 


at  the  angle  of  the  mouth  with  the  other  muscles  inserted  into  this  part.  The 
inner  band  (m.  nasolabialis)  connects  the  upper  lip  to  the  septum  of  the  nose. 
The  interval  between  the  two  inner  bands  corresponds  with  the  depression  called 
the  philtrum  seen  on  the  surface  of  the  skin  beneath  the  septum  of  the  nose.  The 
additional  fibres  for  the  lower  lip  (in.  incisivus  inferior)  arise  from  the  mandible, 
externally  to  the  Levator  menti,  and  arch  outward  to  the  angles  of  the  mouth 
to  join  the  Buccinator  and  the  other  muscles  attached  to  this  part. 

The  Buccinator  (Fig.  294)  is  a  broad,  thin  muscle,  quadrilateral  in  form, 
which  occupies  the  interval  between  the  jaws  at  the  side  of  the  face.  It  arises 
from  the  outer  surface  of  the  alveolar  processes  of  the  maxilla  and  mandible, 
corresponding  to  the  three  molar  teeth,  and,  behind,  from  the  anterior  border  of 
the  pterygomandibular  ligament,  which  separates  it  from  the  Superior  constrictor 
of  the  pharynx.  The  fibres  converge  toward  the  angle  of  the  mouth,  where  the 
central  fibres  intersect  each  other,  those  from  below  being  continuous  with  the 
upper  segment  of  the  Orbicularis  oris,  and  those  from  above  with  the  inferior 
segment;  the  highest  and  lowest  fibres  continue  forward  uninterruptedly  into  the 
corresponding  segment  of  the  lip,  without  decussation. 


376 


THE  MUSCLES  AND  FASCIA 


Relations. — By  its  xwperfidal  surface,  behind,  with  a  large  mass  of  fat,  the  sucking  pad  (i-or- 
pus  adiposum  buc.cae),  which  separates  it  from  the  ramus  of  the  mandible,  the  Masseter,  and 
a  small  portion  of  the  Temporal  muscle.  The  sucking  pad  is  much  more  developed,  relatively,  in 
children  than  in  adults.  It  assists  sucking  by  aiding  the  cheek  to  resist  atmospheric  pressure. 
The  Buccinator  muscle  is  in  relation,  anteriorly,  with  the  Zygomatici,  Risorius,  Levator  anguli 


Fig.  294. — ^Temporal  and  deep  muscles  about  the  mouth.     (Testut.) 

oris,  Depressor  anguli  oris,  and  the  parotid  duct,  which  pierces  it  opposite  the  second  molar 
tooth  of  the  ma.xilla;  the  facial  artery  and  vein  cross  it  from  below  upward;  it  is  also  crossed 
by  the  branches  of  the  facial  and  buccal  nerves.  By  its  deep  surface  it  is  in  relation  with  the 
buccal  glands  and  mucous  membrane  of  the  mouth. 

The  pterygomandibular  ligament  {raphe  pferygomandibularis)  is  a  tendinous 
thickening  of  the  buccopharyngeal  fascia,  attached  by  one  extremity  to  the  apex 
of  the  internal  pterygoid  plate,  and  by  the  other  to  the  posterior  extremity  (lingula) 


THE  TEMPOROMANDIBULAR  REGION  377 

of  the  internal  oblique  line  of  the  mandible.  Its  deep  surface  corresponds  to  the 
cavity  of  the  mouth,  and  is  lined  with  mucous  membrane.  Its  superficial  surface 
is  separated  from  the  ramus  of  the  mandible  by  a  quantity  of  adipose  tissue. 
Its  posterior  border  gives  attachment  to  the  Superior  constrictor  of  the  phapaix; 
its  anterior  border,  to  the  fibres  of  the  Buccinator. 

Tlie  buccopharyngeal  fascia  (fascia  huccopharyngea)  is  a  thin  fascia  covering 
the  superficial  surface  of  the  Buccinator  muscle.  It  is  gradually  lost  in  front  of 
the  angle  of  the  mouth.  Posteriorly,  it  is  continued  over  the  superficial  surface 
of  the  Constrictor  muscles.  Its  thickened  cord-like  portion  is  the  stylomandibular 
ligament. 

The  Risorius  (m.  risorius)  (Fig.  287)  consists  of  a  narrow  bundle  of  fibres 
which  arises  in  the  fascia  over  the  Masseter  muscle,  and,  passing  horizontally 
forward,  is  inserted  with  the  Depressor  anguli  oris  into  the  subcutaneous  and 
muscular  tissue  at  the  angle  of  the  mouth.  It  is  placed  superficial  to  the  Platysma, 
and  is  broadest  at  its  outer  extremity.  This  muscle  varies  much  in  its  size  and 
form. 

Nerves. — The  muscles  in  this  group  are  all  supplied  by  the  facial  nerve. 

Actions. — The  Orbicularis  oris  in  its  ordinary  action  produces  the  direct  closure  of  the  lips; 
by  its  deep  fibres,  assisted  by  the  oblique  ones,  it  closely  applies  the  lips  to  the  alveolar  arch. 
The  superficial  part,  consisting  principally  of  the  decussating  fibres,  brings  the  lips  together 
and  also  protrudes  them  forward.  The  Buccinators  contract  and  compress  the  cheeks,  so 
that,  during  the  process  of  mastication,  the  food  is  kept  under  the  immediate  pressure  of  the 
teeth.  When  the  cheeks  have  been  previously  distended  with  air,  the  Buccinator  muscles  expel 
it  from  between  the  lips,  as  in  blowing  a  trumpet.  Hence  the  name  {buccina,  a  trumpet).  The 
Risorius  retracts  the  angles  of  the  mouth,  and  produces  the  unpleasant  expression  which  is 
sometimes  seen  in  tetanus,  and  is  known  as  risus  sardonicus,  the  sardonic  laugh. 

9.  The  Temporomandibular  Region. 

Masseter.  Temporal. 

The  masseteric  fascia  (fascia  parotideomasseterica)  covers  the  Masseter  muscle. 
It  is  firmly  connected  with  this  muscle  and  is  derived  from  the  deep  cervical 
fascia.  Above,  this  fascia  is  attached  to  the  lower  border  of  the  zygoma,  and 
behind,  it  invests  the  parotid  gland,  constituting  the  parotid  fascia. 

The  Masseter  muscle  {m.  masseter)  (Fig.  287)  is  a  short,  thick  muscle, 
somewhat  quadrilateral  in  form,  consisting  of  two  portions,  the  superficial  and 
the  deep.  The  superficial  portion,  the  larger,  arises  by  a  thick,  tendinous  aponeu- 
rosis from  the  malar  process  of  the  maxilla,  and  from  the  anterior  two-thirds  of 
the  lower  border  of  the  zygomatic  arch;  its  fibres  pass  downward  and  backward, 
to  be  inserted  into  the  angle  and  lower  half  of  the  outer  surface  of  the  ramus  of 
the  mandible.  The  deep  portion  is  much  smaller  and  more  muscular  in  texture; 
it  arises  from  the  posterior  third  of  the  lower  border  and  the  whole  of  the  deep 
surface  of  the  zygomatic  arch;  its  fibres  pass  downward  and  forward,  to  be  inserted 
into  the  upper  half  of  the  ramus  and  outer  surface  of  the  coronoid  process  of  the 
mandible.  The  deep  portion  of  the  muscle  is  partly  concealed,  in  front  by  the 
superficial  portion;  behind,  it  is  covered  by  the  parotid  gland.  The  fibres  of  the 
two  portions  are  continuous  at  their  insertion. 

Relations. — By  its  superficial  surface,  •^\nth  the  Zygomatic!,  the  parotid  gland  (the  socia  paro- 
tidis),  the  parotid  duct,  the  branches  of  the  facial  nerve  and  the  transverse  facial  vessels,  which 
cross  it;  the  masseteric  fascia;  the  Risorius,  Piatysma,  and  the  integument.  By  its  deep  surface 
it  is  in  relation  with  the  Temporal  muscle  at  its  insertion,  the  ramus  of  the  mandible,  the  Buc- 
cinator and  the  long  buccal  nerve,  from  which  it  is  separated  by  a  mass  of  fat  (sucking  pad). 
The  masseteric  nerve  and  artery  enter  in  on  its  deep  surface.  Its  posterior  margin  is  overlapped 
by  the  parotid  gland.  Its  anterior  margin,  which  projects  over  the  Buccinator  muscle,  is  crossed 
below  by  the  facial  vein. 


378 


THE  MUSCLES  AND  FASCIA 


The  temporal  fascia  (Jascia  temporalis)  covers  the  Temporal  muscle.  It  is  a 
strong,  fibrous  investment,  covered,  on  its  superficial  surface,  by  the  Attrahens 
and  AttoUens  aurem  muscles,  the  aponeurosis  of  the  Occipitofrontalis,  and  by 
part  of  the  Orbicularis  palpebrarum.  The  temporal  vessels  and  the  auriculo- 
temporal nerve  cross  it  from  below  upward.  Above,  it  is  a  single  layer,  attached 
to  the  entire  extent  of  the  upper  temporal  ridge;  but  below,  where  it  is  attached 
to  the  zygoma,  it  consists  of  two  layers,  one  of  which  is  inserted  into  the  outer,  and 
the  other  into  the  inner,  border  of  the  zygomatic  arch.  A  small  quantity  of  fat, 
the  orbital  branch  of  the  temporal  artery,  and  a  filament  from  the  orbital,  or 
temporomalar,  branch  of  the  superior  maxillary  nerve  are  contained  between  these 
two  layers.  It  affords  attachment  by  its  deep  surface  to  the  superficial  fibres  of 
the  Temporal  muscle. 

Dissection. — In  order  to  expose  the  Temporal  muscle,  remove  the  temporal  fascia,  which 
may  be  effected  by  separating  it  at  its  attachment  along  the  upper  border  of  the  zygoma  and 
dissecting  it  upward  from  the  surface  of  the  muscle.  The  zygomatic  arch  should  then  be  divided 
in  front  at  its  junction  with  the  malar  bone,  and  behind  near  the  externa!  auditory  meatus, 
and  drawn  downward  with  the  Masseter,  which  should  be  detached  from  its  insertion  into 
the  ramus  and  angle  of  the  mandible.    The  whole  extent  of  the  Temporal  muscle  is  then  exposed 


29.5. — The  Temporal  muscle,  the  zygoma  and  Masseter  having  been  removed. 


The  Temporal  muscle  (m.  temporalis)  (Figs.  294  and  295)  is  a  broad,  radiating 
muscle  situated  at  the  side  of  the  head  and  occupying  the  entire  extent  of  the  tem- 
poral fossa.  It  arises  from  the  whole  of  the  temporal  fossa  except  that  portion 
of  it  which  is  formed  by  the  malar  bone.  Its  attachment  extends  from  the  external 
angular  process  of  the  frontal  in  front  to  the  mastoid  portion  of  the  temporal 
behind,  and  from  the  curved  line  on  the  frontal  and  parietal  bones  above  to  the 
pterygoid  ridge  on  the  greater  wing  of  the  sphenoid  below.  It  is  also  attached 
to  the  inner  surface  of  the  temporal  fascia.  Its  fibres  converge  as  they  descend, 
and  terminate  in  a  flat  tendon,  which  is  inserted  into  the  inner  and  outer  surfaces, 
apex,  and  anterior  border  of  the  coronoid  process  and  the  anterior  border  of  the 
ramus  of  the  mandible,  nearly  as  far  forward  as  the  last  molar  tooth. 

Relations. — By  its  superficial  surface,  with  the  integument,  the  Attrahens  and  Attollens  aurem 
muscles,  the  temporal  vessels  and  nerves,  the  aponeurosis  of  the  Occipitofrontalis,  the  temporal 


THE  PTERYGOMANDIBULAR  REGION 


379 


fascia,  the  zygoma,  and  Masseter;  by  its  Aeej)  surface,  with  the  temporal  fossa,  the  External 
pterygoid  and  part  of  the  Buccinator  muscles,  the  internal  maxillary  artery  and  its  deep  tem- 
poral branches,  and  the  deep  temporal  nerves.  Behind  the  tendon  are  the  masseteric  vessels 
and  nerve,  and  in  front  of  it  the  buccal  vessels  and  nerve.  Its  anterior  border  is  separated  from 
the  malar  bone  by  a  mass  of  fat. 

Nerves. — Both  the  Masseter  and  Temporal  muscles  are  supplied  by  branches  of  the  inferior 
maxillary  division  of  the  trigeminal  nerve. 


10.  The  Pterygomandibular  Region  (Figs.  296,  297). 

External  pterygoid.  ■  Internal  pterygoid. 

Dissection, — The  Temporal  muscle  having  been  examined,  saw  through  the  base  of  the 
coronoid  process  and  draw  it  upward,  together  with  the  Temporal  muscle,  which  should  be 
detached  from  the  surface  of  the  temporal  fossa.  Divide  the  ramus  of  the  mandible  just  below 
the  condyle,  and  also,  by  a  transverse  incision  extending  across  the  middle,  just  above  the  dental 
foramen;  remove  the  fragment,  and  the  Pterygoid  muscles  will  be  exposed. 


Fig.  296. — The  Pterygoid  muscles,  the  zygomatic  arch,  and  a  portion  of  the  ramus  of  the  mandible 
having  been  removed. 

The  External  pterygoid  muscle  (m.  fterygoideus  externus)  is  a  short,  thick 
muscle,  somewhat  conical  in  form,  which  extends  almost  horizontally  between  the 
zygomatic  fossa  and  the  condyle  of  the  mandible.  It  arises  by  two  heads,  sepa- 
rated bya  slight  interval ;  the  upper  head  arises  from  the  inferior  surface  of  the  greater 
wing  of  the  sphenoid  and  from  the  pterygoid  ridge  which  separates  the  zygomatic 
from  the  temporal  fossa;  the  lower  head  arises  from  the  outer  surface  of  the  external 
pterygoid  plate.  Its  fibres  pass  horizontally  backward  and  outward,  to  be  inserted 
into  a  depression  in  front  of  the  neck  of  the  condyle  of  the  mandible  and  into  the 
front  of  the  articular  disk  of  the  temporomandibular  articulation. 

Relations. — By  its  swperfinal  s«r/ac?,  with  the  ramus  of  the  mandible,  the  internal  maxillary 
artery,  which  crosses  it,'  the  tendon  of  the  Temporal  muscle,  and  the  Masseter;  by  its  deep 
surface  it  rests  against  the  upper  part  of  the  Internal  pterygoid  muscle,  the  internal  lateral  liga- 
ment, the  middle  meningeal  artery,  and  inferior  maxillary  nerve;  by  its  upper  border  it  is  in 
relation  with  the  temporal  and  masseteric  branches  of  the  inferior  maxillary  nerve;  by  its  lower 
border  it  is  in  relation  with  the  inferior  dental  and  lingual  nerves.  Through  the  interval 
between  the  two  portions  of  the  muscle,  the  buccal  nerve  emerges  and  the  internal  maxillary 
artery  passes,  when  the  trunk  of  this  vessel  lies  on  the  muscle  (Fig.  292). 

1  This  is  the  usual  relation,  but  in  many  cases  the  artery  will  be  found  below  the  muscle. 


380  THE  MVSCLES  AND  FASCIA 

The  Internal  pterygoid  muscle  {m.  -pterygoideus  iniernits)  is  a  thick,  quadri- 
lateral muscle,  and  resembles  the  Masseter  in  form.  It  arises  from  the  pterygoid 
fossa,  being  attached  to  the  inner  surface  of  the  external  pterygoid  plate  and  to 
the  grooved  surface  of  the  tuberosity  of  the  palate  bone,  and  by  a  second  slip 
from  the  outer  surface  of  the  tuberosities  of  the  palate  and  maxilla :  its  fibres  pass 
downward,  outward,  and  backward,  to  be  inserted,  by  a  strong,  tendinous  lamina, 
into  the  lower  and  back  part  of  the  inner  side  of  the  ramus  and  angle  of  the 
mandible  as  high  as  the  dental  foramen. 

Relations. — By  its  superficial  surface,  with  the  ramus  of  the  mandible,  from  which  it  is  sep- 
arated, at  its  upper  part,  by  the  External  pterygoid  muscle,  the  internal  lateral  ligament,  the 
internal  maxillary  artery,  the  dental  vessels  and  nerves,  and  the  lingual  nerve,  and  a  process 
of  the  parotid  gland.  By  its  deep  surface,  with  the  Tensor  palati,  being  separated  from  the 
Superior  constrictor  of  the  pharynx  by  a  cellular  interval. 

Nerves. — These  muscles  are  supplied  by  branches  of  the  mandibular  division  of  the  tri- 
geminal nerve. 

Actions. — The  Temporal,  Masseter,  and  Internal  pterygoid  raise  the  mandible  against  the 
maxillse  with  great  force.  The  External  pterygoids  assist  in  opening  the  mouth,  but  their  main 
action  is  to  draw  forward  the  condyles  and  articular  disks  so  that  the  mandible  is  protruded  and  the 
inferior  incisors  are  projected  in  front  of  the  upper;  in  this  action  they  are  assisted  by  the  Internal 
pterygoids.  The  mandible  is  retracted  by  the  posterior  fibres  of  the  Temporal.  If  the  Internal 
and  External  pterygoids  of  one  side  act,  the  corresponding  side  of  the  mandible  is  drawn  for- 
ward, while  the  opposite  condyle  remains  comparatively  fixed,  and  lateral  movement,  such  as 
occurs  during  the  trituration  of  the  food,  takes  place. 

Surface  Form. — The  outline  of  the  muscles  of  the  head  and  face  cannot  be  traced  on  the 
siu-face  of  the  body,  except  in  the  case  of  two  of  the  masticatory  muscles.  Those  of  the  head 
are  thin,  so  that  the  outline  of  the  bone  is  perceptible  beneath  them.  Those  in  the  face  are 
small,  covered  by  soft  skin,  and  often  by  a  considerable  layer  of  fat,  so  that  their  outline  is  con- 
cealed, but  they  serve  to  round  off  and  smooth  prominent  borders  and  to  fill  up  what  would  be 
otherwise  unsightly  angular  depressions.  Thus,  the  Orbicularis  palpebrarum  rounds  off  the 
prominent  margin  of  the  orbit,  and  the  Pyramidalis  nasi  fills  in  the  sharp  depression  beneath 
the  glabella,  and  thus  softens  and  tones  down  the  abrupt  depression  which  is  seen  on  the  un- 
clothed bone,  In  like  manner,  the  labial  muscles,  converging  to  the  lips  and  assisted  by  the 
superimposed  fat,  fill  in  the  sunken  hollow  of  the  lower  part  of  the  face.  Although  the  muscles 
of  the  face  are  usually  described  as  arising  from  the  bones  and  inserted  into  the  nose,  lips,  and 
corners  of  the  mouth,  they  have  fibres  inserted  into  the  skin  of  the  face  along  their  whole  extent, 
so  that  almost  every  point  of  the  skin  of  the  face  has  its  muscular  fibre  to  move  it;  hence  it  is 
that  when  in  action  the  facial  muscles  produce  alterations  in  the  skin-surface,  giving  rise  to  the 
formation  of  various  folds  or  wrinkles,  or  otherwise  altering  the  relative  position  of  the  parts, 
so  as  to  produce  the  varied  expressions  with  which  the  face  is  endowed;  hence  these  muscles 
are  termed  the  muscles  of  expression.'-  The  only  two  muscles  in  this  region  which  greatly  influence 
surface  form  are  the  Masseter  and  the  Temporal.  The  Masseter  is  a  quadi'ilateral  muscle, 
which  imparts  fulness  to  the  hinder  part  of  the  cheek.  When  the  muscle  is  firmly  contracted,  as 
when  the  teeth  are  clenched,  its  outline  is  plainly  visible;  the  anterior  border  forms  a  prominent 
vertical  ridge,  behind  which  is  a  considerable  fulness,  especially  marked  at  the  lower  part  of  the 
muscle;  this  fulness  is  entirely  lost  when  the  mouth  is  opened  and  the  muscle  no  longer  in  a 
state  of  contraction.  The  Temporal  muscle  is  fan-shaped,  and  fills  the  temporal  fossa,  sub- 
stituting for  it  a  somewhat  convex  form,  the  anterior  part  of  which,  on  account  of  the  absence 
of  hair  over  the  temple,  is  more  marked  than  the  posterior,  and  stands  out  in  strong  relief  when 
the  muscle  is  in  a  state  of  contraction. 

MUSCLES  AND  FASCIA  OF  THE  NECK. 

The  muscles  of  the  neck  may  be  arranged  into  groups  corresponding  with  the 
region  in  which  they  are  situated. 
These  groups  are  nine  in  number: 

1.  Superficial  Cervical  Region.  5.  Pharyngeal  Region. 

2.  Infrahyoid  Region.  6.  Palatal  Region. 

3.  Suprahyoid  Region.  7.  Anterior  Vertebral  Region. 

4.  Lingual  Region.  8.  Lateral  Vertebral  Region. 

9.  Muscles  of  the  Larynx. 

Man  and  Animals,  and  several  articles  in  the  Journal  of 


MUSCLES  AND  FASCIA  OF  THE  NECK 


381 


The  muscles  contained  in  each  of  these  groups  are  the  following: 


1.  Superficial  Region. 

Platysma. 
Sternomastoid. 


2.  Infrahyoid  Region. 

Sternohyoid. 
Sternothyroid. 
Thyrohyoid. 
Omohyoid. 


3.  Suprahyoid  Region. 

Digastric. 
Stylohyoid. 
Mylohyoid. 
Geniohyoid. 


4.  Lingual  Region. 

Geniohyoglossus. 

Hyoglossus. 

Chondroglossus. 

Styloglossus. 

Palatoglossus. 
^   f  Superior  lingual. 
g  J  Inferior  lingual. 
5  1  Transverse  lingual. 
E\   t  Vertical  lingual. 


W 


5.  Muscles  of  the  Pharynx. 

Inferior  constrictor. 
Middle  constrictor. 
Superior  constrictor. 
Stylopharyngeus. 
Palatopharyngeus. 
Salpingopharyngeus. 

6.  Muscles  of  the  Soft  Palate. 

Levator  palati. 
Tensor  palati. 
Azygos  uvulae. 
Palatoglossus. 
Palatopharyngeus. 
Salpingopharyngeus. 

7.  Muscles  of  the  Anterior  Vertebral 

Region. 

Rectus  capitis  anticus  major. 
Rectus  capitis  anticus  minor. 
Rectus  capitis  lateralis. 
Longus  colli. 

8.  Muscles  of  the  Lateral  Vertebral 

Region . 

Scalenus  anticus. 
Scalenus  medius. 
Scalenus  posticus. 

9.  Muscles  of  the  Larynx  {Intrinsic). 

Included  in  the  description  of  the 
Larynx  (page  1172.) 


1.  The  Superficial  Cervical  Region. 

Platysma.  Sternomastoid. 

Dissection. — A  block  having  been  placed  at  the  back  of  the  neck,  and  the  face  turned  to 
the  side  opposite  that  to  be  dissected,  so  as  to  place  the  parts  upon  the  stretch,  make  two  trans- 
verse incisions,  one  from  the  chin,  along  the  margin  of  the  mandible,  to  the  mastoid  process, 
and  the  other  along  the  upper  border  of  the  clavicle.  Connect  these  by  an  oblique  incision 
made  in  the  course  of  the  Sternomastoid  muscle,  from  the  mastoid  process  to  the  sternum;  the 
two  flaps  of  integument  having  been  removed  in  the  direction  shown  in  Fig.  286,  the  superficial 
fascia  will  be  exposed. 

The  superficial  cervical  fascia  is  a  thin,  aponeurotic  lamina  which  is  hardly 
demonstrable  as  a  separate  membrane.     It  invests  the  Platysma. 

The  Platysma  (^platysma)  (Fig.  287)  is  a  broad,  thin  plane  of  muscle  fibres 
situated  on  the  side  of  the  neck.  It  arises  by  thin,  fibrous  bands  from  the  fascia 
covering  the   upper  part  of  the  Pectoral  and   Deltoid  muscles;   its  fibres  pass 


382  THE  MUSCLES  AND  FASCIA 

over  the  clavicle  and  proceed  obliquely  upward  and  inward  along  the  side  of  the 
neck.  The  anterior  fibres  interlace,  below  and  behind  the  symphysis  menti, 
with  the  fibres  of  the  muscle  of  the  opposite  side;  the  posterior  fibres  pass  over 
the  mandible,  some  of  them  are  attached  to  the  bone  below  the  external  oblique 
line,  others  pass  on  to  be  inserted  into  the  skin  and  subcutaneous  tissue  of  the 
lower  part  of  the  face,  and  many  of  these  fibres  blend  with  the  muscles  about  the 
angle  and  lower  part  of  the  mouth.  Sometimes  fibres  can  be  traced  to  the  Zygo- 
matic muscles  or  to  the  margin  of  the  Orbicularis  oris.  Beneath  the  Platysma 
the  external  jugular  vein  may  be  seen  descending  in  a  line  from  the  angle  of  the 
mandible  to  the  middle  of  the  clavicle. 

Relations, — By  its  superficial  surface,  with  the  integument,  to  which  it  is  united  more  closely 
below  than  above;  by  its  deej}  surface,  with  the  Pectoralis  major  and  Dehoid,  and  with  the 
clavicle.  In  the  nech,  with  the  external  and  anterior  jugular  veins,  the  deep  cervical  fascia,  the 
superficial  branches  of  the  cervical  plexus,  the  Sternomastoid,  Sternohyoid,  Omohyoid,  and 
Digastric  muscles.  Behind  the  Sternomastoid  muscle  the  Platysma  covers  in  the  posterior  tri- 
angle of  the  neck;  on  the  /ace  it  is  in  relation  with  the  parotid  gland,  the  facial  artery  and  vein, 
and  the  Masseter  and  Buccinator  muscles. 

Nerves. — The  lower  division  of  the  facial  nerve  supplies  this  muscle. 

Action. — The  Platysma  produces  a  slight  wrinkling  of  the  surface  of  the  skin  of  the  neck 
in  an  oblique  direction,  when  the  entire  muscle  is  brought  into  action.  Its  anterior  portion, 
the  thickest  part  of  the  muscle,  depresses  the  mandible;  it  also  serves  to  draw  down  the  lower 
lip  and  the  angle  of  the  mouth  on  each  side,  thus  being  one  of  the  chief  agents  in  the  expression 
of  melancholy.  In  the  pressure  upon  the  bloodvessels  of  the  neck  induced  by  strong  inspira- 
tory effort,  this  muscle  draws  away  the  skin  and  fascia,  and  by  so  doing  greatly  diminishes 
the  pressure  on  the  veins. 

The  deep  cervical  fascia  {fascia  colli)  (Fig.  297)  lies  under  cover  of  the  Platysma 
muscle  and  constitutes  a  complete  investment  for  the  neck.  It  also  forms  a 
sheath  for  the  carotid  vessels,  and,  in  addition,  is  prolonged  deeply  in  the  shape 
of  certain  processes  or  lamellae,  which  come  into  close  relation  with  the  structures 
situated  in  front  of  the  vertebral  column. 

The  investing  portion  of  the  fascia  is  attached,  behind,  to  the  ligamentum  nuchae 
and  to  the  spine  of  the  seventh  cervical  vertebra.  It  forms  a  thin  investment 
for  the  Trapezius  muscle,  at  the  anterior  border  of  which  it  is  continued  forward 
as  a  loose  areolar  layer,  which  covers  the  posterior  triangle  of  the  neck;  thence 
it  passes  to  the  posterior  border  of  the  Sternomastoid,  where  it  begins  to  assume 
the  appearance  of  a  fascial  membrane.  Along  the  hinder  edge  of  the  Sternomastoid 
tlie  membrane  divides  to  enclose  this  muscle,  at  the  anterior  edge  of  which  it  once 
more  forms  a  single  lamella,  which  roofs  in  the  anterior  triangle  of  the  neck, 
and,  reaching  forward  to  the  middle  line,  is  continuous  with  the  corresponding 
part  from  the  opposite  side  of  the  neck.  In  the  middle  line  of  the  neck  it  is 
attached  to  the  symphysis  menti  and  to  the  body  of  the  hyoid  bone. 

Above,  the  fascia  is  attached  to  the  superior  curved  line  of  the  occiput,  to  the 
mastoid  process  of  the  temporal,  and  to  the  whole  length  of  the  body  of  the  man- 
dible. Opposite  the  angle  of  the  mandible  the  fascia  is  very  strong,  and  binds 
the  anterior  edge  of  the  Sternomastoid  firmly  to  that  bone.  Between  the  mandible 
and  the  mastoid  process  it  ensheaths  the  parotid  gland — the  layer  which  covers 
the  gland  extending  upward  (parotid  fascia)  to  be  fixed  to  the  zygomatic  arch. 
The  parotid  fascia  is  prolonged  forward  to  cover  the  Masseter  muscle,  the  masse- 
teric fascia.  From  the  layer  which  passes  under  the  parotid  a  strong  band,  the 
stylomandibular  ligament,  reaches  from  the  styloid  process  to  the  angle  of  the 
mandible.  Three  other  bands  may  be  defined — the  internal  lateral  ligament  of 
the  temporomandibular  articulation  (p.  279),  the  pterygomandibular,  and  the 
pterygospinous  ligaments.  The  pterygospinous  ligament  stretches  across  from 
the  upper  half  of  the  posterior  free  border  of  the  external  pterygoid  plate  to  the 
spinous  process  of  the  sphenoid.     It  occasionally  ossifies,  producing  an  adventi- 


THE  SUPERFICIAL  CERVICAL  REGION 


383 


tious  pterygospinous  foramen,  which  transmits  the  branches  of  the  mandibular 
division  of  the  trigeminal  nerve  to  the  muscles  of  mastication. 

Below,  the  cervical  fascia  is  attached  to  the  acromion  process,  the  clavicle,  and 
to  the  manubrium  sterni.  Some  little  distance  above  the  last-named  point,  how- 
ever, it  splits  into  two  layers,  superficial  and  deep.  The  former  is  attached  to 
the  anterior  border  of  the  manubrium,  the  latter  to  its  posterior  border  and  to 
the  interclavicular  ligament.  Between  these  two  layers  is  a  slit-like  interval, 
the  suprasternal  space  (spatium  suprasternale).     It  contains  a  small  quantity  of 


Trochlear  process  of  deep  cervical 
fascia  for  Omohyoid  tendon. 

OMOHYOID. 

Thyioid  body  ' 


Common  caiohd  ai  teiy 


Internal  jugidai  vein 


TERNOMASTO 


Vagus} 

nerve.  y~      U"  '/, 


External "] 
jugtdar   > 


0^- Anterior  jugular  vein. 

STERNOHYOID. 
-STERNOTHYROID, 

Pretracheal  fascia. 
Ti  achea. 


(Esophagus. 
Prevertebral  fascia. 

LONGUS   COLLI, 


■61h  cervical. 
Vertebral  vessels. 


TRAPEZIUS  — 


-SEMISPINALIS    COLLL 


COMPLEXUS. 
SPLENIUS   CAPITIS. 


Fig.  297.— Section  of  the  i 


ck  at  about  the  level  of  the  sixth  cervical  vertebr; 
deep  cervical  fascia. 


Showing  the  arrangement  of  the 


areolar  tissue,  sometimes  a  lymph  node,  the  lower  portions  of  the  anterior  jugular 
veins  and  their  transverse  connecting  branch,  and  also  the  sternal  heads  of  the 
Sternomastoid  muscles. 

The  fascia  which  covers  the  deep  aspect  of  the  Sternomastoid  gives  off  certain  im- 
portant processes,  viz. :  (1)  A  trochlear  process  to  envelop  the  tendon  of  the  Omohy- 
oid, and  bind  it  down  to  the  sternum  and  first  costal  cartilage.  (2)  A  strong  sheath, 
the  carotid  sheath,  for  the  large  vessels  of  the  neck,  enclosed  within  which  are  the 
carotid  artery,  internal  Jugular  vein,  the  vagus,  and  descendens  hypoglossi  nerves. 


384  THE  MUSCLES  AND  FASCIA 

(3)  The  prevertebral  fascia  {fascia  praevertebralis) ,  which  extends  inward  behind 
the  carotid  vessels,  where  it  assists  in  forming  their  sheath,  and  passes  in  front 
of  the  prevertebral  muscles.  It  thus  forms  the  posterior  limit  of  a  fibrous  compart- 
ment which  contains  the  larynx  and  trachea,  the  thyroid  gland,  and  the  pharynx 
and  oesophagus.  The  prevertebral  fascia  is  fixed  above  to  the  base  of  the  skull, 
while  below  it  is  continued  into  the  thorax  in  front  of  the  Longus  colli  muscles. 
Parallel  to  the  carotid  vessels  and  along  their  inner  aspect  it  gives  off  a  thin 
lamina,  the  buccopharyngeal  fascia,  which  closely  invests  the  Constrictor  muscles 
of  the  pharynx,  and  is  continued  forward  from  the  Superior  constrictor  on  to  the 
Buccinator.  The  prevertebral  fascia  is  attached  to  the  prevertebral  layer  by 
loose  connective  tissue  only,  and  thus  an  easily  distended  space,  the  retropharyngeal 
space,  is  found  between  them.  This  space  is  limited  above  by  the  base  of  the 
skull,  while  below  it  extends  behind  the  oesophagus  into  the  thorax,  where  it  is 
continued  into  the  posterior  mediastinum.  This  fascia  is  also  prolonged  downward 
and  outward  behind  the  carotid  vessels  and  in  front  of  the  Scaleni  muscles,  and 
forms  a  sheath  for  the  brachial  plexus  of  nerves  and  for  the  subclavian  vessels  in  the 
posterior  triangle  of  the  neck,  and,  continuing  under  the  clavicle  as  the  axillary 
sheath,  it  becomes  attached  to  the  deep  surface  of  the  costocoracoid  membrane. 
Immediately  above  the  clavicle  an  areolar  space  exists  between  the  investing  layer 
and  the  sheath  of  the  subclavian  vessels,  and  in  it  are  found  the  lower  part  of  the 
external  jugular  vein,  the  descending  clavicular  nerves,  the  suprascapular  and 
transversalis  colli  vessels,  and  the  posterior  belly  of  the  Omohyoid  muscle.  This 
space  extends  downward  behind  the  clavicle,  and  is  limited  below  by  the  fusion 
of  the  costocoracoid  membrane  with  the  anterior  wall  of  the  axillary  sheath. 

(4)  The  pretracheal  fascia,  which  extends  inward  in  front  of  the  carotid  vessels,  and 
assists  in  forming  the  carotid  sheath.  It  is  further  continued  behind  the  Depressor 
muscles  of  the  hyoid  bone,  and,  after  enveloping  the  thyroid  body,  is  prolonged 
in  front  of  the  trachea  to  meet  the  corresponding  layer  of  the  opposite  side. 
Above,  it  is  fixed  to  the  hyoid  bone,  while  below  it  is  carried  downward  in  front  of 
the  trachea  and  large  vessels  at  the  root  of  the  neck,  and  ultimately  blends  with  the 
fibrous  pericardium.  This  layer  is  fused  on  either  side  with  the  prevertebral 
layer,  with  which  it  completes  the  compartment  containing  the  larynx  and  trachea^ 
the  thyroid  gland,  the  pharynx,  and  oesophagus. 

Applied  Anatomy. — The  deep  cervical  fascia  is  of  considerable  importance  from  a  surgical 
point  of  view.  As  will  be  seen  from  tlie  foregoing  description,  it  may  be  divided  into  tliree  layers : 
(1)  A  superficial  layer;  (2)  a  layer  passing  in  front  of  the  trachea,  and  forming  with  the  super- 
ficial layer  a  sheath  for  the  Depressors  of  the  hyoid  bone;  (3)  a  prevertebral  layer  passing  in 
front  of  the  bodies  of  the  cervical  vertebrae,  and  forming  with  the  second  layer  a  space  in  which 
are  contained  the  trachea,  oesophagus,  etc.  The  superficial  layer  forms  a  complete  investment 
for  the  neck.  It  is  attached  behind  to  the  ligamentum  nuchae  and  the  spine  of  the  seventh  cer- 
vical vertebra;  above,  it  is  attached  to  the  external  occipital  protuberance,  to  the  superior  curved 
!ine  of  the  occiput,  to  the  mastoid  process,  to  the  zygoma  and  the  mandible;  below,  it  is  attached 
to  the  manubrium  sterni,  the  clavicle,  theacromion  process,  and  the  spine  of  the  scapula;  in 
front  it  blends  with  the  fascia  of  the  opposite  side.  This  layer  opposes  the  extension  of  abscesses 
or  new  growths  toward  the  surface,  and  pus  forming  beneath  ithas  a  tendency  to  extend  laterally. 
If  pus  is  in  the  posterior  triangle,  it  might  extend  backward  under  the  Trapezius,  forward  under 
the  Sternomastoid,  or  downward  under  the  clavicle  for  some  distance,  until  stopped  by  the 
junction  of  the  cervical  fascia  to  the  costocoracoid  membrane.  If  the  pus  is  contained  in  the 
anterior  triangle,  it  might  find  its  way  into  the  anterior  mediastinum,  being  situated  in  front 
of  the  layer  of  fascia  which  passes  down  into  the  thorax  to  become  continuous  with  the  peri- 
cardium; but  owing  to  the  lesser  density  and  thickness  of  the  fascia  in  this  situation  it  more 
frequently  finds  its  way  through  it  and  points  above  the  sternum.  The  second  layer  of  fascia, 
is  connected  above  with  the  hyoid  bone.  It  passes  down  beneath  the  Depressors  and  in  front 
of  the  thyroid  body  and  trachea  to  become  continuous  with  the  fibrous  layer  of  the  pericardium. 
Laterally  it  invests  the  great  vessels  of  the  neck  and  is  connected  with  the  superficial  layer  beneath 
the  Sternomastoid.  Pus  forming  beneath  this  layer  would  in  all  probability  find  its  way  into 
the  posterior  mediastinum.  The  third  layer  (the  prevertebral  fascia)  is  connected  above  to  the 
base  of  the  skull.    Pus  forming  beneath  this  layer,  in  cases,  for  instance,  of  caries  of  the  bodie? 


THE  SUPEB.FICIA  L   CER  VIVA  L  REGION 


.385 


of  the  cervical  vertebrae,  mislit  extend  toward  the  posterior  and  lateral  part  of  the  neck  and 
point  in  this  situation,  or  inifjht  ])ertorate  this  layer  of  fascia  and  the  pharyngeal  fascia  and 
point  into  the  pharynx  {riiropharyngcal  ahsccss). 

In  cases  of  cut  throat  the  cervical  fascia  is  of  considerable  importance.  When  the  v>ound 
involves  only  the  superficial  layer  the  injury  is  usually  trivial,  the  only  special  danger  being 
injury  to  the  external  jugular  vein,  and  the  only  special  complication  being  diffuse  cellulitis. 
But  where  the  second  of  the  two  layers  has  been  opened  up,  and  where  important  structures  may 
have  been  injured,  serious  results  may  ensue. 

The  Sternomastoid  (?n.  siernocleidomasfoideus)  (Fig.  298)  is  a  large,  thick 
muscle,  which  passes  obliquely  across  the  side  of  the  neck,  being  enclosed  between 
two  layers  of  the  deep  cervical  fascia.  It  is  thick  and  narrow  at  its  central 
part,  but  is  broader  and  thinner  at  each  extremity.  It  arises,  by  two  heads,  from 
the  sternum  and  clavicle.  The  sternal  portion  is  a  rounded  fasciculus,  tendinous 
in  front,  fleshy  behind,  which  arises  from  the  upper  and  anterior  part  of  the  first 
piece  of  the  sternum,  and  is  directed  upward,  outward,  and  backward.  The 
clavicular  portion  arises  from  the  inner  tliird  of  the  superior  border  and  anterior 
surface  of  the  clavicle,  being  composed,  of  fleshy  and  aponeurotic  fibres;  it  is 
directed  almost  vertically  upward.     These  two  portions  are  separated  from  each 


Fig.  29S. — Muscles  of  the  neck  and  boundaries  of  the  triangles. 


other,  at  their  origin,  by  a  triangular  cellular  interval,  but  become  gradually 
blended,  below  the  middle  of  tlie  neck,  into  a  thick,  rounded  muscle,  which  is 
inserted,  by  a  strong  tendon,  into  the  outer  surface  of  tlae  mastoid  process  of  tlie 
temporal  bone,  from  its  apex  to  its  superior  border,  and  by  a  thin  aponeurosis 
into  the  outer  half  of  the  superior  curved  line  of  the  occipital  bone.  The  Sterno- 
mastoid varies  much  in  its  extent  of  attachment  to  the  clavicle;  in  one  case  the 
clavicular  may  be  as  narrow  as  the  sternal  portion ;  in  another,  the  former,  may  be 


386  THE  MUSCLES  AND  FASCIA 

as  much  as  three  inches  in  breadth.  When  the  clavicular  origin  is  broad,  it  is 
occasionallj'  subdivided  into  numerous  slips  separated  by  narrow  intervals. 
More  rarely,  the  corresponding  margins  of  the  Sternomastoid  and  Trapezius 
have  been  found  in  contact. 

Triangles  of  the  Neck. — The  Sternomastoid  muscle  divides  the  quadrilateral  area  of  the  side 
of  the  neck  into  two  triangles,  an  anterior  and  a  posterior.  The  boundaries  of  the  anterior 
triangle  are,  \n  front,  the  median  Hne  of  the  neck;  above,  the  lower  border  of  the  body  of  the 
mandible,  and  an  imaginary  line  drawn  from  the  angle  of  the  mandible  to  the  mastoid  process; 
behind,  the  anterior  border  of  the  Sternomastoid  muscle.  The  apex  of  the  triangle  is  at  the 
upper  border  of  the  sternum.  The  bdundaries  of  the  posterior  triangle  are,  in  front,  the  pos- 
terior border  of  the  Sternomastoid;  helow,  the  middle  third  of  the  clavicle;  behind,  the  anterior 
margin  of  the  Trapezius.'  The  apex  corresponds  with  the  meeting  of  the  Sternomastoid  and  ' 
Trapezius  on  the  occipital  bone. 

Relations. — By  its  superfieial  surface,  with  the  integument  and  Platysma,  from  which  it  is 
separated  by  the  external  jugular  vein,  some  of  the  superficial  branches  of  the  cervical  plexus, 
and  the  superficial  layer  of  the  deep  cervical  fascia.  By  its  deep  surface  it  is  in  relation  with  the 
Sternoclavicular  articulation;  a  process  of  the  deep  cervical  fascia;  the  Sternohyoid,  Sterno- 
thyroid, Omohyoid,  posterior  belly  of  the  Digastric,  Levator  anguli  scapulae,  Splenius  and 
Scaleni  muscles;-  common  carotid  artery,  internal  jugular  vein,  commencement  of  the  internal 
and  external  carotid  arteries,  the  occipital,  subclavian,  transversalis  colli,  and  suprascapular 
arteries  and  veins;  the  phrenic,  vagus,  hypoglossal,  descendens  and  communicans  hypoglossi 
nerves;  the  spinal  accessory  nerve,  which  pierces  its  upper  third;  the  cervical  plexus,  parts 
of  the  thyroid  and  parotid  glands,  and  deep  lymph  nodes. 

Nerves. — The  Sternomastoid  is  supplied  by  the  spinal  accessory  nerve  and  deep  branches 
of  the  cervical  plexus. 

Actions. — When  only  one  Sternomastoid  muscle  acts,  it  draws  the  head  toward  the  shoulder 
of  the  same  side,  assisted  by  the  Splenius  and  the  Obliquus  capitis  inferior  of  the  opposite  side. 
At  the  same  time  it  rotates  the  head  so  as  to  carry  the  face  toward  the  opposite  side.  When 
the  two  muscles  act  together  they  flex  the  head  upon  the  neck.  If  the  head  is  fixed,  the  two 
muscles  assist  in  elevating  the  thorax  in  forced  inspiration. 

Applied  Anatomy. — The  applied  anatomy  of  the  Sternomastoid  muscle  is  of  importance 
chieflv  in  connection  with  the  deformity  known  as  wrij-neck  (torticollis).  Wry-neck  may  be 
either  acquired,  congenital,  or  spasmodic.  The  acquired  may  be  caused  by  acute  glandular 
enlargement,  cellulitis  of  the  neck,  myositis  of  the  Sternomastoid,  or  cervical  caries.  The  con- 
genital variety  is  due  to  injury  of  the  Sternomastoid  during  birth,  which  probably  causes  a 
subsequent  chronic  fibrous  myositis  (Mikulicz).  This  is  best  remedied  by  making  an  open 
horizontal  incision  over  the  origin  of  the  muscle  and  exposing  it.  A  director  is  then  passed 
underneath  and  the  muscle  clearly  divided,  making  sure  that  any  tense  bands  of  fascia  are  thor- 
oughly divided.  Spasmodic  torticollis  is  a  condition  of  adult  life.  It  is  marked  by  clonic  or 
tonic  spasm,  first  of  the  Sternomastoid,  then  of  many  of  the  other  neck  muscles.  It  is  thought 
to  be  a  disease  of  the  central  nerve  system. 

2.  The  Infrahyoid  Region  (Figs.  298,  299). 

Depressors  of  the  Hyoid  Bone  and  Larynx. 

Sternohyoid.  ,  Thyrohyoid. 

Sternothyroid.  Omohyoid. 

Dissection. — The  muscles  in  this  region  may  be  exposed  by  removing  the  deep  fascia  from  the 
front  of  the  neck.  In  order  to  see  the  entire  extent  of  the  Omohyoid  it  is  necessary  to  divide 
the  Sternomastoid  at  its  centre,  and  turn  its  ends  aside,  and  to  detach  the  Trapezius  from  the 
clavicle  and  scapula.    This,  however,  should  not  be  done  until  the  Trapezius  has  been  dissected. 

The  Sternohyoid  (m.  stemohyoideus)  is  a  thin,  narrow,  ribbon-like  muscle, 
which  arises  from  the  inner  extremity  of  the  clavicle,  the  posterior  sternoclavicular 
ligament,  and  the  upper  and  posterior  part  of  the  first  piece  of  the  sternum; 
passing  upward  and  inward,  it  is  inserted,  by  short,  tendinous  fibres,  into  the  lower 
border  of  the  body  of  the  hyoid  bone.     This  muscle  is  separated,  below,  from 

'  The  anatomy  of  these  triangles  will  be  more  exactly  described  with  that  of  the  vessels  of  the  neck. 


THE  INFRAHYOID  REGION 


387 


its  fellow  by  a  considerable  interval;  but  the  two  muscles  come  into  contact  with 
each  other  in  the  middle  of  their  course,  and  from  this  upward  lie  side  by  side. 
It  sometimes  presents,  immediately  above  its  origin,  a  transverse  tendinous 
intersection,  like  those  in  the  Rectus  abdominis.  As  a  rule,  two  bursa?  (hursae 
sternohyoidii)  lie  between  the  cricothyroid  membrane  and  the  Sternohyoid 
muscle. 


Relations. — By  its  superficial  surface,  below,  with  the  sternum,  the  sternal  end  of  the  clavicle, 
and  the  Sternomastoid;  and  above,  with  the  Platysma  and  deep  cervical  fascia;  by  its  deep  sur- 
face, with  the  Sternothyroid,  Cricothyroid,  and  Thyrohyoid  muscles,  the  thyroid  gland,  the 
superior  thyroid  vessels,  the  thyroid  cartilage,  the  cricothyroid  and  thyrohyoid  membranes. 

The  Sternothyroid  (m.  sternothyreoideus)  is  situated  beneath  the  preceding 
muscle,  but  is  shorter  and  wider  than  it.  It  arises  from  the  posterior  surface  of 
the  first  piece  of  the  sternum,  below  the  origin  of  the  Sternohyoid,  and  from  the 
edge  of  the  cartilage  of  the  first  rib,  occasionally  of  the  second  rib  also,  and  is 
inserted  into  the  oblique  line  on  the  side  of  the  ala  of  the  thyroid  cartilage.  This 
muscle  is  in  close  contact  with  its  fellow  at  the  lower  part  of  the  neck,  and  is  occa- 


FlG.  299. — Muscles  of  the  neck.     Anterior  view. 

sionally  traversed  by  a  transverse  or  oblique  tendinous  intersection,  like  those  in 
the  Rectus  abdominis. 

Relations.— By  its  superficial  surface,  with  the  Sternohyoid,  Omohyoid,  and  Sternomastoid; 
by  its  deep  surface,  from  below  upward,  with  the  trachea,  innominate  veins,  common  carotid 
(and  on  the  right  side  the  innominate  artery),  the  thyroid  gland  and  its  vessels,  and  the  lower 
part  ofthe  larynx  and  pharynx.  The  inferior  thyroid  vein  lies  along  its  inner  border,  a  relation 
which  it  is  important  to  remember  in  the  operation  of  tracheotomy.  On  the  left  side  the  deep 
surface  of  the  muscle  is  in  relation  to  the  oesophagus. 

The  Thyrohyoid  {m.  thyreohyoideus)  is  a  small,  quadrilateral  muscle  appear- 
ing like  a  continuation  of  the  Sternothyroid.     It  arises  from  the  oblique  line  on 


388  THE  MUSCLES  AND  FASCIA 

the  side  of  the  thyroid  cartilage,  and  passes  vertically  upward  to  be  inserted  into 
the  lower  border  of  the  body  and  greater  cornu  of  the  hyoid  bone. 

Relations. — By  its  superficial  surface,  with  the  Sternohyoid  and  Omohyoid  muscles;  by  its 
deep  surface,  with  the  thyroid  cartilage,  the  thyrohyoid  membrane,  and  the  superior  laryngeal 
vessels  and  nerve. 

The  Omohyoid  (m.  omoliyoideus)  passes  across  the  side  of  the  neck,  from  the 
scapula  to  the  hyoid  bone.  It  consists  of  two  fleshy  bellies,  united  by  a  central 
tendon.  It  arises  from  the  upper  border  of  the  scapula,  and  occasionally  from  the 
transverse  ligament  which  crosses  the  suprascapular  notch,  its  extent  of  attach- 
ment to  the  scapula  varying  from  one-sixth  of  an  inch  to  an  inch.  From  this 
origin  the  posterior  belly  {venter  inferior)  forms  a  flat,  narrow  fasciculus,  which 
inclines  forward  and  slightly  upward  across  the  lower  part  of  the  neck,  behind 
the  Sternomastoid  muscle,  where  it  becomes  tendinous;  it  then  changes  its  direc- 
tion, forming  an  obtuse  angle,  and  terminates  in  the  anterior  belly  {venter  superior), 
which  passes  almost  vertically  upward,  close  to  the  outer  border  of  the  Sternohyoid, 
to  be  inserted  into  the  lower  border  of  the  body  of  the  hyoid  bone,  just  external  to 
the  insertion  of  the  Sternohyoid.  The  central  tendon  of  this  muscle,  which  varies 
much  in  length  and  form,  is  held  in  position  by  a  process  of  the  deep  cervical 
fascia,  which  includes  it  in  a  sheath.  This  process  is  prolonged  down,  to  be 
attached  to  the  clavicle  and  first  rib.  It  is  by  this  means  that  the  angular  form  of 
the  muscle  is  maintained. 

The  posterior  belly  of  the  Omohyoid  divides  the  posterior  triangle  of  the  neck  into  an  upper 
or  occipital,  and  a  lower  or  subclavian  triangle,  while  its  anterior  belly  divides  the  anterior 
triangle  of  the  neck  into  an  upper  or  carotid,  and  a  lower  or  muscular  triangle. 

Relations. — By  its  superficial  surface,  with  the  Trapezius,  the  Sternomastoid,  deep  cervical 
fascia,  Platysma,  and  integument;  by  its  deep  surface,  with  the  Scaleni  muscles,  phrenic  nerve, 
lower  cervical  nerves  which  go  to  form  the  brachial  plexus,  the  suprascapular  vessels  and  nerve, 
sheath  of  the  common  carotid  artery  and  internal  jugular  vein,  the  Sternothyroid  and  Thyro- 
hyoid  muscles. 

Nerves. — The  Depressors  of  the  hyoid  bone  are  supplied  by  branches  from  the  ansa  ceni- 
calis  formed  by  the  first  three  cervical  nerves. 

Actions. — These  muscles  depress  the  larynx  and  hyoid  bone,  after  they  have  been  drawn 
up  with  the  pharynx  in  the  act  of  deglutition.  The  Omohyoid  muscles  not  only  depress  the 
hyoid  bone,  but  carry  it  backward  and  to  one  side.  This  bone  is  concerned  especially  in  pro- 
longed inspiratory  efforts;  for  by  rendering  the  lower  part  of  the  cervical  fascia  tense  it  lessens 
the  inward  suction  of  the  soft  parts,  which  would  otherwise  compress  the  great  vessels  and  the 
apices  of  the  lungs.  This  action  is  synergistic  with  that  of  the  Platysma.  The  Thyrohyoid 
may  act  as  an  elevator  of  the  thyroid  cartilage  when  the  hyoid  bone  ascends,  drawing  u]jward 
the  thyroid  cartilage,  behind  this  bone.  The  Sternothyroid  acts  as  a  depressor  of  the  thyroid 
cartilage. 

3.  The  Suprahyoid  Region  (Figs.  298,  299). 

Elevators  of  the  Hyoid  Bone — Depressors  of  the  Mandible. 

Digastric.  Mylohyoid. 

Stylohyoid.  Geniohyoid. 

Dissection. — To  dissect  these  muscles  a  block  should  be  placed  beneath  the  back  of  the 
neck,  and  the  head  drawn  backward  and  retained  in  that  position.  On  the  removal  of  the 
deep  fascia  the  muscles  are  at  once  exposed. 

The  Digastric  (m.  digastricus)  consists  of  two  fleshy  bellies  united  by  an  inter- 
mediate, rounded  tendon.  It  is  a  small  muscle,  situated  below  the  side  of  the 
body  of  the  mandible,  and  extending,  in  a  curved  form,  from  the  side  of  the 
head  to  the  symphysis  of  the  mandible.  The  posterior  belly  {venter  posterior), 
longer  than  the  anterior,  arises  from  the  digastric  groove  on  the  inner  side  of  the 
mastoid  process  of  the  temporal  bone,  and  passes  downward,  forward,  and  inward. 


THE  >SUmAHYOn)  REGION 


3S9 


The  anterior  belly  {venter  anterior)  arises  from  a  depression  on  the  inner  side 
of  the  lower  border  of  the  mandible,  close  to  the  symphysis,  and  passes  downward 
and  backward.  The  two  bellies  terminate  in  the  central  tendon  which  per- 
forates the  Stylohyoid,  and  is  held  in  connection  with  the  side  of  the  body  and 
the  greater  cornu  of  the  hyoid  bone  by  a  fibrous  loop,  lined  with  a  synovial  mem- 
brane. A  broad  aponeurotic  layer  is  given  off  from  the  tendon  of  the  Digastric 
on  each  side,  which  is  attaciied  to  the  body  and  greater  cornu  of  the  hyoid  bone; 
this  is  termed  the  suprahyoid  aponeurosis.  It  forms  a  strong  layer  of  fascia  between 
the  anterior  portions  of  the  two  muscles,  and  a  firm  investment  for  the  other  muscles 
of  the  suprahyoid  region  which  lie  deeper. 

Relations. — By  its  superficial  surface,  with  the  mastoid  process,  the  Platysma,  Sternomastoid, 
part  of  the  Splenius,  Trachelomastoid,  and  Stylohyoid  muscles,  and  the  parotid  gland.  By 
its  deep  surface,  the  anterior  belly  lies  on  the  Mylohyoid;  the  posterior  belly  on  the  Styloglossus, 
Stylopharyngeus,  and  Hyoglossus  muscles,  the  external  carotid  artery  and  its  occipital,  lingual, 
facial,  and  ascending  pharyngeal  branches,  the  internal  carotid  artery,  internal  jugular  vein, 
and  hypoglossal  nerve. 

The  Stylohyoid  (m.  stylohyoideus)  is  a  small,  slender  muscle,  lying  in  front  of 
and  above  the  posterior  belly  of  the  Digastric.  It  arises  from  the  back  and  outer 
surface  of  the  styloid  process  of  the  temporal  bone,  near  the  base;  and,  passing 
downward  and  forward,  is  inserted  into  the  body  of  the  hyoid  bone,  just  at  its 
junction  with  the  greater  cornu,  and  immediately  above  the  Omohyoid.  This 
muscle  is  perforated,  near  its  insertion,  by  the  tendon  of  the  Digastric. 


Fig.  300.— Mylohyoid  muscle.     (P. 


d  Charpy.) 


Relations. — By  its  superficial  surface,  above, -viilh- the  parotid  gland  and  deep  cervical  fascia; 
below,  this  muscle  is  superficial,  being  situated  immediately  beneath  the  deep  cervical  fascia. 
By  its  deep  surface,  with  the  posterior  belly  of  the  Digastric,  the  external  carotid  artery,  with 
its  lingual  and  facial  branched,  the  Hyoglossus  muscle,  and  the  hypoglossal  nerve. 

The  Stylohyoid  Ligament  (licjamentum  stylohyoideus). — In  connection  with  the 
Stylohyoid  muscle  may  be  described  a  ligamentous  band,  the  stylohyoid  ligament. 
It  is  a  fibrous  cord,  often  containing  a  little  cartilage  in  its  centre,  which  continues 
the  styloid  process  down  to  the  hyoid  bone,  being  attached  to  the  tip  of  t!ie 
former  and  to  the  lesser  cornu  of  the  latter.  It  is  often  more  or  less  ossified, 
and  in  many  animals  forms  a  distinct  bone,  the  epihyal. 

The  Mylohyoid  (?ra.   mylohyoideus)  (Fig.  300)   is  a  flat,  triangular  muscle, 


390 


THE  MUSCLES  AND  FASCIA 


situated  immediately  beneath  the  anterior  belly  of  the  Digastric,  and  forming, 
with  its  fellow  of  the  opposite  side,  a  muscular  floor  for  the  cavity  of  the  mouth. 
It  arises  from  the  whole  length  of  the  mylohyoid  ridge  of  the  mandible,  extending 
from  the  symphysis  in  front  to  the  last  molar  tooth  behind.  The  posterior  fibres 
pass  inward  and  slightly  downward,  to  be  iiiserted  into  the  body  of  the  hyoid 
bone.  The  middle  and  anterior  fibres  are  inserted  into  a  median  fibrous  raphe, 
extending  from  the  symphysis  of  the  mandible  to  the  hyoid  bone,  where  they 
join  at  an  angle  with  the  fibres  of  the  opposite  muscle.  The  median  raphe  is 
sometimes  wanting;  the  muscle  fibres  of  the  two  sides  are  then  directly  continuous 
with  one  another. 

Relations. — By  its  superficial  surface,  with  the  Platysma,  the  anterior  belly  of  the  Digastric, 
the  suprahvoid  aponeurosis,  the  submaxillary  gland,  submental  vessels,  and  mylohyoid  vessels 
and  nerve;  by  its  deep  surface,  with  the  Geniohyoid,  part  of  the  Hyoglossus  and  Styloglossus 
muscles,  the  hypoglossal  and  lingual  nerves,  the  submaxillary  ganglion,  the  sublingual  gland, 
the  deep  portion  of  the  submaxillary  gland  and  duct;  the  sublingual  and  ranine  vessels,  and 
the  buccal  mucous  membrane. 


Fig.  301. — Muscles  of  the  tongue.    Left  side.i 


Dissection. — The  Mylohyoid  should  now  be  removed,  in  order  to  expose  the  muscles  which 
lie  beneath;  this  is  effected  by  reflecting  it  from  its  attachments  to  the  hyoid  bone  and  man- 
dible, and  separating  it  by  a  vertical  incision  from  its  fellow  of  the  opposite  side. 

The  Geniohyoid  (?«.  geniohyoideus)  (Fig.  301)  is  a  'narrow,  slender  muscle, 
situated  immediately  beneath^  the  inner  border  of  the  Mylohyoid.  It  arises  from 
the  inferior  genial  tubercle  on  the  inner  side  of  the  symphysis  of  the  mandible, 
and  passes  downward  and  backward,  to  be  inserted  into  the  anterior  surface  of 
the  body  of  the  hyoid  bone.  This  muscle  lies  in  close  contact  with  its  fellow  of 
the  opposite  side,  and  increases  slightly  in  breadth  as  it  descends. 

'  The  muscles  and  ligaments  attached  to  the  styloid  process  have  been  termed  the  "  bouquet  of  Riolanua." 
-  This  refers  to  the  depth  of  the  muscles  from  the  skin  in  the  order  of  dissection.     In  the  erect  position  of  the 
bodj'  the  Geniohyoid  is  above  the  Mylohyoid. 


THE  LINGUAL   RF.GION  391 

Relations. — It  is  covered  by  the  Mylohyoid  and  lies  along  the  lower  border  of  the  Genio- 
hyoglossus. 

Nerves. — The  anterior  belly  of  the  Digastric  is  supplied  by  the  mylohyoid  "Sranch  of  the 
inferior  dental;  its  posterior  belly,  by  the  facial;  the  Stylohyoid  is  su|)plicd  by  the  facial;  tlie 
Mylohyoid,  by  the  mylohyoid  branch  of  the  inferior  dental;  the  Geniohyoid,  by  a  branch  from 
the  ansa  cervicalis  which  accompanies  the  hypoglossal  in  a  common  sheath. 

Actions. — This  group  of  muscles  performs  two  very  important  actions.  They  raise  the  hyoid 
bone,  and  with  it  the  base  of  the  tongue,  during  the  act  of  deglutition;  or,  when  the  hyoid  bone 
is  fixed  by  its  Depressors  and  those  of  the  larynx,  they  depress  the  mandible.  During  the  first 
act  of  deglutition,  when  the  mass  is  being  driven  from  the  mouth  into  the  pharynx,  the  hyoid  bone, 
and  with  it  the  tongue,  is  carried  upward  and  forAvard  by  the  anterior  belly  of  the  Digastric, 
the  Mylohyoid,  and  Geniohyoid  muscles.  In  the  second  act,  when  the  mass  is  passing  through 
the  pharynx,  the  direct  elevation  of  the  hyoid  bone  takes  place  by  the  combined  action  of  all 
the  muscles;  and  after  the  food  has  passed,  the  hyoid  bone  is  carried  upward  and  backward 
by  the  posterior  belly  of  the  Digastric  and  Stylohyoid  muscles,  w-hich  assist  in  preventing  the 
return  of  the  bolus  into  the  mouth. 


''-   4.  The  Lingual  Region  (Figs.  301,  302). 

Geniohyoglossus.  Styloglossus. 

Hyoglossus.  Palatoglossus.' 

Chondroglossus. 

Dissection. — After  completing  the  dissection  of  the  preceding  muscles,  saw  through  the 
mandible  just  external  to  the  symphysis.  Then  draw  the  tongue  forw'ard,  and  attach  it,  by  a 
stitch,  to  the  nose;  when  its  muscles,  which  are  thus  put  on  a  stretch,  may  be  examined.    ^ 

The  Geniohyoglossus  {m.  genioglossus)  has  received  its  name  from  its  triple 
attachment  to  the  mandible,  hyoid  bone,  and  tongue.  It  is  a  flat,  triangular 
muscle,  placed  vertically  on  either  side  of  the  middle  line,  its  apex  corresponding 
with  its  point  of  attachment  to  the  mandible,  its  base  with  its  insertion  into  the 
tongue  and  hyoid  bone.  It  arises  by  a  short  tendon  from  the  superior  genial 
tubercle  on  the  inner  side  of  the  symphysis  of  the  mandible,  immediately  above 
the  Geniohyoid;  from  this  point  the  muscle  spreads  out  in  a  fan-like  form,  a  few 
of  the  inferior  fibres  passing  downward,  to  be  attached  by  a  thin  aponeurosis 
into  the  upper  part  of  the  body  of  the  hyoid  bone,  a  few  fibres  passing  between 
the  Hyoglossus  and  Chondroglossus  to  blend  with  the  Constrictor  muscles  of 
the  pharynx;  the  middle  fibres  passing  backward,  and  the  superior  ones  upward 
and  forward,  to  enter  the  whole  length  of  the  under  surface  of  the  tongue,  from 
the  base  to  the  apex.  The  two  muscles  lie  on  either  side  of  the  median  plane; 
behind  they  are  quite  distinct  from  each  other,  and  are  separated  at  their  insertion 
into  the  under  surface  of  the  tongue  by  a  tendinous  raphe,  which  extends  through 
the  middle  of  the  organ.  In  front  the  two  muscles  are  more  or  less  blended; 
distinct  fasciculi  are  to  be  seen  passing  off  from  one  muscle,  crossing  the  middle 
line,  and  intersecting  with  bundles  of  fibres  derived  from  the  muscle  on  the  other 
side. 

Relations. — By  its  deep  surface  this  muscle  is  in  contact  with  its  fellow  of  the  opposite  side; 
by  its  superficial  surface,  with  the  Inferior  lingualis,  the  Hyoglossus,  the  lingual  artery  and 
hypoglossal  nerve,  the  lingual  nerve,  and  sublingual  gland;  by  its  upper  border,  with  the  mucous 
membrane  of  the  floor  of  the  mouth  (fremnn  linguae);  by  its  loiver  border  with  the  Geniohyoid. 

The  Hyoglossus  (m.  hyoc/lossus)  is  a  thin,  flat,  quadrilateral  muscle  which 
arises  from  the  side  of  the  body  and  whole  length  of  the  greater  cornu  of  the 
hyoid  bone,  and  passes  almost  vertically  upward  to  enter  the  side  of  the  tongue, 

I  The  Palatoglossus,  or  constrictor  isthmi  faucitim,  although  one  of  the  muscles  of  the  tongue  which  serA'es 
to  draw  the  base  of  that  organ  upward  during  the  act  of  deglutition,  is  more  nearly  associated,  both  in  situation 
and  function,  with  the  soft  palate.     It  will  consequently  be  described  with  the  group  of  Palatal  muscles. 


392 


THE  MUSCLES  AND  FASCIA 


between  the  Stj'loglossus  and  Lingualis.  The  fibres  of  this  muscle  which  arise 
from  the  body  are  directed  upward  and  backward,  overlapping  those  arising 
from  the  greater  cornu,  which  are  directed  upward  and  forward. 

Relations. — By  its  superficial  surface,  with  the  Digastric,  the  Stylohyoid,  Styloglossus,  and 
Mylohyoid  muscles,  the  submaxillary  ganglion,  the  lingual  and  hypoglossal  nerves,  the  sub- 
maxillary duct,  the  ranine  vein,  the  sublingual  gland,  and  the  deep  portion  of  the  submaxillary 
gland.  By  its  deep  surface,  with  the  Stylohyoid  ligament,  the  Geniohyoglossus,  Lingualis,  and 
Sliddle  constrictor,  the  lingual  vessels,  and  the  glossopharyngeal  nerve. 


The  Chondroglossus  (m.  choiidroglossus)  is  a  distinct  muscular  slip,  though  it  is 
sometimes  described  as  a  part  of  the  Hyoglossus,  from  which,  however,  it  is  sepa- 
rated by  the  fibres  of  the  Geniohyoglossus,  which  pass  to  the  side  of  the  pharynx. 
It  is  about  three-quarters  to  an  inch  in  length;  it  arises  from  the  inner  side  and 
base  of  the  lesser  cornu  and  contiguous  portion  of  the  body  of  the  hyoid  bone, 
and  passes  directly  upward  to  blend  with  the  Intrinsic  muscle  fibres  of  the  tongue, 
between  the  Hyoglossus  and  Geniohyoglossus. 

The  Styloglossus  (m.  styloglossus),  the  shortest  and  smallest  of  the  three  styloid 
muscles,  arises  from  the  anterior  and  outer  side  of  the  styloid  process,  near  the 
apex,  and  from  the  stylomandibular  ligament,  to  which  its  fibres,  in  most  cases, 

are  attached  by  a  thin  aponeurosis.  Passing 
downward  and  forward  between  the  internal 
and  external  carotid  arteries,  and  becoming 
nearly  horizontal  in  its  direction,  this  muscle 
divides  upon  the  side  of  the  tongue  into  two 
portions — one  longitudinal,  which   enters  the 


.^-9 


^^OffilpiU*^ 


OUT   EDGE    OF  SUPERIOR    LINGUALIS. 

Fig.  302. -Muscles  on  the  dorsum  of 
the  tongue. 


Fig.  303. — Coronal  section  of  tongue.  Showing  intrinsic 
muscles,  a.  Lingual  artery.  6.  Inferior  lingualis.  cut  through,  c. 
Fibres  of  Hyoglossus.  d.  Oblique  fibres  of  Styloglossus,  e.  Inser- 
tion of  Transverse  lingualis.  f.  Superior  lingualis.  g.  Papillse  of 
tongue,  h.  Vertical  fibres  of  Geniohyglossus  intersecting  Trans- 
verse lingualis.     i.  Septum.      (Altered  from  Krause.) 


side  of  the  tongue  near  its  dorsal  surface  and  blends  with  the  fibres  of  the 
Lingualis  in  front  of  the  Hyoglossus;  the  other  oblique,  which  overlaps  the 
Hyoglossus  muscle  and  decussates  with  its  fibres. 


Relations. — By  its  superficial  surface,  from  above  downward,  with  the  parotid  gland,  the 
Internal  pterygoid  muscle,  the  lingual  nerve,  and  the  mucous  membrane  of  the  mouth;  by  its 
deep  surface,  with  the  tonsil,  the  Superior  constrictor,  and  the  Hyoglossus  muscle. 

Nerves. — The  muscles  of  this  group  are  supplied  by  the  hypoglossal  nerve. 


THE  LINGUAL  RECflON  393 

The  Muscle  Substance  of  the  Tongue  (Figs.  302  and  303).— The  muscle  fibres  of  the  tongue 
run  in  \:irii)us  directions.  These  fibres  are  divifled  into  two  sets — Extrinsic  and  Intrinsic.  The 
Extrinsic  muscles  of  the.  tongue  are  those  which  have  their  origin  external  to,  and  only  their 
terminal  fibres  contained  ipilhin,  the  substance  of  the  organ.  They  are:  the  Styloglossus,  the 
Ilyoglossus,  the  Palatoglossus,  the  Geniohyoglossus,  and  part  of  the  Superior  constrictor  of  the 
pharynx  (Pharyngoglossus).  The  Intrinsic  muscles  are  those  which  are  contained  entirely 
irithin  the  tongue,  and  which  form  the  giM'alcr  pari  of  its  muscular  structure. 

The  tiinguc  consists  of  .synnuelrical  halves  separated  from  each  other  in  the  middle  line  by 
a  fibrous  septum  [srpium  liiii/iiar).  Kach  half  is  composed  of  muscle  fibres  arranged  in  various 
directions,  containing  much  interposed  fat,  and  .supplied  by  vessels  and  nerves.  Immediately 
beneath  the  mucous  membrane  is  a  submucous  fibrous  layer,  into  which  the  muscle  fibres  whicSi 
terminate  in  this  stratum  of  the  tongue  are  inserted.  Upon  removing  this,  with  the  mucous 
membrane,  the  first  stratum  of  muscle  fibres  is  exposed.  This  belongs  to  the  group  of  Intrinsic 
muscies,  and  has  been  named  the  Superior  lingualis  (m.  longitiidinnli.y  .sw(/«r/«/-).  It  consists 
of  a  thin  layer  of  oblique  and  longitudinal  fibres  which  arise  from  the  siilniiiicous  fibrous  layer, 
close  to  the  epiglottis,  and  fVoiii  the  fibrous  septum,  and  which  pass  forward  and  outward  to  the 
edges  of  the  tongue.  Between  lis  fibres  pass  some  vertical  fibres  derived  from  the  Geniohyo- 
glossus and  from  the  vertical  Intrinsic  muscle,  which  will  be  described  later  on. 

Beneath  this  layer  is  the  second  stratum  of  muscle  fibres,  derived  principally  from  the 
Extrinsic  muscles.  In  front  this  stratum  is  formed  by  the  fibres  derived  from  the  Styloglossus, 
which  run  along  the  side  of  the  tongue  and  which  in  turn  send  out  two  sets  of  fibres.  The  first 
of  these  two  latter  sets  of  fibres  extends  over  the  dorsum  and  runs  obliquely  forward  and  inward 
to  the  middle  line.  The  second  set  of  fibres  goes  on  to  the  under  surface  of  the  sides  of  the  anterior 
part  of  the  tongue,  and  runs  between  the  fibres  of  the  Hyoglossus  muscle  forward  and  inward 
to  the  middle  line.  Behind  this  layer  of  fibres,  derived  from  the  Styloglossus,  are  fibres  derived 
from  the  Hyoglossus,  assisted  by  some  few  fibres  of  the  Palatoglossus.  The  Hyoglossus,  enter- 
ing the  side  of  the  under  surface  of  the  tongue,  between  the  Styloglossus  and  Inferior  lingualis, 
passes  around  its  margin  and  spreads  out  into  a  layer  on  the  dorsum,  which  occupies  the  middle 
third  of  the  organ,  and  runs  almost  transversely  inward  to  the  septum.  It  is  reenforced  by 
some  fibres  from  the  Palatoglossus;  other  fibres  of  this  muscle  pass  more  dee|jly  and  inter- 
mingle with  the  next  layer.  The  posterior  part  of  the  second  layer  of  the  muscle  fibres  of  tlie 
tongue  is  derived  from  those  fibres  of  the  Hyoglossus  which  arise  from  the  lesser  cornu  of  the 
hyoid  bone,  and  are  here  described  as  a  separate  muscle — the  Chondroglossus.  The  fibres 
of  this  muscle  are  arranged  in  a  fan-shaped  manner,  and  spread  out  over  the  posterior  third 
of  the  tongue. 

Beneath  this  layer  is  the  third  layer,  the  great  mass  of  Intrinsic  muscles  of  the  tongue,  which 
is  intersected  at  right  angles  by  the  terminal  fibres  of  one  of  the  Extrinsic  muscles — the  Genio- 
hyoglossus. This  portion  of  the  tongue  is  paler  in  color  and  softer  in  texture  than  that  already 
described,  and  is  sometimes  designated  the  medullary  portion  in  contradistinction  to  the  firmer 
superficial  part,  wliich  is  lerneil  the  cnrliral  portion.  The  medullary  portion  consists  largely 
of  Iransvi-rsc  fibres,  the  Trail,  verse  liimualis,  and  of  vertical  fibres,  the  Vertical  lingualis.  The 
Transverse  Mngualis  (m.  traii^versus  linguae)  forms  the  largest  portion  of  the  third  layer  of 
muscle  fibres  of  the  tongue.  The  fibres  arise  from  the  median  septum,  and  pass  outward  to  be 
inserted  into  the  submucous  fibrous  layer  at  the  sides  of  the  tongue.  Intermingled  with  these  trans- 
\erse  intrinsic  fibres  are  transverse  extrinsic  fibres  derived  from  the  Palatoglossus  and  the  Superior 
constrictor  of  the  pharynx.  These  transverse  extrinsic  fibres,  however,  run  in  the  opposite 
direction,  passing  inward  toward  the  septum.  Intersecting  the  transverse  fibres  are  a  large 
number  of  vertical  fibres  derived  partly  from  the  Geniohyoglossus  and  partly  from  intrinsic 
fibres,  the  Vertical  lingualis.  The  fibres  derived  from  the  Geniohyoglossus  enter  the  under 
surface  of  the  tongue  on  each  side  of  the  median  septum  from  base  to  apex.  They  ascend  in 
a  radiating  manner  to  the  dorsum,  being  inserted  into  the  submucous  fibrous  layer  covering 
the  tongue  on  each  side  of  the  middle  line.  The  Vertical  lingualis  (m.  verticalis  linguae)  is 
found  only  at  the  borders  of  the  forepart  of  the  tongue,  external  to  the  fibres  of  the  Geniohyo- 
glossus. Its  fibres  extend  from  the  upper  to  the  under  surface  of  the  organ,  and  decussate 
with  the  fibres  of  the  other  muscles,  and  especially  with  those  of  the  Transverse  lingualis. 

The  fonrth  layer  of  muscle  fibres  of  the  tongue  consists  partly  of'  extrinsic  fibres  derived  from 
the  Styloglossus,  and  partly  of  intrinsic  fibres,  the  Inferior  lingualis.  At  the  sides  of  the  under 
surface  of  the  organ  are  some  fibres  derived  from  the  Styloglossus,  which,  as  it  runs  forward 
at  the  side  of  the  tongue,  gives  off  fibres  which,  passing  forward  and  inward  between  the  fibres 
of  the  Hyoglossus,  form  an  inferior  oblique  stratum  which  joins  in  front  with  the  anterior  fibres 
of  the  Inferior  lingualis.  The  Inferior  lingualis  (7?;.  longitndinalis  inferior)  is  a  longitudinal 
band,  situated  on  the  under  surface  of  the  tongue,  and  extending  from  the  base  to  the  apex  of  the 
organ.  Behind,  some  of  its  fibres  are  connected  with  the  body  of  the  hyoid  bone.  It  lies  between 
the  Hyoglossus  and  the  Geniohyoglossus,  and  in  front  of  the  Hyoglossus  it  enters  into  relation 
with  the  Styloglossus,  with  the  fibres  of  which  it  blends.  It  is  in  relation  by  its  under  surface 
with  the  ranine  artery. 


394  THE  MUSCLES  AND  FASCIuE 

Applied  Anatomy. — The  fibrous  septum  which  exists  between  the  two  halves  of  the  tongue 
is  almost  complete,  so  that  the  anastomosis  between  the  two  lingual  arteries  is  not  very  free, 
a  fact  often  illustrated  by  injecting  one-half  of  the  tongue  with  colored. gelatin,  while  the  other 
half  is  left  uninjected  or  may  be  injected  with  gelatine  of  a  different  color. 

This  is  a  point  of  considerable  importance  in  connection  with  removal  of  one-half  of  the 
tono-ue  for  cancer,  an  operation  which  is  now  frequently  resorted  to  when  the  disease  is  strictly 
confined  to  one  side  of  the  anterior  portion  of  the  tongue.  If  the  mucous  membrane  is  divided 
lon^ituilinallv  exactly  in  the  middle  line,  the  tongue  can  be  split  into  halves  along  the  median 
rapht'  witli:>ut  any  appreciable  hemorrhage,  and  the  diseased  half  can  then  be  removed. 

Actions. — The  movements  of  the  tongue,  although  numerous  and  complicated,  may  be  under- 
stood by  carefully  considering  the  direction  of  the  fibres  of  its  muscles.  The  Geniohyoglossi 
muscles,  by  means  of  their  posterior  fibres,  draw  the  base  of  the  tongue  forward,  so  as  to  pro- 
trude the  apex  from  the  mouth.  The  anterior  fibres  draw  the  tongue  back  into  the  mouth.  The 
whole  length  of  these  two  muscles,  acting  along  the  middle  line  of  the  tongue,  draw  it  down- 
ward, so  as  to  make  it  concave  from  side  to  side,  forming  a  channel  along  which  fluids  may 
pass  toward  the  pharynx,  as  in  sucking.  The  Hyoglossi  muscles  depress  the  tongue  and  draw 
down  its  sides,  so  as  to  render  it  convex  from  side  to  side.  The  Styloglossi  muscles  draw  the 
tongue  upward  and  backward.  The  Palatoglossi  muscles  draw  the  Isase  of  the  tongue  upward. 
With  regard  to  the  Intrinsic  muscles,  both  the  Superior  and  Inferior  lingualis  tend  to  shorten 
the  tongue,  but  the  former,  in  addition,  turn  the  tip  and  sides  upward  so  as  to  render  the  dorsum 
concave,  while  the  latter  pull  the  tip  downward  and  cause  the  dorsum  to  become  convex.  The 
Transverse  lingualis  narrows  and  elongates  the  tongue,  and  the  Vertical  lingualis  flattens  and 
broadens  it.  The  complex  arrangement  of  the  muscle  fibres  of  the  tongue,  and  the  various 
directions  in  which  they  run,  give  to  this  organ  the  power  of  assuming  the  various  forms  neces- 
sary for  the  enunciation  of  the  different  consonantal  sounds. 


5.  The  Pharyngeal  Region  (Figs.  304,  305). 

Inferior  constrictor.  Superior  constrictor. 

Middle  constrictor.  Stylopharyngeus. 

Palatopharyngeus.       )   ,f^  ,        ,.      s 

Q  1   •         1  I  (See  next  section.) 

balpingopharyngeus.    )  ^  -' 

Dissection  (Fig.  304). — In  order  to  examine  the  muscles  of  the  pharynx,  cut  through  the 
trachea  and  oesophagus  just  above  the  sternum,  and  draw  them  upward  by  dividing  the  loose 
areolar  tissue  connecting  the  pharynx  with  the  front  of  the  vertebral  column.  The  parts  being 
drawn  well  forward,  apply  the  edge  of  the  saw  immediately  behind  the  styloid  processes,  and 
saw  the  base  of  the  skull  through  from  below  upward.  The  pharynx  and  mouth  should  then 
be  stuffed  with  tow,  in  order  to  distend  its  cavity  and  render  the  muscles  tense  and  easier  of 
dissection. 

Tlie  Inferior  constrictor  {m.  constrictor  pharyngis  inferior),  the  most  superficial 
and  thickest  of  the  three  Constrictors,  arises  from  the  side  of  the  cricoid  cartilages, 
in  the  interval  between  the  Cricothyroid  muscle  in  front  and  the  articular  facet 
for  the  thyroid  cartilage  behind;  from  the  oblique  line  on  the  side  of  the  ala  of 
the  thyroid  cartilage,  the  cartilaginous  surface  behind  it,  nearly  as  far  as  its  posterior 
border,  and  from  the  inferior  cornu.  From  these  origins  the  fibres  spread  back- 
ward and  inward,  to  be  inserted  into  the  fibrous  raphe  in  the  posterior  median 
line  of  the  pharynx.  The  inferior  fibres  are  horizontal,  and  continuous  with  the 
fibres  of  the  oesophagus;  the  rest  ascend,  increasing  in  obliquity,  and  overlap 
the  ^Middle  constrictor. 

Relations. — The  Inferior  Constrictor  is  covered  by  a  thin  membrane  which  surrounds  the 
entire  pharynx,  the  buccopharyngeal  fascia  (fascia  buccopharyngea).  Behind,  this  fascia  is  in 
relation  with  the  vertebral  column  and  the  prevertebral  fascia  and  muscles;  laterally,  with  the 
thyroid  gland,  the  common  carotid  artery,  and  the  Sternothyroid  muscle;  by  its  deep  surface, 
with  the  Middle  constrictor,  the  Stylopharyngeus,  Palatopharyngeus,  the  fibrous  coat  and 
mucous  membrane  of  the  pharynx.  The  internal  laryngeal  nerve  and  the  laryngeal  branch 
of  the  superior  thyroid  artery  pass  near  the  upper  border,  and  the  recurrent  laryngeal  nerve 
and  the  laryngeal  branch  of  the  inferior  thyroid  artery,  beneath  the  lower  border  of  this  muscle, 
previous  to  their  entering  the  larynx. 


THE  PHARYNGEAL  REGION 


395 


The  Middle  constrictor  (in.  constrictor  pharyngis  medius)  is  a  flattened,  fan- 
shaped  muscle,  smaller  than  the  preceding.  It  arises  from  the  whole  length  ol 
the  upper  border  of  the  greater  cornu  of  the  hyoid  bone,  from  the  lesser  cornu, 
and  from  the  stylohyoid  ligament.  The  fibres  diverge  from  their  origin,  the  lower 
ones  descending  beneath  the  Inferior  constrictor,  the  middle  fibres  passing  trans- 
versely, and  the  upper  fibres  ascending  and  overlapping  the  Superior  constrictor. 
The  muscle  is  inserted  into  the  posterior  median  fibrous  raph^,  blending  in  the 
middle  line  with  its  fellow  of  the  opposite  side. 

Relations. — Between  this  muscle  and  the  Superior  constrictor  are  the  glossopharyngeal  ner\'e, 
the  Stylopharyngeus  muscle  and  the  stylohyoid  Hgament;  and  between  it  and  the  Inferior  con- 
strictor is  the  superior  laryngeal  nerve.     Behind,  the  Middle  constrictor  lies  on  the  vertebral 
column,    the   Longus    colli,  and    the  Rectus 
capitis  anticus  major.     0?^  each  side  it  is  in 
relation  with  the  carotid  vessels,  the  pharyn- 
geal plexus,  and   some   lymph  nodes.    Near 
its  origin  it  is  covered  by  the  Hyoglossus,  the 
lingual  vessels  being  placed  between  the  two 
muscles.     It  lies  upon  the  Superior  constric- 
tor, the  Stylopharyngeus,  the  Palatopharyn- 
geus,   the     fibrous     coat,    and    the    mucous 
membrane  of  the  pharynx. 

The  Superior  constrictor  (m.  con- 
strictor pliarijiKjis  superior)  is  a  quadri- 
lateral muscle,  thinner  and  paler  than 
the  other  Constrictors,  and  situated 
at  the  upper  part  of  the  pharynx.  It 
arises  from  the  lower  half  of  the  posterior 
margin  of  the  internal  pterygoid  plate 
and  its  hamular  process,  from  the  con- 
tiguous portion  of  the  palate  bone  and 
the  reflected  tendon  of  the  Tensor  palati 
muscle,  from  the  pterygomandibular 
ligament,  from  the  ah'eolar  process 
above  the  posterior  extremity  of  the 
mylohyoid  ridge,  and  by  a  few  fibres 
from  the  side  of  the  tongue.  From 
these  points  the  fibres  curve  backward, 
to  be  inserted  into  the  median  raphe, 
being  also  prolonged  by  means  of  a 
fibrous  aponeurosis  to  the  pharyngeal 
spine  on  the  basilar  process  of  the  occipital  bone.^  The  superior  fibres  arch  beneath 
the  Levator  palati  and  the  Eustachian  tube.  The  interval  between  the  upper 
border  of  the  muscle  and  the  basilar  process  is  deficient  in  muscle  fibres  and  is 
closed  by  a  portion  of  the  pharyngeal  aponeurosis.  This  interval  is  known  as  the 
sinus  of  Morgagni  (Fig.  305). 


cles  of  the  pharynx. 


Relations. — By  its  superficial  surface  the  Superior  constrictor  is  in  relation  with  the  prever- 
tebral fascia  and  muscles,  the  vertebral  column,  the  internal  carotid  and  ascending  pharyngeal 
arteries,  the  internal  jugular  vein  and  pharyngeal  venous  plexus,  the  glossopharyngeal,  vagus, 
spinal  accessory,  hypoglossal,  lingual,  and  sympathetic  nerves,  the  Middle  constrictor  and 
Internal  pterygoid  muscles,  the  styloid  process,  the  stylohyoid  ligament,  and  the  Stylopharyn- 
geus. By  its  deep  surface,  it  is  in  relation  with  the  Palatopharyngeus,  the  tonsil,  the  fibrous, 
coat,  and  the  mucous  membrane  of  the  pharynx. 


liddle  lacerated  toramen  and  descend 


396 


THE  3IUSCLES  AND  FASCIAE 


The  Stylopharyngeus  (m.  stylopharyngeus)  is  a  long,  slender  muscle,  cylindrical 
above,  broad  and  thin  below.  It  arises  from  the  inner  side  of  the  base  of  the 
styloid  process  of  the  temporal  bone,  passes  downward  along  the  side  of  the 
pharynx  between  the  Superior  and  Middle  constrictors,  and  spreads  out  beneath 
the  mucous  membrane,  where  some  of  its  fibres  are  lost  in  the  Constrictor  muscles; 
and  others,  joining  with  the  Palatopharyngeus,  are  inserted  into  the  posterior 
border  of  the  thyroid  cartilage.  The  glossopharyngeal  nerve  runs  on  the  outer 
side  of  this  muscle,  and  crosses  over  it  in  passing  forward  to  the  tongue. 


Acces 

FRO 

OF  TEMPOR 


ilD  PROCE"- -)■;,'  \       \       V= 


STYLOPHARYNGEUS 


Fig.  305. — The  muscles  of  the  pharynx.    On  the  right  side  most  of  the  Inferior  constrictor  has  been  removed, 
on  the  left  side  the  Digastric  and  Stylohyoid  have  been  removed.    (Spalteholz.) 


Relations. — By  its  superficial  surface,  with  the  Styloglossus  muscle,  the  parotid  gland,  the 
external  carotid  artery,  and  the  Middle  constrictor;  by  its  deep  surface,  with  the  internal  carotid, 
the  internal  jugular  vein,  the  Superior  constrictor,  Palatopharyngeus,  and  pharyngeal  mucous 
membrane. 

Nerves. — The  Constrictors  are  supplied  by  branches  from  the  pharyngeal  plexus  formed 
by  the  vagus,  glossopharyngeal,  and  sympathetic  nerves.  The  Inferior  constrictor  also  receives 
an  additional  branch  from  the  external  laryngeal  nerve  and  one  from  the  recurrent  laryngeal 
The  Stylopharyngeus  is  supplied  by  a  branch  from  the  glossopharyngeal  nerve. 


THE  PALATAL  BEG  TON  397 

Actions. — When  deglutition  is  about  to  be  performed,  the  pharynx  is  drawn  upward  and 
dilated  in  different  directions,  to  receive  the  bolus  propelled  into  it  from  the  mouth.  The  Stylo- 
pharyngei,  which  are  much  farther  removed  from  one  another  at  their  origin  than  at  their  inser- 
tion, draw  the  sides  of  the  pharynx  upward  and  outward,  and  so  increase  its  transverse  diameter; 
its  breadth  in  the  antero-posterior  direction  is  increased  by  the  larynx  and  tongue  being  carried 
forward  in  their  ascent.  As  soon  as  the  bolus  is  received  in  the  pharynx,  the  Elevator  muscles 
relax,  the  bag  descends,  and  the  Constrictors  contract  upon  the  bolus,  and  convey  it  gradually 
downward  into  the  (Esophagus.  Besides  its  action  in  deglutition,  the  pharynx  also  exerts  an 
important  influence  in  the  modulation  of  the  voice,  especially  in  the  production  of  the  higher 
tones. 

6.  The  Palatal  Region  (Fig.  306). 

Levator  palati.  Palatoglossu.s. 

Tensor  palati.  Palatopharyngeus. 

Azygos  uvulae.  Salpingopharyngeus. 

Dissection  (Fig.  306). — Lay  open  the  pharynx  from  behind  by  a  vertical  incision  extending 
from  its  upper  to  its  lower  part,  and  partially  divide  the  occipital  attachment  by  a  transverse 
incision  on  each  side  of  the  vertical  one;  the  posterior  surface  of  the  soft  palate  is  then  exposed. 
Having  fixed  the  uvula  so  as  to  make  it  tense,  the  mucous  membrane  and  glands  should  be 
carefully  removed  from  the  posteriar  surfa:'e  of  the  soft  palate,  and  the  muscles  of  this  part 
are  at  once  exposed. 

The  Levator  palati  (m.  levator  veli  palatini)  is  a  long,  thick,  rounded  muscle, 
placed  on  the  outer  side  of  the  posterior  nares.  It  arises  from  the  under  surface 
of  the  apex  of  the  petrous  portion  of  the  temporal  bone,  and  from  the  lower  margin 
of  the  cartilaginous  portion  of  the  Eustachian  tube;  after  passing  into  the  pharynx, 
above  the  upper  concave  margin  of  the  Superior  constrictor,  it  passes  obliquely 
downward  and  inward,  its  fibres  spreading  out  into  the  soft  palate  as  far  as  the 
middle  line,  where  they  blend  with  those  of  the  opposite  side. 

Relations. — By  its  superficial  surface,  this  muscle  is  in  relation  with  the  Tensor  palati,  the 
Superior  constrictor,  and  the  Eustachian  tube;  by  its  deep  surface,  with  the  mucous  membrane 
of  the  pharynx;  posteriorly,  with  the  posterior  fasciculus  of  the  Palatopharyngeus,  the  Azygos 
uvulae,  and  the  mucous  membrane  of  the  soft  palate. 

The  Tensor  palati  (m.  tensor  veli  palatini)  is  a  broad,  thin,  ribbon-like  muscle, 
placed  on  the  outer  side  of  the  Levator  palati,  and  consisting  of  a  vertical  and  a 
horizontal  portion.  The. vertical  portion  arises  by  a  flat  lamella  from  the  scaphoid 
fossa  at  the  base  of  the  internal  pterygoid  plate;  from  the  spine  of  the  sphenoid 
and  from  the  outer  side  of  the  cartilaginous  portion  of  the  Eustachian  tube; 
it  descends  vertically  between  the  internal  pterygoid  plate  and  the  inner  surface 
of  the  Liternal  pterygoid  muscle,  and  terminates  in  a  tendon,  which  winds  around 
the  hamular  process,  being  retained  in  this  situation  by  some  of  the  fibres  of  origin 
of  the  Liternal  pterygoid  muscle.  Between  the  hamular  process  and  the  tendon 
is  a  small  bursa  (bursa  m.  tensoris  veli  palati).  The  tendon  or  horizontal  portion 
then  passes  horizontally  inward,  and  is  inserted  into  a  broad  aponeurosis,  the 
palatal  aponeurosis,  and  into  the  transverse  ridge  on  the  horizontal  portion  of ' 
the  palate  bone. 

Relations, — By  its  superficial  surface,  this  muscle  is  in  relation  with  the  Internal  pterygoid; 
by  its  deep  surface,  with  the  Levator  palati,  from  which  it  is  separated  by  the  Eustachian  tube 
and  Superior  constrictor,  and  with  the  internal  pterygoid  plate.  In  the  soft  palate  its  tendon 
and  the  palatal  aponeurosis  are  anterior  to  those  of  the  Levator  palati,  being  covered  by  the 
Palatoglossus  and  the  mucous  membrane. 

Palatal  Aponeurosis. — Attached  to  the  posterior  border  of  the  hard  palate  is 
a  thin,  firm,  fibrous  lamella  which  supports  the  muscles  and  gives  strength  to  the 


398 


THE  MUSCLES  AND  FASCIJE 


soft  palate.  It  is  thicker  above  than  below,  where  it  becomes  very  thin  and 
difficult  to  define.  Laterally,  it  is  continuous  with  the  pharyngeal  aponeurosis. 
The  Azygos  uvulae  {in.  uvulae)  is  not  a  single  muscle,  as  would  be  inferred 
from  its  name,  but  a  pair  of  narrow  cylindrical  fleshy  fasciculi  placed  on  either 
side  of  the  median  line  of  the  soft  palate.  Each  muscle  arises  from  the  posterior 
nasal  spine  of  the  palate  bone  and  from  the  contiguous  tendinous  aponeurosis 
of  the  soft  palate,  and  descends  to  be  inserted  into  the  uvula. 

Relations. — Anteriorly,  with  the  tendinous  expansion  of  the  Levatores  palati;  'posteriorly, 
with  the  posterior  fasciculus  of  the  Palatopharyngeus  and  the  mucous  membrane. 

The  next  two  muscles  are  exposed  by  removing  the  mucous  membrane  from  the  pillars  of 
the  fauces  throughout  nearly  their  whole  extent. 


«  p  I  a 

Fig.  306. — Muscles  of  the  soft  palate,  the  pharynx  being  laid  open  from  behind  and 

The  Palatoglossus  (??;..  c/lossopalatinus)  is  a  small  fleshy  fasciculus,  narrower 
in  the  middle  than  at  either  extremity,  forming,  with  the  mucous  membrane 
covering  its  surface,  the  anterior  pillar  of  the  soft  palate.  It  arises  from  the  ante- 
rior surface  of  the  soft  palate  on  each  side  of  the  uvula,  and,  passing  downward, 
forward,  and  outward  in  front  of  the  tonsil,  is  inserted  into  the  side  of  the  tongue, 
some  of  its  fibres  spreading  over  the  dorsum,  and  others  passing  deeply  into  the 
substance  of  the  organ  to  intermingle  with  the  Transverse  lingualis.  In  the 
soft  palate  the  fibres  of  this  muscle  are  continuous  with  those  of  the  muscle  of 
the  opposite  side. 

The  Palatopharyngeus  (/».  pharyngopalatinus)  is  a  long,  fleshy  fasciculus, 
narrower  in  the  middle  than  at  either  extremity,   forming,  with  the  mucous. 


THE  PALATAL  REGION  ;399 

membrane  covering  its  surface,  the  posterior  pillar  of  the  soft  palate.  It  is  sepa- 
rated from  the  Palatoglossus  by  an  angular  interval,  in  which  the  tonsil  is  lodged. 
It  arises  from  the  soft  palate  by  an  expanded  fasciculus,  which  is  divided  into 
two  parts  by  the  Levator  palati  and  Azygos  uvulae.  The  posterior  fasciculus 
lies  in  contact  with  the  mucous  membrane,  and  also  joins  with  the  corresponding 
muscle  in  the  middle  line;  the  anterior  fasciculus,  the  thicker,  lies  in  the  soft  palate 
between  the  Levator  and  Tensor,  and  joins  in  the  middle  line  the  corresponding 
part  of  the  opposite  muscle.  Passing  outward  and  downward  behind  the  tonsil, 
the  Palatopharyngeus  joins  the  Stylopharyngeus,  and  is  inserted  with  that  muscle 
into  the  posterior  border  of  the  thyroid  cartilage,  some  of  its  fibres  being  lost  on 
the  side  of  the  pharynx,  and  others  passing  across  the  middle  line  posteriorly 
to  decussate  with  the  muscle  of  the  opposite  side. 

Relations. — In  the  soft  palate  its  posterior  surface  is  covered  by  mucous  membrane,  from 
which  it  is  separated  by  a  layer  of  palatal  glands.  By  its  anterior  surface  it  is  in  relation  -with 
the  Tensor  palati.  Where  it  forms  the  posterior  pillar  of  the  fauces  it  is  covered  by  mucous 
membrane,  excepting  on  its  outer  surface.  In  the  pharynx  it  lies  between  the  mucous  membrane 
and  the  Constrictor  muscles. 

The  Salpingopharyngeus  {m.  salpingopharyngeus)  arises  from  the  inferior 
part  of  the  Eustachian  tube  near  its  orifice;  it  passes  downward  and  blends  with 
the  posterior  fasciculus  of  the  Palatopharyngeus. 

In  a  dissection  of  the  soft  palate  from  its  posterior  or  nasal  surface  to  its  anterior  or  oral  sur- 
face, the  muscles  would  be  exposed  in  the  following  order — viz.,  the  posterior  fasciculus  of  the 
Palatopharyngeus,  covered  over  by  the  mucous  membrane  reflected  from  the  floor  of  the  nasal 
fossEe;  the  Azygos  uvulae;  the  Levator  palati;  the  anterior  fasciculus  of  the  Palatopharvngeus; 
the  aponeurosis  of  the  Tensor  palati,  and  the  Palatoglossus,  covered  over  by  a  reflection  from 
the  oral  mucous  membrane. 

Nerves. — The  Tensor  palati  is  supplied  by  a  branch  from  the  otic  ganglion;  tlie  remaining 
muscles  of  this  group  are  in  all  probability  supplied  by  the  internal  branch  of  the  spinal  accessory, 
the  fibres  of  which  are  distributed  along  with  certain  branches  of  the  vagus  through  the  pharyn- 
geal plexus.' 

Actions. — During  the  first  stage  of  deglutition  the  bolus  of  food  is  driven  back  into  the 
fauces  by  the  pressure  of  the  tongue  against  the  hard  palate;  the  base  of  the  tongue  is,  at  the 
same  time,  retracted,  and  the  larynx  is  raised  with  the  pharynx,  and  carried  forward  under  it. 
During  the  second  stage  the  entrance  to  the  larynx  is  closed,  not,  as  was  formerly  supposed,  by 
the  folding  backward  of  the  epiglottis  over  it,  but,  as  Anderson  Stuart  has  shown,  by  the  draw- 
ing forward  of  the  arytenoid  cartilages  toward  the  cushion  of  the  epiglottis — a  movement 
produced  by  the  contraction  of  the  outer  portion  of  the  TlijToarytenoid,  the  Arytenoid,  and 
Aryteno-epiglottidean  muscles. 

The  bolus  of  food  after  leaving  the  tongue  passes  on  to  the  posterior  or  laryngeal  surface 
of  the  epiglottis,  and  glides  along  this  for  a  certain  distance;'  then  the  Palatoglossi  muscles,  the 
constrictors  of  the  fauces,  contract  behind  the  food;  the  soft  palate  is  slightly  raised  by  the 
Levatores  palati,  and  made  tense  by  the  Tensores  palati;  and  the  Palatopharyngei,  by  their  con- 
traction, pull  the  pharynx  upward  over  the  bolus  of  food,  and  at  the  same  time  come  nearly 
together,  the  uvula  filling  up  the  slight  interval  between  them.  By  these  means  the  food  is 
prevented  from  passing  into  the  upper  part  of  the  larynx  or  the  posterior  nares;  at  the  same 
time  the  latter  muscles  form  an  inclined  plane,  directed  oblicjuely  downward  and  backward, 
along  the  under  surface  of  which  the  bolus  descends  into  the  lower  part  of  the  pharynx.  Each 
Salpingopharyngeus  raises  the  upper  and  lateral  part  of  the  pharynx — i.  e.,  that  part  which  is 
above  the  point  where  the  Stylopharyngeus  is  attached  to  the  pharynx. 

Applied  Anatomy. — After  operation  for  cleft  palate  the  Tensor  palati  and  I,ev:ifor  palati 
retard  union  by  causing  undue  tension  along  the  line  of  suture.  In  order  to  overcome  this 
it  is  necessary  to  divide  these  muscles,  and  this  is  done  by  making  longitudinal  incisions  on 
either  side,  parallel  to  the  cleft  and  just  internal  to  the  hamular  process,  in  such  a  position  as 
to  avoid  the  posterior  palatine  artery. 

1  Journal  of  .\natomy  and  Physiology,  vol.  x.xiii,  p.  .52.3. 

2  We  now  know  that  normal  deelutjtion  can  be  carried  out  when  the  epiglottis  is  so  small  that  it  cannot  cover 
the  opening  into  the  larynx,  or  when  it  has  been  removed  surgically.  In  such  cases  the  sphincter  muscles  which 
surround  the  laryngeal  aperture  contract  during  swallowing  and  prevent  the  entrance  of  foreign  bodies  into  the 
larynx. 


400 


THE  MUSCLES  AND  FASCIAE 


7.  The  Anterior  Vertebral  Region  (Fig.  307). 


Rectus  capitis  anticus  major. 
Rectus  capitis  anticus  minor. 


Rectus  capitis  lateralis. 
Longus  colli. 


The  Rectus  capitis  anticus  major  (/;i.  longus  capitis),  broad  and  thick  above 
and  narrow  below,  appears  like  a  continuation  upward  of  the  Scalenus  anticus. 
It  arises  by  four  tendinous  slips  from  the  anterior  tubercles  of  the  transverse 
processes  of  the  third,  fourth,  fifth,  and  sixth  cervical  vertebra,  and  ascends, 
convei'ging  toward  its  fellow  of  the  opposite  side,  to  be  inserted  into  the  basilar 
process  of  the  occipital  bone. 

Relations. — By  its  anterior  surface,  this  muscle  is  in  relation  with  the  pharynx,  the  inferior  cer- 
vical sympathetic  ganglion  and  nerve,  and  the  sheath  enclosing  the  internal  and  common  cai-otid 
artery,  internal  jugular  vein,  and  vagus  nerve;  by  its  posterior  surface,  with  the  Longus  colli, 
the  Rectus  capitis  anticus  minor,  and  the  upper  cervical  vertebrae. 


Fig.  307. — The  prevertebral  muscles  (ventral  view). 


The  Rectus  capitis  anticus  minor  (m.  rectus  capitis  anterior)  is  a  short,  flat 
muscle,  situated  immediately  behind  the  upper  part  of  the  preceding.  It  arises 
from  the  anterior  surface  of  the  lateral  mass  of  the  atlas  and  from  the  root  of  its 
transverse  process,  and,  passing  obliquely  upward  and  inward,  is  inserted  into 
the  basilar  process  immediately  behind  the  rectus  capitis  anticus  major. 

The  Rectus  capitis  lateralis  (m.  rectus  capitis  lateralis)  is  a  short,  flat  muscle, 
which  arises  from  the  upper  surface  of  the  transverse  process  of  the  atlas  and  is 


THE  LATERAL    VERTEBRAL  REGION  401 

inserted  into  the  under  surface  of  the  jugular  process  of  the  occipital  bone.  This 
muscle  lies  behind  the  internal  jugular  vein,  and  in  front  of  the  upper  portion  of 
the  vertebral  artery. 

The  LongUS  colli  (/«.  longus  colli)  is  a  long,  flat  muscle,  situated  on  the  anterior 
surface  of  the  vertebral  column,  between  the  atlas  and  the  third  thoracic  vertebra. 
It  is  broad  in  the  middle,  narrow  and  pointed  at  each  extremity,  and  consists 
of  three  portions — a  superior  oblique,  an  inferior  oblique,  and  a  vertical  portion. 
The  superior  oblique  portion  arises  from  the  anterior  tubercles  of  the  transverse 
processes  of  the  third,  fourth,  and  fifth  cervical  vertebrae,  and,  ascending  obliquely 
inward,  is  inserted  by  a  narrow  tendon  into  the  tubercle  on  the  anterior  arch  of 
the  atlas.  The  inferior  oblique  portion,  the  smallest  part  of  the  muscle,  arises 
from  the  front  of  the  bodies  of  the  first  two  or  three  thoracic  vertebrae,  and,  ascend- 
ing obliquely  outward,  is  inserted  into  the  anterior  tubercles  of  the  transverse 
processes  of  the  fifth  and  sixth  cervical  vertebrae.  The  vertical  portion  lies  directly 
on  the  front  of  the  vertebral  column;  it  arises,  below,  from  the  front  of  the  bodies 
of  the  upper  three  thoracic  and  lower  three  cervical  vertebrae,  and  is  inserted 
above  into  the  front  of  the  bodies  of  the  second,  third,  and  fourth  cervical  vertebrae. 

Relations. — By  its  superficial  surface,  with  the  prevertebral  fascia,  the  pharynx,  oesophagus, 
sympathetic  nerve,  the  sheath  of  the  great  vessels  of  the  neck,  the  inferior  thyroid  artery,  and  the 
recurrent  laryngeal  nerve;  by  its  deep  surface,  with  the  cervical  and  thoracic  portions  of  the 
\ertebral  cohimn.  Its  inner  border  is  separated  from  the  opposite  muscle  by  a  considerable 
interA-al  below,  but  they  approach  each  other  above. 

Nerves. — The  Rectus  capitis  anticus  minor  and  the  Rectus  lateralis  are  supplied  from  the 
loop  between  the  first  and  second  cervical  nerves;  the  Rectus  capitis  anticus  major,  by  branches 
from  the  second,  third,  and  fourth  cervical;  the  Longus  colli,  by  branches  from  the  second  to 
the  seventh  cervical  nerves. 

Actions. — The  Rectus  anticus  major  and  minor  are  the  direct  antagonists  of  the  muscles 
at  the  back  of  the  neck,  serving  to  restore  the  head  to  its  natural  position  after  it  has  been  drawn 
backward.  These  muscles  also  serve  to  flex  the  head,  and,  from  their  obliquity,  rotate  it,  so 
as  to  turn  the  face  to  one  or  the  other  side.  The  Longus  colli  flexes  and  slightly  rotates  the 
•cervical  portion  of  the  vertebral  column. 


8.  The  Lateral  Vertebral  Region  (Figs.  307,  308). 

Scalenus  anticus.  Scalenus  medius.  Scalenus  posticus. 

The  Scalenus  anticus  {m.  scalenus  anterior)  is  a  conical-shaped  muscle, 
situated  deeply  at  the  side  of  the  neck,  behind  the  Sternomastoid.  It  arises 
from  the  anterior  tubercles  of  the  transverse  processes  of  the  third,  fourth,  fifth, 
and  sixth  cervical  vertebrae,  and,  descending  almost  vertically,  is  inserted  by  a 
narrow,  flat  tendon  into  the  scalene  tubercle  on  the  inner  border  and  upper 
surface  of  the  first  rib.  The  lower  part  of  this  muscle  separates  the  subclavian 
artery  and  vein,  the  latter  being  in  front,  and  the  former,  with  the  brachial  plexus, 
behind. 

Relations. — By  its  superficial  surface,  this  muscle  is  in  relation  with  the  clavicle,  the  Sub- 
•clavius,  Sternomastoid,  and  Omohyoid  muscles,  the  transversalis  colli,  and  the  suprascapular 
arteries,  the  subclavian  vein,  and  the  phrenic  nerve;  by  its  deep  surface,  with  the  Scalenus  medius, 
pleura,  subclavian  artery,  and  brachial  plexus  of  nerves.  It  is  separated  from  the  Longus  colli, 
on  the  inner  side,  by  the  vertebral  artery.  On  the  anterior  tubercles  of  the  transverse  processes 
of  the  cervical  vertebr.'e,  between  the  attachments  of  the  Scalenus  anticus  and  Longus  colli 
lies  the  ascending  cervical  branch  of  the  inferior  thyroid  artery. 

The  Scalenus  medius  (m.  scalenus  medius),  the  largest  and  longest  of  the  three 
Scaleni,  arises  from  the  posterior  tubercles  of  the  transverse  processes  of  the  lower 
six  cervical  vertebrae,  and,  descending  along  the  side  of  the  vertebral  column. 


402 


THE  MUSCLES  AND  FASCIJE 


is  inserted  by  a  broad  attachment  into  the  upper  surface  of  the  first  rib,  behind 
the  o-roove  for  the  subclavian  artery,  as  far  back  as  the  tubercle.  It  is  separated 
from  the  Scalenus  anticus  by  the  subclavian  artery  below  and  by  the  cervical 
nerves  above.  The  posterior  thoracic,  or  nerve  of  Bell,  is  formed  in  the  substance 
of  the  Scalenus  medius  and  emerges  from  it.  The  nerve  to  the  Rhomboids  also 
pierces  it. 

Relations. — By  its  superficial  surface,  with  the  Sternomastoid;  it  is  crossed  by  the  clavicle, 
the  Omohyoid  muscle,  subclavian  artery,  and  cervical  nerves.  To  its  outer  side  is  the  Levator 
anguli  scapulae  and  the  Scalenus  posticus  muscle. 

The  Scalenus  posticus  (m.  scalenus  posterior),  the  smallest  of  the  three  Scaleni, 
arises,  by  two  or  three  separate  tendons,  from  the  posterior  tubercles  of  the  trans- 
verse processes  of  the  lower  two  or  three  cervical  vertebra,  and,  diminishing  as  it 

descends,  is  inserted  by  a  thin  tendon 
into  the  outer  surface  of  the  second 
rib,  behind  the  attachment  of  the  Ser- 
ratus  magnus.    This  is  the  most  deeply 

~ ^"^i    \  placed    of  the  three  Scaleni,    and   is 

occasionally  blended  with  the  Scalenus 
medius. 

Nerves. — The  Scalenus  anticus  receives 
branches  from  the  fourth  to  the  seventh 
cervical;  the  Scalenus  medius  from  the  third 
to  the  eighth  cervical;  and  the  Scalenus 
posticus,  from  the  fom-th  to  the  eighth  cer- 
vical nerves. 

Actions. — The  Scaleni  muscles,  when  they 
take  their  fixed  point  from  above,  elevate 
the  first  and  second  ribs,  and  are,  therefore, 
inspiratory  muscles.  When  they  take  their 
fixed  point  from  below,  they  bend  the  verte- 
bral column  to  one  or  the  other  side.  If  the 
muscles  of  both  sides  act,  lateral  movement 
is  prevented,  but  the  vertebral  column  is 
slightly  flexed.  The  Rectus  lateralis,  acting 
on  one  side,  bends  the  head  laterally. 

Surface  Form. — The  muscles  in  the  neck, 
with  the  exception  of  the  Platysma,  are  in- 
vested by  the  deep  cervical  fascia,  which 
softens  down  their  form,  and  is  of  consid- 
erable importance  in  connection  with  deep 
cervical  abscesses  and  tumors,  modifying 
the  direction  of  the  growth  of  tumors  and 
of  the  enlargement  of  abscesses,  and 
causing  them  to  extend  laterally  instead 
of  toward  thfc  surface.  The  Platysma  does  not  influence  surface  form  except  when  in  action, 
when  it  produces  wrinkling  of  the  skin  of  the  neck,  which  is  thrown  into  oblique  ridges  parallel 
with  the  fasciculi  of  the  muscle.  Sometimes  this  contraction  takes  place  suddenly  and  repeatedly 
as  a  sort  of  spasmodic  twitching,  the  result  of  a  nervous  habit.  The  Sternomastoid  is  the  most 
important  muscle  of  the  neck  as  regards  its  surface  form.  If  the  muscle  is  put  into  action  by 
drawing  the  chin  downward  and  to  the  opposite  shoulder,  its  surface  form  will  be  plainly  out- 
lined. The  sternal  origin  will  stand  out  as  a  sharply  defined  ridge,  while  the  clavicular  origin 
will  present  a  flatter  and  not  so  prominent  outline.  The  fleshy  middle  portion  will  appear  as 
an  oblique  roll  or  elevation,  with  a  thick,  rounded  anterior  border  gradually  becoming  less 
marked  above.  On  the  opposite  side — i.  e.,  on  the  side  to  which  the  head  is  turned — the  outline 
is  lost,  its  place  being  occupied  by  an  oblique  groove  in  the  integument.  When  the  muscle  is 
at  rest  its  anterior  border  is  still  visible,  forming  an  oblique  rounded  ridge,  terminating  below 
in  a  sharp  outline  of  the  sternal  head.  The  posterior  border  of  the  muscle  does  not  show  above 
the  clavicular  head.  The  anterior  border  is  defined  by  drawing  a  line  from  the  tip  of  the  mas- 
toid process  to  the  sternoclavicular  joint.    It  is  an  important  surface-marking  in  the  operation 


Fig.  308. — Scaleni  muscles.     (Poirier  and  Charpy.) 


MUSCLES  AND  FASCIAE  OF  THE  TRUNK 


403 


of  ligation  of  the  common  carotid  artery  and  in  some  other  operations.  Between  the  sternal 
and  clavicular  heads  is  a  slight  depression,  most  marked  when  the  muscle  is  in  action.  This 
is  bounded  below  by  the  prominent  sternal  extremity  of  the  clavicle.  Between  the  sternal  origins 
of  the  two  muscles  is  a  V-shaped  space,  the  suprasternal  notch,  more  pronounced  below,  and 
becoming  toned  down  above,  where  the  Sternohyoid  and  Sternoth ,  roid  muscles,  lying  upon 
the  trachea,  become  more  prominent.  Above  the  hyoid  bone,  in  the  middle  line,  the  anterior 
belly  of  the  Digastric  to  a  certain  extent  influences  surface  form.  It  corresponds  to  a  line  drawn 
from  the  symphysis  of  the  mandible  to  the  side  of  the  body  of  the  hyoid  bone,  and  renders  convex 
this  part  of  the  hyomental  region.  In  the  posterior  triangle  of  the  neck,  the  posterior  belly  of 
the  Omohyoid,  when  in  action,  forms  a  conspicuous  object,  especially  in  thin  necks,  presenting 
a  cord-like  form  running  across  this  region,  almost  parallel  with,  and  a  little  above,  the  clavicle. 


MUSCLES  AND  FASCIiE  OF  THE  TRUNK. 


The  muscles  of  the  Trunk  may  be  arranged  in  four  groups,  corresponding 
with  the  region  in  which  they  are  situated. 


I.  The  Back. 
II.  The  Thorax. 


III.  The  Abdomen. 

IV.  The  Perineinn. 


I.  MUSCLES  OF  THE  BACK. 


The  muscles  of  the  back  are  very  numerous,  and  may  be  subdivided  into  five 
layers: 


First  Layer. 


Trapezius. 
Latissimus  dorsi. 


Second  Layer. 

Levator  anguli  scapulae. 
Rhomboideus  minor. 
Rhomboideus  major. 


Third  Layer. 

Serratus  posticus  superior. 
Serratus  posticus  inferior. 
Splenius  capitis. 
Splenius  colli. 


Fourth  Layer. 
Sacral  and  Lumbar  Regions. 
Erector  spinae 

Dorsal  Region. 

Iliocostalis. 

Musculus  accessorius  ad  iliocostalem 


Longissimus  dorsi. 
Spinalis  dorsi. 


Cervical  Region. 

Cervicalis  ascendens. 
Transversalis  cervicis. 
Trachelomastoid. 
Complexus. 
Biventer  cervicis. 
Spinalis  colli. 


Fifth  Layer. 

Semispinalis  dorsi. 
Semispinalis  colli. 
Multifidus  spinae. 
Rotatores  spinae. 
Supraspinales. 
Interspinales. 
Extensor  coccygis. 
Intertransversalis. 
Rectus  capitis  posticus  major. 
Rectus  capitis  posticus  minor. 
Obliquus  capitis  inferior. 
Obliquus  capitis  superior. 


404 


THE  3IUSCLES  AND  FASCIA 


The  First  Layer  (Fig.  310). 


Trapezius. 


Latissimus  dorsi. 


Dissection  (Fig.  309). — Place  the  body  in  a  prone  position,  with  the  arms  extended  over 
the  sides  of  the  table,  and  the  thorax  and  abdomen  supported  by  several  blocks,  so  as  to  render 
the  muscles  tense.  Then  make  an  incision  along  the  middle  line  of  the  back  from  the  occipital 
protuberance  to  the  coccyx.  Make  a  transverse  incision  from  the  upper  end  of  this  to  the  mas- 
toid process,  and  a  third  incision  from  its  lower  end,  along  the  crest  of  the  ilium  to  about  its 
middle.  This  large  intervening  space  should,  for  convenience  of  dissection,  be  subdivided  by 
a  fourth  incision,  extending  obliquely  from  the  spinous  process  of  the  last  thoracic  vertebra, 
upward  and  outward,  to  the  acromion  process.  This  incision  corresponds  with  the  lower  border 
of  the  Trapezius  muscle.  The  flaps  of  integument  are  then  to  be  removed  in  the  direction  shown 
in  the  figure. 

The  superficial  .fascia  is  exposed  upon  removing  the  skin  from  the  back.  It 
forms  a  layer  of  considerable  thickness  and  strength,  in  which  a  quantity  of 

granular  pinkish  fat  is  contained.  It  is  con- 
tinuous with  the  superficial  fascia  in  other 
parts  of  the  body. 

The  deep  fascia  is  a  dense  fibrous  layer 
attached  to  the  occipital  bone,  the  spines  of 
the  vertebriB,  the  crest  of  the  ilium,  and  the 
spine  of  the  scapula.  It  covers  over  the 
supei-ficial  muscles,  forming  sheaths  for  them, 
and  in  the  neck  forms  the  posterior  part  of  the 
deep  cervical  fascia;  in  the  thorax  it  is  con- 
tinuous with  the  deep  fascia  of  the  axilla  and 
thorax,  and  in  the  abdomen  with  that  covering 
the  abdominal  muscles.  In  the  back  of  the 
thoracic  region  the  deep  fascia  is  called  the 
vertebral  aponeurosis.  It  covers  the  Erector 
spinae  muscles,  and  is  the  dorsal  layer  of  the 
lumbar  fascia. 

The  Trapezius  (m.  trapezius)  is  a  broad,  flat, 
triangular  muscle,  placed  immediately  beneath 
the  skin  and  fascia,  and  covering  the  upper 
and  back  part  of  the  neck  and  shoulders.  It 
arises  from  the  external  occipital  protuberance 
and  the  inner  third  of  the  superior  curved  line 
of  the  occipital  bone;  from  the  ligamentum 
nuchae,  the  spinous  process  of  the  seventh  cer- 
vical, and  the  spinous  processes  of  all  the  thora- 
cic vertebrae ;  and  from  the  corresponding  portion 
of  the  supraspinous  ligament.  From  this  origin 
the  superior  fibres  proceed  downward  and  out- 
ward, the  inferior  ones  upward  and  outward,  the  middle  fibres  horizontally,  and  are 
inserted,  the  superior  ones  into  the  outer  third  of  the  posterior  border  of  the  clavicle 
and  into  the  adjacent  part  of  its  upper  surface.  The  middle  fibres  pass  into  the 
inner  margin  of  the  acromion  process,  and  into  the  superior  lip  of  the  posterior 
border  or  crest  of  the  spine  of  the  scapula;  the  inferior  fibres  converge  near  the 
scapula,  and  terminate  in  a  triangular  aponeurosis,  which  glides  over  a  smooth 
surface  at  the  inner  extremity  of  the  spine,  to  be  inseHed  into  a  tubercle  at  the 
outer  part  of  this  smooth  surface.  The  Trapezius  is  fleshy  in  the  greater  part 
of  its  extent,  but  tendinous  at  its  origin  and  insertion.     At  its  occipital  origin 


Fig.  309, — Dissection  of  the  muscles  of 


OF  THE  BACK 


405 


TiGi  310. — Muscles  of  the  back.     On  the  left  side  is  exposed  the  first  layer;  on  the  right  side,  the  second  '.ayer 
and  part  of  the  third. 


406  THE  MUSCLES  AND  FASCIA 

it  is  connected  to  the  bone  by  a  thin  fibrous  lamina,  firmly  adherent  to  the  skin, 
and  wanting  the  lustrous,  shining  appearance  of  aponeuroses.  At  its  origin  from 
the  spines  of  the  vertebrae  it  is  connected  to  the  bones  by  means  of  a  broad  semi- 
elliptical  aponeurosis,  which  occupies  the  space  between  the  sixth  cervical  and  the 
third  thoracic  vertebrae,  and  forms,  with  the  aponeurosis  of  the  opposite  muscle, 
a  tendinous  ellipse.  The  rest  of  the  muscle  arises  by  numerous  short  tendinous 
fibres.  If  the  Trapezius  is  dissected  on  both  sides,  the  two  muscles  resemble 
a  trapezium  or  diamond-shaped  quadrangle;  two  angles  corresponding  to  the 
shoulders;  a  third  to  the  occipital  protuberance;  and  the  fourth  to  the  spinous 
process  of  the  last  thoracic  vertebra.  The  clavicular  insertion  of  this  muscle 
varies  as  to  the  extent  of  its  attachment;  it  sometimes  advances  as  far  as  the  middle 
of  the  clavicle,  and  may  even  become  blended  with  the  posterior  edge  of  the 
Sternomastoid  or  may  overlap  it.  This  should  be  borne  in  mind  in  the  operation 
for  tying  the  third  part  of  the  subclavian  artery. 

Relations. — By  its  superficial  surface,  the  Trapezius  is  in  relation  with  the  integument;  by  its 
deep  surface,  in  the  neck,  with  the  Complexus,  Splenius,  Levator  anguli  scapulae,  and  Rhom- 
boideus  minor;  in  the  back,  with  the  Rhomboideus  major,  Supraspinatus,  Infraspinatus,  and 
vertebral  aponeurosis  (which  separates  it  from  the  prolongations  of  the  Erector  spinae),  and 
the  Latissimus  dorsi.  The  spinal  accessory  nerve  and  the  superficial  cervical  artery  and  branches 
from  the  third  and  fourth  cervical  nerves  pass  beneath  the  anterior  border  of  this  muscle.  The 
anterior  margin  of  its  cervical  portion  forms  the  posterior  boundary  of  the  posterior  triangle 
of  the  neck,  the  other  boundaries  being  the  Sternomastoid  in  front  and  the  clavicle  below. 

The  Ligamentum  nuchae  (Fig.  310)  is  a  fibrous  membrane,  which,  in  the  neck, 
represents  the  supraspinous  and  interspinous  ligaments  of  the  lower  vertebrae. 
It  extends  from  the  external  occipital  protuberance  to  the  spinous  process  of  the 
seventh  cervical  vertebra.  From  its  anterior  border  a  fibrous  lamina  (fascia 
nuchae)  is  given  off,  which  is  attached  to  the  external  occipital  crest,  the  posterior 
tubercle  of  the  atlas,  and  the  spinous  process  of  each  of  the  cervical  vertebrae,  so 
as  to  form  a  septum  between  the  muscles  on  each  side  of  the  neck.  In  man  it  is 
merely  the  rudiment  of  an  important  elastic  ligament,  which,  in  some  of  the  lower 
animals,  serves  to  sustain  the  weight  of  the  head. 

The  Latissimus  dorsi  (m.  latissimus  dorsi)  is  a  broad,  flat  muscle,  which 
covers  the  lumbar  and  the  lower  half  of  the  thoracic  regions,  and  is  gradually 
contracted  into  a  narrow  fasciculus  at  its  insertion  into  the  humerus.  It  arises 
by  tendinous  fibres  from  the  spinous  processes  of  the  six  inferior  thoracic  vertebrae 
and  from  the  dorsal  layer  of  the  lumbar  fascia  (see  page  410),  by  which  it  is  attached 
to  the  spines  of  the  lumbar  and  sacral  vertebrae  and  to  the  supraspinous  ligament. 
It  also  arises  from  the  external  lip  of  the  crest  of  the  ilium,  behind  the  insertion 
of  the  External  oblique  muscle,  and  by  fleshy  digitations  from  the  three  or  four 
lower  ribs,  which  are  interposed  between  similar  processes  of  the  External  oblique 
(Fig.  317,  page  425).  From  this  extensive  origin  the  fibres  pass  in  different 
directions,  the  upper  ones  horizontally,  the  middle  obliquely  upward,  and  the 
lower  vertically  upward,  so  as  to  converge  and  form  a  thick  fasciculus,  which 
crosses  the  inferior  angle  of  the  scapula,  and  which  usually  receives  a  few  fibres 
of  origin  from  it.  The  muscle  curves  around  the  lower  border  of  the  Teres  major, 
and  is  twisted  upon  itself  so  that  the  superior  fibres  become  at  first  posterior  and 
then  inferior,  and  the  vertical  fibres  at  first  anterior  and  then  superior.  It  ter- 
minates in  a  short  quadrilateral  tendon,  about  three  inches  in  length,  which, 
passing  in  front  of  the  tendon  of  the  Teres  major,  is  inserted  into  the  bottom  of 
the  bicipital  groove  of  the  humerus,  its  insertion  extending  higher  on  the  humerus 
than  that  of  the  tendon  of  the  Pectoralis  major.  The  lower  border  of  the  tendon 
of  this  muscle  is  united  with  that  of  the  Teres  major,  the  surfaces  of  the  two  being 
separated  near  their  insertions  by  a  bursa ;  another  bursa  is  sometimes  interposed 


OF  THE  BACK  407 

between  the  muscle  and  the  inferior  angle  of  the  scapula.     This  muscle  at  its 
insertion  gives  off  an  expansion  to  the  deep  fascia  of  the  arm. 

A  fleshy  slip,  the  axillary  arch,  varying  from  3  to  4  inches  in  length,  and  from  \  to  J  of  an 
inch  in  breadth,  occasionally  arises  from  the  upper  edge  of  the  Latissimus  dorsi  about  the  middle 
of  the  posterior  fold  of  the  axilla,  and  crosses  the  axilla  in  front  of  the  axillary  vessels  and  nerves, 
to  join  the  under  surface  of  the  tendon  of  the  Pectoralis  major,  the  Coracobrachialis,  or  the 
fascia  over  the  Biceps.  The  position  of  this  abnormal  slip  is  a  point  of  interest  in  its  relation 
to  the  axillary  artery,  as  it  crosses  the  vessel  just  above  the  spot  usually  selected  for  the  applica- 
tion of  a  ligature,  and  may  mislead  the  surgeon  during  the  operation.  It  may  be  easily  recog- 
nized by  the  transverse  direction  of  its  fibres.  Dr.  Struther  found  it,  in  8  out  of  105  subjects, 
occurring  seven  times  on  both  sides.  In  most  subjects  there  is  a  fibrous  axillary  arch,  in  only 
a  few  is  the  arch  composed  of  muscle  tissue. 

There  is  usually  a  fibrous  slip  which  passes  from  the  lower  border  of  the  tendon  of  the  Latis- 
simus dorsi,  near  its  insertion,  to  the  long  head  of  the  Triceps.  This  is  occasionally  fleshy, 
and  is  the  representative  of  the  Dorso-rpitrorhlcnris  muscle  of  apes. 

Relations. — The  superficial  surface  of  the  Latissimus  dorsi  is  subcutaneous,  excepting  at  its 
upper  part,  where  it  is  covered  by  the  Tra|)ezius,  and  at  its  insertion,  where  its  tendon  is  crossed 
by  the  axillary  vessels  and  the  brachial  plexus  of  nerves.  By  its  deep  surface  it  is  in  relation 
with  the  lumbar  fascia,  the  Serratus  Dosticus  inferior,  the  lower  External  intercostal  mus- 
cles and  ribs,  the  inferior  angle  of  the  scapula,  Rhomboideus  major.  Infraspinatus,  and  Teres 
major  muscles.  Its  outer  margin  is  separated  below  from  the  External  oblique  by  a  small 
triangular  interval,  the  triangle  of  Petit  (trii/oimm  lumbate  [Petiii]);  and  another  triangular 
interval  exists  between  its  upper  border  and  the  margin  of  the  Trapezius  in  which  the  Rhom- 
boideus major  muscle  is  exposed. 

Nerves. — The  Trapezius  is  supplied  by  the  spinal  accessory,  and  by  branches  from  the  anterior 
divisions  of  the  third  and  fourth  cervical  nerves:  the  Latissimus  dorsi  by  the  sixth,  seventh  and 
eighth  cervical  nerves  through  the  middle  or  long  subscapular  nerve. 

The  Second  Layer  (Fig.  310). 

Levator  anguli  scapulae.  Rhomboideus  minor. 

Rhomboideus  major. 

Dissection. — The  Trapezius  must  be  removed,  in  order  to  expose  the  next  layer;  to  effect 
this,  detach  the  muscle  from  its  attachment  to  the  clavicle  and  spine  of  the  scapula,  and  turn 
it  back  toward  the  vertebral  column. 

The  Levator  anguli  scapulae  (m.  levator  sca-pulae)  is  situated  at  the  hack  part 
and  side  of  the  neck.  It  aris.es  by  tendinous  slips  from  the  transverse  process  of 
the  atlas,  and  from  the  posterior  tubercles  of  the  transverse  processes  of  the  second, 
third,  and  fourth  cervical  vertebrae ;  these,  becoming  fleshy,  are  united  so  as  to 
form  a  flat  muscle,  which,  passing  downward  and  backward,  is  inserted  into  the 
posterior  border  of  the  scapula,  between  the  superior  angle  and  the  triangular 
smooth  surface  at  the  root  of  the  spine. 

The  Rhomboideus  minor  (m.  rhomboideus  minor)  arises  from  the  ligamentum 
nuchae  and  spinous  processes  of  the  seventh  cervical  and  first  thoracic  vertebrae. 
Passing  downward  and  outward,  it  is  inserted  into  the  margin  of  the  triangular 
smooth  surface  at  the  root  of  the  spine  of  the  scapula.  This  small  muscle  is 
usually  separated  from  the  Rhomboideus  major  by  a  slight  cellular  interval. 

The  Rhomboideus  major  (m.  rhomboideus  7najor)  is  situated  immediately 
below  the  preceding,  the  adjacent  margins  of  the  two  being  occasionally  united. 
It  arises  by  tendinous  fibres  from  the  spinous  processes  of  the  four  or  five  upper 
thoracic  vertebrae  and  the  supraspinous  ligament,  and  is  inserted  into  a  narrow 
tendinous  arch  attached  above  to  the  lower  part  of  the  triangular  surface  at  the 
root  of  the  spine;  below,  to  the  inferior  angle,  the  arch  being  connected  to  the 
border  of  the  scapula  by  a  thin  membrane.  When  the  arch  extends,  as  it  occa- 
sionally does,  a  short  distance,  the  muscle  fibres  are  inserted  into  the  scapula 
itself. 


408  THE  MUSCLES  AND  FASCIA 

Nerves. — The  Rhomboid  muscles  are  supplied  by  branches  from  the  anterior  division  of 
the  fifth  cervical  nerve;  the  Levator  anguli  scapulae,  by  the  anterior  divisions  of  the  third  and 
fourth  cervical  nerves,  and  frequently  by  a  branch  from  the  nerve  to  the  Rhomboids. 

Actions. — The  movements  effected  by  the  preceding  muscles  are  numerous,  as  may  be  con- 
ceived from  their  extensive  attachment.  The  whole  of  the  Trapezius  when  in  action  retracts 
the  scapula  and  braces  back  the  shoulder;  if  the  head  is  fixed,  the  upper  part  of  the  Trapezius 
will  elevate  the  point  of  the  shoulder,  as  in  supporting  weights;  when  the  lower  fibres  are  brought 
into  action,  they  assist  in  depressing  the  bone.  The  middle  and  lower  fibres  of  the  muscle  rotate 
the  scapula,  causing  elevation  of  the  acromion  process.  If  the  shoulders  are  fixed,  both  Trapezii, 
acting  together,  will  draw  the  head  directly  backward;  or  if  only  one  acts  the  head  is  drawn  to 
the  corresponding  side.  The  Latissimus  dorsi,  when  it  acts  upon  the  humerus,  depresses  it, 
draws  it  backward,  adducts,  and  at  the  same  time  rotates  it  inward.  It  is  the  muscle  which 
is  principally  employed  in  giving  a  downward  blow,  as  in  felling  a  tree  or  in  sabre  practice.  If 
the  arm  is  fixed,  the  muscle  may  act  in  various  ways  upon  the  trunk;  thus,  it  may  raise  the  lower 
ribs  and  assist  in  forcible  inspiration;  or,  if  both  arms  are  fixed,  the  two  muscles  may  assist 
the  Abdominal  and  great  Pectoral  muscles  in  suspending  and  drawing  the  whole  trunk  for- 
ward, as  in  climbing  or  walking  on  crutches.  The  Levator  anguli  scapulae  raises  the  superior 
angle  of  the  scapula,  and  by  so  doing  depresses  the  point  of  the  shoulder.  It  assists  the  Trape- 
zius in  bearing  weights  and  in  shrugging  the  shoulders.  If  the  shoulder  be  fixed,  the  Levator 
anguli  scapulae  inclines  the  neck  to  the  corresponding  side  and  rotates  it  in  the  same  direction. 
The  Rhomboid  muscles  carry  the  inferior  angle  backward  and  upward,  thus  producing  a  slight 
rotation  of  the  scapula  upon  the  side  of  the  thorax,  the  Rhomboideus  major  acting  especially 
on  the  lower  angle  of  the  scapula  through  the  tendinous  arch  by  which  it  is  inserted.  The  Rhom- 
boid muscles,  acting  together  with  the  middle  and  inferior  fibres  of  the  Trapezius,  will  draw 
the  scapula  directly  backward  toward  the  vertebral  column. 


The  Third  Layer. 

Serratus  posticus  superior.  Serratus  posticus  inferior, 

c  1     •      f  Splenius  capitis. 
*  ^  (  Splenius  colli. 

Dissection. — To  bring  into  view  the  third  layer  of  rnuscles,  remove  the  whole  of  the  second, 
together  with  the  Latissimus  dorsi,  by  cutting  through  the  Levator  anguli  scapulae  and  Rhom- 
boid muscles  near  their  origin,  and  reflecting  them  downward,  and  by  dividing  the  Latissimus 
dorsi  in  the  middle  by  a  vertical  incision  carried  from  its  upper  to  its  lower  part,  and  reflecting 
the  two  halves  of  the  muscle. 

The  Serratus  posticus  superior  {m.  serratus  posterior  superior)  is  a  thin,  flat 
quadrilateral  muscle  situated  at  the  upper  and  back  part  of  the  thorax.  It  arises 
by  a  thin  and  broad  aponeurosis  from  the  ligamentum  nuchae,  and  from  the 
spinous  processes  of  the  last  cervical  and  two  or  three  upper  thoracic  vertebrEe  and 
from  the  supraspinous  ligament.  Inclining  downward  and  outward,  it  becomes 
muscular,  and  is  inserted,  by  four  fleshy  digitations,  into  the  tipper  borders  of  the 
second,  third,  fourth,  and  fifth  ribs,  a  little  beyond  their  angles. 

The  Serratus  posticus  inferior  (m.  serratus  posterior  inferior)  (Fig.  310)  is 
situated  at  the  junction  of  the  thoracic  and  lumbar  regions;  it  is  of  an  irregularly 
quadrilateral  form,  broader  than  the  preceding,  and  separated  from  it  by  a  con- 
siderable interval.  It  arises  by  a  thin  aponeurosis  from  the  spinous  processes  of 
the  last  two  thoracic  and  two  or  three  upper  lumbar  vertebrae,  and  from  the  supra- 
spinous ligaments.  Passing  obliquely  upward  and  outward,  it  becomes  fleshy, 
and  divides  into  four  flat  digitations,  which  are  inserted  into  the  lower  borders  of 
the  four  lower  ribs,  a  little  beyond  their  angles.  The  thin  aponeurosis  of  origin 
is  intimately  blended  with  the  lumbar  fascia. 

The  vertebral  aponeurosis  is  a  thin,  fibrous  lamina,  extending  along  the  whole 
length  of  the  back  part  of  the  thoracic  region,  serving  to  bind  down  the  long 
Extensor  muscles  of  the  back  which  support  the  vertebral  column  and  head,  and 
separate  them  from  those  muscles  which  connect  the  vertebral  column  to  the  upper 


OF  THE  BA  CK  409 

extremity.  It  consists  of  longitudinal  and  transverse  fibres  blended  together, 
forming  a  thin  lamella,  which  is  attached,  in  the  median  line,  to  the  spinous  jjroc- 
esses  of  the  thoracic  vertebrae;  externally,  to  the  angles  of  the  ribs;  and  is  contin- 
uous with  the  intercostal  fascia.  It  is  continuous  below  with  the  aponeurosis 
of  the  Serratus  posticus  inferior  and  a  portion  of  the  lumbar  fascia,  which  gives 
origin  to  the  Latissimus  dorsi;  above,  it  passes  beneath  the  Serratus  posticus 
superior  and  the  Splenius,  and  blends  with  the  deep  fascia  of  the  neck. 

The  lumbar  fascia  or  aponeurosis  (Figs.  310  and  325),  which  may  be  regarded 
as  the  posterior  aponeurosis  of  the  Transversalis  abdominis  muscle,  consists  of 
three  laminte,  which  are  attached  as  follows:  The  dorsal  layer,  to  the  spines  of 
the  lumbar  and  sacral  vertebrte  and  their  supraspinous  ligaments;  the  middle 
layer,  to  the  tips  of  the  transverse  processes  of  the  lumbar  vertebrae  and  their 
intertransverse  ligaments;  the  ventral  layer,  to  the  roots  of  the  lumbar  transverse 
processes.  The  dorsal  layer  is  continued  above  as  the  vertebral  aponeurosis, 
while  inferiorly  it  is  fixed  to  the  outer  lip  of  the  iliac  crest.  With  this  layer  are 
blended  the  aponeurotic  origin  of  the  Serratus  posticus  inferior  and  part  of  that 
of  the  Latissimus  dorsi.  The  middle  layer  is  attached  above  to  the  last  rib,  and 
below  to  the  iliac  crest;  the  ventral  layer  is  fixed  below  to  the  iliolumbar  ligament 
and  iliac  crest;  while  above  it  is  thickened  to  form  the  external  arcuate  ligament 
of  the  Diaphragm,  and  stretches  from  the  tip  of  the  last  rib  to  the  transverse  pro- 
cess of  the  first  or  second  lumbar  vertebra.  These  three  layers,  together  with 
the  vertebral  column,  enclose  two  spaces,  the  posterior  of  which  is  occupied  by 
the  Erector  spinae  muscle,  and  the  anterior  by  the  Quadratus  lumborum. 

Now  detach  the  Serratus  posticus  su])erior  from  its  origin,  and  turn  it  outward,  when  the 
Splenius  muscle  will  be  brought  into  view. 

The  Splenius  muscle  mass  (Fig.  310)  is  situated  at  the  back  of  the  neck  and 
upper  part  of  the  thoracic  region.  At  its  origin  it  is  a  single  muscle,  which  soon 
after  its  origin  becomes  broad,  and  divides  into  two  portions,  which  have  separate 
insertions.  It  arises,  by  tendinous  fibres,  from  the  lower  half  of  the  ligamentum 
nuchae,  from  the  spinous  processes  of  the  last  cervical  and  of  the  six  upper  tho- 
racic vertebrte,  and  from  the  supraspinous  ligament.  From  this  origin  the  fleshy 
fibres  proceed  obliquely  upward  and  outward,  forming  a  broad,  flat  muscle  sheet, 
which  divides  as  it  ascends  into  two  portions,  the  Splenius  capitis  and  Splenius  colli. 

The  Splenius  capitis  (m.  splenius  capitis)  is  inserted  into  the  mastoid  process  of 
the  temporal  bone,  and  into  the  rough  surface  on  the  occipital  bone,  just  beneath 
the  superior  curved  line. 

The  Splenius  colli  {m.  splenius  cervicis)  is  inserted,  by  tendinous  fasciculi,  into  the 
posterior  tubercles  of  the  transverse  processes  of  the  two  or  three  upper  cervical 
vertebrae. 

The  Splenius  muscles  are  separated  from  their  fellows  of  the  opposite  side  by  a 
triangular  interval,  in  which  is  seen  the  Complexus. 

Nerves. — The  Splenius  capitis  and  colli  muscles  are  supplied  from  the  external  branches  of 
the  posterior  primary  divisions  of  the  middle  and  lower  cervical  nerves;  the  Serratus  posticus, 
superior  is  supplied  by  the  external  branches  of  the  upper  three  or  four  intercostal  nerves;  the 
Serratus  posticus  inferior  by  branches  of  the  ninth,  tenth,  and  eleventh  intercostal  nerves. 

Actions. — The  Serrati  are  respiratory  muscles.  The  Serratus  posticus  superior  elevates  the 
ribs;  it  is  therefore  an  inspiratory  muscle;  while  the  Serratus  inferior  draws  the  lower  ribs  down- 
ward and  backward,  and  thus  elongates  the  thorax.  It  also  fixes  the  lower  ribs,  thus  aiding  the 
downward  action  of  the  Diaphragm  and  resisting  the  tendency  which  it  has  to  draw  the  lower 
ribs  upward  and  forward.  It  must  therefore  be  regarded  as  a  muscle  of  inspiration.  This 
muscle  is  also  probably  a  tensor  of  the  vertebral  aponeurosis.  The  Splenii  muscles  of  the  two 
sides,  acting  together,  draw  the  head  directly  backward,  assisting  the  Trapezius  and  Com- 
plexus; acting  separately,  they  draw  the  head  to  one  or  the  other  side,  and  slightly  rotate  it,  turning; 
the  face  to  the  same  side.    They  also  assist  in  supporting  the  head  in  the  erect  position. 


4i0  THE  MUSCLES  AND  FASCIA 


The  Fourth  Layer  (Fig.  311). 

I.  Erector  spinae. 
a.  Outer  Column.  b.  Middle  Column 

Iliocostalis.  Longissimus  dorsi. 

Musculus  accessorius.  Transversalis  cervicis. 

Cervicalis  ascendens.  Trachelomastoid. 

c.  Inner  Column. 
Spinalis  dorsi.  Spinalis  colli. 

II.  ComplexLis. 

Dissection. — To  expose  the  muscles  of  the  fourth  layer,  remove  entirely  the  Serrati  and  the 
vertebral  and  lumbar  fascife.  Then  detach  the  Splenius  by  separating  its  attachment  to  the 
spinous  processes  and  reflecting  it  outward. 

The  Erector  spinae  (m.  sacrospinalis)  and  its  prolongations  in  the  thoracic 
and  cervical  regions  fill  up  the  vertebral  groove  on  each  side  of  the  vertebral  column. 
It  is  covered  in  the  lumbar  region  by  the  lumbar  fascia;  in  the  thoracic  region,  by 
the  Serrati  muscles  and  the  vertebral  aponeurosis;  and  in  the  cervical  region,  by 
a  layer  of  cervical  fascia  continued  beneath  the  Trapezius  and  the  Splenius.  This 
large  muscular  and  tendinous  mass  varies  in  size  and  structure  at  different  parts 
of  the  vertebral  column.  In  the  sacral  region  the  Erector  spinae  is  narrow  and 
pointed,  and  its  origin  is  chiefly  tendinous  in  structure.  In  the  lumbar  region 
the  muscle  becomes  enlarged,  and  forms  a  large,  fleshy  mass.  In  the  thoracic 
region  it  subdivides  into  two  parts,  which  gradually  diminish  in  size  as  they  ascend 
to  be  inserted  into  the  vertebrse  and  ribs. 

The  Erector  spinae  arises  from  the  anterior  surface  of  a  very  broad  and  thick 
tendon,  the  erector  spinae  aponeurosis,  which  is  attached,  iniernally,  to  the  spines 
of  the  sacrum,  to  the  spinous  processes  of  the  lumbar  and  the  eleventh  and  twelfth 
thoracic  vertebrae,  and  to  the  supraspinous  ligament;  externally,  to  the  back  part 
of  the  inner  lip  of  the  crest  of  the  ilium,  and  to  the  series  of  eminences  on  the  pos- 
terior part  of  the  sacrum,  which  represents  the  transverse  processes,  where  it 
blends  with  the  great  sacrosciatic  and  posterior  sacroiliac  ligaments.  Some  of 
its  fibres  are  continuous  with  the  fibres  of  origin  of  the  Gluteus  maximus.  The 
muscle  fibres  form  a  single  large  fleshy  mass,  bounded  in  front  by  the  transverse 
processes  of  the  lumbar  vertebrse  and  by  the  middle  lamella  of  the  lumbar  fascia. 
Opposite  the  last  rib  it  divides  into  three  parts:  (1)  The  Iliocostalis;  (2)  the  Longis- 
simus dorsi;  and  (3)  the  Spinalis  dorsi, 

1.  The  Iliocostalis  (?n..  iliocostalis  liimborum),  the  external  portion  of  the 
Erector  spinae,  is  inserted,  generally,  by  six  or  seven  flattened  tendons  into  the 
inferior  borders  of  the  angles  of  the  six  or  seven  lower  ribs.  The  number  of  the 
tendons  of  this  muscle  is,  however,  quite  variable,  and  therefore  the  number  of 
ribs  into  which  it  is  inserted  varies.  Internally  this  muscle  is  reinforced  by  a  series 
of  muscle  slips  which  arise  from  the  angles  of  the  ribs;  by  means  of  these  the 
Iliocostalis  is  continued  upward  to  the  upper  ribs  and  to  the  cervical  portion  of 
the  vertebral  column.  These  accessory  portions  form  two  additional  muscles, 
the  Musculus  accessorius  and  the  Cervicalis  ascendens. 

The  Musculus  accessorius  (m.  iliocostalis  dorsi)  arises,  by  separate  flattened 
tendons,  from  the  upper  borders  of  the  angles  of  the  six  lower  ribs ;  these  become 
muscular,  and  are  finally  inserted,  by  separate  tendons,  into  the  upper  borders 
of  the  angles  of  the  six  upper  ribs  and  into  the  back  of  the  transverse  processes 
of  the  seventh  cervical  vertebra. 


OF  THE  BACK 

Occipital  hone. 


411 


MULTIFIDUS    SPIN* 


First  thoracic  vertebra 


First  lumbar  verteb: 


First  sacral  vertebra 


Fig.  311.— Muscles  of  the  back.     Deep  layer 


412  THE  MUSCLES  AND  FASCIA 

The  Cervicalis  ascendens  (m.  illocostalis  cervicis)  is  the  continuation  of  the  Acces- 
sorius  upward  into  the  neck;  it  is  situated  on  the  inner  side  of  the  tendons  of  the 
Accessorius,  arising  from  the  angles  of  tlie  four  or  five  upper  ribs,  and  is  inserted 
by  a  series  of  slender  tendons  into  the  posterior  tubercles  of  the  transverse  pro- 
cesses of  the  fourth,  fifth,  and  sixth  cervical  vertebrae. 

2.  The  Longissimus  dorsi  is  the  middle  and  largest  portion  of  the  Erector  spinae. 
In  the  lumbar  region,  where  it  is  as  yet  blended  with  the  Iliocostalis,  some  of  the 
fibres  are  attached  to  the  whole  length  of  the  posterior  surface  of  the  transverse 
processes  and  the  accessory  processes  of  the  lumbar  vertebrse,  and  to  the  middle 
layer  of  the  lumbar  fascia.  In  the  thoracic  region  the  Longissimus  dorsi  is 
inserted,  by  long,  thin  tendons,  into  the  tips  of  the  transverse  processes  of  all  the 
thoracic  vertebra,  and  into  from  seven  to  eleven  of  the  lower  ribs  between  their 
tubercles  and  angles.  This  muscle  is  continued  upward  to  the  cranium  and  cer- 
vical portion  of  the  vertebral  column  by  means  of  two  additional  muscles,  the 
Transversalis  cervicis  and  Trachelomastoid. 

The  Transversalis  cervicis  (m.  longissimus  cervicis),  placed  on  the  inner  side 
of  the  Longissimus  dorsi,  arises  by  long,  thin  tendons  from  the  summits  of  the  trans- 
verse processes  of  the  six  upper  thoracic  vertebrte,  and  is  inserted  by  similar 
tendons  into  the  posterior  tubercles  of  the  transverse  processes  of  the  cervical 
vertebrte,  from  the  second  to  the  sixth  inclusive. 

The  Trachelomastoid  (m.  longissimus  capitis')  lies  on  the  inner  side  of  the  pre- 
ceding, between  it  and  the  Complexus  muscle.  It  arises,  by  tendons,  from  the 
transverse  processes  of  the  five  or  six  upper  thoracic  vertebrse,  and  the  articular 
processes  of  the  three  or  four  lower  cervical  vertebra?.  The  fibres  form  a  small 
muscle,  which  ascends  to  be  inserted  into  the  posterior  margin  of  the  mastoid 
process,  beneath  the  Splenius  and  Sternomastoid  muscles.  This  small  muscle  is 
almost  always  crossed  by  a  tendinous  intersection  near  its  insertion  into  the  mastoid 
process.^ 

3.  The  Spinalis  dorsi  is  situated  at  the  inner  side  of  the  Longissimus  dorsi, 
with  which  it  is  intimately  blended.  It  arises,  by  three  or  four  tendons,  frpm  the 
spinous  processes  of  the  first  two  lumbar  and  the  last  two  thoracic  vertebrse;  these, 
uniting,  form  a  small  muscle,  which  is  inserted,  by  separate  tendons,  into  the 
spinous  processes  of  the  thoracic  vertebrae,  the  number  varying  from  four  to  eight. 
It  is  intimately  united  with  the  Semispinalis  dorsi,  which  lies  beneath  it. 

The  Spinalis  colli  (jn.  spinalis  cervicis)  is  a  small  muscle,  connecting  the  spinous 
processes  of  the  cervical  vertebrse,  and  analogous  to  the  Spinalis  dorsi  in  the  thoracic 
region.  It  varies  considerably  in  its  size  and  in  the  extent  of  its  attachment  to 
the  vertebrffi,  not  only  in  difl^erent  bodies,  but  on  the  two  sides  of  the  same  body. 
It  usually  arises  by  fleshy  or  tendinous  slips,  varying  from  two  to  four  in  ninnber, 
from  the  spinous  processes  of  the  fifth,  sixth,  and  seventh  cervical  vertebrte,  and 
occasionally  from  the  first  and  second  thoracic,  and  is  inserted  into  the  spinous 
process  of  the  axis,  and  occasionally  into  the  spinous  processes  of  the  two  vertebrse 
below  it.     This  muscle  was  found  absent  in  five  cases  out  of  twenty-four. 

The  Complexus  (m.  semispinalis  capitis)  is  a  broad  thick  muscle,  situated  at 
the  upper  and  back  part  of  the  neck,  beneath  the  Splenius,  and  internal  to  the 
Transversalis  cervicis  and  Trachelomastoid.  It  arises,  by  a  series  of  tendons, 
from  the  tips  of  the  transverse  processes  of  the  upper  six  or  seven  thoracic  and  the 
last  cer^'ical  vertebrse,  and  from  the  articular  processes  of  the  three  cervical 
vertebrse  above  this.  The  tendons,  uniting,  form  a  broad  muscle,  which  passes 
obliquely  upward  and  inward,  and  is  inserted  into  the  innermost  depression  be- 
tween the  two  curved  lines  of  the  occipital  bone.     At  about  its  middle  it  is  traversed 

1  These  two  muscles  (Transversalis  cervicis  and  Trachelomastoid)  are  sometimes  described  as  one  having  a 
common  origin,  but  dividing  above  at  their  insertion.  The  Trachelomastoid  is  then  termed  the  Transversalis 
capitis. 


OF  THE  JiA  CK  413 

by  a  transverse  tendinous  intersection.  The  iimer  portion  of  this  muscle  is 
usually  separate  and  is  called  the  biventer  cervicis,  from  the  intervention  of  a 
tendon  between  its  two  fleshy  bellies. 


The  Fifth  Layer  (Fig.  311). 

Semispinalis  dorsi.  Extensor  coccygis. 

Semispinalis  colli.  Intertransversales. 

Multifidus  spinae.  Rectus  capitis  posticus  major. 

Rotatores  spinae.  Rectus  capitis  posticus  minor. 

Supraspinales.  Obliquus  inferior. 

Interspinales.  Obliquus  superior. 

Dissection. — Remove  the  muscles  of  the  preceding  layer  by  dividing  and  turning  aside  the 
Complexus;  then  detach  the  Spinahs  and  Longissimus  dorsi  from  their  attachments,  divide  the 
Erector  spinae  at  its  connection  below  to  the  sacral  lumbar  vertebrae  and  turn  it  outward.  The 
muscles  filling  up  the  interval  between  the  spinous  and  transverse  processes  are  then  exposed. 

The  Semispinalis  dorsi  (m.  semispi)ialis  dorsi)  consists  of  thin,  narrow, 
fleshy  fasciculi  interposed  between  tendons  of  considerable  length.  It  arises 
by  a  series  of  small  tendons  from  the  transverse  processes  of  the  lower  thoracic 
vertebrte,  from  the  tenth  or  eleventh  to  the  fifth  or  sixth;  and  is  inserted,  by  five 
or  six  tendons,  into  the  spinous  processes  of  the  upper  four  thoracic  and  lower 
two  cervical  vertebne. 

The  Semispinalis  colli  {m.  semispinalis  cervicis),  thicker  than  the  preceding, 
arises  by  a  series  of  tendinous  and  fleshy  fibres  from  the  transverse  processes  of 
the  upper  five  or  six  thoracic  vertebrae,  and  is  inserted  into  the  spinous  processes 
of  four  cervical  vertebrae,  from  the  axis  to  the  fifth  cervical.  The  fasciculus 
connected  with  the  axis  is  the  largest,  and  is  chiefly  muscular  in  structure. 

Superficial  to  this  muscle  and  the  preceding  are  the  profunda  cervicis  artery,  the  princeps 
cervicis  artery,  and  the  internal  branches  of  the  posterior  divisions  of  the  first,  second,  and 
third  cervical  nerves;  their  deep  surfaces  lie  upon  the  ]\'Iultifidus  spinae. 

The  Multifidus  spinae  (m.  multifidus)  consists  of  a  number  of  fleshy  and  ten- 
dinous fasciculi  which  fill  up  the  groove  on  either  side  of  the  spinous  processes  of 
the  vertebrae,  from  the  sacrum  to  the  axis.  In  the  sacral  region  these  fasciculi 
arise  from  the  back  of  the  sacrum,  as  low  as  the  fourth  sacral  foramen,  and  from 
the  aponeurosis  of  origin  of  the  Erector  spinae;  from  the  inner  surface  of  the  pos- 
terior superior  spine  of  the  ilium  and  posterior  sacro-iliac  ligaments;  in  the  lumbar 
regions  from  the  mammillary  processes;  in  the  thoracic  region,  from  the  transverse 
processes;  and  in  the  cervical  region,  from  the  articular  processes  of  the  three  or 
four  lower  vertebrae.  Each  fasciculus,  passing  obliquely  upward  and  inward, 
is  inserted  into  the  whole  length  of  the  spinous  process  of  one  of  the  vertebrae 
above.  These  fasciculi  vary  in  length;  the  most  superficial,  the  longest,  pass  from 
one  vertebra  to  the  third  or  fourth  above;  those  next  in  order  pass  from  one 
vertebra  to  the  second  or  third  above;  while  the  deepest  connect  two  contiguous 
vertebriB. 

Its  superficial  surface  is  covered  by  the  Semispinalis  dorsi,  and  the  Semispinalis  colli,  and  its 
deep  surface,  lies  upon  the  laminse  and  spinous  processes  of  the  vertebrfe. 

The  Rotatores  spinae  (mm.  rotatores)  are  found  only  in  the  thoracic  region  of 
the  spine,  beneath  the  Multifidus  spinae;  they  are  eleven  in  number  on  each  side. 
Each  muscle  is  small  and  somewhat  quadrilateral  in  form;  and  arises  from  the 


414  THE  3IUSCLES  AND  FASCIjE 

upper  and  back  part  of  the  transverse  process,  and  is  inserted  into  the  lower 
border  and  outer  surface  of  the  lamina  of  the  vertebra  above,  the  fibres  extending 
as  far  inward  as  the  root  of  the  spinous  process.  The  first  is  found  between  the 
first  and  second  thoracic;  the  last,  between  the  eleventh  and  twelfth.  Sometimes 
the  number  of  these  muscles  is  diminished  by  the  absence  of  one  or  more  from  the 
upper  or  lower  end. 

The  Supraspinales  {mm.  supraspinales)  consist  of  a  series  of  fleshy  bands 
which  lie  on  the  spinous  processes  in  the  cervical  region  of  the  vertebral  column. 

The  Interspinales  (mm.  interspinales)  are  short  muscular  fasciculi,  placed  in 
pairs  between  the  spinous  processes  of  the  contiguous  vertebrae,  one  on  each  side 
of  the  interspinous  ligament.  In  the  cervical  region  they  are  most  distinct,  and 
consist  of  six  pairs,  the  first  being  situated  between  the  axis  and  the  third  vertebra, 
and  the  last  between  the  last  cervical  and  the  first  thoracic  vertebra.  They  are 
small  narrow  bundles,  attached,  above  and  below,  to  the  apices  of  the  spinous 
processes.  In  the  thoracic  region  they  are  found  between  the  first  and  second 
vertebrae,  and  occasionally  between  the  second  and  third;  and  below,  between 
the  eleventh  and  twelfth.  In  the  lumbar  region  there  are  four  pairs  of  these  muscles 
in  the  intervals  between  the  five  lumbar  vertebrae.  There  is  also  occasionally 
one  in  the  interspinous  space  betw^een  the  last  thoracic  and  first  lumbar,  and 
between  the  fifth  lumbar  and  the  sacrum. 

The  Extensor  coccygis  is  a  slender  muscular  fasciculus,  occasionally  present,  -nhicli  extends 
over  the  lower  part  of  the  posterior  surface  of  the  sacrum  and  coccyx.  It  arises  by  tendinous 
fibres  from  the  last  bone  of  the  sacrum  or  first  piece  of  the  coccyx,  and  passes  downward  to  be 
ituerted  into  the  lower  part  of  the  coccyx.  It  is  a  rudiment  of  the  Extensor  muscle  of  the  caudal 
vertebrae  of  the  lower  animals. 

The  Intertransversales  (mm.  iniertransversarii)  are  small  muscles  placed 
between  the  transverse  processes  of  the  vertebrae.  In  the  cervical  region  they  are 
most  developed,  consisting  of  rounded  muscular  and  tendinous  fasciculi,  which  are 
placed  in  pairs,  passing  between  the  anterior  and  the  posterior  tubercles  of  the 
transverse  processes  of  two  contiguous  vertebrae,  separated  from  one  another  by 
the  anterior  division  of  the  cervical  nerve,  which  lies  in  the  groove  between  them. 
In  this  region  there  are  seven  pairs  of  these  muscles,  the  first  pair  being  between 
the  atlas  and  axis,  and  the  last  pair  between  the  seventh  cervical  and  first  thoracic 
vertebrae.  In  the  thoracic  region  they  are  least  developed,  consisting  chiefly  of 
rounded  tendinous  cords  in  the  intertransverse  spaces  of  the  upper  thoracic  verte- 
brae; but  between  the  transverse  processes  of  the  lower  three  thoracic  vertebrae,  and 
between  the  transverse  processes  of  the  last  thoracic  and  the  first  lumbar,  they  are 
muscular  in  structure.  In  the  lumbar  region  they  are  arranged  in  pairs,  on  either 
side  of  the  vertebral  column,  one  set  occupying  the  entire  interspace  between  the 
transverse  processes  of  the  lumbar  vertebrae,  the  intertransversales  laterales;  the 
other  set,  intertransversales  mediales,  passing  from  the  accessory  process  of  one 
vertebra  to  the  mammillary  process  of  the  next  below. 

The  Rectus  capitis  posticus  major  [m.  rectus  capitis  posterior  major)  arises  by 
a  pointed  tendinous  origin  from  the  spinous  process  of  the  axis,  and,  becoming 
broader  as  it  ascends,  is  inserted  into  the  inferior  curved  line  of  the  occipital  bone 
and  the  surface  of  bone  immediately  below  it.  As  the  muscles  of  the  two  sides 
pass  upward  and  outward,  they  leave  between  them  a  triangular  space,  in  which  are 
seen  the  Recti  capitis  postici  minores  muscles.  The  siiperficial  surface  is  crossed 
by  the  Complexus;  its  deep  surface  lies  on  the  posterior  occipito-atlantal  ligament. 

The  Rectus  capitis  posticus  minor  (m.  rectus  capitis  posterior  minor),  the  small- 
est of  the  four  muscles  in  this  region,  is  of  a  triangular  shape;  it  arises  by  a  narrow 
pointed  tendon  from  the  tubercle  on  the  posterior  arch  of  the  atlas,  and,  becom- 
ing broader  as  it  ascends,  is  inserted  into  the  rough  surface  beneath  the  inferior 


OF  THE  BACK  415 

curved  line,  nearly  as  far  as  the  foramen  magnum,  and  nearer  to  the  middle  line 
than  the  preceding. 

The  Obliquus  inferior  (m.  ohliquus  capitis  inferior),  the  larger  of  the  two 
Oblique  muscles,  arises  from  the  apex  of  the  spinous  process  of  the  axis,  and 
passes  outward  and  slightly  upward,  to  be  inserted  into  the  lower  and  back  part 
of  the  transverse  process  of  the  atlas. 

The  Obliquus  superior  (?n.  ohliquus  capitis  superior),  narrow  below,  wide  and 
expanded  above,  arises  by  tendinous  fibres  from  the  upper  surface  of  the  transverse 
process  of  the  atlas;  it  joins  with  the  insertion  of  the  preceding,  and,  passing 
obliquely  upward  and  inward,  is  inserted  into  the  occipital  bone,  between  the  two 
curved  lines,  external  to  the  Complexus. 

The  Suboccipital  triangle  is  the  triangular  interval  between  the  two  oblique  muscles  and  the 
Rectus  capitis  posticus  major.  This  triangle  is  bounded,  above  and  internally,  by  the  Rectus 
capitis  posticus  major;  above  and  externally,  by  the  Obliquus  superior;  below  and  externally, 
by  the  Obliquus  inferior.  It  is  covered  in  by  a  layer  of  dense  fibrofatty  tissue,  situated 
beneath  the  Complexus  muscle.  The  floor  is  formed  by  the  posterior  occipito-atlantal  ligament 
and  the  posterior  arch  of  the  atlas.  It  contains  the  vertebral  artery,  as  it  runs  in  a  deep  groove 
on  the  upper  surface  of  the  posterior  arch  of  the  atlas,  and  the  posterior  division  of  the  sub- 
occipital nerve. 

Nerves. — The  fourth  and  fifth  layers  of  the  muscles  of  the  back  are  supplied  by  the  posterior 
primary  divisions  of  the  spinal  nerves. 

Actions. — When  both  the  Spinales  dorsi  contract,  they  extend  the  thoracic  region  of  the 
vertebral  column;  when  only  one  muscle  contracts,  it  helps  to  bend  the  thoracic  portion  of 
the  vertebral  column  to  one  side.  The  Erector  spinae,  comprising  the  Iliocostalis  and  the 
Longissimus  dorsi  with  their  accessory  muscles,  serves,  as  its  name  implies,  to  maintain  the 
vertebral  column  in  the  erect  posture;  it  also  serves  to  bend  the  trunk  backward  when  it  is 
required  to  counterbalance  the  influence  of  any  weight  at  the  front  of  the  body,  as,  for  instance, 
when  a  heavy  weight  is  suspended  from  the  neck,  or  when  there  is  any  great  abdominal  dis- 
tention, as  in  pregnancy  or  dropsy;  the  peculiar  gait  under  such  circumstances  depends  upon 
the  vertebral  column  being  drawn  backward  by  the  counterbalancing  action  of  the  Erector 
spinae  muscles.  The  muscles  which  form  the  continuation  of  the  Erector  spinae  upward 
steady  the  head  and  neck,  and  fix  them  in  the  upright  position.  If  the  Iliocostalis  and  Lon- 
gissimus dorsi  of  one  side  act,  they  serve  to  draw  down  the  thorax  and  vertebral  column  to  the 
corresponding  side.  The  Cervicales  ascendens,  taking  their  fixed  points  from  the  cervical 
vertebrte,  elevate  those  ribs  to  which  they  are  attached;  taking  their  fixed  points  from  the  ribs, 
both  muscles  help  to  extend  the  neck;  while  one  muscle  bends  the  neck  to  its  own  side.  The 
Transversales  cervicis,  when  both  muscles  act,  taking  their  fixed  point  from  below,  bend  the  neck 
backward.  The  Trachelomastoid,  when  both  muscles  act,  taking  their  fixed  point  from  below, 
bend  the  head  backward;  while  if  only  one  muscle  acts,  the  face  is  turned  to  the  side  on  which 
the  muscle  is  acting,  and  then  the  head  is  bent  to  the  shoulder.  The  two  Recti  muscles 
draw  the  head  backward.  The  Rectus  capitis  posticus  major,  owing  to  its  obliquity,  rotates 
the  cranium,  with  the  atlas,  around  the  odontoid  process,  turning  the  face  to  the  same  side.  The 
Multifidus  spinae  acts  successively  upon  the  different  parts  of  the  vertebral  column;  thus,  the 
sacrum  furnishes  a  fixed  point  from  which  the  fasciculi  of  this  muscle  act  upon  the  lumbar 
region;  these  then  become  the  fixed  points  for  the  fasciculi  moving  the  thoracic  region,  and 
so  on  throughout  the  entire  length  of  the  vertebral  column;  it  is  by  the  successive  contraction 
and  relaxation  of  the  separate  fasciculi  of  this  and  other  muscles  that  the  spine  preserves  the 
erect  posture  without  the  fatigue  that  would  necessarily  have  been  produced  had  this  position 
been  maintained  by  the  action  of  a  single  muscle.  The  Multifidus  spinae,  besides  preserving 
the  erect  position  of  the  vertebral  column,  serves  to  rotate  it,  so  that  the  front  of  the  trunk  is 
turned  to  the  side  opposite  to  that  from  which  the  muscle  acts,  this  muscle  being  assisted  in  its 
action  by  the  Obliquus  externus  abdominis.  The  Com]ilexi  draw  the  head  directly  backward; 
if  one  muscle  acts,  it  draws  the  head  to  one  side,  and  rotates  it  so  that  the  face  is  turned  to  the 
opposite  side.  The  Superior  oblique  draws  the  head  backward,  and,  from  the  obliquity  in 
the  direction  of  its  fibres,  will  slightly  rotate  the  cranium,  turning  the  face  to  the  opposite  side. 
The  Inferior  oblique  rotates  the  atlas,  and  with  it  the  cranium,  around  the  odontoid  process, 
turning  the  face  to  the  same  side.  The  Semispinales,  when  the  muscles  of  the  two  sides  act 
together,  help  to  extend  the  vertebral  column;  when  the  muscles  of  one  side  only  act,  they  rotate 
the  thoracic  and  cervical  parts  of  the  vertebral  column,  turning  the  body  to  the  opposite  side. 
The  Supraspinales  and  Interspinales  by  approximating  the  spinous  processes  help  to  extend 
the  vertebral  column.    The.  Intertransversales  approximate  the  transverse  processes,  and  help- 


416  THE  MUSCLES  AND   FASCIA 

to  bend  the  vertebral  column  to  one  side.  The  Rotatores  spinae  assist  the  Multifidus  spinae  to 
rotate  the  vertebral  column,  so  that  the  front  of  the  trunk  is  turned  to  the  side  opposite  to  that 
from  which  the  muscle  acts. 

Surface  Forms. — The  surface  forms  produced  by  the  muscles  of  the  back  are  numerous  and 
difficult  to  analyze  unless  they  are  considered  in  systematic  order.  The  most  superficial  layer, 
consisting  of  large  strata  of  muscle  tissue,  influences  to  a  certain  extent  the  surface  form,  and 
at  the  same  time  reveals  the  forms  of  the  layers  beneath.  The  Trapezius  at  the  upper  part 
of  the  back,  and  in  the  neck,  covers  over  and  softens  down  the  outline  of  the  underlying  muscles. 
Its  anterior  border  forms  the  posterior  boundary  of  the  posterior  triangle  of  the  neck.  It  forms 
a  slight  undulating  ridge  which  passes  downward  and  forward  from  the  occiput  to  the  junction 
of  the  middle  and  outer  third  of  the  clavicle.  The  tendinous  ellipse  formed  by  a  part  of  the 
origin  of  the  two  muscles  at  the  back  of  the  neck  is  always  to  be  seen  as  an  oval  depression, 
more  marked  when  the  muscle  is  in  action.  A  slight  dimple  on  the  skin  opposite  the  interval 
between  the  spinous  processes  of  the  third  and  fourth  thoracic  vertebrae  marks  the  triangular 
aponeurosis  by  which  the  inferior  fibres  are  inserted  into  the  root  of  the  spine  of  the  scapula. 
From  this  point  the  inferior  border  of  the  muscle  may  be  traced  as  an  undulating  ridge  to  the 
spinous  process  of  the  twelfth  thoracic  vertebra.  In  like  manner  the  Latissimiis  dorsi  softens 
down  and  modulates  the  underlying  structures  at  the  lower  part  of  the  back  and  lower  part  of 
the  side  of  the  thorax.  In  this  waj'  it  modulates  the  outline  of  the  Erector  spinae;  of  the  Serratus 
posticus  inferior,  which  is  sometimes  to  be  discerned  through  it.  The  anterior  border  of  the 
muscle  is  the  only  part  which  gives  a  distinct  surface  form.  This  border  may  be  traced,  when 
the  muscle  is  in  action,  as  a  rounded  edge,  starting  from  the  crest  of  the  ilium,  and  passing 
obliquely  forward  and  upward  to  the  posterior  border  of  the  axilla,  where  it  combines  with 
the  Teres  major  in  forming  a  thick  rounded  fold,  the  posterior  boundary  of  the  axillary  space. 
The  muscles  in  the  second  layer  influence  to  a  very  considerable  extent  the  surface  form  of 
the  back  of  the  neck  and  upper  part  of  the  trunk.  The  Levator  anguli  scapulae  reveals  itself 
as  a  prominent  divergent  line,  running  downward  and  outward,  from  the  transverse  proc- 
esses of  the  upper  cervical  vertebrae  to  the  angle  of  the  scapula,  covered  over  and  toned  down 
by  the  overlying  Trapezius.  The  Rhomboidei  produce,  when  in  action,  a  vertical  eminence 
between  the  vertebral  border  of  the  scapula  and  the  vertebral  furrow,  varying  in  intensity 
according  to  the  condition  of  contraction  or  relaxation  of  the  Trapezius  muscle,  by  which 
they  are  for  the  most  part  covered.  The  lowermost  part  of  the  Rhomboideus  major  is  not 
covered  by  the  Trapezius,  and  forms  on  the  surface  an  oblique  ridge  running  upward  and 
inward  from  the  inferior  angle  of  the  scapula.  Of  the  nmscles  of  the  third  layer  of  the  back, 
the  Serratus  posticus  superior  does  not  in  any  way  influence  surface  form.  The  Serratus  posticus 
inferior,  when  in  strong  action,  may  occasionally  be  revealed  as  an  elevation  beneath  the  Latis- 
simus  dorsi.  The  Splenii  by  their  divergence  serve  to  broaden  out  the  upper  part  of  the  back 
of  the  neck  and  produce  a  local  fulness  in  this  situation,  but  do  not  otherwise  influence  surface 
form.  Beneath  all  these  muscles  those  of  the  fourth  layer — the  Erector  spinae  and  its  continua- 
tions— influence  the  surface  form  in  a  decided  manner.  In  the  loins,  the  Erector  spinae,  bound 
down  by  the  lumbar  fascia,  forms  a  rounded  vertical  eminence,  which  determines  the  depth  of 
the  vertebral  furrow,  and  which  below  tapers  to  a  point  on  the  posterior  surface  of  the  sacrum 
and  becomes  lost  there.  In  the  back  it  forms  a  flattened  plane  which  gradually  becomes  lost. 
In  the  neck  the  only  part  of  this  group  of  muscles  which  influences  surface  form  is  the  Trachelo- 
mastoid,  which  produces  a  short  convergent  line  across  the  upper  part  of  the  posterior  triangle 
of  the  neck,  appearing  from  under  cover  of  the  posterior  border  of  the  Sternomastoid  and  being 
lost  below  beneath  the  Trapezius. 

Applied  Anatomy. — In  cases  of  tuberculous  caries  of  the  vertebral  bodies,  and  in  other  diseases 
affecting  the  vertebral  column,  rigidity  of  the  spinal  muscles  is  one  of  the  earliest  and  most 
constant  symptoms.  A  child  with  commencing  vertebral  disease  always  maintains  the  affected 
portion  of  the  column  in  a  state  of  absolute  rigidity,  to  prevent  the  inflamed  structures  from 
being  moved  against  each  other;  this  is  one  of  the  best  examples  of  nature's  method  of  producing 
rest  of  the  affected  part. 


II.  MUSCLES  AND  FASCI.a!  OF  THE  THORAX. 

The  muscles  belonging  exclusively  to  this  region  are  few  in  number.     They 
are  the 

Intercostales  externi.  Triangularis  sterni. 

Intercostales  interni.  Levatores  costarum. 

Infracostales.  Diaphragm. 


OF  THE  THORAX  417 

Intercostal  Fascia.— A  thin  but  firm  layer  of  fascia  covers  the  outer  surface  of 
the  P^xternal  intercostal  and  the  inner  surface  of  the  Internal  intercostal  muscles; 
and  a  third  layer,  more  delicate,  is  interposed  between  the  two  planes  of  muscle 
fibres.  These  are  the  intercostal  fasciae,  external,  middle,  and  iiiferiial;  they  are  best 
marked  in  those  situations  where  the  muscle  fibres  are  deficient,  as  between  the 
External  intercostal  muscles  and  sternum,  in  front,  and  between  the  Internal 
intercostals  and  vertebral  column,  behind. 

The  Intercostal  muscles  (Figs.  319  and  347)  are  two  thin  planes  of  muscle 
and  tendon  fibres,  place.d  one  over  the  other.  They  fill  up  the  intercostal  spaces, 
and  are  directed  oblic|uely  Ijetween  the  margins  of  the  adjacent  libs.  They 
have  received  the  name  external  and  internal  from  the  position  they  bear  to  each 
other.  Between  them  in  the  grooved  under  surface  of  the  rib  run  the  intercostal 
vessels  and  nerve.  The  tendon  fibres  are  longer  and  more  numerous  than  the 
muscle  fibres;  hence  the  walls  of  the  intercostal  spaces  possess  very  considerable 
strength,  to  which  the  crossing  of  the  muscle  fibres  materially  contributes. 

The  External  intercostals  (mm.  intercostales  externi)  are  eleven  in  number  on 
each  side.  They  extend  from  the  tubercles  of  the  ribs,  behind,  to  the  commence- 
ment of  the  cartilages  of  the  ribs,  in  front,  where  they  terminate  in  a  thin  mem- 
brane, the  anterior  intercostal  membrane,  which  is  continued  forward  to  the  sternum. 
They  arise  from  the  lower  border  of  the  rib  above,  and  are  inserted  into  the  upper 
border  of  the  rib  below.  In  the  two  lowest  spaces  they  extend  to  the  ends  of  the 
cartilages,  and  in  the  upper  two  or  three  spaces  they  do  not  quite  extend  to  the 
ends  of  the  ribs.  Their  fibres  are  directed  obliquely  downward  and  forward,  in 
a  similar  direction  with  those  of  the  External  oblique  muscle  of  the  abdomen. 
They  are  thicker  than  the  Internal  intercostals. 

The  Internal  intercostals  (mm.  intercostales  interni)  are  also  eleven  in  number 
on  each  side.  They  commence  anteriorly  at  the  sternum  in  the  interspaces  between 
the  cartilage  of  the  true  ribs,  and  from  the  anterior  extremities  of  the  cartilages 
of  the  false  ribs,  and  extend  backward  as  far  as  the  angles  of  the  ribs,  whence  they 
are  continued  to  the  vertebral  column  by  a  thin  aponeurosis,  the  -posterior  intercostal 
membrane.  They  arise  from  the  ridge  on  the  inner  surface  of  the  rib  above,  as  well 
as  from  the  corresponding  costal  cartilage,  and  are  inserted  into  the  upper  border 
of  the  rib  below.  Their  fibres  are  directed  obliquely  downward  and  backward, 
passing  in  the  opposite  direction  to  the  fibres  of  the  External  intercostal  muscle. 

The  Infracostales  (mm.  subcostales)  consist  of  muscular  and  aponeurotic  fas- 
ciculi, which  vary  in  number  and  length;  they  are  placed  on  the  inner  surface  of 
the  ribs,  where  the  Internal  intercostal  muscles  cease;  they  arise  from  the  inner 
surface  of  one  rib,  and  are  inserted  into  the  inner  surface  of  the  first,  second,  or 
third  rib  below.  Their  direction,  like  the  Internal  intercostals,  is  usually  oblique. 
They  are  most  frequently  found  between  the  lower  ribs. 

The  Triangularis  sterni  (m.  transversus  thoracis)  (Fig.  312)  is  a  thin  plane  con- 
sisting of  muscle  and  tendon  fibres,  and  is  situated  upon  the  inner  wall  of  the  front 
of  the  thorax.  It  arises  from  the  lower  third  of  the  posterior  surface  of  the  sternum, 
from  the  posterior  surface  of  the  ensiform  cartilage,  and  from  the  sternal  ends  of 
the  costal  cartilages  of  the  three  or  four  lower  true  ribs.  Its  fibres  diverge  upward 
and  outward,  to  be  inserted  by  digitations  into  the  lower  borders  and  inner  surfaces 
of  the  costal  cartilages  of  the  second,  third,  fourth,  fifth,  and  sixth  ribs.  The 
lowest  fibres  of  this  muscle  are  horizontal  in  their  direction,  and  are  continuous 
with  those  of  the  Transversa  lis;  those  which  succeed  are  oblique,  while  the 
superior  fibres  are  almost  vertical.  This  muscle  varies  much  in  its  attachment, 
not  only  in  different  bodies,  but  on  opposite  sides  of  the  same  body.  The  internal 
mammary  artery  runs  between  this  muscle  and  the  costal  cartilages. 

The  Levatores  COStarum  (mm.  levafores  costarum)  (^Fig.  311),  tivelve  in  mmiber 
on  each  side,  are  small  tendinous  and  fleshy  bundles  which  arise  from  the  extrem- 


418 


THE  MUSCLES  AND  FASCIA 


ities  of  the  transverse  processes  of  the  seventh  cervical  and  the  eleven  upper 
thoracic  vertebra.  They  pass  obliquely  downward  and  outward  and  are  inserted 
into  the  upper  border,  between  the  tubercle  and  the  angle  of  the  rib,  immediately 
below  its  vertebra  of  origin.  In  some  instances  the  muscle  divides  into  two 
fascicuH,  one  of  which  is  inserted  as  above  described;  the  other  fasciculus  passes 
down  to  the  second  rib  below  its  origin. 

Nerves. — The  muscles  of  this  group  are  supplied  by  the  intercostal  nerves. 


STERNOMASTO 


SUBCLAVIUS 


Fig.  312.— Posteric 


•  surface  of  sternum  and  costal  cartilages,  showing  Triangularis  sterni  muscle 
ration  in  the  Museum  of  the  Royal  College  of  Surgeons  of  England. ) 


(From  a  prepa- 


The  Diaphragm  (diaphragma)  (Figs.  313  and  314)  is  a  thin,  musculofibrous 
septum  placed  at  the  junction  of  the  upper  with  the  middle  third  of  the  trunk; 
it  separates  the  thoracic  from  the  abdominal  cavity,  its  convex  upper  surface 
forming  the  floor  of  the  former,  and  its  concave  under  surface  the  roof  of  the 
latter.  Its  peripheral  part  consists  of  muscle  fibres  which  arise  from  the  internal 
circumference  of  the  thoracic  outlet,  as  well  as  from  certain  lumbar  vertebrje, 
and  pass  upward  and  inward  to  converge  to  a  central  tendon.  Anteriorly,  the 
Diaphragm  arises  from  the  dorsal  surface  of  the  ensiform  cartilage  by  two  fleshy 
strips  (pars  sternalis);  on  either  side,  from  the  inner  surfaces  of  the  six  lower 
costal  cartilages  (seventh  to  twelfth)  {pars  cosfalis),  interdigitating  with  slips  of 
origin  of  the  Transversalis  abdominis.     Behind,   it   takes  origin   from  certain 


OF  THE  THORAX  419 

lumbar  vertebrte  by  two  crura;  and  from  aponeurotic  arches  named  the  arcuate 
ligaments  {jpars  lumbalis). 

The  criira  are  situated  on  the  bodies  of  the  hmibar  vertebrae,  on  each  side  of 
the  aorta.  Tlie  crura,  at  their  origin,  are  tendinous  in  structure;  the  right  crus, 
larger  and  longer  than  the  left,  arises  from  the  anterior  surface  of  the  bodies  and 
articular  disks  of  the  four  upper  lumbar  vertebra?;  the  left  crus  arises  from  the 
three  upper  lumbar  vertebrae;  both  blend  with  the  anterior  common  ligament  of 
the  vertebral  column. 

The  tendinous  portion  of  each  crus  passes  forward  and  inward  to  meet  the 
corresponding  portion  of  the  opposite  side,  thus  forming  the  tendinous  arch  known 
as  the  middle  arcuate  ligament.  From  this  arch  diverging  muscle  fil^res  arise, 
the  outermost  portion  of  wliich  is  directed  upward  and  outward  to  the  central 
tendon;  the  innermost  portion  decussate  in  front  of  the  aorta,  diverge  in  order 
to  surround  the  oesophagus,  and  likewise  end  in  the  central  tendon.  The  filires 
derived  from  the  right  crus  are  the  more  numerous  and  pass  in  front  of  those 
derived  from  the  left. 

Each  crus,  in  its  tendinous  portion,  is  perforated  by  the  great  and  lesser 
splanchnic  nerves  and  sometimes  the  ascending  lumbar  radicle  of  the  azygos 
veins. 

The  internal  arcuate  ligament  (arcus  lumbocosiaUs  medialis)  is  a  tendinous  arch 
in  the  fascia  covering  the  upper  part  of  the  Psoas  magnus  muscle,  on  each  side 
of  the  vertebral  column.  This  tendinous  arch  is  connected  mesad  to  the  body 
of  the  first  (or  second)  lumbar  vertebrae,  laterad  to  the  front  of  the  tip  of  the 
transverse  process  of  the  first  (or  second)  lumbar  vertebrae. 

The  external  arcuate  ligament  (arcus  lumhocostalis  lateralis)  is  the  thickened 
upper  margin  of  the  anterior  lamella  of  the  lumbar  fascia;  it  arches  across  the 
upper  part  of  the  Quadratus  lumborum  from  the  front  of  the  transverse  process 
of  the  first  (or  second)  lumbar  vertebra  to  the  apex  and  lower  margin  of  the 
twelfth  rib. 

The  fibres  of  the  Diaphragm  derived  from  these  sources  vary  in  length;  those 
arising  from  the  ensiform  cartilage  are  short  and  occasionally  aponeurotic,  con- 
tinuous with  the  posterior  layer  of  the  Rectus  abdominis  sheath.  Those  arising 
from  the  arcuate  ligaments,  and  more  especially  those  from  the  cartilages  of  the 
ribs  at  the  side  of  the  thorax,  are  longer,  describe  well-marked  curves  as  they  ascend, 
and  finally  converge  to  be  inserted  into  the  margin  of  the  central  tendon. 

The  central  tendon  of  the  Diaphragm  (centrum  tendineum)  (Fig.  314)  is  a  thin  but 
strong  tendinous  aponeurosis,  situated  at  the  centre  of  the  \R\\\t  formed  by  the 
muscle,  immediately  below  the  pericardium,  with  which  it  is  partly  blended.  It  is 
shaped  somewhat  like  a  trefoil  leaf,  consisting  of  three  divisions,  or  leaflets,  sepa- 
rated from  one  another  by  slight  indentations.  The  right  leaflet  is  the  largest ;  the 
middle  one,  directed  toward  the  ensiform  cartilage,  the  next  in  size;  and  the  left, 
the  smallest.  In  structure,  the  tendon  is  composed  of  several  planes  of  fibres 
which  intersect  one  another  at  various  angles,  and  unite  into  straight  or  curved 
bundles — an  arrangement  which  aft'ords  it  additional  strength. 

The  openings  in  the  Diaphragm  are  three  large  and  several  smaller  apertures. 
The  former  are  the  aortic,  the  oesophageal,  and  the  opening  for  the  inferior  vena 
cava. 

The  aortic  opening  (hiatus  aorticus)  is  the  lowest  and  the  most  posterior  of  the 
three  large  apertures  connected  with  this  muscle,  being  at  the  level  of  the  first 
lumbar  vertebra.  It  is  situated  slightly  to  the  left  of  the  middle  line,  immediately 
in  front  of  the  bodies  of  the  vertebrae;  and  is,  therefore,  behind  the  Diaphragm,  not 
in  it.  It  is  an  osseoaponeurotic  aperture,  formed  by  a  tendinous  arch  (middle 
arcuate  ligament)  thrown  across  the  front  of  the  bodies  of  the  vertebrae,  from  the 
crus  on  one  side  to  that  on  the  other,  and  it  transmits  the  aorta,  the  vena  azygos 


420 


THE  MUSCLES  AND  FASCIAE 


major,  and  the  thoracic  duct.     Sometimes  the  vena  azygos  major  is  transmitted 
upward  through  the  right  crus.     Occasionally  some  tendinous  fibres  are.pro- 


CESOPHAGUS 


AOHTA 

Fig.  313.^ — The  Diaphragm,  seen  from  above.    (Poirier  and  Charpy.) 


""'iiinii 

'  *■    tcndom 


Fig.  314. — The  Diaphragm,  viewed  from  in  front.     (Testut.) 

longed  across  the  bodies  of  the  vertebrfe  from  the  inner  part  of  the  lower  end  of 
the  crura,  pass  behind  the  aorta,  and  thus  convert  the  opening  into  a  fibrous  ring 


OF  THE  THORAX 


421 


The  oesophageal  opening  {li'iatnH  oesophageus)  is  situated  at  the  level  of  the  tenth 
liioracic  vertebra;  it  is  elliptical  in  form,  oblique  in  direction,  muscular  in  structure, 
and  is  formed  by  the  decussating  fibres  of  the  two  crura.  It  is  placed  above,  and 
at  the  same  time  anterior,  and  a  little  to  the  left  of  the  aortic  opening.  It  transmits 
the  oesophagus  and  vagus  nerves  and  some  small  oesophageal  arteries.  The 
anterior  margin  of  this  aperture  is  occasionally  tendinous,  being  formed  by  the 
margin  of  the  central  tendon.  The  posterior  and  lateral  margins  are  thick  and 
the  gullet  is  in  contact  with  them  for  about  half  an  inch.  The  right  margin  of  the 
CESophageal  opening  is  particularly  prominent  and  lies  in  the  oesophageal  groove 
on  the  posterior  surface  of  the  left  lobe  of  the  liver. 

The  opening  for  the  inferior  vena  cava  (foramen,  venae  cavae)  is  the  highest  open- 
ing, being  about  on  the  level  of  the  dislv  between  the  eighth  and  ninth  thoracic 
vertebrae;  it  is  quadrilateral  in  form,  tendinoi^s  in  structure,  and  is  placed  at  the 
junction  of  the  right  and  middle  leaflets  of  the  central  tendon,  its  margins  being 
adherent  to  the  wall  of  the  inferior  vena  cava. 


" "    ^   A     \\ 


Fig.  315. — The  Diaphragm,  viewed  from  below.     (Testut.) 

The  right  crus  transmits  the  greater  and  lesser  splanchnic  nerves  of  the  right 
side;  the  left  crus  transmits  the  greater  and  lesser  splanchnic  nerves  of  the  left 
side,  and  the  vena  azygos  minor  (inferior).  The  gangliated  cords  of  the  sympa- 
thetic usually  enter  the  abdominal  cavity  by  passing  behind  the  internal  arcuate 
ligaments. 


Serous  Membranes. — The  serous  membranes  in  relation  with  the  Diaphragm  are  four  in 
number,  three  covering  its  upper  or  thoracic  surface,  and  one  its  abdominal  surface.  The  three 
serous  membranes  on  its  upper  surface  are  the  two  pleurre  on  either  side  and  the  pericardium, 
which  covers  the  middle  portion  of  the  tendinous  centre.  The  greater  portion  of  the  under 
surface  of  the  Diaphragm  is  covered  by  the  peritoneum. 

Nerves. — The  Diaphragm  is  supplied  by  the  right  and  left  phrenic  nerves,  derived  from  the 
anterior  primary  divisions  of  the  third,  fourth,  and  fifth  cervical  nerves.  The  nerve  filaments 
which  pass  to  the  Diaphragm  from  the  lower  four  intercostal  nerves  are  sensor  in  function  and 
supply  only  the  peritoneum. 

Actions. — Each  External  intercostal  muscle  elevates  the  rib  below.  Owing  to  the  oblique 
axis  of  the  costovertebral  articulation,  the  curved  obliquity  of  the  ribs  themselves,  and  the 


422  THE  3IUSCLES  AND  FASCIJE 

angular  arrangement  of  the  lower  costal  cartilages,  the  sternum  is  lifted  upward  and  forward, 
the  ribs  upward  and  slightly  outward,  and  the  diameters  of  the  thorax  are  thus  increased. 

The  action  of  the  Internal  intercostals  is  in  dispute.  Haller  long  ago  taught  that  they  act 
together  with  the  External  intercostals  as  inspiratory  muscles.  Investigators  have  since  endeav- 
ored to  show  that  they  act  as  expiratory  muscles.'  Others  believe  that  the  Intercostal  muscles 
contract  simultaneously  and  serve  merely  as  strong  septal  supports  which  prevent  the  inter- 
costal spaces  from  being  pushed  out  or  drawn  in  during  respiration.  Masoin  and  Du  Bois  Rey- 
mond,-  in  experiments  on  animals,  proved  that  the  intercartilaginous  portions  of  the  Internal 
intercostals  contracted  synchronously  with  the  Diaphragm. 

The  Diaphragm  is  the  principal  muscle  of  inspiration,  and  presents  the  form  of  a  dome  con- 
cave toward  the  abdomen.  The  central  part  of  the  dome  is  tendinous,  and  the  pericardium 
is  attached  to  its  upper  surface;  the  circumference  is  muscular.  During  inspiration  the  lowest 
ribs  are  fLxed,  and  from  these  and  the  crura  the  muscle  fibres  contract  and  draw  downward 
and  forward  the  central  tendon  with  the  attached  pericardium.  In  this  movement  the  curva- 
ture of  the  Diaphragm  is  scarcely  altered,  the  dome  moving  downward  nearly  parallel  to  its 
original  position  and  pushing  before  it  the  abdominal  viscera.  The  descent  of  the  abdominal 
viscera  is  permitted  by  the  elasticity  of  the  abdominal  wall,  but  the  limit  of  this  is  soon  reached. 
The  central  tendon  applied  to  the  abdominal  viscera  then  becomes  a  fixed  point  for  the  action 
of  the  Diaphragm,  the  effect  of  which  is  to  elevate  the  lower  ribs  and  through  them  to  push  forward 
the  sternum  and  the  upper  ribs.  The  right  cupola  of  the  Diaphragm,  lying  on  the  liver,  has  a 
greater  resistance  to  overcome  than  the  left,  which  lies  over  the  stomach,  but  to  compensate 
for  this  the  right  crus  and  the  fibres  of  the  right  side  generally  are  stronger  than  those  of  the 
left. 

In  all  expulsive  acts  the  Diaphragm  is  called  into  action  to  give  additional  power  to  each 
expulsive  effort.  Thus,  before  sneezing,  coughing,  laughing,  crying,  or  vomiting,  and  previous 
to  the  expulsion  of  urine  or  feces,  or  of  the  fcetus  from  the  uterus,  a  deep  inspiration  takes  place. 
The  height  of  the  Diaphragm  is  constantly  varying  during  respiration;  it  also  varies  with  the 
degree  of  distention  of  the  stomach  and  intestines  and  with  the  size  of  the  liver.  After  a  forced 
expiration  the  right  cupola  is  on  a  level  in  front  with  the  fourth  costal  cartilage,  at  the  side  with 
the  fifth,  sixth,  and  seventh  ribs,  and  behind  with  the  eighth  rib;  the  left  cupola  is  a  little  lower 
than  the  right.  Halls  Dally  states  that  the  absolute  range  of  movement  between  deep  inspiration 
and  deep  expiration  averages  in  the  male  and  female  30  mm.  on  the  right  side  and  28  mm.  on 
the  left;  in  quiet  respiration  the  average  movement  is  12.5  mm.  on  the  right  side  and  12  mm. 
on  the  left.^ 

Skiagraphy  shows  that  the  height  of  the  Diaphragm  in  the  thorax  varies  considerably  with  the 
position  of  the  body.  It  stands  highest  when  the  body  is  horizontal  and  the  patient  on  his  back, 
and  in  this  position  it  performs  the  largest  respiratory  excursions  with  normal  breathing.  When 
the  body  is  erect  the  dome  of  the  Diaphragm  falls,  and  its  respiratory  movements  become  less. 
The  dome  falls  still  lower  when  the  sitting  posture  is  assumed,  and  in  this  position  its  respiratory 
excursions  are  least  in  extent.  These  facts  may,  perhaps,  explain  v.'hy  it  is  that  patients  suffering 
from  severe  dyspnea  are  most  comfortable  and  least  short  of  breath  when  they  sit  up.  When 
the  body  is  horizontal  and  the  patient  on  his  side,  the  two  halves  of  the  Diaphragm  do  not  behave 
alike.  The  uppermost  half  sinks  to  a  level  lower  even  than  when  the  patient  sits,  and  moves 
little  with  respiration;  the  lower  half  rises  higher  in  the  thorax  than  it  does  when  the  patient 
is  supine,  and  its  respiratory  excursions  are  much  increased.  In  unilateral  disease  of  the  pleura 
or  lungs  analogous  interference  with  the  position  or  movement  of  the  Diaphragm  can  generally 
be  observed  skiagi-aphically. 

It  appears  that  the  position  of  the  Diaphragm  in  the  thorax  depends  upon  three  main  factors, 
viz.:  (1)  The  elastic  retraction  of  the  lung  tissue,  tending  to  pull  it  upward;  (2)  the  pressure 
exerted  on  its  under  surface  by  the  viscera;  this  naturally  tends  to  be  a  negative  pressure, 
or  a  downward  suction,  when  the  patient  sits  or  stands,  and  a  positive  or  an  upward  pressure 
when  he  lies;  (3)  the  intra-abdominal  tension  due  to  the  abdominal  muscles.  These  are  in  a 
state  of  contraction  in  the  standing  position  and  not  in  the  sitting  position;  hence,  the  Diaphragm 
when  the  patient  stands  is  pushed  up  higher  than  when  he  sits. 

The  Levatores  costarum  being  inserted  near  the  fulcra  of  the  ribs  can  exert  but  little  action 
on  them;  they  act  as  rotators  and  lateral  flexors  of  the  vertebral  column. 

The  Triangularis  sterni  draws  down  the  costal  cartilages,  and  is  therefore  a  muscle  of  expi- 
ration. 

Mechanism  of  Respiration. — The  respiratory  movements  must  be  examined  during  (a) 
quiet  respiration,  and  during  (b)  forced  respiration. 

1  Consult  articles  by  Cleland  in  the  Journal  of  Anatomy  and  Physiology.  May,  1867.  p.  209;  B.aumler,  Obser- 
vations on  the  Action  of  the  Intercostal  Muscles,  Erlangen,  1860  fRef.  in  New  Syd.  Soc.'s  Year-Book  for  1861,  p. 
69);  Keen,  Trans.  Coll.  of  Phys.,  Phila.,  Third  series,  vol.  i,  1875.  p.  97;  Flusser,  Ueber  die  Wirkung  der  Mus- 
culi  Intercostales,  Anat.  Anz.,  April  16.  1908;  Boecker,  -Anat.  Anz..  .June  27,  1908. 

^  ZuT  Lehre  von  der  Function  der  Musculi  intercostales  interni,  Archiv  fur  Physiologic.  1896,  p.  8.5. 

^  Inquiry  into  the  Physiological  Mechanism  of  Respiration,  journal  of  Anatomy  and  Physiology,  vol.  xliii^ 
1908. 


OF  THE  ABDOMEN  423 

Quiet  Respiration. — The  first  and  second  pairs  of  ribs  are  fixed  by  the  Scaleni  and  Ijy  the 
resistiiricc  of  llu'  cervical  structures;  the  last  pair,  and  through  it  the  eleventh  pair,  are  fixed 
by  the  Quadratus  lumborum  muscles.  The  other  ribs  are  elevated,  so  that  the  first  two  inter- 
costal spaces  are  diminished  while  the  other  spaces  are  increased  in  width.  It  has  already 
been  shown  (p.  285)  that  elevation  of  the  third,  fourth,  fifth,  and  sixth  ribs  leads  to  an  increase 
in  the  antero-posterior  and  transverse  diameters  of  the  thorax;  the  vertical  diameter  is  increased 
by  the  descent  of  the  diaphragmatic  dome  so  that  the  lungs  are  expanded  in  al!  directions  exce)jt 
backward  and  upward.  Elevation  of  the  eighth,  ninth,  and  tenth  ribs  is  accompanied  by 
an  outward  and  backward  movement,  leading  to  an  increase  in  the  transverse  diameter  of  the 
upper  part  of  the  abdomen;  the  elasticity  of  the  anterior  abdominal  wall  allows  a  slight  increase 
in  the  antero-posterior  diameter  of  this  part,  and  in  this  way  the  decrease  in  the  vertical  diameter 
of  the  abdomen  is  compensated  and  space  provided  for  its  displaced  viscera.  Expiration  is 
effected  by  the  elastic  recoil  of  the  abdominal  walls  and  by  the  action  of  the  abdominal  muscles, 
which  push  back  the  viscera  displaced  downward  by  the  Diaphragm. 

Forced  Respiration. — All  the  movements  of  quiet  respiration  are  here  carried  out,  but  to 
a  greater  extent.  In  inspiration  the  shoulders  and  the  vertebrai  borders  of  the  scapulte  are 
fixed  and  the  limb  muscles,  Trapezius,  Serratus  magnus,  Pectorals,  and  Latissimus  dorsi,  are 
called  into  play.  The  Scaleni  are  in  stronger  action,  and  the  Sternomastoids  also  assist,  when 
the  head  is  fixed,  by  drawing  up  the  sternum  and  by  fixing  the  clavicles.  The  first  rib  is  there- 
fore no  longer  stationary,  but,  with  the  sternum,  is  raised;  with  it  all  the  other  ribs  except  the 
last  are  raised  to  a  higher  level.  In  conjunction  with  the  increased  descent  of  the  Diaphragm 
this  provides  for  a  considerable  augmentation  of  all  the  thoracic  diameters.  The  anterior  abdom- 
inal muscles  come  into  action  so  that  the  umbilicus  is  drawn  upward  and  backward,  and 
this  allows  the  Diaphragm  to  exert  a  more  powerful  infiuence  on  the  lower  ribs;  the  transverse 
diameter  of  the  upper  part  of  the  abdomen  is  greatly  increased  and  the  subcostal  angle  is  opened 
out.  The  deeper  muscles  of  the  back,  e.  g.,  the  Serrati  postici  superiores  and  the  Erectores 
spinae,  are  also  brought  into  action;  the  thoraciccurve  of  thevertebral  column  is  partially  straight- 
ened, and  the  whole  column,  above  the  lower  lumbar  vertebrse,  is  drawn  backward.  This 
increases  the  antero-posterior  diameters  of  the  thorax  and  of  the  upper  part  of  the  abdomen  and 
widens  the  intercostal  spaces.  Forced  expiration  is  effected  by  the  recoil  of  the  abdominal  walls, 
by  the  contraction  of  the  antero-lateral  muscles.of  the  abdominal  wall,  and  of  the  Serrati  postici 
inferiores  and  Triangularis  sterni. 

Halls  Dally  {op.  cit.)  gives  the  following  figures  as  representing  the  average  changes  which 
occur  during  deepest  possible  respiration.  The  manubrium  moves  30  mm.  in  an  upward,  and 
14  mm.  in  a  forward  direction;  the  width  of  the  subcostal  angle,  at  a  level  of  30  mm.  belciw 
the  articulation  of  the  manubrium  with  the  gladiolus,  is  increased  by  26  mm.;  the  umbilicus 
is  retracted  and  drawn  upward  for  a  distance  of  1 3  mm. 

Artificial  Respiration. — By  the  "prone  pressure"  method  of  Prof.  E.  A.  Schafer  advantage  is 
taken  of  the  contour  of  the  diapliragm  and  of  the  elastic  recoil  of  the  thoracic  wall  in  providing 
for  a  tidal  air  exchange  in  the  lungs. 

III.  MUSCLES  OF  THE  ABDOMEN. 

The  muscles  of  the  abdomen  may  be  divided  into  two  groups:  (1)  The 
antero-lateral  muscles  of  the  abdomen.     (2)  The  posterior  muscles  of  the  abdomen. 


1.  The  Antero-lateral  Muscles  of  the  Abdomen. 

The  muscles  of  this  group  are  the 

External  oblique.  Transversalis. 

Internal  oblique.  Rectus. 

Pyramidalis. 

Dissection  (Fig.  316). — To  dissect  the  abdominal  muscles,  make  a  vertical  incision  from  the 
ensiform  cartilage  to  the  symphysis  pubis;  a  second  incision  from  the  umbilicus  obliquely  upward 
and  outward  to  "the  outer  surface  of  the  thorax,  as  high  as  the  lower  border  of  the  fifth  or  sixth 
rib;  and  a  third,  commencing  midway  between  the  umbilicus  and  pubes,  transversely  outward 
to  the  anterior  superior  iliac  spine,  and  along  the  crest  of  the  ilium  as  far  as  its  posterior  third. 


424 


THE  MUSCLES  AND  FASCIA 


Then  reflect  the  three  flaps  included  between  these  incisions  from  within  outward,  in  tne  lines 
of  direction  of  the  muscle  fibres.  If  necessary,  the  abdominal  muscles  may  be  made  tense  bj 
inflating  the  peritoneal  cavity  tlirough  the  umbilicus. 

,  The  superficial  fascia  of  the  abdomen  consists,  over  the  greater  part  of  the 
abdominal  wall,  of  a  single  layer  of  fascia,  which  contains  a  variable  amount  of 
fat;  but  as  this  layer  approaches  the  groin  it  is  easily  divisible  into  two  layers, 
between  which  are  found  the  superficial  vessels  and  nerves  and  the  superficial 
inguinal  lymph  nodes.  The  superficial  layer  of  the  superficial  fascia  {fascia  of 
Camper)  is  thick,  areolar  in  texture,  and  contains  in  its  meshes  adipose  tissue, 
the  quantity  of  which  varies  in  different  subjects.  Below,  it  passes  over  Poupart's 
ligament,  and  is  continuous  with  the  outer  layer  of  the  superficial  fascia  of  the 
thigh.  In  the  male  this  fascia  is  continued  over  the  penis  and  outer  surface  of 
the  cord  to  the  scrotum,  where  it  helps  to  form 
the  dartos.  As  it  passes  to  the  scrotum  it  changes 
its  character,  becoming  thin,  destitute  of  adipose 
tissue,  and  of  a  pale  reddish  color,  and  in  the 
scrotum  it  acquires  some  nonstriated  muscle 
fibres.  From  the  scrotum  it  may  be  traced  back- 
ward to  be  continuous  with  the  superficial  fascia 
of  the  perineum.  In  the  female  this  fascia  is  con- 
tinued into  the  labia  majora.  The  deep  layer  of 
the  superficial  fascia  (fascia  of  Scarpa)  is  thinner 
and  more  membranous  in  character  than  the 
superficial  layer,  and  contains  a  considerable 
quantity  ef  yellow  elastic  fibres.  In  the  middle 
line  it  is  intimately  adherent  to  the  linea  alba  and 
to  the  symphysis  pubis,  and  is  prolonged,  in  the 
male,  on  to  the  dorsum  of  the  penis,  forming  the 
suspensory  ligament  of  the  penis;  above,  it  joins 
the  superficial  layer  and  is  continuous  with  the 
superficial  fascia  over  the  rest  of  the  trunk ;  heloio, 
•it  blends  with  the  fascia  lata  of  the  thigh  a  little 
below  Poupart's  ligament;  and  below  and  in- 
ternally it  is  continued  over  the  penis  and 
spermatic  cord  to  the  scrotum,  where  it  helps  to 
form  the  dartos.  From  the  scrotum  it  may  be  traced  backward  to  be  continuous 
with  the  deep  layer  of  the  superficial  fascia  of  the  perineum  (fascia  of  Colles).  In 
the  female  it  is  continued  into  the  labia  majora. 

The  deep  fascia  invests  the  External  oblique  muscle,  but  is  so  thin  over  the 
aponeurosis  of  the  muscle  as  to  be  scarcely  recognizable. 

The  External  or  Descending  oblique  muscle  (m.  obliquus  extemus  abdominis) 
(Fig.  317)  is  situated  on  the  side  and  fore  part  of  the  abdomen;  being  the  largest 
and  the  most  superficial  of  the  three  flat  muscles  in  this  region.  It  is  broad,  thin, 
and  irregularly  quadrilateral,  its  muscular  portion  occupying  the  side,  its  aponeu- 
rosis the  anterior  wall,  of  the  abdomen.  It  arises,  by  eight  fleshy  digitations, 
from  the  external  surface  and  lower  borders  of  the  eight  inferior  ribs;  these 
•digitations  are  arranged  in  an  oblique  line  running  downward  and  backward; 
the  upper  ones  being  attached  close  to  the  cartilages  of  the  corresponding  ribs; 
the  lowest,  to  the  apex  of  the  cartilage  of  the  last  rib ;  the  intermediate  ones,  to 
the  ribs  at  some  distance  from  their  cartilages.  The  five  superior  serrations 
increase  in  size  from  above  downward,  and  are  received  between  corresponding 
processes  of  the  Serratus  magnus;  the  three  lower  ones  diminish  in  size  from 
above  downward,  receiving  between  them  corresponding  processes  from  the  Latis- 
simus  dorsi.  From  these  attachments,  the  fleshy  fibres  proceed  in  various  direc- 
tions.    Those  from  the  lowest  ribs  pass  nearly  vertically  downward,  to  be  inserted 


Fig.  316. — Dissection  of  abdomen. 


OF  THE  ABDOMEN 


425 


into  the  anterior  half  of  the  outer  Hp  of  the  crest  of  the  ilium;  the  middle  and 
upper  fibres,  directed  downward  and  forward,  terminate  in  an  aponeurosis,  oppo- 
site a  line  drawn  from  the  prominence  of  the  ninth  costal  cartilage  to  the  anterior 
superior  spine  of  the  ilium. 

The  aponeurosis  of  the  External  oblique  is  a  thin,  but  strong  membranous  apon- 
eurosis, the  fibres  of  which  are  directed  obliquely  downward  and  inward.  It  is 
joined  with  that  of  the  oj^posite  muscle  along  the  median  line  and  covers  the  whole 
of  the  front  of  the  abdomen;  above,  it  is  covered  by  and  gives  origin  to  the  lower 
border  of  the  Pectoralis  major;  below,  some  of  its  fibres  are  inserted  into  the  symphy- 


External  abdo- 
minal ring. 
Giinb&rnaVs 


Fig.  317. — The  External  oblique  muscle. 


sis  pubis,  while  others  pass  deeply  through  the  middle  line  to  be  attached  to  the 
crest  and  iliopectineal  line  of  the  opposite  side;  these  latter  fibres  are  termed 
the  triangular  fascia.  But  the  great  majority  of  the  fibres  below  are  closely  aggre- 
gated, and  extend  obliquely  across  from  the  anterior  superior  spine  of  the  ilium 
to  the  spine  of  the  os  pubis  and  the  iliopectineal  line.     In  the  median  line  it  inter- 


426 


THE  MUSCLES  AND  FASCIAE 


laces  with  the  aponeurosis  of  the  opposite  muscle,  forming  the  linea  alba,  which 
extends  from  the  ensiform  cartilage  to  the  symphysis  pubis. 

That  portion  of  the  aponeurosis  which  extends  between  the  anterior  superior 
spine  of  the  ilium  and  the  spine  of  the  os  pubis  is  a  broad  band,  folded  inward, 
and  continuous  below  with  the  fascia  lata;  it  is  called  Poupart's  ligament.  The 
inner  half  inch  of  this  ligament  is  reflected  and  attached  to  the  subjacent 
pectineal  line.     This  reflected  part  is  called  Gimbernat's  ligament. 

In  the  aponeurosis  of  the  External  oblique,  immediately  above  the  crest  of  the 
OS  pubis,  is  a  triangular  space,  the  external  abdominal  ring,  formed  by  a  thinning 
of  the  fibres  of  the  aponeurosis  in  this  situation. 


^COLUMNAR 


RIIV 

G 

im 

^B 

INIBE 

HNAT 

s__— — 

-^ 

liiii 

IH 

LIGAME^ 

T 

1 

nil  1  '111 

^^s 

SAPh 

P^ml 

s 

w 

1 

^^^ 

\ 

M 

\ 

I^K^ 

MOR 

Lor 

L 

*7 

T» 

j«^K^ 

SAPl- 

G 

— 

K' 

Fig.  318. — Right  external  abdominal  ring  and  saphenous  opening  in  the  male.    (Spalteholz.) 

Relations. — By  its  superficial  surface,  the  External  oblique  muscle  is  in  relation  with  the 
superficial  fascia,  superficial  epigastric  and  circumflex  iliac  vessels,  and  some  cutaneous  nerves; 
by  its  deep  surface,  with  the  Internal  oblique,  the  lower  part  of  the  eight  inferior  ribs,  and 
Intercostal  muscles,  the  Cremaster,  the  spermatic  cord  in  the  male,  and  round  ligament  in  the 
female.  Its  posterior  border,  extending  from  the  last  rib  to  the  crest  of  the  ilium,  is  fleshy 
throughout  and  free;  it  is  occasionally  overlapped  by  the  Latissimus  dorsi,  though  generally  a 
triangular  interval  exists  between  the  two  muscles  near  the  crest  of  the  ilium,  in  which  is  seen 
a  portion  of  the  Internal  oblique.  This  triangle,  Petit's  triangle  {trigonum  lumhale)  is  there- 
fore bounded  in  front  by  the  External  oblique,  behind  by  the  Latissimus  dorsi,  below  by  the 
crest  of  the  ilium,  and  its  floor  is  formed  by  the  Internal  oblique  muscle  (Fig.  317). 

The  following  parts  of  the  aponeurosis  of  the  External  oblique  muscle  require 
to  be  further  described: 

External  Abdominal  Ring.  Intercolumnar  Fibres  and  Fascia. 

Poupart's  Ligament.  Gimbernat's  Ligament. 

Triangular  Fascia  of  the  Abdomen. 

The  External  Abdominal  Ring  {annulus  inguinalis  subcutaneous)  (Figs.  318  and 
321). — Just  above  and  to  the  outer  side  of  the  crest  of  the  os  pubis  an  interval 


OF  THE  ABDOMEN  427 

known  as  the  external  abdominal  ring  is  seen  in  the  aponeurosis  of  the  External 
oblique  muscle.  The  interval  is  oblique  in  direction,  corresponding  with  the 
course  of  the  fibres  of  the  aponeurosis,  is  somewhat  triangular  in  form,  and  usually 
measures  about  an  inch  (2.5  cm.)  from  base  to  apex  and  about  half  an  inch 
(1.25  cm.)  transversely.  It  gives  passage  to  the  spermatic  cord  in  the  male  and 
to  the  round  ligament  in  the  female.  It  is  bounded  helow  by  the  crest  of  the  os 
pubis;  above,  by  a  series  of  curved  fibres,  the  external  spermatic  or  the  inter- 
coluninar  fibres  which  pass  across  the  upper  angle  of  the  ring,  thus  increasing  its 
strength;  and  on  each  side,  by  the  margins  of  the  opening  in  the  aponeurosis, 
which  are  called  the  columns  or  pillars  of  the  ring. 

The  external  pillar  (crus  inferius)  is  inferior  from  the  obliquity  of  its  direction. 
It  is  stronger  than  the  internal  pillar;  it  is  formed  by  that  portion  of  Poupart's 
ligament  which  is  inserted  into  the  spine  of  the  os  pubis;  it  is  curved  so  as  to  form 
a  kind  of  groove,  upon  which  the  spermatic  cord  rests. 

The  internal  pillar  (cms  sjtperijis),  a  broad,  thin,  flat  band,  is  formed  by  the 
fibres  of  the  aponeurosis  which  are  inserted  into  the  crest  and  the  symphysis  pubis. 

The  intercolumnar  fibres  {fibrae  iiitercrurales)  (Fig.  318)  are  a  series  of  curved 
tendinous  fibres,  which  arch  across  the  lower  part  of  the  aponeurosis  of  the  External 
oblicjue.  They  have  received  their  name  from  stretching  across  between  the 
two  pillars  of  the  external  ring,  describing  a  curve  with  the  concavity  downward. 
They  are  much  thicker  and  stronger  at  the  -outer  margin  of  the  external  ring, 
where  they  are  connected  to  the  outer  third  of  Poupart's  ligament,  than  internally, 
where  they  are  inserted  into  the  linea  alba.  They  are  more  strongly  developed 
in  the  male  than  in  the  female.  The  intercolumnar  fibres  increase  the  strength 
of  the  lower  part  of  the  aponeurosis,  and  prevent  the  divergence  of  the  pillars 
from  each  other. 

These  intercolumnar  fibres  as  they  pass  across  the  external  abdominal  ring 
are  themselves  connected  together  by  delicate  fibrous  tissue,  thus  forming  a  fascia, 
the  intercolumnar  fascia  or  the  external  spermatic  fascia,  which,  as  it  is  attached 
to  the  piliai's  of  the  ring,  covers  it  in.  This  intercolumnar  fascia  is  continued 
down  as  a  tubular  prolongation  around  the  outer  surface  of  the  cord  and  testis 
or  of  the  round  ligament,  and  encloses  them  in  a  distinct  sheath. 

Applied  Anatomy .^The  sac  of  an  inguinal  hernia,  in  passing  through  the  external  abdominal 
ring,  receives  an  investment  from  the  intercolumnar  fascia.  If  the  finger  is  introduced  a  short 
distance  into  the  external  abdominal  ring  and  the  limb  is  then  extended  and  rotated  outward, 
the  aponeurosis  of  the  External  oblique,  together  with  the  iliac  portion  of  the  fascia  lata,  will 
be  felt  to  become  tense,  and  the  external  ring  much  contracted;  if  the  limb  is,  on  the  contrary, 
flexed  upon  the  pelvis  and  rotated  inward,  this  aponeurosis  will  become  lax  and  the  external 
abdominal  ring  sufficiently  enlarged  to  admit  the  finger  with  comparative  ease;  hence  the  patient 
should  always  be  put  in  the  latter  position  when  the  taxis  is  applied  for  the  reduction  of  an 
inguinal  hernia  in  order  that  the  abdominal  walls  may  be  relaxed  as  much  as  possible. 

Poupart's  Ligament  (ligamentum  inguinale). — Poupart's  ligament  is  the  lower 
border  of  the  aponeurosis  of  the  External  oblique  muscle,  and  extends  from 
the  anterior  superior  spine  of  the  ilium  to  the  pubic  spine.  From  this  latter 
point  it  is  reflected  to  the  iliopectineal  line  for  about  half  an  inch,  thus  forming 
Gimbernat's  ligament.  Its  general  direction  is  curved  downward  toward  the 
thigji,  where  it  is  continuous  with  the  fascia  lata.  Its  outer  half  is  rounded 
and  oblique  in  direction  and  gives  partial  origin  to  the  Internal  oblique  and  Trans- 
versalis  muscles.  Its  inner  half  gradually  widens  at  its  attachment  to  the  os 
pubis,  is  more  horizontal  in  direction,  and  lies  beneath  the  spermatic  cord.  Nearly 
the  whole  of  the  space  included  between  the  femoral  arch  and  the  innominate 
bone  is  filled  in  by  the  parts  which  descend  from  the  abdomen  into  the  thigh  (Fig. 
326).     These  are  referred  to  again  on  a  subsequent  page. 


428  THE  MUSCLES  AND  FASCIA 

Gimbernat's  ligament  {ligamentum  lacunare)  (Figs.  318  and  326)  is  that  part 
of  Poupart's  ligament  which  is  reflected  to  the  iliopectineal  Hne.  It  is  about  half 
an  inch  in  length,  more  prominent  in  the  male  than  in  the  female,  almost  hori- 
zontal in  direction  in  the  erect  posture,  and  of  a  triangular  form  with  the  base 
directed  outward.  Its  base,  or  outer  margin,  is  concave,  thin,  and  sharp,  and  lies 
in  contact  with  the  crural  sheath,  forming  the  inner  boimdary  of  the  femoral  or 
crural  ring  {annulus  femoralis).  Its  a-pex  corresponds  to  the  spine  of  the  os  pubis. 
Its  deep  margin  is  attached  to  the  iliopectineal  line,  and  is  continuous  with  the 
pubic  portion  of  the  fascia  lata.  Its  superficial  margin  is  continuous  with  Pou- 
part's ligament.     Its  surfaces  are  directed  upward  andclownward. 

Triangular  Fascia  {ligamentum  inguinale  reflexwn). — The  triangular  fascia  of 
the  abdomen  is  a  triangular  layer  of  tendinous  fibres,  which  comes  from  the 
aponeurosis  of  the  opposite  External  oblique,  and  is  attached  b_y  its  apex  to 
the  iliopectineal  line,  where  it  is  continuous  with  Gimbernat's  ligament.  It  lies 
beneath  the  spermatic  cord,  behind  the  inner  pillar  of  the  external  abdominal 
ring,  and  in  front  of  the  conjoined  tendon. 

Ligament  of  Cooper  (Fig.  328). — This  is  a  strong  ligamentous  band,  which  was  first 
described  by  Sir  Astley  Cooper.  It  extends  upward  and  backward  from  the  base  of  Gim- 
bernat's ligament  along  the  iliopectineal  line,  to  which  it  is  attached.  It  is  strengthened  by  the 
fascia  transversalis,  by  the  iliopectineal  aponeurosis,  and  by  a  lateral  expansion  from  the  lower 
attachment  of  the  linea  alba  (adminiculum  lineae  albae). 

Dissection. — Detach  the  External  oblique  by  dividing  it  across,  just  in  front  of  its  attach- 
ment to  the  ribs,  as  far  as  its  posterior  border,  and  separate  it  below  from  the  crest  of  the  ilium 
as  far  as  the  anterior  superior  spine;  then  separate  the  muscle  carefully  from  the  Internal  oblique, 
which  lies  beneath,  and  turn  it  toward  the  opposite  side. 

The  Internal  or  Ascending  oblique  muscle  (m.  ohliquus  iniernus  abdominis) 
(Fig.  319),  thinner  and  smaller  than  the  preceding,  beneath  which  it  lies,  is  of 
an  irregularly  quadrilateral  form,  and  is  situated  at  the  side  and  fore  part  of  the 
abdomen.  It  arises,  by  fleshy  fibres,  from  the  outer  half  of  Poupart's  ligament, 
to  the  groove  on  the  upper  surface  of  which  it  is  attached;  from  the  anterior  two- 
thirds  of  the  middle  lip  of  the  crest  of  the  ilium,  and  from  the  posterior  lamella  of 
the  lumbar  fascia  (Fig.  325).  From  this  origin  the  fibres  diverge;  those  from  Pou- 
part's ligament,  few  in  number  and  paler  in  color  than  the  rest,  arch  downward  an.d 
inward  across  the  spermatic  cord  in  the  male  and  across  the  round  ligament  in 
the  female,  and,  becoming  tendinous,  are  inserted,  conjointly  with  those  of  the 
Transversalis,  into  the  crest  of  the  os  pubis  and  iliopectineal  line,  to  the  extent 
of  half  an  inch  or  more,  forming  what  is  known  as  the  conjoined  tendon  of  the 
Internal  oblique  and  Transversalis.  The  fibres  from  the  anterior  third  of  the 
iliac  origin  are  horizontal  in  their  direction,  and,  becoming  tendinous  along 
the  lower  fourth  of  the  linea  semilunaris,  pass  in  front  of  the  Rectus  muscle  to  be 
inserted  into  the  linea  alba;  those  which  arise  from  the  middle  third  of  the  origin 
from  the  crest  of  the  ilium  pass  obliquely  upward  and  inward,  and  terminate 
in  an  aponeurosis  which  divides  at  the  outer  border  of  the  Rectus  muscle  into 
two  lamella?  (Fig.  326),  and  are  continued  forward,  in  front  and  behind  this  muscle, 
to  be  inserted  into  the  linea  alba.  The  posterior  lamella  is  also  connected  to  the 
cartilages  of  the  seventh,  eighth,  and  ninth  ribs;  the  fibres  arising  most  posteriorly 
pass  almost  vertically  upward,  to  be  inserted  into  the  lower  borders  of  the  cartilages 
of  the  three  lower  ribs,  and  are  continuous  with  the  Internal  intercostal  muscles. 
The  lower  fibres  of  this  muscle  are  continuous  with  the  Cremaster. 

The  aponeurosis  of  the  Internal  oblique  is  continued  forward  to  the  middle  of  the 
abdomen,  where  it  joins  with  the  aponeurosis  of  the  opposite  muscle  at  the  linea 
alba,  and  extends  from  the  costal  arch  to  the  os  pubis.  At  the  outer  margin  of 
the  Rectus  muscle  this  aponeurosis,  for  the  upper  three-fourths  of  its  extent. 


OF  THE  ABDOAIEN 


429 


Conjoined  tendon 

CnCMASTER 


Fig.  319.— The  Internal  oblique  muscle. 


VER5ALI5 


DEEP  E( 

GASTRIC  ARTEI 

AND  VE 


LIGAMENT  OF  HENLE  LIGAMENT  OF  HESSELBACH 


Fig.  320. — The  deep  epigastric  artery  and  veins,  ligament  of  Henle  and  ligament  of  Hesselbach,  seen  from 
in  front.     (Modified  from  Braune.) 


430 


THE  3IU8CLE8  AND  FASCIA 


divides  into  two  lamellae,  which  pass,  one  in  front  and  the  other  behind  the  muscle, 
enclosing  it  in  a  kind  of  sheath,  and  reuniting  on  its  inner  border  at  the  linea  alba; 
the  anterior  layer  is  blended  with  the  aponeurosis  of  the  External  oblique  muscle; 
the  posterior  layer  with  that  of  the  Transversalis.  Along  the  lower  fourth  the 
aponeurosis  passes  altogether  in  front  of  the  Rectus  without  any  separation. 
Where  the  aponeurosis  ceases  to  split,  and  passes  altogether  in  front  of  the  Rectus 
muscle,  a  deficiency  is  left  in  the  sheath  of  the  Rectus  behind;  this  is  marked  above 
by  a  sharp  lunated  margin  which  has  its  concavity  downward,  and  is  known  as 
the  semilunar  fold  of  Douglas  Qiiwa  semicircularis)  (Fig.  32.3) . 

Relations. — By  its  superficial  surface  the  Internal  oblique  is  in  relation  with  the  External 
oblique,  Latissinius  dorsi,  spermatic  cord,  and  external  ring;  by  its  deep  surface,  with  the  Trans- 
versalis muscle,  the  lower  intercostal  vessels  and  nerves,  the  iliohypogastric  and  the  ilioinguinal 
nerves.  Near  Poupart's  ligament  it  lies  on  the  fascia  transversalis,  internal  ring,  and  spermatic 
cord.    Its  lower  border  forms  the  upper  boundary  of  the  inguinal  canal. 


Fig.  321.— Diagram  of  sheath  of  Rectus. 


External  oblique 
Internal  oblique 
TranRrprsalis 


Fig.  322. — Diagram  of  a  transve 


section  through  the  anteri 
fold  of  Douglas. 


abdominal  wall,  below  the  semilu 


The  Cremaster  muscle  (m.  cremaster)  (Fig.  319)  is  a  thin  layer  of  muscle,  com- 
posed of  a  number  of  fasciculi  which  arise  from  the  inner  part  of  Poupart's  liga- 
ment, where  its  fibres  are  continuous  with  those  of  the  Internal  oblique  and  also 
occasionally  with  the  Transversalis.  It  passes  along  the  outer  side  of  the  spermatic 
cord,  descends  with  it  through  the  external  abdominal  ring  upon  the  front  and 
sides  of  the  cord,  and  forms  a  series  of  loops  which  differ  in  thickness  and  length 
in  different  subjects.  Those  at  the  upper  part  of  the  cord  are  exceedingly  short, 
but  they  become  in  succession  longer  and  longer,  the  longest  reaching  down  as 
low  as  the  testicle,  where  a  few  are  inserted  into  the  tunica  vaginalis.  These 
loops  are  united  by  areolar  tissue,  and  form  a  thin  covering,  the  cremasteric  fascia, 
over  the  cord  and  testis.  The  fibres  of  this  muscle  ascend  along  the  inner  side 
of  the  cord,  and  are  inserted  by  a  small  pointed  tendon  into  the  crest  of  the  os 
pubis  and  in  front  of  the  sheath  of  the  Rectus  muscle. 

It  will  be  observed  that  the  origin  and  insertion  of  the  Cremaster  is  precisely  similar  to  that 
of  the  lower  fibres  of  the  Internal  oblique.  This  fact  affords  an  easy  explanation  of  the  manner 
in  which  the  testicle  and  cord  are  invested  by  this  muscle.  At  an  early  period  of  fetal  life  the 
testis  is  placed  at  the  lower  and  back  part  of  the  abdominal  cavity,  but  during  its  descent  toward 
the_  scrotum,  which  takes  place  before  birth,  it  passes  beneath  the  arched  fibres  of  the  Internal 
oblique.    As  the  testis  and  cord  go  to  their  destination  in  the  scrotum  they  pass  beneath  this 


OF  THE  ABDOMEN 


431 


muscle  and  carry  with  them  and  retain  fibres  from  its  lower  part.  It  occasionally  happens 
that  the  loops  of  the  Cremaster  surround  the  cord,  some  lying  behind  as  well  as  in  front.  It  is 
probable  that  under  these  circumstances  the  testis,  in  its  descent,  passed  through  instead  of 
beneath  the  fibres  of  the  Internal  obliciue. 

In  the  descent  of  an  inguinal  hernia,  which  takes  the  same  course  as  the  spermatic  cord, 
the  Cremaster  muscle  forms  one  of  its  coverings.  This  muscle  becomes  largely  developed  in 
cases  of  hydrocele  and  large  old  scrotal  hernia.     The  Cremaster  muscle  is  found  only  in  the 


TERIOR  LEAF 
SHEATH   OF 
CTU5  ABDOMINIS 


Fig.  32.3.— The  i 


cles  of  the  abdomen,  showing  the  semilu 
(Spalteholz.) 


Viewed  from  in  front. 


male,  but  almost  constantly  in  the  female  a  few  muscle  fibres  may  be  seen  on  the  surface  of  the 
round  ligament  which  correspond  to  this  muscle,  and  in  cases  of  inguinal  hernia  in  the  female 
a  considerable  amount  of  muscle  tissue  may  be  found  covering  the  sac. 

Relations. — By  its  superficial  surface,  with  the  External  oblique,  Latissimus  dorsi,  spermatic 
cord,  and  external  ring;  by  its  deep  surface,  with  the  Transversalis  muscle,  the  lower  intercostal 


432 


THE  MVSCLES  AND  FASCIA 


vessels  and  nerves,  the  iliohypogastric  and  the  ilioinguinal  nerves.  Near  Poupart's  ligament 
the  Cremaster  lies  on  the  fascia  transversalis,  internal  ring,  and  spermatic  cord.  Its  lower 
border  forms  the  upper  boundary  of  the  spermatic  canal. 

Dissection, — Detach  the  Internal  oblique  in  order  to  expose  the  Transversalis  beneath.  This 
mav  be  effected  by  dividing  the  muscle,  above,  at  its  attachment  to  the  ribs:  below,  at  its  con- 
nection with  Poupart's  ligament  and  the  crest  of  the  ilium;  and  behind,  by  a  vertical  incision 
extending  from  the  last  rib  to  the  crest  of  the  ilium.     The  muscle  should  previously  be  made 


Fig,  324. — The  Transversalis,  Rectus,  and  Pyramidalis  muscles. 

tense  by  drawing  upon  it  with  the  fingers  of  the  left  hand,  and  if  its  division  be  carefully  effected, 
the  cellular  interval  between  it  and  the  Transversalis,  as  well  as  the  direction  of  the  fibres  of  the 
latter  muscle,  will  afford  a  clear  guide  to  their  separation;  along  the  crest  of  the  ilium  the  cir- 
cumflex iliac  vessels  are  interposed  between  them,  and  form  an  important  guide  in  separating 
*iiem.     The  muscle  should  then  be  thrown  inward  toward  the  linea  alba. 

The  Transversalis  muscle  (m.  transversus  abdominis)  (Fig.  324),  so  called 
from  the  direction  of  its  fibres,  is  the  deepest  flat  muscle  of  the  abdominal  wall. 


OF  THE  ABDOMEN  433 

being  placed  immediately  beneath  the  Internal  oblique.  It  arises  by  fleshy  fibres 
from  the  outer  third  of  Poupart's  ligament;  from  the  inner  lip  of  the  crest  of  the 
ilium  for  its  anterior  three-fourths;  from  the  inner  surface  of  the  cartilages  of  the 
six  lower  ribs,  interdigitating  with  the  Diaphragm;  and  from  the  lumbar  fascia 
(Fig.  325),  which  may  be  regarded  as  the  posterior  aponeurosis  of  the  muscle. 
The  muscle  terminates  in  front  in  a  broad  aponeurosis,  the  lower  fibres  of  which 
curve  downward  and  inward,  and  are  inserted,  together  with  those  of  the  Internal 
oblique,  on  the  crest  of  the  os  pubis  and  iliopectineal  line,  thus  forming  what  is 
known  as  the  conjoined  tendon  of  the  Internal  oblique  and  Transversalis  muscles. 
Throughout  the  rest  of  its  extent  the  aponeurosis  passes  horizontally  inward, 
and  is  inserted  into  the  linea  alba,  its  upper  three-fourths  passing  behind  the 
Rectus  abdominis  muscle,  blending  with  the  posterior  lamella  of  the  Internal 
oblique;  its  lower  fourth  passing  in  front  of  the  Rectus. 

The  conjoined  tendon  of  the  Internal  oblicjue  and  Transversalis  is  chiefly  formed 
by  the  lower  part  of  the  tendon  of  the  Transversalis,  and  is  inserted  into  the  crest 
of  the  OS  pubis  and  iliopectineal-  line,  immediately  behind  the  external  abdominal 
ring,  thus  serving  to  protect  what  would  otherwise  be  a  weak  point  in  the  abdominal 
wall.  The  conjoined  tendon  is  sometimes  divided  into  an  outer  and  an  inner 
portion — the /ormer  termed  the  ligament  of  Hesselbach  {ligamentwn  imerfoveolare) ; 
the  latter,  the  ligament  of  Henle  (Fig.  320). 

Relations. — By  its  superficial  surface,  with  the  Internal  oblique,  the  lower  intercostal  nerves, 
and  the  inner  surface  of  the  cartilages  of  the  lower  ribs;  by  its  deep  surface,  with  the  fascia 
transversalis,  which  separates  it  from  the  peritoneum.  Its  lower  border  forms  the  upper 
boundary  of  the  inguinal  canal. 

Dissection. — To  expose  the  Rectus  abdominis  muscle,  open  its  sheath  by  a  vertical  incision 
extending  from  the  costal  arch  to  the  os  pubis,  and  then  reflect  the  two  portions  from  the 
surface  of  the  muscle,  which  is  easily  done,  excepting  at  the  lineae  transversae,  where  so 
close  an  adhesion  exists  that  the  greatest  care  is  requisite  in  separating  them.  Now  raise  the 
outer  edge  of  the  muscle,  in  order  to  examine  the  posterior  layer  of  the  sheath.  By  dividing 
the  muscle  in  the  centre,  and  turning  its  lower  part  downward,  the  point  where  the  posterior 
wall  of  the  sheath  terminates  in  a  thin  curved  margin  will  be  seen. 

The  Rectus  abdominis  (m.  rectus  abdominis)  (Figs.  323  and  324)  is  a  long  flat 
muscle,  which  extends  along  the  whole  length  of  the  front  of  the  abdomen,  being 
separated  from  its  fellow  of  the  opposite  side  by  the  linea  alba.  It  is  much  broader, 
but  thinner,  above  than  below,  and  arises  by  two  tendons;  the  external  or  larger  is 
attached  to  the  crest  of  the  os  pubis,  the  internal,  smaller  portion  interlaces  with 
its  fellow  of  the  opposite  side,  and  is  connected  with  the  ligaments  covering  the 
front  of  the  symphysis  pubis.  The  fibres  ascend,  and  the  muscle  is  inserted  by 
three  portions  of  unequal  size  into  the  cartilages  of  the  fifth,  sixth,  and  seventh 
ribs.  The  longest  portion  attached  principally  to  the  cartilage  of  the  fifth  rib, 
usually  has  some  fibres  of  insertion  into  the  anterior  extremity  of  the  rib  itself. 
Some  fibres  are  occasionally  connected  with  the  costoxiphoid  ligaments  and  side 
of  the  ensiform  cartilage. 

The  Rectus  muscle  is  traversed  by  tendinous  intersections,  three  in  number, 
which  have  received  the  name  of  lineae  transversae  (inscriptiones  tendineae).  One 
of  these  is  usually  situated  opposite  the  umbilicus,  and  two  above  that  point;  of 
the  latter,  one  corresponds  to  the  extremity  of  the  ensiform  cartilage,  and  the  other 
to  the  interval  between  the  ensiform  cartilage  and  the  umbilicus.  These  inter- 
sections pass  transversely  or  obliquely  across  the  muscle  in  a  zigzag  course;  they 
rarely  extend  completely  through  its  substance,  sometimes  they  pass  only  half- 
way across  it,  and  are  intimately  adherent  in  front  to  the  sheath  in  which  the 
muscle  is  enclosed.  Sometimes  one  or  two  additional  lines  may  be  seen,  one 
usually  below  the  umbilicus;  the  position  of  the  other,  when  it  exists,  is  variable. 
These  additional  lines  are  for  the  most  part  incomplete. 


434 


THE  3WSCLE8  AND  EASCI^ 


The  Rectus  is  enclosed  in  a  sheath,  the  rectus  sheath  (vagina  m.  recti  abdominis) 
(Figs.  325  and  326),  formed  by  the  aponeurosis  of  the  Obhque  and  Transversalis 


Fig.  325. — A  transverse  section  of  the  abdomen  in  the  lumbar  region. 


muscles,  which  are  arranged  in  the  following  manner.     Wien  the  aponeurosis  of 
the  Internal  oblique  arrives  at  the  outer  margin  of  the  Rectus  it  divides  into  two 


(anterior  leaf) 


Posterior  k-af       Anterior  leaf 


SHEATH  OF  RECTUS  ABDOMINIS 

Fig.  326. — Transition  of  the  tendon  of  the  right  internal  oblique  into  the  sheath  of  the  rectus.     (Spalteholz.) 

lamellae,  one  of  which  passes  in  front  of  the  Rectus,  blending  with  the  aponeurosis 
of  the  External  oblique;  the  other,  behind  it,  blending  with  "the  aponeurosis  of  the 


OF  THE  ABDOMEN  435 

Transversalis;  and  these,  joining  again  at  its  inner  border,  are  inserted  into 
the  hnea  alba.  This  arrangement  of  the  aponeuroses  exists  along  the  upper 
three-fourths  of  the  muscle;  at  the  commencement  of  the  lower  fourth,  the 
posterior  wall  of  the  sheath  terminates  in  a  thin  curved  margin,  the  semilunar 
fold  of  Douglas  (liiiea  seviicircularis)  (Fig.  323),  the  concavity  of  which  looks 
downward  toward  the  pubes;  the  aponeuroses  of  all  three  muscles  pass  in  front 
of  the  Rectus  without  any  separation.  A  very  thin  aponeurotic  layer  does  pass 
behind  the  lower  one-fourth  of  the  muscle,  but  it  is  trivial  as  compared  with 
the  thickness  of  the  layer  behind  the  upper  three-fourths  of  the  muscle.  This 
sudden  thinning  causes  the  semilunar  fold  of  Douglas.  The  extremities  of  the  fold 
of  Douglas  descend  as  pillars  to  the  os  pubis.  The  inner  pillar  is  attached  to 
the  symphysis  pubis;  the  outer  pillar  passes  downward  as  a  distinct  band  on  the 
inner  side  of  the  internal  abdominal  ring  to  join  with  the  outer  fibres  of  the  con- 
joined tendon,  and  assist  in  forming  the  ligament  of  Hesselbach  (Fig.  320). 
There  its  fibres  divide  into  two  sets,  internal  and  external;  the  internal  fibres  are 
attached  to  the  ascending  ramus  of  the  os  pubis;  the  external  fibres  pass  to  the 
psoas  fascia,  to  the  deep  surface  of  Poupart's  ligament,  and  to  the  tendon  of  the 
Transversalis  on  the  outer  side  of  the  ring.  The  Rectus  muscle,  in  the  situ- 
ation where  its  sheath  is  deficient,  is  separated  from  the  peritoneum  by  the  trans- 
versalis fascia.  Since  the  tendon  of  the  Internal  oblique  and  the  Transversalis 
only  reach  as  high  as  the  costal  margin,  it  follows  that  above  this  level  the  sheath 
of  the  Rectus  is  also  deficient  behind,  the  muscle  resting  directly  on  the  cartilages 
of  the  ribs,  being  covered  merely  by  the  aponeurotic  tendon  of  the  External 
oblique.  The  convex  outer  border  of  the  Rectus  muscle  corresponds  to  the  linea 
.semilunaris. 

The  Pyramidalis  (m.  pyramidalis)  is  a  small  muscle,  triangular  in  shape, 
placed  at  the  lower  part  of  the  abdomen,  in  front  of  the  Rectus,  and  is  contained 
in  the  same  sheath.  It  arises  by  tendinous  fibres  from  the  front  of  the  os  pubis 
and  the  anterior  pubic  ligament;  the  fleshy  portion  of  the  muscle  passes  upward, 
diminishing  in  size  as  it  ascends,  and  terminates  by  a  pointed  extremity,  which  is 
inserted  into  the  linea  alba,  midway  between  the  umbilicus  and  the  os  pubis.  This 
muscle  is  sometimes  found  wanting  on  one  or  both  sides;  the  lower  end  of  the 
Rectus  then  becomes  pi-oportionately  increased  in  size.  Occasionally  it  has  been 
found  double  on  one  side,  or  the  muscles  of  the  two  sides  are  of  unequal  size. 
Its  length  varies  slightly. 

Besides  the  Rectus  and  Pyramidalis  muscles,  the  sheath  of  the  Rectus  contains  the  superior 
and  deep  epigastric  arteries,  the  terminations  of  the  lumbar  arteries  and  of  the  lower  intercostal 
arteries  and  nerves. 

Nerves. — The  abdominal  muscles  are  supplied  by  the  lower  intercostal  nerves.  The  Trans- 
versalis and  Internal  oblique  also  receive  filaments  from  the  hypogastric  branch  of  the  ilio- 
hypogastric and  sometimes  from  the  ilioinguinal.  The  Cremaster  is  supplied  by  the  genital 
branch  of  the  genitofemoral.    The  Pyramidalis  is  supplied  by  the  twelfth  thoracic  nerve. 

The  linea  alba  (Figs.  324  and  325)  is  a  tendinous  raphe  seen  along  the  middle  line  of  the 
abdomen,  extending  from  the  ensiform  cartilage  to  the  superior  pubic  ligament,  to  which  it  is 
attached.  It  is  placed  between  the  inner  borders  of  the  Recti  muscles,  and  is  formed  by  the 
blending  of  the  aponeuroses  of  the  Obliqui  and  Transversales  muscles.  It  is  narrow  below, 
corresponding  to  the  narrow  interval  existing  betvi'een  the  Recti,  but  broader  above,  as  these 
muscles  diverge  from  one  another  in  their  ascent ;  it  becomes  of  considerable  breadth  when  there 
is  great  distention  of  the  abdomen  from  pregnancy  or  from  ascites.  It  presents  numerous  aper- 
tures for  the  passage  of  vessels  and  nerves;  the  largest  of  these  is  the  umbilicus  (Fig.  327).  The 
umbilicus  is  a  fibrous  ring  formed  by  the  fibres  of  the  aponeurosis  of  the  linea  alba',  in  the 
fetus  it  transmits  the  umbilical  vein,  the  two  hypogastric  arteries,  the  allantoic  duct,  and  the 
vitello-intestinal  duct;  but  in  the  adult  the  aperture  is  filled  with  scar  tissue  and  is  obliterated; 
the  resulting  cicatrix  is  stronger  than  the  neighboring  parts;  hence  umbilical  hernia  occurs  in  the 
adult  near  the  umbilicus,  while  in  the  fetus  it  occurs  at  the  umbilicus.  The  remains  of  the  fetal 
structures  are  cord-like  in  character;  and  they  diverge  from  the  umbilicus  within  the  abdomen. 


436 


THE  MUSCLES  AND  FASCIA 


UMBILICUS 


YPOGASTRIC 


— URACHUS 


Fig.  327. — The  umbilicus  of  the  fetus 
seen  from  within  the  abdomen.  (Poirier 
and  Charpy.) 


The  remains  of  the  umbilical  vein  constitute  the  round  ligament  of  the  liver,  and  this  cord 

passes  upward  (Fig.  327).     The  remains  of  the  hypogastric  arteries  pass  dowiiward  (Fig.  327). 

The  remains  of  the  allantois  become  the  lu-achus,  which  passes  to  the  summit  of  the  bladder 

(Fig.  327).     The  depression  of  the  umbilicus  is  created  by  the  virachus. 
The  lineae  semilunares  (Figs  317  and  323)  are  two  curved  tendinous  lines  placed  one  on 

each  side  of  the  linea  alba.     Each  corresponds  with  the  outer  border  of  the  Rectus  muscle,  and 

each  extends  from  the  cartilage  of  the  ninth  rib  to  the 
pubic  spine,  and  is  formed  by  the  aponeurosis  of  the 
Internal  oblique  at  its  point  of  division  to  enclose  the 
Rectus,  where  it  is  reinforced  in  front  by  the  External 
obli(|ue  and  behind  by  the  Transversalis. 

Actions. — The  abdominal  muscles  perform  a  three- 
fold action: 

When  the  pelvis  and  thorax  are  fixed,  they  compress 
the  abdominal  viscera,  by  constricting  the  cavity  of  the 
abdomen,  in  which  action  they  are  materially  assisted  by 
the  descent  of  the  Diaphragm.  By  these  means  assist- 
ance is  given  in  expelling  the  fetus  from  the  uterus,  the 
feces  from  the  rectum,  the  urine  from  the  bladder,  and 
the  contents  of  the  stomach  in  vomiting. 

If  the  pelvis  and  vertebral  column  be  fixed,  these 
muscles  compress  the  lower  part  of  the  thorax,  mate- 
rially assisting  expiration.  If  the  pelvis  alone  is  fixed, 
the  thorax  is  bent  directly  forward  when  the  muscles  of 
both  sides  act,  or  to  either  side  when  those  of  the  two 
sides  act  alternately,  rotation  of  the  trunk  at  the  same 
time  taking  place  to  the  opposite  side. 

If  the  thorax  be  fixed,  these  muscles,  acting  together, 
draw  the  pelvis  upward,  as  in  climbing,  or,  acting  singly, 
they  draw  the  pelvis  upward,  and  bend  the  vertebral 
column  to  one  side  or  the  other.     The  Recti  muscles, 

acting  from  below,  depress  the  thorax,  and  consequently  fiex  the  vertebral  column ;  when  acting 

from    above,  they   fiex  the  pelvis   upon  the   vertebral  column.     The  Pyramidales  are  tensors 

of  the  linea  alba. 

The  fascia  transversalis  {fascia  transversalis)  is  a  thin  aponeurotic  membrane 
which  lies  betM^een  the  deep  surface  of  the  Transversalis  muscle  and  the  extra- 
peritoneal fat.  It  forms  part  of  the  general  layer  of  fascia  which  lines  the  interior 
of  the  abdominal  and  pelvic  cavities,  and  is  directly  continuous  with  the  iliac  and 
pelvic  fasciae.  In  the  inguinal  region  the  transversalis  fascia  is  thick  and  dense 
in  structure,  and  joined  by  fibres  from  the  aponeurosis  of  the  Transversalis 
muscle,  but  it  becomes  thin  and  cellular  as  it  ascends  to  the  Diaphragm,  and  blends 
with  the  fascia  covering  this  muscle.  In  front,  it  unites  across  the  middle  line 
with  the  fascia  on  the  opposite  side  of  the  body,  and  behind  it  becomes  lost  in  the 
fat  which  covers  the  posterior  surfaces  of  the  kidneys.  Beloiv,  it  has  the  following 
attachments:  Posteriorly,  it  is  connected  to  the  whole  length  of  the  crest  of  the 
ilium,  between  the  attachments  of  the  Transversalis  and  Iliacus  muscles;  between 
the  anterior  superior  spine  of  the  ilium  and  the  femoral  vessels  it  is  connected 
to  the  posterior  margin  of  Poupart's  ligament,  and  is  there  continuous  with  the 
iliac  fascia.  Internal  to  the  femoral  vessels  it  is  thin  and  attached  to  the  pubis 
and  to  the  iliopectineal  line,  behind  the  conjoined  tendon,  with  which  it  is  united; 
and,  corresponding  to  the  point  where  the  femoral  vessels  pass  into  the  thigh, 
this  fascia  descends  in  front  of  them,  and  forms  the  anterior  wall  of  the  femoral 
sheath.  Beneath  Poupart's  ligament  the  transversalis  fascia  is  strengthened  by  a 
band  of  fibrous  tissue,  which  is  only  loosely  connected  to  Poupart's  ligament,  and 
is  specialized  as  the  deep  femoral  arch.  The  spermatic  cord  in  the  male  and  the 
round  ligament  in  the  female  pass  through  this  fascia;  the  point  where  they  pass 
through  is  called  the  internal  abdominal  ring.  This  opening  is  not  visible  exter- 
nally, owing  to  a  prolongation  of  the  transversalis  fascia  on  these  structures, 
which  forms  the  infmidibuliform  fascia. 


OF  THE  ABDOMEN 


437 


The  internal  or  deep  abdominal  ring  {anmdus  inguinalis  abdominis)  (Figs.  320 
and  328)  is  situated  in  the  transversalis  fascia,  midway  between  the  anterior 
superior  spine  of  the  ilium  and  the  symphysis  pubis,  and  about  iialf  an  inch  above 
Poupart's  ligament.  It  is  of  an  oval  form,  the  extremities  of  the  oval  directed 
upward  and  downward,  varies  in  size  in  different  subjects,  and  is  much  larger  in 
the  male  than  in  the  female.  The  internal  ring  is  bounded,  abocc  and  externally, 
by  the  arched  fibres  of  the  Trans^■e^salis;  below  and  internally,  by  the  deep 
epigastric  vessels.  It  transmits  the  spermatic  cord  in  the  male  and  the  round 
ligament  in  the  female.  From  its  circumference  a  thin  funnel-shaped  membrane, 
the  infundibuliform  or  internal  spermatic  fascia,  is  continued  around  the  cord  and 
testis,  enclosing  them  in  a  distinct  covering. 


EMORAL  AHTERY 


GIMBERNAT-S  LIGAMENT 
LIGAMENT 

Fia.  328. — The  relation  of  the  femoral  and  internal  abdominal  rings,  seen  fn 
removal  of  the  peritoneum.     (Poirier  and  Charpy.) 


'ithin  the  abdomen  after 


Wien  the  sac.  of  an  oblique  inguinal  hernia  passes  through  the  internal  or  deep  abdominal 
ring,  the  infundibuliform  process  of  the  transversalis  fascia,  .forms  one  of  its  coverings. 

The  Inguinal  or  Spermatic  Canal  (canalis  inguinalis)  (Figs.  329  and  330). — ^The 
inguinal  or  spermatic  canal  contains  the  spermatic  cord  (Junicuhis  sperinaticus)  in 
the  male  and  the  round  ligament  (ligamentum  teres  uteri)  in  the  female.  It  is  an 
oblique  canal  about  an  inch  and  a  half  in  length,  directed  downward  and  inward, 
and  placed  parallel  to  and  a  little  above  Poupart's  ligament.  It  commences  above 
at  the  internal  or  deep  abdominal  ring,  which  is  the  point  where  the  cord  enters 
the  spermatic  canal,  and  terminates  below  at  the  external  ring.  It  is  bounded 
in  front  by  the  aponeurosis  of  the  External  oblique  throughout  its  whole  length, 
and  by  the  Internal  oblique  for  its  outer  third;  behind,  from  within  outward,  by 
the  triangular  fascia  (when  this  is  present),  the  conjoined  tendon,  and  the  trans- 
versalis fascia;  below,  by  Gimbernat's  ligament,  and  by  the  union  of  the  fascia 
transversalis  with  Poupart's  ligament.  The  deep  epigastric  artery  passes  upward 
and  inward  behind  the  canal  lying  close  to  the  inner  side  of  the  internal  abdominal 
ring  (Fig.  320).  The  interval  between  this  artery  and  the  outer  edge  of  the  Rectus 
abdominis  is  named  Hesselbach's  triangle,  the  base  of  which  is  formed  by  Pou- 
part's ligament. 


438 


THE  MUSCLES  AND  FASCIJE 


ien_xe:.jh_im  A,i.^ 


'v" 


EXTERNAL  OBLIQUE 

(reflected  inward) 


Fig.  329. — The  right  inguinal  canal  m  the  m-le,  second  layer,  vu\\( 
Fig  318  )     (Spalteholz 


unt      (The  first  layer  is  shown  i 


Fig.  330.-The  right  inguinal  canal  in  the  male,  third  layer,  viewed  from  in  front.     (Spalteholz.'! 


OF  THE  ABDOMEN  439 

That  form  of  protrusion  in  which  the  intestine  follows  the  course  of  the  spermatic  cord  along 
the  spermatic  canal  is  called  oblique  inguinal  hernia. 

Surface  Form. — The  only  two  muscles  of  this  group  which  have  any  considerable  influence 
on  surface  form  are  the  External  oblique  and  the  Rectus  muscles  of  the  abdomen.  With  regard 
to  the  E.xternal  oblique,  the  upper  digitations  of  its  origin  from  the  ribs  are  well  marked,  and  are 
intermingled  with  the  serrations  of  the  Serratus  magnus;  the  lower  digitations  are  not  visible,  as 
they  are  covered  by  the  thick  border  of  the  Latissimus  dorsi.  The  attachment  of  the  External  ob- 
lique to  the  crest  of  the  ilium,  in  conjunction  with  the  Internal  oblique,  forms  a  thick  oblique  roll, 
which  determines  the  iliac  furrow.  Sometimes  on  the  front  of  the  lateral  region  of  the  abdomen 
an  undulating  outline  marks  the  spot  where  the  muscle  fibres  terminate  and  the  aponeurosis 
commences.  The  outer  border  of  the  Rectus  is  defined  by  the  lima  xiniilunaris,  which  may 
be  exactly  located  by  putting  the  muscle  into  action.  It  corresponds  wiili  ;i  curved  line,  with  its 
convexity  outward,  drawn  from  the  end  of  the  cartilage  of  the  ninth  rib  to  the  spine  of  the  os 
pubis,  so  that  the  centre  of  the  line,  at  or  near  the  umbilicus,  is  three  inches  from  the  median 
line.  The  inner  border  of  the  Rectus  corresponds  to  the  linea  alba,  marked  on  the  surface  of 
the  body  by  a  groove,  the  abdominal  furrow,  which  extends  from  the  infrasternal  fossa  to,  or  to 
a  little  below,  the  umbilicus,  where  il  grailuiiUy  becomes  lost.  The  surface  of  the  Rectus  presents 
three  transverse  fiurows,  the  tiiirac  innisvcrsae.  The  upper  two  of  these,  one  opposite  or  a 
little  below  the  tip  of  the  ensiform  cartilage,  and  another,  midway  between  this  point  and  the 
umbilicus,  are  usually  well  marked;  the  third,  opposite  the  umbilicus,  is  not  so  distinct.  The 
umbilicus,  situated  in  the  linea  alba,  varies  very  much  in  position  as  regards  its  level.  It  is 
always  situated  above  a  zone  drawn  around  the  body  opposite  the  highest  point  of  the  crest  of 
the  ilium,  generally  being  from  three-quarters  of  an  inch  to  an  inch  above  this  line.  It  usually 
corresponds,  therefore,  to  the  articular  disk  between  the  third  and  fourth  lumbar  vertebrae. 


2.  The  Posterior  Muscles  of  the  Abdomen. 

Psoas  magnus.  Iliacus. 

Psoas  parvus.  Quadratus  lumborum. 

The  Psoas  magnus,  the  Psoas  parvus,  and  the  Iliacus  muscles,  with  the  fascia 
covering  them,  will  be  described  with  the  Muscles  of  the  Lower  Extremity. 

The  Fascia  Covering  the  Quadratus  Lumborum  (Fig.  325). — ^This  is  the  most 
anterior  of  the  three  layers  of  the  lumbar  fascia.  It  is  a  thin  layer  of  fascia,  which, 
passing  over  the  anterior  surface  of  the  Quadratus  lumborum,  is  attached,  inter- 
nally, to  the  bases  of  the  transverse  processes  of  the  lumbar  vertebrse;  below,  to 
the  iliolumbar  ligament;  and  above,  to  the  apex  and  lower  border  of  the  last 
rib. 

The  portion  of  this  fascia  which  extends  from  the  transverse  process  of  the 
first  lumbar  vertebra  to  the  apex  and  lower  border  of  the  last  rib  constitutes  the 
ligamentum  arcuatum  externum  of  the  Diaphragm. 

The  Quadratus  lumborum  (w.  quadratus  hnnhormn)  (Fig.  311)  is  situated  in 
the  lumbar  region.  It  is  irregularly  quadrilateral  in  shape,  and  broader  below 
than  above.  It  arises  by  aponeurotic  fibres  from  the  iliolumbar  ligament  and 
the  adjacent  portion  of  the  crest  of  the  ilium  for  about  two  inches,  and  is 
inserted  into  the  lower  border  of  the  last  rib  for  about  half  its  length,  and  by 
four  small  tendons,  into  the  apices  of  the  transverse  processes  of  the  four  upper 
lumbar  vertebrae.  Occasionally  a  second  portion  of  this  muscle  is  found  situ- 
ated in  front  of  the  preceding.  This  arises  from  the  upper  borders  of  the  trans- 
verse processes  of  three  or  four  of  the  lower  lumbar  vertebrae,  and  is  inserted  into 
the  lower  margin  of  the  last  rib.  The  Quadratus  lumborum  is  contained  in  a 
sheath  formed  by  the  anterior  and  middle  lamellte  of  the  lumbar  fasciae. 

Relations. — Its  deep  surface  (or  rather  the  fascia  which  covers  its  anterior  surface)  is  in 
relation  with  the  colon,  the  kidney,  the  Psoas  muscle,  and  the  Diaphragm.  Between  the  fascia 
and  the  muscle  are  the  last  thoracic,  iliohypogastric,  and  ilioinguinal  nerves.  Its  superficial 
surface  is  in  relation  with  the  middle  lamella  of  the  lumbar  fascia,  which  separates  it  from  the 


440 


THE  MUSCLES  AND  FASCIA 


Erector  spinae.  The  Quadratus  luinborum  extends,  however,  beyond  the  outer  border  of  the 
Erector  spinae. 

Nerve-supply. — The  anterior  branches  of  the  last  thoracic  and  the  first  lumbar  nerves,- 
sometimes  also  a  branch  from  the  second  lumbar  nerve. 

Actions. — The  Quadratus  lumborum  draws  down  the  last  rib.  It  acts  as  a  muscle  of  inspi- 
ration by  helping  to  fix  the  origin  of  the  Diaphragm.  If  the  thorax  and  vertebral  column  are 
fixed,  it  may  act  upon  the  pelvis,  raising  it  toward  its  own  side  when  only  one  muscle  is  put  in 
action;  and  when  both  muscles  act  together,  either  from  below  or  above,  they  flex  the  trunk. 


IV.  MUSCLES  AND  FASCI.®  OF  THE  PELVIC  OUTLET. 

The  muscles  and  fasciae  of  the  pelvic  outlet  are  those  structures  which  form  the 
floor  of  the  pelvis.  Perineum  is  a  term  used  to  designate  that  segment  of  the 
structure  lying  dorsal  to  the  pubic  arch  and  subpubic  ligament  and  ventral  to 
a  line  drawn  transversely,  in  front  of  the  anus,  between  the  anterior  part  of  the 
tuberosity  of  the  ischium  of  each  side.  The  ischiorectal  space  is  the  name  given 
to  the  segment  dorsal  to  the  line  above  mentioned  and  ventral  to  the  tip  of  the 
coccyx.     This  space  is  bounded  laterally  by  the  Gluteus  maximus  muscle. 


Fig.  331. — The  perineum.     The  integliment  and  superficial  layer  of  superficial  fascia  reflected. 

The  fascia  of  the  pelvic  outlet  is  most  easily  understood  if  it  is  considered  in 
the  order  of  its  dissection.  Considered  thus,  it  resolves  itself  into  three  strata — 
the  superficial  fascia,  the  triangular  ligament,  and  the  pelvic  fascia.  The  su'per- 
ficial  fascia  is  made  up,  as  in  other  regions  of  the  body,  of  a  superficial  and  a  deep 
layer.  The  fascia  over  the  ischiorectal  region  is  arranged  in  fatty  layers,  which 
fill  the  ischiorectal  fossa  on  each  side  of  the  rectum  and  anus.  In  the  region 
of  the  perineum  the  fascia  requires  fuller  consideration;  here  it  is  definitely 
arranged  into  two  layers — superficial  and  deep.  The  superficial  layer  is  thick, 
loose,  areolar  in  texture,  and,  except  toward  the  scrotum,  contains  in  its  meshes 


OF  THE  PELVIC  OUTLET 


441 


some  adipose  tissue,  the  amount  of  which  varies  in  different  subjects.  In  front 
this  layer  is  continuous  with  the  dartos  of  the  scrotum,  in  the  mid-hne  of  which 
it  dips  deeply  to  form  the  scrotal  septum.     In  the  female  this  structure  enters 


SUPERFICIAL 
LAYER   OF 
TRIANGULAR 
\  LIGAMENT 

TRANSVERSUS 

SUPERFICIALIS 


ANOCOCCYGEAL  LIGAMENT 

Fig.  332. — The  muscles  of  the  male  perineum,  viewed  from  below.     (Spalteholz.) 

into  the  formation  of  the  mons  veneris  and  the  labia  majora.  The  superficial 
layer  is  continuous  on  either  side  with  the  fatty  fascia  on  the  inner  side  of  the 
thighs.  The  deep  layer  of  the  superficial  fascia,  or  the  fascia  of  CoUes  (Fig.  331), 
is  thin,  aponeurotic  in  structure,  and  of  considerable  strength.     It  serves  to  bind 


442 


THE  MUSCLES  AND  FASCIA 


down  the  muscle  of  the  root  of  the  penis.  It  is  continuous  with  the  dartos  of 
the  scrotum,  with  the  fascia  of  the  penis,  and  with  Scarpa's  fascia  on  the  anterior 
surface  of  the  abdomen;  on  either  side  it  is  firmly  attached  to  the  outer  lip  of 
the  ischiopubic  ramus.  Posteriorly  (dorsally)  the  deep  layer  curves  around  the 
superficial  transverse  perineal  muscle  to  blend  with  the  base  of  the  triangular 
ligament.  The  deep  (cephalic)  surface  of  this  fascia  covers  the  superficial  mus- 
cles and  the  superficial  bloodvessels  and  nerves  of  the  perineum  (Fig.  333). 
From  its  deep  surface  a  septum  which  is  incomplete  in  front  is  given  off  and 
divides  the  adjacent  space  in  two. 

The  Central  Tendinous  Point  of  the  Perineum. — This  is  a  fibrous  point  in  the 
middle  line  of  the  pelvic  outlet,  between  the  urethra  and  the  rectum,  and  about 
half  an  inch  in  front  of  the  anus.  At  this  point  four  muscles  converge  and  are 
attached — viz.,  the  External  sphincter  ani,  the  Accelerator  urinae,  and  the  two 
Superficial  transverse  perineal ;  so  that  by  the  contraction  of  these  muscles,  which 
extend  in  opposite  directions,  it  serves  as  a  fixed  point  of  support  (Fig.  333). 


Transversiis  perine 
superjiciahs 


Central  tendinous  point  of 
perineum. 

Superficial  perineal  artery. 
Superficial  perineal  nerve. 
Internal  pudic  nerve. 
Internal  pudic  artery. 


Fig.  333, — The  superficial  muscles  and  vessels  ot  the  perineum. 

The  Muscles  of  the  Perineum  in  the  Male  (Figs.  332,  333). 


Superficial  transverse  perineal. 
Accelerator  urinae. 


Erector  penis. 
Compressor  urethrae. 


The  Superficial  transverse  perineal  muscle  (to.  transversus  perinei  superficialis) 
is  a  narrow  muscular  slip,  which  passes  more  or  less  transversely  across  the  pelvic 
outlet.  It  arises  by  a  small  tendon  from  the  inner  and  fore  part  of  the  tuberosity 
of  the  ischium,  and,  passing  inward,  is  inserted  into  the  central  tendinous  point  of 
the  perineum,  joining  in  this  situation  with  the  muscle  of  the  opposite  side,  the 
External  sphincter  ani  behind,  and  the  Accelerator  urinae  in  front.  The  base 
of  the  triangular  ligament  lies  under  cover  of  this  muscle. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — By  their  contraction  they  serve  to  fix  the  central  tendinous  point  of  the  perineum. 


OF  THE  PERINEUM  IN  THE  31  ALE 


443 


The  Accelerator  urinae  (m.  bulbocavernosus)  is  placed  in  the  middle  line  of 
the  perineum,  immediately  in  front  of  the  anus.     It  consists  of  two  symmetrical 


Superficial  layer  of 
deep  perineal  fascia  removed 
showing 

__ COMPRESSOR   URETHHAE 

_Jniernal  piidic  artery. 
Artery  of  the  bidb. 
'Cowper^s  gland. 


Fig.  334.— Triangular  ligament  or  deep  perineal  fascia.     On  the  left  side  the  anterior  layer  has  been  removed. 


Artery  of  corpus  cavet  nosum 
Dorsal  artery  of  J)ei^)^ 


Artery  of  bulb. 

Internal  pudic  artery. 

Cowper's  gland 


Fig.  335.— a  view  of  the  position  of  the  viscera  at  the  outlet  of  the  pelvis. 


halves,  united  along  the  median  line  by  a  tendinous  raphe.     It  arises  from  the 
central  tendon  of  the  perineum,  and  from  the  median  raphe  in  front.     From  this 


444  THE  MUSCLES  AND  FASCIA 

point  its  fibres  diverge  symmetrically;  the  most  posterior  form  a  thin  layer,  which 
is  lost  on  the  superficial  surface  of  the  triangular  ligament;  the  middle  fibres  encircle 
the  bulb  and  adjacent  parts  of  the  corpus  spongiosum,  and  join  with  the  fibres 
of  the  opposite  side,  on  the  upper  part  of  the  corpus  spongiosum,  in  a  strong 
aponeurosis.  The  anterior  fibres,  the  longest  and  most  distinct,  spread  out 
over  the  sides  of  the  corpus  cavernosum,  and  are  inserted  partly  into  that  body, 
anterior  to  the  Erector  penis  (occasionally  extending  to  the  os  pubis),  and  partly 
terminate  in  a  tendinous  expansion,  which  covers  the  dorsal  vessels  of  the  penis. 
The  latter  fibres  are  best  seen  by  dividing  the  muscle  longitudinally,  and  dissect- 
ing it  outward  from  the  surface  of  the  urethra.  Many  fibres  of  the  External 
sphincter  ani  and  of  the  Superficial  transverse  perineal  muscles  pass  into  this 
muscle. 

This  muscle  is  sometimes  so  developed  that  it  may  be  arranged  under  four  distinct  layers. 
In  such  subjects  the  posterior  and  greatest  part  of  the  muscle  is  composed  of  two  layers.  The 
deeper  invests  the  bulb  of  the  corpus  spongiosum  in  a  cap-like  manner.  It  is  called  the  Com- 
pressor hemisphaerium  bulbi. 

The  superficial  portion,  called  the  Compressor  bulbi,  arises  in  the  central  tendon  of  the  perineum, 
where  it  blends  with  the  Superficial  transversus  perinei  and  the  External  sphincter  ani  muscles, 
and  from  the  greater  portion  of  the  median  tendinous  raphe.  The  muscle  spreads  out  to  cover 
the  bulb  and  adjacent  portion  of  the  corpus  spongiosum,  and  meets  its  fellow  of  the  opposite 
side  in  the  strong  aponeurosis  on  the  upper  part  of  the  corpus  spongiosum.  The  hindmost 
fibers  are  attached  to  the  inferior  surface  of  the  subjacent  triangular  ligament. 

The  Constrictor  radicis  penis  consists  of  the  most  anterior  fibers  of  the  Accelerator  urinae. 
They  take  origin  from  the  portion  of  the  median  raphe  not  occupied  by  the  Compressor  bulbi,  and 
spread  outAvard.  forward,  and  upward  over  the  Corpus  cavernosum,  anterior  to  the  insertion  of  the 
Erector  penis,  and  are  inserted  partly  into  the  Corpus  cavernosum;  other  fibers  terminate  in  a 
tendinous  expansion  which  encircle  the  root  of  the  penis,  and,  therefore,  cover  the  dorsal  vessels 
of  this  organ. 

The  Ischiobulbosus  lies  superficial  to  the  Compressor  bulbi;  it  arises  from  the  tuberosity  of  the 
ischium  and  passes  upward  and  forward  to  be  inserted  into  that  part  of  the  median  raphe  which 
has  to  do  with  the  bulb. 

Action. — This  muscle  serves  to  empty  the  canal  of  the  urethi-a,  after  the  bladder  has  expelled 
its  contents;  during  the  greater  part  of  the  act  of  micturition  its  fibres  are  relaxed,  and  it  only 
comes  into  action  at  the  end  of  the  process.  The  middle  fibres  are  supposed,  by  Krause,  to 
assist  in  the  erection  of  the  corpus  spongiosum,  by  compressing  the  erectile  tissue  of  the  bulb. 
The  anterior  fibres,  on  each  side,  according  to  Tyrrel,  also  contribute  to  the  erection  of  the 
penis,  as  they  are  inserted  into,  and  are  continuous  with,  the  fascia  of  the  penis,  and  thus  com- 
press the  dorsal  vein  during  the  contraction  of  the  muscle. 

The  Erector  penis  {m.  ischiocavernosus)  covers  part  of  the  crus  penis.  It  is  an 
elongated  muscle,  broader  in  the  middle  than  at  either  extremity,  and  situated  on 
either  side  of  the  lateral  boundary  of  the  perineum.  It  arises  by  tendinous  and 
fleshy  fibres  from  the  inner  surface  of  the  tuberosity  of  the  ischium  and  the  great 
sacro-sciatic  ligament  behind  the  crus  penis,  and  from  the  adjacent  portion  of -the 
ramus  of  the  ischium  and  pubis.  From  these  points  fleshy  fibres  succeed,  which 
end  in  an  aponeurosis  which  is  inserted  into  the  sides  and  under  surface  of  the  crus 
penis.  Occasionally  some  of  the  fibres  of  this  muscle  that  arise  from  the  pubic 
ramus  pass  to  the  dorsum  of  the  penis.  To  these  fibres  is  given  the  name  Pubo- 
cavernosus  or  Levator  penis. 

Nerve-supply. — ^The  perineal  branch  of  the  internal  pudic. 

Actions. — This  muscle  compresses  the  crus  penis  and  retards  the  return  of  the  blood  through 
the  veins,  and  thus  serves  to  maintain  the  organ  erect. 

Between  the  muscles  just  examined  a  triangular  space  exists,  bounded  internally  by  the 
Accelerator  urinae,  externally  by  the  Erector  penis,  and  behind  by  the  Transversus  perinei 
superficialis.  The  floor  of  this  space  is  formed  by  the  triangular  ligament  of  the  perineum  (deep 
perineal  fascia),  and  running  in  it  from  behind  forward  (toward  the  pubis)  are  the  superficial 
perineal  vessels  and  nerves,  the  long  pudendal  nerve,  and  the  transverse  perineal  artery,  which 
courses  along  the  posterior  boundary  of  the  space  on  the  Superficial  transverse  perineal  muscle. 


OF  THE  PERINEUM  IN  THE  FEMALE 


445 


The  Muscles  of  the  Perineum  in  the  Female. 


Superficial  transverse  perineal. 
Sphincter  vaginae. 


Erector  clitoridis. 
Compressor  urethrae. 


The  Superficial  transverse  perineal  {m.  transversus  perinei  superficialis)  in 
the  female  is  a  narrow  slip  which  passes  more  or  less  transversely  across  the  back 
part  of  the  perineal  space.  It  arises  by  a  small  tendon  from  the  inner  and  fore  part 
of  the  tuberosity  of  the  ischium,  and,  passing  inward,  is  inserted  into  the  central 
point  of  the  perineum,  joining  in  this  situation  with  the  muscle  of  the  opposite 
side,  the  External  sphincter  ani  behind,  and  the  Sphincter  vaginae  in  fi'ont. 

Sn^penso}^/  Ugainent 
of  cliiorh  Glans  clitoris 


Xexternal  sphincter 
ani  muscle 
MUSCLE  Os  coccyx 

Fig.  336.— The  female  perineum  after  removal  of  the  skin  and  superficial  fascia.     (BardeleDen.) 

Nerve-supply.— The  perineal  branch  of  the  internal  pudic. 

Actions.— By  their  contraction  these  muscles  serve  to  fix  the  central  tendinous  point  of  the 
perineum. 

The  Sphincter  vaginae  (m.  hulhocavernosus)  surrounds  the  orifice  of  the  vagina; 
it  is  homologous  v  ith  the  Accelerator  urinae  in  the  male.  It  arises  posteriorly 
from  the  central  tendiuous  point  of  the  perineum,  where  it  blends  with  the  External 
sphincter  ani.     Its  fibres  pass  forward  on  each  side  of  the  vagina,  where  it  covers 


446  THE  MUSCLES  AND  FASCIA 

the  A-aginal  bulb,  to  be  inserted  into  the  corpora  cavernosa  of  the  clitoris;  a  fas- 
ciculus crosses  over  the  body  of  the  organ  and  compresses  the  dorsal  vein. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — It  diminishes  the  orifice  of  the  vagina.  The  anterior  fibres  contribute  to  the 
erection  of  the  clitoris,  as  they  are  inserted  into  and  are  continuous  with  the  fascia  of  the  clitoris 
and  compress  the  dorsal  vein  during  the  contraction  of  the  muscle. 

The  Erector  clitoridis  (m.  ischiocavernosus)  resembles  the  Erector  penis  in  the 
male,  but  is  smaller.  It  covers  the  unattached  part  of  the  crus  clitoridis.  It  is 
an  elongated  muscle,  broader  at  the  middle  than  at  either  extremity,  and  situated 
on  either  side  of  the  lateral  boundary  of  the  perineum.  It  arises  by  tendinous 
and  fleshy  fibres  from  the  inner  surface  of  the  tuberosity  of  the  ischium,  behind 
the  crus  clitoridis  from  the  surface  of  the  crus,  and  from  the  adjacent  portion  of 
the  ramus  of  the  ischium.  From  these  points  fleshy  fibres  succeed,  ending  in 
an  aponeurosis,  which  is  inserted  into  the  sides  and  under  surface  of  the  crus 
clitoridis. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — It  compresses  the  crus  clitoris  and  retards  the  return  of  blood  through  the  veins, 
and  thus  serves  to  maintain  the  organ  erect. 

The  Triangular  Ligament  in  the  Male  and  in  the  Female. 

The  triangular  ligament  or  the  deep  perineal  fascia  (diaphragma  urogenitale) 
(Figs.  336,  337,  338)  is  stretched  almost  horizontally  across  the  pubic  arch,  so  as 
to  close  in  the  front  part  of  the  outlet  of  the  pelvis.  It  consists  of  two  dense 
membranous  laminae,  which  are  united  along  their  dorsal  borders,  but  are  sep- 
arated ventrally  by  intervening  structures.  The  superficial  layer  {fascia  diaphrag- 
matis  urogenitalis  inferior)  is  triangular  in  shape  and  about  an  inch  and  a  half  in 
depth.  Its  apex  is  directed  forward,  and  is  separated  from  the  subpubic  liga- 
ment by  an  oval  opening  for  the  transmission  of  the  dorsal  vein  of  the  penis. 
A  strengthening  band,  the  transverse  pelvic  ligament  {ligavientum  transversum 
pelvis),  passes  from  one  pubic  bone  to  the  other  below  the  vein.  The  lateral  mar- 
gins of  the  inferior  layer  of  the  triangular  ligament  are  attached  on  each  side 
to  the  rami  of  the  ischium  and  os  pubis,  above  the  crura  penis.  The  base  is 
directed  toward  the  rectum,  and  connected  to  the  central  tendinous  point  of 
the  perineum.  It  is  continuous  with  the  deep  layer  of  the  superficial  fascia 
behind  the  Superficial  transverse  perineal  muscles  (Fig.  337),  and  with  a  thin 
fascia  which  covers  the  cutaneous  surface  of  the  Levator  ani  muscle,  the  anal  or 
ischiorectal  fascia  (Fig.  341). 

This  layer  of  the  triangular  ligament  is  perforated,  about  an  inch  below  the 
symphysis  pubis,  by  the  urethra,  the  aperture  for  which  is  circular  in  form;  by 
the  arteries  to  the  bulb  and  by  the  ducts  of  Cowper's  glands  close  to  the  urethral 
aperture ;  by  the  arteries  to  the  corpora  cavernosa — one  on  each  side,  close  to  the 
pubic  arch  and  about  half-way  along  the  attached  margin  of  the  ligament;  and 
by  the  dorsal  arteries  and  nerves  of  the  penis  near  the  apex  of  the  ligament. 
Its  base  is  also  perforated  by  the  superficial  perineal  vessels  and  nerves,  while 
between  its  apex  and  the  subpubic  ligament  passes  the  dorsal  vein  of  the  penis. 

When  this  superficial  layer  of  the  triangular  ligament  is  detached,  the  follow- 
ing structures  will  be  seen  between  it  and  the  deeper  layer:  The  membranous 
portion  of  the  urethra  and  the  Compressor  urethrae  muscle;  Cowper's  glands 
and  their  ducts;  the  pudic  vessels  and  dorsal  nerve  of  the  penis;  the  artery  and 
nerve  of  the  bulb,  and  a  plexus  of  veins  (Fig.  334). 

The  triangular  ligament  in  the  female  (Fig.  336)  is  not  so  strong  as  in  the  male. 
It  is  divided  in  the  middle  line  by  the  aperture  of  the  vagina,  with  the  external 
coat  of  which  it  becomes  blended;  between  the  vaginal  orifice  and  the  pubis  it  is 


THE  TRIANGULAR  LIGAMENT  IN  MALE  AND  IN  FEMALE     447 


EXTE 
SPHINC- 
TER   ANI 


DEEP  LAYEB  OF 

SUPERFICIAL  FASCU 

OF  PERINEUM 

(CoHes'  fascia) 


Fig.  337. — The  triangular  ligament  of  the  perineu 


DORSAL  VEIN 

OF    PENIS'        Y 
DORSAL  NERVE  I 


DORSAL  ARTERY_  / 
OF    PENIS 


ARTERY  TO 


Fig.  338.— The  superficial  layer  of  the  triangular  ligament.     The  Compressor  urelhrae  muscle  lies  behind  the 
superficial  layer  of  the  triangular  ligament  and  is  shown  la  the  figure  for  convenience.     (Poirier  and  Charpy.) 


448  THE  MUSCLES  AND  FASCIJE 

perforated  by  the  urethra.  Its  base  is  continuous,  as  in  the  male,  with  the  deep 
layer  of  the  superficial  fascia  surrounding  the  Transversus  perinei  muscles.  Like 
the  triangular  ligament  in  the  male,  it  consists  of  two  layers,  between  which  are 
to  be  found  the  following  structures:  The  dorsal  vein  and  nerves  of  the  clitoris, 
a  portion  of  the  urethra  and  the  Compressor  urethrae  muscle,  the  glands  of 
Bartholin  and  their  ducts,  the  pudic  vessels,  the  arteries  of  the  vestibular  bulbs, 
and  a  plexus  of  veins.  The  deep  layer  of  the  triangular  ligament  is  a  part  of  the 
pelvic  fascia,  and  is  described  on  page  449. 

The  Compressor  or  Constrictor  urethrae  {m.  sphincter  urethrae  membranacea)  in 
the  male  surrounds  the  whole  length  of  the  membranous  portion  of  the  urethra,  and 
is  contained  between  the  two  layers  of  the  triangular  ligament.  It  arises,  by  apon- 
eurotic fibres,  from  the  junction  of  the  rami  of  the  os  pubis  and  ischium,  to  the 
extent  of  half  or  three-quarters  of  an  inch — the  point  where  the  crura  penis  join 
the  transverse  ligament  of  the  perineum  and  the  layers  of  the  triangular  liga- 
ment; each  segment  of  the  muscle  passes  inward,  and  divides  into  two  fasciculi, 
which  surround  the  membranous  urethra  and  unite,  at  the  upper  and  lower 
surfaces  of  this  tube,  with  the  muscle  of  the  opposite  side  by  means  of  a  tendinous 
raphe.  This  muscle  is  frequently  discovered  in  two  portions,  an  anterior  and  a 
posterior,  separated  by  a  distinct  interval.  In  such  cases  the  posterior  fibres  are 
called  the  transversus  perinei  profundus,  and  the  anterior  fibres  are  called  the 
sphincter  urethrae  membranaceae.  The  Compressor  urethrae  in  the  female  arises 
as  in  the  male;  passing  mesally,  likewise,  it  divides  into  two  fasciculi;  these  latter, 
however,  have  not  the  same  intimate  functional  relationship  to  the  urethra  as  has 
the  muscle  of  the  male.  One  fasciculus  passes  ventrad  of  the  urethra  to  blend 
with  its  opposite  fellow;  the  posterior  fascicle  inserts  itself  into  the  lateral 
vaginal  wall. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — The  muscles  of  both  sides  act  together  as  a  sphincter,  compressing  the  mem- 
branous portion  of  the  urethra.  During  the  transmission  of  fluid  they,  like  the  Acceleratores 
urinae,  are  relaxed,  and  come  into  action  only  at  the  end  of  the  process,  to  eject  the  last  drops  of 
the  fluid. 

The  Pelvic  Fascia. 

The  pelvic  fascia  binds  strongly  together  the  pelvic  structures,  supports  the 
bloodvessels,  nerves,  and  lymphatics,  and  strengthens  the  floor  of  the  cavity. 
Above,  it  is  loosely  connected  to  the  back  part  of  the  iliopectineal  line,  and  is 
continuous  here  with  the  iliac  fascia.  Posteriorly,  over  the  sacrum,  it  is  very 
thin  and  lies  ventrad  to  the  Pyriformis  muscle  and  to  the  sacral  plexus  of 
nerves.  This  part  is  often  called  the  fascia  of  the  Pyriformis,  and  extends  outward 
along  the  muscle  into  the  gluteal  region.  At  its  sacral  attachments  around  the 
margins  of  the  sacral  foramina  it  comes  into  intimate  association  with  and  en- 
sheathes  the  nerves  as  they  emerge  from  these  foramina.  Anterior  to  its  ilio- 
pectineal attachment  the  pelvic  fascia  sinks  in  its  attachment  below  the  brim  of 
the  pelvis.  It  arches  below  the  obturator  vessels  and  nerves,  completing  the 
obturator  canal,  and  at  the  front  of  the  pelvis  the  line  of  attachment  is  depresesd 
on  the  posterior  surface  of  the  os  pubis,  so  that  at  the  symphysis  it  lies  just  above 
the  inferior  border  of  this  bone.  From  this  line  of  attachment  the  posterior  part 
is  prolonged  outward  on  the  Obturator  internus  into  the  gluteal  region.  The 
middle  portion  descends  on  the  visceral  surface  of  the  Obturator  internus  to  be- 
come attached  to  the  falciform  process  of  the  great  sacrosciatic  ligament.  Be- 
cause of  this  relation  with  the  Obturator  internus  this  part  is  called  the  Obturator 
fascia  (Fig.  340).  The  part  attached  to  the  body  of  the  pubis  descends  to  be 
attached  to  the  ischiopubie  ramus,  and  here  becomes  blended  with  the  base  of 
the  triangular  ligament  (Fig.  .341).     From  the  ischiopubie  ramus  it  is  continued 


THE  PELVIC  FASCIA 


449 


onward  behind  the  Compressor  urethrae  muscle  across  the  pubic  arch,  to  be  con- 
tinuous with  the  fascia  of  the  opposite  side.     Here  it  takes  a  special  name,  the 


ANTERIOR- 
SUPERIOR 
SPINES 


EATER 

CROSCIftTIC 

iAMENT 


FASCIA  OF 

LEVATOR  ANI 

MUSCLE 


Fig.  339. — Pelvic  fascia  (semidiagrammatic). 


deep  layer  of  the  triangular  ligament  {fascia  diaphragmatis  urogenitalis  superior) 
(Figs.  337  and  341).     This  part  of  the  fascia  is  perforated  by  the  urethra;  a  por- 


Jnternal  pitdic  vessels 
and  nerve. 


Fig.  340. — A  transverse  section  of  the  pelvis,  sliowing  tiie  pelvic  fascia  from  beliind. 

tion  of  it  turns  backward  around  the  anterior  extremity  of  the  Levator  ani  mus- 
cle to  join  the  visceral  layer  next  to  be  considered. 

At  the  level  of  a  line  extending  from  the  back  part  of  the  syniphysis  pubis  to 
the  spine  of  the  ischium  is  a  thick,  whitish  band  termed  the  white  line  (arms 

29 


450 


THE  MUSCLES  AND  FASCIA 


tendinexis)  (Fig.  339).  Above  this  line  the  fascia  hes  in  contact  with  the  perito- 
neum and  belongs  to  the  pelvic  cavity.  Below  this  line  the  obturator  fascia  has 
to  do  with  the  ischiorectal  space.  The  pudic  vessels  and  nerves  cross  this  area 
enclosed  in  a  special  sheath  (Alcock's  canal).  At  the  white  line  the  obturator 
fascia  gives  off  a  special  layer  to  the  pelvic  viscera,  Rectovesical  fascia  (fascia 
endopelmna) ;  where  these  two  layers  diverge  partly  arises  the  Levator  ani  (Figs. 
339  and  340).  The  Rectovesical  fascia  lies  superior  (cephalad)  to  the  Levator 
ani  (Fig.  340).  Traced  forward  it  is  seen  to  be  attached  to  the  posterior  surface 
of  the  body  of  the  pubis  three-fourths  of  an  inch  higher  than  the  pelvic  fascia. 
Traced  internally  it  approaches  the  bladder  and  rectum;  here  it  splits  into  several 
layers.  The  upper  layer  invests  the  bladder  and  constitutes  the  lateral  trite  lic/a- 
vient  of  the  bladder;  another  prolongation  invests  the  seminal  vesicle,  passes  be- 
tween the  bladder  and  rectum,  being  continuous  with  the  same  fascia  on  the 


Fig.  341— Side 


of  the  male  subject,  showing  the  pelvic  and  perineal  fasi 


opposite  side;  a  third  in^•estment  is  also  prolonged  downward  on  the  rectum 
within  the  insertion  of  the  Levator  ani  muscle.  In  front  of  the  bladder  the 
fascia  closely  ensheathes  the  prostate  gland  and  prostate  plexus  of  veins,  forming 
the  capsule  of  the  prostate.  That  portion  of  the  fascia  which  is  attached  to  the 
body  of  the  pubis  passes  backward  as  a  narrow  cord-like  band  to  the  upper  part 
of  the  prostate  and  upper  part  of  the  neck  of  the  bladder;  this  is  the  anterior  true 
ligament  of  the  bladder,  or  puboprostatic  ligament  (Figs.  340,  341). 

The  Anal  fascia  is  a  thin,  aponeurotic  fascia  which  clothes  the  under  surface  of 
the  Levator  ani  muscle.  It  arises  from  the  obturator  fascia  just  below  the  origin 
of  the  Levator  ani,  and  extends  inward  and  downward  and  separates  this  muscle 
from  the  ischiorectal  fossa.     (See  page  454.) 

The  Levator  ani  (Fig.  343)  is  a  broad,  thin  muscle,  situated  on  the  side  of  the 
pelvis.  It  is  attached  to  the  inner  surface  of  the  side  of  the  true  pelvis,  and 
descends  to  unite  with  its  fellow  of  the  opposite  side.     Together  these  structures 


THFj  pel  VIC  FASCIA 


451 


form  the  greater  part  of  the  floor  of  the  pelvic  cavity.  They  support  the  viscera 
in  this  cavity  and  surround  the  various  structures  which  pass  through  it.  This 
muscle  arises,  in  front,  from  the  posterior  surface  of  the  body  of  the  pubis  on  the 
outer  side  of  the  symphysis;  behind,  from  the  inner  surface  of  the  spine  of  the 
ischium;  and  between  these  two  points,  from  the  obturator  fascia.  Posteriorly, 
this  fascial  origin  corresponds,  more  or  less  closely,  with  the  white  line  (page  449), 


GLANDS 

Fig.  342. — The  right  Levator  ani  in  the  male,  viewed  from  the  left.    (Spalteholz.)  • 

but  in  front  the  muscle  arises  from  the  fascia  at  a  varying  distance  above  the  white 
line,  in  some  cases  reaching  nearly  as  high  as  the  canal  for  the  obturator  vessels 
and  nerve.  The  fibres  pass  downward  to  the  middle  line  of  the  floor  of  the  pelvis; 
the  most  posterior  are  inserted  into  the  sides  of  the  last  two  segments  of  the  coccyx; 
those  placed  more  anteriorly  unite  with  the  muscle  of  the  opposite  side,  in  a  median 
fibrous  raph^  (anococcygeal  raphe),  which  extends  between  the  coccyx  and  the 
margin  of  the  anus.     The  middle  fibres  are  inserted  into  the  side  of  the  rectum. 


452 


THE  MUSCLES  AND  FASCI.^ 


blending  with  the  fibres  of  the  Sphincter  muscles;  lastly,  the  anterior  fibres 
descend  upon  the  side  of  the  prostate  gland  to  unite  beneath  it  with  the  muscle 
of  the  opposite  side,  joining  with  the  fibres  of  the  External  sphincter  and  Trans- 
versus  perinei  muscles  at  the  central  tendinous  point  of  the  perineum. 

The  anterior  portion  is  occasionally  separated  from  the  rest  of  the  muscle  by 
connective  tissue.  From  this  circumstance,  as  well  as  from  its  peculiar  relation 
with  the  prostate  gland,  descending  by  its  side,  and  surrounding  it  as  in  a  sling, 
it  has  been  described  by  Santorini  and  others  as  a  distinct  muscle,  under  the 
name  of  Levator  prostatae.  In  the  female  the  anterior  fibres  of  the  Levator 
ani  descend  upon  the  side  of  the  vagina. 


I  \  '  ^  l.t.VHIUH      MNI 

r  \  -    ™,„„  .» '//RC- TOCt-tYGEUSlM  ILIOCLl.    i     HU         i        Tjr 

fjL  ^    ill    I     ■'     ^         ,lcvatob\         /- 


^cii^is- 


FiG.  343.— The  levator  a 


Spalteholz.) 


Relations. — By  its  deep,  upper,  or  pehic  surface  the  Levator  ani  is  in  relation  with  the 
rectovesical  fascia,  which  separates  it  from  the  bladder,  prostate,  rectum,  and  peritoneum.  By- 
its  superficial,  lower,  or  perineal  surface  it  forms  the  inner  boundary  of  the  ischiorectal  fossa,  and 
is  covered  by  a  thin  layer  of  fascia,  the  anal  fascia,  given  off  from  the  obturator  fascia.  Its 
posterior  border  is  free  and  separated  from  the  Coccygeus  mviscle  by  a  cellular  interspace.  Its 
anterior  border  is  separated  from  the  muscle  of  the  opposite  side  by  a  triangular  space,  through 
which  the  uretlora,  and  in  the  female  the  vagina,  pass  from  the  pelvis. 

The  Levator  ani  may  be  divided  into  iliococcygeal  and  pubococcygeal  parts.  (Fig.  343.) 
The  Iliococcygeus  arises  from  the  ischial  spine  and  from  the  posterior  part  of  the  pelvic  fascia, 
and  is  attached  to  the  coccyx  and  anococcygeal  raph^;  it  is  usually  thin,  and  may  fail  entirely, 
or  be  largely  replaced  by  fibrous  tissue.  An  accessory  slip  at  its  posterior  part  is  sometimes 
named  the  Iliosacralis.  The  Pubococcygeus  arises  from  the  back  of  the  pubis  and  from  the 
anterior  part  of  the  pelvic  fascia,  and  "  is  directed  backward  almost  horizontally  along  the  side 
of  the  anal  canal  toward  the  coccyx  and  sacrum,  to  which  it  finds  attachment.  Between  the 
termination  of  the  vertebral  column  and  the  anus  the  two  pubococcygeal  muscles  come  together 
and  form  a  thick,  fibromuscular  layer  lying  on  the  raphe  formed  by  the  iliococcygei  "  (Thompson), 
The  greater  part  of  this  muscle  is  inserted  into  the  coccyx  and  into  the  last  one  or  two  pieces  of 
the  sacrum.  This  insertion  into  the  vertebral  column  is,  however,  not  admitted  by  all  observers. 
The  fibres  which  form  a  sling  for  the  rectum  are  named  the  Puborecialis  or  Sphincter  recti. 


THE  PEL  VIC  FASCIA  453 

They  arise  from  the  lower  part  of  the  symphysis  pubis,  and  from  the  upper  layer  of  the  triangular 
ligament.  They  meet  with  the  corresponding  fibres  of  the  opposite  side  around  the  lower  part 
of  the  rectum,  and  form  for  it  a  strong  sling. 

Nerve-supply. — The  Levator  ani  is  supplied  by  a  branch  from  the  fourth  sacral  nerve  and 
by  a  branch  which  is  sometimes  derived  from  the  perineal,  sometimes  from  the  inferior  hemor- 
rhoidal division  of  the  pudic  nerve. 

The  Coccygeus  (?«.  coccygeiis)  (Fig.  343)  is  situated  behind  and  parallel  with 
the  preceding.  It  is  a  triangular  plane  of  muscular  and  tendinous  fibres,  arising 
by  its  apex  from  the  spine  of  the  ischium  and  lesser  sacrosciatic  ligament,  and 
inserted  by  its  base  into  the  margin  of  the  coccyx  and  into  the  side  of  the  lower  piece 
of  the  sacrum.  It  assists  the  Levator  ani  and  Pyriformis  in  closing  in  the  back 
part  of  the  outlet  of  the  pelvis. 

Nerve-supply. — The  Coccygeus  is  supplied  by  a  branch  from  the  fourth  and  fifth  sacral 
nerves. 

Actions. — The  Levatores  ani  constrict  the  lower  end  of  the  rectum  and  vagina.  They  elevate 
and  invert  the  lower  end  of  the  rectum  after  it  has  been  protruded  and  everted  during  the  expul- 
sion of  the  feces.  The  Coccygei  muscles  pull  forward  and  support  the  coccyx,  after  it  has  been 
pressed  backward  during  defecation  or  parturition.  The  Levatores  ani  and  Coccygei  together 
form  a  muscular  diaphragm  which  supports  the  pelvic  viscera. 


Muscles  cf  the  Ischiorectal  Region. 

Corrugator  cutis  ani.  Internal  sphincter  ani. 

External  sphincter  ani.  Levator  ani  (described  on  page  450). 

Coccygeus  (described  above). 

The  Corrugator  Cutis  Ani. — Around  the  anus  is  a  thin  stratum  of  involuntary 
muscle  fibre  which  radiates  from  the  orifice.  hiteriiaUy,  the  fibres  fade  into  the 
submucous  tissue,  while  externally  they  blend  with  the  true  skin.  By  its  con- 
traction it  raises  the  skin  into  ridges  around  the  margin  of  the  anus. 

The  External  sphincter  ani  (?/;.  sphincter  ani  externus)  (Figs.  332,  333,  3.36,  and 
342)  is  a  thin,  flat  plane  of  muscle  fibre,  elliptical  in  shape  and  intimately  adher- 
ent to  the  integument  surrounding  the  margin  of  the  anus.  It  measures  about 
three  or  four  inches  in  length  from  its  anterior  to  its  posterior  extremity,  being 
about  an  inch  in  breadth  opposite  the  anus.  It  consists  of  two  strata,  super- 
ficial and  deep.  The  superficial,  constituting  the  main  portion  of  the  muscle, 
arises  from  a  narrow  tendinous  band,  the  anococcygeal  raphe,  which  stretches 
from  the  tip  of  the  coccyx  to  the  posterior  margin  of  the  anus;  it  forms  two  flattened 
planes  of  muscle  tissue,  which  encircle  the  anus  and  meet  in  front  of  be  inserted 
into  the  central  tendinous  point  of  the  perineum,  joining  with  the  Transversus 
perinei,  the  Levator  ani,  and  the  Accelerator  urinae.  The  deeper  portion  forms 
a  complete  sphincter  to  the  anal  canal.  Its  fibres  surround  the  canal,  closely 
applied  to  the  Internal  sphincter,  and  in  front  blend  with  the  other  muscles  at  the 
central  point  of  the  perineum.  In  a  considerable  proportion  of  cases  the  fibres 
decussate  in  front  of  the  anus,  and  are  continuous  with  the  Transversus  perinei. 
Posteriorly,  they  are  not  attached  to  the  coccyx,  the  fibres  of  opposite  sides  being 
continuous  behind  the  anal  canal.  The  upper  edge  of  the  muscle  is  ill-defined, 
since  fibres  are  given  off  from  it  to  join  the  Levator  ani. 

Nerve-supply. — A  branch  from  the  fourth  sacral  and  twigs  from  the  inferior  hemorrhoidal 
branch  of  the  internal  pudic  supply  the  muscle. 

Actions. — The  action  of  this  muscle  is  peculiar:  (1)  It  is,  like  other  muscles,  always  in  a 
state  of  tonic  contraction,  and  having  no  antagonistic  muscle  it  keeps  the  anal  canal  and  orifice 
closed.  (2)  It  can  be  put  into  a  condition  of  greater  contraction  under  the  influence  of  the  will, 
so  as  more  firmlv  to  occlude  the  anal  aperture  in  expiratory  efforts,  unconnected  with  defecation. 
(3)  Taking  its  fixed  point  at  the  coccyx,  it  helps  to  6x  the  central  point  of  the  perineum,  so  that 
the  Accelerator  urinae  may  act  from  this  fixed  point. 


454  THE  3IUSCLES  AND  FASCIJE 

The  Internal  sphincter  ani  (m.  sphincter  ani  internus)  is  a  ring  of  muscle 
which  surrounds  the  anal  canal  for  about  an  inch ;  its  inferior  border  being  con- 
tiguous with,  but  quite  separate  from,  the  External  sphincter.  This  muscle  is 
about  a  sixth  of  an  inch  in  thickness,  and  is  formed  by  an  aggregation  of  the 
involuntary  circular  fibres  of  the  intestine.  It  surrounds  the  canal  for  about  an 
inch,  its  lower  border  being  about  a  quarter  of  an  inch  from  the  external  orifice. 
It  is  paler  in  color  and  less  coarse  in  texture  than  the  External  sphincter. 

Actions. — Its  action  is  entirely  involuntary.  It  helps  the  External  sphincter  to  occlude  the 
anal  aperture. 

The  Ischiorectal  fossa  {fossa  ischiorectalis)  (Figs.  332  and  342)  is  situated 
between  the  end  of  the  rectum  and  the  ischial  tuberosity.  It  is  triangular  in 
shape;  its  base,  directed  to  the  surface  of  the  body,  is  formed  by  the  integument  of 
the  ischiorectal  region;  its  apex,  directed  upward,  corresponds  to  the  point  of 
division  of  the  obturator  fascia  and  the  thin  membrane  given  off  from  it,  which 
covers  the  outer  surface  of  the  Levator  ani  (anal  fascia).  Its  dimensions  are 
about  an  inch  in  breadth  at  the  base  and  about  two  inches  in  depth,  being  deeper 
behind  than  in  front.  It  is  bounded,  internally,  by  the  Sphincter  ani,  Levator 
ani,  and  the  Coccygeus  muscles;  externally,  by  the  tuberosity  of  the  ischium  and 
the  obturator  fascia,  which  covers  the  inner  surface  of  the  Obturator  internus 
muscle;  in  front,  it  is  limited  by  the  line  of  junction  of  the  deep  layer  of  the  super- 
ficial fascia  with  the  base  of  the  triangular  ligament;  and  behind,  by  the  margin 
of  the  Gluteus  maximus  muscle  and  the  great  sacrosciatie  ligament.  This  space  is 
filled  with  a  large  mass  of  adipose  tissue,  which  explains  the  frequency  with  which 
abscesses  in  the  neighborhood  of  the  rectum  burrow  to  a  considerable  depth. 

The  fascia  covering  the  inferior  surface  of  the  pelvic  diaphragm  is  knoM'n  as 
the  anal  fascia  (fascia  inferior  diaphragrnatis  pelvis).  It  is  attached  above  to  the 
obturator  fascia  along  the  line  of  origin  of  the  Levator  ani,  while  below  it  is  contin- 
uous with  the  deep  layer  of  the  triangular  ligament  and  with  the  fascia  on  the  Inter- 
nal sphincter  ani.  The  layer  covering  the  upper  surface  of  the  pelvic  diaphragm 
(pais  diaphragmatica  fasciae  pelvis)  follows,  above,  the  line  of  origin  of  the  Levator 
ani,  and  is  therefore  somewhat  variable.  In  f7-ont  it  is  attached  to  the  back  of 
the  symphysis  pubis  about  three-quarters  of  an  inch  above  its  lower  border.  It 
can  then  be  traced  outward  across  the  back  of  the  body  of  the  pubis  for  a  distance 
of  about  half  an  inch,  where  it  joins  the  obturator  fascia.  It  is  attached  to  this 
fascia  along  a  line  which  pursues  a  somewhat  irregular  course  to  the  spine  of  the 
ischium.  The  irregularity  of  this  line  is  due  to  the  fact  that  the  origin  of  the  Levator 
ani,  which  in  lower  forms  is  from  the  pelvic  brim,  is  in  man  lower  down,  on  the 
obturator  fascia.  Tendinous  fibres  of  origin  of  the  muscle  are  therefore  often 
found  extending  up  toward,  and  in  some  cases  reaching^  the  pelvic  brim,  and 
on  these  the  fascia  is  carried. 

MUSCLES    AND   FASCI.ffi   OF   THE   UPPER   EXTREMITY. 

The  muscles  of  the  upper  extremity  are  divisible  into  groups,  corresponding 
with  the  different  regions  of  the  limb. 

I.  Of  the  Thoracic  Region.  II.  Of  the  Shoulder  and  Arm. 

1.  Anterior  Thoracic  Region.  3.  Acromial  Region. 

Pectoralis  major.     Pectoralis  minor.  Deltoid. 

Subclavius. 

2.  Lateral  Thoracic  Region.  4.  Anterior  Scapular  Region. 

Serratus  magnus.  Subscapularis. 


THE  ANTERIOR   THORA  CIG  REGION 


455 


5.   Posterior  Scapular  Regie 


Supraspinatus. 
Infraspinatus. 


Teres  minor. 
Teres  major. 


6.  Anterior  Humeral  Region. 

Coracobrachialis.  Biceps. 

Brachialis  anticus. 


7.  Posterior  Humeral  Region. 
Triceps.  Subanconeus. 

III.  Of  the  Forearm. 

8.  Anterior  Radioulnar  Region. 

.       [  Pronator  teres. 

"o  c     Flexor  carpi  radialis. 
u  >^  \  ralmaris  longus. 

Flexor  carpi  ulnaris. 

Flexor  sublimis  digitorum. 

Fiexor  profundus  digitorum. 

Flexor  longus  pollicis. 

Pronator  quadratus. 


9:'v^ 


O 


9.  Radial  Region. 

Brachioradialis. 

Extensor  carpi  radialis  longior. 

Extensor  carpi  radialis  brevior. 


a-  cs' 


10.   Posterior    Radioulnar   Region. 

Extensor  communis  digitorum. 

Extensor  minimi  digiti. 

Extensor  carpi   ulnaris. 

Anconeus. 

Supinator  [brevis]. 
■  Extensor  ossis  metacarpi  pollicis. 

Extensor  brevis  pollicis. 

Extensor  longus  pollicis. 
.  Extensor  indicis. 

IV.  Of  the  Hand. 

11.  Radial  Region. 

Abductor  pollicis. 
Opponens  pollicis. 
Flexor  brevis  pollicis. 
Adductor  oblic(uus  pollicis. 
Adductor  transversus  pollicis. 

12.  Ulnar  Region. 

Palmaris  brevis. 
Abductor  minimi  digiti. 
Flexor  brevis  minimi  digiti. 
Opponens  minimi  digiti. 

13.  Middle  Palmar  Region. 

Lumbricales. 
Interossei  palmares. 
Interossei  dorsales. 


Dissection  of  Pectoral  Region  and  Axilla  (Fig.  344).— The  arm  being  drawn  away  from 
the  side  nearly  at  right  angles  with  the  trunk  and  rotated  outward,  make  a  vertical  incision 
through  the  integument  in  the  median  hne  of  the  thorax,  from  the  upper  to  the  lower  part  of  the 
sternum;  a  second  incision  along  the  lower  border  of  the  Pectoral  muscle,  from  the  ensiform 
cartilage  to  the  inner  side  of  the  axilla;  a  third,  from  the  sternum  along  the  clavicle,  as  far  as  its 
centre;  and  a  fourth,  from  the  middle  of  the  clavicle  obliquely  downward,  along  the  interspace 
between  the  Pectoral  and  Deltoid  muscles,  as  low  as  the  fold  of  the  axilla.  The  flap  of  integu- 
ment is  then  to  be  dissected  ofi'  in  the  direction  indicated  in  the  figure,  but  not  entirely  removed, 
as  it  should  be  replaced  on  completing  the  dissection.  If  a  transverse  incision  is  now  made 
from  the  lower  end  of  the  sternum  to  the  side  of  the  thorax,  as  far  as  the  posterior  fold  of  the 
axilla,  and  the  integument  reflected  outward,  the  axillary  space  will  be  more  completely  exposed. 


I.  THE  MUSCLES  AND  FASCIA  OF  THE  THORACIC  REGION. 
1.  The  Anterior  Thoracic  Region. 


Pectoralis  major 
[Sternalis.] 


Pectoralis  minor. 
Subclavius. 


The  superficial  fascia  of  the  thoracic  region  is  a  loose  cellulofibrous  layer  en- 
closing masses  of  fat  in  its  spaces.  It  is  continuous  with  the  superficial  fascia  of 
the  neck  and  upper  extremity  above,  and  with  that  of  the  abdomen  below.    Oppo- 


456 


THE  3IUSCLES  AND  FASCIAE 


3.  Dissection  of 
Shoulder  and  Arm. 


site  the  mamma  it  divides  into  two  layers,  one  of  which  passes  in  front,  the  other 
behind  that  gland;  and  from  both  of  these  layers  numerous  septa  pass  into  its 
substance,  supporting  its  various  lobes;  from  the  anterior  layer  fibrous  processes 
pass  forward  to  the  integument  and  nipple.  These  processes  were  called  by  Sir 
A.  Cooper  the  suspensory  ligaments,  from, the  support  they  afford  to  the  gland  in 
this  situation. 

The  deep  thoracic  fascia  is  a  thin  aponeurotic  lamina,  covering  the  surface 
of  the  oreat  Pectoral  muscle,  and  sending  numerous  prolongations  between  its 
fascicuH;  it  is  attached,  in  the  mid-line,  to  the  front  of  the  sternum,  and  above 
to  the  clavicle;  externally  and  below  it  becomes  continuous  with  the  fascia  over 
the  shoulder,  axilla,  and  thorax.  It  is  very  thin  over  the  upper  part  of  the  muscle, 
thicker  in  the  interval  between  the  Pectoralis  major  and  Latissimus  dorsi,  where 

it  closes  in  the  axillary  space,  and 
is  known  as  the  axillary  fascia  {fas- 
cia axillaris).  It  passes  behind 
into  the  fascia  of  the  Latissimus 
dorsi  and  Teres  major,  in  front 
into  the  fascia  of  the  Deltoid  and 
outward  into  the  fascia  of  the  arm. 
The  fascia  of  the  Latissimus  dorsi 
divides  at  the  outer  margin  of  the 
muscle  into  two  layers,  one  of 
which  passes  in  front  and  the  other 
behind  it;  these  proceed  as  far  as 
the  spinous  processes  of  the  thora- 
cic vertebrse,  to  which  they  are 
attached.  As  the  axillary  fascia 
leaves  the  lower  edge  of  the  Pecto- 
ralis major  to  pass  across  the  floor 
of  the  axilla  it  sends  a  layer  up- 
ward under  cover  to  the  muscle, 
the  deep  pectoral  fascia;  this  lamina 
splits  to  envelop  the  Pectoralis 
minor,  at  the  upper  edge  of  which 
it  becomes  continuous  with  the 
costocoracoid  membrane  (claripec- 
toral  fascia).  The  hollow  of  the 
axilla,  seen  when  the  arm  is  ab- 
ducted, is  mainly  produced  by  the 
traction  of  this  fascia  on  the 
axillary  floor,  the  axillary  fascia 
hence  it  is  sometimes  named  the  suspensory  ligament  of  the  axilla.  The  axillary 
fascia  is  not  a  distinct  and  complete  rigid  floor  of  the  axillary  space.  Like  all 
Qther  fascise,  it  follows  muscular  planes,  and  splits  to  encompass  vessels,  nerves, 
and  muscles.  In  it  are  numerous  perforations.  At  the  lower  part  of  the  thoracic 
region  the  deep  thoracic  fascia  is  well  developed,  and  is  continuous  with  the 
fibrous  sheath  of  the  Recti  abdominis. 

The  Pectoralis  major  (m.  pectoralis  major)  (Fig.  345)  is  a  broad,  thick,  triangular 
muscle,  situated  at  the  upper  and  fore  part  of  the  thorax,  in  front  of  the  axilla. 
It  arises  from  the  anterior  surface  of  the  sternal  half  of  the  clavicle;  from  half  the 
breadth  of  the  anterior  surface  of  the  sternum,  as  low  down  as  the  attachment 
of  the  cartilage  of  the  sixth  or  seventh  rib;  this  portion  of  its  origin  consists  of 
aponeurotic  fibres,  which  intersect  with  those  of  the  opposite  muscle ;  it  also  arises 
from  the  cartilages  of  all  true  ribs,  with  the  exception,  frequently,  of  the  first 


3.  Bend  of  Elbow. 


4=  Forearm. 


5.  Palm  of  Hand. 


Fig.  344. — Dissection  of  the  upper  extremity. 


THE  ANTERIOR   THORACIC  REGION 


457 


or  the  seventh,  or  both ;  and  from  the  aponeurosis  of  the  External  oblique  muscle 
of  the  abdomen.  The  fibres  from  this  extensive  origin  converge  toward  its  in- 
sertion, giving  to  the  muscle  a  radiated  appearance.  Those  fibres  which  arise 
from  the  clavicle  pass  oblicjuely  outward  and  downward  and  are  usually  separated 
from  the  rest  by  a  cellular  interval;  those  from  the  lower  part  of  the  sternum,  and 
the  cartilages  of  the  lower  true  ribs,  pass  upward  and  outward,  while  the  middle 
fibres  pass  horizontally.     They  all  terminate  in  a  flat  tendon,  about  two  inches 


Fig.  343.— Muscles  of  the  tho 


nd  front  of  the 


broad,  which  is  inserted  into  the  outer  bicipital  ridge  of  the  humerus.  This  tendon 
consists  of  two  laminae,  placed  one  in  front  of  the  other,  and  usually  blended 
together  below.  The  superficial,  the  thicker,  receives  the  clavicular  and  upper 
half  of  the  sternal  portion  of  the  muscle;  and  its  fibres  are  inserted  in  the  same 
order  as  that  in  which  they  arise ;  that  is  to  say,  the  outermost  fibres  of  origin  from 
the  clavicle  are  inserted  at  the  uppermost  part  of  the  tendon;  the  upper  fibres 


458 


THE  MUSCLES  AND  FASCIjE 


of  origin  from  the  sternum  pass  down  to  the  lowermost  part  of  this  superficial 
lamina  of  the  tendon  and  extend  as  low  as  the  tendon  of  the  Deltoid  and  join  with 
it.  The  deef  lamina  of  the  tendon  receives  the  attachment  of  the  lower  half 
of  the  sternal  portion  and  the  deeper  part  of  the  muscle  from  the  costal  cartilages. 
These  deep  fibres,  and  particularly  those  from  the  lower  costal  cartilages  ascend, 
the  higher  turning  backward  successively  behind  the  superficial  and  upper  ones, 
so  that  the  tendon  appears  to  be  twisted.  The  deep  lamina  reaches  higher  on 
the  humerus  than  the  superficial  one,  and  from  it  an  expansion  is  given  ofl^  which 
covers  the  bicipital  groove  and  blends  with  the  capsule  of  the  shoulder-joint. 
From  the  deepest  fibres  of  this  lamina  at  its  insertion  an  expansion  is  given  off 
which  lines  the  bicipital  groove  of  the  humerus,  while  from  the  lower  border 
of  the  tendon  a  third  expansion  passes  downward  to  the  fascia  of  the  arm.  Between 
the  posterior  surface  of  the  tendon  of  the  Great  pectoral  and  the  ^terior  surface 
of  the  long  head  of  the  Biceps  there  is  usually  a  bursa  (bursa  m.  pectoralis  majoris). 


IC   BRANCH   O^ 


ACIC  NERVE 


PECTORALIS 
MAJOR 


^. 


Fig.  346. — Costocoracoid  membrane. 


Relations. — By  its  swperficial  surface,  with  the  integument,  the  superficial  fascia,  the  Platysma, 
some  of  the  branches  of  the  descending  cervical  nerves,  the  mammary  gland,  and  the  deep 
fascia;  by  its  deep  surface:  its  thoracic  portion,  with  the  sternum,  the  ribs  and  costal  cartilages, 
the  costocoracoid  membrane,  the  Subclavius,  Pectoralis  minor,  Serratus  magnus,  and  the 
Intercostals;  its  axillary  portion  forms  the  anterior  wall  of  the  axillary  space,  and  covers  the 
axillary  vessels  and  nerves,  the  Biceps  brachii  and  Coracobrachialis  muscles.  Its  upper  harder 
lies  parallel  with  the  Deltoid,  from  which  it  is  separated  by  a  slight  interspace  in  which  lie  the 
cephalic  vein  and  humeral  branch  of  the  acromial  thoracic  artery.  Its  lower  border  forms  the 
anterior  margin  of  the  axilla,  being  at  first  separated  from  the  Latissimus  dorsi  by  a  considerable 
interval ;  but  both  muscles  gradually  converge  toward  the  outer  part  of  the  space. 


THE  ANTERIOR   THORACIC  REGION 


459 


A  Stemalis  muscle  is  occasionally  found  in  the  pectoral  region;  it  may  be  confined  to  one 
side,  or  may  be  bilateral.  It  is  sometimes  represented  by  delicate  scattered  fibres  overlying  a 
normal  Pectoralis  major,  or  by  a  well-developed  muscle  associated  with  a  defective  Pectoralis 
major.  It  is  often  attached  to  the  sternal  end  of  the  Sternomastoid;  below,  it  becomes  lost  in 
the  presternal  fascia  or  in  the  aponeurosis  of  the  External  oblique.  This  variant  is  regarded 
as  a  displaced  and  rotated  segmt-nt  of  the  Pectoralis  major;  it  is  supplied  by  branches  from  the 
anterior  tiioracic  nerve. 

Dissection. — Detach  the  Pectoralis  major  by  dividing  the  muscle  along  its  attachment  to 
the  clavicle,  and  by  making  a  vertical  incision  through  its  substance  a  little  external  to  its  line  of 
attachment  to  the  sternum  and  costal  cartilages.  The  muscle  should  then  be  reflected  outward, 
and  its  tendon  carefully  examined.  The  Pectoralis  minor  is  now  exposed,  and  immediately 
above  it,  in  the  interval  between  its  upper  border  and  the  clavicle,  a  strong  fascia,  the  costo- 
coracoid  membrane. 


^  Vr,   S 


Fig.  347. — Muscles  of  the  thorax  and  front  of  the  arm,  showing  e 


!  of  the  bounda 


The  Costocoracoid  Membrane,  or  the  Clavipectoral  Fascia  (fascia  coraco- 
clavicularis)  (Fig.  346),  is  a  strong  fascia,  situated  under  cover  of  the  clavicular 
portion  of  the  Pectoralis  major  muscle.  It  occupies  the  interval  between  the 
Pectoralis  minor  and  Subclavius  muscle,  and  protects  the  axillary  ■s'essels  and 
nerves.  Traced  upward,  it  splits  to  enclose  the  Subclavius  muscle,  and  its  two 
layers  are  attached  to  the  clavicle,  one  in  front  of  and  the  other  behind  the  muscle; 
the  deep  layer  fuses  with  the  deep  cervical  fascia  and  with  the  sheath  of  the  axillary 
vessels.  Mesially,  it  blends  w'ith  the  fascia,  co^'ering  the  first  two  intercostal 
spaces,  and  is  attached  also  to  the  first  rib  internal  to  the  origin  of  the  Subclavius 
muscle.     Laterally,  it  is  very  thick  and  dense,  and  is  attached  to  the  coracoid 


460  THE  MUSCLES  AND  FASCIA 

process.  The  portion  extending  from  its  attachment  to  the  first  rib  to  the  cora- 
coid  process  is  often  whiter  and  denser  than  the  rest;  this  is  sometimes  called  the 
costocoracoid  ligament.  Below,  it  is  thin,  and  at  the  upper  border  of  the  Pectoralis 
minor  it  splits  into  two  layers  to  invest  this  muscle;  from  the  lower  border  of  the 
Pectoralis  minor  it  is  continued  downward  to  join  the  axillary  fascia,  and  outward 
to  join  the  fascia  o\'er  the  short  head  of  the  Biceps.  The  costocoracoid  mem- 
brane is  pierced  by  the  cephalic  vein,  the  acromiothoracic  artery  and  vein,  supe- 
rior thoracic  artery,  and  anterior  thoracic  nerve. 

The  Pectoralis  minor  {m.  pectoralis  minor)  (Fig.  347)  is  a  thin,  flat,  triangular 
muscle,  situated  at  the  upper  part  of  the  thorax,  beneath  the  Pectoralis  major. 
It  arises  by  three  tendinous  digitations  from  the  upper  margin  and  outer  surface 
of  the  third,  fourth,  and  fifth  ribs,  near  their  cartilages,  and  from  the  aponeurosis 
covering  the  Intercostal  muscles;  the  fibres  pass  upward  and  outward,  and  con- 
verge to  form  a  flat  tendon,  which  is  inserted  into  the  inner  border  and  upper 
surface  of  the  coracoid  process  of  the  scapula. 

Relations. — By  its  superficial  surface,  with  the  Pectoralis  major  and  the  thoracic  branches  of 
the  acromiothoracic  artery.  By  its  deep  surface,  with  the  ribs.  Intercostal  muscles,  Serratus 
magnus,  the  axillary  space,  and  the  axillary  vessels  and  brachial  plexus  of  nerves.  Its  upper 
border  is  separated  from  th^  clavicle  by  a  narrow  triangular  interval,  occupied  by  the  costocoracoid 
membrane,  behind  which  are  the  axillary  vessels  and  nerves.  The  long  thoracic  artery  runs 
parallel  to  the  lower  border  of  this  muscle  and  the  anterior  thoracic  nerve  pierces  it. 

The  costocoracoid  membrane  should  now  be  removed,  and  the  Subclavius  muscle  will  be 
exposed. 

The  Subclavius  (m.  subclavius)  is  a  small  triangular  muscle,  placed  in  the 
interval  between  the  clavicle  and  the  first  rib.  It  arises  in  front  of  the  rhomboid 
ligament  by  a  short,  thick  tendon  from  the  first  rib  and  its  cartilage  at  their 
junction;  the  fleshy  fibres  proceed  obliquely  upward  and  outward,  to  be  inserted 
into  the  groove  on  the  under  surface  of  the  clavicle.  An  extension  from  the  apon- 
eurosis of  this  muscle  lies  upon  the  subclavian  vein. 

Relations. — Its  deep  surface  is  separated  from  the  first  rib  by  the  subclavian  vessels  and 
brachial  plexus  of  nerves.  Its  superficial  surface  is  separated  from  the  Pectoralis  major  by  the 
costocoracoid  membrane,  which,  with  the  clavicle,  forms  an  osseofibrous  sheath  in  which  the 
musole  is  enclosed. 

If  the  costal  attachment  of  the  Pectoralis  minor  be  divided  across,  and  the  muscle  reflected 
outward,  the  axillary  vessels  and  nerves  are  brought  fully  into  view,  and  should  be  examined. 

Nerves. — The  Pectoral  muscles  are  supplied  by  the  external  and  internal  anterior  thoracic 
nerves;  the  Pectoralis  major  through  these  nerves  receives  filaments  from  all  the  spinal  nerves 
entering  into  the  formation  of  the  brachial  plexus;  the  Pectoralis  minor  receives  its  fibres  from 
the  eighth  cervical  and  first  thoracic  nerves  tlirough  the  internal  anterior  thoracic  nerve.  The 
Subclavius  is  supplied  by  a  filament  derived  from  the  fifth  and  sixth  cervical  nerves. 

Actions. — If  the  arm  has  been  raised  by  the  Deltoid,  the  Pectoralis  major  will,  conjointly 
with  the  Latissimus  dorsi  and  Teres  major,  depress  it  to  the  side  of  the  thorax.  If  acting  alone, 
it  adducts  and  draws  forward  the  arm,  bringing  it  across  the  front  of  the  thorax,  and  at  the  same 
time  rotating  it  inward.  The  Pectoralis  minor  depresses  the  point  of  the  shoulder,  drawing 
the  scapula  downward  and  inward  to  the  thorax,  and  throwing  the  inferior  angle  backward. 
The  Subclavius  depresses  the  shoulder,  drawing  the  clavicle  downward  and  forward.  When 
the  arms  are  fixed,  all  three  muscles  act  upon  the  ribs,  drawing  them  upward  and  expanding  the 
thorax,  and  thus  becoming  very  important  agents  in  forced  inspiration.  During  an  attack  of 
asthma  patients  always  assume  an  attitude  which  fixes  the  shoulders,  so  that  all  these  muscles 
may  be  brought  into  action  to  assist  in  increasing  the  capacity  of  the  thorax. 


THE  LATERAL   TIIOBACIC  REGION  46] 

2.  The  Lateral  Thoracic  Region. 

Serratus  magnus. 

The  Serratus  magnus  (m.  serratus  anterior)  (Fig.  347)  is  a  thin,  irregularly 
quadrilateral  muscle,  situated  between  the  ribs  and  the  scapula  at  the  upper  and 
lateral  part  of  the  thorax.  It  arises  by  fleshy  digitations  or  slips  from  the  outer 
surfaces  and  upper  borders  of  the  upper  eight  or  nine  ribs,  and  from  the  aponeu- 
roses covering  the  intervening  intercostal  muscles.  Each  digitation  (except  the 
first)  arises  from  the  corresponding  rib;  the  first  digitation  arises  from  the  first 
and  second  ribs  and  from  the  fascia  covering  the  first  intercostal  space.  From 
this  extensive  attachment  the  fibres  pass  backward,  closely  applied  to  the  thoracic 
wall,  and  reach  the  vertebral  border  of  the  scapula,  and  are  inserted  into  its 
ventral  aspect  in  the  following  manner.  The  first  digitation,  arising  from  the 
first  and  second  ribs,  is  inserted  into  a  triangular  area  on  the  ventral  aspect  of  the 
superior  angle.  The  next  two  digitations  (from  the  second  and  third  ribs) 
spread  out  to  form  a  thin  triangular  sheet,  the  base  of  which  is  directed  backward 
and  is  inserted  into  nearly  the  whole  length  of  the  ventral  aspect  of  the  vertebral 
border.  The  lower  five  or  six  digitations  converge  to  form  a  fan-shaped  mass, 
the  apex  of  which  is  inserted,  by  muscular  and  tendinous  fibres,  into  a  triangular 
impression  on  the  ventral  aspect  of  the  inferior  angle.  The  lower  four  slips 
interdigitate  at  their  origin  with  the  upper  five  slips  of  the  External  oblicjue  muscle 
of  the  abdomen. 

Relations. — This  muscle  is  partly  covered,  in  front,  by  the  Pectoral  muscles;  behind,  by  the 
Subscapularis.  The  axillary  vessels  and  nerves  lie  upon  its  upper  part,  while  its  deep  surface 
rests  upon  the  ribs  and  intercostal  muscles. 

Nerves. — The  Serratus  magnus  is  supplied  by  the  posterior  thoracic  nerve,  which  is  derived 
from  the  fifth,  sixth,  and  seventh  cervical  nerves. 

Actions. — Tlie  Serratus  magnus,  as  a  whole,  carries  the  scapula  forward,  and  at  the  same 
time  raises  the  vertebral  border  of  the  bone.  It  is  therefore  concerned  in  the  action  of  pushing. 
Its  lower  and  stronger  fibres  move  forward  the  lower  angle  and  assist  the  Trapezius  in  rotating 
the  bone  around  an  axis  through  its  centre,  and  thus  assist  this  muscle  in  raising  the  acromion 
and  supporting  weights  upon  the  shoulder.  It  also  assists  the  Deltoid  in  raising  the  arm, 
inasmuch  as  during  the  action  of  this  latter  muscle  it  fixes  the  scapula  and  so  steadies  the 
glenoid  cavity  in  which  the  head  of  the  humerus  rotates.  After  the  Deltoid  has  raised  the  arm 
to  a  right  angle  with  the  trunk,  the  Serratus  magnus  and  the  Trapezius,  by  rotating  the  scapula, 
raise  the  arro  into  an  almost  vertical  position.  It  is  possible  that  when  the  shoulders  are  fixed 
the  lower  fibres  of  the  Serratus  magnus  may  assist  in  raising  and  everting  the  ribs;  but  it  is  not 
the  important  inspiratory  muscle  which  it  was  formerly  believed  to  be. 

Applied  Anatomy. — ^Vhen  the  muscle  is  paralyzed,  the  vertebral  border,  and  especially  the 
lower  angle  of  the  scapula,  leaves  the  ribs  and  stands  out  prominently  on  the  surface,  giving 
a  peculiar  "winged"  appearance  to  the  back.  The  patient  is  unable  to  raise  the  arm,  and  an 
attempt  to  do  so  is  followed  by  a  further  projection  of  the  lower  angle  of  the  scapula  from  the 
back  of  the  thorax. 

Dissection. — After  completing  the  dissection  of  the  axilla,  if  the  muscles  of  the  back  have 
been  dissected,  the  upper  extremity  should  be  separated  from  the  trunk.  Saw  through  the 
clavicle  at  its  centre,  and  then  cut  through  the  muscles  which  connect  the  scapula  and  arm  with 
the  trunk — viz.,  the  Pectoralis  minor  in  front,  Serratus  magnus  at  the  side,  and  the  Levator 
anguli  scapulae,  the  Rhomboids,  Trapezius,  and  Latissimus  dorsi  behind.  These  muscles  sliould 
be  cleaned  and  traced  to  their  respective  insertions.  Then  make  an  incision  through  the  integu- 
ment, commencing  at  the  outer  third  of  the  clavicle,  and  extending  along  the  margin  of  that  bone, 
the  acromion  process,  and  spine  of  the  scapula;  the  integument  should  be  dissected  from  above 
downward  and  outward,  when  the  fascia  covering  the  Deltoid  will  be  exposed  (Fig.  344,  No.  3) 

II.  MUSCLES  AND  FASCI.a:  OF  THE  SHOULDER  AND  ARM. 

The  superficial  fascia  of  the  upper  extremity  is  a  thin  cellulofibrous  layer,  con- 
taining the  superficial  veins  and  lymphatics,  and  the  cutaneous  nerves.     It  is 


462  THE  MUSCLES  AND  FASCIA 

most  distinct  in  front  of  the  elbow,  and  contains  very  large  superficial  veins  and 
nerves;  in  the  hand  it  is  hardly  demonstrable,  the  integument  being  closely  ad- 
herent to  the  deep  fascia  by  dense  fibrous  bands.  Small  subcutaneous  bursse 
are  found  in  this  fascia  over  the  acromion,  the  olecranon,  and  the  knuckles. 

The  deep  fascia  of  the  upper  extremity  comprises  the  aponeurosis  of  the  shoulder, 
arm,  and  forearm,  the  anterior  and  posterior  annular  ligaments  of  the  carpus, 
and  the  palmar  fascia.  These  will  be  considered  in  the  description  of  the  muscles 
of  the  several  regions. 

3.  The  Acromial  Region. 

Deltoid. 

The  deep  fascia  covering  the  Deltoid  invests  this  muscle  and  sends  down  numer- 
ous prolongations  between  its  fasciculi.  In  front,  it  is  continuous  with  the  fascia 
covering  the  great  Pectoral  muscle;  behind,  with  that  covering  the  Infraspinatus; 
above,  it  is  attached  to  the  clavicle,  the  acromion,  and  spine  of  the  scapula;  heloiv, 
it  is  continuous  with  the  deep  fascia  of  the  arm. 

The  Deltoid  (vi.  deUoideus)  (Fig.  345)  is  a  large,  thick,  triangular  muscle,  which 
gives  the  rounded  outline  to  the  shoulder,  and  has  received  its  name  from  its  resem- 
blance to  the  Greek  letter  J  {delta)  inverted.  It  covers  the  shoulder-joint  in  front, 
behind,  and  on  its  outer  side.  It  arises  from  the  outer  third  of  the  anterior  border 
and  upper  surface  of  the  clavicle;  from  the  outer  margin  and  upper  surface  of 
the  acromion  process,  and  from  the  lower  lip  of  the  posterior  border  of  the  spine 
of  the  scapula,  as  far  back  as  the  triangular  surface  at  its  mesal  end.  From  this 
extensive  origin  the  fibres  converge  toward  their  insertion,  the  middle  passing 
vertically,  the  anterior  obliquely  backward,  the  posterior  obliquely  forward, 
they  unite  to  form  a  thick  tendon,  which  is  inserted  into  a  rough  triangular  promi- 
nence on  the  middle  of  the  outer  side  of  the  shaft  of  the  humerus.  At  its  insertion 
the  muscle  gives  off  an  expansion  to  the  deep  fascia  of  the  arm.  This  muscle 
is  remarkably  coarse  in  texture,  and  the  arrangement  of  its  muscle  fibres  is  some- 
what peculiar;  the  central  portion  of  the  muscle^-that  is  to  say,  the  part  arising 
from  the  acromion  process — consists  of  fibres  having  an  oblique  direction, 
which  arise  in  a  bipenniform  manner  from  the  sides  of  tendinous  intersections, 
generally  four  in  number,  which  are  attached  above  to  the  acromion  process  and 
pass  downward  parallel  to  one  another  in  the  substance  of  the  muscle.  The 
oblique  muscle  fibres  thus  formed  are  inserted  into  similar  tendinous  intersec- 
tions, generally  three  in  number,  which  pass  upward  from  the  insertion  of  the 
muscle  into  the  humerus  and  alternate  with  the  descending  septa.  The  portions 
of  the  muscle  which  arise  from  the  clavicle  and  spine  of  the  scapula  are  not 
arranged  in  this  manner,  but  pass  from  their  origin  above,  to  be  inserted  into 
the  margins  of  the  inferior  tendon. 

Relations. — By  its  superficial  surface,  the  Deltoid  is  in  relation  with  the  integument,  the 
superficial  and  deep  fascije,  Platysma,  and  supra-acromial  nerves.  Its  deep  surface  is  separated 
from  the  capsule  of  the  shoulder-joint  by  a  large  sacculated  synovial  bursa,  the  subdeltoid 
bursa  (bursa  stibdeltoidea) .  This  bursa  often  communicates  with  the  subacromial  bursa  (bursa 
subacromialis) ,  which  is  between  the  acromial  process  and  the  coraco-acromial  ligament  above 
and  the  capsule  of  the  shoulder-joint  and  the  Supraspinatus  muscle  below.  The  deep  surface  of 
the  Deltoid  covers  the  coracoid  process,  coraco-acromial  ligament,  Pectoralis  minor,  Coraco- 
brachialis,  both  heads  of  the  Biceps,  the  tendon  of  the  Pectorahs  major,  the  insertions  of  the 
Supraspinatus,  Infraspinatus,  and  Teres  minor,  the  scapular  and  external  heads  of  the  Triceps, 
the  circumflex  vessels  and  nerve,  and  the  humerus.  Its  anterior  border  is  separated  at  its  upper 
part  from  the  Pectoralis  major  by  a  cellular  interspace,  which  lodges  the  cephalic  vein  and 
humeral  branch  of  the  acromiothoracic  artery;  lower  down  the  two  muscles  are  in  close  con- 
tact.    Its  posterior  border  rests  on  the  Infraspinatus  and  Triceps  muscles. 

Nerves. — The  Deltoid  is  supplied  by  the  fifth  and  sixth  cer\-ical  tlirough  the  circumflex  nerve. 


THE  ANTERIOR  SCAPULAR  REGION 


463 


Actions. — The  Deltoid  raises  the  arm  directly  from  the  side,  so  as  to  bring  it  to  a  right  angle 
nith  the  trunk,  but  this  act  cannot  be  performed  without  the  aid  of  the  Serratus  magnus,  which 
muscle  steadies  the  lower  angle  of  the  scapula.  Its  anterior  fibres,  assisted  by  the  Pectoralis 
major,  draw  the  arm  forward;  and  its  posterior  fibres,  aided  by  the  Teres  major  and  Latissimus 
dorsi,  draw  it  backward. 

Applied  Anatomy. — The  Deltoid  is  very  liable  to  atrophy,  and  when  in  this  condition  dislo- 
cation of  the  shoulder-joint  is  simulated,  as  there  is  flattening  of  the  shoulder  and  apparent 
prominence  of  the  acromion  process;  upon  examination,  however,  it  will  be  found  that  the 
relative  position  of  the  greater  tuberosity  of  the  humerus  to  the  acromion  and  coracoid  process  is 
unchanged.  Atrophy  of  the  Deltoid  may  be  due  to  disuse  or  loss  of  trophic  influence,  either 
from  injury  to  the  circumflex  nerve  (as  in  " cruich-palsy")  or  from  spinal  cord  lesions,  as  m 
infantile  paralysis.  In  the  operation  performed  for  the  obliteration  of  the  subdeltoid  bursa,  the 
incision  through  the  Deltoid  should  be  as  far  anterior  as  possible,  in  order  to  avoid  severing  the 
nerves  which  enter  the  muscle  from  behind. 


4.  The  Anterior  Scapular  Region. 

Subscapularis. 

Dissection. — Divide  the  Deltoid  across,  near  its  upper  part,  by  an  mcision  carried  along  the 
margin  of  the  clavicle,  the  acromion  process  and  spine  of  the  scapula,  and  reflect  it  downward, 
when  the  structures  under  cover  of  it  will  be  seen. 


eUPRASPINATUS 
8UB6CAPULARIS 


Fig.  348. — Diagra 


L  showing  attachment  of  muscles  of  the  shoulder  and  arm. 
Origins,  red;  insertions,  blue. 


Anterior  aspect. 


The  subscapular  fascia  (fascia  subscapularis)  is  a  thin  membrane  attached  to 
the  entire  circumference  of  the  subscapular  fossa,  and  affording  attachment  by 
its  inner  surface  to  some  of  the  fibres  of  the  Subscapularis  muscle. 


464  THE  MUSCLES  AND  FASCIA 

The  Subscapularis  {m.  sithsca-pularis)  (Fig.  347)  is  a  large  triangular  muscle 
which  fills  up  the  subscapular  fossa,  arising  from  its  internal  two-thirds,  with  the 
exception  of  a  narrow  margin  along  the  internal  border,  and  the  surfaces  at  the 
superior  and  inferior  angles  which  afford  attachment  to  the  Serratus  magnus; 
it  also  arises  from  the  lower  two-thirds  of  the  groove  on  the  axillary  border  of  the 
bone.  Some  fibres  arise  from  the  tendinous  laminae,  which  intersect  the  muscle, 
and  are  attached  to  ridges  on  the  bone;  and  others  form  an  aponeurosis,  which 
separates  the  muscles  from  the  Teres  major  and  the  long  head  of  the  Triceps. 
The  fibres  pass  outward,  and,  gradually  converging,  terminate  in  a  tendon, 
which  is  inserted  into  the  lesser  tuberosity  of  the  humerus  and  into  the  neck  of 
the  humerus  just  behind  this  tuberosity  and  into  the  capsular  ligament  of  the 
shoulder-joint.  The  tendon  of  the  muscle  is  in  close  contact  with  the  anterior 
part  of  the  capsular  ligament  of  the  shoulder-joint,  and  glides  over  a  large  bursa 
{bursa  m.  subscapularis),  which  separates  it  from  the  base  of  the  coracoid  process. 
This  bursa  communicates  with  the  cavity  of  the  joint  by  an  aperture  in  the  cap- 
sular ligament. 

Relations. — Its  deep  surface  forms  a  considerable  part  of  the  posterior  wall  of  the  axilla, 
and  is  in  relation  with  the  Serratus  magnus,  Coracobrachialis,  and  Biceps,  the  axillary  vessels 
and  brachial  plexus  of  nerves,  and  the  subscapular  vessels  and  nerves.  By  its  superficial  sur- 
face, with  the  scapula  and  the  capsular  ligament  of  the  shoulder-joint.  Its  lower  border  is  con- 
tiguous to  the  Teres  major  and  Latissimus  dorsi. 

Nerves. — It  is  supplied  by  the  fifth  and  sixth  cervical  nerves  through  the  upper  and  lower 
subscapular  nerves. 

Actions. — The  Subscapularis  rotates  the  head  of  the  humerus  inward;  when  the  arm  is 
raised,  it  draws  the  humerus  forward  and  downward.  It  is  a  powerful  defence  to  the  front  of 
the  shoulder-joint,  preventing  displacement  of  the  head  of  the  bone. 

5.  The  Posterior  Scapular  Region  (Figs.  349,  350). 

Supraspinatus.  Teres  minor. 

Infraspinatus.  Teres  major. 

Dissection. — To  expose  these  muscles,  and  to  examine  their  insertion  into  the  humerus, 
detach  the  Deltoid  and  Trapezius  from  their  attachment  to  the  spine  of  the  scapula  and  acromion 
process.  Remove  the  clavicle  by  dividing  the  ligaments  connecting  it  with  the  coracoid  process, 
and  separate  it  at  its  articulation  wdth  the  scapula;  divide  the  acromion  process  near  its  root 
with  a  saw.  The  fragments  being  removed,  the  tendons  of  the  posterior  Scapular  muscles  will 
be  fully  exposed.  A  block  should  be  placed  beneath  the  shoulder-joint,  so  as  to  make  the 
muscles  tense. 

The  supraspinatus  fascia  (fascia  supraspinata)  is  a  thick  and  dense  membranous 
layer,  which  completes  the  osseofibrous  case  in  which  the  Supraspinatus  muscle 
is  contained;  it  affords  attachment,  by  its  deep  surface,  to  some  of  the  fibres  of 
the  muscle.  It  is  thick  internally,  but  thinner  externally  under  the  coraco- 
acromial  ligament. 

The  Supraspinatus  muscle  (m.  supraspinatus)  occupies  the  whole  of  the  supra- 
spinous fossa,  arising  from  its  internal  two-thirds  and  from  the  strong  fascia 
which  covers  the  surface  of  the  muscle.  The  muscle  fibres  converge  to  a  tendon 
which  passes  across  the  upper  part  of  the  capsular  ligament  of  the  shoulder-joint, 
to  which  it  is  intimately  adherent,  and  is  inseried  into  the  highest  of  the  three 
facets  on  the  greater  tuberosity  of  the  humerus. 

Relations. — By  its  superficial  surface,  with  the  Trapezius,  the  clavicle,  the  acromion,  the  coraco- 
acromial  ligament,  and  the  Deltoid;  by  its  deep  surface,  with  the  scapula,  the  suprascapular 
vessels  and  nerve,  and  upper  part  of  the  shoulder- joint. 

The  infraspinatus  fascia  (fascia  infraspinata)  is  a  dense  fibrous  membrane, 
covering  in  the  Infraspinatus  muscle  and  attached  to  the  circumference  of  the 


THE  POSTERIOR  SCAPULAR  REGION 


465 


infraspinous  fossa;  it  aft'o''ds  attachment,  by  its  inner  surface,  to  some  fibres 
of  tliat  muscle.  At  tiie  point  where  the  Infraspinatus  commences  to  be  covered 
by  the  Deltoid,  this  fascia  divides  into  two  layers;  one  layer  passes  over  the 
Deltoid  muscle,  helping  to  form  the  deltoid  fascia  already  described;  the  other 
passes  beneath  the  Deltoid  to  the  capsule  of  the  shoulder-joint. 


Fig.  349. — Diagram  showing  attachment  of  muscles  of  shoulder  and  arm.     Posterior  aspect. 
Origins,  red;  insertions,  blue. 


The  Infraspinatus  (m.  wfraspinahis)  is  a  thick,  triangular  muscle,  which 
occupies  the  chief  part  of  the  infraspinous  fossa,  arising  by  fleshy  fibres  from  its 
internal  two-thirds,  and  by  tendinous  fibres  from  the  ridges  on  its  surfaces;  it 
also  arises  from  a  strong  fascia  which  covers  it  externally,  and  separates  it  from  the 
Teres  major  and  minor.  The  fibres  converge  to  a  tendon  which  glides  over  the 
external  border  of  the  spine  of  the  scapula,  and,  passing  across  the  posterior  part 
of  the  capsular  ligament  of  the  shoulder-joint,  is  inserted  into  the  middle  impres- 
sion on  the  greater  tuberosity  of  the  humerus.  The  tendon  of  this  muscle  is 
sometimes  separated  from  the  capsule  of  the  shoulder-joint  by  a  synovial  bursa 
(bursa  m.  infraspinati),  which  may  communicate  with  the  joint-cavity. 

Relations. — By  its  superfieial  surface,  with  the  Deltoid,  the  Trapezius,  Latissimus  dorsi, 
and  the  integument;  by  its  deep  surface,  with  the  scapula,  from  which  it  is  separated  by  the  supra- 
scapular and  dorsalis  scapulae  vessels,  and  with  the  capsular  ligament  of  the  shoulder-joint. 
Its  loiver  border  is  in  contact  with  the  Teres  minor,  occasionally  united  with  it,  and  with  the 
Teres  maior. 

^  30 


466 


THE  MU8CLE8  AND  FASCIA 


The  Teres  minor  (m.  teres  minor)  is  a  narrow,  elongated  muscle,  which  arises 
from  the  dorsal  surface  of  the  axillary  border  of  the  scapula  for  the  upper  two- 
thirds  of  its  extent,  and  from  the  two  aponeurotic  lamina,  one  of  which  separates 
this  muscle  from  the  Infraspinatus,  the  other  from  the  Teres  major;  its  fibres 
pass  obliquely  upward  and  outward,  and  terminate  in  a  tendon  which  is  inserted 
into  the  lowest  of  the  three  facets  on  the  greater  tuberosity  of  the  humerus,  and 
by  fleshy  fibres,  into  the  humerus  immediately  below  it.  The  tendon  of  this 
muscle  passes  across  the  posterior  part  of  the  capsular  ligament  of  the  shoulder- 
joint. 

Relations. ^By  its  superficial  surfcwe,  with  the  Deltoid  and  the  integument;  by  its  deep 
surface,  with  the  scapula  and  dorsal  branch  of  the  subscapular  artery,  the  long  head  of  the 
Triceps,  and  the  shoulder-joint;  by  its  upper  border,  with  the  Infraspinatus;  by  its  lower  border, 
with  the  Teres  maior,  from  which  it  is  separated  anteriorly  by  the  long  head  of  the  Triceps. 


Fig.  350. — Muscles  on  the  dorsum  of  the  Scapula  and  the  Triceps. 


The  Teres  major  (m.  teres  major)  is  a  thick  but  somewhat  flattened  muscle, 
which  arises  from  the  oval  surface  on  the  dorsal  aspect  of  the  inferior  angle  of 
the  scapula,  and  from  the  fibrous  septa  interposed  between  it  and  the  Teres 
minor  and  Infraspinatus;  the  fibres  are  directed  upward  and  out^vard,  and  termi- 
nate in  a  flat  tendon,  about  two  inches  in  length,  which  is  inserted  into  the  inner 
bicipital  ridge  of  the  humerus.  The  tendon  of  this  muscle,  at  its  insertion  into 
the  humerus,  lies  behind  that  of  the  Latissimus  dorsi,  from  which  it  is  separated 
by  a  synovial  bursa,  the  two  tendons  being,  however,  united  along  their  lower 
borders  for  a  short  distance.  A  bursa  {bursa  m.  teretis  majoris)  is  found  between 
the  tendon  of  the  Teres  major  and  the  bone. 


THE  ANTERIOR  HUMERAL  REGION  467 

Relations. — By  its  superficial  surface,  with  the  Latissimus  dorsi  below,  and  the  long  head  of 
the  Ti-iceps  above.  By  its  deep  surface,  with  the  Subscapularis,  Latissimus  dorsi,  Coraco- 
brachialis,  short  head  of  the  Biceps  brachii,  the  axillary  vessels,  and  brachial  plexus  of  nerves. 
Its  upper  border  is  at  first  in  relation  with  the  Teres  minor,  from  which  it  is  afterward  separated 
by  the  long  head  of  the  Triceps.  Its  lower  border  forms,  in  conjunction  with  the  Latissimus 
dorsi,  part  of  the  posterior  boundary  of  the  axilla.  The  Latissimus  dorsi  at  first  covers  the 
orio-in  of  the  Teres  major,  then  wraps  itself  obliquely  around  its  lower  border,  so  that  its  tendon 
ultimately  comes  to  lie  in  front  of  that  of  the  Teres  major. 

Nerves. — The  Supra-  and  Infraspinatus  muscles  are  supplied  by  the  fifth  and  sixth  cervical 
nerves  through  the  suprascapular  nerve;  the  Teres  minor,  by  the  fifth  cervical,  through  the 
circumflex;  and  the  Teres  major,  by  the  fifth  and  sixth  cervical,  through  the  lower  subscapular. 

Actions.— The  Supraspinatus  assists  the  Deltoid  in  raising  the  arm  from  the  side,  and  fixes 
the  head  of  the  humerus  in  the  glenoid  cavity.  The  Infraspinatus  and  Teres  minor  rotate  the 
head  of  the  humerus  outward;  when  the  arm  is  raised,  they  assist  in  retaining  it  in  that  position 
and  carrying  it  backward.  One  of  the  most  important  uses  of  these  three  muscles  is  the  great 
protection  they  afford  to  the  shoulder-joint,  the  Supraspinatus  supporting  it  above,  and  pre- 
venting displacement  of  the  head  of  the  humerus  upward,  while  the  Infraspinatus  and  Teres 
■minor  protect  it  behind,  and  prevent  dislocation  backward.  The  Teres  major  assists  the  Latis- 
simus dorsi  in  drawing  the  humerus  downward  and  backward,  when  previously  raised,  and  in 
rotating  it  inward;  when  the  arm  is  fixed,  it  may  assist  the  Pectoral  and  Latissimus  dorsi  muscles 
in  drawing  the  trunk  forward. 


THE  MUSCLES  AND  FASCI.®  OF  THE  ARM. 

6.  The  Anterior  Humeral  Region  (Fig.  347). 

Coracobrachialis.  Biceps.  Brachialis  anticus. 

Dissection. — The  arm  being  placed  on  the  table,  with  the  front  surface  uppermost,  make 
a  vertical  incision  through  the  integument  along  the  middle  line,  from  the  clavicle  to  about 
Lwo  inches  below  the  elbow-joint,  where  it  should  be  joined  by  a  transverse  incision,  extending 
from  the  inner  to  the  outer  side  of  the  forearm;  the  two  flaps  being  reflected  on  either  side,  the 
fascia  should  be  examined  (Fig.  344). 

The  deep  fascia  (fascia  brachii)  of  the  arm  is  continuous  with  that  covering  the 
Deltoid  and  the  great  Pectoral  muscles,  by  means  of  which  it  is  attached,  above, 
to  the  clavicle,  acromion,  and  spine  of  the  scapula,  and  it  is  also  continuous  with 
the  axillary  fascia.  It  forms  a  thin,  loose,  membranous  sheath  investing  the  muscles 
of  the  arm,  sending  down  septa  between  them,  and  is  composed  of  fibres  disposed 
in  a  circular  or  spiral  direction,  and  connected  by  vertical  and  oblique  fibres. 
It  differs  in  thickness  at  different  parts,  being  thin  over  the  Biceps  brachii,  but 
thicker  where  it  covers  the  Triceps,  and  over  the  condyles  of  the  humerus;  it  is 
strengthened  by  fibrous  aponeuroses,  derived  from  the  Pectoralis  major  and 
Latissimus  dorsi,  on  the  inner  side,  and  from  the  Deltoid  externally.  On  either 
side  it  gives  off  a  strong  intermuscular  septuvi,  whicla  is  attached  to  the  supracon- 
dylar ridge  and  to  the  condyle  of  the  humerus.  These  septa  serve  to  separate  the 
muscles  of  the  anterior  froin  those  of  the  posterior  brachial  region.  The  external 
intermuscular  septum  extends  from  the  lower  part  of  the  external  bicipital  ridge, 
along  the  external  supracondylar  ridge,  to  the  outer  condyle;  it  is  blended  with  the 
tendon  of  the  Deltoid,  gives  attachment  to  the  Triceps  behind,  to  the  Brachialis 
anticus,  Brachioradialls,  and  Extensor  carpi  radialis  longior  in  front.  It  is 
perforated  by  the  musculospiral  nerve  and  the  anterior  terminal  branch  of  the 
superior  profunda  artery.  The  internal  intermuscular  septum,,  thicker  than  the 
preceding,  extends  from  the  lower  part  of  the  internal  lip  of  the  bicipital  groove 
below  the  Teres  major,  along  the  internal  supracondylar  ridge  to  the  inner  condyle, 
it  is  blended  with  the  tendon  of  the  Coracobrachialis,  and  aft'ords  attachment  to 
the  Triceps  behind,  and  the  Brachialis  anticus  in  front.  It  is  perforated  by  the 
ulnar  nerve  and  the   inferior  profunda  and  anastomotica  magna  arteries.     At 


468 


THE  MUSCLES  AND  FASCIAE 


the  elbow  the  deep  fascia  is  attached  to  all  the  prominent  points  around  the  joint — 
viz.,  the  condyles  of  the  humerus  and  the  olecranon  process  of  the  ulna — and  is 
continuous  with  the  deep  fascia  of  the  forearm.  Just  below  the  middle  of  the 
arm,  on  its  inner  side,  in  front  of  the  intermuscular  septum,  is  an  oval  opening 
in  the  deep  fascia  which  transmits  the  basilic  vein  and  some  lymphatic  vessels. 


Fig.  351. — Horizontal  section  at  middle  of  right  arm — upper  surface  of  lower  segment.  B.  V.,  basilic  vein. 
CEPH.  v.,  cephalic  vein.  I.  C.  N..  internal  cutaneous  nerve.  I.  P.  -4.,  inferior  profunda  artery.  M.  C.  N.,  mus- 
culocutaneous nerve.  M.  N.,  median  ner\'e.  M.  .S.  N.,  musculospiral  nerve.  S.  P.  A.,  superior  profunda  artery. 
U.  N.,  uln:.r  nerve.     (.A.fter  Braune.) 

The  Coracobrachialis  (m.  coracobrachialis),  the  smallest  of  the  three  muscles 
in  this  region,  is  situated  at  the  upper  and  inner  part  of  the  arm.  It  arises  by 
fleshy  fibres  from  the  apex  of  fhe  coracoid  process,  in  common  with  the  short  head 
of  the  Biceps,  and  from  the  intermuscular  septum  between  the  two  muscles;  the 
fibres  pass  downward,  backward,  and  a  little  outward,  to  be  inserted  by  means  of 
a  flat  tendon  into  an  impression  at  the  middle  of  the  inner  surface  and  internal 
border  of  the  shaft  of  the  humerus  between  the  origins  of  the  Triceps  and  Brachi- 
alis  anticus.  It  is  perforated  by  the  musculocutaneous  nerve.  The  inner  border 
of  the  muscle  forms  a  guide  to  the  position  of  the  terminal  portion  of  the  axillary 
and  upper  part  of  the  brachial  arteries. 

Relations. —By  its  superficial  surface,  with  the  Pectorahs  major  above,  and  at  its  insertion 
with  the  brachial  vessels  and  median  nerve  which  cross  it;  by  its  deep  surface,  with  the  tendons 
of  the  Subscapularis,  Latissimus  dorsi,  and  Teres  major,  the  inner  head  of  the  Triceps,  the 


THE  ANTERIOR  HUMERAL  REGION  469 

humerus,  and  the  anterior  circumflex  vessels;  by  its  inner  border,  with  the  brachial  artery,  and 
the  median  and  musculocutaneous  nerves;  by  its  outer  border,  with  the  short  head  of  the  Biceps 
and  Brachialis  anticus. 

The  Biceps,  or  the  Biceps  flexor  cubiti  (m.  biceps  brachii),  is  a  long  fusiform 
muscle,  occupying  the  whole  of  the  anterior  surface  of  the  arm,  and  divided  above 
into  two  portions  or  heads,  from  which  circumstance  it  has  received  its  name. 
The  short  head  (ca'put  breve)  arises  by  a  thick  flattened  tendon  from  the  apex  of 
the  coracoid  process,  in  common  with  the  Coracobrachialis.  The  long  head 
(caput  loiir/um)  arises  from  the  upper  margin  of  the  glenoid  cavity,  and  is  continu- 
ous with  the  glenoid  ligament.  This  tendon  arches  over  the  head  of  the  humerus, 
being  enclosed  in  a  special  sheath  of  the  synovial  membrane  of  the  shoulder-joint; 
it  then  passes  through  an  opening  in  the  capsular  ligament  at  its  attachment  to 
the  humerus,  and  descends  in  the  bicipital  groove,  in  which  it  is  retained  by  a 
fibrous  prolongation  from  the  tendon  of  the  Pectoralis  major.  Each  tendon  is 
succeeded  by  an  elongated  muscle  belly,  and  the  two  bellies,  although  closely 
applied  to  each  other,  can  readily  be  separated  until  within  about  three  inches 
of  the  elbow-joint.  Here  they  end  in  a  flattened  tendon,  which  is  inserted  into 
the  back  part  of  the  tuberosity  of  the  radius,  a  synovial  bursa,  being  interposed 
between  the  tendon  and  the  front  of  the  tuberosity;  another  bursa  is  often  inter- 
posed between  the  ulna  and  the  tendon.  As  the  tendon  of  the  muscle  approaches 
the  radius  it  becomes  twisted  upon  itself,  so  that  its  anterior  surface  becomes 
external  and  is  applied  to  the  tuberosity  of  the  radius  at  its  insertion;  opposite 
the  bend  of  the  elbow  the  tendon  gives  off,  from  its  inner  side,  a  broad  aponeurosis, 
the  bicipital  fascia  (lacertus  fibrosus),  which  passes  obliquely  downward  and  in- 
ward across  the  brachial  artery,  and  is  continuous  with  the  deep  fascia  covering 
the  origins  of  the  superficial  Flexor  muscles  of  the  forearm  (Fig.  340). ^ 

Relations. — Its  superficial  surface  is  overlapped  above  by  the  Pectoralis  major  and  Deltoid; 
in  the  rest  of  its  extent  it  is  covered  by  the  superficial  and  deep  fasciae  and  the  integument.  Its 
deey  surface  rests  above  on  the  shoulder-joint  and  upper  part  of  the  humerus;  below  it  rests  on 
the  Brachialis  anticus,  with  the  musculocutaneous  nerve  intervening  between  the  two,  and  on 
the  Supinator  [brevis].  Its  inner  border  is  in  relation  with  the  Coracobrachialis,  and  overlaps 
the  brachial  vessels  and  median  nerve;  its  outer  border,  with  the  Deltoid  and  Brachioradialis. 

The  Brachialis  anticus  (m.  brachialis)  is  a  broad  muscle,  which  covers  the 
elbow-joint  and  the  lower  half  of  the  front  of  the  humerus.  It  is  somewhat  com- 
pressed from  before  backward,  and  is  broader  in  the  middle  than  at  either  extrem- 
ity. It  arises  from  the  lower  half  of  the  outer  and  inner  surfaces  of  the  shaft 
of  the  humerus,  and  commences  above  at  the  insertion  of  the  Deltoid,  which  it 
embraces  by  two  angular  processes.  Its  origin  extends  below,  to  within  an  inch 
of  the  margin  of  the  articular  surface,  and  is  limited  on  each  side  by  the  external 
and  internal  borders  of  the  shaft  of  the  humerus.  It  also  arises  from  the  inter- 
muscular septa  on  each  side,  but  more  extensively  from  the  inner,  from  which  it 
is  separated  below  by  the  Brachioradialis  and  Extensor  carpi  radialis  longior.' 
Its  fibres  converge  to  a  thick  tendon,  which  is  inserted  into  a  rough  depression  on 
the  anterior  surface  of  the  coronoid  process  of  the  ulna,  being  received  into  an 
interval  between  two  fleshy  slips  of  the  Flexor  profundus  digitorum. 

Relations. — By  its  superficial  surface,  with  the  Biceps,  the  brachial  vessels,  musculocutaneous 
and  median  nerves;  by  its  deep  surface,  with  the  humerus  and  front  of  the  elbow-joint;  by  its 
inner  border,  with  the  Triceps,  ulnar  nerve,  and  Pronator  teres,  from  which  it  is  separated  by 
the  intermuscular  septum;  by  its  outer  border,  with  the  musculospiral  nerve,  radial  recurrent 
artery,  the  Brachioradialis,  and  Extensor  carpi  radialis  longior. 

'  A  third  head  to  the  Biceps  is  occasionally  found  (Theile  says  as  often  as  once  in  eiijht  or  nine  subjectsi ,  arising 
at  the  upper  and  inner  part  of  the  Brachialis  anticus,  with  the  fibres  of  which  it  is  continuous,  and  inserted 
into  the  bicipital  fascia  and  inner  side  of  the  tendon  of  the  Biceps.  In  most  cases  this  additional  slip  passes 
behind  the  brachial  artery  in  its  course  down  the  arm.  Occasionally  the  third  head  consists  of  two  slips  which 
pass  down,  one  in  front  of,  the  other  behind,  the  artery,  concealing  the  vessel  in  the  lower  half  of  the  arm. 


470  THE  MUSCLES  AND  EASVIJE 

Nerves. — The  muscles  of  this  group  are  supphed  by  the  musculocutaneous  nerve.  The 
Bracliialis  anticus  usually  receives  an  additional  filament  from  the  musculospiral.  The  Coraco- 
brachialis  receives  its  supply  primarily  from  the  seventh  cervical,  the  Biceps  and  Brachialis 
anticus  from  the  fifth  and  sixth  cervical  nerves. 

Actions. — The  Coracobrachial  is  draws  the  humerus  forward  and  inward,  and  at  the  same 
time  assists  in  elevating  it  toward  the  scapula.  The  Biceps  is  a  flexor  of  the  forearm;  it  is  also 
a  powerful  supinator,  and  serves  to  render  tense  the  deep  fascia  of  the  forearm  by  means  of  the 
broad  aponeurosis  given  off  from  its  tendon.  The  Brachialis  anticus  is  a  flexor  of  the  forearm, 
and  forms  an  important  defence  to  the  elbow- joint.  When  the  forearm  is  fixed,  the  Biceps 
and  Brachialis  anticus  flex  the  arm  upon  the  forearm,  as  is  seen  in  efforts  at  climbing. 


7.  The  Posterior  Humeral  Region. 

Triceps.  Subanconeus. 

The  Triceps,  or  the  Triceps  extensor  cubiti  (m.  friceps  brachii)  (Fig.  352)  is 
situated  on  the  back  of  the  arm,  extending  the  entire  length  of  the  posterior 
surface  of  the  humerus.  It  is  of  large  size,  and  is  divided  above  into  three  parts; 
hence  its  name.  These  three  portions  have  been  named:  (1)  the  middle,  scapular, 
or  long  head;  (2)  the  external  or  long  humeral  head;  and  (3)  the  internal  or  short 
humeral  head. 

The  middle  or  scapular  head  (caput  longurri)  arises  by  a  flattened  tendon  from 
a  rough  triangular  depression  on  the  scapula,  immediately  below  the  glenoid 
cavity,  being  blended  at  its  upper  part  with  the  capsular  ligament;  the  muscle 
fibres  pass  downward  between  the  two  other  portions  of  the  muscle,  and  join 
with  them  in  the  common  tendon  of  insertion. 

The  external  head  {caput  laterale)  arises  from  the  posterior  surface  of  the  shaft 
of  the  humerus,  between  the  insertion  of  the  Teres  minor  and  the  upper  part  of 
the  musculospiral  groove;  from  the  external  border  of  the  humerus  and  the 
external  intermuscular  septum;  the  fibres  from  this  origin  converge  toward  the 
common  tendon  of  insertion. 

The  internal  head  (caput  mediale)  arises  from  the  posterior  surface  of  the  shaft 
of  the  humerus,  below  the  groove  for  the  musculospiral  nerve;  commencing 
above,  narrow  and  pointed,  below  the  insertion  of  the  Teres  major,  and  extending 
to  within  an  inch  of  the  trochlear  surface;  it  also  arises  from  the  internal  border 
of  the  humerus,  and  from  the  back  of  the  whole  length  of  the  internal  and  lower 
part  of  the  external  intermuscular  septum.  Certain  fibres  of  this  portion  of  the 
muscle  are  directed  downward  to  the  olecranon,  while  others  converge  to  the 
tendon  of  insertion. 

The  tendon  of  the  triceps  commences  about  the  middle  of  the  back  part  of  the 
muscle;  it  consists  of  two  aponeurotic  laminae,  one  of  which  is  subcutaneous 
and  covers  the  posterior  surface  of  the  muscle  for  the  lower  half  of  its  extent ;  the 
other  is  more  deeply  seated  in  the  substance  of  the  muscle;  after  receiving  the 
attachment  of  the  muscle  fibres,  they  join  above  the  elbow,  and  are  inserted, 
for  the  most  part,  into  the  back  part  of  the  upper  surface  of  the  olecranon  process; 
a  band  of  fibres  is,  however,  continued  downward,  on  the  outer  side,  over  the 
Anconeus,  to  blend  with  the  deep  fascia  of  the  forearm. 

Relations. — By  its  superficial  surface,  the  Triceps  is  in  relatiori  with  the  Deltoid  above;  in 
the  rest  of  its  extent  it  is  subcutaneous;  by  its  deep  surface,  with  the  humerus,  musculospiral 
nerve,  superior  profunda  vessels,  and  back  part  of  the  elbow-joint.  Its  middle  or  long  head  is  in 
relation,  behind,  with  the  Deltoid  and  Teres  minor;  in  front,  with  the  Subscapularis,  Latissimus 
dorsi,  and  Teres  major. 

The  long  head  of  the  Triceps  descends  between  the  Teres  minor  and  Teres  major,  di\"iding 
the  triangulai'  space  between  these  two  muscles  and  the  humerus  into  two  smaller  spaces,  one 
triangular,  the  other  quadrangular  (B'ig.  350).    The  triangular  space  contains  the  dorsalis 


THE  POSTERIOR  HUMERAL  REGION  471 

scapulae  vessels;  it  is  bounded  by  the  Teres  minor  above,  the  Teres  major  below,  and  the  scapular 
head  of  the  Triceps  externally;  the  quadrang^ular  space  transmits  the  posterior  circumflex 
vessels  and  the  circumflex  nerve;  it  is  bounded  Ijy  the  Teres  minor  above,  the  Teres  major 
below,  the  scapular  head  of  the  Triceps  internally,  and  the  humerus  externally. 

The  Subanconeus  is  a  name  given  to  a  few  fibres  from  the  under  surface  of 
the  lower  part  of  the  Triceps  muscle,  which  are  inserted  into  the  posterior  ligament 
of  the  elbow-joint.  By  some  authors  it  is  regarded  as  the  homotype  of  the 
Subcrureus  in  the  lower  limb,  but  it  is  not  a  separate  muscle. 

Nerves. — The  Triceps  is  supplied  by  the  seventh  and  eighth  cervical  nerves  through  the 
musculospiral  nerve. 

Actions. — The  Triceps  is  the  great  Extensor  muscle  of  the  forearm,  serving,  when  the  forearm 
is  flexed,  to  extend  the  elbow-joint.  It  is  the  direct  antagonist  of  the  Biceps  and  Brachialis 
anticus.  When  the  arm  is  extended  the  long  head  of  the  muscles  may  assist  the  Teres  major 
and  Latissimus  dorsi  in  drawing  the  humerus  backward  and  in  adducting  it  to  the  thorax.  The 
long  head  of  the  Triceps  protects  the  under  part  of  the  shoulder-joint,  and  prevents  displacement 
of  the  head  of  the  humerus  downward  and  backward.  The  Subanconeus  draws  up  the'synovial 
membrane  of  the  elbow-joint  out  of  the  way  of  the  advancing  olecranon  process  during  exten- 
sion of  the  forearm. 

Applied  Anatomy. — The  existence  of  the  band  of  fibres  from  the  Triceps  to  the  fascia  of  the 
forearm  is  of  importance  in  excision  of  the  elbow,  and  should  always  be  carefully  preserved 
from  injury  by  the  operator,  as  by  means  of  these  fibres  the  patient  is  enabled  to. extend  the 
forearm,  a  movement  which  would  otherwise  mainly  be  accomplished  by  gravity — that  is  to 
say,  allowing  the  forearm  to  drop  from  its  own  weight. 


III.  MUSCLES  AND  FASCI.a:  OF  THE  FOREARM. 

■  Dissection. — To  dissect  the  forearm,  place  the  limb  in  the  position  indicated  in  Fig.  344, 
make  a  vertical  incision  along  the  middle  line  from  the  elbow  to  the  wrist,  and  a  transverse 
incision  at  the  extremity  of  this;  the  superficial  structures  being  removed,  the  deep  fascia  of 
the  forearm  is  exposed. 

The  deep  fascia  of  the  forearm  {fascia  antibrachii'),^  continuous  above  with  that 
enclosing  the  arm,  is  a  dense,  highly  glistening  aponeurotic  investment,  which 
forms  a  general  sheath  enclosing  the  muscles  in  this  region;  it  is  attached,  behind, 
to  the  olecranon  and  posterior  border  of  the  ulna,  and  gives  off  from  its  inner 
surface  numerous  intermuscidar  septa,  which  enclose  each  muscle  separately. 
Below,  it  is  continuous  in  front  with  the  anterior  amndar  ligament,  and  forms  a 
sheath  for  the  tendon  of  the  Palmaris  longus  muscle,  which  passes  over  the  annular 
ligament  to  be  inserted  into  the  palmar  fascia.  Behind,  near  the  wrist-joint,  it 
becomes  much  thickened  by  the  addition  of  many  transverse  fibres,  and  forms 
the  posterior  annular  ligament.  It  consists  of  circular  and  oblique  fibres,  con- 
nected by  numerous  vertical  fibres.  It  is  much  thicker  on  the  dorsal  than  on 
the  palmar  surface,  and  at  the  lower  than  at  the  upper  part  of  the  forearm,  and  is 
strengthened  above  by  tendinous  fibres  derived  from  the  Brachialis  anticus  and 
Biceps  in  front,  and  from  the  Triceps  behind.  Its  deep  surface  gives  origin  to 
muscle  fibres,  especially  at  the  upper  part  of  the  inner  and  outer  sides  of  the 
forearm,  and  forms  the  boundaries  of  a  series  of  conical-shaped  cavities,  in  which 
the  muscles  are  contained.  Besides  the  vertical  septa  separating  each  muscle, 
transverse  septa  are  given  off  on  the  anterior  and  posterior  surfaces  of  the  forearm, 
separating  the  deep  from  the  superficial  layer  of  muscles.  Numerous  apertures 
exist  in  the  fascia  for  the  passage  of  vessels  and  nerves;  one  of  these,  of  large  size, 
situated  at  the  front  of  the  elbow,  serves  for  the  passage  of  a  communicating 
branch  between  the  superficial  and  deep  veins.  This  fascia  is  also  perforated 
on  its  anterior  surface,  near  the  wrist,  by  the  ulnar  artery  and  nerve. 

*  The  correct  spelling  is  antebrachium,  not  antibrachium.  as  is  gi\'en  in  the  list  of  the  BNA. — [Editor.] 


472 


THE  MUSCLES  AND  FASCIJE 


The  muscles  of  the  forearm  may  be  subdivided  into  groups  corresponding  to 
the  region  they  occupy.  One  group  occupies  the  inner  and  anterior  aspect  of 
the  forearm,  and  comprises  the  Flexor  and  Pronator  muscles,  xlnother  group 
occupies  its  outer  side,  and  a  third  its  posterior  aspect.  The  two  latter  groups 
include  all  the  Extensor  and  Supinator  muscles. 


RADIAL  ARTERY 


PALMARIS 
MEDIAN  NERVE 


Fig.  352. — Transverse  section  through  the  middle  of  the  right  forearm,  in  the  position  of  semipronation. 

(After  Braune.) 


8.  The  Anterior  Radioulnar  Region. 

The  muscles  in  this  region  are  divided  for  convenience  of  description  into  two 
groups  or  layers,  superficial  and  deep. 

The  Superficial  Layer. 

Pronator  teres.  Palmaris  longus. 

Flexor  carpi  radialis.  Flexor  carpi  ulnaris. 

Flexor  sublimis  digitorum. 


These  muscles  take  partial  origin  from  the  internal  condyle  of  the  humerus  by 
a  common  tendon. 

The  Pronator  teres  (m.  pronator  teres)  has  two  heads.  One  (caput  humerale), 
the  larger  and  more  superficial,  arises  from  the  humerus,  immediately  above  the 
internal  condyle,  from  the  tendon  common  to  the  origin  of  the  other  muscles; 
and  from  the  fascia  of  the  forearm  and  the  intermuscular  septum  between  it 
and  the  Flexor  carpi  radialis.     The  deep  head  (caput  uhiare)  is  a  thin  fasciculus 


THE  ANTEBIOlt  RADIOULNAR  REGION 


473 


which  arises  from  the  inner  side  of  the  coronoid  process  of  the  uhia,  joining  the 
preceding  at  an  acute  angle.  The  median  nerve  enters  the  forearm  between  the 
two  heads  of  the  muscle  and  is  separated  from  the  ulnar  artery  by  the  deep  head. 
The  muscle  passes  obliquely  across  the  forearm  from  the  inner  to  the  outer  side, 
and  terminates  in  a  flat  tendon,  which  turns  over  the  outer  margin  of  the  radius, 
and  is  inserted  into  a  rough  impression  at  the  middle  of  the  outer  surface  of  the 
shaft  of  that  bone. 


BRACHI0RAD1ALI6 


EXT.  CARPI  RAD. 


Fig.  353. — Diagram  showing  attachments  of  the  muscles  of  the  forearm  and  hand.    Anterior  aspect.    Origins,  red; 
insertions,  blue.    The  origins  and  insertions  of  the  Palmar  interosseous  muscles  are  omitted.     (See  Fig.  150.) 


Relations, — By  its  superficial  surface,  throughout  the  greater  part  of  its  extent,  with  the 
deep  fascia;  at  its  insertion  the  muscle  is  crossed  by  the  radial  vessels  and  nerve,  and  is  covered 
by  the  Brachioradialis;  by  its  deep  surface,  with  the  Brachiahs  anticus,  Flexor  sublimis  digitorum. 
the  median  nerve,  and  ulnar  artery,  the  small  or  deep  head  being  interposed  between  the  two 
latter  structures.  Its  outer  border  forms  the  inner  boundary  of  a  triangular  space  (anieeuhital 
(space)  (page  641),  in  which  are  placed  the  brachial  artery,  median  nerve,  and  the  tendon  of  the 
Biceps  muscle.     Its  inner  border  is  in  contact  with  the  Flexor  carpi  radiaUs. 

Applied  Anatomy. — This  muscle,  when  suddenly  brought  into  very  active  use,  as  in  the 
game  of  lawn  tennis,  is  liable  to  be  strained,  producing  slight  swelling  and  tenderness,  and  pain 
on  putting  the  muscle  into  action.     This  is  known  as  lawn-tennis  arm. 

The  Flexor  carpi  radialis  (m.  flexor  car-pi  radialis)  lies  on  the  inner  side  of 
the  preceding  muscle.  It  arises  from  the  internal  condyle  by  the  common  tendon, 
from  the  fascia  of  the  forearm,  and  from  the  intermuscular  septa  between  it 
and  the  Pronator  teres,  on  the  outside,  the  Palmaris  longus  internally,  and  the 
Flexor  sublimis  digitorum  beneath.     Slender  and  aponeurotic  in  structure  at 


474 


THE  MUSGLEfi  AND  FASCIJE 


its  commencement,  it  increases  in  size,  and  terminates  in  a  tendon  which  forms 
rather  more  than  the  lower  half  of  its  length.  This  tendon  passes  through  a  canal 
on  the  outer  side  of  the  annular  ligament,  runs  through  a  groove  in  the  os  trapezium 
(which  is  converted  into  a  canal  by  a  fibrous  sheath,  and  is  lined  with  a  synovial 
membrane),  and  is  inserted  into  the  base  of  the 
metacarpal  bone  of  the  index  finger,  and  by  a  slip 
into  the  base  of  the  metacarpal  bone  of  the  middle 
finger. 

Relations. — By  its  superficial  surface,  with  the  deep 
fascia  and  the  integument;  by  its  deep  surface,  with  the 
Flexor  sublimis  digitorum.  Flexor  longus  poUicis,  and 
wrist- joint;  by  its  outer  border,,  with  the  Pronator  teres 
and  the  radial  vessels;  by  its  inner  border,  with  the  Pal- 
maris  longus  above  and  the  median  nerve  below. 

The  Palmaris  longus  (m.  palmaris  longus)  (Fig. 
354)  is  a  slender,  fusiform  muscle,  lying  on  the 
inner  side  of  the  preceding.  It  arises  from  the  in- 
ner condyle  of  the  humerus  by  the  common  tendon, 
from  the  deep  fascia,  and  the  intermuscular  septa 
between  it  and  the  adjacent  muscles.  It  terminates 
in  a  slender  flattened  tendon,  which  passes  over 
the  upper  part  of  the  annular  ligament,  to  end  in 
the  central  part  of  the  palmar  fascia  and  lower  part 
of  the  annular  ligament,  frequently  sending  a  tendi- 
nous slip  to  the  short  muscles  of  the  thumb.  This 
muscle  is  often  absent,  and  is  subject  to  very  con- 
siderable variations;  it  may  be  tendinous  above 
and  muscular  below;  or  it  may  be  muscular  in  the 
centre,  with  a  tendon  above  and  below;  or  it  may 
present  two  muscle  bundles  with  a  central  tendon ; 
or,  finally,  it  may  consist  simply  of  a  mere  tendinous 
band. 

Relations. — By  its  superficial  surface,  with  the  ■  deep 
fascia.  By  its  deep  surface,  with  the  Flexor  sublimis  digi- 
torum. Internally,  with  the  Flexor  carpi  ulnaris.  Exter- 
nally, with  the  Flexor  carpi  radialis.  The  median  nerve 
lies  close  to  the  tendon,  just  above  the  wrist,  on  its  inner 
and  posterior  side. 

The  Flexor  carpi  ulnaris  (m.  flexor  carpi  ulnaris) 
(Fig.  354)  lies  along  the  ulnar  side  of  the  forearm. 
It  arises  by  two  heads,  connected  by  a  tendinous 
arch,  beneath  which  pass  the  ulnar  nerve  and 
posterior  ulnar  recurrent  artery.  One  head  (caput 
humerale)  arises  from  the  inner  condyle  of  the 
humerus,  by  the  common  tendon;  the  other  (caput 
ulnare),  from  the  inner  margin  of  the  olecranon 
and  from  the  upper  two-thirds  of  the  posterior  border  of  the  ulna,  by  an  aponeu- 
rosis, common  to  it  and  the  Extensor  carpi  ulnaris  and  Flexor  profundus  digi- 
torum; and  from  the  intermuscular  septum  between  it  and  the  Flexor  sublimis 
digitorum.  The  fibres  terminate  in  a  tendon  which  occupies  the  anterior  part  of 
the  lower  half  of  the  muscle,  and  is  inserted  into  the  pisiform  bone,  and  is 
prolonged  from  this  to  the  unciform  and  fifth  metacarpal    bones  by  the  piso- 


FlG.  354. — Front  of  the  left  forearm. 
Superficial  muscles. 


THE  ANTERIOR  RADIOULNAR  REGION  475 

unciform  and  pisometacarpal  ligaments;  it  is  also  attached  by  a  few  fibres  to 
the  annular  ligament. 

Relations. — By  its  superficial  surface,  with  the  deep  fascia,  with  which  it  is  intimately  con- 
nected for  a  considerable  extent;  by  its  deep  surface,  with  the  Flexor  sublimis  digitorum,  the 
Flexor  profundus  digitorum,  the  Pronator  quadratus,  and  the  ulnar  vessels  and  nerve;  by  its 
outer  or  radial  border,  with  the  Palmaris  longus  above  and  the  ulnar  vessels  and  nerve  below. 

The  Flexor  sublimis  digitorum  (m.  flexor  digitorum  sublimis)  (Fig.-  354  >  is 
placed  beneath  the  preceding  muscles,  which  therefore  must  be  removed  in  order 
to  bring  its  attachment  into  view.  It  is  the  largest  of  the  muscles  of  the  super- 
ficial layer,  and  arises  by  three  heads.  One  head  (caput  humerale)  arises  from 
the  internal  condyle  of  the  humerus  by  the  common  tendon,  from  the  internal 
lateral  ligament  of  the  elbow-joint,  and  from  the  intermuscular  septum  common 
to  it  and  the  preceding  muscles.  The  second  head  (caput  ulnare)  arises  from 
the  inner  side  of  the  coronoid  process  of  the  ulna,  above  the  ulnar  origin  of  the 
Pronator  teres  (Fig.  14.5,  p.  186).  The  third  head  (caput  radiale)  arises  from  the 
oblique  line  of  the  radius,  extending  from  the  tuberosity  to  the  insertion  of  the 
Pronator  teres.  The  fibres  pass  vertically  downward,  forming  a  broad  and  thick 
muscle,  which  speedily  divides  into  two  planes  of  muscle  fibres,  superficial  and 
deep;  the  superficial  plane  divides  into  two  parts  which  end  in  tendons  for  the 
middle  and  ring  fingers;  the  deep  plane  also  divides  into  two  parts,  which  end  in 
tendons  for  the  index  and  little  fingers,  but  previously  to  having  done  so  it  gives 
off  a  muscular  slip,  which  joins  that  part  of  the  superficial  plane  which  is  intended 
for  the  ring  finger.  As  the  four  tendons  thus  formed  pass  beneath  the  annular 
ligament  into  the  palm  of  the  hand,  they  are  arranged  in  pairs,  the  superficial 
pair  corresponding  to  the  middle  and  ring  fingers,  the  deep  pair  to  the  index  and 
little  fingers.  The  tendons  diverge  from  one  another  as  they  pass  onward. 
Opposite  the  bases  of  the  first  phalanges  each  tendon  divides  into  two  slips 
(chiasma  tendinurn)  to  permit  the  passage  of  the  corresponding  tendon  of  the 
Flexor  profundus  digitorum;  the  tv/o 
portions  of  the  tendon  then  unite  arid 
form  a  grooved  channel  for  the  reception 
of  the  accompanying  deep  Flexor  tendon. 
Finally,  they  subdivide  a  second  time,  to 
be  inserted  into  the  sides  of  the  second 
phalanges  about  their  middle.  The  inser- 
tion in  the  index  finger  is  shown  in  Fig. 
361.  After  leaving  the  palm  the  tendons 
of  the  superficial  Flexor,  accompanied 
by  the  deep  Flexor  tendons,  lie  in  osseo-       j,^^  sss.-Section  passing  through  the  middle 

aponeurotic      canals       (Fig.      356).       Each  third  of  the  first  phalanx  of  the  middle  finger  (frozen 

^  1      1?  1  section).     The  tendon  of  the  Flexor  sublimis   digi- 

Canal   or  theca  extends   from  the  metacar-  torum  is  divided  into  two  small  bands,  which  spread 

,      ,  ,  ,  •       1     ,  •  ,        ,  1  •  laterally  and  engage  themselves   between  the   osss- 

pophalangeal    articulation     to    the    proXl-  ous  plane    .and    the    Flexor    profundus    digitorum. 

mal  end  of  the  distal  phalanx  (Fig.  256).     ^''°'"''  "°''  ^''"''^■' 
It  is  formed    by    strong    fibrous  bands, 

which  arch  across  the  tendons,  and  are  attached  on  each  side  to  the  margins  of 
the  phalanges.  Opposite  the  middle  of  the  proximal  and  second  phalanges  the 
sheath  is  very  strong,  and  the  fibres  pass  transversely;  but  opposite  the  joints  it  is 
much  thinner,  and  the  fibres  pass  obliquely.  It  is  very  thin  over  the  metacarpo- 
phalangeal articulation,  and  is  absent  over  the  distal  phalanx.  Each  sheath 
is  lined  by  a  synovial  membrane,  which  is  reflected  on  the  contained  tendons. 

Relations. — In  the  forearm,  by  its  superficial  surface,  with  the  deep  fascia  and  all  the  pre- 
ceding superficial  muscles;  by  its  deep  surface,  with  the  Flexor  profundus  digitorum.  Flexor 


FLEXOn  PROFUNDI 

JS 

DIGITORUM 

SHEATH  or                       I 

/FLEXOR 

FLEXOR  ~> 

SUBLIMIS 

TENDONS       ,^ 5^>N. 

DIGITORUM 

fKith 

DIGITAL 

ARTERIES 

C  f/^^M 

AND  NERVES 

i^^4 

COMMON  TENDON  C 

\^~^^y 

EXTENSOR  MUSCLE 

~]  — 

OF  FINGERS 

FIRST  PHALANX 

476  THE  MUSCLES  AND  FASCIA 

longus  pollicis,  the  ulnar  vessels  and  nerve,  and  the  median  nerve.  In  the  hand  its  tendons 
are  in  relation,  superficially,  with  the  palmar  fascia,  superficial  palmar  arch,  and  the  branches 
of  the  median  nerve;  deeply,  with  the  tendons  of  the  deep  Flexor  and  the  Lumbricales. 

The  Deep  Layer   (Fig.  356). 

Flexor  profundus  digitorum.  Flexor  longus  pollicis. 

Pronator  quadratus. 

Dissection. — Divide  each  of  the  superficial  muscles  at  its  centre,  and  turn  either  end  aside; 
the  deep  layer  of  muscles,  together  with  the  median  nerve  and  ulnar  vessels,  will  then  be  exposed. 

The  Flexor  profundus  digitorum  {m.  flexor  digitorum  profimdus)  (Fig.  356) 
is  situated  on  the  ulnar  side, of  the  forearm,  immediately  beneath  the  superficial 
Flexors.  It  arises  from  the  upper  three-fourths  of  the  anterior  and  inner  surfaces 
of  the  shaft  of  the  ulna,  embracing  the  insertion  of  the  Brachialis  anticus  above, 
and  extending,  below,  to  within  a  short  distance  of  the  Pronator  quadratus.  It 
also  arises  from  a  depression  on  the  inner  side  of  the  coronoid  process;  by  an 
aponeurosis  from  the  upper  three-fourths  of  the  posterior  border  of  the  ulna, 
in  common  with  the  Flexor  and  Extensor  carpi  ulnaris;  and  from  the  ulnar  half 
of  the  interosseous  membrane.  The  fibres  form  a  fleshy  belly  of  considerable 
size,  which  divides  into  four  tendons;  these  pass  under  the  annular  ligament 
beneath  the  tendons  of  the  Flexor  sublimis  digitorum.  Opposite  the  first 
phalanges  the  tendons  pass  through  the  openings  in  the  tendons  of  the  Flexor 
sublimis  digitorum,  and  are  finally  inserted  into  the  bases  of  the  last  phalanges. 
The  portion  of  the  muscle  for  the  index  finger  (Fig.  360)  is  usually  distinct 
throughout,  but  the  tendons  for  the  three  inner  fingers  are  connected  by  cellu- 
lar tissue  and  tendinous  slips  p.s  far  as  the  palm  of  the  hand.  The  tendons  of 
this  muscle  and  those  of  the  Flexor  sublimis  digitorum,  while  contained  in  the 
osseoaponeurotic  canals  of  the  fingers,  are  invested  in  a  synovial  sheath,  and  are 
connected  to  each  other  and  to  the  phalanges  by  slender  tendinous  filaments, 
called  vincula  accessoria  tendinum  (vincida  tendineae).  Of  these  there  are  two 
sets:  (a)  The  ligamenta  brevia — two  in  each  finger — are  composed  of  triangular 
bands  of  fibres  which  connect  respectively  (1)  the  tendon  of  the  Flexor  sublimis 
digitorum  to  the  front  of  the  first  interphalangeal  joint,  and  (2)  the  head  of  the 
first  phalanx  and  the  tendon  of  the  Flexor  profundus  digitorum  to  the  front  of  the 
second  interphalangeal  joint  and  to  the  head  of  the  second  phalanx,  (b)  The 
ligavienta  longa  connect  the  under  surfaces  of  the  Flexor  sublimis  digitorum  to 
the  proximal  end  of  the  palmar  surface  of  the  first  phalanx,  and  the  under  surface 
of  the  Flexor  profundus  digitorum  to  those  of  the  subjacent  Flexor  sublimis 
digitorum  after  the  tendons  of  the  former  have  passed  through  the  latter  (Fig.  361). 

Four  small  muscles,  the  Lumbricales,  are  connected  with  the  tendons  of  the 
Flexor  profundus  in  the  palm.  They  will  be  described  with  the  muscles  in  that 
region. 

Relations. — By  its  superficial  surface,  in  the  forearm,  with  the  Flexor  sublimis  digitorum. 
the  Flexor  carpi  ulnaris,  the  ulnar  vessels,  and  nerve,  and  the  median  nerve;  and  in  the  hand, 
with  the  tendons  of  the  superficial  Flexor;  by  its  deep  surface,  in  the  forearm,  with  the  ulna,  the 
interosseous  membrane,  the  Pronator  quadratus;  and  in  the  hand,  with  the  Interossei,  Adductor 
pollicis,  and  deep  palmar  arch;  by  its  ulnar  border,  with  the  Flexor  carpi  ulnaris;  by  its  radial 
border,  with  the  Flexor  longus  pollicis,  the  anterior  interosseous  vessels  and  nerve  being  inter- 
posed. 

The  Flexor  longfus  pollicis  (m.  flexor  pollicis  longus)  (Fig.  356)  is  situated  on 
the  radial  side  of  the  forearm,  lying  on  the  same  plane  as  the  preceding.  It  arises 
from  the  grooved  anterior  surface  of  the  shaft  of  the  radius,  commencing  above, 


THE  ANTERIOR  RADIOULNAR  REGION 


477 


Fig.  356. — Front  of  the  left  forearm. 
Deep  muscles. 


Fig.  357. — Posterior  surface  of  the  left  forea 
Superficial  muscles. 


478  THE  3IUSCLES  AND  FASCIA 

immediately  below  the  tuberosity  and  oblique  line,  and  extending  below  to 
within  a  short  distance  of  the  Pronator  quadratus.  It  also  arises  from  the  ad- 
jacent part  of  the  interosseous  membrane  and  generally  by  a  fleshy  slip  from  the 
inner  border  of  the  coronoid  process  or  from  the  internal  condyle  of  the  humerus. 
The  fibres  pass  downward,  and  terminate  in  a  flattened  tendon  which  passes 
beneath  the  annular  ligament,  is  then  lodged  in  the  interspace  between  the  super- 
ficial head  of  the  Flexor  brevis  pollicis  and  the  Adductor  obliquus  poUicis,  and, 
entering  an  osseoaponeurotic  canal  similar  to  those  for  the  other  Flexor  tendons, 
is  inserted  into  the  base  of  the  last  phalanx  of  the  thumb. 

Relations. — By  its  superficial  surface,  with  the  Flexor  sublimis  digitorum,  Flexor  carpi 
radialis,  Brachior'adialis,  and  radial  vessels;  by  its  dee-p  surface,  with  the  radius,  interosseous 
membrane,  and  Pronator  quadratus;  by  its  ulnar  border,  with  the  Flexor  profundus  digitorum, 
from  which  it  is  separated  by  the  anterior  interosseous  vessels  and  nerve. 

The  Pronator  quadratus  {m.  pronator  quadratics)  (Figs.  356  and  365)  is  a 
small,  flat,  quadrilateral  muscle,  extending  transversely  across  the  front  of  the 
radius  and  ulna,  above  their  carpal  extremities.  It  arises  from  the  oblique 
ridge  on  the  lower  part  of  the  anterior  surface  of  the  shaft  of  the  ulna;  from  the 
lower  fourth  of  the  anterior  surface  and  the  anterior  border  of  the  ulna;  and  from 
a  strong  aponeurosis  which  covers  the  inner  third  of  the  muscle.  The  fibres  pass 
outward  and  slightly  downward,  to  be  inserted  into  the  lower  fourth  of  the  anterior 
surface  and  anterior  border  of  the  shaft  of  the  radius. 

Relations. — By  its  superficial  surface,  with  the  Flexor  profundus  digitorum,  the  Flexor 
longus  pollicis.  Flexor  carpi  radialis,  and  the  radial  vessels;  by  its  deep  surface,  with  the  radius, 
ulna,  and  interosseous  membrane. 

Nerves. — All  the  muscles  of  the  superficial  layer  are  supplied  by  the  median  nerve,  excepting 
the  Flexor  carpi  ulnaris,  which  is  supplied  by  the  ulnar  nerve.  The  Pronator  teres  and  the 
Flexor  carpi  radialis  derive  their  supply  primarily  from  the  sixth  and  seventh  cervicals;  the 
Palmaris  longus  from  the  eighth  cervical;  the  Flexor  sublimis  digitorum  from  the  seventh  and 
eighth  cervical  and  first  thoracic,  and  the  Flexor  carpi  ulnaris  from  the  eighth  cervical  and  first 
thoracic  nerves.  Of  the  deep  layer,  the  Flexor  profundus  digitorum  is  supplied  by  the  seventh 
and  eighth  cervicals  and  first  thoracic  through  the  ulnar  and  anterior  interosseous  branch  of  the 
median.  The  remaining  two  muscles,  the  Flexor  longus  pollicis  and  Pronator  quadratus,  are 
also  supplied  by  the  eighth  cervical  and  first  thoracic  through  the  anterior  interosseous  branch 
of  the  median. 

Actions. — These  muscles  act  upon  the  forearm,  the  wrist,  and  hand.  The  Pronator  teres 
helps  to  rotate  the  radius  upon  the  ulna,  rendering  the  hand  prone;  when  the  radius  is  fixed  it 
assists  the  other  muscles  in  flexing  the  forearm.  The  Flexor  carpi  radialis  is  one  of  the  Flexors 
of  the  wrist;  when  acting  alone  it  flexes  the  wrist,  inclining  it  to  the  radial  side.  It  can  also 
assist  in  pronating  the  forearm  and  hand,  and,  by  continuing  its  action,  in  bending  the  elbow. 
The  Flexor  carpi  ulnaris  is  one  of  the  flexors  of  the  wrist;  when  acting  alone  it  flexes  the  wrist, 
inclining  it  to  the  ulnar  side  (adducting  the  wrist),  and,  bv  continuing  to  contract,  it  bends  the 
elbow.  The  Palmaris  longus  is  a  tensor  of  the  palmar  fascia.  It  also  assists  in  flexing  the  wrist 
and  elbow.  The  Flexor  sublimis  digitorum  flexes  first  the  middle  and  then  the  proximal  pha- 
langes. It  assists  in  flexing  the  wrist  and  elbow.  The  Flexor  profundus  digitorum  is  one  of 
the  Flexors  of  the  phalanges.  After  the  Flexor  sublimis  has  bent  the  second  phalanx,  the  Flexor 
profundus  flexes  the  terminal  one,  but  it  cannot  do  so  until  after  the  contraction  of  the  superficial 
muscle.  It  also  assists  in  flexing  the  wrist.  The  Flexor  longus  pollicis  is  the  flexor  of  the 
distal  phalanx  of  the  thumb.  ^Vhen  the  thumb  is  fixed  it  also  assists  in  flexing  the  wrist.  The 
Pronator  quadratus  helps  to  rotate  the  radius  upon  the  ulna,  rendering   the  hand  prone. 

Applied  Anatomy. — ^^'hen  a  finger  is  amputated  so  that  the  fibrous  sheath  of  the  Flexor  ten- 
dons is  divided  in  a  region  in  which  it  is  firm  and  dense,  the  tendon  contracts  but  the  theca  does 
not,  and  the  rigid  theca  constitutes  a  permeable  passage  to  the  palm.  If  the  parts  should  be 
infected  the  theca  will  draw  pus  toward  the  palm.  Hence,  it  is  best  to  close  the  theca  by  sutures. 
"Over  the  terminal  phalanx,  and  over  the  joint  between  the  middle  and  terminal  phalanges, 
there  is  no  fibrous  sheath.  In  front  of  the  metacarpophalangeal  joint  it  is  scarcely  evident. 
Over  the  first  and  second  (proximal  and  middle)  phalanges,  and  in  front  of  the  joint  between 
these  bones,  the  fibrous  sheath  is  well  marked,  and  appears  as  a  rigid  tube  when  cut  across. 
As  the  sheath  crosses  the  metacarpophalangeal  and  first  interphalangeal  joints   it  is  adherent 


THE  RADIAL  REGION  479 

to  tlie  glenoid  (anterior  metacarpophalangeal)  ligament,  and  is  easily  closed  by  two  fine  cat- 
gut sutures  passed  vertically — i.  e.,  from  the  dorsal  to  the  palmar  wall.  Opposite  the  shafts 
of  the  first  and  second  phalanges,  however,  there  is  much  difficulty  in  effecting  closure,  since 
the  sheath  is  united  to  the  periosteum,  and  that  membrane  is  very  thin.  In  these  situations 
the  periosteum  should  be  stripped  up  a  little  from  the  palmar  aspect  of  the  bone,  and  the  orifice 
of  the  tube  secured  by  two  fine  sutures  passed  either  vertically  or  transversely,  as  may  appear 
the  more  convenient.  This  stripping  off  of  periosteum  should  be  effected  before  the  bone  is 
divided."' 

9.  The  Radial  Region  (Figs.  354,  357). 

Brachioradialis  [Supinator  longus].  Extensor  carpi  radialis  longior. 

Extensor  carpi  radialis  brevier. 

Dissection. — Divide  the  integument  in  the  same  manner  as  in  the  dissection  of  the  anterior 
brachial  region,  and,  after  having-  examined  the  cutaneous  vessels  and  nerves  and  deep  fascia, 
remove  all  those  structures.  The  muscles  will  then  be  exposed.  The  removal  of  the  fascia 
will  be  considerably  facilitated  by  detaching  it  from  below  upward.  Great  care  should  be 
taken  to  avoid  cutting  across  the  tendons  of  the  muscles  of  the  thumb,  which  cross  obliquely 
the  larger  tendons  running  down  the  back  of  the  radius. 

Tlie  Brachioradialis  (m.  brachioradialis,  formerly  Supinator  longus)  (Fig.  354) 
is  the  most  superficial  muscle  on  the  radial  side  of  the  forearm;  it  is  fleshy  for  the 
upper  two-thirds  of  its  extent,  and  becomes  tendinous  below.  It  arises  from 
the  upper  two-thirds  of  the  external  supracondylar  ridge  of  the  humerus,  and  from 
the  external  intermuscular  septum,  being  limited  above  by  the  musculospiral 
groove.  The  fibres  terminate  above  the  middle  of  the  forearm  in  a  flat  tendon, 
which  is  inserted  into  the  outer  side  of  the  base  of  the  styloid  process  of  the  radius. 

Relations. — By  its  superficial  surface,  with  the  integument  and  fascia  for  the  greater  part  of 
its  extent;  near  its  insertion  it  is  crossed  by  the  Extensor  ossis  metacarpi  pollicis  and  the 
Extensor  brevis  pollicis;  by  its  deep  surface,  with  the  humerus,  the  Extensor  carpi  radialis 
longior  and  brevior,  the  insertion  of  the  Pronator  teres,  and  the  Supinator  [brevis];  by  its 
inner  border,  above  the  elbow,  with  the  Brachialis  anticus,  the  musculospiral  nerve,  and  the 
radial  recurrent  artery;  and  in  the  forearm  with  the  radial  vessels  and  nerve. 

The  Extensor  carpi  radialis  longior  (m.  extensor  carpi  radialis  longus')  (Fig. 
357)  is  placed  partly  beneath  the  preceding  muscle.  It  arises  from  the  lower 
third  of  the  external  supracondylar  ridge  of  the  humerus,  and  from  the  external 
intermuscular  septum  by  a  few  fibres  from  the  common  tendon  of  origin  of  the 
Extensor  muscles  of  the  forearm.  The  fibres  terminate  at  the  upper  third  of 
the  forearm  in  a  flat  tendon,  which  runs  along  the  outer  border  of  the  radius, 
beneath  the  Extensor  tendons  of  the  thimib ;  it  then  passes  through  a  groove  com- 
mon to  it  and  the  Extensor  carpi  radialis  brevior,  immediately  behind  the  styloid 
process,  and  is  inserted  into  the  base  of  the  metacarpal  bone  of  the  index  finger, 
on  its  radial  side. 

Relations. — By  its  superficial  surface,  with  the  Brachioradialis  and  fascia  of  the  forearm;  its 
outer  side  is  crossed  obliquely  by  the  Extensor  tendons  of  the  thumb;  by  its  deep  surface,  with  the 
elbow-joint,  the  Extensor  carpi  radialis  brevior,  and  back  part  of  the  wrist. 

The  Extensor  carpi  radialis  brevior  (m.  extensor  carpi  radialis  brevis)  (Fig. 
357)  is  shorter,  as  its  name  implies,  and  thicker  than  the  preceding  muscle,  beneath 
which  it  is  placed.  It  arises  from  the  external  condyle  of  the  humerus  by  a  tendon 
common  to  it  and  the  three  following  muscles;  from  the  external  lateral  ligament 
of  the  elbow-joint,  from  a  strong  aponeurosis  which  covers  its  surface,  and  from 

1  Operative  Surgery.     By  Sir  Frederick  Treves. 


480  THE  MUSCLES  AND  FASCIJE 

the  intermuscular  septa  between  it  and  the  adjacent  muscles.  The  fibres  termi- 
nate about  the  middle  of  the  forearm  in  a  flat  tendon  which  is  closely  connected 
with  that  of  the  preceding  muscle,  and  accompanies  it  to  the  %vrist,  lying  in  the 
same  groove  on  the  posterior  surface  of  the  radius;  it  passes  beneath  the  Extensor 
tendons  of  the  thumb,  then  beneath  the  annular  ligament,  and,  diverging  some- 
what from  its  fellow,  is  inserted  into  the  base  of  the  metacarpal  bone  of  the  middle 
finger,  on  its  radial  side.  There  is  often  a  bursa  between  a  portion  of  the  base 
of  the  bone  and  the  tendon. 

The  tendons  of  the  two  preceding  muscles  pass  through  the  same  compartment 
of  the  annular  ligament,  and  are  lubricated  by  a  single  synovial  membrane,  but 
are  separated  from  each  other  by  a  small  vertical  ridge  of  bone  as  they  lie  in  the 
groove  at  the  back  of  the  radius. 

Relations. — By  its  superficial  surface,  with  the  Extensor  carpi  radialis  longior,  and  with  the 
Extensor  muscles'  of  the  thumb  which  cross  it;  by  its  deef  surface,  with  the  Supinator  [brevis], 
tendon  of  the  Pronator  teres,  radius,  and  wrist-joint;  by  its  ulnar  border,  with  the  Extensor 
communis  digitorum. 


10.  The  Posterior  Radioulnar  Region  (Fig.  357). 

The  muscles  in  this  region  are  divided  for  purposes  of  description  into  two 
groups  or  layers,  superficial  and  deep. 

The  Superficial  Layer. 

Extensor  communis  digitorum.  Extensor  carpi  ulnaris. 

Extensor  minimi  digiti.  Anconeus. 

The  Extensor  communis  digitoruni  (m.  extensor  digitorum  communis)  is  situ- 
ated at  the  back  part  of  the  forearm.  It  arises  from  the  external  condyle  of 
the  humerus  by  the  common  tendon,  from  the  deep  fascia,  and  the  intermuscular 
septa  between  it  and  the  adjacent  muscles.  It  divides  below  into  four  tendons 
which  pass,  together  with  that  of  the  Extensor  indicis,  through  a  separate  com- 
partment of  the  annular  ligament,  lubricated  by  a  synovial  membrane.  The 
tendons  then  diverge,  pass  across  the  back  of  the  hand,  and  are  inserted  into  the 
second  and  third  phalanges  of  the  fingers  in  the  following  manner:  The  outermost 
tendon,  accompanied  by  the  Extensor  indicis,  goes  to  the  index  finger  (Figs. 
357  and  360) ;  the  second  tendon  is  sometimes  connected  to  the  first  by  a  thin 
transverse  band,  and  receives  a  slip  from  the  third  tendon  (Fig.  357) ;  it  goes  to 
the  middle  finger;  the  third  tendon  gives  off  the  slip  to  the  second  (Fig.  357), 
and  receives  a  very  considerable  part  of  the  fourth  tendon;  the  fourth,  or  innermost 
tendon,  divides  into  two  parts;  one  goes  to  join  the  third  tendon,  the  other,  rein- 
forced by  the  Extensor  minimi  digiti,  goes  to  the  little  finger.  Each  tendon 
opposite  the  metacarpophalangeal  articulation  becomes  narrow  and  thickened, 
and  gives  off  a  thin  fasciculus  upon  each  side  of  the  joint,  which  blends  with  the 
lateral  ligaments  and  serves  as  the  posterior  ligament;  after  having  passed  the 
joint  it  spreads  out  into  a  broad  aponeurosis,  which  covers  the  whole  of  the  dorsal 
surface  of  the  first  phalanx,  being  reinforced,  in  this  situation,  by  the  tendons  of 
the  Interossei  and  Lumbricales.  Opposite  the  first  phalangeal  joint  this  aponeu- 
rosis divides  into  three  slips,  a  middle  and  two  lateral;  the  former  is  inserted  into 
the  base  of  the  second  phalanx,  and  the  two  lateral,  which  are  continued  onw-ard 
along  the  sides  of  the  second  phalanx,  unite  by  their  contiguous  margins,  and  are 
inserted  into  the  dorsal  surface  of  the  last  phalanx.  As  the  tendons  cross  the 
phalangeal  joints  they  furnish  them  with  posterioi   ligaments.     The  accessory 


THE  POHTEEIOR  RADIOULNAR  REGION 


481 


slips  or  lateral  vincula  which  join  the  tendon  of  the  ring  finger  to  the  tendon  of  the 
little  finger  and  to  the  tendon  of  the  middle  finger  are  constant.  If  the  middle 
and  little  fingers  are  held  flexed  the  lateral  vincula  greatly  limit  the  range  of  exten- 
sion possible  in  the  ring  finger. 

Relations. — By  its  superficial  surface,  with  the  fascia  of  the  forearm  and  hand,  the  posterior 
annular  Ufjauient,  and  integument;  by  its  deep  surface,  with  the  Supinator  [brevis],  the  Extensol 
muscles  of  the  thumb  and  index  finger,  the  posterior  interosseous  vessels  and  nerve,  the  wrist- 
joint,  carpus,  metacarpus,  and  phalanges;  by  its  radial  border,  with  the  Extensor  carpi  radialis 
brevior;  by  its  ulnar  border,  with  the  Extensor  minimi  digiti  and  Extensor  carpi  ulnaris. 


[brevis] 


EXTENSOR  LONGU 

Origin  of  f 
aponeurosis  < 
common  to :  (.flexor 


EXTENSOR  C 

EXTENSOR  INDICIS 


Fig.  358. — Diagram  showing  attachments  of  muscles  of  forearm  and  hand.     Posterior  aspect.     Origins,  red; 
insertions,  blue.     The  origins  and  insertions  of  the  Dorsal  interossei  muscles  are  omitted.     ^See  Fig.  151.) 

The  Extensor  minimi  digiti  (m.  extensor  digiti  quinti  proprius)  is  a  slender 
muscle  placed  on  the  inner  side  of  the  Extensor  communis,  with  which  it  is  gen- 
erally connected.  It  arises  from  the  common  Extensor  tendon  by  a  thin,  tendin- 
ous slip,  and  from  the  intermuscular  septa  between  it  and  the  adjacent  muscles. 
Its  tendon  runs  through  a  separate  compartment  in  the  annular  ligament  behind 
the  inferior  radioulnar  joint,  then  divides  into  two  as  it  crosses  the  hand,  the 
outermost  division  being  joined  by  the  slip  from  the  innermost  tendon  of  the 
common  Extensor,  The  two  slips  thus  formed  spread  into  a  broad  aponeurosis, 
which,  after  receiving  a  slip  from  the  Abductor  minimi  digiti,  is  inserted  into  the 
second  and  third  phalanges  of  the  little  finger.  The  tendon  is  situated  on  the 
ulnar  side  of,  and  is  somewhat  more  superficial  than,  the  common  Extensor. 


482  THE  MUSCLES  AND  FASCIA     ■ 

The  Extensor  carpi  ulnaris  is  the  most  superficial  muscle  on  the  ulnar  side  of 
the  forearm.  It  arises  from  the  external  condyle  of  the  humerus  by  the  common 
Extensor  tendon ;  by  an  aponeurosis  from  the  posterior  border  of  the  ulna  in  common 
with  the  Flexor  carpi  ulnaris  and  the  Flexor  profundus  digitorum;  and  from  the 
deep  fascia  of  the  forearm.  This  muscle  terminates  in  a  tendon  which  runs 
through  a  groove  behind  the  styloid  process  of  the  ulna,  passes  through  a  separate 
compartment  in  the  annular  ligament,  and  is  inserted  into  the  prominent  tubercle 
on  the  ulnar  side  of  the  base  of  the  metacarpal  bone  of  the  little  finger. 

The  Anconeus  (m.  anconaeus)  is  a  small  triangular  muscle  placed  behind  and 
below  the  elbow-joint,  and  appears  to  be  a  continuation  of  the  external  portion  of 
the  Triceps.  It  arises  by  a  separate  tendon  from  the  back  part  of  the  outer 
condyle  of  the  humerus,  and  is  inserted  into  the  side  of  the  olecranon  and  upper 
fourth  of  the  posterior  surface  of  the  shaft  of  the  ulna;  its  fibres  diverge  from  their 
origin,  the  upper  ones  being  directed  transversely,  the  lower  obliquely  inward. 

The  Deep  Layer  (Fig.  362). 

Supinator  [brevis].  Extensor  brevis  pollicis. 

Extensor  ossis  metacarpi  pollicis.  Extensor  longus  pollicis. 

Extensor  indicis. 

The  Supinator  [brevis]  (m.  supinator)  (Figs.  359  and  360)  is  a  broad  muscle, 
of  hollow  cylindrical  form,  curved  around  the  upper  third  of  the  radius.  It  con- 
sists of  two  distinct  planes  of  muscle  fibres,  between  which  lies  the  posterior 
interosseous  nerve  (Fig.  359).  The  two  planes' ame  in  common — the  superficial 
one  by  tendinous,  and  the  deeper  by  muscle  fibres  from  the  external  condyle 
of  the  humerus,  from  the  external  lateral  ligament  of  the  elbow-joint  and  the  orbic- 
ular ligament  of  the  radius;  from  the  ridge  on  the  ulna,  which  runs  obliquely 
downward  from  the  posterior  extremity  of  the  lesser  sigmoid  cavity;  from  the 
triangular  depression  in  front  of  the  cavity;  and  from  a  tendinous  expansion 
which  covers  the  surface  of  the  muscle.  The  superficial  fibres  surround  the 
upper  part  of  the  radius,  and  are  inserted  into  the  outer  edge  of  the  bicipital 
tuberosity  and  into  the  oblique  line  of  the  radius,  as  low  down  as  the  insertion 
of  the  Pronator  teres.  The  upper  fibres  of  the  deeper  plane  form  a  sling-like 
fasciculus,  which  encircles  the  neck  of  the  radius  above  the  tuberosity  and  is 
attached  to  the  back  part  of  its  inner  surface;  the  greater  part  of  this  portion  of 
the  muscle  is  inserted  into  the  posterior  and  external  surface  of  the  shaft,  midway 
between  the  oblique  line  and  the  head  of  the  bone.  Between  the  insertion  of 
the  two  planes  the  posterior  interosseous  nerve  lies  on  the  shaft  of  the  bone 
(Fig.  359). 

Relations. — By  its  superficial  surface,  with  the  superficial  Extensors  and  the  Brachioradialis 
muscles,  and  the  radial  vessels  and  nerve;  by  its  deep  surface,  with  the  elbow-joint,  the  inter- 
osseous membrane,  and  the  radius. 

The  Extensor  ossis  metacarpi  pollicis  (m.  abductor  pollicis  longus)  is  the  most 
external  and  the  largest  of  the  deep  Extensor  muscles;  it  lies  immediately  below 
the  Supinator  [brevis],  with  which  it  is  sometimes  united.  It  arises  from  the  outer 
part  of  the  posterior  surface  of  the  shaft  of  the  ulna  below  the  insertion  of  the 
Anconeus,  from  the  interosseous  membrane,  and  from  the  middle  third  of  the 
posterior  surface  of  the  shaft  of  the  radius.  Passing  obliquely  downward  and 
outward,  it  terminates  in  a  tendon  which  runs  through  a  groove  on  the  outer  side 
of  the  styloid  process  of  the  radius,  accompanied  by  the  tendon  of  the  Extensor 
brevis  pollicis,  and  is  inserted  into  the  base  of  the  metacarpal  bone  of  the  thumb. 


THE  POSTERIOR  RADIOULNAR  REGION 


483 


It  occasionally  gives  ofF  two  slips  near  its  insertion — one  to  the  trapezium,  and  the 
other  to  blend  with  the  origin  of  the  Abductor  pollicis. 


Fig.  359  — Supinator  [brevis].  (From  a  prepa- 
ration in  the  Mubeum  of  the  Royal  College  of 
Surgeons  of   England.) 


Relations. — By  its  superficial  surface, 
with  the  Extensor  communis  digitorum,  Ex- 
tensor minimi  digiti,  and  fascia  of  the  fore- 
arm, and  with  the  branches  of  the  posterior 
interosseous  artery  and  nerve  which  cross 
it;  by  its  deep  surface,  witli  the  ulna,  the 
interosseous  membrane,  the  radius,  the  ten- 
dons of  the  Extensor  carpi  radialis  longior 
and  brevior,  which  it  crosses  obliquely,  and 
at  the  outer  side  of  the  wrist,  with  the 
radial  vessels;  by  its  upper  border,  with  the 
Supinator  [brevis];  by  its  lower  harder,  with 
the  Extensor  brevis  pollicis. 


The  Extensor  brevis  pollicis   (m. 

extensor  pollicis  brevis),  the  smallest 

muscle  of  this  group,  lies  on  the  inner 

side  of  the  preceding.     It  arises  from 

the  posterior  surface  of  the  shaft  of 

the  radius,  below  the  Extensor  ossis  metacarpi  pollicis,  and  from  the  interosseous 

membrane.     Its    direction  is    similar  to  that  of   the  Extensor  ossis  metacarpi 


484 


THE  MUSCLES  AND  FASCIJE 


pollicis,  its  tendon  passing  through  the  same  groove  on  the  outer  side  of   the 
styloid  process,  to  be  inserted  into  the  base  of  the  first  phalanx  of  the  thumb. 

Relations. — The  same  as  those  of  the  Extensor  ossis  metacarpi  polHcis. 

The  Extensor  longus  pollicis  {m.  extensor  -pollicis  longus)  is  much  larger 
than  the  preceding  muscle,  the  origin  of  which  it  partly  covers  in.  It  arises 
from  the  outer  part  of  the  posterior  surface  of  the  shaft  of  the  ulna,  below  the 
origin  of  the  Extensor  ossis  metacarpi  pollicis,  and  from  the  interosseous  mem- 
brane.    It  terminates  in  a  tendon  which  passes  through  a  separate  compartment 


Tendon  of  Ext. 
carpi  rad.  longior 


Tendon  of  Ext. 
conimutiis  digitoru7n 


Wendon  of  Extensor  indicis 


First  LumMcal 


Ligamenta  irevia 


Tendon  of  Ext.  ossis 

tnetacarpi  pollicis 
Trapezium 


■Badial  artery 


Tendon  of  Ext.  brevis  pollicis 


Tendon  of  Ext.  long,  pollicis 


Fhior  suhlimis  digiiorutn 
Flexor p)  of  undus  digitorum 


Fig.  361. — The  tendons  attached  to  the  right  index  finger. 


in  the  annular  ligament,  lying  in  a  narrow,  oblique  groove  at  the  back  part  of 
the  lower  end  of  the  radius.  It  then  crosses  oblicjuely  the  tendons  of  the  Extensor 
carpi  radialis  longior  and  brevior,  being  separated  from  the  other  Extensor  tendons 
of  the  thumb,  by  a  triangular  interval,  in  which  the  radial  artery  is  found,  and  is 
finally  inserted  into  the  base  of  the  last  phalanx  of  the  thumb. 

Relations. — By  its  superficial  surface,  with  the  same  parts  as  the  Extensor  ossis  metacarpi 
polHcis;  by  its  deep  surface,  with  the  ulna,  interosseous  membrane,  the  posterior  interosseous 
nerve,  radius,  the  wrist,  the  radial  vessels,  and  metacarpal  bone  of  the  thumb. 

The  Extensor  indicis  (m.  extensor  indicis  froprins)  (Figs.  357  and  360)  is 
a  narrow,  elongated  muscle  placed  on  the  inner  side  of,  and  parallel  with,  the 


THE  POSTERIOR  RADIOULNAR  REGION  485 

preceding.  It  arises  from  the  posterior  surface  of  the  siiaft  of  the  ulna,  below 
the  origin  of  the  Extensor  longus  pollicis  and  from  the  interosseous  membrane. 
Its  tendon  passes  with  the  Extensor  communis  digitorum  through  the  same  canal 
in  the  annular  ligament,  and  subsequently  joins  the  tendon  of  the  Extensor 
communis  which  belongs  to  the  index  finger,  opposite  the  lower  end  of  the  corre- 
sponding metacarpal  bone,  lying  to  the  ulnar  side  of  the  tendon  from  the  common 
Extensor. 

Nerves. — The  Brachioradialis  is  supplied  by  the  fifth  and  sixth,  the  Extensor  carpi  radialis 
li)ngior  by  the  sixth  and  seventh,  and  the  Anconeus  by  the  seventh  and  eighth  cervical  nerves, 
all  through  the  musculospiral  nerve;  the  remaining  muscles  of  the  radial  and  posterior  brachial 
region  are  supplied  through  the  posterior  interosseous  nerve,  the  Supinator  [brevis]  being  sup- 
plied by  the  sixth  cervical,  the  Extensor  carpi  radialis  brevior  by  the  sixth  and  seventh  cervicals, 
and  all  the  other  muscles  by  the  seventh  cervical. 

Actions. — The  muscles  of  the  radial  and  posterior  brachial  regions,  which  comprise  all  the 
Extensor  and  Supinator  muscles,  act  upon  the  forearm,  wrist,  and  hand;  they  are  the  direct 
antagonists  of  the  Pronator  and  Flexor  muscles.  The  Anconeus  assists  the  Triceps  in  extending 
the  forearm.  The  chief  action  of  the  Brachioradialis  is  that  of  a  Flexor  of  the  elbow-joint,  but 
in  addition  to  this  it  may  act  both  as  a  Supinator  or  a  Pronator;  that  is  to  say,  if  the  forearm  is 
forcibly  pronated  it  will  act  as  a  Supinator,  and  bring  the  bones  into  a  position  midway  between 
supination  and  pronation;  and,  vice  versa,ii  the  arm  is  forcibly  supinated,  it  will  act  as  a  pro- 
nator, and  bring  the  bones  into  the  same  position,  midway  between  supination  and  pronation. 
The  action  of  the  muscle  is  therefore  to  throw  the  forearm  and  hand  into  the  position  they 
naturally  occupy  when  placed  across  the  chest.  The  Supinator  [brevis]  is  a  true  supinator;  that 
is  to  say,  when  the  radius  has  been  carried  across  the  ulna  in  pronation  and  the  back  of  the 
hand  is  directed  forward,  this  muscle  carries  the  radius  back  again  to  its  normal  position  on  the 
outer  side  of  the  ulna,  and  the  palm  of  the  hand  is  again  directed  forward.  The  Extensor  carpi 
radialis  longior  extends  the  wrist  and  abducts  the  hand.  It  may  also  assist  in  bending  the 
elbow-joint;  at  all  events,  it  serves  to  fix  or  steady  this  articulation.  The  Extensor  carpi 
radialis  brevior  assists  the  Extensor  carpi  radialis  longior  in  extending  the  wrist,  and  may  also  act 
slightly  as  an  abductor  of  the  hand.  The  Extensor  carpi  ulnaris  helps  to  extend  the  hand,  but 
•when  acting  alone  inclines  it  toward  the  ulnar  side;  by  its  continued  action  it  extends  the  elbow- 
joint.  The  Extensor  communis  digitorum  extends  the  phalanges,  then  the  wrist,  and  finally 
the  elbow.  It  acts  principally  on  the  proximal  phalanges,  the  middle  and  terminal  phalanges 
being  extended  by  the  Interossei  and  Lumbricales.  It  has  also  a  tendency  to  separate  the 
fingers  as  it  extends  them.  The  Extensor  minimi  digiti  extends  similarly  the  little  finger,  and 
by  its  continued  action  it  assists  in  extending  the  wrist.  It  is  owing  to  this  muscle  that  the  little 
finger  can  be  extended  or  pointed  while  the  others  are  flexed.  The  chief  action  of  the  Extensor 
ossis  metacarpi  pollicis  is  to  carry  the  thumb  outward  and  backward  from  the  palm  of  the  hand, 
and  hence  it  has  been  called  the  Abductor  pollicis  longus.  By  its  continued  action  it  helps  to 
extend  and  abduct  the  wrist.  The  Extensor  brevis  pollicis  extends  the  proximal  phalanx  of  the 
thumb.  By  its  continued  action  it  helps  to  extend  and  abduct  the  wrist.  The  Extensor  longus 
pollicis  extends  the  terminal  phalanx  of  the  thumb.  By  its  continued  action  it  helps  to  extend 
and  abduct  the  wrist.  The  Extensor  indicis  extends  the  index  finger,  and  by  its  continued  action 
assists  in  extending  the  wrist.  It  is  owing  to  this  muscle  that  the  index  finger  can  be  extended 
or  pointed  while  the  others  are  flexed. 

Applied  Anatomy. — The  tendons  of  the  Extensor  muscles  of  the  thumb  are  liable  to  become 
strained  and  their  sheaths  inflamed  after  excessive  exercise,  producing  a  sausage-shaped  swell- 
ing along  the  course  of  the  tendon,  and  giving  a  peculiar  creaking  sensation  to  the  finger  when 
the  muscle  acts;  it  is  known  as  fenosynovitis.  In  piano-players  the  slips  which  join  the  tendons 
of  the  Extensor  communis  digitorum  may  limit  freedom  of  motion  in  individual  fingers.  Their 
complete  extension,  without  operative  interference,  can  only  be  brought  about  by  long-continued 
exertion  in  practice,  when  elongation  of  certain  accessory,  but  restricting,  tendons  is  made  by 
nutritive  growth.  If  there  is  much  limitation,  division  of  the  hindering  slips  is  advisable.'  Par- 
alysis of  the  Extensor  muscles  of  the  hand  is  common  in  lead  poisoning,  and  causes  the  well- 
known  "wrist  drop."  Curiously  enough,  the  Brachioradialis  and  Extensor  ossei  metacarpi 
pollicis  muscles  escape.     The  paralysis  is  due  to  a  neuritis  of  the  musculospiral  nerve. 

1  Prof.  William  S.  Forbes,  in  the  Philadelphia  Medical  Journal,  January  15.  1898. 


486 


THE  MUSCLES  AND  FASCIA 


IV.  MUSCLES  AND  FASCIA  OF  THE  HAND. 

The  muscles  of  the  hand  are  subdivided  into  three  groups:  (1)  Those  of  the 
thumb,  which  occupy  the  radial  side  and  produce  the  thenar  eminence.  (2)  Those 
of  the  little  finger,  which  occupy  the  ulnar  side  and  give  rise  to  the  hypothenar 
eminence.     (3)  Those  in  the  middle  of  the  palm  and  within  the  interosseous  spaces. 

Dissection  (Fig.  344). — Make  a  transverse  incision  across  the  front  of  the  wrist,  and  a  second 
across  the  heads  of  the  metacarpal  bones;  connect  the  two  by  a  vertical  incision  in  the  middle 
line,  and  continue  it  through  the  centre  of  the  middle  finger.  The  anterior  and  posterior  annular 
ligaments  and  the  palmar  fascia  should  then  be  dissected. 


ANTERIOR 
A  N  N  U  LA  R 
LIGAMENT, 


flexor  longus  pollicis 
flexor  carpi  radial1 
:les  of  thumb 


Median  nerve. 
Ulnar 


1st  Metacarp 


Ead  al  i 

EXT.    CARP     R 


EXTENSOR 


EXTENSOR 

Os  magnuni. 


EXTENSOR 
COMMUN  S 
D  G  TORUM 
CIS 


of  the  tendons,  vessels,  and 


The  Anterior  Annular  Ligament  (ligamentuvi  carpi  transverswn)  (Fig.  362)  is  a 
strong,  fibrous  band  which  arches  over  the  carpus,  converting  the  deep  groove  on 
the  front  of  the  carpal  bones  into  a  canal,  beneath  which  pass  the  Flexor  tendons 
of  the  fingers.  It  is  attached,  internally,  to  the  pisiform  bone  and  the  hook  of 
the  unciform  bone,  and  externally  to  the  tuberosity  of  the  scaphoid  and  to  the 
inner  part  of  the  anterior  surface  and  the  ridge  of  the  trapezium.  It  is  continuous, 
above,  with  the  deep  fascia  of  the  forearm,  of  which  it  may  be  regarded  as  a  thick- 
ened portion,  and,  below,  with  the  palmar  fascia.  It  is  crossed  by  the  ulnar  ves- 
sels and  nerve  and  the  cutaneous  branches  of  the  median  and  ulnar  nerves.  At 
its  outer  extremity  is  the  tendon  of  the  Flexor  carpi  radialis,  which  lies  in  the  groove 
on  the  trapezium  between  the  attachments  of  the  annular  ligaments  to  the  bone. 
It  has  inserted  into  its  anterior  surface  a  part  of  the  tendon  of  the  Palmaris  longus 
and  part  of  the  tendon  of  the  Flexor  carpi  ulnaris,  and  has  arising  from  it,  below, 
the  small  muscles  of  the  thumb  and  little  finger.  Beneath  it  pass  the  tendons  of 
the  Flexores  sublimis  and  Profundus  digitorum,  the  tendon  of  the  Flexor  longus 
pollicis,  and  the  median  nerve. 

The  Synovial  Membranes  of  the  Flexor  Tendons  at  the  Wrist. — There  are  two 
vaginal  synovial  membranes  which  enclose  all  the  tendons  as  they  pass  beneath 
this  ligament — one  for  the  Flexores  sublimis  and  Profundus  digitorum,  the 
other  for  the  Flexor  longus  pollicis.  They  extend  up  into  the  forearm  for  about 
an  inch  above  the  annular  ligament,  and  downward  about  half-way  along  the 
metacarpal  bone,  where  they  terminate  in  a  blind  diverticulum  around  each  pair 


OF  THE  HAND 


487 


of  tendons,  with  the  exception  of  those  of  the  thumb  and  little  finger;  in  each 
of  these  two  digits  the  diverticulum  is  continued  on,  and  communicates  with  the 
synovial  sheath  of  the  tendons  in  the  fingers.  In  the  other  three  fingers  the  syno- 
vial sheath  of  the  tendons  begins  as  a  blind  pouch  without  communication  with 
the  large  synovial  sac  (Fig.  363). 

Applied  Anatomy. — This  arrangement  of  the  synovial  sheaths  explains  the  fact  that  thecal 
abscess  in  the  thumb  or  little  finger  is  liable  to  be  followed  by  abscesses  of  the  forearm,  from 
extension  of  the  inflammation  along  the  continuous  synovial  sheaths.    Tuberculous  inflamma- 
tion  is    liable  to  occur   in    this    situation, 
constituting  compound  palmar  ganglion;  it 
presents    an    hour-glass    outline,    with    a 
swelling  in  front  of  the  wrist  and   in   the 
palm  of  the  hand,  and  a  constriction  corre- 
sponding to  the  annular  ligament  between 
the  two.     The  fluid  can  be  forced  from  the 
one  swelling  to  the  other  under  the  liga- 
ment. 

Bursae  about  the  Hand  and  Wrist.— 
BursEe  usually  exist  between  the  distal  ex- 
tremities of  the  metacarpal  bones  (bursae 
intermetacarpophalangeae),  and  a  subcuta- 
neous bursa  often  exists  over  the  dorsal 
surface  of  the  head  of  the  fifth  metacarpal 
bone.  Subcutaneous  digital  dorsal  bursse 
occur  "almost  constantly  in  the  first  finger- 
joints  (between  the  first  and  second  pha- 
lanx), occasionally  in  the  second  joint  of 
the  second  and  fourth  fingers"'  (bursae  sub- 
cutaneae  digitorum,  dorsales).  A  bursa  exists 
between  the  tendon  of  the  Extensor  carpi 
radialis  brevior  and  the  base  of  the  third 
metacarpal  bone;  another  between  the 
Flexor  carpi  ulnaris  and  the  pisiform  bone; 
another  between  the  Flexor  carpi  radialis 
and  the  base  of  the  second  metacarpal  bone. 


363. — Diagram  showing  the  arrangement  of  the 
synovial  sheaths  of  the  palm  and  fingers. 


The  Posterior  Annular  Ligament 
(ligamentum  carpi  dorsale)  is  a  strong 
fibrous  band  extending  obliquely 
downward  and  inward  across  the 
back  of  the  wrist,  and  consisting  of 
the  deep  fascia  of  the  back  of  the 
forearm,  strengthened  by  the  addition 
of  some  transverse  fibres.  It  binds 
down  the  Extensor  tendons  in  their 
passage  to  the  fingers,  being  attached, 
internally,  to  the  styloid  process  of 
the  ulna,  the  cuneiform  and  pisiform 
bones;  externally,  to  the  margin  of  the 
radius;  and,  in  its  passage  across  the 
wrist,  to  the  ridges  on  the  posterior 
surface  of  the  radius.  It  presents  six 
compartments  for  the  passage  of  ten- 
dons, each  of  which  is  lined  with  a  separate  synovial  membrane  (Fig.  364) .  These 
are,  from  without  inward:  (1)  On  the  outer  side  of  the  styloid  process,  for  the 
tendons  of  the  Extensor  ossis  metacarpi  and  Extensor  brevis  pollicis.  (2)  Behind 
the  styloid  process,  for  the  tendons  of  the  Extensor  carpi  radialis  longior  and 


Fig.  364.— Transverse  section  through  the  wrist,  show- 
ing the  annular  ligamenta  and  the  canals  for  the  passage 
of  the  tendons. 


>  Hand  .\tlas  of  Human  Anatomy.     By  Werner  Spalteholz.     Translated  and  edited  by  Lewellys  F.  Barker. 


488 


THE  MVSCLES  AND  FASCIJE 


brevior.  (3)  About  the  middle  of  the  posterior  surface  of  the  radius,  for  the  ten- 
don of  the  Extensor  longus  pollicis.  (4)  To  the  inner  side  of  the  latter,  for  the 
tendons  of  the  Extensor  communis  digitorum  and  Extensor  indicis*  (5)  Oppo- 
site the  interval  between  the  radius  and  ulna,  for  the  Extensor  minimi  digiti. 
(6)  Grooving  the  back  of  the  ulna,  for  the  tendon  of  the  Extensor  carpi  ulnaris. 
The  synovial  membranes  lining  these  sheaths  are  usually  very  extensive,  reaching 
from  above  the  annular  ligament  down  upon  the  tendons  for  a  variable  distance  on 
the  back  of  the  hand. 


Fig.  365.— Palm 


preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 


The  deep  palmar  fascia  (^aponeurosis  palmaris)  (Fig.  365)  forms  a  common 
sheath  which  invests  the  muscles  of  the  hand.  It  consists  of  a  central  and  two 
lateral  portions. 

The  central  portion  occupies  the  middle  of  the  palm,  is  triangular  in  shape,  of 
great  strength  and  thickness,  and  binds  down  the  tendons  and  protects  the  vessels 
and  nerves  in  this  situation.  It  is  narrow  above,  where  it  is  attached  to  the  lower 
margin  of  the  annular  ligament,  and  receives  the  expanded  tendon  of  the  Pal- 
maris longus  muscle.  Below,  it  is  broad  and  expanded,  and  divides  into  four 
slips  for  the  four  fingers.     Each  slip  gives  off  superficial  fibres,  which  are  inserted 


THE  RADIAL  REGION  489 

into  the  skin  of  the  palm  and  finger,  those  to  the  palm  joining  the  skin  at  the  furrow 
corresponding  to  the  metacarpophalangeal  articulation,  and  those  to  the  fingers 
passing  into  the  skin  at  the  transverse  fold  at  the  base  of  the  fingers.  The  deeper 
part  of  each  slip  subdivides  into  two  processes,  which  are  inserted  into  the  lateral 
margins  of  the  anterior  ligament  of  the  metacarpophalangeal  joint.  From  the 
sides  of  these  processes  portions  are  sent  backward  (dorsal)  to  be  attached  to  the  bor- 
ders of  the  lateral  surfaces  of  the  metacarpal  bones  at  their  distal  extremities.  By 
this  arrangement  short  channels  are  formed  on  the  front  of  the  lower  ends  of  the 
metacarpal  bones,  through  which  the  Flexor  tendons  pass.^  The  intervals  left 
in  the  fascia  between  the  four  fibrous  slips  transmit  the  digital  vessels  and  nerves 
and  the  tendons  of  the  Lumbricales.  At  the  points  of  division  of  the  palmar 
fascia  into  the  slips  above  mentioned  numerous  strong,  transverse  fibres  bind  the 
separate  processes  together.  The  palmar  fascia  is  intimately  adherent  to  the 
integument  by  dense,  fibroareolar  tissue,  forming  the  superficial  palmar  fascia, 
and  gives  origin  by  its  inner  margin  to  the  Pal  maris  brevis;  it  covers  the  superficial 
palmar  arch,  the  tendons  of  the  Flexor  muscles,  and  the  branches  of  the  median 
and  ulnar  nerves,  and  on  each  side  it  gives  off  a  vertical  septum,  which  is  continu- 
ous with  the  interosseous  aponeurosis  and  separates  the  two  lateral  from  the 
middle  palmar  group  of  muscles. 

The  lateral  portions  of  the  palmar  fascia  are  thin,  fibrous  layers,  which  cover, 
on  the  radial  side,  the  muscles  of  the  ball  of  the  thumb,  and,  on  the  ulnar  side,  the 
muscles  of  the  little  finger;  they  are  continuous  with  the  dorsal  fascia,  and  in  the 
palm  with  the  central  portion  of  the  palmar  fascia. 

The  Superficial  Transverse  Ligament  of  the  Fingers  is  a  thin  band  of  transverse 
fibres  (fasciculi  transversi);  it  stretches  across  the  roots  of  the  four  fingers,  and  is 
closely  attached  to  the  skin  of  the  clefts,  and  internally  to  the  fifth  metacarpal  bone, 
forming  a  sort  of  rudimentary  web.  Beneath  it  the  digital  vessels  and  nerves 
pass  onward  to  their  destination. 

Applied  Anatomy. — The  palmar  fascia  is  liable  to  undergo  contraction,  producing  a  very 
inconvenient  deformity  known  as  Diipuytren's  contraction.  The  ring  and  little  fingers  are  most 
frequently  implicated,  but  the  middle,  the  index,  and  the  thumb  may  be  involved.  The  proximal 
phalanx  is  flexed  and  cannot  be  straightened,  and  the  two  distal  phalanges  become  similarly 
flexed  as  the  disease  advances. 


11.  The  Radial  Region  (Figs.  366,  367). 

Abductor  pollicis.  Flexor  brevis  pollicis. 

Opponens  pollicis.  Adductor  obliquus  pollicis. 

Adductor  transversus  pollicis. 

The  Abductor  pollicis  (m.  abductor  pollicis  brevis)  (Fig.  357)  is  a  thin,  flat 
muscle,  placed  immediately  beneath  the  integument.  It  arises  from  the  anterior 
annular  ligament,  the  tuberosity  of  the  scaphoid,  and  the  ridge  of  the  trapezium, 
frequently  by  two  distinct  slips;  and,  passing  outward  and  downward,  is  inserted 
by  a  thin,  flat  tendon  into  the  radial  side  of  the  base  of  the  first  phalanx  of  the 
thumb,  sending  a  slip  to  join  the  tendon  of  the  Extensor  longus  pollicis. 

Relations. — By  its  superficial  surface,  with  the  palmar  fascia  and  superficialis  volae  artery, 
which  frequently  perforates  it.  By  its  deep  surface,  with  the  Opponens  pollicis.  Its  inner 
border  is  separated  from  the  Flexor  brevis  pollicis  by  a  narrow  cellular  interval. 

*  Dr.  Keen  describes  a  fifth  slip  as  frequently  found  passing  to  the  thumb. 


490 


THE  MUSCLES  AND  FASCIA 


The  Opponens  pollicis  {vi.  opponens  pollicis)  (Figs.  366  and  367)  is  placed 
beneath  and  partially  to  the  outer  side  of  the  preceding.  It  atises  from  the 
ridge  on  the  trapezium  and  from  the  anterior  annular  ligament,  passes  down- 
ward and  outward,  and  is  inserted  into  the  whole  length  of  the  metacarpal  bone 
of  the  thumb  on  its  radial  side. 

Relations. — By  its  superficial  surface,  with  the  Abductor  and  Flexor  brevis  pollicis.  By  its 
deep  surface,  with  the  first  metacarpal  bone.  By  its  inner  border,  with  the  Adductor  obliquus 
poUicis. 

The  Flexor  brevis  pollicis  (vi.  flexor  pollicis  brevis)  (Fig.  367)  consists  of  two 
portions,  superficial  and  deep.  The  superficial  portion  arises  from  the  outer  two- 
thirds  of  the  lower  border  of  the  anterior  annular  ligaments  and  sometimes  from 


EXT.    LONGUS    POLLIC] 


Mrst  metacarpal  hont- 


FlG.  366.-      Ill        I  I  lie  thumb. 

the  ridge  of  the  trapezium,  and  passes  along  the  outer  side  of  the  tendon  of  the 
Flexor  longus  pollicis;  and,  becoming  tendinous,  has  a  sesamoid  bone  developed 
in  its  tendon,  and  is  inserted  into  the  outer  side  of  the  base  of  the  first  phalanx  of  the 
thumb.  The  deeper  portion  of  the  muscle  is  very  small,  and  arises  from  the  ulnar 
side  of  the  first  metacarpal  bone  beneath  the  Adductor  obliquus  pollicis,  and  is 
inserted  into  the  inner  side  of  the  base  of  the  first  phalanx  with  this  muscle. 

Relations. — By  its  superficial  surface,  with  the  palmar  fascia.  Its  deep  surface  is  separated 
from  the  Adductor  obhquus  pollicis  by  the  tendon  of  the  Flexor  longus  polHcis.  By  its  external 
(radial)  surface,  with  the  Abductor  pollicis. 


The  Adductor  obliquus  pollicis   {m.  adductor  pollicis)   (Figs.  366  and  367) 
arises  by  several  slips  from  the  os  magnum,  the  bases  of  the  second  and  third 


THE  RADIAL  REGION 


491 


metacarpal  bones,  the  anterior  carpal  ligaments,  and  the  sheath  of  the  tendon 
of  the  Flexor  carpi  radialis.  From  this  origin  the  greater  number  of  fibres  pass 
obliquely  downward  and  converge  to  a  tendon,  which,  uniting,  with  the  tendons 
of  the  deeper  portion  of  the  Flexor  brevis  pollicis  and  the  Adductor  transversus, 


Fia.  367.— Muscles  of  the  left  hand.     Palmar  surface. 


is  inserted  into  the  inner  side  of  the  base  of  the  first  phalanx  of  the  thumb,  a 
sesamoid  bone  being  developed  in  the  tendon  of  insertion.  A  considerable  fas- 
ciculus, however,  passes  more  obliquely  outward  beneath  the  tendon  of  the  long 
Flexor  to  join  the  superficial  portion  of  the  short  Flexor  and  the  Abductor 
pollicis.' 

•  This  muscle  is  described  by  some  as  the  deep  portion  of  the  Flexor  brevis  pollicis. 


492  THE  MUSCLES  AND  FASCIJE 

Relations. — By  its  superficial  surface,  with  the  Flexor  longus  pollicis  and  the  superficial 
head  of  the  Flexor  brevis  pollicis.  Its  deep  surface  is  in  relation  with  the  deep  palmar  arch, 
which  passes  between  the  two  Adductors. 

The  Adductor  transversus  pollicis  (m.  adductor  transversus  i)ollicis)  (Figs. 
366  and  367)  is  the  most  deeply  seated  of  this  group  of  muscles.  It  is  of  a  tri- 
angular form,  arising,  by  its  troad  base,  from  the  lower  two-thirds  of  the  meta- 
carpal bone  of  the  middle  finger  on  its  palmar  surface;  the  fibres,  proceeding 
outward,  converge  to  be  inserted,  with  the  deeper  part  of  the  Flexor  brevis  pollicis, 
and  the  Adductor  obliquus  pollicis,  into  the  ulnar  side  of  the  base  of  the  first 
phalanx  of  the  thumb.  From  the  common  tendon  of  insertion  a  slip  is  prolonged 
to  the  Extensor  longus  pollicis. 

Relations. — By  its  superficial  surface,  with  the  tendons  of  the  Flexor  profundus  and  the 
Lumbricales.  Its  deep  surface  covers  the  first  two  interosseous  spaces,  from  which  it  is  separated 
by  a  strong  aponeurosis. 

Three  of  these  muscles  of  the  thumb,  the  Abductor,  the  Adductor  transversus,  and  the  Flexor 
brevis  pollicis,  at  their  insertions  give  off  fibrous  expansions  which  join  the  tendon  of  the  Extensor 
longus  pollicis.  This  permits  of  flexion  of  the  pro:dmal  phalanx  and  extension  of  the  terminal 
phalanx  at  the  same  time. 

Nerves. — The  Abductor,  Opponens,  and  superficial  head  of  the  Flexor  brevis  pollicis  are 
supplied  by  the  sixth  cervical  through  the  median  nerve;  the  deep  head  of  the  Flexor  brevis,  and 
the  Adductors,  by  the  eighth  cervical  through  the  ulnar  nerve. 

Actions. — The  actions  of  the  muscles  of  the  thumb  are  almost  sufficiently  indicated  by 
their  names.  This  segment  of  the  hand  is  provided  with  three  Extensors — an  Extensor  of  the 
metacarpal  bone,  an  Extensor  of  the  first,  and  an  Extensor  of  the  second  phalanx ;  these  occupy 
the  dorsal  surface  of  the  forearm  and  hand.  There  are  also  three  Flexors  on  the  palmar  surface — 
a  Flexor  of  the  metacarpal  bone,  a  Flexor  of  the  proximal,  and  a  Flexor  of  the  terminal  phalanx; 
there  is  also  an  Abductor  and  two  Adductors.  The  Abductor  pollicis  moves  the  metacarpal 
bone  of  the  thumb  outward;  that  is,  away  from  the  index  finger.  The  Opponens  pollicis 
flexes  the  first  metacarpal  bone — that  is,  draws  it  inward  over  the  palm — so  as  to  turn  the  ball  of 
the  thumb  toward  the  fingers,  thus  producing  the  movement  of  opposition.  The  Flexor  brevis 
pollicis  flexes  and  adducts  the  proximal  phalanx  of  the  thumb.  The  Adductores  pollicis  move 
the  metacarpal  bone  of  the  thumb  inward;  that  is,  toward  the  index  finger.  These  muscles 
give  to  the  thumb  its  extensive  range  of  motion.  It  will  be  noticed,  however,  that  in  conse- 
quence of  the  position  of  the  first  metacarpal  bone,  these  movements  differ  from  the  corre- 
sponding movements  of  the  metacarpal  bones  of  the  other  fingers.  Thus  extension  of  the 
thumb  more  nearly  corresponds  to  the  motion  of  abduction  in  the  other  fingers,  and  fiexion 
'  to  adduction. 

12.  The  Ulnar  Region  (Fig.  367). 

Palmaris  brevis.  Flexor  brevis  minimi  digiti. 

Abductor  minimi  digiti.  Opponens  minimi  digiti. 

The  Palmaris  brevis  (m.  palmaris  brevis)  is  a  thin  quadrilateral  muscle  placed 
beneath  the  integument  on  the  ulnar  side  of  the  hand.  It  arises  by  tendinous 
fasciculi  from  the  anterior  annular  ligament  and  palmar  fascia;  the  fleshy  fibres 
pass  inward,  to  be  inserted  into  the  skin  on  the  inner  border  of  the  palm  of  the 
hand. 

The  Abductor  minimi  digiti  (m.  abductor  digiti  quinti)  is  situated  on  the  ulnar 
border  of  the  palm  of  the  hand.  It  arises  from  the  pisiform  bone  and  from  the 
tendon  of  the  Flexor  carpi  ulnaris,  and  terminates  in  a  flat  tendon,  which  divides 
into  two_  slips;  one  is  inserted  into  the  ulnar  side  of  the  base  of  the  first  phalanx 
of  the  little  finger.  The  other  slip  is  inserted  into  the  ulnar  border  of  the 
aponeurosis  of  the  Extensor  minimi  digiti. 


THE  MIDDLE  PALMAR  REGION  493 

Relations. — By  its  superficial  surface,  with  the  inner  portion  of  the  palmar  fascia  and  the 
Palmnris  brevis;  by  its  deep  surface,  with  the  Opponens  minimi  digiti;  by  its  outer  border, 
with  tlie  Flexor  brevis  minimi  digiti. 

The  Flexor  brevis  minimi  digiti  (in.  flexor  digifi  quinti  hrevh)  lies  on  the  same 
plane  as  the  preceding  muscle,  on  its  radial  side.  It  arises  from  the  convex  aspect 
of  the  hook  of  the  unciform  bone  and  anterior  surface  of  the  annular  ligament, 
and  is  inserted  into  the  inner  side  of  the  base  of  the  first  phalanx  of  the  little  finger. 
It  is  separated  from  the  Abductor  at  its  origin  by  the  deep  branches  of  the  idnar 
artery  and  nerve.  This  muscle  is  sometimes  wanting;  the  Abductor  is  then, 
usually,  of  large  size. 

Relations. — By  its  superficial  surface,  with  the  internal  portion  of  the  palmar  fascia  and 
the  Palmaris  brevis;  by  its  deep  surface,  with  the  Opponens.  The  deep  branch  of  the  ulnar 
artery  and  the  corresponding  branch  of  the  uhiar  nerve  pass  between  the  Abductor  and  Flexor 
brevis  minimi  digiti  muscles. 

The  Opponens  minimi  digiti  (m.  opponens  digiti  quinti)  (Fig.  356)  is  of  a 
triangular  form,  and  placed  immediately  beneath  the  preceding  muscles.  It 
arises  from  the  convexity  of  the  hook  of  the  unciform  bone  and  the  contiguous 
portion  of  the  anterior  annular  ligament;  its  fibres  pass  downward  and  inward, 
to  be  inserted  into  the  whole  length  of  the  metacarpal  bone  of  the  little  finger, 
along  its  ulnar  margin. 

Relations. — By  its  superficial  surface,  with  the  Flexor  brevis  and  Abductor  minimi  digiti; 
by  its  deep  surface,  with  the  Interossei  muscles  in'  the  fourth  metacarpal  space,  the  metacarpal 
bone,  and  the  Flexor  tendons  of  the  little  finger. 

Nerves. — All  the  muscles  of  this  group  are  supplied  by  the  eighth  cervical  nerve  through 
the  ulnar  nerve. 

Actions. — The  Abductor  minimi  digiti  abducts  the  little  finger  from  the  middle  line  of  the 
hand.  It  corresponds  to  a  dorsal  interosseous  muscle.  It  also  assists  in  flexing  the  proximal 
phalanx  and  extending  the  second  and  third  phalanges.  The  Flexor  brevis  minimi  digiti 
abducts  the  little  finger  from  the  middle  line  of  the  hand.  It  also  assists  in  flexing  the  proximal 
phalanx.  The  Opponens  minimi  digiti  draws  forward  the  fifth  metacarpal  bone,  so  as  to  deepen 
the  hollow  of  the  palm.  The  Palmaris  brevis  corrugates  the  skin  on  the  inner  side  of  the  palm 
of  the  hand  and  probably  serves  to  protect  the  ulnar  nerve  and  artery  from  damage  by  the 
pressure  of  grasping  a  hard  object. 


1.3.  The  Middle  Palmar  Region. 

Lumbricales.  Interossei  dorsales. 

Interossei  palmares. 

The  Lumbricales  (?nm.  lumbricales)  (Fig.  367)  are  four  small  fleshy  fasciculi, 
accessories  to  the  deep  Flexor  muscle.  They  arise  from  the  tendons  of  the 
Flexor  profundus  digitorum;  the^ir.s'^  and  second,  from  the  radial  side  and  palmar 
surface  of  the  tendons  of  the  index  and  middle  fingers,  respectively;  the  third, 
from  the  contiguous  sides  of  the  tendons  of  the  middle  and  ring  fingers;  and  the 
fourth,  from  the  contiguous  sides  of  the  tendons  of  the  ring  and  little  fingers. 
They  pass  to  the  radial  side  of  the  corresponding  fingers  and  opposite  the  meta- 
carpophalangeal articulation  each  tendon  is  inserted  into  the  tendinous  expansion 
of  the  Extensor  communis  digitorum,  covering  the  dorsal  aspect  of  each  finger. 

The  Interossei  muscles  {mm.  interossei)  (Figs.  368  and  369)  are  so  named 
from  occupying  the  intervals  between  the  metacarpal  bones,  and  are  divided  into 
two  sets,  dorsal  and  palmar. 


494 


THE  3IUSCLES  AND  FASCIJE 


The  Dorsal  interossei  (mm.  interossei  dorsales)  are  four  in  number,  larger  than  the 
palmar,  and  occupy  the  intervals  between  the  metacarpal  bones.  They  are 
bipenniforra  muscles,  arising  by  two  heads  from  the  adjacent  sides  of  the  meta- 
carpal bones,  but  more  extensively  from  the  metacarpal  bone  of  the  finger  into 
which  the  muscle  is  inserted.  They  are  inserted  into  the  bases  of  the  first  phalanges 
and  into  the  aponeurosis  of  the  common  Extensor  tendon.  Between  the  double 
orio-in  of  each  of  these  muscles  is  a  narrow  triangular  interval,  through  the  first 
of  which  passes  the  radial  artery;  through  each  of  the  other  three  passes  a  per- 
forating branch  from  the  deep  palmar  arch. 

The  First  dorsal  interosseous  muscle,  or  Abductor  indicis,  is  larger  than  the  others. 
It  is  flat,  triangular  in  form,  and  arises  by  two  heads,  separated  by  a  fibrous  arch, 
for  the  passage  of  the  radial_  artery  from  the  dorsum  to  the  palm  of  the  hand. 
The  outer  head  arises  from  the  upper  half  of  the  ulnar  border  of  the  first  meta- 
carpal bone;  the  inner  head,  from  almost  the  entire  length  of  the  radial  border 
of  the  second  metacarpal  bone;  the  tendon  is  inserted  into  the  radial  side  of  the 
index  finger.  The  Second  and  Third  dorsal  interossei  are  inserted  into  the  middle 
finger,  the  former  into  its  radial,  the  latter  into  its  ulnar  side.  The  Fourth  is 
inserted  into  the  ulnar  side  of  the  ring  finger. 

The  Palmar  interossei  (mm.  interossei  volares),  three  in  number,  are  smaller  than 
the  Dorsal,  and  placed  upon  the  palmar  surface  of  the  metacarpal  bones,  rather 
than  between  them.  Each  muscle  arises  from  the  entire  length  of  the  meta- 
carpal bone  of  one  finger,  and- is  inserted  into  the  side  of  the  base  of  the  first 


Fig.  368.— The  Dorsal  interossei  of  left  hand.  The 
line  marked  by  an  *  is  that  from  which  abduction  is 
made. 


Fig.  369. — The  Palmar  interossei  of  left  hand.  The 
line  marked  by  an  *  is  that  to  which  adduction  is 
made. 


phalanx  and  aponeurotic  expansion  of  the  common  Extensor  tendon  of  the  same 
finger.  The  First  arises  from  the  ulnar  side  of  the  second  metacarpal  bone,  and 
is  inserted  into  the  same  side  of  the  first  phalanx  of  the  index  finger.  The  Second 
arises  from  the  radial  side  of  the  fourth  metacarpal  bone,  and  is  inserted  into  the 
same  side  of  the  ring  finger.  The  Third  arises  from  the  radial  side  of  the  fifth 
metacarpal  bone,  and  is  inserted  into  the  same  side  of  the  little  finger.     From 


SURFACE  FORM  OF  THE  UPPER  EXTREMITY  495 

this  account  it  may  be  seen  that  each  finger  is  provided  with  two  Interosseous 
muscles,  with  the  exception  of  the  little  finger,  in  which  the  Abductor  muscle 
takes  the  place  of  one  of  the  pair. 

Nerves. — -The  two  outer  Lumbricales  are  supplied  by  the  sixth  cervical  nerve,  through  the 
third  and  fourth  digital  branches  of  the  median  nerve;  the  two  inner  Lumbricales  and  all  the 
Interossei  are  supplied  by  the  eighth  cervical  nerve,  through  the  deep  palmar  branch  of  the 
ulnar  nerve.     The  third  Lumbrical  frequently  receives  a  twig  from  the  median. 

Actions. — The  Palmar  interossei  muscles  adduct  the  finger  to  an  imaginary  line  drawn 
longitudinally  through  the  centre  of  the  middle  finger;  and  the  Dorsal  interossei  abduct  the 
fingers  from  that  line.  In  addition  to  this,  the  Interossei,  in  conjunction  with  the  Lumbricales, 
flex  the  first  phalanges  at  the  metacarpophalangeal  joints,  and  extend  the  second  and  third 
phalanges  in  consequence  of  their  insertion  into  the  expansion  of  the  Extensor  tendons.  The 
Extensor  communis  digitorum  is  believed  to  act  almost  entirely  on  the  first  phalanges. 


SURFACE  F0R:\I  OF  THE  UPPER  EXTREMITY. 

The  Pectoralis  major  muscle  largely  influences  surface  form  and  conceals  a  considerable 
part  of  the  thoracic  wall  in  front.  Its  sternal  origin  presents  a  festooned  border  which  bounds 
and  determines  the  width  of  the  sternal  furrow.  Its  clavicular  origin  is  somewhat  depressed 
and  flattened,  and  between  the  two  portions  of  the  muscle  is  often  an  oblique  depression  which 
differentiates  the  one  from  the  other.  The  outer  margin  of  the  muscle  is  generally  well  marked 
above,  and  bounds  the  infraclavicular  fossa  (Fossa  of  Mohi-enheim),  a  triangular  interval  which 
separates  the  Pectoralis  major  from  the  Deltoid.  It  gradually  becomes  less  marked  as  it 
approaches  the  tendons  of  insertion,  and  becomes  more  closely  blended  with  the  Deltoid  muscle. 
The  lower  border  of  the  Pectoralis  major  forms  the  rounded  anterior  axillary  fold,  and  corresponds 
with  the  direction  of  the  fifth  rib.  The  Pectoralis  minor  muscle  influences  surface  form.  When 
the  arm  is  raised  its  lowest  slip  of  origin  produces  a  local  fulness  just  below  the  border  of  the 
anterior  fold  of  the  axilla,  and  so  serves  to  break  the  sharp  line  of  the  lower  border  of  the  Pec- 
toralis major  muscle,  which  is  produced  when'  the  arm  is  in  this  position.  The  origin  of  the 
Serratus  magnus  muscle  produces  a  very  characteristic  surface  marking.  When  the  arm  is 
raised  from  the  side  in  a  well-developed  subject,  the  five  or  six  lower  serrations  are  plainly 
discernible,  forming  a  zigzag  line,  caused  by  the  series  of  digitations,  which  diminish  in  size 
from  above  downward,  and  have  their  apices  arranged  in  the  form  of  a  curve.  When  the  arm 
is  lying  by  the  side,  the  first  serration  to  appear,  at  the  lower  margin  of  the  Pectoralis  major, 

•is  the  one  attached  to  the  fifth  rib.  The  Deltoid  muscle,  with  the  prominence  of  the  upper 
extremity  of  the  humerus,  produces  the  rounded  outline  of  the  shoulder.  It  is  rounder  and 
fuller  in  front  than  behind,  where  it  presents  a  somewhat  flattened  foi-m.  Its  anterior  border, 
above,  presents  a  rounded,  slightly  curved  eminence,  w'hich  bounds  externally  the  infraclavicular 
fossa;  below,  it  is  closely  united  with  the  Pectoralis  major.  Its  posterior  border  is  thin,  flattened, 
and  scarcely  marked  above;  below,  it  is  thicker  and  more  prominent.  When  the  muscle  is  in 
action,  the  middle  portion  becomes  irregular,  presenting  alternate  longitudinal  elevations  and 
depressions,  the  elevations  corresponding  to  the  fleshy  portions,  the  depressions  to  the  tendinous 
intersections  of  the  muscle.  The  insertion  of  the  Deltoid  is  marked  by  a  depression  on  the 
outer  side  of  the  middle  of  the  arm.  Of  the  scapular  muscles,  the  only  one  which  materially 
influences  surface  form  is  the  Teres  major,  which  assists  the  Latissimus  dorsi  in  forming  the 
thick,  rounded  fold  of  the  posterior  boundary  of  the  axilla.     When  the  arm  is  raised,  the  Coraco- 

■  brachialis  reveals  itself  as  a  long,  narrow  elevation  which  emerges  from  under  cover  of  the 
anterior  fold  of  the  axilla  and  runs  downward,  internal  to  the  shaft  of  the  humerus.  When  the 
arm  is  hanging  by  the  side,  its  front  and  inner  part  presents  the  prominence  of  the  Biceps, 
bounded  on  either  side  by  an  intermuscular  depression.  This  muscle  determines  the  contour  of 
the  front  of  the  arm,  and  extends  from  the  anterior  margin  of  the  axilla  to  the  bend  of  the  elbow. 
Its  upper  tendons  are  concealed  by  the  Pectoralis  major  and  the  Deltoid,  and  its  lower  tendon 
sinks  into  the  space  at  the  bend  of  the  elbow,  \^^len  the  muscle  is  in  a  state  of  complete  con- 
traction— that  is  to  say,  when  the  forearm  has  been  flexed  and  supinated — it  presents  a  rounded 
convex  form,  bulged  out  laterally,  and  its  length  is  diminished.  On  each  side  of  the  Biceps, 
at  the  lower  part  of  the  arm,  the  Brachialis  anticus  is  discernible.  On  the  outer  side  it  forms 
a  narrow  eminence  which  extends  some  distance  up  the  arm  along  the  border  of  the  Biceps. 
On  the  inner  side  it  shows  itself  only  as  a  little  fulness  just  above  the  elbow.  On  the  back  of 
the  arm  the  long  head  of  the  Triceps  may  be  seen  as  a  longitudinal  eminence  emerging  from 
under  cover  of  the  Deltoid,  and  gradually  merging  into  the  longitudinal  flattened  plane  of  the 
tendon  of  the  muscle  on  the  lower  part  of  the  back  of  the  arm.     The  tendon  of  insertion  of  the 


496  THE  MUSCLES  AND  FASCIAE 

muscle  extends  about  half-way  up  the  back  of  the  arm,  where  it  forms  an  elongated  flattened 
plane  when  the  muscle  is  in  action.  Under  similar  conditions  the  surface  forms  produced  by 
the  three  heads  of  the  muscle  are  well  seen. 

On  the  anterior  aspect  of  the  elbow  are  to  be  seen  two  muscular  elevations,  one  on  each 
side,  separated  above  and  converging  below  so  as  to  form  a  triangular  space.  Of  these,  the 
inner  elevation,  consisting  of  the  Flexors  and  Pronators,  forms  the  prominence  along  the  inner 
side  and  front  of  the  forearm.  It  is  a  fusiform  mass,  pointed  above  at  the  internal  condyle 
and  gradually  tapering  off  below.  The  Pronator  teres,  the  innermost  muscle  of  the  group, 
forms  the  boundary  of  the  triangular  space  at  the  bend  of  the  elbow.  It  is  shorter,  less 
prominent,  and  more  oblique  than  the  outer  boundary.  The  most  prominent  part  of  the 
eminence  is  produced  by  the  Flexor  carpi  radialis,  the  muscle  next  in  order  on  the  inner 
side  of  the  preceding  one.  It  forms  a  rounded  prominence  above,  and  can  be  traced  down- 
ward to  its  tendon,  which  can  be  felt  lying  on  the  front  of  the  wrist,  nearer  to  the  radial 
than  to  the  ulnar  border,  and  to  the  inner  side  of  the  radial  artery.  The  Palmaris  longus  pre- 
sents no  surface  marking  above,  but  below  is  the  most  prominent  tendon  on  the  front  of  the 
wrist,  standing  out,  when  the  muscle  is  in  action,  as  a  sharp,  tense  cord  beneath  the  skin.  The 
Flexor  subliinis  digitorum  does  not  directly  influence  surface  form.  The  position  of  its  four 
tendons  on  the  front  of  the  lower  part  of  the  forearm  is  indicated  by  an  elongated  depression 
between  the  tendons  of  the  Palmaris  longus  and  the  Flexor  carpi  ulnaris.  The  Flexor  carpi 
ulnaris  occupies  a  small  part  of  the  posterior  surface  of  the  forearm,  and  is  separated  from  the 
Extensor  and  Supinator  group,  which  occupies  the  greater  part  of  this  surface,  by  the  ulnar 
furrow,  produced  by  the  subcutaneous  posterior  border  of  the  ulna.  Its  tendon  can  be  perceived 
along  the  ulnar  border  of  the  front  of  the  forearm,  and  is  most  marked  when  the  hand  is  flexed 
and  adducted.  The  deep  muscles  of  the  front  of  the  forearm  have  no  direct  influence  on  sur- 
face form.  The  external  group  of  muscles  of  the  forearm,  consisting  of  the  Extensors  and  Supi- 
nators, occupy  the  outer  and  a  considerable  portion  of  the  posterior  surface  of  this  region.  It 
has  a  fusiform  outline,  which  is  altogether  on  a  higher  level  than  the  Pronator  teres  and  Flexors. 
Its  apex  emerges  from  between  the  Triceps  and  Brachialis  anticus  muscles  some  distance  above 
the  elbow-joint,  and  acquires  its  greatest  breadth  opposite  the  external  condyle,  and  thence 
gradually  shades  off  into  a  flattened  surface.  About  the  middle  of  the  forearm  it  divides  into 
two  longitudinal  eminences  which  diverge  from  each  other,  leaving  a  triangular  interval  between 
them.  The  outer  of  these  two  groups  of  muscles  consists  of  the  Brachioradialis  arid  the  Fxtensores 
carpi  radialis  longior  et  brevior,  which  form  a  longitudinal  eminence  descending  from  the  external 
condylar  ridge  in  the  direction  of  the  styloid  process  of  the  radius.  The  other  and  more  pos- 
terior group  consists  of  the  Extensor  communis  digitorum,  the  Extensor  minimi  digiti,  and 
the  Extensor  carpi  ulnaris.  It  commences  above  as  a  tapering  form  at  the  external  condyle 
of  the  humerus,  and  is  separated  behind  at  its  upper  part  from  the  Anconeus  by  a  well-marked 
furrow,  and  below,  from  the  Pronato-flexor  mass,  by  the  ulnar  furrow.  In  the  triangular 
interval  left  between  these  two  groups  the  Extensors  of  the  thumb  and  index  finger  are  seen. ' 
The  only  two  muscles  of  this  region  which  require  special  mention  as  independently  influencing 
surface  form  are  the  Brachioradialis  and  the  Anconeus.  The  inner  border  of  the  Brachio- 
radialis forms  the  outer  boundary  of  the  triangular  space  at  the  bend  of  the  elbow.  It  com- 
mences as  a  rounded  border  above  the  condyle,  and  is  longer,  less  oblique,  and  more  prominent 
than  the  inner  boundary.  Lower  down,  the  muscle  forms  a  full  fleshy  mass  on  the  outer  side  of 
the  upper  part  of  the  forearm,  and  below  tapers  into  a  tendon,  which  may  be  traced  down  to 
the  styloid  process  of  the  radius.  The  Anconeus  presents  a  well-marked  and  characteristic 
surface  form  in  the  shape  of  a  triangular,  slightly  elevated  surface,  immediately  external  to  the 
subcutaneous  posterior  surface  of  the  olecranon,  and  diff'erentiated  from  the  common  Extensor 
group  by  a  well-marked  oblique  longitudinal  depression.  The  upper  angle  of  the  triangle 
corresponds  to  the  external  condyle,  and  is  marked  by  a  depression  or  dimple  in  this  situation. 
In  the  interval  caused  by  the  divergence  from  each  other  of  the  two  groups  of  muscles  into  which 
the  Extensor  and  Supinator  group  is  divided  at  the  lower  part  of  the  forearm  an  oblique  elon- 
gated eminence  is  seen,  caused  by  the  emergence  of  two  of  the  Extensors  of  the  thumb  from 
their  deep  origin  at  the  back  of  the  forearm.  This  eminence,  full  above  and  becoming  flattened 
out  and  partially  subdivided  below,  runs  downward  and  outward  over  the  back  and  outer  sur- 
face of  the  radius  to  the  outer  side  of  the  wrist-joint,  where  it  forms  a  ridge,  especially  marked 
when  the  thumb  is  extended,  which  passes  onward  to  the  posterior  aspect  of  the  thumb.  The 
tendons  of  most  of  the  Extensor  muscles  are  to  be  seen  and  felt  at  the  level  of  the  wrist-joint. 
Most  externally  are  the  tendons  of  the  Extensor  ossis  metacarpi  poUicis  and  the  Extensor  brevis 
2|)ollicis,  forming  a  vertical  ridge  over  the  outer  side  of  the  loint  from  the  styloid  process  of  the 
radius  to  the  thumb.  Internal  to  this  is  the  oblique  ridge  produced  by  the  tendon  of  the  Extensor 
longus  poUicis,  very  noticeable  when  the  muscle  is  in  action.  The  Extensor  carpi  radialis 
longior  is  scarcely  to  be  felt,  but  the  Extensor  carpi  radialis  brevior  can  be  distinctly  perceived 
as  a  vertical  ridge  emerging  from  under  the  inner  border  of  the  tendon  of  the  Extensor  longus 
pollicis,  when  the  hand  is  forcibly  extended  at  the  wrist.     Internal  to  this,  again,  can  be  felt 


APPLIED  ANATOMY  OF  THE  UPPER  EXTREMITY  497 

the  tendons  of  the  Extensor  indicis,  Extensor  communis  digitorum,  and  Extensor  minimi  digiti; 
the  latter  tendon  being  separated  from  those  of  the  common  Extensor  by  a  sh(i;ht  furrow. 

The  muscles  of  the  hand  ai-e  ]irinci|)ally  concerned,  so  far  as  regards  surface  form,  in  producing 
the  thenax  and  hypothenar  eminences,  and  individually  are  not  to  be  distinguished,  on  the  sur- 
face, from  each  other.  The  Adductor  transversus  pollicis  is,  however,  an  exception  to  this; 
its  anterior  border  gives  rise  to  a  ridge  across  the  web  of  skin  connecting  the  thumb  to  the  rest 
of  the  hand.  The  thenar  eminence  is  much  larger  and  rounder  than  the  hi/poiliciicir,  which 
presents  a  longer  and  narrower  eminence  along  the  ulnar  side  of  the  hand.  When  the  Palmaris 
brevis  is  in  action  it  produces  a  wrinkling  of  the  skin  over  the  hypothenar  eminence,  and  a  deep 
dimple  on  the  ulnar  border  of  the  hand.  The  anterior  extremities  of  the  Lumbrical  muscles 
help  to  produce  the  soft  eminences  just  behind  the  clefts  of  the  fingers,  sejjarated  from  each 
other  by  depressions  corresponding  to  the  Flexor  tendons  in  their  sheaths.  Between  the  thenar 
and  hypothenar  eminences,  at  the  wrist-joint,  is  a  slight  groove  or  depression,  widening  out  as 
it  approaches  the  fingers;  beneath  this  we  have  the  strong  cenli'al  part  of  the  palmar  fascia. 
On  the  back  of  the  hand  the  Dorsal  interossei  produce  elongated  markings  between  the  meta- 
carpal bones.  When  the  thumb  is  adducted  the  First  dorsal  interosseous  forms  a  prominent 
fusiform  bulging;  the  other  Interossei  are  not  so  marked. 

The  skin  over  the  inner  side  and  front  of  the  forearm  is  thin,  smooth,  and  sensitive;  it 
contains  few  hairs  and  many  sweat  glands.  Over  the  outer  side  and  back  of  the  arm  and 
forearm  it  is  thicker,  denser,  and  less  sensitive,  and  contains  more  hairs  and  fewer  sweat 
glands.  Over  the  olecranon  the  cuticle  is  thick  and  rough;  the  skin  is  loosely  connected 
to  the  underlying  tissues  and  becomes  transversely  wrinkled  when  the  forearm  is  extended. 
At  the  front  of  the  wrist  the  skin  presents  three  transverse  furrows,  which  correspond  from 
above  downward  to  the  position  of  the  styloid  process  of  the  ulna,  the  wrist-joint,  and  the 
midcarpal  joint,  respectively.  The  skin  of  the  palm  of  the  hand  differs  considerably  from 
that  of  the  forearm.  At  the  wrist  it  suddenly  becomes  hard  and  dense,  and  covered  by 
a  thick  layer  of  cuticle.  The  skin  in  the  thenar  region  presents  these  characteristics  less 
than  elsewhere.  In  spite  of  this  hardness  and  density,  the  skin  of  the  palm  is  exceedingly 
sensitive  and  very  vascular.  It  is  destitute  of  hair,  and  no  sebaceous  follicles  have  been 
found  in  this  region.  It  is  tied  down  by  fibrous  bands  along  the  lines  of  flexion  of  the  digits, 
producing  certain  furrows  of  a  permanent  character.  One  of  these,  starting  from  about  the 
tubercle  of  the  scaphoid,  curves  around  the  thenar  eminence,  and  ends  on  the  radial  border  of 
the  hand,  a  little  above  the  metacarpophalangeal  joint  of  the  index  finger.  It  corresponds  to 
the  outer  border  of  the  central  portion  of  the  palmar  fascia,  and  is  produced  by  the  movements 
of  the  thumb  at  the  carpometacarpal  joint.  A  second  line  begins  at  the  end  of  the  first  and 
extends  oblicjuely  across  the  palm  upward  and  inward,  to  the  ulnar  margin  about  the  middle 
of  the  fifth  metacarpal  bone.  A  third  commences  at  the  ulnar  border  of  the  hand  about  an 
inch  below  the  termination  of  the  second  and  extends  outward  across  the  palm  over  the  heads  of 
the  third,  fourth,  and  fifth  metacarpal  bones.  These  last  two  lines  are  caused  by  the  flexion  of 
the  fingers  at  the  metacarpophalangeal  joints.  Over  the  fingers  the  skin  again  becomes  thinner, 
especially  at  the  flexures  of  the  joints,  and  over  the  terminal  phalanges  it  is  thrown  into  numerous 
ridges  in  consequence  of  the  arrangement  of  the  papillse  in  it.  .These  ridges  form,  in  different 
individuals,  distinctive  and  permanent  patterns,  which  may  be  used  for  purposes  of  identifi- 
cation. (See  page  1150.)  The  superficial  fascia  in  the  palm  is  made  up  of  dense  fibrofatty 
tissue.  This  tissue  binds  down  the  skin  so  firmly  to  the  deep  palmar  fascia  that  very  little 
movement  is  permitted  between  the  two. 


APPLIED  ANATOMY  OF  THE  UPPER  EXTREMITY. 

The  student,  having  completed  the  dissection  of  the  muscles  of  the  upper  extremity,  should 
consider  the  effects  likely  to  be  produced  by  the  action  of  the  various  muscles  in  fracture  of  the 
bones. 

In  considering  the  action  of  the  various  muscles  upon  fractures  of  the  upper  extremity,  the 
most  common  forms  of  injury  have  been  selected  both  for  illustration  and  description. 

Fracture  of  the  middle  of  the  clavicle  (Fig.  370)  is  always  attended  with  considerable  dis- 
placement; the  inner  end  of  the  outer  fragment  is  displaced  inward  and  backward,  while  the 
outer  end  of  the  same  fragment  is  rotated  forward.  The  whole  outer  fragment  is  somewhat 
depressed.  The  deformity  is  described  by  saying  that  the  shoulder  goes  downward,  forwari^, 
and  inward.  "^ 

The  displacement  is  produced  as  follows:  inward,  by  the  muscles  passing  from  the  thorax  to 
the  outer  fragment  of  the  clavicle,  to  the  scapula,  and  to  the  humerus— viz.,  the  Subclavius  and 
the  Pectoralis  minor,  and,  to  a  less  extent,  the  Pectoralis  major  and  the  Latissimus  dorsi;  back- 
ward, in  consequence  of  the  rotation  of  the  outer  fragment.     The  Serratus  magnus  causes  the 

32 


498 


THE  MUSCLES  AND  FASCIA 


scapula  to  rotate  on  the  thoracic  wall;  this  carries  the  acromion  and  outer  end  of  the  outer 
fragment  of  the  clavicle  forward  and  causes  the  piece  of  bone  to  rotate  around  a  vertical  axis 
through  its  centre,  and  so  carries  the  inner  end  of  the  outer  portion  backward.  The  depression 
of  the  whole  outer  fragment  is  produced  by  the  weight  of  the  arm  and  by  the  contraction  of  the 
Deltoid.  The  outer  end  of  the  inner  fragment  appears  to  be  elevated,  the  skin  being  drawn 
tensely  over  it;  this  is  owing  to  the  depression  of  the  outer  fragment,  as  the  inner  fragment  is 
usually  kept  fixed  by  the  costoclavicular  ligament  and  by  the  antagonism  between  the  Sterno- 
mastoid  and  Pectoralis  major  muscles.  But  it  may  be  raised  by  an  unusually  strong  Sterno- 
mastoid,  or  by  the  inner  end  of  the  outer  fragment  getting  below  and  behind  it.  The  causes 
of  displacement  having  been  ascertained,  it  is  easy  to  apply  the  appropriate  treatment.  The 
outer  fragment  is  to  be  drawn  outward,  and,  together  with  the  scapula,  raised  upward  to  a  level 
with  the  inner  fragment,  and  retained  in  that  position.  This  deformity  is  corrected  by  carrying 
the  shoulder  upward,  outward,  and  backward. 

In  fracture  of  the  acromial  end  of  the  clavicle,  between  the  conoid  and  trapezoid  ligaments 
onlv  slight  displacement  occurs,  as  these  ligaments,  from  their  oblique  insertion,  serve  to  hold 

both  portions  of  the  bone  in  apposition.  Fracture,  also, 
of  the  sternal  end,  internal  to  the  costoclavicular  liga- 
ment, is  attended  with  only  slight  displacement,  this 
ligament  serving  to  retain  the  fragments  in  close  ap- 
position. 

Fracture  of  the  acromion  process  usually  arises  from 

violence  applied  to  the  upper  and  outer  part  of  the 

shoulder;  it  is  generally  known   by  the  rotundity  of 

the  shoulder    being    lost,   from   the   Deltoid   drawing 

<J     »*-— -_^,o.j)TR.t.sfl    ts     »/(/  the  fractured  portion  downward  and  forward;  and  the 

'J       ,1^^^^  '°"/\/l     ll  V^       displacement  may  easily  be  discovered  by  tracing  the 

yA   „  --r^  ^^/  //Mm   V'''  I'"'^       margin  of  the  clavicle  outward,  when   the  fragment 

/^        r~\ri.>-7    /m\  \M^'t'Vl"*if'S      will  he  found  resting  on  the  front  and  upper  part  of 

the   head  of    the   humerus.     In    order    to   relax    the 

anterior  and  outer  fibres  of  the  Deltoid  (the  opposing 

muscle),  the  arm  should  be  drawn  forward  across  the 

thorax  and  the  elbow  well  raised,  so  that  the  head  of 

the  bone  may  press  the  acromion  process  upward  and 

retain  it  in  its  position. 

Fracture  of  the  coracoid  process  is  an  extremely 
rare  accident,  and  is  usually  caused  by  a  sharp  blow 
on  the  point  of  the  shoulder.  Displacement  is  here 
produced  by  the  combined  actions  of  the  Pectoralis 
minor,  the  short  head  of  the  Biceps,  and  the  Coraco- 
brachialis,  the  former  muscle  drawing  the  fragment 
inward,  and  the  latter  muscles  directly  downward, 
the  amount  of  displacement  being  limited  by  the 
connection  of  this  process  to  the  acromion  by  means 
of  the  coraco-acromial  ligament.  In  many  cases  there  appears  to  have  been  little  or  no 
displacement,  from  the  fact  that  the  coracoclavicular  ligament  has  remained  intact,  and  has  kept 
the  separated  fragment  from  displacement.  In  order  to  relax  these  muscles  and  replace  the  frag- 
ments in  close  apposition,  the  forearm  should  be  flexed  so  as  to  relax  the  Biceps^  and  the  arm 
drawn  forward  and  inward  across  the  chest,  so  as  to  relax  the  Coracobrachialis;  the  humerus 
should  then  be  pushed  upward  against  the  coraco-acromial  ligament,  and  the  arm  retained  in 
that  position. 

Fracture  of  the  surgical  neck  of  the  humerus  (Fig.  371)  is  very  common,  is  attended  with 
considerable  displacement,  and  its  appearances  correspond  somewhat  with  those  of  dislocation 
of  the  head  of  the  humerus  into  the  axilla.  The  upper  fragment  is  slightly  elevated  under  the 
coraco-acromial  ligament  by  the  muscles  attached  to  the  greater  and  lesser  tuberosities;  the 
lower  fragment  is  drawn  inward  by  the  Pectoralis  major,  Latissimus  dorsi,  and  Teres  major; 
and  the  humerus  is  thrown  obliquely  outward  from  the  side  by  the  Deltoid,  and  occasionally 
elevated  so  as  to  cause  the  upper  end  of  the  lower  fragment  to  project  beneath  and  in  front  of 
the  coracoid  process.  The  deformity  is  reduced  by  fixing  the  shoulder,  and  drawing  the  arm 
outward  and  downward.  To  counteract  the  opposing  muscles,  and  to  keep  the  fragments  in 
position,  a  conical-shaped  pad  should  be  placed  with  the  apex  in  the  axilla;  while  the  forearm 
is  flexedto  an  angle  of  90  degrees  the  shoulder  is  padded  with  cotton,  a  shoulder-cap  of  plaster 
of  Paris  is  applied  to  cover  the  shoulder,  a  portion  of  the  thorax  and  back,  and  the  arm  down  to 
the  external  condyle  (Scudder).  The  arm,  with  the  elbow  slightly  forward,  is  bandaged  to  the 
side.     In  some  cases  a  splint  is  placed  between  the  axillary  pad  and  the  inner  side  of  the  arm. 


APPLIED  ANATOMY  OF  THE  UPPER  EXTREMITY 


499 


In  fracture  of  the  shaft  of  the  humerus  below  the  insertion  of  the  Pectoralis  major,  Latissimus 
dorsi,  and  Teres  major,  and  above  the  insertion  of  the  Deltoid,  there  is  also  considerable 
deformity,  the  upper  fragment  being  drawn  inward  by  the  first-mentioned  muscles,  and  the 
lower  fragment  upward   and   outward  by  the  Deltoid,  pro- 
ducing shortening  of  the  limb   and   a  considerable  promi- 
nence at  the  seat  of  fracture,  from  the  fractured  ends  of  the 
bone  riding  over  one  another,  especially  if  the  fracture  takes 
place  in    an   oblique   direction.     The   fragments    may    be 
brought  into  apposition  by  extension  from  the  elbow,  and 
are  retained  in  that  position  by  adopting  the  same  means 
as  in  the  )jreceding   injury,  or  by    the    use  of   an   internal 
angular  splint  with  three  short  humeral  splints. 

In  fractures  of  the  shaft  of  the  hmiierus  immediately  be- 
low the  insertion  of  the  Deltoid,  the  amount  of  deformity 
depends  greatly  upon  the  direction  of  the  fracture.  If  it 
occurs  in  a  transverse  direction,  only  slight  displacement 
takes  place,  the  upper  fragment  being  drawn  a  little  for- 
ward; but  in  oblic|ue  fracture  the  combined  actions  of  the 
Biceps  and  Brachialis  anticus  muscles  in  front  and  the 
Triceps  behind  draw  upward  the  lower  fragment,  causing 
it  to  glide  over  the  upper  fragment,  either  backward  or  for- 
ward, according  to  the  direction  of  the  fracture.  Simple 
extension  reduces  the  deformity,  and  the  application  of  an 
internal  angular  splint  and  three  short  humeral  splints  will 
retain  the  fragments  in  apposition.  Care  should  be  taken 
not  to  raise  the  elbow,  but  the  forearm  and  hand  may  be  sup- 
ported in  a  sling. 

Fracture  of  the  humerus  (Fig.  372)  above  the  condi/le  deserves  very  attentive  consideration, 
as  the  general  appearances  correspond  somewhat  with  those  produced  by  separation  of  the 
epiphysis  of  the  humerus,  and  with  those  of  dislocation  of  the  radius  and  ulna  backward.  If 
the  direction  of  the  fracture  is  oblique  from  above,  downward  and  forward,  the  lower  fragment 


-Fracture  of  the  h 
the  condyle. 


Fig.  .373. — Fracture  of  the  olecranon. 


is  drawn  upward  by  the  Brachialis  anticus  and  Biceps  in  front  and  the  Triceps  behind;  and 
at  the  same  time  is  drawn  backward  behind  the  upper  fragment  by  the  Triceps.  This  injury 
may  be  differentiated  from  dislocation  by  the  increased  mobility  in  fracture,  the  existence  of 
crepitus,  and  the  fact  of  the  deformity  being  remedied  by  extension,  on  the  discontinuance 
of  which  it  is  reproduced.  The  age  of  the  patient  is  of  importance  in  distinguishing  this  form 
of  injury  from  separation  of  the  epiphysis.  If  fractui'e  occurs  in  the  opposite  direction  to  that 
shown  in  Fig.  362,  the  lower  fragment  is  drawn  upward  and  forward,  causing  a  considerable 
prominence  in  front,  and  the  upper  fragment  projects  backward  beneath  the  tendon  of  the 
Triceps  muscle. 


500 


THE  MUSCLES  AND  FASCIA 


Fracture  of  the  olecranon  process  (Fig.  373)  is  a  frequent  accident.  The  detached  fragment 
is  displaced  upward,  by  the  action  of  the  Triceps  muscle,  from  half  an  inch  to  two  inches;  the 
prominence  of  the  elbow  is  consequently  lost,  and  a  deep  hollow  is  felt  at  the  back  part  of  the 
joint,  which  is  much  increased  on  flexing  the  limb.  The  patient  at  the  same  time  loses,  more 
or  less,  the  power  of  extending  the  forearm.     The  treatment  consists  in  relaxing  the  Triceps  by 

extending  the  limb,  and  retaining  it  in  the 
extended  position  by  means  of  a  long  straight 
splint  applied  to  the  front  of  the  arm;  the 
fragments  are  thus  brought  into  close  appo- 
sition, and  may  be  further  approximated  by 
drawing  down  the  upper  fragment.  The  frag- 
ments may  be  wired  together  and  thus  prevent 
the  formation  of  a  ligamentous  union,  as  is 
generally  the  case  when  wiring  is  not  em- 
ployed; passive  motion  must  be  instituted  at 
the  end  of  the  third  week  to  prevent  ankylosis. 
Fracture  of  the  neck  of  the  radius  is  an 
exceedingly  rare  accident,  and  is  generally 
caused  by  direct  violence.  Its'  diagnosis  is  somewhat  obscure,  on  account  of  the  slight  deformity 
visible,  the  injured  part  being  surrounded  by  a  large  number  of  muscles;  but  the  movements  of 
pronation  and  supination  are  entirely  lost.  The  upper  fragment  is  drawn  outward  by  the 
Supinator  [brevis],  the  extent  of  displacement  being  limited  by  the  attachment  of  the  orbicular 
ligament.  The  lower  fragment  is  drawn  forward  and  slightly  upward  by  the  Biceps,  and  inward  by 
the  Pronator  teres,  its  displacement  forward  and  upward  fjeing  counteracted  in  some  degree  by 
the  Supinator.  The  treatment  essentially  consists  in  relaxing  the  Biceps,  Supinator,  and  Pro- 
nator teres  muscles  by  flexing  the  forearm,  and  placing  it  in  a  position  midw'ay  between  pronation 
and  supination,  extension  having  been  previously  made  so  as  to  bring  the  parts  in  apposition. 


Fig.  374.— Fracture  of  the  shaft  of  th. 


Fig.  375. — Fracture  of  the  lower  end  of  the  radius. 


In  fracture  of  the  radius  below  the  insertion  of  the  Biceps,  but  above  the  insertion  of  the 
Pronator  teres,  the  upper  fragment  is  strongly  supinated  by  the  Biceps  and  Supinator,  and  at 
the  same  time  drawn  forward  and  flexed  by  the  Biceps;  the  lower  fragment  is  pronated  and 
drawn  inward  toward  the  ulna  by  the  Pronators.  Thus,  there  is  extreme  displacement  with 
very  little  deformity.  In  treating  such  a  fracture  the  arm  must  be  put  up  in  a  position  of 
supination,  otherwise  union  will  take  place  with  great  impairment  of  the  movements  of  the 
hand.  In  fractures  of  the  radius  below  the  insertion  of  the  Pronator  teres  (Fig.  374),  the  upper 
fragment  is  drawn  upward  by  the  Biceps  and  inward  by  the  Pronator  teres,  holding  a  position 
midway  between  pronation  and  supination,  and  a  degree  of  fulness  in  the  upper  half  of  the  fore- 
arm is  thus  produced;  the  lower  fragment  is  drawn  downward  and  inward  toward  the  ulna  by 
the  Pronator  quadratus,  and  thrown  into  a  state  of  pronation  by  the  same  muscle;  at  the  same 
time,  the  Brachioradialis,  by  elevating  the  styloid  process,  into  which  it  is  inserted,  will  serve  to 
depress  the  upper  end  of  the  lower  fragment  still  more  toward  the  ulna.  In  order  to  relax  the 
opposing  muscles  the  forearm  should  be  bent,  and  the  limb  placed  in  a  position  midway  between 
pronation  and  supination;  the  fracture  is  then  easily  reduced  by  extension  from  the  wrist  and 
elbow;  well-padded  splints  should  be  applied  on  both  sides  of  the  forearm  from  the  elbow  to 
the  wrist;  the  hand,  being  allowed  to  fall,  will,  by  its  own  weight,  counteract  the  action  of  the 
Pronator  quadratus  and  of  the  Brachioradialis,  and  elevate  the  lower  fragment  to  the  level  of 
the  upper  one. 

In  fracture  of  the  shaft  of  the  ulna  the  upper  fragment  retains  its  usual  position,  but  the  lower 
fragment  is  drawn  outward  toward  the  radius  by  the  Pronator  quadratus,  producing  a  well- 


OF  THE  LOWER  EXTREMITY 


501 


niarked  depression  at  the  seat  of  fracture  and  some  fulness  on  the  dorsal  and  palmar  surfaces 
of  the  forearm.  The  fracture  is  easily  reduced  by  extension  from  the  wrist  and  forearm.  The 
forearm  should  be  flexed,  and  placed  in  a  position  midway  between  pronation  and  supination, 
and  well-padded  splints  applied  from  the  elbow  to  the  ends  of  the  fingers. 

In  fracture  of  the  shajts  of  the  radius  and  ulna  together  the  lower  fragments  are  drawn  ujiward, 
sometimes  forward,  sometimes  backward,  according  to  the  direction  of  the  fracture,  by  the 
combined  actions  of  the  Flexor  and  Extensor  muscles,  producing  a  degree  of  fulness  on  the 
dorsal  or  palmar  surface  of  the  forearm;  at  the  same  time  the  two  fragments  are  drawn  into 
contact  by  the  Pronator  quadratus,  the  radius  being  in  a  state  of  pronation;  the  upper  fragment 
of  the  radius  is  drawn  upward  and  inward  by  the  Biceps  and  Pronator  teres  to  a  higher  level 
than  the  ulna;  the  upper  portion  of  the  ulna  is  slightly  elevated  by  the  Brachialis  anticus.  The 
fracture  may  be  reduced  by  extension  from  the  wrist  and  elbow,  and  the  forearm  should  be  placed 
in  the  same  position  as  in  fracture  of  the  ulna. 

In  fracture  of  the  lower  end  of  the  radius  (Colles'  fracture)  (Fig.  375)  the  displacement  which 
is  produced  is  very  considerable,  and  bears  some  resemblance  to  dislocation  of  the  carpus  back- 
ward, from  which  it  should  be  carefully  distinguished.  The  lower  fragment  is  displaced  back- 
ward and  upward,  but  this  displacement  is  probably  due  to  the  force  of  the  blow  driving  the 
portion  of  the  bone  into  this  position  and  not  to  any  muscular  influence.  The  upper  fragment 
projects  forward,  often  lacerating  the  substance  of  the  Pronator  quadratus,  and  is  drawn  by 
this  muscle  into  close  contact  with  the  lower  end  of  the  ulna,  causing  a  projection  on  the  anterior 
surface  of  the  forearm,  immediately  above  the  carpus,  from  the  Flexor  tendons  being  thrust 
forward.  This  fracture  may  be  distinguished  from  dislocation  by  the  deformity  being  removed 
on  making  sufficient  extension,  when  crepitus  may  be  occasionally  detected;  at  the  same  time, 
on  extension  being  discontinued,  the  parts  immediately  resume  their  deformed  appearance. 
The  age  of  the  patient  will  also  assist  in  determining  whether  the  injury  is  fracture  or  separation 
of  the  epiphysis.  Reduction  is  effected  by  hyperextension,  longitudinal  traction,  and  forced 
flexion.'    The  posterior  straight  splint  with  suitable  pads  is  the  best  dressing. 


MUSCLES  AND  FASCIA  OF  THE  LOWER  EXTREMITY. 

The  muscles  of  the  lower  extremity  are  subdivided  into  groups  corresponding 
with  the  different  regions  of  the  limb. 


I.  Iliac  Region. 


2.  Internal  Femoral  Region. 


Psoas  magnus. 
Psoas  parvus. 
Iliacus. 


Gracilis. 
Pectineus. 
Adductor  longus. 
Adductor  brevis. 
Adductor  magnus. 


II.  Thigh. 

1.  Anterior  Femoral  Region. 

Tensor  fasciae  femoris. 
Sartorius. 
[■  Rectus  femoris. 
Quadriceps  J  Vastus  externus. 
extensor.     |  Vastus  internus. 
I  Crureus. 
Subcrureus. 


III.  Hip. 

3.   Gluteal   Region. 

Gluteus  maximus. 
Gluteus  medius. 
Gluteus  minimus. 
Pyriformis. 
Obturator  internus. 
Gemellus  superior. 
Gemellus  inferior. 
Quadratus  femoris. 
Obturator  externus. 


502 


THE  MUSCLES  AND  FASCIA 


4.  Posterior  Femoral  Region. 

-TT  •     ,.  f  Biceps  femor is. 

Hamstring       o      •*      i- 

,     '^    i  bemitendinosus. 
muscles.      j  o      •         u 

bemimem  branosus. 


.IV.  Leg. 

5.  Anterior  Tibiofibular  Region. 

Tibialis  anticus. 
Extensor  proprius  hallucis. 
Extensor  longus  digitorum. 
Peroneus  tertius. 

6.  Posterior  Tibiofibular  Region. 
Superficial  Layer. 

Gastrocnemius. 

Soleus. 

Plantaris. 

Deep  Layer. 

Popliteus. 

Flexor  longus  hallucis. 
Flexor  longus  digitorum. 
Tibialis  posticus. 

7.  Fibular  Region. 

Peroneus  longus. 
Peroneus  brevis. 


V.  Foot. 

8.  Dorsal  Region. 
Extensor  brevis  digitorum. 

9.  Plantar  Region. 

First  Layer. 

Abductor  hallucis. 
Flexor  brevis  digitorum. 
Abductor  minimi  digiti. 

Second  Layer. 

Flexor  accessorius. 
Lumbricales. 

Third  Layer. 

Flexor  brevis  hallucis. 
Adductor  obliquus  hallucis. 
Flexor  brevis  minimi  digiti. 
Adductor  transversus  hallucis. 

Fourth  Layer. 
Interossei. 


I.  MUSCLES  AND  FASCIiE  OF  THE  ILIAC  REGION. 


Psoas  magnus. 


Psoas  parvus. 


Iliacus. 


Dissection. — No  detailed  description  is  required  for  the  dissection  of  these  muscles.  On 
the  vemoval  of  the  viscera  from  the  abdomen  they  are  exposed,  covered  by  the  peritoneum  and 
a  thin  layer  of  fascia,  the  iliac  fascial 

The  iliac  fascia  (fascia  iliaca)  is  the  aponeurotic  layer  which  lines  the  back 
part  of  the  abdominal  cavity,  and  covers  the  Psoas  and  Iliacus  muscles  throughout 
their  whole  extent.  It  is  thin  above,  and  becomes  gradually  thicker  below  as  it 
approaches  the  femoral  arch. 

The  portion  covering  the  Psoas  is  thickened,  above,  to  form  the  ligamentum 
arcuatum  internum;  internally  it  is  attached,  by  a  series  of  arched  processes,  to  the 
intervertebral  substances,  to  the  prominent  margins  of  the  bodies  of  the  vertebrae, 
and  to  the  upper  part  of  the  sacrum,  the  intervals  so  left,  opposite  the  constricted 
portions  of  the  bodies,  transmitting  the  lumbar  arteries  and  veins  and  the  fila- 
ments of  the  sympathetic  cord.  Externally,  above  the  crest  of  the  ilium,  this 
portion  of  the  iliac  fascia  is  continuous  with  the  anterior  lamella  of  the  lumbar 
fascia  covering  the  front  of  the  Quadratus  lumborum,  but  below  the  crest  of  the 
ilium  it  is  continuous  with  the  fascia  covering  the  Iliacus. 


OF  THE  ILIA  C  REGION 


503 


The  portion  investing  the  Iliacus  is  connected  externally  to  the  whole  length 
of  the  inner  border  of  the  crest  of  the  ilium,  and  internally  to  the  brim  of  the 
true  pelvis,  where  it  is  continuous  with  the  periosteum;  at  the  iliopectineal  emi- 
nence it  receives  the  tendon  of  insertion  of  the  Psoas  parvus,  when  that  muscle 
exists.  External  to  the  external  iliac  vessels,  this  fascia  is  intimately  connected 
to  the  posterior  margin  of  Poupart's  ligament,  and  is  continuous  with  the  fascia 
transversalis.  Immediately  to  the  outer  side  of  the  external  iliac  vessels,  as  they 
pass  beneath  Poupart's  ligament,  the  fascia  iliaca  is  prolonged  backward  and 
inward  from  Poupart's  ligament  as  a  band,  the  iliopectineal  ligament  (Fig.  376), 
and  is  attached  to  the  iliopectineal  eminence.  The  ligament  divides  the  space 
between  Poupart's  ligament 
and  the  horizontal  ramus  of 
the  pubis  into  two  parts,  the 
inner  of  which  {lacuna  vaso- 
rum)  transmits  the  femoral 
vessels,  and  the  femoral  branch 
of  the  genitofemoral  nerve  is 
bounded  internally  by  the 
base  of  Gimbernat's  ligament 
and  contains  the  femoral  ring. 
The  outer  part  (lacuna  mus- 
culorum) transmits  the  Ilio- 
psoas and  the  femoral  nerve 
and  the  external  cutaneous 
nerve  (Fig.  376).  Internal  to 
the  vessels  the  iliac  fascia  is  at- 
tached to  the  iliopectineal  line 
behind  the  conjoined  tendon, 
where  it  is  again  continvious 
with  the  transversalis  fascia; 
and,  corresponding  to  the  point 
where  the  femoral  vessels  pass 
into  the  thigh,  this  fascia  de- 
scends behind  them,  forming 
the  posterior  wall  of  the  fem- 
oral sheath.  This  portion  of 
the  iliac  fascia  which  passes 
behind  the  femoral  vessels  is 
also  attached  to  the  iliopec- 
tineal line  beyond  the  limits 
of  the  attachment  of  the  con- 
joined tendon;  at  this  part  it 

is  continuous  with  the  pubic  portion  of  the  fascia  lata  of  the  thigh.  The  external 
iliac  vessels  lie  in  front  of  the  iliac  fascia,  but  all  the  branches  of  the  lumbar  plexus 
lie  behind  it;  it  is  separated  from  the  peritoneum  by  a  quantity  of  loose  areolar 
tissue.  The  femoral  sheath  (fascia  cruris)  is  formed  by  the  transversalis  fascia 
in  front  of  the  vessels  and  the  iliac  fascia  behind  them.  In  the  thigh  the  fasciae 
join  to  the  inner  side  of  the  femoral  vein,  a  space,  the  femoral  canal  (canalis 
femoralis)  (Fig.  376),  intervening  between  the  vein  and  their  junction. 

Between  the  femoral  vein  and  the  edge  of  Gimbernat's  ligament  is  the  femoral  or 
crmal  ring  (annulus  femoralis)  (Fig.  376).  It  is  the  upper  opening  of  the  femoral 
canal,  just  mentioned,  and  leads  into  the  cavity  of  the  abdomen.  It  is  bounded  in 
front  by  Poupart's  ligament;  behind  by  the  horizontal  ramus  of  the  pubes  covered 
by  the  Pectineus  muscle;  internally  by  the  base  of  Gimbernat's  ligament; 
externally  by  the  fibrous  septum  lying  in  the  inner  side  of  the  femoral  vein.     The 


PECTINEUS 


ligament  and  the  relation  of  the  parts  pass- 
ath  it.     (Poirier  and  Charpy.) 


504  THE  MUSCLES  AND  FASCIJE 

femoral  ring  is  closed  by  the  septum  crurale  of  Cloquet  (septum  femorale  [Cloqueti]), 
which  is  a  process  of  transversalis  fascia  (Fig.  378).  The  femoral  canal  is  the 
interval  between  the  femoral  vein  and  the  inner  wall  of  the  femoral  sheath. 
This  canal  extends  from  the  femoral  ring  to  the  saphenous  opening. 

The  Psoas  magnus  (m.  psoas  major)  (Fig.  379)  is  a  long  fusiform  muscle  placed 
on  the  side  of  the  lumbar  region  of  the  vertebral  column  and  the  margin  of  the  pelvis. 
It  arises  from  the  front  of  the  bases  and  lower  borders  of  the  transverse  processes 
of  the  lumbar  vertebrae  by  five  fleshy  slips;  also  from  the  sides  of  the  bodies  and 
the  corresponding  intervertebral  substances  of  the  last  thoracic  and  all  the  lumbar 
vertebrte.  The  muscle  is  connected  to  the  bodies  of  the  vertebrae  by  five  slips; 
each  slip  is  attached  to  the  upper  and  lower  margins  of  two  vertebrae,  and  to  the 
intervertebral  substance  between  them,  the  slips  themselves  being  connected  by 
the  tendinous  arches  which  extend  across  the  constricted  part  of  the  bodies,  and 
beneath  which  pass  the  lumbar  arteries  and  veins  and  filaments  of  the  sympathetic 
cord.  These  tendinous  arches  also  give  origin  to  muscle  fibres,  and  protect 
the  bloodvessels  and  nerves  from  pressure  during  the  action  of  the  muscle.  The 
first  slip  is  attached  to  the  contiguous  margins  of  the  last  thoracic  and  first  lumbar 
vertebrte;  the  last  to  the  contiguous  margins  of  the  fourth  and  fifth  lumbar  ver- 
tebrae, and  to  the  intervertebral  substance.  From  these  points  the  muscle  descends 
across  the  brim  of  the  pelvis,  and,  diminishing  gradually  in  size,  passes  beneath 
Poupart's  ligament,  and  terminates  in  a  tendon  which,  after  receiving  nearly  =the 
whole  of  the  fibres  of  the  Iliacus,  is  inserted  into  the  lesser  trochanter  of  the  femur. 

Relations. — In  the  lumbar  region,  by  its  anterior  surface,  wliich  is  placed  behind  the  peri- 
toneum, the  Psoas  magnus  is  in  relation  with  the  fascia  which  covers  it,  with  the  ligamentum 
arcuatum  internum,  the  kidney,  Psoas  parvus,  renal  vessels,  ureter,  spermatic  vessels,  genito- 
femoral nerve,  and  the  colon.  In  many  cases  the  vermiform  appendix  rests  upon  the  right  Psoas 
muscle  (page  505).  By  its  posterior  surface,  with  the  transverse  processes  of  the  lumbar  ver- 
tebrte  and  the  Quadratus  lumborum  muscle,  from  which  it  is  separated  by  the  anterior  lamella 
of  the  lumbar  fascia.  The  lumbar  plexus  is  situated  in  the  posterior  part  of  the  substance  of 
the  muscle.  By  its  inner  side  the  muscle  is  in  relation  with  the  bodies  of  the  lumbar  vertebrae, 
the  lum'bar  arteries,  the  ganglia  of  the  sympathetic  cord,  and  their  branches  of  communication 
with  the  spinal  nerves;  the  lumbar  nodes;  the  inferior  vena  cava  on  the  right  and  the  aorta 
on  the  left  side,  and  along  the  brim  of  the  pelvis  with  the  external  iliac  artery.  In  the  thigh 
it  is  in  relation,  superfidaUy,  with  the  fascia  lata;  deeply,  with  the  capsular  ligament  of  the  hip, 
from  which  it  is  separated  by  a  synovial  bursa  {bursa  iliopectinea),  which  frequently  communi- 
cates with  the  cavity  of  the  joint  through  an  opening  of  variable  size;  between  the  tendon  and 
part  of  the  lesser  trochanter  is  the  bursa  iliaca  suhtendinea;  by  its  inner  border,  with  the  Pectineus 
and  internal  circumflex  artery,  and  also  with  the  femoral  artery,  which  slightly  overlaps  it;  by 
its  outer  border,  with  the  femoral  nerve  and  Iliacus  muscle. 

The  Psoas  parvus  (m.  psoas  minor)  (Fig.  379)  is  a  long,  slender  muscle  placed 
in  front  of  the  Psoas  magnus.  It  arises  from  the  sides  of  the  bodies  of  the  last 
thoracic  and  first  lumbar  vertebrae  and  from  the  intervertebral  substance  between 
them.  It  forms  a  small,  flat,  fleshy  bundle,  which  terminates  in  a  long  flat  tendon 
inserted  into  the  iliopectineal  eminence,  and,  by  its  outer  border,  into  the  iliac 
fascia.     This  muscle  is  most  often  absent,  and  is  sometimes  double. 

The  Iliacus  (in.  iliacus)  (Fig.  379)  is  a  fiat,  triangular  muscle  which  fills  up 
the  whole  of  the  iliac  fossa.  It  arises  from  the  upper  two-thirds  of  this  fossa  and 
from  the  inner  margin  of  the  crest  of  the  ilium;  behind,  from  the  iliolumbar  liga- 
ment and  base  of  the  sacrum;  in  front,  from  the  anterior  superior  and  anterior 
inferior  spinous  processes  of  the  ilium,  from  the  notch  between  them.  The 
fibres  converge  to  be  inserted  into  the  outer  side  of  the  tendon  of  the  Psoas,  some 
of  them'  being  prolonged  and  attached  to  the  shaft  of  the  femur  for  about  an  inch 
below  and  in  front  of  the  lesser  trochanter.'  The  most  external  fibres  are  inserted 
into  the  capsule  of  the  hip-joint. 

'  The  Psoas  and  Iliacus  are  often  regarded  as  a  single  muscle — the  Iliopsoas — having  two  heads  of  origin  and 
a  single  insertion. 


THE  ANTERIOR  FEMORAL  REGION  505 

Relations. — Within  the  abdomen,  by  its  anterior  surface,  with  the  ihac  fossa,  which  separates 
the  muscle  from  the  peritoneum,  and  with  the  external  cutaneous  nerve;  on  the  right  side, 
with  the  cecum;  on  the  left  side,  with  the  pelvic  colon;  by  its  posterior  surface,  with  the  iliac 
fossa;  by  its  inner  border,  with  the  Psoas  magnus  and  femoral  nerve.  In  the  thigh,  it  is  in 
relation,  by  its  superficial  surface,  with  the  fascia  lata,  the  Rectus  and  Sartorins  muscles,  and 
the  profunda  femoris  artery;  by  its  deep  surface,  with  the  capsule  of  the  hip-joint,  a  synovial 
bursa  common  to  it  and  the  Psoas  magnus  being  interposed. 

Nerves. — The  Psoas  magnus  is  supplied  by  the  anterior  branches  of  the  second  and  third 
lumbar  nerves;  the  Psoas  parvus,  when  it  exists,  is  supplied  by  the  anterior  branch  of  the  first 
lumbar  nerve;  and  the  Iliacus,  by  the  anterior  branches  of  the  second  and  third  lumbar  nerves 
through  the  femoral. 

Actions. — The  Psoas  and  Iliacus  muscles,  acting  from  above,  flex  the  thigh  upon  the  pelvis. 
Actincf  from  below,  the  femur  being  fixed,  the  muscles  of  both  sides  bend  the  lumbar  portion  of 
the  vertebral  column  and  pelvis  forward.  They  also  serve  to  maintain  the  erect  position,  by 
supporting  the  vertebral  column  and  pelvis  upon  the  femur,  and  assist  in  raising  the  trunk 
when  the  body  is  in  the  recumbent  posture. 

The  Psoas  par\'us  is  a  tensor  of  the  iliac  fascia.  It  assists  in  flexing  the  lumbar  portion  of 
the  vertebral  column  laterally,  the  pelvis  being  its  fixed  point. 

Applied  Anatomy. — There  is  no  definite  septum  between  the  portions  of  the  iliac  fascia 
covering  the  Psoas  and  Iliacus,  respectively,  and  the  fascia  is  only  connected  to  the  subjacent 
muscles  by  a  quantity  of  loose  connective  tissue.  When  an  abscess  forms  beneath  this  fascia, 
as  it  is  very  liable  to  do,  the  pus  is  contained  in  an  osseofibrous  cavity,  which  is  closed  on  all 
sides  within  the  abdomen,  and  is  open  only  at  its  lower  part,  where  the  fascia  is  prolonged  over 
the  muscle  into  the  thigh. 

Abscess  within  the  sheath  of  the  Psoas  muscle  (Psoas  abscess)  is  generally  due  to  tuberculous 
caries  of  the  bodies  of  the  lower  thoracic  or  of  the  lumbar  vertebrae.  When  the  disease  is  in  the 
thoracic  region,  the  pus  courses  down  the  posterior  mediastinum,  in  front  of  the  bodies  of  the 
vertebrae,  and,  passing  beneath  the  ligamentum  arcuatum  internum,  enters  the  sheath  of  the 
Psoas  muscle,  down  which  it  passes  as  far  as  the  pelvic  brim;  it  then  gets  beneath  the  iliac 
portion  of  the  fascia  and  fills  up  the  iliac  fossa.  In  consequence  of  the  attachment  of  the  fascia 
to  the  pelvic  brim,  it  rarely  finds  its  w'ay  into  the  pelvis,  but  passes  by  a  narrow  opening  under 
Poupart's  ligament  into  the  thigh,  to  the  outer  side  of  the  femoral  vessels.  It  thus  follows  that 
a  Psoas  abscess  may  be  described  as  consisting  of  four  parts:  (11  A  somewhat  narrow  channel 
at  its  upper  part,  in  the  Psoas  sheath;  (2)  a  dilated  sac  in  the  iliac  fossa;  (.3)  a  constricted  neck 
under  Poupart's  ligament;  and  (4)  a  dilated  sac  in  the  upper  part  of  the  thigh.  When  the 
lumbar  vertebrte  are  the  seat  of  the  disease,  the  pus  finds  its  way  directly  into  the  substance 
of  the  muscle.  If  a  Psoas  abscess  forms,  the  muscle  fibres  are  destroyed,  and  the  nerve  cords 
contained  in  the  abscess  are  isolated  and  exposed  in  its  interior;  the  femoral  vessels  which  lie  in 
front  of  the  fascia  remain  intact,  and  the  peritoneum  seldom  becomes  implicated.  All  Psoas 
abscesses  do  not,  however,  pursue  this  course;  the  pus  may  leave  the  muscle  above  the  crest 
of  the  ilium,  and,  tracking  backward,  may  point  in  the  loin  (lumbar  abscess);  or  it  may  point 
above  Poupart's  ligament  in  the  inguinal  region;  or  it  may  follow  the  course  of  the  iliac  vessels 
into  the  pelvis,  and,  passing  through  the  great  sacrosoiatic  notch,  discharge  itself  on  the  back 
of  the  thigh;  it  may  open  into  the  bladder  or  find  its  way  into  the  perineum,  or  it  may  pass 
down  the  thigh  to  the  popliteal  space  or  even  lower.  Straiti  of  the  Psoas  muscle  is  not  unusual, 
and  induces  pain  which  may  be  mistaken  for  appendicitis.  The  bursa  beneath  the  tendon  of 
the  Psoas  and  Iliacus  and  the  hip-joint  or  that  between  the  tendon  and  the  lesser  trochanter  may 
greatly  enlarge  and  produce  pain  and  disablement.  Byron  Robinson^  pointed  out  that  trauma 
of  the  Psoas  muscle  may  be  an  important  factor  in  the  etiology  of  appendicitis,  as  it  may  induce 
periappendicular  adhesions  which  interfere  with  the  circulation  of  blood  and  feces.  Robinson 
says,  in  the  previously  quoted  article,  that  in  46  per  cent,  of  men  and  in  20  per  cent,  of  women 
the  appendix  rests  on  the  Psoas  muscle. 

II.  MUSCLES  AND  FASCIA  OF  THE  THIGH. 

1.  The  Anterior  Femoral  Region. 

(  Rectus  femoris. 
Tensor  fasciae  femoris.  Quadriceps  J   Vastus  externus. 

Sartorius.  extensor.    |   Vastus  internus. 

t  Crureus. 
Subcrureus. 

Dissection. — To  expose  the  muscles  and  fasciae  in  this  region,  make  an  incision  along 
Poupart's  ligament,  from  the  anterior  superior  spine  of  the  ilium  to  the  spine  of  the  os  pubis; 

'Annals  of  Surgery.  April,  1901. 


506 


THE  MUSCLES  AND  FASCIyE 


a  vertical  incision  from  the  centre  of  this,  along  the  middle  of  the  thigh  to  below  the  knee-joint; 
and  a  transverse  incision  from  the  inner  to  the  outer  side  of  the  leg,  at  the  lower  end  of  the  ver- 
tical incision.  The  flaps  of  integument  having  been  removed,  the  superficial  and  deep  fasciae 
should  be  examined.  The  more  advanced  student  should  commence  the  study  of  this  region  by 
an  examination  of  the  anatomy  of  femoral  hernia  and  Scarpa's  triangle,  the  incisions  for  the 
dissection  of  which  are  marked  out  in  Fig.  377. 


■  1.  Dissection  of 
femoral  hernia, 
and  Scarpa's 
triangle. 


2.  Front  of  thigh. 


Superficial  Fascia. — The  superficial  fascia  forms  a  continuous  layer  over  the 
whole  of  the  thigh.  It  consists  of  areolar  tissue,  containing  in  its  meshes  much 
fat,  and  is  capable  of  being  separated  into  two  or  more  layers,  between  which  are 

found  the  superficial  vessels  and  nerves.  It 
varies  in  thickness  in  difl^erent  parts  of  the 
limb;  in  the  groin  it  is  thick,  and  the  two 
layers  are  separated  from  one  another  by  the 
superficial  inguinal  lymph  nodes,  the  internal 
\  I  '^  v'  /  ^.  ^~»t.i-i..."...  ></  saphenous  vein,  and  several  smaller  vessels. 
\  I  m  \  f^'noralherma,  q^^^  ^f  ^y^^^^  ^^^  j^^^^.^^  ^j^^  superficial,  is 
continuous  above  with  the  superficial  fascia  of 
the  abdomen.  Internally  it  is  continuous  with 
the  superficial  fascia  of  the  perineum.  The 
deep  layer  of  the  superficial  fascia  is  a  very  thin 
fibrous  layer,  best  marked  on  the  inner  side  of 
the  long  saphenous  vein  and  below  Poupart's 
ligament.  It  is  placed  beneath  the  subcuta- 
neous vessels  and  nerves  and  upon  the  surface 
of  the  fascia  lata.  It  is  intimately  adherent  to 
the  fascia  lata  a  little  below  Poupart's  ligament. 
It  covers  the  saphenous  opening  (Fig.  378) 
in  the  fascia  lata,  being  closely  united  to  the 
margins  of  the  opening,  and  is  connected  to 
the  sheath  of  the  femoral  vessels.  The  portion 
of  the  fascia  covering  this  aperture  is  perfo- 
rated by  the  internal  saphenous  vein  and  by 
numerous  bloodvessels  and  lymphatic  vessels; 
hence,  it  has  been  termed  the  cribriform  fascia 
(fascia  cribrosa).  The  cribriform  fascia  adheres 
closely  both  to  the  superficial  fascia  and  to  the 
fascia  lata,  so  that  it  is  described  by  some  anato- 
mists as  part  of  the  fascia  lata,  but  is  usually 
considered  (as  in  this  work)  as  belonging  to  the 
superficial  fascia.  It  is  not  until  the  cribriform 
fascia  has  been  cleared  away  that  the  saphenous 
opening  is  seen,  so  that  this  opening  does  not 
in  ordinary  cases  exist  naturally,  but  is  the 
result  of  dissection.  A  large  subcutaneous  bursa  {bursa  praepatellaris  subcutanea) 
is  found  in  the  superficial  fascia  over  the  patella,  and  another  (bursa  trochanterica 
subcutanea)  in  the  superficial  fascia  over  the  great  trochanter. 

The  Deep  Fascia,  or  Fascia  Lata  (Fig.  378).— The  deep  fascia  of  the  thigh  is 
exposed  on  the  removal  of  the  superficial  fascia,  and  is  named,  from  its  great 
extent,  the  fascia  lata;  it  forms  a  uniform  investment  for  the  whole  of  this  region 
of  the  limb,  but  varies  in  thickness  in  different  parts;  thus,  it  is  thicker  in  the  upper 
and  outer  part  of  the  thigh,  where  it  receives  a  fibrous  expansion  from  the  Gluteus 
maximus  muscle,  and  where  the  Tensor  fasciae  femoris  is  inserted  between  its 
layers;  it  is  very  thin  behind,  and  at  the  upper  and  inner  part  where  it  covers 
the  Adductor  muscles,  and  again   becomes  stronger  around   the  knee,  receiving 


'3.  Front  of  leg. 


4-  Dorsum  of  foot. 


THE  ANTERIOR  FEMORAL  REGION 


507 


fibrous  expansions  from  tlie  tendons  of  the  Biceps  femoris  externally,  from  the 
Sartorius  internally,  and  from  the  Quadriceps  extensor  in  front.  The  fascia  lata 
is  attached  above,  and  behind,  to  the  back  of  the  sacrum  and  coccyx;  externally, 
to  the  crest  of  the  ilium;  in  front,  to  Poupart's  ligament  and  to  the  body  of  the  os 
pubis;  and  internoUy,  to  the  descending  ramus  of  the  os  pubis,  to  the  ramus  and 
tuberosity  of  the  is<  hium,  and  to  the  lower  border  of  the  great  sacrosciatic  ligament. 
From  its  attachment  to  the  crest  of  the  ilium  it  passes  down  over  the  Gluteus 
medius  muscle  to  (he  upper  border  of  the  Gluteus  maximus,  where  it  splits  into 
two  layers,  one  passing  superficial  to  and  the  other  beneath  this  muscle.  At  the 
lower  border  of  the  muscle  the  two  layers  reunite.  Externally  the  fascia  lata 
receives  the  greater  part  of  the  tendon  of  insertion  of  the  Gluteus  maximus,  and 
becomes  proportionately  thickened.  The  portion  of  the  fascia  lata  arising  from 
the  front  part  of  the  crest  of  the  ilium,  corresponding  to  the  origin  of  the  Tensor 


EXTERNAL 
'ABDOMINAI 
RJNG 


Fig.  378.— Right  external  aljdonmi  1  rint.   tii  i     iphe 


fasciae  femoris,  passes  down  the  outer  side  of  the  thigh  as  two  layers,  one  super- 
ficial to  and  the  other  beneath  this  muscle.  These  layers  at  the  lower  end  of  the 
muscle  become  blended  into  a  thick  and  strong  band,  having  first  received  the 
insertion  of  the  muscle.  This  band  is  continued  downward,  under  the  name  of 
the  iliotibial  band  (tradus  iliotibialis  [Maissidt.i]),  to  be  inserted  into  the  external 
tuberosity  of  the  tibia.  Below,  the  fascia  lata  is  attached  to  all  the  prominent 
points  around  the  knee-joint — viz.,  the  condyles  of  the  femur,  tuberosities  of 
the  tibia,  and  head  of  the  fibula.  On  each  side  of  the  patella  it  is  strengthened 
by  transverse  fibres  given  off  from  the  lower  part  of  the  Vasti  muscles,  which  are 
attached  to  and  support  this  bone.  Of  these,  the  outer  fibres  are  the  stronger, 
and  are  continuous  with  the  iliotibial  band.  From  the  deep  surface  of  the  fascia 
lata  are  given  off  two  strong  intermuscular  septa,  which  are  attached  to  the  whole 
length  of  the  linea  aspera  and  its  prolongations  above  and  below;  the  external 


508  THE  MUSCLES  AND  FASCIA 

intermuscular  septum  (septum  iidermusculare  laterale)  is  the  stronger.  It  extends 
from  the  insertion  of  the  Gluteus  maximus  to  the  outer  condyle,  separates  the 
Vastus  externus  in  front  from  the  short  head  of  the  Biceps  femoris  behind,  and 
gives  partial  origin  to  these  muscles;  the  internal  intermuscular  septum  (septum 
intermusculare  mediale),  the  thinner  of  the  two,  separates  the  Vastus  internus 
from  the  Adductor  and  Pectineus  muscles.  Besides  these  there  are  numerous 
smaller  septa,  separating  the  individual  muscles  and  enclosing  each  in  a  distinct 
sheath.  At  the  upper  and  inner  part  of  the  thigh,  a  little  below  Poupart's  ligament, 
a  large,  oval-shaped  aperture  is  observed;  it  transmits  the  internal  saphenous  vein 
and  other  smaller  vessels,  and  is  termed  the  saphenous  opening  (fossa  ovalis) 
(Fig.  378).  This  opening  is  covered  by  a. portion  of  the  deep  layer  of  the  super- 
ficial fascia,  the  cribriform  fascia.  In  order  more  correctly  to  consider  the  mode 
of  formation  of  this  aperture,  the  fascia  lata  in  this  part  of  the  thigh  is  described 
as  consisting  of  two  portions — an  iliac  portion  and  a  pubic  portion. 

The  iliac  portion  is  all  that  part  of  the  fascia  lata  on  the  outer  side  of  the  saphe- 
nous opening.  It  is  attached,  externally,  to  the  crest  of  the  ilium  and  its  anterior 
superior  spine,  to  the  whole  length  of  Poupart's  ligament  as  far  internally  as  the 
spine  of  the  os  pubis,  and  to  the  iliopectineal  line  in  conjunction  with  Gimbernat's 
ligament.  From  the  spine  of  the  os  pubis  it  is  reflected  downward  and  outward, 
forming  an  arched  margin,  the  falciform  process  or  the  falciform  margin  of  Bums 
(inargo  falciformis).  This  margin  overlies  and  is  adherent  to  the  superficial 
layer  of  the  sheath  of  the  femoral  vessels;  to  its  edge  is  attached  the  cribriform 
fascia;  and,  below,  it  is  continuous  with  the  pubic  portion  of  the  fascia  lata.  The 
femoral  ligament,  or  the  ligament  of  Hey,  is  the  point  at  which  the  falciform  process 
joins  the  base  of  Gimbernat's  ligament. 

The  pubic  portion  is  situated  at  the  inner  side  of  the  saphenous  opening;  at  the 
lower  margin  of  this  aperture  it  is  continuous  with  the  iliac  portion.  Traced 
upward,  the  pubic  portion  covers  the  surface  of  the  Pectineus,  Adductor  longus, 
and  Gracilis  muscles,  and,  passing  behind  the  sheath  of  the  femoral  vessels,  to 
which  it  is  closely  united,  is  continuous  with  the  sheath  of  the  Psoas  and  Iliacus 
muscles,  and  is  attached  above  to  the  iliopectineal  line,  where  it  becomes  continu- 
ous with  the  iliac  fascia.  From  this  description  it  may  be  observed  that  the  iliac 
portion  of  the  fascia  lata  passes  superficial  to  the  femoral  vessels,  and  the  pubic 
portion  behind  them,  so  that  an  apparent  aperture  exists  between  the  two,  through 
which  the  internal  saphenous  joins  the  femoral  vein. 

Applied  Anatomy. — The  iliotihial  hand  at  a  point  between  the  crest  of  the  ihum  and  the 
great  trochanter  is  so  tense  that  it  is  impossible  to  sink  the  fingers  deeply  in  this  region.  Dr. 
Allis  points  out  that  in  fracture  of  the  neck  of  the  femur  the  great  trochanter  mounts  toward 
the  iliac  crest,  the  iliotibial  band  relaxes,  and  the  fingers  can  be  sunk  deeply  into  the  space 
between  the  great  trochanter  and  the  iliac  crest.  Shortening  is  thus  indicated.  This  is  known 
as  Allis'  sign.  A  Psoas  abscess  usually  points  at  the  termination  of  the  Psoas  muscle,  but  the 
tuberculous  pus  may  be  directed  down  the  thigli  beneath  the  fascia  lata,  and  it  may  reach  the 
popliteal  space  or  may  go  even  lower. 

The  Tensor  fasciae  femoris  (m.  tensor  fasciae  lafae)  (Fig.  379)  arises  from  the 
anterior  part  of  the  outer  lip  of  the  crest  of  the  ilium,  from  the  outer  surface  of 
the  anterior  superior  spine,  and  part  of  the  outer  border  of  the  notch  below  it, 
between  the  Gluteus  medius  and  Sartorius,  and  from  the  surface  of  the  fascia 
covering  the  Gluteus  medius.  It  is  inserted  between  two  layers  of  the  fascia  lata, 
about  one-fourth  down  the  outer  side  of  the  thigh.  From  the  point  of  insertion 
the  fascia  is  continued  downward  to  the  external  tuberosity  of  the  tibia  as  a  thick- 
ened band,  the  iliotibial  band. 

The  Sartorius  (m.  sartorius)  (Fig.  379),  the  longest  muscle  in  the  body,  is  flat, 
narrow,  and  ribbon-like;  it  arises  by  tendinous  fibres  from  the  anterior  superior 


THE  ANTERIOR  FEMORAL  REGION 


509 


spine  of  the  ilium  and  the  upper  half  of  the 
notch  below  it,  passes  obliquely  across  the 
upper  and  anterior  part  of  the  thigh,  from 
the  outer  to  the  inner  side  of  the  limb,  then 
descends  vertically,  as  far  as  the  inner  side  of 
the  knee,  passing  behind  the  inner  condyle  of 
the  femur,  and  terminates  in  a  tendon  which, 
curving  oblicjuely  forward,  expands  into  a 
broad  aponeurosis,  to  be  inserted  in  front  of 
the  Gracilis  and  Semitendinosus,  into  the 
upper  part  of  the  inner  surface  of  the  shaft 
of  the  tibia,  nearly  as  far  forward  as  the  crest. 
The  upper  part  of  the  tendon  is  curved  back- 
ward over  the  upper  edge  of  the  tendon  of  the 
Gracilis  in  order  to  be  inserted  behind  it  (Fig. 
185).  An  ofl'set  is  derived  from  the  upper  mar- 
gin of  the  aponeurosis,  which  blends  with  the 
fibrous  capsule  of  the  knee-joint,  and  another, 
gi-ven  off  from  its  lower  border,  blends  with 
the  fascia  on  the  inner  side  of  the  leg. 

Relations. — By  its  swperficial  surface,  with  the 
fascia  lata;  by  its  deep  surface,  with  the  Rectus 
femoris,  Iliacus,  Vastus  internus,  femoral  nerve,  sheath 
of  the  femoral  vessels,  Adductor  longus.  Gracilis, 
Semitendinosus,  long  saphenous  nerve,  and  internal 
lateral  ligament  of  the  knee-joint.  Frequently  there 
is  a  bursa  (bursa  m.  sariorii  propria)  between  the 
tendon  of  the  Sartorius  and  the  tendons  of  the  Gra- 
cilis and  Semimembranosus. 

The  relations  of  this  muscle  to  the  femoral  artery 
should  be  carefully  examined,  as  it  constitutes  the 
chief  guide  in  tying  the  vessel.  In  the  upper  third  of 
the  thigh  it  forms  the  outer  side  of  a  triangular  space, 
Scarpa's  triangle  (trigonum  femorale),  the  inner  side 
of  which  is  formed  by  the  inner  border  of  the  Adductor 
longus,  and  the  base,  which  is  turned  upward,  by 
Poupart's  ligament;  the  femoral  artery  passes  per- 
pendicularly through  the  middle  of  this  space  from 
its  base  to  its  apex.  In  the  middle  third  of  the  thigh 
the  femoral  artery  lies  first  along  the  inner  border, 
and  then  behind  the  Sartorius. 

The  Quadriceps  extensor  (m.  quadriceps 
femoris)  (Fig.  381)  includes  the  four  remaining 
muscles  on  the  front  of  the  thigh.  It  is  the 
great  Extensor  muscle  of  the  leg,  forming  a 
large  fleshy  mass  which  covers  the  front  and 
sides  of  the  femur,  being  united  below  into 
a  single  tendon;  attached  to  the  patella,  and 
above  subdivided  into  separate  portions, 
which  have  received  distinct  names.  Of 
these,  one  occupying  the  middle  of  the  thigh, 
connected  above  with  the  ilium,  is  called  the 
Rectus  femoris,  from  its  straight  course.  The 
other  divisions  lie  in  immediate  connection 
with  the  shaft  of  the  femur,  which  they  cover 
from   the  trochanters  to  the  condyles.      The 


-Muscles  of  the   ihac 
femoral  region. 


510 


THE  MUSCLES  AND  FASCIJE 


PSOAS  MAGNUS 


PyRIFORMia 
PECTINEU8 
fiATOR 


portion  on  the  outer  side  of  the  femur  is  termed  the  Vastus  externus ;  that  cover- 
ing the  inner  side,  the  Vastus  internus;  and  that  covering  the  front  of  the  femur, 
the  Criireus. 

The  Rectus  femoris  {m.  rectus  femoris)  is  situated  in  the  middle  of  the  anterior 
region  of  the  thigh ;  it  is  fusiform  in  shape,  and  its  superficial  fibres  are  arranged 
in  a  bipenniform  manner,  the  deep  fibres  running  straight  down  to  the  deep  apon- 
eurosis. It  arises  by  two  tendons — one,  the  anterior  or  straight,  from  the  anterior 
inferior  spine  of  the  ilium ;  the  other,  the  posterior  or  reflected  tendon,  from  a  groove 
above  the  brim  of  the  acetabulum;  the  two  unite  at  an  acute  angle  and  spread 

into  an  aponeurosis,  which  is  prolonged 
downward  on  the  anterior  surface  of  the 
muscle  and  from  which  the  muscle  fibres 
arise. '^  The  muscle  terminates  in  a  broad 
and  thick  aponeurosis,  which  occupies  the 
lower  two-thirds  of  its  posterior  surface, 
and,  gradually  becoming  narrowed  into  a 
flattened  tendon,  is  inserted  into  the  patella 
in  common  with  the  Vasti  and  Crureus. 
Between  the  tendon  of  origin  and  the  ace- 
tabulum there  is  often  a  bursa  (bursa  m. 
recti  femoris). 

The  Vastus  externus  (m.  vastus  lateralis) 
is  the  largest  division  of  the  Quadriceps 
extensor.  It  arises  by  a  broad  aponeuro- 
sis, which  is  attached  to  the  upper  half 
of  the  anterior  intertrochanteric  line,  to 
the  anterior  and  inferior  borders  of  the 
root  of  the  great  trochanter,  to  the  outer 
lip  of  the  gluteal  ridge,  and  to  the  upper 
half  of  the  outer  lip  of  the  linea  aspera; 
this  aponeurosis  covers  the  upper  three- 
fourths  of  the  muscle,  and  from  its  inner 
surface  many  fibres  take  origin.  A  few 
additional  fibres  arise  from  the  tendon  of 
the  Gluteus  maximus,  and  from  the  ex- 
ternal intermuscular  septum  between  the 
Vastus  externus  and  short  head  of  the 
Biceps.  The  fibres  form  a  large  fleshy 
mass,  which  is  attached  to  a  strong  apon- 
eurosis, placed  on  the  under  surface  of  the 
muscle  at  its  lower  part;  this  becomes  nar- 
rowed and  thickened  into  a  flat  tendon, 
which  is  inserted  into  the  outer  border  of 
the  patella,  blending  with  the  Quadriceps 
extensor  tendon,  and  giving  an  expansion 
to  the  capsule  of  the  knee-joint.  Some  of  the  fibres  run  down  by  the  side  of  the 
patella  to  the  condyle  of  the  tibia,  and  are  called  the  retinaculum  patellae  laterale. 
The  Vastus  internus  and  Crureus  appear  to  be  inseparably  united,  but  when  the 
Rectus  femoris  has  been  reflected,  a  narrow  interval  will  be  observed  extending 
upward  from  the  inner  border  of  the  patella  between  the  two  muscles.  Here 
they  can  be  separated,  and  the  separation  should  be  continued  upward  as  far 


Fig.  380. — Diagram  showing  the  attachments  of 
the  mu.scle3  of  the  thigh.  Anterior  aspect.  Origins, 
red;  insertions,  blue. 


1  Mr.  W.  R.  WiUiams,  in  an  interesting  paper  in  the  Journ.  of  Anat.  and  Phys.,  vol.  xiii,  p.  204,  points  out  that 
the  refiected  tendon  is  the  real  origin  of  the  muscle,  and  is  alone  present  in  early  fetal  life.  The  direct  tendon  is 
merely  an  accessory  band  of  condensed  fascia.  The  paper  will  well  repay  perusal,  though  in  some  particulars  the 
description  in  the  text  is  more  generally  accurate. 


THE  ANTERIOR  FE310RAL  REGION 


511 


as  the  lower  part  of  the  anterior  intertrochanteric  Hne,  where,  however,  the  two 
muscles  are  frequently  continuous. 

The  Vastus  internus  (m.  vastus  medialis)  arises  from  the  lower  half  of  the 
anterior  intertrochanteric  line,  the  inner  lip  of  the  linea  aspera,  the  upper  part 
of  the  internal  supracondylar  line,  the  tendon  of  the  Adductor  magnus,  and 


FEMORAL  ARTERV    -eMORAL  NERVE 


BRANCHES  OF 
OBTURATOR  NERVE 


Fic,  381.— Tri 


section  of  the  thigh  below  the  lesser  troch.inter.     The  femoral  artery,  vein,  and  nerve  are 
seen  in  Hunter's  canal.     (After  Braune.) 

the  internal  intermuscular  septum.  Its  fibres  are  directed  downward  and  for- 
ward, and  are  chiefly  attached  to  an  aponeurosis  which  lies  on  the  deep  surface  of 
the  muscle  and  is  inserted  into  the  inner  border  of  the  patella  and  the  Quadriceps 
extensor  tendon,  an  expansion  being  sent  to  the  capsule  of  the  knee-joint.  Some 
of  the  fibres  run  down  by  the  side  of  the  patella  to  the  condyle  of  the  tibia  and 
are  called  the  retinaculum  patellae  mediale. 

The  Crureus  (m.  vastus  iittermediiis)  arises  from  the  front  and  outer  aspect  of 
the  shaft  of  the  femur  in  its  upper  two-thirds  and  from  the  lower  part  of  the  external 
intermuscular  septum.  Its  fibres  end  in  a  superficial  aponeurosis,  which  forms 
the  deep  part  of  the  Quadriceps  extensor  tendon. 

Relations. — The  inner  edge  of  the  Crureus  is  in  contact  with  the  anterior  edfje  of  the  Vastus 
internus,  but  when  separated  from  each  other,  as  directed  above,  the  latter  muscle  is  seen  merely 
to  overlap  the  inner  aspect  of  the  femoral  shaft  without  taking  any  fibres  of  origin  from  it.  The 
Vastus  internus  is  partly  covered  by  the  Rectus  femoris  and  Sartorius,  but  where  these  separate 
Bear  the  knee  it  becomes  superficial,  and  produces  a  well-marked  prominence  above  the  inner 
aspect  of  the  knee.  In  the  middle  third  of  the  thigh  it  forms  the  outer  wall  of  Hunter's  canal 
(canalis  adductorius  [Hunteri])  (Fig.  381),  which  contains  the  femoral  vessels  and  the  long  saph- 
enous nerve;  the  roof  of  the  canal  is  formed  by  a  strong  fascia  which  e.xtends  from  the  Vastus 
internus  to  the  Adductores  longus  and  magnus.  The  Crureus  is  almost  completely  hidden  by 
the  Rectus  femoris  and  Vastus  extc-nus.  The  deep  surface  of  the  two  muscles  is  in  relation 
with  the  femur  and  Subcrureus  muscles.  A  synovial  bursa  {bursa  suprapatellaris)  is  situated 
between  the  femur  and  the  portion  of  the  Quadriceps  extensor  tendon  above  the  patella;  in 
the  adult  it  communicates  with  the  synovial  cavity  of  the  knee-joint. 


512  THE  MUSCLES  AND  FASCIA 

The  tendons  of  the  different  portions  of  the  Quadriceps  extensor  unite  at  the  lower  part  of 
the  thigh,  so  as  to  form  a  single  strong  tendon,  which  is  inserted  into  the  upper  part  of  the  patella; 
some  few  fibres  pass  over  it  to  blend  with  the  ligamentum  patellae.  Strictly  speaking,  the 
patella  may  be  regarded  as  a  sesamoid  bone,  developed  in  the  tendon  of  the  Quadriceps;  and 
the  ligamentum  patellae,  which  is  continued  from  the  lower  part  of  the  patella  to  the  tuberosity 
of  the  tibia,  as  the  proper  tendon  of  insertion  of  the  muscle.  A  synovial  bursa,  the  deep  patellar 
bursa  {bursa  infrapatetlaris  profunda),  is  interposed  between  the  tendon  and  the  upper  part 
of  the  tubercle  of  the  tibia;  and  another,  the  prepatellar  bursa  (bursa  praepaiellaris  subndavca), 
is  placed  over  the  patella  itself.  This  latter  bursa  often  becomes  enlarged,  constituting  "house- 
maid's knee." 

The  Subcrureus  {m.  articularis  genu)  is  a  small  muscle,  usually  distinct  from 
the  Crureus,  but  occasionally  blended  with  it,  which  arises  from  the  anterior 
surface  of  the  lower  part  of  the  shaft  of  the  femur,  and  is  inserted  into  the  upper 
part  of  the  cul-de-sac  of  the  capsular  ligament,  which  projects  upward  beneath 
the  Quadriceps  for  a  variable  distance.  It  sometimes  consists  of  several  separate 
muscle  bundles. 

Nerves. — The  Tensor  fasciae  femoris  is  supplied  by  the  fourth  and  fifth  lumbar  and  first 
sacral  nerves  through  the  superior  gluteal  nerve;  the  other  muscles  of  this  region,  by  the  second, 
third,  and  fourth  lumbar  nerves,  through  branches  of  the  femoral. 

Actions. — The  Tensor  fasciae  femoris  is  a  tensor  of  the  fascia  lata;  continuing  its  action,  the. 
oblique  direction  of  its  fibres  enables  it  to  abduct  and  to  rotate  the  thigh  inward.  In  the  erect 
posture,  acting  from  below,  it  will  serve  to  steady  the  pelvis  upon  the  head  of  the  femur,  and  by 
means  of  the  iliotibial  band  it  steadies  the  condyles  of  the  femur  on  the  articular  surfaces  of  the^ 
tibia,  and  assists  the  Gluteus  maximus  in  supporting  the  knee  in  the  extended  position.  The  Sar- 
torius  flexes  the  leg  upon  the  thigh,  and,  continuing  to  act,  flexes  the  thigh  upon  the  pelvis;  it  next, 
rotates  the  thigh  outward.  When  the  knee  is  bent  the  Sartorius  assists  the  Semitendinosus,, 
Semimem.branosus,  and  Popliteus  in  rotating  the  tibia  inward.  Taking  its  fixed  point  from  the 
leg,  it  flexes  the  pelvis  upon  the  thigh,  and,  if  one  muscle  acts,  assists  in  rotating  the  pelvis. 
The  Quadriceps  extensor  extends  the  leg  upon  the  thigh.  The  Rectus  muscle  assists  the  Psoas 
and  Iliacus  in  supporting  the  pelvis  and  trunk  upon  the  femur.  It  also  assists  in  flexing  the 
thigh  on  the  pelvis,  or  if  the  thigh  is  fixed  it  will  flex  the  pelvis.  The  Vastus  internus  draws  the 
patella  inward  as  well  as  upward. 

Applied  Anatomy. — A  few  fibres  of  the  Rectus  femoris  muscle  are  liable  to  be  ruptured  from 
severe  strain.  This  accident  is  especially  liable  to  occur  during  the  games  of  football  and  base- 
ball. The  patient  experiences  a  sudden  pain  in  the  part,  as  if  he  had  been  struck,  and  the 
Rectus  muscle  stands  out  and  is  felt  ro  be  tense  and  rigid.  The  accident  is  often  followed  by 
considerable  swelling  from  inflammatory  effusion.  Occasionally  the  Quadriceps  extensor  may 
be  torn  away  from  its  insertion  into  the  patella,  or  the  tendon  of  the  Quadriceps  may  be  rup- 
tured about  an  inch  above  the  bone.  This  accident  is  caused  in  the  same  manner  that  fracture 
of  the  patella  by  muscular  action  is  produced — viz.,  by  a  violent  muscular  effort  to  prevent 
falling  while  the  knee  is  in  a  position  of  semiflexion.  A  distinct  gap  can  be  felt  above  the 
patella,  and,  owing  to  the  retraction  of  the  muscle  fibre's,  union  may  fail  to  take  place.  Sudden 
and  powerful  contraction  of  the  Quadriceps  extensor  femoris  is  the  usual  cause  of  transverse- 
fracture  of  the  patella. 

2.  The  Internal  Femoral  Region. 

Gracilis.  Adductor  longus. 

Pectineus.  Adductor  brevis. 

Adductor  magnus. 

Dissection. — These  muscles  are  at  once  exposed  by  removing  the  fascia  from  the  fore  part 
and  inner  side  of  the  thigh.  The  limb  should  be  abducted,  so  as  to  render  the  muscles  tense  and 
easier  of  dissection. 

The  Gracilis  (???.  gracilis)  (Figs.  379  and  384)  is  the  most  superficial  muscle 
on  the  inner  side  of  the  thigh.  It  is  thin  and  flattened,  broad  abo^•e,  narrowing 
and  tapering  below.  It  arises  by  a  thin  aponeurosis  from  the  posterior  half  of  the 
margin  of  the  symphysis  and  the  anterior  half  of  the  pubic  arch.  The  fibres  pass 
vertically  downward,  and  terminate  in  a  rounded  tendon  which  passes  behind  the 
raidyle  of  the  femur,  and,  curving  around  the  inner  tuberosity  of  the  tibia. 


THE  INTERNAL  FEMORAL  REGION 


513 


becomes  flattened,  and  is  inserted  into  the  upper  part  of  the  inner  surface  of  the 

shaft  of  the  tibia,  below  the  tuberosity.     A  few  of  the  fibres  of  the  lower  part  of 

the  tendon   are    prolonged    into    the    deep 

fascia    of    the    leg.     The    tendon  of    this 

muscle  is  situated  immediately  above  that 

of  the  Semitendinosus,  and  its  upper  edge  is 

overlapped  by  the  tendon  of  the  Sartorius, 

with  which   it   is  in  part  blended.     As  it 

passes  across  the  internal  lateral  ligament 

of  the  knee-joint  it  is  separated  from  it  by 

a  synovial  bursa  {bursa  anserbia)  common  to 

it  and  tiie  Semitendinosus  muscle. 

Relations. — By  its  superficial  surface,  with  the 
fascia  lata  and  the  Sartorius  below;  the  internal 
saphenous  vein  crosses  it  obliquely  near  its  lower 
part,  lying  superficial  to  the  fascia  lata;  the  internal 
saphenous  nerve  emerges  between  its  tendon  and 
that  of  the  Sartorius;  by  its  deep  surface,  with  the 
Adductor  brevis  and  the  Adductor  magnus  and 
the  internal  lateral  ligament  of  the  knee-joint. 

The  Pectineus  (m.  pedineiis)  (Fig.  379) 
is  a  flat,  quadrangular  muscle,  situated  at 
the  anterior  part  of  the  upper  and  inner 
aspect  of  the  thigh.  It  arises  from  the  ilio- 
pectineal  line,  and  to  a  slight  extent  from 
the  surface  of  the  bone  in  front  of  it  between 
the  pectineal  eminence  and  spine  of  the  os 
pubis,  and  from  the  fascia  covering  the 
anterior  surface  of  the  muscle;  the  fibres 
pass  downward,  backward,  and  outward,  to 
be  inserted  into  a  rough  line  leading  from 
the  lesser  trochanter  to  the  linea  aspera. 

Relations. — By  its  superficial  surface,  with  the 
pubic  portion  of  the  fascia  lata,  which  separates  it 
from  the  femoral  vessels  and  internal  saphenous 
vein;  by  its  deep  surface,  with  the  capsular  liga- 
ment of  the  hip-joint,  the  Adductor  brevis  and 
Obturator  externus  muscles,  the  obturator  vessels 
and  nerve  being  mterposed;  by  its  outer  border, 
with  the  Psoas,  a  cellular  interval  separating  them, 
through  which  pass  the  internal  circumflex  vessels; 
by  its  inner  border,  with  the  margin  of  the  Adductor 
longus.  There  is  usually  a  bursa  {bursa  m.  peciinei) 
between  the  Pectineus  and  the  tendon  of  the  Psoas 
and  Iliacus. 

The  Adductor  longus  (m,  adductor  longus) 
(Figs.  379  and  382),  the  most  superficial 
of  the  three  Adductors,  is  a  flat  triangular 
muscle  lying  on  the  same  plane  as  the 
Pectineus.  It  arises,  by  a  flat  narrow  ten- 
don, from  the  front  of  the  os  pubis,  at  the 
angle  of  junction  of  the  crest  with  the  inner 
border;  and  soon  expands  into  a  broad  fleshy  belly,  which,  passing  downward, 
backward,  and  outward,  is  inserted,  by  an  aponeurosis,  into  the  linea  aspera, 

33 


514  THE  MUSCLES  AND  FASCIA 

between  the  Vastus  internus  and  the  Adductor  magnus,  with  both  of  which  it  is 
usually  blended. 

Relations. — By  its  superficial  surface,  with  the  fascia  lata,  the  Sartorius,  and,  near  its  inser- 
tion, with  the  femoral  artery  and  vein;  by  its  deep  surface,  with  the  Adductores  brevis  and 
magnus,  the  anterior  brandies  of  the  obturator  nerve,  and  with  the  profunda  artery  and  vein 
near  its  insertion;  by  its  outer  border,  with  the  Pectineus;  by  its  inner  border,  with  the  Gracilis. 

The  Pectineus  and  Adductor  longus  should  now  be  divided  near  their  origin,  and  turned 
downward,  when  the  Adductor  brevis  and  Obturator  externus  will  be  exposed. 

The  Adductor  brevis  (m.  adductor  brevis)  (Fig.  382)  is  situated  immediately 
behind  the  two  preceding  muscles.  It  is  somewhat  triangular  in  form,  and  arises 
by  a  narrow  origin  from  the  outer  surface  of  the  body  and  descending  ramus  of 
the  OS  pubis,  between  the  Gracilis  and  Obturator  externus.  Its  fibres  passing 
backward,  outward,  and  downward,  are  inserted,  by  an  aponeurosis,  into  the 
lower  part  of  the  line  leading  from  the  lesser  trochanter  to  the  linea  aspera,  and 
the  upper  part  of  the  same  line,  immediately  behind  the  Pectineus  and  upper 
part  of  the  Adductor  longus. 

Relations. — By  its  superficial  surface,  with  the  Pectineus,  Adductor  longus,  profunda  fem- 
oris  artery,  and  anterior  branches  of  the  obturator  nerve;  by  its  deep  surface,  with  the  Adductor 
magnus  and  posterior  branch  of  the  obturator  nerve;  by  its  outer  border,  with  the  internal  cir- 
cumflex artery,  the  Obturator  externus,  and  conjoined  tendon  of  the  Psoas  and  Iliacus;  by  its 
in7ier  border,  with  the  GraciUs  and  Adductor  magnus.  This  muscle  is  pierced,  near  its  insertion, 
by  the  second  or  by  the  first  and  second  perforating  branches  of  the  profunda  femoris  artery. 

The  Adductor  brevis  should  now  be  cut  away  near  its  origin,  and  turned  outward,  when  the 
entire  extent  of  the  Adductor  magnus  will  be  exposed. 

The  Adductor  magnus  (m.,  adductor  magnus)  (Fig.  382)  is  a  large,  triangular 
muscle  forming  a  septum  between  the  muscles  on  the  inner  and  those  on  the  back 
of  the  thigh.  It  arises  from  a  small  part  of  the  descending  ramus  of  the  os  pubis, 
from  the  ramus  of  the  ischium,  and  from  the  outer  margin  of  the  inferior  part  of 
the  tuberosity  of  the  ischium.  Those  fibres  which  arise  from  the  ramus  of  the 
OS  pubis  are  very  short,  horizontal  in  direction,  and  are  inserted  into  the  rough 
line  leading  from  the  great  trochanter  to  the  linea  aspera,  internal  to  the  Gluteus 
maximus.  They  are  considered  by  some  a  distinct  muscle  and  called  the  Adductor 
minimus.  The  fibres  taking  origin  from  the  ramus  of  the  ischium  are  directed 
downward  and  outward  with  different  degrees  of  obliquity,  to  be  inserted,  by  means 
of  a  broad  aponeurosis,  into  the  linea  aspera  and  the  upper  part  of  its  internal 
prolongation  below.  The  internal  portion  of  the  muscle,  consisting  principally 
of  those  fibres  which  arise  from  the  tuberosity  of  the  ischium,  forms  a  thick 
fleshy  mass  consisting  of  coarse  bundles  which  descend  almost  vertically,  and 
terminate  about  the  lower  third  of  the  thigh  in  a  rounded  tendon,  which  is  inserted 
into  the  Adductor  tubercle  on  the  inner  condyle  of  the  femur,  and  is  connected 
by  a  fibrous  expansion  to  the  line  leading  upward  from  the  tubercle  to  the  linea 
aspera.  Between  the  two  portions  of  the  muscle  an  interval  is  left,  tendinous 
in  front  and  fleshy  behind,  for  the  passage  of  the  femoral  vessels  from  Hunter's 
canal  into  the  popliteal  space.  The  external  portion  of  the  muscle  at  its  attachment 
to  the  femur  presents  three  or  four  osseoaponeurotic  openings,  formed  by  tendi- 
nous arches  attached  to  the  bone,  from  which  muscle  fibres  arise.  The  three 
superior  of  these  apertures  are  for  the  three  perforating  arteries,  and  the  fourth, 
when  it  exists,  is  for  the  terminal  branch  of  the  profunda. 

Relations. — By  its  superficial  surface,  with  the  Pectineus,  Adductor  brevis,  Adductor  longus, 
and  the  femoral  and  profunda  vessels  and  obturator  nerve;  by  its  deep  surface,  with  the  great 
sciatic  nerve,  the  Gluteus  maximus,  Biceps  femoris,  Semitendinosus,  and  Semimembranosus. 
By  its  superior  or  shortest  border  it  lies  parallel  to  the  Quadratus  femoris,  the  internal  circumflex 


THE  GLUTEAL  REGION  515 

artery  passing  between  them;  by  its  internal  or  longer  border,  with  the  Gracilis,  Sartorius,  and 
fascia  lata;  by  its  external  or  attached  border  it  is  inserted  into  the  femur  behind  the  Adductor 
brevis  and  Adductor  longus,  which  separate  it  from  the  Vastus  internus,  and  in  front  of  the 
Gluteus  maxinius  and  short  head  of  the  Biceps  femoris,  which  separate  it  from  the  Vastus  externus. 

Nerves. — The  three  Adductor  muscles  and  the  Gracilis  are  supplied  by  the  third  and  fourth 
lumbar  nerves  through  the  obturator  nerve;  the  Adductor  magnus  receiving  an  additional 
branch  from  the  sacral  plexus  through  the  great  sciatic.  The  Pectineus  is  supplied  by  the 
second,  third,  and  fourth  lumbar  nerves  through  the  femoral,  and  by  the  accessory  obturator, 
from  the  third  lumbar,  when  it  exists.  Occasionally  it  receives  a  branch  from  the  obturator 
nerve.' 

Actions, — The  Pectineus  and  three  Adductors  adduct  the  thigh  powerfully;  they  are  espe- 
cially used  in  horseback  riding,  the  flanks  of  the  horse  being  grasped  between  the  knees  by  the 
actions  of  these  muscles.  In  consequence  of  the  obliquity  of  their  insertion  into  the  linea  aspera 
they  rotate  the  thigh  outward,  assisting  the  external  Rotators,  and  when  the  limb  has  been 
abducted  they  draw  it  inward,  carrying  the  thigh  across  that  of  the  opposite  side.  The  Pec- 
tineus and  Adductor  brevis  and  longus  assist  the  Psoas  and  Iliacus  in  flexing  the  thigh  upon  the 
pelvis.  In  progression,  also,  all  these  muscles  assist  in  drawing  forward  the  hinder  limb.  The 
Gracilis  assists  the  Sartorius  in  fle.xing  the  leg;  it  is  also  an  adductor  of  the  thigh.  If  the  lower 
extremities  are  fixed,  these  muscles  may  take  their  fixed  point  from  below  and  act  upon  the  pelvis, 
serving  ti)  maintain  the  body  in  an  erect  posture,  or,  if  their  action  is  continued,  to  flex  the  pelvis 
forward  upim  the  femui'. 

Hunter's  Canal  (canalh  adductorius  {Hunteri^  extends  from  the  apex  of  Scarpa's  triangle  to 
the  opening  in  the  Adductor  magnus  muscle.  The  antero-internal  boundary  or  roof  of  Hunter's 
canal  is  the  Sartorius  and  the  aponeurotic  expansion  from  the  Adductors  to  the  Vastus  internus. 
It  is  bounded  externally  by  the  Vastus  internus.  The  Adductor  longus  and  magnus  constitute 
its  floor  or  the  'posterointernal  boundary.  The  canal  contains  the  femoral  artery,  femoral  vein, 
the  long  saphenous  nerve,  and  the  nerve  to  the  Vastus  internus. 

Applied  Anatomy. — The  Adductor  longus  is  liable  to  be  severely  strained  in  those  who  ride 
much  on  horseback,  or  its  tendons  to  be  ruptured  by  suddenly  gripping  the  saddle.  Occasionally, 
especially  in  cowboys  and  cavalry  soldiers,  the  tendon  of  insertion  of  the  Adductor  magnus 
may  become  ossified,  constituting  the  rider's  bone  (pp.  229,  360). 


III.  MUSCLES    AND    FASCLffl    OF    THE    HIP. 

3.  The  Gluteal  Region  (Figs.  384,  385). 

Gluteus  maximus.  Obturator  internus. 

Gluteus  medius.  Gemellus  superior. 

Gluteus  minimus.  Gemellus  inferior. 

Pyriformis.  Quadratus  femoris. 

Obturator  externus. 

Dissection  (Fig.  383). — The  subject  should  be  turned  on  its  face,  a  block  placed  beneath 
the  pelvis  to  make. the  buttocks  tense,  and  the  limbs  allowed  to  hang  over  the  end  of  the  table, 
with  the  foot  inverted  and  the  thigh  abducted.  Make  an  incision  through  the  integument  along 
the  crest  of  the  ilium  to  the  middle  of  the  sacrum,  and  thence  downward  to  the  tip  of  the  coccyx, 
and  carry  a  second  incision  from  that  point  obliquely  downward  and  outward  to  the  outer  side 
of  the  thigh,  four  inches  below  the  great  trochanter.  The  portion  of  integument  included  between 
these  incisions  is  to  be  removed  in  the  direction  shown  in  the  figure. 

The  Gluteus  maximus  (m.  glutaeus  maximus)  (Fig.  384),  the  most  superficial 
muscle  in  the  gluteal  region,  is  a  very  broad  and  thick,  fleshy  mass  of  a  quadri- 
lateral shape,  which  forms  the  prominence  of  the  buttock.  Its  large  size  is  one 
of  the  most  characteristic  points  in  the  muscular  system  of  man,  connected  as  it 
is  with  the  power  he  has  of  maintaining  the  trunk  in  the  erect  posture.  In  structure 
the  muscle  is  remarkably  coarse,  being  made  up  of  muscle  fasciculi  lying  parallel 

1  Professor  Paterson  describes  the  Pectineus  as  consisting  of  two  incompletely  separated  strata,  of  which 
the  outer  or  dorsal  stratum,  which  is  constant,  is  supplied  by  the  femoral  nerve,  or  in  its  absence  by  the  acces- 
sory obturator,  with  which  it  is  intimately  related:  while  the  inner  or  ventral  strattmi,  when  present,  is  supplied 
by  the  obturator  nerv;. — Journ.  of  Anat.  and  Phys.,  vol.  xxvi,  p.  43. 


516 


THE  3irSCLES  AND  FASCIJE 


to  one  another,  and  collected  into  large  bundles,  separated  by  deep  cellular 
intervals.  It  arises  from  the  superior  curved  line  of  the  ilium,  and  the  portion 
of  bone,  including  the  crest,  immediately  above  and  behind  it;  from  the  posterior 
surface  of  the  lower  part  of  the  sacrum,  the  side  of  the  coccyx,  the  aponeurosis 
of  the  Erector  spinae  muscle,  the  great  sacrosciatic  ligament,  and  the  fascia  cover- 
ing the  Gluteus  medius.  The  fibres  are  directed  oblicjuely  downward  and  outward ; 
those  forming  the  upper  and  large  portion  of  the  muscle,  together  with  the  super- 
ficial fibres  of  the  lower  portion,  terminate  in  a  thick  tendinous  lamina,  which 
passes  across  the  great  trochanter  and  is  inserted  into  the  fascia  lata  covering  the 

duter  side  of  the  thigh;  the  deeper  fibres  of 
the  lower  portion  of  the  muscles  are  inserted 
into  the  rough  line  leading  from  the  great 
trochanter  to  the  linea  aspera  between  the 
Vastus  externus  and  Adductor  magnus. 
1.  Dissection  of 
gluteal  region.  Relations.— By  its  superficial  surface,  with  a  thin 

fascia,  which  separates  it  from  the  subcutaneous 
tissue;  by  its  deep  surface,  from  above  downward, 
with  the  iHum,  sacrum,  coccyx,  and  great  sacrosciatic 
ligament,  part  of  the  Gluteus  medius,  Pyriformis, 
Gemelli,  Obturator  internus,  Quadratus  femoris,  the 
tuberosity  of  the  ischium,  great  trochanter,  the  origin 
of  the  Biceps  femoris,  Semitendinosus,  Semimem- 
branosus, and  Adductor  magnus  muscles.  The 
superficial  part  of  the  gluteal  artery  reaches  the  deep 
surface  of  the  muscle  by  passing  between  the  Pyrifor- 
mis and  the  Gluteus  medius;  the  sciatic  and  internal 
pudic  vessels  and  nerves  and  muscular  branches  from 
the  sacral  plexus  issue  from  the  pelvis  below  the 
Pyriformis.  The  first  perforating  artery  and  the 
terminal  branches  of  the  internal  circumflex  artery 
are  also  found  under  cover  of  the  muscle.  Its  upper 
border  is  thin,  and  connected  with  the  Gluteus  medius 
by  the  fascia  lata.  Its  lower  border  is  free  and  promi- 
nent. 

Several  sjmovial  bursffi  are  found  in  relation  with 
this  muscle.  One  of  these  (bursa  trochanterica  m. 
glutaei  maxirai),  of  large  size,  and  generally  multiloc- 
ular,  separates  it  from  the  great  trochanter.  A  second 
(bursa  iscliiadica  m.  glutaei  ma-xiini),  often  wanting,  is 
situated  on  the  tuberosity  of  the  ischium.  A  third 
bursa  is  found  between  the  tendon  of  this  muscle  and 
the  Vastus  externus.  Two  or  three  small  bursse 
(bursae  glutaeofemorales)  are  placed  between  the  ten- 
don of  the  muscle  and  that  of  the  Vastus  externus. 

Dissection. — Divide  the  Gluteus  maximus  near  its. 
origin  by  a  vertical  incision  carried  from  its  upper  to 
its  lower  border;  a  cellular  interval  will  be  exposed, 
separating  it  from  the  Gluteus  medius  and  External 
rotator  muscles  beneath.  The  upper  portion  of  the  muscle  is  to  be  altogether  detached,  and 
the  lower  portion  turned  outward;  the  loose  areolar  tissue  filling  up  the  interspace  between 
the  trochanter  major  and  tuberosity  of  the  ischium  being  removed,  the  parts  aheady  enumerated 
as  exposed  by  the  removal  of  this  muscle  will  be  seen. 


3    Is.  Back  of  thigh. 


S.  Popliteal  apace. 


4-  /  4-  Back  of  leg. 


5.  Sole  of  foot. 


The  Gluteus  medius  (m.  glutaeus  medius)  (Fig.  384)  is  a  broad,  thick,  radiating 
muscle,  situated  on  the  outer  surface  of  the  pelvis.  Its  posterior  third  is  covered 
by  the  Gluteus  maximus;  its  anterior  two-thirds  by  the  fascia  lata,  which  separates 
it  from  the  integument.  It  arises  from  the  outer  surface  of  the  ilium,  between 
the  superior  and  middle  curved  lines,  and  from  the  outer  lip  of  that  portion,  of 
the  crest  which  is  between  them;  it  also  arises  from  the  dense  fascia,  the  gluteal 
aponeurosis,  covering  its  outer  surface.     The  fibres  converge  to  a  strong  flattened 


THE  GLUTEAL  REGION  517 

tendon  which  is  inserted  into  the  oblic|ue  line  which  traverses  the  outer  surface 
of  the  great  trochanter. 

Relations. — By  its  superficial  surf aee,  with,  the  Gluteus  maximus  behind,  the  Tensor  fasciae 
femoris  and  deep  fascia  in  front;  by  its  deep  surface,  with  the  Gluteus  minimus  and  the  gluteal 
vessels  and  superior  gluteal  nerve.  Its  anterior  border  is  blended  with  the  Gluteus  minimus. 
Its  posterior  border  lies  parallel  to  the  Pyriformis,  the  gluteal  vessels  intervening. 

A  synovial  bursa  (bursa  trochanterica  m.  glutaei  medii  anterior)  separates  the  tendon  of  the 
muscle  frnni  the  summit  of  the  great  trochanter.  There  is  freq^uently  a  bursa  {bursa  trochan- 
terica m.  ijliitaci  mi'dii  posterior)  between  the  tendons  of  the  Gluteus  medius  and  Pyriformis. 

This  muscle  should  now  be  divided  near  its  insertion  and  turned  upward,  when  the  Gluteus 
minimus  will  be  exposed. 

The  Gluteus  minimus  (m.  glutaeus  minimus)  (Fig.  384),  the  smallest  of  the 
three  Glutei,  is  placed  immediately  beneath  the  preceding.  It  is  fan-shaped, 
arising  from  the  outer  surface  of  the  ilium,  between  the  middle  and  inferior 
curved  lines,  and  behind,  from  the  margin  of  the  great  sciatic  notch;  the  fibres 
converge  to  the  deep  surface  of  a  radiated  aponeurosis,  which,  terminating  in 
a  tendon,  is  inserted  into  an  impression  on  the  anterior  border  of  the  great 
trochanter. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  medius  and  the  gluteal  vessels  and 
superior  gluteal  nerve;  by  its  deep  surface,  with  the  ilium,  the  reflected  tendon  of  the  Rectus 
femoris,  and  the  capsular  ligament  of  the  hip-joint.  Its  anterior  margin  is  blended  with  the 
Gluteus  medius;  its  posterior  margin  is  in  contact  and  sometimes  joined  with  the  tendon  of 
the  PjTiformis.  There  is  a  synovial  bursa  (bursa  trochanterica  m.  glutaei  minimi)  between  the 
tendon  of  the  Gluteus  minimus  and  the  great  trochanter. 

The  Pyriformis  {m.  piriformis)  (Figs.  384  and  385)  is  a  fiat  muscle,  pyramidal 
in  shape,  lying  almost  parallel  with  the  posterior  margin  of  the  Gluteus  medius. 
It  is  situated  partly  within  the  pelvis  at  its  posterior  part  and  partly  at  the  back  of 
the  hip-joint.  It  arises  from  the  front  of  the  sacrum  by  three  fleshy  digitations 
attached  to  the  portions  of  bone  between  the  first,  second,  third,  and  fourth 
anterior  sacral  foramina,  and  also  from  the  grooves  leading  from  the  foramina; 
a  few  fibres  also  arise  from  the  margin  of  the  great  sacrosciatic  foramen  and  from 
the  anterior  surface  of  the  great  sacrosciatic  ligament.  The  muscle  passes  out 
of  the  pelvis  through  the  great  sacrosciatic  foramen,  the  upper  part  of  which  it 
fills,  and  is  inserted  by  a  rounded  tendon  into  the  inner  side  of  the  upper  border 
of  the  great  trochanter,  behind,  but  often  partly  blended  with,  the  tendon  of  the 
Obturator  intemus  and  Gemelli  muscles. 

Relations. — By  its  deep  surface,  unthin  the  pelvis,  with  the  rectum  (especially  on  the  left 
side),  the  sacral  plexus  of  nerves,  and  the  branches  of  the  internal  iliac  vessels;  external  to  the 
pelvis,  with  the  posterior  surface  of  the  ischium  and  the  capsular  ligament  of  the  hip-joint)  by 
its  superficial  surface,  within  the  pelvis,  with  the  sacrum,  and  external  to  it,  with  the  Gluteus 
maximus;  by  its  upper  border,  with  the  Gluteus  medius,  from  which  it  is  separated  by  the  gluteal 
vessels  and  superior  gluteal  nerve;  by  its  lower  border,  with  the  Gemellus  superior  and  Coccygeus, 
the  sciatic  vessels  and  ner\es,  the  internal  pudic  vessels  and  nerve,  and  muscular  branches  from 
the  sacral  jilcxus,  pussiiii;  from  the  pelvis  in  the  interval  between  the  two  muscles. 

The  Obttirator  Membrane  (membrana  obturaioria)  (Fig.  240)  is  a  thin  layer  of  interlacing 
fibres  which  closes  almost  completely  the  obturator  foramen.  It  is  attached,  externally,  to 
the  margin  of  the  foramen;  internally,  to  the  posterior  surface  of  the  ischiopubic  ramus,  below 
and  internal  to  the  margin  of  the  foramen.  It  presents  at  its  upper  and  outer  parts  a  small 
canal,  obturator  canal  (canalis  obturatorius)  for  the  passage  of  the  obturator  vessels  and  nerve. 
Both  obturator  muscles  are  connected  with  this  membrane. 

There  is  usually  a  bursa  (bursa  m.  piriformis)  between  the  tendon  of  the  Pyriformis  and  the 
ilium. 

Dissection. — The  next  muscle,  as  well  as  the  origin  of  the  Pyriformis,  can  only  be  seen  when 
the  pelvis  is  divided  and  the  viscera  removed. 


518 


THE  MVSCLES  AND  FASCIA 


Inner  Hamstring 

teTidons. 


Fig.  3S4.— Muscles  of  the  hip  and  thigh. 


The  Obturator  intemus  (m. 

obturator  intemus  (Figs.  384 
and  385),  like  the  preceding 
muscle,  is  situated  partly  within 
the  cavity  of  the  pelvis,  and 
partly  at  the  back  of  the  hip- 
joint.  It  arises  from  the  inner 
surface  of  the  anterior  and  ex- 
ternal wall  of  the  pelvis,  where 
it  surrounds  the  greater  part 
of  the  obturator  foramen,  being 
attached  to  the  descending  ramus 
of  the  OS  pubis  and  the  ramus  of 
the  ischium,  and  at  the  side  to 
the  inner  surface  of  the  innomi- 
nate bone  below  and  behind 
the  pelvic  brim,  reaching  from 
the  upper  part  of  the  great 
sacrosciatic  foramen  above  and 
behind  to  the  obturator  fora- 
men below  and  in  front.  It 
also  arises  from  the  inner  surface 
of  the  obturator  membrane  ex- 
cept at  its  posterior  part,  from 
the  tendinous  arch  which  com- 
pletes the  canal  for  the  passage 
of  the  obturator  vessels  and  nerve 
and  to  a  slight  extent  from  the 
obturator  layer  of  the  pelvic 
fascia,  which  covers  it.  The 
fibres  converge  rapidly,  and  are 
directed  backward  and  down- 
ward, and  terminate  in  four  or 
five  tendinous  bands,  which  are 
found  on  its  deep  surface;  these 
bands  are  reflected  at  a  right 
angle  over  the  inner  surface  of 
the  tuberosity  of  the  ischium, 
which  is  grooved  for  their  recep- 
tion; the  groove  is  covered  by 
cartilage,  and  lined  with  a  syno- 
vial bursa  (bursa  m.  obturatoris 
iuterni).  The  muscle  leaves  the 
pelvis  by  the  lesser  sacrosciatic 
foramen;  and  the  tendinous 
bands  unite  into  a  single  flat- 
tened tendon,  which  passes  hori- 
zontally outward,  and,  after 
receiving  the  attachment  of  the 
Gemelli,  is  inserted  into  the  fore 
part  of  the  inner  surface  of  the 
great  trochanter  in  front  of  the 
Obturator  externus. 


THE  GLUTEAL  REGION 


519 


In  ordri-  to  (lls|iliiy  llic  peculiar  a|>|ic;iriin(c.s  presented  by  the  tendon  of  this  muscle,  it  must 
be  dividrd  near  ils  iiiscrlioii  and  rcllcclcil  inward. 

Relations. --fr/////»  the  prlri.^  (his  muscle  is  in  relation,  by  its  decj)  surface,  with  the  obturator 
membrane  and  inner  surface  of  the  anterior  wall  of  the  pelvis;  by  its  superficial  surface,  with 
the  pelvic  and  obturator  fascise,  which  separate  it  from  the  Levator  ani ;  and  it  is  crossed  by 
the  internal  pudic  vessels  and  nerve.    This  surface  forms  the  outer  boundary  of  the  ischio- 


i\'ed  from  without  and  below.    The  quadratus  having 
!o  not  shown.     (Spalteholz.) 


rectal  fossa.  External  to  the  pelvis  it  is  covered  by  the  Gluteus  maximus,  is  crossed  by  the 
great  sciatic  nerve,  and  rests  on  the  back  part  of  the  hip-joint.  As  the  tendon  of  the  Obturator 
internus  emerges  from  the  lesser  sacrosciatic  foramen  it  is  overlapped  by  the  two  Gemelli,  while 
nearer  its  insertion  the  Gemelli  pass  in  front  of  it  and  form  a  groove  in  which  the  tendon  lies. 
A  synovial  bursa,  narrow  and  elongated  in  form,  is  usually  found'  between  the  tendon  of  this 
muscle  and  the  capsular  ligament  of  the  hip ;  it  occasionally  communicates  with  the  bursa  between 
the  tendon  and  the  tuberosity  of  the  ischium,  the  two  forming  a  single  sac. 


520 


THE  MUSCLES  AND  FASCIA 


The  Gemelli  (Fig.  375)  are  two  small  muscular  fasciculi,  accessories  to  the 
tendon  of  the  Obturator  internus,  which  is  received  into  a  groove  between  them. 
They  are  called  superior  and  inferior. 

The  Gemellus  superior  (m.  gemellus  superior),  the  smaller  of  the  two^  arises 
from  the  outer  surface  of  the  spine  of  the  ischium,  and,  passing  horizontally 
outward,  becomes  blended  with  the  upper  part  of  the  tendon  of  the  Obturator 
internus,  and  is  inserted  with  it  into  the  inner  surface  of  the  great  trochanter. 
This  muscle  is  sometimes  wanting. 

Relations, — By  its  superficial  surface,  with  the  Gluteus  maximus  and  the  sciatic  vessels  and 
nerves;  by  its  deep  surface,  with  the  capsule  of  the  hip-joint;  by  its  upper  border,  with  the  lower 
margin  of  the  Pyriformis;  by  its  lower  border,  with  the  tendon  of  the  Obturator  internus. 


Anterior  division  of 
obtuiato)  ne)ve 


Ante)  10)  jnfettor 
iliac  smne 


the  Museum  of  the  Royal  College  of 

The  Gemellus  inferior  (m.  gemellus  inferior)  arises  from  the  upper  part  of  the 
tuberosity  of  the  ischium,  where  it  forms  the  lower  edge  of  the  groove  for  the 
Obturator  internus  tendon,  and,  passing  horizontally  outward,  is  blended  with 
the  lower  part  of  the  tendon  of  the  Obturator  internus,  and  is  inserted  with  it 
into  the  inner  surface  of  the  great  trochanter. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  and  the  sciatic  vessels  and 
nerves;  by  its  deep  surface,  with  the  capsular  ligament  of  the  hip- joint;  by  its  upper  border, 
with  the  tendon  of  the  Obturator  internus;  by  its  lower  border,  with  the  tendon  of  the  Obturator 
externus  and  Quadratus  femoris. 


The  Quadratus  femoris  (m.  quadratus  femoris)  (Fig.  384)  is  a  short,  flat 
muscle,  quadrilateral  in-  shape,  situated  between  the  Gemellus  inferior  and  the 
upper  margin  of  the  Adductor  magnus.  It  arises  from  the  upper  part  of  the  exter- 
nal lip  of  the  tuberosity  of  the  ischium,  and,  proceeding  horizontall}^  outward,  is 


OF  THE  HIP  521 

inserted  into  the  upper  part  of  the  Hnea  quadrata;  that  is,  the  line  which  crosses 
the  posterior  intertrochanteric  Hne. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  and  the  sciatic  vessels  and 
nerves;  bv  its  deej)  surface,  with  the  tendon  of  the  Obturator  externus  and  trochanter  minor 
and  with  the  capsule  of'  the  hip-joint;  by  its  upper  border,  with  the  Gemellus  inferior.  Its  lower 
border  is  separated  from  the  Adductor  magnus  by  the  terminal  branches  of  the  internal  circumflex 
vessels.  A  synovial  bursa  is  often  found  between  the  under  surface  of  this  muscle  and  the 
lesser  trochanter,  which  it  covers. 

Dissection. — In  order  to  expose  the  next  muscle  (the  Obturator  externus)  it  is  necessary  to 
remove  the  Psoas,  Iliacus,  Pectineus,  and  Adductores  brevis  and  longus  muscles  from  the  front 
and  inner  side  of  the  thigh,  and  the  Gluteus  maximus  and  Quadratus  femoris  from  the  back 
part.  Its  dissection  should,  consequently,  be  postponed  until  the  muscles  of  the  anterior  and 
internal  femoral  regions  have  been  explained. 

The  Obturator  externus  (m.  obturator  externus)  (Figs.  .385  and  386)  is  a  flat, 
triangular  muscle,  which  covers  the  outer  surface  of  the  anterior  wall  of  the  pelvis. 
It  arises  from  the  margin  of  bone  immediately  around  the  inner  side  of  the  obturator 
foramen — viz.,  from  the  body  and  ramus  of  the  os  pubis  and  the  ramus  of  the 
ischium;  it  also  arises  from  the  inner  two-thirds  of  the  outer  surface  of  the  obturator 
membrane,  and  from  the  tendinous  arch  which  completes  the  canal  for  the  passage 
of  the  obturator  vessels  and  nerves.  The  fibres  from  the  pubic  arch  extend  on 
to  the  inner  surface  of  the  bone,  from  which  they  obtain  a  narrow  origin  between 
the  margin  of  the  foramen  and  the  attachment  of  the  membrane.  The  fibres 
converging  pass  backward,  outward,  and  upward,  and  terminate  in  a  tendon 
which  rims  across  the  back  part  of  the  hip-joint,  and  is  inserted  into  the  digital 
fossa  of  the  femur. 

Relations. — In  front,  with  the  Psoas,  Iliacus,  Pectineus,  Adductor  magnus,  and  Adductor 
brevis;  and  more  externally,  with  the  neck  of  the  femur  and  capsule  of  the  hip-joint.  The 
external  and  internal  terminal  branches  of  the  obturator  artery  and  accompanying  veins  lie 
between  this  muscle  and  the  obturator  membrane;  the  superficial  part  of  the  obturator  nerve 
lies  above  the  muscle,  and  the  deep  branch  perforates  it;  by  its  deep  surface,  with  the  obturator 
membrane  and  Quadratus  femoris  at  its  insertion. 

Nerves. — The  Gluteus  maximus  is  supplied  by  the  fifth  lumbar  and  first  and  second  sacral 
nerves  through  the  inferior  gluteal  nerve  from  the  sacral  plexus;  the  Gluteus  medius  and  mini- 
mus, by  the  fom'th  and  fifth  lumbar  and  first  sacral  nerves,  through  the  superior  gluteal;  the 
Pyriformis  is  supplied  by  the  first  and  second  sacral  nerves;  the  Gemellus  inferior  and  Quad- 
ratus femoris  by  the  last  lumbar  and  first  sacral  ner\-e;  the  Gemellus  superior  and  Obturator 
internus  by  the  fifth  lumbar  and  first  and  second  sacral  nerves,  and  the  Obturator  externus  by 
the  second,  third,  and  fourth  lumbar  nerves  through  the  obturator  nerve. 

Actions. — The  Gluteus  maximus,  when  it  takes  its  fixed  point  from  the  pelvis,  extends  the 
femur  and  brings  the  bent  thigh  into  a  line  with  the  body.  Taking  its  fixed  point  from  below, 
it  acts  upon  the  pelvis,  supporting  it  and  the  whole  trunk  upon  the  head  of  the  femur,  which  is 
especially  obvious  in  standing  on  one  leg.  Its  most  powerful  actions  are  to  hold  the  head  of  the 
femur  in  close  approximation  to  the  acetabulum  in  walking  and  to  cause  the  body  to  regain 
the  erect  position  after  stooping  by  drawing  the  pelvis  backward,  being  assisted  in  this  action 
by  the  Biceps,  Semitendinosus,  and  Semimembranosus.  The  Gluteus  maximus  is  a  tensor  of 
the  fascia  lata,  and  by  its  connection  with  the  ihotibial  band  it  steadies  the  femur  on  the  articular 
surface  of  the  tibia  during  standing,  when  the  Extensor  muscles  are  relaxed.  The  lower  part 
of  the  muscle  also  acts  as  an  Adductor  and  External  rotator  of  the  limb.  The  Gluteus  medius 
and  minimus  abduct  the  thigh  when  the  limb  is  extended,  and  are  principally  called  into  action 
in  supporting  the  body  on  one  limb,  in  conjunction  with  the  Tensor  fasciae  femoris.  Their 
anterior  fibres,  by  drawing  the  great  trochanter  forward,  rotate  the  thigh  inward,  in  which 
action  they  are  also  assisted  by  the  Tensor  fasciae  femoris.  The  remaining  muscles  are  power- 
ful Rotators  of  the  thigh  outward.  In  the  sitting  posture,  when  the  thigh  is  flexed  upon  the 
pelvis,  their  action  as  Rotators  cease,  and  they  become  Abductors,  with  the  exception  of  the 
Obturator  externus,  which  still  rotates  the  femur  outward.  When  the  femur  is  fixed,  the 
Pyriformis  and  Obturator  muscles  serve  to  draw  the  pelvis  forward  if  it  has  been  inclined 
backward,  and  assist  in  steadying  it  upon  the  head  of  the  femm-. 


522 


THE  MUSCLES  AND  FASCIA 


4.  The  Posterior  Femoral  Region. 

{Hamstring  Muscles.) 


Biceps  femoris. 


Semitendinosus. 


Semimembranosus. 


Dissection  (Fig.  383). — Make  a  vertical  incision  along  the  middle  of  the  back  of  the  thigh, 
from  the  lower  fold  of  the  buttock  to  about  three  inches  below  the  back  of  the  knee-joint,  and 
there  connect  it  with  a  transverse  incision,  carried  from  the  inner  to  the  outer  side  of  the  leg. 
Make  a  third  incision  transversely  at  the  junction  of  the  middle  with  the  lower  third  of  the 
thigh.  The  integument  having  been  removed  from  the  back  of  the  knee,  and  the  boundaries 
of  the  popliteal  space  having  been  examined,  the  removal  of  the  integument  from  the  remaining 
part  of  the  thigh  should  be  continued,  when  the  fascia  and  muscles  of  this  region  will  be  exposed. 


GLUTE 

ADDUCTOR  MAGNUS 


SEMIMEMBRANOSUS 


P0PLITEU8 

Fig.  387. — Diagram  showing  the  attachments  of  the  muscles  of  the  thigh.     Posterior  aspect. 
Origins,  red;  insertions,  blue. 

The  Biceps  femoris  (m.  biceps  femoris)  is  a  large  muscle,  of  considerable 
length,  situated  on  the  posterior  and  outer  aspect  of  the  thigh  (Figs.  384  and  388). 
It  arises  by  two  heads.  One,  the  long  head  (capid  longum),  arises  from  the  lower 
and  inner  impression  on  the  back  part  of  the  tuberosity  of  the  ischium,  by  a  tendon 


THE  POSTERIOR  FEMORAL  REGION 


523 


common  to  it  and  the  Semitendinosiis,  and  from  the  lower  part  of  the  great  sacro- 
sciatic  Hgament.  The  femoral  or  short  head  (caput  breve)  arises  from  the  outer 
lip  of  the  linea  aspera,  between  the  Adductor  magnus  and  Vastus  externus,  extend- 
ing up  almost  as  high  as  the  insertion  of  the  Gluteus  maximus;  from  the  outer 
prolongation  of  the  linea  aspera  to  within  two  inches  of  the  outer  condyle,  and 
from  the  external  intermuscular  septum.     The  fibres  of  the  long  head  form  a  fusi- 


Fig.  38S.— Region  of  the  knee,  seen  obliquely  from  behind  and  within      Right  limb.     (Toldt.) 

form  belly,  which,  passing  obliquely  downward  and  a  little  outward,  terminates 
in  an  aponeurosis  which  covers  the  posterior  surface  of  the  muscle,  and  receives 
the  fibres  of  the  short  head;  this  aponeurosis  becomes  gradually  contracted  into 
a  tendon,  which  is  inserted  into  the  outer  side  of  the  head  of  the  fibula,  and  by  a 
small  slip  into  the  lateral  surface  of  the  external  tuberosity  of  the  tibia.  At  its 
insertion  the  tendon  divides  into  two  portions,  which  embrace  the  long  external 
lateral  ligament  of  the  knee-joint.     From  the  posterior  border  of  the  tendon  a 


524  THE  MUSCLES  AND  FASCIjE 

thin  expansion  is  given  off  to  the  fascia  of  the  leg.     The  tendon  of  this  muscle 
forms  the  outer  Hamstring. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  and  the  small  sciatic  nerve, 
the  fascia  lata,  and  integument.  By  its  deep  surface,  with  the  Semimembranosus,  Adductor 
magnus,  and  Vastus  externus,  the  great  sciatic  nerve,  and,  near  its  insertion,  with  the  external 
head  of  the  Gastrocnemius,  the  Plantaris,  the  superior  external  articular  arterj',  and  the  external 
popliteal  nerve.  A  bursa  {bursa  m.  bicijntis  femoris  inferior)  is  found  between  the  long  tendon 
of  origin  of  this  muscle  and  the  Semitendinosus  and  Semimembranosus.  Sometimes  there  is  a 
bursa  {bursa  bieipitogastrocneynialis)  between  the  tendon  of  the  insertion  of  the  Biceps  and  the 
origin  of  the  Gastrocnemius,  and  there  is  a  bursa  {bursa  m.  bicipitis  femoris  inferior)  between 
the  tendon  of  the  Biceps  and  the  external  lateral  ligament. 

The  Semitendinosus  (m.  semitendinosus)  (Figs.  384  and  388),  remarkable 
for  the  great  length  of  its  tendon,  is  situated  at  the  posterior  and  inner  aspect 
of  the  thigh.  It  arises  from  the  lower  and  inner  impression  on  the  tuberosity 
of  the  ischium  by  a  tendon  common  to  it  and  the  long  head  of  the  Biceps  femoris; 
it  also  arises  from  an  aponeurosis  which  connects  the  adjacent  surfaces  of  the  two 
muscles  to  the  extent  of  about  three  inches  after  their  origin.  The  Semitendi- 
nosus is  a  fusiform  muscle,  which,  passing  downward  and  inward,  terminates  a 
little  below  the  middle  of  the  thigh  in  a  long  round  tendon  which  lies  along  the 
inner  side  of  the  popliteal  space,  then  curves  around  the  inner  tuberosity  of  the 
tibia,  and  is  inserted  into  the  upper  part  of  the  inner  surface  of  the  shaft  of  that 
bone  nearly  as  far  forward  as  its  anterior  border.  At  its  insertion  it  gives  off 
from  its  lower  border  a  prolongation  to  the  deep  fascia  of  the  leg.  This  tendon 
lies  behind  the  tendon  of  the  Sartorius,  and  below  that  of  the  Gracilis,  to  which 
it  is  united.  A  tendinous  intersection  is  usually  observed  about  the  middle  of 
the  muscles.  The  bursa  anserina  lies  between  the  tendon  of  the  Semitendinosus 
and  the  tibia. 

The  Semimenibranosus  (m.  semimembranosis)  (Figs.  384  and  388),  so  called 
from  its  membranous  tendon  of  origin,  is  situated  at  the  back  part  and  inner 
side  of  the  thigh.  It  arises  by  a  thick  tendon  from  the  upper  and  outer  impression 
on  the  back  part  of  the  tuberosity  of  the  ischium,  above  and  to  the  outer  side  of 
the  Biceps  femoris  and  Semitendinosus,  and  is  inserted  into  the  groove  on  the 
inner  and  back  part  of  the  inner  tuberosity  of  the  tibia,  beneath  the  internal 
lateral  ligament.  The  tendon  of  the  muscle  at  its  origin  expands  into  an  apon- 
eurosis which  covers  the  upper  part  of  its  anterior  surface;  from  this  aponeurosis 
muscle  fibres  arise,  and  converge  to  another  aponeurosis,  which  covers  the  lower 
part  of  its  posterior  surface  and  contracts  into  the  tendon  of  insertion.  The 
tendon  of  the  muscle  at  its  insertion  gives  off  certain  fibrous  expansions;  one  of 
these,  of  considerable  size,  passes  upward  and  outward,  to  be  inserted  into  the 
back  part  of  the  outer  condyle  of  the  femur,  forming  part  of  the  posterior  ligament 
of  the  knee-joint;  a  second  is  continued  downward  to  the  fascia  which  covers 
the  Popliteus  muscle.  The  tendon  also  sends  a  few  fibres  to  join  the  internal 
lateral  ligament  of  the  joint. 

The  tendons  of  the  two  preceding  muscles,  with  that  of  the  Gracilis,  form  the 
inner  Hamstrings. 

Nerves. — The  muscles  of  this  region  are  supplied  by  the  fourth  and  fifth  lumbar  and  the 
first,  second,  and  third  sacral  nerves  through  the  great  sciatic  nerve. 

Actions. — The  Hamstring  muscles  flex  the  leg  upon  the  thigh.  When  the  knee  is  semiflexed, 
the  Biceps,  in  conseciuence  of  its  oblique  direction  downward  and  outAvard,  rotates  the  leg 
slightly  outward;  and  the  Semitendinosus,  and  to  a  slight  extent  the  Semimembranosus,  rotate 
the  leg  inward,  assisting  the  Popliteus.  Taking  their  fixed  point  from  below,  these  muscles, 
especially  the  Semimembranosus,  serve  to  support  the  pelvis  upon  the  head  of  the  femur  and 
to  draw  the  trunk  directly  backward,  as  in  raising  it  from  the  stooping  position  or  in  feats  of 
strength,  when  the  body  is  thrown  backward  in  the  form  of  an  arch.  X'Slien  the  leg  is  extended 
on  the  thigh,  they  limit  the  amount  of  flexion  of  the  trunk  on  the  lower  limbs. 


THE  ANTERIOR  TIBIOFIBULAR  REGION  525 

Applied  Anatomy. — The  Hamstring  tendons  are  occasionally  ruptured.  In  disease  of  the 
knee-joint  the  Hamstrings  may  contract,  flexing  the  knee,  drawing  the  tibia  backward,  and  some- 
times causing  incomplete  dislocation.  The  tendons  of  these  muscles  occasionally  require  sub- 
cutaneous division  in  some  forms  of  spurious  ankylosis  of  the  knee-joint  dependent  upon  per- 
manent contraction  and  rigidity  of  the  Flexor  muscles,  or  from  stiffening  of  the  ligamentous 
other  tissues  surrounding  the  joint,  the  result  of  disease.  Division  of  a  tendon  is  effected  by 
putting  the  tendon  upon  the  stretch,  and  inserting  a  narrow  sharp-pointed  knife  between  it  and 
the  skin;  the  cutting  edge  being  then  turned  toward  the  tendon,  it  should  be  divided,  taking  great 
care  that  the  wound  in  the  skin  is  not  at  the  same  time  enlarged.  The  relation  of  the  external 
popliteal  nerve  to,  the  tendon  of  the  Biceps  must  always  be  borne  in  mind  in  dividing  this  tendon; 
in  fact,  a  complete  exposure  of  the  tendon  is  much  to  be  preferred. 


IV.  MUSCLES  AND  FASCI.ffi  OF  THE  LEG. 

These  may  be  divided  into  three  groups:  those  on  the  anterior,  those  on  the 
posterior,  and  those  on  the  outer  side  of  the  leg. 


5.  The  Anterior  Tibiofibular  Region  (Fig.  390). 

Tibialis  anticus.  Extensor  longus  digitorum. 

Extensor  proprius  halhicis.^  Peroneus  tertius. 

Dissection  (Fig.  377). — The  knee  should  be  bent,  a  block  placed  beneath,  it,  and  the  foot 
kept  in  an  extended  position;  then  make  an  incision  through  the  integument  in  the  middle  line 
of  the  leg  to  the  ankle,  and  continue  it  along  the  dorsum  of  the  foot  to  the  toes.  Make  a  second 
incision  transversely  across  the  ankle,  and  a  third  in  the  same  direction  across  the  bases  of  the 
toes;  remove  the  flaps  of  integimient  included  between  these  incisions  in  order  to  examine  the 
deep  fascia  of  the  leg. 

The  deep  fascia  of  the  leg  (fascia  cruris)  forms  a  complete  investment  to 
tlie  muscles,  but  is  not  continuous  over  the  subcutaneous  surfaces  of  the  bones. 
It  is  continuous  above  witli  the  fascia  lata,  receiving  an  expansion  from  the  tendon 
of  the  Biceps  femoris,  (jn  the  outer  side,  and  from  the  tendons  of  the  Sartorius 
Gracilis,  and  Semitendinosus  on  the  inner  side;  in  front,  it  blends  with  the  peri- 
osteum covering  the  subcutaneous  surface  of  the  tibia,  and  witli  that  covering  the 
head  and  external  malleolus  of  the  fibula;  belotc,  it  is  continuous  with  the  annular 
ligaments  of  the  ankle.  It  is  thick  and  dense  in  the  upper  and  anterior  part  of  the 
leg,  and  gives  attachment,  by  its  deep  surface,  to  the  Tibialis  anticus  and  Extensor 
longus  digitorum  muscles,  but  is  thinner  behind,  where  it  covers  the  Gastrocnemius 
and  Soleus  muscles.  Over  the  popHteal  space  it  is  much  strengthened  by  trans- 
verse fibres  which  stretch  across  from  the  inner  to  the  outer  Hamstring  muscles, 
and  it  is  here  perforated  by  the  external  saphenous  vein.  Its  deep  surface  gives 
off,  on  the  outer  side  of  the  leg,  two  strong  intermuscular  septa  which  enclose  the 
Peronei  mu.scles,  and  separate  them  from  the  muscles  of  the  anterior  and  posterior 
tibial  regions.  It  also  gives  off  several  smaller  and  more  slender  processes  which 
enclose  the  individual  muscles  in  each  region;  at  the  saine  time  a  broad  transverse, 
intermuscular  septum,  called  the  deep  transverse  fascia  of  the  leg,  intervenes  between 
the  superficial  and  deep  muscles  in  the  posterior  tibiofibular  region. 

^There  is  no  such  word  as  "Hallux,  -cis."  It  is  the  result  of  some  ignorant  blunder,  copied  until  it  has 
become  established  by  usage;  it  has  been  thought  better,  therefore,  to  retain  it.  According  to  Lewis  and 
Short,  the  word  is  Allex,  masculine;  genitive,  Allicis,  the  great  toe,  and  the  correct  rendering  would  be 
Extensor  proprixis  allicis.  It  is  a  rare  word,  and  is  sometimes  spelt,  but  not  so  correctly,  "  Hallex."  It  is 
used  by  Plautus,  in  the  "  Pcenulus,"  V,  v.  31,  of  a  little  man,  as  we  might  say,  "  a  hop-o'-my-thumb."  "  Tunc 
hie  amator  audes  esse,  allex  viri"  (To  think  of  you  daring  to  make  up  to  her,  you  hop-o'-my-thumb!).  The 
word  "  alex.**  sometimes  spelt  "  allex,"  a  fish  sauce,  is  probably  a  different  word  altogether.  It  is  used  by 
Horace  and  Pliny. 


526 


THE  MUSCLES  AND  FASCIA 


Remove  the  fascia  by  dividing  it  in  the  same  direction  as  the  integument,  excepting  opposite 
the  ankle,  where  it  should  be  left  entire.  Commence  the  removal  of  the  fascia  from  below, 
opposite  the  tendons,  and  detach  it  in  the  line  of  direction  of  the  muscle  fibres. 

The  Tibialis  anticus  (m.  tibialis  anterior)  is  situated  on  the  outer  side  of  the 
tibia;  it  is  thick  and  fleshy  at  its  upper  part,  tendinous  below.  It  arises  from  the 
outer  tuberosity  and  upper  two-thirds  of  the  external  surface  of  the  shaft  of  the 
tibia;  from  the  adjoining  part  of  the  interosseous  membrane;  from  the  deep  surface 


Fig.  389. — Diagram  showing  the  attachments  of  the  muscies  of  the  leg.     Anterior  aspect. 
Origins,  red;  insertions,  blue. 

of  the  fascia;  and  from  the  intermuscular  septum  between  it  and  the  Extensor 
longus  digitorum;  the  fibres  pass  vertically  downward,  and  terminate  in  a  tendon 
which  is  apparent  on  the  anterior  surface  of  the  muscle  at  the  lower  third  of  the 
leg.  After  passing  through  the  innermost  compartment  of  the  anterior  annular 
ligament,  it  is  inserted  into  the  inner  and  under  surface  of  the  internal  cuneiform 
bone  and  base  of  the  metatarsal  bone  of  the  great  toe.  There  is  usually  a  bursa 
(bursa  subtendinea  m.  tibialis  anterioris)  between  the  tendon  of  the  Tibialis  anticus 
and  the  internal  cuneiform  bone.  At  the  upper  part  of  the  leg  this  muscle  over- 
laps the  anterior  tibial  vessels  and  nerve. 


THE  ANTERIOR   TIBIOFIBULAR  REGION 


527 


The  Extensor  proprius  hallucis  (m.  extensor  hallu- 
cislougiis)  is  a  thin,  elongated,  and  flattened  muscle 
situated  between  the  Tibialis  anticus  and  Extensor 
longus  digitorum.  It  arises  from  the  anterior  surface 
of  the  fibula  for  about  the  middle  two-fourths  of  its 
extent,  its  origin  being  internal  to  that  of  the  Exten- 
sor longus  digitorum;  it  also  arises  from  the  inter- 
osseous membrane  to  a  similar  extent.  The  fibres 
pass  downward,  and  terminate  in  a  tendon  which 
occupies  the  anterior  border  of  the  muscle,  passes 
through  a  distinct  compartment  in  the  lower  portion 
of  the  annular  ligament,  crosses  the  anterior  tibial 
vessels  near  the  bend  of  the  ankle,  and  is  inserted  into 
the  base  of  the  last  phalanx  of  the  great  toe.  Op- 
posite the  metatarsophalangeal  articulation  the  tendon  : 
gives  off  a  thin  prolongation  on  each  side,  which  covers 
the  surface  of  the  joint.  It  usually  sends  an  expan- 
sion from  the  inner  side  of  the  tendon,  to  be  inserted 
into  the  base  of  the  first  phalanx. 

The  Extensor  longus  digitorum  (m.  extensor  dicji- 
torum  longus)  is  an  elongated,  flattened,  penniform 
muscle  situated  the  most  externally  of  all  the  muscles 
on  the  fore  part  of  the  leg.  It  arises  from  the  outer 
tuberosity  of  the  tibia ;  from  the  upper  three-fourths  of 
the  anterior  surface  of  the  shaft  of  the  fibula ;  from  the 
interosseous  membrane;  from  the  deep  surface  of  the 
fascia;  and  from  the  intermuscular  septa  bet^\een  it 
and  the  Tibialis  anticus  on  the  inner  and  the  Peronei 
on  the  outer  side.  The  tendon  enters  a  canal  in  the 
annular  ligament  with  the  Peroneus  tertius,  and  divides 
into  four  slips,  which  run  across  the  dorsum  of  the 
foot  and  are  inserted  into  the  second  and  third  pha- 
langes of  the  four  lesser  toes.  The  mode  in  which 
the  tendons  are  inserted  is  the  following:  Each  of  the 
three  inner  tendons  opposite  the  metatarsophalangeal 
articulation  is  joined,  on  its  outer  side,  by  a  tendon 
from  the  Extensor  brevis  digitorum.  The  outer  ten- 
don does  not  receive  such  a  tendinous  slip.  They  all 
receive  a  fibrous  expansion  from  the  Interossei  and 
Lumbricales,  and  then  spread  out  into  a  broad  aponeu- 
rosis, which  covers  the  dorsal  surface  of  the  first  pha- 
lanx; this  aponeurosis,  at  the  articulation  of  the  first 
with  the  second  phalanx,  divides  into  three  slips — 
a  middle  one,  which  is  inserted  into  the  base  of  the 
second  phalanx,  and  two  lateral  slips,  which,  after 
imiting  on  the  dorsal  surface  of  the  second  phalanx, 
are  continued  onward,  to  be  inserted  into  the  base 
of  the  third. 

The  Peroneus  tertius  (m.  jwronaens  tertius)  is  a 
part  of  the  Extensor  longus  digitorum,  and  might  be 
described  as  its  fifth  tendon.  The  fibres  belonging 
to  this  tendon  arise  from  the  lower  fourth  of  the 
anterior  surface  of  the  fibula,  from  the  lower  part  of 
the  interosseous  membrane,  and   from  an  intermus- 


tJ- 


„nU'" 


Fig.  390.— Muscles  of  the  front  of 
the  leg. 


528  THE  iVUSCLES  AXD  FASCIA 

cular  septum  between  it  and  the  Peroneus  brevis.  The  tendon,  after  passing 
throiigli  the  same  canal  in  the  annular  ligament  as  the  Extensor  longus  digito- 
rum,  is  inserted  into  the  dorsal  surface  of  the  base  of  the  metatarsal  bone  of  the 
little  toe.     This  muscle  is  sometimes  wanting. 

Nerves. — These  muscles  are  supplied  by  the  fourth  and,fifth  lumbar  and  first  sacral  nerves 
through  the  anterior  tibial  nerve. 

Actions. — The  Tibialis  anticus  and  Peroneus  tertius  are  the  direct  Flexors  of  the  foot  at  the 
ankle-joint;  the  former  muscle,  when  acting  in  conjunction  with  the  Tibialis  posticus,  raises 
the  inner  border  of  the  foot  {i.  e.,  inverts  the  foot);  and  the  latter,  acting  with  the  Peroneus 
brevis  and  longus,  draws  the  outer  border  of  the  foot  upward,  and  the  sole  outward  (i.  e.,  everts 
the  foot).  The  Extensor  longus  digitorum  and  Extensor  proprius  hallucis  extend  the  phalanges 
of  the  toes,  and,  continuing  their  action,  flex  the  foot  upon  the  leg.  Taking  their  fixed  point  from 
below,  in  the  erect  posture,  all  these  muscles  serve  to  fix  the  bones  of  the  leg  in  the  perpendicular 
position,  and  give  increased  strength  to  the  anlde-joint. 


6.  The  Posterior  Tibiofibular  Region  (Figs.  388,  394). 

Dissection  (Fig.  .383) . — Make  a  vertical  incision  along  the  middle  line  of  the  back  of  the  leg, 
from  the  lower  part  of  the  popliteal  space  to  the  heel,  connecting  it  below  by  a  transverse  incision 
extending  between  the  two  malleoli;  the  flaps  of  integument  being  removed,  the  fascia  and 
muscles  should  be  examined. 

The  muscles  in  this  region  of  the  leg  are  subdivided  into  two  layers — superficial 
and  deep.  The  superficial  layer  constitutes  a  powerful  muscular  mass,  forming 
the  calf  of  the  leg.  Their  large  size  is  one  of  the  most  characteristic  features  of 
the  muscular  apparatus  in  man,  and  bears  a  direct  connection  with  his  ordinary- 
attitude  and  mode  of  progression. 


The  Superficial  Layer. 
Gastrocnemius.  Soleus.  Plantaris. 

The  Gastrocnemius  (m.  gastrocnemius)  is  the  most  superficial  muscle,  and 
forms  the  greater  part  of  the  calf.  It  arises  by  two  heads,  which  are  connected 
to  the  condyles  of  the  femur  by  two  strong  flat  tendons.  The  inner  and  larger 
head  (caput  mediale)  arises  from  a  depression  at  the  upper  and  back  part  of  the 
inner  condyle  and  from  the  adjacent  part  of  the  femur.  The  outer  head  (caput 
laterale)  arises  from  an  impression  on  the  outer  side  of  the  external  condyle  and 
from  the  posterior  surface  of  the  femur  immediately  above  the  condyle.  Both 
heads,  also,  arise  by  a  few  tendinous  and  fleshy  fibres  from  the  ridges  which  are 
continued  upward  from  the  condyles  !o  the  linea  aspera.  Each  tendon  spreads 
out  into  an  aponeurosis,  which  covers  the  posterior  surface  of  that  portion  of  the 
muscle  to  which  it  belongs;  the  muscle  fibres  of  the  inner  head  form  a  thicker  mass 
and  extend  lower  than  those  of  the  outer.  From  the  anterior  surface  of  these 
tendinous  expansions  muscle  fibres  are  given  off.  The  fibres  in  the  median  line, 
which  correspond  to  the  accessory  portions  of  the  muscle  derived  from  the  bifur- 
cations of  the  linea  aspera,  unite  at  an  angle  upon  a  median  tendinous  raphe 
below;  the  remaining  fibres  converge  to  an  aponeurosis  which  covers  the  anterior 
surface  of  the  muscle,  and  this,  gradually  contracting,  unites  with  the  tendon 
of  the  Soleus,  and  forms  with  it  the  tendo  Achillis. 

Relations. — By  its  superficial  surface,  with  the  fascia  of  the  leg,  which  separates  it  from  the 
external  saphenous  vein  and  nerve;  by  its  deep  surface,  with  the  posterior  ligament  of  the  knee- 
joint,  the  Popliteus,  Soleus,  Plantaris,  popliteal  vessels,  and  internal  popliteal  nerve.  The 
tendon  of  the  inner  head  corresponds  with  the  back  part  of  the  inner  condyle,  from  which  it  is 


THE  POSTERIOR  TIBIOFIBULAR  REGION 


529 


SEMIMEMBRANOSUS 


GASTROCNEMIUS 
AND  SOLEU8 

(Teudo  Achillis) 

Fig.  391. — Diaerara  showing  the  attachments  of  nauscles  of  leg.     Posterior  aspect.     OrijsiDS,  red;  insertions, 
blue,    .The  attachments  of  muscles  of  bones  of  foot  are  given  in  detail  in  Figs.  191  and  192. 

separated  by  a  synovial  bursa,  which,  in  some  cases,  commu- 
nicates with  the  cavity  of  the  knee-joint.  The  tendon  of  the 
outer  head  contains  a  sesamoid  fibrocartilage  (rarely  osseous), 
where  it  plays  over  the  corresponding  outer  condyle;  and 
one  is  occasionally  found  in  the  tendon  of  the  inner  head. 

The  Gastrocnemius  should  be  divided  across,  just  belo\? 
its  origin,  and  turned  downward,  in  order  to  expose  the  next 
two  muscles.  /'  --f  bursa  betwe 

FASCIA  AND 

The  Soleus  {m.  soleus)  is  a  broad  flat  muscle 
situated  immediately  beneath  the  Gastrocnemius.  It 
lias  received  its  name  from  its  resemblance  in  shape 
to  a  sole-fish.  It  arises  by  tendinous  fibres  from  the 
back  part  of  the  head  of  the  fibula  and  from  the  up- 
per third  of  the  posterior  surface  of  its  shaft;  from 
the  oblique  line  of  the  tibia  and  from  the  middle 
third  of  its  internal  border;  some  fibres  also  arise 
from  a  tendinous  arch  placed  between  the  tibial  and 
fibular  origins  of  the  muscle,  beneath  which  the 
popliteal  vessels  and  internal  popliteal  nerve  pass. 
to  an  aponeurosis    which  covers  the  posterior  surface  of   the  muscle,  and  this, 

34 


BURSA  BETWEEN 
TENDON  AND 
CALCANEUS 


-Bursae  of   the   tendo 
(Poirier  and  Charpy.) 


The  fibres  pass  backward 


530 


THE  MUSCLES  AND  FASCIA 


gradually  becoming  thicker  and  narrower,  joins  with  the  tendon  of  the  Gastroc- 
nemius, and  forms  with  it  the  tendo  Achillis. 

Relations. — By  its  superficial  surface,  with  the  Gastrocnemius  and  Plantaris;  by  its  deef 
surface,  with  the  Flexor  longus  digitorum,  Flexor  longus  hallucis,  Tibialis  posticus,  and  posterior 
tibial  vessels  and  nerve,  from  which  it  is  separated  by  the  transverse  intermuscular  septum  or 
deep  transverse  fascia  of  the  leg. 

The  Tendo  Achillis  {tendo  calcaneus),  the  common  tendon  of  the  Gastrocnemius 
and  Soleus,'  is  the  thickest  and  strongest  tendon  in  the  body.  It  is  about  six- 
inches  in  length,  and  commences  about  the  middle  of  the  leg,  but  receives  fleshy 
fibres  on  its  anterior  surface  nearly  to  its  lower  end.  Gradually  becoming  con- 
tracted below,  it  is  inserted  into  the  lower  part  of  the  posterior  surface  of  the 


Fig.  393. — Transverse  section  at  the  middle  of  the  leg.  In  front  of  the  interosseous  membrane  are  the  ante- 
rior tibial  vessels  and  nerve;  in  front  of  the  Soleus,  the  posterior  tibial  vessels  and  nerve;  and  close^to  the 
fibula,  the  peroneal  vessels.     (After  Braune.) 

calcaneus,  a  synovial  bursa  {bursa  tendinis  calcanei  [Achillis])  (Fig.  392)  being 
interposed  between  the  tendon  and  the  upper  part  of  this  surface.  The  tendon 
spreads  out  somewhat  at  its  lower  end,  so  that  its  narrowest  part  is  usually  about 
an  inch  and  a  half  above  its  insertion.  The  tendon  is  covered  by  the  fascia  and 
the  integument,  a  bursa  (bursa  subcutanea  calcanea)  (Fig.  392)  being  often  inter- 
posed between  the  tendon  and  the  fascia.  The  tendon  is  separated  from  the  deep 
muscles  and  vessels  by  a  considerable  interval  filled  up  with  areolar  and  adipose 
tissues.  Along  its  outer  side,  but  superficial  to  it,  is  the  external  saphenous  vein. 
The  Plantaris  {m.  plantaris)  is  an  extremely  diminutive  muscle  placed  between 
the  Gastrocnemius  and  Soleus,  and  remarkable  for  its  long  and  delicate  tendon. 


1  These  two  muscles  with  a  common  tendon  are  by  some  anatomists  classed  together  as  one  muscle,  the  Triceps 
surae,  the  two  heads  of  origin  of  the  Gastrocnemius  and  the  Soleus  constituting  the  three  heads  of  the  Triceps,  and 
the  tendo  Achillis  the  single  tendon  of  insertion. 


THE  POSTERIOR   TIBIOFIBULAR  REGION  531 

It  arises  from  the  lower  part  of  the  outer  prolongation  of  the  linea  aspera  and 
from  the  posterior  ligament  of  the  knee-joint.  It  forms  a  small  fusiform  belly, 
about  three  or  four  inches  in  length,  terminating  in  a  long  slender  tendon  which 
crosses  obliquely  between  the  two  muscles  of  the  calf,  and,  running  along  the  inner 
border  of  the  tendo  Achillis,  is  inserted  with  it  into  the  posterior  part  of  the  cal- 
Oaneus.  This  muscle  is  occasionally  double,  and  is  sometimes  wanting.  Occa- 
sionally its  tendon  is  lost  in  the  internal  annular  ligament  or  in  the  fascia  of  the  leg. 

Nerves. — The  Gastrocnemius  is  supplied  by  the  first  and  second  sacral  nerves,  and  the 
Plantaris  by  the  fourth  and  fifth  lumbar  and  first  sacral  nerves  through  the  internal  popliteal. 
The  Soleus  is  supplied  by  the  fifth  lumbar  and  first  and  second  sacral  nerves  through  the 
internal  popliteal  and  posterior  tibial. 

Actions. — The  muscles  of  the  calf  are  the  chief  Extensors  of  the  foot  at  the  ankle-joint.  They 
possess  considerable  power,  and  are  constantly  called  into  use  in  standing,  walking,  dancing, 
and  leaping;  hence,  the  large  size  they  usually  present.  In  walking,  these  muscles  draw  power- 
fully upon  the  calcaneus,  raising  the  heel,  and  with  it  the  entire  body,  from  the  ground;  the  body 
being  thus  supported  on  the  raised  foot,  the  opposite  limb  can  be  carried  forward.  In  standing, 
the  Soleus,  taking  its  fixed  point  from  below,  steadies  the  leg  upon  the  foot,  and  prevents  the 
body  from  falling  forward,  to  which  there  is  a  constant  tendency  from  the  superincumbent 
weight.  The  Gastrocnemius,  acting  from  below,  serves  to  flex  the  femur  upon  the  tibia,  assisted 
by  the  Popliteus.  The  Plantaris  is  the  rudiment  of  a  large  muscle  which  exists  in  some  of  the 
lower  animals  and  is  continued  over  the  os  calcis  to  be  inserted  into  the  plantar  fascia.  In  man 
it  is  an  accessory  to  the  Gastrocnemius,  extending  the  ankle  if  the  foot  is  free,  or  bending  the 
knee  if  the  foot  is  fixed.  Possibly,  acting  from  below,  by  its  attachment  to  the  posterior  liga- 
ment of  the  knee-joint,  it  may  pull  that  ligament  backward  during  flexion,  and  so  protect  it 
from  being  compressed  between  the  two  articular  surfaces. 

The  Deep  Layer  (Fig.  395). 

Popliteus.  Flexor  longus  digitorum. 

Flexor  longus  hallucis.  Tibialis  posticus. 

Dissection. — Detach  the  Soleus  from  its  attachment  to  the  fibula  and  tibia,  and  turn  it  down- 
ward, when  the  deep  layer  of  muscles  is  exposed,  covered  by  the  deep  transverse  fascia  of  the 
leg. 

The  deep  transverse  fascia  of  the  leg  is  a  transversely  placed,  intermuscular 
septum,  between  the  superficial  and  deep  muscles  in  the  posterior  tibiofibular 
region.  On  either  side  it  is  connected  to  the  margins  of  the  tibia  and  fibula. 
Above,  where  it  covers  the  Popliteus,  it  is  thick  and  dense,  and  receives  an  expan- 
sion from  the  tendon  of  the  Semimembranosus ;  it  is  thinner  in  the  middle  61  the 
leg,  but  below,  where  it  covers  the  tendons  passing  behind  the  malleoli,  it  is  thick- 
ened and  continuous  with  the  internal  annular  ligament. 

This  fascia  should  now  be  removed,  commencing  from  below  opposite  the  tendons,  and 
detaching  it  from  the  muscles  in  the  direction  of  their  fibres. 

The  Popliteus  (m.  popliteus)  (Fig.  388)  is  a  thin,  flat,  triangular  muscle,  which 
forms  part  of  the  floor  of  the  popliteal  space.  It  arises  by  a  strong  tendon,  about 
an  inch  in  length,  from  a  deep  depression  on  the  outer  side  of  the  external  condyle 
of  the  femur,  and  from  the  posterior  ligament  of  the  knee-joint.  The  muscle  is 
inserted  into  the  inner  two-thirds  of  the  triangular  surface  above  the  oblique  line 
on  the  posterior  surface  of  the  shaft  of  the  tibia,  and  into  the  tendinous  expansion 
covering  the  surface  of  the  muscle.  The  tendon  of  the  muscle  is  covered  by  that 
of  the  Biceps  femoris  and  by  the  external  lateral  ligament  of  the  knee-joint;  it 
grooves  the  posterior  border  of  the  external  semilunar  fibrocartilage,  and  is  invested 
by  the  synovial  membrane  of  the  knee-joint. 

Relations. — By  its  superficial  surface,  with  the  fascia  covering  it,  which  separates  it  from 
the  Gastrocnemius,  Plantaris,  popliteal  vessels,  and  internal  popliteal  nerve;  by  its  deep  surface, 
with  the  knee-joint  and  back  of  the  tibia. 


532 


THE  MUSCLES  AND  FASCIA 


The  Flexor  longus  hallucis  {in.  flexor  halliwis  longus)  is  situated  on  the  fibular 
side  of  the  leg,  and  is.  the  most  superficial  and  largest  of  the  three  next  muscles. 


illbO* 


-^  Tendons  of 

ERONEUS    LONGU6 
BRCVIS. 


Fig.  394. — Muac!e3  of  the  back  of  the  right  leg. 
Superficial  layer. 


Fig.  395. — Muscles  of  the  back  of  the 
right  leg.     Deep  layer. 


It  arises  from  the  lower  two-thirds  of  the  posterior  surface  of  the  shaft  of  the 
fibula,  with  the  exception  of  an  inch  at  its  lowest  part;  from  the  lower  part  of 
the  interosseous  membrane;  from  an  intermuscular  septum  between  it  and  the 


THE  POSTERIOR  TIBIOFIBULAR  REGION  533 

Peronei,  externally;  and  from  the  fascia  covering  the  Tibialis  posticus  internally. 
The  fibres  pass  obliquely  downward  and  backward,  and  terminate  in  a  tendon 
which  occupies  nearly  the  whole  length  of  the  posterior  surface  of  the  muscle. 
This  tendon  occupies  a  groove  on  the  posterior  surface  of  the  lower  end  of  the 
tibia;  it  then  lies  in  a  second  groove  on  the  posterior  surface  of  the  astragalus,  and 
finally  in  a  third  groove,  beneath  the  sustentaculum  tali  of  the  calcaneus,  and 
passes  into  the  sole  of  the  foot,  where  it  runs  forward  between  the  two  heads  of 
the  Flexor  brevis  hallucis,  and  is  inserted  into  the  base  of  the  last  phalanx  of  the 
great  toe  (Fig.  397).  The  grooves  in  the  astragalus  and  calcaneus,  which  contain 
the  tendon  of  the  muscle,  are  converted  by  tendinous  fibres  into  distinct  canals 
lined  by  synovial  membrane;  and  as  the  tendon  crosses  the  sole  of  the  foot,  it  is 
connected  to  the  Common  Flexor  by  a  tendinous  slip. 

Relations. — By  its  superficial  surface,  with  the  Soleus  and  tendo  Achillis,  from  which  it  is 
separated  by  the  deep  transverse  fascia ;  by  its  deep  surface,  with  the  fibula,  Tibialis  posticus, 
the  peroneal  vessels,  the  lower  part  of  the  interosseous  membrane,  and  the  ankle-joint;  by  its 
outer  border,  with  the  Peronei;  by  its  inner  border,  with  the  Tibialis  posticus  and  posterior  tibial 
vessels  and  nerve.  In  the  sole  of  the  foot  it  lies  above  the  Abductor  hallucis  and  Flexor  longus 
digitorura. 

The  Flexor  longus  digitorum  (??i.  flexor  digitorum  longus)  is  situated  on  the 
tibial  side  of  the  leg.  At  its  origin  it  is  thin  and  pointed,  but  gradually  increases 
in  size  as  it  descends.  It  arises  from  the  posterior  surface  of  the  shaft  of  the  tibia, 
immediately  below  the  oblique  line  to  within  three  inches  of  its  extremity,  internal 
to  the  tibial  origin  of  the  Tibialis  posticus;  some  fibres  also  arise  from  the  fascia 
covering  the  Tibialis  posticus.  The  fibres  terminate  in  a  tendon  which  runs  nearly 
the  whole  length  of  the  superficial  surface  of  the  muscle.  This  tendon  passes 
behind  the  internal  malleolus  in  a  groove,  common  to  it  and  the  Tibialis  posticus, 
but  separated  from  the  latter  by  a  fibrous  septum,  each  tendon  being  contained 
in  a  special  sheath  lined  by  a  separate  synovial  membrane.  It  then  passes  obliquely 
forward  and  outward,  superficial  to  the  internal  lateral  ligament,  into  the  sole  of 
the  foot  (Fig.  397),  where,  crossing  superficially  to  the  tendon  of  the  Flexor 
longus  hallucis,^  to  which  it  is  connected  by  a  strong  tendinous  slip,  it  becomes 
expanded,  is  joined  by  the  Flexor  accessorius,  and  finally  divides  into  four  tendons, 
which  are  inserted  into  the  bases  of  the  last  phalanges  of  the  four  lesser  toes,  each 
tendon  passing  through  a  fissure  in  the  tendon  of  the  Flexor  brevis  digitorum 
opposite  the  base  of  the  first  phalanges  (Fig.  396). 

Relations. — In  the  leg,  by  its  superficial  surface,  with  the  posterior  tibial  vessels  and  nerve, 
and  the  deep  transverse  fascia,  which  separates  it  from  the  Soleus  muscle;  by  its  deep  surface, 
•Kith  the  TilDia  and  Tibialis  posticus.  In  the  foot  it  is  covered  by  the  Abductor  hallucis  and 
Flexor  brevis  digitorum,  and  crosses  superficial  to  the  Flexor  longus  hallucis. 

The  Tibialis  posticus  (m.  tibialis  'posterior)  lies  between  the  two  preceding 
muscles,  and  is  the  most  deeply  seated  of  all  the  muscles  in  the  leg.  It  com- 
mences above  by  two  pointed  processes,  separated  by  an  angular  interval,  through 
which  the  anterior  tibial  vessels  pass  forward  to  the  front  of  the  leg.  It  arises 
from  the  whole  of  the  posterior  surface  of  the  interosseous  membrane,  excepting 
its  lowest  part,  from  the  outer  portion  of  the  posterior  surface  of  the  shaft  of  the 
tibia,  between  the  commencement  of  the  oblique  line  above,  and  the  junction 
of  the  middle  and  lower  third  of  the  shaft  below;  and  from  the  upper  two-thirds 
of  the  internal  surface  of  tlae  fibula;  some  fibres  also  arise  from  the  deep  transverse 
fascia  and  from  the  intermuscular  septa,  separating  it  from  the  adjacent  muscles 
on  each  side.  This  muscle,  in  the  lower  fourth  of  tlie  leg,  passes  in  front  of  the 
Flexor  longus  digitorum,  and  terminates  in  a  tendon  which  passes  tlirough  a  groove 
behind  the  inner  malleolus  with  the  tendon  of  that  muscle,  but  enclosed  in  a  separ- 

•  That  is,  in  the  order  of  dissection  of  the  sole  of  the  foot. 


634  THE  MUSCLES  AND  FASCIA 

ate  sheath;  it  then  passes  through  another  sheath,  over  the  internal  lateral  ligament 
into  the  foot,  and  then  beneath  the  inferior  calcaneoscaphoid  ligament.  Beyond 
this  sheath  the  tendon  passes  between  the  sustentaculum  tali  and  the  tubercle  of 
the  scaphoid  to  the  plantar  aspect  and  divides  into  two  main  slips.  The  stronrjer 
medial  slip  is  inserted  into  the  tubercle  of  the  scaphoid  and  into  the  internal  cunei- 
form and  sends  an  expansion  to  the  plantar  surface  of  the  sustentaculum  tali.  The 
weaker  lateral  slip  divides  into  lesser  slips,  which  are  inserted  into  the  middle  and 
external  cuneiform,  the  cuboid  and  the  base  of  the  second,  third,  and  fourth  meta- 
tarsal bones.  The  stronger  tendon  as  it  passes  over  the  scaphoid  contains  a 
sesamoid  bone.     A  bursa  is  often  situated  between  the  tendon  and  the  scaphoid. 

Relations. — By  its  superficial  surface,  with  the  Soleus,  from  which  it  is  separated  by  the 
deep  transverse  fascia,  the  Flexor  longus  digitonim,  the  posterior  tibial  vessels  and  nerve,  and 
the  peroneal  vessels;  by  its  dee-p  surface,  with  the  interosseous  ligament,  the  tibia,  fibula,  and 
ankle-joint. 

Nerves. — The  Popliteus  is  supplied  by  the  fourth  and  fifth  lumbar  and  first  sacral  nerves, 
through  the  internal  popliteal;  the  Flexor  longus  digitorum  and  Tibialis  posticus  by  the  fifth 
lumbar  and  first  and  second  sacral ;  and  the  Flexor  longus  hallucis  by  the  fifth  lumbar  and  first 
and  second  sacral  nerves  through  the  posterior  tibial. 

Actions. — The  Popliteus  assists  in  flexing  the  leg  upon  the  thigh;  when  the  leg  is  flexed,  it 
will  rotate  the  tibia  inward.  It  is  especially  called  into  action  at  the  commencement  of  the  act  of 
bending  the  knee,  inasmuch  as  it  produces  a  slight  inward  rotation  of  the  tibia,  M'hich  is  essen- 
tial in  tlie  early  stages  of  this  movement.  The  Tibialis  posticus  is  a  direct  Extensor  of  the  foot 
at  the  ankle-joint;  acting  in  conjunction  with  the  Tibialis  anticus,  it  turns  the  sole  of  the  foot 
inward  (i.  e.,  inverts  the  foot),  antagonizing  the  Peronei,  which  turn  it  outward  (evert  it).  In 
the  sole  of  the  foot  the  tendon  of  the  Tibialis  posticus  lies  directly  below  the  inferior  calcaneo- 
scaphoid ligament,  and  is  therefore  an  important  factor  in  maintaining  the  arch  of  the  foot. 
The  Flexor  longus  digitorum  and  Flexor  longus  hallucis  are  the  direct  Flexors  of  the  phalanges, 
and,  continuing  their  action,  extend  the  foot  upon  the  leg;  the_y  assist  the  Gastrocnemius  and  Soleus 
in  extending  the  foot,  as  in  the  act  of  walking  or  in  standing  on  tiptoe.  In  consequence  of  the 
oblique  direction  of  the  tendon  of  the  long  Flexor,  the  toes  would  be  drawn  inward  were  it  not 
for  the  Flexor  accessorius  muscle,  which  is  inserted  into  the  outer  side  of  its  tendon  and  draws 
it  to  the  middle  line  of  the  foot  during  its  action.  Taking  their  fixed  point  from  the  foot,  these 
muscles  serve  to  maintain  the  upright  posture  by  steadying  the  tibia  and  fibula  perpendicularly 
upon  the  ankle-joint.  They  also  serve  to  raise  these  bones  from  the  oblique  position  they  assume 
in  the  stooping  posture. 

7.  The  Fibular  Region  (Fig.  381). 

Peroneus  longus.  Peroneus  brevis. 

Dissection. — The  muscles  are  readily  exposed  by  removing  the  fascia  covering  their  surface, 
from  below  upward,  in  the  line  of  direction  of  their  fibres. 

The  Peroneus  longus  (in.  peronaeus  longus)  is  situated  at  the  upper  part  of 
the  outer  side  of  the  leg,  and  is  the  more  Superficial  of  the  two  muscles.  It  arises 
from  the  head  and  upper  two-thirds  of  the  outer  surface  of  the  shaft  of  the  fibula, 
from  the  deep  surface  of  the  fascia,  and  from  the  intermuscular  septa  between  it 
and  the  muscles  on  the  front,  and  those  on  the  back  of  the  leg,  occasionally  also 
by  a  few  fibres  from  the  outer  tuberosity  of  the  tibia.  Between  its  attachment 
to  the  head  and  to  the  shaft  of  the  fibula  there  is  a  small  interval  of  bone  from 
which  no  muscle  fibres  arise;  through  this  gap  the  external  popliteal  nerve  passes 
beneath  the  muscle.  The  muscle  terminates  in  a  long  tendon,  which  passes  be- 
hind the  outer  malleolus,  in  a  groove  common  to  it  and  the  tendon  of  the  Peroneus 
brevis,  behind  which  it  lies,  the  groove  being  converted  into  a  canal  by  a  fibrous 
band,  and  the  tendons  being  invested  by  a  common  synovial  membrane;  it  is 
then  reflected  obliquely  forward  across  the  outer  side  of  the  calcaneus,  below  its 
peroneal  tubercle,  being  contained  in  a  separate  fibrous  sheath,  lined  by  a  pro- 
longation of  the  synovial  membrane  which  lines  the  groove  behind  the  malleolus. 
Having  reached  the  outer  side  of  the  cuboid  bone,  it  runs  in  a  groove  on  the  under 


THE  POSTERIOR   TIBIOFIBULAR  REGION  535 

surface  of  that  bone,  which  is  converted  into  a  canal  by  the  long  calcaneocuboid 
ligament,  and  is  lined  by  a  synovial  membrane;  the  tendon  then  crosses  the  sole 
of  the  foot  obliquely,  and  is  inserted  into  the  outer  side  of  the  base  of  the  meta- 
tarsal bone  of  the  great  toe  and  the  internal  cuneiform  bone  (Figs.  397  and  398). 
Occasionally  it  sends  a  slip  to  the  base  of  the  second  metatarsal  bone.  The 
tendon  changes  its  direction  at  two  points — first,  behind  the  external  malleolus; 
secondly,  on  the  outer  side  of  the  cuboid  bone;  in  both  of  these  situations  the 
tendon  is  thickened,  and  in  the  latter  a  sesamoid  fibrocartilage,  or  sometimes  a 
bone,  is  usually  developed  in  its  substance. 

Relations. — By  its  superficial  surface,  with  the  fascia  and  integument;  by  its  deep  surface, 
with  the  fibula,  external  popHteal  nerve,  the  Peroneus  brevis,  calcaneus,  and  cuboid  bone;  by  its 
nnferior  border,  with  an  intermuscular  septum,  which  intervenes  between  it  and  the  Extensor 
longus  digitorum;  by  its  posterior  border,  with  an  intermuscular  septum,  which  separates  it  from 
the  Soleus  above  and  the  Flexor  longus  hallucis  below. 

The  Peroneus  brevis  (m.  peronaeus  brevis)  lies  beneath  the  Peroneus  longus, 
and  is  shorter  and  smaller  than  it.  It  arises  from  the  lower  two-thirds  of  the 
external  surface  of  the  shaft  of  the  fibula,  internal  to  the  Peroneus  longus,  and 
from  the  intermuscular  septa  separating  it  from  the  adjacent  muscles  on  the 
front  and  back  part  of  the  leg.  The  fibres  pass  vertically  downward,  and  termi- 
nate in  a  tendon  which  runs  in  front  of  that  of  the  preceding  muscle  through  the 
same  groove,  behind  the  external  malleolus,  being  contained  in  the  same  fibrous 
sheath  and  lubricated  by  the  same  synovial  membrane.  It  then  passes  through 
a  separate  sheath  on  the  outer  side  of  the  calcaneus,  above  that  for  the  tendon  of 
the  Peroneus  longus,  the  two  tendons  being  here  separated  by  the  peroneal  tuber- 
cle, and  is  finally  inserted  into  the  tuberosity  at  the  base  of  the  metatarsal  bone  of 
the  little  toe,  on  its  outer  side. 

Relations. — By  its  superficial  surface,  with  the  Peroneus  longus  and  the  fascia  of  the  leg 
and  foot;  by  its  deep  surface,  with  the  fibula  and  outer  side  of  the  os  calcis. 

Nerves. — The  Peroneus  longus  and  brevis  are  supplied  by  the  fourth  and  fifth  lumbar  and 
first  sacral  nerves  through  the  musculocutaneous  branch  of  the  external  popliteal  nerve. 

Actions. — The  Peroneus  longus  and  brevis  extend  the  foot  upon  the  leg,  in  conjunction  with 
the  Tibialis  posticus,  antagonizing  the  Tibialis  anticus  and  Peroneus  tertius,  which  are  Flexors 
of  the  foot.  The  Peroneus  longus  also  everts  the  sole  of  the  foot;  hence,  the  extreme  eversion 
occasionally  observed  in  fracture  of  the  lower  end  of  the  fibula,  where  that  bone  offers  no  resist- 
ance to  the  action  of  this  muscle.  From  the  oblique  direction  of  the  Peroneus  longus  tendon 
across  the  sole  of  the  foot  it  is  an  important  agent  in  the  maintenance  of  the  transverse  arch 
of  the  foot.  Taking  their  fixed  point  below,  the  Peronei  serve  to  steady  the  leg  upon  the  foot. 
This  is  especially  the  case  when  standing  upon  one  leg,  when  the  tendency  of  the  superincumbent 
weight  is  to  throw  the  leg  inward;  the  Peroneus  longus  overcomes  this  tendenc_v  by  drawing 
on  the  outer  side  of  the  leg,  and  thus  maintains  the  perpendicular  direction  of  the  limb. 

Applied  Anatomy. — The  student  should  now  consider  the  position  of  the  tendons  of  the 
various  muscles  of  the  leg,  their  relation  with  the  ankle-joint  and  surrounding  bloodvessels,  and 
especially  their  action  upon  the  foot,  as  their  rigidity  and  contraction  give  rise  to  one  or  other  of 
the  kinds  of  deformity  known  as  club-foot.  The  most  simple  and  common  deformity,  and  one 
that  is  rarely,  if  ever,  congenital,  is  the  talipes  equinus,  the  heel  being  raised  by  rigidity  and  con- 
traction of  the  Gastrocnemius  muscle,  and  the  patient  walking  upon  the  ball  of  the  foot.  In 
the  talipes  varus  the  foot  is  forcibly  adducted  and  the  inner  side  of  the  sole  raised,  sometimes 
to  a  right  angle  with  the  ground,  by  the  action  of  the  Tibialis  anticus  and  posticus.  In  the 
talipes  valgus  the  outer  edge  of  the  foot  is  raised  by  the  Peronei  muscles,  and  the  patient  walks 
on  the  inner  ankle.  In  the  talipes  calcaneus  the  toes  are  raised  by  the  Extensor  muscles,  the 
heel  is  depressed,  and  the  patient  walks  upon  it.  Other  varieties  of  deformity  are  met  with, 
as  the  talipes  equinovarus,  equinovalgus,  and  ealcaneovaUjus,  whose  names  sufficiently  indicate 
their  nature.  Of  these,  the  talipes  equinovarus  is  the  most  common  congenital  form;  the  heel 
is  raised  by  the  tendo  Achillis,  the  inner  border  of  the  foot  drawn  upward  by  the  Tibialis 
anticus,  the  anterior  two-thirds  twisted  inward  by  the  Tibialis  posticus,  and  the  arch  increased 
by  the  contraction  of  the  plantar  fascia,  so  that  the  patient  walks  on  the  middle  of  the  outer 
border  of  the  foot.  Each  of  these  deformities  may  sometimes  be  successfully  relieved  by  divi- 
sion of  the  opposing  tendons  and  fascia;  by  this  means  the  foot  regains  its  proper  position, 


536  THE  MUSCLES  AND  FASCIA 

and  the  tendons  subsequently  heal.  The  operation  is  easily  performed  by  putting  thecontracted 
tendon  upon  the  stretch,  and  dividing  it  by  means  of  a  narrow,  sharp-pointed  knife  inserted 
beneath  it.  Pes  caviis,  or  hollow  foot,  is  accentuation  of  the  longitudinal  arch.  Pes  planus,  or 
flat-foot,  has  been  discussed  on  page  349. 

Rupture  of  a  few  of  the  fibres  of  the  Gastrocnemius  may  take  place._  Rupture  of  the  Plantaris 
tendon  not  uncommonly  occurs,  especially  in  men  somewhat  advanced  in  life,  from  some  sudden 
exertion,  and  frequently  occurs  during  the  game  of  lawn  tennis,  and  is  hence  known  as  lawii- 
tennis  leg.  The  accident  is  accompanied  by  a  sudden  pain,  and  produces  a  sensation  as  if  the 
individual  had  been  struck  a  violent  blow  on'  the  part.  The  tendo  Achillis  is  also  sometimes  rup- 
.tured.  It  is  stated  that  John  Hunter  ruptured  his  tendo  Achillis  while  dancing  at  the  age  of  forty. 
The  bursa  interposed  between  the  posterior  surface  of  the  os  calcis  and  the  tendo  Achillis, 
just  above  the  point  of  insertion  of  the  tendon,  may  become  inflamed,  producing  a  disabling 
pain  {achillodynia,  or  Albert's  disease). 


V.  MUSCLES  AND   FASCIA  OF  THE  FOOT. 

The  fibrous  bands,  or  thickened  portions  of  the  fascia  of  the  leg,  which  bind  down  the  tendons 
in  front  of  and  behind  the  ankle  in  their  passage  to  the  foot,  are  termed  the  annular  ligaments, 
and  are  three  in  number — anterior,  internal,  and  external. 

The  Anterior  Annular  Ligament  (Fig.  390)  consists  of  a  superior  or  transverse 
portion  (ligamentum  transversum  cruris),  which  binds  down  the  Extensor  tendons 
as  they  descend  on  the  front  of  the  tibia  and  fibula;  and  an  inferior  or  Y-shaped 
portion  (ligamentum  cruciatum  cruris),  which  retains  them  in  connection  with 
the  tarsus,  the  two  portions  being  connected  by  a  thin  intervening  layer  of  fascia. 
The  transverse  portion  is  attached  externally  to  the  lower  end  of  the  fibula  and 
internally  to  the  tibia;  above  it  is  continuous  with  the  fascia  of  the  leg;  it  contains 
only  one' synovial  sheath,  for  the  tendon  of  the  Tibialis  anticus;  the  other  tendons 
and  the  anterior  tibial  vessels  and  nerve  passing  beneath  it,  but  without  any  dis- 
tinct synovial  sheath.  The  Y-shaped  portion  is  placed  in  front  of  the  ankle- 
joint,  the  stem  of  the  Y,  the  fundiform  ligament  of  Retzius,  being  attached  externally 
to  the  upper  surface  of  the  calcaneus,  in  front  of  the  depression  for  the  interosseous 
ligament;  it  is  directed  inward,  as  a  double  layer,  one  lamina  passing  in  front, 
and  the  other  behind,  the  tendons  of  the  Peroneus  tertius  and  Extensor  longus 
digitorum.  At  the  inner  border  of  the  latter  tendon  these  two  layers  join, 
forming  a  sheath  in  which  the  tendons  are  enclosed,  surrounded  by  a  synovial 
membrane.  From  the  inner  extremity  of  this  sheath  the  two  limbs  of  the  Y 
diverge;  one  passes  upward  and  inward,  to  be  attached  to  the  internal  malleolus, 
passing  over  the  Extensor  proprius  hallucis  and  the  vessels  and  nerves,  but  en- 
closing the  Tibialis  anticus  and  its  synovial  sheath  by  a  splitting  of  its  fibres.  The 
other  limb  extends  downward  and  inward  to  be  attached  to  the  inner  border  of 
the  plantar  fascia,  and  passes  over  the  tendons  of  the  Extensor  proprius  hallucis 
and  Tibialis  anticus  and  also  the -vessels  and  nerves.  These  two  tendons  are  con- 
tained in  separate  synovial  sheaths  situated  beneath  the  ligament. 

The  Internal  Annular  Ligament  (ligamentum  laciniatum)  is  a  strong  fibrous 
band  which  extends  from  the  inner  malleolus  above  to  the  internal  margin  of  the 
calcaneus  below,  converting  a  series  of  grooves  in  this  situation  into  canals  for  the 
passage  of  the  tendons  of  the  Flexor  muscles  and  vessels  into  the  sole  of  the  foot. 
It  is  continuous  by  its  upper  border  with  the  deep  fascia  of  the  leg,  and  by  its  lower 
border  with  the  plantar  fascia  and  the  fibres  of  origin  of  the  Abductor  hallucis 
muscle.  The  four  canals  which  the  ligament  completes  transmit,  counting  from 
before  backward,  first,  the  tendon  of  the  Tibialis  posticus;  second,  the  tendon  of 
the  Flexor  longus  digitorum;  third,  the  posterior  tibial  vessels  and  nerve,  which 
run  through  a  broad  space  beneath  the  ligament;  lastly,  in  a  canal  formed  partly  by 
the  astragalus,  the  tendon  of  the  Flexor  longus  hallucis.  The  canals  for  the  tendons 
are  lined  by  a  separate  synovial  membrane. 


THE  DORSAL  REGION  537 

The  External  Annular  Ligament  is  divided  into  two  portions — a  superior  portion 

(retinaculum  mm.  peronaeorum  su2)erius),  which  extends  from  the  extremity  of 
the  outer  malleohis  to  the  outer  surface  of  the  calcaneus;  it  binds  down  the  tendons 
of  the  Peroneus  longus  and  brevis  muscles  in  their  passage  behind  the  external 
malleolus.  The  two  tendons  are  enclosed  in  one  synovial  sac.  An  inferior  portion 
(retinacvlum  mm.  peronaeorum  inferius),  which  bridges  the  Peronei  on  the  side  of 
the  clacaneus  and  is  attached  to  the  bone  above  and  below  them. 

8.  The  Dorsal  Region  (Fig.  390). 

Extensor  brevis  digitorum. 

Fascia  (fascia  dorsalis  pedis). — The  fascia  on  the  dorsum  of  the  foot  is  a  thin 
membranous  layer  continuous  above  with  the  anterior  margin  of  the  annular 
ligament;  it  becomes  gradually  lost  opposite  the  heads  of  the  metatarsal  bones, 
and  on  each  side  blends  with  the  lateral  portions  of  the  plantar  fascia ;  it  forms  a 
sheath  for  the  tendons  placed  on  the  dorsum  of  the  foot.  On  the  removal  of  this 
fascia  the  muscle  and  tendons  of  the  dorsal  region  of  the  foot  are  exposed. 

The  Extensor  brevis  digitorum  (m.  extensor  digitorum  brevis)  (Fig.  390)  is 
a  broad  thin  muscle  which  arises  from  the  fore  part  of  the  upper  and  outer  sur- 
faces of  the  calcaneus,  in  front  of  the  groove  for  the  Peroneus  brevis,  from  the  exter- 
nal calcaneo-astragaloid  ligament,  and  from  the  common  limb  of  the  Y-shaped 
portion  of  the  anterior  annular  ligament.  It  passes  obliquely  across  the  dorsum 
of  the  foot,  and  terminates  in  four  tendons.  The  innermost,  which  is  the  largest, 
is  inserfed  into  the  dorsal  surface  of  the  base  of  the  first  phalanx  of  the  great  toe, 
crossing  the  dorsalis  pedis  artery;  the  other  three,  into  the  outer  sides  of  the  long 
Extensor  tendons  of  the  second,  third,  and  fourth  toes. 

Nerves. — It  is  supplied  by  the  anterior  tibial  nerve. 

Actions. — The  Extensor  brevis  digitorum  is  an  accessory  to  the  long  Extensor,  extending  the 
phalanges  of  the  four  inner  toes,  but  acting  only  on  the  first  phalanx  of  the  great  toe.  The 
obliquity  of  its  direction  counteracts  the  oblique  movement  given  to  the  toes  by  the  long 
Extensor,  so  that,  both  muscles  acting  together,  the  toes  are  evenly  extended. 


9.  The  Plantar  Region  (Figs.  396,  397). 

The  plantar  fascia  (aponeurosis  plantaris),  the  densest  of  all  the  fibrous  mem- 
branes, is  of  great  strength,  and  consists  of  pearly  white  glistening  fibres,  dis- 
posed, for  the  most  part,  longitudinally;  it  is  divided  into  a  central  and  two 
lateral  portions. 

The  central  portion,  the  thickest,  is  narrow  behind  and  attached  to  the  inner 
tubercle  of  the  calcaneus,  posterior  to  the  origin  of  the  Flexor  brevis  digitorum, 
and,  becoming  broader  and  thinner  in  front,  divides  near  the  heads  of  the  meta- 
tarsal bones  into  five  processes,  one  for  each  of  the  toes.  Each  of  these  processes 
divides  opposite  the  metatarsophalangeal  articulation  into  two  strata,  superficial 
and  deep.  The  superficial  stratum  is  inserted  into  the  skin  of  the  transverse 
sulcus  which  divides  the  toes  from  the  sole.  The  deeper  stratum  divides  into  two 
slips  which  embrace  the  sides  of  the  Flexor  tendons  of  the  toes,  and  blend  with  the 
sheaths  of  the  tendons,  and  laterally  with  the  transverse  metatarsal  ligament,  thus 
forming  a  series  of  arches  through  which  the  tendons  of  the  short  and  long  Flexors 
pass  to  the  toes.  The  intervals  left  between  the  five  processes  allow  the  digital 
vessels  and  nerves  and  the  tendons  of  the  Lumbricales  muscles  to  become  super- 
ficial. At  the  point  of  division  of  the  fascia  into  processes  and  slips  numerous 
transverse  fibres  are  superadded,  which  serve  to  increase  the  strength  of  the  fascia 


538  THE  MUSCLES  AND  FASCIA 

at  this  part  by  binding  the  processes  together  and  connecting  them  with  the  integu- 
ment. The  central  portion  of  the  plantar  fascia  is  continuous  with  the  lateral 
portions  at  each  side,  and  from  its  deep  surface  sends  upward  two  strong 
vertical  intermuscular  septa,  which  separate  the  middle  from  the  external  and 
internal  groups  of  plantar  muscles;  from  these,  again,  thinner  transverse  septa  are 
derived,  which  separate  the  various  layers  of  muscles  in  this  region.  The  deep 
surface  of  this  fascia  gives  attachment  behind  to  the  Flexor  brevis  digitorum  muscle. 

The  lateral  portions  of  the  plantar  fascia  are  thinner  than  the  central  division,  and 
cover  the  sides  of  the  foot.  The  outer  portion  covers  the  under  surface  of  the 
Abductor  minimi  digiti;  it  is  thick  behind,  thin  in  front,  and  extends  from  the 
calcaneus  to  the  base  of  the  fifth  metatarsal  bone,  to  the  outer  side  of  which  it  is 
attached;  it  is  continuous  internally  with  the  central  portion  of  the  plantar  fascia, 
and  externally  with  the  dorsal  fascia.  The  inner  portion  is  very  thin,  and  covers 
the  Abductor  hallucis  muscle;  it  is  attached  to  the  internal  annular  ligament,  and 
is  continuous  around  the  side  of  the  foot  with  the  dorsal  fascia,  and  externally  with 
the  middle  portion  of  the  plantar  fascia. 

The  muscles  in  the  plantar  region  of  the  foot  may  be  divided  into  three  groups, 
in  a  similar  manner  to  those  in  the  hand:  (1)  Those  of  the  internal  plantar  region 
are  connected  with  the  great  toe,  and  correspond  with  those  of  the  thumb;  (2) 
those  of  the  external  plantar  region  are  connected  with  the  little  toe,  and  corre- 
spond with  those  of  the  little  finger;  and  (3)  those  of  the  middle  plantar  region  are 
connected  with  the  tendons  intervening  between  the  two  former  groups.  But  in 
order  to  facilitate  the  dissection  of  these  muscles  it  will  be  found  more  convenient 
to  divide  them  into  four  layers,  as  they  present  themselves,  in  the  order  in  which 
they  are  successively  exposed. 

The   First  Layer. 

Abductor   hallucis.  Flexor   brevis   digitorum. 

Abductor  minimi  digiti. 

Dissection. — Remove  the  fascia  on  the  inner  and  outer  sides  of  the  foot,  commencing  in 
Sront  over  the  tendons  and  proceeding  backward.  The  central  portion  should  be  divided 
transversely  in  the  middle  of  the  foot,  and  the  two  flaps  dissected  forward  and  backward. 

The  Abductor  hallucis  {m.  abductor  hallucis)  lies  along  the  inner  border  of  the 
foot  and  covers  the  first  parts  of  the  plantar  vessels  and  nerves.  It  arises  from 
the  inner  tubercle  on  the  under  surface  of  the  calcaneus  (Fig.  396);  from  the 
internal  annular  ligament ;  from  the  plantar  fascia ;  and  from  the  intermuscular 
septum  between  it  and  the  Flexor  brevis  digitorum.  The  fibres  terminate  in  a 
tendon  which  is  iyiserted,  together  with  the  innermost  tendon  of  the  Flexor  brevis 
hallucis,  into  the  inner  side  of  the  first  phalanx  of  the  great  toe. 

The  Flexor  brevis  digitorum  {m.  flexor  digitorum  brevis)  lies  in  the  middle  of 
the  sole  of  the  foot,  immediately  beneath^  the  plantar  fascia,  with  which  it  is 
firmly  united.  Its  deep  surface  is  separated  from  the  extern.al  plantar  vessels 
and  nerves  by  a  thin  layer  of  fascia.  It  arises  by  a  narrow  tendinous  process, 
from  the  inner  tubercle  of  the  calcaneus  (Fig.  396),  from  the  central  part  of  the 
plantar  fascia,  and  from  the  intermuscular  septa  between  it  and  the  adjacent 
muscles.  It  passes  forward,  and  divides  into  four  tendons,  one  for  each  of  the 
four  outer  toes.  Opposite  the  bases  of  the  first  phalanges  each  tendon  divides 
into  two  slips,  to  allow  of  the  passage  of  the  corresponding  tendon  of  the  Flexc 
longus  digitorum ;  the  two  portions  of  the  tendon  then  unite  and  form  a  grooved 
channel  for  the  reception  of  the  accompanying  long  Flexor  tendon.     Finally, 

iThat  is,  in  order  of  dissection  of  tlie  sole  of  the  foot. 


THE  PLANTAR  REGION 


539 


they  divide  a  second  time,  to  be  inserted  into  the  middle  of  the  sides  of  the  second 
phalanges.  The  mode  of  division  of  the  tendons  of  the  Flexor  brevis  digitorum 
and  their  insertion  into  the  phalanges  is  analogous  to  the  division  and  insertion 
of  the  Flexor  sublimis  digitorum  in  the  hand. 


Fibrous  Sheaths  of  the  Flexor  Tendons.— These  are  not  so  well  marked  as  in  the  fingers. 
The  Flexor  tendons  of  the  toes  as  tliey  run  along  the  phalanges  are  retained  against  the  bones 
by  a  fibrous  sheath,  forming  osseoaponeurotic  canals.       These  sheaths  are  formed  by  strong 
fibrous  bands  which  arch  across  the  tendons  and  are 
attached  on  each  side  to  the  margins  of  the  phalan- 
ges.    Opposite  the  middle  of  the  proximal  and  sec- 
ond phalanges  the  sheath  is  very  strong,  and  the 
fibres  pass  transversely,  but  opposite  the  joints  it  is 
much  thinner,  and  the  fibres  pass  obliquely.     Each 
sheath  is  lined  by  a  synovial  membrane  which  is  re- 
flected upon  the  contained  tendon. 

The  Abductor  minimi  digiti  (m.  abductor 
digiti  quinti)  lies  along  the  outer  border  of 
the  foot,  and  is  in  relation  by  its  inner  mar- 
gin with  the  external  plantar  vessels  and 
nerves.  It  arises,  by  a  very  broad  origin, 
from  the  outer  tubercle  of  the  calcaneus, 
from  the  under  surface  of  the  calcaneus  be- 
tween the  two  tubercles,  from  the  fore  part 
of  the  inner  tubercle  (Fig.  396),  from  the 
plantar  fascia  and  the  intermuscular  septum, 
between  it  and  the  Flexor  brevis  digitorum. 
Its  tendon,  after  gliding  over  a  smooth  facet 
on  the  under  surface  of  the  base  of  the  fifth 
metatarsal  bone,  is  inserted  with  the  short 
Flexor  of  the  little  toe  into  the  outer  side  of 
the  base  of  the  first  phalanx  of  this  toe. 

Dissection. — The  muscles  of  the  superficial  layer 
shovild  be  divided  at  their  origin  by  inserting  the  . 
knife  beneath  each,  and  cutting  obliquely  backward, 
so  as  to  detach  them  from  the  bone;  they  should 
then  be  drawn  forward,  in  order  to  expose  the  sec- 
ond layer,  but  not  cut  away  at  their  insertion. 
The  two  layers  are  separated  by  a  thin  membrane, 
the  deep  plantar  fascia,  on  the  removal  of  which  is 
seen  the  tendon  of  the  Flexor  longus  digitorum,  the 
Flexor  accessorius,  the  tendon  of  tlie  Flexor  longus 
hallucis,  and  the  Lumbricales.  The  long  Flexor 
tendons  diverge  from  each  other  at  an  acute  angle; 
the  Flexor  longus  hallucis  runs  along  the  inner  side 
of  the  foot,  on  a  plane  superior  to  that  of  the  Flexor 
longus  digitorum,  the  direction  of  the  latter  being 
obliquely  outward. 


The  Second  Layer. 


Flexor  accessorius. 


Lumbricales. 


The  Flexor  accessorius  {m.  quadratus  plantae)  is  separated  from  the  muscles 
of  the  first  layer  by  the  external  plantar  vessels  and  nerves.  It  arises  by  two  heads, 
which  are  separated  from  each  other  by  the  long  plantar  ligament;  the  inner  or 
larger  head,  which  is  muscular,  arises  from  the  inner  concave  surface  of  the  cal- 


540 


THE  MUSCLES  AND  FASCIAE 


caneus  below  the  groove  which  lodges  the  tendon  of  the  Flexor  longus  digitorum; 
the  outer  head,  flat  and  tendinous,  arises  from  the  outer  surface  of  the  calcaneus,  in 
front  of  its  lesser  tubercle  (Fig.  397),  and  from  the  long  plantar  ligament;  the  two 
portions  join  at  an  acute  angle,  and  are  inserted  into  the  outer  margin  and  upper 
and  under  surfaces  of  the  tendon  of  the  Flexor  longus  digitorum,  forming  a  kind  of 
groove  in  which  the  tendon  is  lodged.^ 

The  Lumbricales   {vi.  lumbricales)  are  four  small  muscles  accessory  to  the 
tendons  of  the  Flexor  longus  digitorum;  they  arise  from  the  tendons  of  the  long 


FlQ  397  — Muscles  of  the  sole  of  the  right  foot. 
Second  layer. 


FiQ.  398.— Muscles  of  the  sole  of  the  right  foot. 
Third  layer. 


Flexor,  as  far  back  as  their  angle  of  division,  each  arising  from  two  tendons,  except 
the  internal  one.  Each  muscle  terminates  in  a  tendon,  which  passes  forward  on 
the  inner  side  of  the  four  lesser  toes  and  is  inserted  into  the  expansion  of  the  long 
Extensor  tendon  on  the  dorsum  of  the  first  phalanx  of  the  corresponding  toe. 

Dissection. — The  Flexor  tendons  should  be  divided  at  the  back  part  of  the  foot,  and  the 
riexor  accessorius  at  its  origin,  and  drawn  forward,  in  order  to  expose  the  third  layer. 


*  According  to  Turner,  the  fibres  of  the  Flexor  accessorius  end  : 
the  second,  third,  and  fourth  digits. 


aponeurotic  bands,  which  contribute  slips  to 


THE  PLANTAR  REGION  541 

The  Third  Layer. 

Flexor  brevis  hallucis.  Flexor  brevis  minimi  digiti. 

Adductor  obliquus  hallucis.  Adductor  transversus  hallucis. 

The  Flexor  brevis  hallucis  {vi.  flexor  halbwis  brevis)  arises,  by  a  pointed 
tendinous  process,  from  the  inner  part  of  the  under  surface  of  the  cuboid  bone, 
from  the  contiguous  portion  of  the  external  cuneiform,  and  from  the  prolongation 
of  the  tendon  of  the  Tibialis  posticus,  which  is  attached  to  that  bone.  The  muscle 
divides  in  front  into  two  portions  which  are  inserted  into  the  inner  and  outer  sides 
of  the  base  of  the  first  phalanx  of  the  great  toe,  a  sesamoid  bone  being  developed 
in  each  tendon  at  its  insertion.  The  inner  portion  of  this  muscle  is  blended  with 
the  Abductor  hallucis  previous  to  its  insertion,  the  outer  portion  with  the  Adductor 
obliquus  hallucis,  and  the  tendon  of  the  Flexor  longus  hallucis  lies  in  a  gi'oove 
between  them. 

The  Adductor  obliquus  hallucis  (cafut  ohliquum  m.  adductoris  hallucis)  is  a 
large,  thick,  fleshy  mass  passing  obliquely  across  the  foot  and  occupying  the  hollow 
space  between  the  four  inner  metatarsal  bones.  It  arises  from  the  tarsal  extrem- 
ities of  the  second,  third,  and  fourth  metatarsal  bones,  and  from  the  sheath  of  the 
tendon  of  the  Peroneus  longus,  and  is  inserted,  together  with  the  outer  portion  of 
the  Flexor  brevis  hallucis,  into  the  outer  side  of  the  base  of  the  first  phalanx  of  the 
great  toe. 

The  small  muscles  of  the  great  toe,  the  Abductor,  Flexor  brevis,  Adductor  obliquus,  and 
Adductor  transversus,  like  the  similar  muscles  of  the  thumb,  give  off  fibrous  expansions,  at  their 
insertions,  to  blend  with  the  long  Extensor  tendon. 

The  Adductor  transversus  hallucis  (caput  trangversum  m.  adductoris  hallucis) 
is  a  narrow,  flat,  muscular  fasciculus,  stretched  transversely  across  the  heads  of 
the  metatarsal  bones,  between  them  and  the  Flexor  tendons.  It  arises  from  the 
inferior  metatarsophalangeal  ligaments  of  the  three  outer  toes,  sometimes  only 
from  the  third  and  fourth  and  from  the  transverse  ligament  of  the  metatarsus; 
and  is  inserted  into  the  outer  side  of  the  first  phalanx  of  the  great  toe,  its  fibres 
being  blended  with  the  tendon  of  insertion  of  the  Adductor  obliquus  hallucis. 

The  Flexor  brevis  minimi  digiti  {m.  flexor  digiti  quinti  brevis)  lies  on  the  meta- 
tarsal bone  of  the  little  toe,  and  much  resembles  one  of  the  Interossei.  It  arises 
from  the  base  of  the  metatarsal  bone  of  the  little  toe,  and  from  the  sheath  of  the 
Peroneus  longus;  its  tendon  is  inserted  into  the  base  of  the  first  phalanx  of  the 
little  toe  on  its  outer  side.  Occasionally  some  of  the  deeper  fibres  of  the  muscle 
are  inserted  into  the  outer  part  of  the  distal  half  of  the  fifth  metatarsal  bone; 
these  are  described  by  some  as  a  distinct  muscle,  the  Opponens  minimi  digiti. 

The  Fourth  Layer.         * 

The  Interossei. 

The  Interossei  muscles  (mm.  interossei)  in  the  foot  are  similar  to  those  in  the 
hand,  with  this  exception,  that  they  are  grouped  around  the  middle  line  of  the 
second  digit,  instead  of  the  middle  line  of  the  third  digit,  as  in  the  hand.  They 
are  seven  in  number,  and  consist  of  two  groups.  Dorsal  and  Plantar. 

The  Dorsal  Interossei  (???.  interossei  dorsales),  four  in  number,  are  situated  be- 
tween the  metatarsal  bones.  They  are  bipenniform  muscles,  arising  by  two  heads 
from  the  adjacent  sides  of  the  metatarsal  bones,  between  which  they  are  placed; 
their  tendons  are  inserted  into  the  bases  of  the  first  phalanges,  and  into  the  apon- 
eurosis of  the  corresponding  slip  of  the  common  Extensor  tendon.  In  the  angular 
interval  left  between  the  heads  of  each  muscle  at  its  posterior  extremity  the  per- 
forating arteries  pass  to  the  dorsum  of  the  foot,  except  in  the  First  interosseous 
muscle,  where  the  interval  allows  the  passage  of  the  communicating  branch  of  the 


642 


THE  MUSCLES  AND  FASCIA 


dorsalis  pedis  artery.  The  First  dorsal  interosseous  muscle  is  inserted  into  the 
inner  side  of  the  second  toe;  the  other  three  are  inserted  into  the  outer  sides  of 
the  second,  third,  and  fourth  toes. 

The  Plantar  Interossei  (m.  interossei  plantares),  three  in  number,  lie  beneath, 
rather  than  between,  the  metatarsal  bones.  They  are  single  muscles,  and  each 
arises  from  but  one  metatarsal  bone.  They  arise  from  the  base  and  inner  sides 
of  the  shaft  of  the  third,  fourth,  and  fifth  metatarsal  bones,  and  are  inserted  into 
the  inner  sides  of  the  bases  of  the  first  phalanges  of  the  same  toes,  and  into  the 
aponeurosis  of  the  corresponding  slip  of  the  common  Extensor  tendon. 

Nerves. — The  Flexor  brevis  digitorum,  the  Flexor  brevis  and  Abductor  hallucis,  and  the 
innermost  Lumbrical  are  supplied  by  the  medial  plantar  nerve.  All  the  other  muscles  in  the 
sole  of  the  foot  by  the  lateral  plantar.  The  First  dorsal  interosseous  muscle  frequently  receives 
an  extra  filament  from  the  internal  branch  of  the  anterior  tibial  nerve  on  the  dorsum  of  the  foot, 
and  the  Second  dorsal  interosseous  a  twig  from  the  external  bi'anch  of  the  same  nerve. 

Actions. — All  the  muscles  of  the  foot  act  upon  the  toes,  and  for  purposes  of  description  as 
regard  their  action  may  be  grouped  as  Abductors,  Adductors,  Flexors,  or  Extensors.  The  Abduc- 
tors are  the  Dorsal  interossei,  the  Abductor  hallucis,  and  the  Abductor  minimi  digiti.  The  Dorsal 
interossei  are  Abductors  from  an  imaginary  line  passing  through  the  axis  of  the  second  toe,  so  that 
the  first  muscle  draws  the  second  toe  inward,  toward  the  great  toe;  the  second  muscle  draws  the 


Fig.  399. — The  Dorsal  interossei.  Left  foot.  The 
line  marked  by  an  *  is  that  from  which  abduction  is 
performed. 


Fig.  400. — The  Plantar  interossei.  Left  foot.  The 
line  marked  by  an  *  is  that  to  which  adduction  is 
made. 


same  toe  outward ;  the  third  draws  the  third  toe,  and  the  fourth  draws  the  fourth  toe,  in  the  same 
direction.  Like  the  Interossei  in  the  hand,  they  also  help  to  flex  the  proximal  phalanges  and  to 
extend  the  two  terminal  phalanges.  The  Abductor  hallucis  abducts  the  great  toe  from  the  others, 
and  also  flexes  the  proximal  phalanx  of  this  toe.  And  in  the  same  way  the  action  of  the  Abductor 
minimi  digiti  is  twofold — as  an  Abductor  of  this  toe  from  the  others,  and  also  as  a  Flexor  of  the  prox- 
imal phalanx.  The  Adductors  are  the  Plantar  interossei,  the  Adductor  obliquus  hallucis,  and  the 
Adductor  transversus  hallucis.  The  Plantar  interosseous  muscles  adduct  the  third,  fourth,  and 
fifth  toes  toward  the  imaginary  line  passing  through  the  second  toe,  and  by  means  of  their  inser- 
tion into  the  aponeurosis  of  the  Extensor  tendon  they,  with  the  Dorsal  interossei,  flex  the  prox- 
imal phalanges  and  extend  the  two  terminal  phalanges.  The  Adductor  obliquus  hallucis  is 
chiefly  concerned  in  adducting  the  great  toe  toward  the  second  one,  but  also  assists  in  flexing 
this  toe.  The  Adductor  transversus  hallucis  approximates  all  the  toes,  and  thus  increases  the 
curve  of  the  transverse  arch  of  the  metatarsus.  The  Flexors  are  the  Flexor  brevis  digitorum,  the 
Flexor  accessorius,  the  Flexor  brevis  hallucis,  the  Flexor  brevis  minimi  digiti,  and  the  Lum- 
bricales.    The  Flexor  brevis  digitorum  flexes  the  second  phalanges  upon  the  first,  and,  con- 


SURFACE  FORM  OF  THE  LOWER  EXTBEMFFY  543 

tinuing  its  action,  may  flex  the  first  phalanges  also  and  bring  the  toes  together.  The  Flexor 
accessorius  assists  the  long  Flexor  of  the  toes,  and  converts  the  oblique  pull  of  the  tendons  of 
th;u  muscle  into  a  direct  backward  jmll  upon  the  toes.  The  Flexor  brevis  halluces  flexes  and 
slightly  adducts  the  first  phalanx  of  the  great  toe.  The  Plexor  brevis  minimi  digiti  flexes  the 
little  toe  and  draws  its  metatarsal  bone  downward  and  inward.  The  Lumbricales,  like  the 
corresponding  muscles  in  the  hand,  assist  in  flexing  the  proximal  |ihalanx,  and  by  their  insertion 
into  the  long  Extensor  tendon  aid  in  straightening  the  two  terminal  phalanges.  The  only  muscle 
in  the  Extensor  group  is  the  Extensor  brevis  digitorum.  It  extends  tlie  first  phalanx  of  the  great 
toe,  and  assists  the  long  Extensor  in  extending  the  next  three  toes,  and  at  the  same  time  gives  to 
the  toes  an  outward  direction  when  they  are  extended. 

SURFACE  FORM  OF  THE  LOWER  EXTREMITY. 

Of  the  muscles  of  the  thigh,  those  of  the  iliac  region  have  no  influence  on  surface  form,  while 
those  of  the  anterior  femoral  region,  being  to  a  great  extent  superficial,  largely  contribute  to  the 
surface  form  of  this  part  of  the  body.     The  Tensor  fasciae  femoris  produces  a  broad  elevation 
immediately  below  the  anterior  portion  of  the  crest  of  the  ilium  and  behind  the  anterior  supe- 
rior spinous  process.     From  its  lower  border  a  longitudinal  groove,  corresponding  to  the  ilio- 
tibial  band,  may  be  seen  running  down  the  outer  side  of  the  thigh  to  the  outer  side  of  the  knee- 
joint.     The  Sartorius  muscle,  when  it  is  brought  into  action  by  flexing  the  leg  on  the  thigh 
and  the  thigh  on  the  pelvis,  and  rotating  the  thigh  outward,  presents  a  well-marked  surface 
form.    At  its  upper  part,  where  it  constitutes  the  outer  boundary  of  Scarpa's  triangle,  it  forms 
a  prominent  oblique  ridge,  which  becomes  changed  into  a  flattened  plane  below,  and  this  grad- 
ually merges  in  a  general  fulness  on  the  inner  side  of  the  knee-joint.     When  the  Sartorius  is 
not  in  action,  a  depression  exists  between  the  Quadriceps  extensor  and  the  Adductor  muscles, 
running  obliquely  downward  and  inward  from  the  apex  of  Scarpa's  triangle  to  the  inner  side 
of  the  knee,  which  depression  corresponds  to  this  muscle.     In  the  depressed  angle  formed  by 
the  divergence  of  the  Sartorius  and  Tensor  fasciae  femoris  muscles,  just  below  the  anterior 
superior  spinous  process  of  the  ilium,  the  Rectus  femoris  muscle  appears,  and,  below  this,  deter- 
mines to  a  great  extent  the  convex  form  of  the  front  of  the  thigh.     In  a  well-developed  subject 
the  borders  of  the  muscle,  when  in  action,  are  clearly  to  be  defined.     The  Vastus  externus 
forms  a  long  flattened  plane  on  the  outer  side  of  the  thigh,  traversed  by  the  longitudinal  gruo\'e 
formed  by  the  iliotibial  band.     The  Vastus  intemus,  on  the  inner  side  of  the  lower  half  of  the 
thigh,  gives  rise  to  a  considerable  prominence,  which  increases  toward  the  knee  and  terminates 
somewhat  abruptly  in  this  situation  with  a  full,  curved  outline.     The  Crureus  and  Subcrureus 
are  completely  hidden,  and  do  not  directly  influence  surface  form.     The  Adductor  muscles, 
constituting  the  internal  femoral  group,  are  not  to  be  individually  distinguished  from  each 
other,  with  the  exception  of  the  upper  tendon  of  the  Adductor  longus  and  the  lower  tendon  of 
the  Adductor  magnus.     The  upper  tendon  of  the  Adductor  longus,  when  the  muscle  is  in  action, 
stands  out  as  a  prominent  ridge,  which  runs  oblicjuely  downward  and  outw'ard  from  the  neigh-  > 
borhood  of  the  pubic  spine,  and  forms  the  inner  boundary  of  a  flattened  triangular  space  on 
the  upper  part  of  the  front  of  the  thigh,  known  as  Scarpa's  triangle.     The  lower  tendon  of  the 
Adductor  magnus  can  be  distinctly  felt  as  a  short  ridge  extending  down  to  the  Adductor  tubercle 
on  the  internal  condyle,  between  the  Sartorius  and  Vastus  internus.     The  Adductor  group 
of  muscles  fills  in  the  triangular  space  at  the  upper  part  of  the  thigh,  formed  between  the  oblique 
femur  and  the  pelvic  wall,  and  to  them  is  due  the  contour  of  the  inner  border  of  the  thigh,  the 
Gracilis  largely  contributing  to  the  smoothness  of  the  outline.     These  muscles  are  not  marked 
off  on  the  surface  from  those  of  the  posterior  femoral  region  by  any  intermuscular  marking,  but 
on  the  outer  side  of  the  thigh  these  latter  muscles  are  defined  from  the  Vastus  externus  by  a 
distinct  marking,  corresponding  to  the  external  intermuscular  septum.     The  Gluteus  maximus 
and  a  part  of  the  Gluteus  medius  are  the  only  muscles  of  the  buttock  which  influence  surface 
form.     The  other  part  of  the  Gluteus  medius,  the  Gluteus  minimus,  and  the  external  Rotators 
are  completely  hidden.     The  Gluteus  maximus  forms  the  full  rounded  outline  of  the  buttock; 
it  is  more  prominent  behind,  compressed  in  front,  and  terminates  at  its  tendinous  insertion  in 
a  depression  immediately  behind  the  great  trochanter.     Its  lower  border  does  not  correspond 
to  the  gluteal  fold,  but  is  much  more  oblique,  being  marked  by  a  line  drawn  from  the  side  of 
the  coccyx  to  the  junction  of  the  upper  with  the  lower  two-thirds  of  the  thigh  on  the  outer  side. 
From  beneath  the  lower  margin  of  this  muscle  the  Hamstring  muscles  appear,  at  first  narrow 
and  not  well  marked,  but  as  they  descend    becoming  more  prominent  and  widened  out,  and 
eventually  dividing  into  two  well-marked  ridges,  which  constitute  the  upper  boundai'ies  of  the 
popliteal  space,  and  are  formed  by  the  tendons  of  the  inner  and  outer  Hamstring  muscles, 
respectively.     In  the  upper  part  of  the  thigh  these  muscles  are  not  to  be  individually  distin- 
guished from  each  other,  but  lower  dow-n  the  separation  between  the  Semitendinosus  and  Semi- 
membranosus is  denoted  by  a  slight  intermuscular  marking.     The  external  hamstring  tendon, 
formed  by  the  Biceps  is  seen  as  a  thick  cord  running  down  to  the  head  of  the  fibula.     The  inner 
Hamstring  tendons  comprise  the  Semitendinosus,  the  Semimembranosus,  and  the  Gracilis. 
The  Seniit(mdinosus  is  the  most  internal  of  these,  and  can  be  felt,  in  certain  positions  of  the 


544  THE  MUSCLES  AND  FASCIA 

limb,  as  a  sharp  cord;  the  Semimembranosus  is  thick,  and  the  Gracilis  is  situated  a  little  farther 
forward  than  the  other  two.  All  (lie  iimsilcs  on  the  front  of  the  leg  appear  to  a  certain  extent 
somewhere  on  the  surface,  but  the  form  of  (his  region  is  mainly  dependent  upon  the  Tibialis 
anticus  and  the  Extensor  longus  digitorum.  The  Tibialis  anticus  is  well  marked,  and  presents 
a  fusiform  enlargement  at  the  outer  side  of  the  tibia,  and  projects  beyond  the  crest  of  the  shin 
bone.  Frotn  the  muscular  mass  its  tendons  may  be  traced  downward,  standing  out  boldly, 
when  the  muscle  is  in  action,  on  the  front  of  the  tibia  and  ankle-joint,  and  coursing  down  to  its 
insertion  along  the  inner  border  of  the  foot.  A  well-marked  groove  separates  this  muscle  exter- 
nally from  the  Extensor  longus  digitorum,  which  fills  up  the  rest  of  the  space  between  the  upper 
part  of  the  shaft  of  the  tibia  and  fibula.  It  does  not  present  so  bold  an  outline  as  the  Tibialis 
anticus,  and  its  tendon  below,  diverging  from  the  tendon  of  the  Tibialis  anticus,  forms  with  the 
latter  a  sort  of  plane,  in  which  may  be  seen  the  tendon  of  the  Extensor  proprius  hallucis.  A 
groove  on  the  outer  side  of  the  Extensor  longus  digitorum,  seen  most  plainly  when  the  muscle 
is  in  action,  separates  the  tendon  from  a  slight  eminence  corresponding  to  the  Peroneus  tertius. 
The  fleshy  fibres  of  the  Peroneus  longus  are  strongly  marked  at  the  upper  part  of  the  outer 
side  of  the  leg,  especially  when  the  muscle  is  in  action.  It  forms  a  bold  swelling,  separated  by 
furrows  from  the  Extensor  longus  digitorum  in  front  and  the  Soleus  behind.  Below,  the  fleshy 
fibres  terminate  abruptly  in  a  tendon  which  overlaps  the  more  flattened  form  of  the  Peroneus 
brevis.  At  the  external  malleolus  the  tendon  of  the  Peroneus  brevis  is  more  marked  than  that 
of  the  Peroneus  longus.  On  the  dorsum  of  the  foot  the  tendons  of  the  Extensor  muscles, 
emerging  from  beneath  the  anterior  annular  ligament,  spread  out  and  can  be  distinguished 
in  the  following  order:  The  most  internal  and  largest  is  the  Tibialis  anticus,  then  the  Extensor 
proprius  hallucis;  next  comes  the  Extensor  longus  digitorum,  dividing  into  four  tendons  to 
the  four  outer  toes;  and  lastly,  most  externally,  is  the  Peroneus  tertius.  The  flattened  form  of 
the  dorsum  of  the  foot  is  relieved  by  the  rounded  outline  of  the  fleshy  belly  of  the  Extensor 
brevis  digitorum,  which  forms  a  soft  fulness  on  the  outer  side  of  the  tarsus  in  front  of  the  external 
malleolus,  and  by  the  Dorsal  interossei,  which  bulge  between  the  metatarsal  bones.  At  the 
back  of  the  knee  is  the  popliteal  space,  bounded  above  by  the  tendons  of  the  Hamstring  muscle; 
below,  by  the  two  heads  of  the  Gastrocnemius.  Below  this  space  is  the  prominent  fleshy  mass 
of  the  calf  of  the  leg,  produced  by  the  Gastrocnemius  and  Soleus.  When  these  muscles  are 
in  action,  as  in  standing  on  tiptoe,  the  borders  of  the  Gastrocnemius  are  well  defined,  presenting 
two  curved  lines,  which  converge  to  the  tendon  of  insertion.  Of  these  borders,  the  inner  is 
more  prominent  than  the  outer.  The  fieshy  mass  of  the  calf  terminates  somewhat  abruptly 
below  in  the  tendo  Achillis,  which  stands  out  prominently  on  the  lower  part  of  the  back  of  the 
leg.  It  presents  a  somewhat  tapering  form  in  the  upper  three-fourths  of  its  extent,  but  widens 
out  slightly  below.  When  the  muscles  of  the  calf  are  in  action,  the  lateral  portions  of  the  Soleus 
may  be  seen,  forming  curved  eminences,  of  which  the  outer  is  the  longer,  on  either  side  of  the 
Gastrocnemius.  Behind  the  inner  border  of  the  lower  part  of  the  shaft  of  the  tibia  a  well- 
marked  ridge,  produced  by  the  tendon  of  the  Tibialis  posticus,  is  visible  when  this  muscle  is  in 
a  state  of  contraction.  On  the  sole  of  the  foot  the  superficial  layer  of  muscles  influences  surface 
form;  the  Abductor  minimi  digiti  most  markedly.  This  muscle  forms  a  narrow  rounded 
elevation  along  the  outer  border  of  the  foot,  while  the  Abductor  hallucis  does  the  same,  though 
to  a  less  extent,  on  the  inner  side.  The  Flexor  brevis  digitorum,  botmd  down  by  the  plantar 
fascia,  is  not  very  apparent;  it  produces  a  flattened  form,  covered  by  the  thickened  skin  of  the 
sole,  which  is  here  throwm  into  numerous  wrinkles. 

APPLIED   ANATOMY  OF  THE   LOWER  EXTREMITY. 

The  student  should  now  consider  the  efi^ects  produced  by  the  action  of  the  various  muscles 
in  fractures  of  the  bones  of  the  lower  extremity.  The  more  common  forms  of  fractures  are 
selected  for  illustration  and  description. 

In  fracture  of  the  neck  of  the  femur  internal  to  the  capsular  ligament  (Fig.  401)  the  charac- 
teristic marks  are  slight  shortening  of  the  limb  and  eversion  of  the  foot,  neither  of  which  symp- 
toms occurs,  however,  in  certain  cases  until  some  time  after  the  injury.  The  eversion  is  caused 
by  the  weight  of  the  limb  rotating  it  outward.  The  shortening  is  produced  by  the  action  of 
the  Glutei,  and  by  the  Rectus  femoris  in  front  and  the  Biceps,  Semitendinosus,  and  Semimem- 
branosus behind. 

In  fracture  of  the  femur  just  below  the  trochanters  (Fig.  402)  the  upper  fragment,  the  portion 
chiefly  displaced,  is  tilted  forward  almost  at  right  angles  with  the  pelvis  by  the  combined  action 
of  the  Psoas  and  Iliacus,  and,  at  the  same  time,  everted  and  drawm  outward  by  the  external 
Rotator  and  Glutei  muscles,  causing  a  marked  prominence  at  the  upper  and  outer  side  of  the 
thigh,  and  much  pain  from  the  bruising  and  laceration  of  the  muscles.  The  limb  is  shortened, 
in  consequence  of  the  lower  fragment  being  drawn  upward  by  the  Rectus  in  front,  and  the  Biceps, 
Semimembranosus,  and  Semitendinosus  behind,  and  is  at  the  same  time  everted.  This  fracture 
may  be  reduced  by  direct  relaxation  of  all  the  opposing  muscles,  to  effect  which  the  limb  shoidd 
be  put  up  in  such  a  manner  that  the  thigh  is  flexed  on  the  pelvis  and  the  leg  on  the  thigh. 

Oblique  fracture  of  the  femur  immediately  above  the  condyles  (Fig.  403)  is  a  formidable  injury, 
and  attended  with  considerable  displacement.     On  examination  of  the  limb  the  lower  frag- 


APPLIED  ANATOMY  OF  THE  LOWER  EXTREMITY 


545 


ment  may  be  felt  deep  in  the  popliteal  space,  being  drawn  backward  by  the  Gastrocnemius 
and  Plantaris  muscles,  and  upward  by  the  Hamstring  and  Rectus  femoris  muscles.     The  pointed 


Fig.  403. — Fracture  of  the  femur 
above  the  condyles. 


Fig.  404. — Fracture  of 
the  patella. 


546 


THE  2IUSCLES  AND  FASCIA 


end  of  the  upper  fragments  is  drawn  inward  by  the  Pectineus  and  Adductor  muscles,  and  tilted 
forward  by  the  Psoas  and  Iliacus,  piercing  the  Rectus  muscle  and  occasionally  the  integument. 
The  greatest  care  is  requisite  in  keeping  the  pointed  extremity  of  the  upper  fragment  in  proper 
position;  otherwise,  after  union  of  the  fracture,  the  power  of  extension  of  the  limb  is  partially 
destroyed  from  the  Rectus  femoris  muscle  being  held  down  by  the  fractured  end  of  the  bone, 
and  from  the  patella,  when  elevated,  being  drawn  upward  against  the  projecting  fragment. 

In  fracture  of  the  patella  (Fig.  404)  the  fragments  are  separated  by  the  effusion  whichtakes 
place  into  the  joint,  and  by  the  action  of  the  Quadriceps  extensor;  the  extent  of  separation  of 
the  two  fragments  depending  upon  the  degree  of  laceration  of  the  ligamentous  structures  around 
the  bone. 

The  tibia  is  fractured  most  commonly  by  indirect  force  at  the  junction  of  the  middle  third 
with  the  lower  third  of  the  shaft.  Compound  fractures  are  more  common  in  the  leg  than 
in  any  other  region  of  the  body  because  the  tibia  is  such  a  superficial  bone  and  is  so  much, 
exposed  to  injury.     Most  fractures  from  indirect  force  are  oblique. 

In  oblique  fracture  of  the  shaft  of  the  tibia  (Fig.  405),  if  the  fracture  has  taken  place  obliquely 
from  above,  downward  and  forward,  the  fragments  override  each  other,  the  lower  fragments 
being  drawn  backward  and  upward  by  the  powerful  action  of  the  muscles  of  the  calf;  the 
pointed  extremity  of  the  upper  fragment  projects  forward  immediately  beneath  the  integu- 
ment, often  protruding  through  it  and  rendering  the  fracture  a  compound  one.  If  the  direc- 
tion of  the  fractui'e  is  the  reverse  of  that  shown  in  the  figure,  the  pointed  extremity  of  the  lower 
fragment  projects  forward,  riding  upon  the  lower  end  of  the  upper  one.  By  bending  the  knee, 
which  relaxes  the  opposing  muscles,  and  making  extension  from  the  ankle  and  counterexten- 
sion  at  the  knee,  the  fragments  may  be  brought  into  apposition. 


Fig.  406. — Fracture  of  the  fibula,  with  dislocation  of 
the  foot  outward — "Pott's  fracture." 


Fracture  of  the  fibula  tvith  dislocation  of  the  foot  outward  (Fig.  406),  commonly  known  as 
Pott's  fracture,  is  one  of  the  most  frequent  injuries  of  the  ankle-joint.  The  fibula  is  fractured 
about  three  inches  above  the  ankle;  in  addition  to  this  the  internal  malleolus  is  broken  off, 
or  the  deltoid  ligament  torn  through,  and  the  end  of  the  tibia  displaced  from  the  corresponding 
surface  of  the  astragalus.  The  foot  is  markedly  everted,  and  the  sharp  edge  of  the  upper  end 
of  the  fractured  malleolus  presses  strongly  against  the  skin;  at  the  same  time,  the  heel  is  drawn 
up  by  the  muscles  of  the  calf.  This  injury  can  generally  be  reduced  by  flexing  the  leg  at  right 
angles  with  the  thigh,  which  relaxes  all  the  opposing  muscles,  and  by  making  extension  from 
the  ankle  and  counterextension  at  the  knee. 


THE  VASCULAR  SYSTEMS. 


rpHE  vascular  systems  comprise  the  heart  and   bloodvessels  (blood-vascular 
I       system)  for  the  circulation  of  the  blood,  and  the  lymphatics  and  lacteals 
(lymph-vascular  system),  which  collect  the  lymph  from  the  tissues  and  the 
chyle  from  the  digestive  tract  and  conveying  them  to  the  great  veins. 


THE   HEART   AND   BLOODVESSELS. 


Pulmonary  Cajitllaries 


The  heart  is  the  central  organ  of  the  blood-vascular  system,  and  consists  of 
a  hollow  mass  of  muscle  tissue;  by  its  contraction  the  blood  is  forced  to  all 
parts  of  the  body  through  a  complicated  series  of  tubes,  termed  arteries.  The 
arteries  undergo  enormous  ramification  in 
their  course  throughout  the  body,  and  end 
in  very  minute  vessels,  called  arterioles, 
which,  in  their  turn,  open  into  a  close- 
meshed  network  of  microscopic  vessels, 
termed  capillaries.  After  the  blood  has 
passed  through  the  capillaries  it  enters  into 
minute  vessels  called  venules  and  from  them 
it  is  collected  into  a  series  of  larger  vessels, 
called  veins,  by  which  it  is  again  returned 
to  the  heart.  The  passage  of  the  blood 
through  the  heart  and  bloodvessels  consti- 
tutes what  is  termed  the  circulation  of  the 
blood,  of  which  the  following  is  an  outline: 
The  human  heart  is  divided  by  a  septum 
into  right  and  left  halves,  and  each  half  is 
further  separated  into  two  cavities,  termed 
the  auricle  and  the  ventricle.  The  heart, 
therefore,  consists  of  four  chambers,  two, 
the  right  auricle  and  right  ventricle,  form- 
ing the  right  half,  and  two,  the  left  auricle 
and  left  ventricle,  forming  the  left  half.  The 
right  half  of  the  heart  contains  venous  or 
deoxygenated  blood;  the  left,  arterial  or 
oxygenated  blood.  From  the  cavity  of  the 
left  ventricle  the  aerated  blood  passes  into 
a  large  artery,  the  aorta,  through  the 
numerous  branches  of  which  it  is  dis- 
tributed to  all  parts  of  the  body.  In  its 
passage  through  the  capillaries  of  the  body 
the  blood  carries  to  the  tissues  the  mate- 
rials necessary  for  their  growth  and  nourish- 
ment, and  at  the  same  time  receives  from 
the  tissues  the  waste  products  resulting 
from  their  metabolism.  In  doing  so  it 
becomes  changed  from  arterial  into  venous 


Fig.  407. — Diagram  showing  the  course  of  the 
circulation  of  the  blood.  This  diagram  does  not 
show  that  the  liver  also  receives  blood  through 
the  hepatic  artery. 


(547) 


548  THE  VASCULAR  SYSTEMS 

blood,  which  is  collected  by  the  veins  and  through  them  returned  to  the  right 
auricle  of  the  heart.  From  this  cavity  the  deoxygenated  blood  passes  into  the 
right  ventricle,  from  which  it  is  conveyed  through  the  pulmonary  arteries  to  the 
lungs.  In  the  capillaries  of  the  lungs  it  again  becomes  oxygenated,  and  is  then 
carried  to  the  left  auricle  by  the  pulmonary  veins.  From  this  cavity  it  passes  into 
that  of  the  left  ventricle,  from  which  the  cycle  once  more  begins. 

The  course  of  the  blood  from  the  left  ventricle  through  the  body  generally  to 
the  right  side  of  the  heart  constitutes  the  greater  or  systemic  circulation,  while  its 
passage  from  the  right  ventricle  through  the  lungs  to  the  left  side  of  the  heart  is 
termed  the  lesser  or  pulmonary  circulation. 

It  is  necessary,  however,  to  state  that  the  blood  which  circulates  through  the 
spleen,  pancreas,  stomach,  small  intestine,  and  the  greater  part  of  the  large  intes- 
tine is  not  returned  directly  from  these  organs  to  the  heart,  but  is  collected  into 
a  large  vein,  termed  the  portal  vein,  by  which  it  is  carried  to  the  liver.  In  the 
liver  this  vein  divides,  after  the  manner  of  an  artery,  and  ultimately  ends  in  capil- 
lary vessels,  from  which  the  rootlets  of  a  series  of  veins,  called  the  hepatic  veins, 
arise,  these  carry  the  blood  into  the  inferior  vena  cava  (postcava),  whence  it  is 
conveyed  to  the  right  auricle.  From  this  it  will  be  seen  that  the  blood  contained 
in  the  portal  vein  passes  through  two  sets  of  capillary  \'essels — (1)  those  in  the 
spleen,  pancreas,  stomach,  etc.,  and  (2)  those  in  the  liver. 

Speaking  generally,  the  arteries  may  be  said  to  contain  pure  and  the  veins  im- 
pure blood.  This  is  true  of  the  systemic,  but  not  of  the  pulmonary  vessels, 
since  it  has  been  seen  that  the  impure  blood  is  conveyed  from  the  heart  to  the 
lungs  by  the  pulmonary  arteries,  and  the  pure  blood  returned  from  the  lungs  to 
the  heart  by  the  pulmonary  veins.  Arteries,  therefore,  must  be  defined  as  vessels 
which  convey  blood  from  the  heart,  and  veins  as  vessels  which  return  blood  to 
the  heart. 

The  heart  and  lungs  are  contained  within  the  cavity  of  the  thorax,  the  walls  of 
which  afford  them  protection  (Fig.  421).  The  heart  lies  between  the  two  lungs, 
and  is  there  enclosed  within  a  serofibrous  bag,  the  pericardium,  while  each  lung 
is  invested  by  a  serous  membrane,  the  pleura.  The  skeleton  and  cavity  of  the 
thorax  were  described  on  page  154. 

THE  PERICARDIUM. 

The  pericardium  (Fig.  408)  is  a  conical  serofibrous  sac  in  which  the  heart  and 
the  commencement  of  the  great  vessels  are  contained.  It  is  placed  in  the  middle 
mediastinum  and  lies  on  and  is  somewhat  attached  to  the  Diaphragm.  It  consists 
of  two  layers,  an  external  fibrous,  the  fibrous  pericardium,  and  an  internal  serous,  the 
serous  pericardium. 

The  fibrous  pericardium  is  a  strong,  dense  connective  tissue  layer  and  forms  the 
outer  wall  of  the  pericardial  sac.  Of  conical  shape,  its  base  is  applied  to  the 
muscular  substance  and  central  tendon  of  the  diaphragm;  to  the  latter  a  small 
portion  is  inseparably  blended,  the  base  is  pierced  by  the  inferior  vena  cava,  the 
apex  is  directed  upward  and  posteriorly,  and  is  closed  by  fusion  with  the  external 
coat  of  the  great  vessels  and  is  continuous  with  the  pretracheal  layer  of  the  deep 
cervical  fascia. 

In  front,  it  is  separated  from  the  anterior  wall  of  the  thorax,  in  the  greater  part 
of  its  extent,  by  the  lungs  and  pleurae ;  but  a  small  area,  somewhat  variable  in  size, 
and  usually  corresponding  with  the  left  half  of  the  lower  portion  of  the  gladiolus 
of  the  sternum  and  the  inner  extremities  of  the  cartilages  of  the  fourth  and  fifth 
ribs  of  the  left  side,  comes  into  direct  relationship  with  the  thoracic  wall.  The 
sac  is  attached  to  the  posterior  surface  of  the  sternum  by  two  fibrous  bands,  the 
superior  and  inferior  sternopericardial  ligaments  {lig.  sternopericardica)  (Fig.  408); 


THE  PEBTCARDIUM 


549 


the  upper  passing  to  the  manubrium,  and  the  lower  to  the  ensiform  cartilage. 
Behind,  it  rests  upon  the  bronchi,  the  oesophagus,  and  the  descending  aorta. 
Laterally,  it  is  covered  by  the  pleurse,  and  is  in  relation  to  the  inner  surface  of 
the  lungs;  the  phrenic  nerve  with  its  accompanying  vessels  descends  between  the 
pericardium  and  pleura  on  either  side  (Fig.  409). 

The  vessels  receiving  fibrous  prolongation  from  this  membrane  are  the  aorta, 
the  superior  vena  cava,  the  right  and  left  pulmonary  arteries,  the  four  pulmonary 
veins,  and  the  impervious  ductus  arteriosus.  The  inferior  vena  cava  enters 
the  pericardium  through  the  central  tendon  of  the  Diaphragm,  and  consequently 
it  receives  no  covering  from  the  fibrous  layer. 


LIGAMENTS 


Fig.  408. — Ligaments  of  the  pericardium.  (Modified  from  Teutleben.)  Right  lateral  view,  showing  the  right 
vertebropericardial  ligamentS;  the  right  phrenopericardial,  and  the  superior  and  inferior  sternopericardial  liga- 
ments.    (Poirier  and  Charpy.) 


The  Serous  pericardium  is  a  closed  sac  which  lines  the  fibrous  pericardium  and  is 
invaginated  by  the  heart;  it  therefore  consists  of  a  msceral  and  a  parietal  portion. 
The  visceral  portion  or  epicardium  covers  the  heart  and  the  great  vessels,  and  from 
the  latter  is  continuous  with  the  parietal  layer  which  lines  the  fibrous  pericardium. 
The  serous  pericardium  encloses  the  aorta  and  pulmonary  artery  in  a  single  tube, 
but  it  only  partially  covers  the  superior  and  inferior  vena  cava  and  the  four  pul- 
monary veins.  From  these  vessels  the  serous  pericardium  is  reflected  to  the  parietal 
layer  and  presents  the  shape  of  an  inverted  fl  (Fig.  409).  The  cul-de-sac  enclosed 
between  the  limbs  of  the  fl  is  known  as  the  oblique  sinus,  while  the  passage  between 
the  venous  and  arterial  mesocardia — i.  e.,  between  the  aorta  and  pulmonary  artery 


550 


THE  VASCULAR  SYSTEMS 


in  front  and  the  auricles  behind — is  termed  the  transverse  sinus  {simis  transversus 
pericardii).  The  serous  pericardium  is  smooth  and  glistening,  and  transudes  a 
serous  fluid,  which  serves  to  facilitate  the  movements  of  the  heart. 

The  Vestigial  Fold  of  the  Pericardium. — Between  the  left  pulmonary  artery  and  subjacent 
pulmonary  vein  and  behind  the  left  extremity  of  the  transverse  sinus  is  a  triangular  fold  of  the 
serous  pericardium;  it  is  known  as  the  vestigial  fold  of  Marshall  (ligavientum  v.  cavae  sinistrae). 
It  is  formed  by  the  duplicature  of  the  serous  layer  over  the  remnant  of  the  lower  part  of  the 
fetal  left  superior  vena  cava  (».  cam  sinistra),  or  the  duct  of  Cuvier,  which  becomes  impervious 
after  bu-th,  and  remains  as  a  fibrous  band  stretching  from  the  left  superior  intercostal  vein 


Fig.  409. — Posterior  wall  of  the  pericardial 


c,  showing  the  lines  of  reflection  of  the  s 
great  veaaeU. 


!  pericardium  from  the 


to  the  left  auricle,  where  it  is  continuous  with  a  small  vein,  the  oblique  vein  of  Marshall 
(v.  obliqua  atrii  sinistri  [Marshalli]),  which  opens  into  the  coronary  sinus. 

The  arteries  of  the  pericardium  are  derived  from  the  internal  mammary  and  its  mtisculo- 
phrenic  branch,  and  from  the  descending  thoracic  aorta. 

The  nerves  of  the  pericardium  are  derived  from  the  vagi,  the  phrenics,  and  the  sympathetics. 

Applied  Anatomy. — The  effusion  of  fluid  into  the  pericardial  sac  often  occurs  in  acute  rheu- 
_matism  or  pneumonia,  or  in  patients  with  chronic  vascular  and  renal  disease,  embarrassing 
the  heart's  action  and  giving  rise  to  signs  of  cardiac  distress,  such  as  pallor,  a  rapid  and  feeble 
pulse,  dyspnea,  and  restlessness.  On  examination,  the  apical  cardiac  impulse  is  absent,  or 
replaced  by  a  more  extensive  indefinite  and  wavering  pulsation;  it  may  appear  to  be  in  the 
second,  third,  or  fourth  left  space,  and  is  then  not  an  apex  impulse,  as  Potain  has  stated,  but 
due  to  the  impact  of  some  portion  of  the  heart  wall  nearer  its  base.  In  childi-en  the  precordial 
intercostal  spaces  may  bulge  outward.  The  most  striking  sign,  however,  is  the  great  increase 
in  all  directions  of  the  precordial  dulness  on  percussion.     This  becomes  pear-shaped,  the  stalk 


THE  HEART  551 

of  the  pear  reaching  up  to  about  the  left  sternodavioular  articulation;  the  dulness  also  extends 
some  distance  to  the  right  of  the  sternum,  particularly  in  the  fifth  interspace  (Rotch).  The 
fluid  collects  mainly  on  either  side  of  the  heart,  and  below  it,  especially  on  the  left  side,  where 
the  Diaphragm  can  yield  more  readily  to  pressure  than  it  can  on  the  right. 

Paraccnlcsis  of  the  "pericardium  is  often  required  to  relieve  the  urgent  cardiac  or  respiratory 
distress  in  these  cases,  and  should  be  performed  without  hesitation  and  before  the  patient  is  in 
extremis.  It  may  also  be  required  when  the  pericardium  is  filled  with  blood  or  pus,  and  as  it 
is  advisable  to  perform  this  operation  without  transfixing  the  pleura,  the  puncture  should  be 
made  either  in  the  fifth  or  sixth  intercostal  space  on  the  left  side  and  close  to  the  sternum,  so 
as  to  avoid  wounding  the  internal  mammary  artery,  which  descends  about  half  an  inch  from 
the  sternal  margin;  or  the  needle  may  be  entered  -at  the  left  costoensiform  angle  and  made  to 
pass  upward  and  backward  behind  the  lower  end  of  the  body  of  the  sternum  into  the  pericardial 
sac.  It  must  be  remembered  that  even  in  the  largest  pericardial  effusions,  the  heart  itself  lies 
almost  in  contact  with  the  anterior  wall  of  the  thorax,  and  great  care  must  be  exercised  to  avoid 
piercing  this  organ. 

Pericardiotomy  is  required  when  the  effusion  is  of  a  purulent  nature.  In  this  operation  a 
.portion  of  the  fifth  or  sixth  costal  cartilage  is  excised.  An  incision  is  made  along  the  left 
border  of  the  sternum  from  the  upper  border  of  the  fourth  cartilage  to  the  seventh.  Trans- 
verse incisions  an  inch  long  are  then  made  outward  from  either  extremity  of  this,  and  the  rect- 
angular flap  thus  formed  reflected  outward.  The  fifth  costal  cartilage  is  now  separated  from 
the  sternum  by  means  of  a  gouge,  great  care  being  taken  not  to  let  the  instrument  slip  and  pene- 
trate too  deeply.  The  cartilage  is  then  seized  with  lion  forceps  and  raised,  the  tissues  beneath 
it  being  peeled  off,  so  as  to  avoid  wounding  the  internal  mammary  artery  or  the  pleura.  The 
Triangularis  sterni  is  now  scratched  through  with  a  director  or  the  nail  of  the  index  finger  close 
to  the  sternum,  and  the  pericardium  felt  for  and  opened,  the  finger  guarding  the  pleura  and 
left  internal  mammary  artery. 

THE  HEART   (COR). 

The  heart  is  a  hollow  muscular  organ  of  a  somewhat  conical  form,  placed  be- 
tween the  lungs,  and  occupying  the  cavitj'  of  the  pericardium. 

Position  (Fig.  410). — The  heart  is  placed  obliquely  in  the  thorax;  the  broad 
attached  end  or  base  {basis  cordis)  is  directed  backward  and  corresponds  with  the 
thoracic  vertebrae,  from  the  fifth  to  the  eighth  inclusive,  the  apex  (ape.r  cordis) 
is  directed  downward,  forward,  and  to  the  left,  and  corresponds  to  the  space  between 
the  cartilages  of  the  fifth  and  sixth  ribs,  about  three  and  a  quarter  inches  from  the 
middle  line  of  the  sternum.  The  heart  projects  farther  into  the  left  than  into  the 
right  half  of  the  cavity  of  the  chest,  extending  from  the  median  line  over  three 
inches  in  the  former  direction,  and  only  one  and  one-half  in  the  latter ;  about  one- 
third  of  the  heart  lies  to  the  right  ancl  two-thirds  to  the  left  of  the  mesial  plane. 

The  base  of  the  heart  is  formed  by  the  auricles  and  forms  the  whole  of  the 
posterior  surface.  It  is  separated  from  the  fifth,  sixth,  seventh,  and  eighth  thoracic 
vertebrae  by  the  oesophagus,  aorta,  and  thoracic  duct.  Somewhat  quadrilateral 
in  form,  it  is  in  relation  above  with  the  bifurcation  of  the  pulmonary  artery,  and  is 
bounded  below  by  the  posterior  part  of  the  auriculoventricular  sulcus,  containing 
the  coronary  sinus.  On  the  right  it  is  limited  by  the  sulcus  terminalis  (page  554) 
of  the  right  auricle.  This  corresponds  to  a  ridge  in  the  interior  of  the  auricle, 
called  the  crista  terminales.  The  entrance  of  the  two  left  pulmonary  veins  into 
the  left  auricle  forms  the  left  limit  of  the  base.  The  four  pulmonary  veins,  two 
on  either  side,  open  into  the  left  auricle,  while  the  superior  vena  ca^'a  opens  into 
the  upper  and  the  inferior  vena  cava  into  the  lower  part  of  the  right  auricle. 

The  apex  is  directed  downward,  forward,  and  to  the  left,  and  is  overlapped  by 
the  left  lung  and  pleura;  it  lies  behind  the  fifth  left  intercostal  space,  three  and  a 
quarter  inches  (8  cm.)  from  the  midsternal  line,  or  about  an  inch  and  a  half 
(4  cm.)  below  and  three-quarters  of  an  inch  (2  cm.)  to  the  inner  side  of  the  left 
nipple  in  the  male.     The  apex  is  wholly  made  up  of  the  left  ventricle. 

The  antero-superior  surface  {fades  sternocostalis)  (Fig.  412)  is  directed  forward, 
■wpicard,  and  to  the  left.     Its  lower  part  is  convex,  formed  chiefly  by  the  right 


552 


THE  VASCULAR  SYSTEMS 


ventricle,  together  with  a  small  part  of  the  left  ventricle.  It  lies  behind  the  middle 
portion  of  the  sternum  and  the  costal  cartilages  of  the  third,  fourth,  fifth,  and  sixth 
ribs  of  both  sides,  but,  on  account  of  the  heart's  inclination  to  the  left,  only  a  small 
part  of  it  lies  behind  the  cartilages  of  the  right  ribs  (Fig.  412). 

The  postero-inferior  surface  (fades  diaphragmatica)  (Fig.  412),  which  looks 
downward  and  slightly  backward,  is  formed  by  the  ventricles,  chiefly  the  left,  and 
rests  upon  the  central  tendon  and  a  small  part  of  the  left  muscular  portion  of  the 
Diaphragm.     It  is  separated  from  the  base  by  the  posterior  part  of  the  auriculo- 


FlG.  410. — Position  of  the  heart.    The  pericardium  laid  open.     Adult  male 


and  Charpy.) 


ventricular  furrow,  and  is  traversed  obliquely  by  the  posterior  interventricular 
groove.     This  surface  is  flattened  or  slightly  convex. 

The  right  margin  of  the  heart  is  long,  and  is  formed  by  the  right  auricle  above 
and  the  right  ventricle  below.  The  auricular  portion  is  almost  vertical,  and  is 
situated  behind  the  third,  fourth,  and  fifth  right  costal  cartilages  about  3  cm. 
from  the  middle  line.  The  ventricular  portion,  thin  and  sharp,  is  named  the 
nmrfio  acutus;  it  is  nearly  horizontal,  and  extends  from  the  sternal  end  of  the  sixth 
right  costal  cartilage  behind  the  lower  end  of  the  gladiolus  to  the  apex  of  the  heart. 

The  left  margin,  or  margo  obtusus,  is  short,  thick,  and  rounded;  it  is  formed 
mainly  by  the  left  ^'entricle,  but  to  a  slight  extent,  above,  by  the  left  auricle. 
It  extends  from  a  point  in  the  second  left  intercostal  space,  about  4.5  cm.  from 


THE  HEART 


553 


the  mesal  (middle)  line,  obliquely  downward,  with  a  convexity  to  the  left,  to  the 
apex  of  the  heart. 

Component  Parts. — The  heart  cavity  is  subdivided  by  a  muscular  septum  into 
two  lateral  halves,  which  are  named,  respectively,  the  right  or  pulmonary  heart 
and  the  left  or  systemic  heart;  and  a  transverse  constriction  subdivides  each  half 
of  the  organ  into  two  cavities,  the  posterior  cavity  on  each  side  being  called  the 
auricle;  the  anterior,  the  ventricle.  The  heart,  therefore,  consists  oi  jour  cham- 
bers— viz.,  the  right  and  left  auricles,  and  right  and  left  ventricles.  The  course 
of  the  blood  through  the  heart  cavities  and  bloodvessels  has  already  been  de- 
scribed (page  547). 

The  division  of  the  heart  into  four  cavities  is  indicated  upon  its  surface  by 
grooves.     The  groove  scparatiuu'  the  auricles  from  the  ventricles  is  called  the 


LIFT  APPENDIX 

AURICULAE 

LEFT  AURICULO- 

VENTRICULAR 


Fig.  411  — Base  of  the  heart 


tuned  m  red. 


auriculoventricular  groove  (sulcus  coronarius) .  It  contains  the  trunks  of  the 
nutrient  vessels  of  the  heart,  but  is  obliterated  in  front,  where  it  is  crossed  by 
the  root  of  the  pulmonary  artery. 

The  interauricular  groove,  separating  the  two  auricles,  is  scarcely  marked  on  the 
postero-inferior  aspect,-  while  superiorly  it  is  hidden  by  the  pulmonary  artery  and 
aorta.  The  ventricles  are  separated  by  two  furrows,  the  interventricular  grooves 
(sulci  longitudinales) ,  one  of  which  (sulcus  longitudmalis  anterior)  is  situated  on 
the  antero-superior  surface  close  to  the  left  margin  of  the  heart,  the  other  (sulcus 
longitudinalis  posterior)  on  the  postero-inferior  surface  near  the  right  margin; 
these  grooves  extend  from  the  base  of  the  ventricular  portion  to  a  point  n  little  to 
the  right  of  the  apex  of  the  heart.  i 

The  Cavities  of  the  Heart. — Each  of  the  cavities  of  the  heart  is  lined  by  the 
endocardium,  a  thin,  smooth  membrane  which  gives  the  glistening  appearance 
to  their  internal  surfaces  and  by  reduplications  forming  the  valves  (mitral  and 


554 


THE  VASCULAR  SYSTEMS 


tricuspid)  guarding  the  orifices  of  communication  and  the  semilunar  valves  of 
the  aorta  and  pulmonary  artery. 

The  Right  Auricle^  {airium  dextnm)  is  the  larger  of  the  two  auricles,  although 
its  walls  are  somewhat  thinner  than  those  of  the  left,  measuring  about  2  min.  It 
consists  of  two  parts,  a  principal  cavity,  the  sinus  venosus,  situated  posteriorly, 
and  an  antero-superior,  smaller  portion,  the  auricular  appendix. 

The  sinus  venosus  {sinus  venarum)  is  the  large  quadrangular  cavity,  placed 
between  the  two  venae  cavse.  Its  walls,  which  are  extremely  thin,  are  connected 
in  front  and  to  the  left  with  the  right  ventricle,  and  mesally  with  the  left  auricle, 
but  are  free  in  the  rest  of  their  extent. 

The  right  auricular  appendix  {auricula  dextra),  so  called  from  its  fancied  resem- 
blance to  a  dog's  ear,  is  a  small  conical  muscular  pouch,  the  margins  of  which 


Fig.  412. — Showing  relations  of  opened  heart  to  front  of  thor; 


present  a  dentated  edge.     It  projects  from  the  sinus  forward  and  toward  the  left 
side,  overlapping  the  root  of  the  aorta. 

The  separation  of  the  appendix  from  the  sinus  venosus  is  indicated  externally 
by  a  groove,  the  sulcus  terminalis  (His),  which  extends  from  the  front  of  the  supe- 
rior vena  cava  to  the  front  of  the  inferior  vena  cava,  and  represents  the  line  of 
union  of  the  sinus  venosus  of  the  embryo  with  the  primitive  auricle.  In  the 
cavity  of  the  auricle  the  separation  is  marked  by  a  vertical,  smooth,  muscular 
ridge  on  the  anterior  wall,  the  crista  terminalis  (His)  (Fig.  414).  Behind  the 
crista  the  internal  surface  of  the  auricle  is  smooth,  while  in  front  of  it  the  muscle 
fibres  of  the  wall  are  raised  into  parallel  ridges  resembling  the  teeth  of  a  comb,  and 
hence  named  the  musculi  pectinati. 


ilature  the  auricle  is  called  the  atr: 


,  and  the  auricular  appendix  is  called  the  auricle. 


THE  HEART 


555 


To  examine  the  interior  of  the  rifjht  auricle,  an  incision  should  be  made  along  its  right  bor- 
der from  the  entrance  of  the  superior  vena  cava  to  that  of  the  inferior  vena  cava.  A  second 
cut  is  to  be  made  from  the  centre  of  the  first  incision  to  the  tip  of  the  auricular  appendix,  and 
the  flap  raised. 

The  interior  of  the  right  auricle  (Fig.  413)  presents  the  following  parts  for 
examination : 


Openii 


Superior  vena  cava. 
Inferior  vena  cava. 
Coronary  sinus. 
Foramina  Thebesii. 
Auriculoventricular. 
Anterior  cardiac  veins. 

Fossa  ovalis. 

Annulus  ovalis. 

Tuberculum  Loweri. 

Musculi  pectinati. 

Crista  terminalis. 


Y  1        f  Eustachian. 
1  Coronary. 


The  superior  vena  cava  (precava)  returns  the  blood  from  the  upper  half  of  the 
body,  and  opens  into  the  upper  and  back  part  of  the  auricle,  the  direction  of  its 
orifice  being  downward   and  for- 
ward.    Its  opening  has  no  valves. 

The  inferior  vena  cava  (post- 
cava),  larger  than  the  superior 
vena  cava,  returns  the  blood  from 
the  lower  half  of  the-,  body,  and 
opens  into  the  lowest  part  of  the 
auricle  near  the  septum,  the  direc- 
tion of  its  orifice  being  upward 
and  inward,  and  guarded  by  a 
rudimentary  valve,  the  Eusta- 
chian valve.  The  blood  which 
enters  the  auricle  through  the 
superior  vena  cava  is  directed 
downward  and  forward,  i.  e.,  to- 
ward the  auriculoA'entricular  ori- 
fice, while  that  entering  it  through 
the  inferior  vena  cava  is  directed 
upward  and  backward  toward  the 
auricular  septum.  This  is  the 
normal  direction  of  the  two  cur- 
rents in  fetal  life. 

The  coronary  sinus  (sijiiis  coro- 
narius)  opens  into  the  auricle,  be- 
tween the  inferior  vena  cava  and 
the  auriculoventricular  opening. 
It  returns  the  blood  from  the  sub- 
stance of  the  heart,  and  is  protected  by  an  incomplete  semicircular  fold  of  the 
lining  membrane  of  the  auricle,  the  coronary  valve,  or  valve  of  Thebesius. 

The  foramina  Thebesii  ( foramina  venarum  minimarum)  are  depressions  in  the 
walls  of  the  auricle;  the  majority  of  these  are  culs-de-sac,  but  about  one-third  are 
the  orifices  of  minute  veins  (venae  viinimae  cordis),  which  return  the  blood  directly 
from  the  muscle  substance  of  the  heart. 


Bristle  passed  throuah 
right  am  iruloventriculaj  opening 

413  — The  nglit  auricle  and  ventricle  laid  open 
anterior  walls  of  both  being  remo\  ed 


556 


THE   VASCULAR  SYSTEMS 


The  anterior  cardiac  veins  open  into  the  lower  fore  part  of  the  right  auricle. 

The  right  auriculoventricular  opening,  or  the  tricuspid  orifice  {ostium  venosum 
dexirum),  is  the  large  oval  aperture  of  communication  between  the  right  auricle 
and  the  ventricle;  it  will  be  described  with  the  right  ventricle. 

The  Eustachian  valve  (valvula  venae  cavae  inferioris  [Eustachii])  is  situated  in 
front  of  the  orifice  of  the  inferior  vena  cava.  It  is  semilunar  in  form,  its  convex 
margin  being  attached  to  the  anterior  margin  of  the  inferior  caval  orifice;  its  con- 
cave margin,  which  is  free,  terminates  in  two  cornua,  of  which  the  left  is  continuous 
with  the  anterior  edge  of  the  annulus  ovalis,  while  the  right  is  lost  on  the  wall  of 


Fig.  414. — Heart  opened  to  show  the  interior  of  the  right  auricle  and  of  the  two  ventricles,  from  in  front. 
The  wall  of  the  right  auricle  is  turned  back  to  show-  the  musculi  pectinati  and  the  crista  terminalis.  The  ven- 
tricular walls  and  the  ventricular  septum  have  been  cut.  The  aortic  \-alve  is  made  more  prominently  visible  in 
the  drawing  than  it  really  is  in  nature. 


auricle,  containing  a  few  muscle  fibres.  In  the  fetus  this  valve  is  of  large  size, 
and  tends  to  direct  the  blood  from  the  inferior  vena  cava,  through  the  foramen 
ovale,  into  the  left  auricle.  In  the  adult  it  is  occasionally  large,  and  may  assist  in 
preventing  the  reflux  of  blood  into  the  inferior  vena  cava;  more  commonly  it  is 
small,  and  its  free  margin  presents  a  cribriform  or  filamentous  appearance;  occa- 
sionally it  is  altogether  wanting. 

The  coronary  valve  or  valve  of  Thebesius  (valvidae  sinus  coronarii  [Thebesii]) 
is  a  semicircular  fold. of  the  lining  membrane  of  the  auricle,  protecting  the  orifice 
of  the  coronary  sinus.  It  prevents  the  regurgitation  of  blood  into  the  sinus  during 
the  contraction  of  the  auricle.     This  valve  is  occasionally  double. 


THE  HEART  557 

The  fossa  ovalis  is  an  oval  depression  corresponding  to  the  situation  of  the 
foramen  ovale  in  the  fetus.  It  is  situated  at  the  lower  part  of  the  interauricular 
septum,  above  and  to  the  left  of  the  orifice  of  the  inferior  vena  cava.  In  fetal  life 
an  opening,  the  foramen  ovale,  exists  at  this  point  between  the  two  auricles;  almost 
immediately  after  birth  the  valve-like  edge  is  pressed  down  by  the  increased 
pressure  in  the  left  auricle,  and  by  the  tenth  day  it  passes  to  the  annulus  and 
closes  the  opening. 

The  amiulus  ovalis  (limbns  fossae  ovalis  [Vieussenii])  is  the  prominent  oval 
margin  of  the  fossa  ovalis.  It  is  most  distinct  above  and  at  the  sides;  below,  it  is 
deficient.  A  small,  slit-like,  valvular  opening  is  occasionally  found,  at  the  upper 
anterior  margin  of  the  fossa  ovalis,  which  leads  upward  beneath  the  annulus  into 
the  left  auricle;  it  is  the  remains  of  the  fetal  aperture  between  the  two  auricles. 

The  tubercle  of  Lower  {tvhercvlvm  intervenosvm  [Loweri])  is  a  small  projection  on  the  inter- 
auricular septum  between  the  fossa  ovalis  and  the  opening  of  the  superior  vena  cava.  It  is 
most  distinct  in  the  hearts  of  quadrupeds;  in  man  it  is  scarcely  visible.  It  was  supposed  by 
Lower  to  direct  the  blood  from  the  superior  vena  cava  toward  the  auriculoventricular  opening. 

The  internal  surface  of  the  right  auricle  is  smooth,  except  in  the  appendix  and 
adjacent  part  of  the  anterior  wall  of  the  sinus  venosus,  where  the  muscular  wall  is 
thrown  into  parallel  ridges  resembling  the  teeth  of  a  comb,  and  hence  named  the 
musculi  pectinati.  These  end  behind  in  a  vertical  smooth  ridge,  the  crista  termi- 
nalis  (Fig.  414). 

The  Right  Ventricle  (^ventriculus  dexter)  is  pyramidal  in  form,  and  extends  from 
the  right  auricle  to  near  the  apex  of  the  heart.  Its  antero-swperior  surface  is  rounded 
and  convex,  and  forms  the  larger  part  of  the  front  of  the  heart.  Its  under  surface 
is  flattened,  rests  upon  the  Diaphragm,  and  forms  a  small  part  of  the  postero- 
inferior  surface  of  the  heart.  Its  'posterior  wall  is  formed  by  the  septum  between 
the  two  ventricles,  the  interventricular  septum  (septum  ventriculorum) ,  which  bulges 
into  the  right  ventricle,  so  that  a  transverse  section  of  the  cavity  presents  a  semilunar 
outline.  The  basal  and  inner  angle  of  the  ventricle  is  prolonged  into  a  conical 
pouch,  the  infundibulum  {conns  arteriosus),  from  which  the  pulmonary  artery 
arises.  The  balance  of  the  ventricle,  the  body,  is  the  portion  into  which  the  auriculo- 
ventricular orifice  opens.  The  conus  arteriosus  is  marked  off  from  the  body  of 
the  ventricle  by  a  muscular  projection  (crista  supraventricidaris).  The  walls 
■of  the  right  ventricle  are  thinner  than  those  of  the  left,  the  proportion  between 
them  being  as  1  to  3.  The  wall  is  thickest  at  the  base,  and  gradually  becomes 
thinner  toward  the  apex. 

To  examine  the  interior  of  the  right  ventricle,  its  anterior  wall  should  be  turned  downward 
and  to  the  right  in  the  form  of  a  triangular  flap.  This  is  accomplished  by  making  two  incisions: 
(1)  From  the  pulmonary  artery  to  the  apex  of  -the  ventricle  parallel  to,  but  a  little,  to  the  right 
of,  the  anterior  interventricular  furrow;  (2)  another,  starting  from  the  upper  extremity,  of  the 
first  and  carried  outward  parallel  to,  but  a  little  below,  the  auriculoventricular  furrow,  care 
being  taken  not  to  injure  the  auriculoventricular  valve. 

The  interior  of  the  right  ventricle  presents  for  examination: 

(  Auriculoventricular. 
Openings  <  Opening  of  the  pulmonary  artery, 
t  Foramina  Thebesii. 

Valves  I  Tricuspid. 
[  bemilunar. 
Columnae  carneae.  Chordae  tendineae. 

The  right  auriculoventricular  opening,  or  the  tricuspid  orifice  (ostium  venosum 
wntriculi  dextri),  is  the  large  oval  aperture  of  communication  between  the  auricle 
and  ventricle.     It  is  situated  at  the  base  of  the  ventricle,  near  the  right  border  of 


558  THE  VA&'CULAB  SYSTEMS 

the  heart.  The  plane  of  this  opening  is  nearly  vertical.  It  is  oval  and  about 
3.75  cm.  (1.5  inches)  in  diameter  from  side  to  side,  surrounded  by  a  fibrous  ring 
(annuhis  fibrosvs)  and  co^'e^ed  by  the  lining  membrane  of  the  heart;  it  is  consider- 
ably larger  than  the  corresponding  aperture  on  the  left  side,  being  sufficient  to 
admit  the  ends  of  four  fingers.  The  circumference  of  the  orifice  is  about  12  cm. 
(4.8  inches)  in  the  male,  and  10.5  cm.  (4.2  inches)  in  the  female.  It  is  guarded  by 
the  tricuspid  valve. 

The  opening  of  the  pulmonary  artery  {ostium  arteriosum  -pulmonis)  is  circular  in 
form,  and  is  situated  at  the  summit  of  the  conus  arteriosus,  close  to  the  ventricular 
septum.  It  is  placed  above  and  to  the  left  of  the  auriculo ventricular  opening,  and 
is  guarded  by  the  pulmonary  valve. 

Foramina  Thebesii  are  scattered  over  the  interior  of  the  right  ventricle. 

The  tricuspid  valve  (vciMda  trinispidalis)  consists  of  three  segments  or  cusps 
{cuspides)  of  a  triangular  or  trapezoidal  shape,  each  formed  by  a  duplicature  of 
the  lining  membrane  of  the  heart,  strengthened  by  intervening  layers  of  fibrous 
tissue.  The  largest  and  most  movable  segment  is  placed  toward  the  left  side  of 
the  auriculoventricular  opening,  and  is  interposed  between  that  opening  and  the 
infundibulum;  hence  it  is  called  the  left  or  infundibular  cusp  {cuspis  medialw). 
Another  segment  is  in  relation  with  the  right  part  of  the  front  of  the  ventricle,  the 
right  or  marginal  cusp  {cuspis  anterior),  and  a  third  with  its  posterior  wall,  the 
posterior  or  septal  cusp  {cuspis  posterior).  The  central  part  of  each  segment  is 
thick  and  strong;  the  lateral  margins  are  thin  and  translucent.  These  segments 
are  connected  by  their  bases  to  the  oval  fibrous  ring  surrounding  the  auriculoven- 
tricular orifice  {annidus  fibrosus  dexter),  and  by  their  sides  with  one  another,  so 
as  to  form  a  continuous  annular  membrane,  which  is  attached  around  the  margin 
of  the  auriculoventricular  opening;  their  serrated  free  margins  and  ventricular 
surfaces  afford  attachment  to  a  number  of  delicate  tendinous  cords,  the  chordae 
tendineae.  The  chordae  tendineae  are  connected  with  the  adjacent  margins  of  the 
principal  segments  of  the  valve,  and  are  further  attached  to  each  segment  in  the 
following  manner:  (1)  Three  or  four  reach  the  attached  margin  of  each  segment, 
where  they  are  continuous  with  the  auriculoventricular  tendinous  ring.  (2) 
Others,  four  to  six  in  number,  are  attached  to  the  central  thickened  part  of  each 
segment.  (3)  The  most  numerous  and  finest  are  connected  with  the  marginal 
portion  of  each  segment. 

The  columnae  cameae  {trabecidae  carneae)  are  the  rounded  muscle  columns 
which  project  from  nearly  the  whole  of  the  inner  surface  of  the  ventricle,  except- 
ing near  the  opening  of  the  pulmonary  artery,  where  the  wall  is  smooth.  They 
may  be  classified,  according  to  their  mode  of  connection  with  the  ventricle,  into 
three  sets.  The  first  set  merely  forms  prominent  ridges  on  the  inner  surfaces  of 
the  ventricle,  being  attached  by  their  entire  length  on  one  side,  as  well  as  by  their 
extremities.  The  second  set  are  attached  by  their  two  extremities,  but  are  free 
in  the  rest  of  their  extent,  forming  arches;  while  a  third  set  {muscidi  papUlares) 
are  continuous  by  their  bases  with  the  wall  of  the  ventricle,  while  their  apices 
give  origin  to  the  chordae  tendineae,  the  papillary  muscles.  There  are  usually 
two  papillary  muscles  or  groups  of  muscles,  the  anterior  and  the  posterior;  of  these, 
the  anterior  is  the  larger,  its  chordae  tendineae  are  connected  with  the  right  and 
left  segments  of  the  tricuspid  valve.  The  posterior  sometimes  consists  of  two  or 
three  muscle  columns;  its  chordae  tendineae  are  connected  with  the  posterior  and 
the  right  segments  of  the  tricuspid  valve.  In  addition  to  these,  some  few  chordae 
spring  directly  from  the  ventricular  septum,  or  from  small  eminences  on  it,  and 
pass  to  the  left  and  posterior  segments.  A  fleshy  band,  well  marked  in  the  sheep 
and  some  other  animals,  is  frequently  seen  passing  from  the  base  of  the  anterior 
papillary  muscle  to  the  interventricular  septum.  From  its  attachments  it  may 
assist  in  preventing  overdistention  of  the  ventricle,  and  so  has  been  named  the 
moderator  band. 


THE  HEART  659 

The  pulmonary  valve  (Fig.  414)  consists  of  three  semilunar  segments  (valvulae 
scmiluiiart'.t  a.  piilmoiialls),  two  of  which  are  anterior  and  one  of  which  is  posterior, 
formed  by  dupiicatures  of  the  hning  membrane  of  the  ventricle,  strengthened  by 
fibrous  tissue.  They  are  attached,  by  their  outer  convex  margins,  to  the  wall  of 
the  artery,  at  its  junction  with  the  ventricle,  their  inner  borders  being  free,  and 
directed  upward  in  the  lumen  of  the  vessel.  The  free  and  attached  margins  of 
each  are  strengthened  by  a  bundle  of  tendinous  fibres,  and  the  former  presents, 
at  its  middle,  a  small  projecting  thickened  nodule,  consisting  of  bundles  of  inter- 
lacing connective-tissue  fibres  with  branched  connective-tissue  cells  and  some  few 
elastic  fibres.  Such  a  nodule  is  called  the  corpus  Arantii  {nodulus  valvulae  semi- 
lunaris [Arantii]).  From  this  nodule  tendinous  fibres  radiate  through  the  valve 
to  its  attached  margin,  but  are  absent  from  two  narrow  crescentic  portions,  the 
lunulas  {I'unulae  valvularum  semilunarium),  placed  one  on  either  side  of  the  nodule 
immediately  adjoining  the  free  margin. 

The  basal  end  of  the  pulmonary  artery  presents  three  dilatations  opposite  to 
the  valve.  These  are  the  pulmonary  sinuses  of  Valsalva.  Similar  sinuses  exist 
between  the  semilunar  valves  and  the  commencement  of  the  aorta;  they  are  larger 
than  the  pulmonary  sinuses. 

In  order  to  examine  the  interior  of  the  left  auricle,  make  an  incision  on  the  posterior  surface 
of  the  auricle  from  the  pulmonary  veins  on  one  side  to  those  on  the  other,  the  incision  being 
carried  a  little  way  into  the  vessels.  Make  another  incision  from  the  middle  of  the  horizontal 
one  to  the  auricular  appendix. 

The  Left  Auricle  (atrium  sinistrum)  is  rather  smaller  than  the  right,  but  its  walls 
are  thicker,  measuring  about  3  mm.;  it  consists,  like  the  right,  of  two  parts,  a 
principal  cavity  and  an  am^icular  appendix. 

Tlie  principal  cavity  is  cuboidal  in  form,  and  concealed  in  front  by  the  pulmonary 
artery  and  aorta;  in  front  and  to  the  right,  it  is  separated  from  the  right  auricle 
by  the  interauricular  septum  {septum  atriorum);  behind,  it  receives  on  either  side 
two  pidmonary  veins. 

The  left  auricular  appendix  (auricula  sinistra)  is  somewhat  constricted  at  its 
junction  with  the  principal  cavity;  it  is  longer,  narrower,  and  more  curved  than 
that  of  the  right  side,  and  its  margins  are  more  deeply  indented.  It  is  directed 
forward  and  toward  the  right  and  overlaps  the  root  of  the  pulmonary  artery. 

The  interior  of  the  left  auricle  presents  the  following  parts  for  examination: 

The  openings  of  the  four  pulmonary  veins. 
Auriculoventricular  opening. 
Musculi  pectinati. 
Foramina  Thebesii. 

The  pulmonary  veins,  four  in  number,  open  into  the  upper  part  of  the  posterior 
surface  of  the  left  auricle — two  on  either  side  of  its  middle  line.  They  are  not 
provided  with  valves.  The  two  left  veins  frequently  terminate  by  a  common 
opening. 

The  left  auriculoventricular  opening,  or  mitral  orifice  (ostium  venosum  ventriculi 
sinistri),  is  the  aperture  of  communication  between  the  left  auricle  and  the  left 
ventricle.     It  is  rather  smaller  than  the  corresponding  opening  on  the  right  side. 

The  musculi  pectinati,  fewer  and  smaller  than  in  the  right  auricle,  are  confined 
to  the  inner  surface  of  the  auricular  appendix. 

On  the  interauricular  septum  may  be  seen  a  lunated  impression  bounded  below 
by  a  crescentic  ridge  the  concavity  of  which  is  turned  upward.  The  depression  is 
just  above  the  fossa  ovalis  of  the  right  auricle.  The  inner  surface  of  the  left 
auricle  also  shows  foramina  Thebesii  and  venae  minimae  cordis. 


660 


THE   VASCULAR  SYSTEMS 


To  examine  the  interior  of  the  left  ventricle,  make  an  incision  a  little  to  the  left  of  the  anterior 
interventricular  groove  from  the  base  to  the  apex  of  the  heart,  and  carry  it  up  from  thence, 
a  little  to  the  left  of  the  posterior  interventricular  groove,  nearly  as  far  as  the  auriculoventricular 
groove. 

The  Left  Ventricle  (yenfriculus  sinister)  is  longer  and  more  conical  in  shape  than 
the  right  ventricle,  and  on  transverse  section  its  cavity  presents  an  oval  or  nearly 
circular  outline.  It  forms  a  small  part  of  the  anterior  surface  of  the  heart  and  a 
considerable  part  of  its  postero-inferior  surface.  It  also  forms  the  apex  of  the 
heart  by  its  projection  beyond  the  right  ventricle.  Its  walls  are  much  thicker 
than  those  of  the  right  side,  the  proportion  being  as  3  to  1. 

Its  interior  (Fig.  415)  presents  the  following  parts  for  examination: 


(  Auriculoventricular. 
Openings  <  Aortic 

(  Foramina  Thebesii. 
Chordae  tendineae. 


-rr  ,        f  Mitral  or  Bicuspid. 
Valves  \  c>      •! 

t  bemilunar. 

Columnae  carneae. 


The  left  auriculoventricular  opening,  or  the  mitral  orifice  (ostium  venosum  ven- 
iriculi  sinistri),  is  placed  below  and  to  the  left  of  the  aortic  orifice.  It  is  a  little 
smaller  than  the  corresponding  aperture  of  the  opposite  side,  admitting  only  two 


Fig.  415.— The  left  auricle 


Bi  isfle  passed  through  left 
auriculoventricular  opening. 


Passed  thiough  aoitic  opening. 


utricle  laid  open,  the  posterior  walls  of  both  being  removed. 


fingers ;  but,  like  it,  is  broader  in  the  transverse  than  in  the  antero-posterior  diameter. 
Its  right,  posterior,  and  left  sides  are  surrounded  by  a  dense  horseshoe-shaped, 
fibrous  ring  (annuius  fibrosus  sinister).  The  orifice  is  guarded  by  the  mitral 
or  bicuspid  valve. 

The  aort;ic  opening  (ostium  arteriosum)  is  a  circular  aperture,  in  front  and  to 
the  right  side  of  the  auriculoventricular  opening,  from  which  it  is  separated  by 
the  aortic  cusp  of  the  mitral  valve.     Its  orifice  is  guarded  by  the  aortic  valve,  which 


THE  HEART 


561 


consists  of  three  semilunar  segments.  The  portion  of  the  ventricle  immediately 
below  the  aortic  orifice  is  often  termed  the  aortic  vestibule,  and  ]30ssesses  fibrous 
instead  of  muscular  walls. 

The  inner  walls  of  the  left  ventricle  are  dotted  with  foramina  Thebesii. 

The  mitral  or  bicuspid  valve  (valvida  hicuspidalis)  is  attaclied  to  the  circumfer- 
ence of  the  auriculoventricular  orifice  in  the  same  way  that  the  tricuspid  valve  is 
on  the  opposite  side.  It  consists  of  two  triangular  cusps,  formed  by  duplicatures 
of  the  lining  membrane,  strengthened  by  fibrous  tissue,  and  containing  a  few 
muscle  fibres.  The  cusps  are  of  unequal  size,  and  are  larger,  thicker,  and  stronger 
than  those  of  the  tricuspid  valve.  The  larger  segment,  the  anterior  or  aortic  cusp 
(cuspis  anterior),  is  placed  in  front  and  to  the  right  between  the  auriculoventricular 
and  aortic  orifices;  the  smaller,  the  posterior  or  marginal  cusp  (cuspis  posterior),  is 
placed  to  the  left  and  behind  the  opening.  Two  smaller  cusps  are  usually  found  at 
the  angles  of  junction  of  the  larger.  The  cusps  of  the  mitral  valve  are  furnished 
with  chordae  tendineae,  which  are  attached  in  a  manner  similar  to  those  on  the 
right  side;  they  are,  however,  thicker,  stronger,  and  less  numerous. 

The  aortic  valve  consists  of  three  semilunar  segments  (valvulae  semilunares 
aortae),  which  surround  the  orifice  of  the  aorta;  two  are  posterior  (right  and  left) 
and  one  anterior.  They  are  simi- 
lar in  structure  and  in  their  mode 
of  attachment  to  those  of  the 
pulmonary  ^'alve,  but  are  larger, 
thicker,  and  stronger;  the  lunulee 
are  more  distinct  and  the  corpora 
Arantii  thicker  and  more  promi- 
nent. Opposite  the  segments  the 
wall  of  the  aorta  presents  slight 
dilatations,  the  sinuses  of  Val- 
salva, which  are  larger  than  those 
at  the  origin  of  the  pulmonary 
artery. 

The  columnae  carneae  are  of 
three  kinds,  like  those  upon  the 
right  side;  but  they  are  more 
numerous,  and  present  a  dense 
interlacement,  especially  at  the 
apex,  and  upon  the  posterior  wall.  The  musculi  papillares  are  two  in  number, 
one  being  connected  to  the  anterior,  the  other  to  the  posterior  wall;  they  are  of 
large  size,  and  terminate  by  free  rounded  extremities,  from  which  the  chordae 
tendineae  arise.  The  chordae  tendineae  from  each  papillary  muscle  are  con- 
nected to  both  cusps  of  the  mitral  valve. 

The  interventricular  septum  (septum,  ventriculorum)  is  directed  obliquely  back- 
ward and  to  the  right,  and  is  curved  with  the  convexity  toward  the  right  ventricle; 
its  margins  correspond  with  the  interventricular  grooves.  The  greater  portion 
of  it  is  thick  and  fleshy  (septmn  musculare  ventriculorum) ,  but  its  upper  and 
posterior  part,  which  separates  the  aortic  vestibule  from  the  lower  part  of  the  right 
auricle  and  upper  part  of  the  right  ventricle  is  thin  and  fibrous,  and  is  termed 
the  undefended  or  membranous  part  of  the  interventricular  septum  (septum  mem- 
branaceum  ventriculorum).  It  is  deri\'ed  from  the  lower  part  of  the  aortic  septum 
of  the  fetus,  and  an  abnormal  communication  may  exist  at  this  part,  owing  to 
defective  development  of  this  septum. 

Capacity  of  the  Cavities  of  the  Heart. — Each  of  the  cavities  of  the  heart 
is  capable  of  holding  about  100  c.c,  but  this  is  subject  to  considerable  variation 
among  different  individuals. 

36 


Fig.  415. — Base  of  ventr 


possd  by  removal  of  the  auricles. 


562 


THE  VASCULAR  SYSTEMS 


Size  and  Weight  of  the  Heart. — The  normal  heart,  in  the  adult,  measures  five 
inches  in  length,  three  inches  and  a  half  in  breadth  at  the  broadest  part,  and 
two  inches  and  a  half  in  thickness.  The  prevalent  weight,  in  the  male,  varies 
from  ten  to  twelve  ounces  (average,  eleven  ounces) ;  in  the  female,  from  eight  to 
ten;  its  proportions  to  the  body  being  as  1  to  160  in  males;  1  to  150  in  females. 
The  heart  continues  to  increase  in  weight  and  in  size  up  to  an  advanced  period  of 
life ;  this  increase  is  more  marked  in  men  than  in  women. 

Structure  of  the  Heart. — The  heart  is  a  hollow  muscular  organ,  and  its  walls  are  divisible 
into  three  coats — the  endocardium,  myocardium,  and  epicardium,  or  visceral  layer  of  the  peri- 
cardium (page  .549). 

The  endocardium  is  a  thin,  smooth,  serous  membrane  which  lines  and  gives  the  glistening 
appearance  to  the  internal  surface  of  the  heart;  it  assists  in  forming  the  valves  by  reduplications 
and  is  continuous  with  the  endothelial  coat  of  the  bloodvessels  which  pass  to  and  emerge  from 
the  heart.  It  is  composed  of  endothelial  cells  resting  upon  a  fibro-elastic  membrane  which 
contains  some  unstriated  muscle  cells.  The  endocardium  is  more  opaque  on  the  left  than  on  the 
right  side  of  the  heart,  thicker  in  the  auricles  than  in  the  ventricles,  and  thickest  in  the  left  auricle. 
It  is  thin  on  the  musculi  pectinati  and  on  the  columnae  carneae,  but  thicker  on  the  smooth 
parts  of  the  auricular  and  ventricular  walls  and  on  the  tips  of  the  musculi  papillares. 

The  fibrous  rings  {annuli  fibrosi)  surround  the  auriculoventricular  and  arterial  orifices; 
they  are  stronger  upon  the  left  than  on  the  right  side  of  the  heart,  and  are  composed  of  dense 
white  fibrous  connective  tissue.  The  auriculoventricular  rings  serve  for  the  attachment  of  the 
muscle  fibers  of  the  auricles  and  ventricles,  and  also  for  the  mitral  and  tricuspid  valves;  the 
rino-  on  the  left  side  is  closely  connected  by  its  right  margin  with  the  aortic  arterial  ring.  Be- 
tween these  and  the  right  auriculoventricular  ring  is  a  mass  of  fibrous  tissue  (irigoniim  Jibrosum), 
and  in  some  of  the  larger  animals,  as  the  ox  and  elephant,  a  nodule  of  bone,  the  os  cordis. 

The  fibrous  rings  surrounding  the  arterial  orifices  serve  for  the  attachment  of  the  great  vessels 
and  semilunar  valves.  Each  ring  receives,  at  its  ventricular  margin,  the  attachment  of  the 
muscle  fibres  of  the  ventricles;  its  opposite  margin  presents  three  deep  semicircular  notches, 
within  which  the  middle  coat  of  the  artery  (which  presents  three  convex  semicircular  segments) 


Fig.  417.— The 


( Poirior  and  Charpy. ) 


is  firmly  fixed,  the  attachment  of  the  artery  to  its  fibrous  ring  being  strengthened  by  the  thin 
fibrous  "coat  and  serous  membrane  externally  and  by  the  endocardium  within.  It  is  opposite 
the  margins  of  these  semicircular  notches,  in  the  arterial  rings,  that  the  endocardium  by  its 
reduplication,  strengthened  by  white  fibrous  tissue,  forms  the  semilunar  valves,  the  fibrous 
structure  of  the  ring  being  continued  into  each  of  the  segments  of  the  valve.  The  middle 
coat  of  the  artery  in  this  "situation  is  thin,  and  the  sides  of  the  vessels  are  dilated  to  form  the 
sinuses  of  Valsalva. 

The  myocardium  of  the  heart  consists  of  bands  and  layers  of  muscle  tissue  which  present 
an  exceedingly  intricate  interlacement.  It  consists  of  (a)  the  fibres  of  the  auricles,  {b)  the 
fibres  of  the  ventricles,  and  (c)  the  auriculoventricular  bundle  of  His. 

Fibres  of  the  Auricles  (Fig.  417). — These  are  disposed  in  two  layers — a  superficial  layer 
common  to  both  cavities,  and  a  deep  laj^er  proper  to  each.  The  superficial  fibres  are  more 
distinct  on  the  anterior  surface  of  the  auricles,  across  the  bases  of  which  they  run  in  a  transverse 


THE  HEART 


563 


Fig.  418.— The  i 


lacular  arrangement  of  the  apex 
{Poirier  and  Charpy. ) 


direction,  forminf;  a  thin  but  incomplete  layer.  Some  of  these  fibres  pass  into  the  septum 
atrioriun.  The  internal  or  deep  fibres  proper  to  each  auricle  consist  of  two  sets,  looped  and 
annular  fibres.  The  looped  fibres  pass  upward  over  each  auricle,  being  attached  by  two  ex- 
tremities to  the  corresponding  auriculoventricular  rings  in  front  and  behind.  The  annular 
fibres  surroimd  the  auricular  ap- 
pendices, and  form  annular  bands 
around  the  terminations  of  the 
veins  and  around  the  fossa  ovalis. 
The  fibres  of  the  ventricles  are 
arranged  in  a  complex  manner,  and 
various  accoimts  have  been  given 
of  their  course  and  connections. 
The  following  description  is  based 
on  the  work  of  McCallum.'  They 
consist  of  superficial  and  deep 
layers,  all  of  which,  with  the  ex- 
ception of  two,  are  inserted  into 
the  papillary  muscles  of  the  ven- 
tricles. The  superficial  layers  con- 
sist of  the  following:  (a)  Fibres 
which  spring  from  the  tendon  of 
the  conus  arteriosus  and  sweep 
downward  and  toward  the  left 
across  the  anterior  interventricular 
furrow  and  around  the  apex  of  the 
heart,  where  they  pass  upward  and 
inward  to  terminate  in  the  papil- 
lary muscles  of  the  left  ventricle. 
Those  which  spring  from  the  upper 
half  of  the  tendon  of  the  conus  ar- 
teriosus pass  to  the  anterior  papil- 
lary muscle,  those  from  the  lower 
half  to  the  posterior  papillary  mus- 
cle and  the  papillary  muscles  of  the 
septum.  (6)  Fibres  which  arise 
from  the  right  auriculoventricular 
ring  and  nm  diagonally  across  the 
back  of  the  right  ventricle  and 
around  its  right  border  on  to  its 
anterior  surface,  where  they  dip 
beneath  the  fibres  just  described, 
and,  crossing  the  interventricular 
groove,  wind  aroimd  the  apex  of 
the  heart  and  terminate  in  the  pos- 
terior papillary  muscle  of  the  left 
ventricle,  (c)  Fibres  which  spring 
from  the  left  auriculoventricular 
ring,  and,  crossing  the  posterior 
interventricular  fm-row,  pass  suc- 
cessively into  the  right  ventricle 
and  end  in  its  papillary  muscles. 
The  deep  layers  are  tliree  in  num- 
ber; they  arise  in  the  papillary  mus- 
cles of  one  ventricle  and,  curving 
in  an  S-shaped  manner,  turn  in  at 
the  interventricular  furrow  and  end 
in  the  papillary  muscles  of  the 
other  ventricle.  The  layer  which 
is  most  superficial  in  the  right  ven- 
tricle lies  next  the  lumen  of  the 
left,  and  rice  versa.  Those  of  the  first  layer  almost  encircle  the  right  ventricle,  and,  crossing 
in  the  septum  to  the  left,  unite  with  the  superficial  fibres  from  the  right  auriculoventricujai 
ring  to  form  the  posterior  papillary  muscle.  Those  of  the  second  layer  have  a  less  extensive 
course  in  the  wall  of  the  right  ventricle,  and  a  correspondingly  greater  course  in  the  left,  where 
they  join  with  the  superficial  fibres  from  the  anterior  half  of  the  tendon  of  the  conus  arteriosus 

I  Johns  Hopkins  Hospital  Reports,  vol.  ix. 


Fig.  419. — The  arrangement  of  the  muscle  of    the 
(Poirier  and  Charpy.) 


564 


THE  VASCULAR  SYSTEMS 


to  form  the  papillary  muscles  of  the  septum.  Those  of  the  third  layer  pass  almost  entii-ely 
around  the  left  ventricle  and  unite  with  the  superficial  fibres  from  the  lower  half  of  the  tendon 
of  the  conus  arteriosus  to  form  the  anterior  papillary  muscle.  Besides  the  layers  just 
described  there  are  two  bands  which  do  not  end  in  papillary  muscles.  One  springs  from  the 
right  auriculoventricular  ring  and  crosses  in  the  auriculoventricular  septum;  it  then  encircles 
the  deep  laj-ers  of  the  left  ventricle  and  ends  in  the  left  auriculoventricular  ring.  The  second 
band  is  apparently  confined  to  the  left  ventricle;  it  is  attached  to  the  left  auriculoventricular 
ring,  and  encircles  the  portion  of  the  ventricles  adjacent  to  the  aortic  orifice. 

The  auriculoventricular  bundle  of  His  {fasciculus  atrioventricularis)  (Fig.  420)  is  the  only 
direct  muscle  ronnection  known  to  exist  between  the  auricles  and  ventricles.  It  arises 
near  the  opening  of  the  coronary  sinus,  where  it  is  connected  with  the  annular  and  septal 
fibres  of  the  right  auricle.     These  fibres  converge,  form  anode  {node  of  Tawara),  and  continue 


Fig.  420. — Schematic  representation  of  the  auriculoventricular  bundle  of  His.  The  bundle,  represented  in  red, 
originates  near  the  orifice  of  the  coronarj'  sinus,  undergoes  slight  enlargement  to  form  a  node,  passes  forward  to 
the  interventricular  septum,  and  divides  into  two  limbs.    The  ultimate  distribution  cannot  be  completely  shown 


as  a  compact  bundle  which  passes  forward  in  the  lower  part  of  the  pars  memhranacea  scpti  to 
the  upper  limit  of  the  muscle  portion  of  the  ventricular  septum,  and  divides  into  right  and 
left  fasciculi.  These  run  down  to  the  right  and  left  ventricles,  one  on  either  side  of  the  inter- 
ventricular septum,  the  left  limb  being  just  covered  by  endocardium,  while  the  right  limb,  for 
a  part  of  its  course,  is  more  deeply  placed  in  the  muscle  layer.  Each  limb  is  enclosed  in  a 
layer  of  connective  tissue,  which  isolates  it  from  the  musculature  of  the  interventricular  sep- 
tum, but  in  the  lower  parts  of  the  ventricles  each  fasciculus  separates  into  numerous  strands 
which  enter  the  papillary  muscles  and  spread  over  the  entire  internal  surface  of  the  ventricular 
muscle  and  form  histological  connections  with  the  true  cardiac  muscle  fibres.  The  right  limb 
is  the  smaller  of  the  two  and  usually  reaches  the  anterior  papillary  muscle  by  passing  along 
the  moderator  band  when  this  is  present.  The  undivided  portion  of  the  auriculoventricular 
bundle  consists  of  narrow,  somewhat  fusiform  fibres,  but  its  two  divisions  and  their  terminal 


THE  HEART  565 

strands  are  composed  of  Purkinje  fibres.  The  bundle  is  not  always  easily  recognized  in  the 
human  heart,  but  is  readily  demonstrated  in  the  heart  of  the  sheep  or  calf. 

A  constant  bursa  or  lubricating  mechanism  is  in  relation  with  the  main  bundle,  according 
to  Curran,'  and  a  special  artery,  arising  from  the  right  coronary,  enters  the  bundle  at  its  begin- 
ning and  follows  it  in  direction. 

The  Purkinje  fibres  are  very  much  larger  in  size  than  the  cardiac  cells,  and  differ  from  them 
in  several  ways.  In  longitudinal  section  they  are  quadrilateral  in  shape,  being  about  twice  as 
long  as  they  are  broad.  The  central  portion  of  each  fibre  contains  one  or  more  nuclei  and  is 
made  up  of  granular  protoplasm,  with  no  indication  of  striations,  while  the  peripheral  portion  is 
clear  and  has  distinct  transverse  striations.  The  fibres  are  intimately  connected  with  each  other, 
possess  no  definite  sarcolemma,  and  do  not  branch. 

The  epicardium,  or  visceral  layer  of  the  pericardium,  is  a  serous  membrane  analogous  in 
structure  to  the  endocardium,  but  contains  no  smooth  muscle  tissue.  It  is  thin,  smooth,  glisten- 
ing, and  transparent,  and  is  reflected  over  the  roots  of  the  great  vessels  to  the  inner  surface  of  the 
pericardial  sac,  forming  there  the  parietal  layer  of  the  pericardium. 

Applied  Anatomy. — Clinical  and  experimental  evidence  go  to  prove  that  the  auriculoven- 
tricular  bundle  conveys  the  impulse  to  systolic  contraction  from  the  auricular  septum  to  the 
ventricles,  and  much  attention  has  recently  been  paid  to  it,  because  it  appears  to  become 
attacked  by  various  disease  processes  and  to  lose  much  of  its  conducting  power  in  many  cases 
of  Stokes-Adams  disease  (heart  block).  This  condition  is  characterized  by  a  slow  pulse,  a 
tendency  to  syncopal  or  epileptiform  seizures,  and  the  fact  that  while  the  cardiac  auricles 
beat  at  a  normal  rate,  the  ventricles  contract  much  less  frequently.  The  existence  of  a  bursa 
in  relation  with  the  bundle  suggests  the  possibility  of  a  bursitis,  in  view  of  which  these  cardiac 
symptoms  may  be  the  result  of  acute  rheumatism  or  other  febrile  diseases. 

Vessels  and  Nerves. — The  arteries  supplying  the  heart  are  the  right  and  left  coronary  from 
the  aorta. 

The  veins  terminate  in  the  right  auricle,  and  will  be  described  with  the  general  venous  system. 

The  lymphatics  end  in  the  thoracic  and  right  lymphatic  ducts. 

The  nerves  are  derived  from  the  superficial  and  deep  cardiac  plexuses,  and  from  these  plexuses 
obtain  fibres  of  the  vagus,  spinal  accessory,  and  sympathetic.  The  superficial  cardiac  plexus  lies 
under  the  arch  of  the  aorta.  The  deep  cardiac  plexus  is  in  front  of  the  tracheal  bifurcation. 
The  nerves  from  the  plexuses  are  freely  distributed  both  on  the  surface  and  in  the  substance  of 
the  heart,  the  separate  filaments  being  furnished  with  small  ganglia.  A  special  system  of  gan- 
glion cells  and  nerve  fibres  has  been  found-  in  the  auriculoventricular  bimdle. 

The  Cardiac  Cycle  and  the  Action  of  the  Valves.' — By  the  contractions  and  pump- 
ing action  of  the  heart  the  blood  is  forced  through  the  arteries,  capillaries  and  veins 
of  the  systemic  and  pulmonic  v.ascular  systems.  Normally,  these  contractions  are 
rhythmic  in  character  and  occur  at  the  rate  of  about  seventy  per  minute.  Each 
period  of  activity  is  followed  by  a  period  of  rest,  and  during  these  two  periods 
certain  events  take  place  in  the  various  parts  of  the  heart  in  regular  sequential 
order.  The  period  included  between  the  occurrence  of  any  one  of  these  events 
and  the  recurrence  of  the  same  event  constitutes  a  cardiac  cycle,  or  cardiac  revolution. 

The  cardiac  cycle  may  be  conveniently  divided  into  three  phases,  which  succeed 
one  another,  as  follows:  (1)  A  short,  practically  simultaneous  contraction  of  both 
auricles,  termed  the  miricular  systole,  followed,  after  a  slight  pause,  by  (2)  a  simul- 
taneous, but  more  prolonged,  contraction  of  both  ventricles,  named  the  venfriciilar 
systole,  and  (3)  a  period  of  rest  during  which  the  whole  heart  is  relaxed,  i.  e.,  in  a 
state  of  diastole.  The  contraction  process  begins  at  the  venous  openings  or  in  an 
area  in  the  right  auricle  between  the  venae  cavae,  whence  it  spreads,  in  the  form 
of  a  wave,  over  the  auricles  and  then  to  and  over  the  ventricles.  The  quick 
contraction  of  the  auricles  forces  the  blood  contained  in  these  chambers,  through 
the  auriculoventricular  openings  into  the  relaxed  ventricles,  which  become 
fully  distended.  The  contraction  of  the  ventricles  follows  almost  immediately. 
There  ensues  a  rapid  compression  of  the  contained  mass  of  blood  and  a  rela- 
ti\'ely  high  pressure  is  thus  developed  which  occasions  the  forcible  closure  of 
the  auriculoventricular  valves.  These  are  prevented  from  being  everted  into 
the  auricular  cavities  by  their  attachment  to  the  papillary  muscles  through  the 
intermediation  of  the  chordae  tendineae.     The  diminution  in  size  of  the  ventricular 

•The  Anatomical  Record,  December,  1909,  vol.  iii,  No.  12. 

2.T.  Gordon  Wilson,  Proceedings  of  the  Royal  Society,  B.,  1909,  vol.  Ixxxi. 

3  Re\d3ed  by  Dr.  G.  Bachmann. 


566  THE   VASCULAR  SYSTEMS 

cavities  might  be  followed  by  a  slackening  of  these  tendinous  cords  were  it  not 
for  the  compensating  effect  of  the  active  shortening  of  the  papillary  muscles  which 
takes  place  shortly  after  the  onset  of  the  contraction  of  the  general  ventricular 
musculature.  The  pressure  in  the  ventricles  soon  rises  above  that  in  the  pul- 
monary artery  and  aorta.  At  that  moment  the  valves  at  the  orifices  of  these  vessels 
are  forced  open  and  the  blood  is  driven,  by  a  sustained  contraction,  from  the  right 
ventricle  into  the  pulmonary  artery  and  from  the  left  ventricle  into  the  aorta. 
As  soon  as  the  ventricular  systole  ceases  and  the  pressure  in  the  pulmonary  artery 
and  aorta  exceeds  that  in  the  ventricles  the  pulmonary  and  aortic  valves  close,  thus 
preventing  a  regurgitation  of  the  blood  into  the  ventricles.  While  the  ventricle? 
are  contracting  blood  is  flowing  from  the  veins  into  the  auricles,  where  it  accumu- 
lates and  distends  them.  As  the  ventricles  relax,  the  pressure  of  the  blood  in  the 
auricles  opens  the  auriculoventricular  valves  and  blood  now  flows  passively  from 
the  veins  into  the  auricles  and  from  these  into  the  ventricles.  The  rapid  accumu- 
lation of  the  blood  in  the  ventricles  leads  to  a  floating  up  of  the  auriculoventricular 
valves  which  are  shortly  afterward  pushed  aside  during  the  next  succeeding 
auricular  contraction. 

It  will  be  observed  that  each  set  of  chambers  contracts  and  relaxes  alternately. 
However,  the  time  occupied  by  the  auricular  contraction  is  short,  while  that  occu- 
pied by  the  relaxation  is  long  in  comparison  with  the  time  occupied  by  the  similar 
events  in  the  ventricles.  From  the  beginning  of  the  ventricular  diastole  until  the 
beginning  of  the  next  auricular  systole  the  entire  heart  is  at  rest — the  so-called 
common  pause  of  the  heart's  chambers.  The  average  duration  of  a  cardiac  cycle 
is  about  3^  of  a  second,  which  may  be  divided,  approximately,  among  its  different 
phases  as  follows: 

Auricular  systole,  ^.  Auricular  diastole,  ^. 

Ventricular  systole,  -=^5-.  Ventricular  diastole,  ^^. 

Common  pause  -pj. 

As  mentioned  before,  the  contraction  process,  which  begins  at  the  mouths  of 
the  great  veins,  spreads  with  great  rapidity,  over  the  auricles,  and  then  to  and 
over  the  ventricles.  A  slight  delay  is  experienced  by  the  contraction  wave  in 
passing  from  the  auricles  to  the  ventricles.  This  is  due  in  all  probability  to  the 
circumstance  that  the  contraction  wave  must  be  conducted  along  a  narrow  bridge 
of  muscle  tissue  which  is  more  or  less  embryonic  in  character.  This  bridge  of  mus- 
cle tissue  connecting  the  auricles  with  the  ventricles,  morphologically  and  physio- 
logically, is  the  auriculoventricular  bundle  of  His  (page  564).  In  accordance  with 
this  view,  the  origin  and  conduction  of  the  contraction  process  is  a  property  of 
the  muscle  tissue,  and  the  theory  which  embodies  this  view  is  known  as  the  myo- 
genic theory  of  the  heart  beat.  Inasmuch  as  nerve  cells  and  their  axones  are 
found  in  many  parts  of  the  heart,  the  auriculoventricular  bundle  included,  it  is 
thought  by  some  that  the  origin  and  conduction  of  the  stimulus  giving  rise  to 
the  contraction  process  is  a  property  of  the  nerve  tissue.  The  theory  embodying 
this  view  is  known  as  the  neurogenic  theory  of  the  heart  beat.  It  must  be  said, 
however,  that  many  facts  tend  to  demonstrate  that  the  myogenic  theory  is  the  cor- 
rect one.  Whatever  be  the  tissue  in  which  the  heart  beat  originates,  the  cause  of 
the  contraction  must  be  sought  in  the  heart  itself;  for  the  mammalian  heart  can  be 
made  to  beat  for  a  relatively  long  time  when  completely  isolated  from  the  body  of 
the  animal. 
•  The  cardiac  muscle,  therefore,  does  not  depend  for  its  contractions  on  the  dis- 
charge of  nerve  impulses  by  the  central  nerve  system,  although  the  latter, 'through 
the  extracardiac  nerves,  exercises  a  regulative  influence  on  the  heart's  action, 
increasing  or  decreasing  the  rate  or  force  of  the  heart  beats  in  accordance  with 
the  physiological  needs  of  the  body. 


THE  HE  ART 


567 


Surface  Form.— In  order  to  show  the  exlmt  of  the  heart  in  relation  to  the  front  of  the  thorax, 
draw  a  line  from  a  point  in  the  second  Icl'l  intn-co.slal  sjiace,  4.5  cm.  (nearly  two  inches)  from 
the  median  line  to  the  upper  border  of  the  third  rjoht  costal  cartilage,  .3  cm.  (one  inch  and  a 
quarter)  from  the  median  line.  This  represents  the  base  line  or  upper  limit  of  the  organ.  Take 
a  point  in  the  fifth  left  intercostal  space  8  cm.  from  the  median  line  (about  three  and  a  quarter 
inches) ;  this  represents  the  apex  of  the  heart.  Draw  a  line  from  this  apex  point,  with  a  slight 
convexity  downward,  to  the  junction  of  the  seventh  right  costal  cartilage  to  the  sternum  2..5  cm. 
from  the  median  line.  Thi.s  represents  the  lower  limit  of  the  heart.  Join  the  right  extremity 
of  the  first  line— that  is,  the  base  line— with  the  right  extremity  of  this  line— that  is,  to  the  seventh 
right  chondrosternal  joint— with  a  slight  curve  outward,  so  that  it  projects  about  3.5  cm.  (one 
inch  and  a  half)  from  the  mid-line  of  the  sternum.  Lastly,  join  the  left  extremity  of  the  base 
line  and  the  apex  point  by  a  line  curved  slightly  to  the  left. 


,  showing  relation  of  the  heart,  lungs,  etc.,  to  the  ribs  and  sternum.     P.  Pul- 
M.  Left  auriculoventricular  orifice.     Tr.  Right  auriculoventricular  orifice. 

A  portion  of  the  area  of  the  heart  thus  mapped  out  is  uncovered  by  lung,  and  therefore  gives 
a  dull  note  on  percussion;  the  remainder,  being  overlapped  by  the  lung,  gives  a  more  or  less 
resonant  note.  The  former  is  known  as  the  are:i  of  complete  cardiac  dulness.  The  area  of 
complete  cardiac  dulness  is  included  between  a  line  drav^n  from  the  centre  of  the  sternum,  on  a 
level  with  the  fourth  costal  cartilage,  to  the  apex  of  the  heart,  and  a  line  drawn  from  the  same 
point  down  the  lower  third  of  the  midline  of  the  sternum.  Below,  this  area  merges  into  the 
dulness  which  corresponds  to  the  liver. 

Topography  of  the  various  orifices  is  as  follows — viz.,  the  pulmonary  orifice  is  situated 
in  the  upper  angle  formed  by  the  articulation  of  the  third  left  costal  cartilage  with  the  sternum; 
the  aortic  orifice  is  a  little  below  and  internal  to  this,  behind  the  left  border  of  the  sternimi, 
close  to  the  articulation  of  the  third  left  costal  cartilage  to  this  bone.  The  left  avriculore7itricular 
opening  is  behind  the  sternum,  rather  to  the  left  of  the  median  line,  and  opposite  the  fourth 
costal  cartilages.  The  right  auricidoventricular  opening  is  a  little  lower,  opposite  the  fourth 
interspace  and  in  the  middle  line  of  the  body  (Fig.  421). 


568 


THE   VASCULAR  SYSTEMS 


Applied  Anatomy. — Wounds  of  the  heart  are  often  immediately  fatal,  but  not  necessarily 
so.  Thev  nia\'  be  nonpenetrating,  when  death  may  occur  from  hemorrhage,  if  one  of  the  coro- 
nary vessels  has  been  wounded,  or  subsequently  from  pericarditis;  or,  on  the  other  hand,  the 
patient  may  recover.  Even  a  penetrating  wound  is  not  necessarily  fatal,  if  the  wound  is  a  small 
one.  An  attempt  should  be  made  to  save  the  patient  by  means  of  a  surgical  operation.  A 
trap-door  flap  comprising  the  whole  thickness  of  the  thoracic  wall  should  be  made.  The  hinges 
of  the  trap-door  are  the  rib  cartilages.  The  pericardium  is  exposed  and  freely  opened,  clots 
are  removed,  the  wound  in  the  heart  is  sought  for,  and  when  discovered  is  sutured.  In  a  pene- 
trating wound  the  sutures  include  the  whole  thickness  of  the  heart,  except  the  endocardium. 
Interrupted  sutures  should  be  used,  and  each  one  had  better  be  tied  during  diastole.  A  number 
of  successful  operations  of  this  character  have  been  performed. 

Peculiarities  in  the  Vascular  System  of  the  Fetus  (Fig.  423). 

The  chief  peculiarities  in  the  heart  of  the  fetus  are  the  direct  communication 
between  the  two  auricles  through  the  foramen  ovale,  and  the  large  size  of  the 
Eustachian  valve.  There  are  also  several  minor  peculiarities.  Thus,  the  position 
of  the  heart  is  vertical  until  the  fourth  month,  when  it  commences  to  assume  an 
oblique  direction.  Its  size  is  also  very  considerable  as  compared  with  the  body, 
the  proportion  at  the  second  month  being  1  to  50;  at  birth  it  is  as  1  to  120;  while 
in  the  adult  the  average  is  about  1  to  160.  At  an  early  period  of  fetal  life  the  auric- 
ular portion  of  the  heart  is  larger  than  the  ventricular,  the  right  auricle  being 
more  capacious  than  the  left;  but  toward  birth  the  ventricular  portion  becomes 
the  larger.  The  thickness  of  both  ventricles  is  at  first  about  equal,  but  toward 
birth  the  left  becomes  much  the  thicker  of  the  two. 


Fig.  422. — The  right  auricle  of  a  fetal  heart  (eighth  month).    Enlarged.     (Spalteholz.) 

The  foramen  ovale  (Fig.  422)  is  situated  at  the  lower  and  back  part  of  the  inter- 
auricular  septum,  forming  a  communication  between  the  auricles.  It  remains  as  a 
free  oval  opening  until  the  middle  period  of  fetal  life.  About  this  period  a  fold  grows 
up  from  the  posterior  wall  of  the  auricle  to  the  left  of  the  foramen  ovale,  and 
advances  over  the  opening  so  as  to  form  a  sort  of  valve,  which  allows  the  blood 
to  pass  only  from  the  right  to  the  left  auricle,  but  not  in  the  opposite  direction. 

The  Eustachian  valve  (Fig.  422)  projects  upward  in  front  of  the  opening  of 
the  inferior  vena  cava,  and  tends  to  direct  the  bl.ood  from  this  vessel  through 
the  foramen  ovale  into  the  left  auricle. 


THE  HEART 


569 


The  peculiarities  in  the  arterial  system  of  the  fetus  are  the  communication 
between  the  pulmonar.y  artery  and  the  descending  aorta  by  means  of  the  ductus 
arteriosus,  and  the  continuation  of  the  internal  iliac  arteries  as  the  umbilical 
arteries  to  the  placenta. 


Pndus  arteriosus. 


Infe)  nal  iliac  arteri 


Fig.  423. — Plan  of  the  fetal  circulation.     In  this  plan  the  figured  arrows  represent  the  kind  of  blood,  as  well 

as  the  direction  which  it  takes  in  the  vessels.     Thus,  arterial  blood  is  figured  >> — - -> ;  venous  blood, 

>> >;  mixed  (arterial  and  venous)  blood,  >>••• — ••• — >. 


The  ductus  arteriosus  (Fig.  423)  is  a  short  tube,  about  10  mm.  (half  an  inch)  in 
length  at  birth,  and  2  mm.  (one-twelfth  of  an  inch)  in  diameter.  In  the  early 
condition  it  forms  the  continuation  of  the  pulmonary  artery,  and  opens  into  the 
descending  aorta  just  below  the  origin  of  the  left  subclavian  artery,  and  so  con- 


570  THE   VASCULAR  SY8TEM8 

ducts  the  greater  part  of  the  blood  from  the  right  ventricle  into  this  vessel.  When 
the  branches  of  the  pulmonary  artery  have  become  relatively  larger  to  the  ductus 
arteriosus,  the  latter  is  chiefly  connected  to  the  left  pulmonary  artery;  and  the 
fibrous  cord  {ligamentum  arteriosum) ,  which  is  all  that  remains  of  the  ductus 
arteriosus  in  later  life,  will  be  found  to  be  attached  to  the  root  of  that  vessel. 
Occasionally  a  small  lumen  persists  in  the  ligamentum  arteriosum. 

The  umbilical  or  hypogastric  arteries  are  continued  from  the  internal  iliacs, 
along  the  sides  of  the  bladder  to  its  apex;  they  pass  out  of  the  abdomen  at  the 
umbilicus  and  are  carried  in  the  umbilical  cord  to  the  placenta.  They  convey 
the  blood  which  has  circulated  in  the  system  of  the  fetus  to  the  placenta. 

The  peculiarities  in  the  venous  system  of  the  fetus  are  the  communications 
established  between  the  placenta  and  the  liver  and  portal  vein,  through  the  umbil- 
ical vein;  and  between  the  umbilical  vein  and  the  inferior  vena  cava  through  the 
ductus  venosus. 

Fetal  Circulation  (Fig.  423). — ^The  blood  destined  for  the  nutrition  of  the 
fetus  is  returned  from  the  placenta  to  the  fetus  by  the  umbilical  vein.  This  vein 
enters  the  abdomen  at  the  umbilicus,  and  passes  upward  along  the  free  margin  of 
the  suspensory  ligament  of  the  liver  to  the  under  surface  of  that  organ,  where  it 
gives  off  two  or  three  branches  to  the  left  lobe,  one  of  which  is  of  large  size,  and 
others  to  the  quadrate  and  Spigelian  lobes.  At  the  transverse  fissure  it  divides 
into  two  branches;  of  these,  the  larger  is  joined  by  the  portal  vein  and  enters  the 
right  lobe;  the  smaller  branch  continues  outward,  under  the  name  of  the  ductus 
venosus,  and  joins  the  left  hepatic  vein  at  the  point  of  junction  of  that  vessel  with 
the  inferior  vena  cava.  The  blood,  therefore,  which  traverses  the  umbilical  vein 
reaches  the  inferior  vena  cava  in  three  different  ways ;  the  greater  quantity  circu- 
lates through  the  liver  with  the  portal  venous  blood  before  entering  the  inferior 
vena  cava  by  the  hepatic  veins ;  some  enters  the  liver  directly,  and  is  also  returned 
to  the  inferior  vena  cava  by  the  hepatic  veins ;  the  smaller  quantity  passes  directly 
into  the  inferior  vena  cava  by  the  junction  of  the  ductus  venosus  with  the  left  hepatic 
vein. 

In  the  inferior  vena  cava  (postcava)  the  blood  carried  by  the  ductus  venosus  and 
hepatic  veins  becomes  mixed  with  that  returning  from  the  lower  extremities  and 
wall  of  the  abdomen.  It  enters  the  right  auricle,  and,  guided  by  the  Eustachian 
valve,  passes  through  the  foramen  ovale  into  the  left  auricle,  where  it  becomes 
mixed  with  a  small  quantity  of  blood  returned  from  the  lungs  by  the  pulmonary 
veins.  From  the  left  auricle  it  passes  into  the  left  ventricle,  and  from  the  left 
ventricle  into  the  aorta,  by  means  of  which  it  is  distributed  almost  entirely  to 
the  head  and  upper  extremities,  a  small  quantity  being  probably  carried  into  the 
descending  aorta.  From  the  head  and  upper  extremities  the  blood  is  returned 
by  the  tributaries  of  the  superior  vena  cava  to  the  right  auricle,  where  it 
becomes  mixed  with  a  small  portion  of  the  blood  from  the  inferior  vena  cava. 
From  the  right  auricle  it  descends  over  the  Eustachian  valve  into  the  right  ventricle, 
and  from  the  right  ventricle  passes  into  the  pulmonary  artery.  The  lungs  of  the 
fetus  being  inactive,  only  a  small  quantity  of  the  blood  of  the  pulmonary  artery  is 
distributed  to  them  by  the  right  and  left  pulmonary  arteries,  and  is  returned  by  the 
pulmonary  veins  to  the  left  auricle;  the  greater  part  passes  through  the  ductus 
arteriosus  into  the  commencement  of  the  descending  aorta,  where  it  becomes 
mixed  with  the  blood  transmitted  by  the  left  ventricle  into  the  aorta.  Through 
this  vessel  it  descends  to  supply  the  lower  extremities  and  viscera  of  the  abdomen 
and  pelvis,  the  chief  portion  being,  however,  conveyed  by  the  umbilical  arteries 
to  the  placenta. 

From  the  preceding  account  of  the  circulation  of  the  blood  in  the  fetus  it  will 
be  seen — 

1.  That  the  placenta  serves  the  purposes  of  nutrition,  respiration,  and  excretion, 


THE  HEART  571 

receiving  the  impure  blood  from  the  fetus,  and  returning  it  charged  with  addi- 
tional nutritive  material. 

2.  That  nearly  the  whole  of  the  blood  of  the  umbilical  vein  traverses  the  liver 
before  entering  the  inferior  vena  cava;  hence  the  large  size  of  this  organ,  especially 
at  an  early  period  of  fetal  life. 

3.  That  the  right  auricle  is  the  point  of  meeting  of  a  double  current,  the  blood 
in  the  inferior  vena  cava  being  guided  by  the  Eustachian  valve  into  the  left  auricle, 
while  that  in  the  superior  vena  cava  descends  into  the  right  ventricle.  At  an  early 
period  of  the  fetal  life  it  is  somewhat  probable  that  the  two  streams  are  distinct, 
for  the  inferior  vena  cava  opens  almost  directly  into  the  left  auricle,  and  the  Eusta- 
chian valve  would  tend  to  exclude  the  current  along  the  vein  from  entering  the 
right  ventricle.  At  a  later  period,  as  the  separation  between  the  two  auricles 
becomes  more  distinct,  it  seems  more  probable  that  mixture  of  the  two  streams 
must  take  place. 

4.  The  pure  blood  carried  from  the  placenta  to  the  fetus  by  the  umbilical  vein, 
mixed  with  the  blood  from  the  portal  vein  and  the  inferior  vena  cava,  passes  almost 
directly  to  the  arch  of  the  aorta,  and  is  distributed  by  the  branches  of  that  vessel 
to  the  head  and  upper  extremities;  hence  the  large  size  and  advanced  development 
of  those  parts  at  birth. 

5.  The  blood  contained  in  the  descending  aorta,  largely  derived  from  that 
which  has  already  circulated  through  the  head  and  upper  limbs,  together  with  a 
small  quantity  from  the  left  ventricle,  is  distributed  to  the  lower  extremities; 
hence  the  small  size  and  less  advanced  development  of  these  parts  at  birth. 

Changfes  in  the  Vascular  System  at  Birth. — At  birth,  when  respiration  is 
established,  an  increased  amount  of  blood  from  the  pulmonary  artery  passes 
through  the  lungs,  which  now  perform  their  office  as  respiratory  organs,  and  at 
the  same  time  the  placental  circulation  is  cut  off.  Soon  after  birth  the  foramen 
ovale  is  closed  by  the  valvular  edge  being  pressed  against  the  annulus  ovalis,  the 
pressure  being  due  to  respiration,  which  increases  the  pressure  in  the  left  auricle. 
The  structures  fuse,  and  closure  is  usually  complete  by  about  the  tenth  day  after 
birth.  The  valvular  fold  above  mentioned  becomes  adherent  to  the  margins  of 
the  foramen  for  the  greater  part  of  its  circumference,  but  above  a  slit-like  opening 
is  left  between  the  two  auricles  which  sometimes  remains  persistent. 

The  ductus  arteriosus  begins  to  contract  immediately  after  respiration  is  estab- 
lished, usually  becomes  completely  closed  from  the  fourth  to  the  tenth  day,  and 
•ultimately  degenerates  into  an  impervious  cord  {Kg.  arteriosuvi)  which  serves  to 
connect  the  left  pulmonary  artery  to  the  arch  of  the  aorta. 

Of  the  umbilical  or  hypogastric  arteries,  the  portion  continued  on  to  the  bladder 
from  the  trunk  of  the  corresponding  internal  iliac  remains  pervious  as  the  superior 
vesical  artery,  and  the  part  extending  from  the  side  of  the  bladder  to  the  umbilicus 
becomes  impervious  between  the  second  and  fifth  days  after  birth,  and  projects 
as  a  fibrous  cord  toward  the  abdominal  cavity,  carrying  on  it  a  fold  of  peritoneum. 

The  umbilical  win  and  the  ductus  venosus  become  impervious  between  the  second 
and  fifth  days  after  birth,  and  ultimately  dwindle  to  fibrous  cords,  the  former 
becoming  the  rowul  ligament  of  the  liver,  the  latter  the  ligamentum  venosum  of 
the  liver. 


THE  AETERIES. 


The  arteries  are  cylindrical  tubular  vessels  which  serve  to  convey  blood  from 
both  ventricles  of  the  heart  to  every  part  of  the  body.  These  vessels  were  named 
arteries  {i^p,  air;  r/jpslu,  to  contain)  from  the  belief  entertained  by  the  ancients 
tliat  they  contained  air.  Galen  is  believed  to  have  been  the  first  to  show  that 
during  life  they  contain  blood. 

The  distribution  of  the  systemic  arteries  is  like  a  highly  ramified  tree,  the  common 
trunk  of  which,  formed  by  the  aorta,  commences  at  the  left  ventricle  of  the  heart, 
the  smallest  ramifications  corresponding  to  the  periphery  of  the  body  and  the 
contained  organs.  The  arteries  are  found  in  nearly  every  part  of  the  body,  with 
the  exception  of  the  hairs,  nails,  epidermis,  cartilages,  and  cornea;  and  the  larger 
trunks  usually  occupy  the  most  protected  situations,  running,  in  a  limb,  along  the 
flexor  side,  where  they  are  less  exposed  to  injury. 

There  is  considerable  variation  in  the  mode  of  division  of  the  arteries;  occasion- 
ally a  short  trunk  subdivides  into  several  branches  at  the  same  point,  as  we  observe 

in  the  celiac  and  thyroid  axes;  or  the 
j^  B  vessel  may  give  off  several  branches  in 

succession,  and  still  continue  as  the 
main  trunk,  as  is  seen  in  the  arteries  of 
the  limbs;  but  the  usual  division  is 
dichotomous;  as,  for  instance,  the  aorta 
dividing  into  the  two  common  iliacs, 
and  the  common  carotid  into  the  exter- 
nal and  internal  carotids. 

A  branch  of  an  artery  is  smaller  than 
the  trunk  from  which  it  arises;  but  if 
an  artery  divides  into  two  branches,  the 
combined  cross-section  area  of  the  two 
vessels  is,  in  nearly  every  instance, 
somewhat  greater  than  that  of  the 
trunk;  and  the  combined  cross-section 
area  of  all  the  arterial  branches  greatly 
exceeds  that  of  the  aorta ;  so  that  the 
arteries  collectively  may  be  regarded  as 
a  cone,  the  apex  of  which  corresponds  to 
the  aorta,  the  base  to  the  capillary 
system. 

The  arteries,  in  their  distribution,  communicate  with  one  another,  forming 
what  are  called  anastomoses  or  inosculations  ( Fig.  424) ;  and  these  communications 
are  very  free  between  the  large  as  well  as  between  the  smaller  branches.  An  anasto- 
mosis between  trunks  of  equal  size  is  found  where  great  activity  of  the  circulation 
is  requisite,  as  at  the  base  of  the  brain;  here  the  two  vertebral  arteries  unite  to 
form  the  basilar,  and  the  two  internal  carotid  arteries  are  connected  by  a  short 
communicating  trunk;  it  is  also  found  in  the  abdomen,  the  intestinal  arteries  having 
very  ample  anastomoses  between  their  larger  branches.  In  the  limbs  the  anasto- 
moses are  most  numerous  and  of  largest  size  around  the  joints,  the  branches  of  an 
artery  above  anastomosing  with  branches  from  the  vessels  below ;  these  anastomoses 
are  of  considerable  interest  to  the  surgeon,  as  it  is  by  their  enlargement  that  a 
(572) 


Fig.  424. — Diagram  showing  the  anastomosis  of 
arteries.      (Poirier  and  Charpy.) 


THE  ARTERIES  573 

collateral  circulation  is  established  after  the  application  of  a  ligature  to  an  artery. 
The  smaller  branches  of  arteries  anastomose  more  frequently  than  the  larger, 
and  between  the  smallest  twigs  these  inosculations  become  so  numerous  as  to 
constitute  a  close  network  that  pervades  nearly  every  tissue  of  the  body.  A  ter- 
minal artery  is  one  which  forms  no  anastomoses.  Such  vessels  are  believed  to  exist 
in  the  brain,  spleen,  kidneys,  lungs,  mesentery,  and  papillary  layer  of  the  skin. 

Throughout  the  body  generally  the  larger  arterial  branches  usually  pursue  a 
straight  course,  but  in  certain  situations  they  are  tortuous;  thus,  the  facial  arteries 
in  their  course  over  the  face,  and  the  arteries  of  the  lips,  are  extremely  tortuous  in 
their  course,  to  accommodate  themselves  to  the  movements  of  the  parts.  The 
uterine  arteries  are  also  tortuous,  to  accommodate  themselves  to  the  increase  of 
size  which  the  organ  undergoes  during  pregnancy. 

The  arteries  are  dense  in  structure,  of  considerable  strength,  highly  elastic,  and, 
when  divided,  they  usually  preserve,  although  empty,  their  cylindrical  form. 

Histology  of  Arteries  and  Capillaries.— An  artery  consists  of  an  endothelial  tube  covered 

by  certain  accessory  coats. 

The  coats  of  an  artery  are:  (1)  internal  coat,  or  tunica  intima;  (2)  a  middle  coat,  or  tunica 
media;  and  (3)  an  external  coat,  or  tunica  adventitia  (Fig.  409). 

1.  The  inner  coat  ifiiiiira  intima)  consists  of  endothehal  cells  resting  upon  some  subendo- 
thelial  fibroelastic  tissue.  Limiting  the  intima  is  a  "n-avy  band  of  yellow  elastic  tissue  called 
the  internal  elastic  lamina.  In  small  arteries  the  endothelial  cells  rest  upon  the  elastic  lamina. 
In  large  arteries  (aorta,  pulmonary  a.)  the  elastic  tissue  forms  the  fenestrated  membrane  of 
Henle. 

2.  The  middle  coat  (tunica  media)  consists  of  muscle,  elastic  tissue,  and  white  fibrous  tissue. 
In  medium-sized  arteries  the  smooth  muscle  tissue  is  circularly  arranged,  with  only  a  small 
quantity  of  elastic  tissue  here  and  there.     In  small  arteries  the  elastic  tissue  is  absent;  in  the 
large  arteries  the  elastic  tissue  predomi- 
nates; in  some  vessels  (retinal,  first  part 
of    aorta,  and    pulmonary     artery)    the 
elastic   tissue  may    entirely  replace    the 
muscle    tissue.     Occasionally   longitudi- 
nally arranged  muscle  tissue  is  seen  in 
the  media.     In  medium-sized  arteries  the 

media  is  bounded   by  a  layer  of   clastic  „   ^^         ^  ^-  _ 

tissue  called  (he  external  elastic  lamina.      D-fe*CT'^^^*^^'~-§^^ -''^^^^■i     "^  '-''  '^O 

3.  The  external  coat  (inniea  ndvnititia)         Q^^M^^^^^^^^^-^^-^^ 
is  called  the   fibrous    coat.     It  contains  ^'^="-^^&^^^^^^^^^^^^^° 
fibroelastic  tissues,  and  in  some  arteries           Fig.  425.— Transverse  section  of  part  of  the  wall  of  the 
fibres  of    nonstriated     muscle     longitudi-      posterior   tibial   artery.      X    75.      A.    Endothelial  and  sub- 

11  J       Ti  i    ■       ii  X  •      i       endothehal   layers  of   inner  coat.     B.   Elastic    layer  (fenes- 

nally  arranged,  tt  COntams  the  nutrient  trated  membrane)  of  inner  coat,  appearing  as  a  bright  line 
vessels,    nerves,    and     lymphatics  of    the      in  section.     C.  Muscle  layer  (middle  coat)      Z).  Outer  coat, 

,      .  i        ,,  +  '  rl*     *    ■  V,      ■  consistmg  of  connective-tissue  bundles.     In  the  interstices 

arteries,      as    tne     arteries    aiminisn     m      of  the  bundles  are  some  connective-tissue  nuclei,  and,  espe- 
size  the  coats  likewise  become    thinner.      I'ial'y  near  the  muscular  coat,  a  number  of  elastic  fibres  cut 
The  endothelial  cells    rest  upon   the  in- 
ternal elastic  lamina;  the  media  becomes 

reduced  to  a  few  layers  of  muscle  fibres,  and  the  adventitia  is  represented  by  some  bundles  of 
fibroelastic  tissue.  This  represents  the  precapillary  arteriole,  and  it  gradually  becomes  the 
capillary. 

Capillaries  are  small  endothelial  tubes  connecting  arterial  and  venous  systems.  They  vary 
from  joVo  to  2oVo  of  an  inch  (5 /j.  to  13/i)  in  diameter,  and  about  zs  of  an  inch  (500  /i)  in 
length.  The  endothelial  cells  are  thin,  flat,  and  irregular  in  outline;  the  darkly  staining  nucleus 
usually  causes  a  bulging  of  the  cell,  as  it  is  thicker  than  the  protoplasmic  portion  of  the  cells. 
These  cells  are  held  together  by  a  small  amount  of  cement  substance,  and  are  considered  by 
many  to  have  the  property  of  'phagocytosis.  These  cells  are  also  said  to  be  contractile.  Small 
openings  called  stomata  are  frecjuently  noted  between  these  cells,  but  they  are  considered  arti- 
facts. Capillaries  anastomose  and  form  vast  networks.  AmpuUse,  sinusoids,  retia  mirabilia, 
sinuses,  and  anastomoses  are  forms  of  capillaries  seen  in  certain  organs  and  tissues. 

Bloodvessels  of  the  Bloodvessel  Wall. — Many  small  bloodvessels,  the  vasa  vasorum, 
enter  the  adventitia;  from  these  vessels  branches  are  sent  into  the  media,  but  not  the  intima. 
The  latter  is  nourished  bj'  the  blood  that  flows  over  it.  They  may  arise  from  the  vessels  to 
which  they  are  distributed  or  take  origin  from  an  adjacent  vessel.  The  blood  is  returned  from 
the  walls  of  the  vessels  by  small  veins. 


574 


THE   VASCULAR  SYSTEMS 


Lymphatics. — Distinct  lymphatic  vessels  may  exist  in  the  adventitia,  but  are  represented 
by  li/inph  spaces  in  the  other  coats.  Lymph  capillaries  often  surround  small  bloodvessels,  or  a 
small  bloodvessel  may  lie  in  a  perivascular  Ijrmph  space. 

Nerves. — Arteries  are  supplied  with  nerves,  myelinic  and  amyelinic.  A  network  of  nerve 
fibres  may  surround  a  vessel,  and  usually  capillaries  are  so  surrounded.  In  the  arteries  a 
network  of  nerves  exists  in  the  media.  These  nerves  supply  the  muscle  fibres,  and  are  called 
vasomotor  nerves.  According  to  Stohr,  nerve  endings  are  found  in  the  endothelium  of  the 
capillaries,  giving  them  the  power  of  contractility. 

The  Arterial  Sheath  {vagina  vasis)  surrounds  the  artery.  It  is  composed  of  connective 
tissue,  and  is  attached  to  the  vessel  at  numerous  points  by  fibrous  tissue. 


Fig.  426. — Capillaries    from    the  Fig.  427. — Finest  vessels  on  the  arterial  side.     From  the  human 

mesentery     of     a    guinea-pig    after  brain.     Magnified  300  times.    1.  Small  artery.  2.  Transition  vessel, 

treatment  with  a  solution  of  nitrate  3.   Coarsei  capillaries.     4.  Finer  capillaries,     a.  Structureless  mem- 

of  silver,     a.  Cells,     b.  Their  nuclei.  brane  still  with   some  nuclei,  representative  of  the  tunica  adven- 

titia. h.  Nuclei  of  the  muscle  fibre  cells.  c.  Nuclei  within  the 
small  artery;  perhaps  appertaining  to  an  endothelium,  d.  Nuclei 
in  the  transition  vessels. 

Applied  Anatomy. — Arteries  are  liable  to  a  degenerative  process  known  as  atheroma  or  ar- 
teriosclerosis. It  is  essentially  a  senile  change,  although  it  may  begin  at  any  age  and  is  predis- 
posed by  renal  disease,  gout,  diabetes  mellitus,  and  many  other  morbid  states,  and  results  in  the 
replacement  of  the  arterial  elastic  tissue  by  fibrous  tissue.  The  process  results  in  the  rise  of  the 
arterial  blood-pressure  with  a  corresponding  hypertrophy  of  the  heart.  The  weakening  of  the 
vessel  wall,  with  reduction  of  the  calibre,  renders  such  affected  arteries  liable  to  rupture. 

THE   PULMONAEY   ARTERY    (A.  PULMONALIS)    (Figs.  429,  433). 

The  pulmonary  artery  conveys  the  venous  blood  from  the  heart  to  the  lungs. 
It  is  a  short,  wide  vessel,  about  two  inches  (5  cm.)  in  length  and  one  and  one- 
fifth  inches  (30  mm.)  in  diameter,  arising  from  the  left  side  of  the  base  (conns 
arteriosus)  of  the  right  ventricle,  in  front  of  the  aorta.  At  its  origin  are  three 
dilatations,  the  sinuses  of  Valsalva,  described  on  page  559.  It  extends  obliquely 
upward  and  backward,  passing  at  first  in  front  of  and  then  to  the  left  of  the 
ascending  aorta,  as  far  as  the  under  surface  of  the  arch,  where  it  divides,  about 
on  a  level  with  the  intervertebral  disk  between  the  fifth  and  sixth  thoracic  ver- 
tebrse,  into  right  and  left  branches  of  nearly  equal  size. 

Relations. — The  whole  of  the  vessel  is  contained,  together  with  the  ascending  aorta,  in  the 
pericardium.  It  is  enclosed  with  the  aorta  in  a  single  tube  of  the  serous  pericardium,  which  is 
continued  upward  upon  them  from  the  base  of  the  heart  and  connects  them  together.     The 


TI-IE  AORTA  675 

fibrous  layer  of  the  pericardium  becomes  gradually  lost  upon  the  external  coats  of  its  two  branches. 
In  front,  the  pulmonary  artery  is  separated  from  the  anterior  extremity  of  the  second  left  inter- 
costal space  by  the  pleura  and  left  lung,  in  addition  to  the  pericardium;  it  rests  at  first  upon 
the  ascending  aorta,  and  higher  up  lies  in  front  of  the  left  auricle  on  a  plane  posterior  to  the 
ascending  aorta.  On  either  side  of  its  origin  is  the  appendix  of  the  corresponding  auricle  and 
a  coronary  artery,  the  left  coronary  artery  passing,  in  the  first  part  of  its  course,  behind  the 
vessel.  The  superficial  cardiac  plexus  lies  above  its  bifurcation,  between  it  and  the  arch  of 
the  aorta. 

The  right  branch  of  the  pulmonary  artery  (ramus  dexter  a.  ■pulmonalis), 
longer  and  larger  than  the  left,  runs  liorizontally  outward  to  the  root  of  the  right 
lung,  where  it  divides  into  two  branches,  of  which  the  lower  and  larger  supplies 
the  middle  and  lower  lobes;  the  upper  and  smaller  is  distributed  to  the  upper  lobe. 
It  has  ill  front  of  it  the  ascending  aorta,  the  superior  vena  cava,  and  the  right  phrenic 
nerve.  It  has  behind  it  the  right  bronchus.  Above  it  is  the  arch  of  the  aorta. 
Beloiv  it  is  the  right  auricle. 

The  left  branch  of  the  pulmonary  artery  (ramus  sinister  a.  pidmonalis), 
shorter  and  somewhat  smaller  than  the  right,  passes  horizontally  to  the  root  of  the 
left  lung,  where  it  divides  into  two  branches  for  the  two  lobes.  In  front  of  it  and 
below  it  are  the  pulmonary  veins  of  the  left  side.  Behind  are  the  descending  aorta 
and  the  left  bronchus.  Above  it  are  the  arch  of  the  aorta,  the  left  recurrent  laryn- 
geal nerve,  and  the  ligamentum  arteriosum.  The  left  bronchus  in  a  portion  of 
its  course  lies  below  as  well  as  behind. 

The  root  of  the  left  pulmonary  artery  is  connected  to  the  under  surface  of  the 
arch  of  the  aorta  by  a  short  fibrous  cord,  the  ligamentum  arteriosum;  this  is  the 
remains  of  a  vessel  peculiar  to  fetal  life,  the  ductus  arteriosus. 

The  terminal  branches  of  the  pulmonary  artery  will  be  described  with  the 
anatomy  of  the  lung. 

Applied  Anatomy. — Stenosis  of  the  pulmonary  artery,  either  with,  or,  more  rarely,  without 
defective  formation  of  the  interventricular  septum,  is  one  of  the  commonest  congenital  defects 
of  the  heart.  It  may  be  due  either  to  fetal  endocarditis  or  to  maldevelopment  of  the  bulbus 
cordis.  As  in  most  forms  of  congenital  heart  disease,  the  child  is  cyanosed  (morbus  coervleus), 
especially  when  excited  or  on  exertion,  and  rarely  lives  to  adolescence,  commonly  dying  of  heart 
failure  in  infancy,  or  of  pulmonary  tuberculosis  or  intercurrent  disease  in  childhood.  The 
chief  signs  of  the  condition  .ii-e  the  loud,  harsh  systolic  cardiac  murmur  best  heard  over  the 
second  left  costal  cartilage,  cyanosis,  clubbing  of  the  finger  tips,  and  the  presence  of  an  excess 
of  red  corpuscles  in  the  blood. 

Embolism  of  the  pulmonary  artery  by  a  clot  of  blood  coming  from  the  right  side  of  the  heart 
in  patients  with  heart  disease,  or  from  a  thrombosed  vein  in  cases,  for  example,  of  influenza, 
enteric  fever,  puerperal  sepsis,  or  fractured  limbs,  is  a  common  cause  of  sudden  or  rapid  death. 
The  patient  may  cry  out  with  sudden  excruciating  pain  in  the  precordia  when  the  detached 
embolus  lodges,  and  after  a  brief  period  of  intense  dyspnea,  pallor,  and  anguish,  die. 

A  few  cases  of  surgical  interference  in  embolism  of  the  pulmonary  artery  are  on  record.  Sev- 
eral were  in  a  measure  successful,  death  being  usually  due  to  septic  complications,  such  as 
pleurisy  and  pericarditis.     (Cf.  Kreuzer,  Centralblatt  fiir  Chirurgie,  No.  21,  1909.) 

THE   AORTA  (Figs.  428,  429). 

The  aorta,  or  arteria  magna,  is  the  main  trunk  of  a  series  of  vessels  which  convey 
the  oxygenated  blood  to  the  tissues  of  the  body  for  their  nutrition.  It  commences 
at  the  upper  part  of  the  left  ventricle,  where  it  is  about  one  and  one-eighth  inches 
(28  mm.)  in  diameter,  and,  after  ascending  for  a  short  distance,  arches  backward 
and  to  the  left  side,  over  the  root  of  the  left  lung,  then  descends  within  the  thorax 
on  the  left  side  of  the  vertebral  column,  passes  through  the  aortic  opening  in  the 
Diaphragm,  and,  entering  the  abdominal  cavity,  terminates,  considerably  dimin- 
ished in  size,  about  seven-tenths  of  an  inch  (17.5  mm.)  in  diameter,  opposite  the 
lower  border  of  the  fourth  luitibar  vertebra,  where  it  divides  into  the  right  and  left 
common  iliac  arteries.  Hence,  it  is  divided  into  the  ascending  aorta,  the  arch  of 
the  aorta,  and  the  descending  aorta,  which  last  is  again  divided  into  the  thoracic 
aorta  and  the  abdominal  aorta,  from  the  position  of  these  parts. 


576 


THE   VASCULAR  SYSTEMS 


THE  ASCENDING  AORTA  (AORTA  ASCENDENS). 

The  ascending  aorta  is  about  two  inches  (5  to  6  cm.)  in  length.  It  commences 
at  the  base  of  the  left  ventricle,  on  a  level  with  the  lower  border  of  the  third  costal 
cartilage,  behind  the  left  half  of  the  sternum;  it  passes  obliquely  upward,  forward, 
and  to  the  right,  as  high  as  the  upper  border  of  the  second  right  costal  cartilage, 


VAGUS    NERVE 


CARDIAC  NERVE 
SUPERIOR  INTER- 

^ COSTAL   VEIN 

CARDIAC  NERVE 

\ LIGAMENTUA 

RTERIOSUh 


Fig.  428.— The  th 


describing  a  slight  curve  in  its  course,  and  being  situated,  when  distended,  about 
a  quarter  of  an  inch  behind  the  posterior  surface  of  the  sternum.  At  its  origin 
it  presents,  opposite  the  segments  of  the  aortic  valve,  three  small  dilatations  called 
the  sinuses  of  Valsalva,  described  on  page  561.  At  the  union  of  the  ascending 
with  the  transA'erse  part  of  the  aorta  the  caliber  of  the  vessel  is  increased,  owing  to  a 
dilatation  of  its  right  wall.  This  dilatation  is  termed  the  great  sinus  of  the  aorta 
(bulbous  aortae).  A  section  of  the  aorta  through  this  part  is  somewhat  oval  in 
outline.  The  ascending  aorta  is  contained  within  the  pericardium,  and,  to- 
gether with  the  pulmonary  artery,  is  invested  in  a  tube  of  serous  membrane,  con- 
tinued on  to  them  from  the  surface  of  the  heart. 

Relations. — The  ascending  aorta  is  largely  covered  (ventrad)  at  its  commencement  by  the 
trunk  of  the  pulmonary  artery  and  the  right  auricular  appendix,  and,  higher  up,  is  separated 
from  the  sternum  by  the  pericardium,  the  right  pleura,  and  anterior  margin  of  the  right  lung, 


THE  ASCENDING  AORTA 


bll 


some  loose  areolar  tissue,  and  the  remains  of  the  thymus  gland;  behind,  it  rests  upon  the  right 
pulmonary  artery,  left  auricle,  and  the  right  bronchus.  On  the  rirjht  side  it  is  in  relation  with 
the  superior  vena  cava  and  right  auricle;  on  the  left  side,  with  the  pulmonary  artery. 


Riqht  lagiis 


Fig.  430. — Plan  of  the  branches. 


Fig.  429. — The  arch  of  the  aorta  and  its  branches. 


Plan  of  the  Relations  of  the  Ascending  Aorta. 

In  front. 
Pulmonary  artery. 
Right  auricidar  appendix. 
Pericardium. 
Right  pleura  and  lung. 
Remains  of  the  thymus  gland. 


Right  side. 

Superior  vena  cava. 
Right  auricle. 


Behind. 
Right  pulmonary  artery. 
Left  auricle. 
Right  bronchus. 
37 


Left  side. 
Pulmonary  artery. 


578 


THE   VASCULAR  SYSTEMS 


Branches. — The  only  branches  of  the  ascending  aorta  are  the  coronary  arteries 

which  supply  the  heart.  They  are  two  in  number,  right  and  left,  arising  near  the 
commencement  of  the  aorta  immediately  above  the  attached  margin  of  the  semi- 
lunar valves. 

The  Coronary  Arteries  (Fig.  429). — The  right  coronary  artery  (a.  caronoria 
Ycordis]  dextra),  about  the  size  of  a  crow's  quill,  arises  from  the  anterior  sinus  of 
Valsalva.  It  passes  forward  between  the  pulmonary  artery  and  the  right  auricular 
appendix,  then  runs  obliquely  to  the  right  side,  in  the  groove  between  the  right 
auricle  and  ventricle,  and,  curving  around  the  right  border  of  the  heart,  runs  to  the 
left  along  its  postero-inferior  surface  as  far  as  the  postero-inferior  interventricular 
groove,  where  it  divides  into  two  branches,  one  of  which,  the  transverse,  continues 

onward  in  the  groove  between  the 
left  auricle  and  ventricle,  and 
anastomoses  with  the  left  coro- 
nary ;  the  other,  the  descending 
(ramus  descendens  posterior  a. 
coronariae  [cordis]  dextrae^,  courses 
along  the  postero-inferior  inter- 
ventricular furrow,  supplying 
branches  to  both  ventricles  and 
to  the  septum,  and  anastomosing 
at  the  apex  of  the  heart  with  the 
descending  branches  of  the  left 
coronary. 

This  vessel  sends  a  large 
branch,  the  marginal,  along  the 
thin  margin  of  the  right  ventricle, 
to  the  apex,  which  in   its   course 


RIGHT  AURICLE 

Fig.  431. — Horizont.il  section    through    the  sixth    thoracic         .  ™  nil 

vertebra— upper  surface  of  the  lower  segment— showing  the  glVCS  Oil  IlUmerOUS  Small  braUChcS 

ascending  portion  of  the  aortic  arch,  the    tlioracic    aorta,    and  r       .i  ,  i  ]    i*       i  ■• 

related  structures.  to  the  stcmal  and  diaohragmatic 


surfaces  of  the  risht  ventricle.  It 
also  gives  off  a  branch,  the  infundibular,  which  ramifies  over  the  front  part  of  the 
conus  arteriosus  of  the  right  ventricle.  A  small  branch  of  the  right  coronary  is 
said  to  supply  the  auriculoventricular  bundle  of  His  (see  page  564). 

The  left  coronary  artery  (a.  roronaria  [cordis]  sinistra),  larger  than  the  former, 
arises  from  the  left  posterior  sinus  of  ^''alsalva;  it  passes  forward  between  the  pul- 
monary artery  and  the  left  auricular  appendix,  and  divides  into  two  branches. 
Of  these,  one,  the  transverse,  passes  transversely  outward  in  the  left  auriculo- 
ventricular groove,  and  winds  around  the  left  border  of  the  heart  to  its  diaphrag- 
matic surface,  where  it  anastomoses  with  the  transverse  branch  of  the  right 
coronary;  the  other,  the  descending  (ramus  descendens  anterior  a.  coronariae  [cordis'] 
sinistrae),  passes  along  the  antero-superior  interventricular  groove  to  the  apex  of 
the  heart,  where  it  anastomoses  with  the  descending  branches  of  the  right  coronary. 
The  left  coronary  supplies  the  left  auricle  and  its  appendix,  gives  branches  to 
both  ventricles,  and  numerous  twigs  to  the  pulmonary  artery  and  commencement 
of  the  aorta. 

Peculiarities. — These  vessels  occasionally  arise  by  a  common  trunk,  or  their  number  may 
be  increased  to  three,  the  additional  branch  being  of  small  size.  More  rarely  there  are  .two 
additional  branches. 

Appued  Anatomy. — The  sudden  blocking  of  a  coronary  artery  by  an  embolus,  or  its  more 
gradual  obstruction  by  arterial  disease  or  thrombosis,  are  common  causes  of  sudden  death  in 
persons  past  middle  age.  If  the  obstruction  to  the  passage  of  blood  is  incomplete,  true  Angina 
pectoris  may  occur.  In  this  condition  the  patient  is  suddenly  seized  with  a  spasm  of  agonizing 
pam  in  the  precordial  region  and  down  the  left  arm,  together  with  an  indescribable  sense  of 
anguish.  He  may  die  in  such  an  attack,  or  succumb  a  few  hours  or  days  later  from  heart  failure, 
or  he  may  survive  a  number  of  attacks. 


THE  ARCH  OF  THE  AORTA 


579 


THE  ARCH  OF  THE  AORTA  (ARCUS  AORTAE). 

The  arch,  or  transverse  aorta,  commences  at  the  level  of  the  upper  border  of  the 
second  chondrosternal  articulation  of  the  right  side,  and  passes  at  first  upward, 
backward, and  to  the  left  in  front  of  the  trachea;  it  is  then  directed  backward  on  the 
left  side  of  the  trachea,  and  finally  passes  downward  on  the  left  side  of  the  Ijody  of 
the  fourth  thoracic  vertebra,  at  the  lower  border  of  which  it  becomes  continuous  with 

the  descending  aorta.  It  thus 
forms  two  curvatures,  one  with 
its  convexity  upward,  the  other 
with  its  convexity  forward  and 
to  the  left.  Its  upper  border 
is  usually  about  an  inch  below 
the  upper  margin  of  the  ster-' 
num. 

Relations. — The  arch  of  the  aorta 
is  covered  m  frorit  by  the  pleurae  and 
anterior  margins  of  the  lungs,  and 
by  the  remains  of  the  thymus  gland. 
As  the  vessel  runs  backward  its  left 
side  is  in  contact  with  the  left  lung 
and  pleura.  Passing  downward  on 
the  left  side  of  this  part  of  the  arcli 
are  four  nen-es;  in  order  from  be- 
fore backward  these  are  the  left 
phrenic,  the  inferior  cervical  cardiac  branch  of  the  left  vagus,  the  superior  cardiac  branch  of  the 
left  sympathetic,  and  the  trunk  of  the  left  vagus.  As  the  left  vagus  crosses  the  arch  it  gives  off 
its  recurrent  laryngeal  branch,  which  hooks  around  below  the  vessel  and  then  passes  upward 
on  its  right  side.  The  left  superior  intercostal  vein  runs  obliquely  upward  and  forward,  on 
the  left  side  of  the  arch  between  the  phrenic  and  vagus  nerves.  On  the  right  are  the  deep  car- 
diac plexus,  the  left  recurrent  laryngeal  nerve,  the  oesophagus,  and  thoracic  duct;  the  trachea  lies 
behind  and  to  the  right  of  the  vessel.  Above  are  the  innominate,  left  common  carotid,  and 
left  subclavian  arteries,  which  arise  from  the  convexity  of  the  arch  and  are  crossed  close  to  their 
origins  by  the  left  innominate  vein.  Below  are  the  bifurcation  of  the  pulmonary  artery,  the  left 
bronchus,  the  ligamentum  arteriosum,  the  superficial  cardiac  plexus,  and  the  left  recurrent 
laryngeal  nerve.  As  already  stated,  the  ligamentum  arteriosum  connects  the  commencement 
of  the  left  pulmonary  artery  to  the  aortic  arch. 


RIGHT  PLEURA 


MAMMARY  ARTERY 


Fig.  435. — Horizontal  section  through  the  fourth  thoracic 
vertebra — upper  surface  of  the  lower  segment.  The  cut  is  made 
at  the  lower  part  of  the  transverse  portion  of  the  aortic  arch. 


Plan  of  the  Rel.^tions  of  the  Arch  of  the  Aorta. 

Above. 


In  Front. 

Left  innominate  vein. 
Innominate  artery. 
Left  carotid. 
Left  subclavian. 

Behind. 

Pleurse  and  lungs. 
Remains  of  thymus  gland. 
Left  vagus  nerve. 
Left  phrenic  nerve. 
Superficial  cardiac  nerves. 
Left  superior  intercostal  vein. 

[       Arch  of       \ 
1        Aorta.         j 

Trachea. 

Deep  cardiac  plexus. 

Oesophagus. 

Thoracic  duct. 

Left  recurrent  nerve. 

Below. 
Bifurcation  of  pulmonary  artery. 
Ligamentum  arteriosum. 
Superficial  cardiac  plexus. 
Left  recurrent  nerve. 
Left  bronchus. 


580 


THE   VASCULAR  SYSTEMS 


Between  the  origin  of  the  left  subclavian  artery  and  the  attachment  of  the  liga- 
mentum  arteriosum  the  kimen  of  the  fetal  aorta  is  considerably  narrowed,  forming 
what  is  termed  the  aortic  isthmus  {isthmus  aortae),  while  immediately  beyond  the  liga- 
mentum  arteriosus  the  vessel  presents  a  fusiform  dilatation  which  His  has  named  the 
aortic  spindle  (aorfenspinder) — the  point  of  junction  of  the  two  parts  being  mai'ked 
in  the  concavity  of  the  arch  by  an  indentation  or  angle.  These  conditions  persist, 
to  some  extent,  in  the  adult,  where  His  found  that  the  average  diameter  of  the 
spindle  exceeded  that  of  the  isthmus  by  3  mm.  (about  one-eighth  of  an  inch). 

Peculiarities. — The  height  to  which  the  aorta  rises  in  the  thorax  is  usually  about  an  inch 
below  the  upper  border  of  the  sternum;  but  it  may  ascend  nearly  to  the  top  of  that  bone.  Occa- 
sionally it  is  found  an  inch  and  a  half,  more  rarely  two  or  even  three  inches,  below  this  point. 

In  [Direction. — Sometimes  in  man,  as  is  normal  in  birds,  the  aorta  arches  over  the  root  of 
the  right  instead  of  the  left  lung,  and  passes  down  on  the  right  side  of  the  vertebral  column; 
such  an  arrangement  is  usually  found  to  be  associated  with  transposition  of  other  viscera. 
Less  frequently,  the  aorta,  after  arching  over  the  root  of  the  right  lung,  is  directed  to  its  usual 
position  on  the  left  side  of  the  vertebral  column,  this  peculiarity  not  being  accompanied  by  any 
transposition  of  the  viscera. 

In  Conformation. — The  aorta  occasionally  divides,  as  in  some  quadrupeds,  into  an  ascending 
and  descending  trunk,  the  former  of  which  is  directed  vertically  upward,  and  subdivides  into 
three  branches,  to  supply  the  head  and  upper  extremities.  Sometimes  the  aorta  subdivides 
soon  after  its  origin  into  two  branches,  which  soon  reunite. 
In  one  of  these  cases  the  oesophagus  and  trachea  were  found 
to  pass  through  the  interval  left  by  the  division  of  the  aorta; 
this  is  the  normal  condition  of  the  vessel  in  the  reptilia. 

Applied  Anatomy.— Of  all  the  vessels  of  the  arterial 
system,  the  aorta,  and  more  especially  its  arch,  is  most  fre- 
quently the  seat  of  disease;  hence  it  is  important  to  con- 
sider some  of  the  consequences  that  may  ensue  from 
aneurism  of  this  part.  Aortic  aneurisms  usually  occur 
along  a  spiral  line,  the  so-called  "surf-line  of  the  aorta," 
which  begins  at  the  anterior  sinus  of  Valsalva  and  is  lost  in 
the  dorsomesal  wall  of  the  descending  aorta,  as  shown  in 
Fig.  433. 

it  will  be  remembered  that  the  ascending  aorta  is  con- 
tained in  the  pericardium,  just  behind  the  sternum,  being 
crossed  at  its  commencement  by  the  pulmonary  artery  and 
right  auricular  appendix,  and  having  the  right  pulmonary 
artery  behind,  the  superior  vena  cava  on  the  right  side,  and 
the  pulmonary  artery  and  left  auricle  on  the  left  side. 

Aneurism  of  the   asceiiding  aorta,  in  the   situation  of  the 
sinuses  of  Valsalva,  in  the  great  majority  of  cases,  affects  the 
anterior   sinus;   this   is   mainly   owing  to  the  fact  that  the 
regurgitation  of  blood  upon  the  sinuses  seems  to  take  place 
aorta, "  showing  the  commoner  points    chiefly  on  the  anterior  aspect  of  the  vessel.     As  the  aneuris- 
of  origin  of  aneurisms.  mal  sac  enlarges  it  may  compress  any  or  all  of  the  structures 

in  immediate  proximity  to  it,  but  chiefly  project  toward  the 
right  anterior  side,  and,  consequently,  interferes  mainly  with  those  structures'  which  have  a 
corresponding  relation  with  the  vessel.  In  the  majority  of  cases  it  bursts  into  the  cavity  of  the 
pericardium,  the  patient  suddenly  drops  dead,  and',  upon  a  postmortem  examination,  the 
pericardial  sac  is  found  full  of  blood;  or  it  may  compress  the  right  auricle,  or  the  pulmonary 
artery  and  adjoining  part  of  the  right  ventricle,'  and  open  into  one  or  the  other  of  these  parts, 
or  may  press  upon  or  even  rupture  into  the  superior  vena  cava. 

Aneurism  of  the  ascending  aorta,  originating  above  the  sinuses,  most  frequently  implicates 
the  right  anterior  wall  of  the  vessel,  where,  as  has  been  explained,  there  exists  a  normal  dilata- 
tion, the  great  sinus  of  the  aorta;  this  is  probably  mainly  owing  to  the  blood  being  impelled 
agamst  this  part.  The  direction  of  the  aneurism  is  also  chiefly  toward  the  right  of  the  median 
line.  It  attains  a  large  size  and  projects  forward,  it  may  cause  absorption  of  the  sternum  and 
the  cartilages  of  the  ribs,  usually  on  the  right  side,  and  appears  as  a  pulsating  tumor  on  the  front 
of  the  thorax,  just  below  the  manubrium;  or  it  may  burst  into  the  pericardium,  or  mav  compress 
or  open  into  the  right  lung,  the  trachea,  bronchi,  or  oesophagus. 

Regarding  the  arch  of  the  aorta,  the  student  is  reminded  that  the  vessel  lies  on  the  trachea, 
the  oesophagus,  and  thoracic  duct;  that  the  left  recurrent  laryngeal  nerve  winds  around  it;  and 
that  from  its  upper  part  are  given  off  three  large  trunks,  which  supply  the  head,  neck,  and  upper 


Fig.  433.— The    "surf-lii 


THE  ARCH  OF  THE  AORTA 


581 


extremities.  An  aneurismal  tumor,  taking  origin  from  the  posterior  part  of  the  vessel,  may 
press  upon  the  trachea,  impede  the  breathing,  or  produce  cough,  hemoptysis,  or  stridulous 
breathing,  or  it  may  ultimately  burst  into  that  tube,  producing  fatal  hemorrhage.  Again,  its 
pressure  on  the  laryngeal  nerves  may  give  rise  to  symptoms  which  so  accurately  resemble  those 
of  laryngitis  that  the  operation  of  tracheotomy  has  in  some  cases  been  resorted  to,  from  the 
supposition  that  disease  existed  in  the  larynx;  or  it  may  press  upon  the  thoracic  duct  and  destroy 
life  by  inanition;  or  it  may  involve  the  oesophagus,  producing  dysphagia;  or  may  burst  into 
the  oesophagus,  when  fatal  hemorrhage  will  occur.  Again,  the  innominate  artery,  or  the  sub- 
clavian, or  left  carotid,  may  be  so  obstructed  by  clots  as  to  produce  a  weakness,  or  even  a  disap- 
pearance, of  the  pulse  in  one  or  the  other  wrist  or  in  the  left  temporal  artery;  or  the  tumor  may 
present  itself  at  or  above  the  manubrium,  generally  either  in  the  median  line  or  to  the  right  of 
the  sternum,  and  may  simulate  an  aneurism  of  one  of  the  arteries  of  the  neck. 

Branches  (Figs.  429  and  430). — The  branches  given  off  from  the  arch  of  the 
aorta  are  three  in  number — the  innominate,  the  left  common  carotid,  and  the  left 
subclavian  arteries. 


RigJit  pulmonaty 
vein. 

Right  pulmonai  y- 
vein. 


T.pp.  subclavian 
ffi*/o\        a)tery. 


Left  . 

carotid  artery. 


Inf 6)101  thyroid 
I  em 


artery.     Bight  common  carotid  artery. 


-Relation  of  great  vessels  at  base  of  a  fetal  heart,  seen  from  above  (enlarged).     (From  a  preparation 
in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 


Peculiarities.  Position  of  the  Branches. — The  branches,  instead  of  arising  from  the 
highest  part  of  the  arch  (their  usual  position),  may  be  moved  more  to  the  right,  arising  from  the 
commencement  of  the  transverse  or  upper  part  of  the  ascending  portion;  or  the  distance  from 
one  another  at  their  origin  may  be  increased  or  diminished,  the  most  frequent  change  in  this 
respect  being  the  approximation  of  the  left  carotid  toward  the  innominate  artery. 

The  number  of  the  primary  branches  may  be  reduced  to  a  single  vessel,  or  more  commonly 
two,  the  left  carotid  arising  from  the  innominate  artery,  or  (more  rarely)  the  carotid  and  sub- 
clavian arteries  of  the  left  side  arising  from  the  innominate  artery.  But  the  number  may  be 
increased  to  four,  from  the  right  carotid  and  subclavian  arteries  arising  directly  from  the  aorta, 
the  innominate  being  absent.  In  most  of  these  latter  cases  the  right  subclavian  has  been  found 
to  arise  from  the  left  end  of  the  arch;  in  other  cases  it  was  the  second  or  third  branch  given  off 
instead  of  the  first.  Another  common  form  in  which  there  are  four  primary  branches  is  that 
in  which  the  left  vertebral  artery  arises  from  the  arch  of  the  aorta  between  the  left  carotid  and 
subclavian  arteries.  Lastly,  the  number  of  trunks  from  the  arch  may  be  increased  to  five  or 
six;  in  these  instances,  the  external  and  internal  carotids  arise  separately  from  the  arch,  the 
common  carotid  being  absent  on  one  or  both  sides.  In  some  cases  six  branches  have  been 
found,  and  this  condition  is  associated  with  the  origin  of  both  vertebral  arteries  from  the  arch. 

Number  Usual,  Arrangement  Different. — When  the  aorta  arches  over  to  the  right  side, 
the  three  branches  have  an  arrangement  the  reverse  of  that  which  is  usual,  the  innominate  sup- 


582  THE   VASCULAR  SYSTEMS 

plyino-  the  left  side,  and  the  carotid  and  subclavian  (which  arise  separately)  the  right  side.  In 
other'^cases,  where  the  aorta  takes  its  usual  course,  the  two  carotids  may  be  joined  in  a  common 
trunk,  and'the  subclavians  arise  separately  from  the  arch,  the  right  subclavian  generally  arising 
from  the  left  end  of  the  arch. 

In  some  instances  other  arteries  are  found  to  arise  from  the  arch  of  the  aorta.  Of  these  the 
most  common  are  the  bronchial,  one  or  both,  and  the  thyroidea  ima ;  also  the  internal  mammary 
and  the  inferior  thyroid  have  been  seen  to  arise  from  this  part  of  the  vessel. 

The  Innominate  Artery  (A.  Anonyma)  (Figs.  429  and  4.30). 

The  innominate  or  brachiocephalic  artery  is  the  largest  branch  given  off  from 
the  arch  of  the  aorta.  It  arises,  on  a  level  with  the  upper  border  of  the  second 
right  costal  cartilage,  from  the  commencement  of  the  arch  of  the  aorta  in  front 
of  the  left  carotid,  and,  ascending  obliquely  to  the  upper  border  of  the  right  sterno- 
clavicular articulation,  divides  into  the  right  common  carotid  and  right  subclavian 
arteries.     This  vessel  varies  from  an  inch  and  a  half  to  two  inches  in  length. 

Relations. — In  front,  it  is  separated  from  the  first  piece  of  the  sternum  by  the  Sternohyoid 
and  Sternothyroid  muscles,  the  remains  of  the  thymus  gland,  the  left  innominate  and  right 
inferior  thyroid  veins  which  cross  its  root,  and  sometimes  the  inferior  cervical  cardiac  branch 
of  the  right  vagus.  Behind,  it  lies  upon  the  trachea,  which  it  crosses  obliquely,  and  continuing 
upward  it  lies  in  the  right  pleura.  On  the  right  side  is  the  right  innominate  vein,  right  vagus 
nerve,  and  the  pleura;  and  on  the  left  side,  the  remains  of  the  thymus  gland,  the  origin  of  the 
left  carotid  artery,  the  left  inferior  thyroid  vein,  and  the  trachea. 

Plan  of  the  Relations  of  the  Innominate  Artery. 

In  front. 
Sternum. 

Sternohyoid  and  Sternothyroid  muscles. 
Remains  of  the  thymus  gland. 
Left  innominate  and  right  inferior  thyroid  veins. 
Inferior  cervical  cardiac  branch  from  right  vagus  nerve. 

Right  side.  ^''        \  Left  side. 

Right  innominate  vein.  /   innominate    ^  Remains  of  thymus. 

Right  vagus  nerve.  \      Artery.       '  Left  carotid. 

Pleura.  V  /  Left  inferior  thyroid  vein. 

^~-__^^^  Trachea. 

Behind. 

Trachea. 
Right  pleura. 

Branches. — The  innominate  usually  gives  off  no  branches,  but  occasionally  a 
small  branch,  the  thyroidea  ima,  is  given  off  from  this  vessel.  It  also  sometimes 
gives  off  a  thymic  or  bronchial  branch. 

The  thyroidea  ima  (a.  thyroidea  ima),  which  is  occasionally  present,  ascends  in 
front  of  the  trachea  to  the  lower  part  of  the  thyroid  body,  which  it  supplies.  It 
varies  greatly  in  size,  and  appears  to  compensate  for  the  deficiency  or  absence  of 
one  of  the  other  thyroid  vessels.  It  occasionally  is  found  to  arise  from  the  right 
common  carotid  or  from  the  aorta,  the  subclavian,  or  internal  mammary  vessels. 

Applied  Anatomy. — Ligation  of  the  innominate  artery  is  an  extremely  grave  operation. 
Thiswas  first  done  by  Mott.  The  "  operation  of  clioice  "  seems  to  be  that  done  by  Burrell.  "An 
incision  is  made  at  the  anterior  edge  of  the  right  Sternomastoid  muscle,  extending  from  the  level 
of  the  cricoid  cartilage  to  two  inches  below  the  upper  border  of  the  sternum.  From  this  point 
another  incision,  extending  outward  four  inches  in  length  to  the  junction  (right)  of  the  outer 


THE  COMMON  CAROTID  ARTERY  583 

and  middle  thirds  of  the  clavicle.  The  skin  flap  with  the  fascia  and  Platysma  muscle  is  turned 
back.  The  Sternomastoid  is  severed  close  to  its  insertion  into  clavicle  and  sternum.  The  Sterno- 
thyroid, Sternohyoid,  and  Omohyoid  are  also  divided."  The  sternoclavicular  joint  and  the 
right  side  of  the  manubrium  are  honeycombed  by  means  of  a  surgical  engine  or  trephine.  A 
flat  retractor  is  slid  underneath  the  joint  while  the  trephining  is  done  to  protect  the  underlying 
parts.  The  block  of  bone  is  now  removed.  The  right  and  left  innominate  veins  going  down 
to  form  the  superior  vena  cava,  with  the  vagus  and  right  recurrent  laryngeal  nerves  resting  on 
the  innominate  artery,  are  all  Jilainly  to  be  seen.  The  sheath  of  the  innominate  artery  is  now 
opened  and  a  ligature  is  applied.  Burrell  states  that  the  exposure  which  is  given  by  the  removal 
of  a  part  of  the  sternum  is  extremely  satisfactory,  and  he  fails  to  understand  how  a  ligature 
can  be  applied  to  the  innominate  artery  with  any  safety  without  a  clear  view  of  the  anatomical 
structures  involved. 

Peculiarities  in  Point  of  Division.— When  the  bifurcation  of  the  innominate  artery  varies 
from  the  point  above  mentioned  it  sometimes  ascends  a  considerable  distance  abo\'e  the  sternal 
end  of  the  clavicle;  less  frequently  it  divides  below  it.  In  the  former  class  of  cases  its  length 
may  exceed  two  inches,  and  in  the  latter  be  reduced  to  an  inch  or  less.  These  are  points  of  con- 
siderable interest  for  the  surgeon  to  remember  in  connection  with  the  operation  of  tying  this 
vessel. 

Position. — When  the  aorta  arches  over  to  the  right  side,  the  innominate  is  directed  to  the 
left  side  of  the  neck  instead  of  the  right. 

Collateral  Circulation. — Allan  Burns  demonstrated,  on  the  dead  subject,  the  possibility  of 
the  establishment  of  the  collateral  circulation  after  ligation  of  the  innominate  artery,  by  tying 
and  dividing  that  artery,  after  which,  he  says,  "Even  coarse  injection,  impelled  into  the  aorta, 
passes  freely  by  the  anastomosing  branches  into  the  arteries  of  the  right  arm,  filling  them  and 
all  the  vessels  of  the  head  completely."  '  The  branches  by  which  this  circulation  would  be 
carried  on  are  very  numerous;  thus,  all  the  communications  across  the  middle  line  between  the 
branches  of  the  carotid  arteries  of  opposite  sides  would  be  available  for  the  supply  of  blood  to 
the  right  side  of  the  head  and  neck;  while  anastomosis  between  the  superior  intercostal  of 
the  subclavian  and  the  first  aortic  intercostal  (see  page  654  on  the  collateral  circulation  after  ob- 
literation of  the  thoracic  aorta)  would  bring  the  blood,  by  a  free  and  direct  course,  into  the  right 
subclavian;  the  numerous  connections,  also,  between  the  intercostal  arteries  and  the  branches 
of  the  axillary  and  internal  mammary  arteries  would,  doubtless,  assist  in  the  supply  of  blood  to 
the  right  arm,  while  the  deep  e|5igastric,  from  the  external  iliac,  would,  by  means  of  its  anasto- 
mosis with  the  internal  mammary,  compensate  for  any  deficiency  in  the  vascularity  of  the  wall 
of  the  thorax. 

ARTERIES  OF  THE  HEAD  AND  NECK. 

The  chief  artery  which  supplies  the  head  and  neck  on  each  side  is  the  common 
carotid;  it  ascends  in  the  necli  and  divides  into  two  branches:  (1)  The  external 
carotid,  supplying  the  superficial  parts  of  the  head  and  face  and  the  greater  part 
of  the  neck;  (2)  the  internal  carotid,  supplying  to  a  great  extent  the  parts  within 
the  cranial  cavity. 

THE  COMMON  CAROTID  ARTERY  (A.  CAROTIS  COMMUNIS)  (Figs.  428,  429). 

The  common  carotid  arteries  differ  in  length  and  in  their  mode  of  origin.  The 
right  common  carotid  (a.  carotis  communis  dextra)  begins  at  the  bifurcation  of  the 
innominate  artery,  behind  the  right  sternoclavicular  articulation,  and  is  confined 
to  the  neck.  The  left  common  carotid  (a.  carotis  communis  sinistra)  arises  from 
the  highest  part  of  the  arch  of  the  aorta  to  the  left  of  and  on  a  plane  posterior  to 
the  innominate  artery,  and  therefore  consists  of  a  thoracic  and  a  cervical  portion. 

The  thoracic  portion  of  the  left  common  carotid  artery  ascends  from  the  arch  of 
the  aorta  through  the  superior  mediastinum  to  the  level  of  the  left  sternoclavicular 
joint,  where  it  continues  as  the  cervical  portion. 

Relations. — In  front,  it  is  separated  from  the  first  piece  of  the  sternum  by  the  Sternohyoid 
ami  Sterudlhyroid  muscles,  the  anterior  portions  of  the  left  pleura  and  lung,  the  left  innominate 
vein,  and  (he  remains  of  the  thymus  gland;  behind,  it  lies  on  the  trachea,  oesophagus,  thoracic 

*  Surgical  Anatomy  of  the  Head  and  Neck,  p.  62. 


584  THE   VA&CVLAB  SYSTEMS 

duct,  and  the  left  recurrent  laryngeal  nerve.  To  its  right  side,  it  is  in  relation  with  the  innomi- 
nate artery,  inferior  thyroid  veins,  and  remains  of  the  thymus  gland.  To  its  left  side,  with  the 
left  vagus  nerve,  left  pleura,  and  left  lung.  The  left  subclavian  artery  is  posterior  and  slightly 
external  to  it. 


Plan  of  the  Relations  of  the  Left  Common  Carotid. 
Thoracic  Portion. 

In  front. 

1 

Sternum. 

Sternohyoid  and  Sternothyroid  muscles. 

Left  innominate  vein. 

Remains  of  the  thymus  gland. 


Intemallv.  /  \  Externally. 

^  I  1  .aft     P^mmnTi  \  "^ 


Innominate  artery.  I       Thoracic  Left  vagus  nerve. 

Inferior  thyroid  veins.  \      Portion.      /  Left  pleura  and  lung. 

Remains  of  the  thymus  gland.  \_^  /  Left  subclavian  artery. 

Behind. 
Trachea. 
Oesophagus. 
Thoracic  duct. 
Left  recurrent  laryngeal  nerve. 

The  cervical  portions  of  the  two  common  carotids  resemble  each  other  so  closely 
that  one  description  will  apply  to  both.  Each  vessel  passes  obliquely  upward 
from  behind  the  sternoclavicular  articulation  to  a  level  with  the  upper  border  of 
the  thyroid  cartilage,  opposite  the  fourth  cervical  vertebra,  where  it  divides  into 
the  external  and  internal  carotid  arteries. 

At  the  lower  part  of  the  neck  the  two  common  carotid  arteries  are  separated 
from  each  other  by  a  small  interval,  which  contains  the  trachea;  but  at  the  upper 
part,  the  thyroid  body,  the  larynx,  and  pharynx  project  forward  between  the  two 
vessels,  and  give  the  appearance  of  their  being  placed  farther  back  in  this  situa- 
tion. The  common  carotid  artery  is  contained  in  a  sheath  derived  from  the 
deep  cervical  fascia,  which  also  encloses  the  internal  jugular  vein  and  vagus  nerve, 
the  vein  lying  on  the  outer  side  of  the  artery,  and  the  nerve  between  the  artery 
and  vein,  on  a  plane  posterior  to  both.  On  opening  the  sheath  these  three  struc- 
tures are  seen  to  be  separated  from  one  another,  each  being  enclosed  in  a  separate 
fibrous  investment. 

Relations. — At  the  lower  part  of  the  neck  the  common  carotid  artery  is  very  deeply  seated, 
being  covered  by  the  integument,  superficial  fascia,  Platysma,  and  deep  cervical  fascia,  the 
Sternomastoid,  Sternohyoid,  and  Sternothyroid  muscles,  and  by  the  Omohyoid,  opposite  the 
cricoid  cartilage;  but  in  the  upper  part  of  its  course,  near  its  termination,  it  is  more  superficial, 
being  covered  merely  by  the  integument,  the  superficial  fascia,  Platysma,  deep  cervical  fascia, 
and  inner  margin  of  the  Sternomastoid,  and,  when  the  latter  is  drawn  backward,  it  is  seen  to 
be  contained  in  a  triangular  space,  bounded  behind  by  the  Sternomastoid,  abote  by  the  pos- 
terior belly  of  the  Digastric,  and  below  by  the  anterior  belly  of  the  Omohyoid.  This  part  of 
the  artery  is  crossed  obliquely,  from  within  outward,  by  the  sternomastoid  artery;  it  is  crossed 
also  by  the  superior  and  middle  thyroid  veins,  which  terminate  in  the  internal  jugular;  and, 
descending  on  its  sheath  in  front,  is  seen  the  descendens  hypoglossi  nerve,  this  filament  being 
joined  by  one  or  two  branches  from  the  cervical  nerves,  which  cross  the  vessel  from  without 
inward.  Sometimes  the  descendens  hypoglossi  is  contained  within  the  sheath.  The  middle 
thyroid  vein  crosses  the  artery  about  its  middle,  and  the  anterior  jugular  vein  below;  the  latter, 
however,  is  separated  from  the  artery  by  the  Sternohyoid  and  Sternothyroid  muscles.  Behind, 
the  artery  is  separated  from  the  transverse  processes'  of  the  vertebree  by  the  Longus  colli  and 


THE  COMMON  CAROTID  ARTERY 


585 


Rectus  capitis  anticus  major  muscles,  the  sympathetic  cord  being  interposed  between  it  and 
the  muscles.  The  recurrent  laryngeal  nerve  and  inferior  thyroid  artery  cross  behind  the  vessel 
at  its  lower  part.  Internally,  it  is  in  relation  with  the  trachea  and  thyroid  gland,  the  latter 
overlapping  it,  the  inferior  thyroid  artery  and  recurrent  laryngeal  nerve  being  interposed;  higher 
up,  with  the  larynx  and  pharynx.  On  its  outer  side  are  placed  the  internal  jugular  vein  and 
vagus  nerve.     At  the  lower  part  of  the  neck  the  internal  jugular  vein  on  the  right  side  diverges 


Fig.  435. —  Applied  anatomy  of  the  arteries  of  the 


homing  the  carotid  and  subcla\ian  arteries  ^ 


from  the  artery,  but  on  the  left  side  it  approaches  it,  and  often  overlaps  its  lower  part.  This 
is  an  important  fact  to  bear  in  mind  during  the  performance  of  any  operation  on  the  lower  part 
of  the  left  common  carotid  artery.  In  this  region  the  relation  which  the  right  and  left  recurrent 
laryngeal  nerves  bear  to  the  arteries  is  not  identical.  The  left  recurrent  laryngeal  nerve  lies 
behind  the  thoracic  portion  of  the  left  common  carotid  artery  and  internal  to  the  cervical  portion 
of  the  vessel.  The  right  nerve  passes  obliquely  upward  and  inward  behind  the  right  common 
carotid  to  reach  its  inner  side. 


1  The  hypoglossal  nerve  is  not  rightly  placed  in  this  drawinR.  It  forms  the  upper  side  of  a  triangle,  the  two 
lower  sides  of  which  are  the  two  bellies  of  the  Diga.stric.  The  lingual  artery  would  then  run  under  the  Hyoglossus 
muscle,  below  the  hypoglossal  nerve.     (See  Fig.  437.) 


586  THE   VASCULAR  SYSTE3IS 


Plan  of  the  Relations  of  the  Common  Carotid  Artery. 

In  front. 

Integument  and  superficial  fascia.  Omohyoid. 

Deep  cervical  fascia.  Descendens  and  communicans  hypoglossi 

Platysma.  nerves. 

Sternomastoid.  Sternomastoid  artery. 

Sternohyoid.  Superior  and  middle  thyroid  veins. 

Sternothyroid.  Anterior  jugular  vein. 


Externally. 

Internally. 

Internal  jugular  vein. 
Vagus  nerve. 

I        Common        | 
1        Carotid.        ) 

Trachea. 

Thyroid  gland. 

Recurrent  laryngeal  nerve. 

Inferior  thyroid  artery. 

Larynx. 

Pharynx. 

Behind. 
Longus  colli.  Sympathetic  cord. 

Rectus  capitis  anticus  major.  Inferior  thyroid  artery. 

Recurrent  laryngeal  nerve. 

On  the  posterior  aspect  of  the  angle  of  bifurcation  of  the  common  carotid  is  a  reddish-brown 
oval  body  known  as  the  caiotid  gland.     (See  Ductless  Glands.) 

Peculiarities  as  to  Origin. — The  right  common  carotid  may  arise  above  or  below  the  upper 
border  of  the  sternoclavicular  articulation.  This  variation  occurs  in  one  out  of  about  eight 
cases  and  a  half,  and  the  origin  is  more  frequently  below  than  above;  or  the  artery  may  arise 
as  a  separate  branch  from  the  arch  of  the  aorta  or  in  conjunction  with  the  left  carotid.  The 
left  common  carotid  varies  more  frequently  in  its  origin  than  the  right.  In  the  majority  of  abnor- 
mal cases  it  arises  with  the  innominate  artery,  or,  if  the  innominate  artery  is  absent,  the  two 
carotids  arise  usually  by  a  single  trunk.  It  rarely  joins  with  the  left  subclavian,  except  in  cases 
of  transposition  of  the  arch. 

Peculiarities  as  to  Point  of  Division. — In  the  majority  of  abnormal  cases  this  occurs  higher 
than  usual,  the  artery  dividing  into  two  branches  opposite  the  hyoid  bone,  or  even  higher;  more 
rarely  it  occurs  below,  opposite  the  middle  of  the  larynx  or  the  lower  border  of  the  cricoid  car- 
tilage; and  one  case  is  related  by  Morgagni  where  the  common  carotid,  only  an  inch  and  a 
half  in  length,  divided  at  the  root  of  the  neck.  Very  rarely  the  common  carotid  ascends  in  the 
neck  without  any  subdivision,  the  internal  carotid  being  wanting;  and  in  a  few  cases  the  com- 
mon carotid  has  been  found  to  be  absent,  the  external  and  internal  carotids  arising  directly 
from  the  arch  of  the  aorta.  This  peculiarity  existed  on  both  sides  in  some  instances,  on  one 
side  in  others. 

Occasional  Branches. — Each  common  carotid  usually  gives  off  no  branch  previous  to  its 
bifurcation;  but  it  occasionally  gives  origin  to  the  superior  thj'roid  or  its  laryngeal  branch,  the 
ascending  pharyngeal,  the  inferior  thyroid,  or,  more  rarely,  the  vertebral  artery. 

Surface  Marking. — The  course  of  each  common  carotid  artery  is  indicated  by  a  line  drawn 
from  the  sternal  end  of  the  clavicle  below,  to  a  point  midway  between  the  angle  of  the  mandible 
and  the  mastoid  process  above.  That  portion  of  the  line  below  the  level  of  the  upper  border 
of  the  thyroid  cartilage  would  represent  the  course  of  the  vessel. 

Applied  Anatomy. — The  operation  of  tying  the  common  carotid  artery  may  be  necessary 
in  a  case  of  woimd  of  that  vessel  or  its  branches,  in  aneurism,  or  in  a  case  of  pulsating  tumor  of 
the  orbit  or  skull.  If  the  wound  involves  the  trunk  of  the  common  carotid,  it  will  be  necessary 
to  tie  the  artery  through  the  wound  above  and  below  the  wounded  part.  If  the  wound  is  too 
small  to  admit  of  safe  and  rapid  work  it  must  be  enlarged.  In  cases  of  aneurism,  or  where  one 
of  the  branches  of  the  common  carotid  is  wounded  in  an  inaccessible  situation,  it  may  be  judged 
necessary  to  tie  the  trunk.  In  such  cases  the  whole  of  the  artery  is  accessible,  and  any  part  may 
be  tied  except  close  to  either  end.  When  the  case  is  such  as  to  allow  of  a  choice  being  made, 
the  lower  part  of  the  carotid  should  never  be  selected  as  the  spot  upon  which  to  place  a  ligature, 
for  not  only  is  the  artery  in  this  situation  placed  very  deeply  in  the  neck,  but  it  is  covered  by 
three  layers  of  muscles,  and,  on  the  left  side,  in  the  great  majority  of  cases,  the  interna!  jugular 
vein  passes  obliquely  in  front  of  it.  Neither  should  the  upper  end  be  selected,  for  here  the 
superior  thyroid  vein  and  its  tributaries  would  give  rise  to  very  considerable  difficulty  in  the  appli- 
cation of  a  ligature.  The  point  most  favorable  for  the  operation  is  that  part  of  the  vessel  which 
is  at  the  level  of  the  cricoid  cartilage.     It  occasionally  happens  that  the  carotid  artery  bifm-cates 


THE  COMMON  CAROTID  ABTEBY  587 

below  its  usual  position;  if  the  artery  be  exposed  at  its  point  of  bifurcation,  both  divisions  of 
the  vessel  should  be  tied  near  their  origin,  in  preference  to  tying  the  trunk  of  the  artery  near  its 
termination;  and  if,  in  consequence  of  the  entire  absence  of  the  common  carotid  or  from  its 
early  division,  two  arteries,  the  external  and  internal  carotids,  are  met  with,  the  ligature  should 
be  placed  on  that  vessel  which  is  found  on  corajiression  to  be  connected  with  the  diseased  area. 

Ligation  of  the  Carotid  at  the  Level  of  the  Cricoid  Cartilage  {Lujation  in.  fhc  Triangle 
of  Election).' — The  triangle  of  election  is  bounded  posteriorly  hy  the  anterior  edge  of  the  Ster- 
nomastoid;  is  bounded  above  by  the  posterior  belly  of  the  Digastric;  is  bounded  below  hy 
the  anterior  belly  of  the  Omohyoid.  In  this  operation  the  direction  of  the  vessel  and  the 
inner  margin  of  the  Sternomastoid  are  the  chief  guides  to  its  performance.  The  patient  should 
be  placed  on  his  back  with  the  head  thrown  back  and  tui-ned  slightly  to  the  opposite  side;  an 
incision  is  to  be  made,  three  inches  long,  in  the  direction  of  the  anterior  border  of  the  Sterno- 
mastoid, so  that  the  centre  corresponds  to  the  level  of  the  cricoid  cartilage;  after  dividing  the 
inteo-ument,  superficial  fascia,  and  Platysma,  the  deep  fascia  must  be  cut  through  on  a  director, 
so  as  to  avoid  wounding  numerous  small  veins  that  are  usually  found  beneath.  The  head  may 
now  be  brought  forward  so  as  to  relax  the  parts  somewhat,  and  the  margins  of  the  wound  are 
held  asunder  by  retractors.  The  descendens  hypoglossi  nerve  may  now  be  exposed,  and  must 
be  avoided,  and,  the  sheath  of  the  vessel  having  been  raised  by  forceps,  is  to  be  opened  to  a  small 
extent  over  the  artery  at  its  inner  side.  The  internal  jugular  vein  may  present  itself  alternately 
distended  and  relaxed;  this  should  be  compressed  both  above  and  below,  and  drawn  outward, 
in  order  to  facilitate  the  operation.  The  aneurism  needle  is  passed  from  the  outside,  care 
being  taken  to  keep  the  needle  in  close  contact  with  the  artery,  and  thus  avoid  the  risk  of  injuring 
the  internal  jugular  vein  or  including  the  vagus  nerve.  Before  the  ligature  is  tied  it  should  be 
ascertained  that  nothing  but  the  artery  is  included  in  it. 

Ligation  of  the  Common  Carotid  at  the  Lower  Part  of  the  Neck  (Ligation  in  the  Triangle 
of  Necessity)} — Tlie  triangle  of  necessity  is  bounded  aljove  by  the  anterior  belly  of  the  Omo- 
hyoid; is  bounded  behind  by  the  anterior  margin  of  the  Sternomastoid;  is  bounded  in  front 
by  the  mid-line  of  the  neck.  This  operation  is  sometimes  required  in  cases  of  aneurism  of  the 
upper  part  of  the  carotid,  especially  if  the  sac  is  of  large  size.  It  is  best  performed  by  dividing 
the  sternal  origin  of  the  Sternomastoid  muscle,  but  may  be  done  in  some  cases,  if  the  aneurism 
is  not  of  very  large  size,  by  an  incision  along  the  anterior  border  of  the  Sternomastoid,  extending 
down  to  the  sternoclavicular  articulation,  and  by  then  retracting  the  muscle.  The  easiest  and 
best  plan,  however,  is  to  make  an  incision  two  or  three  inches  long  down  the  lower  part  of  the 
anterior  border  of  the  Sternomastoid  muscle  to  the  sternoclavicular  joint,  and  a  second  incision, 
starting  from  the  termination  of  the  first,  along  the  upper  border  of  the  clavicle  for  about  two 
inches.  This  incision  is  made  through  the  superficial  and  deep  fascia,  and  the  sternal  origin 
of  the  muscle  is  exposed.  This  is  to  be  divided  on  a  director,  and  turned  up,  with  the  super- 
ficial structures,  as  a  triangular  flap.  Some  loose  connective  tissue  is  to  be  divided  or  torn 
through,  and  the  outer  border  of  the  Sternohyoid  muscle  exposed.  In  doing  this  care  must 
be  taken  not  to  wound  the  anterior  jugular  vein,  which  crosses  the  muscle  to  reach  the  external 
jugular  or  subclavian  vein.  The  Sternohyoid,  and  with  it  the  Sternothyroid,  are  to  be  drawn 
inward  by  means  of  a  retractor,  and  the  sheath  of  the  vessel  is  exposed.  This  must  be  opened 
with  great  care  on  its  inner  or  tracheal  side,  so  as  to  avoid  the  internal  jugular  vein.  This_  is 
especially  necessary  on  the  left  side,  where  the  artery  is  commonly  overlapped  by  the  vein. 
On  the  right  side  there  is  usually  an  interval  between  the  artery  and  the  vein,  and  not  the  same 
risk  of  wounding  the  latter. 

The  common  "carotid  artery,  being  a  long  vessel  without  any  branches,  is  particularly  suitable 
for  the  performance  of  Brasdor's  operation  for  the  cure  of  an  aneurism  of  the  lower  part  of  the 
vessel.  Brasdor's  procedure  consists  in  ligating  the  artery  on  the  distal  side  of  the  aneurism, 
and  in  the  case  of  the  common  carotid  there  are  no  branches  given  off  from  the  vessel  between 
the  aneurism  and  the  site  of  the  ligature;  hence,  the  flow  of  blood  through  the  sac  of  the  aneurism 
is  diminished,  and  cm-e  takes  place  in  the  usual  way,  by  the  deposit  of  laminated  fibrin. 

Collateral  Circulation. — After  ligation  of  the  common  carotid  the  collateral  circulation  can 
be  perfectly  established  by  the  free  communication  which  exists  between  the  carotid  arteries 
of  opposite"  sides,  both  without  and  within  the  cranium,  and  by  enlargement  of  the  branches  of 
the  subclavian  artery  on  the  side  corresponding  to  that  on  which  the  vessel  has  been  tied — the 
chief  communication  outside  the  skull  taking  place  between  the  superior  thyroid  from  the  external 
carotid  and  the  inferior  thyroid  from  the  subclavian,  the  profunda  cervicis  from  the  subclavian 
and  the  superior  intercostal  with  the  arteria  princeps  cervicis  of  the  occipital;  the  vertebral 
taking  the  place  of  the  internal  carotid  within  the  cranium. 

1  For  description  of  the  triangles  of  the  neck,  see  page  602. 


588 


THE   VASCULAR  SYSTEMS 


The  External  Carotid  Artery  (A.  Carotis  Externa)   (Figs.  434,  435). 

The  external  carotid  artery  commences  opposite  the  upper  border  of  the  thyroid 
cartilage,  and,  taking  a  slightly  curved  course,  passes  upward  and  forward,  and 
then  inclines  backward  to  the  space  between  the  neck  of  the  condyle  of  the  man- 
dible and  the  external  meatus,  where  it  divides  into  the  superficial  temporal  and 
internal  maxillary  arteries.  It  rapidly  diminishes  in  size  in  its  course  up  the  neck, 
owing  to  the  number  and  large  size  of  the  branches  given  off  from  it.  In  the 
child  it  is  somewhat  smaller  than  the  internal  carotid,  but  in  the  adult  the  two 
vessels  are  of  nearly  equal  size.  At  its  origin  this  artery  is  more  superficial  and 
placed  nearer  the.  middle  line  than  the  internal  carotid,  and  is  contained  in  the 
triangular  space  bounded  by  the  Sternomastoid  behind,  the  anterior  belly  of  the 
Omohyoid  below,  and  the  posterior  belly  of  the  Digastric  and  the  Stylohyoid 
above  (i.  e.,  the  superior  carotid  triangle). 

Relations. — It  is  covered  by  the  skin,  superficial  fascia,  Platysma,  deep  fascia,  and  anterior 
margin  of  the  Sternomastoid,  and  is  crossed  by  the  hypoglossal  nerve,  and  by  the  lingual  and 
facia]  veins;  it  is  afterward  crossed  by  the  Digastric  and  Stylohyoid  muscles,  and  higher  up 
passes  deeply  into  the  substance  of  the  parotid  gland,  where  it  lies  beneath  the  facial  nerve  and 
the  junction  of  the  temporal  and  internal  maxillary  veins.  Internally  is  the  hyoid  bone,  wall 
of  the  pharynx,  the  superior  laryngeal  nerve,  and  the  ramus  of  the  mandible,  from  which  it  is 
separated  by  a  portion  of  the  parotid  gland.  Externally,  in  the  lower  part  of  its  course,  is  the 
internal  carotid  artery.  Behind  it,  near  its  origin,  is  the  superior  laryngeal  nerve;  and  higher  up, 
it  is  separated  from  the  internal  carotid  by  the  Styloglossus  and  Stylopharyngeus  muscles,  the 
glossopharyngeal  nerve,  and  part  of  the  parotid  gland. 


Plan  of  the  Relations  of  the  External  Carotid. 

In  front. 

Skin,  superficial  fascia. 
Platysma  and  deep  fascia. 
Anterior  border  of  Sternomastoid. 
Hypoglossal  nerve. 
Lingual  and  facial  veins. 
Digastric  and  Stylohyoid  muscles. 

Parotid  gland  with  facial  nerve  and  temporomaxillary 
vein  in  its  substance. 


Internally. 

Hyoid  bone. 

Pharynx. 

Superior  laryngeal  nerve. 

Parotid  gland. 

Ramus  of  mandible. 


Externally. 

Internal  carotid  artery 
(lower  part). 


Behind. 

Superior  laryngeal  nerve. 
Styloglossus. 
Stylopharyngeus. 
Glossopharyngeal  nerve. 
Parotid  gland. 


Surface  Marking. — The  position  of  the  external  carotid  artery  may  be  marked  out  with 
sufficient  accuracy  by  a  line  drawn  from  the  front  of  the  meatus  of  the  external  ear  to  the  side 
of  the  cricoid  cartilage,  slightly  arching  the  median  line. 

Applied  Anatomy. — The  application  of  a  ligature  to  the  external  carotid  may  be  required 
m  case  of  wounds  of  this  vessel,  or  of  its  branches  when  these  cannot  be  tied,  and  in  some  cases 
of  pulsating  tumor  of  the  scalp  or  face.     The  operation  has  not  received  the  attention  which  it 


THE  EXTERNAL   CAROTID  ARTERY  589 

deserves,  owing  to  the  fear  which  surgeons  have  entertained  of  secondary  hemorrhage,  on  account 
of  the  number  of  branches  given  off  from  the  vessel.  This  fear,  however,  has  been  shown  by 
Mr.  Cripps  not  to  be  well  founded.'  I^igation  is  often  very  useful  as  a  means  of  preventing 
excessive  hemorrhage  in  operations  about  the  face,  jaws,  and  mouth.  It  is  sometimes  employed 
with  the  hope  of  lessening  the  growth  of  tumors  by  cutting  off  the  blood  supply,  but  ligation  is 
useless  for  this  purpose.  Ligation  of  one  external  carotid  artery  arrests  the  circulation  for  only 
a  brief  period,  and  within  a  very  few  days  the  circulation  is  practically  freely  reestablished. 
This  result  is  seen  to  be  inevitable  when  we  recall  the  numerous  branches  of  the  external  carotid, 
their  free  anastomoses,  and  the  fact  that  a  very  great  number  of  extremely  minute  vessels  in 
the  middle  line  join  the  external  carotid  system  of  one  side  to  that  of  the  other  side.  Robert 
H.  M.  Dawbarn  points  out  that  ligation  of  both  external  carotids  produces  only  temporary 
anemia,  for  "  inside  of  a  week  or  ten  days  thereafter  the  pulse  can  again  be  felt  in  the  temporals 
and  facials  upon  both  sides."'  Dawbarn  points  out  that  even  after  excision  of  the  external 
carotids,  with  separate  ligation  of  each  of  the  eight  branches,  blood  can  still  reach  the  nose, 
tongue,  etc.,  from  outside  systems  by  twenty-nine  distinct  routes.  Whereas  ligation  of  even  both 
carotids  will  not  prevent  the  growth  of  a  malignant  tumor,  excision  of  each  external  carotid, 
with  separate  control  of  its  eight  branches,  will  sometimes  prove  of  great  value  in  retarding  the 
progress  of  a  growth.  It  "starves"  the  growth  and  may  cause  it  to  shrink  (Dawbarn 's  oper- 
ation). To  tie  the  external  carotid  near  its  origin,  below  the  point  where  it  is  crossed  by  the 
Digastric,  an  incision  about  three  inches  in  length  should  be  made  along  the  margin  of  the  Sterno- 
mastoid,  from  the  angle  of  the  mandible  to  the  upper  border  of  the  thyroid  cartilage.  The  ligature 
should  be  applied  between  the  lingual  and  superior  thyroid  branches.  To  tie  the  vessel  above 
the  Digastric,  between  it  and  the  parotid  gland,  an  incision  should  be  made,  from  the  lobe  of  the 
ear  to  the  greater  cornu  of  the  hyoid  bone,  dividing  successively  the  skin,  Platysma,  and  fascia. 
By  drawing  the  Sternomastoid  outward,  the  posterior  belly  of  the  Digastric  and  Stylohyoid 
muscles  downward,  and  separating  them  from  the  parotid  gland,  the  vessel  will  be  exposed, 
and  a  ligature  may  be  applied  to  it.  The  circulation  is  at  once  reestablished  by  the  free  com- 
munication between  most  of  the  large  branches  of  the  artery  (facial,  lingual,  superior  thyroid, 
occipital)  and  the  corresponding  arteries  of  the  opposite  side  and  by  the  anastomosis  of  its 
branches  with  those  of  the  internal  carotid,  and  of  the  occipital  with  the  branches  of  the  sub- 
clavian, etc. 

Branches. — The  external  carotid  artery  gives  off  eight  branches,  which,  for 
convenience  of  description,  may  be  divided  into  four  sets.  (See  Fig.  436,  Plan  of 
the  Branches.) 

Anterior.  Posterior.  Ascending.  Terminal. 

Superior  Thyroid.     Occipital.  Ascending  Phar-       Superficial  Temporal. 

Lingual.  Posterior  Auric-         yngeal.  Internal  Maxillary. 

Facial.  ular. 

The  student  is  here  reminded  that  many  variations  are  met  with  in  the  number, 
origin,  and  course  of  these  branches  in  different  subjects;  but  the  above  arrange- 
ment is  that  which  is  found  in  the  great  majority  of  cases. 

1.  The  superior  thyroid  artery  (a.  thyroidea  superior)  (Figs.  435  and  436) 
arises  from  the  external  carotid  artery,  just  below  the  greater  cornu  of  the  hyoid 
bone,  and  terminates  in  the  thyroid  gland. 

Relations. — From  its  origin  under  the  anterior  border  of  the  Sternomastoid  it  runs  upward 
and  forward  for  a  short  distance  in  the  superior  carotid  triangle,  where  it  is  covered  by  the 
integument,  fascia,  and  Platysma;  it  then  arches  downward  and  forward  beneath  the  Omo- 
hyoid, Sternohyoid,  and  Sternothyroid  muscles.  To  the  inner  side  are  the  Inferior  constrictor 
of  the  pharynx  and  the  external  branch  of  the  laryngeal  nerve.  It  distributes  numerous  branches 
to  the  upper  part  of  the  gland,  anastomosing  with  its  fellow  of  the  opposite  side  and  with  the 
inferior  thyroid  arteries.  The  terminal  branches  supplying  the  gland  are  generally  two  in 
number;  one,  the  largest,  the  anterior  branch  (ramus  anterior),  descends  at  the  anterior  border 
of  the  lateral  lobe  of  the  gland,  reaches  the  upper  border  of  the  isthmus,  and  then  passes  in  the 
substance  of  the  isthmus  to  the  middle  line  of  the  neck,  where  it  anastomoses  with  the  corre- 
sponding artery  of  the  opposite  side;  the  posterior  branch  {ramus  fosterior)  descends  along 


590 


THE  VASCULAR  SYSTEMS 


the  posterior  border  of  the  lateral  lobe  of  the  gland,  the  anterior  and  posterior  branches  anasto- 
mose with  each  other  and  with  branches  of  the  inferior  thyroid,  and  both  of  them  send  branches 
to  the  thyroid  gland  (rami  glandidares) .  Besides  the  arteries  distributed  to  the  muscles  by 
which  it  is  covered  and  to  the  substance  of  the  gland. 

Branches. — The  branches  of  the  superior  thyroid  are  the  following: 


Infrahyoid. 
Sternomastoid. 


Superior  Laryngeal. 
Cricothyroid. 


The  infrahyoid  branch  (ramus  hyoideus)  is  small,  and  runs  along  the  lower  border 
of  the  hyoid  bone  beneath  the  Thyrohyoid  muscle;  after  supplying  the  muscles 
connected  to  that  bone,  it  forms  an  arch,  by  anastomosing  with  the  vessel  of  the 
opposite  side. 

The  sternomastoid  branch  (ramus  stern ocleidomastoideus')  runs  downward  and  out- 
ward across  the  sheath  of  the  common  carotid  artery,  and  supplies  the  Sterno- 
mastoid and  neighboring  muscles  and  integument.  There  is  frequently  a  separate 
branch  from  the  external  carotid  distributed  to  the  Sternomastoid  muscle. 

The  superior  laryngeal  (a.  laryngea  sujxrior),  larger  than  either  of  the  preceding, 
accompanies  the  internal  branch  of  the  superior  laryngeal  nerve,  beneath  the 
Thyrohyoid  muscle;  it  pierces  the  thyrohyoid  membrane,  and  supplies  the  muscles, 
mucous  membrane,  and  glands  of  the  larynx,  anastomosing  with  the  branch  from 
the  opposite  side. 

The  cricothyroid  (ramus  cricothyreoidetis)  is  a  small  branch  which  runs  trans- 
versely across  the  cricothyroid  membrane,  and  communicates  with  the  artery  of 
the  opposite  side. 

Applied  Anatomy.  —  The  superior  thyroid,  or  one  of  its  branches,  is  often  divided  in. 
cases  of  cut  throat,  giving  rise  to  considerable  hemorrhage.    In  such  cases  the  artery  should 

be  secured,  the  wound  being  enlarged  for  that  pur- 
pose, if  necessary.  The  operation  may  be  easily 
performed,  the  position  of  the  artery  being  very 
superficial,  and  the  only  structures  of  importance 
covering  it  being  a  few  small  veins.  The  superior 
and  inferior  thyroid  arteries  of  the  involved  side  are 
ligated  before  extirpating  a  goitrous  lobe  of  the 
thyroid  gland. 

The  position  of  the  superficial  descending  branch 
is  of  importance  in  connection  with  the  operation  of 
ligation  of  the  common  carotid  artery.  It  crosses 
and  lies  on  the  sheath  of  this  vessel,  and  may  be 
wounded  in  opening  the  sheath.  The  position  of 
the  cricothyroid  branch  should  be  remembered,  as  it 
may  prove  the  source  of  troublesome  hemorrhage 
during  the  operation  of  laryngotomy.  In  performing 
the  operation  of  quick  laryngotomy  the  cricothyroid 
membrane  should  be  incised  transversely  in  order 
to  avoid  this  vessel. 


2.  The  lingual  artery  (a.  Ungualis)  (Figs. 
435  and  436)  arises  from  the  external  carotid 
between  the  superior  thyroid  and  facial;  it 
first  runs  obliquely  upward  and  inward  to  the 
great  cornu  of  the  hyoid  bone;  it  then  curves 
downward  and  forward,  forming  a  loop  which 
is  crossed  bv  the  hypoglossal  nerve,  and  pass- 
ing beneath  the  Digastric  and  Stylohyoid  muscles,  it  runs  horizontally  forward, 
beneath  the  Hyoglossus,  and  finally,  ascending  almost  perpendicularly  to  the 
tongue,  turns  forward  on  its  under  surface  as  far  as  the  tip,  under  the  name  of 
the  ranine  artery. 


Fig.  437.— Showing  the  relation  of  the 
hngua)  artery  and  hypoglossal  nerve;  Lesser's 
triangle  is  liounded  above  by  the  nerve,  below 
by  the  posterior  belly  of  the  Digastric,  and  in 
front  by  the  posterior  border  of  the  Mylohyoid, 
indicated  by  a  solid  line.  The  floor  of  the 
triangle  is  occupied  by  the  Hyoglossus. 


THE  EXTERNAL   CAROTID  ARTERY  591 

Relations. — Xi^jirst,  or  oblique,  portion  is  superficial,  being  contained  in  the  same  triangular 
space  as  the  superior  thyroid  artery,  resting  upon  the  Middle  constrictor  of  the  pharynx,  and 
covered  by  the  Platysma  and  fascia  of  the  neck.  Its  second,  or  curved,  portion  also  lies  upon  the 
Middle  constrictor,  being  covered  at  first  by  the  tendon  of  the  Digastric  and  the  Stylohyoid 
muscle,  and  afterward  by  the  Hyoglossus,  the  latter  muscle  separating  it  from  the  hypoglossal 
nerve.  Its  third,  or  horizontal,  portion  lies  between  the  Hyoglossus  and  Geniohyoglossus 
muscles.  The  fourth,  or  terminal,  part,  under  the  name  of  the  ranine,  runs  along  the  under 
surface  of  the  tongue  to  its  tip;  it  is  very  superficial,  being  covered  only  by  the  mucous  mem- 
brane, and  rests  on  the  Lingualis  on  the  outer  side  of  the  Geniohyoglossus.  The  hypoglossal 
nerve  crosses  the  lingual  artery,  and  then  becomes  separated  from  it,  in  the  second  part  of  its 
course,  by  the  Hj'oglossus  muscle. 

Branches. — The  branches  of  the  lingual  artery  are  the 

Suprahyoid.  Sublingual. 

Dorsalis  Linguse.  Ranine. 

The  suprahyoid  branch  (ramus  hyoideus)  runs  along  the  upper  border  of  the 
hyoid  bone,  supplying  the  muscles  attached  to  it  and  anastomosing  with  its  fellow 
of  the  opposite  side. 

The  dorsalis  linguae  {ramus  dorsalis  linguae)  (Fig.  496)  arises  from  the  lingual 
artery  beneath  the  Hyoglossus  muscle;  it  ascends  to  the  back  of  the  dorsum  of 
the  tongue,  and  supplies  the  mucous  membrane,  the  tonsil,  soft  palate,  'and 
epiglottis,  anastomosing  with  its  fellow  from  the  opposite  side.  This  artery  is 
frequently  represented  by  two  or  three  small  branches. 

The  sublingual  (a.  sublingualis),  which  may  -be  described  as  a  branch  of  bifur- 
cation of  the  lingual  artery,  arises  at  the  anterior  margin  of  the  Hyoglossus  muscle, 
and  runs  forward  between  the  Geniohyoglossus  and  the  sublingual  gland.  It 
supplies  the  substance  of  the  gland,  giving  branches  to  the  Mylohyoid  and  neigh- 
boring muscles,  the  mucous  membrane  of  the  mouth  and  gums.  One  branch  runs 
behind  the  alveolar  process  of  the  mandible  in  the  substance  of  the  gum  to  anas- 
tomose with  a  similar  artery  from  the  other  side. 

The  ranine,  or  deep  lingual  (a.  profunda  linguae),  may  be  regarded  as  the  other 
branch  of  bifurcation.  It  is  usually  described  as  the  continuation  of  the  lingual 
artery;  it  runs  along  the  under  surface  of  the  tongue,  resting  on  the  Inferior  lin- 
gualis, and  covered  by  the  mucous  membrane  of  the  mouth;  it  lies  on  the  outer  side 
of  the  Geniohyoglossiis,  accompanied  by  the  lingual  nerve.  On  arriving  at  the 
tip  of  the  tongue  it  is  said  to  anastomose  with  the  artery  of  the  opposite  side,  but 
this  is  denied  by  Hyrtl.  In  the  mouth  these  vessels  are  placed  one  on  either  side 
of  the  frenum. 

Applied  Anatomy. — The  lingual  artery  may  be  divided  near  its  origin  in  cases  of  cut  throat, 
a  complication  that  not  infrequently  happens  in  this  class  of  wounds;  or  severe  hemorrhage 
which  cannot  be  restrained  by  ordinary  means  may  ensue  from  a  wound  or  deep  ulcer  of  the 
tongue.  In  the  former  case  the  primary  wound  may  be  enlarged  if  necessary,  and  the  bleeding 
vessels  secured.  In  the  latter  case  it  has  been  suggested  that  the  lingual  artery  should  be  tied 
near  its  origin.  Ligation  of  the  lingual  artery  is  also  occasionally  practised,  as  a  palliative 
measure,  in  cases  of  cancer  of  the  tongue,  in  order  to  check  the  progress  of  the  disease  by  starving 
the  growth  and  it  is  often  tied  as  a  preliminary  measure  to  removal  of  the  tongue.  The  operation 
is  a  somewhat  difficult  one,  on  account  of  the  depth  of  the  artery,  the  number  of  important 
structures  by  which  it  is  surrounded,  the  loose  and  yielding  nature  of  the  parts  upon  which  it  is 
supported,  and  its  occasional  irregularity  of  origin.  An  incision  is  to  be  made  in  a  curved  direc- 
tion from  a  point  one  finger's  breadth  external  to  the  symphysis  of  the  mandible  downward  to  the 
cornu  of  the  hyoid  bone,  and  then  upward  to  near  the  angle  of  the  mandible.  Care  must  be  taken 
not  to  carry  this  incision  too  far  backward,  for  fear  of  endangering  the  facial  vein.  In  the  first 
incision  the  skin,  superficial  fascia,  and  Platysma  will  be  divided,  and  the  deep  fascia  exposed. 
The  deep  fascia  is  then  to  be  incised,  and  the  submaxillary  gland  exposed  and  pulled  upward  by 
retractors.  A  triangular  space  is  now  exposed.  Leaser's  triangle  (Fig.  437),  bounded  internally 
by  the  posterior  border  of  the  Mylohyoid  muscle;  below  and  externally,  by  the  tendon  of  the 
Digastric;    and  above,  by  the  hypoglossal  nerve.      The  floor  of  the  space  is  formed  by  the 


592 


THE   VASCULAB  SYSTEMS 


Hyoglossus  muscle,  beneath  which  the  artery  lies.  The  fibres  of  this  muscle  are  now  to  be  cut 
through  horizontally  and  the  vessel  exposed,  care  being  taken,  while  near  the  vessel,  not  to 
open  the  pharynx. 

Troublesome  hemorrhage  may  occur  in  the  division  of  the  frenum  in  children  if  the  ranine 
arteries,  which  lie  on  each  side  of  it,  are  wounded.  The  student  should  remember  that  the  oper- 
ation is  always  to  be  performed  with  a  pair  of  blunt-pointed  scissors,  and  the  mucous  membrane 
only  is  to  be  divided  by  a  very  superficial  cut,  which  cannot  endanger  any  vessel.  The  scissors, 
also,  should  be  directed  toward  the  floor  of  the  mouth.  Any  further  liberation  of  the  tongue 
which  may  be  necessary  can  be  effected  by  tearino-. 

3.  The  facial  artery  (a.  maxillaris  externa)  (Figs.  435  and  438)  arises  a  little 
above  the  lingual,  and  passes  obliquely  upward,  beneath  the  Digastric  and  Stylo- 
hyoid muscles,  and  frequently  beneath  the  hypoglossal  nerve;  it  now  runs  forward 


1  teria  septi  nasi, 
uperior  coronary. 


Inferior  coronary. 
Infei  ior  labial. 


Fig.  438. — The  arteries  of  the  face  and  scalp.     The  muscle  tissue  of  the  lips  must  be  supposed  to  have  beea 
cut  away,  in  order  to  show  the  course  of  the  coronary  arteries. 


under  cover  of  the  body  of  the  mandible,  lodged  in  a  groove  on  the  posterior  surface 
of  the  submaxillary  gland;  this  may  be  called  the  cervical  part  of  the  artery.  It 
then  curves  upward  over  the  body  of  the  mandible  at  the  anterior  inferior  angle 
of  the  Masseter  muscle;  passes  forward  and  upward  across  the  cheek  to  the  angle 
of  the  mouth,  then  upward  along  the  side  of  the  nose,  and  terminates  at  the  inner 
canthus  of  the  eye,  under  the  name  of  the  angular  artery.  The  facial  artery,  both 
in  the  neck  and  on  the  face,  is  remarkably  tortuous;  in  the  former  situation  its  tor- 
tuosity enables  it  to  accommodate  itself  to  the  movements  of  the  pharynx  in  deglu- 
tition, and  in  the  latter  to  the  movements  of  the  mandible  and  the  lips  and  cheeks. 


THE  EXTERNAL  CAROTID  ARTERY  593 

Relations. — In  the  neck  its  orlp;in  is  .su|)erfieial,  being  covered  by  the  integument,  Piatysnia, 
and  fascia;  it  then  passes  beneath  ihc  ])igaslric  and  Stylohyoid  muscles  and  part  of  the  sub- 
maxillary gland.  It  lies  upon  the  ^Middle  constrictor  of  the  pharynx,  and  is  separated  from 
the  Styloglossus  and  Hyoglossus  muscles  by  a  portion  of  the  submaxillary  gland.  On  the  face, 
where  it  passes  over  the  body  of  the  mandible,  it  is  comparatively  superficial,  lying  immediately 
beneath  the  Platysma.  In  this  situation  its  pulsation  may  be  distinctly  felt,  and  compression 
of  the  vessel  against  the  bone  can  be  eflectually  made.  In  its  course  over  the  face  it  is  covered 
by  the  integument,  the  fat  of  the  cheek,  and,  near  the  angle  of  the  mouth,  by  the  Platysma, 
Risorius,  and  Zygomatic  muscles.  It  rests  on  the  Buccinator,  the  Levator  anguli  oris,  and  the 
Levator  labii  superioris  (sometimes  piercing  or  else  passing  under  this  last  muscle).  The 
facial  vein  lies  to  the  outer  side  of  the  artery,  and  takes  a  more  direct  course  across  the  face, 
where  it  is  separated  from  the  artery  by  a  considerable  interval.  In  the  neck  it  lies  superficial 
to  the  artery.  The  branches  of  the  facial  nerve  cross  the  artery,  and  branches  of  the  infra- 
orbital nerve  lie  beneath  it. 

Branches. — The  branches  of  this  vessel  may  be  divided  into  two  sets — those 
given  off  below  the  mandible  (cervical),  and  those  on  the  face  (facial). 

Cervical  Branches.  Facial  Branches. 

Ascending  Palatine.  Inferior  labial. 

Tonsillar.  Inferior  labial  coronary. 

Submaxillary.  Superior  labial  coronary. 

Submental.  Lateral  nasal. 

Angular. 

Muscular. 

The  ascending  palatine  (a.  palatine  ascendens)  passes  up  between  the  Styloglossus 
and  Stylopharyngeus  to  the  outer  side  of  the  pharynx,  along  which  it  is  continued 
between  the  Superior  constrictor  and  the  Internal  pterygoid  to  near  the  base  of 
the  skull.  It  divides,  near  the  Levator  palati,  into  two  branches;  one  follows 
the  course  of  the  Levator  palati,  and,  winding  over  the  upper  border  of  the  Superior 
constrictor,  supplies  the  soft  palate  and  the  palatal  glands,  anastomosing  with  its 
fellow  of  the  opposite  side  and  with  the  posterior  palatine  branch  of  the  internal 
maxillary  artery;  the  other  pierces  the  Superior  constrictor  and  supplies  the  tonsil 
and  Eustachian  tube,  anastomosing  with  the  tonsillar  and  ascending  pharyngeal 
arteries. 

The  tonsillar  branch  (ramus  tonsillaris)  passes  up  between  the  Internal  pterygoid 
and  Styloglossus,  and  then  ascends  along  the  side  of  the  pharynx,  perforating  the 
Superior  constrictor,  to  ramify  in  the  substance  of  the  tonsil  and  root  of  the  tongue. 

The  submaxillary  or  glandular  branches  (ra^ni  glandulares)  consist  of  three  or 
four  large  vessels,  which  supply  the  submaxillary  gland,  some  being  prolonged  to 
the  neighboring  muscles,  lymph  nodes,  and  integument. 

The  submental  (a.  submentalis)  (Fig.  435),  the  largest  of  the  cervical  branches, 
is  given  off  from  the  facial  artery  just  as  that  vessel  emerges  from  the  submaxillary 
gland;  it  runs  forward  upon  the  Mylohyoid  muscle,  just  below  the  body  of  the 
mandible  and  beneath  the  Digastric;  after  supplying  the  surrounding  muscles, 
and  anastomosing  with  the  sublingual  artery  by  branches  which  perforate  the 
Mylohyoid  muscle,  it  arrives  at  the  symphysis  of  the  mandible,  where  it  turns 
over  the  border  of  the  mandible  and  divides  into  a  superficial  and  a  deep  branch; 
the  former  passes  between  the  integument  and  Depressor  labii  inferioris,  supplies 
both,  and  anastomoses  with  the  inferior  labial.  The  deep  branch  passes  between 
the  latter  muscle  and  the  bone,  supplies  the  lip,  and  anastomoses  with  the  inferior 
labial  and  mental  arteries. 

The  inferior  labial  (a.  labialis  inferior)  (Fig.  438)  passes  beneath  the  Depressor 
anguli  oris,  to  supply  the  muscles  and  integument  of  the  chin  and  lower  lip,  anasto- 
mosing with  the  inferior  labial  coronary  and  submental  branches  of  the  facial,  a<nd 
with  the  mental  branch  of  the  inferior  dental  artery. 

38 


594 


THE  VASCULAR  8YSTEMS 


The  inferior  labial  coronary  (Figs.  438  and  439)  is  derived  from  the  facial  artery, 
near  the  angle  of  the  mouth;  it  passes  upward  and  inward  beneath  the  Depressor 
anguli  oris,  and,  penetrating  the  Orbicularis  oris  muscle,  runs  in  a  tortuous  course 
along  the  edge  of  the  lower  lip  between  this  muscle  and  the  mucous  membrane, 
anastomoses  with  the  artery  of  the  opposite  side.  This  artery  supplies  the  labial 
glands,  the  mucous  membrane,  and  muscles  of  the  lower  lip,  and  anastomoses 
with  the  inferior  labial  from  the  facial  and  the  mental  branch  of  the  inferior 
dental  artery. 

The  superior  labial  coronary  (a.  labialis  superior)  (Figs.  438  and  439)  is  larger  and 
more  tortuous  in  its  course  than  the  preceding.  It  follows  the  same  course  along 
the  edge  of  the  upper  lip,  lying  between  the  mucous  membrane  and  the  Orbicu- 
laris oris,  and  anastomoses  with  the  artery  of  the  opposite  side.  It  supplies  the 
tissues  of  the  upper  lip,  and  gives  off  in  its  course  two  or  three  vessels  which  ascend 
to  the  nose.  One,  named  the  inferior  artery  of  the  septum,  ramifies  on  the  septum 
of  the  nostrils  as  far  as  the  point  of  the  nose;  another,  the  artery  of  the  ala,  supplies 
the  ala  of  the  nose. 

The  lateralis  nasi  is  derived  from  the  facial,  as  that  vessel  is  ascending  along 
the  side  of  the  nose ;  it  supplies  the  ala  and  dorsum  of  the  nose,  anastomosing  with 
its  fellow,  the  nasal  branch  of  the  ophthalmic,  the  inferior  artery  of  the  septum, 
the  artery  of  the  ala,  and  the  infraorbital. 


Fig.  439.- — The  labial  coronary  arteries,  the  glands  of  the  lips, 
posterior  surface  after  removal  of  the  mucous  m( 


serves  of  the  right  side  seen  from  the 
(Poirier  and  Charpy.) 


The  angular  artery  (a.  annularis)  is  the  termination  of  the  trunk  of  the  facial; 
it  ascends  to  the  inner  angle  of  the  orbit,  embedded  in  the  fibres  of  the  Levator 
Jabii  superioris  alaeque  nasi,  and  accompanied  by  a  large  vein,  the  angular  vein; 
it  distributes  some  branches  on  the  cheek  which  anastomose  with  the  infraorbital. 
After  supplying  the  lacrimal  sac  and  Orbicularis  palpebrarum  muscle,  the  angular 
artery  terminates  by  anastomosing  with  the  nasal  branch  of  the  ophthalmic  artery. 

The  muscular  branches  are  distributed  to  the  Internal  pterygoid  and  Stylohyoid 
in  the  neck,  and  to  the  Masseter  and  Buccinator  on  the  face. 

The  anastomoses  of  the  facial  artery  are  very  numerous,  not  only  with  the 
vessel  of  the  opposite  side,  but,  in  the  neck,  with  the  sublingual  branch  of  the  lingual; 
with  the  ascending  pharyngeal;  and  with  the  posterior  palatine,  a  branch  of  the 
internal  maxillary,  by  its  ascending  palatine  and  tonsillar  branches;  on  the  face, 
with  the  mental  branch  of  the  inferior  dental  as  it  emerges  from  the  mental  foramen, 
with  the  transverse  facial,  a  branch  of  the  temporal;  with  the  infraorbital,  a  branch 
of  the  internal  maxillary,  and  with  the  nasal  branch  of  the  ophthalmic. 

Peculiarities, — The  facial  artery  not  infrequently  arises  by  a  common  trunk  with  the  lingual. 
This  vessel  is  also  subject  to  some  variations  in  its  size  and  in  the  extent  to  which  it  supplies 
the  face.     It  occasionally  terminates  as  the  submental,  and  not  infrequently  supplies  the  face 


THE  EXTERNAL   CAROTID  ARTERY 


595 


only  ns  liioh  as  tlie  niiffle  of  the  mouth  or  nose.     The  deficiency  is  then  supplied  by  enlargement 
of  one  of  ilic  lu'l^'hhorini^  arteries. 

Applied  Anatomy.— The  passage  of  the  facial  artery  over  the  body  of  the  mandible  would 
appear  to  afl'ord  a  favorable  position  for  the  application  of  pressure  in  case  of  hemorrhage  from  the 
lips,  the  result  either  of  an  accidental  wound  or  during  an  operation;  but  its  application  is  useless, 
e.xcept  for  a  very  short  time,  on  account  of  the  free  communication  of  this  vessel  with  its  fellow 
and  with  numerous  branches  from  different  sources.  In  a  wound  invohmg  the  lip  it  is  better 
to  seize  the  part  between  the  fingers,  and  evert  it,  when  the  bleeding  vessel  may  be  at  once  secured 
with  pressure  forceps.  In  order  to  prevent  hemorrhage  in  cases  of  removal  "of  diseased  growths 
from  the  part,  the  lip  should  be  compressed  on  each  side  between  the  fingers  and  thumb  or  by 
a  pair  of  specially  devised  clamp  forceps,  while  the  surgeon  excises  the  diseased  part.  In  order 
to  stop  hemorrhage  where  the  lip  has  been  divided  in  an  operation,  it  is  necessary,  in  uniting 
the  edges  of  the  wound,  to  pass  the  sutures  through  the  cut  edges  from  the  skin  almost  as  deep 
as  the  mucous  surface;  by  these  means  not  only  are  the  cut  surfaces  more  neatly  and  securely 
adapted  to  each  other,  but  the  possibility  of  hemorrhage  is  prevented  by  including  in  the  suture 
the  divided  artery.  If  the  suture  is,  on  the  contrary, 
passed  through  merely  the  cutaneous  portion  of  the  wound, 
hemorrhage  occurs  into  the  cavity  of  the  mouth.  Lastly, 
the  relation  of  the  angular  artery  to  the  lacrimal  sac  should 
be  observed,  and  it  will  be  seen  that,  as  the  vessel  passes  up 
along  the  inner  margin  of  the  orbit,  it  ascends  on  the 
nasal  side.  In  operating  iov  fistula  lacrimalis  the  sac  should 
always  be  opened  on  its  outer  side,  in  order  that  this  vessel 
may  be  avoided. 

4.  The  occipital  artery  (a.  occipitalis)  (Figs. 
435  and  440)  arises  from  the  posterior  part  of  the 
external  carotid,  opposite  the  facial,  near  the  lower 
margin  of  the  Digastric  muscle. 

Relations. — At  its  origin  it  is  covered  by  the  posterior 
belly  of  the  Digastric  muscle  and  the  Stylohyoid  muscle, 
and  the  hypoglossal  nerve  winds  around  it  from  behind 
forward;  higher  up,  it  passes  across  the  internal  carotid 
artej-y,  the  internal  jugular  vein,  and  the  vagus  and  spinal 
accessory  nerves;  it  then  ascends  to  the  interval  between  the 
transverse  process  of  the  atlas  and  the  mastoid  process  of 
the  temporal  bone,  and  passes  horizontally  backward  in  the 
occipital  groove  on  the  mastoid  portion  of  the  temporal, 
being  covered  by  the  Sternumastoid,  Splenius,  Trachelo- 
mastoid,  and  Digastric  muscles,  and  resting  upon  the 
Rectus  lateraHs,  the  Superior  oblique,  and  Complexus 
muscles;  it  then  changes  its  course  and  passes  vertically 
upward,  pierces  the  fascia  which  connects  the  cranial 
attachment  of  the  Trapezius  with  the  Sternomastoid,  and 
ascends  in  a  tortuous  course  over  the  occiput,  as  high  as  the  vertex,  where  it  divides  into 
numerous  branches.  It  is  accompanied  in  the  latter  part  of  its  course  by  the  great  occipital 
nerve,  and  occasionally  by  a  cutaneous  filament  from  the  suboccipital  nerve. 

Branches. — ^The  branches  given  off  from  this  vessel  are: 

Muscular.  Meningeal  or  diiral. 

Sternomastoid.  Mastoid. 

Auricular.  Arteria  princeps  cervicis. 

Cranial  branches. 

The  muscular  branches  (rami  musculares)  supply  the  Digastric,  Stylohyoid, 
Splenius,  and  Trachelomastoid  muscles. 

The  sternomastoid  fa.  steriiocleidomastoidea)  is  a  large  and  constant  branch, 
generally  arising  from  the  artery  close  to  its  commencement,  but  sometimes  spring- 
ing directly  from  the  external  carotid.  It  first  passes  downward  and  backT\-ard 
over  the  hypoglossal  nerve,  and  enters  the  substance  of  the  muscle  in  company 
with  the  spinal  accessory  nerve. 


Fig.  440. — The  loop  of  the  hypo- 
glossal nerve  and  the  branches  of  the 
external  carotid  artery. 


596  THE  VASCULAR  SYSTEMS 

The  auricular  branch  {ramus  auricularis)  supplies  the  back  part  of  the  concha. 
It  frequently  gives  off  a  branch,  which  enters  the  skull  through  the  mastoid  foramen 
and  supplies  the  dura,  the  diploe,  and  the  mastoid  cells. 

The  meningeal  or  dural  branch  {ramus  meningeus)  ascends  with  the  internal 
juo'ular  vein,  and  enters  the  skull  through  the  foramen  lacerum  posterius,  or 
through  the  anterior  condylar  foramen,  to  supply  the  dura  in  the  posterior  fossa. 

The  mastoid  branch  {ramus  mastoideus)  is  a  small  vessel,  by  no  means  constant. 
It  passes  into  the  skull  through  the  mastoid  foramen  and  is  distributed  upon  the 
dura  of  the  posterior  fossa. 

The  arteria  princeps  cervicis  {ravmis  descendens),  the  largest  branch  of  the 
occipital,  descends  along  the  back  part  of  the  neck  and  divides  into  a  superficial 
and  a  deep  branch.  The  superficial  branch  runs  beneath  the  Splenius,  giving  off 
branches  which  perforate  that  muscle  to  supply  the  Trapezius,  and  then  anasto- 
mose with  the  superficial  cervical  artery,  a  branch  of  the  transversalis  colli;  the 
deep  branch  passes  beneath  the  Complexus  between  it  and  the  Semispinalis  colli, 
and  anastomoses  with  branches  from  the  vertebral  and  with  the  deep  cervical 
artery,  a  branch  of  either  the  superior  intercostal  or  the  subclavian.  The 
anastomosis  between  these  vessels  helps  to  establish  the  collateral  circulation 
after  ligation  of  the  carotid  or  subclavian  artery. 

The  cranial  branches  {rami  occipitales)  of  the  occipital  artery  are  distributed  upon 
the  occiput ;  they  are  very  tortuous^  and  lie  between  the  integument  and  Occipito- 
frontalis,  anastomosing  with  the  artery  of  the  opposite  side,  the  posterior  auricular 
and  temporal  arteries.  They  supply  the  back  part  of  the  Occipitofrontalis  muscle, 
the   integument,  and  pericranium. 

5.  The  posterior  auricular  artery  {a.  auricidarls  'posterior')  (Figs.  436  and  438) 
is  a  small  vessel  which  arises  from  the  external  carotid,  above  the  Digastric  and 
Stylohyoid  muscles,  opposite  the  apex  of  the  styloid  process.  It  ascends,  under 
cover  of  the  parotid  gland,  on  the  styloid  process  of  the  temporal  bone,  to  the 
groove  between  the  cartilage  of  the  ear  and  the  mastoid  process,  immediately 
above  which  it  divides  into  its  two  terminal  branches,  the  auricular  and  mastoid. 
Just  before  arriving  at  the  mastoid  process,  this  artery  is  crossed  by  the  facial 
nerve,  and  has  beneath  it  the  spinal  accessory  nerve. 

Branches. — Besides  several  small  branches  to  the  Digastric,  Stylohyoid,  and 
Sternomastoid  muscles  and  to  the  parotid  gland,  this  vessel  gives  ofi'  three  branches : 

Stylomastoid.  Auricular.  Mastoid. 

The  stylomastoid  branch  {a.  stylomastoidea)  enters  the  stylomastoid  foramen, 
and  supplies  the  tympanum,  mastoid  cells,  and  semicircular  canals.  In  the  young 
subject  a  branch  from  this  vessel  forms,  with  the  tympanic  branch  from  the  in- 
ternal maxillary,  a  vascular  circle,  which  surrounds  the  tympanic  membrane, 
and  from  which  delicate  vessels  ramify  on  that  membrane.  It  anastomoses  with 
the  petrosal  branch  of  the  middle  meningeal  artery  by  a  twig,  which  enters  the 
hiatus  Fallopii. 

The  auricular  branch  {ramus  auricidaris),  one  of  the  terminal  branches,  ascends 
behind  the  ear,  beneath  the  Retrahens  aurem  muscle,  and  is  distributed  to  the  back 
part  of  the  cartilage  of  the  ear,  upon  which  it  ramifies  minutely,  some  branches 
curving  around  the  margin  of  the  fibrocartilage,  others  perforating  it,  to  supply 
its  anterior  surface.  It  anastomoses  with  the  posterior  branch  and  also  with  the 
anterior  auricular  branches  of  the  superficial  temporal. 

The  mastoid  branch  {ramus  mastoideus)  passes  backward,  over  the  Sternomastoid 
muscle,  to  the  scalp  above  and  behind  the  ear.  It  supplies  the  posterior  belly  of 
the  Occipitofrontalis  muscles  and  the  scalp  in  this  situation.  It  anastomoses 
with  the  occipital  artery. 


THE  EXTERNAL  CAROTID  ARTERY  597 

6.  The  ascending  pharyngeal  artery  {n.  ■pharyngea  ascendens)  (Figs.  435  and 
436),  the  smallest  branch  of  the  external  carotid,  is  a  long,  slender  vessel,  deeply 
seated  in  the  neck,  beneath  the  other  branches  of  the  external  carotid  and  the 
Stylopharyngeus  muscle.  It  arises  from  the  back  part  of  the  external  carotid,  near 
the  commencement  of  that  vessel,  and  ascends  vertically  between  the  internal 
carotid  and  the  side  of  the  pharynx,  to  the  under  surface  of  the  base  of  the  skull, 
lying  on  the  Rectus  capitis  anticus  major  muscle. 

Branches. — Its  branches  may  be  subdivided  as  follows: 

Prevertebral.  Palatine. 

Pharyngeal.  Tympanic. 

Meningeal  or  dural. 

The  prevertebral  branches  are  numerous  small  vessels  which  supply  the  Recti 
capitis  antici  and  Longus  colli  muscles,  the  sympathetic,  hypoglossal,  and  vagus 
nerves,  and  the  lymph  nodes.  They  anastomose  with  the  ascending  cervical 
artery,  a  branch  of  the  inferior  thyroid. 

The  pharyngeal  branches  (rami  pharyiigei)  are  three  or  four  in  number.  Two 
of  these  descend  to  supply  the  Middle  and  Inferior  constrictors  and  the  Stylo- 
pharyngeus, ramifying  in  the  substance  of  the  muscles  and  in  the  submucous 
tissue  of  the  mucous  membrane  lining  them. 

The  palatine  branch  varies  in  size,  and  may  take  the  place  of  the  ascending 
palatine  branch  of  the  facial  artery,  when  that  vessel  is  small.  It  passes  inward 
upon  the  Superior  constrictor,  and  sends  ramifications  to  the  soft  palate  and  tonsil, 
and  supplies  a  branch  to  the  Eustachian  tube. 

The  tympanic  branch  (a.  tym-panica  inferior)  is  a  small  artery  which  passes 
through  a  minute  foramen  in  the  petrous  portion  of  the  temporal  bone,  in  com- 
pany with  the  tympanic  branch  of  the  glossopharyngeal  nerve  to  supply  the  inner 
wall  of  the  tympanum  and  anastomose  with  the  other  tympanic  arteries. 

The  meningeal  or  dural  branches  consist  of  several  small  vessels,  which  pass 
through  foramina  in  the  base  of  the  skull,  to  supply  the  dura.  One,  the  posterior 
meningeal  or  postdural  (a.  meningea  posterior),  enters  the  cranium  through  the 
foramen  lacerum  posterius;  a  second  passes  through  the  foramen  lacerum  medium; 
and  occasionally  a  third  through  the  anterior  condylar  foramen. 

Applied  Anatomy. — The  ascending  pharyngeal  artery  has  been  -nounded  from  the  throat, 
as  in  the  case  in  which  the  stem  of  a  tobacco-pipe  was  driven  into  the  vessel,  causing  fatal  hemor- 
rhage. After  removal  of  the  tonsil  there  is  sometimes  severe  bleeding.  This  is  almost  never 
due  to  wounding  of  the  internal  carotid  artery,  as  the  latter  vessel,  if  normally  placed,  is  too 
far  away  to  be  damaged.  The  bleeding  comes  from  the  branches  of  the  ascending  pharyngeal, 
tonsillar,  or  ascending  palatine  arteries. 

7.  The  superficial  temporal  artery  (a.  temporalis  superficialis)  (Figs.  435  and 
438) ,  the  smaller  of  the  two  terminal  branches  of  the  external  carotid,  appears,  from 
its  direction,  to  be  the  continuation  of  that  vessel.  It  commences  in  the  substance 
of  the  parotid  gland,  behind  the  neck  of  the  mandible,  and  crosses  over  the  posterior 
root  of  the  zygoma,  passes  beneath  the  Attrahens  aurem  muscle,  lying  on  the  tem- 
poral fascia,  and  divides,  about  two  inches  above  the  zygomatic  arch,  into  two 
branches,  an  anterior  and  a  posterior.  This  vessel  is  accompanied  by  the  auriculo- 
temporal nerve. 

Relations. — The  superficial  temporary  artery,  as  it  crosses  the  zygoma,  is  covered  by  the 
Attrahens  aurem  muscle,  and  by  a  dense  fascia  given  off  from  the  parotid  gland;  it  is  crossed 
bv  the  temporofacial  division  of  the  facial  nerve  and  one  or  two  veins,  and  is  accompanied  by 
the  auriculotemporal  nerve,  which  lies  behind  it. 


698  THE  VASCULAR  SYSTEMS 

Besides  some  twigs  to  the  parotid  gland,  the  articulation  of  the  mandible,  and 
the  Masseter  muscle,  its  branches  are: 

Transverse  facial.  Anterior  auricular. 

Middle  temporal.  Anterior  temporal. 

Orbital.  Posterior  temporal. 

The  transverse  facial  branch  (a.  transversa  faciei)  is  given  off  from  the  tem- 
poral before  that  vessel  quits  the  parotid  gland;  running  forward  through  its 
substance,  it  passes  transversely  across  the  face,  between  the  parotid  duct  and 
the  lower  border  of  the  zygoma,  and  divides  on  the  side  of  the  face  into  numerous 
branches,  which  supply  the  parotid  gland,  the  Masseter  muscle,  and  the  integu- 
ment, anastomosing  with  the  facial,  masseteric,  and  infraorbital  arteries.  This 
vessel  rests  on  the  Masseter,  and  is  accompanied  by  one  or  two  branches  of  the 
facial  nerve.     It  is  sometimes  a  branch  of  the  external  carotid. 

The  middle  temporal  artery  (a.  temporalis  media)  arises  immediately  above 
the  zygomatic  arch,  and,  perforating  the  temporal  fascia,  gives  branches  to  the 
Temporal  muscle,  anastomosing  with  the  deep  temporal  branches  of  the  internal 
maxillary.  It  occasionally  gives  off  an  orbital  branch,  which  runs  along  the  upper 
border  of  the  zygoma,  between  the  two  layers  of  the  temporal  fascia,  to  the  outer 
angle  of  the  orbit.  This  branch,  which  may  arise  directly  from  the  superficial 
temporal  artery,  supplies  the  Orbicularis  palpebrarum,  and  anastomoses  with 
the  lacrimal  and  palpebral  branches  of  the  ophthalmic  artery. 

The  orbital  artery  (a.  zijgomaticoorbitalis)  comes  off  from  the  temporal  just 
above  the  zygoma  and  is  distributed  to  the  upper  orbital  margin. 

The  anterior  auricular  branches  (rami  aurimdares  anteriores)  are  distributed  to 
the  anterior  portion  of  the  pinna,  the  lobule,  and  part  of  the  external  meatus, 
anastomosing  with  branches  of  the  posterior  auricular. 

The  anterior  temporal  runs  tortuously  upward  and  forward,  to  the  forehead, 
supplying  the  muscles,  integument,  and  pericranium  in  this  region,  and  anasto- 
moses with  the  supraorbital  and  frontal  arteries.  The  terminal  portion  of  the 
anterior  branch  is  called  the  frontal  artery  (ramus  frontalis). 

The  posterior  temporal,  larger  than  the  anterior,  curves  upward  and  backward 
along  the  side  of  the  head,  lying  superficial  to  the  temporal  fascia,  and  inosculates 
with  its  fellow  of  the  opposite  side,  and  with  the  posterior  auricular  and  occipital 
arteries.  The  terminal  portion  of  the  posterior  branch  is  named  the  parietal 
artery  (ramus  parietalis). 

Applied  Anatomy. — The  temporal  artery,  as  it  crosses  the  zygoma,  Hes  immediately  beneath 
the  skin,  and  its  pulsations  may  be  readily  felt  during  the  administration  of  an  anesthetic,  or 
under  circumstances  where  the  radial  pulse  is  not  available;  or  it  may  be  easily  compressed 
against  the  bone  in  order  to  check  bleeding  from  the  temporal  region  of  the  scalp.  When  a  flap 
is  raised  from  this  part  of  the  head,  as  in  the  operation  of  trephining,  the  incision  should  be 
shaped  like  a  horseshoe,  with  its  convexity  upward,  so  that  the  flap  shall  contain  the  temporal 
artery  which  insures  a  sufficient  supply  of  blood.  The  same  principle  is  applied,  as  far  as 
possible,  in  making  incisions  to  raise  flaps  in  other  parts  of  the  scalp. 

8.  The  internal  maxillary  artery  (a.  maxillaris  interna)  (Figs.  441  and  442), 
the  larger  of  the  two  terminal  branches  of  the  external  carotid,  arises  behind  the 
neck  of  the  mandible,  and  is  at  first  embedded  in  the  substance  of  the  parotid  gland; 
it  passes  inward  between  the  ramus  of  the  mandible  and  the  internal  lateral  liga- 
ment, and  then  upon  the  outer  surface  of  the  External  pterygoid  muscle  to  the 
sphenomaxillary  fossa  to  supply  the  deep  structures  of  the  face.  For  convenience 
of  description  it  is  divided  into  three  portions — a  maxillary,  a  pterygoid,  and  a 
sphenomaxillary. 

The  first  or  maxillary  portion  passes  horizontally  forward  and  inward,  between 
the  ramus  of  the  mandible  and  the  internal  lateral  ligament,  where  it  lies  parallel 


THE  EXTERNAL   CAROTID  ARTERY 


599 


to  and  a  little  below  the  auriculotemporal  nerve;  it  crosses  the  inferior  dental  nerve, 
and  lies  along  the  lower  border  of  the  External  pterygoid  muscle. 

The  second  or  pterygoid  portion  runs  obliquely  forward  and  upward  under  co\er 
of  the  ramus  of  the  mandible,  on  the  outer  (very  frequently  on  the  inner)  surface  of 
the  External  pterygoid  muscle;  it  then  passes  between  the  two  heads  of  origin 
of  this  muscle  and  enters  the  sphenomaxillary  fossa. 


^Buccal 
r  dental  ^  \\  Internal  pterygoid 

Fig.  442. — Plan  of  the  branches  of  the  internal  maxillary  artery. 

The  third  or  sphenomaxillary  portion  lies  in  relation  with  Meckel's  ganglion. 
The  branches  of  this  vessel  may  be  divided  into  three  groups,  corresponding 
with  its  three  divisions. 

Branches  of  the  maxillary  portion  (Fig.  442) : 

Anterior  tympanic.  Middle  meningeal  or  Medidural. 

Deep  auricular.  Small  meningeal  or  Parvidural. 

Inferior  dental. 


600  THE  VASCULAR  SYSTEMS 

The  anterior  tympanic  branch  (a.  tyvifanica  anterior)  passes  upward  behind 
the  articulation  of  the  mandible,  enters  the  tympanum  through  the  Glaserian 
fissure,  and  ramifies  upon  the  membrana  tympani,  forming  a  vascular  circle 
around  the  membrane  with  the  stylomastoid  artery,  and  anastomosing  with  the 
Vidian  and  the  tympanic  branch  from  the  internal  carotid. 

The  deep  auricular  branch  (a.  auricularis  'profunda)  often  arises  in  common 
with  the  preceding.  It  ascends  in  the  substance  of  the  parotid  gland,  behind  the 
temporomaxillary  articulation,  pierces  the  cartilaginous  or  bony  wall  of  the  external 
auditory  meatus,  and  supplies  its  cuticular  lining  and  the  outer  surface  of  the 
tympanic  membrane.     It  gi^•es  a  branch  to  the  temporomandibular  joint. 

The  middle  meningeal  or  medidural  branch  (a.  meningea  media)  is  the  largest 
of  the  branches  which  supply  the  dura.  It  ascends  between  the  internal  lateral 
ligament  and  the  neck  of  the  mandible,  and  passes  vertically  upward  between 
the  two  roots  of  the  auriculotemporal  nerve  to  the  foramen  spinosum  of  the  sphe- 
noid bone,  through  which  it  enters  the  cranium;  it  then  runs  upward  and  forward 
in  a  groove  on  the  greater  wing  of  the  sphenoid  bone  and  divides  into  two  branches, 
anterior  and  posterior.  The  anterior  branch,  the  larger,  crosses  the  greater  wing 
of  the  sphenoid,  and  reaches  the  groove,  or  canal,  in  the  antero-inferior  angle  of 
the  parietal  bone,  and  then  divider  into  two  branches  which  spread  out  between  the 
dura  and  internal  surface  of  the  cranium,  some  passing  upward  as  far  as  the  ver- 
tex, and  others  backward  to  the  occipital  region.  The  posterior  branch  crosses  the 
squamous  portion  of  the  temporal,  and  on  the  inner  surface  of  the  parietal  bone 
divides  into  branches  which  supply  the  posterior  part  of  the  dura  and  cranium. 
The  branches  of  this  vessel  are  distributed  pardy  to  the  dura,  but  chiefly  to  the 
bones;  they  anastomose  with  the  arteries  of  the  opposite  side,  and  with  the  anterior 
and  posterior  meningeal  arteries. 

The  middle  meningeal  on  entering  the  cranium  gives  off  the  following  collateral  branches: 
(1)  Numerous  small  vessels  to  the  Gasserian  ganglion,  and  to  the  dura  in  this  situation.  (2) 
A  branch,  the  petrosal  branch  (ramiin  prtrnsiis  superficialis),  which  enters  the  hiatus  Fallopii, 
supplies  the  facial  nerve,  and  anaslomoscs  with  the  stylomastoid  branch  of  the  posterior  auricular 
artery.  (3)  A  minute  superior  tympanic  branch  (a.  tyvifamca  superior),  which  runs  in  the 
canai  for  the  Tensor  tympani  muscle,  and  supplies  this  muscle  and  the  lining  membrane  of  the 
canal.  (4)  Orbital  branches,  which  pass  through  the  sphenoidal  fissure,  or  through  separate 
canals  in  the  greater  wing  of  the  sphenoid  to  anastomose  with  the  lacrimal  or  other  branches  of 
the  ophthalmic  artery.  (5)  Temporal  or  anastomotic  branches,  which  pass  through  the  fora- 
mina in  the  greater  wing  of  the  sphenoid  bone  and  anastomose  in  the  temporal  fossa  with  the 
deep  temporal  arteries. 

Applied  Anatomy. — The  middle  meningeal  is  an  artery  of  considerable  surgical  importance, 
as  it  may  be  injured  in  fractures  of  the  temporal  region  of  the  skull.  The  vessel  may  be  ruptured 
by  traumatism,  even  though  the  skull  escape  fracture.  Rupture  of  the  middle  meningeal  artery 
will  be  followed  by  considerable  hemorrhage  between  the  bone  and  dura,  which  may  cause 
compression  of  the  brain  and  require  the  operation  of  trephining  for  its  relief.  This  artery 
crosses  the  anterior  inferior  angle  of  the  parietal  bone  at  a  point  1  i  inches  (3.75  cm.)  behind 
the  external  angular  process  of  the  frontal  bone,  and  If  inches  (4.-5  cm.)  above  the  zygoma. 
From  this  point  the  anterior  branch  passes  upward  and  slightly  backward  to  the  sagittal  suture, 
lying  about  \  inch  (12  mm.)  to  f  inch  (18  mm.)  behind  the  coronal  suture.  The  posterior 
branch  passes  upward  and  backward  over  the  squamous  portion  of  the  temporal  bone.  In 
order  to  expose  the  artery  as  it  lies  in  the  groove  in  the  parietal  bone,  a  semilunar  incision,  with 
its  convexity  upward,  should  be  made,  commencing  an  inch  behind  the  external  angular  process, 
and  carried  backward  for  two  inches.  The  structures  cut  through  are:  (1)  Skin;  (2)  superficial 
fascia,  with  branches  of  the  superficial  temporal  vessels  and  nerves;  (3)  the  fascia  continued 
down  from  the  aponeurosis  of  the  Occipitofrontalis;  (4)  the  two  layers  of  the  temporal  fascia; 
(.5)  the  Temporal  muscle;  (6)  the  deep  temporal  vessels;  (7)  the  pericranium.  The  bone  is 
trephined,  the  clot  removed,  and  the  vessel  secured  by  ligatures,  suture  ligatures,  or  gauze 
packing. 

The  small  meningeal  or  parvidural  branch  {ramus  meningeus  accessorius)  is  some- 
times derived  from  the  preceding.  It  enters  the  skull  through  the  foramen 
ovale,  and  supplies  the  Gasserian  ganglion  and  dura. 


THE  EXTERNAL   CABOTJD  ARTERY  601 

The  inferior  dental  branch  (a.  alveolaris  inferior)  descends  with  the  inferior  dental 
nerve  to  the  foramen  on  the  inner  side  of  the  ramus  of  the  mandible.  It  runs 
along  the  dental  canal  in  the  substance  of  the  bone,  accompanied  by  the  nerve, 
and  opposite  the  first  bicuspid  tooth  divides  into  two  branches,  the  incisor  and 
mental;  the  incisor  branch  is  continued  forward  beneath  the  incisor  teeth  as  far  as 
the  symphysis,  where  it  anastomoses  with  the  artery  of  the  opposite  side;  the 
mental  branch  (o.  mentalis)  escapes  with  the  nerve  at  the  mental  foramen,  supplies 
the  structures  composing  the  chin,  and  anastomoses  with  the  submental,  inferior 
labial,  and  inferior  coronary  arteries.  Near  its  origin  the  inferior  dental  artery  gives 
off  a  lingual  branch,  which  descends  with  the  lingual  nerve  and  supplies  the  mucous 
membrane  of  the  mouth.  As  the  inferior  dental  artery  enters  the  foramen  it  gives 
off  a  mylohyoid  branch  (ramus  mylohyoideus),  which  runs  in  the  mylohyoid  groove, 
and  ramifies  on  the  under  surface  of  the  Mylohyoid  muscle.  The  inferior  dental 
artery  and  its  incisor  branches  during  their  course  through  the  substance  of  the 
bone  give  off  a  few  twigs  which  are  lost  in  the  cancellous  tissue,  and  a  series  of 
branches  which  correspond  in  number  to  the  roots  of  the  teeth;  these  enter  the 
minute  apertures  at  the  extremities  of  the  fangs  and  supply  the  pulp  of  the  teeth. 

Branches  of  the  pterygoid  portion  (Fig.  442): 

Deep  temporal.  Masseteric. 

Pterygoid.  Buccal. 

These  branches  are  distributed,  as  their  names  imply,  to  the  muscles  in  the 
maxillary  region. 

The  deep  temporal  branches,  two  in  number,  anterior  (a.  temporalis  frofunda 
anterior)  and  posterior  (a.  temporalis  profunda  posterior),  each  occupy  that  part 
of  the  temporal  fossa  indicated  by  its  name.  Ascending  between  the  Temporal 
muscle  and  pericranium,  they  supply  the  muscle  and  anastomose  with  the  middle 
temporal  artery.  The  anterior  branch  communicates  with  the  lacrimal  artery 
by  means  of  small  branches  which  perforate  the  malar  bone  and  greater  wing  of 
the  sphenoid. 

The  pterygoid  branches  (rami  pteri/goidei),  irregular  in  their  number  and  origin, 
supply  the  Pterygoid  muscles. 

The  masseteric  (a.  masseterica)  is  a  small  branch  which  passes  outward,  above 
the  sigmoid  notch  of  the  mandible,  to  the  deep  surface  of  the  Masseter  muscle. 
It  supplies  that  muscle,  and  anastomoses  with  the  masseteric  branches  of  the  facial 
and  with  the  transverse  facial  artery. 

The  buccal  (a.  buccinator ia)  is  a  small  branch  which  runs  obliquely  forward 
lietween  the  Internal  pterygoid  and  the  ramus  of  the  mandible,  to  the  outer  surface 
of  the  Buccinator,  to  which  it  is  distributed,  anastomosing  with  branches  of  the 
facial  artery. 

Branches  of  the  sphenomaxillary  portion  (Fig.  442) : 

Alveolar  or  Posterior  dental.  Vidian. 

Infraorbital.  Pterygopalatine. 

Descending  palatine.  Naso-  or  sphenopalatine. 

The  alveolar  or  posterior  dental  branch  (a.  alveolaris  superior  posterior)  is  given 
off  from  the  internal  maxillary  in  conjunction  with  the  infraorbital,  and  just  as 
the  trunk  of  the  vessel  is  passing  into  the  sphenomaxillary  fossa.  "Descending 
upon  the  tuberosity  of  the  maxilla,  it  divides  into  niunerous  branches,  some  of  which 
enter  the  posterior  dental  canals,  to  supply  the  upper  molar  and  bicuspid  teeth 
and  the  lining  of  the  antrum,  while  others  are  continued  forward  on  the  alveola^ 
process  to  supply  the  gums. 


602  THE  VASCULAR  SYSTEMS 

The  infraorbital  (a.  infraorbiiaiis)  appears,  from  its  direction,  to  be  the  con- 
tinuation of  the  trunk  of  the  internal  maxillary,  but  often  it  arises  from  that  vessel 
in  conjunction  with  the  preceding  branch.  It  runs  along  the  infraorbital  canal 
with  the  superior  maxillary  nerve,  and  emerges  upon  the  face  at  the  infraorbital 
foramen,  beneath  the  Levator  labii  superioris  muscle.  While  in  the  canal,  it 
gives  off  (a)  branches  which  ascend  into  the  orbit,  and  assist  in  supplying  the 
Inferior  rectus  and  Inferior  oblique  muscles  and  the  lacrimal  gland,  and  (b)  the 
anterior  dental  branches  (aa.  alveolares  siiperiores  anteriores),  which  descend  through 
the  anterior  dental  canals  in  the  bone  to  supply  the  mucous  membrane  of  the 
antrum  and  the  front  teeth  of  the  maxilla.  On  the  face,  some  branches  pass 
upward  to  the  inner  angle  of  the  orbit  and  the  lacrimal  sac,  anastomosing  with 
the  angular  branch  of  the  facial  artery;  others  run  inward  toward  the  nose,  anas- 
tomosing with  the  nasal  branch  of  the  ophthalmic;  and  others  descend  beneath  the 
Levator  labii  superioris  muscle,  and  anastomose  with  the  transverse  facial  and 
buccal  arteries. 

The  four  remaining  branches  arise  from  that  portion  of  the  internal  maxillary 
which  is  contained  in  the  sphenomaxillary  fossa. 

The  descending  palatine  (a.  palatum  desceiidens)  descends  through  the  posterior 
palatine  canal  with  the  anterior  palatine  branch  of  the  sphenopalatine  (Meckel's) 
ganglion,  and,  emerging  from  the  posterior  palatine  foramen,  runs  forward  in  a 
groove  on  the  inner  side  of  the  alveolar  border  of  the  hard  palate  to  the  anterior 
palatine  canal,  where  the  terminal  branch  of  the  artery  passes  upward  through  the 
incisive  canal  (foramen  of  Stenson)  to  anastomose  with  the  nasopalatine  artery. 
Branches  are  distributed  to  the  gums,  the  mucous  membrane  of  the  hard  palate, 
and  the  palatine  glands.  In  the  palatine  canal  it  gives  off  branches  which  descend 
in  the  accessory  palatine  canals  to  supply  the  soft  palate  and  tonsil,  anastomosing 
with  the  ascending  palatine  artery. 

Applied  Anatomy. — The  position  of  the  descending  palatine  artery  on  the  hard  palate 
should  be  borne  in  mind  in  performing  an  operation  for  the  closure  of  a  cleft  in  tlie  hard  palate, 
as  the  vessel  is  in  danger  of  being  wounded,  and  may  give  rise  to  formidable  hemorrhage.  In 
case  it  should  be  wounded  it  may  be  necessary  to  plug  the  posterior  palatine  canal  in  order  to 
arrest  the  bleeding. 

The  Vidian  branch  (a.  canalis  pierygoidei)  passes  backward  along  the  Vidian 
canal  with  the  Vidian  nerve.  It  is  distributed  to  the  upper  part  of  the  pharynx 
and  Eustachian  tube,  sending  a  small  branch  into  the  tympanum,  which  anasto- 
moses with  the  other  tympanic  arteries. 

The  pterygopalatine,  a  very  small  branch,  runs  backward  through  the  pterygo- 
palatine canal  with  the  pharyngeal  nerve,  and  is  distributed  to  the  upper  part  of 
the  pharynx  and  Eustachian  tube. 

The  naso-  or  sphenopalatine  (a.  sphenopalatina)  passes  through  the  spheno- 
palatine foramen  into  the  cavity  of  the  nose,  at  the  back  part  of  the  superior  meatus, 
and  divides  into  several  branches.  One,  the  nasopalatine,  or  artery  of  the  septum, 
courses  obliquely  downward  and  forward  along  the  septum  nasi,  supplies  the 
mucous  membrane,  and  anastomoses  in  front  with  the  terminal  branch  of  the  de- 
scending palatine;  the  other  branches,  two  or  three  in  number,  are  distributed  to 
the  lateral  wall  of  the  nose,  the  antrum,  and  to  the  ethmoidal  and  sphenoidal  cells. 


THE  TRIANGLES  OF  THE  NECK  (Fig.  443). 

The  student  having  considered  the  relative  anatomy  of  the  large  arteries  of  the 
neck  and  their  branches,  and  the  relations  they  bear  to  the  veins  and  nerves,  should 
now  examine  these  structures  collectively,  as  they  present  themselves  in  certain 


THE  TRIANGLE8  OF  THE  NECK 


603 


regions  of  the  neck,  in  each  of  which  important  operations  are  constantly  being 
performed. 

The  side  of  the  neclc  presents  a  somewhat  quadrilateral  outline,  limited,  above, 
by  the  lower  border  of  the  body  of  the  mandible,  and  an  imaginary  line  extending 
from  the  angle  of  the  mandible  to  the  mastoid  process;  heloiv,  by  the  prominent 
upper  border  of  the  clavicle;  in  front,  by  the  median  line  of  the  neck;  behind,  by 
the  anterior  margin  of  the  Trapezius  muscle.  This  space  is  subdivided  into  two 
large  triangles  by  the  Sternomastoid  muscle,  which  passes  obliquely  across  the 
neck,  from  the  sternum  and  clavicle  below  to  the  mastoid  process  above.  The 
triangular  space  in  front  of  this  muscle  is  called  the  anterior  triangle;  and  that 
behind  it,  the  posterior  triangle. 


Suprahyoid  triangh 
Submaxillary  triangle.       V 

A 


Superior  carotid 
triangle 


Occipital  triangle. 


Subclavian  triamiJr. 
Fig.  443.— Tlie  triangleb  of  tl 


The  anterior  triangle  is  bounded,  in  front,  by  a  line  extending  from  the  symphy- 
sis menti  to  the  sternum;  behind,  by  the  anterior  margin  of  the  Sternomastoid;  its 
base,  directed  upward,  is  formed  by  the  lower  border  of  the  body  of  the  mandible 
and  a  line  extending  from  the  angle  of  the  mandible  to  the  mastoid  process;  its 
apex  is  below,  at  the  sternum.  This  space  is  subdivided  into  four  smaller  tri- 
angles by  the  Digastric  muscle  above  and  the  anterior  belly  of  the  Omohyoid  below. 
These  smaller  triangles  are  named  from  below  upward,  the  inferior  carotid,  the 
superior  carotid,  the  submaxillary,  and  the  suprahyoid  triangles. 

The  inferior  carotid  triangle,  or  the  triangle  of  necessity,  is  bounded,  in  front,  by 
the  median  line  of  the  neck;  behind,  by  the  anterior  margin  of  the  Sternomastoid; 
above,  by  the  anterior  belly  of  the  Omohyoid;  and  is  covered  by  the  integument, 
superficial  fascia,  Platysma,  and  deep  fascia,  ramifying  between  which  are  some 
of  the  descending  branches  of  the  superficial  cervical  plexus.  Beneath  these 
superficial  structures  are  the  Sternohyoid  and  Sternothyroid  muscles,  which, 
together  with  the  anterior  margin  of  the  Sternomastoid,  conceal  the  lower  part  of 
the  common  carotid  artery.^     The  floor  of  this  triangle  is  formed  by  the  Longus 


1  Therefore,  the  common  carotid  artery  and  internal  jugular  vein  are  not,  strictly  speaking,  contained  in  this 
triangle,  since  they  are  covered  by  the  Sternomastoid  muscle;  that  is  to  say,  lie  behind  the  anterior  bordei 
of  that  muscle,  which  forms  the  posterior  border  of  the  triangle.  But,  as  they  lie  very  close  to  the  structures 
which  are  really  contained  in  the  triangle,  and  whose  position  it  is  essential  to  remember  in  operating  on  this 
part  of  the  artery,  it  has  seemed  expedient  to  study  the  relations  of  all  these  parts  together. 


604  THE   VAtiCULAB  SYSTEMS 

colli  muscle  below  and  by  the  Scalenus  anticus  muscle  above,  between  which 
muscles  the  vertebral  artery  and  vein  will  be  found  passing  into  the  foramen  of 
the  transverse  process  of  the  sixth  cervical  vertebra.  A  small  portion  of  the  origin 
of  the  Rectus  capitis  anticus  major  may  also  be  seen  on  the  floor  of  the  space. 

The  common  carotid  artery  is  enclosed  within  its  sheath,  together  with  the 
internal  jugular  vein  and  vagus  nerve;  the  vein  lying  on  the  outer  side  of  the 
artery  on  the  right  side  of  the  neck,  but  overlapping  it  below  on  the  left  side; 
the  nerve  lying  between  the  artery  and  vein,  on  a  plane  posterior  to  both.  In 
front  of  the  sheath  are  a  few  filaments  descending  from  the  loop  of  communication 
between  the  descendens  and  communicans  hypoglossi;  behind  the  sheath  are  seen 
the  inferior  thyroid  artery,  the  recurrent  laryngeal  nerve,  and  the  sympathetic 
cord';  and  on  its  inner  side,  the  trachea,  the  thyroid  gland — much  more  prominent 
in  the  female  than  in  the  male — and  the  lower  part  of  the  larynx.  By  cutting  into 
the  upper  part  of  this  space  and  slightly  displacing  the  Sternomastoid  muscle 
the  common  carotid  artery  may  be  tied  below  the  Omohyoid  muscle. 

The  superior  carotid  triangle,  or  the  triangle  of  election,  is  bounded,  behind,  by 
the  Sternomastoid;  below,  by  the  anterior  belly  of  the  Omohyoid;  and  above, 
by  the  posterior  belly  of  the  Digastric  muscle.  It  is  covered  by  the  integument, 
superficial  fascia,  Platysma,  and  deep  fascia,  ramifying  between  which  are  branches 
of  the  facial  and  superficial  cervical  nerves.  Its  floor  is  formed  by  parts  of  the 
Thyrohyoid  and  Hyoglossus  muscles,  and  the  Inferior  and  INIiddle  constrictor 
muscles  of  the  pharynx.  This  space,  when  dissected,  is  seen  to  contain  ^he  upper 
part  of  the  common  carotid  artery,  which  bifurcates  opposite  the  upper  border 
of  the  thyroid  cartilage  into  the  external  and  internal  carotid.  These  vessels  are 
occasionally  somewhat  concealed  from  view  by  the  anterior  margin  of  the  Sterno- 
mastoid muscle,  which  overlaps  them.  The  external  and  internal  carotid  lie 
side  by  side,  the  external  being  the  more  anterior  of  the  two.  The  following 
branches  of  the  external  carotid  are  also  met  with  in  this  space,  the  superior  thyroid 
running  forward  and  downward,  the  lingual  directly  forward,  the  facial  forward 
and  upward,  the  occipital  backward,  and  the  ascending  pharyngeal  directly  up- 
ward on  the  inner  side  of  the  internal  carotid.  The  veins  met  with  are  the  internal 
jugular,  which  lies  on  the  outer  side  of  the  common  and  internal  carotid  arteries, 
and  veins  corresponding  to  the  above-mentioned  branches  of  the  external  carotid 
— viz.,  the  superior  thyroid,  the  lingual,  facial,  ascending  pharyngeal,  and  some- 
times the  occipital,  all  of  which  accompany  their  corresponding  arteries  and  ter- 
minate in  the  internal  jugular.-  The  nerves  in  this  space  are  the  following:  In 
front  of  the  sheath  of  the  common  carotid  is  the  descendens  hypoglossi.  The  hypo- 
glossal nerve  crosses  both  the  internal  and  external  carotids  above,  curving  around 
the  occipital  artery  at  its  origin.  Within  the  sheath,  between  the  artery  and  vein, 
and  behind  both,  is  the  vagus  nerve;  behind  the  sheath,  the  sympathetic  cord. 
On  the  outer  side  of  the  vessels  the  spinal  accessory  nerve  runs  for  a  short  dis- 
tance before  it  pierces  the  Sternomastoid  muscle;  and  on  the  inner  side  of  the 
external  carotid,  just  below  the  hyoid  bone,  may  be  seen  the  internal  branch  of 
the  superior  laryngeal  nerve;  and,  still  more  inferiorly,  the  external  branch  of  the 
same  nerve.  The  uppef  part  of  the  larynx  and  lower  part  of  the  pharynx  are 
also  found  in  the  front  part  of  this  space. 

The  submaxillary  triangle  corresponds  to  the  part  of  the  neck  immediately  beneath 
the  body  of  the  mandible.  It  is  bounded,  above,  by  the  lower  border  of  the  body  of 
the  mandible  and  a  line  drawn  from  its  angle  to  the  mastoid  process ;  below,  by  the 
posterior  belly  of  the  Digastric  muscle  and  the  Stylohyoid  muscle;  in  front,  by  the 
anterior  belly  of  the  Digastric.  It  is  covered  by  the  integument,  superficial  fascia, 
Platysma,  and  deep  fascia,  ramifying  between  which  are  branches  of  the  facial 
and  ascending  filaments  of  the  superficial  cervical  nerves.  Its  floor  is  formed 
by  the  Mylohyoid  and  Hyoglossus  muscles.     This  space  contains,  in  front,  the 


THE  TRIANGLES  OF  THE  NECK  605 

submaxillary  gland,  superficial  to  which  is  the  facial  vein,  while  embedded  in  it  are 
the  facial  artery,  and  its  glandular  branches;  beneath  this  gland,  <m  the  surface  of 
the  Mylohyoid  muscle,  are  the  submental  artery  and  the  mylohyoid  artery  and 
nerve.  The  posterior  part  of  this  triangle  is  separated  from  the  anterior  part 
by  the  stylomaxillary  ligament;  it  contains  the  external  carotid  artery,  ascending 
deeply  in  the  substance  of  the  parotid  gland;  this  vessel  here  lies  in  front  of,  and 
superficial  to,  the  internal  carotid,  being  crossed  by  the  facial  nerve,  and  gives  ofi'  in 
its  course  the  posterior  auricular,  temporal,  and  internal  maxillary  branches;  more 
deeply  are  the  internal  carotid  artery,  the  internal  jugular  vein,  and  the  vagus 
nerve,  separated  from  the  external  carotid  by  the  Styloglossus  and  Stylopharyn- 
geus  muscles  and  the  glossopharyngeal  nerve/ 

The  suprahyoid  triangle  is  limited  behind  by  the  anterior  belly  of  the  Digastric, 
m  front  by  the  middle  line  of  the  neck  between  the  symphysis  menti  and  the  hyoid 
bone,  helo'w  by  the  body  of  the  hyoid  bone;  its  floor  is  formed  by  the  Mylohyoid. 
It  contains  one  or  two  lymph  nodes  and  some  small  veins;  the  latter  unite  to 
form  the  anterior  jugular  vein. 

The  posterior  triangle  is  bounded,  in  front,  by  the  Sternomastoid  muscle;* 
hehind,  by  the  anterior  margin  of  the  Trapezius;  its  base  corresponds  to  the  middle 
third  of  the  clavicle;  its  apex,  to  the  occiput.  The  space  is  crossed,  about  an  inch 
above  the  clavicle,  by  the  posterior  belly  of  the  Omohyoid,  which  divides  it  un- 
equally into  two,  an  upper  or  occipital  and  a  lower  or  subclavian  triangle. 

The  occipital  triangle,  the  larger  division  of  the  posterior  triangle,  is  bounded, 
in  front,  by  the  Sternomastoid;  behind,  by  the  Trapezius;  beloiv,  by  the  Omo- 
hyoid. Its  floor  is  formed  from  above  downward  by  the  Splenius,  Levator  anguli 
scapulae,  and  the  Middle  and  Posterior  scaleni  muscles.  It  is  covered  by  the 
integument,  the  Platysma  below,  the  superficial  and  deep  fascine;  the  spinal 
accessory  nerve  is  directed  obliquely  across  the  space  from  the  Sternomastoid, 
which  it  pierces,  to  the  under  surface  of  the  Trapezius;  below,  the  descending 
branches  of  the  cervical  plexus  and  the  transversalis  colli  artery  and  vein  cross 
the  space.  A  chain  of  lymph  nodes  is  also  found  running  along  the  posterior 
border  of  the  Sternomastoid,  from  the  mastoid  process  to  the  root  of  the  neck. 

The  subclavian  triangle,  the  smaller  of  the  two  posterior  triangles,  is  bounded, 
above,  by  the  posterior  belly  of  the  Omohyoid;  below,  by  the  clavicle,  its  base, 
directed  forward,  being  formed  by  the  Sternomastoid.  The  size  of  the  subclavian 
triangle  varies  according  to  the  extent  of  attachment  of  the  clavicular  portion  of  the 
Sternomastoid  and  Trapezius  muscles,  and  also  according  to  the  height  at  which 
the  Omohyoid  crosses  the  neck  above  the  clavicle.  Its  height  also  varies  much 
according  to  the  position  of  the  arm,  being  much  diminished  by  raising  the  limb, 
on  account  of  the  ascent  of  the  clavicle,  and  increased  by  drawing  the  arm  down- 
ward, when  that  bone  is  depressed.  This  space  is  covered  by  the  integument, 
the  Platysma,  the  superficial  and  deep  fascite,  and  crossed  by  the  descending 
branches  of  the  cervical  plexus.  Just  above  the  level  of  the  clavicle  the  third 
portion  of  the  subclavian  artery  curves  outward  and  downward  from  the  outer 
margin  of  the  Scalenus  anticus,  across  the  first  rib,  to  the  axilla.  Sometimes  this 
vessel  rises  as  high  as  an  inch  and  a  half  above  the  clavicle,  or  to  any  point  inter- 
mediate between  this  and  its  usual  level.  Occasionally  it  passes  in  front  of  the 
Scalenus  anticus  or  pierces  the  fibres  of  that  muscle.  The  subclavian  vein  lies 
behind  the  clavicle,  and  is  usually  not  seen  in  this  space;  but  it  occasionally  rises 
as  high  up  as  the  artery,  and  has  even  been  seen  to  pass  with  that  vessel  behind 
the  Scalenus  anticus.  The  brachial  plexus  of  nerves  lies  above  the  artery,  and 
in  close  contact  with  it.     Passing  transversely  behind  the  clavicle  are  the  supra- 

'  The  remark  made  about  the  carotid  triangle  applies  also  to  this  one.  The  structures  enumerated  OS  con- 
tained in  its  posterior  part  lie,  strictly  speaking,  beneath  the. muscles  which  form  the  posterior  boundary  of 
the  triangle:  but  as  it  is  very  important  to  bear  in  mind  their  close  relation  to  the  parotid  gland,  aU  these  parts 
are  spoken  of  together. 


606 


THE   VASCULAR  SYSTEMS 


scapular  vessels,  and  traversing  its  upper  angle  in  the  same  direction,  the  trans- 
versalis  colli  artery  and  vein.  The  external  jugular  vein  runs  vertically  downward 
behind  the  posterior  border  of  the  Sternomastoid  muscle,  to  terminate  in  the 
subclavian  vein;  it  receives  the  transverse  cervical  and  suprascapular  veins,  which 
occasionally  form  a  plexus  in  front  of  the  artery,  and  a  small  vein  which  crosses 
the  clavicle  from  the  cephalic.  The  small  nerve  to  the  Subclavius  muscle  also 
crosses  this  triangle  about  its  middle.  A  lymph  node  is  also  found  in  the  space. 
Its  floor  is  formed  by  the  first  rib  with  the  first  digitation  of  the  Serratus  magnus. 


1st  Aortic  Iflte'''^"' 

Fig.  444. — The  internal  carotid  and  vertebral  arteries.     Right  side. 

The  Internal  Carotid  Artery  (A.  Carotis  Interna). 

The  internal  carotid  artery  supplies  the  anterior  part  of  the  brain,  the  eye  and 
its  appendages,  and  sends  branches  to  the  forehead  and  nose.     Its  size  in  the 


THE  INTERNAL   CAROTID  ARTERY  607 

adult  is  equal  to  that  of  the  external  carotid,  though  in  the  child  it  is  larger  than 
that  vessel.  It  is  remarkable  for  the  number  of  curvatures  that  it  presents  ii\ 
different  parts  of  its  course.  It  occasionally  has  one  or  two  flexures  near  the  base 
of  the  skull,  while  in  its  passage  through  the  carotid  canal  and  along  the  side  of 
the  body  of  the  sphenoid  bone  it  describes  a  double  curve  which  resembles  some- 
what the  letter  S. 

In  considering  the  course  and  relations  of  this  vessel  it  may  be  conveniently 
divided  into  four  portions — the  cervical,  petrous,  cavernous,  and  cerebral  portions. 

Cervical  Portion. — ^This  portion  of  the  internal  carotid  commences  at  the 
bifurcation  of  the  common  carotid,  opposite  the  upper  border  of  the  thyroid 
cartilage,  and  runs  perpendicularly  upward,  in  front  of  the  transverse  processes 
of  the  upper  three  cervical  vertebra,  to  the  carotid  canal  in  the  petrous  portion 
of  the  temporal  bone.  It  is  comparatively  superficial  at  its  commencement, 
where  it  is  contained  in  the  superior  carotid  triangle,  and  lies  behind  and  to  the 
outer  side  of  the  external  carotid,  overlapped  by  the  Sternomastoid  and  covered 
by  the  deep  fascia,  Platysma,  and  integument;  it  then  passes  beneath  the  parotid 
gland,  being  crossed  by  the  hypoglossal  nerve,  the  Digastric  and  Stylohyoid  muscles, 
and  the  occipital  and  posterior  auricular  arteries.  Higher  up,  it  is  separated  from 
the  external  carotid  by  the  Styloglossus  and  Stylopharyngeus  muscles,  the  tip  of 
the  styloid  process  and  the  stylohyoid  ligament,  the  glossopharyngeal  nerve,  and 
pharyngeal  branch  of  the  vagus. 

Relations. — It  is  in  relation,  behind,  with  the  Rectus  capitis  anticus  major,  the  superior 
cervical  ganglion  of  the  sympathetic,  and  superior  laryngeal  nerve;  externally,  with  the  internal 
jugular  vein  and  vagus  nerve,  the  nerve  lying  on  a  plane  posterior  to  the  artery;  internally, 
with  the  pharynx,  tonsil,  the  superior  laryngeal  nerve,  and  ascending  pharyngeal  artery.  At 
the  base  of  the  skull  the  glossopharyngeal,  vagus,  spinal  accessory,  and  hypoglossal  nerves  lie. 
between  the  artery  and  the  internal  jugular  vein. 


Plan  of  the  Relations  of  the  Internal  Carotid  Artery  in  the  Neck. 

In  front. 

Skin,  superficial  and  deep  fascia. 

Platysma. 

Sternomastoid. 

Occipital  and  posterior  auricular  arteries. 

Hypoglossal  nerve. 

Parotid  gland. 

Styloglossus  and  Stylopharyngeus  muscles. 

Glossopharyngeal  nerve. 

Pharyngeal  branch  of  the  vagus. 

ExternalUj.  /         ~X  Internally. 

Internal  jugular  vein.  /      internal     \  Pharynx. 

TT  ■  Carotid  o         '  ■        i  i 

Vagus  nerve.  \       Artery.      /  buperior  laryngeal  nerve. 


Ascending  pharyngeal  artery. 
Tonsil. 


Behind. 


Rectus  capitis  anticus  major. 

Sympathetic. 

Superior  laryngeal  nerve. 

Petrous  Portion. — When  the  internal  carotid  artery  enters  the  canal  in  the 
petrous  portion  of  the  temporal  bone,  it  first  ascends  a  short  distance,  then  curves 
forward  and  inward,  and  again  ascends  as  it  leaves  the  canal  to  enter  the  cavity  of 


608  THE  VASCULAR  SYSTEMS 

the  skull  between  the  lingiila  and  petrosal  process.  In  this  canal  the  artery  lies 
at  first  below  and  in  front  of  the  cochlea  and  tympanum;  behind  and  internal  to 
the  canals  for  the  Eustachian  tube  and  Tensor  tympani ;  from  the  tympanum  it  is 
separated  by  a  thin,  bony  lamella.  Farther  forward  it  is  separated  from  the 
Gasserian  ganglion  by  a  thin  plate  of  bone,  which  forms  the  floor  of  the  fossa  for 
the  ganglion  and  the  roof  of  the  horizontal  portion  of  the  canal.  Frequently  this 
bony  plate  is  more  or  less  deficient,  and  then  the  ganglion  is  separated  from  the 
artery  by  a  fibrous  membrane.  The  artery  is  separated  from  the  bony  wall  of 
the  carotid  canal  by  a  prolongation  of  the  dura,  and  is  surrounded  by  a  number  of 
small  veins  and  by  filaments  of  the  carotid  plexus,  derived  from  the  ascending- 
branch  of  the  superior  cervical  ganglion  of  the  sympathetic. 

Cavernous  Portion. — The  internal  carotid  artery  in  this  part  of  its  course  i;i 
situated  between  the  layers  of  the  dura  forming  the  cavernous  sinus,  but  is  covered 
by  the  lining  membrane  of  the  sinus.  It  at  first  ascends  to  the  posterior  clinoid 
process,  then  passes  forward  by  the  side  of  the  body  of  the  sphenoid  bone,  and 
again  curves  upward  on  the  inner  side  of  the  anterior  clinoid  process,  and  perfor- 
ates the  dura  forming  the  roof  of  the  sinus.  In  this  part  of  its  course  it  is  sur- 
rounded by  filaments  of  the  sympathetic  nerve,  and  has  in  relation  with  it  ex- 
ternally the  abducent  nerve. 

Cerebral  Portion. — Having  perforated  the  dura,  on  the  inner  side  of  the  anterior 
clinoid  process,  the  internal  carotid  passes  between  the  optic  and  oculomotor 
nerves  to  the  anterior  perforated  substance  at  the  inner  extremity  of  the  sylvian 
fissure,  where  it  gives  oft'  its  terminal  or  cerebral  branches.  This  portion  of  the 
artery  has  the  optic  nerve  on  its  inner  side,  and  the  oculomotor  nerve  externally. 

Peculiarities. — The  length  of  the  internal  carotid  varies  according  to  the  length  of  the  neck, 
and  also  according  to  the  point  of  bifurcation  of  the  common  carotid.  Its  origin  sometimes 
takes  place  from  the  arch  of  the  aorta;  in  such  rare  instances  this  vessel  has  been  found  to  be 
placed  nearer  the  middle  line  of  the  neck  than  the  external  carotid,  as  far  up^vard  as  the  larynx, 
when  the  latter  vessel  crossed  the  internal  carotid.  The  course  of  the  vessel,  instead  of  being 
straight,  may  be  very  tortuous.  A  few  instances  are  recorded  in  which  this  vessel  was  altogether 
absent;  in  one  of  these  the  common  carotid  passed  up  the  neck,  and  gave  off  the  usual  branches 
of  the  external  carotid,  the  cranial  portion  of  the  internal  carotid  being  replated  by  two  branches 
of  the  internal  maxillary,  which  entered  the  skull  through  the  foramen  rotundum  and  the  foramen 
ovale  and  joined  to  form  a  single  vessel. 

Applied  Anatomy. — The  cervical  part  of  the  internal  carotid  is  very  rarely  wounded.  ^Ir. 
Cripps,  in  an  interesting  paper  in  the  Medico-Chirurgical  Transactions,  compares  the  rareness 
of  a  wound  of  the  internal  carotid  with  one  of  the  external  carotid  or  its  branches.  It  is,  however, 
sometimes  injured  by  a  stah  or  gunshot  wound  in  the  neck,  or  even  occasionally  by  a  siah  from 
within  the  mouth,  as  when  a  person  receives  a  thrust  from  the  end  of  a  parasol  or  falls  down 
with  a  tobacco-pipe  in  his  mouth.  It  used  to  be  believed  that  the  internal  carotid  was  occa- 
sionally wounded  in  the  removal  of  the  tonsil.  Such  an  accident  cannot  happen  if  the  artery  is 
normally  placed.  The  severe  and  sometimes  fatal  hemorrhage  which  has  followed  this  oper- 
ation in  a  few  instances  probably  had  as  its  source  enlarged  branches  of  the  ascending  pharyn- 
geal, tonsillar,  or  ascending  palatine  arteries.  Recently,  however.  Dr.  Gwilym  G.  Davis,  of 
Philadelphia,  demonstrated  a  specimen  in  which  the  internal  carotid  could  have  been  wounded 
by  incision  of  the  tonsil.  The  indications  for  ligation  are  wounds,  when  the  vessel  should  be 
exposed  by  a  careful  dissection  and  tied  above  and  below  the  bleeding  point;  and  aneurism, 
which  if  non-traumatic  may  be  treated  by  ligation  of  the  common  carotid,  but  if  traumatic  in 
origin  by  exposing  the  sac  and  tying  the  vessel  above  and  below.  The  incision  for  ligation  of 
the  cervical  portion  of  the  internal  carotid  should  be  made  along  the  anterior  border  of  the 
Sternomastoid,  from  the  angle  of  the  mandible  to  the  upper  border  of  the  thyroid  cartilage.  The 
superficial  structures  being  divided  and  the  Sternomastoid  defined  and  drawn  outward,  the 
cellular  tissue  must  be  carefully  separated  and  the  posterior  belly  of  the  Digastric  muscle  and 
the  hypoglossal  nerve  sought  for  as  guides  to  the  vessel.  'When  the  artery  is  found  the  external 
carotid  should  be  drawn  inward  and  the  Digastric  muscles  upward,  and  the  aneurism  needle 
passed  from  without  inward. 

Obstruction  of  the  internal  carotid  by  embolism  or  thrombosis  may  give  rise  to  symptoms  of 
cerebral  anemia  and  softening  if  the  collateral  circulation  is  ill-developed.  The  patient  sufFers 
from  giddiness,  with  failure  of  mental  powers,  and  convulsions,  coma,  or  hemiplegia  on  the 
opposite  side  of  the  body,  may  be  observed. 


THE  INTERNAL  CAROTID  ARTERY 


609 


The  branches  given  off  from  the  internal  carotid  artery  are: 

„  ,      „  r.      •  f  Tympanic  (internal  or  deep). 

From  the  Petrous  Portion      I  -^^idJan 

(  Arteriae  Receptaculi. 
From  the  Cavernous  Portion  -^  AjitenoLAIeningeal. 

(  O^hthalniic. 

I'  Anterior  Cerebral. 
„  ,     ,^      ,     ,   Ti    ,•         J   ^liddle  Cerebral. 

From  the  Cerebral  Portion     <  Pogtg^Tc^Uumicating. 

t  Anterior  Choroid  or  Prechoroid. 

The  cervical  portion  of  the  internal  carotid  gives  off  no  branches. 

1.  The  tympanic  (ramus  caroticotym-panicus)  is  a  small  branch  from  the  petrous 
portion,  which  enters  the  cavity  of  the  tympanum  through  a  minute  foramen  in 
the  carotid  canal,  and  anastomoses  with  the  tympanic  branch  of  the  internal 
maxillary,  and  with  the  stylomastoid  artery. 


Nasal.        Palpebral. 


Supraorbital. 


Anterior  ethmoidal 


Posterior  ethmoidal 


Temporal  branches 
of  lacrimal, 

nitety  of  letina. 

L  icrimal 


Ophthalmic 


Internal  carotid. 


Fig.  445. — The  ophthalmic  artery  and  its  branches,  the  roof  of  the  orbit  having  been  removed. 

2.  The  Vidian  is  a  small,  inconstant  branch  which  passes  through  the  Vidian 
canal  and  anastomoses  with  the  Vidian  branch  of  the  internal  maxillary  artery. 

3.  The  arteriae  receptaculi  are  numerous  small  vessels,  derived  from  the  inter- 
nal carotid  in  the  cavernous  sinus;  they  supply  the  hypophysis  (pituitary  body), 
the  Gasserian  ganglion,  and  the  walls  of  the  cavernous  and  inferior  petrosal 
sinuses.  Some  of  these  branches  anastomose  with  branches  of  the  middle 
meningeal. 

4.  The  anterior  meningeal  (o.  vieningea  anterior)  is  a  small  branch  which 
passes  over  the  lesser  wing  of  the  sphenoid  to  supply  the  dura  of  the  anterior 

39 


610  THE   VASCULAR  SYSTEMS 

fossa;  it  anastomoses  with  the  diiral  branch  from  the  posterior  ethmoidal 
artery. 

5.  The  ophthalmic  artery  (a.  ophthalmica)  arises  from  the  internal  carotid, 
just  as  that  vessel  is  emerging  from  the  cavernous  sinus,  on  the  inner  side  of  the 
anterior  clinoid  process,  and  enters  the  orbit  through  the  optic  foramen,  below  and 
on  the  outer  side  of  the  optic  nerve.  It  then  passes  over  the  nerve  to  the  inner  wall 
of  the  orbit  and  thence  horizontally  forward,  beneath  the  lower  border  of  the 
Superior  oblique  muscle,  to  a  point  behind  the  internal  angular  process  of  the 
frontal  bone,  where  it  divides  into  two  terminal  branches,  the  frontal  and  nasal 
branches.  As  the  artery  crosses  the  optic  nerve  it  is  accompanied  by  the  nasal 
nerve,  and  is  separated  from  the  frontal  nerve  by  the  Rectus  superior  and  Levator 
palpebrae  superioris  muscles. 

Branches. — The  branches  of  this  vessel  may  be  divided  into  an  orbital  group, 
which  are  distributed  to  the  orbit  and  surrounding  parts,  and  an  ocular  group, 
which  supply  the  muscles  and  globe  of  the  eye: 


Orbital  Group. 

Ocular  Group. 

Lacrimal. 

Short  ciliary. 

Supraorbital. 

Long  ciliary. 

Posterior  ethmoidal. 

Anterior  ciliary. 

Anterior  ethmoidal. 

Central  artery  of  the  retina, 

Internal  palpebral. 

Muscular. 

Frontal. 

Nasal. 

The  lacrimal  (a.  lacrimalis)  is  one  of  the  largest  branches  derived  from  the 
ophthalmic,  arising  close  to  the  optic  foramen;  not  infrequently  it  is  given  off  from 
the  ophthalmic  artery  before  it  enters  the  orbit.  It  accompanies  the  lacrimal 
nerve  along  the  upper  border  of  the  External  rectus  muscle,  and  is  distributed  to 
the  lacrimal  gland.  Its  terminal  branches,  escaping  from  the  gland,  are  distributed 
to  the  eyelids  and  conjunctiva;  of  those  supplying  the  eyelids,  two  are  of  consider- 
able size  and  are  named  the  external  palpebral  {aa.  palpebrales  laterales) ;  they  run 
inward  in  the  upper  and  lower  lids  respectively,  and  anastomose  with  the  internal 
palpebral  arteries,  forming  an  arterial  circle  in  this  situation.  The  lacrimal  artery 
gives  off  one  or  two  malar  branches,  one  of  which  passes  through  a  foramen  in 
the  malar  bone,  to  reach  the  temporal  fossa,  and  anastomoses  with  the  deep  tem- 
poral arteries;  the  other  appears  on  the  cheek  through  the  malar  foramen,  and 
anastomoses  with  the  transverse  facial.  A  recurrent  branch  passes  backward 
through  the  sphenoidal  fissure  to  the  dura,  and  anastomoses  with  a  branch  of 
the  middle  meningeal  artery. 

Peculiarities. — The  lacrimal  artery  is  sometimes  derived  from  one  of  the  anterior  branches 
of  the  middle  meningeal  artery. 

The  supraorbital  artery  {a.  supraorbitalis)  arises  from  the  ophthalmic  as  thai . 
vessel  is  crossing  over  the  optic  nerve.  Ascending  so  as  to  arise  above  all  the  muscles 
of  the  orbit,  it  passes  forward,  with  the  supraorbital  nerve,  between  the  periosteum 
and  Levator  palpebrae  muscle;  and,  passing  through  the  supraorbital  foramen, 
divides  into  a  superficial  and  deep  branch,  which  supply  the  integument,  the 
muscles,  and  the  pericranium  of  the  forehead,  anastomosing  with  the  frontal,  the 
anterior  branch  of  the  temporal,  and  the  supraorbital  artery  of  the  opposite  side. 
This  artery  in  the  orbit  supplies  the  Superior  rectus  and  the  Levator  palpebrae 
muscles,  and  sends  a  branch  inward,  across  the  pulley  of  the  Superior  oblique 
muscle,  to  supply  the  parts  at  the  inner  canthus.  At  the  supraorbital  foramen 
it  frequently  transmits  a  branch  to  the  diploe. 


THE  INTERNAL   CAROTID  ARTERY 


611 


The  ethmoidal  branches  are  two  in  number — posterior  (a.  cthmoidalis  posterior')' 
and  anterior  (a.  cthmoidalis  anterior).  The  posterior  ethmoidal  artery,  which  is 
the  smaller,  passes  through  the  posterior  ethmoidal  foramen,  supplies  the  posterior 
ethmoidal  cells,  and,  entering  the  cranium,  gives  off  a  meningeal  or  dural  branch, 


FiQ.  446. — The  arteries  of  the  base  of  the  brain.  The  right  half  of  the  cerebellum  and  pons  have  been 
removed.  N.  B. — It  will  be  noticed  that  the  two  anterior  cerebral  arteries  have  been  drawn  at  a  considerable 
distance  from  each  other;  this  makes  the  anterior  communicating  artery  appear  very  much  longer  than  it 
really  is. 

which  supplies  the  adjacent  dura;  and  nasal  branches  which  descend  into  the 
nose  through  apertures  in  the  cribriform  plate,  anastomosing  with  branches  of  the 
sphenopalatine.  The  anterior  ethmoidal  artery  accompanies  the  nasal  nerve  through 
the  anterior  ethmoidal  foramen,  supplies  the  anterior  ethmoidal  cells  and  frontal 


612 


THE  VASCULAR  SYSTEMS 


■  sinuses,  and,  entering  the  cranium,  gives  off  a  dural  branch  which  supplies  the 
adjacent  dura;  and  nasal  branches,  which  descend  into  the  nose,  through  the  slit 
by  the  side  of  the  crista  galli,  and,  running  along  the  groove  on  the  under  surface 
of  the  nasal  bone,  supply  the  skin  of  the  nose. 

The  internal  palpebral  arteries  (aa.  palpebrales  mediales),  two  in  number,  supe- 
rior and  inferior,  arise  from  the  ophthalmic,  opposite  the  pulley  of  the  Superior 
oblique  muscle;  they  leave  the  orbit  to  encircle  the  eyelids  near  their  free  margin, 
formino-  a  superior  tarsal  arch  (arcus  tarseus  superior)  and  an  inferior  tarsal  arch 
(arcm  tarseus  inferior),  which  lie  between  the  Orbicularis  muscle  and  the  tarsal 
plates.  The  superior  palpebral  anastomoses,  at  the  outer  angle  of  the  orbit,  with 
the  orbital  branch  of  the  temporal  artery,  and  with  the  upper  of  the  two  external 
palpebral  branches  from  the  lacrimal  artery;  the  inferior  palpebral  anastomoses, 


Fig.  447. — Vascular  area  of  the  upper  surface  of  the  cerebrum.  I.  The  part  supplied  by  the  external  and 
inferior  frontal  artery.  II.  The  part  supplied  by  the  ascending  frontal.  III.  The  part  suppUed  by  the  ascending 
parietal.     IV.  The  part  supphed  by  the  sphenoparietal  artery.     (After  Buret.) 


at  the  outer  angle  of  the  orbit,  with  the  lower  of  the  two  external  palpebral  branches 
from  the  lacrimal  and  with  the  transverse  facial  artery,  and  at  the  inner  side  of  the 
lid  with  a  branch  from  the  angular  artery.  From  this  last  anastomosis  a  branch 
passes  to  the  nasal  duct,  ramifying  in  its  mucous  membrane,  as  far  as  the  inferior 
meatus. 

The  frontal  artery  (a.  frontalis),  one  of  the  terminal  branches  of  the  ophthalmic, 
leaves  the  orbit  at  its  inner  angle  with  the  supratrochlear  ner\'e,  and,  ascending 
on  the  forehead,  supplies  the  integument,  muscles,  and  pericranium,  anastomosing 
with  the  supraorbital  artery  and  with  the  frontal  artery  of  the  opposite  side. 

The  nasal  artery  (a.  dorsalis  iiasi),  the  other  terminal  branch  of  the  ophthalmic, 
emerges  from  the  orbit  above  the  tendo  oculi,  and,  after  giving  a  branch  to  the 
upper  part  of  the  lacrimal  sac,  divides  into  two  branches,  one  of  which  crosses 


THE  INTERNAL   CAROTID  ARTERY 


613 


the  root  of  the  nose,  the  transverse  nasal,  and  anastomoses  with  the  angular  artery; 
the  other,  the  dorsalis  nasi,  runs  along  the  dorsum  of  the  nose,  supplies  its  outer 
surface,  and  anastomoses  with  the  artery  of  the  opposite  side  and  with  the  lateral 
nasal  branch  of  the  facial. 

The  ciliary  arteries  (o.  ciUarcs)  are  divisible  into  three  groups — the  short,  long, 
and  anterior.  The  short  ciliary  arteries  (aa.  ciliares  posieriores  breves),  from  sLx 
to  twelve  in  number,  arise  from  the  ophthalmic  or  some  of  its  branches ;  they  sur- 
round the  optic  nerve  as  they  pass  forward  to  the  posterior  part  of  the  eyeball, 
pierce  the  sclera  around  the  entrance  of  the  nerve,  and  supply  the  choroid  coat 
and  ciliary  processes.  The  long  ciliary  arteries  (aa.  ciliares  posteriores  longae), 
two  in  number,  pierce  the  posterior  part  of  the  sclera  at  some  little  distance  from 
the  optic  nerve,  and  run  forward,  along  each  side  of  the  eyeball,  between  the 
sclera  and  choroid,  to  the  ciliary  muscle,  where  they  divide  into  two  branches; 
these  form  an  arterial  circle,  the  circulus  major,  around  the  circumference  of  the 
iris,  from  which  numerous  radiating  branches  pass  forward,  in  its  substance,  to 
its  pupillary  aperture,  where  they  form  a  second  arterial  circle,  the  circulus  minor. 

Cnilrnl  Fisnire 


Fig.  448. — Vascular  area  of  the  internal  surface  of  the  cerebrum.  I.  The  part  supplied  by  the  anterior 

internal  frontal.     II.  The  part  supplied  by  the  middle  internal  frontal.  III.  The  part  supplied  by  the  posterior 

internal  frontal.     IV.  The  part  supplied  by  the  posterior  temporal.     V.  The  part  supplied  by  the  occipital,  both 
terminal  branches  of  the  posterior  cerebral.     (After  Duret.) 


The  anterior  ciliary  arteries  {aa.  ciliares  anteriores)  are  derived  from  the  muscular 
branches  (see  below) ;  they  pass  to  the  front  of  the  eyeball  in  company  with  the 
tendons  of  the  Recti  muscles,  form  a  vascular  zone  beneath  the  conjunctiva,  and 
then  pierce  the  sclera  a  short  distance  from  the  cornea  and  terminate  in  the  circu- 
lus major  of  the  iris. 

The  central  artery  of  the  retina  {arteria  centralis  retinae)  is  the  first  and  one  of  the 
smallest  branches  of  the  ophthalmic  artery.  It  runs  for  a  short  distance  within 
the  dural  sheath  of  the  optic  nerve,  but  about  half  an  inch  behind  the  eyeball  it 
pierces  the  optic  nerve  obliquely,  and  runs  forward  in  the  centre  of  its  substance, 
and  enters  the  globe  of  the  eye  through  the  porus  opticus.  Its  mode  of  distribu- 
tion will  be  described  in  the  section  on  the  anatomy  of  the  eye. 

The  muscular  branches  {rami  musculares),  two  in  number,  superior  and  inferior, 
frequently  spring  from  a  common  trunk.  The  superior,  the  smaller,  often  want- 
ing, supplies  the  Levator  palpebrae,  Superior  rectus,  and  Superior  oblique.  The 
inferior,  more  constant  in  its  existence,  passes  forward  between  the  optic  nerve  and 
the  Inferior  rectus  muscle,  and  is  distributed  to  the  External,  Internal,  and  Inferior 
recti,  and  Inferior  oblique.     This  vessel  gives  off  most  of  the  anterior  ciliary 


614 


THE    VASCULAR  SYSTEMS 


arteries.  Additional  muscular  branches  are  given  off  from  the  lacrimal  and  supra- 
orbital arteries  or  from  the  ophthalmic  itself. 

(For  the  Circulus  or  Circle  of  Willis,  the  posterior  cerebral  artery,  and  rhe 
bloodvessels  of  the  cerebellum,  see  page  617.) 

The  anterior  cerebral  (a.  cerebri  anterior)  arises  from  the  internal  carotid 
at  the  inner  extremity  of  the  sylvian  fissure.  It  passes  forward  and  inward 
across  the  anterior  perforated  substance,  above  the  optic  nerve,  to  the  commence- 
ment of  the  intercerebral  fissure.  Here  it  comes  into  close  relationship  with 
the  anterior  cerebral  artery  of  the  opposite  side,  and  the  two  vessels  are  con- 
nected by  a  short  anastomosing  trunk,  about  two  lines,  \  inch  (4  mm.)  in  length, 
the  anterior  communicating  artery.  From  this  point  the  two  vessels  run  side  by 
side  in  the  intercerebral  fissure,  curve  around  the  genu  of  the  corpus  callosum, 
and,  turning  backward,  continue  along  its  upper  surface  to  its  posterior  part, 
where  they  terminate  by  anastomosing  with  the  posterior  cerebral  arteries. 


Fig.  449. — Vascular  area  of  the  inferior  surface  of  the  cerebrum.  I.  The  part  supplied  by  the  anterior  tem- 
poral from  the  posterior  cerebral  artery.  II.  The  part  supplied  by  the  posterior  temporal"  from  the  posterior 
cerebral  artery.     III.  The  part  supplied  by  the  occipital  from  the  posterior  cerebral  artery.     (After  Duret.) 

Branches. — In  their  course  the  anterior  cerebral  arteries  give  off  the  following 
branches: 


Antero-median  ganglionic. 
Inferior  internal  frontal. 


Anterior  internal  frontal. 
Aliddle  internal  frontal. 


Posterior  internal  frontal 


The  antero-median  ganglionic  are  a  group  of  small  arteries  which  arise  at  the 
commencement  of  the  anterior  cerebral  artery;  they  pierce  the  anterior  perforated 


THE  INTERNAL    CAROTID  ARTERY 


615 


substance  and  lamina  terminalis,  and  supply  the  rostrum  of  the  corpus  callosum, 
the  septum  lucidum,  and  the  head  of  the  caudate  nucleus. 

The  inferior  internal  frontal  branches,  two  or  three  in  number,  are  distributed 
to  the  orbital  surface  of  the  frontal  lobe,  where  they  supply  the  olfactory  lobe, 
gyrus  rectus,  and  internal  orbital  (mesorbital)  convolution. 

The  anterior  internal  frontal  supply  a  part  of  the  mesal  surface  of  the  prefrontal 
region,  and  send  branches  over  the  edge  of  the  hemisphere  to  the  superfrontal 
and  medifrontal  gyre  and  upper  part  of  the  precentral  gyre. 

The  middle  internal  frontal  supplies  the  corpus  callosum,  the  callosal  gyre,  the 


ANTEf^lOR  CHOR 


3LANDOF  REIL-t _^//yl  (       /  / 


X.     C.«,CUU,T.     r/ 


INT.    GENICULATE    ^--^a^ / )l 

BODY        ^"v-ir  y 


MIDDLE  CORN 
OF  LATERE 
VENTRICLE 


Fig.  4.50. — The  anterior  cerebral  and  choroid  arteries.     (Spalteholz.) 


mesal  surface  of  the  superfrontal  convolution,  and  the  dorsal  part  of  the  pre- 
central gyre. 

The  posterior  internal  frontal  supplies  the  precuneus  and  adjacent  outer  sur- 
face of  the  hemisphere. 

The  anterior  communicating  artery  {a.  communicans  anterior,  a.  praecommuni- 
cans)  is  a  short  branch,  about  4  mm.  in  length,  but  of  moderate  size,  connecting 
the  two  anterior  cerebral  arteries  across  the  intercerebral  fissure.  Sometimes 
this  vessel  is  wanting,  the  two  arteries  joining  to  form  a  single  trunk,  which 
afterward  divides.     Or  the  vessel  may  be  wholly  or  partially  divided  into  two; 


616 


THE   VASCULAR  SYSTEMS 


frequently  it  is  longer  and  smaller  than  usual.  It  gives  off  some  of  the  antero- 
median ganglionic  group  of  vessels,  which  are,  however,  principally  derived  from 
the  anterior  cerebral. 


PERCALLOSAL 


INTERNAL  POSTERIOR         POSTERIOR 

CAROTID  COMMUNICATING  CEREBRAL 
ARTERY  ARTERY  ARTERY 

Fig.  451. — The  arteries  of  the  medial  surface  of  the  right  cerebral  hemisphere.     (Spalteholz.) 

The  middle  cerebral  artery  (a.  cerebri  media)  (Fig.  452),  the  largest  branch  of 
the  internal  carotid,  passes  obliquely  outward  along  the  sylvian  fissure,  and 
divides  on  the  surface  of  the  insula  into  its  terminal  branches. 


Fig.  452. — The  distribution  of  the  middle  cerebral  artery.     The  trunk  of  the  middle  cerebral  artery  Ues  i 
depths  of  the  sylvian  cleft.     (After  Charcot.) 

Branches. — The  branches  of  the  middle  cerebral  arterv  are: 


Antero-lateral  ganglionic. 
Inferior  external  frontal. 
Ascending  frontal. 


Ascending  parietal. 
Parietotemporal . 
Temporal. 


THE  ARTERIES  OF  THE  BRAIN  617 

The  antero-lateral  ganglionic  branches,  a  group  of  small  arteries  which  arise  at 
the  commencement  of  the  middle  cerebral  artery,  are  arranged  in  two  sets;  one, 
the  internal  striate,  passes  upward  through  the  inner  segment  of  the  lenticular 
nucleus,  and  supplies  it,  the  caudate  nucleus,  and  the  internal  capsule;  the  other, 
the  external  striate,  ascends  through  the  outer  segment  of  the  lenticular  nucleus, 
and  supplies  the  caudate  nucleus  and  the  thalamus.  One  artery  of  this  group 
(also  called  lenticulostriate  artery)  is  of  larger  size  than  the  rest,  and  is  of  special 
importance,  as  being  the  artery  in  the  brain  most  frequently  ruptured;  it  has  been 
termed  by  Charcot  the  artery  of  cerebral  hemorrhage.  It  passes  up  between  the 
lenticular  nucleus  and  the  external  capsule,  and  ultimately  ends  in  the  caudate 
nucleus. 

The  inferior  external  frontal  supplies  the  subfrontal  convolution  (Broca's  convolu- 
tion) and  the  outer  part  of  the  orbital  surface  of  the  frontal  lobe. 

Tile  ascending  frontal  supplies  the  precentral  gyre. 

The  ascending  parietal  is  distributed  to  the  postcentral  convolution  and  the 
lower  part  of  the  superior  parietal  convolution. 

The  parietotemporal  supplies  the  supramarginal  and  angular  gyres,  the  super- 
temporal,  and  part  of  the  meditemporal  gyre. 

The  temporal  branches,  two  or  three  in  number,  are  distributed  to  the  outer 
surface  of  the  temporal  lobe. 

The  posterior  communicating  artery  (a.  communicans  posterior)  runs  backward 
from  the  internal  carotid,  and  anastomoses  with  the  posterior  cerebral,  a  branch 
of  the  basilar.  This  artery  varies  considerably  in  size,  being  sometimes  small, 
and  occasionally  so  large  that  the  posterior  cerebral  may  be  considered  as  aris- 
ing from  the  internal  carotid  rather  than  from  the  basilar.  It  is  frequently  larger 
on  one  side  than  on  the  other.  From  the  posterior  half  of  this  vessel  are  given 
off  a  number  of  small  branches,  the  postero-median  ganglionic  branches,  which, 
with  similar  vessels  from  the  posterior  cerebral,  pierce  the  posterior  perforated 
substance  and  supply-^the  internal  surfaces  of  the  thalami  and  the  walls  of  the 
third  ventricle. 

The  choroid  artery  (a.  chorioidea)  is  a  small  but  constant  branch  which  arises 
from  the  back  part  of  the  internal  carotid,  near  the  posterior  communicating 
artery.  Passing  backward  and  outward  between  the  temporal  lobe  and  the  crus, 
it  enters  the  descending  horn  of  the  lateral  ventricle  through  the  choroidal  fis- 
sure and  ends  in  the  choroid  plexus.  It  is  distributed  to  the  hippocampus, 
fimbria,  velum  interpositum,  and  choroid  plexus. 

THE  ARTERIES  OF  THE  BRAIN. 

Investigations  show  that  the  mode  of  distribution  of  the  vessels  of  the  brain  has 
an  important  bearing  upon  a  considerable  number  of  the  anatomical  lesions  of 
which  this  part  of  the  nerve  system  may  be  the  seat;  it  is  therefore  important  to 
consider  a  little  more  in  detail  the  manner  in  which  the  cerebral  vessels  are 
distributed. 

The  cerebral  arteries  are  derived  from  the  internal  carotid  and  the  vertebral, 
which  at  the  base  of  the  brain  form  a  remarkable  anastomosis  known  as  the  circle 
of  Willis  (circulus  arteriosus)  (Fig.  453).  It  is  formed  in  front  by  the  anterior 
cerebral  arteries,  branches  of  the  internal  carotid,  which  are  connected  by  the  ante- 
rior communicating;  behind  by  the  two  posterior  cerebrals,  branches  of  the  basilar, 
which  are  connected  on  each  side  to  the  internal  carotid  by  the  posterior  communi- 
cating (Fig.  446).  The  parts  of  the  brain  included  within  this  arterial  circle 
are  the  lamina  terminalis,  the  chiasm  or  commissure  of  the  optic  nerves,  the  tuber 
cinereum,  the  corpora  albicantia,  and  the  posterior  perforated  substance.  This 
arrangement  of  the  vessels  of  the  circle  is  not  invariable;  according  to  Windle,  it 


618 


THE  VASCULAR  SYSTEMS 


is  maintained  in  little  more  than  half  the  recorded  cases.     In  the  other  cases 
there  are  different  variations. 

The  three  trunks  which  together  supply  each  cerebral  hemisphere  arise  from 
the  circle  of  Willis.  From  its  anterior  part  proceed  the  two  anterior  cerebrals, 
from  its  antero-lateral  part  the  middle  cerebrals,  and  from  its  posterior  part  the 
posterior  cerebrals.  Each  of  these  principal  arteries  gives  origin  to  two  ^'e^y  dif- 
ferent systems  of  secondary  vessels.  One  of  these  systems  has  been  named  the 
central  ganglionic  system,  and  the  vessels  belonging  to  it  supply  the  central  ganglia 
of  the  brain;  the  other  has  been  named  the  cortical  arterial  system,  and  its  vessels 
ramify  in  the  pia  and  supply  the  cortex  and  subjacent  medullary  substance.  These 
two  systems,  although  they  have  a  common  origin,  do  not  communicate  at  any 
point  of  their  peripheral  distribution,  and  are  entirely  independent  of  each  other, 
representing  terminal  arteries.  Though  some  of  the  arteries  of  the  cortical  system 
approach,  at  their  terminations,  the  regions  supplied  by  the  central  ganglionic 
system,  no  communication  between  the  two  sets  of  vessels  takes  place,  and  there 
is  between  the  parts  supplied  by  the  two  systems  a  borderland  of  diminished 
nutritive  activity.  In  the  brains  of  old  people  softening  is  especially  apt  to  occur 
in  this  ill-nourished  territory. 


Anterior  cerebral- 


Middle  cerebral 

Anterior  choroit 
Posterior  communicating- 
Posterior  cerebral- 


Anterior  cojnmunicating 


Superior  cerebellar- 
Basilar 
Anterior  inferior  cerebellar- 

Interior  auditory 
Posterior  inferior  cerebellar 
Vertebral 


E.  A.  S. 


Posterior  spinal'  "Anterior  spinal 

Fig.  453. — Diagram  of  the  arteries  at  the  base  of  the  brain,  including  the  circle  of  Willis.  I.  Antero-median 
group  of  ganglionic  branches.  II.  Poatero-median  group.  III.  Right  and  left  antero-lateral  group.  IV.  Right 
and  left  postero-Iateral  group. 

The  Central  Ganglionic  System. — All  the  vessels  belonging  to  this  system 
are  given  off  from  the  circle  of  Willis  or  from  the  vessels  immediately  after  their 
origin  from  it,  so  that  if  a  circle  is  drawn  at  a  distance  of  about  an  inch  from  the 
circle  of  Willis,  it  will  include  the  origin  of  all  the  arteries  belonging  to  this  system 
(Fig.  453).  The  vessels  of  this  system  form  four  principal  groups:  (I)  The  antero- 
median group,  derived  from  the  anterior  cerebrals  and  anterior  communicating; 
(II)  the  postero-median  group,  from  the  posterior  cerebrals  and  posterior  communi- 
cating; (III)  the  right  and  left  antero-lateral  group,  from  the  middle  cerebrals; 
and  (IV)  the  right  and  left  postero-Iateral  group,  from  the  posterior  cerebrals,  after 
they  have  wound  around  the  crura.  The  vessels  belonging  to  this  system  are  larger 
than  those  of  the  cortical  sj'stem,  and  are  what  Cohnheim  has  termed  terminal 
arteries — that  is  to  say,  vessels  which  from  their  origin  to  their  termination  neither 


THE   VERTEBRAL  ARTERY 


619 


supply  nor  receive  any  anastomotic  branches,  so  that  by  one  of  the  small  vessels 
only  a  limited  area  of  the  central  ganglia  can  be  injected;  and  the  injection  cannot 
be  driven  beyond  the  area  of  the  part  supplied  by  the  particular  vessel  which  is 
the  subject  of  the  exjieriment. 

The  Cortical  Arterial  System. — The  vessels  forming  this  system  are  the  ter- 
minal branches  of  the  anterior,  middle,  and  posterior  cerebral  arteries,  descriljed 
above.  These  vessels  divide  and  ramify  in  the  substance  of  the  pia,  and  give  off 
nutrient  arteries  which  penetrate  the  cortex  perpendicularly.  These  nutrient  ves- 
sels are  divisible  into  two  classes — the  long  and  short.  The  long — or,  as  they  are 
sometimes  called,  the  medullary — arteries  pass  through  the  gray  substance  to  pene- 
trate the  centrum  ovale  to  the  depth  of  about  an  inch  and  a  half,  without  intercom- 
municating otherwise  than  by  very  fine  capillaries,  and  thus  constitute  so  many 


Fig.  454. — Distribution  of  the  cortical  arteries.  1.  Medullary  arteries,  1'.  Group  of  medullary  arteries  in 
the  sulcus  between  two  adjacent  convolutions,  1",  Arteries  situated  among  the  short  association  fibres.  2,  2, 
Cortical  arteries,  a.  Capillary  network  with  fairly  wide  meshes,  situated  beneath  the  pia.  h.  Network  with 
more  compact,  polygonal  meshes,  situated  in  the  cortex,  c.  Transitional  network,  with  wider  meshes,  d. 
Capillary  network  in  the  white  substance,     (,\fter  Charcot.) 


independent  small  systems.  The  short  vessels  are  confined  to  the  cortex,  where 
they  form  with  the  long  vessels  a  compact  network  in  the  middle  zone  of  the  gray 
substance,  the  outer  and  inner  zones  being  sparingly  supplied  with  blood  (Fig,  454), 
The  vessels  of  the  cortical  arterial  system  are  not  so  strictly  terminal  as  those  of 
the  central  ganglionic  system,  but  they  approach  this  type  very  closely,  so  that 
injection  of  one  area  from  the  vessel  of  another  area,  though  it  may  be  possible, 
is  frequently  very  difficult,  and  is  only  effected  through  vessels  of  small  caliber. 
As  a  result  of  this,  obstruction  of  one  of  the  main  branches  or  its  divisions  may  have 
the  effect  of  producing  softening  in  a  very  limited  area  of  the  cortex. 

The  Vertebral  Artery  (A.  Vertebralis). 

The  vertebral  artery  (a.  vertebralis)  (Figs,  444  and  455)  is  generally  the  first  and 
largest  branch  of  the  subclavian;  in  rare  instances  it  springs  independently  from 
the  arch  of  the  aorta.  It  arises  from  the  upper  and  back  part  of  the  first  portion 
of  the  vessel,  and,  passing  upward,  enters  the  foramen  in  the  transverse  process  of 


620  THE  VASCULAR  SYSTEMS 

the  sixth  cervical  vertebra/  and  ascends  through  the  foramina  in  the  transverse 
processes  of  all  the  vertebrae  above  this.  Above  the  upper  border  of  the  axis  it 
inclines  outward  and  upward  to  the  foramen  in  the  transverse  process  of  the  atlas, 
through  which  it  passes;  it  then  winds  backward  behind  its  articular  process, 
runs  in  a  deep  groove  on  the  upper  surface  of  the  posterior  arch  of  this  bone  (Fig. 
16),  and,  passing  beneath  the  posterior  occipito-atlantal  ligament  (Figs.  224  and 
227),  pierces  the  dura  and  arachnoid,  and  enters  the  skull  through  the  foramen 
magnum.  It  then  passes  forward  and  upward,  inclining  from  the  lateral  aspect 
to  the  front  of  the  medulla  oblongata.  It  unites  in  the  middle  line  with  the  vessel 
of  the  opposite  side  at  the  lower  border  of  the  pons  to  form  the  basilar  artery 
(Fig.  426). 

Relations. — At  its  origin  it  is  situated  behind  the  internal  jugular  and  vertebral  veins,  and 
is  crossed  by  the  inferior  thyroid  artery;  it  lies  between  the  Longus  colli  and  Scalenus  anticus 
muscles,  having  the  thoracic  duct  in  front  of  it  on  the  left  side.  It  rests  on  the  transverse  process 
of  the  seventh  cervical  vertebra  and  the  sympathetic  cord.  Within  the  foramina  formed  by 
the  transverse  processes  of  the  vertebrfe  it  is  accompanied  by  a  plexus  of  nerves  from  the  inferior 
cervical  ganglion  of  the  sympathetic,  and  is  surrounded  by  a  dense  plexus  of  veins  which  unite 
to  form  the  vertebral  vein  at  the  lower  part  of  the  neck.  It  is  situated  in  front  of  the  cervical 
nerves,  as  they  issue  from  the  intervertebral  foramina.  While  winding  around  the  articular 
process  of  the  atlas,  it  is  contained  in  the  suboccipital  triangle — a  triangular  space  formed  by 
the  Rectus  capitis  posticus  major,  the  Obliquus  capitis  superior  and  the  Obliquus  capitis 
inferior  muscles.  The  suboccipital  nerve  here  lies  between  the  artery  and  the  posterior  arch  of 
the  atlas.  Within  the  skull,  as  the  artery  winds  around  the  oblongata,  it  is  placed  between  the 
hypoglossal  nerve  and  the  anterior  root  of  the  suboccipital  nerve,  beneath  the  first  digitation  of 
the  ligamentum  denticulatum,  and  finally  ascends  between  the  basilar  process  of  the  occipital 
bone  and  the  anterior  surface  of  the  medulla  oblongata. 

Applied  Anatomy. — The  vertebral  artery  has  been  tied  in  several  instances.  (1)  For  wounds 
or  traumatic  aneurism;  (2)  after  ligation  of  the  innominate,  either  immediately  to  prevent  hem- 
orrhage, or  later  on  to  arrest  bleeding  where  it  has  occurred  at  the  seat  of  ligation.  The  oper- 
ation of  ligation  of  the  vertebral  is  performed  by  making  an  incision  along  the  posterior  border 
of  the  Sternomastoid  muscle,  just  above  the  clavicle.  The  muscle  is  pulled  to  the  inner  side, 
and  the  anterior  tubercle  of  the  transverse  process  of  the  sixth  cervical  vertebra  is  sought  for. 
A  deep  layer  of  fascia  being  now  divided,  the  interval  between  the  Scalenus  anticus  and  the 
Longus  colli  muscles  just  below  their  attachment  to  the  tubercle  is  defined,  and  the  artery  and 
vein  are  found  in  the  interspace.  The  vein  is  to  be  drawn  to  the  outer  side,  and  the  aneurism 
needle  is  passed  from  without  inward.  Drs.  Ramskill  and  Bright  have  pointed  out  that  severe 
pain  at  the  back  of  the  head  may  be  symptomatic  of  disease  of  the  vertebral  artery  just  before 
it  enters  the  skull.  This  is  explained  by  the  close  connection  of  the  artery  with  the  suboccipital 
nerve  in  the  groove  on  the  posterior  arch  of  the  atlas.  Disease  of  the  same  artery  has  been  also 
said  to  affect  speech,  from  pressure  on  the  hypoglossal  nerve  where  it  is  in  relation  with  the 
vessel,  leading  to  paratysis  of  the  muscles  of  the  tongue. 

Branches. — These  may  be  divided  into  two  sets — those  given  off  in  the  neck 
and  those  within  the  cranium. 

Cervical  Branches.  Cranial  Branches. 

Spinal  rami,  or  Lateral  spinal.  Posterior  meningeal. 

Muscular.  Anterior  spinal,  or  Ventral  spinal. 

Posterior  spinal,  or  Dorsal  spinal. 

Posterior  inferior  cerebellar. 

Bulbar. 

The  spinal  branches  (rami  spinales)  enter  the  vertebral  canal  through  the  inter- 
vertebral foramina  and  divide  into  two  branches.  Of  these,  one  passes  along  the 
roots  of  the  nerves  to  supply  the  spinal  cord  and  its  membranes,  anastomosing 
with  the  other  arteries  of  the  spinal  cord;  the  other  divides  into  an  ascending  and 

^  ^  The  vertebral  artery  sometimes  enters  the  foramen  in  the  transverse  process  of  the  fifth  vertebra.  Dr. 
Smyth,  who  tied  this  artery  in  the  living  STibject,  found  it,  in  one  of  his  dissections,  passing  into  the  forameD 
in  the  seventh  vertebra. 


THE   VERTEBRAL  ARTERY  621 

a  descending  branch,  which  unite  with  similar  branches  from  the  artery  above 
and  below,  so  that  two  hxteral  anastomotic  chains  are  formed  on  the  posterior 
surface  of  the  vertebrEe  near  the  attachment  of  the  pedicles.  From  these  anasto- 
motic chains  branches  are  given  off  to  supply  the  periosteum  and  the  bodies  of  the 
vertebrte,  and  to  communicate  with  similar  branches  from  the  opposite  side;  from 
these  communicating  branches  small  branches  are  given  off  which  join  similar 
branches  above  and  below,  so  that  a  central  anastomotic  chain  is  formed  on  the 
posterior  surface  of  the  bodies  of  the  vertebrae. 

Muscular  branches  are  given  off  to  the  deep  muscles  of  the  neck,  where  the  ver- 
tebral artery  curves  around  the  articular  process  of  the  atlas.  They  anastomose 
with  the  occipital  and  with  the  ascending  and  deep  cervical  arteries. 

The  posterior  meningeal  (ramus  meningeus)  is  a  small  branch  given  off  from 
the  vertebral  opposite  the  foramen  magnum.  It  ramifies  between  the  bone  and 
dura  in  the  cerebellar  fossa^,  and  supplies  the  falx  cerebelli.  It  is  frequently  repre- 
sented by  two  small  branches. 

The  anterior  or  ventral  spinal  (a.  spinalis  anterior)  is  a  small  .branch  which 
rises  near  the  termination  of  the  vertebral,  and,  descending  ventrad  of  the 
medulla  oblongata,  unites  with  its  fellow  on  the  opposite  side  at  about  the 
level  of  the  foramen  magnum.  One  of  these  \'essels  is  usually  larger  than  the 
other,  but  occasionally  they  are  about  ecjual  in  size.  The  single  trunk  thus  formed 
descends  on  the  front  of  the  spinal  cord,  and  is  reinforced  by  a  succession  of  small 
branches  which  enter  the  vertebral  canal  through  the  intervertebral  foramina; 
these  branches  are  derived  from  the  vertel^ral  artery  and  the  ascending  cervical 
branch  of  the  inferior  thyroid  artery  in  the  neck;  from  the  intercostal  in  the 
thoracic  region;  and  from  the  lumbar,  iliolumbar,  and  lateral  sacral  arteries  in 
the  lower  part  of  the  vertebral  column.  They  unite,  by  means  of  ascending  and 
descending  branches,  to  form  a  single  terminal  artery,  which  extends  as  far  as 
the  lower  part  of  the  spinal  cord.  This  vessel  is  placed  in  the  pia  along  the 
anterior  median  fissure;  it  supplies  that  membrane  and  the  substance  of  the  cord, 
and  sends  oft'  branches  at  its  lower  part  to  be  distributed  to  the  cauda  equina, 
and  ends  on  the  central  fibrous  prolongation  of  the  cord. 

The  posterior  or  dorsal  spinal  (a.  spinalis  posterior)  arises  from  the  vertebral 
at  the  side  of  the  medulla  oblongata;  passing  backward  to  the  dorsal  aspect 
of  the  spinal  cord,  it  descends  on  each  side,  lying  behind  the  dorsal  roots  of  the 
spinal  nerves,  and  is  reinforced  by  a  succession  of  small  branches  which  enter 
the  vertebral  canal  through  the  intervertebral  foramina,  and  by  which  it  is  con- 
tinued to  the  lower  part  of  the  cord  and  to  the  cauda  equina.  Branches  from 
the  posterior  spinal  arteries  form  a  free  anastomosis  around  the  dorsal  roots 
of  the  spinal  nerves,  and  communicate,  by  means  of  very  tortuous  transverse 
branches,  with  the  vessel  of  the  opposite  side.  Close  to  its  origin  each  gives  off 
an  ascending  branch,  which  terminates  at  the  side  of  the  fourth  ventricle. 

Applied  Anatomy. — Bleeding  into  the  spinal  membranes  or  into  the  substance  of  the  spinal 
cord  itself  is  not  common,  but  may  occur  from  injuries  received  at  birth  when  labor  is  imduly 
prolonged  or  instruments  are  used.  It  is  also  met  with  in  chronic  insanity,  and  in  tetanus  and 
strychnine  poisoning. 

The  posterior  inferior  cerebellar  artery  (a.  cerebelli  inferior  posterior)  (Fig.  446), 
the  largest  branch  of  the  vertebral,  winds  backward  around  the  upper  part 
of  the  medulla  oblongata,  passing  between  the  origin  of  the  vagus  and  spinal 
accessory  nerves,  over  the  restiform  body  to  the  under  surface  of  the  cerebel- 
lum, where  it  divides  into  two  branches — an  internal,  which  is  continued  back- 
ward to  the  notch  between  the  two  hemispheres  of  the  cerebellum;  and  an  ex- 
ternal, which  supplies  the  under  surface  of  the  cerebellum  as  far  as  its  outer 


622  THE  VASCULAR  SYSTEMS 

border,  where  it  anastomoses  with  the  anterior  inferior  cerebellar  and  the  supe- 
rior cerebellar  branches  of  the  basilar  artery.  Branches  from  this  artery  supply 
the  choroid  plexus  of  the  fourth  ventricle. 

The  bulbar  arteries  comprise  several  minute  vessels  which  spring  from  the 
vertebral  and  its  branches  and  are  distributed  to  the  medulla  oblongata. 

The  basilar  artery  (a.  hasilaris)  (Fig.  446),  so  named  from  its  position  at  the  base 
of  the  skull,  is  a  single  trunk  formed  by  the  junction  of  the  two  vertebral  arteries; 
it  extends  from  the  posterior  to  the  anterior  border  of  the  pons,  lying  in  the  median 
pontile  groove,  under  cover  of  the  arachnoid.  It  ends  by  dividing  into  the  two 
posterior  cerebral  arteries. 

Branches. — Its  branches  on  either  side  are  the  following: 

Transverse.  Anterior  inferior  cerebellar. 

Internal  auditory.  Superior  cerebellar. 

Posterior  cerebral. 

The  transverse  or  pontile  branches  {rami  ad  ponteni^  are  a  number  of  small  vessels 
which  come  off  at  right  angles  on  either  side  of  the  basilar  artery  and  supply  the 
pons  and  adjacent  parts  of  the  brain. 

The  internal  auditory  (a.  auditiva  interna),  a  long  slender  branch,  arises  from 
near  the  middle  of  the  artery;  it  accompanies  the  corresponding  auditory  nerve 
into  the  internal  auditory  meatus  and  is  distributed  to  the  internal  ear. 

The  anterior  inferior  cerebellar  artery  (a.  cerebelli  inferior  anterior)  passes  back- 
ward to  be  distributed  to  the  anterior  part  of  the  under  surface  of  the  cerebellum, 
anastomosing  with  the  posterior  inferior  cerebellar  branch  of  the  vertebral. 

The  superior  cerebellar  artery  (a.  cerebelli  superior)  arises  near  the  termination 
of  the  basilar.  It  passes  outward,  immediately  behind  the  oculomotor  nerve, 
which  separates  it  from  the  posterior  cerebral  artery,  winds  around  the  crus,  close 
to  the  trochlear  nerve,  and,  arriving  at  the  upper  surface  of  the  cerebellum, 
divides  into  branches  which  ramify  in  the  pia  and,  reaching  the  circumference  of 
the  cerebellum,  anastomose  with  the  branches  of  the  inferior  cerebellar  artery. 
Several  branches  are  given  to  the  epiphysis,  the  superior  medullary  velum,  and 
the  velum  interpositum. 

The  posterior  cerebral  artery  (a.  cerebri  posterior)  (Figs.  446  and  453)  is  larger 
than  the  preceding,  from  which  it  is  separated  near  its  origin  by  the  oculomotor 
nerve.  Passing  outward,  parallel  to  the  superior  cerebellar  artery,  and  receiving 
the  posterior  communicating  from  the  internal  carotid,  it  winds  around  the  crus, 
and  passes  to  the  under  surface  of  the  temporal  lobe  of  the  cerebrum,  and  divides 
up  into  branches  for  the  supply  of  the  temporal  and  occipital  lobes. 

The  branches  of  the  posterior  cerebral  artery  are: 

(  Postero-median  ganglionic.  (  Anterior  temporal. 

Ganglionic    -^   Posterior  choroid.  Cortical    <  Posterior  temporal, 

t  Postero-lateral  ganglionic.  (  Occipital. 

Ganglionic. — The  postero-median  ganglionic  branches  (Fig.  453)  are  a  group  of 
small  arteries  which  arise  at  the  commencement  of  the  posterior  cerebral  artery; 
these,  with  similar  branches  from  the  posterior  communicating,  pierce  the  posterioT 
perforated  substance,  and  supply  the  internal  surfaces  of  the  thalamus  and  the 
wails  of  the  third  ventricle.  The  posterior  choroid  enters  the  interior  of  the  brain 
beneath  the  splenium  of  the  corpus  callosum,  and  supplies  the  velum  interpositum 
and  the  choroid  plexus.  The  postero-lateral  ganglionic  branches  are  a  group  of 
small  arteries  which  arise  from  the  posterior  cerebral  artery,  after  it  has  turned 
around  the  crus;  they  supply  a  considerable  portion  of  the  thalamus. 


THE  SUBCLA  VIAJST  ARTERY  623 

Cortical. — The  cortical  branches  are  the  anterior  temporal  branches,  to  the  basal 
surface  of  the  anterior  portion  of  the  temporal  lobe;  the  posterior  temporal  branches, 
to  the  external  surface  of  the  occipital  lobe  and  the  subtemporal  convolution; 
and  the  occipital  branches,  to  the  mesal  and  lateral  surfaces  of  the  occipital  lobe. 

ARTERIES  OF  THE  UPPER  EXTREMITY. 

The  artery  which  supplies  the  upper  extremity  continues  as  a  single  trunk 
from  its  commencement  down  to  t4ie  elbow,  but  different  portions  of  it  have 
received  different  names  according  to  the  region  through  which  it  passes.  That 
part  of  the  vessel  which  extends  from  its  origin  to  the  outer  border  of  the  first 
rib  is  termed  the  subclavian  artery;  beyond  this  point  to  the  lower  border  of  the 
axilla  it  is  termed  the  axillary  artery;  and  from  the  lower  margin  of  the  axillary 
space  to  the  bend  of  the  elbow  it  is  termed  the  brachial  artery;  here  the  single  trunk 
terminates  by  dividing  into  two  branches,  the  radial  and  ulnar. 

THE  SUBCLAVIAN  ARTERY  (A.  SUBCLAVIA)  (Fig.  456). 

On  the  right  side  the  subclavian  artery  arises  from  the  innominate  artery  opposite 
the  right  sternoclavicular  articulation;  on  the  left  side  it  arises  from  the  arch 
of  the  aorta.  The  two  vessels,  therefore,  in  the  first  part  of  their  course,  differ 
in  length,  direction,  and  relation  with  neighboring  structures. 

In  order  to  facilitate  the  description  of  these  vessels,  more  especially  from  a 
surgical  point  of  view,  each  subclavian  artery  has  been  divided  into  three  parts. 
The  first  portion,  on  the  right  side,  passes 

upward  and  outward  from  the  origin  of  the  f) 

vessel  to  the  inner  border  of  the  Scalenus  .// 

anticus.     On  the  left  side  it  ascends  nearly  /<^^~~^ 

vertically,  to  gain  the  inner  border  of  that  /^/ 

muscle.     The  second  part  passes  outward,  Clgj^^.,-- Ih     M 

behind  the  Scalenus  anticus;  and  the  third  "^^^^grt^N/^      l|)  ^ 

part  passes  from  the  outer  margin  of  that  ^;ir?iS^^---~^l=/~-J~/  \       \ 

muscle,  beneath   the   clavicle,  to  the  outer  ^^^jand   /  /g^^^^^\\       \ 

border  of  the  fii-st  rib,  where  it'  becomes  the         /'^*^'°tLi^^^VTi~~^     '^^  \ 

axillary  artery.     The  first  portion  of  these     <^i^*/-^^P- ■■'   )  ||     l\  fX  °*  \ 

two  vessels  differs  so  much  in  its  course  and     ^^"'^    ■■'"        J/^      %\  \  \ 

in    its    relations    with    neighboring    parts  '^^  yj      \ ,j 

that  it  will   be   described  separatelv.     The 

second  and  third  parts  are  alike  on  "the  two       ^"'-  ^^^-^'j^ubdal^ln^Se*'.'  °'  *'  "^^^ 

sides. 

First  Part  of  the  Right  Subclavian  Artery  (Fig.  4.56).— The  first  part  of  the 
right  subclavian  artery  arises  from  the  innominate  artery,  opposite  the  upper 
part  of  the  right  sternoclavicular  articulation,  and  passes  upward  and  outward 
to  the  inner  margin  of  the  Scalenus  anticus  muscle  (Fig.  456).  It  ascends  a  little 
above  the  clavicle,  the  extent  to  which  it  does  so  varying  in  different  cases. 

Relations. — It  is  covered,  iti  front,  by  the  integument,  superficial  fascia,  Platysma,  deep 
fascia,  the  clavicular  origin  of  the  Sternomastoid,  the  Sternohyoid,  and  the  Sternoth}Toid  muscles, 
and  another  layer  of  deep  fascia.  It  is  crossed  by  the  internal  jugular  and  vertebral  veins, 
and  by  the  vagus  nerve  and  the  cardiac  branches  of  the  vagus  and  sympathetic  nerves.  A  loop 
of  the  sympathetic  nerve  itself  also  crosses  the  artery,  forming  a  ring  (misa  suhdavia)  around 
the  vessel.  The  anterior  jugular  vein  passes  outward  in  front  of  the  artery,  but  is  not  in  contact 
with  it,  being  separated  from  it  by  the  Sternohyoid  and  Sternothyroid  muscles.  Below  and 
behind  the  artery  is  the  pleura;  behind  is  the  gangliated  cord  of  the  sympathetic,  the  Longus  colli 
muscle  and  the  first  thoracic  vertebra.  The  right  recurrent  laryngeal  nerve  winds  aroimd  the 
lower  and  back  part  of  the  vessel. 


624 


THE  VASCULAR  SYSTEMS 

PJnentc  nerve      Ve>tehal  aiteiy 


Supi  ascapula) 

at  te)  y    \        ,^^^  ^..cl 

net  i€ 


Subclavian 

at tery 
Extei  nal  jugu- 
lai  letn 
Eiqht  ttmomi- 

nate  lein 
Jnnomi 

nate  aitety. 


\ 

-■S 


-Subscapular 
artery. 


-Musculospiral  nerve. 


Fig.  456. — The  subclavian  artery,  showing  its  relations.     (From  a  preparatic 
College  of  Surgeons  of  England.) 


the  Museum  of  the  Royal 


Plan  op  the  Relations  of  First  Portion  of  the  Right  Subclavian  Artery. 

In  front. 
Skin,  superficial  fascia. 
Platysma,  deep  fascia. 
Clavicular  origin  of  Sternomastoid. 
Sternohyoid  and  Sternothyroid. 

Anterior  jugular,  internal  jugular,  and  vertebral  veins. 
Vagus  and  cardiac  nerves. 
Loop  from  the  sympathetic. 

Beneath. 

Pleura. 

Recurrent  laryngeal  nerve. 

Behind. 
Recurrent  laryngeal  nerve. 
Sympathetic. 
Pleura  and  apex  of  lung. 
Longus  colli. 
First  thoracic  vertebra. 


THE  SUBCLAVIAN  ARTERY 


625 


First  Part  of  the  Left  Subclavian  Artery  (Figs.  428  and  429).— The  first 
part  of  the  left  subclavian  artery  ariaes  from  the  arch  of  the  aorta,  behind  the 
left  common  carotid,  and  at  the  level  of  the  fourth  thoracic  vertebra;  it  ascends 
nearly  vertically  to  the  root  of  the  neck  and  then  arches  outward  to  the  inner 
margin  of  the  Scalenus  anticus  muscle. 

Relations. — It  is  in  relation,  in  front,  with  the  vagus,  cardiac,  and  phrenic  nerves,  which 
lie  parallel  with  it,  the  left  carotid  artery,  left  internal  jugular  and  vertebral  veins,  and  the  com- 
mencement of  the  left  innominate  vein,  and  is  covered  by  the  Sternothyroid,  Sternohyoid,  and 
Sternomastoid  muscles.  A  loop  of  the  sympathetic  encircles  the  artery,  forming  the  an-sa  snb- 
clavia.  Behind',  it  is  in  relation  with  the  oesophagus,  thoracic  duct,  inferior  cervical  ganglion 
of  the  sympathetic,  and  Longus  colli  muscle;  higher  up,  however,  the  oesophagus  and  thoracic 
duct  lie  to  its  right  side;  the  latter  ultimately  arching  over  the  vessel  to  join  the  angle  of  union 
between  the  subclavian  and  internal  jugular  veins.  To  its  inner  side  are  the  oesophagus,  trachea, 
thoracic  duct,  and  left  recurrent  laryngeal  nerve;  to  its  outer  side,  the  left  pleura  and  lung. 

Plan  of  the  Relations  of  First  Portion  of  the  Left  Subclavian  Artery. 

In  front. 
Vagus,  cardiac,  and  phrenic  nerves. 
Left  carotid  artery. 
Thoracic  duct. 

Left  internal  jugular,  vertebral,  and  innominate  veins. 
Sternothyroid,  Sternohyoid,  and  Sternomastoid  muscles. 
Inner  side. 


Older  side. 
Pleura  and  left  lung. 


Trachea. 

(Esophagus. 

Thoracic  duct. 

Left  recurrent  laryngeal  nerve. 

3chind. 

(Esophagus  and  thoracic  duct. 
Inferior  cervical  ganglion  of  sympathetic. 
Longus  colli. 

Second  and  Third  Parts  of  the  Subclavian  Artery  (Figs.  432  and  456). — 
The  second  portion  of  the  subclavian  artery  lies  behind  the  Scalenus  anticus  muscle; 
it  is  very  short,  and  forms  the  highest  part  of  the  arch  described  by  that  vessel. 

Relations. — It  is  covered,  in  front,  by  the  skin,  superficial  fascia,  Platysma,  deep  cervical 
fascia,  the  Sternomastoid  and  the  Scalenus  anticus  muscles.  On  the  right  side  the  phrenic 
nerve  is  separated  from  the  second  part  of  the  artery  by  the  Scalenus  anticus  muscle,  while  on 
the  left  side  the  nerve  crosses  the  first  part  of  the  artery  immediately  to  the  inner  edge  of  the 
muscle.  Behind,  it  is  in  relation  with  the  pleura  and  the  Scalenus  medius  muscle.  Above,  is 
the  brachial  plexus  of  nerves;  below,  the  pleura.  The  subclavian  vein  lies  below  and  in  front 
of  the  artery,  separated  from  it  by  the  Scalenus  anticus  muscle. 

Plan  of  the  Relations  of  Second  Portion  of  Subclavian  Artery. 

In  front. 
Skin  and  superficial  fascia. 
Platysma  and  deep  cervical  fascia. 
Sternomastoid. 
Phrenic  nerve. 
Scalenus  anticus. 
Subclavian  vein. 


Above. 
Brachial  plexus. 


Below. 
Pleura. 


Behind. 
Pleura  and  Middle  Scalenus. 

10 


626  2!£rz;   VASCULAB  SYSTEMS 

The  third  portion  of  the  subclavian  artery  passes  downward  and  outward  from 
the  outer  margin  of  the  Scalenus  anticus  muscle  to  the  outer  border  of  the  first 
rib,  where  it  becomes  the  axillary  artery.  This  portion  of  the  vessel  is  the  most 
superficial,  and  is  contained  in  tlie  subclavian  triangle  (see  page  606). 

Relations. — It  is  covered,  in  front,  by  the  skin,  the  superficial  fascia,  the  Platysma,  the 
descending  clavicular  branches  of  the  cervical  plexus,  and  the  deep  cervical  fascia;  by  the 
clavicle,  the  Subclavius  muscle,  the  suprascapular  artery  and  vein,  and  the  transverse  cervical 
vein;  the  nerve  to  the  Subclavius  muscle  passes  vertically  downward  in  front  of  the  artery. 
The  external  jugular  vein  crosses  the  artery  at  its  inner  side,  and  receives  the  suprascapular 
and  transverse  cervical  veins,  which  frequently  form  a  plexus  in  front  of  it.  The  subclavian 
vein  is  below  and  in  front  of  the  artery,  lying  close  behind  the  clavicle.  Behind,  it  lies  on  the 
Middle  Scalenus  muscle  and  the  lowest  cord  of  the  brachial  plexus,  formed  by  the  union  of 
the  last  cervical  and  first  thoracic  nerves.  Above  and  to  its  outer  side  are  the  upper  trunks 
of  the  brachial  plexus  and  the  Omohyoid  muscle.  Below,  it  rests  on  the  upper  surface  of  the 
first  rib,  or  on  the  cervical  rib  if  one  be  present. 

Plan  of  the  Relations  of  Third  Portion  of  Subclavian  Artery. 

In  front. 

Skin  and  superficial  fascia. 

Platysma  and  deep  cervical  fascia. 

Descending  branches  of  cervical  plexus.     Nerve  to  Subclavius  muscle. 

Subclavius  muscle,  suprascapular  artery,  and  vein. 

The  external  jugular  and  transverse  cervical  veins. 

The  clavicle. 


Above.  /  Subclavian    \  BeloW 


Brachial  plexus.  [       ™J'^'l       j  First  rib. 

Omohyoid. 

,  Behind. 

Scalenus  medius. 

Lower  cord  of  brachial  plexus. 

Peculiarities. — The  subclavian  arteries  vary  in  their  origin,  their  course,  and  the  height  to 
which  they  rise  in  the  neck. 

The  origin  of  the  right  subclavian  from  the  innominate  takes  place,  in  some  cases,  above  the 
sternoclavicular  articulation,  and  occasionally,  but  less  frequently,  in  the  cavity  of  the  thorax, 
below  that  point.  Or  the  artery  may  arise  as  a  separate  trunk  from  the  arch  of  the  aorta.  In 
such  cases  it  may  be  either  the  first,  second,  third,  or  even  the  last  branch  derived  from  that 
vessel;  in  the  majority  of  cases  it  is  the  first  or  last,  rarely  the  second  or  third.  When  it  is  the 
first  branch,  it  occupies  the  ordinary  position  of  the  innominate  artery;  when  the  second  or  third, 
it  gains  its  usual  position  by  passing  fjehind  the  right  carotid;  and  when  the  last  branch,  it  arises 
from  the  left  extremity  of  the  arch,  at'  its  upper  or  back  part,  and  passes  obliquely  toward  the 
right  side,  usually  behind  the  trachea,  oesophagus,  and  right  carotid,  sometimes  between  the 
oesophagus  and  trachea  to  the  upper  border  of  the  first  rib,  whence  it  follows  its  ordinary  course. 
Its  manner  of  development  is  such  that  the  inferior  laryngeal  nerve  is  not  looped  under  the  ves- 
sel, but  passes  in  a  nearly  straight  course  on  its  way  to  the  larynx.  In  very  rare  instances  this 
vessel  arises  from  the  thoracic  aorta,  as  low  down  as  the  fourth  thoracic  vertebra.  Occasionally 
it  perforates  the  Scalenus  anticus  muscle;  more  rarely  it  passes  in  front  of  that  muscle.  Some- 
times the  subclavian  vein  passes  wdth  the  artery  behind  the  Scalenus  anticus  muscle.  The 
artery  may  ascend  as  high  as  an  inch  and  a  half  above  the  clavicle  or  any  intermediate  point 
between  this  and  the  upper  border  of  the  bone,  the  right  subclavian  usually  ascending  higher 
than  the  left. 

The  left  subclavian  is  occasionally  joined  at  its  origin  with  the  left  common  carotid. 

Surface  Marking. — The  course  of  the  subclavian  artery  in  the  neck  may  be  mapped  out 
by  describing  a  curve,  with  its  convexity  upward  at  the  base  of  the  posterior  triangle.    The  inner 


THE  SVBCLA  VIAN  ARTERY  627 

end  of  this  curve  corresponds  to  the  sternoclavicular  joint,  the  outer  end  of  the  centre  of  the 
lower  border  of  the  clavicle.  The  curve  is  to  be  drawn  with  such  an  amount  of  convexity  that 
its  mid-point  reaches  half  an  inch  above  the  upper  l^order  of  the  clavicle.  The  left  subclavian 
artery  is  more  deeply  placed  than  the  right  in  the  first  part  of  its  course,  and,  as  a  rule,  does  not 
reach  quite  as  high  a  level  in  the  neck.  It  should  be  borne  in  mind  that  the  posterior  border  of 
the  Sternomastoid  muscle  corresponds  to  the  outer  border  of  the  Scalenus  anticus  muscle,  so 
that  the  third  portion  of  the  artery,  that  part  most  accessible  for  operation,  lies  immediately 
external  to  the  posterior  border  of  the  Sternomastoid  muscle. 

Applied  Anatomy. — The  relations  of  the  subclavian  arteries  of  the  two  sides  having  been 
examined,  the  student  should  direct  his  attention  to  a  consideration  of  the  best  position  in  which 
compression  of  the  vessel  may  be  effected,  or  in  what  situation  a  ligature  may  be  best  applied  in 
cases  of  aneurism  or  wound. 

Compression  of  the  subclavian  artery  is  required  in  cases  of  operation  about  the  shoulder, 
in  the  axilla,  or  at  the  upper  part  of  the  arm;  and  the  student  will  observe  that  there  is  only 
one  situation  in  which  it  can  be  effectually  applied — viz.,  where  the  artery  passes  across  the 
upper  surface  of  the  first  rib.  In  order  to  compress  the  vessel  in  this  situation,  the  shoulder 
should  be  depressed,  and  the  surgeon,  grasping  the  side  of  the  neck,  should  press  with  his  thumb 
in  the  angle  formed  by  the  posterior  border  of  the  Sternomastoid  with  the  upper  border  of  the 
clavicle,  downward,  backward,  and  inward  against  the  rib;  if  from  any  cause  the  shoulder 
cannot  be  sufficiently  depressed,  pressure  may  be  made  from  before  backward,  so  as  to  compress 
the  artery  against  the  Scalenus  medius  muscle  and  the  transverse  process  of  the  seventh  cervical 
vertebra.  In  appropriate  cases  a  preliminary  incision  may  be  made  through  the  cervical  fascia, 
and  the  finger  may  be  pressed  down  directly  upon  the  artery. 

Ligation  of  the  subclavian  artery  may  be  required  in  cases  of  wounds  or  of  aneurism  in  the 
axilla,  or  in  cases  of  aneurism  on  the  cardiac  side  of  the  point  of  ligation;  and  the  third  part  of 
the  artery  is  that  which  is  most  favorable  for  an  operation,  on  account  of  its  being  compara- 
tively superficial  and  most  remote  from  the  origin  of  the  large  branches.  In  those  cases  where 
the  clavicle  is  not  displaced,  this  operation  may  be  performed  with  comparative  facility;  but 
where  the  clavicle  is  pushed  up  by  a  large  aneurisaial  tmnor  in  the  axilla  the  artery  is  placed  at 
a  great  depth  from  the  surface,  which  materially  increases  the  difficulty  of  the  o]ieration.  Under 
these  circumstances  it  becomes  a  matter  of  importance  to  consider  the  height  to  which  this 
vessel  reaches  above  the  bone.  In  ordinary  cases  its  arch  is  about  half  an  inch  above  the  clavicle, 
occasionally  it  is  as  high  as  an  inch  and  a  half,  and  sometimes  so  low  as  to  be  on  a  level  with 
the  upper  laorder  of  the  clavicle.  If  the  clavicle  is  displaced,  these  variations  will  necessarily 
make  the  operation  more  or  less  difficult,  according  as  the  vessel  is  more  or  less  accessible. 

The  procedure  in  the  operation  of  tying  the  third  portion  of  the  subclavian  artery  is  as  fol- 
lows: The  patient  being  placed  on  a  table  in  the  supine  position,  with  the  head  drawn  over  to 
the  opposite  side  and  the  shoulder  depressed  as  much  as  possible,  the  integument  should  be 
drawn  downward  over  the  clavicle,  and  an  incision  made  through  it,  upon  that  bone,  from  the 
anterior  border  of  the  Trapezius  to  the  posterior  border  of  the  Sternomastoid,  to  which  may  be 
added  a  short  vertical  incision  meeting  the  inner  end  of  the  preceding.  The  object  in  drawing 
the  skin  downward  is  to  avoid  any  risk  of  wounding  the  external  jugular  vein,  for  as  it  perforates 
the  deep  fascia  above  the  clavicle,  it  cannot  be  drawn  downward  with  the  skin.  The  soft  parts 
should  now  be  allowed  to  glide  up,  and  the  cervical  fascia  should  be  divided  upon  a  director, 
and  if  the  interval  between  the  Trapezius  and  Sternomastoid  muscles  be  insufficient  for  the  per- 
formance of  the  operation,  a  portion  of  one  or  both  may  be  divided.  The  external  jugular  vein 
will  now  be  seen  toward  the  inner  side  of  the  wound;  this  and  the  suprascapular  and  transverse 
cervical  veins,  which  terminate  in  it,  should  be  held  aside.  If  the  external  jugular  vein  is  at  all 
in  the  way  and  exposed  to  injury,  it  should  be  tied  in  two  places  and  divided.  The  suprascapular 
artery  should  be  avoided,  and  the  Omohyoid  muscle  held  aside  if  necessary.  In  the  space 
beneath  this  muscle  careful  search  must  be  made  for  the  vessel;  a  layer  of  deep  fascia  and  some 
connective  tissue  having  been  divided  carefully,  the  outer  margin  of  the  Scalenus  anticus  muscle 
must  be  felt  for,  and,  the  finger  being  guided  by  it  to  the  first  rib,  the  pulsation  of  the  subclavian 
artery  will  be  felt  as  it  passes  over  the  rib.  The  sheath  of  the  vessels  having  been  opened, 
the  aneurism  needle  may  then  be  passed  around  the  artery  from  above  downward  and  inward,  so 
as  to  avoid  including  any  of  the  branches  of  the  brachial  plexus.  If  the  clavicle  is  so  raised  by 
the  tumor  that  the  application  of  the  ligature  cannot  be  effected  in  this  situation,  the  artery  may 
be  tied  above  the  first  rib,  or  even  behind  the  Scalenus  anticus  muscle;  the  difficulties  of  the 
operation  in  such  a  case  will  be  materially  increased,  on  account  of  the  greater  depth  of  the  artery 
and  the  alteration  in  position  of  the  surrounding  parts. 

The  second  part  of  the  subclavian  artery,  from  being  that  portion  which  rises  highest  in  the 
neck,  has  been  considered  favorable  for  the  application  of  the  ligature  when  it  is  difficult  to  tie 
the  arterv  in  the  third  part  of  its  course.  There  are,  however,  many  objections  to  the  oper- 
ation in  this  situation.  It  is  necessary  to  divide  the  Scalenus  anticus  muscle,  upon  which  lies 
the  phrenic  nerve,  and  at  the  inner  side  of  which  is  situated  the  internal  jugular  vein;  and  a 


628  THE    VASCULAR  SYSTEMS 

wound  of  either  of  these  structures  might  lead  to  the  most  dangerous  consequences.  Again, 
the  artery  is  in  contact,  below,  witli  the  pleura,  which  must  also  be  avoided;  and,  lastly,  the 
proximity  of  so  many  of  its  large  branches  arising  internal  to  this  point  must  be  a  still  further 
objection  to  the  operation.  In  cases,  however,  where  the  sac  of  an  axillary  aneurism  encroaches 
on  the  neck,  it  may  be  necessary  to  divide  the  outer  half  or  two-thirds  of  the  Scalenus  anticus 
musdle,  so  as  to  place  the  ligature  on  the  vessel  at  a  greater  distance  from  the  sac.  The  oper- 
ation is  performed  exactly  in  the  same  way  as  a  ligation  of  the  third  portion,  until  the  Scalenus 
anticus  is  exposed,  when  it  is  to  be  divided  on  a  director  (never  to  a  greater  extent  than  its  outer 
two-thirds),  and  it  immediately  retracts.  The  operation  is  therefore  merely  an  extension  of 
ligation  of  the  third  portion  of  the  vessel. 

In  those  cases  of  aneurism  of  the  axillary  or  subclavian  artery  in  which  the  aneurism  encroaches 
upon  the  outer  portion  of  the  Scalenus  muscle  to  such  an  extent  that  a  ligature  cannot  be  applied 
in  that  situation,  it  may  be  deemed  advisable,  as  a  last  resource,  to  tie  the  first  portion  of  the 
subclavian  artery.  On  the  left  side  this  operation  has  been  regarded  as  almost  impracticable; 
the  great  depth  of  the  artery  from  its  surface,  its  intimate  relation  with  the  pleura,  and  its  close 
proximity  to  the  thoracic  duct  and  to  so  many  important  veins  and  nerves,  presents  a  series  of 
difficulties  which  it  is  very  difficult  to  overcome.  Nevertheless,  it  has  been  successfully  done 
several  times.  The  main  objection  to  the  operation  in  this  situation  is  the  smallness  of  the 
interval  which  usually  exists  between  the  commencement  of  the  vessel  and  the  origin  of  the 
nearest  branch.  The  operation  may  be  performed  in  the  following  manner:  The  patient  being 
placed  on  the  table  in  the  supine  position  witli  the  neck  extended,  an  incision  should  be  made 
along  the  upper  border  of  the  inner  part  of  the  clavicle,  and  a  second  along  the  inner  border  of 
the  Sternoinastoid,  meeting  the  former  at  an  angle.  The  attachment  of  both  heads  of  the 
Sternomastoid  must  be  divided  on  a  director  and  turned  outward;  a  few  small  arteries  and 
veins,  and  occasionally  the  anterior  jugular  vein,  must  be  avoided,  or,  if  necessary,  ligated  in 
two  places  and  divided,  and  the  Sternohj'oid  and  Sternothyroid  muscles  are  to  be  divided  in 
the  same  manner  as  the  preceding  muscle.  After  tearing  through  the  deep  fascia,  the  internal 
jugular  vein  will  be  seen  crossing  the  subclavian  artery;  this  should  be  pressed  aside  and  the 
artery  secured  by  passing  the  needle  from  below  upward,  by  which  the  pleura  is  more  effectually 
avoided.  The  exact  position  of  the  vagus,  the  recurrent  laryngeal,  the  phrenic  and  sympathetic 
nerves  should  be  remembered,  and  the  ligature  should  be  applied  near  the  origin  of  the  verte- 
bral, in  order  to  afford  as  much  room  as  possible  for  the  formation  of  a  coagulum  between  the 
ligature  and  the  origin  of  the  vessel.  It  should  be  remembered  that  the  right  subclavian  artery 
is  occasionally  deeply  placed  in  the  first  part  of  its  course  when  it  arises  from  the  left  side  of  the 
aortic  arch,  and  passes  in  such  cases  behind  the  cesophagus  or  between  it  and  the  trachea. 

Branches. — The  branches  given  ofF  from  the  subclavian  artery  are: 

Vertebral.  Internal  mammary. 

Superior  intercostal. 

( Inferior  thyroid. 
Thyroid  axis<!  Suprascapular. 

(Transverse  cervical. 

On  the  left  side  all  four  branches  generally  arise  from  the  first  portion  of  the 
vessel,  but  on  the  right  side  the  superior  intercostal  usually  arises  from  the  second 
portion  of  the  vessel.  On  both  sides  of  the  body  the  first  three  branches  arise  close 
together  at  the  inner  margin  of  the  Scalenus  anticus;  in  the  majority  of  cases  a 
free  interval  of  from  half  an  inch  to  an  inch  exists  between  the  commencement 
of  the  artery  and  the  origin  of  the  nearest  branch.  The  vertebral  artery 
arises  from  the  upper  and  posterior  part  of  the  subclavian  artery,  the  internal 
mammary  from  the  lower  part  of  the  artery;  the  thyroid  axis  from  in  front  and 
the  superior  intercostal  from  behind. 

The  vertebral  artery,  the  first  branch  of  the  subclavian,  is  distributed  entirely 
to  the  head  and  neck,  chiefly  supplying  the  posterior  portion  of  the  brain.  It 
has  been  described  on  pages  619  to  623. 

The  thyroid  axis  (iruncus  thyreocervicalis)  (Figs.  435  and  458)  is  a  short  thick 
trunk  which  arises  from  the  fore  part  of  the  first  portion  of  the  subclavian  artery. 


THE  SUBCLA  VIAN  ARTERY  629 

close  to  the  inner  border  of  the  Scalenus  anticus  muscle,  and  divides,  almost 
immediately  after  its  origin,  into  three  branches — the  inferior  thyroid,  supra- 
scapular, and  transverse  cervical. 

The  inferior  thyroid  artery  (a.  thyreoidea  inferior)  (Fig.  4.35)  passes  upward,  in 
front  of  the  vertebral  artery  and  Longus  colli  muscle;  then  turns  inward  behind  the 
sheath  of  the  common  carotid  artery  and  internal  jugular  vein,  and  also  behind 
the  sympathetic  cord,  the  middle  cervical  ganglion  resting  upon  the  vessel,  and, 
reaching  the  lower  border  of  the  lateral  lobe  of  the  thyroid  gland,  it  divides  into 
two  branches,  which  supply  the  postero-inferior  parts  of  the  gland,  and  anasto- 
mose with  the  superior  thyroid  and  with  the  corresponding  artery  of  the  opposite 
side.  The  recurrent  laryngeal  nerve  passes  upward,  generally  behind,  but  occa- 
sionally in  front  of,  the  artery.     Its  branches  are : 

Inferior  laryngeal.  OEsophageal. 

Tracheal.  Ascending  cervical. 

Muscular. 

The  inferior  larjmgeal  branch  (a.  laryngea  inferior)  ascends  upon  the  trachea 
to  the  back  part  of  the  larynx,  in  company  with  the  recurrent  laryngeal  nerve, 
and  supplies  the  muscles  and  mucous  membrane  of  this  part,  anastomosing  with 
the  inferior  laryngeal  branch  from  the  opposite  side  and  with  the  laryngeal  branch 
from  the  superior  thyroid  artery. 

The  tracheal  branches  (rami  tracheales)  are  distributed  upon  the  trachea,  anasto- 
mosing below  with  the  bronchial  arteries. 

The  oesophageal  branches  (rami  oesophagei)  are  distributed  to  the  oesophagus, 
and  anastomose  with  the  oesophageal  branches  of  the  aorta. 

The  ascending  cervical  (a.  cervicalis  ascendens)  is  a  small  branch  which  arises 
from  the  inferior  thyroid  just  where  that  vessel  is  passing  behind  the  common 
carotid  artery,  and  runs  up  on  the  anterior  tubercles  of  the  transverse  processes 
of  the  cervical  vertebrtie  in  the  interval  between  the  Scalenus  anticus  and  Rectus 
capitis  anticus  major  muscles.  It  gives  branches  to  the  muscles  of  the  neck, 
which  anastomose  with  branches  of  the  vertebral,  and  sends  one  or  two  branches 
into  the  vertebral  canal  through  the  intervertebral  foramina  to  be  distributed  to 
the  spinal  cord  and  its  membranes,  and  to  the  bodies  of  the  vertebrae  in  the  same 
manner  as  the  lateral  spinal  branches  from  the  vertebral.  It  anastomoses  with 
the  ascending  pharyngeal  and  occipital   arteries. 

The  muscular  branches  supply  the  Depressors  of  the  hyoid  bone,  the  Longus 
colli,  the  Scalenus  anticus,  and  the  Inferior  constrictor  of  the  pharynx.  One 
of  the  muscular. branches  passes  between  the  transverse  processes  of  the  fourth 
and  fifth  cervical  vertebrae  and  reaches  the  deep  muscles  of  the  neck.  It  is  called 
the  ramus  profundus. 

The  suprascapular  artery  (a.  transversa  scapulae)  (Figs.  4.35  and  457)  passes 
at  first  downward  and  outward  across  the  Scalenus  anticus  and  phrenic  nerve, 
being  covered  by  the  Sternomastoid;  it  then  crosses  the  subclavian  artery  and  the 
cords  of  the  brachial  plexus,  and  runs  outward,  behind  and  parallel  with  the 
clavicle  and  Subclavius  muscle,  and  beneath  the  posterior  belly  of  the  Omohyoid, 
to  the  superior  border  of  the  scapula,  where  it  passes  over  the  transverse  ligament 
of  the  scapula,  which  separates  it  from  the  suprascapular  nerve,  and  reaches  the 
supraspinous  fossa.  In  this  situation  it  lies  close  to  the  bone,  and  ramifies  be- 
tween it  and  the  Supraspinatus  muscle,  to  which  it  supplies  branches.  It  then 
passes  downward  behind  the  neck  of  the  scapula,  to  reach  the  infraspinous  fossa, 
where  it  anastomoses  with  the  dorsalis  scapulae  branch  of  the  subscapular  artery 
and  branches  of  the  posterior  scapular  arteries.  Besides  distributing  branches 
to  the  Sternomastoid,  Subclavius,  and  neighboring  muscles,  it  gives  off  a  supra- 


630 


THE  VASCULAR  SYSTEMS 


sternal  branch,  which  crosses  over  the  sternal  end  of  the  clavicle  to  the  skin  of  the 
upper  part  of  the  thorax;  and  a  supra-acromial  branch  {ramus  acromialls),  which 
piercing  the  Trapezius  muscle,  supplies  the  skin  over  the  acromion,  anastomosing 
with  a  branch  of  the  acromiothoracic  artery.  A  small  subscapular  branch  is  given 
off  as  the  artery  passes  over  the  transverse  ligament  of  the  scapula;  it  descends  into 
the  subscapular  fossa,  ramifies  beneath  the  Subscapular  muscle,  and  anastomoses 
with  the  posterior  and  subscapular  arteries.  The  suprascapular  artery  also  sends 
branches  to  the  acromioclavicular  and  shoulder-joints,  and  a  nutrient  artery  to 
the  clavicle. 


Posterior  scapular. 


Suprascapular. 


rminaiion  of 
suhscapular. 

Fig.  457. — The  scapular  and  circumflex  arteries. 


The  transverse  cervical  artery  (a.  transversa  colli)  (Fig.  435),  larger  than  the 
suprascapular,  passes  transversely  outward,  across  the  upper  part  of  the  sub- 
clavian triangle,  to  the  anterior  margin  of  the  Trapezius  muscle,  beneath  which 
it  divides  into  two  branches,  the  superficial  cervical  and  the  posterior  scapular. 
In  its  passage  across  the  neck  it  crosses  in  front  of  the  phrenic  nerve,  Scaleni 
muscles,  and  the  brachial  plexus,  between  the  divisions  of  which  it  sometimes 
passes,  and  is  covered  by  the  Platysma,  Sternomastoid,  Omohyoid,  and  Trapezius 
muscles. 

The  superficial  cervical  (ramus  ascendens)  ascends  beneath  the  anterior  margin 
of  the  Trapezius,  distributing  branches  to  it  and  to  the  neighboring  muscles  and 
lymph  nodes  in  the  neck,  and  anastomosing  with  the  superficial  branch  of  the 
arteria  princeps  cervicis. 

The  posterior  scapular  (ramus  descendens)  (Fig.  435)  passes  beneath  the  Levator 
anguli  scapulae  muscle  to  the  superior  angle  of  the  scapula,  and  then  descends 
along  the  posterior  border  of  that  bone  as  far  as  the  inferior  angle.  In  its  course 
it  is  covered  by  the  Rhomboid  muscles,  supplying  them  and  the  Latissimus  dorsi 
and  Trapezius,  and  anastomosing  with  the  suprascapular  and  subscapular  arteries, 
and  with  the  posterior  branches  of  some  of  the  intercostal  arteries. 

PecuUarities. — The  superficial  cervical  frequently  arises  as  a  separate  branch  from  the  thy- 
roid axis;  and  the  posterior  scapular,  from  the  third,  more  rarely  from  the  second,  part  of  the 
subclavian. 


THE  SUBCLA  VIAN  ARTERY 


631 


The  internal  mammary  artery  (a.  mammaria  interna)  (Fig.  458)  arises  from 
the  under  surface  of  the  first  portion  of  the  subclavian  artery,  opposite  the  thyroid 


Scalenus 
anticus. 


iiiterio}  uitei  costal 
branches 


Musculo- 
pli7'emc     ^AaW 


Fig.  458.— The  internal  iiuimma 


■External 
iliac. 


iteiy  and  its  branches. 


axis.  It  descends  behind  the  cartilages  of  the  upper  six  ribs  at  a  distance  of 
about  half  an  inch  from  the  margin  of  the  sternum;  and  at  the  level  of  the  sixth 
intercostal  space  divides  into  the  musculophrenic  and  superior  epigastric  arteries. 


632  THE  VASCULAR  8YSTEM8 

Relations. — At  its  origin  it  is  cohered  by  the  internal  jugular  and  subclavian  veins,  and  as 
it  enters  the  thorax  is  crossed  from  without  inward  by  the  phrenic  nerve,  and  then  passes  for- 
ward close  to  the  outer  side  of  the  innominate  vein.  In  the  upper  part  of  the  thorax  it  lies  behind 
the  costal  cartilages  and  Internal  intercostal  muscles,  and  is  crossed  by  the  terminations  of  the 
upper  six  intercostal  nerves.  Behind  it  lies  upon  the  pleura,  as  far  as  the  third  costal  cartilage; 
below  this  level  upon  the  Triangularis  sterni  muscle.  It  is  accompanied  by  two  venae  comites; 
these  unite  into  a  single  vein,  which  passes  to  the  inner  side  of  the  artery  and  ends  in  the  corre- 
sponding innominate  vein. 

Branches. — The  branches  of  the  internal  mammary  are: 

■Comes  nervi  phrenici.  Anterior  intercostal. 

Mediastinal.  Perforating. 

Pericardiac.  Musculophrenic. 

Sternal.  Superior  epigastric. 

The  comes  nervi  phrenici  (a.  pericardiacophrenica^  is  a  long  slender  branch 
which  accompanies  the  phrenic  nerve,  between  the  pleura  and  pericardium,  to 
the  Diaphragm  to  which  it  is  distributed;  it  anastomoses  with  the  other  phrenic 
branches  from  the  internal  mammary  and  with  phrenic  branches  of  the  abdominal 
aorta. 

The  mediastinal  branches  (aa.  mediastinales  anteriores)  are  small  vessels  which 
are  distributed  to  the  areolar  tissue  and  lymph  nodes  in  the  anterior  medias- 
tinum and  to  the  remains  of  the  thymus  gland. 

The  pericardiac  branches  supply  the  upper  part  of  the  anterior  surface  of  the 
pericardium,  the  lower  part  receiving  branches  from  the  musculophrenic  artery. 

The  sternal  branches  (rami  sternales)  are  distributed  to  the  Triangularis  sterni 
and  to  the  posterior  surface  of  the  sternum. 

The  mediastinal,  pericardiac,  and  sternal  branches,  together  with  some  twigs 
from  the  comes  nervi  phrenici,  anastomose  with  branches  from  the  intercostal  and 
bronchial  arteries,  and  form  a  minute  plexijs  beneath  the  pleura,  which  has  been 
named  by  Turner  the  subpleural  mediastinal  plexus. 

The  anterior  intercostal  arteries  (rami  intercostales)  supply  the  five  or  six  upper 
intercostal  spaces.  The  branch  corresponding  to  each  space  soon  divides  into 
two,  or  the  two  branches  may  come  off  separately  from  the  parent  trunk.  The 
small  vessels  pass  outward  in  the  intercostal  spaces,  one,  the  larger,  lying  near 
the  lower  margin  of  the  rib  above,  and  the  other,  the  smaller,  near  the  upper 
margin  of  the  rib  below,  and  anastomose  with  the  intercostal  arteries  from  the 
aorta.  They  are  at  first  situated  between  the  pleura  and  the  Internal  intercostal 
muscles,  and  then  between  the  Internal  and  External  intercostal  muscles.  They 
supply  the  Intercostal  muscles,  and,  by  branches  which  perforate  the  External 
intercostal  muscle,  reach  the  Pectoral  muscles  and  the  mammary  gland. 

The  perforating  arteries  (rami  perforantes)  correspond  to  the  five  or  six  upper 
intercostal  spaces.  They  ari.se  from  the  internal  mammary,  pass  forward  through 
the  intercostal  spaces,  and,  curving  outward,  supply  the  Pectoralis  major  and  the 
integument.  Those  which  correspond  to  the  second,  third,  and  fourth  spaces  are 
distributed  to  the  mammary  gland.  In  females,  during  lactation,  these  branches 
are  of  large  size. 

The  musculophrenic  artery  (a.  muscidophreiiica)  is  directed  obliquely  down- 
ward and  outward,  behind  the  cartilages  of  the  false  ribs,  perforating  the  Dia- 
phragm at  the  eighth  or  ninth  rib,  and  terminating,  considerably  reduced  in  size, 
opposite  the  last  intercostal  space.  It  gives  off  anterior  intercostal  arteries  to 
each  of  the  intercostal  spaces  across  which  it  passes;  these  diminish  in  size  as  the 
spaces  decrease  in  length,  and  are  distributed  in  a  manner  precisely  similar  to 


THE  AXILLA  633 

the  anterior  intercostals  from  the  internal  mammary.  The  musculophrenic  also 
gives  branches  to  the  lower  part  of  the  pericardium,  and  others  which  run  back- 
ward to  the  Diaphragm  and  downward  to  the  Abdominal  muscles. 

The  superior  epigastric  (a.  epicjasirica  superior)  continues  in  the  original  direc- 
tion of  the  internal  mammary;  it  descends  through  the  cellular  interval  between 
the  costal  and  sternal  attachments  of  the  Diaphragm,  and  enters  the  sheath  of  the 
Rectus  abdominis  muscle,  at  first  lying  behind  the  muscle,  and  then  perforating 
it  and  supplying  it,  and  anastomosing  with  the  deep  epigastric  artery  from  the 
external  ihac.  Some  branches  perforate  the  sheath  of  the  Rectus  and  supply  the 
muscles  of  the  abdomen  and  the  integument,  and  a  small  branch,  which  passes 
inward  upon  the  side  of  the  ensiforUi  appendix,  anastomoses  in  front  of  that 
cartilage  with  the  superior  epigastric  artery  of  the  opposite  side.  It  also  gives 
some  twigs  to  the  Diaphragm,  while  from  the  artery  of  the  right  side  small  branches 
extend  into  the  falciform  ligament  of  the  liver  and  anastomose  with  the  hepatic 
artery. 

The  superior  intercostal  (truncus  costocervicaUs)  (Figs.  444  and  464)  arises  from 
the  upper  and  back  part  of  the  subclavian  artery,  behind  the  Scalenus  anticus  mus- 
cle on  the  right  side  and  to  the  inner  side  of  that  muscle  on  the  left  side.  Passing 
backward,  it  gives  off  the  deep  cervical  branch,  and  then  descends  behind  the 
pleura  in  front  of  the  necks  of  the  first  two  ribs,  and  anastomoses  with  the  first 
aortic  intercostal.  As  it  crosses  the  neck  of  the  first  rib  it  lies  to  the  inner  side 
of  the  anterior  division  of  the  first  thoracic  ner^'e  and  to  the  outer  side  of  the  first 
thoracic  ganglion  of  the  sympathetic  cord. 

In  the  first  intercostal  space  it  gives  off  a  branch  which  is  distributed  in  a  manner 
similar  to  the  distribution  of  the  aortic  intercostals.  The  branch  for  the  second 
intercostal  space  usually  joins  with  one  from  the  highest  aortic  intercostal.  Each 
intercostal  gives  off  a  branch  to  the  posterior  spinal  muscles,  and  a  small  branch 
which  passes  through  the  corresponding  intervertebral  foramen  to  the  spinal  cord 
and  its  membranes. 

The  deep  cervical  branch  (a.  ccrvicalis  profunda)  arises,  in  most  cases,  from 
the  superior  intercostal,  and  is  analogous  to  the  posterior  branch  of  an  aortic 
intercostal  artery;  occasionally  it  arises  as  a  separate  branch  from  the  subclavian 
artery.  Passing  backward,  above  the  eighth  cervical  nerve  and  between  the 
transverse  process  of  the  seventh  cervical  vertebra  and  the  first  rib,  it  runs  up  the 
back  part  of  the  neck,  between  the  Complexus  and  Semispinalis  colli  muscles, 
as  high  as  the  axis  vertebra,  supplying  these  and  adjacent  muscles,  and  anasto- 
mosing with  the  deep  branch  of  the  arteria  princeps  cervicis  of  the  occipital, 
and  with  Ijranches  which  pass  outward  from  the  vertebral.  It  gives  off  a  special 
branch  which  enters  the  vertebral  canal  through  the  intervertebral  foramen 
between  the  seventh  cervical  and  first  thoracic  vertebrae. 


THE  AXILLA. 

The  axilla  or  armpit  is  a  pyramidal  space,  situated  between  the  upper  and  lateral 
part  of  the  thorax  and  the  inner  side  of  the  arm. 

Boundaries. — Its  apex,  which  is  directed  upward  toward  the  root  of  the  neck, 
corresponds  to  the  interval  between  the  first  rib,  the  upper  edge  of  the  scapula, 
and  the  clavicle,  through  which  the  axillary  vessels,  the  brachial  plexus  of  ner\es, 
and  the  long  thoracic  nerve  pass.  This  interval  is  the  cervico-axillary  passage. 
The  base,  directed  downward,  is  formed  by  the  integument  and  a  thick  layer  of 
fascia,  the  axillary  fascia  (fascia  axillaris)  (Fig.  346),  extending  between  the  lo\\-er 
border  of  the  Pectoralis  major  in  front  and  the  lower  border  of  the  Latissimus 


634  THE   VASCULAR  SYSTEMS 

dorsi  behind  (page  406).  The  axilla  is  broad  internally  at  the  thorax,  but  narrow 
and  pointed  externally  at  the  arm.  The  anterior  wall  is  formed  by  the  Pectoralis 
major  and  minor  muscles,  the  former  covering  the  whole  of  the  anterior  wall  of 
the  axilla,  the  latter  covering  only  its  central  part,  the  costocoracoid  membrane, 
the  clavicle,  and  the  Subclavius  muscle.  The  posterior  boundary,  which  extends 
somewhat  lower  than  the  anterior,  is  formed  by  the  Subscapularis  above,  the  Teres 
major  and  Latissimus  dorsi  below.  On  the  inner  side  are  the  first  four  ribs  with 
their  corresponding  Intercostal  muscles,  and  part  of  the  Serratus  magnus.  On 
the  outer  side,  where  the  anterior  and  posterior  boundaries  converge,  the  space  is 
narrow,  and  bounded  by  the  humerus,  the  Coracobrachialis  and  Biceps  muscles. 

Contents. — It  contains  the  axillary  vessels,  and  the  brachial  plexus  of  nerves, 
with  their  branches,  some  branches  of  the  intercostal  nerves,  and  a  large  number 
of  lymph  nodes,  all  connected  by  a  quantity  of  fat  and  loose  areolar  tissue. 

Position  of  the  Contents. — The  axillary  artery  and  vein,  with  the  brachial  plexus 
of  nerves,  extend  obliquely  along  the  outer  boundary  of  the  axilla,  from  its  apex 
to  its  base,  and  are  placed  much  nearer  the  anterior  than  the  posterior  wall,  the 
vein  lying  to  the  inner  or  thoracic  side  of  the  artery  and  partially  concealing 
it.  At  the  fore  part  of  the  axilla,  in  contact  with  the  Pectoral  muscles,  and  along 
the  anterior  margin  are  the  thoracic  branches  of  the  axillary  artei-y,  and  along 
the  lower  margin  of  the  Pectoralis  minor  the  long  thoracic  artery  extends  to  the 
side  of  the  thorax.  At  the  back  part,  in  contact  with  the  lower  margin  of  the  Sub- 
scapularis muscle,  are  the  subscapular  vessels  and  nerves;  winding  around  the 
outer  border  of  this  muscle  is  the  dorsalis  scapulae  artery  and  veins ;  and,  close 
to  the  neck  of  the  humerus,  the  posterior  circumflex  vessels  and  the  circumflex 
nerve  are  seen  curving  backward  to  the  shoulder. 

Along  the  inner  or  thoracic  side  no  vessel  of  any  importance  exists,  the  upper 
part  of  the  space  being  crossed  merely  by  a  few  small  branches  from  the  superior 
thoracic  artery.  There  are  some  important  nerves,  however,  in  this  situation — 
viz.,  the  long  thoracic  nerve,  descending  on  the  surface  of  the  Serratus  magnus, 
to  which  it  is  distributed ;  and  perforating  the  upper  and  anterior  part  of  this  wall, 
the  intercostohumeral  nerve  or  nerves,  passing  across  the  axilla  to  the  inner  side 
of  the  arm. 

The  cavity  of  the  axilla  is  filled  by  a  quantity  of  loose  areolar  tissue  and  a  large 
number  of  small  arteries  and  veins,  all  of  which  are,  however,  of  inconsiderable 
size,  and  numerous  lymph  nodes,  the  position  and  arrangement  of  which  are 
described  on  a  subsequent  page. 

Applied  Anatomy. — The  axilla  is  a  space  of  considerable  surgical  importance.  It  trans- 
mits the  large  vessels  and  nerves  to  the  upper  extremity,  and  these  may  be  the  seat  of  injury  or 
disease;  it  contains  numerous  lymph  nodes  \Yhich  may  require  removal  when  diseased;  in 
it  is  a  quantity  of  loose  connective  and  adipose  tissue  which  may  be  readily  infiltrated  with  blood 
or  pus.  The  axilla  may  be  the  seat  of  rapidly  growing  tumors.  Moreover,  it  is  covered  at  its 
base  by  thin  skin,  largely  supplied  with  sebaceous  and  sweat  glands,  which  is  frequently  the 
seat  of  small  cutaneous  abscesses  and  bcrils,  and  of  eruptions  due  to  irritation. 

In  suppuration  in  the  axilla  the  arrangement  of  the  fascife  plays  a  very  important  part  in  the 
direction  which  the  pus  takes.  As  described  on  p.  456,  the  costocoracoid  membrane,  after 
covering  in  the  space  between  the  clavicle  and  the  upper  border  of  the  Pectoralis  minor,  splits 
to  enclose  this  muscle,  and,  reblending  at  its  lower  border,  becomes  incorporated  with  the  axillary 
fascia  at  the  anterior  fold  of  the  axilla.  Suppuration  may  take  place  either  superficial  to  or 
beneath  tnis  layer  of  fascia;  that  is,  either  between  the  Pectorals  or  beneath  the  Pectoralis  minor; 
in  the  former  case  the  pus  would  point  either  at  the  anterior  border  of  the  axillary  fold  or  in 
the  groove  between  the  Deltoid  and  the  Pectoralis  major;  in  the  latter  instance,  the  pus  would 
have  a  tendency  to  surround  the  vessels  and  nerves  and  ascend  into  the  neck,  that  being  the  direc- 
tion in  which  there  is  least  resistance.  Its  progress  toward  the  skin  is  prevented  by  the  axillary 
fascia;  its  progress  backward,  by  the  Serratus  magnus;  forward,  by  the  costocoracoid  fascia; 
inward,  by  the  wall  of  the  thorax;  and  outward,  by  the  upper  limb.     The  pus  in  these  cases, 


THE  AXILLARY  ARTERY 


635 


after  extending  into  the  neck,  has  been  known  to  spread  through  the  suiicrior  ojjcning  of  the 
thorax  into  the  mediastinum. 

In  opening  an  axillary  abscess  the  knife  should  be  entered  in  the  floor  of  the  axilla,  midway 
between  the  anterior  and  posterior  margins  and  near  the  thoracic  side  of  the  space.  It  is  well 
to  use  a  director  and  dressing  forceps  after  an  incision  has  been  made  through  the  skin  and  fascia 
in  the  manner  directed  by  the  late  Mr.  Hilton. 

The  relations  of  the  vessels  and  nerves  in  the  several  parts  of  the  axilla  are  important,  for  it  is 
the  universal  plan  to  remove  the  nodes  from  the  axilla  in  operating  for  cancer  of  {he  breast. 


Fig.  459. — The  axillary  artery 


The  Axillary  Artery  (A.  Axillaris)  (Fig.  459). 

The  axillary  artery,  the  continuation  of  the  suljclavian,  commences  at  the 
outer  border  of  the  first  rib,  and  terminates  at  the  lower  border  of  the  tendon 
of  the  Teres  major  muscle,  where  it  talces  the  name  of  brachial.  Its  direction 
varies  with  the  position  of  the  limb;  when  the  arm  lies  by  the  side  of  the  thorax, 
the  vessel  forms  a  gentle  curve,  the  convexity  being  upward  and  outward;  when 
the  arm  is  directed  at  right  angles  with  the  trimk,  the  vessel  is  nearly  straight; 
and  when  the  arm  is  elevated  still  higher,  the  arteries  describe  a  curve  the  con- 
cavity of  which  is  directed  upward.  At  its  commencement  the  artery  is  very  deeply 
'situated,  but  near  its  termination  it  is  superficial,  being  covered  only  by  the  skin 
and  fascia.  The  description  of  the  relations  of  this  vessel  is  facilitated  by  its 
division  into  three  portions,  the  first  portion  being  above,  the  second  portion  be- 
hind, and  the  third  below  the  Pectoralis  minor. 


Relations. — The  first  portion  of  the  axillary  artery  is  in  relation,  in  front,  with  the  clavicular 
portion  of  the  Pectoralis  major,  the  costocoracoid  membrane,  the  external  anterior  thoracic  nerve, 
and  the  acromiothoracic  and  cephalic  veins;  behind,  with  the  first  intercostal  space,  the  corre- 


636  THE  VASCULAR  SYSTEMS 

spending  Intercostal  muscle,  the  first  and  second  digitations  of  the  Serratus  magnus,  and  the 
Long  thoracic  nerve;  on  its  outer  side,  with  the  brachial  plexus,  from  which  it  is  separated  by 
a  little  areolar  tissue;  on  its  inner  or  thoracic  side,  with  the  axillary  vein,  which  overlaps  the 
artery.  It  is  enclosed,  together  with  the  axillary  vein  and  the  brachial  plexus,  in  a  fibrous 
sheath — the  axillary  sheath — continuous  above  with  the  cervical  fascia. 


Relations  of  the  First  Portion  of  the  Axillary  Artery. 

In  front. 

Pectoralis  major. 
Costocoracoid  membrane. 
External  anterior  thoracic  nerve. 
Acromiothoracic  and  cephalic  veins. 


Outer  side.  I     Axillary     \        ■  Inner  side. 

Artery.         1 

Brachial  plexus.  I  i^"^'  portion.  /  Axillary  vein. 

Behind.  "(B? 

First  Intercostal  space  and  Intercostal  muscle. 
First  and  Second  digitations  of  Serratus  magnus. 
Long  thoracic  and  internal  anterior  thoracic  nerves. 

The  second  portion  is  covered,  in  front,  by  the  Pectoralis  major  and  minor  muscles;  behind 
it  is  the  posterior  cord  of  the  brachial  plexus  and  some  areolar  tissue  which  intervenes  between 
it  and  the  Subscapularis;  on  the  inner  side  is  the  axillary  vein,  separated  from  the  artery  by  the 
inner  cord  of  the  brachial  plexus  and  the  internal  anterior  thoracic  nerve;  on  the  outer  side  is 
the  outer  cord  of  the  brachial  plexus.  The  brachial  plexus  of  nerves  thus  surrounds  the  artery 
on  three  sides,  and  separates  it  from  direct  contact  with  the  vein  and  adjacent  muscles. 


Relations  of  the  Second  Portion  of  the  Axillary  Artery. 

In  front. 
Pectoralis  major  and  minor. 


Outer  side. 


Inner  side. 


Axillary  vein. 
Outer  cord  of  brachial  plexus.  \      porUon.     J  •     Inner  cord  of  brachial  plexus. 

Internal  anterior  thoracic  nerve. 

Behind. 
Subscapularis. 
Posterior  cord  of  brachial  plexus. 

The  third  portion  of  the  axillary  artery  extends  from  the  lower  border  of  the  Pectoralis 
minor  to  the  lower  border  of  the  tendon  of  the  Teres  major.  It  is  in  relation,  infroni,  with 
the  lower  part  of  the  Pectoralis  major  above,  being  covered  only  by  the  integument  and  fascia 
below;  behind,  with  the  lower  part  of  the  Subscapularis  and  the  tendons  of  the  Latissimus  dorsi 
and  Teres  major;  on  its  outer  side,  with  the  Coracobrachialis;  on  its  inner  or  thoracic  side,  with 
the  axillary  vein.  The  nerves  of  the  brachial  plexus  bear  the  following  relation  to  the  artery 
in  this  part  of  its  course;  on  the  outer  side  is  the  median  nerve  and  the  musculocutaneous  for  a 
short  distance;  on  the  inner  side,  the  ulnar  nerve  (between  the  vein  and  artery)  and  the  lesser 
internal  cutaneous  nerve  (to  the  inner  side  of  the  vein);  m  front  are  the  inner  head  of  the  median 
and  the  internal  cutaneous  nerve,  and  behind,  the  musculospiral  and  circumflex,  the  latter 
extending  only  as  far  as  the  lower  border  of  the  Subscapularis  muscle. 


THE  AXILLAE V  ARTERY  637 

Relations  of  the  Third  Portion  of  the  Axillary  Artery. 

In  front. 

Integument  and  fascia. 
Pectoralis  major. 
Inner  head  of  median  nerve. 
Internal  cutaneous  nerve. 

Outer  side.  /^  \^  Inner  side. 

Coracobrachialis.  i      Artery^      |  Ulnar  nerve. 

Median  nerve.  I  Third  portion.  /  Axillary  vein. 

Musculocutaneous  nerve.  V  /  Lesser  internal  cutaneous  nerve. 

Behind. 
Subscapularis. 

Tendons  of  Latissimus  dorsi  and  Teres  major. 
Musculospiral  and  circumflex  nerves. 

Peculiarities. — The  axillary  artery,  in  about  one  case  out  of  every  ten,  gives  off  a  large 
branch,  which  forms  either  one  of  the  arteries  of  the  forearm  or  a  large  muscular  trunk.  In  the 
first  set  of  cases  this  artery  is  most  frequently  the  radial  (1  in  3.3),  sometimes  the  ulnar  (1  in  72) 
and,  very  rarely,  the  interosseous  (1  in  506).  In  the  second  set  of  cases  the  trunk  has  been 
found  to  give  origin  to  the  subscapular,  circumflex,  and  profunda  arteries  of  the  arm.  Some- 
times only  one  of  the  circumflex,  or  one  of  the  profunda  arteries,  arises  from  the  trunk.  In 
these  cases  the  brachial  plexus  surrounded  the  trunk  of  the  branches  and  not  the  main  vessel. 

Suriace  Marking. — The  course  of  the  axillary  artery  may  be  marked  out  by  raising  the 
arm  to  a  right  angle  with  the  body  and  drawing  a  line  from  the  middle  of  the  clavicle  to  the 
point  where  the  tendon  of  the  Pectoralis  major  crosses  the  prominence  caused  by  the  Coraco- 
brachialis as  it  emerges  from  under  cover  of  the  anterior  fold  of  the  axilla.  The  third  portion 
of  the  artery  can  be  felt  pulsating  beneath  the  skin  and  fascia,  at  the  junction  of  the  anterior 
with  the  middle  third  of  the  space  between  the  anterior  and  posterior  folds  of  the  axilla,  close  to 
the  inner  border  of  the  Coracobrachialis  muscle. 

Applied  Anatomy. — Compression  of  the  vessel  may  be  required  in  the  removal  of  tumors 
or  in  amputation  of  the  upper  part  of  the  arm;  and  the  only  situation  in  which  this  can  be  efi'ect- 
ually  made  is  in  the  lower  part  of  its  course;  by  pressing  on  it  in  this  situation  from  within 
outward  against  the  humerus  the  circulation  may  be  effectually  arrested. 

With  the  exception  of  the  popliteal,  the  axillary  artery  is  perhaps  more  frequently  lacerated 
than  any  other  artery  in  the  body  by  violent  movements  of  the  extremity,  especially  in  those 
cases  where  its  coats  are  diseased.  It  has  occasionally  been  ruptured  in  attempts  to  reduce  old 
dislocations  of  the  shoulder-joint.  This  accident  is  most  likely  to  occur  during  the  preliminary 
breaking  down  of  adhesions,  in  consequence  of  the  artery  having  become  fixed  to  the  capsule 
of  the  joint.  Aneurism  of  the  axillary  artery  is  of  frequent  occurrence,  a  large  percentage  of 
the  cases  being  traumatic  in  their  origin,  due  to  the  violence  to  which  the  vessel  is  exposed  in 
the  varied,  extensive,  and  often  violent  movements  of  the  limb. 

The  application  of  a  ligature  to  the  axillary  artery  may  be  required  in  cases  of  aneurism  of 
the  upper  part  of  the  brachial  or  as  a  distal  operation  for  aneurism  of  the  subclavian ;  and  there 
are  only  t(vo  situations  in  which  the  vessel  can  be  secured — viz.,  in  the  first  and  in  the  third 
parts  of  its  course;  for  the  axillary  artery  at  its  central  part  is  so  deeply  seated,  and,  at  the  same 
time,  so  closely  surrounded  with  large  nerve  trunks,  that  the  application  of  a  ligature  to  it  in 
that  situation  would  be  almost  impracticable. 

In  the  third  part  of  its  course  the  operation  is  most  simple,  and  may  be  performed  in  the 
following  manner:  The  patient  being  placed  on  a  bed  and  the  arm  separated  from  the  side,  with 
the  hand  supinated,  an  incision  about  two  inches  in  length  is  made  through  the  integument 
forming  the  floor  of  the  axilla,  the  cut  being  a  little  nearer  to  the  anterior  than  the  posterior 
fold  of  the  axilla.  After  carefully  dissecting  through  the  areolar  tissue  and  fascia,  the  median 
nerve  and  axillary  vein  are  exposed;  the  former  having  been  displaced  to  the  outer  and  the 
latter  to  the  inner  side  of  the  arm,  the  elbow  being  at  the  same  time  bent,  so  as  to  relax  the 
structures  and  facilitate  their  separation,  the  ligature  may  be  passed  around  the  artery  from  the 
ulnar  to  the  radial  side. 

This  portion  of  the  artery  is  occasionally  crossed  by  a  muscular  slip,  the  axillary  arch,  derived 
from  the  Latissimus  dorsi,  which  may  mislead  the  surgeon  during  an  operation.  The  occasional 
existence  of  this  muscle  fasciculus  was  spoken  of  in  the  description  of  the  muscles.  It  may 
easily  be  recognized  by  the  transverse  direction  of  its  fibres. 


638  THE  VASCULAR  SYSTEMS 

The  first  portion  of  the  axillary  artery  may  be  tied  in  cases  of  aneurism  encroaching  so  far 
upward  that  a  ligature  cannot  be  applied  in  the  lower  part  of  its  course.  Notwithstanding  that 
this  operation  has  been  performed  in  some  few  cases,  and  with  success,  its  performance  is  attended 
with  much  difficulty  and  danger.  The  student  will  remark  that  in  this  situation  it  would  be 
necessary  to  divide  a  thick  muscle,  and,  after  incising  the  costocoracoid  membrane,  the  artery 
would  be  exposed  at  the  bottom  of  a  more  or  less  deep  space,  with  the  cephalic  and  axillary 
veins  in  such  relation  with  it  as  must  render  the  application  of  a  ligature  to  this  part  of  the  vessel 
particularly  hazardous.  Under  such  circumstances  it  is  an  easier,  and  at  the  same  time  more 
advisable,  operation  to  tie  the  subclavian  artery  in  the  third  part  of  its  course. 

The  vessel  in  the  first  part  of  its  course  can  best  be  secured  through  a  curved  incision  the 
convexity  of  which  is  downward.  This  incision  passes  from  a  point  half  an  inch  external  to 
the  sternoclavicular  joint  to  a  point  half  an  inch  internal  to  the  coracoid  process.  The  limb 
is  to  be  well  abducted  and  the  head  inclined  to  the  opposite  side,  and  this  incision  is  carried 
through  the  superficial  structures,  care  being  taken  to  avoid  the  cephalic  vein  at  the  outer 
angle  of  the  incision.  The  clavicular  origin  of  the  Pectoralis  major  is  then  divided  in  the  whole 
extent  of  the  wound.  The  arm  is  now  to  be  brought  to  the  side,  and  the  upper  edge  of  the 
Pectoralis  minor  defined  and  drawn  downward.  The  costocoracoid  membrane  is  to  be  care- 
fully divided  close  to  the  coracoid  process,  and  the  axillary  sheath  exposed;  this  is  to  be  opened 
with  especial  care,  on  account  of  the  vein  overlapping  the  artery.  The  needle  should  be  passed 
from  below,  so  as  to  avoid  wounding  the  vein. 

In  a  case  of  wound  of  the  vessel  the  general  practice  of  cutting  down  upon  and  tying  it  above 
and  below  the  wounded  point  should  be  adopted  in  all  cases. 

Branches. — The  branches  of  the  axillary  artery  are: 

V.         /?    J        J    f  Superior  thoracic.  j^  ,        ,   f  Long  thoracic. 

r  rom  first  pari  i  »  •  ^.i  ■  ^  fom  second  part  i  .  i      ^i 

•'        ^        (^Acromiothoracic.  ^         [Alar  thoracic. 

{Subscapular. 
Posterior  circumflex. 
Anterior  circumflex. 

The  superior  thoracic  (a.  thoracalis  suprema^  is  a  small  artery  which  arises 
from  the  axillary  separately  or  by  a  common  trunk  with  the  acromiothoracic. 
Running  forward  and  inward  along  the  upper  border  of  the  Pectoralis  minor,  it 
passes  between  it  and  the  Pectoralis  major  to  the  side  of  the  thorax.  It  supplies 
these  muscles  and  the  parietes  of  the  thorax,  anastomosing  with  the  internal  mam- 
mary and  intercostal  arteries. 

The  acromiothoracic  (a.  thoracoacromialis)  is  a  short  trunk  which  arises 
from  the  fore  part  of  the  axillary  artery,  its  origin  being  generally  overlapped 
by  the  upper  edge  of  the  Pectoralis  minor.  Projecting  forward  to  the  upper 
border  of  the  Pectoralis  minor,  it  divides  into  four  sets  of  branches — ^thoracic, 
acromial,  descending,  and  clavicular. 

The  thoracic  branches  (rami  pectorales),  two  or  three  in  number,  are  distributed 
to  the  Serratus  magnus  and  Pectoral  muscles,  anastomosing  with  the  intercostal 
branches  of  the  internal  mammary. 

The  acromial  branch  (ramus  acromialis)  is  directed  outward  toward  the  acro- 
mion, supplying  the  Deltoid  muscle,  and  anastomosing,  on  the  surface  of  the 
acromion,  with  the  suprascapular  and  posterior  circumflex  arteries. 

The  descending  or  humeral  branch  (ramus  delioideus)  runs  in  the  space  between 
the  Pectoralis  major  and  Deltoid,  in  the  same  groove  as  the  cephalic  vein,  and 
supplies  both  muscles. 

The  clavicular  branch  (ramus  clavicularis),  which  is  very  small,  runs  upward 
to  the  Subclavius  muscle. 

The  long  thoracic  or  the  external  mammary  (a.  thoracalis  lateralis)  -passes 
downward  and  inward  along  the  lower  border  of  the  Pectoralis  minor  to  the  side 
of  the  thorax,  supplying  the  Serratus  magnus,  the  Pectoral  muscles,  and  mammary 
gland,  and  sending  branches  across  the  axilla  to  the  axillary  nodes  and  Sub- 
scapularis;  it  anastomoses  with  the  interiml  mammary  and  intercostal  arteries. 


THE  AXILLARY  ARTERY 


639 


The  alar  thoracic  is  a  small  branch  which  supplies  the  nodes  and  areolar 
tissue  of  the  axilla.  Its  place  is  frequently  supplied  by  branches  from  some  of 
the  other  thoracic  arteries. 

The  subscapular  (a.  siibscapidaris),  the  largest  branch  of  the  axillary  artery, 
arises  opposite  the  lower  border  of  the  Subscapularis  muscle,  and  passes  down- 
ward and  backward  along  its  lower  margin  to  the  inferior  angle  of  the  scapula, 
where  it  anastomoses  with  the  long  thoracic  and  intercostal  arteries  and  with  the 
posterior  scapular  branch  of  the  trans- 
verse cervical,  and  terminates  by  sup- 
plying branches  to  the  muscles  in  the 
neighborhood.  About  an  inch  and  a 
half  from  its  origin  it  gives  off  a  large 
branch,  the  dorsalis  scapulae. 

The  dorsalis  scapulae  (a.  circumflexa 
scapulae)  is  generally  larger  than  the 
continuation  of  the  subscapular.  It 
curves  around  the  axillary  border  of  the 
scapula,  leaving  the  axilla  through  the 
space  between  the  Teres  minor  above, 
the  Teres  major  below,  and  the  long 
head  of  the  Triceps  externally  (Fig. 
457),  and  enters  the  infraspinous  fossa 
by  passing  under  cover  of  the  Teres 
minor,  where  it  anastomoses  with  the 
posterior  scapular  and  suprascapular 
arteries.  In  its  course  it  gives  off  two 
branches:  one  (infrascapular)  enters  the 
subscapular  fossa  beneath  the  Subscap- 
ularis, which  it  supplies,  anastomosing 
with  the  posterior  scapular  and  supra- 
scapular arteries;  the  other  is  continued 
along  the  axillary  border  of  the  scapula, 
between  the  Teres  major  and  minor, 
and,  at  the  dorsal  surface  of  the  inferior 
angle  of  the  bone,  anastomoses  with  the 
posterior  scapular.  In  addition  to  these, 
small  branches  are  distributed  to  the 
back  part  of  the  Deltoid  muscle  and  the 
long  head  of  the  Triceps,  anastomosing 
witli  an  ascending  branch  of  the  superior 
profunda  of  the  brachial. 

The  circumflex  arteries  wind  around 
the  surgical  neck  of  the  himierus.  The 
posterior  circumflex  (a.  circumflexa  hum- 
eri posterior)  (Fig.  457),  the  larger  of 
the  two,  arises  from  the  back  part  of  the 
axillary  opposite   the  lower   border    of 

the  Subscapularis  muscle,  and,  passing  backward  with  the  circumflex  veins  and 
nerve  through  the  quadrangular  space  bounded  by  the  Teres  major  and  minor,  the 
scapular  head  of  the  Triceps  and  the  humerus,  winds  around  the  neck  of  that  bone 
and  is  distributed  to  the  Deltoid  muscle  and  shoulder-joint,  anastomosing  with  the 
anterior  circumflex  and  acromial  thoracic  arteries,  and  with  the  superior  profunda 
branch  of  the  brachial  artery.  The  anterior  circumflex  (a.  circumflexa  humeri  ante- 
rior) (Figs.  457  and  459),  considerably  smaller  than  the  preceding,  arises  nearly 


Anastonotica 
magna. 


The  bnchial  artery 


640  THE  VASCULAR  SYSTE3IS 

opposite  that  vessel  from  the  outer  side  of  the  axillary  artery.  It  passes  horizon- 
tally outward  beneath  the  Coracobrachialis  and  short  head  of  the  Biceps  lying 
upon  the  fore  part  of  the  neck  of  the  humerus,  and,  on  reaching  the  bicipital 
groove,  gives  ofT  an  ascending  branch  which  passes  upward  along  the  groove 
to  supply  the  head  of  the  bone  and  the  shoulder-joint.  The  trunk  of  the  vessel 
is  then  continued  outward  beneath  the  Deltoid,  which  it  supplies,  and  anasto- 
moses with  the  posterior  circumflex  artery. 


The  Brachial  Artery  (A,  BrachiaUs)  (Fig.  460). 

The  brachial  artery  (a.  brachialis)  commences  at  the  lower  margin  of  the  tendon 
of  the  Teres  major,  and,  passing  down  the  inner  and  anterior  aspect  of  the  arm, 
terminates  about  half  an  inch  below  the  bend  of  the  elbow,  where  it  divides  into 
the  radial  and  ulnar  arteries.  At  first  the  brachial  artery  lies  internal  to  the  humerus, 
but  as  it  passes  down  the  arm  it  gradually  gets  in  front  of  the  bone,  and  at  the  bend 
of  the  elbow  it  lies  midway  between  the  two  condyles. 

Relations . — This  artery  is  superficial  throughout  its  entire  extent,  being  covered,  in  front, 
by  the  integument,  the  superficial  and  deep  fasciae;  the  bicipital  fascia  separates  it  opposite  the 
elbow  from  the  median  basilic  vein;  the  median  nerve  crosseg  it  at  its  middle;  behind,  it  is 
separated  from  the  long  head  of  the  Triceps  by  the  musculospiral  nerve  and  superior  profunda 
artery.  It  then  lies  upon  the  inner  head  of  the  Triceps,  next  upon  the  insertion  of  the  Coraco- 
brachialis, and  lastly  on  the  Brachialis  anticus.  By  its  outer  side,  it  is  in  relation  with  the 
commencement  of  the  median  nerve  and  the  Coracobrachialis  and  Biceps  muscles,  the  two 
muscles  overlapping  the  artery  to  a  considerable  extent.  By  its  iiiner  side,  its  upper  half  is  in 
relation  with  the  internal  cutaneous  and  ulnar  nerves,  its  lower  lialf  with  the  median  nerve. 
The  basilic  vein  lies  on  the  inner  side  of  the  artery,  but  is  separated  from  it  in  the  lower  part 
of  the  arm  by  the  deep  fascia.  The  brachial  artery  is  accompanied  by  two  venae  comites, 
which  lie  in  close  contact  with  the  artery,  being  connected  at  intervals  by  short  transverse 
communicating  branches. 


Plan  of  the  Relations  of  the  Brachial  Artery. 

In  front. 

Integument  and  fasciae. 
Bicipital  fascia,  median  basilic  vein. 
Median  nerve  (in  middle  portion). 
Overlapped  by  Coracobrachialis  and  Biceps. 

Outer  side.         \  /^  ^\  Inner  side. 

Median  nerve  (above).  j      Brachial      j      Internal  cutaneous  and  ulnar  nerves. 

Coracobrachialis.  \        '  '"^^'       /      Median  nerve  (below). 

Biceps.  ^^  y       Basilic  vein 

Behind. 

Triceps  (long  and  inner  heads). 
Musculospiral  nerve. 
Superior  profunda  artery. 
Coracobrachialis. 
Brachialis  anticus. 


A^^ATOMY  OF  THE  BEND  OF  THE  ELBOW  G41 

THE  ANATOMY  OF  THE   BEND  OF  THE  ELBOW  (ANTECUBITAL 

FOSSA). 

At  the  bend  of  the  elbow  the  brachial  artery  sinks  deeply  into  a  triangular  inter- 
val, the  antecubital  fossa,  the  base  of  \\hich  is  directed  upward,  and  may  be  repre- 
sented by  a  line  connecting  the  two  condyles  of  the  humerus;  the  sides  are  bounded, 
externally,  by  the  inner  edge  of  the  Brachioradialis;  inteniallij,  by  the  outer  "mar- 
gin of  the  Pronator  teres;  its  floor  is  formed  by  the  Brachialis  anticus  and  Supi- 
nator [brevis].  This  space  contains  the  brachial  artery  with  its  accompanying 
veins,  the  radial  and  ulnar  arteries,  the  median  and  musculospiral  nerves,  and  the 
tendon  of  the  Biceps.  The  brachial  artery  occupies  the  middle  line  of  this  space, 
and  divides  opposite  the  neck  of  the  radius  into  the  radial  and  ulnar  arteries;  it  is 
covered,  in.  front,  by  the  integument,  the  superficial  fascia,  and  the  median  basilic 
vein,  the  vein  being  separated  from  direct  contact  with  the  artery  by  the  bicipital 
fascia.  Behind,  it  lies  on  the  Brachialis  anticus,  which  separates  it  from  the 
elbow-joint.  The  median  nerve  Ires  on  the  inner  side  of  the  artery,  close  to  it 
above,  but  separated  from  it  below  by  the  coronoid  origin  of  the  Pronator  teres. 
The  tendon  of  the  Biceps  lies  to  the  outer  side  of  the  space,  and  the  musculospiral 
nerve  still  more  externally,  situated  upon  the  Supinator  [brevis]  and  partly  con- 
cealed by  the  Brachioradialis. 

Peculiarities  of  the  Brachial  Artery  as  Regards  its  Course. — The  brachial  artery,  accom- 
panied bv  the  median  nerve,  may  leave  die  inner  border  of  the  Biceps  and  descend  toward  the 
inner  condyle  of  the  humerus,  where  it  usually  cui\es  around  a  prominence  of  bone,  the  supra- 
condylar process.  From  this  process,  in  most  subjects,  a  fibrous  arch  is  thrown  over  the  artery. 
The  vessel  then  inclines  outward,  beneath  or  thi-ough  the  substance  of  the  Pronator  teres 
muscle,  to  the  bend  of  the  elbow.  The  variation  bears  considerable  homology  to  the  normal 
condition  of  the  artery  in  some  of  the  carnivora;  it  has  been  referred  to  in  the  description  of  the 
humerus  (page  181). 

As  Regards  its  Division. — Occasionally,  the  artery  is  divided  for  a  short  distance  at  its  upper 
part  into  two  trunks  which  are  united  above  and  below.  A  similar  peculiarity  occurs  in  the 
main  vessel  of  the  lower  limb. 

The  vessels  concerned  in  the  high  division  of  the  brachial  artery  are  three — viz.,  radial,  ulnar, 
and  interosseous.  Most  frequently  the  radial  is  given  off  high  up,  the  other  limb  of  the  bifurca- 
tion consisting  of  the  ulnar  and  interosseous.  In  some  instances  the  ulnar  arises  from  the 
brachial  above  the  ordinary  level,  and  the  radial  and  interosseous  form  the  other  limb  of  the 
division;  and  occasionally  the  interosseous  arises  high  up. 

Sometimes  long  slender  vessels,  vasa  aberrantia,  connect  the  brachial  or  axillary  arteries 
with  one  of  the  arteries  of  the  forearm  or  a  branch  from  them.  These  vessels  usually  join  the 
radial. 

Varieties  in  Muscular  Relations.' — The  brachial  artery  is  occasionally  concealed  in  some 
part  of  its  course  by  muscular  or  tendinous  slips  derived  from  the  Coracobrachialis,  Biceps, 
Brachialis  anticus,  and  Pronator  teres  muscles. 

Surface  Marking. — The  direction  of  the  brachial  artery  is  marked  by  a  line  drawn  along 
the  inner  edge  of  the  Biceps  from  the  junction  of  the  anterior  and  middle  thirds  of  the  axillary 
outlet  to  the  middle  of  the  front  of  the  elbow-joint. 

Applied  Anatomy.— Compression  of  the  brachial  artery  is  required  in  cases  of  amputation 
and  some  other  operations  in  the  arm  and  forearm;  and  it  will  be  observed  that  it  may  be  efi'ected 
in  almost  any  part  of  the  course  of  the  artery.  If  pressure  is  made  in  the  upper  part  of  the 
limb,  it  should  be  directed  from  within  outward,  and  if  in  the  lower  part,  from  before  backward, 
as  the  arterv  lies  on  the  inner  side  of  the  humerus  above  an<l  in  front  of  the  humerus  below. 
The  most  favorable  situation  is  about  the  middle  of  the  arm,  where  it  lies  on  the  tendon  of  the 
Coracobrachialis  on  the  inner  flat  side  of  the  humerus. 

The  application  of  a  ligature  to  the  brachial  artery  may  be  required  in  case  of  wound  of  the 
vessel  and  in  some  cases  of  wound  of  the  palmar  arch.  It  is  also  sometimes  necessary  in  cases 
of  aneurism  of  the  brachial,  the  radial,  ulnar,  or  interosseous  arteries.  The  artery  may  be 
secured  in  any  part  of  its  course.  The  chief  guides  in  determining  its  position  are  the  sur- 
face markings  produced  by  the  inner  margin  of  the  Coracobrachialis  and  Biceps,  the  known 

'  See  Struther's  Anatomical  and  Physiological  Observations. 


642  THE   VASCULAR  SYSTEMS 

course  of  the  vessel,  and  its  pulsation,  which  should  be  carefully  felt  for  before  any  operation  is 
performed,  as  the  vessel  occasionally  deviates  from  its  usual  position  in  the  arm.  In  whatever 
situation  the  operation  is  performed,  great  care  is  necessary,  on  account  of  the  extreme  thinness 
of  the  parts  covering  the  artery  and  the  intimate  connection  which  the  vessel  has  throughout  its 
whole  coiu-se  with  important  nerves  and  veins.  Sometimes  a  thin  layer  of  muscle  fibre  is 
met  with  concealing  the  artery;  if  such  is  the  case,  it  must  be  cut  across  in  order  to  expose  the 
vessel. 

In  the  upper  third  of  the  arm  the  artery  may  be  exposed  in  the  following  manner:  The  patient 
being  placed  supine  upon  a  table,  the  affected  limb  should  be  raised  from  the  side  and  the  hand 
supinated.  An  incision  about  two  inches  in  length  should  be  made  on  the  inner  side  of  the 
Coracobrachialis  muscle,  and  the  subjacent  fascia  cautiously  divided,  so  as  to  avoid  wounding 
the  internal  cutaneous  nerv-e  or  basilic  vein,  which  sometimes  runs  on  the  surface  of  the  artery 
as  high  as  the  axillary.  The  fascia  having  been  divided,  it  should  be  remembered  that  the  ulnar 
and  mternal  cutaneous  nerves  lie  on  the  inner  side  of  the  artery,  the  median  on  the  outer  side, 
the  latter  nerve  being  occasionally  superficial  to  the  artery  in  this  situation,  and  that  the  venae 
comites  are  also  in  relation  with  the  vessel,  one  on  either  side.  These  being  carefully  separated, 
the  aneurism  needle  should  be  passed  around  the  artery  from  the  inner  to  the  outer  side. 

In  the  case  of  a  high  division,  the  two  arteries  are  usually  placed  side  by  s'de;  and  if  they 
are  exposed  in  an  operation,  the  surgeon  should  endeavor  to  ascertain,  by  alternately  pressing 
on  each  vessel,  which  of  the  two  communicates  with  the  wound  or  aneurism,  when  a  ligature 
may  be  applied  accordingly;  or  if  pulsation  or  hemorrhage  ceases  only  when  both  vessels  are 
compressed,  both  vessels  may  be  tied,  as  it  may  be  concluded  that  the  two  communicate  above 
the  seat  of  disease  or  are  reunited. 

It  should  also  be  remembered  that  two  arteries  may  be  present  in  the  arm  in  a  case  of  high 
division,  and  that  one  of  these  may  be  found  along  the  inner  intermuscular  septum^  in  a  line 
toward  the  inner  condyle  of  the  humerus,  or  in  the  usual  position  of  the  brachial,  but  deeply 
placed  beneath  the  common  trunk;  a  knowledge  of  these  facts  w'ill  suggest  the  precautions 
necessary  in  every  case,  and  indicate  the  measures  to  be  adopted  when  anomalies  are  met  with. 

In  the  middle  of  the  arm  the  brachial  artery  may  be  exposed  by  making  an  incision  along 
the  inner  margin  of  the  Biceps  muscle.  The  forearm  being  bent  so  as  to  relax  the  muscle,  it 
should  be  drawn  slightly  aside,  and,  the  fascia  being  carefully  divided,  the  median  nerve  will  be 
exposed  lying  upon  the  artery  (sometimes  beneath) ;  this  being  drawn  inward  and  the  muscle 
outward,  the  artery  should  be  separated  from  its  accompanying  veins  and  secured.  In  this 
situation  the  inferior  profunda  may  be  mistaken  for  the  main  trunk,  especially  if  enlarged,  from 
the  collateral  circulation  having  become  established;  this  may  be  avoided  by  directing  the 
incision  externally  toward  the  Biceps,  rather  than  inward  or  backward  toward  the  Triceps. 

The  lower  part  of  tlw  brachial  artery  is  of  interest  from  a  surgical  point  of  view,  on  account  of  the 
relation  which  it  bears  to  the  veins  most  commonly  opened  in  venesection.  Of  these  vessels, 
the  median  basilic  is  the  largest  and  most  prominent,  and,  consecjuently,  the  one  usually  selected 
for  the  operation.  It  should  be  remembered  that  this  vein  runs  parallel  with  the  brachial 
artery,  from  which  it  is  separated  by  the  bicipital  fascia,  and  that  care  should  be  taken  in  opening 
the  vein  not  to  carry  the  incision  too  deeply,  so  as  to  endanger  the  artery. 

Collateral  Circulation. — After  the  application  of  a  ligature  to  the  brachial  artery  in  the 
upper  third  of  the  arm,  the  circulation  is  carried  on  by  branches  from  the  circumflex  and  sub- 
scapular arteries,  anastomosing  with  ascending  branches  from  the  superior  profunda.  If  the 
brachial  is  tied  below  the  origin  of  the  profunda  arteries,  the  circulation  is  maintained  by  the 
branches  of  the  profundse,  anastomosing  with  the  recurrent  radial,  ulnar,  and  interosseous 
arteries. 

Branches. — ^The  branches  of  the  brachial  artery  are: 

Superior  profunda.  Inferior  profunda. 

Nutrient.  Anastomotica  magna. 

Muscular. 

The  superior  profunda  artery  (a.  profunda  brachii)  arises  from  the  inner  ana 
back  part  of  the  brachial,  just  below  the  lower  border  of  the  Teres  major,  and 
passes  backward  to  the  interval  between  the  outer  and  inner  heads  of  the  Triceps 
muscle;  accompanied  by  the  musculospiral  nerve  it  winds  around  the  back  part  of 
the  shaft  of  the  humerus  in  the  spiral  groove,  between  the  outer  head  of  the  Triceps 
and  the  bone,  to  the  outer  side  of  the  humerus,  where  it  reaches  the  external  inter- 
muscular septum  and  divides  into  two  terminal  branches.  One  of  these  pierces 
the  external  intermuscular  septum^  and  descends,  in  company  with  the  musculo- 


AJSTATOMY  OF  THE  BEND  OF  THE  ELBOW 


643 


SadiaX  recurrent. 


spiral  nerve,  to  the  space  between  the  Brachialis  anticus  and  Brachioradialis, 
where  it  anastomoses  with  the  recurrent  branch  of  the  radial  artery;  while  the 
other,  much  the  larger  of  the  two, 
descends  along  the  back  of  the  exter- 
nal intermuscular  septum  to  the  back 
of  the  elbow-joint,  where  it  anasto- 
moses with  the  posterior  interosseous 
recurrent,  and  across  the  back  of  the 
humerus  with  the  posterior  ulnar  re- 
current, the  anastomotica  magna,  and 
inferior  profunda  (Fig.  464).  The 
superior  profunda  supplies  the  Tri- 
ceps muscle  and  gives  off  a  nutrient 
artery  which  enters  the  bone  at  the 
upper  end  of  the  musculospiral 
groove.  Near  its  commencement  it 
sends  off  a  branch  which  passes  up- 
ward between  the  external  and  long 
heads  of  the  Triceps  muscle  to  anas- 
tomose with  the  posterior  circumflex 
artery,  and,  while  in  the  groove,  a 
small  branch  which  accompanies 
a  branch  of  the  musculospiral  nerve 
through  the  substance  of  the  Tri- 
ceps muscle  and  ends  in  the  Anco- 
neus below  the  outer  condyle  of  the 
humerus. 

The  nutrient  artery  {a.  nutricia 
humeri)  of  the  shaft  of  the  humerus 
arises  from  the  brachial,  about  the 
middle  of  the  arm.  Passing  down- 
ward it  enters  the  nutrient  canal  of 
that  bone  near  the  insertion  of  the 
Coracobrachialis  mucle. 

The  inferior  profunda  (a.  collat- 
eralis  ulnaris  superior),  of  small  size, 
arises  from  the  brachial,  a  little  below  ^"■P'>-fi'='<'^'' ' 
the  middle  of  the  arm;  piercing 
the  internal  intermuscular  septum,  it 
descends  on  the  surface  of  the  inner 
head  of  the  Triceps  muscle  to  the 
space  between  the  inner  condyle  and 
olecranon,  accompanied  by  the  ulnar 
nerve,  and  terminates  by  anastomos- 
ing with  the  posterior  ulnar  recurrent 
and  anastomotica  magna.  It  some- 
times supplies  a  branch  to  the  front 
of  the  internal  condyle,  which  anas- 
tomoses with  the  anterior  ulnar  re- 
current. 

The  anastomotica  magna  (a.  collat- 
eralis  ulnaris  inferior)  arises  from  the 
brachial  about  two  inches  above  the  elbow-joint.  It  passes  transversely  inward  upon 
the  Brachialis  anticus,   and,  piercing  the  internal  intermuscular  septum,  winds 


Fig.  461. — The  radial  and  ulnar  arteries. 


644 


THE  VASCULAR  SYSTEMS 


around  the  back  of  the  humerus  between  the  Triceps  and  the  bone,  forming  an  arch 
above  the  olecranon  fossa  by  its  junction  with  the  posterior  articular  branch  of 
the  superior  profunda.  As  this  vessel  lies  on  the  Brachialis  anticus,  branches 
ascend  to  join  the  inferior  profunda,  and  others  descend  in  front  of  the  inner 
condyle  to  anastomose  with  the  anterior  ulnar  recurrent.  Behind  the  internal 
condyle  an  offset  is  given  off  which  anastomoses  with  the  inferior  profunda  and 
posterior  ulnar  recurrent  arteries  and  supplies  the  Triceps. 

The  muscular  (rami  musculares)  are  three  or  four  large  branches,  which  are 
distributed  to  the  muscles  in  the  course  of  the  artery.  They  supply  the  Coraco- 
brachialis,  Biceps,  and  Brachialis  anticus  muscles. 

The  Anastomosis  around  the  Elbow-joint  (Fig.  462). — The  vessels  engaged 
in  this  anastomosis  may  be  conveniently  divided  into  those  situated  in  front  and 

behind  the  internal  and  external 
condyles.  The  branches  anasto- 
mosing in  front  of  the  internal 
condyle  are  the  anastomotica 
magna,  the  anterior  ulnar  recur- 
rent, and  the  anterior  terminal 
branch  of  the  inferior  profunda. 
Those  hehind  the  internal  condyle 
are  the  anastomotica  magna,  the 
posterior  ulnar  recurrent,  and  the 
posterior  terminal  branch  of  the 
inferior  profunda.  The  branches 
anastomosing  in  front  of  the  ex- 
ternal condyle  are  the  radial  re- 
current and  the  anterior  terminal 
branch  of  the  superior  profunda. 
Those  hehind  the  external  condyle 
(perhaps  more  properly  described 
as  being  situated  between  the  ex- 
ternal condyle  and  the  olecranon) 
are  the  anastomotica  magna,  the 
interosseous  recurrent,  and  the 
posterior  terminal  branch  of  the 
superior  profunda.  There  is  also 
a  large  arch  of  anastomosis  above 
the  olecranon,  formed  by  the  in- 
terosseous recurrent,  joining  with 
the  anastomotica  magna  and 
posterior  ulnar  recurrent. 

From  this  description  it  will  be 
observed    that  the    anastomotica 
magna  is  the  vessel  most  engaged,  the  only  part  of  the  anastomosis  in  which  it  is 
not  employed  being  that  in  front  of  the  external  condyle. 


Anterior  branch  of 
superior  profunda 


Posterior  branch  oj 
superior  profunda 


Radial  recurrent 


Interosseous     g  I 
recurrent.      11 


Superior  profunda. 


M  \\ Inferior  profunda. 


Anastomotica 
7nagna. 


Anterior  ulnar 
recurrent. 


Posterior  idnar 
recurrent. 


Interosseous. 
Postei  lor 
znterosseous. 

^       Anterior 

interosseous. 


i  462. — Diagram  of  the  anastomosis  around  the  right 
elbow-joint. 


The  Radial  Artery  (A.  Radialis)  (Figs.  461,  463). 

The  radial  artery  appears,  from  its  direction,  to  be  the  continuation  of  the 
brachial,  but  in  size  it  is  smaller  than  the  ulnar.  It  commences  at  the  bifurcation 
of  the  brachial,  just  below  the  bend  of  the  elbow,  and  passes  along  the  radial  side  of 
the  forearm  to  the  wrist;  it  then  winds  backward,  around  the  outer  side  of  the 
carpus,  beneath  the  Extensor  tendons  of  the  thumb,  to  the  upper  end  of  the 


THE  RADIAL  ARTERY  645 

space  between  the  metacarpal  bones  of  the  thumb  and  index  finger,  and  finally 
passes  forward,  between  the  two  heads  of  the  First  dorsal  interosseous  muscle, 
into  the  palm  of  the  hand,  where  it  crosses  the  metacarpal  bones  to  the  ulnar  border 
of  the  hand,  to  form  the  deep  palmar  arch.  At  its  termination  it  anastomoses  with 
the  profunda  branch  of  the  ulnar  artery.  The  relations  of  this  vessel  may  thus 
be  conveniently  divided  into  three  parts — viz.,  in  the  forearm,  at  the  back  of  the 
wrist,  and  in  the  hand. 

Relations. — In  the  forearm  this  vessel  extends  from  opposite  the  neck  of  the  radius  to  the 
fore  part  of  the  styloid  process,  being  placed  to  the  inner  side  of  the  shaft  of  the  bone  above  and 
in  front  of  it  below.  It  is  overlapped  in  the  upper  part  of  its  course  by  the  fleshy  belly  of  the 
Brachioradialis  muscle;  throughout  the  rest  of  its  course  it  is  superficial,  being  covered  by  the 
integument,  the  superficial  and  deep  fascije.  In  its  course  downward  it  lies  upon  the  tendon 
of  the  Biceps,  the  Supinator  [brevis],  the  Pronator  teres,  the  radial  origin  of  the  Flexor  subliniis 
digitorum,  the  Flexor  longus  polHcis,  the  Pronator  quadratus,  and  the  lower  extremity  of  the 
radius.  In  the  upper  third  of  its  course  it  lies  between  the  Brachioradialis  and  the  Pronator 
teres;  in  the  lower  two-thirds,  between  the  tendons  of  the  Brachioradialis  and  the  Flexor  carpi 
radialis.  The  radial  nerve  lies  close  to  the  outer  side  of  the  artery  in  the  middle  third  of  its 
course,  and  some  filaments  of  the  musculocutaneous  nerve,  after  piercing  the  deep  fascia,  run 
along  the  lower  part  of  the  artery  as  it  winds  around  the  wrist.  The  vessel  is  accompanied  by 
venae  comites  throughout  its  whole  course. 


Plan  of  the  Relations  of  the  Radial  Artery  in  the  Forearm. 

In  front. 

Skin,  superficial  and  deep  fasciae. 
Brachioradialis. 


Inner  side.  /  \  Outer  side. 


Pronator  teres.  I     pore'i'rm"     ]  Brachioradialis. 

Flexor  carpi  radialis.  \  J  Radial  nerve  (middle  third). 

Behind. 

Tendon  of  Biceps. 

Supinator  [brevis]. 

Pronator  teres. 

Flexor  sublimis  digitorum. 

Flexor  longus  pollicis. 

Pronator  quadratus. 

Radius. 

At  the  wrist,  as  it  winds  around  the  outer  side  of  the  carpus  from  the  styloid  process  to  the 
first  interosseous  space,  it  lies  upon  the  external  lateral  ligament,  and  then  upon  the  scaphoid 
bone  and  trapezium,  being  covered  by.  the  Extensor  tendons  of  the  thumb,  subcutaneous  veins, 
some  filaments  of  the  radial  nerve,  and  the  integument.  It  is  accompanied  by  two  veins  and  a 
filament  of  the  musculocutaneous  nerve. 

In  the  hand  it  passes  from  the  upper  end  of  the  first  interosseous  space,  between  the  heads 
of  the  Abductor  indicis  or  First  dorsal  interosseous  muscle,  transversely  accross  the  palm,  to 
the  base  of  the  metacarpal  bone  of  the  little  finger,  where  it  anastomoses  with  the  communi- 
cating branch  from  the  ulnar  artery,  forming  the  deep  palmar  arch. 

The  deep  palmar  arch  (arcus  volaris  frofundus)  (Fig.  463)  lies  upon  the 
carpal  extremities  of  the  metacarpal  bones  and  the  Interossei  muscles,  being 
covered  by  the  Adductor  obliquus  pollicis,  the  Flexor  tendons  of  the  fingers,  the 
Lumbricales,  the  Opponens,  and  Flexor  brevis  minimi  digiti.  Alongside  of  it, 
but  running  in  the  opposite  direction — that  is  to  say,  from  within  outward — is 


646  '         THE  VASCULAR  SYSTEMS 

the  deep  branch  of  the  ulnar  nerve.     The  branches  of  the  deep  palmar  arch  are  the 
palmar  interosseous,  perforating  and  palmar  recurrent  vessels  (page  648). 

Peculiarities. — The  origin  of  the  radial  artery,  according  to  Quain,  is,  in  nearly  one  case  in 
eight,  higher  than  usual;  more  frequently  arising  from  the  axillary  or  upper  part  of  the  brachial, 
than  from  the  lower  part  of  this  vessel.  The  variations  in  the  position  of  this  vessel  in  the  arm 
and  at  the  bend  of  the  elbow  have  been  already  mentioned.  In  the  forearm  it  deviates  less  fre- 
quently from  its  position  than  the  ulnar.  It  has  been  found  lying  over  the  fascia  instead  of 
beneath  it.  It  has  also  been  observed  superficial  to  the  Brachioradialis,  instead  of  under  its 
inner  border;  and  in  turning  around  the  wrist  it  has  been  seen  lying  over,  instead  of  beneath, 
the  Extensor  tendons  of  the  thumb. 

Surface  Markiug. — The  position  of  the  radial  artery  in  the  forearm  is  represented  by  a  line 
drawn  from  the  outer  border  of  the  tendon  of  the  Biceps  in  the  centre  of  the  hollow  in  front 
of  the  elbow-joint  with  a  straight  course  to  the  inner  side  of  the  forepart  of  the  styloid  process 
of  the  radius. 

Aj^lied  Anatomy. — The  radial  artery  is  much  exposed  to  injury  in  its  lower  third,  and  is 
frequently  wounded.  The  injury  is  often  followed  by  a  traumatic  aneurism,  for  which  the 
operation  of  extirpation  or  laying  open  the  sac  after  securing  the  vessel  above  and  below  is 
required. 

The  operation  of  tying  the  radial  artery  is  required  in  cases  of  wounds  either  of  its  trunk  or 
of  some  of  its  branches,  or  for  aneurism;  and  it  will  be  observed  that  the  vessel  may  be  exposed 
in  any  part  of  its  course  through  the  forearm  without  the  division  of  any  muscle  fibres.  The 
operation  in  the  middle  or  inferior  third  of  the  forearm  is  easily  performed,  but  in  the  upper 
third,  near  the  elbow,  it  is  attended  with  some  difficulty,  from  the  greater  depth  of  the  vessel 
and  from  its  being  overlapped  by  the  Brachioradialis  muscle.. 

To  tie  the  artery  in  the  upper  third  an  incision  three  inches  in  length  should  be  made  thi-ough 
the  integument,  in  a  line  drawn  from  the  centre  of  the  bend  of  the  elbow  to  the  front  of  the  styloid 
process  of  the  radius,  avoiding  the  branches  of  the  median  vein;  the  fascia  of  the  arm  being 
divided  and  the  Brachioradialis  drawn  a  little  outward,  the  artery  will  be  exposed.  The  venae 
comites  should  be  carefully  separated  from  the  vessel,  and  the  hgature  passed  from  the  radial  to 
the  ulnar  side. 

In  the  middle  third  of  the  forearm  the  artery  may  be  exposed  by  making  an  incision  of  similar 
length  on  the  inner  margin  of  the  Brachioradialis.  In  this  situation  the  radial  nerve  lies  in 
close  relation  with  the  outer  side  of  the  artery,  and  should,  as  well  as  the  veins,  be  carefully 
avoided. 

In  the  lower  third  the  artery  is  easily  secured  by  dividing  the  integument  and  fascia  in  the 
interval  between  the  tendons  of  the  Brachioradialis  and  Flexor  carpi  radialis  muscles. 

Branches  (Figs.  461  and  463). — ^The  branches  of  the  radial  artery  may  be 
divided  into  three  groups,  corresponding  with  the  three  regions  in  which  the  vessel 
is  situated. 

f  Radial  recurrent.  C  Posterior  radial  carpal. 

In  the    J  Muscular.  At  the  J  First  dorsal  interosseous. 

Forearm   ]  Anterior  radial  carpal.  Wrist   ]  Dorsales  pollicis. 
t  Superficialis  volae.  I.  Dorsalis  indicis. 

r  Princeps  pollicis. 
Radialis  indicis. 
In  the  Hand  ■{  Perforating. 

Palmar  interos.seous. 
.  Palmar  recurrent. 

The  radial  recurrent  (a.  recurrens  radialis)  (Fig.  463)  is  given  off  imme- 
diately below  the  elbow.  It  ascends  between  the  branches  of  the  musculospiral 
nerve  lying  on  the  Supinator  [brevis],  and  then  between  the  Brachioradialis  and 
Brachialis  anticus,  supplying  these  muscles  and  the  elbow-joint,  and  anastomosing 
with  the  anterior  terminal  branch  of  the  superior  profunda. 

The  muscular  branches  (rami  musculares)  are  distributed  to  the  muscles  on 
the  radial  side  of  the  forearm. 


THE  RADIAL  ARTERY  647 

The  anterior  radial  carpal  {ramus  carpeus  volaris)  (Fig.  463)  is  a  small  vessel 
which  arises  from  the  radial  artery  near  the  lower  border  of  the  Pronator  quad- 
ratus,  and,  running  inward  in  front  of  the  radius,  anastomoses  with  the  ante- 
rior carpal  branch  of  the  ulnar  artery.  In  this  way  an  arterial  anastomosis,  the 
anterior  carpal  arch  (rete  carpi  volare)  is  formed  in  front  of  the  wrist;  it  is  joined  by 
branches  from  the  anterior  interosseous  above,  and  by  recurrent  branches  from 
the  deep  palmar  arch  below,  and  gives  off  branches  which  descend  to  supply  the 
articulations  of  the  wrist  and  carpus. 

The  superficialls  volae  (ramus  volaris  superficialis)  (Fig.  463)  arises  from  the 
radial  artery,  just  where  this  vessel  is  about  to  wind  around  the  wrist.  Running 
forward,  it  passes  between,  occasionally  over,  the  muscles  of  the  thumb,  which  it 
supplies,  and  sometimes  anastomoses  with  the  palmar  portion  of  the  ulnar  artery, 
completing  the  superficial  palmar  arch.  This  vessel  varies  considerably  in  size; 
usually  it  is  very  small,  and  terminates  in  the  muscles  of  the  thumb;  sometimes 
it  is  as  large  as  the  continuation  of  the  radial. 

The  posterior  radial  carpal  (ramus  carpeus  dorsalis)  (Fig.  464)  is  a  small 
vessel  which  arises  from  the  radial  artery  beneath  the  Extensor  tendons  of  the 
thiunb;  crossing  the  carpus  transversely  to  the  inner  border  of  the  hand,  it  anasto- 
moses with  the  posterior  carpal  branch  of  the  ulnar,  forming  the  posterior  carpal 
arch  (i-ete  carpi  dorsale),  which  is  joined  by  the  termination  of  the  anterior  inter- 
osseous artery.  From  this  arch  are  given  off  descending  branches,  the  dorsal 
interosseous  arteries  (aa.  metacarpeae  do'rsales)  for  the  second,  third,  and  fourth 
interosseous  spaces,  which  run  forward  on  the  Second,  Third,  and  Fourth  dorsal 
interossei  muscles,  and  divide  into  dorsal  digital  branches  (aa.  digitales  dorsales), 
which  supply  the  adjacent  sides  of  the  index,  middle,  ring,  and  little  fingers, 
respectively,  communicating  with  the  digital  arteries  of  the  superficial  palmar 
arch.  The  dorsal  interosseous  arteries  anastomose  with  the  perforating  branches 
from  the  deep  palmar  arch. 

The  first  dorsal  interosseous  arises  beneath  the  Extensor  tendons  of  the  thumb, 
sometimes  with  the  posterior  radial  carpal;  running  forward  on  the  Second  dorsal 
interosseous  muscle,  it  divides  into  two  dorsal  digital  branches,  which  supply  the 
adjoining  sides  of  the  index  and  middle  fingers;  it  forms  anastomoses  similar 
to  those  of  the  two  other  dorsal  interosseous  arteries. 

The  dorsales  poUicis  (Fig.  464)  are  two  vessels  which  run  along  the  sides  of 
the  dorsal  aspect  of  the  thumb.  They  usually  ari.se  separately,  but  occasionally 
by  a  common  trunk,  near  the  base  of  the  first  metacarpal  bone. 

The  dorsalis  indicis  (Fig.  464),  also  a  small  branch,  runs  along  the  radial  side 
of  the  back  of  the  index  finger,  sending  a  few  branches  to  the  Abductor  indicis. 

The  princeps  pollicis  (a.  princeps  pollicis)  (Fig.  463)  arises  from  the  radial  just  as 
it  turns  inward  to  the  deep  part  of  the  hand;  it  descends  between  the  Abductor 
indicis  and  Adductor  oblicjuus  pollicis,  then  between  the  Adductor  transversus 
pollicis  and  Adductor  obliquus  pollicis,  along  the  ulnar  side  of  the  metacarpal 
bone  of  the  thumb,  to  the  base  of  the  first  phalanx,  where  it  lies  beneath  the  tendon 
of  the  Flexor  longus  pollicis  and  divides  into  two  branches.  These  make  their  ap- 
pearance between  the  inner  and  outer  insertions  of  the  Adductor  obliquus  pollicis, 
and  run  along  the  sides  of  the  palmar  aspect  of  the  thumb,  forming  on  the  palmar 
surface  of  the  last  phalanx  an  arch,  from  which  branches  are  distributed  to  the 
integument  and  subcutaneous  tissue  of  the  thiunb. 

The  radialis  indicis  (a.  volaris  indicis  radialis)  (Fig.  463)  arises  close  to  the  pre- 
ceding, descends  between  the  First  dorsal  interosseous  and  Adductor  transversus 
pollicis,  and  runs  along  the  radial  side  of  the  index  finger  to  its  extremity,  where  it 
anastomoses  v/ith  the  collateral  digital  artery  from  the  s  uperficial  palmar  arch.  At  the 
lower  border  of  the  Adductor  transversus  pollicis  this  vessel  anastomoses  with  the 
princeps  pollicis,  and  gives  a  communicating  branch  to  the  superficial  palmar  arch. 


648 


THE   VASCULAR  SYSTEMS 


Anastomotica 
magna. 


Anterior  ulnar 
recurrent. 

Posterior  tdnar 
recurrent. 


The  perforating  arteries  {rami  perforantes)  (Fig.  463),  three  in  number,  pass 
backward  from  the  deep  palmar  arch  through  the  second,  third,  and  fourth  inter- 
osseous spaces  and  between  the 
»  .v,  heads  of  the  corresponding  Inter- 

ossei,  to  anastomose  with  the 
dorsal  interosseous  arteries. 

The  palmar  interosseous  (aa. 
vietacarpeae  volares)  (Fig.  463), 
three  or  four  in  number,  arise 
from  the  convexity  of  the  deep 
palmar  arch;  they  run  downward 
upon  the  Interossei  muscles,  and 
anastomose  at  the  clefts  of  the 
fingers  with  the  digital  branches 
of  the  superficial  arch. 

The  palmar  recurrent  branches 
arise  from  the  concavity  of  the 
deep  palmar  arch.  They  ascend 
in  front  of  the  wrist,  supplying 
the  carpal  articulations  and  anas- 
tomosing with  the  anterior  carpal 
arch. 


The  Ulnar  Artery  (A.  Ubiaris) 

(Figs.  461,  463). 

The  ulnar  artery,  the  larger  of 
the  two  terminal  branches  of  the 
brachial,  commences  a  little  below 
the  bend  of  the  elbow,  and  passes 
obliquely  across  the  inner  side  of 
the  forearm  to  a  point  about  mid- 
way between  the  elbow  and  the 
wrist.  It  then  runs  along  the 
ulnar  border  to  the  wrist,  crosses 
the  annular  ligament  on  the  radial 
side  of  the  pisiform  bone,  and 
immediately  beyond  this  bone 
divides  into  two  branches  which 
enter  into  the  formation  of  the 
superficial  and  deep  palmar 
arches. 


Fig.  463  — Ulnar  and  radial  arteries      Deep  view. 


Relations. — In  the  Forearm.  —  In 

its  upper  half  it  is  deeply  seated,  being 
covered  by  all  the  superficial  Flexor  muscles,  excepting  the  Flexor  carpi  ulnaris;  the  median 
nerve  is  in  relation  with  the  inner  side  of  the  artery  for  about  an  inch  and  then  crosses  the  vessel, 
being  separated  from  it  by  the  deep  head  of  the  Pronator  teres;  it  lies  upon  the  Brachialis 
anticus  and  Flexor  profundus  digitorum  muscles.  In  the  lower  half  of  the  forearm  it  lies  upon 
the  Flexor  profundus,  being  covered  by  the  integument,  the  superficial  and  deep  fasciae,  and  is 
placed  between  the  Flexor  carpi  ulnaris  and  Flexor  sublimis  digitorum  muscles.  It  is  accom- 
panied by  two  venae  comites;  the  ulnar  nerve  lies  on  its  inner  side  for  the  lower  h\'0-thirds  of 
its  extent,  and  a  small  branch  from  the  nerve  descends  on  the  lower  part  of  the  vessel  to  the 
palm  of  the  hand. 


THE  ULNAR  ARTERY  649 

Plan  of  Relations  of  the  Ulnar  Artery  in  the  Forearm. 

In  front. 

TJnn  r  H  7/ .(Superficial  layer  of  Flexor  muscles. 
"'  •'  (Median  nerve. 

Lower  Half — Superficial  and  deep  fasciae. 


Inner  side. 


Outer  side. 


Flexor  carpi  uluaris.  ... 

Ulnar  nerve  (lower  two-thirds).  \  !''"«"'"•     /  Flexor  sublimis  digitorum. 


Behind. 

Brachialis  anticus. 

Flexor  profundus  digitorum. 

At  the  wrist  (Fig.  461)  the  ulnar  artery  is  covered  by  the  integument  and  fascia,  and  lies 
upon  the  anterior  annular  ligament.  On  its  inner  side  is  the  pisiform  bone,  and  somewhat 
behind  the  artery,  the  ulnar  nerve.  The  nerve  and  artery  are  crossed  by  a  band  of  fibres,  which 
extends  from  the  pisiform  bone  to  the  anterior  annular  ligament. 

Peculiarities. — The  idnar  artery  has  been  found  to  vary  in  its  origin  nearly  in  the  propor- 
tion of  one  in  thirteen  cases,  in  one  case  arising  lower  than  usual,  about  two  or  three  inches 
below  the  elbow,  and  in  all  other  cases  much  higher,  the  brachial  being  a  more  frequent  source 
of  origin  than  the  axillary. 

Variations  in  the  position  of  this  vessel  are  more  frequent  than  in  the  radial.  When  its  origin 
is  normal,  the  course  of  the  vessel  is  rarely  changed.  When  it  arises  high  up  it  is  almost  in- 
variably superficial  to  the  Flexor  muscles  in  the  forearm,  lying  commonly  beneath  the  fascia, 
more  rarely  l)et\\  een  the  fascia  and  integument.  In  a  few  cases  its  position  was  subcutaneous  in 
the  upper  ]iai-t  of  the  forearm,  subaponeurotic  in  the  lower  part. 

Surface  Marking. — On  account  of  the  curved  direction  of  the  ulnar  artery  the  line  on  the 
surface  of  the  body  which  indicates  its  course  is  somewhat  complicated.  First,  draw  a  line  from 
the  front  of  the  internal  condyle  of  the  hmnerus  to  the  radial  side  of  the  pisiform  bone;  the 
lower  two-thirds  of  this  line  represents  the  course  of  the  middle  and  lower  third  of  the  ulnar 
artery.  Secondly,  draw  a  line  from  the  centre  of  the  antecubital  fossa  to  the  Junction  of  the 
upper  and  middle  third  of  the  first  line;  this  represents  the  course  of  the  upper  third  of  the 
artery. 

Applied  Anatomy. — The  application  of  a  ligatiu-e  to  this  vessel  is  required  in  cases  of  wound 
of  the  artery  or  of  its  branches,  or  in  consequence  of  aneurism.  In  the  upper  half  of  the  fore- 
arm the  artery  is  deeply  seated  beneath  the  Superficial  Flexor  muscles,  and  the  application  of  a 
ligature  in  this  situation  is  attended  with  some  difficulty.  An  incision  is  to  be  made  in  the 
course  of  a  line  drawn  from  the  front  of  the  internal  condyle  of  the  humerus  to  the  outer  side 
of  the  pisiform  bone,  so  that  the  centre  of  the  incision  is  three  fingers'  breadth  below  the  internal 
condyle.  The  skin  and  superficial  fascia  having  been  divided  and  the  deep  fascia  exposed, 
the  white  line  which  separates  the  Flexor  carpi  ulnaris  from  the  other  Flexor  muscles  is  to  be 
sought  for,  and  the  fascia  incised  in  this  line.  The  Flexor  carpi  ulnaris  is  now  to  be  carefully 
separated  from  the  other  muscles,  when  the  ulnar  nerve  will  be  exposed,  and  must  be  drawn 
aside. 

Some  little  distance  below  the  nerve  the  artery  will  be  found  accompanied  by  its  venae 
comites,  and  it  may  be  ligated  by  passing  the  needle  from  within  outward.  In  the  middle  and 
lower  third  of  the  forearm  this  vessel  may  be  easily  secured  by  making  an  incision  on  the  radial 
side  of  the  tendon  of  the  Flexor  carpi  ulnaris;  the  deep  fascia  being  divided,  and  the  Flexor 
carpi  ulnaris  and  its  companion  muscle,  the  Flexor  sublimis,  being  separated  from  each  other, 
the  vessel  will  be  exposed,  accompanied  by  its  venae  comites,  the  ulnar  nerve  lying  on  its  inner 
side. 

The  veins  being  separated  from  the  artery,  the  ligature  should  be  passed  from  the  ulnar  to 
the  radial  side,  taking  care  to  avoid  the  ulnar  nerve. 


650  THE   VASCULAR  SYSTEMS 

Branches  (Figs.  463  and  464). — The  branches  of  the  ulnar  artery  may  be 
arranged  in  the  following  groups: 

Anterior  ulnar  recurrent. 

Posterior  ulnar  recurrent. 

Forearm  {  t  ,  f  Anterior  interosseous, 

interosseous       i  u    .    •      •  ^ 

1^  rostenor  mterosseous. 

L  Muscular. 
Tu-  ■  f  j  Anterior  ulnar  carpal. 

\  Posterior  ulnar  carpal. 
rr      if  Profunda. 

\  Superficial  palmar  arch. 

The  anterior  ulnar  recurrent  (a.  recurrentes  ulnaris  anterior)  (Fig.  463)  arises  im- 
mediately below  the  elbow-joint,  passes  upward  and  inward  between  the  Brachialis 
anticus  and  Pronator  teres,  supplies  twigs  to  those  muscles,  and,  in  front  of  the 
inner  condyle,  anastomoses  with  the  anastomotica  magna  and  inferior  profunda. 
The  posterior  ulnar  recurrent  (a.  recurrentes  ulnaris  posterior)  (Figs.  463  and 
464)  is  much  larger,  and  arises  somewhat  lower  than  the  preceding.  It  passes 
backward  and  inward,  beneath  the  Flexor  sublimis,  and  ascends  behind  the  inner 
condyle  of  the  humerus.  In  the  interval  between  this  process  and  the  olecranon 
it  lies  beneath  the  Flexor  carpi  ulnaris,  and  ascending  between  the  heads  of  that 
muscle,  in  relation  with  the  ulnar  nerve;  it  supplies  the  neighboring  muscles  and 
joint,  and  anastomoses  with  the  inferior  profunda,  anastomotica  magna,  and 
interosseous  recurrent  arteries. 

The  interosseous  artery  (a.  interossea  communis)  (Fig.  463)  is  a  short  trunk 
about  half  an  inch  in  length,  and  of  considerable  size,  which  arises  immediately 
Ijelow  the  tuberosity  of  the  radius,  and,  passing  backward  to  the  upper  border  of 
the  intei'osseous  membrane,  divides  into  two  branches,  the  anterior  and  posterior 
interosseous. 

The  anterior  interosseous  (a.  interossea  volaris)  (Fig.  463)  passes  down  the  fore- 
arm on  the  anterior  surface  of  the  interosseous  membrane,  to  which  it  is  connected 
by  a  thin  aponeurotic  arch.  It  is  accompanied  by  the  interosseous  branch  of  the 
median  nerve,  and  overlapped  by  the  contiguous  margins  of  the  Flexor  profundus 
digitorum  and  Flexor  longus  pollicis  muscles,  giving  off  in  this  situation  muscular  - 
branches  and  the  nutrient  arteries  of  the  radius  and  ulna.  At  the  upper  border 
of  the  Pronator  quadratus  a  branch,  anterior  communicating  artery,  descends 
beneath  the  muscle  to  anastomose  in  front  of  the  carpus  with  the  anterior  carpal 
arch.  The  continuation  of  the  artery  passes  behind  the  Pronator  quadratus,  and, 
piercing  the  interosseous  membrane,  reaches  the  back  of  the  forearm,  and  anasto- 
moses with  the  posterior  interosseous  artery  (Fig.  464) .  It  then  descends  to  the 
back  of  the  wrist  to  join  the  posterior  carpal  arch.  The  anterior  interosseous  gives 
off  a  long,  slender  branch,  the  comes  nervi  mediana  artery  (a.  mediana),  which 
accompanies  the  median  nerve  and  gives  branches  to  its  substance.  This  artery 
is  sometimes  much  enlarged,  and  accompanies  the  nerve  into  the  palm  of  the  hand. 
The  posterior  interosseous  artery  (a.  interossea  dorsales)  (Figs.  463  and  464) 
passes  backward  through  the  interval  between  the  oblique  ligament  and  the 
upper  border  of  the  interosseous  membrane.  It  appears  between  the  contiguous 
borders  of  the  Supinator  [brevis]  and  the  Extensor  ossis  metacarpi  pollicis,  and 
runs  down  the  back  part  of  the  forearm,  between  the  superficial  and  deep  layer 
of  muscles,  to  both  of  which  it  distributes  branches  (Fig.  464).  Where  it  lies 
upon  the  Extensor  ossis  metacarpi  pollicis  and  the  Extensor  brevis  pollicis,  it  is 
accompanied  by  the  posterior  interosseous  nerve.  At  the  lower  part  of  the  forearm 
it  anastomoses  with  the  termination  of  the  anterior  interosseous  artery  and  with 
the  posterior  carpal  arch.     Then,  continuing  its  course  over  the  head  of  the  ulna, 


THE  ULNAR  ARTERY 


051 


superior  profunda. 


Ana.itomotica 
magna. 


Posterior  ulnar 
recurrent. 


Posterior  ntierosseous. 


it  joins  the  jjosterior  carpal  l^raneh  of  the  uhiar  artery.     This  artery  gives  ofF, 
near  its  origin,  the  interosseous  recurrent  l)ranch. 

The  interosseous  recurrent  artery  (a.  intcrossea  recurrens)  (Fig.  464)  is  a  large 
vessel  which  ascends  to  the  interval  between  the  external  condyle  and  olecranon, 
on  or  through  the  fibres  of  the  Supinator  [brevis],  but  beneath  the  Anconeus, 
anastomosing  with  a  branch 

from   tire    superior   profunda,  /  J^  _  Descending  branch  from 

and  with  the  posterior  ulnar  / 

recurrent    and   anastomotica 

magna. 

The  muscular  branches 
(rami  musculares)  are  dis- 
tributed to  the  muscles  along 
the  ulnar  side  of  the  forearm. 

The  anterior  ulnar  carpal 
{ramus  carpeus  volaris)  (Fig. 

463)  is  a  small  vessel  which 
crosses  the  front  of  the  car- 
pus beneath  the  tendons  of 
the  Flexor  profundus  and  in- 
osculates with  a  correspond- 
ing branch  of  the  radial  artery. 

The  posterior  ulnar  carpal 
(ramus  carpeus  dorsalis)  (Fig. 

464)  arises  immediately  above 
the  pisiform  bone,  and  winds 
backward  beneath  the  tendon 
of  the  Flexor  carpi  ulnaris; 
it  passes  across  the  dorsal 
surface  of  the  carpus  be- 
neath the  Extensor  tendons 
to  anastomose  with  a  corre- 
sponding branch  of  the  radial 
artery  and  complete  the  pos- 
terior carpal  arch  (rete  carpi 
dorsale)  (Fig.  464).  Imme- 
diately after  its  origin  it  gives 
off  a  small  branch,  which  runs 
along  the  ulnar  side  of  the  fifth 
metacarpal  bone,  and  supplies 
the  ulnar  side  of  the  dorsal  sur- 
face of  the  little  finger. 

The  profunda  branch  (rom- 
us  volaris  profundus)  (Fig. 
463)  passes  deeply  inward  be- 
tween the  Abductor  minimi 
digiti  and  Flexor  brevis  min- 
imi digiti,  near  their  origins; 
it  anastomoses  with  the  termi- 
nation of  the  radial  artery, 
completing  the  deep  palmar 
arch. 

The  continuation  of  the  trimk  of  the  ulnar  artery  in  the  hand  forms  the  greater 
part  of  the  superficial  palmar  arch. 


Termination  of  an^ 
tenor  interosseous. 


Posterior  carpal 

(radial). 
Radial. 
^Do7'saUs  poinds, 
■salis  indicis. 


Fig.  464. — Artertes  of  the  back  of  the  forearm 


652  THE   VASCULAR  SYSTEMS 

The  superficial  palmar  arch  (circus  volaris  superficialis)  (Fig.  461)  is  formed 
by  the  uhiar  artery  in  tlie  hand,  and  is  usually  completed  on  the  outer  side  by 
a  branch  from  the  radialis  indicis,  but  sometimes  by  the  superficialis  volae  or  the 
princeps  pollicis  of  the  radial  artery.  The  arch  passes  across  the  palm,  describing 
a  curve,  with  its  convexity  downward. 

Relations. — The  superficial  palmar  arch  is  covered  by  the  skin,  the  Palmaris  brei'is,  and 
the  palmar  fascia.  It  lies  upon  the  annular  ligament,  the  Flexor  brevis  and  Opponens  minimi 
digiti,  the  tendons  of  the  Flexor  sublimis  digitorum,  the  Lumbrical  muscles,  and  the  divisions 
of  the  median  and  ulnar  nerves. 

Plan  of  the  Relations  of  the  Superficial  Palmar  Arch. 


Behind. 
Annular  ligament. 
Flexor  brevis  minimi  digiti. 
Opponens  minimi  digiti. 
Tendons  of  Flexor  sublimis  digitorum. 
Lumbrical  muscles. 
Branches  of  median  and  ulnar  nerves. 

Branches. — The  branches  of  the  Superficial  palmar  arch  are: 

Four  Digital  Arteries. 

Four  digital  arteries  (aa.  dig  Hales  volares  covnntines')  (Fig.  461)  are  given  off 
from  the  convexity  of  this  arch.  The  innermost  accompanies  the  inner  digital 
branch  of  the  ulnar  nerve,  and  runs  along  the  ulnar  side  of  the  little  finger;  it  is 
joined  by  a  twig  from  the  deep  palmar  arch  or  from  the  innermost  palmar  inter- 
osseous artery.  The  three  outer  run  downward  in  front  of  the  three  inner  inter- 
osseous spaces,  superficial  to  the  corresponding  nerves  and  Lumbrical  muscles. 
A  little  above  the  interdigital  clefts  they  are  joined  by  the  palmar  interosseous 
arteries,  and  by  the  inferior  perforating  branches  of  the  dorsal  interosseous  arteries. 
Each  then  divides  into  coliateral  digital  arteries  (aa.  digitales  volares  propriae) 
for  the  supply  of  the  contiguous  sides  of  the  index,  middle,  ring,  and  little  fingers. 
These  collateral  branches  lie  behind  the  corresponding  digital  nerves;  they 
anastomose  freely  in  the  subcutaneous  tissue  of  the  finger  tip  and  by  smaller 
branches  near  the  interphalangeal  joints.  Each  supplies  a  couple  of  dorsal 
branches  which  anastomose  with  the  dorsal  digital  arteries,  and  supply  the  soft 
parts  on  the  back  of  the  second  and  third  phalanges,  including  the  matrix  of  the 
finger  nail. 

Surface  Marking. — The  superficial  palmar  arch  is  represented  by  a  curved  line,  starting 
from  the  outer  side  of  the  pisiform  bone  and  carried  downward  as  far  as  the  middle  third  of 
the  palm,  and  then  ciu-ved  outward  on  a  \exe\  with  the  upper  (proximal)  end  of  the  cleft  between 
the  thumb  and  index  finger.  The  deep  palmar  arch  is  situated  about  half  an  inch  nearer  to  the 
carpus. 

Applied  Anatomy. — Wounds  of  the  palmar  arches  are  of  special  interest,  and  are  always 
difficult  to  deal  with.  When  the  superficial  arch  is  wounded  it  is  generally  possible,  by  enlarging 
the  wound  if  necessary,  to  secure  the  vessel  and  tie  it;  or  in  cases  where  it  is  found  impossible  to 


THE  DESCENDING  AORTA  653 

encircle  the  vessel  with  a  ligature,  a  pair  of  hemostatic  forceps  may  be  applied  and  left  on  for 
twenty-four  or  forty-eight  hours.  Wounds  of  the  deep  arch  are  not  so  easily  dealt  with.  It  may 
be  possible  to  secure  the  vessel  by  ligature  or  by  forcipressure  forceps,  which  may  be  left  on; 
or,  failing  in  this,  the  wound  may  be  carefully  plugged  with  gauze  and  an  outside  dressing  care- 
fully bandaged  on.  The  plug  should  be  allowed  to  remain  untouched  for  three  or  four  days. 
In  wounds  of  the  deep  palmar  arch  a  ligature  may  be  ap])lied  to  the  bleeding  points  from  the 
dorsum  of  the  hand  by  resection  of  the  upper  part  of  the  third  metacarpal  bone.  It  is  useless 
in  these  cases  to  ligate  one  of  the  arteries  of  the  forearm  alone,  and,  indeed,  simultaneous  liga- 
tion of  both  radial  and  ulnar  arteries  above  the  wrist  is  often  unsuccessful,  on  account  of  the 
anastomosis  carried  on  by  the  carpal  arches.  Therefore,  if  unable  to  ligate  the  divided  ends 
of  the  arch,  upon  the  failure  of  pressure  to  arrest  hemorrhage,  it  is  expedient  to  apply  a  ligature 
to  the  brachial  artery. 

ARTERIES  OF  THE  TRUNK.  . 

THE  DESCENDING  AORTA  (Figs.  465,  466). 

The  descending  aorta  is  divided  into  two  portions,  the  thoracic  and  abdominal, 
in  correspondence  with  the  two  great  cavities  of  the  trunk  in  which  it  is  situated. 

The  Thoracic  Aorta  [aorta  thoracalis)  (Fig.  465). — The  thoracic  aorta  is 
contained  in  the  back  part  of  the  posterior  mediastinum  and  commences  at  the 
lower  border  of  the  fourth  thoracic  vertebra,  on  the  left  side,  and  terminates  at 
the  aortic  opening  in  the  Diaphragm,  in  front  of  the  lower  border  of  the  last 
thoracic  vertebra.  At  its  commencement  it  is  situated  on  the  left  side  of  the 
vertebral  column;  it  approaches  the  median  line  as  it  descends,  and  at  its 
termination  lies  directly  in  front  of  the  vertebral  column.  The  direction  of  this 
vessel  being  influenced  by  the  vertebral  column,  upon  which  it  rests,  it  describes 
a  curve  which  is  concave  forward  in  the  thoracic  region.  As  the  branches  given 
off  from  it  are  small,  the  diminution  in  the  size  of  the  vessel' is  inconsiderable. 

Relations. — It  is  in  relation,  in  front,  from  above  downward,  with  the  root  of  the  left  lung, 
the  pericardium,  the  oesophagus,  and  the  Diaphragm;  behind,  with  the  vertebral  column  and 
the  azygos  minor  veins;  on  the  right  side,  with  the  vena  azygos  major  and  thoracic  duct;  on  the 
left  side,  with  the  left  pleura  and  lung.  The  oesophagus,  with  its  accompanying  nerves,  lies  on 
the  right  side  of  the  aorta  above;  but  at  the  lower  part  of  the  thorax  it  passes  in  front  of  the 
aorta,  and  close  to  the  Diaphragm  is  situated  to  its  left  side. 

Plan  of  the  Relations  of  the  Thoracic  Aorta. 

In  front. 

Root  of  left  lung. 
Pericardium. 
(Esophagus  (middle). 
Diaphragm. 

Right  side.  /  >v  Left  side. 

CEsophagus  (above).  (      Thoracic      I  Pleura. 

Vena  azygos  major.  I       '^°'''*"      j  Left  lung. 

Thoracic  duct.  \  /  CEsophagus  (below). 

Behind. 

Vertebral  column. 

Superior  and  inferior  azygos  minor  veins. 

Peculiarities. — The  aorta  is  occasionally  found  to  be  obliterated  at  a  particular  spot — viz., 
at  the  junction  of  the  arch  with  the  thoracic  aorta  just  below  the  ligamentum  arteriosum.  Whether 
this  is  the  result  of  disease  or  of  congenital  malformation  is  immaterial  to  oiu-  present  purpose; 
it  affords  an  interesting  opportunity  of  observing  the  resoiu-ces  of  the  collateral  circulation. 


654  THE  VASCULAR  SYSTEMS 

The  course  of  the  anastomosing  vessels,  by  which  the  blood  is  brought  from  the  upper  to  the 
lower  part  of  the  artery,  will  be  found  well  described  in  an  account  of  two  cases  in  the  Fafho- 
logical  Transactiowt,  vols,  viii  and  x.  In  the  former  (p.  162)  Mr.  Sydney  Jones  thus  sums  up 
the  detailed  description  of  the  anastomosing  vessels:  "The  principal  communications  by  which 
the  circulation  was  carried  on  were:  First,  the  internal  mammary,  anastomosing  with  the 
intercostal  arteries,  with  the  phrenic  of  the  abdominal  aorta  by  means  of  the  musculophrenic 
and  comes  nervi  phrenici,  and  largely  with  the  deep  epigastic.  Secondly,  the  superior  inter- 
costal, anastomosing  anteriorly  by  means  of  a  large  branch  with  the  first  aortic  intercostal, 
and  posteriorly  with  the  posterior  branch  of  the  same  artery.  Thirdly,  the  inferior  thyroid, 
by  means  of  a  branch  about  the  size  of  an  ordinary  radial,  formed  a  communication  with  the 
first  aortic  intercostal.  Fourthly,  the  transverse  cervical,  by  means  of  very  large  communi- 
cations with  the  posterior  branches  of  the  intercostals.  Fifthly,  the  branches  (of  the  subclavian 
and  axillary)  going  to  the  side  of  the  thorax  were  large,  and  anastomosed  freely  with  the  lateral 
branches  of  the  intercostals."  In  the  second  case  also  (vol.  x,  p.  97)  Mr.  Wood  describes  the 
anastomoses  in  a  somewhat  similar  manner,  adding  the  remark  that  "the  blood  which  was 
brought  into  the  aorta  through  the  anastomoses  of  the  intercostal  arteries  appeared  to  be  ex- 
pended principally  in  supplying  the  abdomen  and  pelvis,  while  the  supply  to  the  lower  extremities 
had  passed  through  the  internal  mammary  and  epigastrics." 

Applied  Anatomy. — The  student  should  now  consider  the  effects  likely  to  be  produced  by 
aneurism  of  the  thoracic  aorta,  a  disease  of  common  occurrence.  When  we  consider  the  great 
depth  of  the  vessel  from  the  surface  and  the  number  of  important  structures  which  surround  it 
on  every  side,  it  may  easily  be  conceived  what  a  variety  of  obscure  symptoms  may  arise  from  dis- 
ease of  this  part  of  the  arterial  system,  and  how  they  may  be  liable  to  be  mistaken  for  those  of 
other  affections.  Aneurism  of  the  thoracic  aorta  most  usually  extends  backward  along  the  left 
side  of  the  vertebral  column,  producing  absorption  of  the  bodies  of  the  vertebrte,  with  curvature 
of  the  spine;  while  the  irritation  or  pressure  on  the  spinal  cord  will  give  rise  to  pain,  either  in 
the  thorax,  back,  or  loins,  with  radiating  pain  in  the  left  upper  intercostal  spaces,  from  pressure 
on  the  intercostal  nerves;  at  the  same  time  the  tumor  may  project  backward  on  each  side  of  the 
vertebral  column,  beneath  the  integument,  as  a  pulsating  swelling,  simulating  abscess  connected 
with  diseased  bone,  or  it  may  displace  the  oesophagus  and  compress  the  lung  on  one  or  the 
other  side.  If  the  tumor  extend  forward,  it  may  press  upon  and  displace  the  heart,  giving  rise 
to  palpitation  and  other  symptoms  of  disease  of  that  organ ;  or  it  may  displace,  or  even  com- 
press, the  oesophagus,  causing  pain  and  difficulty  of  swallowing,  as  in  stricture  of  that  tube;  and 
ultimately  even  open  into  it  by  ulceration,  producing  fatal  hemorrhage.  If  the  disease  extends 
to  the  right  side,  it  may  press  upon  the  thoracic  duct;  or  it  may  burst  into  the  pleural  cavity 
or  into  the  trachea  or  lung;  and,  lastly,  it  may  open  into  the  posterior  mediastinum.  The 
diagnosis  of  thoracic  aneurism  is  facilitated  by  the  use  of  the  a-'-rays. 

Branches  of  the  Thoracic  Aorta. — 

I  Bronchial.  ^f   ,  ^  , 

^      ,  ,  I  Intercostal. 

n    ■       r  ^  '  Parietal  ■{  Subcostal, 
rencardial.  1  ^         •        i 

Mediastinal.  I  Superior  phrenic. 

The  bronchial  arteries  (aa.  hronchiales)  are  the  nutrient  vessels  of  the  lungs, 
and  vary  in  number,  size,  and  origin.  There  is,  as  a  rule,  only  one  right  bronchial 
artery,  which  arises  from  the  first  aortic  intercostal,  or  from  the  left  bronchial. 
The  left  bronchial  arteries,  usually  two  in  number,  arz.se  from  the  thoracic  aorta, 
one  a  little  lower  than  the  other.  Each  vessel  runs  along  the  back  part  of  the 
corresponding  bronchus,  dividing  and  subdividing  along  the  bronchial  tubes, 
supplying  them,  the  cellular  tissue  of  the  lungs,  the  bronchial  nodes,  and  the 
oesophagus. 

The  oesophageal  arteries  (aa.  oesophageae),  usually  four  or  five  in  number, 
arise  from  the  front  of  the  aorta,  and  pass  obliquely  downward  to  the  oesophagus, 
forming  a  chain  of  anastomoses  along  that  tube,  anastomosing  with  the  oesopha- 
geal branches  of  the  inferior  thyroid  arteries  above,  and  with  ascending  branches 
from  the  phrenic  and  gastric  arteries  below. 

The  pericardial  (rami  pericardiaci)  are  a  few  small  vessels,  irregular  in  their 
origin,  distributed  to  the  pericardium. 

The  mediastinal  branches  (rami  mediastinales)  are  numerous  small  vessels 
which  supply  the  nodes  and  loose  areolar  tissue  in  tne  posterior  mediastinum. 


THE  DESCENDING  AORTA 


655 


The  intercostal  arteries  {aa.  intercostales)  (Fig.  465)  arise  from  the  back  of  the 
aorta.  The  aortic  intercostals  are  usually  nine  in  number  on  each  side,  the  two 
superior  intercostal  spaces  being  supplied  by  the  superior  intercostal,  a  branch 
of  the  subclavian.  The  right  aortic  intercostals  are  longer  than  the  left,  on  account 
of  the  position  of  the  aorta  on  the  left 
side  of  the  vertebral  column;  they  pass 
across  the  bodies  of  the  vertebrte,  behind 
the  oesophagus,  thoracic  duct,  and  the 
vena  azygos  major,  and  are  covered  by  the 
right  lung  and  pleura.  The  left  aortic 
intercostals  run  backward  on  the  sides 
of  the  vertebrae  and  are  covered  by  the 
left  lung  and  'pleura;  the  two  upper  are 
crossed  by  the  left  superior  intercostal 
vein,  the  lower  vessels  by  the  azygos  minor 
veins.  Opposite  the  heads  of  the  ribs 
the  sympathetic  cord  passes  downward 
in  front  of  them,  and  the  splanchnic 
nerves  also  descend  in  front  of  the  lower 
arteries.  Each  artery  crosses  the  cor- 
responding intercostal  space  obliquely 
toward  the  angle  of  the  upper  rib  and 
thence  is  continued  forward  in  the  sub- 
costal groove.  It  is  placed  at  first  be- 
tween the  pleura  and  the  posterior  inter- 
costal membrane,  then  pierces  this 
membrane  and  lies  between  it  and  the 
External  intercostal  muscle  as  far  as  the 
rib  angle;  from  this  onward  it  runs  be- 
tween the  External  and  Internal  inter- 
costal muscles  and  anastomoses  with  the 
anterior  intercostal  branches  of  the  inter- 
nal mammary  or  musculophrenic.  Each 
intercostal  artery  is  accompanied  by  a 
vein  and  nerve,  the  former  being  above, 
and  the  latter  below,  except  in  the  upper 
intercostal  spaces,  where  the  nerve  is  at 
first  above  the  artery.  The  first  aortic 
intercostal  anastomoses  with  the  superior  intercostal  branch  of  the  subclavian, 
and  the  last  two  intercostals  continue  anteriorly  from  the  intercostal  spaces  into 
the  abdominal  wall,  anastomosing  with  the  superior  epigastric,  subcostal  and 
lumbar  arteries. 

Branches. — Each  intercostal  artery  gives  off  numerous  muscular  and  cutaneous 
branches. 


Fig.  465. — Thoncic  aorta      (Testut.) 


Posterior  or  dorsal. 
Muscular. 


Collateral  intercostal. 
Lateral  cutaneous. 


The  posterior  or  dorsal  branch  {ramus  posterior')  runs  with  the  posterior  division 
of  a  spinal  nerve  and  passes  backward  through  a  small  opening  which  is  bounded 
above  and  helow  by  the  necks  of  the  ribs  and  adjacent  transverse  processes, 
internally  by  the  vertebral  body,  and  externally  by  the  anterior  costotransverse 
ligament.  It  gives  off  a  spinal  branch,  which  enters  the  vertebral  canal  through 
the  intervertebral  foramen,  is  distributed  to  the  spinal  cord  and  its  membranes. 


656 


THE    VASCULAR  SYSTEMS 


and  to  the  bodies  of  the  vertebrae  in  the  same  manner  as  the  lateral  spinal 
branches  from  the  vertebral. 

The  collateral  intercostal  branch  comes  off  from  the  intercostal  artery  near  the 
angle  of  the  rib,  and  descends  to  the  upper  border  of  the  rib  below,  along  which  it 
courses  to  anastomose  with  the  anterior  intercostal  branch  of  the  internal  mam- 
mary. 


Fig.  466. — The  abdominal  aorta  and  its  branches. 


Muscular  branches  {rami  musculares)  are  given  to  the  Intercostal  and  Pectoral 
muscles  and  to  the  Serratus  magnus;  they  anastomose  with  the  superior  and 
long  thoracic  branches  of  the  axillary  artery. 

The  lateral  cutaneous  branches  (rami  cutanei  lateraJes)  accompany  the  lateral 
cutaneous  branches  of  the  intercostal  nerves,  and  divide  into  anterior  and  posterior 
branches. 


THE  ABDOMINAL  AORTA  G57 

Mammary  branches  are  given  off  by  the  intercostal  arteries  in  the  third,  fourth, 
and  fifth  spaces.  They  supply  the  mammary  gland,  and  increase  considerably 
in  size  during  the  period  of  lactation. 

Applied  Anatomy.  The  liusitinn  of  the  intercostal  vessels  should  be  borne  in  mind  in 
perforniini;-  tin-  (i|iciaiiiin  of  pnran  iili:-;ix  tJioracis.  The  puncture  should  never  be  made  nearer 
the  middle  hue  pnstc-riorly  thnii  .he  angle  of  the  rib,  as  the  artery  crosses  the  space  internal  to 
this  point.  In  the  lateral  portion  of  the  thorax,  where  the  puncture  is  iisually  made,  the  artery 
lies  at  the  upper  part  of  the  intercostal  space,  and  therefore  the  puncture  should  be  made  just 
above  the  upper  border  of  the  rib  forming  the  lower  boundary  of  the  space. 

The  Abdominal  Aorta  (aorta  ahdominalis)  (Fig.  466). — The  abdominal  aorta 
commences  at  the  aortic  opening  of  the  Diaphragm,  in  front  of  the  lower  border 
of  the  body  of  the  last  thoracic  vertebra,  and,  descending  a  little  to  the  left  side  of 
the  vertebral  column,  terminates  on  the  body  of  the  fourth  lumbar  vertebra, 
usually  a  little  to  the  left  of  the  middle  line,'  by  dividing  into  the  two  common 
iliac  arteries.  It  diminishes  rapidly  in  size,  in  consequence  of  the  many  large 
branches  which  it  gives  off.  As  it  lies  upon  the  bodies  of  the  vertebra?,  the 
curve  which  it  describes  is  convex  forward,  the  greatest  convexity  corresponding 
to  the  third  lumbar  vertebra,  which  is  a  little  above  and  to  the  left  side  of  the 
umbilicus. 

Relations. — It  is  covered,  in  front,  by  the  lesser  omentum  and  stomach,  behind  which  are 
the  branches  of  the  coeliac  axis  and  the  solar  plexus;  below  these,  by  the  splenic  vein,  the  pan- 
creas, the  left  renal  vein,  the  transverse  portion  of  the  duodenum,  the  mesentery,  and  aortic 
plexus.  Behind,  it  is  separated  from  the  lumbar  vertebrae  and  intervening  disks  by  the  anterior 
common  ligament  and  left  lumbar  veins.  On  the  riyht  side  it  is  in  relation  with  the  inferior 
vena  cava  (the  right  crus  of  the  Diaphragm  being  interposed  above),  the  vena  azygos  major, 
thoracic  duct,  and  right  semilunar  ganglion;  on  the  left  side,  with  the  gangliated  cord  of  the 
sympathetic  and  left  semilunar  ganglion  the  fourth  part  of  the  duodenum  and  some  coils  of  the 
small  intestine. 

Plan  of  the  Relations  of  the  Abdominal  Aorta. 

In  front. 

Lesser  omentum  and  stomach. 
Branches  of  the  coeliac  axis  and  solar  plexus. 
Splenic  vein. 
Pancreas. 
Left  renal  vein. 
Transverse  duodenum. 
Mesentery. 
Aortic  plexus. 
Right  side.  Left  side. 

Right  crus  of  Diaphragm.  /  \  Gangliated  cord. 

Inferior  vena  cava.  j    Abdominal   \  Left  semilunar  ganglion. 

Vena  azygos  major. 

Thoracic  duct. 

Right  semilunar  ganglion. 

Belmid. 

Left  lumbar  veins. 
Vertebral  column. 

Surface  Marking.— In  order  to  map  out  the  abdominal  aorta  on  the  surface  of  the  abdomen, 
a  line  must  be  drawn  from  the  middle  line  of  the  body,  on  a  level  with  the  costal  extremity  ol 
the  seventh  costal  cartilage,  doAvnward  and  slightly  to  the  left,  so  that  it  just  skirts  the  umbilicus, 
to  a  zone  drawn  around  the  body  opposite  the  highest  point  of  the  crest  of  the  ilium.     This  point 

1  Lord  Lister,  having  accurately  examined  30  bodies  in  order  to  'ascertain  the  exact  point  of  termination  of 
this  vessel,  found  it  "either  absolutelj',  or  almost  absolutely,  mesal  in  15.  while  in  13  it  deviated  more  or  les8 
to  the  left,  and  in  2  was  slightly  to  the  right"  (System  of  Surgery,  edited  by  T.  Holmes.  2d  ed.,  \-ol.  v.  p  632). 


658  THE  VASCULAR  SYSTEMS 

is  generally  half  an  inch  below  and  to  the  left  of  the  umbilicus,  but  as  the  position  of  this  struc- 
ture varies  with  the  obesity  of  the  individual,  it  is  not  a  reliable  landmark  as  to  the  situation  oi 
the  bifurcation  of  the  aorta. 

Applied  Anatomy. — Aneurisms  of  the  ahdominal  aorta  near  the  coeliac  axis  communicate  in 
nearly  equal  proportion  with  the  anterior  and  posterior  parts  of  the  artery. 

When  an  aneurismal  sac  is  connected  with  the  back  part  of  the  abdominal  aorta,  it  usually 
produces  absorption  of  the  bodies  of  the  vertebrae,  and  forms  a  pulsating  tumor  that  presents 
itself  in  the  left  hypochondriac  or  epigastric  regions,  and  is  accompanied  by  symptoms  of  dis- 
turbance in  the  alimentary  canal.  Pain  is  invariably  present,  and  is  usually  of  two  kinds — a 
fixed  and  constant  pain  in  the  back,  caused  by  the  tumor  pressing  on  or  displacing  the  branches 
of  the  solar  plexus  and  splanchnic  nerves;  and  a  sharp  lancinating  pain,  radiating  along  those 
branches  of  the  lumbar  nerves  which  are  pressed  on  by  the  tumor;  hence  the  pain  in  the  loins, 
the  testes,  the  hypogastrium,  and  in  the  lower  limb  (usually  of  the  left  side).  This  form  of 
aneurism  usually  bursts  into  the  peritoneal  cavity  or  behind  the  peritoneum  in  the  left  hypo- 
chondriac region;  or  it  may  form  a  large  aneurismal  sac,  extending  down  as  low  as  Poupart's 
ligament;  hemorrhage  in  these  cases  being  generally  very  extensive,  but  slowly  produced,  and 
not  rapidly  fatal. 

When  an  aneurismal  sac  is  connected  with  the  front  of  the  aorta  near  the  coeliac  axis  it  forms 
a  pulsating  tumor  in  the  left  hypochondriac  or  epigastric  region,  usually  attended  with  symptoms 
of  disturbance  of  the  alimentary  canal,  as  nausea,  dyspepsia,  or  constipation,  and  is  accom- 
panied by  pain,  which  is  constant,  but  nearly  always  fixed  in  the  loins,  epigastrium,  or  some 
part  of  the  abdomen;  the  radiating  pain  being  rare,  as  the  lumbar  nerves  are  seldom  implicated. 
This  form  of  aneurism  may  burst  into  the  peritoneal  cavity  or  behind  the  peritoneum,  between 
the  layers  of  the  mesentery,  or,  more  rarely,  into  the  duodenum;  it  seldom  extends  backward 
so  as  to  affect  the  vertebral  column. 

The  abdominal  aorta  has  been  tied  several  times,  and  although  none  of  the  patients  perma- 
nently recovered,  still,  as  Prof.  Keen's  lived  forty-eight  days,  the  possibility  of  the  reestablish- 
ment  of  the  circulation  is  proved.  In  the  lower  animals  this  artery  has  been  often  successfully 
tied.  The  chief  difficulty  consists  in  isolating  the  artery  in  consequence  of  its  great  depth;  and 
the  embarrassment  resulting  from  the  proximity  of  the  aneurismal  tumor,  and  the  great  prob- 
ability of  disease  in  the  vessel  itself,  add  to  the  dangers  and  difficulties  of  this  formidable  opera- 
tion. 

The  collateral  circulation  would  be  carried  on  by  the  anastomosis  between  the  internal  mam- 
mary and  the  deep  epigastric;  by  the  free  communication  between  the  superior  and  inferior 
mesenteries  if  the  ligature  were  placed  above  the  latter  vessel:  or  by  the  anastomosis  between 
the  inferior  mesenteric  and  the  internal  pudic  when  (as  is  more  common)  the  point  of  ligation 
is  below  the  origin  of  the  inferior  mesenteric;  and  possibly  by  the  anastomoses  of  the  lumbar 
arteries  with  the  branches  of  the  internal  iliac. 

Branches. — The  branches  of  the  abdominal  aorta  comprise  visceral,  parietal,  and 
terminal  arteries.     The  branches  in  order  of  origin  are  as  follows : 

1.  Right  and  left  inferior  phrenics  (p). 

(  Gastric  ~1 

2.  Coeliac  axis  <  Hepatic  >{v.). 

(Splenic  j 

3.  Right  and  left  suprarenals  (v.). 

4.  Right  and  left  first  lumbars  (p.). 

5.  Superior  mesenteric  {v.). 

6.  Right  and  left  renal  («.). 

7.  Right  and  left  spermatics  or  ovarian  (».). 

8.  Right  and  left  second  lumbars  {p.). 

9.  Inferior  mesenteric  (d.). 

10.  Right  and  left  third  lumbars  (p.). 

11.  Right  and  left  fourth  lumbars  {p.). 

12.  Right  and  left  common  iliac  it.). 

13.  Middle  sacral  (^p.). 

{]}.),  Parietal;  (».),  visceral;  (t.),  terminal. 

The  inferior  phrenic  arteries  (aa.  phrenicae  inferiores)  (Fig.  466)  are  two  small 
vessels  which  present  much  \'ariety  in  their  origin.     They  may  arise  separately 


THE  ABDOMINAL  AORTA 


659 


from  the  front  of  the  aorta,  immediately  above  the  coeliac  axis,  or  by  a  common 
truniv,  which  may  spring  either  from  the  aorta  or  from  the  coehac  axis.  Some- 
times one  is  derived  from  tlie  aorta,  and  the  other  from  one  of  the  renal  arteries. 
In  only  one  out  of  thirty-six  cases  examined  did  these  arteries  arise  as  two  separate 
vessels  from  the  aorta.  They  diverge  from  one  another  across  the  crura  of  the 
Diaphragm,  and  then  pass  obliquely  upward  and  outward  upon  the  under  surface 
of  the  Diaphragm.  The  left  phrenic  passes  behind  the  oesophagus  and  runs  for- 
ward on  the  left  side  of  the  oesophageal  opening.  The  right  phrenic  passes  behind 
the  inferior  vena  cava,  and  ascends  along  the  right  side  of  the  aperture  for  trans- 
mitting that  vein.  Near  the  back  part  of  the  central  tendon  each  vessel  divides 
into  two  branches.  The  internal  branch  runs  forward  to  the  front  of  the  thorax, 
supplying  the  Diaphragm,  and  anastomosing  with  its  fellow  of  the  opposite  side, 
and  with  the  musculophrenic  and  comes  nervi  phrenici  branches  of  the  internal 
mammary.  The  external  branch  passes  toward  the  side  of  the  thorax  and  anasto- 
moses with  the  intercostal  arteries  and  with  the  musculophrenic.  The  internal 
branch  of  the  right  phrenic  gives  off  a  few  vessels  to  the  inferior  vena  cava,  and 
the  left  one  some  branches  to  the  oesophagus.     Each  vessel  also  sends  glandular 


Cy»tic  artery 


Fio.  467— The  ccel 


and  its  branches,  the  liver  having  been  raised  and  the  lesser  omentum  removed. 


branches  {rami  suprarenales  superior)  to  the  suprarenal  glands  of  its  own  side. 
The  spleen  and  the  liver  also  receive  a  few  branches  from  the  left  and  right 
vessels  respectively. 

The  coeliac  axis,  or  artery  (a.  coeliaca)  (Figs.  467  and  468),  is  a  short,  thick 
trunk,  about  half  an  inch  in  length,  which  arises  from  the  aorta,  close  to  the 
margin  of  the  opening  in  the  Diaphragm,  behind  the  posterior  parietal  perito- 


660 


THE    VASCULAR  SYSTEMS 


neum,  above  the  pancreas,  and  below  the  twelfth  thoracic  vertebra,  and,  passing 
nearly  horizontally  forward  (in  the  erect  posture),  divides  into  three  large 
branches,  the  gastric,  hepatic,  and  splenic,  occasionally  giving  off  one  of  the 
phrenic  arteries. 

Relations. — It  is  covered  by  the  lesser  omentum.  On  the  right  side  it  is  in  relation  with 
the  right  semilunar  ganglion;  on  the  left  side,  with  the  left  semilunar  ganglion  and  cardiac  end  of 
the  stomach.     Below,  it  rests  upon  the  upper  border  of  the  pancreas. 


Great 


Fig.  468.— The  cceli: 


}  and  its  branches,  the  stomach  having  been  raised  and  the  transverse  mesocolon  removed 
( semidiagrammatic ) . 


The  gastric  or  coronary  artery  (a.  gastrica  siyiistra)  (Figs.  467  and  468),  the  small- 
est of  the  three  branches  of  the  coeliac  axis,  passes  upward  and  to  the  left  side, 
behind  the  peritoneum  of  the  lesser  peritoneal  cavity.  It  continues  this  course 
until  it  nearly  reaches  the  lesser  curvature  of  the  stomach  just  below  the  cardia. 
It  then  turns  to  the  front  and  curves  forward,  distributing  branches  to  the  oesoph- 
agus which  anastomose  with  the  aortic  oesophageal  arteries;  others  supply  the 
cardiac  end  of  the  stomach,  anastomosing  with  branches  of  the  splenic  artery; 
it  then  passes  from  left  to  right,  along  and  upon  the  lesser  curvature  of  the 
stomach  and  beneath  the  peritoneum  to  the  pylorus,  lying  in  its  course  between 
the  layers  of  the  lesser  omentum,  and  sometimes  dividing  into  two  vessels,  which 
run  along  each  side  of  the  lesser  curvature.  One  vascular  arch  gives  branches  to 
the  antero-superior  wall  of  the  stomach  and  the  other  to  the  postero-inferior  wall; 
at  its  termination  it  anastomoses  with  the  pyloric  branches  of  the  hepatic.     The 


THE  ABDOMINAL  AORTA  661 

(Esophageal  branches  {rami  oesophagel)  anastomose  with  the  oesoj^haj^eal  hranchcs 
from  the  thoracic  aorta  and  the  inferior  phrenic.  Occasionally  the  j^astric  artery 
gives  off  an  hepatic  branch  of  variable  size,  which  is  usually  distributed  to  the 
left  lobe  of  the  liver. 

The  hepatic  artery  (a.  hepatica)  (Figs.  467  and  468)  in  the  adult  is  intermediate 
in  size  between  the  gastric  and  splenic;  in  the  fetus  it  is  the  largest  of  the  three 
branches  of  the  coeliac  axis.  It  runs  forward  and  to  the  right,  to  be  distributed 
to  the  upper  margin  of  the  pyloric  end  of  the  stomach;  in  its  course  it  forms  the 
lower  boundary  of  the  foramen  of  ^^'i^slow.  It  then  passes  upward  between  the 
layers  of  the  lesser  omentum,  and  in  front  of  the  foramen  of  Winslow,  to  the  trans- 
verse fissure  of  the  liver,  where  it  divides  into  two  branches,  right  and  left,  which 
supply  the  corresponding  lobes  of  that  organ,  accompanying  the  ramifications  of 
the  portal  vein  and  hepatic  duct.  The  hepatic  artery,  in  its  course  along  the  right 
border  of  the  lesser  omentum,  is  in  relation  witli  the  common  bile  duct  and  portal 
vein,  the  duct  lying  to  the  right  of  the  artery  and  the  portal  vein  behind. 

Its  branches  (Figs.  467  and  468)  are: 

Pyloric. 

rrastrndundenal  I  ^'S^*  gastroepiploic. 

I  buperior  pancreaticoduodenal. 
Cystic. 

The  pyloric  (a.  gastrica  dextrd)  arises  from  the  hepatic,  above  the  pylorus, 
descends  between  the  layers  of  the  lesser  omentum  to  the  pyloric  end  of  the 
stomach,  and  passes  from  right  to  left  along  its  lesser  curvature,  supplying  it  with 
branches  and  anastomosing  with  the  terminal  branches  of  the  gastric  artery. 

The  gastroduodenal  {a.  gastrodvodenalis)  (Fig.  468)  is  a  short  but  large  branch, 
which  descends  near  the  pylorus,  behind  the  first  portion  of  the  duodenum,  and 
divides  at  the  lower  border  of  this  viscus  into  two  branches,  the  right  gastro- 
epiploic (a.  c/astroepiploica  dextra)  and  the  superior  pancreaticoduodenal.  Previous 
to  its  division,  it  gives  off  two  or  three  small  inferior  pyloric  branches,  to  the 
pyloric  end  of  the  stomach  and  pancreas. 

The  right  gastroepiploic  runs  from  right  to  left  along  the  greater  curvature  cf 
the  stomach,  between  the  layers  of  the  great  omentum,  anastomosing  about  the 
middle  of  the  greater  curvature  of  the  stomach  with  the  left  gastro-epiploic  from  the 
splenic  artery.  This  vessel  gives  off  numerous  branches,  some  of  which  ascend 
to  supply  both  surfaces  of  the  stomach,  while  others  descend  to  supply  the  great 
omentum  (rami  epiploici). 

The  superior  pancreaticoduodenal  (a.  pancreaticoduodenalis  superior)  descends 
between  the  contiguous  margins  of  the  duodenum  and  pancreas.  It  supplies 
the  head  of  the  pancreas  by  means  of  the  ravii  pancreatica,  and  the  duodenum  by 
means  of  the  rami  duodenalis,  and  anastomoses  with  the  inferior  pancreatico- 
duodenal branch  of  the  superior  mesenteric  artery  and  with  the  pancreatic  branches 
of  the  splenic. 

The  cystic  artery  (a.  cystica)  (Fig.  467),  usually  a  branch  of  the  right  hepatic, 
passes  downward  and  forward  along  the  cystic  duct  to  the  gall-bladder  and  divides 
into  two  branches,  one  of  whicla  ramifies  on  its  free  surface  beneath  the  peritoneum, 
the  other  between  the  gall-bladder  and  the  substance  of  the  liver. 

The  splenic  artery  (a.  lienalis)  (Figs.  467  and  468),  in  the  adult,  is  the  largest  of 
the  three  branches  of  the  coeliac  axis,  and  is  remarkable  for  the  extreme  tortuosity 
of  its  course.  It  passes  horizontally  to  the  left  side,  behind  the  peritoneum  and 
along  the  upper  border  of  the  pancreas,  accompanied  by  the  splenic  vein,  which 
lies  below  it;  it  crosses  in  front  of  the  upper  part  of  the  left  kidney,  and  on  arriving 
near  the  spleen  divides  into  branches,  some  of  which  enter  the  hilum  of  that 
organ  between  the  two  layers  of  the  lienorenal  ligament  to  be  distributed  to  its 


662  THE  VASCULAR  SYSTEMS 

structure;  some  branches,  given  off  along  its  course,  are  distributed  to  the  pan- 
creas, while  others  pass  to  the  greater  curvature  of  the  stomach  between  the  two 
layers  of  the  gastrosplenic  omentum.     Its  branches  are: 

Pancreatic.  Vasa  brevia. 

Left  gastroepiploic. 

The  pancreatic  branches  (rami  pancreatici)  are  numerous  small  branches 
derived  from  the  splenic  as  it  runs  behind  the  upper  border  of  the  pancreas, 
supplying  its  middle  and  left  parts.  One  of  these,  larger  than  the  rest,  is  sometimes 
given  off  from  the  splenic  near  the  left  extremity  of  the  pancreas;  it  runs  from 
left  to  right  near  the  posterior  surface  of  the  gland,  following  the  course  of  the 
pancreatic  duct,  and  is  called  the  pancreatica  magna.  These  vessels  anastomose 
with  the  pancreatic  branches  of  the  pancreaticoduodenal  arteries,  derived  from 
the  hepatic  on  the  one  hand  and  the  superior  mesenteric  on  the  other. 

The  vasa  brevia  (aa.  gastricae  breves)  consist  of  from  five  to  seven  small  branches, 
which  arise  either  from  the  end  of  the  splenic  artery  or  from  its  terminal  branches. 
They  pass  from  left  to  right,  between  the  layers  of  the  gastrosplenic  omentum, 
are  distributed  to  the  greater  curvature  of  the  stomach,  anastomosing  with  branches 
of  the  gastric  and  left  gastroepiploic  arteries. 

The  left  gastroepiploic  (a.  gastroepiploica  sinistra^,  the  largest  branch  of  the 
splenic,  runs  from  left  to  right  along  but  distinctly  below  the  greater  curvature 
of  the  stomach,  between  the  layers  of  the  great  omentum,  and  anastomoses  with 
the  right  gastroepiploic.  In  its  course  it  distributes  several  ascending  branches 
to  both  surfaces  of  the  stomach;  others  descend  to  supply  the  greater  omentum. 

Applied  Anatomy. — The  operation  of  pylorectomy  can  be  made  an  almost  bloodless  pro- 
cedure by  tying  the  gastric,  the  pyloric,  and  the  right  and  left  gastroepiploic  arteries.  "The 
gastric  is  doubly  tied  about  one  inch  below  the  cardiac  orifice  at  a  point  where  it  joins  the  lesser 
curvature  and  is  divided  between  the  ligatures.  The  pyloric  is  doubly  tied  and  di\'ided.  The 
fingers  are  passed  beneath  the  pylorus,  raising  the  gastrocolic  omentum  from  the  transverse 
mesocolon,  and  in  this  way  safe  ligation  behind  the  pylorus  of  the  right  gastro-epiploic  artery, 
or  in  most  cases  its  parent  vessel,  the  gastroduodenal,  is  secured.  The  left  gastro-epiploic  is 
now  tied  at  an  appropriate  point,  and  the  necessary  amount  of  gastrocolic  omentum  doubly 
tied  and  cut."'  EmboHsm  of  branches  of  the  splenic  artery  is  not  uncommon  in  heart  disease, 
the  embolus  coming  from  the  left  side  of  the  heart.  It  is  characterized  by  the  occurrence  of  a 
sudden  sharp  pain  or  "stitch"  in  the  splenic  region,  with  subsequent  local  enlargement  of  the 
spleen  from  the  formation  of  an  infarct  in  its  substance. 

The  suprarenal  artery  (a.  suprarenalis  media)  (Fig.  466),  or  capsular  artery, 
arises,  one  from  each  side  of  the  aorta,  opposite  the  superior  mesenteric  artery. 
It  is  a  small  vessel  which  passes  obliquely  upward  and  outward,  over  the  corre- 
sponding crus  of  the  Diaphragm,  to  the  under  surface  of  the  suprarenal  gland, 
to  which  it  is  distributed,  anastomosing  with  capsular  branches  from  the  phrenic 
and  renal  arteries.  In  the  adult  these  arteries  are  of  small  size;  in  the  fetus  they 
are  as  large  as  the  renal  arteries. 

The  lumbar  arteries  (aa.  liimbales)  are  in  series  with  the  intercostals.  They 
are  usually  four  in  number  on  either  side,  and  arise  from  the  back  part  of  the  aorta 
opposite  the  bodies  of  the  upper  four  lumbar  vertebrte.  A  fifth  pair,  small  in 
size,  is  occasionally  present;  it  arises  from  the  middle  sacral  artery.  They  run 
outward  and  backward  on  the  bodies  of  the  lumbar  vertebrae,  behind  the  sympa- 
thetic cord,  to  the  intervals  between  the  adjacent  t^ans^"erse  processes,  and  are 
then  continued  into  the  abdominal  wall.  The  arteries  of  the  right  side  pass  behind 
the  inferior  vena  cava,  and  the  upper  two  on  each  side  run  behind  the  corresponding 
crus  of  the  Diaphragm.  The  arteries  of  both  sides  pass  beneath  the  tendinous 
arches  which  give  origin  to  the  Psoas  magnus,  and  are  then  continued  behind  this 

'William  J.  Mayo,  Annals  of  Surgery,  March,  1904. 


THE  ABDOMINAL  AORTA  663 

muscle  and  the  lumbar  plexus.  They-  now  cross  the  Quadratus  lumborum,  the 
upper  three  arteries  running  behind,  the  last  usually  in  front  of  the  muscle.  At 
the  outer  border  of  the  Quadratus  lumborum  they  pierce  the  posterior  aponeurosis 
of  the  Transversalis  abdominis  and  are  carried  forward  between  this  muscle 
and  the  Internal  oblique.  They  anastomose  with  the  lower  intercostals,  the  sub- 
costal, the  iliolumbar,  the  deep  circumflex  iliac,  and  the  deep  epigastric  arteries. 

Branches. — In  the  interval  between  the  adjacent  transverse  processes  each 
lumbar  artery  gives  off  a  dorsal  branch  {ramus  dorsalis),  which  is  continued  back- 
ward between  the  transverse  processes  and  is  distributed  to  the  muscles  and  skin 
of  the  back.  It  gives  off  a  spinal  branch  (ramus  sjnnalis)  which  enters  the  verte- 
bral canal  and  is  distributed  in  a  similar  manner  to  the  lateral  spinal  branches  of 
the  vertebral  (page  620).  Muscular  branches  are  supplied  from  each  lumbar 
artery  and  from  its  dorsal  branch  to  the  neighboring  muscles. 

The  superior  mesenteric  artery  (a.  mesenterica  superior)  (Figs.  466  and  470) 
is  a  vessel  of  large  size  which  supplies  the  whole  length  of  the  small  intestine, 
except  the  first  part  of  the  duodenum;  it  also  supplies  the  cecum  and  the  ascending 
and  transverse  parts  of  the  colon.  It  arises  from  the  front  of  the  aorta  about  half, 
an  inch  below  the  coeliac  axis,  and  is  covered  at  its  origin  by  the  splenic  vein  and 
the  neck  of  the  pancreas.  It  passes  downward  and  forward  in  front  of  the  lower 
part  of  the  head  of  the  pancreas — processus  uncinatus — and  the  third  portion  of 
the  duodenum,  and  descends  between  the  layers  of  the  mesentery  to  the  right 
iliac  fossa,  where,  considerably  diminished  in  size,  it  anastomoses  with  one  of  its 
own  branches — viz.,  the  ileocolic.  In  its  course  it  forms  an  arch,  the  convexity  of 
which  is  directed  forward  and  downward  to  the  left  side,  the  concavity  backward 
and  upward  to  the  right.  It  is  accompanied  by  the  superior  mesenteric  vein,  and 
is  surrounded  by  the  superior  mesenteric  plexus  of  nerves. 

Dissection. — In  order  to  expose  the  superior  mesenteric  artery  raise  the  great  omentum  and 
transverse  colon,  draw  down  the  small  intestines,  and  cut  through  the  peritoneum  where  the 
transverse  mesocolon  and  mesentery  join;  the  artery  -n-ill  then  be  exposed  just  as  it  issues  from 
over  the  unciform  process  of  the  head  of  the  pancreas. 

Branches. — Its  branches  are: 

Inferior  pancreaticoduodenal.  Ileocolic. 

Vasa  intestini  tenuis.  Right  colic. 

Middle  colic. 

The  inferior  pancreaticoduodenal  (a.  fancreaticoduodenalis  inferior')  is  given  off 
from  the  superior  mesenteric,  or  from  its  first  intestinal  branch  behind  the  pan- 
creas. It  courses  to  the  right  between  the  head  of  the  pancreas  and  duodenum, 
and  then  ascends  to  anastomose  with  the  superior  pancreaticoduodenal  artery. 
It  distributes  branches  to  the  head  of  the  pancreas  and  to  the  second  and  third 
portions  of  the  duodenum. 

The  vasa  intestini  tenuis  (aa.  intestinales)  arise  from  the  convex  side  of  the 
superior  mesenteric  artery.  They  are  usually  from  twelve  to  fifteen  in  number, 
and  are  distributed  to  the  jejunum  (aa.  jejunales)  and  ileum  {aa.  ileae).  They 
run  parallel  with  one  another  between  the  layers  of  the  mesentery,  each  vessel 
dividing  into  two  branches,  which  iniite  with  similar  branches  on  each  side, 
forming  a  series  of  arches  the  convexities  of  which  are  directed  toward  the  intes- 
tine. From  this  first  set  of  arches  branches  arise,  which  again  unite  with  similar 
branches  from  either  side,  and  thus  a  second  series  of  arches  is  formed;  and  from 
these  latter,  a  third  and  a  fourth,  or  even  a  fifth,  series  of  arches  is  constituted, 
diminishing  in  size  the  nearer  they  approach  the  intestine.  From  the  terminal 
arches  numerous  small  straight  vessels  arise  which  encircle  the  intestine,  upon 
which    they   are   distributed,    ramifying   between    its   coats.     Throughout    their 


664 


THE   VASCULAR  SYSTEMS 


course  small  branches  are  given  ofF  to  the  nodes  and  other  structures  between 
the  layers  of  the  mesentery.  (See  the  description  of  the  vascular  loops  in  the 
section  upon  the  Intestines.) 

The  ileocolic  artery  (a.  ileocolica)  is  the  lowest  branch  given  off  from  the  con- 
cavity of  the  superior  mesenteric  artery.  It  descends  between  the  layers  of 
the  mesentery  to  the  right  iliac  fossa,  where  it  divides  into  two  branches.  Of 
these,  the  inferior  division  anastomoses  with  the  termination  of  the  superior  mesen- 
teric artery,  forming  with  it  an  arch,  from  the  convexity  of  which  branches 
proceed  to  supply  the  termination  of  the  ileum,  the  cecum,  the  vermiform  appen- 
dix, and  the  ileocecal  valve.  The  superior  division  anastomoses  with  the  right 
colic  and  supplies  the  commencement  of  the  colon. 


Fig.  469. — Arteries  and 


appendix  seen  from  behind.     (Poirier  and  Cliarpy  > 


The  descending  branch  of  the  ileocolic  runs  toward  the  upper  border  of  the 
ileocecal  junction  and  gives  off  the  following  branches: 

(a)  Colic,  which  passes  upward  on  the  ascending  colon;  (h)  anterior  and 
posterior  cecal  (or  ileocecal),  which  are  distributed  to  the  front  and  back  of  the 
cecum;  (c)  appendicular  [a.  appendicularis) ,  which  passes  downward  behind  the 
terminal  part  of  the  ileum  and  runs  in  the  mesoappendix  close  to  its  free  margin 
for  the  supply  of  the  appendix;  and  {d)  ileal,  which  runs  upward  and  to  the  left 
on  the  terminal  part  of  the  ileum  and  anastomoses  with  the  termination  of  the 
superior  mesenteric  (Fig.  469). 

The  right  colic  artery  (a.  colica  dextra)  arises  from  about  the  middle  of  the 
concavity  of  the  superior  mesenteric  artery;  it  passes  to  the  right  behind  the 
peritoneum  to  the  middle  of  the  ascending  colon,  and  divides  into  two  branches — a 
descending  branch,  which  anastomoses  with  the  ileocolic,  and  an  ascending  branch, 
which  anastomoses  with  the  middle  colic.  These  branches  form  arches,  from  the 
convexity  of  which  vessels  are  distributed  to  the  ascending  colon. 

The  middle  colic  artery  (a.  colica  media)  arises  from  the  upper  part  of  the 
concavity  of  the  superior  mesenteric,  and,  passing  downward  and  forward  between 
the  layers  of  the  transverse  mesocolon,  divides  into  two  branches,  the  one  on  the 
right  side  anastomosing  with  the  right  colic;  that  on  the  left  side,  with  the  left 
colic,  a  branch  of  the  inferior  mesenteric.  From  the  arches  formed  by  their 
anastomosis  branches  are  distributed  to  the  transverse  colon.  The  branches  of 
this  vessel  lie  between  the  two  layers  of  the  transverse  mesocolon. 


THE  ABDOMINAL  AORTA  665 

The  renal  arteries  (are.  renales)  (Fig.  466)  are  two  larjje  trunks  which  arise 
from  the  sides  of  the  aorta  immediately  below  the  superior  mesenteric  artery. 
Each  is  directed  outward  across  the  corresponding  crus  of  the  Diaphragm,  so  as 
to  form  nearly  a  right  angle  with  the  aorta.  The  right  is  longer  than  the  left,  on 
account  of  the  position  of  the  aorta;  it  passes  behind  the  inferior  ^ena  cava.  The 
left  is  somewhat  higher  than  the  right.  Before  reaching  the  hilum  of  the  kidney, 
each  artery  usually  di-\'ides  into  four  branches.  Two  of  these  vessels  enter  the 
anterior  portion  and  two  the  posterior  portion  of  the  kidney.  The  anterior 
branches  supply  three-fourths  of  the  kidney,  the  posterior  supply  one-fourth. 
Each  vessel  gives  off  a  small  branch  to  the  suprarenal  gland  {a.  supraraialis 
inferior)  and  branches  to  the  ureter,  ureteral  branches,  and  to  the  surrounding  cel- 
lular tissue  and  muscles,  perirenal  branches.  The  two  circulations  are  distinct 
and  do  not  anastomose  even  at  the  periphery.  Between  these  two  sets  of  vessels 
is  a  nearly  bloodless  zone,  the  exsanguinated  renal  zone  of  Hyrtl,  which  does  not 
correspond  to  the  lateral  border,  but  is  one-half  inch  dorsal  to  the  external 
border  of  the  kidney.  The  ventral  or  anterior  segment  is  much  the  larger.  In 
very  rare  instances  the  bloodless  zone  corresponds  to  the  lateral  border  (Kiimmel) . 

Applied  Anatomy. — An  incision  of  the  middle  third  of  the  kidney  exactly  at  the  junction  of 
the  two  segments  does  not  divide  large  vessels.  As  the  incision  approaches  either  pole  there  is 
danger  of  cutting  a  large  branch  (Schede).  Frequently  there  is  a  second  renal  artery,  which  is 
gi\en  off  from  the  abdominal  aorta  either  above  or  below  the  renal  artery  proper,  the  former 
being  the  more  common  position.  Instead  of  entering  the  kidney  at  the  hilum,  one  or  more 
accessory  renal  arteries  often  pierce  the  upper  or  the  lower  part  of  the  gland. 

The  spermatic  arteries  (aa.  spermaticae  internae)  (Fig.  466)  are  distributed 
to  the  testes.  They  are  two  slender  vessels  of  considerable  length,  which  arise 
from  the  front  of  the  aorta  a  little  below  the  renal  arteries.  Each  artery  passes 
obliquely  outward  and  downward  behind  the  peritoneum,  resting  on  the  Psoas 
muscle,  the  right  spermatic  lying  in  front  of  the  inferior  vena  cava,  the  left  behind 
the  sigmoid  flexure  of  the  colon.  It  then  crosses  obliquely  over  the  ureter  (to 
which  it  sends  a  few  branches)  and  the  lower  part  of  the  external  iliac  artery  to 
reach  the  internal  abdominal  ring,  through  which  it  passes,  and  accompanies 
the  other  constituents  of  the  spermatic  cord  along  the  inguinal  canal  to  the  scrotum, 
where  it  becomes  tortuous  and  divides  into  several  branches.  Two  or  three  of 
these  accompany  the  vas  deferens,  anastomosing  with  the  artery  of  the  vas  defer- 
ens, and  are  distributed  to  the  epididymis ;  others  pierce  the  back  part  of  the  tunica 
albuginea  and  supply  the  substance  of  the  testis.  The  spermatic  artery  in  the 
inguinal  canal  gives  off  cremasteric  branches  to  supply  the  Cremaster  muscle. 
In  the  canal  and  scrotimi  the  artery  lies  behind  the  pampiniform  plexus  and  in 
front  of  the  vas  deferens. 

The  ovarian  arteries  {aa.  ovaricae)  (Fig.  473)  in  the  female  correspond  to  the 
spermatic  arteries  in  the  male.  They  supply  the  ovaries,  and  are  shorter  than  the 
spermatic.  The  origin  and  course  of  the  first  part  of  each  artery  are  the  same  as 
the  spermatic  in  the  male,  but  on  arriving  at  the  margin  of  the  pelvis  the  o^•arian 
artery  passes  inward,  between  the  two  layers  of  the  broad  ligament  of  the  uterus, 
to  be  distributed  to  the  ovary.  Small  branches  go  to  the  Fallopian  tube,  the 
ureter,  and  the  broad  ligament;  and  one  passes  on  to  the  side  of  the  uterus  and 
anastomoses  with  the  uterine  artery.  Other  offsets  are  continued  along  the 
round  ligament  through  the  inguinal  canal,  to  the  integument  of  the  labium  and 
groin. 

At  an  early  period  of  fetal  life,  when  the  testes  or  ovaries  lie  at  the  side  of  the 
vertebral  column  below  the  kidneys,  the  spermatic  or  ovarian  arteries  are  short; 
but  as  these  organs  descend  from  the  abdomen  into  the  scrotum  or  pelvis,  the 
arteries  gradually  become  lengthened. 


666 


THE  VASCULAR  SYSTEMS 


The  inferior  mesenteric  artery  {a.  mesenterica  inferior)  (Figs.  466  and  471) 
supplies  the  descending  colon,  the  sigmoid  flexure  of  the  colon,  and  the  greater 
part  of  the  rectum.  It  is  smaller  than  the  superior  mesenteric,  and  arises  from 
the  front  and  toward  the  left  side  of  the  aorta,  between  one  and  two  inches  above 
the  division  of  that  vessel  into  the  common  iliacs.  It  passes  downward  to  the 
left  iliac  fossa,  and  then  descends  between  the  layers  of  the  mesorectum,  into  the 
pelvis,  under  the  name  of  the  superior  hemorrhoidal  artery.  It  lies  at  first  in  close 
relation  with  the  left  side  of  the  aorta,  and  then  passes  as  the  superior  hemor- 
rhoidal in  front  of  the  left  common  iliac  artery. 


Fig.  470. — The  superior  mesenteric  artery  and  its  branches. 


Dissection. — In  order  to  expose  the  inferior  mesenteric  artery  clraw  the  small  intestines  and 
mesentery  over  to  the  right  side  of  the  abdomen,  raise  the  transverse  colon  toward  the  thorax, 
and  divide  the  peritoneum  covering  the  front  of  the  aorta. 


Branches. — Its  branches  are: 


Left  colic. 


Superior  hemorrhoidal. 


Sigmoid. 


The  left  colic  artery  (a.  colica  sinistra)  passes  behind  the  peritoneum,  in  front 
of  the  left  kidney,  to  reach  the  descending  colon;  it  divides  into  an  ascending 


THE  ABDOMINAL  AORTA 


667 


branch  which  anastomoses  with  the  middle  colic,  and  a  descending  branch  which 
anastomoses  with  the  upper  sigmoid  artery.  From  the  arches  formed  by  these 
anastomoses,  branches  are  distributed  to  the  descending  colon. 

The  sigmoid  arteries  {aa.  sigvioideae)  run  obliquely  downward  and  outward 
behind  the  peritoneum  across  the  Psoas  muscle  to  the  sigmoid  flexure  of  the  colon. 
They  divide  into  branches  which  supply  the  lower  part  of  the  descending  colon  and 
the  sigmoid  flexure,  anastomosing  above  with  the  left  colic,  and  below  with  the 
superior  hemorrhoidal  artery. 


Inferior  liemorrhmda!  iiJA 


Fig.  471. — The  inferior  raesent 


The  superior  hemorrhoidal  artery  (a.  hemorrhoidalis  superior)  (Figs.  471  and  472), 
the  terminal  portion  of  the  inferior  meseixteric,  descends  into  the  pelvis  between 
the  layers  of  the  mesorectum,  crossing,  in  its  course,  the  left  ureter  and  left  common 
iliac  vessels.  Opposite  the  middle  of  the  sacrum  it  divides  into  two  branches, 
which  descend  one  on  either  side  of  the  rectum,  and  about  five  inches  from  the 
anus  break  up  into  several  small  branches,  which  pierce  the  muscular  coat  of  the 
bowel  and  run  downward,  as  straight  vessels,  placed  at  regular  intervals  from 
each  other  in  the  wall  of  the  intestine  between  its  muscular  and  mucous  coat,  to  the 
level  of  the  Internal  sphincter;  here  they  form  a  series  of  loops  around  the  lower 
end  of  the  rectum,  and  communicate  with  the  middle  hemorrhoidal  arteries,  which 
are  branches  of  the  internal  iliac,  and  with  the  inferior  hemorrhoidal  branches  of 
the  internal  pudic. 


668 


THE   VASCULAR  SYSTEMS 


THE  COMMON  ILIAC  ARTERIES  (AA.  ILIACAE  COMMUNES)  (Figs.  466,  472). 

The  abdominal  aorta  divides  on  the  left  side  of  the  body  of  the  fourth  lumbal 
vertebra  into  the  two  common  iliac  arteries.  Each  is  about  two  inches  in  length. 
They  diverge  from  the  termination  of  the  aorta,  pass  downward  and  outward  to 
the  margin  of  the  pelvis,  and  divide,  opposite  the  intervertebral  disk,  between  the 
last  Umibar  vertebra  and  the  sacrum,  into  two  branches,  the  internal  and  external 
iliac  arteries,  the  latter  supplying  the  lower  extremity;  the  former,  the  viscera  and 
parietes  of  the  pelvis. 

The  right  common  iliac  is  somewhat  longer  than  the  left,  and  passes  more 
obliquely  across  the  body  of  the  last  lumbar  vertebra.  In  front  of  it  are  the  peri- 
toneum, the  small  intestines,  branches  of  the  sympathetic  cord,  and,  at  its  point 
of  division,  the  ureter.  Behind,  it  is  separated  from  the  bodies  of  the  fourth  and 
fifth  lumbar  vertebrae,  and  the  intervening  intervertebral  disk,  by  the  two  common 
iliac  veins.  On  its  outer  side,  it  is  in  relation  above  with  the  inferior  vena  cava 
and  the  right  common  iliac  vein;  and  below,  with  the  Psoas  magnus  muscle.  On 
its  inner  side,  above,  is  the  left  common  iliac  vein. 

The  left  common  iliac  is  in  relation,  iji  front,  with  the  peritoneum,  small  intes- 
tines, branches  of  the  sympathetic  cord,  and  the  superior  hemorrhoidal  artery; 
and  is  crossed  at  its  point  of  bifurcation  by  the  ureter.  It  rests  on  the  bodies  of  the 
fourth  and  fifth  lumbar  vertebrae,  with  the  intervening  disk.  The  left  common 
iliac  vein  lies  partly  on  the  inner  side,  and  partly  behind  the  corresponding  artery; 
on  its  outer  side,  the  artery  is  in  relation  with  the  Psoas  magnus  muscle. 

Plan  of  the  Relations  of  the  Common  Iliac  Arteries. 


In  front. 
Peritoneum. 
Small  intestines. 
Sympathetic  cord. 
Ureter. 

In  front. 
Peritoneum. 
Sympathetic  cord. 
Superior  hemorrhoidal  artery. 
Ureter. 

^      ~\ 

Onter  side. ' 

Inner  side. 

/^        N             ^           -. 

/       Right       \ 

Common 
I         Iliac.        J 

,  Inferior  vena  cava. 
1  Right  common 

iliac  vein. 
Psoas  muscle. 

Left  common  / 
iliac  vein.     1 

'       .  ,^       \           Outer  side. 
Left         \ 

^mS""     j      Psoas  magnus 
y           '       /             muscle. 

Behind. 

Behind. 

Fourth  and  fifth  lumbar  vertebrae. 
Right  and  left  common  iliac  veins. 

Fourth  and  fifth  lumbar  vertebrae. 
Left  common  iliac  vein. 

Branches. — The  common  iliac  arteries  give  off  small  branches  to  the  perito- 
neum. Psoas  magnus,  ureters,  and  the  surrounding  areolar  tissue,  and  occasionally 
give  origin  to  the  iliolumbar  or  to  the  accessory  renal  arteries. 

Peculiarities. — The  -point  of  origin  varies  according  to  the  bifurcation  of  the  aorta.  In 
three-fourths  of  a  large  number  of  cases  the  aorta  bifurcated  either  upon  the  fourth  lumbar 
vertebra  or  upon  the  intervertebral  disk  between  it  and  the  fifth,  the  bifurcation  being,  in  one 
case  out  of  nine  below,  and  in  one  out  of  eleven  above,  this  point.  In  ten  out  of  every  thirteen 
cases  the  vessel  bifurcated  within  half  an  inch  above  or  below  the  level  of  the  crest  of  the  ilium, 
more  frequently  below  than  above. 

The  point  of  division  is  subject  to  great  variety.  In  two-thirds  of  a  large  number  of  cases 
it  was  between  the  last  lumbar  vertebra  and  the  upper  border  of  the  sacrum,  being  above  that 
point  in  one  case  out  of  eight  and  below  it  in  one  case  out  of  six.  The  left  common  iliac  artery- 
divides  lower  down  more  frequently  than  the  right. 

The  relative  lengths,  also,  of  the  two  common  iliac  arteries  vary.  The  right  common  iliac 
was  the  longer  in  sixty-three  cases,  the  left  in  fifty-two,  while  they  were  both  equal  in  fifty-three. 
The  length  of  the  arteries  varied  in  five-sevenths  of  the  cases  examined  from  an  inch  and  a  half 


THE  INTEltXAL  ILIAC  ARTERY  669 

.to  three  inches;  in  about  half  of  the  remaining  cases  the  artery  was  longer  and  in  the  other  half 
shorter,  the  iTiiniraura  length  being  less  than  half  an  inch,  the  maximum  four  and  a  hall  inches. 
In  two  insiaiK-es  the  right  common  iliac  has  been  found  wanting,  the  external  and  internal 
iliaes  arising  dirccily  from  the  aorta. 

Surface  Marking.  -Draw  a  line  between  the  highest  points  of  the  iliac  crests;  this  is  usually 
half  an  inch  below  the  umbilicus;  in  this  line  take  a  point  lialf  an  inch  to  the  left  of  the  middle 
line.  From  this  draw  two  lines  to  points  midway  between  the  anterior  superior  sjjines  of  the 
ilium  and  the  symphysis  pubis.  These  two  diverging  lines  will  represent  the  course  of  the 
common  and  external  iliac  arteries.  Draw  a  second  line  corresponding  to  the  level  of  the  ante- 
rior su]5erior  spines  of  the  ilium;  the  portion  of  the  diverging  lines  between  these  two  levels  will 
represeiil  the  course  of  the  common  iliac  artery;  the  portion  below  the  lower  zone,  that  of  the 
external  iliac  artery. 

Applied  Anatomy. — The  application  of  a  ligature  to  the  common  iliac  artery  may  be  re- 
quired on  account  of  aneurism  or  hemorrhage  implicating  tlie  external  or  internal  iliacs;  The 
abdomen  is  opened  by  an  incision  in  either  the  semilunar  line  or  the  hnea  alba;  the  intestines 
are  drawn  to  one  side  and  the  peritoneum  covering  the  artery  divided.  The  sheath  is  then 
opened,  and  the  needle  passed  from  within  outward.  On  the  right  side  great  care  must  be 
exercised  in  passing  the  needle,  since  both  the  common  iliac  veins  lie  behind  the  artery.  After 
the  vessel  has  been  tied  the  incision  in  the  peritoneum  over  the  artery  sliould  be  sutured.  In 
amputation  of  the  hip-joint  the  common  iliac  can  be  compressed  most  certainly  and  safely  by 
opening  the  abdomen  and  compressing  the  vessel  by  means  of  the  fingers  against  the  Psoas 
muscle  (McBurney's  method). 

Collateral  Circulation. — The  principal  agents  in  carrying  on  the  collateral  circulation  after 
the  application  of  a  ligature  to  the  common  iliac  are  the  anastomoses  of  the  hemorrhoidal 
branches  of  the  internal  iliac  with  the  superior  hemorroidal  from  the  inferior  mesenteric;  the 
anastomoses  of  the  uterine  and  ovarian  arteries  and  of  the  vesical  arteries  of  opposite  sides;  of 
the  lateral  sacral  with  the  middle  sacral  artery;  of  the  epigastric  with  the  internal  mammary 
inferior  intercostal,  and  lumbar  arteries;  of  the  circumflex  iliac  with  the  lumbar  arteries;  of  the 
iliolumbar  with  the  last  lumbar  artery;  of  the  obturator  artery,  by  means  of  its  pubic  branch, 
with  the  vessel  of  the  opposite  side  and  with  the  deep  epigastric. 

From  the  back  part  of  the  aorta,  just  at  its  bifurcation,  arises  the  middle 
sacral  artery  (a.  sacralis  media)  (Fig.  472).  It  is  a  small  vessel,  and  descends  upon 
the  last  lumbar  vertebra,  along  the  middle  line  of  the  front  of  the  sacrum,  to  the 
upper  part  of  the  coccyx,  where  it  anastomoses  with  the  lateral  sacral  arteries, 
and  terminates  in  the  coccygeal  body.  From  it  minute  branches  arise  which  run 
through  the  mesorectura  to  supply  the  posterior  surface  of  the  rectum.  Other 
branches  are  given  off  on  each  side,  which  anastomose  with  the  lateral  sacral 
arteries,  and  send  branches  into  the  anterior  sacral  foramina.  It  is  crossed  by  the 
left  common  iliac  vein,  and  is  accompanied  by  a  pair  of  venae  comites;  these 
unite  to  form  a  single  vessel  which  opens  into  the  left  common  iliac  vein. 

This  artery  and  its  lateral  branches  probably  represent  fused  segmental  arteries 
(see  page  763). 

The  Internal  Iliac  Artery  (Figs.  466,  472). 

The  internal  iliac  or  hypogastric  artery  (a.  hypogastrica)  supplies  the  walls  and 
viscera  of  the  pelvis,  the  l)uttock,  the  generative  organs,  and  inner  side  of  the 
thigh.  It  is  a  short  thick  vessel,  smaller  in  the  adult  than  the  external  iliac,  and 
about  an  inch  and  a  half  in  length.  It  arises  at  the  bifurcation  of  the  common 
iliac,  opposite  the  lumbosacral  articulation,  and,  passing  downward  to  the  upper 
margin  of  the  great  sacrosciatic  foramen,  divides  into  two  large  trunks,  an  anterior 
and  a  posterior.  From  its  anterior  division  a  partially  impervious  cord,  a  part  of  the 
fetal  hypogastric  artery,  extends  forward  to  the  bladder. 

Relations.— 7n  front,  with  the  ureter,  which  is  between  the  artery  and  the  peritoneum. 
Behind,  with  the  internal  iliac  vein,  the  lumbosacral  cord,  and  Pyritormis  muscle.  On  its  outer 
side,  near  its  origin  with  the  external  iliac  vein,  which  lies  between  it  and  the  Psoas  magnu3 
muscle;  lower  down,  with  the  obturator  nerve. 


670 


THE  VASCULAR  SYSTEMS 


Plan  of  the  Relations  of  the  Internal  Iliac  Artery. 


Outer  side. 
Psoas  masnus. 


Behind. 
Internal  iliac  vein. 
Lumbosacral  cord. 
Pyfiformis  muscle. 


Fig.  472. — Arteries  of  the  pel 


In  the  fetus  the  hypogastric  artery  is  twice  as  large  as  the  external  iliac,  and 
appears  to  be  the  continuation  of  the  common  iliac.  Instead  of  dipping  into  the 
pelvis,  it  passes  forward  to  the  bladder,  and  ascends  along  the  sides  of  that  viscus 
to  its  summit,  to  which  it  gives  branches;  it  then  passes  upward  along  the  back 
part  of  the  anterior  wall  of  the  abdomen  to  the  umbilicus,  converging  toward 
its  fellow  of  the  opposite  side.     Having  passed  through  the  umbilical  opening, 


THE  INTERNAL  ILIAC  ARTERY  -  671 

the  two  arteries,  now  termed  umbilical,  enter  the  umbilical  cord,  where  they  are 
coiled  around  the  umbilical  vein  and  ultimately  ramify  in  tlie  placenta. 

At  birth,  when  the  placental  circulation  ceases,  the  portion  of  tlie  hypogastric 
artery  which  extends  from  the  summit  of  the  bladder  to  the  umbilicus,  contracts, 
and  ultimately  dwindles  to  a  solid  fibrous  cord,  the  impervious  hypogastric  artery 
(lig.  umbilicale  laferalc),  but  the  lower  portion,  extending  from  its  origin  Jn  what 
is  now  the  internal  iliac  artery)  for  about  an  inch  and  a  half  to  the  wall  of  tlie 
bladder,  and  thence  to  the  summit  of  that  organ,  is  not  totally  impervious,  though 
it  becomes  considerably  reduced  in  size,  and  serves  to  convey  blood  to  the  bladder 
under  the  name  of  the  superior  vesical  artery. 

Peculiarities  as  Regards  Length. — In  two-thirds  of  a  large  number  of  cases  the  length  of 
the  internal  iliac  varied  between  an  inch  and  an  inch  and  a  half:  in  the  remaining  third  it  was 
more  frequently  longer  than  shorter,  the  maximum  length  being  three  inches,  the  minimum 
half  an  inch. 

The  lengths  of  the  common  and  internal  iliac  arteries  bear  an  inverse  proportion  to  each 
other,  the  internal  iliac  arfcrv  being  long  when  the  common  iliac  is  short,  and  vice  versa. 

As  Regards  its  Place  of  Division.— The  place  of  division  of  the  internal  iliac  varies  between 
the  upper  margin  of  the  siicnnn  ami  llie  upper  border  of  the  sacrosciatic  foramen. 

The  arteries  of  the  two  .sides  in  a  series  of  cases  often  differed  in  length,  but  neither  seemed 
constantly  to  exceed  the  other. 

Applied  Anatomy. — The  application  of  a  ligature  to  the  internal  iliac  artery  may  b«  required 
in  cases  of  aneurism  or  hemorrhage  affecting  one  of  its  branches.  The  best  method  of  tying  the 
internal  iliac  artery  is  by  an  abdominal  section  in  the  median  line  and  reaching  the  vessel  through 
the  peritoneal  cavity.  This  plan  has  been  advocated  by  Dennis,  of  New  York,  on  the  following 
grounds;  (1)  It  in  no  way  increases  the  danger  of  the  operation;  {'2)  it  prevents  a  series  of  acci- 
dents which  have  occurred  during  ligature  of  the  artery  by  the  older  methods;  (3)  it  enables  the 
surgeon  to  ascertain  the  exact  extent  of  disease  in  the  main  arterial  trunk,  and  select. his  spot  for 
the  application  of  the  ligature;  and  (4)  it  occupies  much  less  time.  ' 

Collateral  Circulation. — The  circulation  after  ligature  of  the  internal  iliac  artery'  is  carried 
on  by  the  anastomoses  of  the  uterine  and  ovarian  arteries;  of  the  opposite  vesical  arteries;  of 
the  hemorrhoidal  branches  of  the  internal  iliac  with  those  from  the  inferior  mesenteric;  of  the 
obturator  artery,  by  means  of  its  pubic  branch,  with  the  vessel  of  the  opposite  side  and  with  the 
epigastric  and  internal  circumflex;  of  the  circumflex  and  perforating  branches  of  the  profunda 
femoris  with  the  sciatic;  of  the  gluteal  with  the  posterior  branches  of  the  sacral  arteries;  of  the 
iliolumbar  with  the  last  lumbar;  of  the  lateral  sacral  with  the  middle  sacral;  and  of  the  cir- 
cumflex iliac  with  the  iliolumbar  and  gluteal. 

Branches  (Fig.  472). — The  branches  of  the  internal  iliac  are: 

From  the  Anterior  Trunk.  From  the  Posterior  Trunk. 

Superior  vesical.  Iliolumbar. 

Middle  vesical.  Lateral  sacral. 

Inferior  vesical.  Gluteal. 

Middle  hemorrhoidal. 
Obturator. 
Internal  pudic. 
Sciatic. 

vlgiiml    }  ^«*''«/e'^^«««- 

The  superior  vesical  (a.  ■vesicalis  superior)  (Fig.  472)  represents  the  pervious 
portion  of  the  fetal  hypogastric  artery.  It  extends  to  the  side  of  the  bladder, 
distributing  numerous  branches  to  the  apex  and  body  of  the  organ.  From  one 
of  these  a  slender  vessel  is  deriv'ed  which  accompanies  the  ^'as  deferens  in  its 
course  to  the  testis,  where  it  anastomoses  with  the  spermatic  artery.  This  is 
the  artery  of  the  vas  deferens.     Other  branches  supply  the  ureter. 

^  For  a  description  of  a  case  in  which  Owen  made  a  dissection  ten  years  after  ligature  of  the  internal  iliac 
artery,  see  Medico-Chirurgical  Transactions,  vol.  xvi. 


672 


THE  VASCULAB  SYSTEMS 


The  middle  vesical  (a.  vesicalis  medialis)  (Fig.  472),  usually  a  branch  of  the 
superior,  is  distributed  to  the  base  of  the  bladder  and  under  surface  of  the 
seminal  vesicles. 

The  inferior  vesical  (a.  vesicalis  inferior)  (Fig.  472)  frequently  arises  in  com- 
mon with  the  middle  hemorrhoidal,  and  is  distributed  to  the  base  of  the  bladder, 
the  prostate  gland,  and  seminal  vesicles.  The  branches  distributed  to  the  pros- 
tate communicate  with  the  corresponding  vessel  of  the  opposite  side. 

The  middle  hemorrhoidal  artery  (a.  haemorrhoidalis  media)  (Fig.  472)  usually 
arises  together  with  the  preceding  vessel.  It  is  distributed  to  the  rectum,  anasto- 
mosing with  the  superior  and  inferior  hemorrhoidal  arteries.  It  gives  branches 
to  the  seminal  vesicle  and  prostate  gland. 


Vaginal  arterie. 
Fig.  473. — The  arteries  of  the  internal  organs  of  generatic 


of  the  female,  seen  from  behind.     (After  Hyrtl.) 


The  uterine  artery  {a.  uterina)  (Fig.  473)  arises  from  the  anterior  division 
of  the  internal  iliac  and  runs  inward  on  the  Levator  ani  to  the  neck  of  the  uterus. 
About  three-quarters  of  an  inch  from  the  cervix  it  crosses  the  front  of  the  ureter, 
to  which  it  supplies  a  small  branch.  Ascending  in  a  tortuous  course  on  the  side 
of  the  uterus,  between  the  layers  of  the  broad  ligament,  it  distributes  branches 
to  its  substance  and  to  the  round  ligament  and  the  Fallopian  tube  (ramus  tubarius), 
anastomosing  near  its  termination  with  the  ovarian  artery.  It  gives  a  branch  to 
the  ovary  (ramus  ovarii),  which  anastomoses  with  a  branch  from  the  ovarian 
branches  to  the  cen^ix  of  the  uterus,  cervicouterine,  and  a  branch  which  descends 
on  the  vagina,  the  cervicovaginal,  and,  joining  with  branches  from  the  vaginal 
arteries,  form  a  median  longitudinal  vessel  both  in  front  and  behind;  these 
descend  on  the  anterior  and  posterior  surfaces  of  the  vagina,  and  are  named 
the  azygos  arteries  of  the  vagina. 

The  vaginal  artery  (a.  vaginalis)  usually  corresponds  to  the  inferior  vesical 
in  the  male;  it  descends  upon  the  vagina,  supplying  its  mucous  membrane,  and  sends 
branches  to  the  bulb  of  the  vestibule,  the  neck  of  the  bladder,  and  the  contiguous 


THE  INTERNAL  ILIAC  ARTERY  G73 

part  of  the  rectum.  It  assists  in  forming  the  azygos  arteries  of  the  vagina,  which 
are  anterior  and  posterior  vessels,  running  longitudinally,  and  due  to  anastomoses 
of  the  branches  of  the  vaginal  from  each  side  and  the  cervicovaginal  artery.  The 
vaginal  artery  is  frequently  represented  by  two  or  three  branches. 

Luschka,  HyrtI,  Waldeyer,  Robinson,  and  others,  instead  of  describing  the  ovarian  and 
uterine  arteries  as  two  distinct  vessels,  regard  them  as  constituting  the  chief  parts  of  one  vessel, 
the  arterja  uterina  ovarica.  What  has  been  called  "the  circle  of  Robinson"  is  composed  of  a 
spiral  segment  (the  arteria  uterina  ovarica),  with  a  portion  of  the  abdominal  aorta,  common 
iliacs,  and  internal  iliacs. 

Robinson'  has  made  a  careful  study  of  this  vascular  circle;  he  shows  that  it  is  of  gfeat  impor- 
tance in  certain  surgical  procedures,  and  that  its  remarkable  "capacity  for  extension"  saves  it 
from  damage  when  the  uterus  is  enormously  distended  by  pregnancy,  or  when  it  is  "drawn 
through  the  pudendum  with  traction  forceps  for  palpation,  inspection,  or  repair." 

The  author  just  quoted  says  further  that  the  utero-ovarian  artery  has  three  origins,  because 
it  develops  from  the  Wolffian  body:  The  ovarian  segment  ariseif  from  the  abdominal. aorta. 
The  uterine  segment  arises  from  the  anterior  branch  of  the  internal  iliac  artery.  The  artery 
of  the  round  ligament  arises  from  the  deep  e[)igastric.  The  arteria  uterina  ovarica  secures 
nutrition  to  the  uterus  by  bringing  blood  from  three  sources.  It  is  spiral  throughout  its  entire 
course,  in  certain  parts  is  convoluted  or  looped,  and  it  is  accompanied  by  the  pampiniform 
plexus  of  veins. 

The  three  origins  of  this  vessel  are  freely  united  by  anastomoses,  and  rami  laterales  are  given 
off,  which  unite  the  bilateral  vessels  in  the  median  line.  Robinson  describes  three  bifurcations 
of  the  utero-ovarian  artery.  The  distal  bifurcation,  which  is  "about  midway  between  the  uterus 
and  the  pelvic  wall,"  forms  an  acute  angle  with  the  main  vessel.  This  bifurcation  indicates 
the  point  of  division  of  the  external  from  the  internal  genitals.  The  cervicovaginal  artery 
supplies  the  external  genitals.  The  proximal  bifurcation  marks  the  situation  of  the  ovary. 
The  artery  bifurcates  at  an  acute  angle  into  two  branches  to  supply  the  ovary  and  Fallopian 
tube.  The  middle  bifurcation  consists  of  (1)  the  division  of  the  uterine  segment  at  the  angle 
formed  by  the  uterus  and  oviduct  ("forming  the  ramus  oviductus  and  ramus  ovarii"),  and  (2) 
"the  bifurcation  of  the  ramus  oviductus  forming  the  ramus  oviductus  and  the  ramus  ligamenti 
teretis,  or  the  segment  of  the  round  ligament."' 

Applied  Anatomy. — As  pointed  out  by  Robinson,  the  source  of  bleeding  after  vaginal  hys- 
terectomy is  usually  the  torn  and  undamped  cervicovaginal  artery. 

As  previously  mentioned,  the  spiral  and  convoluted  course  of  the  utero-ovarian  artery  allows 
the  uterus,  ovary,  and  tube  to  be  drawn  into  the  vagina  without  injury  to  the  vessels.  Robinson 
points  out  that  in  vaginal  hysterectomy  the  genital  circle  is  not  divided  and  only  the  rami  laterales 
which  go  to  the  uterus  are  cut,  the  ovaries  retaining  a  normal  blood  supply  and  continuing  to 
fimctionate. 

The  obturator  artery  (a.  obturator ia)  (Fig.  472)  passes  forward  and  down- 
ward on  the  lateral  wall  of  the  pelvis,  to  the  upper  part  of  the  obturator  foramen, 
and,  escaping  from  the  pelvic  cavity  through  a  short  canal,  formed  by  a  groove 
on  the  under  surface  of  the  ascending  ramus  of  the  os  pubis  and  the  arched  border 
of  the  obturator  membrane,  it  divides  into  an  internal  and  external  branch.  In 
the  pelvic  cavity  this  vessel  is  in  relation,  externally,  with  the  obturator  fascia; 
internally,  with  the  ureter,  vas  deferens,  and  peritoneum;  while  a  little  below  it  is 
the  obturator  nerve. 

Branches. — Within  the  pelvis,  the  obturator  artery  gives  off  an  iliac  branch  (ramus 
iliacus)  to  the  iliac  fossa,  which  supplies  the  bone  and  the  Iliacus  muscle,  and 
anastomoses  with  the  iliolumbar  artery;  a  vesical  branch  (ramus  vesicalis),  which 
runs  backward  to  supply  the  bladder;  and  a  pubic  branch  (ramus  pubicus),  which 
is  given  off  from  the  vessel  just  before  it  leaves  the  pelvic  cavity.  The  pubic 
branch  ascends  upon  the  back  of  the  pubis,  communicating  with  offshoots  from 
the  deep  epigastric  artery  and  with  the  corresponding  vessel  of  the  opposite  side; 
it  is  sometimes  placed  on  the  inner  side  of  the  femoral  ring. 

Outside  the  pelvis,  the  obturator  artery  divides  into  an  internal  and  an  external 
branch,  which  are  deeply  situated  between  the  Obturator  externus  and  the  pelvis. 

•  F.  BjTon  Robinson.    The  Utero-ovarian  Artery,  or  the  Genital  Vascular  Circle,  1903. 


674  THE   VASCULAB  SYSTEMS 

The  internal  branch  {ramus  anterior)  curves  backward  along  the  inner  margin 
of  the  obturator  foramen,  lying  between  it  and  the  Obturator  externus  muscle ;  it 
distributes  branches  to  the  Obturator  externus,  Pectineus,  Adductors  and  Gracilis, 
and  anastomoses  with  the  external  branch,  and  with  the  internal  circumflex  artery. 

The  external  branch  {ramus  posterior)  curves  backward  around  the  outer  margin 
of  the  obturator  foramen,  also  lying  between  the  obturator  foramen  and  the 
Obturator  externus  muscle,  to  the  space  between  the  Gemellus  inferior  and 
Quadratus  femoris,  where  it  divides  into  two  branches.  One,  the  smaller, 
courses  inward  around  the  lower  margin  of  the  foramen  and  anastomoses  with  the 
internal  branch  and  with  the  internal  circumflex;  the  other  inclines  outward  in 
the  groove  below  the  acetabulum  (a.  acetabulis) ,  and  supplies  the  muscles  attached 
to  the  tuberosity  of  the  ischium  and  anastomoses  with  the  sciatic  artery.  It 
sends  through  the  cotyloid  notch  a  branch  to  the  hip-joint,  which  ramifies  on 
the  ligamentum  teres  as  far  as  the  head  of  the  femur. 

Peculiarities  (Figs.  474  and  475). — The  obturator  artery  sometimes  arises  from  the  main 
stem  or  from  the  posterior  trunk  of  the  internal  iUac,  from  the  deep  epigastric  (28  per  cent.), 
or  it  may  arise  from  the  external  iliac  (1.2  per  cent.). 


Figs.  474  and  475. — Variations  in  origin  and  course  of  the  obturator  artery. 

When  the  obturator  artery  arises  at  the  front  of  the  pelvis  from  the  deep  epigastric,  it  descends 
almost  vertically  to  the  upper  part  of  the  obturator  foramen.  The  artery  in  this  course  usually 
lies  in  contact  with  the  external  iliac  vein  and  on  the  outer  side  of  the  femoral  ring  (Fig.  474) ; 
in  such  cases  it  would  not  be  endangered  in  the  operation  for  femoral  hernia.  Occasionally, 
however,  it  curves  inward  along  the  free  margin  of  Gimbernat's  ligament  (Fig.  475),  and  under 
such  circumstances  would  almost  completelj'  encircle  the  neck  of  the  hernial  sac,  and  would 
be  in  great  danger  of  being  wounded  if  an  operation  were  performed  for  strangulation. 

The  internal  pudic  artery  {a.  pudenda  interna)  (Figs.  476  and  477)  is  the 
smaller  of  the  two  terminal  branches  of  the  anterior  trunk  of  the  internal  iliac, 
and  supplies  the  external  organs  of  generation.  Though  the  course  of  the  artery 
is  the  same  in  the  two  sexes,  the  vessel  is  much  smaller  in  the  female  than  in  the 
male,  and  the  distribution  of  its  branches  somewhat  different.  The  description  of 
its  arrangement  in  the  male  will  first  be  given,  and  subsequently  the  differences 
which  it  presents  in  the  female  will  be  mentioned. 

The  internal  pudic  artery  in  the  male  passes  downward  and  outward  to  the 
lower  border  of  the  great  sacrosciatic  foramen,  and  emerges  from  the  pelvis  be- 
tween the  Pyriformis  and  Coccygeus  muscles;  it  then  crosses  the  spine  of  the 
ischium  and  enters  the  pelvis  through  the  lesser  sacrosciatic  foramen.  The 
artery  now  crosses  the  Obturator  internus  muscle  along  the  outer  wall  of  the  ischio- 
rectal fossa,  being  situated  about  an  inch  and  a  half  above  the  lower  margin  of 
the  ischial  tuberosity.  It  gradually  approaches  the  margin  of  the  ramus  of  the 
ischium,  passes  forward  between  the  two  layers  of  the  triangular  ligament  of  the 
perineum ;  it  then  runs  forward  along  the  inner  margin  of  the  ramus  of  the  pubis 
and  about  half  an  inch  behind  the  subpubic  ligament  it  pierces  the  superficial 
layer  of  the  triangular  ligament  and  divides  into  its  two  terminal  branches,  the 
dorsal  artery  of  the  penis  and  the  artery  of  the  corpus  cavemosum. 


THE  INTERNAL  ILIAC  ARTERY  675 

Relations. — Within  the  pelvis,  at  its  beginning,  it  lies  in  front  of  the  Pyrifomiis  muscle  and 
sacral  plexus  of  nerves,  and  the  sciatic  artery,  and  on  the  outer  side  of  the  rectum  (on  the  left 
side).  As  it  crosses  the  spine  of  the  ischium  it  is  covered  by  the  Gluteus  maximus  and  over- 
lapped by  the  great  sacrosciatic  ligament.  Here  the  pudic  nerve  lies  to  the  inner  side  and  the 
nerve  to  the  Obturator  interniis  to  the  outer  side  of  the  vessel.  On  entering  the  pelvis  it  lies 
on  the  outer  side  of  the  ischiorectal  fossa,  upon  the  surface  of  the  Obturator  internus  muscle, 
contained  in  a  fibrous  canal  (Alcock's  canal),  formed  by  the  splitting  of  the  obturator  fascia. 
It  is  accompanied  by  the  pudic  veins  and  the  pudic  nerve. 

Peculiarities. — The  internal  pudic  is  sometimes  smaller  than  usual,  or  fails  to  give  off  one 
or  two  of  its  usual  branches;  in  such  cases  the  deficiency  is  supplied  by  branches  derived  from 
an  additional  vessel,  the  accessory  pudic,  which  generally  arises  from  the  internal  pudic  artery 
before  its  exit  from  the  orcat  .siu  ru.sciatic  foramen.  It  passes  forward  along  the  lower  part  of 
the  bladder  and  across  the  side  of  tlie  prostate  gland  to  the  root  of  the  penis,  where  it  perforates 
the  triangular  ligament  and  gives  off  the  branches  usually  derived  from  the  pudic  artery.  The 
deficiency  most  frequently  met  with  is  that  in  which  the  internal  pudic  ends  as  the  artery  of  the 
bulb,  the  artery  of  the  corpus  cavernosum  and  dorsal  artery  of  the  penis  being  derived  from  the 
accessory  pudic.  Or  the  pudic  may  terminate  as  the  superficial  perineal,  the  artery  of  the  bulb 
being  derived,  with  the  other  two  branches,  from  the  accessory  vessel.  Occasionally  the  acces- 
sory pudic  artery  is  derived  from  one  of  the  other  branches  of  the  internal  iliac,  most  frequently 
the  inferior  vesical  or  the  obturator. 

Branches. — The  branches  of  the  internal  pudic  artery  are: 

Muscular.  Artery  of  the  bulb. 

Inferior  hemorrhoidal.  Urethral  artery. 

Superficial  perineal.  Artery  of  the  corpus  cavernosum. 

Transverse  perineal.  Dorsal  artery  of  the  penis. 

The  muscular  branches  consist  of  two  sets — one  given  off  in  the  pelvis,  the 
other  as  the  vessel  crosses  the  ischial  spine.  The  former  are  several  small  offshoots 
which  supply  the  Levator  ani,  the  Obturator  internus,  the  Pyriformis,  and  the 
Coccygeus  muscles.  The  branches  given  off  outside  the  pelvis  are  distributed  to 
the  adjacent  part  of  the  Gluteus  maximus  and  External  rotator  muscles.  They 
anastomose  with  branches  of  the  sciatic  artery. 

The  inferior  hemorrhoidal  artery  (a.  haernorrhoidalis  inferior)  arises  from 
the  internal  pudic  as  it  passes  above  the  tuberosity  of  the  ischium.  Crossing 
the  ischiorectal  fossa  it  is  distributed  by  two  or  three  terminal  branches  to  the 
muscles  and  integument  of  the  anal  region.  Instead  of  one  inferior  hemor- 
rhoidal artery  two  or  three  small  vessels  may  arise  from  the  internal  pudic. 

The  superficial  perineal  artery  (a.  periiiei)  (Fig.  476)  supplies  the  scrotum  and  the 
muscles  and  integument  of  the  perineum.  It  arises  from  the  internal  pudic  in 
front  of  the  preceding  branches,  and  turns  upward,  crossing  either  over  or  under 
the  Transversus  perinei  superficialis  muscle,  and  runs  forward,  parallel  to  the 
pubic  arch,  in  the  interspace  between  the  Accelerator  urinae  (??i.  bidbocavernosus) 
and  Erector  penis  (m.  ischiocavernosus)  muscles,  both  of  which  it  supplies,  and  is 
finally  distributed  to  the  skin  and  dartos  of  the  scrotum.  In  its  passage  through 
the  perineum  it  lies  beneath  the  superficial  perineal  fascia. 

The  transverse  perineal  artery  is  a  small  branch  which  arises  either  from  the 
internal  pudic  or  from  the  superficial  perineal  artery  as  it  crosses  the  Transversus 
perinei  muscle.  It  runs  transversely  inward  along  the  cutaneous  surface  of  the 
Transversus  perinei  superficialis  muscle  and  anastomoses  with  the  like  vessel 
of  the  opposite  side,  and  with  the  superficial  perineal  and  inferior  hemorrhoidal 
arteries.  It  supplies  the  Transversus  perinei  and  the  structures  between  the 
anus  and  bulb  of  the  urethra. 

The  artery  of  the  bulb  (o.  bulbi  urethrae)  is  a  short  vessel  of  large  caliber  which 
arises  from  the  internal  pudic  between  the  two  layers  of  the  triangular  ligament; 
it  passes  nearly  transversely  inward,  through  the  fibres  of  the  Compressor  urethrae 
muscle,  pierces  the  superficial  layer  of  the  triangular  ligament,  and  gives  oft' 


676 


THE  VASCULAR  SYSTEMS 


branches  which  ramify  in  the  bulb  of  the  urethra.  It  is  then  continued  forward 
in  the  corpus  spongiosum  to  the  glans  penis.  It  gives  off  a  small  branch  to 
Cowper's  gland. 

The  urethral  artery  (a.  urethralis)  is  a  small  vessel  which  passes  to  the  corpus 
spongiosum  at  the  angle  of  the  converging  crura  of  the  penis.  It  reaches  the  glans 
penis  and  anastomoses  with  the  artery  of  the  corpus  cavernosum  and  the  dorsal 
artery  of  the  penis.     This  vessel  is  quite  often  absent. 

The  artery  of  the  corpus  cavernosum  (a.  profunda  penis),  one  of  the  terminal 
branches  of  the  internal  pudic,  arises  just  after  that  vessel  has  perforated  the 
superficial  triangular  ligament,  and,  quickly  entering  the  crus  penis  obliquely, 
runs  forward  in  the  centre  of  the  corpus  cavernosum,  to  which  its  branches  are 
distributed. 


Transversus  peniin 
ficialf. 


■Superficial  perineal  artery. 
■Superficial  perineal  nerve. 
Internal  pudic  nerve. 
Internal  pudic  artery. 


Fig.  476. — The  superficial  muscles  and  vessels  of  the  perine 


The  dorsal  artery  of  the  penis  (a.  dorsalis  penis)  ascends  between  the  crus  and 
pubic  symphysis,  and  passes  between  the  two  layers  of  the  suspensory  ligament 
of  the  penis,  and  runs  forward  on  the  dorsum  of  the  penis  to  the  glans,  where  it 
divides  into  two  branches  which  supply  the  glans  and  prepuce.  On  the  dorsum 
of  the  penis  it  lies  immediately  beneath  the  integument,  between  the  dorsal  nerve 
and  the  deep  dorsal  vein,  the  former  being  on  its  outer  side.  It  supplies  the  integ- 
ument and  fibrous  sheath  of  the  corpus  cavernosum,  sending  branches  through 
the  sheath  to  anastomose  with  the  preceding  vessel. 

The  internal  pudic  artery  in  the  female  is  smaller  than  in  the  male.  Its  origin 
and  course  are  similar,  and  there  is  considerable  analogy  in  the  distribution  of 
its  branches.  The  superficial  perineal  artery  supplies  the  labia  pudendi;  the 
artery  of  the  bulb  supplies  the  bulbi  vestibuli  and  the  erectile  tissue  of  the  vagina; 
the  artery  of  the  corpus  cavernosum  (a.  profunda  cUtoridis)  supplies  the  cavernous 
body  of  the  clitoris;  and  the  dorsal  artery  of  the  clitoris  (o.  dorsalis  clitoridis) 
supplies  the  dorsum  of  that  organ,  and  terminates  in  the  glans  and  in  the  mem- 
branous fold  corresponding  to  the  prepuce  of  the  male. 


THE  INTERNAL  ILIAC  ARTERY 


677 


The  sciatic  artery  (a.  ghitaea  inferior)  (Fig.  477),  the  larger  of  the  two  terminal 
branches  of  tiie  anterior  trunk  of  the  internal  iliac,  is  distributed  chiefly  on  the 
buttock  and  back  of  the  thigh.  It  passes  down  to  the  lower  part  of  the  great 
sacrosciatic  foramen  behind  the  internal  pudic  artery,  resting  on  the  sacral  plexus 
of  nerves  and  Pyriformis  muscle,  and  escapes  from  the  pelvis  through  this  foramen 
between  the  Pyriformis  and 
Coccygeus.  '  It  then  descends 
in  the  interval  between  the  tro- 
chanter major  and  tuberosity 
of  the  ischium,  accompanied 
by  the  sciatic  nerves,  and 
covered  by  the  Gluteus  maxi- 
mus,  and  is  continued  down 
the  back  of  the  thigh  supplying 
the  skin,  and  anastomosing 
with  branches  of  the  perfora- 
ting arteries. 

Within  the  pelvis  it  distrib- 
utes branches  to  the  Pyriformis, 
Coccygeus,  and  Levator  ani 
muscles;  some  hemorrhoidal 
branches,  which  supply  the 
rectum,  and  occasionally  take 
the  place  of  ithe  middle  hemor- 
rhoidal artery;  and  vesical 
branches  to  the  base  and  neck 
of  the  bladder,  seminal  vesicles, 
and  prostate  gland.  Outside 
the  pelvis  it  gives  off  the  fol- 
lowing branches: 

Muscular. 

Coccygeal. 

Comes  nervi  ischiadic!. 

Anastomotic. 

Articular. 

Cutaneous. 

The  muscular  branches  sup- 
ply the  Gluteus  maximus, 
anastomosing  with  the  gluteal 
artery  in  the  substance  of  the 
muscle;  the  External  rotators, 
anastomosing  with  the  internal 
pudic  artery;  and  the  muscles 
attached  to  the  tuberosity  of  the 
ischium,  anastomosing  with  the 
external  branch  of  the  obturator 
and  the  internal  circumflex 
arteries. 

The  coccygeal  branch  runs  inward,  pierces  the  great  sacrosciatic  ligament,  and 
supplies  the  Gluteus  maximus,  the  integument,  and  other  structures  on  the  back 
of  the  coccyx. 

The  comes  nervi  ischiadic!  (a.  comitans  n.  ischiadici)  is  a  long,  slender  vessel 
which  accompanies  the  great  sciatic  nerve  for  a  short  distance;  it  then  penetrates 
it  and  runs  in  its  substance  to  the  lower  part  of  the  thigh. 


Superior  intet  md, 
artictilai . 


Superior  external 
articular. 


Inferior  muscular 


Fig.  477.— The  arter">3  of  the  gluteal  and  posterior  femoral 
regionb 


678  THE  VASCULAR  SYSTEMS 

The  anastomotic  artery  is  directed  downward  across  the  External  rotators  and 
assists  in  forming  the  so-called  crucial  anastomosis  by  anastomosing  with  the 
superior  perforating  and  the  internal  and  external  circumflex  arteries. 

The  articular  branch,  generally  derived  from  the  anastomotic,  is  distributed  to 
the  capsule  of  the  hip-joint. 

The  cutaneous  branches  are  distributed  to  the  skin  of  the  buttock  and  back  of 
the  thigh. 

The  iliolumbar  artery  (a.  iliolumhalis),  given  off  from  the  posterior  trunk  of 
jhe  internal  iliac,  turns  upward  and  outward  between  the  obturator  nerve  and 
lumbosacral  cord,  to  the  inner  margin  of  the  Psoas  muscle,  behind  which  it  divides 
into  a  lumbar  and  an  iliac  branch. 

The  lumbar  branch  (ramus  lumhalis)  supplies  the  Psoas  and  Quadratus  lum- 
borum  muscles,  anastomosing  with  the  last  lumbar  artery,  and  sends  a  small 
spinal  branch  (ramus  spinalis)  through  the  intervertebral  foramen,  between  the 
last  lumbar  vertebra  and  the  sacrum,  into  the  vertebral  canal,  to  supply  the 
Cauda  equina. 

The  iliac  branch  (ramus  iliacus)  descends  to  supply  the  Iliacus  muscle;  some 
offshoots,  running  between  the  muscle  and  the  bone,  anastomose  with  the  iliac 
branch  of  the  obturator;  one  of  these  enters  an  oblique  canal  to  supply  the  diploe, 
while  others  run  along  the  crest  of  the  ilium,  distributing  branches  to  the  Gluteal 
and  Abdominal  muscles,  and  anastomose  in  their  course  with  the  gluteal  circum- 
flex iliac,  and  external  circumflex  arteries. 

The  lateral  sacral  arteries  (a.  sacralis  lateralis)  (Fig.  472)  are  usually  two 
in  number — superior  and  inferior. 

The  superior,  which  is  of  large  size,  passes  inward,  and,  after  anastomosing 
with  branches  from  the  middle  sacral,  enters  the  first  or  second  anterior  sacral 
foramen,  supplies  branches  to  the  contents  of  the  sacral  canal,  and,  escaping  by 
the  corresponding  posterior  sacral  foramen,  is  distributed  to  the  skin  and  muscles 
on  the  dorsum  of  the  sacrum,  anastomosing  with  the  gluteal. 

The  inferior  passes  obliquely  across  the  front  of  the  Pyriformis  muscle  and 
sacral  nerves  to  the  inner  side  of  the  anterior  sacral  foramina,  descends  on  the 
front  of  the  sacrum,  and  anastomoses  over  the  coccyx  with  the  middle  sacral  and 
opposite  lateral  sacral  artery.  In  its  course  it  gives  off  branches  which  enter  the 
anterior  sacral  foramina  (rami  spinales);  these,  after  supplying  the  contents  of  the 
sacral  canal,  escape  by  the  posterior  sacral  foramina,  and  are  distributed  to  the 
muscles  and  skin  on  the  dorsal  surface  of  the  sacrum,  anastomosing  with  the  gluteal. 

The  gluteal  artery  (a.  glutaea  superior)  (Fig.  477)  is  the  largest  branch  of 
the  internal  iliac,  and  appears  to  be  the  continuation  of  the  posterior  division  of 
that  -s-essel.  It  is  a  short,  thick  trunk  which  runs  backward  between  the  lumbo- 
sacral cord  and  the  first  sacral  nerve,  and,  passing  out  of  the  pelvis  above  the 
upper  border  of  the  Pyriformis  muscle,  immediately  divides  into  a  superficial 
and  a  deep  branch.  AVithin  the  pelvis  it  gives  off  a  few  muscular  branches  to  the 
Iliacus,  Pyriformis,  and  Obturator  internus,  and,  just  previous  to  emerging  from 
that  cavity,  a  nutrient  artery  which  enters  the  ilium. 

The  superficial  branch  enters  the  deep  surface  of  the  Gluteus  niaximus,  and 
divides  into  numerous  branches,  some  of  which  supply  the  muscle,  while  others  per- 
forate its  tendinous  origin,  and  supply  the  integument  covering  the  posterior  sur- 
face of  the  sacrum,  anastomosing  with  the  posterior  branches  of  the  sacral  arteries. 

The  deep  branch  lies  under  the  Gluteus  medius  and  almost  immediately  sub- 
divides into  two.  Of  these,  the  superior  division  (ramus  superior),  continuing  the 
original  course  of  the  vessel,  passes  along  the  upper  border  of  the  Gluteus  mini- 
mus to  the  anterior  superior  spine  of  the  ilium,  anastomosing  with  the  circumflex 
iliac  and  ascending  branches  of  the  external  circumflex  artery.  The  inferior 
division  (ramus  inferior)  crosses  the  Gluteus  minimus  obliquely  to  the  trochanter 


THE  EXTERNAL  ILIAC  ARTERY  679 

major,  distributing  branches  to  the  Gluteus  muscles,  and  anastomoses  with  the 
external  circumflex  artery.  Some  branches  pierce  the  Gluteus  minimus  to  supply 
the  hip-joint. 

Surface  Marking. — The  position  of  the  three  main  branches  of  the  internal  iliac,  the 
sciatic,  internal  pudic,  and  gluteal,  which  may  occasionally  be  I  he  objcil  of  siii-;.i(al  inlcrference, 
is  indicated  on  the  surface  in  the  following  way:  A  line  is  to  br  drau  n  Iniin  ilji'  |ii»(iTior  suije- 
rior  iliac  spine  to  the  posterior  superior  angle  of  the  great  troehanlcr,  willi  the  hinb  .slightly 
fie.xed  and  rotated  inward;  the  point  of  emergence  of  the  gluteal  artery  from  the  upper  part  of 
the  sciatic  notch  will  correspond  with  the  junction  of  the  upper  with  the  middle  third  of  this 
line.  A  second  line  is  to  be  drawn  from  the  same  point  to  the  outer  part  of  the  tuberosity  of 
the  ischium;  the  junction  of  the  lower  with  the  middle  third  marks  the  point  of  emergence  of 
the  sciatic  and  pudic  arteries  from  the  great  sciatic  notch. 

Applied  Anatomy. — Any  of  these  three  vessels  may  require  ligating  for  a  wound  or  for 
aneurism,  which  is  generally  traumatic.  The  gluteal  artery  is  ligated  by  turning  the  patient 
two-thirds  over  on  his  face  and  making  an  incision  from  the  posterior  superior  spine  of  the  ilium 
to  the  upper  and  posterior  angle  of  the  great  trochanter.  This  must  expose  the  Gluteus  maxi- 
mus  muscle,  and  its  fibres  are  to  be  separated  through  the  whole  thickness  of  the  muscle  and 
pulled  apart  with  retractors.  The  contiguous  margins  of  the  Gluteus  medius  and  Pyriformis 
are  now  to  be  separated  from  each  other,  and  the  artery  will  be  exposed  emerging  from  the 
sciatic  notch.  In  ligation  of  the  sciatic  artery,  the  incision  should  be  made  parallel  with  that 
for  ligation  of  the  gluteal,  but  one  inch  and  a  half  lower  down.  After  the  fibres  of  the  Gluteus 
maximus  have  been  separated,  the  vessel  is  to  be  sought  for  at  the  lower  border  of  the  Pyri- 
formis; the  great  sciatic  nerve,  which  lies  just  above  it,  forms  the  chief  guide  to  the  artery. 
The  internal  pudic  can  be  reached  through  the  incision  used  to  reach  the  sciatic. 

The  External  Iliac  Artery  (A.  Iliaca  Externa)  (Fig,  472). 

The  external  iliac  artery  is  larger  in  the  adult  than  is  the  internal  iliac.  It 
passes  obliquely  downward  and  outward  along  the  inner  border  of  the  Psoas 
muscle,  from  the  bifurcation  of  the  common  iliac  to  a  point  beneath  Poupart's 
ligament,  midway  between  the  anterior  superior  spine  of  the  ilium  and  the  sym- 
physis pubis,  where  it  enters  the  thigh  and  becomes  the  femoral  artery. 

Relations. — In  front,  the  artery  is  in  relation  with  the  peritoneum,  subperitoneal  areolar 
tissue,  the  termination  of  the  ileum  on  the  right  side,  and  the  sigmoid  flexure  on  the  left,  and  a 
thin  layer  of  fascia  derived  from  the  iliac  fascia,  which  surrounds  the  artery  and  vein.  At  its 
origin  it  is  crossed  by  the  ovarian  artery  in  the  female,  and  occasionally  by  the  ureter.  The 
spermatic  vessels  descend  for  some  distance  upon  it  near  its  termination,  and  it  is  crossed  in 
this  situation  by  the  genital  branch  of  the  genitofemoral  nerve  and  the  deep  circumflex  iliac 
vein;  the  vas  deferens  in  the  male,  and  the  round  ligament  in  the  female,  curve  down  along  its 
inner  side.  Behind,  it  is  in  relation  with  the  inner  border  of  the  Psoas  muscle,  from  which  it  is 
separated  by  the  iliac  fascia.  At  the  upper  part  of  its  course,  the  external  iliac  vein  lies  partly 
behind  it,  but  lower  down  lies  entirely  to  its  inner  side.  Externally,  it  rests  against  the  Psoas 
muscle,  from  which  it  is  separated  by  the  iliac  fascia.  Numerous  lymphatic  vessels  and  nodes 
are  found  lying  on  the  front  and  inner  side  of  the  vessel. 

Plan  of  the  Relations  of  the  External  Iliac  Artery. 

In  front. 
Peritoneum,  intestines,  and  fascia. 
vr  (  Lymphatic  vessels  and  nodes. 

p  t'     J  Spermatic  vessels. 

J  .   "       ,    j  Genitofemoral  nerve  (genital  branch). 
"  '  V  Deep  circumflex  iliac  vein. 

Outer  side.  /  \  Inner  side. 

Psoas  magnus.  I        iiiac.  External  iliac  vein  and  vas  deferens 


Iliac  fascia.  \  /  near  Poupart's  ligament. 


Behind. 
External  iliac  vein. 

Psoas  magnus. 


680  THE   VASCULAB  SYSTEMS 

Surface  Marking. — The  surface  line  indicating  the  course  of  the  external  iliac  artery  has 
been  already  given  (see  page  669). 

Applied  Anatomy. — The  application  of  a  ligature  to  the  external  iliac  may  be  reciuired  in 
cases  of  aneurism  of  the  femoral  artery  or  for  a  wound  of  the  artery.  This  vessel  may  be  secured 
in  any  part  of  its  course,  excepting  near  its  upper  end,  which  is  to  be  avoided  on  account  of  the 
proximity  of  the  internal  iliac,  and  near  its  lower  end,  which  should  also  be  avoided,  on  account 
of  the  proximity  of  the  deep  epigastric  and  circumflex  iliac  vessels.  The  patient  having  been 
placed  in  the  supine  position,  an  incision  should  be  made,  commencing  below  at  a  point  about 
three-quarters  of  an  inch  above  Poupart's  ligament,  and  a  little  external  to  its  middle,  and  run- 
ning upward  and  outward,  parallel  to  Poupart's  ligament,  to  a  point  one  inch  internal  and  one 
inch  above  the  anterior  superior  spine  of  the  ilium.  When  the  artery  is  deeply  seated  more 
room  will  be  required,  and  may  be  obtained  by  curving  the  incision  from  the  point  last  named 
inward  toward  the  umbilicus  for  a  short  distance.  The  Abdominal  muscles  and  transversalis 
fascia  having  been  cautiously  divided,  the  peritoneum  should  be  separated  from  the  iliac  fossa 
and  raised  toward  the  peh-is;  and  on  introducing  the  finger  to  the  bottom  of  the  wound,  the  artery 
may  be  felt  pulsating  along  the  inner  border  of  the  Psoas  muscle.  The  external  iliac  vein  is 
generally  found  on  the  inner  side  of  the  artery,  and  must  be  cautiously  separated  from  it  by  the 
finger  nail  or  handle  of  the  knife,  and  the  aneurism  needle  should  be  introduced  on  the  inner  side, 
between  the  artery  and  the  vein. 

Ligation  of  the  external  iliac  artery  is  also  performed  by  a  transperitoneal  method.  An  incis- 
ion four  inches  in  length  is  made  in  the  semilunar  line,  commencing  about  an  inch  below  the  um- 
bilicus and  carried  tlu-ough  the  abdominal  wall  into  the  peritoneal  cavity.  The  intestines  are 
then  pushed  upward  and  held  out  of  the  way  by  a  broad  abdominal  retractor,  and  an  incision  is 
made  through  the  peritoneum  at  the  brim  of  the  pelvis  in  the  course  of  the  arterj-,  and  the 
vessel  is  seciu'ed  in  any  part  of  its  course  which  may  seem  desirable  to  the  operator.  The  advan- 
tages of  this  operation  appear  to  be  that  if  it  is  found  necessary  the  common  iliac  artery  can  be 
ligated  instead  of  the  external  iliac  without  extension  or  modification  of  the  incision:  and  secondly, 
that  the  vessel  can  be  ligated  without  in  any  way  interfering  with  the  co\-erings  of  the  sac 
of  an  aneurism.  Possibly  a  disadvantage  may  exist  in  the  greater  risk  of  hernia  after  this 
method. 

Collateral  Circulation. — The  principal  anastomoses  in  carrying  on  the  collateral  circulation, 
after  the  application  of  a  ligature  to  the  external  iliac,  are  the  iliolumbar  with  the  circumflex 
iliac;  the  gluteal  with  the  external  circumflex;  the  obturator  with  the  internal  circumflex;  the 
sciatic  with  the  superior  perforating  and  circumflex  branches  of  the  profunda  artery;  and  the 
internal  pudic  with  the  external  pudic.  When  the  obturator  arises  from  the  epigastric  it  is 
supplied  with  blood  by  branches,  either  from  the  internal  iliac,  the  lateral  sacral,  or  the  internal 
pudic.  The  epigastric  receives  its  supply  from  the  internal  mammary  and  inferior  intercostal 
arteries,  and  from  the  internal  iliac  by  the  anastomoses  of  its  branches  with  the  obturator.' 

Branches. — Besides  several  small  branches  to  the  Psoas  muscle  and  the  neigh- 
boring lymph  nodes,  the  external  iliac  gives  oflf  two  branches  of  considerable 
size — the  deep  epigastric  and  deep  circumfle.^  iliac  arteries.  ( 

The  deep  epigastric  artery  (a.  epigasfrica  inferior)  (Fig.  472)  arises  from 
the  external  iliac  above  Poupart's  ligament.  It  curves  forward  below  the  peri- 
toneum, and  then  ascends  obliqtiely  along  the  inner  margin  of  the  internal  ab- 
dominal ring,  Ij'ing  between  the  transversalis  fascia  and  peritoneum;  continuing 
its  course  upward,  it  pierces  the  transversalis  fascia,  and  passing  over  the  semi- 
lunar fold  of  Douglas,  ascends  between  the  Rectus  and  the  posterior  lamella  of 
its  aponeurotic  sheath.  It  finally  divides  mto  numerous  branches  which  anasto- 
mose, above  the  umbilicus,  with  the  superior  epigastric  branch  of  the  internal 
mammary  and  with  the  lower  intercostal  arteries  (Fig.  458).  As  the  deep  epi- 
gastric artery  passes  obliquely  upward  and  inward  from  its  origin  it  lies  along  the 
lower  and  inner  margin  of  the  internal  abdominal  ring  and  behind  the  commence- 
ment of  the  spermatic  cord.  This  part  of  the  vessel  is  crossed  by  the  vas  deferens 
in  the  male  and  the  round  ligament  of  the  uterus  in  the  female. 

Branches. ^The  branches  of  this  vessel  are:  The  cremasteric  (a.  spermafica 
externa  in  the  male,  a.  ligamenti  teretis  uteri  in  the  female),  which  accompanies  the 
spermatic  cord,  and  supplies  the  Cremaster  muscle  and  other  coverings  of  the 

1  Sir  Astley  Cooper  describes  the  dissection  of  a  limb  eighteen  years  after  successful  ligation  of  the  external  iliac 
artery  in  Vol.  I  of  Guy's  Hospital  Reports. 


THE  EXTERNAL  ILIAC  ARTERY 


681 


spermatic  cord,  anastomosing  with  the  spermatic  artery  in  the  male,  and  which 
accompanies  the  round  ligament  in  the  female;  a  pubic  branch  {ramus  puhicu.i), 
which  runs  along  Poupart's  ligament,  and  then  descends  behind  the  os  pubis 
to  the  inner  side  of  the  femoral  ring,  and  anastomoses  with  offshoots  from  the 
obturator  artery;  muscular  branches,  some  of  which  are  distributed  to  the  Abdominal 
muscles  and  peritoneum,  anastomosing  with  the  lumbar  and  circumflex  iliac 
arteries;  cutaneous  branches,  which  perforate  the  tendon  of  the  External  oblique, 
and  supply  the  integument,  anastomosing  with  branches  of  the  superficial  epi- 
gastric.    . 


Fig.  478. — Femoral  sheath  laid  open  to  sh 


compartments. 


:  portion  of  fascia  lata  removed. 


Peculiarities. — The  origin  of  the  deep  epigastric  may  take  place  from  any  part  of  the  external 
iliac  between  Poupart's  ligament  and  two  inches  and  a  half  above  it,  or'  it  may  arise  below  this 
ligament,  from  the  common  femoral  or  from  the  deep  femoral.  It  frequentl_y  arises  from  the 
external  iliac  by  a  common  trunk  with  the  obturator.  Sometimes  the  epigastric  arises  from 
the  obturator,  the  latter  vessel  being  furnished  by  the  internal  iliac,  or  the  epigastric  may  be 
formed  by  two  branches,  one  derived  from  the  external  iliac,  the  other  from  the  internal  iliac. 

Applied.  Anatomy. — The  deep  epigastric  artery  follows  a  line  drawn  from  the  middle  of 
Poupart's  ligament  toward  the  umbilicus;  but  shortly  after  this  line  cro.sses  the  linea  semilunaris 
the  direction  changes,  and  the  course  of  the  vessel  is  directly  upward  in  the  line  of  junction  of 
the  inner  third  with  the  outer  two-thirds  of  the  Rectus  muscle.  It  has  important  surgical  rela- 
tions, in  addition  to  the  fact  that  it  is  one  of  the  principal  means,  through  its  anastomosis  with 
the  internal  mammary,  in  establishing  the  collateral  circulation  after  ligation  of  either  the  com- 
mon or  external  iliac  arteries.  It  lies  close  to  the  internal  abdominal  ring,  and  is  therefore 
internal  to  an  oblique  inguinal  hernia,  but  external  to  a  direct  inguinal  hernia,  as  the  hernip 
emerges  from  the  abdomen.  It  forms  the  outer  boundary  of  Hesselbach's  triangle.  It  is  ii. 
close  relationship  with  the  spermatic  cord,  which  lies  in  front  of  it  in  the  inguinal  canal,  separatefl 
only  by  the  transversalis  fascia.     The  vas  deferens  curves  round  its  outer  side. 


682 


THE  VASCULAR  SYSTEMS 


The  deep  circumflex  iliac  artery  (o.  cireumflexa  ilium  -profunda)  (Fig.  471) 
arises  from  the  outer  side  of  the  external  ihac  nearly  opposite  the  epigastric  artery. 
It  ascends  obliquely  outward  behind  Poupart's  ligament,  contained  in  a  fibrous 
sheath  formed  by  the  junction  of  the  transversalis  and  iliac  fascite,  to  the  anterior 
superior  spinous  process  of  the  ilium.  It  then  runs  along  the  inner  surface  of  the 
crest  of  the  ilium  to  about  its  middle,  where  it  pierces  the  Transversalis,  and 
runs  backward  between  that  muscle  and  the  Internal  oblique,  to  anastomose  with 
the  iliolumbar  and  gluteal  arteries.  Opposite  the  anterior  superior  spine  of  the 
ilium  it  gives  off  a  large  branch  which  ascends  between  the  Internal  oblique  and 
Transversalis  muscles,  supplying  them,  and  anastomosing  with  the  lumbar  and 
epigastric  arteries.     It  also  gives  off  cutaneous  branches. 


Femoral 
Pouimrt's  hgament.     branch    Femoral ; 


External 
cutaneous  nerve. 


Iliac  portion  of        Sheath  of 
fascia  lata. 


Femoral  vein. 
Femoral  rifig.^ 

GimberiviV 


Femoral  artery. 
Fig.  479. — Structures  which  pass  beneath  the  crural  arch. 


ARTERIES  OF  THE  LOWER  EXTREMITY 


The  artery  which  supplies  the  greater  part  of  the  lower  extremity  is  the  direct 
continuation  of  the  external  iliac.  It  continues  as  a  single  trunk  from  Poupart's 
ligament  to  the  lower  border  of  the  Popliteus  muscle,  and  here  divides  into  two 
branches,  the  anterior  and  posterior  tibial.  For  convenience  of  description,  the 
upper  part  of  the  main  trunk  is  named  femoral,  the  lower  part,  popliteal. 


THE  FEMORAL  ARTERY 


G83 


THE  FEMORAL  ARTERY  (A.  FEMORALIS)  (Figs.  4S1  and  4S-2). 

The  femoral  artery  commences  immediately  behind  Poupart's  ligament,  midway 
between  the  anterior  superior  spine  of  the  ilium  and  the  symphysis  pubis,  and, 
passing  down  the  fore  part  and  inner  side  of  the  thigh,  terminates  at  the  opening 
in  the  Adductor  raagnus,  at  the  junction  of  the  middle  with  the  lower  third  of  the 
thigh,  where  it  becomes  the  popliteal  artery.  The  vessel,  at  the  upper  part  of 
the  thigh,  lies  in  front  of  the  hip-joint,  on  a  line  with  the  innermost  part  of  the 
head  of  the  femur;  in  the  lower  part  of  its  course  it  is  in  close  relation  with  the 
inner  side  of  the  shaft  of  the  bone,  and  between  these  two  parts  the  vessel  is  some 
distance  from  the  bone.  The  first  inch  and  a  half  of  the  vessel  is  enclosed, 
together  with  the  femoral  vein,  in  a  fibrous  sheath — the  femoral  sheath.  In  the 
upper  third  of  the  thigh  it  is  contained  in  a  triangular  space  called  Scarpa's  triangle, 
and  in  this  space  it  gives  off  its  largest  branch,  the  deep  femoral.  In  the  middle 
third  of  the  thigh  it  is  contained  in  an  aponeurotic  canal  called  Hunter's  canal. 
That  portion  of  the  femoral  artery  which  extends  from  Poupart's  ligament  to  the 
origin  of  the  deep  femoral  is  sometimes  called  the  common  femoral;  its  continua- 
tion is  the  superficial  femoral. 


Fig.  480.— The  relation 


of  the  femoral  and  internal  abdominal  rings,  seen  from  within  the  abdomen. 
Right  side. 


The  femoral  or  crural  sheath  (Fig.  479)  is  a  continuation  downward  of  the 
fasciffi  that  line  the  abdomen,  the  transversalis  fascia  passing  down  in  front  of  the 
femoral  vessels,  and  the  iliac  fascia  descending  behind  them ;  these  fascia^  are  directly 
continuous  on  the  iliac  side  of  the  femoral  artery,  but  a  small  space  exists  between 
the  femoral  vein  and  the  point  where  they  are  continuous  on  the  pubic  side  of  that 
vessel,  which  constitutes  the  femoral  or  crural  canal  (Fig.  479).  The  femoral 
sheath  is  closely  adherent  to  the  contained  vessels  about  an  inch  below  the  saphe- 
nous opening,  tjcing  blended  with  the  sheath  of  the  vessels,  but  opposite  Pou- 
part's ligament  it  is  much  larger  than  is  required  to  contain  them;  hence  the 
funnel-shaped  form  which  it  presents.  The  outer  border  of  the  sheath  is  perfo- 
rated by  the  femoral  nerve.  Its  inner  border  is  pierced  by  the  internal  saphenous 
vein  and  numerous  lymphatic  vessels.  In  front  it  is  covered  by  the  iliac  portion 
of  the  fascia  lata;  and  behind  it  is  the  pubic  portion  of  the  same  fascia. 


684 


THE  VASCULAR  SYSTEMS 


The  anterior  wall  of  the  sheath  is  a  thickened  band  of  fascia  continuous  above 
Poupart's  ligament  with  the  transversalis  fascia,  called  the  deep  crural  arch.  From 
it  stretch  two  septa,  one  between  the  femoral  artery  and  the  vein,  the  other  lying 
just  internal  to  the  vein,  and  cutting  off  a  small  space  between  the  vein  and 
the  inner  wall  of  the  sheath.  The  septa  are  stretched  between  the  anterior  and 
posterior  walls  of  the  sheath,  so  that  each  vessel  is  enclosed  in  a  separate  compart- 
ment.    The  interval  left  between  the  vein  and  the  inner  wall  of  the  sheath  is  not 


CIRCUMFLEX 


DEEP 

EXTERNAL 

PUDIC 

INTERNAL 

CIRCUMFLEX 


SUPERIOR  EXTER 
NAL  ARTtCULAI 
BRANCH  O 
POPLITEAL 


Fig.  4S1. — Scheme  of  the  femoral  artery. 


and  Charpy.) 


filled  up  by  any  structure,  excepting  a  little  loose  areolar  tissue,  a  few  lymphatic 
vessels,  and  occasionally  by  a  small  lymph  node;  this  is  the  femoral  or  crural 
canal  through  which  the  intestine  descends  in  femoral  hernia. 

The  femoral  or  crural  canal  (canalis  femoralis)  (Figs.  479  and  480)  is  the 
narrow  interval  between  the  femoral  vein  and  the  inner  wall  of  the  femoral  sheath. 
It  exists  as  a  distinct  canal  only  when  the  sheath  has  been  separated  from  the  vein 
by  dissection  or  by  the  pressure  of  a  hernia  or  tumor.     Its  length  is  from  a  quarter 


THE  FEMORAL  ARTERY 


G85 


to  half  an  inch,  and  it  extends  from  the  femoral  ring  to  the  upper  part  of  (he 
saphenous  opening. 

This  canal  has  two  orifices — an,  upper  one,  tiie  femoral  or  crural  ring,  closed  by 
the  septum  crurale;  and  a  lower  one,  the  saphenous  opening,  closed  l)y  the  cribri- 
form fascia. 

-  The  femoral  or  crural  ring  (afinulus  femoralis)  (Figs.  462  and  463)  is  the  upper 
opening  of  the  femoral  canal,  and  leads  into  the  cavity  of  the  abdomen.  It  is 
of  an  oval  form;  its  long  diameter, 
directed  transversely,  measures 
about  half  an  inch,  and  it  is  larger 
in  the  female  than  in  the  male, 
which  is  one  of  the  reasons  of 
the  greater  frequency  of  femoral 
hernia  in  the  former  sex. 

Scarpa's  triangle  (trigomim 
femorale)  corresponds  to  the  de- 
pression seen  immediately  below 
the  fold  of  the  groin.  It  is  a 
triangular  space,  the  apex  of 
which  is  directed  downward,  and 
the  sides  formed  externally  by  the 
Sartorius,  internally  by  the  inner 
margin  of  the  Adductor  longus, 
and  above  by  Poupart's  ligament. 
The  floor  of  the  space  is  formed 
from  without  inward  by  the  Ilia- 
cus,  Psoas,  Pectineus  (in  some 
cases  a  small  part  of  the  Adduc- 
tor brevis),  and  the  Adductor 
longus  muscles;  and  it  is  divided 
into  two  nearly  equal  parts  by 
the  femoral  vessels,  which  extend 
from  the  middle  of  its  base  to  its 
apex,  the  artery  giving  off  in  this 
situation  its  superficial  and  pro- 
funda branches,  the  vein  receiving 
the  deep  femoral  and  internal 
saphenous.  On  the  outer  side  of 
the  femoral  artery  is  the  femoral 
nerve  dividing  into  its  branches. 
In  the  outer  corner  of  the  space 
is  the  external  cutaneous  nerve. 
Within  the  sheath  of  the  artery, 
and  lying  upon  the  outer  side  of 
the  vessel,  is  the  femoral  branch 
of  the  genitofemoral  nerve.  At 
the  base  of  the  triangle  the  vein 
is  to  the  inner  side  of  the  artery; 
at  the  apex  of  the  triangle  it  is 
passing  behind  the  artery.  Besides 
the  vessels  and  nerves,  this  space 
contains  some  fat  and  lymphatics. 

Hunter's  canal,  or  the  adductor  canal  (canalis  adductorius  [HtDtteri])  (Fig. 
381),  is  the  aponeurotic  space  in  the  middle  third  of  the  thigh,  extending  from 


Lonq  •saphenous 
net  ve. 

■inastomotica 
magna 


Ana'itomotica 


Iiifetio}  internal 
ailicithty. 


Fig.  4S2. — The  femoral  artery. 


686  THE  VASCULAR  SYSTEMS 

the  apex  of  Scarpa's  triangle  to  the  femoral  opening  in  the  Adductor  magnus 
muscle.  It  is  bounded,  externally,  by  the  Vastus  internus;  internally,  by  the 
Adductors  longus  and  magnus  muscles;  and  is  covered  in  by  a  strong  aponeurosis 
which  extends  transversely  from  the  Vastus  internus  across  the  femoral  vessels 
to  the  Adductor  longus  and  magnus;  lying  on  which  aponeurosis  is  the  Sartorius 
muscle.  It  contains  the  femoral  artery  and  vein  enclosed  in  their  own  sheath  of 
areolar  tissue,  the  vein  being  behind  and  on  the  Outer  side  of  the  artery,  and  the 
internal  or  long  saphenous  nerve  lying  at  first  on  the  outer  side  and  then  in  front 
of  the  vessels. 

Relations. — The  relations  of  the  artery  differ  along  its  course.  In  Scarpa's  triangle  the 
femoral  artery  is  very  superficial,  being  covered  by  the  skin  and  superficial  fascia,  superficial 
inguinal  lymph  nodes,  the  iliac  portion  of  the  fascia  lata,  and  the  anterior  part  of  the  femoral 
sheath.  The  femoral  branch  of  the  genitofemoral  nerve  courses  for  a  short  distance  within  the 
outer  compartment  of  the  femoral  sheath  and  lies  at  first  in  front  and  then  on  the  outer  side  of 
the  artery.  Near  the  apex  of  Scarpa's  triangle  the  internal  cutaneous  nerve  crosses  the  artery 
from  without  inward. 

Behind  the  artery  are  the  posterior  part  of  the  femoral  sheath,  the  pubic  portion 
of  the  fascia  lata,  the  inner  part  of  the  tendon  of  the  Psoas,  the  Pectineus  and 
Adductor  longus.  The  artery  is  separated  from  the  capsule  of  the  hip-joint  by 
the  tendon  of  the  Psoas,  from  the  Pectineus  by  the  femoral  vein  and  profunda 
vessels,  and  from  the  Adductor  longus  by  the  femoral  vein.  The  nerve  to  the 
Pectineus  passes  inward  behind  the  artery.  On  the  outer  side  of  the  artery,  but 
separated  from  it  by  some  fibres  of  the  Psoas,  is  the  femoral  nerve.  The  femoral 
vein  is  on  the  inner  side  of  the  upper  part  of  the  artery,  but  is  behind  the  vessel 
in  the  lower  part  of  Scarpa's  triangle. 


Plan  of  the  Relations  of  the  Femoral  Artery  in  Scarpa's  Triangle. 

In  front. 

Skin  and  superficial  fascia. 
Superficial  inguinal  nodes. 
Iliac  portion  of  fascia  lata. 
Prolongation  of  transversalis  fascia. 
Femoral  branch  of  genitofemoral  nerve. 
•  Superficial  circumflex  iliac  vein. 

Superficial  epigastric  vein. 


Inner  side. 


Outer  side. 


Small     part  of  Psoas  muscle, 
Femoral  vein.  \     Artery,     j  separating  the  artery  from 

the  femoral  nerve. 

Behind. 

Prolongation  of  fascia  covering  the  Iliacus  muscle. 

Pubic  portion  of  fascia  lata. 

Nerve  to  Pectineus. 

Tendon  of  Psoas  muscle. 

Pectineus  muscle. 

Capsule  of  hip-joint. 

In  Hunter's  canal  the  femoral  artery  is  more  deeply  situated,  being  covered 
by  the  integument,  the  superficial  and  deep  fascite,  the  Sartorius  and  the  fibrous 
roof  of  the  canal;  it  is  crossed  from  without  inward  by  the  long  saphenous  nerve. 
Behind  the  artery  are  the  Adductores  longus  et  magnus;  in  front  and  to  its  outer 
side  is  the  Vastus  internus.  The  femoral  vein  lies  behind  the  upper  part,  and  on 
the  outer  side  of  the  lower  part  of  the  artery.     As  the  artery  passes  out  of  Scarpa's 


THE  FEMORAL  ARTERY 


687 
it  for 


triangle  into  Hunter's  canal,  the  Iliacus  and  Pectineus  muscles  lie  heliiiu 
a  short  distance  (Fig.  482). 

That  portion  of  the  femoral  artery  which  extends  from  Poupart's  ligament 
to  the  origin  of  the  profunda  is  sometimes  named  the  common  femoral. 

Plan  of  the  Relations  of  the  Femoral  Artery  in  Hunter's  Canal. 

In  front. 
Skin,  superficial  and  deep  fasciie. 
Internal  cutaneous  nerve. 
Sartorius. 

Aponeurotic  covering  of  Hunter's  canal. 
Internal  saphenous  nerve. 


Inner  side. 

Adductor  longus. 
Adductor  magnus. 
Sartorius. 


•  Behind. 


Outer  side. 

Long  saphenous  nerve. 
Nerve  to  Vastus  internus. 
Vastus  internus. 
Femoral  vein  (below). 


Femoral  vein  (above). 
Profunda  artery  and  vein. 
Pectineus  and  Iliacus  (high  up). 
Adductor  longus. 
Adductor  magnus. 

Peculiarities,  Double  Femoral  Reunited.— Several  cases  are  recorded  in  which  the  femoral 
artery  divided  into  two  trunl;s  below  the  origin  of  the  profunda,  and  became  reunited  near  the 
opening  of  the  Adductor  magnus  so  as  to  form  a  single  popliteal  artery.  One  of  them  occurred 
in  a  patient  operated  upon  for  popliteal  aneurism. 

Change  of  Position.— A  few  cases  have  been  recorded  in  which  the  femoral  artery  was 
situated  at  the  back  of  the  thigh,  the  vessel  being  continuous  above  with  the  internal  iliac,  escap- 
ing from  the  pelvis  through  the  great  sacrosciatic  foramen,  and  accompanying  the  great  sciatic 
nerve  to  the  po])Hteal  space,  where  its  division  occurred  in  the  usual  manner.  The  external 
iliac  in  these  cases  was  small,  and  terminated  in  the  profunda. 

Position  of  the  Vein. — The  femoral  vein  is  occasionally  placed  along  the  inner  side  of  the 
artery,  throughout  the  entire  extent  of  Scarpa's  triangle,  or  it  may  be  divided  so  that  a  large 
vein  is  placed  on  each  side  of  the  artery  for  a  greater  or  less  extent. 

Surface  Marking. — The  upper  two-thirds  of  a  line  drawn  from  a  point  midway  between 
the  anterior  superior  spine  of  the  ilium  and  the  symphysis  pubis  to  the  adductor  tubercle  on 
the  inner  condyle  of  the  femur,  with  the  thigh  abducted  and  rotated  outward,  will  indicate  the 
course  of  the  femoral  artery. 

AppUed  Anatomy. — Compression  of  the  femoral  artery,  which  is  constantly  requisite  in 
amputations  and  other  operations  on  the  lowerlimbs,  and  also  for  the  cure  of  popliteal  aneurisms, 
is  most  effectually  made  immediately  below  Poupart's  ligament.  In  this  situation  the  artery  is 
very  superficial,  and  is  merely  separated  from  the  ascending  ramus  of  the  os  pubis  by  the  Psoas 
muscle;  so  that  the  surgeon,  by  means  of  his  thumb  or  a  compressor,  may  effectualiy  control  the 
circulation  through  it.  This  vessel  may  also  be  compressed  in  the  middle  third  of  the  thigh  by 
placing  a  compress  over  the  artery,  beneath  the  tourniquet,  and  directing  the  pressure  from 
within  outward,  so  as  to  compress  the  vessel  against  the  inner  side  of  the  shaft  of  the  femur. 

The  application  of  a  ligature  to  the  femoral  artery  may  be  required  in  the  cases  of  wound  or 
aneurism  of  the  arteries  of  the  leg,  of  the  popliteal  or  femoral;'  and  the  vessel  may  be  exposed 
and  tied  in  any  part  of  its  course.  The  great  depth  of  this  vessel  at  its  lower  part,  its  close  con- 
nection with  important  structures,  and  the  density  of  its  sheath  render  the  operation  in  this 
situation  one  of  much  greater  difficulty  than  the  application  of  a  ligature  at  its  upper  part,  where 
it  is  more  superficial. 

Ligation  of  the  common  femoral  artery  is  usually  considered  unsafe,  on  account  of  the  con- 
nection of  large  branches  with  it — viz.,  the  deep  epigastric  and  the  deep  circumflex  iliac  arising 
just  above  Poupart's  ligament;  on  account  of  the  number  of  small  branches  which  arise,  from 
it  in  its  short  course;  and  on  account  of  the  uncertainty  of  the  origin  of  the  profunda  femoris, 
which,  if  it  arise  high  up,  would  be  too  close  to  the  ligature  for  the  formation  of  a  firm  coag- 
ulum.      The  profunda  sometimes  arises  higher  than  the  point  above  mentioned,  and  rarely 

'  Ligation  of  the  femoral  artery  has  been  also  recommended  and  performed  for  elephantiasis  of  the  leg  and 
acute  inflammation  of  the  knee-joint  (Maunder,  CUn.  See.  Trans.,  vol.  ii,  p.  37). 


688  THE  VASCULAR  SYSTEMS 

between  two  or  three  inches  (in  one  case  four)  below  Poupart's  ligament.  It  would  appear,  then, 
that  the  most  favorable  situation  for  the  application  of  a  ligature  to  the  femoral  is  on  the  super- 
ficial femoral  at  the  apex  of  Scarpa's  triangle.  In  order  to  expose  the  artery  in  this  situation, 
an  incision  between  three  and  four  inches  long  should  be  made  in  the  course  of  the  vessel,  the 
patient  lying  in  the  recumbent  position,  with  the  limb  slightly  flexed  and  abducted,  and  rotated 
outward.  A  large  vein  is  frequently  met  with,  passing  in  the  course  of  the  artery  to  join  the 
internal  saphenous  vein;  this  must  be  avoided,  and  the  fascia  lata  having  been  cautiously  divided 
and  the  Sartorius  exposed,  that  muscle  must  be  drawn  outward  in  order  to  expose  fully  the 
sheath  of  the  vessels.  The  finger  being  introduced  into  the  wound  and  the  pulsation  of  the 
artery  felt,  the  sheath  should  be  opened  on  the  outer  side  of  the  vessel  to  a  sufficient  extent  to 
allow  of  the  introduction  of  the  ligature,  but  no  farther;  otherwise  the  nutrition  of  the  coats  of 
the  vessel  may  be  interfered  with,  or  muscular  branches  which  arise  from  the  vessel  at  irregular 
intervals  may  be  divided.  In  this  part  of  the  operation  the  long  saphenous  nerve  and  the  nerve 
to  the  Vastus  internus,  which  is  in  close  relation  with  the  sheath,  should  be  avoided.  The 
aneurism  needle  must  be  carefully  introduced  and  kept  close  to  the  artery,  to  avoid  the  femoral 
vein,  which  lies  behind  the  vessel  in  this  part  of  its  course. 

To  expose  the  artery  in  Hunter's  canal,  an  incision  should  be  made  between  three  and  four 
inches  in  length,  a  finger's  breadth  internal  to  the  line  of  the  artery,  in  the  middle  of  the  thigh 
' — i.  e.,  midway  between  the  groin  and  the  knee.  The  integument  is  first  divided.  The  fascia 
lata  having  been  divided,  and  the  outer  border  of  the  Sartorius  muscle  exposed,  it  should  be 
draAvn  inward,  when  the  strong  fascia  which  is  stretched  across  from  the  Adductors  to  the  Vastus 
internus  will  be  exposed,  and  must  be  freely  divided;  the  sheath  of  the  vessels  is  now  seen, 
and  must  be  opened,  and  the  artery  secured  by  passing  the  aneurism  needle  between  the  vein 
and  artery  in  the  direction  from  without  inward.  The  femoral  vein  in  this  situation  lies  on  the 
outer  side  of  the  artery  and  the  long  saphenous  nerve  on  the  anterior  and  outer  side  of  the  artery. 

It  has  been  seen  that  the  femoral  artery  occasionally  divides  into  two  trunks  below  the  origin 
of  the  profunda.  If  in  the  operation  for  tying  the  femoral  two  vessels  are  met  with,  the  surgeon 
should  alternately  compress  each,  in  order  to  ascertain  which  vessel  is  connected  with  the 
aneurismal  tumor  or  with  the  bleeding  from  the  wound,  and  that  one  only  should  be  tied  which 
controls  the  pulsation  or  hemorrhage.  If,  however,,  it  is  necessary  to  compress  both  vessels 
before  the  circulation  in  the  tumor  is  controlled,  both  .should  be  tied,  as  it  would  be  probable  that 
they  became  reunited,  as  in  the  instances  referred  to  above. 

In  wounds  of  the  femoral  artery  the  question  of  the  mode  of  treatment  is  of  considerable 
importance.  If  the  wound  in  the  superficial  structures  is  a  large  one,  the  injured  vessel  must 
be  exposed  and  tied;  but  if  the  wound  is  a  punctured  one  and  the  bleeding  has  ceased,  the  ques- 
tion will  arise  whether  to  cut  down  upon  the  artery  or  to  trust  to  pressure.  Mr.  Cripps  advises 
that  if  the  wound  is  in  the  "  upper  part  of  the  thigh — that  is  to  say,  in  a  position  where  the  fem- 
oral artery  is  comparatively  superficial — the  surgeon  may  enlarge  the  opening  with  a  good 
prospect  of  finding  the  wounded  vessel  without  an  extensive  or  prolonged  operation.  If  the 
wound  be  in  the  lower  half  of  the  thigh,  owing  to  the  greater  depth  of  the  artery  and  the  possi- 
bility of  its  being  the  popliteal  that  is  wounded,  the  search  is  rendered  a  far  more  severe  and 
hazardous  operation,  and  it  should  not  be  undertaken  until  a  thorough  trial  of  pressure  has 
proved  ineffectual." 

Great  care  and  attention  are  necessary  for  the  successful  application  of  pressure.  The  limb 
should  be  carefully  bandaged  from  the  foot  upward  to  the  wound,  which  is  not  covered,  and  then 
onward  to  the  groin.  The  wound  is  then  dusted  with  iodoform  or  boracic  powder  and  a  conical 
pad  applied  o\'er  the  wound.  Rollers  the  thickness  of  the  index  finger  are  then  placed  along 
the  course  of  the  vessel  above  and  below  the  wound,  and  the  whole  carefully  bandaged  to  a  back 
splint  with  a  foot  piece. 

Collateral  Circulation. — After  ligation  of  the  femoral  artery,  the  main  channels  for  carry- 
ing on  the  circulation  are  the  anastomoses  between  (1)  the  gluteal  and  sciatic  branches  of 
the  internal  iliac  with  the  internal  and  external  circumflex  and  superior  perforating  branches 
of  the  profunda  femoris;  (2)  the  obturator  branch  of  the  internal  iliac  with  the  internal  circumflex 
of  the  profunda;  (.3)  the  internal  pudic  of  the  internal  iliac  with  the  superficial  and  deep  external 
pudic  of  the  common  femoral;  (4)  the  deep  circumflex  iliac  of  the  external  iliac  with  the  external 
circumflex  of  the  profunda  and  the  superficial  circumflex  iliac  of  the  femoral;  and  (.5)  the  sciatic 
and  comes  nervi  ischiadici  of  the  internal  iliac  with  the  perforating  branches  of  the  profunda. 

Branches  (Figs.  481  and  482). — The  branches  of  the  femoral  artery  are: 

Superficial  epigastric.  Muscular. 

Superficial  circumflex  iliac.  (  External  circumflex. 

Superficial  external  pudic.  Profunda  femoris  <  Internal  circumflex. 

Deep  external  pudic.  (  Three  perforating. 

Anastomotica  magna. 


THE  FEMOR. \L  AR TER  Y  GS9 

The  superficial  epigastric  (a.  cpigasirica  superficialis)  arises  from  the  fem- 
oral about  lialF  an  inch  helow  Poiipart's  ligament,  and,  passing  through  the 
saphenous  opening  in  the  fascia  lata,  ascends  on  the  abdomen  in  the  superficial 
fascia  covering  the  External  oblique  muscle,  nearly  as  high  as  the  umbilicus.  It 
distributes  branches  to  the  superficial  inguinal  nodes,  the  superficial  fascia,  and 
the  integument,  anastomosing  with  branches  of  the  deep  epigastric. 

The  superficial  circumflex  iliac  (a.  circumflexa  ilium  superficialis),  the  smallest 
of  the  cutaneous  branches,  arises  close  to  the  preceding,  and,  piercing  the  fascia 
lata,  runs  outward,  parallel  with  Poupart's  ligament,  as  far  as  the  crest  of  the 
ilium,  dividing  into  branches  which  supply  the  integument  of  the  groin,  the 
superficial  fascia,  and  the  superficial  inguinal  lymph  nodes,  anastomosing  with 
the  deep  circumflex  iliac  and  with  the  gluteal  and  external  circumflex  arteries. 

The  superficial  external  pudic  (a.  pudenda  externa  superficialis)  arises  from 
the  inner  side  of  the  femoral  artery,  close  to  the  preceding  vessels,  and,  after 
passing  through  the  saphenous  opening,  courses  inward,  across  the  spermatic 
cord  or  round  ligament,  to  be  distributed  to  the  integument  on  the  lower  part  of 
the  abdomen,  the  penis  and  scrotum  in  the  male,  and  the  labium  majus  in  the 
female,  anastomosing  with  branches' of  the  internal  pudic. 

The  deep  external  pudic  (a.  p^idenda  externa  profunda),  more  deeply  seated 
than  the  preceding,  passes  inward  across  the  Pectineus  and  Adductor  longus 
muscles,  covered  by  the  fascia  lata,  which  it  pierces  at  the  inner  border  of  the 
thigh,  its  branches  being  distributed,  in  the  male,  to  the  integument  of  the  scrotum 
and  perineum;  and  in  the  female  to  the  labium  majus,  anastomosing  with  branches 
of  the  superficial  perineal  artery. 

Muscular  branches  (rami  musculares)  are  supplied  by  the  femoral  to  the 
Sartorius,  Vastus  internus,  and  Adductors. 

The  deep  femoral,  or  the  profunda  femoris  (a.  profunda  femoris)  (Fig.  481 
and  482),  is  a  large  vessel  arising  from  the  outer  and  back  part  of  the  femoral 
artery,  from  one  to  two  inches  below  Poupart's  ligament.  It  at  first  lies  on  the 
outer  side  of  the  superficial  femoral,  and  then  passes  behind  it  and  the  femoral 
vein  to  the  inner  side  of  the  femur,  and,  passing  downward  beneath  the  Adductor 
longus,  terminates  at  the  lower  third  of  the  thigh  in  a  small  branch  which  pierces 
the  Adductor  magnus  (and  from  this  circumstance  is  sometimes  called  the  fourth 
perforating  artery),  and  is  distributed  to  the  Flexor  muscles  on  the  back  of  the  thigh, 
anastomosing  with  branches  of  the  popliteal  and  inferior  perforating  arteries. 
The  deep  femoral  supplies  all  the  tissues  on  the  back  and  outer  side  of  the  thigh 
not  supplied  by  the  sciatic  and  gluteal  arteries. 

Relations. — Behind,  it  lies  first  upon  the  Iliacus,  and  then  on  the  Pectineus,  Adductor 
brevis,  and  Adductor  magnus  muscles.  In  front,  it  is  separated  from  the  superficial  femoral 
artery,  above  by  the  femoral  and  profunda  veins,  and  below  by  the  Adductor  longus.  On  its 
outer  side  the  origin  of  the  Vastus  internus  separates  it  from  the  femur. 

Plan  of  the  Relations  of  the  Profunda  Artery. 

In  front. 
Superficial  femoral  artery. 
Femoral  and  profunda  veins. 
Adductor  longus. 

Outer  side. 
Vastus  internus. 

Beliind. 
Iliacus. 
Pectineus. 
Adductor  brevis. 
Adductor  magnus. 
44 


690  THE  VASCULAR  SYSTEMS 

Peculiarities  of  Origin  of  the  Profunda.— This  vessel  occasionally  arises  from  the  inner 
side,  and,  more  rarely,  from  the  back  of  the  common  trunk;  but  the  more  important  peculiarity, 
from  a  surgical  point  of  view,  is  that  which  relates  to  the  height  at  which  the  vessel  arises  from  the 
femoral.  In  three-fourths  of  a  large  number  of  cases  it  arose  between  one  to  two  inches  below 
Poupart's  ligament;  in  a  few  cases  the  distance  was  less  than  an  inch;  more  rarely,  opposite  the 
ligament;  and  in  one  case,  above  Poupart's  ligament,  from  the  external  iliac.  Occasionally, 
the  distance  between  the  origin  of  the  vessel  and  Poupart's  ligament  exceeds  two  inches,  and  in 
one  case  it  was  found  to  be  as  much  as  four  inches. 

Branches. — The  profunda  gives  off  the  following-named  branches: 

External  circumflex.  Four  perforating. 

Internal  circumflex.  Muscular. 

The  external  circumflex  artery  (a.  circumflexa  femoris  lateralis)  supplies  the 
muscles  on  the  front  of  the  thigh.  It  arises  from  the  outer  side  of  the  profunda, 
passes  horizontally  outward,  between  the  divisions  of  the  femoral  nerve  and 
behind  the  Sartorius  and  Rectus  muscles,  and  divides  into  three  sets  of  branches — 
ascending,  transverse,  and  descending. 

The  ascending  branch  {ramus  ascendens)  passes  upward,  beneath  the  Tensor 
fasciae  femoris  muscle,  to  the  outer  side  of  the  hip,  anastomosing  with  the  terminal 
branches  of  the  gluteal  and  deep  circumflex  iliac  arteries.  It  sends  out  muscular 
branches. 

The  descending  branch  (ramus  descendens)  passes  downward,  behind  the  Rectus, 
upon  the  Vasti  muscles,  to  which  its  branches  are  distributed,  one  or  two  passing 
beneath  the  Vastus  externus  as  far  as  the  knee,  anastomosing  with  the  superior 
articular  branches  of  the  popliteal  artery.  These  are  accompanied  by  the  branch 
of  the  femoral  nerve  to  the  Vastus  externus. 

The  transverse  branch,  the  smallest,  passes  outward  over  the  Crureus,  pierces 
the  Vastus  externus,  and  winds  around  the  femur  to  its  back  part,  just  below  the 
great  trochanter,  anastomosing  at  the  back  of  the  thigh  with  the  internal  circum- 
flex, sciatic,  and  superior  perforating  arteries. 

The  internal  circumflex  artery  (a.  circumf.exa  femoris  medialis),  smaller  than 
the  external,  arises  from  the  inner  and  back  part  of  the  profunda,  and  winds 
around  the  inner  side  of  the  femur,  between  the  Pectineus  and  Psoas  muscles.  On  ' 
reaching  the  upper  border  of  the  Adductor  brevis  it  gives  off  two  muscular  branches, 
one  of  which  passes  inward  to  be  distributed  to  the  Adductor  muscles,  the  Gracilis, 
and  Obturator  externus,  anastomosing  with  the  obturator  artery;  the  other 
descends,  and  passes  beneath  the  Adductor  brevis,  to  supply  it  and  the  great 
Adductor;  while  the  continuation  of  the  vessel  passes  backward  and  divides  into 
an  ascending  and  a  transverse  branch  (Fig.  386).  The  ascending  branch  (ramius 
-profundus)  passes  obliquely  upward  upon  the  tendon  of  the  Obturator  externus 
and  under  cover  of  the  Quadratus  femoris  toward  the  digital  fossa,  where  it 
anastomoses  with  twigs  from  the  gluteal  and  sciatic  arteries.  The  transverse 
branch  {ramus  superficialis),  larger  than  the  ascending,  appears  between  the 
Quadratus  femoris  and  upper  border  of  the  Adductor  magnus,  anastomosing  with 
the  sciatic,  external  circumflex,  and  superior  perforating  arteries,  the  crucial  anas- 
tomosis. Opposite  the  hip-joint  the  artery  gives  off  an  articular  vessel  {ramus 
acetabuli),  which  enters  the  joint  beneath  the  transverse  ligament;  and,  after  sup- 
plying the  adipose  tissue,  passes  along  the  round  ligament  to  the  head  of  the  bone. 

The  perforating  arteries  (Figs.  481  and  482),  usually  three  in  number,  are 
so  called  from  their  perforating  the  tendon  of  the  Adductor  magnus  muscle  to 
reach  the  back  of  the  thigh.  They  pass  backward  close  to  the  linea  aspera  of  the 
femur,  under  cover  of  small  tendinous  arches  in  the  Adductor  magnus.  The 
first  is  given  off  above  the  Adductor  brevis,  the  second  in  front  of  that  muscle, 
and  the  third  immediately  below  it 


THE  POPLITEAL  ARTERY  G91 

The  first  perforating  artery  (a.  perfnrans  prima)  passes  backward  between  the 
Pectineus  and  Adductor  brevis  (sometimes  perforates  the  hxtter);  it  then  pierces 
the  Adductor  magnus  close  to  the  linea  aspera.  It  gives  off  branches  whicli  supply 
the  Adductor  brevis,  the  Adductor  magnus,  the  Biceps,  the  Ghiteus  maximus 
muscles,  and  anastomoses  with  the  sciatic,  internal  and  external  circumflex,  and 
second  perforating  arteries. 

The  second  perforating  artery  (a.  perforans  secunda),  larger  than  the  first,  pierces 
the  tendons  of  the  Adductor  brevis  and  Adductor  magnus  muscles,  and  divides 
into  ascending  and  descending  branches,  which  supply  the  Flexor  muscles  of  the 
thigh,  anastomosing  with  the  first  and  third  perforating  arteries.  The  second 
artery  frequently  arises  in  common  with  the  first.  The  nutrient  artery  of  the 
femur  (a.  nidricia  femoris)  is  usually  given  off  from  this  branch. 

The  third  perforating  artery  (a.  perforans  tertia)  is  given  off  below  the  Adductor 
brevis;  it  pierces  the  Adductor  magnus,  and  divides  into  branches  which  supply 
the  Flexor  muscles  of  the  thigh;  anastomosing  above  with  the  higher  perforating 
arteries,  and  below  with  the  terminal  branches  of  the  profunda  and  the  muscular 
branches  of  the  popliteal. 

A  fourth  perforating  artery  is  represented  by  the  termination  of  the  profunda 
femoris  artery. 

Numerous  muscular  branches  arise  from  the  profunda;  some  of  these  end  in  the 
Adductor  muscles,  others  pierce  the  Adductor  magnus,  give  branches  to  the  Ham- 
string muscles,  and  anastomose  with  the  internal  circumflex  artery  and  with  the 
upper  muscular  branches  of  the  popliteal. 

The  anastomotica  magna  (a.  genu  suprema)  (Figs.  481  and  482)  arises  from 
the  femoral  artery  just  before  it  passes  through  the  tendinous  opening  in  the 
Adductor  magnus  muscle,  and  immediately  divides  into  a  superficial  and  deep 
branch. 

The  superficial  branch  {ramus  saphenus)  pierces  the  aponeurotic  covering  of 
Hunter's  canal,  and  accompanies  the  long  saphenous  nerve  to  the  inner  side  of  the 
thigh.  It  passes  between  the  Sartorius  and  Gracilis  muscles,  and,  piercing  the 
fascia  lata,  is  distributed  to  the  integument  of  the  upper  and  inner  part  of  the  leg, 
anastomosing  with  the  inferior  internal  articular  artery. 

The  deep  branch  (ramus  musculoarticularis)  descends  in  the  substance  of  the 
Vastus  internus,  lying  in  front  of  the  tendon  of  the  Adductor  magnus,  to  the  inner 
side  of  the  knee,  where  it  anastomoses  with  the  superior  internal  articular  artery 
and  the  anterior  recurrent  branch  of  the  anterior  tibial.  A  branch  from  this 
vessel  crosses  outward  above  the  articular  surface  of  the  femur,  forming  an  anas- 
tomotic arch  with  the  superior  external  articular  artery,  and  supplies  branches  to 
the  knee-joint. 

THE  POPLITEAL  ARTERY  (A.  POPLITEA)  (Figs.  477  and  481). 

The  popliteal  artery  commences  at  the  termination  of  the  femoral  at  the  opening 
in  the  Adductor  magnus,  and,  passing  obliquely  downward  and  outward  behind 
the  knee-joint  to  the  lower  border  of  the  Popliteus  muscle,  divides  into  the  anterior 
and  posterior  tibial  arteries.  A  portion  of  the  artery  lies  in  the  popliteal  space; 
but  above  and  below,  to  a  considerable  extent,  it  is  covered  by  the  muscles  which 
form  the  boundaries  of  the  space,  and  is  therefore  beyond  the  confines  of  the  space. 

The  Popliteal  Space  (Fig.  483). 

Dissection. — A  vertical  incision  about  eight  inches  in  length  should  be  made  along  the  back 
part  of  the  knee-joint,  connected  above  and  below  by  a  transverse  incision  from  the  hiner  to  the 
outer  side  of  the  limb.  The  flaps  of  integument  included  between  these  incisions  should  be 
reflected  in  the  direction  shown  in  Fig.  3S3,  p.  518. 


692 


THE  VASCULAR  SYSTEMS 


Boundaries. — The  popliteal  space  is  a  lozenge-shaped  space,  widest  at  the 
back  part  of  the  knee-joint,  and  deepest  above  the  articular  end  of  the  femur. 
It  is  bounded  externaMy,  above  the  joint,  by  the  Biceps,  and  below  the  joint  by  the 

Plantaris  and  external  head  of  the  Gastroc- 
nemius. Internally,  above  the  joint,  by  the 
Semimembranosus,  Semitendinosus,  Gracilis, 
and  Sartorius;  below  the  joint,  by  the  inner 
head  of  the  Gastrocnemius. 

Above,  it  is  limited  by  the  apposition  of  the 
inner  and  outer  Hamstring  muscles;  below, 
by  the  junction  of  the  two  heads  of  the  Gas- 
trocnemius. The  floor  is  formed  by  the  lower 
part  of  the  posterior  surface  of  the  shaft  of 
the  femur,  the  posterior  ligament  of  the 
knee-joint,  the  upper  end  of  the  tibia,  and 
the  fascia  covering  the  Popliteus  muscle,  and 
the  space  is  covered  in  by  the  fascia  lata. 

Contents. — It  contains  the  popliteal  vessels 
and  their  branches,  together  with  the  termi- 
nation of  the  external  saphenous  vein,  the 
internal  and  external  popliteal  nerves  and 
some  of  their  branches,  the  lower  extremity 
of  the  small  sciatic  nerve,  the  articular  branch 
from  the  obturator  nerve,  a  few  small  lymph 
nodes,  and  a  considerable  quantity  of  loose 
adipose  tissue. 

Position  of  Contained  Parts. — The  in- 
ternal popliteal  nerve  descends  in  the  middle 
line  of  the  space  lying  superficial  and  cross- 
ing the  artery  from  without  inward.  The 
external  popliteal  nerve  descends  on  the 
outer  side  of  the  upper  part  of  the  space, 
lying  close  to  the  tendon  of  the  Biceps 
muscle.  More  deeply  at  the  bottom  of  the 
space  are  the  popliteal  vessels,  the  vein  lying 
superficial  to  the  artery,  to  which  it  is  closely 
united  by  dense  areolar  tissue;  it  is  a  thick- 
walled  vessel,  and  lies  at  first  to  the  outer 
side  of  the  artery,  and  then  crosses  it  to  gain 
the  inner  side  below;  sometimes  the  vein  is 
double,  the  artery  lying  between  the  two 
venae  comites,  which  are  usua'ly  connected 
■  by  short  transverse  branches.  More  deeply 
and,  at  its  upper  part,  close  to  the  surface  of 
the  bone  is  the  popliteal  artery,  and  passing 
off  from  it  at  right  angles  are  its  articular 
branches.  The  articular  branch  from  the 
obturator  nerve  descends  upon  the  popliteal 
artery  to  supply  the  knee,  and  occasionally 
there  is  found  deep  in  the  space  an  artic- 
ular filament  from  the  great  sciatic  nerve. 

The  popliteal  lymph  nodes,  four  or  five 
Fig.  483.— The  popliteal,  posterior  tibial,  and    in  number,  are  found  surrouuding  the  artery; 

peroneal  arteries.    The  external  popliteal  (or  per-  ,,        ,.  r    •    i      ,         ,^  'i 

oneal)  nerve  has  been  removed.    (See  Fig.  776.)      0116     USUally     llCS     Superficial     tO     the     VCSSel; 


THE  POPLITEAL  ARTERY 


693 


another  is  situated  between  it  and  the  bone,  and  the  rest  are  placed  on  either 
side  of  it. 

The  popliteal  artery,  in  its  course  downward  from  the  aperture  in  the  Adductor 
magnus  to  the  lower  Ijorder  of  the  Popliteus  muscle,  rests  hrst  on  the  inner  surface 
of  the  femur,  and  is  then  separated  by  a  little  fat  from  the  hollowed  popliteal 
surface  of  the  bone;  in  the  middle  of  its  course  it  rests  on  the  posterior  ligament 
of  the  knee-joint,  and  below  on  tlie  fascia  covering  the  Popliteus  muscle.  Super- 
ficiallij,  it  is  covered  above  by  the  Semimembranosus;  in  the  middle  of  its  course, 
by  a  quantity  of  fat,  whicli  separates  it  from  the  deep  fascia  and  integument;  and 
below  it  is  overlapped  by  the  Gastrocnemius,  Plantaris,  and  Soleus  muscles,  the 
popliteal  vein,  and  the  internal  popliteal  nerve.  The  popliteal  vein,  which  is 
intimately  attached  to  the  artery,  lies  superficial  and  external  to  it  above;  it  then 
crosses  it  and  lies  to  its  inner  side.  The  internal  popliteal  nerve  is  still  more  super- 
ficial and  external  above,  but  below  the  joint  it  crosses  the  artery  and  lies  on  its 
inner  side.  Laterally,  the  artery  is  bounded  by  the  muscles  which  are  situated  on 
either  side  of  tlie  popliteal  space. 


Plax  of  the  Rel.\tions  of  the  Popliteal  Artery. 


Inner  side. 

Semimembranosus. 
Internal  condyle. 
Gastrocnemius  (inner 


In  front. 
Femiu-. 

Posterior  ligament. 
Popliteus. 


Outer  side. 

Biceps. 

External  condyle. 
Gastrocnemius  (outer  head). 
Plantaris. 


Behind. 

Semimembranosus. 

Fascia. 

Popliteal  vein. 

Internal  popliteal  nerve. 

Gastrocnemius. 

Plantaris. 

Soleus. 


Peculiarities  in  Point  of  Division.— Occasionally  the  popliteal  artery  divides  prematurely 
into  its  terminal  branches;  this  unusual  division  occurs  most  frequently  opposite  the  knee-joint. 
The  anterior  tibial  under  these  circumstances  may  pass  in  front  of  the  Popliteus  muscle. 

Unusual  Branches. — The  artery  sometimes  divides  into  the  anterior  tibial  and  peroneal,  the 
posterior  tibial  being  wanting  or  very  small.  Occasionally  the  popliteal  is  found  to  divide  into 
three  branches,  the  anterior  and  po.sterior  tibial  and  peroneal. 

Surface  Marking. — The  course  of  the  upper  part  of  the  popliteal  artery  is  indicated  by 
a  line  di'awn  from  the  outer  border  of  the  Semimembranosus  muscle  at  the  junction  of  the  middle 
and  lower  third  of  the  thigh  obliquely  downward  to  the  middle  of  the  popliteal  space,  exactly 
behind  the  knee-joint.  From  this  point  it  passes  vertically  downward  to  the  level  of  a  line 
drawn  through  the  lower  part  of  the  tubercle  of  the  tibia. 

Applied  Anatomy. — The  popliteal  artery  is  not  infrequently  the  seat  of  injury.  It  mav  be 
torn  by  direct  violence,  as  by  the  passage  of  a  cart-wheel  over  the  knee  or  by  hyperextension  of 
the  knee;  and  in  the  dead  body,  at  all  events,  the  middle  and  internal  coats  may  be  ruptured  by 
extreme  flexion.  It  may  also  be  lacerated  by  fracture  of  the  lower  part  of  the  shaft  of  the  femur 
or  by  antero-posterior  dislocation  of  the  knee-joint.  It  has  been  torn  in  breaking  down  adhesions 
in  cases  of  fibrous  ankylosis  of  the  knee,  and  is  in  danger  of  being  wounded,  and,  in  fact,  has  been 
wounded,  in  performing  Macewen's  operation  for  osteotomy  of  the  lower  end  of  the  femur  for 
genu  valgum.  In  addition,  Spencer  records  a  case  in  which  the  popliteal  artery  was  woimded 
from  in  front  by  a  stab  just  below  the  knee,  the  knife  passing  through  the  interosseous  space. 


694  THE  VASCULAR  SYSTEMS 

The  popliteal  artery  is  more  frequently  the  seat  of  aneurism  than  is  any  other  artery  in  the 
body,  with  the  exception  of  the  thoracic  aorta.  This  is  due,  no  doubt,  in  a  great  measure,  to 
the  amount  of  movement  to  which  it  is  subjected,  and  to  the  fact  that  it  is  supported  b}'  loose  and 
lax  tissue  only,  and  not  by  muscles,  as  is  the  case  with  most  arteries. 

Ligation  of  the  popliteal  artery  is  required  in  cases  of  wound  of  that  vessel,  but  for  aneurism 
of  the  posterior  tibial  it  is  preferable  to  tie  the  superficial  femoral.  The  popliteal  may  be  tied 
in  the  upper  or  lower  part  of  its  course;  but  in  the  middle  of  its  course  the  operation  is  attended 
with  considerable  difficulty,  from  the  great  depth  of  the  artery  and  from  the  extreme  degree  of 
tension  of  the  lateral  boundaries  of  the  space. 

In  order  to  expose  the  vessel  in  the  upper  part  of  its  course,  the  patient  should  be  placed  in 
the  supine  position,  with  the  knee  flexed  and  the  thigh  rotated  outward,  so  that  it  rests  on  its 
outer  surface;  an  incision  three  inches  in  length,  beginning  at  the  junction  of  the  middle  and 
lower  third  of  the  thigh,  is  to  be  made  parallel  to  and  immediateh-  behind  the  tendon  of  the 
Adductor  magnus,  and  the  skin,  superficial  and  deep  fascia  divided.  The  tendon  of  the  muscle 
is  thus  exposed,  and  is  to  be  drawn  forward  and  the  Hamstring  tendons  backward.  A  quantity 
of  fatty  tissue  will  now  be  exposed,  in  which  the  artery  will  be  felt  pulsating.  This  is  to  be 
separated  with  the  point  of  a  director  until  the  artery  is  exposed.  The  vein  and  nerve  will  not 
be  seen,  as  they  lie  to  the  outer  side  of  the  artery.  The  sheath  is  to  be  opened  and  the  aneurism 
needle  passed  from  before  backward,  keeping  its  point  close  to  the  artery  for  fear  of  injuring  the 
vein.  The  only  structure  to  avoid  is  the  long  saphenous  vein  in  the  superficial  incision.  The 
upper  part  of  the  popliteal  artery  may  also  be  tied  by  an  incision  on  the  back  of  the  limb,  along 
the  outer  margin  of  the  Semimembranosus,  but  the  operation  is  a  more  difficult  one,  as  the 
internal  popliteal  nerve  and  the  popliteal  vein  are  first  exposed,  and  great  care  has  to  be  exercised 
in  separating  them  from  the  artery. 

To  expose  the  vessel  in  the  lower  part  of  its  course,  w'here  the  artery  lies  between  the  two 
heads  of  the  Gastrocnemius,  the  patient  should  be  placed  in  the  prone  position  with  the  limb 
extended.  An  incision  should  then  be  made  through  the  integument  in  the  middle  line,  com- 
mencing opposite  the  bend  of  the  knee-joint,  care  being  taken  to  avoid  the  external  saphenous 
vein  and  nerve.  After  dividing  the  deep  fascia  and  separating  some  dense  cellular  membrane, 
the  artery,  vein,  and  nerve  will  be  exposed,  descending  between  the  two  heads  of  the  Gastroc- 
nemius. Some  muscular  branches  of  the  popliteal  should  be  avoided  if  possible,  or,  if  divided, 
tied  immediately.  The  leg  being  now  flexed,  in  order  the  more  effectually  to  separate  the  two 
heads  of  the  Gastrocnemius,  the  nerve  should  be  drawn  inward  and  the  vein  outward,  and  the 
aneurism  needle  passed  between  the  artery  and  vein  from  without  inward. 

Branches. — The  branches  of  the  popliteal  artery  are: 

-  ,        J  Superior.  Superior  external  articular. 

Muscular     ^^  inferior  or  sural.  Azygos  articular. 

Cutaneous.  Inferior  internal  articular. 

Superior  internal  articular.  Inferior  external  articular. 

The  superior  muscular  branches,  two  or  three  in  number,  arise  from  the 
upper  part  of  the  popliteal  artery,  and  are  distributed  to  the  lower  part  of  the 
Adductor  magnus  and  Flexor  muscles  of  the  thigh,  anastomosing  with  the  fourth 
perforating  branch  of  the  profunda. 

The  inferior  muscular  or  sxiral  (aa.  surales)  are  two  large  branches  which  are 
distributed  to  the  two  heads  of  the  Gastrocnemius  and  to  the  Plantaris  muscle 
They  arise  from  the  popliteal  artery  opposite  the  knee-joint. 

The  cutaneous  branches  arise  separately  from  the  popliteal  artery  or  from 
some  of  its  branches;  they  descend  between  the  two  heads  of  the  Gastrocnemius 
muscle,  and,  piercing  the  deep  fascia,  are  distributed  to  the  integument  of  the 
calf.  One  branch  usually  accompanies  the  short,  or  external,  saphenous  vein, 
the  superficial  sural  artery. 

The  superior  articular  arteries,  two  in  number,  arise  one  on  each  side  of  the 
popliteal,  and  wind  around  the  femur  immediately  above  its  condyles  to  the  front 
of  the  knee-joint.  The  internal  branch  (a.  genu  superior  medialis)  winds  inward 
beneath  the  Hamstring  muscles,  to  which  it  supplies  branches,  above  the  inner 
head  of  the  Gastrocnemius,  and,  passing  beneath  the  tendon  of  the  Adductor 
magnus,  divides  into  two  branches,  one  of  which  supplies  the  Vastus  internus. 


THE  POPLITEAL  ARTERY 


695 


anastomosing  with  the  anastoraotica  magna  and  inferior  internal  articular;  the 
other  ramifies  close  to  the  surface  of  the  femur,  supplying  it  and  the  knee-joint, 
and  anastomosing  with  the  superior  external  articular  artery.  This  branch  is 
frequently  of  small  size,  a  condition  which  is  associated  with  an  increase  in  the 
size  of  the  anastomotica  magna.  The  external  branch  (a.  cjenu  superior  lateralis) 
passes  above  the  outer  condyle,  beneath  the  tendon  of  the  Biceps,  and  divides  into 
a  superficial  and  deep  branch;  the  superficial  branch  supplies  the  Vastus  externus, 
and  anastomoses  with  the  descending  branch  of  the  external  circumflex  and  the 
inferior  external  articular  arteries;  the  deep  branch  supplies  the  lower  part  of 
the  femur  and  knee-joint,  and  forms  an  anastomotic  arch  across  the  bone  with 
the  anastomotica  magna  and  the  inferior  internal  articular  arteries. 

The  azygos  articular  (o.  (jenu  media)  is  a  small  branch  arising  from  the  pop- 
liteal artery  opposite  the  bend  of  the  knee-joint.  It  pierces  the  posterior  ligament, 
and  supplies  the  ligaments  and  synovial  membrane  in  the  interior  of  the  articu- 
lation. 


Descending  branch   f      \\ 
external  circumflex 


Superior  e  eternal 
articular 


Inferior  external  J^^/ 
articular  i  iC 


Superior  fibular  -4- 

Anterior  recurrent 
tibial. 


Ana'^tomotica 
magna 


Deep  branch  of  anas~ 

iomoiica  magna. 
Superficial  branch  of 
anastomotica  magna. 

^\^     V^   Superior  internal 
articular. 


Inferior  internal 
articular. 


Fig   484  — Circumpatellar  anastomosis. 


The  inferior  articular  arteries,  two  in  number,  arise  from  the  popliteal  be- 
neath the  Gastrocnemius,  and  wind  around  the  head  of  the  tibia  below  the  joint. 
The  internal  branch  {a.  genu  inferior  medialis)  first  descends  along  the  upper  mar- 
gin of  the  Popliteus  muscle,  to  which  it  gives  branches;  it  then  passes  below  the 
inner  tuberosity,  beneath  the  internal  lateral  ligament,  at  the  anterior  border  of 
which  it  ascends  to  the  front  and  inner  side  of  the  joint,  to  supply  the  head  of  the 
tibia  and  the  articulation  of  the  knee,  anastomosing  with  the  inferior  external 
articular  and  superior  internal  articular  arteries.  The  external  branch  (a.  genu 
inferior  laterali.s)  passes  outward  alx)ve  the  head  of  the  fibula,  to  the  front  of  the 
knee-joint,  passing  in  its  course  beneath  the  outer  head  of  the  Gastrocnemius,  the 


696 


THE  VASCULAB  SYSTEMS 


external  lateral  ligament,  and  the  tendon  of  the  Biceps  muscle,  and  divides  into 
branches  which  anastomose  with  the  inferior  internal  articular  artery,  the  superior 
external  articular  artery,  and  the  anterior  recurrent  branch  of  the  anterior  tibial. 

Circumpatellar  Anastomosis.  — 
Around  and  above  the  patella,  and 
on  the  contiguous  ends  of  the  femur 
and  tibia,  is  a  large  network  of  vessels, 
forming  a  superficial  and  a  deep 
plexus.  The  superficial  plexus  is 
situated  between  the  fascia  and  skin 
around  about  the  patella;  the  deep 
Infetim  internal    plgxus,  which  forms  a  close  network 

mti,r.ular  i^„  it  i  n  n     i 

or  vessels,  lies  on  the  surtace  ot  the 
lower  end  of  the  femur  and  upper 
end  of  the  tibia  around  their  articular 
surfaces,  and  sends  numerous  off- 
shoots into  the  interior  of  the  joint. 
The  arteries  from  which  this  plexus 
is  formed  are  the  two  internal  and 
two  external  articular  branches  of  the 
popliteal,  the  anastomotica  magna, 
the  terminal  branch  of  the  profunda, 
the  descending  branch  from  the  ex- 
ternal circumflex,  and  the  anterior  re- 
current branch  of  the  anterior  tibial. 


The  Anterior  Tibial  Artery  (A. 
Tibialis  Anterior)  (Fig.  485). 

The  anterior  tibial  artery  com- 
mences at  the  bifurcation  of  the 
popliteal  at  the  lower  border  of  the 
Popliteus  muscle,  passes  forward  be- 
tween the  two  heads  of  the  Tibialis 
posticus,  and  through  the  large  oval 
aperture  above  the  upper  border  of 
the  interosseous  membrane  to  the 
deep  part  of  the  front  of  the  leg;  it 
here  lies  close  to  the  inner  side  of  the 
neck  of  the  fibula;  it  then  descends 
on  the  anterior  surface  of  the  inter- 
osseous membrane,  gradually  ap- 
JDroaching  the  tibia;  and  at  the  lower 
part  of  the  leg  lies  on  this  bone,  and 
then  on  the  anterior  ligament  of  the 
ankle  to  the  bend  of  the  ankle-joint, 
where  it  lies  more  superficially,  and 
becomes  .the  dorsalis  pedis. 

Relations. — In  the  upper  two-thirds  of 
its  extent  it  rests  upon  the  interosseous 
membrane,  to  which  it  is  connected  by  deli- 
cate fibrous  arches  thrown  across  it;  in  the 
lower  third,  upon  the  front  of  the  tibia  and 


Communicating. 


-Applied  anatomy  of  the  anterior  tibial  and 
dorsalis  pedis  arteries. 


THE  ANTERIOR  TIBIAL  ARTERY  097 

ihe  anterior  ligament  of  the  ankle-joint.  In  the  upper  third  of  its  course  it  lies  between  the 
Tibialis  anticus  and  Extensor  longus  digitorum;  in  the  middle  third,  between  the  Tibialis  anti- 
cus  and  Extensor  proprius  hallucis.  At  the  bend  of  the  ankle  it  is  crossed  by  the  tendon  of 
the  Extensor  proprius  hallucis,  and  lies  between  it  and  the  innermost  tendon  of  the  Extensor 
longus  digitorum.  It  is  covered,  in  the  upper  two-thirds  of  its  course,  by  the  muscles  which 
lie  on  either  side  of  it  and  by  the  deep  fascia;  in  the  lower  third,  by  the  integument  anterior 
annular  ligament  and  fascia. 

The  anteriot  tibial  artery  is  accompanied  by  two  veins,  venae  comites,  which  lie  one  on  each 
side  of  the  artery;  the  anterior  tibial  nerve,  coursing  around  the  outer  side  of  the  neck  of  the 
fibula,  comes  into  relation  with  the  outer  side  of  the  artery  shortly  after  it  has  passed  through  the 
opening  in  the  interosseous  membrane;  about  the  middle  of  the  leg  it  is  placed  superficial  to  it; 
at  the  lower  part  of  the  artery  the  nerve  is  generally  again  on  the  outer  side. 

Plan  op  the  Relations  of  the  Anterior  Tibial  Artery. 

In  front. 

Integument,  superficial  and  deep  fasciiB. 

Anterior  tibial  nerve. 

Tibialis  anticus  (overlaps  it  in  the  upper  part  of  the  leg). 

Extensor  longus  digitorum  \  /     „„i„„  %  „r„ i,*i  \ 
T,  ^  ^  •      7   II     •    ?  (overlap  it  slightly), 

iixtensor  proprius  hallucis  i  '  s     j  / 

Anterior  annular  ligament. 
Inner  s-ide.  '  ^ v  Outer  side. 

Tibialis  anticus.  /      .„,„,,„,     \  Anterior  tiliial  nerve. 

.        1     11      .  I       Anterior       \  .  ,.    . 

Extensor  proprius  hallucis  1       Tibial.       I  Extensor  longus  digitorum. 

(crosses   it   at  its   lower  \  /  Extensor  proprius  hallucis.  , 

part).  v^^_^/ 

Behind. 
Interosseous  membrane. 
Tibia. 
Anterior  ligament  of  ankle-joint. 

Peculiarities  in  Size. — This  vessel  may  be  very  small,  may  be  deficient  to  a  greater  or  less 
extent,  or  may  be  entirely  wanting,  its  place  being  supplied  hy  perforating  branches  from  the 
posterior  tibial  or  by  the  anterior  division  of  the  peroneal  artery. 

Course. — The  artery  occasionally  deviates  in  its  course  toward  the  fibular  side  of  the  leg, 
regaining  its  usual  position  beneath  the  annular  ligament  at  the  front  of  the  ankle.  In  two 
instances  the  vessel  has  been  found  to  approach  the  surface  in  the  middle  of  the  leg,  being  covered 
merely  by  the  integument  and  fascia  below  that  point. 

Surface  Marking. — Draw  a  line  from  the  inner  side  of  the  head  of  the  fibula  to  midway 
between  the  two  malleoli.  In  this  line  take  a  point  one  inch  and  a  quarter  below  the  head  of 
the  fibula,  and  the  portion  of  the  line  below  this  point  will  mark  the  course  of  the  artery'. 

Applied  Anatomy. — The  anterior  tibial  artery  may  be  tied  in  the  upper  or  lower  part  of 
the  leg.  In  the  upper  part  the  operation  is  attended  with  great  difficulty,  on  account  of  the 
depth  of  the  vessel  from  the  surface.  An  incision,  about  four  inches  in  length,  should  be  made 
through  the  integument,  midway  between  the  tubercle  of  the  tibia  and  the  outer  margin  of  the 
fibula,  and  the  deep  fascia  exposed.  The  wound  must  now  be  carefully  dried,  its  edges  retracted, 
and  the  white  line  separating  the  Tibialis  anticus  from  the  Extensor  longus  digitorum  sought  for. 
When  this  has  been  clearly  defined,  the  deep  fascia  is  to  be  divided  in  this  line,  and  the  Tibialis 
anticus  separated  from  the  adjacent  muscles  with  the  handle  of  the  scalpel  or  a  director  until  the 
interosseous  membrane  is  reached.  The  foot  is  to  be  flexed  in  order  to  relax  the  muscles,  and 
upon  drawing  them  apart  the  artery  will  be  found  lying  on  the  interosseous  membrane  with  the 
nerve  on  its  outer  side  or  on  top  of  the  artery.  The  nerve  should  be  drawn  outward,  and  the 
venae  comites  separated  from  the  artery  and  the  needle  passed  around  it. 

To  tie  the  vessel  in  the  lower  third  of  the  leg  above  the  ankle-joint  an  incision  about  three 
inches  in  length  should  be  made  through  the  integument  between  the  tendons  of  the  Tibialis 
anticus  and  Extensor  proprius  hallucis  muscles,  the  deep  fascia  being  divided  to  the  same  extent. 
The  tendon  on  either  side  should  be  held  aside,  when  the  vessel  will  be  seen  lying  upon  the  tibia, 
K'ith  the  nerve  on  the  outer  side  and  one  of  the  venae  comites  on  either  side. 

Branches. — The  branches  of  the  anterior  tibial  artery  are: 

Posterior  recurrent  tibial.  Muscular.  * 

Superior  fibular.  Internal  malleolar. 

Anterior  recurrent  tibial.  External  malleolar. 


698  THE  VASCULAR  SYSTEMS 

The  posterior  recurrent  tibial  (a.  recurrens  tibialis  posterior)  is  not  a  constant 
branch,  and  is  given  off  from  the  anterior  tibial  before  that  vessel  passes  through 
the  interosseous  space.  It  ascends  beneath  the  Popliteus  muscle,  which  it  supplies, 
and  anastomoses  with  the  lower  articular  branches  of  the  popliteal  artery,  giving 
an  offshoot  to  the  superior  tibiofibular  joint. 

The  superior  fibular  is  sometimes  given  off  from  the  anterior  tibial,  sometimes' 
from  the  posterior  tibial.  It  passes  outward,  around  the  neck  of  the  fibula,  through 
the  Soleus,  which  it  supplies,  and  ends  in  the  substance  of  the  Peroneus  longus. 

The  anterior  recurrent  tibial  (a.  recurrens  tibialis  anterior)  arises  from  the 
anterior  tibial  as  soon  as  that  vessel  has  passed  through  the  interosseous  space; 
it  ascends  in  the  Tibialis  anticus  muscle,  and  ramifies  on  the  front  and  sides 
of  the  knee-joint,  anastomosing  with  the  articular  branches  of  the  popliteal,  with 
the  anastomotica  magna,  and  the  external  articular  branches  of  the  popliteal 
assisting  in  the  formation  of  the  circumpatellar  plexus. 

The  muscular  branches  are  numerous;  they  are  distributed  to  the  muscles 
which  lie  on  each  side  of  the  vessel,  some  cutaneous  branches  piercing  the  deep 
fascia  to  supply  the  integument,  others  passing  through  the  interosseous  mem- 
brane, and  anastomosing  with  branches  of  the  posterior  tibial  and  peroneal  arteries. 

The  internal  malleolar  branch  (a.  malleolaris  anterior  mediaUs)  arises  about  two 
inches  above  the  articulation,  and  passes  beneath  the  tendons  of  the  Extensor 
proprius  hallucis  and  Tibialis  anticus  to  the  inner  ankle,  upon  which  it  ramifies, 
anastomosing  with  branches  of  the  posterior  tibial  and  internal  plantar  arteries 
and  with  the  internal  calcanean  from  the  posterior  tibial. 

The  external  malleolar  branch  (a.  malleolaris  anterior  lateralis)  passes  beneath 
the  tendons  of  the  Extensor  longus  digitorum  and  Peroneus  tertius,  and  supplies 
the  outer  ankle,  anastomosing  with  the  anterior  peroneal  artery  and  with  ascending 
branches  from  the  tarsal  branch  of  the  dorsalis  pedis. 

The  Dorsalis  Pedis  Artery  (A.  Dorsalis  Pedis)  (Figs.  485,  486). 

The  dorsalis  pedis,  the  continuation  of  the  anterior  tibial,  passes  forward  from  the 
ankle  along  the  tibial  side  of  the  foot  to  the  back  part  of  the  first  intermetatarsal 
space,  where  it  divides  into  two  branches,  the  dorsalis  hallucis  and  communicating. 

Relations. — This  vessel,  in  its  course  forward,  rests  upon  the  astragalus,  navicular,  and 
middle  cuneiform  bones  and  the  ligaments  connecting  them,  being  covered  by  the  integument  and 
fascia,  anterior  annular  ligament,  and  crossed  near  its  termination  by  the  innermost  tendon  of 
the  Extensor  brevis  digitorum.  On  its  tibial  side  is  the  tendon  of  the  Extensor  proprius  hallucis; 
on  its.  fibular  side,  the  innermost  tendon  of  the  Extensor  longus  digitorum,  and  the  termination  of 
the  anterior  tibial  nerve.  The  nerve  is,  however,  quite  as  often  upon  the  tibial  side  of  the  artery. 
The  artery  is  accompanied  by  two  veins. 

Plan  of  the  Relations  of  the  Dorsalis  Pedis  Artery. 

7/1  front. 
Integument  and  fascia. 
Anterior  annular  ligament. 
Innermost  tendon  of  Extensor  brevis  digitorum. 


Tibial  side. 


Fibular  side. 


Ts   ,  •      i_  11     •  \        f  eaiB.       1  Extensor  longus  digitorum. 

Extensor  proprius  hallucis.  ^  J  Anterior  tibial  nerve. 

Behind. 
Astragalus. 
Navicular. 
Middle  cuneiform. 
And  their  ligaments. 


THE  BORSALIS  PEDIS  ARTERY 


699 


Peculiarities  in  Size. — The  dorsal  artery  of  the  foot  may  be  hirger  than  usual,  to  compen- 
sate for  a  deficient  plantar  artery;  or  it  may  be  deficient  in  its  terminal  branches  to  the  toes, 
which  are  then  derived  from  the  internal  plantar;  or  its  place  may  be  supplied  altogether  by  a 
large  anterior  peroneal  artery. 

Position. — This  artery  frequently  curves  outward,  lying  external  to  the  line  between  the 
middle  of  the  ankle  and  the  back  part  of  the  first  interosseous  space. 

Surface  Marking. — The  dorsalis  pedis  artery  is  indicated  on  the  surface  of  the  dorsum  of 
the  foot  by  a  line  drawn  from  the  centre  of  the  space  between  the  two  malleoli  to  the  back  of  the 
first  intermetatarsal  space. 

Applied  Anatomy. — This  artery  may  be  tied,  by  making  an  incision  through  the  integu- 
ment between  two  and  three  inches  in  length,  on  the  fibular  tide  of  the  tendon  of  the  Extensor 
proprius  hallucis,  in  the  interval  between  it  and  the  inner  border  of  the  short  Extensor  muscle. 
The  incision  should  not  ex- 
tend farther  forward  than  the 
back  part  of  the  first  inter- 
metatarsal space,as  the  artery 
divides  in  that  situation.  The 
deep  fascia  being  divided  to 
the  same  extent,  the  artery 
will  be  exposed,  the  nerve 
lying  upon  its  outer  side. 

Branches.  —  The 
branches  of  the  dorsalis 
pedis  are: 

Cutaneous. 
Tarsal. 

Metatarsal  —  Interos- 
seous. 
Dorsalis  hallucis. 
Communicating. 

Cutaneous    branches 

go  to  the  skin  of  the  dor- 
sum and  inner  surface  of 
the  foot. 

The  tarsal  artery  (o. 
tarsea  lateralis)  arises 
from  the  dorsalis  pedis, 
as  that  vessel  crosses  the 
navicular  bone;  it  passes 
in  an  arched  direction 
outward,  lying  upon  the 
tarsal  bones,  and  covered 
by  the  Extensor  brevis 
digitorum;  it  supplies 
that  muscle  and  the  articulations  of  the  tarsus,  and  anastomoses  with  branches 
from  the  metatarsal,  external  malleolar,  peroneal,  and   external  plantar  arteries. 

The  metatarsal  (a.  arcuata)  arises  a  little  anterior  to  the  preceding;  it  passes 
outward  lu  the  outer  part  of  the  foot,  over  the  bases  of  the  metatarsal  bones, 
beneath  the  tendons  of  the  short  Extensor,  its  direction  being  influenced  by  its 
point  of  origin;  and  it  anastomoses  with  the  tarsal  and  external  plantar  arteries. 
This  vessel  gives  off  three  branches,  the  dorsal  interosseous  arteries  (aa.  meta- 
tarseae  dorsales),  which  pass  forward  upon  tlie  three  outer  Dorsal  interossei  mus- 
cles, and,  in  the  clefts  between  the  toes,  divide  into  two  dorsal  collateral  branches 
for  the  adjoining  toes  (aa.  digitales  dorsales).  At  the  back  part  of  each  inter- 
osseous space  these  vessels  receive  the  posterior  perforating  branches  from  the 
plantar  arch,  and  at  the  fore  part  of  each  interosseous  space  they  are  joined  by 


Fig.  486. — Diagram  of  the  arteries  of  the  dorsal  surface  of  the  foot. 
(Poirjer  and.Charpy.) 


700  THE   VASCULAR  SYSTEMS 

the  anterior  perforating  branches  from  the  digital  arteries.  The  outermost  inter- 
osseous artery  gives  oil  a  branch  which  suppHes  the  outer  side  of  the  Httle  toe. 

The  dorsalis  hallucis,  or  the  first  dorsal  interosseous  (a.  dorsalis  hallucis),  is  one 
of  the  terminal  branches  of  the  dorsalis  pedis.  It  runs  forward  along  the  outer 
border  of  the  first  metatarsal  bone,  and  at  the  cleft  between  the  first  and  second 
toes  divides  into  two  branches,  one  of  which  passes  inward,  beneath  the  tendon 
of  the  Extensor  proprius  hallucis,  and  is  distributed  to  the  inner  border  of  the 
great  toe;  the  outer  branch  bifurcates,  to  supply  the  adjoining  sides  of  the  great  and 
second  toes. 

The  communicating  artery  (ramus  plantaris  profundus),  the  other  terminal 
branch  of  the  dorsalis  pedis,  dips  down  into  the  sole  of  the  foot,  between  the  two 
heads  of  the  First  dorsal  interosseous  muscle,  and  anastomoses  with  the  termina- 
tion of  the  external  plantar  artery,  to  complete  the  plantar  arch.  It  here  gives 
off  its  plantar  digital  branch,  which  is  named  the  arteria  magna  hallucis,  or  the 
princeps  hallucis.  This  artery  passes  forward  along  the  first  interosseous  space, 
and,  after  sending  a  branch  along  the  inner  side  of  the  great  toe,  bifurcates  for 
the  supply  of  the  adjacent  sides  of  the  great  and  second  toes. 

The  Posterior  Tibial  Artery  (A.  Tibialis  Posterior)  (Fig.  4S3). 

The  posterior  tibial  is  an  artery  of  large  size,  which  extends  obliquely  down- 
ward from  the  lower  border  of  the  Popliteus  muscle,  along  the  tibial  side  of  the 
leg,  to  the  fossa  between  the  inner  malleolus  and  the  heel,  where  it  divides  beneath 
the  origin  of  the  Abductor  hallucis,  on  a  level  with  a  line  drawn  from  the  point 
of  the  internal  malleolus  to  the  centre  of  the  convexity  of  the  heel,  into  the  internal 
and  external  plantar  arteries.  At  its  origin  it  lies  opposite  the  interval  between 
the  tibia  and  fibula;  as  it  descends,  it  approaches  the  inner  side  of  the  leg,  lying 
behind  the  tibia,  and,  in  the  lower  part  of  its  course,  is  situated  midway  between 
the  inner  malleolus  and  the  tuberosity  of  the  os  calcis. 

Relations. — The  posterior  tibial  artery  lies  successively  upon  the  Tibialis  posticus,  the 
Flexor  longus  digitorum,  the  tibia,  and  the  back  part  of  the  ankle-joint.  It  is  covered  by  the  deep 
transverse  fascia,  which  separates  it  above  from  the  Gastrocnemius  and  Soleus  muscles;  at  its 
termination  it  is  covered  by  the  Abductor  hallucis  muscle.  In  the  lower  third,  where  it  is  more 
superficial,  it  is  covered  only  bj'  the  integument  and  fascia,  and  runs  parallel  with  the  inner 
border  of  the  tendo  Achillis.  It  is  accompanied  by  two  veins  and  by  the  posterior  tibial  nerve, 
which  lies  at  first  to  the  inner  side  of  the  artery,  but  soon  crosses  it,  and  is,  in  the  greater  part 
of  its  course,  on  its  outer  side. 

Plan  of  the  Relations  of  the  Posterior  Tibial  Artery. 

In  front. 
Tibialis  posticus. 
Flexor  longus  digitorum. 
Tibia. 
Ankle-joint. 


Inner  side.  /  \  Outer  side. 


Posterior  tibial  nerve,  I       T'}'^^^       j  Posterior  tibial  nerve, 

upper  third.  \  '    /  lower  two-thirds. 

Behind. 
Integument  and  fascia. 
Gastrocnemius. 
Soleus. 

Deep  transverse  fascia. 
Posterior  tibial  nerve. 
Abductor  hallucis. 


THE  POSTERIOR  TIBIAL  ARTERY  701 

Behind  the  inner  malleolus  the  tendons  and  bloodvessels  are  arranged,  under  cover  of  the 
internal  annular  ligament,  in  the  following  order,  from  within  outward:  First,  the  tendons  of 
the  Tibialis  posticus  and  Flexor  longus  digitorum,  lying  in  the  same  groove,  behind  the  inner 
malleolus,  the  former  being  the  more  internal.  External  to  these  is  the  posterior  tibial  artery, 
having  a  vein  on  either  side,  and,  still  more  externally,  the  posterior  tibial  nerve.  About  half 
an  inch  nearer  the  heel  is  the  tendon  of  the  Flexor  longus  hallucis. 

Peculiarities  in  Size. — The  posterior  tibial  is  not  infrequently  smaller  than  usual,  or  absent, 
its  place  being  supplied  by  a  large  peroneal  artery  which  passes  inward  at  the  lower  end  of  the 
tibia,  and  either  joins  the  small  tibial  artery  or  continues  alone  to  the  sole  of  the  foot. 

Surface  Marking. — The  course  of  the  posterior  tibial  artery  is  indicated  by  a  line  drawn  from 
a  point  one  inch  In-low  the  centre  of  the  popliteal  space  to  midway  between  the  tip  of  the  internal 
mallc:ilus  anil  the  c<'ntre  of  the  convexity  of  the  heel. 

Applied  Anatomy. — The  appliration  of  a  ligature  to  the  posterior  tibial  may  be  required 
in  cases  of  wound  of  the  sole  of  the  foot  attended  with  great  hemorrhage,  when  the  vessel  should 
be  tied  at  the  inner  ankle.  In  cases  of  wound  of  the  posterior  tibial  it  will  be  necessary  to  enlarge 
the  opening  so  as  to  expose  the  vessel  at  the  woimded  point,  excepting  where  the  vessel  is  injured 
by  a  punctured  wound  from  the  front  of  the  leg.  In  cases  of  aneurism  from  wound  of  the  artery 
low  down,  the  vessel  should  be  tied  in  the  middle  of  the  leg.  But  in  aneurism  of  the  posterior 
tibial  high  up  it  would  be  better  to  tie  the  femoral  artery. 

To  tie  the  posterior  tibial  artery  at  the  ankle,  a  semUunar  incision,  convex  backward,  should 
be  made  through  the  integument,  about  two  inches  and  a  half  in  length,  midway  between  the  ' 
heel  and  the  inner  ankle  or  a  little  nearer  the  latter.  The  subcutaneous  cellular  tissue  having 
been  divided,  a  strong  and  dense  fascia,  the  internal  annular  ligament,  is  exposed.  This  liga- 
ment is  continuous  above  with  the  deep  fascia  of  the  leg,  covers  the  vessels  and  nerves,  and  is 
intimately  adherent  to  the  sheaths  of  the  tendons.  This  having  been  cautiously  divided  upon  a 
director,  the  sheath  of  the  vessels  is  exposed,  and,  being  opened,  the  artery  is  seen  with  one  of 
the  venae  comites  on  each  side.  The  aneurism  needle  should  be  passed  around  the  vessel  from 
the  heel  toward  the  ankle,  in  order  to  avoid  the  posterior  tibial  nerve,  care  being  taken  at  the 
same  time  not  to  include  the  venae  comites. 

The  vessel  may  also  be  tied  in  the  lower  third  of  the  leg  by  making  an  incision,  about  three 
inches  in  length,  parallel  with  the  inner  margin  of  the  tendo  Achillis.  The  internal  saphenous 
vein  being  carefully  avoided,  the  two  layers  of  fascia  must  be  divided  upon  a  director,  when  the 
artery  is  exposed  along  the  outer  margin  of  the  Flexor  longus  digitorum,  with  one  of  its  venae 
comites  on  either  side  and  the  nerve  lying  external  to  it. 

To  tie  the  posterior  tibial  in  the  middle  of  the  leg  is  a  very  difficult  operation,  on  account  of 
the  great  depth  of  the  vessel  from  the  surface.  The  patient  being  placed  in  the  recumbent  posi- 
tion, the  injured  limb  should  rest  on  its  outer  side,  the  knee  being  partially  bent  and  the  foot 
extended,  so  as  to  relax  the  muscles  of  the  calf.  An  incision  about  four  inches  in  length  should 
then  be  made  through  the  integument  a  finger's  breadth  behind  the  inner  margin  of  the  tiljia, 
taking  care  to  avoid  the  internal  saphenous  \ein.  The  deep  fascia  having  been  divided,  the 
margin  of  the  Gastrocnemius  is  exposed,  and  must  be  drawn  aside,  and  the  tibial  attachment  of 
the  Soleus  divided,  a  director  being  previously  passed  beneath  it.  The  artery  may  now  be 
felt  pulsating  beneath  the  deep  fascia  about  an  inch  from  the  margin  of  the  tibia.  The  fascia 
having  been  divided,  and  the  limb  placed  in  such  a  position  as  to  relax  the  muscles  of  the  calf 
as  much  as  possible,  the  veins  should  be  separated  from  the  artery,  and  the  aneurism  needle 
passed  around  the  vessel  from  without  inward,  so  as  to  avoid  wounding  the  posterior  tibial  nerve. 

Branches. — The  branches  of  the  posterior  tibial  artery  are: 

Peroneal.  Cutaneous. 

Nutrient.  Communicating. 

Muscular.  Internal  calcaneal. 

Malleolar  cutaneous. 

The  peroneal  artery  (a.  pcronaea)  (Fig.  483)  lies,  deeply  seated,  along  the  back 
part  of  the  fibular  side  of  the  leg.  It  arises  from  the  posterior  tibial  about  an  inch 
below  the  lower  border  of  the  Popliteus  muscle,  passes  obliquely  outward  to  the 
fibula,  and  then  descends  along  the  inner  border  of  that  bone,  contained  in  a 
fibrous  canal  between  the  Tibialis  posticus  and  the  Flexor  longus  hallucis,  or  in 
the  substance  of  the  latter  muscle  to  the  lower  third  of  the  leg,  where  it  gives  off' 
the  anterior  peroneal.  It  then  passes  across  the  articulation  between  the  til>ia  and 
filjula  to  the  outer  side  of  the  os  calcis,  where  it  gives  off  its  terminal  branches,  the 
external  calcaneal. 


702 


THE   VASCULAB  SYSTEMS 


Relations. — This  vessel  rests  at  first  upon  the  Tibialis  posticus,  and  then,  for  the  greater 
part  of  its  course,  in  a  fibrous  canal  between  the  origins  of  the  Flexor  longus  hallucis  and  Tibialis 
posticus,  covered  or  surrounded  by  the  fibres  of  the  Flexor  longus  hallucis.  It  is  covered,  in  the 
upper  pmi  of  its  course,  by  the  Soleus  and  deep  transverse  fascia;  below,  by  the  Flexor  longus 
hallucis. 

Plan  of  the  Relations  of  the  Peroneal  Artery. 

hi  front. 
Tibialis  posticus. 
Flexor  longus  hallucis. 


Outer  side. 

Fibula. 

Flexor  longus  hallucis. 


Inner  side. 
Flexor  longus  hallucis. 


Behind. 
Soleus. 

Deep  transverse  fascia. 
Flexor  longus  hallucis. 

Peculiarities  in  Origin. — The  peroneal  artery  may  arise  three  inches  below  the  Popliteus, 
or  from  the  posterior  tibial  high  up,  or  even  from  the  popliteal. 

Its  size  is  more  frequently  increased  than  diminished;  and  then  it  either  reinforces  the  poste- 
rior tibial  by  its  junction  with  it,  or  altogether  takes  the  place  of  the  posterior  tibial  in  the  lower 
part  of  the  leg  and  foot,  the  latter  vessel  only  existing  as  a  short  muscular  branch.  In  those 
rare  cases  where  the  peroneal  artery  is  smaller  than  usual  a  branch  from  the  posterior  tibial 
supplies  its  place,  and  a  branch  from  the  anterior  tibial  compensates  for  the  diminished  anterior 
peroneal  artery.     In  one  case  the  peroneal  artery  has  been  found  entirely  wanting. 

The  anterior  peroneal  is  sometimes  enlarged,  and  takes  the  place  of  the  dorsal  artery  of  the 
foot. 


Branches. — ^The  branches  of  the  peroneal  are: 

Muscular.  Communicating. 

Nutrient.  Posterior  peroneal. 

Anterior  peroneal.  External  calcaneal. 

Muscular  Branches. — The  peroneal  artery  in  its  course  gives  off  branches  to  the 
Soleus,  Tibialis  posticus,  Flexor  longus  hallucis,  and  Peronei  muscles. 

The  nutrient  artery  (a.  nutricia  fibulae)  supplies  the  fibula. 

The  anterior  peroneal  (ramus  perforans)  (Fig.  486)  pierces  the  interosseous 
membrane,  about  two  inches  above  the  outer  malleolus,  to  reach  the  fore  part  of 
the  leg,  and,  passing  down  beneath  the  Peroneus  tertius  to  the  outer  ankle,  rami- 
fies on  the  front  and  outer  side  of  the  tarsus,  anastomosing  with  the  external 
malleolar  and  tarsal  arteries. 

The  communicating  (ramus  cominunicans)  is  given  off  from  the  peroneal  about 
an  inch  from  its  lower  end,  and,  passing  inward,  joins  the  communicating  branch 
of  the   posterior  tibial. 

The  posterior  peroneal  passes  down  behind  the  outer  ankle  to  the  back  of  the 
external  malleolus,  to  terminate  in  branches  which  ramify  on  the  outer  surface 
and  back  of  the  os  calcis. 

The  external  calcaneal  (ramus  calcaneus  lateralis)  are  the  terminal  branches  of  the 
peroneal  artery;  they  pass  to  the  outer  side  of  the  heel,  and  communicate  with  the 
external  malleolar,  and,  on  the  back  of  the  heel,  with  the  internal  calcaneal  arteries. 

Cutaneous  branches  come  from  the  posterior  tibial  and  supply  the  skin  of 
the  inner  side  and  back  of  the  leg. 

The  nutrient  artery  of  the  tibia  (a.  nutricia  tibiae)  arises  from  the  posterior 
tibial  near  its  origin,  and,  after  supplying  a  few  muscular  branches,  enters  the 


THE  POSTERIOR  TIBIAL  ARTERY 


703 


nutrient  canal  of  that  bone,  which  it  traverses  obliquely  from  above  downward. 
This  is  the  largest  nutrient  artery  of  bone  in  the  body. 

The  muscular  branches  of  the  posterior  tibial  are  distributed  to  the  Soleus  and 
deep  muscles  along  the  back  of  the  leg. 

The  communicating  branch  (ramus  communicans),  to  join  a  similar  branch 
of  the  peroneal,  runs  transversely  across  the  back  of  the  tibia,  about  two  inches 
above  its  lower  end,  passing  beneath  the  Flexor  longus  hallucis. 

The  malleolar  or  internal  malleolar  (a.  malleolar  is  posterior  medialis)  lies 
upon  the  tibia,  sends  branches  over  the  inner  ankle,  and  anastomoses  with  the 
inner  malleolar  branch  of  the  anterior  tibial. 

The  internal  calcaneal  (rami  calcanei  mediales')  are  several  large  arteries 
which  arise  from  the  posterior  tibial  just  before  its  division;  they  are  distributed 
to  the  fat  and  integument  behind  the  tendo  Achillis  and  about  the  heel,  and  to  the 
muscles  on  the  inner  side  of  the  sole,  anastomosing  with  the  peroneal  and  internal 
malleolar,  and,  on  the  back  of  the  heel,  with  the  external  calcaneal  arteries. 


CoMmunieating 

branch  of 
dorsalis  pedis. 
Its  digilal 
branches. 


Fig.  487. — The  plantar  arteries.     Superficial  view. 


Fig.  488. — The  plantar  arteries.     Deep 


The  internal  plantar  artery  (a.  planfaris  medialis)  (Figs.  487  and  488),  much 
smaller  than  the  external,  passes  forward  along  the  inner  side  of  the  foot.  It  is 
at  first  situated  above^  the  Abductor  hallucis,  and  then  between  it  and  the  Flexor 
brevis  digitorum,  both  of  which  it  supplies.  At  the  base  of  the  first  metatarsal 
bone,  where  it  has  become  much  diminished  in  size,  it  passes  along  the  inner 
border  of  the  great  toe,  anastomosing  with  its  digital  branch.  Small  superficial 
digital  branches  (ramus  superficialis)  accompany  the  digital  branches  of  the 
medial  plantar  nerve  and  join  the  plantar  digital  arteries  of  the  three  inner  spaces. 
In  addition,  this  vessel  gives  off  numerous  cutaneous  branches. 

The  external  plantar  artery  (a.  plantaris  lateralis)  (Figs.  487  and  488),  much 
larger  than  the  internal,  passes  obliquely  outward  and  forward  to  the  base  of  the 

>  This  refers  to  the  erect  position  of  the  body.  In  the  ordinary  position  for  dissection  the  artery  is  deeper 
than  the  muscle. 


704  THE  VASCULAR  SYSTEMS 

fifth  metatarsal  bone.  It  then  turns  obHquely  inward  to  the  interval  between 
the  bases  of  the  first  and  second  metatarsal  bones,  where  it  anastomoses  with  the 
communicating  branch  from  the  dorsalis  pedis  artery,  thus  completing  the  plantar 
arch  (areas  plantaris)  (Fig.  488).  As  this  artery  passes  outward,  it  is  first  placed 
between  the  os  calcis  and  Abductor  hallucis,  and  then  between  the  Flexor  brevis 
digitorum  and  Flexor  accessorius,  and  as  it  passes  forward  to  the  base  of  the  little 
toe  it  lies  more  superficially  between  the  Flexor  brevis  digitorum  and  Abductor 
minimi  digiti,  covered  by  the  deep  fascia  and  integument.  The  remaining  portion 
of  the  vessel  is  deeply  situated;  it  extends  from  the  base  of  the  metatarsal  bone 
of  the  little  toe  to  the  back  part  of  the  first  interosseous  space,  and  forms  the 
plantar  arch;  it  is  convex  forward,  lies  below  or  on  the  plantar  aspect  of  the 
tarsal  ends  of  the  second,  third,  and  fourth  metatarsal  bones  and  the  correspond- 
ing Interosseous  muscles  and  upon  the  Adductor  obliquus  hallucis. 

Surface  Marking. — The  course  of  the  internal  plantar  artery  is  represented  by  a  line 
drawn  from  the  mid-point  between  the  tip  of  the  internal  malleolus  and  the  centre  of  the  con- 
\'exity  of  the  heel  to  the  middle  of  the  under  suface  of  the  great  toe;  the  external  plantar  by 
a  line  from  the  same  point  to  within  a  finger's  breadth  of  the  tuberosity  of  the  fifth  metatarsal 
bone.  The  plantar  arch  is  indicated  by  a  line  drawn  from  this  point — i.  e.,  a  finger's  breadth 
internal  to  the  tuberosity  of  the  fifth  metatarsal  bone  transversely  across  the  foot  to  the  back  of 
the  first  interosseous  space. 

Applied  Anatomy. — Wounds  of  the  plantar  arch  are  always  serious,  on  account  of  the 
depth  of  the  vessel  and  the  important  structures  which  must  be  interfered  with  in  an  attempt 
to  ligate  it.  They  must  be  treated  on  similar  lines  to  those  of  wounds  of  the  palmar  arches 
(see  page  654).  Delorme  has  shown  that  the  plantar  arch  may  be  ligated  from  the  dorsum  of 
the  foot  in  almost  any  part  of  its  course  by  removing  a  portion  of  one  of  the  three  middle  meta- 
tarsal bones. 

Branches. — The  plantar  arch,  besides  distributing  numerous  branches  to  the 
muscles,  integument,  and  fasciae  in  the  sole,  gives  off  the  following  branches: 

Posterior  perforating.  ■  Digital. 

The  posterior  perforating  (raini  perforanfes  posferiores)  are  three  small  branches 
which  ascend  through  the  back  part  of  the  three  outer  interosseous  spaces, 
between  the  heads  of  the  Dorsal  interossei  muscles,  and  anastomose  with  the 
interosseous  branches  from  the  metatarsal  artery. 

The  digital  branches  (aa.  metatarseae  plantares)  are  four  in  number,  and  supply 
the  three  outer  toes  and  half  the  second  toe.  It  will  be  remembered  that  the 
arteria  princeps  hallucis  is  the  plantar  digital  branch  of  the  communicating 
rami  in  the  first  interosseous  space  and  supplies  the  adjacent  sides  of  the  great 
and  second  toes.  The  first  digital  branch  of  the  plantar  arch  passes  outward 
from  the  outer  side  of  the  plantar  arch,  and  is  distributed  to  the  outer  side  of  the 
little  toe,  passing  in  its  course  beneath  the  Abductor  and  short  Flexor  muscles. 
The  second,  third,  and  fourth  run  forward  along  the  interosseous  spaces,  and  on 
arriving  at  the  clefts  between  the  toes  each  divides  into  collateral  digital  branches 
{aa.  digitales  plantares),  which  supply  the  adjacent  sides  of  the  three  outer  toes  and 
the  outer  side  of  the  second.  At  the  bifurcation  of  the  toes  each  digital  artery 
sends  upward,  through  the  fore  part  of  the  corresponding  interosseous  space,  a 
small  branch  which  anastomoses  with  the  interosseous  branches  of  the  metatarsal 
artery.     These  are  the  anterior  perforating  branches  (rami  perforantes  anteriores). 

From  the  description  given  it  will  be  seen  that  both  sides  of  the  three  outer  toes 
and  the  outer  side  of  the  second  toe  are  supplied  by  branches  from  the  plantar 
arch;  both  sides  of  the  great  toe  and  the  inner  side  of  the  second  are  supplied  by 
the  communicating  branch  of  the  dorsalis  pedis  (princeps  hallucis). 


THE  VEINS. 


The  Veins  convey  the  blood  from  the  capillaries  of  the  different  parts  of  the 
body  toward  the  heart.  They  consist  of  two  distinct  sets  of  vessels,  the  pulmonary 
and  systemic  veins,  and  an  appendage  to  the  systemic,  the  portal  system. 

The  Pulmonary  Veins  are  concerned  in  the  circulation  of  the  blood  through  the 
lungs.  Unlike  other  vessels  of  this  kind,  they  contain  arterial  blood,  which  they 
return  from  the  lungs  to  the  left  auricle  of  the  heart. 


\ 


Fig.  489. — Valves  of  a  vein.  In  the  lower  part 
of  the  figure  are  seen  the  parietal  valves;  the 
upper  part  shows  the  mouth  of  a  vein  guarded 
by  a  valve.     (Poirier  and  Charpy.) 


La. 


X. 


Fig,  490. — Collateral  anastomosis  of  veins.  The  arrows 
indicate  the  direction  of  the  flow  of  blood  (schematic). 
(Poirier  and  Charpy.) 


The  Systemic  Veins  are  concerned  in  the  general  circulation;  they  return  the 
venous  blood  from  the  body  generally  to  the  right  auricle  of  the  heart. 

The  Portal  Vein  and  its  radicles  constitute  the  portal  system.  The  portal  system 
is  in  reality  an  appendage  to  the  systemic  venous  system,  and  is  confined  to  the 
abdominal  cavity,  returning  the  venous  blood  from  the  viscera  of  the  digestive 
system,  and  carrying  it  to  the  liver  by  a  single  trunk  of  large  size,  the  portal  vein. 
This  vessel  ramifies  in  the  substance  of  the  liver  and  breaks  up  into  a  minute 
network  of  capillaries.  These  capillaries  then  re-collect  to  form  the  hepatic  veins, 
by  which  the  blood  is  conveyed  to  the  inferior  vena  cava. 

The  veins,  like  the  arteries,  are  found  in  nearly  every  tissue  of  the  body.  They 
commence  by  minute  plexuses  which  receive  the  blood  from  the  capillaries.    The 

45  (705) 


706 


THE   VASCULAR  SYSTEMS 


branches  which  have  their  commencement  in  these  plexuses  unite  into  trunks, 
and  these,  in  their  passage  toward  the  heart,  constantly  increase  in  size  as  they 
receive  tributaries  or  join  other  veins.  The  veins  are  larger  and  altogether  more 
numerous  than  the  arteries;  hence  the  capacity  of  the  venous  system  is  much 
greater  than  that  of  the  arterial,  the  pulmonary  veins  excepted,  which  only 
slightly  exceed  in  capacity  the  pulmonary  arteries.  From  the  combined  area  of 
the  smaller  venous  tributaries  being  greater  than  the  main  trunks,  it  results  that 
the  venous  system  represents  a  cone,  the  summit  of  which  corresponds  to  the 
heart,  its  base  to  the  periphery  of  the  body.  In  form  the  veins  are  cylindrical, 
like  the  arteries,  their  walls  collapsing  when  empty,  and  the  uniformity  of  their 
surface  being  interrupted  at  intervals  by  slight  dilatations,  which  indicate 
the  existence  of  valves  in  their  interior  (Fig.  489).  They  usually  retain,  however, 
about  the  same  calibre  as  long  as  they  receive  no  tributaries,  but  not  so  uniformly 
as  do  the  arteries. 

The  veins  communicate  very  freely  with  one  another  (Fig.  491),  especially  in 
certain  regions  of  the  body,  and  this  communication  exists  between  the  larger 
trunks  as  well  as  between  the  smaller 
tributaries.  Thus,  in  the  cavity  of  the 
cranium  and  between  the  veins  of  the 
neck,  where  obstruction  would  be  at- 
tended with  imminent  danger  to  the 
cerebral  venous  system,  we  find  that 
the  sinuses  and  larger  veins  have  large 


Fig.  491.— The  venous  circle  of  Braune  (schematic). 
The_  arrows  indicate  the  direction  of  the  blood  current. 
(Poirier  and  Charpy.) 


Fig.  492.— Part   of 
I  inferior  of 


section    of   the  vena 
(Szymonowicz.) 


and  very  frequent  anastomoses  (Fig.  490).  The  same  free  communication  exists 
throughout  the  whole  extent  of  the  vertebral  canal,  and  between  the  veins 
composing  the  various  venous  plexuses  in  the  abdomen  and  pelvis,  as  the  sper- 
matic, uterine,  vesical,  and  prostatic  plexuses. 

Veins  have  thinner  walls  than  arteries,  the  difference  in  thickness  being  due 
to  the  small  amount  of  elastic  and  muscular  tissues  which  the  veins  contain. 
The  superficial  veins  usually  have  thicker  coats  than  the  deep  veins,  and  the 
veins  of  the  lower  limb  are  thicker  than  those  of  the  upper. 

Histology  of  the  Veins. — As  previously  stated,  capillaries  enter  into  venules  orpost- 
capiUary  veins.  ^  The  venules  empty  into  larger  veins.  Vein  walls  are  much  thinner  than 
arterial  walls.  The  coats  are:  tunica  intima,  tunica  media,  and  tunica  adventitia.  A  vein 
has  a  much  thinner  media   and  much  less  elastic  tissue  than  an  artery,  and  a  very  strongly 


THE  PULMONARY  VEINS  707 

developed  adventitia.  The  intima  is  a  connective-tissue  layer  containing  a  small  num- 
ber of  elastic  fibers  and  lined  with  endothelium.  The  internal  elastic  lamina  is  usually 
poorly  developed.  The  valves  are  duplications  of  the  intima.  The  media  consists  chiefly 
of  white  fibrous  tissue  containing  some  circular  muscle  fibres  and  some  fine  elastic  fibres. 
In  some  veins  the  media  is  thoroughly  well  developed  (veins  of  the  lower  extremities),  in 
others  it  is  practically  absent  (veins  of  the  retina,  of  the  pia,  of  bone,  the  superior  vena  cava). 
The  adventitia  is  dense  and  strong,  and  is  composed  of  fibre-elastic  tissue  and  non-striated 
muscle  fibres  longitudinally  placed.  Fig.  492  shows  a  transverse  section  of  part  of  the  wall 
of  a  vein.  The  large  veins  and  the  veins  of  medium  size  possess  vasa  vasorum  in  the  adven- 
titia and  to  some  extent  in  the  media.  The  walls  of  veins  contain  vasomotor  ner^•es.  LjTnjjh 
capillaries  often  surround  the  smaller  bloodvessels  and  sometimes  by  spaces  lined  with  endo- 
thelium and  which  are  in  communication  with  the  lymphatic  system;  these  spaces  are  called 
perivascular  lymph  spaces. 

The  systemic  veins  are  subdivided  into  three  sets — superficial,  deep,  and  sinuses. 

The  Superficial  or  Cutaneous  Veins  are  found  between  the  layers  of  the  super- 
ficial fascia,  immediately  beneath  the  integument;  they  return  the  blood  from 
these  structures,  and  communicate  with  the  deep  veins  by  perforating  the  deep 
fascia. 

The  Deep  Veins  accompany  the  arteries,  and  are  usually  enclosed  in  the  same 
sheath  with  tho.se  vessels.  With  the  smaller  arteries — as  the  radial,  ulnar,  brachial, 
tibial,  and  peroneal — they  exist  generally  in  pairs,  one  lying  on  each  side  of  the 
vessel,  and  are  called  venae  comites.  The  larger  arteries — as  the  axillary,  sub- 
clavian, popliteal,  and  femoral — have  usually  only  one  accompanying  vein.  In 
certain  organs  of  the  body,  however,  the  deep  veins  do  not  accompany  the  arteries; 
for  instance,  the  veins  in  the  skull  and  vertebral  canal,  the  hepatic  veins  in  the 
liver,  and  the  larger  veins  returning  blood  from  the  osseous  tissue. 

Sinuses  are  venous  channels  which,  in  their  structure  and  mode  of  distribution, 
differ  altogether  from  the  veins.  They  are  found  only  in  the  interior  of  the  skull, 
and  consist  of  channels  formed  by  a  separation  of  the  two  layers  of  the  dura,  their 
outer  coat  consisting  of  fibrous  tissue,  their  inner  of  an  endothelial  layer  con- 
tinuous with  the  lining  membrane  of  the  veins. 


THE  PULMONARY  VEINS  (V.  PULMONALES)  (Fig.  493). 

The  pulmonary  veins  return  the  arterialized  blood  from  the  lungs  to  the  left 
auricle  of  the  heart.  They  are  four  in  number,  two  for  each  lung,  and  are  destitute 
of  valves.  They  commence  in  a  capillary  network  upon  the  walls  of  the  air-cells, 
where  they  are  continuous  with  the  capillary  ramifications  of  the  pulmonary  artery, 
and  uniting,  form  one  vessel  for  each  lobule.  These  vessels,  uniting  successively 
form  a  single  trunk  for  each  lobe,  three  for  the  right  and  two  for  the  left  lung. 
Each  venous  trunk  is  about  1.5  cm.  in  length  and  of  about  the  same  calibre. 
The  vein  from  the  middle  lobe  of  the  right  lung  generally  unites  with  that  from 
the  upper  lobe.  Thus,  two  trunks  are  formed  on  each  side,  which'open  separately 
into  the  left  auricle.  Occasionally  the  three  veins  on  the  right  side  remain  sepa- 
rate. Not  infrequently  the  two  left  pulmonary  veins  terminate  by  a  common 
opening. 

Within  the  lung,  the  tributaries  of  the  pulmonary  artery  are  in  front,  the  veins 
behind,  and  the  bronchi  between  the  two. 

At  the  root  of  the  lung,  the  upper  pulmonary  vein  lies  in  front  of  and  a  little  below 
the  pulmonary  artery;  the  lower  is  situated  below  the  other  structures  in  the  lung 
root,  and  on  a  plane  posterior  to  the  upper  vein;  behind  the  pulmonary  artery  is 
the  bronchus. 

Within  the  pericardium,  their  anterior  surfaces  are  invested  by  the  serous  layer 
of  this  membrane.  The  right  pulmonary  veins  pass  behind  the  right  auricle  and 
ascending  aorta  and  superior  vena  cava;  the  left  pass  in  front  of  the  thoracic  aorta. 


708 


THE   VASCULAR  SYSTEMS 


Applied  Anatomy. —  Thrombosis  of  larger  or  smaller  tributaries  of  the  pulmonary  veins 
is  common  in  inflamed  areas  of  the  lung;  or  as  a  consequence  of  pressure  from  tumors,  but  it 
does  not  give  rise  to  any  special  symptoms. 


ENTRANCE    OF 
VENA     AZYGOS 
BRANCH    OF    PUL- 
MONARY   ARTERY 


Fig.  493. — Pulmonary  veins,  seen  in  a  dorsal  view  of  the  heart  and  lungs  lie  iett  lui  g  is  pulled  to  the 
left,  and  the  right  lung  has  been  partly  cut  away  to  show  the  ramifications  of  the  air  tubes  and  bloodvessels. 
(Testut.) 


THE  SYSTEMIC  VEINS. 

The  systemic  veins  may  be  arranged  into  three  groups:  (1)  The  cardiac  veins, 
which  open  directly  into  the  right  auricle  of  the  heart.  (2)  Those  of  the  head 
and  neck,  upper  extremity,  and  thorax,  which  terminate  in  the  superior  vena  cava. 
(3)  Those  of  the  lower  extremity,  abdomen,  and  pelvis,  which  terminate  in  the 
inferior  vena  cava. 


THE    CARDIAC    VEINS. 

The  coronary  sinus  (sinus  coronarius)  is  a  wide  venous  channel  about  an 
inch  in  length  which  receives  the  majority  of  the  veins  draining  the  blood  from 
the  substance  of  the  heart.  It  is  situated  in  the  posterior  part  of  the  auriculo- 
ventricular  groove,  and  is  partly  covered  by  muscle  fibres  from  the  left  auricle.  It 
terminates  in  the  right  auricle  between  the  opening  of  the  inferior  vena  cava  and 
the  auriculoventricular  aperture,  its  orifice  being  guarded  by  a  semilunar  A'ahe, 
the  coronary  valve,  or  valve  of  Thebesius. 

Tributaries. — 


Great  cardiac  or  left  coronary.  Middle  or  posterior  cardiac. 

Small  cardiac  or  right  coronary.  Posterior  vein  of  the  left  ventricle. 

Oblique  vein  of  Marshall. 


CARDIAC  VEINS 


709 


1.  The  great  cardiac  or  left  coronary  vein  {v.  cordis  magna)  begins  at  the  apex 
of  the  heart  and  ascends  along  the  anterior  interventricular  groove  to  the  base 
of  the  ventricles.  It  then  curves  to  the  left  in  the  auriculoventricular  groove 
to  the  back  of  the  heart,  and  opens  into  the  left  extremity  of  the  coronary  sinus. 
It  receives  tributaries  from  the  left  auricle,  and  from  both  ventricles;  one  of  these, 
the  left  marginal  vein,  is  of  considerable  size,  and  ascends  along  the  left  margin 
of  the  heart. 

2.  The  small  cardiac  or  right  coronary  vein  {v.  cordis  parva)  runs  in  the  groove 
between  the  right  auricle  and  ventricle,  and  opens  into  the  right  extremity  of  the 
coronary  sinus.  It  receives  blood  from  the  back  of  the  right  auricle  and  ventricle; 
its  largest  tributary,  the  right  marginal  vein,  ascends  along  the  right  margin  of 
the  heart  and  joins  it  in  the  auriculoventricular  groove. 

3.  The  middle,  or  posterior,  cardiac  vein  (v.  cordis  media)  commences  at  the  apex 
of  the  heart,  ascends  in  the  posterior  interventricular  groove,  and  ends  in  the 
coronary  sinus  near  its  right  extremity. 


..PULMONARY 
VEINS 
LEFT 

AURICLE 


Fig,  494. — Cardiac  veina,  dorsal  view.     (Testut.) 


4.  The  posterior  vein  of  the  left  ventricle  (v.  posterior  ventriculi  sinistri)  ascends 
on  the  back  of  the  left  ventricle  to  the  coronary  sinus,  but  may  end  in  the  great 
cardiac  vein. 

5.  The  oblique  vein  of  Marshall  (v.  ohliqiia  airii  sinistri)  is  a  small  vessel  which 
descends  obliquely  on  the  back  of  the  left  auricle  and  ends  in  the  coronary 
sinus  near  its  right  extremity;  it  is  continuous  above  with  the  vestigial  fold  of 
Marshall,  and  the  two  structures  form  the  remnant  of  the  left  Cuvierian  duct. 

The  following  cardiac  veins  do  not  terminate  in  the  coronary  sinus:  (1)  The 
anterior  cardiac  veins  (uv.  cordis  anteriores),  comprising  three  or  four  small  vessels 
which  collect  blood  from  the  front  of  the  right  ventricle  and  open  into  the  right 
auricle.  The  right  marginal  vein  frequently  opens  into  the  right  auricle,  and  is 
therefore  sometimes  regarded  as  belonging  to  this  group.  (2)  The  veins  of 
Thebesius  (vv.  cordis  minimae),  consisting  of  a  number  of  minute  veins  which  arise 
in  the  muscular  wall  of  the  heart;  the  majority  open  into  the  auricles,  but  a  few 
empty  their  blood  into  the  ventricles. 


710  THE   VASCULAB  SYSTEMS 


VEINS  OF  THE  HEAD  AND  NECK. 

The  veins  of  the  head  and  neck  may  be  subdivided  into  three  groups:  (1)  The 
veins  of  the  exterior  of  tlie  head  and  face.  (2)  The  veins  of  the  neck.  (3)  The 
veins  of  the  diploe  and  the  interior  of  the  cranium. 


Veins  of  the  Exterior  of  the  Head  and  Face  (Fig.  495). 
The  veins  of  tlie  exterior  of  the  head  and  face  are: 

Frontal.  Superficial  temporal. 

Supraorbital.  Internal  maxillary. 

Angular.  Temporomaxillary. 

Facial.  Posterior  auricular. 
Occipital. 

The  frontal  vein  {v.  frontalis)  commences  on  the  anterior  part  of  the  skull  in 
a  venous  plexus  which  communicates  with  the  anterior  tributaries  of  the  super- 
ficial temporal  vein.  The  veins  converge  to  form  a  single  trunk,  which  runs 
downward  near  the  middle  line  of  the  forehead  parallel  with  the  vein  of  the  oppo- 
site side.  The  two  veins  are  joined,  at  the  root  .of  the  nose,  by  a  transverse  branch 
called  the  nasal  arch  (_v.  nasofrontalis),  which  receives  some  small  veins  from  the 
dorsum  of  the  nose.  Occasionally  the  frontal  veins  join  to  form  a  single  trunk, 
which  bifurcates  at  the  root  of  the  nose  into  the  two  angular  veins.  At  the  root  of 
the  nose  the  veins  diverge  and  join  the  supraorbital  vein,  at  the  inner  angle  of 
the  orbit,  to  form  the  angular  vein. 

The  supraorbital  vein  (y.  supraorbitalis)  commences  on  the  forehead,  com^ 
municating  with  the  anterior  temporal  vein,  and  runs  downward  and  inward, 
superficial  to  the  Occipitofrontalis  muscle,  receiving  tributaries  from  the  neigh- 
boring structures,  and  from  the  frontal  vein  of  the  diploe,  and  joins  the  frontal 
vein  at  the  inner  angle  of  the  orbit  to  form  the  angular  vein.  Previous  to  its 
junction  with  the  frontal  vein,  it  sends  through  the  supraorbital  notch  into  the 
orbit  a  branch  which  communicates  with  the  ophthalmic  vein.  As  this  vessel 
passes  through  the  notch,  it  receives  a  diploic  vein  from  the  diploe  of  the  frontal 
bone,  through  a  foramen  at  the  bottom  of  the  notch. 

The  angular  vein  (u.  angularis),  formed  by  the  junction  of  the  frontal  and 
supraorbital  veins,  runs  obliquely  dowaiward  and  outward  on  the  side  of  the  root 
of  the  nose  to  the  level  of  the  lower  margin  of  the  orbit,  where  it  becomes  the  facial 
vein.  It  receives  the  veins  of  the  ala  nasi  on  its  inner  side  and  the  superior  pal- 
pebral veins  on  its  outer  side;  it,  moreover,  communicates  with  the  ophthalmic 
vein,  thus  establishing  an  important  anastomosis  between  the  facial  vein  and  the 
cavernous  sinus. 

The  facial  vein  (v.  facialis  anterior)  commences  at  the  side  of  the  root  of  the  nose, 
being  a  direct  continuation  of  the  angular  vein.  It  lies  behind  and  follows  a 
less  tortuous  course  than  the  facial  artery.  It  passes  obliquely  downward  and  out- 
ward, beneath  the  Zygomaticus  major  and  minor  muscles,  descends  along  the 
anterior  border  of  the  Masseter,  crosses  over  the  body  of  the  mandible  with  the 
facial  artery  to  beneath  the  angle,  and  unites  with  the  anterior  division  of  the 
temporomaxillary  vein  to  form  the  common  facial  vein. 

The  common  facial  vein  iv.  facialis  communis)  is  formed  hy  the  union  of  the 
facial  and  the  anterior  division  of  the  temporomaxillary  vein,  just  beneath  the 
angle  of  the  mandible.  The  vein  is  covered  by  the  Platysma,  runs  downward  and 
backward  beneath  the  Sternomastoid  muscle,  crosses  the  external  carotid  artery, 


VEINS  OF  THE  EXTERIOR   OF  THE  HEAD  AND  FACE      711 

and  empties  into  the  internal  jugular  vein  at  the  level  of  the  iiyoid  line.  It  receives 
a  large  communicating  branch  at  the  anterior  border  of  the  Sternomastoid  muscle, 
which  comes  from  tlie  anterior  jugular  vein  in  the  suprasternal  fossa. 

Tributaries  of  Facial  Veins. — The  facial  vein  receives,  near  the  angle  of  tlie  mouth, 
communicating  tributaries  of  considerable  size,  the  deep  facial  (or  anterior  in- 
ternal maxillary  vein),  from  the  pterygoid  plexus.  It  is  also  joined  by  the  inferior 
palpebral,  the  superior  and  inferior  bbial  veins,  the  buccal  veins  from  the  cheek, 


Interior 
facial. 


(  uDunon 
1 1  ml 


A^Supeuor  iJiywid. 


Fig.  495. — Veins  of  the  head  and  neck. 


and  the  masseteric  veins.  The  common  facial  vein  receives  the  submental;  the 
inferior  palatine,  which  returns  the  blood  from  the  plexus  around  the  tonsil  and 
soft  palate;  the  submaxillary  vein,  which  commences  in  the  submaxillary  gland; 
and,  generally,  the  ranine  vein. 

Applied  Anatomy. — There  are  some  points  about  the  facial  vein  which  render  it  of  great 
importance  in  sui'oery.  It  is  not  so  flaccid  as  are  most  superficial  veins,  and,  in  consequence  of 
this,  remains  more  patent  when  divided.  It  has,  moreover,  no  valves.  It  communicates  freely 
with  the  intracranial  channels,  not  only  at  its  commencement  by  its  tributaries,  the  angulai' 
and  supraorbital  veins,  communicating  with  the  ophthalmic  vein,  a  tributary  of  the  cavernous 


712  THE   VASCULAR  SYSTEMS 

sinus,  but  also  by  its  deep  tributaries,  which  communicate  through  the  pterygoid  plexus  with  the 
cavernous  sinus  by  tributaries  which  pass  through  the  foramen  ovale  and  foramen  lacerum  medium. 
These  facts  have  an  important  bearing  upon  the  surgery  of  some  diseases  of  the  face,  for  on 
account  of  its  patency  the  facial  vein  favors  septic  absorption,  and  therefore  any  phlegmonous 
inflammation  of  the  face  following  a  poisoned  wound  is  liable  to  set  up  thrombosis  in  the  facial 
vein,  and  detached  portions  of  the  clot  may  give  rise  to  purulent  foci  in  other  parts  of  the  body. 
On  account  of  its  communications  with  the  cerebral  sinuses  these  thrombi  are  apt  to  extend 
upward  into  them  and  so  induce  a  fatal  issue. 

The  superficial  temporal  vein  {w.  temporales  superficiales)  commences  by  a 
minute  plexus  on  the  side  and  vertex  of  the  skull,  which  communicates  with  the 
frontal  and  supraorbital  veins  in  front,  the  corresponding  vein  of  the  opposite 
side,  and  the  posterior  auricular  and  occipital  veins  behind.  From  this  network 
anterior  and  posterior  branches  are  formed  which  unite  above  the  zygoma,  form- 
ing the  trunk  of  the  vein.  The  trunk  is  joined  in  this  situation  by  a  large  vein, 
the  middle  temporal  (v.  temporalis  media),  which  receives  blood  from  the  sub- 
stance of  the  Temporal  muscle  and  pierces  the  fascia  at  the  upper  border  of 
the  zygoma.  The  junction  of  the  superficial  temporal  and  the  middle  temporal 
vein  forms  the  common  temporal  vein  which  descends  between  the  external  auditory 
meatus  and  the  condyle  of  the  mandible,  enters  the  substance  of  the  parotid 
gland,  and  unites  with  the  internal  maxillary  vein  to  form  the  temporomaxillary 
vein. 

Tributaries. — The  common  temporal  vein  receives  in  its  course  some  parotid 
veins,  an  articular  branch  from  the  articulation  of  the  mandible,  anterior  auricular 
veins  from  the  external  ear,  and  a  vein  of  large  size,  the  transverse  facial  {v.  trans- 
versa faciei) ,  from  the  side  of  the  face.  The  middle  temporal  vein,  previous  to  its 
junction  with  the  temporal  vein,  receives  a  branch,  the  orbital  vein  (i'.  orbitalis), 
which  is  formed  by  some  external  palpebral  branches,  and  passes  backward 
between  the  layers  of  the  temporal  fascia. 

The  pterygoid  plexus  {plexus  pterygoideus)  is  of  considerable  size,  and  is  situ- 
ated between  the  Temporal  and  External  pterygoid,  and  partly  between  the  two 
Pterygoid  muscles.  It  receives  tributaries  corresponding  with  the  branches  of 
the  internal  maxillary  artery.  Thus,  it  receives  the  middle  meningeal  veins,  the 
deep  temporal,  the  pterygoid,  masseteric,  buccal,  alveolar,  some  palatine  veins,  the 
inferior  dental,  and  a  branch  which  communicates  with  the  ophthalmic  vein  through 
the  sphenomaxillary  fissure.  This  plexus  communicates  very  freely  with  the 
facial  vein  and  with  the  cavernous  sinus  by  branches  through  the  foramen  Vesalii, 
foramen  ovale,  and  foramen  lacerum  medium,  at  the  base  of  the  skull. 

The  internal  maxillary  vein  (i'.  maxillaris  interna)  is  a  short  trunk  which 
accompanies  the  first  part  of  the  internal  maxillary  artery.  It  is  formed  by  a 
confluence  of  the  veins  of  the  pterygoid  plexus,  and  passes  backward  between 
the  internal  lateral  ligament  and  the  neck  of  the  mandible,  and  unites  with  the 
superficial  temporal  vein  to  form  the  temporomaxillary  vein. 

The  temporomaxillary  vein  (v.  facialis  posterior),  formed  by  the  union  of 
the  superficial  temporal  and  internal  maxillary  veins,  descends  in  the  substance 
of  the  parotid  gland,  superficial  to  the  external  carotid  artery,  but  beneath  the 
facial  nerve  between  the  ramus  of  the  mandible  and  the  Sternomastoid  muscle. 
It  divides  into  two  vessels,  an  anterior,  sometimes  called  the  deep  facial  vein, 
which  passes  inward  to  join  the  facial  vein,  and  a  posterior,  which  is  joined  by  the 
posterior  auricular  vein  and  becomes  the  external  jugular. 

The  posterior  auricular  vein  (v.  auricidaris  posterior)  commences  upon  the 
side  of  the  head  by  a  plexus  which  communicates  with  the  tributaries  of  the  tem- 
poral and  occipital  veins.  It  descends  behind  the  external  ear,  and  joins  the 
posterior  division  of  the  temporomaxillary  vein,  forming  the  external  jugular. 
It  receives  the  stylomastoid  vein  and  some  tributaries  from  the  back  part  of  the 
external  ear. 


THE   VEINS  OF  THE  NEVK  713 

The  occipital  vein  (y.  occipitalis)  commences  in  a  plexus  at  the  back  part  of 
the  vertex  of  tlie  skull.  From  the  plexus  the  vein  follows  the  course  of  the  occipital 
artery,  passing  deeply  beneath  the  muscles  of  the  back  part  of  the  neck,  and  ter- 
minating in  the  suboccipital  triangle  by  becoming  continuous  with  the  posterior 
vertebral  vein  (v.  cervicalis  profunda).  Sometimes  it  is  more  superficial,  and  in 
this  case  is  a  tributary  of  the  external  jugular  vein.  As  it  passes  across  the  mastoid 
portion  of  the  temporal  bone,  it  receives  the  mastoid  vein,  which  thus  establishes 
a  communication  with  the  lateral  sinus. 


The  Veins  of  the  Neck  (Fig.  495). 

The  veins  of  the  neck,  which  return  the  blood  from  the  head  and  face,  are: 

External  jugular.  Anterior  jugular. 

Posterior  external  jugular.  Internal  jugular. 

Vertebral. 

The  external  jugular  vein  (v.  jugularis  externa)  receives  the  greater  part  of 
the  blood  from  the  exterior  of  the  cranium  and  deep  parts  of  the  face,  and  is 
formed  by  the  junction  of  the  posterior  division  of  the  temporomaxillary  and 
the  posterior  auricular  veins.  It  commences  in  the  substance  of  the  parotid  gland, 
on  a  level  with  the  angle  of  the  mandible,  and  runs  perpendicularly  down  the  neck 
in  the  direction  of  a  line  drawn  from  the  angle  of  the  mandible  to  the  middle  of  the 
clavicle.  In  its  course  it  crosses  the  Sternomastoid  muscle,  and  runs  parallel 
with  its  posterior  border  as  far  as  its  attachment  to  the  clavicle,  where  it  perforates 
the  deep  fascia,  and  terminates  in  the  subclavian  vein,  on  the  outer  side  of,  or  in 
front  of,  the  Scalenus  anticus  muscle.  It  is  separated  from  the  Sternomastoid 
by  the  investing  layer  of  the  deep  cervical  fascia,  and  is  covered  by  the  Platysma, 
the  superficial  fascia,  and  the  integument.  This  vein  crosses  about  its  middle 
the  superficial  cervical  nerve,  and  throughout  the  upper  half  of  its  course  is 
accompanied  by  the  great  auricular  nerve.  The  external  jugular  vein  varies 
in  size,  bearing  an  inverse  proportion  to  that  of  the  other  veins  of  the  neck;  it  is 
occasionally  double.  It  is  provided  with  two  pairs  of  valves,  the  lower  pair  being 
placed  at  its  entrance  into  the  subclavian  vein,  the  upper  pair  in  most  cases  about 
an  inch  and  a  half  above  the  clavicle.  The  portion  of  vein  between  the  two  sets 
of  valves  is  often  dilated,  and  is  termed  the  sinus.  These  valves  do  not  prevent 
the  regurgitation  of  the  blood  or  the  passage  of  injection  masses  from  below 
upward. 

Tributaries. — This  vein  receives  the  occipital  occasionally,  the  posterior  external 
jugular,  and,  near  its  termination,  the  suprascapular,  transverse  cervical,  and 
anterior  jugular  veins;  in  the  substance  of  the  parotid  gland  a  large  branch  of 
communication  from  the  internal  jugular  joins  it. 

The  posterior  external  jugular  vein  (r.  jugularis  posterior)  commences  in 
the  occipital  region,  and  returns  the  blood  from  the  integument  and  superficial 
muscles  in  the  upper  and  back  part  of  the  neck,  lying  between  the  Splenius  and 
Trapezius  muscles.  It  runs  down  the  back  part  of  the  neck,  and  opens  into  the 
external  jugular  just  below  the  middle  of  its  course. 

The  anterior  jugular  vein  (v.  jugularis  anterior)  commences  near  the  hyoid 
bone  from  the  convergence  of  the  inferior  labial  coronary,  the  submental  and  the 
mental  veins,  and  communicating  branches.  It  passes  down  between  the  median 
line  and  the  anterior  border  of  the  Sternomastoid,  and  at  the  lower  part  of  the 
neck  passes  beneath  that  muscle  to  open  into  the  termination  of  the  external 
jugular,  or,  in  some  instances,  into  the  subclavian  vein  (Fig.  .514).  It  varies  con- 
siderably in  size,  bearing  almost  always  an  inverse  proportion  to  the  external 


714 


THE   VASCULAR  SYSTEMS 


jugular.  Most  frequently  there  are  two  anterior  jugulars,  a  right  and  left,  but 
occasionally  only  one.  Its  tributaries  are  some  laryngeal  veins,  and  occasionally 
a  small  thyroid  vein.  Just  above  the  sternum  the  two  anterior  jugular  veins  com- 
municate by  a  transverse  trunk,  which  receives  tributaries  from  the  inferior  thyroid 
veins;  each  also  communicates  with  the  internal  jugular.  There  are  no  valves 
in  this  vein. 

The  internal  jugular  vein  (v.  jug^daris  interna)  collects  the  blood  from  the 
interior  of  the  cranium,  from  the  superficial  parts  of  the  face,  and  from  the  neck. 
It  is  directly  continuous  with  the  lateral  sinus,  and  commences  in  the  posterior 
compartment  of  the  jugular  foramen,  at  the  base  of  the  skull  (Fig.  507).  At  its 
origin  it  is  somewhat  dilated,  and  this  dilatation  is  called  the  sinus  or  bulb  of  the 
internal  jugular  vein  (bulbus  v.  fugularis  superior).  The  vein  runs  down  the 
side  of  the  neck  in  a  vertical  direction,  lying  at  first  on  the  outer  side  of  the  internal 
carotid  artery,  and  then  on  the  outer  side  of  the  common  carotid  artery,  and  at 


HYPOGLOSS 


Fig.  496. — Veins  of  the  tongue.      (Testut,  modified  from  Hirschfeld.) 

Note. — The  hypoglossal  nerve  has  been  displaced  downward  in  this  preparation.  The  cor- 
rect relations  of  the  nerve  and  the  lingual  artery  are  shown  in  Fig.  437. 

the  root  of  the  neck  unites  with  the  subclavian  vein  to  form  the  innominate  vein. 
Just  before  its  termination  it  is  again  distinctly  dilated  (bulbus  v.  fugularis  in- 
ferior). The  internal  jugular  vein,  at  its  commencement,  lies  upon  the  Rectus 
capitis  lateralis,  and  behind  the  internal  carotid  artery  and  the  nerves  passing 
through  the  jugular  foramen;  lower  down,  the  vein  and  artery  lie  upon  the  same 
plane,  the  glossopharyngeal  and  hypoglossal  nerves  passing  forward  between 
them;  the  vagus  descends  between  and  behind  them  in  the  same  sheath,  and 
the  spinal  accessory  passes  obliquely  outward,  behind  or  in  front  of  the  vein.  At 
the  root  of  the  neck  the  vein  of  the  right  side  is  placed  at  a  little  distance  from  the 
artery;  on  the  left  side  it  usually  lies  over  the  artery  at  its  lower  part.  The  right 
internal  jugular  vein  crosses  the  first  part  of  the  subclavian  artery.  The  internal 
jugular  vein  is  of  considerable  size,  but  varies  in  different  individuals,  the  left 
one  being  usually  the  smaller.  It  is  provided  with  a  pair  of  valves,  which  are 
placed  about  an  inch  above  its  termination. 

Tributaries. — This  vein  receives  in  its  course  the  inferior  petrosal  sinus,  the 
common  facial,  lingual,  pharyngeal,  superior,  and  middle  thyroid  veins,  and 
sometimes  the  occipital.  A  tributary  from  the  cochlea  opens  into  the  bulb  of 
the  internal  jugular  vein.  A  venous  plexus  from  the  lateral  sinus  {^plexus  venosus 
caroticus  internus)  surrounds  the  internal  carotid  artery  in  the  carotid  canal  and 


THE   VEINS  OF  THE  NECK 


715 


empties  into  the  internal  jugular  vein.     At  its  point  of  junction  with  the  com- 
mon facial  vein  it  becomes  increased  in  size.     (See  Facial  Veins,  p.  710.) 

The  inferior  petrosal  sinus  leaves  the  skull  through  the  anterior  compartment 
of  the  jugular  foramen,  and  joins  the  vein  near  its  commencement.  Sometimes 
the  inferior  petrosal  sinus  is  not  a  direct  tributary  of  the  internal  jugular  vein, 
the  blood  being  conveyed  to  it  by  a  venous  plexus  in  the  hypoglossal  canal. 


TEMPORO- 


SUBCLAVIAN 

Fig.  497.— The  veins  of  the  neck,  viewed  from  in  front.      (Spalteholz.) 


The  lingual  veins  (lu'.  linguales)  (Fig.  496)  commence  on  the  dorsum,  sides,  and 
under  surface  of  the  tongue,  and,  passing  backward  along  the  course  of  the  lingual 
artery  and  its  branches,  terminate  in  the  Internal  jugular.  The  ranine  vein, 
a  tributary  of  considerable  size  commencing  below  the  tip  of  the  tongue,  may 
join  the  lingual;  generally,  however,  it  passes  backward  on  the  Hyoglossus  muscle 
in  company  with  the  hypoglossal  nerve,  and  joins  the  facial.  The  lingual  veins 
receive  the  sublingual  and  the  dorsal  lingual  veins. 

The  pharyngeal  veins  {vv.  phari/iigeae)  commence  in  the  pharyngeal  plexus  on 
the  wall  of  the  pharynx,  and,  after  receiving  meningeal  tributaries,  the  dural  or 
meningeal  veins,  the  Vidian  veins,  and  the  sphenopalatine  veins,  terminate  in 
the  internal  jugular.  They  occasionally  open  into  the  facial,  lingual,  or  superior 
thyroid  vein. 

The  superior  thyroid  vein  (v.  thyreoidea  superioris)  (Fig.  497)  commences  in  the 
substance  and  on  the  surface  of  the  thyroid  gland  by  tributaries  corresponding 


716 


THE  VASCULAR  SYSTEMS 


mth  the  branches  of  the  superior  thyroid  artery,  and  terminates  in  the  upper 
part  of  the  internal  jugular  vein.  It  receives  the  superior  laryngeal  and  crico- 
thyroid veins. 


Fig,  498. — Diagram  showing  common  arrangement  of  thyroid  ' 


(Kocher.) 


SUPERIOR 


Fig.  499.— The  fasci 


Ivoclier  the  thjreoidea 


The  \eins  here  desismted  the  mfenor  thjroid  are  called  by 


(.Poiner  and  Charpj  ) 


The  middle  thyroid  vein  (Fig.  483)  collects  the  blood  from  the  lower  part  of  the 
lateral  lobe  of  the  thyroid  gland,  and  after  being  joined  by  some  veins  from  the 
larynx  and  trachea,  terminates  in  the  lower  part  of  the  internal  jugular  vein.     Often 


THE   VEINS  OF  THE  NECK  717 

in  place  of  the  middle  thyroid  vein  there  are  two  veins,  the  superior  and  inferior 
accessory  thyroid.     These  veins  pass  into  the  internal  jugular. 

The  facial  and  occipital  veins  have  been  described  on  pages  710  and  713. 

Applied  Anatomy. — The  internal  jugular  vein  occasionally  requires  ligation  in  cases  of  septic 
thrombosis  of  the  lateral  sinus  from  suppuration  of  the  middle  ear.  This  is  done  in  order  to 
prevent  septic  emboli  being  carried  into  the  general  circulation.  This  operation  has  been  per- 
formed in  a  number  of  cases,  with  satisfactory  results.  The  cases  are  generally  those  of  chronic 
disease  of  the  middle  ear,  with  discharge  of  pus  which  perhaps  has  existed  for  many  years. 
The  patient  is  seized  with  acute  septic  inflammation,  spreading  to  the  mastoid  cells,  and,  con- 
sequent on  this,  septic  thrombosis  of  the  lateral  sinus  extending  to  the  internal  jugular  vein. 
Such  cases  are  always  extremely  grave,  for  there  is  danger  that  a  portion  of  the  septic  clot  will 
be  detached  and  cause  septic  embolism  in  the  thoracic  viscera.  If  thrombophlebitis  of  the 
sinus  is  suspected  the  mastoid  should  be  opened  and  cleansed  and  the  sinus  should  be  at  once 
exposed  and  explored.  If  the  sinus  is  found  to  be  thrombosed  the  surgeon  should  at  once  pro- 
ceed to  ligate  the  internal  jugular  vein,  by  an  incision  along  the  anterior  border  of  the  sterno- 
mastoid,  the  centre  of  which  is  on  a  level  with  the  greater  cornu  of  the  hyoid  bone.  The  vein 
should  be  ligated  in  two  places  or  opened  between.  After  the  vessel  has  been  secured  and 
divided  the  lateral  sinus  is  to  be  thoroughly  cleared  out,  and,  by  removing  the  ligature  from  the 
upper  end  of  the  divided  vein,  all  septic  clots  may  be  removed  by  syringing  from  the  sinus  through 
the  vein.  If  hemorrhage  occurs  from  the  distal  end  of  the  sinus,  it  can  be  arrested  by  careful 
plugging  with  gauze. 

The  internal  jugular  vein  is  also  surgically  important,  because  it  is  surrounded  by  a  large 
number  of  the  deep  chain  of  cervical  lymph  nodes;  and  when  these  are  enlarged  in  tuloerculous 
or  malignant  disease,  they  are  liable  to  become  adherent  to  the  vessel,  rendering  their  removal 
difficult  and  often  dangerous.  The  proper  course  to  pursue  in  these  cases  is  to  ligate  the  vessel 
above  and  below  the  glandular  mass,  and  resect  the  included  portion  together  with  the  nodes. 

Cardiac  pulsation  is  often  demonstrable  in  the  internal  jugular  vein  at  the  root  of  the  neck. 
There  are  no  valves  in  the  innominate  veins  or  superior  vena  cava;  in  consequence,  the  systole 
of  the  right  auricle  causes  a  wave  to  pass  up  these  vessels,  and  when  the  conditions  are  favorable 
this  wave  appears  as  a  somewhat  feeble  flicker  over  the  internal  jugular  vein  at  the  root  of  the 
neck,  quite  distinct  from,  and  just  preceding,  the  more -forcible  impulse  transmitted  from  the 
underlying  common  carotid  artery  and  due  to  the  ventricular  s\'stole.'  This  auricular  systolic 
venous  impulse  is  much  increased  in  conditions  in  which  the  right  auricle  is  abnormally  distended 
with  blood  or  is  hypertrophied,.  as  is  often  the  case  in  disease  of  the  auriculoventricular  valves. 
In  Stokes-Adams'  disease  (p.  56.5)  it  is  this  pulsation  which  gives  evidence  of  the  fact  that  the 
auricles  are  beating  faster — often  two  or  three  times  faster — than  the  ventricles. 

The  vertebral  vein  (v.  vertebralis)  (Fig.  500)  is  formed  in  the  suboccipital 
iriangle,  from  numerous  small  tributaries  which  spring  from  tlie  intraspinal  venous 
plexuses  (plexus  venosi  ■vertehrales)  and  issue  from  the  vertebral  canal  above  the 
posterior  arch  of  the  atlas.  They  unite  with  small  veins  from  the  deep  muscles  at 
the  upper  and  back  part  of  the  neck,  and  form  a  vessel  which  passes  outward 
and  enters  the  foramen  in  the  transverse  process  of  the  atlas,  and  descends,  forming 
a  dense  plexus  around  the  vertebral  artery,  in  the  canal  formed  by  the  foramina 
in  the  transverse  processes  of  the  cervical  vertebrte.  This  ple.xus  unites  at  the 
lower  part  of  the  neck  into  a  single  trunk,  which  emerges  from  the  foramen  in  the 
transverse  process  of  the  sixth  cervical  vertebra,  and  terminates  at  the  root  of 
the  neck  in  the  back  part  of  the  innominate  vein  near  its  origin,  its  mouth  being 
guarded  by  a  pair  of  valves.  On  the  right  side,  it  crosses  the  first  part  of  the  sub- 
clavian artery. 

Tributaries. — In  its  course  the  vertebral  vein  communicates  with  a  vein  trans- 
mitted from  the  lateral  sinus  of  the  skull  through  the  posterior  condylar  foramen. 
It  anastomoses  with  the  occipital  vein  and  receives  muscular  veins  from  the  muscles 
in  the  prevertebral  region;  intraspinal  veins,  from  the  back  part  of  the  cervical 
portion  of  the  vertebral  column;  meningorachidian  veins,  from  the  interior  of 
the  vertebral  canal;  the  anterior  and  posterior  vertebral  veins;  and  close  to  its 
termination  it  is  sometimes  joined  by  the  first  intercostal  vein. 

The  ascending  cervical  or  anterior  vertebral  vein  commences  in  a  plexus  around  the 
transverse  processes  of  the  upper  cervical  vertebrae,  descends  in  company  with  the 

'The  Interpretation  of  the  Venous  Pulse,  by  G.  Bachmann,  Amer.  Jour.  Med.  Sei.,  November,  1908. 


718 


THE   VASCULAR  SYSTEMS 


ascending  cervical  artery  between  the  Scalenus  anticus  and  Rectus  capitis  anticus 
major  muscles,  and  opens  into  the  vertebral  vein  just  before  its  termination. 


VERTEBRAL- 


ERTEBRAL 


POSTERIOR 

EXTERNAL 

JUGULAR 


POSTERroR 

DEEP 

CERVICAL 


Fig.  500.— The  vertebral 


The  posterior  vertebral  or  posterior  deep  cervical  vein  (v.  cervicalis  profunda^ 
(Fig.  500)  accompanies  the  deep  cervical  artery,  lying  between  the  Complexus 
and  Semispiiialis  colli.  It  commences  in  the  suboccipital  region  by  communicating 
branches  from  the  occipital  vein  and  tributaries  from  the  deep  muscles  at  the  back 
of  the  neck.  It  receives  tributaries  from  the  plexuses  around  the  spinous  processes 
of  the  cervical  vertebrae;  and  terminates  in  the  lower  end  of  the  vertebral  vein. 


The  Veins  of  the  Diploe  (Venae  Diploicae)  (Fig.  501). 

The  diploic  spaces  of  the  cranial  bones  in  the  adult  contain  a  number  of 
tortuous  canals,  the  diploic  canals  (canales  diploid  [Brescheti]),  which  are  bounded 
by  a  more  or  less  complete  layer  of  compact  osseous  tissue.  The  veins  they 
contain  are  large  and  capacious,  their  walls  being  thin,  and  formed  only  of 
endothelium  resting  upon  a  layer  of  elastic  tissue;  they  present  at  irregular 
intervals  pouch-like  dilatations,  or  culs-de-sac,  which  serve  as  reservoirs  for  the 
blood. 

In  adult  life,  so  long  as  the  cranial  bones  are  distinct  and  separable,  these 
veins  are  confined  to  the  particular  bones;  but  in  old  age,  when  the  sutures  are 
united,  they  communicate  with  one  another  and  increase  in  size.  They  communi- 
cate, in  the  interior  of  the  cranium,  with  the  veins  and  the  sinuses  of  the  dura, 
and  on  the  exterior  of  the  skull  with  the  veins  of  the  pericranium.  They  consist 
of  (1)  the  frontal  diploic  vein  (v.  di.ploica  frontalis),  which  opens  into  the  supra- 
orbital vein  by  an  aperture  in  the  supraorbital  notch;  (2)  the  anterior  temporal 
diploic  vein  (v.  di.ploica  temporalis  anterior),  which  is  coniined  chiefly  to  the 
frontal  bone,  and  opens  into  one  of  the  deep  temporal  veins  through  an  aper- 
ture in  the  greater  wing  of  the  sphenoid;  (3)  the  posterior  temporal  vein  (v.  diploica 


THE  CEREBRAL    VEINS  719 

temporalis  posterior),  which  is  situated  in  the  parietal  bone,  and  terminates  in  the 
lateral  sinus  through  an  aperture  at  the  postero-inferior  angle  of  the  parietal  bone 
or  through  the  mastoid  foramen;  and  (4)  the  occipital  diploic  vein  (v.  diploica 
occipitalis),  the  largest  of  the  four,  which  is  confined  to  the  occipital  bone,  and 
opens  into  the  lateral  sinus  or  the  torcular  Herophili. 
The  emissary  veins  are  considered  on  page  727. 


Fig.  501  — Veins  of  the  diplo    as  displived  by  the  remo\aI  of  the  outer  table  of  the  skull. 


The  meningeal  or  dural  veins  (w.  meningeae)  chiefly  correspond  with  the 
middle  meningeal  artery  and  its  branches,  as  its  two  venae  comites.  The  veins 
accompany  the  middle  meningeal  artery,  are  united  to  the  sphenoparietal  sinus, 
pass  through  the  foramen  spinosum,  and  join  the  pterygoid  plexus.  The  other 
dural  veins  correspond  somewhat  to  the  anterior  and  posterior  meningeal  distribu- 
tion and  empty  into  the  neighboring  sinuses. 

The  Cerebral  Veins  (Venae  Cerebri). 

The  cerebral  veins  possess  no  valves,  and  their  walls,  owing  to  the  absence  of 
muscle  tissue,  are  extremely  thin.  They  pierce  the  arachnoid  membrane  and  the 
inner  or  meningeal  layer  of  the  dura  and  open  into  the  cranial  venous  sinuses. 
They  may  be  divided  into  two  sets,  cerebral  and  cerebellar. 

The  cerebral  veins  consist  of  (a)  the  superficial  veins,  which  are  placed  on  the 
surface  of  the  brain,  and  (/j)  the  deep  veins,  which  lie  in  its  interior. 

The  superficial  cerebral  veins  ramify  upon  the  surface  of  the  brain,  being  lodged 
in  the  fissures  between  the  convolutions,  a  few  running  across  the  convolutions. 
They  receive  tributaries  from  the  substance  of  the  brain  and  terminate  in  the 
sinuses.     They  are  divisible  into  two  sets,  superior  and  inferior. 

The  superior  cerebral  veins  {vv.  cerebri  superiores),  eight  to  twelve  in  number 
on  each  side,  return  the  blood  from  the  convolutions  on  the  superior  surface 
of  the  hemisphere;  they  pass  forward  and  inward  toward  the  intercerebral  fissure, 
where  they  receive  the  veins  from  the  mesal  surface  of  the  hemisphere ;  near  their 
terminations  they  become  invested  with  tubular  sheaths  of  the  arachnoid,  and 
open  into  the  longitudinal  sinus  in  the  opposite  direction  to  the  course  of  the  cur- 
rent of  the  blood  in  the  sinus. 


720  THE  VASCVLAR  SYSTEMS 

The  inferior  cerebral  veins  {\w.  cerebri  mferiores)  ramify  on  the  lower  part 
of  the  outer  and  on  the  under  surfaces  of  the  cerebral  hemisphere.  Some, 
collecting  tributaries  from  the  under  surface  of  the  frontal  lobes  of  the  brain, 
terminate  in  the  cavernous  sinus.  One  vein  of  large  size,  the  middle  cerebral 
or  superficial  sylvian  vein  (y.  cerebri  media),  commences  on  the  under  surface  of 
the  temporal  lobe,  and,  running  along  the  sylvian  fissure,  opens  into  the  cavernous 
sinus.  Another  large  vein,  the  great  anastomotic  vein  of  Trolard,  connects  the  supe- 
rior sagittal  sinus  with  the  cavernous  sinus  by  Ijecoming  continuous  above  with 
one  of  the  superior  cerebral  veins  and  below  by  joining  the  middle  cerebral  vein. 
A  third,  the  posterior  anastomotic  vein  connects  the  middle  cerebral  vein  with  the 
lateral  sinus  by  coursing  over  the  temporal  lobe.  A  fourth,  the  basilar  vein 
(v.  basilis  [Rosenthali]),  is  formed  at  the  anterior  perforated  spot  by  the  union 
of  (a)  a  small  anterior  cerebral  vein,  which  accompanies  the  anterior  cerebral  artery 
(6)  the  deep  sylvian  vein,  which  receives  tributaries  from  the  island  of  Reil  (or 
insula)  and  neighboring  convolutions,  and  runs  in  the  lower  part  of  the  sylvian 
fissure;  and  (c)  the  inferior  striate  veins,  which  leave  the  corpus  striatum  through 
the  anterior  perforated  substance.  The  basilar  vein  passes  backward  around  the 
crus  cerebri,  and  ends  in  the  vein  of  Galen;  it  receives  tributaries  from  the  inter- 
peduncular space,  the  descending  horn  of  the  lateral  ventricle,  the  uncinate  gyre, 
and  the  midbrain.  Small  inferior  cerebral  veins  from  the  under  surface  of  the 
frontal  lobe  end  in  the  cavernous  sinus;  others  from  the  temporal  lobe  terminate 
in  the  superior  petrosal  and  lateral  sinuses. 

The  deep  cerebral  veins,  or  veins  of  Galen  (vv.  cerebri  internae)  (Fig.  725), 
are  two  in  number.  Each  is  formed  by  the  union  of  two  veins,  the  vena  cor- 
poris striati,  and  the  choroid  vein,  on  either  side.  They  run  backward,  parallel 
with  each  other,  between  the  layers  of  the  velum  interpositum,  and  beneath 
the  splenium,  and  in  the  region  of  the  pineal  body  unite  to  form  a  short  trunk, 
the  vena  magna  Galeni  {v.  cerebri  magna),  which  passes  out  of  the  brain  at  the  great 
transverse  fissure,  and  ends  in  the  anterior  extremity  of  the  straight  sinus.  The 
two  velar  veins  receive  tributaries  from  the  callosal  region,  from  a  portion  of 
the  occipital  lobe,  and  just  before  their  union  each  vein  receives  the  corresponding 
basilar  vein.     Each  vena  magna  Galeni  also  receives  the  superior  cerebellar  veins. 

The  vena  corporis  striati  on  each  side  coimnences  in  the  groove  between  the 
corpus  striatum  and  thalamus,  receives  numerous  veins  from  both  of  these  parts, 
and  unites,  behind  the  anterior  pillars  of  the  fornix,  with  the  choroid  vein  to 
form  one  of  the  deep  cerebral  veins. 

The  choroid  vein  {v.  choroidea)  originates  in  the  extreme  end  of  the  middle 
horn  of  the  lateral  ventricle  and  runs  along  the  whole  length  of  the  outer  border 
of  the  choroid  plexus,  receiving  veins  from  the  hippocampus,  the  fornix,  and 
corpus  callosum,  and  unites,  at  the  anterior  extremity  of  the  choroid  plexus,  with 
the  vein  of  the  corpus  striatum  to  form  the  deep  cerebral  veins  of  that  side. 

The  superficial  cerebellar  veins  (Fig.  723)  occupy  the  surface  of  the  cerebellum, 
and  are  disposed  in  two  sets,  superior  and  inferior. 

The  superior  superficial  cerebellar  veins  (ra.  cerebelli  siiperiores)  pass  partly  for- 
ward and  inward,  across  the  superior  vermis  (prevermis),  to  terminate  in  lateral 
branches  which  pass  partly  to  the  tentorial  sinus  and  partly  outward  to  the  lat- 
eral and  superpetrosal  sinuses. 

The  subcerebellar  or  inferior  superficial  cerebellar  veins  (vv.  cerebelli  inferiores), 
of  large  size,  terminate  in  the  lateral,  subpetrosal,  and  occipital  sinuses. 

The  deep  cerebellar  veins  bring  blood  from  the  interior  of  the  cerebellum  to 
the  superficial  veins. 

Veins  of  the  Pons. — Veins  come  from  the  interior  of  the  pons,  the  deep  veins, 
and  enlpty  into  a  plexus  of  superficial  veins.  From  this  superficial  venous  plexus 
a  superior  vein  passes  to  the  basilar  vein,  and  an  inferior  vein  either  into  a  cere- 
bellar vein  or  into  the  superpetrosal  sinus. 


THE  SIiYUSUS  OF  THE  DURA  721 

Veins  of  the  Medulla  Oblongata. — ^'ein.s  jjass  from  the  interior  of  the  medulla 
oblongata  and  end  in  a  plexus  on  the  surface.  From  this  plexus  comes  an  anterior 
median  vein,  which  is  a  prolongation  of  a  like  vein  of  the  spinal  cord — a  posterior 
median  vein  corresponding  to  a  lilve  vein  of  the  cord — and  small  branches  which 
pass  with  the  roots  of  the  glossopharyngeal,  -vagus,  spinal  accessory,  and  hvpo- 
glossal  nerves,  and  empty  into  the  occipital  and  the  subpetrosal  sinuses. 

The  perivascular  lymph  spaces  are  especially  found  in  connection  with  the  vessels  of  the 
brain.  These  vessels  are  enclosed  in  a  sheath,  which  acts  as  a  lymphatic  channel,  through 
which  the  lymph  is  carried  to  the  subarachnoid  and  subdural  spaces,  from  which  it  is  returned 
into  the  seneral  circulation. 


The  Sinuses  of  the  Dura  (Sinus  Durae  Matris)  (Figs.  502,  503). 
Ophthalmic  Veins  and  Emissary  Veins. 

The  sinuses  of  the  dura  are  venous  channels  which  drain  the  blood  from  the 
brain;  they  are  situated  between  the  two  layers  of  the  dura  and  are  lined  by 
endothelium  continuous  with  that  which  lines  the  veins.  They  are  sixteen  in 
number,  of  which  six  are  single  and  situated  in  the  mesal  plane;  the  other  ten  are 
paired,  five  being  placed  on  either  side  of  the  mesal  plane.  They  are  divided 
into  two  sets:  {\)  Those  situated  at  the  upper  and  back  part  of  the  skull;  (2) 
those  at  the  base  of  the  skull.     The  former  are : 

Superior  sagittal  sinus.  Tentorial  or  straight  sinus. 

Inferior  sagittal  sinus.  Lateral  sinuses. 

Occipital  sinus. 

The  superior  sagittal  sinus  (sinus  sagittalis  superior)  (Figs.  502  and  50.3)  oc- 
cupies the  attached  margin  of  the  falx  cerebri.  Commencing  at  the  foramen 
cecum,  through  which  it  usually  communicates  by  a  small  branch  with  the 
veins  of  the  nasal  fossse,  it  runs  from  before  backward,  grooving  the  inner  sur- 
face of  the  frontal,  the  adjacent  margins  of  the  two  parietals,  and  the  supe- 
rior division  of  the  crucial  ridge  of  the  occipital;  near  the  internal  occipital 
protuberance  it  usually  deviates  toward  the  right,  and  is  continued  as  the  corre- 
sponding lateral  sinus.  The  sinus  is  triangular  on  transverse  section,  is  narrow 
in  front,  and  gradually  increases  in  size  as  it  passes  backward.  Its  inner  surface 
presents  the  internal  openings  of  the  superior  cerebral  veins,  which  run,  for  the 
most  part,  from  behind  forward,  and  open  chiefly  at  the  back  part  of  the  sinus, 
their  orifices  being  concealed  by  valve-like  folds;  numerous  fibrous  bands,  chordae 
Willisii  (Fig.  504),  are  also  seen  extending  transversely  across  the  inferior  angle 
of  the  sinus;  and  some  small,  white,  projecting  bodies,  the  glandulae  Pacchioni 
(granulationes  arachuoidales).  This  sinus  communicates  by  numerous  small 
apertures  with  spaces  in  the  dura  known  as  lacunae  laterales,  or  parasinoidal  spaces 
(Fig.  504).  The  arachnoid  villi  project  into  these  spaces.  The  superior  sagittal 
sinus  receives  the  superior  cerebral  veins,  numerous  veins  from  the  diploe  and 
dura,  the  outlets  of  the  parasinoidal  spaces,  and,  at  the  posterior  extremity  of 
the  sagittal  suture,  veins  from  the  pericranium,  which  pass  through  the  parietal 
foramina.  Sometimes  the  sagittal  sinus  receives  a  twig  from  the  nose  which 
passes  through  the  foramen  cecum. 

The  inferior  sagittal  sinus  (sirms  sagittalis  inferior,  s.  falcialis)  (Fig.  503)  is  con- 
tained in  the  posterior  half  or  two-thirds  of  the  free  margin  of  the  falx  cerebri. 
It  is  of  a  cylindric  form,  increases  in  size  as  it  passes  backward,  and  terminates 
in  the  straiglit  sinus.  It  receives  several  A-eins  from  the  falx  cerebri,  and  occa- 
sionally a  few  from  the  mesal  surface  of  the  hemispheres. 

46 


722 


THE   VASCULAR  SYSTEMS 


The  straight  or  tentorial  sinus  {sinus  rectus,  s.  tentorii)  (Figs.  502  and  503) 
is  situated  at  tiie  line  of  junction  of  the  falx  cerebri  with  tiie  tentorium  cerebelli. 
It  is  triangular  on  section,  increases  in  size  as  it  proceeds  backward,  and  runs 
obliquely  downward  and  backward  from  the  termination  of  the  inferior  sagittal 


Fig.  502. — Coronal  i 


ction  of  the  skull  to  show  the  situatious 
(Poirier  and  Charpy.) 


nd  shapes  of  the  chief  i 


sinus  to  the  lateral  sinus  of  the  opposite  side  to  that  into  which  the  sagittal  sinus 
is  prolonged.  Its  terminal  part  communicates  by  a  cross-branch  with  the  torcular 
Herophili  (confluence  of  the  sinuses).  Besides  the  inferior  sagittal  sinus,  it  re- 
ceives the  vena  magna  Galeni  and  the  superior  cerebellar  veins.  A  few  transverse 
bands  cross  its  lumen. 


Torcular  herophili. 


Foramen  cecum. 


Fig.  503. — Sagittal  section  of  the  skull,  showing  the  sinuses  of  the  du: 


The  lateral  sinuses  (Figs.  502  and  503)  are  of  large  size  and  commence  at  the 
internal  occipital  protuberance;  one,  generally  the  right,  being  the  direct  continua- 
tion of  the  superior  sagittal  sinus,  the  other  of  the  straight  sinus.  Each  lateral 
sinus  {sinus  transversus)  passes  outward  and  forward,  describing  a  slight  curve 
with  its  convexity  upward,  to  the  base  of  the  petrous  portion  of  the  temporal 


THE  SINUSES  OF  THE  D  URA 


723 


bone,  and  is  situated,  in  this  part  of  its  course,  in  the  attached  margin  of  the 
tentorium  cerebelli;  it  then  leaves  the  tentorium,  curves  downward  and  inward 
to  reach  the  jugular  foramen,  where  it  terminates  in  the  internal  jugular  vein. 
In  its  course  it  rests  upon  the  inner  surface  of  the  occipital,  the  postero-inferior 
angle  of  the  parietal,  the  mastoid  portion  of  the  temporal  bone,  and  on  the  occipital 
again,  at  the  jugular  process,  just  before  its  termination.  The  portion  of  the  sinus 
which  occupies  the  groove  on  the  mastoid  portion  of  the  temporal  bone  is  known 
as  the  sigmoid  sinus.  The  lateral  sinuses  are  frequently  of  unequal  size,  that 
formed  by  the  sagittal  sinus  being  the  larger,  and  they  increase  in  size  as  they 
proceed  from  behind  forward.  The  horizontal  portion  is  triangular  on  section, 
the  curved  portion  semicylindric.  Their  inner  surface  is  smooth,  and  not  crossed 
by  the  fibrous  bands  found  in  the  other  sinuses.  The  lateral  sinuses  receive 
the  blood  from  the  superior  petrosal  sinuses  at  the  base  of  the  petrous  portion  of 


Fig  504. — Sagittal  sinus  seen  from  above  after  removal  of  the  skullcap.  The  chordae  Willisii  are  clearly 
■'/isible.  The  parasinoidal  sinuses  are  also  well  shown.  Probes  passing  from  the  latter  to  the  longitudinal 
sinus  show  that  they  communicate.     (Poirier  and  Charpy.) 

the  temporal  bone,  and  they  unite  with  the  inferior  petrosal  sinus,  just  external 
to  the  jugular  foramen,  to  form  the  internal  jugular  vein  (Fig.  50S).  They  com- 
municate with  the  veins  of  the  pericranium  by  means  of  the  mastoid  and  posterior 
condylar  veins,  and  they  receive  some  of  the  inferior  cerebral  and  inferior  cere- 
bellar veins,  some  veins  from  the  diploe,  and  often  veins  from  the  internal  ear 
(yv.  audiiivae  internae),  which  come  out  of  the  internal  auditory  meatus.  The 
petrosquamous  sinus,  when  present,  runs  backward  along  the  junction  of  the 
petrous  and  squamous  portions  of  the  temporal  bone,  and  opens  into  the  lateral 
sinus. 

The  occipital  sinus  (sinus  occipitalis)  (Fig.  503)  is  the  smallest  of  the  cranial 
.sinuses.     It  is  generally  single,  but  occasionally  there  are  two.     It  is  situated  in 


724  THE   VASCULAR  SYSTEMS 

the  attached  margin  of  the  falx  cerebelH.  It  commences  by  several  small  veins 
around  the  margin  of  the  foramen  magnum,  one  of  which  joins  the  termination 
of  the  lateral  sinus;  it  communicates  with  the  posterior  spinal  veins  and  terminates 
in  the  torcular  Herophili. 

The  torcular  Herophili,  or  confluence  of  the  sinuses  (confluens  simmm),  is  the 
term  applied  to  the  dilated  extremity  of  the  superior  sagittal  sinus.  It  is  of  irreg- 
ular form,  and  is  lodged  on  one  side  (generally  the  right)  of  the  internal  occipital 
protuberance.  From  it  the  lateral  sinus  of  the  side  to  which  it  is  deflected  is 
derived.  It  also  receives  the  blood  from  the  occipital  sinus,  and  is  connected 
across  the  middle  line  with  the  commencement  of  the  lateral  sinus  of  the  opposite 
side. 

The  sinuses  at  the  base  of  the  skull  are: 

Two  cavernous  sinuses.  Two  superior  petrosal  sinuses. 

Two  sphenoparietal  sinuses.  Two  inferior  petrosal  sinuses. 

Circular  sinus.  Transverse  sinus. 

The  cavernous  sinuses  (Figs.  507  and  508)  are  so  named  because  they  present 
a  reticulated  structure,  due  to  their  being  traversed  by  numerous  interlacing 
filaments  (Fig.  505).  They  are  of  irregular  form,  larger  behind  than  in  front, 
and  are  placed  one  on  each  side  of  the  sella  turcica,  extending  from  the  sphenoidal 
fissure  to  the  apex  of  the  petrous  portion  of  the  temporal  bone.  Each  cavernous 
sinus  (sinus  cavernosus)  receives  anteriorly  the  superior  ophthalmic  vein  through 
the  sphenoidal  fissure,  and  opens  behind  into  the  petrosal  sinuses.  On  the  inner 
wall  of  each  sinus  is  the  internal  carotid  artery,  accompanied  by  filaments  of  the 
carotid  plexus  and  by  the  abducent  nerve;  and  on  its  outer  wall,  the  oculomotor, 
trochlear,  ophthalmic,  and  superior  maxillary  divisions  of  the  trigeminal  nerve 
(Fig.  505).  These  parts  are  separated  from  the  blood  fiowing  along  the  sinus 
by  the  lining  membrane,  which  is  continuous  with  the  inner  coat  of  the  veins. 
Each  cavernous  sinus  receives  some  of  the  cerebral  veins,  and  also  the  spheno- 
parietal sinus.  It  communicates  with  the  lateral  sinus  by  means  of  the  superior 
petrosal  sinus;  with  the  internal  jugular  vein  through  the  inferior  petrosal  sinus 
and  through  a  plexus  of  veins  on  the  internal  carotid  artery;  with  the  pterygoid 
plexus  through  the  foramen  ovale,  and  with  the  angular  vein  through  the  ophthal- 
mic vein.  The  two  sinuses  also  communicate  with  each  other  by  means  of  the 
circular  sinus. 

Applied  Anatomy. — An  arteriovenous  communication  may  be  established  between  the 
cavernous  sinus  and  the  internal  carotid  artery,  as  it  lies  in  it,  giving  rise  to  a  pulsating  tumor  in 
the  orbit.  Such  a  communication  may  be  the  result  of  injury,  such  as  a  bullet  wound,  a  stab,  or 
a  blow  or  fall  sufficiently  severe  to  cause  a  fracture  of  the  base  of  the  skull  in  this  situation,  or 
it  may  occur  from  the  rupture  of  an  aneurism  or  a  diseased  condition  of  the  internal  carotid 
artery.  The  disease  begins  with  sudden  noise  and  pain  in  the  head,  followed  by  exophthalmos, 
swelling  and  congestion  of  the  lids  and  conjunctivEe.  A  pulsating  tumor  develops  at  the  margin 
of  the  orbit,  with  thrill  and  the  characteristic  bruit;  accompanying  these  symptoms  there  may  be 
impairment  of  the  sight,  paralysis  of  the  iris  and  orbital  muscles,  and  pain  of  varying  intensity. 
In  some  cases  the  opposite  orbit  becomes  affected  by  the  passage  of  the  arterial  blood  into  the 
opposite  sinus  by  means  of  the  circular  sinus.  Or  the  arterial  blood  may  find  its  way  through 
the  emissary  veins  into  the  pterygoid  plexus,  and  thence  into  the  veins  of  the  face.  Pulsating 
tumors  of  the  orbit  may  also  be  due  to  traumatic  aneurism  of  one  of  the  orbital  arteries,  and 
symptoms  resembling  those  of  pulsating  tumor  may  be  produced  by  pressure  on  the  ophthalmic 
vein,  as  it  enters  the  sinus,  by  an  aneurism  of  the  internal  carotid  artery.  Ligation  of  the  internal 
or  the  common  carotid  artery  has  been  performed  in  these  cases  with  some  degree  of  success. 

Of  recent  years  more  attention  has  been  paid  to  thrombosis  of  the  cavernous  sinus  than  for- 
merly, and  it  is  now  well  established  that  caries  in  the  upper  parts  of  the  nasal  fossae  and  sup- 
puration in  certain  of  the  accessory  sinuses  of  the  nose,  are  frequently  responsible  for  septic 
tlu-ombosis  of  the  cavernous  sinuses,  in  exactly  the  same  way  as  lateral  sinus  thrombosis  is  due 
to  septic  disease  in  the  mastoid  process.  Manj'  deaths  from  meningitis,  hitherto  unaccounted 
for,  are  in  reality  due  to  the  spread  of  an  infection  from  an  ethmoidal  or  sphenoidal  air  cell  to 
the  cavernous  sinus,  and  thence  to  the  meninges.  It  is  obvious,  therefore,  that  no  case  of  clu-onic 
nasal  suppuration  should  be  left  untreated. 


THE  SINUSES  OF  THE  DURA 


725 


The  sphenoparietal  sinuses  may  be  regarded,  together  with  the  ophthalmic  veins, 
as  the  commencement  of  the  corresponding  cavernous  sinuses.  Each  of  these 
sinuses  {sinus  sphenoparidaUs)  is  lodged  in  the  dura  on  the  under  surface  of  the 
lesser  wing  of  the  sphenoid  bone.     It  takes  origin  from  one  of  the  middle  meningeal 


TRANSVERSE 


Fig.  505. — Frontil  section  through  the  light  ( 


enlarged.     (Spalteholz.) 


veins,  usually  receives  l^lood  from  the  diploe  of  the  skull,  passes  inward,  and  ends 
in  the  anterior  part  of  the  cavernous  sinus. 

The  ophthalmic  veins  are  two  in  number,  superior  and  inferior. 

The  superior  ophthalmic  vein  {v.  ophfhalmica  superior)  (Fig.  506)  begins  as  the 
nasofrontal  vein  ( v.  nasofrontalis),  which  communicates  with  the  angular  vein  at 
the  inner  angle  of  the  orbit.     It  joins  the  angular  vein  with  the  cavernous  sinus; 


Fig.  506. — Veins  of  the  orbit.      (Poirier  and  Charpy.) 

it  pursues  the  same  course  as  the  ophthalmic  artery,  and  receives  tributaries  cor- 
responding to  the  branches  derived  from  that  vessel.  Forming  a  short  single 
trunk,  it  passes  through  the  inner  extremity  of  the  sphenoidal  fissure,  and  termi- 
nates in  the  cavernous  sinus.  It  anastomoses  with  the  inferior  ophthalmic  vein 
and  receives  lacrimal,  anterior  and  posterior  ethmoidal,  and  muscular  branches, 
and  veins  of  the  eyelids  and  of  the  eyeball  (vv.  wrticosae) . 


726 


THE  VASCULAR  SYSTEMS 


The  inferior  ophthalmic  vein  {v.  ophthalmica  inferior)  (Fig.  506)  arises  in  the 
veins  of  the  eyehds  and  lacrimal  sac,  receives  the  veins  from  the  floor  of  the 
orbit,  and  either  passes  out  of  the  orbit  through  the  sphenoidal  fissure  to  join 
the  pterygoid  plexus  of  veins,  or  else,  passing  backward  through  the  sphenoidal 
fissure,  it  enters  the  cavernous  sinus,  either  by  a  separate  opening,  or,  more  fre- 
quently, in  common  with  the  superior  ophthalmic  vein.  It  receives  muscular 
tributaries  and  veins  of  the  eyeball,  and  anastomoses  with  the  superior  ophthal- 
mic and  deep  facial  vein. 

The  circular  sinus  (sinus  circularis)  (Figs.  505  and  507)  is  formed  by  two 
transverse  vessels,  the  anterior  and  posterior  intracavernous  sinuses  (sinus  inter- 
cavernosus  anterior  and  si7itis  intercavernosus  posterior),  which  connect  the  two 
cavernous  sinuses;  one  passes  in  front  of  and  the  other  behind  the  pituitary  body, 
and  thus  they  form  with  the  cavernous  sinuses  a  venous  circle  around  that  body. 
The  anterior  one  is  usually  the  larger  of  the  two,  and  one  or  other  is  occasionally 
absent. 

The  superior  petrosal  sinus  (sifius  petrosus  superior)  (Figs.  503  and  507)  is 
situated  along  the  superior  border  of  the  petrous  portion  of  the  temporal  bone, 

in  the  front  part  of  the 
attached  margin  of  the 
tentorium  cerebelli.  It  is 
small  and  narrow,  and 
connects  the  cavernous 
and  lateral  sinuses  at  each 
side.  It  receives  some 
cerebellar  and  inferior 
cerebral  veins,  and  veins 
from  the  tympanic  cavity. 
The  inferior  petrosal 
sinus  (sijiits  petrosus  infe- 
rior) (Fig.  503)  is  situated 
in  the  groove  formed  by 
the  junction  of  the  pos- 
-openmgof  mastoid  teTioT  border  of  the  pe- 
trous portion  of  the  tem- 
poral with  the  basilar 
process  of  the  occipital 
bone.  It  commences  in 
front  at  the  termination 
of  the  cavernous  sinus, 
and,  passing  through  the 
anterior  compartment  of 
the  jugular  foramen,  ends 
in  the  commencement  of  the  internal  jugular  vein.  The  inferior  petrosal  sinus 
receives  a  vein  from  the  internal  ear  {vv.  auditavae  internae)  and  also  veins  from 
the  medulla  oblongata,  pons,  and  under  surface  of  the  cerebellum. 

The  exact  relation  of  the  parts  to  one  another  in  the  foramen  is  as  follows :  The 
inferior  petrosal  sinus  is  in  front,  with  the  meningeal  branch  of  the  ascending 
pharyngeal  artery,  and  is  directed  obliquely  downward  and  backward;  the  lateral 
sinus  is  situated  at  the  back  part  of  the  foramen  with  a  meningeal  branch  of  the 
occipital  artery,  and  between  the  two  are  the  glossopharyngeal,  vagus,  and  spinal 
accessory  nerves.  These  three  sets  of  structures  are  divided  from  each  other 
by  two  processes  of  fibrous  tissue.  The  junction  of  the  inferior  petrosal  sinus 
with  the  internal  jugular  vein  takes  place  superficial  to  the  nerves,  so  that  these 
latter  lie  a  little  internal  to  the  venous  channels  in  the  foramen. 


YTorcular  Serophili. 
Fig.  507. — The  sinuses  at  the  base  of  the  skull. 


VEINS  OF  THE  UPPER  EXTREMITY  AND  THORAX  727 

The  transverse  or  basilar  sinus  {'plexus  basilarin)  (Fig.  507)  consists  of  se\erai 
interlacing  veins  between  the  layers  of  the  dura  over  the  basilar  process  of  the 
occipital  bone,  which  serve  to  connect  the  two  inferior  petrosal  sinuses.  They 
communicate  with  the  anterior  spinal  veins. 

The  emissary  veins  (emissaria)  are  vessels  which  pass  through  apertures  in 
the  cranial  wall  and  establish  communications  between  the  sinuses  inside  the 
skull  and  the  diploic  veins  in  the  diploe,  and  the  veins  external  to  the  skull. 
Some  of  these  are  always  present,  others  only  occasionally  so.  They  vary 
much  in  size  in  difi'erent  individuals.  The  principal  emissary  veins  are  the 
following:  (1)  A  vein  (emissarium  mastoideum)  almost  always  present,  runs 
through  the  mastoid  foramen  and  connects  the  lateral  sinus  with  the  posterior 
auricular  or  with  the  occipital  vein.  (2)  A  vein  (emissarium  pariefale)  which 
passes  through  the  parietal  foramen  and  connects  the  superior  sagittal  sinus  with 
the  veins  of  the  scalp.  (.3)  A  plexus  of  minute  veins  (rete  canalis  hypoglossi), 
which  pass  through  the  anterior  condylar  (hypoglossal)  foramen  and  connect 
the  occipital  sinus  with  the  vertebral  vein  and  deep  veins  of  the  neck.  (4)  An 
inconstant  vein  {emissarium  condyloideum)  which  passes  through  the  posterior 
condylar  foramen  and  connects  the  lateral  sinus  with  the  deep  veins  of  the  neck. 
(5)  A  plexus  of  veins  (rete  foraminis  ovalis)  connects  the  cavernous  sinus  with 
the  pterygoid  and  pharyngeal  plexuses  through  the  foramen  ovale.  (6)  Two 
or  three  small  veins  run  through  the  foramen  lacerum  medium  and  connect  the 
cavernous  sinus  with  the  pterygoid  and  pharyngeal  plexuses.  (7)  There  is  some- 
times a  small  vein  connecting  the  same  parts  and  passing  through  the  inconstant 
foramen  of  Vesalius  opposite  the  root  of  the  pterygoid  process  of  the  sphenoid 
bone.  (8)  A  plexus  of  veins  {plexus  venosus  caroticus  internus)  traverses  the 
carotid  canal  and  connects  the  cavernous  sinus  with  the  internal  jugular  vein.  (9) 
A  small  vein  {emissarium  occipitale)  usually  connects  the  occipital  vein  with 
the  lateral  sinus  or  the  torcular  Herophili  and  the  occipital  diploic  vein.  (10)  A 
vein  is  usually  transmitted  through  the  foramen  cecum  and  connects  the  superior 
sagittal  sinus  with  the  veins  of  the  mucous  membrane  of  the  nose. 

Applied  Anatomy. — These  emissary  veins  are  of  great  importance  in  surgery.  In  addition 
to  them  there  are,  however,  other  communications  between  the  intra-  and  extracranial  chan- 
nels, as,  for  instance,  the  communication  of  the  angular  and  supraorbital  veins  with  the  ophthal- 
mic vein  at  the  inner  angle  of  the  orbit,  and  the  communication  of  the  veins  of  the  scalp  with 
the  diploic  veins.  Through  these  communications  inflammatory  processes  commencing  on  the 
outside  of  the  skull  may  travel  inward,  leading  to  osteophlebitis  of  the  diploe  and  inflammation 
of  the  membranes  of  the  brain.  This  is  one  of  the  principal  dangers  of  scalp  wounds  and  other 
injuries  of  the  scalp. 

By  means  of  these  emissary  veins  blood  may  be  abstracted  almost  directly  from  the  intra- 
cranial vessels.  For  instance,  leeches  applied  behind  the  ear  abstract  blood  almost  directly 
from  the  lateral  sinus  by  means  of  the  vein  passing  through  the  mastoid  foramen.  Again,  epis- 
taxis  in  children  will  frequently  relieve  severe  headache,  the  blood  which  flows  from  the  nose 
being  derived  from  the  superior  sagittal  sinus  by  means  of  the  vein  which  passes  through  the 
foramen  cecum. 


VEINS  OF  THE  UPPER  EXTREMITY  AND  THORAX. 

The  veins  of  the  upper  extremity  are  divided  into  two  sets,  superficial  and  deep. 

The  Superficial. Veins  are  placed  immediately  beneath  the  integument  between 
the  layers  of  the  superficial  fascia. 

The  Deep  Veins  accompany  the  arteries,  and  constitute  the  venae  comites  of 
those  vessels. 

Both  sets  of  vessels  are  provided  with  valves,  which  are  more  numerous  in  the 
deep  than  in  the  superficial  veins. 


728 


THE  VASCULAR  SY8TE3IS 


Fig.  508.— The 


on  the  dorsum  of  the  hand.     (Bourgery.) 


The  Superficial  Veins  of  the  Upper  Extremity  (Fig.  509). 

The  superficial  veins  of  the  upper  extremity  are: 

Superficial  veins  of  the  hand.  Median. 

Anterior  ulnar.  Median  cephalic 

Posterior  ulnar.  Median  basilic. 

Common  ulnar.  Basilic. 

Radial.  Cephalic. 

The  superficial  veins  of  the  hand  and  fingers  (Figs.  508  and  509)  are  prin- 
cipally situated  on  the  dorsal  surface.  These  dorsal  veins  begin  in  each  finger 
as  a  venous  plexus,  in  which  are  distinct  veins  running  in  a  longitudinal  direction 
and  called  dorsal  digital  veins  {vv.  digitales  dorsales  propriae).  The  dorsal  digital 
veins  terminate  over  the  first  phalanges  in  the  venous  arches  of  the  fingers  {amis 


THE  SUPERFICIAL   VEINS  OF  THE  UPPER  EXTREMITY     729 


venosi  diriifalcs).  From  these  arches  take  origin  the  four  dorsal  interosseous  or 
the  interdigital  veins  (m.  metacarpeae  dorsales).  These  veins  form  tlie  dorsal 
venous  plexus  of  the  hand  {rete  venosum 
dorsalc  manus).  This  plexus  hes  in  a 
hne  with  the  lower  ends  of  the  shafts 
of  the  metacarpal  bones.  It  receives 
the  dorsal  interosseous  veins,  the  radial 
digital  vein  of  the  index  finger,  and 
numerous  superficial  veins  from  the 
back  of  the  hand.  It  gives  origin  to  the 
superficial  radial  vein  and  the  posterior 
ulnar  vein.  The  superficial  veins  of 
the  palmar  surface  are  of  less  size  and 
number  than  the  dorsal  veins.  They 
arise  from  each  of  the  phalanges  by  a 
plexus  ivv.  digiiales  volares  projmae). 
Vessels  at  the  borders  of  the  fingers 
take  most  of  the  blood  to  the  dorsal 
veins.  There  are  also  veins  in  the 
finger  webs  {m.  intercajyitidares) ,  which 
convey  the  blood  from  the  palm  to 
the  dorsum.  A  superficial  plexus,  the 
palmar  plexus,  lies  upon  the  palmar 
fascia,  the  fascia  of  the  thenar  emi- 
nence, and  the  fascia  of  the  hypothenar 
eminence. 

The  anterior  ulnar  vein  (Fig.  509) 
commences  on  the  anterior  surface  of 
the  ulnar  side  of  the  hand  and  wrist, 
and  ascends  along  the  anterior  surface 
of  the  ulnar  side  of  the  forearm  to  the 
bend  of  the  elbow,  w^here  it  joins  with 
the  posterior  ulnar  vein  to  form  the 
common  ulnar.  Occasionally  it  opens 
separately  into  the  median  basilic  vein. 
It  communicates  with  tributaries  of  the 
median  vein  in  front  and  with  the  pos- 
terior ulnar  behind. 

The  posterior  ulnar  vein  (Fig.  508) 
commences  on  the  posterior  surface 
of  the  ulnar  side  of  the  wrist.  It 
runs  on  the  posterior  surface  of 
the  ulnar  side  of  the  forearm,  and 
just  below  the  elbow  unites  with 
the  anterior  ulnar  vein  to  form  the 
common  ulnar,  or  else  joins  the  median 
basilic  and  helps  to  form  the  basilic.  It 
communicates  with  the  deep  veins  of 
the  palm  by  a  vein  which  emerges  from 
beneath  the  Abductor  minimi  digiti 
muscle. 

The  common  ulnar  vein  (Fig.  509) 
is  a  short  trunk  which  is  not  constant. 

TjTi  . ,  •   j_       -J.     ■        J-  J     u        J.1        Fig.  509. — The  superficial  veins  of  the  flexor  aspect  of 

When     it     exists     it     is     JOnned     by     the  the  upper  extremity. 


Median  cephalic 

Evtet  nal 
cutaneous  nei  ve 


730  THE  VASCULAR  SYSTEMS 

junction  of  the  two  preceding  veins,  and,  passing  upward  and  outward,  joins 
the  median  basihc  to  form  the  basilic  vein.  When  it  does  not  exist  the  anterior 
and  posterior  ulnar  veins  open  separately  into  the  median  basilic  vein. 

The  radial  vein  {v.  radialis)  (Figs.  509  and  510)  commejices  upon  the  dorsal 
surface  of  the  wrist,  and  communicates  with  the  deep  veins  of  the  palm  by  a  branch 
which  passes  through  the  first  interosseous  space.  The  radial  vein  soon  forms  a 
large. vessel,  which  ascends  along  the  radial  side  of  the  forearm  and  receives 
numerous  veins  from  both  its  surfaces.  At  the  bend  of  the  elbow  it  unites  with 
the  median  cephalic  to  form  the  cephalic  vein. 

The  median  vein  {v.  mediana  cubiti)  (Fig.  509)  ascends  on  the  front  of  the 
forearm,  and  communicates  with  the  anterior  ulnar  and  radial  veins.  At  the  bend 
of  the  elbow  it  receives  a  branch  of  communication  from  the  deep  veins,  the  deep 
median  vein,  and  divides  into  two  trunks,  the  median  cephalic  and  median  basilic, 
which  diverge  from  each  other  as  they  ascend. 

The  median  cephalic  (v.  mediana  cephalica)  (Fig.  509),  usually  the  smaller  of 
the  two,  passes  outward  in  the  groove  between  the  Brachioradialis  and  Biceps 
muscles,  and  joins  with  the  radial  to  form  the  cephalic  vein.  The  branches 
of  the  external  cutaneous  nerve  pass  beneath  this  vessel. 

The  median  basilic  vein  {v.  mediana  basilica)  (Fig.  509)  passes  obliquely  in- 
ward, in  the  groove  between  the  Biceps  and  Pronator  teres  muscles,  and  joins  the 
common  ulnar  to  form  the  basilic.  This  vein  passes  in  front  of  the  brachial 
artery,  from  which  it  is  separated  by  a  fibrous  expansion,  the  bicipital  fascia, 
which  is  given  off  from  the  tendon  of  the  Biceps  to  the  fascia  covering  the  Flexor 
muscles  of  the  forearm.  Filaments  of  the  internal  cutaneous  nerve  pass  in  front 
as  well  as  behind  this  vessel. 

Venesection  is  usually  performed  at  the  bend  of  the  elbow,  and  as  a  matter  of  practice  the 
largest  vein  in  this  situation  is  commonly  selected.  This  is  usually  the  median  basilic,  and 
there  are  anatomical  advantages  and  disadvantages  in  selecting  this  vein.  The  advantages  are, 
that,  in  addition  to  its  being  the  largest,  and  therefore  yielding  a  greater  supply  of  blood,  it  is 
the  least  movable  and  can  be  easily  steadied  on  the  bicipital  fascia  on  which  it  rests.  The  dis- 
advantages are,  that  it  is  in  close  relationship  with  the  brachial  artery,  separated  only  by  the 
bicipital  fascia;  and  formerly,  when  venesection  was  frequently  practised,  arteriovenous  aneu- 
rism was  no  uncommon  result  of  this  practice.  Another  disadvantage  is,  that  the  median  basilic 
is  crossed  by  some  of  the  branches  of  the  internal  cutaneous  nerve,  and  these  may  be  divided  in 
the  operation,  giving  rise  to  "traumatic  neuralgia  of  extreme  intensity"  (Tillaux). 

Intravenous  infusion  of  normal  saline  solution  is  very  frequently  required  for  all  conditions  of 
severe  shock  and  after  profuse  hemorrhages.  The  patient's  arm  is  surrounded  by  a  tight  band- 
age so  as  to  impede  the  venous  return,  and  a  small  incision  is  made  over  the  largest  vein  visible 
in  front  of  the  elbow;  a  double  ligature  is  now  passed  around  the  vein,  and  the  lower  one  is  tied; 
the  vein  is  then  opened  and  a  cannula  connected  with  a  funnel  by  tubing  and  filled  with  warm 
saline  solution  is  inserted.  The  bandage  is  next  removed  from  the  arm,  and  two,  three,  or  more 
pints  of  fluid  are  allowed  to  flow  into  the  vein ;  when  a  sufficient  quantity  has  gone  in,  the  upper 
ligatiffe  around  the  vein  is  tied  and  a  stitch  put  in  the  skin  wound. 

The  basilic  vein  (v.  basilica)  (Figs.  509  and  511)  is  of  considerable  size  and 
is  formed  by  the  coalescence  of  the  common  ulnar  vein  with  the  median  basilic. 
It  passes  upward  along  the  inner  side  of  the  Biceps  muscle  and  pierces  the  deep 
fascia  a  little  below  the  middle  of  the  arm.  The  opening  in  the  fascia  is  known 
as  the  semilunar  hiatus.  The  vein  ascends  in  the  course  of  the  brachial  artery 
to  the  lower  border  of  the  tendons  of  the  Latissimus  dorsi  and  Teres  major  muscles, 
and  is  continued  onward  as  the  axillary  vein. 

The  cephalic  vein  («.  cephalica)  (Fig.  509)  is  formed  by  the  union  of  the  median 
cephalic  and  the  radial  veins.  It  courses  along  the  outer  border  of  the  Biceps 
muscle,  lying  in  the  same  groove  with  the  upper  external  cutaneous  branch  of 
the  musculospiral  nerve,  to  the  upper  third  of  the  arm ;  it  then  passes  in  the  inter- 
val between  the  Pectoralis  major  and  Deltoid  muscles,  lying  in  the  same  groove 


THE  DEEP    VEINS  OF  THE   UPPER  EXTREMITY  731 

with  the  descending  or  humeral  branch  of  tiie  acromiothoracic  artery.  It  pierces 
the  costocoracoid  membrane,  and,  crossing  the  axillary  artery,  terminates  in  the 
axillary  vein  just  below  the  clavicle.  This  vein  is  occasionally  connected  with 
the  external  jugular  or  subclavian  by  a  branch  which  passes  from  it  upward  in 
front  of  the  clavicle. 

The  accessory  cephalic  vein  (y.  cephalica  accessoria)  arises  either  from  a  small 
tributary  plexus  on  the  back  of  the  forearm  or  from  the  ulnar  side  of  the  dorsal 
venous  arch;  it  joins  the  cephalic  above  the  elbow.  In  some  cases  the  accessory 
cephalic  springs  from  the  cephalic  above  the  wrist  and  joins  it  again  higher  up. 
A  large  oblique  branch  frequently  connects  the  basilic  and  cephalic  veins  on  the 
back  of  the  forearm.^ 


The  Deep  Veins  of  the  Upper  Extremity, 

The  deep  veins  of  the  upper  extremity  (Fig.  510)  follow  the  course  of  the 
arteries,  forming  their  venae  comites,  or  companion  veins.  Usually  there  is  one 
vein  lying  on  each  side  of  the  corresponding  artery,  and  they  are  connected  at 
intervals  by  short  transverse  branches. 

Two  digital  veins  accompany  each  artery  along  the  sides  of  the  fingers;  these, 
uniting  at  their  base,  pass  along  the  interosseous  spaces  in  the  palm,  and  terminate 
in  the  two  venae  comites  which  accompany  the  superficial  palmar  arch.  Branches 
from  these  vessels  on  the  radial  side  of  the  hand  accompany  the  superficialis 
volae,  and  on  the  ulnar  side  terminate  in  the  deep  ulnar  veins  (Fig.  510).  The 
deep  ulnar  veins,  as  they  pass  in  front  of  the  wrist,  communicate  with  the  inter- 
osseous and  superficial  veins,  and  at  the  elbow  unite  with  the  deep  radial  veins 
to  form  the  venae  comites  of  the  brachial  artery.  The  venae  comites  of  the  brachial 
communicate  by  numerous  transverse  branches,  which  cross  over  or  under  the 
artery. 

The  interosseous  veins  (Fig.  510)  accompany  the  anterior  and  posterior 
interosseous  arteries.  The  anterior  interosseous  veins  commence  in  front  of  the 
wrist,  where  they  communicate  with  the  deep  radial  and  ulnar  veins;  at  the  upper 
part  of  the  forearm  they  receive  the  posterior  interosseous  veins,  and  terminate  in 
the  venae  comites  of  the  ulnar  artery. 

The  deep  palmar  veins  accompany  the  deep  palmar  arch,  being  formed  by 
tributaries  which  accompany  the  ramifications  of  that  vessel.  At  the  wrist  they 
receive  a  dorsal  and  a  palmar  tributary  from  the  thumb.  The  deep  palmar  veins 
communicate  with  the  deep  ulnar  veins  at  the  inner  side  of  the  hand,  and  on  the 
outer  side  terminate  in  the  deep  radial  veins  (Fig.  510),  which  are  the  venae  comites 
of  the  radial  artery.  Accompanying  the  radial  artery  the  deep  radial  veins  ter- 
minate in  the  venae  comites  of  the  brachial  artery. 

The  brachial  veins  {vv.  brachiales)  (Fig.  510)  are  placed  one  on  each  side  of 
the  brachial  artery;  receiving  tributaries  corresponding  with  the  branches  given 
off  from  that  vessel ;  at  the  lower  margin  of  the  Subscapularis  muscle  they  join  the 
axillary  vein. 

These  deep  veins  have  numerous  anastomoses,  not  only  with  each  other,  but 
also  with  the  superficial  veins.  One  of  the  brachial  veins  empties  into  the  axillary, 
the  other,  usually  the  smaller,  generally  unites  with  the  basilic. 

The  axillary  vein  (v.  axillaris)  (Fig.  511)  is  of  large  size,  and  is  the  continuation 
upward  of  the  basilic  vein.  It  comviences  at  the  lower  border  of  the  tendon  of  the 
Teres  major  muscle,  increases  in  size  as  it  ascends,  by  receiving  tributaries  corre- 

'  Concerning  the  variations  in  the  arrangement  and  course  of  the  veins  of  the  upper  extremity,  consult  the 
article  by  W.  Krause  in  Henle's  Handbuch  der  Anatomic. 


732 


THE  VASCULAR  SYSTEMS 


spending  with  the  branches  of  the  axillary  artery,  and  terminates  immediately 
beneath  the  clavicle  at  the  outer  border  of  the  first  rib,  where  it  becomes  the 
subclavian  vein.  This  vessel  is  covered  in  front  by  the  Pectoral  muscles  and  costo- 
coracoid  membrane,  and  lies  on  the  thoracic  side  of  the  axillary  artery,  which  it  par- 
tially overlaps.  Near  the  lower 
margin  of  the  Subscapularis 
it  receives  the  venae  comites 
of  the  brachial  artery,  and, 
near  its  termination,  the  ceph- 
alic vein.  This  vein  is  pro- 
vided with  a  pair  of  valves 
iTEs  oppositethe  lowerborderof  the 
"■  Subscapularis  muscle;  valves 
are  also  found  at  the  termina- 
tion of  the  cephalic  and  sub- 
scapular veins. 

Other  tributaries  of  the  axil- 
lary vein  are : 

The  long  thoracic  vein  (y. 
thoracalis  lateralis)  (Fig.  511), 
which  receives  the  thoracico- 
epigastric  vein  {v.  fhoracoepi- 
(jastrica),  and  which  comes 
from  the  superficial  epigastric 
or  from  the  femoral  vein; 
and  the  costoaxillary  veins 
(yv.  costoaxillares)  (Fig.  511), 
which  come  from  the  first  six 
intercostal  spaces  and  convey 
the  blood  from  the  intercostal 
veins  to  the  axillary. 


ANASTOMOSIS 


Fig.  510. — The  deep  ^ems  of  the  upper  extremity.     (Bourgery.) 


Applied  Anatomy.— There  are 

several  points  of  surgical  interest 
in  connection  with  the  axillary  vein. 
Being  more  superficial,  larger,  and  slightly  overlapping  the  axillary  artery,  it  is  more  liable 
to  be  wounded  in  the  operation  of  extirpation  of  the  axillary  nodes,  especially  as  these  nodes, 
when  diseased,  are  liable  to  become  adherent  to  the  vessel.  When  wounded  there  is  always 
danger  of  air  being  drawn  into  its  interior,  in  which  case  death  is  usually  the  result.  This 
is  due  not  only  to  the  fact  that  it  is  near  the  thorax,  and  therefore  liable  to  be  influenced 
by  the  respiratory  movements,  but  also  because  it  is  adherent  by  its  anterior  surface  to  the 
costocoracoid  membrane,  and  therefore  if  wounded  is  likely  to  remain  patulous  and  favor  the 
chance  of  air  being  sucked  in.  This  adhesion  of  the  vein  to  the  fascia  prevents  its  collapsing, 
and  therefore  favors  the  furious  bleeding  which  takes  place  in  these  cases. 

To  avoid  wounding  the  axillary  vein  in  the  extirpation  of  nodes  from  the  axilla  no  undue 
force  should  be  used  in  isolating  the  nodes.  If  the  vein  is  found  to  be  so  embedded  in  the 
malignant  deposit  that  the  latter  cannot  be  removed  without  taking  away  a  part  of  the  vein, 
this  must  be  done,  the  vessel  having  been  first  ligated  above  and  below  the  diseased  area. 

The  subclavian  vein  {v.  subclavia)  (Figs.  512  and  513),  the  continuation  of  the 
axillary,  extends  from  the  outer  border  of  the  first  rib  to  the  inner  end  of  the  clav- 
icle, where  it  unites  with  the  internal  jugular  to  form  the  innominate  vein.  It  is  in 
relation,  m  front,' Wii\\  the  clavicle  and  the  Subclavius  muscle;  behind  and  above, 
with  the  subclavian  artery,  from  which  it  is  separated  internally  by  the  Scalenus 
anticus  muscle  and  phrenic  nerve.  Beloiv,  it  rests  in  a  depression  on  the  first 
rib  and  upon  the  pleura.  Above,  it  is  covered  by  the  cervical  fascia  and  integu- 
ment. 


THE  DEEP   VEINS  OF  THE   UPPER  EXTREMITY 


733 


An  expansion  of  the  aponeurosis  of  the  Subclavius  muscle  lies  upon  the  vein 
(Fig.  512). 

The  subclavian  vein  occasionally  rises  in  the  neck  to  a  level  with  the  third  part 
of  the  subclavian  artery,  and  in  two  instances  has  been  seen  passing  with  this 
vessel  behind  the  Scalenus  anticus.  It  is  usually  provided  with  a  pair  of  valves 
about  an  inch  from  its  termination. 


O^ 


Fig.  511.— The 


COSTOAXILLARY 
LONG  THORACIC 

i  of  the  right  axilla,  viewed  from  in  front.      (Spalteholz.) 


PECTORALIS 


Fig.  512. — The  aponeurotic  expansion  of  the  Subclaviuf 
muscle  over  the  subclavian  vein.     (Poirier  and  Charpy.) 


Tributaries. — It  receives  the  ex- 
ternal jugular  vein,  sometimes  the 
anterior  jugular  vein,  and  occasion- 
ally a  small  branch  from  the  ceph- 
alic. At  the  angle  of  junction  with 
the  internal  jugular  the  left  sub- 
clavian vein  receives  the  thoracic 
duct  (Fig.  513),  while  the  right 
subclavian  vein  receives  the  right 
lymphatic  duct. 
The  innominate  or  brachio- 
cephalic veins  (yv.  anonymae)  (Fig.  514)  are  two  large  trunks,  placed  one  on 
either  side  of  the  root  of  the  neck,  and  formed  by  the  union  of  the  internal 
jugular  and  subclavian  veins  of  the  corresponding  side. 

The  right  innominate  vein  (y.  anonyma  dextra)  is  a  short  vessel,  an  inch  in 
length,  which  commences  at  the  inner  end  of  the  clavicle,  and,  passing  almost 
vertically  downward,  joins  with  the  left  innominate  vein  just  below  the  cartilage 
of  the  first  rib,  close  to  the  right  border  of  the  sternum,  to  form  the  superior  vena 
cava.  It  lies  superficial  and  external  to  the  innominate  artery;  on  its  right  side 
is  the  phrenic  nerve,  and  the  pleura  is  here  interposed  between  it  and  the  apex 
of  the  lung.     This  vein,  at  the  angle  of  junction  of  the  internal  jugular  with  the 


734 


THE   VASCULAR  SYSTEMS 


subclavian,  receives  the  right  vertebral  vein,  and,  lower  down,  the  right  internal 
mammary,  right  inferior  thyroid,  and  sometimes  the  right  thyroidea  ima  and  the 
right  superior  intercostal  veins. 

The  left  innominate  vein  (v.  anonyma  sinistra),  about  two  and  a  half'  inches 
in  length,  and  larger  than  the  right,  passes  from  left  to  right  across  the  upper  and 
front  part  of  the  thorax,  at  the  same  time  inclining  downward,  and  unites  with 
the  right  innominate  vein  to  form  the  superior  vena  cava.  It  is  in  relation,  in 
front,  with  the  first  piece  of  the  sternum,  from  which  it  is  separated  by  the  Sterno- 
hyoid and  Sternothyroid  muscles,  the  thymus  gland  or  its  remains,  and  some  loose 
areolar  tissue.  Behind  it  are  the  three  large  arteries  arising  from  the  arch  of  the 
aorta,  together  with  the  vagus  and  phrenic  nerves.  This  vessel  is  joined  by  the 
left  vertebral,  left  internal  mammary,  left  inferior  thyroid,  left  thyroidea  ima, 
and  the  left  superior  intercostal  veins,  and  occasionally  some  thymic  and  peri- 
cardiac veins.     There  are  no  valves  in  the  innominate  veins. 


LONGUS  COLLI   MUSCLE 

COMMON   CAROTID 

AHTERV 

LEFT    VAGUS 

NERVE 

VERTEBRAL  ARTERY 

VERTEBRAL  VEIN 
THORACIC  DUCT 

INTERNAL  JUGULAR 

VEIN 

EXTERNAL  JUGULAR 

VEIN 

ANTERIOR  JUGULAR 

VEIN 

SUBCLAVIAN 

VEIN 


Fig.  513. — The  bend  of  the  thoracic  duct  at  its  termination  in  the  subclavian  vein.     (Poirier  and  Charpy.) 


Peculiarities. — Sometimes  the  innominate  veins  open  separately  into  the  right  auricle;  in 
such  cases  the  right  vein  takes  the  ordinary  course  of  the  superior  vena  cava;  but  the  left  vein 
— the  left  superior  vena  cava,  as  it  is  termed — after  communicating  by  a  small  branch  with  the 
right  one,  passes  in  front  of  the  root  of  the  left  lung,  and,  turning  to  the  back  of  the  heart,  receives 
the  cardiac  veins,  and  terminates  in  the  back  of  the  right  auricle.  This  occasional  condition 
in  the  adult  is  due  to  the  persistence  of  the  early  fetal  condition,  and  is  the  normal  state  of  things 
in  birds  and  some  mammalia. 

The  internal  mammary  veins  (w.  mammariae  internae),  two  to  each  internal 
mammary  artery,  follow  the  course  of  that  vessel,  and  receive  tributaries  corre- 
sponding to  the  branches  of  the  artery.  The  two  veins  unite  into  a  single  trunk 
which  terminates  in  the  corresponding  innominate  vein.  It  receives  the  twelve 
anterior  intercostal  veins  from  the  upper  six  intercostal  spaces  of  the  corresponding 
side — six  anterior  perforating  veins  (rami  perforantes) — veins  from  the  surface  of 
the  sternum  (rami  sternales) — muscular  veins,  and  vessels  from  the  mediastinum 
and  pleura.  The  internal  mammary  veins  anastomose  below  with  the  venae 
comites  of  the  musculophrenic  and  superior  epigastric  arteries.  The  superior 
phrenic  vein  (i.  e.,  the  vein  accompanying  the  arteria  comes  nervi  phrenici)  usually 
opens  into  the  internal  mammary  vein. 

The  vertebral  vein  (see  p.  717). 

The  inferior  thjToid  veins  (vv.  thyreoideae  inferiores)  (Fig.  499),  two,  frequently 
three  or  four,  in  number,  arise  in  the  venous  plexus  on  the  thyroid  body  (plexus 
thyreoideus  imfar),  communicating  with  the  middle  and  superior  thyroid  veins. 
They  form  a  plexus  in  front  of  the  trachea,  behind  the  Sternothyroid  muscles. 


THE  DEEP    VEINS  OF  THE   UPPER  EXTREMITY 


735 


Superior  thyroid. 
Middle  thyioul  f  _ 


II  al  jugular 


From  this  plexus  a  left  vein  descends  and  joins  the  left  innominate  trunk,  and 
a  right  vein  passes  obliquely  downward  and  outward  across  the  innominate  artery 
to  open  into  the  right  innominate  vein,  just  at  its  junction  with  the  superior  vena 
cava.     The  thyreoidea  ima 
vein    (v.    thyreoidea    ima) 
passes  downward  in  front 
of  the  trachea  and  termi- 
nates in  the  left  innomi- 
nate vein.      These   veins 
receive  tributaries  from  the 
tracheal  veins  (vv.  irache- 
ales),  from  the  oesophageal 
veins    (vv.    oesophageae), 
from  the  inferior  laryngeal 
veins  (v.  lari/iif/ea  inferior). 

The  superior  intercos- 
tal veins  (right  and  left) 
drain  the  blood  from  two 
or  three  of  the  intercostal 
spaces  below  the  first. 
The  right  superior  inter- 
costal vein  ( V.  intercostalis 
sufrema  dextra)  passes 
downward  and  inward  and 
opens  into  the  vena  azygos 
major;  the  left  superior 
intercostal  vein  (v.  intercos- 
talis swprema  sinister)  runs 
across  the  arch  of  the 
aorta  and  opens  into  the 
left  innominate  vein.  It 
usually  receives  the  left 
bronchial  and  left  superior 
phrenic  vein,  and  commu- 
nicates below  with  the 
vena  azygos  minor  supe- 
rior. The  vein  from  the 
first  intercostal  space  opens 
directly  into  the  corre- 
sponding vertebral  or  in- 
nominate vein. 

The  superior  vena  cava 
{v.  cava  superior;  precava) 
(Fig.  514)-  receives  the 
blood  which  is  conveyed 
io  the  heart  from  the 
whole  of  the  upper  half  of 
the  body.  It  is  a  short 
trunk,  varying  from  two 
inches  and  a  half  to  three 
inches  in  length,  formed 
by  the  junction  of  the  two 
innominate  veins.  It  com- 
■mences  at  the  level  of  the 


Fig.  514. — The  A-ense  cav 


736  THE  VA8GULAR  SYSTEMS 

lower  border  of  the  cartilage  of  the  first  rib  close  to  the  sternum  on  the  right 
side,  and,  descending  vertically,  enters  the  pericardium  about  an  inch  and  a  half 
above  the  heai-t,  and  terminates  in  the  upper  part  of  the  right  auricle  opposite 
the  upper  border  of  the  third  right  costal  cartilage.  In  its  course  it  describes  a 
slight  curve,  the  convexity  of  which  is  to  the  right  side. 

Relations, — In  front,  with  the  pericardium  and  process  of  cervical  fascia  which  is  con- 
tinuous with  it;  these  separate  it  from  the  thymus  gland,  the  sternum,  and  the  second  and  third 
right  costal  cartilages;  behind,  with  the  root  of  the  right  lung.  On  its  right  side,  it  is  in  relation 
with  the  phrenic  nerve  and  right  pleura;  on  its  left  side,  with  the  commencement  of  the  innom- 
inate artery  and  ascending  part  of  the  aorta,  the  latter  somewhat  overlapping  it.  The  portion 
contained  within  the  pericardium  is  covered  in  front  and  laterally  by  the  serous  layer  of  that 
membrane.  It  receives  the  .vena  azygos  major  just  before  it  enters  the  pericardium,  and  several 
small  veins  from  the  pericardium  and  parts  in  the  mediastinum.  The  superior  vena  cava  has  no 
valves. 

The  azygos  veins  are  three  in  number;  they  collect  the  blood  from  the  majority 
of  the  intercostal  spaces,  and  connect  the  superior  and  inferior  vense  cavse. 

The  vena  azygos  major  {v.  azygos)  (Fig.  514)  commences  opposite  the  first  or 
second  lumbar  vertebra  by  a  branch  from  the  right  lumbar  veins,  called  the  right 
ascending  lumbar  vein  {v.  lumbalis  ascendens);  sometimes  by  a  branch  from  the 
right  renal  vein  or  from  the  inferior  vena  cava.  It  enters  the  thorax  through 
the  aortic  opening  in  the  Diaphragm,  and  passes  along  the  right  side  of  the  ver- 
tebral column  to  the  fourth  thoracic  vertebra,  where  it  arches  forward  over  the 
root  of  the  right  lung,  and  terminates  in  the  superior  vena  cava  just  before  that 
vessel  enters  the  pericardium.  While  passing  through  the  aortic  opening  of  the 
Diaphragm  it  lies  with  the  thoracic  duct  on  the  right  side  of  the  aorta;  and  in  the 
thorax  it  lies  upon  the  intercostal  arteries  on  the  right  side  of  the  aorta  and  thoracic 
duct,  and  is  partly  covered  by  pleura. 

Tributaries. — It  receives  the  lower  ten  posterior  intercostal  veins  of  the  right  side, 
the  upper  two  or  three  of  these  opening,  first  of  all,  into  the  right  superior  inter- 
costal vein.  On  the  left  side  the  first  posterior  intercostal  vein  follows  the  same 
course  as  the  right  and  empties  into  the  vertebral  or  innominate  vein.  The 
second,  third,  and  fourth  posterior  intercostal  veins  unite  and  form  the  left 
superior  intercostal  vein.  This  vein  then  passes  forward  across  the  arch  of  the 
aorta  and  unites  with  the  left  innominate  vein.  The  fifth,  sixth,  and  seventh 
posterior  intercostals  of  the  left  side  contribute  to  the  vena  azygos  minor  superior. 
The  rest  of  the  posterior  intercostal  veins  of  the  left  side  terminate  in  the  vena 
azygos  minor  inferior.  It  receives  the  azygos  minor  veins,  several  oesophageal 
mediastinal  and  pericardial  veins;  near  its  termination,  the  right  bronchial  vein. 
A  few  imperfect  valves  are  found  in  this  vein;  but  its  tributaries  are  provided 
with  complete  valves. 

The  intercostal  veins  {m.  intercostalis)  are  divided  into  anterior  and  pos- 
terior intercostals. 

The  anterior  intercostal  veins  are  tributaries  of  the  internal  mammary  or  the 
musculophrenic  veins  (p.  734). 

The  posterior  intercostal  veins  (Fig.  514)  number  eleven  on  each  side,  there 
being  one  vein  in  each  intercostal  space.  Each  vein  lies  in  the  groove  at  the 
lower  margin  of  the  rib  above  the  corresponding  intercostal  artery.  On  the  right 
side  the  first  posterior  intercostal  vein  crosses  the  neck  of  the  first  rib  anteriorly 
and  opens  into  the  vertebral  vein  or  the  innominate  vein.  The  posterior  inter- 
costals of  the  right  side,  from  the  fifth  to  the  eleventh  inclusive,  open  individually 
into  the  vena  azygos  major.  The  second,  third,  and  fourth  intercostals  of  this 
side  unite  to  form  a  common  trunk,  the  right  superior  intercostal  vein,  which  then 
joins  the  vena  azygos  major. 

The  vena  azygos  minor  inferior  {v.  lieviiazygos)  (Fig.  514)  commences  in  the 
lumbar  region  by  a  branch  from  one  of  the  lumbar  veins,  ascending  lumbar  («. 


THE  SPINAL    VEINS  737 

lumhalis  ascendens),  or  from  the  left  renal.  It  enters  the  thorax  through  the  left 
crus  of  the  Diaphragm,  and,  ascending  on  the  left  side  of  the  vertebral  column  as 
high  as  the  eighth  or  ninth  thoracic  vertebra,  passes  across  the  vertebral  column, 
behind  the  aorta,  oesophagus,  and  thoracic  duct,  to  terminate  in  the  major  azygos 
vein.  It  receives  the  four  or  five  lower  intercostal  veins  of  the  left  side,  and  some 
oesophageal  and  mediastinal  veins. 

The  vena  azygos  minor  superior  {v.  hemiazygos  accessoria)  varies  inversely  in  size 
with  the  left  superior  intercostal.  It  receives  veins  from  the  intercostal  spaces 
between  the  left  superior  intercostal  vein  and  highest  tributary  of  the  vena  azygos 
minor  inferior.  They  are  usually  three  or  four  in  number,  usually  the  fifth,  sixth, 
and  seventh  left  posterior  intercostal  veins.  They  join  to  form  a  trunk  which  ends 
in  the  major  azygos  vein  or  in  the  vena  azygos  minor  inferior.  When  this  vein  is 
small  or  altogether  wanting,  the  left  superior  intercostal  vein  will  extend  as  low  as 
the  fifth  or  sixth  intercostal  space.     It  sometimes  receives  the  left  bronchial  vein. 

Applied  Anatomy. — In  obstruction  of  the  inferior  vena  cava,  the  azygos  veins  are  one  of 
the  principal  means  by  which  the  venous  circulation  is  carried  on,  connecting  as  they  do  the 
superior  and  inferior  venae  cavae,  and  communicating  with  the  common  iliac  veins  by  the  ascend- 
ing lumbar  veins  and  with  many  of  the  tributaries  of  the  inferior  vena  cava. 

Thrombosis  of  the  superior  vena  cava  is  oftenest  due  to  pressure  exerted  on  the  vessel  by 
an  aneurism  or  a  tumor;  it  may  also  occur  by  propagation  of  clotting  from  a  tributary  peripheral 
vein.  If  occlusion  of  the  vessel  take  jjlace  slowly,  a  collateral  venous  circulation  may  be  estab- 
lished; the  patient  will  have  some  oedema  with  dilatation  and  congestion  of  the  veins  about  the 
head  and  neck,  and  may  also  suffer  from  attacks  of  dyspnea  and  recurrent  pleural  effusion. 
In  most  cases,  however,  the  blockage  of  the  superior  vena  cava  takes  place  rapidlj',  and  is 
rapidly  fatal. 

The  bronchial  veins  (vv.  bronchiales  anteriores  et  posteriores)  return  the  blood 
from  the  larger  bronchi  and  from  the  structures  at  the  roots  of  the  lungs ;  that  of 
the  right  side  opens  into  the  vena  azygos  major,  near  its  termination;  that  of 
the  left  side  opens  into  the  left  superior  intercostal  vein  or  the  vena  azygos  minor 
superior.  A  considerable  quantity  of  the  blood  which  is  carried  to  the  lungs 
through  the  bronchial  arteries  is  returned  to  the  left  side  of  the  heart  by  the  pul- 
monary veins. 

The  Vertebral  Veins. 

The  vertebral  veins  may  be  arranged  into  four  groups — viz.: 

1.  The  extra  vertebral  veins. 

2.  The  intravertebral  veins. 

3.  The  veins  of  the  bodies  of  the  vertebrae. 

4.  The  veins  of  the  spinal  cord. 

1.  The  extravertebral  veins  (plexus  venosi  vertebrales  eiierni)  commence  by 
small  branches  which  receive  their  blood  from  the  integument  of  the  back  of  the 
vertebral  column  and  from  the  muscles  in  the  vertebral  grooves.  They  form 
two  plexuses,  an  anterior  plexus  {plexus  venosi  vertebrales  anteriores),  upon  the 
vertebral  bodies,  and  a  posterior  plexus  (plexv^  venosi  vertebrales  posteriores) , 
which  surrounds  the  spinous  processes,  the  laminae,  and  the  transverse  and 
articular  processes  of  all  the  vertebrae.  At  the  bases  of  the  transverse  processes 
they  communicate,  by  means  of  ascending  and  descending  branches,  with  the 
veins  surrounding  the  contiguous  vertebrae,  and  they  join  with  the  veins  in  the 
vertebral  canal  by  branches  which  perforate  the  ligamenta  subflava.  Other 
branches  pass  obliquely  forward,  between  the  transverse  processes,  and  com- 
municate with  the  intravertebral  veins  through  the  intervertebral  foramina  {vv. 
intervertebrales) .  The  extravertebral  veins  terminate  by  joining  the  \ertebral 
veins  in  the  neck,  the  intercostal  veins  in  the  thorax,  and  the  lumbar  and  lateral 
sacral  veins  in  the  loins  and  pelvis. 

47 


738 


THE   VASCULAR  SYSTEMS 


2.  The  intravertebral  veins  {plexus  venosi  vertebrales  interni)  are  situated 
between  the  spinal  dura  and  the  vertebrae.  They  consist  of  two  longitudinal  plex- 
uses, one  of  which  runs  along  the  posterior  surface  of  the  bodies  of  the  vertebrae, 
anterior  longitudinal  vertebral  veins.  The  other  plexus,  posterior  longitudinal  ver- 
tebral veins,  is  placed  on  the  inner  or  anterior  surface  of  the  laminae  of  the  vertebrae. 

The  anterior  longitudinal  vertebral  veins  (sinus  vertebrales  longitudinales)  consist 
of  two  large,  tortuous  veins  which  extend  along  the  whole  length  of  the  vertebral 
column,  from  the  foramen  magnum,  where  they  communicate  with  each  other 
by  a  venous  ring  around  that  opening  and  with  the  basilar  and  occipital  sinuses 
through  the  foramen,  to  the  base  of  the  coccyx,  being  placed  one  on  each  side 
of  the  posterior  surface  of  the  bodies  of  the  vertebrae  along  the  margin  of  the 
posterior  common  ligament.  These  veins  communicate  opposite  each  vertebrae 
by  transverse  trunks  which  pass  beneath  the  ligament.  Each  transverse  trunk 
receives  the  large  vena  basis  vertebrae  {v.  basivertebralis)  from  the  interior  of  the 
body  of  the  vertebra.  The  anterior  longitudinal  vertebral  veins  are  least  devel- 
oped in  the  cervical  and  sacral  regions.     They  are  not  of  uniform  size  throughout. 


The  exfra-vertehral  veins. 


Fig.  515. — Transverse   section   of   a 
showing  the  vertebral 


Vertical   section  of  two  thoracic  vertebrce 
showing  the  vertebral  veins. 


being  alternately  enlarged  and  constricted.  At  the  intervertebral  foramina  they 
communicate  with  the  extravertebral  veins,  and  with  the  vertebral  veins  in  the 
neck,  with  the  intercostal  veins  in  the  thoracic  region,  and  with  the  lumbar  and 
sacral  veins  in  the  corresponding  regions. 

The  posterior  longitudinal  vertebral  veins,  smaller  than  the  anterior,  are  situated 
one  on  either  side,  between  the  inner  surface  of  the  laminte  and  the  theca  yerte- 
bralis.  They  communicate  (like  the  anterior)  opposite  each  vertebra  by  trans- 
verse trunks,  and  with  the  anterior  longitudinal  veins  by  lateral  transverse  branches 
which  pass  from  behind  forward.  The  posterior  longitudinal  veins,  by  branches 
which  perforate  the  ligamenta  subflava,  join  with  the  extravertebral  veins.  From 
them  branches  are  given  off  which  pass  through  the  intervertebral  foramina  and 
join  the  vertebral,  intercostal,  lumbar,  and  sacral  veins. 

The  intervertebral  veins  (vv.  intervertebrales)  accompany  the  spinal  nerves  in 
the  intervertebral  foramina,  receive  veins  from  the  spinal  cord,  and  join  the 
intra-  and  extravertebral  veins. 

3.  The  veins  of  the  bodies  of  the  vertebrae  (vv.  basivertehrales)  emerge  from 
the  foramen  on  the  posterior  surface  of  each  vertebra  and  join  the  transverse 


THE  SUPERFICIAL    VEINS  OF  THE  LOWER  EXTREMITY     739 

trunk  connecting  the  anterior  longitudinal  vertebral  veins.  They  are  contained 
in  large,  tortuous  channels  in  the  substance  of  the  bones,  similar  in  every  respect 
to  tiiose  found  in  the  diploe  of  the  cranial  bones.  These  canals  lie  parallel  to  the 
upper  and  lower  surfaces  of  the  bones.  They  commence  by  small  openings  on  the 
front  and  sides  of  the  bodies  of  the  vertebrffi,  through  which  communicating 
branches  from  the  veins  external  to  the  bone  pass  into  its  substance,  and  converge 
to  the  principal  canal,  which  is  sometimes  double  toward  its  posterior  part.  They 
open  into  the  corresponding  transverse  branch  uniting  the  anterior  longitudinal 
veins.     They  become  greatly  enlarged  in  advanced  age. 

4.  The  veins  of  the  spinal  cord  iyv.  spinales)  emerge  from  the  cord  substance 
and  form  a  minute,  tortuous,  venous  plexus  which  covers  the  entire  surface  of  the 
cord,  being  situated  between  the  pia  and  arachnoid.  In  this  plexus  there  are 
(1)  two  median  longitudinal  veins,  one  in  front  of  the  ventral  fissure,  and  the  other 
behind  the  dorsal  groove  of  the  cord;  and  (2)  four  lateral  longitudinal  veins  which 
run  behind  the  nerve  roots;  These  vessels  are  largest  in  the  lumbar  region. 
Near  the  base  of  the  skull  they  unite,  and  form  two  or  three  small  trunks,  which 
communicate  with  the  vertebral  veins,  and  terminate  in  the  inferior  cerebellar 
veins  or  in  the  inferior  petrosal  sinuses.  Each  of  the  spinal  nerves  is  accompanied 
by  a  radicular  efferent  vessel  as  far  as  the  intervertebral  foramina,  where  it  joins 
the  other  veins  from  the  vertebral  canal. 

There  are  no  valves  in  the  vertebral  veins. . 

VEINS    OF    THE    LOWER    EXTREMITY,    ABDOMEN,    AND    PELVIS 

(Figs.  517,  518). 

The  veins  of  the  lower  extremity  are  subdivided,  like  those  of  the  upper,  into 
two  sets,  superficial  and  deep;  the  superficial  veins  are  situated  beneath  the  integu- 
ment, between  the  two  layers  of  superficial  fascia,  the  deep  veins  accompanying 
the  arteries,  and  forming  the  venae  comites  of  those  vessels.  Both  sets  of  veins 
are  provided  with  valves,  which  are  more  numerous  in  the  deep  than  in  the  super- 
ficial set.  These  valves  are  also  more  numerous  in  the  lower  than  in  the  upper 
limb. 

The  Superficial  Veins  of  the  Lower  Extremity. 

The  Superficial  Veins  of  the  Foot. — In  the  sole  of  the  foot  there  is  a  sub- 
cutaneous venous  plexus  {rele  venosum  plantare  cutaneuni),  from  which  some 
branches  go  to  the  deep  veins,  but  most  of  the  branches  pass  around  the  margins 
to  the  dorsum  of  the  foot.  There  is  a  transverse  venous  arch  at  the  root  of  the 
toes  which  receives  plantar  vessels  from  the  toes  and  sends  branches  between  the 
toes  {yv.  intercapitulares)  to  the  venous  arch  of  the  dorsum.  On  the  dorsum  of 
each  toe  the  veins  gather  into  two  vessels,  known  as  the  dorsal  digital  veins  (vv. 
digitales  pedis  dorsalis).  The  dorsal  digital  veins  from  the  opposed  margins  of 
t^Ao  toes  unite  to  form  a  dorsal  intercligital  vein.  There  are  four  dorsal  inter- 
digital  veins  (I'f .  digitales  communes  pedis),  and  they  pass  into  the  venous  arch 
of  the  dorsum.  The  dorsal  digital  vein,  fi'om  the  inner  surface  of  the  great  toe, 
passes  directly  into  the  internal  saphenous  vein,  and  the  dorsal  digital  vein,  from 
the  outer  surface  of  the  little  toe,  passes  directly  into  the  external  saphenous  vein. 

The  venous  arch  of  the  dorsum  of  the  foot  {arciis  venosus  dorsalis  pedis)  is  sit- 
uated in  the  superficial  structures  over  the  anterior  extremities  of  the  metatarsal 
bones.  It  has  its  convexity  directed  forward,  and  receives  digital  tributaries 
from  the  upper  surface  of  the  toes ;  at  its  concavity  it  is  joined  by  numerous  small 
veins  which  form  a  plexus  on  the  dorsum  of  the  foot  (rele  venosum  dorsale  pedis 
cutaneum).  The  arch  terminates  internally  in  the  long  saphenous,  externally 
in  the  short  saphenous  vein. 


740 


THE  VASCULAR  SYSTEMS 


The  chief  superficial  veins  of  the  lower  extremity  are  the  internal  or  long 
saphenous  and  the  external  or  short  saphenous. 

The  internal  or  long  saphenous  vein  {v.  saphena  magna)  (Figs.  517  and  520) 
commences  at  the  inner  side  of  the  arch  on  the  dorsum  of  the  foot;  it  ascends  in 


i  /.'Ss7 


Pig.  517. — The   internal   or    long 
saphenous  vein  and  its  tributaries. 


Fig.  518. — External  or  short  saphenous  vein. 

front  of  the  inner  malleolus  and  along  the  inner  side 
of  the  leg,  behind  the  inner  margin  of  the  tibia,  ac- 
companied by  the  internal  saphenous  nerve.  At  the 
knee  it  passes  backward  behind  the  inner  condyle  of 
the  femur,  ascends  along  the  inside  of  the  thigh,  and, 
passing  through  the  saphenous  opening  in  the  fascia 
lata,  terminates  in  the  femoral  vein  about  an  inch 
and  a  half  below  Poupart's  ligament.  This  vein 
receives  in  its  course  cutaneous  tributaries  from  the 
leg  and  thigh,  and  at  the  saphenous  opening  receives 
the  superficial  epigastric,  superficial  circumflex  iliac, 
and  external  pudic  veins.  The  veins  from  the  inner 
and  back  part  of  the  thigh  frequently  unite  to  form 
a  large  vessel,  which  enters  the  main  trunk  near  the 
saphenous  opening;  and  sometimes  those  on  the  outer 


THE  DEEP   VEINS  OF  THE  LOWER  EXTREMITY  741 

side  of  the  thigh  join  to  form  another  large  vessel ;  so  that  occasionally  three  large 
veins  are  seen  converging  from  different  parts  of  the  thigh  toward  the  saphenous 
opening.  The  internal  saphenous  vein  communicates  in  the  foot  with  the  internal 
plantar  vein;  in  the  leg,  with  the  posterior  tibial  veins  by  branches  which  perforate 
the  tibial  origin  of  the  Soleus  muscle,  and  also  with  the  anterior  tibial  veins; 
at  the  knee,  with  the  articular  veins;  in  the  thigh,  with  the  femoral  vein  by  one 
or  more  branches.  The  valves  in  this  vein  vary  from  two  to  six  in  number;  they 
are  more  numerous  in  the  thigli  than  in  the  leg. 

The  external  or  short  saphenous  vein  {v.  saphena  parva)  (Fig.  518)  com- 
mences at  the  outer  side  of  the  arch  on  the  dorsum  of  the  foot;  it  ascends  behind  the 
outer  malleolus,  and  along  the  outer  border  of  the  tendo  Achillis,  across  which  it 
passes  at  an  acute  angle  to  reach  the  middle  line  of  the  posterior  aspect  of  the  leg. 
Passing  directly  upward,  it  perforates  the  deep  fascia  in  the  lower  part  of  the 
popliteal  space,  and  terminates  in  the  popliteal  vein,  between  the  heads  of  the 
Gastrocnemius  muscle.  It  receives  numerous  large  tributaries  from  the  back  part 
of  the  leg,  and  communicates  with  the  deep  veins  on  the  dorsum  of  the  foot  and 
behind  the  outer  malleolus.  Before  it  perforates  the  deep  fascia  it  gives  off  a 
communicating  branch,  which  passes  upward  and  inward  to  join  the  internal 
saphenous  vein.  This  vein  contains  from  nine  to  twelve  valves,  one  of  which  is 
always  found  near  its  termination  in  the  popliteal  vein.  The  external  saphenous 
nerve  lies  close  beside  this  vein. 

Applied  Anatomy. — A  varicose  condition  of  the  saphenous  veins  is  more  frequently  met 
with  than  in  the  other  veins  of  the  body,  except  perhaps  the  spermatic  and  hemorrhoidal  veins. 
The  course  of  the  internal  saphenous  is  in  front  of  the  tip  of  the  inner  malleolus,  over  the  sub- 
cutaneous surface  of  the  lower  end  of  the  tibia,  and  then  along  the  internal  border  of  this  bone 
to  the  back  part  of  the  internal  condyle  of  the  femur,  whence  it  follows  the  course  of  the  Sar- 
torius  musde,  and, is  represented  on  the  surface  by  a  line  drawn  from  the  posterior  border  of 
the  Sartorius  on  a  level  with  the  internal  condyle  to  the  saphenous  opening.  The  external  saph- 
enous lies  behind  the  external  malleolus,  and  from  this  follows  the  middle  line  of  the  calf  to  just 
below  the  ham.  It  is  not  generally  so  apparent  beneath  the  skin  as  the  internal  saphenous. 
Both  these  veins  in  the  leg  are  accompanied  by  nerves,  the  internal  saphenous  being  joined  by 
its  companion  nerve  just  below  the  level  of  the  knee-joint.  No  doubt  much  of  the  pain  of  vari- 
cose veins  in  the  leg  is  due  to  this  fact. 

Operations  for  the  relief  of  varicose  veins  are  frequently  required,  portions  of  the  veins  being 
removed  after  having  been  ligated  above  and  below.  It  is  important  to  note  whether  the  main 
varicose  area  drains  into  the  internal  or  the  external  saphenous  vein — the  former  condition 
being  much  the  more  common — and  to  control  the  venous  return  by  removing  a  small  portion 
of  the  main  trunk  just  before  it  opens  into  the  deep  vein  by  passing  through  the  deep  fascia; 
thus  in  most  cases  a  piece  should  be  removed  from  the  internal  saphenous  just  before  it  passes 
through  the  saphenous  opening,  and  in  addition  the  affected  veins  should  be  excised  just  above 
and  just  below  the  level  of  the  knee-joint.  In  other  cases  the  external  saphenous  will  have  to 
be  dealt  with  immediately  below  the  point  where  it  pierces  the  fascial  roof  of  the  popliteal  space. 

The  Deep  Veins  of  the  Lower  Extremity. 

The  deep  veins  of  the  lower  extremity  accompany  the  arteries  and  their  branches 
and  are  called  the  venae  comites  of  those  vessels.  The  venae  comites  in  the  lower 
extremity  pass  into  one  trunk,  the  popliteal  vein,  whereas  in  the  upper  extremity 
the  venae  comites  continue  with  the  artery  to  the  axilla. 

The  Deep  Veins  of  the  Foot. — The  plantar  digital  veins  (vv.  digifales  plantares) 
form  the  plantar  metatarsal  veins  (ri\  mctalarscac  plaiifarc.s-),  which  communicate 
with  the  veins  of  the  dorsinii  of  the  foot  by  perforating  veins  and  also  communicate 
with  the  deep  venous  arch  of  the  sole  of  the  foot  {amis  venosus  plantaris).  The 
plantar  arch  gives  oft'  lateral  or  external  plantar  veins,  which  unite  with  median 
or  internal  plantar  veins  to  form  the  posterior  tibial  veins.  On  the  dorsum  of  the 
foot  the  deep  \eins  begin  as  the  dorsal  metatarsal  veins  {m.  metafarseae  dorsales 
jxdis),  which  form  the  venae  comites  of  the  dorsalis  pedis  artery. 


742 


THE   VASCULAR  SYSTEMS 


The  posterior  tibial  veins  {vv.  tihiales  posteriores)  accompany  the  posterior 
tibial  artery  and  are  joined  by  the  peroneal  veins. 

The. anterior  tibial  veins  (vv.  tibialis  anteriores)  are  formed  by  a  continuation 
upward  of  the  venae  comites  of  the  dorsalis  pedis  artery.    They  pass  lietween  the 
tibia  and  fibula,  through  the  large  oval  aperture  above  the  interosseous  membrane, 
and  form,  by  their  junction  with  the  posterior  tibial,  the  popliteal  vein. 
The  valves  in  the  deep  veins  are  very  numerous. 

The  popliteal  vein  (v.  poplitea)  (Fig.  519)  is  formed  by  the  junction  of  the 
anterior  and  posterior  tibial  veins;  it  ascends  through  the  popliteal  space  to  the 
aperture  in  the  Adductor  magnus  tendon,  where  it 
becomes  the  femoral  vein.  In  the  lower  part  of  its 
course  it  is  placed  internal  to  the  artery;  between  the 
heads  of  the  Gastrocnemius  it  is  superficial  to  that 
vessel;  but  above  the  knee-joint  it  is  close  to  the 
outer  side  of  the  artery.  It  receives  the  sural  veins 
from  the  Gastrocnemius  muscle,  the  articular  veins, 
and  the  external  saphenous  veins.  The  valves  in  this 
vein  are  usually  four  in  niunber. 

The  femoral  vein  (y.  femoralis)  (Figs.  520  and 
521)  accompanies  the  femoral  artery  through  the 
upper  two-thirds  of  the  thigh.  In  the  lower  part  of 
its  course  it  lies  external  to  the  artery;  higher  up  it 
is  behind  it;  and  at  Poupart's  ligament  it  lies  to 
its  inner  side  and  on  the  same  plane.  It  receives 
numerous  muscular  tributaries,  and  about  an  inch 
and  a  half  below  Poupart's  ligament  it  is  joined  by 
the  deep  femoral;  near  its  termination  it  is  joined 
by  the  internal  saphenous  vein.  The  valves  in  the 
femoral  vein  are  four  or  five  in  number. 

The  deep  femoral  vein  (v.  profunda  femoris)  Teceives 
tributaries  corresponding  to  the  perforating  branches 
of  the  profunda  artery,  and  through  these  establishes 
communications  with  the  popliteal  vein  below  and 
the  sciatic  vein  above.  It  also  receives  the  internal 
and  external  circumflex  veins. 

The  external  iliac  vein  (v.  iliaca  externa)  (Figs. 
521  and  523)  commences  at  the  termination  of  the 
femoral,  beneath  the  crural  arch,  and,  passing  upward 
along  the  brim  of  the  pelvis,  terminates  opposite  the 
sacroiliac  joint  by  uniting  with  the  internal  iliac  to  form  the  common  iliac  vein. 
On  the  right  side  it  lies  at  first  along  the  inner  side  of  the  external  iliac  artery, 
but  as  it  passes  upward  gradually  inclines  behind  it.  On  the  left  side  it  lies 
altogether  on  the  inner  side  of  the  artery.  It  receives,  immediately  above  Pou- 
part's ligament,  the  deep  epigastric  and  deep  circumflex  iliac  veins  and  a  small 
pubic  vein,  corresponding  to  the  pubic  branch  of  the  obturator  artery.  It  fre- 
quently contains  one  and  sometimes  two  valves. 

Tributaries. — The  external  iliac  vein  receives  the  deep  epigastric,  deep  circumflex 
iliac,  and  pubic  veins. 

The  deep  epigastric  vein  (v.  epigastrica  inferior)  (Fig.  521)  is  formed  by  the 
anion  of  the  venae  comites  of  the  deep  epigastric  artery,  which  communicates 
above  with  the  superior  epigastric  vein;  it  joins  the  external  iliac  about  half  an 
inch  above  Poupart's  ligament. 

The  deep  circumflex  iliac  vein  (v.  circumflexa  ilium  profunda)  (Fig.  521) 
is  formed  b}'  the  union  of  the  venae  comites  of  the  deep  circumflex  iliac  artery, 


Fig.  519. — The  popliteal  vein. 
(Poirier  and  Charpy.) 


THE  BEEP   VETNS  OF  THE  LOWER  EXTREMITY 


74.3 


and  joins  the  external  iliac  vein  about  three-quarters  of  an  inch  above  Poupart's 
ligament. 

The  pubic  vein  communicates  with  the  obturator  \em  in  the  obturator  fora- 
men, and  ascends  on  the  back  of  the  pubis  to  terminate  in  the  external  iliac  \-ein. 

The  internal  iliac  vein  {v.  hypoc/astrica)  commences  near  the  upper  part  of 
the  great  sacrosciatic  foramen,  passes  upward  behind  and  slightly  to  the  inner 
side  of  the  internal  iliac  artery,  and  at  the  brim  of  the  pelvis  joins  with  the 
external  iliac  to  form  the  common  iliac. 


UMBfLICUS 


SUPERFICIAL 

EXTERNAL 

CIRCUMFLEX 


SUPERFICIAL 

INTERNAL 

CIRCUMFLEX 


Fig.  520.— The  femoral 


Dtl  its  tributaries.     (Poirier  and  Charpy.) 


Tributaries. — With  the  exception  of  the  fetal  umbilical  vein,  which  passes  up- 
ward and  backward  from  the  umbilicus  to  the  liver,  and  the  iliolumbar  vein  which 
usually  joins  the  common  iliac  vein,  the  tributaries  of  the  internal  iliac  vein  corre- 
spond with  the  branches  of  the  internal  iliac  artery.  It  receives  (a)  the  gluteal, 
sciatic,  internal  pudic,  and  obturator  veins,  which  have  their  origins  outside  the 
pelvis;  (b)  the  lateral  sacral  veins,  which  lie  in  front  of  the  sacrum;  and  (c)  the 
middle  hemorrhoidal,  vesical,  uterine,  and  vaginal  veins,  which  originate  in  venous 
plexuses  connected  with  the  pelvic  viscera. 

I.  The  gluteal  veins  (vv.  glutaeae  super  lores)  or  venae  comites  of  the  gluteal 
artery,  receive  tributaries  from  the  buttock  corresponding  with  the  branches  of 


744 


THE  VASCULAR  SYSTEMS 


the  artery;  they  enter  the  pelvis  through  the  great  sacrosciatic  foramen,  above 
the  Pyriformis,  and  frequently  unite  before  ending  in  the  internal  iliac  vein. 

2.  The  sciatic  veins  {m.  glidaeae  inferiores) ,  or  venae  comites  of  the  sciatic 
artery,  begin  on  the  upper  part  of  the  back  of  the  thigh,  where  they  anastomose 
with  the  internal  circumflex  and  first  perforating  veins.  They  enter  the  pelvis 
through  the  lower  part  of  the  sacrosciatic  foramen  and  join  to  form  a  single 
stem  which  opens  into  the  lower  part  of  the  internal  iliac  vein. 

3.  The  internal  pudic  veins  are  the  venae  comites  of  the  internal  pudic  artery. 
They  covimejice  in  the  veins  which  issue  from  the  corpus  cavernosum,  accom- 
pany the  internal  pudic  artery,  and  unite  to  form  a  single  vessel,  which  ends 
in  the  internal  iliac  vein.  They  receive  the  veins  from  the  bulb  of  the  urethra, 
the  superficial  perineal,  and  the  inferior  hemorrhoidal  veins  {m.  hemorrhoidales 
inferiores).  The  deep  dorsal  vein  of  the  penis  communicates  with  the  internal 
pudic  veins,  but  ends  mainly  in  the  vesicoprostatic  venous  plexus. 


veins.     (Poirier  and  Charpy.) 


4.  The  obturator  vein  (v.  obturatoria)  begins  in  the  upper  portion  of  the  adductor 
region  of  the  thigh  and  enters  the  pelvis  through  the  anterior  part  of  the  obturator 
foramen.  It  runs  backward  and  upward  on  the  lateral  wall  of  the  pelvis  below 
the  obturator  artery,  and  then  passes  between  the  ureter  and  the  internal  iliac 
artery,  to  end  in  the  internal  iliac  vein. 

5.  The  lateral  sacral  veins  (vv.  sacrales  laterales)  accompany  the  lateral  sacral 
arteries  on  the  anterior  surface  of  the  sacrum  and  terminate  in  the  internal  iliac 
vein. 

6.  The  middle  hemorrhoidal  vein  {v.  hemorrhoidal  is  media)  takes  origin  in  the 
hemorrhoidal  plexus  and  receives  tributaries  from  the  bladder,  prostate  gland, 
and  seminal  vesicle;  it  runs  outward  on  the  pelvic  surface  of  the  Levator  ani  to 
end  in  the  internal  iliac  vein. 


THE  DEEP   VEINS  OF  THE  LOWER  EXTREMITY 


745 


The  hemorrhoidal  plexus  surrounds  the  rectum,  and  communicates  in  front 
with  the  vesicoprostatic  plexus  in  the  male,  and  the  uterovaginal  plexus  in  the 
female.  It  consists  of  two  parts,  an  internal  in  the  submucosa,  and  an  external 
outside  the  muscular  coat.  Below,  the  internal  plexus  presents  a  series  of  dilated 
pouches  which  are  arranged  in  a  circle  around  the  tube  immediately  above  the 
anal  orifice  and  are  connected  by  transverse  branches. 

The  lower  part  of  the  external  plexus  is  drained  by  the  inferior  hemorrhoidal 
veins  into  the  internal  pudic;  its  middle  part  by  the  middle  hemorrhoidal  vein, 
which  joins  the  internal  iliac;  and  its  upper  part  by  the  superior  hemorrhoidal 
vein,  which  forms  the  commencement  of  the  inferior  mesenteric  vein,  a  tributary 
of  the  portal  vein.  A  free  communication  between  the  portal  and  systemic  venous 
systems  is  established  through  the  hemorrhoidal  plexus. 


Fig.  522. — Scheme  of  the  anastomosis  of  the  veins  of  the  rectum.     (Poirier  and  Charpy.) 

The  vesicoprostatic  plexus  surrounds  the  prostate  gland  and  the  neck  of 
the  bladder,  and  lies  partly  in  the  fascial  sheath  of  the  prostate  and  partly  between 
the  sheath  and  the  capsule  of  the  gland.  In  front  it  receives  the  deep  dorsal  vein 
of  the  penis;  behind,  it  Cv->mmunicates  with  the  hemorrhoidal  and  vesical  plexuses, 
and  derives  tributaries  from  the  vasa  deferentia  and  seminal  vesicles.  It  is  drained 
into  the  internal  iliac  veins  by  one  or  more  vessels  on  either  side.  The  correspond- 
ing plexus  in  the  female  is  named  the  vesicovaginal. 

The  vesical  plexus  lies  on  the  muscular  coat  of  the  bladder,  and  is  best  marked 
toward  the  base  and  sides  of  this  viscus;  it  drains  into  the  vesicoprostatic  plexus. 

Applied  Anatomy. — The  veins  of  the  hemorrhoidal  plexus  are  liable  to  become  dilated  and 
varicose,  and  form  piles.  This  is  due  to  several  anatomical  reasons:  the  ve.ssels  are  contained 
in  verj'  loose,  lax  connective  tissue,  so  that  they  get  less  support  from  surrounding  structures 
than  most  other  veins,  and  are  less  capable  of  resisting  increased  blood  pressure;  the  condition 
is  favored  by  gravitation,  being  influenced  by  the  erect  posture,  either  sitting  or  standing,  and 
by  the  fact  that  the  superior  hemorrhoidal  and  portal  veins  have  no  valves;  the  veins  pass 


746 


THE  VASCULAR  SYSTEMS 


through  muscle  tissue  and  are  liable  to  be  compressed  by  its  contraction,  especially  during  the 
act  of  defecation;  they  are  affected  by  every  form  of  portal  obstruction. 

The  prostatic  plexus  of  veins  is  liable  to  become  congested  in  many  inflammatory  conditions 
in  the  neighborhood,  such  as  acute  gonorrheal  prostatitis.  It  is  owing  to  the  free  communi- 
cation which  exists  between  this  and  the  middle  hemorrhoidal  plexus  that  great  relief  can  be 
given  by  free  saline  purgation. 

Hemorrhage  may  be  very  profuse  from  the  prostatic  plexus  after  operations  on  that  gland,  but 
can  usually  be  checked  by  hot  fluid  irrigation.  Septic  thrombosis  sometimes  occurs  after 
operations,  and  infected  emboli  may  find  their  way  into  the  general  circulation. 


THIRD  LUMBAR 


VESICAL  PLEXUS 


Fig.  523. — The  veins  of  the  male  pelvis,  right  half,  viewed  from  the  left.     The  Psoas  n 
and  the  rectum  drawn  down  somewhat  to  the  side.     (Spalteholz.) 


cle  has  been  removed 


The  dorsal  veins  of  the  penis  are  two  in  number,  a  superficial  and  a  deep. 
The  superficial  vein  drain.?  the  prepuce  and  skin  of  the  penis,  and,  running  back- 
ward in  the  subcutaneous  tissue,  incHnes  to  the  right  or  left,  and  opens  into  the 
corresponding  superficial  external  pudic  vein,  a  tributary  of  the  internal  or  long 
saphenous  vein.  The  deep  vein  receives  the  blood  from  the  glans  penis  and 
corpora  cavernosa;  it  courses  backward  in  the  middle  line  between  the  dorsal 
arteries,  beneath  the  deep  fascia,  and  near  the  root  of  the  penis  passes  between 


THE  DEEP   VEINS  OF  THE  LOWER  EXTREMITY 


747 


SUPERFICIAL  DOR- 
SAL  VEIN 
ARTERV      I     .DEEP    DORSAL  VEIN 


the  two  parts  of  the  suspensory  ligament  and  then  through  an  aperture  between 

the  subpubic  hgament  and  the  apex  of  the  triangular  ligament,  and  divides  into 

two  branches,  which  enter  the  vesicoprostatic  plexus.     The  dorsal  vein  of  the 

clitoris    corresponds    in    woman    to 

the  dorsal  vein  of  the  penis  in  man, 

and  empties  into  the  inferior  vesical 

plexus. 

The  Vaginal  Plexuses  and  Veins 
(Fig.  525). — The  vaginal  plexuses 
are  placed  at  the  sides  of  the 
vagina,  being  especially  developed 
at  the  orifice  of  the  canal.  They 
receive  vessels  from  the  vaginal 
walls.  The  plexuses  communicate 
with  the  uterine  plexus  above,  with 
the  bulbar  veins  below,  with  the 
inferior  vesical  plexus  in  front,  and 
with  the  hemorrhoidal  plexus  be- 
hind, and  are  drained  by  the  vaginal  veins,  one  on  either  side,  into  the  internal 
iliac  veins. 

The  uterine  plexuses  (Fig.  525)  are  situated  along  the  sides  and  superior  angles 
of  the  uterus,  between  the  two  layers  of  the  broad  ligament,  and  communicate 
with  the  ovarian  and  vaginal  plexuses.     They  are  drained  by  the  uterine  veins 


Fig.  524. — The  penis  in  transverse  section,  showing  the 
the  blood-vesaels.    (Testut.) 


VAGINAL  VENOUS    PLEXUS 


OS    UTERI         VAGINA    CUT    OPEN    BEHIND 

Fig  525  — \  essels  of  the  uterus  and  its  appendages  rear  view.     (Testut.) 


(ot.  uterinae)  (Fig.  525)  which  arise  from  the  lower  part  of  the  plexus.  There 
are  usually  two  veins  on  each  side,  and  they  are  not  provided  with  vah'es.  These 
veins  for  the  first  portion  of  their  course  are  placed  in  the  base  and  inner  portion 
of  the  broad  ligament;  they  then  pass  back  with  the  uterine  artery  and  terminate 
in  the  internal  iliac  vein. 

During  pregnancy  the  uterine  veins  become  greatly  enlarged. 

The  common  iliac  veins  (Figs.  521  and  523)  are  formed  by  the  union  of  the 
external  and  internal  iliac  veins  in  front  of  the  sacroiliac  articulation;  passing 
obliquely  upward  toward  the  right  side,  each  ^-ein  terminates  upon  the  inter\-erte- 
bral  substance  between  the  fourth  and  fifth  lumbar  vertebrje,  where  the  -veins  of 


748  THE  VASCULAR  SYSTEMS 

the  two  sides  unite  at  an  acute  angle  to  form  the  inferior  vena  cava.  The  right 
common  iliac  (y.  iliaca  communis  dextra)  is  shorter  than  the  left,  nearly  vertical  in 
its  direction,  and  ascends  behind  and  then  to  the  outer  side  of  its  corresponding 
artery.  The  left  common  iliac  (v.  iliaca  communis  sinistra),  longer  than  the  right, 
and  more  oblique  in  its  course,  is  at  first  situated  on  the  inner  side  of  the  corre- 
sponding artery,  and  then  behind  the  right  common  iliac.  Each  common  iliac 
receives  the  iliolumbar,  and  sometimes  the  lateral  sacral  veins.  The  left  receives, 
in  addition,  the  middle  sacral  vein.     No  valves  are  found  in  these  veins. 

The  middle  sacral  veins  (Figs.  521  and  522)  accompany  the  corresponding 
artery  along  the  front  of  the  sacrum,  and  join  to  form  a  single  vein  {y.  sacralis 
media),  which  terminates  in  the  left  common  iliac  vein;  occasionally  in  the  angle 
of  junction  of  the  two  iliac  veins.  The  middle  sacral  veins  communicate  with 
the  inferior  hemorrhoidal. 

The  iliolumbar  veins  (vv.  ilioluvibales)  receive  branches  from  the  iliac  fossae, 
spinal  muscles,  and  vertebral  canal.  One  vein  on  each  side  runs  with  the  artery, 
passes  posterior  to  the  Psoas  muscle,  and  joins  the  common  iliac  vein. 

Peculiarities. — The  left  common  iliac  vein,  instead  of  joining  with  the  right  in  its  usual 
position,  occasionally  ascends  on  the  left  side  of  the  aorta  as  high  as  the  kidney,  where,  after 
receiving  the  left  renal  vein,  it  crosses  over  the  aorta,  and  then  joins  with  the  right  vein  to  form 
a  short  inferior  vena  cava.  In  these  cases  the  two  common  iliacs  are  connected  by  a  small 
communicating  branch  at  the  spot  where  they  are  usually  united. 

The  inferior  vena  cava  (v.  cava  inferior;  postcava)  (Figs.  514  and  521)  returns 
to  the  heart  the  blood  from  nearly  all  the  parts  below  the  Diaphragm.  It  is  formed 
by  the  junction  of  the  two  common  iliac  veins  on  the  right  side  of  the  intervertebral 
substance  between  the  fourth  and  fifth  lumbar  vertebrae.  It  passes  upward  along 
the  front  of  the  vertebral  column  on  the  right  side  of  the  aorta,  and,  having 
reached  the  liver,  is  contained  in  a  groove  on  its  posterior  surface.  It  then 
passes  through  the  Diaphragm  between  the  mesal  and  right  portions  of  the  central 
tendon;  it  subsequently  inclines  forward  and  inward  for  about  an  inch,  and, 
piercing  the  fibrous  pericardium,  passes  behind  the  serous  pericardium  to  open 
into  the  lower  and  back  part  of  the  right  auricle.  In  front  of  its  auricular  orifice 
is  a  semilunar  valve,  the  Eustachian  valve;  this  is  rudimentary  in  the  adult,  but 
is  of  large  size  and  exercises  an  important  function  in  the  fetus. 

Relations.— /ra/ron/,  from  below  upward,  with  the  mesentery,  right  spermatic  artery,  trans- 
verse portion  of  the  duodenum,  the  pancreas,  portal  vein,  and  the  posterior  surface  of  the  liver, 
which,  in  most  cases,  partly  and  occasionally  completely  surrounds  it;  behind,  with  the  verte- 
bral column,  the  right  crus  of  the  Diaphragm,  the  right  renal  and  lumbar  arteries,  the  right 
semilunar  ganghon,  and  the  inner  part  of  the  right  suprarenal  gland;  on  the  right,  side,  with 
the  right  kidney  and  ureter;  on  the  left  side,  with  the  aorta.  The  thoracic  portion  is  short  and 
covered  anterolaterally  by  the  serous  layer  of  the  pericardium. 

Peculiarities. — In  Position. — This  vessel  is  sometimes  placed  on  the  left  side  of  the  aorta, 
as  high  as  the  left  renal  veins,  after  receiving  which  it  crosses  over  to  its  usual  position  pn  the 
right  side;  or  it  may  be  placed  altogether  on  the  left  side  of  the  aorta,  as  far  upward  as  its  ter- 
mination in  the  heart;  in  such  cases  the  abdominal  and  thoracic  viscera,  together  with  the  great 
vessels,  are  all  transposed.  The  vessel  may  be  double,  due  to  the  bilateral  persistence  of  the 
cardinal  veins. 

Point  of  Termination. — Occasionally  the  inferior  vena  cava  joins  the  vena  azygos  major, 
which  is  then  of  large  size.  In  such  cases  the  superior  vena  cava  receives  the  whole  of  the 
blood  from  the  body  before  transmitting  it  to  the  right  auricle,  except  the  blood  from  the 
hepatic  veins,  which  passes  directly  into  the  right  auricle. 

Applied  Anatomy.— Thrombosis  of  the  inferior  vena  cava  is  due  to  much  the  same  causes 
as  that  of  the  superior  (see  page  737).  It  usually  causes  edema  of  the  legs  and  back,  without 
ascites;  if  the  renal  veins  are  involved,  blood  and  albumin  will  often  appear  in  the  urine.  An 
extensive  collateral  venous  circulation  is  soon  estabhshed  by  enlargement  either  of  the  super- 
ficial or  of  the  deep  veins,  or  of  both.     In  the  first  case  the  epigastric,  the  circumflex  iliac,  the 


THE  DEEP   VEINS  OF  THE  LOWER  EXTREMITY 


749 


long  thoracic,  the  internal  mammary,  the  intercostals,  the  external  pudic,  and  the  lumbcvertebral 
anastomotic  veins  of  Braune  effect  the  communication  with  the  superior  cava;  in  the  second, 
the  deep  anastomosis  is  made  by  the  azygos  major  and  minor  and  the  lumbar  veins. 


Tributaries. — It  receives  in  its  course  the  following  veins: 


Lumbar. 

Right  spermatic,  or  ovarian. 

Renal. 


Suprarenal. 
Inferior  phrenic. 
Hepatic. 


The  lumbar  veins  (vv.  himhales),  four  in  number  on  each  side,  collect  the 
blood  by  dorsal  tributaries  from  the  muscles  and  integument  of  the  loins  and  by 
abdominal  tributaries  from  the  walls  of  the  abdomen,  where  they  communicate 
with  the  epigastric  veins.  At  the  vertebral  column  they  receive  veins  from  the 
spinal  plexuses,  and  then  pass  forward,  around  the  sides  of  the  bodies  of  the 


Fig.  526.— Spermatic  veins.     (Testut.) 

vertebrae  beneath  the  Psoas  magnus  muscle,  and  terminate  at  the  back  part  of 
the  inferior  vena  cava.  The  left  lumbar  veins  are  longer  than  the  right,  and 
pass  behind  the  aorta.  The  lumbar  veins  of  either  side  are  connected  by  a 
longitudinal  vein  which  passes  in  front  of  the  transverse  processes  of  the  lumbar 
vertebrae,  and  is  called  the  ascending  lumbar  vein  (c.  lumbalis  ascendens)  (Fig. 
514).     It  forms  the  most  frequent  origin  of  the  corresponding  azygos  vein,  and 


750 


THE   VASCULAR  SYSTEMS 


serves  to  connect  the  common  iliac,  iliolumbar,  lumbar,  and  azygos  veins  of  the 
corresponding  side  of  the  body. 

The  spermatic  veins  {m.  sperviaticae)  (Fig.  526)  emerge  from  the  back  of  the 
testis,  and  receive  tributaries  from  the  epididymis;  they  unite  and  form  a  convo- 
luted  plexus  called  the  spermatic  plexus  {plexus  pampiniformis),  which  constitutes 
the  greater  mass  of  the  cord;  the  vessels  composing  this  plexus  are  very  numerous, 
and  ascend  along  the  cord  in  front  of  the  vas  deferens;  below  the  external  abdom- 
inal ring  they  unite  to  form  three  or  four  veins,  which  pass  along  the  inguinal 
canal,  and,  entering  the  abdomen  through  the  internal  abdominal  ring,  coalesce 
to  form  two  veins,  which  ascend  on  the  Psoas  muscle  behind  the  peritoneum, 
lying  one  on  either  side  of  the  spermatic  artery.  These  unite  to  form  a  single 
vein,  which  opens  on  the  right  side  into  the  inferior  vena  cava  at  an  acute  angle; 
on  the  left  side  into  the  left  renal  vein  at  a  right  angle  (Fig.  527).     The  spermatic 


Fig.  527. — Terminations  of  tlie  right  and  left  spermatic  veins.     (Poirier  and  Charpy.) 

veins  are  provided  with  valves,  particularly  at  the  termination.     The  left  sper- 
matic vein  passes  behind  the  sigmoid  flexure  of  the  colon. 


^  Applied  Anatomy. — The  spermatic  veins  are  very  frequently  varicose,  constituting  the  dis- 
ease known  as  varicocele.  Though  it  is  quite  possible  that  the  originating  cause  of  this  affection 
may  be  a  congenital  abnormality  either  in  the  size  or  number  of  the  veins  of  the  spermatic  plexus, 
still  it  must  be  admitted  that  there  are  many  anatomical  reasons  why  these  veins  should  become 
varicose — viz.,  the  imperfect  support  afforded  to  them  by  the  loose  tissue  of  the  scrotum;  their 
great  length;  their  vertical  course;  their  dependent  position;  their  plexiform  arrangement  in 
the  scrotum,  with  their  termination  in  one  small  vein  in  the  abdomen;  their  few  and  imperfect 
valves;  and  the  fact  that  they  may  be  subjected  to  pressure  in  their  passage  through  the  abdom-. 
inal  wall.  The  left  veins  more  often  become  varicose  than  the  right  veins,  probably,  as  Brinton 
suggests,  because  the  right  spermatic  vein  practically  always  has  a  valve  and  opens  into  the 
inferior  vena  cava  at  an  acute  angle,  whereas  the  left  spermatic  vein  is  not  unusually  destitute 
of  a  valve  at  its  opening  and  passes  into  the  left  renal  vein  at  a  right  angle. 

The  operation  for  the  removal  of  a  varicocele  consists  in  making  a  small  incision  just  over 
the  external  abdominal  ring  and  passing  an  aneurism  needle  around  the  mass  of  veins,  taking 
care  that  the  vas  deferens  is  not  included.  The  veins  are  isolated  from  the  vas  and  ligated 
above  and  below,  as  high  and  as  low  as  possible,  and  the  intermediate  portion  cut  away";  the 
divided  ends  are  fixed  together  with  a  suture,  and  the  skin  wound  closed. 


THE  PORTAL  SYSTEM  OF  VEINS  751 

The  ovarian  veins  {w.  ovaricae)  (Fig.  525)  correspond  with  the  spermatic  in  the 
male;  they  form  a  plexus  in  the  broad  ligament  near  the  ovary  and  about  the 
Fallopian  tube,  and  communicate  with  the  uterine  plexus.  They  terminate  in 
the  same  way  as  the  spermatic  veins  in  the  male.  Valves  are  occasionally  found 
in  these  veins.  Like  the  uterine  veins,  these  vessels  become  greatly  enlarged 
during  pregnancy. 

The  renal  veins  (vu.  renales)  (Fig.  515)  are  of  large  size,  and  are  placed  in  front 
of  the  renal  arteries.  The  left  is  longer  than  the  right,  and  passes  in  front  of  the 
aorta,  just  below  the  origin  of  the  superior  mesenteric  artery.  It  receives  the  left 
spermatic,  the  left  inferior  phrenic,  and,  generally,  the  left  suprarenal  veins.  It 
opens  into  the  inferior  vena  cava  a  little  higher  than  the  right. 

The  suprarenal  veins  (yy.  suprarenales)  (Fig.  514)  are  two  in  number;  that  on 
the  right  side  terminates  in  the  inferior  vena  cava;  that  on  the  left  side,  in  the  left 
renal  or  in  the  left  phrenic  vein. 

The  inferior  phrenic  veins  (vv.  phrenicae  inferiores)  follow  the  course  of  the 
phrenic  arteries;  the  right  ends  in  the  inferior  vena  cava,  the  left  in  the  left  renal 
vein. 

The  hepatic  veins  (dv.  hepaticae)  commence  in  the  substance  of  the  liver,  in  the 
capillary  terminations  of  the  portal  vein  and  hepatic  artery,  iatralobular  veins; 
these  tributaries,  gradually  uniting  into  sublobular  veins,  usually  form  three  large 
hepatic  veins,  which  converge  toward  the  posterior  surface  of  the  liver  and  open 
into  the  inferior  vena  cava,  where  that  vessel  is  situated  in  the  groove  at  the  back 
part  of  this  organ.  Of  these  three  veins,  one  from  the  right  and  another  from  the 
left  lobe  open  obliquely  into  the  inferior  vena  cava,  that  from  the  middle  of  the 
organ  and  lobulus  Spigelii  having  a  straight  course.  The  hepatic  veins  run  singly, 
and  are  in  direct  contact  with  the  hepatic  tissue.     They  are  destitute  of  valves. 


THE  PORTAL  SYSTEM  OF  VEINS  (Fig.  528). 

The  portal  system  includes  all  the  veins  which  drain  the  blood  from  the  abdom- 
inal part  of  the  alimentary  canal  (with  the  exception  of  the  lower  part  of  the 
rectum)  and  from  the  spleen,  pancreas,  and  gall-bladder.  From  these  viscera  the 
blood  is  conveyed  to  the  liver  by  the  portal  vein.  In  the  substance  of  the  liver 
the  portal  vein  ramifies  like  an  artery  and  terminates  in  the  portal  capillaries 
(sinusoids),  from  which  the  blood  is  conveyed  to  the  inferior  vena  cava  by  the 
hepatic  veins.  From  this  it  will  be  seen  that  the  blood  of  the  portal  system 
passes  through  two  sets  of  capillary  vessels — viz.,  (a)  the  capillaries  of  the  alimen- 
tary canal,  spleen,  pancreas,  and  gall-bladder;  and  (b)  the  portal  capillaries  in  the 
substance  of  the  liver.     The  portal  vein  and  its  tributaries  are  destitute  of  valves. 

The  portal  vein  (vena  portae)  is  about  three  inches  in  length,  and  is  formed 
at  the  level  of  the  second  lumbar  vertebra  by  the  junction  of  the  superior  mesen- 
teric and  splenic  veins,  the  union  of  these  veins  taking  place  in  front  of  the  inferior 
vena  cava  and  behind  the  neck  of  the  pancreas.  It  passes  up-\\-ard  behind  the 
first  part  of  the  duodenum  and  then  ascends  near  the  right  border  of  the  lesser 
omentum  to  the  right  extremity  of  the  transverse  fissure  of  the  liver,  where  it 
divides  into  right  and  left  branches,  which  accompany  the  corresponding  branches 
of  the  hepatic  artery  into  the  substance  of  the  liver.  In  the  lesser  omentum  it 
is  placed  behind  and  between  the  common  bile  duct  and  the  hepatic  artery,  the 
former  lying  to  the  right  of  the  latter.  It  is  surrounded  by  the  hepatic  plexus 
of  nerves,  and  is  accompanied  by  numerous  lymphatic  vessels  and  some  lymph 
nodes.  The  right  branch  of  the  portal  vein  enters  the  right  lobe  of  the  liver, 
but  before  doing  so  generally  receives  the  cystic  vein.  The  left  branch,  longer 
but  of  smaller  caliber  than  the  right,  crosses  the  longitudinal  fissure,  gives  branches 


752 


THE   VASCULAR  SYSTEMS 


to  the  caudate  and  Spigelian  lobes,  and  then  enters  the  left  lobe  of  the  liver.  As 
it  crosses  the  longitudinal  fissure  it  is  joined  in  front  by  a  fibrous  cord,  the  liga- 
mentuvi  teres  of  the  liver  or  impervious  umbilical  vein,  and  is  united  to  the  inferior 
vena  cava  by  a  second  fibrous  cord,  the  ligamentum  venosum  or  impervious 
ductus  venosus. 

The  tributaries  of  the  portal  vein  are: 


Splenic. 

Superior  mesenteric. 

Gastric. 


Pyloric. 

Cystic. 

Parumbilical, 


Fig.  528. — Portal  vein  and  its  tributaries. 


Note. — In  this  diagram  the  right  gastroepiploic  vein  opens  into  the  splenic  vein;  generally 
it  empties  into  the  superior  mesenteric,  close  to  its  termination. 

The  splenic  vein  {v.  lienalis)  (Fig.  528)  covimences  by  five  or  six  large  branches 
which  return  the  blood  from  the  substance  of  the  spleen.     These,  uniting,  form  a 


THE  PORTAL  SYSTEM  OF  VEINS  753 

single  vessel,  which  passes  from  left  to  right,  grooving  the  upper  and  back  part  of 
the  pancreas  below  the  artery,  and  terminates  at  its  greater  end  by  uniting  at  a 
right  angle  with  the  superior  mesenteric  to  form  the  portal  vein.  The  splenic 
vein  is  of  large  size,  and  not  tortuous  like  the  artery. 

Tributaries. — The  splenic  vein  receives  the  vasa  brevia  from  the  left  extremitv 
of  the  stomach,  the  left  gastroepiploic  vein,  the  pancreatic  veins,  and  the  inferior 
mesenteric  vein. 

(a)  The  short  gastric  veins  (yv.  gastricae  breves),  some  four  or  five  in  number, 
drain  the  fundus  and  left  part  of  the  greater  curvature  of  the  stomach,  and  pass 
between  the  two  layers  of  tiie  gastrosplenic  omentum  to  terminate  in  the  splenic 
vein  or  in  one  of  its  large  trii)Utaries. 

(b)  Tiie  left  gastroepiploic  vein  (v.  gastroepiploica  sinistra)  receives  tributaries 
from  the  anterior  and  posterior  surfaces  of  the  stomach  and  from  the  great  omen- 
tum; it  runs  from  right  to  left  along  the  greater  curvature  of  the  stomach  and  ends 
in  the  commencement  of  the  splenic  vein. 

(c)  The  pancreatic  veins  (iw.  pancreaticae)  consist  of  several  small  vessels  which 
■drain  the  body  and  tail  of  the  pancreas,  and  open  into  the  trunk  of  the  splenic 
vein. 

{d)  The  inferior  mesenteric  vein  (v.  mesenterica  inferior)  returns  blood  from 
the  rectum,  and  the  pelvic,  iliac,  and  descending  parts  of  the  colon.  It  begins  in 
the  rectum  as  the  superior  hemorrhoidal  vein  (v.  haemorrhoidalis  superior),  which 
has  its  origin  in  the  hemorrhoidal  plexus,  and  through  this  plexus  communicates 
with  tiie  middle  and  inferior  hemorrhoidal  veins.  The  superior  hemorrhoidal 
vein  leaves  the  pelvis  and  crosses  the  iliac  vessels  in  company  with  the  superior 
hemorrhoidal  artery,  and  is  continued  upward  as  the  inferior  mesenteric  vein. 
This  vein  lies  to  the  left  of  the  inferior  mesenteric  artery,  and  ascends  behind  the 
peritoneum  and  in  front  of  the  left  Psoas;  it  then  passes  behind  the  body  of  the 
pancreas  and  opens  into  the  splenic  vein;  sometimes  it  terminates  in  the  angle  of 
imion  of  the  splenic  and  superior  mesenteric  veins. 

Tributaries. — ^The  inferior  mesenteric  vein  receives  the  sigmoid  veins  (vv.  sig- 
mojdeae)  from  the  sigmoid  flexure  and  the  left  colic  vein  (v.  colica  sinistra)  from 
the  descending  colon  and  splenic  flexure. 

The  superior  mesenteric  vein  (v.  mesenterica.  superior)  returns  the  blood  from 
the  small  intestine,  and  from  the  cecum  and  ascending  and  transverse  portions 
of  the  colon.  It  begins  in  the  right  iliac  fossa  by  the  union  of  the  veins  which 
drain  the  terminal  part  of  the  ileum,  the  cecum,  and  vermiform  appendix,  and 
ascends  between  the  two  layers  of  the  mesentery  on  the  right  side  of  the  supe- 
rior mesenteric  artery.  In  its  upward  course  it  passes  in  front  of  the  right 
ureter,  the  inferior  vena  cava,  the  third  part  of  the  duodenum,  and  the  uncinate 
process  of  the  head  of  the  pancreas.  Behind  the  neck  of  the  pancreas  it  unites 
with  the  splenic  vein  to  form  the  portal  vein. 

Tributaries. — Besides  the  tributaries  which  correspond  with  the  branches  of 
the  superior  mesenteric  artery — viz.,  the  veins  of  the  small  intestine  (vv.  intesti- 
nalcs),  the  ileocolic  (v.  ileocolica),  the  right  colic  (ra.  colica  dextrac),  and  the  middle 
coUc  (v.  colica  media) — the  superior  mesenteric  vein  is  joined  by  the  right  gastro- 
epiploic and  pancreaticoduodenal  veins. 

The  right  gastroepiploic  vein  {v.  gastroepiploica  dextra)  receives  tributaries  from 
the  great  omentum  and  from  the  lower  parts  of  the  anterior  and  posterior  surfaces 
of  the  stomach ;  it  runs  from  left  to  right  along  the  greater  cur^-ature  of  the  stomach 
between  the  two  layers  of  the  great  omentum. 

The  pancreaticoduodenal  veins  {vv.  pancrealicoduodenales)  accompany  their  cor- 
responding arteries;  the  lower  of  the  two  frequently  joins  the  right  gastroepiploic 
vein. 

The  gastric  vein  {v.  coronaria  ventriculi)  derives  tributaries  from  both  surfaces 

48 


754  THE   VASCULAR  SYSTEMS 

of  the  stomach ;  it  runs  from  right  to  left  along  the  lesser  curvature  of  the  stomach, 
between  the  two  layers  of  the  gastrohepatic  omentum,  to  the  oesophageal  end 
of  the  stomach,  where  it  receives  some  oesophageal  veins.  It  then  turns  backward 
and  passes  from  left  to  right  behind  the  lesser  sac  of  the  peritoneum  and  ends 
in  the  portal  vein. 

The  pyloric  vein  is  of  small  size,  and  runs  from  left  to  right  along  the  pyloric 
portion  of  the  lesser  curvature  of  the  stomach,  between  the  two  layers  of  the  gastro- 
hepatic omentum,  to  terminate  in  the  portal  vein. 

The  cystic  vein  {v.  cystica)  (Fig.  528)  drains  the  blood  from  the  gall-bladder, 
and,  ascending  along  the  cystic  duct,  usually  terminates  in  the  right  branch  of  the 
portal  vein. 

Parumbilical  Veins  (yv.  parumbilicales). — In  the  course  of  the  ligamentum 
teres  of  the  liver  and  of  the  urachus  small  veins  (panimbilicar)  are  found,  which 
establish  an  anastomosis  between  the  veins  of  the  anterior  abdominal  wall  and 
the  portal  and  iliac  veins.  The  best  marked  of  these  small  veins  is  one  which 
commences  at  the  umbilicus  and  runs  backward  and  upward  in,  or  on  the  surface 
of,  the  ligamentum  teres  between  the  layers  of  the  falciform  ligament  to  terminate 
in  the  left  branch  of  the  portal  vein. 

Anastomoses  between  the  Portal  and  Systemic  Veins. — Some  tributaries  of 
the  portal  vein  communicate  with  certain  neighboring  systemic  veins.  The  more 
important  communications  are  between  (a)  the  gastric  veins  and  the  (jesophageal 
veins  which  empty  into  the  vena  azygos  minor;  (b)  the  parumbilical  veins,  which 
anastomose  with  the  deep  epigastric  and  internal  mammary  veins;  (c)  the  superior 
and  middle  hemorrhoidal  veins,  the  latter  opening  into  the  internal  iliacs. 

Applied  Anatomy. — Obstruction  to  the  portal  vein  may  produce  ascites,  and  this  may 
arise  from  many  causes,  as  (1)  the  pressure  of  a  tumor  on  the  portal  vein,  such  as  cancer  or 
hydatid  cyst,  in  the  Uver,  enlarged  lymph  nodes  in  the  lesser  omentum,  or  cancer  of  the 
head  of  the  pancreas;  (2)  from  cirrhosis  of  the  liver,  when  the  radicles  of  the  portal  vein  are 
pressed  upon  by  the  contracting  fibrous  tissue  in  the  portal  canals;  (3)  from  valvular  disease 
of  the  heart,  and  back  pressure  on  the  hepatic  veins,  and  so  on  the  whole  of  the  circulation 
through  the  liver.  In  this  condition  the  prognosis  as  regards  life  and  freedom  from  ascites 
may  be  much  improved  by  the  establishment  of  a  good  collateral  venous  circulation  to  relieve 
the  portal  obstruction  in  the  liver.  This  is  effected  by  communications  between  (a)  the  gastric 
veins,  and  the  oesophageal  veins  emptying  themselves  into  the  vena  azygos  minor  inferior,  which 
often  project  as  a  varicose  bunch  into  the  stomach;  (b)  the  veins  of  the  colon  and  duodenum, 
and  the  left  renal  vein;  (c)  the  accessory  portal  system  of  Sappey,  branches  of  which  pass  in 
the  round  and  falciform  ligaments  (particularly  the  latter),  to  unite  with  the  epigastric  and 
internal  mammary  veins,  and  through  the  diaphragmatic  veins  with  the  azygos;  a  single  large  vein 
shown  to  be  a  parumbilical  vein,  may  pass  from  the  hilus  of  the  liver  by  the  round  ligament  to 
the  umbilicus,  producing  there  a  bunch  of  prominent  varicose  veins  known  as  the  Caput  Medusae; 
(d)  the  veins  of  Retzius,  which  connect  the  intestinal  veins  with  the  inferior  vena  cava  and  its 
retroperitoneal  branches;  (e)  the  inferior  mesenteric  veins,  and  the  hemorrhoidal  veins  that 
open  into  the  internal  iliacs;  (f)  very  rarely  the  ductus  venosus  remains  patent,  affording  a 
direct  connection  between  the  portal  vein  and  the  inferior  vena  cava. 

An  operation  for  the  relief  of  portal  obstruction  on  these  lines  has  been  advocated  by  Ruther- 
ford Morison  and  by  Talma.  It  consists  in  curetting  the  opposed  surfaces  of  the  liver  and 
diaphragm  and  stitching  them  together,  so  as  to  secure  vascular  inflammatory  adhesions  between 
the  two.  The  great  omentum  may  with  advantage  be  interposed  between  them,  so  as  to  increase 
the  amount  of  the  adhesions,  and  the  spleen  has  been  similarly  scraped  and  sutured  to  or  into 
the  abdominal  wall.     The  operation  should  not  be  deferred  until  the  patient  is  moribund. 

Thrombosis  of  the  portal  vein,  or  pylethrombosis,  is  a  very  serious  event,  and  is  oftenest  due 
to  pathological  processes  causing  compression  of  the  vessel  or  injury  to  its  wall,  such  as  tumors 
or  inflammation  about  the  pylorus,  head  of  the  pancreas,  or  appendix,  or  to  gallstones  or  cir- 
rhosis of  the  liver.  If  the  thrombus  is  infected  with  bacteria,  as  is  often  the  case  when  it  is  due 
to  appenaicitis,  septic  or  suppurative  pylephlebitis  results;  this  condition  is  known  also  as 
portal  pyemia.  Fragments  of  the  infected  clot  break  off  and  are  carried  away  to  lodge  in  the 
smaller  veins  in  the  liver,  with  the  development  of  multiple  abscesses  in  its  substance  and  a 
rapidly  fatal  result.  When  the  thrombus  is  sterile,  the  chief  signs  produced  are  enlargement 
of  the  spleen,  recurrent  ascites,  and  the  establishment  of  a  collateral  venous  circulation,  the 
case  clinically  resembling  one  of  atrophic  cirrhosis  of  the  liver. 


DEVELOPMENT  OF  THE  BLOOD-VASCVLAR  SYSTEM        755 


DEVELOPMENT  OF  THE   BLOOD-VASCULAR   SYSTEM. 

There  are  three  distinct  stages  in  the  develo])im'iit  of  the  C'irculatory  system,  each  in  accord- 
ance with  the  manner  in  which  nourishment  is  i)r()\idcd  for  ;it  different  periods  of  the  existence 
of  the  individual.  In  the  first  stage  there  is  the  eitcUinc  circulation,  during  which  nutriment  is 
extracted  from  the  vitellus  or  contents  of  the  yolli  sac.  In  the  second  stage  there  is  the 
placental  circulation,  during  which  nutriment  is  obtained  by  means  of  the  placenta  from  the 
blood  of  the  mother.  In  the  third  stage,  commencing  after  birth,  there  is  the  complete  circu- 
lation of  the  adult,  during  which  nutrition  is  provided  for  by  the  organs  of  the  individual.' 


I  Mesoderm. 
Entoderm. 
Blood-island. 
Fig.  529. — Section  through  vascular  area  to  show  commencing  development  of  bloodvessel.      (Semidiagrammatic.) 

Bloodvessels  first  make  their  appearance  in  the  mesodermal  wall  of  the  yolk  sac,  i.  e.,  outside 
the  body  of  the  embryo.  Here  the  cells  become  arranged  into  solid  strands  or  cords  which  join 
to  form  a  close-meshed  network.  The  peripheral  cells  of  these  strands  become  flattened  and 
joined  to  each  other  by  their  edges  to  form  the  walls  of  the  primitive  bloodvessels.  Fluid  col- 
lects within  the  strands  and  converts  them  into  tubes,  and  the  more  centrally  situated  cells  of 
the  cell  cords  are  thus  pushed  to  the  sides  of  the  vessels  and  appear  as  masses  of  loosely  arranged 
cells  which  project  toward  the  lumen  of  the  tube.  These  masses  are  termed  hlood  islands  (Fig. 
529);  their  cells  acquire  coloring  matter  (hemoglobin),  and  are  then  detached  to  form  the  blood- 
corpuscles  or  erythroblasts  (Fig.  530).^    Later,  red  cells  are  formed  in  organs  where  the  circulation 


Vessel  wall.       Blood-corpuscles. 
Fig.  530. — Later  stage. 

is  sluggish,  as  liver,  spleen,  and  bone-marrow.  At  birth  this  function  is  lost  by  the  liver  and 
spleen.  The  earliest  blood  corpuscles  are  all  nucleated;  they  are  also  capable  of  subdivision  and 
of  executing  ameboid  movements,  and  in  these  respects  resemble  colorless  blood  corpuscles. 
Soon,  however,  true  colorless  blood  corpuscles  make  their  appearance,  and,  according  to  Beard,' 
are  first  derived  from  the  rudiments  of  the  thymus. 

Coincidently  with  the  development  of  the  bloodvessels  in  the  vascular  area,  the  first  rudi- 
ment of  the  heart  appears  as  a  pair  of  tubular  vessels  which  are  developed  in  the  splanchno- 
pleure  of  the  pericardial  area  in  the  precephalic  part  of  the  embryonic  area.  These  are  named 
the  primitive  aorta;,  and  a  direct  continuity  is  soon  established  between  them  and  the  vessels 
of  the  vascular  area.  Each  receives  precardially  a  vein — the  vitelline  vein — from  the  yolk  sac, 
and  is  prolonged  backward  on  the  lateral  aspect  of  the  notochord  under  the  name  of  the  dorsal 
aorta.  The  dorsal  aortfe  end  at  first  on  the  yolk  sac;  but  with  the  development  of  the  allantois, 
they  are  continued  onward  through  the  body  stalk  as  the  umbilical  arteries  to  the  villi  of  the 
chorion  frondosum. 

By  the  forward  growth  and  flexure  of  the  head  the  pericardial  area  and  the  precardial  portions 
of  the  primitive  aortse  are  folded  caudad  on  the  ventral  aspect  of  the  fore-gut,  and  the  original 

1  That  the  umbilical  circulation  precedes  the  vitelline  in  the  human  embryo  seems  to  be  shown  by  Eternod's 
and  Dandy's  independent  observations.  CoTisult  the  latter's  article,  A  Human  Embryo  with  Seven  Pairs  of 
Somites,  American  Journal  of  Anatomy,  January,  1910. 

-  -Iticording  to  Dandy  (loc.  cil.)  there  is  at  first  no  apparent  connection  between  this  blood-formmg  area  and 
the  vascular  system  of  the  very  young  human  embryo,  and  that  the  presence  of  blood  corpuscles  in  the  latter 
is  probably  explained  by  endothelial  proliferation  from  the  capillaries  in  the  chorionic  membrane. 

^  .Anatomischer  Anzeiger,  December,  19D0. 


756 


THE  VASCULAR  SYSTEMS 


relation  of  the  layers  of  the  pericardial  area  is  reversed.  Each  primitive  aorta  now  consists  of 
a  ventral  and  a  dorsal  part  connected  cephalad  by  an  arched  vessel  traversing  the  first  or  man- 
dibular branchial  arch.  In  each  succeeding  branchial  arch  a  similar  vessel  develops,  so  that  in 
all  nx  pairs  of  aortic  arches  are  formed,  of  which  the  fifth  atrophies  early. 


Primitive  jugu  lar 
vein 


Chorionic  villi 


Pig.  531. — Human  embryo  of  about  fourteen  days  old  with  yolk  sac.     (After  His,  from  Kollmann's 
Entwickelungsgeschiclite.) 

In  the  pericardial  region  the  two  primitive  aortse  grow  together  and  fuse  to  form  the  single- 
chambered  primitive  heart  tube  (Fig.  532),  the  caudal  end  of  which  receives  the  two  vitelline 
veins,  while  from  its  cephalic  end  the  two  ventral  aortje  emerge.  By  the  rhythmic  contraction 
of  the  tubular  heart  the  blood  is  forced  through  the  aortre  and  bloodvessels  of  the  vascular  area, 


Auricle' 
Sinus  venosus- 

Vitelline  veins 


Fig.  532.—  Diagram  to  illustrate  the  simple  tubular 
condition  of  the  heart.  (Drawn  from  Ecker-Ziegler 
model.) 


Vitelline  veins 


Fig.    533. — Heart  further  advanced  than  in  Fig. 
532.    (Drawn  from  Ecker-Ziegler  model.) 


from_  which  it  is  returned  to  the  heart  by  the  vitelline  veins;  by  this  vitelline  circulation  the 
nutriment  is  absorbed  from  the  vitellus. 

Umbilical  or  Placental  Circulation.— With  the  atrophy  of  the  yolk  sac  the  vitelline  circu- 
lation diminishes  and  ultimately  ceases,  while  an  increasing  amount  of  blood  is  carried  through 


DEVELOPMENT  OF  THE  BLOOD-VASCULAR  SYSTEM        757 

the  umbilical  arteries  to  the  villi  of  the  chorion.  Subsequently,  as  the  nonplacental  chorionic 
villi  atrophy,  their  vessels  disappear,  and  then  the  umbilical  arteries  convey  the  whole  of  the 
blood  to  the  placenta,  whence  it  is  returned  to  the  heart  by  the  umbilical  veins.  In  this  manner 
the  placental  circulation  is  established,  and  by  means  of  it  nutritive  materials  are  absorbed 
from,  and  waste  products  given  up  to,  the  maternal  blood. 


■  Optic  reside. 


Auricle.-— yi.- 


--  T 


OmphaloTtiesen- 
feric  veins. 


ed  from  the  ventral  surface.    X  26. 

The  umbilical  veins,  like  the  vitelline,  become  interrupted  by  the  liver,  and  the  blood  returned 
by  them  passes  through  this  organ  before  reaching  the  heart.  Ultimately  the  right  umbilical 
vein  largely  disappears,  being  represented  in  the  adult  by  a  small  vein  of  the  belly  wall. 

During  the  occurrence  of  these  changes  great  alterations  take  place  in  the  primitive  heart  and 
bloodvessels,  and  now  r('(|iiirc  description. 

Further  Development  of  the  Heart.— The  simple  tubular  heart,  already  described,  be- 
comes elongated  and  bent  on  itself  so  as  to  form  an  S-shaped  loop,  the  cephalic  part  bending  to 
the  right  and  the  caudal  part  to  the  left.  The  intermediate  portion  arches  transversely  from 
right  to  left,  and  then  turns  sharply  forward  into  the  cephalic  part  of  the  loop.     Slight  con- 


Ventricle.' 
Vena  cava  siiperio 


Umtilical  vein.- 


Maxillary  process. 
StomodEeum. 
Mandibular  2)rocess. 


Fig.  535. — Heart  of  human  embryo  of  about  fifteen  days.     (Reconstruction  by  His.) 

strictions  make  their  appearance  in  the  tube  and  divide  it  from  behind  forward  into  four  parts, 
viz.:  (1)  The  sinus  venosus;  (2)  the  primitive  auricle;  (3)  the  primitive  ventricle;  (4)  the  aortic 
bulb,  which  consists  of  two  portions,  a  proximal  muscular  portion  known  as  the  bulbiis  cordis, 
and  a  distal  portion,  the  primitive  aortic  stem  (Figs.  532  to  534).  The  constriction  between  the 
auricle  and  ventricle  constitutes  the  auricular  canal,  and  indicates  the  site  of  the  future  auriculo- 
ventrieular  valves. 

The  sinus  venosus  is  at  first  situated  in  the  septum  transversum  behind  the  common  auricle, 
and  is  formed  by  the  union  of  the  vitelline  veins.     The  veins  or  ducts  of  Cuvier  from  the  body  of 


758 


THE  VASCULAR  SYSTEMS 


the  embryo  and  the  umbilical  veins  from  the  placenta  subsequently  open  into  it  (Fig.  54.5).  The 
sinus  is  at  first  placed  transversely,  and  opens  by  a  median  aperture  into  the  common  auricle. 
Soon,  however,  it  assumes  an  oblique  position,  and  becomes  crescentic  in  form;  its  right  half 
or  horn  increases  more  rapidly  than  the  left,  while  the  opening  into  the  auricle  now  communi- 
cates with  the  right  portion  of  the  auricular  cavity.  The  right  horn  ultimately  becomes  incor- 
porated with  and  forms  a  part  of  the  right  auricle,  the  line  of  union  between  it  and  .the  auricle 
proper  being  indicated  in  the  interior  of  the  adult  auricle  by  a  vertical  crest  {crista  terminalis  of 
His).     The  left  horn,  which  ultimately  receives  only  the  left  duct  of  Cuvier,  persists  as  the 


Right  auricle- 
Bulhus  cordi 


—Left  auricle 


Fig.  536. — Heart  showing  expansion  of  auricles.      (Drawn  from  Edier-Ziegler  model.) 

coronary  sinus  (Fig.  494).  The  vitelline  and  umbilical  veins  are  soon  replaced  by  a  single 
vessel,  the  inferior  vena  cava,  and  the  three  veins  (inferior  vena  cava  and  right  and  left  Cuvierian 
ducts)  open  into  the  dorsal  aspect  of  the  auricle  by  a  common  slit-like  aperture  (Fig.  542). 
The  upper  part  of  this  aperture  represents  the  opening  of  the  adult  superior  vena  cava,  the 
lower  that  of  the  inferior  vena  cava,  and  the  intermediate  part  the  orifice  of  the  coronary 
sinus.  The  slit-like  aperture  lies  obliquely,  and  is  guarded  by  two  valves,  the  right  and  left 
venous  valves,  which  unite  with  each  other  above  the  opening  and  are  continuous  with  a  fold 
named  the  septum  spurium.  The  left  venous  valve  practically  disappears,  while  the  right  is 
subsequently  divided  to  form  the  Eustachian  and  Thebesian  valves.     At  the  lower  extremity 


Aortic  bitlb 
Left  auricle 
Left  rentricle.^ 


Might  auricle. 


.Superior  vena  cava. 
•Septum  transversitm. 

■Umbilical  vein. 


Vitelline  or  Omphalomesenteric  vein. 
Fig.  537. — Heart  of  human  embryo,  4.2  mm.  long,  seen  from  behind.     fHis.) 

of  the  slit  is  a  triangular  thickening,  the  spina  vestibuli  of  His,  which  partly  closes  the  aperture 
between  the  two  auricles,  and,  according  to  His,  takes  a  part  in  the  formation  of  both  the  inter- 
auricular  and  interventricular  septa. 

The  auricular  canal  is  at  first  a  short  straight  tube  connecting  the  auricular  with  the  ven- 
tricular portion  of  the  heart,  but  its  growth  is  relatively  slow,  and  it  becomes  overlapped  by  the 
auricles  and  ventricles  so  that  its  position  on  the  surface  of  the  heart  is  indicated  only  by  an 
annular  constriction.  (Fig.  536).  Its  lumen  is  reduced  to  a  transverse  slit,  and  two  thickenings 
appear,  one  on  its  dorsal  and  another  on  its  ventral  wall.  These  thickenings,  or  evdocardial 
cushions  (Fig.  542),  as  they  are  termed,  project  into  the  canal,  and,  meeting  in  the  middle  line. 


DEVELOPMENT  OF  THE  BLOOD- VASCULAR  SYSTEM        759 

iirjite  to  form  the  septum  inlermedium  which  divides  the  canal  into  two  channels,  the  future 
right  and  left  auriculo\entricular  orifices. 

The  primitive  aurirular  ca\  ity  becomes  subdivided  into  right  and  left  auricles  by  an  incom- 
plete septum,  the  septum  primiim  (Fig.  542),  which  grows  downward  into  the  auricular  cavity. 
For  a  time  the  two  auricles  communicate  with  each  other  by  an  opening,  the  ostium  primum  of 
Born,  below  the  free  margin  of  the  septum.  This  opening  is,  however,  closed  by  the  union  of  the 
septum  primum  with  the  septum  intermedium,  and  the  communication  between  the  auricles 
is  reestablished  through  an  opening  which  is  developed  in  the  upper  part  of  the  septum  primum; 


Aortic  sepiiim. 

Common  aurioulo- 
ventricular  orifice. 


■  Right 
veyiiricle.  Septum 

inferius. 

Figs.  538  and  539.— Diagn 


.•entride.      ^J**"™  inferius.   ventricle. 

t  to  show  the  development  of  the  septum  of  the  aortic  bulb  and  of  the  ventricles. 
(Born.) 


this  opening  is  known  as  the  foramen  ovale  (ostium  secimdum  of  Born),  and  persists  until  shortly 
after  birth.  A  second  septinn,  the  septum  secundum,  semilunar  in  shape,  grows  downward 
from  the  upper  wall  of  the  auricle  to  tlie  right  of  the  primary  septum  and  foramen  ovale,  forming 
the  ventral  and  lower  boundary  of  the  latter.  This  fold  becomes  continuous  with  the  Eustachian 
valve  and  forms  the  adult  annulus  ovalis.  Shortly  after  birth  it  fuses  with  the  primary  septum, 
and  by  this  means  the  foramen  ovale  is  closed,  but  sometimes  the  fusion  is  incomplete  and  the 
upper  part  of  the  foramen  remains  patent. 

The  primitive  ventricle  becomes  divided  bj^  a  septum,  the  septum  inferius  or  interventricular 
septum  (Figs.  538,  539,  542),  which  grows  upward  from  the  lower  part  of  the  ventricle,  its  position 


Fig.  540. — Diagrams  to  illustrate  the  transformation  of  the  bulbus  cordis.     Ac.  Primitive  aortic  stem.     Au.  Auricle. 
B.  Bulbus  cordis.     RV.  Right  ventricle.     LV.  Left  ventricle.     P.  Pulmonary  artery.     (Keith.) 

being  indicated  on  the  surface  of  the  heart  by  a  fiu^row.  Its  dorsal  part  grows  more  rapidly 
than  its  ventral  portion,  and  fvises  with  the  dorsal  part  of  the  septum  intermedium.  For  a  time 
an  interventricular  foramen  exists  above  its  ventral  portion,  but  this  foramen  is  ultimately  closed 
by  the  fusion  of  the  aortic  septum  with  the  interventricular  septum. 

As  already  stated,  the  aortic  hnlh  consists  of  a  proximal  muscular  portion,  the  hidhns  cordis, 
and  a  distal  portion,  the  primitive  aortic  stem.  When  the  heart  assumes  its  S-shaped  form  the 
bulbus  cordis  lies  ventral  to  or  in  front  of  the  primitive  ventricle.  The  adjacent  walls  of  the 
bulbus  cordis  and  ventricle  approximate,  fuse,  and  finally  disappear,  and  the  bulbus  cordis  now 
communicates  freely  with  the  right  ventricle,  while  the  jimction  of  the  bulbus  with  the  primitive 


760 


THE   VASCULAR  SYSTEMS 


aortic  stem  is  brought  directly  ventral  to  and  applied  to  the  auricular  canal.  By  the  upgrowth 
of  the  interventricular  septum  the  bulbus  cordis  is  in  great  measure  separated  from  the  left 
ventricle,  but  remains  an  integral  part  of  the  right  ventricle,  of  which  it  forms  the  infundibidum. 
The  primitive  aortic  stem  is  divided  by  the  aortic  septum  (Fig.  541).  This  makes  its  appear- 
ance as  two  lateral  ridge-like  thickenings  which  project  into  the  lumen  of  the  tube  from  just 
above  the  level  of  the  sixth  arch  vessels;  these  increase  in  size,  and  ultimately  meet  and  fuse  to 
form  the  septum   and  thus  the  primitive  aortic  stem  is  divided  into  the  pulmonarv  artery  and 


Fig.  541. — Transverse  sections  through  the  aortic  bulb  to  show  the  growth  of  the  aortic  septum.    The  lowest  section 
is  on  the  left,  the  highest  on  the  right  of  the  figure.     (After  His.) 


the  aorta.  The  aortic  septum  takes  a  spiral  course  toward  the  proximal  end  of  the  stem,  so  that 
the  two  vessels  lie  side  by  side  above,  but  near  the  heart  the  pulmonary  artery  is  in  front  of  the 
aorta  (Fig.  414).  The  septum  grows  down  into  the  ventricle  as  an  oblique  partition,  which  ul- 
timately blends  with  the  interventricular  septum  in  such  a  way  as  to  bring  the  bulbous  cordis 
into  communication  with  the  pulmonary  artery,  and  through  the  latter  with  the  sixth  pair  of 
aortic  arches;  while  the  left  ventricle  is  brought  into  continuity  with  the  aorta  which  communi- 
cates with  the  remaining  aortic  arches. 

Sej}tain  spitrium 

Opening  of  sinus  venosus 
Left  venous  valve 
mn  p)u. 


Sejjtum  inferius 
Fig   542. — Interior  of  dorsal  half  of  heart  from  a  human  embryo  10  mm.  long.      (His.) 

The  Valves  of  the  Heart. — The  auriculoventricular  valves  are  developed  in  relation  to 
the  auricular  canal.  By  the  upward  expansion  of  the  bases  of  the  ventricles  the  canal  becomes 
invaginated  into  the  ventricular  cavities.  The  invaginated  margin  forms  the  rudiments  of  the 
lateral  cusps  of  the  auriculoventricular  valves;  the  mesal  or  septal  cusps  of  the  \-alves  are 
developed  as  downward  prolongations  of  the  septum  intermedium.  The  aortic  and  pulmonary 
valves  are  formed  from  four  endocardial  thickenings — an  anterior,  a  posterior,  and  two  lateral 
— which  appear  at  the  proximal  end  of  the  primitive  aortic  stem.  As  the  aortic  se|)tum  grows 
dow-nward  it  divides  each  of  the  lateral  thickenings  into  two,  thus  giving  rise  to  six  thickenings 
— the  rudiments  of  the  semilunar  valves — three  at  the  aortic  and  three  at  the  pulmonary  orifice. 


DEVELOPMENT  OF  THE  BLOOD-VASCULAR  SYSTEM        761 

Further  Development  of  the  Arteries. — It  has  been  seen  (p.  756)  that  each  primitive  aorta 
consists  of  a  ventral  and  a  dorsal  stem,  which  are  continuous  tlirough  the  first  aortic  acch.  The 
dorsal  aortis  at  first  run  backward  separately  on  either  side  of  the  notochord,  but  about  the 
third  week  they  fuse  from  about  the  level  of  the  fourth  thoracic  to  that  of  the  foitfth  lumbar 
segment  to  form  a  single  trunk,  the  descending  aorta.  The  first  aortic  arches  pass  through  the 
mandibular  arches,  and  caudad  of  them  five  additional  pairs  are  developed  within  the  branchial 
arches;  so  that,  in  all,  six  pairs  of  aortic  arches  are  formed  (Fig.  544).  The  first  and  second 
arches  pass  between  the  ventral  and  dorsal  aortse,  while  the  others  arise  at  first  by  a  common 
trunk  from  the  aortic  bulb,  but  terminate  separately  in  the  dorsal  aortse.  As  the  neck  elongates, 
the  ventral  aort«  are  lengthened,  and  the  third  and  fourth  arches  arise  directly  from  these 
vessels. 


Second  aortic  arch. 
Third  aortic  arch. 


Auditor!/  vesicle 

Primitive 
jugular  veiti.^^-^ 

Fourth  aortic  arch. 

Fifth  aortic 
arch. 


Cardinal  vein.- 


First  aortic  arch. 


■Olfactory  pit. 


Maxillary  process. 

Hyomandihular  cleft. 

•Mandibular  arcli. 

■Aortic  hidb. 

Auricle. 

■Duct  of  Cuvier. 

.Ventricle. 


Allantois. 
Umbilical  {allantoi< 


rtery). 


Fig.  543. — Profile  view  of  a  human  erabryo  estimated  at  twenty  or  twenty-one  days  old,     (.\fter  His.) 


In  fishes  these  arches  persist  and  give  off  branches  to  the  gills,  in  ^^■hieh  the  blood  is  oxygenated. 
In  mammals  some  of  them  remain  as  permanent  structures,  while  others  disappear  or  become 
imi>ervious  (Fig.  544). 

The  Ventral  Aortae. — These  persist  on  both  sides.  The  right  forms  (a)  the  innominate 
artery,  (6)  the  right  common  and  external  carotid  arteries.  The  left  give's  rise  to  (a)  the  short 
portion  of  the  aortic  arch,  which  reaches  from  the  origin  of  the  innominate  artery  to  that 
of  the  left  common  carotid  artery;  (6)  the  left  common  and  external  carotid  trunks. 

The  Aortic  Arches.— The  first  and  second  disappear;  the  third  {carotid  arch)  constitutes 
the  commencement  of  the  internal  carotid  artery.  The  fourth  right  arch  forms  the  right  sub- 
clavian as  far  as  the  origin  of  its  internal  mammary  branch;  while  the  fourth  left  arr-h  con- 
stitutes the  arch  of  the  aorta  between  the  origin  of  the  left  carotid  artery  and  the  termination  of 
the  ductus  arteriosus.     The  fifth  arch  disappears  on  both  sides.     The  sixth  right  arch  disappears ; 


762 


THE  VASCULAR  SYSTEMS 


the  sixth  left  arch  gives  off  the  pulmonary  arteries  and  forms  the  ductus  arteriosus;  this  duct 
remains  pervious  throughout  fetal  life,  but  becomes  impervious  a  few  days  after  birth.' 

The  Dorsal  Aortae. — Cephalad  of  the  third  aortic  arches  the  dorsal  aortse  persist  and  form 
the  headward  continuation  of  the  internal  carotid  arteries.  Caudad  of  the  third  arch  the  right 
dorsal  aorta  disappears  as  far  as  the  point  where  the  two  dorsal  aortfe  fuse  to  form  the  descending 
aorta.  The  part  of  the  left  dorsal  aorta  which  intervenes  between  the  third  and  fourth  arches 
disappears,  while  the  remainder  persists  to  form  the  descending  part  of  the  arch  of  the  aorta. 
A  constriction,  the  aortic  isthmus,  is  sometimes  seen  in  the  aorta  between  the  origin  of  the  left 
subclavian  and  the  attachment  of  the  ligamentum  arteriosum.  Below  this  isthmus  the  aorta 
expands  slightly  to  form  the  aortic  spindle. 

Sometimes  the  right  subclavian  artery  arises  from  the  aortic  arch  beyond  the  origin  of  the  left 
subclavian  and  passes  upward  and  to  the  right  behind  the  trachea  and  oesophagus.  This  con- 
dition may  be  explained  by  the  persistence  of  the  right  dorsal  aorta  and  the  obliteration  of  the 
fourth  right  arch. 

In  birds  the  fourth  right  arch  forms  the  arch  of  the  aorta;  in  reptiles  the  foiu-th  arch  on  both 
sides  persists  and  gives  rise  to  the  double  aortic  arch  in  these  animals. 

The  heart  originally  lies  on  the  ventral  aspect  of  the  pharynx,  immediately  caudad  of  the  stoma- 
todeum.  With  the  elongation  of  the  neck  and  development  of  the  lungs  it  recedes  within  the 
thorax,  and,  as  a  consequence,  the  anterior  ventral  aortee  are  drawn  out  and  the  original  position 
of  the  fourth  and  fifth  arches  is  greatly  modified.     Thus,  on  the  right  side  the  fourth  recedes  to 


-External  carotid 
Ventral  aorta 

Internal  carotid 

Common  carotid 
Aortic  arch 


Right  subclavian 
artery 


Right  piil?nonary 
artery 


Trunk  of  pulmonary, 
artery 


Ductus  arteriosus 
Vertebral  artery 


Subclavian  artery 
Left  pulmonary  artery 


Fig.  544. — Scheme  of  the  aortic  arches  and  their  derivatives.     (Modified  from  Kollmann.) 

the  root  of  the  neck,  while  on  the  left  side  it  is  withdrawn  within  the  thorax.  The  recurrent 
laryngeal  nerves  originally  pass  to  their  distribution  under  the  sixth  pair  of  arches,  and  are 
therefore  pulled  backward  with  the  descent  of  these  structures,  so  that  in  the  adult  the  left  hooks 
around  the  ligamentum  arteriosum;  owing  to  the  disappearance  of  the  fifth  and  the  sixth  right 
arches  the  right  nerve  hooks  around  that  immediately  above  them,  i.  e.,  the  commencement  of  the 
subclavian  artery.  A  series  of  segmental  arteries  arises  from  the  primitive  dorsal  aortas,  those  in 
the  neck  alternating  with  the  cervical  segments  of  the  vertebral  column.  The  seventh  segmental 
artery,  which  lies  between  the  sixth  and  seventh  cervical  segments,  is  of  special  interest,  since  it 
forms  the  lower  part  of  the  vertebral  artery  and,  when  the  forelimb  bud  appears,  sends  a  branch 
to  it  (i.  e.,  the  subclavian  artery);  the  upper  part  of  the  vertebral  artery  is  formed  by  an  inter- 
segmental anastomosis  between  the  higher  segmental  arteries.  From  the  seventh  segmental 
arteries  the  entire  left  subclavian  and  the  greater  part  of  the  right  subclavian  are  formed. 

The  subclavian  artery  is  prolonged  into  the  limb  under  the  names  of  the  axillary  and  brachial 
arteries,  and  these  together  constitute  the  arterial  stem  for  the  upper  arm.  The  direct  con- 
tmuation  of  this  stem  into  the  forearm  forms  the  anterior  interosseous  artery;  while  the  radial 
and  ulnar  vessels,  which  ultimately  exceed  this  artery  in  size,  are  in  reality  lateral  branches  of  the 
main  stem. 

The  formation  of  the  primary  caudal  branches  has  already  been  referred  to  (p.  755),  and  the 
fusion  of  the  dorsal  aortse  to  form  the  greater  part  of  the  systemic  aorta  has  been  pointed  out 


1  His  found  that  in  the  young  embryo  the  right  and  left  sixth  arches  each  give 
that  later  both  pulmonary  arteries  take  origin  from  the  left  arch. 


L  branch  to  the  lungs,  but 


DEVELOPMENT  OF  THE  JSLOOB-VASCULAJi  SYSTEM        763 

(page  761).  The  middle  sacral  artery  of  the  adult  was  formerly  regarded  as  the  direct  con- 
tinuation of  the  adult  aorta,  but  Young  and  Robinson'  maintain  that  it  is  a  secondary  branch, 
probably  representing  fused  segmental  arteries.  The  caudal  continuations  of  the  aortte  in  the 
adult  are  the  common  iliac,  internal  ihac,  and  the  partially  impervious  hypogastric  arteries. 

The  hypogastric  arteries  are  continued  into  the  umbiUcal  cord  as  tlie  imabilical  arteries.  After 
birth  they  become  impervious  cords  from  the  umbilicus  as  far  as  the  origin  of  the  superior  vesical 
arteries. 

The  primary  arterial  stem  for  the  lower  limb  is  formed  by  the  sciatic  artery,  which  accom- 
panies the  great  sciatic  nerve  along  the  posterior  aspect  of  the  thigh  to  the  back  of  the  knee, 
where  it  is  continued  as  the  peroneal  artery.  The  femoral  artery  arises  later  as  a  branch  of  the 
common  iliac,  and,  passing  down  the  front  and  inner  side  of  the  thigh  to  the  bend  of  the  knee, 
joins  the  sciatic  artery.  The  femoral  quickly  enlarges,  and  coincidently  with  this  the  part  of 
the  sciatic  immediately  above  the  knee  undergoes  atrophy.  The  anterior  and  posterior  tibial 
arteries  are  branches  of  the  main  arterial  stem. 


Eight  '•primitive  jugular  rein. 


Right  cardinal 
Right  duct  of  Cuviei 

Sinus  venosits 
Right  hepatic  r^in. 

Portal 


Portal  vein- 
Right  umbiUcal  vein 


Umbilical  cord.  _, 


;,___>. -'Le/^  cardinal  vein. 


'Left  duct  of  Cuvier, 

-Left  hepatic  dcih. 
-Ductus  venosus. 


Left  umbilical  vein. 


Fig.  S45. — Human  embryo  with  heart  and  anterior  body  wall  removed  to  show  the  sinus  venosus  and 
its  tributaries.     (After  His,  from  Kollmann's  Entwickelungsgeschichte.) 

Further  Development  of  the  Veins. — The  formation  of  the  great  veins  of  the  embryo  maj 
be  best  considered  by  dividing  them  into  two  groups,  visceral  and  parietal. 

The  visceral,  veins  are  the  two  vitelline  or  omphalomesenteric  veins  bringing  the  blood  from 
the  yolk  sac,  and  the  two  umbilical  or  allantoic  veins  returning  the  blood  from  the  placenta; 
these  four  veins  open  close  together  into  the  sinus  venosus  (Fig.  547). 

The  vitelline  veins  run  cephalad  at  first  in  front,  and  subsequently  on  either  side  of  the  intestinal 
canal.  They  unite  on  the  ventral  aspect  of  the  canal,  and  beyond  this  are  connected  to  one 
another  by  two  cross  branches,  the  first  on  the  dorsal,  the  second  on  the  ventral  aspect  of  the 
duodenal  portion  of  the  intestine,  which  is  thus  encircled  by  two  venous  rings  (Fig.  546).  The 
portions  of  the  veins  above  the  upper  ring  become  invaded  by  the  developing  liver  and  broken 
up  by  it  into  a  plexus  of  small  capillary-like  vessels  termed  sinusoids  (Minot).  The  branches 
conveying  the  blood  to  this  plexus  are  named  the  venae  advehentes,  and  become  the  branches  of  the 


I  Journal  of  .^atomy  and  Physiology,  vol.  xxxii 


764 


THE  VASCULAR  SYSTEMS 


portal  vein;  while  the  vessels  draining  the  plexus  into  the  sinus  venosus  are  termed  the  venae, 
revehentes,  and  form  the  future  hepatic  veins  (Figs.  545  and  546).  Ultimately  the  left  vena 
revehens  no  longer  communicates  directly  with  the  sinus  venosus,  but  opens  into  the  right  vena 
revehens.  The  lower  part  of  the  yortal  vein  is  formed  from  the  fused  vitelline  veins  which 
receive  the  veins  from  the  alimentary  canal;  its  upper  part  is  derived  from  the  venous  rings  by  the 
persistence  of  the  left  half  of  the  lower  and  the  right  half  of  the  upper  ring,  so  that  the  vessel 
forms  a  spiral  turn  round  the  duodenum  (Fig.  546). 

The  two  umbilical  veins  fuse  early  to  form  a  single  trunk  in  the  body  stalk,  but  remain  separate 
within  the  embryo  and  pass  forward  to  the  sinus  venosus  in  the  side  walls  of  the  body.  Like  the 
vitelline  veins,  their  direct  connection  with  the  sinus  venosus  becomes  interrupted  by  the  inva- 
sion of  the  liver,  and  thus  at  this  stage  the  whole  of  the  blood  from  the  yolk  sac  and  placenta 
passes  through  the  substance  of  the  liver  before  it  reaches  the  heart.  The  right  umbilical  vein 
becomes  disconnected  from  the  sinus  venosus,  shrivels,  and  forms  a  small  vein  of  belly  wall; 
the  left,  on  the  other  hand,  becomes  enlarged  and  opens  into  the  upper  venous  ring  of  the 
vitelline  veins.  Finally,  a  direct  channel  is  established  between  this  ring  and  the  heart; 
this  channel  is  called  the  ductus  venosus,  and,  enlarging  rapidly,  forms  a  wide  channel 
tlirough  which  most  of  the  blood,  returned  from  the  placenta,  is  carried  directly  to  the  heart 
without  being  obliged  to  pass  through  the  liver.  The  left  umbilical  vein  and  ductus  venosus 
become  impervious  after  birth,  and  form,  respectively,  the  Ugamentum  teres  and  Ugamentinn 
venosimi  of  the  liver  (Fig.  1071). 

Ventral  detached  portions 

of  umbilical  veins.  y- , 


Stomach. 

Venae  advehentes.  -  ~ 
Pancreas.  -' 
Bile  duct.  -- 


Obliterated  portions 
of  venous  rings. 


Right  umbilical  vein. 


Ductus  venosits. 


Left  umbilical  vein. 


Fig.  546. — The  liver,  and  the  veins  in  connection  with  it,  of  a  human  embryo,  twenty-four  or  twenty-five 
days  old,  as  seen  from  the  visceral  surface.     (After  His.)     (Copied  from  Milnes  Marshall's  Embryology.) 


The  Parietal  Veins. — The  first  indication  of  a  parietal  system  consists  in  the  appearance  of 
two  short  transverse  veins  (the  ducts  of  Cuvier),  which  open,  one  on  either  side,  into  the  sinus 
>'enosus.  Each  of  these  ducts  receives  an  ascending  and  descending  vein.  The  ascending 
veins  return  the  blood  from  the  parietes  of  the  trunk  and  from  the  mesonephroi,  and  are  called 
postcardinal  veins.  The  descending  veins  return  the  blood  from  the  head  and  upper  limbs, 
and  are  called  the  precaxdinal  or  primitive  jugular  veins  (Fig.  547).  The  blood  from  the 
lower  limbs  is  collected  by  the  right  niid  li'I'l  iliar  veins,  which,  in  the  earlier  stages  of  develop- 
ment, ojien  into  the  corresponding  right  and  left  pustcardinals  (Fig.  548);  later  on,  a  transverse 
channel  (the  left  common  iliac  vein)  is  developed  between  the  caudal  parts  of  the  two  post- 
cardinal  veins  (Fig.  549),  and  through  this  the  blood  is  carried  to  the  right  postcardinal  vein. 
The  portion  of  the  left  postcardinal  vein  below  the  level  of  the  left  renal  vein  atrophies  and  dis- 
appears up  to  the  point  of  entrance  of  the  left  spermatic  vein;  above  this  level  the  left  post- 
cardinal  persists  as  the  superior  and  inferior  azygos  minor  veins.  The  right  postcardinal  vein, 
which  now  j-eceives  the  blood  from  both  lower  limbs,  forms  a  large  venous  trunk  along  the  posterior 
abdominal  wall.  Above  the  level  of  the  renal  veins  the  right  postcardinal  vein  persists  as  the 
vena  azygos  major,  and  receives  the  right  intercostal  veins,  while  the  azygos  minor  veins  are 
brought  into  communication  with  it  by  the  develo]3ment  of  transverse  anastomotic  channels  in 
front  of  the  vertebral  column  (Fig.  514). 


DEVELOPMENT  OF  THE'  BLOOD-VASCULAR  SYSTEM 


765 


Inferior  Vena  Cava. — The  development  of  the  inferior  vena  cava  is  associated  with  the 
formation  of  two  pairs  of  veins,  the  snhnirdhinl  and  .suj)racar(iiual  veins  (Figs.  548  and  549),  and 
with  the  ductus  venoms.  The  subcardinal  veins  lii-  piirnllel  to,  and  ventrad  of,  the  postcardinal 
veins  and  originate  as  longitudinal  anasloniosing  channels  which  communicate  with  the  post- 


Sinus  venosus 


Precardinal 
Subclavian 

Duct  of  Cuvier 
Vitelline 
Umbilical 
^Postcardinal 

Subcardinal 
■RcJial 


External  iliac 
Internal  iliac 


Fig.  547. — Scheme  of  arrangement 
cf  parietal  veins. 


Internal  Jugular 
■External  jugular 
Subclavian 


Duct  of  Cuvier 

Left  postcardinal 
-Ductus  venosus 

Benal 

Subcardinal 

■External  iliac 
— Internal  iliac 


Fig.  548. — Scheme  showing  early  stages  of 
development  of  the  inferior  vena  cava. 


cardinals  above  and  below  and  also  with  each  other  by  a  series  of  transverse  channels.  Of  the 
transverse  channels,  only  one  persists  to  join  each  renal  vein.  The  left  subcardinal  vein  practi- 
cally disappears,  while  the  right  subcardinal  enlarges  and  joins  the  ductus  venosus  cephalad  and 
the  right  postcardinal  caudad.  At  this  stage  the  blood  draining  the  lower  extremities  passes 
along  a  right-sided  channel  which  courses  ventrad  of  the  lu-eter. 


Internal 
jugular 


'^'Subclavian 


Suprarenal 
Benal 
Simrynatie 


A  B 

Fig.  549. — Diagram  illustrating  the  development  of  the  inferior  vena  cava  in  the  cat.  The  cardinal  and 
subcardinal  veins  and  ductus  venosus  are  blue  and  the  supracardinal  black.  (Adapted  from  McClure  and 
Huntington.) 

The  supracardinal  veins  develop  as  bilaterally  symmetrical  channels  dorsomesad  of  the 
postcardinals,  l>y  lonoitudinal  anastomoses  between  parietal  postcardinal  tributaries  fHuntington 
and  McClure).     Each  vein  extends  from  where  the  posterior  limb  veins  open  into  the  post 


766  THE  VASCULAR  SYSTEMS 

cardinals  to  the  junction  of  the  primitive  renal  vein  with  the  transverse  subcardinal  segment, 
and  is  situated  dorsad  of  the  corresponding  ureter.  The  two  supracardinals  fuse  almost  wholly 
into  a  single  channel  and  largely  replace  the  postrenal  segment  of  the  primitive  postcardinal  sys- 
tem. To  review,  it  is  seen  that  the  inferior  vena  cava  is  a  composite  vessel  made  up  of  the  fol- 
lowing parts,  enumerated  in  order  from  the  heart:  (1)  The  part  of  the  ductus  venosus  between  the 
hepatic  veins  and  the  heart;  (2)  the  cephalic  part  (renal  level)  of  the  right  subcardinal;  (3)  the 
fused  supracardinals,  the  caudal  portions  only  remaining  separate  to  drain  the  right  and  left 
Uiacs  (Fig.  549). 

In  consequence  of  the  atrophy  of  the  Wolffian  bodies  the  postcardinal  veins  diminish  in  size; 
the  precardinal  veins,  on  the  other  hand,  become  enlarged,  owing  to  the  rapid  development 
of  the  head  and  brain.  They  are  further  augmented  by  receiving  the  veins  (subclavian)  from 
the  upper  extremities,  and  so  come  to  form  the  chief  veins  of  the  Cuvierian  ducts;  these  ducts 
gradually  assume  an  almost  vertical  position  in  consequence  of  the  descent  of  the  heart  into 
the  thorax.  The  right  and  left  Cuvierian  ducts  are  originally  of  the  same  diameter,  and  are 
frequently  termed  the  right  and  left  superior  venae  cavae.  By  the  development  of  a  transverse 
channel  (the  left  hrachiocephalic  vein)  between  the  two  precardinal  veins,  the  blood  is  carried 
across  from  the  left  to  the  right  precardinal  (Fig.  547).  The  portion  of  the  right  primitive 
jugular  vein  between  the  left  brachiocephalic  and  the  vena  azygos  major  forms  the  upper  part 
of  the  superior  vena  cava  of  the  adult;  the  lower  part  of  this  vessel  {i.  e.,  below  the  entrance  of 
the  vena  azygos  major)  is  formed  by  the  right  Cuvierian  duct.  Below  the  origin  of  the  trans- 
verse channel  the  left  primitive  jugular  vein  and  left  Cuvierian  duct  atrophy,  the  former  con- 
stituting the  upper  part  of  the  left  superior  intercostal  vein,  while  the  latter  is  represented  by 
the  vestigial  fold  and  oblique  vein  of  Marshall.  Both  right  and  left  superior  venae  cavae  are 
present  in  some  animals,  and  are  occasionally  found  in  the  adult  human  being.  The  oblique 
vein  of  Marshall  passes  downward  across  the  back  of  the  left  auricle  to  open  into  the  coronary 
sinus,  which,  as  already  indicated,  represents  the  persistent  left  horn  of  the  sinus  \  enosus. 

The  primitive  jugular  or  precardinal  veins  are  situated  on  the  ventral  surface  of  the  brain, 
on  the  mesal  side  of  the  cranial  nerve  roots.  A  considerable  portion  of  each  of  these  veins 
disappears  and  is  replaced  by  a  vein  which  is  developed  on  the  lateral  aspect  of  the  cranial 
nerves  from  the  fifth  to  the  twelfth,  inclusive.  This  new  vein  (vena  capitis  lateralis)  leaves  the 
skull  in  company  with  the  facial  nerve.  The  blood  from  the  hind-brain  is  collected  into  a  vein 
(the  fidure  lateral  sinus)  which  passes  through  the  foramen  jugulare  on  the  lateral  aspect  of 
the  vagus  nerve;  here  the  two  vessels  join  to  form  the  internal  jugular  vein.  On  the  dorsal 
aspect  of  the  ear  capsule  an  anastomotic  channel  is  opened  up  between  the  vena  capitis  lateralis 
and  the  lateral  sinus;  and,  coincident  with  this,  the  ])ortion  of  the  former  vein  which  extends 
from  the  fifth  to  the  tenth  cranial  nerve  becomes  obliterated,  and  thus  the  whole  of  the  blood 
from  the  brain  is  ultimately  drained  away  by  the  lateral  sinuses.  The  primitive  jugular  vein 
is  therefore  represented  in  the  adult  by  the  internal  jugular,  and  not  by  the  external  jugular, 
as  is  usually  stated.'  The  external  jugular  vein  is  a  vessel  of  later  formation,  which  at  first 
drains  the  region  behind  the  ear  (posterior  auricular)  and  enters  the  primitive  jugular  as  a  lateral 
tributary.  A  group  of  veins  from  the  face  and  lingual  region  converge  to  form  a  common  vein, 
the  linguofacial,-  which  also  terminates  in  the  primitive  jugular.  Later,  cross  communications 
develop  between  the  external  jugular  and  the  linguofacial,  with  the  result  that  the  posterior 
group  of  facial  veins  are  transferred  to  the  external  jugular. 

The  development  of  the  lymphatics  will  be  described  at  the  beginning  of  the  section  on  the 
lymph-vascular  system. 

1  Consult  Die  Entwickelung  des  Blutgefitss-sy stems,  by  Hochstetter.  in  Hertwig's  Entwicltelungslelire;  and 
also  an  article  by  Mall  in  the  American  Journal  of  Anatomy,  December,  1904,  vol.  iv. 

2  Heuer,  American  Journal  of  Anatomy,  February,  1909,  vol.  ix.  No.  1. 


THE  LYMPHATIC  SYSTEM. 


The  lymphatic  system'  includes  the  lymphatic  vessels  and  lymph  nodes  or 
lymphatic  glands.  The  lymphatic  vessels  of  the  small  intestine  receive  the  special 
designation  of  lacteals  or  chyliferous  vessels;  they  differ  in  no  respect  from  the 
lymphatic  vessels,  except  that  during  digestion  they  contain  a  milk-white  fluid, 
the  chyle. 

It  is  now  generally  held  that  the  lymphatic  system  is  a  closed  system  peripher- 
ally, and  that  the  tissue  spaces  are  not  in  direct  communication  with  lymphatics, 
although  Mall  has  shown  that  granules  injected  into  the  portal  vein  are  returned 
by  both  lymphatics  and  veins.  Elsewhere,  apparently,  the  absorption  of  the 
lymph  is  carried  on  by  transudation  through  the  endothelial  lining  of  the  lymph 
vessels  and  not  by  permanent  openings  (the  so-called  stomata)  between  the  endo- 
thelial cells. 

The  tissue  spaces  {lymph  spaces)  are  found  in  practically  all  tissues  and  organs, 
and  may  be  classified  as  pericellular  or  intercellular,  perivascular  and  perineural 
spaces,  which  are  not  lined  by  endothelium.  The  lymph  exudes  into  these  spaces 
out  of  the  blood  capillaries  and  transudes  into  the  lymphatic  capillaries  wherever 
such  exist.  Spaces  like  the  subdural  and  subarachnoid,  and  the  serous  cavities 
of  the  body  (pleural,  pericardial,  peritoneal,  synovial  bursse)  are  lined  by  endo- 
thelium, through  which  the  lymph  transudes  by  osmosis,  while  the  lymphocytes 
may  actually  traverse  the  membrane.  The  ventricles  of  the  brain  and  the  central 
canal  of  the  spinal  cord,  lined  by  the  ependyma,  contain  a  similar  fluid  derived 
from  the  plasma  of  the  blood  in  the  choroid  plexuses,  and  they  communicate  with 
the  subarachnoid  space  through  the  foramen  of  Magendie  and  those  of  Key  and 
Retzius. 

Lymph  is  a  transparent,  colorless  or  slightly  yellow  fluid  of  a  specific  gravity 
of  1.015,  more  dilute  than  the  blood  plasma  from  which  it  is  derived,  containing 
only  about  5  per  cent,  of  proteins  and  1  per  cent,  of  salts  and  extractives.  It 
contains  formed  elements  of  the  lymphocyte  class,  and  is  slightly  coagulable. 

Chyle  is  the  intestinal  lymph  which  is  of  a  milky  appearance  during  digestion 
on  account  of  the  emulsified  fats  absorbed  by  the  lacteals. 

The  lymphatic  vessels  are  arranged  into  a  superficial  and  a  deep  set.  On  the 
surface  of  the  body  the  superficial  lymphatic  vessels  are  placed  immediately  beneath 
the  integument,  accompanying  the  superficial  veins;  they  join  the  deep  lymphatics 
in  certain  situations  by  perforating  the  deep  fascia.  In  the  interior  of  the  body  the 
lymphatics  lie  in  the  submucous  areolar  tissue  throughout  the  whole  length  of 
the  gastropulmonary  and  genitourinary  tracts,  and  in  the  subserous  tissue  of  the 
thoracic  and  abdominal  cavities.  In  the  cranial  cavity  the  perivascular  sheaths 
are  lymph  spaces.  A  plexiform  network  of  minute,  closed,  capillary  lymphatics 
may  be  found  interspersed  among  the  proper  elements  and  bloodvessels  of  the 
several  tissues,  the  vessels  composing  which,  as  well  as  the  meshes  between  them, 
are  much  larger  than  those  of  the  capillary  bloodvessel  plexus.  From  these 
networks  small  collecting  vessels  emerge,  pass  to  a  neighboring  node,  and  divide 

•  In  the  revision  of  the  section  on  the  lymphatic  system,  the  editor  has  consulted  the  work  by  Poirier  and 
Cundo,  translated  by  Cecil  H.  Leaf,  1904;  the  articles  by  Sabin,  Lewis,  and  Heuer  in  the  American  Journal  of 
Anatomy,  February  1,  1909;  and  the  articles  by  Huntington,  McClure,  and  others  (symposium)  in  the  Anatom- 
ical Record,  May,  1908.  Consult  also  G.  S.  Huntinffton  and  C.  F.  W.  McClure,  on  the  Anatomy  and  Develop- 
ment of  the  Jugular  Lymph  Sacs  in  the  Domestic  Cat  (Fells  domestica),  American  Journal  of  Anatomy,  April, 
1910,  vol.  X,  No.  2,  and  several  articles  by  various  authors  in  the  Anatomical  Record,  vol.  vi.  No.  6,  June  20,  1912. 

(767) 


THE  VASCULAR  SYSTEMS 


into  a  capillary  network  in  the  node.  Numerous  small  vessels  emerge  from  the 
node,  which  unite  into  one  lymphatic  vessel,  which  joins  a  larger  lymphatic 
trunk,  which  empties  into  a  tributary  of  the  superior  vena  cava.  The  deep 
lymphatics,  fewer  in  number  and  larger  than  the  superficial,  accompany  the  deep 
bloodvessels.  Their  mode  of  origin  is  probably  similar  to  that  of  the  superficial 
vessels.  The  lymphatics  of  any  part  or  organ  exceed  the  veins  in  number  and  in 
capacity,  but  in  size  they  are  much  smaller.  Their  anastomoses  also,  especially 
those  of  the  large  trunks,  are  more  frequent,  and  are  effected  by  vessels  equal  in 
calibre  to  those  which  they  conneci,  the  continuous  trunks  retaining  the  same 
diameter  throughout. 

The  lymph  nodes,  or  lymphatic  glands  (lymphoglandulae) ,  are  small,  solid,  gland- 
like bodies  situated  in  the  course  of  the  lymphatic  and  lacteal  vessels.  They 
vary  from  microscopic  dimensions  to  the  size  of  an  olive,  and  their  color,  on  section, 
is  of  a  pinkish-gray  tint,  excepting  the  bronchial 
nodes,  which  in  the  adult  are  mottled  with  black, 
the  hepatic  nodes,  which  are  yellow,  and  the  splenic 
nodes,  which  are  brown.  Each  node  has  a  layer  or 
capsule  of  cellular  tissue  investing  it,  from  which 
prolongations  dip  into  its  substance,  forming  parti- 
tions. The  lymphatic  and  lacteal  vessels  traverse 
these  nodes  in  their  passage  to  the  lymphatic  ducts. 
Before  entering  a  node  a  lymphatic  or  lacteal  vessel 
divides  into  several  small  branches,  which  are  named 
afferent  vessels  (yasa  affereniia).  As  they  enter,  the 
external  coat  becomes  continuous  with  the  capsule  of 
the  node,  and  the  vessels  becoming  much  thinned, 
and  consisting  only  of  their  internal  or  endothelial 
coat,  pass  into  the  node,  and  branch  out  upon  and 
in  the  tissue  of  the  capsule,  these  branches  opening 
into  the  lymph  sinuses  of  the  node.  There  is  an  ex- 
tensive sinus  beneath  the  capsule;  from  this  subcap- 
sular sinus  numerous  channels  run  inward  to  a  central 
sinus.  From  both  sinuses  fine  branches  proceed  to 
form  a  plexus,  the  vessels  of  which  unite  to  form  a 
single  efierent  vessel  {yas  efferens),  which,  on  emerg- 
ing from  the  node,  is  again  invested  with  an  external 
coat  from  the  gland  capsule.  The  lymph  nodes  are 
filters  or  traps  through  which  lymph  and  chyle  flow, 
and  also  have  a  cytogenic  function.  In  the  nodes  are  masses  of  newly  formed 
lymphocytes  which  attack  any  bacteria  in  the  lymph  or  chyle. 

Like  the  lymphatics,  the  lymph  nodes  are  arranged  in  superficial  and  deep  sets; 
they  are  usually  embedded  in  fat  and  are  distinctly  movable.  Occasionally  a 
node  exists  alone,  but,  as  a  rule,  from  eight  to  twelve,  or  even  more,  are  assembled 
in  communities  or  chains,  and  are  usually  arranged  around  bloodvessels.  The 
nodes  have  a  plentiful  blood  supply,  and  contain  not  only  vasomotor  nerves,  but 
definite  nerve  plexuses.  Besides  the  nodes,  the  body  contains  numerous  lymphoid 
areas,  which,  in  structure  and  function,  are  allied  to  lymph  nodes  (tonsils,  Beyer's 
patches,  etc.). 

Hemolymph  nodes  exist  in  various  regions,  but  are  most  common  in  the  abdomen 
in  front  of  the  vertebrae.  They  are  like  ordinary  lymph  nodes  in  form  and  also 
in  size,  but  differ  from  them  in  being  deep  red  instead  of  light  pink.  Their  func- 
tion is  to  destroy  red  blood  cells  and  to  form  lymphocytes,  phagocytes,  and  eosino- 
philes.  Hemolymph  nodes  develop  like  the  ordinary  lymphatic  nodes  except  that 
the  sinuses  are  blood  channels. 


Fig.  550, — A  lymph  node  with  its 
afferent  and  efferent  vessels.  (Tes- 
tut.) 


rilE  LYMPHATIC  SYSTEM  769 

Structure  of  Lymphatics. — The  lymphatic  \essels,  including  in  this  term  the  lacteal  vessels, 
which  are  identical  in  structure  with  them,  are  composed  of  three  coats.  The  internal  is  an 
endothelial  and  elastic  coat.  It  is  thin,  transparent,  slightly  elastic,  and  ruptures  more  easily 
than  the  other  coats.  It  is  composed  of  a  layer  of  elongated  endothelial  cells  with '  serrated 
margins,  by  which  the  adjacent  cells  are  dovetailed  into  one  another.  These  are  supported  on 
a  fibro-elastic  membrane.  The  middle  coat  is  composed  of  smooth  muscle  and  fine  elastic 
fibres,  disposed  in  a  transverse  direction.  The  external  coat  consists  of  connective  tissue,  inter- 
mixed with  smooth  muscle  fibres,  longitudinally  or  obliquely  disposed.  It  forms  a  protective 
covering,  to  the  other  coats,  and  serves  to  connect  the  vessel  with  the  neighboring  structures. 
The  above  description  applies  only  to  the  larger  lymphatics;  in  the  smaller  vessels  there  is  no  mus- 
cular or  elastic  coat,  and  the  wall  consists  only  of  a  connective-tissue  coat,  Kned  by  endothelium. 
The  thoracic  duct  has  a  more  complex  structure  than  the  other  lymphatics;  it  presents  a  distinct 
subendothelial  layer  of  branched  cells,  similar  to  that  foimd  in  the  arteries,  and  m  the  middle 
coat  is  a  layer  of  connective  tissues  with  its  fibres  arranged  longitudinally.  The  lymphatics  are 
supplied  by  nutrient  vessels,  which  are  distributed  to  their  outer  and  middle  coats;  and  here 
also  have  been  traced  many  amyelinic  nerve  fibres  in  the  form  of  several  fine  plexuses  of 
fibrils. 

The  lymphatics  are  very  generally  provided  with  valves,  which  assist  materially  in  effecting 
the  flow  of  the  lymph.  These  valves  are  formed  of  thin  layers  of  fibrous  tissue,  covered  on  both 
surfaces  by  endothelium,  which  presents  the  same  arrangement  upon  the  two  surfaces  as  was 
described  in  connection  with  the  valves  of  veins.  In  form  they  are  semikmar;  they  are  attached 
by  their  convex  edges  to  the  sides  of  the  vessel,  the  concave  edges  being  free  and  directed  along 
the  course  of  the  contained  current.  Usually  two  such  valves,  of  equal  size,  are  found  oppo- 
site each  other;  but  occasionally  exceptions  occiu",  especially  at  or  near  the  anastomoses  of 
lymphatic  vessels.  Thus,  one  valve  may  be  of  very  rudimentary  size  and  the  other  increased  in 
proportion. 

The  valves  in  the  lymphatic  vessels  are  placed  at  much  shorter  intervals  than  in  the  veins. 
They  are  most  numerous  near  the  lymphatic  nodes,  and  are  found  more  frecjuently  in  the  lym- 
phatics of  the  neck  and  upper  extremity  than  in  those  of  the  lower  extremity.  The  wall  of  a 
l^'mphatic  immediately  above  the  point  of  attachment  of  each  segment  of  a  valve  is  expanded  into 
a  pouch  or  sinus,  which  gives  to  these  vessels,  when  distended,  the  knotted  or  beaded  appearance 
which  they  present.  Valves  are  wanting  in  the  vessels  composing  the  plexiform  network  in  which 
the  lymphatics  usually  originate  on  the  surface  of  the  body. 

Lymphatic  vessels  have  been  found  in  nearly  every  tissue  and  organ  of  the  body  which  con- 
tains bloodvessels;  nonvascular  structures,  such  as  cartilage,  the  nails,  cuticle,  and  hair,  have 
none.  Lymphatic  vessels  have  not  been  demonstrated  in  the  brain,  spinal  cord,  eyeball,  and 
internal  ear;  the  pathway  of  the  lymph  is  apparently  along  the  intercellular  and  perivascular 
tissue  spaces. 

Origin  of  Lymphatics. — The  finest  lymphatic  ve.ssels  (lymphatic  capillaries) 
form  a  plexiform  network  in  the  tissues  and  organs,  and  their  walls  consist  of  a 
single  layer  of  endothelial  plates,  with  more  or  less  sinuous  margins;  the  vessels 
of  the  lymphatic  system,  therefore,  form  a  series  of  closed  tubes  similar  to  those  of 
the  blood-vascular  system.  The  lymphatic  vessels,  for  the  most  part,  accompany 
the  arteries  or  veins  throughout  the  body;  sometimes  a  minute  artery  may  be  seen 
to  be  ensheathed  for  a  certain  distance  by  a  lymphatic  capillary  vessel,  which  is 
often  many  times  wider  than  a  blood  capillary.  These  are  known  as  perivascular 
lymphatics. 

Terminations  of  Lymphatics. — The  lymphatics,  including  the  lacteals,  dis- 
charge their  contents  into  the  veins  at  two  points,  namely,  at  the  angles  of  junction 
of  the  subclavian  and  internal  jugular  veins — on  the  left  side  by  means  of  the 
thoracic  duct,  and  on  the  rig-lit  side  by  the  right  lymphatic  duet. 

Development  of  the  Lymphatic  Vessels. — The  lymphatic  system  begins  as  a  series  of  sacs 
at  the  points  of  junction  of  certain  of  the  embryonic  veins.  These  lymph  spaces  are  developed 
from  their  first  inception  as  independent  perivenous  mesenchymal  intercellular  clefts.  The 
cells  lining  these  spaces  develop  into  a  lymphatic  intimal  endothelium.' 

In  the  human  embryo  thp  lymph  sacs  from  which  the  lymphatic  vessels  are  derived  are  six 
in  number — two  paired,  the  jugular  and  the  caudal  lymph  sacs;  and  two  unpaired,  the  retro- 
peritoneal and  the  cisterna  chyli.  In  lower  mammals  an  additional  pair,  subclavian,  is  present, 
but  in  the  human  embryo  these  are  merely  extensions  of  the  jugular  sacs. 

'Cf.  Huntington,  Anatomical  Record,  vol.  iv,  No.  11,  November,  1910, 
49 


770 


THE  VASCULAR  SYSTEMS 


The  position  of  the  sacs  is  as  follows:  (1)  jugular  sac,  at  the  junction  of  the  subclavian  vein 
with  the  primitive  jugular;  (2)  caudal  sac,  at  the  junction  of  the  iliac  vein  with  the  postcardi- 
nal;  (3)  retroperitoneal,  in  the  position  of  the  cross-branch  between  the  renal  veins;  (4)  cistema 
chyli,  at  the  site  of  the  cross-branch  between  the  two  iliac  veins  (Fig.  551).  From  the  lymph 
sacs  the  lymphatic  vessels  bud  out  along  fixed  lines  corresponding  more  or  less  closely  to  the 
course  of  the  embryonic  bloodvessels.  Both  in  the  body  wall  and  in  the  wall  of  the  intestine 
the  deeper  plexuses  are  the  first  to  be  developed;  by  continued  growth  of  these  the  vessels  in  the 
superficial  layers  are  gradually  formed.  By  the  confluence  of  peri-azygos  lymphatic  segments  the 
thoracic  duct  is  formed;  this  gains  connection  with  the  venous  system  at  the  site  of  the  jugular 
lymph  sac.  At  its  connection  with  the  cistema  chyli  it  is  at  first  double,  but  the  right  vessel  soon 
joins  with  the  left. 

All  the  lymph  sacs  except  the  cisterna  chyli  are,  at  a  later  stage,  divided  up  by  slender 
connective-tissue  bridges  and  transformed  into  groups  of  lymph  nodes.  The  lower  portion  of 
the  cisterna  chyli  is  similarly  converted,  but  its  upper  portion  remains  as  the  receptaculum 
chyli. 


Ijeft  innominate 


Jiigular  lymph-sac 
Bight  innominate 

Vena  cava  superior^ 


In  ternaljugular 
External  jugular. 


Duct  of  Cuvier 
Left  •postcardirwl 


Prerenal  part  of 

vena  cava  inferior    j;  ^1^  Left  capsular 
'     '^^\r°^  Left  renal 

J Retroperitoneal 

Postrenal  part  of lymph-sac 

vena  cava  inferior        ' 


Cistema  chyli 
Caudal  lymph-sac  — 


■  External  iliac 
~  Internal  iliac 


Fig.  551. — Scheme  showing  relative  positions  of  primary  lymphatic  sacs  based  on  the  description  given  by 
Florence  Sabin. 


Applied  Anatomy. — The  lymphatic  channels  and  nodes  draining  any  infected  area  of  the 
body  are  very  liable  to  become  infected,  and  do  so  with  the  production  of  acute  or  chronic  lymph- 
angitis aud  lijmphadenitis.  In  acute  cases  the  paths  of  the  superficial  lymphatics  are  often 
marked  out  on  the  skin  by  the  appearance  over  them  of  the  four  cardinal  signs  of  inflammation — 
pain,  redness,  heat,  and  swelling — while  the  nodes  swell  and  may  suppurate.  Chronic  inflam- 
mation leads  to  growth  and  fibrosis  of  the  lymphatics  and  the  connective  tissue  around  thepi; 
obstruction  to  the  passage  of  the  lymph  results,  as  the  fibrous  tissue  contracts  and  causes  stenosis 
or  obliteration  of  the  lymphatic  channels,  and  hard  edema  of  the  involved  skin  and  subcutaneous 
tissue  follows  {pachydermia  lymphangiectatica).  Chronic  lymphangitis,  together  with  the 
blocking  of  numerous  lymphatic  vessels  by  the  escaped  ova  of  the  minute  parasitic  worm  Micro- 
filaria nocturna,  is  the  cause  of  elephantiasis,  a  condition  common  in  the  tropics  and  subtropics, 
and  characterized  by  enormous  enlargement  and  thickening  of  the  integument  of  some  part  of 
the  body,  most  frequently  the  leg.  Tubercular  and  syphilitic  enlargements  of  the  lymphatics 
and  nodes  are  both  very  commonly  met  with.  Primary  tumors  of  the  lymphatics  are  lymphan- 
gioma and  endothelioma;  the  so-called  "congenital  cystic  hygroma"  of  the  neck,  arm,  trimk, 
or  thigh  is  a  cystic  lymphangioma.  .Primary  tumors  of  the  lymph  nodes  may  be  benign  (lymph- 
adenoma,  myxoma,  chondroma)  or  malignant  (lymphosarcoma);  cancer  is  an  extremely  common 
secondary  affection. 

In  an  operation  for  cancer  it  is  not  sufficient  to  cut  wide  of  the  growth  and  remove  it;  it  is 
imperatively  necessary  to  remove  the  lymph  nodes  which  receive  lymph  from  the  diseased 


THE  L  YMPHATIC  SYSTEM 


771 


area,  and  also,  when  possible,  the  lymphatic  vessels  between  the  cancer  and  the  nodes.  Nodes 
are  diseased  very  early  in  cancer,  long  before  they  are  palpably  enlarged,  and  are  usually  infected 
by  emboli  of  cancer  cells.  The  rule  is  in 
any  cancer,  however  recent,  to  regard  the 
associated  nodes  as  diseased,  whether  en- 
larged or  not^  and  to  remove  them  thor- 
oughly, if  possible,  in  one  piece,  with  the 
interveuiiii;  Iviiiph  vessels  and  the  area  of 
primary  malignant  growth. 


THE  THORACIC  DUCT. 

The  thoracic  duct  (ductus  thorac- 
icus)  (Fig.  552)  conveys  the  great 
inass  of  lymph  and  chyle  into  the 
blood.  It  is  the  common  trunk  of 
all  the  lymphatic  vessels  of  the  body, 
excepting  those  of  the  right  side  of 
the  head  and  neck,  the  right  upper 
extremity,  the  right  lung,  right  side 
of  the  heart,  and  part  of  the  convex 
surface  of  the  liver.  In  the  adult  it 
varies  in  length  from  15  to  18  inches 
(38-45  cm.),  and  extends  from  the 
second  lumbar  vertebra  to  the  root 
of  the  neck.  It  commences  in  the 
abdomen  at  a  triangular  or  fusi- 
form dilatation,  the  receptaculum 
chyli,  which  is  situated  upon  the 
front  of  the  bodies  of  the  first  and 
of  the  second  lumbar  vertebra?,  to 
the  right  side  and  behind  the  aorta, 
overlapped  by  the  Tight  crus  of  the 
Diaphragm.  It  enters  the  thorax 
through  the  aortic  opening  in  the 
Diaphragm,  lying  to  the  right  of 
the  aorta,  and  is  then  placed  in 
the  posterior  mediastinum  between 
the  aorta  and  vena  azygos  major. 
Here  it  lies  in  front  of  the  vertebral 
column,  from  which  it  is  separated 
by  the  right  intercostal  arteries, 
and  by  the  azygos  minor  veins  as 
they  cross  the  middle  line  to  open 
into  the  vena  azygos  major.  Op- 
posite the  fifth  thoracic  vertebra  it 
inclines  toward  the  left  side,  enters 
the  superior  mediastinum,  and 
ascends  behind  the  arch  of  the  aorta 
on  the  left  side  of  the  oesophagus,  and  behind  the  first  portion  of  the  left  sub- 
clavian artery,  to  the  upper  opening  of  the  thorax.  Opposite  the  seventh  cer^'ical 
vertebra  it  turns  outward  in  front  of  the  vertebral  artery  and  vein,  behind  the  left 
common  carotid  artery  and  vagus  nerve,  and  then  curves  downward  over  the 
subclavian  artery  and  in  front  of  the  Scalenus  anticus  muscle  and  the  phrenic 
nerve,  so  as  to  form  an  arch;  it  terminates  in  the  angle  of  junction  of  the  left 


Fig.  552. — The  thoracic  and  right  lymphatic  ducts. 


772 


THE  VASCULAR  SYSTEMS 


subclavian  artery  and  in  front  of  tiie  Scalenus  anticus  muscle  and  the  phrenic- 
nerve,  so  as  to  form  an  arch;  it  terminates  in  the  angle  of  junction  of  the  left 
subclavian  vein  with  the  left  internal  jugular  vein.  It  usually  opens  at  the  apex 
of  the  angle  in  the  superior  and  outer  surface,  but  may  open  on  the  posterior 
surface.  Sometuiies  it  terminates  by  two  or  more  branches.  Figs.  552  and  554 
show  the  termination  of  the  thoracic  duct.  The  thoracic  duct,  at  its  commence- 
ment, is  about  2  to  3  mm.  in  diameter,  diminishes  considerably  in  its  caliber  in 
the  middle  of  the  thorax,  and  is  again  dilated  just  before  its  termination,  the 
ampulla.  It  is  generally  flexuous  in  its  course,  the  older  the  person  the  greater 
the  flexuosity,  and  it  is  constricted  at  intervals  so  as  to  present  a  varicose  appear- 
ance. The  thoracic  duct  not  infrequently  divides  in  the  middle  of  its  course  into 
two  branches  of  unequal  size,  which  soon  reunite,  or  divides  into  several  branches, 
which  form  a  plexiform  interlacement.  It  occasionally  divides,  at  its  upper  part, 
into  two  vessels,  of  which  the  one  on  the  left  side  terminates  in  the  usual  manner, 
while  that  on  the  right  opens  into  the  right  subclavian  vein,  in  connection  with  the 
right  lymphatic  duct.  The  thoracic  duct  has  several  valves  throughout  its  whole 
course,  but  they  are  more  numerous  in  the  upper  than  in  the  lower  part,  and  the 
lower  valves  are  not  competent;  at  its  termination  it  is  provided  with  a  pair  of 
competent  valves,  the  free  borders  of  which  are  turned  toward  the  vein,  so  as  to 
prevent  the  passage  of  venous  blood  into  the  duct. 


Fig.  553. — Modes  of  origin  of  the  thoracic  duct:  a.  Thoracic  duct.  a'.  Receptaculum  chyli.  6,  c.  Efferent  trunks 
from  lateral  aortic  nodes,  d.  An  efferent  passing  through  the  left  crus  of  the  diaphragm,  e,  f.  Lateral  aortic 
nodes,  g.  Preaortic  node.  h.  Retroaortic  node.  i.  Common  intestinal  trunk,  j.  Descending  tributary  from 
intercostal  lymphatics.     (Poirier  and  Charpy.) 

The  receptaculum  chyli  (cisterna  chyli)  (Figs.  552  and  553)  receives  the  two  lumbar 
lymphatic  trunks,  right  and  left,  and  the  intestinal  lymphatic  trunk.  The  lumbar 
lymphatic  trunks  (trunci  lumhales)  are  formed  by  the  union  of  the  efferent  vessels 
from  the  lateral  aortic  lymph  nodes.  They  receive  the  lymph  from  the  lower 
limbs,  from  the  walls  and  viscera  of  the  pelvis,  from  the  kidneys  and  suprarenal 
bodies,  and  the  deep  lymphatics  of  the  greater  part  of  the  abdominal  wall.  The 
intestinal  lymphatic  trunk  (truncus  intestinalis)  receives  the  lymph  from  the 
stomach  and  small  intestine,  from  the  pancreas  and  spleen,  and  from  the  lower 
and  front  part  of  the  liver. 

Tributaries. — Opening  into  the  commencement  of  the  thoracic  duct,  on  either 
side,  is  a  descending  trunk  from  the  posterior  intercostal  nodes  of  the  lower  six 
or  seven  intercostal  spaces.  In  the  thorax  the  duct  is  joined,  on  either  side,  by 
a  trunk  which  drains  the  upper  lumbar  nodes  and  pierces  the  crus  of  the  Dia- 
phragm. It  also  receives  the  efferents  from  the  posterior  mediastinal  nodes  and 
from  the  posterior  intercostal  nodes  of  the  upper  six  left  spaces.  In  the  neck  it 
is  joined  by  the  left  jugular,  left  siibclaman,  and  internal  mammary  trunks,  and  some- 
times by  the  left  hronchoviediastinal  trunk;  the  last  named,  howe^'er,  usually  opens 
independently  into  the  junction  of  the  left  subclavian  and  internal  jugular  Aeins. 


THE  RIGHT  LYMPHATIC  DUCT 


112, 


Structure. — The  thoracic  duet  is  composed  of  three  coats,  which  differ  in  some  respects 
from  those  of  the  lymphatic  vessels.  The  internal  coat  consists  of  a  single  layer  of  flattened 
endothelial  cells;  of  a  subendothelial  layer,  similar  to  I  hut  found  in  the  arteries;  and  an  elastic 
fibrous  layer,  the  fibres  of  which  run  in  a  longitu<linal  liircclion.  Each  endothelial  cell  is  shaped 
like  a  lance-head  and  has  serrated  borders.     The  middle  coat  consists  of  a  longitudinal  layer 


lAL  ARTERY 
VERTEBRAL  VEJN 
THORACrc  DUCT 


Fig.  654. — The  bend  of  the  thoracic  duct  at  its  termination  in  the  subclavian  vein.     (Poirier  and  Charpy.) 


of  white  connective  tissue  with  elastic  fibres,  external  to  which  are  several  laminae  of  muscle 
tissue,  the  fibres  of  which  are  for  the  most  part  disposed  transversely,  but  some  are  oblique  or 
longitudinal.  The  muscle  fibres  are  intermixed  with  elastic  fibres.  The  external  coat  is 
composed  of  areolar  tissue,  with  elastic  fibres  and  isolated  fasciculi  of  nonstriated  muscle  fibres. 


The  Right  Lymphatic  Duct  (Ductus  Lymphaticus  Dexter)  (Figs.  552,  555). 

The  right  lymphatic  duct,  about  half  an  inch  in  length,  courses  along  the  inner 
border  of  the  Scalenus  anticus  at  the  root  of  the  neck  and  terminates  in  the  right 


Fig.  555. — Terminal  collecting  trunks  of  the  right  side :  a.  Jugular  trunk  6.  Subclavian  trunk,  c.  Broncho- 
mediastinal trunk,  d.  Right  lymphatic  trunk,  e.  Node  of  the  internal  mammary  chain,  f.  Node  of  the  deep 
■cervical  chain.      (Poirier  and  Charpy.) 

subclavian  vein  at  its  angle  of  junction  with  the  right  internal  jugular  vein.  The 
orifice  of  the  right  lymphatic  duct  is  guarded  by  two  semilunar  valves,  which 
prevent  the  passage  of  venous  blood  into  the  duct. 

Tributaries. — It  receives  the  lymph  from  the  right  side  of  the  head  and  neck 
through  the  right  jugular  trunk;  from  the  right  upper  extremity  through  the  right 
subclavian  trunk;  from  the  right  side  of  the  thorax,  the  right  lung,  and  right  side 
of  the  heart,  and  from  part  of  the  convex  surface  of  the  liver,  through  the  right 
bronchomediastiiial  trunk.  These  three  collecting  trunks  frecjuently  open  sepa- 
rately in  the  angle  of  union  of  the  two  veins. 


774  THE  VASCULAR  SYSTEMS 

Applied  Anatomy. — Blockage  of  the  thoracic  duct  by  mature  specimens  of  the  minute 
parasitic  worm  Microfilaria  nodurna  gives  rise  to  stasis  of  the  chyle,  and  to  its  passage  in  various 
abnormal  directions  on  its  course  past  the  obstruction.  The  neighboring  abdominal,  renal, 
and  pelvic  lymphatics  become  enlarged,  varicose,  and  tortuous,  and  chyle  may  make  its  way 
into  the  urine  (chyluria),  the  tunica  vaginalis  (chylocele),  the  abdominal  cavity  {chylous  ascites), 
or  the  pleural  cavity  (chylous  pleural  effusion),  in  consequence  of  rupture  of  some  of  these 
distended  lymphatic  vessels. 

The  thoracic  duct  may  be  secondarily  infected  in  intestinal  or  pulmonary  tuberculosis,  and 
may  contain  either  miUary  tubercles,  caseating  tuberculous  masses,  or  even  tuberculous  ulcers. 
It  is  often  the  seat  of  secondary  carcinomatous  deposits  in  cases  of  cancer  of  some  abdominal 
viscus,  becoming  infihrated  throughout  until  it  becomes  a  stiff  moniliform  rod  as  thick  as  a 
pencil,  with  multiple  stenoses  and  dilatations  of  its  lumen;  in  such  cases  the  left  supraclavicular 
nodes  often  become  infected  and  enlarged,  while  the  lungs  remain  entirely  free  from  secondary 
growths. 

LYMPHATICS  OF  THE  HEAD,  FACE,  AND  NECK. 

Intracranial  lymphatics  have  not  been  demonstrated.  It  is  probable,  but  not 
yet  conclusively  demonstrated,  that  the  perivascular  spaces  around  the  cerebral 
arteries  are  the  beginning  of  a  cerebral  lymph  system,  and  that  these  perivascular 
lymph  channels  pass  out  of  the  cranium  with  the  arteries  and  the  internal  jugular 
veins  and  terminate  in  the  superior  deep  cervical  nodes.  It  is  also  probable 
that  lymph  spaces  surround  the  dural  bloodvessels  and  terminate  in  the  superior 
deep  cervical  and  the  internal  maxillary  nodes.  The  lymphatics  of  the  nasal 
fossEe  can  be  injected  from  the  subdural  and  subarachnoid  spaces. 

The  extracranial  lymphatics  are  divided  into  superficial  and  deep,  and  the  two 
systems  freely  communicate.  All  of  these  vessels  run  into  nodes  about  the 
head  and  neck.  The  superficial  lymphatics  take  origin  in  the  subcutaneous 
tissue  and  superficial  muscles.  The  deep  vessels  arise  in  the  orbit,  mouth,  nose, 
pharynx,  oesophagus,  tongue,  larynx,  and  the  muscular,  ligamentous,  and  osseous 
structures. 

The  Lymph  Nodes  of  the  Head  and  Face. 

The  lymphatic  nodes  of  the  head  and  face  are  as  follows: 

1.  The  Occipital. 

2.  The  Posterior  Auricular. 

3.  The  Parotid  and  Subparotid. 

4.  The  Facial. 

5.  The  Internal  Maxillary. 

6.  The  Lingual. 

7.  The  Retropharyngeal. 

The  occipital  nodes  (lymphoglandulae  occipitales)  (Fig.  556),  one  to  three 
in  number,  are  situated  upon  the  occipital  insertion  of  the  Complexus  muscle, 
at  the  lateral  border  of  the  Trapezius,  and  beneath  the  deep  fascia.  Their 
afferents  drain  the  occipital  region  of  the  scalp,  while  their  efferents  pass  to  the 
upper  deep  cervical  nodes. 

The  posterior  auricular  or  mastoid  nodes  (lymphoglandulae  auriculares 
posteriores  (Fig.  556),  usually  two  in  numl>er,  are  situated  upon  the  mastoid 
insertion  of  the  Sternomastoid  muscle.  Their  afferents  drain  the  posterior  part 
of  the  temporoparietal  region,  the  upper  part  of  the  internal  surface  of  the  pinna, 
and  the  posterior  surface  of  the  external  auditory  canal ;  their  efferents  pass  to 
the  upper  deep  cervical  nodes. 

The  parotid  lymph  nodes  {lymphocjlandulae  parotideae)  (Figs.  556  and  557)  are 
divided  into  three  groups,  superficial,  deep,  and  the  subparotid. 


THE  LYMPH  NODES  OF  THE  HEAD  AND  FACE  775 

The  superficial  parotid  or  preauricular  lymph  nodes  {lymphoylandulae  avricvlares 
anteriores)  are  situated  between  the  parotid  fascia  and  the  parotid  sahvary  gland. 


DEEP 
CERVICAL- 
CHAIN 


0  n\/?vw,  6 ^ 


Fig.  556. — General  arrangen 


1'^  of  the  head  and  neck.     (Poirier  and  Charpy.) 


UBMAXILLARY 


NODE  OF 

INTERNAL  JUGULAR 
CHAIN 


Fig.  557. — The  lymphatics  of  the  neck.      (Kuttner.) 


The  deep  parotid  lymph  nodes,  from  fifteen  to  twenty  in  number,  are  embedded 
in  the  substance  of  the  parotid  gland.     The  afferents  of  the  superficial  and  deep 


776 


THE    VASCULAR  SYSTEMS 


parotid  nodes  drain  the  eyelids,  eyebrows,  the  root  of  the  nose,  upper  portion 
of  the  cheek,  frontotemporal  portion  of  the  scalp,  from  the  outer  surface  of  the 
pinna,  from  the  external  auditory  canal,  and  from  the  tympanum.  Their 
efferents  pass  to  the  upper  deep  cervical  nodes. 

The  subparotid  nodes  lie  beneath  the  parotid  gland,  on  the  lateral  wall  of  the 
pharynx,  and  they  are  close  to  the  internal  carotid  artery  and  the  internal  jugular 
vein.  Their  afferents  drain  the  posterior  part  of  the  nasal  fossa,  nasopharynx, 
and  Eustachian  tube;  their  efferents  pass  to  the  upper  deep  cervical  nodes. 

The  facial  nodes  comprise  three  groups  in  the  course  of  the  afferents  of  the 
submaxillary  nodes.  (1)  A  maxillary,  over  the  infraorbital  region;  (2)  a  buccal, 
upon  the  outer  surface  of  the  Buccinator  where  that  muscle  is  pierced  by  the 
parotid  duct;  (3)  a  mandibular  group,  upon  the  outer  surface  of  the  mandible, 
at  the  anterior  margin  of  the  Masseter  muscle,  beneath  the  Platysma  and  in 
contact  with  the  facial  vessels.  Their  afferent  vessels  drain  the  eyelids,  the 
conjunctiva,  integument,  and  mucous  membrane  of  the  nose  and  cheek.  Their 
efferents  pass  to  both  submaxillary  and  upper  deep  cervical  nodes. 

The  internal  maxillary  nodes  (lymphoglandulae  faciales  profundae)  are  deeply 
placed  beneath  the  ramus  of  the  mandible  on  the  outer  surface  of  the  External 


Fig,  558. — The  retropharyngeal  nodes.     (Poirier  and  Charpy.) 

pterygoid,  in  relation  with  the  internal  maxillary  artery.  Their  afferent  vessels 
drain  the  temporal  and  zygomatic  fossae  and  the  nasopharynx;  their  efferents 
pass  to  the  upper  nodes  of  the  deep  cervical  group  and  to  the  submaxillary  nodes. 

The  lingual  nodes  (lymqihoglandulae  lingitales)  are  two  or  three  small  nodules 
lying  on  the  Hyoglossus  and  under  the  Geniohyoglossus.  They  form  merely  nodal 
substations  in  the  course  of  the  lymphatic  vessels  of  the  tongue. 

The  retropharyngeal  nodes  (Fig.  558)  lie  in  the  buccopharyngeal  fascia, 
behind  the  upper  part  of  the  pharynx  and  in  front  of  the  arch  of  the  atlas,  being 
separated,  however,  from  the  latter  by  the  Rectus  capitis  anticus  major.  Their 
afferents  drain  an  extensive  area,  comprising  the  nasal  fossae,  the  nasopharynx, 
and  the  Eustachian  tube  as  far  as  the  tympanum;  their  efferents  pass  to  the 
upper  nodes  of  the  deep  cervical  group. 

The  lymphatic  vessels  of  the  scalp  are  divisible  into  (a)  those  of  the  frontal 
region,  which  terminate  in  the  parotid  nodes;  ih)  those  of  the  temporoparietal 
region,  which  end  in  the  parotid  and  postauricular  nodes;  and  (c)  those  of  the 


THE  LYMPH  NODES  OF  THE  HEAD  AND  FACE  777 

occipital  region,  which  terminate  partly  in  the  occipital  nodes  and  partly  in  a 
trunk  which  runs  down  along  the  posterior  border  of  the  Sternomastoid  to  end 
in  the  lower  group  of  deep  cervical  nodes. 

The  lymphatic  vessels  of  the  pinna  and  external  auditory  meatus  are  also  divisible 
into  three  groups:  (a)  an  anterior,  from  the  outer  surface  of  the  pinna  and  anterior 
wall  of  the  canal  to  the  parotid  nodes;  {h)  a  posterior,  from  the  margin  of  the 
pinna,  the  upper  part  of  its  inner  surface,  the  internal  surface  and  posterior  wall 
of  the  meatus  to  the  postauricular  and  upper  deep  cervical  nodes ;  (c)  an  inferior, 
from  the  floor  of  the  canal  and  from  the  lobule  to  the  external  jugular  and  upper 
deep  cervical  nodes. 

The  lymphatic  vessels  of  the  face  are  more  numerous  than  those  of  the  scalp. 
Those  from  the  eyelids  and  conjunctivae  terminate  partly  in  the  submaxillary, 
but  mainly  in  the  parotid  nodes.  The  vessels  from  the  posterior  part  of  the 
cheek  also  pass  to  the  parotid  nodes,  while  those  of  the  anterior  portion  of  the 
cheek,  the  side  of  the  nose,  the  upper  lip,  and  the  lateral  portions  of  the  lower 
lip  terminate  in  the  submaxillary  nodes.  The  deeper  vessels  from  the  temporal 
and  zygomatic  fossag  pass  to  the  internal  maxillary  and  upper  deep  cervical 
nodes.  The  deeper  vessels  of  the  cheek  and  lips  terminate,  like  the  superficial, 
in  the  submaxillary  nodes.  Both  superficial  and  deep  vessels  of  the  central 
part  of  the  lower  lip  run  to  the  suprahyoid  nodes. 

The  lymphatic  vessels  of  the  nasal  fossae  can  be  injected  from  the  subdural  and 
subarachnoid  spaces.  Those  from  the  anterior  parts  of  the  fossae  terminate 
in  the  submaxillary  nodes;  those  from  the  posterior  two-thirds  of  the  fossae  and 
from  the  communicating  air  sinuses  pass  partly  to  the  retropharyngeal  nodes 
and  partly  to  the  upper  deep  cervical  nodes. 

The  lymphatic  vessels  of  the  mouth  terminate  as  follows:  (a)  Those  of  the  gums 
terminate  in  tlie  submaxillary  nodes;  (b)  those  of  the  hard  palate  terminate  in 
the  upper  deep  cervical  and  subparotid  nodes;  (c)  those  of  the  soft  palate,  in  the 
retropharyngeal  and  upper  deep  cervical  nodes;  (d)  those  of  the  anterior  part  of 
the  floor  of  the  mouth  pass  through  the  submental  and  suprahyoid  nodes  to  the 
upper  deep  cervical  group;  (e)  those  from  the  rest  of  the  floor  of  the  mouth  ter- 
minate in  the  submaxillary  and  upper  deep  cervical  nodes. 

The  lymphatic  vessels  of  the  tongue  (Fig.  559)  are  drained  chiefly  into  the  deep 
cervical  nodes  lying  between  the  posterior  belly  of  the  Digastric  and  the  posterior 
belly  of  the  Omohyoid;  one  node  situated  at  the  bifurcation  of  the  common 
carotid  artery  is  so  intimately  associated  with  these  vessels  that  it  is  known  as 
the  principal  node  of  the  tongue.  The  apical  vessels  of  the  tongue  pass  to  the 
suprahyoid  nodes  and  principal  node  of  the  tongue;  the  marginal  vessels  pass 
partly  to  the  submaxillary  and  partly  to  the  upper  deep  cervical  nodes.  The 
base  of  the  tongue  in  the  region  of  the  circumvallate  papillae  is  drained  by  vessels 
which  terminate  in  the  upper  deep  cervical  nodes. 

The  lymph  nodes  of  the  neck  include  the  following  groups: 

I.  The  Superficial  Cervical,  including — 
(a)  External  Jugular. 

(6)  Anterior  Cervical  (superficial). 

(c)  Submaxillary. 

(f^)  Submental  or  Suprahyoid. 

II.  The  Deep  Cervical,  including — 
(a)  Anterior  Cervical  (deep). 

(6)  Retropharyngeal. 

(c)  Sternomastoid. 

(d)  Supraclavicular. 

The  superficial  cervical  nodes  {hjmphoriktndulaecervicalessiiperficialcs)  (Fig.  557) 
are  composed  of  two  groups,  the  external  jugular  and  the  anterior  cervical  nodes. 


778  THE  VASCZILAM  SYSTEMS 

The  external  jugular  nodes  (Figs.  557  and  560)  are  superficial  to  the  Sterno- 
mastoid  muscle.  They  are  four  to  six  in  number  and  lie  along  the  external 
jugular  vein  upon  the  outer  surface  of  the  deep  cervical  fascia,  each  node  occupy- 
inc-  a  depression  in  the  fascia.  They  are  usually  gathered  in  a  group  a  little  below 
the  parotid  gland,  but  sometimes  extend  to  the  middle  of  the  vein.  Their  afferents 
drain  the  lower  part  of  the  pinna  and  parotid  region,  while  their  efferents  pass 
around  the  anterior  margin  of  the  Sternomastoid  and  terminate  in  the  upper  deep 
cervical  nodes. 


MARGINAL  COL- 
LECTING TRUNKS 

TRUNKS  OF 


^  TRUNKS  FROM 
r  MARGIN  OF 
J  TONGUE 


Fig.  559.— The  lymphatics  of  the  tongue,  lateral  view.      (Poirier  and  Charpy.) 


The  submaxillary  nodes  (lympJioglandulae  submaxillar es)  (Figs.  556  and 
557),  three  to  sLx  in  number,  are  placed  in  the  submaxillary  triangle  beneath 
the  body  of  the  mandible  in  the  submaxillary  triangle  and  rest  on  the  superficial 
surface  of  the  sheath  of  the  submaxillary  gland.  One  node  (the  middle  gland 
of  Stahr),  which  lies  on  the  facial  artery  as  it  turns  over  the  mandible,  is  the  most 
constant  of  the  series.  Small  lymph  nodes  are  sometimes  found  on  the  deep 
surface  of  the  submaxillary  gland.  Their  afi'erents  drain  the  inner  canthus  of 
the  eye,  the  cheek,  the  side  of  the  nose,  the  upper  lip,  the  outer  part  of  the  lower 
lip,  the  gums,  and  the  anterior  part  of  the  margin  of  the  tongue;  efferent  vessels 
from  the  facial  and  suprahyoid  nodes  also  enter  the  submaxillary  nodes.  Their 
efferent  vessels  pass  to  the  upper  nodes  of  the  deep  cervical  group. 


THE  LYMPH  NODES  OF  THE  HEAD  AND  FACE 


779 


The  submental  or  suprahyoid  nodes  (Figs.  556  and  559)  are  usually  two 
nodes  situated  between  the  anterior  bellies  of  the  two  Digastric  muscles  and 
upon  the  IMylohyoid  muscle.  They  receive  lymph  from  the  cutaneous  surface 
of  the  ch.in,  from  the  cutaneous  and  mucous  surfaces  of  the  central  portion  of 
the  lower  lip,  from  the  central  portion  of  the  gums,  from  the  floor  of  the  mouth, 
and  from  the  tip  of  the  tongue.  They  send  some  vessels  to  the  submaxillary 
lymph  nodes,  and  frequently  a  node  is  interposed  on  the  anterior  belly  of  the 
Digastric  muscle.     They  send  other  vessels  to  the  upper  deep  cervical  nodes. 

The  anterior  cervical  nodes  form  an  irregular  and  inconstant  group  on  the 
front  of  the  larynx  and  trachea.  They  may  be  divided  into  (a)  a  superficial 
set,  placed  on  the  anterior  jugular  vein;  (6)  a  deeper  set,  which  is  further  sub- 
divided into  prelaryngeal,  on  the  cricothyroid  membrane,  and  pretracheal,  on 
the  front  of  the  trachea.  The  superficial  set  receives  lymph  from  the  posterior 
auricular  and  occipital  nodes;  their  efferents  empty  into  the  upper  deep  cervical 
nodes.  The  deeper  set  drains  the  lower  part  of  the  larynx,  the  thyroid  body,  and 
the  upper  part  of  the  trachea;  their  efferents  pass  to  the  lower  nodes  of  the  upper 
deep  cervical  group. 

The  retropharyngeal  nodes  have  been  described  on  page  776. 


MASTOID    NODES 


,      STERNOMA5TOID 

-i^NODE  (extcmul 
If    group) 


I.  JUGULAR 


Fig.  560.— Deep  cervical  ch.ain.     (Po 


The  deep  cervical  nodes  (lymphoglandulae  cervicales  profimdae)  (Figs.  556 
and  560)  are  nimaerous  and  of  large  size;  they  form  a  chain  along  the  carotid 
sheath  lying  by  the  side  of  the  pharynx,  oesophagus,  and  trachea,  and  extending 
from  the  base  of  the  skull  to  the  root  of  the  neck.  They  are  usually  described 
in  two  groups:  (1)  an  upper  or  substemo mastoid  group  {lymphoglandulae  cervi- 
cales profimdae  superiores)  lying  under  the  Sternomastoid  in  close  relation  with 
the  spinal  accessory  nerve  and  the  internal  jugular  vein,  some  of  the  nodes  lying 
in  front  of  and  others  behind  the  vessel;  (2)  a  lower  or  supraclavicular  group  (lympho- 
glandulae cervicales  profundae  inferiores)  extending  beyond  the  posterior  margin 
of  the  Sternomastoid  into  the  supraclavicular  triangle,  where  they  are  closely 
related  to  the  brachial  plexus  and  subclavian  vein.  A  few  minute  nodes  are 
situated  alongside  the  recurrent  laryngeal  nerves  on  the  lateral  aspects  of  the; 
trachea  and  oesophagus.  The  upper  deep  cervical  nodes  drain  the  occipital 
portion  of  the  scalp,  the  pinna,  and  the  back  of  die  neck,  the  tongue,  larynx, 
thyroid  body,  trachea,  nasopharynx,  nasal  fossEe,  palate,  and  oesophagus.     They 


780  THE  VASCULAR  SYSTEMS 

receive  also  the  efferent  vessels  from  all  the  other  nodes  of  the  head  and  neck, 
except  those  from  the  lower  deep  cervical  group.  The  lower  deep  cervical  nodes 
drain  the  back  of  the  scalp  and  neck,  the  superficial  pectoral  region,  part  of 
the  arm  (see  page  783),  and  occasionally  part  of  the  upper  surface  of  the  liver. 
In  addition,  they  receive  vessels  from  the  upper  group.  The  efferents  of  the  upper 
deep  cervical  nodes  pass  partly  to  the  lower  group  and  pardy  to  a  trunk  which 
unites  with  the  efferent  trunk  of  the  lower  deep  cervical  nodes  and  forms  the 
jugular  trunk  {truncus  jugularis).  This  trunk,  on  the  right  side,  ends  in  the  junc- 
tion of  the  internal  jugular  and  subclavian  veins,  while  on  the  left  side  it  joins 
the  thoracic  duct. 

The  lymphatic  vessels  of  the  skin  and  muscles  of  the  neck  pass  to  the  deep  cervical 
nodes.  From  the  upper  part  of  the  pharynx  the  lymphatic  vessels  pass  to  the 
retropharyngeal,  from  the  lower  part  to  the  deep  cervical  nodes.  From  the 
larynx  two  sets  of  vessels  arise,  an  upper  and  a  lower.  The  vessels  of  the  upper 
set  pierce  the  thyrohyoid  membrane  and  join  the  upper  deep  cervical  nodes. 
Of  the  lower  set,  some  pierce  the  cricothyroid  membrane  and  join  the  pretracheal 
and  prelaryngeal  nodes;  others  run  between  the  cricoid  and  first  tracheal  ring 
and  enter  the  lower  deep  cervical  nodes.  The  lymphatic  vessels  of  the  thyroid 
body  consist  of  two  sets,  an  upper,  which  accompanies  the  superior  thyroid  artery 
and  enters  the  upper  deep  cervical  nodes,  and  a  lower,  which  runs  partly  to  the 
pretracheal  and  partly  to  the  small  nodes  which  accompany  the  recurrent  laryn- 
geal nerve.  These  latter  nodes  receive  also  the  lymphatic  vessels  from  the  cervical 
portion  of  the  trachea. 

Applied  Anatomy. — The  cervical  nodes  are  very  frequently  the  seat  of  tuberculous  dis- 
ease. This  condition  is  most  usually  set  up  by  some  lesion  in  those  parts  from  which  they  receive 
their  lymph.  It  is  very  desirable,  therefore,  that  the  surgeon,  in  dealing  with  these  cases,  possess 
a  knowledge  of  the  relation  of  the  respective  groups  of  nodes  to  the  periphery,  while  in  order  to 
eradicate  them  by  operation  a  long  and  difficult  dissection  may  be  required.  Sir  Frederick 
Treves  prepared  a  table  to  show  to  what  group  lymph  from  each  region  is  sent.  The  table  is 
practically  as  follows:  ■        i        .      i 

Sfo/p— Posterior  part  =  suboccipital  and  mastoid  nodes.  Frontal  and  parietal  portions  = 
parotid  nodes. 

Lymphatic  vessels  from  the  scalp  also  enter  the  superficial  cervical  set  of  nodes. 

Skin  of  face  and  neck  =  submaxillary,  parotid,  and  superficial  cervical  nodes. 

External  ear  =  superficial  cervical  nodes. 

Lower  lip  =   submaxillary  and  suprahyoid  nodes. 

Buccal  cavity  =  submaxillary  and  upper  set  of  deep  cervical  nodes. 
■    Gums  of  lower  jaw  =  suhmaniWavy  nodes. 

Tongue — Anterior  portion  =  suprahyoid  and  submaxillary  nodes.  Posterior  portion  = 
upper  set  of  deep  cervical  nodes. 

Tonsils  and  palate  =  upper  set  of  deep  cervical  nodes. 

Pharynx. — Upper  part  =  parotid  and  retropharyngeal  nodes.  Lower  part  =  upper  set  of 
deep  cervical  nodes. 

Larynx,  orbit,  and  roof  of  mouth  =  upper  set  of  deep  cervical  nodest 

Nasal  fossce  =  retropharyngeal  nodes,  upper  set  of  deep  cervical  nodes.  Some  lymphatic 
vessels  from  posterior  part  of  the  fossse  enter  the  parotid  nodes. 

Treves'  table  indicates  the  nodes  usually  involved,  but  the  seat  of  primary  disease  cannot 
invariably  be  affirmed  from  a  knowledge 'of  the  seat  of  glandular_  involvement,  because  the 
course  of  the  lymphatic  vessels  is  sometimes  varied  from  that  which  usually  maintains;  for 
instance,  in  sorne  cases  lymphatics  from  the  right  side  of  the  tongue  pass  to  nodes  in  the  left 
side  of  the  neck. 

A  retropharyngeal  abscess  begins  laterad  of  the  pharynx.  It  enlarges  toward  the  centre  rather 
than  from  it,  because  the  Constrictors  of  the  pharynx  limit  the  outward  progTcss  of  the  pus. 

The  nodes  withiii  the  parotid  salivary  glands  not  unusually  become  tuberculous,  and  the 
surgeon  may  be  led  to  believe  that  the  salivary  gland  is  the  seat  of  primary  disease. 

Sometimes,  though  seldom,  after  the  extensive  removal  of  lymph  nodes  the  region  drained 
by  their  tributaries' becomes  the  seat  of  persistent  hard  edema  (lymph  edema).  It  used  to  be 
thought  that  wounds  of  the  thoracic  duct  were  of  necessity  fatal,  but  it  is  now  loiown  that,  unless 
close"to  the  vein,  they  are  seldom  even  very  dangerous.  It  may  be  possible  to  suture  a  partly 
divided  duct.  In  an  unsutured  wound  of  the  duct  recovery  follows  if  a  collateral  lymphatic 
circulation  is  established. 


THE  LYMPH  NODES  OF  THE  UPPER  EXTREMITY  781 

THE  LYMPHATICS  OF  THE  UPPER  EXTREMITY. 


The  Lsrmph  Nodes  of  the  Upper  Extremity. 

The  lymph  nodes  of  the  upper  extremity  are  divided  into  two  sets,  superficial 
and  deep. 


Axillary  nodes. 


X.,.  ^i^- 


Fig.  561, — The  superficial  Iwiipbatics  and  nodes  of  the  upper  extremity. 

The  superficial  Ijonph  nodes  (Fig.  561)  of  the  upper  extremity  are  few  in 
number  and  small  in  size.  They  lie  in  the  subcutaneous  tissue.  They  are  not 
receiving  depots  of  great  areas,  but  interrupt  lymphatic  vessels  here  and  there. 
The  nodes  in  the  axilla  receive  all  of  the  lymphatic  vessels,  superficial  and  deep. 

There  may  be  three  sets  of  superficial  nodes.  One  set,  the  antecubital  nodes,  lie 
in  front  of  the  elbow.  These  nodes  are  often  absent.  When  these  nodes  are  pres- 
ent they  receive  vessels  from  the  anterior  portion  of  the  forearm  and  the  middle 


782 


THE  VASCULAR  SYSTEMS 


of  the  palm.  The  vessels  from  them  pass  along  the  front  and  inner  aspect  of  the 
arm. 

One  or  two  superficial  nodes  lie  above  the  internal  condyle.  This  is  the 
supratrochlear  or  epitrochlear  group  of  nodes.  There  is  usually  but  one  node,  but 
there  may  be  two  or  more.  It  receives  vessels  from  the  three  inner  fingers,  the 
inner  portion  of  the  hand,  and  the  inner  portion  of  the  forearm,  but,  because 
of  free  anastomoses,  also  may  receive  lymph  from  any  portion  of  the  hand  and  fore- 
arm. Lymph  vessels  from  the  supratrochlear  node  pass  up  along  the  basilic 
vein  to  the  axillary  nodes. 

There  are  sometimes  several  small  nodes  along  the  cephalic  vein  in  the  groove 
between  the  Deltoid  and  the  great  Pectoral  muscle.  These  are  called  infra- 
clavicular nodes,  the  efferents  of  which  drain  into  the  subclavian  nodes. 


IN     EXTERNAL  GRO 

EXTE 


MAMMARY  LYMPHATIC 
ENDING  IN  SUB- 
CLAVIAN NODES 


PECTORAL 

GROUP 
MAMMARY  COL- 
LECTING TRUNKS 


CUTANEOUS  COLLECTING 

TRUNK  FROM  THE 

THORACIC  WALL 


LLECTING  TRUNKS 
SSING  TO  INTERNAL 
AMMARY  NODES 


Fig.  562. — Axillary  nodes  and  lymphatics  of  the  breast.      (Poirier  and  Charpy.) 

The  Deep  Lyniph  Nodes  of  the  Upper  Extremity  or  the  Axillary  Nodes 

(lymphoglandulae  axillares)  (Figs.  562  and  563). — The  chief  deep  nodes  are  situ- 
ated adjacent  to  the  axillary  vessels.  There  are  also  a  few  small  nodes  along 
the  radial,  ulnar,  and  brachial  arteries  which  receive  deep  lymphatics  from  bones, 
muscles,  and  ligaments,  and  send  lymphatics  to  the  axillary  nodes.  The  axillary 
nodes  number  from  fifteen  to  thirty-five  in  each  axilla.  They  are  embedded 
in  the  axillary  fat  and  receive  the  lymphatic  vessels  from  the  upper  extremity, 
from  the  skin  of  the  upper  portion  of  the  thorax,  from  the  Pectoral  muscles,  and 
from  the  mammary  gland.     They  may  be  arranged  in  the  following  groups: 

(1)  An  external  group,  the  humeral  chain,  lying  on  the  inner  surface  of  the  vessels 
and  nerves,  particularly  the  axillary  vein,  to  the  sheath  of  which  they  are  adherent. 
Occasionally  one  or  several  of  these  nodes  are  found  beneath  the  vein.  Some 
of  the  vessels  from  these  nodes  pass  into  the  central  group  of  lymph  nodes;  others 
enter  the  subclavian  nodes;  others  pass  above  the  clavicle  and  terminate  in  nodes 
situated  in  that  region.  (2)  An  anterior  or  pectoral  group  (lymphoglaiididae 
pectorales),  situated  along  the  lower  border  of  the  Pectoralis  minor  and  in  relation 


THE  L  YMPH  NODES  OF  THE   UPPER  EXTREMITY  783 

with  the  long  thoracic  artery.  The  afierents  of  this  group  drain  the  skin  and 
muscles  of  the  pectoral  and  subaxillary  regions  of  the  thorax  and  part  of  the 
mammary  gland;    their  eft'erents  pass  to  the  central   and  subclavicular  nodes. 

(3)  A  posterior  group,  the  subscapular  chain,  lying  along  the  subscapular  artery. 
Their  afferents  drain  the  skin  and  muscles  of  the  lower  part  of  the  neck  and  of  the 
posterior  thoracic  wall;  their  ett'erents  pass  to  the  central  axillary  group  of  nodes. 

(4)  A  central  or  intermediate  group  of  three  or  four  large  nodes  situated  in  the  adi- 
pose tissue  near  the  base  of  the  axilla,  their  afferents  draining  all  the  preceding 
groups  of  axillary  nodes;  their  efferent  vessels  end  in  the  subclavicular  nodes. 
The  nodes  of  the  central  group  in  many  individuals  protrude  through  the  opening 
in  the  axillary  fascia  known  as  the  foramen  of  Langer.  (5)  A  subclavian  group, 
situated  behind  the  upper  margin  of  the  Pectoralis  minor.  From  the  axillary 
nodes  come  many  vessels  which,  by  anastomosing,  form  the  infraclavicular  plexus; 
they  then  unite  into  a  trunk,  the  subclavian  trunk  {truncus  subclavius),  which 
courses  between  the  subclavian  vein  and  Subclavius  muscle.  On  the  right  side 
it  empties  into  the  junction  of  the  internal  jugular  and  subclavian  vein  or  unites 
with  the  jugular  trunk  to  form  the  right  lymphatic  duct.  On  the  left  side  it  may 
empty  into  the  venous  junction  or  into  the  thoracic  duct. 


PECTORAL  GROUP 


Fig.  563. — Scheme  of  the  axillary  nodes.     The  dotted  line  indicates  the  position  of  the  clavicle. 


The  Lymphatic  Vessels  of  the  Upper  Extremity  (Figs.  561,  564). 

The  lymphatic  vessels  of  the  upper  extremity  are  divided  into  the  superficial 
and  the  deep. 

The  superficial  lymphatic  vessels  of  the  upper  extremity  begin  as  plexuses 
in  the  skin  and  form  vessels  which  ascend  in  the  subcutaneous  tissue.  These 
plexuses  are  particularly  plentiful  in  the  palm  and  palmar  surface  of  the  digits 
(Fig.  564).  On  each  side  of  each  finger  two  lymph  vessels  are  formed;  they 
ascend  toward  the  hand,  cross  the  dorsum,  and  anastomose  frecjnently  with  each 
other.  The  vessels  from  the  dorsum  of  the  hand  join  the  lymph  vessels  of  the 
forearm,  which  ascend  chiefly  along  the  superficial  veins.  The  lymph  vessels 
which  ascend  with  the  superficial  ulnar  vein  pass  into  the  supratrochlear  node. 
The  vessels  which  accompany  the  median  veins  pass  into  the  antecubital  or 
supratrochlear  nodes.  Some  of  the  lymph  vessels  on  the  radial  side  of  the  fore- 
arm run  up  along  the  cephalic  vein  and  terminate  in  the  infracla^'icular  nodes. 
All  the  other  lymph  vessels  of  the  upper  extremity  pass  direct  to  the  axillary 


784 


THE  VASCULAR  SYSTEMS 


nodes.     In  the  forearm  there  are  about  thirty  vessels,  in  the  middle  of  the  arm 

there  are  from  fifteen  to  eighteen  (Sappey). 
The  deep  lymphatic  vessels  of  the  upper  extremity  convey  the  lymph  from 

bone,  periosteum,  muscle,  ligament,  etc.     They  pass  up  the  limb  with  the  chief 

vessels,  there  usually  being  two  trunks  to  each  artery.     In  the  arm  there  are 

two  or  three  vessels.  Some  few 
vessels  terminate  in  the  small  nodes 
along  the  radial,  ulnar,  and  brach- 
ial arteries,  but  most  of  them  pass 
directly  to  the  axillary  nodes. 

Applied  Anatomy.  —  In  malignant 
diseases,  or  other  affections  implicating 
the  upper  part  of  the  back  and  shoulder, 
the  front  of  the  thorax  and  mammae,  the 
upper  part  of  the  front  and  side  of  the 
abdomen,  or  the  hand,  forearm,  or  arm, 
the  axillary  nodes  are  liable  to  be  found 
enlarged. 

In  secondary  syphilis 'the  supratroch- 
lear node  is  found  to  be  enlarged.  This 
node  is  subcutaneous  and  readily  palpa- 
ble against  the  subjacent  bone  when 
enlarged.  Normal  axillary  nodes  cannot 
be  palpated.  The  axilla  is  a  passage- 
way for  structures  between  the  neck  or 
thorax  and  the  upper  extremity,  and 
purulent  collections  or  tumors  may  extend 
from  the  neck  or  thorax  into  the  axilla  or 
from  the  axiUa  into  the  neck  or  thorax. 

The  axillary  nodes  are  involved  early 
in  cases  of  cancer  of  the  mammary  gland, 
and  later  the  lower  deep  cervical  nodes 
are  involved,  and,  as  Snow  has  pointed 
out,  regurgitation  of  lymph  containing 
cancer  cells  leads  to  retrosternal  involve- 
ment and  to  secondary  cancer  of  the  head 
of  the  humerus.  In  operating  for  cancer 
of  the  breast,  follow  the  principle  of  Hal- 
sted  and  remove  the  breast,  the  skin  over 
it,  the  muscles  and  fascia,  the  lymph 
vessels,  and  the  axillary  nodes  in  one 
piece.  By  this  plan  thorough  removal  is  possible,  and  as  lymph  vessels  containing  carcinoma 
cells  are  not  cut  across,  the  wound  is  not  grafted  with  malignant  epithelial  cells.  Diseased 
axillary  nodes  are  apt  to  adhere  to  the  sheath  of  the  vein.  In  removing  cancerous  nodes 
always  excise  the  sheath  of  the  vein. 


Fig.  564.- 


-Lymphatic  vessels  of  the  dorsal  surface  of  the 
hand.      (Sappey.) 


THE  LYMPHATICS  OF  THE  LOWER  EXTREMITY. 


The  Lymph  Nodes  of  the  Lower  Extremity. 

The  lymph  nodes  of  the  lower  extremity  consist  of  the  anterior  tibial  node  and 
the  popliteal  and  inguinal  nodes,  all  deeply  situated. 

The  anterior  tibial  node  (lynrphoc/Iandida  tibialis  anterior)  is  small  and  lies 
on  the  interosseous  membrane  in  relation  to  the  upper  part  of  the  anterior  tibial 
vessels,  and  constitutes  a  substation  in  the  course  of  the  anterior  tibial  lymphatic 
trunks.  Its  efferents  cross  to  the  inner  side  of  the  leg  just  below  the  knee  and  pass 
to  the  superficial  inguinal  nodes. 

The  popliteal  nodes  (lymphoglandulae  popliteae),  small  in  size  and  some  six 
or  seven  in  number,  are  embedded  in  the  fat  contained  in  the  popliteal  space. 


'THE  LYMPH  NODES  OF  THE  LOWER  EXTREMITY 


785 


One  lies  immediately  beneath  the  popliteal  fascia,  near  the  terminal  part  of  the 
external  saphenous  vein,  and  drains  the  region  from  which  this  vein  derives  its 
tributaries.  Another  is  placed  between  the  popliteal  artery  and  the  posterior 
ligament  of  the  knee;  it  receives  the  lymphatic  vessels  from  the  knee-joint 
together  with  those  which  accompany  the  articular  arteries.  The  others  lie 
at  the  sides  of  the  popliteal  vessels,  and  receive  as  afferents  the  trunks  which 
accompany  the  anterior  and  posterior  tibial  vessels.  The  efferents  of  the  pop- 
liteal nodes  pass  almost  entirely  alongside  of  the  femoral  vessels  to  the  deep 
inguinal  nodes,  but  a  few  may  accompany  the  internal  saphenous  vein,  and  end 
in  the  nodes  of  the  superficial  inguinal  group. 

The  inguinal  nodes  vary  from  twelve  to  twenty  in  number  and  are  arranged 
in  two  groups,  superficial  and  deep. 


Fig.  565. — Nodes  of  the  inguinal  region  with  the  afferent  and  some  of  the  efferent  lymphatics. 
(Poirier  and  Charpy.) 


The  superficial  inguinal  lymph  nodes  (Figs.  565  and  566),  placed  immediately 
beneath  the  superficial  fascia  in  Scarpa's  triangle,  are  of  large  size,  and  vary  in 
number  from  ten  to  twenty.  It  is  customary  to  divide  these  nodes  into  groups 
according  to  the  region  in  which  they  are  found.  A  horizontal  line  carried  through 
the  saphenous  opening  divides  the  nodes  into  two  groups,  a  superior  group  and  an 
inferior  group.  The  nodes  of  the  superior  group  (lymphoglandulae  ingumales) 
form  a  chain  immediately  below  Poupart's  ligament.  They  ^ecei^'e  as  afferents 
lymphatic  vessels  from  the  integument  of  the  penis,  scrotum,  perineum,  buttock, 
and  lower  abdominal  wall.  The  nodes  of  the  inferior  group  (lymphoglandulae 
suhinguinales)  are  placed  on  either  side  of  the  upper  part  of  the  saphenous  vein, 
and  receive  as  afferents  the  lymphatic  vessels  of  the  lower  extremity  and  also 
some  lymphatics  from  the  penis,  scrotum,  clitoris,  labia,  perineum,  and  buttock. 

50 


786 


THE  VASCULAR  SYSTEMS 


Fig.  566. — The  superficial  lymphatics  and  nodet 
of  the  lower  extremity. 


The  deep  inguinal  nodes  (lymphoglan- 
dulae  suhinc/uinales  profundae)  (Fig.  565) 
vary  from  one  to  three  in  number,  and 
are  placed  under  the  fascia  lata,  on  the 
inner  side  of  the  femoral  vein.  When 
three  are  present,  the  lowest  is  situated 
just  below  the  junction  of  the  internal 
saphenous  and  femoral  veins,  the  middle 
in  the  femoral  (crural)  canal,  and  the 
highest  in  the  outer  part  of  the  femoral 
ring.  The  middle  is  the  most  incon- 
stant of  the  three,  but  tlie  highest  one, 
tlie  node  of  Cloquet,  or  Rosenmiiller,  is 
also  frequently  absent.  They  receive  as 
afferents  the  deep  lymphatic  trunks 
which  accompany  the  femoral  vessels, 
the  lymphatics  from  the  glans  penis  or 
glans  clitoridis,  and  also  some  efferents 
from  the  superficial  inguinal  nodes. 

Applied  Anatomy. — Inflammation  and  sup- 
puration of  the  popliteal  nodes  are  most  com- 
monly due  to  a  sore  on  the  outer  side  of  the 
heel. 

The  inguinal  nodes  frequently  become  en- 
larged in  diseases  implicating  the  parts  from 
which  their  lymphatics  originate.  Thus,  in 
malignant  or  syphilitic  affections  of  the  prepuce 
and  penis,  or  labia  majora,  in  cancer  scroti,  in 
abscess  in  the  perineum,  or  in  similar  diseases 
affecting  the  integument  and  superficial  struc- 
tures in  those  parts,  or  the  subumbilical  part 
of  the  abdominal  wall,  or  the  gluteal  region, 
the  upper  chain  of  nodes  is  almost  invariably 
enlarged,  the  lower  chain  being  implicated  in 
diseases  affecting  the  lower  limb. 


The  Lymphatic  Vessels  of  the  Lower 
Extremity. 

The  lymphatic  vessels  of  the  lower 
extremity  consist  of  two  sets,  superficial 
and  deep,  and  in  their  distribution  corre- 
spond closely  with  the  veins. 

The  superficial  lymphatic  vessels  of 
the  lower  extremity  are  placed  beneath 
the  integument  in  the  superficial  fascia, 
and  are  divisible  into  three  sets — trunks 
which  follow  the  course  of  the  internal 
saphenous  vein,  trunks  which  accompany 
the  external  saphenous,  and  trunks  from 
the  gluteal  region.  (1)  Trunks  which  fol- 
low the  course  of  the  internal  saphenous 
vein  arise  from  a  plexus  on  the  dorsum 
of  the  foot,  which  plexus  obtains  lym- 
phatics from  all  the  toes,  the  sole,  and  both 


THE  LYMPHATICS  OF  THE  PELVIS  AND  ABDOMEN        787 

borders  of  the  foot.  The  internal  trunks,  three  or  four  in  number,  pass  to  the 
superficial  inguinal  nodes.  The  external  trunks  run  upward  and  inward  and 
end  in  the  internal  trunks.  (2)  The  trunks  which  follow  the  external  saphenous 
vein  numlter  two  or  three,  and  they  take  origin  from  the  heel  and  from  the  posterior 
half  of  the  outer  edge  of  the  foot.  They  empty  into  the  superficial  inguinal 
nodes.  (3)  The  lymph  trunks  from  the  gluteal  region  join  vessels  from  the  anus 
a-nd  enter  the  superficial  inguinal  nodes. 

The  deep  lymphatic  vessels  of  the  lower  extremity  are  few  in  number,  and 
accompany  tiie  deep  bloodvessels.  In  the  leg  they  consist  of  three  sets,  the  anterior 
tibial,  peroneal,  and  posterior  tibial,  which  accompany  the  corresponding  blood- 
vessels, two  or  three  to  each  artery;  they  ascend  with  the  bloodvessels  and  enter 
the  lymph  nodes  in  the  popliteal  space;  the  efferent  vessels  from  these  nodes 
accompany  the  femoral  vein  and  join  the  deep  inguinal  nodes;  from  these  nodes 
vessels  pass  beneath  Poupart's  ligament  and  communicate  with  the  chain. of  nodes 
surrounding  the  external  iliac  vessels.  The  deep  lymphatic  vessels  of  the  gluteal 
and  sciatic  regions  follow  the  course  of  the  bloodvessels,  and  join  the  gluteal  and 
sciatic  nodes  at  the  great  sacrosciatic  foramen. 


THE  LYMPHATICS  OF  THE  PELVIS  AND  ABDOMEN. 

The  lymphatics  of  the  pelvis  and  abdomen  may  be  divided  from  their  situation 
into  (a)  parietal,  lying  retroperitoneally  and  in  close  association  with  the  larger 
bloodvessels;  and  (6)  visceral,  which  are  found  in  relation  to  the  visceral  arteries. 

The  parietal  nodes  (Fig.  567)  include  the  following  groups: 

External  iliac.  (  Lateral  aortic. 

Internal  iliac.  Lumbar  <    Preaortic. 

Common  iliac.  (  Retroaortic. 

The  external  iliac  nodes  form  three  chains  around  the  external  iliac  vessels. 
An  external  chain  of  three  or  four  nodes  lies  between  the  artery  and  the  Psoas 
muscle.  A  middle  chain  of  three  nodes  lies  upon  the  front  surface  of  the  external 
iliac  vein.  An  internal  chain  of  three  or  four  nodes  is  placed  to  the  inner  side 
of  the  external  iliac  vein.  An  obturator  node  belongs  to  the  inner  chain  of  external 
iliac  nodes.  The  external  iliac  nodes  receive  vessels  from  the  superficial  and 
deep  inguinal  nodes,  from  the  glans  penis  or  glans  clitoris,  deep  lymphatics  from 
the  umbilicus  and  lower  part  of  the  belly  wall,  vessels  from  the  superior  portion 
of  the  vagina,  the  uterine  cervix,  the  prostate  gland,  the  bladder,  the  membranous 
portion  of  the  urethra,  and  the  internal  iliac  nodes,  and  the  obturator  node 
receives  deep  lymph  vessels  from  along  the  course  of  the  obturator  vessels. 
The  external  iliac  nodes  send  vessels  direct  to  the  common  iliac  nodes  and  also 
lymphatics  to  join  vessels  from  the  internal  iliac  nodes  on  their  way  to  the 
comnoon  iliac  group.  The  nodes  along  the  epigastric  artery  and  those  along 
the  deep  circumflex  iliac  artery  are  accessory  chains  to  the  main  group  of  external 
iliac  nodes. 

The  internal  iliac  or  hypogastric  nodes  (lymphoglandulae  hypogasfricae)  sur- 
round the  internal  iliac  vessels,  and  receive  the  lymphatics  corresponding  to  the 
distribution  of  the  branches  of  the  internal  iliac  artery;  ?'.  e.,  lymphatics  from 
all  the  pelvic  viscera,  from  the  deeper  parts  of  the  perineum  including  the  mem- 
branous and  penile  portions  of  the  urethra,  from  the  deep  tissues  of  the  posterior 
portion  of  the  thigh,  and  from  the  buttocks.  Their  efferents  pass  to  the  common 
iliac  nodes  and  also  to  the  external  iliac  nodes. 


788 


THE   VASCULAR  SYSTEMS 


The  sacral  nodes  belong  to  this  group,  but  are  placed  in  the  concavity  of  the 
sacrum;  they  receive  lymphatics  from  the  rectum  and  posterior  wall  of  the  pelvis. 

The  common  iliac  nodes  are  found  about  the  common  iliac  artery  and  are 
divided  into  an  external  group,  which  lies  upon  the  inner  edge  of  the  Psoas 
muscle;  a  middle  group,  behind  the  artery,  and  an  internal  group,  which  lies  upon 
the  front  of  the  body  of  the  fifth  lumbar  vertebra  or  upon  the  sacrovertebral 
articulation.  They  receive  vessels  from  the  external  and  internal  iliac  nodes  and 
their  efferents  pass  to  the  lateral  aortic  nodes. 


,-r 


PHOMONTORV 

n 

COMMON    ILIAC 

1 

, 

(external  cliain) 


/ 


l/>,/r,t, 


-COMMON  ILIAC 
-EXTERNAL  ILIAC 

_EXTfHNAL  ILIAC 

(middle  chain) 


OBTURATOR 

NERVE 

OBTURATOR 

.  ARTERY 


Fig.  567. — Iliopelvic  lymph  nodes.     (Po 


The  lumbar  nodes  (lympJioglandulae  lumbales)  are  very  numerous,  and  consist 
of  right  and  left  lateral  aortic,  preaortic,  and  retroaortic  groups. 

The  right  lateral  aortic  nodes  are  situated  partly  in  front  of  the  inferior  vena 
cava,  near  the  termination  of  the  renal  vein,  and  partly  behind  it  on  the  origin 
of  the  Psoas,  and  on  the  right  crus  of  the  Diaphragm.  The  left  lateral  aortic 
nodes  form  a  chain  on  the  left  side  of  the  abdominal  aorta  in  front  of  the  origin 
of  the  Psoas  and  left  crus  of  the  Diaphragm.  The  nodes  on  either  side  receive 
(o)  the  efferents  of  the  common  iliac  nodes;  (6)  the  lymphatics  from  the  testicle 
in  the  male  and  from  the  ovary.  Fallopian  tube,  and  body  of  the  uterus  in  the 
female;  (c)  the  lymphatics  from  the  kidney  and  suprarenal  body;  and  (d)  the 


THE  LYMPHATIC  VESSELS  OF  THE  ABDOMEN  AND  PELVIS    789 

lymphatics  draining  the  lateral  abdominal  muscles  and  accompanying  tlie  luml)ar 
veins.  Most  of  the  efferent  vessels  of  the  lateral  aortic  nodes  converge  to  form 
the  right  and  left  lumbar  trunks  (trunci  lumbales)  which  join  the  receptaculum 
chyli,  but  some  enter  the  preaortic  and  retroaortic  nodes,  and  others  pierce  the 
crura  of  the  Diaphragm  to  join  the  lower  end  of  the  thoracic  duct.  The  preaortic 
nodes  lie  in  front  of  the  aorta,  and  may  be  divided  into  celiac,  superior  mesenteric, 
and  inferior  mesenteric  groups,  arranged  around  the  origins  of  the  corresponding 


RNAL  ILIAC 


*     j-  INTERNAL  ILIAC 
SATELLITE  TRUNK 
OF   INTERNAL 
PUDIC  VESSELS 


L  VESSELS 


7^ 

PROSTATIC  COL- 
LECTING TRUNK 

Fig.  568. — The  iliopelvic  nodes  (lateral  view).     (Poirier  and  Charpy.) 

arteries.  They  receive  a  few  vessels  from  the  lateral  aortic  nodes,  but  their 
principal  afferents  are  derived  from  the  viscera  supplied  by  the 'three  arteries 
with  which  they  are  associated.  Some  of  their  efl'erents  pass  to  the  retroaortic 
nodes,  but  the  majority  unite  to  form  a  common  trunk,  the  truncus  intestinalis, 
which  enters  the  receptaculum  chyli.  The  retroaortic  nodes  are  placed  below 
the  receptaculum  chyli,  on  the  bodies  of  the  third  and  fourth  lumbar  vetebrie. 
They  receive  lymphatic  trunks  from  the  lateral  and  preaortic  nodes,  while  their 
efferents  terminate  in  the  receptaculum  chyli. 


The  Lymphatic  Vessels  of  the  Abdomen  and  Pelvis. 


The  lymphatic  vessels  of  the  walls  of  the  abdomen  and  pelvis  may  be  divided 
into  two  sets,  superficial  and  deep. 

The  superficial  vessels  follow  the  course  of  the  superficial  bloodvessels  and 
converge  to  the  upper  group  of  the  superficial  inguinal  nodes.  Those  derived 
from  the  integument  of  the  front  of  the  abdomen  below  the  umbilicus  follow 


790       -  THE  VASCULAB  SYSTEMS 

the  course  of  the  superficial  epigastric  vessels,  and  those  from  the  sides  of  the  lum- 
bar part  of  the  abdominal  wall  pass  along  the  crest  of  the  ilium,  with  the  super- 
ficial circumflex  iliac  vessels.  The  superficial  lymphatic  vessels  of  the  gluteal 
region  turn  horizontally  round  the  outer  side  of  the  buttock,  and  join  the  super- 
ficial inguinal  nodes. 

The  deep  vessels  run  alongside  the  principal  bloodvessels.  Those  of  the 
parietes  of  the  pelvis,  which  accompany  the  gluteal,  sciatic,  and  obturator  vessels, 
follow  the  course  of  the  internal  iliac  artery,  and  ultimately  join  the  lateral  aortic 
nodes. 

Lymphatic  Vessels  of  the  Perineum  and  External  Genitals. — The  lymphatic  vessels 
of  the  perineum  and  of  the  integument  of  the  penis,  and  of  the  scrotum  (or 
vulva),  follow  the  course  of  the  external  pudic  vessels,  and  terminate  in  the 
superficial  inguinal  nodes.  Those  of  the  glans  penis  (or  glans  clitoridis)  termi- 
nate partly  in  the  deep  inguinal  nodes  and  partly  in  the  external  iliac  nodes. 

The  visceral  nodes  are  associated  with  the  branches  of  the  coeliac  axis, 
superior  and  inferior  mesenteric  arteries.  Those  related  to  the  branches  of  the 
coeliac  axis  artery  form  three  chains,  gastric,  hepatic,  and  splenic,  which  accom- 
pany the  corresponding  branches  of  the  artery. 

The  nodes  of  the  gastric  chain  (lymphoglandtdae  gastricae  swperiores)  are 
divisible  into  three  groups— viz. :  (a)  upper  gastric,  on  the  stem  of  the  artery;  (h) 
lower  gastric,  accompanying  the  descending  branches  of  the  artery  along  the 
cardiac  half  of  the  lesser  curvature  of  the  stomach,  between  the  two  layers  of  the 
small  omentum;  and  (c)  paracardial,  "outlying  members  of  the  coronary  chain, 
disposed  in  a  manner  comparable  to  a  chain  of  beads  around  the  neck  of  the 
stomach"  (Jamieson  and  Dobson*). 

The  nodes  of  the  gastric  chain  receive  their  aflerents  from  the  lesser  curvature 
and  contiguous  surfaces  of  the  stomach;  their  eflerents  pass  to  the  coeliac  group 
of  preaortic  nodes. 

The  nodes  of  the  hepatic  chain  (lymfJioglandulae  hepaticae)  (Fig.  574)  consist 
of  the  following  groups:  (a)  hepatic,  on  the  stem  of  the  hepatic  artery  and  along 
the  common  bile  duct,  between  the  two  layers  of  the  gastrohepatic  omentum 
as  far  as  the  transverse  fissure  of  the  liver;  the  cystic  node,  a  member  of.  this 
group,  is  placed  near  the  neck  of  the  gall-bladder;  (6)  subpyloric,  four  or  five  in 
number,  at  the  bifurcation  of  the  gastroduodenal  artery  at  the  angle  between  the 
first  and  second  parts  of  the  duodenum;  (c)  one  or  two  retropyloric  nodes  along 
the  pyloric  artery;  (cl)  right  gastroepiploic  (lymphoglavdvlae  gastricae  infer  lores), 
four  to  seven  in  number,  between  the  two  layers  of  the  greater  omentum,  along 
the  pyloric  half  of  the  greater  curvature  of  the  stomach.  The  nodes  of  the 
hepatic  chain  receive  afferents  from  the  pyloric  portion  of  the  stomach,  duodenum, 
liver,  gall-bladder,  and  the  head  of  the  pancreas;  their  efPerents  pass  to  the  coeliac 
group  of  preaortic  nodes. 

-  The  splenic  nodes  {lymphoglandidae  pancreaticolienales)  accompany  the  splenic 
artery  and  are  situated  in  relation  to  the  dorsal  surface  and  upper  border  of  the 
pancreas  and  in  the  lienorenal  ligament.  Their  afferents  are  derived  from  the 
fundus  of  the  stomach,  from  the  spleen,  and  from  the  pancreas;  their  efferents 
pass  to  the  coeliac  group  of  preaortic  nodes. 

The  superior  mesenteric  nodes  comprise  three  groups — mesenteric,  ileocolic, 
and  mesocolic. 

The  mesenteric  nodes  (lymphoglamhdae  mesenfericae)  (Fig.  572)  lie  between 
the  layers  of  the  mesentery,  and  vary  from  one  hundred  to  one  hundred  and  fifty 
in  number.  One  set  is  situated  close  to  the  wall  of  the  small  intestine,  among  the 
terminal  twigs  of  the  superior  mesenteric  artery;  a  second  is  in  relation  with  the 

1  Lancet,  April  20  to  27,  1907. 


THE  LYMPHATIC  VESSELS  OF  THE  ABDOMEN  AND  PELVIS    791 

loops  and  primary  branches  of  the  vessel;  while  a  third  set  of  larger  nodes  lies 
along  the  trunk  of  the  artery. 

Applied  Anatomy. — Enlargement  of  the  mesenteric  lymph  nodes  is  seen  in  most  diseased 
conditions  of  the  intestinal  tract,  and  is  well  marked  in  enteric  fever,  tuberculous  ulceration  or 
malignant  growths  of  the  bowel.  The  enlarged  nodes  can  often  be  palpated  through  the  wall 
of  the  abdomen. 

The  ileocolic  nodes  (Fig.  573),  from  ten  to  twenty  in  number,  form  a  chain 
around  the  ileocolic  artery,  but  show  a  tendency  to  subdivision  into  two  groups, 
one  near  the  duodenum  and  another  on  the  lower  part  of  the  trunk  of  the  artery. 
Where  the  vessel  divides  into  its  terminal  branches  the  chain  is  broken  up  into  sev- 
eral groups — viz. :  (a)  ileal,  in  relation  to  the  ileal  branch  of  the  artery;  (&)  anterior 
ileocolic,  usually  of  three  or  more  nodes,  in  the  ileocolic  fold,  near  the  wall  of  the 


Fig.  569. — Lymphatics  of  cot 


cecum;  (c)  posterior  ileocolic,  mostly  placed  in  the  angle  between  the  ileum  and  the 
colon,  but  partly  lying  behind  the  cecum  at  its  junction  with  the  ascending 
colon;  (d)  appendicular,  usually  a  single  node,  between  the  layers  of  the  meso- 
appendix,  near  its  free  edge;  (e)  right  colic,  along  the  inner  side  of  the  ascending 
colon. 

The  mesocoUc  nodes  are  numerous,  and  lie  between  the  layers  of  the  transverse 
mesocolon,  in  close  relation  to  the  transverse  colon;  they  are  best  developed  in 
the  neighborhood  of  the  hepatic  and  splenic  flexures.  One  or  two  small  nodes 
are  occasionally  seen  along  the  trunk  of  the  right  colic  artery,  and  others  are  found 
in  relation  to  the  trunk  and  branches  of  the  middle  colic  artery. 

The  superior  mesenteric  nodes  receive  afferents  from  the  jejunum,  ileum, 
cecum,  appendix,  and  the  ascending  and  transverse  parts  of  the  colon;  their 
efferents  pass  to  the  superior  mesenteric  nodes. 

The  inferior  mesenteric  nodes  (Fig.  569)  consist  of:  («)  Small  nodes  on  the 
branches  of  the  left  colic  and  sigmoid  arteries;  (6)  a  group  in  the  pelvic  mescolon 


792 


THE   VASCULAR  SYSTEMS 


around  the  superior  hemorrhoidal  artery;  and  (c)  a  pararectal  group  in  contact 
with  the  muscle  coat  of  the  rectum.  Their  afFerents  drain  the  descending  colon, 
sigmoid  flexure,  and  upper  portion  of  the  rectum;  their  efFerents  pass  to  the 
inferior  mesenteric  nodes. 


SUBPYLORI 


NODE  /^ 


"M_J 


Fig.  570. — General  view  of  the  subperitoneal  lymphatic  plexus  of  the  stomach  prepared  by  the  nicthod  of 

Gerota.     (Cun^o.) 


The  Lymphatic  Vessels  of  the  Abdominal  and  Pelvic  Viscera, 

These  consist  of:  (1)  Those  of  the  subdiaphragmatic  portion  of  the  alimentary 
canal  and  its  associated  glands,  the  liver  and  pancreas;  (2)  those  of  the  spleen 
and  suprarenal  bodies;  (3)  those  of  the  urinary  organs;  (4)  those  of  the  repro- 
ductive organs. 

1.  The  lymphatic  vessels  of  the  subdiaphragmatic  portion  of  the  alimentary 
canal  are  situated  partly  in  the  mucosa  and  partly  in  the  seromuscular  coats, 
but  as  the  former  system  drains  into  the  latter,  the  two  may  be  considered  as  one. 

The  lymphatic  vessels  of  the  stomach  (Fig.  570)  are  continuous  at  the  cardiac 
end  with  those  of  the  oesophagus,  and  at  the  pyloric  end  with  those  of  the  duo- 
denum. They  mainly  follow  the  bloodvessels,  and  may  be  arranged  in  four  sets. 
Those  of  the  first  set  accompany  the  branches  of  the  gastric  artery,  receiving 
tributaries  from  a  large  area  on  either  surface  of  the  stomach,  and  terminate 
in  the  nodes  of  the  gastric  chain.  Those  of  the  second  set  drain  the  fundus  of 
the  stomach,  draining  the  area  supplied  by  the  vasa  brevia  and  left  gastroepiploic 
arteries,  and  ending  in  the  splenic  nodes.      The  vessels  of  the  third  set  drain 


L  Y3IPHA  TIC  VESSELS  OF  ABDOMINAL  AND  PEL  VIC  VISCERA     793 

the  right  portion  of  the  greater  curvature  and  end  in  the  right  gastroepiploic 
nodes,  the  eft'erents  of  which  pass  to  the  subpyloric  group.  Those  of  tlie  fourth 
set  drain  the  pyloric  canal  and  pass  to  the  hepatic  and  subpyloric  nodes,  and, 
in  part,  also  to  the  coronary  chain,  thence  to  the  coeliac  group. 


RIGHT 

GASTnO-EPIPLOIC 

CURRENT 


Fig.  571. — Lymphatic 


of  the  stomach,     (Cundo.) 


Applied  Anatomy. — Mikulicz  pointed  out  the  early  infection  of  the  nodes  of  the  lesser  curva- 
ture in  pyloric  cancer,  and  insisted  that  in  operation  for  pyloric  cancer  the  entire  lesser  curvature 
must  be  removed.  Cuneo  showed  that  in  pyloric  cancer  the  fundus  and  two-thirds  of  the 
greater  curvature  usually  remain  free  from  disease,  because  the  lymph  current  is  toward  the 
pylorus  and  not  from  it.  Of  course,  if  the  lymphatics  become  blocked,  the  lymph  current  may 
be  reversed  (regurgitation),  and  then  infection  of  these  parts  can  occur.  William  J.  Mayo  has 
noted  the  "lymphatic  isolation"  of  the  dome  of  the  stomach.  In  operating  for  cancer  of  the 
pylorus,  make  the  section  of  the  stomach  as  directed  by  Hartmann,  that  is,  a  section  which 
removes  all  of  the  lesser  curvature  and  cuts  the  greater  curvature  well  to  the  left  of  the  subpyloric 
nodes. 


Fig.  572. — Lymphatics  of  the  small  intestine,     (Poirier  and  Charpy.) 


The  lymphatic  vessels  of  the  duodenum  consist  of  an  anterior  and  a  pos- 
terior set  which  open  into  a  series  of  small  pancreaticoduodenal  nodes  on  the 
anterior  and  posterior  aspects  of  the  groove  between  the  head  of  the  pancreas 
and  the  duodenum.  The  efferents  from  these  nodes  run  in  two  directions, 
upward  to  the  hepatic  nodes  and  downward  to  the  superior  mesenteric  nodes. 

The  lymphatic  vessels  of  the  small  intestine  (Fig.  572)  are  called  lacteals, 
from  the  milk-white  fluid  thev  usually  contain.     Thev  take  origin  in  the  intestinal 


794 


THE  VASCULAR  SYSTEMS 


villi  and  in  lymphatic  sinuses  around  the  bases  of  the  solitary  nodules.  Lymphatic 
plexuses  exist  in  the  submucous  tissue,  the  muscular  coat,  and  the  subserous 
tissue.  The  lymphatic  vessels  pass  between  the  layers  of  the  mesentery,  enter 
the  mesenteric  nodes,  and  finally  unite  to  form  two  or  three  large  trunks  which 
terminate  separately  in  the  receptaculum  chyli;  frequently,  however,  they  unite 
to  form  a  single  large  trunk,  termed  the  intestinal  lymphatic  trunk  (Figs.  553 
and  576). 

The  lymphatic  vessels  of  the  large  intestine  consist  of  three  sets — those 
of  the  cecum,  ascending  and  transverse  colon,  which,  after  passing  through  their 
proper  nodes,  enter  the  mesenteric  nodes;  those  of  the  descending  colon  and 
sigmoid  flexure,  which  pass  to  the  lumbar  nodes,  and  those  of  the  rectum  and  anus, 
which  pass  to  the  sacral  and  superficial  inguinal  nodes. 


Fig.  573. — Ventral 


The  lymphatic  vessels  of  the  anus  and  rectum  take  origin  from  two  net- 
works, one  from  the  skin  and  mucous  membrane  and  the  other  from  the  mus- 
cular coat.  The  lymph  vessels  from  the  skin  at  the  anal  margin  pass  to  the  super- 
ficial inguinal  nodes.  Some  vessels  from  the  skin  of  the  anus  ascend  and  reach 
the  submucous  plexus  of  the  rectum,  from  which  region  lymph  vessels  pass  to 
the  pararectal  nodes,  to  the  nodes  along  the  middle  hemorrhoidal  artery,  and 
along  the  inferior  hemorrhoidal  artery,  and  to  a  pelvic  node  near  the  origin  of  the 
internal  pudic  artery.  The  efferents  from  these  nodes  terminate  in  the  inferior 
mesenteric  nodes. 

The  lymphatic  vessels  of  the  liver  are  divisible  into  two  sets,  superficial  and 
deep.  The  former  arise  in  the  subperitoneal  areolar  tissue  over  the  entire  sur- 
face of  the  organ,  and  may  be  grouped  into  (a)  those  on  the  convex  surface, 
(b)  those  on  the  inferior  surface. 

(a)  On  the  convex  surface.  The  vessels  from  the  back  part  of  this  surface 
reach  their  terminal  nodes  by  three  different  routes;  the  vessels  of  the  middle 
set,  five  or  six  in  number,  pass  through  the  canal  opening  in  the  Diaphragm 
and  end  in  one  or  two  nodes  which  are  situated  around  the  terminal  part  of 
the  inferior  vena  cava;  a  few  vessels  from  the  left  side  pass  backward  toward 


L  YMPHA  TIC  VESSELS  OF  A  BD  OMINA  L  A  ND  PEL  VIC  VISCERA     795 

the  oesophageal  opening,  and  terminate  in  the  paracardial  nodes  of  the  gastric 
chain;  the  vessels  from  the  right  side,  one  or  two  in  number,  run  on  the  abdominal 
surface  of  the  Diaphragm,  and,  after  crossing  its  right  cms,  terminate  in  the 
coeliac  nodes  {lymphoglandulae  codiacae).  From  the  portions  of  the  right  and 
left  lobes  adjacent  to  the  falciform  ligament,  the  lymphatic  vessels  converge  to 
form  two  trunks,  one  of  which  accompanies  the  inferior  vena  cava  through  the 
Diaphragm,  and  ends  in  the  nodes  around  the  terminal  part  of  this  vessel ;  the  other 
runs  downward  and  forward,  and,  turning  around  the  anterior  sharp  margin  of 
the  liver,  accompanies  the  upper  part  of  the  ligamentum  teres,  and  ends  in  the 
upper  hepatic  nodes.  From  the  anterior  surface  a  few  additional  vessels  turn 
around  the  anterior  sharp  margin  to  reach  the  upper  hepatic  nodes. 

Some  of  the  lymph  of  the  upper  part  of  the  li^ver  traverses  the  Diaphragm  along 
several  lymphatic  vessels  which  drain  into  the  anterior  diaphragmatic  nodes  on 
the  superior  surface  of  the  Diaphragm,  just  behind  the  ensiform  cartilage  and  also 


LEFT  LATERAL 


Fig.  574. — Lymphatics  of  the  inferior  surface  of  the  liver.     (Sappey.) 

near  the  termination  of  the  inferior  vena  cava,  and  some  to  the  middle  diaphragm- 
atic, some  to  the  posterior  mediastinal  groups.  The  efferents  from  the  anterior 
diaphragmatic  nodes  pass  to  the  internal  mammary  chain,  a  fact  which  may  ex- 
plain the  involvement  of  the  supraclavicular  nodes,  particularly  of  the  left  side,^ 
secondary  to  an  abdominal  carcinoma. 

Q>)  On  the  inferior  surface.  The  vessels  from  this  surface  mostly  converge  to 
the  transverse  fissure,  and  accompany  the  deep  lymphatics  emerging  from  this 
fissure  to  the  hepatic  nodes;  one  or  two  from  the  posterior  parts  of  the  right 
and  Spigelian  lobes  accompany  the  inferior  vena  cava  through  the  Diaphragm, 
and  end  in  the  nodes  around  the  terminal  part  of  this  vein. 

The  deep  lymphatics  of  the  li'S'er  converge  to  ascending  and  descending  trunks. 
The  ascending  tnniks  accompany  the  hepatic  veins  and  pass  through  the  Dia- 
phragm to  end  in  the  nodes  around  the  terminal  part  of  the  inferior  vena  cava. 
The  descending  trunks  emerge  from  the  transverse  fissure,  and  end  in  the  hepatic 
nodes. 

The  lymphatic  vessels  of  the  gall-bladder  pass  to  the  hepatic  nodes  in  the 

*  Osier,  Principles  and  Practice  of  Medicine,  7th  edition,  1909,  page  4S5. 


796  THE  VASCULAR  SYSTEMS 

transverse  fissure  of  the  liver;  those  of  the  common  bile  duct  to  the  hepatic  nodes 
along  the  duct  and  into  the  upper  pancreaticoduodenal  nodes. 

The  lymphatic  vessels  of  the  pancreas  arise  from  a  network  about  the  pan- 
creatic lobules.  The  collecting  trunks  anastomose  freely  among  themselves  and 
with  the  lymphatics  of  the  duodenum,  spleen,  and  in  the  mesentery  and  meso- 
colon ;i  some  end  in  the  pancreaticoduodenal  nodes,  and  others  in  the  superior 
mesenteric  nodes. 

2.  The  lymphatics  of  the  spleen  and  suprarenal  glands. 

The  lymphatic  vessels  of  the  spleen,  both  superficial  and  deep,  pass  to  the 
splenic  nodes  in  the  lienorenal  ligament  and  along  the  superior  border  of  the 
pancreas. 

The  lymphatic  vessels  of  the  suprarenal  glands  usually  accompany  the  supra- 
renal veins,  and  end  in  the  lateral  aortic  nodes;  occasionally  some  of  them  pierce 
the  crura  of  the  Diaphragm  and  terminate  in  the  nodes  of  the  posterior  medi- 
astinum. 

3.  The  lymphatic  vessels  of  the  urinary  organs. 

The  lymphatic  vessels  of  the  kidney  form  three  plexuses — one  in  the  substance 
of  the  kidney,  a  second  beneath  its  fibrous  capsule,  and  a  third  in  the  perinephric 
fat;  the  second  and  third  communicate  freely  with  each  other. 

The  vessels  from  the  plexus  in  the  kidney  substance  converge  to  form  four  or 
five  trunks  which  issue  at  the  hilum.  Here  they  are  joined  by  vessels  from  the 
plexus  under  the  capsule,  and,  following  the  course  of  the  renal  vein,  end  in  the 
lateral  aortic  nodes.  The  perinephric  plexus  is  drained  directly  into  the  upper 
lateral  aortic  nodes. 

The  lymphatic  vessels  of  the  ureter  run  in  different  directions.  Those  from 
its  upper  portion  end  partly  in  the  efferent  vessels  of  the  kidney  and  partly  in  the 
lateral  aortic  nodes;  those  from  the  portion  immediately  above  the  pelvic  brim 
are  drained  into  the  common  iliac  nodes;  while  the  vessels  from  the  intrapelvic 
portion  of  the  tube  join  the  eft'erents  from  the  bladder,  or  terminate  in  the  internal 
iliac  nodes. 

The  lymphatic  vessels  of  the  bladder  (Fig.  575)  originate  in  two  plexuses,  an 
intramuscular  and  an  extramuscular,  it  being  generally  admitted  that  the  mucous 
membrane  is  devoid  of  lymphatics.^  The  efferent  vessels  are  arranged  in  two 
groups,  one  from  the  anterior  and  another  from  the  posterior  surface  of  the 
bladder.  The  vessels  from  the  anterior  surface  pass  to  the  external  iliac  nodes, 
but  in  their  course  minute  nodes  are  situated.  These  minute  nodes  are  arranged 
in  two  groups,  an  anterior  vesical  group,  in  front  of  the  bladder,  and  a  lateral 
vesical,  in  relation  to  the  hypogastric  artery.  The  vessels  from  the  posterior 
surface  pass  to  the  internal,  external,  and  common  iliac  nodes;  those  draining 
the  upper  part  of  this  surface  traverse  the  lateral  vesical  nodes. 

The  lymphatic  vessels  of  the  prostate  (Fig.  575)  terminate  chiefly  in  the  internal 
iliac  and  sacral  nodes,  but  one  trunk  from  the  posterior  surface  ends  in  the 
external  iliac  nodes,  and  another  from  the  anterior  surface  joins  the  vessels  which 
drain  the  membranous  part  of  the  urethra. 

Lymphatic  Vessels  of  the  Urethra. — The  lymphatics  of  the  fenile  portion  of 
the  urethra  accompany  those  of  the  glans  penis,  and  terminate  with  them  in 
the  deep  inguinal  and  external  iliac  nodes.  Those  of  the  membranous  and 
prostatic  portions,  and  those  of  the  whole  urethra  in  the  female,  pass  to  the  internal 
iliac  nodes. 

4.  The  lymphatic  vessels  of  the  reproductive  organs. 

The  lymphatic  vessels  of  the  testes  consist  of  two  sets,  superficial  and  deep, 
the  former  commencing  on  the  surface  of  the  tunica  vaginalis,  the  latter  in  the 
epididymis  and  body  of  the  testis.     They  form  several  large  trunks  which  ascend 

'  p.  Bartels,  Ueber  die  Lymphgetasse  des  Pankreas,  Arohiv  f.  Anat,  u.  Physiol.,  1907. 

-  Some  authorities  maintain  that  a  plexus  of  lymphatic  vessels  does  exist  in  the  mucous  membrane  of  tli^ 
bladder  (consult  Medecine  op^ratoire  des  Voies  urinaires,  par  J.  Albarran,  Paris.  1909). 


LYMPHATIC  VESSELS  OF  ABDOMINAL  AND  PELVIC  VISCERA     797 


with  the  spermatic  cord,  and,  accompanying  the  spermatic  vessels  into  the  abdo- 
men, terminate  in  the  lateral  aortic  nodes. 

The  lymphatic  vessels  of  the  vas  deferens  pass  to  the  external  iliac  nodes;  those 
of  the  vesiculae  seminales  partly  to  the  internal  and  partly  to  the  external  iliac 
nodes. 


P'''''"t'\;lllV^il", 


Node  in  front  of 
sacral  promontory 


\    \\    External  iliac 
\  '  \  '     node 


External  iliac 
nodes 

Vessd  draining 
into  external 
iliac  nodes 


lymph  nodes 
Vessels  draining 
into  node  on 
sacral  promontory 


^  Vessels  draining 

into  node  on  sacral 
promontory 


Middle  hemor- 
rhoidal node 
Middle  hemor- 
rhoidal lymphatic 


Fig   575  — Lymphatics  of  the  prostate.      (Cuneo  and  Ma 


The  lymphatic  vessels  of  the  ovary  are  similar  to  those  of  the  testicle,  and  ascend 
with  the  ovarian  artery  to  the  lateral  aortic  nodes. 

The  lymphatic  vessels  of  the  Fallopian  tube  pass  partly  with  those  of  the  ovary 
and  partly  with  those  of  the  uterus. 

The  lymphatic  vessels  of  the  uterus  (Fig.  1149)  consist  of  two  sets,  superficial 
and  deep,  the  former  being  placed  beneath  the  peritoneum,  the  latter  in  the  sub- 
stance of  the  organ.  The  lymphatics  of  the  cervix  uteri  run  in  three  directions — 
transversely  to  the  external  iliac  nodes,  postero-Jaterally  to  the  internal  iliac  nodes, 
and  posteriorly  to  the  common  iliac  nodes.  The  majority  of  the  vessels  of  the 
body  and  fundus  of  the  uterus  pass  outward  in  the  broad  ligaments,  and  are  con- 
tinued up  with  the  ovarian  vessels  to  the  lateral  aortic  nodes;  a  few,  however, 
run  to  the  external  iliac  nodes,  and  one  or  two  to  the  superficial  inguinal  nodes. 
In  the  unimpregnated  uterus  the  lymphatic  vessels  are  very  small,  but  during 
gestation  are  greatly  enlarged. 

The  l3Tnphatic  vessels  of  the  vagina  extend  in  three  directions — those  of  the 
upper  part  to  the  external  iliac  nodes,  those  of  the  middle  part  to  the  internal 
iliac  nodes,  and  those  of  the  lower  part  to  the  common  iliac  nodes.  On  the 
course  of  those  from  the  middle  and  lower  parts  small  nodes  are  situated.  Some 
lymphatics  from  the  lower  part  of  the  vagina  join  those  of  the  vulva  and  pass  to 
the  superficial  inguinal  nodes.  The  lymphatics  of  the  vagina  anastomose  with 
those  of  the  cervix  uteri,  vulva,  and  rectimi,  but  not  with  those  of  the  bladder. 


798  THE  VASCULAB  SYSTEMS 

THE  LYMPHATICS  OF  THE  THORAX. 

The  lymph  nodes  of  the  thorax  may  be  divided  into  parietal  and  visceral — the 
former  being  situated  in  the  thoracic  wail,  the  latter  in  relation  to  the  viscera. 

The  parietal  Isrmph  nodes  include  the  internal  mammary,  intercostal,  and 
diaphragmatic  nodes. 

1.  The  internal  mammary  nodes  are  placed  at  the  anterior  extremities  of  the 
intercostal  spaces,  by  the  side  of  the  internal  mammary  artery.  They  derive 
aft'erents  from  the  mammary  gland,  from  the  deeper  structures  of  the  anterior 
abdominal  wall  above  the  level  of  the  umbilicus,  from  the  upper  surface  of  the 
liver  through  a  small  group  of  nodes  which  lie  behind  the  ensiform  cartilage, 
and  from  the  deeper  parts  of  the  anterior  portion  of  the  thoracic  wall.  Their 
efferents  usually  unite  to  form  a  single  trunk  on  either  side;  this  may  open  directly 
into  the  junction  of  the  internal  jugular  and  subclavian  veins,  or  that  of  the  right 
side  may  join  the  right  subclavian  trunk  and  that  of  the  left  the  thoracic  duct. 

2.  The  intercostal  nodes  (lymphoglandulae  intercostales)  occupy  the  posterior 
parts  of  the  intercostal  spaces,  in  relation  to  the  intercostal  vessels.  They  receive 
the  deep  lymphatics  from  the  postero-lateral  aspect  of  the  thorax;  some  of  these 
vessels  are  interrupted  by  small  lateral  intercostal  nodes.  The  efl'erents  of  the 
nodes  in  the  lower  four  or  five  spaces  unite  to  form  the  descending  lumbar  trunk, 
which  descends  and  opens  either  into  the  receptaculum  chyli  or  into  the  commence- 
ment of  the  thoracic  duct.  The  efferents  of  the  nodes  in  the  upper  spaces  of  the 
left  side  terminate  in  the  thoracic  duct;  those  of  the  corresponding  right  spaces, 
in  the  right  lymphatic  duct. 

3.  The  diaphragmatic  nodes  lie  on  the  thoracic  aspect  of  the  Diaphragm,  and 
consist  of  three  sets — anterior,  middle,  and  posterior. 

The  anterior  set  consists  of  (a)  two  or  three  small  nodes  behind  the  base  of 
the  ensiform  (xiphisternum),  which  receive  afferents  from  the  convex  surface 
of  the  liver,  and  (b)  one  or  two  nodes  on  either  side  near  the  junction  of  the  seventh 
rib  with  its  cartilage,  which  receive  lymphatic  vessels  from  the  front  part  of  the 
Diaphragm.  The  efferent  vessels  of  the  anterior  set  pass  to  the  chain  of  internal 
mammary  nodes. 

The  middle  set  consists  of  two  or  three  nodes  on  either  side  close  to  where  the 
phrenic  nerves  enter  the  Diaphragm.  On  the  right  side  some  of  the  nodes 
o(  this  group  lie  within  the  fibrous  sac  of  the  pericardium,  in  front  of  the  inferior 
vena  cava.  The  afferents  of  this  set  are  derived  from  the  middle  part  of  the 
Diaphragm,  those  on  the  right  side  also  receiving  afferents  from  the  convex 
surface  of  the  liver.     Their  efferents  pass  to  the  posterior  mediastinal  nodes. 

The  posterior  set  consists  of  a  few  nodes  situated  on  the  back  of  the  diaphrag- 
matic crura,  and  connected  on  the  one  hand  with  the  lumbar  nodes  and  on  the 
other  with  the  posterior  mediastinal  nodes. 

The  superficial  lymphatic  vessels  of  the  thoracic  wall  ramify  beneath  the 
skin  and  converge  to  the  axillary  nodes.  Those  over  the  Trapezius  and  Latis- 
simus  dorsi  run  forward  and  unite  to  form  ten  or  twelve  trunks  which  end  in  the 
subscapular  group.  Those  over  the  pectoral  region,  including  the  vessels  from 
the  skin  covering  the  peripheral  part  of  the  mamma,  run  backward,  and  those 
over  the  Serratus  magnus  upward,  to  the  pectoral  group.  Others  near  the  lateral 
margin  of  the  sternum  pass  inward  between  the  rib  cartilages  and  end  in  the 
internal  mammary  nodes,  while  the  vessels  of  opposite  sides  anastomose  across 
the  front  of  the  sternum.  A  few  vessels  from  the  upper  part  of  the  pectoral 
region  pass  upward  over  the  clavicle  to  the  supraclavicular  group  of  cervical  nodes. 

The  lymphatic  vessels  of  the  mammary  gland  (Fig.  562)  originate  in  a  plexus 
in  the  interlobular  spaces  and  on  the  walls  of  the  galactiferous  ducts.  Those  from 
the  central  part  of  the  gland  pass  to  an  intricate  plexus  beneath  the  areola  (suh- 


THE  LYMPHATICS  OF  THE  THORAX  799 

areolar  plexus),  a  plexus  which  also  receives  the  lymphatics  from  the  skin  o'v-er 
the  central  part  of  the  gland.  Its  efl'erents  are  collected  into  two  trunks  which 
pass  to  the  pectoral  group  of  axillary  nodes.  The  vessels  which  drain  the  inner 
(mesal)  part  of  the  gland  pierce  the  thoracic  wall  and  end  in  the  internal  mammary 
nodes,  while  a  vessel  may  occasionally  emerge  from  the  upper  part  of  the  gland 
and,  piercing  the  Pectoralis  major,  terminate  in  the  subclavian  nodes  (Fig. 
562). 
The  deep  lymphatics  of  the  thoracic  wall  consist  of: 

1.  The  lymphatics  of  the  muscles  which  lie  on  the  ribs;  most  of  these  terminate 
in  tlie  axillary  nodes,  but  some  from  the  Pectoralis  major  pass  to  the  internal 
mammary  nodes. 

2.  The  intercostal  lymphatic  vessels  which  drain  the  Intercostal  muscles  and 
parietal  pleura.  Those  draining  the  External  intercostal  muscles  run  backward 
and,  after  receiving  the  vessels  which  accompany  the  posterior  branches  of  the 
intercostal  arteries,  terminate  in  the  posterior  intercostal  nodes.  Those  of  the 
Internal  intercostal  muscles  and  parietal  pleura  consist  of  a  single  trunk  in  each 
space.  These  trunks  run  forward  in  the  subpleural  tissue  and  the  upper  six 
open  separately  into  the  internal  mammary  nodes  or  into  the  vessels  which  unite 
them;  those  of  the  lower  spaces  unite  to  form  a  single  trunk  which  terminates  in 
the  lowest  of  the  internal  mammary  nodes. 

3.  The  lymphatic  vessels  of  the  Diaphragm,  which  form  two  plexuses,  one  on 
its  thoracic  and  another  on  its  abdominal  surface.  These  plexuses  anasto- 
mose freely  with  each  other,  and  are  best  marked  on  the  parts  covered  respectively 
by  the  pleurte  and  peritoneum.  That  on  the  thoracic  surface  communicates 
with  the  lymphatics  of  the  costal  and  mediastinal  parts  of  the  pleura,  and  its 
efferents  consist  of  three  groups:  (a)  anterior,  passing  to  the  nodes  which  lie 
near  the  junction  of  the  seventh  rib  with  its  cartilage;  (b)  middle,  to  the  nodes  on 
the  oesophagus  and  to  those  around  the  termination  of  the  inferior  vena  cava; 
and  (c)  posterior,  to  the  nodes  which  surround  the  aorta  at  the  point  where  this 
vessel  leaves  the  thoracic  cavity. 

The  plexus  on  the  abdominal  surface  is  composed  of  fine  vessels,  and  anasto- 
moses with  the  lymphatics  of  the  liver  and,  at  the  periphery  of  the  Diaphragm, 
with  those  of  the  subperitoneal  tissue.  The  efferents  from  the  right  half  of  this 
plexus  terminate  partly  in  a  group  of  nodes  on  the  trunk  of  the  corresponding 
inferior  phrenic  artery,  while  others  end  in  the  right  lateral  aortic  nodes.  Those 
from  the  left  half  of  the  plexus  pass  to  the  preaortic  and  lateral  aortic  nodes 
and  to  the  nodes  on  the  terminal  portion  of  the  oesophagus. 

AppUed  Anatomy. — The  fact  emphasized  by  Robinson  that  the  peritoneum  is  a  great 
lymph  sac  expkuns  the  quick  absorption  of  septic  material  and  the  rapid  spread  of  infectious  pro- 
cesses. If  the  exudate  clots  and  blocks  the  lymph  channels,  absorption  is  slow  and  life  may  be 
saved.  If  it  does  not  clot,  absorption  is  rapid  and  death  is  certain.  Whether  it  clots  or  not 
depends  on  the  nature  of  the  bacteria  present.  Fowler,  impressed  by  the  fact  that  absorption 
takes  place  most  rapidly  from  the  diaphragmatic  region  and  least  rapidly  from  the  pelvic  region, 
advises  placing  the  victim  of  peritonitis  in  bed,  with  his  head  and  body  elevated. 

A  knowledge  of  the  lymphatics  of  the  breast  and  of  the  nodes  into  which  the  lymphatics  drain 
is  of  the  first  importance  to  a  surgeon.  Certain  surgical  deductions  from  the  anatomj'  of  this 
region  are  perfectly  obvious — viz.:  (1)  If  the  skin  of  the  mammary  gland  is  involved  in  carci- 
noma, the  thoracic  group  of  axillary  nodes  of  the  same  side  is  involved.  If  the  skin  over  the 
sternal  margin  of  the  gland  is  involved,  the  nodes  of  the  opposite  axilla  may  be  cancerous,  as 
from  this  point  lymph  vessels  rise  and  pass  across  the  midline.  If  the  skin  of  the  sternal  margin 
is  involved  the  prognosis  is  worse  than  if  it  is  free,  the  opposite  axilla  may  be  cancerous,  and  the 
opposite  breast  may  become  diseased.  (2)  When  lymphatic  vessels  become  blocked  by  cancer 
cells  the  lymph  backs  up,  flows  backward  instead  of  in  its  proper  direction,  and  may  cause  infec- 
tion in  the  most  unsuspected  situations.  For  instance,  a  block  in  the  cutaneous  lymphatics  of 
a  portion  of  the  breast  may  lead  to  infection  of  the  opposite  breast  and  axilla,  though,  of  course, 
it  is  not  so  likely  to  as  is  cancer  of  the  skin  of  the  sternal  margin.     By  regurgitation  of  lymph 


800  THE  VASCULAR  SYSTEMS 

the  head  of  the  humerus  or  the  retrosternal  structures  may  become  diseased  in  mammary  cancer. 
(3)  If  the  nipple  or  areola  is  cancerous,  the  entire  gland  is  sure  to  be  diseased,  as  the  lymphatic 
network  of  this  region  empties  into  the  subareolar  plexus,  and  most  of  the  trunks  coming  from 
the  gland  also  enter  this  plexus.  (4)  If  the  mammary  gland  is  cancerous,  all  of  the  axillary 
nodes  are  regarded  as  diseased,  as  the  main  lymphatic  channel  from  the  breast  reaches  the 
nodes  on  the  inner  wall  of  the  axilla  upon  the  third  digitation  of  the  Serratus  magnus.  Further- 
more, in  many  cases  an  accessory  lymph  channel  comes  off  from  the  lower  portion  of  the  mam- 
mary gland  and  passes  directly  to  the  axilla.  (5)  The  subclavian  nodes  are  to  be  regarded 
as  diseased,  because  in  a  certain  proportion  of  cases  (the  exact  proportion  being  uncertain)  an 
accessory  lymph  channel  comes  off  from  the  posterior  surface  of  the  mammary  gland,  passes 
through  the  great  Pectoral  muscle,  and  ascends  between  the  greater  and  lesser  Pectorals  to  reach 
the  subclavian  nodes.  (6)  The  element  which  greatly  interferes  with  the  cure  of  mammary 
carcinoma  is  the  existence  of  lymph  channels  which  arise  from  the  inner  portion  of  the  mam- 
mary gland,  pierce  the  greater  Pectoral  and  Internal  intercostal  muscles,  and  reach  the  internal 
mammary  nodes.  Mediastinal  involvement  is  apt  to  be  earlier  in  carcinoma  of  the  inner  por- 
tion of  the  breast  than  in  carcinoma  of  other  portions,  and  the  prognosis  is  particularly  bad 
in  cancer  of  the  inner  portion  of  the  breast.  What  is  known  as  the  sternal  symptom,  of  Snow  is 
bulging  of  the  sternum  due  to  involvement  of  the  thymus  gland.  (7)  The  sternal  portion  of 
the  great  Pectoral  and  the  tissue  between  it  and  the  lesser  Pectoral  muscle  are  to  be  regarded 
as  diseased,  because  in  some  cases  an  accessory  lymph  channel  from  the  breast  penetrates  the 
greater  Pectoral  and  ascends  to  the  subclavian  nodes.  This  trunk  has  several  interrupting  or 
satellite  nodes,  the  retropectoral  nodes,  in  the  tissue  back  of  the  great  Pectoral  muscle.  (8) 
When  the  great  Pectoral  muscle  is  diseased,  cancer  cells  soon  spread  widely  through  the  sternal 
portion  of  the  muscle,  and  this  entire  portion  of  the  muscle  becomes  cancerous.  The  clavicular 
portion  does  not  suffer  early,  but  escapes  until  the  cancer  becomes  extensive,  as  it  is  anatomically 
distinct  from  the  sternal  portion.  If  the  fibres  of  the  great  Pectoral  are  extensively  diseased, 
the  thoracic  group  of  axillary  nodes,  the  subclavian  nodes,  and  possibly  the  internal  mammary 
nodes  are  involved.  (9)  The  only  operation  in  cancer  of  the  breast  which  offers  any  real  hope 
of  cure  is  one  which  is  done  early  and  is  radical.  (10)  It  must  be  done  early,  because  delay 
permits  in\'olvement  of  the  mediastinum,  and  if  the  disease  has  entered  the  mediastinum  opera- 
tion is  hopeless.  If  the  sternum  is  bulged  operation  is  useless,  and  nothing  short  of  amputation 
at  the  shoulder-joint  could  be  of  help  if  the  head  of  the  humerus  is  enlarged  by  the  disease. 
Even  this  radical  procedure  is  of  no  avail,  because  the  mediastinum  is  certainly  involved  if  the 
head  of  the  humerus  is  diseased.  (11)  If  the  lymph  nodes  above  the  clavicle  are  extensively 
diseased  operation  is  useless,  as  in  such  cases  the  mediastinum  is  sure  to  be  involved.  (12)  A 
radical  operation  means  the  removal  of  the  skin  of  the  breast  with  the  nipple  and  areola,  the 
subcutaneous  tissue  of  this  region,  the  entire  breast,  the  sternal  portion  of  the  great  Pectoral 
with  its  fascia,  the  retropectoral  nodes  and  tissue,  all  the  contents  of  the  axilla  except  vessels 
and  nerves,  the  nodes  and  cellular  tissue  beneath  the  anterior  margin  of  the  Latissimus  dorsi, 
and  the  subclavian  nodes.  It  is  probably  always  wisest  to  open  above  the  clavicle  as  well  as 
below  to  facilitate  the  removal  of  nodes.  It  is  seldom  necessary  to  remove  the  clavicular  por-. 
tion  of  the  greater  Pectoral.  The  lesser  Pectoral  does  not  require  removal,  but  it  should  be  taken 
away,  because  of  the  added  safety  and  speed  thus  obtained  in  cleaning  the  great  vessels  and 
because  its  retention  does  not  improve  the  functional  result.  The  surgeon  must  remember  that 
the  female  mammary  gland  is  a  much  larger  organ  than  we  used  to  think,  and  all  of  its  irregular 
projections  and  outlying  lobules  must  be  removed  (p.  784).  Formerly,  surgeons  did  not  com- 
pletely remove  the  breast,  but  only  got  rid  of  a  large  portion  of  it. 

The  visceral  lymph  nodes  consist  of  three  groups — viz.,  anterior,  mediastinal, 
posterior  mediastinal,  and  tracheobronchial. 

The  anterior  mediastinal  nodes  (lymphoglandulae  mediastinales  anteriores)  are 
placed  in  the  anterior  part  of  the  superior  mediastinum,  in  front  of  the  arch  of 
the  aorta  and  in  relation  to  the  innominate  veins  and  the  large  arterial  trunks 
which  arise  from  the  aortic  arch.  They  receive  afferents  from  the  thymic  nodes; 
their  efferents  unite  with  those  of  the  tracheobronchial  nodes,  to  form  the  right 
and  left  bronchomediastinal  trunks. 

The  posterior  mediastinal  nodes  {lympJio gland ulae  mediastinales  posteriores)  lie 
behind  the  pericardium  in  relation  to  the  oesophagus  and  descending  thoracic 
aorta.  Their  afferents  are  derived  from  the  oesophagus,  the  posterior  part  of  the 
pericardium,  the  Diaphragm,  and  convex  surface  of  the  liver.  Their  efferents 
mostly  terminate  in  the  thoracic  duct,  but  some  join  the  tracheobronchial  nodes. 

The  tracheobronchial  nodes  form  three  main  groups  in  relation  to  the  bifurca- 
tion of  the  trachea — one  on  either  side  of  the  trachea  above  the  bronchi  and 


THE  LYMPHATICS  OF  THE  THORAX 


801 


one  in  the  angle  between  the  bronchi  {lymphoglandulae  tracheales) ;  other  nodes, 
termed  interbronchial  {lymphoglandulae  bronchiales) ,  are  found  at  the  points  of 
division  of  the  larger  bronchi.  The  afferents  of  the  tracheobronchial  nodes 
drain  the  lungs  and  bronchi,  the  thoracic  part  of  the  trachea  and  the  heart;  some 


MEDIASTINAL 

NODES  AND 

VESSELS 


INTERCOSTAL 

NODES  AND 

VESSELS 


RECEPTACULUM 


"•""  \    ,1         ^M^-^A  ryy  ^  \  'w^/jii  tinaltrut 


Fig.  576. — Deep  lymph  nodes  and  vessels  of  the  thorax  and  abdomen  (diagrammatic).     Afferent  i 
represented  by  continuous  lines,  and  efferent  and  internodular  vessels  by  dotted  lines.     (Cunnin 


of  the  efferents  of  the  posterior  mediastinal  nodes  also  terminate  in  this  group. 
Their  efferent  vessels  ascend  upon  the  trachea  and  unite  with  efferents  of  the 
internal  mammary  and  anterior  mediastinal  nodes  to  form  the  right  and  left 
bronchomediastinal  tninks.  The  right  bronchomediastinal  trunk  may  join  the 
right  lymphatic  duct,  and  the  left  the  thoracic  duct,  but  more  frequently  they 


802  THE  VAHGULAB  SYSTEMS 

open  independently  of  these  ducts  into  the  junction  of  the  internal  jugular  and 
subclavian  veins  of  their  own  side. 

Applied  Anatomy. — In  all  town  dwellers  there  are  continually  being  swept  into  those  nodes 
from  the  bronchi  and  alveoli  large  quantities  of  the  dust  and  black  carbonaceous  pigment  that  are 
so  freely  inhaled  in  cities.  At  first  the  nodes  are  moderately  enlarged,  firrij,  inky  black,  and 
gritty  on  section;  later  they  enlarge  still  further,  often  becoming  fibrous  from  the  irritation  set 
up  by  the  minute  foreign  bodies  with  which  they  are  crammed,  and  may  break  down  into  a  soft 
slimy  mass  or  may  calcify.  In  tuberculosis  of  the  lungs  these  nodes  are  practically  always 
infested;  they  enlarge,  being  filled  with  tuberculous  deposits  that  may  soften,  or  become  fibrous, 
or  calcify.  Not  infrequently  an  enlarged  tuberculous  node  perforates  into  a  bronchus,  dis- 
charging its  contents  into  the  tube.  When  this  happens  there  is  great  danger  of  acute  pul- 
monary tuberculosis,  the  infecting  node-substance  being  rapidly  spread  throughout  the  bronchia! 
system  by  the  coughing  its  presence  in  the  air-passages  excites. 

The  lymphatic  vessels  of  the  thoracic  viscera  consist  of  those  of  the  heart 
and  pericardium,  lungs  and  pleura,  thymus  and  oesophagus. 

The  lymphatic  vessels  of  the  heart  consist  of  two  plexuses:  (a)  deep,  immediately 
under  the  endocardium,  and  (5)  superficial,  subjacent  to  the  visceral  pericardium. 
The  deep  plexus  opens  into  the  superficial,  the  efferents  of  which  form  right 
and  left  collecting  trunks.  The  left  trunks,  two  or  three  in  number,  ascend  in 
the  anterior  interventricidar  furrow,  receiving,  in  their  course,  aft'erents  from  both 
ventricles.  On  reaching  the  auriculoventricular  furrow  they  are  joined  by  a  large 
trunk  from  the  back  of  the  heart,  and  then  unite  to  form  a  single  vessel  which 
descends  between  the  pulmonary  artery  and  the  left  auricle  and  ends  in  one 
of  the  tracheobronchial  nodes.  The  right  trunk  receives  its  afi'erents  from  the 
right  auricle  and  from  the  right  border  and  posterior  surface  of  the  right  ventricle. 
It  ascends  in  the  posterior  auriculoventricular  groove  and  then  runs  forward  in 
the  auriculoventricular  groove,  and  passes  up  behind  the  pulmonary  artery,  to 
end  in  one  of  the  tracheobronchial  nodes. 

The  lymphatic  vessels  of  the  lungs  originate  in  two  plexuses,  a  superficial  and 
a  deep.  The  superficial  plexus  is  placed  beneath  the  visceral  pleura.  The  deep 
accompanies  the  branches  of  the  pulmonary  vessels  and  the  ramifications  of  the 
bronchi.  In  the  case  of  the  larger  bronchi  the  deep  plexus  consists  of  two  net- 
works, one,  submucous,  beneath  the  mucous  membrane,  and  another,  peribron- 
chial, outside  the  walls  of  the  bronchi.  In  the  smaller  bronchi  there  is  but  a 
single  plexus,  which  extends  as  far  as  the  bronchioles,  but  fails  to  reach  the  alveoli, 
in  the  walls  of  which  there  are  no  traces  of  lymphatic  vessels.  The  superficial 
efferents  turn  around  the  borders  of  the  lungs  and  the  margins  of  their  fissures, 
and  converge  to  end  in  some  nodes  situated  at  the  hilum;  the  deep  efferents  are 
conducted  to  the  hilum  along  the  pulmonary  vessels  and  bronchi,  and  end  in  the 
tracheobronchial  nodes.  Little  or  no  anastomosis  occurs  between  the  superficial 
and  deep  lymphatics  of  the  lungs,  except  in  the  region  of  the  hilus. 

The  lymphatic  vessels  of  the  pleura  consist  of  two  sets — one  in  the  visceral 
and  another  in  the  parietal  part  of  the  membrane.  Those  of  the  visceral  pleura 
drain  into  the  superficial  efferents  of  the  lung,  while  the  lymphatics  of  the  parietal 
pleura  have  three  modes  of  ending — viz. :  (a)  those  of  the  costal  portion  join 
the  lymphatics  of  the  Internal  intercostal  muscles  and  so  reach  the  internal 
mammary  nodes;  (6)  those  of  the  diaphragmatic  part  are  drained  by  the  efferents 
of  the  Diaphragm;  while  (c)  those  of  the  mediastinal  portion  terminate  in  the 
posterior  mediastinal  nodes. 

The  lymphatic  vessels  of  the  thymus  gland  terminate  in  the  superior  medias- 
tinal, tracheobronchial,  and  internal  mammary  nodes. 

The  lymphatic  vessels  of  the  oesophagus  form  a  plexus  around  that  tube,  the 
collecting  vessels  from  which  drain  into  the  posterior  mediastinal  nodes. 


THE  NEEVE  SYSTEM. 

THE  SPINAL  CORD  AND  BRAIN,  WITH  THEIR 

MENINOES. 


THE  nerve  system  of  man  is  an  apparatus  by  means  of  which  he  appreciates 
and  becomes  influenced  by  impressions  from  the  outer  world,  reacts  on 
tliese  impressions,  and  Iience  is  enabled  to  adapt  himself  to  his  environment. 
It  is  the  organic  substratum  for  those  manifestations  of  nerve  force  engaged  in  the 
characteristic  attributes  of  animal  life — sensation  and  motion.  Broadly  stated, 
the  nerve  system  connects  the  various  parts  of  the  body  with  one  another  and 
coordinates  them  into  one  harmonious  whole  in  order  to  carry  on  the  bodily 
functions  methodically  and  to  control  the  physiological  division  of  labor  through- 
out the  organism.  With  the  evolution  of  the  higher  forms  of  animal  life  through 
an  immense  phylogenetic  past  the  nerve  system  has  undergone  remarkable  differ- 
entiation and  specialization,  attaining  its  maximum  as  to  dominant  position  and 
complexity  of  structure  in  the  human  species. 

The  description  of  the  nerve  system  is  assisted  by  the  accommodation  of  physio- 
logical data  to  the  anatomical  basis  in  order  to  demonstrate  more  clearly  and 
to  render  more  practical  our  knowledge  of  the  mutual  relations  of  its  structure 
and  function.  The  cycle  of  events  which  accompanies  nerve  action  is  determined 
by  impressions  received  by  the  peripheral  organs,  apperception  and  reflexes 
of  tliese  impressions  in  the  lower  nerve  centres,  correlation  of  these  with  other 
impressions  in  higher  centres,  as  well  as  voluntary  reactions  or  inhibitions,  liber- 
ated in  compliance  with  the  organic  or  higher  needs  of  the  individual. 

Conventionally,  the  nerve  system  is  usually  considered  as  consisting  of  (1) 
the  cerebrospinal  system,  comprising  (a)  the  central  nerve  axis  (brain  and  spinal 
cord)  and  (7;)  the  peripheral  nerves  (cranial  and  spinal),  and  (2)  the  sympathetic 
nerve  system.  This  subdivision,  like  others  formulated  by  various  authors, 
is  an  arbitrary  one.  No  part  of  the  system  stands  isolated,  and  the  manifold 
groupings  and  chainings  of  the  units  of  the  system  intimately  connect  the  central 
nerve  organs  with  the  peripheral  nerve  endings,  the  organs  of  special  sense  and 
the  vegetative  organs.  The  distinction  between  the  central  and  the  sympathetic 
systems  has  been  too  absolute,  and  the  only  justification  for  adhering  to  the 
classification  given  above  is  based  upon  the  fact  that  the  sympathetic  system  is 
prepondei'atingly  related  to  the  interconnection  and  coordination  of  the  nutritive 
(digestive,  respiratory,  and  blood  and  lymph)  apparatus,  and,  therefore,  exer- 
cises a  special  control  over  its  activities. 

Structurally  considered,  the  nerve  system  consists  of  cell-elements  peculiarly 
differentiated  from  all  other  tissue  cells  in  that  their  protoplasm  is  extended,  often 
to  great  distances  from  the  nuclear  region,  in  the  form  of  processes.  The  cell- 
elements  are  held  in  place  by  supporting  tissues,  partly  of  ectodermal  and  partly 
of  mesodermal  origin,  and  receive  an  abundant  blood  supply. 

The  cell  element  of  the  nerve  system  is  called  the  neurone.     The  neurone  is 

(803) 


804  THE  NEB  VE  SYSTEM 

the  developmental,  structural,  rwA  functional  unit  of  the  nen'e  system.  It  is  in 
reality  a  single  cell  presenting  unusual  structural  modifications.  It  comprises  not 
only  the  nerve-cell  body  with  its  numerous  protoplasmic  processes  or  dendrites,  but 
also  the  axone,  which  may  vary  in  length  from  a  fraction  of  a  millimetre  to  fully 
half  a  man's  stature;  so  that,  despite  the  delicacy  of  the  axone,  its  bulk  may  be 
almost  two  hundred  times  greater  than  that  of  the  cell  body  from  which  it  pro- 
ceeds. The  long  axones  serve  to  make  a  connection  with  a  peripheral  or  distant 
nerve  cell,  muscle  cell,  or  gland  cell,  while  the  shorter  axones  of  certain  neurones 
divide  into  terminal  branches  in  the  immediate  vicinity  of  its  cell  body,  presumably 
to  come  into  relation  with  other  nerve  cells  in  the  same  or  adjacent  groups. 

Neurones,  being  devoted  to  the  maintenance  of  functions  manifested  by  various 
phenomena  of  nerve  force,  are  differentiated  in  their  polarity,  both  structurally 
and  dynamically.  Receptive  neurones  are  so  arranged  as  to  receive  afferent  nerve 
impulses  from  other  tissues;  emissive  or  excitor  neurones  give  out  efferent  nerve 
impulses.  The  former  are  generally  termed  sensor  neurones,  the  latter  motor 
(excitomotor)  neurones  if  connected  with  muscle,  excito glandular  if  connected 
with  gland  cells.  Were  the  nei-ve  system  made  up  solely  of  such  initial  and  ter- 
minal neurones,  the  apparatus  would  be  merely  a  system  of  reflex  arcs.  Such  it 
is  in  low  forms  of  animal  life  which,  by  their  very  organization,  and  because  of 
the  close  juxtaposition  of  their  sensor  and  motor  elements,  are  compelled  to 
react  to  stimuli  from  without.  In  higher  forms,  with  more  profoundly  differ- 
entiated nerve  systems,  the  sensor  impression  must  pass  through  an  interposed 
medium  which  is  capable  of  either  transmitting  the  molecular  change  in  the  form 
of  an  excitomotor  impulse  or,  on  the  other  hand,  is  capable  of  reducing  or  check- 
ing the  impulse.  In  other  words,  reaction  is  not  imperative;  there  is  a  freedom 
of  choice  exercised  by  intermediate  neurones  endowed  with  inhibitory  function. 
The  simple  arc,  composed  of  an  afferent  sensor  neurone  and  an  efferent  motor 
neurone,  would  act  independently  of  all  other  arcs  were  it  not  for  the  interposition 
of  this  intermediate  neurone  and  of  other  association  neurones  which,  hy  their 
relations  toward  similar  arc  elements,  produce  harmony  of  action.  The  basis, 
then,  of  the  nerve  system  is  a  series  of  neurones,  with  projecting  and  association 
processes,  coordinated  for  the  purpose  of  performing  specific  actions  manifested 
either  by  motion,  by  trophic  changes,  or  by  the  apperception  of  stimuli  of  a 
chemical,  mechanical  (tactile  and  auditory),  thermal,  or  photic  nature.  When 
we  consider  the  profoundly  complex  manifestations  of  nerve  phenomena  in  the 
mental  and  physical  life  of  man  it  is  not  surprising  to  learn  that  his  nerve  system 
is  made  up  of  an  immense  multitude  of  aggregations  of  neurones. 

Fundamental  Facts  Regarding  the  Development  of  the  Nerve  System. — 
The  nerve  system  is  formed  by  a  remarkable  metamorphosis  of  the  ectodermic 
layer  of  the  developing  ovum.  Along  the  mid-dorsal  line  of  the  embryonic  mass 
a  thickening  of  the  ectoderm  forms  a  well-defined  layer  of  cells,  the  neural  plate. 
The  proliferative  process  passes  rapidly  from  the  cephalic  toward  the  caudal 
end,  and  as  development  advances  it  is  seen  that  the  most  intense  growth  energy 
takes  place  at  the  cephalic  end,  indicative  of  the  higher  functional  potentiality 
of  what  is  to  become  the  brain.  The  neural  plate  undergoes  a  trough-like  for- 
mation as  its  edges  become  elevated  cephalad  and  laterally  to  form  the  neural 
groove  (Fig.  577).  The  edges  become  more  and  more  elevated  and  bend  toward 
the  median  line  until  the  margins  of  the  groove  coalesce  to  form  a  tube,  the  neural 
tube,  which  sinks  into  the  subjacent  mesodermal  tissues.  The  fusion  of  the  mar- 
gins of  the  neural  plate  occurs  first  in  the  cervical  region  and  rapidly  continues 
both  cephalad  and  caudad.  The  cephalic  portion,  destined  to  become  the  brain, 
expands  and  grows  considerably,  while  the  caudal  portion  elongates  to  form  the 
spinal  cord. 

Eventually  the  neural  tube,  as  it  sinks  into  the  subjacent  mesodermal  tissue. 


THE  SPINAL   CORD  AND  BBAIN 


805 


severs  all  connection  with  the  ectoderm  from  which  it  developed;  but  for  a  brief 
period  the  continuity  is  preserved  in  an  attenuated  septal  mass,  the  neural  crest 
(Fig.  577).  The  cell  elements  of  this  crest  subsequently  become  detached  from 
the  superficial  ectoderm,  the  continuity  of  which  is  again  restored  to  form  the 
integument.     They  then  pass  ventrad  to  either  side  of  the  neural  tube,  prolifer- 


NEURAL     PLAT 


30MAT0PLEURE- 


RNCHNOPLEURE-i 


ENTODERM 


Fig.  577. — Diagrams  showing  development  of  neural  tube  and  crest. 

ate  by  mitosis,  and  accumulate  in  paired  masses,  corresponding  in  number  to 
the  segments  of  the  body,  to  become,  in  part  at  least,  the  cerebrospinal  ganglion 
cells  of  the  afferent  system,  while  other  similarly  paired  masses  migrate  farther 
ventrad  to  a  prevertebral  position  to  form  the  gangliated  cord  and  widely  spread 
plexuses  of  the  sympathetic  system.     From  the  tissues  of  the  wall  of  the  neural 


NEURAL  TU 


ENTRAL  ROOT 


MOTOCHOR 


MESONEPHROS 


MESENTERY 


Fig.  578. — Diagram  showing  development  of  a  spinal  nerve  and  its  components,  together  with  the 
spinal  and  sympathetic  ganglia. 


tube  and  its  temporary  crest  the  entire  nerve  system  of  complex  and  intricate 
structure  is  developed.  The  cavity  of  the  tube  shares  in  the  developmental 
growth  changes  to  become  the  ventricular  .system  of  the  brain  and  central  canal 
of  the  spinal  cord.  The  major  details  of  the  development  of  the  principal  divisions 
will  be  considered  in  appropriate  chapters. 


§06  THE  NERVE  SYSTEM 

Development  of  Nerve  Tissue.  1 .  In  the  Wall  of  the  Neural  Tube.-The  single  layer  of 
nucleated  epithelial  cells  of  ectodermal  origin  whi.h  makes  up  the  wall  of  the  neural  tube  early 
becomes  modified  into  a  layer  of  tall  columnar  cells  called  spongioblasts  (Fig.  o/9).  Their 
protoplasmic  ends  undergo  differentiation  in  that  the  central  ends  become  elongated  and  atten- 
uated or  collapsed  to  form  a  series  of  striated  pillars 
with  intervening  spaces.  The  central  ends  retain 
their  breadth,  however,  and  form  an  internal  limiting 
membrane.  The  ectal  ends  undergo  differentiation 
to  form  a  spongy  reticulum  (myelospongium  net- 
work); eventually  these  spongioblasts  become  (a) 
ciliated  ependymal  cells  and  (6j  neuroglia. 

In  the  intercellular  spaces  of  the  central  zone  there 
appear  spherical  cells  of  different  structure  and 
density.  These  are  the  germinal  cells,  seen  in  very 
early  stages  and  proliferating  lapidly  by  karyokine- 
sis. "  They  soon  lose  their  sjiherical  form,  becoming 
pear-shaped  as  a  protoplasmic  process  extends 
ectad.  These  pear-shaped  cells  are  now  termed 
neuroblasts  (Fig.  579),  the  protons  of  the  neurones, 
and  as  development  advances  they  leave  the  central 
zone  and  migrate  into  the  marginal  reticulum  to 
the  positions  in  which  they  are  found  in  the  gray 
substance  of  the  brain  and  spinal  cord.  The  proto-  n 
plasmic  process  is  at  first  slightly  bulbous  and  elon- 


■Myelospongium 
networlc. 


^^^^ 


Fig.  579. — Transverse  section  of  the  spinal  cord  of  a 
human  embryo  at  the  beginning  of  the  fourth  week. 
Top  of  figure  corresponds  to  hning  of  central  canal. 
(.«ter  His.) 


Fig.  580. — Scheme  of  central  motor  neurone. 
(I.  type  of  Golgi.)  The  motor  cell  body,  together 
with  all  its  protoplasmic  processes,  its  axis-cylinder 
process,  collaterals,  and  end  ramifications,  repre- 
sent parts  of  a  single  cellorneuroTie.  a.h.  Axone- 
hillock  devoid  of  Nissl  bodies,  and  showing  fibril- 
ation.  c.  Cytoplasm  showing  Nissl  bodies  and 
lighter  ground  substance,  n'.  Nucleolus.  (Barker.) 


gates  to  form  the  axone  extending  toward  other  nerve-cells  or  to  the  peripheral  tissue  elements 
with  which  they  become  associated  by  the  contiguity  of  the  terminal  arborizations  into  which  the 
bulbous  extremity  develops.  The  precision  w'ith  which  the  axones  travel  toward  their  allotted 
goal  is  one  of  the  most  remarkable  manifestations  of  organic  development.  An  American  experi- 
menter, Ross  G.  Harrison,  has  devised  a  method  for  directly  observing  the  living,  growing 
nerve.  In  isolated  pieces  of  frog  embryos  the  differentiation  of  the  living  nerve  elements  could 
be  observed  from  day  to  day  during  several  weeks.  The  bulbous  end  of  the  outflowing  pro- 
toplasmic fibre,  showing  a  faint  fibrillation,  was  seen  to  reveal  a  continuous  change  of  form 
particularly  in  a  number  of  fine  simple  and  branched  filaments  which  w-ere  in  constant  ameboid 


THE  SPINAL  COBD  AND  BRAIN 


807 


movement.  Tlarrison's  demonstration'  is  of  great  significance  in  connection  with  the  "retraction 
theory"  and  oll.cr  ideas  related  to  the  neurone  doctrine. 

2.  In  the  Neural  Crest  Tissues. — The  nerve  tissue  elements  of  the  sympathetic  system  and 
of  the  ganglia  of  the  cranial  nerves  and  dorsal  roots  of  the  s]>inal  nerves  are  derived  from  the 
neural  crest.  Omitting,  for  the  present,  the  development  of  the  sympathetic  system,  it  is  found 
that  the  cells  of  the  paired  masses  which  eventually  become  the  cerebrospinal  ganglia  are  at 
first  somewhat  spherical,  then  oval  in  form, 
sending  out  from  cither  extremity  or  pole 
a  protoplasmic  process.  One  process  mi- 
grates centrad,  the  other  towarii  the  tissues 
of  the  periphery.  The  central  process 
penetrates  the  tissues  of  the  neural  tube 
and,  assuming  the  typical  form  of  an  axone 
with  its  collaterals  and  end  arborizations, 
comes  into  contiguous  association  with  cer- 
tain cells  of  the  central  axis.  The  periph- 
eral process  is  in  reality  an  unusually 
long  dendrite,  for  it  is  centripetal  in  func- 
tion; but  owing  to  the  fact  that  it  is 
usually  provided  with  a  myelin  sheath  it 
is  also  termed  the  peripheral  axone  of  an 
afferent  (or  sensor)  neurone.  The  central 
processes  of  the  cells  of  a  single  spinal  nerve 
ganglion  form  the  dorsal  nerve  roots;  the 
peripheral  processes  constitute  the  afferent 
portion  of  a  spinal  nerve.  The  cells  them- 
selves are  transformed  from  bipolar  into 
apparently  unipolar  cells  by  the  migration 
of  the  cell  body  to  one  side  and  the  con- 
sequent approximation  of  the  two  pro- 
cesses to  form  a  common  pedicle  in  a 
T-shaped  manner  (Fig.  586). 

Structure  of  the  Nerve  System.— The 
whole  of  the  nerve  system  is  composed  of 
nerve  tissue  and  supporting  connective 
tissue.  The  neurones  constitute  the  nerve 
tissue,  while  the  supporting  tissue  is  com- 
posed of  the  neuroglia  and  of  white  fibrous 
tissue  derived  either  from  the  investing 
membrane  or  from  the  sheaths  of  its 
numerous  vascular  channels. 

The  Neurone. — The  neurone  or  nerve 
cell  element,  whose  individuality  has 
already  been  pointed  out,  exhibits  remark- 
able variations  as  to  external  characters, 
dimensions,  and  form.  The  neurone  pre- 
sents a  concentrated  or  swollen  cell  mass 
and  nucleus,  formerly  known  as  the  nerve 
cell  (ganglion  cell)  and  still  retaining  the 
name.     From  this  cell  body  are  given  off  a 

number  of  processes  of  two  distinct  kinds:  (1)  protoplasmic  processes  which  are  commonly 
branched  and  generally-  called  the  dendrites ;  (2)  a  single,  thinner,  and  paler  process,  the  axone 
(axis-cylinder  proc(>ss;  iicuraxone). 

Varied  Forms  of  Neurones. — Bearing  in  mind  that  each  neurone  includes  not  onlj'  the  cell 
body  and  its  dendritic  processes,  but  also  the  axone  or  axis-cylinder  process  with  all  its  rami- 
fications, we  may  consider  each  of  these  divisions  under  separate  heads. 

1.  Nerve  Cell  Body.  External  Morphology. — The  bodies  of  nerve  cells  vary  much  in  size, 
measuring  from  4  to  135  microns  or  more  in  diameter.  The  largest  cells  are  found  in  the  ventral 
horns  of  the  spinal  cord,  in  the  spinal  ganglia,  in  the  large  pyramidal  cell  layer  of  the  cere- 
bral cortex,  in  the  Purkinjean  cell  layer  of  the  cerebellum,  and  in  the  cohmm  of  Clarke 
(dorsal  nucleus)  of  the  spinal  cord.  Very  small  cells  are  found  in  the  olfactory  bulbs,  in  the 
granular  layers  of  the  cerebral  and  the  cerebellar  cortex,  and  in  the  caput  gliosum  of  the  cord. 

Although  all  nerve  cells  begin  in  the  embryonic  ectoderm  as  spherical  germinal  cells,  they 
later  assume,  in  different  regions,  very  different  shapes.     These  external  morphological  relations 


Fig.  581. — Showing  some  varieties  of  cell  bodies  of 
neurones  (diagrnmniatic.)  A.  Unipolar  (amacrine)  cell 
from  the  retina.  B.  Bipolar  cell  from  vestibular  gang- 
lion. C  Multipolar  ceil,  with  long  axone,  from  spinal 
cord.  D.  "Golgi  cell,"  with  short  axone  breaking  up  into 
nmnerous  terminal  twigs.  E.  Pyramidal  cell  from  cere- 
bral cortex,     a.  Axone.     clt.  Collaterals,     t,  Telodendria. 


al  of  Anatomy,  June  1,  1907,  vii,  1.     (Anatomical  Record,  p.  UC  ; 


808  THE  NERVE  SYSTEM 

have  been  liest  revealed  by  the  methods  of  Ehrlich  and  Golgi.  According  to  the  number  ot 
processes  arising  from  the  cell  body,  neurones  are  referred  to  as  (1)  unipolar,  (2)  bipolar,  and 
(3)  multipolar  nerve  cells. 

1.  Unipolar  cells  are  met  with  frequently  in  early  stages  of  embryonic  development,  but  are 
rare  in  the  adult,  being  found  only  in  the  retina,  olfactory  bulb,  and  within  the  baskets  of  the 
Purkinjean  cells  of  the  cerebellum.  They  are  called  amacrine  cells.  The  cells  of  the  cerebro- 
spinal ganglia  (excepting  the  cochlear  and  vestibular)  are  apparently  unipolar,  but  they  are 
developmentally  and  functionally  of  bipolar  nature. 

2.  Bipolar  cells  are  found  almost  exclusively  in  the  peripheral  sensor  systems,  as  in  the 
olfactory  membrane,  in  the  retina,  in  the  cochlear  and  vestibular  ganglia,  and  in  the  cerebro- 
spinal ganglia  of  the  embryo. 

.3.  Multipolar  cells  are  the  most  numerous  and  form  the  principal  elements  of  nerve  centres 
throughout  the  system.  They  are  termed  multipolar  because  of  the  greater  or  less  number  of 
dendrites  given  ofT  in  addition  to  the  single  axone.' 

The  terms  "unipolar"  and  "multipolar"  must  be  restricted  to  the  morphological  sense;  dynamic- 
ally all  nerve  cells  are  bipolar. 

According  to  the  relations  of  the  axone  we  distinguish,  after  Golgi,  two  kinds  of  neurones: 

I.  Neurones  with  long  axones  which  become  the  axis  cylinder  of  a  central  or  peripheral  nerve 
fibre.  The  axones  give  off  several  collaterals  v/hich,  like  the  parent  stem,  break  into  finely 
branched  terminals  or  telodendria. 

II.  Neurones  with  relatively  short  axones  which  do  not  go  into  the  formation  of  a  nerve 
fibre,  but  break  up  into  terminal  twigs  in  the  vicinity  of  the  cell-bodies  from  which  they  arise. 
Type  II  is  genially  termed,  for  brevity's  sake,  the  Golgi  ceU. 


Fig.  582. — Purkinjean  cell  from  human  cerebellu: 
plane  transverse  to  tbe  long  axis  of  a  cerebellar  iolii 
clt.  Collaterals.     (Golgi  method.) 


Fig.  583.— Profile  view  of  Purkin- 
jean cell,  in  the  plane  of  the  long  axis 
of  a  cerebellar  folium. 


According  to  the  morphological  relations  of  the  dendrites,  neurones  are  classified  as  follows: 

(a)  Stellate  cells,  the  dendrites  of  which  spring  at  intervals  from  the  whole  circumference 
of  the  cell  body  and  pass  toward  all  directions  (motor  cells  in  ventral  horn  and  tract  cells  of  the 
cord). 

(6)  Cells  with  one  principal  stout  dendrite  (among  other  lesser  dendrites)  which  gives  off  side 
branches  and  ends  in  fine  terminal  twigs  (pyramidal  cells  of '  cerebral  cortex;  mitral  cells  of 
olfactory  bulb). 

(c)  Arboriform  cells,  giving  off  branched  dendrites  from  both  base  and  apex,  resembling  the 
roots  and  the  branches  of  a  tree;  the  axone  often  springs  from  the  base  of  one  of  the  root-like 
dendrites  (pyramidal  cells  of  the  hippocampus). 


;  axone  has  been  observed  arising  from  a  single  cell,  as  in  the  Cajal  cells  of  the 


THE  SPINAL  CORD  AND  BRAIN 


809 


(d)  Cells  with  monopolar  dendrites.  Several  main  dendritic  steins  spring  from  one  pole  of 
the  cell  and,  undergoing  frequent  subdivision,  break  up  into  a  fine  terfninal  arborization.  '^I'he 
axone  .springs  from  the  opposite  pole  (Purkinjean  cells  of  the  cerebellum;  granular  cells  of  the 
fasciola  cinerea). 

2.  Nerve  Cell  Body.  Internal  Morpholocjy. — The  nucleus  of  the  nerve  cell  differs  in  no  essen- 
tial from  the  typic  nuclear  structure.  Regarding  the  organization  of  the  cytoplasm  several 
conflicting  views  exist.  In  the  present  state  of  our  knowledge 
concerning  this  still  obscure  field  of  investigation  it  may  be 
said  that  the  nerve  cell  protoplasm  is  roughly  di\'ided  into 
a  peripheral  exoplasmic  portion  and  a  central  endoplasmic 
portion.  There  is  shown  throughout  the  ex'toplasm  a  tendency 
to  fibrillar  structure,  more  pronounc'cd  in  the  exoplasmic 
portion.  Within  the  meshes  of  a  more  or  less  homogeneous 
ground  substance,  which  pervades  the  whole,  are  deposited 
larger  and  smaller  masses  of  a  granular  substance.  Nerve 
cells  fixed  and  stained  by  the  methods  of  Nissl  and  Held 
show  that  the  granuic  m.Tsses  are  "stainable"  (chromatophiles; 
tigroid  bodies;  Nissl  bodies),  probably  of  the  nature  of  a 
nucleoproleid  (Mact 'allum)  and  looked  upon  as  a  sort  of 
nutritive  reserve.  Many  of  the  lai-ger  cells  possess  more 
or  less  pigmented  material,  adjacent  to  the  nucleus.  The 
cells  of  the  substantia  nigra  (intercalatnm)  and  of  the 
locus  caeruleus  contain  an  abundance  of  such  pigment 
granules. 

The  "  unstainable"  homogeneous  ground  substance  of  the 
cytoplasm  is  probably  the  more  important  functionally,  for 
numerous  delicate  neurofibrils  have,  by  special  methods,  been  shown  to  traverse  the  cell  body 
and  its  processes,  crossing  and  interlacing,  perhaps  anastomosing  with  each  other,  and  traceable 
into  the  axone.'  Nissl,  after  years  of  painstaking  investigation,  has  classified  nerve  cells  into 
a  great  many  different  species  in  accordance  with  their  reaction  to  staining  agents. 


Fig.  584. — Motor  nerve  cell  from 
ventral  horn  of  spinal  cord  of  rabbit. 
The  angular  and  spindle-shaped  Nissl 
bodies  are  well  shown.      (After  Nissl.) 


-Axone. 

'Mil  sheath. 


Pig.  585. — Bipolar  nerve  cell  from  a  spinal  ganglion  Fig.  586. — Three  stages  in  the  development  of  a  cell 

of  the  pike.'    (After  Kblliker.)  from  a  spinal  ganglion. 

The  Dendrites. — The  dendrites  are  attenuated  processes,  usually  numerous,  resembling 
in  structure  and  staining  reactions  the  cytoplasm,  of  which,  as  extensions,  they  increase  the 
functional  expanse  of  the  surface  of  the  cell  body.     Emerging  by  a  broad  base,  they  become 


1  That  the  neurofibrils  form  such  an  intracellular  network  and  that  the  axones  arise  therefrom  is  disputed 
■by  Ramon  y  Cajal,  Bielschowsky,  and  others. 


810 


THE  NERVE  SYSTEM 


narrower  as  they  divide  into  many  branches  in  a  dichotomous  or  arborescent  manner  to  end  free, 
according  to  most  observers,  or  to  be  joined  with  the  dendrites  of  other  neurones  by  means  of 
minute  fibrillaj  (as  claimed  by  Apathy)  or  by  concrescence  (Held).  The  contour  of  the  dendrite, 
while  occasionally  irregular  in  some  specimens,  with  varicosities  along  its  course,  is,  as  a  rule, 
beset  with  numerous  lateral  buds  called  gemmules.  ^'arious  hypotheses  have  been  advanced 
in  explanation  of  these  appearances,  it  being  held  by  some  investigators  that  they  are  related  to- 
conditions  of  activity  as  contrasted  to  those  of  repose,  while  others  believe  them'  to  be  artefacts 
produced  by  the  fixing  and  staining  methods  at  present  employed.  However,  it  is  no  longer 
disputed  that  the  function  of  the  dendrites  is  receptive  and  conductive  (or  cellulipetal)  for  nerve 
impulses,  although  they  probably  serve  the  nutritional  requirements  of  the  cell  body  as  well. 

This  functional  distinction  gives  the  clue  to  the  correct  interpretation  of  the  central  and 
peripheral  prolongations  of  the  cerebrospinal  ganglionic  neurones.  The  cells  of  these  ganglia 
are  at  first  bipolar  in  form,  but  gradually  undergo  transformation  into  apparently  unipolar  cells 
by  the  migration  of  the  cell  body  to  one  side  and  the  consequent  approximation  of  the  two 
processes  to  form  a  common  pedicle  in  a  T-shaped  manner  so  typical  of  the  spinal  ganglion  cell  of 
the  adult  (Fig.  586).  The  central  branch  invariably  remains  cellulifugal,  the  peripheral  branch 
invariably  remains  cellulipetal,  and  as  such  is  equivalent  to  the  dendrites  of  all  other  neurones. 
It  is  merely  a  modified  dendrite  in  that  it  courses  a  longer  distance  without  branching  until  it 
reaches  the  periphery  and  is  usually  myelinic.  Such  a  peripheral  prolongation  of  the  ganglioa 
cell  is  also  termed  a  centripetal  nerve  fibre  or  myelinic  (medullaied)  peripheral  axone  of  an  afferent 


B 


Fig.  587. — A.  Myelinic  axones  in  fresh  state,  showing  a  few  nodes,     B.  Portion  of  a  myelinic  axone  treated 
with  iioiling  ether  and  alcohol  to  remove  the  myelin  and  leaving  the  neurokeratin  network,     a,  Axone. 

The  Axone. — The  axone  is  usually  much  longer  than  any  of  the  dendrites,  thin,  pale,  smooth, 
emerging  from  the  nerve  cell  as  a  direct  continuation  of  the  neurofibrillar  ground  substance 
of  the  cell  body,  and  devoid,  so  far  as  at  present  known,  of  chromatophile  granules.  Its 
calibre  varies  for  the  different  cells,  corresponding  in  general  to  the  length  of  its  course, 
but  it  is  practically  of  uniform  diameter  throughout  its  extent.  Axones  may  be  extremely 
short  or  fully  a  meter  in  length.  Most  cells  give  rise  to  only  one  axone  (monaxonic  neurones), 
but  in  certain  localities  diaxonic  (two  axones)  and  polyaxonic  (several  axones)  neurones  are 
found.  In  a  Golgi  preparation  axones  stand  out  like  pieces  of  black  thread,  taking  a  more 
direct  course  than  do  the  irregular  dendrites,  and  rarely  branching  before  reaching  the  ultimate 
termination,  although  giving  off  collaterals  along  their  course.  The  central  axones  of  spinal 
ganglion  (sensor)  neurones  are  the  principal  exception  to  this  rule  in  that  they  bifurcate  in  a 
Y-shaped  manner  after  their  entrance  into  the  central  nerve  system.  In  the  case  of  another 
group  of  neurones,  Golgi's  Cell,  Type  II,  the  axone  is  observed  to  break  up  into  numerous 


THE  SPINAL   CORD  AND  BRAIN 


811 


branches  soon  after  its  tlqwrture  from  the  cell;  such  axoncs  ai\-  called  dendraxones.     The 
axones  and  their  collaterals  end  in  terminal  arborizations,  tlu'  telodendria. 

The  axone  is  the  distriljulive  or  emissive  (cellulifugal)  conductor  of  nerve  im|)ulses.  There 
is,  therefore,  a  functional  opposition  attributable  to  the  two  extremities  of  the  neurone,  based 
upon  its  dynamic  polarity  and  upon  a  physiologic  principle  which  is  established  by  all  experi- 
ments   to   which    the    nerve    system    is    submitted, 

namely,  that  nerve  impulses  pass  through   the  neu-  a  d 

rone  in  a  definite  direction  which  is  invariable  and 
admitting  of  anatomic  localization. 

The  majority  of  the  peripheral  spinal  and  cerebral 
axones  as  well  as  those  constituting  the  white  sub- 
stance of  the  brain  and  cord  are  invested  by  a  myelin 
sheath. 

The  Collaterals  (para.vones). — The  collaterals  are 
accessory  branchings  of  the  axones  which  are  more 
numerous  in  the  cyto]5roximal  portion  and  are  usually 
directed  at  right  angles  to  the  parent  stem.  Some 
axones  possess  few  or  no  collaterals,  while  others 
possess  many.  The  collaterals,  especially  those  in  the 
gray  substance  of  the  central  axis,  are  frequently  mye- 
linic. They  unquestionably  play  an  important  part 
in  the  grouping  and  chaining  of  neurones  within  the 
system,  in  yielding  up  to  neighboring  neurones  a  por- 
tion of  the  impulse  that  the  cell  has  received  by  its 
dendrites  and  transmits  along  its  axone  to  a  distance. 

Varieties  of  Axones.— Axones  are  divided  into 
two  main  groups  depending  upon  the  ]3resence  or 
absence  of  a  myelin  sheath — (I)  myelinic  axones  and 
(II)  amyelinic  axones,  or  medullated  and  nomnedul- 
lated  axones. 

Myelinic  axones  or  medullated  axis-cylinder 
processes  are  axones  enveloped  by  a  relatively  thick 
sheath  composed  of  semifluid  phosphorized  fat,  which 
gives  to  the  bundles  of  these  structiu'es  their  opaque, 
white  appearance.  The  myelin  sheath  is  in  tm-n 
invested  by  a  delicate  membrane  (neurilemma)  in 
one  group,  while  another  group  is  devoid  of  such 
covering,  giving  rise  to  the  further  subdivision  into 
(a)  myelinic  axones  with  a  neurilemma;  (h)  myelinic 
axones  without  a  neurilemma. 

(I,  a)  Myelinic  axones  with  a  neurilemma  consti- 
tute the  bulk  of  the  cerebr(jsi>iiial  iiervc,^,  and,  in  lesser 
proportion,  of  the  syin))athetic  nerves.  The  myelin 
sheath  {medullary  sheath  of  Schwarm)  (Figs.  587  aiul 
588)  does  not  invest  the  axone  tluoughout  its  course  nor 
in  a  uniform  manner.  The  axone  after  its  emergence 
from  the  cell  body  and  likewise  in  its  preterminal  por- 
tion is  naked;  and  the  delicate  external  membrane 
or  neurilemma  comes  in  contact  with  the  axone. 
The  myelin  sheath  consists  of  a  number  of  tubular 
segments  tleuiarcated  by  nodal  intersections  which 
are  only  0.08  mm.  apart  in  the  very  small  myelinic 
axones,  while  for  large  axones  the  intervals  may  be 
1  mm.  or  more.  At  the  nodes  {constrictions  of  Ran- 
vier)  the  neurilemma  dips  into  the  constriction  to 
come  in  contact  with  the"  axone,  and  any  branches  of  the  axone  are  invariably  given  off  at 
such  points.  The  interruptions  in  the  continuity  of  the  myelin  sheath  have  been  assumed  to 
be  provisions  facilitating  nutritive  diffusion  lietween  the  axone  and  the  surrounding  lymph, 
and  here  only  may  collaterals  be  given  off.  Each  internodal  myelinic  segment  is  further'  char- 
acterized by  oblique  clefts,  irregularly  distributed — the  incisures  of  Schmidt-Lantermann — 
seen  only  in  fixed  specimens  and  probably  artifacts.  Extraction  of  the  fatty  substance  of 
the  myelin  sheath  by  boiling  alcohol  and  ether  brings  out  a  fine  network  which  resists  trypsin 
digestion,  and  is  termed  neurokeratin  on  account  of  its  resemblance  to  the  keratin  of  epidermal 
structures. 

The  neurilemma  {primitive  sheath  of  Schwann;  neurolemma),  a  delicate  structureless  mem- 
brane, encloses  the  myelin  and  the  axone,  wherever  the  myelin  sheath  is  wanting.     Against  the 


Flo.  .588. — A.  Amyelinic  axones  with  a 
neurilemm.i  only,  the  nuclei  of  which  can  be 
seen.  B.  Diagram  showing  structure  of  a 
myelinic  axone  and  illustrating  two  views 
regarding  the  relations  of  the  sheaths  at  the 
node  (compare  the  two  sides).  C.  Trans- 
section  of  a  group  of  myelinic  axones,  stained 
with  osmic  acid,  showing:  NF.  Axonic  neu- 
rofibrils.    M.  Myelin.     F.  Endon 


812  THE  NERVE  SYSTEM 

inner  surface  of  the  neurilemma,  and  embedded  as  it  were  in  the  myelin,  usually  midway  between 
two  nodes,  lies  the  oval-shaped  nucleus  of  the  neurilemma. 

Myelinic  axones  are  usually  from  4  to  10  microns  in  diameter;  the  extremes  range  from  2  to 
20  microns. 

(I,  6)  Myelinic  axones  without  a  neurilemma  constitute  the  white  substance  of  the  brain 
and  spinal  cord,  as  well  as  the  optic  nerves.  They  differ  from  the  axones  just  described  in  twd 
particulars — the  neurilemma  is  absent  and  there  are  no  nodes  interrupting  the  continuity  of  the 
mj'elin  sheath.     A  network  of  neuroglia  replaces  the  neurilemma  as  a  supporting  tissue. 

(11,  a)  Amyelinic  axones  with  a  neurilemma  (Remak's  fibres;  sympathetic  nerve  fibres) 
constitute  the  majority  of  the  sympathetic  axones  and  the  axones  of  the  olfactory  nerves.  The 
myelin  sheath  is  absent  and  the  axone  is  invested,  more  or  less  completely,  by  a  nucleated  cellular 
sheath  or  neurilemma. 

(II,  h)  Amyelinic  axones  without  a  neurilemma  are  naked  axones,  most  numerous  in  the 
central  ganglia.  Most  axones  of  longer  course  are  devoid  of  any  sheath  in  the  cytoproximal  and 
preterminal  portions,  whatever  investment  they  may  receive  in  the  intermediate  portion. 


NERVE   CELL  NIDI  OR  NUCLEI. 

Nerve  cells  are  more  or  less  definitely  grouped  in  the  gray  substance  of  tlie  brain 
and  cord  to  form  what  are  conventionally  termed  "nuclei."  Inasmuch  as  the 
term  nucleus  has  long  been  given  to  the  vesicular  body  in  the  interior  of  all  cells, 
ambiguity  would  be  avoided  by  designating  such  nerve  cell  groups  by  the  term 
nidi  (plural  of  nidus,  "a  nest"). 


"NERVE  FIBRES"  AND  NERVES. 

Prior  to  the  general  adoption  of  the  neurone  concept  it  was  customary  to  desig- 
nate the  conducting  elements  of  the  nerve  system  by  the  term  nerve  fibres  in  dis- 
tinction from  the  nerve  cells.  As  has  been  pointed  out  above,  the  distinction 
no  longer  holds,  but  the  designation  "nerve  fibre"  is  still  retained  in  anatomic 
vocabulary  and  recurs  so  frequently  in  common  parlance  that,  even  with  the  new 
conception  which  has  been  formed  of  the  architecture  of  the  nerve  system,  the 
term  cannot  yet  be  entirely  discarded  in  favor  of  "axone,"  although  it  probably 
will  eventually. 

Nerves  are  round  or  flattened  bundles  of  axones  which  serve  to  bring  the  central 
axis  into  relation  with  the  periphery  and  other  tissues  of  the  body.  The  nerves 
of  the  body  are  subdivided  into  two  great  classes — the  cerebrospinal,  which  are 
attached  to  the  cerebrospinal  axis,  and  the  sympathetic  or  ganglionic  nerves,  which 
are  attached  to  the  ganglia  of  the  sympathetic.  The  cerebrospinal  nerves  con- 
sist of  numerous  nerve  fibres  (myelinic  axones)  collected  together  into  small  or 
large  bimdles  or  fasciculi  and  enclosed  in  a  membranous  sheath. 

Structure  of  Nerves. — In  structure  the  common  membranous  investment,  or  sheath  of  the 
whole  nerve,  which  is  called  the  epineuriiun,  as  well  as  the  septa  given  off  from  it,  and  which 
separate  the  fasciculi,  consists  of  connective  tissue,  composed  of  white  and  yellow  elastic  fibres, 
the  latter  existing  in  great  abundance.  The  tubular  sheath  of  the  smaller  fasciculi  composing 
the  nerve  trunk,  called  the  perineurium,  consists  of  a  fine,  smooth,  transparent  membrane, 
which  may  be  easily  separated,  in  the  form  of  a  tube,  from  the  fibres  it  encloses;  in  structure 
it  consists  of  connective  tissue  which  has  a  distinctly  lamellar  arrangement,  being  composed  of 
several  lamellae,  separated  from  each  other  by  spaces  containing  lymph.  The  nerve  fibres  are 
held  together  and  supported  within  the  fascicuhis  by  delicate  connective  tissue  called  the  endo- 
nem-ium  (sheath  of  Henle).  It  is  continuous  with  septa  which  pass  inward  from  the  innermost 
layer  of  the  perineurium,  and  consists  of  a  ground  substance  in  which  are  embedded  fine  bundles 
of  fibrous  connective  tissue  which  run  for  the  most  part  longitudinally.  It  serves  to  support  the 
capillary  vessels,  which  are  arranged  so  as  to  form  a  network  with  elongated  meshes.  The 
cerebrospinal  nerves  consist  almost  e.xclusively  of  myelinic  axones,  the  amyelinic  axones  existing 
in  very  small  proportions. 


NERVE  FIBRES  AND  NERVES  81 3 

The  bloodvessels  supplying  a  nerve  terminate  in  a  minute  capillary  plexus,  the  vessels  com- 
posing which  pierce  the  perineurium  and  run,  for  the  most  part,  parallel  with  the  fibres;  they 
are  connected  by  short,  transverse  vessels,  forming  narrow,  oblong  meshes,  similar  to  the  capillary 
system  of  muscle.  Fine  amyelinic  axones  accompany  these  cajjillary  vessels,  the  vasomotor 
fibres,  and  break  up  into  elementary  fibrils,  which  form  a  network  around  the  vessel.  Horsley 
has  also  demonstrated  certain  myelinic  fibres  as  running  in  the  epineurium  and  terminating 
in  small  bulboid  tactile  corpuscles  or  end-bulbs  of  Krause.  These  nerve  fibres,  believed  to 
be  sensor,  and  termed  nervi  nervorum,  are  considered  to  have  an  important  bearing  upon 
certain  neuralgic  pains. 

Nerves,  in  their  course,  subdivide  into  branches,  and  these  frequently  communicate  with 
branches  of  a  neighboring  nerve. 

The  axones,  so  far  as  is  at  present  known,  do  not  coalesce,  but  pursue  an  uninterrupted  course 
from  the  centre  to  the  periphery.  In  separating  a  nerve,  however,  into  its  component  fasciculi, 
it  may  be  seen  that  they  do  not  pursue  a  perfectly  insulated  course,  but  occasionally  join  at  a 
very  acute  angle  with  other  fasciculi  proceeding  in  the  same  direction;  from  this  branches  are 
given  off,  to  join  again  in  like  manner  with  other  fasciculi.  It  must  be  distinctly  understood,  how- 
ever, that  in  these  communications  the  axones  do  not  coalesce,  but  merely  pass  into  the  sheath 
of  the  adjacent  nerve,  become  intermixed  with  its  axones,  and  again  pass  on,  to  become  blended 
with  the  axones  in  some  adjoining  fasciculus. 

The  communications  which  take  place  between  two  or  more  nerves  form  what  is  called  a 
plexus.  Sometimes  a  plexus  is  formed  by  the  primary  branches  of  the  trunks  of  the  nerves — 
as  the  cervical,  brachial,  lumbar,  and  sacral  plexuses — and  occasionally  by  the  terminal  fasciculi, 
as  in  the  plexuses  formed  at  the  periphery  of  the  body.  In  the  formation  of  a  plexus  the  com- 
ponent nerves  divide,  then  join,  and  again  subdivide  in  such  a  complex  manner  that  the  indi- 
vidual fasciculi  become  interlaced  most  intricately;  so  that  each  branch  leaving  a  plexus  may 
contain  filaments  from  each  of  the  primary  nerve-trunks  which  form  it.  In  the  formation  also 
of  smaller  plexuses  at  the  periphery  of  the  body  there  is  a,  free  interchange  of  the  fasciculi  and 
primitive  fibres.  In  each  case,  however,  the  individual  filaments  or  axones  remain  separate  and 
distinct. 

It  is  probable  that  through  this  interchange  of  fibres,  every  branch  passing  oif  from  a  plexus 
has  a  more  extensive  connection  with  the  spinal  cord  than  if  it  had  proceeded  to  its  distribution 
without  such  connections  with  other  nerves.  Consequently  the  parts  supplied  by  these  nerves 
have  more  extended  relations  with  the  nerve  centres;  by  this  means,  also,  groups  of  muscles 
may  be  associated  for  combined  action,  as  is  best  exemplified  in  the  formation  of  the  limb 
plexuses. 

The  sympathetic  nerves  are  constructed  in  the  same  manner  as  the  cerebrospinal  nerves, 
but  consist  mainly  of  amyelinic  axones,  collected  into  fasciculi  and  enclosed  in  a  sheath  of  con- 
nective tissue.  There  is,  however,  in  these  nerves  a  certain  admixture  of  myelinic  axones, 
and  the  amount  varies  in  different  nerves,  and  may  be  known  by  their  color.  Those  branches 
of  the  sympathetic  which  present  a  well-marked  reddish-gray  color  are  composed  more  especially 
of  amyelinic  axones,  intermixed  with  a  few  myelinic  axones;  while  those  of  a  white  color  contain 
more  of  the  latter  and  a  few  of  the  former.  Occasionally,  the  gray  and  white  cords  run  together 
in  a  single  nerve,  without  any  intermixture,  as  in  the  branches  of  communication  between  the 
sympathetic  ganglia  and  the  spinal  nerves,  or  in  the  communicating  cords  between  the  ganglia. 
The  nerves,  both  of  the  cerebrospinal  and  sympathetic  systems,  convey  impressions  of  a  two- 
fold kind.  The  afferent  or  centripetal  nerves,  generally  called  sensor,  transmit  to  the  nerve 
centres  impressions  made  upon  the  peripheral  ends  of  their  components,  to  produce  reflexes 
in  the  lower  centres  while  the  mind,  through  the  medium  of  the  brain,  becomes  conscious  of 
environmental  conditions  or  changes.  The  efferent  or  centrifugal  (in  large  part  "motor") 
nerves  transmit  impulses  from  the  centres  to  the  parts  to  which  the  nerves  are  distributed;  these 
impulses  either  excite  muscle  contraction  or  influence  the  processes  of  nutrition,  growth,  and 
secretion. 

The  ganglia  may  be  regarded  as  separate  small  aggregations  of  nerve  cells, 
connected  with  each  other,  with  the  cerebrospinal  axis,  and  with  the  nerves  in 
various  situations.  They  are  found  on  the  dorsal  root  of  each  of  the  spinal  nerves ; 
on  the  sensor  root  of  the  trigeminus;  on  the  facial  and  auditory  nerves;  and  on 
the  glossopharyngeal  and  vagus  nerves.  They  are  also  found  in  a  connected 
series  along  each  side  of  the  vertebral  column,  forming  the  gangliated  cord  or 
trunk  of  the  sympathetic;  and  on  the  branches  of  that  nerve,  generally  in  the 
plexuses  or  at  the  point  of  junction  of  two  or  more  nerves  with  each  other  or 
with  branches  of  the  cerebrospinal  system.  On  section  they  are  seen  to  consist 
of  a  reddish-gray  substance,  traversed  by  nimierous  white  nerve  fibres;  they  vary 


814 


THE  NER  VE  SYSTEM 


considerably  in  form  and  size;  the  largest  are  found  on  the  sensor  root  of  the 
trigeminus  and  in  the  cavity  of  the  abdomen;  the  smallest,  not  visible  to  the  naked 
eye,  exist  in  considerable  numbers  upon  the  nerves  distributed  to  the  different 
viscera.  The  ganglia  are  invested  by  a  smooth  and  firm,  closely  adhering  mem- 
branous envelope,  consisting  of  dense  areolar  tissue;  this  sheath  is  continuous 
with  the  perineurium  of  the  nerves,  and  sends  numerous  processes  into  the 
interior  of  the  ganglion,  which  support  the  bloodvessels  supplying  its  substance. 
Origin  and  Termination  of  Nerves. — To  the  central  and  the  peripheral  ending 
'of  a  nerve  are  usually  given  the  names  of  "origin"  and  "termination."  These 
designations  have  been  rendered  inappropriate,  in  many  cases,  by  the  newer 
concept  of  neuronic  arrangement.  They  have  not  yet  become  obsolete,  however, 
particularly  in  dissecting-room  anatomy,  and  warrant  description  here  with  a 
certain  degree  of  reserve  alluded  to  above. 


Fig.  5S9. — Diagrams  of  motor  nerve  endings  in  A.  Striated  muscle.     B.   Cardiac  muscle.     C.   Nonstriated 
muscle,     a.  Axone.     (.  Telodendria.     (After  Huber,  Bolim  and  Davidoff,  and  others.) 


Origin. — The  origin  in  some  cases  is  single — that  is  to  say,  the  whole  nerve 
emerges  from  the  nerve  centre  by  a  single  root;  in  other  instances  the  nerve  arises 
by  two  or  more  roots,  which  come  off  from  different  parts  of  the  nerve  centre, 
sometimes  widely  apart  from  each  other;  and  it  often  happens,  when  a  nerve 
arises  in  this  way  by  two  roots,  that  the  functions  of  these  two  roots  are  different; 
as,  for  example,  in  the  spina!  nerves,  each  of  which  arises  by  two  roots,  the  ventral 
of  which  is  motor  and  the  dorsal  sensor.  The  point  where  the  nerve  root  or  roots 
emerge  from  the  nerve  centre  is  named  the  superficial  or  apparent  origin,  but  the 
axones  of  which  the  nerve  consists  can  be  traced  for  a  certain  distance  into  the 
nerve  centre  to  some  portion  of  the  gray  substance,  which  constitutes  the  deep 
or  real  origin  of  the  nerve.  The  manner  in  which  these  fibres  arise  at  their  deep 
crigin  varies  with  their  functions.  The  centrifugal  or  efferent  nerve  fibres 
originate  in  the  nerve  cells  of  the  gray  substance,  the  axones  of  these  cells  being 
prolonged  to  form  the  fibres.  In  the  case  of  the  centripetal  or  afferent  nerves 
the  axones  grow  inward  either  from  nerve  cells  in  the  organs  of  special  sense 
(e.  g.,  the  retina)  or  from  nerve  cells  in  the  ganglia.     Having  entered  the  nerve 


NERVE  FIBRES  AND  NERVES 


815 


centre,  they  branch  and  send  their  uUimate  twigs  among  the  cells,  without,  how- 
ever, uniting  with  thera. 

Termination. — Axones  terminate  periplierally  in  various  ways  and  may  he  most 
conveniently  studied  in  the  efferent  and  afferent  systems  respectively.  The 
so-called  periph-eral  terminations  of  afferent  neurones  are  Ijetter  called  peripheral 
nerve  beginnings,  on  account  of  their  functional  relations;  the  impulse  is  excited 
in  the  peripheral  end  and  conducted  centrad  through  the  rest  of  the  neurone. 


Fig.  590. — Showing  some  v.-xrieties  of  peripheral  terminations  of  afferent  neurones  (or  "peripheral  nerve 
beginnings"):  A.  Terminal  fibrillEe  in  epithelium  (after  Retzius).  B.  Tactile  corpuscle  (Meissner's,  after 
Dogiel).  C.  Bulboid  corpuscle  (Krause's,  after  Dogiel).  D.  Lamellated  corpuscle  (Pacini's,  after  Dogiel.  Sala, 
and  others).     E.  Genital  nerve  corpuscle  from  human  glans  penis  (after  Dogiel).     a,  Axone.     /.  Telodendria. 


Modes  of  Termination  of  Axones. — The  ultimate  terminals  of  the  axones  and  their 
collaterals  are  called  telodendrions  (or  telodendria).  So  far  as  can  be  determined 
by  present  methods  they  invariably  end  "free,"  commonly  by  exhaustion  through 
multiple  division.  This  manifold  branching  presumably  puts  the  neurone  in  a 
condition  to  influence  the  proce.sses  of  many  other  neurones  ("avalanche  con- 
duction" of  Ramon  y  Cajal).  In  some  localities  the  formation  by  axonic  terminals 
of  pericellular  and  peridendritic  networks   has  been  observed.     Upon   muscle 


816 


THE  NERVE  SYSTEM 


fibres  the  axone  terminals  form  chains  of  flattened  disks,  the  motor  end  plates. 
Among  gland  cells  the  terminal  fibrils  form  more  or  less  intricate  plexuses. 

Peripheral  Nerve  Beginnings  of  Centripetal  Neurones. — Nerve  beginnings  of  the 
centripetal  (sensor)  fibres  are  found  in  nearly  all  the  tissues  of  the  body.  They 
are  peculiarly  differentiated  and  of  various  forms  in  different  localities,  and  their 
function  is  apparently  the  conversion  of  mechanical,  thermal,  chemical,  and  other 
stimuli  into  nerve  impulses.  The  organs  of  vision,  hearing,  smell,  and  taste 
possess  variously  modified  nerve  beginnings  which  are  described  under  appro- 
priate titles  in  the  chapter  on  the  Organs  of  Special  Sense.  The  organs  of  the 
centripetal  neurones  collecting  bodily  impressions  (tactile  sense,  muscle  sense) 
and  connected  with  the  central  axis  are  often  very  complicated  structures.  The 
principal  varieties  are : 

'  Terminal  (peripheral)  fibrillse. 
Tactile  corpuscles  (Meissner's). 
"Ruffini's  endings." 
,  <|  Lamellated  corpuscles  (Pacini's). 
I  Bulboid  corpuscles  (Krause's). 

Genital  (nerve)  corpuscles. 
L  Articular  (nerve)  corpuscles. 
^^    f  Neuromuscular  spindles  (Ruffini). 
■  I  Neurotendinous  spindles  (Golgi). 

(I,  a)  Peripheral  fibrillse  are  best  demonstrable  in  the  epithelium  of  the  skin, 
mucous  membranes,  and  cornea.  The  axone  is  seen  to  break  up  into  its  con- 
stituent fibrillae,  which  often  present  regular  varicosities  and  anastomose  with 
each  other  in  a  plexiform  manner. 

(I,  h)  Tactile  corpuscles  (corpuscula  tactus;  touch  corpuscles  of  Meissner  and 
Wagner)  consist  of  elongated  oval  lobules  of  delicate  epithelioid  tissue  invaded  by 
one  or  more  axones  which  divide  into  their  primitive  fibrils,  each  terminal  branch 
ending  free  usually  as  a  somewhat  flattened,  disk-like  plate  in  among  the  wedge- 
shaped  cells  of  the  corpuscle.  Tactile  corpuscles  occur  in  large  numbers  in  the 
cutaneous  papilla;  of  the  finger-tips,  in  the  conjunctiva,  and,  less  abundantly,  in 
the  rest  of  the  skin;  they  appear  to  be  concerned  with  the  finer  tactile  sensations. 


Nerve  fibres. 


Connective-tissue  sheath. 


ending  of  Ruffini.     (After  Ruffini.) 


(I,  c)  Ruffini  has  described  a  special  variety  of  sensor  ner-\-e  beginning  in  the  sub- 
cutaneous tissue  of  the  human  finger  (Fig.  591).  They  are  principally  situated 
at  the  junction  of  the  cerium  with  the  subcutaneous  tissue;  they  are  of  oval 
shape,  and  consist  of  a  strong  connective-tissue  sheath  within  which  the  axone 
divides  into  numerous  varicose  fibrils  ending  in  small,  free  knobs. 

(I,  d)  Lamellated  corpuscles  {corpusnda  lamellosa;  Pacinian  corpuscles;  Vater's 
corpuscles;  Herbst's  corpuscles)  are  among  the  largest  of  the  tactile  end  organs 
and  are  found  chiefly  in  the  palmar  surface  of  the  hand,  the  sole  of  the  foot,  the 


NERVE  FIBRES  AND  NERVES 


817 


genital  organs,  the  serous  membranes,  and  many  other  structures.  Each  cor- 
puscle consists  of  a  number  of  capsular  connective-tissue  lamellEe  arranged  more 
or  less  concentrically  around  a  central  granular  protoplasmic  core,  pierced  by  a 
single  axone  which  usually  divides  into  two  or  more  branches  giving  off  col- 
laterals of  beaded  appearance  and  terminating  in  rounded  knobs. 

(I,  e)  Bulboid  corpuscles  {corpuscida  bidboidea;  Krause's  end  bulbs)  are  minute 
cylindrical  or  oval  bodies,  consisting  of  a  capsule  continuous  with  the  perineurium 
which  encloses  a  core  (inner  bidb)  of  semifluid,  finely  granular  protoplasm. 
The  axone  is  bulbed  peripherally  and  quite  free  distally,  or,  as  is  frequently 
observed,  di^•ides  into  a  number  of  branches,  to  each  of  which  is  attached  an 
end  bulb. 


Dendritic  branchinqs. 


Spirals  J  ■' 
Fig.  592. — Middle  third  of  a  terminal  plaqu 


the  muscle  spindle  of  an  adult  cat.     (.\fter  Rufiini.) 


(I,/)  The  genital  corpuscles  (corpuscida  nervonim  genitcdia)  and  the  articular  cor- 
puscles (corpuscida  nervorum  articidaria)  very  much  resemble  the  bulboid  cor- 
puscles just  described.  The  genital  corpuscles  form  aggregations  of  from  two 
to  six  knob-like  masses  in  the  penis  and  clitoris.  The  articular  corpuscles  are 
found  in  the  syno\'ial  membranes  of  the  joints. 

II,  a)  Neuromuscular  spindles  (muscle  spindles  of  Kiihne)  are  found  in  nearly  all 
the  skeletal  muscles  and  are  most  numerous  in  the  Extrinsic  muscles  of  the  tongue, 
in  the  small  muscles  of  the  hand  and  foot,  and  in  the  Intercostal  muscles.  jMost 
elaborate  investigations  upon  these  spindles  have  been  conducted  recently  by 
RufBni  in  Italy,  Sihler,  Huber,  and  De  Witt  in  America.  Neuromuscular 
spindles  are  usually  found  in  the  fibrous  septa  of  the  perimysium,  and  consist  of 
the  flattened  nerve  fibrils  of  centripetal  axones  arranged  in  one  or  all  of  three 
ways:  (1)  annular,  where  the  fibrils  surround  the  muscle  fibres  in  rings;  (2) 
spiral,  and  (3)  dendritic  or  branched  (Fig.  592) .  They  are  doubtlessly  concerned 
with  the  so-called  muscle  sense. 

(II,  b)  Neurotendinous  Spindles  (organs  of  Golgi). — The  nerves  convejdng  sensor 
impulses  from  the  tendons  have  a  special  modification  of  the  peripheral  fibres,  in 
the  form  of  numerous  fibrils  with  branching  end  plates  or  of  an  annular  and 
spiral  arrangement  resembling  the  neuromuscular  spindles.  They  usually  occur 
at  the  junction  of  the  tendon  bundles  with  the  muscle  fibres  (Fig.  593). 


818 


THE  NEB  VE  SYSTEM 


The  Neurone  Doctrine. — The  results  of  the  investigations  of  Golgi,  Cajal,  Forel, 
and  others  prompted  Waldeyer  to  enunciate  a  theory  with  regard  to  the  nerve 
mechanism  of  the  neurone.  This  hypothesis  is  generally  known  as  the  neurone 
theory  and  assumes  that  (1)  each  neurone  is  a  distinct  and  separate  entity;  (2) 
the  collaterals  and  other  terminals  of  the  neurone  form  no  connections  among 
themselves;  (3)  neurones  are  associated,  and  impulses  conveyed,  by  contact 
or  contiguity  of  the  axonic  terminals  of  one  axone  with  the  cell  body  or  dendrites  of 
another  neurone.  The  theory  postulates  a  nerve  cell  amebism  analogous  to 
the  extension  and  retraction  of  the  pseudopodia  of  an  ameba,  and  the  "retraction 
theory"  has  been  propounded  in  explanation  of  certain  functional  dissociation 
phenomena  attending  nerve  force  manifestations. 


■Nerve  fibres. 


Organ  of  Golgi,  showing  Tendon  bundles, 

ramification  of  nerve  fibrils. 
Muscle  fibres. 
Fig.  593. — Neurotendinous  spindle  organ  of  Golgi  from  the  human  tendo  calcaneus  (Achillis).     (After  Ciaccio.) 


Opposed  to  the  "neurone  theory"  or  "contact  theory"  is  the  more  recent 
continuity  theory  which  is  being  earnestly  advocated  by  Apathy,  Bethe,  and 
Nissl.  In  behalf  of  this  theory  it  is  claimed  that  the  neurofibrils  are  continuous 
not  only  within  the  cell  and  its  processes,  but  through  an  extracellular  network 
as  well.  The  dispute  now  being  waged  does  not,  however,  affect  our  funda- 
mental ideas  regarding  the  individuality  of  neurones  with  regard  to  their  dynamic 
condition. 

The  Supporting  Tissue  Elements  of  the  Nerve  System.— A  fine  meshwork  of  non-neural 
tissue,  more  or  less  dense  in  different  localities,  but  apparently  restricted  to  the  central  axis, 
serves  to  support  the  neurones.  This  sustentacular  tissue  is  of  two  kinds:  (1)  the  neuroglia; 
(2) .  connective-tissue  trabeculse  derived  from  (a)  the  pia  or  (b)  vascular  channels. 

The  Neuroglia. — The  neuroglia  consists  of  glia  cells  of  varied  forms  and  glia  fibres.  Glia 
cells  are  divisible  into  two  species — ependjrmal  cells  and  astrocytes  of  long-rayed  and  short- 
rayed  type. 

Ependymal  cells  are  the  columnar  epithelial  cells  which  line  the  neural  canal  throughout. 
In  the  embryonic  condition  each  cell  is  seen  to  project  a  long  multibranched  filament  toward 
the  periphery  of  the  neural  tube,  while  the  free  end  carries  a  tuft  of  cilia.  In  adult  life  both  the 
cilia  and  the  radial  filament  are  apparently  lost  or  very  much  reduced. 

Regarding  the  structure  of  the  glia  cells  proper  as  well  as  of  the  glia  fibres  there  is  a  variance 
of  opinion  among  different  investigators.  The  astrocytes,  as  they  are  commonly  revealed  in 
Golgi  preparations,  may,  as  pointed  out  by  Weigert  and  others,  be  due  to  an  extension  of  the 
silver  deposit  upon  glia-cell  nuclei  as  well  as  upon  adjacent  filaments.  Huber,'  Hardesty,^  and 
others  regard  neuroglia  tissue  as  a  syncitium  resulting  from  an  early  fusion  of  the  protoplasm 
of  the  cells  of  the  neural  tube  which  at  first  were  individual  and  definitely  bounded.  The  fila- 
mentous reticulum  of  glia  fibres  ordinarily  seen  in  adult  tissues  seems  to  result  from  an  increase 
of  the  fine  threads  of  the  spongioplasmic  network  of  the  original  cell  protoplasm.  Neuroglia 
occurs  in  both  gray  and  white  substances  as  an  all-pervading  supporting  tissue.  In  certain 
localities,  as  upon  the  surface  of  the  brain  and  cord,  the  neuroglia  tissue  is  disposed  in  the  form 
of  a  thin  layer. 


'  American  Journal  of  Anatomy,  1901,  pp.  45  to  61. 
'  Aid.,  1904,  pp.  229  to  268. 


THE  CENTRAL  NER  VE  SYSTEM 


819 


Besides  the  neuroglia,  the  central  nerve  system  contains  as  supporting  tissues  numerous  fine 
and  coarse  septa  or  tralieeulfe  derived  from  the  investing  pia,  or  from  the  sheaths  of  bloodvessels. 

Chemical  Composition. — The  amount  of  water  in  nerve  tissue  varies  with  the  siUiation. 
Thus,  in  the  gray  substance  of  the  cerebrum  it  constitutes  about  83  per  cent.,  in  the  white  sub- 
stance from  tiie  same  region  about  70  per  cent.,  while  in 
the  peripheral  nerves,  such  as  the  sciatic,  it  may  fall  to 
(iO  per  cent. 

The  solids  consist  of  neuroalbumins,  neuroglobulins, 
nucleoproteins,  neurokeratin  (in  the  gray  substance 
proteins  constitute  about  one-third  of  the  total  solids), 
lecithins,  cerebrosides  (chiefly  phrenosin),  cholesterin, 
unidentified  organic  sulphocompounds,  aminofatty  sub- 
stances, nitrogenous  extractives,  and  inorganic  salts 
with  some  collagen,  fat,  etc.,  in  the  adherent  connective 
tissue  (W.  J.  Gies). 

THE  CENTRAL  NERVE  SYSTEM. 

The  central  nerve  system,  as  it  is  convention- 
ally distinguished  from  the  sympathetic  system, 
is  composed  of  a  central  axial  aggregation  of 
ganglia  forming  the  brain  and  spinal  cord, 
which  are  connected  with  the  other  tissues  of 
the  body  by  43  pairs  of  nerves,  of  which  12 
pairs  are  attached  to  the  brain  and  31  pairs  to 
the  spinal  cord.  The  functional  relations  of 
the  central  mechanisms  with  the  periphery  are 
inaintained  by  the  essential  cell  elements  of  the 
nerve  tissues,  the  neurones.  The  chief  task  in 
the  study  and  analysis  of  the  structure  of  the 
nerve  system  lies  in  the  dovetailing  of  features 
visible  to  the  naked  eye  with  those  visible  only 
imder  high  magnifying  powers.  By  the  com- 
l)ination  of  macroscopic  with  microscopic  fea- 
tures the  attentive  student  is  enabled  to  resolve 
or  reconstruct  in  the  three  dimensions  of  space, 
and  see  with  his  mental  eye  the  opaque  interior 
transparently  resolved  into  intricate  yet  well- 
defined  projecting  and  associating  mechanisms. 
Assistance  in  sucli  study  may  be  derived  from 
illustrations  depicting  hidden  structures  in  ac- 
cordance with  this  principle. 

Preliminary  Considerations.  White  Substance 
and  Gray  Substance. — The  central  axis  of  the 
nerve  system  contains  two  categories  of  sub- 
stance, their  difference  to  the  eye  being  one  of 
color.  They  are  coitventionally  designated  the 
white  and  gray  substance.  The  white  substance 
(substantia  alba),  which  forms  about  two-thirds 
of  the  neural  axis,  is  the  conducting  substance, 
and  its  characteristic  appearance  is  due  to  the 
myelin  sheaths  which  invest  the  axones  in  it. 
The  gray  substance  (substantia  grisea;  cinerea)  is  the  sentient  and  reacting  mass 
containing  the  cell  bodies  of  neurones.  Its  color  is  due  to  its  translucency,  its 
greater  vascularity,  and  to  a  certain  amount  of  pigment  material  in  the  cell  ele- 
ments.    The  white  and  the  gray  substance  is  not  sharply  demarcated  everywhere, 


Fig.  594.  —  Neuroglia  cells  of  brain 
shown  by  Golgi's  method.  A.  Cell  with 
branched  processes.  B.  Spider-cell  with 
unbranched  processes.  _(.\fter  Andriezen.) 
(From  Schafer's  Essentials  of  Histology.) 


820 


THE  NERVE  SYSTE3I 


for  although  the  white  substance  is  exclusively  conducting  substance,  the  gray 
is  not  exclusively  ganglionic,  for  the  former  encroaches  on  the  latter;  in  some  local- 
ities, as  in  the  ventral  horns  of  the  spinal  gray,  in  parts  of  the  cerebral  cortex,  in 
the  reticular  formation  of  the  pons  and  medulla  oblongata,  and  in  the  column  of 
Clarke  (dorsal  nucleus),  the  admixture  of  myelinic  fibres  is  considerable.  Both 
white  and  gray  substance  is  pervaded  by  the  neuroglia. 

The  specific  graAaty  of  the  cortical  gray  substance  is  1.021;  of  the  great  gan- 
glia, 1.034;  of  the  gray  substance  in  the  cerebellum  and  mesencephalon,  1.040; 
and  of  the  white  substance,  1.028. 

For  convenience  of  study,  and  somewhat  in  correspondence  with  phyletic 
development,  the  central  axis  of  the  nerve  system  is  divided  into  (1)  the  spinal 
cord  and  (2)  the  brain,  grossly  subdivided  into  (a)  medulla  oblongata,  pons,  and 
cerebellum;  (6)  mid-brain;  and  (c)  fore-brain.  This  gross  subdivision  is  arbitrary 
and  the  interrelations  of  the  parts  would  be  obscured  were  two  much  stress  laid 
upon  any  mode  of  separation. 


THE   SPINAL  CORD   (MEDULLA  SPINALIS;  MYELON). 

The  spinal  cord  is  the  attenuated,  nearly  cylindrical  part  of  the  cerebrospinal 
axis  which  lies  in  the  vertebral  canal,  occupying  its  upper  two-thirds  in  the  adult. 

It  extends  from  about  the  level  of  the 
atlooccipital  articulation  (or  lower  bor- 
der of  the  pyramid  decussation)  to  the 
level  of  the  lower  border  of  the  body 
of  the  first  lumbar  vertebra,  where  it 
terminates  in  a  slender  filament  of 
gray  substance  enveloped  by  pia,  and, 
further  caudad,  by  a  sheath  of  dura 
which  is  attached  to  the  dorsum  of  the 
coccyx.     The  spinal  cord  is  continuous 


J'l'i^'^       8     OENTICULATUM 


LIGAMENTU^ 


Fig.  595. — Showing  the  relation  of  the  spinal  cord 
to  the  dorsal  surface  of  the  trunk.  The  vertebrae  are 
shown  in  red  outlines. 


-^      fi  E.  A.  S. 


Fig.  596. — Ventral  view  of  medulla  oblongata 
nd  upper  part  of  spinal  cord.  Dura  and  arach- 
oid  cut  along  median  line  and  folded  aside.  .1 
nd  B  are  fairly  constant  velar  folds  of  the  arach- 
oid.     (.-Vfter  Key  and  Retzius.) 


THE  SPINAL  CORD 


821 


cephalad  with  the  medulla  oblongata.  Its  length  is  45  cm.  (44  to  50  cm.)  or 
eighteen  to  twenty  inches  in  the  male  and  43.5  cm.  (39.5  to  47  cm.)  or  sixteen 
to  nineteen  inches  in  the  female.  In  the  course  of  fetal  development  the  spinal 
cord  occupies  the  entire  length  of  the  vertebral  canal  up  to  the  third  month,  but 
after  this  period  it  gradually  recedes  cephalad  owing  to  the  more  rapid  growth 
of  the  vertebral  column,  so  that  at  Ijirth  the  caudal  end  of  the  spinal  cord  has 
risen  to  the  level  of  the  third  lumbar  vertebra. 

The  spinal  cord  does  not  entirely  hi!  the  vertebral  canal.  A  wide  space  or 
rather  a  concentric  series  of  spaces  intervene  between  its  surface  and  the  walls 
of  the  canal,  affording  a  marked  freedom  of  movement  of  the  vertebral  column 
without  exerting  undue  tension  upon  the  spinal  cord.  These  spaces,  three  in 
number,  which  concentrically  surround  the  cord,  are  demarcated  by  the  three 
protective  membranes — (1)  pia,  (2)  arachnoid,  and  (3)  dura — which  are  continuous 
with  the  like  meninges  of  the  brain.  The  arrangement  of  the  spaces  and  the 
membranes  may  be  shown  thus: 


Epidural 
space. 
(Areolo- 
fatty 
tissue 
and 
plexus 

of 
veins.) 


Subdural 
space. 

(Cerebro- 
spinal 
fluid.) 


Subarachnoid 

space 

and 

subarachnoid 

reticulum. 

(Cerebrospinal 

fluid.) 


The  pia  {pia  mater  spinalis)  closely  invests  the  entire  surface  of  the  spinal  cord 
and  sends  septal  ingrowths  into  its  substance  as  well  as  a  fold  occupying  the  an- 
terior median  fissure.  A  leaf-like,  serrated  fold  of  pia,  the  ligamentum  denticula- 
tum,  passes  from  each  lateral  border  to  the  inner  surface  of  the  dural  sheath  and 
helps  to  support  the  cord  within  the  subarachnoid  space.  The  arachnoid  and  the 
pia  are  not  separable  in  gross  dissection  as  they  merge  insensibly,  though  usually 
described  as  distinct  membranes.  The  arachnoid  (araclmoidea  spinalis)  is  in 
reality  an  exceedingly  delicate  and  transparent  web-like  reticulum  whose  meshes 
constitute  a  relatively  wide  cavity  filled  with  cerebrospinal  fluid.  The  dura 
(dura  mater  spinalis)  constitutes  the  outermost  and  thickest  sheath,  while  the 
narrow  interval  between  the  dura  and  the  vertebral  canal  is  filled  by  a  fine  ^'enous 
plexus,  together  with  soft,  areolofatty  tissue.  The  tubular  sheath  of  dura  ends 
in  a  pointed  cul-de-sac  at  the  level  of  the  lower  border  of  the  second  sacral  segment. 
Of  the  three  spaces  which  surround  the  cord,  only  the  two  innermost  contain 
fluid,  and  that  of  a  serous  character;  the  amount  in  the  subdural  space  is  ^^ery 
small,  just  sufficient  to  moisten  the  contiguous  endothelial  surfaces  of  the  dura  and 
arachnoid;  that  in  the  subarachnoidal  space  is  considerable.  (For  detailed 
description  see  section  on  the  Meninges.) 

Weight. — The  weight  of  the  spinal  cord,  exclusive  of  all  nerve  roots,  averages 
28  grams,  or  1  ounce  avoirdupois,  being  slightly  less  in  the  female.  Including  the 
nerve  roots  as  ordinarily  cut  in  postmortem  procedure,  the  weight  averages  45 


822 


THE  NEB  VE  SYSTEM 


grams  in  the  male  and  40  grams  in  the  female.  The  ratio  of  weight  in  proportion 
to  that  of  the  brain  among  mammalia  is  lowest  in  the  human  species,  being  1 
to  51  in  the  male  and  1  to  49.8  in  the  female.  In  the  newborn  the  ratio  is  1  to 
115.     Its  specific  gravity  is  1.038. 

External  Morphology. — In  situ  the  spinal  cord  exhibits  slight  curvatures  in  the 
sagittal  plane,  lieing  convex  ventrad  in  the  transition  from  cervical  to  thoracic 
portion  and  slightly  concave  ventrad 
to  the  lumbar  portion.  Its  position 
varies  also  according  to  the  degree  of 
curvature  of  the  spinal  column,  being 
raised  slightly  (a  few  millimeters  only) 
in  flexion  of  the  vertebral  column. 

The  intrinsically  segmental  nature 
of  the  spinal  cord  is  expressed  by  the 
association  of  each  definite  segment 
with  the  somatic  segment  supplied  by 
its  nerves.  Thirty-one  pairs  of  spinal 
nerves    are     commonly    enumerated, 


thoracic- 


Fig.  597. — Showing  the  relations  of  the  cord  and 
erve  origins  to  the  levels  at  which  the  nerves  emerge 
irough  the  intervertebral  foramina  (diagrammatic). 


Fig.  59S.— The  c 


althougli  two  additional,  rudimentary  pairs,  relics  of  a  tailed  vertebrate  ancestry, 
are  demonstrable. 

The  first  pair  of  spinal  nerves  emerges  between  the  occiput  and  atlas,  and  is 
designated  the  first  cervical;  the  other  cervical  pairs  are  named  after  the  lower 
of  the  two  vertebrse  which  form  the  intervertebral  foramen  through  which  the 


THE  SPINAL   CORD 


823 


nerve  emerges.  Very  inconsistently  the  pair  emerging  between  the  seventh  cervi- 
cal and  first  thoracic  vertebrte  is  called  the  eighth  cervical  pair.  The  remaininp- 
spinal  nerves  are  named  after  the  upper  of  the  two  vertebrte  forming  the  corre- 
sponding foramen.     In  all  there  are: 

Cervical  pairs 8 

Thoracic  pairs 12 

Lumbar  pairs 5 

Sacral  pairs 5 

Coccygeal  pairs 1 

31 

All  spinal  nerves  are  made  up  of  two  roots  by  which  they  spring  from  the  lateral 
aspects  of  the  cord,  symmetrically  arranged,  and  these  nerve  root  attachments 
are  the  only  guides  to  the  demarcation  of  the  various  segments  of  the  spinal  cord. 
The  two  roots  are  generally  termed  the  posterior  or  dorsal  (afferent  or  sensor) 
root,  which  enters  the  cord  along  the  dorsolateral  fissure,  and  the  anterior  or  ventral 
(efferent  or  motor)  root,  which  emerges  along  the  ventrolateral  fissure. 

Although  the  cervical  nerves  pass  outward  through  the  intervertebral  foramina 
at  nearly  a  right  angle  to  the  long  axis  of  the  cord,  those  of  the  lower  series  slope 
more  and  more  caudad  or  downward,  so  that  the  fifth  lumbar  pair  emerges  six 
vertebral  bodies  lower  than  it  originates.  In  fact,  the  lumljar  and  sacral  nerves 
descend  as  parallel  bundles  in  a  brush-like  manner  to  form  the  cauda  equina, 
enclosed  by  the  dural  sheath  as  far  as  about  the  middle  of  the  sacral  canal.  The 
topographical  relations  of  the  levels  of  origin  and  exit  of  the  spinal  nerves  to  the 
spinous  processes  of  the  vertebra  are  shown  in  Fig.  597. 

Corresponding  with  the  degree  of  development  of  the  periphery,  the  spinal  cord 
is  more  massive  in  those  segments  which  are  associated  with  the  limbs.  Thus, 
in  the  ground-mole,  the  cervical  portion  is  very  much  enlarged  in  conformity 
with  the  powerfully  developed  forelimbs,  while  in  the  kangaroo  or  the  ostrich, 
with  powerful  legs,  the  lumbar  portion  of  the  spinal  cord  is  proportionately 
enlarged.  In  man,  both  the  cervical  and  lumbar  portions  are  enlarged,  and  while 
the  bulk  of  the  lower  limbs  exceeds  that  of  the  upper,  the  cervical  enlargement 
of  the  spinal  cord  is  greater  because  it  innervates  a  limb  which  is  functionally 
niore  differentiated,  capable  of  much  more  skilful  and  complex  movements,  and 
endowed  with  more  acutely  developed  tactile  sensibility. 

The  Enlargements  of  the  Spinal  Cord. — The  spinal  cord  is  marked  by  two 
spindle-shaped  enlargements  in  its  cervical  and  lumbar  portions,  while  the  inter- 
vening thoracic  portion  is  nearly  cylindrical,  being  slightly  I'educed  in  its  antero- 
posterior diameter.  The  cervical  enlargement  (intumescentia  cerviccilis)  extends 
from  the  first  or  second  cervical  segment  to  the  level  of  the  second  thoracic 
vertebra,  acquiring  a  maximum  breadth  (13  to  14  mm.)  at  the  sixth  cervical  ver- 
tebra. At  its  junction  with  the  medulla  oblongata  its  breadth  is  about  11  mm. 
The  thoracic  portion  is  about  10  mm.  in  breadth  (minimum  at  a  little  below  its 
middle)  while  its  sagittal  diameter  is  8  mm.  The  lumbar  enlargement  (intumescen- 
tia lumbalis)  begins  at  the  level  of  the  tenth  thoracic  vertebra,  and  acquires  its 
maximum  breadth  (12  mm.;  sagittal  diameter  =  9  mm.)  opposite  the  twelfth 
thoracic  vertebra.  Below  the  lumbar  enlargement  the  cord  gradually  tapers  to 
form  a  cone  (conus),  the  apex  of  which,  at  the  level  of  the  lower  border  of  the 
body  of  the  first  lumbar  vertebra,  is  continuous  with  the  attenuated  filum. 

The  cervical  enlargement  is  characterized  by  a  relatively  greater  breadth  than 
the  remaining  portions  of  the  cord  which,  on  section,  appear  nearly  circular. 

Conus  (conns  medullaris). — The  conus  is  the  conical  extremity  of  the  cord. 
The  lower  three  sacral  segments  and  the  coccygeal  segment  are  usually  included 


824 


THE  NERVE  SYSTEM 


under  this  term.     Its  diameter  becomes  reduced  to  2  mm.  (y^g-  inch),  to  be  con- 
tinued below  as  the  filum. 


C.l 


C2. 


C5. 


C.8: 


TA2. 


ma. 


Th.l2. 


L.5. 


S.2. 


Coc. 


*4LARGEMENT 


Ventral  aspect.     Dorsal  aspect. 
Pig.  600. — Diagram  of  the  spinal  cord  and  its  fissures. 


THE  SPINAL   CORD 


825 


Filum  ifilum  terminale)  .—The  delicate  terminal  thread  called  the  filum,  contin- 
uous with  the  tapered  end  of  the  conus,  is  about  24  cm.  (10  inches)  in  length. 
As  far  as  the  level  of  the  second  sacral  vertebral  segment  it  is  enclosed,  together 
with  the  Cauda  equina,  in  the  tapering  sheath  of  the  dura.  Within  the  dural  sac 
it  is  called  the  filum  internum,  in  contradistinction  to  the  filum  externum,  which  is 
an  attenuated  process  of  connective  and  glia  tissue  closely  invested  by  a  prolonga- 
tion of  the  dura,  which  finally  attaches  to  the  periosteum  of  the  dorsum  of  the 
cocc>-x.  The  filum  externum  occupies  one-third  of  the  total  length  of  the  filum. 
Morphologically,  the  filum  is  the  caudal  representative  of  the  cord,  and  its  Intra- 
dural portion  is  usuallj'  accompanied  by  slender  fascicles  of  nerve  fibres,  which  are 
rudimentary  second  and  third  coccygeal  pairs  of  spinal  nerves. 


Central  canal. 


— Nuclei  of  spongio^ 


..  ,   .— , , Neuroblasts. 

*^^  >..  ^;^x^j^    Processes  of  neuroblasts 
~~''"'    '         growing  out  to  form 
ventral  nerve  root. 


Ventral  column- 


fiOl. — Section  of  spinal  cord  of  a  four  weeks*  embryo.      (His.) 


Fissures  and  Grooves. — The  spinal  cord  is  a  bilaterally  symmetrical  structure 
and  exhibits  a  deep  ventral  fissure  and  a  slight  dorsal  groove  partially  subdividing 
the  cord  into  the  right  and  left  halves.  The  ventral  fissure  (/.  mediana  anterior) 
extends  throughout  the  entire  length  of  the  cord,  being  shallower  in  the  cervical 
and  thoracic  portions  (less  than  one-third  of  the  sagittal  diameter)  than  in  the 
lumbar  portion.  It  is  surfaced  by  a  fold  of  pia  which  conveys  the  more  im- 
portant nutritive  vessels  to  the  depths  of  the  cord  substance.  In  the  depth  of  this 
fissure  lies  the  white  (ventral)  commissure  of  the  cord.  The  dorsal  groove  (sulcus 
medianus  posterior)  has  been  regarded,  erroneously,  as  being  analogous  to  the  ven- 
tral fissure.  Unlike  the  ventral  fissure,  however,  the  pia  does  not  descend  into 
its  depths,  but  passes  continuously  over  it.  The  shallow  groove  marks  the  site 
of  a  septum  made  up  of  neuroglial  and  ependyma)  elements.  An  actual  groove 
is  best  demonstrable  in  part  of  the  lumbar  cord  and  in  the  medulla  oblongata,  where 
it  constitutes  a  veritable  fissure  between  the  clavse. 

Each  lateral  half  is  marked  by  the  lines  of  root  attachment  of  the  spinal  nerves. 
The  dorsal  nerve  root  fascicles  enter  the  cord  in  linear  series  and  in  a  depression 
or  true  sulcus  termed  the  dorsolateral  fissiu'e  {.sulcus  lateralis  posterior).  The 
ventral  nerve  root  fascicles  emerge,  irregularly  scattered,  out  of  a  greater  circum- 
ferential area,  and  no  true  ventrolateral  fissure  can  be  said  to  exist.  The  line  of 
emergence  of  the  outermost  fascicles  is  usually  taken  as  an  arbitrary  boundary 
between  the  ventral  and  lateral  districts  of  the  cord,  while  the  dorsolateral  fissure 
more  distinctly  maps  off  the  lateral  from  the  dorsal  district.     An  additional  fissure. 


826 


THE  NERVE  SYSTEM 


observed  most  distinctly  in  the  cervical  and  upper  thoracic  portions,  termed  the 
dorsoparamedian  fissure  (sulcus  intermedms  -posterior),  demarcates  the  two  principal 
divisions  of  the  dorsal  columns,  the  gracile  and  the  cuneate  columns.     The  dorso- 


SOMATIC    SENSOR 


VISCERAL  SENSOR 
VISCERAL    MOTOR 


SOMATIC    MOTOR 


Fig.  602. — A  diagram  of  the  component  elements  in  tile  spinal  cord  and  the  nerve  roots  in  a  trunk  segment 
to  illustrate  the  four  functional  divisions  of  the  nerve  system.      (After  Johnston.) 

paramedian  fissure  is  an  exceedingly  shallow  groove  and  is  best  denoted  in  sections 
of  the  cord  by  its  continuance  as  a  connective-tissue  {glia)  septum  into  the  sub- 
stance of  the  dorsal  column.     An  analogous  ventroparamedian  fissure  (sulcus  inter- 


SPONGIOBLAST- 


GERMINAL   CELL 


Fig.  603. — Trans-section  through  neural  tube,  early  and  later  stages,  diagrammatic.  Earliest  stages  shown 
on  left  side.  On  the  right,  the  maturing  neuroblasts  are  seen  sending  their  axonic  processes  toward  the 
periphery  or  to  other  regions  of  the  central  axis,  and  the  central  processes  of  the  spinal  ganglionic  cells  are 
seen  to  invade  the  dorsolateral  region. 

medius  anterior)  is  sometimes  observable  close  to  the  ventral  fissure,  demarcating 
the  ventral  (or  direct)  pyramidal  fasciculus. 

Columns  of  the  Cord  (funiculi  medullae  spinalis). — Each  half  of  the  spinal 
cord  is  thus  divided,  with  respect  to  its  white  substance,  into  three  chief  columns 


THE  SPINAL   CORD 


827 


or  funiculi.  The  dorsal  column  occupies  the  area  between  the  dorsal  septum  and 
groove  and  the  line  of  attachment  of  the  dorsal  nerve  roots;  this  column  in  its 
turn  is  generally  subdivided  into  the  column  of  GoU  {funiculus  gracilis)  and  the 
column  of  Burdach  {funiculus  cuneatus)  by  the  shallow  dorsoparamedian  groove 
and  o-lia  septum  referred  to  above.  The  ventral  column  {funimdus  axterinr) 
occupies  the  area  between  the  ventral  fissure  and  the  outermost  fascicles  of  the 
ventral  nerve  roots — an  arbitrary  boundary  line.  The  lateral  column  (funiculus 
lateralis)  constitutes  the  remainder  of  the  cord,  between  the  posterior  and  anterior 
nerve  root  attachments.  Each  of  these  columns  is  subdivided  into  its  component 
bundles  or  fasciculi,  best  studied  in  sections  of  the  cord. 


LOCATION  OF  THE  SEGMENTS  FOR 

SIBILITY.  MOTILITY. 


.VtiscUs  0/  expression  {tower  facial) 
Palatal  and  pharyngeal  musctr* 
Muscles  of  tlie  larynx 
Muscles  of  tlie  tongue 


Diaphragm 

Delt.,  liceps,  pectoral,  maj.  iclavic.  portion)  "i 
Brachial,  antic,  supinator  longus  > 

Triceps, latis.dorsifPect. maj. {costal    "     )) 
Extenaores  carpi  et  digitoruvft 

digitorum    j  ^■"■"•"^ 
Interossei,  lumhricales  \ 

Thenar,  hypothenar     i 


Fig.  604.— Explanation  of  abbreviations:  tr.  olf.,  olfactory  tract;  c.  (7.  I.,  lateral  geniculate  body;  P,  r,  cr,  .4, 
indicate  approximately  the  location  of  the  reflex  centres  for  the  pupillary  (p),  the  respiratory  (r),  cremasteric 
(cr).  patellar  (.pat),  and  tendo-Achillis  (A)  reflexes.  The  vesical  centre  lies  in  the  third  and  fourth  sacral  seg- 
ments; the  anal  centre  in  the  fourth  and  fifth  (represented  by  circles);  the  centres  for  erection,  ejaculation, 
labor  pains  (?)  are  probably  also  situated  in  this  region.  In  reality,  the  divisions  between  the  various  seg- 
ments are,  of  course,  not  so  sharp  as  they  are  shown  in  the  diagr.am,so  that  a  given  muscle  or  cutaneous  region 
derives  some  of  its  controlling  nerve-roots  from  the  segments  lying  immediately  above  and  below  the  principal 
segment.  The  sensor  segment  for  any  given  region  is  regularly  somewhat  higher  than  the  corresponding  motor 
segment.      (.Jakob.) 

Development  of  the  Spinal  Cord. — The  elongated  postcranial  portion  of  the  neural  tube 
becomes  the  spina!  cord,  while  the  primitive  cavity  within  is  preserved  as  the  central  canal  of 


828 


THE  NERVE  SYSTEM 


the  cord.  The  metamorphosis  of  the  neuroepithelial  columnar  cells  has  been  described  (p.  806). 
The  lateral  walls  thicken  considerably,  the  central  slit-like  canal  widens  as  the  walls  bulge  out- 
ward in  an  angular  manner,  and  the  central  tubular  gray  becomes  a  fluted  column  with  dorsal 
and  ventral  ridges  (or  horns)  enveloped  by  a  rapidly  growing  mantle  of  axone  bundles  which 
become  myelinic  in  successive  stages.  The  bulging  of  the  thickening  walls  in  the  dorsal  and 
ventral  as  well  as  lateral  directions  produces  the  ventral  fissure  and  the  postseptum. 

The  segmental  nature  of  the  spinal  cord  has  been  alluded  to  before  with  regard  to  the  seg- 
mental derivation  of  the  cerebrospinal  ganglia  and  the  disposition  of  the  outgrowing  nerve 


Ventral  aspect. 


Dorsal  aspect. 


Fig.  605. — Distribution  of  cutaneous  nerves. 


btmdles.  There  is  a  further  mode  of  division  into  longitudinal  systems  based  upon  functional 
relationships.  Two  main  categories  of  acti\'ity  characterize  the  mechanism  of  the  nerve  system 
and  find  somatic  expression  in  its  architectural  plan:  First,  actions  in  relation  to  the  external 
world  (somatic — involving  skin,  muscle,  skeleton,  etc.);  second,  internal  activities  concerned 
with  the  processes  of  nutrition  and  reproduction  (visceral — involving  the  alimentary  tract,  vas- 
cular [blood  and  lymph],  excretory,  and  reproductive  systems).  In  each  there  is  a  twofold 
activity  on  the  part  of  the  nerve  system:  reception  of  stimuli  and  motor  responses.  In  the  cord 
(and  to  some  extent  in  the  brain  as  well)  the  following  functional  divisions  may  be  distinguished 
and  located  anatomically  (Fig.  602): 


Somatic  sensor  elements. 
Somatic  motor  elements. 


Visceral  sensor  elements. 
Visceral  motor  elements. 


THE  SPINAL  CORD 


829 


This  functional  differentiation  of  the  neural  axis  into  sensor  and  motor  divisions  apparently 
finds  organic  expression  in  an  important  modification  of  the  developing  neural  tube.  Each 
lateral  wall  of  the  neural  tube  is  early  demarcated  into  a  dorsal  and  a  ventral  lamina  and  the 
slit-like  central  canal  becomes  more  or  less  lozenge-shaped  on  trans-section,  owing  to  the  forma- 
tion of  a  lateral  longitudinal  furrow  within.  The  dorsal  lamina  or  zone  is  preponderatingly 
sensor  in  function,  while  the  ventral  zone  is  principally  motor  in  function.  This  fundamental 
fact  has  been  of  the  greatest  aid  in  the  correct  interpretation  of  many  hitherto  obscure  facts  re- 
garding the  mechanism  of  the  nerve  system,  and  will  be  found  to  underlie  our  method  of  descrip- 
tion throughout. 

The  muscular  supply  from  motor  segments  of  the  cord  is  shown  in  Fig.  604, 
and  the  cutaneous  supply  in  Fig.  605. 

Internal  Structure  of  the  Spinal  Cord. — If  a  transverse  section  of  the  spinal 
cord  be  made,  it  will  be  seen  to  consist  of  white  and  gray  nerve  substance.  The 
white  substance  is  made  up  of  myelinated  axones;  the  gray  contains  the  cell 
bodies  of  neurones  and  nonmyelinated  axones  with  only  few  myelinated  axones. 
The  color  of  the  gray  substance,  so-called,  varies  according  to  the  degree  of  capil- 
lary injection  and  the  age  of  the  individual.  It  is  usually  of  a  faint,  reddish-gray 
tinge,  the  gray  preponderating  in  older  persons,  but  various  shades  of  red,  yellow, 


-LATERAL 


ERAL   HORN 


TRAL    HORN 


*''V7-R),L    BOC*      VENTRAL    FISSURE 

Fig.  606. — Trans-section  of  the  spinal  cord  at  the  mid-thoracic  region. 


and  light  slate-color  may  be  noted.  Nor  is  the  color  uniform  even  in  the  same 
section.  Around  the  central  canal  and  at  the  periphery  of  the  dorsal  horn  the 
gray  substance  is  very  translucent  and  is  termed,  according  to  its  situation,  the 
gelatinosa  centralis  (gliosa  centralis)  and  gelatinosa  Rolandi  or  caput  gliosum  (gliosa 
cornualis).  The  white  substance  surrounds  the  gray  column  as  a  variously 
thickened  tunic,  closely  invested  by  the  pia,  which  sends  numerous  delicate,  vessd- 
bearing  ingrowths  into  the  substance  of  the  cord.  The  relative  area  of  the  white 
substance,  as  seen  on  section, (increases  cephalad;  the  absolute  area  of  both  white 
and  gray  is  the  largest  in  the  region  of  the  enlargements  (Fig.  607). 

Gray  Substance  of  the  Cord  (siibstantia  grisea  centraUs;  entocinerea). — A  plastic 
conception  of  the  gray  substance  of  the  cord  is  essential  to  an  understanding  of 
the  internal  architecture.  The  gray  core  must  be  imagined  not  alone  in  the 
relations  in  which  it  is  conventionally  studied,  as  exposed  in  trans-sections,  but 


830 


THE  NER  VE  SYSTEM 


also  as  a  fluted  column  having  a  continuous  extent  throughout  the  cord.     This 

oray  column  is  drawn  into  ventral  and    dorsal  ridges,  connected   respectively 

with  the  ventral  and  dorsal  nerve  roots,  while  the  white  substance  fills  out  the 

irregularities  and  completes  the  nearly  cylindrical  outline  of  the  cord  (Fig.  608). 

On  viewing  a  trans-section,  it  is  seen  that  the  gray  substance  is  so  arranged  as  to 

present,  in  each  lateral  half  of  the  cord,  a  crescentic  or  comma-shaped  mass,  the 

concavity  of  which  is  directed  laterad.     The  two  lateral  masses  are  connected 

by  a  transverse  bar  or  band  of  gray  substance,  termed  the  gray  commissure  (com- 

missura  cinerea  [griseaj),  and  containing  the  central  canal,  which  extends  the 

entire  length  of  the  cord.     The  dorsal  septum  of  the  cord  reaches  quite  to  the 

gray  commissure,  there  being  but  a    few  white  com- 

40    20    0    20   M  missural  fibres  in  the  dorsal  zone.     Ventrad,  however, 

a  lamina  of  white  substance,  the  commissura  ventralis 

alba,  separates  the  gray  commissure   from  the  ventral 

fissure  (Fig.  606). 

In  trans-sections  of  the  cord  it  is  seen  that  the 
lateral  crescentic  gray  masses,  united  across  the  middle 
line  by  a  gray  commissure,  have  the  aggregate  appear- 
ance of  the  letter  H.  Each  crescentic  mass  presents 
projections  which  are  more  or  less  pronounced  accord- 
ing to  the  segment  of  the  cord  under  consideration. 
Broadly  stated  and  without  reference  to  special  levels, 
the  most  marked  projections  are  the  dorsal  and  ventral 
horns  or  comua. 

The  dorsal  horn,  directed  dorsolaterad,  is  elongated 
and  narrow,  and  its  apex  is  composed  of  a  trans- 
lucent, V-shaped  mass  termed  the  caput  gelatinosa 
Bolandi. 

The  attenuated  apex  of  the  dorsal  cornu  approaches 
the  surface  of  the  cord  along  the  line  of  entrance  of 
th'e  dorsal  nerve  roots.  The  apex  of  the  dorsal  horn  is 
wider  in  the  regions  of  the  enlargements  and  the  gelat- 
inosa is  most  marked  in  the  higher  cervical  segments. 
The  base  or  cervix  of  the  dorsal  horn  is  constricted 
somewhat  except  in  the  thoracic  portion,  where  its 
greater  breadth  is  due  to  the  presence  of  Clarke's  col- 
umn (micleus  dorsalis). 

The  ventral  horn  is  shorter,  thicker,  and  more  blunt, 
and  is  separated  from  the  ventral  and  lateral  surfaces 
of  the  cord  by  a  tolerably  thick  lamina  of  white 
substance.  Its  margin,  in  trans-sections,  presents  a 
dentate  or  stellate  appearance  due  to  the  emergence  of 
fascicles  of  efferent  or  ventral  root  axones  on  their  way 
to  the  ventral  surface  of  the  cord. 
What  is  known  as  the  lateral  horn  projects  as  a  lateral  peninsular  extension  of 
the  central  gray  nearly  on  the  line  of  the  gray  commissure.  It  is  best  marked  as 
a  triangular  projection  in  the  upper  thoracic  segments.  In  the  cervical  enlarge- 
ment it  is  merged  with  the  greatly  expanded  ventral  horn,  but  it  again  becomes 
prominent  in  the  upper  cervical  segments. 

The  gray  substance  of  the  cord  is  not  everywhere  sharply  demarcated  from  the 
white  owing  to  the  invasion  of  myelinic  and  amyelinic  nerve  fibres.  Facing  the 
lateral  column,  in  the  angle  between  the  dorsal  and  ventral  horns,  small  fascicles 
of  white  fibres  are  embedded  in  the  gray  so  that  it  is  broken  up  in  a  peculiar 
basket-work  pattern  termed  the  reticular  formation.     This  gray  network  is  best 


Fig.  607. — Pro.iection  upon  a 
plane  of  the  absolute  and  relative 
extent  of  the  gray  and  white  sub- 
stance of  the  cord  as  determined 
by  successive  sectional  areas. 
Gray  substance  shown  in  black, 
(Adapted  from  the  measurements 
of  Stilling.) 


THE  SPINAL  CORD 


831 


marked  in  the  cervical  region  and  becomes  more  abundant  in  the  medulla  oblon- 
gata. 

The  mode  of  arrangement  of  the  gray  substance  and  its  amount  in  proportion 
to  the  white  vary  in  different  parts  of  the  cord.  Thus,  the  dorsal  horns  are  long 
and  narrow  in  the  cervical  region;  short  and  narrower  in  the  thoracic;  short  but 
wider  in  the  lumbar  region.  In  the  cer\-ical  region  the  crescentic  portions  are 
small,  and  the  white  substance  more  abundant  than  in  any  other  region  of  the 
cord.  In  the  thoracic  region  the  gray  substance  is  least  developed,  the  white 
substance  being  also  small  in  quantity.  In  the  lumbar  region  the  gray  substance 
is  more  abundant  than  in  any  other  region  of  the  cord.  Toward  the  lower  end 
of  the  cord  the  white  substance  gradually  ceases.  The  crescentic  portions  of  the 
gray  substance  soon  blend  into  a  single  mass,  which  forms  the  only  constituent 
of  the  lower  extremity  of  the  cord. 


E.  A.  S. 

VENTRAL    FISSURE 

Fig.  608. — Showing  origin  of  two  pairs  of  spinal  nerves  (schematic). 


The  gray  commissure  which  connects  the  two  crescentic  masses  of  gray  substance 
consists  of  myelinic  and  amyelinic  nerve  fibres  and  neuroglia.  The  fibres  pass 
transversely,  spreading  out  at  various  angles,  into  the  lateral  gray  masses.  In 
the  gray  commissure,  and  extending  the  whole  length  of  the  cord,  is  a  minute 
channel,  the  central  canal  {canalis  centralis;  myelocele),  which  is  barely  visible  to 
the  naked  eye,  but  is  proportionately  larger  in  some  of  the  lower  vertebrates. 
Cephalad,  in  the  medulla  oblongata,  it  opens  out  into  the  fourth  ventricle; 
caudad  it  is  continued  for  a  short  distance  into  the  filum,  in  which  it  ends 
blindly.  The  canal  is  very  minute,  less  than  0.1  mm.  (g^o^inch),  except  in  the 
terminal  part  of  the  conns,  where  it  expands  into  a  fusiform  dilatation,  the  sinus 
terminalis.  The  central  canal  is  lined  by  a  layer  of  columnar  cells  which  are  seen 
to  be  ciliated  in  the  embryo  and  are  in  all  respects  identical  with  the  ependymal 
cells  lining  the  ventricles  of  the  brain.  Surrounding  the  ependymal  lining  of  the 
central  canal  and  gradually  merging  into  the  spongy  substance  which  constitutes 
the  remainder  of  the  gray  commissure  is  a  finely  granular  and  reticulated  substance, 
the  gelatinosa  centralis,  almost  entirely  composed  of  neuroglia,  with  a  few  fine 
fibrils  apparently  proceeding  from  the  ependymal  cells,  and  having  a  translucent, 
gelatinous  appearance. 

The  gray  substance  of  the  cord  is  composed  of  (1)  the  gelatinosa  or  gliosa, 
which  envelops  the  head  of  the  dorsal  horn  and  which  encircles  the  central  canal 
of  the  cord ;  (2)  the  spongiosa,  which  forms  the  crescentic  horns  (except  the  heads 
of  the  posterior  horns  and  the  envelope  of  the  central  canal).  Further,  it  may  be 
stated  that  the  gray  substance  consists  of  nerve-fibres  of  variable  but  smaller 


832 


THE  NERVE  SYSTEM 


average  diameter  than  those 
of  the  white  columns;  (3) 
nerve  cells  of  various  shapes 
and  sizes,  with  few  or  many 
processes;  (4)  bloodvessels, 
lymphatic  channels,  and 
connective  tissue. 

The  nerve  fibres  of  the 
gray  substance  of  the -pos- 
terior horn  are  for  the  most 
part  composed  of  a  dense 
interlacement  of  minute 
fibrils,  intermingled  with 
nerves  of  a  larger  size.  This 
interlacement  is  formed 
partly  by  the  axones  and 
dendrites  of  the  cells  of  the 
gray  substance,  and  partly 
by  fibres  which  enter  the 
gray  substance  and  which 
come  from  various  sources. 
The  nerve  cells  of  the  gray 
substance  are  collected  into 
groups  {iiidi  or  nuclei)  as 
seen  on  transverse  section, 
but  they  really  form  columns 
of  cells  placed  longitudinally ; 
or  else  they  are  found  scat- 
tered throughout  the  whole 
of  the  gray  substance  (Fig. 
609). 

In  the  ventral  horn  four 
main  groups  of  cells  may  be 
distinguished  which  are  not 
wholly  represented,  how- 
ever, in  all  regions  of  the 
cord:  (1)  A  ventral  group  of 
cells,  separable  in  the  cervi- 
cal and  lumbar  regions  into 
ventromedial  and  ventro- 
lateral sub-groups;  (2)  a 
dorsomedial  group,  situated 
in  the  cervix  of  the  ventral 
horn,  usually  demonstrable 
in  the  thoracic  portion  as 
well  as  a  few  contiguous 
cervical  and  lumbar  seg- 
ments; (3)  a  lateral  group, 
separable  in  the  lower  cer- 
vical and  lumbar  regions 
into  ventrolateral  and  dorsolateral  sub-groups,  and  supplying  the  muscles  of  the 
extremities;  (4)  a  central  group  of  cells  in  the  lumbar  and  sacral  regions. 

In  the  lateral  horn,  which  is  most  prominent  in  the  thoracic  and  upper  cervical 
segments,  lies  an  intermediate  group  of  cells,  a  long,  slender  column  which  is 
nearly  restricted  to  the  thoracic  portion  of  the  cord,  but  is  seen  to  reappear  in  the 


TRO-MEDIAL 


Fig.  609. — Trans-sections  of  the  spinal  cord  at  different  levels  to  show 
the  topographical  arrangement  of  the  principal  cell  groups. 


THE  SPINAL  CORD 


833 


upper  three  cervical  and  in  the  third  and  fourth  sacral  segments.  The  axones 
from  these  cells  probably  do  not  pass  out  with  the  ventral  nerve  roots,  but  rather 
course  within  the  cord  to  terminate  at  various  levels  on  the  same  as  well  as  on 
the  opposite  side.  A  close  connection  with  the  sympathetic  nerve  system,  and 
with  vasomotor  and  sweat-gland  nerves,  has  been  suggested. 

In  the  dorsa)  horn  the  most  conspicuous  group  of  cells  is  a  columniform  nucleus 
commonly  termed  Clarke's  column  (nucleus  dorsalis),  which  extends  between  the 
seventh  cervical  and  second  (or  third)  lumbar  segments  of  the  cord.  The  cells 
are  large  and  the  group  presents  an  oval 
outline  in  trans-sections,  lying  in  the  medial 
part  of  the  cervix  of  the  dorsal  horn.  The 
axones  of  these  cells  pass  out  of  the  gray 
into  the  lateral  column  of  the  cord  to  form 
the  spinocerebellar  tract,  and  convey  tactile 
impulses  to  the  cerebellum.  It  is  repre- 
sented in  other  regions  of  the  cord  by  scat- 
tered cells  which  are  aggregated  to  form 
the  cervical  nucleus  opposite  the  third  cer- 
vical nerve,  and  a  sacral  nucleus  in  the  middle 
and  lower  part  of  the  sacral  region.  The 
axones  of  these  cells  form  the  homolateral 
direct  cerebellar  tract. 

The  cells  of  the  dorsal  horn  are  not 
grouped  very  definitely,  and  for  the  purposes 
of  description  they  are  subdivided  accord- 
ing to  their  location.  The  cells  vary  much 
in  form  and  size  and  their  branched  axones 
pass  toward  other  regions  within  the  gray 
substance  at  various  levels  on  the  same  or 
on  opposite  sides,  or  via  the  ground  bun- 
dles. Many  fibres  of  the  dorsal  nerve  roots 
are  in  relation  with  the  dorsal  horn  cells. 

The  various  groups  of  cells  enumerated 
above  are  frecjuently  demarcated  from 
neighboring  groups  by  nerve  fibre  intervals, 
which  may  be  straight,  curved,  interlaced,  or 
loop-shaped. 

Through  the  gelatinosa  Rolandi  (gliosa 
corimalis)  pass  niunerous  fine  fibrils, 
chiefly  the  afferent  dorsal  nerve  root  fibres, 
but  in  addition  this  peculiar,  gelatinous, 
and  semitranslucent  substance  contains  numerous  small,  stellate  cells;  the  region 
is  so  densely  filled  with  axones  and  collaterals,  as  well  as  neuroglia  cells,  that  until 
staining  methods  became  sufficiently  developed  the  importance  of  this  substance 
remained  in  dispute.  In  man  the  gelatinosa  Rolandi  shows  convolutions  feebly 
imitating  those  of  the  olivary  body,  and  its  structure  is  analogous.  Dorsad  of  the 
gliosa  lies  the  ultimate  zone  of  the  dorsal  horn;  this  gray  substance  resembles 
the  spongiosa  in  its  essential  characters. 

The  White  Substance  of  the  Cord  {substantia  alba). — The  white  substance  of  the 
cord,  consisting  chiefly  of  longitudinally  disposed  myelinic  fibres,  with  blood- 
vessels, neuroglia,  and  connective-tissue  septa,  forms  a  thick  mantle  which  invests 
the  central  gray  column.  When  stained  with  carmine,  a  transverse  section  of 
the  white  substance  is  seen  to  be  studded  all  over  with  minute  dots  surrounded 
by  unstained  circular  areas.  The  dots  are  the  transversely  cut  axones ;  the  lighter 
areas  are  the  myelin  sheaths.     The  mass  of  white  substance  is  closely  invested  by 


E.  A.  S. 


Fig.  610. — Showing  the  dorsal  nucleus  (of 
Clarke),  and  its  cervical  and  sacral  extensions 
on  one  side,  and  the  direct  spinocerebellar  tract 
on  the  other.  The  fibres  of  the  tract  ascend  on 
the  same    side  as    the  nucleus     in    which    they 


834  THE  NERVE  SYSTEM 

a  sheath  of  neuroglia  immediately  beneath  the  pia.  Numerous  septa,  derived  from 
the  pia,  but  always  coated  by  a  thin  layer  of  neuroglia,  pass  into  the  white  sub- 
stance to  separate  the  respective  bundles  of  fibres  and  are  often  interwoven  between 
individual  nerve  fibres,  acting  as  a  supporting  framework  in  which  they  are  em- 
bedded. In  addition  to  the  longitudinal  fibres  there  are  shorter  and  less  numerous 
trans\-erse  fibres  forming  the  white  commissure. 

The  longitudinal  fibres  constitute  the  conducting  tracts.  Although  a  purely 
anatomical  examination  fails  to  reveal  the  functional  relations  in  these  fibre 
bundles,  the  structural  alterations  which  ensue  (in  accordance  with  the  laws 
of  Waller)  in  the  distal  portion  of  a  neurone  whose  proximal  portion  has  been 
destroyed,  the  progressive  myelinization  of  separate  tracts  in  the  embryo  and 
infant  (as  proved  by  the  researches  of  jMeynert  and  Flechsig),  the  comparative 
anatomy  method  and  electrophysiological  experimentation  have  rendered  possible 
the  demonstration  of  the  origin  and  destination  of  the  various  conducting  systems 
or  tracts  with  almost  mathematical  accuracy.  While  some  fibres  pursue  a  lengthy 
course,  serving  as  conduction  paths  between  the  brain  centres  and  the  various 
spinal  centres,  others  are  shorter  and  serve  to  associate  different  spinal  levels — 
in  juxtaposition  or  relatively  not  far  distant.  It  rhust  be  borne  in  mind  that  the 
gray  substance,  intercalated  as  it  is  in  the  course  of  the  impulses  which  pass  to  and 
fro  in  the  cord,  contains  the  neural  elements  which  are  either  (a)  the  source 
or  (b)  the  destination  of  these  impulses,  and  thus  complete  the  ner^'e  cycle  requisite 
for  the  organization  of  the  functions  belonging  to  the  cord.  The  motor  and 
sensor  phenomena,  though  interacting,  depend  upon  distinct  nerve  elements 
which,  because  of  their  functional  relationships,  or  because  of  the  direction  in 
which  they  convey  impulses,  are  generally  referred  to  as  motor  or  efferent  and  sen- 
sor or  afferent  neurones;  and  in  the  spinal  cord  usage  has  sanctioned  the  employ- 
ment of  the  terms  descending  and  ascending  for  tracts  conveying  motor  and  sensor 
impulses,  respectively.  Anatomically  speaking,  however,  it  is  preferable  to  de- 
scribe the  tracts  with  reference  to  their  origins  and  termini  (as  cerebrospinal, 
spinothalamic,  etc.),  when  known,  or  to  their  topographical  relations  as  studied 
in  trans-sections  of  the  cord. 

For  the  purposes  of  description  it  is  convenient  to  classify  the  longitudinal 
fibres  into  three  general  systems:  (1)  The  cerebrospinal  system  of  axones  forming 
conduction  paths  for  efferent  impulses  from  the  cerebrum  to  the  spinal  centres 
for  peripheral  organs,  and  axones  for  afferent  impulses  received  in  the  spinal 
centres  from  the  periphery  and  conveyed  in  turn  to  the  cerebrum.  (2)  The 
spinocerebellar  system,  consisting  of  conduction  paths,  afferent  and  eft'erent  between 
the  cerebellum  and  the  spinal  centres.  (3)  Numberless  association  systems 
strictly  confined  within  the  cord  (or  only  extending  into  the  medulla  oblongata), 
composed  of  shorter  or  longer  axones  which  serve  to  associate  not  only  different 
levels  of  the  same  spinal  segment,  but  also  the  dift'erent  segments  that  are  in  juxta- 
position or  more  remotely  situated.  These  spinal  association  axones  form 
bundles  in  close  contact  with  the  central  gray  column  and  are  termed  the  fasciculi 
proprii  or  ground  bundles. 

Tracts  of  the  Spinal  Cord. — In  the  dorsal  column  there  are  the  following  tracts: 

Ascendinj: 

1.  Fasciculus  gracilis  (Golli). 

2.  Fasciculus  cuneatus  (Burdachi). 
Descending : 

1.  Comma  tract  (Schultze). 

2.  Median  oval  tract  (Flechsig). 
Associating : 

1.  Fasciculus  dorsalis  proprius. 

2.  Dorsal  cornucommissural  tract. 

3.  Septomarginal  tract  (Bruce). 


THE  SPINAL  CORD 


835 


Another  tract,  usually  described  as  belonging  to  the  lateral  column,  but 
functionally  more  intimately  related  to  the  sensor  neurone  system  of  the  dorsai 
column  is  the  fasciculus  marginalis  (of  Spitzka  and  Lissauer,  described  on 
page  836). 

The  great  majority  of  the  axones  constituting  the  dorsal  column  are  the  afferent 
(sensor)  axones  arising  from  the  spinal  ganglion  cells,  entering  the  cord  by  the 
dorsal  roots.  These  dorsal  root  axones  bifm'cate  in  the  region  of  the  dorsal 
horn,  one  branch  ascending  a  little  obliquely  at  first,  then  vertically,  while  the  other 
branch  takes  a  similar  downward  course  for  a  shorter  distance  (Fig.  613).  As 
additional  groups  of  fibres  are  contributed  by  each 
successive  dorsal  nerve  root  the  mass  of  white 
substance  in  the  dorsal  column  accumulates  as 
the  cord  is  ascended,  though  it  must  be  noted  that 
not  all  of  these  afferent  fibres  traverse  the  whole  of 
the  cord  above,  but  end  in  relation  with  cells  in 
the  gray  substance  at  various  levels.  The  succes- 
sive accessions  of  afferent  fibres  are  disposed  in 
a  laminated  manner  so  that  the  lumbar  fibres 
come  to  lie  laterad  of  the  sacral  bundle,  the 
thoracic  laterad  of  the  lumbar,  and  so  on  as  the 
cord  is  ascended.  A  section  of  the  cord  at  its 
highest  level  would  therefore  traverse  a  collection 
of  bundles  derived  from  all  of  the  dorsal  nei-ve  roots 
of  the  cord,  arranged  as  shown  in  Fig.  611. 

In  the  upper  segments  of  the  cord  it  is  possible 
to  distinguish  a  division  of  the  dorsal  column  into 
two  principal  fasciculi  owing  to  the  presence  of 
a  distinct  connective-tissue  septum  which  passes 
into  the  substance  of  the  dorsal  column  along  the 
dorsoparamedian  groove.  These  fasciculi  are 
termed  the  fasciculus  gracilis,  or  Goll's  column,  and 
the  fasciculus  cuneatus,  or  Burdach's  column;  in  the 
consideration  of  the  external  morphology  of  the 
cord,  these  have  already  been  referred  to  as  the 
funiculus  gracilis  and  funiculus  cuneatus,  respec- 
tively. 

It  has  been  noted  that  even  in  the  fresh  cord, 
when  sectioned,  the  gracile  bundle  has  a  different 
tinge  and  stains  more  deeply  with  carmine  than 
does  the  cuneate  bundle. 

The  caudal  or  descending  branches  of  tlie  bifur- 
cate dorsal  root  axones  are  considerably  shorter 
than  the  ascending  branches.  They  terminate  in 
the  gray  substance  in  relation  with  its  cells  and, 
by  numerous  collaterals  which  are  shorter  or  longer 
and  given  off  at  various  intervals,  serve  to  asso- 
ciate different  levels  of  the  cord.  Some  of  these 
collaterals  cross  the  median  line  in  the  dorsal  (gray) 
commissure  to  come  into  relation  with  neurones  of  the  opposite  side.  Certain 
of  the  longer  descending  branches  show  a  tendency  to  collect  into  a  feebly  marked 
bundle  along  the  mesal  border  of  the  cuneate  fasciculus,  called,  because  of  its 
outline  in  trans-sections — as  seen  in  cases  of  descending  degeneration  from 
injury  at  a  higher  level — the  comma  tract  of  Schultze.  A  similar  bundle,  situated 
along  the  dorsal  septum,  best  demonstrable  in  the  lumbar  cord,  and  with  its  fellow 


^      Lumbar 
\\      neries 


Fig  611  — Formation  of  the  fascic- 
ulus gracilis  Spmil  cord  viewed  from 
behmd  To  the  left  the  fasciculus 
gracilis  is>  shaded.  To  the  right,  the 
drawing  shows  that  the  fasciculus 
gracilis  is  formed  by  the  long  fibres  of 
the  posterior  roots,  and  that  in  this 
tract  the  sacral  nerves  lie  next  the 
mesal  plane,  the  lumbar  to  their  outer 
side,  and  the  thoracic  still  more  later- 
ally.     (Poirier.) 


836 


THE  NER  VE  SYSTEM 


of  the  opposite  side  of  tlae  oval  outline  as  seen  on  section,  is  called  the  oval 
bundle  of  Flechsig  (fractus  cervkolumbalis  [Edinger];  dorsomediales  Sakralfeld 
[Obersteiner]). 


WHrXE    VENT 


?'  ?i  — Sc.ctions  of  the  spinal  cord  at  the  level  of  the  sixth  cervical,  sixth  thoracic,  and  third  lumbar  seg- 
ments, the  conductmg  tracts  being  indicated  on  the  right  side  of  each  section:  C.  Comma  tract  of  Schultze. 
tl.   Ulivospinal  tract  of  Helweg.     .1/.   Marginal  tract  of  Spitzka-Lissauer.     O.    Oval  field  of  Flechsig. 

Marginal  Tract. — Not  all  the  axones  of  the  dorsal  nerve  root  enter  the  dorsal 
column.     Another  group   elsewhere   described  passes   into  the  dorsal   horn  as 


THE  SPINAL  CORD 


837 


well  as  toward  Clarke's  column,  while  a  third  group  of  fibres  forms  the  so-called 
marginal  tract/  situated  close  to  or  among  the  entering  fibres  of  the  dorsal  roots, 
but  frec[uently  described  as  lying  in  the  lateral  column.  The  tract  is  demonstrable 
in  all  levels  and  is  made  up  of  successive  increments  of  relatively  short  axones 
(traversing  not  more  than  three  or  four  segments)  to  end  in  relation  with  the  cells 
in  the  gdafiiiosa  Rolandi. 

Ground  Btindle  of  the  Dorsal  Column. — A  zone  of  fibres  contiguous  with  the 
dorsal  face  of  the  gray  column,  and  termed  the  fasciculus  dorsalis  proprius  or  dorsal 


D.R 


D.R 


D.R.  -n 


D.R 


Fig.  613. — Ramifications  of  the  central  processes  (axones)  of  afferent  neurones  entering  the  spinal  cord  as 
seen  in  longitudinal  section  (schematic) :  D.R.  Axones  of  dorsal  roots,  b.  Their  bifurcation.  cU.  Collaterals. 
t.  Telodendria  ending  in  proximity  of  cells  in  the  gray  substance.     F.C.  Axones  of  gracile  and  cuneate  fasciculi. 

ground  bundle,  is  composed  of  axones  arising  from  the  smaller  cells  of  the  dorsal 
horn,  which,  after  entering  the  white  substance  and  bifurcating  into  ascending 
and  descending  branches,  come  into  relation  with  other  levels  of  the  gray  column 
by  means  of  collaterals  and  terminating  in  it  after  a  comparatively  short  course. 
They  are  therefore  to  be  regarded  purely  as  association  or  "longitudinal  com- 
missural" fibres.  The  dorsal  comucommissural  tract  (ventrales  Hinterstrangs- 
hundel  [Striimpell];  zone  cor nucommiss urate  [Marie]),  occupying  a  triangular 
interval  at  the  apex  of  the  trans-sected  dorsal  column,  and  the  septomarginal 
tract  [of  Bruce],  in  apposition  with  the  postseptum,  belong  to  this  category  of  asso- 
ciation bundles.     Both  tracts  are  most  evident  in  the  lumbar  portion  of  the  cord. 


First  described  by  E.  C   Spitzka  (1885)  and  Lissauer  (1886),  and  usually  bearing  the  name  of  the  latter. 


g3§  THE  NERVE  SYSTEM 

In  the  lateral  column  the  following  tracts  may  be  enumerated: 
Ascending : 

1.  Dorsolateral  spinocerebellar  tract  (Flechsig). 

2.  Superficial  ventrolateral  spinocerebellar  tract  (Gowers). 

3.  Spinothalamic  tract. 

4.  Spinomesencephalic  tract. 
Descending : 

1.    Crossed  pyramidal  tract. 
it!  [2.    Rubrospinal  tract. 

"S^  I  3.    Cerebellospinal  tract  (Marchi  and  Lowenthal). 
I  i  I  4.    Lateral  vestibulospinal  tract. 
"-  Is.    Olivospinal  tract  of  Hehveg. 

Associating: 

1.    Fasciculus  lateralis  proprius. 

The  dorsolateral  spinocerebellar  or  direct  cerebellar  tract  (fasc.  cerebellosjnnalis) 
lies  at  the  periphery,  laterad  of  the  crossed  pyramidal  tract.  Its  axones  arise 
from  the  cells  of  Clarke's  column  and  ascend  uninterruptedly  to  the  medulla 
oblongata,  and  thence  to  the  vermis  of  the  cerebellum  in  its  inferior  or  post- 
peduncle.     The  tract  becomes  more  massive  as  the  cord  is  ascended  (Fig.  610). 

The  superficial  ventrolateral  spinocerebellar  tract,  or  tract  of  Gowers  (fasc.  antero- 
lateralis  superfidalis  [Gowersi]),  also  courses  along  the  periphery,  but  farther 
ventrad.  The  origin  of  its  axones  is  yet  in  dispute;  they  probably  arise  from  cells 
in  the  gray  substance  of  both  sides,  in  the  zone  between  the  dorsal  and  ventral 
horns  as  well  as  from  some  of  the  ventral  horn  cells.  The  destination  of  the  ax- 
ones of  this  tract  is  equally  uncertain,  but  most  of  the  fibres  have  been  traced 
through  the  dorsolateral  region  of  the  medulla  oblongata  and  the  pontile  retioula, 
whence  it  turns  dorsimesad,  to  enter  the  cerebellum  through  the  superior  medullary 
velum  and  ends  in  the  dorsal  vermis.  A  lesser  portion  of  the  tract  has  been  traced 
to  the  quadrigeminal  bodies,  while  other  groups  of  axones  end  in  various  levels  of 
the  gray  substance. 

The  spinothalamic  and  spinomesencephalic  (tractus  spinotectalis)  tracts  are 
not  gathered  into  compact  bundles,  but  are  rather  scattered  among  the  fibres  of 
the  lateral  column  just  mesad  of  the  superficial  ventrolateral  spinocerebellar 
tract  (Gowers).  The  axones  of  both  systems  arise  from  cells  in  the  dorsal  horn 
and  its  cervix  of  the  opposite  side,  coursing  through  the  white  ventral  commissure 
and  ascending  the  cord,  the  spinothalamic  fibres  ending  in  the  thalamus,  the 
spinomesencephalic  fibres  ending  in  the  region  of  the  quadrigeminal  bodies. 
The  two  tracts  are  collectively  called  tractus  spinotectalis  et  thalamicus. 

The  crossed  P3n:amidal  tract  (fasciculus  cerebrospinalis  lateralis)  occupies  an  ap- 
proximately triangular  or  oval  area  in  the  dorsal  portion  of  the  lateral  column, 
just  mesad  of  the  direct  cerebellar  tract,  except  in  the  lumbar  cord,  where  it  lies 
at  the  surface.  The  axones  of  this  tract  arise  from  the  pyramidal  cells  of  the 
cerebral  cortex  (motor  area)  of  the  opposite  side.  After  having  descended 
through  the  internal  capsule,  crusta,  pons,  to  the  pyramis  of  the  medulla  oblongata, 
the  major  portion  (85  to  90  per  cent.)  of  the  fibres  derived  from  one-half  of  the 
brain  decussate  with  those  of  the  other  half,  crossing  the  median  line  to  descend 
in  the  lateral  column  of  the  cord.  The  fibres  which  do  not  decussate  constitute 
the  direct  pyramidal  tract  in  the  ventral  column.  As  the  crossed  pyramidal 
tract  descends  it  diminishes  in  size  as  its  axones  become  distributed  to  the  ventral 
horn,  where  they  terminate  either  in  contiguity  with  the  ventral  motor  cells  which 
give  rise  to  the  fibres  of  the  ventral  (motor)  nerve  roots,  or  else  in  contiguity  with 
the  dendrites  of  interposed  neurones,  which,  in  turn,  convey  the  impulse  to  several 
associated  niotor  neurones  presiding  over  the  actions  of  associated  muscles. 
The  bundle  becomes  exliausted  as  a  distinct  strand  at  the  level  of  the  fourth 
sacral  seament. 


THE  SPTNAL   CORD  839 

The  rabrospinal,  cerebellospinal,  lateral  vestibulospinal,  and  olivospinal  tracts 
consist  of  descending  axones  which  are  intermingled  so  that  their  mutual  topo- 
graphical relations  cannot  at  present  be  described.  Collectively  they  constitute 
the  fasciculus  intermedius  of  Lowenthal  and  Bechterew  (intermediolateral  tract 
of  Bruce  and  Campbell)  and  they  lie  ventrad  of  the  crossed  pyramidal  tract  and 
mesad  of  the  combined  spinothalamic  and  spinomesencephalic  tracts. 

The  rubrospinal  tract  (^lonakow's  tract;  prepyramidal  tract)  originates  in  the 
red  nucleus  in  the  tegmentum  of  the  mid-brain  of  the  opposite  side  and  its  axones 
terminate  in  relation  with  ventral  horn  cells!  In  their  course  these  fibres  are  seen 
to  invade  the  area  of  the  crossed  pyramidal  tract. 

The  cerebellospinal  tract  (Marchi's  tract)  is  supposed  to  arise  in  the  cortex  of 
the  cerebellar  hemispheres,  to  become  distributed  to  the  motor  centres  in  the 
ventral  horn. 

The  lateral  vestibulospinal  tract  arises  in  the  lateral  nucleus  of  the  vestibular 
nerve  (Deiters'  nucleus),  and  by  its  relations  with  spinal  centres  establishes  a 
connection  with  the  equilibratory  apparatus. 

The  olivospinal  tract  of  Helweg  (Helweg's  Dreikantenbahn ;  Bechterew's  Oliven- 
biindel)  is  found  only  in  the  higher  segments  of  the  cord,  at  its  periphery  and  just 
laterad  of  the  emergence  of  the  ventral  nerve  roots.  Its  connections  and  functional 
direction  are  uncertain;  some  investigators  have  traced  its  fibres  between  the  olive 
and  certain  ventral  horn  cells;  Obersteiner  suggests  a  relationship  with  the  pyram- 
idal tract.  The  coincidence,  in  point  of  time,  of  the  myelinization  of  both  tracts' 
is  significant  in  this  connection. 

Several  other  descending  tracts  ending  in  the  spinal  cord  and  arising  in  higher 
centres  like  the  corpora  quadrigemina,  central  gray  substance  of  the  mesencephalon, 
and  the  cerebellum  have  been  recently  described  by  Held,  Boyce,  and  Bechterew. 

Ground  Bundle  of  the  Lateral  Column  {fasciculus  lateralis  proprius). — This  lies 
in  the  concavity  of  the  lateral  aspect  of  the  gray  column  and  consists  of  axones 
of  neurones  having  a  purely  commissural  function.  In  the  regions  where  the 
reticula  is  best  marked  it  is  subdivided  into  a  group  of  smaller  bundles  by  numerous 
glial  septa. 

In  the  ventral  column  are  described  the  following  tracts: 

Descending: 

1.  Direct  pyramidal  tract. 

2.  Sulcomarginal  tract. 

3.  Ventral  vestibulospinal  tract. 
Associating : 

1.  Association  axones  between  spinal  centres  and  several  cranial  nerve  nuclei. 

2.  Fasciculus  ventralis  proprius. 

The  direct  P3n-amidal  tract  {fasciculus  cerebrospinalis  anterior)  is  the  uncrossed 
portion  of  the  pyramidal  tract  below  the  decussation  in  the  medulla  oblongata, 
and  constituting  only  10  to  15  per  cent,  of  the  fibre  system  arising  in  the  motor 
cortex  of  the  same  side.  It  is  a  small,  oblong  bundle,  as  seen  on  trans-section, 
lying  parallel  with  the  ventral  fissure,  from  which  it  is  separated  in  the  higher 
segments  by  the  relatively  narrow  sulcomarginal  tract.  The  tract  diminishes  in 
bulk  as  the  cord  is  descended,  to  disappear  in  the  thoracic  portion  of  the  cord; 
though,  in  rare  instances,  it  has  been  obser\ed  to  extend  throughout  the  lumbar 
portion  as  well.  This  diminution  and  eventual  disappearance  of  the  tract  is  due 
to  the  successive  decussation  of  its  fibres  throughout  its  course,  for,  with  a  few 
exceptions,  these  cross  in  the  ventral  white  commissure  to  come  into  relation  with 
the  ^"entral  horn  cells  (motor  cells)  of  the  opposite  side.  This  partial  longitudinal 
extension  of  the  pyramidal  decussation  and  consequent  formation  of  an  uncrossed, 
ventrally  situated  pyramidal  tract  is  peculiar  to  the  primate  order  of  verte- 
brates. 


840  THE  NERVE  SYSTEM 

The  sulcomarginal  tract  (tractus  tectospinalis)  is  a  thin  bundle  whose  axones 
arise  in  the  corpora  quadrigemina  of  the  opposite  side,  immediately  decussating 
and  descending  through  the  medulla  oblongata,  to  be  distributed  to  various  spinal 
centres  in  a  manner  not  yet  accurately  ascertained.  This  tract,  which  is  most 
developed  in  the  cervical  region  of  the  cord,  is  assumed  because  of  its  proximity 
to  the  lower  optic,  ocular  muscle,  and  acoustic  nuclei. 

The  ventral  vestibulospinal  tract  (liowenthal's  tract;  anterior  marginal  fascic- 
ulus; ventral  cerebellospinal  tract)  lies  at  the  periphery  of  the  ventral  column, 
extending,  as  seen  on  trans-section,  from  the  ventral  root  zone  to  the  ventral 
fissure.  Its  axones  arise  from  (1)  the  lateral  (Deiters')  and  (2)  superior  (Bech- 
terew's)  nuclei  of  the  vestibular  nerve;  and  (3)  from  the  nucleus  fastigii  of  the 
cerebellum.  Their  termination  about  the  ventral  horn  cells  has  been  traced  as 
far  as  the  sacral  region  of  the  cord. 

As  in  the  lateral  column,  and  continuous  with  the  like  formation,  there  is  in  the 
ventral  column  an  intermediate  zone  of  mixed  systems  of  axones  which  serve  to 
associate  various  levels  of  the  cord  with  ganglionic  masses  in  the  medulla  oblongata, 
as  well  as  with  the  cerebellum  and  corpora  quadrigemina.  The  nuclei  of  the  tri- 
geminus, facial,  auditory,  glossopharyngeal,  and  vagus  nerves,  together  with  the 
olive  and  the  cerebellum,  seem  most  intimately  associated  with  the  spinal  centres 
for  movements  of  the  head  and  neck. 

Ground  Bundle  of  the  Ventral  Column. — The  white  substance  of  the  ventral  column 
contiguous  with  the  central  gray  is  made  up  of  intersegmental  axones  of  associa- 
tion connecting  different  levels  of  the  cord. 

The  ventral  (white)  commissure  (coviviissura  anterior  alba)  is  composed  of 
myelinic  fibres  which  decussate  with  or  cross  each  other  and,  on  trans-section,  are 
seen  to  form  a  narrow  band  connecting  the  ventral  columns  of  the  two  sides.  The 
axones  composing  it  are  chiefly  (1)  those  arising  from  ventral  horn  cells,  which 
after  crossing  the  midline,  course  horizontally  or  cephalad  and  caudad  to  come 
into  relation  with  neurones  at  the  same  or  at  different  levels  of  the  gray  substance; 
(2)  the  decussating  axones  of  the  direct  pyramidal  tract;  (3)  numerous  collaterals 
from  the  ventral  and  lateral  column  axones.  The  white  commissure  is  most 
massive  in  the  enlargements  where  the  associations  of  the  limb  centres  are  neces- 
sarily greater  in  number. 

Myelinization  of  the  Axones  of  the  Cord. — The  acquisition  of  the  myelin  sheath 
is  not  cotemporary  for  all  axones  in  the  cord,  but  is  characterized  by  a  regular 
progression  in  the  myelinization  of  separate  fasciculi.  As  a  rule,  those  axone 
systems  which  are  concerned  with  simpler  or  intrinsically  spinal  reflexes  become 
myelinic  or  "mature"  at  an  earlier  stage  of  fetal  development  than  do  those  con- 
cerned in  the  more  elaborate  connections  of  the  cord  with  the  Ijrain. 

According  to  Flechsig  and  Trepinski  the  order  of  myelinization  is  as  follows: 
I.  a,  b.  Ventral  and  dorsal  roots  during  fifth  month. 
II.  a,  b,  c.  Ground  bundles  and  intermediolateral  tracts  during  sixth  month. 

III.  a,  b,  c.  Dorsal  columns  during  fifth  to  seventh  month. 

IV.  Direct  spinocerebellar  tract,  seventh  month. 

V.  Ventral  spinocerebellar  (Gowers')  tract,  seventh  to  eighth  month. 
VI.  Pyramidal  (crossed  and  direct)  tracts,  at  or  soon  after  birth. 

VII.  Olivospinal  (Helweg's)  tract,  ninth  month  or  later. 

The  order  of  myelinization  of  the  separate  fasciculi  is  indicated  in  Fig.  614. 

Summary. — The  Gray  Substance. — The  gray  substance  consists,  aside  from  its 
supporting  tissues,  of  sentient  and  reacting  nerve  cells,  with  their  dendrites  and 
axones,  and  of  the  terminals  of  axones  entering  from  without.  These  nerve 
cells  may  be  classified  as  follows: 

(a)  Nerve  cells  whose  axones  pass  directly  out  of  the  cord.  These  lie  in  the 
ventral  horn,  are  "motor"  in  function,  and  their  axones  form  the  ventral  nerve 


THE  SPINAL  CORD 


841 


roots.  Certain  nerve  cells  situated  in  the  cervix  of  the  ventral  horn  are  believed 
to  send  splanchnic  efferent  axones  in  company  with  the  motor  axones  in  the  ven- 
tral root,  while  very  few  similar  efferent  axones  leave  by  means  of  the  dorsal  root. 
(h)  Nerve  cells  whose  axones  pass  into  the  white  substance,  usually  bifurcating 
into  a  shorter  descending  and  a  longer  ascending  branch.  Two  kinds  of  cells 
are  distinguished:  , 

1.  Strand  or  tract  cells  whose  axones  (ascending  branches)  traverse  the  cord, 
to  come  into  relation  with  higher  centres  in  the  brain. 

2.  Association  cells  whose  axones,  after  a  comparatively  brief  course  in  the 
white  substance,  reenter  the  gray  substance  and  serve  to  coordinate  different 
levels  of  the  cord. 


Fig.  614. — Diagram  showing  the  order  of  myelinization  of  the  various  tracts  in  the  spinal  cord  (cervical 
level).  The  tracts  are  named  on  the  right  side;  the  Roman  numerals  on  the  left  side  correspond  with  the 
enumeration  given  in  the  text,     H.  Olivospinal  tract  of  Helweg.     M.  Marginal  tract.  O.  Oval  tract  of  Flechsig. 

The  tract  cells  may  be  further  divided  into  two  categories — homolateral  and 
contralateral  tract  cells.  Homolateral  cells  are  those  whose  axones  enter  the  white 
columns  of  the  same  side;  contralateral  cells  are  those  whose  axones  traverse  the 
white  (ventral)  commissure  to  the  other  side.  Tract  cells  exist  in  all  parts  of  the 
gray  substance,  and  are  termed,  according  to  their  situation,  ventral,  lateral,  and 
dorsal  horn  cells.  The  contralateral  tract  cells  preponderate  in  the  dorsal  horn, 
its  cervix,  and  in  the  intermediate  zone,  and,  on  account  of  their  course,  are  also 
called  commissural  cells. 

(c)  Nerve  cells  of  Golgi's  type  II,  or  cells  with  short,  multibranched  axones. 

The  motor  ventral  horn  cells  and  the  splanchnic  efferent  cells  differ,  therefore, 
from  the  other  categories  in  that  they  alone  send  their  axones  out  of  the  centra! 
axis  to  the  periphery.  The  tract  cells,  commissural  cells,  and  the  Golgi  type  II 
cells  are  strictly  confined  to  the  central  axis;  the  tract  cells  serve  to  coordinate 
the  separate  units  of  the  spinal  neurone  system  with  higher  centres;  the  asso- 
ciation cells  maintain  the  paths  of  conduction  between  higher  and  lower  cell 
complexes;  while  the  cells  of  Golgi's  type  II  are  limited  to  a  narrower  field  of 
nerve  activity  as  nerve  links  in  the  chaining  together  of  neurones. 

White  Substance. — The  white  substance  consists  essentially  of  axones  the  great 
majority  of  which  are  disposed  longitudinally.     These  axones  comprise : 


842  THE  NEB  VE  SYSTEM 

(a)  Axones  arising  in  the  cerebral  cortex,  the  gray  ganglionic  masses  in  the 
mid-brain,  pons,  and  cerebellum,  and  descending  to  their  terminations  in  different 
levels  of  the  cord. 

(b)  Axones  which,  conversely,  arise  in  the  gray  substance  of  the  cord  (tract  cell 
axones),  to  terminate  in  the  higher  brain  centres. 

(c)  Axones  which  coordinate  difiFerent  levels  of  the  cord  with  each  other  (associa- 
tion cell  axones). 

(d)  Axones  which,  arising  from  the  spinal  ganglion  cells  of  the  dorsal  nerve 
roots,  enter  the  cord  and  ascend  in  the  dorsal  columns. 

Dissection. — ^To  dissect  the  cord  and  its  membranes  it  will  be  necessary  to  lay  open  the 
whole  length  of  the  vertebral  canal.  For  this  purpose  the  muscles  must  be  separated  from  the 
vertebral  grooves,  so  as  to  expose  the  spinous  processes  and  laminae  of  the  vertebrae;  and  the 
latter  must  be  sawed  through  on  each  side,  close  to  the  roots  of  the  transverse  processes,  from 
the  third  or  fourth  cervical  vertebra  above  to  the  sacrum  below.  The  vertebral  arches  having 
been  displaced  by  means  of  a  chisel  and  the  separate  fragments  removed,  the  dura  will  be  ex- 
posed, covered  by  a  plexus  of  veins  and  a  quantity  of  loose  areolar  tissue,  often  infiltrated  with 
serous  fluid.  The  arches  of  the  upper  vertebrae  are  best  divided  by  means  of  a  strong  pair  of 
cutting  bone-forceps  or  by  a  rachitome. 

Applied  Anatomy. — Contusion  of  the  spine  may  cause  an  efFusion  of  blood  or  traumatic 
zonal  inflammation  of  the  spinal  cord  with  paralysis  which  may  disappear  without  surgical 
intervention.  Concussion  ("railway  spine")  is  followed  by  temporary  or  rarely  permanent 
impairment  of  function.  Punctured  wounds  are  usually  caused  by  the  knife,  and  are  most  com- 
monly inflicted  upon  the  cervical  and  upper  thoracic  divisions  and  more  often  involving  one- 
half  of  the  cord.  The  course  is  generally  an  aseptic  one;  operation  is  indicated  when  infection 
of  the  cord  ensues  or  when  there  is  a  compression  from  hemorrhage.  This  may  be  relieved  by 
lumbar  puncture  (p.  68)  with  a  large  needle.  Hemorrhage  into  the  substance  of  the  cord 
(hematomyelia)  usually  occurs  in  the  4-6  cervical  segments.  If  the  hemorrhage  is  confined  to 
the  gray  substance,  there  is  wasting  of  muscle  and  anesthesia  of  the  pectoral  limb;  the  reflexes 
below  the  lesion  are  abolished.  If  the  white  substance  is  involved,  paraplegia  below  the  level 
of  the  lesion  ensues.  The  cord  may  be  injured  by  fracture  or  dislocation  of  vertehroe  (p.  69). 
Gunshot  ivounds  are  usually  of  serious  nature.  Operation  is  indicated  by  symptoms  of  com- 
pression by  the  bullet  or  by  fragments  of  bone.  If  the  compression  is  due  to  accumulated  blood, 
lumbar  puncture  may  be  resorted  to. 

The  cord  usually  shares  in  the  congenital  malformation  known  as  spina  bifida,  resulting 
from  failure  of  coalescence  of  the  margins  or  lateral  ridges  of  the  neural  plate.  The  defect  may 
be  complete  {rachischisis  totalis)  or  confined  to  a  few  segments  of  the  cord.  Tumors  of  many 
varieties,  originating  in  the  vertebra,  meninges,  or  even  in  the  substance  of  the  cord  itself  (glioma, 
tuberculoma,  etc.),  give  rise  to  many  sensor  and  motor  disturbances  which  afford  a  clue  to  the 
localization  of  such  growths  as  indicated  on  page  831.  Inflammation  of  the  spinal  cord  (myelitis) 
may  follow  any  of  the  acute  specific  fevers,  occasioning  more  or  less  complete  paralyses  and 
anesthesia.  In  infantile  spinal  paralysis  {acute  anterior  poliomyelitis)  due  to  an  infection 
which  results  in  the  destruction  of  ventral  horn  (motor)  cells  and  consequent  permanent 
paralysis  and  nutritional  disturbances  of  the  limbs  whose  centres  are  thus  affected.  Further, 
the  muscles  which  normally  antagonize  the  affected  groups  of  muscles  tend  to  assume  a  state 
of  spastic  contraction.  The  deformity  thus  produced  may  be  relieved  by  tenotomy,  transplan- 
tation of  tendons,  or  even  amputation.  Syringomyelia  is  a  chronic  condition  in  which  an 
abnormal  prohferation  of  the  spinal  neuroglia  takes  place,  generally  near  the  central  canal  and 
in  the  cervical  enlargement,  and  later  this  mass  becomes  absorbed,  leaving  an  irregular  cavity 
in  its  place.  This  gives  rise  to  a  number  of  interesting  symptoms,  such  as  analgesia  (or  insen- 
sitiveness  to  pain),  inability  to  distinguish  between  heat  and  cold,  progressive  atrophy  of  the 
muscles  of  the  hands  and  arms,  trophic  changes  in  the  bones  and  joints,  and  painless  whitlows. 


THE  MEMBRANES  OF  THE   CORD. 

The  membranes  which  envelop  the  spinal  cord  are  three  in  number.  The  most 
external  is  the  dura,  a  strong  fibrous  membrane  which  forms  a  loose  sheath  around 
the  cord.  The  most  internal  is  the  pia,  a  cellulovascular  membrane  which  closely 
invests  the  entire  surface  of  the  cord.  Between  the  two  is  the  arachnoid,  an 
avascular  membrane  which  envelops  the  cord  and  is  connected  to  the  pia  by 
slender  filaments  of  connective  tissue. 


THE  SPINAL  DURA 


843 


The  Spinal  Dura  (Dura  Mater  Spinalis)  (Figs.  G15,  617). 
The  spinal  dura  represents  only  the  meningeal  or  supporting  layer  of  the  cranial 
dura.  The  endocranial  or  endosteal  layer  ceases  at  the  foramen  magnum  dor- 
sally,  but  reaches  as  low  as  the  third  cervical  vertebra  ventrad;  below  these 
levels  its  place  is  taken  by  the  periosteum.  The  dura  forms  a  loose  sheath  which 
surrounds  the  cord  and  the  cauda  equina,  and  is  loosely  connected  with  the 
vertebral  periosteum  and  the  ligaments  by  a  quantity  of  lax  areolar  tissue  and  a 
plexus  of  veins,  the  meningorachidian  veins  (plexus  venosi  vertebrales  intern  i).  The 
space  containing  the  fat  and  veins  is  called  the  epidural  space  {cavum  epidurale). 
The  situation  of  the  veins  between  the  dura  and  the  periosteum  of  the  vertebra 
corresponds  therefore  to  that  of  the  cranial 
sinuses  between  the  endocranial  and  sup- 
porting layers.  The  dura  is  attached  to 
the  circumference  of  the  foramen  mag- 
num and  to  the  axis  and  third  cervical 
vertebra;  it  is  also  fixed  to  the  posterior 


Fig.  Clo. — The  spinal  cord  and  its  membranes. 


Fig  file — ihe  dentate  ligament.  The  dura 
has  been  opened  and  turned  back.  The  ventral 
surface  is  seen.     (Hirscbfeld.) 


common  ligament,  especially  near  the  lower  end  of  the  spinal  canal,  by  fibrous 
slips;  it  extends  below  as  far  as  the  second  or  third  piece  of  the  sacrum,  where 
its  cavity  terminates,  and,  ensheathing  the  filum  terminale,  constitutes  the  fllum 
durae  matris  spinalis  (Fig.  598),  and  descends  to  the  dorsum  of  the  coccyx,  to  blend 
with  the  periosteum.  This  part  of  the  dura  is  called  the  coccygeal  ligament  (Fig. 
617).  The  dura  is  much  more  capacious  than  is  necessary  for  its  contents,  and  its 
size  is  greater  in  the  cervical  and  lumbar  regions  than  in  the  thoracic.  Its  inner 
surface  is  smooth.  On  each  side  may  be  seen  the  double  openings  which  transmit 
the  two  roots  of  the  corresponding  spinal  nerve,  the  fibrous  layer  of  the  dura 
being  continued  in  the  form  of  a  tubular  prolongation  on  them  as  they  pass  through 
these  apertures.  These  prolongations  of  the  dura  are  short  in  the  upper  part  of 
the  vertebral  column,  but  gradually  become  longer  below,  forming  a  number  of 
tubes  of  fibrous  membrane,  which  enclose  the  sacral  nerves,  and  are  contained 
in  the  vertebral  canal. 


844 


THE  NERVE  SYSTEM 


The  chief  peculiarities  of  the  dura  of  the  cord,  as  compared  with  that  investing 
the  brain,  are  the  following:  The  dura  of  the  cord  is  not  closely  adherent  to  the 
bones  of  the  vertebral  canal,  and  is  not,  as  is  the  cranial  dura,  the  internal  peri- 
osteum of  the  vertebrae.    The  vertebrae  have  an  independent  periosteum.    It  does 


Fig.  617. —  The  filum  terminale  (schematic).     (Poirier  and  Charpy.) 


not  send  partitions  into  the  fissures  of  the  cord,  as  the  cranial  dura  sends  partitions 
into  certain  fissures  of  the  brain.  Its  fibrous  laminae  do  not  separate  to  form  venous 
sinuses,  as  in  the  cranium.     It  contains  no  arachnoid  villi  [Pacchionian  bodies). 

Structure. — The  dura  consists  of  white  fibrous  and  elastic  tissue  arranged  in  bands  or 
lamellse,  which,  for  the  most  part,  are  parallel  with  one  another  and  have  a  longitudinal  arrange- 
ment. Each  surface  is  covered  by  a  layer  of  endothelial  cells.  It  is  sparingly  supplied  with 
vessels,  and  some  few  nerves  have  been  traced  into  it. 


The  Arachnoid  (Arachnoidea  Spinalis)  (Figs.  596,  615). 

The  arachnoid  is  exposed  by  slitting  the  dura  and  reflecting  that  membrane 
to  either  side.  It  is  a  thin,  delicate,  tubular  membrane  which  invests  the  surface 
of  the  cord,  and  is  connected  to  the  pia  by  slender  filaments  of  connective  tissue. 
Above,  it  is  continuous  with  the  cranial  arachnoid;  on  each  side  it  is  continued 
on  the  various  nerves,  so  as  to  form  a  sheath  for  them  as  they  pass  outward  to 
the  intervertebral  foramina.  The  outer  surface  of  the  arachnoid  is  in  contact 
with  the  inner  surface  of  the  dura,  and  the  two  are,  here  and  there,  joined  together 
by  isolated  connective-tissue  trabeculae.  These  trabeculae  are  especially  numerous 
on  the  dorsal  surface  of  the  cord.     For  the  most  part,  however,  these  membranes 


THE  PIA  OF  THE  CORD  845 

are  not  connected  together,  and  the  interval  between  them  is  named  the  subdural 
space  (c.avivm  suhduralc).  The  subdural  space  contains  a  very  small  amount 
of  lymph-like  fluid.  There  is  no  communication  between  the  .nibdural  and  the  nuh- 
arachnoid  spaces.  The  subdural  space  is  prolonged  laterad  for  a  short  distance 
on  each  emerging  nerve  and  communicates  with  the  lymph  tract  of  the  nerve. 
The  inner  surface  of  the  arachnoid  is  separated  from  the  pia  by  a  considerable 
interval,  which  is  called  the  subarachnoid  space  {cavum  suharachnoideale).  The 
space  is  largest  at  the  lower  part  of  the  spinal  canal,  and  encloses  the  mass  of 
nerves  which  forms  the  cauda  equina.  Cephalad  it  is  continuous  with  the  cranial 
subarachnoid  space,  and  communicates  with  the  general  ventricular  cavity  of  the 
brain  by  means  of  openings  in  the  pia,  in  the  roof  of  the  fourth  ventricle,  the 
foramen  of  Majendie  or  metapore  and  foramina  of  Key  and  Retzius.  It  contains 
an  abundant  serous  secretion,  the  cerebrospinal  fluid.  This  secretion  is  sufficient 
in  amount  to  expand  the  arachnoid,  and  thus  to  distend  completely  the  whole  of 
the  space  included  in  the  dura.  The  subarachnoid  space  is  occupied  by  trabeculse 
of  delicate  endothelial-covered  connective  tissue,  connecting  the  pia  on  the  one 
hand  with  the  arachnoid  on  the  other.     This  is  named  subarachnoid  tissue. 

In  addition  to  this  the  space  is  partially  subdivided  by  a  longitudinal  mem- 
branous partition,  the  septum  posticum  or  the  dorsal  fenestrated  septum,  which 
serves  to  connect  the  arachnoid  with  the  pia,  opposite  the  dorsoniedian  fissure 
of  the  spinal  cord.  It  is  a  partition,  but  an  incomplete  and  cribriform  partition, 
which  consists  of  bundles  of  white  fibrous  tissue  interlacing  with  each  other,  and 
is  coated  with  endothelium.  The  dentate  ligament  {ligamentwn  denticiilatwn) , 
which  runs  from  the  pia  to  the  dura  on  either  side  of  the  cord,  divides  the  subarach- 
noid space  into  an  anterior  or  ventral  and  a  posterior  or  dorsal  space,  which  joins 
like  spaces  in  the  cavity  of  the  cranium.  The  external  spinal  veins  {venae  spinales 
externae)  lie  in  the  subarachnoid  space. 

Structure. — The  arachnoid  is  a  delicate  membrane  made  up  of  closely  arranged  interlacing 
bundles  of  connective  tissue  in  several  layers.  It  contains  many  elastic  fibers,  and  is  covered 
on  each  side  by  endothelial  cells.     The  arachnoid  contains  neither  vessels  nor  nerves. 


The  Pia  of  the  Cord  (Pia  Mater  Spinalis). 

The  pia  of  the  cord  is  exposed  on  the  removal  of  the  arachnoid  (Figs.  615 
and  616).  It  covers  the  entire  surface  of  the  cord,  to  which  it  is  very  intimately 
adherent,  forming  its  neurilemma,  and  sending  a  fold  into  its  ventral  fissure. 
It  also  forms  a  sheath  for  each  of  the  filaments  of  the  spinal  nerves,  and  invests 
the  nerves  themselves.  A  longitudinal  fibrous  band  extends  along  the  middle 
line  on  its  ventral  surface,  the  linea  splendens;  and  a  somewhat  similar  band,  which 
forms  the  ligamentum  denticulatum,  is  situated  on  each  side.  At  the  point  where 
the  cord  terminates  the  pia  becomes  contracted,  and  is  continued  caudad  as  a 
long,  slender  filament,  the  iilum  terminate  (Fig.  617),  which  descends  within  the 
sheath  of  the  dura  and  the  arachnoid  and  through  the  centre  of  the  mass  of  nerves 
forming  the  cauda  equina.  It  unites  with  tlie  dura  and  arachnoid  altout  the  level 
of  the  third  sacral  vertel)ra,  and  as  the  central  ligament  of  the  spinal  cord,  the  coccy- 
geal ligament,  or  the  filum  dm-ae  spinalis  the  fused  membranes  extend  caudad  as 
far  as  the  base  of  the  coccyx,  where  they  blend  with  the  periosteum.  It  assists 
in  maintaining  the  cord  in  its  position  during  the  movements  of  the  trunk.  It 
contains  a  little  gray  nerve  substance,  which  may  be  traced  for  some  distance 
into  its  upper  part,  and  is  accompanied  by  a  small  artery  and  vein.  At  the  upper 
part  of  the  cord  the  pia  presents  a  grayish,  mottled  tint,  which  is  due  to  yellow 
or  brown  pigment  cells  scattered  among  the  elastic  fibres. 


846 


THE  NERVE  SYSTEM 


Arachnoid 
Dorsal  root 
Ventral  root 


Fig.  618. — Transverse    section    of    th 
cord  and  its  membranes.     (Gegenbg 


spinal 
r.) 


Structure.— The  pia  of  the  cord  is  less  vascular  in  structure,  but  thicker  and  denser,  than 
the  pia  of  the  brain,  with  which  it  is  continuous.  It  consists  of  two  layers;  an  outer,  resembling 
the  arachnoid,  composed  of  bundles  of  connective-tissue  fibres,  arranged  for  the  most  part  longi- 
tudinally; and  an  inner  (intima  pia),  consisting  of  stiff  circular  bundles  of  the  same  tissue, 
which  present  peculiar  angular  bends.  It  is  covered  on  both  surfaces  by  a  layer  of  endothelium. 
Between  the  two  layers  are  a  number  of  cleft-like  lymphatic  spaces  which  communicate  with 
the  subarachnoid  cavity,  and  a  number  of  bloodvessels  which  are  enclosed  in  perivascular 

sheaths,  derived  from  the  inner  layer  of  the  pia, 
into  which  the  lymphatic  s|xices  ojm'u.  The  pia 
contains  the  anterior  or  ventral  spinal  artery  and 
its  branches,  the  two  posterior  or  dorsal  spinal 
arteries,  and  numerous  veins  which  pass  to  the 
external  spinal  veins.  It  is  also  supplied  with 
nerves,  which  are  derived  in  part  from  the  sym- 
pathetic and  in  part  from  the  cerebrospinal  nerves. 
These  nerves  supply  the  walls  of  the  bloodvessels 
and  enter  the  cord  with  the  vessels. 

Both  the  arachnoid  and  the  pia  may  be  referred 
to  by  the  compound  name  pia-arachnoid,  inasmuch 
as  these  meningeal  components  are  with  difficulty 
separable  from  each  other. 

va^a  veriebraiia  rpj^^  dentate  ligament  (ligamentum  denti- 

culaimii)  (Figs.  596  and  616)  is  a  narrow, 
fibrous  band,  situated  on  each  side  of  the 
spinal  cord,  throughout  its  entire  length, 
running  from  the  pia  to  the  dura,  and  separating  the  ventral  from  the  dorsal 
roots  of  the  spinal  nerves.  It  has  received  its  name  from  the  serrated  appearance 
Vi^hich  it  presents.  Its  inner  border  is  continuous  with  the  pia  at  the  side  of  the 
cord.  Its  outer  border  presents  a  series  of  triangular,  dentated  serrations,  the 
points  of  which  are  fixed  at  intervals  to  the  dura.  These  serrations  are  twenty- 
one  in  number  on  each  side,  the  first  being  attached  to  the  dura  opposite  the 
margins  of  the  foramen  magnum  between  the  vertebral  artery  and  the  hypoglossal 
nerve,  and  the  last  near  the  lower  end  of  the  cord.     Its  use  is  to  support  the  cord. 

Applied  Anatomy. — Evidence  of  value  in  the  diagnosis  of  meningitis  may  be  obtained  by 
the  operation  of  lumbar  punciiirc,  that  is,  by  puncturing  the  theca  of  the  cord  and  withdrawing 
some  of  the  cerebrospinal  fluid,  and  the  operation  is  regarded  by  some  as  curative,  under  the 
supposition  that  the  draining  away  of  the  cerebrospinal  fluid  relieves  the  patient  by  diminish- 
ing the  intercranial  pressure.  Lumbar  puncture  may  give  important  diagnostic  aid  after  a 
head  injury  by  disclosing  bloody  cerebrospinal  fluid.  The  operation  is  performed  by  inserting 
a  trocar  of  the  smallest  size  below  the  level  of  the  fourth  lumbar  vertebra.  In  an  adult  the 
cord  terminates-  at  the  lower  border  of  the  first  lumbar  vertebra,  and  in  a  child  opposite  the 
body  of  the  third  lumbar  vertebra.  The  canal  may  be  punctured  below  the  fourth  vertebra 
without  much  risk  of  injuring  its  contents.  The  point  of  puncture  is  indicated  by  laying  the 
child  on  its  side  and  dropping  a  perpendicular  line  from  the  highest  point  of  the  crest  of  the 
ilium;  this  will  cross  the  upper  border  of  the  spine  of  the  fourth  lumbar  vertebra.  In  a  child 
the  puncture  is  made  just  below  this  spine;  in  adults,  one-half  an  inch  to  one  side  of  the  end 
of  this  spine.  However  the  preliminary  puncture  is  made,  the  needle  penetrates  the  dura 
in  the  midline.  In  entering  the  needle  it  should  be  directed  upward  and  forward  in  a  child; 
upward,  forward,  and  slightly  inward  in  an  adult. 


THE  BRAIN  OR  ENCEPHALON. 


The  brain  is  that  greatly  modified  and  enlarged  portion  of  the  cerebrospinal 
axis  which,  with  its  membranes,  almost  completely  fills  the  cavity  of  the  cranium. 
It  is  a  complex  organ  in  which  reside  the  highest  functions — consciousness, 
ideation,  judgment,  volition,  and  intellect — together  with  the  centres  of  special 
sense  and  for  the  mechanisms  of  life  (respiration  and  circulation),  and  it  is  the 
a2:ent  of  the  will. 


THE  BRAIN  OB  ENCEPHALON  847 

General  Appearance  and  Topography  of  the  Brain. — Corresponding  to  the 
varieties  of  cranial  form,  the  shape  of  tlie  fresh  or  the  successfully  preserved  brain 
varies  from  the  ovoid  to  the  nearly  spherical  form,  as  viewed  dorsally.  The 
frontal  pole  is  usually  narrower,  though  more  squarely  formed;  while  the  parieto- 
occipital portion  is  more  massive,  but  more  sharply  pointed  in  each  half.  The 
outline  is  often  rather  that  of  an  irregular  pentagon  with  its  angles  rounded  off. 
A  dorsal  view  (Fig.  672)  shows  only  the  extensive  convex  surface  of  the  two  great 
convoluted  cerebral  hemispheres  (hemicerebra)  separated  by  a  median  cleft,  the 
intercerebral  fissure  (fissura  hngitudinalis  cerebri).  On  divaricating  the  cerebral 
halves  it  is  seen  that  the  separation  is  not  a  total  one,  for  in  the  depths  of  the  fissure 
a  broad  commissural  mass  of  white  fibres — the  corpus  callosum — joins  the  cerebral 
hemispheres.  Frontad  the  longitudinal  fissure  is  continued  to  the  ventral  or  basal 
aspect  of  the  brain;  caudad  it  passes  into  the  fissura  transversa  cerebri  (tentorial 
hiatus)  or  interval,  separating  the  cerebrum  from  the  cerebellum. 

In  a  lateral  view  (Fig.  67.3)  the  continuity  of  the  spinal  cord  with  the  medulla 
oblongata,  then  the  pons  and  cerebellum  are  seen  in  part,  overlapped  by  the  cere- 
brum. Prominent  is  the  temporal  lobe  with  its  rounded  pole,  separated  from  the 
frontal  and  parietal  lobes  by  a  deep  cleft,  the  sylvian  fissure,  in  whose  depths — 
overlapped  by  the  opercula  of  the  adjacent  lobes — lies  the  island  of  Reil  or  insula. 

A  ventral  view  (Fig.  619)  presents  many  of  the  subdivisions  of  the  brain.  Here 
is  seen  the  continuity  of  the  spinal  cord,  with  the  short  and  slightly  expanding 
medulla  oblongata  lying  ventrad  of  the  cerebellum  and  somewhat  buried  in  its  val- 
lecula or  depression  between  the  lateral  hemispheres,  which  alone  are  visible.  The 
cerebellum  is  a  grayish-colored  mass  of  considerable  size  and  easily  recognized 
by  its  foliated  appearance,  due  to  the  numerous  parallel  and  closely  set  curved 
fissures.  A  mass  of  white  fibres,  the  pons,  passes  transversely  from  one  cere- 
bellar hemisphere  to  the  other,  ventrad  of  the  upper  portion  of  the  medulla 
oblongata.  Above  the  pons  are  seen  two  large  bundles,  the  crura  cerebri,  one  on 
either  side,  diverging  to  pass  into  the  cerebral  halves.  The  inter\'al  between  the 
divergent  crura  cerebri  and  temporal  poles  laterad  and  the  orbital  portions  of 
the  cerebrum  frontad  contains  a  number  of  important  structures.  Encircling 
the  crura  cerebri  and  meeting  in  the  fore  part  of  the  fossa  are  the  optic  tracts, 
decussating  in  the  median  plane  to  form  the  optic  chiasm  and  continuing  frontad 
as  the  optic  nerves.  The  arch  of  the  optic  tracts  and  optic  chiasm  and  the  crura 
cerebri  enclose  the  intercnnal  space,  in  which  may  be  seen  (1)  the  posterior  per- 
forated space  (substantia  perforata  -posterior;  postperforatum) ;  (2)  the  corpora 
albicantia  (c.  mamillaria);  (3)  the  tuber  cinereum  and  the  stalk  of  the  pituitary 
body.  A  groove  marking  the  lateral  boundary  of  the  fossa  along  each  crus  is 
termed  the  oculomotor  sulcus,  as  the  root  fibres  of  the  oculomotor  nerve  have  their 
superficial  origin  therein.  The  posterior  perforated  space  is  a  gray  area  with 
numerous  minute  apertures  for  the  entrance  of  postperforant  branches  of  the 
posterior  cerebral  artery.  The  corpora  albicantia  are  two  small,  pea-like,  white 
eminences  closely  set  side  by  side.  The  tuber  cinereum  is  a  conical  projection 
between  the  corpora  albicantia  and  the  optic  chiasm,  to  which  the  hypophysis 
(pituitary  body),  resting  in  the  sella  of  the  sphenoid,  is  attached.  In  the  re- 
moval of  the  brain  from  the  skull  the  stalk  of  the  hypophysis  is  usually  torn 
through  and  an  orifice,  the  lura,  leading  to  the  infundibular  recess  of  the  third 
ventricle,  is  thus  exposed.  In  the  interval  between  the  optic  tract  and  the  orbital 
surface  of  each  cerebral  hemisphere  is  a  small,  depressed,  triangular  area  of  gray 
substance  leading  laterad  into  the  basisylvian  fissure  and  dotted  with  numerous 
apertures  for  the  minute  basal  branches  of  the  middle  cerebral  artery  and  called 
the  anterior  perforated  space  (preperf oratum) . 

If  the  optic  chiasm  be  drawn  somewhat  ventrad,  a  delicate  gray  lamina,  the 
lamina  terminalis  (terma),  is  seen  attached  to  the  dorsal  surface  of  the  optic 


848 


THE  NERVE  SYSTEM 


chiasm  and  passing  dorsad  into  the  intercerebral  cleft  to  the  region  of  the  anterior 
commissure. 

Parallel  to  the  mesal  border  of  the  orbital  surface  of  each  cerebral  hemisphere  lie 
the  olfactory  tract  and  bulb,  torn  away  from  the  fila  olfactoria  as  these  pass  through 
the  lamina  cribrosa  of  the  ethmoid.  The  olfactory  tract  may  be  traced  to  its 
root  area,  the  olfactory  trigone,  just  frontad  of  the  anterior  perforated  space. 

The  superficial  origin  of  nearly  all  of  the  cranial  nerves  may  be  seen  upon  the 
basal  aspect  of  the  brain  (Fig.  619).  These  nerves,  their  superficial  attachments 
to  the  brain,  and  the  foramen  of  exit  in  the  skull  are  enumerated  in  the  following 
table : 

Tabulation  of  the  Cranial  Nerves,  their  Superficial  Attachments  to 
THE  Brain,  and  the  Foramina  of  Exit  in  the  Skull. 


I. 

II. 

III. 

IV. 

V. 


Olfactory  fila. 
Optic  nerve. 
Oculomotor  nerve. 

Trochlear  nerve. 

Trigeminal  nerve. 


TI. 

Abducent  nerve. 

\ll. 

Facial  nerve. 

VIII. 

Acoustic  nerve. 

IX. 

Glossopharyngeal 
nerve. 

X. 

Vagus  nerve. 

XL 

Spinal      Accessory 
nerve. 

SnPERFici.\L,   "Origin"   or  At- 
tachment TO  THE  Brain. 


XII.  Hypoglossal  nerve. 


Olfactory  bulb  and  tract. 

Optic  chiasm. 

Oculomotor  groove  along  medial 
border  of  crus. 

Valve  of  Vieussens  laterad  of  fren- 
ulum. 

Prelateral  part  of  pons. 


Postpontile    groove    (prepyram- 
idal  part). 

Postpontile    groove    (laterad    of 
abducent   nerve  in  preolivary 
.  part) . 

Postpontile    groove    (laterad    of 
facial  nerve). 

Dorsolateral  groove  of  medulla 
oblongata. 

Dorsolateral   groove   of  medulla 
oblongata. 

(a)  Encephalic  part :  Dorsolateral 
groove  of  medulla  oblongata. 

(6)  Spinal  part:  Lateral  column 
of  spinal  cord,  between  ven- 
tral and  dorsal  roots  of  cer- 
vical nerves  as  far  as  the  fifth 
and  sixth  cervical  nerves. 

Pyramido-olivary  groove. 


Foramen  of  Exit  from  the 
Skull. 


Ethmoidal  cribrosa. 
Optic  foramen. 
Sphenoidal  fissure. 

Sphenoidal  fissure. 


(o)  Ophthalmic    ramus,    sphe- 
noidal fissure. 
(6)  Maxillar}-     ramus,     foramen 

rotundum. 
(e)  Mandibular   ramus,   foramen 

ovale. 


Sphenoidal  fissure. 


Porus  acusticus  internus;  meatus 
■  acusticus  internus ;  facial  canal; 
stylomastoid  foramen. 

Porus  acusticus  internus. 


Jugular  foramen. 
Jugular  foramen. 
Jugular  foramen. 


Canalis     hypoglossi     ("  anterior 
condylar  foramen"). 


The  olfactory,  optic,  and  acoustic  nerves  are  afferent  or  sensor  nerves. 
The  trigeminal,  glossopharyngeal,  and  vagus  nerves  are  mixed  nerves. 

The  oculomotor,  trochlear,  abducent,  facial,  spinal  accessory,  and  hypoglossal  nerves  are 
or  motor  nerves. 


THE  BBAiy  OR  ENCEPHALON 


.S4<J 


Dimensions. — The  sagittal  or  occipitofrontal  diameter  of  the  wliite  male  adult 
brain  averages  16  to  17  cm.  (6.4  to  6.8  inches),  the  maxinuim  width  in  the 
parietal  region  averages  13  to  14  cm.  (5.2  to  5.(5  inches),  while  the  maximum  height 
is  about  12.5  cm.  (5  inches).  The  dimensions  of  the  female  brain  are  usually 
somewhat  less.  The  brains  of  dolichocephalic  individuals  are  naturally  longer 
and  narrower  than  those  of  brachycephalic,  and  other  differences  in  size  and 
shape  are  found  in  conformity  with  the  cranial  configuration  and  other  factors. 

Weight  of  the  Brain. — ^The  average  weight  of  the  brain  in  the  adult  male  is  1400 
grams  (49.5  ounces  avoirdupois);  that  of  the  female,  1250  grams  (44  ounces 
avoirdupois).  Among  1500  brains  of  males  the  brain  weights  ranged  from  960 
grams  to  over  1900  grams;  the  great  majority  of  this  series  ranged  from  1250 
grams  to  1500  grams.  The  average  weight  in  the  newborn  is  400  grams  (14.1 
ounces  avoirdupois)  in  the  male  and  .380  grams  (13.4  ounces  avoirdupois)  in  the 
female.  The  weight  is  doubled  at  the  end  of  the  first,  and  trebled  at  the  end  of  the 
fourth  or  fifth  year,  the  female  brain  growing  less  rapidly  than  the  male  brain. 
Brain  growth  generally  ceases  in  the  eighteenth  or  twentieth  year,  earlier'  in  the 
female  than  the  male.  After  the  sixtieth  year  the  brain  loses  weight,  at  first 
slowly,  but  more  rapidly  in  advanced  senescence.  Other  factors,  besides  age  and 
sex,  which  influence  brain  weight  are  stature,  body  weight,  cranial  form,  and  race. 
Persons  of  large  stature  average  heavier  brains  than  those  of  short  stature  in  abso- 
lute figures,  but  not  relatively.  Brachycephalic  persons  average  heavier  brains 
than  the  dolichocephalic.  A  most  profound  influence  upon  brain  weight  appears 
to  be  exerted  by  racial  differences.  Representatives  of  the  white  race  have  heavier 
brains  than  those  of  the  other  races,  although  data  are  not  sufficient  to  make  a 
positive  statement.  Thus,  the  few  Eskimo  brains  that  have  been  secured  so  far 
are  notable  for  their  size  and  weight.  The  following  table  gives  approximately 
accurate  averages  based  upon  greater  or  less  numbers  of  brain  weights: 


I             Males. 

Females. 

C  Germans        

1425 

1260 

Bohemians 

1420 

1290 

Scots  

1420 

1260 

'WTiite  race 

Swedes 

Russians 

1415 
1.395 

1260 
1260 

English 

1380 

1255 

Italians 

1375 

1240 

1360 
1365 

1250 

Japanese  . 

1215 

Chinese     . 

1360 

Negroes  (var 

ous  races) '  . 

1390-1200 

1330 
1250 

Australians 

. 

1185 

The  intellectual  status  is  in  some  way  reflected  in  the  mass  and  weight  of  the 
brain.  The  average  brain  weight  of  100  men  eminent  in  the  professions,  arts, 
and  sciences,  with  an  average  age  of  sixty- two  years,  was  1470  grams  (nearly 
52  ounces  avoirdupois),  exceeding  the  average  weight  of  the  ordinary  population 
of  about  the  same  age  by  more  than  100  grams  (nearly  4  ounces  avoirdupois). 
A  further  analysis  shows  that  the  brains  of  men  devoted  to  the  higher  intellectual 
occupations,  such  as  the  mathematical  sciences,  involving  the  most  complex 
mechanisms  of  the  mind,  those  of  men  who  have  devised  original  lines  of  research, 
and  those  of  forceful  character  are  among  the  heaviest  of  all.^ 


'  A  Study  of  the  Brains  of  Six  En 


Qt  Scientists  and  Scholars,  etc.,"  Trans.  An 


850 


THE  NERVE  SYSTEM 


The  brains  of  the  microcephalic  idiots  are  far  under  the  minimal  size  necessary 
for  mental  integrity,  which  is  about  1000  grams  (35  ounces  avoirdupois)  in  the 
male  and  900  grams  (31.7  ounces  avoirdupois)  in  the  female.  Certain  idiotic 
individuals  possess  brains  of  normal  size  or  even  abnormally  large  brains,  but 
structural  defects  underlie  these  forms  of  idiocy. 

The  whale,  porpoise,  dolphin,  and  elephant  possess  larger  brains  than  man, 
but  relative  to  the  size  and  weight  of  the  body  the  human  brain  is  proportionately 
larger. 


The  Development  of  the  Brain  and  the  Usual  Classifications  of  its  Sub- 
divisions.— The  cephalic  region  of  the  embryonic  neural  plate  is  characterized, 
as  already  pointed  out  (p.  804),  by  a  rapid  process  of  expansion  and  intensity  of 
growth  energy  which  seems  to  indicate  the  higher  functional  potentiality  of  what 
is  to  become  the  brain.  The  fusion  of  the  margins  of  the  neural  plate,  proceeding 
rapidly  cephalad  and  caudad  from  about  the  cervical  region,  soon  effects  the 
complete  closing  in  of  the  brain  portion  of  the  neural  tube  and  its  complete  separa- 
tion from  the  overlying  ectoderm.  For  a  brief  period  prior  to  the  completion  of 
the  tube  formation  there  exists  a  minute  opening  affording  communication  be- 
tween the  interior  of  the  neural  tube  and  the  surrounding  amniotic  cavity;  this 
temporary  passage  is  called  the  neuropore  (Fig.  620),  and  is  morphologically 
the  cephalic  end  of  the  tube.     Its  adult  position  is  probably  in  the  hypophyseal 


THE  BRAIN  OR  ENCEPHALON 


851 


The  simple  brain  tube  expands  very  early  in  intrauterine  life  in  a  sac-like 
manner,  with  the  formation  of  three  dilatations  or  pouches — the  primary  brain 
vesicles — demarcated  by  two  constrictions.'  The  vesicles  are  designated  respec- 
tively the 

Fore-brain  (Prosencephalon).  Mid-brain  (Mesencephalon). 

Hind-brain  (Rhombencephalon  or  Metencephalon). 


NEUROPORE  -\ 


l_2  IFORE.-BRAJN 


Fio.  620. — Brain  tube  of  embryo  salamander,  sagittal  section, 
showing  neural  segmentation  (neuromeres):  F.l.~lll.  Fore-brain 
neuronieres.  M.  l.-II.  Mid-brain  neuromeres.  H.  I.-VI.  Hind- 
brain  neuromeres.     (Adapted  from  Kupffer.) 


i-PROTOVERTEBRA  I. 


Fig,  621.— Brain  tube  of  chick  (25j^ 
hours),  showing  partly  closed  brain 
tube  with  eleven  folds  or  neuromeres. 
(After  C.  Hill.) 


This  classification  has  been 
found  acceptable  from  every  com- 
parative standpoint  in  brain  mor- 
phology, but  attempts  have  been 
made  to  establish  a  further  seg- 
mentation into  definite  anatomical 
divisions  regarding  which  opinions 
and  usages  differ  widely  and  have 
proved  to  be  a  hindrance,  rather 
than  an  aid  to  the  homologization 
of  brain  structures  in  the  vertebrate 
series.  The  difficulties  in  formu- 
lating a  satisfactory  schema  of  the 
segmental  divisions  of  the  brain 
will  be  overcome,  perhaps,  only 
by  distinguishing  the  neuromeres 
or  neural  segments  conforming  to. 
the  general  segmental  plan  of  the 
vertebrate  body.  The  existence 
of  a  neuromerism  that  is  akin  to  the  metamerism  or  serial  segmentation  of  the 
body,  or  to  the  branchiomerism  characterizing  the  arrangement  of  the  branchial 
arches,  is  indicated  in  several  ways,  but  thus  far  only  the  earliest  embryonic 


Middle  peduncle 
Injtrior  peduncle 


Medulla  oblongata 


Fig.  622.— Sche 


!  showing  the  connection  of  the  several 
parts  of  the  brain. 


'  The  constriction  between  mid-  and  hind-brain  has  been  called  thi 
he  regards  it  as  coordinate  with  the  other  segments  recognized  by  h 
a  definitive  segmental  value  tha 
prosencephaii. 


Ihvms  rhomhencephali  by  Prof.  His,  and 

>.>...c,  o=6."=—  .^.^B"- .»  the  region,  however,  no  more  deserves 

uld  the  cephalic  constriction  even  if  it  were  dignified  by  the  term  ulhmua 


852 


THE  NERVE  SYSTEM 


stages  and  the  disposition  of  certain  of  the  cranial  nerves  afford  a  clue  to  the  defi- 
nitive segmentation  of  the  brain.  According  to  the  most  recent  researches,  as 
many  as  eleven,  sixteen,  and  even  more  neuromeres  have  been  established  in 
various  vertebrate  brains.  The  hind-brain  alone  shows  from  six  to  eight  such 
neural  segments  (Figs.  620  and  621).  The  whole  matter  is  yet  so  obscUre  that 
confusion  will  be  avoided  by  restricting  our  description  to  the  three  primary 
divisions  and  their  derivatives  without  insisting  upon  the  recognition  of  further 
definitive  segments  proposed  by  various  authors  in  consequence  of  preconceived 
ideas  obtained  from  the  complicated  adult  structure  of  the  brain.  At  this  transi- 
tional period  the  student  is,  however,  obliged  to  be  familiar  with  the  commonly 
accepted — yet  provisional — schemes  of  segmentation  and  a  comparative  view 
is  given  in  the  following  table: 


Table  Showing  Comparison  of  the  Segmental  Schemas  Adopted  by 


The  Anatomische  Gesellschaft 
in  1895. 


Partes  ventrales. 


Partes  dorsales. 


VI.  Telencephalox. 


-n  4--      1,        ii,  1  „•        (Corpus   striatum;    rhinen- 

Pars  optica  hypothalami.     |     cephalon;  paUium. 


V.    DiENCEPHALON. 

■D      „  „„•!     ■   u       j-u  1  „•     (Thalamus;  metathala- 
Pars  mammilaris  hypothalami.  |     ^^s  gpithalamus. 

IV.  Mesencephalon. 
Pedunculi  cerebri.  Corpora  quadrigemina. 

III.  Isthmus  Rhombencephali. 

Pedunculi  cerebri. 


f  Brachia  conjunctiva;  ve- 
\    lum  meduUare  anterius. 


II.  Metencbphalon. 
Pons.  Cerebellum. 

I.  Myelencephalon. 
Medulla  oblongata. 


The  Association  of  American 
Anatomists  in  1897. 

I.  Rhinencephalon. 

Bulbi  olfactorii  with  their  tracts; 
part  of  the  aula  and  of  the  pre- 
commissure. 

II.  Pkosbncephalon. 

Palliums,  connected  by  part  of  the 
aula  and  part  of  the  precommis- 
sure. 

III.  DiENCEPH.A-LON. 

'  Thalami,     including     the     chiasm; 
geniculate  bodies. 

IV.  Mesencephalon. 
Crura  and  quadrigeminum. 

V.  Epbncephalon. 
Cerebellum:  pons;  preoblongata. 

.     VI.  Metencbphalon. 
Postoblongata. 


Brief  Consideration  of  the  Phases  of  Development  of  the  Brain  Tube, 
I.  Fore-brain. — The  cephalic  or  fore-brain  vesicle  widens  and  expands  most 
rapidly  and  attains  to  a  comparatively  large  size  even  before  the  mid-  and  hind- 
brain  vesicles  become  markedly  defined.  A  series  of  remarkable  developmental 
changes  ensue  in  the  following  order :  (o)  Optic  vesicles  appear  as  two  diverticula, 
each  budding  from  either  side  of  the  primary  fore-brain  vesicle,  their  distal  ends 
growing  considerably  and  coming  into  contact  with  the  overlying  epidermis, 
while  the  proximal  or  attached  ends  assume  a  stalk-like  shape.  The  distal 
sac-like  end  becomes  invaginated  and  forms  the  retina  of  the  eye,  while  the 
stalk  upon  obliteration  of  its  cavity  forms  the  optic  nerve.  It  is  necessary  to 
state  here  that  as  development  proceeds  the  optic  stalks  become  relatively  shifted 
caudad  and  form  more  intimate  connections  with  the  thalamus  and  mid-brain. 

(b)  A  second  pair  of  budding  vesicles  arises  cephalad  in  the  dorsal  portion  of 
the  fore-brain  vesicle  and  is  destined  to  develop  into  the  ponderous  cerebral  hemi- 


THE  BRAIN  OR  ENCEPHALON 


853 


spheres  with  their  great  gangha,  growing  with  great  rapidity  and  exceeding  in 
this  respect  all  other  parts  of  the  brain.  The  growth  of  these  secondary  fore- 
brain  vesicles  is  principally  in  the  distal  parts,  and  in  this  manner  each  forms 
a  great  pouch  whose  interior  communicates  with  the  primary  neural  cavity  through 
a  small  opening,  the  foramen  of  Monro  (i)orta).     It  must  be  remembered  that  in 


MUlbmm. 
Hindifdin 


Auditory  vesicle. 


Head  fold  of  amnion. 
Forehraiii. 
' — Optic  vesicle. 


-I -j--  Heart. 


•Omphalo-mesenteric  vein 


-A-4---  )  Profovertebrie  or 

[      mesoblastic  somites. 


'f-,-3— ^-S---Sjn«s  rhomboidalis. 


Remains  of  primitive  - 
streak. 


Fig.  623. — Chick  embryo  of  thirty-three  hours'  incubation,  viewed  from  the  dorsal  aspect.      X  30. 
(From  Duval's  Atlas  d'Embryologie.) 

these  initial  stages  the  vesicles  are  all  extremely  thin-walled,  but  later  the  walls 
thicken  or  hypertrophy  to  a  marked  degree,  so  that  the  neural  cavity  becomes 
relatively  small. 

(c)  Meanwhile  (in  the  fourth  week)  the  most  ceplialic  portion  of  the  fore-brain 
also  becomes  differentiated.  As  the  enlarging  vesicles  of  the  cerebral  hemisphere 
crowd  upon  the  median,  slower-growing  portion,   there  is  observed,  on  either 


854 


THE  NERVE  SYSTEM 


side,  the  development  of  a  groove  or  furrow,  the  primary  arcuate  fissure,  which 
demarcates  the  olfactory  region  (^rhiiioicephalon)  into  a  cephalic  and  a  caudal 

portion.  The  cephalic  portion  develops  into 
a  blind  tubular  diverticulum,  which  grows 
cephalad  to  form  the  olfactory  bulb  and  tract, 
its  central  cavity  becoming  obliterated  (persist- 
ent in  certain  other  mammals),  while  the  caudal 
portion  forms  the  roots  of  the  olfactory  nerves, 
the  anterior  perforated  space  or  preperforatum  and 
the  subcallosal  gyre. 

(d)  At  the  ventral  margin  of  the  hemicerebral 
or  secondary  fore-brain  vesicle  an  excessive 
proliferation  of  cells  results  in  the  production  of 
several  ganglionic  masses — the  basal  ganglia, 
of  which  the  largest  are  the  lenticular  nucleus 
(lenticula)  and  caudate  nucleus  (caudatum). 

(e)  The  median  cephalic  terminal  wall  inter- 
vening between  the  large  hemicerebral  vesicles 
persists  as  a  thin  and  relatively  undeveloped 
lamina,  the  lamina  terminalis. 

(J)  The  remainder  of  the  fore-brain  undergoes 
great  hypertrophy  in  its  lateral  walls  to  form  the 
optic  thalami,  while  the  ventral  portion  develops 
moderately  to  form  the  hypothalamus,  tuber  cine- 
reum,  posterior  lobe  of  pituitary  body,  and  corporffl 
albicantia.  The  dorsal  wall  fails  to  develop, 
and  remains  epithelial  except  at  a  point  imme- 
diately adjacent  to  the  quadrigeminal  lamina  of 
the  mid-brain;  here  a  diverticulum  grows  out 
to  forin  the  pineal  body  or  epiphysis  (a  rudi- 
mentary structure  in  man,  but  undoubtedly  of 
functional  use  in  ancestral  vertebrates). 

(cj)  The  cavity  of  the  primary  fore-brain  vesicle 
ode  of    undergoes  alterations  in  form  as  the  secondary 


\) 


Fig.  624.— Plan    showing    the    m 

iaTtt°cenlli''earaf  ofthetin-5  cSrS!    metamorphoscs  of  its  walls  procccd  in  the  course 
c;'lS'e?ere^pt\on.''-fl^^  of  development.     The  hollow  cerebral  buds  so 

E.  Myeiencephaion.    F.  Central  canal  of    rapidly  outstrip  all  Other  parts  of  thc  braiu  that 

cord.    G.  Lateral  ventricle.    H.  Foramen       ^.      ■'.  <:  .  .  ^ 

of  Monro.    (After  Gerrish.)  their    mternal    cavities,    the    lateral    ventricles, 

Netiral  canal 

Neural  i 


Pie 

tonial  caLity  ^ 

Splauchnopleure 

Omphalo- 
mesenteric vein 
Fig.  625. — Transverse  section  of  a  portion  of  a  chick  embryo  of  twenty-nine  hours  incubation, 
(From  Duval's  Atlas  d'Embryologie.) 

become  the  most  spacious  of  the  ventricular  system.     The  great  hypertrophy  of 
the  thalamic  ganglia  in  the  lateral  walls  of  the  primary  for^-brain  determine  the 


THE  BRAIN  OB  ENCEPHALON  855 

sagittally  placed,  slit-like  form  of  the  so-called   third  ventricle.     The  cavities  of 
the  optic  and  olfactory  buds  become  obliterated. 

II.  Mid-brain. — The  second  primary  vesicle  becomes  .somewhat  later  differen- 
tiated and  takes  a  less  prominent  part  in  the  adult  brain.  Its  dorsal  wall  goes 
into  the  formation  of  four  eminences,  the  corpora  quadrigemina,  while  the  lateral 
and  ventral  sections  grow  considerably  to  form  the  crura  cerebri.  The  neural 
cavity  within  the  mid-brain  persists  as  the  narrow  aqueduct  joining  the  third  and 
fourth  ventricles. 

III.  Hind-brain. — ^The  third  primary  brain  vesicle  is  demarcated  from  the  mid- 
brain by  a  marked  constriction  to  which  has  been  given  the  term  isthmus  rhomb- 
encephali.  The  hind-brain  is  specially  characterized  by  the  great  expansion  of 
its  thinned-out,  membranous  dorsal  wall  caudad,  while  cephalad  the  dorsal  wall 
becomes  very  much  thickened  as  the  proton  or  "  anlage  "  of  the  cerebellum. 

The  ventral  and  lateral  parts  undergo  thickening  to  form  the  pons  and  medulla 
oblongata. 


Invaglnatioti  of  Ectoderm 
to  form  the  tens  ntdimenf 


Fig,  626. — Trans-section  of  head  of  chick  embryo  of  forty-eight  hours'  incubation.     X  55. 
(From  Duval's  Atlas  d'Embryologie.) 

Flexures  of  the  Brain  Tube. — The  difference  in  growth  rate  of  the  differ- 
ent parts  of  the  brain  tube  and  the  marked  disproportion  between  the  rapid 
brain  growth  and  slower  head  growth  causes  the  encephalic  neural  tube  to  become 
sharply  bent  upon  itself  at  certain  points.  The  first  flexure  to  occur  is  involved 
in  a  bending  of  the  entire  head  and  takes  place  in  the  region  of  the  mid-brain; 
this  flexure  is  termed  the  cephalic  flexure.  A  second  bending  of  the  tube  occurs 
at  the  junction  of  the  spinal  cord  and  hind-brain;  this  is  termed  the  cervical  flexure, 
and  is  so  pronounced  in  the  fifth  week  of  intrauterine  life  that  the  lirain  tube  and 
spinal  cord  form  a  right  angle  with  each  other.  A  third  flexure  is  produced,  in 
consequence  of  the  other  two,  in  the  region  of  the  future  pons,  and  is  therefore 
called  the  pontile  flexure.  Subsequently  the  cervical  and  j^ontile  flexures  are 
obliterated  by  a  gradual  straightening  of  this  portion  of  the  l)rain  axis. 

Dorsal  and  Ventral  Laminae  or  Longitudinal  Zones  of  the  Brain.— Quite 
like  the  longitudinal  division  of  the  developing  spinal  cord,  there  is  a  differ- 
entiation of  the  brain  tube  into  dorsal  and  ventral  zones,  though  much  less  clearly 
shown.  The  limiting  furrow  between  the  two  is  not  demonstrable  in  the  fore- 
brain;  at  least  it  is  disputed,  on  good  grounds,  that  it  exists  there.  It  is  claimed 
even  that  three  such  longitudinal  divisions  exist  on  each  side  (Kupfi'er)  and  the 
formation  of  the  cranial  nerves  is  not  quite  comparable  to  the  spinal  nerves, 
although  there  is  a  fair  homology  with  their  dorsal-sensor  and  ventral-motor  func- 
tional differentiation,  despite  their  frequent  admixture  in  some  cranial  nerves  or 
the  total  absence  of  the  one  category  in  others.  Thus  the  motor  elements  do 
not  extend  higher  than  the  mid-brain  and  the  dorsal  division  preponderates 
in  the  more  highly  organized  parts  of  the  brain,  becoming  predominant  in  the 
higher  vertebrate  species — particularly  in  man. 


856 


THE  NERVE  SYSTEM 


In  its  simplest  expression  the  brain  is  a  tube  like  the  rest  of  the  central  nerve 
axis,  but  a  remarkably  modified  one.     There  is  the  same  primitive  ependymal 


^(0^R4,^ 


3LFACTORY    FOLD 


Fig.  627. — Profile  view  of  the  brain  of  hum 

A.  Brain  of  an  embryo  of  about  fifteen  days. 

Brain  of  an  embryo  about  seven  and  a  half  weeks' old 


embryos  at  three  several  stages,  reconstructed  from  sections: 
B.  Brain  of  an  embryo  about  three  and  a  half  weeks  old.     C. 
•  '       (After  His.) 


lining  throughout  its  interior;  there  is  likewise  a  central  tubular  gray  mass  of 
ganglionic   tissue   which,    however,    undergoes   nuclear   differentiation   in   some 


THE  BBAIN  OR  ENCEPHALON 


857 


portions,  atrophies  in  others,  while  in  certain  localities  it  is  crowded  away  from 
the  central  cavity  by  the  intrnsion  of  white  fibre  masses  which  are  chiefly  com- 
missural. A  total  atrophy  occurs  in  a  part  of  the  dorsal  wall  of  both  fore-brain 
and  hind-brain;  partial  atrophy  is  ol)servable  in  the  floor  of  the  third  ventricle, 
near  the  optic  chiasm,  once  perhaps  the  optic  centre  in  the  earliest  of  the  ancestral 
vertebrates,  but  atrophied  in  higher  forms  as  the  visual  tract  became  secondarily 
projected  in  the  thalamus  and  mid-brain.  Great  hypertrophy  characterizes  the 
growth  of  the  ganglionic  gray  in  the  floor  of  the  lateral  ventricle  (cerebral  vesicle), 
resulting  in  the  formation  of  nugget-like  masses,  the  caudate,  lenticular,  and  amyg- 
daline  nuclei.  The  central  gray  of  the  primary  fore-brain  also  undergoes  great 
hypertrophy,  but  in  the  lateral  walls  only,  to  form  the  large,  compact  thalami. 


Thalamus. 
Foramen  of  Monro, 


Posterior  cnmmi. 
Pineal  body. 


Quadrigeminai  plate. 
'  Cerebellum. 


IT.  Ventricle. 


Cerebral  hemisphere.     Olfactory  lobe  or  :■;         •     ] 

rhinencephalor   . .   '^         ,     | 

Lamina  terminalis.  1    '        |     J 

Optic  nerve.  J     i   , 

Optic  chiasm.^      i     | 

Pitnilary  body.'^ 

Tuber  cinereum. 


1   Pons.     MedulJa 
j  oblongata. 

Corpus 

ilbicans. 


Spinal  cord. 


Fig.  628. — Median  section  of  brain  of  human  fetus  during  the  third  month.     (After  His.) 

As  in  the  cord,  fibre  masses  develop  ectad  of  the  central  tubular  gray  in  some 
localities,  while  in  other  regions  the  ganglionic  gray  remains  at  the  surface  and 
the  white  conducting  substance  is  developed  on  its  inner  aspect.  Thus  we  have, 
secondarily,  the  formation  of  superficial  gray  substance  as  the  cortex  (or  rind)  of 
the  cerebrum  and  cerebellum.  The  isolation  of  ganglionic  gray  masses  from  the 
primitive  central  tubular  gray  and  their  difi^erentiation  into  nerve  cell  nidi  is  also 
observable  in  the  reticular  ganglionic  formation  of  the  medulla  oblongata  and  pons 
as  well  as  in  the  roof  of  the  mid-brain.  Certain  aggregations  of  gray  ganglionic 
tissue  are  intercalated  in  the  course  of  fibre  strands,  receive  an  admixture  of  these, 
and  are  regarded  as  terminal,  interrupting,  or  as  condensing  stations  not  unlike 
some  very  complex  relay  telegraph  system.  The  olive,  dentate  nucleus,  red  nu- 
cleus, the  nuclei  of  the  gracile  and  cuneate  funiculi,  the  basketwork  intercalations 
of  the  reticular  and  lemniscus  fields  belong  to  this  intrafascicular  type  of  ganglionic 
structures. 


858 


THE  NEB  VE  SYSTEM 


The  plan  of  structure  of  the  brain  differs,  tlierefore,  from  the  comparatively 
sim  3le  arrangement  of  the  gray  and  white  substance  in  the  spinal  cord.  In  the 
brain  tlie  gray  substance  is  not  centrally  situated  throughout,  and  there  is  a  tendency 
to  nuclear  differentiation  of  great  and  small  ganglionic  masses.  These  are  con- 
nected with  each  other  and  with  the  centres  in  the  cord  by  longitudinal  strands 
of  fibres  of  greater  and  less  length,  as  well  as  by  transverse  associating  fibres 


RHOMBOIDAL 


Fig.  629. — Three  stages  in  the  development  of  the  medulla  oblongata,  showing  the  metamorphosis  of 
the  rhomboidal  lip.      (Modified  after  His.) 

uniting  the  bilateral  nuclei  of  the  same  ganglionic  category;  with  the  periphery 
they  gain  connection  through  the  cranial  nerves  and  [via  the  spinal  cord)  the 
spinal  nerves. 

In  tracing  the  various  structures  of  the  brain  from  the  medulla  oblongata  to  the 
cerebral  cortex  we  follow  anatomically  what  nature  has  done  in  the  evolution 
of  the  highest  type  of  brain  from  that  of  the  simplest  and  most  ancient  vertebrate. 
In  the  medulla  oblongata  lie  the  centres  which  exert  a  very  direct  influence  over 
those  of  the  entire  cord.  The  striate  bodies  and  the  thalami  form  a  connecting 
link  between  the  higher  cerebral  cortex  and  the  medulla  oblongata  and  cord  below. 
The  extensive  cerebral  cortex,  an  aggregation  of  psychic  centres  and  therefore 
the  seat  of  the  will,  controls  the  activities  of  the  fore-brain  ganglia  (corpus  striatum, 
thalamus)  and  the  cerebellar  cortex,  and  these  in  turn  preside  over  the  functions 


THE  BRAIN  OR  ENCEPIIALON 


859 


of  lower  centres,  as  in  the  way  of  motor  responses  to  external  impressions;  such 
reactions  may  be  delayed  or  immediate  according  to  the  exercise  of  the  will  power 
residing  in  the  cerebral  cortex. 

This  control  by  the  will  is  intensified  the  higher  we  ascend  the  animal  scale; 
the  pyramidal  tract,  which  originates  in  the  cerebral  cortex  and  threads  its  way 
to  the  motor  centres  of  tiie  spinal  cord  without  interruption  along  the  brain  axis, 
is  better  developed  in  man  than  in  any  other  animal.  In  the  course  of  evolution 
the  lower  or  more  automatic  ganglia  and  tracts  remain  relatively  about  the  same 
in  mass  as  in  other  mammalia,  but  the  higher,  more  intellectual  ganglia  surpass 
these  in  growth,  so  that  there  is  an  apparent  but  not  real  diminution  of  the  auto- 
matic systems  observed  in  the  human  brain. 


oeR£.^RO-co,j 


J5>t 


(floor  of 
iicle    and 
queduct) 


Fig.  630. — Schematic  representation  of  the  chief  ganglionic  categories  {I  to  V).     Accurate  topographical  relations 
and  interconnections  are  shown  in  other  figures. 

It  has  been  seen  from  the  foregoing  brief  accounts  of  the  development  of  the 
nerve  system  that  the  most  prominent  feature  is  the  redundant  growth  of  the 
cephalic  or  brain  end  of  the  neural  tube.  Comparative  neuroanatomic  re- 
searches have  thrown  much  light  upon  the  probable  genesis  of  this  remarkable 
characteristic.  The  ancestral  vertebrate,  built  upon  the  segmental  type,  was  a 
swimming  animal,  and  its  locomotion  took  place  in  the  direction  of  its  long  axis. 
In  its  progress  through  the  water  the  cephalic  (or  anterior)  segments  were  those 
which  first  encountered  the  foreign  objects  floating  in  the  same  medium.  It  was 
for  these  segments  to  determine  the  quality  of  the  objects  encountered — whether 


860 


THE  NERVE  tiYHTEM 


they  were  inimical  or  indifferent  or  beneficial  to  its  individual  ends.  The  sensor 
periphery,  in  consequence  of  the  demands  of  evolution,  underwent  specialization 
in  the  development  of  olfactory  and  gustatory  organs  for  testing  the  quality  of  the 
food  and  of  the  surrounding  medium;  optic  organs  for  perceiving  rays  of  light; 
auditory  organs  for  the  appreciation  of  certain  oscillations  of  the  surrounding 
medium;  while  others,  strictly  tactile  in  nature,  underwent  elaboration  as  such  in 
the  development  of  sensitive  antenna  or  tentacles.  Motor  contrivances,  useful 
in  the  quest  for  food  or  in  encounters  with  the  enemy,  were  developed  in  the  way 
of  powerful  jaws  and  masticatory  muscles.     In  brief,  a  remarkable  specialization 

and  differentiation  of  structure 
attended  the  development  of  the 
head  end,  and  with  it  the  central 
organ  of  control  kept  pace.  In 
the  human  species  we  find  certain 
of  these  structural  characteristics 
in  a  highly  developed  condition, 
while  others  have  dwindled  or 
disappeared  in  the  course  of  evo- 
lution. Thus,  in  the  myxinoid 
fishes  and  the  lamprey  the  cere- 
bral hemispheres  themselves  are 
mere  appendages  of  the  olfactory 
lobes;  the  sense  of  smell  was  prob- 
ably the  most  important  in  lower 
animals.  In  the  brain  of  man 
conditions  are  reversed  and  the 
olfactory  system  is  seen  to  have 
dwindled  to  an  extreme  degree  as 
compared  with  the  immense  size 
of  the  cerebrum;  this  in  conformity  with  the  relatively  slight  use  made  of  the  smell 
sense  in  the  mental  life  of  man.  Other  organs  of  special  sense,  however,  became 
augmented,  and  these,  together  with  the  nerve  mechanisms  controlling  the  vital 
functions  (respiration,  circulation),  required  a  more  and  more  elaborate  central 
nerve  organ  for  the  harmonious  interaction  of  the  several  elements.  This  central 
organ  or  brain  developed,  in  bulk  and  complexity,  hand  in  hand  with  the  increase 
of  the  intellectual  faculties.  Man's  most  manifest  distinction  from  other  animals 
has  resulted  from  a  remarkable  evolutionary  growth  in  brain  size  and  brain 
power;  and  as  the  brain  is  the  material  organ  of  mental  and  moral  manifesta- 
tions, we  find  in  mankind  the  highest  degree  of  superiority  and  culture — not 
only  as  compared  with  the  nearest  related  apes,  but  of  the  civilized  and  progressive 
races  as  compared  with  the  primitive  and  unprogressive  races. 


^'^j—MiO.dXe  peduncle 
-Inferior  peduncle 


-Medulla  oblongata 


-Scheme   showing   the  connection  of    the 
parts  of  the  brain. 


DESCRIPTIVE  ANATOMY  OF  THE  ADULT  HUMAN  BRAIN. 

Morphologically  considered,  the  brain  consists  of  a  common  trunk  (or  brain 
axis)  from  which  the  two  cerebral  hemispheres  crop  out  like  swollen  terminal  buds, 
while  the  cerebellum  is  an  excrescence  of  the  trunk  itself.  The  axially  situated 
brain  axis  or  ^'brain  stem"^  comprises,  roughly  speaking,  the  axial  parts  of  all 


■  Also  "brain  isthmus,"  a  loosely  used  term.  It  may  here  be  remarked  that  most  extant  accounts  of  the 
anatoray  of  the  brain  overemphasize  the  distinction  of  brain  parts  from  each  other.  Some  authors  follow 
one  or  anotjier  system  based  upon  the  theories  of  the  segmentation  of  the  brain  tube;  others  divide  the  brain 
into  (a)  rhombencephalon  or  hind-brain  and  {b)  cerebrum,  comprising  mid-  and  fore-brain.  None  of  the 
classifications  proposed  are,  as  already  pointed  out,  quite  satisfactory.  The  continuity  of  the  parts  can  only 
be  interrupted  arbitrarily,  and  such  procedure  leads,  to  a  too  narrow  conception  of  brain  structures  single  and 
apart  rather  than  serial  and  connected. 


PARTS  DERIVED  FROM   THE  HJXD-BRAIN 


-SGI 


three  primary  divisions  of  tiie  l)r;un  tuhe — (a)  medulla  oblongata,  (h)  pons,  (r)  mid- 
brain, (d)  thalamic  division  of  fore-brain.  In  this  brain  stem  lie  tiie  majority  i.f  (he 
ganglionic  masses  enumerated  al)ove,  togetiier  witii  tiie  nerve  tracts  uniting  the 
various  ceil  nests  in  (presumable)  automatic  coordination  as  well  as  the  great 
nerve  tracts  connecting  the  spinal  gray  with  the  cerebral  hemispheres,  the  thalami, 
cerebellum,  and  the  ganglia  of  the  medulla  oblongata  (including  the  cranial  nerve 
nuclei),  and  still  other  tracts  connecting  the  medulla  oblongata  with  the  cerebral 
hemispheres,  the  cerebellum,  and  the  special  ganglia  of  the  pons  and  mid-brain. 


Parts  Derived  from  the  Hind-brain  (Rhombencephalon). 
Morphology. 


External 


The  Medulla  Oblongata  (myelencephalon  oblongata;  spina!  bulb;  postoblon- 
gata  of  Wilder). — The  medulla  oblongata  is  the  continuation  cephalad  of  the 
spinal  cord,  the  transition  lying  at  the  level  of  the  foramen  magnum  and  marked 
by  the  decussation  of  the  pyramids.  Its  cephalic  limit  is  sharply  defined  ventrad 
by  the  rounded  margin  of  the  pons,  while  its  dorsal  surface  is  sunk  into  the  cere- 
bellar vallecula.  The  length  of  the  medulla  oblongata  along  its  ventral  surface 
is  f  to  1  inch  (20  to  25  mm.) ;  its  maximum  width  at  the  pontile  end  is  |  inch  (17 
to  18  mm.),  and  half  as  much  at  its  transition  into  the  spinal  cord;  its  maximum 


OF  TRIGEMINAL 

NERVE 

FACIAL 

NERVE 

N.  INTEBMEDIUS 

ACOUSTIC 

NERVE 

GLOSSO PHARYNGEAL 

NERVE 

VAGUS 

NERVE 

SPINAL  ACCESSORY 

NERVE 

HYPOGLOSSAL 

NERVE 

I.    CERVICAL    NERVE 


ASILAR    GROOVE 


Fig.  632. — Ventral  view  of  pons  and  medulla  oblongata,  showing  the  attachments  of  certain  cr.inial  nerves  on 
one  side.     *  The  inter-radieular  pons  tract  or  corpus  pontobulbare,  described  in  the  text. 

thickness  is  about  15  mm.  (|  inch).  Its  expansion  as  it  approaches  the  pons 
gives  it  the  form  of  a  truncated  cone.  The  ventral  surface  rests  upon  the  basilar 
groove  of  the  occipital  bone. 

Fissures. — The  ventral  and  dorsal  fissures  of  the  cord  are  continued  upon 
the  medulla  oblongata,  making  it  a  bilaterally  symmetrical  structure.  The 
ventral  or  ventromedian  fissiu-e  (fissura  mediana  anterior)  at  the  level  of  the  foramen 
magnum  is  interrupted  by  a  number  of  obliquely  intercrossing  fibres,  called  the 


862  THE  NERVE  SYSTEM 

decussation  of  the  pyramids.  Beyond  this  interruption  the  ventral  fissure  passes 
cephalad  to  end  at  the  ventrocaudal  border  of  the  pons  in  a  recess  called  the 
postpontile  recess  or  foramen  cecum. 

The  dorsal  or  dorsomedian  fissure  (fissura  mediana  posterior)  is  of  short  extent 
upon  the  medulla  oblongata,  for  the  neural  cavity  is  here  expanded  into  a  rhom- 
boidal  fossa  whose  dorsal  wall,  profoundly  atrophied,  is  represented  only  by  a 
delicate  membranous  lamina;  the  dorsal  fissure  rapidly  becomes  shallower  as 
it  ascends,  to  cease  at  the  caudal  apex  of  the  "fourth  ventricle." 

Like  the  spinal  cord,  the  surface  of  each  half  of  the  medulla  oblongata  is  divided 
into  three  longitudinal  districts  by  fissures  called  the  ventrolateral  and  dorsolateral 
fissures.  Of  these,  the  latter  only  is  a  continuation  of  the  fissure  of  the  same 
name  in  the  spinal  cord. 

The  ventrolateral  fissure  (sulcus  lateralis  anterior)  of  the  medulla  oblongata 
demarcates  the  ventral  column  (pyramid)  from  the  lateral  column  as  well  as  the 
oli\'e,  and  the  roots  of  the  hypoglossal  nerve,  arranged  in  linear  order,  emerge 
from  this  fissure. 

(The  ventrolateral  fissure  of  the  spinal  cord  becomes  obscured  as  it  ascends  into  the  oblon- 
gata! region,  for  cephalad  of  the  emergence  of  the  ventral  roots  of  the  first  cervical  nerve  a 
band  of  superficial  arcuate  fibres  usually  obliterates  all  traces  of  the  furrow.) 

The  dorsolateral  fissure  {sulcus  lateralis  posterior)  of  the  medulla  oblongata  is 
directly  continuous  with  the  same-named  fissure  of  the  spinal  cord,  and  the  root 
bundles  of  the  spinal  accessory,  vagus,  and  glossopharyngeal  nerves  are  attached 
along  the  bottom  of  this  fissure.  Unlike  the  dorsal  roots  of  the  spinal  nerves, 
the  root  bundles  of  these  three  cranial  nerves  are  not  all  composed  of  afferent 
fibres  arising  in  extraneous  ganglionic  cells  and  entering  the  medulla  oblongata, 
for  the  accessory  nerve  is  purely  efferent  and  the  vagus  contains  both  afferent 
and  efferent  fibres. 

Areas. — The  ventrolateral  and  dorsolateral  fissures  with  their  rows  of  nerve 
fascicles  divide  the  surface  of  the  medulla  oblongata  on  each  side  into  three  dis- 
tricts which  appear  to  be  continuous  with  the  three  columns  of  the  spinal  cord; 
they  are  not  so  in  reality,  however,  owing  to  the  rearrangement  of  the  fibre  tracts 
and  the  central  ganglionic  mass  in  the  myel-oblongatal  transition.  This  portion 
of  the  brain  axis  is  sculptured  into  several  eminences  and  depressions ;  of  the  emi- 
nences, some,  like  the  olives,  the  tubercula  cinerefe,  and  the  clavse,  are  due  to  the 
accumulation  of  gray  substance  beneath  the  surface  at  that  point;  others,  like  the 
pyramids  and  restiform  bodies,  are  due  to  the  prominence  at  certain  points  of 
the  surface  of  the  great  nerve  tracts. 


Areas  of  the  Medulla  Oblongata. 

I.  Ventral  Area: 

Pyramid. 
II.  Lateral  Area: 

(a)  Lateral  tract. 

(b)  Olive. 

III.  Dorsal  Area,  marked  by  slight  furrows  dividing  it  into: 

(a)  Funiculus  gracilis. 

(b)  Funiculus  cuneatus. 

(c)  Funiculus  lateralis  and  tuberculum  cinereum. 

The  last  three  structures  mentioned  appear  to  become  fused  cephalad  to  continue  as  the 
restiform  body  or  restis;  in  reality  the  restiform  body  is  formed  in  a  different  manner. 


AREAS  OF  THE  MEDULLA    OBLONGATA  863 

I.  The  Pyramids  {pyramides  meduUae  oblongafae)  constitute  the  ohlongatal 
portion  of  the  direct  cerebrospinal  efferent  tracts  conveying  (voluntary)  motor 
impulses  from  the  precentral  cortex,  through  the  internal  capsule,  crusta,  and 
ventral  pons  to  descend  in  the  crossed  and  direct  pyramidal  tracts  to  the  efferent 
(motor)  cell  groups  in  the  ventral  horns  of  the  spinal  gray.  In  their  external 
appearance  in  the  medulla  oblongata  they  are  moderately  constricted  at  their 
pontile  ends,  appear  to  become  somewhat  expanded,  to  again  taper  as  they  pass, 
partlv  into  the  ventral  columns  of  the  cord,  partly,  by  decussation,  into  the  lateral 
columns.  The  pyramids  are  separated  from  each  other  by  the  ventral  (or  ventro- 
median)  fissure  except  where  this  is  more  or  less  completely  obliterated  by  the 
decussating  bundles.  Each  pyramid  is  bounded  laterally  by  a  slight  furrow,  the 
ventrolateral  or  pyramido-olivary  groove,  in  which  arise  the  hypoglossal  nerve 
roots  and  which  separates  the  pyramid  from  the  olive.  The  pontile  end  of  each 
pyramid  is  frequently  traversed  by  a  band  of  arched  fibres  {fibrae  amiatae  externae); 
ponticulus  of  Arnold  (not  the  ponticulus  of  Henle),  the  ectal  arcuate  fibres. 

The  decussation  of  the  pyramids  (decussatio  pyramidum)  is  a  term  given  to  the 
obliquely  intercrossing  bundles  seen  at  the  oblongata-myelon  transition.  The 
extent  to  which  this  decussation  occurs  and  the  degree  of  its  visibility  varies  in 
different  individuals.  While  in  most  cases  the  majority  (90  per  cent.)  of  the  fibres 
cross  the  median  line  in  this  decussation  to  continue  as  the  crossed  or  lateral 
pyramidal  tract,  it  is  sometimes  observed  that  a  larger  share  of  the  fibres  pass 
into  the  direct  or  uncrossed  pyramidal  tract  with  a  corresponding  reduction  of  the 
crossed  tract.  Occasionally  the  decussating  bundles  are  so  deeply  situated  in  the 
ventral  fissure  as  not  to  be  visible. 

II.  The  Lateral  Area  of  the  medulla  oblongata  is  continuous  with  that  of  the 
spinal  cord,  and  is  bounded  by  the  dorsolateral  and  ventrolateral  fissures.  It 
is  composed  of  the  tract  of  Gowers  (fa.tricvhts  antrrnlaferaJis  superficialis) ,  the 
ventrolateral  ground  bimdle  {jaficiruhis  jirajirius  anicrolutrntUs),  and  the  direct 
spinocerebellar  tract  {fasciculus  cerebellospinal  is  [Flechsig]),  while  it  is  invaded  from 
above  by  the  crossed  pyramidal  tract.  The  olive  is  interpolated  in  the  cephalic 
part  of  this  area. 

The  olive  (oliva;  olivary  body)  is  a  prominent,  elongated  oval  mass  bulging  from 
the  cephalic  part  of  the  la  teral  area  of  the  medulla  oblongata,  bounded  by  shallow 
grooves,  of  which  one,  for  the  hypoglossal  nerve  roots  (ventrolateral  fissure) 
separates  it  from  the  pyramid,  while  the  other,  containing  the  nerve  fascicles  of 
the  vagus,  glossopharyngeal  and  spinal  accessory  nerves,  separates  the  olive  from 
the  restiform  body.  From  the  pons  it  is  separated  by  a  shallow  groove  in  which 
a  band  of  arched  fibres  is  sometimes  seen.  Numerous  white  fibres  (external  or 
ectal  arcuate  fibres)  emerging  from  the  ventral  fissure  and  traversing  the  pyramid 
loop  across  the  lower  parts  of  the  olive  to  enter  the  restiform  body.  The  olive 
is  formed  by  the  olivary  nucleus,  embedded  in  a  thin  layer  of  white  substance. 

The  olive  is  about  12  mm.  (|  inch)  in  length  and  5  mm.  (^  inch)  in  breadth. 

III.  Dorsal  Area. — (a)  The  funiculus  gracilis  is  the  direct  continuation  of  the 
tract  of  the  same  name  in  the  spinal  cord.  It  is  a  narrow  white  band  placed  along 
the  dorsomedian  fissure,  and  separated  from  the  funiculus  cuneatus  by  the  dorso- 
paramedian  furrow  (sulcus  intermedius  posterior).  At  the  caudal  apex  of  the  rhom- 
boidal  fossa  (fourth  ventricle)  each  funiculus  gracilis  diverges  from  the  median 
plane,  presenting  at  this  point  a  club-like  enlargement,  the  clava.  The  promi- 
nence of  the  funiculus  gracilis  (and  clava)  is  due  to  the  gray  nucleus  funiculi 
gracilis  beneath  the  surface. 

{//)  The  fimiculus  cuneatus  is  the  direct  continuation  of  the  tract  of  the  same 
name  in  the  spinal  cord.  It  enlarges  as  it  ascends,  exhibiting  a  slight  eminence 
or  enlargement,  the  cuneate  tubercle,  which  is  marked  only  in  the  medulla  ob- 
longata of  young  individuals,  and  is  due  to  the  nucleus  funiculi  cuneati  beneath 
the  surface. 


864  THE  NER  VE  SYSTEAr 

(c)  The  funiculus  lateralis  is  a  longitudinal  prominence  which  gradually  en- 
larges cephalad  into  a  slight  tubercle,  the  tuberculum  cinereum,  marking  the  ap- 
proach of  the  gelatinosa  to  the  surface  so  as  to  form  a  prominence  at  a  level  with 
the  lower  border  of  the  olive. 

The  restiform  body  {corpus  restiforme;  restis)  occupies  the  upper  dorsolateral 
area  of  the  medulla  oblongata  on  each  side,  lying  between  the  floor  of  the  fourth 
ventricle  and  the  roots  of  the  vagus  and  glossopharyngeal  nerves.  This  structure 
might  at  first  glance  appear  to  be  the  continuation  of  the  three  funiculi  just 
described.  But  as  a  matter  of  fact  it  is  made  up  of  the  direct  spinocerebellar  tract, 
a  set  of  external  or  ectal  arcuate  fibres  {fibrae  arcuatae  externae)  and  a  set  of  internal 
or  ental  arcuate  fibres  {fibrae  arcuatae  internae).  Each  restiform  body  assists  in 
forming  the  lower  part  of  the  lateral  boundaries  of  the  fourth  ventricle  and  then 
enters  the  cerebellum  as  the  inferior  peduncle  of  that  body. 

The  Pons  {pons  [Varolii]) . — The  pons  is  a  prominent  white  mass  on  the  ventral 
aspect  of  the  brain  stem  which  is  interposed  between  the  medulla  oblongata 
and  the  crura  cerebri.  It  is  convex  from  side  to  side,  and  its  fibres,  running  chiefly 
in  a  transverse  arched  direction,  are  gathered  into  rounded,  compact  strands 
on  either  side,  to  continue  as  the  middle  peduncles  into  the  white  substance  of 
the  corresponding  cerebellar  hemisphere.  The  fibre  bundles  of  the  pyramidal 
tracts  thread  their  way  through  the  pons  on  either  side  of  the  median  plane  and 
small  aggregations  of  gray  substance  {nuclei  pontis)  are  packed  in  the  intervals 
between  the  transverse  pontile  and  longitudinal  pyramidal  fibre  bundles. 

The  Basilar  or  Ventral  Surface  of  the  pons  is  in  relation  with  the  basilar  process 
of  the  occipital  and  the  dorsum  sellae  of  the  sphenoid.  A  shallow  mesal  groove 
lies  between  the  eminences  produced  by  the  pyramidal  tracts  in  their  course  through 
the  pons.  The  groove  is  called  the  basilar  groove  {sulcus  basilaris),  as  the  basilar 
artery  is  usually  accommodated  in  it;  the  artery  is  not,  however,  a  factor  in  the 
production  of  the  groove.  The  large  sensor  and  small  motor  root  bundles  of  the 
trigeminal  nerve  pierce  the  mass  of  the  pons  near  the  anterior  pontile  border,  and 
a  line  drawn  from  this  nerve  root  to  that  of  the  facial  nerve  is  usually  employed 
as  an  arbitrary  boundary  between  the  pons  proper  and  the  middle  peduncle 
of  the  cerebellum.  The  abducent  nerve  emerges  from  the  posterior  pontile  bor- 
der (prepyramidal  part) ;  the  facial  and  acoustic  nerves  are  attached  farther 
laterad. 

While  most  of  the  superficial  fibre  bundles  -of  the  pons  are  seen  to  arch  trans- 
versely, certain  small  compact  bundles'  are  seen  to  extend  in  an  obliquely  longitu- 
dinal direction  from  the  region  of  the  trigeminal  nerve  root  to  and  among  the 
roots  of  the  facial  and  acoustic  nerves. 

The  Pars  DorsaUs  Pontis  {pars  metencephalica  viedullae  oblongatae;  preoblongata). 
— The  pars  dorsalis  pontis,  or  tegmental  part,  is  not  sharply  demarcated  from  the 
medulla  oblongata  or  the  tegmentum  and  crusta  of  the  mid-brain,  and  the  margins 
of  the  pons  on  the  ventral  surface  afford  only  arbitrary  boundary  lines;  for  in  the 
vertebrate  series  the  pons  varies  greatly  in  width  and  its  margins  can  hardly  be 
accepted  as  the  boundaries  of  a  definite  brain  segment.  The  dorsal  surface 
of  the  pars  dorsalis  pontis  is  continuous  with  that  of  the  oblongatal  ventricular 
surface,  and  its  description  more  properly  belongs  to  a  consideration  of  the  anatomy 
of  the  fossa  rhomboidalis  or  "floor  of  the  fourth  ventricle." 

Fourth  Ventricle  of  the  Brain  {ventriculus  quartus). — ^In  a  previous  section 
on  brain  development  it  has  been  pointed  out  how  the  growth  changes  and  differ- 
entiations in  the  hind-brain  differ  from  those  of  the  rest  of  the  neural  tube  in  that 
there  is  a  marked  disproportion  in  the  degree  of  growth  in  the  dorsal  and  ventral 
walls.    While  the  ventral  wall  thickens  greatly  throughout  to  form  the  pons-oblon- 

^  Called  the  inter-radicular  pons  tract  by  E.  C.  Spitzka  (1884),  and  more  recently  described  as  part  of  the  corpus 
pontobulbare  by  Essick  (American  Journal  of  Anatomy,  vii,  1). 


AREAS  OF  THE  MEBVLLA    OBLONGATA  866 

gata,  the  dorsal  wall  hypertrophies  in  its  cephalic  portion  to  form  the  cerebellum, 
while  caudad  thereof  the  roof  atrophies  and  expands  and  becomes  so  attenuated 
as  to  be  represented  merely  by  a  thin  epithelial  membrane.  The  outward  folding 
of  the  walls  of  the  neural  tube  in  this  region  creates  an  expansion  of  the  central 
cavity  in  the  form  of  a  rhomboidal  fossa  roofed  in  by  the  cerebellum  and  a  thin 
epithelial  layer.  A  time-honored  custom  enumerates  this  as  the  fourth  of  a  system 
of  ventricles  of  which  the  other  three  lie  in  the  fore-brain. 

A  cast  of  the  cavity  (Fig.  696)  shows  it  to  be  irregularly  pyramidal,  with  a 
lozenge-shaped  base  and  ridge-like  apex  extending  from  side  to  side,  corresponding 
to  the  acute-angled  recessus  tecti  in  the  fastigium  ("gable  roof")  formed  by  the 
valve  of  Vieussens  and  inferior  medullary  velum.  Such  a  cast  also  indicates 
the  ventral  extension  of  the  cavity  from  the  lateral  angles  of  the  rhomboidal 
base  in  the  form  of  the  lateral  recesses. 

It  is  customary  to  describe  for  the  fourth  ventricle  a  roof  and  a  floor,  although  an 
examination  of  a  sagittal  section  of  a  brain  hardened  in  situ  shows  the  floor  to  be 
in  a  vertical  'plane  in  the  erect  attitude.  Caudad  the  cavity  is  continuous  wi(h 
the  minute  central  canal  of  the  spinal  cord  and  postoblongata  (in  part);  cephalad 
it  passes  into  the  aqueduct  or  mesocele.     The  dorsal  wall  or  "roof"  is  formed 


by  the  valvula  (velum  medullare  anterius),  the  superior  peduncles,  tela  choroidea 
ventriculi  quarti,  and  fastigium  of  the  cerebellum.  The  ventral  wall  or  "floor"  is 
the  rhomboidal  fossa  occupied  by  the  expanded  central  gray  of  the  pre-  and  post- 
oblongatal  portions  of  the  hind-brain. 

"Floor"  of  the  Fourth  Ventricle  {fossa  rhomboidea). — The  "floor"  of  the  fourth 
ventricle  is  lozenge-shaped  and  exhibits  regional  elevations,  depressions,  and 
color  differences  which  are  in  relation  with  the  deep  anatomy  of  the  medulla  ob- 
longata and  tegmentum  of  the  pons  (preoblongata).  It  is  divided  longitudinally 
into  symmetrical  hah'es  by  a  median  groove,  and  each  lateral  half  is  subdivided 
into  a  larger  cephalic  and  a  smaller  caudal  triangle  by  white,  transverse  striae, 
composed  of  bundles  of  myelinic  fibres  connected  with  the  acoustic  tract  and  ap- 
pearing to  sink  beneath  the  surface  near  the  median  groove.  The  portion  occupied 
by  these  striae  acusticae  {striae  medullares)  is  termed  by  His  the  pars  intermedia 
as  distinguished  from  the  pars  superior  and  pars  inferior,  or  frontal  and  caudal  tri- 
angles respectively.  Much  variation  is  met  with  in  regard  to  the  course  and  degree 
of  prominence  of  the  striae  acusticae  (Fig.  633).  There  may  be  none  visible  or 
as  many  as  twelve  distinct  bundles;  bilateral  symmetry  is  the  exception,  and 
not  infrequently  one  or  more  bundles  run  obliquely  cephalolaterad — the  striae 


866  THE  NER  VE  SYSTEM 

obliquae  (conductor  sonorus).  This  irregularity  of  the  acoustic  strise  has  led 
to  another  mode  of  division  of  the  "floor"  for  descriptive  purposes — each  side  to 
be  divided  into  a  median  and  a  lateral  area,  indicated  by  a  more  or  less  well- 
marked  groove,  the  lateral  furrow  {sulcus  limitans),  connecting  the  superior  and 
inferior  (ala  cinerea)  foveae.  This  groove  probably  corresponds  to  one  of  the 
interzonal  sulci  of  the  embryonic  tube,  and  in  a  gross  way  it  separates  the  motor 
and  sensor  fields  of  the  "floor."  The  median  area  is  usually  a  continuous  ridge 
which  is  quite  accentuated  in  the  cephalic  division  as  the  eminentia  abducentis, 
while  caudad  it  becomes  narrowed  as  it  approaches  the  closed  part  of  the  medulla 
oblongata.  The  convergence  of  the  median  and  lateral  furrows  at  the  caudal 
apex  of  the  rhomboidal  fossa  gi^'es  the  appearance  of  the  point  of  an  ancient  writ- 
ing reed  or  quill  pen;  hence  the  term  calamus  scriptorius. 

In  the  caudal  quarter  triangle  a  middle  area  is  occupied  by  an  elongated  tri- 
angular field  whose  depressed  apex  is  directed  frontad.  A  slight  oblique  ridge, 
the  fxmiculus  separans,  composed  chiefly  of  neuroglia,  separates  the  area  postrema 
caudally  from  the  trigonum  vagi  or  ala  cinerea  of  a  pronounced  grayish  color.  The 
whole  depression  has  been  termed  the  fovea  inferior.  Mesally  lies  a  narrow 
triangular  field  with  its  apex  directed  caudad  and  with  slightly  raised  surface — • 
the  trigonum  hypoglossi.  This  area  is  resolved  into  two  fields  by  a  single  or  double 
formation  of  oblique  rugae  affording  a  "  feathered"  appearance  to  the  lateral  field, 
the  area  plumiformis.  I^aterad  of  the  trigonum  vagi  lies  the  caudal  portion  of  the 
lateral  area  of  the  "floor,"  also  called  (in  part)  the  area  vestibularis  (area  acustica) 
and  crossed  over  its  middle  by  the  striae  acusticae  when  these  are  present.  The 
area  vestibularis  is  an  irregularly  triangular  raised  surface  with  its  convex  base 
toward  the  median  line,  and  extending  laterally  to  the  attachment  of  the  tela 
choroidea  and  into  the  lateral  recess.  In  the  fetus  and  in  certain  lower  vertebrates 
the  area  is  more  prominent  and  is  designated  the  tuberculum  acusticum  s.  vestibu- 
laris. 

The  "frontal"  division  of  the  floor  or  triangular  quarter-field  is  marked  by  a 
depression  at  about  its  middle,  the  superior  fovea  {fovea  trigemini),iTom  which  the 
slight  "lateral  furrow"  runs  caudad,  and  but  for  the  intervention  of  the  striae 
would  reach  the  inferior  fovea.  Cephalad  of  the  superior  fovea,  and  continuing 
some  distance  along  the  aqueduct,  is  the  locus  caeruleus,  which  owes  its  color  to  the 
refraction  of  the  pigmented  cells,  the  substantia  ferruginea,  by  the  milky-white 
ependyma.  At  this  altitude,  the  medial  elevation  between  the  superior  fovea  and 
the  median  sulcus  is  accentuated  into  a  fairly  pronounced  eminence,  the  eminentia 
abducentis  {eminentia  medialis;  e.  teres),  overlying  the  nucleus  of  the  abducent 
nerve  and  the  genu  of  the  root  of  the  facial  nerve.  The  portion  of  the  median  sul- 
cus intervening  between  the  eminentia  abducentia  is  correspondingly  depressed  to 
form  the  fovea  mediana. 

The  ventricular  features  enumerated  above  correspond  in  a  crude  way  to  the 
deep  structures  of  the  pons-oblongata,  and  most  of  the  cranial  nerve  nuclei  are 
held  in  a  rhomboidal  frame  formed  by  the  superior  and  inferior  peduncles.  The 
surface  markings  are  only  imperfect  replicas  of  the  subjacent  structures ;  the  various 
cell  nests  overlap  each  other  more  or  less  and  their  relations  can  best  be  studied  in 
the  projection  drawing  in  Fig.  6.34. 

Membranous  Portion  of  the  "Roof"  of  the  Fourth  Ventricle. — The  caudal  exten- 
sion of  the  hypertrophied  cerebellum  hides  from  view  the  whole  of  the  rhomboidal 
fossa,  but  this  structure,  as  before  stated,  forms  but  a  part  of  the  actual  dorsal 
wall  or  "roof."  This  includes  the  converging  superior  peduncles,  the  velum  medul- 
lare  anterius  intervening  between  these,  the  fastigium  of  the  cerebellum,  tlie  velum 
medullare  posterius,  and  the  tela  choroidea  ventriculi  quarti. 

The  velum  medullare  posterius  is  a  thin  and  narrow  lamina  of  white  substance 
continued  laterad  as  the  flocculi  of  the  cerebellum.  At  its  caudal  edge,  /.  e., 
where  nerve  tissue  ceases,  the  ependymal  or  ventricular  lining  epithelium  and  the 


AREAS  OF  THE  MEDULLA    OliLONdATA 


8(37 


pia  over  this  portion  coalesce  to  form  a  delicate  membrane — the  tela  choroidea — 
attached  along  the  caudolateral  boundary  line  of  the  rhomboidal  fossa.  Along 
this  attachment  there  is  another  intrusion  of  nerve  substance  between  the  ependynial 
and  pial  layers;  this  reenforced  lamina  is  usually  termed  the  Ugula  and  may  be 
traced  to  the  clava  and  cuneate  tubercle,  thence  laterad  over  the  restiform  body 
to  bound  the  lateral  recess.  The  structure  is  probably  a  vestige  of  the  secondar). 
rhomboidal  lip  and  has  actually  been  found  to  be  a  part  of  the  pontobulbar  body 
referred  to  above.  Another  small  semilunar  lamina  of  nerve  tissue  bridges  the 
caudal  apex  of  the  fourth  ventricle  and  is  called  the  obex.  This  structure  is 
often  devoid  of  nerve  tissue,  and  is  then  a  mere  membranous  lamina. 

Except  in  rare  instances,  the  tela  choroidea  is  perforated  a  short  distance  from 
the  calamus  region.  The  opening  is  of  variable  shape  and  size;  it  permits  of 
communication  between  the  ventricular  cavity  and  the  subarachnoid  space  and  is 
termed  the  foramen  of  Majendie  {apertura  medialis   v'entricidi  qvarti;  metapore). 


N.  V 

STRIA    PONTIS 


LOCUS     CfRULEUS 

FOVEA    MEDIANA 

FOVEA    TRIGEMINI 


AREA  VESTIBULA 


EMINENT 


NUCL     GRACILIS 


-Surface  markings  and  topography  of  the  principal  nuclei  of  the  floor  of  the  fourth  ^ 
(Modified  from  Streeter.) 


Similar  apertures  at  the  extremities  of  the  lateral  recesses,  and  called  the 
foramina  Luschkae  (apertura  lateralis  ventriculi  quarti)  also  permit  of  a  tidal  flow 
of  the  cerebrospinal  fluid. 

The  choroid  plexuses  of  the  fourth  ventricle  (metaplexuses)  are  highly  ^•ascular 
infoldings  of  the  tela  choroidea,  one  on  either  side  of  the  median  plane,  from  each 
of  which  offshoots  extend  laterad  into  the  lateral  recesses.  As  the  choroid  plexuses 
of  the  brain  are  always  formed  by  infoldings  or  invaginations  of  the  membranous 
portions  of  the  brain  tube,  the  ependymal  continuity  upon  them  is  interrupted 
only  at  the  margins  of  the  foramina. 

liiternal  Structure  of  the  Medulla  Oblongata. — While  the  spinal  cord  remains 
a  closed  tube  with  centrally  situated  gray,  the  medulla  oblongata  opens  out  on  the 
dorsal  aspect  so  as  to  uncover  its  part  of  the  neural  canal  as  the  "floor"  of  the  fourth 


868 


THE  NEB  YE  SYSTEM 


ventricle.     This  involves  a  tilting  of  the  functionally  differentiated  gray  segments 
and,  after  a  gradual  transition  in  the  medulla  oblongata,  the  motor  gray  is  to  be 


Inferior 
medullary  velum 

Choroid  plexus 
Cisterna  basalis  of  subarachnoid  apace 

Central  canal 
Fig-  635. — Scheme  of  roof  of  fourth  ventricli 


DECUSSATION 


Fig.  636. — Schema  of  the  pyramidal  decussation 


Cisterna  pontis  of 
suharach^wid  space 


the  foramen  of  Majendie. 


sought  nearest  the  middle  line, 
the  mixed  gray  just  ectad,  while 
the  sensor  is  the  outermost  of  all. 
Instead  of  the  ventral,  lateral, 
and  dorsal  horns  of  each  half  of 
the  spinal  cord,  we  have  an  ental, 
middle,  and  ectal  comu  in  each 
half  of  the  medulla  oblongata. 
The  positions  alone  have  changed ; 
the  functional  relations  to  nerve 
roots  having  corresponding  func- 
tions are  homologous.  Thus, 
the  motor  hypoglossal  nucleus  is 
placed  in  the  mesal  part  of  the 
ventricular  floor,  while  the  termi- 
nal nuclei  of  the  aflferent  vagus, 
glossopharyngeal,  and  auditory 
nerves  lie  in  the  lateral  part. 

Another  cardinal  change  in  the 
internal  structure  of  the  mpdulla 
oblongata,  accompanying  the  pre- 
ponderating development  of  the 
cerebrum  and  great  basal  gan- 
glia, is  caused  by  interrupting  and 
decussating  fibre  systems  which 
seek  passage  through  the  brain 
stem  and  encroach  more  or  less 
on     its     primitive    architecture. 


While  in  the  spinal  cord  there  is  a  perfect  continuity  of  the  central  tubular  grav,  we 
find  in  the  medulla  oblongata  more  pronounced  peninsular  and  isolated  insular 
nuclei  or  ganglionic  gray  masses. 


AREAS   OF  THE  MEDULLA    OBLONGATA 


869 


Pyramidal  Decussation  {decussatio  pyramidum). — An  important  change  in  the 
internal  structure  is  caused  by  the  passage  of  the  fibres  of  the  pyramidal  tract  as 
these  pass  to  the  same  and  opposite  sides  of  the  cord,  the  latter  category  forming 
the  pyramidal  decussation.     In  consequence  of  this  passage  of  white  (crossed 


DORSO-MED 


"ixaiw 


Fig.  637. — Transverse  section  of  the  medulla  oblongata 
at  its  lower  end.     (Testut.) 


Fig.  638. — Transverse  section  of  the  medulla 
oblongata  at  the  decussation  of  the  pyramids. 
(Testut,  after  Duval.) 


TRAPEZIUM' 


Fig,  639. — Diagram  showing  thi 


of  the  lemnisci  (fillets)  and  their  decussation. 


870 


THE  NERVE  SYSTEM 


pyramidal)  fibres  through  its  substance  the  ventral  gray  horn  is  broken  up  into  a 
coarse  network,  while  one  portion  of  it,  the  caput  comu,  is  entirely  separated  from 
the  rest;  only  a  small  portion  of  the  base  of  the  cornu  remains  intact  close  to  the 
ventrolateral  aspect  of  the  central  canal.  The  caput  cornu,  thus  separated,  is 
displaced  laterally,  and  comes  to  lie  close  to  the  caput  cornu  dorsalis,  which  has 
also  shifted  its  position.     In  consequence  of  this  breaking  up  of  the  greater  part 


-HEAD  OF  DORSAL  HORN 
BASE  OF  VENTRAL  HORN 
HEAD  OF  VENTRAL  HORN 


^HYPOGLOSSAL  NERVE 

Fig.  640. — Tr.^nsverse  section  of  the  medulla  oblongata  at  the  crossing  of  the  lemnisci  or  fillets.      (Testut.) 

of  the  ventral  gray  cornu  by  white  fibres  a  coarse  network  is  formed  in  the  anterior 
and  lateral  areas  of  the  medulla  oblongata,  which  is  named  the  formatio  reticularis. 
The  gelatinosa  Rolandi  {gliosa  cornualis)  of  the  dorsal  horn  is  continued  into 
the  oblongata,  but  becomes  insignificant,  relatively,  in  the  pars  dorsalis  pontis. 
The  spinal  root  of  the  trigeminal  nerve  is  in  ectal  relation  with  the  gelatinosa 
Rolandi;  at  higher  levels  the  spinal  root  of  the  vestibular  nerve  intervenes. 


FLOOR    OF    FOURTH    VENTRICLE 


UCLEUS    GRACILIS 


NUCLEUS    CUNEATUS 


3F    DORSAL    HORN 
AGUS    NERVE 
EAD    OF   VENTRAL    HORN 


TRAL   PYRAMID 


Fig.  641.— Transv 


of  of  the  fourth 


Decussation  of  the  Lemnisci  {fillets). — ^A  similar  change,  dorsad  and  cephalad  of 
the  pyramidal  decussation,  is  caused  by  the  decussation  of  axone  bundles  arising 
in  the  nuclei  of  the  gracile  and  cuneate  fasciculi  (Goll  and  Burdach).  At  this 
level  the  base  of  the  dorsal  gray  cornu  undergoes  change  in  the  form  of  two  thick 
dorsal  peninsular  outgrowths  which  form  the  nuclei  of  termination  of  the  axones 
in  the  gracile  and  cuneate  fasciculi ;  externally  these  gray  masses  produce  the  emi- 
nences of  the  clava  and  cuneate  tubercle.  The  axones  from  these  nuclei  stream 
mesad  and  cephalad  in  a  series  of  concentric  arches,  decussating  in  the  raph^ 
with  the  bundles  of  the  opposite  side  to  form  the  decussation  of  the  lemnisci'  or 
sensor  decussation.  Cephalad  of  this  decussation  the  lemnisci  are  two  bundles 
of  fibres  coursing  on  either  side  of  the  raphe  between  the  olives,  and  just  dorsad 

1  Also  called  "mesal  lemnisci"  in  contradistinction  to  the  "lateral  lemnisci" — of  different  origin. 


AREAS  OF  THE  MEDULLA    OBLONGATA 


871 


of  the  pyramids;  their  further  course  toward  the  cerebrum  will  be  described 
farther  on. 


Fasciculi  • 
jiyramidales 
Fig.  642. — Trans-section  of  the  medulla  oblongata  at  the  decussation  of  the  pyramidal  tracts. 

Canalis  centralis 

Nucleus  nervi  hypoglossi 
Nucleus  alae  cinereae 

Nucleus  fasciculi  gracilis 

Nucleus  fatciculi 
'cimeati 


iiuileus  aicuatus 


Raphe 
Fig.  043. — Trans-section  of  the  medulla  oblongata  at  the  lower  end  of  the  olives. 

With  the  extension  of  the  central  gray  to  form  the  floor,  of  the  fourth  ventricle, 
the  caput  cornu  dorsale  is  displaced  ectad  so  as  to  almost  reach  the  surface, 


872 


THE  NERVE  SYSTEM 


where  it  forms  a  projection,  the  funiculus  lateralis  (Rolandi),  which  enlarges 
cephalad  into  a  distinct  prominence,  the  tuberculum  cinereum.  At  a  higher  level 
the  caput  is  separated  from  the  surface  by  the  spinal  root  of  the  trigeminal  nerve 
and  by  the  external  arcuate  fibres  (Fig.  644).  The  cervix  of  the  cornu  becomes 
broken  up  into  a  reticular  formation  by  the  decussating  fibres.  A  portion  of  the 
base  is  placed  ectad  of  the  nucleus  funiculi  cuneati  and  is  called  the  accessory 
cuneate  nucleus,  supposed  to  be  a  continuation  of  Clarke's  column. 

The  formatio  reticularis  (Fig.  644)  consists  of  diffusely  scattered  gray  substance 
in  a  meshwork  of  white  fibres.  It  is  far  more  abundant  in  the  medulla  oblongata 
than  in  the  cord.  In  trans-sections  of  the  medulla  oblongata  it  is  seen  to  be  divided 
by  the  hypoglossal  nerve  root  fascicles  into  a  mesal  and  a  lateral  field.  In  the 
mesal  field  the  gray  substance  is  scanty,  and  white  fibres — principally  longitudinal 
ones — preponderate;  this  is  called  the  formatio  reticularis  alba  in  contradistinction 
to  the  lateral  grayer  reticulated  field,  the  formatio  reticularis  grisea.  Its  numerous 
nerve  cells  mostly  possess  short  axones  and  for  the  most  part  exercise  associative 


DESCENDING    ROOT   VIII 


dorsal|^  accessor* 

(  OLIVE 

MESIAL  ) 


EXT.  ARCUATE    FIBERS 


HYPOGLOSSAL    NERVE 


HILUM    OLIVjE 
ARCUATE    NUCLEUS 

Fig.  644. — Trans-section  of  the  medulla  oblongata  at  about  the  middle  of  the  olive. 

functions  for  the  constantly  active  centres  of  respiration  (nuclei  of  the  vagus, 
phrenic,  facial,  etc.).  Certain  axones  of  longer  course  are  collected  into  a  small 
compact  bundle  just  ventrad  of  the  ventricular  floor  and  central  canal  (and  aque- 
duct in  the  mid-brain),  and  known  as  the  medial  longitudinal  fasciculus  (posterior 
longitudinal  bundle).  This  tract  is  in  intimate  association  with  the  cranial  nerve 
nuclei.  The  formatio  alba  is  principally  made  up  of  this  tract  and  the  lemniscus 
(interolivary  stratum). 

The  raphe  (Fig.  644)  is  situated  in  the  middle  line  of  the  medulla  oblongata 
above  the  decussation  of  the  pyramids.  It  consists  of  nerve  fibres  intermingled 
with  nerve  cells.  The  fibres  have  different  directions,  which  can  only  be  seen  in 
suitable  microscopic  sections,  thus:  (1)  Some  run  dorsoventrad ;  these  are  con- 
tinuous with  the  external  or  superficial  arcuate  fibres.  (2)  Some  are  longitu- 
dinal; these  are  derived  from  the  arcuate  fibres,  which  on  entering  the  raphe 
change  their  direction  and  become  longitudinal.  (3)  Some  are  oblique;  these  are 
continuous  with  the  internal  or  deep  arcuate  fibres  which  pass  from  the  raphe. 


AREAS  OF  THE  MEDULLA    OBLONGATA  873 

The  nerve  cells  of  the  raphe  are  multipolar;  some  are  connected  with  tlie  dorso- 
ventral  fibres,  others  with  the  superficial  arcuate  fibres. 

The  restiform  body  succeeds  the  gracile  and  cuneate  nuclei,  in  the  dorsolateral 
part  of  the  medulla  oblongata.  Its  fibres  converge  from  various  sources  and 
ultimately  enter  the  cerebellum  as  its  inferior  peduncle.  For  a  description  of  these 
fibre  systems  see  the  section  on  the  "peduncles  of  the  cerebellum." 

The  nucleus  of  the  olive  or  inferior  olivary  nucleus  (nucleus  olivarius  inferior) 
is  a  corrugated  lamina  of  gray  substance  whose  extent  nearly  corresponds  to  that 
of  the  external  elevation  called  the  olive.  It  can  be  compared  to  a  hollow  oval 
sac  or  purse,  slit  on  its  mesal  aspect  and  the  edges  of  the  slit  everted.  The  opening 
is  called  the  hilum.  Numerous  fibres  stream  into  the  interior  through  the  hilum, 
while  others  cut  through  the  lamina  to  join  the  fibre  arches  of  the  reticular  field 
and  then  pass  toward  the  restiform  body. 

What  are  known  as  accessory  olivary  nuclei  (nuclei  olivarii  accessorii)  are  smaller 
detached  or  semidetached  portions  of  the  olivary  nucleus  named,  according  to 
their  position,  the  dorsal  and  medial  accessory  olivary  nuclei  (nuclei  olivarii 
accessorii,  dorsalis  et  medialis). 

The  olivary  nuclei  play  an  important  part  as  relay  stations  in  cerebellar,  con- 
nections.  A  considerable  mass  of  fibres,  the  olivocerebellar  fibres  (fibrae  ccrehello- 
olivares),  originate  in  the  olivary  nucleus  of  one  side  to  enter  the  cerebellum 
along  the  restiform  body  of  the  opposite  side.  A  much  less  number  of  fibres, 
running  contrariwise,  reach  the  olivary  nuclei  from  the  opposite  cerebellar  hemi- 
spheres— the  cerebello-olivary  (vestibulo-olivary  tract)  fibres.  Each  olivary 
nucleus  is  the  terminus  of  the  thalamo-olivary  fibres,  and  Helweg's  olivospinal 
tract  is  believed  to  originate  therein. 

The  Arcuate  Fibre  Systems. — The  arcuate  fibre  systems  comprise  two  sets  of 
fibres  according  as  they  course  dorsad  or  ventrad  of  the  olivary  nuclei : 

1.  The  internal  or  deep  arcuate  fibres  comprise  the  olivocerebellar  fibres,  just 
described,  and  a  number  of  commissural  systems  for  the  association  of  the  teg- 
mental reticular  gray  ganglia  and  cranial-nerve  nuclei.  Others  pass  cerebralward. 
others  to  the  cerebellum. 

2.  The  external  or  superficial  arcuate  fibres  take  origin  (a)  from  the  gracile 
and  cuneate  nuclei  and  enter  the  restiform  body  of  the  same  side;  (h)  from  the 
same  nuclei  of  the  opposite  side,  decussating  in  the  raphe  and  sweeping  ventrad 
over  the  pyramid  and  olive,,  forining  a  thin  layer  over  them  and  ultimately  reaching 
the  restiform  body.  Many  of  these  fibres  are  interrupted,  on  each  side,  in  the 
nucleus  arcuatus,  a  thin,  isolated  lamina  of  gray  substance  lying  on  the  ventral 
aspect  of  the  pyramid. 

The  nucleus  lateralis  is  seen  in  the  lateral  column  (lower  part  of  medulla  ob- 
longata) as  a  difl^use  gray  mass  lying  between  the  gelatinosa  Rolandi  and  tlie  olive; 
it  gradually  disappears  cephalad. 

The  nucleus  intercalatus  (of  Staderini  and  Van  Gehuchfen)  forms  the  elongated, 
wedge-shaped  elevation  in  the  medial  triangle  of  the  caudal  portion  of  the  ventric- 
ular floor  called  the  area  plumiformis  (p.  869);  the  nucleus  derives  its  name  from 
its  (intercalated)  position  between  the  hypoglossal  and  dorsovagal  nuclei.  Its 
functional  connections  are  not  yet  precisely  known. 

A  nucleus  postremus  has  been  described  (J.  T.  Wilson)  as  lying  subjacent  to 
the  area  postrema. 

The  nucleus  funiculi  teretis  lies  close  to  the  median  sulcus  in  the  altitude  of  the 
acoustic  striie,  and  seems  to  bear  an  intimate  relation  to  these. 
Summary  of  the  Gray  Masses  in  the  Medulla  Oblongata: 
*Central  tubular  gray  (in  "closed"  part). 
*Gray  floor  of  fourth  ventricle  (in  "open"  part). 
*Gelatinosa  Rolandi  or  gliosa. 
^Nucleus  funiculi  gracilis. 


874 


THE  NERVE  SYSTEM 


*Nucleus  funiculi  cuneatus. 
*Nucleus  funiculi  cuneati  accessorius. 
*Nucleus  lateralis. 
*Nucleus  olivaris  inferior. 
*Nucleus  olivaris  accessorius  dorsalis. 
*Nucleus  olivaris  accessorius  medialis. 
^Nucleus  arcuatus. 

Nucleus  nervi  hypoglossi. 
^Nucleus  intercalatus. 
*Nucleus  postremus. 
Nucleus  vagi  (alae  cinereae). 
Nucleus  vestibularis  (spinal  division). 
^Nucleus  funiculi  teretis. 
Nucleus  ambiguus. 
Nucleus  tractus  solitarii. 
Nucleus  tractus  spinalis  n.  trigemini. 
*Formatio  reticularis. 
In  the  foregoing  enumeration  of  the  gray  masses  of  the  medulla  oblongata,  those 
marked  with  an  asterisk  have  been  described  above;  the  remaining  structures 
relate  to  the  deep  connections  of  the  cranial  nerves,  and  will  be  discussed  in  detail 
under  that  head. 

Internal  Structure  of  the  Pons  and  Pars  Dorsalis  Pontis. — ^Trans-sections  of 
the  pons  also  pass  through  the  tegmental  part  of  the  pons.     To  consider  first  the 


Fourth  ventricU 


Forniatio  reticularis 
I     Nucleus  emiTientiae 
\    medialis 
Fasciculus       \ 
lonqitudmahs  \ 


^-fF 


mediahs 

\ 


JjCmniscus  mediahs 


Fasciculi  pyramidales 


Corpus  trapezoideum 


apesoides 


Fig.  645. — Trans-section  of  the  pons  at  its  middle,  showing  the  trapezoid  body. 


internal  structure  of  the  pons  proper  (or  jjcirs  basilaris  imntis):  The  pons  is  com- 
posed chiefly  of  (1)  transverse  fibres  arranged  in  coarse  bundles,  (2)  longitudinal 
fibres  gathered  in  compact  bundles,  and  (3)  diffusely  scattered  masses  of  gray 
substance  among  the  fibre  bundles,  the  nuclei  pontis. 

The  transverse  fibres,  corresponding  to  the  large  size  of  the  cerebellum,  are  more 


AREAS  OF  THE  MEDULLA    OBLONGATA 


875 


Fourth  ventricle:  its 
ependyma  m  yellow 


abundant  in  man,  relatively,  than  in  any  other  animal.     They  form  a  massive 
series  of  bundles  coursing  ventrad  of  the  brain  axis  from  one  cerebellar  hemisphere 

Valve  of 
Vieussens 
Su-frior  medullary  velum     lAngida 
Section  of  superior.  ' 

_    cerebellar  peduncle 
Sylvian  root  of  trigeminal 

Nene  cells^^ 
Posterior  lonqitudmal  f 
fasciculus      ^-    ' 
Lateral  lemm^cti 
Formatio  retxcidaiv 
Lateral  sulcu^^^^z:^ 
Medial       //^S^ 
lemniscus  /^r^X 

Transverse    I   /  ^  ■'•'< 
fibres  of      '    ^^ 
pons 


ji^  Trigeminal 
^/-*  iramidal 
fibres 


tiaphi 


"""-^i^J^iL-bdC*""-^ 


Transverse  fibres  of  pons 

Fig.  646. — Section  of  the  pons,  at  its  upper  part. 

to  the  other.     At  the  caudal  border  of  the  pons  they  embrace  the  pyramidal  tracts 
as  well,  but  farther  cephalad  the  transverse  pontile  fibres  are  seen  to  intersect 


Decussation  of  trochlear  nerves 


Locus  c(eruleu5 

Mesencephalic  root  of 
trigeminal  nerve 

Medial  longitudinal 

bundle 
Lateral  lemniscus 
■Gower's  tract 

Rubrospinal  tract 


Beginning  of  decussation 
■of  superior  peduncles 
of  cerebellum 


Fig.  647.— Section  of  the 


ta  junction  with  mid-brain.     (Higher  leve!  than  Fig.  646.) 


the  pyramidal  tracts,  breaking  these  up  into  pyramidal  fasciculi;  still  farther 
cephalad  the  pyramidal  tracts  are  wholly  embedded  in  the  mass  of  t^ans^•e^se 
pontile  fibres,  so  that  these  in  turn,  with  reference  to  the  location  of  the  pyramidal 


876  THE  NEBVE  SYSTEM 

tracts,  may  be  divided  into  a  superficial  and  a  deep  set.  Laterad  they  are  gathered 
together  to  form  the  middle  peduncles  (described  on  p.  890). 

The  longitudinal  fibres  consist  chiefly  of  the  pyramidal  tracts,  M'hich  are  solid 
strands  at  their  entrance  to  and  exit  from  the  pons,  but  are  broken  up  into  lesser 
bundles  at  its  middle.  A  certain  number  of  the  pyramidal  fibres,  as  well  as 
other  cerebropontile  fibre  tracts,  terminate  in  relation  with  the  cells  of  the  nuclei 
pontis,  as  well  as  certain  of  the  efferent  cranial  nerve  nuclei.  This  fact  accounts 
for  the  demonstrable  diminution  in  bulk  of  the  pyramidal  tract  in  its  course 
through  the  pons. 

The  nuclei  pontis  are  small  aggregations  of  gray  substance  (which  in  serial 
sections  show  them  to  be  continuations  of  the  arcuate  nuclei)  diffusely  scattered 
among  the  fibre  systems  of  the  pons  proper.  They  are  intercalated  in  the  course 
(1)  of  tracts  passing  from  one  cerebellar  hemisphere  to  the  other,  and  (2)  of  de- 
scending cerebropontile  tracts.  The  cells  of  the  pontile  nuclei  send  their  axones 
chiefly  to  the  opposite  cerebellar  hemisphere  and  play  an  important  part  as  links 
in  the  complex  chain  of  the  neurone  systems  which  make  the  cerebellum  such  an 
important  organ  of  sensomotor  coordination. 

In  the  contact  zone  of  pons  proper  and  the  pontile  tegmentum  lies  a  group  of 
transversely  decussating  fibres  with  interspersed  gray  masses  with  large  cells 
called  the  trapezium.  This  body  will  be  more  fully  described  in  connection  with 
the  central  auditory  paths. 

The  tegmental  part  of  the  pons  is  of  much  smaller  bulk  than  the  pons  proper, 
as  seen  on  trans-sections.  On  the  dorsal  surface  is  spread  a  layer  of  gray  substance 
covered  by  ependyma,  which  forms  the  floor  of  the  cephalic  part  of  the  fourth 
ventricle.  Beneath  this  gray  substance  lies  the  formatio  reticulans  divided  into 
symmetrical  halves  by  the  raphe — continued  from  the  medulla  oblongata.  Em- 
bedded in  the  formatio  reticularis  are  various  isolated  masses  of  gray  substance 
and  various  more  or  less  compact  fibre  tracts.  Among  the  gray  masses  are  several 
of  the  cranial  nerve  nuclei,  to  be  described  in  a  separate  section,  and  the  following: 

The  superior  olivary  nucleus  {nucleus  olivarius  superior)  is  a  small  gray  mass 
or  aggregation  of  several  smaller  masses  situated  laterad  of  the  trapezium,  inter- 
calated in  the  path  of  the  trapezial  fibres  and  forming  a  link  in  the  central  acoustic 
chain  (Fig.  651). 

The  nucleus  incertus  (Streeter)  is  an  aggregation  of  gray  substance  in  the  floor  of 
the  fourth  ventricle  near  the  median  sulcus  and  forming  a  slight,  rounded  elevation 
which  extends  to  the  aqueduct.     Its  functional  relations  are  unknown. 

Fibre  Tracts  in  the  Pars  Dorsalis  Pontis. — Among  the  fibre  tracts  in  the  tegmental 
part  of  the  pons  the  chief  ones  are  (1)  the  medial  lemnisci,  (2)  the  lateral  lemnisci, 
(3)  the  medial  longitudinal  bundle,  and  (4)  the  superior  peduncles  of  the  cerebellum. 

Each  medial  lemniscus,  or  medial  fillet,  in  its  passage  through  the  tegmental 
part  of  the  pons  is  gathered  into  a  compact,  ribbon-like  bundle  along  the  contact 
zone  of  the  tegmentum  and  pons  proper,  lateroventrad  of  the  trapezium,  some 
fibres  of  which  traverse  it  on  their  way  toward  the  raphe.  The  medial  lemniscus 
has  been  described  in  the  medulla  oblongata  as  occupying  the  field  between  raphe 
and  inferior  olivary  nucleus  (the  interolivary  stratum);  in  its  ascent  the  medial 
lemniscus  gradually  trends  laterad,  so  that  it  almost  reaches  the  surface  (Figs. 
639  and  647). 

The  lateral  lemniscus  is  a  constituent  of  the  central  auditory  path,  and  will  be 
described  more  fully  on  pages  881  and  898.  In  trans-sections  above  the  level  of 
the  trigeminal  nuclei  the  lateral  lemniscus  is  seen  as  a  flattened  band  spreading 
over  the  surface  (externally  the  trigonum  lemnisci)  ectad  of  the  superior  peduncle. 
Its  fibres  are  interrupted  by  an  intercalated  nucleus  of  the  lateral  lemniscus. 

The  medial  longitudinal  bimdle  (posterior  longitudinal  bundle)  maintains  its 
position  just  \'entrad  of  the  central  gray,  close  to  the  raphe. 

The  superior  peduncle  of  the  cerebellum  or  prepeduncle  is  seen  in  trans-sections 


AREAS  OF  THE  MEDULLA    OBLONGATA 


877 


to  be  a  very  compact  bundle  of  crescentic  outline  with  the  concavity  turned 
toward  the  ventricular  cavity.  Its  dorsimesal  edge  is  joined  to  the  superior 
medullary  velum;  its  ventral  border  is  sunk  into  the  tegmentum,  and  in  its  ascent 
it  becomes  submerged  laterally  beneath  the  lateral  lemniscus,  dorsally  beneath 
the  quadrigeminal  plate  of  the  mid-brain. 
Summary  of  the  Gray  Masses  in  the  Pars  Dorsalis  Pontis: 

Nucleus  of  Abducent  Nerve. 

Nucleus  of  Facial  Nerve. 

Afferent  and  Efferent  Nuclei  of  Trigeminal  Nerve. 

Nucleus  of  Spinal  Root  of  Trigeminal  Nerve. 

o    ui        T-\-  •  •         /  Dorsal  Nucleus. 
Cochlear  Division     \  -.j     .     ,  ^.y    , 

[  Ventral  Nucleus. 

{Medial  Nucleus. 
Lateral  Nucleus. 
Superior  Nucleus. 


Nuclei  of  Acoustic  Nerve 


*Superior  Olivary  Nucleus. 

Nucleus  of  Trapezium. 
*Reticular  Ganglionic  Formation. 
*Nucleus  Incertus. 

Nucleus  of  Lateral  Lemniscus. 


Those  marked  with  an  asterisk  have  already  been  described;  the  remaining 
structures  relate  to  the  deep  connections  of  several  cranial  nerves  to  be  described 
in  the  succeeding  section. 

Central  Connections  of  the  Cranial  Nerves  Attached  to  the  Hind-brain.— 
Eight  of  the  twelve  pairs  of  cranial  nerves  are  attached  to  the  hind-brain  portion 
of  the  central  axis.  Their  superficial  or  apparent  origin  and  the  cranial  foram- 
ina of  exit  are  enumerated  in  the  table  on  page  848.  In  coordination  with 
the  internal  descriptive  anatomy  of  the  hind-brain  the  central  connections  of 
these  eight  cranial  nerves  must  now  be  considered.     They  comprise : 


Purely  efferent  or  motor 
nerves    .... 


Mixed  nerves 


Purely  afferent  or  sensor 


XII.  Hypoglossal  nerve. 
XI.  Spinal  accessory  nerve. 


VII.  Facial  nerve  (proper). 
VI.  Abducent  nerve. 

X.  Vagus  nerve. 

IX.  Glossopharyngeal  nerve. 
V.  Trigeminal  nerve. 

fVIII.  Acoustic  nerve. 


1 


Motor  to  muscles  of  tongue. 

(a)  Motor     accessory     to     vagus 

nerve : 

(b)  Motor  to  Trapezius  and  Sterno- 

mastoid  muscles. 
Motor   to    muscles   of   scalp   and 

face. 
Motor  to   External  rectus  muscle 

of  eyeball. 

Sensomotor  to  respiratory  tract 
and  upper  part  of  alimentary 
tract. 

Sensor  to  tongue  (and  motor?) 
to  Stylopharyngeal  muscle. 

Sensor  to  face,  tongue,  teeth; 
motor  to  muscles  of  mastica- 
tion. 

(a)  Cochlear  division  forbearing. 

(b)  Vestibular   division    for   equi- 

librium. 


Another  nerve  which  pursues  a  remarkably  aberrant  course,  becoming  asso- 
ciated with  three  of  the  above-mentioned  cranial  nerves,  is  the  nervus  intermedius, 
known  peripherally  as  the  chorda  tyiapani.  It  is  chiefly  sensor  (taste)  in  function, 
but  also  contains  eiferent  fibres  which  are  exdtoglandulaf  for  the  submaxillary 
and  sublingual  salivary  glands. 

In  the  hind-brain  axis  lie  certain  gray  masses  which  are  functionally  homol- 
ogous with  the  nuclear  masses  in  the  different  parts  of  the  spinal  central  gray. 


878 


THE  NEB  VE  8YSTEM 


These  defined  nests  of  nerve  elements,  from  their  relations  to  the  cranial  nerve 
roots,  are  called  the  cranial  nerve  nidi  or  nuclei.  Their  analogy  to  the  origins 
of  the  spinal  nerves  extends  to  the  shape  and  character  of  their  cell  elements 
and  their  differentiation  into  (a)  nuclei  of  origin  and  (b)  nuclei  of  termination  or 
recipient  nuclei. 

The  nuclei  of  origin  or  motor  nuclei  are  cell  clusters  from  which  arise  the  axones 
of  efferent  nerves  or  the  efferent  components  of  the  mixed  nerves.  Some  of  these 
nuclei  are  in  line  with  the  basal  portion  of  the  ventral  gray  horn  in  the  cord  below 

and  are  termed,  owing  to  their  situ- 
ation near  the  mesal  plane,  the 
medial  nuclei  of  origin.  Other  nuclei 
are  isolated  cell  columns  in  the  line 
of  the  caput  comu  ventrale  detached 
by  the  ducussation  of  the  pyramids, 
termed,  from  their  position  in  the 
tegmental  substance,  the  lateral  nuclei 
of  origin.  The  different  nuclei  of 
origin  of  the  efferent  cranial  nerves 
are  under  the  dominance  of  the  cere- 
bral cortex  by  way  of  the  cortico- 
tegmental  (or  corticobulbar)  path — 
usually  included  in  the  pyramidal 
tract. 

The  nuclei  of  termination  or  sen- 
sor cranial  nerve  nidi  are  likewise 
repetitions  in  structure  of  the  dorsal 
horn  of  the  spinal  gray,  but  with  less 
regularity  and  definiteness  of  posi- 
tion. Thus,  while  the  gelatinosa 
Rolandi  of  the  cord  is  continuous 
with  the  nucleus  of  the  spinal  root  of 
the  trigeminal  nerve,  other  recipient 
or  afferent  nuclei  are  more  or  less 
isolated  in  the  tegmental  substance, 
while  the  two  (lateral  and  ventral) 
nuclei  of  the  cochlear  nerve  actually 
lie  on  the  surface  of  the  brain  stem. 
The  afferent  impulses  carried  in 
by  the  sensor  cranial  nerves  excite 
impulses  in  the  neurones  of  the  nuclei 
of  termination;  their  axones  enter 
the  tegmental  substance  as  arcuate 
fibres,  cross  the  mesal  plane  to  join 
the  lemnisci  to  connect  with  the  thal- 
amus and  posterior  quadrigeminal 
body  and  via  thalamus  and  posterior 
quadrigeminal  body  with  the  cerebral 
cortex.  The  location  of  the  various  cranial  nerve  nuclei  in  the  brain  stem  may  be 
understood  by  a  reference  to  the  diagrams  in  Figs.  634,  648,  649,  and  650. 

Hypoglossal  Nerve  Nucleus. — The  nucleus  of  origin  of  the  hypoglossal  nerve  is 
a  rod-like  cell  column  close  to  the  mesal  plane,  extending  for  about  7  mm.  (^  inch) 
in  the  caudal  portion  of  the  fourth  ventricle,  while  its  extraventricular  portion 
extends  about  5  mm.  (i  inch)  caudad  of  the  tip  of  the  calamus.  Its  efferent 
axones  course  ventrad  between  the  formatio  reticularis  alba  and  grisea,  thence 


Fig.  64S. — The  crani-al  nerve  nuclei  schematically  repre- 
sented in  a  supposedly  transparent  brain  stem,  dorsal 
view.  Motor  nuclei  in  red;  primary  terminal  nuclei  of 
afferent  (sensor)  nerves  in  blue,  (Optic  and  olfactory 
centres  are  omitted,) 


AREAS  OF  THE  MEDULLA    OBLONGATA 


879 


between  the  olivary  and  medial  accessory  olivary  nuclei,  sometimes  mesad  of  the 
latter,  to  emerge  between  pyramid  and  olive.  None  of  the  ribres  decussate  across 
the  middle  line,  but  the  nuclei  are  coordinated  by  commissural  fibres.  x\xones 
from  cerebrocortical  cells  (ventrad  third  of  precentral  gyre)  terminate  in  relation 
with  the  cells  of  the  hypoglossal  nucleus. 

The  hypoglossal  nucleus  permits  of  subdivision  into  groups:  (a)  a  medial  and 
(6)  a  lateral  sub-group.  The  lateral  group  innervates  the  Palatoglossus  and 
Pharyngoglossus,  while  the  medial  nuclear  group  innervates  the  remainder  of  the 
tongue  muscles  (Lingualis  transversus  and  inferior,  Genioglossus  and  Hyoglossus). 

The  Spinal  Accessory  Nerve  Nucleus. — The  spinal  accessory  nerve  is  also  a  purelv 
motor  or  efferent  nerve  whose  axones  arise  from  an  attenuated  nucleus,  with 
large  multipolar  cells,  in  direct  continuation  with  the  nucleus  ambiguus  (of  the 


CERVICAL  NERVES  ' 


Fig.  649. — Nuclei  of  origin  of  the  cranial  motor  nerves  schematically  represented  : 
transparent  brain  stem,  lateral  view. 


a  supposedly 


ninth  and  tenth  nerves)  cephalad,  and  with  the  dorsolateral  cell  column  of  the 
ventral  horn  of  the  upper  five  or  six  segments  of  the  cord.  The  oblongatal  portion 
of  the  nucleus  gives  rise  to  the  encephalic  root  of  the  accessory  nerve  and  its  axones 
join  the  vagus  to  innervate  the  laryngeal  muscles.  Hence  it  may  also  be  termed 
the  nidus  laryngei  (in  contradistinction  to  the  nidus  pharyngei  or  nucleus  ambiguus, 
whose  axones  join  the  vagus  and  glossopharyngeal  nerves  to  be  distributed  to 
the  pharynx).  The  ventrolateral  division  of  this  cell  column  is  believed  to  be 
the  cardioinhibitor  centre.  The  axones  from  the  spinal  nucleus  are  distributed 
to  the  Trapezius  and  Sternomastoid  muscles. 

The  nucleus  of  the  spinal  accessory  nerve  is  likewise  under  the  dominion  of  the 
cerebral  cortex  by  way  of  the  pyramidal  tract,  and  a  reflex  arc  is  completed  by 
afferent  axones  from  the  dorsal  roots  of  the  spinal  nerves. 


880 


THE  NEB  VE  SYSTEM 


The  Vagus  and  GlossopharjTigeal  Nuclei  are  usually  considered  in  their  aggregate, 
justified  not  only  by  their  similarity  in  origin  and  central  connections,  but  also 
by  the  uncertainty  which  prevails  regarding  their  peripheral  interlacement  and 
complex  terminations.  Both  nerves  are  in  greater  part  afFerent,  but  also  contain 
efferent  axones. 

1.  Afferent  Portions. — The  afferent  axones  of  the  vagus  arise  from  the  cells  in  the 
jugular  ganglion  and  ganglion  nodosum  (ganglion  of  the  trunk);  the  afferent  axones 
of  the  glossopharyngeal  arise  from  the  cells  in  its  ganglion  superius  and  ganglion 
petrosum.  The  root  fascicles  of  both  nerves  enter  the  medulla  oblongata  along 
its  dorsolateral  groove,  and  the  axones  then  undergo  bifurcation  into  ascending 
and  descending  rami,  similar  to  those  of  the  dorsal  roots  of  the  spinal  nerves. 


Fig.  650. — Primary  terminal  nuclei  of  the  afferent  (sensor)  cranial  nerves  schematically  represented  in  a.  sup- 
posedly transparent  brain  stem,  lateral  view.     The  optic  and  olfactory  centres  are  omitted. 

The  ascending  rami  end  in  the  nucleus  alae  cinereae  {jiudeus  vagi  et  glossopharyn- 
cjei);  the  descending  rami  collect  to  form  a  compact  bundle  called  the  tractus 
solitarius  or  trineural  fasciculus,'  and  terminating  in  a  gray  cell  column  called  the 
nucleus  of  the  solitary  tract- — a  caudal  prolongation  of  the  nucleus  alae  cinereae. 
Both  tract  and  nucleus  become  attenuated  caudad,  to  disappear  in  the  fourth 
cervical  segment  (relation  with  phrenic  nerve  nucleus),  while  cephalad  it  has 
been  traced  as  far  as  the  region  of  the  locus  caeruleus  (relation  with  trigeminaS 
nerve  nuclei). 

From  the  cells  of  the  nucleus  alae  cinereae  and  nucleus  tractus  solitarii  axones 
pass  across  the  raphe  to  the  contralateral  interolivary  stratum  to  join  the  medial 


'There  are  other  "solitary"  fasciculi  in  the  nerve  system,  and  the  name  "trineural  fasciculus"  aptly 
characterizes  a  tract  which  has  for  its  object  the  mutual  interchange  of  functions  among  the  central  nuclei  of 
the  accessory,  vagus,  and  glossopharyngeal  nerves. 

-  The  nucleus  of  the  solitary  tract  lies  to  the  mesal  side  of  the  tract.  Another  nucleus  has  been  described 
by  Melius,  lying  laterad  of  the  tract. 


AREAS  OF  THE  MEDULLA    OBLONGATA  881 

lemniscus,  establishing  connections  with  the  thalamus  and  c(jrtex;  other  axones 
join  the  tractus  nucleocerebellaris. 

2.  Efferent  Portions. — The  efferent  components  of  the  vagus  and  glossopharyn- 
geal ner\cs  come  from  two  sources — (a)  the  dorsal  efferent  (vagal)  nucleus  and 
(&)  the  nucleus  ambiguus. 

The  dorsal  efferent  nucleus  lies  ventromesad  of  the  principal  nucleus  alae  cinereae 
and  laterad  of  the  hypoglossal  nucleus.  The  axones  from  its  cells  pass  obliquely 
ventrolaterad  to  enter  the  root  fascicles  of  the  vagus  and  to  become  distributed  to 
the  oesophagus,  stomach,  trachea,  and  bronchi.  Whether  the  glossopharyngeal 
nerve  receives  efferent  axones  or  not  is  still  in  debate. 

The  nucleus  ambiguus  (nidus  pharyngei — so  termed  in  contradistinction  to  the 
nidus  laryngei)  is  a  rod-like  mass  of  large,  multipolar  cells  seen,  in  trans-sections, 
lying  in  the  gray,  reticular  formation  midway  between  olive  and  fasciculus  soli- 
tarius  and  apparently  a  cephalic  continuation  of  the  accessory  nerve  nucleus. 
The  axones  arising  from  its  cells  run  dorsimesad  at  first,  then  turn  abruptly  ectad 
to  join  the  vagus  (and  glossopharyngeal  ?)  nerve-root  fascicles,  becoming  dis- 
tributed to  the  pharyngeal  muscles,  oesophagus.  Cricothyroid,  and  the  other 
Laryngeal  muscles. 

The  Acoustic  Nerve  Nuclei. — The  acoustic  nerve  consists  of  a  cochlear  and  a 
vestibular  divisioi);  the  former  is  concerned  with  the  sense  of  hearing,  the  latter 
with  the  sense  of  equilibrium. 

1.  The  cochlear  or  true  auditory  nerve  arises  in  the  bipolar  cells  of  the  cochlear 
spiral  ganglion;  its  axones  terminate  in  (o)  the  dorsal  nucleus  (tuberculum  acusti- 
cum),  a  pyriform  mass  on  the  dorsolateral  aspect  of  the  restiform  body,  and  (b) 
the  ventral  nucleus,  somewhat  detached  from  the  former. 

From  the  dorsal  nucleus  cells  arise  the  axones  which  compose  the  striae  acusticae, 
myelinic  fibre  bundles  traversing  the  ventricular  surface  to  near  the  median 
sulcus,  dipping  into  the  tegmental  substance,  crossing  to  the  opposite  side  in  the 
raphe,  and  eventually  joining  the  lateral  lemniscus  to  end  in  the  posterior  quadri- 
geminal  body  and  internal  geniculate  body. 

From  the  ventral  nucleus  cells  arise  the  axones  which  course  transversely  to  form 
the  trapezium  at  the  contact  zone  of  the  pons  proper  and  tegmentum.  Additional 
axones  from  cells  in  the  superior  olives  of  both  sides  and  in  the  trapezium  itself 
increase  the  bulk  of  this  tract;  some  of  the  primary  axones  end  in  relation  with 
these  cells.  These  axone  groups  form  the  contralateral  lemniscus  lateralis,  which 
contains  the  intercalated  nucleus  of  the  lateral  lemniscus  as  a  relay  station,  to  be 
continued  to  the  posterior  quadrigeminal  and  to  the  internal  geniculate  bodies 
and  thence  to  the  cortical  auditory  "centre"  in  the  supertemporal  gyre. 

2.  The  vestibular  nerve  axones  arise  in  the  bipolar  vestibular  ganglion  cells 
(G.  of  Scarpa),  enter  the  brain  stem,  and  bifurcate  into  ascending  and  descending 
rami,  which  terminate  as  follows:  The  ascending  rami  end  in  the  medial  nucleus 
(Schwalbe's);  the  descending  rami  end  in  the  spinal  vestibular  nucleus,  which 
extends  clown  to  the  gracile  and  cuneate  nuclear  level;  another  group  of  axones 
ends  in  the  lateral  nucleus  (nucleus  magnocellularis)  (Deiters');  while  a  fourth 
and  last  group  ends  in  the  superior  nucleus  (Bechterew's).  From  the  cells  of  all 
these  nuclei  of  termination  axones  proceed  toward  the  cortex,  dentate  nucleus, 
and  nucleus  fastigii  of  the  cerebellum,  as  part  of  the  nucleocerebellar  tract,  to  the 
nuclei  of  the  abducent,  trochlear,  trigeminal,  and  oculomotor  nerves  by  collaterals 
from  axones  in  the  medial  longitudinal  bundle,  to  the  thalamus,  and  to  the  ventral 
horn  nuclei  of  the  spinal  cord  along  the  tractus  vestibulospinalis  (ventral  and  lat- 
eral). The  far-reaching  and  complex  connections  of  the  vestibular  nerve  with  the 
cerebellum  and  the  centres  for  eye  muscles  and  the  spinal  centres  for  bodily  mo\-e- 
ments  make  this  cranial  nerve  a  most  interesting  subject  for  the  active  research 
now  going  on. 

56 


882  THE  NERVE  SYSTEM 

The  Facial  Nerve  Nucleus. — The  facial  nerve  proper  is  to  be  distinguished  from 
its  so-called  sensor  root,  or  pars  intermedia,  or  nervus  intermedius. 

The  axones  of  the  efferent  facial  nerve  arise  from  cells  forming  the  facial  nucleus 
in  the  ventrolateral  region  of  the  reticular  formation,  in  line  with  the  nucleus 
ambiguus  or  nidus  pharyngei,  a  little  over  4  mm.  {\  inch)  from  the  \-entricular 
floor.  These  axones  converge  toward  the  ventricular  floor  to  form  a  compact 
bundle  which  curves  over  the  abducens  nucleus  from  behind,  overlying  it  like  a 
horseshoe  over  a  ball  {genu  facialis  internum) ;  not  as  a  straight  but  as  a  bent 
horseshoe,  bent  so  that  its  cephalic  branch  is  directed  more  laterad  than  its  caudal 
branch.  After  having  encircled  the  abducens  nucleus,  the  facial  root  passes 
ventrolaterad,  passing  its  own  nucleus  ectad,  and  emerging  in  the  postpontile 
groove  (recessus  facialis).^ 

Pyramidal  fibres  from  the  precentral  cortex  place  this  nucleus  under  the  in- 
fluence of  the  will;  it  also  receives  fibres  from  the  trigeminal  and  acoustic  central 
systems. 

The  nervus  intermedius  is  a  mixed  nerve,  containing  afferent  (taste)  fibres  and 
efferent  (excitoglandular  or  secretory)  fibres.  With  respect  to  its  afferent  com- 
ponent it  may  be  regarded  as  an  aberrant  portion  of  the  glossopharyngeal  nerve. 


Bestiform 


Nucleus  .of  cerebellar 

Beckterew.  fibres.\  jf.^^eus  ofFil 


-Raphe. 


Fillet. 


Inf.  sensory  .  „ 
of  trigeminal 

Fibres  taking 
oblique  course. 
Pyramidal  tract.' 

linal  nuclei  of  the  vestibular  root  of  the  auditory  nerve, 
(Schematic.)     (Testut.) 


'ith  their  upper 


1.  Afferent  Portion.- — These  axones  arise  from  the  cells  of  the  geniculate  ganglion, 
implanted  upon  the  genu  facialis  externum,  and  terminate  in  a  nuclear  extension 
cephalad  of  the  nucleus  tractus  solitarii.  They  probably  convey  gustatory  sense 
impulses  from  the  anterior  two-thirds  of  the  tongue  and  the  pillars  of  the  soft  palate. 

2.  Efferent  Portion. — A  nucleus  of  origin  for  the  excitoglandular  elements  has 
been  described  as  a  group  of  cells  extending  beneath  the  ventricular  floor  from 
the  level  of  the  facial  nucleus  to  that  of  the  motor  trigeminal  nerve,  close  to  the 
raphe,  and  called  the  nucleus  salivatorius.    (Fig.  745). 

Peripherally  we  shall  study  this  nerve  as  the  chorda  tympani.  The  mixed  nature 
of  the  nervus  intermedius  and  of  the  geniculate  ganglion  makes  it  probable  that 
they  combine  the  elements  of  a  sympathetic  and  a  spinal  ganglion;  the  nerve,  at 
least,  contains  both  vegetative  and  sensorial  elements. 


'  The  peculiar  course  of  the  deep  root  of  the  facial 
ffandering  of  the  facial  nucleus  in  the  embryonic  period. 


has  been  shown  by  Streeter  to  be  due  to  a 


AREAS  OF  THE  MEDVLLA   OBLONGATA 


883 


The  Abducent  Nerve  Nucleus. — The  abducent  nerve  is  a  small  motor  ner\-e, 
supplying  the  External  rectus  muscle  of  the  eyeball.  Its  nucleus  of  origin 
with  large,  multipolar  cells,  lies  close  to  the  median  plane  beneath  the  eminentia 
abducentis.  The  axones  from  these  cells  pass  ventrad  through  the  tegmentum 
and  trapezium,  and  laterad  of  the  pyramidal  tract,  to  emerge  in  the  postpontile 
groove.  The  nuclei  are  brought  under  the  dominion  of  the  cerebral  cortex  by 
pyramidal  fibres  of  the  opposite  side.  They  are  likewise  brought  into  intimate 
relation  with  the  trigeminal,  acoustic,  and  opposite  oculomotor  nerve  nuclei. 


Demssaling  fibres  Direct  fiires  to  Restiform^fff'^f  fi'"!^^ 
to    sup.    olivary     sup.    olivary       body.       <>f  ("i^rculun 
body  of  opposite    body  of  same 
side.  N  side. 


of  tuberculum 
acusticum. 


Efferent  fibres  of 
accessory  nucleus. 


Superior  olivary^ 
body. 


Central  acoustic 
tract  {lateral 
fillet). 

Tuberculum 

acusticum. 


Accessory  nucleus 

\\    of  auditory  nerve. 

Decussating  fibres  to  sup. 
olivary  body  of  oppo- 
site side. 


Trapezoid  body. 


Trapezoid  nucleus. 


Pyramidal  tract. 


Fig.  652. — Terminal  nuclei  of  the  cochlear  nerve,  with  their  upper  connections.  (Schematic.)  The  vestib- 
ular root  with  its  terminal  nuclei  and  thin  efferent  fibres  have  been  suppressed.  On  the  other  hand,  in  order 
not  to  obscure  the  trapezoid  body,  the  efferent  fibres  of  the  terminal  nuclei  on  the  right  side  have  been 
resected  in  a  considerable  portion  .of  their  e.xtent.  The  trapezoid  body,  therefore,  shows  only  one-half  of  its 
fibres — viz.,  those  which  come  from  the  left.     (Testut.) 


The  Trigeminal  Nerve  Nucleus. — The  trigeminal  is  relatively  enormous  and  has 
correspondingly  extensive  central  connections,  including  nuclei  in  the  mid-brain, 
pars  dorsalis  pontis  and  oblongata,  and  spinal  cord.  It  is  a  mixed  sensomotor 
nerve  and  the  afferent  and  efferent  divisions  must  be  considered  separately. 

1.  Afferent  Portion. — The  axones  of  the  afferent  or  sensor  root  arise  in  the  cells 
of  the  large  semilunar  (Gasserian)  ganglion.  As  in  the  dorsal  roots  of  the  spinal 
nerves,  these  axones  bifurcate,  on  entering  the  brain  axis,  into  ascending  and 
descending  rami.  These  terminate  in  a  cephalic  nuclear  extension  of  the  gela- 
tinosi  Rolandi  of  the  cord;  the  ascending  rami  terminate  in  the  so-called  sensor 
nucleus  of  the  trigeminus,  the  descending  rami  in  the  nucleus  of  the  spinal  tract 
of  the  trigeminus,  which  extends  as  far  as  the  second  cervical  segment  of  the  cord. 
The  sensor  nucleus,  at  the  level  of  the  entrance  of  the  nerve,  is  quite  massive, 
becoming  attenuated  cephalad.  The  spinal  tract,  in  its  descent,  likewise  decreases 
rapidly  as  it  gives  off  its  terminal  axones  to  the  nucleus  of  the  tract.  The  cells 
of  these  terminal  nuclei  send  out  axones  which  cross  the  median  plane,  giving  off 
collaterals  to  the  facial  nucleus,  to  join  the  medial  lemniscus  to  reach  the  thal- 
amus, and,  via  thalamus,  the  somestlietic  cerebral  cortex.  Other  axones  are 
distributed  (a)  to  the  motor  or  efferent  nucleus  of  the  trigeminus  and  (5)  to  the 
motor  or  efferent  cranial  nerve  nuclei. 

2.  Efferent  Portion. — The  eiferent  or  motor  component  of  the  trigeminal  nerve 
consists  of  axones  arising  from  cells  in  two  nidi:  (a)  the  principal  nucleus  in  the 


884 


THE  NERVE  SYSTEM 


dorsolateral  part  of  the  pontile  tegmentum,  dorsomesad  of  the  sensor  nucleus; 
(b)  a  small,  slender,  so-called  mesencephalic  root  nucleus  (nucleus  radicis  asceiid- 
entis  nervi  trigemini)  extending  cephalad  of  the  region  of  the  locus  coeruleus»to 
lie  along  the  aqueduct  in  the  mid-brain.  The  fibres  from  the  principal  nucleus 
supply  the  muscles  of  mastication.  The  distribution  of  the  fibres  from  the  mesen- 
cephalic root  is  not  precisely  known.  Kolliker  suggests  that  they  may  supply 
the  Tensor  veli  palatini,  Tensor  tympani.  Mylohyoid,  and  anterior  belly  of  the 
Digastric. 

Like  other  motor  nuclei,  these  efferent  divisions  of  the  trigeminus  are  under  the 
dominion  of  the  cerebral  cortex  via  pyramidal  fibres. 

The  Cerebellum. — The  cerebellum  occupies  the  greater  part  of  the  posterior 
fossa  or  cerebellar  part  of  the  skull,  and  is  the  largest  portion  of  the  hind-brain. 
It  is  overlapped  by  the  occipital  poles  of  the  cerebrum,  being  separated  from  these 
by  the  tentorium.  It  lies  dorsad  of  the  pons  oblongata  and  partly  embraces  this 
portion  of  the  brain  stem.  It  is  composed  of  a  white  central  core  with  scattered 
gray  masses  and  a  surface  layer  of  gray  substance  that  is  of  darker  hue  than  the 
cerebral  cortex. 


Ala  lobuli  centralis. 
I  centralis.  > 


Great 
horizontal 
'Jissure. 


Pre-clival  fissure. 

clival  ] 


Fig.  6o3.- — Upper  surface  of  the  cerebellum.     (Schiifer.) 


The  cerebellum  is  convoluted  on  a  plan  entirely  different  from  that  of  the  cere- 
brum. Each  primary  fold  is  folded  by  secondary  and  these  in  turn  by  tertiary 
folds,  so  that  on  sagittal  section  a  cypress-leaf  appearance  is  noted,  the  arbor 
vitae  cerebelli.  The  interior  or  medullary  white  substance  follows  all  these 
branchings  and  sub-branchings,  forming  a  skeleton  of  the  minute  folds  which  are 
called  folia.  These  folia  are  demarcated  on  the  surface  by  numerous  curved 
and  more  or  less  parallel  fissures  of  various  depths. 

The  cerebellum  is  connected  to  the  brain  stem  by  three  pairs  of  peduncles  and 
by  vestigial  portions  of  the  primitive  dorsal  wall  of  the  brain  tube.  Among  the 
latter  the  medullary  vela  or  laminae  are  most  important;  they  are  the  superior 
medullary  velum  (valvula),  and  the  inferior  medullary  velum  (velum)  which  enter 
into  the  formation  of  the  "roof"  of  the  fourth  ventricle. 

The  rounded  margin  of  the  cerebellum  demarcates  two  surfaces  looking  re- 
spectively "upward"  and  "downward,"  or  cephalic  and  caudal  surfaces.  Both 
are  convex,  the  inferior  or  caudal  surface  more  so  than  the  upper  or  cephalic. 
The  inferior  surface  shows  a  deep  median  depression,  the  vallecula,  into  which 
the  medulla  oblongata  is  sunk.  The  ventral  margin  is  widely  notched  to  partly 
embrace  the  brain  stem  (tegmental  part  of  the  pons  and  corpora  quadrigemina) ; 
a  dorsal  notch  {incisura  cerebelli  posterior),  which  is  smaller  and  narrower  and 


THE  CEREBELLUM 


885 


lodges  the  cerebellar  falx,  separates  the   hemispheres  as  tliese  project  beyond 
the  inferior  vermis. 

♦^rhe  cerebellum  is  arbitrarily  subdivided  into  a  medial  segment,  the  vermis  or 
worm,  from  its  annulated  appearance,  and  two  lateral  portions,  commonly  called 
the  cerebellax  "hemispheres."  The  vermis  may,  according  to  the  aspect  in  which 
it  is  viewed,  be  divided  into  the  superior  vermis  or  prevermis  on  the  upper  or  cephalic 
surface,  and  the  inferior  vermis  or  postvermis  on  the  inferior  or  caudal  aspect. 
The  superior  vermis  is  hardly  distinguished  from  the  adjacent  sloping  surfaces 
of  the  hemispheres;  occasionally  a  slight  furrow  exists  on  either  side.  Ordinarily 
the  term  is  to  be  restricted  to  the  high  median  elevation  usually  called  the  mon- 
ticulus  cerebelli.  The  inferior  vermis  is  more  distinctly  bounded  by  a  deep  fissure, 
the  sulcus  valleculae,  on  each  side,  separating  it  from  the  corresponding  lateral 
hemisphere. 

Among  the  many  fissures  which  traverse  the  surface  of  the  cerebellum,  one  is 
particularly  conspicuous  as  a  deep  cleft  which  may  be  traced  along  the  dorso- 
lateral margin  from  the  dorsal  notch  to  the  point  of  entrance  of  the  cerebellar 


Post-noclular  Jis. 


Great 
zontal 
ssnre. 


pyramidal 
fissure. 


■  valvulse. 
Fig.  654. — Under  surface  of  the  cerebellu 


(Schafer.) 


peduncles.  This  is  the  peduncular  sulcus  or  great  horizontal  sulcus  (sulcus  horizon- 
talis  cerebelli),  and  it  divides  the  cerebellum  into  a  cephalic  or  upper  and  caudal 
or  lower  part.  The  sulcus  is  usually  quite  deep  in  the  hemispheral  portion,  but 
it  frequently  fails  to  traverse  the  vermis.  Other  deep  fissures  demarcate  the  lobes 
or  major  subdivisions  of  the  intricately  convoluted  surface  of  the  cerebellum. 
Conventionally  the  lobes  and  fissures  or  sulci  are  described  upon  the  "upper"  and 
"lower"  surfaces  respectively,  and  this  mode  of  description  is  partially  adhered  to 
here.  A  better  idea  of  the  topographical  relations  of  the  lobes  and  sulci  in  the 
vermis  and  the  hemispheres  may  be  gained  frorn  a  study  of  the  divisions  of  the 
cerebellum  as  if  extended  in  one  plane  as  well  as  on  sagittal  sections  through 
the  mesal  and  lateral  planes. 

Lobes  and  Fissures  of  the  Cerebellum. — The  surface  of  the  cerebellum  is  traversed 
by  eight  more  or  less  curved  and  deep  fissures  demarcating  nine  lobar  subdivisions. 
Distinctive  names  are  given  to  the  portions  of  each  lobe  in  the  hemispheres  as 
contrasted  with  that  in  the  vermis,  although  often  without  warrant,  as  the  two  are 
quite  continuous  and  merit  no  such  distinction.  This  burdensome  nomenclature 
seems  so  firmly  rooted  in  descriptive  anatomy  that  the  vai-ioiis  terms  must  be 


886  THE  NEBVE  8rSTE3I 

repeated  here.  The  arrangement  of  the  fissures  and  lobes  will  be  understood  by 
reference  to  the  following  schema,  in  which  structures  are  named  from  "before 
backward,"  or  cephalocaudad :  • 

^"ER1IIS.  Hemisphere. 

Lingula.  Vincula  lingualae. 

<: — —     Precentral  Fissure.  ^ 

Lobulus  centralis.  Ala  lobuli  centralis. 

<: Postcentral  Fissure.         > 

Culmen  monticuli.  Anterior  crescentic  lobe.' 

< — ' —     Preclival  Fissure.  > 

Clivus  monticuli.  Posterior  crescentic  lobe. 

< Postdival  Fissure.  > 

Folium  cacuminis.  Superior  semilunar  lobe. 

< Peduncular  Fissure.         ^ 

(  Inferior  semilunar  lobe.  ") 

Tuber  vermis.  ^  < Postgracile  fissure.    >  [  Postero-inferior  lobule. 

(,  Gracile  lobe.  j 

<$- Postpyramidal  Fissure. >■ 

Pj'ramis.  Biventral  lobe. 

•< Prepyramidal  Fissure.     >   . 

Uvula.  Tonsilla  (Amygdala). 

C  ■  '       Postnodular  Fissure.  •  •  > 

I-  Xodulus.  Flocculus. 

The  lingula  (lingula  cerebelli)  is  a  tongue-shaped  process  of  the  vermis  lying  in 
the  ventral  cerebellar  notch,  ventrad  of  the  central  lobe,  and  is  partially  or  com- 
pletely concealed  by  it.  It  consists  of  five,  six,  or  seven  lamellffi  lying  upon  and 
connected  with  the  dorsum  of  the  valvula.  At  either  side  the  lingula  gradually 
shades  off,  being  prolonged  only  for  a  short  distance  toward  the  region  of  the 
peduncles  as  the  vincula  Ungulae. 

The  central  lobe  (lobulus  centralis)  is  a  small  median  mass  situated  in  the  ventral 
notch,  dorsad  of  and  overlapping  the  lingula.  Its  lateral,  wing-iike  prolongation 
is  called  the  ala  lobuli  centralis. 

The  culminal  lobe  is  much  larger  than  the  two  lobes  just  described,  and  con- 
stitutes, with  the  succeeding  lobe  (the  clival  lobe),  the  bulk  of  the  superior  vermis 
and  "upper"  surface  of  the  cerebellum.  It  pardy  overlaps  the  central  lobe.  Its 
lateral  extensions  are  also  termed  the  anterior  crescentic  lobes. 

The  clival  lobe  is  of  considerable  size,  separated  from  the  culminal  lobe  by 
the  preclival  fissure  and  from  the  cacuminal  lobe  by  the  postclival  fissure.  Its 
lateral  extensions  are  also  termed  the  posterior  crescentic  lobes.  ^ 

The  anterior  and  posterior  crescentic  lobes  of  either  side  have  been  described 
by  sonie  writers  as  the  pars  anterior  and  pars  posterior  of  the  quadrate  lobe  or  lobulus 
quadr  annularis. 

The  cacuminal  lobe  or  superior  semilunar  lobe  (folium  vermis)  is  a  short,  narrow 
band  at  the  dorsal  margin  of  the  \-ermis,  which  expands  in  either  hemisphere 
into  a  lobe  of  considerable  size,  of  semilunar  shape,  and  bounded  caudad  by  the 
peduncular  fissure. 

'The  anterior  and  posterior  crescentic  lobes  are  often  called  the  para  anterior  and  pars  posterior,  respectively, 
of  the  "lobulus  quadrangularis." 


THE  CEREBELLUM 


887 


The  tuberal  lobe  is  of  small  size  in  the  region  of  the  inferior  vermis,  but  laterally 
spreads  out  into  the  large  inferior  semilunar  (lobulus  semilunaris  Inferior)  and 
g^acile  lobes  demarcated  by  the  intervening  postgracile  fissure.  These  lol^es  com- 
prise at  least  two-thirds  of  the  "inferior"  surface  of  the  cerebellar  hemispheres. 


Fig.  655. — Diagram  showing  fissures  ( 
U.   UA'ula.     Pu.   Pyramid. 


nder  surface  of  the  cerebellum.     F.  Flocculus.     A^.  Nodule. 
I.  Amygdala  or  Tonsilla.     Bivent.    Biventral  lobe. 


The  gracile  lobe  is  often  divided  by  an  intragracile  fissure  into  pre-  and  post- 
gracile lobes. 

The  pyramidal  lobe  is  a  conical  projection,  forming  the  largest  prominence 
of  the  inferior  vermis.  It  is  continued  laterad  into  the  hemisphere  as  the  biventral 
lobe  {lobulus  biventer);  the  demarcation  between  the  latter  and  the  pyramis  proper 
is  accentuated  by  the  deep  sulcus  valleculfe. 


•  peduncles 
ebellum. 


Grea 
horhoih 
Jisstf 


Amygdala  or  TousiUa.     Nodtile. 


Fig.  656. — Sagittal  section  of  the  cerebellum,  near  the  junction  of  the 

(Schafer.) 


Foiu-tli  ventricle. 

I'ith  the  hemisphere. 


The  uvular  lobe  (uvula  vermis)  occupies  a  considerable  portion  of  the  inferior 
vermis  as  the  uvula,  while  its  lateral  extension  in  either  hemisphere,  the  amygdala 
or  tonsilla  {tonsilla  cerebelli;  amygdaline  nucleus),  is  a  rounded  mass  lying  in  a  deep 
fossa  between  the  uvula  and  biventral  lobe.     (This  fossa  was  termed  by  the 


THE  NERVE  SYSTEM 


older  anatomists  the  nidus  avis  or  "bird's  nest"  [Reil  and  Vieq  d'Azyr].")  The 
junction  of  uvula  and  tonsilla  is  an  attenuated  isthmus  marked  by  a  few  shallow 
furrows  and  termed  the  furrowed  band. 

The  nodular  lobe  comprises  the  nodulus  (nodulus  vermis)  (in  the  inferior  vermis) 
and  the  flocculus  {flocculi  secondarii)  of  each  side,  connected  by  a  delicate  lamina 
of  white  substance,  the  velum  medullare  posterius.  Each  flocculus  lies  adjacent  to 
the  ventrolateral  surface  of  the  peduncular  mass,  extending  into  the  ventral  ex- 
tremity of  the  peduncular  fissure.  The  flocculi  of  the  two  sides  are  connected 
with  each  other  by  a  band  of  white  substance,  termed  the  posterior  medullary  velum 
in  its  medial  portion,  while  its  lateral  expansions  toward  the  flocculi  are  termed 
the  peduncles  of  the  flocculli. 

Sulcus  preclivalis 


Sidms  pustcVivalis 


Sulcus  postgrneii 

[  Sulcus  piegracilis 

Sulcus 
intragracilis 

Fig.  657. — Internal  structure  of  the  cerebellum. 


The  Internal  Structure  of  the  Cerebellum. — In  any  section  of  the  cerebellum  we 
may  recognize  the  interior  white  substance,  corpus  medullare,  and  the  periph- 
eral gray  cortex.  The  white  substance  in  each  lateral  hemisphere  is  more 
bulky  than  in  the  median  vermis,  while  the  cortex  is  of  more  uniform  thick- 
ness throughout.  In  a  sagittal  section  in  the  mesal  plane  the  central  white  core 
is  seen  to  divide  into  two  main  branches — anterior  ramus  or  preramus  and  posterior 
ramus  or  postramus;  these  main  branches  divide  and  subdivide  into  a  series  of 
medullary  laminte  surmounted  by  the  foliated  cortex,  and  presenting  the  charac- 
teristic appearance  known  as  the  arbor  vitae  cerebelli. 

Isolated  Gray  Masses  or  Nuclei  of  the  Cerebellum. — Embedded  in  the  white 
matter  of  the  cerebellum  are  several  gray  masses.  They  are  four  in  number 
on  each  side: 

1.  Dentate  nucleus  or  dentatum. 

2.  Nucleus  emboliformis  or  embolus. 

3.  Nucleus  globosus  or  globulus. 

4.  Nucleus  fastigii  or  fastigatum. 

The  nucleus  dentatus  is  the  largest  and  best  studied  of  the  cerebellar  nuclei.  It 
is  located  in  the  mesal  part  of  the  corresponding  cerebellar  hemisphere,  in  the  direct 
prolongation  of  the  superior  peduncle  of  the  cerebellum,  which  appears  to  enter  it. 
It  consists  of  a  folded  lamina  of  gray  substance  convoluted  like  the  similar  nucleus 
of  the  olive,  and  opens  cephalomesad  where  its  hilum  (hilus  nuclei  dentati)  permits 
of  the  entrance  and  exit  of  fibres  from  various  sources. 


THE  CEREBELLUM 


889 


The  nucleus  emboliformis  is  a  small  mass  of  gray  substance,  elongated  cephalo- 
caudad,  and  placed  entad  of  the  dentate  nucleus,  partly  covering  its  hilum. 

The  nucleus  globosus  consists  of  several  small  round  or  oval  masses  connected 
with  each  other  and  lying  entad  of  the  preceding. 

The  nucleus  fastigii  (nucleus  of  the  "roof")  is  second  in  size  to  the  dentate 
nucleus,  situated  close  to  the  mesal  plane  directly  dorsad  of  the  fourth  ventricle, 
or  in  the  fastigium  of  the  cerebellum,  and  within  the  inferior  vermis.  The  nuclei 
of  opposite  sides  approach  each  other  so  nearly  as  almost  to  fuse. 

The  Cerebellar  Peduncles. — Three  pairs  of  peduncles  constitute  the  chief  avenues 
for  the  entrance  and  emergence  of  the  fibres  composing  the  white  substance  of 


Fig.  658. — Diagram  showing  the  origin  and  ( 


JHed.jpL 

rse  of  the  fibres  of  the  peduncles  of  the  cerebellum.     (Edinger.) 


the  cerebellum  and  connecting  adjacent  parts  of  the  brain  stem  therewith.     The 
peduncles  are,  on  each  side,  the  superior,  middle,  and  inferior  peduncles. 

The  inferior  peduncle  {corpus  restifonne;  postpedunculus)  is  the  continuation  of 
the  restiform  body  of  the  medulla  oblongata.  It  contains  both  afferent  and 
efferent  fibres,  connecting  the  cerebellar  cortex  with  structures  situated  caudad; 
(1)  The  dorsal  or  direct  spinocerebellar  tract,  composed  of  axones  arising  in  Clarke's 
column  (spinal  cord)  and  terminating  in  the  cortex  of  the  superior  vermis  on  both 
sides  of  the  median  line,  but  chiefly  on  the  opposite  side.     (2)  The  olivocerebellar 


890 


THE  NERVE  SYSTEM 


tract,  composed  of  axones  (chiefly  internal  arcuate  fibres)  arising  in  the  (niferior) 
ohvary  nuclei— principally  from  the  contralateral  or  opposite  olive,  and  termniat- 
ing  in  the  cortex  of  the  superior  vermis  and  adjacent  hemispheral  portions,  as  well 


Fig.  659. — The  peduncles  of  the  cerebellum.  On  the  left  the  three  peduncles  have  been  cut  at  their 
entrance  into  the  cerebellum;  on  the  right  side  they  are  shown  penetrating  the  cerebellar  hemisphere. 
(Poirier  and  Charpy.) 

as  in  the  dentate  nucleus.     (3)  External  arcuate  fibres  from  the  homolateral  and 
contralateral  nuclei  of  the  gracile  and  cuneate  funiculi.     (4)  The  nucleocerebellar 

tract,  composed  of  axones  from  the 
recipient  nuclei  of  certain  cranial  nerves 
{vestibular,  trigeminal).  (5)  The  cere- 
bellospinal (descending)  tract,  termi- 
nating in  relation  with  the  ventral 
horn  cells  at  various  levels  of  the  spinal 
cord. 

The  middle  peduncles  {bracJiia  pontis; 
medipedunculi)  are  the  largest  of  the 
three  pairs.  They  consist  of  a  mass 
of  curved  fibres  comprising  the  pons 
and  entering  either  cerebellar  hemi- 
sphere between  the  parted  lips  of  the 
ventral  end  of  the  peduncular  fissure, 
just  ectad  of  the  inferior  peduncle. 
Each  peduncle  contains  axones  cours- 
ing in  opposite  directions  and  in  large 
part  may  be  considered  as  purely  com- 
missural fibres.  Some  of  the  axones 
terminate,  however,  in  the  nuclei  pontis  to  convey  impulses  to  the  cells  therein ; 
these  in  turn  send  their  axones  (tractus  pontocerebellares)  into  the  opposite  mid- 
dle peduncle,  and  therefore  constitute  interrupted  commissural  systems.     A  few 


Fig.  660. — Semidiagram  of  the  three  cerebella 
peduncles.     (Testut.) 


THE  CEREBELLU3I  891 

fibre  systems  in  the  middle  peduncles  establish  relations  with  certain  other 
structures  in  the  brain  stem,  notably  the  nuclei  of  the  oculomotor,  trochlear, 
and  abducent  cranial  nerves. 

The  superior  peduncles  {brachia  conjimcim;  prepedunculi)  emerge  cephalad 
from  the  cerebellum  entad  of  the  middle  peduncles.  As  they  extend  cephalad 
thev  converge  to  form  the  lateral  boundaries  of  the  fourth  ventricle  and  partly 
roof  it  in.  On  trans-section  they  appear  of  oval  outline,  somewhat  concave 
toward  the  cavity  of  the  ventricle.  The  superior  medullary  velum  or  valvula,  a 
thin  lamina  of  white  substance,  spans  the  interval  between  the  converging  superior 
peduncles,  and  thus  completes  the  roofing-in  of  the  cephalic  portion  of  the  fourth 
ventricle. 

The  superior  peduncles  consist  almost  wholly  of  axones  arising  from  the  cells 
of  the  dentate  nucleus,  the  ectal  part  of  the  nucleus  fastigii  of  the  same  side,  and 
mesal  part  of  the  nucleus  fastigii  of  the  opposite  side.  In  their  course,  converging 
cephalad,  tliese  bundles  pass  into  the  tegmentum  of  the  mid-brain  ventrad  of 
the  inferior  corpora  quadrigemina,  and  decussate  almost  wholly.  The  fibres  of 
each  pedimcle  terminate  in  the  red  nucleus  of  the  opposite  side,  although  a  few 
continue  to  enter  the  thalamus. 

This  system  of  fibres  is  also  called  the  tractus  cerebellotegmentalis,  and  axones 
of  inverse  functional  direction  have  been  included  therein. 

The  ventrolateral  spinocerebellar  tract  (Gowers'  tract)  is  in  relation  with  the  supe- 
rior peduncle  and  superior  medullary  velum.  Unlike  the  dorsal  or  direct  spinocere- 
bellar tract,  it  does  not  enter  the  cerebellum  along  the  inferior  peduncle.  Its 
fibres  pass  farther  cephalad,  through  the  reticular  formation  of  the  pars  dorsalis 
pontis  and  medulla  oblongata,  to  become  reflected  dorsocaudad  at  the  level  of 
the  isthmus  of  the  hind-brain,  and  entering  the  superior  medullary  velum,  proceed 
with  the  superior  peduncle  into  the  cerebellum. 

The  medullary  vela  are  two  thin,  relatively  undeveloped  laminse  of  white  sub- 
stance, representatives  of  the  mid-dorsal  wall  of  the  brain  tube  adjacent  to  the 
cerebellar  proton,  and  in  the  adult  brain  appear  as  prolongations  of  the  white 
central  core  of  the  cerebellum.  They  are  the  anterior  or  superior  medullary  velum 
(valvula;  or  valve  of  Meussens)  and  the  posterior  or  inferior  medullary  velum  (velum). 

The  superior  medullary  velum  is  a  thin  lamina  of  white  sul^stance  spanning  the 
interval  between  the  converging  superior  peduncles,  and  with  these  assisting  in 
the  formation  of  tlie  "roof"  of  the  fourth  ventricle.  Caudad  it  is  continuous 
with  the  white  substance  of  the  cerebellum,  while  on  its  dorsal  surface  lie  the  five 
to  seven  folia  of  the  lingula.  Cephalad  it  narrows  as  the  corpora  quadrigemina 
are  approached,  and  a  slight  median  ridge,  the  frenulum,  descends  upon  the  dorsal 
surface  of  its  apical  portion  from  between  the  posterior  quadrigemina;  on  either 
side  of  the  frenulum  may  be  seen  the  superficial  origin  of  the  trochlear  nerve. 
The  majority  of  the  fibres  in  the  superior  medullary  velum  are  longitudinal; 
as  already  described  (p.  838),  the  ventral  spinocerebellar  (Gowers')  tract  reaches 
the  cerebellum  along  the  superior  medullary  velum. 

The  inferior  medullary  velum  is  a  still  thinner  lamina  of  white  substance  which 
6ears  the  same  relations  to  the  nodulus  that  the  superior  medullary  velum  pre- 
sents to  the  lingula.  Laterad  it  extends  to  the  flocculus  of  either  side.  The 
inferior  medullary  velum  ends  in  a  free  crescentic  edge  and  its  ependymal  and 
pial  coverings  continue  as  a  fused,  delicate  membrane,  the  tela  choroidea  ven- 
triculi  quarti. 

The  superior  and  inferior  medullary  vela  enter  the  cerebellum  at  an  acute 
angle,  forming  the  peaked  roof  (fastigium),  while  the  tent-like  recess  is  called  the 
recessus  tecti. 

The  Fibres  Proper  of  the  Cerebellum. — The  librae  propriae  of  tiie  cerebellum  are 
of  two  kinds:  (1)  commissural  fibres,  which  cross  the  middle  line  to  connect  the 


892 


THE  NER  VE  SYSTEM 


opposite  halves  of  the  cerebellum,  some  at  the  anterior  part  and  others  at  the 
posterior  part  of  the  vermis;  (2)  association  fibres,  whicli  are  homolateral  fibres 
connecting  adjacent  lamina  with  each  other. 

Microscopic  Appearance  of  the  Cerebellar  Cortex. — The  cerebellar  cortex,  on 
•  section,  presents  two  marked  layers — an  outer,  of  a  pale  gray  color,  the  molecular 
layer,  and  an  inner,  of  a  rusty-brown  tint,  the  granular  layer.  At  the  contact  line 
of  these  two  layers,  but  more  within  the  molecular  than  the  granular,  are  found 
the  characteristic  nerve  elements  of  the  cerebellum,  the  flask-shaped  Purkinjean 
nerve  cells. 

The  molecular  or  ectal  layer  consists  of  cells  and  delicate  fibrillse  embedded  in  a 
neuroglial  network.     The  cells  are  small  and  are  characterized  by  the  course  of 


PURKINJEA 


^MOLECULAR 


OLGI  CELL 


SMALL  CELL 

OF  MOLECULAR' 

LAYER 


eaSKET  CELL 


Fig.  661. — Trans-section  of  a  cerebellar  folii 


AXONE  OF 


MOSSY  FIBRE 

(Diagrammatic  after  Cajal  and  Kolliker.) 


their  branching  axones  which  run  parallel  with  the  surface  of  the  folium,  give 
off  numerous  collaterals  which  pass  in  a  vertical  direction  toward  the  cell  bodies 
of  the  Purkinjean  elements  and  embrace  these  in  a  basket-like  network.  Hence 
these  cells  are  called  basket  cells  (Fig.  661). 

The  Purkinjean  cells  are  flask-shaped,  and  form  a  stratum  at  the  junction  of 
the  molecular  and  granular  layers,  their  bases  directed  toward  the  latter.     Each 


THE  MID-BBAIN  893 

cell  gives  off  an  axone  entad,  while  ectad  it  gives  off  numerous  dichotomously 
branching  dendrites  covering  a  very  large  field  of  the  molecular  layer.  The  axone, 
after  giving  oft'  several  collaterals  which  pass  toward  different  parts  of  the  granular 
layer,  becomes  myelinic  not  far  from  the  cell  body  and  passes  into  the  white 
substance  to  establish  connections  with  other  folia  within  the  cerebellum  or 
with  more  distinct  brain  structures. 

The  granular  or  ental  layer  is  characterized  liv  containing  numerous  small  nerve 
cells  or  granules  of  a  reddish-brown  color,  together  with  many  nerve  fibrils.  Most 
of  the  cells  are  nearly  spherical  and  provided  with  short  dendrites,  which  spread 
out  in  a  spider-like  manner  in  the  granular  layer.  Their  axones  pass  outward 
into  the  molecular  layer,  and,  bifurcating  at  right  angles,  run  horizontally  for 
some  distance.  In  the  outer  part  of  the  granular  layer  are  also  to  be  observed 
some  larger  cells,  of  the  type  termed  Golgi  cells  (Fig.  661).  Their  axones  undergo 
frequent  division  as  soon  as  they  leave  the  nerve  cells,  and  pass  into  the  granular 
layer,  while  their  dendrites  ramify  chiefly  in  the  molecular  layer. 

Finally,  in  the  gray  substance  of  the  cerebellar  cortex  fibres  are  to  be  seen  which 
come  from  the  white  centre  and  penetrate  the  cortex.  The  cell  origin  of  these 
fibres  is  unknown,  though  it  is  believed  that  it  is  probably  in  the  gray  substance  of 
the  spinal  cord.  Some  of  these  fibres  end  in  the  granular  layer,  by  dividing  into 
numerous  branches,  on  which  are  to  be  seen  peculiar  moss-like  appendages;  hence 
they  have  been  termed  by  Ramon  y  Cajal  the  moss  fibres  (Fig.  661);  they  form 
an  arborescence  around  the  cells  of  the  granular  layer.  Other  fibres  derived 
from  the  medullary  centre  can  be  traced  into  the  molecular  layer,  where  their 
branches  cling  around  the  dendrites  of  Purkinje's  cells,  and  hence  they  have  been 
named  the  clinging  or  tendril  fibres  (Fig.  661). 

The  cerebellum  is  an  important  sensomotor  organ,  transmuting  sensor  im- 
pressions into  motor  impulses  under  the  dominance  of  the  cerebral  centres. 
Its  connections  with  other  brain  portions  and  the  spinal  cord  are  established  by 
the  peduncular  fibres.  It  is  essentially  an  apparatus  for  the  coordination  of 
movements  and  the  space-sense  perceptions  or  orientation  of  the  body  and  its 
parts  in  space.  These  functions  depend  principally  upon  the  reception  of  sensor 
impulses  frorn  (1)  the  vestibular  nerve  (from,  the  semicircular  canals)  and  (2) 
the  spinocerebellar  (ascending)  tracts  conveying  sensor  impulses  from  the  skin, 
muscles  and  joints.  Motor  impulses  pass  along  (1)  the  cerebellospinal  (descend- 
ing) tracts  to  the  ventral  horn  nuclei  of  the  cervical  cord;  (2)  the  tractus  rubro- 
spinalis,  which  arises  in  the  red  nucleus — an  intercalated  ganglionic  mass  con- 
nected with  the  cerebellar  cortex  by  the  superior  peduncles,  or  tractus  cerebello- 
tegmentalis.  The  tractus  rubrospinalis  is  a  tract  for  voluntary  motor  impulses 
next  in  importance  to  the  pyramidal  tract. 

Weight  of  the  Cerebellum. — Its  average  weight  in  the  male  is  165  grams  (5.8 
ounces  avoirdupois)  and  155  grams  (5.4  ounces  avoirdupois)  in  the  female. 
It  attains  its  maximum  between  the  twenty-fifth  and  thirty-fifth  years,  its  increase 
in  weight  after  the  fourteenth  year  being  relatively  greater  in  the  female  than  in 
the  male.  The  proportion  between  the  cerebellum  and  the  cerebrum  is  as  1  to 
7.5;  among  eminent  men  it  is  1  to  8.5,  owing  to  the  preponderance  in  bulk  of  the 
cerebrum  or  thought-apparatus  proper.     In  the  newborn  the  ratio  is  as  1  to  20. 

The  Mid-brain  (Mesencephalon). 

The  mid-brain  is  the  short  and  constricted  portion  of  the  brain  which  lies  in 
the  opening  of  the  tentorium  cerebelli  {incisura  \entoni)  and  which  connects  the 
pons  with  the  inter-brain  and  hemispheres,  and  hence  it  is  frequently  called  the 
isthmus  cerebri.  It  is  developed  from  the  second  brain  vesicle,  the  canity  of 
which  becomes  the  aqueduct.     It  comprises  the  crura  cerebri,  the  corpora  quadri- 


894  THE  NERVE  SYSTEM 

gemina,  the  internal  geniculate  bodies,  and  the  aqueduct.  Its  two  surfaces  are  ven- 
tral and  dorsal.  They  are  free,  but  concealed;  the  ventral  surface  by  the  apices  of 
the  temporal  lobes  which  overlap  it;  the  dorsal,  by  the  overhanging  cerebral  hemi- 
spheres. The  ventral  surface,  when  exposed  by  drawing  aside  the  temporal  lobes, 
is  seen  to  consist  of  two  cylindrical  bundles  of  white  substance,  which  emerge 
from  the  pons  and  diverge  as  they  pass  forward  and  outward,  to  enter  the  inner 
and  under  part  of  either  hemisphere.  They  are  the  crura  cerebri,  and  between 
them  is  a  triangular  area,  the  intercfural  space;'  near  the  point  of  divergence  of  the 
crura  cerebri  the  roots  of  the  third  nerve  are  seen  to  emerge  in  several  bundles 
from  a  groove,  the  sulcus  oculomotorius  (sulcus  nervi  oculomotorii)  (Fig.  619). 
The  dorsal  surface  is  not  visible  until  a  considerable  portion  of  the  cerebral  hemi- 
spheres and  other  overlying  structures  have  been  removed.  It  then  presents 
four  rounded  eminences  placed  in  pairs,  two  cephalad  and  two  caudad,  and  sepa- 
rated from  one  another  by  a  crucial  depression.     These  are  termed  the  corpora 


FRENULUM--               '                                                          -^..r-TAENlA  PONTIS 
TROCHLEAR  NERVe'  ^B TRIGEMINAL    NERVE 


SUPERIOR  MEDULLAR    ^/^^^ 
VELUM  (cut)  ^^^ 


1ERVE 
USTIC  NERVE 

RESTIFORM   BODY ^  ^±J     ^iHBI^3^  GLOSSOPHARYNGEAL 

AND  VAGUS  NERVES 

CUNEATC   TUBERCLE  -^'  Wi--^^^ ^^S/^  HYPOGLOSSAL  NERVE 
TUBERCULUM    CINEREUIV 


Fig.  662. — The  brain  stem,  showing  medulla  oblongata,  pons,  mid-brain,  and  part  of-  the  optic  thalami. 

quadrigemina  (Fig.  662).  The  ventral  and  dorsal  surfaces  meet  on  the  side  of  the 
mid-brain,  and  are  separated  from  each  other  by  a  furrow,  the  lateral  groove 
{sulcus  lateralis  viesencejjhali) ,  which  runs  caudocephalad  (Fig.  662). 

External  Morphology.  Dorsal  Surface. — The  corpora  quadrigemina  are  four 
rounded  eminences  placed  in  pairs  separated  by  a  shallow  median  groove  and  a 
more  sharply  cut  transverse- furrow.  The  cephalic  pair,  the  superior  quadrigeminal 
bodies  (superior  collicuR;  pregemina;  the  nates  of  older  authors),  are  the  larger, 
and  the  pineal  body  rests  in  the  flattened  depression  between  them.  The  superior 
quadrigeminal  bodies  are  oval,  their  long  diameter  being  directed  cephalolaterad, 
and  are  of  a  yellowish-gray  color.     The  inferior  quadrigeminal  bodies  (colliculi  in- 

^  Also  called  interpeduncular  space,  or  posterior  perforated  space. 


THE  MID-BRAIN  895 

feriores;  postgemina;  the  testes  of  older  authors)  are  hemispherical  in  form  and 
lighter  in  color  than  the  preceding.  The  lamina  quadrigemina,  comprising  the 
whole  of  the  dorsal  wall  of  the  mid-brain,  extends  from  the  root  region  (posterior 
commissure)  of  the  pineal  body  to  the  cephalic  end  of  the  superior  medullary 
velum. 

Each  superior  and  inferior  quadrigeminal  body  is  continued  lateroventrad  in 
prominent  white  bands,  the  brachia.  The  band  from  the  superior  quadrigeminal 
body  is  termed  the  superior  brachium  or  prebrachium ;  that  from  the  inferior  quad- 
rigeminal body  is  called  the  inferior  brachium  or  postbrachium. 

The  superior  brachium  or  prebrachium  (brachium  quadricjeminum  siiperius) 
proceeds  cephaloventrad  between  the  overhanging  pulvinar  and  a  light-gray 
eminence,  the  internal  geniculate  body.  In  reality  it  is  a  continuation  of  a  part 
of  the  optic  tract.  The  inferior  brachium  or  postbrachium  (brachmm  quadricjem- 
inum  inferius)  proceeds  in  a  similar  direction  to  disappear  beneath  the  internal 
geniculate  body. 

Of  the  two  geniculate  bodies,  on  either  side,  the  external  geniculate  body  belongs 
rather  to  the  thalamus  (p.  905),  while  the  internal  geniculate  body  may  properly 
be  considered  here  among  the  structures  of  the  mid-brain. 

The  internal  geniculate  body  or  postgeniculum  {corpus  geniculatum  mediale) 
is  a  small  oval  eminence  of  the  lateral  surface  of  the  mid-brain  in  which  the 
mesal  root  of  the  optic  tract  appears  to  terminate.  The  inferior  brachium  like- 
wise appears  to  run  into  this  body;  as  a  matter  of  fact,  so  far  as  is  known,  the 
internal  geniculate  body  is  (1)  a  way-station  for  auditory  impulses  in  their  course 
toward  the  cerebrum;  (2)  the  origin  and  terminus  for  the  infracommissure  of 
Gudden  (commissura  mferior  [Guddeni]),  by  means  of  which  circuitous  path, 
through  the  optic  chiasm,  and  along  the  mesal  root  of  the  optic  tract,  the  internal 
geniculate  bodies  of  the  two  sides  are  connected. 

The  quadrigeminal  lamina  is  continuous  caudad  with  the  superior  peduncles 
of  the  cerebellum  and  the  intervening  superior  medullary  velum.  A  slight,  median 
ridge-like  projection,  the  frenulum  valvulae,  descends  from  between  the  inferior 
quadrigeminal  bodies  onto  the  superior  medullary  velum;  on  either  side  of  the 
frenulum  emerge  the  slender  trochlear  nerves. 

The  crura  cerebri  constitute  the  bulk  of  this  portion  of  the  brain  stem.  Upon 
the  ventral  aspect  of  the  brain  they  appear  as  two  large,  white,  rope-like  strands 
emerging  from  the  pons  and  diverging  to  either  cerebral  hemisphere,  becoming 
embraced  by  the  optic  tracts.  Each  crus  is  composed  of  a  dorsal  tegmental 
part — a  continuation  of  the  tegmentum  of  the  hind-brain — and  a  ventral  crusta 
or  pes.  These  parts  are  demarcated  from  each  other  on  the  external  surface 
by  the  oculomotor  sulcus  ventrad  (which  looks  into  the  intercrural  space)  and  the 
sulcus  lateralis  mesencephali  on  the  lateral  aspect.  The  lateral  surface  shows  dor- 
sally  the  superior  cerebellar  peduncle  dipping  into  the  substance  of  the  mid-brain, 
while  between  it  and  the  crusta  is  a  small  triangular  field  of  oblique  fibre  strands, 
not  always  well  defined,  called  the  trigonum  lemnisci  because  the  lateral  lemniscus 
tends  to  reach  the  surface  of  the  brain  stem  at  this  situation  (Fig.  662) . 

The  surface  of  the  crura  cerebri  shows  a  rope-like  twist  in  the  course  of  its 
fibre  bundles.  Oblique  or  transverse  fasciculi  are  sometimes  seen  upon  the  sur- 
face, two  of  which  are  fairly  constant.  They  are  (1)  the  taenia  pontis,  and  (2) 
Gudden's  tractus  peduncularis  transversus  (cimbia). 

The  taenia  pontis,  as  Horsley  has  shown,  takes  origin  contralaterally  in  the 
gray  substance  continuous  with  the  "interpeduncular  ganglion,"  but  ventral  to 
it.  The  taenia  then  passes  over  the  lateral  lemniscus  and  superior  cerebellar 
peduncle  to  the  dentate  nucleus  and  nucleus  fastigii. 

The  tractus  peduncularis  transversus,  or  cimbia,^  may  be  traced  from  the  supe- 

^  In  architecture,  a  band  or  fillet  about  a  column.    Also  called  fasciculus  arciformis  pedis. 


896 


THE  NERVE  SYSTEM 


rior  quadrigeminal  body  and  internal  geniculate  body  over  the  surface  of  the 
crus  cerebri  to  near  the  ventromeson,  disappearing  from  view  in  the  oculomotor 
sulcus. 

Internal  Structures  of  the  Mid-brain. — If  a  cross-section  be  made  through 
the  mesencephalon  it  will  be  seen  that  each  lateral  half  is  divided  into  two  unequal 
portions  by  a  lamina  of  deeply  pigmented  gray  substance,  named  the  substantia 
nigra  (intercalatum;  ganglion  of  Soemmering).     The  postero-superior  portion  of 


LEMNISCUS 


Fig.  663. — Trans-section  of  the  mid-brain  through  the  level  of  the  inferioi  quadrigeminal  body. 

the  crus  is  named  the  tegmentum,  and  the  antero-inferior  the  crusta  or  pes.  The 
substantia  nigra  is  curved  on  section  with  its  concavity  upward,  and  extends  from 
the  lateral  groove  externally  to  the  oculomotor  sulcus  internally.  The  two  crustae 
are  in  contact  in  front  of  the  pons,  from  which  point  they  diverge  from  each 
other,  but  the  two  halves  of  the  tegmentum  are  joined  to  each  other  in  the  mesal 


AQUEDUCT 


CLEUS  OF 
MOTOR 
ERVE 


3RACHIUM 
EDIAL  LONQI- 
JDINAL  FASCIC- 
ULUS 


OCULOMOTOR 
NERVE 

Fig.  664. — Trans-section  of  the  mid-brain  through  the  level  of  the  superior  quadrigeminal  body. 


plane  by  a  forward  prolongation  of  the  raphe  or  median  septum  of  the  pons. 
Laterally  the  tegmenta  are  free,  but  dorsally  they  blend  with  the  corpora  quadri- 
gemina. 

Traversing  the  mid-brain  in  the  median  plane  and  nearer  the  dorsal  surface  is 
the  aqueduct,  surrounded  by  the  central  tubular  gray,  which  in  this  brain  seg- 


THE  MID-BUAIN  ■  897 

ment  has  retained  the  comparathely  primitive  arrangement  of  the  embryonic 
brain  tube. 

The  Aqueduct  (mesocele)  and  Central  Aqueduct  Gray. — The  aqueduct  is  a  nar- 
row canal  connecting  the  third  with  the  fourth  -ventricle,  and  demarcating  the 
lamina  quadrigemina  dorsad  from  the  tegmental  zone.  Its  shape  on  trans- 
section  varies  at  diiferent  levels,  being  T-shaped  caudad,  oval  or  quadrangular 
along  its  middle,  and  triangular  cephalad.  It  is  lined  by  the  ependyma  (columnar 
ciliated  epithelium)  and  surrounded  by  the  central  aqueduct  gray.  The  central 
gray  is  separated  dorsally  from  the  corpora  quadrigemina  by  the  stratum  lemnisci; 
ventrad  near  the  median  plane  lie  the  medial  longitudinal  bundles.  Within  the 
gray  substance  lie  certain  well-defined  cell  clusters,  the  nuclei  of  origin  of  the 
oculomotor  and  trochlear  nerves  and  the  mesencephalic  root  of  the  trigeminal 
nerve.     These  will  be  described  in  detail  later. 

The  substantia  nigra  or  intercalatum  is  a  crescentic  layer  of  deeply  pigmented 
gray  substance  interpolated  between  the  crusta  and  the  tegmentum.  IVIesad  it 
nearly  touches  its  fellow  of  the  opposite  side,  being  separated  by  the  rudimentary 
ganglionic  gray  (the  posterior  perforated  substance  or  postperforatum)  in  the  inter- 
crural  space.  Its  ventral  face  sends  numerous  ramifying  prolongations  among 
the  fasciculi  of  the  crusta.  It  extends  from  the  cephalic  border  of  the  pons  to 
the  subthalamic  region,  while  its  lateral  edge  reaches  the  surface  along  the  lateral 
sulcus.  Its  cells  are  medium-sized,  multipolar,  their  bodies  approaching  the 
fusiform  or  angular  in  outline.  The  cells  are  characterized  by  a  pigment  (marked 
only  in  man)  which  varies  from  a  pale  brown  in  the  young  to  an  absolute  blackness 
in  the  \'ery  aged.  The  axones  arising  from  the  cells  proceed  in  various  directions 
toward  the  tegmentum  and  crusta,  but  their  exact  course  is  not  known.  Experi- 
mental excitation  of  this  ganglionic  mass  elicits  movements  of  deglutition  accom- 
panied by  respiratory  changes.  JNIellus  has  found  in  the  monkey  that  a  portion 
of  the  pyramidal  tracts  is  interrupted  in  the  substantia  nigra. 

The  corpora  quadrigemina  are  largely  composed  of  gray  substance,  but  the 
superior  and  inferior  corpora  quadrigemina  differ  distinctly  in  structure. 

The  inferior  corpora  quadrigemina  or  postgemina  are  more  homogeneous  in 
texture,  comprising  a  pair  of  compact  ganglia  which  on  trans-section  have  the 
shape  of  biconvex  lenses,  encapsulated  by  white  substance.  The  cells  are  small, 
multipolar,  and  very  numerous,  embedded  in  a  fine  molecular  groundwork. 
The  white  stratum  zonale  is  principally  derived  from  the  fibres  of  the  lateral 
lemniscus,  which  terminate  in  the  central  gray  of  the  inferior  quadrigeminal  body 
as  well  as  in  the  internal  geniculate  body.  The  axones  of  the  cells  in  the  inferior 
quadrigeminal  body  coiu'se  cephalad  in  the  inferior  brachium,  dip  beneath  the 
internal  geniculate  body  into  the  tegmentum,  and  proceed  to  the  thalamus.  The 
inferior  quadrigeminal  bodies  are  important  links  in  the  chain  of  the  auditory 
neurone  system,  and  are  special  localities  for  the  reflexion  of  auditory  impulses. 

The  tegmentum  of  the  mid-brain  is  continuous  with  the  like  formations  in  the 
hind-brain  stem  and  consists  of  longitudinal  fibre  bundles  intersected  by  transverse 
arched  fibre  systems  with  gray  substance  irregularly  scattered  in  the  interstices, 
composing  the  formatio  reticularis.  In  its  ventral  portion,  on  either  side,  and  at 
the  level  of  the  superior  quadrigeminal  body,  lies  a  gray  ganglionic  mass,  the 
red  nucleus. 

The  superior  corpora  quadrigemina  or  pregemina  present  a  true  cortical  type, 
which  is  more  evident  in  the  optic  lobes  of  lower  vertebrates.  In  man  the  thin, 
outermost  white  layer — the  stratum  zonale — is  an  expansion  of  the  optic  tract. 
Beneath  this  lies  a  gray  nucleus,  with  numerous  small  cells — the  stratum  cinereum — • 
a  cup-like  layer  of  crescentic  outline  on  trans-section.  The  succeeding  ental 
layer  is  a  white  stratum,  also  derived  from  the  optic  tract — the  stratum  opticum. 
Between  this  and  the  underlying  stratum  lemnisci  is  a  second  gray  layer,  less 
defined  because  of  the  diffuse  interlacinff  of  white  fibres. 


898  THE  NERVE  SYSTEM 

Each  superior  quadrigeminal  body  is  one  of  a  series  of  primary  centres  of  vision 
related  more  to  eye-muscle  reflexes  resulting  from  optic  and  auditory  stimuli 
than  to  actual  light  and  color  perception.  Fibres  from  the  retina,  for  the  most 
part,  form  the  stratum  zonale  and  end  in  the  ganglionic  gray;  others  enter  into  the 
formation  of  the  stratum  opticum.  Return  fibres  from  the  occipital  cortex  also 
enter  the  stratum  opticum.  The  retinal  and  occipital  fibers  determine  the  forma- 
tion of  the  superior  brachium.  Other  fibres  reach  the  superior  quadrigeminal 
body  through  the  lateral  and  medial  lemnisci — from  both  sides — to  end  in  rela- 
tion with  the  deeper  cells  of  the  stratum  cinereum.  The  connections  of  the 
superior  quadrigeminal  body  with  the  cochlear  centres  aft'orded  by  the  lateral 
lemniscus  establishes  the  so-called  optic-acoustic  reflex  path. 

The  red  nucleus  or  rubrum  (nucleus  iegmenti;  nucleus  ruber),  so  termed  from  its 
reddish  tinge  in  the  fresh  brain,  which  it  owes  to  the  pigmentation  of  its  cells  as 
well  as  to  its  great  vascularity,  is  found  subjacent  to  the  superior  quadrigeminal 
body  in  tliose  section-levels  where  the  substantia  nigra  has  its  greatest  expansion. 
In  trans-sections  its  outline  is  irregularly  circular;  in  sagittal  sections  an  elongated 
oval.  The  red  nucleus  is  the  end  station  for  the  majority  of  the  decussated 
fibres  of  the  superior  peduncles  of  the  cerebellum,  for  fibres  from  the  cerebral 
cortex,  and  from  the  corpus  striatum.  These  fibre  bundles  form  for  the  nucleus 
a  capsule  which  is  thicker  on  its  ental  surface.  From  the  cells  of  each  of  the 
nuclei  arise  axones  which  pass  (1)  to  the  thalamus  and  cerebral  cortex  (links  in 
the  cerebello-cortical  neurone-chain),  and  (2)  axones  which  descend  into  the 
spinal  cord  to  form  the  tractus  rubrospinalis  (Monakow's) — a  continuation  of  an 
indirect  motor  path  from  the  cerebral  cortex  to  the  peripheral  motor  nerve.  The 
tracts  arising  from  the  red  nuclei  of  the  two  sides  decussate  with  each  other  and 
descend  in  the  tegmentum. 

In  the  intercrural  space  lies  a  primitive  gray  ganglionic  mass,  the  posterior 
perforated  substance  or  postperforatum.  In  this  posterior  perforated  substance, 
cephalad  of  the  pons  and  in  the  median  line,  lies  a  cluster  of  cells,  the  interpeduncu- 
lar nucleus  (Gudden).  The  fasciculus  retroflexus  (^leynert),  whose  fibres  arise 
in  the  habenal  ganglion,  descends  to  end  in  the  interpeduncular  ganglion. 

The  principal  longitudinal  fibre  tracts  in  the  tegmentum  of  the  mid-brain  are  (1) 
the  medial  longitudinal  fasciculus,  (2)  the  lateral  lemniscus,  (3)  the  medial  lenmiscus., 
(4)  the  decussating  superior  cerebellar  peduncles,  (5)  the  decussating  rubrospinal 
tracts,  and  (6)  the  central  tegmental  tracts. 

The  medial  longitudinal  bimdle  lies  on  each  side  of  the  median  plane,  just  ventrad 
of  the  central  aqueduct  gray  in  the  mid-brain  and  continuous  throughout  the  brain 
stem  in  its  formatio  reticularis.  It  is  the  continuation  and  the  equivalent,  but 
in  a  more  differentiated  form,  of  the  ventral  basis  bundle  of  the  spinal  cord. 
It  is  formed  by  association  neurones  and  acts  as  an  associating  agent  with  regard 
to  many  cranial  and  spinal  nerve  centres  for  the  performance  of  certain  definite 
functions.  Its  neurones  receive  impulses  from  afferent  elements  and  transmit 
them  to  motor  or  efferent  elements.  It  particularly  brings  into  relation  the  sensor 
cranial  nerve  nuclei  and  the  corpora  quadrigemina  with  the  motor  nerves  of 
the  eye  (III,  IV,  and  VI),  of  the  face  (VII),  and  of  the  trunk.  A  special  nucleus 
for  the  bundle  is  described  as  being  situated  in  the  gray  floor  of  the  third  ventricle, 
at  its  junction  with  the  aqueduct.  The  axones  from  the  cells  of  this  nucleus  cross 
to  the  opposite  side  through  the  posterior  commissure  (Fig.  665). 

The  lateral  lemniscus,  we  have  learned,  is  a  continuation  of  the  auditory  path 
in  its  course  to  the  cerebral  cortex.  Its  formation  is  described  on  page  884.  In 
the  mid-brain  the  fibres  of  the  lateral  lemniscus  course  through  the  lateral  part 
of  the  tegmentum,  near  the  surface,  and  most  of  them  end  in  the  gray  nucleus 
of  the  inferior  corpora  quadrigemina  and  in  the  internal  geniculate  body.  A  few 
fibres  are  carried  into  the  superior  quadrigeminal  body. 


THE  MID-BRAIN 


899 


The  medial  lemniscus,  or  principal  conduction  path  for  sensor  impulses  from 
the  trunk  and  extremities,  and  already  discussed  in  the  preceding  (p.  876), 
ascends  in  the  tegmentum  of  the  mid-brain  in  the  contact  zone  with  the  crusta. 
In  its  ascent  it  is  deflected  slightly  dorsolaterad  by  the  red  nucleus.  The  lateral 
border  of  the  ribbon-like  bundle  is  in  contact  with  the  lateral  lemniscus,  and 
forms  an  angle  with  it,  as  seen  on  trans-section  (Figs.  663  and  664). 


Fig.  665. — The  medial  longitudinal  bundle  in  black  and  red.     Lateral  lemniscus  i 
identified  by  comparison  with  Fig.  648.) 


Many  of  the  fibres  of  the  medial  lemniscus  terminate  in  the  superior  quadri- 
geminal  body;  the  remainder  proceed  to  the  thalamus. 

The  superior  peduncles  or  prepeduncles  of  the  cerebellum  sink  into  the  mid-brain 
tegmentum  in  a  cephaloventral  direction,  the  two  superior  peduncles  converging 
and  their  fibres  undergoing  a  complete  decussation  (Wernekinck's  commissure) 
subjacent  to  the  inferior  quadrigeminal  body.  The  crossed  fibres  end,  for  the 
most  part,  in  the  red  nucleus  of  each  side;  others  circumvent  the  nucleus  forming 


900      ,  THE  NERVE  SY>STE3I 

a  white  capsule  for  it  which  is  thicker  on  its  ental  surface,  and  proceed  to  the 
thalamus. 

The  tractus  nibrospinalis  (Monakow's)  is  composed  of  axones  arising  in  the 
red  nucleus,  decussating  with  those  of  the  opposite  tract,  and  descending  in 
the  tegmentum  to  the  lateral  intermedial  fasciculus  of  the  cord,  to  terminate 
in  relation  with  ventral-horn  cells. 

The  central  tegmental  tract  (olivary  fasciculus)  probably  arises  in  the  inferior 
olivary  nucleus  and  ascends  in  the  tegmentum.  In  the  pars  dorsalis  pontis 
it  is  best  seen  in  trans-sections  as  a  compact  longitudinal  bundle  along  the  dorsi- 
m^sal  aspect  of  the  superior  olive.  Cephalad  it  is  said  to  end  in  the  lenticular 
nucleus. 

Fountain  Decussation.' — A  dense  decussation  may  be  found  in  the  space  between 
the  two  red  nuclei.  The  fibres  composing  the  decussating  bundles  arise  from 
cells  in  the  superior  corpora  quadrigemina  and  central  aqueduct  gray.  After 
having  crossed  the  middle  line  they  descend  as  the  tectospinal  tract,  join  the  medial 
longitudinal  fasciculus,  and  give  off  collaterals  to,  or  terminate  in  the  nuclei  of, 
the  eye  muscle  nerves,  as  well  as  to  spinal  centres  for  movements  of  the  head  and 
neck. 

The  crusta  or  pes  is  somewhat  crescentic  in  outline  on  section  and  is  composed 
of  longitudinal  fibre  bundles — the  continuation  of  the  internal  capsule — divisible 
into  three  sectors.  The  middle  sector  comprises  three-fifths  of  the  cross-section 
area  of  the  crusta,  and  comprises  the  pyramidal  tract  on  its  way  from  the  cerebral 
cortex  (motor  area)  to  cranial  and  spinal  centres  below.  The  ectal  sector,  or 
lateral  one-fifth,  comprises  the  tempore  pontile  tract;'  its  axones  arise  from  the 
cortical  cells  in  the  temporal  lobe  and  end  in  fine  terminal  arborizations  in  relation 
with  cells  of  the  nuclei  pontis.  The  ental  sector,  or  mesal  one-fifth  of  the  crusta, 
comprises  the  frontopontile  tract;  its  axones  arise  from  cells  in  the  cortex  of  the 
frontal  lobe  and  terminate  in  the  nuclei  pontis. 

The  pyramidal  tract  is  a  direct  voluntary  motor  tract;  the  two  corticopontile 
tracts  enumerated  above  are  links  in  a  chain  of  neurones  which  constitute  an 
indirect  motor  tract.  The  series  of  neurones  in  the  chain  of  the  indirect  motor 
tract  may  be  shown  in  the  following  order:  Corticopontile  tract;  nuclei  pontis; 
cerebellocortex ;  dentate  nucleus;  superior  cerebellar  peduncle;  red  nucleus;  tractus 
rubrospinalis ;  spinal  gray;  spinal  nerve;  muscle. 

Summary  of  the  Gray  Masses  in  the  Mid-brain: 
*Central  aqueduct  gray. 

(a)  Oculomotor  n.  nucleus. 

(b)  Trochlear  n.  nucleus. 

Nucleus  radicis  descendentis  nervi  trigemini. 
^Nucleus  of  medial  longitudinal  bundle  and  postcommissure, 
*Formatio  reticularis. 
*Substantia  nigra  (intercalatum). 
*Red  nucleus  (rubrum). 

^Stratum  cinereum  of  superior  corpora  quadrigemina. 
*Nucleus  of  inferior  corpora  quadrigemina. 
*"  Interpeduncular"  ganglion. 

Structures  marked  with  an  asterisk  have  been  considered  in  the  preceding 
description.  The  central  connections  of  the  oculomotor,  trochlear,  and  trigem- 
inal nerves  may  now  be  described. 

Deep  Origin  of  Cranial  Nerves  Arising  in  the  Mid-brain. —The  mesen- 
cephalic root  of  the  trigeminal  nerve  has  been  described  on  page  884. 

^Decussatio  fontinalis,  so  called  because  of  the  resemblance  of  the  scattering  strands  to  the  jets  of  a  fountain. 


THE  MID-BRAIN 


001 


The  Trochlear  Nerve  Nucleus. — The  trochlear  nerve  iiiicleu.s  is  situated  in  the 
level  of  the  cephalic  half  of  the  inferior  quadrigeminal  body.  It  is  a  small 
oval  mass  of  gray  substance  in  the  ventral  part  of  the  central  acjueduct  gray. 
The  cells  are  large,  sometimes  stellate  in  appearance.  The  root  fibres  pursue 
a  peculiar  course;  they  accumulate  in  the  lateroventral  angle  of  the  aqueduct 
gray,  run  caudad,  gradually  rising  dorsad,  and  suddenly  turn  mesad  to  undergo 
a  complete  decussation  with  the  root  of  the  opposite  side  in  the  superior  medul- 
lary velum,  emerging  laterad  of  the  frenulum,  or  at  the  inner  border  of  the  superior 
peduncle. 

The  nucleus  is  placed  under  the  dominion  of  the  cerebral  cortex  by  pyramidal 
fibres,  and  it  is  associated  with  other  nuclei  in  the  brain  stem  by  the  medial  longitu- 
dinal bundle. 

The  Oculomotor  Nerve  Nucleus. — The  oculomotor  nerve  nucleus  is  a  group  of 
cell  clusters  in  the  ventral  portion  of  the  aqueduct  gray,  subjacent  to  the  superior 
quadrigeminal  body,  and  extending  cephalad  to  become  lost  in  the  gray  wall 
of  the  third  ventricle  at  the  slope  formed  by  the  opening  out  of  the  aqueduct. 
Its  nerve  elements  are  arranged  in  definite  groups.  The  most  cephalic  of  these 
is  composed  of  smaller  elements,  closely  crowded  and  embedded  in  deeply  staining 


Antero-exteriial  nuclcu^.-^ 

Aniero-internaZ  nu 

Nucleus  of  Bdingt 
Westphal. 


Third  ventricle. 


Central  nucleus. 

A  nterior  dorsal  nucleus. 

Anterior  ventral  nucleus. 


_Posierior  ventral 

nucleus. 
-Posterior  dorsal  nucleus. 


-Crossed  fibres. 


^Xucleus  of  origin  of 
trochlear  nerve. 


Decussation  of  trocMear 
nerve. 


-Trochlear  nerve. 


riG.  666. — Showing  the  different  groups  of  cells,  which  constitute,  according  to  Perlia.  the  nucleus  of  origin 
of  the  oculomotor  nerve.     (Testut. ) 

molecular  ground  substance.  In  a  flat-wise  section  of  the  brain  stem  the  outline 
of  this  nucleus  resembles  an  inverted  L  or  the  tip  of  a  boat  hook;  the  axones  from 
the  cells  of  this  nucleus  (of  Edinger  and  Westphal)  supply  the  Ciliary  muscle  and 
Sphincter  iridis  (pupillary  motion).  The  main  nucleus,  composed  of  several 
sub-groups,  lies  caudolaterad  of  the  preceding,  and  is  composed  of  larger  cell 
elements. 

The  root  fibre  bundles  from  this  nuclear  group  pass  ventrad,  breaking  through 
the  medial  longitudinal  fasciculus,  separating  like  the  strands  of  a  horse's  tail  by 
the  interference  of  the  red  nucleus,  to  become  gathered  into  more  compact  bun- 
dles between  the  mesal  edge  of  the  substantia  nigra  and  intercrural  region,  and 
emerging  by  eight  to  twelve  fascicles  which  compose  the  trunk  of  the  oculomotor 
nerve. 


902 


THE  NERVE  SYSTEM 


External 
rectus 


The  origin  of  each  nerve  is  not  Hmited  to  the  nuclei  of  its  side;  a  part  is  decus- 
sated and  the  decussated  origin  is  related  to  the  innervation  of  the  Internal  rectus. 

By  means  of  association  neu- 
juteniai  rones  in  the  medial  longitu- 

dinal fasciculus  the  oculo- 
motor and  abducens  nuclei 
of  one  side  are  brought  into 
relation,  affording  an  organic 
basis  for  the  synergism  exist- 
ing between  the  Internal  and 
External  recti  muscles  in  the 
conjugated  lateral  eye  move- 
ments. 

The  paradox  of  the  facial 
nerve  supplying  muscles  un- 
der the  reflex  dominion  of 
the  retina  (Orbicularis  oculi) 
instead  of  the  oculomotor 
may  be  explained  by  the 
assumed  existence  of  fibres 
emerging  from  the  oculomotor  nucleus,  entering  the  medial  longitudinal  fasciculus 
and  joining  the  root  of  the  facial. 

Parts  Derived  from  the  Fore-brain. 

The  fore-brain  or  prosencephalon  includes  those  portions  of  the  brain  which  are 
derived  from  the  cephalic  one  of  the  three  primary  brain  vesicles.  It  includes, 
according  to  prevailing  schemas,  a  thalamic  portion  (the  thalamencephalon  or 
diencephalon)  and  the  telencephalon.  The  two' divisions  constitute  a  structural 
continuity  and  exhibit  a  mutual  dependency  so  close  that  the  arbitrary  distinction 
now  in  vogue  tends  to  mislead.  The  relations  of  "diencephalon"  and  "telen- 
cephalon" are  further  complicated  by  the  intimate  fusion  of  the  sides  of  the 
former  (thalami)  with  the  floors  of  the  latter;  this  caudatothalamic  fusion,  in  the 
adult  brain,  gives  rise  to  some  difficulty  in  distinguishing  the  two  segments.  The 
internal  capsule  which  intervenes  between  thalamus  and  lenticular  nucleus  also  in- 
tervenes between  lenticular  nucleus  and  caudate  nucleus,  both  telencephalic  parts. 

External  Morphology. — The  diencephalon  or  thalamencephalon  comprises  the 
thalami,  the  pineal  body  or  epiphysis  and  habenulse,  the  external  geniculate  bodies, 
and  the  pars  mamillaris  hypothalami.  (Other  classifications  include  also  the 
pars  optica,  with  tuber  cinereum,  infimdibulum,  optic  chiasm,  and  pituitary  body  or 
hypophysis.  It  is  also  defined  as  so  much  of  the  fore-brain  as  does  not  enter  into 
the  formation  of  the  cerebral  hemispheres.)  Caudad  it  is  continuous  with  the 
mid-brain,  cephalad  with  the  cerebral  hemispheres.  Its  primitive  cavity  becomes 
metamorphosed  in  the  adult  into  the  third  ventricle  or  diacele  as  the  lateral  walls 
hypertrophy  to  form  the  thalami.  Its  ventral  surface  is  the  relatively  insignificant 
gray  lamina  in  the  intercrural  space.  Its  dorsal  surface  is  concealed  from  view 
by  the  massive  hemispheres  and  their  great  commissure,  the  corpus  callosum, 
and  by  the  fornix.  Its  actual  roof,  separating  it  from  the  overlapping  cerebral 
parts,  is  a  delicate  membranous  fold,  the  velum  interpositum  or  diatela. 

The  Thalami.' — The  thalami  constitute  the  bulk  of  this  portion  of  the  brain. 
They  are  large  ovoid  masses  of  gray  substance  so  named  by  the  ancients  after  their 
resemblance  to  a  pair  of  couches.  Each  thalamus  is  smaller  frontad  than  caudad 
and  the  caudal  ends  are  more  widely  separated  from  each  other.     The  mesal  or 


^  Thalamos,  bed  or  couch;  bed-chamber. 


PARTS  DERIVED  FROM  THE  FORE-BRAIN 


903 


ventricular  surface  is  largely  free,  except  for  an  area,  of  variable  size,  by  which 
the  two  thalami  are  fused  in  90  per  cent,  of  brains.  The  thalamic  fusion  is  also 
called  the  middle  commissure  or  medicommissure.  The  free  surface  is  co\'ered  by 
ependyma  and  is  of  smooth  contour.  Its  dorsal  limit  is  marked  by  an  ependymal 
ridge,  usually  torn  through  in  dissection,  the  taenia  thalami  or  ripa,'  fortified  by 
a  subjacent  narrow  band  of  fibres  called  the  stria  meduUaris,  which  may  be  traced 
to  the  habenular  nucleus  and  habenular  commissure  (or  "stalk"  of  the  pineal 
body) .  Caudad  lies  a  depressed  triangular  area — the  trigonum  habenulae,  situated 
cephalad  of  the  superior  cjuadrigeminal  body. 

The  dorsal  surface  is  usually  described  as  being  free,  but  only  a  narrow  ectal 
portion  can  be  so  described,  the  ependyma  of  the  lateral  ventricle  being  slightly 


rORAMEN  OF  MONRO 


LE  COMMISSURE 
HOROIO    PLEXUS  OF 
HIHD  VENTRICLE 


l/ENTRICLE 


Fig.  668. — Mesal  aspect  of  a  brain  sectioned  in  the  median  sagittal  plane. 

reflected  upon  it  (the  lamina  affixa)  before  entering  into  the  formation  of  the 
choroid  plexus  of  the  lateral  ventricle.  The  rest  of  the  dorsal  surface  is  not  lined 
by  ependyma,  but  is  in  contact  with  the  pial  fold  called  the  velum  interpositum. 
This  surface  is  of  a  whitish  color  owing  to  a  thin  layer,  of  white  fibres,  the  stratum 
zonale.  A  faint  oblique  groove  crosses  this  surface  in  a  caudolateral  direction, 
corresponding  to  the  ectal  edge  of  the  fornix.  Laterad  it  is  demarcated  from  the 
caudate  nucleus  by  a  groove  which  is  occupied  by  the  striatal  vein  and  a  slender 
band  of  fibres,  called  the  taenia  semicircularis  or  stria  terminalis.  The  surface  is 
not  of  e^en  contour  throughout,  usually  showing  three  eminences  (in  addition 
to  the  puh'inar)  corresponding  to  the  main  nuclear  aggregations  within  the  thal- 
amus— viz.:  Tuberculum  anterius,  mediahs,  and  lateralis. 


3  formed  by  tiie  rupture  of  the  ependyma  along  the  lines  of  its  reflection  from  entoccelian  ^ventricular) 


904 


THE  NERVE  SYSTEM 


The  tuberculum  anterius  forms  a  marked  bulging  frontal  extremity,  which  helps 
to  form  the  boundary  of  the  foramen  of  Monro  or  aperture  of  communication 
between  lateral  and  third  ventricles. 

The  caudal  extremity  of  the  thalamus  is  a  prominent  bolster-like  projection 
which  overhangs  the  brachia  of  the  corpora  quadrigemina  and  is  called  the  pul- 
vinar.  A  smaller  oval  prominence,  situated  ventrolaterad  of  the  pulvinar,  is 
termed  the  external  geniculate  body  or  pregeniculum  (corpus  geniculatum  lateral e) 
■ — a  partial  end  station  for  the  optic  tract. 


■  FIFTH   VENTRICLE 
SEPTUM    LUCIDUM 


ENULAE 

TERIOR 
COMMISSURE 
SUPERIOR  QUADRI' 


FRENULUM 


-Dissection  showing  the  two  th; 


clei,  and  adjacent  parts. 


The  lateral  surface  of  the  thalamus  is  in  contact  with  the  internal  capsule — that 
great  concentration  of  fibre  tracts  coursing  to  and  from  cerebral  centres  and 
forming  the  crusta  below.  To  this  white  stratum  the  thalamus  itself  contributes 
fibres  destined  to  reach  the  cortex,  and  in  return  it  receives  fibres  from  the  cortex. 
These  thalamocortical  and  corticothalamic  sets  of  fibres  constitute  the  thalamic 
radiation,  forming  a  more  or  less  distinct  reticulated  capsular  zone  {stratum 
reticulatum;  external  medullary  lamina)  for  the  thalamus. 


PARTS  DERIVED  ER03I  THE  FORE-BRAIN  905 

The  ventral  or  inferior  stirface  is  continuous  with  the  hypothalamic  tefjmental 
substance  and  with  the  central  gray  substance  of  the  third  ventricle  lining  its  sides 
and  floor. 

Internal  Structure  of  the  Thalamus. — The  thalamus  is  composed  of  gray  substance, 
with  large  multipolar  cells,  which  is  subdivided  into  a  number  of  distinct  nuclei; 
twenty  such  have  been  described;  three  are  universally  recognized.  They  are 
separated  from  each  other  by  a  white  layer  (lamina  medullaris  interna)  which 
runs  parallel  to  the  wall  of  the  third  ventricle  for  its  greater  length;  caudally 
it  runs  mesad,  overlapped  by  the  ectal  nucleus,  and  numerous  sub-laminie  run 
into  it.  Frontad  the  internal  medullary  lamina  subdivides  into  two  branches, 
thus  permitting  the  intrusion  of  the  nucleus  anterius  between  the  two  main  nuclei 
(medial  and  lateral). 

The  nucleus  anterius  lies  fronto4orsad ;  in  it  terminate  the  axones  of  the  fasciculus 
thalamomamillaris  (fasciculus  albicantiothalami ;  bundle  of  Vicq  d'Azyr).  The 
nucleus  medialis  is  lined  mesad  by  the  central  gray  of  the  third  ventricle  and  is 
usually  fused  with  its  fellow  of  the  opposite  side  (middle  commissure).  A  special 
spheroidal  cell  cluster  in  this  nucleus  is  called  the  centrum  medianum  (Luys). 
The  nucleus  lateralis  is  the  largest  of  the  three,  extending  the  entire  length  of  the 
thalamus  and  including  the  pulvinar.  A  special  semilunar  cluster  of  cells  in  the 
ventral  portion  of  this  nucleus  is  called  the  nucleus  semilunaris  (Flechsig). 

The  Connections  of  the  Thalamus. — The  thalamus  is  a  ganglion  interposed 
between  the  sensor  tracts  in  the  tegmentum  and  the  cerebral  cortex,  as  well  as 
an  important  link  in  the  optic  path.  It  also  gives  rise  to  motor  tracts  concerned 
with  instinctive  movements  of  an  emotional  nature.  It  is  a  relay  station  for 
the  various  tracts  which  convey  sensations  of  touch,  temperature,  and  pain  from 
the  body,  extremities,  head  and  neck,  of  muscle  cense,  and  of  the  special  senses. 
It  transmits  these  impulses  to,  and,  reciprocally,  receives  impulses  from  the 
cerebral  cortex.  As  an  "emotional"  centre  it  is  also  under  the  inhibitory  influence 
of  the  cerebral  cortex,  which,  if  the  emotion  be  not  too  strong,  prevents  its  external 
manifestation. 

The  thalamocortical  and  corticothalamic  fibres,  with  the  internal  capsule,  enter 
into  the  corona  radiata  or  fan-like  formation  of  the  white  substance  of  the  cerebral 
hemisphere.  Although  there  is  no  anatomic  subdivision  into  distinct  groups  of 
these  fibres  as  they  stream  to  and  from  the  thalamus,  it  is  customary  to  distinguish 
a  frontal,  a  parietal,  an  occipital,  and  a  ventral  stalk.  The  frontal  and  parietal 
stalks,  as  their  names  indicate,  pass  between  the  thalamus  and  frontoparietal 
cortex,  as  well  as  to  the  lenticular  nucleus  and  caudate  nucleus.  The  occipital 
stalk  is  composed  of  fibres  passing  in  both  directions  between  the  pulvinar  and 
occipital  cortex,  constituting  the  so-called  optic  radiation.  The  ventral  stalk 
comprises  the  ansa  lenticularis  (thalamolenticxdar)  and  the  ansa  peduncularis 
(thalamotemporal  and  thalamoinsular).    They  will  be  described  in  detail  farther  on. 

The  external  geniculate  body,  or  pregeniculum  (corpus  geniculatum  laterale)  is  an 
intercalar  ganglion  proper  to  the  optic  ner\e,  derived  from  the  thalamus.  On 
section  it  is  seen  to  be  characterized  by  the  regular  alternation  of  deeply  gray  and 
white  laminae.  The  latter  are  thicker  and  composed  of  fibres  which  enter  the 
external  geniculate  body  from  the  optic  tract  and  optic  radiation.  The  nerve 
cells  in  the  gray  substance  are  large,  multipolar,  and  pigmented. 

[Note. — The  external  geniculate  body  and  the  more  isolated  internal  genicu- 
late body  are  generally  included  under  the  head  of  metathalaimis .] 

The  hypothalamic  tegmental  substance,  continuous  with  the  mid-brain  tegmen- 
tum, is  interpolated  between  the  ventral  face  of  the  thalamus,  the  red  nucleus, 
and  a  continuation  of  the  substantia  nigra  known  as  the  corpus  hypothalamicus 
or  body  of  Luys.     Through  the  hypothalamic  tegmentum  stream  the  fibres  of 


906  THE  NERVE  SYSTEM 

the  medial  lemniscus,  of  the  superior  peduncle  of  the  cerebellum,  and  from  the  red 
nucleus,  to  end  in  relation  with  thalamic  cells.  The  corpus  hypothalamicus  is 
a  grayish-brown,  lentiform  mass  which  lies  in  the  ideal  continuation  frontad  of 
the  lateral  part  of  the  substantia  nigra,  and,  like  it,  situated  between  pes  and  teg- 
mentum. It  is  made  up  of  fine  myelinated  fibres  crowded  in  great  profusion 
and  confusion,  with  numerous  delicate,  coiled  capillaries  and  sparse,  multipolar, 
more  or  less  pigmented,  nerve  elements  of  moderate  size.  The  outline  of  the  body 
is  defined  by  a  white  capsule,  some  of  the  fibres  of  which  are  seen  to  decussate 
in  the  floor  of  the  third  ventricle  with  those  of  the  opposite  side,  dorsocaudad  of 
the  corpora  albicantia. 

The  Pineal  Body  {corpus  pineale;  epiphysis)  (Figs.  668  and  669). — The  pineal 
body  (from  its  shape  resembling  a  fir-cone — pinus)  is  a  small,  reddish-gray 
body  placed  between  the  caudal  ends  of  the  thalami  and  occupying  the  depression 
between  the  two  superior  quadrigeminal  bodies.  It  is  covered  by  the  velum  inter- 
positum,  which  intervenes  between  it  and  the  splenium  of  the  corpus  callosum. 
It  is  an  outgrowth  which  is  not  regarded  as  an  important  neural  ingredient  of 
the  human  brain  and  is  generally  believed  to  be  a  rudimentary  relic,  representing 
a  Cyclopean  eye'  of  some  extinct  ancestral  vertebrate,  homologous  with  the  parietal 
organ,  resembling  a  molluscan  eye  of  a  living  species  of  Prosaurlan  (the  Hatteria  of 
New  Zealand).  Its  attached  base  is  a  hollow  peduncle  divisible  into  a  dorsal  and 
ventral  part  by  the  intrusion  of  the  epiphyseal  recess  {recessus  pinealis)  of  the  third 
ventricle.  The  dorsal  stalk  continues  on  either  side  and  upon  each  thalamus 
as  the  stria  medullaris;  it  is  reenforced  by  commissural  fibres  joining  the  habenulte 
of  the  two  sides;  hence  another  name  for  the  dorsal  stalk  is  the  habenular  com- 
missure (supracommissure  of  Osborn).  The  ventral  stalk  is  folded  over  another 
commissural   band — the   posterior   commissure. 

Structure. — The  pineal  body  consists  of  a  number  of  follicles,  lined  by  epithelium  and 
connected  by  ingrowths  of  connective  tissue.  The  follicles  contain  a  transparent  viscid  fluid 
and  a  quantity  of  sabulous  matter  named  brain  sand  (acervus  cerebri),  composed  of  phos- 
phate and  carbonate  of  lime,  phosphate  of  magnesia  and  ammonia,  with  a  little  animal 
matter.  These  concretions  are  almost  constant  in  their  existence,  and  are  present  at  all  periods 
of  life. 

In  the  interval  between  the  pineal  body  and  the  caudal  end  of  the  thalamus 
lies  a  small  triangular  depression  (sometimes  an  elevation)  known  as  the  tri- 
gonum  habenulae,  marking  the  position  of  the  nidus,  or  ganglion  habenulae,  a  group 
of  small  angular  cells.  The  axones  from  these  cells  are  collected  ventrad  into  the 
fasciculus  retroflexus  (Meynert),  which  courses  through  the  tegmentum  mesad  of 
the  red  nucleus  to  end  in  the  interpeduncular  ganglion  (Gudden)  in  the  posterior 
perforated  sulistance.  In  addition  to  this  fasciculus,  the  habenula  is  the  reunion 
point  for  two  other  sets  of  fibres:  (1)  the  stria  medullaris  and  (2)  habenular 
commissure.  The  stria  medullaris  (p.  903)  is  made  up  of  axones  arising  from 
two  sources:  (1)  cells  in  the  hippocampus  {via  fornix)  and  (2)  cells  in  the  ganglion 
opticum  basale.  These  join  near  the  anterior  pillar  of  the  fornix  and  run  caudad 
on  the  mesal  thalamic  surface,  to  end  in  the  habenular  ganglion  of  the  same 
side  and,  by  crossing  in  the  dorsal  stalk  of  the  epiphysis,  help  to  form  the 
habenular  commissure,  to  end  in  the  corresponding  nidus  habenulae  of  the 
opposite  side. 

The  posterior  commissure  is  a  round  band  of  white  fibres  crossing  from  side  to 
side  in  the  ventral  stalk  of  the  pineal  body  bridging  the  aqueduct  at  its  continua- 

1  Although  most  vertebrates  show  a  single  pineal  body  or  parietal  organ,  it  is  double  in  the  lamprey  and  certain 
reptiles;  the  two  bodies  lie  one  in  front  of  the  other — not  side  by  side  (although  probably  paired  organs  originally). 
The  frontal  organ  sends  its  fibres  into  the  habenular  nucleus:  the  caudal  organ  to  the  region  of  the  posterior  com- 
missure (tectum  opticum). 


PARTS  DERIVED  FROM  THE  FORE-BRAIN 


907 


tion  into  the  third  ventricle.  The  posterior  commissure  shares  rehition  with  both 
fore-brain  and  mid-brain  structures  and  is  formed  of  decussating  jfibres  which 
may  be  enumerated  in  the  following  systems:  (o)  fibres  arising  in  the  special 
nucleus  (described  on  p.  898)  for  the  medial  longitudinal  bundle;  (6)  fibres  con- 
necting the  two  thaland;  (c)  fibres  connecting  the  habenular  nidi;  {d)  fibres  connect- 
ing the  superior  quadrigemina. 

[Note. — The  habenular,  pineal  body,  and  posterior  commissure  are  generally 
included  under  the  head  of  epitkalamus.] 

The  posterior  perforated  substance  or  postperforatum  has  be,en  described  on  page 
898.  It  marks  the  situation  of  the  "interpeduncular  ganglion,"  which  is  small 
in  man,  but  very  large  in  rodent  brains.  From  the  cells  in  this  primitive  gray 
lamina  arise  the  fibre  tracts  already  described  as  the  taenia  pontis  (p.  895),  and 
often  -vdsible  at  the  point  of  emergence  from  the  gray  substance  of  the  intercrural 
space. 

The  corpora  albicantia  (Fig.  673),  or  corpora  mamiUaria,  are  two  symmetrical, 


I  jinirhjmal  lininrj 

of  veiHricle 
V  em  of  corpus 
/    -  ^■a.~-i\  -^      striatum 

Lateral  ventricle '''^    \  /  //     BKSti     -run!   amuc      /  Choroid  plexus  of 

lateral  ventricle 


Velum  interpositum 
Veins  of  Galen 


Ependymal  lining  of' 
ventricle 


Choroid  plexuses  of 
third  ventricle 


Third  ventricle 


Fig.  670. — Coronal  section  of  lateral  and  third  ventricles.      (Diagrammatic.) 


small,  round,  white  protuberances  situated  side  by  side  in  the  intercrural  space 
cephalad  of  the  posterior  perforated  substance,  at  a  point  where  the  floor  of  the 
third  ventricle  rapidly  decreases  in  thickness  to  form  the  tuber  cinereum.  The 
color  of  each  corpus  albicans  is  white,  owing  to  a  superficial  stratum  of  fibres 
derived  from  the  fornix.  Within  lie  three  nuclear  masses — two  medial,  consti- 
tuting the  main  mass,  and  a  smaller  lateral  nucleus  applied  against  the  former, 
so  as  to  represent  a  crescent  on  cross-section. 

The  fibres  of  the  fornix  terminate  in  the  corpus  albicans.  From  its  cells  arise 
two  fasciculi  which  have  a  common  neurone  origin.  Cajal  discovered,  and  Kolliker 
confirmed  the  fact,  that  the  axones  from  the  medial  nucleus  cells  bifurcate;  one 
set  of  limbs  passes  fronto-dorsad  to  form  the  bundle  of  Vicq  d'Azyr  (fasciculus 
thalamomamiUaris),  which  ends  in  the  nucleus  anterius  of  the  thalamus,  while  the 
other  set  of  limbs  of  the  primary  axones  passes  caudad  to  form  the  fasciculus 
pedunculomamillaris  in  the  mid-brain  tegmentum;  its  destination  is  doubtful. 
The  axones  from  the  lateral  nucleus  join  the  latter  bundle. 

[Note. — The  posterior  perforated  substance  and  the  corpora  albicantia  are 
generally  included  under  the  head  of  the  Pars  Mainillaris  Hypothalami.] 

Third  Ventricle  {ventriculus  tertius)  (Fig.  668). — The  third  ventricle  is  the 
adult  representative  of  the  cavity  of  the  primary  fore-brain  vesicle,  but  only  so 


908  THE  NERVE  SYSTEM 

much  of  it  as  is  not  carried  laterad,  on  either  side,  in  the  rapidly  growing,  eventually 
huge  cerebral  hemisphere  buds  to  form  the  lateral  ventricles.  It  is  a  narrow, 
cleft-like  interval  between  the  two  thalami  and  hypothalamic  gray,  limited  f rontad 
by  the  terma,  continuous  caudad  with  the  aqueduct  and  laterad,  through  the 
foramina  of  Monro,  with  the  lateral  ventricles.  Its  roof  is  destitute  of  nerve 
tissue  and  is  formed  by  a  delicate,  fused  ependymal  and  pial  layer,  invaginated 
on  either  side  of  the  median  plane  by  the  plexuses  of  the  lateral  ventricle.  The 
pial  layer  is  one  of  the  constituents  of  the  fold  known  as  the  velum  interpositum. 
The  floor  of  the  ventricle  is  formed  by  structures  already  described  on  the  basal 
aspect  in  the  intercrural  ^pace — viz.,  the  tuber  cinereum,  corpora  albicantia,  and 
posterior  perforated  substance,  as  well  as  the  optic  chiasm  and  a  portion  of  the 
tegmentum  of  the  crura  cerebri.  Much  of  the  floor,  it  may  be  noted,  is  formed 
by  the  primitive,  undifferentiated  central  gray;  and  although  the  optic  vesicle 
develops  from  its  ventrocephalic  portion,  the  caudal  shifting  of  central  optic 
connections  to  thalamus  and  mid-brain  has  made  this  portion  of  the  neural  tube 
wall  comparatively  insignificant.  The  lateral  avails  are  formed  in  part  by  the 
thalami,  in  part  by  the  hypothalamic  gray  ventral  extension.  The  fornix  may  be 
seen,  shining  through  a  thin  lamina  of  gray  substance  and  the  ependyma,  coursing 
caudoventrad  to  the  corpus  albicans.  A  slight  furrow,  the  aulix  or  sulcus  of 
Monro,  may  sometimes  be  traced  from  the  aqueduct  to  the  foramen  of  Monro, 
curving  ventrad  of  a  bridge-like  fusion  of  the  two  thalami —  the  middle  commissure 
(medicommissvire) .  (The  term  commissure  is  inappropriate,  as  no  commissural 
fibres  appear  to  pass  from  one  thalamus  to  the  other  in  this  "thalamic  fusion"; 
it  is  absent  in  about  10  per  cent,  of  brains  examined.) 

The  cephalic  wall  is  formed  by  the  lamina  terminalis  or  terma,  the  rudimentary 
mediancephalic  wall  of  the  neural  tube.  The  terma  is  attached  to  the  dorsum 
of  the  optic  chiasm;  dorsally  it  is  reinforced  by  the  anterior  commissure. 

As  seen  in  mesal  section  or  as  shown  by  a  cast  of  the  ventricle  (Fig.  696)  it 
is  seen  to  be  of  irregular  outline.  Frontad  is  the  optic  recess,  dorsad  of  the 
optic  chiasm;  caudad  thereof  is  the  infundibular  recess  in  the  tuber.  The  epi- 
physeal recess  is  seen  between  the  habenular  commissure  and  the  posterior  com- 
missure. Dorsad  of  the  pineal  body  is  a  diverticular  recess  of  variable  extent 
{recessus  siqjrapinealis) . 

If  the  segmentation  of  the  fore-brain  into  two  divisions  be  adopted  ultimately,  il  will  be 
necessary  to  allot  one  portion  of  the  third  ventricle  (between  the  thalami)  to  the  diencephalon 
(hence  diacele),  and  the  rest  to  the  telencephalon  (the  medial  cavity  of  which  is  termed  the 
aula  by  Wilder). 

In  anticipation  of  the  description  of  the  cerebral  hemispheres  we  may  consider 
here  the  remaining  structures  in  the  floor  of  the  third  ventricle,  usually  included 
under  the  head  of  the  pars  optica  hypothalami  of  the  telencephalon,  in  order  to  lead 
up  to  a  description  of  the  cerebral  connections  of  the  optic  tract. 

External  Morphology  of  the  Optic  Portion  of  the  Hypothalamus.  This  in- 
cludes the  tuber  cinereum  and  pituitary  body  or  hypophysis,  the  lamina  terminalis, 
the  optic  chiasm,  and  the  optic  tracts. 

The  tuber  cinereum  (Fig.  668)  is  a  thin-walled  conical  projection  in  the  inter- 
crural space  cephalad  of  the  corpora  albicantia.  Its  apical  portion  is  attenuated 
to  form  the  stalk  of  the  pituitary  body;  this  is  generally  termed  the  infundibulum, 
while  the  cavity  of  the  funnel-shaped  diverticulum  is  called  the  infundibular 
recess  of  the  third  ventricle.  The  gray  lamina  composing  the  tuber  is  continuous 
with  the  central  ventricular  gray,  and  therefore  with  the  lamina  terminalis. 


PARTS  DERIVED  FROM  THE  FORE-BRAIN 


909 


The  pituitary  body  or  hypophysis^  is  a  structure  of  twofold  origin,  giving  rise 
to  a  division  into  a  prehypophysis  and  a  posthjrpophysis.  Tlie  po.sthypophysis 
alone  is  of  neural  origin,  developing  as  a  ventral  diverticulum  from  the  primitive 
neural  tube.  The  prehypophysis  or  epithelial  lobe,  develops  from  the  stomodeum, 
or  buccal  cavity,  as  a  tubular  diverticulum  (Rathke's),  which  eventually  loses  its 
connection^  with  the  oral  tissues  to  become  included  within  the  cranial  cavity 
and  intimately  attached  to  the  neural  bud.  Both  pre-  and  posthypophysis  are 
therefore  of  ectodermal  origin  and  have  developed  from  a  conjunction  of  surface 
tissues  which  have  migrated  from  opposed  (ventral  and  dorsal)  parts  through  the 
head!  The  prehypophysis  is  much  the  larger  and  somewhat  embraces  the  post- 
hypophysis;  the  two  are  insepai-able,  however,  and  together  occupy  the  fossa 
hypophyseos  of  the  sphenoid. 


CORPUS  ALBICANS 
POSTERIOR  CEREBF 


Fig.  671.— The  pituitar\  boch 


■LM,uphx-i- 


i  median  sagittal  section.     (Testut.) 


The  two  parts  of  the  pituitary  body  are  as  distinct  in  structure  as  they  are  in  embryonic 
origin.  The  posthypophysis  consists  of  a  mass  of  nerve  cells,  neuj-ogha,  connective  tissue,  and 
bloodvessels;  the  structure  of  the  prehypophysis  is  distinctly  glandular,  resembling  that  of  the 
parathjToid  bodies.  It  is  surmised  that  the  latter  is  the  functional  part  of  the  pituitary  body — 
concerned  with  the  internal  secretions,  and  usually  involved  in  the  pathological  form  of  giantism 
called  acromegaly. 

The  lamina  terminalis  or  terma  (Fig.  668)  is  a  thin,  easily  torn  lamina  between 
the  optic  chiasm  and  the  anterior  commissure,  limited  laterally  by  the  closely  ap- 
proximated cerebral  hemispheres  and  constituting  the  primitive,  undifferentiated 
cephalic  boundary  of  the  original  neural  tube. 

The  Optic  Tract  and  its  Central  Connections. — In  the  section  on  the  development 
of  the  brain  it  was  learned  that  the  optic  nerve  is  not  a  peripheral  nerve;  it  is 
rather  a  central  brain  tract  extruded  from  the  neural  tube.  E\idence  is  at  hand 
that  in  ancestral  vertebrates  the  general  cutaneous  sensor  system  was  also  capable 
of  light  perception.  With  the  recession  of  the  neural  tube  from  the  surface  and 
in  company  with  the  morphological  differentiation  of  the  head  end,  a  light- 
perceiving  pair  of  organs  arose  as  a  special  development.  The  distal  end  of  the 
optic  brain  vesicle  becomes  the  retina,  in  structure  like  the  brain  wall,  whose  cell 
axones  carry  afferent  impulses  to  the  brain.     Although  the  optic  fibres  enter  the 


•  F.  Tilney  :  Study  of  the  hypophysis  cerebri  with  especial  reference  to  its  comparative  histology. 
2  of  Wistar  Institute  of  Anatomy  and  Biology,  1912. 

2  Occasionally  the  channel  persists  as  the  craniopharyngeal  canal. 


910  THE  NERVE  SY,STE3I 

ventral  wall  of  the  brain,  the  retina  is  originally  derived  from  the  dorsolateral 
(sensor)  wall  of  the  second  neuromere  (Fig.  627).  The  parietal  organs,  also 
light-perceiving,  likewise  developed  as  paired  dorsal  buds  farther  caudad,  eventu- 
ally to  atrophy,  as  the  more  frontal  optic  organs  better  subserved  the  purposes 
of  the  organism. 

The  remarkable  and  as  yet  unexplained  fact  regarding  the  optic  apparatus 
is  that  the  afferent  fibres  from  the  retinal  cells  pass  into  the  ventral  wall  to  cross 
to  the  opposite  side,  forming  a  decussation  which  is  total,  or  nearly  so,  in  verte- 
brates below  the  mammals ;  the  more  laterally  placed  the  eyes  are  the  more  nearly 
total  is  the  decussation.' 

Although  the  optic  vesicle  is  a  diverticulum  of  the  fore-brain  in  its  cephalic 
portion,  the  optic  tract  in  its  central  connections  becomes  intimately  related  with 
the  external  geniculate  body  and  pulvinar,  the  occipital  cortex  of  the  cerebrum,  and 
with  the  superior  quadrigeminal  body  of  the  mid-brain.  Some  of  these  central 
structures  are  way-stations  in  reflex  paths;  the  occipital  cortex  alone  is  the 
actual  visual  centre,  though  visual  perceptions  are  here  brought  into  association 
with  tactile,  auditory,  and  other  impulses. 

Optic  Chiasm. — From  the  retina  of  each  eye  the  so-called  optic  ner^^es  converge 
to  partially  decussate  at  the  base  of  the  brain  to  form  the  optic  chiasm,  a  white  quad- 
rangular plate  which  presses  in  the  primitive  central  gray  floor  of  the  third  ven- 
tricle, as  previously  described.  Approximately  one-third  of  the  fibres  of  each 
optic  nerve  do  not  cross  to  the  opposite  side.  The  optic  chiasm  is  further  re- 
enforced  by  the  infracommissure  (of  Gudden)  and  other  lesser  fibre  tracts  (com- 
missura  superior  [^Nleynerti]  and  commissura  ansata  [Kolliker]).  The  fibres  in 
the  chiasm  are  so  complexly  interwoven  that  only  through  exhaustive  experi- 
mental development  and  pathological  studies  has  it  been  possible  to  under- 
stand its  structure.  Broadly  stated,  the  fibres  from  the  medial  (or  nasal) 
halves  of  the  retinae  decussate  in  Mo,  while  those  from  the  lateral  (or  tempo- 
ral) halves  do  not  cross.  Leaving  the  optic  chiasm,  the  crossed  medial  and 
uncrossed  lateral  fibres  form  the  slightly  flattened  optic  tracts  coursing  caudo- 
laterad,  embracing  the  crura  cerebri  and  dividing  in  the  neighborhood  of  the 
lateral  geniculate  body  into  two  "roots,"  a  mesal  and  a  lateral  root.  The 
mesal  root  is  in  reality  not  a  part  of  the  true  optic  path;  it  is  a  separate  fascicu- 
lar representation  of  the  infracommissure  of  Gudden,  composed  of  fibres  form- 
ing a  reciprocal  bond  of  union  (commissural)  between  the  internal  geniculate 
bodies  of  the  two  sides  and  coursing  through  the  chiasm  (Fig.  672) .  The  lateral 
root  of  the  optic  tract  is  the  true  visual  path,  composed  of  (a)  the  uncrossed 
fibres  from  the  lateral  half  of  the  retina  of  the  same  side  and  (b)  the  crossed 
fibres  from  the  mesal  half  of  the  retina  of  the  opposite  side.  The  fibres  of  the 
lateral  root  are  distributed  to  the  primary  or  lower  optic  centres  as  follows:  (1) 
INIost  fibres  end  in  the  external  geniculate  body;  (2)  a  less  number  end  in  the 
pulvinar;  (3)  the  remainder  end  in  the  nucleus  of  the  superior  quadrigeminal 
body. 

The  lateral  geniculate  body  and  pulvinar  are  ganglionic  way-stations  or  inter- 
nodes  in  which  visual  impulses  are  reflected,  in  large  part,  to  the  visual  cortex 
in  the  occipital  lobe;  the  superior  quadrigeminal  body,  on  the  other  hand,  plays 
no  part  in  the  conduction  of  impulses  perceived  as  light  or  color;  it  presides  rather 
over  the  eye-muscle  reflexes  to  visual-  stimuli,  and  in  its  turn  is  under  the  dominion 
of  the  higher  cortical  centre.  Reflex  impulses  are  sent  to  the  oblongata  and  spinal 
centres  along  axones  entering  into  the  formation  of  the  medial  longitudinal  bundle. 

1  Possibly  the  reflex  contraction  of  the  muscles  on  one  side  of  the  body  in  the  ancestral  vertebrate  followed  the 
perception  of  a  menacing  object  by  the  eye  of  the  opposite  side;  hence  the  advantage  of  a  decussation. 

2  And  auditory  stimuli  as  well  (  see  p.  898). 


JPAMTS  DERIVED  FROM  THE  FORE-BRAIN 


mi 


The  axones  of  corticifiigal  neurones  proceed  to  the  nucleus  of  the  superior  quadri- 
geminal  body  along  the  optic  radiation/ 

Some  fibres  are  detached  from  the  optic  tract  and  course  through  the  crus 
cerebri  to  the  oculomotor  nucleus.  These  fibres  are  small,  and  are  believed  to  he 
afjferent  branches  for  the  Sphincter  pupillse  and  Ciliary  muscles. 

The  connections  of  the  external  geniculate  body  and  pulvinar  with  the  higher 
cortical  centre  of  vision  are  established  by  neurones,  the  cells  of  which  lie  in  the 
two  ganglia  just  mentioned,  and  whose  a.xones  stream  in  an  arched,  more  or  less 


PULVINAR  — 1 
LAT.  GENICULI 


MEDIAL    GENICU- 
LATE BODY 
SUPERIOR  QUADRI- 
GEMINAL   BODY 


OCULOMOTOR 


OCCIPITAL  CORTEX 

Fig.  672. — Scheme  showing  central  connections  of  the  optic  nerve  and  optic  tract. 

compact  bundle  in  the  white  substance  of  the  cerebral  hemisphere  toward  the 
occipital  cortex.  Another  system  of  neurones,  whose  cells  lie  in  the  cortex,  sends 
its  axones  in  the  reverse  direction  (cortifugal)  to  the  two  lower  centres.  The 
cerebral  tract  thus  formed  between  primary  and  secondary  (cortical)  centres  is 
called  the  optic  radiation  (Fig.  712),  to  be  studied  more  fully  in  the  sequel.  The 
components  of  the  optic  path  are  delineated  schematically  in  Fig.  672. 


*  Centrifugal  fibres  ending  in  the  retina,  and  probably  arising  from  cells 
been  discovered  in  the  optic  tracts. 


I  the  superior  quadrigeininal  body,  have 


912 


THE  NEBVE  SYSTESr 
The  Cerebral  Hemispheres. 


External  Morphology. — Of  all  the  component  parts  of  the  brain,  the  cerebral 
hemispheres  form  the  largest  part,  and  their  preponderance  and  remarkable 
specialization  underlie  the  extraordinary  manifestations  of  the  intellect  so  highly 
amplified  in  man. 


Fig.  673. — ^Tesal  aspect  of  a  brain  sectioned  in  the  median  sagittal  plane. 

The  term  cerebrum,  often  employed  loosely  as  embracing  several  brain  parts, 
is  here  intended  to  include  the  brain  mantle  and  the  olfactory  lobe — equivalent  to 
the  telencephalon  of  His,  with  the  exception  of  the  pars  optica  hypothalami.  As 
already  indicated  in  the  section  on  brain  development,  there  has  occurred,  in  the 
evolutionary  history  of  man's  vertebrate  ancestry,  a  progressive  increase  of  the 
secondary  fore-brain,  with  concomitant  reduction  of  the  rkinencephalon,  or  smell 
brain — the  most  archaic  portion  because  of  the  important  relations  of  the  smell 
sense  to  the  life  history  of  the  earliest  \'ertebrates.^ 

In  a  mesal  view  of  a  hemisected  brain  (Fig.  673)  may  be  seen  the  various  parts 
of  the  brain  stem  and  the  cerebellum  overlapped  by  the  preponderatingly  greater 
cerebrum.  Among  the  many  notable  features  exposed  to  view  in  this  brain 
section  are  certain  fibre  masses,  commissures,  extending  across  the  meson,  and 
therefore  divided  by  the  knife  in  this  preparation.  Of  the  commissures  pertaining 
to  the  cerebrum  one  is  conspicuous  for  its  size  and  firm  consistency.  This  great 
fore-brain  commissure  is  the  corpus  callosum  already  mentioned  as  being  demon- 
strable in  the  depths  of  the  intercerebral  cleft  on  divaricating  the  lips  of  this 
fissure.  The  corpus  callosum  constitutes  a  massive  system  of  association  fibres 
for  the  bilateral  coordination  of  corresponding  cortical  parts.  It  is  thickened 
caudally,  forming  the  splenium  of  the  corpus  callosum;  frontad  it  bends  on  itself 

•  For  a  more  thorough  discussion  on  the  natural  subdi-vision  of  the  fore-brain,  based  upon  comparative  morphol- 
ogy, see  the  paper  by  G.  Elliott  Smith,  Journal  of  Anatomy  and  Physiology,  1901. 


THE  CEREBRAL  HEMISPHERES 


913 


ventrocaudad  to  form  the  genu  ("knee"),  including;  an  interval,  between  the  two 
limbs,  which  is  flanked  on  both  sides  by  a  thin  lamina  (hemiseptum)  and  bounded 
ventrad  by  the  fornix,  constituting  a  closed  cavitj',  the  pseudocele  icamim  seyti 
'peUucidi).  The  recurved  ventral  part  of  the  genu  tapers  into  a  thinner,  beak- 
shaped  part,  the  rostrum.  The  rostrum  is  joined  to  the  lamina  terminalis,  frontad 
of  the  anterior  commissure,  by  a  thin  lamina,  the  copula  {lamina  rostralis) . 


Fig.  674. — The  cerebral  hemispheres  viewed  from  above.      (Spalteholz.) 

An  arched  structure  composed  of  longitudinal  fibre  bundles  comes  to  view 
in  front  of  and  below  the  junction  of  the  splenium  with  the  body  of  the  corpus 
callosum,  proceeds  frontoventrad  with  its  convexity  frontad,  to  sink  from  view  in 
the  substance  of  the  hypothalamic  gray  at  a  point  just  caudad  of  the  anterior 
commissure.  This  white  arched  bundle  is  the  fornix.  Between  it  and  the  corpus 
callosum,  rostrum,  and  copula  stretches  a  thin,  translucent  lamina  of  nerve 
tissue — the  hemiseptum.  The  hemisepta  of  the  two  sides  together  have  usually 
been  termed  the  septum  pellucidum,  while  the  enclosed  narrow  cavity  is  called  the 
pseudocele  or  fifth  ventricle.  The  subjacent  parts  revealed  in  this  section  have 
already  been  described;  the  morphology  and  internal  relations  of  the  corpus 
callosum,  fornix,  and  hemiseptum  will  be  described  at  a  later  stage. 

58 


914 


THE  NERVE  SYSTEM 


The  cerebral  hemispheres  together,  as  viewed  from  above  or  dorsally,  appear 
as  two  symmetrical  masses  in  close  apposition,  conforming  in  outline  to  that  of 
the  cranial  cavity,  which  they  so  nearly  fill.  The  frontal  extremities  or  poles  are 
massive  and  rounded,  preponderatingly  so  in  comparison  with  the  brains  of  any 
related  primate  species.  The  occipital  poles  are  each  more  pointed  but  expand 
frontad  into  the  widest  part  of  the  cerebrum — the  parietal  lobes.  The  cerebral 
hemispheres  or,  briefly,  the  hemicerebra  are  partially  separated  from  each  other 
by  the  intercerebral  cleft  or  great  longitudinal  fissure  (fissura  longitudinalis  cerebri), 
into  which  fits  a  fold  of  the  dura — the  falx  cerebri.  By  means  of  a  large  com- 
missural band  of  white  fibres — the  corpus  callosum — the  cerebral  halves  are  joined 
together  in  the  depths  of  the  intercerebral  cleft.  All  adjacent  parts  of  the  brain 
are  overlapped  by  the  ponderous  cerebrum  so  as  to  entirely  conceal  the  thalamic 
portion  and  the  mid-brain,  while  the  occipital  lobes  overlap  the  cerebellum  with 


Fig.  675. — Principal  fissures  and  lobes  of  the  cerebrum 


the  intervening  tentorium — another  fold  of  the  dura.  Further  description  will 
be  restricted  to  each  cerebral  hemisphere. 

Configuration  of  Each  Cerebral  Hemisphere. — ^Each  cerebral  hemisphere 
presents  an  outer  convex  surface  {fades  convexa  cerebri),  applied  to  the  correspond- 
ing half  of  the  cranial  vault;  a  mesal  flattened  surface  (fades  medialis  cerebri), 
which  lies  in  a  sagittal  plane,  applied  to  the  corresponding  surface  of  the  opposite 
cerebral  hemisphere,  with  the  great  longitudinal  fissure  intervening,  and  for  the 
most  part  in  contact  with  the  falx  cerebri;  and  a  basal  or  ventral  surface,  of 
irregular  form,  resting  frontad  upon  the  floors  of  the  anterior  and  middle  cranial 
fossae,  and  caudad  upon  the  tentorium  cerebelli. 

Prominent  in  the  lateral  and  ventral  views  is  the  blunt  projection  of  the  temporal 
pole,  while  at  the  ventrolateral  border,  nearer  the  occipital  pole,  is  a  slightly 
marked  indentation  usually  called  the  preoccipital  notch.  The  deep  vallecular 
depression  between  the  orbital  surface  and  the  temporal  pole  accommodates  the 
lesser  wing  of  the  sphenoid. 

More  or  less  distinct  borders  demarcate  the  surfaces.     The  arched  dorsimesal 


THE  CEREBRAL  IIE3nSPHERES  915 

border  intervenes  between  the  mesal  and  the  convex  surfaces;  a  straight  rncsorhifal 
border  intervenes  between  the  orbital  and  mesal  surfaces  of  the  frontal  lobe;  a 
ventrolateral  border  separates  the  tentorial  siu'face  from  the  lateral,  convex  sur- 
face of  the  occipital  and  temporal  lobes;  v/hile  an  obtuse  border — the  mesoventral 
or  internal  oecipital  border — separates  the  tentorial  from  the  mesal  siu'faces. 

Cerebral  Fissures  and  Gyres. — -The  surface  of  each  cerebral  hemisphere  presents 
alternatino-  depressions  or  fissures  which  demarcate  gyral  elevations — the  convolu- 
tions or  gyres}  The  fissures  vary  in  depth  from  that  of  a  mere  shallow  groove 
to  as  much  as  30  mm.,  and  may  attain  a  length  of  15  cm.  They  are  more  or  less 
sinuous  and  ramified.  They  mark  the  surface  with  fairly  approximate  uniformity, 
that  is,  one  rarely  finds  an  unfissured  surface  more  than  15  to  20  mm.  (|^  inch  to 
f  inch)  in  width.  Numerous  functional  and  mechanical  influences  must  be 
credited  with  bringing  about  the  complex  foldings  of  the  cerebral  surface,  prin- 
cipally (a)  resistance  of  the  cranium  to  the  expanding  brain  or  "mechanical 
packing;"  (b)  difl:'erences  of  growth  rate  in  different  parts  of  the  cortical  surface; 
(c)  differences  of  growth  rate  of  different  fibre  bundles  retarding  cortical  expansion 
along  the  fissure  lines  and  elongating  to  help  in  the  formation  of  the  gyres.  The 
obvious  result,  whatever  the  influences  may  be,  is  an  expansion  of  the  cerebral 
cortex  to  an  enormous  degree,  so  that,  instead  of  having  a  surface  area  of  only 
60,000  sq.  mm.  (if  unconvoluted),  the  average  adult  cerebrum  has  a  cortical  area 
of  200,000  sq.  mm.  or  more.  Furthermore,  the  vascular  pia,  closely  investing 
the  surface  and  dipping  into  every  fissure,  is  expanded  in  a  like  manner,  affording 
an  ample  and  uniform  supply  of  blood  for  the  entire  cerebral  cortex. 

The  cerebral  vesicle  of  the  fetal  brain  presents  a  smooth  surface  during  the 
first  half  of  intrauterine  life,"  except  for  the  depressed  fossa  at  the  site  of  the  future 
island  of  Reil — destined  to  become  buried  in  the  depths  of  the  sylvian  cleft  formed 
by  the  apposition  of  the  more  energetically  growing  contiguous  parts  of  the  cerebral 
mantle.  Some  of  the  cerebral  fissures  develop  early  as  infoldings  of  the  com- 
paratively thin  wall  of  the  vesicle,  and  hence  produce  corresponding  projections 
into  the  cerebral  cavity;  these  are  termed  the  total  or  complete  fissures.  The 
remaining  fissures  are  only  linear  depressions  of  the  surface  not  involving  the  entire 
thickness  of  the  wall — the  partial  or  incomplete  fissures.  The  complete  fissures  and 
their  correlative  projections  into  the  cerebral  cavity  (lateral  ventricle)  are: 


Fissure.  Internal  Eminence. 

Hippocampal  fissure.  Hippocampus. 

Calcarine  fissure.  Calcar. 

Collateral  fissure.  Collateral  eminence. 

Occipital  fissure.  Occipital  eminence. 


Among  the  remaining  cerebral  fissures,  of  which  over  fifty  have  been  recog- 
nized and  named,  some  are  constant  in  representation  in  all  normal  brains,  while 
others  are  of  variable  occurrence  in  diii'erent  individual  specimens.  The  constant 
fissures  are  those  which  regularly  exist  as  interlobar  and  intergyral  boundary 
lines  forming  a  common  pattern  for  all  normal  brains,  but  these,  like  all  cerebral 
fissures,  are  subject  to  many  individual  variations  as  to  course,  depth,  length, 

I  Consistent  with  the  use  of  the  English  Johe  and  lohes  (for  lohus  and  lohi),  the  English  gyre  and  gyres  are 
preferable  to  gyrus  and  gyri.  The  term  iissure  is  here  uniformly  employed  for  all  anfractuosities  of  the  sur- 
face, though  sulcus  (pi.  sulci)  is  quite  as  generally  used;  sometimes  both  terms  are  indiscriminately  mi.xed 
in  other  works  on  this  subject. 

-  The  so-called  transitory  fissures  of  older  descriptions  may  be  neglected,  since  the  researches  of  Retzius, 
Hochstetter,  and  Mall  have  shown  these  to  be  iii  reality  artifacts  due  to  postmortem  swelling. 


916 


THE  NERVE  SYSTEM 


mode  of  branching,  and  anastomosis  with  neighboring  fissures  or  manner  of 
interruption  by  gyral  isthmuses.  The  range  of  individual  variations  is  so  great 
that  no  two  brains  can  be  said  to  be  exactly  ahke;  in  fact,  one  may  find  numberless 
stages  of  complexity  in  the  cerebral  surface  configuration  from  the  simply  fissured 
brains  of  mentally  inferior  individuals  and  races  to  the  complexly  fissured  and 
more  highly  organized  brains  of  vigorous  thinkers  and  talented  geniuses  among 
the  highly  intellectual  races  of  man. 


INTERCEREBRAL  F. 


FISSURE 
GYRE 


Fig.  676. — Cerebral  fissures  and  gyres  ■< 


Cerebral  Lobes  and  Fissures. — The  cerebral  surface  is  divided  into  five  prin- 
cipal areas,  called  lobes,  demarcated  by  certain  constant  fissures  which  are  more 
or  less  conspicuous,  and  were  therefore  selected  by  the  older  anatomists  as  arbi- 
trary boundary  lines;  these  are  termed  the  interlobar  fissures. 

The  lobes  are:  (1)  the  frontal;  (2)  the  parietal;  (3)  the  temporal;  (4)  the  occipital; 
(5)  the  island  of  Rail  or  insula.  The  interlobar  fissures  are:  (1)  the  sylvian;  (2) 
the  central;  (3)  the  occipital;  (4)  the  calcarine;  (5)  the  circuminsular.  A  series  of 
fissures  demarcating  die  rhinencephalon  from  the  pallium  or  cerebral  mantle 
proper  will  be  considered  at  a  later  stage. 

The  Interlobar  Fissures.  The  Sylvian  Fissure  and  Its  Rami  [fissura  cerebri  later- 
alis [SylmiJ). — This  fissure  is  a  well-marked  cleft  on  the  base  and  side  of  the 
cerebral  hemisphere.  Traced  laterad  from  the  region  of  the  anterior  perforated 
substance,  it  begins  as  a  deep  depression  between  the  orbital  surface  of  the  frontal 
lobe  and  the  temporal  pole,  corresponding  to  the  bony  ridge  formed  by  the  lesser 
wing  of  the  sphenoid  and  extending  to  the  convex  surface.      This  portion  of  the 


THE  CEREBRAL  HEMISPHERES  917 

fissure  is  termed  the  basisylvian  fissure  or  vallecula  sylvii,  as  far  as  the  sylvian  point.' 
The  sylvian  point  marks  tlie  fonjunction  of  the  main  portion  of  the  sylvian  fissure 
with  its  basisylvian  part  as  well  as  one  or  two  rami.  These  rami  are  (!)  the 
presylvian  ramus  and  (2)  the  subsylvian  ramus. 

The  presylvian  ramus"  usually  proceeds  dorsad,  slightly  inclined  frontad,  for 
a  distance  of  2  to  .')  cm.  into  the  subfrontal  gyre. 

The  subsylvian  ramus  {anterior  horizontal  limh)  extends  frontad  for  a  distance 
of  1.5  to  2  cm.,  parallel  to  the  orbitofrontal  (superciliary)  margin. 

These  two  rami  often  spring  as  shorter  branches  from  a  common  stem,  and  both 
may  be  replaced  by  a  single  unbranched  limb. 

The  sylvian  fissure  proper  is  the  most  conspicuous  part.  It  extends  from  the 
sylvian  point  in  a  caudal  direction,  inclined  slightly  dorsad,^  on  the  lateral  surface 
of  the  cerebrum  for  a  distance  averaging  6  cm.  (2|  inches).  It  separates  the 
temporal  lobe  wholly  from  the  frontal  and  partly  from  the  parietal  lobe.  It  usu- 
ally ends  in  an  upturned  manner,  in  the  parietal  lobe,  the  change  of  direction 
being  oftener  abrupt  than  gi-adual;  this  terminal  piece  receives  the  name  of  epi- 
sylvian  ramus.  Occasionally  a  short  ramus  is  sent  ventrad  into  the  supertemporal 
gyre  and  is  called  the  hyposylvian  ramus. 

The  sylvian  fissure  ranges  in  depth  from  15  mm.  or  less  at  the  presylvian  point 
to  25  or  30  mm.  (1  inch  to  li  inches)  at  the  postsylvian  point,  correlative  with 
the  contour  of  the  island  of  Reil,  which  lies  in  its  depths.  If  the  lips  of  the  sylvian 
fissure  be  divaricated,  the  island  of  Reil  is  revealed  as  a  cortical  district,  of  tetra- 
hedral  form,  which  is  normally  completely  concealed  by  overlapping  portions  of 
the  cerebral  hemisphere  called  the  opercula.  These  are  four  in  number:  (1)  the 
operculum  proper,  (2)  the  preoperculum,  (3)  the  suboperculum,  and  (4)  the  post- 
operculum. 

The  operculum  (frontoparietal  operculum)  is  composed  of  the  adjacent  portions 
of  the  ventral  border  of  the  frontal  and  parietal  lobes,  the  syh'ian  fissure  inter- 
vening between  it  and  the  postoperculum,  which  is  the  overlapping  part  of  the 
temporal  lobe.  The  preoperculum  is  a  small  triangular  portion  embraced  by  the 
presylvian  and  subsyh'ian  rami,  and  is  also  called  the  pars  triangularis  or  Broca's 
cap.  The  suboperculum  (orbital  operculum)  is  small,  demarcated  by  the  sub- 
sylvian ramus,  and,  for  the  most  part,  on  the  orbital  face  of  the  frontal  lobe, 
projecting  slightly  over  the  frontal  part  of  the  island  of  Reil,  with  its  margin 
separated  from  the  temporal  pole  by  the  basisylvian  cleft. 

The  overlapping  opercula  are  demarcated  from  the  island  of  Reil  by  the  cir- 
cuminsular  fissure  {sulcus  circularis  Reili). 

Development  of  the  Island  of  Reil  and  the  Sylvian  Cleft. — The  insular  cortical 
district  is  topographically  correlative  with  the  great  gray  ganglia  of  the  cerebral 
hemisphere,  particularly  the  lenticular  nucleus,  from  whose  ectal  surface  the  insular 
cortex  is  but  little  removed.  As  will  be  learned  at  a  later  stage,  few  if  any  pro- 
jection fibres  pass  to  and  from  the  island  of  Reil;  its  function  is  almost  wholly 
associative  for  adjacent  parts  of  the  cerebral  mantle.  The  island  of  Reil  there- 
fore becomes  buried  beneath  the  more  energetically  growing  and  bulging  parts 
immediately  around  it.  There  is  at  first  a  slight  fossa  (observable  in  the  tenth 
to  twelfth  week)  which,  as  development  proceeds,  and  as  the  overhanging  opercula 
encroach  upon  the  island  of  Reil,  becomes  more  deeply  situated  as  a  cleft-like 
depression  until  at  birth  the  fossa  has  become  a  fissure,  with  the  island  of  Reil 
perhaps  slightly  exposed  near  its  cephalic  extremity,  where  the  incomplete  apposi- 

'  So  called  in  cranial  topography.  ,    .    „ 

'  Also  called  the  anterior  ascending  limh.  In  BNA  terms  the  name  for  this  fissural  brtvnch  is  Ramus  anlenor 
ascendens  iissvrae  cerebri  lateralis. 

5  Its  inclination  to  the  horizontal  plane  is  called  the  sylvian  angle,  approximately  15  degrees. 


918 


THE  NERVE  SYSTEM 


tion  of  the  opercula  leaves  a  triangular  space.  This  space  is  usually  obliterated 
in  childhood,  but  is  commonly  met  with  in  certain  races  (negro,  Australian) 
and  in  brains  showing  developmental  defects  or  arrest.  The  mechanics  of  the 
formation  of  the  surface  outline  of  the  sylvian  fissure  by  the  apposition  of  the 
growing  and  plastic  opercula  may  be  understood  by  a  reference  to  Fig.  682. 


POSTCENT 


INTERLOCKING 


Fig.  677. — Central  fissure  fully  opened  up,  so  as  to  exhibit  the  interlocking  gyres. 


The  central  fissure  {fissure  of  Rolando  [sulcus  ce7itralis])  is  situated  at  about  the 
middle  of  the  convex  surface,  and,  coursing  obliquely  laterofrontad,  divides  this 
surface  into  approximately  equal  parts,  intervening  between  the  frontal  and  parietal 
lobes.     It  may  be  traced  from  a  point  at  or  near  the  dorsimesal  border,  about' 

1  cm.  (f  inch)  caudad  of  the  mid-point  of  the  occipitofrontal  arc.  It  then  runs 
sinuously  laterofrontad  to  within  a  short  distance  of  the  sylvian  fissure,  about 

2  cm.  (A  inch)  caudad  of  the  sylvian  point;  its  line  of  general  direction  makes  an 
angle  of  about  70  degrees  with  the  median  line  (Rolandic  angle).  If  measured 
■along  its  sinuosities,  its  length  averages  10.5  cm.  (4  inches).  Its  curved  course 
may  be  analyzed  into  five  alternate  curves  (sometimes  more  or  less),  of  which 
three  are  convex  frontad  and  two  caudad.  It  is  rarely  very  much  branched  and 
does  not  often  anastomose  with  neighboring  fissures.  Its  dorsal  end  bears  a  con- 
stant relation  to  the  caudal  limb  of  the  paracentral,  frontad  of  which  it  can  be  found 
as  a  hook-like  curve  (Figs.  676  and  679) .  If  the  lips  of  the  central  fissure  be  divari- 
cated, interdigitating  sub-gyres  are  commonly  seen  in  its  depths  (Fig.  677). 
These  interlocking  gyres  are  often  fused  to  a  greater  or  less  degree,  and  a  total 
interruption  of  the  fissui-e  has,  in  rare  instances,  been  observed.  The  central 
fissure  develops  at  about  the  end  of  the  fifth  month  of  intrauterine  life,  not  as 
a  single  integer,  but  as  the  result  of  the  union  of  two  segments — a  short  dorsal  and 
a  longer  ventral  segment.  As  development  proceeds  these  segments  eventually 
unite  end  to  end,  and  at  the  site  of  this  union  a  vadum  (or  shallow  uprising  of  the 
floor  of  the  fissure)  or  even  a  complete  isthmus  may  be  demonstrated  in  the  adult 
brain.     Only  three  cases  of  bilateral  interruption  are  on  record. 

The  occipital  fissure  (fissura  occipitalis)  is  a  deep  cleft  across  the  dorsimesal 
border  trans-secting  the  occipitofrontal  arc  at  about  5  cm.  (2  inches)  from  the 
occipital  pole,  and  extending  upon  both  the  mesal  and  the  convex  surfaces.  On 
the  meson  it  attains  a  length  of  .3  to  3.5  cm.  (li  to  If  inches)  (to  its  junction  with 
the  calcarine  fissure)  while  its  lateral  extent  is  shorter  (2  to  2.5  cm.,  f  to  1  inch). 
It  is  quite  deep  throughout  and  usually  shows  a  number  of  interdigitating  sub- 
gyres. 


THE  CEREBRAL  HEMISPHERES  919 

The  calcarine  fissure  {fissura  calcarina)  is  a  slightly  arched  fissure  wiiich  is 
usually  Joined  with  die  occipital  fissure  at  the  apex  of  the  cuneus  and  extends 
caudad  to  the  occipital  pole,  ending  in  a  bifurcation.  The  fissure  is  composed  of 
two  integers  which  may  be  partially  or  completely  separated  (by  a  vadum  or  an 
isthmus);  the  caudal  segment  may  then  be  distinguished  as  the  postcalcarine 
fissure. 

The  occipital  and  calcarine  fissures  join  to  form  a  Y-shaped  junction;  the  two 
limbs  of  the  Y  embrace  the  cuneus,  while  the  stem  is  continued  as  the  occipito- 
calcarine  stem  for  a  distance  of  about  .3  cm.  This  fissural  stem  is  allotted  to  the 
occipital  fissure  by  some  and  to  the  calcarine  fissure  by  other  authors.  As  there 
is  no  greater  frequency  of  confluence  with  one  as  against  the  other,  so  far  as  present 
statistics  go,  it  is  preferable  to  assign  no  special  relationship  for  this  stem  to  one 
or  the  other  principal  fissure. 

I.  Frontal  Lobe.  FissuKES  of  the  Frontal  Lobe. — 1.  The  lateral  surface 
is  bounded  by  the  dorsimesal  arched  border,  by  the  fronto-orbital  (or  superciliary) 
border,  by  the  sylvian  fissure  (in  part),  and  by  the  central  fissure.  The  principal 
fissures  marking  this  surface  demarcate  four  gyres:  (1)  the  precentral,  (2)  super- 
frontal,  (3)  medifrontal,  and  (4)  subfrontal  gyres.  The  fissures  are  (1)  the  pre- 
central, (2)  superfrontal,  and  (3)  subfrontal  fissures.  In  addition  must  be  described 
certain  fissures  which  are  intragyral  and  of  more  or  less  constant  occurrence. 

The  Precentral  Fissural  Complex  (sulcus  praecentralis). — Two  fissural  integers 
which  are  sometimes  joined  extend  more  or  less  parallel  with  the  central  fissure. 
The  mesally  situated  piece  is  usually  of  zygal  (^yoke-shaped)  shape  or  triradiate,  and 
usually  anastomoses  with  the  superfrontal  fissure.  From  its  position  it  is  termed 
the  supercentral  or  superior  precentral  fissure  (sulcus  praecentralis  superior).  The 
laterally  situated  piece  is  of  longer  extent,  sometimes  straight  or  slightly  sinuous, 
sometimes  arched  like  an  inverted  L,  or  T-shaped.  It  usually  anastomoses  with 
the  subfrontal  fissure.  The  two  precentral  segments  demarcate  the  precentral 
gyre  from  the  remaining  three  gyres  of  the  lateral  surface  of  the  frontal  lobe. 

The  superfrontal  fissiu'e  (sulcus  frontalis  superior)  usually  springs  from  the 
supercentral  and  pursues  a  sinuous  course  frontad,  to  become  lost,  as  a  rule,  in 
the  zigzag  or  transverse  ramifications  of  the  prefrontal  region.  It  is  usually  cjuite 
ramified  and  often  anastomoses  with  other  fissures.  It  demarcates  the  superfrontal 
from  the  medifrontal  gyre. 

The  subfrontal  fissure  {sulcus  frontalis  inferior)  is  most  often  confiuent  with  the 
precentral,  less  often  with  the  supercentral  fissure.  It  proceeds  frontad  in  an 
arched  course,  to  end  either  in  a  bifurcation  or  by  anastomosing  with  other  fissures 
(radiate  fissure,'  orbitofrontal  fissure,  or  medifrontal  fissure).  The  subfrontal 
fissure  demarcates  the  medifrontal  from  the  subfrontal  gyre. 

Both  the  superfrontal  and  medifrontal  gyres  are  characterized  by  a  more  or 
less  pronounced  longitudinal  subdivision  by  less  constant  fissural  segments.  They 
are:  (1)  the  paramesal  fissure  occupying  an  intermediate  position  between  the 
superfrontal  fissure  and  the  dorsimesal  border,  in  the  superfrontal  gyre,  more  often 
composed  of  a  series  of  short  segments  which  become  lost  in  the  more  complex 
configuration  of  the  prefrontal  region;  (2)  the  medifrontal  fissure  situated  in  the 
prefrontal  part  of  the  medifrontal  gyre,  rarely  extending  throughout,  and  usually 
ending  cephalad  in  a  widely  spread  bifurcation  which  constitutes  the  orbitofrontal 
fissure  when  independent.  The  medifrontal  fissure  is  usually  very  much  ramified 
and  frecjuently  anastomoses  with  neighboring  fissures.  The  fissure  is  a  char- 
acteristic of  human  and  anthropoid  brains  only. 

By  the  occurrence  of  either  or  both  paramesal  and  medifrontal  fissures,  the 
ordinary  three-tier  type  of  frontal  lobe  is  converted  into  a  four-tier  and  five-tier 
type;  the  latter  more  often  in  the  brains  of  the  more  highly  intellectual — a  feature 


920 


THE  NERVE  SYSTEM 


which  is  concomitant  with  the  comparatively  late  phyletic  and  embryonic  develop- 
ment of  the  two  secondary  fissures  described. 

Other,  less  important,  fissures  are:  (1)  the  inflected  fissure  (fissura  inflexa), 
incising  the  dorsimesal  border  between  the  central  fissure  and  the  cephalic  limb 
of  the  paracentral;  (2)  the  radiate  fissure,  near  the  lateral  orbitofrontal  border;  (3) 
the  transprecentral,  a  short  oblique  piece  ventrad  of  the  central  and  usually  dipping 
into  the  syhian  cleft;  and  (4)  the  diagonal  fissure  between  the  presylvian  ramus 
and  the  ventral  end  of  the  central,  and  often  confluent  with  the  precentral  (Fig. 
678). 

2.  The  mesal  surface  of  the  frontal  lobe  is  bounded  by  the  dorsimesal  border, 
the  mesorbital  border,  and  the  callosal  fissure  An  arcuate  fissure  or  system 
of  fissures  intermediate  between  the  dorsimesal  margin  and  the  supercallosal 
fissure  divides  this  surface  into  the  superfrontal  gyre,  mesal  aspect,  and  the  callosal 
gyre.  The  name  "callosomarginal"  was  usually  applied  to  this  fissure,  but  an 
examination  of  many  brains  reveals  a  certain  integrality  of  fissural  parts,  which 
are  not  always  connected.  One  constant  segment  from  its  relations  with  the 
central  fissure  is  called  the  paracentral  fissure,  composed  of  a  main  stem  with  a 
cephalic  and  a  caudal  limb,  embracing  the  paracentral  gyre.  Frontad  thereof 
extends  the  supercallosal  fissure,  often  in  two  segments,  running  a  concentric 
course  between  the  arched  dorsimesal  border  and  the  genu  of  the  callosum. 
The  supercallosal  may  be  confluent  with  the  paracentral.     The  supercallosal  is. 


SUPERCENTRAL  F. 


f,  =  FISSURE 
G.  =  GYRE 
R.  =  RAMUS 

Fig.  678.— Fissures  and  gyres  of  the  lateral  surface  of  the  left  hemicerebrum. 

as  a  rule,  quite  ramified,  its  branches  transcribing  the  superfrontal  gyre.  In 
the  prefrontal  region  and  ventrad  of  the  genu  of  the  corpus  callosum  lie  one  or 
two  fissures,  more  or  less  parallel  to  the  mesorbital  border,  and  called,  respect- 
ively, the  rostral  and  subrostral  fissures. 

3!  The  orhiial  surface  of  the  frontal  lobe  is  constantly  marked  by  a  straight 
fissure,  the  olfactory  fissure  {sulcus  olfactoriiis) ,  which  runs  parallel  to  the  mesorbital 
border  and  is  occupied  h\  the  olfactory  bulb  and  tract.  It  is  about  5  cm.  in  length 
and  demarcates  the  mesorbital  gyre  from  the  remaining  orbital  gyres.     This 


THE  CEREBRAL  HEMISPHERES 


921 


orbital  surface  is  marlved  by  a  fissural  system  (^sulci  orhitales)  that  is  usually  of 
zygal  type,  H-shaped  or  K-shaped,  quadriradiate,  or,  rarely,  triradiate.  Wlien  tlie 
transverse  element  is  sufficiently  pronounced  it  merits  the  name  of  transorbital 
fissure,  demarcating  the  preorbital  from  the  postorbital  gyral  field. 

Gyres  of  the  Frontal  Lobe  (lobus  frontalis).  1.  Lateral  Surface. — The  pre- 
central  gyre  {gyrus  centralis  anterior),  one  of  the  chief  motor  areas  of  the  cerebi-al 
cortex,  is  a  moderately  sinuous  gyre  extending  from  the  dorsimesal  border  to 
the  sylvian  fissure  and  demarcated  by  the  central  and  the  precentral  fissures 
(supercentral  +  precentral). 


G,  =  GYRE 
F.=  FISSURE 
E.  A.  S. 

Fig.  679. — Fissures  and  gyres  of  the  mesal  surface  of  the  left  hemicerebrum. 

The  superfrontal  gyre  is  limited  laterally  by  the  superfrontal  fissure,  while  it 
is  continuous  over  the  dorsimesal  border  with  its  mesal  surface.'  It  merges 
insensibly  with  the  medifrontal  gyre  in  the  prefrontal  region,  while  it  may  be 
partially  subdivided  by  the  paramesal  fissure. 

The  medifrontal  gyre  {gyrus  frontalis  medius)  is  broader  than  the  preceding, 
demarcated  by  the  superfrontal  and  subfrontal  fissures,  and  often  marked  by  the 
medifrontal  fissure  in  its  prefrontal  portion. 

The  subfrontal  gyre  {gyrus  frontalis  inferior)  is  limited  by  the  subfrontal  fissure 
and  the  basisylvian  +  sylvian  proper.  It  is  traversed  by  the  presylvian  and  sub- 
sylvian  rami,  embracing  the  preoperculum  or  pars  triangularis.  The  gyre  is  of 
historic  importance  since  Broca,  in  1861,  declared  it  to  be  the  seat  of  speech  con- 
trol.    (See  Cerebral  Localization.) 

2.  Mesal  Surface. — On  the  mesal  surface  of  the  frontal  lobe  and  embracing 
the  dorsal  end  of  the  central  fissure  lies  an  oval  lobule  or  gyre  called  the  paracentral 
gyre  (lobulus  paracentralis),  limited  by  the  paracentral  fissure  with  its  caudal 
and  cephalic  limbs.  Frontad  tliereof  extends  the  large  arched  mesal  surface  of 
the  superfrontal  gyre  {gyrus  frontalis  superior),  limited  by  the  supercallosal  fissure. 
Between  the  latter  fissure  and  the  callosal  fissure,  concentrically  situated  with 
respect  to  the  superfrontal,  lies  the  callosal  gyre  {the  "gyrus  fornicatus"  of  other 
authors). 


'  There  being  no  fissure  at  this  border,  it  is  improper  to  give  the  mesal  surface  of  this  gyre  a  different  name 
e.,  "marginal  gyrus"  of  the  authors). 


922 


THE  NERVE  SYSTEM 


Frontad  these  two  gjTes  arch  around  the  genu  of  the  corpus  callosum,  to  become 
merged  through  the  disappearance  of  the  intervening  supercallosal  fissure,  and  the 
rostral  fissures  alone  mark  this  surface. 


INTERCEREBRAL  F. 


SSURE 
GYRE 


Fig.  680. — Fissures  and  gyres  of  the  basal  surface  of  the  cerebrum. 

3.  Orbital  Surface. — ^The  olfactory  fissure  and  the  mesorbital  border  boiuid 
the  mesorbital  gyre  (gyrus  rectus).  The  remaining  orbital  surface  is  not  regularly 
divisible  on  account  of  the  great  variability  of  the  orbital  fissures;  when  the  trans- 
orbital fissure  is  pronounced,  a  pre-  and  postorbital  gyre  may  be  distinguished. 

The  postorbital  limbus  is  a  formation  occasionally  met  with  on  the  orbital  sur- 
face. It  consists  of  a  curved,  welt-shaped  eminence  demarcated  by  an  incisure 
created  by  the  lesser  wing  of  the  sphenoid,  and  due,  apparently,  to  the  intrusion 
of  the  postorbital  portion  into  the  middle  fossa  of  the  skull. 

II.  Parietal  Lobe  (lobus  ■parietalis).  Fissures  of  the  Parietal  Lobe. — 1. 
The  lateral  surface  is  bounded  by  the  dorsimesal  border  above,  by  the  central 
fissure  in  front,  and  by  a  part  of  the  sylvian  fissure  below;  it  is  only  partially  de- 
marcated from  the  occipital  lobe  by  the  occipital  fissure,  and  merges  gradually 
into  the  temporal  lobe. 

The  principal  fissures  marking  its  surface  consist  of  a  group  of  integral  segments 
showing  various  degrees  of  confluence .  in  different  individuals  and  formerly 
known  in  the  aggregate  as  the  intraparietal  sulcus  of  Turner  (sulcus  interparietalis. 
Two  of  the  fissural  segments  present  mucli  the  same  parallelism  to  the  central  fis- 
sure which  was  noted  for  the  precentral  group,  and  hence  these  are  termed  the 
postcentral  fissural  complex. 

The  postcentral  fissural  complex  comprises  a  longer  mesal  and  a  shorter  lateral 


THE  CEREBRAL  HEMISPHERES  923 

(and  ventral)  segment,  which  are  confluent  in  about  75  per  cent,  of  brains  and 
then  very  much  resemble  in  length,  continuity,  and  course  the  central  fissure. 
This  appearance  has  given  rise  to  reports  of  alleged  duplication  of  the  central; 
an  analysis  of  the  relations  of  the  dorsal  ends  of  the  fissures  in  question  with  the 
caudal  limb  of  the  paracentral  removes  all  doubt. 

The  postcentral  fissure  (proper)  is  the  longer  mesal  (and  dorsal)  segment.  Its 
dorsal  end  is  frequently  bifurcated  and  then  usually  embraces  the  dorsal  exten- 
sion of  the  caudal  limb  of  the  paracentral.  The  subcentral  fissure  constitutes  the 
shorter  lateroventral  segment. 

The  parietal  fissure  is  usually  a  slightly  arched  fissure  inclining  mesocaudad, 
sometimes  independent  but  more  often  confluent,  with  one  or  both  of  the  post- 
central segments  just  described.  It  demarcates  the  parietal  gyre  from  the  sub- 
parietal  district. 

The  paroccipital  fissure,  in  whole  or  in  part,  probably  represents  a  part  of  the 
simian  exoccipital  or  "  Att'enspalte,"  isolated  by  the  upgrowth  of  gyral  protons 
which  are  totally  submerged  in  the  ape  brain,  but  rose  to  the  surface  concomitant 
with  the  rise  in  functional  dignity  of  cortical  areas  so  important  in  the  human 
brain.  The  fissure  is  almost  invariably  of  zygal  shape,  its  stem  directed  sagittally, 
its  ends  bifurcated.  Its  confluence  with  the  parietal  fissure  seems  to  be  subject 
to  some  morphologic  law;  continuity  is  the  rule  on  the  left  side  (77  per  cent.),  and 
occurs  less  often  on  the  right.  The  combination  of  continuity  on  the  right  and 
separation  on  the  left  is  a  rare  one  (6  per  cent.). 

Less  constant  fissures  are  the  transparietal,  in  the  parietal  lobe,  and  the  inter- 
medial (Fig.  678).  In  the  subparietal  district  terminate  the  upturned  ends  of 
the  sylvian  (i.  e.,  episylvian  ramus)  of  the  supertemporal  and  the  meditemporal 
fissures. 

2.  The  mesal  surface  of  the  parietal  lobe  is  equivalent  to  the  quadrangular 
precuneus,  limited  by  the  paracentral  and  occipital  fissures,  while  ventrad  it  is 
imperfectly  separated  from  the  callosal  gyre  by  the  precuneal  fissure  (postlimbic 
sulcus),  usually  of  zygal  or  triradiate  form  and  occasionally  confluent  with  the 
paracentral. 

Gyres  of  the  Parietal  Lobe.  1.  Lateral  Surface. — The  postcentral  gyre 
{gyrus  centralis  posterior)  is  one  of  the  chief  somesthetic  areas  of  the  cortex.  It 
is  a  long,  more  or  less  sinuous  convolution  extending  obliquely  from  the  dorsimesal- 
border  to  the  sylvian  fissure  and  demarcated  by  the  central  and  the  postcentral  + 
subcentral  fissures. 

The  parietal  gyre  {lobulus  parietalis  superior)  lies  between  the-  dorsimesal  border 
and  the  parietal  fissure,  bounded  cephalad  by  the  postcentral,  caudad  partly  by 
the  occipital  fissure,  the  transition  to  the  occipital  lobe  being  maintained  by  the 
arched  paroccipital  gyre. 

The  subparietal  district  or  lobule  (lobulus  parietalis  inferior)  is  divided  into 
three  convolutions  which  arch  around  the  upturned  ends  of  the  sylvian,  super- 
temporal,  and  meditemporal,  and  merge  insensibly  with  the  adjacent  temporo- 
occipital  gyres.  The  marginal  gyre  {gyrus  supramarginalis)  arches  over  the  ex- 
tremity of  the  episylvian  ramus  and  is  connected  frontad  with  the  postcentral 
gyre,  ventrad  with  the  supertemporal  gyre.  The  angular  gyre  {gyrus  a)igularis) 
arches  over  the  upturned  extremity  of  the  supertemporal  fissure,  and  its  limbs 
fuse  with  the  supertemporal  and  meditemporal  gyres.  The  postparietal  gyre  is 
not  always  clearly  defined;  it  arches  around  the  upturned  end  of  the  meditem- 
poral or  its  representative  segment;  mesally  it  is  bounded  by  the  paroccipital 
fissure.  Variable  intermedial  fissures  sometimes  help  to  define  the  angular  gyre 
from  its  two  neighbors. 

2.  The  mesal  surface  of  the  parietal  lobe  has  already  been  described  as  equiva- 


924  THE  NERVE  SYSTEM 

lent  to  the  precuneus,  from  its  position  in  "  front"  of  the  cuneus  or  quadrate  lobo 
from  its  general  shape.  It  is  sometimes  marked  by  a  mesal  extension  of  the 
transparietal  fissure  or  by  intraprecuneal  fissures. 

III.  Occipital  Lobe  (lohus  ocripilolis).  Fissures  of  the  Occipital  Lobe. — 
1.  The  lateral  surface  of  the  occipital  lobe  is  imperfectly  demarcated  from  the 
adjacent  parietal  and  temporal  lobes  in  most  brains.  The  sharply  defined 
exoccipital  fissure  or  "  AiTenspalte"  of  other  primates  has,  in  the  ancestry  of  man, 
been  reduced  to  a  series  of  fissural  segments  by  the  upgrowth  of  submerged  cor- 
tical parts.  The  paroccipital  fissure,  we  have  already  learned,  probably  repre- 
sents one  of  the  gaps  in  the  series;  another  may  be  the  sulcus  lunatus  (Elliott 
Smith),  usually  termed  the  lateral  occipital  by  the  authors;  lastly,  a  fissure  some- 
times called  the  inferior  occipital  (suboccipital),  and  usually  embraced,  on  the 
occipital  pole,  by  the  bifurcate  limbs  of  the  postcalcarine,  may  complete  the  series. 
Further  researches  are  necessary  to  elucidate  the  morphology  of  this  region. 

2.  The  mesal  surface  is  equivalent  to  the  wedge-shaped  region  embraced  by 
the  occipital  and  calcarine  fissures,  and  called  the  cuneus.  A  fairly  constant 
cuneal  fissure  traverses  its  surface  parallel  to  the  calcarine. 

If  it  is  ever  determined  that  the  morphological  boundary  of  the  occipital  lobe  is 
as  outlined  above,  the  lobe  is  practically  excluded  from  the  basal  surface  of  the 
hemicerebrum. 

IV.  Temporal  Lobe  (lobus  temporalis).  Fissures  of  the  Temporal  Lobe. — 1. 
The  lateral  surface  of  the  temporal  lobe  is  bounded  by  the  basisylvian  and  sylvian 
fissures  and  by  the  ventrolateral  border;  caudally  it  merges  into  the  adjacent 
parietal  and  occipital  lobes. 

The  supertemporal  fissure  {sulcus  temporalis  superior)  is  a  deep,  long  (10  to  12 
cm.),  and  usually  continuous  fissure  which  begins  near  the  temporal  pole,  proceeds 
ventrad  of  but  parallel  with  the  sylvian,  to  become  upturned  in  the  parietal  lobe 
and  embraced  by  the  arched  angular  gyre. 

The  meditemporal  fissure  (sulcus  temporalis  medius)  is  rarely  continuous;  more 
often  it  is  represented  by  a  series  of  segments,  two,  three,  or  four  in  number,  the 
caudal  segment  running  more  vertically  into  the  parietal  lobe  to  be  embraced  by 
the  postparietal  gyre.  The  meditemporal  fissural  segments  run  nearly  parallel 
with  the  supertemporal  and  demarcate  the  meditemporal  from  the  subtemporal 
gyre. 

2.  Tentorial  or  Ventral  Surface. — Close  to  the  ventrolateral  margm  and  more 
or  less  parallel  with  it  runs  the  subtemporal  fissure  (sulcus  temporalis  inferior), 
extending  from  near  the  temporal  to  near  the  occipital  pole.  It  is  rarely  continu- 
ous, being  usually  broken  up  into  two  or  more  segments.  It  demarcates  the  sub- 
temporal from  the  subcollateral  gyre. 

The  collateral  fissure  (fissura  collateralis)  is  a  well-marked,  long  (8  to  12  cm.),  and 
deep  fissure  extending  from  near  the  occipital  to  near  the  temporal  pole.  Caudally 
it  demarcates  the  subcalcarine  gyre  from  the  subcollateral;  frontad  it  intervenes 
between  the  latter  gyre  and  the  hippocampal  gyre.  Its  middle  part  is  correlative 
with  the  collateral  eminence.  On  the  ventromesal  aspect  of  the  temporal  lobe 
and  near  its  pole,  cephalad  of  the  uncus,  is  a  moderately  marked  fissure  or  groove, 
called,  because  of  its  topographic  relation  to  the  amygdaline  nucleus — a  gray, 
ganglionic  mass — the  amygdaline  fissure  (fissura  ectorhinalis  s.  postrhinalis),  or 
incisura  temporalis. 

3.  The  dorsal  or  opercular  surface  of  the  temporal  lobe  enters  into  the  formation 
'  of  the  sylvian  cleft.     It  is  but  slightly  marked  by  a  few  oblique  or  transverse 

furrows  (transtemporal  fissures)  demarcating  slightly  elevated  transtemporal  gyres. 

Gyres  of  the  Temporal  Lobe. — The  five  principal  fissures  named  subdivide 

the  lobe  into  five  gyres.     On  the  lateral  surface  lie  the  supertemporal,  meditemporal, 


THE  CEREBRAL  HEiMISPHERES 


925 


and  subtemporal  gyres  (c/f/.  feiiif oralis  superior,  mcdius  cf  inferior);  on  the  ten- 
torial surface  are  the  subcalcarine  (gyrus  lingualis),  subcollateral  (gyrus  fusiformis; 
g.  occipitoteruporalis)  and  part  of  the  subtemporal. 

The  hippocampal  gyre  (gyrus  hippocampi),  formerly  inchided  in  the  "  limbic 
lobe,"  but  morphologically  belonging  to  the  neopallium,  occupies  the  dorsimesal 
part  of  the  ventral  surface  of  the  temporal  lobe.  The  longer  or  shorter  extension 
of  the  occipitocalcarine  stem  partially  (forming  the  isthmus  gyri  hippocampi) 
interrupts  its  continuity  with  the  callosal  gyre.  It  is  demarcated  by  the  collateral 
fissure  (in  part)  and  the  hippocampal  fissure,  broadens  out  toward  the  temporal 
pole,  and  appears  to  become  bent  upon  itself  dorsally  to  form  the  uncinate  gyre 
(uncus).  As  will  be  learned  in  the  sequel,  the  hippocampal  gyre  is  demarcated 
from  the  uncus  proper  by  the  intervention  of  the  frenulum  Giacomini — an  exten- 
sion of  the  narrow,  gray,  dentate  gyre. 


Fig.  681. — Brain  of  a  six-months'  hu 
natural  size,  right  side.  The  insula 
(Kolliker.)      . 


Fig.  682. — Cerebrum  of  an  eight-months'  human  embryo, 
leftside.    The  insula  is  nearly  covered  in.     (Testut.j 


Near  the  temporal  pole  it  is  demarcated  from  the  subcollateral  gyre  by  the 
fissura  rhinica,^  or  postrhinal  fissure;  this  fissure  is  not  infrequently  confluent  with 
the  collateral. 

The  surface  of  the  hippocampal  g,yre,  particularly  in  the  zone  along  the  liippo- 
campal  fissure,  is  of  a  more  whitish  color  than  is  characteristic  of  other  cerebral 
gyres;  this  is  due  to  a  white  reticular  stratum  of  fibres,  the  substantia  reticularis 
alba.  The  con-\'ex,  broader  part  of  the  gyre  is  marked  by  numerous  small, 
wart-like  eminences,  resembling  the  skin  of  an  amphibian,  and  called  by  Retzius 
the  verrucae  gyri  hippocampi.  Just  ventrad  of  the  uncinate  portion,  or  the  ter- 
minus of  the  hippocampal  fissure,  lies  a  groove  marking  the  impression  of  the 
free  edge  of  the  tentorium  cerebelli. 

The  Island  of  Reil  (insula;  central  lobe)  (Figs.  682,  683).— The  island  of  Reil 
lies  deeply  in  the  sylvian  cleft  and  can  only  be  seen  when  the  lips  of  that  cleft  are 
widely  separated,  since  it  is  overlapped  by  the  opercula  already  described.  With 
the  opercula  removed,  the  island  of  Reil  presents  a  tetrahedral  shape  with  its  apex 
or  pole  directed  fronto ventrad.  Its  borders  are  sharply  outlined  by  the  cir- 
cuminsular  fissure  except  in  the  depths  of  the  basisylvian  cleft,  where  the  insular 
cortex  is  continuous  with  the  gray  substance  of  the  anterior  perforated  substance — 
the  threshold  or  limen  insulae  (belonging  to  the  rhinencephalon).  An  oblique 
transinsular  or  central  insular  fissure  divides  this  district  into  a  larger  preinsula 
and  a  smaller  postinsula.  The  postinsula  is  usually  a  single  long  gyre  (gyrus 
longxis  iiisulae),  while  the  preinsula  is  subdivided  by  shallow  fissures  into  three. 


1  Called  by  Wilder, 
calls  it  tin  part)  the 


'ith  the  amygdaline  nucleus,  the  amygdaline  fissure.    Schwalbe 


926 


THE  NER  VE  SYSTEM 


four,  or  five  shorter  preinsular  gyres  {gyri  breves  insulae),  built  upon  a  radiate  plan, 
converging  in  the  region  of  the  insular  pole.  As  already  hinted,  the  island  of 
Reil  represents  an  area  of  the  brain  mantle  whose  growth  did  not  keep  pace  with 
that  of  the  surrounding  parts;  hence  its  submergence  by  them.  The  close  appo- 
sition of  the  insular  region  to  the  subjacent  basal  ganglia,  and  the  failure  of  devel- 
opment of  great  masses  of  projection  fibres  so  prominent  elsewhere,  were  doubt- 
lessly factors  therein.  The  insular  cortex  is  uninterruptedly  continuous  with  the 
rest  of  the  cortex,  but  it  has  become  specialized  into  the  purest  association  centre 
in  the  cerebrum,  and  we  shall  learn  of  its  intimate  relations  to  the  faculty  of  speech 
on  page  961. 


L  supposedly  transparent  cerebral  hemisphere, 
w  by  the  opercLila. 

The  Rhinencephalon,  or  Olfactory  Lobe  {lobus  olfactorius)  (Figs.  684,  685). — 
The  grouping  of  the  parts  constituting  the  central  olfactory  structures  under  the 
term  "rhinencephalon"  as  distinguished  from  the  rest  of  the  fore-brain  (pallium) 
was  first  clearly  made  by  Turner  and  proved  by  His  to  be  embryologically  well 
founded  and  by  Edinger  to  agree  with  phylogenetic  development.  More  light 
has  been  thrown  upon  the  subject  recently  by  Retzius  and  Elliott  Smith.  The 
sense  of  smell,  while  highly  useful  in  the  quest  for  food  in  earlier  and  lower  forms 
of  vertebrates,  is  relatively  litde  used  in  the  mental  life  of  man.  The  enormous 
preponderance  of  the  cerebral  mantle  and  the  concomitant  atrophy  of  the  rhinen- 
cephalon in  the  human  brain  afford  one  of  the  most  striking  contrasts  in  brain 
morphology.  This  relatively  feeble  development  in  bulk  of  the  olfactory  apparatus 
in  the  human  brain  by  no  means  renders  its  description  simple.  In  fact,  not 
until  its  development  in  lower  macrosmatic  animals  was  studied  could  anatomists 
form  even  an  approximately  clear  conception  of  the  seemingly  disjointed  remnants 
in  the  human  brain  of  an  olfactory  apparatus  so  relatively  huge  in  lower  animals. 
The  great  expansion  of  the  cerebral  hemispheres  and  of  the  great  commissure 
which  connects  them  (the  corpus  callosum)  has  been  an  important  factor  in  widely 
displacing  primitively  connected  parts.  The  developmental  history  must  be 
sought  for  in  the  writings  of  Edinger,  Retzius,  and  Elliott  Smith. 


THE  CEREBRAL  HEMISPHERES 


927 


The  Rhinencephalon  comprises: 

1.  Peripheral  parts. 

2.  Central  or  Cortical  parts. 

A  comprehensive  term  for  the  peripheral  part  is  lobus  olfactorius,  divisible  into 
pre-  and  postolfactory  parts. 


Preolfactory  lobe 


1.  Bulbus  olfactorius. 

2.  Tractus  olfactorius. 

3.  Tuberculum  olfactorium  and  trigonum. 

4.  Area  parolfactoria  (Br oca). 

5.  Stria  olfactoria  medialis. 

6.  Stria  olfactoria  intermedialis. 
.  7.  Stria  olfactoria  lateralis. 


p        If    f        1  K   /  ^"  ^'^terior  perforated  substance. 

i'ostoltactory  lobe  |  g    g^^^^  suhcallosm  and  Broca's  diagonal  hand. 


Fig.  684. — Schematic  representation  of  the  rhinencephalon,  basal  aspect. 

The  Preolfactory  Division. — The  olfactory  bulb  and  tract  form  a  long  and 
slender  band  with  a  bulbous  extremity  situated  on  the  basal  aspect  of  the  frontal 
lobe  and  constituting  a  rudimentary  remnant  of  a  relatively  large  diverticulum, 
developed  from  the  sensor  ectoderm  close  to  the  border  of  the  neural  plate  before 
it  becomes  converted  into  the  neural  tube  and  situated  on  either  side  of  the  neu- 
ropore  at  the  extreme  frontal  end.  Although  hollow  at  first,  the  cavity  (rhinocele) 
soon  becomes  obliterated. 

The  olfactory  bulb  (bulbus  olfactorius)  is  an  oval  mass  of  reddish-gray  color, 
which  rests  on  the  cribriform  plate  of  the  ethmoid  and  is  received  in  the  olfactory 
fissure  on  the  orbital  surface  of  the  frontal  lobe.  It  receives  the  numerous 
olfactory  nerves  (fila  olfactoria)  from  the  nasal  mucous  membrane.  The  olfactory 
tract  (trachis  olfactorius)  is  a  band  of  white  substance,  of  prismatic  outline  on 


928  THE  NERVE  SYSTEM 

section,  its  apical  ridge  fitting  into  the  olfactory  fissure.  Toward  its  root  region 
it  is  somewhat  narrowed. 

The  medial  and  lateral  olfactory  gyres  are  also  termed  the  medial  and  lateral 
roots  of  the  tract,  and  diverge  in  the  region  of  the  trigonum.  The  olfactory 
tubercle  is  best  seen  if  the  bulb  and  tract  be  lifted  away  from  the  olfactory  fissure ; 
the  tubercle  appears  as  a  small  pyramidal  elevation,  its  apex  buried  in  the  olfac- 
tory fissure,  its  irregularly  triangular  base  forming  the  trigonum  olfactorium,  a 
small  gray  area  frontad  of  the  anterior  perforated  substance.  This  area  is  marked 
by  ridge-like  elevations  which  appear  like  radiating  roots  of  the  tract,  and  named, 
according  to  their  position,  the  medial,  intermediate,  and  lateral  roots,  striae  or 
gyres.  The  lateral  olfactory  stria  is  continuous  with  the  limen  insulae  in  the  depths 
of  the  basisyh-ian  cleft,  and  thence  passes  to  the  uncus  to  end  in  the  gyrus  ambiens 
and  gyrus  semilunaris.  The  sharp  turn  made  at  the  limen  insulae  is  called  the 
angulus  lateralis.  The  medial  olfactory  stria,  a  narrow  gyral  band,  proceeds 
mesad  and  merges  with  the  adjacent  cerebral  surface;  its  extension  on  the 
mesal  surface  is  known  as  the  parolfactory  area  (Broca)  limited  frontad  by  the 
anterior  parolfactory  sulcus  {sulcus  parolfadoriiis  anterior)  and  separated  from 
the  subcallosal  gyre  by  the  posterior  parolfactory  sulcus  (stdcns  parolfactorius 
'posterior). 

The  intermediate  stria  is  not  always  very  distinct;  when  present  it  may  be  traced 
from  the  proximal  end  of  the  olfactory  tract  for  a  short  distance  over  the  gray 
field  of  the  trigonum,  to  plunge  into  the  gray  of  the  anterior  perforated  sub- 
stance. 

PosTOLFACTORY  DIVISION. — The  anterior  perforated  substance  or  space  oc- 
cupies an  irregular  quadrate  field  between  the  olfactory  trigone  and  the  optic 
chiasm  and  tract.  A  more  or  less  marked  groove  {sulcus  parolfactorius  posterior), 
which  is  identical  with  the  fissitra  prima  (His)  of  the  embryo,  separates  the  trigo- 
num from  the  anterior  perforated  substance.  Its  frontal  part,  much  perforated, 
is  of  a  darker  color  than  the  hind  portion;  the  latter  is  distinguished  by  the  name 
of  Broca's  diagonal  band.  This  courses  obliquely  laterad  along  the  optic  tract 
toward  the  uncus;  mesally  the  bands  of  the  two  sides  converge,  frontad  of  the 
lamina  terminalis,  and  proceed  toward  the  rostrum  of  the  corpus  callosum  as 
narrow  fields  which  taper  to  curve  around  the  genu  and  continue  in  the  indusium 
of  the  corpus  callosum  as  the  striae  longitudinales.  The  narrow  field  seen  on  the 
mesal  aspect  frontad  of  the  lamina  terminalis  and  anterior  commissure  is  known 
as  the  gyrus  subcallosus  {formerly  peduncle  of  the  corpus  callosum).  The  con- 
tinuity of  the  various  parts  may  be  understood  by  reference  to  Figs.  684  and 
685. 

The  cortical  and  central  part  of  the  rhinencephalon  comprise: 

1.  The  hippocampus.' 

2.  The  uncus. 

3.  Gyrus  dentatus. 

4.  Fasciola  cinerea. 

5.  Indusium,  medial  and  lateral  longitudinal  strise  upon  the  corpus 
callosum. 

6.  Gyri  Andreae  Retzii. 
[    7.  Gyri  subcallosi. 

18.  Fornix  and  fimbria. 
9.  Corpus  albicans  and  albicantiothalamic  tract. 
10.  Part  of  anterior  commissure  (precommJ.ssure). 
11.  Part  of  septum  pellucidum. 

>  Not  to  be  confounded  with  the  hippocampal  gyre  of  the  pallium* 


Cortical 


THE  CEREBRAL  HEMISPHERES 


929 


Central  or  Cortical  Parts  of  the  Rhinencephalon. — Following  the  sug- 
gestion made  by  Broca  in  187S,  it  has  been  customary  to  designate  these  various 
parts  by  the  comprehensive  term  limbic  lobe.  Broca's  notion  of  the  limbic 
lobe  in  man  was  founded  upon  attempts  to  homologize  the  human  cerebral  con- 
figurations with  those  found  in  lower  animals.  More  recent  researches  have 
proved  that  Broca's  "limbic  lobe"  included  parts  belonging  to  the  neopalliimi  and 
not  to  the  rhinencephalon.  The  term  is  therefore  inappropriate  in  a  morphologic 
sense. 

The  hippocampus  is  the  submerged,  peculiarly  folded  margin  of  the  cerebral 
hemisphere  produced  by  the  hippocampal  fissure.  Its  architecture  can  best 
be  understood  by  referring  to  a  frontal  section  (Fig.  686).  It  is  seen  that  the 
whole  cerebral  marginal  wall  is  pushed  into  the  ventricular  cavity  (middle  cornu) 
as  a  fold  caused  by  the  intrusion  of  the  hippocampal  fissure.  A  secondary 
fold  not  produced  by  a  fissure,  however — constitutes  the  gyrus  dentatus.  Super- 
imposed lies  a  prominent  white  band — the  fimbria — composed  of  axones  from 


INOUSIUM    AND   STRI/E 


FUSION   OF  FASCIOLA 
CINEREA     AND    D  E  N- 
E    GVHE 


L    FISSURE 


Fig.  685. — Schematic  representation  of  the  rhinencephalon.  mesal  aspect. 

the  hippocampal  cells,  assisting  in  the  formation  of  a  white  lamina,  subjacent 
to  the  ependyma  of  the  ventricle,  and  called  the  alveus.  The  whole  formation 
is  characteristic  of  this  region,  and  from  its  fancied  resemblance  to  a  ram's  horn — 
a  symbol  used  on  the  temple  of  Jupiter  Ammon — the  name  of  cornu  ammonis' 
has  been  given;  the  name  hippocampus  was  applied  because  of  a  fancied  resem- 
blance to  the  marine  animal  of  the  same  name.  The  ventricular  relations  and 
internal  structm-e  of  the  hippocampus  will  be  given  farther  on  (p.  942). 

The  uncus,  with  the  atrophied  lateral  olfactory  stria,  is  all  that  remains  in  the 
human  brain  of  the  relatively  large  pyriform  lobe  of  lower  forms.  It  appears 
to  be  a  hook-like  retroflexion  of  the  hippocampal  gyre  which  is  partially  encircled 
by  the  gyrus  dentatus.  Morphologically  speaking,  it  is  only  the  apical  portion, 
or  that  which  lies  caudad  of  the  dentate  gyre  which  is  the  true  uncus  (the  ciyrus 
intralimbicus  of  Retzius);  the  remainder  is  neopallial  and  a  part  of  the  hippo- 
campal gyre.     The  uncinate  or  intralimbic  gyre  may  be  traced  caudad  in  the 


^  FreQuently,  but  incorrectly,  gi\'€ 


930 


THE  NER  VE  SYSTEM 


depths  of  the  fimbriodentate  fissure,  along  the  dentate  gyre,  the  dentatofasciolar 
groove  intervening,  to  be  continued  as  the  fasciola  cinerea  (gyrus  fasciolaris  of 
lletzius)  over  the  splenium  of  the  corpus  callosum. 

If  the  hippocampal  gyre  be  depressed  for  the  purpose  of  examining  the  depths 
of  the  hippocampal  fissure,  there  is  revealed  a  narrow,  gray  band  whose  surface 
is  scored  by  numerous  incisures  and  whose  edge  is  notched  at  frequent  intervals. 
This  corrugated  band  is  the  dentate  gyre  or  fascia  dentata.  Partly  overlapping  it, 
but  farther  laterad,  lies  a  white  band — the  fimbria — extending  caudad  from  the 
uncus  to  become  continued  as  the  fornix. 


Fig.  686. — Trans-section  of  the  hippocampal  gyrus,      (Edinger.) 


The  dentate  gyre  is  demarcated  from  the  hippocampal  gyre  by  the  hippocampal 
fissure,  from  the  fimbria  by  the  fimbriodentate  fissure,  in  whose  depths  lies  the 
narrow  continuation  of  the  uncus  or  gyrus  intralimbicus — the  fasciola  cinerea. 
Extending  caudad,  and  for  the  most  part  parallel  with  the  fimbria,  it  loses  its 
corrugated  appearance  on  approaching  the  splenium,  then  fuses  with  the  fasciola 
cinerea,  parting  company  with  the  fimbria  (which  now  becomes  fornix),  to  be 
continued  upon  the  corpus  callosum  as  a  thin,  broad  plate  of  gray  substance — 
the  indusium  or  gyrus  epicallosus.  At  the  uncus  the  dentate  gyre  makes  an  abrupt 
turn  to  appear  upon  the  mesal  surface,  out  of  the  depths  of  the  hippocampal  fissure, 
and  encircles  the  neck  of  the  uncus,  forming  the  frenulum  Giacomini.  Beyond 
this  point  it  can  be  traced,  in  rare  instances,  to  the  gyrus  semilunaris. 

The  gyri  Andreae  Retzii  are  rudimentary  gyral  formations  consisting  of  small, 
rounded,  oval  or  spirally  corrugated  eminences  situated  ventrad  of  the  splenium 
in  the  angular  interval  between  the  dentate  and  the  hippocampal  gyres.  Struc- 
turally they  have  been  shown  to  belong  to  the  hippocampal  formation. 


THE  CEREBRAL  HEMISPHERES 


931 


The  indusium  (gyrus  epicallosus  s.  supracallosus),  considered  to  be  a  vestige 
of  the  hippocampus,  is  a  thin  strip  of  gray  substance  superimposed  upon  the 
corpus  caUosum  and  raised  into  two  paired  ridges  by  longitudinal  fibre  bundles 
which  constitute  the  mesal  and  lateral  longitudinal  striae.'  The  indusium  and  its 
striae  are  continued  cephalad  into  the  gyrus  subcallosus;  perhaps,  also,  into  the 
parolfactory  area  (Fig.  685). 

The  central  connections  of  the  rhinencephalon  will  be  considered  in  the  de- 
scription of  the  internal  configuration  of  the  hemisphere.  (See  Fornix,  Anterior 
Commissure,  etc.) 

Internal  Configuration. — Each  cerebral  hemisphere  contains  a  cavity,  the 
lateral  ventricle  (paracele),  an  extension  of  the  primitive  neural  cavity  carried 
outward,  its  contours  modified  by  the  developmental  changes  in  the  growth  history 
of  the  secondary  fore-brain  vesicle.  This  central  cavity  is  surrounded  by  the  thick, 
convoluted  walls  of  nerve  tissue  which  make  up  the  bulky  cerebral  hemispheres. 
The  cerebral  tissue,  as  elsewhere  in  the  central  axis,  is  made  up  of  gray  and  white 


Z'' 


Fig.  687.  — Mesal 


,  partly  dissented  cerebral  hemisphere,  to  show  the  relation 
cinerPa.  dentate  gyre,  and  uncus. 


of  fimbria,  faaciola 


substances.  Two  well-marked  types  of  gray  substance  are  recognizable:  (a) 
the  cortical,  so  named  because  its  situation  upon  an  interior  white  centre  invites 
comparison  with  the  rind  (cortex)  of  a  fruit;  (b)  the  massive  ganglionic  or  nugget- 
like masses  not  dissimilar  from  the  thalamus  already  described,  comprising,  in 
this  division  of  the  brain,  the  caudate,  lenticular,  and  amygdaline  nuclei.  The 
•white  substance  fills  out  the  entire  space  intervening  between  the  cortex,  the  cavity 
of  the  lateral  ventricle,  and  the  great  basal  ganglia,  and  is  composed  of  myelinic 
axones  which  connect  the  elements  of  the  cortex  with  other  parts  of  the  nerve 
system,  or  with  other  regions  of  the  cortex  of  the  same  or  the  opposite  cerebral 
hemisphere. 

If  a  brain,  resting  upon  its  basal  surface,  be  sliced  by  successive  horizontal 
sections  from  above,  the  peripheral  gray  and  internal  white  are  brought  into  view. 

'  The  mesal  stri:p  are  also  called  Striae  Lancisii;  the  lateral  stria;,  Teniae  lectae. 


932 


THE  NERVE  SYSTEM 


The  more  superficial  sections  reveal  relatively  more  gray  than  white  substance; 
deeper  sections  show  a  reverse  condition,  and  a  section  immediately  dorsad  of  the 
corpus  callosum  reveals,  in  each  cerebral  hemisphere,  a  very  extensive  semioval 
field  of  white  substance,  the  centrum  semiovale,  surrounded  on  all  sides  by  a  narrow, 
convoluted  margin  of  gray  substance,  the  cortex.  A  close  examination  of  the  cut 
surface,  in  a  fresh  and  normal  brain,  shows  it  to  be  studded  with  numerous  minute 
red  dots  (puncta  vasculosa)  produced  by  the  escape  of  blood  from  divided  blood- 
vessels. 

The  Cortex. — The  cortex,  as  revealed  in  such  a  section,  is  not  of  uniform  thickness 
throughout;  difi^erent  regions  show  different  cortical  thicknesses.  In  general,  the 
cortex  is  somewhat  thicker  at  the  summit  of  a  gyre  than  in  the  depths  of  an 
adjoining  fissure,  and  it  is  thicker  upon  the  convex  than  upon  the  mesal  or  basal 
surfaces.     The  maximum  thickness  is  observed  in  the  cortex  of  the  central  gyres 


t  IG    bSb  — Corpus  callosum      ( 


and  the  insula;  the  minimum  at  the  frontal  and  occipital  poles,  notably  the  latter. 
Not  only  is  the  cortex  not  of  uniform  thickness,  but  it  is  not  of  homogeneous 
structure  as  seen  with  the  naked  eye.  An  alternation  of  gray  and  white  stripes 
is  discernible,  particularly  in  the  occipital  cortex,  where  a  white  band  runs  parallel 
with  the  cortical  surface  between  two  gray  strata;  this  while  stripe,  first  described 
by  Gennari  and  usually  bearing  his  name,  is  also  called  the  band  of  Vicq  d'Az3rr. 

The  preponderance  of  white  substance  over  gray  substance  in  the  cerebrum  is  a  human  charac- 
teristic concomitant  with  the  relative  increase  of  the  association  cortex,  in  turn  demanding  a  more 
intricate  interconnection  of  the  ma-ny  nerve  cells  by  a  multitude  of  association  neurones.     These 


THE  CEREBRAL  HEMISPHERES 


933 


coordinating  fibre  systems  are  as  truly  representative  of  the  complexity  of  man's  thought  appa- 
ratus as  the  number  of  interconnecting  wires  within  a  telephone  "  central"  station  is  indicative 
of  the  amplitude  of  connections  possible  in  that  system.  The  proportions  of  gray  and  -n'hite 
substances  are  expressed  in  the  following  tabulation: 

Gray  substance    |  Cortex 33  per  cent. 

•'  ( Ganglia b  per  cent. 

White  substance 61  per  cent. 

The  removal,  by  successive  slices,  of  the  dorsal  parts  of  the  cerebrum  soon 
brings  into  view  the  large  expanse  of  transverse  myelinic  fibres,  the  corpus  callosum, 
which  connects  the  two  hemispheres. 

The  Corpus  Callosum  (Trabs  cerebri ;  commissura  maxima) . — ^The  corpus  callosum 
is  a  thick  stratum  of  transversely  directed  nerve  fibres,  by  which  almost  e\'ery  part 
of  one  cerebral  hemisphere  is  connected  with  the  corresponding  part  of  the  other 
cerebral  hemisphere  (Figs.  689  and  690).     The  axones  composing  it  arise  from  the 


Fig.  689. — Diagram  of  coronal  section  of  cerebrum  to 
show  course  of  fibres  of  corpus  callosum.     (Testut.) 


i.  690.— Diagr, 
.  to  show 
(Testut.) 


small  pyramidal  or  the  polymorphous  cells  of  the  cerebral  cortex,  or  they  may 
be  collaterals  from  the  long  association  or  even  the  projection  neurones.  They 
pass  in  both  directions  and  within  the  centrum  semiovale  radiate  in  various  direc- 
tions (radiatio  callosi)  between  the  fibres  of  the  corona  radiata  to  terminate  in 
the  layer  of  small  pyramidal  cells  of  the  cortex,  thus  forming  a  great  transverse 
commissural  system,  and  at  the  same  time  roofing  in  the  greater  part  of  the  lateral 
ventricle  in  each  half.  A  portion  of  the  dorsal  surface  is  free  for  a  width  of  about 
1  cm.  on  either  side  of  the  mesal  plane,  partly  covered  by  the  indusium  and 
overlapped  by  the  callosal  gyres  of  the  two  sides,  a  fold  of  pia  intervening. 

The  mass  of  radiating  fibres  may,  for  convenience  of  description,  be  sub- 
divided into  a  pars  frontalis,  a  pars  parietalis,  and  a  pars  occipitotemporalis.  The 
frontal  and  occipitotemporal  portions  are  compressed  or  thickened  mesally  because 
the  fibres  cannot  pass  directly  across,  but  curve,  respectivelv,  frontad  and  caudad 
in  each  hemicerebrum  to  form  two  tong-like  bundles,  the  forceps  anterior  s.  minor 
(pref creeps) ,  and  forceps  posterior  s.  major  (postforceps).  The  pars  parietalis 
constitutes  the  greater  part  of  the  "body"  of  the  corpus  callosum.  The  fibres 
traversing  the  body  {frimcus  corporis  callosi)  and  the  adjacent  part  of  the  splenium 
curve  around  the  posterior  cornu  and  trigonum  \'entriculi  of  the  lateral  ventricle, 
to  form  a  thin  but  definite  white  stratum,  the  tapetum,  in  the  roof  and  ectal  wall 
of  these  parts  of  the  cavity. 

The  transverse  direction  of  the  fibres  is  rendered  apparent  in  a  dorsal  view 
of  the  exposed  corpus  callosum  in  the  form  of  the  striae  transversae.     These  are 


934  THE  NER  VE  SYSTEM 

but  little  obscured  by  a  thin,  gray  lamina — the  indusiiun — which  is  thickened 
longitudinally  by  two  symmetrically  situated  fibre  strands,  the  mesal  (striae 
Lancisii)  and  lateral  longitudinal  striae  (teniae  tectae),  already  mentioned  as  rudi- 
ments of  the  rhinencephalon. 

The  best  conception  of  the  size  and  form  of  the  corpus  callosum  is  obtained  from 
a  view  of  a  mesal  section.  It  is  then  seen  to  be  a  long,  thick,  somewhat  flattened 
arch  which  bends  sharply  upon  itself  frontad  to  form  the  genu  (^c/enu  corporis 
callosi),  while  its  caudal  end  is  rounded  and  somewhat  folded  closely  upon  itself 
to  form  the  splenium.  The  corpus  callosum  ranges  in  length  from  7  to  10  cm., 
its  cross-section  area  from  5  to  10  sq.  cm.,  being  longer  and  larger  in  heavier 
brains  and  in  those  of  the  highly  intellectual  as  compared  with  smaller  and  less 
highly  efficient  brains.  It  extends  to  within  4  cm.  of  the  frontal  pole  and  to  within 
6  cm.  of  the  occipital  pole.  The  thickness  of  the  "body"  averages  5  mm.;  of  the 
splenium,  9  mm.  or  more,  while  the  maximum  thickness  of  the  genu  is  about 
13  to  15  mm.  The  reflected  portion  or  rostrum  (rostrum  corporis  callosi)  gradually 
tapers  into  a  very  thin  lamina,  the  copula  {lamina  rostralis),  which  in  turn  joins 
the  lamina  terminalis  frontad  of  the  anterior  commissure. 

The  splenium  (splenium  corporis  callosi)  projects  as  a  rounded  welt  over  the 
mid-brain,  but  is  separated  from  it  by  a  pial  fold — the  velum  interpositum. 
Farther  frontad  the  fornix  becomes  fused  to  the  ventral  surface  of  the  corpus 
callosum  for  a  short  distance,  to  again  leave  it  in  its  more  arched  course  toward 
the  corpus  albicans.  Two  thin  laminse,  one  on  either  side  of  the  median  plane, 
but  closely  applied  to  each  other  and  frequently  partially  fused,  occupy  the  interval 
between  corpus  callosum  and  the  fornix  of  each  side.  The  laminse  together 
are  termed  the  septum  lucidum  of  the  authors,  each  one  being  called  a  hemiseptum; 
the  enclosed  cavity  is  called  the  fifth  ventricle  or  pseudocele,  though  not  derived 
from  the  original  neural  cavity. 


.COMMISSURE  J        ^ —  /  /  7^ E.  A.  S. 

REGION    OF 
ANT.  COM. 


RMINALIS 


Fig.  69J. — Schemata  showing  the  development  of  the  corpus  callosum  and  its  relations  to  hippocampus, 
fornix,  and  anterior  commissure.  Lamina  terminalis  (terma)  in  heavy  black,  corpus  callosum  dotted.  *  Rep- 
resents the  attenuated  indusium  and  longitudinal  strise  already  described. 

Development. — The  corpus  callosum  develops  as  a  mass  of  commissural  fibres  which  grow 
from  side  to  side  in  the  lamina  terminaHs  (terma).  The  lamina  terminalis  serves  as  a  matrix 
for  several  commissural  systems — viz.,  the  hippocampal  commissure  and  the  anterior  commissure, 
in  addition  to  the  corpus  callosum.  The  last  develops  rapidly  in  higher  mammalian  brains, 
thrusts  aside  the  hippocampal  margin  of  the  pallium  so  that  it  atrophies  in  large  part,  and 
stretches  out  within  its  sharply  bent  arch  a  portion  of  the  precommissural  wall  of  each 
cerebral  vesicle.  It  thus  withdraws  a  part  of  the  intercerebral  cleft,  eventually  enclosing  it 
entirely  as  the  fifth  ventricle.  The  stages  of  development  are  shown  schematically  in  Fig.  691 
and  its  development  in  the  human  embryo  is  shown  in  Fig.  692.  The  corpus  callosum  is  most 
fully  developed  in  man  and  does  not  appear  below  the  marsupials.  Its  growth  kept  pace  with 
the  preponderatingly  greater  development  of  the  neopallium  in  higher  forms,  and  it  may  be 
looked  upon  as  an  index  of  the  elaboration  of  at  least  one  division  of  the  association  systems^ 
those  concerned  with  bilateral  coordinations. 


THE  CEREBRAL  HEMLHPIIEREH 


935 


Figs.  692-695. — Brains  of  human  embryos;  mesa!  aspects  of  median  sagittal  section  show  the  development  of 
the  corpus  callosum.  Fig.  692.  Fourth  month.  Fig.  .693.  Fifth  month.  Fig.  694.  Sixth  month.  Fig.  695. 
Seventh  month. 


936 


THE  NERVE  SYSTEM 


The  Lateral  Ventricles. — An  incision  through  the  corpus  callosum,  on  either  side 
of  the  median  plane,  will  expose  two  large,  irregular,  symmetrically  situated 
cavities,  the  lateral  ventricles,  extending  through  a  great  part  of  each  cerebral 
hemisphere.  Each  lateral  ventricle  communicates  with  the  third  ventricle 
through  a  small  opening,  the  foramen  of  Monro,  situated  between  the  forni- 
column  (anterior  pillar  of  fornix)  and  frontal  end  of  thalamus.  The  cavity  is 
lined  throughout  by  ependyma;  it  is  narrow  in  some  and  wide  in  other  localities, 
and  contains  cerebrospinal  fluid. 

The  shape  of  the  lateral  ventricle  is  best  understood  by  reference  to  a  cast  of  its 
interior,  and  its  location  within  the  cerebrum  may  be  appreciated  by  a  study  of 
Figs.  696  and  697.  Conventionally  the  lateral  ventricle  or  paracele  is  described  as 
being  composed  of  a  body  or  cella  and  three  horn-like  extensions  or  comua.  Viewed 
laterally  its  contour  corresponds  to  that  of  the  cerebral  hemisphere  and  its  cornua 
project  toward  the  three  poles — viz.,  frontal,  occipital,  and  temporal. 


. — Showing  tbe  ventricular  system  of  the  brain  as  a  sohd  cast  as  if  seen  through  a  transparent  brain. 


The  body  {jpars  centralis  ventriculi  lateralis)  or  cella  of  the  lateral  ventricle  is 
defined  as  that  portion  which  extends  from  the  foramen  of  Monro  to  the  region 
of  the  splenium.  Its  frontal  prolongation  is  called  the  anterior  horn  or  precomu. 
Near  the  splenium  the  cavity  may  be  traced  ventrolaterad  into  a  capacious  part 
(trigonum  ventriculi),  from  which  the  posterior  horn  (postcornu)  and  middle  horn 
(medicornu)  are  prolonged,  respectively,  toward  the  occipital  and  temporal  poles. 

The  anterior  horn  or  precomu  {cornu  anterius)  passes  frontad,  inclined  slightly 
ventrolaterad.  Its  floor  is  the  head  (caput)  of  the  caudate  nucleus,  forming  a 
rounded  incline  sloping  mesad  toward  a  trench-like  recess  floored  by  the  rostrum 
of  the  corpus  callosum.  Its  roof  is  the  anterior  forceps  of  the  corpus  callosum. 
Its  mesal  wall  is  formed  by  a  portion  of  the  hemiseptum  of  the  septum  lucidum^ 
Laterally  it  is  limited  by  the  apposition,  at  an  acute  angle,  of  the  corpus  callosum 
and  the  caudate  nucleus.     Its  apex  reaches  the  ventricular  surface  of  the  genu  of 


THE  CEREBRAL  HEMISPHERES 


937 


the  corpus  callosum.     The  general  outhne  of  this  part  of  the  ventricle,  in  a 
.frontal  section,  is  triangular  (Fig.  707). 

The  body  of  the  cavity  is  curved  with  its  convexity  dorsad;  its  outline  in  trans- 
sections  varies  from  the  triangular  to  a  mere  slit  which  slopes  slightly  meso- 
ventrad.  It  is  wholly  roofed  in  by  the  corpus  callosum  {'pars  fronioparietalis). 
Its  floor  is  formed  by  the  following  structures  named  in  order  from  its  ectal  toward 


COMMISSUR 


Fig.  697. — Dissection  showing  the  left  lateral 


posed. 


its  ental  limit:  (1)  caudate  nucleus  or  caudatum;  (2)  a  groove  which  marks  the 
line  of  coalescence  of  caudate  nucleus  and  thalamus  and  lodges  the  iaenial  rein 
and  a  narrow  fibre  strand — the  taenia  semicircularis,  beneath  the  ependyma; 
(3)  a  reflexion  of  the  ependyma  onto  a  narrow  area  of  the  thalamus;  (4)  the 
choroid  plexus  of  the  lateral  ventricle;  (5)  the  thin,  sharp  (fimbriated)  edge  of  the 
fornix.     The  caudate  nucleus  narrows  rapidly  as  it  passes  caudad.     The  taenia 


938 


THE  NER  VE  SYSTEM 


semicircularis,  lying  along  the  ental  border  of  the  ventricular  surface  of  the 
caudate  nucleus,  is  a  small  band  of  white  fibres  arching  from  the  amygdaline 
nucleus  (near  the  temporal  pole)  to  the  anterior  perforated  substance.  The 
entrance  of  a  part  of  the  thalamus  into  the  formation  of  the  floor  of  the  lateral 
ventricle  is  apparent  enough,  but  morphologically  it  should  be  strictly  excluded 
therefrom.  The  thalamus  is  in  no  way  formed  from  the  parietes  of  the  secondary 
fore-brain  vesicles  (telencephalon),  for  it  is,  in  fact,  excluded  by  a  layer  of  ependyma 
(lamina  afRxa)  reflected  onto,  and  often  separable  from,  the  surface  of  the  thala- 
mus, so  that  it  appears  as  a  constituent  of  the  floor  because  of  the  transparency  of 
the  ependymal  sheet.  The  choroid  plexus  of  the  lateral  ventricle  is  a  richly 
vascular  invagination  over  which  the  ependyma  is  continuous  to  again  become 
reflected  onto  the  fornix  along  its  sharp  edge.  A  reference  to  Fig.  670,  show- 
ing the  topographical  relations  of  these  structures  in  a  frontal  section,  may  be  of 
assistance. 

The  cavity  is  thence  continued  ventrolaterad  in  a  bold  sweep  to  become  ex- 
panded as  an  obliquely  pyramidal  space  of  a  somewhat  triangular  outline  on 
section,  and  placed  subjacent  to  the  parietal  lobe — the  trigonum  ventriculi  (tri- 
gonuin  coUaterale).  A  conspicuous  feature  in  its  floor  is  the  collateral  eminence, 
correlated  with  the  collateral  fissure.  From  the  trigonum,  the  most  capacious 
part  of  the  lateral  ventricle,  the  cavity  is  prolonged  in  opposite  directions  as  the 
middle  and  posterior  cornua. 


Tail  of  caudate  nucleui 


Choroid  lylexus 

Ex>iihelial  lining  of  ventricle 


Pia  mater 

Fimbria 
Fintbrio-dentate, 
fissure 

Alveus 

Dentate  gyrus' 

Dentate  fissure/ 

Fig.  698.  — Coronal  section  of  descending  horn  of  tlie  lateral  ventricle.      (Diagrammatic.) 


The  middle  horn  or  medicomu  (cornu  inferius)  is  a  prolongation  of  the  ventricular 
cavity,  from  its  trigone  toward  the  temporal  pole,  which  pursues  a  curved  course 
with  its  convexity  directed  ventrolaterad  (Figs.  696  and  697),  corresponding 
to  the  curved  contour  of  the  temporal  lobe,  and  situated  at  a  depth  of  about  3  cm. 
from  its  lateral  surface  as  well  as  from  the  temporal  pole.  The  roof  is  formed  by 
(a)  the  tapetum  of  the  corpus  callosum;  (h)  the  Cauda  (tail)  of  the  caudate  nucleus; 
(c)  the  taenia  semicircularis.  The  medial  wall  is  principally  composed  of  the 
hippocampus,  a  prominent  welt-like  eminence  bulging  into  the  cavity,  largely 
filling  it,  and  produced  by  the  hippocampal  fissure.  The  hippocampus  nearly 
conceals  from  view  the  actual  floor,  which  is  of  variable  extent  in  different  brains 
and  usually  marked  by  an  extension  of  the  collateral  eminence  previously  described. 
Surmounting  the  corrugated  hippocampal  formation  and  projecting  slightly 
into  the  cavity,  is  the  fimbria,  and  from  its  sharp  edge  the  ventricular  ependyma 


THE  CEREBRAL  HEMISPHERES 


939 


Is  reflected  upon  the  invaginated  choroid  plexus  of  the  lateral  ventricle.  The 
choroid  plexus  of  the  middle  cornu  is  more  voluminous  than  that  of  the  body 
of  the  ventricle,  and  must  be  lifted  in  order  to  expose  the  whole  of  the  ventricular 
aspect  of  the  hippocampus. 

At  the  apex  of  the  middle  cornu  the  roof  presents  a  more  or  less  pronounced 
bulging,  the  amygdaloid  tubercle,  due  to  the  presence  of  -the  amygdaline  nucleus, 
a  small  mass  of  ganglionic  gray  from  which  the  taenia  semicircularis  arises  and  in 
which  the  caudate  nucleus  apparendy  ends. 

The  posterior  cornu  or  postcomu  is  a  shorter  diverticulum  which  passes  toward 
the  occipital  pole  in  a  gently  curved  course,  with  its  convexity  directed  laterad. 
It  is  not  very  capacious,  usually  slit-like  on  section,  and  tapers  to  a  point  within 
2  or  3  cm.  of  the  occipital  pole.     Its  roof,  slanting  lateroventrad,  is  formed  by  the 


Fig.  609.— Diag: 


tapetum  of  the  corpus  callosum.  On  the  inner  or  mesal  ivall  two  elongated 
bulgings  may  be  observed.  The  upper  or  dorsal  elevation,  called  the  occipital 
bulb  or  bulb  of  the  cornu  (bulbus  cornu  posterioris,  callosal  eminence  [Wilder]), 
is  formed  by  the  compact  arched  posterior  forceps  of  the  corpus  callosum  as  it 
curves  around  the  very  deep  occipital  fissure.  The  occipital  bulb  is  not  always 
well  marked.  Ventrad  of  it  lies  a  more  constant  limbus  or  welt-like  elevation, 
the  calcar  (calcar  avis;  hippocampus  minor),  a  projection  produced  by  the  infolding 
of  the  cerebral  wall  along  the  calcarine  fissure.  The  floor  is  continuous  with  the  col- 
lateral eminence  in  front.     The  choroid  plexus  does  not  enter  the  posterior  cornu. 


940  THE  NERVE  SYSTEM 

The  choroid  fissure  or  rima  (fissure  of  Bichat)  is  not  a  true  fissure,  and  only 
becomes  one  when  the  choroid  plexus  of  the  lateral  ventricle  is  torn  from  its 
connections.  The  choroid  fissure  is  nevertheless  a  gap  between  the  diencephalic 
part  and  the  overlapping  and  recurved  telencephalon  produced  by  the  extension 
of  the  secondary  fore-brain  vesicles  in  an  arcuate  manner.  It  is  along  this  arcuate 
and  fissure-like  gap  (Fig,  700)  that  the  richly  vascular  (pial)  choroid  plexus  invag- 
inates  the  atrophied  parietes  of  the  secondary  fore-brain  to  form  the  choroid  plexus 
which  is  everywhere  covered  by  ependyma.  The  choroid  fissure  extends  from  the 
foramen  of  Monro  to  near  the  tip  of  the  middle  cornu  in  an  arcuate  course,  and 
ependymal  reflections  everywhere  close  in  this  gap  except  at  the  foramen  of  Monro. 
The  manner  in  which  this  is  accomplished  may  best  be  understood  by  a  study 
of  a  trans-section  showing  the  ependymal  reflections  from  the  ventricular  wall 
onto  the  invaginated  choroid  plexus  (Figs.  670  and  698).  The  caudatothalamic 
fusion  and  the  intrusion  of  the  great  fibre  masses  constituting  the  cerebral  crura 
play  their  parts  in  complicating  the  relations  in  brains  of  higher  type. 


Fig.  700. — Diagram  showing  the  choroid  fissure.     (BichAt.) 


The  Choroid  Plexus  of  the  Lateral  Ventricle  and  Velum  Interpositum. — The  cho- 
roid plexus  is  a  highly  vascular,  fringe-like  structure  composed  of  pia  which  is 
invaginated  into  the  lateral  ventricle  along  the  choroid  fissure,  or  gap  between 
cerebral  hemisphere  and  diencephalon.  The  portion  of  the  choroid  plexus 
protruding  into  the  "body"  of  the  lateral  ventricle  is  the  fringed  vascular  bor- 
der— a  triangular  fold  of  pia — the  velum  interpositum  {tela  choroidea  superior), 
which,  as  its  name  implies,  is  interposed  between  the  relatively  small  primary 
fore-brain  and  the  enormous  overlapping  secondary  fore-brain,  and  is  produced 
by  the  overgrowth  of  the  latter  onto  the  former.  Inasmuch  as  the  nerve  tissue 
in  the  roof  of  the  third  ventricle  atrophies  totally,  the  ventral  fold  of  the  pia  comes 
into  contact  with  the  ependyma  of  that  ventricle  and  here  permits  a  similar 
vascular  invagination  in  the  form  of  two  parallel  fringes  hanging  into  the  cavity 
(diaplexus  or  choroid  plexuses  of  the  third  ventricle).  The  dorsal  leaf  of  the  pial 
fold  is  in  contact  with  the  ventral  face  of  the  body  of  the  fornix.  Frontad,  the 
velum  interpositum  tapers  toward  the  region  of  the  two  foramina  of  Monro, 
where  the  choroid  plexuses  of  the  two  sides  are  continuous  with  each  other. 
The  ventricular  surface  of  the  choroid  plexuses  is  everywhere  covered  by  ependyma 
which  is  reflected  from  it  to  the  fimbriated  edge  of  the  fornix  on  the  one  hand  and 
to  the  line  of  the  taenia  semicircularis  (over  the  thalamus  by  the  lamina  affixa) 
on  the  other.  Its  vascular  components,  in  addition  to  undefined  lymphatic 
channels,  are  the  anterior  choroid  artery,  a  branch  of  the  internal  carotid,  entering 


THE  CEREBRAL  IIEBIISPHERES 


941 


Fornix 

Thalamus 
Corpora  qnadr 


Fig.  701. — Diagram  showing  the  mode  of  formation  of  the  velum  interpositura. 


Fig.  702.— The  fornix,  velum  iuterpositum,  and  middle  cornu  of  the  lateral  ventricle 


942 


THE  NERVE  SYSTE3I 


the  plexus  of  the  middle  cornu ;  and  the  posterior  choroid  artery  from  the  posterior 
cerebral  artery  reaching  the  choroid  plexus  in  the  neighborhood  of  the  splenium. 
The  venules  of  the  plexus  join  to  form  a  tortuous  middle  cornual  vein  which 
terminates  frontad  by  joining  one  of  the  velar  veins. 

The  velar  veins  (veins  of  Galen),  one  on  either  side  close  to  the  median  line, 
running  in  the  fold  of  the  velum  interpositum,  are  formed  by  the  union  of  the 
tenial,  striatal,  and  middle  cornual  veins.  The  two  velar  veins  unite  to  form  a 
common  trunk  which  empties  into  the  straight  sinus. 

The  Hippocampus  and  Fornix. — The  hippocampus  and  the  fornix  merit  special 
description.  The  hippocampus,  as  seen  in  the  middle  cornu,  is  a  white  eminence 
about  5  cm.  (2  inches)  in  length,  of  a  curved  elongated  form,  enlarging  cephalad 
and  tapering  caudad  as  the  hippocampal  fissure  decreases  in  depth.  The  enlarged 
extremity  is  marked  by  alternate  elevations  and  depressions,  usually  three  in 
number,  the  hippocampal  digitations;  because  of  its  resemblance  to  a  lion's  paw  it 
is  sometimes  called  the  pes  leonis  or  pes  hippocampi.  The  white  appearance 
of  the  ventricular  aspect  of  the  hippocampus  is  due  to  a  stratum  of  white  substance, 
the  alveus,  made  up  of  myelinic  axones  from  hippocampal  cells  and  continued 
into  the  fimbria.     The  fimbria  is  folded  so  that  its  sharp  margin  is  directed 


Choroid  plexus 

Bulb  of  posterior  cornu 
Ccdcar 


Fissure  o/, 
Sylvius 


Fig.  703. — Posterior  and  descending 


Eminentia  collateralis 
Fimbria 
Hippocatnpus 
of  left  lateral  ventricle  exposed  from  the  aide. 


toward  the  cavity  of  the  middle  cornu;  eventually  its  fibres  will  be  seen  to  enter 
into  the  formation  of  the  fornix.  The  formation  of  the  hippocampus  is  best  ob- 
served in  a  coronal  section  (Fig.  686).  In  this  view  it  is  seen  to  be  a  peculiarly 
folded  margin  of  the  cerebral  cortex,  corrugated  by  the  intrusion  of  the  hippo- 
campal and  fimbriodentate  fissures.  Morphologically  it  is  a  vestigial  sub- 
merged portion  of  the  rhinencephalon,  as  a  part  of  which  it  has  already  been 
described  (p.  929). 

The  fornix  (Figs.  704,  705)  is  really  a  paired  structure  consisting  of  bilaterally 
symmetrical  halves  composed  of  longitudinally  directed  fibres  which  arch  on  each 
side  from  the  region  of  the  uncus  to  the  corpus  albicans.  The  two  lateral  parts 
join  each  other  in  the  mesal  plane  along  the  summit  of  the  arch  to  form  the  body 
of  the  fornix  {corpus  fornicis).     Frontad  they  diverge  slightly  as  they  proceed 


THE  CEREBRAL  HEMISPHERES 


943 


toward  the  corpus  albicans;  caudacl  they  diverge  more  widely.  The  paired 
diverging  portions  are  called  respectively  the  anterior  and  posterior  pillars  of  the 
fornix.  The  fibres  of  each  half  fornix  arise  from  the  pyramidal  cells  in  the  hippo- 
campus, and  their  course  will  be  traced  from  this  source  to  the  ending  in  the  corpus 


POCAMPAL 


Fig.  704. — The  fornix,  hippoc.ampal  commissure,  sple 


n,  and  dentate  gyre  seen  from  tiie  basal  aspect. 


albicans.  Beginning  at  first  as  a  stratum  of  white  substance  {alvevs)  consti- 
tuting the  ectal  surface  of  the  ventriculor  bulge  of  the  hippocampus,  the  fibres 
become  collected  along  its  medial  border  in  a  narrow  but  distinct  folded  band, 
the  fimbria.     This  increases  in  diameter  as  increments  are  added  to  it  along 


Fia.  70.5.— Diagram  of  the  fornix.     (E.  A.  S,) 


its  course,  until,  at  the  apical  region  of  the  trigonum  ventriculi,  it  leaves  the 
dwindling  hippocampus  to  ascend  in  a  curved  course  (dorsimesad)  toward  the 
subsplenial  callosal  surface  as  a  thick,  flattened  band.  Once  free  from  the  hippo- 
campus on  each  side,  the  two  converging  bands  of  opposite  sides  are  called  the 


944 


THE  NERVE  SYSTEM 


posterior  pillars  or  crura  fornicis.  The  majority  of  the  fibres  continue  frontad 
in  each  half  fornix,  but  a  number  course  transversely  to  enter  the  crus  fornicis 
of  the  opposite  side  to  end  in  the  hippocampal  formation.  These  fibres,  of 
transverse  course,  form  a  thin  lamina  filling  in  the  small  triangular  space  in  the 
subsplenial  region  between  the  converging  crura  fornicis  and  constituting  the 
hippocampal  commissure  (lyra;  psalterium).  Occasionally  a  small  recess  called 
Verga's  ventricle  is  formed  between  the  corpus  callosum  and  the  hippocampal 
commissure. 

The  two  half  fornices  now  become  joined  in  the  mesal  plane  and,  leaving  the 
subsplenial  surface  of  the  corpus  callosum,  dip  frontoventrad  in  an  arch — the 
body  of  the  fornix.  Its  caudal  part  is  broad  and  each  half  is  of  triangular  outline 
(on  section)  with  a  sharp  edge  directed  laterad.  Where  it  is  not  in  contact  with 
the  corpus  callosum  it  affords  attachment,  on  each  side  of  the  mesal  plane,  to 
the  hemiseptum  of  the  septum  lucidum.  Laterad  of  these  lines  of  attachment 
the  dorsal  surface  of  each  fornix  enters  into  the  formation  of  the  floor  of  the  lateral 


corpus  callosum 

caudate  nucleus 
Icaput) 

ANTERIOR   CORNl 
LATERAL  VENTRICLE^ 


E.  A.  S. 

PSEUDOCELE 

I  section  of  the  brain  slightly  caudad  of  the  genu  of  the  corpus  callosum. 


ventricle  and  is  covered  by  ependyma  (Fig.  697).  The  ventral  surface  rests 
upon  the  velum  interpositum,  which  separates  it  from  the  third  ventricle  and  the 
dorsal  surface  of  the  thalamus  (Fig.  670). 

Near  the  region  of  the  anterior  commissure  the  fornix  again  divides  into  its 
constituent  lateral  halves,  separating  as  rounded  strands  called  the  anterior 
pillars.  These  curve  ventrad  to  form  the  frontal  boundary  of  the  foramen 
of  Monro  and  thence  plunge  into  the  hypothalamic  gray,  inclined  slightly  caudad, 
to  end  in  the  corpus  albicans.  The  terminals  of  the  fornix  fibres  come  into  rela- 
tion with  the  cells  of  the  nucleus  of  the  corpus  albicans,  which,  in  turn,  give 
off  the  bifurcating  Y-shaped  axone  bundles  already  described  (p.  907). 

In  rare  instances  each  anterior  pillar  has  been  seen  to  divide  on  approaching 
the  anterior  commissure  a  part  passing  frontad  thereof  as  an  anomalous  pre- 
commissural pillar  of  the  fornix.  The  fornix,  in  its  course  from  hippocampus 
to  corpus  albicans,  gives  oft",  in  addition  to  those  described  as  hippocampal 
commissural  fibres,  axones  (a)  to  the  opposite  half  fornix,  decussating  in  the 
fused  portion  (body),  (6)  to  the  hemiseptum  of  the  septum  lucidum,  and  (c)  to 


THE  CEREBRAL  HEMISPHERES 


945 


the  gray  tissues  of  the  anterior  perforated  substance  (Fig.  685).  It  constitutes 
an  inner  olfactory  arc  as  distinguished  from  the  epicallosal  or  outer  arc,  repre- 
sented by  the  atrophied  indusium  and  its  longitudinal  striae. 


LATERAL  VENTRICLE 
CORPUS  CALLOSUNl 

(rostrum) 


Fig.  708.— a  coronal  section  of  the  brain  in  the  plane  of  the  anterior  commissure. 

The  Septum  Lucidum  {septum  pelhwidum). -The  so-called  septum  lucidum 
reallv  consists  of  two  vertically  placed  lamina  or  hemisepta.  Between  them  hes 
a  narrow,  enclosed  space,  the  cavum  septi  pellucidi  (pseudocele;  fifth  ^ent^lclej, 

60 


946  THE  NERVE  SYSTEM 

roofed  in  by  the  corpus  callosum,  while  the  floor  consists  of  the  fused  fornices 
and  the  rostrum.  Each  hemiseptum  bounds  a  part  of  the  anterior  cornu  and  body 
of  the  lateral  ventricle  in  its  mesal  wall,  and  in  a  lateral  view  is  of  triangular  out- 
line. The  hemisepta  represent  the  thin,  undeveloped  parts  of  the  mesal  walls 
of  the  cerebral  vesicles,  which  were  enclosed  within  the  rapidly  developing  arch  of 
the  corpus  callosum.  The  cavum  septi  pellucidi  is  therefore  a  closed-off  part 
of  the  original  intercerebral  cleft  and  not  a  part  of  the  neural  cavity,  as  its  older 
name,  "fifth  ventricle,"  seems  to  imply. 

The  Anterior  Commissure. — The  anterior  commissure,  or  precommissure,  is  a  bun- 
dle of  white  fibres,  of  oval  outline  in  a  sagittal  section,  which  crosses  the  midline  as 
a  localized  reenforcement  of  the  lamina  terminalis,  slightly  bulging  into  the  frontal 
part  (aula)  of  the  third  ventricle  and  clothed  by  its  ependyma.  It  is  a  comparatively 
insignificant  intercerebral  commissure  in  the  human  brain,  having  become  dimin- 
ished as  the  corpus  callosum  increased  in  mammalian  development.  It  courses 
from  side  to  side  frontad  of  the  anterior  pillars  of  the  fornix,  ventrad  of  the  head 
of  the  caudate  nucleus,  and  passes,  in  part,  through  the  frontal  end  of  the  lenticular 
nucleus  (Fig.  708) .  Its  fibres  radiate  chiefly  to  the  cortex  of  the  temporal  lobe  and 
to  certain  parts  of  the  rhinencephalon. 

The  bundle  is  slightly  twisted  in  each  lateral,  buried  part.  Two  divisions  are 
distinguishable:  (1)  The  pars  anterior  or  frontal  part  (in  the  median  plane)  con- 
tains two  groups  of  fibres  belonging  to  the  olfactory  apparatus — (a)  fibres  arising 
from  the  mitral  cells  in  the  olfactory  bulb  of  one  side  to  the  same  layer  in  the 
opposite  bulb;  (6)  fibres  which  associate  the  uncus  of  one  side  with  that  of  the 
other.  (2)  The  pars  posterior  contains  the  fibres  passing  between  the  cortices 
of  the  two  temporal  lobes. 

Gray  Masses  in  the  Cerebral  Hemisphere. — Aside  from  the  cortex,  the  cerebral 
hemisphere  contains  certain  gray  ganglionic  masses  in  its  interior,  more  or  less 
embedded  in  the  white  centrum,  and  called,  because  of  their  proximity  to  the  base 
of  the  cerebrum,  the  basal  ganglia.  These  comprise  the  caudate,  the  lenticular^ 
and  the  amygdaline  nuclei.  It  i*^  usual  to  include  the  claustrum  among  the  basal 
ganglia,  but  morphologically  this  structure  belongs  rather  to  the  insular  cortex  of 
the  island  of  Reil. 

Conventionally  the  caudate  nucleus  and  lenticular  nucleus  together  are  described 
as  the  corpus  striatum  (striatum),  a  ganglionic  mass  which  in  earlier  vertebrate 
brains  bore  intimate  relations  with  the  olfactory  apparatus,  but  later,  with  the 
rise  in  functional  dignity  and  growth  of  the  neopallium,  underwent  specialization 
and  difi^erentiation  concomitant  with  the  reduction  of  the  rhinencephalon.  The 
intrusion  of  great  projection  fibre  masses,  thrusting  the  cortical  gray  outward, 
has  not  been  everywhere  uniform,  and  we  still  find,  in  the  human  brain,  a  common 
ground  in  which  the  neopahial  cortical  gray,  the  corpus  striatum,  rhinencephalon, 
and  amygdaline  nucleus  meet^the  site  of  fusion  being  in  the  gray  substance 
of  the  anterior  perforated  substance.  To  the  cortical  mantle  they  are  regarded 
as  bearing  the  relation  of  subordinate  (subcortical)  centres.  In  the  human  brain 
the  corpus  striatum — so  called  because  of  its  striated  appearance  in  sections — 
is  composed  of  two  masses,  the  caudate  and  lenticular  nuclei,  directly  continuous 
with  each  other  at  their  frontal  ends  (Fig.  710).  The  connecting  gray  bridge 
becomes  broken  up  into  numerous  small  bands  of  gray  substance  as  the  fibre 
masses  of  the  internal  capsule  insinuate  themselves  between  the  two  nuclei 
(Fig.  707). 

The  caudate  nucleus  (nucleus  caudatiis;  caudatum)  (Figs.  709,  710)  presents  a 
ventricular  and  a  capsular  surface;  the  ventricular  surface,  covered  by  ependyma, 
forms  part  of  the  floor  of  the  body  and  anterior  cornu  of  the  lateral  ventricle,  while 
in  the  middle  cornu  it  is  a  constituent  of  its  roof,  owing  to  its  arched  contour  in  cor- 
respondence with  the  sweeping  curve  of  the  ventricle  itself.     It  is  of  a  pyriform 


THE  CEREBRAL  HEMISPHERES 


947 


shape  with  a  very  much  attenuated  tail.  The  large,  thick  head  projects  into  the 
anterior  cornu,  while  its  thinner  tail  is  prolonged  caudolaterad,  separated  from  the 
thalamus  by  the  narrow  taenia  semicircularis.  Following  the  curved  contour  of 
the  A'entricle  it  is  prolonged  as  a  narrow  gray  band  in  the  roof  of  the  middle  cornu, 
where  it  joins  the  amygdaline  nucleus.  The  nonventricular  or  capsular  surface  is 
embedded  in  the  white  substance  of  the  cerebral  hemisphere,  and  is  chiefly  related 
to  the  internal  capsule. 


The  ventricular  surface  shows,  in  microscopic  sections,  a  dense  ependymal 
lining.  The  capsular  face  is  not  sharply  outlined,  numerous  strands  of  fibres, 
to  and  from  the  internal  capsule,  entering  it  obliquely  so  as  to  appear  as  streaks 
which  extend  to  about  the  middle  of  the  ganglion,  there  separating  into  finer 
and  finer  strands  which  become  lost  to  the  naked  eye. 

The  lenticular  nucleus  (lenticula)  (Figs.  708  and  709)  is  wholly  embedded  in  the 
white  substance,  and  must  be  studied  in  sections.  In  its  shape  it  resembles  an 
irregular  triangular  pyramid  with  its  convex  base  directed  laterad  and  parallel  with 
and  near  to  the  cortical  expanse  of  the  island  of  Reil  and  of  about  the  same  extent. 
Its  ental,  apical  portion  is  directed  toward  the  interval  between  caudate  nucleus 


948 


THE  NERVE  SYSTE3I 


-AMYGDALA 


(head)  and  thalamus.  The  contour  and  slope  of  the  surfaces  of  the  ental  pyra- 
midal face  may  be  judged  from  the  model  pictured  in  Fig.  710.  Its  outline,  as 
revealed  in  sections  passing  in  different  planes,  is  shown  in  Figs.  708  and  711. 

Sections  of  the  lenticular  nucleus  show  it  to  be  composed  of  three^  concentric 
segments  separated  by  two  white  medullary  laminae.  The  segments  are  known  as 
articuli;  the  ectal  one  is  designated  the  putamen;  the  two  ental  zones  constitute 

the  globus  pallidas  (pallidum) .  The  puta- 
men is  the  larger  and  of  a  deeper  reddish- 
gray  tint;  the  two  mesal  divisions  are 
lighter  in  color  owing  to  a  greater  pro- 
portion of  radiating  streaks  of  white 
fibres  passing  to  and  from  the  internal 
capsule.  The  ectal  outline  of  the  puta- 
men is  sharply  defined  against  a  white 
lamina,  the  external  capsule. 

The  amygdaline  nucleus  (amygdala) 
is  usually  regarded  as  an  hypertrophied 
aggregation  of  the  temporal  cortex  which 
has  become  nearly  isolated  from  its 
cortical  connection  by  intruding  white 
substance.  It  is  a  rounded,  gray,  striated 
mass  situated  in  the  fore  part  of  the 
temporal  lobe  in  the  roof  of  the  middle 
cornu  at  its  apex,  where  it  produces  the 
bulging  called  the  amygdaloid  tubercle. 
Caudad  it  is  joined  by  the  tail  of  the 
caudate  nucleus;  frontad  it  is  continuous 
with  the  putamen.  Except  for  the 
marked  streaking  shown  in  sections, 
its  structure  is  like  that  of  the  cortex. 
Its  cells  apparently  give  rise  to  the  narrow 
band  of  fibres — the  taenia  semicircularis — 
which  courses  along  the  mesal  margin  of 
the  ventricular  surface  of  the  caudate  nucleus  throughout  its  arched  course 
and  ends  in  the  gray  of  the  anterior  perforated  substance,  so  that  it  nearly 
completes  a  circle. 

The  claustrum  is  a  thin  plate  of  gray  substance  embedded  in  the  white  substance 
which  intervenes  between  the  putamen  and  the  cortex  of  the  island  of  Reil, 
and  corresponds  in  extent  to  these.  Its  dorsal  edge  is  very  much  attenuated; 
traced  ventrad  it  thickens  considerably  and  becomes  continuous  with  the  surface 
gray  at  the  anterior  perforated  substance.  Its  ectal  surface  presents  alternate 
ridges  and  depressions  which  correspond  to  the  corrugations  of  the  cortex  of  the 
island  of  Reil.  The  "external  capsule"  intervenes  between  its  ental  face  and 
the  putamen  of  the  lenticular  nucleus.  From  the  cortex  of  the  island  of  Reil 
proper  it  is  separated  by  a  white  lamina  which  may  be  termed  the  periclaustral 
lamina  or  capsula  extrema.  Apparently  the  claustrum  is  the  thickened  and  isolated 
spindle-cell  stratum  of  the  cortex  of  the  island  of  Reil,  a  feature  which  may  be 
of  significance  in  relation  to  the  preponderatingly  associative  function  of  the  insular 
region. 

Internal  Capsule-  (Fig.  711). — Between  the  lenticular  nucleus  on  the  one  hand 
and  the  caudate  nucleus  and  thalamus  on  the  other  lies  the  internal  capsule,  a  broad 

1  Four  and  eveu  five  have  been  observed. 

^  The  terms  internal  capsule  and  external  capsule  owe  their  derivation  to  the  fact  that  the  lenticular  nucleus 
is  almost  completely  enveloped  by  white  substance  in  the  form  of  a  capsule.  Of  these  the  internal  or  mesal 
portion  is  relatively  massive,  while  the  external  or  lateral  portion  is  thin. 


Fig.  710.  -Two  views  of 
Lateral  aspect. 


I  model  of  the  striatum;  A. 
B.  Mesal  aspect.  (E.  A.  S.) 


THE  CEREBRAL  HEMISPHERES 


949 


band  of  white  fibres  which,  as  seen  on  horizontal  section,  appears  bent,  very  much 
as  a  leg  is  bent  on  the  thigh,  with  the  knee  (genu)  directed  mesad.  The  frontal 
or  caudatolenticular  division  or  limb  is  confined  between  the  opposed  faces  of 
the  caudate  nucleus  and  lenticular  nucleus.  The  genu  receives  the  mesal  apex 
of  the  lenticular  nucleus  in  its  hollow,  while  the  caudal  or  thalamolenticular 
limb  lies  between  the  opposed  faces  of  lenticular  nucleus  and  thalamus.  The 
frontal  limb  constitutes  about  one-third,  the  caudal  limb  two-thirds  of  the  internal 
capsule  mass. 


LAT.  VEN 

CAVUM  SE 

PELLUC 

CORTEX  OF  ISLfl 


EPIPHYSIS 

TAIL  OF  CAUDATE 

NUCLEUS 

HIPPOCAMPUS 

CHOROID    PLEXUS. 

OPTIC    RADIATIO 


-Horizontal  section  through  the  cerebrum 
appearance  on  the  right  sidi 


The  term  "internal  capsule"  is  often  loosely  employed  and  is  variously  stated 
to  include  fibre  tracts  which  do  not  course  between  the  cerebral  cortex  and  the 
"lower"  brain  centres.  In  a  strict  sense  it  is  a  mass  of  fibres  which  converge, 
like  the  sticks  of  a  fan,  toward  the  cerebral  base  and  into  the  crusta.  Dorsad 
of  the  basal  ganglia  the  fibres  radiate  in  various  directions,  streaming  among  the 
radiating  callosal  fibres  and  forming  the  so-called  corona  radiata.  Yet  other 
fibre  tracts  leave  and  enter  the  great  ganglia  at  various  altitudes  along  the  internal 
capsule,  and  we  must  therefore  distinguish  the  following  cerebral  fibre  systems. 

Projecting  systems,  ascending  and  descending  (in  the  functional  sense),  of 
longer  and  shorter  course,  connecting  the  cerebral  cortex  with  (a)  spinal  gray 
centres;  (h)  mid-brain  and  pontile  nuclei;  (c)  basal  ganglia  and  thalamus.     The 


950 


THE  NEBVE  SYSTEM 


last-mentioned  system  traverses  the  internal  capsule  to  a  greater  or  less  extent, 
but  does  not  continue  into  the  crusta.  These  various  systems  are  summarized  on 
page  956.  It  may  here  be  mentioned  that  the  internal  capsule,  topographically, 
exhibits  a  functional  dissociation  in  that  its  frontal  or  lenticulocaudate  limb  is 
composed  of  preponderatingly  corticipetal  fibres,  while  corticifugal  fibres  form  the 
major  portion  of  the  thalamolenticular  limb  (Fig.  712).     In  the  frontal  limb 

are  the  thalamofrontal  and  thala- 
mostriate fibres,  the  former  ending 
in  the  cortex  of  the  frontal  lobe, 
the  latter  in  the  caudate  and 
lenticular  nuclei.  The  chief  cor- 
ticifugal components  are  the  fron- 
topontile  tract,  and  fewer  fronto- 
thalamic  and  striatothalamic  fibres. 
The  frontopontile  tract  arises  in 
the  cortex  of  the  prefrontal  region, 
traverses  the  frontal  limb  of  the 
internal  capsule,  forms  the  ental 
sector  (one-fifth)  of  the  crusta, 
and  ends  in  the  nuclei  pontis. 

In  the  genu  and  the  thalamo- 
lenticular limb  of  the  internal 
capsule  course  several  important 
fibre  tracts  which  are  chiefly  cor- 
ticifugal. 

The  pyramidal  (motor)  tract,  in 
its  course  from  the  precentral 
cortex  to  the  lower  motor  centres, 
occupies  the  frontal  half  of  this 
limb.  The  portion  in  the  genu, 
often  designated  the  geniculate 
tract,  comprises  the  pyramidal 
fibres  which  are  destined  to  go  to 
the  facial  and  hypoglossal  nerve 
nuclei;  farther  caudad  lie,  in  suc- 
cession, the  fibres  going  to  the 
motor  centres  for  the  upper  and 
the  lower  extremity  and  trunk. 
More  posteriorly  pass  the  corti- 
cipetal fibre-systems  conveying 
sensor  impressions  from  the  per- 
iphery via  thalamus  (Fig.  712). 
The  most  caudal  segment  (also 
called  the  retrolenticular  part)  of 
the  internal  capsule  contains  (a) 
the  optic  radiation,  composed  of 
fibres  coursing  in  both  directions 
between  the  occipital  cortex  and  the  pulvinar,  external  geniculate  and  superior 
quadrigeminal  bodies;  (6)  the  auditory  radiation,  composed  of  fibres  passing 
in  both  directions  between  the  cortex  of  the  temporal  lobe  (auditory  centre) 
and  the  posterior  quadrigeminal  and  internal  geniculate  bodies;  (c)  the  occipito- 
pontile  and  temporopontile  tracts  from  the  occipital  and  part  of  the  temporal 
cortex,  coursing  through  the  caudal  segment  of  the  internal  capsule,  constituting 
the  ectal  (one-fifth)  sector  of  the  crusta  and  ending  in  the  nuclei  pontis.  In  ad- 
dition there  are  scattered  fibre  bundles  which  arise  from  the  ventral   portion  of 


Fig.  712. — Diagram  of  the  tracts  in  the  internal  capsule. 
Motor  tract  red.  The  sensor  tract  (blue)  is  not  direct,  but 
formed  of  neurones  receiving  impulses  from  below  in  the  thala- 
mus and  transmitting  them  to  the  cortex.  The  optic  radiation 
(occipitothalamic)  is  shown  in  violet. 


THE  CEREBRAL  IIEAIISPIIERES 


951 


the  thalamus,  enter  the  internal  capsule  to  pass  toward  the  cortex,  in  part  through 
the  lenticular  nucleus,  in  part  in  the  sublenticular  zone,  to  form  the  ansa  lenticu- 
laris.  The  reenforcement  of  this  sublenticular  white-fibre  tract  by  cortico- 
thalamic fibres  from  the  temporal  lobe  to  thalamus  forms  the  ansa  peduncularis. 
The  topographic  relations  of  the  various  tract  masses  as  seen  in  a  flatwise  section 
is  schematically  shown  in  Fig.  713;  on  the  whole,  they  cori'espond  to  the  cortical 
areas  with  which  they  are  connected. 


Fig.  713. — The  motor  tract.     (Modified  from  Poirier.) 

The  external  capsule  (Fig.  711)  is  a  thin  lamina  of  white  substance  interposed 
between  the  ectal  face  of  the  lenticular  nucleus  and  the  claustrum.  Dorsally, 
frontad  and  caudad,  at  the  corresponding  borders  of  the  lenticular  nucleus,  it 
joins  the  internal  capsule  mass,  while  ventrally  it  is  continuous  with  the  white 
centrum  of  the  temporal  lobe.  Its  comparatively  few  projection  fibres  course 
to  and  from  the  ventral  parts  of  the  thalamus;  its  chief  constituents  are  associa- 
tion axones  for  the  circuminsular  cortical  areas. 

Minute  Structure  of  the  Cerebral  Cortex  and  its  Special  Types  in  Different  Regions 

(Fig.  714). — A  section  of  the  cerebral  cortex  reveals  a  tendency  on  the  part  of  its  constituent 
cells  to  arrange  themselves  in  layers  which  alternate  with  zones  less  rich  in  cellular  elements. 
Among  the  cells  course  the  axones  arising  from  them  or  terminating  in  their  neighborhood. 
The  axones  are  chiefly  amyelinic,  though  some  are  myelinic  for  a  part  of  their  intracortical 


952 


THE  NER  VE  SYSTEM 


j?r- 


■1' 


y  MOLECULAR    LAVCH 


T' 


wMm 

mm 

Mm 

W 
m 


f 


course.     The  cells,  of  various  sizes  and  shapes,  together  with  their  dendrites  and  axones,  are 
embedded  in  a  matrix  of  neuroglia. 

The  nerve  cells  in  a  ti/pical  section  of  the  cortex  are  arranged  in  five  tangential  layers,  as  fol- 
lows: (1)  the  molecular  layer;  /2)  the  ectal  poljrmorphous  cell  layer;  ^.3)  the  layer  of  small 
pyramidal  cells;  (4J  the  layer  of  large  pyramidal  cells;  (5)  the  ental  polymorphous  cell  layer. 

The  molecular  layer  {neuroglia  layer)  lies  imme- 
diately subjacent  to  the  pia,  and  is  chiefly  made  up 
of  glia  cells  and  fibres,  among  which  the  dendrites  of 
the  subjacent  layer  of  cells  intrude. 

The  ectal  poljrmorphous  layer  cells  are  polygonal, 
triangular,  and  fusiform  in  shape,  and  tend  to  gather 
in  groups  in  certain  cortical  regions.  The  fusiform 
cells  are  placed  with  their  long  axes  parallel  (i.  e., 
tangential)  to  the  gyral  surface  and  are  presumably 
associative  in  function. 

The  Layer  of  Small  and  the  Layer  of  Large 
Pyramidal  Cells. — The  cells  in  the  second  and  third 
layers  may  be  studied  together,  since,  with  the  excep- 
tion of  the  difference  in  size  and  the  more  superficial 
position  of  the  smaller  cells,  they  resemble  each 
other.  The  body  of  each  cell  is  pyramidal  in  shape, 
its  base  being  directed  to  the  deeper  parts  and  its 
apex  toward  the  surface.  It  contains  granular  pig- 
ment, and  stains  deeply  with  ordinary  reagents. 
The  nucleus  is  nucleolated,  of  large  size,  and  round 
or  oval  in  shape.  The  base  of  the  cell  gives  off 
the  axone,  and  this  passes  into  the  central  white 
substance,  giving  off  collaterals  in  its  course  to  be 
distributed  as  a  projection,  commissural,  or  asso- 
ciation fibre.  Both  the  apical  and  basal  parts  of 
the  cell  give  off  dendrites.  The  apical  dendrite  is 
directed  toward  the  surface,  and  ends  in  the  molec- 
ular layer  by  dividing  into  numerous  branches,  all 
of  which  may  be  seen  to  be  studded  with  projecting 
bristle-like  processes  when  prepared  by  the  silver  or 
methylene-blue  method.  The  larger  pyramidal  cells, 
especially  in  the  precentral  gyre,  may  exceed  50  // 
in  length  and  40  /i  in  breadth,  and  are  termed  giant 
cells.  The  chief  function  of  the  small  pyramidal 
cells  is  commissural  and  associative.  The  chief 
function  of  the  large  pyramidal  cells  in  the  pre- 
central and  paracentral  cortex  is  motor,  but  they 
have  also  commissural  and  associative  functions. 

Layer  of  Ental  Polymorphous  Cells.— The  cells 
in  this  layer,  as  their  name  implies,  vary  greatly  in 
contour,  the  commonest  varieties  being  of  a  spindle, 

(,  \X\i]yC't//'i  ^,1  star,  oval,  or  triangular  shape.     Their  dendrites  are 

1  yn    \^\\'TiSli'i  directed    outward,    toward,    but    do    not  reach,  the 

'    '    ■*  molecular  layer;  their  axones  pass  into  the  subjacent 

white  substance.  From  this  layer  come  commissural 
fibres,  long  association  fibres,  and  some  projection 
fibres. 

There  are  two  other  kinds  of  cells  in  the  cerebral 
cortex,  but  their  axones  pass  in  a  direction  opposite 
to  that  of  the  pyramidal  and  polymorphous  cells, 
among  which  they  lie.  They  are:  (a)  the  cells  of 
Golgi,  the  axones  of  which  do  not  become  myelin- 
ated, but  divide  immediately  after  their  origin  into 
a  large  number  of  branches,  which  are  directed  toward  the  surface  of  the  cortex;  (6)  the  cells 
of  Martinotti,  which  are  chiefly  found  in  the  polymorphous  layer.  Their  dendrites  are  short, 
and  may  have  an  ascending  or  descending  course,  while  their  axones  pass  out  into  the  molec- 
ular layer  and  form  an  extensive  horizontal  arborization. 

Nerve  Fibres  in  the  Cortex.— These  fill  up  a  large  part  of  the  intervals  between  the  cells. 
Some  of  these  fibres  form  fasciculi;  some  are  isolated,  and  others  are  arranged  in  plexuses. 
They  may  be  myelinic  or  amyelinic,  the  latter  comprising  the  axones  of  the  smallest  pyramidal 
cells  and  the  cells  of  Golgi.     In  their  direction  the  fibres  may  be  either  transverse,  the  transverse 


m 


i 


'•f, 


^7« 


\m^i\ 


714. — Typical    arrangement   of    the   cell 
layers  in  the  cerebral  cortex. 


THE  CEREBRAL  HEMISPHERES  953 

tangential  or  horizontal  fibres,  or  vertical,  the  vertical  or  radial  fibres.    The  tangential  fibres 

run  parallel  to  the  .surface  of  the  hemisphere,  intersecting  the  vertical  fibres  at  a  riirht  an^le. 
They  consist  of  several  strata,  of  which  the  following  are  the  most  important:  (1)  A  stratum 
of  white  fibres  covering  the  superficial  aspect  of  the  molecular  layer;  (2j  the  band  of  Bech- 
terew,  found  in  certain  parts  of  the  superficial  portion  of  the  layer  of  the  smaller  pyramidal 
cells;  (3)  the  external  or  outer  band  of  Badllarger  or  the  band  of  Gennari,  which  runs  through 
the  layer  of  large  pyramidal  cells;  (4)  the  internal  band  of  Baillarger,  which  intervenes  between 
the  layer  of  large  pyramidal  cells  and  the  polymor]jhous  layer.  According  to  Cajal,  the  tangen- 
tial fibres  consist  of  (a)  the  collaterals  of  the  pyramidal  and  polymorphous  cells  and  of  the 
cells  of  Martinotti;  (6)  the  arborizations  of  the  axones  of  Golgi's  cells;  (c)  the  collaterals  and 
terminal  arborizations  of  the  projection,  commissural,  or  association  fibres.  The  vertical  fibres: 
Some  of  these — viz.,  the  axones  of  the  pyramidal  and  polymorphous  cells — are  directed  toward 
the  central  white  substance,  while  others — the  terminations  of  the  commissural,  projection,  or 
association  fibres — pass  outward  to  end  in  the  cortex.  The  axones  of  the  cells  of  Martinotti  are 
also  ascending  fibres. 

In  certain  parts  of  the  cortex  this  typical  structure  is  departed  from.  The  chief  of  these 
regions  are  (1)  the  occipital  lobe,  (2)  tlie  transtemporal  gjnres,  (3)  the  hippocampus,  (4)  the 
dentate  gyre,  and  (.5)  the  olfactory  bulb. 

Special  Types  of  Gray  Substance.  1.  The  Occipital  Lobe.— In  the  cuneus  and  the  calcarine 
fissure  of  the  occipital  lobe  Cajal  has  recently  described  as  many  as  nine  layers.  Here  the  inner 
band  of  Baillarger  is  absent;  the  outer  band  of  Baillarger  or  band  of  Gennari  is,  on  the  other 
hand,  of  considerable  thickness.  If  a  section  be  examined  microscopically,  an  additional  layer 
is  seen  to  be  interpolated  between  tire  molecular  layer  and  the  layer  of  small  pyramidal  cells. 
This  extra  layer  consists  of  two  or  three  strata  of  fusiform  cells,  the  long  axes  of  which  are  at 
right  angles  to  the  surface.  Each  cell  gives  off  two  dendrites,  external  and  internal,  from  the 
latter  of  which  the  axone  arises  and  passes  into  the  white  central  substance.  In  the  layer  of 
small  pyramidal  cells,  fusiform  cells,  identical  with  the  above,  are  seen,  as  well  as  ovoid  or  star- 
like elements  with  ascending  axones,  the  cells  of  Martinotti.  This  area  of  the  cortex  forms  the 
visual  centre,  and  it  has  been  shown  by  Dr.  .1.  S.  Bolton'  that  in  old-standing  cases  of  optic 
atrophy  the  thickness  of  Gennari's  band  is  reduced  by  nearly  .50  per  cent. 

2.  The  Transtemporal  Gyres  are  distinguished  by  a  reduction  of  thickness  of  the  pyramidal 
cell  layer  with  closer  approximation  of  the  giant  cells  to  each  other,  while  the  fusiform  cell  layer 
is  more  deeply  situated  than  elsewhere.  This  cortical  formation  is  the  end  station  for  cochlear 
nerve  projections. 

3.  In  the  Hippocampus  (Fig.  6S6)  the  molecular  layer  is  very  thick  and  contains  a  large  number 
of  Golgi  cells.  It  has  been  divided  into  three  strata :  (a)  S.  convolutum  or  S.  granulosimi,  con- 
taining many  tangential  fibres;  (6)  S.  lacunosum,  presenting  numerous  lymphatic  or  vascular 
spaces;  (c)  S.  radiatum,  exhibiting  a  rich  plexus  of  fibrils.  The  two  layers  of  pyramidal  cells  are 
condensed  into  one,  and  these  are  mostly  of  large  size.  The  axones  of  the  cells  in  the  polymorphous 
layer  may  run  in  an  ascending,  descending,  or  horizontal  direction.  Between  the  polymorphous 
layer  and  the  ventricular  ependyma  is  the  white  substance  of  the  alveus. 

4.  The  Dentate  Gyre. — In  the  rudimentary  dentate  convolution  the  molecular  layer  contains 
some  pyramidal  cells,  while  the  pyramidal  layer  is  almost  entirely  represented  by  small  ovoid 
elements. 

5.  The  Olfactory  Bulb  (Fig.  715). — In  many  of  the  lower  animals  tliis  contains  a  cavity  which 
communicates  through  the  hollow  olfactory  stalk  with  the  cavity  of  the  lateral  ventricle.  In  man 
the  original  cavity  is  filled  by  neuroglia  and  its  wall  becomes  thickened,  but  much  more  so  on  its 
ventral  than  on  its  dorsal  aspect.  Its  dorsal  part  contains  a  small  amount  of  gray  and  white 
substance,  but  this  is  scanty  and  ill  defined.  A  section  through  the  ventral  part  shows  it  to 
consist  of  the  following  layers  from  without  inward:  (1)  A  layer  of  olfactory  nerve  fibres,  which 
are  the  myelinated  axones  prolonged  from  the  olfactory  cells  of  the  nose,  and  which  reach  the 
bulb  by  passing  through  the  cribriform  plate  of  the  ethmoid  bone.  At  first  they  cover  the  bulb, 
and  then  penetrate  it  to  end  by  forming  synapses  with  the  dendrites  of  the  mitral  cells,  presently 
to  be  described.  (2)  Glomerular  layer  {stratum  glomerulosinn):  This  contains  numerous  sphe- 
roidal reticulated  enlargements,  termed  glomeruh,  which  are  produced  by  the  branching  and 
arborization  of  the  processes  of  the  olfactory  nerve  fibres  with  the  descending  dendrites  of  the 
mitral  cells.  (3)  Molecular  layer:  This  layer  is  formed  of  a  matrix  of  neuroglia,  embedded  in 
which  are  the  mitral  cells.  These  cells  are  pyramidal  in  shape,  and  the  basal  part  of  each  gives 
off  a  thick  dendrite  which  descends  into  the  glomerular  layer,  where  it  arborizes  as  above,  or,  on 
the  other  hand,  interlaces  with  similar  dendrites  of  neighboring  mitral  cells.  The  axones  pass 
through  the  next  layer  into  the  white  substance  of  the  bulb,  from  which,  after  becoming  bent  on 
themselves  at  a  right  angle,  they  are  continued  into  the  olfactory  tract.  (4)  Xervc  fibre  layer: 
This  lies  next  the  central  core  of  neuroglia,  and  its  fibres  consist  of  the  axones  or  aflerent  processes 
of  the  mitral  cells  which  are  passing  on  their  way  to  the  brain;  some  efferent  fibres  are,  however, 

'  Phil.  Trans,  of  Royal  Society,  Series  B,  vol.  cxciii,  p.  165. 


954 


THE  NERVE  SYSTEM 


also  present,  and  terminate  in  the  molecular  layer  and  presumably  come  via  the  anterior  com- 
missure from  the  mitral  cells  of  the  opposite  bulb. 

The  claustrum,  although  usually  enumerated  among  the  basal  ganglia,  is  probably  the  thick- 
ened and  isolated  deepest  layer  of  fusiform  cells  belonging  to  the  cortex  of  the  island  of  Reil. 
The  white  lamina'  intervening  between  it  and  the  cortex  proper  consists  of  association  axones 
of  longer  and  shorter  course 

Summary  of  the  Cerebral  Fibre  Systems. — ^The  white  substance  of  the  cerebrum 
consists  of  myelinic  fibres  intricately  interwoven  but  permitting  of  classification 
into  three  systems  arranged  according  to  the  course  they  take.  These  systems 
comprise:  (1)  association  fibres,  which  connect  neighboring  or  distant  parts 
within  the  same  cerebral  hemisphere;  (2)  commissural  fibres,  which  unite  allied 
parts  in  the  two  cerebral  halves  and  come  transversely  across  the  midline  to  form 
the  commissures;  (3)  projection  fibres,  which  connect  the  cerebral  cortex  with 
lower  centres  in  the  brain  and  spinal  cord,  and,  conversely,  those  fibres  which 
connect  lower  centres  with  the  cerebral  cortex. 


'Wliite  substance  {dorsal  part) 


Neuroglia 


ance  [ventral- 
part) 

Medullary  layer 
Mitral  cells 


Glomerular  layer 


Layer  of  olfactory  nerve  fibres 
Fig.  715. — Coronal  section  of  olfactory  bulb.     (Schwalbe.) 

1.  The  association  fibres  (Fig.  716)  connect  different  structures  in  the  same  hemi- 
spheres, and  are  in  or  near  to  the  cortex.  They  take  origin  from  the  small  pyram- 
idal and  polymorphous  cells  of  the  deep  layer  of  the  cortex.  Their  direction  is 
parallel  to  the  surface  of  the  hemisphere,  and  in  their  course  they  cross  the  pro- 
jection and  commissural  fibres.  They  are  of  two  kinds:  (1)  Those  which  unite 
adjacent  convolutions,  short  association  fibres;  (2)  those  which  pass  between  more 
distant  parts  in  the  same  hemisphere,  long  association  fibres. 

The  short  association  fibres  are  situated  immediately  beneath  the  gray  cortex  of 
the  hemispheres,  and  connect  adjacent  convolutions.  Tlaey  constitute  subcortical 
tracts  and  are  divided  into  arcuate  fibres  and  tangential  fibres.  Thus,  some  of 
these  fibres  connect  the  "visual  sensor  area  with  the  visual  memory  area,  and 
the  auditory  sensor  with  the  auditory  memory  area." 

The  long  association  fibres  associate  cerebral  centres  which  are  far  apart.  They 
are  gathered  into  bundles  and  dip  down  deep  into  the  centrum  ovale.  They 
include  the  following:  (o)  the  uncinate  fasciculus;  (b)  the  superior  longitudinal 
fasciculus;  (c)  the  inferior  longitudinal  fasciculus  (doubtful);  (d)  the  cingulum;  and 
(e)  the  fasciculus  rectus. 


'  Previously  described  as  the  periclaustral  Ian 


capsula  extrema  (p.  94S\ 


THE  CEREBRAL  HEMISPHERES 


955 


(a)  The  uncinate  fasciculus  (/.  uncinatvs)  passes  between  the  uncinate  gyre 
and  the  orbital  portion  of  the  frontal  lobe;  in  its  course  it  curves  beneath  the 
depths  of  the  basisylvian  fissure  (Fig.  716). 

(b)  The  superior  longitudinal  fasciculus  (/.  longitudinal  is  superior)  (Fig.  716) 
is  beneath  the  convex  surface  of  the  hemisphere  arching  over  the  lenticular 
nucleus.  It  joins  the  frontal  cortex  with  the  parietal  and  temporal  cortex  and 
brings  into  relation  the  motor  speech  centres  and  the  centres  of  auditory  and 
visual  memories. 

(c)  The  inferior  longitudinal  fasciculus  (f.  longitudinalis  inferior)  is  usually 
described  as  a  tract  associating  the  centres  of  auditory  and  visual  memory.  Such 
association  fibres  undoubtedly  exist,  but  it  is  doubtful  whether  they  are  collected 
into  a  distinct  fasciculus.     The  bundle  which  is  usually  designated  by  this  term 


E.  A.  S. 
Fig.  716. — Diagram  showing  the  principal  systems  of  associating  fibres  in  the  cerebrum. 

has  been  proved  to  be  in  part  the  projection  system  between  the  occipital  cortex  and" 
the  thalamus  and  external  geniculate  body  (E.  Redlich)  and  in  part  also  the  fibres 
from  the  temporal  cortex  (meditemporal  and  subtemporal  gyre)  to  the  crusta.' 

(d)  The  cingulum,  also  called  the  fornix  periphericus,  is  a  band  of  white  fibres 
that  course  in  the  white  substance  of  the  callosal  gyre  and  runs  excentrically  to 
the  corpus  callosum.  Its  fibres  may  be  traced  frontad  into  the  mesal  olfactory 
stria  and  the  anterior  perforated  substance,  while  caudad  they  radiate  into  the 
hippocampus.  It  may  be  regarded  as  an  association  tract  of  the  rhinencephalon 
akin  to  the  fornix. 

(e)  The  fasciculus  rectus  or  perpendicular  fasciculus  runs  dorsoventrad  in  the 
occipitoparietal  transition  and  associates  the  subparietal  gyres  with  the  medi- 
and  subtemporal  gyres;  a  part  of  the  fasciculus  associates  the  dorsal  occipital 
region  with  its  ventral  part  and  with  the  subcollateral  gyre  (Fig.  716). 

■  The  fornix,  previously  described,  may  be  enumerated  among  the  long  associa- 
tion tracts;  it  belongs  exclusively  to  the  olfactory  apparatus. 

2.  The  commissural  fibres  are  grouped  under  the  following  heads:  (a)  the 
corpus  callosum,  described  on  page  933;  (h)  the  anterior  commissure,  described  on 
page  946;  and  (c)  the  hippocampal  commissure,  described  on  page  944. 


^E.  J.  Curran  (Jour.  Comp.  Neurol,  and  Psychol.,  : 
ferior  "  coursing  ventrolaterad  of  the  lenticular  nuclei 


.  6,  Dec,  1909)  describes  a  "fasciculus  occipitofrontalis 


956 


THE  NERVE  SYSTEM 


3.  The  projection  fibres  connect  the  cerebral  cortex  with  lower  brain  centres 
(caudate  and  lenticular  nuclei,  thalamus,  hypothalamic  region,  corpora  quadri- 
gemina,  pons,  medulla  oblongata),  and  with  the  spinal  cord  centres.  They 
either  project  impulses  from  the  cortex  to  the  periphery  or  bring  in  impressions 
from  without.  Their  radiations  to  and  from  the  cortex,  together  with  the  radia- 
tions of  the  callosal  fibres,  give  rise  to  the  characteristic  appearance  of  the  corona 
radiata.  We  may  distinguish  the  projection  tracts  of  long  course  from  those  of 
short  course,  and,  in  the  functional  sense,  those  that  are  centrifugal,  descending, 
or  motor,  from  those  that  are  centripetal,  ascending,  or  sensor.  The  last  mode 
of  classification  is  more  desirable. 


PRECENTB<i, 


CENTRAL    FISSURE 


Fig.  717. — The  projection  tracts  joining  the  cortex  with  lower  nerve  centres.  Sagittal  section  showing  the 
arrangements  of  tracts  in  the  internal  capsule-  A.  Tract  from  the  frontal  lobe  to  the  frontal  half  of  the  capsule, 
thence  in  part  to  the  optic  thalamus,  A-,  and  in  part  to  the  pons,  and  thus  to  the  cerebellar  hemisphere  of  the 
opposite  side.  B.  Motor  tract  from  the  precentral  convolution  to  the  facial  nucleus  in  the  pons  and  to  the 
spinal  cord.  C.  Sensor  tract  from  dorsal  columns  of  the  cord,  through  the  dorsal  part  of  the  medulla  oblon- 
gata, pons,  crus,  and  capsule  to  the  parietal  lobe.  Z>.  Visual  tract  from  the  thalamus  (OT)  to  the  occipital 
lobe.  E.  Auditory  tract  from  the  internal  geniculate  body  (to  which  a  tract  passes  from  the  VIII  N.  nucleus) 
to  the  temporal  lobe.  F.  Superior  peduncle.  G.  Middle  peduncle.  H.  Inferior  peduncle.  CN.  Caudate 
nucleus.     CQ.  Corpora  quadrigemina.     The  numerals  refer  to  the  cranial  nerves.     (Starr.) 


1.  Descending  (corticifugal)  tracts  are  composed  of  axones  arising  from  the 
cortical  pyramidal  cells. 

(a)  The  pyramidal  or  motor  tract  from  the  "motor  area,"  comprising  the  pre- 
central gyre  and  paracentral  gyre,  courses  through  the  genu  and  frontal  two- 
thirds  of  the  thalamolenticular  limb  of  the  internal  capsule,  forms  the  middle 
(three-fifths)  sector  of  the  crusta,  and  passes  through  the  pons  into  the  medulla 
oblongata  and  spinal  cord.  The  tract  may  be  subdivided  into  a  corticobulbar  and 
a  corticospinal  division. 

The  corticobulbar  division  is  the  pyramidal  tract  to  the  efferent  cranial  nerve 
nuclei.  Only  those  fibres  which  are  destined  to  go  to  the  facial  and  hypoglossal 
can  be  traced  throughout.  They  originate  in  the  ventral  part  of  the  precentral 
gyre  (face  and  tongue  centre),  course  through  the  genu  of  the  internal  capsule. 


THE  CEREBRAL  HEMISPHERES 


957 


and  end,  contralaterally,  in  relation  with  the  facial  and  hypoglossal  nerve  nuclei 
(also  called  the  emissary  speech  tract). 

The  corticospinal  division  arises  from  the  remainder  of  the  motor  area,  courses 
throuoh  the  frontal  two-thirds  of  the  posterior  limb  of  the  internal  capsule, 
through  crusta,  pons,  and  medulla  oblongata,  to  form  the  pyramids,  and,  under- 
going partial  decussation,  forms  the  direct  and  the  crossed  pyramidal  tracts 
described  in  the  spinal  cord. 

(h)  The  frontopontile  tract  {Arnold's  bundle)  arises  in  the  midfrontal  cortex, 
courses  through  the  internal  capsule  (caudal  part  of  frontal  limb),  forms  the  mesal 
sector  (one-fifth)  of  the  crusta,  and  ends  in  the  nuclei  pontis. 

(c)  The  temporopontile  tract  {Tiirck's  bundle)  arises  in  the  cortex  of  the  tem- 
poral lobe,  descends  through  the  internal  capsule  (caudal  segment),  forms  the 
ectal  (one-fifth)  sector  of  the  crusta,  and  ends  in  the  nuclei  pontis.  The  existence 
of  occipitopontile  fibres  is  denied  by  Archambault  in  a  recent  contribution  (1906). 

(d)  The  occipitomesenceph{ilic  tract  arises  in  the  visual  area  (cuneus  and  cal- 
carine  formation),  courses  through  the  retrolenticular  part  of  the  internal  capsule, 
to  end  in  the  superior  quadrigeminal  body  and  in  relation  with  the  nuclei  for  move- 
ments of  the  eyeball. 

(e)  Part  of  the  fibres  composing  the  optic  radiation  are  corticipetal,  arising  in 
the  occipital  cortex  and  ending  in  the  pulvinar  of  the  thalamus  and  the  external 
geniculate  body. 


GRANULE 


Fig.  71S. — Schema  of  the  olfactory  bulb  and  tract  neurones. 

2.  Ascending  (corticipetal)  tracts  arise  mostly  from  the  nuclei  of  the  thalamus 
and  hj'pothalamus,  mid-brain,  and  cerebellum. 

(a)  The  terminal  or  cerebral  part  of  the  general  sensor  pathway  of  the  body 
comprises  the  axones  arising  in  the  cells  of  the  lateral  nucleus  of  the  thalamus 
and  the  hypothalamic  nucleus — interposed  way-stations  which  transfer  the  im- 
pressions carried  along  the  medial  lemniscus  from  the  nuclei  of  the  gracile  and 
cuneate  fasciculi  in  the  myeloblongata  transition.  They  convey  sensor  impres- 
sions from  the  body  periphery  to  the  somesthetic  area  of  the  cortex — chiefly  the 
postcentral  and  parietal  gyres. 

(b)  The  terminal  or  cerebral  part  of  the  general  sensor  pathway  of  the  head  and 
neck  comprises  the  axones  which  arise  from  the  alferent  cranial  nerve  nuclei 
(excepting  the  auditory)  and  course  along  the  medial  lemniscus  to  the  thalamus 
and  hypothalamic  nucleus,  to  be  thence  projected  to  the  somesthetic  cerebral 
cortex. 

(c)  The  terminal  or  cerebral  part  of  the  auditory  pathway  from  the  inferior  quadri- 
geminal body,  internal  geniculate  body,  and  the  interposed  nucleus  of  the  lateral 
lemniscus,  ending  in  the  auditory  sphere  of  the  cerebral  cortex. 

(d)  The  terminal  part  of  the  visual  pathway,  described  on  pages  909-911. 


958  THE  NEB  VE  SYSTEM 

(e)  The  terminal  (ascending)  cerebellocortical  pathway,  arising  as  the  fibres  of 
the  superior  peduncles  of  the  cerebellum,  decussating  and  ending  in  the  red  nucleus 
and  lateral  nucleus  of  thalamus,  is  thence  directly  projected  by  new  axones  to  the 
somesthetic  cortical  area,  or  indirectly  projected  via  thalamus  (lateral  nucleus). 

Connections  of  the  Corpus  Striatum. — The  connections  of  the  caudate  and  len- 
ticular nuclei  with  each  other  and  with  the  cortex  may  be  summarized  as  follows: 

(a)  Fibres  from  the  cortex  to  the  caudate  and  lenticular  nuclei,  entering  into 
the  formation  of  the  corona  radiata. 

(6)  Fibres  from  the  caudate  nucleus  and  putamen  of  the  lenticular  nucleus 
coursing  to  the  thalamus  and  hypothalamic  region.  Those  from  the  caudate 
nucleus  pass  through  the  internal  capsule  to  traverse  the  globus  pallidus,  are  joined 
by  the  fibres  from  the  putamen  to  again  traverse  the  internal  capsule  and  end 
in  the  thalamus,  forming  the  striatothalamic  radiation. 

(c)  Fibres  coursing  ventrad  in  the  medullary  laminse  of  the  lenticular  nucleus, 
and  reenforced  by  additional  fibres  from  the  globus  pallidus,  course  mesad  to 
the  hypothalamic  region  to  form  the  subthalamic  radiation  or  ansa  lenticularis 
(described  on  p.  951).  This  radiation  is  further  reenforced  by  the  ventral  stalk 
of  the  thalamocortical  radiation  to  form  the  ansa  peduncularis  (described  on  p.  951). 

The  Olfactory  Pathways.  1.  Peripheral  Pathway. — Impressions  from  the 
upper  portion  of  the  Schneiderian  mucous  membrane  pass  along  the  olfactory  fila 
(central  processes  of  the  intraepithelial  bipolar  olfactory  cells)  to  the  glomeruli 
olfactorii  in  the  olfactory  bulb  (Fig.  718). 

2.  Central  Pathway. — In  the  glomeruli  the  impression  is  transmitted  to  the 
brush-like,  dendritic  endings  of  the  mitral  ceils  and  brush  cells;  the  axones  of 
these  cells  carry  the  impression  centrad  to  the  gray  masses  of  the  olfactory  tract, 
trigonum  olfactorium,  anterior  perforated  substance,  and  adjacent  parts  (Fig. 
713).    These  constitute  the  primary  centres. 

The  primary  centres  are  connected  with  secondary  or  cortical  centres  (hippo- 
campus, gyrus  dentatus,  uncus)  by  the  following  tracts:  (1)  Lateral  olfactory 
strise,  from  the  olfactory  trigone  to  the  uncus,  ending  in  the  gyrus  ambiens  and 
gyrus  semilunaris  (p.  928).  (2)  Axones  from  cells  in  the  olfactory  trigonal 
gray  through  the  fornix  to  hippocampus.  (3)  Striae  mediales  (Lancisii)  from  the 
trigone  into  gyrus  subcallosus  around  the  corpus  callosum  to  gyrus  dentatus  and 
hippocampus. 

The  amygdaline  nucleus  is  by  some  regarded  as  a  cortical  centre  to  which 
impressions  are  carried  by  the  taenia  semicircularis. 

The  fornix  fibres  arise  from  the  pyramidal  cells  in  the  hippocampus  and  the 
polymorphous  cells  of  the  dentate  gyre.  Some  fibres  traverse  the  median  plane 
as  the  hippocampal  commissure  to  the  opposite  hippocampus;  the  remainder  end 
in  the  corpus  albicans,  gray  nucleus,  or,  in  small  part,  are  retroflexed  as  the  stria 
medullaris  thalami  to  the  habenular  ganglion.  In  the  corpus  albicans  impressions 
are  transmitted  to  the  cells  of  two  nuclear  masses;  from  the  medial  nucleus  arise 
axones  constituting  the  fasciculus  albicantis  princeps,  each  axone  bifurcating 
and  the  diverging  bundles  forming,  respectively,  the  albicantiothalamic  and  the 
albicantiotegraental  fasciculi  (p.  907). 

The  stria  medullaris  thalami  consists  of  the  following  bundles  ending  in  the 
habenular  ganglion:  (a)  Axones  from  hijppocampus  via  fornix — the  cortico- 
habenular  tract;  (b)  axones  from  the  hemiseptum  of  the  septum  lucidum  and 
olfactory  gray — the  olfactohabenular  tract;  (c)  axones  from  the  thalamus  to  the 
habenular  ganglion — the  thalamohabeoular  tract.  In  the  habenular  ganglion 
axones  arise  which  pass  as  a  distinct  bundle  ventrad  through  the  tegmentum  to 
the  gray  of  the  posterior  perforated  substance  (ganglion  interpeduncidare  [inter- 
crurale]  of  Gudden) — the  fasciculus  retroflexus  of  Meynert. 

The  primary  olfactory  centres  of  the  two  sides  are  connected  by  the  'pars 


CORTICAL  LOCALIZATION  OF  FUNCTION 


959 


olfacforia  of  the  anterior  commissure,  a  bundle  of  fibres  passing  from  side  to  side 
to  end  in  the  tract,  granular  stratum,  and  glomerular  layer  of  the  bulb.  Further 
connections  are  established  with  the  tuber  cinereura,  mid-brain,  and  even  spinal 
centres;  one  division  has  been  named  the  olfactomesencephalic  tract  (Wallenberg). 
The  cingulum  or  fornix  periphcricus  is  an  arcuate  association  bundle,  or 
rather  an  arcuate  series  of  short  bundles  which  establishes  the  connections  of  the 
rhinencephalon  with  the  adjacent  cortical  areas  (p.  955). 

CORTICAL  LOCALIZATION  OF  FUNCTION. 

Patient  researches  conducted  along  clinicopathological,  experimental,  physiological,  and  de- 
velopmental lines  have  furnished  us  with  a  topographic  map  of  the  somesthetic  and  sense 
areas,  and,  inferentially,  of  the  association  areas  of  the  cerebral  cortex.  The  somesthetic  and 
sense  areas  constitute  less  than  one-third  of  the  cortical  area,  while  the  remainder  is  presumed 
to  be  devoted  to  the  elaboration  of  the  higher  mental  activities  manifested  by  abstract  thought, 
ideation,  reasoning,  and  language.  The  acquisition  of  these  specifically  human  mental  attri- 
butes has  been  the  chief  factor  in  bringing  about  the  superior  structure  of  the  human  brain,  and 
those  cortical  regions  which  were  subjected  to  increased  associations  rose  in  functional  dignity 
and  increased  in  size.  With  over  nine  billion  functional  nerve  cells  in  the  human  cerebral 
cortex  devoted  to  the  mental  processes,  and  less  than  one-third  of  these  concerned  with  emissary 
and  receptive  functions,  the  intricacy  and  capacity  of  the  human  brain  for  the  manifold  registra- 
tion of  sensations  and  the  numerous  transformations  that  characterize  man's  mental  processes 
far  exceed  that  of  any  other  animal. 


-Mesal  view  of  left  cerebral  hemisphere,  showing  localization  of  functions, 
fissin-es  and  gyres  is  the  same  as  in  Fig.  679. 


The  schema  of  the 


The  delineation  of  areas  called  motor,  visual,  auditory,  etc.,  is  not  to  be  deemed  as  mathe- 
matically accurate  or  sharply  defined  as  the  boundaries  of  a  State,  county,  or  township.  The 
areas  rather  shade  off  in  a'difi'use  manner,  and  the  arbitrary  demarcations  employed  in  the 
appended  figures  merely  show  the  maximum  concentration  of  those  cortical  parts  which  most 
distinctly  appertain  to  the  function  alleged  for  them. 

The  ]>rliii'i|ial  areas  that  are  known  to  be  functionally  differentiated  are  the  following: 
1.  Motor  Area.— The  motor  area  comprises  the  precentral  gyre  and  parts  of  the  frontal  gyres 
adjacent  thereto,  together  with  the  paracentral  gyre  and  the  adjacent  portion  of  the  superfrontal 
gyre  on  its  mesal  face.  Stimulation  of  various  parts  of  this  area  causes  movement,  while  their 
destruction  impairs  or  abolishes  voluntary  movements.  Within  this  motor  area  may  be  defined 
districts  which  are  cortical  projections  of  the  muscular  systems  of  the  body.  Thus,  movements 
of  the  lower  limb  seem  to  be  controlled  by  the  dorsal  part  of  the  precentral  and  the  paracentral 
gyre;  the  trunk  musculature  by  the  area  lying  frontad  both  on  the  mesal  aspect  and  in  the  dorsal 


960 


THE  NER  VE  SYSTEM 


superfrontal;  the  upper  limb  seems  to  be  controlled  by  the  midportion  of  the  precentral;  while 
the  facial  musculature  is  projected  in  the  ventral  part.  The  motor  regions  for  the  tongue, 
larynx,  muscles  of  mastication,  and  pharynx  lie  in  the  frontal  opercular  part;  and  the  movements 
of  the  head  and  eye  are  dominated  by  the  medifrontal  gyre,  adjacent  to  the  precentral.  Re- 
calling the  fact  that  the  pyramidal  (motor)  tract  decussates  in  its  course  to  the  primary  motor 
centres,  it  follows  that  the  motor  centres  in  one  cerebral  hemisphere  control  the  movements  of 
the  opposite  side  of  the  body.  As  elsewhere  in  the  cortex,  these  motor  areas  gradually  pass  one 
into  the  other  and  the  boundaries  are  indeterminate.  The  localization  of  motor  function  is 
rather  for  coordinated  groups  of  muscles  than  for  individual  muscles;  as  a  rule,  the  most  powerful 
articulation,  as  the  thigh  and  the  shoulder,  is  localizable  frontad  in  the  respective  limb  centres, 
while  the  smaller  articulations  and  those  differentiated  as  regards  motility  (digits,  etc.)  are  local- 
izable more  posteriorly. 

2.  Sensor  Areas. — (a)  The  area  for  tactile  and  temperature  impressions  is  more  intensely 
localized  in  the  postcentral  gyre  and  in  corresponding  order  with  its  neighboring  precentral 
motor  areas;  that  is  to  say,  there  is  the  most  intimate  intercommunication  between  the  sensor 
and  the  motor  regions  which  preside  over  corresponding  parts  of  the  body.  So  closely  coupled 
are  the  related  sensor  and  motor  cells  in  the  highest  category  of  the  reflex  arc  system  represented 
in  the  cerebral  cortex  that  both  sensor  and  motor  areas  are  included  under  the  term  of  somes- 
thetic  or  sensomotor  area,  devoted  to  the  registration  of  cutaneous  impressions,  impressions 


The  schema  of  the  fissures 


from  the  muscles,  tendons,  and  joints;  in  short,  the  sense  of  movement.  The  cortical  area 
embraced  by  the  parietal  gyre,  together  with  its  extension  in  the  precuneus  on  the  mesal 
aspect,  appears  to  be  devoted  to  the  concrete  perception  of  the  form  and  solidity  of  objects, 
and  is  therefore  termed  the  stereognostic  sense  area. 

(6)  The  auditory  area  is  localized  in  the  middle  and  posterior  thirds  of  the  supertemporal  gjTe 
and  in  the  adjacent  transtemporal  gyres  in  the  sylvian  cleft. 

(c)  The  visual  area  is  most  intensely  localizable  in  the  region  of  the  calcarine  fissure  as  well 
as  in  the  cuneus  as  a  whole.  There  seems  to  be  an  interrelation  between  the  visual  function  and 
the  special  type  of  cortex  already  described,  and  chiefly  characterized  by  the  stripe  of  Gennari. 

{d)  The  olfactory  area  comprises  the  uncus,  frontal  part  of  hippocampus,  indusium,  sub- 
callosal g}Te,  |iarolfactory  area,  and  anterior  perforated  substance. 

(e)  The  gustatory  area  has  not  yet  been  accurately  localized;  presumably  it  lies  in  the  neigh- 
borhood of  the  olfactory  area  in  the  temporal  lobe  (uncinate  and  hippocampal  gyre?). 

3.  The  Language  Areas. — The  cortical  zone  of  language  comprises  certain  specialized  areas 
which  take  part  in  the  intimate  relations  of  speech  to  thought  expression,  to  memory,  in  its 
reading  form  to  sight,  in  writing  to  manual  muscular  innervation,  and  in  "word  understanding" 
to  hearing. 

(a)  The  emissive  {articular)  centre  for  speech  is  localized  in  the  region  of  the  junction  of  the 
subfioiital  gyie  with  the  precentral  gyre — a  region  known  to  be  intimately  related  to  the  control 


CORTICAL  LOCALIZA  TION  OF  FUNCTION 


961 


of  the  muscles  used  in  speech  (larynx,  tongue,  jaw  muscles).     Destruction  of  this  region  at  least 
causes  a  loss  or  disturbance  of  articulation  of  words. 

(6)  The  auditory  perceptive  centre,  clinically  known  as  the  centre  of  "word  deafness,"  is 
localized  in  the  marginal  gyre  and  adjacent  parts  of  the  super-  and  meditcMi])oral  gyres,  espe- 
cially the  latter.  A  patient  suffering  with  a  lesion  of  this  area  may  cicaiiy  liciir  hut  not  under- 
stand the  spoken  word.  This  division  of  the  centre  might  also  be  called  the  lalognmtic  (word- 
understanding)  centre. 

(c)  The  visual  perceptive  centre,  clinically  known  as  the  centre  of  "word  blindness,"  is  local- 
ized in  the  angular  gyre  Lesion  of  this  area  renders  the  patient  incapable  of  understand- 
ing the  significance  of  the  words  and  objects  which  he  sees. 

(d)  An  emissive  "writing"  centre,  not  positively  proved  to  exist,  has  been  localized  in  the 
medifrontal  gyre,  frontad  of  the  motor  area  for  the  upper  limb. 

((?)  Of  not  a  lift  le  importance  with  reference  to  the  intellectual  control  of  the  faculty  of  language 
is  the  island  of  Reil,  purely  an  association  centre,  serving  to  connect  the  various  receptive  sense 
areas  relating  to  the  understanding  of  the  written  and  spoken  word  with  the  somesthetic  emissary 
centre  related  to  articulate  speech  and  writing;  in  other  words,  a  centre  for  language-arrangement. 


divaricated  to  expose  the  island  of  Reil. 


The  union  of  the  various  centres  enumerated  above  forms  the  cortical  zone  of  language, 
and  is  most  intensely,  if  not  exclusively,  localized,  or  at  least,  active,  in  the  left  cerebral  hemi- 
sphere in  right-handed  persons,  and  vice  versa  in  left-handed  persons, 

4.  The  Association  Areas. — The  remaining  area  of  the  cerebral  cortex  is  presumably  the 
organic  substratum  for  the  higher  psychic  activities.  At  the  present  time  not  much  is  known 
about  them,  but  broadly  stated  the  frontal  association  area  is  concerned  rather  with  the  powers 
of  thought  in  the  abstract — creative,  constructive,  and  philosophic.  The  parieto-occipito- 
temporal  association  area,  on  the  other  hand,  seems  to  be  more  concerned  with  the  powers  of 
concepliim  of  the  concrete,  for  the  comprehension  of  analogies,  comparing,  generalizing,  and 
systemaliziiig  things  heard,  observed,  and  felt. 

The  great  extent  of  the  association  areas  in  the  human  brain  is  a  somatic  expression  of  man's 
possession  of  an  associative  memory  or  ability  to  register  and  compare  sensations  far  greater  than 
that  of  the  highest  ape.  The  pattern  of  the  ifissures  and  gyres  in  the  brains  of  the  higher  anthro- 
poids and  man  presents  the  same  general  features  in  all  these  types.  In  the  course  of  evolution, 
however,  the  regions  known  as  association  areas  assumed  a  greater  energy  of  growth  and  ex- 
panded in  proportion  to  the  rise  in  functional  dignity  of  these  areas.  They  are  regions  of  "  un- 
stable equilibrium"  which  afford  greater  and  more  complex  associations  as  mental  development 
goes  on  in  the  species,  and  concomitant  with  this  great  cortical  expansion  the  associating  or 
coordinating  fibre  systems  became  more  elaborate,  complex,  and  far-reaching. 

With  the  aid  of  the  microscope  the  matin-ing  of  the  brain  elements  can  be  followed  from  the 
earliest  stages  of  embryonic  life  to  the  adult  period.  The  Flechsig  method  has  shown  how  the 
function  of  nerve  fibres  within  the  brain  is  only  established  when  the  myelin  sheath  has  developed. 

61 


962 


THE  NERVE  SYSTEM 


But  this  development  of  mature  nerve  fibres  does  not  occur  simultaneously  throughout  the  brain, 
but  step  by  step  in  a  definite  order  of  succession;  equally  important  bundles  are  myelinated 
simultaneously,  but  those  of  dissimilar  importance  develop  one  after  another  in  accordance 
with  Flechsig's  law.  The  successive  myelinization  of  fibre  bundles  to  and  from  the  cerebral 
cortex  corresponds  to  the  successive  awakenings  of  mental  activities  and  faculties  in  the  growing 
child.  Flechsig's  method  of  investigation  has  been  of  great  service  in  the  elucidation  of  the 
problems  of  cerebral  localization. 

Craniocerebral  Topography. — The  position  of  the  principal  fissures  and  convolutions  of  the 
cerebrum  and  their  relation  to  the  outer  surface  of  the  scalp  (Fig.  677)  have  been  the  subject  of 
much  investigation,  and  many  systems  have  been  devised  by  which  one  may  localize  these  parts 
from  an  exploration  of  the  external  surface  of  the  head. 

These  plans  can  only  be  regarded  as  approximately  correct  for  several  reasons;  in  the  first 
place,  because  the  relations  of  the  convolutions  and  fissures  to  the  surface  are  found  to  be  quite 


Fig.  722. — Drawing  to  illustrate  t-r.-iniocerebra]  topography.     (Taken  from  a  cast  in  the  Museu 
College  of  Surgeons  of  Kngland,  prepared  by  Professor  Cunningham.) 


I  of  the  Royal 


variable  in  different  individuals;  secondly,  because  the  surface  area  of  the  scalp  is  greater  than 
the  surface  area  of  the  brain,  so  that  lines  drawn  on  the  one  cannot  correspond  exactly  to  fissures 
or  convolutions  on  the  other;  thirdly,  because  the  fissures  and  convolutions  in  two  individuals 
are  never  precisely  alike.  Nevertheless,  the  principal  fissures  and  convolutions  can  be  mapped 
out  with  sufficient  accuracy  for  all  practical  purposes,  so  that  any  particular  convolution  can  be 
generally  exposed  by  removing  with  the  trephine,  or  by  the  flap  method,  a  certain  portion  of  the 
skull.  An  excellent  method  is  given  by  Chipault  in  his  Chirurgie  operatoire  du  systeme  nerveux, 
1894,  vol.  i.     The  following  systems  have  been  the  longest  in  vogue: 

The  various  landmarks  on  the  outside  of  the  skull,  which  can  be  easily  felt,  and  which  serve 
as  indications  of  the  position  of  the  parts  beneath,  have  been  already  referred  to,  and  the  rela- 
tion of  the  fissures  and  convolutions  to  these  landmarks  is  as  follows: 

Intercerebral  or  Longitudinal  Fissure. — ^This  corresponds  to  a  line  drawn  from  the 
glabella  at  the  root  of  the  nose  to  the  external  occipital  protuberance.  | 


CORTICAL  LOCALIZATION  OF  FUNCTION 


963 


The  Sylvian  Fissure. — The  position  of  the  sylvian  fissure  is  marked  by  a  Hne  starting 
from  a  point  3  cm.  (I5  inches)  horizontally  behind  the  external  angular  process  of  the  frontal 
bone  to  a  point  2  cm.  (5  inch)  below  the  most  prominent  point  of  the  parietal  eminence.  The 
first  2  cm.  (5  inch)  will  represent  the  basisylvian  fissure,  the  remainder  the  sylvian  fissure  proper. 
The  sylvian  point  is  therefore  5  cm.  (2  inches)  behind  and  about  1  cm.  (|  inch)  above  the  level 
of  the  external  angular  process.  The  presylvian  ramus  of  the  fissure  passes  upward  from  this 
point  parallel  to,  and  immediately  behind,  the  coronal  suture. 

The  Tentorial  Hiatus  or  Transverse  Fissure.— This  is  between  the  cerebrum  and  cere- 
bellum, and  corresponds  to  a  line  drawn  from  the  inion  to  the  external  auditory  meatus. 


A 

r 

a/ 

s 

Supra  orbital  line 
(Superior  Horizontal)  K 

Ax 

B 

K' 

Orbital-auricular  line 
( Base  line } 

Z       A  M 

Fig.  723. — Kronlein's  method  for  determining  the  portions  of  certain  fissures  of  the  brain. 

Central  Fissure. — To  find  the  dorsal  end  of  the  central  fissure,  a  measurement  should  be 
taken  from  the  glabella  to  the  external  occipital  protuberance.  The  position  of  the  top  of  the 
fissure  will  be,  measuring  from  in  front,  .5.5.6  per  cent,  of  the  whole  distance  from  the  glabella  to 
the  external  occipital  protuberance.  Professor  Thane  adopts  a  somewhat  simpler  method.  He 
divides  the  distance  from  the  glabella  to  the  external  occipital  protuberance  over  the  top  of  the 
head  into  two  equal  parts,  and,  having  thus  defined  the  middle  point  of  the  vertex,  he  takes  a 
point  half  an  inch  behind  it  as  the  top  of  the  sulcus.  This  is  not  quite  so  accurate  as  the  former 
method;  but  it  is  sufficiently  so  for  all  practical  purposes,  and  on  account  of  its  simplicity  is  very 
generally  adopted.  From  this  point  the  fissure  runs  downward  and  forward  for  9  to  10  cm. 
(3$  to  4  inches),  its  axis  making  an  angle  of  about  70  degrees  with  the  middle  line.  In  order 
to  mark  this  groove,  two  strips  of  metal  may  be  employed — one,  the  shorter,  being  fixed  to  the 
middle  of  the  other  at  the  angle  mentioned.  If  the  longer  strip  is  now  placed  along  the  sagittal 
suture  so  that  the  junction  of  the  two  strips  is  over  the  point  corresponding  to  the  top  of  the  furrow , 


964  THE  NEB  VE  SYSTEM 

the  shorter,  oblique  strip  will  indicate  the  direction  and  9  to  10  cm.  will  mark  the  length  of  the 
furrow.  Dr.  Wilson  has  devised  an  instrument,  called  a  cyrtometer,  which  combines  the  scale 
of  measurements  for  localizing  the  fissure  with  data  for  representing  its  length  and  direction.' 

The  Occipital  Fissure  on  the  dorsal  surface  of  the  cerebrum  runs  outward  at  right  angles  to  the 
great  longitudinal  fissure  for  about  2  to  3  cm.  (f  to  li  inches),  from  a  point  0.5  cm.  (j  inch) 
in  front  of  the  lambda.  Reid  states  that  if  the  sylvian  line  be  continued  onward  to  the  sagittal 
suture,  the  last  2  to  3  cm.  of  this  line  will  indicate  the  position  of  the  fissure. 

The  Precentral  Fissure  begins  2  cm.  (|  inch)  in  front  of  the  middle  of  the  central  fissure  and 
extends  nearly,  but  not  quite,  to  the  sylvian  fissure. 

The  Superfrontal  Fissure  runs  backward  from  the  supraorbital  notch,  parallel  with  the  line 
of  the  longitudinal  fissure  to  1  cm.  (-|  inch)  in  front  of  the  line  indicating  the  position  of  the 
central  fissure. 

The  Subfrontal  Fissure  follows  the  course  of  the  supertemporal  ridge  on  the  frontal  bone. 

The  Intraparietal  Fissure,  comprising  the  parietal,  subcentral,  and  paroccipital  fissm-es,  begins 
on  a  level  with  the  junction  of  the  middle  and  lower  third  of  the  central  fissure,  on  a  line  carried 
across  the  head  from  the  back  of  the  root  of  one  auricle  to  that  of  the  other.  After  passing  up- 
ward it  curves  backward,  lying  parallel  to  the  longitudinal  fissure,  midway  between  it  and  the 
parietal  eminence;  then  curves  downward  to  end  midway  between  the  posterior  fontanelle 
(lambda)  and  the  parietal  eminence. 

Kronlein's  method  for  determining  the  portions  of  certain  fissures  of  the  brain  is  very  useful 
and  easy  of  application  (Fig.  723).  It  is  as  follows:  (1)  The  base  line,  Z  M,  is  a  horizontal 
line  running  at  the  level  of  the  lower  border  of  the  orbit  and  the  upper  border  of  the  e.xternal 
auditory  meatus.  (2)  Another  horizontal  line,  K  K',  is  drawn  parallel  to  Z  M.  The  second 
horizontal  line  is  on  a  level  with  the  supraorbital  ridge.  (3)  A  vertical  line,  Z  K,  is  erected 
from  Z  M  at  the  middle  of  the  zygoma  and  is  carried  to  the  line  K  K'.  (4)  Another  vertical  line, 
A  R,  is  erected  from  the  base  line  at  the  level  of  the  articulation  of  the  mandible  and  is  carried 
to  R.  (5)  A  third  vertical  line,  M  P,  is  erected  from  the  base  line  at  the  posterior  border  of  the 
mastoid  process  and  is  carried  to  the  middle  line  of  the  skull,  which  is  marked  P.  (6)  A  line  is 
drawn  from  K  to  P.  The  portion  of  this  line  between  R  and  P'  corresponds  to  the  central 
fissure.  (7)  The  angle  P  K  K'  is  bisected  by  the  line  K  S.  K  S  corresponds  to  the  sylvian  fis- 
sure, and  K  is  directly  over  the  sylvian  point.  To  reach  the  a^nterior  branch  of  the  middle 
meningeal,  apply  the  trephine  at  K;  to  reach  the  posterior  branch,  apply  it  at  K'.  In  abscess 
of  the  temporal  lobe  the  trephine  should  be  applied,  according  to  von  Bergmann,  in  the  region 
AaKM. 


THE   MENINGES,  OR   MENINGEAL    MEMBRANES    OF    THE    BRAIN 
(MENINGES  ENCEPHALI). 

Dissection. — To  examine  the  brain  with  its  membranes,  the  skullcap  must  be  removed. 
In  order  to  effect  this,  saw  through  the  external  table,  the  section  commencing,  in  front,  about 
2  cm.  (i  inch)  above  the  margin  of  the  orbits,  and  extending,  behind,  to  a  little  above  the  level  of 
the  occipital  protuberance.  Then  break  the  internal  table  with  the  chisel  and  hammer,  to  avoid 
injuring  the  investing  membranes  or  brain;  loosen  and  forcibly  detach  the  skullcap,  and  the 
dura  will  be  exposed.  The  adhesion  between  the  bone  and  the  dura  often  is  very  intimate, 
particularly  along  the  sutures. 

The  membranes  of  the  brain  are  from  without  inward — tlie  dura,  arachnoid, 
and  the  pia. 

The  Dura  of  the  Brain  (Dura  Mater  Encephali)  (Figs.  724,  729). 

The  dura  of  the  brain  is  a  thick  and  dense,  inelastic,  fibrous  membrane 
which  lines  the  interior  of  the  sicull.  It  is  a  covering  for  the  brain  and  is  also 
the  internal  cranial  periosteum.  It  is  composed  of  two  layers  closely  connected, 
except  in  certain  situations,  where,  as  already  described  (p.  721),  they  separate 
to  form  sinuses  for  the  passage  of  venous  blood.  Upon  the  outer  surface  of 
the  cranial  dura,  in  the  situation  of  the  longitudinal  sinus,  may  be  seen  numerous 
small  whitish  bodies,  the  glandulae  Pacchionii  (gramdationes  arachnoideales). 
Its  outer  surface  is  rough  and  fibrillated,  and  adheres  closely  to  the  inner  surface 

I  Lancet.  1888,  vol.  i.  d.  408 


THE  DURA    OF  THE  BRAIN 


965 


of  the  bones,  the  adhesion  being  most  marked  opposite  the  sutures  and  at  the  base 
of  the  skuH.  Its  inner  surface  is  smooth  and  Hned  by  a  layer  of  endothelium. 
It  sends  inward  four  processes  which  divide  the  cavity  of  the  skull  into  a  series 
of  freely  communicating  compartments,  for  the  lodgement  and  protection  of  the 
different  parts  of  the  brain;  and  it  is  prolonged  to  the  outer  surface  of  the  skull, 
through  the  various  foramina  whicii 
exist  at  the  base,  and  thus  becomes 
continuous  with  the  pericranium;  its 
fibrous  layer  forms  sheaths  for  the 
nerves  which  pass  through  these  aper- 
tures. At  the  base  of  the  skull  it 
sends  a  fibrous  prolongation  into  the 
foramen  cecum;  it  sends  a  series  of 
tubular  prolongations  around  the  fila- 
ments of  the  olfactory  nerves  as  they 
pass  through  the  cribriform  plate,  and 
another  around  the  nasal  nerve  as  it  passes  through  the  nasal  slit;  a  prolongation 
is  also  continued  through  the  sphenoidal  fissure  into  the  orbit,  and  another  is 
carried  into  the  same  cavity  through  the  optic  foramen,  forming  a  sheath  for  the 
optic  nerve,  which  is  continued  as  far  as  the  eyeball.     In  the  posterior  fossa  it 


^1     LAYER 

DOTHEI.IAL 
LINING 

Fig.  724. — The  structure  of  the  dura.  Section  through 
the  cranial  vault  of  a  child,  slightly  enlarged.  (Poirier 
and  Charpy.) 


HRAGMA  SELL  AE 


Fig.  725.— The  tentorium  oerebell 


sends  a  process  into  the  internal  auditory  meatus,  ensheathing  the  facial  and 
auditory  nerves;  another  through  the  jugular  foramen,  forming  a  sheath  for  the 
structures  which  pass  through  this  opening;  and  a  third  through  the  anterior  con- 
dylar foramen.  Around  the  margin  of  the  foramen  magnum  it  is  closely  adherent 
to  the  bone,  and  is  continuous  with  the  spinal  dura. 


966 


THE  NERVE  SYSTEM 


Processes  of  the  Dura  {processus  durae  matris). — The  processes  of  the  dura 
which  project  into  the  cavity  of  the  skull  are  formed  by  reduplication  of  the  inner 
or  meningeal  layer  of  the  membrane,  and  are  four  in  number — the  falx  cerebri, 
the  tentorium  cerebelli,  the  falx  cerebelli,  and  the  diaphragma  sellae. 

The  falx  cerebri  (Figs.  725  and  726),  so  named  from  its  sickle-like  form,  is 
a  strong  arched  process  which  descends  vertically  in  the  intercerebral  fissure 
between  the  two  hemispheres  of  the  brain.  It  is  narrow  in  front,  where  it  is 
attached  to  the  crista  galli  of  the  ethmoid  bone,  and  broad  behind,  where  it  is 
connected  with  the  upper  surface  of  the  tentorium  cerebelli.  Its  upper  margin 
is  convex,  and  attached  to  the  inner  surface  of  the  skull,  in  the  middle  line,  as 
far  back  as  the  internal  occipital  protuberance;  it  contains  the  superior  or  great 
longitudinal  sinus  {sinus  sagittalis  superior).     Its  lower  rnargin  is  free,  concave,  and 


NTERNAL  JUGULAR 

Fig.  726, --Falx  cerebri  and  tentorium  cerebelli.  left  lateral  view.     (Testut.) 

presents  a  sharp,  curved  edge,  which  contains  the  falcial  or  inferior  longitudinal 
sinus  {sinus  sagittalis  inferior).  The  tentorial  or  straight  sinus  {sinus  rectus)  is 
formed  by  the  attachment  of  the  falx  cerebri  to  the  tentorium  cerebelli. 

The  tentorium  cerebelli  (Figs.  725  and  726)  is  an  arched  lamina  of  dura,  elevated 
in  the  middle  and  slightly  inclined  toward  the  circumference.  It  intervenes 
between  the  upper  surface  of  the  cerebellum  and  the  occipital  lobes  of  the  cerebrum. 
It  is  attached,  Isehind,  by  its  convex  border  to  the  transverse  ridges  upon  the  inner 
surface  of  the  occipital  bone,  and  there  encloses  on  each  side  the  transverse  or 
lateral  sinus  (sinus  transversus);  frontad,  to  the  superior  margin  of  the  petrous  por- 
tion of  the  temporal  bone  on  either  side,  there  enclosing  the  superpetrosal  sinus 
{sinus  petrosus  superior);  and  at  the  apex  of  this  bone  the  free  or  internal  border 
and  the  attached  or  external  border  meet,  and,  crossing  one  another,  are  continued 
forward,  to  be  attached  to  the  anterior  and  posterior  clinoid  processes  respectively. 


THE  DURA    OF  THE  BBAIN 


967 


Along  the  middle  line  of  its  upper  surface  the  posterior  border  of  the  falx  is  attached, 
the  tentorial  or  straight  sinus  being  placed  at  their  point  of  junction.  Its  frontal 
border  is  free  and  concave,  and  with  the  dorsum  sellae  forms  a  large  oval  opening. 
This  opening  is  called  the  incisura  tentorii  and  transmits  the  mesencephalon. 

The  falx  cerebelli  (falcula)  (Fig.  725)  is  a  small  triangular  process  of  dura 
received  into  the  indentation  tjetween  the  two  lateral  lobes  of  the  cereljellum 
behind.  Its  base  is  attached,  above,  to  the  under  and  back  part  of  the  tentorium 
cerebelli;  its  posterior  margin,  to  the  lower  division  of  the  vertical  crest  on  the 
inner  surface  of  the  occipital  bone.  As  it  descends  it  sometimes  divides  into  two 
smaller  folds,  which  are  lost  on  the  sides  of  the  foramen  magnum. 

The  diaphragma  sellae  (Fig.  725)  is  a  small,  circular,  horizontal  fold,  which 
constitutes  a  roof  for  the  sella  turcica.  This  almost  completely  covers  the 
hypophysis,  presenting  merely  a  small  central  opening  (foramen  diaphrac/matis 
sellae)  for  the  passage  of  the  infundibulum. 

Structure  (Fig.  724). — The  dura  consists  of  \yhite  fibrous  tissue  with  connective-tissue 
cells  and  elastic  fibres  arranged  in  flattened  lamintie,  which  are  imperfectly  sejiarated  by  lacunar 
spaces  and  bloodvessels  into  two  layers,  endosteal  and  meningeal.  The  endosteal  layer  is 
the  internal  periosteum  for  the  cranial  bones  and  contains  the  bloodvessels  for  their  supply 


FALX  CEREBELLI 


1.     Frontal  section  passing  through  the  tentorium 
seen  in  the  centre.     (Poirier  and  Charpy.) 


FiQ.  727. — Crucial  prolongation  of  the  dui 
torcular  herophili  i 

At  the  margin  of  the  foramen  magniun  it  l)econies  continuous  with  the  periosteum  lining  the 
vertebral  canal.  The  meningeal  or  supporting  layer  is  lined  on  its  inner  surface  by  a  layer  of 
nucleated  endothelium,  similar  to  that  found  cm  serous  membranes.  By  its  reduplication  the 
meningeal  layer  forms  the  falx  cerebri,  the  tentorium  cerebelli  and  falx  cerebelli,  and  the 
diaphragma  sellae.     The  two  layers  are  connected  by  fibres  which  intersect  each  other  obliquely. 

The  arteries  of  the  dura  (see  section  on  Arteries)  are  very  numerous,  but  are  chiefly  distributed 
to  the  bones.  Those  found  in  the  anterior  fossa  are  the  anterior  meningeal  branches  of  the 
anterior  and  posterior  ethmoidal  and  internal  carotid,  and  a  branch  from  the  middle  meningeal. 
Those  in  the  middle  fossa  are  the  middle  and  small  meningeal  branches  of  the  internal  maxil- 
lary; a  branch  from  the  ascending  pharyngeal,  whiiii  cnlcrs  the  .skull  through  (lie  foramen 
lacerum  medium;  branches  from  the  internal  carotid,  and  a  recurrent  branch  from  the  lac- 
rimal. Those  in  the  jiosterior  fossa  are  meningeal  branches  from  the  occipital,  one  of  which 
enters  the  skull  through  the  jugular  foramen,  and  the  other  through  the  mastoid  foramen;  the 
posterior  meningeal  from  thie  vertebral;  occasional  meningeal  branches  from  the  ascending 
pharyngeal,  which  enter  the  skull  through  the  jugular  and  anterior  condylar  foramina;  and  a 
branch  from  the  middle  meningeal. 

The  veins  which  return  the  blood  from  the  dura  (see  p.  717),  and  partly  from  the  bones, 
anastomose  with  the  diploic  veins  (see  p.  727).  They  terminate  in  the  various  sinuses,  with  the 
exception  of  two  which  accompany  the  middle  meningeal  artery,  and  pass  out  of  the  skull  at  the 
foramen  spinosum  to  join  the  internal  maxillary  vein;  above,  the  meningeal  veins  communicate 
with  the  superior  longitudinal  sinus.    The  sinuses  are  considered  on  pages  721  to  727  inclusive. 


968 


THE  NERVE  SYSTE3I 


On  either  side  of  the  superior  longitudinal  sinus,  especially  near  its  middle,  and  also  near  the 
lateral  and  straight  sinuses,  are  numerous  spaces  in  the  dura  which  communicate  with  the  sinus, 
either  by  a  small  opening  or  a  distinct  venous  channel.  These  spaces  are  the  parasinoidal  sin- 
uses (lacunae  laterales).  Many  of  the  meningeal  veins  do  not  open  directly  into  the  sinuses, 
but  indirectl.Y  tlu-ough  the  parasinoidal  sinuses.  These  venous  lacunae  are  often  invaginated  by 
arachnoid  villi,  and  they  communicate  with  the  underlying  cerebral  veins,  and  also  with  the 
diploic  and  emissary  veins. 

The  nerves  of  the  dura  are  filaments  from  the  trochlear,  the  ophthalmic  division  of  the  tri- 
geminal, the  semilunar  or  Gasserian  ganghon,  the  vagus,  the  hypoglossal,  and  the  sjonpa- 
thetic. 

The  Arachnoid  (Arachnoidea  Encephali)  (Fig.  728). 

The  cranial  arachnoid  is  a  delicate  membrane  which  envelops  the  brain,  lying 
between  the  pia  internally  and  the  dura  externally;  from  this  latter  membrane 
it  is  separated  by  a  very  fine  slit  or  space,  the  subdural  space  (cavum  subdurale). 
The  subdural  space  contains  a  very  minute  quantity  of  fluid  of  the  nature  of  lymph. 


OLFACTORY 


ARACHNOID 

FlQ.  728. — The  arachnoid  upon  the  base  of  the  brain.     On  the  right  the  arachnoid  has  been  partly  removed 
to  show  the  cerebrum  and  cerebellum  with  their  superficial  veins.      (Poirier  and  Charpy.) 

The  arachnoid  is  prolonged  upon  emerging  nerves  and  joins  the  lymph  spaces  of  the 
nerves.  The  subdural  space  does  not  communicate  with  the  subarachnoid  space. 
The  arachnoid  invests  the  brain  loosely,  being  separated  from  direct  contact 
with  the  cerebral  substance  by  the  pia,  and  a  quantity  of  loose  areolar  tissue,  the 
subarachnoidean  areolar  tissue.     On  the  upper  surface  of  the  cerebrum  the  arachnoid 


THE  ARACHNOID 


969 


is  thin  and  transparent,  and  may  be  easily  demonstrated  by  injecting  a  stream  of 
air  beneath  it  by  means  of  a  blowpipe;  it  passes  over  the  convolutions  without 
dipping  down  into  the  fissures  between  them,  but  does  pass  into  the  sylvian  and 
intercerebral  fissures  and  is  prolonged  upon  the  nerves  as  a  sheath.  At  the  base 
of  the  brain  the  arachnoid  is  thicker,  and  slightly  opaque  toward  the  central  part; 
it  covers  the  orbital  surface  of  the  anterior  lobes  and  extends  across  between  the 
two  temporal  lobes  so  as  to  leave  a  considerable  interval  between  it  and  the  brain, 
the  cistema  basalis. 

The  subarachnoid  space  (cavum  subarachnoideale)  (Fig.  729)  is  the  interval 
between  the  arachnoid  and  pia.  It  is  not  only  on  the  surface,  but  dips  between 
the  convolutions.  It  is  not,  properly  speaking,  a  space,  for  it  is  occupied  every- 
where by  a  spongy  tissue  consisting  of  trabecular  of  delicate  connective  tissue 
covered  with  endothelium,  which  pass  from  the  pia  to  the  arachnoid,  and  in  the 
meshes  of  which  the  subarachnoid  fluid  is  contained.  This  so-called  space  is 
small  on  the  surface  of  the  cerebrum ;  but  at  the  base  of  the  brain  the  subarachnoid 
tissue  is  less  abundant  and  its  meshes  larger. 


Emusarp  vein 
Venous  lacuna        \       Cerebral  vein 


Sup.  longitufUnnl  sinit^ 

Pacchionian  body 


Subdural  space 
Subaraclinoid  space 


Dura  mater 
Arachnoid 
Cerebral  cortex 


-Diagrammatic  representation  of  a  section  across  the  top  of  the  skull, 
etc.    (Modified  from  Testut.) 


the  membranes  of  the  brain, 


In  certain  regions  the  arachnoid  and  pia  are  farther  apart  than  was  pre\"iously 
indicated,  and  these  spaces  are  called  subarachnoid  cisternse  (cisternae  svbarach- 
noidales).  The  largest  space  is  the  continuation  of  the  posterior  part  of  the  sub- 
arachnoid space  of  the  spinal  cord.  It  is  called  the  postcistema  or  cistema  magna 
{cisierna  cerebellomeduUaris) .  It  is  a  space  formed  by  the  arachnoid  passing  across 
the  back  and  under  portions  of  the  medulla  oblongata  and  cerebellum.  It  com- 
municates with  the  fourth  ventricle  by  three  foramina.  The  largest  opening  is 
the  foramen  of  Magendie  (apertura  medialis  ventrindi  quarti;  metapore).  It  is  in 
the  middle  line  of  the  tela  choroidea.  At  the  end  of  each  recessus  lateralis  of  the 
fourth  ventricle  there  is  also  an  opening,  and  each  opening  is  called  the  foramen  of 
Luschka  or  of  Key  and  Retzius  {apertura  lateralis  ventriculi  quarti).    The  cisterna 


970  THE  NERVE  SYSTEM 

pontis  is  the  continuation  upward  of  the  anterior  part  of  the  subarachnoid  space  of 
the  cord.  About  the  medulla  oblongata  it  is  continuous  with  the  postcisterna,  so 
this  important  nerve  centre  is  surrounded  by  a  large  subarachnoid  space.  The 
cistema  basalis  {cisterna  interi)eduncularis)  is  formed  by  the  arachnoid  extending 
between  the  two  temporal  lobes.  There  is  a  cisterna  between  the  inferior  edge  of 
the  falx  cerebri  and  the  superior  surface  of  the  corpus  callosum  which  contains 
the  anterior  cerebral  arteries,  a  cisterna  in  the  sylvian  fissure  {cisterna  sijhiana) 
which  contains  the  middle  cerebral  artery,  and  a  cisterna  between  the  corpora 
quadrigemina  which  contains  the  vena  magna  Galeni. 

The  cerebrospinal  fluid  (coeliolympha;  liquor  cerebrosplnalis)  fills  the  subarach- 
noid space.  It  is  a  clear,  limpid  fluid,  having  a  saltish  taste  and  a  slightly 
alkaline  reaction.  According  to  Lassaigne,  it  consists  of  98.5  parts  of  water, 
the  remaining  1.5  per  cent,  being  solid  matters,  animal  and  saline.  It  varies  in 
quantity,  being  most  abundant  in  old  persons,  and  is  quickly  reproduced.  Its 
chief  use  is  probably  to  afford  mechanical  protection  to  the  nerve  centres,  and 
to  prevent  the  effects  of  concussions  communicated  from  without. 

Structure. — The  arachnoid  consists  of  bundles  of  connective  tissue,  the  fine  fibres  of  which 
form  one  layer  and  cross  each  other  in  every  direction.  At  the  level  of  the  large  fissures,  and 
especially  around  the  circle  of  Willis,  it  is  reenforced  by  thick  fibrous  tissue.  Both  surfaces  are 
covered  with  endothelium.  There  are  no  bloodvessels  in  the  arachnoid;  the  vessels  which 
appear  to  be  in  it  are  really  in  the  pia.  There  is  no  positive  proof  that  nerves  are  present  in 
the  arachnoid.  It  is  true  that  Bochdalek  and  Luschka  long  ago  described  arachnoid  nerves, 
but  these  observations  have  never  been  corroborated. 


The  Arachnoid  Villi  or  Pacchionian  Bodies  (Granulationes  Arachnoideales). 

The  arachnoid  villi,  erroneously  called  glandulae  Pacchioni,  are  numerous 
small  whitish  or  purplish  projections,  usually  collected  into  clusters  of  variable 
size,  which  are  found  in  the  following  situations:  (1)  Upon  the  outer  surface  of  the 
dura,  in  the  vicinity  of  the  superior  longitudinal  sinus,  being  received  into  small 
depressions  on  the  inner  surface  of  the  calvarium.  (2)  On  the  inner  surface  of  the 
dura.     (3)  In  the  superior  longitudinal  sinus  and  the  other  sinuses. 

A  hasty  examination  would  lead  us  to  suppose  that  these  bodies  spring  from 
the  dura,  but,  as  a  matter  of  fact,  they  originate  from  the  arachnoid.  They  are 
not  glandular  in  structure,  but  are  simply  enlarged  normal  villi  of  the  arachnoid. 
In  their  growth  they  appear  to  perforate  the  dura,  and  when  a  group  of  villi  is 
of  large  size  it  causes  absorption  of  the  bone,  and  comes  to  be  lodged  in  a  pit  or 
depression  (foveola  gramdaris  [Pacchioni])  on  the  inner  table  of  the  skull.  Their 
manner  of  growth  is  as  follows:  At  an  early  period  they  project  through  minute 
holes  in  the  inner  layer  of  the  dura,  which  open  into  large  venous  spaces  situated 
in  the  tissues  of  the  membrane,  on  either  side  of  the  longitudinal  sinus  and  com- 
municating with  it.  In  their  onward  growth  the  villi  push  the  outer  layer  of  the 
dura  before  them,  and  this  forms  over  them  a  delicate  membranous  sheath.  In 
structure  they  consist  of  spongy  trabecular  tissue,  covered  over  by  a  membrane, 
which  is  continuous  with  the  arachnoid.  The  space  between  these  two  coverings, 
derived  from  the  dura  and  arachnoid  respectively,  corresponds  to  and  is  con- 
tinuous Avith  the  subdural  space.  The  spongy  tissue  of  which  they  are  composed 
is  continuous  with  the  trabecular  tissue  of  the  subarachnoid  space;  so  that  fluid 
injected  into  the  subarachnoid  space  finds  its  way  into  the  Pacchionian  bodies, 
and  through  their  coverings  filters  into  the  superior  longitudinal  sinus.  They  are 
supposed  to  be  a  means  of  getting  rid  of  an  excess  of  cerebrospinal  fluid  when 
its  quantity  is  increased  £^bove  normal,  or  for  replenishing  the  cerebrospinal 
fluid  from  the  blood  plasma  when  needed.     Another  means  of  getting  rid  of 


THE  PI  A    OF  THE  BRAIN 


971 


cerebrospinal  fluid  is  absorption  by  the  lymph  spaces  of  the  cranial  nerves, 
which  possess  sheaths  of  arachnoid  up  to  the  points  at  which  they  emerge  from 
the  skulh 

These  bodies  are  not  found  in  infancy,  and  very  rarely  until  the  third  year. 
They  are  usually  found  after  the  tenth  year;  and  from  this  period  they  increase 
in  number  as  age  advances.     Occasionally  they  are  wanting. 


GALCNI 

Fig  730  — \  elum  interpositum.    (Poirier  and  Charpy.) 


The  Pia  of  the  Brain  (Pia  Mater  EncephaU)  (Figs.  729,  730). 

The  pia  of  the  brain  is  a  vascular  membrane,  and  derives  its  blood  from  the 
internal  carotid  and  vertebral  arteries.  It  consists  of  a  minute  plexus  of  blood- 
vessels held  together  by  an  extremely  fine  areolar  tissue.  It  invests  the  entire 
surface  of  the  brain,  dipping  down  between  the  convolutions  and  laminae,  and 
is  prolonged  into  the  interior,  forming  the  velum  interpositum  and  the  choroid 
plexuses  of  the  lateral  and  fourth  ventricles. 

The  velum  interpositum  or  the  tela  chorioidea  superior  (tela  chorioidea  xen- 
triculi  tertii)  (Fig.  730)  is  the  prolongation  of  the  pia  into  the  interior  of  the  brain 
through  the  medium  of  the  transverse  fissure.  It  is  a  double  triangular  vascular 
fold,  that  lies  between  the  body  of  the  fornix  above  and  the  thalami  and  the 
epithelial  roof  of  the  third  ventricle  below,  and  passes  forward  to  the  foramen  of 
Monro.  At  each  edge  of  the  velum  interpositum  is  the  choroid  plexus  {-plexus 
chorioideus  ventriculi  laieralis;  paraplexus)  of  the  corresponding  lateral  ventricle. 
In  front  the  two  plexuses  join  behind  the  foramen  of  Monro,  and  at  the  point 
of  junction  two  lesser  choroid  plexuses  pass  back  along  the  under  surface  of 
the  velum  interpositum  to  the  third  ventricle,  the  diaplexus  or  median  plexus 
(plexus  chorioideus  ventriculi  tertii).  The  velar  veins  or  veins  of  Galen  (p.  720) 
are  two  veins  which  lie  on  either  side  of  the  middle  of  the  velum  interpositum 
and  pass  back.  Each  velar  vein  is  formed  by  the  union  of  the  vein  from  the 
corpus  striatum  and  the  choroid  vein  from  the  choroid  plexuses.  The  two  velar 
veins  unite  and  form  the  vena  magna  (Galeni) ,  which  empties  into  the  straight 
sinus. 

The  pia  of  the  surfaces  of  the  hemispheres,  where  it  covers  the  gray  substance 


972  THE  NEB  VE  SYSTEM 

of  the  convolutions,  is  very  vascular,  and  gives  off  from  its  inner  surface  a  multi- 
tude of  minute  vessels,  which  extend  perpendicularly  for  some  distance  into  the 
cerebral  substance.  At  the  base  of  the  brain,  in  the  situation  of  the  anterior  and 
posterior  perforated  substance,  a  number  of  long,  straight  vessels  are  given  off, 
which  pass  through  the  white  substance  to  reach  the  gray  substance  in  the  interior. 
On  the  cerebellum  the  membrane  is  more  delicate,  and  the  vessels  from  its  inner 
surface  are  shorter.  The  pia  of  the  spinal  cord  is  thicker,  firmer,  and  less  vascular 
than  that  of  the  brain,  and  as  it  is  traced  upward  over  the  medulla  oblongata 
it  is  seen  to  preserve  these  characters.  At  the  upper  border  of  the  medulla  ob- 
longata it  is  prolonged  over  the  lower  half  of  the  fourth  ventricle,  forming,  before 
it  is  reflected  onto  the  imder  surface  of  the  cerebellum,  a  covering  for  the  fourth 
^•ent^icle  called  the  tela  chorioidea  inferior  {tela  chorioidea  ventricidi  quarti;  metatela) ; 
this  carries  the  choroid  plexus  of  the  fourth  ventricle  {plexus  chorioideus  ventricidi 
quarti). 

The  arteries  of  the  pia  (see  pp.  614,  617,  and  621)  (Figs.  4.50  and  451)  are  the  anterior,  middle, 
and  posterior  cerebral,  anterior  choroid  and  choroid,  superior,  anterior  inferior,  and  posterior 
inferior  cerebellar.  (The  vessels  of  the  cerebral  ganglionic  system  and  of  the  cortical  arterial 
system  are  considered  on  p.  618.) 

The  veins  of  the  pia  (see  pp.  719,  720,  and  721)  are  the  basilar  vein,  the  velar  veins  (Fig. 
730),  the  veins  constituting  the  choroid  plexuses  of  the  third  ventricle,  the  lateral  ventricles, 
and  the  fourth  ventricle;  the  cerebral  veins  (Fig.  728)  and  the  cerebellar  veins  (Fig.  728). 

The  nerves  of  the  pia  accompany  the  branches  of  the  arteries  and  are  derived  chiefly  from 
the  sympathetic.  A  few  fibres  are  derived  from  certain  cranial  nerves,  all  of  which  are  prob- 
ably of  the  afferent  variety. 

THE  CRANIAL  NERVES  (NERVI  CEREBRALES). 

The  irregularities  of  origin  and  distribution  of  the  cranial  nerves,  as  compared 
with  the  relatively  simple  spinal  nerves,  are  so  great  and  their  functions  were  for- 
merly so  little  known  that  the  older  anatomists  contented  themselves  with  number- 
ing them  in  order,  beginning  at  the  frontal  end  of  the  brain,  and  named  them 
with  reference  to  their  anatomic  connections.  The  enumeration  of  the  cranial 
nerves  was  as  variously  given,  almost,  as  there  were  writers  upon  the  subject; 
the  systems  of  Willis  and  of  Sommering  were  most  in  vogue  for  a  time,  but  the 
latter  prevails  today.  In  Sommering's  arrangement  twelve  pairs  of  cranial  nerves 
are  recognized,  but,  on  morphological  and  functional  grounds,  the  nerves  of 
the  seventh  and  eighth  pairs  should  each  be  considered  as  being  composed  of  two 
nerves,  the  eleventh  pair  should  be  included  with  the  nerves  of  the  tenth,  and  the 
optic  "nerve"  is  rather  a  diverticulum  of  the  brain  itself  than  a  nerve  in  the  strict 
sense.  Furthermore,  while  some  of  the  nerves  are  sensor  or  motor  in  a  sense 
strictly  comparable  with  the  spinal  nerves,  others  are  mixed  in  function,  and 
yet  others  constitute  nerves  of  special  sense  and  lack  general  sensibility.  The 
numerical  names,  based  upon  the  order  in  which  they  pass  through  the  foramina 
in  the  base  of  the  cranium,  are  being  abandoned  gradually  for  the  more  appro- 
priate functional  names,  but  not  yet  entirely  so.  Thus  glossopharyngeal  has 
not  yet  given  way  to  '''gustatory;"  "vagus"  is  shorter  than  " pneumogastric" — 
a  term  which  is  misleading  for  a  nerve  which  is  distributed  not  only  to  lungs 
and  stomach,  but  also  to  the  meninges,  the  pharynx  and  oesophagus,  larynx  and 
trachea,  heart  and  pericardium,  liver  and  spleen. 

The  cranial  nerves,  as  usually  enumerated,  together  with  their  superficial 
"origin"  or  attachment  to  the  brain  and  their  foramina  of  exit  from  the  skull,  are 
tabulated  on  page  849.  The  central  olfactory  pathway  is  described  on  page  958, 
and  the  central  connections  of  the  optic  tracts  are  given  on  page  911.  The  central 
connections  of  the  remaining  cranial  nerves  are  described  on  pages  877  to  902. 


THE  FIRST  OR  OLFACTORY  NERVE 


973 


The  following  is  a  brief  summary  of  the  twelve  pairs  of  cranial  nerves,  indicating 
their  functional  nature: 


No. 

Name. 

Functional  nature. 

I. 

Olfactory  (fila). 

Smell  sense. 

II. 

Optic. 

Visual  sense. 

III. 

Oculomotor. 

Motor  to  muscles  of  eyeball  and  orbit. 

IV. 

Trochlear. 

Motor  to  Superior  oblique  muscle  of  eyeball. 

V. 

Trigeminal. 

Mixed:  Sensor  to  face,  tongue,  and  teeth;  motor  to 
muscles  of  mastication. 

VI. 

Abducent. 

Motor  to  External  rectus  muscle  of  eyeball. 

VII. 

Facial. 

Motor  to  muscles  of  scalp  and  face. 

Nervus  intermedins. 

Mixed:  Sensor  (gustatory)  to  tongue;  excitoglandular  to 
submaxillary  and  sublingual  salivary  glands. 

VIII. 

Acoustic: 

I.  Cochlearis. 

Hearing  sense. 

II.  Vestibularis. 

Equilibratory. 

IX. 

Glossopharyngeal. 

Mixed-  Sensor  (and  gustatory)  to  tongue  and  pharynx; 
motor  ( ?)  to  Stylopharyngeus  muscle. 

X. 

Vagus. 

Mixed :  Sensorimotor  to  respiratory  tract  and  part  of  ali- 
mentary tract. 

XI. 

Spinal  accessory. 

I.  Accessory  to  vagus. 

Motor  to  muscles  of  palate,  pharynx,  etc.;  respiratory  or- 
gans; inhibitory  to  heart. 

II.  Spinal  part. 

Motor  to  Trapezius  and  Sternomastoid  muscles. 

XII. 

Hypoglossal. 

Motor  to  muscles  of  tongue. 

THE  FIRST  OR  OLFACTORY  NERVE  (N.  OLFACTORIUS). 

The  olfactory  nerves  or  fila  are  the  special  nerves  of  the  sense  of  smell,  and  are 
about  twenty  in  number  on  each  side.  These  filaments  constitute  the  first  or 
olfactory  nerves  and  are  the  axones  of  the  olfactory  cells,  lying  in  the  small  olfac- 
tory region  in  the  upper  part  of  the  superior  turbinated  process  of  the  ethmoid 
and  corresponding  portion  of  the  nasal  septum  and  are  macroscopically  differenti- 
ated from  the  respiratory  region  in  being  of  a  more  brownish  hue  (Fig.  731)., 
The  olfactory  fila  are  arayelinic  and  exhibit  a  plexiform  arrangement  in  the  deeper 
layers.  After  piercing  the  cribriform  plate  of  the  ethmoid  they  become  attached 
to  the  under  surface  of  the  olfactory  bulb,  an  oval  mass  of  a  grayish  color,  which 
rests  on  the  cribriform  plate  of  the  ethmoid  bone  and  forms  the  anterior  expanded 
extremity  of  a  slender  process  of  brain  substance,  named  the  olfactory  tract. 
The  olfactory  tract  and  bulb  have  already  been  described  (p.  927).  The  olfactory 
tubercle  (trigonum  olfactoriunn)  is  a  small  triangular  mass  of  gray  substance  between 
the  diverging  roots  of  the  optic  tract  (p.  928). 

Each  nerve  is  surroimded  by  tubular  prolongations  from  the  dura  and  pia, 
the  former  being  lost  on  the  periosteum  lining  the  nose,  the  latter  in  the  neuri- 
lemma of  the  nerve.  The  nerves,  as  they  enter  the  nares,  are  divisible  into  two 
groups — an  inner  group,  larger  than  those  on  the  outer  wall,  spread  out  over  the 
upper  third  of  the  septum;  and  an  outer  set,  which  is  distributed  over  the  superior 
turbinated  process  and  the  surface  of  the  ethmoid  in  front  of  it.  As  the  filaments 
descend,  they  appear  to  unite  in  a  plexiform  network,  and  are  believed  by  most 
observers  to  terminate  by  becoming  continuous  with  the  deep  extremities  of  the 
olfactory  cells. 

The  olfactory  nerves  differ  in  structure  from  other  nerves  in  being  composed 
exclusively  of  amyelinic  fibres.  They  are  deficient  in  the  white  substance  of 
Schwann,  and  consist  of  axones  with  a  distinct  nucleated  sheath,  in  which  there 
are,  however,  fewer  nuclei  than  in  ordinary  amyelinic  fibres. 

The  central  olfactory  pathways  are  described  on  page  958). 


974  THE  NER  VE  SYSTEM 

Applied  Anatomy. — Destruction  of  the  olfactory  tract  of  one  side  causes  loss  of  smell  {anos- 
mia) on  the  side  of  the  injury,  because  the  olfactory  tract  is  practically  uncrossed.  In  severe 
injuries  to  the  head  the  olfactory  bulb  may  become  separated  from  the  olfactory  nerves,  thus 
producing  loss  of  the  sense  of  smell,  and  with  this  a  considerable  loss  in  the  sense  of  taste,  as  much 
of  the  perfection  of  the  sense  of  taste  is  due  to  the  sapid  substances,  being  also  odorous  and 


Fig.  731. — Extent  of  true  olfactory  mucous  membrane 


simultaneously  exciting  the  sense  of  smell.  When  the  sense  of  smell  is  lost,  an  individual 
cannot  distinguish  the  flavor  of  food,  but  he  can  distinguish  that  a  substance  is  salt,  or  sweet, 
or  bitter,  or  acid.  The  most  usual  cause  of  injury  to  the  olfactory  nerve  is  fracture  of  the  base 
of  the  skull,  the  line  of  fracture  passing  through  the  cribriform  plate  of  the  ethmoid  bone,  but  a 
blow  upon  the  face,  forehead,  or  back  of  the  head  which  does  not  produce  fracture  may  injure 
the  nerves. 


THE  SECOND  OR  OPTIC  NERVE  (N.  OPTICUS). 

The  fibres  of  the  optic  nerve,  the  special  nerve  of  the  sense  of  sight,  are  the  central 
processes  of  the  retinal  ganglion  cells  which,  after  converging  to  the  optic  papilla, 
leave  the  eyeball  by  piercing  its  fibrous  and  vascular  tunics  as  a  cylindric  cord. 
The  point  of  emergence  is  situated  a  little  mesad  (3  to  4  mm. — \  to  ^  inches) 
of  the  posterior  pole  of  the  globe.  Behind  the  eyeball  the  nerve  passes  back- 
ward and  inward  through  the  orbital  fat  and  optic  foramen  to  enter  the  middle 
fossa  of  the  cranium.  The  total  length  of  the  nerve  averages  45  to  50  mm. 
(If  to  2  inches).  The  two  nerves  converge  to  decussate  partially,  forming  the 
chiasm. 

The  optic  chiasm  (chiasma  opticum)  (Figs.  732  and  733  and  p.  910)  is  somewhat 
quadrilateral  in  form,  rests  upon  the  olivary  eminence  and  on  the  anterior  part  of 
the  diaphragma  sellae,  being  bounded  above  by  the  lamina  terminalis;  behind  by 
the  tuber  cinereum;  on  either  side  by  the  anterior  perforated  substance.  Within 
the  commissure  the  optic  nerves  of  the  two  sides  undergo  a  partial  decussation 
(Figs.  672  and  733),  described  in  detail  on  pages  910  and  911. 


THE  SECOND   OR   OPTIC  NER  VE 


975 


From  the  optic  chiasm  the  optic  tracts  wind  as  flattened  bands  obliquely  caudo- 
laterad  around  the  crura  cerebri  to  subdivide,  each  into  two  bands,  one  (mesal 
root)  passing  to  the  medial  geniculate  body  and  not  a  true  continuation  of  the 
optic  path  (see  Gudden's  commissure,  p.  910),  the  other  (lateral  root)  passing  to 
the  lateral  geniculate  body,  the  pulvinar,  and  the  superior  quadrigeminal  body 
(p.  910). 

The  optic  path  has  been  described  on  pages  909  to  911. 

Applied  Anatomy. — The  optic  nerve  is  peculiarly  liable  to  become  the  seat  of  neuritis  or 
undergo  atrophy  in  affections  of  the  central  nerve  system,  and,  as  a  rule,  the  pathological  rela- 
tionship between  the  two  affections  is  exceedingly  difficult  to  trace.  There  are,  however,  certain 
points  in  connection  with  the  anatomy  of  this  nerve  which  tend  to  throw  light  upon  the  frequent 
association  of  these  affections  with  intracranial  disease:  (1)  From  its  mode  of  development 
and  from  its  structure  the  optic  nerve  must  be  regarded  as  a  prolongation  of  the  brain  substance, 
rather  than  as  an  ordinary  cerebrospinal  nerve.  (2)  As  it  passes  from  the  brain  it  receives 
sheaths  from  the  three  cerebral  membranes — a  perineural  sheath  from  the  pia,  an  intermediate 
sheath  from  the  arachnoid,  and  an  outer  sheath  from  the  dura,  which  is  also  connected  with 
the  periosteum  as  it  passes  through  the  optic  foramen.  These  sheaths  are  separated  from  each 
other  by  spaces  which  communicate  with  the  subdural  and  subarachnoid  spaces  respectively. 
The  innermost  or  perineural  sheath  sends  a  process  around  the  arteria  centralis  retinae  into  the 
interior  of  the  nerve,  and  enters  immediately  into  its  structure.  Thus,  inflammatory  infections 
of  the  meninges  or  of  the  brain  may  readily  extend  themselves  along  these  spaces  or  along  the 
interstitial  connective  tissue  in  the  nerve. 


To  optic  nerve 
^^^   of  same  side. 
^^^0/  opposite 
side. 


Fig.  732.— The  left  optic  nerve  and  optic  tracts.  Fig.  733. — Course  of  the  fibres  in  the  optic  chiasm. 


The  course  of  the  fibres  in  the  optic  chiasm  has  an  important  pathological  bearing,  and  has 
been  the  subject  of  much  controversy.  Microscopic  examination,  experiments,  and  pathology 
all  seem  to  point  to  the  fact  that  there  is  a  partial  decussation  of  the  fibres,  each  tract  supplying 
the  corresponding  half  of  each  eye,  so  that  the  right  tract  supplies  the  right  half  of  each  eye,  and 
the  left  tract  the  left  half  of  each  eye.  At  the  same  time,  Charcot  believes — and  his  view  has 
met  with  general  acceptation — that  the  fibres  which  do  not  decussate  at  the  optic  chiasm  will 
decussate  in  the  corpora  quadrigemina,  so  that  lesion  of  the  cerebral  centre  of  one  side  causes 
complete  blindness  of  the  opposite  eye,  because  both  sets  of  decussating  fibres  are  destroyed. 
Whereas  should  one  tract — say  the  right — be  destroyed  by  disease,  there  will  be  blindness  of 
the  right  half  of  both  retinte. 

A  sagittal  section  through  the  optic  chiasm  would  divide  the  decussating  fibres,  and  would 
therefore  produce  blindness  of  the  inner  half  of  each  eye;  while  a  section  at  the  margin  of  the 
side  of  the  optic  chiasm  would  produce  blindness  of  the  external  half  of  the  retina  of  the  same 
side. 

The  optic  nerve  may  also  be  affected  in  injuries  or  diseases  involving  the  orbit,  in  fractures 
of  the  anterior  fossa  of  the  base  of  the  skull,  in  tumors  of  the  orbit  itself,  or  those  invading  this 
cavity  from  neighboring  parts. 


976 


THE  NEBVE  SYSTEM 


Tnfratrochlem 
nerve.     ~~ 


THE   THIRD   OR   OCULOMOTOR   NERVE    (N.    OCULOMOTORroS) 

(Figs.  734,  735). 

The  third  or  oculomotor  nerve  supplies  all  the  muscles  of  the  orbit  except  the 
Superior  oblique  and  External  rectus;  it  also  supplies,  through  its  connection 
with  the  ciliary  ganglion,  the  Sphincter  muscle  of  the  iris  and  the  Ciliary  muscle. 
It  is  a  rather  large  nerve,  of  cylindric  form  and  firm  texture. 

Its  apparent  origin  is  from  the  oculomotor  groove  along  the  ventromesal  border 
of  the  crus.  The  deep  origin  may  be  traced  through  the  substantia  nigra,  red 
nucleus,  and  tegmentum  of  the  crus  to  a  nucleus  situated  on  either  side  of  the 
median  line  beneath  the  floor  of  the  aqueduct.  The  nucleus  of  the  oculomotor 
nerve  also  receives  fibres  from  the  abducent  nerve  of  the  opposite  side.  The 
nucleus  of  the  oculomotor  nerve,  considered  from  a  physiological  standpoint, 

can  be  subdivided  into  several 
smaller  groups  of  cells,  each  group 
controlling  a  particular  muscle  (see 
p.  901). 

On  emerging  from  the  brain,  the 
nerve  is  invested  with  a  sheath  of 
pia,  and  enclosed  in  a  prolongation 
from  the  arachnoid.  It  passes 
between  superior  cerebellar  and 
posterior  cerebral  arteries,  and  then 
pierces  the  dura  in  front  of  and 
external  to  the  posterior  clinoid 
process,  passing  between  the  two 
processes  from  the  free  and  attached 
borders  of  the  tentorium,  which 
are  prolonged  forward  to  be  con- 
nected with  the  anterior  and  poste- 
rior clinoid  processes  of  the  sphe- 
noid bone.  It  passes  along  the 
outer  wall  of  the  cavernous  sinus 
(Figs.  505  and  506);  above  the  other 
orbital  nerves,  receiving  in  its  course 
one  or  two  filaments  from  the 
cavernous  plexus  of  the  sympa- 
thetic, and  a  communicating  branch 
from  the  first  division  of  the  tri- 
geminal nerve.  It  then  divides  into 
two  branches,  which  enter  the  orbit 
through  the  sphenoidal  fissure,  be- 
tween the  two  heads  of  the  External 
rectus  muscle  (Fig.  734).  On 
passing  through  the  fissure,  the  nerve  is  placed  below  the  trochlear  nerve  and 
the  frontal  and  lacrimal  branches  of  the  ophthalmic  nerve,  while  the  nasal  nerve  is 
placed  between  its  two  divisions  (Fig.  743). 

The  superior  division  (ramus  superior)  (Fig.  735),  the  smaller,  passes  inward 
over  the  optic  nerve,  and  supplies  the  Superior  rectus  and  Levator  palpebrae 
muscles.  The  inferior  division  (ramus  inferior)  (Fig.  735),  the  larger,  divides 
into  three  branches.  One  passes  beneath  the  optic  nerve  to  the  Internal  rectus; 
another,  to  the  Inferior  rectus;  and  the  third,  the  longest  of  the  three,  passes 
forward  between  the  Inferior  and  External  recti  to  the  Inferior  oblique.     From 


Motor » 
Sensory  root. 
Fig.  734. — Nerves  of  the  orbit,  seen  from  above. 


iciirrent  filo^ment 
to  dura  mater. 


THE  FOURTH  OR  TROCHLEAR  NERVE 


977 


this  latter  a  short,  thick  branch,  radix  brevis  ganglii  ciliaris,  is  given  off  to  the  lower 
])art  of  the  ciliary  or  lenticular  ganglion  and  forms  its  short  or  motor  root  (Figs. 
735  and  738).  All  these  branches  enter  the  muscles  on  their  ocular  surface, 
except  that  to  the  Inferior  oblique,  which  enters  its  posterior  border. 

Applied  Anatomy. — Paralysis  of  the  oculomotor  nerve  may  be  the  result  of  many  causes: 
as  cerel)ral  disease;  conditions  causing  pressure  on  the  cavernous  sinus;  periostitis  of  the  bone 
entering  into  the  formation  of  the  sphenoidal  fissure;  fracture  of  the  orbit.  It  results,  when 
complete,  in  (1)  ptosis,  or  drooping  of  the  upper  eyelid,  in  consequence  of  the  Levator  palpebrae 
being  paralyzed;  (2)  external  strabismus,  on  account  of  the  unopposed  action  of  the  External 
rectus  muscle,  which  is  not  supplied  by  the  oculomotor  nerve,  and  is  not  therefore  paralyzed; 
(.3)  dilatation  of  the  pupil,  because  the  sphincter  fibres  of  the  iris  are  paralyzed;  (4)  loss  of 
power  of  accommodation,  as  the  Sphincter  pupillje,  the  Ciliary  muscle,  and  the  Internal  rectus 
are  paralyzed;  (5)  slight  prominence  of  the  eyeball,  owing  to  most  of  its  muscles  being  relaxed. 


^^Ocutomotor    Nerve 


Fig.  735.— Plan  of  the  oculomotor  nerve. 

Occasionally  paralysis  may  affect  only  a  part  of  the  nerve;  that  is  to  say,  there  may  be,  for  ex- 
ample, a  dilated  and  fixed  pupil,  with  ptosis,  but  no  other  signs.  Irritation  of  the  nerve  causes 
spasm  of  one  or  other  of  the  muscles  supplied  by  it;  thus,  there  may  be  internal  strabismus  from 
spasm  of  the  Internal  rectus;  accommodation  for  near  objects  only  from  spasm  of  the  Ciliary 
muscle,  or  contraction  of  the  pupil  (myosis),  from  irritation  of  the  sphincter  of  the  pupil. 

The  oculomotor  nerve  is  particularly  liable  to  become  involved  in  a  syphilitic  periarteritis 
where  it  passes  between  the  superior  cerebellar  and  posterior  cerebral  arteries;  associated  with 
locomotor  ataxia  various  partial  or  complete  paralyses  of  the  nerve  are  often  seen. 


THE  FOURTH  OR  TROCHLEAR  NERVE  (N.  TROCHLEARIS)  (Figs.  633,  734). 

The  fourth  or  trochlear  nerve  is,  with  the  exception  of  the  n.  intermedius,  the 
smallest  of  the  cranial  nerves,  and  supplies  the  Superior  oblique  muscle. 

It  arises  from  a  nucleus  in  the  floor  of  the  mid-brain  aqueduct  at  t!ie  level  of 
the  inferior  quadrigeminal  body.  From  its  origin  the  nerve  runs  outward,  curving 
around  the  central  aqueduct  gray  to  turn  inward  and  l)ackward  into  the  superior 
medullary  velum,  decussating  with  the  corresponding  nerve  of  the  opposite  side 
and  emerging  from  the  surface  laterad  of  the  frenulum  veli,  immediately  behind 
(or  caudad  of)  the  posterior  quadrigeminal  body. 

Emerging  from  the  superior  medullary  velum,  the  nerve  is  directed  outward 
across  the  superior  peduncle  of  the  cerebellum,  and  then  winds  forward  around 
the  outer  side  of  the  crus  cerebri,  immediately  above  the  pons,  pierces  the  dura 
in  the  free  border  of  the  tentorium,  just  behind,  and  external  to,  the  posterior 
clinoid  process,  and  passes  forward  in  the  outer  wall  of  the  cavernous  sinus, 
between  the  oculomotor  nerve  and  the  ophthalmic  division  of  the  trigeminal 
nerve  (Figs.  505  and  506).       It   crosses   the  oculomotor   nerve   and  enters  the 

C2 


978  THE  NEB  VE  SYSTEM 

orbit  through  the  sphenoidal  fissure  (Fig.  743).  It  now  becomes  the  highest 
of  all  the  nerves,  lying  at  the  inner  extremity  of  the  fissure  internal  to  the  frontal 
nerve.  In  the  orbit  it  passes  inward,  above  the  origin  of  the  Levator  palpe- 
brae,  and  finally  enters  the  orbital  surface  of  the  Superior  oblique  muscle. 

Branches  of  Communication. — In  the  outer  wall  of  the  cavernous  sinus  it  forms 
communications  with  the  cavernous  plexus  of  the  sympathetic  and  with  the 
ophthalmic  division  of  the  trigeminal  nerve.  In  the  sphenoidal  fissure  it  occa- 
sionally gives  oS  a  branch  to  assist  in  the  formation  of  the  lacrimal  nerve. 

Branches  of  Distribution. — It  gives  off  a  recurrent  branch,  which  passes  backward 
between  the  layers  of  the  tentorium  cerebelli,  dividing  into  two  or  three  filaments 
whicli  may  be  traced  as  far  back  as  the  wall  of  the  lateral  sinus. 

Applied  Anatomy. — The  trochlear  nerve  when  paralyzed  causes  loss  of  function  in  the  Su- 
perior oblique,  so  that  the  patient  is  unable  to  turn  his  eye  downward  and  outward.  Should  the 
patient  attempt  to  do  this,  the  eye  on  the  affected  side  is  twisted  inward,  producing  diplopia  or 
double  vision.  Accordingly,  it  is  said  that  the  first  symptom  of  this  disease  which  presents  itself 
is  giddiness  when  going  down  hill  or  in  descending  stairs,  owing  to  the  double  vision  produced 
by  the  patient  looking  at  his  steps  while  descending. 

THE  FIFTH,  TRIGEMINAL,  OR  TRIFACIAL  NERVE  (N.  TRIGEMINUS) 

(Figs.  737,  738). 

The  fifth,  trigeminal,  or  trifacial  nerve  is  the  largest  cranial  nerve.  It  resembles 
a  spinal  nerve  (1)  in  having  two  roots,  motor  and  sensor;  (2)  in  having  a  ganglion 
developed  on  its  sensor  root.  It  is  the  great  sensor  nerve  of  the  head  and  face  and 
the  motor  nerve  of  the  muscles  of  mastication ;  its  upper  two  divisions  are  entirely 
sensor,  the  third  division  is  partly  sensor  and  partly  motor.  It  arises  by  two  roots; 
of  these,  the  ventral  is  the  smaller,  and  is  the  motor  root  (Fig.  649) ;  the  dorsal,  the 
larger  and  sensor  root.  It  emerges  from  the  side  of  the  pons  near  the  upper  border, 
by  a  small  motor  and  a  large  sensor  root.  The  small  root  consists  of  three  or  four 
bundles;  the  large  root  consists  of  numerous  bundles  of  fibres,  varying  in  number 
from  seventy  to  a  hundred.  The  two  roots  are  separated  from  each  other  by  a  few 
of  the  transverse  fibres  of  the  pons.  The  deep  termination  of  the  large  or  sensor 
root  is  chiefly  in  a  long  tract  in  the  medulla  oblongata,  the  lower  sensor  nucleus, 
which  is  continuous  below  with  the  substantia  gelatinosa  Rolandi.  The  fibres 
from  this  nucleus  form  the  so-called  ascending  root  of  the  fifth  nerve ;  they  pass 
upward  through  the  pons  and  join  with  fibres  from  the  upper  sensor  nucleus  (Fig. 
650),  which  is  situated  to  the  outer  side  of  the  motor  nucleus,  from  which  the  lower 
part  of  the  motor  root  takes  origin.  The  deep  origin  of  the  small  or  motor  root 
is  derived  partly  from  a  nucleus  embedded  in  tlie  gray  substance  of  the  upper 
part  of  the  floor  of  the  fourth  ventricle  and  partly  from  a  collection  of  nerve  cells 
situated  at  the  side  of  the  aqueduct  from  which  the  fibres  pass  caudad  under  the 
name  of  the  mesencephalic  or  descending  root  of  the  fifth  nerve  (Fig.  650). 

The  two  roots  of  the  nerve  pass  forward  below  the  tentorium  as  it  bridges  over 
the  notch  on  the  inner  part  of  the  superior  border  of  the  petrous  portion  of  the 
temporal  bone  (Fig.  737) ;  they  then  run  between  the  bone  and  the  dura  to  the 
apex  of  the  petrous  portion  of  the  temporal  bone,  where  the  fibres  of  the  sensor 
root  appear  to  enter  into  the  formation  of  the  large  semilunar  or  Gasserian  ganglion 
(Figs.  736  and  737),  while  the  motor  root  passes  beneath  the  ganglion  without 
having  any  connection  with  it,  and  joins  outside  the  cranium  with  one  of  the 
trunks  derived  from  it  (Figs.  736  and  737). 

The  Gasserian  or  semilunar  ganglion^  (ganglion  semilunare)  (Figs.  736  and 
737)  is  lodged  in  an  osteofibrous  space,  the  cavum  Meckelii  (Fig.  726),  near  the 

1  A  Viennese  anatomist,  Raimund  Balthasar  Hirsch  (1765),  was  the  first  who  recognized  the  ganglionic  nature 
of  the  swelling  on  the  sensor  root  of  the  fifth  nerve,  and  called  it,  in  honor  of  his  otherwise  unlinown  teacher, 
Jon.  Laur,  Gasser,  the  "Ganglion  Gasseri."  Julius  Casserius.  whose  name  is  given  to  the  musculocutaneous 
nerve  of  the  arm,  was  professor  at  Padua,  1.545  to  1605.     (See  Hyrtl.  Lehrbuch  der  Anatomis,  p.  895  and  p.  55.) 


THE  FIFTH,    TRIGEMINAL,    OB   TRIFACIAL  NERVE 


979 


apex  of  the  petrous  portion  of  the  temporal  bone.  The  ganglion  is  of  somewhat 
crescentic  form,  with  its  convexity  turned  forward.  Its  upper  surface  is  intimately 
adherent  to  the  dura.  Besides  the  small  or  motor  root,  the  large  superficial  petrosal 
nerve  lies  underneath  the  ganglion. 


MOTOR   PORTION 


Fig.  736.— The  right  semilunar  or  G; 


NERVE 

on,  viewed  from  the  medial  aide.     (Enlarged.)     (Spalteholz.) 


Branches  of  Communication. — This  ganglion  receives  on  its  inner  side  filaments 
from  the  carotid  plexus  of  the  sympathetic. 

Branches  of  Distribution. — It  gives  off  minute  branches  to  the  tentorium  cerebelli 
and  the  dura  in  the  middle  fossa  of  the  cranium.  From  its  anterior  (convex) 
harder,  which  is  directed  forward  and  outward,  three  large  branches  proceed — • 
the  ophthalmic,  superior  maxillary,  and 
inferior  maxillary.  The  ophthalmic 
and  superior  maxillary  consist  exclu- 
sively of  fibres  derived  from  the  large 
root  and  ganglion,  and  are  solely 
nerves  of  common  sensation.  The 
third  division,  or  inferior  maxillary, 
is  joined  outside  the  cranium  by  the 
motor  root,  and  is,  therefore,  strictly 
speaking,  the  only  portion  of  the  tri- 
geminal nerve  which  can  be  said  to 
resemble  a  spinal  nerve. 

Associated  with  the  three  divisions 
of  the  trigeminal  nerve  are  four  small 
ganglia — the  ophthalmic,  sphenopala- 
tine, otic,  and  submaxillary  ganglia. 

The  ophthalmic  nerve  (/(.  ophthal- 
micus), or  first  division  of  the  tri- 
geminal, is  a  sensor  nerve.  It  supplies 
sensor  branches  to  the  cornea,  ciliary 
muscle,  and  iris^  to  the  lacrimal  gland, 
to  a  part  of  the  mucous  lining  of  the  nasal  fossae,  and  to  the  integument  of  the 
eyelids,  eyebrow,  forehead,  and  nose  (Fig.  742).  It  is  the  smallest  of  the  three 
divisions  of  the  fifth,  arising  from  the  upper  part  of  the  Gasserian  ganglion.  It 
is  a  short,  flattened  band,  about  2  cm.  (4  inch)  in  length,  which  passes  forward 


PETROSAL  SINUS 


SENSOR  ROOT 

-The  course  of  the  motor  root  of  the  trigeminal 
nerve.     (Poirier  and  Charpy.) 


980  THE  NERVE  SYSTEM 

along  the  outer  wall  of  the  cavernous  sinus  (Figs.  505  and  506) ,  below  the  oculo- 
motor and  trochlear  nerves  (Fig.  736),  and  just  before  entering  the  orbit,  through 
the  sphenoidal  fissure,  divides  into  three  branches — lacrimal,  frontal,  and  nasal. 

Branches  of  Communication. — The  ophthalmic  nerve  is  joined  by  filaments 
from  the  cavernous  plexus  of  the  sympathetic,  and  gives  off  minute  branches 
to  communicate  with  the  oculomotor  and  abducent  nerves,  and  not  infrequently 
with  the  trochlear. 

Branches  of  Distribution. — It  gives  off  recurrent  filaments  {n.  tentorii)  which 
pass  between  the  layers  of  the  tentorium  cerebelli,  and  then  divides  into — 

Lacrimal.  Frontal.  Nasal. 

The  lacrimal  nerve  (n.  lacrimalis)  (Figs.  738  and  739)  is  the  smallest  of  the  three 
branches  of  the  ophthalmic.  It  sometimes  receives  a  filament  from  the  trochlear 
nerve,  but  this  is  possibly  derived  from  the  branch  of  communication  which 
passes  from  the  ophthalmic  to  the  trochlear.  It  passes  forward  in  a  separate 
tube  of  dura,  and  enters  the  orbit  through  the  narrowest  part  of  the  sphenoidal 
fissure  (Fig.  743).  In  the  orbit  it  runs  along  the  upper  border  of  the  External 
rectus  muscle,  with  the  lacrimal  artery,  and  communicates  with  the  temporomalar 
branch  of  the  superior  maxillary  nerve.  It  enters  the  lacrimal  gland  and  gives 
ofl^  several  filaments,  which  supply  the  gland  and  the  conjunctiva.  Finally,  it 
pierces  the  superior  palpebral  ligament,  and  terminates  in  the  integument  of  the 
upper  eyelid,  joining  with  filaments  of  the  facial  nerve.  The  lacrimal  nerve  is 
occasionally  absent,  when  its  place  is  taken  by  the  temporal  branch  of  the  superior 
maxillary.  Sometimes  the  latter  branch  is  absent,  and  a  continuation  of  the 
lacrimal  is  substituted  for  it. 

The  frontal  nerve  (ji.  frontalis)  (Figs.  734  and  738)  is  the  largest  division  of  the 
ophthalmic,  and  may  be  regarded,  both  from  its  size  and  direction,  as  the  continu- 
ation of  the  nerve.  It  enters  the  orbit  above  the  muscles,  through  the  sphenoidal 
fissure  (Fig.  738),  and  runs  forward  along  the  middle  line,  between  the  Levator 
palpebrae  and  the  periosteum.  Midway  between  the  apex  and  the  base  of  the 
orbit  it  divides  into  two  branches,  supratrochlear  and  supraorbital. 

The  supratrochlear  branch  («.  supratrochlearis)  (Fig.  734)  the  smaller  of  the 
two,  passes  inward,  above  the  pulley  of  the  Superior  oblique  muscle,  and  gives 
off  a  descending  filament,  which  joins  with  the  infratrochlear  branch  of  the  nasal 
nerve.  It  then  leaves  the  orbit  between  the  pulley  of  the  Superior  oblique  and 
the  supraorbital  foramen,  curves  up  on  to  the  forehead  close  to  the  bone,  ascends 
beneath  the  Corrugator  supercilii  and  Occipitofrontalis  muscles,  and,  dividing 
into  branches  which  pierce  these  muscles,  it  supplies  the  integument  of  the  lower 
part  of  the  forehead  on  either  side  of  the  middle  line  and  sends  filaments  to  the 
conjunctiva  and  skin  of  the  upper  eyelid. 

The  supraorbital  branch  (/l  swpraorhitalis)  (Fig.  743)  passes  forward  through 
the  supraorbital  foramen,  and  gives  off,  in  this  situation,  palpebral  filaments  to 
the  upper  eyelid.  It  then  ascends  upon  the  forehead,  and  terminates  in  cutaneous 
and  pericranial  branches.  The  cutaneous  branches,  two  in  number,  an  inner  and 
an  outer,  supply  the  integument  of  the  cranium  as  far  back  as  the  vertex.  They 
are  at  first  situated  beneath  the  Occipitofrontalis,  the  inner  branch  perforating 
the  frontal  portion  of  the  muscle,  the  outer  branch  its  tendinous  aponeurosis. 
The  pericranial  branches  are  distributed  to  the  pericranium  over  the  frontal  and 
parietal  bones. 

The  nasal  nerve  («.  nasociliaris)  (Figs.  734  and  738)  is  intermediate  in  size 
between  the  frontal  and  lacrimal,  and  is  more  deeply  placed  than  the  other  branches 
of  the  ophthalmic.  It  enters  the  orbit  by  way  of  the  sphenoidal  fissure  (Fig. 
743)  between  the  two  heads  of  the  External  rectus,  and  passes  obliquely  inward 
across  the  optic  nerve,  beneath  the  Superior  rectus  and  Superior  oblique  muscles, 


THE  FIFTH,    TRIGEMINAL,    OB   TRIFACIAL  NERVE 


981 


to  the  inner  wall  of  the  orbit.  Here  it  passes  through  the  anterior  ethmoidal 
foramen,  and,  entering  the  cavity  of  the  cranium,  traverses  a  shallow  groove 
on  the  front  of  the  cribriform  plate  of  the  ethmoid  bone,  and  passes  down,  through 
the  slit  by  the  side  of  the  crista  galli,  into  the  nose  (Fig.  740),  where  it  divides 
into  two  branches,  an  internal  and  an  external  branch.  The  internal  branch 
(rami  nasales  mediales)  supplies  the  mucous  membrane  near  the  fore  part  of  the 
septum  of  the  nose.  The  external  branch  (rami  nasales  laterales)  descends  in  a 
groove  on  the  inner  surface  of  the  nasal  bone,  and  supplies  a  few  filaments  to  the 
mucous  membrffne  covering  the  fore  part  of  the  outer  wall  of  the  nares  as  far  as 
the  inferior  turbinate  process;  it  then  leaves  the  cavity  of  the  nose,  between  the. 
lower  border  of  the  nasal  bone  and  the  upper  lateral  cartilage  of  the  nose,  and, 
passing  down  beneath  the  Compressor  nasi,  supplies  the  integument  of  the  ala 
and  the  tip  of  the  nose,  joining  with  the  facial  nerve. 

The  branches  of  the  nasal  nerve  are  the  ganglionic,  long  ciliary,  and  infratrochlear. 

The  ganglionic  branch  or  the  long  root  of  the  ciliary  ganglion  [radix  loiiga  (janglii 
ciliaris)  (Figs.  735  and  738)  is  a  slender  branch,  about  1  to  2  cm.  in  length,  which 
usually  arises  from  the  nasal  nerve,  between  the  two  heads  of  the  External  rectus 


Fig.  738. — Nerves  of  the  orbit  and  ophthalmic  ganglion,  side 


muscle.  It  passes  forward  on  the  outer  side  of  the  optic  nerve,  and  enters  the 
postero-superior  angle  of  the  ciliary  ganglion,  forming  its  long  root.  It  is  some- 
times joined  by  a  filament  from  the  cavernous  plexus  of  the  sympathetic  or  from 
the  superior  division  of  the  oculomotor  nerve. 

The  long  ciliary  nerves  (nn.  ciliares  longi),  two  or  three  in  number,  are  given 
off  from  the  nasal  as  it  crosses  the  optic  nerve.  They  accompany  the  short  ciliary 
nerves  (Figs.  735  and  738)  from  the  ciliary  ganglion,  pierce  the  posterior  part  of 
the  sclera,  and,  running  forward  between  it  and  the  choroid,  are  distributed  to 
the  Ciliary  muscle,  iris,  and  cornea. 

The  infratrochlear  branch  (n.  infratrochlear  is)  (Fig.  734)  is  given  off  just  before 
the  nasal  nerve  passes  through  the  anterior  ethmoidal  foramen.  It  runs  forward 
along  the  upper  border  of  the  Internal  rectus  muscle,  and  is  joined,  beneath 
the  pulley  of  the  Superior  oblique,  by  a  filament  from  the  supratrochlear  nerve. 
It  then  passes  to  the  inner  angle  of  the  eye,  and  supplies  the  integument  of  the 
eyelids  and  side  of  the  nose,  the  conjunctiva,  the  lacrimal  sac,  and  the  cariuicula 
lacrimalis. 


982  THE  NERVE  SYSTEM 

The  ophthalmic,  lenticular,  or  ciliary  ganglion  (ganglion  ciliare)  is  a  small,  quad- 
rangular, flattened  ganglion  of  a  reddish-gray  color,  and  about  the  size  of  a  pin's 
head,  situated  at  the  back  part  of  the  orbit  between  the  optic  nerve  and  the  External 
rectus  muscle,  lying  generally  on  the  outer  side  of  the  ophthalmic  artery.  It  is 
enclosed  in  a  quantity  of  loose  fat,  which  makes  its  exposure  by  dissection  some- 
what difficult. 

Its  branches  of  communication  or  roots  are  three,  all  of  which  enter  its  posterior 
border.  One,  the  long  or  sensor  root  (radix  longa  gamjlii  ciliaris),  is  derived 
from  the  nasal  branch  of  the  ophthalmic  and  joins  its  postere-superior  angle. 
The  second,  the  short  or  motor  root  (radix  brevis  ganglii  ciliaris),  is  a  short,  thick 
nerve,  occasionally  divided  into  two  parts,  which  is  derived  from  the  branch  of 
the  oculomotor  to  the  Inferior  oblique  muscle,  and  is  connected  with  the  postero- 
inferior  angle  of  the  ganglion.  The  third,  the  sympathetic  root  (radix  sympa- 
thetica ganglii  ciliaris),  is  a  slender  filament  from  the  cavernoua  plexus  of  the 
sympathetic.  This  is  frequently  blended  with  the  long  root,  although  it  some- 
times passes  to  the  ganglion  separately.  The  ganglion  occasionally  receives  a 
filament  of  communication  from  the  sphenopalatine  ganglion. 

Its  branches  of  distribution  are  the  short  ciliary  nerves  (nu.  ciliares  breves)  (Figs. 
735  and  738).  These  are  delicate  filaments,  from  six  to  ten  in  number,  which 
arise  from  the  fore  part  of  the  ganglion  in  two  bundles,  connected  with  its  superior 
and  inferior  angles;  the  lower  bundle  is  the  larger.  They  run  forward  with  the 
ciliary  arteries  in  a  wavy  course,  one  set  above  and  the  other  below  the  optic  nerve, 
and  are  accompanied  by  the  long  ciliary  branches  of  the  nasal  nerve.  They  pierce 
the  sclera  at  the  back  part  of  the  globe,  pass  forward  in  delicate  grooves  on  its 
inner  surface,  and  are  distributed  to  the  Ciliary  muscle,  iris,  and  cornea.  One 
small  branch  is  said  to  penetrate  the  optic  nerve  with  the  arteria  centralis  retinae. 

The  superior  maxillary  nerve  (u.  maxillaris)  (Figs.  734  and  737),  or  second 
division  of  the  trigeminal,  is  a  sensor  nerve.  It  is  intermediate,  both  in  position 
and  size,  Ijetween  the  ophthalmic  and  inferior  maxillary.  It  commences  at  the 
middle  of  the  Gasserian  ganglion  as  a  flattened  plexiform  band,  and,  passing 
horizontally  forward,  it  leaves  the  skull  through  the  foramen  rotundum,  where  it 
becomes  more  cylindrical  in  form  and  firmer  in  texture.  It  then  crosses  the 
sphenomaxillary  fossa  (Fig.  67),  inclines  outward  on  the  back  of  the  maxilla, 
and  enters  the  orbit  through  the  sphenomaxillary  fissure;  it  traverses  the  infra- 
orbital canal  in  the  floor  of  the  orbit,  and  appears  upon  the  face  at  the  infra- 
orbital foramen.^  At  its  termination  the  nerve  lies  beneath  the  Levator  labii 
superioris  muscle,  and  divided  into  a  leash  of  branches,  which  spread  out  upon 
the  side  of  the  nose,  the  lower  eyelid,  and  upper  lip,  joining  with  filaments  of  the 
facial  nerve. 

Branches  of  Distribution. — The  branches  of  this  nerve  may  be  divided  into  four 
groups:  (1)  Those  given  off  in  the  cranium.  (2)  Those  given  off  in  the  spheno- 
maxillary fossa.     (3)  Those  in  the  infraorbital  canal.     (4)  Those  on  the  face. 

In  the  cranium  ....         Meningeal  or  dural. 

(  Orbital  or  temporomalar. 
Sphenomaxillary  fossa        .      j  Sphenopalatine. 

V  Posterior  superior  dental. 
Infraorbital  canal    .      .      .       |  Middle  superior  dental 

( Anterior  superior  dental, 
r  Palpebral. 
On  the  face       .      .      .      .      j  Nasal. 

V  Labial. 

'  After  it  enters  the  mfrax>rbital  canal  the  nerve  is  usually  called  the  infraorbital  (n.  infraorhitalis),  and  is, 
therefore,  the  terminal  branch,  of  the  superior  maxillary  nerve  (Fig.  742J. 


THE  FIFTH,    TRIGEMINAL,    OB   TRIFACIAL  NERVE 


983 


The  Meningeal  or  Dural  Branch  (n.  meiiiiigeiis  medius)  is  given  off  from  the  supe- 
rior maxillary  nerve  directly  after  its  origin  from  the  Gasserian  ganglion;  it  accom- 
panies the  middle  meningeal  artery  and  supplies  the  dura  of  the  middle  fossa 
of  the  base  of  the  skull. 

The  Orbital  or  Temporomalar  Branch  {n.  zygomaticus)  (Figs.  738  and  739)  arises 
in  the  sphenomaxillary  fossa,  enters  the  orbit  by  the  sphenomaxillary  fissure, 
and  divides  at  the  back  of  that  cavity  into  two  branches,  temporal  and  malar. 

The  temporal  branch  (ramus  zygomaticotemporalis)  runs  along  the  outer  wall 
of  the  orbit  in  a  groove  in  the  malar  bone,  receives  a  branch  of  communication 
from  the  lacrimal,  and,  passing  through  a  foramen  in  the  malar  bone,  enters  the 
temporal  fossa.  It  ascends  between  tlae  bone  and  the  substance  of  the  Temporal 
muscle,  pierces  this  muscle  and  the  temporal  fascia  about  an  inch  above  the 


739. — Distribution  of  the  second  and  third  divisions  of  the  trigeminal 


d  submaxillary  ganglion. 


zygoma,  and  is  distributed  to  the  integument  coveiing  the  temple  and  side  of 
the  forehead,  communicating  with  the  facial  and  the  auriculotemporal  branch  of 
the  inferior  maxillary  nerve.  As  it  pierces  the  temporal  fascia  it  gives  oft"  a  slender 
twig,  which  runs  between  the  two  layers  of  the  fascia  to  the  outer  angle  of  the 
orbit.  The  malar  branch  (ramus  zygomaticofacialis)  passes  along  the  external 
inferior  angle  of  the  orbit,  emerges  upon  the  face  through  a  foramen  in  the  malar 
bone,  and,  perforating  the  Orbicularis  palpebrarum  muscle,  supplies  the  skin 
on  the  prominence  of  the  cheek,  where  it  is  named  the  subcutaneus  malae.  It 
joins  with  the  facial  and  the  palpebral  branches  of  the  superior  maxillary. 

The  Sphenopalatine  Branches  (/(/(.  sphetwpalafiiu  (Fig.  739),  two  in  number, 
descend  to  the  sphenopalatine  ganglion,  of  which  ganglion  they  are  the  sensor 
or  short  roots. 


984  THE  NERVE  SYSTEM 

The  Posterior  Superior  Dental  Branches  {rami  aheolares  superiores  jMsteriores) 
(Fig.  739)  arise  from  the  trunk  of  the  nerve  just  as  it  is  about  to  enter  the  infra- 
orbital canal;  they  are  generally  two  in  number,  but  sometimes  arise  by  a  single 
trunk,  and  immediately  divide  and  pass  downward  on  the  tuberosity  of  the 
maxilla.  They  give  off  several  twigs  to  the  gums  and  neighboring  parts  of  the 
mucous  membrane  of  the  cheek,  superior  gingival  branches  (rami  gingivales 
superiores).  They  then  enter  the  posterior  dental  canals  on  the  zygomatic  surface 
of  the  maxilla,  and,  passing  from  behind  forward  in  the  substance  of  the  bone, 
communicate  with  the  middle  dental  nerve  by  a  plexus  formation,  and  give  off 
branches  to  the  lining  membrane  of  the  antrum  and  three  twigs  to  each  molar 
tooth.  These  twigs  enter  the  foramina  at  the  apices  of  the  fangs  and  supply 
the  pulp. 

The  Middle  Superior  Dental  Branch  (ramus  alveolaris  superior  medius)  is  given 
off  from  the  superior  maxillary  nerve  in  the  back  part  of  the  infraorbital  canal, 
and  runs  downward  and  forward  in  a  special  canal  in  the  outer  wall  of  the  antrum 
to  supply  the  two  bicuspid  teeth.  It  communicates  with  the  posterior  and  anterior 
dental  branches  by  a  plexus  formation  {plexus  dentalis  superior). 

At  its  point  of  communication  with  the  posterior  branch,  above  the  root  of  the  second  bicuspid 
tooth,  is  a  slight  thickening  which  is  the  so-called  ganglion  of  Valentin;  and  at  its  point  of 
communication  with  the  anterior  branch  is  a  second  enlargement,  which  is  called  the  ganglion 
of  Bochdalek.     Neither  of  these  is  a  true  ganglion. 

The  Anterior  Superior  Dental  Branch  {ramus  alveolaris  superior  anteriores),  of 
large  size,  is  given  off  from  the  superior  maxillary  nerve  just  before  its  exit  from 
the  infraorbital  foramen;  it  enters  a  special  canal  in  the  anterior  wall  of  the  antrum, 
and  divides  into  a  series  of  branches  which  supply  the  incisor  and  canine  teeth. 
It  communicates  with  the  middle  dental  nerve  by  a  plexus,  and  gives  off  a  nasal 
branch,  which  passes  through  a  minute  canal  into  the  nasal  fossa,  and  supplies 
the  mucous  membranes  of  the  fore  part  of  the  inferior  meatus  and  the  floor  of  the 
cavity,  commimicating  with  the  nasal  branches  from  the  sphenopalatine  ganglion. 

The  Palpebral  Branches  {rami  palpebrales  inferiores)  pass  upward  beneath  the 
Orbicularis  palpebrarum  muscle.  They  supply  the  integument  and  conjunctiva 
of  the  lower  eyelid,  joining  at  the  outer  angle  of  the  orbit  with  the  facial  nerve 
and  the  malar  branch  of  the  orbital. 

The  Nasal  Branches  (rami  nasales  interni)  pass  inward;  they  supply  the  integu- 
ment of  the  side  of  the  nose  and  join  with  the  nasal  branch  of  the  ophthalmic. 

The  Labial  Branches  (rami  labiales  superiores),  the  largest  and  most  numerous, 
descend  beneath  the  Levator  labii  superioris  muscle,  and  are  distributed  to  the 
integument  of  the  upper  lip,  the  mucous  membrane  of  the  mouth,  and  the  labial 
glands. 

All  these  branches  are  joined,  immediately  beneath  the  orbit,  by  filaments 
from  the  facial  nerve,  forming  an  intricate  plexus,  the  infraorbital  plexus. 

The  Sphenopalatine  or  Meckel's  Ganglion  {ganglion  sphenopalafiimm)  (Fig. 
740),  the  largest  of  the  ganglia  associated  with  the  branches  of  the  trigeminal 
nerve,  is  deeply  placed  in  the  sphenomaxillary  fossa,  close  to  the  sphenopalatine 
foramen.  It  is  triangular  or  heart-shaped,  of  a  reddish-gray  color,  and  is  situated 
just  below  the  superior  maxillary  nerve  as  it  crosses  the  fossa. 

Branches  of  Communication. — Like  the  other  ganglia  of  the  trigeminal  nerve,  it 
possesses  a  motor,  a  sensor,  and  a  sympathetic  root.  Its  sensor  root  is  derived 
from  the  superior  maxillary  nerve  through  its  two  sphenopalatine  branches 
(p.  983).  These  branches  of  the  nerve,  given  off  in  the  sphenomaxillary  fossa, 
descend  to  the  ganglion.  Their  fibres,  for  the  most  part,  pass  in  front  of  the 
ganglion,  as  they  proceed  to  their  destination,  in  the  palate  and  nasal  fossa,  and 
are  not  incorporated  in  the  ganglionic  mass;  some  few  of  the  fibres,  however, 


THE  FIFTH,    TRIGEMINAL,    OR   TRIFACIAL  NERVE 


985 


enter  the  ganglion,  constituting  its  sensor  root.  Its  motor  root  is  derived  from  tlie 
facial  nerve  through  the  large  superficial  petrosal  nerve,  and  its  sympathetic 
root  from  the  carotid  plexus,  through  the  large  deep  petrosal  nerve.  These  two 
nerves  join  together  before  their  entrance  into  the  ganglion  to  form  a  single  nerve, 
the  Vidian. 

The  large  or  great  superficial  petrosal  branch  (h.  petrosus  superficialis  major) 
(Fig.  744)  is  given  off  from  tlie  geniculate  ganglion  implanted  on  the  external  genu 
of  the  facial  nerve  in  the  facial  canal  or  aquaeductus  Fallopii;  it  passes  through 
the  hiatus  canalis  facialis,  enters  the  cranial  cavity,  and  runs  forward,  being 
contained  in  a  groove  on  the  anterior  surface  of  the  petrous  portion  of  the  temporal 
bone,  and  lies  beneath  the  dura.  It  then  enters  the  cartilaginous  substance  which 
fills  in  the  foramen  lacerum  medium,  and,  joining  with  the  large  deep  petrosal 
nerve,  forms  the  Vidian  nerve. 


Fig.  740. — The  sphenopalatine  or  Meckel's  ganglion  and  its  branches 


The  large  deep  petrosal  nerve  (?i.  pefrosus  profundus)  (Fig.  745)  is  given  off 
from  the  carotid  plexus  of  the  sympathetic  upon  the  internal  carotid  artery, 
and  runs  through  the  carotid  canal  on  the  outer  side  of  the  internal  carotid  artery. 
It  then  enters  the  cartilaginous  substance  which  fills  in  the  foramen  lacerum 
medium,  and  joins  with  the  large  superficial  petrosal  nerve  to  form  the  Vidian. 

The  Vidian  nerve  (;i.  canalis  pterygoidei)  (Fig.  740),  formed  by  the  junction  of 
the  two  preceding  nerves  in  the  cartilaginous  substance  which  fills  in  the  middle 
lacerated  foramen,  passes  forward,  through  the  Vidian  canal,  with  the  artery  of 
the  same  name,  and  is  joined  by  a  small  ascending  nerve  branch,  the  sphenoidal 
branch,  from  the  otic  ganglion.  Finally,  it  enters  the  sphenomaxillary  fossa,  and 
joins  the  posterior  angle  of  the  sphenopalatine  ganglion. 

Branches  of  Distribution  of  the  Sphenopalatine  Ganglion. — These  are  divisible 
into  four  groups — ascending,  which  pass  to  the  orbit;  descending,  to  the  palate; 
internal,  to  the  nose;  and  posterior  branches,  to  the  nasopharynx. 


986  THE  NERVE  SYSTEM 

The  ascending  branches  (rami  orhitales)  are  two  or  three  delicate  filaments  which 
enter  the  orbit  by  the  sphenomaxillary  fissure,  and  supply  the  periosteum  and  the 
nonstriated  muscle  parts  of  the  Levator  palpebrae  or  Superior  tarsal  muscle, 
the  Inferior  tarsal  muscle,  and  the  Orbital  muscle  of  Miiller.  According  to 
Luschka,  some  filaments  pass  through  foramina  in  the  suture  between  the  os 
planum  of  the  ethmoid  and  frontal  bone  to  supply  the  mucous  membrane  of 
the  posterior  ethmoidal  and  sphenoidal  sinuses. 

The  descending  or  palatine  branches  {nn.  palatini)  (Fig.  740)  are  distributed 
to  the  roof  of  the  mouth,  the  soft  palate,  tonsil,  and  lining  membrane  of  the  nose. 
They  are  almost  a  direct  continuation  of  the  sphenopalatine  branches  of  the 
superior  maxillary  nerve,  and  are  three  in  number — anterior,  middle,  and  posterior. 

The  anterior  palatine  nerve'  (n.  palatinus  anterior)  descends  through  the  posterior 
palatine  canal,  emerges  upon  the  hard  palate  at  the  posterior  palatine  foramen, 
and  passes  forward  in  a  groove  in  the  hard  palate,  nearly  as  far  as  the  incisor 
teeth.  It  supplies  the  gums,  the  mucous  membrane,  and  glands  of  the  hard  palate, 
and  communicates  in  front  with  the  termination  of  the  nasopalatine  nerve  (see 
below).  While  in  the  posterior  palatine  canal  it  gives  off  inferior  nasal  branches 
(rami  nasales  posteriores  inferiores),  which  enter  the  nose  through  openings  in 
the  palate  bone  and  ramify  over  the  turbinated  bone  and  middle  and  inferior 
meatuses;  and,  at  its  exit  from  the  canal,  a  palatine  branch  is  distributed  to  both 
surfaces  of  the  soft  palate. 

The  middle  palatine  nerve  (n.  palatinus  medius)  descends  through  one  of  the 
accessory  posterior  palatine  canals,  distributing  branches  to  the  uvula,  tonsil, 
and  soft  palate.     It  is  occasionally  wanting. 

The  posterior  palatine  nerve  (?i.  palatinus  posterior)  descends  with  a  minute 
artery  through  the  posterior  palatine  canal,  and  emerges  by  a  separate  opening 
behind  the  posterior-  palatine  foramen.  It  supplies  the  soft  palate,  tonsil,  and 
uvula.  The  middle  and  posterior  palatine  join  with  the  tonsillar  branches  of 
the  glossopharyngeal  to  form  a  plexus  around  the  tonsil  (circulus  tonsillaris). 

The  internal  branches  are  distributed  to  the  septum  and  oucer  M'all  of  the  nasal 
fossae.     They  are  the  superior  nasal  and  the  nasopalatine. 

The  superior  nasal  branches  (rami  nasales  posteriores  superiores),  four  or  five 
in  number,  enter  the  back  part  of  the  nasal  fossa  by  the  sphenopalatine  foramen. 
They  supply  the  mucous  membrane  covering  the  superior  and  middle  turbinated 
processes,  and  that  lining  the  posterior  ethmoidal  cells,  a  few  being  prolonged 
to  the  upper  and  back  part  of  the  septum. 

The  nasopalatine  nerve  (n.  nasopalatinus)  also  enters  the  nasal  fossa  through 
the  sphenopalatine  foramen;  it  passes  inward  across  the  roof  of  the  nose,  below 
the  orifice  of  the  sphenoidal  sinus,  to  reach  the  septum,  and  then  runs  obliquely 
downward  and  forward  along  the  lower  part  of  the  septum,  to  the  anterior  palatine 
foramen,  lying  between  the  periosteum  and  mucous  membrane.  It  descends 
to  the  roof  of  the  mouth  through  the  anterior  palatine  canal  (Fig.  740).  The  two 
nerves  are  here  contained  in  separate  and  distinct  canals,  situated  in  the  inter- 
maxillary suture,  and  termed  the  foramina  of  Scarpa,  the  left  nerve  being  usually 
anterior  to  the  right  one.  In  the  mouth  they  become  united,  supply  the  mucous 
membrane  behind  the  incisor  teeth,  and  join  with  the  anterior  palatine  nerves. 
The  nasopalatine  nerve  furnishes  a  few  small  filaments  to  the  mucous  membrane 
of  the  septum. 

Posterior  Branch. — The  pharyngeal  or  pterygopalatine  nerve  (Fig.  740)  is  a  small 
branch  arising  from  the  back  part  of  the  sphenopalatine  ganglion.  It  passes 
through  the  pterygopalatine  canal  with  the  pterygopalatine  artery,  and  is  dis- 
tributed to  the  mucous  membrane  of  the  upper  part  of  the  pharynx,  behind  the 
Eustachian  tube. 

*  Formerly  called  the  great  palatine  nerve. 


THE  FIFTH,   TRIGEMINAL,   OB  TRIFACIAL  NERVE  987 

The  Inferior  Maxillary  or  Mandibular  Nerve  {n.  mandihularis)  (Figs.  738 
and  739). — The  inferior  maxillary  or  third  division  of  the  trigeminal  nerve  dis- 
tributes branches  to  the  teeth  and  gums  of  the  mandible,  the  integument  of  the 
temple  and  external  ear,  the  lower  part  of  the  face  and  lower  lip,  and  the  muscles 
of  mastication;  it  also  supplies  the  tongue  with  a  large  branch.  It  is  the  larcrest 
of  the  three  divisions  of  the  trigeminal,  and  is  made  up  of  two  roots — a  large  or 
sensor  root,  proceeding  from  the  inferior  angle  of  the  Gasserian  ganglion;  and  a 
small  or  motor  root,  wliich  passes  beneath  the  ganglion  and  unites  with  the  sensor 
root  just  after  its  exit  from  the  skull  through  the  foramen  ovale  (Figs.  736  and  739). 
Immediately  beneath  the  base  of  the  skull  this  nerve  divides  into  two  trunks, 
anterior  and  posterior.  Previous  to  its  division  the  primary  trunk  gives  off  from 
its  inner  side  a  recurrent  (meningeal)  branch  and  the  nerve  to  the  Internal  ptery- 
goid muscle. 

The  Recurrent  or  Meningeal  Branch  (ii.  spinosus)  is  given  off  directly  after  its  exit 
from  the  foramen  ovale.  It  passes  backward  into  the  skull  through  the  foramen 
spinosura  with  the  middle  meningeal  artery.  It  divides  into  two  branches,  anterior 
and  posterior,  which  accompany  the  main  divisions  of  the  artery  and  supply  tlie 
dura.  The  posterior  branch  also  supplies  the  mucous  lining  of  the  mastoid  cells. 
The  anterior  branch  communicates  with  the  dural  branch  of  the  superior  maxillary 
nerve. 

The  Internal  Pterygoid  Nerve  («.  pterygoideus  interims),  given  off  from  the 
inferior  maxillary  previous  to  its  division,  is  intimately  connected  at  its  origin 
with  the  otic  ganglion.  It  is  a  long  and  slender  branch,  which  passes  inward  to 
enter  the  deep  surface  of  the  Internal  pterygoid  muscle. 

The  anterior  and  smaller  division  of  the  inferior  maxillary  nerve,  which  receives 
nearly  the  whole  of  the  motor  root  of  the  trigeminal  nerve,  divides  into  branches 
which  supply  the  muscles  of  mastication.  They  are  the  masseteric,  deep  temporal, 
buccal,  and  external  pterygoid  branches  (Fig.  739). 

The  masseteric  branch  {a.  massetericus)  passes  outward,  above  the  External 
pterygoid  muscle,  in  front  of  the  temporomandibular  articulation  and  behind 
the  tendon  of  the  Temporal  muscle;  it  crosses  the  sigmoid  notch  with  the  masse- 
teric artery,  to  the  deep  surface  of  the  Masseter  muscle,  in  which  it  ramifies 
nearly  as  far  as  its  anterior  border.  It  gives  a  filament  to  the  temporoman- 
dibular joint. 

The  deep  temporal  branches  (nii.  iemporales  profundi),  two  in  number,  anterior 
and  posterior,  supply  the  deep  surface  of  the  Temporal  muscle.  The  posterior 
branch  (n.  temporalis  profundus  posterior),  of  small  size,  is  placed  at  the  back  of 
the  temporal  fossa.  It  sometimes  arises  in  common  with  the  masseteric  branch. 
The  anterior  branch  (n.  temporalis  profundus  anterior)  is  frequently  given  off  with 
the  buccal  nerve;  it  is  reflected  upward,  at  the  pterygoid  ridge  of  the  sphenoid, 
to  the  front  of  the  temporal  fossa.  Frequently  a  third  branch  (middle  deep  tem- 
poral) is  present. 

The  buccal  or  buccinator  branch  (n.  buccinatorius)  passes  foi'ward  between  the 
two  heads  of  the  External  pterygoid;  and  downward  beneath  or  through  the  fibres 
of  the  Temporal  muscle;  it  gives  a  branch  to  the  External  pterygoid  during  its 
passage  through  that  muscle,  and  a  few  ascending  filaments  to  the  Temporal 
muscle,  one  of  which  occasionally  joins  with  the  anterior  branch  of  the  deep  tem- 
poral nerve.  The  superior  or  upper  branch  supplies  the  integument  and  upper 
part  of  the  Buccinator  muscle,  joining  with  the  facial  nerve  around  the  facial 
vein.  The  inferior  or  lower  branch  passes  forward  to  the  angle  of  the  mouth; 
it  supplies  the  integument  and  Buccinator  muscle,  as  well  as  the  mucous  membrane 
lining  the  inner  surface  of  that  muscle,  and  joins  the  facial  nerve.' 

'  There  seems  to  be  no  reason  to  doubt  that  the  branch  supplying  the  Buccinator  muscle  is  entirely  a  nerve  of 
ordinary  sensation,  and  that  the  true  motor  supply  of  this  muscle  is  from  the  facial. 


988  THE  NEB  VE  SYSTE3I 

The  external  pterygoid  nerve  (».  pterygoideus  externus)  is  most  frequently 
derived  from  the  buccal,  but  it  may  be  given  off  separately  from  the  anterior 
trunk  of  the  inferior  maxillary  nerve.     It  enters  the  muscle  on  its  inner  surface. 

The  posterior  and  larger  division  of  the  inferior  maxillary  nerve  is  for  the  most 
part  sensor,  but  receives  a  few  filaments  from  the  motor  root.  It  divides  into  three 
branches — auriculotemporal,  lingual,  and  inferior  dental  (Fig.  739). 

The  auriculotemporal  nerve  (ji.  auriculotemporalis)  (Fig.  741)  generally  arises 
by  two  roots,  between  which  the  middle  meningeal  artery  passes.  It  runs  back- 
ward beneath  the  External  pterygoid  muscle  to  the  inner  side  of  the  neck  of  the 
mandible.  It  then  turns  upward  with  the  temporal  artery,  between  the  external 
auditory  canal  and  the  condyle  of  the  mandible,  under  cover  of  the  parotid  gland, 
and,  escaping  from  beneath  this  structure,  ascends  over  the  zygoma  and  divides 
into  two  temporal  branches. 

The  branches  of  communication  of  the  auriculotemporal  nerve  are  with  the  facial 
and  with  the  otic  ganglion.  The  branches  of  communication  with  the  facial 
(rami  anastomotici  cum  n.faciali),  usually  two  in  number,  pass  forward  from  behind 
the  neck  of  the  condyle  of  the  mandible,  to  join  this  nerve  at  the  posterior  border 
of  the  Masseter  muscle.  The  filaments  of  communication  with  the  otic  ganglion 
are  derived  from  the  commencement  of  the  auriculotemporal  nerve. 

The  branches  of  distribution  are: 

Anterior  auricular.  Parotid. 

Articular.  Superficial  temporal. 

Branches  to  the  external  auditory  meatus. 

The  anterior  auricular  branches  (nn.  auricnlares  arderiores)  are  usually  two  in 
number.  They  supply  the  front  of  the  upper  part  of  the  pinna,  being  distributed 
principally  to  the  skin  covering  the  front  of  the  helix  and  tragus. 

A  branch  to  the  temporomandibular  articulation,  the  articular  branch,  is  usually 
derived  from  the  auriculotemporal  nerve. 

The  parotid  branches  (rami.parotidei)  supply  the  parotid  gland. 

The  superficial  temporal  branches  (rami  temporales  superficiales)  accompany  the 
temporal  artery  to  the  vertex  of  the  skull,  and  supply  the  integument  of  the  tem- 
poral region,  communicating  with  the  facial  nerve,  and  with  the  temporal  branch 
of  the  temporomalar  from  the  superior  maxillary  nerve. 

The  branches  to  the  external  auditory  meatus  (n.  meatus  auditorii  externi),  two 
in  number,  enter  the  canal  between  the  bony  and  cartilaginous  portion  of  the 
meatus.  They  supply  the  skin  lining  the  meatus;  the  upper  one  sending  a  filament 
to  the  membrana  tympani  (ramus  memhranae  tympani). 

The  lingual  nerve  (n.  lingualis)  (Fig.  739)  supplies  the  papilla  and  mucous 
membrane  of  the  anterior  two-thirds  of  the  tongue,  and  is  deeply  placed  throughout 
the  whole  of  its  course.  It  lies  at  first  beneath  the  External  pterygoid  muscle, 
being  placed  to  the  inner  side  and  in  front  of  the  inferior  dental  nerve,  and  is 
occasionally  joined  to  this  nerve  by  a  branch  which  may  cross  the  internal  maxil- 
lary artery.  The  chorda  tympani  nerve  also  joins  it  at  an  acute  angle  in  this  situ- 
ation. The  nerve  then  passes  between  the  Internal  pterygoid  muscle  and  the 
inner  side  of  the  ramus  of  the  mandible,  and  crosses  obliquely  to  the  side  of  the 
tongue  over  the  Superior  constrictor  of  the  pharynx  and  the  Styloglossus  muscles, 
and  then  between  the  Hyoglossus  muscle  and  the  deep  part  of  the  submaxillary 
gland;  the  nerve  finally  runs  across  the  submaxillary  or  Wharton's  duct,  and  along 
the  side  of  the  tongue  to  its  apex,  lying  immediately  beneath  the  mucous  membrane. 

The  branches  of  communication  are  with  the  inferior  dental  and  hypoglossal 
nerves  and  the  submaxillary  ganglion,  and,  apparently  only,  with  the  facial  through 
the  chorda  tympani.     The  branches  to  the  submaxillary  ganglion  are  two  or  three 


THE  FIFTH,   TRIGEMINAL,   OB  TRIFACIAL  NERVE  989 

in  number;  those  connected  with  the  hj'poglossal  nerve  form  a  plexus  at  the  anterior 
margin  of  the  Hyoglossus  muscle. 

The  branches  of  distribution  supply  the  mucous  membrane  of  the  mouth,  the 
gums,  the  sublingual  gland,  and  the  mucous  membrane  of  the  anterior  two- 
thirds  of  the  tongue;  the  terminal  filaments  communicate  at  the  tip  of  the  tongue, 
with  the  hypoglossal  nerve.  The  chorda  tympani  fibres  which  join  the  lingual 
nerve  are  probably  taste  fibres  and  excitoglandular  for  the  submaxillary  and  sub- 
lingual salivary  glands. 

The  inferior  dental  nerve  (»,.  alveolaris  inferior)  (Fig.  739)  is  the  largest  of  the 
branches  of  the  inferior  maxillary  nerve.  It  passes  downward  with  the  inferior 
dental  artery,  at  first  beneath  the  External  pterygoid  muscle,  and  then  between 
the  internal  lateral  ligament  and  the  ramus  of  the  mandible  to  the  dental  foramen. 
It  then  passes  forward  in  the  dental  canal  of  the  mandible,  lying  beneath  the  teeth, 
as  far  as  the  mental  foramen,  where  it  divides  into  two  terminal  branches,  incisor 
and  mental. 

The  branches  of  the  inferior  dental  are  the  mylohyoid,  dental,  incisor,  and 
mental. 

The  mylohyoid  (/;.  mijlohi/oideus)  is  derived  from  the  inferior  dental  just  as  that 
nerve  is  about  to  enter  the  dental  foramen.  It  descends  in  a  groove  on  the  inner 
surface  of  the  ramus  of  the  mandible,  in  which  it  is  retained  by  a  process  of  fibrous 
membrane.  It  reaches  the  under  surface  of  the  Mylohyoid  muscle,  and  supplies 
it  and  the  anterior  belly  of  the  Digastric. 

The  dental  branches  supply  the  molar  and  bicuspid  teeth.  They  correspond 
in  number  to  the  fangs  of  those  teeth,  each  nerve  entering  the  orifice  at  the  point 
of  the  fang  and  supplying  the  pulp  of  the  tooth. 

The  incisor  branch  is  continued  onward  within  the  bone  to  the  middle  line,  and 
supplies  the  canine  and  incisor  teeth. 

The  dental  branches  and  the  incisor  branch  form  a  plexus  (plexus  dentalis  infe- 
rior), and  from  this  plexus  come  the  branches  to  the  teeth  (rami  dentales  inferiores) 
and  to  the  gums  {rami  gingivales  inferiores). 

The  mental  branch  («.  menialis)  emerges  from  the  bone  at  the  mental  foramen, 
and  divides  beneath  the  Depressor  anguli  oris  muscle  into  two  or  three  branches; 
one  descends  to  supply  the  skin  of  the  chin,  and  another  (sometimes  two)  ascends 
to  supply  the  skin  and  mucous  membrane  of  the  lower  lip.  These  branches  com- 
municate freely  with  the  facial  nerve. 

Two  small  ganglia  are  connected  with  the  inferior  maxillary  nerve — the  otic 
■with  the  trunk  of  the  nerve,  and  the  submaxillary  with  its  lingual  branch. 

The  Otic  Ga,nglion( gang! ion  oticum)  (Fig.  739)  is  a  small,  oval-shaped,  flattened 
ganglion  of  a  reddish-gray  color,  situated  immediately  below  the  foramen  ovale, 
on  the  inner  surface  of  the  inferior  maxillary  nerve,  and  surrounding  the  origin 
of  the  internal  pterygoid  nerve.  It  is  in  relation,  externally,  with  the  trunk  of 
the  inferior  maxillary  nerve,  at  the  point  where  the  motor  root  joins  the  sensor 
portion;  internally,  with  the  cartilaginous  part  of  the  Eustachian  tube,  and  the 
origin  of  the  Tensor  palati  muscle;  behind,  it  lies  in  relation  with  the  middle 
meningeal  artery. 

Branches  of  Communication. — ^This  ganglion  is  connected  with  the  internal 
pterygoid  branch  of  the  inferior  maxillary  nerve  by  two  or  three  short,  delicate 
filaments.  From  this  nerve  the  ganglion  may  obtain  a  motor  root,  and  possibly 
also  a  sensor  root,  as  these  filaments  from  the  nerve  to  the  Internal  pterygoid 
perhaps  contain  sensor  fibres.  The  otic  ganglion  communicates  with  the  glosso- 
pharyngeal and  facial  nerves  through  the  small  superficial  petrosal  nerve  (Figs.  741 
and  744)  continued  from  the  tympanic  plexus,  and  through  this  communication 
it  probably  receives  its  sensor  root  from  the  glossopharjmgeal  and  its  motor  root 
from  the  facial;  its  communication  with  the  symoathetic  is  effected  by  a  filament 


990 


THE  NERVE  SYSTEM 


from  the  plexus  surrounding  the  middle  meningeal  artery.  The  ganglion  also 
communicates  with  the  auriculotemporal  nerve  (ramus  anastomoticus  cum  n. 
auriculotemporali).  This  communicating  filament  is  probably  a  branch  from 
the  glossopharyngeal  which  passes  to  the  ganglion,  and  through  it  and  the  auriculo- 
temporal nerve  to  the  parotid  gland.  A  slender  filament,  the  sphenoidal,  ascends 
from  it  to  the  Vidian  nerve. 

Branches  of  Distribution. — Its  branches  of  distribution  are  a  filament  to  the 
Tensor  tympani  (n.  tensoris  tympani)  and  one  to  the  Tensor  palati  (n.  tensoris 
veil  palatini).  The  former  passes  backward  on  the  outer  side  of  the  Eustachian 
tube;  the  latter  arises  from  the  ganglion,  near  the  origin  of  the  internal  pterygoid 
nerve,  and  passes  forward.  The  fibres  of  these  nerves  are,  however,  mainly 
derived  from  the  nerve  to  the  Internal  pterygoid  muscle. 

The  Submaxillary  Ganglion  (ganglion  submaxillare)  (Fig.  739)  is  of  small  size, 
fusiform  in  shape,  and  situated  above  the  deep  portion  of  the  submaxillary  gland, 
near  the  posterior  border  of  the  Mylohyoid  muscle,  being  connected  by  filaments 
with  the  lower  border  of  the  lingual  nerve. 


Fig.  741. — The  otic  ganglion  and  its  branches 


Branches  of  Communication. — ^This  ganglion  is  suspended  from  the  lingual  nerve 
by  two  filaments  (rami  communicanies  cum  n.  linguali),  which  join  it  separately 
at  its  fore  and  back  part.  It  also  receives  a  branch  from  the  chorda  tympani, 
and  communicates  with  the  sympathetic  by  filaments  from  the  sympathetic  plexus 
around  the  facial  artery. 

Branches  of  Distribution. — These  are  five  or  six  in  number;  they  arise  from  the 
lower  part  of  the  ganglion,  and  supply  the  mucous  membrane  of  the  mouth  and 
the  submaxillary  or  Wharton's  duct,  some  being  lost  in  the  submaxillary  gland 
(rami  submaxillar es).  The  branch  of  communication  from  the  lingual  nerve 
to  the  fore  part  of  the  ganglion  is  by  some  regarded  as  a  branch  of  distribution, 
by  which  filaments  of  the  chorda  tympani  pass  from  the  ganglion  to  the  lingual 
nerve,  and  by  it  are  conveyed  to  the  sublingual  gland  and  the  tongue. 

Surface  Marking. — It  will  be  seen  from  the  above  description  that  the  three  terminal 
branches  of  the  three  divisions  of  the  trigeminal  nerve  emerge  from  foramina  in  the  bones  of 
the  skull  and  pass  on  to  the  face;  the  terminal  branch  of  the  first  division  emerging  through  the 


THE  FIFTH,    TRIGEMINAL,    OR   TRIFACIAL  NERVE 


991 


supraorbital  foramen;  that  of  the  second  through  the  infraorbital  foramen;  and  the  third  throujjh 
the  mental  foramen.  The  supraorbital  foramen  is  situated  at  the  junction  of  the  internal  and 
middle  third  of  the  supraorbital  arch.  If  a  straight  line  is  drawn  from  this  point  to  the  lower 
border  of  the  mandibfe,  so  that  it  passes  between  the  two  bicuspid  teeth  of  the  mandible,  it  will 
pass  over  the  infraorbital  and  mental  foramina,  the  former  being  situated  about  one  centimetre 
(two-fifths  of  an  inch)  below  the  margin  of  the  orbit,  and  the  latter  varying  in  jjosition  according 
to  the  age  of  the  individual.  In  the  adult  it  is  midway  between  the  upper  and  lower  borders  of 
the  mandible;  in  the  child  it  is  nearer  the  lower  border;  and  in  the  edentulous  jaw  of  old  age 
it  is  close  to  the  upper  margin. 

Applied  Anatomy. — In  fracture  of  the  hose  of  the  skull  the  trigeminal  nerve  or  one  of  its 
brandies  may  be  injured.  It  seems  certain  that  occasionally,  though  seldom,  the  trigeminal 
nerve  may  be  actually  divided  by  such  an  injury.  The  trigeminal  nerve  may  be  aft'ected  in  its 
entirety,  or  its  sensor  or  motor  root  may  be  affected,  or  one  of  its  primary  main  divisions.  In 
injury  to  the  sensor  root  there  is  anesthesia  of  the  half  of  the  face  on  the  side  of  the  lesion,  with 
the  exception  of  the  skin  over  the  parotid  gland;  insensibility  of  the  conjunctiva,  followed,  if 
the  eye  is  not  temporarily  protected  with  a  watch  glass,  by  destructive  inflammation  of  the  cornea, 


MENTAL  NtRVE- 


FlG.  742. — Sensor  areas  of  the  head,  showing  the  general  distribution  of  the  three  dii 
nerve.     Gerrish'3  Anatomy.      (Modified  from  Testut.) 


partly,  it  is  held,  from  loss  of  trophic  influence,  and  partly  it  is  certain,  from  the  irritation  pro- 
duced by  the  presence  of  foreign  bodies  on  it,  which  are  not  perceived  by  the  patient,  and  there- 
fore not  e.xpelled  by  the  act  of  winking;  dryness  of  the  nose,  loss  to  a  considerable  extent  of  the 
sense  of  taste,  and  diminished  secretion  of  the  lacrimal  and  salivary  glands.  In  injury  to  the 
motor  root  there  is  impaired  action  of  the  mandible  from  paralysis  of  the  muscles  of  mastication 
on  the  affected  side. 

The  trigeminal  nerve  is  often  the  seat  of  neuralgia,  and  each  of  the  three  divisions  has  been 
divided  or  a  portion  of  the  nerve  excised  for  this  affection.  The  supraorbital  nerve  may  be  ex- 
posed by  making  an  incision  an  inch  and  a  half  in  length  along  the  supraorbital  margin  below  the 
eyebrow,  which  is  to  be  drawn  upward,  the  centre  of  the  incision  corresponding  to  the  supra- 
orbital notch.  The  skin  and  Orbicularis  palpebrarum  having  been  divided,  the  nerve  can  be 
easily  found  emerging  from  the  notch  and  lying  in  some  loose  cellular  tissue.  It  should  be  drawn 
up  by  a  blunt  hook  and  divided,  or,  what  is  better,  a  portion  of  it  should  be  removed. 

The  infraorbital  nerve  has  been  divided  at  its  exit  by  an  incision  on  the  cheek;  or  the  floor  of  the 
orbit  has  been  exposed,  the  infraorbital  canal  opened  up,  and  the  anterior  part  of  the  nerve 
resected;  or  the  whole  nerve,  together  with  Meckel's  ganglion  as  far  back  as  the  foramen  rotun- 
dum,  has  been  removed.  This  latter  operation,  though  undoubtedly  a  severe  proceeding, 
appears  to  have  been  followed  by  better  results  than  has  nerve  resection.  The  ojieration  is  per- 
formed as  fellows.  The  maxilla  is  first  exposed  by  a  T-shaped  incision,  one  limb  of  the  incision 


992  THE  NER  VE  SYSTEM 

passing  along  the  lower  margin  of  the  orbit,  the  other  from  the  centre  of  the  first  cut  vertically 
down  the  cheek  toward  the  angle  of  the  mouth.  The  nerve  is  then  found,  is  divided,  and  a 
piece  of  silk  is  tied  to  it  as  a  guide.  A  small  trephine  (one-half  inch)  is  then  applied  to  the  bone 
below,  but  including  the  infraorbital  foramen,  and  the  antrum  opened.  '  The  trephine  is  now 
applied  to  the  posterior  wall  of  the  antrum,  and  the  sphenomaxillary  fossa  exposed.  The 
infraorbital  canal  is  now  opened  up  from  below  by  fine  cutting  pliers  or  a  chisel,  and  the  nerve 
drawn  down  into  the  trephine  hole,  it  being  held  on  the  stretch  by  means  of  the  piece  of  silk; 
it  is  severed  with  fine  curved  scissors  as  near  the  foramen  rotundum  as  possible,  any  branches 
coming  off  from  the  ganglion  being  also  divided.' 

The  mental  branch  of  the  inferior  dental  nerve  may  be  divided  at  its  exit  from  the  foramen 
through  an  incision  made  through  the  mucous  inembrane  where  it  is  reflected  from  the  alveolar 
process  on  to  the  lower  lip ;  or  a  portion  of  the  trunk  of  the  inferior  dental  nerve  may  be  resected 
through  an  incision  on  the  cheek  through  the  Masseter  muscle,  exposing  the  outer  sm'face  of 
the  ramus  of  the  mandible.  A  trephine  is  then  applied  over  the  position  of  the  inferior  dental 
foramen  and  the  outer  table  removed,  so  as  to  expose  the  inferior  dental  canal.  The  nerve  is 
dissected  out  of  the  portion  of  the  canal  exposed,  and,  having  been  divided  after  its  exit  from 
the  mental  foramen,  it  is  by  traction  on  the  end  exposed  in  the  trephine  hole,  drawn  out  entire,  and 
cut  off  as  high  up  as  possible.^  The  inferior  dental  nerve  has  also  been  divided  through  an  in- 
cision within  the  mouth,  the  bony  point  guarding  the  inferior  dental  foramen  forming  the  guide 
to  the  nerve.  The  buccal  nerve  may  be  divided  by  an  incision  through  the  mucous  membrane 
of  the  mouth  and  the  Buccinator  muscle  just  in  front  of  the  anterior  border  of  the  ramus  of  the 
mandible  (Stimson). 

In  inveterate  neuralgia  of  one  or  two  of  the  branches  of  the  trigeminal  nerve  a  peripheral 
operation  may  cure  the  case,  but  seldom  does.  It  often  gives  relief,  perhaps  for  months.  In 
neuralgia  of  the  second  division  or  third  division,  or  of  the  second  division  and  third  division, 
Abbe,  of  New  York,  opens  the  skull  and  divides  the  nerve  or  nerves  by  an  intracranial  opera- 
tion, removes  a  piece  of  nerve  so  that  the  foramen  of  exit  is  empty,  and  covers  the  foramen  with 
rubber  tissue,  to  hinder  regrow'th  of  the  nerve.  Other  operators,  after  removing  a  piece  from 
each  nerve,  have  plugged  the  foramina  of  the  exit  with  dentists'  cement  or  silver  foil. 

Rose's  method  of  neurectomy  is  very  valuable  for  neuralgia  of  the  second  division.  It  is  a 
modification  of  the  Braun-Lossen  method.  The  infraorbital  nerve  is  exposed,  a  ligature  is 
tied  about  it,  the  roof  of  the  infraorbital  canal  is  chiselled  open,  and  the  nerve  is  freed  as  far 
back  as  possible.  An  incision  is  made  from  below  the  external  angular  process  outward  along 
the  zygoma  to  in  front  of  the  lobule  of  the  ear,  downward  to  just  above  the  angle  of  the  mandible, 
and  forward  for  two  inches.  The  flap  is  raised  and  the  zygoma  is  exposed.  The  root  of  the 
zygoma  is  drilled  at  two  points,  and  the  zygomatic  process  of  the  temporal  bone  is  drilled  at  two 
points.  The  bone  is  sawed  in  two  places  between  the  drill  holes.  The  freed  arch  is  lifted  down 
and  back,  the  tendon  of  the  Temporal  muscle  is  drawn  backward,  and  the  pterygomaxillary 
fossa  is  thus  exposed.  The  internal  maxillary  artery  is  divided  between  two  ligatures.  The 
External  pterygoid  muscle  is  separated  from  the  greater  wing  of  the  sphenoid  and  from  the  root 
of  the  external  pterygoid  process.  The  superior  maxillary  nerve  is  grasped  and  twisted  off  as 
near  the  ganglion  as  possible.  The  entire  nerve  is  then  drawn  back  from  the  infraorbital  foramen 
and  removed.  The  wound  is  then  closed.  If  the  third  division  is  also  haunted  by  neuralgia, 
it  too  should  be  removed  a  few  weeks  after  the  performance  of  Rose's  operation. 

If  a  peripheral  operation  fails,  or  if  all  the  branches  of  the  trigeminal  are  involved,  the  Gas- 
serian  ganglion  must  be  removed,  or  the  sensor  root  of  the  trigeminal  must  be  divided,  as  sug- 
gested by  Frazier  and  Spiller. 

Removal  of  the  Gasserian  ganglion  was  suggested  by  J.  Ewing  Mears  in  1884,  and  was  first 
carried  out  by  Rose  in  1890.  The  method  chiefly  in  vogue  was  devised  by  Hartley,  and  was 
first  performed  by  him  in  1891.  An  osteoplastic  flap  is  made  in  front  of  the  ear,  the  dura  is 
exposed  and  lifted.  FoUowing  Krause's  advice,  the  third  division  is  exposed  and  clamped. 
The  second  division  is  exposed  and  clamped.  The  nerves  are  loosened  from  their  beds  and 
then  are  rolled  about  the  clamps.  This  twisting  pulls  out  the  ganglion  intact  along  with  the 
motor  root,  and  also  the  sensor  root  from  the  pons.  A  difficulty  in  the  Hartley  operation  is  the 
danger  of  division  of  the  middle  meningeal  artery.  If  this  happens,  the  surgeon  may  be  able 
to  arrest  bleeding  and  proceed  with  the  operation.  If  the  vessel  is  torn  off  at  the  foramen  spi- 
nosum,  it  will  be  necessary  to  pack  the  wound  and  postpone  any  further  operative  manipulation 
for  forty-eight  hours.  Dr.  Harvey  Gushing  has  modified  Hartley's  operation  by  trephining  the 
wall  of  the  temporal  fossa  very  low  down.  He  opens  the  skull  below  the  arch  of  the  meningeal 
vessels,  and  thus  avoids  the  middle  meningeal  artery  at  the  foramen  spinosum,  and  also  the 
sulcus  arteriosus  of  the  parietal  bone.  After  the  removal  of  the  ganglion.  Professor  Keen, 
in  order  to  prevent  undue  inflammation  of  the  eye,  sews  the  eyelids  of  the  affected  side  together, 
leaving  a  space  open  at  each  angle,  and  covers  the  eye  with  a  watch  crystal.     Boric  acid  solution 

1  Carnochan,  American  .Journal  of  the  Medical  Sciences,  1858,  p    136. 

2  Hears,  Transactions  of  the  American  Surgical  Association,  vol.  ii,  p,  469. 


THE  SIXTH  OR  ABDUCENT  NERVE 


993 


is  flushed  into  tde  opening  at  the  external  angle  at  frequent  intervals.     The  stitches  are  removed 
from  the  lid  in  from  eight  to  ten  days. 

The  lingual  nerve  is  occasionally  divided  with  the  view  of  relieving  the  pain  in  cancerous 
disease  of  the  tongue.  This  may  be  done  in  that  part  of  its  course  where  it  lies  below  and  behind 
the  last  molar  tooth.  If  a  line  is  drawn  from  the  middle  of  the  crown  of  the  last  molar  tooth  to 
the  angle  of  the  mandible,  it  will  cross  the  nerve,  which  lies  about  half  an  inch  behind  the  tooth, 
parallel  to  the  bulging  alveolar  ridge  on  the  inner  side  of  the  body  of  the  bone.  If  the  knife  is 
entered  three-quarters  of  an  inch  behind  and  below  the  last  molar  tooth  and  carried  down  to  the 
bone,  the  nerve  will  be  divided.  Hilton  divided  it  opposite  the  second  molar  tooth,  where  it 
is  covered  only  by  the  mucous  membrane,  and  Lucas  pulls  the  tongue  forward  and  over  to  the 
opposite  side,  when  the  nerve  can  be  seen  standing  out  as  a  firm  cord  under  the  mucous  mem- 
brane by  the  side  of  the  tongue  and  can  be  easily  seized  with  a  sharp  hook  and  divided  or  a 
portion  excised.  This  is  a  simple  enough  operation  on  the  cadaver,  but  when  the  disease  is 
extensive  and  has  extended  to  the  floor  of  the  mouth,  as  is  generally  the  case  when  division  of 
the  nerve  is  thought  of,  the  operation  is  not  practicable. 


THE  SIXTH  OR  ABDUCENT  NERVE  (N.  ABDUCENS)  (Fig.  738). 

The  sixth  or  abducent  nerve  supplies  the  External  rectus  muscle.  Its  super- 
ficial origin  is  by  several  filaments  from  the  postpontile  groove,  between  pons  and 
pyramid.  Its  deep  origin  is  from  the  upper  part  of  the  floor  of  the  fourth  ventricle, 
close  to  the  median  line,  beneath  the  eminentia  abducentis  (Fig.  650).  From  the 
nucleus  of  the  abducent  nerve  some  fibres  are  supposed  to  pass  through  the 
medial  longitudinal  bundle  to  the  oculomotor  nucleus  of  the  opposite  side  and 
into  the  oculomotor  nerve,  along  which  they  are  carried  to  the  Internal  rectus 
muscle.     See,  however,  the  description  already  given  on  page  901). 

The  nerve  pierces  the  dura  on  the  basilar  surface  of  the  sphenoid  bone,  runs 
through  a  notch  immediately  below  the  posterior  clinoid  process,  and  enters  the 
cavernous  sinus.  It  passes  forward  through  the  sinus,  lying  on  the  outer  side 
of  the  internal  carotid  artery  (Fig.  505).  It  enters  the  orbit  through  the  sphenoidal 
fissure,  and  lies  above  the  oph- 
thalmic vein,  from  which  it  is 
separated  by  a  lamina  of  dura 
(Fig.  743).  It  then  passes  be- 
tween the  two  heads  of  the 
External  rectus  muscle,  and  is 
distributed  to  that  muscle  on 
its  ocular  surface. 

Branches  of  Communication. 
— It  is  joined  by  several  fila- 
ments from  the  carotid  and 
cavernous  plexuses,  and  by 
one  from  the  ophthalmic  nerve. 

Relations  to  One  Another  of 
the  Oculomotor,  Trochlear,  Oph- 
thalmic Division  of  the  Trigeminal,  and  Abducent  Nerves  as  they  Pass  to  the  Orbit. 
— The  oculomotor,  trochlear,  the  ophthalmic  division  of  the  trigeminal,  and  tlie 
abducent  nerves,  as  they  pass  to  the  orbit,  bear  a  certain  relation  to  one  another 
in  the  cavernous  sinus,  at  the  sphenoidal  fissure,  and  in  the  cavity  of  the  orbit, 
which  will  now  be  described. 

In  the  cavernous  sinus  (Figs.  505  and  506)  the  oculomotor,  trochlear,  and 
ophthalmic  division  of  the  trigeminal  are  placed  on  the  outer  wall  of  the  sinus, 
in  their  numerical  order,  both  from  above  downward  and  from  within  outward. 
The  abducent  nerve  lies  at  the  outer  side  of  the  internal  carotid  artery.  As  these 
nerves  pass  forward  to  the  sphenoidal  fissure,  the  oculomotor  and  trigeminal 
nerves  become  divided  into  branches,  and  the  abducent  nerve  approaches  the  rest 
so  that  their  relative  position  becomes  considerably  changed. 

63 


lufur 
Aliihicen 
Ophthalmic  vein 


^upm  }  division  of  ociilo-motor, 
division  of  oculo-motor. 


-Relations  of  structures  passing  through  the 
sphenoidal  fissure 


994  THE  NERVE  SYSTEM 

In  the  sphenoidal  fissure  (Fig.  743)  the  trochlear  nerve  and  the  frontal  and 
lacrimal  branches  of  the  ophthalmic  division  of  the  trigeminal  lie  upon  the  same 
plane,  the  former  being  most  internal,  the  latter  external,  and  they  enter  the  cavity 
of  the  orbit  above  the  muscles.  The  remaining  nerves  enter  the  orbit  between 
the  two  heads  of  the  External  rectus  muscle.  The  superior  division  of  the 
oculomotor  nerve  is  the  highest  of  these;  beneath  this  lies  the  nasal  branch  of 
the  ophthalmic  nerve;  then  the  inferior  division  of  the  oculomotor  nerve;  and 
the  abducent  nerve  lowest  of  all. 

In  the  orbit  (Figs.  734  and  738)  the  trochlear  nerve  and  the  frontal  and  lacrimal 
divisions  of  the  ophthalmic  nerve  lie  on  the  same  plane  immediately  beneath  the 
periosteum,  the  trochlear  nerve  being  internal  and  resting  on  the  Superior  oblique 
muscle,  the  frontal  nerve  resting  on  the  Levator  palpebrae  muscle,  and  the  lacrimal 
nerve  on  the  External  rectus  muscle.  Next  in  order  comes  the  superior  division 
of  the  oculomotor  nerve,  lying  immediately  beneath  the  Superior  rectus  muscle, 
and  then  the  nasal  branch  of  the  ophthalmic  nerve,  crossing  the  optic  nerve 
from  the  outer  to  the  inner  side  of  the  orbit.  Below  these  is  found  the  optic 
nerve,  surrounded  in  front  by  the  ciliary  nerves,  and  having  the  ciliary  ganglion 
on  its  outer  side,  between  it  and  the  External  rectus  muscle.  Below  the  optic 
nerve  is  the  inferior  division  of  the  oculomotor  nerve  and  the  abducent  nerve 
which  lie  on  the  outer  side  of  the  orbit. 

Applied  Anatomy. — It  is  often  stated  that  the  abducent  nerve  is  more  frequently  involved  in 
fractures  of  the  hose  of  the  skull  than  any  other  of  the  cranial  nerves.  As  a  matter  of  fact,  however, 
it  is  injured  in  only  about  2  per  cent,  of  cases  of  fracture  of  the  skull  (Putscher).  Cases  have  been 
reported  in  which  the  nerve  was  actually  severed.  The  nerve  may  be  injured  by  traction, 
pressure  of  a  blood  clot,  of  a  tumor,  or  of  an  arteriovenous  aneurism.  The  result  of  paralysis  of 
this  nerve  is  internal  or  convergent  squint.  When  injured  so  that  its  function  is  destroyed,  there 
is,  in  addition  to  the  paralysis  of  the  External  rectus  muscle,  often  a  certain  amount  of  contrac- 
tion of  the  pupil,  because  some  of  the  sympathetic  fibres  to  the  radiating  muscle  of  the  iris  pass 
along  with  this  nerve. 


THE  SEVENTH  OR  FACIAL  NERVE  (N.  FACIALIS)  (Figs.  744,  745). 

The  seventh  or  facial  nerve  is  the  motor  nerve  of  all  the  muscles  of  expression 
in  the  face,  and  of  the  Platysma  and  Buccinator;  the  muscles  of  the  external  ear, 

the  posterior  belly  of  the  Digas- 

E=cten^alsuperfiaalpe^rosal.ff2C2^'^^r'^''f||§A  *"'''     """"^     the     Stylohyoid.       The 

Brancii  to  join  smau  ««pf';\\L£_jL/viW.-^S«a»^    '/  \        chorda  tvmpani  (or  nervus  mter- 

fieial  petrosal>A^l.        I  TV~'iA-g'^c>    ^^aSi;,      \  __         ■'.      ^  .        ^  . 


Large mperfidca petrosal.-  \  .|f  w^A U N^^>\       '    \      medius)  IS  reterreci  to  as  the  sen- 

Geniculate  ganglion.  ~\^J^^=:^^^^^^  |        SOr  portion  of  the  facial.- 

Its  superficial  origin  is  from  the 
upper  end  of  the  medulla  oblon- 
gata, in  the  groove   between  the 
Fig.  744,-The  ™;;[7^^1.^^°™|f «™^°f  '•>«  ^^"^1  ""^         olive  and  restiform body.    Its  deep 

origin  is  from  a  nucleus  situated  in 
the  floor  of  the  fourth  ventricle,  beneath  the  superior  fovea  (Fig.  650).  The  facial 
nucleus  is  deeply  placed  in  the  reticular  formation  of  the  lower  part  of  the  pars 
dorsalis  pontis,  a  litde  external  and  ventral  to  the  nucleus  of  the  abducent  nerve. 
From  this  origin  the  fibres  pursue  a  curved  course  in  the  substance  of  the  pars 
dorsalis  pontis.  They  first  pass  backward  and  inward,  and  then  turn  upward 
and  forward,  forming  the  genu  internum,  which  with  the  nucleus  abducentis 
produces  an  eminence,  the  eminentia  teres  or  abducentis,  on  the  floor  of  the  fourth 
ventricle,  and  finally  bend  sharply  downward  and  outward  around  the  upper  erid 
of  the  nucleus  of  origin  of  the  abducent  nerve,  to  reach  their  superficial  origin 
between  the  olive  and  restiform  body.     From   the  nucleus  of  the  oculomotor 


THE  SEVENTH  OB  FACIAL  NERVE 


095 


nerve  some  fibres  arise  which  descend  in  the  medial  longitudinal  Ijundle  and  join 
the  facial  just  before  it  leaves  the  pars  dorsalispontis;  these  fibres  are  said  to  supply 
the  anterior  belly  of  the  Occipitofrontalis,  the  Orbicularis  palpebrarum,  and  the 
Corrugator  supercilii,  as  these  muscles  have  been  observed  to  escape  paralysis 
in  lesions  of  the  nucleus  of  the  facial  nerve.  _ 

The  acoustic  or  auditory  nerve  lies  to  the  outer  side  of  the  facial  nerve;  and  betv.een  the 
two  Is  a  small  fasciculus,  the  nervus  intermedius  or  pars  intermedia  of  Wrisberg,  which 
apparently  arises  from  the  medulla  oblongata  and  joins  the  farial  nerve  in  the  internal  auditory 
meatus.  The  central  processes  of  the  ganglion  cells,  known  as  the  nervus  intermedius,  end 
in  the  upper  end  of  the  nucleus  of  the  glossopharyngeal  nerve.  If  it  is  to  be  classified  as  part 
of  the  facial  then  the  nervus  intermedius  may  be  regarded  as  the  sensor  root  of  the  facial 
nerve,  analogous  to  the  sensor  root  of  the  trigeminal,  and  its  real  nucleus  of  origin  consists  of 
the  geniculate  ganglion  (see  p.  882).  It  will  be  remembered  that  a  portion  of  the  nervus  inter- 
medius is  efferent  (excitoglandular),  arising  from  the  nucleus  salivatorius  (p.  882). 


Nucleus  Salivator 


Spheno- 

^„rjf palatine 

\>  4  Oanglton 


Communicating  Branch 


To  Digastric 
To  Styio-hijoid 


E.  A.  S. 
Fig.  745. — Plan  of  the  facial  and  intermediate  i 


Ajferent  Uastc)  fibers 


'  Efferent  iexcito-glanduiari 
fibers  to  submaxillary  and 
sublingual  ganglia  and  glands 

ommunication  with  other  nerves. 


The  facial  nerve,  firmer,  rounder,  and  smaller  than  the  auditory,  passes  forward 
and  outward  upon  the  middle  peduncle  of  the  cerebellum,  and  enters  the  internal 
auditory  meatus  with  the  auditory  nerve  and  artery.  Within  the  meatus  the  facial 
nerve  lies  in  a  groove  along  the  upper  and  anterior  part  of  the  auditory  nerve, 
and  the  nervus  intermedius  is  placed  between  the  two  and  joins  the  inner  angle 
of  the  geniculate  ganglion.  Beyond  the  ganglion  its  fibres  are  generally  regarded 
as  forming  the  chorda  tympani  (see  p.  997). 

At  the  bottom  of  the  meatus  the  facial  nerve  enters  the  canalis  facialis  or  aquae- 
ductus  Fallopii  and  follo^^s  the  course  of  that  canal  through  the  petrous  portion  of 
the  temporal  bone,  from  its  commencement  at  the  internal  meatus  to  its  termina- 
tion at  the  stylomastoid  foramen  (Figs.  50  and  744).  It  is  at  first  directed  outward 
between  the  cochlea  and  vestibule  toward  the  inner  wall  of  the  tympanum;  it 


In  the  internal  auditory  meatus 


996  THE  NERVE  8Y8TEM 

then  bends  suddenly  backward  and  arches  downward  behind  the  tympanum 
to  the  stylomastoid  foramen.  At  the  point  in  the  aqueduct  of  Fallopius  where  the 
nerve  changes  its  direction  (geiiiculum  n.  facialis),  it  presents  a  reddish,  gangli- 
form  swelling,  the  geniculate  ganglion  (ganglion  geniculi)  or  intumescentia  ganglio- 
formis  (Fig.  744).  The  geniculate  ganglion  receives  a  branch  from  the  vestibular 
division  of  the  auditory  nerve.  On  emerging  from  the  stylomastoid  foramen 
the  facial  nerve  runs  forward  in  the  substance  of  the  parotid  gland,  crosses  the 
external  carotid  artery,  and  divides  behind  the  ramus  of  the  mandible  into  two 
primary  branches,  temporofacial  and  cervicofacial,  from  which  numerous  offshoots 
are  distributed  over  the  side  of  the  head,  face,  and  upper  part  of  the  neck,  supply- 
ing the  superficial  muscles  in  these  regions.  As  the  primary  branches  and  their 
offshoots  diverge  from  each  other,  they  present  somewhat  the  appearance  of  a 
bird's  claw;  hence  the  name  of  pes  anserinus  is  given  to  the  divisions  of  the  facial 
nerve  in  and  near  the  parotid  gland. 

Branches  of  Communication  (Fig.  745). — The  communications  of  the  facial 
nerve  may  be  thus  arranged : 

'With  the  acoustic  nerve.  The  nervus 
intermedins,  which  is  between  the 
facial  and  acoustic,  is  supposed  to  give 
branches  to  both.  The  branch  given 
to  the  acoustic  accompanies  it  for  a 
certain  distance,  and  then  departs 
from  it  to  join  the  geniculate  ganglion. 
With  the  acoustic  as  explained  above. 
With   the   sphenopalatine    ganglion  by 

the  large  superficial  petrosal  nerve. 
With  the   otic  ganglion   by   the   small 

superficial  petrosal  nerve. 
With   the   sympathetic,  on    the    middle 
meningeal  artery  by  the  external  super- 
ficial petrosal  nerve. 

In  the  canalis  facialis  or  Fallopian  1      -itt-.i    ^i  •     i      u        \     e  ^\. 

,     ^                                '^        -      With  the  auricular  brancii  or  the  vagus. 
aqueduct  j  ° 

iWith  the  glossopharyngeal. 
With  the  vagus. 
With  the  great  auricular. 
With  the  auriculotemporal. 

Behind  the  ear With  the  small  occipital. 

On  the  face With  three  divisions  of  the  trigeminal. 

In  the  neck .         With  the  superficial  cervical. 

In  the  internal  auditory  meatus  some  minute  filaments  pass  between  the  facial 
and  acoustic  nerves. 

The  large  superficial  petrosal  nerve  arises  from  the  geniculate  ganglion  and  con- 
sists chiefly  of  sensor  branches  which  are  distributed  to  the  mucous  membrane 
of  the  soft  palate.  It  probably  also  contains  a  few  motor  fibres  which  form  the 
motor  root  of  the  sphenopalatine  (Meckel's)  ganglion.  It  passes  forward  through 
the  hiatus  canalis  facialis  (Fallopii)  and  runs  in  a  groove  on  the  anterior  surface 
of  the  petrous  portion  of  the  temporal  bone  beneath  the  Gasserian  ganglion  to 
the  foramen  lacerum  medium.  It  receives  a  twig  from  the  tympanic  plexus, 
and  in  the  foramen  is  joined  by  the  great  deep  petrosal,  from  the  sympathetic 
plexus  on  the  internal  carotid  artery,  to  form  the  Vidian  nerve.  This  nerve  passes 
through  the  Vidian  canal  and  ends  in  the  sphenopalatine  (Meckel's)  ganglion. 
The  geniculate  ganglion  is  connected  with  the  otic  ganglion  by  a  branch  which 


From  the  geniculate  ganglion 


THE  SEVENTH  OR  FACIAL  NERVE  997 

joins  the  small  superficial  petrosal  nerve;  and  also  with  the  sympathetic  filaments 
accompanying  the  middle  meningeal  artery,  by  the  external  petrosal  nerve  (Bidder). 
From  the  gangliform  enlargement,  according  to  Arnold,  a  twig  is  sent  back  to 
the  auditory  nerve.  Just  before  the  facial  nerve  emerges  from  the  stylomastoid 
foramen  it  generally  receives  a  twig  of  commimication  from  the  auricular  branch 
of  the  vagus. 

After  its  exit  from  the  stylomastoid  foramen,  it  sends  a  twig  to  the  glosso- 
pharyngeal, another  to  the  vagus  nerve,  and  communicates  with  the  great  auricular 
branch  of  the  cervical  plexus,  with  the  auriculotemporal  branch  of  the  inferior 
maxillary^  nerve  in  the  parotid  gland,  with  the  small  occipital  nerve  behind  the 
ear,  on  the  face  with  the  terminal  branches  of  the  three  divisions  of  the  fifth, 
and  in  the  neck  with  the  transverse  cervical. 

Branches  of  Distribution  (Fig.  745). — ^The  branches  of  distribution  of  the  facial 
nerves  may  be  thus  arranged: 

Within  the  canalis  facialis  or  aquae-      J  Tympanic,    to    the   Stapedius    muscle, 
ductus  Fallopii \  Chorda  tympani. 

At   its   exit   from   the   stylomastoid       f  Posterior  Auricular. 
e  •{   Digastric. 

foramen c^  i  i      -j 

1^  btylohyoid. 

{Temporal. 
Malar. 
^..... ,  Infraorbital. 

I  Jjuccal. 
[^  Cervicofacial     .      .       <   Mandibular. 
(^  Cervical. 

The  Tympanic  Branch  (n.  stapedius)  (Fig.  745)  arises  from  the  nerve  opposite 
the  pyramid;  it  passes  through  a  small  canal  in  the  pyramid  and  supplies  the 
Stapedius  muscle. 

The  Chorda  Tympani  (Figs.  744  and  745)  is  apparently  given  off  from  the  facial 
as  it  passes  vertically  downward  at  the  back  of  the  tympanum,  about  5  mm. 
(3-  inch)  before  its  exit  from  the  stylomastoid  foramen.  It  passes  from  below 
upward  and  forward  in  a  distinct  canal,  and  enters  the  cavity  of  the  tympanum 
through  an  aperture  (iter  chordae  posterius)  on  its  posterior  wall  between  the  open- 
ing of  the  mastoid  cells  and  the  attachment  of  the  membrana  tympani,  and  be- 
comes invested  with  mucous  membrane.  It  traverses  the  cavity  of  the  tympanum, 
between  the  fibrous  and  mucous  layers  of  the  membrana  tympani,  crosses  over  the 
handle  of  the  malleus,  emerges  from  the  cavity  through  a  foramen  at  the  inner 
end  of  the  Glaserian  fissure,  which  is  called  the  canal  of  Huguier  (iter  chordae 
anterius).  It  then  descends  between  the  two  Pterygoid  muscles  on  the  inner 
aspect  of  the  spine  of  the  sphenoid,  which  it  sometimes  grooves,  and  joins  the 
lingual  nerve  at  an  acute  angle.  A  portion  of  the  nerve  (excitoglandular  division) 
passes  to  the  submaxillary  ganglion;  the  rest  is  continued  onward  through  the 
muscular  substance  of  the  tongue  to  the  mucous  membrane  covering  its  anterior 
two-thirds.  These  constitute  the  nerves  of  taste  for  this  portion  of  the  tongue. 
A  few  of  its  fibres  probably  pass  through  the  submaxillary  ganglion  to  the  sublin- 
gual gland.  Before  joining  the  lingual  nerve  it  receives  a  small  communicating 
branch  from  the  otic  ganglion.  As  already  stated,  the  chorda  tympani  nerve 
is  regarded  as  the  peripheral  portion  of  the  nervus  intermedins  (see  p.  989). 

The  Posterior  Auricular  Nerve  {n.  auricularis  postenor)  (Figs.  745  and  746)  arises 
close  to  the  stylomastoid  foramen,  and  passes  upward  in  front  of  the  mastoid 
process  and  between  the  mastoid  process  and  the  external  ear,  where  it  is  joined 
by  a  filament  from  the  auricular  branch  of  the  vagus,  and  communicates  with  the 


998  THE  NER  VE  SYSTEM 

mastoid  branch  of  the  great  auricular  and  with  the  small  occipital.  As  it  ascends 
between  the  external  auditory  meatus  and  the  mastoid  process  it  divides  into  two 
branches,  the  auricular  and  the  occipital  branches.  The  auricular  branch  sup- 
plies the  Retrahens  aurem  and  the  small  muscles  on  the  cranial  surface  of 
the  pinna.  The  occipital  branch  (ramus  occipitalis),  the  larger,  passes  backward 
along  the  superior  curved  line  of  the  occipital  bone,  and  supplies  the  occipital 
portion  of  the  Occipitofrontalis. 

The  Digastric  Branch  of  the  Facial  Nerve  (ramus  digastricus)  arises  close  to  the 
stylomastoid  foramen;  it  divides  into  several  filaments,  which  supply  the  posterior 
belly  of  the  Digastric;  one  of  these  perforates  that  muscle  to  join  the  glo^opharyn- 
geal  nerve. 

The  Stylohyoid  Branch  (ramus  stylohyoideus)  frequently  arises  by  a  common 
trunk  with  the  digastric;  it  is  long  and  slender,  and  passes  inward  to  enter  the 
Stylohyoid  muscle  about  its  middle. 

The  Temporo facial  Division  (Figs.  745  and  746),  the  larger  of  the  two  terminal 
branches  of  the  facial,  passes  upward  and  forward  through  the  parotid  gland, 
crosses  the  external  carotid  artery  and  temporomaxillary  vein,  and  passes  over 
the  neck  of  the  condyle  of  the  mandible,  being  connected  in  this  situation  with 
the  auriculotemporal  branch  of  the  inferior  maxillary  nerve.  It  breaks  up  into 
branches  which  are  distributed  over  the  temple  and  upper  part  of  the  face;  these 
are  divided  into  three  sets — temporal,  malar,  and  infraorbital. 

The  temporal  branches  (rami  temporales)  cross  the  zygoma  to  the  temporal 
region,  supplying  the  Attrahens  and  Attollens  aurem  muscles,  and  join  with 
the  temporal  branch  of  the  temporomalar  division  of  the  superior  maxillary 
nerve,  and  with  the  auriculotemporal  branch  of  the  inferior  maxillary  nerve. 
The  more  anterior  branches  supply  the  frontal  portion  of  the  Occipitofrontalis, 
the  Orbicularis  palpebrarum,  and  Corrugator  supercilii  muscles,  and  join  with 
the  supraorbital  and  lacrimal  branches  of  the  ophthalmic. 

The  malar  branches  (rami  zygomatici)  pass  across  the  malar  bone  to  the  outer 
angle  of  the  orbit,  where  they  supply  the  Orbicularis  palpebrarum  muscle  and  join 
with  filaments  from  the  lacrimal  nerve  and  the  malar  branch  (subcutaneus  malae) 
of  the  superior  maxillary  nerve. 

The  infraorbital  branches  of  larger  size  than  the  rest,  pass  horizontally  forward 
to  be  distributed  between  the  lower  margin  of  the  orbit  and  the  mouth.  The 
superficial  branches  run  beneath  the  skin  and  above  the  superficial  muscles  of 
the  face,  which  they  supply;  some  branches  are  distributed  to  the  Pyramidalis 
nasi,  joining  at  the  inner  angle  of  the  orbit  with  the  infratrochlear  and  nasal 
branches  of  the  ophthalmic.  The  deep  branches  pass  beneath  the  Zygomatici  and 
the  Levator  labii  superioris,  suppljang  the  Levator  anguli  oris,  the  Levator  labii 
superioris  alaeque  nasi,  and  the  small  muscles  of  the  nose,  and  form  a  plexus, 
infraorbital  plexus,  by  joining  with  the  branches  of  the  infraorbital  branch  of  the 
superior  maxillary  nerve  and  the  buccal  branches  of  the  cervicofacial. 

The  Cervicofacial  Division  of  the  facial  nerve  passes  obliquely  downward  and 
forward  through  the  parotid  gland,  crossing  the  external  carotid  artery.  In 
this  situation  it  is  joined  by  branches  from  the  great  auricular  nerve.  Opposite 
the  angle  of  the  mandible  it  divides  into  branches  which  are  distributed  on  the 
lower  half  of  the  face  and  upper  part  of  the  neck.  These  may  be  divided  into 
three  sets — buccal,  mandibular,  and  cervical. 

The  buccal  branches  (rami  buccales)  cross  the  Masseter  muscle.  They  supply 
the  Buccinator  and  Orbicularis  oris,  and  join  with  the  infraorbital  branches  of 
the  temporofacial  division  of  the  nerve,  and  with  filaments  of  the  buccal  branch 
of  the  inferior  maxillary  nerve. 

The  mandibular  branch  (ramus  marginalis  mandihulae)  passes  forward  beneath 


THE  SEVENTH  OR  FACIAL  NERVE 


999 


the  Platysma  and  Depressor  anguli  oris,  supplying  the  muscles  of  the  lower  lip  and 
chin,  and  communicating  with  the  mental  branch  of  the  inferior  dental  nerve. 

The  cervical  branch  (ramtis  colli)  runs  forward  beneath  the  Platysma,  and  forms 
a  series  of  arches  across  the  side  of  the  neck  over  the  suprahyoid  region.  A  branch 
descends  vertically  to  join  with  the  superficial  cervical  nerve  from  the  cervical 
plexus;  others  supply  the  Platysma. 


Fig.  746. — ^The  nerves  of  the  scalp,  face,  and  side  of  thi 


Applied  Anatomy. — The  facial  nerve  is  more  frequently  paralyzed  than  any  of  the  other 
of  the  cranial  nerves.  The  paralysis  [facial  'palsy)  may  depend  either  upon  (1)  central  causes 
— i.  e.,  blood  clots  or  intracranial  tumors  pressing  on  the  nerve  before  its  entrance  into  the 
internal  auditory  meatus.  It  is  also  one  of  the  nerves  involved  in  bulbar  -paralysis.  Or  (2)  it 
may  be  paralyzed  in  its  passage  through  the  petrous  bone  by  damage  due  to  middle-ear  disease 
or  by  fractures  of  the  base  of  the  skull.  Or  (3)  it  may  be  afl'ected  at  or  after  its  exit  from  the 
stylomastoid  foramen.  This  is  commonly  known  as  Bell's  paralysis.  It  may  be  due  to  exposure 
to  cold  or  to  injury  of  the  nerve,  either  from  accidental  wounds  of  the  face  or  during  some  surgical 
operation,  as  removal  of  parotid  tumors,  opening  of  abscesses,  or  operations  on  the  mandible. 

When  the  cause  is  central,  the  abducent  nerve  is  usually  paralyzed  as  well,  and  there  is  also 
hemiplegia  on  the  opposite  side.  In  these  cases  the  electric  reactions  are  the  same  as  in  health; 
whereas,  when  the  paralysis  is  due  to  a  lesion  in  the  course  of  the  nerve,  the  reactions  of  degenera- 
tion develop.  When  the  nerve  is  paralyzed  in  the  petrous  bone,  in  addition  to  the  paralysis  of  the 
muscles  of  expression,  there  is  loss  of  taste  in  the  anterior  part  of  the  tongue,  and  the  patient  is 


1000  THE  NERVE  SYSTEM 

unable  to  recognize  the  difference  between  bitters  and  sweets,  acids  and  salines,  from  involvement 
of  the  chorda  tympani.  The  mouth  is  dry,  because  the  salivary  glands  are  not  secreting;  the 
sense  of  hearing  is  affected  from  paralysis  of  the  Stapedius,  but  there  is  no  hemiplegia.  When  the 
cause  of  the  paralysis  is  from  fracture  of  the  base  of  the  skull,  the  acoustic  nerve  and  the  petrosal 
nerves,  which  are  connected  with  the  intumescentia  ganglioformis,  are  also  involved.  When 
the  injury  to  the  nerve  is  after  its  exit  from  the  stylomastoid  foramen,  all  the  muscles  of  expression 
except  the  Levator  palpebrae,  together  with  the  posterior  belly  of  the  Digastric  and  Stylohyoid, 
are  paralyzed.  There  is  smoothness  of  the  forehead,  and  the  patient  is  unable  to  frown;  the 
eyelids  cannot  be  closed,  and  the  lower  lid  droops,  so  that  the  punctum  is  no  longer  in  contact 
with  the  globe,  and  the  tears  run  down  the  cheek;  there  is  smoothness  of  the  cheek  and  loss  of 
the  nasolabial  furrow;  the  nostril  of  the  paralyzed  side  cannot  be  dilated;  the  mouth  is  drawn 
to  the  sound  side,  and  there  is  inability  to  whistle;  food  collects  between  the  cheek  and  gum 
from  paralysis  of  the  Buccinator. 

The  facial  nerve  is  at  fault  in  cases  of  so-called  histrionic  spasm,  which  consists  in  an  almost 
constant  and  uncontrollable  twitching  of  the  muscles  of  the  face.  This  twitching  is  sometimes 
so  severe  as  to  cause  great  discomfort  and  annoyance  to  the  patient  and  to  interfere  with  sleep, 
and  for  its  relief  the  facial  nerve  has  been  stretched.  The  operation  is  performed  by  making  an 
incision  behind  the  ear  from  the  root  of  the  mastoid  process  to  the  angle  of  the  mandible.  The 
parotid  is  turned  forward,  and  the  dissection  carried  along  the  anterior  border  of  the  Sterno- 
mastoid  muscle  and  mastoid  process  until  the  upper  border  of  the  posterior  belly  of  the  Digas- 
tric is  found.  The  nerve  is  parallel  to  this  on  about  a  level  with  the  middle  of  the  mastoid  process. 
When  found,  the  nerve  may  be  stretched  by  passing  a  blunt  hook  beneath  it  and  pulling  it  for- 
ward and  outward.  Too  great  force  must  not  be  used,  for  fear  of  permanent  injury  to  the  nerve. 
In  facial  paralysis  of  extracerebral  origin  it  may  be  advisable  to  expose  the  nerve,  cut  it  across,  and 
anastomose  the  distal  end  of  the  paralyzed  nerve  to  the  accessory  nerve,  or,  better,  to  the  hypo- 
glossal nerve  (facioaccessory  anastomosis  or  faciohypoglossal  anastomosis).  The  idea  was  first 
proposed  by  Ballance,  and  has  been  put  in  practice  by  Ballance  and  Stewart,  Keen,  Gushing, 
Paure,  Kennedy,  and  others. 


THE  EIGHTH  OR  ACOUSTIC  NERVE  (N.  ACUSTICUS)  (Fig.  747). 

The  eighth  or  acoustic  or  auditory  nerve  comprises  two  distinct  sets  of  fibres 
which,  although  both  are  devoted  to  the  transmission  of  afferent  impulses,  differ 
in  their  peripheral  distribution  and  in  their  central  connections.  The  two  divi- 
sions appear  blended  in  the  interval  between  the  medulla  oblongata  and  the  in- 
ternal auditory  meatus,  running  obliquely  laterofrontad  in  company  with  the 
facial  nerve  and  internal  auditory  artery.  At  the  internal  auditory  meatus  the 
two  divisions  of  the  nerve  are  separable,  the  vestibular  division  above,  the  cochlear 
below. 

The  cochlear  nerve  (radix  cochlearis)  is  the  true  nerve  of  hearing,  lacking 
general  sensibility,  however,  and  therefore  a  nerve  of  special  sense.  The  fibres 
of  this  division  arise  from  the  cells  of  the  spiral  ganglion  of  the  cochlea  as  axones 
of  bipolar  cells  whose  dendrites  or  peripheral  processes  terminate  about  the 
(auditory)  hair  cells  of  the  organ  of  Corti  (p.  1143).  The  central  connections  of 
the  cochlear  division  are  described  on  page  881. 

The  vestibular  nerve  (radix  vestibidaris)  conducts  impulses  of  equilibratory 
sense  from  the  semicircular  canals,  utricle,  and  saccule  to  the  vestibular  nuclei. 
The  ganglion  of  origin  of  this  nerve  differs  from  ordinary  sensor  ganglia  in  that 
its  cells  are  of  bipolar  structure,  having  retained  this  embryonic  characteristic 
of  the  ganglion  cells  throughout  life.  The  central  processes  of  the  cells  of  the 
vestibular  ganglion  (or  ganglion  of  Scarpa)  enter  the  medulla  oblongata  with  the 
trunk  of  the  cochlear  nerve  in  the  postpontile  groove,  laterad  of  the  facial  nerve, 
to  establish  central  connections  already  described  on  page  881.  The  peripheral 
processes  constitute  the  two  main  branches  of  the  nerve — viz.,  (a)  the  utriculo- 
ampullar and  (b)  the  sacculoampuUar. 

The  upper  or  utriculoampullar  branch  divides  into: 

(a)  The  utricular  branch,  passing  through  the  superior  macula  cribrosa  of  the 
vestibule  to  end  in  the  macula  acustica  of  the  utricle. 


THE  EIGHTH  OR  ACOUSTIC  NEIiVE  1001 

(b)  The  superior  ampullar  branch,  accomjjanying  the  utricular  l^ranch,  to  end 
in  the  crista  acustica  of  the  ampulla  of  the  superior  semicircular  canal. 

(c)  The  lateral  ampullar,  to  the  ampulla  of  the  lateral  semicircular  canal. 
The  lower  or  sacculoampuUar  branch  is  somewhat  longer  and  divides  into: 

(a)  The  posterior  ampullar,  passing  through   the  foramen  singulare  and  the 
inferior  macula  cribrosa  to  end  in  the  ampulla  of  the  posterior  semicircular  canal. 

(b)  The  saccular  branch,  passing  through  the  middle  macula  cribrosa  to  end  in 
the  macula  acustica  of  the  sacculus. 


Fig.  747. — Distribution  of  the  acoustic  nerve.     (Semidiagrammatic.)     (Testut.) 

Applied  Anatomy. — The  acoustic  nerve  is  frequently  injured,  together  with  the  facial  nerve, 
in  fractures  of  the  middle  fossa  of  the  base  of  the  skull  implicating  the  internal  auditory  meatus. 
Tiie  nerve  may  be  either  torn  across,  producing  permanent  deafness,  it  may  be  bruised,  or  it  may 
be  pressed  upon  by  extravasated  blood  or  inflammatory  exudation,  when  the  deafness  will  in  all 
probability  be  temporary.  The  nerve  may  also  be  injured  by  violent  blows  on  the  head  without 
fracture,  and  deafness  may  follow  loud  explosions  of  dynamite,  etc.,  probably  from  some  lesion 
of  this  nerve,  which  is  more  liable  to  be  injured  than  the  other  cranial  nerves  on  account  of  its 
structure.  The  test  that  the  nerve  is  destroyed  and  that  the  deafness  is  not  due  to  some  lesion 
of  the  auditory  apparatus  is  obtained  by  placing  a  vibrating  tuning-fork  on  the  head.  The 
vibrations  will  be  heard  in  cases  where  the  auditory  apparatus  is  at  fault,  but  not  in  cases  of 
destruction  of  the  auditory  nerve. 

Tinnitus  aurium  is  commonly  present  in  cases  of  ear  disease.  The  sounds  are  variable  in 
intensity  and  nature — buzzing,  hissing,  whistling,  rushing,  bell-ringing,  and  so  forth.  In  the 
insane,  tinnitus  is  associated  with  delusions  and  hallucinations  of  hearing,  and  may  be  due  to 
nothing  more  than  impacted  cerumen  in  the  meatus.  Meniere's  disease  is  discussed  in  the 
Applied  Anatomy  of  the  Labyrinth. 

THE  NINTH  OR  GLOSSOPHARYNGEAL  NERVE  (N.  GLOSSOPHARYNGEUS) 

(Figs.  748,  749). 

The  ninth  or  glossopharyngeal  nerve  is  distributed,  as  its  name  implies,  to  the 
tongue  and  pharynx,  being  the  nerve  of  ordinary  sensation  to  the  mucous  mem- 
brane of  the  pharynx,  fauces,  and  tonsil;  and  the  nerve  of  taste  to  all  parts  of 
the  tongue  to  which  it  is  distributed. 


1002  THE  NEB  VE  SYSTEM 

Its  (apparent)  superficial  origin  is  hy  three  or  four  filaments,  closely  connected, 
from  the  upper  part  of  the  medulla  oblongata,  in  the  dorsolateral  groove  (Fig.  748) . 
The  central  connections  are  described  on  page  880.  The  small  motor  component 
arises  from  cells  in  the  nucleus  ambiguus.  The  real  origin  of  the  sensor  fibres 
of  the  glossopharyngeal  must  be  looked  for  in  the  jugular  and  petrosal  ganglia 
which  are  developed  from  the  neural  crest. 

From  its  superficial  origin  it  passes  outward  across  the  flocculus,  and  leaves 
the  skull  at  the  central  part  of  the  jugular  foramen,  in  a  separate  sheath  of  the 
dura  external  to  and  in  front  of  the  vagus  and  spinal  accessory  nerves  (Fig.  749). 
In  its  passage  through  the  jugular  foramen  it  grooves 
ju.guiiiraa^i.  the  lower  border  of  the  petrous  portion  of  the  temporal 

rvMoaf^i.  bone,  and  at  its  exit  from  the  skull  passes  forward 
Tympa^  .  bgt^ggjj  ]^^  jugular  vciu  and  internal  carotid  artery, 
and  descends  ventrad  of  the  latter  vessel,  and  beneath 
the  styloid  process  of  the  temporal  bone  and  the 
muscles  connected  with  it,  to  the  lower  border  of  the 
Stylopharyngeus  muscle.  The  nerve  now  curves  in- 
ward, forming  an  arch  on  the  side  of  the  neck,  and 
lying  upon  the  Stylopharyngeus  muscle  and  the  ^liddle 
vagui  constrictor  of  the  pharynx.     It  then  passes  beneath 

eomm  JS&n'if  tbe1fiSfh%         the  Hyoglossus   musclc,  and  is   finally  distributed  to 
and  eleventh  cranial  nerves.  the  mucous  membrane  of  the  fauccs  and  base  of  the 

tongue,  and  the  mucous  glands  of  the  mouth  and  tonsil. 
In  passing  through  the  jugular  foramen  the  nerve  presents,  in  succession,  two 
gangliform  enlargements.     The  superior  and  smaller  is  called  the  jugular  ganglion; 
the  inferior  and  larger,  the  petrous  ganglion  or  the  ganglion  of  Andersch. 

The  superior  or  jugular  ganglion  (ganglion  superius)  is  situated  in  the  upper 
part  of  the  groove  in  which  the  nerve  is  lodged  during  its  passage  through  the 
jugular  foramen.  It  is  of  very  small  size,  and  involves  only  part  of  the  trunk  of 
the  nerve.  It  is  usually  regarded  as  a  detached  portion  from  the  lower  ganglion. 
The  inferior  or  petrous  ganglion  (ganglion  inferius)  is  situated  in  a  depression 
in  the  lower  border  of  the  petrous  portion  of  the  temporal  bone;  it  is  larger  than 
the  superior  ganglion  and  involves  the  whole  of  the  fibres  of  the  nerve.  From 
this  ganglion  arise  those  filaments  which  connect  the  glossopharyngeal  with  the 
vagus  and  sympathetic  nerves. 

Branches  of  Communication. — The  branches  of  communication  are  with  the 
vagus,  sympathetic,  and  facial. 

The  branches  to  the  vagus  are  two  filaments,  arising  from  the  petrous  ganglion, 
one  of  which  passes  to  the  auricular  branch  ,of  the  vagus,  and  one  to  the  upper 
ganglion  of  the  vagus. 

The  petrous  ganglion  is  connected  by  a  filament  with  the  superior  cervical 
ganglion. 

The  branch  of  communication  with  the  facial  perforates  the  posterior  bell}^  of 
the  Digastric  muscle.  It  arises  from  the  trunk  of  the  nerve  below  the  petrous 
ganglion,  and  joins  the  facial  just  after  its  exit  from  the  stylomastoid  foramen. 

Branches  of  Distribution. — The  branches  of  distribution  are  the  tympanic, 
carotid,  pharyngeal,  muscular,  tonsillar,  and  lingual. 

The  Tympanic  Branch  or  Jacobson's  Nerve  (;(.  tympanicus)  arises  from  the  petrous 
ganglion,  and  enters  a  small  bony  canal  {canaJicithis  tympanicus)  in  the  lower 
surface  of  the  petrous  portion  of  the  temporal  bone,  the  lower  opening  of  which 
is  situated  on  the  bony  ridge  which  separates  the  carotid  canal  from  the  jugular 
fossa.  It  ascends  to  the  tympanum,  enters  that  cavity  by  an  aperture  in  its 
floor  close  to  the  inner  wall,  and  divides  into  branches  which  are  contained  in 
grooves  upon  the  surface  of  the  promontory.     These  branches  form  a  tympanic 


THE  TENTH,    VAGUS,   OR  PNEUiMOGASTRIC  NERVE       1003 

plexus  {plexus  tyvipanicus).  This  plexus  gi^^es  off  (1)  the  small  superficial 
petrosal  nerve  (Fig.  745);  (2)  a  branch  to  join  the  great  superficial  petrosal 
nerve;  and  (3)  branches  to  the  tympanic  cavity,  all  of  which  will  be  described 
in  connection  with  the  anatomy  of  the  ear. 

The  Carotid  Branches  (u.  caroticofympanicus  superior  and  u.  caroticotympaiiicus 
inferior)  descend  along  the  trunk  of  the  internal  carotid  artery  as  far  as  its  com- 
mencement, communicating  with  the  pharyngeal  branch  of  the  vagus  and  with 
branches  of  the  sympathetic. 

The  Pharyngeal  Branches  (rami  pharyngei)  are  three  or  four  filaments  which 
unite  opposite  the  Middle  constrictor  of  the  pharynx  with  the  pharyngeal  1)ranches 
of  the  vagus  and  sympathetic  nerves  to  form  the  pharyngeal  plexus,  brandies 
from  which  perforate  the  muscular  coat  of  the  pharynx  to  supply  tlie  muscles 
and  mucous  membrane. 

The  Muscular  Branch  (ramus  sfylophari/ngeus)  is  distributed  to  the  Stylo- 
pharyngeus  muscle. 

The  Tonsillar  Branches  (rami  tonsillares)  supply  the  tonsil,  forming  a  plexus 
(circulus  tonsillaris)  around  this  body,  from  which  branches  are  distributed  to 
the  soft  palate  and  fauces,  where  they  communicate  with  the  palatine  nerves. 

The  Lingual  Branches  {rami  linguales)  are  two  in  number;  one  supplies  the  cir- 
cumvallate  papillsB  and  the  mucous  membrane  covering  the  surface  of  the  base 
of  the  tongue;  the  other  perforates  its  substance,  and  supplies  the  mucous  mem- 
brane and  follicular  glands  of  the  posterior  one-third  of  the  tongue  and  communi- 
cates with   the  lingual   nerve. 

The  Gustatory  Path. — The  impressions  of  taste  reach  the  glossopharyngeal 
nucleus  in  the  medulla  oblongata  in  two  ways.  From  the  posterior  one-third 
of  the  tongue  and  from  the  palate  they  reach  the  nucleus  by  the  glossopharyngeal 
nerve.  From  the  anterior  two-thirds  of  the  tongue  impulses  of  taste  are  conveyed 
by  the  chorda  tympani  or  portion  of  the  nervus  intermedius.  From  the  glosso- 
pharyngeal nucleus  gustatory  impressions  pass  by  way  of  the  medial  fillet  to  the 
thalamus  of  the  opposite  side,  and  from  the  thalamus  through  ventral  thalamo- 
cortical radiation  to  the  gyrus  hippocampi,  where  the  cortical  gustatory  centre 
is  situated. 

Applied  Anatomy. — Injury  may  produce  hemorrhage  about  the  roots  of  the  nerve.  Berg- 
mann  reported  such  a  case.  The  patient  died  from  edema  of  the  glottis  after  presenting  evi- 
dences of  disorder  of  speech  and  difSculty  in  swallowing.  Disease  of  the  glossopharyngeal 
nerve  alone  cannot  usually  be  diagnosticated. 


THE  TENTH,  VAGUS,  OR  PNETJMOGASTRIC  NERVE  (N.  VAGUS) 
(Figs.  748,  749). 

The  tenth,  vagus,  or  pneumogastric  nerve  has  a  more  extensive  distribution 
than  any  of  the  other  cranial  nerves,  passing  through  the  neck  and  thorax  to  the 
upper  part  of  the  abdomen.  It  is  composed  of  both  motor  and  sensor  fibres. 
It  supplies  the  organs  of  voice  and  respiration  with  motor  and  sensor  fibres,  and 
the  pharynx,  oesophagus,  stomach,  and  heart  with  motor  fibres.  Its  superficial 
origin  (Fig.  748)  is  by  eight  or  ten  filaments  from  the  groove  between  the  olive 
and  the  restiform  body  below  the  glossopharyngeal;  its  central  connections  are 
described  on  page  880. 

The  real  origin  of  the  sensor  fibres  of  the  vagus  is  to  be  found  in  the  cells  of 
the  ganglia  on  the  nerve — viz.,  the  ganglion  of  the  root  and  the  ganglion  of  the 
trunk.  The  filaments  become  united  and  form  a  flat  cord,  which  passes  outward 
beneath  the  flocculus  to  the  jugular  foramen,  through  which  it  emerges  from  the 
cranium  (Fig.  749).  In  passing  through  this  opening  the  vagus  accompanies 
the  spinal  accessory  nerve,  being  contained  in  the  same  sheath  of  dura  with  it,  a 


1004 


THE  NERVE  SYSTEM 


Gh'!Sophari/ngeal  \ 
Spinal 


membranous  septum  separating  them  from  the  glossopharyngeal,  which  lies  in 
front  (Fig.  749).     The  nerve  in  this  situation  presents  a  well-marked  ganghonic 

enlargement,  which  is  called  the 
superior  ganglion,  or  jugular 
ganglion;  to  it  the  vagal  ac- 
cessory part  of  the  spinal  ac- 
cessory nerve  is  connected  by 
one  or  two  filaments.  After 
its  exit  from  the  jugular  fora- 
men the  nerve  is  joined  by  the 
accessory  portion  of  the  spinal 
accessory  nerve  and  enlarges 
into  a  second  gangliform  swell- 
ing, called  the  inferior  ganglion 
or  the  ganglion  of  the  trunk  of 
the  nerve,  through  which  the 
fibres  of  the  spinal  accessory 
nerve  pass  unchanged,  being 
principally  distributed  to  the 
pharyngeal  and  superior  laryn- 
geal branches  of  the  vagus ;  but 
some  of  the  filaments  from  it 
are  continued  into  the  trunk  of 
the  vagus  below  the  ganglion 
to  be  distributed  with  the  re- 
current laryngeal  nerve,  and 
probably  also  with  the  cardiac 
nerves.  The  vagus  nerve  passes 
vertically  down  the  neck  within 
the  sheath  of  the  carotid  ves- 
sels lying  between  the  internal 
carotid  artery  and  the  internal 
jugular  vein  as  far  as  the  thy- 
roid cartilage, and  then  between 
the  same  vein  and  the  common 
carotid  to  the  root  of  the  neck 
(Fig.  749).  From  here  the 
course  of  the  nerve  differs  on 
the  two  sides  of  the  body. 

On  the  right  side  (Fig.  749) 
the  nerve  passes  across  the  sub- 
clavian artery  between  it  and 
the  right  innominate  vein,  and 
descends  by  the  side  of  the 
trachea  to  the  back  part  of  the 
root  of  the  right  lung,  where  it 
spreads  out  in  a  plexiform  net- 
work, the  posterior  pulmonary 
plexus  (plexus  pulmonalis  pos- 
terior), from  the  lower  part 
of  which  two  cords  descend  upon  the  oesophagus,  on  which  tube  they  divide, 
forming,  with  branches  from  the  opposite  nerve,  the  oesophageal  plexus  (plexus 
gulae);  below,  these  branches  are  collected  into  a  single  cord,  which  runs  along 
the  back  part  of  the  oesophagus,  enters  the  abdomen,  and  is  distributed  to  the 


Vagus 

-Course  and  distribution  of  the  glossopharyngeal,  ' 
and  spinal  accessory  ] 


THE  TENTH,    VAGUS,    OB,  PNEUMOGA8T11IC  NEliVE        1005 

posterior  surface  of  the  stomach,  joining  the  left  side  of  the  solar  plexus,  and  send- 
ing filaments  to  the  splenic  plexus  and  a  considerable  branch  to  the  coeliac  plexus. 

On  the  left  side  the  vagus  nerve  enters  the  thorax  between  the  left  carotid  and 
subclavian  arteries,  behind  the  left  innominate  vein.  It  crosses  the  arch  of 
the  aorta  and  descends  behind  the  root  of  the  left  lung,  forming  the  posterior  pul- 
monary plexus  [plexus  fulvionalis  posterior),  and  along  the  anterior  surface  of  the 
oesophagus,  where  it  unites  with  the  nerve  of  the  right  side  in  forming  the  oesopha- 
geal plexus.  It  passes  to  the  stomach,  distributing  branches  over  the  anterior 
surface  of  that  viscus,  some  extending  over  the  fundus,  and  others  along  the  lesser 
curvature.  Filaments  from  these  branches  enter  the  gastrohepatic  omentum  and 
join  the  hepatic  plexus. 

The  ganglion  of  the  root  or  the  jugular  ganglion  (ganglion  jugulare)  is  of  a 
grayish  color,  circular  in  form,  about  4  mm.  or  ^  inch  in  diameter. 

Branches  of  Communication. — To  this  ganglion  the  accessory  portion  of  the 
spinal  accessory  nerve  is  connected  by  several  delicate  filaments;  it  also  communi- 
cates by  a  twig  with  the  petrous  ganglion  of  the  glossopharyngeal,  with  the  facial 
nerve  by  means  of  its  auricular  branch,  and  with  the  sympathetic  by  means  of 
an  ascending  filament  from  the  superior  cervical  ganglion. 

The  ganglion  of  the  trunk  or  the  inferior  ganglion  (ganglion  nodosum)  is  a 
plexiform  cord,  cylindrical  in  form,  of  a  reddish  color,  and  about  an  inch  (2  cm.) 
in  length;  it  involves  the  whok  of  the  fibres  of  the  nerve,  and  passing  through  it 
is  the  vagal  accessory  portion  of  the  spinal  accessory  nerve,  which  blends  with 
the  vagus  below  the  ganglion,  to  be  then  continued  principally  into  its  pharyngeal 
and  superior  laryngeal  branches. 

Branches  of  Communication. — This  ganglion  is  connected  with  the  hypoglossal, 
the  superior  cervical  ganglion  of  the  sympathetic,  and  the  loop  between  the  first 
and  second  cervical  nerves. 

Branches  of  Distribution. — The  branches  of  the  vagus  are: 

In  the  jugular  fossa  .      .      .        }  Meningeal  or  dural. 
■'  °  (  Auricular. 

r  Pharyngeal. 
In  the  neck \   Superior  laryngeal. 

I    Recurrent  laryngeal. 

L  Cervical  cardiac. 

[  Thoracic  cardiac. 
In  the  thorax       ....<!   Anterior  or  ventral  pulmonary. 

I    Posterior  or  dorsal  pulmonary. 

'^  CEsophageal. 
In  the  abdomen  ....  Gastric. 

The  Meningeal  or  Dural  Branch  (ramus  meningeus)  is  a  recurrent  filament 
given  off  from  the  ganglion  of  the  root  on  the  jugular  foramen.  It  passes  back- 
ward, and  is  distributed  to  the  dura  lining  the  posterior  fossa  of  the  base  of  the 
skull. 

The  Auricular  Branch  or  Arnold's  Nerve  (ramus  aurimdaris)  (Fig.  750)  arises 
from  the  ganglion  of  the  root,  and  is  joined  soon  after  its  origin  by  a  filament 
from  the  petrous  ganglion  of  the  glossopharyngeal;  it  passes  outward  behind  the 
jugular  vein,  and  enters  a  small  canal  on  the  outer  wall  of  the  jugular  fossa. 
Traversing  the  substance  of  the  temporal  bone,  it  crosses  the  facial  canal  or 
aquaeductus  Fallopii  about  4  mm.  (^  inch)  above  its  termination  at  the  stylo- 
mastoid foramen;  here  it  gives  off  an  ascending  branch,  which  joins  the  facial. 
The  continuation  of  the  nerve  reaches  the  surface  by  passing  through  the  auricular 
fissure  between  the  mastoid  process  and  the  external  auditory  meatus,  and  divides 


1006 


THE  NERVE  SYSTEM 


into  tw'o  branches,  one  of  which  communicates  with  the  posterior  auricular  nerve, 
while  the  other  suppHes  the  integument  at  the  back  part  of  the  pinna  and  the 
posterior  part  of  the  external  auditory  meatus. 

The  Pharyngeal  Branch  (ramus  pharyiigeus),  the  principal  motor  nerve  of  the 
pharynx,  arises  from  the  upper  part  of  the  ganglion  of  the  trunk  of  the  vagus. 
It  consists  principally  of  filaments  from  the  vagal  accessory  portion  of  the  spinal 
accessory  nerve;  it  passes  across  the  internal  carotid  artery  to  the  upper  border 
of  the  ^Middle  constrictor  of  the  pharynx,  where  it  divides  into  numerous  filaments 
which  join  with  those  from  the  glossopharyngeal  the  superior  laryngeal  (its 
external  branch),  and  sympathetic,  to  form  the  pharyngeal  plexus  (plexus  pharyii- 
geus), from  which  branches  are  distributed  to  the  muscles  and  mucous  membrane 
of  the  pharynx  and  the  muscles  of  the  soft  palate,  except  the  Tensor  palati.  From 
the  pharyngeal  plexus  a  minute  filament  is  given  off,  which  descends  and  joins 
the  hypoglossal  nerve  as  it  winds  around  the  occipital  artery. 


to  external  auditory 
me'Xijus  and  back 


Fig.  750.— Plan  of  Arnold's  nerve.     (W.  Keiller.) 


Fig.  751. — Relations  of  vagus  and  recurrent  laryn- 
geal nerves  to  the  great  vessels:     (W.  Keilier.) 


The  Superior  Laryngeal  Nerve  (;;.  laryugeus  superior)  (Figs.  748  and  749)  is 
larger  than  the  preceding,  and  arises  from  the  middle  of  the  ganglion  of  the 
trunk  of  the  vagus.  In  its  course  it  receives  a  branch  from  the  superior  cervical 
ganglion  of  the  sympathetic.  It  descends  by  the  side  of  the  pharynx  behind  the 
internal  carotid  artery,  where  it  divides  into  two  branches,  the  external  and  internal 
Laryngeal. 

The  external  laryngeal  branch  (ramus  externus)  (Fig.  749)  the  smaller,  descends 
by  the  side  of  the  larynx,  beneath  the  Sternothyroid,  to  supply  the  Cricothyroid 
muscle.  It  gives  branches  to  the  pharyngeal  plexus  and  the  Inferior  constrictor, 
and  communicates  with  the  superior  cardiac  nerve,  behind  the  common  carotid. 

The  internal  laryngeal  branch  (ramus  intermis)  descends  to  the  opening  in  the 
thyrohyoid  membrane,  through  which  it  passes  with  the  superior  laryngeal  artery, 
and  is  distributed  to  the  mucous  membrane  of  the  larynx.  A  small  branch  com- 
municates with  the  recurrent  laryngeal  nerve.  The  branches  to  the  mucous 
membrane  are  distributed,  some  in  front  to  the  epiglottis,  the  base  of  the  tongue, 
and  the  epiglottidean  glands;  while  others  pass  backward,  in  the  arytenoepi- 
glottidean  fold,  to  supply  the  mucous  membrane  surrounding  the  superior  orifice 
of  the  larynx,  as  well  as  the  membrane  which  lines  the  cavity  of  the  larynx  as 
low  down  as  the  vocal  cord.     The  filament  which  joins  with  the  recurrent  laryn- 


THE  TENTH,    VAGUS,    OB  PNEUMOGASTBIC  NERVE        1007 

geal  descends  beneath  the  mucous  membrane  on  the  inner  surface  of  the  thyroid 
cartilage,  where  the  two  nerves  become  imited. 

The  Inferior  or  Recurrent  Laryngeal  Branch  of  the  Vagus  (n.  recvrrens)  Figs. 
749  and  751),  so  called  from  its  reflected  course,  is  the  motor  nerve  of  the  lar- 
ynx. It  arises,  on  the  right  side,  in  front  of  the  subclavian  artery;  winds  from 
before  backward  around  that  vessel,  and  ascends  oblkiuely  to  the  side  of  the  trachea 
behind  the  common  carotid  artery,  and  either  in  front  of  or  behind  the  inferior 
thyroid  artery.  On  the  left  side  it  arises  in  front  of  the  arch  of  the  aorta,  and 
winds  from  before  backward  around  the  aorta  at  the  point  where  the  impervious 
ductus  arteriosus  is  attached,  and  then  ascends  to  the  side  of  the  trachea.  The 
nerve  on  each  side  ascends  in  the  groove  between  the  trachea  and  oesophagus, 
and,  passing  under  the  lower  border  of  the  Inferior  constrictor  muscle,  enters  the 
larynx  behind  the  articulation  of  the  inferior  cornu  of  the  thyroid  cartilage  with 
the  cricoid,  being  distributed  to  all  the  muscles  of  the  larynx  except  the  Crico- 
thyroid. It  communicates  with  the  superior  laryngeal  nerve  and  gives  off  a 
few  filaments  to  the  mucous  membrane  of  the  lower  part  of  the  larynx. 

The  recurrent  laryngeal,  as  it  winds  around  the  subclavian  artery  and  aorta, 
gives  off  several  cardiac  filaments,  which  unite  with  the  cardiac  branches  from 
the  vagus  and  sympathetic.  As  it  ascends  in  the  neck  it  gives  off  oesophageal 
branches,  more  numerous  on  the  left  than  on  the  right  side,  which  supply  the 
mucous  membrane  and  muscular  coat  of  the  oesophagus;  tracheal  branches  to 
the  mucous  membrane  and  muscular  fibres  of  the  trachea;  and  some  pharyngeal 
filaments  to  the  Inferior  constrictor  of  the  pharynx. 

The  Cervical  Cardiac  Branches  (rami  cardiaci  superiores),  two  or  three  in  number, 
arise  from  the  vagus,  at  the  upper  and  lower  parts  of  the  neck. 

The  superior  branches  are  small,  and  communicate  with  the  cardiac  branches 
of  the  sympathetic.     They  can  be  traced  to  the  great  or  deep  cardiac  plexus. 

The  inferior  branches,  one  on  each  side,  arise  at  the  lower  part  of  the  neck, 
just  above  the  first  rib.  That  from  the  right  vagus  passes  ventrad  or  by  the 
side  of  the  innominate  artery,  and  communicates  with  one  of  the  cardiac  nerves 
proceeding  to  the  great  or  deep  cardiac  plexus;  that  from  the  left  runs  across  the 
left  side  of  the  arch  of  the  aorta  and  joins  the  superficial  cardiac  plexus. 

The  Thoracic  Cardiac  Branches  (rami  cardiaci  inferiores),  on  the  right  side, 
arise  from  the  trunk  of  the  vagus  as  it  lies  by  the  side  of  the  trachea,  and  from  its 
recurrent  laryngeal  branch,  but  on  the  left  side  from  the  recurrent  nerve  only; 
passing  inward,  they  terminate  in  the  deep  cardiac  plexus. 

The  Anterior  or  Ventral  Pulmonary  Branches,  two  or  three  in  number,  and  of 
small  size,  are  distributed  on  the  anterior  aspect  of  the  root  of  the  lungs.  They 
join  with  filaments  from  the  sympathetic,  and  form  the  anterior  pulmonary  plexus 
(plexus  pulmonalis  anterior). 

The  Posterior  or  Dorsal  Pulmonary  Branches,  more  numerous  and  larger  than 
the  anterior,  are  distributed  on  the  posterior  aspect  of  the  root  of  the  lung;  they 
are  joined  by  filaments  from  the  third  and  fourth  (sometimes  also  from  the  first 
and  second)  thoracic  ganglia  of  the  sympathetic,  and  form  the  posterior  pulmonary 
plexus  (plexus  pulmonalis  posterior).  Branches  from  both  plexuses  accompany 
the  ramifications  of  the  bronchi  through  the  substance  of  the  lungs  (rami  hronchiales 
anteriores  and  rami  hronchiales  posteriores). 

The  (Esophageal  Branches  (rami  oesophagei)  are  given  ofT  from  the  vagus  both 
above  and  below  the  pulmonary  branches.  The  lower  are  more  numerous  and 
larger  than  the  upper.  They  form,  together  with  branches  from  the  opposite 
nerve,  the  (esophageal  plexus.  From  this  plexus  branches  are  distributed  to  the 
back  of  the  pericardium. 

The  Gastric  Branches  (rami  gastrici)  (Fig.  749)  are  the  terminal  filaments  of 
the  vagus  nerve.     The  nerve  on  the  right  side  is  distributed  to  the  posterior 


1008  THE  NER  VE  SYSTEM 

surface  of  the  stomach.  The  right  vagus  sends  branches  to  the  coeliac  plexus 
{rami  coeliaci),  to  the  splenic  plexus  (rami  lienales),  and  to  the  renal  plexus  {rami 
renales).  The  nerve  on  the  left  side  is  distributed  over  the  anterior  surface  of 
the  stomach  and  along  the  lesser  curvature.  They  unite  with  branches  of  the 
right  nerve  and  with  the  sympathetic,  some  filaments  {rami  hepatica)  passing 
through  the  lesser  omentum  to  the  hepatic  plexus.' 

Applied  Anatomy. — It  is  a  well-recognized  fact  that  disease  or  injury  of  the  vagus  may  induce 
serious  symptoms.  Bruising  may  cause  such  symptoms;  so  may  injury  of  the  nerve  by  a  stab, 
a  bullet,  or  during  surgical  operations.  Either  accidental  ligation  or  crushing  with  clamp  for- 
ceps is  particularly  dangerous.  Michaux  accidentally  ligated  the  vagus,  and  the  patient  became 
Qomatose  and  ceased  to  breathe,  but  was  restored  on  removing  the  ligature.  Tillmanns,  while 
removing  a  cancer,  accidentally  caught  and  crushed  a  portion  of  the  nerve  in  a  clamp,  and  both 
pulse  and  respiration  ceased.  The  clamp  was  removed,  the  patient  was  restored  with  difficulty, 
and  the  nerve  was  sutured.  Recovery  followed.  It  thus  becomes  evident  that  division  of  the 
vagus  on  one  side  is  not,  as  was  so  long  taught,  a  necessarily  fatal  accident;  in  fact,  it  is  sometimes 
undertaken  deliberately  in  removing  tumors  adherent  to  the  nerve.  Division  of  a  nerve  which 
has  been  long  compressed  is  probably  not  so  dangerous  as  division  of  a  healthy  nerve,  as  in  the 
former  case  the  opposite  vagus  has  probably  assumed  some  of  its  colleague's  duties.  A  number 
of  cases  of  deliberate  division  have  been  reported.  Twenty-three  cases  are  referred  to  in  the 
system  of  surgery  by  von  Bergmann  and  Mikulicz,  and  in  twelve  the  patients  died,  but  in  none 
of  the  deaths  was  the  removal  of  the  vagus  the  apparent  cause  of  the  fatality.  Three  American 
cases  are  notable:  One  was  operated  upon  by  Dr.  W.  Joseph  Hearn,  one  by  Dr.  Melvin  Franklin, 
and  one  by  Dr.  J.  Chalmers  Da  Costa.  All  three  recovered,  and  not  one  presented  any  serious 
disturbance,  although  each  had  hoarseness  and  weakness  of  voice. 

One  would  assume  that  after  division  of  the  vagus  below  the  superior  laryngeal  nerve  and 
above  the  recurrent  laryngeal  nerve  (the  region  usually  attacked)  there  would  be  paralysis 
of  all  the  muscles  of  one  side  of  the  larynx,  except  the  Cricothyroid,  and  widespread  aberration 
evinced  by  disturbances  of  the  heart,  stomach,  and  lungs.  As  a  matter  of  fact,  this  has  not  been 
the  case.  It  might  be  and  probably  would  be  the  case,  were  a  healthy  nerve  divided;  but  the 
surgeon  who  deliberately  divides  the  nerve  does  so  during  the  removal  of  a  tumor  which  has  long 
made  pressure.  In  most  cases  there  is  no  change  in  the  pulse  or  respiration.  In  some  cases 
dysphagia  and  pneumonia  arise,  but  they  may  be  due  to  other  causes  than  vagus-nerve  injury 
(the  formidable  nature  and  the  duration  of  the  operation — the  ligation  of  vessels  of  large  size — 
the  age  of  the  subject). 

Larj'ngeal  symptoms,  to  a  greater  or  less  degree,  are  always  noted.  The  difference  in  the 
degree  of  the  palsy  is  explainable  when  we  recall  Exner's  statement  that  the  muscles  supplied 
by  the  recurrent  laryngeal  also  receive  some  innervation  from  the  superior  laryngeal.  In  fact. 
Mills  points  out  that  a  portion  of  the  recurrent  laryngeal  has  been  resected  without  completely 
paralyzing  the  muscles  supposed  to  be  supplied  solely  by  the  recurrent  laryngeal.  The  laryngeal 
symptoms  result  from  unilateral  laryngeal  paralysis,  in  which  there  is  paralysis  of  the  muscles 
which  open  the  glottis.  The  voice  may  be  lost  or  may  be  hoarse.  Usually,  after  a  time,  this  is, 
to  a  great  extent,  compensated  for  by  the  opposite  vocal  cord,  although  the  voice  may  always 
remain  weak,  and  the  patient  will  tire  easily  on  talking.  If  both  vagi  were  to  be  divided  death 
would  ensue. 

The  laryngeal  nerves  are  of  considerable  importance  in  considering  some  of  the  morbid  con- 
ditions of  the  larynx.  When  the  peripheral  terminations  of  the  superior  laryngeal  nerve  are 
irritated  by  some  foreign  body  passing  over  them,  refle.r  spasm  of  the  glottis  is  the  result.  When 
the  trunk  of  the  same  nerve  is  pressed  upon  by,  for  instance,  a  goitre  or  an  aneurism  of  the  upper 
part  of  the  carotid,  we  have  a  peculiar,  dry,  brassy  cough.  When  the  nerve  is  paralyzed  we 
have  anesthesia  of  the  mucus  membrane  of  the  larynx,  so  that  foreign  bodies  can  readily  enter- 
the  cavity,  and,  in  consequence  of  its  supplying  the  Cricothyroid  muscle,  the  vocal  cords  cannot 
be  made  tense,  and  the  voice  is  deep  and  hoarse.  Paralysis  of  the  superior  laryngeal  nerves 
may  be  the  result  of  bulbar  paralysis,  may  be  a  sequel  to  diphtheria,  when  both  nerves  are 
usually  involved,  or  it  may,  though  less  commonly,  be  caused  by  the  pressure  of  tumors  or 
aneurisms,  when  the  paralysis  is  generally  unilateral.  Irritation  of  the  inferior  laryngeal  nerves 
produces  spasm  of  the  muscles  of  the  larynx.  When  both  the  recurrent  nerves  are  paralyzed 
the  vocal  cords  are  motionless  in  the  so-called  cadaveric  position — that  is  to  say,  in  the  position 
in  which  they  are  found  in  ordinary  tranquil  respiration — neither  closed  as  in  phonation,  nor 
open  as  in  deep  inspiratory  effort.  When  one  recurrent  nerve  is  paralyzed,  the  cord  of  the  same 
side  is  motionless,  while  the  opposite  cord  crosses  the  middle  line  to  accommodate  itself  to  the 
affected  one;  hence  phonation  is  present,  but  the  voice  is  altered  and  weak  in  timbre.  The  recur- 
rent laryngeal  nerves  may  be  paralyzed  in  bulbar  paralysis  or  after  diphtheria,  when  the  paralysis 
usually  affects  both  sides;  or  they  may  be  affected  by  the  pressure  of  aneurisms  of  the  aorta. 


THE  ELEVENTH  OR  SPINAL  ACCESSORY  NERVE  100!) 

innominate  or  subclavian  arteries;  by  mediastinal  tumors;  by  bronchocele;  or  by  cancer  of  the 
upper  part  of  the  oesophagus,  when  the  paralysis  is  often  unilateral.-  .The  nerve  may  he  acci- 
dentally divided  during  the  operation  for  goitre. 


THE  ELEVENTH  OR  SPINAL  ACCESSORY  NERVE  (N.  ACCESSORIUS) 

(Figs.  748,  749). 

The  eleventh  or  spinal  accessory  nerve  consists  of  two  parts,  one  the  accessory 
part  to  the  vagus,  and  the  other  the  spinal  portion. 

The  bulbar  or  vagal  accessory  part  (ramus  interims)  is  the  smaller  of  the  two. 
It  is  accessory  to  the  vagus.  Its  superficial  origin  (Fig.  748)  is  by  four  or  five 
delicate  filaments  from  the  side  of  the  medulla  oblongata,  below  the  roots  of  the 
vagus.  Its  dee-p  origin,  is  described  in  detail  on  page  879.  It  passes  outward 
to  the  jugular  foramen,  where  it  interchanges  fibres  with  the  spinal  portion  or 
becomes  united  to  it  for  a  short  distance;  it  is  also  connected,  in  the  foramen, 
with  the  upper  ganglion  of  the  vagus  by  one  or  two  filaments.  It  then  passes 
through  the  foramen  (Fig.  749),  and  becoming  again  separated  from  the  spinal 
portion  it  is  continued  over  the  surface  of  the  ganglion  of  the  trunk  of  the  vagus, 
being  adherent  to  its  surface,  and  is  distributed  principally  to  the  pharyngeal 
and  superior  laryngeal  branches  of  the  vagus.  Through  the  pharyngeal  branch 
it  probably  supplies  the  Azygos  uvulae  and  Levator  palati  muscles  (see  p.  399). 
Some  few  filaments  from  it  are  continued  into  the  trunk  of  the  vagus  below  the 
ganglion,  to  be  distributed  with  the  recurrent  laryngeal  nerve  to  supply  most 
of  the  laryngeal  muscles  and  probably  also  with  the  cardiac  nerves. 

The  spinal  portion  (ramus  externus)  is  firm  in  texture.  Its  superficial  origin 
(Fig.  748)  is  by  several  filaments  or  rootlets  from  the  lateral  tract  of  the  cord, 
as  low  down  as  the  sixth  cervical  nerve.  Its  deep  origin  (Fig.  650)  may  be  traced 
to  the  intermediolateral  tract  of  the  gray  substance  of  the  cord.  The  rootlets 
of  origin  join  and  form  a  trunk  which  ascends  in  the  subdural  space  between  the 
ligamentum  denticulatum  and  the  anterior  roots  of  the  spinal  nerves,  enters  the 
skull  through  the  foramen  magnum,  and  is  then  directed  outward  to  the  jugular 
foramen,  through  which  it  passes,  lying  in  the  same  sheath  as  the  vagus,  but 
separated  from  it  by  a  fold  of  the  arachnoid.  In  the  jugular  foramen  it  receives 
one  or  two  filaments  from  the  vagal  accessory  portion.  At  its  exit  from  the  jugular 
foramen  it  passes  backward,  either  in  front  of  or  behind  the  internal  jugular  vein, 
and  descends  obliquely  behind  the  Digastric  and  Stylohyoid  muscles  to  the  upper 
part  of  the  Sternomastoid  muscle.  It  pierces  that  muscle,  and  passes  obliquely 
across  the  posterior  triangle,  to  terminate  in  the  deep  surface  of  the  Trapezius 
muscle.  During  its  passage  through  the  Sternomastoid  muscle  it  gives  several 
branches  to  the  muscle,  and  joins  in  its  substance  with  branches  from  the  second 
cervical.  In  the  posterior  triangle  it  joins  with  the  second  and  third  cervical 
nerves,  while  beneath  the  Trapezius  it  forms  a  sort  of  plexus  with  the  third  and 
fourth  cervical  nerves,  and  from  this  plexus  fibres  are  distributed  to  the  muscle. 

Applied  Anatomy. — Division  of  the  external  branch  of  the  spinal  accessory  nerve  causes 
paralysis  of  the  Sternomastoid  and  Trapezius  muscles;  not  absolute  paralysis,  for  these  muscles 
also  receive  nerves  from  the  cervical  plexus.  In  cases  of  spaismodic  torticollis  in  which  all  pal- 
liative treatment  has  failed,  division  or  excision  of  a  portion  of  the  external  branch  of  the  spinal 
accessory  nerve  has  been  suggested  by  Keen.'  This  may  be  done  either  along  the  anterior  or 
posterior  border  of  the  Sternomastoid  muscle.  The  former  operation  is  performed  by  making 
an  incision  from  the  apex  of  the  mastoid  process,  three  inches  in  length,  along  the  anterior  border 
of  the  Sternomastoid  muscle.  The  anterior  border  of  the  muscle  is  defined  and  pulled  back- 
ward, so  as  to  stretch  the  nerve,  which  is  then  to  be  sought  for  beneath  the  Digastric  muscle, 
about  two  inches  below  the  apex  of  the  mastoid  process.  The  other  operation  consists  in 
making  an  incision  along  the  posterior  border  of  the  muscle,  so  that  the  centre  of  the  incision  cor- 
responds to  the  middle  of  this  border  of  the  muscle.     The  superficial  structures  having  been 


1010 


THE  NERVE  SYSTEM 


divided  and  the  border  of  the  muscle  defined,  the  nerve  is  to  be  sought  for  as  it  emerges  from 
the  muscle  to  cross  the  occipital  triangle.  When  found,  it  is  to  be  traced  upward  through  the 
muscle,  and  a  portion  of  it  is  excised  above  the  point  where  it  gives  off  its  branches  to  the  Sterno- 
mastoid.  In  this  operation  one  of  the  descending  branches  of  the  superficial  cervical  plexus  is 
liable  to  be  mistaken  for  the  nerve. 


THE  TWELFTH  OR  HYPOGLOSSAL  NERVE  (N.  HYPOGLOSSUS) 

(Figs.  752,  753). 

The  twelfth  or  hypoglossal  nerve  is  the  motor  nerve  of  the  tongue.  Its  super- 
ficial origin  is  by  several  filaments,  from  ten  to  fifteen  in  number,  from  the  groove 
between  the  pyramidal  and  olivary  bodies  of  the  medulla  oblongata,  in  a  continuous 
line  with  the  ventral  roots  of  the  spinal  nerves.  Its  deep  origin  can  be  traced  to  a 
nucleus  of  gray  substance  (nucleus  hi/poglossi)  in  the  floor  of  the  fourth  ventricle, 
described  on  page  878. 


To  Dura  mater 


Trunk  of  Vagus 


"  To  Sternohyoid 
To  Sternothyroid 
To  Posterior  Belly  oj  Omohyoid 

Fig.  752. — Plan  of  the  hypoglossal  nerve. 

The  filaments  of  this  nerve  are  collected  into  two  bundles,  which  perforate  the 
dura  separately,  opposite  the  anterior  condylar  foramen,  and  unite  together 
after  their  passage  through  it.  In  those  cases  in  which  the  anterior  condylar 
or  hypoglossal  foramen  in  the  occipital  bone  is  double,  these  two  portions  of  the 
nerve  are  separated  by  the  small  piece  of  bone  which  divides  the  foramen.  The 
nerve  descends  almost  vertically  to  a  point  corresponding  with  the  angle  of  the 
mandible.  It  is  at  first  deeply  seated  beneath  the  internal  carotid  artery  and  internal 
jugular  vein,  and  is  intimately  connected  witli  the  vagus  nerve  (Fig.  753);  it  then 


THE  TWELFTH  OR  HYPOGLOSSAL  NERVE  1011 

passes  forward  between  the  vein  and  artery,  and  lower  down  in  the  neck  becomes 
superficial  below  the  Digastric  muscle.  The  nerve  then  loops  around  the  occipital 
artery,  and  crosses  the  external  carotid  and  its  lingual  branch  below  the  tendon 
of  the  Digastric  muscle.  It  passes  beneath  the  tendon  of  the  Digastric,  the 
Stylohyoid,  and  the  Mylohyoid  muscles,  lying  between  the  last-named  muscle 
and  the  Hyoglossus  (Fig.  753),  and  communicates  at  the  anterior  border  of  the- 
Hyoglossus  with  the  lingual  nerve  (Fig.  752);  it  is  then  continued  forward  in  the 
fibres  of  the  Geniohyoglossus  muscle  as  far  as  the  tip  of  "the  tongue,  distributing 
branches  to  its  muscle  substance. 

Branches  of  Communication  (Fig.  752). — The  branches  of  communication  are 
with  the — 


JS.  First  and  second  cervical  nerves. 

Sympathetic.  Lingual. 

The  communication  with  the  vagus  takes  place  close  to  the  exit  of  the  nerve 
from  the  skull,  numerous  filaments  passing  between  the  hypoglossal  and  the  gan- 
glion of  the  trunk  of  the  vagus  through  the  mass  of  connective  tissue  which  unites 
the  two  nerves.  It  also  communicates  with  the  pharyngeal  plexus  by  a  minute 
filament  as  it  winds  around  the  occipital  artery. 

The  communication  with  the  sympathetic  takes  place  opposite  the  atlas  by 
branches  derived  from  the  superior  cervical  ganglion,  and  in  the  same  situation 
the  nerve  is  joined  by  filaments  derived  from  the  loop  connecting  the  first  two 
cervical  nerves. 

The  communication  with  the  lingual  nerve  takes  place  near  the  anterior  border 
of  the  Hyoglossus  muscle  by  numerous  filaments  which  ascend  upon  it. 

Branches  of  Distribution  (Fig.  752). — ^The  branches  of  distribution  are: 

Meningeal  or  Dural.  Thyrohyoid. 

Descendens  hypoglossi.  Muscular. 

Of  these  branches,  the  descendens  hypoglossi  and  the  branches  to  the  Infra- 
hyoid muscles  are  not  actually  derived  from  the  hypoglossal  nerve,  but,  as  is 
shown  in  Fig.  752,  are  branches  from  the  loop  formation  (better  called  avsa 
cervicalis)  of  the  first  with  the  second  and  third  cervical  nerves.  A  part  of  the 
loop,  commonly  called  the  descendens  hypoglossi,  is  enclosed,  for  a  short  distance, 
in  the  sheath  which  invests  the  hypoglossal  nerve. 

Meningeal  or  Dural  Branches  (Fig.  752). — As  the  hypoglossal  nerve  passes 
through  the  anterior  condylar  foramen  it  gives  off,  according  to  Luschka,  several 
filaments  to  the  dura  in  the  posterior  fossa  of  the  base  of  the  skull. 

The  Descendens  Cervicalis  or  Descendens  Hypoglossi  {ramus  descendens)  (Figs. 
752  and  753)  is  a  long  slender  branch,  which  leaves  the  hypoglossal  where  it  tiu-ns 
around  the  occipital  artery.  It  consists  mainly  of  fibres  which  pass  along  the 
sheath  of  the  hypoglossal  nerve  from  the  first  and  second  ce^^•ical  nerves  in  the 
above-mentioned  communication.  It  descends  in  front  of  or  within  the  sheath  of 
the  common  carotid  artery,  giving  ofi^  a  branch  to  the  anterior  belly  of  the  Omo- 
hyoid, and  then  joins  the  communicating  branches  from  the  second  and  third 
cervical  nerves,  just  below  the  middle  of  the  neck,  to  form  a  loop,  the  ansa  cer- 
vicalis (hypoglossi) .  From  the  convexity  of  this  loop  branches  pass  to  supply  the 
Sternohyoid,  Sternothyroid,  and  the  posterior  belly  of  the  Omohyoid. 

The  Thyrohyoid  Branch  {ramus  thyreohyoidevs)  (Fig.  752)  is  a  small  branch 
arising  from  the  hypoglossal  near  the  posterior  border  of  the  Hyoglossus;  it 
passes  obliquely  across  the  great  cornu  of  the  hyoid  bone  and  supplies  the  Thyro- 
hyoid muscle. 


1012 


THE  NERVE  SYSTEM 


The  Muscular  Branches  (Fig.  752)  are  distributed  to  the  Styloglossus,  Hyo- 
glossus,  Geniohyoid,  and  Geniohyoglossus  muscles  and  to  the  Chondroglossus, 
when  present.  At  the  under  surface  of  the  tongue  numerous  slender  branches 
{rami  linguales)  pass  upward  into  the  substance  of  the  organ  to  supply  its  In- 
trinsic muscles. 


Applied  Anatomy. — A  wound  in  the  submaxillary  region  may  injure  the  hypoglossal  nerve 
and  result  in  motor  paralysis  of  the  corresponding  half  of  the  tongue.  The  hypoglossal  nerve  is 
an  important  guide  in  the  operation  of  ligation  of  the  lingual  artery  (see  p.  591).  It  runs  for- 
vfard  on  the  Hyoglossus  muscle  just  above  the  great  cornu  of  the  hyoid  bone,  and  forms  the 
upper  boundary  of  the  triangular  space  (Lesser's  triangle)  in  which  the  artery  is  to  be  sought  for 
by  cutting  through  the  fibres  of  the  Hyoglossus  muscle. 

THE  SPINAL  NERVES  (NERVI  SPINALES). 

The  spinal  nerves  spring  from  the  spinal  cord,  and  are  transmitted  through 
the  intervertebral  foramina  on  either  side  of  the  spinal  column.  There  are 
thirty-one  pairs  of  spinal  nerves,  which  are  arranged  in  the  following  groups, 
corresponding  to  the  region  of  the  vertebral  column  through  which  they  pass : 

Cervical 8  pairs. 

Thoracic 12     " 

Lumbar 5     " 

Sacral 5     " 

Coccygeal       .............        1  pair. 


THE  SPINAL  NEBVES 


1013 


POSTERrOR 
NERVE  , 
ROOTS  ) 


(  ANTERIOR 


It  will  be  observed  that  each  group  of  nerves  corresponds  in  number  with  the 
vertebrae  in  that  region,  except  the  cervical  and  coccygeal.  Sometimes  there  is  no 
thirty-first  pair.  Occasionally  below  the  thirty-first  pair  there  may  be  one  or 
even  two  filamentous  pairs  which  do  not  pass  out  of  the  vertebral  canal. 

P^ach  spinal  nerve  arises  by  two  roots,  an  anterior,  ventral,  or  motor  root  and  a 
posterior,  dorsal,  or  sensor  root,  the  latter  being  distinguished  by  a  ganglion  termed 
the  spinal  ganglion. 

The  Anterior  or  Ventral  Root  (radix  anterior). — The  superficial  origin  is  from 
the  antero-lateral  columns  of  the  cord,  corresponding  to  the  situation  of  the 
anterior  cornu  of  gray  substance.  Each  root  is  composed  of  from  four  to  eight 
filaments. 

The  deep  origin  can  be  traced  from  cells  in  the  gray  substance  of  the  anterior 
cornu  of  the  same  as  well  as  of  the  opposite  side.  The  majority  of  the  axones 
arise  from  the  various  groups  of  cells  in  the  anterior  cornu  of  the  same  side, 
while  others  arise  from  the  large  cells 
of  the  anterior  cornu  of  the  opposite 
side,  the  axones  passing  across  the 
median  plane  in  the  anterior  white 
commissure.  The  axone  bundles,  after 
leaving  the  gray  substance,  penetrate 
horizontally  through  the  longitudinal 
bundles  of  the  antero-lateral  column 
to  emerge  as  described  above. 

The  Posterior  or  Dorsal  Root  (radix 
posterior). — The  superficial  origin  is  by 
filaments  (fila  radicularia),  from  the 
postero-lateral  fissure  of  the  cord.  The 
real  origin  of  these  fibres  is  from  the 
nerve  cells  in  the  posterior  root  gan- 
glion, from  which  they  can  be  traced 
into  the  cord  in  two  main  bundles, 
the  course  of  which  has  already  been 
studied  (p.  835).  The  posterior  or 
dorsal  root  of  the  first  cervical  nerve  is 
exceptional  in  that  it  is  smaller  than 
the  anterior;  it  is  occasionally  wanting. 

Within  the  vertebral  canal  the  nerve 
roots  are  separated  from  each  other  by 
\he lig amentum denticidatum^Fig.  755). 
In  the  cervical  region  the  spinal  portion 
of  the  spinal  accessory  nerve  separates 
the  roots. 

The  spinal  ganglia  are  collections  of 
nerve  cells  on  the  posterior  root  of  each 
of  the  spinal  nerves.  Each  ganglion  is  oval  in  shape  and  of  a  reddish  color; 
and  its  size  bears  a  proportion  to  that  of  the  nerve  root  upon  which  it  is  situated;  it 
is  bifid  internally  where  it  is  joined  by  the  two  bundles  of  the  posterior  nerve  root. 
The  ganglia  are  usually  placed  in  the  intervertebral  foramina,  ectad  of  the  point 
where  the  nerves  perforate  the  dura.  There  are,  however,  exceptions  to  this 
rule.  Thus,  the  ganglia  upon  the  first  and  second  cervical  nerves  lie  on  the  neural 
arches  of  the  atlas  and  axis  respectively;  those  of  the  sacral  nerves  are  placed 
within  the  vertebral  canal;  and  that  on  the  coccygeal  nerve,  also  in  the  canal, 
is  situated  at  some  distance  from  the  apparent  origin  of  the  posterior  root. 


I — n> 


_  Fig.  754. — A  portion  of  the  spinal  cord,  showing  its 
right  lateral  surface.  The  dura  is  opened  and  arranged 
to  show  the  nerve  roots.     (Testut.) 


1014  THE  NEBVE  SYSTEM 

Structure. — The  ganglion  in  an  embryo  is  composed  of  bipolar  nerve  cells.  In  an  adult  the 
bipolar  nerve  cells  by  fusion  of  their  two  poles  form  unipolar  elements.  The  process  of  each 
unipolar  cell  divides' into  two  a  short  distance  from  the  cell.  One  of  the  processes  from  each 
cell  passes  to  the  spinal  cord,  and  the  other  passes  into  the  spinal  nerve.  Two  other  forms  of 
cells  are,  however,  present — viz.:  (a)  the  cells  of  Dogiel,  whose  axones  ramify  close  to  the  cell 
(type  II  of  Golgi),  and  are  distributed  entirely  within  the  ganglion;  and  (6)  multipolar  cells 
similar  to  those  found  in  the  sympathetic  ganglia.  On  the  posterior  roots  of  the  lumbar  and 
sacral  nerves,  between  the  spinal  ganglia  and  the  cord,  small  cellular  masses  occasionally  exist. 
They  are  called  accessory  or  aberrant  ganglia  (gaiujlia  abermntia). 

Each  tvpic  spinal  nerve  contains  somatic  and  splanchnic  fibre  systems,  as  well  as  fibres 
connecting  these  systems  with  each  other. 

1.  The  somatic  fibres  are  eft'erent  and  afferent.  The  efferent  fibres  originate  in  the  cells  of 
the  anterior  cornu  of  the  spinal  gray  substance,  and  run  outward  through  the  anterior  nerve  roots 
to  the  spinal  nerve.  They  convey  impulses  to  the  voluntary  muscles  and  are  continuous  from  their 
origin  to  their  peripheral  distribution.  The  afferent  fibres  (peripheral  axones)  convey  impres- 
sions from  the  -skin,  etc.,  and  originate  in  the  unipolar  nerve  cells  of  the  spinal  ganglia.  The 
central  axones  enter  the  spinal  cord  through  the  posterior  nerve  roots,  to  be  continued  to  the 
medulla  oblongata,  to  end  in  the  nuclei  of  the  gracile  and  cuneate  funiculi  (Goll  and  Burdach), 
or  they  may  end  by  arborization  around  efferent  neurones  in  the  same  or  opposite  side  of  the 
cord,  completing  in  this  way  reflex  arcs. 

2.  The  sympathetic  fibres  are  also  efferent  and  afferent.  The  efferent  fibres  originate  in  the 
visceral  motor  gray  substance  of  the  spinal  cord  and  are  conveyed  through  the  anterior  nerve  root 
and  the  white  ramus  communicans  to  the  corresponding  ganglion  of  the  sympathetic  chain;  here 
they  may  end  by  forming  synapses  around  its  cells,  or  may  run  through  the  ganglion  to  end  in 
another  "of  the  chain  or  in  a' more  distally  placed  ganglion  in  one  of  the  sympathetic  plexuses,  the 
impulses  being  relayed  in  other  neurones  to  be  carried  to  the  bloodvessels  of  the  trunk  and 
limbs  or  to  the  viscera. ,  The  afferent  fibres  are  derived  partly  from  unipolar  and  partly  from 
the  multipolar  cells  of  the  spinal  ganglia.  Their  peripheral  processes  are  carried  outward 
through  the  white  rami  communicantes,  and  after  passing  through  one  or  more  sympathetic 
ganglia  without  interruption,  terminate  in  the  tissues  of  the  viscera.  The  central  processes  of 
the  Imipolar  cells  enter  the  spinal  cord  thi-ough  the  posterior  nerve  root  and  form  synapses 
around  either  somatic  or  visceral  efferent  neurones,  thus  completing  reflex  arcs.  The  dendrites 
of  the  multipolar  nerve  cells  form  synapses  around  the  cells  of  Dogiel  in  the  spinal  ganglia,  and 
by  this  path  the  original  impulse  is  transferred  from  the  sympathetic  to  the  somatic  system, 
through  which  it  is  conveyed  to  the  sensorium. 

Points  of  Emergence  of  the  Spinal  Nerves. — ^The  roots  of  the  spinal  nerves 
from  their  origin  in  the  cord  run  obliquely  caudad  to  their  point  of  exit  from  the 
intervertebral  foramina,  the  amount  of  obliquity  varying  in  different  regions  of 
the  spine,  and  being  greater  in  the  lower  than  in  the  upper  part.  The  level  of 
their  emergence  from  the  cord  is  within  certain  limits  variable,  and  of  course 
does  not  correspond  to  the  point  of  emergence  of  the  nerve  from  the  intervertebral 
foramina  (Fig.  757). 

Each  nerve  root  receives  a  covering  from  the  pia,  and  is  loosely  invested  by  the 
arachnoid,  the  latter  being  prolonged  as  far  as  the  points  where  the  roots  pierce 
the  dura.  The  two  roots  pierce  the  dura  separately,  each  receiving  a  sheath 
from  this  membrane;  this  sheath  is  continuous  with  the  epineurium  of  the  nerve 
where  the  roots  join  to  form  the  spinal  nerve. 

Divisions. — Immediately  beyond  the  ganglion  the  two  roots  coalesce,  their 
fibres  intermingle,  and  the  trunk  thus  formed  constitutes  the  spinal  nerve;  it 
passes  out  of  the  intervertebral  foramen,  and  divides  into  a  posterior  or  dorsal 
primary  division  for  the  supply  of  the  dorsal  part  of  the  body,  and  an  anterior  or 
ventral  primary  division  for  the  supply  of  the  ventral  part  of  the  body  (Fig.  755). 
Each  division  contains  fibres  from  both  roots. 

Before  dividing,  each  spinal  nerve  gives  off  a  small  recurrent  or  meningeal 
branch  (ramus  meningeus)  (Fig.  755)  which  reenters  the  vertebral  canal  through 
the  intervertebral  foramen  and  supplies  the  membranes  and  bloodvessels  of  the 
cord,  the  vertebrae,  and  the  vertebral  ligaments. 

The  posterior  or  dorsal  primary  divisions  (rami  posteriores)  (Fig.  755)  of  the 
spinal  nerves  are  generally  smaller  than  the  anterior;  they  arise  from  the  trunk 


THE  SPINAL  NERVES 


1015 


resulting  from  the  union  of  tlie  roots,  in  the  intervertebral  foramina;  and,  passing 
dorsad,  divide  into  internal  or  medial  and  external  or  lateral  branches,  which  are 
distributed  to  the  muscles  and  integument  behind  the  spine.      The   posterior 


Fig.  755. — Plan  of  the  constitution  of  a  spinal  nerve.     (W.  Keiller,  in  Gerrish's  Text-book  of  Anatomy.) 

primary  divisions  of  the  spinal  nerves  form  two  small  plexuses,  the  posterior 
cervical  plexus  and  the  posterior  sacral  plexus.  The  first  cervical,  the  fourth  and 
fifth  sacral,  and  the  coccygeal  nerves  do  not  divide  into  external  and  internal 
branches. 


Sympathetic 
ganglion 


Fig.  756. — Scheme  showing  structure  of  a  typical  spinal  nerve. 

The  anterior  or  ventral  primary  divisions  {rami  anteriores)  (Fig.  755)  of  the 
spinal  nerves  supply  the  parts  of  the  body  ventrad  of  the  spine,  including  the  limbs. 
They  are  for  the  most  part  larger  than  the  posterior  primary  divisions.  Each 
division,  soon  after  its  origin,  receives  a  slender  filament  from  the  sympathetic 
which  is  called  the  gray  ramus  commimicans.     In  the  thoracic  region  the  anterior 


1016 


THE  NERVE  8YS2EM 


primary  divisions  of  the  spinal  nerves  are  quite  separate  from  each  other,  and 
are  uniform  in  their  distribution;  but  in  the  cervical,  lumbar,  and  sacral  regions 
they  form  intricate  plexuses  previous  to  their  distribution.  The  anterior  primary 
divisions  of  certain  thoracic,  lumbar,  and  sacral  nerves  give  off  a  delicate  col- 
lection of  nerve  filaments  to  the  sympathetic  cord.  These  are  called  the  white 
rami  communicantes  or  the  visceral  branches  of  the  spinal  nerves. 

Posterior  or  Dorsal  Primary  Divisions  of  the  Spinal  Nerves. — ^The  posterior 
or  dorsal  primary  divisions  are  here  described  together,  inasmuch  as  they  do  not 
enter  into  the  formation  of  the  important  plexuses  (cervical,  lumbar,  and  sacral) 
exclusively  made  up  of  the  anterior  primary  divisions. 


Fig.  757. — Ventral  aspect. 

Figs.  757  and  758. — Distributii 


Fig.  758. — Dorsal  aspect, 
utaneous  nerves. 


The  Posterior  or  Dorsal  Divisions  of  the  Cervical  Nerves  {rami  postcriores). — 
The  posterior  division  of  the  first  cervical  nerve  (Fig.  759)  differs  from  the  pos- 
terior divisions  of  the  other  cervical  nerves  in  not  dividing  into  an  internal  and 
external  branch.  It  is  larger  than  the  anterior  division,  and  escapes  from  the 
vertebral  canal  between  the  occipital  bone  and  the  posterior  arch  of  the  atlas 
and  beneath  the  vertebral  artery.     It  enters  the  suboccipital  triangle  formed  by 


THE  SPINAL  NERVES 


1017 


the  Rectus  capitis  posticus  major,  the  Obliquus  superior  and  Obiiquus  inferior; 
it  gives  branches  also  to  the  Rectus  capitis  posticus  minor  and  to  the  Complexus. 
From  the  branch  which  supplies  the  Inferior  oblicjue  a  communicating  filament 
is  given  off  which  joins  the  second  cervical  nerve.  This  nerve  also  occasionally 
gives  off  a  cutaneous  filament,  which  accompanies  the  occipital  artery  and  com- 
municates with  the  occipitalis  major  and  minor  nerves. 

The  posterior  division  of  the  second  cervical  nerve  is  much  larger  than  the 
anterior  division,  and  is  the  largest  of  all  the  posterior  cervical  divisions.  It 
emerges  from  the  vertebral  canal  between  the  anterior  arch  of  the  atlas  and  lamina 
of.  the  axis,  below  the  Inferior  oblique.  It  supplies  a  twig  to  this  muscle,  and 
receives  a  communicating  filament  from  the  first  cervical.  It  then  divides  into 
an  internal  or  medial  and  an  external  or  lateral  branch. 

The  internal  or  medial  branch,  called,  from  its  size  and  distribution,  the  great 
occipital  nerve  (?i.  occipitalis  major)  {Pig.  759),  ascends  obliquely  inward  between 
the  Obliquus  inferior  and  the  Complexus,  and  pierces  the  latter  muscle  and  the 
Trapezius  near  their  attachments  to  the  occipital  bone.  It  is  now  joined  by  a 
filament  from  the  posterior  division  of  the  third  cervical  nerve,  the  anastomotic, 
and,  ascending  on  the  back  part  of  the  head  with  the  occipital  artery,  divides 
into  two  branches,  which  supply  the  integument  of  the  scalp  as  far  forward  as 
the  vertex,  communicating  with  the  occipitalis  minor.  It  gives  ofT  an  auricular 
branch  to  the  back  part  of  the  ear  and  muscular  branches  to  the  Complexus. 

The  external  or  lateral  branch  is  often  joined  by  the  external  branch  of  the  pos- 
terior division  of  the  third  cervical  nerve,  and  supplies  the  Splenius,  Trachelo- 
mastoid,  and  Complexus. 


VERTEBRAL   ARTERY 


Fig.  759. — Posterior  primary  divisions  of  the  upper  three  cervical  nerves,     (Testut.l 


The  posterior  division  of  the  third  cervical  nerve  (Fig.  759)  is  intermediate 
in  size  between  those  of  the  second  and  fourth.  Its  internal  or  cutaneous  branch 
passes  between  the  Complexus  and  Semispinalis,  and,  piercing  the  Splenius 
and  Trapezius,  supplies  the  skin  over  the  latter  muscle;  while  under  the  Trapezius 
it  gives  off  a  branch  called  the  third  occipital  nerve  (n.  occipitalis  iertius),  which 
pierces  the  Trapezius  and  supplies  the  skin  on  the  lower  and  back  part  of  the  head. 
It  lies  to  the  inner  side  of  the  occipitalis  major,  with  which  it  is  connected.  The 
external  branch  often  joins  that  of  the  second  cervical. 

The  posterior  division  of  the  suboccipital  nerve  and  the  internal  branches  of 
the  posterior  divisions  of  the  second  and  third  cervical  nerves  are  occasionally 


1018  THE  NEBVE  SYSTEM 

Joined  beneath  the  Complexus  by  communicating  loops  to  form  the  posterior 
cervical  plexus  (Cruveilhier). 

The  posterior  divisions  of  the  lower  five  cervical  nerves  pass  dorsad,  and  divide, 
behind  the  Intertransversales  muscles,  into  internal  or  medial  and  external  or 
lateral  branches. 

The  internal  branches,  the  larger,  are  distributed  differently  in  the  upper  and 
lower  part  of  the  neck.  Those  derived  from  the  fourth  and  fifth  nerves  pass 
between  the  Complexus  and  Semispinalis  muscles,  and,  having  reached  the  Spinous 
processes,  perforate  the  aponeurosis  of  the  Splenius  and  Trapezius,  and  are  con- 
tinued outward  to  the  integument  over  the  Trapezius,  while  those  derived  from 
the  three  lowest  cervical  nerves  are  the  smallest,  and  are  placed  beneath  the  Semi- 
spinalis colli,  which  they  supply,  and  then  pass  into  the  Interspinalis,  Multifidus 
spinae,  and  Complexus,  and  send  twigs  through  this  latter  muscle  to  supply  the 
integument  near  the  spinous  processes. 

The  external  branches  supply  the  muscles  at  the  side  of  the  neck — viz.,  the 
Cervicalis  ascendens,  Transversalis  colli,  and  Trachelomastoid. 

The  Posterior  Divisions  of  the  Thoracic  Nerves  (rami  foster  lores). — ^The 
posterior  divisions  of  the  thoracic  nerves  are  smaller  than  the  anterior,  pass 
dorsad  between  the  transverse  processes,  and  divide  into  internal  or  medial  and 
external  or  lateral  branches. 

The  internal  or  medial  branches  of  the  posterior  divisions  of  the  six  upper  thoracic 
nerves  pass  inward  between  the  Semispinalis  dorsi  and  Multifidus  spinae  muscles, 
which  they  supply,  and  then,  piercing  the  origins  of  the  Rhpmboidei  and  Trapezius 
muscles,  become  cutaneous  by  the  side  of  the  spinous  processes  and  ramify  in 
the  integument.  The  medial  branches  of  the  six  lower  thoracic  nerves  are  dis- 
tributed to  the  Multifidus  spinae,  without  giving  off  any  cutaneous  filaments. 

The  external  or  lateral  branches  increase  in  size  from  above  downward.  They 
pass  through  the  Longissimus  dorsi  muscle  to  the  cellular  interval  between  it  and 
the  Iliocostalis  muscle,  and  supply  those  muscles,  as  well  as  their  continuations 
upward  to  the  head,  and  also  the  Leva  tores  costarum  muscles;  the  five  or  six 
lower  nerves  also  give  off  cutaneous  filaments,  which  pierce  the  Serratus  posticus 
inferior  and  Latissimus  dorsi  muscles  in  a  line  with  the  angles  of  the  ribs,  and 
then  ramify  in  the  integument. 

The  cutaneous  branches  of  the  posterior  primary  divisions  of  the  thoracic  nerves 
are  twelve  in  number.  From  each  ramus  medialis  of  the  upper  six  nerves  comes 
a  ramus  cutaneus  medialis,  and  from  each  ramus  lateralis  of  the  lower  six  nerves 
comes  a  ramus  cutaneus  lateralis.  The  six  upper  cutaneous  nerves  are  derived 
from  the  internal  branches  of  the  posterior  divisions  of  the  thoracic  nerves.  They 
pierce  the  origins  of  the  Rhomboidei  and  Trapezius  muscles,  and  become  cutaneous 
by  the  side  of  the  spinous  processes,  and  then  ramify  in  the  integument.  They 
are  frequently  furnished  with  gangliform  enlargements.  The  six  lower  cuta- 
neous nerves  are  derived  from  the  external  branches  of  the  posterior  divisions 
of  the  thoracic  nerves.  They  pierce  the  Serratus  posticus  inferior  and  Latissi- 
mus dorsi  muscles  in  a  line  with  the  angles  of  the  ribs,  and  then  ramify  in  the 
integument. 

The  Posterior  Divisions  of  the  Lumbar  Nerves  (rami  posteriores). — The 
posterior  divisions  of  the  lumbar  nerves  diminish  in  size  from  above  downward; 
they  pass  postero-laterad  between  the  transverse  processes,  and  divide  into  internal 
or  medial  and  external  or  lateral  branches. 

The  internal  branches  (rami  mediales),  the  smaller,  pass  inward  close  to  the 
articular  processes  of  the  vertebrae,  and  supply  the  Multifidus  spinae  and  Inter- 
spinales  muscles. 

The  external  branches  (rami  laterales)  supply  the  Erector  spinae  and  Inter- 
transverse muscles.     The  three  upper  branches  give  off  cutaneous  nerves  which 


THE  SPINAL  NUBVES  '  1019 

pierce  the  aponeurosis  of  the  Latissimiis  dorsi  muscle  and  descend  over  the  back 
part  of  the  crest  of  the  ilium,  to  be  distributed  to  the  integument  of  the  gluteal 
region,  some  of  the  filaments^assing  as  far  as  the  trochanter  major  (Fig.  778). 

The  posterior  division  of  the  fifth  lumbar  nerve  usually  sends  a  branch  which 
forms  a  loop  with  the  posterior  division  of  the  first  sacral  nerve. 

The  Posterior  Divisions  of  the  Sacral  Nerves  (rami  posteriores)  (Fig.  779). — ■ 
The  posterior  divisions  of  the  sacral  nerves  are  small,  diminish  in  size  from  above 
downward,  and  emerge,  except  the  last,  from  the  sacral  canal  by  the  posterior 
sacral  foramina.  The  upper  three  are  covered  at  their  exit  from  the  sacral  canal 
by  the  IMultifidus  spinae  muscle,  and  divide  into  internal  or  medial  and  external 
or  lateral  branches. 

The  internal  branches  (rarni  mediales)  are  small,  and  supply  the  Multifidus 
spinae  muscle. 

The  external  branches  (rami  laterales)  join  with  one  another,  and  with  the 
last  lumbar  and  fourth  sacral  nerves,  in  the  form  of  loops  on  the  posterior  surface 
of  the  sacrum,  constituting  the  posterior  sacral  plexus.  From  these  loops  branches 
pass  to  the  outer  surface  of  the  great  sacrosciatic  ligament,  where  they  form 
a  second  series  of  loops  beneath  the  Gluteus  maximus  muscle.  Cutaneous 
branches  from  this  second  series  of  loops,  usually  two  or  three  in  number,  pierce 
the  •Gluteus  maximus  muscle  along  the  line  drawn  from  the  posterior  superior 
spine  of  the'  ilium  to  the  tip  of  the  coccyx.  They  supply  the  integument  over  the 
posterior  part  of  the  gluteal  region.  , 

The  posterior  divisions  of  the  lower  two  sacral  nerves  are  small  and  lie  below 
the  Multifidus  spinae  muscle.  They  do  not  divide  into  internal  and  external 
branches,  but  join  with  each  other,  and  \\\i\\  the  posterior  division  of  the  coccygeal 
nerve  to  form  the  posterior  sacrococcygeal  nerve,  which  passes  through  the  sacro- 
sciatic ligament,  and  forms  loops  on  the  back  of  the  sacrum,  filaments  from  which 
supply  the  integument  over  the  coccyx. 

The  Posterior  Division  of  the  Coccygeal  Nerve. — ^The  coccygeal  nerve  divides 
into  its  anterior  and  posterior  divisions  in  the  vertebral  canal.  The  posterior 
division  is  the  smaller,  and  it  does  not  divide  into  internal  and  external  branches, 
but  receives,  as  already  stated,  a  communicating  branch  from  the  last  sacral, 
and  is  lost  in  the  integument  over  the  dorsum  of  the  coccyx. 

Anterior  or  Ventral  Primary  Divisions  of  the  Spinal  Nerves. — ^l"'he  anterior 
primary  divisions  of  the  spinal  nerves  (rami  anteriores)  supply  the  antero-lateral 
parts  of  the  trunks  and  the  limbs;  they  are,  for  the  most  part,  larger  than  the 
posterior  divisions.  In  the  thoracic  region  they  run  independently  of  one  another, 
but  in  the  cervical,  lumbar,  and  sacral  regions  they  unite  near  their  origins  to 
form  plexuses. 

The  Anterior  or  Ventral  Divisions  of  the  Cervical  Nerves  (rami  anteriores). — 
The  anterior  primary  divisions  of  the  cervical  nerves,  with  the  exception  of  the  first, 
pass  laterad  between  the  anterior  and  posterior  Intertransverse  muscles,  lying 
on  the  grooved  upper  surfaces  of  the  transverse  processes,  and  emerge  between 
the  muscles  attached  to  the  anterior  and  posterior  tubercles  of  these  processes. 
The  anterior  primary  division  of  the  first  or  suboccipital  nerve  issues  from  the 
vertebral  canal  above  the  posterior  arch  of  the  atlas  and  runs  forward  around  the 
lateral  aspect  of  its  superior  articular  process,  internal  to  the  vertebral  artery. 
In  most  cases  it  descends  internal  to  and  in  front  of  the  Rectus  lateralis,  but  in 
some  cases  it  pierces  the  muscle. 

The  anterior  primary  divisions  of  the  upper  four  cervical  nerves  unite  to  form 
the  cervical  plexus,  and  each  receives  a  gray  ramus  communicans  from  the  superior 
cervical  ganglion  of  the  sympathetic  cord.  Those  of  the  lower  four  cervical, 
together  with  the  greater  part  of  the  first  thoracic,  form  the  brachial  plexus.     They 


1020 


THE  NEBVJE  SYSTEM 


each  receive  a  gray  ramus  communicans,  those  for  the  fifth  and  sixth  being  derived 
from  the  middle,  and  those  for  the  seventh  and  eighth  from  the  inferior,  cervical 
ganglion  of  the  sympathetic. 


THE  CERVICAL  PLEXUS  (PLEXUS  CERVICALIS)  (Figs.  760,  761). 

The  cervical  plexus  is  formed  by  the  anterior  divisions  of  the  four  upper  cervical 
nerves.  It  is  situated  opposite  the  four  upper  cervical  vertebrae,  resting  upon  the 
Levator  anguli  scapulae  and  Scalenus  medius  muscles,  and  covered  in  by  the 
Sternomastoid. 

Its  branches  may  be  divided  into  two  groups,  superficial  and  deep,  which  may 
be  thus  arranged: 

2,C. 
2, 3,  C. 

2. 3,  C. 
3,4,C. 

3. 4,  C. 
3, 4,  C. 
1,2,C. 
1,2,C. 

,  2,  3, 4,  C. 

1,C. 

1,2,C. 

2,  3,  C. 
3, 4,  5,  C. 
2,  3,  4,  C. 

2,C. 

3,  4,  C. 
3, 4,  C. 
3, 4,  C. 


[Ascending    /Small  occipital 

"     (^  (jreat  auricular 

Superficial  \  Transverse     Superficial  cervical 

[  Sternal     . 
[  Descending  or  Supraclavicular    \  Clavicular 
[  Acromial 
f  with  hypoglossal 
r  Communicating     I  with  vagus    . 

i  with  sympathetic 
f  Rectus  lateralis  . 


Deep  . 


Internal 


L  Muscular 


'■  External 


I  Anterior  Recti    .... 
j  Communicantes  hypoglossi 

1^  Phrenic 

Communicating  with  spinal  accessory     . 

r  Sternomastoid 

Muscular      Trapezius           .     .           .     .      . 
JLevator  anguli  scapulae 
I  Scalenus  medius 


The  Superficial  Branches  of  the  Cervical  Plexus. — ^The  Small  Occipital  Nerve 
{n.  occipitalis  minor)  (Fig.  760)  arises  from  the  second  cervical  nerve,  sometimes 
also  from  the  third ;  it  curves  around  the  posterior  border  of  the  Sternomastoid, 
and  ascends,  running  parallel  to  the  posterior  border  of  the  muscle,  to  the  back 
part  of  the  side  of  the  head.  Near  the  cranium  it  perforates  the  deep  fascia, 
and  is  continued  upward  along  the  side  of  the  head  behind  the  ear,  supplying 
the  integument,  and  communicating  with  the  great  occipital,  great  auricular, 
and  with  the  posterior  auricular  branch  of  the  facial. 

This  nerve  gives  off  an  auricular  branch,  which  supplies  the  integument  of  the 
upper  and  back  part  of  the  auricle,  communicating  with  the  mastoid  branch 
of  the  great  auricular.  The  auricular  branch  is  occasionally  derived  from  the 
great  occipital  nerve.     The  small  occipital  varies  in  size;  it  is  occasionally  double. 

The  Great  Auricular  Nerve  (?i.  auricularis  magnus)  (Fig.  760)  is  the  largest  of 
the  ascending  branches.  It  arises  from  the  second  and  third  cervical  nerves, 
winds  around  the  posterior  border  of  the  Sternomastoid,  and,  after  perforating 
the  deep  fascia,  ascends  upon  that  muscle  beneath  the  Platysma  to  the  parotid 
gland,  where  it  divides  into  facial,  auricular,  and  mastoid  branches. 

The  facial  branches  are  distributed  to  the  integument  of  the  face  over  the  parotid 
gland;  others  penetrate  the  substance  of  the  gland  and  communicate  with  the 
facial  nerve. 

The  auricular  branches  ascend  to  supply  the  integument  of  the  back  of  the  pinna, 
except  at  its  upper  part,  communicating  with  the  auricular  branches  of  the  facial 
and  vagus  nerves.  A  filament  pierces  the  pinna  to  reach  its  outer  surface,  where 
it  is  distributed  to  the  lobule  and  lower  part  of  the  concha. 

The  mastoid  branch  communicates  with  the  small  occipital  and  the  posterior 


THE  CERVICAL  PLEXUS 


1021 


auricular  branch  of  the  facial,  and  is  distributed  to  the  integument  l)ehind  the 
ear. 

The  Superficial  or  Transverse  Cervical  Nerve  (n.  cutaneus  colli)  (Fig.  760)  arises 
from  the  second  and  third  cer\ical  nerves,  turns  around  the  posterior  border  of 
the  Sternomastoid  about  its  middle,  and,  passing  obliquely  forward  beneath  the 
external  jugular  vein  to  the  ventral  border  of  the  muscle,  perforates  the  deep 
cervical  fascia,  and  divides  beneath  the  Platysma  into  two  branches,  which  are 
distributed  to  the  antero-lateral  parts  of  the  neck. 


BRANCHEa. 
OF  FAC1A6,  " 
NERVE 


\  VI  f/JA,  'fk  "  ''''''^'^^° 


Fig.  760.— The  cutaneous  branches  of  the  right  cervical  plexus  viewed  from  the  right.     The  Platysma 
h.a.s  been  partly  removed.      (Spalteholz.) 

The  ascending'  branch  (ramus  superior)  gives  a  filament  which  accompanies  the 
external  jugular  vein;  it  then  passes  upward  to  the  submaxillary  region,  and  divides 
into  branches,  some  of  which  form  a  plexus  with  the  cervical  branches  of  the 
facial  nerve  beneath  the  Platysma;  others  pierce  that  muscle  and  are  distributed 
to  the  integument  of  the  upper  half  of  the  neck,  at  its  fore  part,  as  high  as  the  chin. 

The  descending  branches  (rami  inferiores),  usually  represented  by  two  or  more 
filaments,  pierce  the  Platysma,  and  are  distributed  to  the  integument  of  the  side 
and  front  of  the  neck,  as  low  as  the  sternum. 


1022 


THE  NERVE  SYSTEM 


The  Descending  or  Supraclavicular  Branches  {nn.  supraclavicular es)  (Fig.  760) 
arise  from  the  third  and  fourth  cervical  nerves;  emerging  beneath  the  posterior 
border  of  the  Sternomastoid,  they  descend  in  the  posterior  triangle  of  the  neck 
beneath  the  Platysma  and  deep  cervical  fascia.  Near  the  clavicle  they  perforate 
the  fascia  and  Platysma  to  become  cutaneous,  and  are  arranged,  according  to 
their  position,  into  three  groups. 


Fig.  761.— Plan  of  the 


'al  plexus.  _   (Gerrish.) 


The  Inner  or  Sternal  Branches  {nn.  supraclaviculare.s  anteriores)  cross  obliquely 
over  the  external  jugular  vein  and  the  clavicular  and  sternal  attachments  of  the 
Sternomastoid  muscle,  and  supply  the  integument  as  far  as  the  median  line. 
They  furnish  one  or  two  filaments  to  the  sternoclavicular  joint. 

The  Middle  or  Clavicular  Branches  {nn.  supraclaviculares  medii)  cross  the  clavicle, 
and  supply  the  integument  over  the  Pectoral  and  Deltoid  muscles,  communicating 
with  the  cutaneous  branches  of  the  upper  intercostal  nerves. 

The   External   or   Acromial   Branches    {nn.    supraclaviculares   posferiores)   pass 


THE  CERVICAL  PLEXUS 


1023 


obliquely  across  the  outer  surface  of  the  Trapezius  and  the  acromion,  and  supply 
the  integument  of  the  upper  and  back  part  of  the  shoulder. 

The  Deep  Branches  of  the  Cervical  Plexus  (Fig.  761).  Internal  Series.— The 
Communicating  Branches  consist  of  several  filaments  which  pass  from  the  loop 
between  the  first  and  second  cervical  nerves  to  the  vagus,  hypoglossal,  and  sympa- 
thetic.    The  branch  accompanying  the  hypoglossal  in  its  sheath  ultimately  leaves 


PP«'-HI-l       / 


V 


t         ,        \x     INFERIOR 
Wt       \         CERVICAL 

V       /gsnglion 

•  ""■vV       INFERIOR 
Vv.iSX'LAByNGEAL 


UNICATING 
ROM 
PLEXUS 

C  CARDIAC 


*,     /^  <S  ^AV  im  >J    \laryngeal 


Fig.  762.— The  phn 


rith  the  vagus  nerve.     (Toldt.) 


that  nerve  as  a  series  of  branches — viz.,  the  descendens  cervicalis,  the  nerve  to 
the  Thyrohyoid,  and  the  nerve  to  the  Geniohyoid  (see  p.  1011).  Branches  (gray 
rami  communicantes)  from  all  four  cervical  nerves  pass  to  the  superior  cervical 
ganglion  of  the  sympathetic,  while  another  communicating  branch  passes  from 
the  fourth  to  the  fifth  cervical. 

Muscular  branches  supply  the  Anterior  recti  and  Rectus  lateralis  muscles.  Those 
to  the  Anterior  recti  proceed  from  the  first  cervical  nerve,  and  from  the  loop  formed 
between  it  and  the  second.  The  Rectus  lateralis  is  supplied  by  the  second,  third, 
and  fourth  cervical  nerves. 

The  Communicantes  Cervicales  (Hypoglossi)   (Fig.  761)  consist  usually  of  two 


1024 


THE  NERVE  SYSTEM 


filaments,  one  being  derived  from  the  second  and  the  other  from  the  third  cervical. 
These  filaments  usually  join  to  form  the  descendens  cervicis,  which  passes  down- 
ward on  the  outer  side  of  the  internal  jugular  vein,  crosses  in  front  of  the  vein  a 
little  below  the  middle  of  the  neck,  and  forms  a  loop  {ansa  hypoglossi;  ansa  cer- 
vicalis)  with  the  descendens  hypoglossi  in  front  of  the  sheath  of  the  carotid  vessels. 
Occasionally,  the  junction  of  these  nerves  takes  place  within  the  sheath. 


DESCENDING 
BRANCH  OF 
HYPOGLOSSAL 


'/W/''^m 


Fig.  763. — The  right  brachial  plexus  with  its  short  branches,  viewed  from  in  front.  The _ Sternomastoid 
and  Trapezius  muscles  have  been  completely,  the  Omohyoid  and  Subclavius  have  been  partially,  removed; 
a  piece  has  been  sawed  out  of  the  clavicle;  the  JPectoralis  muscles  have  been  incised  and  reflected.     (Spalteholz.) 

The  Phrenic  or  the  Internal  Respiratory  Nerve  of  Bell  {n.  phrenicus)  (Figs.  761  and 
762)  arises  chiefly  from  the  fourth  cervical  nerve,  with  a  few  filaments  from  the 
third  and  a  branch  from  the  fifth,  although  this  branch  is  occasionally  derived 
from  the  nerve  to  the  Subclavius.  It  descends  to  the  root  of  the  neck,  running 
obliquely  across  the  front  of  the  Scalenus  anticus,  and  beneath  the  Sternomastoid, 
the  posterior  belly  of  the  Omohyoid  muscles,  and  the  transversalis  colli  and 
suprascapular  vessels.  It  next  passes  over  the  first  part  of  the  subclavian  artery, 
between  it  and  the  subclavian  vein,  and,  as  it  enters  the  thorax,  crosses  the  internal 
mammary  artery  near  its  origin.  Within  the  thorax  it  descends  nearly  vertically 
in  front  of  the  root  of  the  lung  and  by  the  side  of  the  pericardium,  between  it  and 
the  mediastinal  portion  of  the  pleura,  to  the  Diaphragm,  where  it  divides  into 
branches,  some  few  of  which  are  distributed  to  its  thoracic  surface,  but  most  of 
which  separately  pierce  that  muscle  and  are  distributed  to  its  under  surface  (rami 
phren.icoabdominales).  In  the  thorax  it  is  accompanied  by  a  branch  of  the  internal 
mammary  artery,  the  arteria  comes  nervi  phrenici.  The  two  phrenic  nerves  differ 
in  their  length,  and  also  in  their  relations  at  the  upper  part  of  the  thorax. 

The  right  phrenic  nerve  is  situated  more  deeply,  and  is  shorter  and  more  vertical 
in  direction  than  the  left;  it  lies  on  the  outer  side  of  the  right  innominate  vein 
and  superior  vena  cava. 


THE  CERVICAL  PLEXUS 


1025 


The  left  phrenic  nerve  is  rather  longer  than  the  right,  from  the  inclination  of 
the  heart  to  the  left  side,  and  from  the  Diaphragm  being  lower  on  this  than  on 
the  opposite  side.  It  enters  the  thorax  behind  the  left  innominate  vein,  and 
crosses  in  front  of  the  vagus  and  the  arch  of  the  aorta  and  the  root  of  the  hmg. 

Each  nerve  supplies  filaments  to  the  pericardium  and  pleura,  and  near  the 
thorax  is  joined  by  a  filament  from  the  sympathetic,  and,  occasionally,  by  one 
from  the  ansa  cervicalis.  Branches  have  been  described  as  passing  to  the  peri- 
toneum. 


MUSCULOCUTANEOUS 


3 
■t  ^       ,1  LflTrPAL  CUTANEOUS 

I     ~i.  Jl    I  Inr  ■vr  th  of 


5^^^   THIRD  INTERCOSTAL 


Fig.  764. — The  right  brachial  plexus  (infraclavicular  portion)  in  the  axillary  fossa,  viewed  from  below  and 
in  front.  The  Pectoralis  major  and  minor  muscles  have  been  in  large  part  removed;  their  attachments  have 
been  reflected.     (Spalteholz.) 


From  the  right  nerve  one  or  two  filaments  pass  to  join  in  a  small  ganglion  with 
phrenic  branches  of  the  solar  plexus;  and  branches  from  this  ganglion  are  dis- 
tributed to  the  hepatic  plexus,  the  suprarenal  gland,  and  inferior  vena  cava.  From 
the  left  nerve  filaments  pass  to  join  the  phrenic  plexus  of  the  sympathetic,  but 
without  any  ganglionic  enlargement. 

Applied  Anatomy. — Irritation  of  the  phrenic  nerve  causes  hiccough  and  persistent  cough. 
Bilateral  paralysis  of  the  phrenic  causes  death  from  paralysis  of  the  Diaphragm.  This  form  of 
death  is  seen  by  the  surgeon  in  fracture  dislocation  of  the  third  cervical  vertebra.  Division  of 
the  phrenic  on  one  side  is  not  fatal,  and  is  occasionally  practised  by  the  surgeon  in  removing 
a  tumor  of  the  neck.  In  Hearn's  and  Franklin's  cases  of  removal  of  the  vagus  the  phrenic 
was  also  divided.  Unilateral  division  of  the  phrenic  nerve  causes  paralysis  of  the  corresponding 
half  of  the  Diaphragm,  which  is  difficult  of  recognition,  because,  as  Gowers  points  out,  the 
patient  can  still  take  deep  inspirations,  the  thoracic  muscles  not  being  paralyzed. 

The  Deep  Branches  of  the  Cervical  Plexus.  External  Series.  Communi- 
cating Branches, — The  deep  branches  of  the  external  series  of  the  cervical  plexus 

65 


1026 


THE  NERVE  SYSTEM 


communicate  with  the  spinal  accessory  nerve,  in  the  substance  of  the  Sterno- 
mastoid  muscle,  in  the  posterior  triangle,  and  beneath  the  Trapezius. 

Muscular  branches  are  distributed  to  the  Sternomastoid,  Trapezius,  Levator 
anguli  scapulae,  and  Scalenus  medius. 

The  branch  for  the  Sternomastoid  is  derived  frojn  the  second  cervical;  the 
Trapezius  and  Levator  anguli  scapulae  receive  branches  from  the  third  and 
fourth.  The  branch  for  the  Scalenus  medius  is  derived  sometimes  from  the  third, 
sometimes  from  the  fourth,  and  occasionally  from  both  nerves. 


SCULO  SPIRAL 


Fig.  765. — Plan  of  the  brachial  plexus.      (Gerrish.) 

Applied  Anatomy. — The  cervical  plexus  may  be  damaged  by  wounds  or  contusions,  which 
may  or  may  not  be  associated  with  fracture  of  the  clavicle.  Paralysis  ensues,  the  extent  depend- 
ing on  the  degree  of  damage.  After  a  contusion  the  paralysis  is  apt  to  be  temporary  and  to 
be  followed  by  pain  and  muscular  spasm  in  the  arm.  Paralysis  of  the  arm  due  to  plexus  injury 
may  be  partial  or  complete.  In  some  cases  there  is  complete  motor  palsy  and  partial  sensor 
palsy,  the  sensor  impulses  passing  along  undamaged  collaterals.  In  certain  spasmodic  diffi- 
culties the  surgeon  occasionally  stretches  the  cervical  plexus.  It  is  reached  by  an  incision  at  the 
posterior  margin  of  the  Sternomastoid  muscle.  This  incision  begins  t\vo  inches  below  the  level 
of  the  tip  of  the  mastoid  and  is  carried  downward  for  three  inches. 


THE  BRACHIAL  PLEXUS   (PLEXUS  BRACHIALIS)   (Figs.  763,   764). 

The  brachial  plexus  is  formed  by  the  union  of  the  anterior  primary  divisions 
of  the  lower  four  ce^^'^cal  nerves  and  the  greater  part  of  the  first  thoracic  nerve, 
receiving  usually  a  fasciculus  from  the  fourth  cervical  nerve,  and  frequently  one 
from  the  second  thoracic  nerve.  It  extends  from  the  lower  part  of  the  side  of  the 
neck  to  the  axilla.  It  is  very  broad,  and  presents  little  of  a  plexiform  arrangement 
at  its  commencement.  It  is  narrow  opposite  the  clavicle,  becomes  broad  and 
forms  a  more  dense  interlacement  in  the  axilla,  and  divides  opposite  the  coracoid 
process  into  numerous  branches  for  the  supply  of  the  upper  limb.  The  nerves 
which  form  the  plexus  are  all  similar  in  size,  and  their  mode  of  communication  is 
subject  to  considerable  variation,  so  that  no  one  plan  can  be  given  as  applying  to 


THE  BRACHIAL  PLEXUS  1027 

every  case/  The  following  appears,  however,  to  be  the  most  constant  arrangement : 
above  the  clavicle  {'pars  supraclavicularis)  the  fifth  and  sixth  cervical  unite  soon 
after  their  exit  from  the  intervertebral  foramina  to  form  a  common  trunk.  The 
eighth  cervical  and  first  thoracic  also  unite  to  form  one  trunk.     So  that  the  nerves 


Fig.  766. — Cutaneous  nerves  of  right  upper  Fig.  767. — Cutaneous  nerves  of  right  upper 

extremity      Anterior  view  extremity.     Posterior  view. 

forming  the  plexus,  as  they  lie  on  the  Scalenus  medius  at  the  outer  border  of  the 
Scalenus  anticus  muscle,  are  blended  into  three  trunks — an  upper  one,  formed 

'  Kerr,  Bardeen,  and  Elting,  from  a  study  of  175  brachial  plexuses,  recognized  seven  types.  In  58  per  cent, 
the  outer  cord  was  formed  from  the  fourth  to  the  seventh,  the  inner  cord  froni  the  eighth  to  the  ninth  spina] 
nerve,  and  the  posterior  or  dorsal  cord  from  the  fourth  to  the  ninth.  In  30  per  cent,  the  outer  cord  was  formed 
from  the  fifth  to  the  seventh,  the  inner  cord  from  the  eighth  to  the  ninth,  and  the  posterior  cord  frcm  the  fiftl« 
to  the  ninth. 


1028  THE  NEB  VE  SYSTEM 

by  the  junction  of  the  fifth  and  sixth  cervical  nerves;  a  middle  one,  consisting  of 
the  seventh  cervical  nerve;  and  a  lower  one,  formed  by  the  junction  of  the  eighth 
cervical  and  first  thoracic  nerves.  As  they  pass  beneath  the  clavicle,  to  compose 
the  infraclavicular  part  of  the  plexus  (pars  infraclavicular  is),  each  of  these  three 
trunks  divides  into  two  branches,  an  anterior  and  a  posterior.  The  anterior  divi- 
sions of  the  upper  and  middle  trunks  then  unite  to  form  a  common  cord,  which 
is  situated  on  the  outer  side  of  the  middle  part  of  the  axillary  artery,  and  is  called 
the  outer  cord  of  the  brachial  plexus  (fasciculus  lateralis).  The  anterior  division 
of  the  lower  trunk  passes  distally  on  the  inner  side  of  the  axillary  artery  in  the 
middle  of  the  axilla,  and  forms  the  inner  cord  of  the  brachial  plexus  (fasciculus 
medialis).  The  posterior  divisions  of  all  three  trunks  unite  to  form  the  posterior 
cord  of  the  brachial  plexus  (fasciculus  posterior),  which  is  situated  behind  the  second 
portion  of  the  axillary  artery.  From  this  posterior  cord  are  given  off  the  two 
lower  subscapular  nerves,  the  upper  subscapular  nerve  being  given  off  from 
the  posterior  division  of  the  upper  trunk  prior  to  its  junction  with  the  posterior 
division  of  the  lower  and  middle  trunks.  The  posterior  cord  divides  into  the 
circumflex  and  musculospiral  nerves. 

Branches  of  Communication. — ^The  brachial  plexus  communicates  with  the  cer- 
vical plexus  by  a  branch  from  the  fourth  to  the  fifth  cervical  nerve,  and  with  the 
phrenic  nerve  by  a  branch  from  the  fifth  cervical,  which  joins  that  nerve  on  the 
Anterior  scalenus  muscle;  the  fifth  and  sixth  cervical  nerves  are  joined  by  filaments 
to  the  middle  cervical  ganglion  of  the  sympathetic,  the  seventh  and  eighth  cervical 
to  its  inferior  ganglion,  and  the  first  thoracic  nerve  to  its  first  thoracic  ganglion. 
Close  to  their  exit  from  the  intervertebral  foramina  the  nerves  give  ofT  the  filaments 
to  the  ganglia. 

Relations, — In  the  neck,  the  brachial  plexus  lies  in  the  posterior  triangle,  being  covered 
by  the  skin,  Platysma,  and  deep  fascia;  it  is  crossed  by  the  posterior  belly  of  the  Omohyoid 
muscle  and  by  the  transversalis  colli  artery.  When  the  dorsalis  scapulae  artery  arises  from  the 
third  part  of  the  subclavian  it  usually  passes  between  the  roots  of  the  plexus.  The  plexus  lies 
at  first  between  the  Scalenus  anticus  and  medius,  and  then  above  and  to  the  outer  side  of  the 
subclavian  artery;  it  next  passes  behind  the  clavicle  and  Subclavius  muscle,  lying  upon  the  first 
serration  of  the  Serratus  magnus,  and  the  Subscapularis  muscles.  It  is  in  close  relation  with 
the  apex  of  the  lung  (Luschka).  In  the  axilla  it  is  placed  on  the  outer  side  of  the  first  portion  of 
the  axillary  artery;  it  surrounds  the  artery  in  the  second  part  of  its  course,  one  cord  lying  upon 
the  outer  side  of  that  vessel,  one  on  the  inner  side,  and  one  behind  it,  and  at  the  lower  part  of  the 
axillary  space  gives  off  its  terminal  branches  to  the  upper  extremity. 

Branches  of  Distribution. — ^The  branches  of  the  brachial  plexus  are  arranged 
in  two  groups — viz.,  those  given  off  above  the  clavicle,  and  those  below  the  clavicle. 

SuPBACLA^^cuLAH  Branches. 

Communicating     /with  phrenic  „  ^  5' S" 

"      (^  with  sympathetic 5,  6,  7,  8,  C.  1,  T. 

Rhomboids  (posterior  scapular) 5,  C. 

Supraspinatus  )  „                   ,  _  „  ^ 

Infraspinatus    [Suprascapular      ......  5, 6,  C. 

Muscular    .      .     ^Subclavius 5,6,C. 

Serratus  magnus  (posterior  thoracic)    .....  5,  6,  7,  C. 

Longus  colli 5,  6,  7,  8,  C. 

LScaleni 5, 6,7,8.  C. 

The  Communicating  Branch  (Figs.  762  and  765)  with  the  phrenic  is  derived  from 
the  fifth  cervical  nerve  or  from  the  loop  between  the  fifth  and  sixth;  it  joins  the 
phrenic  on  the  Anterior  scalenus  muscle.  The  communications  with  the  sympa- 
thetic have  already  been  referred  to. 

The  Muscular  Branches  (rami  nvusculares)  supply  the  Longus  colli,  Scaleni, 
Rhomboidei,  and  Subclavius  muscles.     Those  for  the  Loneus  colli  and  Scaleni 


THE  BRACHIAL  PLEXUS  1029 

arise  from  the  four  lower  cervical  nerves  at  their  exit  from  the  intervertebral 
.  foramina. 

The  nerve  to  the  Subclavius  {ti.  subclavius)  is  a  small  filament  which  arises 
from  the  fifth  cervical  at  its  point  of  junction  with  the  sixth  nerve;  it  descends 
in  front  of  the  third  part  of  the  subclavian  artery  to  the  Subclavius  muscle,  and  is 
usually  connected  by  a  filament  with  the  phrenic  nerve. 

The  posterior  scapular  nerve  (k.  dorsalis  scapulae)  (Figs.  763  and  765)  arises 
from  the  fifth  cervical,  pierces  the  Scalenus  medius,  and  passes  beneath  the  Levator 
anguli  scapulae,  which  it  occasionally  supplies  to  the  Rhomboid  muscles. 

The  Long  Thoracic  or  the  External  Respiratory  Nerve  of  Bell  or  Posterior  Thoracic 
Nerve  (;;.  fhoracalis  longus)  (Figs.  763  and  770)  supplies  the  Serratus  magnus 
muscle,  and  is  remarkable  for  the  length  of  its  course.  It  usually  arises  by  three 
roots  from  the.  fifth,  sixth,  and  seventh  nerves,  but  the  root  from  the  seventh 
may  be  absent.  The  roots  from  the  fifth  and  sixth  nerves  pierce  the  Scalenus 
medius,  while  that  from  the  seventh  emerges  in  front  of  that  muscle.  The  nerve 
passes  down  behind  the  brachial  plexus  and  the  axillary  vessels,  resting  on  the 
outer  surface  of  the  Serratus  magnus.  It  extends  along  the  side  of  the  thorax 
to  the  lower  border  of  that  muscle,  supplying  filaments  to  each  of  the  muscular 
digitations. 

The  Suprascapular  Nerve  (n..  suprascapularis)  (Figs.  765  and  770)  arises  from  the 
trimk  formed  by  the  fifth  and  sixth  cervical  nerves;  passing  obliquely  outward 
beneath  the  Trapezius  and  the  Omohyoid,  it  enters  the  supraspinous  fossa  below 
the  transverse  or  suprascapular  ligament,  passes  beneath  the  supraspinatus 
muscle,  and  curves  around  the  external  border  of  the  spine  of  the  scapula  to  the 
infraspinous  fossa.  In  the  supraspinous  fossa  it  gives  ofF  two  branches  to  the 
Supraspinatus  muscle,  and  an  articular  filament  to  the  shoulder-joint;  and  in 
the  infraspinous  fossa  it  gives  off  two  branches  to  the  Infraspinatus  muscle, 
besides  some  filaments  to  the  shoulder-joint  and  scapula. 

The  Infraclavicular  Branches  (Figs.  764  and  765)  are  derived  from  the  three 
cords  of  the  brachial  plexus.  The  fasciculi  of  which  they  are  composed  may  be 
traced  through  the  plexuses  to  the  spinal  nerves  from  which  they  originate.  They 
are  as  follows: 

f  Musculocutaneous 5,  6,  C. 

Outer  cord    .         External  anterior  thoracic 5, 6, 7,  C. 

I  Outer  head  of  median 6,  7,  C. 

f  Internal  anterior  thoracic 8,  C.  1,T. 

Internal  cutaneous 8,  C.1,T. 

Inner  cord     .      •!  Lesser  internal  cutaneous .  (8,  C.)1,T. 

j  Ulnar S,C.  1,T. 

I  Inner  head  of  median 8,  C.  1,T. 

r  Upper  subscapular 5,  6,  C. 

Middle        "  5, 6, 7,  C. 

Posterior  cord     -j  Lower  "  '.  5, 6,  C. 

Circumflex 5,  6,  C. 

I  Musculospiral .     .     .    (.5),  6,  7,  8,  C.  (1,  T). 

These  branches  from  below  the  clavicle  may  be  arranged  according  to  the 
parts  they  supply: 

To  the  thorax Anterior  thoracic. 

To  the  shoulder    ......       /  Subscapulars. 

\   Circumflex. 
r  Musculocutaneous. 
Internal  cutaneous. 
To  the  arm,  forearm,  and  hand        .        J    Cesser  internal  cutaneous. 

I   Median. 

Ulnar. 
_^  Musculospiral. 


1030  THE  NEBVE  SYSTEM 

The  Anterior  Thoracic  Nerves  {nn.  thoracales  anteriores)  (Figs.  764  and  765), 
two  in  number,  supply  the  Pectoral  muscles. 

The  external  anterior  thoracic  nerve  (Figs.  763  and  770),  the  larger  of  the  two, 
arises  from  the  outer  cord  of  the  brachial  plexus,  through  which  its  fibres  may  be 
traced  to  the  fifth,  sixth,  and  seventh  cervical  nerves.  It  passes  inward,  across 
the  axillary  artery  and  vein,  pierces  the  costocoracoid  membrane,  and  is  dis- 
tributed to  the  under  surface  of  the  Pectoralis  major  muscle.  It  sends  down 
a  communicating  filament  to  join  the  internal  anterior  thoracic  nerve,  and  this 
communicating  filament  forms  a  loop  around  the  inner  side  of  the  axillary  artery. 

The  internal  anterior  thoracic  nerve  arises  from  the  inner  cord  and  through  it 
from  the  eighth  cervical  and  first  thoracic  nerves.  It  passes  behind  the  first  part 
of  the  axillary  artery,  then  curves  forward  between  the  axillary  artery  and  vein, 
and  joins  with  the  filament  from  the  external  nerve.  It  then  passes  to  the  under 
surface  of  the  Pectoralis  minor  muscle,  where  it  divides  into  a  number  of  branches, 
which  supply  the  muscle  on  its  under  surface.  Some  two  or  three  branches 
pass  through  the  muscle  and  reach  the  Pectoralis  major. 

The  Subscapular  Nerves  Qui.  subscapulares)  (Figs.  764  and  765),  three  in  number, 
arise  from  the  posterior  cord  of  the  plexus  and  supply  the  Subscapularis,  Teres 
major,  and  Latissimus  dorsi  muscles,  and  give  filaments  to  the  shoulder-joint. 
The  fasciculi  of  which  they  are  composed  may  be  traced  to  the  fifth,  sixth,  seventh, 
and  eighth  cervical  nerves. 

The  upper  or  short  subscapular  nerve,  the  smallest,  arises  from  the  posterior  divi- 
sion of  the  upper  trunk  of  origin  of  the  brachial  plexus,  and  enters  the  upper  part 
of  the  Subscapularis  muscle;  this  nerve  is  frequently  represented  by  two  branches. 

The  lower  subscapular  nerve  arises  from  the  posterior  cord  of  the  brachial  plexus, 
enters  the  axillary  border  of  the  Subscapularis,  and  terminates  in  the  Teres  major. 
The  latter  muscle  is  sometimes  supplied  by  a  separate  branch. 

The  middle  or  long  subscapular  nerve  (n.  thoracodorsalis)  (Fig.  764),  the  largest 
of  the  three,  arises  from  the  posterior  cord  of  the  brachial  plexus  and  follows 
the  course  of  the  subscapular  artery,  along  the  posterior  wall  of  the  axilla  to  the 
Latissimus  dorsi  muscle,  through  which  it  may  be  traced  as  far  as  its  lower  border. 
The  Circumflex  Nerve  (n.  axillaris)  (Figs.  765  and  771)  supplies  some  of  the 
muscles,  the  shoulder-joint,  and  the  integument  of  the  shoulder  (Figs.  767  and 
768).  It  arises  from  the  posterior  cord  of  the  brachial  plexus,  in  common  with 
the  musculospiral  nerve,  and  its  fibres  may  be  traced  through  the  posterior  cord 
to  the  fifth  and  sixth  cervical  nerves.  It  is  at  first  placed  behind  the  axillary 
artery,  between  it  and  the  Subscapularis  muscle,  and  passes  downward  and  out- 
ward to  the  lower  border  of  that  muscle.  It  then  winds  posteriorly  in  company 
with  the  posterior  circumflex  artery,  through  a  quadrilateral  space  bounded  above 
by  the  Teres  minor  muscle,  below  by  the  Teres  major  muscle,  internally  by  the 
long  head  of  the  Triceps  muscle,  and  externally  by  the  neck  of  the  humerus. 
The  nerve  then  divides  into  two  branches. 

The  upper  branch  (Fig.  771)  winds  posteriorly  around  the  surgical  neck  of  the 
humerus,  beneath  the  Deltoid,  with  the  posterior  circumflex  vessels,  as  far  as  the  an- 
terior border  of  that  muscle,  supplying  it,  and  giving  off  cutaneous  branches,  which 
pierce  the  muscle  and  ramify  in  the  integument  covering  its  lower  part  (Fig.  768), 
The  lower  branch  (Fig.  771).  at  its  origin,  distributes  filaments  to  the  Teres 
minor  and  back  part  of  the  Deltoid  muscles.  Upon  the  filaments  to  the  former 
muscle  an  oval  enlargement  usually  exists.  The  nerve  then  pierces  the  deep 
fascia,  and  supplies  the  integument  over  the  lower  two-thirds  of  the  posterior 
surface  of  the  Deltoid  (n.  cidaneus  brachii  lateralis),  as  well  as  that  covering 
the  long  head  of  the  Triceps  (Fig.  772). 

The  circumflex  nerve,  before  its  division,  gives  off  an  articular  filament,  which 
enters  the  shoulder- joint  below  the  Subscapularis  muscle. 


THE  BRACHIAL  PLEXUS 


1031 


The  Musculocutaneous  (n.  nuisculocutaneus)  (Figs.  765  and  770)  arises  from 
the  outer  cord  of  the  brachial  plexus,  opposite  the  lower  border  of  the  Pectoralis 
minor  muscle,  receiving  fila- 
ments from  the  fifth,  sixth, 
and  seventh  cervical  nerves. 
It  perforates  the  Coraco- 
brachialis  muscle  (Fig.  770), 
passes  obliquely  betvi^een  the 
Biceps  and  Brachialis  anticus 
muscles  to  the  outer  side  of 
the  arm,  and,  a  little  above 
the  elbow,  winds  around  the 
outer  border  of  the  tendon  of 
the  Biceps,  and,  perforating 
the  deep  fascia,  becomes  cu- 
taneous (Fig.  766).  In  its 
course  through  the  arm  this 
nerve  supplies  the  Coraco- 
brachialis,  Biceps,  and  the 
greater  part  of  the  Brachialis 
anticus  muscles.  The  branch 
to  the  Coracobrachialis  is 
given  off  from  the  nerve 
close  to  its  origin,  and  in 
some  instances  as  a  separate 
filament  from  the  outer  cord 
of  the  plexus.  The  branches 
to  the  Biceps  and  Brachialis 
anticus  are  given  off  after  the 
nerve  has  pierced  the  Coraco- 
brachialis. The  nerve  also, 
sends  a  small  branch  to  the 
humerus,  which  enters  the 
nutrient  foramen  with  the 
accompanying  artery,  and  a 
filament  from  the  branch 
supplying  the  Brachialis  anti- 
cus goes  to  the  elbow-joint. 
The  musculocutaneous  fur- 
nishes the  chief  nerve  supply 
to  this  joint. 

The  cutaneous  portion  of 
the  musculocutaneous  nerve 
(?!.  cutaneus  antebrachii  lat- 
eralis) passes  behind  the 
median  cephalic  vein,  and 
divides,  opposite  the  elbow- 
joint,  into  an  anterior  and  a 
posterior  branch. 

The  anterior  branch  de- 
scends along  the  radial  border 
of  the  forearm  to  the  wrist,  and  supplies  the  integument  over  the  outer  half  of 
its  anterior  surface.  At  tlie  wrist-joint  it  is  placed  in  front  of  the  radial  artery,  and 
some  filaments,  piercing  the  deep  fascia,  accompany  that  vessel  to  the  dorsum  of 


Fig.  708  — Cutaneous 
(W     Keillcr    I 


1032 


THE  NERVE  SYSTEM 


the  wrist,  supplying  tlie  carpus.     The  nerve  then  passes  downward  to  the  ball  of 
the  thumb,  where  it  terminates  in  cutaneous  filaments.     It  communicates  with  a 

branch  from  the  radial  nerve 
and  with  the  palmar  cuta- 
neous branch  of  the  median. 

The  posterior  branch  passes 
downward  along  the  back 
part  of  the  radial  side  of  the 
forearm  to  the  wrist.  It  sup- 
plies the  integument  of  the 
lower  third  of  the  forearm, 
communicating  with  the 
radial  nerve  and  the  external 
cutaneous  branch  of  the  mus- 
culospiral.  The  cutaneous 
areas  supplied  by  the  mus- 
culocutaneous nerve  are  in- 
dicated in  Figs.  768  and  769. 

Variations. — The  musculocu- 
taneous nerve  presents  frequent 
irregularities.  It  may  adhere  for 
some  distance  to  the  median  and 
then  pass  outward,  beneath  the 
Biceps,  instead  of  through  the 
Coracobrachialis.  Frequently 
some  of  the  fibres  of  the  median 
run  for  some  distance  in  the  mus- 
culocutaneous and  then  leave  it  to 
join  their  proper  trunk.  Less 
frequently  the  reverse  is  the  case, 
and  the  median  sends  a  branch  to 
join  the  musculocutaneous.  In- 
stead of  piercing  the  Coracobra- 
chialis muscle  the  nerve  may  pass 
under  it  or  through  the  Biceps. 
Occasionally  it  gives  a  filament  to 
the  Pronator  teres  muscle,  and  it 
has  been  seen  to  supply  the  back 
of  the  thumb  when  the  radial 
nerve  was  absent. 

The  Internal  Cutaneous 
Nerve  {n.  cutaneus  antebrachii. 
medialis)  (Figs.  765  and  770). 
or  medial  cutaneous  nerve  of 
the  forearm,  is  one  of  the 
smallest  branches  of  the  bra- 
chial plexus.  It  arises  from 
the  inner  cord  in  common 
with  the  ulnar  nerve  and 
internal  head  of  the  median 
nerve,  and,  at  its  commence- 
ment, is  placed  on  the  inner 
side  of  the  axillary  artery, 
and  afterward  of  the  brachial  artery.  It  derives  its  fibres  from  the  eighth  cervical 
and  first  thoracic  nerves.  This  nerve  gives  off,  near  the  axilla,  a  cutaneous 
filament,  which  pierces  the  fascia  and  supplies  the  integument  covering  the  Biceps 


769. —Cutaneous  nerves  of  the  upper  limb,  posterior  aspect. 
CW.  Keiller,  in  Gerrish's  Text-book  of  Anatomy.) 


THE  BRACHIAL  FLEXU8 


1033 


muscle  nearly  as  far  as   the   elbow.     This  filament  lies  a  little  external  to  the 
common  trunk,  from  which  it  arises.     It  passes  down  the  inner  side  of  the  arm, 


Eit")  nal  ante)  lor  thoracic. 

lull  1  nal  anterior  thoracic, 
MvKculocutaneoas, 


Mu'iculospiral. 

Paste)  lor 

mte)  osseous. 


Old  terms. 


t.)tte)ior 
i))te)Oi,seou3. 


New  terms 


Intercostohumeral   =  Intercostobrachial. 

Posterior  thoracic     =  Long  thoracic. 

Kerve  of  Wrisberg  =  Medial  cutaneous  nerve  of  upper  arm, 

(N.  cutaneus  brachii  medialis.) 
Internal  cutaneous  =  lledial  nerve  of  forearm. 

(N.  cutaneus  antebrachii  mediahs.) 


Fig.  770. — Nerves  of  the  left  upper  extremity. 


1034  THE  NERVE  SYSTEM 

pierces  the  deep  fascia  with  the  basih'c  vein,  about  the  middle  of  the  limb,  and, 
becoming  cutaneous,  divides  into  two  branches,  anterior  and  posterior. 

The  anterior  branch,  the  larger  of  the  two,  passes  usually  in  front  of,  but  occa- 
sionally behind,  the  median  basilic  vein.  It  then  descends  on  the  anterior  surface 
of  the  ulnar  side  of  the  forearm,  distributing  filaments  to  the  integument  as  far 
as  the  wrist,  and  communicating  with  a  cutaneous  branch  of  the  ulnar  nerve 
(Fig.  766). 

The  posterior  branch  passes  obliquely  downward  on  the  inner  side  of  the  basilic 
vein,  passes  in  front  of,  or  over,  the  internal  condyle  of  the  humerus  to  the  back 
of  the  forearm,  and  descends  on  the  posterior  surface  of  its  ulnar  side  as  far  as 
the  wrist,  distributing  filaments  to  the  integument  (Fig.  767).  It  communicates, 
above  the  elbow,  with  the  lesser  internal  cutaneous  nerve,  the  lower  external 
cutaneous  branch  of  the  musculospiral,  and  above  the  wrist  with  the  posterior 
cutaneous  branch  of  the  ulnar  nerve.  The  cutaneous  areas  supplied  by  the 
internal  cutaneous  nerve  are  indicated  in  Figs.  768  and  769). 

The  Lesser  Internal  Cutaneous  Nerve,  or  the  Nerve  of  Wrisberg  (?;,.  cutaneus  brachii 
medialis)  (Figs.  765  and  770),  is  distributed  to  the  integument  on  the  inner  side 
of  the  arm.  It  is  the  smallest  of  the  branches  of  the  brachial  plexus,  and,  arising 
from  the  inner  cord,  receives  its  fibres  from  the  first  thoracic  "herve.  It  passes 
through  the  axillary  space,  at  first  lying  behind,  and  then  on  the  inner  side  of,  the 
axillary  vein,  and  communicates  with  the  intercostohumeral  nerve.  It  descends 
along  the  inner  side  of  the  brachial  artery  to  the  middle  of  the  arm,  where  it 
pierces  the  deep  fascia,  and  is  distributed  to  the  integument  of  the  back  of  the 
lower  third  of  the  arm,  extending  as  far  as  the  elbow  (Figs.  767  and  768),  where 
some  filaments  are  lost  in  the  integument  in  front  of  the  inner  condyle,  and 
others  over  the  olecranon.  It  communicates  with  the  posterior  branch  of  the 
internal  cutaneous  nerve. 

In  some  cases  the  nerve  of  Wrisberg  and  the  intercostohumeral  nerve  are  con- 
nected by  two  or  three  filaments  which  form  a  plexus  at  the  back  part  of  the 
axilla.  In  other  cases  the  intercostohumeral  is  of  large  size,  and  takes  the  place 
of  the  nerve  of  Wrisberg,  receiving  merely  a  filament  of  communication  from  the 
brachial  plexus,  which  filament  represents  the  latter  nerve.  In  other  cases  this 
filament  is  wanting,  the  place  of  the  nerve  of  Wrisberg  being  supplied  entirely  by 
the  intercostohumeral. 

The  Median  Nerve  (n.  medianus)  (Figs.  764  and  770)  extends  along  the  middle 
of  the  arm  and  forearm  to  the  hand,  lying  between  the  ulnar  and  musculospiral 
nerves,  and  the  ulnar  and  the  radial  nerves.  It  arises  by  two  roots,  one  from  the 
outer  and  one  from  the  inner  cord  of  the  brachial  plexus ;  these  embrace  the  lower 
part  of  the  axillary  artery,  uniting  either  in  front  or  on  the  outer  side  of  that  vessel. 
The  median  nerve  receives  filaments  from  the  sixth,  seventh,  and  eighth  cervical 
and  the  first  thoracic  nerves,  and  sometimes  from  the  fifth  cervical  as  well.  -  As  it 
descends  through  th*  arm,  it  lies  at  first  on  the  outer  side  of  the  brachial  artery, 
crosses  that  vessel  in  the  middle  of  its  course,  usually  in  front,  but  o(jcasionaliy 
behind  it,  and  lies  on  its  inner  side  to  the  bend  of  the  elbow,  where  it  is  situated 
beneath  the  bicipital  fascia,  and  is  separated  from  the  elbow-joint  by  the  Brachialis 
anticus  muscle.  In  the  forearm  it  passes  between  the  two  heads  of  the  Pronator 
teres  muscle  and  crosses  the  ulnar  artery,  but  is  separated  from  that  vessel  by  the 
deep  head  of  the  Pronator  teres.  It  descends  beneath  the  Flexor  sublimis  muscle, 
lying  on  the  Flexor  profundus  muscle,  to  within  two  inches  (5  cm.)  above  the 
annular  ligament,  where  it  becomes  more  superficial,  lying  between  the  tendons 
of  the  Flexor  sublimis  and  Flexor  carpi  radialis  muscles,  beneath,  and  rather  to 
the  radial  side  or  under  the  tendon  of  the  Palmaris  longus,  covered  by  the  integu- 
ment and  fascia.  It  tlien  passes  through  the  carpal  canal  beneath  the  annular 
ligament  into  the  palm  of  the  hand.     In  its  course  through  the  forearm  iz  is 


•THE  BRACHIAL  PLEXUS  1035 

accompanied  by  the  arteria  comes  nervi  mediani,  a  branch  of  the  anterior  interos- 
seous artery. 

Branches. — ^With  the  exception  of  the  nerve  to  the  .Pronator  teres  muscle,  which 
sometimes  arises  above  the  elbow-joint,  and  filaments  to  tlie  elbow-joint,  the 
median  nerve  gives  off  no  branches  in  the  arm.  In  the  forearm  its  branches  are 
the  muscular,  anterior  interosseous,  and  palmar  cutaneous. 

The  muscular  branches  (rami  musculares)  are  derived  from  the  nerve  near  the 
elbow  and  supply  all  the  superficial  muscles  on  the  front  of  the  forearm  except 
the  Flexor  carpi  ulnaris. 

The  anterior  or  volar  interosseous  (n.  interosseiis  [antebrachii]  volaris)  (Fig.  770) 
supplies  the  deep  muscles  on  the  front  of  the  forearm,  except  the  inner  half  of  the 
Flexor  profundus  digitorum.  It  accompanies  the  anterior  interosseous  artery 
along  the  interosseous  membrane,  in  the  interval  between  the  Flexor  longus 
pollicis  and  Flexor  profundus  digitorum  muscles,  both  of  whicli  it  supplies,  and 
terminates  below  in  tlie  Pronator  quadratus  muscle,  sending  filaments  to  the 
inferior  radioulnar  articulation  and  the  wrist-joint. 

The  palmar  cutaneous  branch  (ramus  cutaneus  palmaris  n.  mediani)  arises  from 
the  median  nerve  at  the  lower  part  of  the  forearm.  It  pierces  the  fascia  above 
the  annular  ligament,  and,  descending  over  that  ligament,  divides  into  two  branches, 
of  which  the  outer  branch  supplies  the  skin  over  the  ball  of  the  thumb,  and  com- 
municates with  the  anterior  cutaneous  branch  of  the  musculocutaneous  nerve; 
and  the  inner  branch  supplies  the  integument  of  the  palm  of  the  hand,  communi- 
cating with  the  cutaneous  branch  of  the  ulnar. 

In  the  palm  of  the  hand  the  median  nerve  is  covered  by  the  integument  and 
palmar  fascia  and  is  crossed  by  the  superficial  palmar  arch.  It  rests  upon  the 
tendons  of  the  flexor  muscles.  In  tliis  situation  it  becomes  enlarged,  somewhat 
flattened,  of  a  reddish  color,  and  divides  into  two  branches.  Of  these,  the  external 
branch  supplies  a  muscular  branch  to  some  of  the  muscles  of  the  thumb  and 
digital  branches  to  the  thumb  and  radial  side  of  the  index  finger;  the  internal 
branch  supplies  digital  branches  to  the  contiguous  sides  of  the  index  and  middle 
and  of  the  middle  and  ring  fingers.  Tlie  digital  branches,  before  they  subdivide, 
are  called  common  palmar  digital  branches  of  the  median  nerve  (nn.  digitales  volares 
communes). 

The  branch  to  the  muscles  of  the  thumb  (ramus  mucularis)  is  a  short  nerve  whicli 
divides  to  supply  the  Abductor,  Opponens,  and  the  superficial  head  of  the  Flexor 
brevis  pollicis  muscles,  the  remaining  muscles  of  this  group  being  supplied  by 
the  ulnar  nerve. 

The  digital  branchss  (hh.  digitales  volares  proprii)  are  five  in  number.  The 
first  and  second  pass  along  the  borders  of  the  thumb,  the  external  branch  communi- 
cating with  branches  of  the  radial  nerve.  The  third  passes  along  the  radial  side 
of  the  index  finger,  and  supplies  the  First  lumbricalis  muscle.  The  fourth  sub- 
divides to  supply  the  adjacent  sides  of  the  index  and  middle  fingers,  and  sends 
a  branch  to  the  Second  lumbricalis  muscle.  The  fifth  supplies  the  adjacent 
sides  of  the  middle  and  ring  fingers,  and  communicates  with  a  branch  from  the 
ulnar  nerve. 

Each  digital  nerve,  opposite  the  base  of  the  first  phalanx,  gives  oft'  a  dorsal  branch, 
which  joins  the  dorsal  digital  nerve  from  the  radial  nerve  and  runs  along  the  side 
of  the  dorsum  of  the  finger,  to  end  in  the  integument  over  the  last  phalanx.  At 
the  end  of  the  finger  the  digital  nerve  divides  into  a  palmar  and  a  dorsal  branch, 
the  former  of  which  supplies  the  extremity  of  the  finger,  and  the  latter  ramifies 
around  and  beneath  the  nail. 

The  digital  nerves,  as  they  run  along  the  fingers,  are  placed  superficial  to  the 
digital  arteries.  The  cutaneous  areas  supplied  by  the  median  nerve  are  shown 
in  Figs.  768  and  769).  * 


1036  THE  NERVE  SYSTEM 

The  Ulnar  Nerve  {n.  ulnaris)  (Figs.  764  and  770)  is  situated  along  the  inner  or 
ulnar  side  of  the  upper  limb,  and  is  distributed  to  the  muscles  and  integument 
of  the  forearm  and  hand.  It  is  smaller  than  the  median,  behind  which  it  is 
placed,  diverging  from  it  in  its  course  down  the  arm.  It  arises  from  the  inner 
cord  of  the  brachial  plexus,  in  common  with  the  inner  head  of  the  median  and  the 
internal  cutaneous  nerves,  and  derives  its  fibres  from  the  eighth  cervical  and  first 
thoracic  nerves.  At  its  origin  it  lies  to  the  inner  side  of  the  axillary  artery,  and 
liolds  the  same  relation  with  the  brachial  artery  to  the  middle  of  the  arm.  Here 
it  pierces  the  intermuscular  septum,  runs  obliquely  across  the  internal  head  of 
the  Triceps,  and  descends  to  the  groove  between  the  internal  condyle  and  the  olec- 
ranon, accompanied  by  the  inferior  profunda  artery.  At  the  elbow  it  rests  upon 
the  back  of  the  inner  condyle,  and  passes  into  the  forearm  between  the  two  heads 
of  the  Flexor  carpi  ulnaris  muscle.  In  the  forearm  it  descends  in  a  perfectly 
straight  course  along  the  ulnar  side  of  the  extremity,  lying  upon  the  Flexor  pro- 
fundus digitorum  muscle,  its  upper  half  being  covered  hy  the  Flexor  carpi  ulnaris 
muscle,  its  lower  half  lying  on  the  outer  side  of  the  muscle,  being  covered  by  the 
integument  and  fascia.  In  the  upper  third  of  its  course,  it  is  separated  from  the 
ulnar  artery  by  a  considerable  interval,  but  in  the  rest  of  its  extent  the  nerve  lies 
to  the  inner  side  of  the  artery.  At  the  wrist  the  ulnar  nerve  crosses  the  annular 
ligament  on  the  outer  side  of  the  pisiform  bone,  to  the  inner  side  of  and  a  little 
behind  the  ulnar  artery,  and  immediately  beyond  this  bone  divides  into  two 
branches,  the  superficial  and  the  deep  palmar. 

Branches. — ^The  branches  of  the  ulnar  nerve  are: 


In  the  forearm 


Articular  (elbow). 

Muscular.  ,  p,         n  ■  i      , 

Cutaneous.  In  the  hand  /  Superficial  palmar. 
-P,        I       J.  I  Deep  palmar. 

Dorsal  cutaneous.  "^         ^  ^ 


^  Articular  (wrist). 

The  articular  branches  to  the  elbow-joint  consist  of  several  small  filaments. 
They  arise  from  the  nerve  as  it  lies  in  the  groove  between  the  inner  condyle  of  the 
humerus  and  the  olecranon. 

The  muscular  branches  (rami  musculares),  two  in  number,  arise  from  the  trunk 
of  the  nerve  near  the  elbow;  one  supplies  the  Flexor  carpi  ulnaris;  the  other,  the 
inner  half  of  the  Flexor  profundus  digitorum. 

The  cutaneous  branches  are  two  in  number,  palmar  and  dorsal. 

The  palmar  cutaneous  branch  (ramus  cutaneus  palmaris)  arises  from  the  ulnar 
nerve  at  about  the  middle  of  the  forearm  and  runs  downward  on  the  ulnar  artery, 
giving  off  some  filaments  entwining  around  the  vessel.  Just  above  the  annular 
ligament  it  pierces  the  deep  fascia  and  ends  in  the  integument  of  the  palm,  com- 
municating with  the  palmar  cutaneous  branch  of  the  median  nerve. 

The  dorsal  cutaneous  branch  {ramus  dorsalis  manus)  arises  about  two  inches 
aI)ove  the  wrist;  it  passes  posteriorly  beneath  the  Flexor  carpi  ulnaris,  perforates 
the  deep  fascia,  and,  running  along  the  ulnar  side  of  the  back  of  the  wdst  and  hand, 
divides  into  branches  (nn.  digitales  dorsales) ;  one  of  these  supplies  the  inner  side 
of  the  little  finger;  a  second  supplies  the  adjacent  sides  of  the  little  and  ring  fingers; 
a  third  joins  the  branch  of  the  radial  nerve  which  supplies  the  adjoining  sides  of 
the  middle  and  ring  fingers,  and  assists  in  supplying  them;  a  fourth  is  distributed 
to  the  metacarpal  region  of  the  hand,  communicating  with  a  branch  of  the  radial 
nerve. 

On  the  little  finger  the  posterior  digital  branches  extend  only  as  far  as  the  base 
of  the  terminal  phalanx,  and  on  the  ring  finger  as  far  as  the  base  of  the  second 
phalanx;  the  more  distal  parts  of  these  digits  are  supplied  by  posterior  branches 
derived  from  the  palmar  digital  branches  of  the  ulnar. 


THE  BRACHIAL  PLEXUS  1037 

The  superficial  palmar  branch  (ramus  superficialis  n.  tdnaris)  supplies  the 
Palmaris  brevis  and  the  integument  on  the  inner  side  of  the  iiand,  and  terminates 
in  two  digital  branches,  which  are  distributed,  one  to  the  ulnar  side  of  the  litde 
finger,  the  other  to  the  adjoining  sides  of  the  little  and  ring  fingers,  the  latter 
communicating  with  a  branch  from  the  median.  The  digital  branches  are  dis- 
tributed to  the  fingers  in  the  same  manner  as  the  digital  branches  of  the  median. 

The  deep  palmar  branch  (ramus  profundus  n.  idnaris),  accompanied  by  the 
deep  branch  of  the  ulnar  artery,  passes  between  the  Abductor  and  Flexor  brevis 
minimi  digiti  muscles;  it  then  perforates  the  Opponens  minimi  digiti  and  follows 
the  course  of  the  deep  palmar  arch  beneath  the  flexor  tendons.  At  its  origin  it 
supplies  the  muscles  of  the  little  finger.  As  it  crosses  the  deep  part  of  the  hand 
it  sends  two  branches  to  each  interosseous  space,  one  for  the  Dorsal  and  one  for 
the  Palmar  interosseous  muscle,  the  branches  to  the  Second  and  Third  palmar 
interossei  supplying  filaments  to  the  two  inner  Lumbrical  muscles.  At  its  ter- 
mination between  the  thumb  and  index  finger  it  supplies  the  Adductores  trans- 
versus  et  obliquus  poUicis  and  the  inner  head  of  the  Flexor  brevis  pollicis.  It  also 
sends  articular  filaments  to  the  wrist-joint. 

It  will  be  remembered  that  the  inner  part  of  the  Flexor  profundus  digitorum 
muscle  is  supplied  by  the  ulnar  nerve;  the  two  inner  Lumbricales,  which  are 
connected  with  the  tendons  of  this  part  of  the  muscle,  are  therefore  supplied  by 
the  same  nerve.  The  outer  part  of  the  Flexor  profundus  is  supplied  by  the  median 
nerve;  the  two  outer  Lumbricales,  which  are  connected  with  the  tendons  of  tiiis 
part  of  the  muscle,  are  therefore  supplied  by  the  same  nerve.  Brooks  states 
that  in  twelve  instances  out  of  twenty-one  he  found  that  the  Third  lumbrical 
received  a  twig  from  the  median  nerve,  in  addition  to  its  branch  from  the  ulnar. 
The  cutaneous  areas  supplied  by  the  ulnar  nerve  are  shown  in  Figs.  768  and  769. 

The  Musculospiral  Nerve  (n.  radialis)  (Figs.  770  and  771),  the  largest  branch 
of  the  brachial  plexus,  supplies  the  muscles  of  the  back  part  of  the  arm  and 
forearm,  and  the  integument  of  the  same  parts,  as  well  as  that  of  the  back  of 
the  hand  (Figs.  768  and  769).  It  arises  from  the  posterior  cord  of  the  brachial 
plexus,  of  which  it  may  be  regarded  as  the  continuation.  Its  fibres  are  derived 
from  the  sixth,  seventh,  and  eighth,  and  sometimes  also  from  the  fifth  cervical 
and  first  thoracic  nerves.  At  its  commencement  it  is  placed  first  behind  the  axil- 
lary artery  and  then  behind  the  upper  part  of  the  brachial  artery,  passing  down  in 
front  of  the  tendons  of  the  Latissimus  dorsi  and  Teres  major.  It  winds  around 
from  the  inner  to  the  outer  side  of  the  humerus  in  the  musculospiral  groove  with 
the  superior  profunda  artery,  between  the  internal  and  external  heads  of  the 
Triceps  muscle  (Fig.  771).  It  pierces  the  external  intermuscular  septum,  and 
descends  between  the  Brachialis  anticus  and  Braehioradialis  muscles  to  the  front 
of  the  external  condyle  of  the  humerus,  where  it  divides  into  the  radial  and  pos- 
terior interosseous  nerves. 

The  branches  of  the  musculospiral  nerve  are: 

Muscular.  Radial. 

Cutaneous.  Posterior  interosseous. 

The  muscular  branches  {rami  musculares  n.  radialis)  are  derived  from  the  nerve 
at  the  inner  side,  back  part,  and  outer  side  of  the  arm  respectively;  they  supply 
the  Triceps,  Anconeus,  Braehioradialis,  Extensor  carpi  radialis  longior,  and  Bra- 
chialis anticus  muscles.  The  internal  muscular  branches  supply  the  inner  and 
middle  heads  of  the  Triceps  muscle.  That  to  the  inner  head  of  the  Triceps  is 
a  long,  slender  filament  which  lies  close  to  the  ulnar  nerve,  as  far  as  the  lower  tliird 
of  the  arm,  and  is  therefore  frecjuently  spoken  of  as  the  ulnar  collateral  branch. 
The  posterior  muscular  branch,  of  large  size,  arises  from  the  nerve  in  the  groove 
between  the  Triceps  muscle  and  the  humerus.     It  divides  into  branches  which 


1038 


THE  NERVE  SYSTEM 


Circumfiex. 


supply  the  outer  and  Inner  heads  of  the  Triceps  and  Anconeus  muscles.  _  The 
branch  for  the  latter  muscle  is  a  long,  slender  filament  which  descends  in  the 
substance  of  the  Triceps  to  the  Anconeus.     The  external  muscular  branches  supply 

the  Brachioradialis,  Extensor 
Suprascapuiary\  carpi     radialis     longior,    and 

(usually)  the  outer  part  of  the 
I3rachialis  anticus  muscles. 

The  cutaneous  branches  are 
three  in  number,  one  internal 
and  two  external.  The  inter- 
nal cutaneous  branch  (n.  cuia- 
neus  brachii  posterior)  arises 
in  the  axillary  space  with  the 
inner  muscular  branch.  It  is 
of  small  size,  and  passes 
through  the  axilla  to  the  inner 
side  of  the  arm,  supplying  the 
integument  on  its  posterior 
aspect  nearly  as  far  as  the 
olecranon.  In  its  course  it 
crosses  beneath  the  intercosto- 
humeral  nerve,  with  which  it 
communicates.  The  external 
cutaneous  branch  (n.  cutaneus 
antehrachii  dorsalis)  divides 
into  two  branches,  and  each 
one  perforates  the  outer  head 
of  the  Triceps  muscle  at  its 
attachment  to  the  humerus. 
The  upper  and  smaller  one 
passes  to  the  front  of  the 
elbow,  lying  close  to  the 
cephalic  vein,  and  supplies  the 
integument  of  the  lower  half  of 
the  arm  on  its  anterior  aspect. 
The  lower  branch  pierces  the 
deep  fascia  below  the  insertion 
of  the  Deltoid  muscle,  and 
passes  down  along  the  outer 
side  of  the  arm  and  elbow, 
and  then  along  the  back  part 
of  the  radial  side  of  the  fore- 
arm to  the  wrist,  supplying 
the  integument  in  its  course, 
and  joining,  near  its  termi- 
nation, with  the  posterior 
cutaneous  branch  of  the  mus- 
culocutaneous nerve. 
The  Radial  Nerve  (ramus  superficialis  n.  radialis)  (Fig.  770),  passes  along  the 
front  of  the  radial  side  of  the  forearm  to  the  commencement  of  its  lower  third. 
It  lies  at  first  a  little  to  the  outer  side  of  the  radial  artery,  concealed  beneath  the 
Brachioradialis.  In  the  middle  third  of  the  forearm  it  lies  beneath  the  same 
muscle,  in  close  relation  with  the  outer  side  of  the  artery.  It  leaves  the  artery 
about  three  inches  above  the  wrist,  passes  beneath  the  tendon  of  the  Brachio- 


FiG.  771. — The  suprascapular,  circumflex,  and  mu 


THE  BRACHIAL  PLEXU8  1039 

radialis,  and,  piercing  the  deep  fascia  at  the  outer  border  of  the  forearm,  divides 
into  two  branches.  The  external  branch,  the  smaller  of  the  two,  supplies  the 
integument  of  the  radial  side  and  ball  of  the  thumb,  joining  with  the  anterior 
branch  of  the  musculocutaneous  nerve.  The  internal  branch  communicates,  above 
the  wrist,  with  the  posterior  cutaneous  branch  from  the  musculocutaneous,  and  on 
the  back  of  the  hand  forms  an  arch  with  the  dorsal  cutaneous  branch  of  the  ulnar 
nerve.  It  then  divides  into  four  digital  nerves  {tin.  digitales  dorsales),  which  are 
distributed  as  follows:  The  first  supplies  the  ulnar  side  of  the  thumb;  the 
second,  the  radial  side  of  the  index  finger;  the  third,  the  adjoining  sides  of  the 
index  and  middle  fingers;  and  the  fourth,  the  adjacent  borders  of  the  middle 
and  ring  fingers.^  The  latter  nerve  communicates  with  a  filament  from  the 
posterior  branch  of  the  ulnar  nerve. 

The  Dorsal  or  Posterior  Interosseous  Nerve  (ji.  interosseous  [antebrachii]  dorsalis) 
(Figs.  770  and  771)  winds  to  the  back  of  the  forearm  around  the  outer  side  of  the 
radius,  passes  between  the  two  planes  of  fibres  of  the  Supinator  [brevis]  muscle, 
and  is  prolonged  downward,  between  the  superficial  and  deep  layer  of  muscles, 
to  the  middle  of  the  forearm.  Considerably  diminished  in  size,  it  descends  on 
the  interosseous  membrane,  beneath  the  Extensor  longus  pollicis  muscle,  to  the 
back  of  the  carpus,  where  it  presents  a  gangliform  enlargement  from  which  fila- 
ments are  distributed  to  the  inferior  radioulnar  articulation,  to  the  wrist-joint, 
and  to  the  ligaments  and  articulations  of  the  carpus.  It  supplies  all  the  muscles 
of  the  radial  and  posterior  cubital  regions,  excepting  the  Anconeus,  Supinator 
longus,  and  Extensor  carpi  radialis  longior. 

Applied  Anatomy. — The  brachial  plexus  may  be  severed  by  traction  on  the  limb,  leading 
to  complete  paralysis.  Bristow^  has  reported  three  cases  of  avulsion  of  the  plexus  and  has 
described  twenty-four  cases.  In  these  cases  it  is  generally  believed  that  the  lesion  is  rather  a 
tearing  away  of  the  nerves  from  the  spinal  cord  than  a  solution  of  continuity  of  the  nerve  fibres 
themselves.  In  a  case  operated  upon  by  Bristow  it  was  found  that  the  plexus  had  given  way 
where  the  four  cervical  nerves  and  the  first  thoracic  nerve  unite  to  form  three  trunks.  In  supra- 
clavicular division  of  the  brachial  plexus,  not  only  will  there  be  motor  and  sensor  paralysis  in  the 
limb,  but  the  Serratus  magnus  muscle  will  probably  be  paralyzed,  because  of  injury  to  the  poste- 
rior thoracic  nerves.  In  the  axilla  any  of  the  nerves  forming  the  brachial  plexus  may  be  injured 
by  a  wound  of  this  part,  the  median  being  the  one  which  is  most  frequently  damaged  from  its 
exposed  position.  The  musculospiral,  on  account  of  its  sheltered  and  deep  position,  is  least 
often  wounded.  The  brachial  plexus  in  the  axilla  is  often  damaged  from  the  pressure  of  a 
crutch,  producing  the  condition  known  as  crutch  paralysis.  In  these  cases  the  musculospiral 
is  the  nerve  most  frequently  implicated;  the  ulnar  nerve  being  the  one  that  appears  to  suffer  next 
in  frequency. 

The  circumflex  nerve  is  of  particular  surgical  interest.  On  account  of  its  course  around  the 
surgical  neck  of  the  humerus,  it  is  liable  to  be  torn  in  fractures  of  this  part  of  the  bone,  and 
in  dislocations  of  the  slioulder-joint,  leading  to  paralysis  of  the  Deltoid,  and,  according  to  Erb, 
inflammation  of  the  shoulder-joint  is  liable  to  be  followed  by  a  neuritis  of  this  nerve  from  exten- 
sion of  the  inflammation  to  it. 

Hilton  takes  the  circumflex  nerve  as  an  illustration  of  a  law  which  he  lays  down,  that 
"  the  same  trunks  of  nerves  whose  branches  supply  the  groups  of  muscles  moving  a  joint  furnish 
also  a  distribution  of  nerves  to  the  skin  over  the  insertions  of  the  same  muscles,  and  the  interior 
of  the  joint  receives  its  nerves  from  the  same  source."  In  this  way  he  explains  the  fact  that  an 
inflamed  joint  becomes  rigid,  because  the  same  nerves  which  supply  the  interior  of  the  joint 
supply  the  muscles  which  move  that  joint. 

The  median  nerve  is  liable  to  injury  in  wounds  of  the  forearm.  When  paralyzed,  there  is 
loss  of  flexion  of  the  second  phalanges  of  all  the  fingers  and  of  the  terminal  phalanges  of  the 
index  and  middle  fingers.  Flexion  of  the  terminal  phalanges  of  the  ring  and  middle  fingers  can 
still  be  effected  by  that  portion  of  the  Flexor  profundus  digitorum  which  is  supplied  by  the  ulnar 
nerve.  There  is  power  to  flex  the  proximal  phalanges  through  the  Interossei.  The  thumi) 
cannot  be  flexed  or  opposed,  and  is  maintained  in  a  position  of  extension  and  adduction.  All 
power  of  pronation  is  lost.     The  wrist  can  be  flexed,  if  the  hand  is  first  adducted,  by  the  action 

^  According  to  Hutchinson,  the  digital  nerve  to  the  thumb  reaches  only  as  high  asthe  root  of  the  nail;  the 
one  to  the  forefinoter  as  high  as  the  middle  of  the  second  phalanx,  and  the  one  to  the  middle  and  ring  fingers  not 
higher  than  the  first  phalangeal  joint  (London  Hospital  Gazette,  vol.  iii,  p.  319). 

2  Annals  of  Surgery,  September,  1902. 


1040  THE  NERVE  SYSTEM 

of  the  Flexor  carpi  ulnaris.  There  is  loss  or  impairment  of  sensation  on  the  palmar  surface 
of  the  thumb,  index,  middle,  and  outer  half  of  the  ring  fingers,  and  on  the  dorsal  surface  of  the 
same  fingers  over  the  last  two  phalanges;  except  in  the  thumb,  where  the  loss  of  sensation  is 
limited  to  the  back  of  the  last  phalanx.  In  order  to  expose  the  median  nerve  for  the  purpose 
of  stretching  it  an  incision  should  be  made  along  the  radial  side  of  the  tendon  of  the  Palmaris 
longus  muscle,  which  serves  as  a  guide  to  the  nerve. 

The  ulnar  nerve  is  liable  to  be  injured  in  wounds  of  the  forearm.  When  paralyzed,  there 
is  loss  of  power  of  flexion  in  the  ring  and  little  fingers;  there  is  impaired  power  of  ulnar  flexion 
and  adduction  of  the  hand;  there  is  inability  to  spread  out  the  fingers  from  paralysis  of  the 
Interossei;  and  there  is  inability  to  adduct  the  thumb.  The  fingers  cannot  be  flexed  at  the  first 
joints,  and  cannot  be  extended  at  the  other  joints.  A  daw  hand  develops,  the  first  phalanges 
being  overextended  and  the  others  flexed.  Sensation  is  lost  or  impaired  in  the  skin  of  the  ulnar 
side  of  the  hand  anteriorly  and  posteriorly,  involving  the  little  finger,  the  ring  finger,  and  the 
ulnar  half  of  the  middle  finger  posteriorly,  and  anteriorly  involving  the  little  finger  and  the  ulnar 
half  of  the  ring  finger.  In  order  to  expose  the  nerve  in  the  lower  part  of  the  forearm,  an 
incision  should  be  made  along  the  outer  border  of  the  tendon  of  the  Flexor  carpi  ulnaris,  and 
the  nerve  will  be  found  lying  on  the  ulnar  side  of  the  ulnar  artery. 

The  7nusculospiral  nerve  is  probably  more  frequently  injured  than  any  other  nerve  of  the 
upper  extremity.  In  consequence  of  its  close  relationship  to  the  humerus  as  it  lies  in  the  mus- 
culospiral  groove,  it  is  frequently  torn  or  injured  in  fractures  of  this  bone,  or  subsequently 
involved  in  the  callus  that  may  be  thrown  out  around  a  fracture,  and  thus  pressed  upon  and  its 
functions  interfered  with.  It  is  also  liable  to  be  squeezed  against  the  bone  by  kicks  or  blows; 
it  may  be  divided  by  wounds  of  the  arm.  When  paralyzed,  the  hand  is  flexed  at  the  wrist  and 
lies  flaccid.  This  condition  is  known  as  drop  wrist.  The  fingers  are  also  flexed,  and  on  an 
attempt  being  made  to  extend  them  the  last  two  phalanges  only  will  be  extended  through  the 
action 'of  the  Interossei,  the  first  phalanges  remaining  flexed.  There  is  no  power  of  extending  the 
wrist.  Supination  is  completely  lost  when  the  forearm  is  extended  on  the  arm,  but  is  possible  to 
a  certain  extent  if  the  forearm  is  flexed  so  as  to  allow  of  the  action  of  the  Biceps.  The  power 
of  extension  of  the  forearm  is  lost  on  account  of  paralysis  of  the  Triceps.  Loss  of  sensation 
may  be  considerable  or  slight.  Its  area  is  shown  in  Fig.  769.  The  best  position  in  which  to 
expose  the  nerve  for  the  purpose  of  stretching  is  to  make  an  incision  along  the  inner  border  of 
the  Brachioradialis  muscle,  just  above  the  level  of  the  elbow-joint.  The  skin  and  superficial 
structures  are  to  be  divided  and  the  deep  fascia  exposed.  The  white  line  in  this  structure  indi- 
cating the  border  of  the  muscle  is  to  be  defined,  and  the  deep  fascia  divided  in  this  line.  By  now 
raising  the  Brachioradialis  the  nerve  will  be  found  lying  beneath  it,  on  the  Brachialis  anticus 
muscle. 

Postajiesthctic  paralf/sis.  When  a  person  emerges  from  the  influence  of  a  general  anesthetic 
palsy  of  the  arm  may  be  found  to  exist.  The  brachial  plexus  may  have  been  compressed  during 
the  operation  by  drawing  the  arm  strongly  from  the  body  or  elevating  it  by  the  side  of  the  head. 
In  such  a  case  the  plexus  was  compressed  by  the  head  of  the  humerus  (Braun). 

The  median  nerve  is  stretched  when  the  arm  is  rotated  externally  and  drawn  backward  and 
outward.  The  ulnar  nerve  is  stretched  when  the  forearm  is  flexed  and  supinated  (Braun). 
Garrigues  believes  that  in  most  cases  of  postanesthetic  paralysis  the  brachial  plexus  was  squeezed 
between  the  collar  bone  and  the  first  rib  by  the  head  of  the  patient  being  drawn  to  the  opposite 
side  or  being  allowed  to  fall  back. 

The  Anterior  or  Ventral  Divisions  of  the  Thoracic  Nerves  (rami  anteriores). — 
The  anterior  primary  divisions  of  the  thoracic  nerves  are  twelve  in  number  on 
each  side.  Eleven  of  them  are  situated  between  the  ribs,  and  are  therefore 
termed  intercostal;  the  twelfth  lies  below  the  last  rib.  Each  nerve  is  connected 
with  the  adjoining  ganglion  of  the  sympathetic  by  one  or  two  filaments  (ramus 
communicans).  The  intercostal  nerves  are  distributed  chiefly  to  the  parietes 
of  the  thorax  and  abdomen  and  differ  from  the  anterior  divisions  of  the  other 
spinal  nerves  in  that  there  is  no  plexus  formation,  each  nerve  running  an  inde- 
pendent course.  The  first  two  nerves  supply  fibres  to  the  upper  limb  in  addition 
to  their  thoracic  branches;  the  next  four  are  limited  in  their  distribution  to  the 
parietes  of  the  thorax;  the  five  lower  supply  the  parietes  of  the  thorax  and  abdomen; 
the  twelfth  thoracic  is  distributed  to  the  abdominal  wall  and  the  skin  of  the  buttock. 

The  Anterior  Division  of  the  First  Thoracic  Nerve  divides  into  two  branches; 
one,  the  larger,  leaves  the  thorax  in  front  of  the  neck  of  the  first  rib,  and  enters 
into  the  formation  of  the  brachial  plexus;  the  other  and  smaller  branch  runs  along 
the  first  intercostal  space,  forming  the  first  intercostal  nerve  (n.  intercostalis  I), 


ANTERIOR  THORACIC  NERVE8 


1041 


giving  off  muscular  branches,  and  terminates  on  the  anterior  part  of  the  thorax 
by  forming  the  first  anterior  cutaneous  nerve  (ramus  cutaneus  anterior  n.  inter- 
costalis  I)  of  the  thorax.  Occasionally  this  anterior  cutaneous  branch  is  wanting. 
The  first  intercostal  nerve,  as  a  rule,  gives  off  no  lateral  cutaneous  branch,  but 
sometimes  a  small  branch  is  given  off  which  communicates  with  the  intercosto- 
humeral.  It  frequently  receives  a  connecting  twig  from  the  second  thoracis? 
nerve,  which  passes  upward  over  the  neck  of  the  second  rib. 


Fig.  772. — Anterior  aspect. 


Figs.  772  and  773. — Distribution  of  cutaneous  nerves. 


Fig.  773.— Posterior  aspect. 


The  Anterior  Divisions  of  the  Second,  Third,  Fourth,  Fifth,  and  Sixth  Thoracic  Nerves 
and  the  Small  Branch  from  the  First  Thoracic  Nerve  (nn.  intercostales)  are  confined 
to  the  parietes  of  the  thorax,  and  are  named  thoracic  intercostal  nerves.  They 
pass  forward  in  the  intercostal  spaces  below  the  intercostal  vessels.  At  the  back 
of  the  thorax  they  lie  between  the  pleura  and  the  posterior  intercostal  membrane, 
piercing  the  latter,  and  course  between  the  two  planes  of  Intercostal  muscles  as 
far  as  the  middle  of  the  rib.  They  then  enter  the  substance  of  the  Internal 
intercostal  muscles,  and,  running  amidst  their  fibres  as  far  as  the  costal  cartilages, 
they  gain  the  inner  surface  of  the  muscles,  and  lie  between  them  and  the  pleura. 


1042 


THE  NEB  VE  SYSTEM 


Near  the  sternum,  they  cross  in  front  of  the  internal  mammary  artery  and  Tri- 
ano-ularis  sterni  muscle,  pierce  the  Internal  intercostal  muscles,  the  anterior 
intercostal  membrane,  and  Pectoralis  major  muscle,  and  supply  the  integument 
of  the  anterior  wall  of  the  thorax  and  over  the  mammary  gland,  forming  the 
anterior  cutaneous  nerves  of  the  thorax;  the  branch  from  the  second  nerve  is 
joined  with  the  supraclavicular  nerves  of  the  cervical  plexus. 

Branches. — ^Numerous  slender  muscular  filaments  {rami  musculares)  supply  the 
""Intercostals,  the  Infracostales,  the  Levatores  costarum,  the  Serratus  posticus 
superior,  and  the  Triangularis  sterni  muscles.  At  the  front  of  the  thorax  some 
of  these  branches  cross  the  costal  cartilages  from  one  intercostal  space  to  another. 


ANTERIOR  CUTANEOUS 

Fig.  774. — Plan  of  a  typical  intercostal  nerve 


The  lateral  cutaneous  nerves  (rami  cidanei  laterales)  are  derived  from  the  inter- 
costal nerves,  midway  between  the  vertebrfe  and  sternum;  they  pierce  the  External 
intercostal  and  Serratus  magnus  muscles,  and  divide  into  anterior  and  posterior 
branches.  The  anterior  branches  (rami  anteriores)  are  reflected  forward  to  the 
side  and  fore  part  of  the  thorax,  supplying  the  skin  of  the  thorax  and  mamma; 
those  of  the  fifth  and  sixth  nerves  supply  the  upper  digitations  of  the  External 
oblique.  The  posterior  branches  (rami  posteriores)  are  reflected  posteriorly 
to  supply  the  integument  over  the  scapula  and  over  the  Latissimus  dorsi  muscle. 

The  lateral  cutaneous  branch  of  the  second  intercostal  nerve  (n.  intercostohrachialis) 
is  of  large  size,  and  does  not  divide,  like  the  other  nerves,  into  an  anterior  and  a 
posterior  branch.  It  is  named,  from  its  origin  and  distribution,  the  intercosto- 
humeral  or  intercostobrachial  nerve  (Figs.  757  and  770).  It  pierces  the  External 
intercostal  muscle,  crosses  the  axilla  to  the  inner  side  of  the  arm,  and  joins  with 
a  filament  from  the  lesser  internal  cutaneous  nerve  of  the  upper  arm  (nerve  of 
Wrisherg).     It  then  pierces  the  fascia,  and  supplies  the  skin  of  the  upper  half  of 


ANTERIOR  THORACIC  NERVES  1043 

the  inner  and  back  part  of  the  arm  (Figs.  768  and  769),  communicating  with  the 
internal  cutaneous  branch  of  the  musculospiral  nerve.  The  size  of  this  nerve 
is  in  inverse  proportion  to  the  size  of  the  other  cutaneous  nerves,  especially  the 
nerve  of  Wrisberg.  A  second  intercostohumeral  nerve  is  frequently  given  ofi  from 
the  third  intercostal.  It  supplies  filaments  to  the  armpit  and  inner  side  of  the  arm. 
It  may  or  may  not  send  a  branch  to  the  intercostohumeral. 

The  Anterior  Divisions  of  the  Seventh,  Eighth,  Ninth,  Tenth,  and  Eleventh  Thoracic 
Nerves  are  continued  anteriorly  from  the  intercostal  spaces  into  tlie  al)dominal 
wall;  hence  these  nerves  are  named  thoracoabdominal  intercostal  nerves.  They 
have  the  same  arrangement  as  the  upper  ones  as  far  as  the  anterior  extremities 
of  the  intercostal  spaces,  where  they  pass  behind  the  costal  cartilages,  and  between 
the  Internal  oblicjue  and  Transversalis  muscles,  to  the  sheath  of  the  Rectus,  which 
they  perforate.  They  supply  the  Rectus  muscle,  and  terminate  in  branches 
which  become  subcutaneous  near  the  linea  alba.  These  branches  are  named 
the  anterior  or  ventral  cutaneous  nerves  of  the  abdomen.  They  are  directed  outward 
as  far  as  the  lateral  cutaneous  nerves,  supplying  the  integument  of  the  front  of 
the  belly.  The  lower  intercostal  nerves  supply  the  Intercostals,  Serratus  posticus 
inferior,  and  Abdominal  muscles,  and,  about  the  middle  of  their  course,  give  off 
lateral  cutaneous  branches  which  pierce  the  External  intercostal  and  External 
oblic|ue  muscles,  in  the  same  line  as  the  lateral  cutaneous  nerves  of  the  thorax, 
and  divide  into  anterior  and  posterior  branches,  which  are  distributed  to  the  integu- 
ment of  the  abdomen  and  l:)ack;  the  ventral  branches  supply  the  digitations  of 
the  External  oblique  and  extend  downward  and  forward  nearly  as  far  as  the  margin 
of  the  Rectus  muscle;  the  posterior  branches  pass  backward  to  supply  the  skin 
over  the  Latissimus  dorsi. 

The  Anterior  Division  of  the  Last  Thoracic  Nerve  is  larger  than  that  of  the  other 
thoracic  nerves;  it  runs  along  the  lower  border  of  the  last  rib,  and  passes  under 
the  external  arcuate  ligament  of  the  Diaphragm.  It  then  runs  in  front  of  the 
Quadratus  lumborum  muscle,  perforates  the  Transversalis  muscle,  and  passes 
between  it  and  the  Internal  oblique  muscle,  to  be  distributed  in  the  same  manner 
as  the  lower  intercostal  nerves.  It  communicates  with  the  iliohypogastric  branch 
of  the  lumbar  plexus,  and  is  frequently  connected  with  the  first  lumbar  nerve 
by  a  slender  branch,  the  thoracicolumbar  nerve,  which  descends  in  the  substance 
of  the  Quadratus  lumborum  muscle.    It  gives  a  branch  to  the  Pyramidalis  muscle. 

The  lateral  cutaneous  branch  of  the  last  thoracic  is  remarkable  for  its  large  size. 
It  does  not  divide  into  an  anterior  and  a  posterior  branch,  like  the  other  lateral 
cutaneous  branches  of  the  intercostal  nerves,  but  perforates  the  Internal  and  Ex- 
ternal oblique  muscles,  passes  over  the  crest  of  the  ilium  in  front  of  the  iliac  branch 
of  the  iliohypogastric,  and  is  distributed  to  the  integument  of  the  front  part  of 
the  gluteal  region,  some  of  its  filaments  extending  as  low  down  as  the  trochanter 
major. 

Applied  Anatomy. — The  lower  seven  intercostal  nerves  and  the  iliohypogastric  from  the 
first  lumbar  nerve  supply  the  skin  of  the  abdominal  wall.  -They  run  downward  and  inward 
fairly  equidistant  from  each  other.  Tlie  sixth  and  seventh  supply  the  skin  over  the  "pit  of  the 
stomach;"  the  eighth  corresponds  to  about  the  position  of  the  middle  linea  transversa;  the  tenth 
to  the  umbilicus;  and  the  iliohypogastric  supplies  the  skin  over  the  pubes  and  external  abdominal 
ring.  There  are  several  points  of  surgical  signiScance  about  the  distribution  of  these  nerves, 
and  it  is  important  to  remember  their  origin  and  course,  for  in  many  diseases  affecting  the  nerve 
trunks  at  or  near  their  origin  the  pain  is  referred  to  their  peripheral  origin?.  Thus,  in 
Pott's  disease  of  the  spine  children  will  often  he  brought  to  the  surgeon  sufTering  from  pain 
in  the  belly.  This  is  due  to  the  fact  that  the  nerves  are  irritated  at  the  seat  of  disease  as  they 
issue  from  the  vertebral  canal.  When  the  irritation  is  confined  to  a  single  pair  of  nerves,  the  sen- 
sation complained  of  is  often  a  feeling  of  constriction,  as  if  a  cord  ^ere  tied  around  the  abdomen; 
and  in  these  cases  the  situation  of  the  sense  of  constriction  may  serve  to  localize  the  disease  in 


10-14  THE  NER  VE  SYSTEM 

the  spinal  column.  In  other  cases,  where  the  bone  disease  is  more  extensive  and  two  or  more 
nerves  are  involved,  a  more  diffused  pain  in  the  abdomen  is  complained  of.  A  similar  condition 
is  sometimes  present  in  affections  of  the  cord  itself,  as  in  tabes  dorsalis. 

Again,  it  must  be  borne  in  mind  that  the  same  nerves  which  supply  the  skin  of  the  abdomen 
supply  also  the  muscles  which  constitute  the  greater  part  of  the  abdominal  wall.  Hence  it  follows 
that  any  irritation  applied  to  the  peripheral  terminations  of  the  cutaneous  branches  in  the 
skin  of  the  abdomen  is  immediately  followed  by  reflex  contraction  of  the  abdominal  muscles. 
A  good  practical  illustration  of  this  may  sometimes  be  seen  in  watching  two  surgeons  examine 
the  abdomen  of  the  same  patient.  One,  whose  hand  is  cold,  causes  the  muscles  of  the  abdom- 
inal wall  to  contract  at  once  and  the  belly  to  become  rigid,  and  thus  not  nearly  so  suitable 
for  examination;  the  other,  who  has  taken  the  precaution  to  warm  his  hand,  examines  the 
abdomen  without  exciting  any  reflex  contraction.  The  supply  of  both  muscles  and  skin  from 
the  same  source  is  of  importance  in  protecting  the  abdominal  viscera  from  injury.  A  blow 
on  the  abdomen,  even  of  a  severe  character,  will  do  no  injury  to  the  viscera  if  the  muscles  are 
in  a  condition  of  firm  contraction;  whereas  in  cases  where  the  muscles  have  been  taken  unawares, 
and  the  blow  has  been  struck  while  they  were  in  a  state  of  rest,  an  injury  insufficient  to  produce 
any  lesion  of  the  abdominal  wall  has  been  attended  with  rupture  of  some  of  the  abdominal  con- 
tents. The  importance,  therefore,  of  immediate  reflex  contraction  upon  the  receipt  of  an  injury 
cannot  be  overestimated,  and  the  intimate  association  of  the  cutaneous  and  muscular  fibres  in 
the  same  nerve  produces  a  much  more  immediate  response  on  the  part  of  the  muscles  to  any 
peripheral  stimulation  of  the  cutaneous  filaments  than  would  be  the  case  if  the  two  sets  of  fibres 
were  derived  from  independent  sources. 

Again,  the  nerves  supplying  the  aljdominal  muscles  and  skin  are  derived  from  the  lower  inter- 
costal nerves  and  are  intimately  connected  with  the  sympathetic  supplying  the  abdominal  viscera 
through  the  lower  thoracic  ganglia  from  which  the  splanchnic  nerves  are  derived.  In  conse- 
quence of  this,  in  rupture  of  the  abdominal  viscera  and  in  acute  peritonitis  the  muscles  of  the 
belly  wall  become  firmly  contracted,  and  thus  as  far  as  possible  preserve  the  abdominal  contents 
in  a  condition  of  rest. 

THE  LUMBOSACRAL  PLEXUS. 

The  anterior  primary  divisions  of  the  lumbar,  sacral,  and  coccygeal  nerves 
form  the  hunbosacral  plexus,  the  first  lumbar  nerve  being  frequently  joined  by  a 
branch  from  the  twelfth  thoracic.  For  descriptive  purposes  this  plexus  is  usually 
divided  into  three  parts — the  lumbar,  sacral,  and  pudendal  plexuses. 

The  Anterior  or  Ventral  Divisions  of  the  Lumbar  Nerves  (rami  anteriores). — 
The  anterior  divisions  of  the  lumbar  nerves  increase  in  size  from  above  downward. 
They  are  joined,  near  their  origins,  hy  gray  rami  communicaiifes  from  the  lumbar 
ganglia  of  the  sympathetic  cord.  These  consist  of  long,  slender  filaments,  which 
accompany  the  lumbar  arteries  around  the  sides  of  the  bodies  of  the  vertebrae 
beneath  the  Psoas  magnus  muscle.  Their  arrangement  is  somewhat  irregular; 
one  ganglion  may  give  rami  to  two  lumbar  nerves,  or  one  lumbar  nerve  may  receive 
rami  from  two  ganglia.  The  first  and  second  and  sometimes  the  third  and 
fourth  lumbar  nerves  are  each  connected  with  the  lumbar  part  of  the  sympathetic 
cord  by  a  ivhite  ramus  communicans.  The  nerves  pass  obliquely  outward  behind 
the  Psoas  magnus,  or  between  its  fasciculi,  distributing  filaments  to  it  and  the 
Quadratus  lumborum  muscles.  The  first  three  and  the  greater  part  of  the  fourth 
are  connected  together  in  this  situation  by  anastomotic  loops,  and  form  the  lumbar 
plexus.  The  anterior  division  of  the  fifth  lumbar,  joined  with  a  branch  from  the 
fourth,  descends  across  the  base  of  the  sacrum  to  join  the  anterior  division  of  the 
first  sacral  nerve  and  assists  in  the  formation  of  the  sacral  plexus.  The  cord 
resulting  from  the  union  of  the  fifth  lumbar  and  the  branch  from  the  fourth  is 
called  the  lumbosacral  cord  {truncus  lumbosacralis)  (Figs.  776  and  781). 

The  Lumbar  Plexus  {plexus  lumhalis)  (Figs.  775  and  776). — The  lumbar 
plexus  is  formed  by  the  loops  of  communication  between  the  anterior  divisions 
of  the  four  upper  lumliar  nerves.  The  plexus  is  narrow  above,  and  often  con- 
nected with  the  last  thoracic  nerve  by  a  slender  branch.  The  plexus  is  broad 
below,  where  it  is  joined  to  the  sacral  plexus  by  the  lumbosacral  cord.  The 
lumbar  plexus  is  situated  in  the  substance  of  the  Psoas  magnus  muscle  near 
its  posterior  part,  in  front  of  the  transverse  processes  of  the  lumbar  vertebrae. 


THE  LUMBOSACRAL  PLEXUS 


1045 


The  mode  in  which  the  plexus  is  arranged  varies  in  different  subjects.^  It 
differs  from  the  brachial  plexus  in  not  forming  an  intricate  interlacement,  but  the 
several  nerves  of  distribution  arise  from  one  or  more  of  the  spinal  nerves  in  the 
following  manner:  The  first  lumbar  nerve  receives  a  branch  from  the  last  tho- 
racic, gives  off  a  larger, 
upper  branch,  which  sub- 
divides into  the  iliohypo- 
gastric and  ilioinguinal 
nerves;  and  a  smaller 
lower  branch  which  unites 
with    a     branch    of    the 

second    lumbar,    to    form  — --i-— :=S-^/  /     i- " 

the     genitofemoral    nerve.       iuiohvpogasth 

The    remainder    of     the  ilio-inguin — ^  ^^^        /    •/         ^^  y.  m 

second     nerve     and     the 
third   and  fourth    lumbar 

...  .  GENITOFEMOI,-^    -  ^  ,     i_  /  /       ^  ^      1      lu 

nerves  divide  mto  anterior  ^^^^  ^ '  /t^//^/  ^^    l  iv 

and      posterior     divisions.  cutaneous 

The   anterior   division   of 

the  second  unites  with  the  /    /^  /^/  j//  //  ..-■-  l  v 

anterior    division  of    the 

third  nerve  and  a  part  of  ^°  '"^"I.Tacosv 

the    anterior    division    of     femoral  (antei 

the  fourth  nerve   to  form  cruraO^^^  obturator^ 

the    obturator    nerve.       The  Fig.  775.— Diagram  of  the  lumbar  plexus. 

remainder  of  the  anterior 

division  of  the  fourth  nerve  passes  down  to  communicate  with  the  fifth  lumbar 
nerve.  The  posterior  divisions  of  the  second  and  third  nerves  divide  into  two 
branches,  a  smaller  branch  from  each  uniting  to  form  the  external  or  lateral 
cutaneous  nerve,  and  a  larger  branch  from  each,  joining  with  the  posterior  division 
of  the  fourth  lumbar  nerve  to  form  the  femoral  or  anterior  crural  nerve.  The 
accessory  obturator,  when  it  exists,  is  formed  by  the  union  of  two  small  branches 
given  off'  from  the  third  and  fourth  nerves. 

The  branches  of  the  lumbar  plexus  may  therefore  be  arranged  as  follows: 

Iliohypogastric • ^  1,L. 

Ilioinguinal 1,L. 

Genitofemoral 1,2,  L. 

Dorsal  Divisions. 

External  (or  lateral)  cutaneous 2,  .3,  L. 

Femoral  (or  anterior  crural) 2,  3,  4,  L. 

.  Ventral  Divisions. 

Obturator \   •     • 2, 3,4,L.      ' 

Accessory  obturator 3, 4,  L. 

The  Iliohypogastric  Nerve  (?;.  iliohypogastricus)  (Figs.  775  and  776)  arises  from 
the  first  lumbar  nerve.  It  emerges  from  the  lateral  border  of  the  Psoas  magnus 
muscle  at  its  upper  part,  and  crosses  obliquely  in  front  of  the  Quadratus  lumborum 
to  the  crest  of  the  ilium.  It  then  perforates  the  Transversalis  muscle  posteriorly 
near  the  crest  of  the  ilium.  It  gives  oft"  muscular  branches  (rami  musculares)  to 
the  abdominal  wall,  and  divides  between  the  Transversalis  and  the  Internal  oblique 
into  two  cutaneous  branches,  iliac  and  hypogastric. 


1  For  statistical  studies  of  the  variations 
the  American  Journal  of  Anatomy,  vol.  vi. 


tered  in  different  individuals,  see  the  article  by  Bardeen,  in 


1046 


THE  NERVE  SYSTEM 


The  iliac  branch  (ramus  cutaneus  lateralis)  pierces  the  Internal  and  External 
oblique  muscles  immediately  above  the  crest  of  the  ilium,  and  is  distributed  to  the, 
integument  of  the  gluteal  region,  behind  the  lateral  cutaneous  branch  of  the  last 
thoracic  nerve  (Fig.  782).  The  size  of  this  nerve  bears  an  inverse  proportion  to 
that  of  the  lateral  cutaneous  branch  of  the  last  thoracic  nerve. 

The  hypogastric  branch  (ramus  cutaneus  anterior)  (Fig.  777)  continues  onward 
between  the  Internal  oblique  and  Transversalis  muscles.  It  then  pierces  the 
Internal  oblique,  and  becomes  cutaneous  by  perforating  the  aponeurosis  of  the 
External  oblique,  about  an  inch  (2.5  cm.)  above  and  a  little  laterad  of  the  external 
abdominal  ring,  and  is  distributed  to  the  integument  of  the  hypogastric  region. 
The  iliohypogastric  nerve  communicates  with  the  last  thoracic  and  ilioinguinal 
nerves. 


Fig   776  — ^The  lumbar  plexus  and  its  branches. 

The  Ilioinguinal  Nerve  (n.  ilioinguinalis)  (Figs.  776  and  777),  smaller  than  the 
preceding,  arises  with  it  from  the  first  lumbar  nerve.  It  emerges  from  the  lateral 
border  of  the  Psoas  magnus  muscle  just  below  the  iliohypogastric  nerve,  and, 
passing  obliquely  across  the  Quadratus  lumborum  and  Iliacus  muscles,  perforates 
the  Transversalis  near  the  fore  part  of  the  crest  of  the  ilium,  and  communicates 
with  the  iliohypogastric  nerve  between  that  muscle  and  the  Internal  oblique. 
The  nerve  then  pierces  the  Internal  oblique,  distributing  muscular  branches  (rami 
musculares)  to  it,  and,  accompanying  the  spermatic  cord  through  the  external 
abdominal  ring,  is  distributed  to  the  integument  of  the  upper  and  inner  part 
of  the  thigh,  to  the  skin  covering  the  root  of  the  penis,  and  to  the  scrotum  in  the 


THE  LUMBOSACRAL  PLEXUS  1047 

male  (jin.  scrotates  auteriores)  and  to  the  skin  covering  the  mons  veneris  and 
labium  majus  in  the  female  (//«.  lahiales  anteriores).  The  size  of  this  nerve  is 
in  inverse  proportion  to  that  of  the  iliohypogastric.  Occasionally  it  is  very  small, 
and  ends  by  joining  the  iliohypogastric;  in  such  cases  a  branch  from  the  iliohypo- 
gastric takes  the  place  of  the  ilioinguinal,  or  the  ilioinguinal  nerve  may  be  alto- 
gether absent. 

The  genitofemoral  or  genitocrural  nerve  (h.  genitofemoralis)  (Figs.  775  and  776) 
arises  from  the  first  and  second  lumbar  nerves.  It  passes  oblicjuely  through 
the  substance  of  the  Psoas  magnus  muscle,  and  emerges  from  its  inner  border  at 
a  level  corresponding  to  the  intervertebral  substance  between  the  third  and  fourth 
lumbar  vertebrfe;  it  then  descends  on  the  surface  of  the  Psoas  muscle,  under  cover 
of  the  peritoneimi,  and  divides  into  a  genital  and  a  femoral  branch. 

The  genital  branch  or  external  spermatic  nerve  (n.  spermaticus  externus)  passes 
outward  on  the  Psoas  magnus,  and  pierces  the  fascia  transversalis,- or  passes 
through  the  internal  abdominal  ring;  in  the  male  it  then  descends  along  the  back 
part  of  the  spermatic  cord  to  the  scrotum,  and  supplies  the  Cremaster  muscle. 
In  the  female  it  accompanies  the  round  ligament,  and  is  lost  upon  it. 

The  femoral  branch  or  lumboinguinal  nerve  {ii.  lumhoingidnalis)  (Fig.  777) 
descends  on  the  external  iliac  artery,  sending  a  few  filaments  around  it,  and, 
passing  beneath  Poupart's  ligament  to  the  thigh,  enters  the  sheath  of  the  femoral 
vessels,  lying  superficial  and  a  little  external  to  the  femoral  artery.  It  pierces  the 
anterior  layer  of  the  sheath  of  the  vessels,  and,  becoming  superficial  by  passing 
through  the  fascia  lata,  it  supplies  the  skin  of  the  anterior  aspect  of  the  thigh  as 
far  as  midway  between  the  pelvis  and  knee.  On  the  front  of  the  thigh  it  com- 
municates with  the  outer  branch  of  the  middle  cutaneous  nerves,  derived  from  the 
femoral  nerve.  A  few  filaments  from  this  nerve  may  be  traced  on  to  the  femoral 
artery;  they  are  derived  from  the  nerve  as  it  passes  beneath  Poupart's  ligament. 

The  External  or  Lateral  Cutaneous  Nerve  {n.  cutaneus  femoris  lateralis)  (Figs. 
776  and  777)  arises  from  the  second  and  third  lumbar  nerves.  It  emerges  from 
the  lateral  border  of  the  Psoas  magnus  muscle,  about  its  middle,  and  crosses  the 
Iliacus  muscle  obliquely,  toward  the  anterior  superior  spine  of  the  ilium.  It  then 
passes  under  Poupart's  ligament  and  over  the  Sartorius  muscle  into  the  thigh, 
where  it  divides  into  two  branches,  anterior  and  posterior. 

The  anterior  branch  descends  in  an  aponeurotic  canal  formed  in  the  fascia  lata, 
becomes  superficial  about  four  inches  below  Poupart's  ligament,  and  divides 
into  branches  which  are  distributed  to  the  integument  along  the  anterior  and  outer 
part  of  the  thigh,  as  far  down  as  the  knee.  The  terminal  filaments  of  this  nerve 
frequently  communicate  with  the  middle  and  internal  cutaneous  and  with  the 
patellar  branch  of  the  long  saphenous  nerve,  forming  with  them  the  patellar  plexus. 

The  posterior  branch  pierces  the  fascia  lata,  and  subdivides  into  branches  which 
pass  backward  across  the  outer  and  posterior  siu'face  of  the  thigh,  supplying  the 
integument  from  the  level  of  the  great  trochanter  to  the  middle  of  the  thigh. 

The  Obturator  Nerve  {n.  ohturatorius)  (Figs.  776  and  778)  supplies  the  Obturator 
externus  and  Adductor  muscles  of  the  thigh,  the  articulations  of  the  hip  and  knee, 
and  occasionally  the  integument  of  the  thigh  and  leg.  It  arises  from  the  second, 
the  third,  and  the  fourth  lumbar  nerves.  Of  these,  the  branch  from  the  third 
is  the  largest,  while  that  from  the  second  is  often  very  small.  It  descends  through 
the  inner  fibres  of  the  Psoas  magnus  muscle,  and  emerges  from  its  inner  border 
near  the  brim  of  the  pelvis;  it  then  passes  behind  the  external  iliac  vessels,  which 
separate  it  from  the  ureter,  and  runs  along  the  lateral  wall  of  the  pelvis,  above  the 
obturator  vessels,  to  the  upper  part  of  the  obturator  foramen.  Here  it  enters 
the  thigh,  and  divides  into  anterior  and  posterior  branches,  which  are  separated 
by  some  of  the  fibres  of  the  Obturator  externus  muscle,  and  lower  down  by  the 
Adductor  brevis  muscle. 


1048 


THE  NERVE  SYSTEM 


Femoral  or  anteri 
crural. 


-Anterior  tiiidL 


Anterior  division 

of  obturator. 
Internal 
cutaneous. 


Fig.  777. — Cutaneous  nerves  of  right  lower 
extremity.     Front  view. 


THE  LUMBOSACRAL  PLEXUS  1049 

The  anterior  branch  (ramus  anterior)  (Fig.  778)  passes  down  in  front  of  the 
Adductor  hrevis,  being  covered  by  the  Pectineus  and  Adductor  longiis;  at  the 
lower  border  of  the  latter  muscle,  it  communicates  with  the  internal  cutaneous  and 
internal  saphenous  nerves,  forming  a  kind  of  plexus.  It  then  descends  upon  the 
femoral  artery,  upon  ^^■hich  it  is  finally  distributed.  The  nerve,  near  the  obturator 
foramen,  gives  off  an  articular  branch  to  the  hip-joint.  Behind  the  Pectineus  it 
distributes  muscular  branches  to  the  Adductor  longus  and  Gracilis,  and  usually 
to  the  Adductor  brevis,  and  in  rare  instances  to  the  Pectineus,  and  receives  a 
communicating  branch  from  the  accessory  obturator  nerve  when  that  nerve  is 
present. 

Occasionally  the  communicating  branch  to  the  internal  cutaneous  and  interna! 
saphenous  nerves  is  continued  down,  as  a  cutaneous  branch  (ramus  cutaneus), 
to  the  thigh  and  leg.  ^^^len  this  is  so,  it  emerges  from  beneath  the  lower  border 
of  the  Adductor  longus,  descends  along  the  posterior  margin  of  the  Sartorius 
to  the  inner  side  of  the  knee,  where  it  pierces  the  deep  fascia,  communicates  with 
the  internal  or  long  saphenous  nerve,  and  is  distributed  to  the  integument  of  the 
inner  side  of  the  leg  as  low  down  as  its  middle.  When  this  communicating 
branch  is  small  its  place  is  supplied  by  the  internal  cutaneous  nerve. 

The  posterior  branch  (ramus  posterior')  pierces  the  anterior  part  of  the  Obturator 
externus,  sending  branches  to  supply  this  muscle,  and  passes  behind  the  Adductor 
brevis  on  the  front  of  the  Adductor  magnus,  where  it  divides  into  numerous 
muscular  branches,  which  supply  the  Adductor  magnus,  and  the  Adductor  brevis 
when  the  latter  does  not  receive  a  branch  from  the  anterior  division  of  the  nerve. 
It  also  gives  off  a  filament  to  the  knee-joint. 

The  articular  branch  for  the  knee-joint  is  sometimes  absent;  it  either  perforates 
the  lower  part  of  the  Adductor  magnus,  or  passes  through  the  opening  which 
transmits  the  femoral  artery,  and  enters  the  popliteal  space;  it  then  descends  upon 
the  popliteal  artery,  as  far  as  the  back  part  of  the  knee-joint,  where  it  perforates 
the  posterior  ligament,  and  is  distributed  to  the  synovial  membrane.  It  gives 
filaments  to  the  artery  in  its  course. 

The  Accessory  Obturator  Nerve  (n.  obturatorius  accessorms)  (Fig.  781)  is  present 
in  about  29  per  cent,  of  cases.  It  is  of  small  size,  and  arises  by  separate  filaments 
from  the  third  and  fourth  lumbar  nerves.  It  descends  along  the  inner  border 
of  the  Psoas  magnus  muscle,  crosses  the  ascending  ramus  of  the  os  pubis,  and 
passes  under  the  outer  border  of  the  Pectineus  muscle,  where  it  divides  into  numer- 
ous branches.  One  of  these  supplies  the  Pectineus,  penetrating  its  deep  surface; 
another  is  distributed  to  the  hip-joint;  while  a  third  communicates  with  the  anterior 
branch  of  the  obturator  nerve.  When  this  nerve  is  absent  the  hip-joint  receives 
two  branches  from  the  obturator  nerve.  Occasionally  it  is  very  small,  and 
becomes  lost  in  the  capsule  of  the  hip-joint. 

The  Femoral  or  Anterior  Crural  Nerve  (n.  femoralis)  (Figs.  776  and  778)  is  the 
largest  branch  of  the  lumbar  plexus.  It  supplies  muscular  branches  to  the  Iliacus, 
Pectineus,  and  all  the  muscles  on  the  front  of  the  thigh,  excepting  the  Tensor 
fasciae  femoris;  cutaneous  filaments  to  the  front  and  inner  side  of  the  thigh,  and 
to  the  leg  and  foot  (Fig.  772) ;  and  articular  branches  to  the  hip-  and  knee-joint. 
It  arises  from  the  second,  third,  and  fourth  lumbar  nerves,  sometimes  from  the 
first  or  fifth  as  well.  It  descends  through  the  fibres  of  the  Psoas  magnus,  emerging 
from  this  muscle  at  the  lower  part  of  its  outer  border,  and  passes  downward  be- 
tween it  and  the  Iliacus  muscle,  and  beneath  Poupart's  lig&ment,  into  the  thigh, 
where  it  becomes  somewhat  flattened,  and  divides  into  an  anterior  and  a  posterior 
part.  Under  Poupart's  ligament  it  is  separated  from  the  femoral  artery  by  a 
portion  of  the  Psoas  magnus. 

Within  the  abdomen  the  femoral  nerve  gives  off  from  its  outer  side  some  small 
muscular  branches  to  the  Iliacus,  and  a  branch  to  the  femoral  arterj'  which  is 


1050  THE  NERVE  SYSTEM 

distributed  upon  the  upper  part  of  that  vessel.     The  origin  of  this  branch  varies; 
it  occasionally  arises  higher  than  usual,  or  it  may  arise  lower  down  in  the  thigh. 
In  the  thigh  the  following  branches  are  given  off: 

From  the  Anterior  Division.  From  the  Posterior  Division. 

Middle  cutaneous.  Long  saphenous. 

Internal  cutaneous.  Muscular. 

Muscular.  Articular. 

The  middle  and  internal  cutaneous  branches  of  the  femoral  nerve  are  the 
rami  cutanei  anteriores  n.  femoralis  of  the  BNA. 

The  middle  cutaneous  nerve  (Figs.  777  and  778)  pierces  the  fascia  lata  (and 
generally  the  Sartorius)  about  three  inches  (8  cm.)  below  Poupart's  ligament,  and 
divides  into  two  branches  (Fig.  777),  which  descends  in  immediate  proximity 
along  the  fore  part  of  the  thigh,  to  supply  the  integument  as  low  as  the  front  of  the 
knee.  Here  they  communicate  with  the  internal  cutaneous  nerve  and  the  patellar 
branch  of  the  internal  saphenous  nerve,  to  form  the  patellar  plexus.  In  the  upper 
part  of  the  thigh  the  outer  division  of  the  middle  cutaneous  nerve  communicates 
with  the  femoral  branch  of  the  genitofemoral  nerve. 

The  internal  cutaneous  nerve  (Fig.  777)  passes  obliquely  across  the  upper  part 
of  the  sheath  of  the  femoral  artery,  and  divides  in  front  or  at  the  inner  side  of  that 
vessel  into  two  branches,  anterior  and  posterior  or  internal. 

The  internal  cutaneous  nerve,  before  dividing,  gives  off  a  few  filaments,  which  pierce  the 
fascia  lata  (accompanying  the  long  saphenous  vein)  to  supply  the  integument  of  the  inner  side 
of  the  thigh.  One  of  these  filaments  passes  through  the  saphenous  opening;  a  second  becomes 
subcutaneous  about  the  middle  of  the  thigh  (Fig.  777);  and  a  third  pierces  the  fascia  at  its 
lower  third  (Fig.  777). 

The  anterior  branch  runs  downward  on  the  Sartorius,  perforates  the  fascia  lata 
at  the  lower  third  of  the  thigh,  and  divides  into  two  branches,  one  of  which  supplies 
the  integument  as  low  down  as  the  inner  side  of  the  knee;  the  other  crosses  to  the 
outer  side  of  the  patella,  communicating  in  its  course  with  the  nervus  cutaneus 
patellae,  a  branch  of  the  long  or  internal  saphenous  nerve.  The  posterior  or 
internal  branch  descends  along  the  inner  border  of  the  Sartorius  muscle  to  the  knee, 
where  it  pierces  the  fascia  lata,  communicates  with  the  long  saphenous  nerve, 
and  gives  off  several  cutaneous  branches.  It  then  passes  down  to  supply  the  integ- 
ument of  the  inner  side  of  the  leg.  Beneath  the  fascia  lata,  at  the  lower  border 
of  the  Adductor  longus,  it  joins  with  branches  of  the  long  saphenous  and  obturator 
nerves  to  form  a  plexiform  network  (suhsartorial  flex-US')  (Fig.  778).  When  the 
communicating  branch  from  the  obturator  nerve  is  large  and  continued  to  the 
integument  of  the  leg,  the  internal  branch  of  the  internal  cutaneous  is  small  and 
terminates  in  the  plexus,  occasionally  giving  off  a  few  cutaneous  filaments. 

The  Muscular  Branches  of  the  Anterior  Division  (rami  viuscidares).'— The  nerve 
to  the  Pectineus  arises  from  the  femoral  nerve  immediately  below  Poupart's  liga- 
ment, and  passes  inward  behind  the  femoral  sheath  to  enter  the  anterior  sm-face 
of  the  muscle;  it  is  often  duplicated.  The  nerve  to  the  Sartorius  arises  in  common 
with  the  middle  cutaneous. 

The  long  or  internal  saphenous  nerve  (n.  saphenus)  (Figs.  777  and  778)  is  the 
largest  of  the  cutaneous  branches  of  the  femoral  nerve.  It  approaches  the  femoral 
artery  where  this  vessel  passes  beneath  the  Sartorius,  and  lies  in  front  of  it,  beneath 
the  aponeurotic  covering  of  Hunter's  canal,  as  far  as  the  opening  in  the  lower  part 
of  the  Adductor  magnus.  It  then  leaves  the  artery,  and  proceeds  distally  along  the 
inner  side  of  the  knee,  beneath  the  Sartorius  muscle,  pierces  the  fascia  lata  opposite 
the  interval  between  the  tendons  of  the  Sartorius  and  Gracilis  muscles,  and  becomes 


THE  LUMBOSACRAL  PLEXUS  1051 

subcutaneous.  The  nerve  then  passes  along  the  inner  side  of  the  leg  (Fig.  777), 
accompanied  by  the  internal  saphenous  vein,  descends  behind  the  internal  border 
of  the  tibia,  and  at  the  lower  third  of  the  leg  divides  into  two  branches;  one 
continues  its  course  along  the  margin  of  the  tibia,  terminating  at  the  inner  ankle; 
the  other  passes  in  front  of  the  ankle,  and  is  distributed  to  the  integument  along 
the  inner  side  of  the  foot,  as  far  as  the  great  toe,  communicating  with  the  internal 
branch  of  th'e  musculocutaneous  nerve. 

The  long  saphenous  nerve  about  the  middle  of  the  thiyh  gives  off  a  communicating 
branch  which  joins  the  subsartorial  plexus. 

At  the  inner  side  of  the  knee  it  gives  off  a  large  patellar  branch  (ramus  infrapatel- 
laris),  which  pierces  the  Sartorius  and  fascia  lata,  and  is  distributed  to  the  integu- 
ment in  front  of  the  patella.  This  nerve  commimicates  above  the  knee  with  the 
anterior  branch  of  the  internal  cutaneous  and  with  the  middle  cutaneous;  below 
the  knee,  with  other  branches  of  the  long  saphenous;  and  on  the  outer  side  of  the 
joint,  with  branches  of  the  external  cutaneous  nerve,  forming  a  plexiform  network, 
the  patellar  plexus.  The  patellar  branch  is  occasionally  small,  and  terminates  by 
joining  the  internal  cutaneous,  which  supplies  its  place  in  front  of  the  knee. 

Below  the  knee  the  branches  of  the  long  saphenous  nerve  are  distributed  to  the 
integument  of  the  front  and  inner  side  of  the  leg,  communicating  with  the  cutaneous 
branches  from  the  internal  cutaneous  or  from  the  obturator  nerve. 

The  Muscular  Branches  of  the  Posterior  Division  supply  the  four  parts  of  the 
Quadriceps  extensor  muscle. 

The  branch  to  the  Rectus  femoris  enters  its  under  surface  high  up,  sending  oft'  a 
small  filament  to  the  hip-joint. 

The  branch  to  the  Vastus  extemus,  of  large  size,  follows  the  course  of  the  descend- 
ing branch  of  the  external  circumflex  artery  to  the  lower  part  of  the  muscle.  It 
gives  off  an  articular  filament  to  the  knee-joint. 

The  branch  to  the  Vastus  internus  is  a  long  branch  which  runs  down  on  the 
outer  side  of  the  femoral  vessels  in  company  with  the  long  saphenous  nerve. 
It  enters  the  muscle  about  its  middle,  and  gives  off  a  filament  which  can  usually 
be  traced  downward  on  the  surface  of  the  muscle  to  the  knee-joint. 

The  branches  to  the  Crureus  are  two  or  three  in  number,  and  enter  the  muscle 
on  its  anterior  surface  about  the  middle  of  the  thigh;'a  filament  from  one  of  these 
descends  through  the  muscle  to  the  Subcrureus  and  the  knee-joint. 

The  articular  branch  to  the  hip-joint  is  derived  from  the  nerve  to  the  Rectus 
muscle. 

The  articular  branches  to  the  knee-joint  are  three  in  number.  One,  a  long  slender 
filament,  is  derived  from  the  nerve  to  the  Vastus  externus  muscle;  it  penetrates 
the  capsular  ligament  of  the  joint  on  its  anterior  aspect.  Another  is  derived  from 
the  nerve  to  the  Vastus  internus  muscle.  It  can  usually  be  traced  downward 
on  the  surface  of  this  muscle  to  near  the  joint;  it  then  penetrates  the  muscle  and 
accompanies  the  deep  branch  of  the  anastomotica  magna  artery,  pierces  the  cap- 
sular ligament  of  the  joint  on  its  inner  side,  and  supplies  the  synovial  membrane. 
The  third  branch  is  derived  from  the  nerve  to  the  Crureus. 

The  Anterior  or  Ventral  Divisions  of  the  Sacral  and  Coccygeal  Nerves 
(rami  aiiteriores)  (Fig.  781). — ^The  anterior  primary  divisions  of  the  sacral  and 
coccygeal  nerves  form  the  sacral  and  pudendal  plexuses.  The  anterior  divisions 
of  the  upper  four  sacral  nerves  enter  the  pelvis  through  the  anterior  sacral  foramina, 
that  of  the  fifth  between  the  sacrum  and  coccyx,  while  that  of  the  coccygeal 
nerve  curves  forward  below  the  rudimentary  transverse  process  of  the  first  piece 
of  the  coccyx.  The  first  and  second  sacral  are  large;  the  third,  fourth,  and  fifth 
diminish  progressively  from  above  downward.  Each  nerve  receives  a  c/ray 
ramus  conmiunicans  from  the  corresponding  ganglion  of  the  sympathetic  cord, 


1052 


THE  NERVE  SYSTEM 


^  Bi    to 

COCCYGEUS, 

_  I  i  tu  ( t/qeal. 

^B\    to'       j       Bi    to 

LEVATOR  ANI.   SPHINSTER  ANI 

Fig.  7S0. — Side  view  of  pelvis,  sbowina:  sacral  nervea 


THE  SACIiAL  PLEXUS 


1053 


while  from  the  third,  and  frequendy  from  the  second  and  fourth  anterior  sacral 
divisions,  tohite  rami  communicanies  are  given  to  the  pelvic  plexuses  of  the  sym- 
pathetic. 

THE  SACRAL  PLEXUS   (PLEXUS  SACRALIS)   (Fig.  781). 

The  sacral  plexus  is  formed  liy  the  lumbosacral  cord,  the  anterior  primary 
division  of  the  first  and  portions  of  the  anterior  primary  divisions  of  the  second 
and  third  sacral  nerves. 

The  lumbosacral  cord  comprises  the  whole  of  the  anterior  primary  division  of 
the  fifth  and  a  part  of  the  anterior  primary  division  of  the  fourth  lumbar  nerves, 
it  appears  at  the  inner  margin  of  the  Psoas  magnus  and  runs  downward  (caudad) 
over  the  pelvic  brim  to  join  the  first  sacral  nerve.  The  third  sacral  nerve  divides 
into  an  upper  and  a  lower  branch,  the  former  entering  the  sacral  and  the  latter 
the  pudendal  plexus 


FOURTH   LUMBAR 


FTH   LUMBAR 


SECOND   SACRAL 

THIRD   SACRAL 
FOURTH   SACRAL 

EAL  Bn.  TO  SPHINCTEl 
A  LEVATOR  ANI 

FTH   SACRAL 

TO  COCCYGEUS 

-COCCYGEAL 


with  the  pudendal  plexus.      CGerrish.)     (See  text  for  variations  in  origin  of 
the  perforating  cutaneous  nerve.) 


The  branches  or  divisions  forming  the  sacral  plexus  converge  toward  the  lower 
part  of  the  great  sacrosciatic  foramen,  and  unite  to  form  a  flattened  band, 
from  the  anterior  and  posterior  surfaces  of  which  several  branches  arise.  The 
band  itself  is  continued  as  the  great  sciatic  nerve,  which  splits  on  the  back  of  the 
thigh  into  the  internal  and  external  popliteal  nerves;  these  two  nerves  sometimes 
arise  separately  from  the  plexus,  and  in  all  cases  their  independence  can  be  shown 
by  dissection. 

Relations. — The  sacral  plexus  lies  on  the  anterior  or  ventral  surface  of  the  pelvic  part  of 
the  Pyriformis  and  is  covered  in  front  by  the  pelvic  fascia,  which  separates  it  from  the  internal 
iliac  vessels,  the  ureter  and  the  pelvic  colon.  The  gluteal  vessels  run  between  the  lumbosacral 
cord  and  the  first  sacral  nerve,  and  the  sciatic  vessels  between  the  second  and  third  sacral  nerves. 


1054  THE  NERVE  SYSTEM 

All  the  nerves  entering  the  plexus,  with  the  exception  of  the  third  sacral,  split  into  anterior 
and  posterior  divisions,  and  the  nerves  arising  from  these  are  as  follows: 

Anterior  or  Ventral       Posterior  or  Dorsal 
Divisions.  Divisions. 

Nerve  to  Quadratus  femoris  and  Gemellus  inferior  4,  5,  L.  1,  S. 

Nerve  to  Obturator  internus  and  Gemellus  superior  5,  L.  1,2,  S. 

Nerve  to  Pyriformis (1),2,  S. 

Superior  gluteal 4,  5,  L.  1 ,  S. 

Inferior  gluteal 5,  L.  1,2,  S. 

Small  sciatic 1, 2,  3,  S. 

„      ,     .  ,.      f  Internal  popliteal 4, 5,  L.  1.2.  3,  S. 

Great  sciatic    |  External  popliteal 4,5,L.1,2,S. 

The  nerve  to  the  Quadratus  femoris  and  Gemellus  inferior  arises  from  the  anterior 
divisions  of  the  fourth  and  fifth  kimbar  and  first  sacral  nerves;  it  leaves  the  pelvis 
through  the  great  sacrosciatic  foramen,  below  the  Pyriformis,  and  runs  downward 
beneath  the  great  sciatic  nerve,  the  Gemelli,  and  the  tendon  of  the  Obturator 
internus,  enters  the  anterior  surface  of  these  muscles;  it  gives  off  an  articular 
branch  to  the  hip-joint. 

The  nerve  to  the  Obturator  internus  arises  from  the  anterior  divisions  of  the 
fifth  lumbar  and  first  and  second  sacral  nerves;  it  leaves  the  pelvis  throiigh  the 
great  sacrosciatic  foramen  below  the  Pyriformis  muscle,  crosses  the  ischial  spine, 
reenters  the  pelvis  through  the  small  sacrosciatic  foramen,  and  ends  in  the  Obturator 
internus,  after  entering  the  pelvic  surface  of  that  muscle.  The  branch  to  the 
Gemellus  superior  enters  the  upper  part  of  the  posterior  surface  of  that  muscle. 

The  nerve  to  the  Pyriformis  arises  from  the  posterior  division  of  the  second, 
or  the  posterior  divisions  of  the  first  and  second  sacral  nerves,  and  enters  the 
anterior  surface  of  the  muscle;  this  nerve  may  be  double. 

The  Superior  Gluteal  Nerve  {n.  giutaeus  superior)  (Figs.  781  and  783)  arises 
from  the  posterior  divisions  of  the  fourth  and  fifth  lumbar  and  first  sacral 
nerves;  it  leaves  the  pelvis  through  the  great  sacrosciatic  foramen  above  the  Pyri- 
formis, accompanied  by  the  gluteal  vessels,  and  divides  into  a  superior  and  an 
inferior  branch.  The  superior  branch  accompanies  the  upper  branch  of  the  deep 
division  of  the  gluteal  artery,  and  ends  in  the  Gluteus  minimus  after  giving  off 
branches  to  supply  a  part  of  the  Gluteus  medius.  The  inferior  branch  accompanies 
the  lower  branch  of  the  gluteal  artery  across  the  Gluteus  minimus;  it  gives  fila- 
ments to  the  Gluteus  medius  and  Gluteus  minimus,  and  ends  in  the  Tensor 
fasciae  femoris. 

The  Inferior  Gluteal  Nerve  (?!.  giutaeus  inferior)  (Fig.  781)  arises  from  the 
posterior  divisions  of  the  fifth  lumbar  and  first  and  second  sacral  nerves ;  it  leaves 
the  pelvis  through  the  great  sacrosciatic  foramen,  below  the  Pyriformis  muscle, 
and  divides  into  branches,  which  enter  the  deep  surface  of  the  Gluteus  maximus. 

The  Small  Sciatic  [n.  cutaneus  femoris  posterior)  (Figs.  781  and  783),  or  post- 
femoral  cutaneous  nerve  supplies  the  integument  of  the  perineum  and  back  part 
of  the  thigh  and  leg.  It  arises  partly  from  the  anterior  and  pardy  from  the  pos- 
terior divisions  of  the  first,  second,  and  third  sacral  nerves,  and  emerges  from  the 
pelvis  through  the  great  sacrosciatic  foramen  below  the  Pyriformis.  It  then 
descends  beneath  the  Gluteus  maximus  with  the  sciatic  artery,  and  passes  down 
the  back  part  of  the  thigh  beneath  the  fascia  lata,  and  over  the  long  head  of  the 
Biceps  to  the  lower  part  of  the  popliteal  region,  here  it  pierces  the  fascia  and 
accompanies  the  external  saphenous  vein  {v.  saphena  parva)  to  about  the  middle 
of  the  back  of  the  leg,  its  terminal  filaments  communicating  with  the  sural  or 
external  saphenous  nerve. 

The  branches  of  the  small  sciatic  nerve  are  all  cutaneous,  and  are  grouped  as 
follows:  gluteal,  perineal,  and  femoral. 


THE  SACBAL  PLEXUS  1055 

The  gluteal  cutaneous  branches  {nn.  chmium  inferiores  [laterales]),  two  or  three 
in  number,  turn  upward  around  the  lower  border  of  the  Gluteus  maximus  to 
supply  the  skin  covering  the  lower  and  outer  part  of  that  muscle. 

The  perineal  cutaneous  branches  {rami  perineales)  are  distributed  to  the  skin  at 
the  upper  and  inner  side  of  the  thigh,  on  its  posterior  aspect.  One  branch, 
longer  than  the  rest,  the  inferior  pudendal  or  long  scrotal  nerve  (Fig.  783),  curves 
forward  below  the  ischial  tuberosity,  pierces  the  fascia  lata,  and  runs  forward 
beneath  the  superficial  fascia  of  the  perineum  to  be  distributed  to  the  skin  of  tire 
scrotum  in  the  male  and  the  labium  majus  in  the  female,  communicating  with  the 
superficial  perineal  and  inferior  liemorrhoidal  nerves. 

The  femoral  cutaneous  branches  consist  of  numerous  descending  filaments 
derived  from  botli  sides  of  the  nerve,  and  are  distributed  to  the  back  and  inner 
sides  of  the  thigh,  to  the  skin  covering  the  popliteal  space,  and  to  the  upper  part 
of  the  leg. 

The  Great  Sciatic  Nerve  (n.  ischiadicus)  (Figs.  781  and  883)  supplies  nearly 
the  whole  of  the  integument  of  tlie  leg,  the  muscles  of  the  back  of  the  thigh,  and 
those  of  the  leg  and  foot.  It  is  tlie  largest  nerve  cord  in  the  body,  measuring 
three-quarters  of  an  inch  in  breadth,  and  is  the  continuation  of  the  flattened  band 
of  the  sacral  plexus.  It  passes  out  of  the  pelvis  through  the  great  sacrosciatic 
foramen,  below  the  Pyriformis  muscle.  It  descends  between  the  great  trochanter 
of  the  femur  and  the  tuberosity  of  the  ischium,  along  the  back  part  of  the  thigh,  to 
about  its  lower  third,  where  it  divides  into  two  large  branches,  the  internal  popliteal 
or  tibial  and  external  popliteal  or  peroneal  nerves  (Fig.  783).  This  division  may  take 
place  at  any  point  between  the  sacral  plexus  and  the  lower  third  of  the  thigh. 
When  the  division  occurs  at  the  plexus  (in  10  per  cent,  of  cases)  the  two  nerves 
descend  together  side  by  side;  or  they  may  be  separated,  at  their  commencement, 
by  the  interposition  of  part  or  the  whole  of  the  Pyriformis  muscle. 

As  the  nerve  descends  along  the  back  of  the  thigli,  it  rests  upon  the  posterior 
surface  of  the  ischium,  the  nerve  of  the  Quadratus  femoris.  and  the  External 
rotator  muscles  of  the  thigh,  in  company  with  the  small  sciatic  nerve  and  arteryji^lt^: 
and  is  covered  by  the  Gluteus  maximus;  lower  down,  it  lies  upon  the  Adductor 
magnus,  and  is  covered  by  the  long  head  of  the  Biceps. 

The  branches  of  the  nerve,  before  its  division,  are  articular  and  muscular. 

The  articular  branches  (rami  ariiculares)  arise  from  the  upper  part  of  the  nerve; 
they  supply  the  hip-joint,  perforating  the  posterior  part  of  its  fibrous  capsule. 
Tliese  branches  are  sometimes  derived  directly  from  the  sacral  plexus. 

The  muscular  branches  (rami  inusculares)  are  distributed  to  the  flexors  of  the  leg 
— ^viz.,  the  Biceps,  Semitendinosus,  and  Semimembranosus,  and  to  the  Adductor 
magnus.  The  nerve  to  the  short  liead  of  the  Biceps  comes  from  the  external 
popliteal  part  of  the  great  sciatic,  while  the  other  muscular  branches  arise  from  tlie 
internal  popliteal  portion,  as  may  be  seen  in  those  cases  where  the  two  popliteal 
nerves  emerge  separately  on  the  buttock. 

The  Internal  Popliteal  or  Tibial  Nerve  {n.  tibialis)  (Figs.  781  and  783),  the  larger 
of  the  two  terminal  branches  of  the  great  sciatic,  arises  from  the  anterior  primary 
branches  of  tlie  last  two  lumbar  and  first  three  sacral  nerves.  It  descends  along 
the  back  part  of  the  thigh,  tlirough  the  middle  of  the  popliteal  space,  to  the  lower 
part  of  tlie  Popliteus  muscle,  where  it  passes  with  the  artery  beneath  the  arch  of 
the  Soleus  and  becomes  the  posterior  tibial.  It  is  overlapped  by  the  Hamstring 
muscles  above,  and  then  becomes  more  superficial,  and  lies  to  the  outer  side  of, 
and  some  distance  from,  the  popliteal  vessels;  opposite  the  knee-joint  it  is  in  close 
relation  with  tlie  vessels,  and  crosses  to  the  inner  side  of  the  artery.  Below,  it 
is  overlapped  by  the  Gastrocnemius. 

The  branches  of  this  nerve  are  the  articular  and  muscular,  and  a  cutaneous  branch, 
the  commimicans  tibialis. 


1056 


THE  NER  VE  SYSTEM 


f\ 


Piidic 
Nerve  to 
obturaior  intemus 


Fig.  7S2.— Cut; 

extremity.     Posti 

^N.  B. — In  this  diagram  the  communicans  tibialis  and  communicans  peronei  are  not  in  their  normal  position. 
They  have  been  displaced  by  the  removal  of  the  superficial  muscles.  The  external  saphenous  nerve  is  formed  by  the 
junction  of  the  two  communicantes. 


THE  SACRAL  PLEXUS  1057 

The  articular  branches  {rami  ariiculares),  usually  three  in  number,  supply  the 
knee-joint;  two  of  these  branches  accompany  the  superior  and  inferior  internal 
articular  arteries,  and  a  third,  the  azygos  articular  artery. 

The  muscular  branches  (rami  muficularea),  four  or  five  in  number,  arise  from  the 
nerve  as  it  lies  between  the  two  heads  of  the  Gastrocnemius;  they  supply  that 
muscle  and  the  Plantaris,  Soleus,  and  Popliteus.  The  branch  which  supplies 
the  Popliteus  turns  around  its  lower  border  and  is  distributed  to  the  deep  surface 
of  the  muscle. 

The  communicans  tibialis  (n.  cutaneus  surae  medialis)  descends  between  the  two 
heads  of  the  Gastrocnemius,  and  about  the  middle  of  the  back  of  the  leg  pierces 
the  deep  fascia,  and  joins  a  communicating  branch  (ramus  anastomoiicus  pero- 
naeus)  from  the  external  popliteal  nerve  to  form  the  short  or  external  saphenous 
nerve  (Fig.  783).  The  external  saphenous  nerve,  formed  by  the  communicating 
branches  of  the  internal  and  external  popliteal  nerves,  passes  downward  and  out- 
ward near  the  outer  margin  of  the  tendo  Achillis,  lying  close  to  the  external  saphe- 
nous vein,  to  the  interval  between  the  external  malleolus  and  the  os  calcis.  It 
divides  into  two  branches,  the  posterior  of  which  breaks  up  into  lateral  calcaneal 
branches  (rami  calcanei  lateralcs).  The  anterior  branch  (n.  cutaneus  dorsalis 
lateralis)  winds  around  the  outer  malleolus,  and  is  distributed  to  the  integument 
along  the  outer  side  of  the  foot  and  little  toe,  communicating  on  the  dorsum  of 
the  foot  with  the  musculocutaneous  nerve.  In  the  leg  its  branches  communicate 
with  those  of  the  small  sciatic.  The  cutaneous  area  supplied  by  the  external 
saphenous  nerve  is  indicated  in  Fig.  785. 

The  Posterior  Tibial  Nerve  (Fig.  783),  the  direct  continuation  of  the  internal  pop- 
liteal nerve,  commences  at  the  lower  border  of  the  Popliteus  muscle,  and  passes 
along  the  back  part  of  the  leg  with  the  posterior  tibial  vessels  to  the  interval 
between  the  inner  malleolus  and  the  heel,  where  it  divides  into  the  external  and 
internal  plantar  nerves.  It  lies  upon  the  deep  muscles  of  the  leg,  and  is  covered 
above  by  the  muscles  of  the  calf,  lower  down  by  the  skin  and  fascia.  In  the 
upper  part  of  its  course  it  lies  to  the  inner  side  of  the  posterior  tibial  artery,  but  it 
soon  crosses  that  vessel,  and  lies  to  its  outer  side  as  far  as  the  ankle.  In  the  lower 
third  of  the  leg  it  is  placed  parallel  with  the  inner  margin  of  the  tendo  Achillis. 

The  branches  of  the  posterior  tibial  nerve  are  muscular,  internal  calcaneal,  and 
articular. 

The  muscular  branches  {rami  musculares)  arise  either  separately  or  by  a  common 
trunk  from  the  upper  part  of  the  nerve.  They  supply  the  Soleus,  Tibialis  pos- 
ticus. Flexor  longus  digitorum,  and  Flexor  longus  hallucis  muscles;  the  branch 
to  the  latter  muscle  accompanies  the  peroneal  artery.  The  branch  to  the  Soleus 
enters  the  deep  surface  of  the  muscle,  while  that  from  the  internal  popliteal  enters 
the  superficial  surface. 

The  internal  calcaneal  branches  (rami  calcanei  mediales)  perforate  the  internal 
annular  ligament,  and  supply  the  integument  of  the  heel  and  inner  side  of  the  foot 
(Fig.  785)_. 

The  articular  branch  (ramus  articidaris  ad  articulationem  talocruralem)  is  given 
oft'  just  above  the  bifurcation  of  the  nerve  and  supplies  the  ankle-joint. 

The  Internal  Plantar  Nerve  (n.  plantaris  medialis)  (Fig.  784),  the  larger  of  the 
two  terminal  branches  of  the  internal  popliteal,  accompanies  the  internal  plantar 
artery  along  the  inner  side  of  the  foot.  From  its  origin  at  the  inner  ankle  it  passes 
beneath  the  Abductor  hallucis,  and  then  forward  between  this  muscle  and  the 
Flexor  brevis  digitorum;  it  divides  opposite  the  bases  of  the  metatarsal  bones  into 
four  plantar  digital  branches  (nn.  digifales  plantares  communes)  and  communicates 
with  the  plantar  nerve. 

Branches. — In  its  course  the  internal  plantar  nerve  gives  oft'  cutaneous  branches, 
which  pierce  the  plantar  fascia  and  supply  the  integument  of  the  sole  of  the  foot 


1058 


THE  ]S,ERVE  SYSTEM 


(Fig.  785);  muscular  branches,  \\hich  supply  the  Abductor  hallucis  and  Flexor 
brevis  digitorum;  articular  branches,  to  the  articulations  of  the  tarsus  and  meta- 
tarsus; and  four  plantar  digital  branches  (/;«.  digitales  plantares  proprii).  The 
first  (innermost)  branch  becomes  cutaneous  about  the  middle  of  the  sole,  between 
the  Adductor  hallucis  and  Flexor  brevis  digitorum;  the  three  outer  branches  pass 
between  the  divisions  of  the  plantar  fascia  in  the  clefts  between  the  toes.  They 
are  distributed  in  the  following  manner:  The  first  supplies  the  inner  border  of 
the  great  toe,  and  sends  a  filament  to  the  Flexor  brevis  hallucis  muscle;  the  second 
bifurcates,  to  supply  the  adjacent  sides  of  the  great  and  second  toes,  sending  a  fila- 
ment to  the  First  lumbrical  muscle ;  the  third  supplies  the  adjacent  sides  of  the  second 
and  third  toes;  the  fourth  supplies  the  corresponding  sides  of  the  third  and  fourth 
toes,  and  receives  a  communicating  branch  from  the  external  plantar  nerve  (Fig. 
784).  Each  digital  nerve  gives  off  cutaneous  and  articular  filaments;  and  opposite 
the  last  phalanx  sends  a  dorsal  branch,  which  supplies  the  structures  around  the 

nail,  the  continuation  of  the  nerve  being  dis- 
tributed to  the  ball  of  the  toe.  It  will  be 
observed  that  the  distribution  of  these  branches 
is  precisely  similar  to  that  of  the  median  nerve 
in  the  hand. 

The  External  Plantar  Nerve  (n.  plantaris  later- 
alis) (Fig.  784),  the  smaller  of  the  two,  completes 
the  nerve  supply  to  the  structures  of  the  sole  of 
the  foot  (Fig.  785),  being  distributed  to  the  little 


Lateral 
plantar. 


Fig  784. — The  plantar  nervea 


Fig,  785. — Areas  of  distribution  of  the  cutaneous  nerves  of  the 
sole      (W   Keiller,  in  Gerrish's  Text-book  of  Anatomy. 5 


toe  and  outer  half  of  the  fourth,  as  well  as  to  most  of  the  deep  muscles,  its  dis- 
tribution being  similar  to  that  of  the  ulnar  nerve  in  the  hand.  It  passes  obliquely 
forward  with  the  external  plantar  artery  to  the  outer  side  of  the  foot,  lying  between 
the  Flexor  brevis  digitorum  and  Flexor  accessorius ;  and  in  the  interval  between 
the  former  muscle  and  Abductor  minimi  digiti,  divides  into  a  superficial  and  a 
deep  branch.  Before  its  division  it  supplies  the  Flexor  accessorius  and  Abductor 
minimi  digiti. 

The  superficial  branch  {ramus  superficialis)  separates  into  two  digital  nerves. 
One,  the  smaller  of  the  two,  supplies  the  outer  side  of  the  little  toe,  the  Flexoi 
brevis  minimi  digiti,  and  the  two  Interosseous  muscles  of  the  fourth  metatarsal 


THE  SACRAL  PLEXUS  1059 

space;  the  other  and  larger  digital  branch  supplies  the  adjoining  sides  of  the  fourth 
and  fifth  toes,  and  communicates  with  the  internal  plantar  nerve. 

The  deep  or  muscular  branch  (ramus  profundus)  accompanies  the  external  plantar 
artery  into  the  deep  part  of  the  sole  of  the  foot,  beneath  the  tendons  of  the  Flexor 
muscles,  and  Adductor  obliquus  hallucis,  and  supplies  all  the  Interossei  (except 
those  in  the  fourth  metatarsal  space),  the  three  outer  Lumbricales,  the  Adductor 
obliquus  hallucis,  and  the  Adductor  transversus  hallucis. 

The  External  Popliteal  or  Peroneal  Nerve  (/(.  peronaeiis  communis)  (Figs.  781 
and  783),  about  one-half  the  size  of  the  internal  popliteal,  is  derived  from  the 
posterior  branches  of  the  last  two  lumbar  and  first  two  sacral  nerves.  It  descends 
obliquely  along  the  outer  sides  of  the  popliteal  space  to  the  head  of  the  fibula, 
close  to  the  inner  margin  of  the  Biceps  muscle.  It  is  easily  felt  beneath  the  skin 
behind  the  head  of  the  fibula  at  the  inner  side  of  the  tendon  of  the  Biceps.  It 
passes  between  the  tendon  of  the  Biceps  and  outer  head  of  the  Gastrocnemius, 
winds  around  the  neck  of  the  fibula,  between  the  Peroneus  longus  and  the  bone, 
and  divides  beneath  the  muscle  into  the  anterior  tibial  and  musculocutaneous 
nerves. 

The  branches  of  the  external  popliteal  nerve,  previous  to  its  division,  are  articular 
and  cutaneous. 

The  articular  branches  (rami  articulares)  are  three  in  number:  two  of  these 
accompany  the  superior  and  inferior  external  articular  arteries  to  the  outer  side 
of  the  knee.  The  upper  one  occasionally  arises  from  the  great  sciatic  nerve 
before  its  bifurcation.  The  third  (recurrent)  articular  nerve  is  given  off  at  the 
point  of  division  of  the  external  popliteal  nerve;  it  ascends  with  the  anterior 
recurrent  tibial  artery  through  the  Tibialis  anticus  muscle  to  the  front  of  the  knee, 
which  it  supplies. 

The  Lateral  Cutaneous  Branch  (?;.  cutaneous  surae  lateralis). — There  may  be 
two  or  three  of  these  branches.  They  supply  the  integument  along  the  back 
part  and  outer  side  of  the  leg.  The  largest  cutaneous  branch  of  the  peroneal 
is  the  communicans  peronei  (ramus  anastomoticus  -peronaeu-s) ,  which  arises  near  the 
head  of  the  fibula,  crosses  the  external  head  of  the  Gastrocnemius  to  the  middle  of 
the  leg,  and  joins  with  the  communicans  tibialis  to  form  the  external  saphenous 
nerve.  This  nerve  occasionally  exists  as  a  separate  branch,  which  is  continued 
as  far  down  as  the  heel. 

The  Anterior  Tibial  Nerve  or  Deep  Peroneal  (n.  peronaeus  profundus)  (Fig.  778) 
commences  at  the  bifurcation  of  the  peroneal  nerve,  between  the  fibula  and  upper 
part  of  the  Peroneus  longus,  passes  obliquely  downward  beneath  the  Extensor 
longus  digitorum  muscle  to  the  fore  part  of  the  interosseous  membrane,  and 
gets  into  relation  with  the  anterior  tibial  artery  above  the  middle  of  the  leg; 
it  then  descends  with  the  artery  to  the  front  of  the  ankle-joint,  where  it  divides 
into  an  external  and  an  internal  branch.  This  nerve  lies  at  first  on  the  outer  side 
of  the  anterior  tibial  artery,  then  in  front  of  it,  and  again  at  its  outer  side  at  the 
ankle-joint. 

The  branches  of  the  anterior  tibial  nerve  in  its  course  through  the  leg  are  the 
muscular  branches  (rami  miiscidares)  to  the  Tibialis  anticus.  Extensor  longus 
digitorum,  Peroneus  tertius,  and  Extensor  proprius  hallucis  muscles,  and  an 
articular  branch  to  the  ankle-joint. 

The  external  or  tarsal  branch  of  the  anterior  tibial  nerve  passes  outward  across  the 
tarsus,  beneath  the  Extensor  brevis  digitorum,  and,  having  become  enlarged 
like  the  posterior  interosseous  nerve  at  the  wrist,  supplies  the  Extensor  brevis 
digitorum  muscle.  From  the  enlargement  three  minute  interosseous  branches 
are  given  off  which  supply  the  tarsal  joints  and  the  metatarsophalangeal  joints 
of  the  second,  third,  and  fourth  toes.  The  first  of  these  sends  a  filament  to  the 
Second  dorsal  interosseous  muscle. 


1060  THE  NERVE  8YBTEM 

The  internal  branch,  the  continuation  of  the  nerve,  accompanies  the  dorsalis 
pedis  artery  along  the  inner  side  of  the  dorsum  of  the  foot,  and  at  the  first  inter- 
osseous space  divides  into  two  dorsal  digital  branches  {nn.  digitales  dorsales  hal- 
lucis  lateralis  et  digiti  secundi  medialis),  which  supply  the  adjacent  sides  of  the 
great  and  second  toes,  communicating  with  the  internal  branch  of  the  musculo- 
cutaneous nerve.  Before  it  divides  it  gives  off  to  the  first  space  an  interosseous 
branch  which  supplies  the  metatarsophalangeal  joint  of  the  great  toe  and  sends  a 
branch  to  the  First  dorsal  interosseous  muscle. 

The  Musculocutaneous  Nerve  (;;.  peronaeus  superficialis)  (Fig.  778)  supplies  the 
muscles  on  the  fibular  side  of  the  leg  and  the  integument  over  the  greater  part 
of  the  dorsum  of  the  foot.  It  passes  forward  between  the  Peronei  muscles  and 
the  Extensor  longus  digitorum,  pierces  the  deep  fascia  at  the  lower  third  of  the 
leg  on  its  front  and  outer  side,  and  divides  into  two  branches.  This  nerve  in 
its  course  between  the  muscles  gives  off  muscular  branches  to  the  Peroneus  longus 
and  brevis,  and  cutaneous  branches  to  the  integument  of  the  lower  part  of  the  leg. 

The  internal  dorsal  cutaneous  branch  (n.  cutaneus  dorsalis  medialis)  of  the  muscu- 
locutaneous nerve  passes  in  front  of  the  ankle-joint  and  divides  into  three  dorsal 
digital  branches  («;;.  digitales  dorsales  pedis).  The  internal  branch  supplies  the 
skin  of  the  dorsum  of  the  foot  and  the  inner  side  of  the  great  toe,  and  communicates 
with  the  internal  saphenous  nerve.  The  intermediate  branch  runs  to  the  space 
between  the  great  and  second  toes,  supplies  the  adjacent  sides  of  these,  and  com- 
municates with  the  anterior  tibial  nerve.  The  external  branch  passes  to  the 
space  between  the  second  and  third  toes  and  supplies  the  adjacent  sides  of  these. 

The  external  dorsal  cutaneous  branch  (h.  cutaneus  dorsalis  intermediu-s),  the 
smaller,  passes  along  the  outer  side  of  the  dorsum  of  the  foot,  and  divides  into  two 
dorsal  digital  branches,  the  inner  being  distributed  to  the  adjacent  sides  of  the 
third  and  fourth  toes,  the  outer  to  the  adjacent  sides  of  the  fourth  and  fifth  toes. 
It  also  supplies  the  integument  of  the  outer  ankle  and  outer  side  of  the  foot  and 
communicates  with  the  external  saphenous  nerve. 

The  branches  of  the  musculocutaneous  nerve  supply  all  the  toes  excepting  the 
outer  side  of  the  little  toe,  which  is  supplied  by  the  small  saphenous  nerve.  The 
adjoining  sides  of  the  great  and  second  toes  are  also  supplied  by  the  internal  branch 
of  the  anterior  tibial.  It  frequently  happens  that  some  of  the  outer  branches  of 
the  musculocutaneous  are  absent,  their  place  being  then  taken  by  branches  of 
the  external  saphenous  nerve. 


THE  PUDENDAL  PLEXUS   (PLEXUS  PUDENDUS), 

The  pudendal  plexus  (Fig.  781)  is  not  sharply  marked  off  from  the  sacral 
plexus,  some  of  the  branches  which  spring  from  it  may  arise  in  conjunction  with 
those  of  the  sacral  plexus.  It  lies  on  the  posterior  wall  of  the  pelvis  and  is  usually 
formed  by  branches  from  the  ventral  primary  divisions  of  the  second  and  third 
sacral  nerves  the  whole  of  the  anterior  primary  divisions  of  the  fourth  and  fifth 
sacral  nerves,  and  the  coccygeal  nerve. 

It  gives  off  the  following  branches; 

Perforating  cutaneous  (variable) .  (2,  3.  S.)  (3, 4,  S.)  (4,  5,  S.) 

Pudic , .,„...  2, 3, 4,  S, 

Visceral    .  '    .      .     .     3, 4,  S. 

Muscular  . ,     .     .  4,  S. 

Anococcygeal ,  4, 5,  S,  and  Cocc. 

The  Perforating  Cutaneous  Nerve  (Fig.  781)  is  not  always  present.  It  sometimes 
arises  from  the  second  and  third  sacral  nerves,  or  from  the  third  and  fourth,  or 


•       THE  PUDENDAL  PLEXUS  1061 

even  fourth  and  fifth  sacral  nerves,  and  is  of  small  size.  When  present,  it  pierces 
the  lower  part  of  the  great  sacrosciatic  ligament,  and,  winding  around  the  lower 
border  of  the  Gluteus  maximus,  supplies  the  integument  covering  the  inner  and 
lower  part  of  that  muscle.  When  absent,  its  place  is  taken  either  by  a  cutaneous 
branch  of  the  small  sciatic,  or  by  the  greater  coccygeal  jxrforafing  nerve  of  Eisler. 

The  Pudic  Nerve  (h.  imdendus)  (Figs.  781  and  783)  derives  its  fibres  from  the 
anterior  branches  of  the  second,  third,  and  fourth  sacral  nerves.  It  leaves  the 
pelvis  below  the  Pyriformis  through  the  great  sacrosciatic  foramen.  It  then  crosses 
the  spine  of  the  ischium,  and  enters  the  pelvis  through  the  lesser  sacrosciatic 
foramen.  It  accompanies  the  pudic  vessels  upward  and  forward  along  the  outer 
wall  of  the  ischiorectal  fossa,  being  contained  in  a  sheath  of  the  obturator  fascia, 
termed  Alcock's  canal,  and  divides  into  two  terminal  branches,  the  perineal  nerve, 
and  the  dorsal  nerve  of  the  penis  or  clitoris.  Before  its  division  it  gives  off  the 
inferior  hemorrhoidal  nerve. 

The  inferior  hemorrhoidal  nsrve  {ii.  hemorrhoidalis  inferior)  is  occasionally 
derived  separately  from  the  sacral  plexus  (3d  S.).  It  passes  across  the  ischio- 
rectal fossa,  with  its  accompanying  vessels,  toward  the  lower  end  of  the  rectum, 
and  is  distributed  to  the  Sphincter  ani  externus  and  to  the  integument  around  the 
anus.  Branches  of  this  nerve  communicate  with  the  inferior  pudendal  and  super- 
ficial perineal  nerves  at  the  fore  part  of  the  perineum. 

The  perineal  nerve  (n.  perinei),  the  inferior  and  larger  of  the  two  terminal 
branches  of  the  pudic,  is  situated  below  the  pudic  artery.  It  accompanies  the 
superficial  perineal  artery  in  the  perineum,  dividing  into  cutaneous  and  muscular 
branches. 

The  cutaneous  branches  (superficial  perineal)  are  two  in  number,  posterior  and 
anterior.  The  posterior  or  external  branch  pierces  the  base  of  the  triangular  liga- 
ment of  the  urethra,  and  passes  forward  along  the  outer  side  of  the  urethral 
triangle  in  company  with  the  superficial  perineal  artery;  it  is  distributed  to  the 
skin  of  the  scrotum  (nn.  scrotales  posteriores)  or  to  the  labium  majus  in  the  female 
(mi.  labiales  posteriores).  It  communicates  with  the  inferior  hemorrhoidal,  the 
inferior  pudendal,  and  the  other  superficial  perineal  nerve.  The  anterior  or 
internal  branch  also  pierces  the  base  of  the  triangular  ligament,  and  passes  forward 
nearer  to  the  middle  line,  to  be  distributed  to  the  inner  and  back  part  of  the  scro- 
tum.    Both  these  nerves  supply  the  labium  majus  in  the  female. 

The  muscular  branches  are  distributed  to  the  Transversus  perinaei,  Accelerator 
urinae.  Erector  penis,  and  Compressor  urethrae.  A  distinct  branch  is  given  off 
from  the  nerve  to  the  Accelerator  urinae,  pierces  this  muscle,  and  supplies  the 
corpus  spongiosum,  ending  in  the  mucous  membrane  of  the  urethra.  This  is  the 
nerve  to  the  bulb. 

The  Dorsal  Nerve  of  the  Penis  (??.  dorsalis  penis)  is  the  deepest  division  of  the 
pudic  nerve;  it  accompanies  the  pudic  artery  along  the  ramus  of  the  ischium;  it 
then  runs  forward  along  the  inner  margin  of  the  ramus  of  the  os  pubis,  between 
the  superficial  and  deep  layers  of  the  triangular  ligament.  Piercing  the  superficial 
layer,  it  gives  a  branch  to  the  corpus  cavernosum,  and  passes  forward,  in  company 
with  the  dorsal  artery  of  the  penis,  between  the  layers  of  the  suspensory  ligament, 
on  to  the  dorsum  of  the  penis,  along  which  it  is  carried  as  far  as  the  glans  on  which 
it  ends. 

In  the  female  the  dorsal  nerve  is  very  small,  and  supplies  the  clitoris  (/(.  dorsalis 
cliforidis). 

The  visceral  branches  arise  from  the  third  and  fourth,  and  sometimes  the  second, 
sacral  nerves  and  are  distributed  to  the  bladder  and  rectum,  and,  in  the  female, 
to  the  vagina;   they  communicate  with  the  pelvic  plexuses  of  the  sympathetic. 

The  muscular  branches  are  derived  from  the  fourth  sacral,  and  supply  the  Levator 
ani,  Coccygeus,  and  Sphincter  ani  externus.     The  branches  to  the  Levator  ani 


1062  THE  NEB  VE  SYSTEM 

and  Coccygeus  enfer  their  pelvic  surfaces;  that  to  the  Sphincter  ani  externu? 
(perineal  branch)  reaches  the  ischiorectal  fossa  by  piercing  the  Coccygeus  or  by 
passing  between  it  and  the  Levator  ani.  Cutaneous  branches  from  this  branch 
supply  the  skin  between  the  anus  and  the  coccyx. 

Anococcygeal  Branches  (nn.  anococcygei). — The  fifth  sacral  nerve  receives  a 
communicating  branch  from  the  fourth,  and  unites  with  the  coccygeal  nerve  to 
form  the  coccygeal  plexus  (plexus  coccygeus).  From  this  plexus  the  anococcygeal 
nerves  take  origin;  they  consist  of  a  few  fine  filaments  which  pierce  the  great 
sacrosciatic  ligament  to  supply  the  skin  in  the  region  of  the  coccyx. 

Applied  Anatomy. — The  lumbar  plexus  is  formed  in  the  Psoas  magnus,  and,  therefore,  in 
Psoa,s  abscess  any  or  all  of  its  branches  may  be  irritated,  causing  severe  pain  in  the  parts  to  which 
the  irritated  nerves  are  distributed.  The  genitofemoral  nerve  is  the  one  which  is  most  frequently 
implicated.  Tiie  nerve  is  also  of  importance,  as  it  is  concerned  in  one  of  the  reflexes  employed 
in  the  investigation  of  diseases  of  the  spine.  If  the  skin  over  the  inner  side  of  the  thigh  just 
below  Poupart's  ligament,  the  part  supplied  by  the  femoral  branch  of  the  genitofemoral  nerve, 
be  gently  tickled  in  a  male  child,  the  testicle  will  be  noticed  to  be  drawn  upward  through  the 
action  of  the  Cremaster,  which  is  supplied  by  the  genital  branch  of  the  same  nerve.  The  same 
result  may  sometimes  be  noticed  in  adults,  and  can  almost  always  be  produced  by  severe  stimu- 
lation. This  reflex,  when  present,  shows  that  the  portion  of  the  cord  from  which  the  first  and 
second  lumbar  nerves  are  derived  is  in  a  normal  condition. 

The  femoral  or  anterior  crural  nerve  is  in  danger  of  being  injured  in  fractures  of  the  true  pelvis, 
since  the  fracture  most  commonly  takes  place  through  the  ascending  ramus  of  the  os  pubis,  at  or 
near  the  point  where  this  nerve  crosses  the  bone.  It  is  also  liable  to  be  injured  in  fractures  and 
dislocations  of  the  femur,  and  in  some  tumors  growing  in  the  pelvis  is  likely  to  be  pressed  upon, 
and  its  functions  impaired.  Moreover,  on  account  of  its  superficial  position,  it  is  exposed  to 
injury  in  wounds  and  stabs  in  the  groin.  When  this  nerve  is  paralyzed,  the  patient  is  unable  to  flex 
his  hip  completely,  on  account  of  the  loss  of  motion  in  the  Iliacus;  or  to  extend  the  knee  on  the 
thigh,  on  account  of  paralysis  of  the  Quadriceps  extensor  cruris;  there  are  complete  paralysis  of 
the  Sartorius  and  partial  paralysis  of  the  Pectineus.  There  is  loss  of  sensation  down  the  front  and 
inner  side  of  the  thigh,  except  in  that  part  supplied  by  the  femoral  branch  of  the  genitofemoral 
nerve,  and  by  the  ilioinguinal  nerve.  There  is  also  loss  of  sensation  down  the  inner  side  of  the 
leg  and  foot  as  far  as  the  ball  of  the  great  toe. 

The  obturator  nerve  is  of  special  surgical  interest.  It  is  rarely  paralyzed  alone,  but  occa- 
sionally is  paralyzed  in  association  with  the  femoral  (anterior  crural).  The  principal  interest 
attached  to  it  is  in  connection  with  its  supply  to  the  knee;  pain  inthe  knee  being  symptomatic 
of  many  diseases  in  which  the  trunk  of  this  nerve,  or  one  of  its  branches,  is  irritated,  Thus,  it  is 
well  known  that  in  the  earlier  stages  of  hip-joint  disease  the  patient  does  not  complain  of  pain  in 
that  articulation,  but  on  the  inner  side  of  the  knee,  or  in  the  knee-joint  itself,  botli  these  articu- 
lations being  supplied  by  the  obturator  nerve,  the  final  distribution  of  the  nerve  being  to  the 
knee-joint.  Again,  the  same  thing  occurs  in  sacroiliac  disease:  pain  is  complained  of  in  the 
knee-joint  or  on  its  inner  side.  The  obturator  nerve  is  in  close  relationship  with  the  sacroiliac 
articulation,  passing  over  it,  and,  according  to  some  anatomists,  distributing  filaments  to  it. 
Again,  in  cancer  of  the  sigmoid  flexure,  and  even  in  cases  where  masses  of  hardened  feces  are 
impacted  in  this  portion  of  the  gut,  pain  is  complained  of  in  the  knee.  The  left  obturator  nerve 
lies  beneath  the  sigmoid  flexure,  and  is  readily  pressed  upon  and  irritated  when  disease  exists  in 
this  part  of  the  intestine.  Finally,  pain  in  the  knee  forms  an  important  diagnostic  sign  in  ob- 
turator hernia.  The  hernial  protrusion  as  it  passes  through  the  opening  in  the  obturator  mem- 
brane presses  upon  the  nerve  and  causes  pain  in  the  parts  supplied  by  its  peripheral  filaments. 
\Vlien  the  obturator  nerve  is  paralyzed,  the  patient  is  unable  to  press  his  knees  together  or  to 
cross  one  leg  over  the  other,  on  account  of  paralysis  of  the  Adductor  muscles.  Rotation  outward 
of  the  thigh  is  impaired  from  paralysis  of  the  Obturator  externus.  Sometimes  there  is  loss  of 
sensation  in  the  upper  half  of  the  inner  side  of  the  thigh. 

The  great  sciatic  nerve  is  liable  to  be  pressed  upon  by  various  pelvic  tumors,  giving  rise  to 
pain  along  its  trunk,  to  which  the  term  sciatica  is  applied.  Tumors  growing  from  the  pelvic 
viscera,  or  bones,  aneurisms  of  some  of  the  branches  of  the  internal  iliac  artery,  calculus  in  the 
bladder,  when  of  large  size,  accumulation  of  feces  in  the  rectum,  may  all  cause  pressure  on  the 
nerve  inside  the  pelvis,  and  give  rise  to  sciatica.  Outside  the  pelvis  exposure  to  cold,  violent 
movements  of  the  hip-joint,  exostoses  or  other  tumors,  growing  from  the  margin  of  the  sacro- 
sciatic foramen,  may  also  give  rise  to  the  same  condition.  When  paralyzed  there  is  loss  of 
motion  in  all  the  muscles  below  the  knee,  and  loss  of  sensation  in  the  same  situation,  except  the 
upper  half  of  the  back  of  the  leg,  supplied  by  the  small  sciatic  and  the  upper  half  of  the  inner 
side  of  the  leg,  when  the  communicating  branch  of  the  obturator  is  large. 

The  great  sciatic  nerve  has  been  frequently  cut  down  upon  and  stretched,  or  has  been  acU' 


THE  SYMPATHETIC  NERVE  SYSTEM  1063 

punctured  for  the  relief  of  sciatica.  The  nerve  has  also  been  stretched  in  cases  of  locomotor 
ataxia,  the  anesthesia  of  leprosy,  etc.  In  order  to  define  it  on  the  surface,  a  point  is  taken  at 
the  junction  of  the  middle  and  lower  third  of  a  line  stretching  from  the  posterior  superior  spine 
of  the  ilium  to  the  outer  part  of  the  tuber  ischii,  and  a  line  is  drawn  from  this  point  to  the  middle 
of  the  upper  part  of  the  popliteal  space.  The  line  must  be  slightly  curved  with  its  convexity 
outward,  and  as  it  passes  downward  to  the  lower  border  of  the  Gluteus  maximus  is  slightly 
nearer  the  tuberosity  of  the  ischium  than  to  the  great  trochanter,  as  it  crosses  a  line  drawn  between 
these  two  points.  The  operation  of  stretching  the  sciatic  nerve  is  performed  by  making  an 
incision  over  the  course  of  the  nerve  about  the  centre  of  the  thigh.  The  skin,  superficial  struc- 
tures, and  deep  fascia  having  been  divided,  the  interval  between  the  inner  and  outer  Hamstrings 
is  to  be  defined,  and  these  muscles  respectively  pulled  inward  and  outward  with  retractors. 
The  nerve  will  be  found  a  little  to  the  inner  side  of  the  Biceps.  It  is  to  be  separated  from  the 
surrounding  structures,  hooked  up  with  the  finger,  and  stretched  by  steady  and  continuous  trac- 
tion for  two  or  three  minutes.  The  sciatic  nerve  may  also  be  stretched  by  what  is  known  as  the 
"  dry"  method.  The  patient  is  laid  on  his  back,  the  foot  is  extended,  the  leg  flexed  on  the  thigh, 
and  the  thigh  strongly  flexed  on  the  abdomen.  While  the  thigh  is  maintained  in  this  position 
the  leg  is  forcibly  extended  to  its  full  extent,  and  the  foot  as  fully  flexed  on  the  leg.  This  last- 
named  method  is  uncertain. 

The  position  of  the  external  popliteal  nerve,  close  behind  the  tendon  of  the  Biceps  on  the  outer 
side  of  the  ham,  should  be  remembered  in  subcutaneous  division  of  the  tendon.  After  it  is  divided, 
a  cord  often  rises  up  close  beside  it,  which  might  be  mistaken  for  a  small  undivided  portion  of  the 
tendon,  and  the  surgeon  might  be  tempted  to  reintroduce  his  knife  and  divide  it.  This  must 
never  be  done,  as  the  cord  is  the  external  popliteal  nerve,  which  becomes  prominent  as  soon  as 
the  tendon  is  divided.     (See  also  page  52.5). 

THE  SYMPATHETIC  NERVE  SYSTEM  (SYMPATHICUS)  (Fig.  786). 

The  distinction  of  the  sympathetic  nerve  system  from  the  cerebrospinal  system 
is  made  merely  for  reasons  of  convenience.  The  two  systems  are  intimately 
connected  and  the  sympathetic  is  morphologically  a  derivative  of  the  central  axis 
disseminated  in  connection  with  the  nutritive  apparatus  and  establishing  relation- 
ships among  the  vegetative  organs. 

The  sympathetic  nerve  system  consists  of  (1)  a  series  of  central  ganglia  (gan- 
glia trunci  sympathici)  connected  by  a  great  ganglionic  cord,  the  gangliated  cord 
(truncus  sympathicus),  extending  from  the  base  of  the  skull  to  the  coccyx, 
one  gangliated  cord  on  each  side  of  the  middle  line  of  the  body,  ventrolaterad 
of  the  vertebral  column;  (2)  of  three  great  gangliated  plexuses  (plexus  sympathici)  or 
aggregations  of  nerves  and  ganglia,  situated  ventrolaterad  of  the  vertebral  column 
in  the  thoracic,  abdominal,  and  pelvic  cavities  respectively;  (3)  of  smaller  or 
terminal  ganglia,  situated  in  relation  with  the  abdominal  viscera;'  and  (4)  of 
numerous  nerve  fibres.  These  latter  are  of  two  kinds — communicating,  by  which 
the  ganglia  communicate  with  each  other  and  with  the  cerebrospinal  nerves;  and 
distributory,  supplying  the  internal  viscera  and  the  coats  of  the  bloodvessels. 

Each  gangliated  cord  may  be  traced  upward  from  the  base  of  the  skull  into  the 
cranial  cavity  by  an  ascending  branch,  which  passes  through  the  carotid  canal, 
forms  a  plexus  on  the  internal  carotid  artery  and  in  the  cavernous  sinus  (Fig.  789), 
and  communicates  with  certain  cranial  nerves  (p.  1067);  the  lower  ends  of  the 
two  cords  converge  and  end  in  a  single  ganglion,  the  ganglion  impar  (ganglion 
coccygeum  impar),  situated  ventrad  of  the  coccyx.  The  ganglia  of  the  cord  are 
distinguished  as  cervical,  thoracic,  lumbar,  and  sacral,  and  except  in  the  neck  they 
closely  correspond  in  number  to  the  vertebra  against  which  they  lie.  They 
are  arranged  thus: 

Cervical  portion 3  pairs  of  ganglia. 

Thoracic      " 10  to  12     "               " 

Lumbar       " 4     "               " 

Sacral           " 4  or    5    "               " 

1  The  ciliary,  sphenopalatine,  otic,  and  submaxillary  ganglia,  already  described  in  connection  with  the  tri- 
geminal nerve,  may  be  regarded  as  belonging  to  the  sympathetic  system. 


1064 


THE  NERVE  SYSTEM 


MIDDLE  CEHVI- 


In  the  neck  the  ganglia  are  situated  in  front  of  the  transverse  processes  of  the 
vertebra ;  in  the  thoracic  region,  in  front  of  the  heads  of  the  ribs ;  in  the  lumbar  region, 

on  the  sides  of  the  bodies  of  the 
spifOL  vertebrae;    and    in    the     sacral 

region,  in  front  of  the  sacrum. 

Connections  with  the  Spinal 
Nerves. — Communications  are 
established  between  the  sym- 
pathetic and  spinal  nerves 
through'  what  are  known  as 
gray  and  white  rami  communi- 
cantes  (Fig.  786),  the  gray  rami 
conveying  sympathetic  fibres 
into  the  spinal  nerves,  and  the 
white  rami  transmitting  afferent 
and  efferent  fibres  to  the  sym- 
pathetic. Each  spinal  nerve 
receives  a  gray  ramus  com- 
municans  from  the  gangliated 
cord  of  the  sympathetic,  but 
white  rami  are  not  supplied  by 
all  the  spinal  nerves.  The 
white  rami  are  derived  from  the 
first  thoracic  to  the  first  lum- 
bar, inclusive,  while  the  visceral 
branches  which  run  from  the 
second,  third  and  fourth  sacral 
nerves  directly  to  the  pelvic  plex- 
uses of  the  sympathetic  belong 
to  this  category.  The  majority 
of  the  fibres  which  spring  from 
the  sympathetic  ganglia  are 
amyelinic  (_^6res  of  Remak);  the 
fibres  which  reach  the  sympa^ 
thetic  through  the  white  ramus 
communicans  are  myelinated. 

The  branches  of  distribution, 
or  sympathetic  nerves,  derived 
from  the  gangliated  cords  from 
the  prevertebral  plexuses,  and 
also  from  the  smaller  ganglia, 
are  principally  destined  for  the 
bloodvessels  and  thoracic  and 
abdominal  viscera,  supplying 
the  involuntary  muscle  fibres 
of  the  coats  of  the  vessels  and 
the  hollow  viscera,  and  the  se- 
creting   cells,    as    well    as    the 

Fio.  786.-Anterior  surface  of  the  spinal  cord,  showing  the  mUSCular  COatS  of  the  Vessds  in 
Bpinal  nerves  and  their  connections  with  the  sympathetic  trunk  on  j^q  o-landular  VlSCera.  1  ney 
one  side.     (Testut.)  -^        i>      n.  ,  ^      a:  j. 

consist  of  efferent  and  aiierent 

fibres,  for  the  origin  and  course  of  which  see  pages  1014  and  1015  (Fig.  756). 

The  three  great  gangliated  plexuses  (collateral  ganglia)  are  situated  m  front  of  tne 

vertebral  column  in  the  thoracic,  abdominal,  and  pelvic  regions,  and  are  named, 


MBAR    GANGLIA 


THE  SYMPATHETIC  NERVE  SYSTEM 


1065 


respectively,  the  cardiac,  the  solar  or  coeliac,  and  the  hypogastric  plexus.  They  consist 
of  collections  of  nerves  and  ganglia,  the  nerves  being  derived  from  the  ga'no-Iiated 
cords  and  from  the  cerebrospinal  nerves.     They  distribute  branches  to  the  v-iscera. 


Carotid  plex 


3Iiddle  cemcnl  qannhon 

/ 
Inferior  cervical  ganglion 


■^Pharyngeal  hranche. 
Ca)  diac  branches. 


Deep  ca>  diac  plexus. 

Supeificial  cardiac  plexus. 


f^olar  plexus. 


Aortic  plexus. 


Hypogastric  plexus 


Sacral  gangh 


Ganglion  impai 


Fig.  7S7.— The  sympathetic  nerve  syste 


1066  THE  NEB  VE  SYSTEM 

THE  GANGLIATED  CORD  (TRUNCUS  SYMPATHETICUS). 
Cervicocephalic  Portion  of  the  Gangliated  Cord  (Figs.  788,  789). 

The  cervicocephalic  portion  of  each  gangliated  cord  {ipars  cephalica  et  cervicalis 
s.  sympathici)  consists  of  three  ganglia,  distinguished,  according  to  their  position, 
as  the  superior,  middle,  and  inferior  cervical,  connected  by  intervening  cords. 
This  portion  of  the  sympathetic  cord  receives  no  white  rami  communicantes  from 
the  cervical  spinal  nerves,  its  spinal  fibres  being  derived  from  the  white  rami 
of  the  upper  thoracic  nerves  which  enter  the  corresponding  thoracic  ganglia  of  the 
sympathetic  and  through  these  ascend  into  the  cervical  portion. 

The  superior  cervical  ganglion  (ganglion  cervicale  superius)  (Figs.  787  and 
788),  the  largest  of  the  three,  is  about  three-quarters  of  an  inch  in  length.  It  is 
placed  opposite  the  second  and  third  cervical  vertebrte.  It  is  of  a  reddish-gray 
color,  is  usually  fusiform  in  shape,  is  sometimes  broad  and  flattened,  and  is 
occasionally  constricted  at  intervals;  it  is  believed  that  it  is  formed  by  the  coales- 
cence of  the  four  ganglia  corresponding  to  the  four  upper  cervical  nerves.  It  is 
in  relation,  in  front,  Avith  the  sheath  of  the  internal  carotid  artery  and  internal 
jugular  vein;  behind,  it  lies  on  the  Rectus  capitis  anticus  major. 

Its  branches  may  be  divided  into  superior,  inferior,  eJrtemal,  internal,  and 
anterior. 

The  superior  branch  (n.  caroiicus  iniernus)  (Fig.  744)  appears  to  be  a  direct 
prolongation  of  the  ganglion.  It  is  soft  in  texture  and  of  a  reddish  color.  It 
ascends  by  the  side  of  the  internal  carotid  artery,  and,  entering  the  carotid  canal 
in  the  temporal  bone,  divides  into  two  branches,  which  lie,  one  on  the  outer,  and 
the  other  on  the  inner,  side  of  that  vessel. 

The  outer  branch,  the  larger  of  the  two,  distributes  filaments  to  the  internal 
carotid  artery  and  forms  the  carotid  plexus. 

The  inner  branch  also  distributes  filaments  to  the  internal  carotid  artery,  and, 
continuing  onward,  forms  the  cavernous  plexus. 

The  Carotid  Plexus  (plexus  caroiicus  intermis)  (Figs.  787  and  788)  is  situated 
on  the  outer  side  of  the  internal  carotid  artery.  Filaments  from  this  plexus  occa- 
sionally form  a  small  gangliform  swelling,  the  carotid  ganglion,  on  the  under  surface 
of  the  artery.  The  carotid  plexus  communicates  with  the  Gasserian  ganglion, 
the  abducent  nerve,  and  the  sphenopalatine  ganglion;  it  distributes  filaments  to 
the  wall  of  the  carotid  artery,  and  also  communicates  with  Jacobson's  nerve 
(the  tympanic  branch  of  the  glossopharyngeal). 

The  communicating  branches  to  the  abducent  nerve  consist  of  one  or  two  filaments 
which  join  that  nerve  as  it  lies  upon  the  outer  side  of  the  internal  carotid  artery. 
The  communication  with  the  sphenopalatine  ganglion  is  efFected  by  a  branch,  the 
large  deep  petrosal  nerve  (Fig.  745),  given  off  from  the  plexus  on  the  outer  side 
of  the  artery;  this  branch  passes  through  the  cartilage  filling  up  the  foramen 
lacerum  medium,  and  joins  the  large  superficial  petrosal  from  the  facial  to  form 
the  Vidian  nerve  (Figs.  740  and  745).  The  Vidian  nerve  then  proceeds  through 
the  Vidian  canal  to  the  sphenopalatine  ganglion.  The  communication  with 
Jacobson's  nerve  is  effected  by  two  branches,  one  of  which  is  called  the  deep 
petrosal  nerve,  and  the  other  the  caroticotympanic  nerve;  the  latter  may  consist 
of  two  or  three  delicate  filaments. 

The  Cavernous  Plexus  (plexus  cavernosus)  (Fig.  788)  is  situated  below  and  in- 
ternal to  that  part  of  the  internal  carotid  which  is  placed  by  the  side  of  the  sella 
turcica,  in  the  cavernous  sinus,  and  is  formed  chiefly  by  the  internal  division  of 
the  ascending  branch  from  the  superior  cervical  ganglion.  It  commimicates 
with  the  oculomotor,  the  trochlear,  the  ophthalmic  division  of  the  trigeminal. 


CERVICOCEPHALIC  PORTION  OF  THE  GANGLIATED   CORD      1067 

and  the  abducent  nerves,  and  with  the  ciliary  or  lenticular  ganglion,  and  distri- 
butes filaments  to  the  wall  of  the  internal  carotid  artery,  and  to  the  hypophysis. 
The  branch  of  communication  with  the  oculomotor  nerve  joins  it  at  its  point  of 
division;  the  branch  to  the  trochlear  nerve  joins  it  as  it  lies  on  the  outer  wall  of 
the  cavernous  sinus;  other  filaments  are  connected  with  the  under  surface  of  the 
trunk  of  the  ophthalmic  nerve;  and  a  second  filament  of  communication  joins  the 
abducent  nerve. 


EXTERN 

CVIUSC 


CILIARY    ^ 


SENSORY 

OF  CILIARY  — 
GANGLIO 


OPHTHALMIC  N. 
GASSERIAN 
GANGLION 

(lurned  forward) 


TEMPORO- 

MAXILLARY 

ARTICULATION 


CAHOTICOTYMPAN   C  I 


ANGLION 

MOTOR 

1ANCH 
MOTOR 

fMPATHETIC  ROOT  OF 
LIARY  GANGLION 
OCULOMOTOR  NERVE 


ABDUCENT    NERVE 


UCENT    NERVE 


INTE 
CAROTID 
ARTERY 


Fig.  788. — The  cephalic  portion  of  the  sympathetic  nerve  system,  seen  obliquely  from  above  and 
behind.     (Toldt.) 


The  filaments  of  connection  with  the  ciliary  ganglion  (Fig.  735)  arise  from  the 
anterior  part  of  the  cavernous  plexus  and  enter  the  orbit  through  the  sphenoidal 
fissure;  they  may  join  the  nasal  Id  ranch  of  the  ophthalmic  nerve  or  be  continued 
forward  as  a  separate  branch. 

The  terminal  filaments  from  the  carotid  and  cavernous  plexuses  are  prolonged 
along  the  internal  carotid  artery,  forming  plexuses  which  entwine  around  the 
anterior  and  middle  cerebral  arteries  and  the  ophthalmic  artery;  along  the  former 
vessels  they  may  be  traced  on  to  the  pia;  along  ;he  latter,  into  the  orbit,  where  they 
accompany  each  of  the  branches  of  the  vessel.  The  filaments  prolonged  to  the 
anterior  communicating  artery  connect  the  sympathetic  nerves  of  the  right  and 
left  sides. 

The  so-called  inferior  branch  of  the  superior  cervical  ganglion  communicates 
with  the  middle  cervical  ganglion. 

The  external  branches  are  comimmicaling,  and  consist  of  gray  rami  communi- 
cantes  to  the  upper  four  cervical  nerves  and  to  certain  of  the  cranial  nerves. 
Sometimes  the  btanch  to  the  fourth  cervical  nerve  may  come  from  the  cord 
connecting  the  superior  and  middle  cervical  ganglia.  The  branches  to  the  cranial 
nerves  consist  of  delicate  filaments,  which  run  to  the  ganglion  of  the  trunk  of 


1068 


THE  NERVE  SYSTEM 


CAVERNOUS    PLEXUS 


the  vagus,  and  to  the  hypoglossal  nerve.     A  separate  filament  {nenus  jugidaris) 
passes  upward  to  the  base  of  the  skull,  and  subdivides  to  join  the  petrous  ganglion 

of  the  glossopharyngeal,  and  the 
ganglion  of  the  root  of  the  vagus 
in  the  jugular  foramen. 

The  internal  branches' are  per- 
ipheral,  and  consist  of  the  pharyn- 
geal and  laryngeal  branches,  and 
the  superior  cardiac  nerve. 

The  pharyngeal  branches  (rajni 
pharyngei)  (Fig.  787)  pass  in- 
ward to  the  side  of  the  pharynx, 
where  they  join  with  branches 
from  the  glossopharyngeal, 
vagus,  and  external  laryngeal 
nerves  to  form  the  pharyngeal 
plexus. 

The  laryngeal  branches  join 
the  superior  laryngeal  nerve  and 
its  branches. 

The  superior  cardiac  nerve  {71. 
cardiacus  superior)  (Figs.  787) 
arises  by  two  or  more  branches 
from  the  superior  cervical  gan- 
glion, and  occasionally  receives 
a  filament  from  the  cord  of 
communication  between  the  first 
and  second  cervical  ganglia.  It 
runs  down  the  neck  behind  the 
common  carotid  artery,  lying 
upon  the  Longus  colli,  and 
crosses  in  front  of  the  inferior 
thyroid  artery  and  recurrent 
laryngeal  nerve. 

The  course  of  the  nerves  on 

the  two  sides  then  differs.     The  right  superior  cardiac  nerve,  at  the  root  of  the 

neck,  passes  either  in  front  of  or  behind  the  subclavian  artery^  and  along  the  in- 
nominate artery,  to  the  back  part  of  the 

arch  of  the  aorta,  where  it  joins  the  deep 

cardiac  plexus.     It  is  connected  with  other 

branches   of   the   sympathetic;  about   the 

middle  of   the   neck  it   receives   filaments 

from  the  external  laryngeal  nerve;  lower 

down  it  obtains  one  or  two  twigs  from  the 

vagus,  and  as  it  enters  the  thorax  it   is 

joined  by  a  filament   from   the  recurrent 

laryngeal.     Filaments  from  the  nerve  com- 
municate with  the  thyroid  branches  from 

the  middle  cervical  ganglion. 
The  left   superior  cardiac    nerve,  in  the 

thorax,  runs  by  the  side  of  the  left  common 

carotid  artery,  and  in  front  of  the  arch  of  the  aorta  to  the  superficial  cardiac  plexus. 
The  anterior  branches  (nil.  carotid  externi)  (Fig.  789)  ramify  upon  the  external 

carotid  artery  and  its  branches,  forming  around  each  a  delicate  plexus,  on  the 


EIGHTH 

CERVrCA 

NERVE 


FIRST 

THORACIC 

NERVE 


Fig.  789. — Diagra 


:  of  the  cervical  sympathetic  cord. 
(Testut,) 


CERVICAL  GANGLION 


Fig.  790. — The  subclavian  loop  passing  from  the 
middle  to  the  inferior  cervical  ganglia. 


CERVICOCEPHALIC  POUTION  OF  THE  GANGLIATED  VOUD     1069 

nerves  composing  which  small  ganglia  are  occasionally  found.  The  plexuses 
accompanying  some  of  these  arteries  have  important  communications  with  other 
nerves.  That  surrounding  the  external  carotid  artery  (^plexus  caroticus  externus) 
is  connected  with  the  branch  of  the  facial  nerve  to  the  Stylohyoid  muscle;  that 
surrounding  the  facial  artery  communicates  with  the  submaxillary  ganglion  by 
one  or  two  filaments;  and  that  accompanying  the  middle  meningeal  artery  sends 
an  ofi'shoot  which  passes  to  the  otic  ganglion  and  a  second,  the  external  superficial 
petrosal  nerve  (Fig.  745),  to  the  geniculate  ganglion  of  the  facial  nerve. 

The  middle  cervical  ganglion  (ganglion,  cervicale  medium)  (Figs.  787  and  789) 
is  the  smallest  of  the  three  cervical  ganglia,  and  is  occasionally  altogether  wanting. 
It  is  placed  opposite  the  sixth  cervical  vertebra,  usually  upon,  or  close  to,  the 
inferior  thyroid  artery.  It  is  probably  formed  b}^  the  coalescence  of  two  ganglia 
corresponding  to  the  fifth  and  sixth  cervical  nerves. 

It  is  joined  by  gray  rami  communicantes  to  the  fifth  and  sixth  cervical  nerves. 

It  gives  off  the  thyroid  and  middle  cardiac  nerves. 

The  thyroid  branches  are  small  filaments  which  accompany  the  inferior  thyroid 
artery  to  the  thyroid  gland,  forming  the  inferior  thjrroid  plexus  (plexus  thyroideus 
inferior);  they  communicate,  on  the  artery,  with  the  superior  cardiac  nerve,  and, 
in  the  gland,  with  branches  from  the  recurrent  and  external  laryngeal  nerves. 

The  middle  or  great  cardiac  nerve  (n.  cardiacus  medius)  (Fig.  787),  the  largest 
of  the  three  cardiac  nerves,  arises  from  the  middle  cervical  ganglion  or  from  the 
cord  between  the  middle  and  inferior  ganglia.  On  the  right  side  it  descends  behind 
the  common  carotid  artery,  and  at  the  root  of  the  neck  passes  either  in  front  of 
or  behind  the  subclavian  artery;  it  then  descends  on  the  trachea,  receives  a  few 
filaments  from  the  recurrent  laryngeal  nerve,  and  joins  the  right  side  of  the  deep 
cardiac  plexus.  In  the  neck  it  communicates  with  the  superior  cardiac  and  re- 
current laryngeal  nerves.  On  the  left  side  the  middle  cardiac  nerve  enters  the 
thorax  between  the  left  carotid  and  subclavian  arteries,  and  joins  the  left  side  of 
the  deep  cardiac  plexus.  If  the  middle  cervical  ganglion  is  absent^  the  above- 
named  branches  arise  from  the  gangliated  cord. 

The  inferior  cervical  ganglion  (ganglion  cervicale  inferius)  (Figs.  787  and  789) 
is  situated  between  the  base  of  the  transverse  process  of  the  last  cervical  vertebra 
and  the  neck  of  the  first  rib  on  the  inner  side  of  the  superior  intercostal  artery. 
Its  form  is  irregular;  it  is  larger  in  size  than  the  preceding,  and  is  frequently  joined 
to  the  first  thoracic  ganglion.  It  is  probably  formed  by  the  coalescence  of  two 
ganglia  which  correspond  to  the  last  two  cervical  nerves.  It  is  connected  to 
the  middle  ganglion  by  two  or  more  cords,  one  of  which  forms  a  loop  around 
the  subclavian  artery  and  supplies  offshoots  to  it.  This  loop  is  named  the  ansa 
subclavii  (Vieussenii).     , 

The  ganglion  is  joined  to  the  seventh  and  eighth  cervical  and  the  first  thoracic 
nerves  by  gray  rami  communicantes. 

It  gives  off  the  inferior  cardiac  nerve  and  offshoots  to  bloodvessels. 

The  inferior  cardiac  nerve  (n.  cardiacus  inferior)  arises  from  the  inferior  cervical 
or  first  thoracic  ganglion.  It  passes  down  behind  the  subclavian  artery  and  along 
the  front  of  the  trachea  to  join  the  deep  cardiac  plexus.  It  communicates  freely 
behind  the  subclavian  artery  with  the  recurrent  laryngeal  and  middle  cardiac 
nerves. 

The  offshoots  to  bloodvessels  accompany  the  vertebral  artery,  and  form  a  plexus 
around  it;  this  plexus  (plexus  vertebralis)  supplies  filaments  to  the  vessel,  and  is 
continued  up  the  vertebral  and  basilar  arteries  to  the  cerebral  and  cerebellar 
arteries. 

Applied  Anatomy.— The  situation  of  the  cervical  sympathetic  makes  wounds  of  it  rare. 
Thirteen  cases  of  traumatic  injury  to  the  cervical  symija'thetics  were  collected  by  Seeligmtiller. 
In  ten  cases  paralysis  existed;  in  three,  irritation.     Tumors  of  the  neck  may  cause  irritation  or 


1070 


THE  NERVE  SYSTE3I 


paralysis.  In  irritation  of  the  sympathetic  the  corresponding  side  of  the  face  becomes  pale,  the 
pupil"  dilates,  the  palpebral  fissure  widens,  and  the  eyeball  protrudes.  In  many  cases  there  is 
acceleration  of  the  heart  beats.  In  paralysis  of  the  sympathetic  the  pupil  contracts,  the  pal- 
pebral fissure  is  narrowed  by  partial  ptosis,  the  corresponding  side  of  the  face  reddens,  there  is 
an  increase  in  the  flow  of  tears,  and  recession  of  the  eyeball. 

The  surgeon  occasionally  resects  the  sympathetic.  Jonnesco  recommends  bilateral  removal 
of  the  superior  cervical  ganglia  for  glaucoma,  and  bilateral  removal  of  all  the  cervical  sympa- 
thetic ganglia  for  epilepsy  and  for  exophthalmic  goitre.  The  results  of  resection  do  not  appear 
to  justify  the  operation. 


The  Thoracic  Portion  (Pars  Thoracalis)  of  the  Gangliated  Cord  (Fig.  791). 

The  thoracic  portion  of  the  gangliated  cord  consists  of  a  series  of  ganglia 
which  usually  correspond  in  number  to  that  of  the  vertebrae;  but,  from  the  occa- 


RENAL    PLEXUS 

Fig.  791. — Plan  of  the  right  sympathetic  cord  and  splanchnic  nerves.     (Testut.) 

sional  coalescence  of  two,  their  number  is  uncertain.     The  ganglia  are  placed 
on  each  side  of  the  spine,  resting  against  the  heads  of  the  ribs,  and  are  covered  by 


THE  LUMBAR  PORTION  OF  THE  GANGLIATED  CORD      1071 

the  costal  pleura;  the  last  two  ganglia  are,  however,  anterior  to  the  rest,  being 
placed  on  the  side  of  the  bodies  of  the  eleventh  and  twelfth  thoracic  vertebrte.  The 
ganglia  are  small  in  size  and  of  a  grayisli  color.  The  hrst  ganglion,  larger  than 
the  others,  is  of  an  elongated  form  and  is  frequently  blended  with  the  last  cervical 
ganglion.     They  are  connected  by  the  intervening  portions  of  the  cord. 

Two  rami  communicantes,  one  white  and  the  other  gray,  connect  each  ganglion 
with  its  corresponding  spinal  nerve. 

The  branches  from  the  uf per  five  ganglia  are  very  small;  they  supply  filaments 
to  the  thoracic  aorta  and  its  branches,  and  to  the  bodies  of  the  vertebrae  and  their 
ligaments.  Branches  from  the  second,  third,  and  fourth  ganglia  enter  the  posterior 
pulmonary  plexus. 

The  branches  from  the  lower  seven  ganglia  are  large,  and  white  in  color;  they 
distribute  filaments  to  the  aorta,  and  unite  to  form  the  three  splanchnic  nerves. 
These  are  named  the  great,  the  lesser,  and  the  smallest,  or  renal  splanchnic. 

The  great  splanchnic  nerve  (/;.  splanchnicus  major)  is  white  in  color,  firm  in 
texture,  and  is  formed  by  branches  from  the  thoracic  ganglia  between  the  fifth  or 
sixth  and  the  ninth  or  tenth;  but  the  fibres  in  the  higher  roots  may  be  traced 
upward  in  the  sympathetic  cord  as  far  as  the  first  or  second  thoracic  ganglion. 
These  roots  unite  to  form  a  cord  of  considerable  size.  It  descends  oblicjuely 
inward  in  front  of  the  bodies  of  the  ve  tebrte  along  the  posterior  mediastinum, 
perforates  the  crus  of  the  Diaphragm,  and  terminates  in  the  semilunar  ganglion  of 
the  solar  plexus  (Fig.  791),  distributing  filaments  to  the  renal  and  suprarenal 
plexuses.  A  ganglion  {ganglion  splanchnicum)  exists  on  this  nerve  opposite  the 
eleventh  or  twelfth  thoracic  vertebra. 

The  lesser  splanchnic  nerve  (h.  splanchnicus  minor)  is  formed  by  filaments  from 
the  tenth  and  eleventh  ganglia,  and  from  the  cord  between  them.  It  pierces  the 
Diaphragm  near  or  with  the  preceding  nerve,  and  joins  the  aorticorenal  ganglion 
of  the  solar  plexus  (Fig.  791).  It  communicates  in  the  thorax  with  the  great 
splanchnic  nerve,  and  ends  in  the  solar  plexus. 

The  least  splanchnic  nerve  (n.  splanchnicus  imus)  arises  from  the  last  thoracic 
ganglion,  and,  piercing  the  Diaphragm,  terminates  in  the  renal  plexus.  It  occa- 
sionally communicates  with  the  preceding  nerve. 

A  striking  analogy  appears  to  exist  between  the  splanchnic  and  the  cardiac 
nerves.  The  cardiac  nerves  are  three  in  number,  they  arise  from  the  three  cer- 
vical ganglia,  and  are  distributed  to  a  large  and  important  organ  in  the  thoracic 
cavity.  The  splanchnic  nerves,  also  three  in  number,  are  connected  probably 
with  all  the  thoracic  ganglia,  and  are  distributed  to  important  organs  in  the 
abdominal  cavity. 


The  Lumbar  Portion  (Pars  Lumbalis)  of  the  Gangliated  Cord  (Fig.  787). 

The  lumbar  portion  of  the  gangliated  cord  is  situated  in  front  of  the  vertebral 
column  along  the  inner  margin  of  the  Psoas  magnus.  It  consists  usually  of  four 
ganglia,  connected  together  by  interganglionic  cords.  It  is  continuous  above  with 
the  thoracic  portion  beneath  the  internal  arcuate  ligament  of  the  Diaphragm, 
and  below  with  the  sacral  portion  behind  the  common  iliac  artery.  The  ganglia 
are  of  small  size,  and  placed  much  nearer  the  median  line  than  the  thoracic  ganglia. 

Gray  rami  communicantes  connect  all  the  ganglia  with  the  lumbar  spinal 
nerves.  There  may  be  two  from  each  ganglion,  but  the  arrangement  is  not  so 
uniform  as  in  other  regions.  The  first  and  second,  and  sometimes  the  third, 
lumbar  nerves  send  white  rami  communicantes  to  the  upper  two  or  three  ganglia. 

From  the  situation  of  the  lumbar  ganglia  these  branches  are  longer  than  in  the 
other  regions.     They  accompany  the  lumbar  arteries  around  the  sides  of  the  bodies 


1072  THE  NER  VE  SYSTEM 

of  the  vertebrae,  passing  beneath  the  fibrous  arches  from  which  some  of  the  fibres 
of  the  Psoas  magnus  arise. 

Of  the  branches  of  distribution  some  branches  pass  inward,  in  front  of  the  aorta, 
and  lielp  to  form  the  abdominal  aortic  plexus  {plexus  aorticus  abdominalis)  (Fig. 
787).  Other  branches  descend  in  front  of  the  common  iliac  arteries,  and,  joining 
over  the  promontory  of  tlie  sacrum,  assist  in  forming  the  hypogastric  plexus  {'plexus 
hypogastricus)  (Fig.  787).  Numerous  delicate  filaments  are  also  distributed  to 
the  bodies  of  the  vertebras  and  the  ligaments  connecting  them. 

Pelvic  Portion  (Pars  Pelvina)  of  the  Gangliated  Cord  (Fig.  787). 

The  pelvic  portion  of  the  gangliated  cord  is  situated  in  front  of  the  sacrum 
along  the  inner  side  of  the  anterior  sacral  foramina.  It  consists  of  four  or  five 
small  ganglia  on  each  side,  connected  by  interganglionic  cords.  Below,  these 
cords  converge  and  unite  on  the  front  of  the  coccyx  by  means  of  a  small  ganglion, 
the  coccygeal  ganglion  or  ganglion  impar  {ganglion  coccygeuvi  impar)  (Fig.  787). 

Gray  rami  comraunicantes  pass  from  the  ganglia  to  the  sacral  and  coccygeal 
nerves.  No  white  rami  communicantes  join  this  part  of  the  gangliated  cord, 
but  the  visceral  brandies  which  arise  from  the  third  and  fourth,  and  sometimes 
from  the  second,  sacral  are  regarded  as  homologous  witli  white  rami  communi- 
cantes 

The  branches  of  distribution  communicate  on  the  front  of  the  sacrum  with  the 
corresponding  branches  from  the  opposite  side;  some,  from  the  first  two  ganglia, 
pass  to  join  the  pelvic  plexus,  while  others  form  a  plexus  which  accompanies  the 
middle  sacral  artery,  from  which  plexus  filaments  pass  to  the  coccygeal  gland. 

THE  GREAT  PLEXUSES  OF  THE  SYMPATHETIC  SYSTEM. 

The  great  plexuses  of  the  sympathetic  are  the  large  aggregations  of  nerves 
and  ganglia,  previously  alluded  to,  situated  in  the  thoracic,  abdominal,  and  pelvic 
cavities  respectively,  and  named  the  cardiac,  pulmonary,  oesophageal,  coeliac,  and 
hypogastric  plexuses  respectively.  They  consist  not  only  of  sympathetic  fibres 
derived  from  tlie  ganglia,  but  also  of  fibres  from  the  central  nerve  system  which 
are  conveyed  through  the  white  rami  communicantes.  i'rom  them  are  derived 
the  branches  which  supply  the  viscera. 

The  Cardiac  Plexus  (Plexus  Cardiacus)  (Fig.  787). 

The  cardiac  plexus  is  situated  at  the  base  of  tht  heart,  and  is  divided  into  a 
superficial  part,  which  lies  in  tlie  concavity  of  the  arch  of  the  aorta,  and  a  deep 
part,  which  lies  between  the  trachea  and  aorta.  The  two  plexuses  are,  however, 
closely  connected. 

The  superficial  cardiac  plexus  lies  beneath  the  arch  of  the  aorta,  in  front  of 
the  riglit  pulmonary  artery.  It  is  formed  by  the  left  superior  cardiac  nerve,  the 
left  (and  occasionally  also  the  right)  inferior  cervical  cardiac  branches  of  the  vagus, 
and  filaments  from  the  deep  cardiac  plexus.  A  small  ganglion,  the  cardiac  ganglion 
of  Wrisberg  {ganglion  cardiacum  [Wrisbergi])  is  occasionally  found  connected  with 
these  nerves  at  their  point  of  junction.  This  ganglion,  when  present,  is  situated 
immediately  beneath  the  arch  of  the  aorta  on  the  right  side  of  the  ductus 
arteriosus.  The  superficial  cardiac  plexus  gives  branches  to  the  deep  cardiac 
plexus  beneath  the  arcli  of  the  aorta  to  the  right  or  anterior  coronary  plexus  and 
to  tlie  left  anterior  pulmonary  plexus. 

The  deep  cardiac  plexus  is  situated  in  front  of  the  trachea  at  its  bifurcation,. 


THE  CCELIAC  OB  SOLAR  PLEXUS  1073 

above  the  point  of  division  of  the  puhnonary  artery  and  behind  the  arch  of  the 
aorta.  It  is  formed  by  the  cardiac  nerves  derived  from  the  cervical  ganglia  of 
the  sympathetic  and  the  cardiac  branches  of  the  recurrent  laryngeal  and  vagus. 
The  only  cardiac  nerves  which  do  not  enter  into  the  formation  of  this  plexus  are 
the  left  superior  cardiac  nerve  and  the  inferior  cervical  cardiac  branch  from  the 
left  vagus. 

The  branches  from  the  right  side  of  this  plexus  pass,  some  in  front  of,  and  others 
behind,  the  right  pulmonary  artery;  the  former,  the  more  numerous,  transmit 
a  few  filaments  to  the  anterior  pulmonary  plexus,  and  are  then  continued  onward 
to  form  part  of  the  right  coronary  plexus;  those  behind  the  pulmonary  artery  dis- 
tribute a  few  filaments  to  the  right  auricle,  and  are  then  continued  onward  to  form 
a  part  of  the  left  coronary  plexus. 

The  left  side  of  the  plexus  is  connected  with  the  superficial  cardiac  plexus  and 
gives  filaments  to  the  left  auricle  of  the  heart,  and  to  the  anterior  pulmonary 
plexus,  and  is  then  continued  to  form  the  greater  part  of  the  left  coronary  plexus. 

The  left  coronary  plexus  (plexus  coronarius  posterior)  is  larger  than  the  right, 
and  accompanies  the  left  coronary  artery;  it  is  chiefly  formed  by  filaments  pro- 
longed from  the  left  side  of  the  deep  cardiac  plexus,  and  by  a  few  from  the  right 
side.     It  gives  branches  to  the  left  auricle  and  ventricle. 

The  right  coronary  plexus  {plexus  coronarius  anterior)  is  formed  partly  from  the 
superficial  and  partly  from  the  deep  cardiac  plexus.  It  accompanies  the  right 
coronary  artery,  and  gives  branches  to  the  right  auricle  and  ventricle. 

Although  sympathetic  filaments  enter  into  the  formation  of  the  anterior  and 
posterior  pulmonary  and  the  oesophageal  plexuses,  these  are  usually  regarded  as 
portions  of  the  vagus  nerve  (p.  1007). 

The  Coeliac  or  Solar  Plexus  (Plexus  Coeliacus)  (Figs.  787,  792). 

The  coeliac  or  solar  plexus  supplies  the  viscera  in  the  abdominal  cavity.  It 
consists  of  a  great  network  of  nerves  and  ganglia,  situated  behind  the  pancreas 
and  the  lesser  peritoneal  cavity  and  in  front  of  the  aorta  and  crura  of  the 
Diaphragm.  It  surrounds  the  coeliac  axis  and  root  of  the  superior  mesenteric 
artery,  extending  downward  as  low  as  the  pancreas  and  outward  to  the  suprarenal 
glands.  This  plexus,  and  the  ganglia  connected  with  it,  receive  the  great,  the  small, 
and  the  least  splanchnic  nerves  of  both  sides,  and  some  filaments  from  the  right 
vagus  nerve.  It  distributes  filaments  which  accompany,  under  the  name  of 
plexuses,  all  the  branches  from  the  front  of  the  abdominal  aorta. 

Of  the  ganglia  of  which  the  solar  plexus  is  partly  composed  the  principal 
are  the  two  semilunar  ganglia  {ganglia  coeliaca)  (Figs.  792  and  793),  which  are 
situated  one  on  each  side  of  the  plexus,  and  are  the  largest  ganglia  in  the  body. 
They  are  large,  irregular,  gangliform  masses  formed  by  the  aggregation  of  smaller 
ganglia,  having  interspaces  between  them.  They  are  situated  in  front  of  the 
crura  of  the  Diaphragm,  close  to  the  suprarenal  glands;  the  one  on  the  right 
side  lies  beneath  the  inferior  vena  cava.  The  upper  part  of  each  ganglion  is 
joined  by  the  great  splanchnic  nerve,  and  to  the  inner  side  of  each  the  branches 
of  the  solar  plexus  are  connected.  The  lower  portion  of  each  semilunar  ganglion 
is  detached,  and  is  named  the  aorticorenal  ganglion. 

From  the  coeliac  plexus  are  derived  the  following: 

Phrenic  or  Diaphragmatic  plexus.  Gastric  plexus. 

Suprarenal  plexus.  Splenic  plexus. 

Renal  plexus.  Hepatic  plexus. 

Spermatic  |    i    ,  Superior  mesenteric  plexus. 

Ovarian     j  "    '     '  ^^  Aortic  plexus. 


1074 


THE  NERVE  SYSTEM 


The  Phrenic  Plexus  {plexus  phrenicus)  (Fig.  792)  accompanies  the  inferior 
phrenic  artery  to  the  Diaphragm,  some  filaments  passing  to  the  suprarenal  gland. 
It  arises  from  the  upper  part  of  the  semilunar  ganglion,  and  is  larger  on  the  right 
than  on  the  left  side.  It  receives  one  or  two  branches  from  the  phrenic  nerve. 
At  the  point  of  junction  with  the  phrenic  nerve  is  a  small  ganglion,  the  phrenic 
ganglion  (ganglion  phrenicum)  (Fig.  793),  which  lies  on  the  under  surface  of  the 
Diaphragm,  near  the  right  suprarenal.  Its  branches  are  distributed  to  the 
inferior  vena  cava,  suprarenal,  and  hepatic  plexus.  There  is  no  phrenic  ganglion 
on  the  left  side. 


CCELIAC    LEFT 

PHRENrC  PLEXUS    VAGU 

PLEXUS 


Fig.  792.— The  semilunar  gaogli; 


FEHIOR 
:SENTERIC 
LEXUS 


'ith  the  sympathetic  plexuses  of  the  abdominal  viscera  radiating  from 
the  gangha.     (Toldt.) 


The  Suprarenal  Plexus  (plexus  suprarenalis)  (Fig.  792)  is  formed  by  branches 
from  the  coeliac  plexus,  from  the  semilunar  ganglion,  and  from  the  phrenic  and 
great  splanchnic  nerves,  a  ganglion  being  formed  at  the  point  of  junction  of  the 
latter  nerve.  It  supplies  the  suprarenal  gland,  being  chiefly  distributed  to  its 
medullary  portion.  The  branches  of  this  plexus  are  remarkable  for  their  large 
size  in  comparison  with  the  size  of  the  organ  they  supply. 


THE  CCELIAC  OR  SOLAR  PLEXUS 


1075 


The  Renal  Plexus  {plexus  renalis)  (Figs.  792  and  793)  is  formed  bj'  filaments 
from  the  ca-Hac  plexus,  the  lower  part  of  the  semilunar  ganglion  (aorticorenal 
o-ancdion)  and  the  aortic    plexus.     It   is   also   joined    by  the   least   splanclinic 


Phrenic  qanqhon 
Suprarenal  plexus 


Ltft  lenal  artery, 
&upei  wi  mesenteric  ganglion. 


Infei  lot  mesenteric  artery. 


.Infeno)  mesenteric  ganglion. 


Sacioiettebral  angle. 

( ommon  ihac  vein. 

-Common  iliac  artery. 


Fig.  793.— Lumbar  portion  of  the  gangliated  cord,  with  the  ccsliac  and  hypogastric  plextises.     (.\fter  Henle.) 


1076.  THE  NEJRVi:  SYSTEM 

nerve.  The  nerves  from  these  sources,  fifteen  or  twenty  in  number,  have  numerous 
ganglia  developed  upon  them.  They  accompany  the  branches  of  the  renal 
artery  into  the  kidney,  some  filaments  on  the  right  side  being  distributed  to  the 
inferior  vena  cava,  and  others,  on  both  sides,  to  the  spermatic  plexuses. 

The  Spermatic  Plexus  (plexus  sfermaticus)  (Fig.  792)  is  derived  from  the  renal 
plexus,  receiving  branches  from  the  aortic  plexus.  It  accompanies  the  spermatic 
vessels  to  the  testis. 

In  the  female  the  ovarian  plexus  {plexus  arteriae  ovaricae)  arises  like  the  sper- 
matic plexus,  and  is  distributed  to  the  ovaries.  Fallopian  tubes,  and  fundus  of  the 
uterus. 

The  Gastric  or  Coronary  Plexus  {plexus  gastricus  superior)  (Fig.  792)  accompa- 
nies the  gastric  artery  along  the  lesser  curvature  of  the  stomach,  and  joins  with 
branches  from  the  left  vagus  nerve. 

The  Splenic  Plexus  {plexus  lienalis)  (Fig.  792)  is  formed  by  branches  from  the 
coeliac  plexus,  the  left  semilunar  ganglion,  and  from  the  right  vagus  nerve.  It 
accompanies  the  splenic  artery  and  its  branches  to  the  substance  of  the  spleen, 
giving  off,  in  its  course,  filaments  to  the  pancreas,  the  pancreatic  plexus,  and  the 
left  gastroepiploic  plexus,  which  accompanies  the  left  gastroepiploic  artery  along 
the  greater  curvature  of  the  stomach. 

The  Hepatic  Plexus  {plexus  hepaticus)  (Fig.  792),  the  largest  offshoot  from  the 
coeliac  plexus,  receives  filaments  from  the  left  vagus  and  right  phrenic  nerves. 
It  accompanies  the  hepatic  artery,  ramifying  in  the  substance  of  the  liver  upon 
the  branches  of  the  portal  vein  within  the  substance  of  the  liver. 

Branches  from  this  plexus  accompany  all  the  divisions  of  the  hepatic  artery. 
Thus,  there  is  a  pyloric  plexus  accompanying  the  pyloric  branch  of  the  hepatic, 
which  joins  with  the  gastric  plexus  and  vagi  nerves.  There  is  also  a  gastro- 
duodenal  plexus,  which  subdivides  into  the  pancreaticoduodenal  plexus,  which 
accompanies  the  pancreaticoduodenal  artery,  to  supply  the  pancreas  and  duo- 
denum, joining  with  branches  from  the  mesenteric  plexus.  The  gastroepiploic 
plexus,  which  accompanies  the  right  gastroepiploic  artery  along  the  greater 
curvature  of  the  stomach,  and  which  is  said  to  anastomose  with  branches  from 
the  splenic  plexus,  is  in  reality  derived  from  the  splenic  plexus.  A  cystic  plexus, 
which  supplies  the  gall-bladder,  also  arises  from  the  hepatic  plexus  near  the  liver. 

The  Superior  Mesenteric  Plexus  {plexus  mesentericus  superior)  (Fig.  792)  is  a 
continuation  of  the  lower  part  of  the  great  solar  plexus,  receiving  a  branch  from  the 
junction  of  the  right  vagus  nerve  with  the  coeliac  plexus.  It  surrounds  the  superior 
mesenteric  artery,  which  it  accompanies  into  the  mesentery,  and  divides  into  a 
number  of  secondary  plexuses,  which  are  distributed  to  all  parts  supplied  by  the 
artery — ^viz.,  pancreatic  branches  to  the  pancreas;  intestinal  branches,  which  supply 
the  whole  of  the  small  intestine ;  and  ileocolic,  right  colic,  and  middle  colic  branches, 
which  supply  the  corresponding  parts  of  the  large  intestine.  The  nerves  composing 
this  plexus  are  white  in  color  and  firm  in  texture;  in  the  upper  part  of  the  plexus 
close  to  the  origin  of  the  superior  mesenteric  artery  is  a  ganglion  {ganglion  mesen- 
tericum  super ius). 

The  Abdominal  Aortic  Plexus  {plexus  aorticus  abdominalis)  (Figs.  792  and  79.3) 
is  formed  by  branches  derived,  on  either  side,  from  the  coeliac  plexus,  receiving 
filaments  from  some  of  the  lumbar  ganglia.  It  is  situated  upon  the  sides  and  front 
of  the  aorta,  between  the  origins  of  the  superior  and  inferior  mesenteric  arteries. 
From  this  plexus  arise  part  of  the  spermatic,  the  inferior  mesenteric,  and  the  hypo- 
gastric plexuses ;  it  also  distributes  filaments  to  the  inferior  vena  cava. 

The  Inferior  Mesenteric  Plexus  {plexus  mesentericus  inferior)  (Fig.  792)  is  derived 
chiefly  from  the  left  side  of  the  aortic  plexus.  It  surrounds  the  inferior  mesenteric 
artery,  and  divides  into  a  number  of  secondary  plexuses,  which  are  distributed  to 
all  the  parts  supplied  by  the  artery — viz.,  the  left  colic  and  sigmoid  plexuses,  which 


THE  PELVIC  PLEXUSES  1077 

supply  the  descending  and  sigmoid  flexure  of  the  colon;  and  the  superior  hemor- 
rhoidal plexus  (plexus  hemorrhoidalis  superior),  which  supplies  the  upper  part 
of  the  rectum  and  joins  in  the  pelvis  with  l)ranches  from  the  pelvic  plexus. 

The  Hypogastric  Plexus  (Plexus  Hypogastricus)  (Figs.  787,  793). 

The  hypogastric  plexus  supplies  the  viscera  of  the  pelvic  cavity.  It  is  situated 
in  front  of  the  promontory  of  the  sacrum,  between  the  two  common  iliac  arteries, 
and  is  formed  by  the  union  of  numerous  filaments,  which  descend  on  each  side 
from  the  abdominal  aortic  plexus  and  from  the  lumbar  ganglia.  This  plexus  con- 
tains no  evident  ganglia;  it  bifurcates,  below,  into  two  lateral  portions,  right  and 
left,  which  form  the  pelvic  plexuses. 

The  Pelvic  Plexuses. 

The  pelvic  plexuses  supply  the  viscera  of  the  pelvic  cavity,  and  are  situated  at 
the  side  of  the  rectum  in  the  male,  and  at  the  sides  of  the  rectum  and  vagina 
in  the  female.  They  are  formed  by  a  continuation  of  the  hypogastric  plexus,  by 
the  visceral  branches  from  the  second,  third,  and  fourth  sacral  nerves,  and  by  a 
few  filaments  from  the  first  two  sacral  ganglia.  At  the  points  of  junction  of 
these  nerves  small  ganglia  are  found.  From  these  plexuses  numerous  branches 
are  distributed  to  the  rectum  and  bladder  in  the  male,  and  to  the  rectum,  bladder, 
uterus,  and  vagina  in  the  female.  They  accompany  the  branches  of  the  internal 
iliac  artery.  These  secondary  plexuses  are  (1)  the  inferior  hemorrhoidal,  (2) 
vesical,  (3)  prostatic,  (4)  vaginal,  and  (5)  uterine  plexuses. 

The  Inferior  Hemorrhoidal  Plexus  (plexus  haemorrhoidalis  inferior)  arises  from 
the  upper  part  of  the  pelvic  plexus.  It  supplies  the  rectum,  joining  with  branches 
of  the  superior  hemorrhoidal  plexus. 

The  Vesical  Plexus  {plexus  vesicalis)  arises  from  the  fore  part  of  the  pelvic 
plexus.  The  nerves  composing  it  are  nmnerous,  and  contain  a  large  proportion 
of  spinal  nerve  fibres.  They  accompany  the  vesical  arteries,  and  are  distributed 
to  the  side  and  base  of  the  bladder.  Numerous  filaments  also  pass  to  the  vesiculae 
seminales  and  vasa  deferentia;  those  accompanying  the  vas  deferens  join,  on  the 
spermatic  cord,  with  branches  from  the  spermatic  plexus. 

The  Prostatic  Plexus  (plexus  prostaticus)  is  continued  from  the  lower  part  of 
the  pelvic  plexus.  The  nerves  composing  it  are  of  large  size.  They  are  distributed 
to  the  prostate  gland,  seminal  vesicles,  and  erectile  tissue  of  the  penis.  The 
nerves  supplying  the  erectile  tissue  of  the  penis  consist  of  two  sets,  the  small  and 
large  cavernous  nerves.  They  are  slender  filaments,  which  arise  from  the  fore  part 
of  the  prostatic  plexus,  and,  after  joining  with  branches  from  the  internal  pudic 
nerve,  pass  for%\'ard  beneath  the  pubic  arch. 

The  small  cavernous  nerves  (jin.  cavernosi  penis  minores)  perforate  the  fibrous 
covering  of  the  penis,  near  its  root. 

The  large  cavernous  nerve  (n.  cavernosus  penis  major)  passes  forward  along  the 
dorsum  of  the  penis,  joins  with  the  dorsal  nerve  of  the  penis,  and  is  distributed 
to  the  corpora  cavernosa  and  corpus  spongiosum. 

The  uterine  and  vaginal  plexuses  in  reality  constitute  one  plexus,  the  utero- 
vaginal plexus  (plexus  uferovagiualis). 

The  Vaginal  Plexus  arises  from  the  lower  part  of  the  pelvic  plexus.  It  is  dis- 
tributed to  the  walls  of  the  vagina,  to  the  erectile  tissue  of  the  vestibule,  and  to  the 
clitoris.  The  nerves  composing  this  plexus  contain,  like  the  vesical,  a  large 
proportion  of  spinal  nerve  fibres. 

The  Uterine  Plexus  accompanies  the  uterine  artery  to  the  side  of  the  uterus 
between  the  layers  of  the  broad  ligament;  it  communicates  with  the  ovarian  plexus. 


THE  OEGANS  OF  SPECIAL  SENSE. 


m, 


^HE  organs  of    the    senses  {orgaiia  scnsuuin)  are  five  in  number — those  of 
I       smell,  sight,  hearing,  taste,  and  touch. 


THE  NOSE. 


The  nose  is  the  peripheral  portion  of  the  organ  of  smell  (prganon  olfactus);  by 
means  of  the  peculiar  properties  of  its  nerves  it  protects  the  lungs  from  the  inhala- 
tion of  deleterious  gases  and  assists  the  organ  of  taste  in  discriminating  the  prop- 
erties of  food.  The  organ  of  smell  consists  of  two  parts — one  external,  the  outer 
nose,  which  projects  from  the  centre  of  the  face,  and  an  internal,  the  cavum  nasi, 
which  is  divided  by  a  septum  into  the  right  and  left  nasal  fossae. 


THE  OUTER  NOSE   (NASUS  EXTERNUS). 

The  outer  nose  is  the  more  anterior  and  prominent  part  of  the  organ  of  smell. 
Of  a  pyramidal  form,  it  is  directed  downward,  and  projects  from  the  centre  of 
the  face  immediately  above  the  upper  lip.  Its  root  (radix  nasi)  is  connected 
directly  with  the  forehead.  Its  base  (basi^  nasi)  presents  two  elliptical  orifices, 
the  nostrils  or  anterior  nares  (nares),  separated  from  each  other  by  an  antero- 
posterior septum,  the  columna  (septum  mobile  nasi).  The  margins  of  the  nostrils 
are  provided  with  a  number  of  stiff  hairs  or  vibrissas,  which  arrest  the  passage 
of  foreign  substances  carried  with  the  current  of  air  intended  for  respiration. 
The  point  (apex  nasi)  is  the  free  extremity  of  the  nose.  The  lateral  surfaces  of 
the  nose  form,  by  their  union  in  the  middle  line,  the  dorsum  (dorsum  nasi),  the 
direction  of  which  varies  considerably  in  different  individuals.  The  portion 
of  the  dorsum  over  the  nasal  bones  is  the  bridge.  Each  lateral  surface  terminates 
below  in  a  rounded  eminence,  the  wing  or  ala  nasi,  which,  by  its  lower  margin 
(margo  nasi),  forms  the  outer  boundary  of  the  corresponding  nostril.  Above  the 
ala  is  a  depression,  the  alar  sulcus. 

Structure. — ^The  nose  is  composed  of  a  framework  of  bones  and  cartilages,  the  latter  being 
slightly  acted  upon  by  certain  muscles.  It  is  covered  externally  by  the  integument,  internally 
by  mucous  membrane,  and  is  supplied  with  vessels  and  nerves. 

The  bony  framework  occupies  the  upper  part  of  the  organ;  it  consists  of  the  nasal  bones  and 
the  nasal  processes  of  the  maxillae  ("pp.  99  and  104). 

The  cartilaginous  framework  {cartilagiiu's  nasi)  (Figs.  794  and  795)  consists  of  five  pieces — 
the  two  upper  and  the  two  lower  lateral  cartilages  and  the  cartilage  of  the  septvun. 

The  upper  lateral  cartilage  (cartilago  7iasi  lateralis)  of  each  side  is  situated  below  the  free 
margin  of  the  nasal  bone  and  is  flat  and  triangular  in  shape.  Its  anterior  margin  is  thicker  than 
the  posterior,  and  continuous  aliove  with  the  cartilage  of  the  septum.  Its  posterior  margin  is 
attached  to  the  nasal  process  of  the  maxilla.  Its  inferior  margin  is  connected  by  fibrous  tissue 
with  the  lower  lateral  cartilage;  one  surface  is  tiu-ned  outward,  the  other  inward  toward  the 
nasal  cavity. 

The  lower  lateral  cartilage  (cartilago  alaris  major)  is  a  thin,  fiexible  plate  situated  immediately 
below  the  preceding,  and  bent  upon  itself  in  such  a  manner  as  to  form  the  inner  and  outer  walls 
of  the  orifice  of  the  nostril.  The  portion  which  forms  the  inner  wall  {cms  mediale),  thicker 
than  the  rest,  is  loosely  connected  with  the  corresponding  portion  of  the  opposite  cartilage  to 

(1079) 


1080 


THE  ORGANS  OF  SPECIAL  SENSE 


form  a  small  part  of  the  columna.  Its  inferior  border,  free,  rounded,  and  projecting,  forms, 
with  the  thickened  integimient  and  subjacent  tissue  and  the  corresponding  parts  of  the  opposite 
side,  the  mobile  septum.     The  part  of  the  cartilage  which  forms  the  outer  wall  {cms  laterale)  is 


Seen  from  below. 


le  view. 


■cer  lateral  cart 


Sesamoid  cartilages. 


Figs.  794  and  795. — Cartilages  of  the 

curved  to  correspond  with  the  ala  of  the  nose;  it  is  oval  and  flattened,  narrow  behind,  where  it 
is  connected  with  the  nasal  process  of  the  maxilla  by  a  tough  fibrous  membrane,  in  which  are 
found  three  or  four  small  cartilaginous  plates,  the  sesamoid  or  lesser  alar  cartilages  {cartilagines 
dares  minores).  _  Above,  it  is  connected  by  fibrous  tissue  to  the  upper  lateral  cartilage  and  front 
part  of  the  cartilage  of  the  septum;  below,  it  falls  short  of  the  margin  of  the  nostril;  the  ala 
being  completed  by  dense  cellular  tissue  covered  by  skin.  In  front  the  lower  lateral  cartilages 
are  separated  by  a  notch  which  corresponds  with  the  point  of  the  nose. 

The  cartilage  of  the  septum  (carfilago 
septi  nasi)  (Figs.  794  and  796)  is  somewhat 
quadrilateral  in  form,  thicker  at  its  margins 
than  at  its  centre,  and  completes  the  sepa- 
ration between  the  nasal  fossa  in  front.  Its 
anterior  margin,  thickest  above,  is  connected 
with  the  nasal  bones,  and  is  continuous  with 
the  anterior  margins  of  the  two  upper  lateral 
cartilages.  Below,  it  is  connected  to  the 
inner  portions  of  the  lower  lateral  cartilages 
by  fibrous  tissue.  Its  posterior  margin  is 
connected  with  the  perpendicular  lamella  of 
the  ethmoid;  its  inferior  margin  with  the 
vomer  and  the  palate  processes  of  the  max- 
illa? (Fig.  796). 

It  may  be  prolonged  backward  (especially 
In  children)  for  some  distance  between  the 
vomer  and  perpendicular  plate  of  the  eth- 
moid, forming  what  is  termed  the  sphenoidal 
process  (processus  sphenoidalis  septi  cartila- 
ginei).  The  septal  cartilage  does  not  reach 
as  far  as  the  lower  part  of  the  nasal  septum. 
This  i.i  formed  by  the  thinnest  portions  of  the 
lower  lateral  cartilages  and  by  the  skin;  it  is  freely  movable,  and  hence  is  termed  the  mobile 
septum. 

Along  the  lower  margin  of  the  anterior  half  of  the  cartilage  of  the  septum  is  another  cartilage 
which  is  attached  to  the  vomer  and  is  known  as  the  vomerine  cartilage,  or  cartilage  of  Jacobson 
(cartilagovomeronasalis). 

These  various  cartilages  are  connected  to  each  other  and  to  the  bones  by  a  tough  fibrous 
membrane,  which  allows  the  utmost  facility  of  movement  between  them. 

The  muscles  of  the  nose  are  situated  beneath  the  integument;  they  are  (on  each  side)  the 
Pyramidalis  nasi,  the  Levator  labii  superiores  alaeque  nasi,  the  Dilatator  naris,  anterior  and  pos- 


-Bones  and  cartilacce  of 
Right  side. 


eptum  of  the  nose. 


THE  NASAL  F088M 


1081 


terior,  the  Compressor  nasi,  the  Compressor  narium  minor,  and  the  Depressor  alae  nasi.  They 
have  been  previously  described  (p.  372). 

The  integiunent  co\'ering  the  dorsum  and  the  .sides  of  the  nose  is  thin,  and  loosely  connected 
with  the  subjacent  parts;  but  the  integument  of  the  tip  and  the  alas  of  the  nose  is  thicker  and 
more  firmly  adherent,  and  is  furnished  with  a  large  number  of  sebaceous  follicles,  the  orifices  of 
which  are  usually  very  distinct. 

The  mucous  membrane  lining  the  interior  of  the  nose  is  continuous  with  the  skin  externally 
and  with  the  mucous  membrane  which  lines  the  nasal  fossse  within. 

The  arteries  of  the  nose  are  the  lateralis  nasi  from  the  facial,  and  the  inferior  artery  of  the 
septum  from  the  superior  coronarij,  which  supply  the  alii?  and  septum,  the  sides  and  dorsum  being 
supplied  from  the  nasal  branch  of  the  ophthalmic  and  the  infraorbital.  The  veins  of  the  nose 
terminate  in  the  facial  and  ophthalmic.  The  Ijrmphatics  of  the  outer  nose  are  shown  in  Fig. 
557.  They  empty  chiefly  into  the  submaxillary  lymph  nodes.  The  nerves  for  the  muscles  of 
the  nose  are  derived  from  the  facial,  while  the  skin  receives  its  branches  from  the  infraorbital, 
infratrochlear,  and  na^al  branches  of  the  ophthalmic. 


THE  NASAL  FOSS.ffi  (CAVUM  NASI). 

The  nasal  fossae  are  two  irregular  cavities  situated  in  the  middle  of  the  face, 
one  on  each  side  of  the  mesal  plane.  They  open  in  front,  when  the  soft  parts 
are  in  place,  by  the  two  nostrils  or  anterior  nares,  and  terminate,  behind,  in  the 
nasopharynx  by  the  posterior  nares. 


Bccessus  splieno  ethmoidalis 


Orifice  of  Eustachian  tube     Fossa  of 

Rosenmilller 

Fig.  797. — Outer  wall  of  nasal  fossa. 

The  anterior  nares  (nares)  are  somewhat  pear-shaped  apertures,  each  measur- 
ing about  one  inch  (2.5  cm.)  antero-posteriorly  and  half  an  inch  (1.2  cm.)  trans- 
versely at  their  widest  part.  The  nasal  fossae  in  the  dry  skull  open  in  front  by 
the  anterior  nasal  aperture  (aperhira  pyriformis). 

The  posterior  nares  (choanae)  are  two  oval  openings,  which  are  smaller  in  the 
living  or  recent  subject  than  in  the  skeleton,  because  they  are  narrowed  by  the 


1082 


THE  ORGANS  OF  SPECIAL  SENSE 


mucous  membrane.  Each  measures  an  inch  (2.5  cm.)  in  the  vertical  and  half 
an  inch  (1.2  cm.)  in  the  transverse  direction  in  a  M^ell-developed  adult  skull. 

For  the  description  of  the  bony  boundaries  of  the  nasal  fossae  see  page  138. 

Inside  the  aperture  of  the  nostril  is  a  slight  dilatation,  the  vestibule  (vestibulum 
nasi),  which  extends  as  a  small  pouch,  the  ventricle,  toward  the  point  of  the  nose. 
Above  and  behind  the  vestibule  is  surrounded  by  a  prominence  (limen  nasi). 
Below  the  prominence  the  vestibule  ic  lined  with  skin;  above  and  behind  it  the 
fossa  is  lined  with  mucous  membrane.  The  fossa,  above  and  behind  the  vesti- 
bule, has  been  divided  into  two  parts — an  olfactory  portion  (regio  olfactoria),  a  slit- 


PROBE    P^g 
SINUS   THfloJl^O 

''""it. 


Fig.  798. — External  wall  of  right  nasal  fossa,  parts  of  the  turbinates  having  been  cut  away  to  show  the  orifices  of 
the  sinuses  which  open  into  the  meatuses.     (Testut.) 

like  cavity,  comprising  the  upper  and  central  part  of  the  septum  and  the  superior 
turbinated  process,  and  a  respiratory  portion  {regio  respiratoria),  which  comprises 
the  rest  of  the  fossa. 

The  Outer  Wall  (Figs.  797  and  798). — The  superior,  middle,  and  inferior  meati 
(meatus  nasi  superior,  niediiis,  and  inferior)  are  described  on  page  141.  The 
sphenoidal  air  sinus  opens  into  the  sphenoethmoidal  recess  (recessus  sphenoeth- 
moidalis),  a  narrow  recess  above  the  superior  turbinated  process  (Fig.  798). 
The  posterior  ethmoidal  cells  open  into  the  front  and  upper  part  of  the  superior 
meatus  (Fig.  797).  Where  the  middle  turbinated  process  joins  the  nasal  process  of 
the  maxilla  there  is  often  an  elevation,  agger  nasi,  presumably  a  representative  of 
another  turbinate.  On  raising  or  cutting  away  the  middle  turbinated  process 
the  outer  wall  of  the  middle  meatus  is  fully  exposed  (Figs.  798  and  799)  and  pre- 
sents (1)  a  rounded  elevation,  termed  the  bulla  ethmoidalis,  opening  on  or  immedi- 
ately above  which  are  the  orifices  of  the  middle  ethmoidal  cells;  (2)  a  deep,  narrow, 
curved  groove,  in  front  of  the  bulla  ethmoidalis,  termed  the  hiatus  semilunaris, 
into  which  the  anterior  ethmoidal  cells  and  the  maxillary  sinus  open,  the  orifice 
of  the  latter  being  placed  near  the  level  of  its  roof.  The  middle  meatus  is  pro- 
longed, above  and  in  front,  into  the  infxmdibulum,  which  leads  into  the  frontal 
sinus.  The  anterior  extremitj^  of  the  meatus  is  continued  into  a  depressed  area 
which  lies  above  the  vestibule  and  is  named  the  atrium  {atrium  meatus  medii  nasi). 


THE  NASAL  FOSS^ 


1083 


The  nasal  duct  opens  into  the  anterior  part  of  the  inferior  meatus,  the  opening 
being  frequently  overlapped  by  a  fold  of  mucous  membrane.' 

The  Inner  Wall  (Fig.  799). — The  inner  wall  or  septum  is  frequently  more  or 
less  deflected  from  the  mesal  plane  (Fig.  799),  thus  limiting  the  size  of  one  fossa 
and  increasing  that  of  the  other.  Ridges  or  spurs  of  bone  growing  outward  from 
the  septum  are  also  sometimes  present.  Immediately  over  the  incisi\e  foramen 
at  the  lower  edge  of  the  cartilage  of  the  septum  a  depression,  the  nasopalatine 
recess  {recessus  nasopalathms) ,  may  be  seen.  In  the  septum  close  to  this  recess 
a  minute  orifice  may  be  discerned;  it  leads  into  a  blind  pouch,  the  rudimentary 
organ  of  Jacobson  {organon  wmeronasale) ,  which  is  well  developed  in  some  of  the 
lower  animals,  but  is  rudimentary  in  man.     The  organ  is  supported  by  a  plate 


Eye  ball 


J  oijve  (hiatus  semilunaris) 
leading  to  infundibiUum 
Middle  turbinated  vrocejis 

Middle  meatus 


Turbinated  boiie 


f  Buccal  cai  ity 

\  ^pace  beiueen  cheek  and  gum 
Molai  tooth  upper  jaw 


Root  t-J  molar  tooth 


Fig.  799— Tr: 


Tongue         Hard  palnf' 

Nasal 
septum 

^  vertical  section  of  the  nasal  fossje.    Tlie  section  i 
processes.     (Cryer.) 


made  anterior  to  the  superior  turbinated 


of  cartilage,  distinct  from  the  cartilage  of  the  septum,  tlie  cartilage  of  Jacobson 
(p.  1080).  The  cartilage  of  Jacobson  is  to  the  outer  side  of  the  lower  edge  of 
the  cartilage  of  the  septum.  Just  below  the  opening  of  the  blind  poucli  is  an  ele- 
vation, tlie  eminence  of  Jacobson. 

The  Mucous  Membrane  (membrana  mucosa  nasi). — The  mucous  membrane  lining 
the  nasal  fossse  is  sometimes  called  the  Schneiderian  membrane.-  It  is  closely 
adherent  to  the  periosteum  or  perichondrium,  upon  \Ahich  it  lies.  It  is  continuous 
externally  with  the  skin  through  the  anterior  nares,  and  with  the  mucous  mem- 
brane of  the  nasopharynx  through  the  posterior  nares.  From  the  nasal  fosste 
its  continuity  may  be  traced  with  the  conjuncti-\-a  through  the  nasal  duct  and 
lacrimal  canals;  with  the  lining  membrane  of  the  tympanum  and  mastoid  cells 

I  J.  p.  Schaeffer:  "  Types  of  Ostia  Nasolacrimalia,  etc.,"  Amer.  Jour,  of  Anat.,  vol.  xiii.  No.  2,  1912. 
2After  Conrad  Victor  Schneider  (1614-16S0),  Professor  of  Anatomy  at  Wittemberg. 


1084 


THE  ORGANS  OF  SPECIAL  SENSE 


through  the  Eustachian  tube;  and  with  the  frontal,  ethmoidal,  and  sphenoidal 
sinuses,  and  the  maxillary  sinus  through  the  several  openings  in  the  meatuses.  The 
mucous  membrane  is  thickest  and  most  vascular  over  the  turbinated  processes  and 
bone.    It  is  also  thick  over  the  septum,  but  in  the  intervals  between  the  spongy  bones 

and  on  the  floor  of  the 
nasal  fossae  it  is  very 
thin.  Where  it  lines 
the  various  sinuses  it 
is  thin  and  pale. 

Owing  to  the  great 
thickness  of  this  mem- 
brane, the  nasal  fossae 
are  much  narrower, 
and  the  turbinated 
processes  and  bones 
appear  larger  and 
more  prominent  than 
in  the  dried  skull. 
From  the  same  cir- 
cumstance, also,  the 
various  apertures  com- 
municating with  the 
meatuses  are  consid- 
erably narrowed. 


Epithelial 

hvier 


Branch  of 
olfactory  nerre'f 


Tunica  propr 


Olfactory  gland- 


C'ross-section 
of  nerve' 


Fig.  800. — Vertical  i 


Suppm-ting  cell 


Structure  of  the  Mucous  Membrane  (Figs.  800  and  801). — The  epithelium  covering  the 
mucous  membrane  differs  in  its  character  according  to  the  functions  of  the  part  of  the  nose 
in  which  it  is  found.  In  the  respirator}'  portion  of  the  nasal  cavity  the  epithelium  is  columnar 
and  ciliated,  which  is  also  the  type  found  in  the  accessory  sinuses,  with  the  exception  of  the 
maxillary,  where  the  epithelium  is  of  the 
simple  polygonal  variety.  Interspersed 
among  the  columnar  ciliated  cells  are  gob- 
let or  mucin  cells,  while  between  their  bases 
are  found  smaller  pyramidal  cells.  In  this 
region,  beneath  the  epithelium  and  its  base- 
ment membrane,  is  a  fibrous  layer  infil- 
trated with  leukocytes,  so  as  to  form  in 
many  parts  diffuse  lymphoid  tissue,  which 
is  particularly  plentiful  in  children ;  beneath 
this  is  a  nearly  continuous  layer  of  smaller 
and  larger  glands,  some  mucous  and  some 
serous,  the  ducts  of  which  open  upon  the 
surface.  In  the  respiratory  portion  of  the 
mucous  membrane  there  is  an  extensive 
anastomosing  plexus  of  veins,  which  in  some 
regions  forms  a  distinct  cavernous  tissue 
(plexus  caveniosus  concharum).  The  cav- 
ernous tissue  is  particularly  distinct  over  the  inferior  turbinated  bones.  In  the  olfactory 
region  the  mucous  membrane  is  yellowish  in  color  and  the  epithelial  cells  are  columnar  and 
non-ciliated;  they  are  of  two  kinds,  supporting  cells  and  olfactory  cells. 

The  supporting  cells  are  irregular  pigmented  elements  that  contain  oval  nuclei,  situated  in 
the  deeper  parts  of  the  cells;  the  free  surface  of  each  cell  presents  a  sharp  outline,  and  its  deep 
extremity  is  prolonged  into  a  process  which  runs  inward,  branching  to  communicate  with  similar 
processes  from  neighboring  cells,  so  as  to  form  a  network  in  the  deep  part  of  the  mucous  mem- 
brane. Lying  between  these  central  processes  of  the  supporting  cells  are  a  large  number  of 
spindle-shaped  cells,  the  olfactory  cells,  which  consist  of  a  large  spherical  nucleus  surrounded 
by  a  small  amount  of  granular  protoplasm,  and  possessing  two  processes,  of  M'hich  one  runs 
outward  between  the  columnar  epithelial  cells,  and  projects  on  the  surface  of  the  mucous  mem- 
brane as  a  fine,  hair-like  process,  the  olfactory  hair;  the  other  or  deep  process  runs  inward,  is 
frequently  beaded,  and  is  continuous  with  one  of  the  filaments  of  the  olfactory  nerves.  Beneath 
the  epithelium,  extending  through  the  thickness  of  the  mucous  membrane,  is  a  layer  of  tubular. 


Fig.  801. — From  a  vertical  section  through  the  mucous 
embrane  of  the  regio  olfactoria  of  a  quite  young  dog.  Gol- 
's  method.     X  -ioO.     (Szymonowitz.) 


THE  NASAL  F088JE  1085 

often  branched,  glands,  the  glands  of  Bowman  (glandulac  olfadoriac),  identical  in  structure  with 
serous  glands. 

The  accessory  spaces,  sphenoidal,  frontal,  maxillary,  sinuses,  and  ethmoidal  cells  are  lined 
by  an  extension  of  the  nasal  mucosa.  The  mucosa  is  thin,  and  consists  of  stratified  ciliated  and 
goblet  cells  upon  a  basement  membrane  and  supported  by  a  thin  fibroelastic  tunica  propria. 
The  glands  are  few  in  number  and  racemose  in  structiu'e. 

The  arteries  of  the  nasal  fossae  are  the  anterior  and  posterior  ethmoidal,  from  the  ophthalmic, 
which  supply  the  ethmoidal  cells,  frontal  sinuses,  and  roof  of  the  nose;  the  sphenopalatine, 
from  the  internal  maxillary,  which  supplies  the  mucous  membrane  covering  the  spongy  bones, 
the  meatuses,  and  septum;  the  inferior  artery  of  the  septum,  from  the  superior  coronary  of  the 
facial;  and  the  infraorbital  and  alveolar  branches  of  the  internal  maxillary,  which  supply  the 
lining  membrane  of  the  antrum.  The  ramifications  of  these  vessels  form  a  close,  plexiform 
network,  beneath  and  in  the  substance  of  the  mucous  membrane. 

The  veins  of  the  nasal  fossse  form  a  close,  cavgrnous-like  network  beneath  the  mucous  mem- 
brane. This  cavernous  appearance  is  especially  well  marked  over  the  lo«  er  part  of  the  septum 
and  over  the  middle  turbinated  process  and  inferior  turbinated  bones.  Some  of  the  veins  pass, 
with  those  accompanying  the  sphenopalatine  artery,  through  the  sphenopalatine  foramen;  and 
others,  tlirough  the  alveolar  branch,  to  join  the  facial  vein;  some  accompany  the  ethmoidal 
arteries,  and  terminate  in  the  ophthalmic  vein;  and,  lastly,  a  few  communicate  with  the  veins  in 
the  interior  of  the  skull,  through  the  foramina  in  the  cribriform  plate  of  the  ethmoid  bone,  and 
the  foramen  cecum. 

The  lymphatics  have  already  been  described  (p.  777). 

The  nerves  of  ordinary  sensation  are  the  nasal  branch  of  the  ophthalmic,  filaments  from  the 
anterior  dental  branch  of  the  superior  maxillary,  the  Vidian,  the  nasopalatine,  the  large  or 
anterior  ])alatine,  and  nasal  branches  of  the  sphenopalatine  ganglion.  The  nasal  branch  of  the 
ophthalmic  ilivision  of  the  trigeminal  nerve  distributes  filaments  to  the  fore  part  of  the  septum 
and  outer  wall  of  the  nasal  fossre.  Filaments  from  the  anterior  dental  branch  of  the  superior  max- 
illary supply  the  inferior  meatus  and  inferior  turbinated  bone.  The  Vidian  nerve  supplies  the 
upper  and  back  part  of  the  septum  and  superior  turbinated  process,  and  the  upper  anterior  nasal 
branches  from  the  sphenopalatine  ganglion  have  a  similar  distribution.  The  nasopalatine 
nerve  supplies  the  middle  of  the  septum.  The  larger  or  anterior  palatine  nerve  supplies  the 
lower  nasal  branches  to  the  middle  turbinated  process  and  the  turbinated  bone.  The 
olfartori/  nn  vrs,  the  special  nerves  of  the  sense  of  smell,  are  distributed  to  the  olfactory  region, 
and  ha\e  liccn  already  referred  to  (p.  973). 

Applied  Anatomy. — Instances  of  congenital  deformity  of  the  nose  are  occasionally  met  with, 
such  as  complete  absence  of  the  nose,  an  aperture  only  being  present;  or  perfect  development 
on  one  side,  and  suppression  or  malformation  on  the  other;  or  there  may  be  imperfect  apposi- 
tion of  the  nasal  bones,  so  that  the  nose  presents  a  median  cleft  or  furrow.  Deformities  which 
have  been  acquired  are  much  more  common,  such  ils  flattening  of  the  nose  {saddle  nose),  the  result 
of  syphilitic  necrosis,  imperfect  development  of  the  nasal  bones  in  cases  of  congenital  syphilis,  or 
a  lateral  deviation  of  the  nose  may  result  from  fracture. 

The  skin  over  the  ahe  and  tip  of  the  nose  is  thick  and  closely  adherent  to  subjacent  parts. 
Inflammation  of  this  part  is  therefore  very  painful,  on  account  of  the  tension.  The  skin  is  largely 
supplied  with  blood,  and  the  circulation  here  being  terminal,  vascular  engorgement  is  liable  to 
occur,  especially  in  women  at  the  menopause  and  in  both  sexes  from  disorders  of  digestion,  ex- 
posure to  cold,  etc.  The  skin  of  the  nose  also  contjtins  a  large  number  of  sebaceous  glands,  and 
these,  as  a  result  of  intemperance,  are  apt  to  become  affected,  and  the  nose  becomes  reddened, 
congested,  and  irregularly  swollen.  To  this  condition  the  term  grog  blossom  is  popularly'  applied- 
[n  some  of  these  cases  there  is  enormous  hypertrophy  of  the  skin  and  subcutaneous  tissues,  pro- 
ducing pendulous  masses,  termed  lipomata  nasi.  Ordinary  epithelioma  and  rodent  ulcer  may 
attack  the  nose,  the  latter  being  the  more  common  of  the  two.  Lupus  and  syphilitic  ulceration 
frecfuently  attack  the  nose,  and  may  destroy  the  whole  of  the  cartilaginous  portion.  In  fact, 
lupus  vulgaris  begins  more  frequently  on  the  ala  of  the  nose  than  in  any  other  situation. 

Cases  of  congenital  occlusion  of  one  or  both  nostrils,  or  adhesion  betw'een  the  ala  and  septum 
may  occur,  and  may  recjuire  immediate  operation,  since  the  obstruction  much  interferes  with 
niu-sing.     Bony  closure  of  the  posterior  nares  may  also  occur. 

To  examine  the  nasal  cavities,  the  head  should  be  thrown  back  and  the  nose  drawn  upward, 
the  parts  being  dilated  by  some  form  of  speculum.  The  posterior  nares  can  be  exjilored  by  the 
aid  of  reflected  light  from  the  mouth,  by  which  the  posterior  nares  can  be  illuminated.  The 
examination  is  very  difficult  to  carry  out,  and,  as  a  rule,  sufficient  information  regarding  the 
presence  of  foreign  bodies  or  tumors  in  the  nasopharynx  can  be  obtained  by  the  introduction 
of  the  finger  behind  the  soft  palate  through  the  mouth.  The  septmn  of  the  nose  is  sometimes  dis- 
placed or  deviates  from  the  middle  line;  this  may  be  the  result  of  an  injury  or  some  congenital 
defect  in  its  development;  in  the  latter  case  the  deviation  usually  occurs  along  the  line  of  union 
of  the  vomer  and  mesethmoid,  and  rarely  occurs  before  the  seventh  year.  Sometimes  the  de\'ia- 
tion  may  be  so  great  that  the  septum  may  come  in  contact  with  the  outer  wall  of  the  nasal  fossa, 
and  may  even  become  adherent  to  it,  thus  producing  complete  obstruction.     Perforation,  of  the 


1086  THE  ORGANS  OF  SPECIAL  SENSE 

septum  is  not  an  uncommon  affection  and  may  arise  from  several  causes — syphilitic  or  tubercu- 
lous ulceration,  blood  tumor  or  abscess  of  the  septum,  and  especially  in  workmen  exposed  to  the 
vapor  of  bichromate  of  potash,  from  the  irritating  and  corrosive  action  of  its  fumes.  When 
small,  the  perforation  may  cause  a  peculiar  whisthng  sound  during  respiration.  When  large, 
it  may  lead  to  the  falling  in  of  the  bridge  of  the  nose. 

Epistaxis  is  a  very  common  affection  in  children.  It  is  rarely  of  much  consequence,  and  will 
almost  always  subside,  but  in  the  more  violent  hemorrhages  of  later  life  it  may  be  necessary 
to  plug  the  posterior  nares.  In  performing  this  operation  it  is  desirable  to  remember  the  size 
of  the  posterior  nares.  A  ready  method  of  regulating  the  size  of  the  plug  to  fit  the  opening 
is  to  make  it  of  the  same  size  as  the  terminal  phalanx  of  the  thumb  of  the  patient  to  be  operated  on. 

Foreign  bodies,  such  as  boot  buttons,  are  frequently  inserted  into  the  nostrils  by  children,  and 
require  some  care  in  their  removal,  as  unskilled  attempts  only  result  in  pushing  the  foreign  body 
farther  into  the  nasal  fossa.  Bodies  which  remain  in  the  nose  any  length  of  time  are  apt  to 
set  up  an  ulceration  of  the  mucosa,  which  may  spread  to  the  bone;  a  unilateral  nasal  discharge 
in  a  child  is  always  suggestive  of  the  presence  of  a  foreign  body.  A  foreign  body  is  best 
removed  under  anesthesia,  placing  the  left  forefinger  in  the  nasopharynx  to  prevent  the  passage 
of  the  body  into  the  air-passages,  and  then  removing  the  foreign  body  through  the  anterior  naris 
by  a  suitable  scoop  or  forceps  manipulated  by  the  right  hand. 

Nasal  poll/pus  is  a  very  common  disease,  and  presents  itself  in  three  forms — the  gelatinous, 
the  fibrous,  and  the  malignant.  The  first  is  by  far  the  most  common.  It  grows  from  the  mucous 
membrane  of  the  outer  wall  of  the  nasal  fossa,  where  there  is  an  abundant  layer  of  highly  vas- 
cular submucous  tissue;  rarely  from  the  septum,  where  the  mucous  membrane  is  closely  adher- 
ent to  the  cartilage  and  bone,  without  the  intervention  of  much,  if  any,  submucous  tissue.  The 
most  common  seat  of  gelatinous  polyps  is  probably  the  middle  turbinated  process.  The  fibrous 
polypus  generally  grows  from  the  base  of  the  skull  behind  the  posterior  nares  or  from  the  roof 
of  the  nasal  fossae.  The  malignant  polypi,  both  sarcomatous  and  carcinomatous,  may  arise 
in  the  nasal  cavities  and  the  nasopharynx;  or  they  may  originate  in  the  antrum,  and  protrude 
through  its  inner  wall  into  the  nasal  fossa. 

Rhiiwlitlis  or  nose-stones  may  sometimes  be  found  in  the  nasal  cavities.  They  arise  from 
the  deposition  of  phosphate  of  lime  upon  either  a  foreign  body  or  a  piece  of  inspissated  secretion. 

The  nasal  passages  furnish  a  secretion  of  their  own  and  receive  secretion  from  other  parts 
(tears  and  secretions  of  the  accessory  sinuses).  The  nasal  cavities  contain  the  ethmoidal  laby- 
rinths, the  lateral  masses  of  the  ethmoid  (which  form  the  superior  and  middle  turbinated 
processes),  and  the  inferior  turbinated  bones.  The  nasal  cavity  is  surrounded  by  four  pairs  of 
pneumatic  spaces,  the  accessory  sinuses.  These  are  the  maxillary  sinuses  (p.  103),  the  fron- 
tal sinuses  (p.  79),  the  sphenoidal  sinuses  (p.  99),  and  the  cells  of  the  ethmoidal  labyrinth  (p. 
97).  The  lacrimal  duct  opens  into  the  inferior  meatus  Inflammation  of  the  air-cells  may  fol- 
low inflammation  of  the  nasal  mucous  membrane  or  bone  disease  One  set  of  cells  or  many 
may  suffer.  Suppuration  may  occur;  pus  may  be  retained;  death  of  bone  may  ensue.  The  most 
serious  conditions  may  follow  (abscess  of  brain,  sinus  thrombosis,  septicemia),  and  an  operation 
is  necessary  to  obtain  relief. 

THE  EYE. 

The  eyeball  or  globe  {bidhiis  oculi)  (Figs.  802  and  804)  is  contained  in  the  ante- 
rior part  of  the  cavity  of  the  orbit.  In  this  situation  it  is  securely  protected  from 
injury,  while  its  position  is  such  as  to  insure  the  most  extensive  range  of  sight. 
It  is  acted  upon  by  nimierous  muscles,  by  which  it  is  capable  of  being  directed 
to  different  parts;  it  is  supplied  by  vessels  and  nerves,  and  is  additionally  pro- 
tected in  front  by  the  orbital  margins,  eyelids,  etc. 

The  eyeball  is  embedded  in  the  fat  of  the  orbit,  but  is  partly  surrounded  by 
II  thin  membranous  sac,  the  capsule  of  T€non,  which  isolates  it,  so  as  to  allow  of 
free  movement. 

The  Capsule  of  T6non  (fascia  bulbi  [Tenoni])  (Figs.  802  and  803)  consists 
of  a  thin  membrane  which  envelops  the  eyeball  from  the  optic  nerve  to  the  ciliary 
region,  separating  it  from  the  orbital  fat  and  forming  a  socket  in  which  it  plays. 
Its  inner  surface  is  smooth,  and  is  in  contact  with  the  outer  siu-face  of  the  sclera, 
the  periscleral  or  suprascleral  lymph  space  only  intervening.  This  lymph  space 
is  continuous  with  the  subdural  and  sul>arachnoid  spaces,  and  is  traversed  by 
delicate  bands  of  connecti^^e  tissue  which  extend  between  the  capsule  and  the 
sclera.  This  lymph  space  forms  a  flexible  pocket,  in  which  the  globe  rotates. 
The  capsule  is  perforated  behind  by  the  ciliary  vessels  and  nerves  and  by  the 
optic  nerve,  being  continuous  with  the  sheath  of  the  latter.     In  front  it  blends  with 


THE  EYE 


1087 


the  ocular  conjunctiva,  and  with  it  is  attached  to  the  clhary  region  of  the  eyeball. 
It  is  perforated  by  the  ocular  muscles,  and  is  reflected  backward  on  each  as  a 
tubular  sheath.     The  sheath  of  the  Superior  oblique  is  carried  as  far  as  the  fibrous 


ERtOR 
TARSAL 
MUSCLE 


OPTIC    NERV 


Fig.  802. — The  right  eye  in  sagittal  section,  showing  the  capsule  of  T6non  (semidiagrammatic*.     (Testut.) 


pulley  of  that  muscle;  that  on  the 
Inferior  oblique  reaches  as  far  as  the 
floor  of  the  orbit,  to  which  it  gives 
off  a  slip.  The  sheaths  on  the  Recti 
are  gradually  lost  in  the  epimysium, 
but  they  give  off  important  expan- 
sions. The  expansion  from  the 
Superior  rectus  blends  with  the  ten- 
don of  the  Levator  palpebrae;  that 
of  the  Inferior  rectus  is  attached  to 
the  inferior  tarsal  plate.  These  two 
Recti,  therefore,  will  exercise  some 
influence  on  the  movements  of  the 
eyelids.  The  expansions  from  the 
sheaths  of  the  Internal  and  External 
recti  are  strong,  especially  the  one 
from  the  latter  muscle,  and  are  at- 
tached to  the  lacrimal  and  malar 
bones  respectively.  As  they  probably 
check  the  action  of  these  two  Recti, 
they  liave  been  named  the  internal 
and  external  check  ligaments. 

Lockwood  has  also  described  a  thickening  of  tlie  lower  part  of  the  capsule  of 
Tenon  which  he  has  named  the  suspensory  ligament  of  the  eye.     It  is  slung  like  a 


Fig.  S03.— The  capsule  of  Ti^non.  The  aponeurosis  is 
seen  from  behind  forward  on  the  posterior  hemisphere  of 
the  globe,  a.  Cellulofibrous  intermuscular  lamina.  6.  Deep 
leaf  of  the  sheath  incised  at  the  point  where  it  leaves  the 
muscle  to  fold  itself  on  the  posterior  hemisphere  when 
it  forms  the  posterior  capsule,  d.  Partly  incised,  c. 
Serous  membrane.     (Poirier  and  Charpy.) 


1088 


THE  ORGANS  OF  SPECIAL  SENSE 


hammock  below  the  eyeball,  being  expanded  in  the  centre,  and  narrow  at  its 
extremities,  which  are  attached  to  the  malar  and  lacrimal  bones  respectively.' 
The  anterior  one-third  of  the  globe  is  covered  by  the  conjunctiva,  or  mucous 
membrane,  reflected  from  the  inner  surfaces  of  the  lids  (Fig.  805).  A  lateral  view 
of  the  globe  shows  that  it  is  composed  of  segments  of  two  spheres  of  different  sizes 
(Figs.  804  and  805).  The  anterior  segment  is  one  of  a  small  sphere,  and  forms 
about  one-sixth  of  the  eyeball.  It  is  more  prominent  than  the  posterior  seg- 
ment, which  is  one  of  a  much  larger  sphere,  and  forms  about  five-sixths  of  the  globe. 
Between  the  small,  anterior  or  corneal  segment  and  the  large,  posterior  or  scleral 
segment  is  a  shallow  and  narrow  groove,  the  scleral  sulcus  {sulcus  sclerae).  The 
anterior  pole  is  the  centre  of  the  anterior  portion  of  the  cornea.  The  posterior 
pole  is  the  centre  of  the  posterior  portion  of  the  sclera.     A  straight  line  joining 


OCULAR 

CO 

^ 

CTIVA 

CILlftRY 
-^"MUSCLE 

=«= 

^4 

>\^PARSCIL 

ARIS 

•^ 

Sr\     RETINAE 

^,\      ORA  SERRATA 

EXCAVATION 

Fig.  804. — The  right  ey 


MACULA  LUTEA 

AND 

FOVEA    CENTRALIS 


tal  section.     (Toldt.) 


these  two  poles  is  the  sagittal  or  optic  axis  (cixis  optica)  (Fig.  804).  A  line  drawn 
around  the  eyeball  equally  distant  at  all  points  from  the  two  poles  is  called  the 
equator  (Fig.  804).  The  plane  of  the  equator  divides  the  globe  in  an  anterior 
and  a  posterior  hemisphere.  The  visual  axis  (linea  visus)  (Fig.  804)  passes  in  a 
straight  line  from  the  first  nodal  point  on  the  cornea  to  the  fovea  centralis  of  the 
yellow  spot  on  the  retina.  A  nodal  point  is  the  point  of  intersection  of  convergent 
rays  with  the  visual  axis.  The  first  nodal  point  is  6.9685  mm.  behind  the  summit 
of  the  cornea.  The  axes  of  the  eyeballs  are  nearly  parallel  to  the  mesal  plane, 
and  therefore  do  not  correspond  to  the  axes  of  the  orbits,  which  are  inclined  to  this 
plane,  forming  with  it  an  anterior  angle  of  about  30  degrees.     The  optic  nerves 


*  See  a  paper  by  C.  B.  Lockwood,  Journal  of  Anatomy  and  Physiology,  vol.  xx,  part  i,  p.  1. 


THE  SCLERA  AND  CORNEA 


1089 


follow  the  direction  of  the  axes  of  the  orbits  and  are  therefore  oot  parallel,  each 
nerve  either  leaves  or  connects  with  its  eyeball  about  1  mm.  below  and  3  mm, 
to  the  inner  or  nasal  side  of  the  posterior  pole  (Fig.  804).  The  eyeball  measures 
rather  more  in  its  transverse  and  antero-posterior  diameters  than  in  its  vertical 
diameter,  the  former  amounting  to  about  24  mm.  (nearly  an  inch),  the  latter  to 
about  23.5  mm.  (nine-tenths  of  an  inch).  The  diameters  in  the  female  are  some- 
what less  than  in  the  male.  At  birth  the  eyeball  has  a  transverse  diameter  of 
about  17,5  mm.,  while  at  puberty  it  measures  from  20  to  21  mm. 

The  eyeball  is  composed  of  three  investing  tunics  and  of  three  main  refracting 
media. 


Fig.  805. — Di.igram  of  a  horizontal  section  of  the  right  eye,  showing  the  upper  surface  of  the  lower 
segment.     (Testut.) 


THE    TUNICS    OF    THE    EYE. 

From  without  inward  the  three  tunics  are: 


I.  Sclera  and  Cornea. 
II.  Choroid,  Ciliary  Body,  and  Iris. 
III.  Retina. 


I.  The  Sclera  and  Cornea  (Tunica  Fibrosa  Oculi). 

The  sclera  and  cornea  (Figs.  805  and  SOG)  form  the  external  tunic  of  the  eyeball; 
they  are  essentially  fibrous  in  structure,  the  sclera  being  opaque,  and  forming 
the  posterior  five-sixths  of  the  globe;  the  cornea,  which  forms  the  remaining  sixth,, 
is  transparent. 


1090  THE  ORGANS  OF  SPECIAL  SENSE 

The  Sclera  {ayXrjpb-,  hard). — The  sclera  has  received  its  name  from  its  extreme 
density  and  toughness;  it  is  a  firm,  unyielding,  opaque,  fibrous  membrane  serving 
to  maintain  the  form  of  the  globe.  It  is  much  thicker  behind  than  in  front. 
Its  external  surface  is  of  a  white  color,  and  is  in  contact  with  the  inner  surface  of 
the  capsule  of  Tenon,  a  lymph  space  intervening;  it  is  C]uite  smooth,  except  one- 
quarter  of  an  inch  back  of  the  sclerocorneal  junction,  at  the  points  where  the 
Recti  and  Obliqui  muscles  are  attached  to  it,  and  its  anterior  part  is  covered  by 
the  conjunctival  membrane  (Fig.  829);  hence  the  whiteness  and  brilliancy  of  the 
front  of  the  eyeball.  Its  inner  surface  is  stained  a  brown  color,  marked  by  grooves, 
in  which  are  lodged  the  ciliary  nerves  and  vessels  (Figs.  814  and  815);  the  inner 
surface  of  the  sclera  is  loosely  connected  with  the  outer  surface  of  the  choroid  by  a 
layer  of  exceedingly  fine  cellular  pigmented  tissue  (lamina  fusca),  which  traverses  an 
extensive  lymph  space,  the  perichoroidal  space  (spatium  perichoroideale)  (Figs.  814 
and  829)  intervening  between  the  sclera  and  choroid.  Behind,  the  sclera  is  pierced 
by  the  optic  nerve  and  is  continuous  with  the  fibrous  sheath  of  the  nerve,  which  is 
derived  from  the  dura  (Fig.  809).  At  the  point  where  the  optic  nerve  passes 
through  the  sclera,  the  lamina  fusca  is  represented  by  an  arrangement  of  the  fibrous 
tissue  which  forms  a  thin  network,  the  cribriform  lamina  (lamina  cribrosa  sclerae) 
(Fig.  819);  the  minute  orifices  in  this  lamina  serve  for  the  transmission  of  nerve 
filaments,  and  the  fibrous  septa  dividing  them  from  one  another  are  continuous 
with  the  membranous  processes  which  separate  the  bundles  of  nerve  fibres.  One 
of  these  openings  (jporus  opticus),  larger  than  the  rest,  occupies  the  centre  of  the 
lamella;  it  transmits  the  arteria  centralis  retinae  to  the  interior  of  the  eyeball  (Fig 
819).  Around  the  cribriform  lamella  are  numerous  small  apertures  for  the  trans- 
mission of  the  ciliary  nerves  and  the  short  ciliary  arteries,  and  about  midway  between 
the  margin  of  the  cornea  and  the  entrance  of  the  optic  nerve  are  four  or  five  large 
apertures,  for  the  transmission  of  veins  {venae  vorticosae)  (Fig.  809).  In  front, 
the  fibrous  tissue  of  the  sclera  is  continuous  with  the  substantia  propria  of  the 
cornea  (Fig.  829),  but  the  opaque  sclera  slightly  overlaps  the  outer  surface  of  the 
transparent  cornea. 

Structure. — The  sclera  is  formed  of  white  fibrous  tissue  int'^rmixed  with  fine  elastic  fibres, 
and  of  flattened  connective-tissue  cells,  some  of  which  are  pigmented,  contained  in  cell  spaces 
between  the  fibres  (Fig.  819).  These  fibres  are  aggregated  into  bundles,  some  of  which  are 
arranged  in  layers  having  an  equatorial  direction,  but  most  of  which  are  arranged  in  layers 
lying  in  meridian  lines.  Its  vessels  (Figs.  809  and  810)  are  not  numerous,  the  capillaries  being 
of  small  size  and  uniting  at  long  and  wide  intervals.  It  obtains  arterial  blood  from  the  short 
posterior  ciliary  and  the  anterior  ciliary  arteries.  The  venous  blood  is  removed  by  the  vetiae 
vorticosae  and  the  anterior  ciliary  vein^.  There  are  lymph  spaces  between  the  cells  which  empty 
into  the  periscleral  (Fig.  802  and  p.  1086)  and  perichoroidal  lymph  spaces  (Fig.  814).  Its  nerves 
are  derived  from  the  ciliary  nerves  (Fig.  808) .  They  lose  their  myelin  sheaths  and  enter  among 
the  bundles  of  fibrous  tissue,  but  it  is  not  known  how  they  terminate. 

The  Cornea  (Figs.  804  and  809). — The  cornea  is  the  projecting  transparent 
part  of  the  external  tunic  of  the  eyeball,  and  forms  the  anterior  sixth  of  the  surface 
of  the  globe.  It  is  almost,  but  not  quite,  circular  in  shape,  occasionally  a  little 
broader  in  the  transverse  than  in  the  vertical  direction.  It  is  convex  anteriorly, 
and  projects  forward  from  the  sclera  in  the  same  manner  that  a  watch-glass  does 
from  the  case.  Its  degree  of  curvature  varies  in  difi^erent  individuals,  and  in  the 
same  individual  at  different  periods  of  life,  it  being  more  prominent  in  youth 
than  in  advanced  life.  Usually  the  curvature  is  slighdy  greater  in  the  vertical 
plane  than  in  the  horizontal  plane;  at  its  centre  than  at  its  periphery,  and  at  its 
temporal  than  at  its  nasal  side.  The  cornea  is  dense  and  of  uniform  thickness 
throughout;  its  posterior  surface  is  perfectly  circular  in  outline,  and  exceeds  the 
anterior  surface  slightly  in  extent,  as  the  latter  is  overlapped  by  the  sclera. 
The  anterior  surface  is  covered  with  conjunctival  epithelium  (Fig.  814). 


THE  SCLERA  AND  CORNEA 


1091 


Structure  (Fig.  S06). — The  cornea  consists  of  five  layers — namely:  (1)  the  anterior  or  epi- 
thelial layer;  (2)  the  anterior  elastic  membrane;  (3)  the  substantia  propria;  (4)the  posterior  elastic 
membrane;  (5)  the  posterior  or  endothelial  layer. 

1.  The  anterior  layer  (epilhdium  corneae)  is  composed  of  stratified  epithelium  and  is  contin- 
uous witli  the  cells  iif  till-  conjunctiva  at  the  borders  of  the  cornea.  There  are  from  five  to  eight 
strata    of    nuclcutcd    cells    in    the  


epithelium 


Anterior 

elastic 

membrane 


\^Substantia 
f  propria 


anterior  layer.  The  deepest 
are  columnar.  Above  the  columnar 
cells  are  several  layers  of  polygonal 
cells,  most  of  which  have  finger- 
like processes  and  are  called  jirh-kle 
cells.  At  the  surface  the  cells  and 
nuclei  become  flat. 

2.  The  anterior  elastic  or  anterior 
limiting  membrane,  or  Bowman's  \. 
membrane  (lamina  clasfica  anterior), 
is  less  than  half  the  thickness  of  the 
laj'er  of  stratified  epithelium.  It  re- 
sembles in  some  respects,  but  is  not, 
elastic  tissue,  and  is  thicker  in  the 
centre  than  at  the  periphery.  It 
shows  evidences  of  fibrillary  struc- 
ture, and  does  not  display  a  tendency 
to  curl  inward  or  to  undergo  frac- 
tiu'e  when  detached  from  the  other 
layers  of  the  cornea.  It  consists 
of  extremely  close  interwoven  fibrils, 
similar  to  those  found  in  the  rest  of 
the  cornea  proper,  but  contains  no 
corneal  corpuscles.  It  ought,  there- 
fore, to  be  regarded  as  a  part  of  the 
proper  tissue  of  the  cornea,  appar- 
ently representing  a  basement  mem- 
brane. 

3.  The  substantia  propria  or 
proper  substance  of  the  cornea 
forms  the  main  thickness  of  that 
structure.  It  is  fibrous,  tough,  un- 
yielding, perfectly  transparent,  and 
continuous  with  the  sclera.  It  is 
composed  of  about  sixty  flattened 
lamellae,  superimposed  one  on 
another.  These  lamellae  are  made 
up  of  bundles  of  modified  connec- 
tive tissue,  the  fibres  of  which  are 
directly  continuous  with  the  fibres 
of  the  sclera.  The  fibres  of  each 
lamella  are  for  the  most  part 
parallel  with  each  other;  those  of 
alternating  lamellEe  at  right  angles 
to  each  other.  Fibres,  however, 
frequently  pass  obliquely  from  one 
lamella  to  the  next  (fibrae  arcnatae). 

The  lamella?  are  connected  with 
each  other  by  an  interstitial  cement  substance,  in  which  are  spaces,  the  corneal  spaces  (Fig.  SOT). 
The  spaces  are  stellate  in  shape,  and  have  numerous  off'shoots  or  cailaliculi  (Fig.  sOT).  Iiy  which 
they  communicate  with  one  another.  Each  space  contains  a  cell,  the  large  corneal  corpuscle 
(Fig.  807),  which  resembles  in  form  the  space  in  which  it  is  lodged,  but  it  does  not  entirely  fill  it, 
the  remainder  of  the  space  containing  lymph.  In  the  aged  the  margin  of  the  cornea  becomes 
opaque  gray.  This  rim  is  called  the  arcus  senilis,  and  is  due  to  fat  deposit  in  the  lamella;  and 
corneal  corpuscles. 

4.  The  posterior  elastic  membrane,  the  membrane  of  Descemet,  or  of  Demours  {lamina  elasiica 
posterior),  which  covers  the  posterior  surface  of  the  substantia  propria  of  the  cornea,  presents 
no  structure  recognizable  under  the  microscope.  It  consists  of  an  elastic  and  perfectly  trans- 
parent homogeneous  membrane  of  extreme  thinness,  which  is  not  rendered  opaque  by  either 
water,  alcohol,  or  acids.     It  is  very  brittle,  but  its  most  remarkable  property  is  its  extreme  elas- 


FlG.  806.— Vertical 


ction  through   the  cornea  of 
X  200.     (Szymonowicz.) 


Posterior 
epithelium 
newborn  child. 


1092 


THE  ORGANS  OF  SPECIAL  SENSE 


Fig.  807. — From  a  horizontal  section  of  an  ox's  cornea.  Positive 
picture  of  the  canal  system  drmonstrated  by  the  gold  chloride 
method.     X  450.      (Szymouowicz.) 


licity  and  the  tendency  which  it  presents  to  curl  up,  or  roll  upon  itself,  with  the  attached  surface 
innermost,  when  separated  from  the  proper  substance  of  the  cornea.  Its  use  appears  to  be 
"to  preserve  the  requisite  permanent  correct  curvature  of  the  flaccid  cornea  proper"  (Jacob). 

At  the  margin  of  the  cornea  this  posterior  elastic  membrane  breaks  up  into  fibres  to  form  a 
reticular  structure  at  the  outer  angle  of  the  anterior  chamber,  the  intervals  between  the  fibres 

forming   small   cavernous  spaces, 
Corneal  cell  in  the   spaces   of  Fontana    (spatia 

Lymph  canaliculi  lymph  space  anguli  iridis)   (Fig.  S14).     These 

]!< — • — ~7" — 1  little  spaces  communicate  with  a 
circular  canal  in  the  deeper  parts 
of  the  corneoscleral  junction. 
This  is  the  canal  of  Schlemm 
{sinus  venosus  sderae)  (Figs.  814 
and  829) ;  it  communicates  inter- 
nally with  the  anterior  chamber 
through  the  spaces  of  Fontana, 
and  externally  with  the  scleral 
veins.  Some  of  the  fibres  of  this 
reticulated  structure  are  continued 
into  the  front  of  the  iris,  forming 
the  Ugamentum  pectinatum  iri- 
dis; while  others  are  connected 
with  the  fore  part  of  the  sclera 
and  choroid. 

5.  The  posterior  layer  or  the 
corneal  endothelium  (endothelium 
cainerae  anterioris)  lines  the 
aqueous  chamber  and  prevents 
the  absorption  of  the  aqueous 
humor.  It  covers  the  posterior  surface  of  the  elastic  lamina,  is  reflected  upon  the  front  of 
the  iris,  and  also  lines  the  spaces  of  Fontana.  It  consists  of  a  single  layer  of  polygonal,  flattened, 
transparent,  nucleated  cells,  similar  to  those  lining  other  serous  cavities. 

Arteries  and  Nerves. — The  fetal  cornea  contains  bloodvessels  which  pass  from  the  margin 
almost  to  the  centre.  The  adult  cornea  contains  no  bloodvessels,  except  at  its  margin.  The 
capillaries  from  the  sclera  and  conjunctiva  form  loops  at  the  corneal  margin,  and  many  of  these 
loops  enter  the  cornea  for  a  distance  of  1  mm.  (Fig.  810).  The  balance  of  the  cornea  is  non- 
vascular and  obtains  its  nourishment  from  the  lymph  in  the  laeunae  and  canaliculi.  Lymphatic 
vessels  have  not  as  yet  been  demonstrated  in  it,  but  are  represented  by  the  channels  in  which 
the  bundles  of  nerves  run;  these  channels  are  lined  by  endothelium  and  are  continuous  with  the 
cell  spaces.  The  nerves  are  numerous,  and  they  are  derived  from  the  ciliary  nerves;  they  form 
the  annular  plexus,  at  the  corneal  margin,  and  enter  the  laminated  tissue  of  the  cornea,  lose 
their  myelin  sheaths,  and  ramify  tliroughout  the  substantia  propria  as  the  plexus  of  the  stroma. 
From  this  deep  plexus  come  perforating  fibres,  which  pass  tlirough  the  anterior  elastic  lamina 
and  form  the  subepithelial  plexus,  and  from  it  fibres  are  given  off  which  ramify  between  the  epi- 
thelial cells,  forming  a  network  which  is  termed  the  intra-epithelial  plexus.  Nerve  fibres  from 
the  annular  plexus  and  from  the  plexus  of  the  stroma  come  into  close  relation  with  the  corneal 
corpuscles. 

Dissection. — In  order  to  separate  the  sclera  and  cornea,  so  as  to  expose  the  second  tunic, 
the  eyeball  should  be  immersed  in  a  small  vessel  of  water  and  held  between  the  finger  and  thumb. 
The  sclera  is  then  carefully  incised,  in  the  equator  of  the  globe,  till  the  choroid  is  exposed.  One 
blade  of  a  pair  of  probe-pointed  scissors  is  now  introduced  through  the  opening  thus  made, 
and  the  sclera  divided  around  its  entire  circumference,  and  removed  in  separate  portions.  The 
front  segment  being  then  drawn  forward,  the  handle  of  the  scalpel  should  be  pressed  gently 
against  it  at  its  connection  with  the  iris,  and,  these  being  separated,  a  quantity  of  perfectly  trans- 
parent fluid  will  escape;  this  is  the  aqueous  humor.  In  the  course  of  the  dissection  the  ciliary 
nerves  (Fig.  808)  may  be  seen  lying  in  the  loose  cellular  tissue  between  the  choroid  and  sclera 
or  continued  in  delicate  grooves  on  the  inner  surface  of  the  latter  membrane. 


II.  The  Choroid,  Ciliary  Body,  and  Iris  (Tunica  Vasculosa  Oculi) 

(Figs.  SOS,  S29). 

The  middle  tunic  of  the  eye  is  formed  from  behind  forward  by  the  choroid, 
the  ciliary  body,  and  the  iris. 

The  choroid  invests  the  posterior  five-sixths  of  the  globe,  and  extends  as  far 
forward  as  the  ora  serrata  of  the  retina;  the  ciliary  body  connects  the  choroid 


THE  CHOROID,   CILIARY  BODY,  AND  IRIS 


1093 


to  the  circumference  of  the  iris.  The  iris  is  the  circular  septum,  which  hangs 
vertically  behind  the  cornea,  presenting  in  its  centre  a  large  rounded  aperture, 
the  pupil. 

The  Choroid  (chorioidea)  is  a  thin,  highly  vascular  membrane,  of  a  dark-brown 
or  chocolate  color,  which  invests  the  posterior  five-sixths  of  the  globe,  and  is 
pierced  behind  by  the  optic  nerve,  and  in  this  situation  is  firmly  adherent  to  the 
sclera.  It  is  thicker  behind  than  in  front.  Externally,  it  is  loosely  connected 
by  the  lamina  fusca  with  the  inner 
surface  of  the  sclera  (p.  1090).  Its 
inner  surface  is  attached  to  the 
retina. 

Structure. — The  choroid  consists  of  a 
dense  capillary  plexus  and  of  small  arte- 
ries and  veins,  carrying  the  blood  to  and 
returning  it  from  this  plexus  (Fig.  SIO), 
and  of  branched  and  pigmented  cells 
which  lie  in  connective  tissue.  There  are 
three  layers  in  the  choroid.  Named  from 
without  inward,  they  ai'e  the  lamina 
suprachoroidea,  the  choroid  proper,  and 
lamina  basalis. 

1.  The  lamina  suprachoroidea  is  on 
the  external  surface,  that  is,  the  surface 
next  to  the  sclera.  It  resembles  the 
lamina  fusca  of  the  sclera.  It  is  com- 
posed of  delicate  nonvascular  lamellas, 
each  lamella  consisting  of  a  network  of 
fine  elastic  fibres,  among  which  are 
branched  pigment  cells.  The  spaces 
between  the  lamellfe  are  lined  by  endo- 
thelium, and  open  freely  into  the  peri- 
choroidal lymph  space,  which,  in  its  turn, 
communicates  with  the  periscleral  space 
by  the  perforations  in  the  sclera  through 
which  the  vessels  and  nerves  are  trans- 
mitted. 

2.  The  choroid  proper  is  internal  to  the  lamina  suprachoroidea.  In  consequence  of  the 
small  arteries  and  veins  of  the  choroid  proper  being  arranged  on  the  outer  surface  of  the  capillary 
network,  it  is  customary  to  describe  this  as  consisting  of  two  layers — the  outer  {lamina  vasculosa), 
composed  of  small  arteries  and  veins,  with  pigment  cells  interspersed  between  them,  and  the 
imier  {lamina  choriocapiUaris),  consisting  of.  a  capillary  plexus.  The  external  layer  of  the 
choroid  proper  or  the  lamina  vasculosa  consists,  in  part,  of  the  larger  branches  of  the  short 
posterior  ciliary  arteries  (Figs.  809  and  812),  which  run  forward  between  the  veins,  before  they 
bend  inward  to  terminate  in  the  capillaries;  but  this  layer  is  formed  principally  of  veins,  which 
have  a  whorl-like  arrangement  and  empty  into  four  or  five  large  equidistant  trunks,  the  venae 
vorticosae  (Figs.  809  and  810),  which  pierce  the  sclera  midway  between  the  margin  of  the  cornea 
and  the  attachment  of  the  optic  nerve.  Interspersed  between  the  vessels  are  dark  star-shaped 
pigment-cells,  the  processes  of  which,  communicating  with  similar  branchings  from  neighboring 
cells,  form  a  delicate  network  of  stroma,  which  toward  the  inner  surface  of  the  choroid  loses  its 
pigmentary  character.  The  inner  layer  of  the  choroid  proper  consists  of  an  exceedingly  fine 
capillary  plexus,  formed  by  the  short  ciliary  vessels  (Fig.  810),  and  is  known  as  the  membrane 
of  Ruysch  {lamina  choriocapiUaris).  The  network  is  close,  and  finer  at  the  hinder  jiart  of  the 
choroid  than  in  front.  About  1.2  cm.  behind  the  cornea  its  meshes  become  larger,  and  are  con- 
tinuous with  those  of  the  ciliary  processes.  These  two  laminae  are  connected  by  an  interme- 
diate stratmn  {boundary  zone),  which  is  destitute  of  pigment  cells  and  consists  of  fine  elastic 
fibres.  On  the  inner  svu-face  of  the  lamina  choriocapiUaris  is  a  very  thin,  structiu-eless,  or  faintly 
fibrous  membrane,  called  the  lamina  basalis  (membrane  of  Bruch) ;  it  is  closely  connected  with 
the  stroma  of  the  choroid,  and  separates  it  from  the  pigmentary  layer  of  the  retina;  the  cells  of 
the  latter  are  found  attached  to  this  membrane. 

Dissection. — The  ciliary  body  should  now  be  examined.  It  may  be  exposed  either  by  de- 
taching the  iris  from  its  connection  with  the  CiUary  muscle  or  by  making  a  transverse  section  of 
the  globe  and  examining  it  from  behind. 


Fig.  80S.— The  choroid  ; 


(Enlarged.) 


1094 


THE  ORGANS  OF  SPECIAL  SENSE 


The  Ciliary  Body  (corpus  ciliare)  (Fig.  813)  joins  the  choroid  to  the  margin 
of  the  iris.  It  is  in  reality  a  process  of  the  choroid  and  comprises  the  orbicularis 
ciliaris,  the  ciliary  processes,  and  the  Ciliary  muscle. 

The  orbiculus  ciliaris  (Figs.  811  and  812)  is  a  zone  of  about  4  mm.  (|  inch) 
in  width,  directly  continuous  -Rath  the  anterior  part  of  the  choroid;  it  presents 
numerous  ridges  arranged  in  a  radial  manner.  The  depressions  between  the  ridges 
are  filled  with  retinal  pigment  epithelium  (Szymonowicz).  The  orbiculus  contains 
no  lamina  choriocapillaris. 


ANTERrOR 

CILIARY 

RTERY 


Fig.  809. — Vessels  and  nerves  of  the  choroid  and  iris,  seen  from  above 
been  largely  removed.     (Testut.) 


The  sclera  and  cornea  have 


The  ciliary  processes  (processus  ciliares)  (Figs.  813  and  829)  are  formed  by  the 
plaiting  and  folding  inward  of  the  various  layers  of  the  choroid  (i.  e.,  the  choroid 
proper  and  the  lamina  basalis)  at  its  anterior  margin,  and  are  received  between 
corresponding  foldings  of  the  suspensory  ligament  of  the  lens,  thus  establishing 
a  connection  between  the  choroid  and  inner  tunic  of  the  eye.  They  are  arranged 
in  a  circle,  and  form  a  sort  of  plaited  frill,  the  corona  ciliaris,  behind  the  iris,  round 
the  margin  of  the  lens  (Figs.  813  and  829).  They  vary  between  sixty  and  eighty 
in  number,  lie  side  by  side,  and  may  be  divided  into  large  and  small;  the  latter, 
consisting  of  about  one-third  of  the  entire  number,  are  situated  in  the  spaces 
between  the  former,  but  without  regular  alternation.  The  larger  processes  are 
each  about  2.5  mm.  (one-tenth  of  an  inch)  in  length,  and  are  attached  by  their 
periphery  to  three  or  four  of  the  ridges  of  the  orbiculus  ciliaris,  and  are  continuous 
with  the  layers  of  the  choroid;  the  opposite  margin  is  free,  and  rests  upon  the 
circumference  of  the  lens.  Their  anterior  surface  is  turned  toward  the  back  of 
the  iris,  with  the  circumference  of  which  they  are  continuous.  The  posterior 
surface  is  connected  with  the  suspensory  ligament  of  the  lens. 


THE  CHOROID,   CILIARY  BODY,  AND  IRIS 


1095 


Structure. — The  ciliary  processes  are  similar  in  structure  to  the  choroid,  but  the  vessels  are 
larger,  and  have  chiefly  a  longitudinal  direction.  They  constitute  the  most  vascular  portion  of 
the  eyeball.  The  processes  are  covered  on  their  inner  surface  by  two  strata  of  black  pigment 
cells,  which  are  continued  forward  from  the  retina,  and  are  named  the  pars  ciliaris  retinae  (Fig. 
814).  In  the  stroma  of  the  ciliary  processes  there  are  also  stellate  pigment  cells,  which,  how- 
ever, are  not  so  numerous  as  in  the  choroid  itself. 


''//i 


Fig.  810. — Diagram  of  the  bloodvessels  of  the  eye,  as  seen  in  a  horizontal  section.     (Leber,  after  Stohr.) 

Course  of  vasa  centralia  retinae:  a.  Al-teria.  ai.  Vena  centralis  retinae.  /^.  Anastomosis  with  vessels  of  outer 
coats     7.  Anastomosis  with  branches  of  short  posterior  ciliary  arteries,    ri.  Anastomosis  with  chorioideal  vessels. 

Course  of  vasa  ciliar.  postic.  brev. :  I.  Arteriae,  and  Ii.  Venae  ciliar.  postic.  brev.  II.  Episcleral  artery.  IIi. 
Episcleral  vein.     III.  Capillaries  of  lamina  choriocapiilaris. 

Course  of  vasa  ciliar.  postic.  long.:  1.  a.  ciliar.  post,  longa.  2.  Circulus  iridis  major  cut  across.  3.  Branches 
to  ciliary  body.     4.  Branches  to  iris.  ' 

Course  of  vasa  ciliar.  ant.:  a.  Arteria.  ai.  Vena  ciliar.  ant.  b.  Junction  with  the  circulus  iridis  major. 
c.  Junction  with  lamina  choriocapill.  d.  Arterial,  and  d\.  Venous  episcleral  branches,  e.  Arterial,  and  ei. 
Venous  branches  to  conjunctiva  sclerae.  f.  Arterial,  and  fi.  Venous  branches  to  corneal  border.  V.  Vena 
vorticosa.     S.  Transverse  section  of  sinus  venosus  sclerae. 


The  Ciliary  muscle  (Bowman's  muscle)  (m.  ciliaris)  (Figs.  814  and  816)  con- 
sists of  unstriped  fibres;  it  forms  a  grayish,  semitransparent,  circular  band,  about 
3  mm.  (one-eighth  of  an  inch)  broad,  on  the  outer  surface  of  the  fore  part  of  the 
choroid,  between  the  choroid  and  the  iris  and  back  of  the  sclerocorneal  junction. 
It  is  thickest  in  front  and  gradually  becomes  thinner  behind.  It  consists  of  two 
sets  of  fibres,  radial  and  circular.     The  radial  fibres  (fibme  meridiauales)  (Figs. 


1096 


THE  ORGANS  OF  SPECIAL  SENSE 


INNER 

SURFACE' 

OF  SCLERA 


terior  surface) 


Fig.  811. — The  middle  or  vascular  coat  of  the  eye- 
ball exposed  from  without.  Left  eye,  seen  obliquely 
from  above  and  before.     (Toldt.) 


814  and  829),  the  more  numerous,  arise  at  the  point  of  Junction  of  the  cornea 
and  sclera,  and  partly  also  from  the  ligamentum  pectinatum  iridis,  and,  passing 
backward,  are  attached  to  the  choroid  opposite  to  the  ciliary  processes.  One 
bundle,  according  to  Waldeyer,  is  continued  backward  to  be  inserted  into  the 
sclera.     The  circular  fibres  (fibrae  circulares  [Mulleri])  (Figs.  814  and  829)  are 

internal  to  the  radial  ones  and  to  some 
extent  unconnected  with  them,  and 
have  a  circular  course  around  the  at- 
tachment of  the  iris.  They  are  some- 
times called  the  "ring  muscle"  of  Miiller, 
and  were  formerly  described  as  the 
ciliary  ligament.  They  are  well  devel- 
oped in  hypermetropic,  but  are  rudi- 
mentary or  absent  in  myopic  eyes.  The 
Ciliary  muscle  is  admitted  to  be  the 
chief  agent  in  accommodation — i.  e.,  in 
adjusting  the  eye  to  the  vision  of  near 
objects.  When  the  Ciliary  muscle 
contracts,  it  draws  the  choroid  for- 
ward, and  relaxes  the  suspensory 
ligament.  The  elasticity  of  the  lens  at 
once  allows  it  to  bulge  forward  until 
it  is  again  checked  by  the  tension  of  the  capsule;'  the  pupil  is  at  the  same  time 
slightly  contracted. 

The  Iris  (iris,  a  rainbow)  (Figs.  815  and  817)  has  received  its  name  from  its 
various  colors  in  different  individuals.  It  is  a  thin,  circular  contractile  curtain, 
suspended  in  the  aq.ueous  humor  between  the  cornea  and  the  lens,  being  perfo- 
rated a  little  to  the  nasal  side  of  its  centre  by  a  circular  aperture,  the  pupil  (pMpiYZa) 
(Fig.  817),  for  the  transmission 
©f  light.  The  pupil  of  a  living 
person  varies  in  size  under  the 
influence  of  light  and  in  efforts 
at  accommodation.  In  looking 
at  a  near  object  the  pupil  is 
small;  in  looking  at  a  distant 
object  it  is  large.  In  light  the" 
pupil  contracts,  in  darkness  it 
dilates;  hence  the  pupil  is  a 
window  which  permits  light  to 
pass  into  the  interior  of  the 
eye.  The  size  of  this  window 
depends  on  the  contraction  or 
relaxation  of  the  iris.  The  iris 
divides  the  aqueous  chamber  (the 
space  between  the  cornea  and 
lens)  into  an  anterior  chamber  and 
a  posterior  chamber  which  com- 
municate through  the  pupil  (Fig. 

804).  By  its  circumference  or  ciliary  margin  (margo  ciliaris)  (Figs.  814  and  815) 
the  iris  is  continuous  with  the  ciliary  body,  and  it  is  also  connected  with  the  posterior 
elastic  lamina  of  the  corneaby  means  of  the  pectinate  ligament  {ligamentum  pecfliia- 
tum  iridis)  (Fig.  829) .  The  pectinate  ligament  of  the  iris  is  derived  from  the  posterior 


;  of  the  choroid  and  iris.     The  sclera  has 
)stiy  removed.      (Enlarged.) 


>  Stewart,  Manual  ot  Physiology. 


THE  CHOROID,   CILIARY  BODY,  AXD  IRIS 


1097 


elastic  layer  of  the  cornea.    In  this  hgament  are  numerous  lymph  spaces,  the  spaces 
of  Fontana  (spatia  angidi  iridis)  [Fo7ita7iae])  (Fig.  814),  and  they  join  the  canal  of 


Fig.  813. — A  portion  of  the  corona  eiliaris  magnified.     The  ciliary  processes  and  the  ciliary  folds,      CToldt.) 


Schlemm  to  the  anterior  chamber  of  the  eye.  The  inner  or  free  edge  of  the  iris 
forms  the  margin  of  the  pupil,  and  is  called  the  pupillary  margin  (jnargo  pupillaris) 
(Fig.  815).  The  surfaces  of  the  iris  are  flattened,  and  look  forward  and  backward, 
the  anterior  toward  the  cornea,  the  posterior  toward  the  ciliary  processes  and  lens. 


Circ.  fibres 

of  Oitiwy  musilc 

Fig.  814. — Section  of  the  eye,  showing  the  relations  of   the  cornea,  sclera,  and  iris,  together  with  the  Ciliarj 
niuscle  and  the  cavernous  spaces  near  the  angle  of  the  anterior  chamber.     ^\^  aldeyer.) 

The  iris  is  pigmented  and  the  color  of  an  individual's  eyes  depends  upon  this 
pigment.     The  anterior  surface  (fades  anterior)  (Figs.    815  and  829)  of  the  iris 


1098 


THE  ORGANS  OF  SPECIAL  SENSE 


is  variously  colored  in  different  individuals,  and  is  marked  by  lines  which  converge 
toward  the  pupil.  The  posterior  surface  {fades  posterior)  (Figs.  813  and  829) 
is  of  a  deep  purple  tint,  from  being  covered  by  two  layers  of  pigmented,  columnar 
epithelium,  which  layers  are  continuous  posteriorly  with  the  pars  ciliaris  retinae. 
This  pigmented  epithelium  is  termed  the  pars  iridica  retinae,  though  it  is  sometimes 
named  uvea,  from  its  resemblance  in  color  to  a  ripe  grape. 


CILIARY  MA 


ATTACHED 
REMNANT  Op 
CORNEAL 
MARGIN 


E  BORDER 
'IGMENTARY 
LAYER 


Fig.  815. — Section  of  the  i 


Anterior  surface  magnified.     (Toldt.) 


Structure. — The  iris  is  composed  of  the  following  structures: 

1.  In  front  is  a  layer  of  flattened  endothelial  cells  placed  on  a  delicate  hyalin  basement 
membrane.  This  layer  is  continuous  with  the  endothelial  layer  covering  the  membrane  of 
Descemet,  and  in  men  with  dark-colored  irides  the  cells  contain  pigment  granules. 


CILIARY 
GANGLIATEO 
EXUS 


POSTER 
LONG  CILIARY 
ARTER 


OR  RADICLES 
OF  THE 
VORTICOSE  VEINS 


-The  ciliary  gangliated  plexus  and  the  ciliary  nerves  entering  the  plexus, 
middle  or  vascular  coat  of  the  eyeball.     (Toldt.) 


Outer  surface  of  the 


2.  The  stroma  (stroma  iridis)  consists  of  fibres  and  cells.  The  former  are  made  up  of  fine,  deli- 
cate bundles  of  fibrous  tissue,  of  which  some  few  fibres  have  a  circular  direction  at  the  circum- 
ference of  the  iris,  but  the  chief  mass  consists  of  fibres  radiating  toward  the  pupil.  They  form, 
by  their  interlacement,  delicate  meshes,  in  which  the  vessels  and  nerves  are  contained.  Inter- 
spersed between  the  bundles  of  connective  tissue  are  numerous  stellate  cells  with  fine  processes. 


THE  CHOROID,   CILIARY  BODY,  AND  IRIS  1099 

Many  of  them  in  dark  eyes  contain  pipjmcnt  njranules,  but  in  blue  eyes  and  the  pink  eyes  of 
albinos  they  are  unpigraented.  The  muscle  fibres  are  unstriated  and  consist  of  circular  and 
radial  fibres.  The  circular  fibres  (»;.  spliindcr  pupillae)  surround  the  margin  of  the  pupil  on  the 
posterior  surface  of  the  iris,  like  a  sphincter,  forming  a  narrow  band  about  one-thirtieth  of  an 
inch  (0.8  mm.)  in  width,  those  near  the  free  margin  being  closely  aggregated;  those  more 
external  somewhat  separated,  and  forming  less  complete  circles.  The  radial  fibres  (m.  dilatator 
pupillae)  converge  from  the  circumference  toward  the  centre,  and  blend  with  the  circular  fibres 
near  the  margin  of  the  pupil.     These  fibres  are  regarded  by  some  as  elastic,  not  muscular. 

3.  Pigmented  epithelium  (pars  iridica  retinae).  This  is  a  continuation  of  the  pars  ciliaris 
retinae,  and  consisls  of  two  layers  of  pigmented,  columnar  epithelial  cells.  The  situation  of  the 
pigment  differs  in  different  irides.  In  the  various  shades  of  blue  eyes  the  only  pigmentation  is 
that  of  the  pigmented  epithelium.  The  color  of  the  eye  in  these  individuals  is  due  to  this  coloring 
matter  showing  more  or  less  through  the  te.xture  of  the  iris.  In  the  albino  even  this  pigment  is 
absent.  In  the  gray,  brown,  and  black  eye  there  are,  as  mentioned  above,  pigment  granules 
to  be  found  in  the  connective  tissue  cells  of  the  stroma  and  in  the  endothelial  layers  on  the  front  of 
the  iris;  to  these  the  dark  color  of  the  eye  is  due. 


ANTERIOR    CILIARY    ARTERIES 


ANTERIOR  CILIARY  ARTERIES 

Fig.  S17.— Iris,  front  view.     (Testut.) 

The  arteries  of  the  Choroid  and  Iris  (Figs.  809  and  817). — The  short  posterior  ciliary  arteries, 
from  six  to  twelve  in  number,  arise  from  the  ophthalmic,  or  some  of  its  branches;  they  pass  for- 
ward around  the  optic  nerve  to  the  posterior  part  of  the  eyeball,  pierce  the  sclera  around  the 
entrance  of  the  nerve,  and  supply  the  choroid  coat  and  ciliary  processes.  The  arteries  of  the  iris 
are  derived  from  the  long  posterior  ciliary  and  anterior  ciliari/  arteries  and  from  the  vessels  of  the 
ciliary  processes  (see  p.  613).  The  long  posterior  ciliary  arteries  (Figs.  809  and  SIO),  two  in 
number,  pass  through  the  sclera,  one  on  the  inner  and  one  on  the  outer  side  of  the  optic  nerve, 
and  pass  forward  between  the  sclera  and  choroid,  and,  having  reached  the  attached  margin 
of  the  iris  (Figs.  809  and  817),  divide  into  an  upper  and  a  lower  branch,  and.  encircling  the 
iris,  anastomose  with  corresponding  branches  from  the  opposite  side;  into  this  vascular  zone 
(eirculus  i-ridis  major)  (Fig.  829)  the  anterior  ciliary  arteries  (Fig.  829),  from  the  lacrimal  and 
anterior  cUiary  from  the  muscular  branches  of  the  ophthalmic,  pour  their  blood.  From  this 
zone  vessels  converge  to  the  free  margin  of  the  iris,  and  these  communicate  by  branches  from  one 
to  another  and  thus  form  a  second  zone  (circuhis  iridis  minor)  in  this  situation.  The  veins  pass 
toward  the  ciliary  margin  and  communicate  with  the  veins  of  the  ciliary  processes  and  of  the 
canal  of  Schlemm  (Pigs.  809  and  810). 

The  nerves  of  the  Choroid  and  Iris  (Fig.  808)  are  the  short  ciliary,  the  ciliary  branches  of 
the  lenticular  ganglion,  and  the  long  ciliary  from  the  nasal  branch  of  the  ophthalmic  division 
of  the  trigeminal.     They  pierce  the  sclera  around  the  entrance  of  the  optic  nerve,  and  run  for- 


1100 


THE  ORGANS  OF  SPECIAL  SENSE 


ward  in  the  perichoroidal  lymph  space,  in  which  they  form  a  plexus,  from  which  plexus  filaments 
pass  to  supply  the  bloodvessels  of  the  choroid.  After  reaching  the  iris  they  form  a  plexus  around 
its  attached  margin;  from  this  are  derived  amyelinic  fibres  which  terminate  in  the  circular  and 
radial  muscle  fibres.  Their  exact  mode  of  termination  has  not  been  ascertained.  Other 
fibres  from  the  plexus  terminate  in  a  network  on  the  anterior  surface  of  the  iris.  The  fibres 
derived  from  the  motor  root  of  the  lenticular  ganglion  (oculomotor  nerve)  supply  the  circular 
fibres,  while  those  derived  from  the  sympathetic  supply  the  radial  fibres. 

Membrana  Pupillaris. — In  the  fetus  the  pupil  is  closed  by  a  delicate  transparent 
vascular  membrane,  the  membrana  pupillaris,  which  divides  the  space  into  which 
the  iris  is  suspended  into  two  distinct  chambers.  This  membrane  contains  numer- 
ous minute  vessels,  continued  from  the  margin  of  the  iris  to  those  on  the  front  part 
of  the  capsule  of  the  lens.  These  vessels  have  a  looped  arrangement,  and  converge 
toward  each  other  without  anastomosing.  Between  the  seventh  and  eighth  months 
the  membrane  begins  to  disappear,  by  gradual  absorption  from  the  centre  toward 
the  circumference,  and  at  birth  only  a  few  fragments  remain.  It  is  said  sometimes 
to  remain  permanent  and  produce  blindness. 


III.  The  Retina,  or  Tiuiica  Interna  (Figs.  808,  809). 

The  retina  is  a  delicate  nerve  membrane,  in  which  the  fibres  of  the  optic  nerve 
are  spread  out  and  upon  the  surface  of  which  the  images  of  external  objects  are 
received.  Its  outer  surface  is  in  contact  with  the  choroid;  its  inner  with  the  vitre- 
ous body.  Behind,  it  is  continuous 
with  the  optic  nerve;  it  gradually 
diminishes  in  thickness  from  behind 
forward;  and,  in  front,  extends  nearly 
as  far  as  the  ciliary  body,  where  it 
appears  to  terminate  in  a  jagged 
margin,  the  ora  serrata  (Figs.  810 
and  829).  Here  the  nerve  tissues 
of  the  retina  end,  but  a  thin  pro- 
longation of  the  jnembrane  extends 
forward  over  the  back  of  the  ciliary 
processes  and  iris,  forming  the  pars 
ciliaris  retinae  and  pars  iridica  reti- 
nae, already  referred  to.  This  for- 
ward prolongation  consists  of  the 
pigmentary  layer  of  the  retina,  to- 
gether with  a  stratum  of  columnar 
epithelium.  The  retina  is  soft,  semi- 
transparent,  and  of  a  purple  tint  in 
the  fresh  state,  owing  to  the  presence 
of  a  coloring  material  named  rhodopsin  or  visual  ptu:ple;  but  it  soon  becomes 
clouded,  opaque,  and  bleached  when  exposed  to  sunlight.  Exactly  in  the  centre 
of  the  front  surface  of  the  posterior  part  of  the  retina,  corresponding  to  the  visual 
axis,  and  at  a  point  in  which  the  sense  of  vision  is  most  perfect,  is  an  oval  yellowish 
spot,  called  the  yellow  spot  {macula  lute  a)  (Figs.  804  and  818),  having  a  central 
depression,  the  fovea  centralis.  The  retina  in  the  situation  of  the  fovea  centralis 
is  exceedingly  thin,  and  the  dark  color  of  the  choroid  is  distinctly  seen  through  it 
Itexistsonly  in  man,  the  quadrumana,  and  some  saurian  reptiles.  About  3  mm. 
(one  eighth  of  an  inch)  to  the  nasal  side  of  the  yellow  spot,  and  about  1  mm. 
below  it,  is  the  point  of  attachment  of  the  optic  nerve,  the  optic  disk  {jporus  opticus) 
Figs.  818  and  819),   the  circumference  of  which  is  slightly  raised  so  as  to  form 


Fig.  SIS.^ — The  arteria  centralis  retinae,  yellow  spot, 
etc.,  the  anterior  half  of  the  eyeball  being  removed. 
(iEnlarged.) 


THE  RETINA,    OB  TUNICA  INTERNA 


1101 


an  eminence,  the  optic  papilla  (colliculiis  nervi  optici);  the  central  portion  is 
depressed  and  is  called  the  optic  cup  (excavatio  papillae  nervi  optici).  The  arteria 
centralis  retinae  pierces  its  centre.  This  is  the  only  part  of  the  surface  of  the 
retina  from  which  the  power  of  vision  is  absent,  and  is  termed  the  blind  spot. 


CHOROID 


POSTERIOR 

HORT  CILIARY 

ARTERY  AND~ 

VEIN 


Fig.  819. — The  terminal  portion  of  the  optic  nerve  and  its  entrance  into  the  eyeball,  : 

(Toldt.) 


,  Structure. — The  retina  is  an  exceedingly  complex  structure,  and,  when  examined  micro- 
scopically by  means  of  sections  made  perpendicularly  to  its  surface,  is  found  to  consist  of  many 
layers  of  nerve  elements  bound  together  and  supported  by  the  sustentacula!  fibres.  The  layers 
of  the  retina  are: 

1.  Membrana  limitans  interna. 

2.  Layer  of  nerve  fibres  (stratum  opticum). 

3.  Ganglionic  layer,  consisting  of  nerve  cells. 

4.  Inner  plexiform  layer. 

5.  Inner  nuclear  layer,  or  outer  ganglionic  layer. 

6.  Outer  plexiform  layer. 

7.  Outer  nuclear  layer,  or  layer  of  outer  granules. 

8.  Membrana  limitans  externa. 

9.  Jacob's  membrane  (layer  of  rods  and  cones). 
10.  Pigmentary  layer  (tapetiun  nigrimi). 

1.  The  membrana  limitans  interna  is  the  most  internal  layer  of  the  retina  and  is  in  contact 
■with  the  hyaloid  membrane  of  the  vitreous  humor.  It  is  derived  from  the  supporting  frame- 
work of  the  retina,  with  which  tissue  it  will  be  described. 

2.  The  layer  of  the  nerve  fibres  consists  of  the  axones  proceeding  from  the  nerve  cells  in  the 
inner  ganglionic  layer.  They  are  amyelinic,  and,  concentrating  at  the  porus  opticus,  pass  through 
all  the  layers  of  the  retina  except  the  membrana  hmitans  interna.  On  passing  through  the 
lamina  cribrosa  of  the  sclera  these  axones  acquire  myelin  sheaths  and  leave  the  eyeball  as  a  com- 
pact rounded  bundle  called  the  optic  nerve  A  few  of  the  fibres  in  tliis  layer  are  centrifugal,  being 
axones  of  ganglion  cells  within  the  brain,  to  terminate  in  the  inner  plexiform  and  outer  ganglionic 
layers.  The  layer  of  nerve  fibers  is  thickest  at  the  optic  nerve  exit  and  gradually  diminishes  in 
thickness  toward  the  ora  serrata. 

3.  The  ganglionic  layer  consists  of  a  single  layer  of  large  ganglion  cells,  except  in  the  macula 
lutea,  where  there  are  several  strata.  The  cells  are  somewhat  flask-shaped,  the  rounded  internal 
surface  of  each  cell  resting  on  the  preceding  layer  and  sending  off  an  axone  which  is  prolonged 
as  a  nerve  fibre  into  the  fibre  layer.  From  the  opposite  extremity  numerous  dendritesextend 
into  the  inner  plexiform  layer,  where  they  branch  out  into  flattened  arborizations  at  different 
levels  (Fig.  820).     The  ganglion  cells  vary  much  in  size,  and  the  dendrites  of  the  smaller  ones. 


1102 


THE  ORGANS  OF  SPECIAL  SENSE 


as  a  rule,  arborize  in  the  inner  plexiform  layer  as  soon  as  they  enter  it;  while  the  processes  of  the 
(arger  cells  ramify  close  to  the  inner  nuclear  layer. 

4.  The  inner  plexiform  layer  is  made  up  of  a  dense  reticulum  of  minute  fibrils,  formed  by  the 
interlacement  of  the  dendrites  of  the  ganglion  cells  with  those  of  the  cells  contained  in  the  next 
layer,  immediately  to  be  described.  Within  the  reticulum  formed  by  these  fibrils,  a  few 
branched  spongioblasts  are  sometimes  embedded. 


Membrana 
limitans  ijifema 
Nerve-fibre  layer 

Ganglionic  layer  — 


Inner  plexiform.... 
layer 


Centrifugal  fibre'' 


Outer  nuclear 
layer 


Metnbrana 
limitans  externa 


Layer  of  rods 
and  cones 


Diffuse  amacrine 
cell 


''Amacrine  cells 
••Horizontal  cell 


7  Bod  bipolars 
--•."Cone  bipolars 


'—Pigmented  layer 


Fig.    820.' — Plan  of  retinal  neurones.     (After  Cajal.) 


5.  The  inaer  nuclear  or  inner  granular  layer  consists  of  a  number  of  closely  packed  cells,  of 
which  there  are  three  varieties — viz.:  (1)  A  large  number  of  oval  cells,  which  are  commonly 
regarded  as  bipolar  nerve  cells,  and  are  much  more  numerous  than  either  of  the  other  kind. 
They  each  consist  of  a  large  oval  body  placed  vertically  to  the  surface,  and  containing  a  distinct 
nucleus.  The  protoplasm  is  prolonged  into  two  processes;  one  of  these  passes  inward  into  the 
inner  plexiform  layer,  is  varicose  in  appearance,  and  ends  in  a  terminal  ramification,  which  is 
often  in  close  proximity  to  the  ganglion  cells.  The  outer  process  passes  outward  into  the  outer 
plexiform  layer,  and  there  breaks  up  into  a  number  of  branches.  There  are  two  varieties  of  these 
bipolar  cells — one  in  which  the  outer  process  arborizes  around  the  knobbed  ends  of  the  rod 
fibres,  and  the  inner  around  the  cells  of  the  ganglionic  layer;  these  are  called  rod  bipolars  (Fig. 
820);  the  others  are  those  in  which  the  outer  process  breaks  up  in  a  horizontal  ramification, 
in  contact  with  the  end  of  a  cone  fibre;  these  are  the  cone  bipolars,  and  their  inner  process 
breaks  up  into  its  terminal  ramification  in  the  inner  molecular  layer.  (2)  At  the  innermost 
part  of  this  inner  nuclear  layer  is  a  stratum  of  cells,  which  are  named  amacrine  cells  (of  Cajal), 
from  the  fact  that  they  have  no  axis-cylinder  process,  but  they  give  a  number  of  short  proto- 
plasmic processes  which  extend  into  the  inner  plexiform  layer  and  there  ramify  (Fig.  820). 
There  are  also  at  the  outermost  part  of  this  layer  some  cells,  the  processes  of  which  extend  into 
and  ramify  in  the  outer  molecular  layer.  These  are  the  horizontal  cells  (of  Cajal).  (3)  Some 
few  cells  are  also  found  in  this  layer,  connected  with  the  fibres  of  ]Miiller,  and  will  be  described 
with  those  structures. 

6.  The  outer  plexiform  layer  is  much  thinner  than  the  inner  plexiform  layer;  but,  like  it, 
consists  of  a  dense  network  of  minute  fibrils,  derived  from  the  processes  of  the  horizontal  cells 
of  the  preceding  layer  and  the  outer  processes  of  the  bipolar  cells,  which  ramify  in  it,  forming 
arborizations  around  the  ends  of  the  rod  fibres  and  with  the  branched  foot  plates  of  the  cone 
fibres.  In  the  neighborhood  of  the  macula  lutea,  elongations  from  the  inner  segments  of  rod 
fibres  and  cone  fibres  form  the  so-called  Henle's  fibre  layer. 


THE  RETINA,    OR   TUNICA  INTERNA 


1103 


7.  The  outer  nuclear  or  outer  granular  layer,  like  the  inner  nuclear  layer,  contains  several 
strata  of  clear  oval  nuclear  bodies;  they  are  of  two  kinds,  and  on  account  of  their  being  respec- 
tively connected  with  the  rods  and  cones  of  Jacob's  membrane  (rod  fibres  and  cone  fibres)  are 
named  rod  granules  and  cone  granules.  The  rod  granules  are  much  the  more  numerous,  and 
are  jjlaced  at  different  levels  throufihout  the  layer.  Their  nuclei  present  a  peculiar  cross-striped 
appearance,  and  prolonged  from  either  extremity  of  the  granule  isa  fine  process;  the  outer 
process  is  continuous  with  a  single 
rod  of  Jacob's  membrane;  the  inner 

passes    inward    toward    the     outer  -Jio 

plexiform  layer  and  terminates  in  an  I  4,7  it. 

enlarged  extremity,  and  is  embedded  X)2.5jt 

in  the  tuft  into  which  the  outer  pro- 
cess of  the  rod  bipolars  break  up. 
In  its  course  it  presents  numerous 
varicosities.  The  cone  granules, 
fewer  in  number  than  the  rod  gran- 
ules, are  placed  close  to  the  mem- 
brana  limitans  externa,  througl 
which  they  are  continuous  with  th: 
cones  of  Jacob's  membrane.  Thej^ 
do  not  present  any  cross-striping, 
but  contain  a  pyriforra  nucleus 
which  almost  completely  fills  the 
cell.  From  their  inner  extremity  a 
thick  process  passes  inward  to  the 
outer  plexiform  layer,  upon  which 
it  rests  by  a  somewhat  pyramidal 
enlargement,  from   which   are  given 


External 
segment 


Intermediary 
(Use- 
ElUptoid- 

Myoid- — 


^^    '  '  *  Fig.  822. — Cones  in  the  different  regions  of  the  retina.    7.  Near 

the  era  serrata.     11.  At  3  mm.  from  the  ora  serrata.     ///.  At  an 

equal  distance  from  the  ora  serrata  and  the  papilla.     IV.  At  the 

periphery  of  the  fovea  centralis.      V.  In  the  fovea  centralis.      VI. 

Fig.  821. — The  cells  of  the  rods  of    the    At  the  centre  of  the  fovea  centralis.     E.  Length  of  the  external 

retina  in  the  frog.     A.  Red  rod.     B.  Green    segment.     /.  Length  of  the    internal    segment.     D.  Diameter   of 

rod.     (Poirier  and  Charpy.)  the  internal  segment.     (Poirier  and  Charpy.) 


off  numerous  fine  fibrils,  which  enter  the  outer  plexiform  layer,  where  they  come  in  contact 
■with  the  outer  processes  of  the  cone-bipolars. 

8.  The  membrana  limitans  externa,  like  the  membrana  limitans  interna,  is  derived  from 
the  fibres  of  Miiller,  with  which  structures  it  will  be  described. 

9.  Jacob's  membrane,  or  the  layer  of  rods  and  cones,  consists  of  visual  cells,  and  the  ele- 
ments which  compose  it  are  of  two  kinds,  rod  cells  and  cone  cells,  the  former  being  much  more 
numerous  than  the  latter.  The  rod  cells  (Fig.  S21)  are  of  nearly  uniform  size,  and  arranged 
perpendicularly  to  the  surface.  A  rod  cell  consists  of  a  rod  and  a  rod  fibre,  and  the  fibre  con- 
tains the  nucleus.  The  rods  are  cylindrical  and  each  consists  of  two  portions,  an  outer  segment 
and  an  inner  segment,  which  are  of  about  equal  length.  The  segments  differ  from  each  other 
as  regards  refraction  and  in  their  behavior  with  coloring  reagents,  the  inner  portion  becoming 
stained  by  carmine,  iodine,  etc.,  the  outer  portion  remaining  unstained  with  these  reagents,  but 
staining  yellowish  brown  with  osmic  acid.     The  outer  portion  of  each  rod  is  marked  by  trans- 


1104  THE  ORGANS  OF  SPECIAL  SENSE 

verse  strise,  and  is  made  up  of  a  number  of  thin  disks  superimposed  on  one  another.  It  also 
exhibits  faint  longitudinal  marliings.  The  inner  portion  of  each  rod,  at  its  deeper  part  where 
it  is  joined  to  the  outer  process  of  the  rod  granule,  is  indistinctly  granular;  its  more  superficial 
part  presents  a  longitudinal  striation,  being  composed  of  fine,  bright,  highly  refracting  fibres. 
The  visual  purple,  or  rhodopsin,  is  found  only  in  the  outer  segments  of  the  rods.  At  its  inner 
end  each  rod  is  prolonged  into  a  very  fine  fibre,  the  rod  fibre,  which  contains  a  nucleus,  and 
which  terminates  in  the  outer  nuclear  layer,  being  somewhat  enlarged  at  its  termination. 

The  cone  cells  (Fig.  822)  are  conical,  or  flask-shaped,  their  broad  ends  resting  upon  the  mem- 
brana  limitans  externa,  the  narrow  pointed  extremity  being  turned  to  the  choroid.  Each  cone 
cell  consists  of  two  parts,  the  cone  and  the  cone  fibre.  The  outer  segment  or  cone  is  a  short 
conical  process,  which,  like  the  outer  segment  of  a  rod,  presents  transverse  stria".  The  inner 
segment  (cone  fibre)  resembles  the  inner  portion  of  the  rods  in  structure,  but  differs  from  it  in 
size,  being  shorter  and  bulged  out  laterally  in  a  flask-shaped  manner,  and  at  the  junction  of  the 
cone  with  the  fibre  is  the  nucleus  of  the  cone  cell.  The  cone  fibre  passes  to  the  outer  nuclear 
layer,  and  terminates  as  an  expansion  from  which  very  minute  fiorils  are  given  off.  The  chem- 
ical and  optical  characters  of  the  rod  cells  and  cone  cells  are  identical. 

10.  The  pigmentary  layer  or  tapetum  nignmi,  the  most  external  layer  of  the  retina,  for- 
merly regarded  as  a  part  of  the  choroid,  consists  of  a  single  layer  of  hexagonal  epithelial  cells, 
loaded  with  pigment  granules.  Each  cell  contains  a  flattened  nucleus  in  the  outer  portion  of 
the  cell  which  is  free  from  pigment  at  this  point.  These  cells  are  smooth  externally,  where  they 
are  in  contact  with  the  choroid,  but  internally  they  are  prolonged  into  fine,  straight  processes, 
which  extend  between  the  rods,  this  being  especially  the  case  when  the  eye  is  exposed  to  light. 
The  pigment  changes  its  position  under  the  influence  of  light,  and  is  distributed  through  the 
entire  cell.  In  the  eyes  of  albinos,  the  cells  of  the  pigmentary  layer  are  present,  but  they  contain 
no  coloring  matter. 

Supporting  Framework  of  the  Retina. — Almost  all  these  layers  of  the  retina  are  con- 
nected by  a  supporting  framework,  formed  by  the  supporting  cells  or  supporting  fibres  of 
Miiller  or  radiating  fibres,  from  which  the  membrana  limitans  interna  et  externa  are  derived. 
These  fibres  are  found  stretched  between  the  two  limiting  layers,  "like  columns  between  a  floor 
and  a  roof,"  and  they  pass  through  all  the  neural  layers  except  Jacob's  membrane^  Each  com- 
mences on  the  inner  surface  of  the  retina  by  a  conical  hollow  base,  which  sometimes  contains  a 
spheroidal  body  which  stains  deeply  with  hematoxylin,  the  edges  of  the  bases  of  adjoining 
fibres  being  united  and  thus  forming  a  boundary  line,  which  is  the  membrana  limitans  interna. 
As  they  pass  through  the  nerve  fibre  and  ganglionic  layers  they  give  off  few  lateral  branches; 
in  the  inner  nuclear  layer  they  give  off  numerous  lateral  processes  for  the  support  of  the  inner 
granules,  while  in  the  outer  nuclear  layer  they  form  a  network,  the  fibre  baskets,  around  the 
rod  and  cone  fibrils,  and  unite  to  form  the  external  limiting  membrane  at  the  bases  of  the  rods 
and  cones.  In  the  inner  nuclear  layer  each  fibre  of  Miiller  presents  a  clear  oval  nucleus,  which 
is  sometimes  situated  at  the  side  of,  sometimes  altogether  within,  the  fibre.  The  supporting 
framework  of  the  retina  contains  neuroglia  cells. 

The  Path  of  Light  Stimuli. — The  stimulus  is  supposed  to  be  first  received  by  the  rod  and  cone 
cells  (the  visual  cells),  and  is  transmitted  to  the  bipolar  cells  of  the  inner  nuclear  layer  and  then 
to  the  cells  of  the  ganglionic  layer,  which  send  fibres  by  way  of  the  optic  nerve  and  tract  to  the 
brain  (see  p.  909). 

Macula  Lutea  and  Fovea  Centralis.— The  structure  of  the  retina  at  the  yellow  spot  presents 
some  modifications.  In  the  macula  lutea  (1)  the  nerve  fibres  are  wanting  as  a  continuous  layer; 
(2)  the  ganglionic  layer  consists  of  several  strata  of  cells,  instead  of  a  single  layer;  (.3)  in  Jacob's 
membrane  there  are  no  rods,  but  only  cones,  and  these  are  longer  and  narrower  than  in  other 
parts;  and  (-1)  in  the  outer  nuclear  layer  there  are  only  cone  fibres,  which  are  very  long  and 
arranged  in  curved  lines.  At  the  fovea  centralis  the  only  parts  which  exist  are  the  cones  of 
Jacob's  membrane,  the  outer  nuclear  layer,  the  cone  fibres  of  which  are  almost  horizontal  in 
direction,  and  an  exceedingly  thin  inner  granular  layer,  the  pigmentary  layer,  which  is  thicker 
and  its  pigment  more  pronounced  than  elsewhere.  The  color  of  the  macula  seems  to  imbue 
all  the  layers  except  .Facob's  membrane;  it  is  of  a  rich  yellow,  deepest  toward  the  centre,  and 
does  not  appear  to  consist  of  pigment  cells,  but  simply  a  staining  of  the  constituent  parts. 

At  the  ora  serrata  (Fig.  810)  the  nerve  layers  of  the  retina  terminate  abruptly,  and  the  retina 
is  continued  onward  as  a  single  layer  of  elongated  columnar  cells  covered  by  the  pigmentary 
layer.  This  prolongation  is  known  as  the  pars  ciliaris  retinae  (Fig.  814),  and  can  be  traced  for- 
ward from  the  ciliary  processes  on  to  the  back  of  the  iris,  where  it  is  termed  the  pars  iridica 
retinae  or  uvea. 

From  the  description  given  of  the  nerve  elements  of  the  retina  it  will  be  seen  that  there  is  no 
direct  continuity  between  the  structures  which  form  its  different  layers  except  between  the 
ganglionic  and  nerve  fibre  layers  the  majority  of  the  nerve  fibres  being  formed  of  the  axones 
of  the  ganglionic  cells.  In  the  inner  molecular  layer  the  dendrites  of  the  ganglionic  layer  inter- 
lace with  those  of  the  cells  of  the  inner  nuclear  layer,  while  in  the  outer  molecular  layer  a 


THE   VITREOUS  BODY 


1105 


likf   synapsis  occurs  between   the   processes   of   the  inner  granules   and   the  rofl   and   cone 
elements. 

The  arteria  centralis  retinae  (Fig.  SIO)  and  its  accompanying  vein,  vena  centralis  retinae, 
pierce  the  optic  nerve,  and  enter  the  globe  of  the  eye  through  the  porus  opticus.  They  bifurcate 
on  the  surface  of  the  papilla  or  just  beneath  it  into  an  upper  and  a  lower  branch,  and  each  of 
these  again  divides  into  an  inner  or  nasal,  and  an  outer  or  temporal  branch;  these  at  first  run 
between  the  hyaloid  membrane  and  the  nerve  layer;  but  they  soon  enter  the  latter,  and  pass 
forward,  dividing  dichotomously.  From  these  branches  a  minute  capillary  plexus  is  given  off, 
which  does  not  extend  beyond  the  inner  nuclear  layer.  The  macula  receives  small  twigs  from 
the  temporal  branches  and  others  directly  from  the  central  artery;  these  do  not,  however,  reach 
as  far  as  the  fovea  centralis,  which  has  no  bloodvessels.  The  branches  of  the  arteria  centralis 
retinae  do  not  anastomose  with  each  other — in  other  words,  they  are  "terminal  arteries."  In 
the  fetus,  a  small  vessel  passes  forward,  through  the  hyaloid  canal  in  the  vitreous  body,  to  the 
posterior  surface  of  the  capsule  of  the  lens  (Fig.  805). 

THE  REFRACTING  MEDIA. 

The  Refracting  media  are  three — viz.: 

Aqueous  humor.  Vitreous  body.  Crystalline  lens, 


I.  The  Aqueous  Humor  (Humor  Aqueus). 

The  aqueous  humor  completely  fills  the  lymph  space  known  as  the  aqueous 
chamber,  the  space  which  is  bounded  in  front  by  the  cornea  and  behind  by  the 
lens  and  its  suspensory  ligament  and  the  ciliary  body  (Fig.  829).  The  aqueous 
chamber  is  partly  divided  by  the  iris  into  two 
communicating  parts,  the  anterior  and  posterior 
chambers  (Figs.  805  and  829).  The  posterior 
chamber  (camera  oculi  posterior')  is  only  a  narrow 
chink  between  the  peripheral  part  of  the  iris,  the 
suspensory  ligament  of  the  lens,  and  the  ciliary 
processes.  The  anterior  chamber  (camera  oculi 
anterior)  is  bounded  in  front  by  the  cornea  and 
behind  by  the  iris.  The  external  angle  of  the 
anterior  chamber  is  bounded  by  the  periphery  of 
the  cornea  and  of  the  iris.     It  is  called  the  angle  .  , 

,,        „,,      ..  ,/  7         •■7-\      Ti'l  which  the  lens  lies.    Seen  obliquely  from 

or  the  filtration  angle  (a?i(/?/ms  (r;rf;.s).   It  is  by  way    the  side  and  before.    (Toidt.) 

of  the  filtration  angle  that  any  excess  of  aqueous 

humor  passes  by  way  of  the  spaces  of  Fontana  and  the  canal  of  Schlemm  (Fig. 

814)    to  the  anterior   ciliary  veins  and  relieves   tension.     The    aqueous  humor 

is  small  in  quantity,  has  an  alkaline  reaction,  in  composition  is  litde  more  than 

water,  less  than  2  per  cent,  of  its  weight  being  solid  matter,  chiefly  sodium  chloride. 


Fig.  823. — The  vitreous  body  removed 
from  the  eye  in  the  fresh  state,  with  the 
shaped  hollow  ( fossa  hyaloidea) 


II.  The  Vitreous  Body  (Corpus  Vitreum)  (Figs.  805,  825). 

The  vitreous  body  occupies  about  four-fifths  of  the  entire  globe.  It  is  composed 
of  a  jelly-like  tissue  containing  98  per  cent,  water,  some  salts,  and  a  litde  albumin, 
and  called  the  vitreous  humor  (humor  vitreus),  connective-tissue  fibres,  and  con- 
nective-tissue cells.  It  fills  the  concavity  of  the  retina,  and  is  hollowed  in  front, 
forming  a  deep  concavity,  fossa  hyaloidea  (Fig.  82.3),  for  the  reception  of  the  lens. 
It  is  perfectly  transparent,  of  the  consistence  of  thin  jelly,  and  is  composed  of  an 
albuminous  fluid  enclosed  in  a  deliciite  transparent  membrane,  the  hyaloid  mem- 
brane (membrana  hyaloidea),  the  outside  of  which  is  in  contact  with  the  membrana 
limitans  interna  of  the  retina.  In  the  fetus  a  peculiar  fibrous  texture  pervades 
the  mass,  the  fibres  joining  at  the  numerous  points,  and  presenting  minute  nuclear 


1106 


THE  ORGANS  OF  SPECIAL  SENSE 


granules  at  their  point  of  junction.  In  the  centre  of  the  vitreous  humor,  running 
from  the  entrance  of  the  optic  nerve  to  the  posterior  surface  of  the  lens,  is  a  canal, 
filled  with  fluid  and  lined  by  a  prolongation  of  the  hyaloid  membrane.  This  is 
the  hyaloid  canal  (canalis  hyaloideus)  (Fig.  805),  which  in  the  embryonic  vitreous 
humor  conveyed  the  minute  vessel  from  the  central  artery  of  the  retina  to  the  back 
of  the  lens. 

The  hyaloid  membrane  encloses  the  whole  of  the  vitreous  humor.  In  front  of 
the  ora  serrata  it  is  thickened  by  the  accession  of  radial  fibres  and  is  termed  the 
zonule  of  Zinn  (zonula  ciliaris)  (Figs.  824  and  829).  Here  it  presents  a  series  of 
radially  arranged  furrows,  in  which  the  ciliary  processes  are  accommodated  and  to 
which  they  are  adherent,  as  evidenced  by  the  fact  that  when  removed  some  of  their 
pigment  remains  attached  to  the  zonule.^    The  zonule  of  Zinn  splits  into  two 


CHORIOIDEA 


Fig.  824.— The  zonule  of  Zi] 


•  suspenboiv  lig  iment  of  the  len=i  Mew 
he  lens  and  the  cihary  bod\       (Toldt 


ed  from  behind  in  connection  with 


layers,  one  of  which  is  thin  and  lines  the  fossa  hyaloidea;  the  other  is  named  the 
suspensory  ligament  of  the  lens;  it  is  thicker,  and  passes  over  the  ciliary  body  to  be 
attached  to  the  capsule  of  the  lens  a  short  distance  in  front  of  its  equator.  Scattered 
and  delicate  fibres  are  also  attached  to  the  region  of  the  equator  itself.  This 
ligament  retains  the  lens  in  position,  and  is  relaxed  by  the  contraction  of  the  radial 
fibres  of  the  Ciliary  muscle,  so  that  the  lens  is  allowed  to  become  more  convex. 
Behind  the  suspensory  ligament  there  is  a  sacculated  canal,  the  canal  of  Petit 
(spatia  zonularia),  which  encircles  the  margin  of  the  lens  and  which  can  be  easily 
inflated  through  a  fine  blowpipe  inserted  through  the  suspensoiy  ligament.  It 
is  bounded  in  front  by  the  anterior  layer  of  the  suspensory  ligament  of  the  lens, 
behind  by  the  membrana  hyaloidea,  and  internally  by  the  capsule  of  the  lens. 
The  canal  of  Petit  is  a  lymph  space.  All  of  the  spaces  of  the  canal  of  Petit  com- 
municate with  the  posterior  chamber  of  the  eye. 

No  vessels  penetrate  the  vitreous  body,  although  a  lymph  channel  remains; 
so  that  its  nutrition  must  be  carried  on  by  the  vessels  of  the  retina  and  ciliary 
processes,  situated  upon  its  exterior. 


III.  The  Crystalline  Lens  (Lens  Crystallina)  (Figs.  825,  826). 

The  crystalline  lens,  enclosed  in  its  capsule,  is  situated  immediately  behind  the 
pupil,  in  front  of  the  vitreous  body,  and  is  encircled  by  the  ciliary  processes,  which 
slightly  overlap  its  margin. 


'  F.  A.  Woll:  A  Simple  Technique  for  the  Removal  of  the  Hyaloid  Me 
Intact.    Anat.  Rec,  vol.  6,  No.  9,  September,  1912. 


"ith  Contents  and  Attachments 


THE  CRYSTALLINE  LENS 


1107 


The  capsule  of  the  lens  {capsuhi  kntis)  (Fig.  785)  is  a  transparent,  liiglily  elastic, 
and  brittle  niemljranc,  which  closely  surrounds  the  lens,  and  is  composed  in  part  of 
cuticular  and  in  part  of  connective  tissues.  It  is  not  white  fibrous  tissue,  anfi  is 
not  true  elastic  tissue  (Szymonowicz).  Its  outer  surface  is  composed  of  lamella' 
and  possesses  transverse  striations.  It  rests,  hehind,  in  the  fossa  hyaloidea  in 
the  fore  part  of  the  vitreous  body  (Fig.  823) ;  in  front,  it  is  in  contact  with  the  free 
border  of  the  iris,  this  latter  receding  from  it  at  the  circumference,  thus  forming 
the  posterior  chamber  of  the  eye  (Fig.  829);  and  it  is  retained  in  its  position  chiefly 
by  the  suspensory  ligament  of  the  lens,  already  described  (Fig.  829).  The  capsule 
is  much  thicker  in  front  than  behind,  and  when  ruptured  the  edges  roll  up  with  the 
outer  surface  innermo.st,  like  the  elastic  lamina  of  the  cornea. 


Fig.  825. — The  crystalline  lens,  hardened 
and  divided.     (Enlarged.) 


Fig.  82G. — The  terms  used  in  the  orientation  of 
the  lens.     (Toldt.) 


The  lens  is  a  transparent,  biconvex  body,  the  convexity  of  the  posterior  surface 
being  greater  than  that  of  the  anterior,  "^rhe  central  points  of  these  surfaces  are 
termed  respectively  the  anterior  and  posterior  poles  (pohis  anterior  et  polus  posterior 
lentis).  A  line  connecting  the  poles  constitutes  the  axis  of  the  lens  (axis  leniis), 
while  the  marginal  circumference  is  termed  the  equator  (aequator  lentis).  The 
lens  measures  from  9  to  10  mm.  in  the  transverse  and  vertical  diameters  and 
about  4  mm.  from  anterior  to  posterior  pole. 


Figs.  827  and  828 


-Diagram  to  show  the  direction  and  arrangement  of  the  radiating  lines  on  the  front  and  back  of 
the  fetal  lens.     Fig.  827.  From  the  front.     Fig.  828.  From  the  back. 


Structure. — The  lens  consists  of  an  outer,  soft  part,  easily  detached  (siibstanfia  cortical  is) ,  and 
a  central,  firm  part  (nucleus  leniis)  (Fig.  82.5).  Faint  lines  (radii  lentis)  radiate  from  the  poles 
to  the  equator.  In  the  adult  there  may  be  six  or  more  of  these  lines,  but  in  the  fetus  they  are  only 
three  in  number  and  diverge  from  each  other  at  angles  of  120  degrees  (Figs.  827  and  828).  On 
the  anterior  surface  one  line  ascends  vertically  and  the  other  two  diverge  downward  and  outward. 
On  the  posterior  surface  one  ray  descends  vertically  and  the  other  two  diverge  upward.  They 
correspond  with  the  free  edges  of  an  equal  number  of  septa  composed  of  an  amorphous  sub- 
stance, which  dip  into  the  substance  of  the  lens.  When  the  lens  has  been  hardened  (as  in  alcohol), 
it  is  seen  to  consist  of  concentric  layers,  or  laminae,  each  of  which  is  interrupted  at  the  septa. 
Each  lamina  is  built  up  of  a  number  of  parallel,  hexagonal  lens  fibres  {fihrae  lentis),  the  edges  of 
which  are  serrated  to  fit  similar  serrations  of  adjacent  lens  fibres,  while  the  ends  of  the  fibres 


1108 


THE  ORGANS  OF  SPECIAL  SENSE 


come  into  apposition  with  the  septa.  The  fibres  run  in  a  curved  manner  from  the  septa  on  the 
anterior  surface  to  those  on  the  posterior  surface.  No  fibres  pass  from  pole  to  pole,  but  ihey 
are  arranged  in  such  a  way  that  filj«-es  which  commence  near  the  pole  on  the  one  aspect  of  the 
lens  terminate  near  the  peripheral  extremity  of  the  plane  on  the  other,  and  vice  versa.  Each 
■  fibre  of  the  outer  layers  of  the  lens  contains  a  nucleus,  and  these  nuclei  form  a  layer,  the  nuclear 
layer,  on  the  surface  of  the  lens.  The  nuclear  layer  is  most  distinct  toward  the  circumference 
of  the  lens.  The  anterior  surface  of  the  lens  is  covered  by  a  single  layer  of  transparent,  columnar, 
nucleated  epithelial  cells  {epithelium  lentis).  At  the  equator  these  cells  become  elongated  and 
their  gradual  transition  into  lens  fibres  can  be  traced. 


rrjsE 

TENDON  OF  S 
RECTOS 


POSTERIOR 


Fig.  829. — The  upper  half  of  a  sagittal  section  through  the  front  of  the  eyeball.      fToldt.J 


The  changes  produced  in  the  lens  by  age  are  the  following : 

In  the  fetus  its  form  is  nearly  spherical,  its  color  of  a  slightly  reddish  tint,  it  is  not  perfectly 
transparent,  and  is  so  soft  as  to  disintegrate  readily  on  the  slightest  pressure.  A  small  branch 
from  the  arteria  centralis  retinae  runs  forward,  as  already  mentioned,  tlirough  the  vitreous 
humor  to  the  posterior  part  of  the  capsule  of  the  lens,  where  its  branches  radiate  and  form  a. 
plexiform  network,  wliich  covers  its  surface,  and  they  are  continuous  around  the  margin  of  the 
capsule  with  the  vessels  of  the  pupillary  membrane  and  "ndtli  those  of  the  iris. 

In  the  adult  the  posterior  surface  is  more  convex  than  the  anterior;  it  is  colorless,  transparent, 
firm  in  texture,  and  devoid  of  bloodvessels. 

In  old  age  it  becomes  flattened  on  both  surfaces,  slightly  opaque,  of  an  amber  tint,  and  in- 
creases in  density. 

Vessels  and  Nerves  of  the  Globe  of  the  Eye. — The  arteries  of  the  globe  of  the  eye  are  the 
short  posterior  ciliary,  long  posterior  ciliary,  and  anterior  ciliary  arteries,  and  the  arteria  centralis 
retinae.     They  have  been  already  described  (p.  613). 


THE  CRYSTALLINE  LENS  1109 

The  ciliary  veins  are  seen  on  the  outer  surface  of  the  choroid,  and  are  named  from  tlieir 
arrangement,  the  venae  vorticosae  (p.  1094).  They  converge  to  four  or  five  equidistant  trunlcs, 
which  pierce  the  sclera  midway  between  the  margin  of  the  cornea  and  the  porus  opticus.  An- 
otlier  set  of  veins  accompanies  the  aiilerior  ciliary  arteries  and  opens  into  the  ophthalmic  vein. 

The  Lymphatic  Passages  of  the  Eyeball.— The  conjunctiva  contains  lymph  vessels. 
The  eyeball  contains  lymph  spaces,  i)ut  no  lymph  vessels.  There  are  two  sets  of  lymph  spaces 
in  the  eyeball,  the  anterior  and  posterior.  The  anterior  l5miph  spaces  are  the  spaces  of  the 
cornea,  of  the  iris,  of  the  anterior  chamber,  and  of  the  posterior  chamber.  The  lymph  from  the 
intralamellar  lymph  spaces  of  the  cornea  enters  the  conjunctival  lymphatics  at  the  margin  of  the 
cornea.  The  lymph  spaces  of  the  iris  open  into  the  anterior  chamber  by  the  crypts  of  the  iris, 
and  at  the  margin  of  the  iris  join  the  spaces  of  Fontana.  The  aqueous  humor  fills  the  anterior 
and  posterior  chambers,  but  is  furnished  by  the  vessels  in  the  posterior  chamber;  in  part  by  the 
vessels  of  the  ciliary  body,  and  in  part  by  the  vessels  of  the  posterior  surface  of  the  iris.  The 
lymph  passes  by  way  of  the  ))upil  into  the  anterior  chamber,  and  then  is  taken  up  by  the  spaces 
of  Fontana,  the  canal  of  Schlemm,  and  the  anterior  ciliary  veins. 

The  posterior  Ijraiph  spaces  are  the  hyaloid  canal,  the  perichoroidal  lymph  space,  the  space 
of  Tenon,  the  intervaginal  space  of  the  optic  nerve,  and  the  supravaginal  space. 

The  hyaloid  canal  (Figs.  S02  and  805). passes  between  the  posterior  surface  of  the  lens  and  the 
optic  disk.  The  hyaloid  canal  opens  into  the  intervaginal  space  of  the  optic  nerve.  Between 
the  sclera  and  the  choroid  is  the  perichoroidal  lymph  space  (Fig.  829).  It  is  around  the  choroid 
vessels  and  the  venae  vorticosae,  and  empties  into  I'enon's  space  by  means  of  openings  through 
the  sclera  about  the  venae  vorticosae.  Tenon's  space  (Figs.  802  and  803)  is  between  the  sclera 
and  the  capsule  of  Tenon.  It  receives  lymph  from  the  perichoroidal  space,  and  empties  into  the 
supravaginal  space. 

The  optic  nerve  (Fig.  S19)  has  a  sheath  of  dura  and  a  sheath  of  pia,  and  between  these  sheaths 
is  the  intervaginal  lymph  space.  It  is  divided  by  a  prolongation  of  the  cerebral  arachnoid  into 
a  subdural  space  and  a  subarachnoid  space,  which  empty  into  the  corresponding  spaces  of  the 
membranes  of  the  lirain.  The  supravaginal  space  is  lictHcen  the  dural  portion  of  the  sheath 
of  the  optic  nerve  and  a  posterior  jirolongation  of  Tenon's  capsule.' 

The  Nerves  of  the  Globe  of  the  Eye. — The  long  cihary  nerves  (tm.  ciliares  longi),  two 
in  number,  are  derived  from  the  nasal  branch  of  the  ophthalmic,  and  the  short  ciliary  nerves 
{nn.  ciliares  breves),  twelve  to  fifteen  in  number,  are  derived  from  the  ciliary  or  ophthalmic  gan- 
glion. Both  the  long  and  short  ciliary  nerves  perforate  the  sclera  in  the  neighborhood  of  the 
optic  nerve  (Fig.  809).  They  pass  along  the  perichoroidal  lymph  space,  forming  a  plexus 
which  sends  filaments  to  the  choroidal  vessels.  In  front  of  the  Ciliary  muscle  they  form  a  second 
plexus,  and  from  it  come  branches  which  go  to  the  Ciliary  muscle  and  the  muscle  fibres  and 
vessels  of  the  iris,  sclera,  choroid,  ciliary  body,  and  iris  (Fig.  816).  The  ciliary  nerves  supply 
the  cornea.  The  circular  fibres  of  the  iris  are  innervated  by  the  oculomotor  nerve  and  the 
radial  fibres  by  the  sympathetic. 

Applied  Anatomy. — From  a  surgical  point  of  view  the  cornea  may  be  regarded  as  consist- 
ing of  three  layers:  (1)  Of  an  external  epithelial  laj'er,  developed  from  the  ectoderm,  and  con- 
tinuous with  the  external  epithelial  covering  of  the  rest  of  the  body,  and  therefore  its  lesions 
resemble  those  of  the  epidermis;  (2)  of  the  cornea  proper,  derived  from  the  mesoderm,  and 
associated  in  its  diseases  with  the  fibrovascular  structures  of  the  body;  and  (.3)  the  posterior 
elastic  layer  with  its  endothelium,  also  derived  from  the  mesoderm  and  having  the  characters 
of  a  serous  membrane,  so  that  inflammation  of  it  resembles  inflammation  of  the  other  serous 
and  synovial  membranes  of  the  body. 

The  corn-ea  contains  no  bloodvessels,  except  at  its  periphery,  where  numerous  delicate  loops, 
derived  from  the  anterior  ciliary  arteries,  may  be  demonstrated  on  the  anterior  surface  of  the 
cornea.  The  rest  of  the  cornea  is  nourished  by  lymph,  which  gains  access  to  the  proper  sub- 
stance of  the  cornea  and  the  posterior  layer  through  the  spaces  of  Fontana  (spatia  anguli  iridis). 
This  lack  of  direct  blood  supply  renders  the  cornea  very  apt  to  become  inflamed  in  the  cachectic 
and  ill-nourished.  In  spite  of  the  absence  of  bloodvessels,  wounds  of  the  cornea  usually  heal 
rapidly.  A  wound  which  penetrates  the  cornea  opens  the  anterior  chamber,  and  aqueous  humor 
escapes.  An  ulcer  may  also  open  the  anterior  chamber.  Through  a  wound  or  a  perforated 
ulcer  the  papillary  margin  of  tlie  iris  may  prolapse.  A  trivial  injury  of  the  cornea  is  repaired  by 
-transparent  tissue.  A  severe  injury  is  repaired  by  fibrous  tissue,  and  opaciti/  results.  A  slight 
opacity  resembling  a  cloud  of  gray  smoke  is  called  nebula;  a  more  marked  white  opacity  is  called 
leuc.oma.  In  abscess  of  the  cornea  pus  gravitates  between  the  layers  to  the  lower  part  of  the 
cornea  and  the  purulent  collection  assumes  a  crescentic  shape  (om/x).  The  arciis  senilis,  seen 
in  the  aged,  is  a  condition  of  haziness  or  opacity  at  the  corneal  margin  due  to  fatty  degeneration 
of  the  tissues  of  the  cornea.  It  signifies  interference  with  the  blood  supply,  because  of  senile 
degeneration  of  adjacent  vessels.  In  cases  of  trachoma  there  is  a  peculiar  affection  of  the  cornea, 
called  pannus,  in  which  the  anterior  layers  of  the  cornea  become  vascularized,  and  a  rich  network 

■  For  the  lymphatic  channels  of  the  eyeball  see  Deaver's  Surgical  .\natomy,  vol.  ii,  p.  392. 


1110  THE  ORGANS  OF  SPECIAL  SENSE 

of  bloodvessels  may  be  seen  on  the  cornea;  and  in  interstitial  keratitis  new  vessels  extend  into  the 
cornea,  giving  it  a  pinkish  hue,  to  which  the  term  salmon  patch  is  applied.  The  cornea  is  richly 
iupplied  with  nerves,  derived  from  the  ciliary  nerves,  which  enter  the  cornea  through  the  fore  part 
of  the  sclera  and  form  plexuses  in  the  stroma,  terminating  between  the  epithelial  cells  by  free 
ends  or  in  corpuscles.  In  cases  of  glaucoma  the  ciliary  nerves  may  be  pressed  upon  as  they 
course  between  the  choroid  and  sclera  (Fig.  808),  and  in  consequence  of  the  pressure  upon 
them,  the  cornea,  to  which  they  are  distributed,  becomes  anesthetic.  When  a  scar  forms  on  the 
cornea  and  the  iris  becomes  adlierent,  the  scar  and  the  iris,  and  sometimes  even  the  lens,  may 
bulge  forward  from  intraocular  tension.  This  condition  is  staphyloma  of  the  cornea.  In  con- 
ditions of  impaired  nutrition  the  cornea  may  be  bulged  forward  by  intraocular  pressure.  The 
line  of  least  resistance  is  a  little  below  the  centre  of  the  cornea,  and  it  is  bulged  forward  and 
strongly  curved.     This  condition  is  known  as  conical  cornea. 

The  sclera  has  very  few  bloodvessels  and  nerves.  The  bloodvessels  are  derived  from  the 
anterior  ciliary,  and  form  an  open  plexus  in  its  substance.  As  they  approach  the  corneal  margin 
this  arrangement  is  peculiar.  Some  branches  pass  through  the  sclera  to  the  ciliary  body;  others 
become  superficial  and  lie  in  the  episcleral  tissue,  and  form  arches,  by  anastomosing  with  each 
other,  some  little  distance  behind  the  corneal  margin.  From  these  arches  nimaerous  straight 
vessels  are  given  off,  which  run  forward  to  the  cornea,  forming  its  marginal  plexus.  In  inflamma- 
tion of  the  sclera  and  episcleral  twsue  these  vessels  become  conspicuous,  and  form  a  pinkish 
zone  of  straight  vessels  radiating  from  the  corneal  margin,  commonly  known  as  the  zone  of  ciliary 
injection.  In  inflammation  of  the  iris  and  ciliary  body,  this  zone  is  present,  since  the  sclera 
speedily  becomes  involved  when  these  structures  are  inflamed.  But  in  inflammation  of  the  cornea 
the  sclera  is  seldom  much  affected,  though  the  cornea  and  sclera  are  structurally  continuous. 
This  would  appear  to  be  due  to  the  fact  that  the  nutrition  of  the  cornea  is  derived  from  a  different 
source  from  that  of  the  sclera.  The  sclera  may  be  ruptured  subcutaneously  without  any  lacer- 
ation of  the  conjunctiva,  and  the  rupture  usually  occurs  near  the  corneal  margin,  where  the 
tunic  is  thinnest.  It  may  be  complicated  with  lesions  of  adjacent  parts — laceration  of  the 
choroid,  retina,  iris,  or  suspensory  ligament  of  the  lens — and  is  then  often  attended  with  hemor- 
rhage into  the  anterior  chamber,  which  masks  the  nature  of  the  injury.  In  some  cases  the  lens 
has  escaped  through  the  rent  in  the  sclera,  and  has  been  found  under  the  conjunctiva.  Wounds 
of  the  sclera,  if  they  do  not  perforate,  usually  heal  readily.  If  they  extend  through  the  sclera 
they  cause  diminished  tension,  are  always  dangerous,  and  are  often  followed  by  inflammation, 
suppuration,  and  by  sympathetic  ophthalmia.  The  sclera  may  be  weakened  by  injury,  inflam- 
mation, etc.,  and  the  weakened  portion  may  bulge  from  intraocular  pressure,  and  even  a  healthy 
sclera  may  bulge  from  excessive  intraocular  pressure.  According  to  its  situation  the  lesion  is 
known  as  ciliary  staphyloma,  equatorial  staphyloma,  or  posterior  staphyloma. 

One  of  the  functions  of  the  choroid  is  to  provide  nutrition  for  the  retina. and  to  convey  ves- 
sels and  nerves  to  the  ciliary  body  and  iris.  Inflammation  of  the  choroid  is  therefore  followed 
by  grave  disturbance  in  the  nutrition  of  the  retina,  and  is  attended  with  early  interference  with 
vision.  Purulent  choroiditis  is  not  confined  to  the  choroid;  the  retina,  the  vitreous,  and  the  entire 
uveal  tract  become  involved,  and  even  other  structures  may  suiTer.  In  its  diseases  it  bears  a  con- 
siderable analogy  to  those  which  aff'ect  the  skin,  and,  like  it,  is  one  of  the  places  from  which 
melanotic  sarcomata  may  grow.  These  tumors  contain  a  large  amount  of  pigment  in  their  cells, 
and  grow  only  from  those  parts  where  pigment  is  naturally  present.  The  choroid  may  be  rup- 
tured without  injury  to  the  other  tunics,  as  well  as  participating  in  general  injuries  of  the  eyeball. 
In  cases  of  uncomplicated  rupture  the  injury  is  usually  at  its  posterior  part,  and  is  the  result  of  a 
blow  on  the  front  of  the  eye.  It  is  attended  by  considerable  hemorrhage,  which  for  a  time  may 
obscure  vision,  but  in  most  cases  this  is  restored  as  soon  as  the  blood  is  absorbed. 

The  iris  is  the  seat  of  a  malformation,  termed  coloboma,  which  consists  in  a  deficiency  or  cleft, 
which  in  a  great  number  of  cases  is  clearly  due  to  an  arrest  in  development.  In  these  cases  it  is 
found  at  the  lower  aspect,  extending  directly  downward  from  the  pupil,  and  the  gap  frequently 
extends  through  the  choroid  to  the  attachment  of  the  optic  nerve.  In  some  rarer  eases  the  gap 
is  round  in  other  parts  of  the  iris,  and  is  then  not  associated  with  any  deficiency  of  the  choroid. 
The  iris  is  abundantly  supplied  with  bloodvessels  and  nerves,  and  is  therefore  very  prone  to 
become  inflamed.  When  inflamed,  in  consequence  of  the  fact  that  the  iris  and  ciliary  body  are 
continuous,  and  that  their  vessels  communicate,  iritis  is  usually  associated  with  cyclitis,  the  dis- 
ease being  called  iridocyclitis.  And,  in  addition,  inflammation  of  adjacent  structures,  the  cornea 
and  sclera,  is  apt  to  spread  into  the  iris.  The  iris  is  covered  with  endothelium,  and  partakes  of 
the  character  of  a  serous  membrane,  and,  like  these  structures,  is  liable  to  pour  out  a  plastic  exuda- 
tion when  inflamed,  and  contract  adhesions,  either  to  the  cornea  in  front  (synechia  anterior),  or 
to  the  capsule  of  the  lens  behind  (synechia  posterior).  In  iritis  the  lens  may  become  involved, 
and  the  condition  known  as  secondary  cataract  may  be  set  up.  Tumors  occasionally  commence 
in  the  iris;  of  these,  cysts,  which  are  usually  congenital  and  sarcomatous  tumors,  are  the  most 
common  and  require  removal.  Gummata  are  not  infrequently  found  in  this  situation.  In  some 
forms  of  injury  of  the  eyeball,  as  the  impact  of  a  spent  shot,  a  flying  cork,  the  rebound  of  a  twig, 
or  a  blow  with  a  whip,  the  iris  may  be  detached  from  the  Ciliary  muscle,  the  amount  of  detach- 


THE  CRYSTALLINE  LENS 


1111 


ment  varying  from  the  slightest  degree  to  the  separation  of  the  whole  iris  from  its  ciliary  con- 
nection. 

The  Argyll-Robertson  pupil  shows  no  reaction  to  light,  but  retains  reaction  to  accommodation 
and  vision  remains  good. 

The  retina,  with  the  exception  of  its  pigment  layer,  and  its  vessels  is  perfectly  transparent, 
and  is  invisible  when  examined  by  the  ophthalmoscope,  so  that  its  diseased  conditions  are  rec- 
ognized by  its  loss  of  transparency.  In  rctiniii.'i,  for  instance,  there  is  more  or  less  dense  and 
extensive  opacity  of  its  structure,  and  not  infrequently  extravasations  of  blood  info  its  sub- 
stance. Hemorrhages  may  also  take  place  into  the  retina  from  rupture  of  a  bloodvessel  without 
inflammation.  In  optic  neuritis,  papillitis,  or  choked  .disk,  the  ophthalmoscope  shows  increase 
in  vascularity,  and  swelling  and  opacity  of  the  nerve,  which  extend  beyond  the  disk  margins. 
Optic  atrophy  is  apt  to  follow.  (Fig.  S.30  shows  a  normal  optic  disk.)  The  retina  may  become 
displaced  from  effusion  of  serum  between  it  and  the  choroid  or  by  blows  on  the  eyeball,  or  may 
occur  without  apparent  cause  in  progressive  mijopia,  and  in  this  case  the  ophthalmoscope  shows 
an  opac|ue,  tremulous  cloud.  Glioma,  a  form  of  sarcoma,  and  essentially  a  disease  of  early  life, 
is  occasionally  met  with  in  connection  with  the  retina. 

The  lens  has  no  bloodvessels,  nerves,  or  connective  tissue  in  its  structure,  and  therefore  is 
not  subject  to  those  morbid  changes  to  which  tissues  containing  these  structures  are  liable.  It 
does,  however,  present  certain  morbid  or  abnormal  conditions  of  various  kinds.  Thus,  variations 
in  shape,  absence  of  the  whole  or  a  part  of  the  lens,  and  displacements  are  among  its  congenital 
defects.  Opacities  may  occur  from  injury,  senile  changes,  malnutrition,  or  errors  in  growth  or 
development.  An  opacity  of  the  capsule,  of  the  lens,  or  of  both,  is  known  as  a  cataract.  Senile 
changes  may  take  place  in  the  lens,  impairing  its  elasticity  and  rendering  it  harder  than  in  youth, 


Fig.  S30. — Ophthalmoscopic  appearance  of  healthy 
fundus  in  a  person  of  very  fair  complexion.  Scleral 
ring  well  marked.  Left  eye,  inverted  image.  (Wecker 
and  Jaeger.) 


Fig.  831. — Ophthalmoscopic  appearance  of  severe 
recent  papillitis.  Several  elongated  patches  of  blood 
near  border  of  disk.     (After  Hughlings  Jackson.) 


SO  that  its  curvature  can  only  be  altered  to  a  limited  extent  by  the  Ciliary  muscle.  And,  finally, 
the  lens  may  be  dislocated  or  displaced  by  blows  upon  the  eyeball,  and  its  relations  to  surround- 
ing structures  altered  by  adhesions  or  the  pressure  of  newgrowths. 

There  are  two  particular  regions  of  the  eye  which  require  special  notice;  one  of  these  is  known 
as  the  "  filtration  area,"  and  the  other  as  the  "  dangerous  area."  The  filtration  area  is  the  circum- 
corneal  zone  immediately  in  front  of  the  iris.  Here  are  situated  the  cavernous  spaces  of  Fon- 
tana,  which  communicate  with  the  canal  of  Schlemm,  through  which  the  chief  transudation  of 
fluid  from  the  eye  is  now  believed  to  take  place.  The  dangerous  area  of  the  eye  is  the  region  in 
the  neighborhood  of  the  ciliary  body,  and  wounds  or  injuries  in  this  situation  are  peculiarly 
■dangerous;  for  inflammation  of  the  ciliary  body  is  liable  to  spread  to  many  of  the  other  structures 
of  the  eye,  especially  to  the  iris  and  choroid,  which  are  intimately  connected  by  nerve  and  vas- 
cular supplies.  Moreover,  wounds  which  involve  the  ciliary  region  are  especially  liable  to  be 
followed  by  sympathetic  ophthalmia,  in  which  destructive  inflammation  of  one  eye  is  excited  by 
some  irritation  in  the  other. 

Emmctropia  is  normal  vision.  In  normal  vision  the  practically  parallel  light  rays  from  distant 
olijects  focus  on  the  retina  without  effort;  divergent  rays  from  near  objects  are  focussed  on  th« 
retina  by  an  effort  of  accommodation. 

Hyperopia  or  hypermctropia  is  far-sightedness.  In  this  condition  the  retina  is  in  front  of  th^ 
principal  focus  when  the  eye  is  at  rest.     The  patient  endeavors  to  correct  the  failure  by  constant 


1112  THE  ORGANS  OF  SPECIAL  SENSE 

and  tiresome  efforts  at  accommodation.  The  condition  is  usually  due  to  inordinate  shortness  of 
the  axis  of  the  eye,  but  may  be  due  to  loss  of  the  lens,  decreased  convexity  of  the  refractive  sur- 
faces, or  lessened  refractive  power  in  the  refractive  media  of  the  eye.  It  is  corrected  by  the  use 
of  convex  glasses. 

Myopia  is  near-sightedness.  In  this  condition  the  rays  of  light  come  to  a  focus  in  front  of  the 
retina,  and  the  patient  is  subjected  to  continued  eye-strain.  It  is  usually  due  to  too  great  length 
of  the  axis  of  the  eye,  but  may  result  from  increase  in  refractive  power  of  refractive  media.  It  is. 
corrected  by  concave  glasses.  Sometimes,  as  a  person  with  hyperopia  begins  to  age,  an  increased 
refractive  power  of  the  lens  causes  myopia.  The  occurrence  of  myopia  in  a  hyperopic  eye  is 
called  second  sirjM,  and  it  enables  the  individual  to  cease  wearing  convex  glasses. 

Exenteration  of  the  contents  of  the  orbit  means  removal  of  all  the  contents  except  those  at  the 
orbital  apex.     Even  the  periosteum  is  taken  away.     It  is  performed  for  malignant  disease. 

Evisceration  of  the  eyeball  is  performed  by  making  a  circular  incision  at  the  corneal  margin  and 
removing  the  internal  and  middle  coats  and  the  contents  of  the  globe.  The  sclera  is  not  removed. 
A  glass  ball  is  inserted  into  the  scleral  sheath,  and  the  sclera  is  closed  over  the  ball  by  vertical 
stitches,  and  the  conjunctiva  is  closed  over  it  by  transverse  stitches.  The  operation  is  performed 
for  leucoma  or  staphyloma  of  the  cornea.  An  artificial  eye  (a  shell)  is  placed  over  the  stump- 
when  healing  is  complete. 

Enucleation,  or  excision  of  the  eyeball,  differs  from  exenteration  of  the  orbital  contents  in  the- 
fact  that  only  the  eyeball  is  removed.  A  circular  incision  through  the  ocular  conjunctiva  is 
carried  around  and  near  to  the  corneal  margin.  The  conjunctiva  and  capsule  of  Tenon  are- 
pushed  back  and  the  Rectus  muscles  are  clamped  and  divided  back  of  the  clamp.  Traction 
is  made  upon  the  globe  in  a  forward  and  inward  direction,  and  the  optic  nerve  and  adjacent 
structures  are  cut  with  scissors  from  the  outer  aspect  of  the  globe.  The  eye  is  then  pulled  out  of 
the  orbit,  and  all  structures  which  tend  to  retain  it  are  divided.  The  stumps  of  the  Recti  muscles 
are  sewed  tosiether. 


THE  APPENDAGES  OF  THE   EYE  (ORGANA  OCULI  ACCESSORIA). 

The  appendages  of  the  eye  include  the  eyebrows,  the  eyelids,  the  conjunctiva, 
and  the  lacrimal  apparatus — viz.,  the  lacrimal  gland,  the  lacrimal  sac,  and  the  nasal 
duct. 

The  Eyebrows  (supercilia)  are  two  arched  eminences  of  integument  wliich  sur- 
mount the  upper  circumference  of  the  orbit  on  each  side,  and  support  numerous 
short,  thick  hairs,  directed  obhquely  on  the  surface.  The  hairs  may  entangle 
foreign  bodies  and  lessen  somewhat  the  force  of  blows.  In  structure  the  eyebrows 
consist  of  thickened  integument,  connected  beneath  with  the  Orbicularis  palpe- 
brarum, Corrugator  supercilii,  and  Occipitofrontalis  muscles.  These  muscles 
serve,  by  their  action  on  this  part,  to  control  to  a  certain  extent  the  amount  of 
light  admitted  into  the  eye. 

The  Eyelids  (palpebrae)  (Figs.  832  and  833)  are  two  thin,  movable  folds  placed 
in  front  of  the  eye,  and  protecting  it  from  injury  by  their  closure.  The  eyelids 
are  composed  of  skin,  superficial  fascia,  and  areolar  tissue,  fibres  of  the  Orbicu- 
laris palpebrarum  muscle,  palpebral  and  orbitotarsal  ligaments,  tarsal  plates, 
and  conjunctiva.  The  upper  lid  also  contains  the  Levator  palpebrae  superioris 
muscle.  In  the  lids  are  bloodvessels,  lymph  vessels,  nerves,  and  ^Meibomian 
glands.  There  are  two  lids,  the  upper  (palpebra  superior)  and  the  lower  {palpehra 
inferior);  the  groundwork  of  both  lids  is  made  up  of  a  fascial  membrane  called 
the  orbital  septum  {septwn  orbitale).  The  upper  lid  is  the  larger  and  the  more 
movable  of  the  two,  and  is  furnished  with  a  separate  elevator  muscle,  the  Levator 
palpebrae  superioris.  The  orbital  septum,  in  each  lid,  consists  of  two  portions. 
The  part  near  the  orbital  margin  is  called  the  orbital  portion.  The  part  in  which 
the  tarsus  lies  is  called  the  tarsal  portion.  Between  the  two  portions  in  each  lid 
^%  a  sulcus,  called,  in  the  upper  lid,  the  superior  orbitopalpebral  sulcus,  and  in  the 
rower  lid,  the  inferior  orbitopalpebral  sulcus.  When  the  eyelids  are  opened  an 
elliDtical  space,  the  interpalpebral  slit  {rima  palpebrarum),  is  left  between  their 


THE  APPENDAGES  OF  THE  EYE 


1113 


margins,  the  angles  of  which  eorrespond  to  tlie  junction  of  the  upper  and  lower 
lids,  and  are  called  canthi. 

The  outer  canthus  (commissura  palpebrarum  laterallii)  is  more  acute  than  the 
inner,  and  the  lids  here  lie  in  close  contact  with  the  globe;  but  the  inner  canthus 
(commissura  palpebrarum  medialis)  is  prolonged  for  a  short  distance  inward 
toward  the  nose,  and  the  two  lids  are  separated  at  the  inner  canthus  by  a  triangular 
space,  the  lacus  lacrimalis.  At  the  commencement  of  the  lacus  lacrimalis,  on  the 
margin  of  each  eyelid,  is  a  small  conical  elevation,  the  lacrimal  papilla,  the  apex  of 
which  is  pierced  by  a  small  orifice,  the  punctum  lacrimale  ( Fig.  8o7),  the  commence- 
ment of  the  lacrimal  canal  (Fig.  835).  AVhen  the  lids  are  closed  a  space  remains 
between  them  and  the  globe  to  permit  of  the  flow  of  tears  inward  (rivus  lacri- 
malis). 

The  Eyelashes  (cilia)  (Fig.  833)  are  attached  to  the  free  edges  of  the  eyelids; 
they  are  short,  thick,  curved  hairs,  arranged  in  a  double  or  triple  row  at  the  margin 
of  the  lids;  those  of  the  upper  lid,  more  numerous  and  longer  than  the  lower, 
curve  upward;  those  of  the  lower  lid  curve  downward.  Because  of  this  arrange- 
ment the  two  sets  do  not  interlace  in  closing  the  lids.  Near  the  attachment  of 
the  eyelashes  are  the  openings  of  sebaceous  glands  (glandulae  sebaceae)  (Fig.  833) 
and  of  a  number  of  glands,  glands  of  Moll  (glandulae  ciliares  [Molli])  (Fig.  833), 
arranged  in  several  rows  close  to  the  free  margin  of  the  lid.  They  are  regarded 
as  enlarged  and  modified  sweat  glands. 


Fig.  832.— T1 


(Testut.) 


Structure  of  the  Eyelids  (Fig.  791). — The  eyelids  are  composed  of  the  following  structures, 
taken  in  their  order  from  without  inward :  Integument,  areolar  tissue,  fibres  of  the  Orbicularis 
muscle,  tarsal  plate,  and  its  ligament,  Meibomian  glands,  and  conjunctiva.  The  upper  lid  has, 
in  addition,  the  aponeurosis  of  the  Levator  palpebrae,  while  both  lids  contain  a  certain  amount 
of  non-striated  muscle,  called,  res])('ctlvcly,  the  Superior  and  Inferior  tarsal  muscles  (see  p.  369) 
(Fig.  802).  The  integument  is  cxtrcinrly  thin,  and  coiitinuoii-;  at  flu-  inaruiu  of  the  hds  with 
the  conjunctiva.  The  subcutaneous  areolar  tissue  is  very  lax  and  delicate,  selilom  contains  any 
fat,  and  is  extremely  liable  to  serous  infiltration.  The  Palpebral  fibres  of  the  Orbicularis  oculi 
muscle  (m.  ciliaris  [Riolani])  are  thin,  pale  in  color,  and  possess  an  involuntary  action. 

The  tarsal  plates  (Fig.  832)  are  two  thin,  elongated,  wedge-shaped  plates  of  dense  connective 
tissue  about  2.5  cm.  (1  inch)  in  length.  They  are  placed  one  in  each  lid,  beneath  the  conjunc- 
tival siu-face,  contributing  to  their  form  and  support.  The  superior  tarsal  plate,  superior 
tarsus,  or  superior  tarsal  body  (famus  siipcrioi)  (Fig.  832),  the  larger,  is  of  a  semilunar  form, 
about  8  mm.  (J  inch)  in  breadth  at  the  centre,  and  becoming  gradually  narrowed  at  each 
extremity.  To  the  anterior  siu-face  of  this  jjlate  the  aponeurosis  of  the  Levator  palpebrae 
is  attached.     The  inferior  tarsal  plate,  inferior  tarsus,  or  inferior  tarsal  body  (fare».y  inferior} 


1114 


THE  ORGANS  OF  SPECIAL  SENSE 


(Fig.  832),  the  smaller  of  the  two,  is  thinner  and  of  an  elliptical  form.  The  free  or  ciliary 
margin  of  these  plates  is  thick,  and  presents  a  perfectly  straight  edge.  The  attached  or  orbital 
margin  is  connected  to  the  circumference  of  the  orbit  by  the  fibrous  membrane  of  the  lids,  with 
which  it  is  continuous.  The  outer  angle  of  each  plate  is  attached  to  the  malar  bone  bj'  the  ex- 
ternal tarsal  ligament  {raphe  palpebralis  lateralis)  (Fig.  832).  The  inner  angles  of  the  two 
plates  terminate  at  the  commencement  of  the  lacus  lacrimalis;  they  are  attached  to  the  nasal 
process  of  the  superior  maxilla  by  the  internal  tarsal  ligament  or  the  tendo  oculi  {ligamentiim 
palpebrale  mediale)  (Fig.  832) .  In  reality  these  so-called  ligaments  are  fascial  expansions  situated 
one  in  each  lid,  and  are  attached  marginally  to  the  edge  of  the  orbit,  where  they  are  continuous 

\Aith  the  periosteum.  The  superior  ligament 
blends  with  the  tendon  of  the  Levator  palpe- 
brae,  the  inferior  with  the  inferior  tarsal  plate. 
Externally,  the  superior  and  infei'ior  ligaments 
fuse  to  form  the  external  tarsal  ligament  just 
referred  to;  internally  they  are  much  thinner, 
and,  becoming  separated  from  the  internal  tarsal 
ligament,  are  fixed  to  the  lacrimal  bone  imme- 
diately behind  the  lacrimal  sac.  The  whole 
fascial  sheet  spanning  the  orbit,  and  reenforced 
by  these  ligaments,  constitutes  the  orbital  sep- 
tum {septum  orbitale),  which  is  perforated  by 
the  vessels  and  nerves  which  pass  from  the 
orbital  cavity  to  the  face  and  scalp. 


The   Meibomian  or  Tarsal  Glands 

{glandulae  tarsales  [Meihomi^)  (Figs.  833 
and  835)  are  situated  in  the  tarsal  plates, 
and  may  be  distinctly  seen  through  the 
conjunctiva  on  everting  the  eyelids,  pre- 
senting the  appearance  of  parallel  strings 
of  pearls.  They  are  about  thirty  in 
number  in  the  upper  eyelid,  and  some- 
what fewer  in  the  lower.  They  corre- 
spond in  length  with  the  breadth  of  each 
plate,  and  are,  consequently,  longer  in 
the  upper  than  iit  the  lower  eyelid.  Their 
ducts  open  on  the  free  margin  of  the  lids 
by  minute  foramina,  which  correspond  in 
number  to  the  follicles.  The  use  of  their 
secretion  is  to  prevent  adhesions  of  the 
lids. 


Structure. — These  glands  are  a  variety  of  the 
cutaneous  sebaceous  glands,  each  consisting  of 
a  single  straight  tube  or  duct,  having  a  cecal 
termination,  and  with  numerous  small  alveoli 
opening  into  it.  The  tubes  consist  of  basement 
membrane,  lined  at  the  mouths  of  the  tubes  by 

stratified  epithelium;  the  deeper  parts  of  the  tubes  and  the  alveoli  are  filled  with  polyhedral 

cells.     They  are  thus  identical  in  structure  with  the  sebaceous  glands. 


Fig.  833.- — Vertical  section  through  the  upper  eye- 
lid, a.  Skin.  h.  Orbicularis  palpebrarum,  h' .  Mar- 
ginal fasciculus  of  Orbicularis  (ciliary  bundle),  c. 
Levator  palpebrae.  rf.  Conjunctiva,  e.  Tarsal  plate, 
f.  Meibomian  gland,  ff.  Sebaceous  gland,  h.  Eye- 
lashes, i.  Small  hairs  of  skin.  j.  Sweat-glands,  h.  Ac- 
'  lacrimal  glands.     (After  Waldeyer.) 


The  Conjunctiva  (Figs.  834  and  835)  is  the  mucous  membrane  of  the  eye.  It 
lines  the  inner  surface  of  the  eyelids,  is  reflected  over  the  fore  part  of  the  sclera 
and  cornea,  and  joins  the  lids  to  the  eyeball.  In  each  of  these  situations  its  struc- 
ture presents  some  peculiarities. 

The  palpebral  portion  (tunica  coiijuucfiva  palpebrarum)  (Fig.  835)  of  the  con- 
junctiva lines  the  posterior  surface  of  the  lids.  It  is  thick,  opaque,  highly  vascular, 
and  covered  with  numerous  papillre,  its  deeper  parts  presenting  a  considerable 
amount  of  lymphoid  tissue.     At  the  margins  of  the  lids  it  becomes  continuous 


THE  APPENDAGES  OF  THE  EYE  1115 

with  the  lining  memhrane  of  the  ducts  of  the  Meibomian  glands,  and,  through  the 
lacrimal  canals,  with  the  lining  membrane  of  the  lacrimal  sac  and  nasal  duct. 
At  the  outer  angle  of  the  upper  lid  the  lacrimal  ducts  open  on  its  free  siu-face; 
and  at  the  inner  angle  of  the  eye  it  forms  a  semilunar  fold,  the  plica  semilunaris 
{■plica  semilunaris  conjunctivae)  (Fig.  837).  The  folds  formed  by  tlie  reflection 
of  the  conjunctiva  from  the  lids  on  to  the  eye  are  called  the  superior  and  inferior 
palpebral  folds,  the  former  being  the  deeper  of  the  two.  These  folds  form  the 
superior  and  inferior  conjunctival  fornix  (Fig.  834). 

The  Bulbar  Portion  {tunica  conjunctiva  bulbi). — ^Llpon  the  sclera  the  conjunc- 
tiva is  loosely  connected  to  the  globe;  it  becomes  thinner,  loses  its  papillary  struc- 
ture, is  transparent,  and  only  slighdy  vascular  in  health.  Upon  the  cornea  the  con- 
junctiva consists  only  of  epithelium,  constituting  the 
anterior  layer  of  the  cornea  (conjunctival  epithelium) 
already  described  (p.  1091).  Lymphatics  arise  in  the 
conjunctiva  in  a  delicate  zone  around  the  cornea,  from 
which  the  vessels  run  to  the  ocular  conjunctiva. 

Fornices  of  Conjunctiva. — At  the  line  of  reflection  of 
each  fold  of  the  conjunctiva  from  each  lid  on  to  the  globe 
of  the  eye  a  pocket  or  arch  is  formed.  These  arches  are 
termed    the   fornices    conjunctivae,    superior    and   inferior       '     "^^^^ ^inferior  fohnjx 

(rig.  bo4).  j-jQ     834.— Sagittal  section 

Glands  of  Conjunctiva. — In  the  conjunctiva  there  are    ?f/y?'  showing  superior  and 

,  ''  •'     ^  '-w        T  •    ^       inferior    fornices  of    the    con- 

a  number  ot  mucous  glands  {gl.  mucosae  [Krausei\)  which   junctiva.    (Xestut.) 
are  much  convoluted.     They  are  chiefly  found  in  the  up- 
per lid.     Other  glands,  analogous  to  lymphoid  follicles,  and  called  by  Henle 
trachoma  glands,  are  found  in  the  conjunctiva,  and,  according  to  Stromeyer,  are 
chiefl>'  situated  near  the  inner  canthus  of  the  eye. 

The  caruncula  lacrimalis  is  a  small,  reddish,  conical-shaped  body,  situated  at 
the  inner  cantlius  of  the  eye,  and  filling  up  the  small  triangular  space  in  this  situ- 
ation, the  lacus  lacrimalis.  It  consists  of  an  island  of  skin  containing  sebaceous 
and  sweat  glands,  and  is  the  source  of  the  whitish  secretion  which  constantly 
collects  at  the  inner  angle  of  the  eye.  A  few  slender  hairs  are  attached  to  its 
surface.  On  the  outer  side  of  the  caruncula  is  a  slight  semilunar  fold  of  conjunc- 
tiva, the  concavity  of  which  is  directed  toward  the  cornea;  it  is  called  the  plica 
semilunaris  (Fig.  837).  Miiller  found  smooth  muscle  fibres  in  this  fold,  and  in 
some  of  the  domesticated  animals  a  thin  plate  of  dense  white  fibrous  tissue  has 
been  discovered.  This  structure  is  considered  to  be  the  rudiment  of  the  third 
eyelid  in  birds,  the  membrana  nictitans. 

The  nerves  in  the  conjunctiva  are  numerous  and  form  rich  plexuses.  Accord- 
ing to  Krause  they  terminate  in  a  peculiar  form  of  tactile  corpuscle,  the  "terminal 
bulb." 

The  Lacrimal  Apparatus  {apparatus  lacrimalis)  (Figs.  835  and  837)  consists  of 
the  lacrimal  gland,  which  secretes  the  tears,  and  its  excretory  ducts,  which  con- 
A-ey  the  fluid  to  the  surface  of  the  eye.  This  fluid  is  carried  away  by  the 
lacrimal  canals  into  the  lacrimal  sac,  and  along  the  nasal  duct  into  the  cavity  of 
the  nose. 

The  Lacrimal  Gland  {glandula  lacrimalis)  is  lodged  in  a  depression  at  the  upper 
and  outer  angle  of  the  orbit,  on  the  inner  side  of  the  external  angular  process  of  the 
frontal  bone.  It  is  of  an  oval  form,  about  the  size  and  shape  of  an  almond.  Its 
upper  convex  surface  is  in  contact  with  the  periosteum  of  the  orbit,  to  which  it  is 
connected  by  a  few  fibrous  bands.  Its  under  concave  surface  rests  upon  the  convex- 
ity of  the  eyeball  and  upon  the  Superior  and  External  recti  muscles.  Its  vessels 
and  nerves  enter  its  posterior  border,  while  its  anterior  margin  is  closely  adherent 


1116 


THE  ORGANS  OF  SPECIAL  SENSE 


to  the  back  part  of  the  upper  eyelid,  where  it  is  covered  to  a  slight  extent  hy  the 
reflection  of  the  conjunctiva.  The  fore  part  of  the  gland  is  separated  from  the 
rest  by  a  fibrous  septum;  hence  it  is  sometimes  described  as  a  separate  lobe, 
called  the  inferior  lacrimal  gland  (glandula  lacrimalis  inferior),  the  back  part  of 
the  gland  then  being  called  the  superior  lacrimal  gland  {glandula  lacrimalis  superior)^ 
The  ducts  of  the  lacrimal  gland,  from  six  to  twelve  in  number,  run  obliquely 
beneath  the  mucous  membrane  for  a  short  distance,  and,  separating  from  each 
other,  open  by  a  series  of  minute  orifices  on  the  upper  and  outer  half  of  the  con- 
junctiva near  its  reflection  on  to  the  globe.  These  orifices  are  arranged  in  a  row, 
so  as  to  disperse  the  secretion  over  the  surface  of  the  membrane. 


Fig.  835. — The  Meibomian 


surface  of  the  eyelids. 


Structure. — In  structure  and  general  appearance  the  lacrimal  resembles  the  serous  salivary 
glands.  In  the  recent  state  the  cells  are  so  crowded  with  granules  that  their  limits  can  hardly 
be  defined.     Each  cell  contains  an  oval  nucleus,  and  the  cell  protoplasm  is  finely  fibrillated. 

The  Lacrimal  Canals  (Fig.  837)  commence  at  the  minute  orifices,  puncta  lacri- 
malia,  on  the  summit  of  small  conical  elevations,  the  lacrimal  papillae  (papillae 
lacrimalis),  seen  on  the  margin  of  the  lids  at  the  outer  extremity  of  the  lacus 
lacrimalis.  The  superior  canal  (ductus  lacrimalis  superior),  the  smaller  and  shorter 
of  the  two,  at  first  ascends,  and  then  bends  at  an 
acute  angle,  and  passes  inward  and  downward  to 
the  ampulla  of  the  lacrimal  sac.  The  inferior 
canal  (ductus  lacrimalis  inferior)  at  first  descends, 
and  then  passes  almost  horizontally  inward  to  the 
ampulla.  These  canals  are  dense  and  elastic  in 
structure  and  somewhat  dilated  at  their  angles. 
The  mucous  membrane  is  covered  with  stratified 
epithelium  upon  a  basement  membrane.  Outside 
the  latter  is  a  layer  of  striped  muscle  continuous 
with  the  Tensor  tarsi.  The  two  canals  join  in  a 
dilatation,  the  ampulla  (ampulla  ductus  lacrimalis),  which  empties  into  the 
lacrimal  sac. 

The  Lacrimal  Sac  (saccus  lacrimalis)  (Fig.  837)  is  the  upper  dilated  extremity 
of  the  nasal  duct,  and  is  lodged  in  a  deep  groove  formed  by  the  lacrimal  bone  and 
the  nasal  process  of  the  maxilla  bone.  It  is  oval  in  form,  its  upper  extremity 
being  closed  in  and  rounded,  while  below  it  is  continued  into  the  nasal  duct. 
It  is  covered  by  a  fibrous  expansion  derived  from  the  tendo  oculi,  and  on  its  deep 


oli  of    lacrimal    gland. 


THE  APPENDAGES  OF  THE  EYE 


1117 


surface  it  is  crossed  by  the  Tensor  tarsi  muscle  (Horner's  muscle,  p.  367),  which 
is  attached  to  the  ridge  on  the  lacrimal  bone. 

Structure. — The  lacrimal  sac  consists  of  a  fibrous  elastic  coat,  lined  internally  by  mucous 
memlirane,  the  latter  being  continuous,  through  the  ampulla  and  lacrimal  canals,  with  the 
mucous  lining  of  the  conjunctiva,  and,  through  the  nasal  duct,  with  the  mucous  membrane  of 
the  nose. 


Fig.  S37 — The  lacrimal  apparatus.     Eight 


The  Nasal  Duct  (ductus  nasolacrimalis)  (Fig.  837)  is  a  membranous  canal, 
about  2  cm.  (three-quarters  of  an  inch)  in  length,  which  extends  from  the  lower 
part  of  the  lacrimal  sac  to  the  inferior  meatus  of  the  nose,  where  it  terminates  by 
a  somewhat  expanded  orifice,  provided  with  an  imperfect  valve,  the  valve  of 
Hasner  (plica  lacrhnalis  [Hasneri]), 
formed  by  a  fold  of  mucous  mem- 
brane. It  is  contained  in  an  osseous 
canal  formed  by  the  maxilla,  the  lac- 
rimal, and  the  turbinated  bones,  is 
narrower  in  the  middle  than  at  each 
extremity,  and  takes  a  direction  down- 
ward, backward,  and  a  little  out- 
ward. It  is  lined  by  mucous  mem- 
brane, which  is  continuous  below  with 
that  of  the  nasal  fossae.  The  mem- 
brane in  the  lacrimal  sac  and  nasal  duct 
is  coA'ered  with  columnar  epithelium,  as 
in  the  nose;  this  epithelium  is  in  places 
ciliated. 

Surface  Form.— The  palpebral  fissure,  or 
opening  between  the  eyelids,  is  elliptic  in 
shape,  and  differs  in  size  in  different  individ- 
uals and  in  different  races  of  mankind.  In 
the  Mongolian  races,  for  instance,  the  opening  is  very  small,  merely  a  narrow  fissure,  and  this 
makes  the  eyeball  appear  small  in  these  races,  whereas  the  size  of  the  eye  is  relatively  very 
constant.  The  normal  direction  of  the  fissure  is  slightly  oblique,  in  a  direction  upward  and  out- 
ward, so  that  the  outer  angle  is  on  a  slightly  higher  level  than  the  inner.  This  is  especially 
noticeable  in  the  Mongolian  races,  in  whom,  owing  to  the  upward  projection  of  the  malar  bone 
and  the  shortness  of  the  external  angular  process  of  the  frontal  bone,  the  tarsal  plate  of  the 
upper  lid  is  raised  at  its  outer  part  and  gives  an  oblique  direction  to  the  palpebral  fissure. 
When  the  eyes  are  directed  forward,  as  in  ordinary  vision,  the  upper  part  of  the  cornea  is 
covered  by  the  upper  lid,  and  the  lower  margin  of  the  cornea  corresponds  to  the  level  of  the  lower 
lid,  so  that  about  the  lower  thi-ee-fourths  of  the  cornea  is  exposed  under  ordinary  circumstances. 

On  the  margin  of  the  lids,  about  1  cm.  from  the  inner  canthus,  are  two  small  openings,  the 
puiicta  lacrimalia,  the  commencement  of  the  lacrimal  canals.  They  are  best  seen  by  everting 
the  eyelids.  In  the  natural  condition  they  are  in-  contact  with  the  conjunctiva  of  the  eyeball, 
and  are  maintained  in  this  position  by  the  Tensor  tarsi  muscle,  so  that  the  tears  running  over  the 
surface  of  the  globe  easily  find  their  way  into  the  lacrimal  canals.  The  position  of  the  lacrimal 
sac  into  which  the  canals  open  is  indicated  by  a  little  tubercle,  which  is  plainly  to  be  felt  on  the 
lower  margin  of  the  orbit.  The  lacrimal  sac  lies  immediately  above  and  to  the  inner  side  of  this 
tubercle,  and  a  knife  passed  through  the  skin  in  this  situation  would  open  the  cavity.  The  posi- 
tion of  the  lacrimal  sac  may  also  be  indicated  by  the  tendo  ociili  or  internal  tarsal  ligament.  If 
both  lids  be  drawn  outward,  so  as  to  tighten  the  skin  at  the  inner  angle,  a  prominent  cord  will  be 
seen  beneath  the  tightened  skin.  This  is  the  tcndo  oculi,  which  lies  immediately  over  the  lacrimal 
sac,  bisecting  it,  and  thus  forming  a  useful  guide  to  its  situation.  A  knife  entered  immediately 
beneath  the  tense  cord  would  open  the  lower  part  of  the  sac.  A  probe  introduced  through  this 
opening  can  be  readily  passed  downward  through  the  duct  into  the  inferior  meatus  of  the  nose. 
The  direction  of  the  duct  is  downward,  outward,  and  backward,  and  this  course  should  be  borne 
in  mind  in  passing  the  probe,  otherwise  the  point  may  be  driven  through  the  thin  bony  walls  of 
the  canal.  A  convenient  plan  is  to  direct  the  probe  in  such  a  manner  that  if  it  were  pushed 
•onward  it  would  strike  the  first  molar  tooth  of  the  lower  jaw  on  the  same  side  of  the  body.  In 
other  words,  the  surgeon  standing  in  front  of  his  patient  should  carry  in  his  mind  the  position  of 


1118  THE  ORGANS  OF  SPECIAL  SENSE 

the  first  molar  tooth,  and  should  push  his  probe  onward  in  such  a  way  as  if  he  desired  to  reach 
this  structure. 

Beneath  the  internal  aiigular  process  of  the  frontal  bone  the  pulley  of  the  Superior  oblique 
muscle  of  the  eye  can  be  plainly  felt  by  pushing  the  finger  backward  between  the  upper  and  inner 
angle  of  the  eye  and  the  roof  of  the  orbit;  passing  backward  and  outward  from  this  pulley,  the 
tendon  can  be  felt  for  a  short  distance. 

Applied  Anatomy. — The  eyelids  are  composed  of  various  tissues,  and  consequently  are  liable 
to  a  variety  of  diseases.  The  skin  which  covers  them  is  exceedingly  thin  and  delicate,  and  is 
supported  on  a  cjuantity  of  loose  and  lax  subcutaneous  tissue  which  contains  no  fat.  In  conse- 
quence of  this  it  is  very  freely  movable,  and  is  liable  to  be  drawn  down  by  the  contraction  of 
neio-hboring  cicatrices.  Such  contractions  may  produce  an  eversion  of  the  lid  known  as  ectropion. 
Inversion  of  the  lids  {entropion)  from  spasm  of  the  Orbicularis  palpebrarum  or  from  chronic 
inflammation  of  the  palpebral  conjunctiva  may  also  occur.  In  some  individuals  there  is  an. 
extra  row  of  eyelashes  on  the  inner  margin  of  the  lid,  directed  toward  the  cornea  (distichiasis). 
Trichiasis  is  a  condition  in  which  the  lashes  are  directed  toward  the  eye,  but  there  is  not  inversion 
of  the  lid.  The  eyelids  are  richly  supplied  with  blood,  and  are  often  the  seat  of  vascular  growths, 
such  as  noevi.  Rodent  ulcer  also  frequently  connnences  in  this  situation.  The  loose  cellular  tissue 
beneath  the  skin  is  liable  to  become  extensively  infiltrated  either  with  l)lood  or  inflammatory 
products,  producing  very  great  swelling.  Even  from  very  slight  injuries  to  this  tissue  the  extrava- 
sation of  blood  may  be  so  great  as  to  produce  considerable  swelling  of  the  lids  and  complete 
closure  of  the  eye,  and  the  same  is  the  ease  when  the  inflammatory  products  are  poured  out.  The 
follicles  are  liable  to  become  inflamed,  constituting  the  disease  known  as  marginal  blepharitis, 
blepharitis  ciliaris,  or  "blear-eye."  Irregular  or  disorderly  growth  of  the  eyelashes  not  infre- 
quentlv  occurs,  some  of  them  being  turned  toward  the  eyeball  and  producing  inflammation  and 
follicles  of  the  eyelashes,  or  the  sebaceous  glands  associated  with  these  follicles  may  be  the  seat  of 
inflammation,  constituting  the  ordinary  hordeolum  or  "sty."  The  Meibomian  glands  are  aft'ected 
in  the  so-called  "tarsal  tumor;"  the  tumor,  according  to  some,  being  caused  by  the  retained  secre- 
tion of  these  glands;  by  others  it  is  believed  to  be  a  neoplasm  connected  with  the  gland.  The 
Orbicularis  palpebrarum  may  be  the  seat  of  spasm  (blepharospasm),  either  in  the  form  of  slight 
quivering  of  the  lids  or  repeated  twitchings,  most  commonly  due  to  errors  of  refraction  in  children, 
or  more  continuous  spasm,  due  to  some  irritation  of  the  trigeminal  or  facial  nerves.  The  Orbicu- 
laris may  be  paralyzed,  generally  associated  with  paralysis  of  the  other  facial  muscles.  Under 
these  circumstances  the  patient  is  unable  to  close  the  lids,  and  if  he  attempts  to  do  so,  rolls  the 
eyeball  upward  under  the  upper  lid.  The  tears  overflow  from  displacement  of  the  lower  lid, 
and  the  conjunctiva  and  cornea,  being  constantly  exposed  and  the  patient  being  unable  to  wink, 
become  irritated  from  dust  and  foreign  bodies.  As  a  result  there  may  be  ulceration  of  the 
cornea,  and  possibly  eventually  complete  destruction  of  the  eye.  In  paralysis  of  the  Levator 
palpebrae  superioris  there  is  drooping  of  the  upper  eyelid  (ptosis)  and  other  symptoms  of  impli- 
cation of  the  oculomotor  nerve.  The  eyelids  may  be  the  seat  of  bruises,  wounds,  or  burns.  After 
wounds  or  burns  adhesions  of  the  margins  of  the  lids  to  each  other  or  adhesion  of  the  lids  to 
the  globe  may  take  place.  The  eyelids  are  sometimes  the  seat  of  emphysema  after  fracture  of 
some  of  the  thin  bones  forming  the  inner  wall  of  the  orbit.  If  shortly  after  such  an  injury  the 
patient  blows  his  nose,  air  is  forced  from  the  nostrils  through  the  lacerated  structure  into  the 
connective  tissue  of  the  eyelids,  which  suddenly  swell  up  and  present  the  peculiar  crackling  on 
pressure  v^hich  is  characteristic  of  this  affection. 

Foreign  bodies  frequently  get  into  the  conjunctival  sac  and  cause  great  pain,  especially  if 
they  come  in  contact  with  the  corneal  surface,  during  the  movements  of  the  lid  and  the  eye  on 
each  other.  The  conjunctiva  is  frequently  involved  in  severe  injuries  of  the  eyeball,  but  is  seldom 
ruptured  alone;  the  most  common  form  of  injury  to  the  conjunctiva  alone  is  from  a  burn,  either 
from  fire,  strong  acids,  or  lime.  In  these  cases  the  union  is  apt  to  take  place  between  the  eyelid 
and  the  eyeball.  The  conjunctiva  is  often  the  seat  of  inflammation  arising  from  many  different 
causes,  and  the  arrangement  of  the  conjunctival  vessels  should  be  remembered  as  affording  a 
means  of  diagnosis  between  this  condition  and  injection  of  the  sclera,  which  is  present  in  inflam- 
mation of  the  deeper  structures  of  the  globe.  The  inflamed  conjunctiva  is  bright  red;  the 
vessels  are  large  and  tortuous,  and  greatest  at  the  circumference,  shading  off  toward  the  corneal 
margin;  they  anastomose  freely  and  form  a  dense  network,  and  they  can  be  emptied  by  gentle 
pressure. 

The  lacrimal  gland  is  occasionally,  though  rarely,  the  seat  of  inflammation  (dacryoademtis). 
either  acute  or  chronic;  it  is  also  sometimes  the  seat  of  tumors,  benign  or  malignant,  and  for  these 
may  require  removal.  This  may  be  done  by  an  incision  through  the  skin  just  below  the  eyebrow ; 
and  the  gland,  being  invested  with  a  special  capsule  of  its  own,  may  be  isolated  and  removed 
without  opening  the  general  cavity  of  the  orbit.  The  canals  may  be  obstructed,  either  as  a  con- 
genital defect  or  by  some  foreign  body,  as  an  eyelash  or  a  dacryolith,  causing  the  tears  to  run 
over  the  cheek.  The  canals  may  also  become  occluded  as  the  result  of  burns  or  injury:  over- 
flow of  tears  may,  in  addition,  result  from  deviation  of  the  puncta  or  from  chronic  inflammation 
of  the  lacrimal  sac.     When  there  is  failure  of  the  lacrimal  tubes  to  drain  off  the  tears  and  the 


THE  EXTERNAL  EAR 


1119 


fluid  gathers  beneath  and  flows  over  the  Hds,  the  condition  is  known  as  epiphora  or  stUlicidium. 
This  latter  condition  is  set  up  by  some  obstruction  to  the  nasal  duct  frequently  occurring  in  tuber- 
culous subjects.  In  consequence  of  this  the  tears  and  mucus  accumulate  in  the  lacrimal  sac, 
distending  it.  Suppuration  in  the  lafrimal  sac  (daeryocystiiis)  is  sometimes  met  with;  this 
may  be  the  sequel  of  a  chronic  inflammation;  or  may  occur  after  some  of  the  eruptive  fevers 
in  cases  where  the  lacrimal  jjassages  were  previously  quite  healthy.  It  may  lead  to  lacrimal 
fistula. 

THE  EAR  (ORGANON  AUDITUS). 

The  organ  of  hearing  is  divisible  into  three  parts — the  external  ear.  the  middle 
ear  or  tympanum,  and  the  internal  ear  or  labyrinth. 


THE  EXTERNAL  EAR  (AURIS  EXTERNA). 

.  The  external  ear  consists  of  an  expanded  portion  named  pinna  or  auricula,  and 
the  auditory  canal  or  meatus.  The  former  serves  to  collect  the  vibrations  of  the  air 
by  which  sound  is  produced;  the  latter  conducts  those  vibrations  to  the  tympanum. 


DARWINIAN 


Fig.  838. — The  right  pinna 


thout.     (Spalteholz.) 


The  Pinna,  or  Auricula  (Fig.  838),  is  attached  to  the  side  of  the  head  midway 
between  the  forehead  and  occiput.  It  is  of  an  ovoid  form,  with  its  larger  end 
directed  upward.  Its  outer  surface  is  irregularly  concave,  directed  slightly  for- 
ward, and  presents  numerous  eminences  and  depressions  which  result  from  the 
foldings  of  its  fibrocartilaginous  element.  To  each  of  these,  names  have  been 
assigned.  Thus,  the  external  prominent  rim  of  the  auricle  is  called  the  helix. 
Another  curved  prominence,  parallel  with  and  in  front  of  the  helix,  is  called  the 


1120 


THE  OBGANS  OF  SPECIAL  SENSE 


INSERTION 


-antihelix;  this  bifurcates  above  and  forms  the  crura  (crura  anthelicis),  which  en- 
close a  triangular  depression,  the  fossa  of  the  antihelix  (fossa  triangularis  [auric- 
ulae]). The  narrow  curved  depression  between  the  helix  and  antihelix  is  called 
the  fossa  of  the  helix  or  the  scaphoid  fosSa  (scapha);  the  antihelix  describes  a  curve 

around  a  deep,  capacious  cavity, 
the  concha  auriculae,  which  is 
partially  divided  into  two  parts 
by  the  crus  of  the  helix  (crus 
helicis),  or  the  commencement  of 
the  helix;  the  upper  part  is  termed 
the  cymba  conchae,  the  lower  part 
the  cavum  conchae.  In  front  of 
the  concha,  and  projecting  back- 
ward over  the  meatus,  is  a  small 
pointed  eminence,  the  tragus,  so 
called  from  its  being  generally 
covered  on  its  under  surface  with 
a  tuft  of  hair  resembling  a  goat's 
beard.  Opposite  the  tragus,  and 
separated  from  it  by  a  deep  notch 
(incisura  intertragica),  is  a  small 
tubercle,  the  antitragus.  Below 
this  is  the  lobule  (lohulus  auricu- 
lae), composed  of  tough  areolar  and  adipose  tissue,  wanting  the  firmness  and  elas- 
ticity of  the  rest  of  the  pinna.  Sometimes  the  lobule  does  not  hang  freely,  but 
is  adherent. 


CARTILAGE 

■  EXTERNAL 

AUDITORY 

MEATUS 


TRANSVERSE 

AURICULAR 

MUSCLE 


iFiG.  839. — The  cartilage  of  the  right  pinna,  isolated,  with  the 
muscles,  viewed  from  the  inside.     (Spalteholz.) 


Where  the  helix  turns  downward  a  small  tubercle,  tubercle  of  Darwin  (hiberculum  auriculae 
'IDarwiniJ),  is  frequently  seen.  This  tubercle  is  very  evident  about  the  sixth  month  of  fetal  life; 
at  this  stage  the  human  pinna  has  a  close  resemblance  to  that  of  some  of  the  adult  monkeys. 

The  cranial  surface  of  the  pinna 
presents  elevations  which  correspond 
to  the  depressions  on  its  outer  surface 
and  after  which  they  are  named,  e.  g., 
'eminentia  conchae,  eminentia  fossae 
triangularis,  etc. 

Structure. — The  pinna  is  composed 
of  a  thin  plate  of  yellow  fibrocartilage, 
covered  with  integument  and  connected 
to  the  surrounding  parts  by  the  extrinsic 
ligaments  and  muscles,  and  to  the  com- 
mencement of  the  external  auditory 
■canal  by  fibrous  tissue. 

The  integument  is  thin,  closely  ad- 
herent to  the  cartilage,  and  covered 
with  hairs  furnished  with  sebaceous 
glands  which  are  most  numerous  in.  the 
concha  and  scaphoid  fossa.  The  hairs 
are  most  numerous  and  largest  on  the 
tragus  and  antitragus. 

The  cartilage  of  the  pinna  (cartilago 
■auriculae)  (Fig.  840)  consists  of  one  single 
piece;  it  gives  form  to  this  part  of  thS  ear,  and  upon  its  surface  are  found  all  the  eminences  and 
depressions  above  described.  It  does  not  enter  into  the  construction  of  all  parts  of  the  pinna;  thus, 
it  does  not  form  a  constituent  part  of  the  lobule;  it  is  deficient  also  between  the  lamina  of  the 
tragus  and  beginning  of  the  crus  helix,  the  notch  between  them  (incisura  ferminalis  auris)  being 
filled  up  by  dense  fibrous  tissue.  At  the  front  part  of  the  pinna,  where  the  helix  bends  upward, 
is  a  small  projection  of  cartilage,  called  the  spine  of  the  helix  (spina  helicis),  while  the  lower 
part  of  the  helix  is  prolonged  downward  as  a  tail-like  process,  the  Cauda  helicis;  this  is  separated 
from  the  antihelix  by  a  fissure,  the  fissura  antitragohelicina.     The  cranial  aspect  of  the  cartilage 


FISSURA 

ANTITHAGICO- 

HELICINA 


INCISURA 

TERMINALIS 

AUniS 


ANTITRAGUS 

-The  right  ear  cartilage,  isolated, 
without.      (Spalteholz.) 


THE  EXTERNAL  EAR 


1121 


exhibits  a  transverse  furrow,  the  sulcus  antihelicus  transversus,  which  separates  the  prominenee 
produced  by  the  concha  from  that  caused  by  the  fossa  triangularis.  A  vertical  ridge  {iion- 
ticiiliis)  upon  the  eminentia  conchae  gives  attachment  to  the  Retrahens  aurem  muscle.  The 
fissure  of  the  helix  is  a  short  vertical  slit,  situated  at  the  fore  part  of  the  pinna.  Another  fissure, 
the  fissure  of  the  tragus,  is  seen  upon  the  anterior  siu-face  of  the  tragus.  Anteriorly  and  infe- 
riorly  the  ciirUhi^r  of  the  pinna  is  continuous  with  the  cartilage  of  the  external  auditory  canal 
b\-  a  cartilaginous  isthmus  (isihmiis  cartilaginis  auris).  Some  authors  regard  the  tragus  as 
part  of  the  cartilanc  of  the  canal.  The  cartilage  of  the  pinna  is  very  pliable,  elastic,  of  a  yel- 
lowish color,  and  belongs  to  that  form  of  cartilage  wlucli  is  known  under  the  name  of  yellow 
fibrocartilage. 

The  ligaments  of  the  pinna  {ligamenii  auricularia  [Valsalvae])  consist  of  two  sets:  1.  The 
extrinsie  set,  or  those  connecting  it  to  tlie  siile  of  the  head.  2.  The  intrinsic  .set,  or  those 
connecting  the  various  parts  of  its  cartil:ij,'c  toi^cthcr.  The  extrinsic  ligaments,  the  most 
important,  are  three  in  number — superior,  anterior,  and  posterior.  The  superior  ligament 
{lignmenUim  auriculare  superius)  extends  from  the  suprameatal  spine  to  the  s]jine  of  the  helix. 
The  anterior  ligament  {ligamentum  auriculare  anterius)  extends  from  the  spina  helicis  and 
tragus  to  the  root  of  the  zygoma.  The  posterior  ligament  (ligamentum.  auriculare  posterius) 
passes  from  the  posterior  surface  of  the  concha  to  the  outer  surface  of  the  mastoid  process  of 
the  temporal  bone.  The  chief  intrinsic  ligaments  are:  (1)  A  strong  fibrous  band  stretching 
across  from  the  tragus  to  the  commencement  of  the  helix,  completing  the  meatus  in  front,  and 
partly  encircling  the  boundary  of  the  concha;  and  (2)  a  band  which  extends  between  the  anti- 
helix  and  the  cauda  helicis.  Other  less  important  bands  are  found  on  the  cragial  surface  of  the 
pinna . 

The  muscles  of  the  pinna  (Figs.  839  and  841)  consist  of  two  sets:  (1)  The  extrinsic,  which 
connect  it  with  the  side  of  the  head,  moving  the  pinna  as  a  whole — viz.,  the  Attollens,  Attrahens, 
and  Retrahens  aurem  (p.  366).  (2)  The  intririsic,  which  extend  from  one  part  of  the  auricle 
to  another — viz.: 


Helicis  major. 
Helicis  minor. 
Tragicus. 


Antitragicus. 
Transversus  auriculae. 
Obliquus  auriculae. 


The  Helicis  major  {m.  helicis  major)  is  a  narrow  vertical  band  of  muscle  fibres,  situated  upon 
the  anterior  margin  of  the  helix.     It  arises,  below,  from  the  spina  hehcis,  and  is  inserted  into 
the  anterior  border  of  the  helix,  just  where 
it  is  about  to  curve  backward. 

Tlie  Helicis  minor  {m.  helicis  minor)  is 
an  oblique  fasciculus  which  covers  the 
crus  helicis. 

The  Tragicus  (?».  tragicus)  is  a  short, 
flattened  band  of  muscle  fibres  situated 
upon  the  outer  surface  of  the  tragus,  the 
direction  of  its  fibres  being  vertical. 

The  Antitragicus  (m.  antitragicus)  arises 
from  the  outer  part  of  the  antitragus;  its 
fibres  are  inserted  into  the  cauda  helicis 
and  antihelix.  This  muscle  is  usually 
very  distinct. 

The  Transversus  auriculae  (m.  trans- 
versus auriculae)  is  placed  on  the  cranial 
surface  of  the  pinna.  It  consists  of  scat- 
tered fibres,  partly  tendon  and  partly 
muscle,  extending  from  the  convexity  of 
the  concha  to  the  prominence  correspond- 
ing with  the  groove  of  the  helix. 

The  Obliquus  auriculae  (Tod)  (m. 
obliquus  auriculae)  consists  of  a  few  fibres 
extending  from  the  upper  and  back  part 
of  the  concha  to  the  convexity  immediately 
above  it. 

The  arteries  of  the  pinna  are  the  pos- 
terior auricular  from  the  external  carotid, 
the  anterior  auricular  from  the  temporal, 
and  an  auricular  branch  from  the  occip- 
ital artery.  The  veins  of  the  pinna  ac- 
company the  corresponding  arteries.    The  Fig.  S4l.-The  muscles  of  the  pinna. 


1122 


THE  ORGANS  OF  SPECIAL  SENSE 


lymphatics  enter  into  the  preauricular  nodes  and  the  nodes  upon  the  Sternomastoid  muscle 
at  its  insertion.  Tlie  nerves  of  the  pinna  are  the  great  auricular,  from  the  cervical  plexus; 
the  auricular  branch  of  the  vagus;  the  auriculotemporal  branch  of  the  inferior  maxillai'v  nerve; 
the  small  occipital  from  the  cervical  plexus,  and  the  great  occipital  or  internal  branch  of  the 
dorsal  division  of  the  second  cervical  nerve.  The  muscles  of  the  pinna  are  supplied  by  the 
facial  nerve. 

The  Auditory  Canal,  or  Meatus  (meatus  acusticus  extemus),  extends  from  the 
bottom  of  the  concha  to  the  membrana  tympani  (Figs.  842  and  843).  It  is  about 
3.7  cm.  (an  inch  and  an  half)  in  length  if  measured  from  the  tragus ;  from  the  bottom 
of  the  concha  its  length  is  about  2.5  cm.  (an  inch).  It  forms  a  sort  of  S-shaped 
curve,  and  is  directed  at  first  inward,  forward,  and  slightly  upward  (pans  externa); 
it  then  passes  inward  and  backward  {jpars  media),  and  lastly  is  carried  inward, 
forward,  and  slightly  downward  {jpars  interna).  It  forms  an  oval  cylindrical 
canal,  the  greatest  diameter  being  in  the  vertical  direction  at  the  external  orifice, 

but  in  the  transverse  direction 
at  the  tympanic  end.  It  pre- 
sents two  constrictions,  one 
near  the  inner  end  of  the  carti- 
laginous portion,  and  another, 
the  isthmus,  in  the  osseous 
portion,  about  2  cm.  (three- 
quarters  of  an  inch)  from  the 
bottom  of  the  concha.  The 
membrana  tympani  (Figs.  842 
and  843),  which  closes  the 
inner  end  of  the  canal,  is 
directed  obliquely,  in  conse- 
quence of  which  the  floor  of 
the  canal  is  longer  than  the 
roof,  and  the  anterior  wall 
longer  than  the  posterior. 
The  auditory  canal  is  formed 
partly  by  cartilage  and  membrane,  partly  by  bone,  and  is  lined  by  perichondrium 
and  periosteum,  covered  by  skin. 

The  cartilaginous  portion  (meatus  acusticus  extemus  cartilagineus)  is  about 
8  mm.  (one-third  of  an  inch)  in  length;  it  is  formed  by  the  cartilage  of  the  pinna, 
prolonged  inward,  and  firmly  attached  to  a  greater  portion  of  the  circimiference 
of  the  auditory  process  of  the  temporal  bone.  The  cartilage  is  deficient  at  its 
upper  and  back  part,  its  place  being  supplied  by  a  fibrous  membrane.  This 
part  of  the  canal  is  rendered  extremely  movable  by  two  or  three  deep  fissures,  the 
fissures  of  Santorini  (incisurae  cartilaginis  meatus  acustici  externi  YSantoriniJ), 
which  extend  through  the  cartilage  in  a  vertical  direction. 

The  osseous  portion  (meatus  acusticus  extemus  osseus)  is  about  16  mm.  (two- 
thirds  of  an  inch)  in  length,  and  narrower  than  the  cartilaginous  portion.  It  is 
directed  inward  and  a  little  forward,  forming  a  slight  curve  in  its  coiu'se,  the  con- 
vexity of  which  is  upward  and  backward.  Its  inner  end,  which  communicates, 
in  the  dry  bone,  with  the  cavity  of  the  tympanum,  is  smaller  than  the  outer  and 
sloped,  the  anterior  wall  projecting  beyond  the  posterior  about  4  mm.  (one-sixth 
of  an  inch);  it  is  marked,  except  at  its  upper  part,  by  a  narrow  groove,  the  tympanic 
sulcus  (sulcus  tynipanicus),  in  which  the  circumferential  margin  of  the  membrana 
tympani  is  attached.  Its  outer  edge  is  dilated  and  rough  in  the  greater  part  of 
its  circumference,  for  the  attachment  of  the  cartilage  of  the  pinna.  Its  transverse 
section  is  oval,  the  greatest  diameter  being  from  above  downward  and  backward. 
The  front  and  lower  parts  of  this  canal  are  formed  by  a  curved  plate  of  bone. 


Cat  tilags  of  (he  ezt 
auditory  meatui, 


Fig.  S42. — Transverse  section  of  external  auditorj" 
panum.     Leftside.     (Gegenbaur.) 


THJ<:  EXTERNAL  EAR 


1123 


the  tympanic  plate,  which,  in  the  fetus,  exists  as  a  separate  ring  (avmilii.s-  tijin- 
panicus),  incomplete  at  its  upper  part.     (See  Section  on  Osteology,  p.  87.) 

The  skin  lining  the  meatus  is  very  thin,  adheres  closely  to  the  cartilaginous  and 
osseous  portions  of  the  tube,  and  covers  the  surface  of  the  membrana  tympani, 
forming  a  very  thin  outer  layer.  After  maceration  the  thin  pouch  of  epidermis, 
when  withdrawn,  preserves  the  form  of  the  canal.  In  the  thick  subcutaneous 
tissue  of  the  cartilaginous  part  of  the  meatus  are  numerous  ceruminous  glands 
(glandulae  ceruminosae)  which  secrete  the  ear  ivax  or  ceruvien.  They  resemble 
in  structure  sweat  glands,  and  their  ducts  open  on  the  surface  of  the  skin. 


-Vertical  section  through  the  external  auditory  canal   and  tympanum,  passing  i 
ovalis.     (Testut.) 


,  front  of  the  fenestra 


Relations  of  the  Canal. — In  front  of  the  osseous  part  is  the  glenoid  fossa,  which  receives  the 
condyle  of  the  mandible  (Fig.  100),  which,  however,  is  separated  from  the  cartilaginous  part  by 
the  retromandibular  part  of  the  parotid  gland.  The  movements  of  the  mandible  influence  to  some 
extent  the  lumen  of  the  cartilaginous  portion.  Behind  tlie  osseous  part  are  the  mastoid  air  cells 
{cellulae  mastoideae),  separated  from  it  by  a  thin  layer  of  bone  (Fig.  S4o). 

The  arteries  supplying  the  external  canal  are  branches  from  the  posterior  am-iciilar,  internal 
maxillary,  and  superficial  temporal. 

The  veins  of  the  external  canal  accompany  the  corresponding  arteries  and  pass  to  the  in- 
ternal maxillary,  temporal,  and  posterior  auricular  veins.  The  lymphatics  accompany  the 
veins  and  enter  the  parotid  and  posterior  auricular  lymph  nodes.  The  nerves  are  chiefly 
derived  from  the  auriculotemporal  branch  of  the  inferior  maxillary  nerve,  the  auricularis 
magnus,  and  the  auricular  branch  of  the  vagus. 

The  point  of  junction  of  the  osseous  and  cartilaginous  portions  of  the  tube  is  an  obtuse  angle, 
which  projects  into  the  canal  at  its  antero-inferior  wall.  This  produces  a  sort  of  constriction 
in  this  situation,  and  renders  it  the  narrowest  portion  of  the  canal — an  important  point  to  be 
borne  in  mind  in  connection  with  the  presence  of  foreign  bodies  in  the  ear.  The  cartilaginous 
is  connected  to  the  bony  part  by  fibrous  tissue,  which  renders  the  outer  part  of  the  tube  very 
movable,  and  therefore  by  drawing  the  pinna  upward  and  backward  the  canal  is  rendered 
almost  straight.  At  the  external  orifice  are  a  few  short  crisp  hairs  which  serve  to  prevent  the 
entrance  of  small  particles  of  dust,  flies,  or  other  insects.  In  the  external  auditory  canal  the 
secretion  of  the  ceruminous  glands  serves  to  catch  any  small  particles  which  may  find  their  way 
into  the  canal,  and  prevent  their  reaching  the  membrana  tympani,  where  their  presence  might 
excite  irritation.  In  young  children  the  canal  is  short,  the  osseous  part  being  very  deficient, 
and  consisting  merely  of  a  bony  ring  {annulus  tympanicus),  which  supports  the  membrana 
tympani.     In  the  fetus  the  osseous  part  is  entirely  absent.     The  shortness  of  the  canal  in  children 


1124  THE  ORGANS  OF  SPECIAL  SENSE 

should  be  borne  in  mind  in  introducing  the  aural  speculum,  so  that  it  shall  not  be  pushed  in  too 
far,  at  the  risk  of  injuring  the  membrana  tympani;  indeed,  even  in  the  adult  the  speculum 
should  never  be  introduced  beyond  the  constriction  which  marks  the  junction  of  the  osseous 
and  cartilaginous  portions.  In  using  this  instrument  it  is  advisable  that  the  pinna  should  be 
drawn  upward,  backward,  and  a  little  outward,  so  as  to  render  the  canal  as  straight  as  possible, 
and  thus  assist  the  operator  in  obtaining,  by  the  aid  of  reflected  light,  a  good  view  of  the  membrana 
tympani.  .Just  in  front  of  the  membrane  is  a  well-marked  depression,  situated  on  the  floor  of 
the  canal  and  bounded  by  a  somewhat  prominent  ridge;  in  this  foreign  bodies  may  become 
lodged.  By  aid  of  the  speculum,  combined  with  traction  of  the  auricle  upward  and  backward, 
the  whole  of  the  membrana  tympani  is  rendered  visible.  It  is  a  pearly-gray  membrane,  slightly 
glistening  in  the  adult,  placed  obliquely,  so  as  to  form  with  the  floor  of  the  canal  a  very  acute 
angle  (about  5.5  degrees),  while  with  the  roof  it  forms  an  obtuse  angle.  At  birth  it  is  more  hori- 
zontal— being  situated  in  almost  the  same  plane  as  the  base  of  the  skull.  About  midway  between 
the  anterior  and  posterior  margins  of  the  membrane,  and  extending  from  the  centre  obliquely 
upward,  is  a  reddish-yellow  streak;  this  is  the  handle  of  the  malleus,  which  is  attached  to  the 
membrane  (Fig.  846).  At  the  upper  part  of  this  streak,  close  to  the  roof  of  the  canal,  a  little 
white  rounded  prominence  is  plainly  to  be  seen;  this  is  the  processus  brevis  of  the  malleus, 
projecting  against  the  membrane.  The  membrana  tympani  does  not  present  a  plane  surface; 
on  the  contrary,  its  centre  is  drawn  inward,  on  account  of  its  connection  with  the  handle  of  the 
malleus,  and  thus  the  external  surface  is  rendered  concave. 

The  connections  of  the  nerves  of  the  auditory  canal  explain  the  fact  that  the  occurrence,  in  cases 
of  any  irritation  of  the  canal,  of  constant  coughing  and  sneezing  from  implication  of  the  vagus, 
or  of  yawning  from  implication  of  the  auriculotemporal,  of  vomiting  which  may  follow  syring- 
ing the  ears  of  children,  and  the  occasional  heart  faihu-e  similarly  induced  in  elderlj'  persons. 
No  doubt  also  the  association  of  earache  with  toothache  in  cancer  of  the  tongue  is  due  to  im- 
plication of  the  inferior  maxillary,  which  supplies  also  the  teeth  and  the  tongue.  The  upper 
half  of  the  membrana  tympani  is  much  more  richly  supplied  with  blood  than  the  lower  half. 
For  this  reason,  and  also  to  avoid  the  chorda  tympani  nerve  and  ossicles,  incisions  through  the 
viemhraiii-  should  'ne  made  at  the  lower  and  posterior  part. 

Applied  Anatomy. — Malformations,  such  as  imperfect  development  of  the  external  parts, 
absence  of  the  canal,  or  supernumerary  auricles,  are  occasionally  met  with.  Or  the  pinna  may 
present  a  congenital  fistula,  "which  is  due  to  defective  closure  of  the  first  visceral  cleft,  or  rather 
of  that  portion  of  it  which  is  not  concerned  in  the  formation  of  the  Eustachian  tube,  tympanum, 
and  meatus.  In  some  cases  the  cephaloauricular  angle  is  almost  absent;  in  others,  it  is  nearly 
a  rio-ht  angle.  Projecting  ears  and  long  ears  are  said  by  some  observers  to  be  more  common 
among  degenerates,  criminals,  and  the  insane  than  among  the  normal,  the  non-criminal,  and 
the  sane.  The  skin  of  the  auricle  is  thin  and  richly  supplied  with  blood,  but  in  spite  of  this  it 
is  frequently  the  seat  oi  frost-bite,  due  to  the  fact  that  it  is  much  exposed  to  cold,  and  lacks  the 
usual  underlying  subcutaneous  fat  found  in  most  other  parts  of  the  body.  A  collection  of  blood 
is  sometimes  found  between  the  cartilage  and  perichondrium  {hematoma  auris),  usuall_v  the 
result  of  traumatism,  but  not  necessarily  due  to  this  cause.  It  is  said  to  occur  most  frequently 
in  the  ears  of  the  insane.  Keloid  sometimes  grows  in  the  auricle  around  the  puncture  made  for 
ear-rings,  and  epithelioma  occasionally  affects  this  part.  Deposits  of  urate  of  soda  are  often  met 
with  in  the  pinna  in  gouty  subjects. 

The  external  auditory  canal  can  be  most  satisfactorily  examined  by  light  reflected  tlirough  a 
funnel-shaped  speculum;  by  gently  moving  the  latter  in  different  directions  and  by  gently 
drawing  the  pinna  upward,  backward,  and  a  little  outward,  so  as  to  render  the  canal  as  straight 
as  possible,  the  whole  of  the  canal  and  membrana  tympani  can  be  brought  into  view.  The 
points  to  be  noted  are  the  presence  of  wax  or  foreign  bodies,  the  size  of  the  canal,  and  the  con- 
dition of  the  membrana  tympani.  The  accumulation  of  wax  (impacted  cerumen)  is  often  the 
cause  of  deafness,  and  may  give  rise  to  very  serious  consequences,  causing  ulceration  of  the 
membrane  and  even  absorption  of  the  bony  wall  of  the  canal.  Foreign  bodies  are  not  infrequently 
introduced  into  the  ear  by  children,  and,  when  situated  in  the  first  portion  of  the  canal,  maj'  be 
removed  with  tolerable  facility  by  means  of  a  minute  hook  or  loop  of  fine  wire,  the  parts  being 
illuminated  with  reflected  light;  but  when  they  have  slipped  beyond  the  narrow  middle  part  of 
the  meatus,  their  removal  is  in  nowise  easy,  and  attempts  to  efi'ect  it,  in  inexperienced  hands, 
may  be  followed  by  destruction  of  the  membrana  tympani  arid  possibly  injury  of  the  contents  of 
the  tympanum.  The  caliber  of  the  external  auditory  canal  may  be  narrowed  by  inflammation 
of  its  lining  membrane,  running  on  to  suppuration;  by  periostitis;  by  polypi.,  sebaceous  tumors, 
and  exostoses. 

THE  MIDDLE  EAR,  DRUM,  OR  TYMPANUM  (AURIS  MEDIA) 

(Figs.  844,  848). 

The  middle  ear  or  tympanum  is  an  irregular  cavity,  compressed  laterally, 
and  situated  within  the  petrous  portion  of  the  temporal  bone.     It  is  placed  above 


THE  MIDDLE  EAR,   DRUM,    OR   TYMPANUM 


1125 


the  jugular  fossa;  the  carotid  canal  lying  in  front,  the  mastoid  cells  behind,  the 
external  auditory  canal  externally,  and  the  labyrinth  internally.  It  is  lined 
with  mucous  membrane,  is  filled  with  air,  and  communicates  ^\■ith  the  mastoid 
cells,  through  the  mastoid  antrum,  and  with  the  nasopharynx  by  the  Eustachian 
tube.  The  tympanum  is  traversed  by  a  chain  of  movable  bones,  which  connect 
the  membrana  tympani  with  the  labyrinth,  and  serve  to  convey  the  vibrations 
communicated  to  the  membrana  tympani  across  the  cavity  of  the  tympanum 
to  the  internal  ear.  In  shape  it  is  roughly  biconcave,  the  concave  surfaces  being 
placed  vertically  and  forming  the  external  and  internal  walls.  The  cavity  forms 
an  angle  of  45  degrees  with  the  sagittal  plane. 

The  Tympanic  Cavity  {cavum  tym'pani)  (Figs.  848  and  849)  consists  of  two 
parts — the  atrium  or  tympanic  cavity  proper  (Fig.  849),  opposite  the  tympanic  mem- 
brane, and  the  attic  or  epitympanic  recess  {rccessus  epitympanicKs)  (Figs.  847  and 
848),  above  the  level  of  the  upper  part  of  the  membrane;  the  latter  contains  the 
upper  half  of  the  malleus  and  the  greater  part  of  the  incus.  The  diameter  of  the 
tympanic  cavity,  including  the  attic,  measures  about  15  mm.  (three-fifths  of  an 
inch)  vertically  and  anteroposteriorly.  From  without  inward  it  measures  about 
G  mm.  (one-quarter  of  an  inch)  above  and  4  mm.  (one-sixth  of  an  inch)  below; 
opposite  the  centre  of  the  tympanic  membrane  it  is  only  about  2  mm.  (one- 
twelfth  of  an  inch).  It  is  bounded  externally  by  the  membrana  tympani  and 
meatus;  internally,  by  the  outer  surface  of  the  internal  ear;  it  communicates  behind 
\\\t\\  the  mastoid  antrum  and  through  it  with  the  mastoid  cells,  and  in  from  with 
the  Eustachian  tube. 


Chorda  tympnm 


Fig    S4-i  — \  ie\\  of  the  inner  w  all  of  the  tympanum  (enl 


The  roof  of  the  tympanum  (paries  tegmentalis)  is  broad,  flattened,  and  formed 
of  a  thin  plate  of  bone  (legmen  tympani)  (Fig.  848),  which  separates  the  cranial 
and  tympanic  cavities.  It  is  situated  on  the  anterior  surface  of  the  petrous  portion 
of  the  temporal  bone,  close  to  its  angle  of  junction  with  the  squamous  portion  of 
the  same  bone,  and  is  prolonged  backward  so  as  to  roof  in  the  mastoid  antrum; 
it  is  also  carried  forward  to  cover  in  the  canal  for  the  Tensor  tympani  muscle. 
Its  outer  edge  corresponds  with  the  remains  of  the  petrosquamous  suture. 

The  floor  (paries  jugularis)  (Fig.  848)  is  narrow,  and  is  separated  by  a  thin 
plate  of  bone  (fundus  tympani)  from  the  jugular  fossa.  It  presents,  near  the 
inner  wall,  a  small  aperture,  the  opening  of  the  canaliculus  tympanicus,  for  the 
transmission  of  Jacobson's  nerve  (».  tympanicus).  On  the  floor  near  the  posterior 
wall  there  is  often  to  be  found  a  slight  bony  projection  (prominentia  styloideae). 

The  outer  wall  (Fig.  843)  is  formed  mainly  by  the  membrana  tympani,  partly 
by  the  ring  of  bone  into  which  this  membrane  is  inserted.  This  ring  of  bone  is. 
incomplete  at  its   upper  part,   forming  a   notch   (incisura  tympanica  [Riviiii]) 


1126  THE  ORGANS  OF  SPECIAL  SENSE 

(Fig.  S44),  close  to  whicli  are  three  small  apertures — the  iter  chordae  posterius, 
the  Glaserian  fissure,  and  the  iter  chordae  anterius. 

The  iter  chordae  posterius  {canaliculus  chordae  tympani)  (Fig.  804)  is  in  the  angle 
of  junction  between  the  posterior  and  external  walls  of  the  tympanum,  immediately 
behind  the  membrana  tympani  and  on  a  level  with  the  upper  end  of  the  handle 
of  the  malleus;  it  leads  into  a  minute  canal,  which  descends  in  front  of  the  facial 
canal  and  terminates  in  the  aqueduct  near  the  stylomastoid  foramen.  Through 
it  the  chorda  tympani  nerve  enters  the  tympanum. 

The  Glaserian  or  petrotympanic  fissure  {fissura  petrotympanica.)  [Glaseri])  (Fig. 
847)  opens  just  above  and  in  front  of  the  ring  of  bone  into  which  the  membrana 
tympani  is  inserted;  in  this  situation  it  is  a  mere  slit  about  2  mm.  in  length.  It 
lodges  the  long  process  and  anterior  ligament  of  the  malleus,  and  gives  passage 
to  the  tympanic  branch  of  the  internal  maxillary  artery. 

The  iter  chordae  anterius  or  canal  of  Huguier  (Fig.  847)  is  seen  at  the  inner  end 
of  the  preceding  fissure;  through  it  the  chorda  tympani  nerve  leaves  the  tympanum. 

The  inner  wall  of  the  tympanum  (paries  labyrinthica)  (Figs.  844  and  848)  is 
adjacent  to  the  labyrinth;  it  is  vertical  in  direction,  and  looks  direcdy  outward. 
It  presents  for  examination  the  following  parts: 

Fenestra  ovalis.  Promontory. 

Fenestra  rotunda.  Ridge  of  the  facial  canal. 

Prominence  of  the  lateral  semicircular  canal. 

The  fenestra  ovalis  {fenestra  vestibuli)  (Fig.  844)  is  a  reniform  opening  leading 
from  the  tympanum  into  the  vestibule  of  the  internal  ear.  Its  long  diameter 
is  directed  horizontally,  and  its  convex  border  is  upward.  In  the  recent  state 
it  is  occupied  by  the  base  of  the  stapes  (Figs>  843  and  849),  the  circumference 
of  which  is  connected  to  the  margin  of  the  foramen  by  an  annular  ligament. 

The  fenestra  rotunda  {fenestra  cochleae)  (Fig.  844)  is  situated  below  and  a  little 
behind  the  fenestra  ovalis,  from  which  it  is  separated  by  a  rounded  elevation,  the 
promontory;  at  its  border  is  a  narrow  ridge  of  bone  {crista  fenestrae  cochleae). 
The  fenestra  rotunda  is  closed  in  the  recent  state  by  a  membrane  (membrana 
tympani  secundaria) ;  this  membrane  is  concave  toward  the  tympanum,  convex 
toward  the  cochlea.  It  consists  of  three  layers — the  external  or  mucous,  derived 
from  the  mucous  lining  of  the  tympanum;  the  internal,  from  the  lining  membrane 
of  the  cochlea;  and  an  intermediate  or  fibrous  layer. 

The  promontory  (promontorium)  (Fig.  848)  is  a  rounded  hollow  prominence, 
formed  by  the  projection  outward  of  the  first  turn  of  the  cochlea;  it  is  placed 
between  the  fenestrte,  and  is  furrowed  on  its  surface  {sulcus  promontorii)  for  the 
lodgement  of  the  tympanic  plexus.  A  minute  spicule  of  bone  frequently  connects 
the  promontory  to  the  pyramid. 

The  prominentia  canalis  facialis  (Fig.  848)  indicates  the  position  of  the  b.ony 
canal  in  which  the  facial  nerve  is  contained;  this  canal  traverses  the  inner  wall 
of  the  tympanum  above  the  fenestra  ovalis,  and  behind  that  opening  curves 
nearly  vertically  downward  along  the  posterior  wall. 

The  posterior  wall  of  the  tympanum  {paries  mastoidea)  (Fig.  848)  is  wider 
above  than  below,  and  presents  for  examination  the — 

Opening  of  the  antrum.  Fossa  incudis. 

Pyramid. 

The  opening  of  the  antrum  is  a  large  irregular  aperture,  which  extends  back- 
ward from  the  epitympanic  recess  and  leads  into  a  considerable  air  space,  the 
mastoid  antrum  {antrum  tympanicwn)  (see  p.  83).     The  antrum  communicates 


THE  MIDDLE  EAR,  DRUM,   OB  TrMPANUM  1127 

witli  lartje  irregular  cavities  contained  in  the  interior  of  the  mastoid  process,  the 
mastoid  air  cells.  These  cavities  vary  considerably  in  nuinher,  size,  and  form; 
they  are  Hned  by  mucous  membrane  continuous  with  that  Hning  the  cavity  of 
the  tympanum. 

Tlie  fossa  incudis  (Fig.  848)  is  placed  in  the  posterior  and  inferior  part  of  the 
epitympanic  recess.     It  lodges  the  short  process  of  the  incus. 

The  pyramid  (emine)tti.a  pijramidalis)  (Fig.  844)  is  a  conical  eminence  situated 
immediately  behind  the  fenestra  ovalis,  and  in  front  of  the  vertical  portion  of 
the  facial  canal;  it  is  hollow  in  the  interior,  and  contains  the  Stapedius  muscle; 
its  summit  projects  forward  toward  the  fenestra  ovalis  and  presents  a  small  aper- 
ture which  transmits  the  tendon  of  the  muscle.  The  cavity  in  the  pyramid  is 
prolonged  into  a  minute  canal,  which  communicates  with  the  facial  canal  and 
transmits  the  twig  from  the  facial  nerve  which  supplies  the  Stapedius. 

The  anterior  wall  of  the  tympanum  (paries  carotica)  is  wider  abo^-e  than  below; 
it  corresponds  with  the  carotid  canal,  from  which  it  is  separated  by  a  thin  plate 
of  bone  (Fig.  848),  perforated  by  the  caroticotympanic  canaliculus,  which  transmits 
the  tympanic  branch  of  the  internal  carotid  artery  and  the  caroticotympanic 
nerves.     It  presents  for  examination  the — 

Canal  for  the  Tensor  tympani.  Orifice  of  the  Eustachian  tube. 

The  processus  cochleariformis. 

The  orifice  of  the  canal  foi-  the  Tensor  tympani  and  the  orifice  of  the  Eustachian 
tube  are  situated  at  the  upper  part  of  the  anterior  wall,  being  incompletely  sepa- 
rated from  each  other  by  a  thin,  delicate,  horizontal  plate  of  bone,  the  processus 
cochleariformis  (septum  canalis  musculotubarii) _(Figs.  844  and  848).  The  canalis 
musculotubarius  is  divided  by  this  long  process  into  the  canal  for  the  Tensor 
tympani  and  the  canal  for  the  Eustachian  tube.  These  canals  run  from  the 
tympanum  forward,  inward,  and  a  little  downward,  to  the  angle  between  the 
squamous  and  petrous  portions  of  the  temporal  bone. 

The  canal  for  the  Tensor  tympani  (semicanalis  m.  tensor  is  tympani)  (Figs.  844 
and  848)  is  the  superior  and  the  smaller  of  the  two;  it  is  rounded  and  lies  beneath 
the  forward  prolongation  of  the  tegmen  tympani.  It  extends  on  to  the  inner  wall 
of  the  tympanum  and  ends  immediately  above  the  fenestra  ovalis.  The  processus 
cochleariformis  passes  backward  below  this  part  of  the  canal,  forming  its  outer 
wall  and  floor;  it  expands  above  the  anterior  extremity  of  the  fenestra  ovalis 
and  terminates  by  curving  outward  so  as  to  form  a  pulley  over  which  the  tendon 
passes.  The  bony  wall  of  this  canal  is  incomplete,  and  the  osseous  vacancy  is 
filled  by  tough  connective  tissue. 

The  Eustachian  tube  (tuba  audiiiva  [Eustackii])  (Figs.  844  and  845)  is  the 
channel  through  which  the  tympanum  communicates  with  the  nasopharynx.  Its 
length  is  36  mm.  (an  inch  and  a  half),  and  its  direction  downward,  inward,  and 
forward,  forming  an  angle  of  about  4.5  degrees  with  the  sagittal  plane  and  one  of 
from  .30  to  40  degrees  with  the  horizontal  plane.  The  canal  for  the  Eustachian 
tube  (semicanalis  tuhae  auditivae)  (Fig.  845)  is  formed  partly  of  bone,  partly  of 
cartilage  and  fibrous  tissue. 

The  osseous  portion  (pars  ossea  tubae  aiiditivae)  is  about  12  mm.  (half  an  inch) 
in  length.  It  is  the  outer  portion  of  the  tube.  It  commences  in  the  anterior  wall 
of  the  tympanum,  below  the  processus  cochleariformis.  and,  gradually  narrowing, 
terminates  at  the  angle  of  junction  of  the  petrous  and  squamous  portions  of  the 
temporal  bone,  its  extremity  presenting  a  jagged  margin  which  ser^•es  for  the  attach- 
ment of  the  cartilaginous  portion. 

The  cartilaginous  portion  (pars  cartilaginea  iuhae  auditivae),  about  2.5  cm.  (an 
inch)  in  length,  is  formed  of  a  triangular  plate  of  elastic  fibrocartilage  (cartilago 


1128 


THE  ORGANS  OF  SPECIAL  SENSE 


tuhae  aiiditivae),  the  apex  of  which  is  attached  to  the  margin  of  the  inner  extremity 
of  the  osseous  canal,  while  its  base  lies  directly  under  the  mucous  membrane  of 
the  nasopharynx,  where  it  forms  an  elevation  or  cushion  above  and  behind  the 
pharyngeal  orifice  of  the  tube.  The  upper  edge  of  the  cartilage  is  curled  upon 
itself,  being  bent  outward  so  as  to  present  on  transverse  section  the  appearance  of 
a  hook  (lamina  lateralis);  a  groove  or  furrow  is  thus  produced,  which  opens  below 
and  externally,  and  this  part  of  the  canal  is  completed  by  fibrous  membrane. 
On  transverse  section  the  cartilage  exhibits  the  laminse  which  above  are  continuous 
with  each  other — the  hard,  thick  lamina  medialis  and  the  thin  and  hooked  lamina 
lateralis.  The  cartilage  of  the  Eustachian  tube,  with  a  hood  plate  of  cartilage, 
forms  the  posterior  portion  of  the  inner  wall  (the  lamina  medialis).  The  cartilage 
is  fixed  to  the  base  of  the  skull,  and  lies  in  a  groove  (sulcus  tuhae  auditivae)  between 


Fig.  845. — Eustachian  tube,  laid  open  by  a  cut  in  its  long  axis.     (Testut.) 


the  petrous  portion  of  the  temporal  and  the  greater  wing  of  the  sphenoid;  this 
groove  ends  opposite  the  middle  of  the  internal  pterygoid  plate,  in  a  projection,  the 
processus  tubarius.  The  cartilaginous  and  bony  portions  of  the  tube  are  not 
in  the  same  plane,  the  former  inclining  downward  a  little  more  than  the  latter. 
They  join  each  other  at  a  large  obtuse  angle,  open  below.  The  diameter  of  the 
canal  is  not  uniform  throughout,  being  greatest  at  the  pharyngeal  orifice  and 
least  at  the  junction  of  the  bony  and  cartilaginous  portions,  where  it  is  named 
the  isthmus  (isthmus  tuhae  auditivae^ ;  it  again  expands  somewhat  as  it  approaches 
the  tympanic  cavity.  The  position  and  relations  of  the  pharyngeal  orifice  are 
described  with  the  anatomy  of  the  nasopharynx.  The  mucous  membrane  of  the 
tube  is  continuous  in  front  with  that  of  the  nasopharynx,  and  behind  with  that 
which  lines  the  tympanum;  it  is  covered  with  ciliated  epithelium  and  is  thin  in 
the  osseous  portion,  while  in  the  cartilaginous  portion  it  contains  many  mucous 
glands  and  near  the  pharyngeal  orifice  a  considerable  amount  of  lymphoid  tissue, 
which  has  been  named  by  Gerlach  the  tubal  tonsil.  The  tube  is  opened  during 
deglutition  by  the  Salpingopharyngeus  and  Dilatator  tubse  muscles. 

The  Membrana  Tympani  (Figs.  846  and  847)  separates  the  cavity  of  the  tym- 
panum from  the  bottom  of  the  external  canal.     It  is  a  thin,  semitransparent 


THE  MIDDLE  EAR,   DRUM,    OR   TYMPANUM 


1129 


POSTERIOR 
TYMPANIC^ 
SPINE 


MARGIN    OF 

MEMBRANA 

1  ITMPANI 

OR  LIMBUS 


TENSE  PORTION 
OF  MEMBRANA 
TYMPANI 


Fig.  846.— The  right  membrana  tympani,  viewed  from  the  oulside,  from  in  front,  and  from  below.     (Spalteholz.) 


SUPERIOR   LIGAMENT 


NECK  OF 

MALLEUSV 

ANTERIOR  LIGAMENT 

AND   ANTERIOR 

PROCESS  OF 

MALLEOLUS 

INSERTION 

OF  TENSOR 

TYMPANI 


Fig.  847. — The  right  membrana  tympani  with  the  hammer  and  the  chorda  tympani,  viewed  from  within, 
from  behind,  and  from  above.     (Spalteholz.) 


1130 


THE  ORGANS  OF  SPECIAL  SENSE 


membrane,  nearly  oval  in  form,  somewhat  broader  above  than  below,  and  directed 
A'ery  obliquely  downward  and  inward,  so  as  to  form  an  angle  of  about  55  degrees 
with  the  floor  of  the  canal  (Fig.  843).  The  antero-inferior  portion  is)  therefore, 
placed  at  the  greatest  distance  from  the  external  orifice  of  the  meatus.  In  a  new- 
born child  the  membrana  tympani  is  almost  horizontal.  The  greatest  diameter 
of  the  membrana  tympani  is  from  9  to  10  mm.;  its  least  diameter  is  from  8  to  9 
mm.  The  greater  part  of  its  circumference  (limbiis  memhranae  tymimnae)  is 
thickened  and  fixed  in  a  groove,  the  sulcus  tympanicus,  at  the  inner  extremity  of 
the  external  meatus.  This  sulcus  is  deficient  superiorly  at  the  incisure  or  notch 
of  Rivinus  (Fig.  846).  From  the  extremities  of  the  notch  two  folds,  the  anterior 
and  posterior  malleolar  folds,  are  prolonged  to  the  short  process  of  the  malleus 
(Fig.  846).     The  small,  somewhat  triangular  part  of  the  membrane   situated 


RECESS 

PROMINENCE  OF  EXTERNAL 
SEMICIRCULAR  CANAL 

E  OF  AQUEDUCT 
OF  FALLOPIUS 

TENDON   OF 

STAPEDIUS  MUSCLE 

PLICA 

STAP 

/  /  X       PROCESSUS 

COCHLCARIFORMI5 

^  TENSOR  TYMPANI 

uscLE  (cut  through) 


Fig.  848. — The  medial  wall  and  part  of  the  posterior  and  anterior  walls  of  the  right  tympanic  cavity,  lateral  ^ 

(Spalteholz.) 


above  these  folds  is  lax  and  thin,  and  is  named  the  membrana  fiaccida  of  Shrapnell 
(Figs.  846  and  847);  in  it  a  small  orifice  is  sometimes  seen.  The  larger  lower 
portion  of  the  tympanic  membrane  is  stretched  tightly,  and  is  called  the  tense 
portion  or  pars  tensa  (Figs.  846  and  847). 

The  handle  of  the  malleus  is  firmly  attached  to  the  inner  aspect  of  the  mem- 
brana tympani  as  far  as  its  centre  (Fig.  847),  which  it  draws  inward  toward  the 
tympanic  cavity.  The  most  depressed  part  of  the  concavity  is  called  the  umbo 
{itinbo  memhranae  tympanae)  (Fig.  846).  On  the  outer  surface  of  the  drum 
membrane  a  light  stripe  {stria  malleolaris)  is  seen.  It  runs  from  in  front  and 
above  downward  and  backward,  and  is  produced  by  the  handle  of  the  malleus, 
showing  through  the  membrane  (Fig.  846). 

Structure. — The  tympanic  membrane  is  composed  of  tliree  layers — an  external  {cutwular) ,  a 
middle  {fibrous),  and  an  internal  {mvcous).  The  cuticular  layer  {stratum  cuianeiim)  is  derived 
from  the  integument  lining  the  external  canal.    The  fibrous  or  middle  layer  {membrana  propria) 


THE  MIDDLE  EAR,  DRUM,   OR  TYMPANUM 


lV.il 


consists  of  two  strata — an  external,  of  radiating  fibres  (sfrafiim  rndiatiim),  whirh  diverge  from 
the  handle  of  the  malleus,  and  an  internal,  of  circular  fibres  {xlralmii  rin'iilarr),  which  are  plenti- 
ful around  the  circumference,  but  sparse  and  scattei'cd  ncai'  the  centre  of  the  membrane. 
Branched  i>r  dendritic  fibres,  as  pointed  out  by  Grliber,  are  also  present,  especially  in  the  pos- 
terior half  (if  the  iiiciiiKi-ane. 

The  arteries  arc  ilcriwd  from  the  deep  auricular  branch  of  the  internal  maxillary,  which 
ramifies  beneath  the  cuticular  layer  and  from  the  stylomastoid  branch  of  the  posterior  auricular 
and  tympanic  branch  of  the  internal  maxillary,  which  are  distributed  on  the  mucous  surface. 
The  arteries  of  the  cutaneous  set  anastomose  with  the  arteries  of  the  mucous  set  by  minute 
branches  which  penetrate  the  drum  membrane  near  its  margin.  The  superficial  veins  open 
into  the  external  jugular;  those  on  the  mucous  surface  drain  partly  into  the  lateral  sinus  and 
veins  of  the  dura  and  partly  into  a  plexus  on  the  Eustachian  tube.  The  outer  surface  of  the 
drum  membrane  receives  its  nerve  supply  from  the  auriculotemporal  branch  of  the  inferior 
maxillary  and  the  auricular  branch  of  the  vagus.  The  inner  surface  is  supplied  by  the  tym- 
panic branch  of  the  glossopharyngeal. 

There  are  two  sets  of  lymphatics,  the  cutaneous  and  mucous,  which  freely  communicate.  Tht 
spaces  between  the  dendritic  fibres  of  Grliber  are  lymph  spaces  (Kessel). 


The  Ossicles  of  the  Tympanum  (ossicida  aiditus)  (Fig,  849).— The  tym- 
panum contains  in  its  upper  part  a  chain  of  movable  bones,  three  in  number, 
the  malleus,  incus,  and  stapes.  The  first  is  attached  to  the  membrana  tympani, 
the  last  to  the  fenestra  ovalis,  the  incus  being 
placed  between  the  two,  and  connected  to 
both  by  delicate  articulations. 

The  Malleus  (Fig.  850),  so  named  from  its 
fancied  resemblance  to  a  hammer,  is  placed 
farthest  in  front  and  outward.  It  consists 
of  a  head,  neck,  and  three  processes — the 
handle,  or  manubrium,  the  processus  gracilis,  and 
the  processus  brevis. 

The  head  (capitulum  mallei)  is  the  large 
upper  extremity  of  the  bone,  and  is  situated 
in  the  epitympanic  recess  (Fig,  847).  It  is 
oval  in  shape,  and  articulates  posteriorly  with 
the  incus,  being  free  in  the  rest  of  its  extent. 
The  facet  for  articulation  with  the  incus  is 
covered  by  cartilage;  it  is  constricted  near 
the  middle,  and  is  divided  by  a  ridge  into  an 
upper,  greater,  and  a  lower,  lesser  part;  which 
form  nearly  a  right  angle  with  each  other. 
Opposite  the  constriction  the  lower  margin  of 
the  facet  projects  in  the  form  of  a  process, 
the  cog  tooth,  or  spur  of  the  malleus.  On  the 
back  of  the  head  below  the  spur  is  a  crest 
(crista  mallei),  to  which  the  posterior  ligament 
of  the  malleus  is  attached. 

The  neck  (c-ollum  mallei)  is  the  narrow  contracted  part  just  beneath  the  head; 
below  this  is  a  prominence,  to  which  the  various  processes  are  attached.  The 
chorda  tympani  nerve  crosses  the  inner  surface  (Fig.  847). 

The  handle  (^manubrium  mallei)  is  a  vertical  process  of  bone,  which  is  connected 
by  its  outer  margin  with  the  fibrous  layer  of  the  membrana  tympani,  its  entire 
length  being  fastened  to  the  fibrous  layer  of  the  drum  membrane  by  its  own  peri- 
osteum and  by  a  layer  of  cartilage  (Figs.  847  and  849).  It  is  directed  downward, 
inward,  and  backward;  it  decreases  in  size  toward  its  extremity,  where  it  is  curved 
slightly  forward,  and  is  flattened  from  within  outward.  The  handle  forms  a 
variable  angle  with  the  head  of  the  hammer.  It  averages  about  130  degrees, 
.  but  is  always  greater  in  the  right  ear  than  in  the  left.     It  forms  an  angle  -nith  the 


Fig.  849 — Chain  of  ossicles  and  their  liga- 
ments, seen  from  the  front  in  a  vertical, 
transverse  section  of  the  tympanum.  (Testut.) 


1132 


THE  ORGANS  OF  SPECIAL  SENSE 


horizontal,  averaging  on  the  right  side  50  degrees  and  on  the  left  side  45  degrees 
(Spalteholz).  Internally  the  handle  is  covered  by  the  mucous  membrane  of  the 
tympanum.  On  the  inner  side,  near  its  upper  end,  is  a  slight  projection,  into 
which  the  tendon  of  the  Tensor  tympani  is  inserted  (Fig.  847). 

The  processus  gracilis  (processus  anterior  [Folii])  is  a  long  and  delicate  process, 
which  springs  from  the  eminence  below  the  neck  and  is  directed  forward  and 
outward  to  the  Glaserian  fissure,  to  which  it  is  connected  by  ligamentous  fibres. 
In  the  fetus  this  is  the  longest  process  of  the  malleolus,  and  is  in  direct  continuity 
with  the  cartilage  of  Meckel. 


MANUBRIUM 


INSERTION 

OF  TENSOR 

TYMPANI 

MUSC 


INSERTION  Ol 
EXTERNAL 
LIGAMENT 
OF  MALLEUS 


PROCESS 


Fig.  850.— Viewed  fr< 


in  front.  Fig.  Sol. — Viewed  from  behind.     (Spalteliolz.) 

Figs.  850  and  851. — The  right  malleus  (enlarged). 


The  processus  brevis  (processus  lateralis)  is  a  slight  conical  projection,  which 
springs  from  the  root  of  the  manubrium;  it  is  directed  outward  and  is  attached 
to  the  upper  part  of  the  tympanic  membrane  by  cartilage  and  to  the  margins  of 
the  notch  of  Rivinus  by  the  two  tympanomalleolar  folds. 

The  Incus  (Figs.  852  and  853)  has  received  its  name  from  its  supposed 
resemblance  to  an  anvil,  but  it  is  more  like  a  bicuspid  tooth  with  two  roots. 


ARTICULAR 
^      SURFACE  FOR 
■     ' HEAD  OF 

MALLEUS 


ARTICULAR  SURFACE 
FOR  HEAD  OF  MALLEUS 


Fig.  852. — Lateral  view.  Fig.  853. — Medial  and  front  view.      (Spalteholz 

Figs.  862  and  853. — The  right  incus  (enlarged.) 


which  differ  in  length,  and  are  widely  separated  from  each  other.  It  consists  of 
a  body  and  two  processes.  The  body  and  the  short  process  are  placed  in  the 
epitympanic  recess  (Fig.  849). 

The  body  (corpus  incudis)  is  somewhat  quadrilateral,  but  compressed  laterally. 
On  its  anterior  surface  is  a  deeply  concavo-convex  facet,  which  articulates  with 
the  head  of  the  malleus,  and  the  lower  part  is  hollowed  for  the  spur  of  the  malleus. 

The  two  processes  diverge  from  each  other  at  an  angle  of  from  90  to  100  degrees. 


THE  MIDDLE  EAR,  DRUM,   OB  TYMPANUM  1133 

The  short  process  (crus  breve),  somewhat  conical  in  shape,  projects  almost, 
horizontally  backward,  and  articulates  with  a  depression,  the  fossa  incudis,  in  the 
lower  and  back  part  of  the  epitympanic  recess. 

The  long  process  (crus  longuvi),  longer  and  more  slender  than  the  preceding, 
descends  nearly  vertically  behind  and  parallel  to  the  handle  of  the  malleus,  and, 
bending  inward,  terminates  in  a  rounded  globular  projection,  the  os  orbiculare  or 
lenticular  process  (processus  lenticular  is), 
which    is    tipped   with    cartilage,   and 
articulates  with  the  head  of  the  stapes. 
In  the  fetus  the  os  orbiculare  exists  as 
a  separate  bone.  anter 

The  Stapes  (Figs.  854  and  855),  so  "' 

called  from  its  close  resemblance  to  a 
stirrup,  consists  of  a  head,  neck,  two  qase  or  stapes 

crura,  and  a  base.     The  stapes  is  the  p^^  gg^ 

only  one   of  the  tympanic  ossicles  that  Fiqs.  854  and  SSS.— The  right  stapes  (enlarged).    Fig. 

■I  •,  854.      Viewed  from  above.       Fig.   855.      Medial    view. 

lias  a  marrow  cavity.  rspaitehoiz.) 

The  head   (capituhim  stapedis)  pre- 
sents a  depression,  tipped  with  cartilage,  which  articulates  with  the  os  orbiculare. 

The  neck,  the  constricted  part  of  the  bone  succeeding  the  head,  receives  the 
insertion  of  the  Stapedius  muscle. 

The  two  crura  (crus  anterius  and  crus  posterius)  diverge  fron^  i,he  neck  and  are 
connected  at  their  extremities  by  a  flattened,  oval-shaped  plate,  the  base  (basis 
stapedis),  which  forms  the  foot-plate  of  the  stapes  and  is  fixed  to  the  margin  of 
the  fenestra  ovalis  by  ligamentous  fibres.  The  foot-plate  almost  fills  the  oval 
window  (Fig.  843).  Of  the  two  crura,  the  anterior  is  shorter  and  less  curved 
than  the  posterior.  In  a  recent  specimen  a  membrane  will  be  observed  filling 
the  space  between  the  crura  and  the  foot-plate.  This  membrane  is  connective 
tissue  and  is  called  the  membrana  obturatoria  stapedis.  The  stapes  lies  practically 
horizontal. 

Articulations  of  the  Ossicles  of  the  Tympanum  {articulationes  ossicuhrum  auditus)  (Fig* 
840).  —These  small  bones  are  t  onnected  with  each  other  and  with  the  walls  of  the  tympanum  by 
ligaments,  and  are  moved  by  small  muscles.  The  articular  surfaces  of  the  malleus  and  incus 
and  the  orbicular  process  of  the  incus  and  head  of  the  stapes  are  covered  by  cartilage,  con- 
nected by  delicate  capsular  ligaments  and  lined  by  synovial  membrane. 

Ligaments  Connecting  the  Ossicula  with  the  Walls  of  the  Tympanum  dig.  osdculorum 
auiUtus). — The  malleus  is  fastened  to  the  wall  of  the  tympanum  by  three  ligaments — the 
anterior,  superior,  and  external  ligaments. 

The  anterior  ligament  of  the  malleus  {tig.  mallei  anterius)  is  attached  by  one  extremity  to  the 
neck  of  the  malleus  just  aljove  the  jirocessus  gracilis,  and  by  the  other  to  the  anterior  wall  of  the 
tympanum,  ilo.sc  to  tlic  (ilascrlau  fi.ssure,  some  of  its  fibres  being  prolonged  through  the  fisstue 
to  reach  the  alar  sjiiuc  of  the  ^j)lnii(ji(l. 

The  superior  ligament  of  the  malleus  [Ug.  mallei  supcrius)  is  a  delicate  round  bundle  of 
fibres  which  descends  perpendiculaily  lidni  the  roof  of  the  epitympanic  recess  to  the  head  of  the 
malleus.     It  is  sometimes  callcil  the  suspensory  ligciment. 

The  external  ligament  of  the  malleus  (tig.  mallei  latcralc)  is  a  triangular  plane  of  fibres  passing 
from  the  posterior  part  of  the  notch  in  the  tympanic  ring  to  the  head  of  the  malleus.  The  mal- 
leus rotates  around  an  a.xis  composed  of  the  external  and  anterior  ligaments,  hence  these  two 
ligaments  constitute  what  Helmholtz  called  the  axis  ligament  of  the  malleus. 

Tlie  incus  is  fastened  to  the  wall  of  the  tympanum  by  two  ligaments,  the  posterior  and  the 
superior. 

The  posterior  hgament  of  the  incus  {Ug.  incudis  posterius)  is  a  short,  thick,  ligamentous  band 
■which  connects  the  extremhy  of  the  short  process  of  the  incus  to  the  posterior  and  lower  part  of 
the  epitympanic  recess,  near  the  margin  of  the  opening  of  the  mastoid  cells. 

A  superior  ligament  of  the  incus  (Kg.  incudis  superius)  has  been  described,  but  it  is  little 
more  than  a  fold  of  mucous  membrane. 

The  vestibular  surface  and  the  circumference  of  the  base  of  the  stapes  are  covered  by  hyaline 
cartilage,  and  the  annular  ligament  of  the  stapes  {Kg.  annulare  baseos  stapedis)  connects  the 
circumference  of  the  base  to  the  margin  of  the  fenestra  ovalis. 


1134  THE  ORGANS  OF  SPECIAL  SENSE 

•     The  muscles  of  the  tympanum  (?re.  ossiculorum  avditus)  are  two  :* 

Tensor  tympani.  Stapedius. 

The  Tensor  tympani  (m.  tensor  tympani)  (Fig.  848),  the  larger,  is  contained  in  the  bony 
canal  above  the  osseous  portion  of  the  Eustachian  tube,  from  which  it  is  separated  by  the  pro- 
cessus cochleariformis.  It  arises  from  the  under  surface  of  the  petrous  bone,  from  the  carti- 
laginous portion  of  the  Eustachian  tube,  and  from  the  osseous  canal  in  which  it  is  contained. 
Passing  backward  through  the  canal,  it  terminates  in  a  slender  tendon  which  enters  the  tym- 
panum and  makes  a  sharp  bend  outward  around  the  extremity  of  the  processus  cochleariformis, 
and  is  inserted  into  the  handle  of  the  malleus  near  its  root.  Its  nerve  supply  is  from  the  motor 
root  of  the  trigeminal  nerve  by  way  of  the  otic  ganglion. 

The  Stapedius  (m.  stapedius)  (Fig.  848),  the  smallest  constant  muscle  in  the  body,  weighing 
only  1  grain,  arises  from  the  side  of  a  conical  cavity  hollowed  out  of  the  interior  of  the  pjTamid; 
its  tendon  emerges  from  the  orifice  at  the  apex  of  the  pjo-amid,  and,  passing  forward,  is  inserted 
into  the  neck  of  the  stapes.  Its  surface  is  aponeurotic,  its  interior  fleshy,  and  its  tendon  occasion- 
ally contains  a  slender  bony  spine,  which  is  constant  in  some  mammalia.  It  is  supplied  by  the 
tympanic  branch  of  the  facial  nerve. 

Actions. — The  Tensor  tympam  draws  the  handle  of  the  malleus  inward  and  thus  increases 
the  tension  of  the  tympanic  membrane.  When  the  Stapedius  contracts  it  draws  the  head  of 
the  stapes  backward,  and  in  consequence  the  anterior  end  of  the  foot-plate  passes  outward 
toward  the  tympanum,  and  the  posterior  end  inward  toward  the  vestibule,  and  the  annular 
ligament  is  made  tense.     It  probably  com]iresses  the  contents  of  the  vestibule. 

Movements  of  the  Ossicles  of  the  Tympanum. — The  chain  of  bones  is  a  lever-like  arrange- 
ment, by  means  of  which  the  vibrations  of  the  membrana  tympani  are  transferred  to  the  mem- 
brane covering  the  oval  window,  and  from  this  to  the  perilymph  in  the  labyrinth.  When  the 
tympanic  membrane  moves  inward,  the  handle  of  the  malleus  moves  with  it.  The  movement 
of  the  malleus  moves  the  incus,  and  the  movement  of  the  incus  drives  the  foot  of  the  stapes 
toward  the  labyrinth.  When  the  handle  of  the  malleus  moves  inward,  the  spur  on  the  head 
becomes  locked  with  the  body  of  the  incus.  During  outward  movement  it  is  unlocked.  The 
ordinary  outward  movement  of  the  drum  membrane  causes  the  above-described  movements  to 
be  reversed.  When  there  is  overforcible  outward  movement  the  incus  does  not  go  outward 
quite  as  far  as  the  malleus,  but  slides  at  the  joint  between  the  malleus  and  incus.  This 
reluctance  of  the  incus  saves  the  foot  of  the  stapes  from  being  pulled  away  from  the  oval 
window. 

The  mucous  membrane  of  the  tjrmpanum  (tunica  mucosa  tympanica)  is  continuous  with  that 
of  the  nasopharynx  through  the  Eustachian  tube.  It  invests  the  ossicles,  and  the  muscles  and 
nerves  contained  in  the  tympanic  cavity,  forms  the  internal  layer  of  the  membrana  tympani,  and 
is  reflected  into  the  mastoid  antrum  and  air  cells,  which  it  lines  throughout.  It  forms  several 
vascular  folds  {plicae),  which  extend  from  the  walls  of  the  tympanum  to  the  ossicles,  enveloping 
these  as  well  as  the  chorda  tympani  nerve  and  the  Tensor  tympani  muscle. 

The  anterior  malleolar  fold  {plica  malleolaris  anterior)  comes  off  from  the  membrana  tympani 
between  the  anterior  edge  of  the  notch  of  Rivinus  and  the  handle  of  the  malleus,  envelops  the 
processus  gracilis  of  the  malleus,  the  anterior  ligament  of  the  malleus,  and  the  anterior  portion 
of  the  chorda  tympani  nerve,  and  terminates  in  a  free  concave  edge.  The  posterior  malleolar 
fold  {plica  malleolaris  posterior)  is  the  larger  of  the  two  It  comes  off  from  the  margin  of  the 
notch  of  Rivinus,  envelopes  the  external  ligament  of  the  malleus,  the  posterior  part  of  the 
chorda  tympani  nerve,  is  attached  to  the  handle  of  the  malleus,  and  ends  in  a  free  concave 
margin.  The  fold  of  the  incus  {plica  inciidis)  takes  origin  from  the  roof  of  the  epitympanic 
recess  and  passes  to  the  body  and  short  process  of  the  incus;  and  a  similar  fold  passes  from 
the  head  of  the  malleus  to  the  anterior  wall  of  the  epitympanic  recess.  The  entire  stapes, 
with  its  obtiu-ator  membrane,  is  enwrapped  by  the  fold  of  the  stapes  {plica  stapedis).  This 
fold  also  ensheaths  the  tendon  of  the  Stapedius  muscle  and  often  reaches  to  the  posterior  wall 
of  the  cavity  of  the  tympanum.  These  folds  separate  off  pouch-like  cavities,  and  give  the 
interior  of  the  tympanum  a  somewhat  honeycombed  appearance. 

The  inferior  external  pouch  of  the  tympanmn  or  the  pouch  of  Frussak  (recessus  mcmhranae 
tympani  superior)  is  between  the  flaccid  portion  of  the  membrana  tympani,  the  external  liga- 
ment of  the  malleus,  and  the  neck  of  the  malleus.  The  anterior  and  posterior  malleolar  folds 
with  the  tymiianic  membrane  form  two  pouches.  These  are  the  anterior  and  posterior  pouches 
or  recesses  of  Troeltsch  {ncrxxn.i  nn'mbranae  tympani,  anterior  and  posterior).  The  anterior 
pouch  is  lilind  alxne  and  has  a  slit-like  opening  below.  The  posterior  pouch  is  continued  into 
the  blind  superior  pouch  of  the  tympanic  membrane.  In  the  tympanum  this  membrane  is  pale, 
thin,  slightly  vascular,  and  covered  for  the  most  part  with  columnar  ciliated  epithelium,  but  that 

*  Two  additional  muscles  have  been  described  as  the  Mm.  laxator  tympani  major  et  minor;  they  correspond  to  the 
anterior  and  lateral  ligaments  of  the  malleus,  but  often  show  striated  muscle  tissue.     (D.  G.  Methenj-.} 


THE  MIDDLE  EAR,  DRUM,   OR  TYMPANUM  1135 

covering  the  pyramid,  ossicula,  and  membrana  tympani  possesses  a  flattened,  nonciliated  epi- 
thelium. In  the  antrum  and  mastoid  cells  its  epithelium  is  also  nonciliated.  In  the  osseous 
portion  of  the  Eustachian  tube  the  membrane  is  thin,  but  in  the  cartilaginous  jiortion  it  is  very 
thick,  highly  vascular,  covered  with  ciliated  epithelium,  and  provided  with  numerous  mucous 
glands. 

Vessels  and  Nerves. — The  arteries  supplying  the  tympanum  are  six  in  number.  Two  of 
them  are  larger  than  the  rest — viz.,  the  tympanic  branch  of  the  internal  maxillary,  which  enters 
by  way  of  the  petrotympanic  or  Glaserian  fissure  and  supplies  the  membrana  tympani;  and  the 
stylomastoid  branch  of  the  posterior  auricular,  which  passes  through  the  stylomastoid  foramen 
and  the  facial  canal,  and  supplies  the  inner  wall  and  floor  of  the  tympanum,  the  mastoid  cells 
and  antrum,  and  the  Stapedius  muscle.  This  vessel  anastomoses  around  the  tympanic  mem- 
brane with  the  tympanic.  The  middle  meningeal  sends  a  small  branch  to  the  Tensor  tympani 
muscle  near  its  origin.  The  petrosal  branch  of  the  middle  meningeal  enters  the  tympanum  by 
way  of  the  hiatus  canalis  facialis.  Minute  branches  from  the  posterior  branch  of  the  middle 
meningeal  pass  through  the  petrosquamous  fissure  and  are  distributed  to  the  antrum  and  epi- 
tympanic  recess.  Two  tympanic  branches  come  off  from  the  internal  carotid  artery  in  its  course 
through  the  carotid  canal.  A  branch  from  the  ascending  pharyngeal  and  another  from  the 
Vidian  accompany  the  Eustachian  tube.  The  two  tympanic  branches  from  the  internal  carotid 
are  given  off  in  the  carotid  canal  and  perforate  the  thin  anterior  wall  of  the  tympanum.  The 
veins  of  the  tympaniun  terminate  in  the  pterygoid  plexus,  the  middle  meningeal  vein,  and  the 
superior  petrosal  sinus. 

The  nerves  of  the  tympanum  constitute  the  tjmipanic  plexus  (plexus  tympanicus  [Jacobsoni]), 
which  ramifies  upon  the  surface  of  the  promontory  (Fig.  848).  The  plexus  is  formed  by  (1)  the 
tympanic  branch  of  the  glossopharyngeal;  (2)  the  small  deep  petrosal  nerve;  (.3)  the  small  super- 
ficial petrosal  nerve;  and  (4)  a  branch  which  joins  the  great  superficial  petrosal. 

The  t3rmpanic  branch  of  the  glossopharjmgeal  or  Jacobson's  nerve  {n.  fijmpanicus)  enters 
the  tympanum  by  an  aperture  in  its  flcior  close  to  the  inner  wall  and  divic'e^  info  branches, 
which  ramify  on  the  promontory  and  enter  into  the  formation  of  the  plexus.  The  small  deep 
petrosal  nerve  (;i.  pelrosiis  profundus),  from  the  carotid  plexus  of  the  sympathetic,  passes 
through  the  wall  of  the  carotid  canal,  and  joins  the  branches  of  Jacobson's  nerve.  The  branch 
to  the  great  superficial  petrosal  passes  through  an  opening  on  the  inner  wall  of  the  tympanum 
in  front  of  the  fenestra  ovalis.  The  small  superficial  petrosal  nerve  (n.  pdrosus  siiperjicmlis 
minor),  derived  from  the  otic  ganglion,  passes  through  a  foramen  {canaliculus  innominafus) 
in  the  middle  fossa  of  the  base  of  the  skull  (sometimes  through  the  foramen  ovale),  passes 
backward  and  enters  the  petrous  bone  through  a  small  aperture,  situated  external  to  the  hiatus 
canalis  facialis  on  the  anterior  surface  of  this  bone;  it  then  courses  downward  through  the 
bone,  and,  passing  by  the  geniculate  ganglion,  receives  a  connecting  filament  from  it  (Fig.  845) 
and  enters  the  tympanic  cavity,  where  it  communicates  with  Jacobson's  .nerve,  and  assists  in 
forming  the  tympanic  plexus. 

The  branches  of  distribution  of  the  tympanic  plexus  are  supplied  to  the  mucous  membrane  of 
the  tympanum;  one  special  branch  passing  to  the  fenestra  ovalis,  another  to  the  fenestra  ro- 
tunda, and  a  third  to  the  Eustachian  tube.  The  small  superficial  petrosal  may  be  looked  "upon 
as  the  continuation  of  the  tympanic  nerve  (Jacobson's)  through  the  plexus  to  the  otic  ganglion. 

In  addition  to  the  tympanic  plexus  there  are  the  nerves  supplying  the  muscles.  The  Tensor 
tympani  is  supplied  by  a  branch  from  the  third  division  of  the  trigeminal  through  the  otic  gan- 
glion, and  the  Stapedius  by  the  tympanic  branch  of  the  facial. 

The  chorda  tympani  (Figs.  835  and  838)  crosses  the  tympanic  cavity.  It  is  apparently  given 
off  from  the  facial  as  it  passes  vertically  downward  at  the  back  of  the  tympammi,  about  6  mm. 
(a  quarter  of  an  inch)  before  its  exit  from  the  stylomastoid  foramen.  It  passes  from  below 
upward  and  forward  in  a  distinct  canal,  and  enters  the  cavity  of  the  tympanum  through  an 
aperture,  iter  chordae  posterius,  already  described  (p.  1 126),  and  becomes  invested  with  mucous 
membrane.  It  passes  forward,  through  the  cavity  of  the  tympanum,  crossing  internal  to  the 
membrana  tympani  and  over  the  handle  of  the  malleus  to  the  anterior  inferior  angle  of  the  tym- 
panum, and  emerges  from  that  cavity  through  the  iter  chordae  anterius  or  canal  of  Hugtiier 
(p.  1126). 

Applied  Anatomy. — The  principal  point  in  connection  with  the  surr/ical  anatomy  of  the 
ti/mpanum  is  its  relations  to  other  parts.  Its  roof  is  formed  by  a  thin  plate  of  bone,  which,  with 
the  dura,  is  all  that  separates  it  from  the  temporal  lobe  of  the  brain.  Its  floor  is  immediately 
above  the  jugular  fossa  and  the  carotid  canal,  the  fossa  being  behind  and  the  canal  in  front.  Its 
posterior  wall  presents  the  opening  of  the  viastoid  cells.  On  its  anterior  wall  is  the  opening  of 
the  Eustachian  tube.  Thus,  it  follows  that  in  disease  of  the  middle  ear  we  may  get  subdural 
abscess,  septic  meningitis,  or  abscess  of  the  cerebrum  or  cerebellum,  from  extension  of  the  inflam- 
mation through  the  bony  roof;  thrombosis  of  the  lateral  si7ius,  with  or  without  pyemia,  by  ex- 
tension through  the  floor; or  mastoid  abscess  by  extension  backward.  In  addition  to  this,  there 
may  be  fatal  hemorrhage  from  the  internal  carotid  in  destructive  changes  of  the  middle  ear; 
and  in  tliroat  disease  we  may  get  the  inflammation  extending  up  the  Eustachian  tube  to  the 


1136 


THE  ORGANS  OF  SPECIAL  SENSE 


.  middle  ear.  The  Eustachian  tube  is  accessible  from  the  nose.  If  the  nose  and  mouth  be  closed 
and  an  attempt  made  to  expire  air,  a  sense  of  pressure  with  dulness  of  hearing  is  produced  in 
both  ears,  from  the  air  finding  its  way  up  the  Eustachian  tube  and  bulging  out  the  membrana 
tympani.  During  the  act  of  swallowing,  the  pharyngeal  orifice  of  the  tube,  which  is  normally 
closed,  is  opened,  probably  by  the  action  of  the  Dilatator  tubse  muscle.  This  fact  was  employed 
by  Politzer  in  devising  an  easy  method  of  inflating  the  tube.  The  nozzle  of  a  rubber  swinge  is 
inserted  into  the  nostril ;  the  patient  takes  a  mouthful  of  water  and  holds  it  in  his  mouth,  both 
nostrils  are  closed  with  the  finger  and  thumb  to  prevent  the  escape  of  air,  and  the  patient  is  then 
requested  to  swallow;  as  he  does  so  the  surgeon  squeezes  the  bulb  and  the  air  is  forced  out  of  the 
syringe  into  the  nose,  and  is  driven  into  the  Eustachian  tube,  which  is  now  open.  The  impact 
of  the  air  against  the  membrana  tympani  can  be  heard  by  the  surgeon,  if  the  membrane  is  intact, 
sound  being  conveyed  by  means  of  a  piece  of  rubber  tubing,  one  end  of  which  is  inserted  into 
the  meatus  of  the  patient's  ear,  the  other  into  that  of  the  surgeon.  The  direct  examination  of 
the  Eustachian  tube  is  made  by  the  Eustachian  catheter.  This  is  passed  along  the  floor  of  the 
nostril,  close  to  the  septum,  with  the  point  touching  the  floor,  to  the  posterior  wall  of  the  pharynx. 
^Vhen  this  is  felt,  the  catheter  is  to  be  withdrawn  about  half  an  inch,  and  the  point  rotated  out- 
ward through  a  quarter  of  a  circle,  and  pushed  again  slightly  backward,  when  it  will  enter  the 
orifice  of  the  tube,  and  will  be  found  to  be  caught,  and  air  forced  into  the  catheter  will  be  heard 
impinging  on  the  tympanic  membrane  if  the  ears  of  the  patient  and  surgeon  are  connected  by  a 
rubber  tube. 

THE  INTERNAL  EAR,  OR  LABYRINTH  (AURIS  INTERNA). 

The  internal  ear  is  the  essential  part  of  the  organ  of  hearing  and  of  orientation  in 
space.  It  is  called  the  labyrinth,  from  the  complexity  of  its  shape,  and  consists 
of  two  parts,  the  osseous  labyrinth,  a  series  of  cavities  channelled  out  of  the  sub- 
stance of  the  petrous  portion  of  the  temporal  bone,  and  the  membranous  labyrinth, 
the  latter  being  contained  within  the  former. 


Opening  of  aqiiedudui  leibbuh 
Bristle  passed  thi ough  fot  amen  lotundum 

Opening  of  aqueductus  coUileje 

Fig.  856. — The  osseous  labyrinth  laid  open  (enlarged.) 

The  Osseous  Labyrinth  (labyrinthus  osseus)  (Fig.  856)  consists  of  three  parts 
• — the  vestibule,  semicircular  canals,  and  cochlea.  These  are  cavities  hollowed  out 
of  the  substance  of  the  bone,  and  lined  by  periosteum  and  endothelium.  A  clear 
fluid  is  contained  in  the  space  between  the  osseous  labyrinth  and  the  membranous 
labyrinth.  The  space  is  called  the  perilymph  space,  and  the  fluid  is  called  peri- 
lymph. 

The  Vestibule  {testihidiim)  (Figs.  849  and  856)  is  the  common  central  cavity  of 
communication  between  the  parts  of  the  internal  ear.  It  is  situated  on  the  inner 
side  of  the  tympanum,  behind  the  cochlea,  and  in  front  of  the  semicircular  canals. 


THE  INTERNAL  EAR,   OR  LABYRINTH  1137 

It  is  somewhat  ovoid  in  shape,  flattened  from  within  outward,  and  measures 
about  5  mm.  (one-fifth  of  an  inch)  from  before  backward,  as  well  as  from  above 
downward,  and  about  3  mm.  (one-eiolith  of  an  inch)  from  without  inward.  On 
its  outer  or  tympanic  wall  is  the  fenestra  ovalis  {fenestra  vesfibuli),  closed,  in  the 
recent  state,  by  the  base  of  the  stapes,  and  its  annular  ligament.  On  its  inner  wall, 
at  the  fore  part,  is  a  small  circular  depression,  the  spherical  recess  (recessus  sphaeri- 
cus),  in  which  the  saccule  is  placed.  This  recess  is  perforated,  at  its  anterior  and 
inferior  part,  by  about  a  dozen  minute  holes  ( macula  cribrosa  media),  for  the  passage 
of  filaments  of  the  vestibular  nerve  to  the  saccule.  Above  and  behind  this 
depression  is  an  oblique  ridge,  the  crista  vestibuli,  the  anterior  extremity  of  which 
is  called  the  pyramid  {pyramis  vestibuli).  This  ridge  bifurcates  posteriorly  to 
enclose  a  small  depression,  the  recessus  cochlearis,  which  is  perforated  by  eight 
small  holes  for  the  passage  of  filaments  of  the  auditory  nerve  which  supply  the 
basal  end  of  the  ductus  cochlearis.  An  oval  depression  is  placed  in  the  roof 
and  inner  wall  of  the  vestibule  above  and  behind  the  crista  vestibuli.  It  is 
called  the  fovea  hemielliptica,  elliptical  recess,  or  spherical  recess  (recessus  ellipticus), 
and  receives  the  utricle.  The  pyramid  and  the  adjacent  elliptical  recess  are  per- 
forated by  numerous  minute  foramina  {macula  cribrosa  superior).  The  openings 
in  the  pyramid  transmit  filaments  from  the  vestibular  nerve  to  the  utricle;  the 
openings  in  the  elliptical  recess  transmit  filaments  from  the  vestibular  nerve  to 
the  ampullse  of  the  superior  and  lateral  semicircular  canals.  Below  and  behind 
the  elliptical  recess  is  a  groove  which  deepens  into  a  canal  and  is  called  the  aquae - 
ductus  vestibuli.  This  canal  passes  to  the  posterior  surface  of  the  petrous  portion 
of  the  temporal  bone  and  opens  as  a  mere  crack  between  the  internal  auditory 
meatus  and  the  groove  for  the  lateral  sinus.  It  transmits  a  small  vein,  and  con- 
tains a  tubular  prolongation  of  the  lining  membrane  of  the  vestibule,  the  ductus 
endolymphaticus,  which  ends  in  a  cul-de-sac  between  the  layers  of  the  dura  mater 
within  the  cranial  cavity.  Behind,  the  semicircular  canals  open  into  the  vestibule 
by  five  orifices.  In  froiit  is  an  elliptical  opening,  which  communicates  with  the 
scala  vestibuli  of  the  cochlea  by  an  orifice,  apertura  scalae  vestibuli  cochleae.  This 
opening  is  bounded  below  by  a  thin  plate  of  bone  (lamina  spiralis  ossea),  which 
takes  origin  from  the  vestibular  floor  external  to  the  spherical  recess  and  in  the 
cochlea  forms  the  bony  portion  of  the  partition  between  the  scala  tympani  and  the 
scala  vestibuli.  In  the  anterior  portion  of  the  vestibular  floor  is  a  fissure  (fissura 
vestibuli),  which  passes  into  the  bony  part  of  the  canal  of  the  cochlea.  The 
external  boundary  of  this  fissure  is  a  small,  thin  plate  of  bone  (lamina  spiralis 
secundaria). 

The  Bony  Semicircular  Canals  (canales  semicirculares  ossei  )  (Fig.  S56)  are  three 
bony  canals  situated  above  and  behind  the  vestibule.  They  are  of  unequal 
length,  compressed  from  side  to  side,  and  each  describes  the  greater  part  of  a 
circle.  They  measure  about  0.8  mm.  (one-thirtieth  of  an  inch)  in  diameter,  and 
each  presents  a  dilatation  at  one  end,  called  the  ampulla  ossea,  which  measures 
more  than  twice  the  diameter  of  the  tube.  These  canals  open  into  the  vestibule 
by  five  orifices,  one  of  the  apertiu'es  being  common  to  two  of  the  canals. 

The  superior  semicircular  canal  (canalis  semicircidaris  superior),  15  to  20  mm. 
in  length,  is  vertical  in  direction,  and  is  placed  transversely  to  the  long  axis  of  the 
petrous  portion  of  the  temporal  bone,  on  the  anterior  surface  of  which  its  arch 
forms  a  round  projection.  It  describes  about  two-thirds  of  a  circle.  Its  outer 
extremity,  which  is  ampullated,  communicates  by  a  distinct  orifice  with  the 
upper  part  of  the  vestibule;  the  opposite  end  of  the  canal,  which  is  not  dilated, 
joins  Math  the  corresponding  part  of  the  posterior  canal  to  form  the  cms  commune, 
which  opens  into  the  upper  and  inner  part  of  the  vestibule. 

The  posterior  semicircular  canal  (canalis  semicircidaris  posterior),  also  vertical 
in  direction,  is  directed  backward,  nearly  parallel  to  the  posterior  surface  of  the 


1138 


THE  ORGANS  OF  SPECIAL  SENSE 


petrous  bone;  it  is  the  longest  of  the  three,  measuring  from  18  to  22  mm. ;  its  ampul- 
iated  end  commences  at  the  lower  and  back  part  of  the  vestibule,  its  opposite  end 
joining  to  form  the  common  canal  already  mentioned.  In  the  wall  of  the  ampulla 
of  the  posterior  canal  are  a  number  of  small  openings  (macula  cribrosa  inferior) 
for  the  passage  of  nerves  to  the  ampulla. 

The  lateral  or  horizontal  canal  (canalis  semicircidaris  lateralis)  is  the  shortest 
of  the  three.  It  measures  from  12  to  15  mm.,  and  its  arch  is  directed  outward 
and  backward;  thus  each  semicircular  canal  stands  at  right  angles  to  the  other 
two.  Its  ampullated  end  corresponds  to  the  upper  and  outer  angle  of  the  vesti- 
bule, just  above  the  fenestra  ovalis,  where  it  opens  close  to  the  ampullar^  end  of 
the  superior  canal;  its  opposite  end  opens  by  a  distinct  orifice  at  the  upper  and 
back  part  of  the  vestibule. 

The  cochlea  (Figs.  856  and  857)  bears  some  resemblance  to  a  common  snail- 
shell;  it  forms  the  anterior  part  of  the  labyrinth,  is  conical  in  form,  and  placed 
almost  horizontally  in  front  of  the  vestibule;  its  apex  (cufula)  is  directed  forward 
and  outward,  with  a  slight  inclination  downward,  toward  the  upper  and  front  part 


Fig.  857. — Osseous  cochlea  in  vertical  section.     The  broken,  white  lines  indicate  the  position  of  the  basilar 
membrane  of  the  canal  of  the  cochlea.     Semidiagrammatic.      (Testut.) 

of  the  inner  wall  of  the  tympanum;  its  base  (basis  cochleae)  corresponds  with  the 
anterior  depression  at  the  bottom  of  the  internal  auditory  meatus,  and  is  perforated 
by  numerous  apertures  for  the  passage  of  the  cochlear  divisions  of  the  auditory 
nerve.  It  measures  nearly  a  quarter  of  an  inch  (5  mm.)  from  base  to  apex,  and 
its  breadth  across  the  base  is  somewhat  greater  (about  9  mm.).  It  consists  of 
a  conical-shaped  central  axis,  the  modiolus;  of  a  canal,  the  bony  canal  of  the  cochlea, 
the  inner  wall  of  which  is  formed  by  the  central  axis,  wound  spirally  around  it  for 
two  turns  and  three-quarters,  from  the  base  to  the  apex,  and  of  a  delicate  lamina, 
the  lamina  spiralis  ossea,  which  projects  from  the  modiolus,  and,  following  the 
windings  of  the  canal,  partially  subdivides  it  into  two.  In  the  recent  state  a  mem- 
brarie,  the  membrana  basilaris,  stretches  from  the  free  border  of  this  lamina,  to  the 
outer  wall  of  the  cochlea,  and  separates  this  canal  into  two  passages,  except 
where  they  communicate  with  each  other  at  the  apex  of  the  modiolus  by  a  small 
opening,  named  the  heUcotrema. 

The  Modiolus  (Figs.  858  and  859)  is  the  central  axis  or  pillar  of  the  cochlea. 
It  is  conical  in  form,  and  extends  from  the  base  to  the  apex  of  the  cochlea.  Its 
base  (basis  modioli)  is  broad,  and  appears  at  the  bottom  of  the  internal  auditory 


THE  INTERNAL  EAB,   OB  LAB  YBINTH 


1139 


meatus,  where  it  corresponds  with  the  area  cochleae.  It  is  perforated  hy 
numerous  orifices,  which  transmit  fihxments  of  the  cochlear  division  of  tiie  audi- 
tory nerve,  the  nerves  for  the  first  turn  and  a  half  being  transmitted  through  the 
foramina  of  the  tractus  spiralis  f oraminosus ;  those  for  the  apiCal,  turn  through  the 


TRACTUS 

SPIRALIS 

FORAMINOSUS 


LAMINA 

SPIRALIS 

OSSEA 


Fig.  858. — Vertical  section  through  the  right  cochleo,  medial  portio 


1  the  lateral  side.    (Spalteholzj. 


foramen  centrale.  The  foramina  of  the  tractus  spiralis  foraminosus  pass  up 
through  the  modiolus  and  successively  bend  outward  to  reach  the  attached  margin 
of  the  lamina  spiralis  ossea.  Here  they  become  enlarged,  and  by  their  apposition 
form  a  spiral  canal  (canalis  spiralis  modioli),  which  follows  the  course  of  the  attached 


Fig.  859. — The  cochlea  laid  open  (enlarged). 

margin  of  the  lamina  spiralis  ossea  and  lodges  the  ganglion  spirals  (of  Corti) 
(ganglion  spirale  cochleae).  The  foramen  centrale  is  continued  as  a  canal  up  the 
middle  of  the  modiolus  to  its  apex,  and  from  this  canal  numerous  minute  foramina 
pass  outward  to  the  unattached  edge  of  the  lamina  spiralis.  In  the  foramina 
are  vessels  and  nerves.  The  modiolus  diminishes  rapidly  in  size  in  the  second 
and  succeeding'  coil. 


1140  '^'HE  ORGANS  OF  SPECIAL  SENSE 

The  bony  canal  or  the  spiral  canal  of  the  cochlea  (canalis  spiralis  cochleae)  (Fig. 
859)  takes  two  turns  and  three-quarters  around  the  modiolus.  The  first  turn 
of  the  canal  is  called  the  basal  coil,  the  second  is  called  the  central  coil,  the  third 
turn  is  called  the  apical  coil.  The  promontory  on  the  inner  wall  of  the  tympanic 
cavity  is  caused  by  the  basal  coil.  The  bony  canal  of  the  cochlea  is  a  little  over 
an  inch  (about  30  mm.)  in  length,  and  diminishes  gradually  in  size  from  the  base 
to  the  summit,  where  it  terminates  in  the  cupola  (cupula),  which  forms  the  apex  of 
the  cochlea.  The  commencement  of  this  canal  is  about  a  tenth  of  an  inch  (2.5 
mm.)  in  diameter;  it  diverges  from  the  modiolus  toward  the  tympanum  and  vesti- 
bule, and  presents  three  openings.  One,  the  fenestra  rotunda,  communicates  with 
the  tympanum;  in  the  recent  state  this  aperture  is  closed  by  a  membrane,  the  mem- 
brana  tympani  secundaria.  Another  aperture,  of  an  elliptical  form,  opens  into  the 
vestibule.  The  third  is  the  aperture  of  the  aquaeductus  cochleae,  leading  to  a 
minute  funnel-shaped  canal,  which  opens  on  the  basilar  surface  of  the  petrous 
bone  internal  to  the  jugular  fossa,  and  transmits  a  small  vein,  and  also  forms 
a  communication  between  the  subarachnoidean  space  of  the  skull  and  the  peri- 
lymph space  in  the  scala  tympani. 

The  lamina  spiralis  ossea  is  a  bony  shelf  or  ledge  which  projects  outward  from 
the  modiolus  into  the  interior  of  the  spiral  canal,  and,  like  the  canal,  takes  nearly 
two  and  three-quarter  turns  around  the  modiolus.  It  reaches  about  half-way 
toward  the  outer  wall  of  the  spiral  canal,  and  partially  divides  its  cavity  into  two 
passages  or  scalae,  of  which  the  upper  is  named  the  scala  vestibuli,  while  the  lower 
is  termed  the  scala  tympani.  Near  the  summit  of  the  cochlea  the  lamina  terminates 
in  a  hook-shaped  process,  the  hamulus  {hamulus  laminae  spiralis),  which  assists 
in  forming  the  boundary  of  a  small  opening,  the  helicotrema,  by  which  the  two  scalae 
communicate  with  each  other.  From  the  canalis  spiralis  modioli  numerous 
foramina  pass  outward  through  the  osseous  spiral  lamina  as  far  as  its  outer 
or  free  edge.  In  the  lower  part  of  the  first  turn  a  second  bony  lamina  (lamina 
spiralis  secundaria)  projects  inward  from  the  outer  wall  of  the  bony  tube;  it  does 
not,  however,  reach  the  primary  osseous  spiral  lamina,  so  that  if  viewed  from  the 
vestibule  a  narrow  fissure,  the  fissura  vestibuli,  is  seen  between  them. 

The  fundus  of  the  internal  auditory  meatus  is  described  on  page  85. 

The  Membranous  Labyrinth  (lahyrinthus  viembranaceus)  (Figs.  860  and  861) 
is  contained  within  the  bony  cavities  just  described,  having  the  same  general  form 
as  the  cavities  in  which  it  is  contained,  though  considerably  smaller,  being  separated 
from  the  bony  walls  by  a  quantity  of  fluid,  the  perilymph  (perilympha).  It  does 
not,  however,  float  loosely  in  this  fluid,  but  in  places  is  fixed  to  the  walls  of  the 
cavity.  The  membranous  sac  contains  fluid,  the  endolymph  (endolympha),  and 
on  the  sac  the  ramifications  of  the  auditory  nerve  are  distributed. 

Within  the  osseous  vestibule  the  membranous  labyrinth  does  not  quite  preserve 
the  form  of  the  bony  cavity,  but  presents  two  membranous  sacs,  the  utricle  and 
the  saccule. 

The  Utricle  (utricidtis)  is  the  larger  of  the  two,  of  an  oblong  form,  compressed 
laterally,  and  occupies  the  upper  and  back  part  of  the  vestibulcj  lying  in  contact 
with  the  fovea  semielllptica  and  the  part  below  it.  The  highest  portion  of  the 
utricle  is  called  the  recess  (recessus  utriculi);  it  is  placed  in  the  elliptical  recess, 
and  opening  into  it  are  the  ampullae  of  the  superior  and  lateral  semicircular 
canals.  The  central  portion  of  the  recess  of  the  utricle  receives  upon  the  side  the 
lateral  semicircular  canal.  This  opening  has  no  ampulla.  The  superior  sinus  is 
a  prolongation  upward  and  backward  from  the  central  portion  of  the  utricle  and 
in  the  superior  sinus  the  crus  commune  and  the  superior  and  posterior  semi- 
circular canals  open.  The  lower  and  inner  portion  of  the  utricle  is  the  inferior 
sinus,  and  into  it  the  ampulla  of  the  posterior  semicircular  canal  opens.  The 
floor  and  anterior  wall  of  the  recess  of  the  utricle  are  much  thicker  than  else- 


THE  INTERNAL  EAR,    OR  LAB  YRINTH 


1141 


where,  and  form  the  macula  acustica  utriculi,  which  receives  the  utricular  filaments 
of  the  auditory  nerve  and  has  attached  to  its  internal  surface  a  layer  of  calcareous 
particles  which  are  called  otoliths,    The  cavity  of  the  utricle  communicates  behind 


^      Ductus 
Endolymphaticus 

Fig.   S60. — The  membranous  labyrinth   (enlarged). 

with  the  membranous  semicircular  canals  by  five  orifices.  From  its  anterior  wall 
is  given  off  a  small  canal  (ductus  utriculosaccularis),  which  joins  with  a  canal  from 
the  saccule,  the  ductus  endolymphaticus. 

The  Saccule  {sacculiis)  is  the  smaller  of  the  two  sacs;  it  is  globular  in  form,  lies 
in  the  recessus  sphaericus  near  the  opening  of  the  scala  vestibuli  of  the  coch- 


BRANCH  OF 

VESTIBULAR 

NERVE 


DUCT  OF 
SUPERIOR 
SEMICIRCULAR 
CANAL 


AMPULLA  OF 

EXTERNAL 

MEMBRANO 


Fig.  861. — The  right  membranous  labyrinth  of  an  adult,  isolated,  medial  and  poste 


view.     (Spalteholz.) 


lea.  Its  anterior  part  exhibits  an  oval  thickening,  the  macula  acustica  sac- 
culi,  to  which  are  distributed  the  saccular  filaments  of  the  auditory  nerve.  Its 
cavity  does  not  directly  communicate  with  that  of  the  utricle.     From  the  pos- 


1142 


THE  ORGANS  OF  SPECIAL  SENSE 


terior  wall  is  given  off  a  canal,  the  ductus  endolymphaticus.  This  duct  is  joined 
by  the  ductus  utriculosaccularis,  and  then  passes  along  the  aquaeductus  vestibuli 
and  ends  in  a  blind  pouch  on  the  posterior  surface  of  the  petrous  portion  of  the  tem- 
poral bone,  where  it  is  in  contact  with  the  dura.  From  the  lower  part  of  the  saccule 
a  short  tube,  the  canalis  reuniens  of  Hensen  {ductus  reuniens  [Henseni]),  passes 
downward  and  outward  to  open  into  the  ductus  cochlearis  near  its  vestibular 
extremity. 

The  Membranous  Semicircular  Canals  (ductus  seniicircidares)  are  about  one-third 
the  diameter  of  the  osseous  canals,  but  in  number,  shape,  and  general  form  they 
are  precisely  similar,  and  each  presents  at  one  end  an  ampulla  (ampullae  mem- 
branaceae).  The  canals  open  by  five  orifices  into  the  utricle,  one  opening  being 
common  to  the  inner  end  of  the  superior  and  the  upper  end  of  the  posterior 
canal.  In  the  ampulla;  the  wall  is  thickened,  and  projects  into  the  cavity  as 
a  fiddle-shaped,  transversely  placed  elevation,  the  septum  transversum,  in  which 
the  nerves  end. 

The  utricle,  saccule,  and  membranous  canals  are  attached  here  and  there  to 
the  bone  by  numerous  fibrous  bands,  the  so-called  ligaments  (ligamenta  lahy- 
rinthi  canalicular U7n). 


Otolithic 
membrane 

C%lia 


Fig.  862.- — Floor  of  scala  media,  showing  the  organ  of  Corti,  etc. 


Outtcnla 
membrani' 
Hair  cells  — L 

Sustentacular  \^_ 
cells 


Epitlielium  of 


-sC^      propria. 


Fig.  S63. — Trans-section  of  the  maigin  of  the  maculi  sacculi  of  a  guinea-pig.     X  325.     (After  KoUiker.) 

Structure. — The  walls  of  the  utricle,  saccule,  and  membranous  semicircular  canals  consist 
of  three  layers.  The  outer  layer  is  a  loose  and  flocculent  structiu-e,  apparently  composed  of  ordi- 
.  nary  fibrous  tissue,  containing  bloodvessels  and  pigment  cells.  The  middle  layer,  thicker  and 
more  transparent,  bears  some  resemblance  to  the  hyaloid  membrane,  but  it  presents  on  its  inter- 
nal siu-f ace,  especially  in  the  semicircular  canals,  numerous  papilliform  projections,  and,  on  the 


THE  INTERNAL  EAR,    OR  LABYRINTH 


1143 


addition  of  acetic  acid,  presents  an  appearance  of  longitudinal  fibrillation  and  elongated  nuclei. 
The  inner  layer  is  formed  of  simple  polygonal  epithelial  cells.  In  the  macula;  of  the  utricle 
and  sncculc,  and  in  the  transverse  septa  of  the  ampuUse  of  the  canals,  the  middle  coat  is  thickened; 
the  (■i)ith(liiim  is  columnar,  is  increased  in  height,  and  passes  into  the  neuroepithelium.  The 
neuroepithelium  consists  of  supporting  cells  and  hair  cells. 

1.  The  supporting  cells  are  long  and  fusiform,  and  contain  an  oval  nucleus.  Their  deep  ends 
are  attached  to  the  membrana  propria,  while  their  free  extremities  are  united  to  form  a  thin 
cuticle.     The  protoplasm  contains  yellowish  pigment  granules. 

2.  The  hair  cells  are  columnar,  with  bulged  lower  ends  and  free  upper  ends.  The  bulged 
lower  ends,  each  of  which  contains  a  spherical  nucleus,  do  not  reach  higher  than  the  middle  of 
the  epithelial  layer.  Each  free  upjier  end  is  surmounted  by  a  long,  tapering  filament.  These 
filaments  constitute  auditory  hair,  and  they  project  into  the  cavity.  Each  filament  is  found  to 
consist  of  many  fine  hairs.  The  filaments  of  the  auditory  nerve  enter  these  parts,  and,  having 
pierced  the  outer  and  thickened  middle  layer,  they  lose  their  myelin  sheaths,  and  their  axones 
divide  into  three  or  four  branches  at  the  larger  and  deeper  ends  of  the  hair  cells.  These  branches 
form  a  horizontal  plexus  {stratwrti  plexifomie). 

Numerous  small  prismatic  bodies  termed  statoUths,  otoconia,  or  otoUths,  and  consisting  of  a 
mass  of  minute  crystalline  grains  of  carbonate  of  lime,  held  together  in  a  gelatinous  substance, 
are  contained  in  the  walls  of  the  utricle  and  saccule  opposite  the  distribution  of  the  nerves.  The 
membrane  is  called  the  otolith  membrane.  A  calcareous  material  is  also,  according  to  Bowman, 
.sparingly  scattered  in  the  cells  lining  the  ampullfe  of  the  semicircular  canals.  The  conical 
thickening  in  the  ampulla  corresponds  to  the  otolith  membrane. 


OCHLEAR    NERVE 
^L^'      AND    GANGLION 


Fig.  S64. — Cochlea  in  transverse  section. 


Observe  especially  the  canal  of  the  cochle 
branous  labyrinth.     (Testut. ) 


part  of  the  mem- 


The  membranous  cochlea,  ductus  cochlearis,  or  scala  media  consists  of  a  spirally 
arranged  tube  enclosed  in  the  bony  canal  of  the  coclilea  and  lying  along  its  outer 
wall. 

The  osseous  spiral  lamina,  as  already  stated,  extends  only  part  of  the  distance 
between  the  modiolus  and  the  outer  bony  wall  of  the  cochlea.  A  membrane, 
the  basilar  membrane  {membrana  basilaris)  (Fig.  862),  stretches  from  its  free  edge 


1144 


THE  ORGANS  OF  SPECIAL  SENSE 


NERVE-FIBRES  PASSING  OUT 

GANGLION      SPIRAL      BETWE  EN  TH  E  TWO   LAYERS  I 

SPIRALE      FIBRES      LAM    N  A  SPI  RALIS  OSSEA 


to  the  outer  wall  of  the  cochlea,  and  completes  the  roof  of  the  scala  tympani. 
A  second  and  more  delicate  membrane,  the  membrane  of  Reissner  (memhraiia 
vestibularis  [Reissneri])  (Fig.  862),  extends  from  the  thickened  periosteum  covering 
the  lamina  spiralis  ossea,  at  an  angle  of  about  45  degrees,  to  the  outer  wall  of 
the  cochlea,  to  which  it  is  attached  at  some  litde  distance  above  the  membrana 
basilaris.  A  canal  is  thus  shut  off  between  the  scala  tympani  below  and  the 
scala  vestibuli  above;  this  is  the  membranous  canal  of  the  cochlea  (ductus  cochlearis 
or  scala  media)  (Fig.  863).  It  is  triangular  on  transverse  section,  its  roof  being 
formed  by  the  membrane  of  Reissner,  its  outer  wall  by  the  periosteum  which  lines 
the  bony  canal,  and  its  floor  by  the  membrana  basilaris,  and  the  outer  part  of 
the  lamina  spiralis  ossea,  on  the  former  of  which  is  placed  the  organ  of  Corti. 
Reissner's  membrane  is  thin  and  homogeneous,  and  is  covered  on  its  upper  and 
under  surfaces  by  a  layer  of  epithelium.     The  periosteum,  which  forms  the  outer 

wall  of  the  ductus  cochlearis,  is  greatly 
thickened  and  altered  in  character; 
forming  what  is  called  the  spiral  liga- 
ment of  the  cochlea  (ligamentum  spirale 
cochleae)  {Fig.  862).  It  projects  in- 
ward below  as  a  triangular  promi- 
nence, the  crista  basilaris,  which  gives 
attachment  to  the  outer  edge  of  the 
membrana  basilaris,  and  immediately 
above  which  is  a  concavity,  the  sulcus 
spiralis  extemus  (Fig.  862).  The 
upper  portion  of  the  ligamentum 
spirale  contains  numerous  capillary 
loops  and  small  bloodvessels  within 
the  epithelium,  and  forms  what  is  termed  the  stria  vascularis.  The  stria  is  limited 
below  by  a  prominence  {prominentia  spiralis),  in  which  a  bloodvessel  {yas  pronii- 
nens)  is  distinctly  visible. 

The  lamina  spiralis  ossea  (Fig.  86.3)  consists  of  two  plates  of  bone  extending 
outward;  between  these  are  the  canals  for  the  transmission  of  the  filaments  of  the 
auditory  nerve.  On  the  upper  plate  of  that  part  of  the  osseous  spiral  lamina 
which  is  outside  Reissner's  membrane  the  periosteum  is  thickened  to  form  the 
limbus  laminae  spiralis,  and  this  terminates  externally  in  a  concavity,  the  sulcus 
spiralis  intemus,  which  presents,  on  section,  the  form  of  the  letter  C;  the  upper 
part  of  the  letter,  formed  by  the  overhanging  extremity  of  the  limbus,  is  named 
the  labium  vestibulare ;  the  lower  part,  prolonged  and  tapering,  is  called  the  labium 
tympanicum,  and  is  perforated  by  numerous  foramina  (foramina  nervosa)  for  the 
passage  of  the  component  parts  of  the  cochlear  nerve.  Externally,  the  labium 
tympanicum  is  continuous  with  the  membrana  basilaris.  The  upper  surface 
of  the  labium  vestibulare  is  intersected  at  right  angles  by  a  number  of  furrows, 
between  which  are  numerous  elevations;  these  present  the  appearance  of  teeth 
along  the  free  margin  of  the  labium,  and  have  been  named  by  Huschke  the  audi- 
tory teeth.  The  basilar  membrane  may  be  divided  into  two  areas,  inner  and 
outer.  The  inner  is  thin,  and  is  named  the  zona  arcuata  or  zona  tecta  (Fig.  862) ; 
it  supports  the  organ  of  Corti.  The  outer  is  thicker  and  striated,  and  is  termed 
the  zona  pectinata.  The  under  surface  of  the  membrane  is  covered  by  a  layer  of 
vascular  connective  tissue.  One  of  these  vessels  is  somewhat  larger  than  the  rest, 
and  is  named  the  vas  spirale  (Fig.  866) ;  it  lies  below  Corti's  tunnel. 

The  organ  of  Corti^  (organon  spirale  [Cortii])  (Figs.  866  and  867)  is  situated 
upon  the  inner  part  of  the  membrana  basilaris  within  the  canal  of  the  ductus 


T^G.  865. — Part  of  the  cochlear  nerve,  highly  magnified. 
(Henle.) 


1  Corti's  original  paper  is  in  the  Zeitschrift  f.  Wissen.  Zool.,  iii,  109. 


THE  INTERNAL  EAJR,    OB  LABYRINTH 


1145 


cochlearis  and  appears  as  a  ridge  {crista  spiralis),  winding  spirally  throughout  the 
whole  length  of  the  ductus  cochlearis.  It  is  seen  to  be  composed  of  a  remarkable 
arrangement  of  cells,  which  may  be  likened  to  the  keyboard  of  a  piano.  Of  these 
cells,  the  central  ones  are  rod-like  bodies  and  are  called  the  inner  and  outer  rods  or 
pillars  of  Corti.     Their  bases  are  expanded  and  placed  on  the  basilar  membrane, 


Memhiana  iectona 


Outer  hair  cells 


Deiters 
Ovter  rod. 
Basilar  membrane. 
Fig.  866. — Section  through  the  organ  of  Corti.     Magnified.     (G.  Retzius.) 


Aeri'e  fibres. 


at  some  little  distance  from  each  other,  while  their  intermediate  portions  are 
inclined  toward  each  other,  so  as  to  meet  at  their  opposite  extremities,  and  form 
a  series  of  arches  roofing  over  a  minute  tunnel,  the  canal  or  tunnel  of  Corti,  be- 
tween them  and  the  basilar  membrane,  which  ascends  spirally  through  the  whole 
length  of  the  cochlea. 


Fig.  867. — Organ  of  Corti.     Diagr.imm:itic  riew  of  a  small  portion.     (Testut.) 

The  inner  rods  (Fig.  866),  some  6000  in  number,  are  more  numerous  than  the 
outer  ones,  and  rest  on  the  basilar  membrane,  close  to  the  labium  tympanicum; 
they  project  obliquely  upward  and  outward,  and  terminate  above  in  ex-panded 
extremities  which  resemble  in  shape  the  upper  end  of  the  ulna,  with  its  sigmoid 
cavity,  coronoid  and  olecranon  processes.     On  the  outer  side  of  the  rod,  in  the 


1146 


THE  ORGANS  OF  SPECIAL  SENSE 


angle  formed  between  it  and  the  basilar  membrane,  is  a  nucleated  mass  of  proto- 
plasm; while  on  the  inner  side  is  a  row  of  epithelial  cells,  the  inner  hair  cells  (Fig. 
866),  surmounted  by  a  brush  of  fine,  stiff,  hair-like  processes.  On  the  inner  side 
of  these  cells  are  two  or  three  rows  of  columnar  supporting  cells,  which  are  con- 
tinuous with  the  cubical  cells  lining  the  sulcus  spiralis  internus. 

The  outer  rods  (Fig.  866) ,  numbering  about  4000,  also  rest  by  broad  foot-plates 
on  the  basilar  membrane;  they  incline  upward  and  inward,  and  their  upper  extrem- 
ity resembles  the  head  and  bill  of  a  swan;  the  back  of  the  head  fitting  into  the 
concavity — the  analogue  of  the  sigmoid  cavity — of  one  or  more  of  the  internal  rods, 
and  the  bill  projecting  outward  as  a  phalangeal  process  of  the  membrana  reticu- 
laris, presently  to  be  described. 

In  the  head  of  these  outer  rods  is  an  oval  portion,  where  the  fibres  of  which 
the  rod  appears  to  be  composed  are  deficient,  and  which  stains  more  deeply  with 
carmine  than  the  rest  of  the  rod.  At  the  base  of  the  rod,  on  its  internal  side — ■ 
that  is  to  say,  in  the  angle  formed  by  the  rod  with  the  basilar  membrane — is  a 
similar  protoplasmic  mass  to  that  found  on  the  outer  side  of  the  base  of  the  inner 


Fig.  868. — Longitudinal  section  of  the  cochlea,  showing  the  relations  of  the  scalse,  the  ganglion  spirale, 
etc.  5.V".  Scalavestibuli.  5.2*.  Scala  tympani.  S.ilf.  Scala  media.  L.»S.  Ligamentum  spirale.  G'..S.  Ganglion 
spirale. 


rod;  these  masses  of  protoplasm  are  probably  the  undifferentiated  portions  of  the 
cells  from  which  the  rods  are  developed.  External  to  the  outer  rod  are  three  or 
four  successive  rows  of  epithelial  cells,  more  elongated  than  those  found  on  the 
internal  side  of  the  inner  rod,  but,  like  them,  furnished  with  minute  hairs  or  cilia. 
These  are  termed  the  outer  hair  cells,  in  contradistinction  to  the  inner  hair  cells 
above  referred  to.  There  are  about  12,000  outer  hair  cells,  and  about  3500  inner 
hair  cells. 

The  hair  cells  are  somewhat  oval  in  shape;  their  free  extremities  are  on  a 
level  with  the  heads  of  Corti's  rods,  and  from  each  some  twenty  fine  cilia 
project  and  are  arranged  in  the  form  of  a  crescent,  the  concavity  of  which  opens 
inward.  The  deep  ends  of  the  cells  are  rounded  and  contain  large  nuclei;  they 
reach  only  as  far  as  the  middle  of  Corti's  rods,  and  are  in  contact  with  the  rami- 
fications of  the  nerve  filaments.  Between  the  rows  of  the  outer  hair  cells  are 
rows  of  supporting  cells,  called  the  cells  of  Deiters;  their  expanded  bases  are  planted 
on  the  basilar  membrane,  while  their  opposite  ends  present  a  clubbed  extremity 
or  phalangeal  process.     Immediately  to  the  outer  side  of  Deiters'  cells  are  some 


THE  INTERNAL  EAR,   OB  LABYRINTH  1147 

five  or  six  rows  of  columnar  cells,  the  supporting  cells  of  Hensen.  Their  Ijases  are 
narrow,  while  their  upper  parts  are  expanded  and  form  a  rounded  elevation  on 
the  floor  of  the  ductus  cochlearis.  The  columnar  cells  lying  outside  Hensen's 
cells  are  termed  the  cells  of  Claudius.  A  space  is  seen  between  the  outer  rods 
of  Corti  and  the  adjacent  hair  cells;  this  is  called  the  space  of  Nuel. 

The  lamina  reticuhris,  or  membrane  of  Kolliker,  is  a  delicate  framework  perfo- 
rated by  rounded  holes.  It  extends  from  the  inner  rods  of  Corti  to  the  external 
row  of  the  outer  hair  cells,  and  is  formed  by  several  rows  of  "minute  fiddle-shaped 
cuticular  structures"  called  phalanges,  between  which  are  circular  apertures 
containing  the  free  ends  of  the  hair  cells.  The  innermost  row  of  phalanges 
consists  of  the  phalangeal  processes  of  the  outer  rods  of  Corti;  the  outer  rows  are 
formed  by  the  modified  free  ends  of  Deiters'  cells. 

Covering  over  these  structures,  but  not  touching  them,  is  the  membrana  tectoria 
or  membrane  of  Corti  (Figs.  862  and  866),  which  is  attached  to  the  vestilnilar  sur- 
face of  the  lamina  spiralis  close  to  the  attachment  of  the  membrane  of  Reissner. 
It  is  thin  near  its  inner  margin,  and  overlies  the  auditory  teeth  of  Huschke.  Its 
outer  half  is  thick,  and  along  its  lower  edge,  opposite  the  inner  hair  cells,  is  a 
clear  band,  named  Hensen's  stripe.  Externally,  the  membrane  becomes  much 
thinner,  and  is  attached  to  the  outer  row  of  Deiters'  cells  (Retzius).  It  is  made 
up  of  multitudes  of  delicate  fibres  embedded  in  a  transparent  matrix  of  a  soft, 
transparent  collagenous  character  with  marked  adhesiveness  (Hardesty). 

The  osseous  labyrinth  is  lined  by  an  exceedingly  thin  fibroserous  membrane, 
analogous  to  a  periosteum,  from  its  close  adhesion  to  the  inner  surfaces  of  these 
cavities,  and  performing  the  office  of  a  serous  membrane  by  its  free  surface.  It 
lines  the  vestibule,  and  from  this  cavity  is  continued  into  the  semicircular  canals 
and  the  scala  vestibuli  of  the  cochlea,  and  through  the  helicotrema  into  the  scala 
tympani.  A  delicate  tubular  process  is  prolonged  along  the  aqueduct  of  the  vesti- 
bule to  the  inner  surface  of  the  dura.  This  membrane  is  continued  across  the 
fenestra  ovalis  and  fenestra  rotunda,  and  consequently  has  no  communication 
with  the  lining  membrane  of  the  tympanum.  Its  attached  surface  is  rough  and 
fibrous,  and  closely  adherent  to  the  bone;  its  free  surface  is  smooth  and  pale, 
covered  with  a  layer  of  epithelium,  and  secretes  a  thin,  limpid  fluid,  the  perilymph. 

The  scala  media  (ductus  cochlearis)  is  closed  above  and  below.  The  upper  blind 
extremity  is  termed  the  lagena,  and  is  attached  to  the  cupola  at  the  upper  part  of 
the  helicotrema;  the  lower  end  is  lodged  in  the  recessus  cochlearis  of  the  vesti- 
bule. Near  this  blind  extremity,  the  scala  media  receives  the  canalis  reuniens  of 
Hensen  (Fig.  860),  a  very  delicate  canal,  by  which  the  ductus  cochlearis  is  brought 
into  continuity  with  the  saccule. 

The  auditory  nerve  (n.  acusticiis),  the  special  nerve  of  the  senses  of  hearing 
and  of  equilibrium,  divides,  at  the  bottom  of  the  internal  auditory  meatus,  into 
two  branches,  the  cochlear  and  vestibular. 

The  vestibular  nerve  {n.  vestibularis),  the  posterior  of  the  two,  presents,  as  it 
lies  in  the  internal  auditory  meatus,  a  ganglion,  the  vestibular  ganglion  or  the 
ganglion  of  Scarpa  (ganglion  vestibulare) ;  the  nerve  divides  into  three  branches 
which  pass  through  minute  openings  at  the  upper  and  back  part  of  the  bottom  of 
the  meatus  (area  vestibularis  posterior),  and,  entering  the  vestibule,  are  distributed 
to  the  utricle  and  to  the  ampulla  of  the  external  and  superior  semicircular  canals. 
The  nerve  filaments  enter  the  ampullary  enlargements  opposite  the  septum  trans- 
versum,  and  arborize  around  the  hair  cells.  In  the  utricle  and  saccule  the  nerve 
fibres  pierce  the  membrana  propria  of  the  maculie,  and  end  in  arborizations 
around  the  hair  cells. 

"The  cochlear  nerve  (n.  cochlearis)  gives  off  the  branch  to  the  saccule,  the  fila- 
ments of  which  are  transmitted  from  the  internal  auditory  meatus  through  the 
foramina  of  the  area  vestibularis  inferior,  which  lies  at  the  lower  and  back  part 


1148 


THE  ORGANS  OF  SPECIAL  SENSE 


of  the  floor  of  the  meatus.  It  also  gives  off  the  branch  for  the  ampulla  of  the  pos- 
terior semicircular  canal,  which  leaves  the  meatus  through  the  foramen  singnlare. 
The  rest  of  the  cochlear  nerve  divides  into  numerous  filaments  at  the  base 
of  the  modiolus;  those  for  the  basal  and  middle  coils  pass  through  the  foramina 
in  the  tractus  foraminosus,  those  for  the  apical  coil  through  the  canalis  centralis, 
and  the  nerves  bend  outward  to  pass  between  the  lamellae  of  the  osseous  spiral 
lamina.  Occupying  the  spiral  canal  of  the  modiolus  is  the  spiral  ganglion,  or 
ganglion  of  Corti  (ganglion  spirale),  consisting  of  bipolar  nerve  cells,  which  really 
constitute  the  true  cells  of  origin  of  this  nerve,  one  pole  being  prolonged  centrally 
to  the  brain  and  the  other  peripherally  to  the  hair  cells  of  Corti's  organ.  Reaching 
the  outer  edge  of  the  osseous  spiral  lamina,  the  nerve  fibres  pass  through  the  foram- 
ina in  the  labium  tympanicum.  Some  of  these  fibres  end  by  arborizing  around 
the  bases  of  the  inner  hair  cells,  while  others  pass  between  Corti's  rods  and  across 
the  tunnel,  to  terminate  in  a  similar  manner  in  relation  to  the  outer  hair  cells. 

The  arteries  of  the  Iab\Tinth  are  the  internal  auditory,  from  the  basilar,  and  the  stylomas- 
toid, from  the  posterior  auricular.  The  internal  auditory  divides  at  the  bottom  of  the  internal 
auditory  meatus  into  two  branches,  cochlear  and  vestibular.  The  cochlear  artery  divides  into 
numerous  minute  branches,  which  enter  foramina  in  the  tractus  spiralis  foraminosa  and  course 
in  the  lamina  spiralis  ossea  to  reach  the  membranous  structures.  The  largest  of  the  cochlear 
branches  is  in  the  canalis  centralis.  The  vestibular  branches  accompany  the  nerves,  and  sup- 
ply the  membranous  structures  in  the  vestibule  and  semicircular  canals.  Tno  arteries  go  to  each 
canal.  The  two  vessels  enter  opposite  extremities  of  the  canal,  and  anastomose  at  the  summit 
of  the  canal.  The  vestibular  vessels  form  a  minute  capillary  network  in  the  substance  of  each 
membranous  labyrinth. 

The  veins  of  the  vestibule  and  semicircular  canals,  the  auditory  veins,  accompany  the 
arteries,  and  receive  those  of  the  cochlea  at  the  base  of  the  modiolus,  to  form  the  internal 
auditory  vein  {vv.  auditivae  internae),  which  opens  into  the  posterior  part  of  the  inferior  petrosal 
sinus  or  into  the  lateral  sinus. 

THE  ORGANS  OP  TASTE  (ORGANON  GUSTUS). 

The  peripheral  organs  of  the  sense  of  taste  consist  of  certain  flask-shaped 
groups  of  modified  epithelial  cells,  termed  taste  buds  (calyculi  gusfatorii),  situated 
on  the  tongue  and  adjacent  parts.     They  occupy  nests  in  the  stratified  epithelium 


W -?^*^f ''''^'  ^:'^'.%s^ 


Fig.    869. — Section  of  part  of  the  papilla  foliata  of  a  rabbit.     (Magnified.) 

and  are  present  in  large  numbers  on  the  sides  of  the  circumvallate  papillae  (Fig- 
869),  and  to  a  less  extent  on  their  opposed  walls.  They  are  also  found  on  the 
fungiform  papillae  over  the  back  part  and  sides  of  the  tongue,  and  in  the  general 


THE  SKIN  1149 

epithelial  covering  of  the  same  areas.  They  are  very  plentiful  over  the  fimbriae 
linguae,  and  are  also  present  on  the  under  aspect  of  the  soft  palate,  uvula,  and 
on  the  lingual  surface  of  the  epiglottis. 

Each  taste  bud  is  flask-like  in  shape,  its  broad  base  resting  on  the  corium,  and 
the  neck  opening  by  an  orifice,  the  gustatory  pore,  between  the  cells  of  the  epithe- 
lium. The  bud  is  formed  by  two  kinds  of  cells,  supporting  cells  and  gustatory 
cells.  The  supporting  cells  are  mostly  arranged  like  the  staves  of  a  cask,  and  form 
an  outer  envelope  for  the  I)ud.  Some,  however,  are  found  in  the  interior  of  the 
bud  between  the  gustatory  cells.  The  gustatory  cells  occupy  the  central  portion 
of  the  bud;  they  are  spindle-shaped,  and  each  possesses  a  large  spherical  nucleus 
near  the  middle  of  the  cell.  The  peripheral  end  of  the  cell  terminates  at  the 
gustatory  pore  in  a  fine,  hair-like  filament,  the  gustatory  hair.  The  central  pro- 
cess passes  toward  the  deep  extremity  of  the  bud,  and  there  ends  in  a  single  or 
bifurcated  varicose  filament,  which  was  formerly  supposed  to  be  continuous  with 
the  terminal  fibril  of  a  nerve;  the  investigations  of  Lenhossek  and  others  would 
seem  to  prove,  however,  that  this  is  not  so,  but  that  the  nerve  fibrils  after  losing 
their  myelin  sheaths  enter  the  taste  bud,  and  terminate  in  fine  extremities  between 

Guntatory  knirs  Taste  pore 


Epithelium- 


Tunica  propria — r^- 


FiG.  870. — Taste  buds  from  the  papilla  foliata  of  a  rabbit.     X  850.     (Szymonowicz.) 

the  gustatory  cells.  Other  nerve  fibrils  may  be  seen  ramifying  between  the  sup- 
sporting  cells  and  terminating  in  fine  extremities;  these,  however,  are  believed  to 
be  nerves  of  ordinary  sensation,  and  not  gustatory.  "The  latest  researches  have 
shown  that  dendrites  of  sensor  neurones  (sensor  nerves)  enter  the  taste  buds  and 
end  free  in  telodendria.  The  latter  surround  the  neuroepithelial,  and,  to  some 
extent,  the  sustentacular  cells,  their  relations  depending  on  contact.'" 

Nerves  of  Taste. — The  chorda  tympani  nerve  is  generally  regarded  as  the  nerve  of  taste 
for  the  anterior  two-thirds  of  the  tongue;  the  nerve  for  the  posterior  third  is  the  glosso- 
pharyngeal. 

THE  SKIN  (INTEGUMENTUM  COMMUNE). 

The  skin  covers  the  body  surface  and  is  continuous  with  the  mucous  membrane 
at  the  origin  and  termination  of  the  alimentary  canal  and  at  the  openings  of  other 
canals.  The  skin  is  a  protective  coat,  a  regulator  of  body  temperature,  contains 
multitudes  of  the  terminations  of  sensor  nerves,  and  is  the  seat  of  the  organ  0/ 

'  Journ.il  of  Anatomy  and  Physiology,  1891. 


1150 


THE  ORGANS  OF  SPECIAL  SENSE 


touch  (organon  tactus).  These  nerve  organs  are  connected  with  nerve  fibres  of 
temperature,  pressure,  and  pain.  Connected  with  the  skin  are  sw'eat  glands 
which  have  important  excretory  functions  and  sebaceous  glands.  From 
its  superficial  part  come  appendages,  the  hairs,  and  nails.  The  skin  is  elastic 
and  varies  in  thickness  from  0.5  mm.  to  4  mm.  (-gig-  to  \  inch).  It  is  thinnest 
in  the  eyelids  and  prepuce,  and  thickest  over  the  back  of  the  neck,  back  of  the 
shoulders,  palms  of  the  hands,  and  soles  of  the  feet.  Its  color  depends  in  part 
on  the  blood  within  it,  and  in  part  upon  pigment.  The  deepest  hue  is  about  the 
anus,  in  the  genital  region,  in  the  axillae,  over  the  mammary  glands,  and  in  the 
parts  exposed  to  air,  light,  and  varied  temperatures.  The  color  varies  with  age, 
being  pinkish  in  extreme  youth  and  becoming  yellow  in  old  age.     It  varies  with 

exposure  and  with  climate,  being 
deepest  in  those  who  brave  all 
weathers  and  temperatures  and  in 
those  who  dwell  beneath  a  tropical 
sun.  It  also  varies  with  race,  and 
this  is  so  well  recognized  that  races 
are  classified  by  the  color  of  the 
skin  into  the  White,  Yellow,  Brown, 
and  Black  races.  The  color  of  the 
skin  is  also  affected  in  certain  dis- 
eases; being  extremely  pale  in 
anemia,  bi-own  in  Addison's  disease, 
yellow  in  jaundice,  etc. 

In  most  situations  the  skin  is  mov- 
able, but  in  some  it  is  attached  closely 
to  underlying  structures,  and  is  con- 
sequently immovable  on  the  scalp, 
the  palms  of  the  hands,  the  soles  of 
the  feet,  and  the  outer  portion  of  the 
pinna  of  the  ear.  The  skin  is  fairly 
smooth,  but  close  examination  dis- 
closes multitudes  of  openings,  creases,  furrows,  depressions,  folds,  and  hairs. 
Hair  follicles  open  upon  the  surface,  and  the  ducts  of  sebaceous  glands  and  of 
sweat  glands  perforate  the  skin. 

About  the  joints  are  folds  of  skin  (retinacula  cutis),  and  temporary  folds  or 
wrinkles  are  created  by  the  contraction  of  superficial  muscles.  The /aciaZ  wrinkles 
of  advancing  years  are  due  to  habitual  expression  and  loss  of  skin  elasticity.  A 
dimple  is  a  permanent  pit  or  depression  due  to  adhesion  of  the  surface  to  parts 
beneath.  The  ridges  and  furrows  on  the  palms,  soles,  and  flexor  aspects  of  the 
digits  are  permanent,  and  over  the  palmar  surface  of  the  digits  they  are  arranged 
in  definite  forms  which  endure  through  life  and  are  so  distinctive  that  they  have 
been  utilized  by  police  officials  in  determining  the  identity  of  individuals.  These 
folds  are  due  to  the  papillae  of  the  skin  being  arranged  in  rows ;  some  of  the  papillae 
proliferate,  and  linear  depressions  occur  in  the  horny  layer  (Philippson). 

Fig.  871  shows  skin  ridges  (cristae  cutis),  skin  furrows  (sulci  cutis),  furrows 
opposite  joints  due  to  acts  of  flexion,  and  called  flexure  furrows,  and  longitudinal 
furrows. 

When  the  skin  is  punctured  by  a  round  awl  it  tends  to  split  in  a  definite  direc- 
tion, which  direction  varies  with  the  region  stabbed.  These  clefts  are  known 
as  the  cleavage  lines  of  Langer  (Figs.  872  and  873) ,  and  depend  upon  the  arrange- 
ment of  the  connective-tissue  bundles  of  the  corium.  These  connective-tissue 
bundles  certainly  influence  the  formation  of  folds  and  fiu'rows.  In  many  portions 
of  the  body  the  cutaneous  surface  is  divided  by  linear  furrows  into  irregularly 


LONGITUD1NA 


R<IDGES  OF  SKIN 
INTERRUPTED  BY 
LONGITUDINAL"^' 
FURROWS 


Fig.  S71. — The  furroTvs  and  ridges  of  the  surface  of 
the  skin  from  the  palm  or  surface  of  the  middle  finger. 
(Toldt.) 


THE  SKIN 


1151 


shaped  areas  (Fig.  874).     The  skin  consists  of  two  layers:  a  superficial  layer, 
the  epidermis,  and  a  deep  layer,  the  corium  or  dermis. 

Tlie  Cuticle,  Scarf  Skin,  or  Epidermis  (Figs.  875  and  876)  is  composed  of 
layers  of  epithelium  and  is  derived  from  the  ectoderm.     The  epithelium  is  strati- 


FlG.  872. — Anterior  surface. 


Fig.  S73. — Posterior  surface. 


The  general  course  of  the  connective-tissue  bundles  of  the  corium.  determined  by  the  direction  assumed  by  the 
linear  clefts  made  in  the  skin  when  it  is  punctured  by  a  round  awl.     (Langer.) 


Red,  and  is  devoid  of  bloodvessels.     Two  layers  can  be  readily  made  out,  the 
superficial  or  homy  layer  and  the  deeper  or  Malpighian  layer. 

Tlie  homy  layer  (stratum  corneum)  is  formed  by  several  layers  of  non-nucleated 
scaly  cells.     The  cells  consist  of  keratin.     The  surface  cells  of  the  horny  layers 


1152 


THE  ORGANS  OF  SPECIAL  SENSE 


are  being  constantly  rubbed  off,  and  are  being  replaced  by  cells  from  the  Mal- 
pighian  layer,  which  are  converted  into  keratin  as  they  approach  the  surface. 

The  Malpighian  layer  (stratum  Malpighii)  of  the  epidermis  is  divided  into 
f&ur  layers,  named,  from  without  inward,  the  stratum  lucidum,  the  stratum  granu- 
losum,  the  stratum  mucosum,  and  the  stratum  germinativum. 


S=^       w       .^ 


^<!" 


r 


fff 


Fig.  874. — The  furrows  of  the  skin  and  the  areas  which  these  furrows  delimit,  reproduced  from  an  impression  ot 
the  dorsal  surface  of  the  wrist.     (Toldt.) 

The  stratum  lucidum  is  the  most  superficial  part  of  the  Malpighian  layer.  It 
consists  of  several  layers  of  flat  cells,  the  nuclei  of  which  are  beginning  to  disappear. 
The  cells  contain  eleidin  granules.  In  regions  where  the  epidermis  is  thin  the 
stratum  lucidum  is  absent. 

The  stratum  granulosum  consists  of  several  layers  of  nucleated  flat  cells,  con- 
taining keratohyaline  granules.  These  granules  are  probably  formed  from  the 
disintegrating  nucleus,  and  in  the  stratum  lucidum  are  converted  into  eleidin, 
an  intermediate  substance  in  the  formation  of  keratin.  It  is  best  developed  in  the 
sole  and  palms. 


FURROWS  OF  SKIN 


RIDGES  OF  SKIN 


ERMIS^ 


TOOCH  CORPUSCLE^ 

STRATUM  CORNEUM 

STRATUM  LUCIDUM 

RETE  MUCOSUM 


f      STRATUM     PA 
^STRATUM    RETI 


kPILLARE  I 
ICULARE  (. 


BODY  OF 

SUDORIFEROUS 

GLAND 


Fig.  875. — Vertical  section  through  the  skin  ot  the  finger-tip.     The  layers  of  the  epidermis  and  of  the 
The  subcutaneous  areolar  tissue-     The  sudoriferous  or  sweat-gland.      (Toldt.) 


The  mucous  layer  or  the  stratum  mucosum  consists  of  numerous  layers  of  nucle- 
ated, polygonal,  spine-shaped  cells  known  as  prickle  cells  or  finger  cells.  Between 
the  cells  of  the  stratum  mucosum  are  spaces  containing  pigment  granules  and 
leukocytes.  Processes  from  the  prickle  cells  join  adjacent  cells.  This  layer 
contains  numerous  connective-tissue  fibres  arranged  in  a  network,  and  known  as 
epidermic  fibrils. 

The  stratum  cylindricum  or  stratum  germinativum  is  composed  of  cylindrical 
or  prickle  cells,  the  points  of  which  are  directed  downward.     Fine  fibrils  pass  up 


THE  SKIN  1153 

from  the  coriiim  between  the  cells,  and  there  is  cement  substance  as  well  between 
them. 

The  Corium,  Cutis  Vera,  Dennis,  or  True  Skin  (Figs.  876  and  880)  is  a  con- 
nective-tissue structure  which  arises  from  the  mesoderm.  It  consists  especially 
of  connective  tissue  and  elastic  fibres;  it  contributes  elasticity  to  the  skin,  and  is 
the  seat  of  the  sense  organs.  The  corium  is  composed  of  two  layers,  the  papillary 
and  the  reticular. 


Duct  of  _'^' 
sweat    '      '      ~    ' 


Adipose  tiss 


Fig.  876. — Diagrammatic  sectional  view  of  the  skin.     (Magnified.) 

The  superficial  or  papillary  layer  or  corpus  papillare  of  the  corium  (stratum  papil- 
lare)  lies  just  beneath  the  epidermis,  contains  the  papilla?,  and  is  composed  of  a 
network  of  fine  bundles  of  fibrous  tissue.  The  papilla;  are  composed  of  fine 
strands  of  connective  tissue  and  elastic  tissue.  They  project  from  the  corium 
beneath  the  epidermis  and  enter  into  depressions  of  the  epidermis.  They  vary 
greatly  in  size,  averaging  y^  of  an  inch  in  height  and  ^to"  ^^^  ^^  '""^'^  '"  width 
at  the  base.  In  the  face,  especially  in  the  eyelids,  they  are  insignificant.  On  the 
glans  penis,  the  palms  of  the  hands,  and  the  soles  of  the  feet,  and  in  the  nipples, 
they  are  large.  In  the  palmar  surfaces  of  the  hands  and  fingers  and  the  plantar 
surfaces  of  the  feet  and  toes  they  produce  permanent  ridges  (Fig.  879).  A  ridge 
is  composed  of  two  or  more  rows  of  papilh?,  and  the  ducts  of  sweat  glands  emerge 

73 


1154 


THE  ORGANS  OF  SPECIAL  SENSE 


between  rows  of  papilUe,  and  open  on  the  curved  surface  ridges  (Fig.  875).  Most 
of  the  papillae  contain  loops  of  capillaries,  and  are  called  vascular  papillae.  Some 
contain  nerve  terminations,  and  are  called  nerve  papilla.     Between  the  papillary 


stratum  lucidttm 
Stratum  grannJosum 


Stratum  niucosum 
Malpiqhii 


Stratum  ger-minativum 


-  Nerve  Jiirila, 


Fig.  877. — Section  of  epide: 


layer  of  the  cerium  and  the  epidermis  is  a  very  thin  and  structureless  membrane 
called  the  basal  membrane. 

The  deep  or  reticular  layer  (stratum  reticulare)  rests  upon  the  subcutaneous 
tissue.     It  passes  superficially  into  the  papillary  layer,  and  at  most  places  into 

the  subcutaneous  tissue  without  a  sharp 
«HRECTOR      HAIR  liuc  of  differentiation.     At  some  places, 

PILl    MUSCLE       FOLLICLE      CORIUM       EPIDERMIS  r.  •  •  i  -ill 

tor  mstance  m  the  nipple,  the  deep 
layer  of  the  corium  rests  upon  a  layer 
of  muscle  tissue.  In  the  face  this 
muscle  tissue  is  striated  and  sends  pro- 
longations to  the  papillary  layer;  in  the 
nipple  and  scrotum  it  is  nonstriated. 
The  reticular  layer  is  composed  of  bun- 
dles of  white  fibrous  tissue,  arranged 
in  a  network.  In  the  meshes  of  the 
network  are  fat,  bloodvessels,  lymphat- 
ics, sebaceous  glands,  sweat  glands, 
and  hair  follicles. 

The  subcutaneous  areolar  tissue,  or 
tela  subcutanea  (panniculus  adiposiis), 
connects  the  skin  to  the  parts  beneath; 
it  is  composed  of  bundles  of  connective 
tissue  which  cross  repeatedly  and  form 
spaces.  In  almost  all  regions  the  spaces  contain  fat,  but  in  the  scrotum,  exter- 
nal ear,  penis,  and  eyelid  they  do  not  contain  fat.  When  the  connective-tissue 
fibres  of  the  panniculus  adiposus  are  long  and  nearly  parallel  to  the  skin  surface. 


Fig.  878. — Vertical  section  through  the  skin  of  the 
trunk  in  the  region  of  the  arch  of  the  ribs.  One 
of  the  small  hairs  is  seen  in  longitudinal  section. 
(Toldt.) 


THE  SKIN 


1155 


the  skin  becomes  wrinkled;  when  they  are  short  and  nearly  at  riglit  angles  to  the 
surface,  the  skin  cannot  wrinkle. 

Pigmentation  of  the  Skin. — As  previously  stated,  in  certain  regions  the  skin  of  the 
white  race  is  brown  because  of  pigmentation  (areoUie,  nipples,  around  the  anus, 


PAPILLjE  o 


^■S>'^Vn'1''^'*>>VM'      ''■^VW'Jt.'S'*  ^-     FURROWS 


Fig.  879. — The  furrows  ; 


id  ridges  of  true  skin  on  the  pahnar  .surface 
having  been  removed.     (Toldt.) 


;  of  the  fingers,  the  epidermis 


axillse,  scrotum,  labia  majora).  This  is  due  to  pigment  within  the  epithelial  and 
connective-tissue  cells  of  the  papillary  layer  of  the  corium,  and  in  the  basal  cells 
of  the  epidermis.  There  are  few  or  none  of  these  pigmented  cells  in  the  stratum 
corneum  of  one  of  the  Caucasian  race. 

"In  negroes  and  other  colored  races  the  deep  pigmentation  is  due  to  a  similar 
distribution  of  the  pigment  granules  in  the  entire  epidermis;  but  even  here  the 


Fig.  880. — The  distribution  of  the  bloodvessels  in  the  skin  of  the  sole  of  the  foot.     (Spalteholz.J 

pigmentation  decreases  toward  the  surface,  although  the  uppermost  cells  of  the 
stratum  corneum  always  contain  some  pigment.  The  nuclei  of  the  cells  are  always 
free  from  coloring  matter.  The  Cjuestion  as  to  the  origin  of  the  pigment  is  as  yet 
unsolved.'" 


1  A  Text-book  of  Histology.     By  A.  A.  Bohm  and  M.  von  DavidoS.     Translated  and  edited  by  G.  Carl  Huber. 


1156 


THE  ORGANS  OF  SPECIAL  SENSE 


The  arteries  supplying  the  skin  vary  in  number,  and  vary  much  in  size,  being  largest  in  re- 
gions exposed  to  pressure,  as  the  skin  of  the  palms,  soles,  and  buttocks.  The  arteries  enter  the 
skin  from  a  network  in  the  subcutaneous  tissue,  and  by  an  anastomosis  in  the  deepest  part  of  the 
corium  form  a  network  {rete  arteriosuni  cutaneum).  The  vessels  send  branches  to  the  fat  and 
to  the  sweat  glands.  Branches  from  the  network  just  described  ascend  and  form  a  second  net- 
work in  the  corium  beneath  the  papillae.  This  is  called  the  subpapillary  network  (rete  arfe- 
riosum  subpapillare).  From  this  network  fine  capillary  vessels  pass  into  liic  papiihe,  forming,  in 
the  smaller  papillae,  a  single  capillary  loop,  but  in  the  larger  a  more  or  less  comoluted  vessel. 
From  this  network  branches  go  to  the  hair  follicles  and  sebaceous  glands.  The  blood  from 
the  papillae  passes  into  a  plexus  (rete  venosum)  beneath  the  papillae.  This  commimicates  x^ith 
another  plexus  between  the  corium  and  subcutaneous  tissue.  In  some  regions  one  or  more  retia 
are  interposed  between  these  two.  The  veins  from  the  sweat  glands,  sebaceous  glands,  superficial 
fat,  and  hair  follicles  are  received  by  the  retia  venosa.  From  the  deepest  rete  veins  pass  to 
the  subcutaneous  tissue,  and  these  veins  enter  the  large  subcutaneous  veins. 

There  are  numerous  lymphatics  supplied  to  the  skin  which  form  two  networks,  superficial 
and  deep,  communicating  with  each  other  and  with  the  lymphatics  of  the  subcutaneous  tissue  by 
oblique  branches.     They  originate  in  the  cell  spaces  of  the  tissue. 

The  nerves  of  the  skin  terminate  partly  in  the  epidermis  (Fig.  867)  and  partly  in  the  cutis 
vera  (Fig.  876).  The  former  are  prolonged  into  the  epidermis  from  a  dense  plexus  in  the  su])er- 
ficial  layer  of  the  corium  and  terminate  between  the  cells  in  bulbous  extremities;  or,  according 
to  some  observers,  in  the  deep  epithelial  cells  themselves.  The  latter  terminate  in  end  bulbs, 
touch  corpuscles,  or  Pacinian  bodies  (Figs.  590  and  866),  in  the  manner  already  described 
(p.  815),  and,  in  addition  to  these,  a  considerable  number  of  fibrils  are  distributed  to  the  hair 
follicles,  which  are  said  to  entwine  about  the  follicle  in  a  circular  manner.  Other  ner^-e  fibres 
are  supplied  to  the  smooth  muscle  fibres  {mm.  arrectorcs  •pilormri)  of  the  hair  follicles  and  to  the 
muscle  coat  of  the  bloodvessels.     These  are  probably  amyelinic  fibres. 


THE  APPENDAGES  OF  THE  SKIN. 

The  appendages  of  the  skin  are  the  nails,  the  hairs,  the  sudoriferous  and  seba- 
ceous glands,  and  their  ducts. 

The  nails  and  hairs  are  peculiar  modifications  of  the  epidermis,  consisting 
essentially  of  the  same  cellular  structure  as  that  tissue. 


Stratum  a  i 
of  the  nail 
gi oove 


St)  atum 
cot  Ileum. 

^f<  atum 
q}  atiutosum. 

(  UIIUM 


Fig.  SSI.' — Longitudinal  section  through  human  nail  and  its  c 
Davidoff's  Histology.) 


,il  groove  (sulcus).      (From  Bohm  and 


The  Nails  (ungues)  (Figs.  881  and  884)  are  flattened,  elastic  structures  of 
a  horny  te.xture,  placed  upon  the  dorsal  surface  of  the  terminal  phalanges  of  the 
fingers  and  toes.  Each  nail  is  convex  on  its  outer  surface,  concave  within.  Its 
chief  mass,  called  the  body  {corpus  unguis),  lies  upon  the  nail  bed.  The  free  edge 
is  called  the  margo  liber.  Each  lateral  margin  (margo  lateralis),  like  the  pro.ximal 
short  edge  of  the  nail  (margo  occultus),  lies  in  a  groove  of  the  cutis,  the  ungual  sulcus 
(sulcus  matricis  unguis).  The  ungual  wall  (vallum  unguis)  overlies  the  lateral  and 
posterior  edges.  The  nail  is  implanted  by  means  of  a  portion,  called  the  root 
(radix  unguis),  into  a  groove  in  the  skin.  The  root  is  beneath  the  ungual  wall 
and  is  composed  of  cells  which  have  not  j'et  become  horny.  It  is  white  in  color. 
The  nail  has  a  very  firm  adhesion  to  the  cutis  vera,  being  accurately  moulded 


THE  APPEND  A  GES  OF  THE  SKIN 


11. -,7 


upon  the  surface  of  the  true  skin,  as  the  epidermis  is  in  other  parts.  The  part 
of  the  cutis  beneath  the  body  and  root  of  the  nail  is  called  the  matrix  (matrix 
unguis),  because  it  is  the  part  from  which  the  nail  is  produced.  Correspondint; 
to  the  body  of  the  nail,  the  matrix  is  thick,  and  raised  into  a  series  of  longitudinal 
ridges  (cristae  viatricis  unguis),  which  are  very  vascular,  and  the  color  is  seen 
through  the  transparent  tissue.  Behind  this,  near  the  root  of  the  nail,  the  papilla? 
are  small,  less  vascular,  and  have  no  regular  arrangement,  and  here  the  tissue 

Nn,l 
Stratum  Malptqlm 

Nml  V II  '  '^i— '  rt  _^^ 


Nml  g7  u 


^f  mill  III  rnnieiiin. 
^/i  ittinii  iiramihsuii}. 


Fig.  882. — Transverse  section  through  hu 


lil  and  ifci  sulcus.     (From  Btihm  and  Davidoff's  Histology.) 


of  the  nail  is  somewhat  more  opaque;  hence  this  portion  is  of  a  whiter  color, 
and  is  called  the  lunula  on  account  of  its  crescentic  shape. 

The  cuticle,  as  it  passes  forward  on  the  dorsal  surface  of  the  finger  or  toe,  is 
attached  to  the  surface  of  the  nail,  a  little  in  advance  of  the  nail  root;  at  the 
extremity  of  the  finger  it  is  connected  with  the  under  surface  of  the  nail  a  little 
behind  its  free  edge.  The  cuticle  and  the  horny  substance  of  the  nail  (both  epi- 
dermic structures)  are  thus  directly  continuous  with  each  other.  The  nails  con- 
sist of  a  greatly  thickened  stratum  lucidum,  the  stratum  corneum  forming  merely 


OF  FINGER 

:  section  through  tiie  nail 


nd  tlie  terminal  portion  of  the  ring  finger,      (Toldt.) 


the  thin  cuticular  fold  (eponychium)  which  overlaps  the  lunula.  The  cells  have 
a  laminated  arrangement,  and  are  essentially  similar  to  those  composing  the 
epidermis.  The  deepest  layer  of  cells,  which  lie  in  contact  with  the  papillre 
of  the  matrix,  are  columnar  in  form  and  arranged  perpendicularly  to  the  surface; 
those  which  succeed  them  are  of  a  rounded  or  polygonal  form,  the  more  superficial 
ones  becoming  broad,  thin,  and  flattened,  and  so  closely  compacted  as  to  make  the 
limits  of  each  cell  very  indistinct.  It  is  by  the  successive  growth  of  new  cells  at 
the  root  and  under  surface  of  the  body  of  the  nail  that  it  advances  forward  and 


1158 


THE  ORGANS  OF  SPECIAL  SENSE 


maintains  a  due  thickness,  while,  at  the  same  time,  the  growth  of  the  nail  in  the 
proper  direction  is  secured.  As  these  cells  in  their  turn  become  displaced  by 
the  growth  of  new  oneS;  they  assume  a  flattened  form  and  finally  become  closely 


MATRIX  OF  NAIL 


FREE  EDGE 


CONCEALED  MARGIN 


Fig.  884. — The  finger-nail  com- 
pletely isolated,  seen  from  the  con- 
vex side.     (Toldt.) 


Fig.  88.5.  —The  matrix  of  the 
nail  or  nail  bed,  with  the  nail  fold 
and  nail  walls  displayed  by  the 
removal  of  the  epidermic  portion 
of  the  nail  or  nail  proper  and  the 
surrounding  epidermis.      (Toldt.) 


Fig.  886.— Matrix  of  the 
nail  with  partly  opened  mar- 
ginal groove  of  the  nail  bed, 
(Toldt.) 


AH    PAPILLA 


Fig.  887.— a  hair  of  the  head  still  in  the  course  of  growth,  with  hair  bulb  in  longitudinal  section.     (Toldt.) 


compacted  together  into  a  firm  dense,  horny  texture.  In  chemical  composition  the 
nails  resemble  the  upper  layers  of  the  epidermis,  containing,  however,  a  some- 
what larger  proportion  of  carbon  and  sulphur  (Mulder). 


THE  APPENDAGES  OF  THE  SKIN 


1159 


The  Hairs  (pili)  (Figs.  SSS  and  889)  are  peculiar  modifications  of  tlie  epi- 
dermis, and  consist  essentially  of  the  same  structure  as  that  membrane.  They 
are  found  on  nearly  every  part  of  the  sin-face  of  the  body,  excepting  the  palms  of 
the  hands,  soles  of  the  feet,  the  nipples,  the  inner  surface  of  the  prepuce,  and  the 
glans  penis.  Hairs  include  hairs  of  the  head  (capilU);  of  the  eyebrows  (supcrcilia); 
of  the  beard  (barha);  of  the  ears  (fr<if/i);  of  the  nostrils  (vihri.ssir);  the  eyelashes 
(cilia);  hairs  of  the  axilla  (Jilrci);  of  (he  pubes  (ptibes);  and  the  small  hairs  of  the 
skin  or  woolly  hairs  [lanugo).  They  \ai-y  much  in  length,  thickness,  and  color 
in  different  parts  of  the  body  and  in  different  races  of  mankind.  In  some  parts, 
as  in  the  skin  of  the  eyelids,  they  are  so  short  as  not  to  project  beyond  the  follicles 
containing  them;  in  others,  as  upon  the  scalp,  they  are  of  considerable  length; 
again,  in  other  parts,  as  the  eyelashes,  the  hairs  of  the  pubic  region,  and  the  whis- 
kers and  beard,  they  are  remarkalile  for  their  thickness.    Straight  hairs  are  stronger 


EPIDERMIS 


CORIUM     - 


HAIR    FOLLICLE 
ROOT 


Fig.  888. — Vertical  section  through  the  skin  of  the  head.     The  hairs  of  the  head  in  longitudinal  section.     (Toldt.) 


than  curly  hairs,  and  present  on  transverse  section  a  cylindrical  or  oval  oudine; 
curly  hairs,  on  the  other  hand,  are  flattened.  The  hairs  are  usually  oblique  to 
the  surface  from  which  they  arise  (Fig.  888).  Their  direction  depends  upon  the 
region  from  which  they  spring,  being  fairly  regular  in  certain  regions.  Thus- 
are  formed  hair  streams  {flumina  pilcrum)  and  hair  whirlpools  (vortices  pilorum). 

A  hair  consists  of  the  root,  the  part  implanted  in  the  skin;  the  shaft,  the  portion 
projecting  from  its  surface;  and  the  point. 

The  root  of  the  hair  (radix  pili)  presents  at  its  extremity  a  bulbous  enlargement, 
the  hair  bulb  (hulhus  pili)  (Fig.  887),  which  is  whiter  in  color  and  softer  in  texture 
than  the  shaft,  and  is  lodged  in  a  follicular  involution  of  the  epidermis  called  the 
hair  follicle  (folliculus  pili)  (Fig.  878).  ^M:ien  the  hair  is  of  considerable  length 
the  follicle  extends  into  the  subcutaneous  cellular  tissue.  The  hair  follicle  com- 
mences on  the  surface  of  the  skin  with  a  funnel-shaped  opening,  and  passes  inward 
in  an  oblique  or  curved  direction — the  latter  in  curly  hair — to  become  dilated  at 
its  deep  extremity  or  fundus  (fundus  folliculi  pili),  whei'e  it  corresponds  with  the 
bulbous  condition  of  the  hair  which  it  contains.  It  has  opening  into  it,  near  its 
free  extremity,  the  orifices  of  the  ducts  of  one  or  more  sebaceous  glands  (Figs. 
887  and  888).  At  the  bottom  of  each  hair  follicle  is  a  small,  conical,  vascular 
eminence  or  papilla,  the  hair  papilla  (papilla  pili)  (Figs.  887  and  888),  similar 
in  every  respect  to  the  papillae  found  upon  the  surface  of  the  corium;  it  is  continu- 
ous with  the  dermic  layer  of  the  follicle,  is  highly  vascular,  and  is  probably  supplied 


1160 


THE  ORGANS  OF  SPECIAL  SENSE 


with  nerve  fibrils.     In  structure  the  hair  folUcle  consists  of  two  root  sheaths — an 
outer  or  dermic,  and  an  inner  or  epidermic  (Figs.  887  and  889). 

The  outer  or  dermic  root  sheath  is  formed  mainly  of  fibrous  tissue;  it  is  continuous 
with  the  corium,  is  highly  vascular,  and  is  supplied  by  numerous  minute  nerve 
filaments.  It  consists  of  three  layers.  The  most  internal,  the  cuticular  lining 
of  the  follicle,  consists  of  a  hyaline  basement  membrane,  the  hyaline  layer,  having 
a  glassy,  transparent  appearance,  which  is  well  marked  in  the  larger  hair  follicles, 
but  is  not  very  distinct  in  the  follicles  of  minute  hairs.  It  is  continuous  with  the 
basement  membrane  of  the  surface  of  the  corium.  External  to  this  is  the  inner 
fibrous  layer,  a  compact  layer  of  fibres  and  spindle-shaped  cells  arranged  circularly 
around  the  follicle.  This  layer  extends  from  the  bottom  of  the  follicle  as  high  as 
the  entrance  of  the  ducts  of  the  sebaceous  glands.  Externally  is  the  outer  fibrous 
layer,  a  thick  layer  of  connective  tissue,  arranged  in  longitudinal  bundles,  forming 
a  more  open  texture  and  corresponding  to  the  reticular  part  of  the  corium.  In  this 
are  contained  the  bloodvessels  and  nerves. 


ROOT    SHEATH 


ROOT  SHEATH 


The  inner  or  epidermic  layer  is  closely  adherent  to  the  root  of  the  hair,  so  that 
when  the  hair  is  plucked  from  its  follicle  this  layer  most  commonly  adheres  to  it 
and  forms  what  is  called  the  root  sheath.  It  consists  of  two  strata,  named  respec- 
tively the  outer  and  inner  root  sheaths;  the  former  of  these  corresponds  with  the 
Malpighian  layer  of  the  epidermis,  and  resembles  it  in  the  rounded  form  and 
soft  character  of  its  cells;  at  the  bottom  of  the  hair  follicles  these  cells  become 
continuous  with  those  of  the  root  of  the  hair.  The  inner  root  sheath  consists  of 
a  delicate  cuticle  next  the  hair,  composed  of  a  thin  layer  of  imbricated  scales  having 
a  downward  direction,  so  that  they  fit  accurately  over  the  upwardly  directed 
imbricated  scales  of  the  hair  itself;  then  of  one  or  two  layers  of  horny,  flattened 
nucleated  cells,  known  as  Huxley's  layer;  and  finally  of  a  single  layer  of  horny 
oblong  cells  without  visible  nuclei,  called  Henle's  layer. 

The  hair  follicle  contains  the  root  of  the  hair,  which  terniinates  in  a  bulbous 
extremity,  and  is  excavated  so  as  to  exactly  fit  the  papilla  from  which  it  grows. 
The  bulb  is  composed  of  polyhedral  epithelial  cells,  which  as  they  pass  upward 
into  the  root  of  the  hair  become  elongated  and  spindle-shaped,  except  some  in 
the  centre,  which  remain  polyhedral  Some  of  these  latter  cells  contain  pigment 
granules,  which  give  rise  to  the  color  of  the  hair.  It  occasionally  happens  that 
these  pigment  granules  completely  fill  the  cells  of  the  medullary  substance  in 
the  centre  of  the  bulb,  which  gives  rise  to  the  dark  tract  of  pigment  often  found, 
of  greater  or  less  length,  in  the  axis  of  the  hair. 


THE  APPENDAGES  OE  THE  SKIN  1161 

Tlie  shaft  of  the  hair  (scapiis  pili)  (Fig.  887)  consists  of  a  central  pitli  or  medulla, 
the  fibrous  part  of  the  hair,  and  the  true  cuticle  externally.  The  medulla  (■itih- 
stantia  meduUaris  pili)  occupies  the  centre  of  the  shaft  and  ceases  toward  the 
point  of  the  hair.  It  is  usually  wanting  in  the  fine  hairs  covering  the  surface  of 
the  body,  and  commonly  in  those  of  the  head.  It  is  found  in  the  shafts  of  all  thick 
hairs  and  in  the  deeper  parts  of  the  root  of  most  hairs.  It  is  more  opaque  and 
deeper  colored  when  ^■iewed  by  transmitted  light  than  the  fibrous  part;  but  when 
viewed  by  reflected  light  it  is  white.  It  is  composed  of  rows  of  polyhedral  cells, 
\\hich  contain  granules  of  eleidin  and  frequently  air  spaces.  The  cortical  substance 
of  the  hair  {substantia  corticalis  pili)  constitutes  the  chief  part  of  the  shaft;  its 
cells  are  elongated  and  unite  to  form  flattened  fusiform  cells.  Between  the  cells 
are  found  minute  spaces  which  contain  either  pigment  granules  in  dark  hair  or 
minute  air  spaces  in  white  hair.  In  addition  to  this  there  is  also  a  diffused  pig- 
ment contained  in  the  cells.  The  cells  which  form  the  outer  hair  membrane  or 
true  cuticle  icuticula  pili)  consist  of  a  single  layer  which  surrounds  those  of  the 
cortical  part;  they  are  converted  into  thin,  flat  scales,  having  an  imbricated  ar- 
rangement. 

Connected  with  the  hair  follicles  are  minute  bundles  of  involuntarj'  muscle 
fibres,  termed  Arrectores  pilonun  {mm.  arrectores  pilorum)  (Figs.  878  and  887). 
They  arise  from  the  superficial  layer  of  the  corium,  and  are  inserted  into  the  outer 
surface  of  the  hair  follicle,  below  the  entrance  of  the  duct  of  the  sebaceous  gland. 
They  are  placed  on  the  side  toward  which  the  hair  slopes,  and  by  their  action 
elevate  the  hair.^  When  the  hair  is  elevated  a  depression  forms  over  the  seat  of 
origin  of  the  muscle,  and  the  parts  about  the  hair  are  elevated.  This  condition 
is  known  as  goose  skin.  It  is  probable  that  the  contraction  of  these  muscles  aids 
in  emptying  sebaceous  glands. 

Bloodvessels  and  Nerves  (Fig.  878). — ^A  hair  follicle  possesses  a  rich  network  of  capillaries 
about  the  hyaline  membrane,  and  capillary  loops  pass  to  the  papilla.  We  have  little  knowledge 
as  to  nerve  terminations  of  the  human  hair. 

The  Sebaceous  Glands  (glandulae  sebaceae)  are  small,  sacculated,  glandular 
organs,  lodged  in  the  substance  of  the  corium.  They  are  found  in  most  parts  of 
the  skin,  but  are  especially  abundant  in  the  scalp  and  face ;  they  are  also  very  numer- 
ous around  the  apertures  of  the  anus,  nose,  mouth,  and  external  ear,  but  are  want- 
ing in  the  palms  of  the  hands  and  soles  of  the  feet.  Each  gland  consists  of  a 
single  duct,  more  or  less  capacious,  which  terminates  in  a  cluster  of  small  secreting 
pouches  or  saccules.  The  sacculi  connected  with  each  duct  vary  in  number, 
as  a  rule,  from  two  to  five,  but  in  some  instances  may  be  as  many  as  twenty. 
They  are  composed  of  a  transparent,  colorless  membrane,  enclosing  a  number 
of  epithelial  cells.  Those  of  the  outer  or  marginal  layer  are  small  and  polyhedral, 
and  are  continuous  with  the  lining  cells  of  the  duct.  The  remainder  of  the  sac 
is  filled  with  larger  cells,  containing  fat,  except  in  the  centre,  where  the  cells  have 
become  broken  up,  leaving  a  cavity  containing  their  debris  and  a  mass  of  fatty 
matter,  which  constitutes  the  sebaceous  secretion.  The  orifices  of  the  ducts 
open  most  frequently  into  the  hair  follicles,  but  occasionally  upon  the  general 
surface,  as  in  the  labia  minora  and  the  free  margins  of  the  lips.  On  the  nose 
and  face  the  glands  are  of  large  size,  distinctly  lobulated,  and  often  become  much 
enlarged  from  the  accumulation  of  pent-up  secretion.  The  largest  sebaceous 
glands  are  those  found  in  the  eyelids — the  ^Meibomian  glands. 

The  Sudoriferous  or  Sweat  Glands  {glandulae  sudoriferae)  (Figs.  878  and  888) 
are  the  organs  by  which  a  large  portion  of  the  aqueous  and  gaseous  materials 

'  Arthur  Thomson  suggests  that  the  contraction  of  these  muscles  on  follicles  which  contain  weak,  fiat  hairs  will 
tend  to  produce  a  permanent  curve  in  the  follicle,  and  this  curve  will  be  impressed  on  the  hair  which  is  moulded 
within  it,  so  that  the  hair,  on  emerging  through  the  skin,  will  be  curled.  Curved  hair  follicles  are  characteristic  of 
the  scalp  of  the  Bushman. 


1162  THE  ORGANS  OF  SPECIAL  SENSE 

is  excreted  by  the  skin.  They  are  found  in  almost  every  part  of  this  structure, 
being  absent  on  the  red  border  of  the  lips,  the  glans  penis,  and  inner  surface  of 
the  prepuce.  On  the  eyelids  they  are  somewhat  modified,  and  are  called  ciliary 
glands  (glandulae  ciliares  [MoUi]);  about  the  anus  they  are  extremely  large,  and 
are  called  circumanal  glands  {glandulae  circumanales).  The  sweat  glands  are 
situated  in  small  pits  below  the  under  surface  of  the  coriiun,  or,  more  frequently, 
in  the  subcutaneous  areolar  tissue,  surrounded  by  a  quantity  of  adipose  tissue. 
They  are  small,  lobular,  reddish  bodies,  consisting  of  a  single  convoluted  tube, 
from  which  the  efferent  duct  (ductus  sudoriferus)  proceeds  outward  through  the 
corium  and  cuticle,  becomes  somewhat  dilated  at  its  extremity,  and  opens  on  the 
surface  of  the  cuticle  by  an  oblique  valve-like  aperture  (porus  siidoriferus).  The 
duct,  as  it  passes  through  the  epidermis,  presents  a  spiral  arrangement,  being 
twisted  like  a  corkscrew,  in  those  parts  where  the  epidermis  is  thick;  where, 
however,  the  epidermis  is  thin,  the  spiral  arrangement  does  not  exist.  In  the 
superficial  layers  of  the  corium  the  duct  is  straight,  but  in  the  deeper  layers  it  is 
convoluted  or  even  twisted.  The  spiral  course  of  these  ducts  is  especially  distinct 
in  the  thick  cuticle  of  the  palm  of  the  hand  and  sole  of  the  foot.  The  size  of  the 
glands  varies.  They  are  especially  large  in  those  regions  where  the  flow  of  perspi- 
ration is  copious,  as  in  the  axillfe,  whei'e  they  form  a  thin,  mamillated  layer  of  a 
reddish  color,  which  corresponds  exactly  to  the  situation  of  the  hair  in  this  region; 
they  are  large  also  in  the  groin.  Their  number  varies.  They  are  most  numerous 
on  the  palm  of  the  hand,  presenting,  according  to  Krause,  2800  orifices  on  a  square 
inch  of  the  integument,  and  are  rather  less  numerous  on  the  sole  of  the  foot.  In 
both  of  these  situations  the  orifices  of  the  ducts  are  exceedingly  regular,  and  open 
on  the  curved  surface  ridges.  In  other  situations  they  are  more  irregularly 
scattered,  but  the  number  in  a  given  extent  of  surface  presents  a  fairly  uniform 
average.  In  the  neck  and  back  they  are  least  numerous,  their  number  amounting 
to  417  on  the  square  inch  (Krause).  Their  total  number  is  estimated  by  the  same 
writer  at  2,381,248,  and  supposing  the  aperture  of  each  gland  to  represent  a  surface 
of  -g^  of  an  inch  in  diameter,  he  calculates  that  the  whole  of  these  glands  would 
present  an  evaporating  surface  of  about  eight  square  inches.  Each  gland  consists 
of  a  single  tube  intricately  convoluted,  terminating  at  one  end  by  a  blind  extremity, 
and  opening  at  the  other  end  upon  the  surface  of  the  skin.  The  wall  of  the  duct 
is  thick,  the  lumen  seldom  exceeding  one-third  of  the  diameter  of  the  tubes.  The 
tube,  both  in  the  gland  and  where  it  forms  the  excretory  duct,  consists  of  two 
layers  (except  in  the  epidermis,  where  the  epithelium  of  this  layer  forms  the  wall) 
— an  outer,  formed  by  fine  areolar  tissue,  and  an  inner  layer  of  epithelium.  The 
external  coat  is  thin,  continuous  with  the  superficial  layer  of  the  corium,  and  extends 
only  as  high  as  the  surface  of  the  corium.  The  epithelial  lining  in  the  distal 
part  of  the  coiled  tube  consists  of  a  single  layer  of  cubical  cells,  supported  on  a 
basement  membrane.  Between  the  epithelium  and  the  fibrocellular  coat  lies  a 
layer  of  longitudinally  or  obliquely  arranged  involuntary  muscle  fibres,  the  con- 
traction of  which  aid  in  the  expulsion  of  the  sweat.  In  the  proximal  part  there 
are  two  or  more  layers  of  polyhedral  cells  lined  on  the  internal  surface  (next  the 
lumen  of  the  tube)  by  a  delicate  membrane  devoid  of  muscle  fibres.  The  contents 
of  the  smaller  sweat  glands  is  quite  fluid;  but  in  the  larger  glands  the  contents 
are  semifluid  and  opaque,  and  contain  a  number  of  colored  granules  and  cells 
which  appear  analogous  to  epithelial  cells. 

The  bloodvessels  are  branches  from  the  subcutaneous  vessels  and  the  arterial  plexus  of  the 
deep  part  of  the  corium.  Numerous  amyelinic  nerve  fibres  lie  upon  the  membrana  propria  of  a 
sweat  gland.  From  them  fibrils  pass  inward  and  terminate  by  end  bulbs  upon  the  cells  of  the  gland. 


THE  ORGANS  OF  VOICE  AND  EESPIEATION. 


THE  respiratory  organs  (apparattis  respiratorius)  consist  of  the  larynx,  or  organ  of 
voice,  the  trachea,  bronchi,  lungs,  and  pleurae. 


THE  LARYNX. 

The  larynx,  or  organ  of  voice,  is  placed  at  the  upper  part  of  the  air  passage. 
It  is  situated  between  the  trachea  and  base  of  the  tongue,  at  the  upper  and  fore 
part  of  the  neck,  where  it  forms  a  considerable  projection  in  the  middle  line. 
On  either  side  of  it  lie  the  great  vessels  of  the  neck;  behind,  it  forms  part  of  the 
boundary  of  the  pharynx,  and  is  covered  by  the  mucous  membrane  lining  that 
cavity.  Its  vertical  extent  corresponds  to  the  fourth,  fifth,  and  sixth  cervical  ver- 
tebrae, but  it  is  placed  somewhat  higher  in  the  female  and  also  during  child- 
hood. 

According  to  Sappey,  the  average  measurements  of  the  adult  larynx  are  as 
follows : 

In  males.  In  females. 

Vertical  diameter 44  mm.  36  mm. 

Transverse  diameter 43     "  41     " 

Antero-posterior  diameter 36     "  26     " 

Circumference 136     "  112     " 

Until  puberty  there  is  no  marked  difTerence  between  the  larynx  of  the  male  and  that  of  the 
female.  In  the  latter  its  fiu-ther  increase  in  size  is  only  slight,  whereas  in  the  former  the  increase 
is  great;  all  the  cartilages  are  enlarged,  and  the  thyroid  becomes  prominent  as  the  pomum  Adami 
in  the  middle  line  of  the  neck,  while  the  length  of  the  glottis  is  nearly  doubled. 

The  larynx  is  broad  above,  where  it  presents  the  form  of  a  triangular  box, 
flattened  behind  and  at  the  sides,  and  bounded  in  front  by  a  prominent  vertical 
ridge.  Below,  it  is  narrow  and  cylindrical.  It  is  composed  of  cartilages,  which 
are  connected  by  ligaments  and  moved  by  numerous  muscles.  It  is  lined  by 
mucous  membrane,  which  is  continuous  above  with  that  lining  the  pharynx  and 
below  with  that  of  the  trachea.  On  each  side  internal  to  the  thyroid  cartilage 
a  small  recess,  the  recessus  pyriformis,  extends  forward  from  the  cavity  of  the 
pharynx  (p.  1231). 

The  Cartilages  of  the  Larynx  {cartilagines  laryncjis)  are  nine  in  number,  three 
single  and  three  pairs: 

Thyroid.  Two  Arytenoid. 

Cricoid.  Two  Cornicula  Laryngis. 

Epiglottis.  Two  Cuneiform. 

The  Thyroid  Cartilage  (cartilago  thijroidea)  (Figs.  891  and  892)  is  the  largest 
cartilage  of  the  larynx.  It  consists  of  two  lateral  lamellee  or  alae,  united  at  an  acute 
angle  in  front,  forming  a  vertical  projection  in  the  midline,  which  is  prominent 

(1163) 


1164 


THE  ORGANS  OF  VOICE  AND  BESPIBATION 


above  and  called  the  pomum  Adami  {prominentia  laryngea).  This  prominence 
is  subcutaneous,  is  more  distinct  in  the  male  than  in  the  female,  and  is  often 
separated  from  the  integument  by  a  bursa,  the  bursa  subcutanea  prominentiae 
laryngeae.  The  anterior  borders  of  the  alse  of  the  thyroid  cartilage  which  are 
continuous  below  are  separated  above  by  a  V-shaped  notch,  the  thyroid  notch 
{incisura  thyroidea  superior).  The  posterior  borders  are  free,  rounded,  and 
somewhat  thickened,  and  are  extended  in  the  form  of  superior  and  inferior 
cornua. 

The  Older  surface  of  each  ala  (Fig.  891)  presents  an  oblique  ridge  {linea  obliqua), 
which  passes  downward  and  forward  from  a  tubercle  situated  near  the  root  of  the 
superior  cornu,  the  superior  tubercle  (tuberculum.  thyroideum  superitis),  to  a  small 
tubercle  near  the  anterior  part  of  the  lower  border,  the  inferior  tubercle  (tuberculum 
thyroideum'  inferius).  This  ridge  gives  attachment  to  the  Sternothyroid  and  Thyro- 
hyoid muscles,  and  the  portion  of  cartilage  included  between  it  and  the  posterior 
border  gives  attachment  to  part  of  the  Inferior  constrictor  muscle. 


ASCENDtNa 


Fig.  890. — Sagittal  section  of  a  man  twenty 
(After  W.  Braune.) 


of  the  thjToid  and 


The  inner  surface  (Fig.  892)  of  each  ala  is  smooth,  slightly  concave,  and  covered 
by  the  mucous  membrane  of  the  outer  wall  of  the  sinus  pyriformis  above  and 
behind;  but  in  front,  in  the  receding  angle  formed  by  the  junction  of  the  alse, 
are  attached  the  epiglottis,  the  true  and  false  vocal  cords,  the  Thyroarj'tenoid 
and  Thyroepiglottidean  muscles,  and  the  thyroepiglottidean  ligament. 

The  upper  border  (Fig.  891)  is  sinuously  curved,  being  concave  at  its  posterior 
part,  then  rising  into  a  convex  outline  in  front;  it  gives  attachment  throughout 
its  whole  extent  to  the  thyrohyoid  membrane. 

The  lower  border  (Fig.  892)  is  nearly  straight  in  front,  but  behind,  close  to  the 
cornu,  it  is  concave,  the  two  parts  being  separated  by  the  inferior  tubercle.  A 
small  part  of  it,  in  and  near  the  median  line,  is  connected  to  the  cricoid  cartilage  by 


THE  LARYNX 


1165 


the  middle  portion  of  the  cricothyroid  membrane  (membrcma  cricothyroidca) ;  and,  on 
either  side,  by  the  Cricothyroid  muscle. 

The  posterior  borders  (Fig.  892)  are  thick  and  rounded,  and  eacli  terminates 
above,  in  a  superior  comu  (cornu  superius),  and  below,  in  an  inferior  comu  {cornu 
inferius).  The  two  superior  cornua  are  long  and  narrow,  directed  upward,  l^ack- 
ward,  and  inward,  and  terminate  in  conical  extremities,  which  give  attachment 
to  the  lateral  thyrohyoid  ligaments.  The  two  inferior  cornua  are  short  and  thick; 
they  pass  downward,  with  a  slight 
inclination  forward  and  inward, 
and  each  presents  on  its  inner  sur- 
face a  small  oval  articular  facet  for 
articulation  with  the  side  of  the 
cricoid  cartilage  (Fig.  891).  The 
posterior  border  receives  the  in- 
sertion of  the  Stylopharyngeus  and 
Palatopharyngeus  muscles  on  each 
side. 

Daring  infancy  the  alte  of  the  thyroid 
cartilage  are  joined  to  each  other  by  a 
narrow,  lozenge-shaped  strip,  named  the 
intrathyroid  cartilage.  This  strip  ex- 
tends from  the  upper  to  the  lower  border 
of  the  thyroid  cartilage  in  the  middle 
line,  and  is  distinguished  from  the  al;e 
by  being  more  transparent  and  more 
flexible. 


Epiglott 


Thyroid. 


Cuneiform  cartilage. 


Arytenoid. 


PiMerior 
iiiiface. 


The  Cricoid  Cartilage  {cartilago 
cricoidea)  (Figs.  891  and,  892)  is  so 
called  from  its  resemblance  to  a 
signet  ring  {^f)cxo(;,  a  ring).  It  is 
smaller,  but  thicker  and  stronger 
than  the  thyroid  cartilage,  and 
forms  the  lower  and  back  part  of 
the  cavity  of  the  larynx.  It  is  hya- 
line cartilage,  and  consists  of  two 
parts — a  quadrate  portion,  situated 
behind,  and  a  narrow  ring,  or  arch, 
one-fourth  or  one-fifth  the  depth 
of  the  posterior  part,  situated  in 
front.  The  posterior  scjuare  por- 
tion rapidly  narrows  at  the  sides  of 
the  cartilage,  at  the  expense  of  the 
upper  border,  into  the  anterior 
portion. 

Its  posterior  portion,  or  lamina 
(lamina  cartilaginis  cricoideae),  is  very  deep  and  broad,  and  measures  from  above 
downward  about  an  inch  (2.5  cm.);  it  presents,  on  its  posterior  surface,  in  the 
middle  line,  a  vertical  ridge  for  the  attachment  of  the  longitudinal  fibres  of  the 
oesophagus,  and  on  either  side  a  broad  depression  for  the  Cricoarytenoideus 
posticus  muscle. 

Its  anterior  portion,  or  arcus  {arcus  cartilaginis  cricoideae),  is  narrow  and  convex, 
and  measures  vertically  about  one-fourth  or  one-fifth  of  an  inch  (6  to  5  mm.); 
it  affords  attachment  externally  in  front  and  at  the  sides  to  the  Cricothyroid 
muscles,  and,  behind,  to  part  of  the  Inferior  constrictor. 


Cricoid. 

Articula  r  facet  for 
arytoioid  cartilage. 

A rlicular  facet  for 
inferior  cornu  of 
thyroid  cartilage. 


Fig.  892. — The  cartilages  of  the  laryi 


1166  THE  ORGANS  OF  VOICE  AND  BESPIBA  TION 

At  the  junction  of  the  posterior  quadrate  portion  with  the  rest  of  the  cartilage 
is  a  small  round  articular  eminence,  for  articulation  with  the  inferior  cornu  of  the 
thyroid  cartilage. 

The  lower  border  of  the  cricoid  cartilage  is  horizontal,  and  connected  to  the 
uppermost  ring  of  the  trachea  by  fibrous  membrane  (Figs.  891  and  892). 

Its  upper  border  is  directed  obliquely  upward  and  backward,  owing  to  the  great 
depth  of  the  posterior  surface.  It  gives  attachment,  in  front,  to  the  middle 
portion  of  the  cricothyroid  membrane ;  at  the  sides,  to  the  lateral  portion^  of  the 
same  membrane  and  to  the  lateral  Cricoarytenoid  muscle ;  hehind,  it  presents,  in 
the  middle,  a  shallow  notch,  and  on  each  side  of  this  is  a  smooth,  oval  surface, 
directed  upward  and  outward,  for  articulation  with  the  base  of  an  arytenoid 
cartilage. 

The  inner  surface  of  the  cricoid  cartilage  is  smooth,  and  covered  by  mucous 
membrane. 

The  Arytenoid  Cartilages  {cartilagines  arytenaideae)  (Fig.  892)  are  two  in  number, 
and  situated  at  the  upper  border  of  the  cricoid  cartilage,  at  the  back  of  the  larynx 
in  the  interval  between  the  posterior  borders  of  the  alffi  of  the  thyroid  cartilages. 
Each  cartilage  is  in  form  a  three-sided  pyramid,  and  presents  for  examination 
three  surfaces,  a  base,  and  an  apex. 

The  posterior  surface  is  triangular,  smooth,  concave,  and  gives  attachment  to 
the  transverse  portion  of  the  Arytenoid  muscle. 

The  antero-extemal  surface  is  somewhat  convex  and  rough.  It  presents,  near 
its  apex,  a  small  elevation,  the  colliculus;  from  this  a  ridge  (crista  arcuata)  passes 
backward  and  then  forward  and  downward  into  a  sharp-pointed  process,  the 
vocal  process.  This  ridge  separates  a  deep  depression  above,  the  fovea  triangularis, 
from  a  broader  and  shallower  depression  below,  the  fovea  oblonga.  A  short  dis- 
tance above  the  base  a  small  tubercle  on  the  anterior  border  gives  origin  to  the 
ligament  of  the  false  vocal  cord,  the  superior  thyroarytenoid  ligament.  To  the 
outer  part  of  the  ridge,  as  well  as  the  surface  above  and  below,  is  attached  the 
Thyroarytenoid  muscle. 

The  internal  surface  is  narrow,  smooth,  and  flattened,  and  forms  the  lateral 
boundary  of  the  respiratory  part  of  the  glottis. 

The  base  (basis)  of  each  cartilage  is  broad,  and  presents  a  concave  smooth 
surface,  for  articulation  with  the  cricoid  cartilage.  Two  of  its  angles  require 
special  mention:  The  external  angle,  which  is  short,  rounded,  and  prominent, 
projects  backm'ard  and  outward,  and  is  termed  the  muscular  process  (processus 
muscularis),  from  receiving  the  insertion  of  the  Posterior  and  Lateral  crico- 
arytenoid muscles.  The  anterior  angle,  also  prominent,  but  more  pointed,  pro- 
jects horizontally  forward,  and  gives  attachment  to  the  inferior  thyroarytenoid 
ligament,  the  supporting  ligament  of  the  true  vocal  cord.  This  angle  is  called 
the  vocal  process  (processus  vocalis). 

The  apex  of  each  cartilage  is  pointed,  curved  backward  and  inward,  and  sur- 
mounted by  a  small  conical,  cartilaginous  nodule,  the  comiculum  laryngis,  articu- 
lated with  or  united  to  the  arytenoid  cartilage. 

The  Comicula  Laryngis  or  Cartilages  of  Santorini  (cartilagines  corniculatae)  (Figs. 
892  and  898)  are  two  small  conical  nodules,  consisting  of  yellow  elastic  cartilage, 
which  articulate  with  the  summits  of  the  arytenoid  cartilages  and  serve  to  pro- 
long them  backward  and  inward.  They  are  situated  in  the  posterior  parts  of  the 
arytenoepiglottic  folds,  and  are  sometimes  united  to  the  arytenoid  cartilages. 

The  Cuneiform  Cartilages  or  Cartilages  of  Wrisberg  (cartilagines  cuneiformes) 
(Figs.  892  and  897)  are  two  small,  elongated  pieces  of  yellow  elastic  cartilage, 
placed  one  on  each  side,  in  the  arytenoepiglottic  fold  (plica  aryepiglottica)  (Fig. 
897),  where  they  give  rise  to  small  whitish  elevations  on  the  inner  surface  of  the 
mucous  membrane,  jtist  in  front  of  the  arytenoid  cartilages. 


THE  LARYNX  1167 

The  Epiglottis  {cartilaqo  epiqlottlca)  (Figs.  892  and  893)  is  a  thin,  flexible  lamella 
of  fibrocartilage,  of  a  yellowish  color,  shaped  like  a  leaf,  and  projecting  behind  the 
tongue  in  front  of  the  superior  opening  of  the  larynx.  The  projecting  extremity  is 
broad  and  rounded;  its  attached  part  or  apex  (pctiolus  epigloUidis)  is  long,  narrow, 
and  connected  to  the  receding  angle  between  the  two  ahe  of  the  thyroid  cartilage, 
just  below  the  median  notch,  by  a  ligamentous  band,  the  thyroepiglottic  ligament 
(Fig.  894).  The  lower  part  of  its  anterior  surface  is  connected  to  the  upper  Ijorder 
of  the  body  of  the  hyoid  bone  by  an  elastic  ligamentous  band,  the  hyoepiglottic 
ligament. 

Its  anterior  or  lingual  surface  is  curved  forward,  toward  the  tongue,  and  covered 
at  its  upper,  free  part  by  mucous  membrane,  which  is  reflected  on  to  the  sides  and 
base  of  the  organ,  forming  a  median  and  two  lateral  folds,  the  glossoepiglottic 
folds  (Fig.  897);  the  lateral  folds  are  partly  attached  to  the  wall  of  the  pharynx. 
The  depressions  between  the  epiglottis  and  base  of  the  tongue  on  each  side  of  the 
median  fold  are  named  the  valleculae.  The  lower  part  of  the  anterior  surface  of 
the  epiglottis  lies  behind  the  hyoid  bone,  the  thyrohyoid  membrane,  and  upper 
part  of  the  thyroid  cartilage,  but  is  separated  from  these  structures  by  a  mass  of 
fatty  tissue. 

Its  posterior  or  laryngeal  surface  is  smooth,  concave  from  side  to  side,  concavo- 
convex  from  above  downward;  its  lower  part  projects  backward  as  an  elevation, 
the  tubercle  or  cushion  (iuberculwn  epiglotticum)  (Fig.  893).  When  the  mucous 
membrane  is  removed,  the  surface  of  the  cartilage  is  seen  to  be  indented  by 
a  number  of  small  pits,  in  which  mucous  glands  are  lodged.  To  its  sides  the 
arytenoepiglottic  folds  are  attached  (Fig.  897). 

Structure. — The  cornicula  laryngis  and  cuneiform  cartilages,  the  epiglottis,  and  the  apices 
of  the  arytenoids  at  first  consist  of  hyaline  cartilage,  but  later  elastic  fibres  grow  in  from  the 
perichondrium,  and  eventually  they  are  converted  into  yellow  fibrocartilage;  they  show  little 
tendency  to  calcification.  The  thyroid,  cricoid,  and  the  greater  part  of  the  arytenoids  consist 
of  hyaline  cartilage,  and  become  more  or  less  ossified  as  age  advances.  Ossification  commences 
aljout  the  twenty-fifth  year  in  the  thyroid  cartilage,  somewhat  later  in  the  cricoid  and  aryte- 
noids; by  the  sixty-fifth  year  these  cartilages  may  be  completely  converted  into  bone. 

Ligaments. — ^The  ligaments  of  the  larynx  are  extrinsic — i.  e.,  those  connecting 
the  thyroid  cartilage  and  epiglottis  with  the  hyoid  bone,  and  the  cricoid  cartilage 
with  the  trachea;  and  i)iiriusic,  those  which  connect  the  several  cartilages  of  the 
larynx  to  each  other. 

Extrinsic  Ligaments. — ^The  ligaments  connecting  the  thyroid  cartilage  with  the 
hyoid  bone  are  foin-  in  number — the  thyrohyoid  membrane,  the  two  lateral 
thyrohyoid  ligaments,  and  the  hyoepiglottic  ligament. 

The  Thyrohyoid  Membrane  (membraiia  hyothyreoidea)  (Fig.  894)  is  a  broad, 
fibroelastic,  membranous  layer,  attached  below  to  the  upper  border  of  the  thyroid 
cartilage,  and  above  to  the  upper  margin  of  the  posterior  surface  of  the  body  and 
greater  cornua  of  the  hyoid  bone,  thus  passing  behind  the  posterior  surface  of 
the  hyoid,  and  being  separated  from  it  by  a  synovial  bursa  (bursa  m.  sternohyoidei), 
which  facilitates  the  upward  movement  of  the  larynx  during  deglutition.  It 
is  thicker  in  the  middle  line  dian  at  either  side.  This  thickening  is  due  to  elastic 
Hbres,  and  constitutes  the  middle  thyrohyoid  ligament  (ligamentum  hyothyreoidcum 
medium).  On  each  side  the  posterior  extremity  of  the  membrane  is  thickened 
by  elastic  fibres,  constituting  the  lateral  thyrohyoid  ligament  (ligamenium  hyothy- 
reoidemn  laterale).  The  thyrohyoid  membrane  is  pierced  on  each  side  by  the  supe- 
rior laryngeal  vessels  and  the  internal  branch  of  the  superior  laryngeal  nerve.  The 
anterior  surface  of  the  thyrohyoid  membrane  is  in  relation  with  the  Thyrohyoid, 
Sternohyoid,  and  Omohyoid  muscles  and  with  the  body  of  the  hyoid  bone.  The 
two  lateral  ligaments  are  rounded,  elastic  cords,  which  pass  between  the  superior 


1168 


THE  ORGANS  OF  VOICE  AND  RESPIRATION 


EPIGLOTTIDEUS 


cornua  of  the  thyroid  cartilage  and  the  extremities  of  the  greater  cornua  of  the 
hyoid  bone.  A  small  cartilaginous  nodule  (cartilago  iriiicea),  sometimes  bony, 
is  frequently  found  in  each. 

The  ligament  connecting  the  epiglottis  with  the  hyoid  bone  is  the  hyoejnglqtiic. 
In  addition  to  this  extrinsic  ligament,  the  epiglottis  is  connected  to  the  tongue  by 
the  three  glossoepiglottic  folds  of  mucous  membrane,  which  may  also  be  considered 
as  extrinsic  ligaments  of  the  epiglottis.  The  hyoepiglottic  ligament  {ligameutmn 
hyoepiglotticum)  is  an  elastic  band,  which  extends  from  the  anterior  surface  of 
the  epiglottis,  near  its  apex,  to  the  upper  border  of  the  body  of  the  hyoid  bone. 
The  cricotracheal  ligament  (ligameiitum  cricotracheale)  connects  the  cricoid 
cartilage  with  the  first  ring  of  the  trachea.  It  resembles  the  fibrous  membrane 
which  connects  the  cartilaginous  rings  of  the  trachea. 

Intrinsic  Ligaments. — ^The  ligaments  connecting  the  thyroid  cartilage  to  the 
cricoid  are  three  in  number — the  cricothyroid  membrane  and  the  two  capsular 
ligaments. 

The  Cricothyroid  Membrane  (conus  elasticus)  (Figs.  891  and  901)  is  composed 
mainly  of  yellow  elastic  tissue.  It  consists  of  three  parts,  a  central  triangular 
portion  and  two  lateral  portions.     The  central  part  (ligamentum  cricothyreoideiim 

mediuvi)  is  thick  aiid  strong, 
narrow  above  and  broaden- 
ing out  below.  It  connects 
the  contiguous  margins  of  the 
thyroid  and  cricoid  cartilages. 
It  is  convex,  concealed  on 
each  side  by  the  Cricothyroid 
muscle,  but  subcutaneous  in 
the  middle  line;  it  is  crossed 
horizontally  by  a  small  anas- 
tomotic arterial  arch,  formed 
by  the  junction  of  the  two 
cricothyroid  arteries.  The 
lateral  portions  are  thinner 
and  lie  close  under  the  mucous 
membrane  of  the  larynx. 
They  extend  from  the  superior 
border  of  the  cricoid  cartilage 
to  the  inferior  margin  of  the 
true  vocal  cords  with  which 
they  are  continuous.  These 
cords  may  therefore  be  re- 
garded as  the  free  borders  of 
the  lateral  portions  of  the 
cricothyroid  membrane;  they 
extend  from  the  vocal  processes  of  the  arytenoid  cartilages  to  the  receding 
angle  of  the  thyroid  cartilage  near  its  centre.  The  lateral  portions  are  lined 
internally  by  mucous  membrane,  and  are  separated  from  the  thyroid  cartilage 
by  the  Cricoarytenoideus  lateralis  and  Thyroarytenoideus  muscles. 

A  capsular  ligament,  strengthened  posteriorly  by  a  well-marked  fibrous  band, 
encloses  the  articulation  of  the  inferior  cornu  of  the  thyroid  with  the  cricoid 
cartilage  on  each  side.     The  articulation  is  lined  by  synovial  membrane. 

Each  arytenoid '  cartilage  is  connected  to  the  cricoid  by  a  capsular  ligament 
(capsula  articularis  cricoarytaenoidea)  and  a  posterior  cricoarytenoid  ligament 
(ligamentum  cricoarytenoideum  posterius).  The  capsular  ligament  is  thin  and 
loose,  and  is  attached  to  the  margin  of  the  articular  surfaces,  and  lined  by  synovial 


-Coronal  section  of  lary 
(Testut.) 


THE  LARYNX 


1169 


membrane.     The  posterior  cricoarjrtenoid  ligament  extends  from  the  cricoid  to 
the  inner  and  back  part  of  the  base  of  the  arytenoid  cartilage. 

The  thyroepiglottic  ligament  (ligmnentum  thyreoepigloHlcum)  (Fig.  894)  is  a 
long,  .slender  elastic  cord  which  connects  the  apex  of  the  epiglottis  with  the  internal 
surface  of  the  receding  angle  of  the  thyroid  cartilage,  immediately  beneath  the 
^nedian  notch,  above  the  attachments  of  the  false  and  true  vocal  cords. 

Movements. — The  articulation  between  the  inferior  cornu  of  the  thyroid  and  the  cricoid 
cartilage  on  either  side  is  a  diarthroidal  one,  and  permits  of  rotary  and  gliding  movements. 
The  rotary  movement  is  one  in  which  the  inferior  cornua  of  the  thyroid  cartilage  rotate  upon 
the  cricoid  cartilage  around  an  axis  passing  transversely  through  both  joints.  The  gliding 
movement  consists  in  a  limited  shifting  of  the  cricoid  on  the  thyroid  in  different  directions. 

The  articulation  between  the  arytenoid  cartilages  and  the  cricoid  is  also  a  diarthrodial  one, 
and  permits  of  two  varieties  of  movement — one  a  rotation  of  the  arytenoid  on  a  vertical  axis, 
whereby  the  vocal  process  is  moved  outward  or  inward  and  the  opening  of  the  rima  glottidis 
increased  or  diminished;  the  other  is  a  gliding  movement  and  allows  the  arytenoid  cartilages 
to  approach  or  recede  from  each  other;  from  the  direction  and  slope  of  the  articular  surfaces 
outward  gliding  is  accompanied  by  a  forward  and  downward  movement.  The  two  movements 
of  gliding  and  rotation  are  associated,  the  gliding  inward  being  connected  with  inward  rota- 
tion, and  the  gliding  outward  with  outward  rotation.  The  posterior  cricoarytenoid  ligaments 
limit  the  forward  movement  of  the  arytenoid  cartilages  on  the  cricoid. 

Interior  of  the  Larynx  (Figs.  893,  894,  and  897).— The  cavity  of  the  larynx 
(cavum  laryngis)  extends  from  the  superior  aperture  of  the  larynx  to  the  lower 
border  of  the  cricoid  cartilage.  It  is  divided  into  two  parts  by  the  projection 
inward  of  the  true  vocal 
cords,  between  which  is 
a  narrow  triangular  fis- 
siu'e  or  chink,  the  rima 
glottidis.  The  portion 
of  the  cavity  of  the 
larynx  above  the  true 
vocal  cords,  sometimes 
called  the  vestibule 
(vestibulum  laryngis),  is 
wide  and  triangular  in 
shape,  its  base  or  an- 
terior wall  presenting, 
however,  about  its  centre 
the  backward  projection 
of  the  cushion  of  the 
epiglottis.  It  contains 
the  false  vocal  cords 
(plicae  veniriculares), 
and  between  these  and 
the  true  vocal  cords  are 
the  ventricles  of  the 
larynx.  The  portion 
below  the  true  vocal 
cords  is  at  first  of  an 
elliptical  form,  but  lower 

down  it  widens  out,  assumes  a  circular  form,  and  is  continuous  with  the  tube  of 
the  trachea. 

The  Superior  Aperture  of  the  Lar3mx  (aditus  laryngis)  (Figs.  893  and  897)  is 
a  triangular  or  cordiform  opening,  wide  in  front,  narrow  behind,  and  sloping 
obliquely  downward  and  backward.  It  is  bounded,  in  front,  by  the  epiglottis; 
behind,  by  the  apices  of  the  arytenoid  cartilages  and  the  cornicula  laryngis;  and 

74 


Fig.  S94. — Sagittal  section  of  larynx,  right  half.     (Testut.) 


1170 


THE  OBGAWS  OF  VOICE  AND  BESPIBA  TION 


laterally,  by  a  fold  of  mucous  membrane,  enclosing  ligamentous  and  muscle 
fibres,  stretched  between  the  side  of  the  epiglottis  and  the  apex  of  the  arytenoid 
cartilage;  this  is  the  arytenoepiglottic  fold  (Figs.  894  and  897),  on  the  margin  of 
which  the  cuneiform  cartilage  forms  a  more  or  less  distinct  whitish  prominence. 
The  superior  or  false  vocal  cords  {plicae  ventriculares)  (Figs.  893  and  894),  so 
called  because  they  are  not  directly  concerned  in  the  production  of  the  voice, 
are  two  thick  folds  of  mucous  membrane,  each  enclosing  a  very  narrow  band  of 
connective  tissue,  the  so-called  superior  thyroarjrtenoid  ligament.  This  is  attached 
in  front  to  the  angle  of  the  thyroid  cartilage  immediately  below  the  attachment 
of  the  epiglottis,  and  behind  to  the  antero-external  surface  of  the  arytenoid  carti- 
lage. The  lower  border  of  this  ligament,  enclosed  in  mucous  membrane,  forms  a 
free  crescentic  margin,  which  constitutes  the  upper  boundary  of  the  ventricle 
of  the  larynx. 


Fig.  895. — Muscles  of  larynx,  front '\ 
thyroids  and  right  Thyrohyoid  hav 
(Testut.) 


Fig    896  — Muscles  of  larynx,  from  behind 
(Testut.) 


The  inferior  or  true  vocal  cords  {plicae  vocales)  (Figs.  893  and  894),  so  called 
from  their  being  concerned  in  the  production  of  sound,  are  two  strong  bands 
named  the  inferior  thyroarytenoid  ligaments.  Each  ligament  consists  of  a  band 
of  yellow  elastic  tissue,  attached  in  front  to  the  depression  between  the  alse  of  the 
thyroid  cartilage,  and  behind  to  the  vocal  process  at  the  base  of  the  arytenoid. 
Its  lower  border  is  continuous  with  the  thin  lateral  part  of  the  cricothyroid  mem- 
brane. Its  upper  border  forms  the  lower  boundary  of  the  ventricle  of  the  larynx. 
Externally,  the  Thyroarytenoideus  muscle  lies  parallel  with  it.  It  is  covered 
internally  by  mucous  membrane,  which  is  extremely  pale,  thin,  and  closely  ad- 
herent to  its  surface.  The  node-like  attachment  of  the  ligament  to  the  thyroid 
cartilage  appears  as  a  yellow  spot  {macula  flava) ;  the  vocal  process  also  shines 
through  the  mucosa  as  a  yellowish  spot. 

The  ventricle  of  the  larynx  or  laryngeal  sinus  {ventriculus  laryngis  [Morgagnii]) 
(Figs.  893  and  894)  is  an  oblong  fossa,  situated  between  the  superior  and  inferior 
vocal  cords  on  each  side,  and  extending  nearly  their  entire  length.  This  fossa  is 
bounded,  above,  by  the  free  crescentic  edge  of  the  false  vocal  cord;  below,  bj-  the 
straight  margin  of  the  true  vocal  cord ;  externally,  by  the  mucous  membrane  cover- 


THE  LARYNX 


1171 


ing  the  corresponding  Thyroarytenoideus  muscle.  The  anterior  part  of  the  ven- 
tricle leads  up  by  a  narrow  opening  into  a  cecal  pouch  of  mucous  membrane  of 
variable  size,  called  the  laryngeal  saccule. 

The  larjTHgeal  saccule  [appoidix  vcntricidi)  (Fig.  893),  or  laryngeal  pouch,  is 
a  membranous  sac,  placed  between  the  superior  vocal  cord  and  the  inner  surface 
of  the  thyroid  cartilage,  occasionally  extending  as  far  as  its  upper  border  or  even 
higher;  it  is  conical  in  form,  and  curved  slightly  backward.  On  the  surface 
of  its  mucous  membrane  are  the  openings  of  si.xty  or  seventy  mucous  glands, 
which  are  lodged  in  the  submucous  areolar  tissue.  This  sac  is  enclo.sed  in  a 
fibrous  capsule,  continuous  below  with  the  superior  thyroarytenoid  ligament; 
its  laryngeal  surface  is  covered  by  a  few  delicate  muscle  fasciculi  wliich  arise 
from  the  apex  of  the  arytenoid  cartilages  and  Ijecome  lost  in  the  fold  of  mucous 
membrane  extending  between  the  arytenoid  cartilage  and  the  side  of  the  epiglottis 
{they  were  named  by  Hilton  the  compressor  sacculi  laryngis);  while  its  exterior 
is  covered  by  the  Thyroarytenoideus  and  Thyroepiglottideus  muscles.  These 
muscles  compress  the  laryngeal  saccule,  and  express  the  secretion  it  contains  upon 
the  vocal  cords  to  lubricate  their  surfaces.  The  saccule  assists  in  imparting 
resonance  to  the  voice. 


APEX    OF   SUP.   HORN    OF 


-^1. 


CORNICULUM 


FORM 
CARTILAGE 
RYTENO    EPIGLOT- 
TIDIAN   FOLD 
PEX    OF    GREAT 
ORN    OF   HYOID 


Fig.  897.— Larynx, 


SLOTTIDIAN    FO 

wed  from  abo 


The  Rima  Glottidis  (Figs.  893  and  897)  is  the  elongated  fissure  or  chink  between 
the  true  vocal  cords  in  front,  and  between  the  bases  and  vocal  processes  of  the 
arytenoid  cartilages  behind.  It  is  therefore  frequently  subdivided  into  an  anterior, 
interligamentous  or  vocal  portion,  the  glottis  vocaUs  (pars  intermenibrauacea), 
and  a  posterior,  intercartilaginous  or  respiratory  portion,  the  glottis  respiratoria 
(pars  infercartilaginea).  Posteriorly  it  is  limited  by  the  mucous  membrane  passing 
between  the  arytenoid  cartilages.  The  vocal  portion  averages  about  three- 
fifths  of  the  length  of  the  entire  aperture.  It  is  the  narrowest  part  of  the  cavity 
of  the  larynx,  and  its  level  corresponds  to  the  bases  of  the  arytenoid  cartilages. 
Its  length,  in  the  male,  measures  rather  less  than  an  inch  (23  mm.);  in  the  female 
it  is  shorter  (16  to  20  mm.).  The  width  and  shape  of  the  rima  glottidis  vary 
with  the  movements  of  the  vocal  cords  and  arytenoid  cartilages  during  respiration 
and  phonation.  In  the  condition  of  rest — /.  e.,  when  those  structures  are  unin- 
fluenced by  muscular  action,  as  in  quiet  respiration,  the  glottis  vocalis  is  triangular, 
with  its  apex  in  front  and  its  base  behind,  the  latter  being  represented  by  a  line 


1172  THE  ORGANS  OF  VOICE  AND  RESPIRATION 

about  8  mm.  {\  inch)  long,  connecting  the  anterior  extremities  of  the  vocal 
processes,  while  the  inner  surfaces  of  the  arytenoids  are  parallel  to  each  other, 
and  hence  the  glottis  respiratoria  is  rectangular.  During  extreme  adduction 
of  the  cords,  as  in  the  emission  of  a  high  note,  the  glottis  vocalis  is  reduced  to  a 
linear  slit  by  the  apposition  of  the  cords,  while  the  glottis  respiratoria  is  triangular, 
its  apex  corresponding  to  the  anterior  extremities  of  the  vocal  processes  of  the 
arytenoids,  which  are  approximated  by  the  inward  rotation  of  the  cartilages. 
Conversely  in  extreme  abduction  of  the  cords,  as  in  forced  inspiration,  the  aryte- 
noids and  their  vocal  processes  are  rotated  outward,  and  the  glottis  respiratoria 
is  triangular  in  shape,  but  with  its  apex  directed  backward.  In  this  condition 
the  entire  glottis  is  somewhat  lozenge-shaped,  the  sides  of  the  glottis  vocalis 
diverging  from  before  backward,  those  of  the  glottis  respiratoria  diverging  from 
behind  forward,  the  widest  part  of  the  aperture  corresponding  with  the  attachment 
of  the  cords  to  the  vocal  processes. 

Muscles  of  the  Larynx. — The  extrinsic  muscles  are  those  which  pass  between 
the  larynx  and  parts  around — these  have  been  described  on  pages  387  to  389, 
The  intrinsic  muscles,  confined  entirely  to  the  larynx,  are: 

Cricothyroideus.  Cricoarytenoideus  lateralis. 

Cricoarytenoideus  posticus.  Arytenoideus. 

Thyroarytenoideus, 

The  Arytenoideus  is  a  single  muscle,  the  other  four  are  paired. 

Dissection. — In  order  to  expose  the  Lateral  cricothyroid  and  Thyroarvtenoid  muscles 
the  thyroid  cartilage  of  one  side  must  be  removed.  Begin  by  taking  away  the  Cricothyroid 
muscle,  then  dividing  the  lateral  thyrohyoid  ligament,  disarticulate  the  inferior  cornu  of  the 
thyroid  cartilage  from  the  cricoid  cartilage,  then  carefully  cut  through  the  thyroid  cartilage  a- 
short  distance  from  its  union  with  its  twin. 

The  Cricothyroid  (??i.  cricothyreoideus)  (Figs.  898  and  899)  is  triangular  in  form,, 
and  situated  at  the  fore  part  and  side  of  the  cricoid  cartilage.  It  arises  from  the 
front  and  lateral  part  of  the  cricoid  cartilage;  its  fibres  diverge,  passing  obliquely 
upward  and  outward  to  be  inserted  into  the  lower  border  of  the  thyroid  cartilage 
and  into  the  anterior  border  of  the  lower  cornu.  The  inner  borders  of  these 
two  muscles  are  separated  in  the  middle  line  by  a  triangular  interval  occupied 
by  the  central  part  of  the  cricothyroid  membrane. 

The  Posterior  Cricoarytenoid  {in.  cricoarytaenoideus  posterior)  (Figs.  898  and  899) 
arises  from  the  broad  depression  occupying  each  lateral  half  of  the  posterior 
surface  of  the  cricoid  cartilage;  its  fibres  pass  upward  and  outward,  converging 
to  be  inserted  into  the  outer  angle  (muscular  process)  of  the  base  of  the  arytenoid 
cartilage.  The  upper  fibres  are  nearly  horizontal,  the  middle  oblique,  and  the 
lower  almost  vertical. 

The  Lateral  Cricoarytenoid  (m.  cricoarytaenoideus  lateralis)  (Figs.  898  and  899), 
a  paired  muscle,  is  smaller  than  the  preceding,  and  of  an  oblong  form.  It  arises- 
from  the  upper  border  of  the  side  of  the  cricoid  cartilage,  and,  passing  obliquely 
upward  and  backward,  is  inserted  into  the  muscular  process  of  the  arytenoid 
cartilage  in  front  of  the  posterior  Cricoarytenoid  muscle.  The  deep  surface 
is  applied  to  the  cricothyroid  membrane,  its  external  or  superficial  surface  is 
subjacent  to  the  thyroid  cartilage. 

The  Arytenoideus  (Figs.  898  and  899)  is  a  single  muscle  filling  up  the  posterior 
concave  surface  of  the  arytenoid  cartilages.  It  arises  from  the  posterior  surface 
and  outer  border  of  one  arytenoid  cartilage,  and  is  inserted  into  the  corre- 
sponding parts  of  the  opposite  cartilage.  It  consists  of  three  planes  of  fibres, 
two  oblique  and  one  transverse.     The  oblique  fibres  {vi.  arytenoideus  obliqmis)^ 


THE  LARYNX 


1173 


the  most  superficial,  form  two  fasciculi,  which  pass  from  the  base  of  one  cartilage 
to  the  apex  of  the  opposite  one,  and  which,  therefore,  cross  each  other  like  the 
limbs  of  the  letter  X.  The  transverse  fibres  (m.  arijtaenoideus  transversus),  the 
deepest  and  most  numerous,  pass  transversely  across  between  the  two  cartilages. 
A  few  of  the  oblique  fibres  are  continued  around  the  outer  margin  of  the  cartilage, 
and  blend  with  the  Thyroarytenoid  in  the  arytenoepiglottic  fold,  and  are  called 
the  Aryepiglotticus  muscle. 

The  Thj^oarytenoid  (m.  thyroanjtenokleus)  (Figs.  S9S  and  899),  a  paired  muscle, 
is  broad  and  flat.  It  lies  parallel  with  the  outer  side  of  the  true  vocal  cord.  It 
arises  in  front  from  the  lower  half  of  the  receding  angle  of  the  thyroid  cartilage, 
and  from  the  cricothyroid  membrane.  Its  fibres  pass  backward  and  outward,  to 
be  inserted  into  the  base  and  antero-external  surface  of  the  arytenoid  cartilage. 
This  muscle  consists  of  two  fasciculi.'  The  inner  portion  (?w.  vocalis)  is  a  tri- 
angular band  which  is  inserted  into  the 
vocal  process  of  the  arytenoid  cartilage, 
and  into  the  adjacent  portion  of  its  antero- 
external  surface;  it  lies  parallel  with  the 
true  vocal  cord,  to  which  it  is  adherent. 
This    fasciculus    on    its    deeper   surface 


Articular  facet  for 
inferior  corntt  of 
thyroid  cartilage. 


Fig.   89S.— Muscles  of  larynx.     Side  view, 
of  thyroid  cartilage  removed. 


Right  ala 


seen  from  above. 


gives  off  some  fibres  which  are  attached  to  the  true  vocal  cord.  These  are  called 
the  Aryvocalis  (Ludwig).  The  outer  portion  (m.  thyreoarytenoideus),  the  thinner, 
is  inserted  into  the  antero-external  surface  and  outer  border  of  the  arytenoid 
cartilage  above  the  preceding  fibres ;  it  lies  on  the  outer  side  of  the  laryngeal  saccule, 
immediately  beneath  the  mucous  membrane. 

A  considerable  number  of  the  fibres  of  the  Thyroarytenoideus  are  prolonged 
into  the  arytenoepiglottic  fold,  where  some  of  them  become  lost,  while  others 
are  continued  forward  to  the  margin  of  the  epiglottis.  They  have  received  a 
distinctive  name,  Thyroepiglotticus  (m.  thyreoepiglotticus),  and  are  sometimes 
described  as  a  separate  muscle. 


'  Henle  describes  these  two  portio 
thyroarytenoids. 


separate  muscles,  under  the  names  of  the  External  and   Internal 


1174  THE  ORGANS  OF  VOICE  AND  BESPIBATION 

Actions. — In  considering  the  action  of  the  muscles  of  the  larynx,  they  may  be  conveniently 
divided  into  two  groups — viz.:  (1)  Those  which  open  and  close  the  glottis.  (2)  Those  which 
regulate  the  degree  of  tension  of  the  vocal  cords. 

1.  The  muscles  which  open  the  glottis  are  the  two  Posterior  cricoarytenoids;  and  those 
which  close  it  are  the  Arytenoideus  and  the  two  Lateral  cricoarytenoids. 

2.  The  muscles  which  regulate  the  tension  of  the  vocal  cords  are  the  two  Cricothyroids,  which 
render  tense  and  elongate  them,  and  the  two  Thyroarytenoids,  which  relax  and  shorten  them. 

The  Posterior  cricoarytenoids  separate  the  chordae  vocales,  and  consequently  open  the  glottis, 
by  rotating  the  arytenoid  cartilages  outward  around  a  vertical  axis  passing  through  the  crico- 
arytenoid joints,  so  that  their  vocal  processes  and  the  vocal  cords  attached  to  them  become  widely 
separated. 

The  Lateral  cricoarytenoids  close  the  glottis  by  rotating  the  arytenoid  cartilages  inward  so 
as  to  approximate  their  vocal  processes. 

The  Arytenoideus  muscle  approximates  the  arytenoid  cartilages,  and  thus  closes  the  opening 
of  the  glottis,  especially  at  its  back  part. 

The  Cricothyroid  muscles  produce  tension  and  elongation  of  the  vocal  cords.  This  is  effected 
as  follows:  the  thyroid  cartilage  is  fixed  by  its  Extrinsic  muscles;  then  the  Cricothyroid  muscles, 
when  they  act,  draw  upward  the  front  of  the  cricoid  cartilage,  and  so  depress  the  posterior  por- 
tion, which  carries  with  it  the  arytenoid  cartilages,  and  thus  elongate  the  vocal  cords. 

The  Thyroarytenoid  muscles,  consisting  of  two  parts  having  different  attachments  and  dif- 
ferent directions,  are  rather  complicated  as  regards  their  action.  Their  main  use  is  to  draw 
the  arytenoid  cartilages  forward  toward  the  thyroid,  and  thus  shorten  and  relax  the  vocal  cords. 
But,  owing  to  the  connection  of  the  inner  portion  with  the  vocal  cord,  this  part,  if  acting  sepa- 
rately, is  supposed  to  modify  its  elasticity  and  tension,  and  the  outer  portion,  being  inserted 
into  the  outer  part  of  the  anterior  surface  of  the  arytenoid  cartilage,  may  rotate  it  inward,  and 
thus  narrow  the  rima  glottidis  by  bringing  the  two  cords  together. 

The  manner  in  which  the  superior  aperture  of  the  larynx  is  closed  during  deglutition  is  referred 
to  on  page  399. 

The  mucous  membrane  of  the  larsmx  is  continuous  above  with  that  lining  the  mouth  and 
pharynx,  and  it  is  prolonged  through  the  trachea  and  bronchi  into  the  lungs.  It  lines  the  pos- 
terior surface  and  the  anterior  part  of  the  upper  surface  of  the  epiglottis,  to  which  it  is  closely 
adherent.  In  the  rest  of  the  larynx,  above  the  true  vocal  cords,  it  is  lax  and  rests  upon  a  con- 
siderable submucous  layer.  The  mucous  membrane,  with  the  submucous  coat,  ligamentous 
and  muscular  fibres,  forms  the  arytenoepiglottic  folds,  which  folds  are  the  lateral  boundaries 
of  the  superior  aperture  of  the  larynx.  It  lines  the  whole  of  the  cavity  of  the  larynx,  forms 
by  its  reduplication  the  chief  part  of  the  superior  or  false  vocal  cord,  and,  from  the  ventricle, 
is  continued  into  the  laryngeal  saccule.  It  is  then  refiected  over  the  true  vocal  cords,  where  it 
is  thin  and  very  intimately  adherent;  covers  the  inner  surface  of  the  cricothyroid  membrane 
and  cricoid  cartilage;  and  is  ultimately  continuous  with  the  lining  membrane  of  the  trachea. 
The  fore  part  of  the  anterior  surface  and  the  upper  half  of  the  posterior  surface  of  the  epiglottis, 
the  upper  part  of  the  arytenoepiglottic  folds,  and  the  true  vocal  cords  are  covered  by  stratified 
squamous  epithelium;  the  rest  of  the  laryngeal  mucous  membrane  is  covered  by  stratified  ciliated 
cells. 

The  mucous  membrane  above  the  rima  glottidis  is  extremely  sensitive,  and  during  life  the 
lightest  touch  of  a  foreign  body  produces  cough. 

Glands. — The  mucous  membrane  of  the  larynx  is  furnished  with  numerous  muciparous 
glands,  the  orifices  of  which  are  found  in  nearly  every  part;  they  are  very  numerous  upon  the 
epiglottis,  being  lodged  in  little  pits  in  its  substance;  they  are  also  found  in  large  numbers  along 
the  posterior  margin  of  the  arytenoepiglottic  fold,  in  front  of  the  arytenoid  cartilages,  where 
they  are  termed  the  arytenoid  glands.  They  exist  also  in  large  numbers  upon  the  inner  surface 
of  the  laryngeal  saccule.     None  are  found  on  the  surface  of  the  true  vocal  cords. 

Vessels  and  Nerves. — The  arteries  of  the  larynx  (Fig.  900)  are  the  laryngeal  branches 
derived  from  the  superior  and  inferior  thyroid.  The  superior  laryngeal  artery  from  the 
superior  thyroid  accompanies  the  internal  branch  of  the  superior  laryngeal  nerve;  the  inferior 
laryngeal  artery  from  the  inferior  thjrroid  courses  along  with  the  recurrent  laryngeal  nerve. 
The  veins  accompany  the  arteries;  those  accompanying  the  superior  laryngeal  artery  join  the 
superior  thyroid  vein,  which  opens  into  the  internal  jugular  vein;  while  those  accompanying 
the  inferior  laryngeal  artery  join  the  inferior  thyroid  vein,  which  opens  into  the  innominate 
vein.  The  Ijrmphatics  consist  of  two  sets,  superior  and  inferior.  The  superior  accompany  the 
superior  laryngeal  artery,  pierce  the  thjTohyoid  membrane,  and  terminate  in  the  nodes  situated 
at  the  bifurcation  of  the  carotid  artery.  Of  the  inferior  lymphatics,  some  pass  through  the 
cricothyroid  membrane  to  terminate  in  a  node  lying  in  front  of  that  membrane  or  in  front  of 
the  upper  part  of  the  trachea,  while  others  pass  to  the  deep  cervical  nodes  and  to  the  nodes 
along  the  inferior  thyroid  artery. 

The  nerves  are  derived  from  the  internal  and  external  laryngeal  branches  of  the  superior 
laryngeal  nerve,  from  the  inferior  or  recurrent  laryngeal,  and  from  the  sjmipathetic.     The 


THE  TRACHEA  AND  BRONCHI 


1175 


internal  laryngeal  nerve  is  almost  entirely  sensor,  but  some  motor  filaments  are  said  to  be  carried 
by  it  to  the  Arytenoideus  muscle.  It  divides  into  a  branch  which  is  distributed  to  both  surfaces 
of  the  epiglottis,  a  second  to  the  arytenoepiglottic  folds,  and  a  third,  the  largest,  which  sup])iies 
the  mucous  membrane  over  the  back  of  the  larynx  and  communicates  with  the  recurrent  laryn- 
geal. The  external  laryngeal  branch  sujiplies  the  Cricothyroid  muscle.  The  recurrent  laryn- 
geal passes  upward  under  the  lower  border  of  the  Inferior  constrictor,  and  enters  the  larynx 
between  the  cricoid  and  thyroid  cartilages.  It  supplies  all  the  muscles  of  the  larynx  except  the 
Cricothyroid  and  part  of  the  Arytenoideus.  The  sensor  branches  of  the  laryngeal  nerves  form 
subepithelial  plexuses,  from  which  fibres  ascend  to  end  between  the  cells  covering  the  mucous 
membrane.     Sympathetic  filaments  accompany  all  of  the  laryngeal  nerves. 

Over  the  posterior  surface  of  the  epiglottis,  in  the  arytenoepiglottidean  folds,  and  less  regu- 
larly in  some  other  parts,  taste  buds,  similar  to  those  in  the  tongue,  are  found. 


Fig.  900.— The  origin  and  distribution  of  the  arteries  of  the  larynx.     (Luschka.) 


THE  TRACHEA  AND  BRONCHI  (Fig.  901). 

The  trachea,  or  windpipe,  is  a  cartilaginous,  membranous,  elastic,  cylindrical 
tube,  flattened  posteriorly,  which  extends  from  the  lower  part  of  the  laryixs,  on  a 
level  with  the  sixth  cervical  vertebra,  to  opposite  the  body  or  upper  border  of  the 
fifth  thoracic  vertebra,  where  it  divides  (bifurcatio  tracheae)  into  two  stem  bronchi, 
one  for  each  lung.  The  trachea  is  nearly,  but  not  quite,  cylindrical,  being  flattened 
posteriorly  (Fig.  903).  The  largest  diameter  of  the  tube  is  at  the  middle;  from  this 
point  the  diameter  diminishes  toward  the  bronchi  and  toward  the  laryngeal  end. 
The  trachea  measures  about  four  inches  and  a  half  (U  cm.)  in  length;  its  diameter, 
in  the  cadaver,  from  side  to  side  is  from  three-c|uarters  of  an  inch  to  an  inch 
(19  to  25  mm.),  being  always  greater  in  the  male  than  in  the  female.  Its  calibre 
is  not  quite  uniform  throughout;  the  middle  third  is  somewhat  w-ider  than  the 
rest  of  the  tube,  while  just  below,  before  its  bifurcation,  the  trachea  is  slighdy 
diminished  in  diameter  where  it  is  in  relation  with  the  arch  of  the  aorta.  In  the 
living  subject,  owing  to  the  muscle  tone  of  the  wall,  the  transverse  diameter  is 
12.5  mm.  (0.5  inch);  the  antero-posterior,  11  mm.  (0.44  inch). 

Relations. — The  anterior  surface  of  the  trachea  is  convex,  and  covered  in  the  neck,  from 
above  downward,  by  the  isthmus  of  the  thyroid  gland,  the  inferior  thyroid  veins,  the  arteria 
thvroidea  ima  (when  that  vessel  exists),  the  Sternohyoid  and  SternothjToid  muscles,  the  cervical 


1176 


THE  ORGANS  OF  VOICE  AND  RESPIRATION 


fascia,  and,  more  superficially,  by  the  anastomosing  branches  between  the  anterior  jugular  veins; 
in  the  thorax  it  is  covered  from  before  backward  by  the  first  piece  of  the  sternum,  the  remains 
of  the  thymus  gland,  the  left  innominate  vein,  the  arch  of  the  aorta,  the  innominate  and  left  com- 
mon carotid  arteries,  and  the  deep  cardiac  plexus.  Posteriorly,  it  is  in  relation  with  the  oesoph- 
agus; laterally,  in  the  neck,  it  is  in  relation  with  the  common  carotid  arteries,  the  lateral  lobes 
of  the  thyroid  gland,  the  inferior  thyroid  arteries,  and  recurrent  laryngeal  nerves;  and,  in  the 
thorax,  it  lies  in  the  upper  part  of  the  interpleural  space  (superior  viedia.itinuvi),  and  is  in  relation 
on  the  right  with  the  pleura  and  right  vagus,  and  near  the  root  of  the  neck  with  the  innominate 
artery;  on  its  left  side  are  the  recurrent  laryngeal  nerve,  the  aortic  arch,  the  left  common  carotid 
and  subclavian  arteries. 


PIGLOTTIS 


THYROID 


Fig.  901. — Front  \-iew  of  cartilages  of  larynx,  the  trachea  and  bronchi. 

The  Right  Bronchus  (bronchus  dexter)  (Fig.  901),  wider,  shorter,  and  more 
vertical  in  direction  than  the  left,  is  about  an  inch  in  length  (2.5  cm.),  and  enters 
the  hihim  of  the  right  lung  opposite  the  fifth  thoracic  vertebra.     It  forms  an  angle 


THE  TEA  CHE  A   AND  BRONCHI 


in? 


to  the  median  plane  of  about  25  degrees.  The  vena  azygos  major  arches 
over  it  from  behind;  and  the  right  pulmonary  artery  lies  below  and  then  in  front 
of  it.  About  one  inch  from  its  commencement  it  gi^•es  off  a  branch  to  the 
upper  lobe  of  the  right  lung.  This  is  termed  the  eparterial  branch  bronchus 
(ramus  bronchialis  eparferialis),  because  it  is  given  off  above  the  right  pulmonary 

artery.  The  bronchus  now  passes  below  the 
artery,  is  known  as  the  hyparterial  branch  bron- 
chus (ramus  bronchialis  hyparterialis),  and 
divides  into  two  branches  for  the  middle  and 
lower  lobes. 

The  Left  Bronchus  (bronchus  sinister')  (Fig. 
901)  is  smaller  and  longer  than  the  right,  being 
nearly  two  inches  in  length.  It  forms  an  angle 
to  the  median  plane  of  about  46  degrees.  It  is 
slightly  curved  and  enters  the  root  of  the  left 
lung,  opposite  the  sixth  thoracic  vertebra,  about 
an  inch  lower  than  the  right  bronchus.  It 
passes  beneath  the  arch  of  the  aorta,  crosses  in 
front  of  the  oesophagus,  the  thoracic  duct,  and 
the    descending  aorta,   and   has   the   left  pul- 


Left 


Fig.  903. — Transverse  section  of  the  trachea,  just 
bifurcation,  with  a  bird's-eye  view  of  the  inteiior,  sh( 
carina  tracheae. 


monary  artery  lying  at  first  above,  and  then  behind  it.  The  left  bronchus  has 
no  branch  corresponding  to  the  eparterial  branch  of  the  right  bronchus  in  the 
sense  that  it  is  given  off  above  the  pulmonary  artery.  The  first  hyparterial  branch 
bronchus  of  the  left  side  is  the  morphological  equivalent  of  the  right  eparterial 
branch  bronchus,  as  shown  by  Huntington.^ 

The  further  subdivision  of  the  bronchi  will  be  considered  with  the  anatomy 
of  the  lung. 

If  a  transverse  section  of  the  trachea  is  made  a  short  distance  above  its  point 
of  bifurcation,  and  a  bird's-eye  view  taken  of  its  interior  (Fig.  90.3),  the  septum 
(carina  tracheae)  placed  at  the  bottom  of  the  trachea  and  separating  the  two  bron- 
chi will  be  seen  to  occupy  the  left  of  the  median  line,  and  the  right  bronchus  appears 
to  be  a  more  direct  continuation  than  the  left,  so  that  any  solid  body  dropping  into 
the  trachea  would  naturally  be  directed  toward  the  right  bronchus.  This  tend- 
ency is  aided  by  the  larger  size  of  the  right  tube  as  compared  with  its  fellow.  This 
fact  serves  to  explain  why  a  foreign  body  in  the  trachea  more  frequently  falls  into 
the  right  bronchus  than  into  the  left.- 

Structure  of  the  Trachea. — The  trachea  is  composed  of  incomplete  cartilaginous  rings, 
fibrous  membrane,  muscle  fibres,  mucous  membrane,  and  glands. 

The  Cartilages  \ary  from  si.xteen  to  twenty  in  number;  each  forms  an  incomplete  ring,  which 
siuTOunds  about  two-thirds  of  the  cylinder  of  the  trachea,  being  imperfect  behind,  where  the 

'  The  Eparterial  Bronchial  System  of  the  Mammalia,  Annals  N.  Y.  Acad.  Sci.,  1898. 

2  Reigel  asserts  that  the  entrance  of  a  foreign  body  into  the  left  bronchus  is  by  no  means  so  infrequent  as  is  gener- 
ally supposed.     See  also  Med.-Chir.  Transactions,  vol.  Ixxi,  p.  121. 


1178 


THE  ORGANS  OF  VOICE  AND  RESPIRATION 


tube  is  completed  by  muscle  and  fibrous  tissue.  The  cartilages  are  placed  horizontally  above  each 
other,  separated  by  narrow  intervals  bridged  by  fibroelastic  tissue.  They  measure  about  J  of 
an  inch  in  depth,  and  ^V  of  an  inch  in  thickness,  tapering  at  their  posterior  ends.  Their  outer 
sm-faces  are  flattened,  but  internally  they  are  convex,  from  being  thicker  in  the  middle  than  at 
the  margins.  Two  or  more  of  the  cartilages  often  unite,  partially  or  completely,  and  are  some- 
times bifurcated  at  their  extremities.  They  are  highly  elastic,  but  sometimes  become  calcified 
in  advanced  life.  In  the  right  bronchus  the  cartilages  vary  in  number  from  six  to  eight;  in  the 
left,  from  nine  to  twelve.  They  are  shorter  and  narrower  than  those  of  the  trachea.  The 
peculiar  cartilages  of  the  trachea  are  the  first  and  the  last. 

The  first  cartilage  is  broader  than  the  rest,  and  sometimes  divided  at  one  end;  it  is  con- 
nected by  fibrous  membrane  with  the  lower  border  of  the  cricoid  cartilage,  with  which  or  with 
the  succeeding  cartilage  it  is  sometimes  blended. 

The  last  cartilage  is  thick  and  broad  in  the  middle,  in  consequence  of  its  lower  border  being 
prolonged  into  a  triangular  hook-shaped  process  which  curves  downward  and  backward  between 
the  two  bronchi.  It  terminates  on  each  side  in  an  imperfect  ring  which  encloses  the  com- 
mencement of  the  bronchi.  The  cartilage  above  the  last  is  often  somewhat  broader  than  the 
rest  at  its  centre. 


Ventral  view.  Dorsal  v 

js.  904  and  905. — Radiographs  of  trachea  and  bronchi  filled  with  fusible  metal. 


(After  J.  A.  Blake.) 


The  Fibrous  Membrane. — The  cartilages  are  enclosed  in  a  fibroelastic  membrane  which 
forms  a  double  layer,  one  layer,  the  thicker  of  the  two,  passing  over  the  outer  surface  of  the 
ring,  the  other  over  the  inner  surface;  at  the  upper  and  lower  margins  of  the  cartilages  these  two 
layers  blend  together  to  form  a  single  membrane,  which  intervenes  between  the  rings.  They 
are  thus,  as  it  were,  embedded  in  the  membrane.  In  the  space  behind,  between  the  extremities 
of  the  rings,  the  membrane  forms  a  single  distinct  layer. 

The  muscle  fibres  are  disposed  in  two  layers,  longitudinal  and  transverse. 

The  longitudinal  fibres  are  external,  and  consist  merely  of  a  few  scattered  longitudinal  bundles 
of  fibres. 

The  transverse  fibres,  the  Trachealis  muscle  of  Todd  and  Bowman,  foriii  a  thin  internal 
layer  which  extends  transversely  lietween  the  ends  of  the  cartilages  and  the  intervals  between 
them,  thus  extending  the  entu-e  length  of  the  posterior  part  of  the  trachea.  The  muscle  fibres 
are  of  the  unstriped  variety. 

The  mucous  membrane  is  continuous  above  with  that  of  the  larynx,  and  below  with  that  of 
the  bronchi.  Microscopically,  it  consists  of  stratified  ciliated  epithelial  cells,  among  which  a 
number  of  goblet  cells  are  seen;  the  basal  cells  are  often  branched  and  rest  upon  the  basement 
membrane,  beneath  which  is  a  layer  of  fibroelastic  tissue  containing  diffuse  lymphoid  tissue. 
The  tunica  propria  blends  with  the  next  coat,  the  submucosa,  and  here  are  found  the  cartilage 
rings  and  a  number  of  mucous  glands,  the  tracheal  glands. 

The  tracheal  glands  (glnudiilae  tracheales)  are  found  in  great  abundance  at  the  posterior  part 
of  the  trachea.  Thev  are  racemose  glands,  and  consist  of  a  basement  membrane  lined  by  col- 
umnar mucus-secreting  cells.  They  are  situated  at  the  back  of  the  trachea,  outside  the  layer 
of  muscle  tissue,  between  it  and  the  outer  fibrous  layer.     Their  excretory  ducts  pierce  the 


THE  TRACHEA   AND  BRONCHI 


1179 


muscle  and  inner  fibrous  layers,  and  pass  through  the  submucous  and  mucous  layers  to  open 
on  the  surface  of  the  mucous  membrane.  Some  glands  of  smaller  size  are  also  found  at  the 
sides  of  the  trachea,  between  the  layers  of  fibrous  tissue  connecting  the  rings,  and  others  imme- 
diately beneath  the  mucous  coat.  The  secretion  from  these  glands  serves  to  lubricate  the  inner 
surface  of  the  trachea. 

Vessels  and  Nerves. — The  trachea  is  supplied  with  blood  by  the  inferior  thyroid  arteries. 
The  veins  terminate  in  the  thyroid  venous  plexus.  The  nerves  are  derived  from  the  vagus  and 
its  recurrent  branches  and  from  the  sympathetic. 

Lymph  Nodes. — The  trachea  is  surrounded  by  lax  connective  tissue  which  contains  nu- 
merous lymph  nodes,  known  as  the  peritracheobronchial  nodes.  They  are  divided  into  four 
groups  (Barely).  A  group  to  the  right  side,  in  the  angle  between  the  trachea  and  right  bronchus 
and  ascending  to  the  region  of  the  subclavian  vessels.  A  group  to  the  left  side,  in  the  ancrje 
formed  by  the  trachea  and  left  bronchus,  and  ascending  to  about  the  arch  of  the  aorta  and  the 
recurrent  laryngeal  nerve.  The  two  groups  just  described  are  usually  called  tracheal  nodes 
[lymphoglandulae  trachcale.i).  A  third  group  is  in  the  angle  formed  by  the  bifurcation  of  the 
trachea.     These  constitute  the  bronchial  nodes  {lym,phoglandvlae  hronchiales),  ten  or  twelve  in 


MPH   NODES 


Fig.  906. — The  tracheobronchial  and  interbronchial  lymph  nodes,  seen  from  in  front.  The  dotted  lymph  nodes 
and  lymph  vessels  are  not  visible  from  in  front:  d',  d-.  First  and  second  dorsal  branch  bronchi.  !)',  v^.  First  and 
second  ventral  branch  bronchi.     (Sukiennikow.  > 


number.  A  fourth  group,  the  interbronchial  nodes,  are  found  in  angles  of  bifurcation  of  the 
larger  bronchi  in  the  lung  parenchyma.  Very  early  in  life  the  peritracheobronchial  nodes 
become  dark  or  even  black  from  the  deposition  of  carbonaceous  substance  brought  by  the  leuko- 
cytes from  the  bronchial  tubes.     This  condition  is  called  anthracosis. 

Surface  Form.— In  the  middle  line  of  the  neck  some  of  the  cartilages  of  the  larvnx  can  readily 
be  distinguished.  In  the  angle  below  the  chin  the  hyoid  bone  can  easily  be  distinguished,  and 
a  finger's  breadth  below  it  is  the  pomum  Adami,  the  prominence  between  the  upper  borders  of 
the  two  alae  of  the  thyroid  cartilage.  About  an  inch  below  this,  in  the  middle  line,  is  a  depres- 
sion corresponding  to  the  cricothyroid  space,  in  which  the  operation  of  laryngotomy  is  per- 
formed. This  depression  is  bounded  below  by  a  prominent  arch,  the  anterior  ring  of  the  cricoid 
cartilage,  below  which  the  trachea  can  be  felt",  though  it  is  only  in  the  emaciated  adult  that  the 
separate  rings  can  be  distinguished.  The  lower  part  of  the  trachea  is  not  easily  observed,  for 
as  it  descends  in  the  neck,  following  the  curvature  of  the  vertebral  column,  it  takes  a  deeper 
position,  and  is  farther  removed  from  the  surface.  The  level  of  the  vocal  cords  corresponds  to 
the  middle  of  the  anterior  margin  Of  the  thyroid  cartilage. 

With  the  laryngoscope,  the  following  structures  can  be  seen.  The  base  of  the  tongue  and 
the  lingual  surface  of  the  epiglottis,  with  the  glossoepiglottic  ligaments;  the  superior  aperture  of 


1180  THE  ORGANS  OF  VOICE  AND  BESPIBATION 

the  larynx,  bounded  on  either  side  by  the  arytenoepiglottidean  folds,  in  which  may  be  seen  two 
rounded  eminences  corresponding  to  the  cornicular  and  cuneiform  cartilages.  Beneath  these, 
the  false  and  true  vocal  cords,  with  the  ventricle  between  them.  Still  deeper,  the  cricoid  car- 
tilage and  s(jnie  of  the  anterior  parts  of  the  rings  of  the  trachea,  and  sometimes,  in  deep  inspira- 
tion, the  bifurcation  of  the  trachea. 

Applied  Anatomy. — Foreign  bodies  often  find  their  way  into  the  air  passages.  These  may 
be  large,  soft  substances,  as  a  piece  of  meat,  which  may  become  lodged  in  the  upper  aperture 
of  the  larynx  or  in  the  rima  glottidis,  and  cause  speedy  suffocation  unless  rapidly  got  rid  of,  or 
unless  an  opening  is  made  into  the  air  passages  below,  so  as  to  enable  the  patient  to  breathe. 
Smaller  bodies,  frequently  of  a  hard  nature,  such  as  cherry-  or  plum-stones,  small  pieces  of  bone, 
buttons,  etc.,  may  find  their  way  through  the  rima  glottidis  into  the  trachea  or  bronchus,  or  may 
become  lodged  in  the  ventricle  of  the  larynx.  The  dangers  then  depend  not  so  much  upon  the 
mechanical  obstruction  as  upon  the  spasm  of  the  glottis  which  they  excite  from  reflex  irritation. 
When  lodged  in  the  ventricle  of  the  larynx,  they  may  produce  very  few  symptoms  beyond  sudden 
loss  of  voice  or  alteration  in  the  voice  sounds,  immediately  following  the  inhalation  of  the  foreign 
body.  When,  however,  they  are  situated  in  the  trachea,  they  are  constantly  striking  against 
the  vocal  cords  during  expiratory  efforts,  and  produce  attacks  of  dyspnea  from  spasm  of  the 
glottis.  When  lodged  in  the  bronchus,  they  .usually  become  fixed  there,  and,  occluding  the 
lumen  of  the  tube,  cause  a  loss  of  the  respiratory  murmur  on  the  affected  side,  which  is,  as 
stated  above,  more  often  the  right. 

Beneath  the  mucous  membrane  of  the  upper  part  of  the  air  passages  there  is  a  considerable 
amount  of  submucous  tissue  which  is  liable  to  become  much  swollen  from  effusion  in  inflamma- 
tory affections,  constituting  the  disease  known  as  "edema  of  the  glottis."  This  effusion  does 
not  extend  below  the  level  of  the  true  vocal  cords,  on  account  of  the  fact  that  the  mucous  mem- 
brane is  closely  adherent  to  these  structures,  without  the  intervention  of  any  submucous  tissue. 
So  that,  in  cases  of  this  disease  in  which  it  is  necessary  to  open  the  air  passages  to  prevent  suffo- 
cation, the  operation  of  laryngotomy  is  sufficient. 

Chronic  laryngitis  is  an  inflammation  of  the  mucous  membrane  of  the  larynx,  which  occurs  in 
those  who  speak  much  in  public,  and  is  due  to  the  dryness  induced  by  the  large  amount  of  cold 
air  drawn  into  the  air  passages  during  prolonged  speaking,  which  incites  increased  activity  in 
the  mucous  glands  to  keep  the  parts  moist,  and  this  eventually  terminates  in  inflammation  of 
these  structures. 

.  Ulceration  of  the  larynx  may  occur  from  syphilis,  either  as  a  superficial  ulceration,  or  from 
the  softening  of  a  gumma;  from  tuberculous  disease  (laryngeal  phthisis),  or  from  malignant 
disease  (epithelioma). 

The  air  passages  may  be  opened  surgically  in  two  different  situations — through  the  cricothyroid 
membrane  (laryngotomy),  or  in  some  part  of  the  trachea  (tracheotomy);  and  to  these  some  sur- 
geons have  added  a  third  method — opening  the  cricothyroid  membrane  and  dividing  the  car- 
tilage with  the  upper  ring  of  the  trachea  (laryngotracheotomy). 

Laryngotomy  is  anatomically  the  more  simple  operation;  it  can  readily  be  performed,  and 
should  be  employed  in  those  cases  where  the  air  passages  require  opening  in  an  emergency  for 
the  relief  of  some  sudden  obstruction  to  respiration.  The  cricothyroid  membrane  is  very  super- 
ficial, being  covered  in  the  middle  line  only  by  the  skin,  superficial  fascia,  and  the  deep  fascia. 
On  each  side  of  the  middle  line  it  is  also  covered  by  the  Sternohyoid  and  Sternothyroid  muscles, 
which  diverge  from  each  other  at  their  upper  parts,  leaving  a  slight  interval  between  them.  On 
these  muscles  rest  the  anterior  jugular  veins.  The  only  vessel  of  any  importance  in  connec- 
tion with  this  operation  is  the  cricothjToid  artery,  which  crosses  the  cricothyroid  membrane,  and 
which  may  be  wounded,  but  rarely  gives  rise  to  any  trouble.  The  operation  is  performed  thus: 
The  head  being  thrown  back  and  steadied  by  an  assistant,  the  finger  is  passed  over  the  front 
of  the  neck,  and  the  cricothyroid  depression  felt  for.  A  vertical  incision  is  then  made  through 
the  skin,  in  the  middle  line  over  this  spot,  and  carried  down  through  the  fascia  until  the  crico- 
thyroid membrane  is  exposed.  A  cross-cut  is  then  made  through  the  membrane,  close  to  the 
upper  border  ol  the  cricoid  cartilage,  so  as  to  avoid,  if  possible,  the  cricothyroid  artery,  and  a 
tracheotomy  tube  is  introduced.  It  has  been  recommended,  as  a'  more  rapid  way  of  performing 
the  operation,  to  make  a  transverse  instead  of  a  longitudinal  cut,  through  both  the  superficial  and 
deep  structures,  and  thus  to  open  at  once  the  air  passages.  It  will  he  seen,  however,  that  in 
opening  in  this  way  the  anterior  jugular  veins  would  be  in  danger  of  being  wounded. 

Tracheotomy  may  be  performed  either  above  or  below  the  isthmus  of  the  thyroid  body,  or 
this  structure  may  be  divided  and  the  trachea  opened  behind  it. 

The  isthmus  of  the  thyroid  gland  usually  crosses  the  second  and  third  rings  of  the  trachea; 
along  its  upper  border  is  frequently  to  be  found  a  large  transverse  communicating  branch  between 
the  superior  thwoid  veins;  and  the  isthmus  itself  is  covered  by  a  venous  plexus  formed  between 
the  thyroid  veins  of  the  opposite  sides.  Theoretically,  therefore,  it  is  advisable  to  avoid  dividing 
this  structure  in  opening  the  trachea. 

Above  the  isthmus  the  trachea  is  comparatively  superficial,  being  covered  by  the  skin,  super- 
ficial fascia,  deep  fascia,  Sternohyoid  and  Sternothyroid  muscles,  and  a  second  layer  of  the  deep 


THE  PLEURA  1181 

fascia,  which,  attached  above  to  the  lower  border  of  the  hyoid  bone,  descends  beneath  the  muscles 
to  the  thyroid  body,  where  it  divides  into  two  layers  and  encloses  the  istiiiuus. 

Below  the  isthmus  the  trachea  lies  much  more  deeply,  and  is  covered  by  the  Sternohyoid 
and  the  Sternothyroid  muscles  and  a  quantity  of  loose  areolar  tissue  in  which  is  a  plexus  of  veins, 
some  of  them  of  large  size;  they  converge  to  two  trunks,  the  inferior  thyroid  veins,  which  descend 
on  either  side  of  the  median  line  on  the  front  of  the  trachea  and  open  into  the  innominate  vein. 
In  the  infant  the  thymus  gland  ascends  a  variable  distance  along  the  front  of  the  trachea,  and 
opposite  the  episternal  notch  the  windpipe  is  crossed  by  the  left  innominate  vein.  Occasionally, 
also,  in  young  subjects,  the  innominate  artery  crosses  the  tube  obliquely  above  the  level  of  the 
sternum.  The  thyroidea  ima  artery,  when  that  vessel  exists,  passes  from  below  upward  along 
the  front  of  the  trachea. 

From  these  observations  it  must  be  evident  that  the  trachea  can  be  more  readily  opened  above 
than  below  the  isthmus  of  the  thyroid  body. 

Tracheotomy  above  the  isthmus  is  performed  thus:  The  patient  should,  if  possible,  be  laid 
on  his  back  on  a  table  in  a  good  light.  A  pillow  is  to  be  placed  under  the  shoulders  and  the 
head  thrown  back  and  steadied  by  an  assistant.  The  surgeon,  standing  on  the  right  side  of  his 
patient,  makes  an  incision  from  an  inch  and  a  half  to  two  inches  in  length  in  the  median  line  of 
the  neck  from  the  top  of  the  cricoid  cartilage.  The  incision  must  be  made  exactly  in  the  middle 
line,  so  as  to  avoid  the  anterior  jugular  veins,  and  after  the  superficial  structures  have  been 
divided  the  interval  between  the  Sternohyoid  muscles  must  be  found,  the  raph^  divided,  and 
the  muscles  drawn  apart.  The  lower  border  of  the  cricoid  cartilage  must  now  be  felt  for,  and 
the  upper  part  of  the  trachea  exposed  from  this  point  downward  in  the  middle  line.  Bose  has 
recommended  that  the  layer  of  fascia  in  front  of  the  trachea  should  be  divided  transversely  at 
the  level  of  the  lower  border  of  the  cricoid  cartilage,  and,  having  been  seized  with  a  pair  of  for- 
ceps, pressed  downward  with  the  handle  of  the  scalpel.  By  this  means  the  isthmus  of  the  thyroid 
gland  is  depressed,  and  is  saved  from  all  danger  of  being  wounded,  and  the  trachea  is  cleanly 
exposed.  The  trachea  is  now  transfixed  with  a  sharp  hook  and  drawn  forward  in  order  to 
steady  it,  and  is  then  opened  by  inserting  the  knife  into  it  and  dividing  the  two  or  three  upper 
rincs  from  below  upward.  If  the  trachea  is  to  be  opened  below  the  isthmus,  the  incision  to 
expose  it  must  be  made  from  a  little  below  the  cricoid  cartilage  to  the  top  of  the  sternum. 

In  the  child  the  trachea  is  smaller,  more  deeply  placed,  and  more  movable  than  in  the  adult. 
In  fat  or  short-necked  people,  or  in  those  in  whom  the  muscles  of  the  neck  are  prominently 
developed,  the  trachea  is  more  deeply  placed  than  in  others. 

A  portion  of  the  larynx  or  the  whole  of  it  has  been  removed  for  malignant  disease,  laryngec- 
tomi/.  Some  surgeons"  do  preliminary  tracheotomy,  insert  a  Trendelenburg  cannula  to  prevent 
the  flow  of  blood  downward  into  the  lungs,  and  then  remove  the  larynx.  Other  surgeons  do 
not  employ  preliminary  tracheotomy.  Perier's  method  of  laryngectomy  is  as  follows:  Make 
a  vertical  incision  in  tlie  median  line  from  the  level  of  the  hyoid  bone  to  below  the  level  of  the 
cricoid  cartilage.  Make  a  transverse  incision  at  each  end  cf  the  vertical  incision.  This  makes 
an  I-shaped  wound.  Separate  the  soft  parts  from  the  larynx  and  upper  part  of  the  trachea,  and 
separate  these  two  structures  from  the  oesophagus.  After  arresting  bleeding,  divide  the  trachea 
below  the  cricoid  cartilage,  introduce  a  special  cannula,  complete  the  removal  of  the  larynx, 
suture  the  opening  of  the  trachea  to  the  lower  angle  of  the  wound,  and  close  the  rest  of  the  wound 
after  securing  drainage.  In  malignant  disease  of  the  larynx  the  associated  lymph  nodes  must 
be  removed.  Partial  laryngectomy,  according  to  Sir  F.  Semon,  is  the  removal  of  not  less  than 
one  wing  of  the  thyroid  cartilage.  Removal  of  a  lesser  piece  of  the  thyroid  or  of  a  bit  of  the 
arytenoid  or  cricoid  he  considers  with  the  operation  of  thyrotomy. 


THE  PLEURiE  (Figs.  889,  919). 

Each  lung  is  invested  by  an  exceedingly  delicate  serous  membrane,  the  pleura, 
which  encloses  the  organ  as  far  as  its  root,  and  is  then  reflected  on  to  the  peri- 
cardium, thoracic  wall,  and  Diaphragm.  The  portion  of  the  serous  membrane 
investing  the  surface  of  the  lung  and  dipping  into  the  fissures  between  its  lobes 
is  called  the  visceral  layer  of  the  pleura  (pleura  pulmonalis)  (Fig.  907),  wiiile  that 
which  lines  the  inner  surface  of  the  thorax  is  called  the  parietal  layer  of  the  pleura 
{-pleura  parietalis)  (Fig.  907),  The  space  between  these  two  layers  is  called  the 
cavity  of  the  pleura  (cavum  pleurae),  and  contains  a  very  litde  clear  fluid.  It  must 
be  borne  in  mind  that  in  the  healthy  condition  the  two  layers  are  in  contact,  and 
there  is  no  real  cavity.  When  the  lung  becomes  collapsed  a  separation  of  it 
from  the  wall  takes  place  and  a  cavity  results.     Each  pleura  is  therefore  a  shut 


1182 


THE  ORGANS  OF  VOICE  AND  BESPIBATION 


sac,  one  occupying  the  right,  the  other  the  left  half  of  the  thorax,  and  they  do  not 
communicate  with  each  other.     The  two  pleurae  do  not  meet  in  the  middle  line 


Pleura  Pulmonalis, 
a  Costalis. 


Sympathetic  Nave 
Thoracic  Duct 

Fig    907  — A  trans^  erse  section  of  the  thor-i-s.    showing  the  relative  position  of  the  viscera  and  the 
reflections  of  the  pleurEe. 


\ena  izyqob  Major. 
Vagus  Ne>  ves 


of  the  thorax,  excepting  anteriorly  opposite  the  second  and  third  pieces  of  the  ster- 
num. The  region  left  between  them  contains  all  the  thoracic  viscera  excepting 
the  lungs,  and  is  named  the  mediastinum  or  interpleural  septum. 


Fig.  908. — The  dome  of  the  pleura.     (Poirier  and  Charpy.) 


Different  portions  of  the  parietal  pleura  have  received  special  names  which 
indicate  their  position;  thus,  that  portion  which  lines  the  inner  surfaces  of  the  ribs 


THi:  PLEURJE 


1183 


and  Intercostal  muscles  is  the  costal  pleura  (pleura  costalis);  that  which  covers 
the  convex  surface  of  the  Diaphragm  is  the  diaphragmatic  pleura  [pleura  diaplmuj- 
matica);  that  which  rises  in  the  neck,  over  the  apex  of  tlie  lung,  is  the  cervical  pleura 
(cupula  pleurae);  and  that  which  is  applied  to  the  adjacent  structures  of  the 
mediastinum  is  tiie  mediastinal  pleura  [pleura  mediastinalis). 

Reflections  of  the  Pleurae  (Fig.  907).— Commencing  at  the  sternum,  the  pleura 
passes  laterad,  covers  the  inner  surfaces  of  the  ribs  and  costal  cartilages,  and  Internal 
intercostal  muscles,  and  at  the  back  part  of  the  thorax  passes  over  the  gangliated 
cord  of  the  sympathetic  and  its  branches,  and  is  reflected  upon  the  sides  of  the 
bodies  of  the  vertebrae  where  it  is  separated  by  a  narrow  interval,  the  posterior 
mediastinum  [cavum  mediastinale  poster ius),  from  the  opposite  pleura.  From 
the  vertebral  column  the  pleura  passes  to  the  side  of  the  pericardium,  which  it 


SCALENUS 
MINIMUS 
MUSCLE 


Fig.  909.— The  supports  of  the  pli 


aside  to  show  the  pleural  reenforcementi 


d  arteries  have  been  cut  and  pulled 


covers  to  a  slight  extent;  it  then  covers  the  back  part  of  the  root  of  the  lung,  from 
the  lower  border  of  which  a  triangular  sheet  descends  vertically  by  the  side  of 
the  posterior  mediastinum  to  the  Diaphragm,  but  is  not  attached  thereto.  This 
sheet  is  the  posterior  layer  of  a  wide  fold,  known  as  the  broad  ligament  of  the  lung 
(ligamentum  pulmonale  or  ligamentum  latum  pulmonis).  From  the  -posterior 
aspect  of  the  lung  root,  the  pleura  may  be  traced  over  the  convex  surface  of  the 
lung,  the  apex,  and  base,  and  also  into  the  fissures  between  the  lobes,  on  to  its 
inner  surface  and  the  front  part  of  its  root;  it  is  continued  from  the  lower  margin 
of  the  root  as  the  anterior  layer  of  the  broad  ligament,  and  from  this  it  is  reflected 
on  to  the  pericardium,  and  from  it  to  the  back  of  the  sternum.  Beloiv,  it  covers 
the  upper  surface  of  the  Diaphragm,  and  extends,  in  front,  as  low  as  the  costal 
cartilage  of  the  seventh  rib;  at  the  side  of  the  thorax,  to  the  lower  border  of  the 
tenth  rib  on  the  left  side  and  to  the  upper  border  of  the  same  rib  on  the  right  side; 
and  hehiiid,  it  reaches  as  low  as  the  twelftii  rib,  and  sometimes  even  as  low  as 
the  transverse  process  of  the  first  lumbar  vertebra.  Above,  its  apex  projects, 
through  the  superior  aperture  of  the  thorax  into  the  neck,  extending  from  one  to 
two  inches  (2.5  to  5  cm.)  above  the  anterior  extremity  of  the  first  rib ;  this  portion  of 
the  sac  is  strengthened  by  a  dome-like  expansion  of  fascia  (Sibson's  fascia)  (Fig. 
909),  attached  in  front  to  the  inner  border  of  the  first  rib,  and  behind  to  the  ante- 


1184 


THE  ORGANS  OF  VOICE  AND  RESPIRATION 


rior  border  of  the  transverse  process  of  the  seventh  cervical  vertebra.  This  is  cov- 
ered and  strengthened  by  a  few  spreading  muscle  fibres  derived  from  the  Scaleni. 
In  the  front  of  the  thorax,  where  the  parietal  layer  of  the  pleura  is  reflected 
backward  to  the  pericardium,  the  two  pleural  sacs  are  nearly  in  contact  for  a  short 
distance  (Fig.  919).  At  the  upper  part  of  the  thorax,  behind  the  manubrium,  they 
are  not  in  contact,  the  point  of  reflection  being  represented  by  a  line  drawn  from 
the  sternoclavicular  articulation  to  the  midpoint  of  the  junction  of  the  manubrium 
with  the  body  of  the  sternum.  From  this  point  the  two  pleurae  descend  in  close  con- 
tact to  the  level  of  the  fourth  costal  cartilages,  and  the  line  of  reflection  on  the  riyht 
side  is  continued  downward  in  nearly  a  straight  line  to  the  lower  end  of  the  gladi- 
olus, and  then  turns  outward,  while  on  the  left  side  the  line  of  reflection  diverges 
slightly  outward  and  is  continued  downward,  close  to  the  left  border  of  the  ster- 
num as  far  as  the  sixth  costal  cartilage.  The  inferior  limit  of  the  pleura  is  on  a  con- 
siderably lower  level  than  the  corresponding 
limit  of  the  lung,  but  does  not  extend  to  the 
attachment  of  the  Diaphragm,  so  that  below 
the  line  of  reflection  of  the  pleura  from  the 
thoracic  wall  on  to  the  Diaphragm  the  latter 
is  in  direct  contact  with  the  rib  cartilages  and 
the  Internal  intercostal  muscles.  In  ordinary 
inspiration  the  thin  margin  of  the  base  of  the 
lung  does  not  extend  as  low  as  the  line  of 
pleural  reflection,  with  the  result  that  the  costal 
and  diaphragmatic  pleura  are  here  in  contact, 
the  narrow  slit  between  the  two  being  termed 
HRENic  the  costophienic  sinus  {sinus  ■phrenicocostalis) 
(Fig.  910).  A  similar  condition  exists  behind 
the  sternum  and  rib  cartilages,  where  the 
anterior  thin  margin  of  the  lung  falls  short  of 
the  line  of  pleural  reflection,  and  where  the 
slit-like  cavity  between  the  two  layers  of  pleura 
'  forms  what  is  sometimes  called  the  costome- 

diastinal  sinus  {sinus  costomediastinalis) . 

The  line  along  which  the  ric/hf  plevra  is  re- 
flected from  the  thoracic  wall  to  the  Diaphragm 
starts  in  front,  immediately  below  the  seventh 
costosternal  joint,  and  runs  downward  and 
backward  behind  the  seventh  costal  cartilage 
Fig.  910.— Section  of  the  wall  of  the  thorax,  so  as  to  cross  the  tenth  rib  in  the  mid-axillary 

showing  the  phrenicocostal  sinus.     (Poirier  and    ,.  ,,  ,.,..  ,  ,  , 

Charpy.)  Imc,  trom  which  it  is  prolonged  to  the  spine 

of  the  twelfth  thoracic  vertebra.  The  reflection 
of  the  left  pleura  follows  at  first  the  ascending  part  of  the  sixth  costal  cartilage, 
and  in  the  rest  of  its  course  is  slightly  higher  than  that  of  the  right  side. 

The  free  surface  of  the  pleura  is  smooth,  polished,  and  moistened  by  a  serous 
fluid;  its  attached  surface  is  intimately  adherent  to  the  surface  of  the  lung,  and  to 
the  pulmonary  vessels  as  they  emerge  from  the  pericardium;  it  is  also  adherent  to 
the  upper  surface  of  the  Diaphragm;  throughout  the  rest  of  its  extent  it  is  some- 
what thicker,  and  may  be  separated  from  the  adjacent  parts  with  extreme  facility. 

The  right  pleural  sac  is  shorter,  wider,  and  reaches  higher  in  the  neck  than 
the  left. 

Ligamentum  Latum  Pulmonis. — From  the  above  description  it  will  be  seen  that 
the  root  of  the  lung  is  covered  in  front,  above,  and  behind  by  the  pleura,  and  that 
at  its  lower  border  the  investing  layers  come  into  contact.  Here  they  form  a  sort  of 
.  mesenteric  fold,  the  ligamentum  latum  pulmonis  (lig.  pulmonale),  which  extends 


THE  MEDIASTINUM,    OR  INTERPLEURAL  SPACE  1185 

as  far  as  the  Diaphragm  (but  is  not  attached  thereto)  between  the  pericardium 
and  the  lower  part  of  the  inner  surface  of  the  lung,  having  a  free  falciform  border 
below,  between  the  lung  and  the  Diaphragm.  It  serves  to  retain  the  lower  part 
of  the  lung  in  position  (Figs.  913  and  914). 

Structure  of  the  Pleura. — The  pleura  is  composed  of  fibroelastic  connective  tissue,  its  free 
surface  being  covered  with  a  single  layer  of  flat  endothelial  cells.  It  is  fastened  to  adjacent 
structures  liy  suliscrous  fibroelastic  tissue.  The  subserous  tissue  of  the  visceral  pleura  is  con- 
tinuous with  tlie  fibroelastic  tissue  of  the  lung. 

Vessels  and  Nerves. — The  arteries  of  the  pleura  are  derived  from  the  intercostal,  the  internal 
mammary,  the  musculophrenic,  thymic,  pericardiac,  and  bronchial  arteries.  Tlie  veins  cor- 
respond to  the  arteries.  The  lymphatics  are  very  niunerous  in  the  jileura  and  suliserous  tissue. 
The  lyni|)hatics  of  the  visceral  layer  eraply  inri)  the  superficial  pulmonary  trunks;  the  Ivm- 
lihatiis  (if  ihe  costal  pleura  empty  into  the  intercostal  trunks;  of  the  (lia|ihriii;i]ialic  pleura,  into 
the  diaphragmatic  trunks;  of  the  mediastinal  pleura,  into  the  posterior  mediastinal  nodes.  The 
nerves  are  derived  from  the  phrenic  and  sympathetic  (Luschka). 

Applied  Anatomy. — In  operations  upon  the  kidncij  it  must  be  borne  in  mind  that  the  pleura 
may  sometimes  extend  below  the  level  of  the  last  rib,  and  may  therefore  be  opened  in  these 
operations,  especially  when  the  last  rib  is  removed,  in  order  to  give  more  room.  It  is  best  to 
keep  the  incision  at  least  one  inch  below  the  last  rib,  enlarging  the  wound  afterward,  when  the 
finger  can  be  introduced  as  a  guide. 

In  wounds  of  the  Diaphragm  the  pleura  may  be  injured.  In  operations  about  the  root  of  the 
neck,  especially  in  the  removal  of  lymph  nodes  and  the  ligation  of  the  first  part  of  the  subclavian 
artery,  the  pleura  may  be  injured. 

Punctured  wounds  of  the  root  of  the  neck  are  apt  to  reach  the  pleura. 

Empyema  is  a  surgical  disease.  In  acute  empyema  the  treatment  is  drainage.  A  portion  of 
the  fifth  or  sixth  rib  in  the  axillary  line  is  removed  by  subperiosteal  resection,  the  pleura  is  opened, 
and  a  tube  is  introduced.  In  chronic  empyema  the  lung  is  contracted  and  adherent  and  cannot 
expand;  hence  drainage  will  not  cure  it.  It  is  necessary  to  perform  multiple  rib  resection  in 
order  to  permit  the  thoracic  wall  to  sink  in  and  obliterate  the  cavity,  which,  as  the  lung  is  unable 
to  expand,  it  cannot  do.  The  necessary  operation  may  be  the  one  of  either  Estlander,  Schede, 
or  Fowler  (p.  168). 

If  a  large  wound  admits  suddenly  a  quantity  of  air  into  the  pleura,  dangerous  or  fatal  pneumo- 
thorax arises,  and  the  lung  collapses.  This  is  usually  met  during  operations  by  using  the  Fell- 
O'Dwyer  apparatus  for  artificial  respiration,  as  advised  by  Matas.'  This  apparatus  keeps  the 
lung  expanded,  in  spite  of  the  entrance  of  air  into  the  pleural  sac.  A  surgeon  can  open  the  pleura 
widely  without  any  fear  of  the  lung  collapsing  if  he  operates  in  a  Sauerbruch  chamber.  The 
pressure  within  this  chamber  is  negative.  The  patient's  head  is  outside  of  the  chamber,  his  body 
is  within  it.  The  bronchioles  are  distended  by  the  patient  inhaling  air  at  the  ordinary  pressure, 
but  the  exposed  lung  is  subjected  to  negative  pressure,  hence  the  lung  does  not  collapse  in  spite  of 
a  large  wound  in  the  pleura.  In  surgical  pneumothorax  the  lung  may  be  sutured  to  the  thoracic 
wall,  so  as"  to  block  the  opening.  Sometimes,  in  order  to  arrest  dangerous  pulmonary  bleeding,  a 
surgeon  deliberately  induces  pneumothorax,  in  the  hope  that  the  collapse  of  the  lung  will  arrest 
bleeding. 

When  an  abscess  of  the  liver  is  posterior  and  on  the  dorsum,  transpleural  hepatotomi/  is  per- 
formed. A  portion  of  the  tenth  and  eleventh  ribs  below  the  angle  of  the  scapula  is  removed. 
As  a  rule,  the  pleura  is  found  obliterated  at  this  point.  If  it  is  opened,  it  is  at  once  sutured  or 
closed  with  gauze  packing.  The  exposed  Diaphragm  is  incised,  and,  as  it  is  usually  adherent  to 
the  liver,  the  abscess  cavity  is  entered.  If  it  is  not  adherent,  the  liver  is  exposed  and  the  abscess 
sought  for  with  an  aspirating  needle. 

Grocco's  sign  is  the  presence  of  a  triangular  area  of  paravertebral  dulness  above  the  level  of 
the  twelfth  rib  on  the  side  opposite  to  a  pleural  effusion.  The  dulness  is  believed  to  be  due  to  a 
displacement  of  the  contents  of  the  posterior  mediastinum  by  the  fluid. 


THE  MEDIASTINUM,   OR  INTERPLEURAL  SPACE. 

The  mediastinum  is  the  space  left  in  the  median  portion  of  the  thorax  by  the  non- 
apposition  of  the  two  pleurte.  In  reality  it  is  an  "interpleural  septum."  It  ex- 
tends from  the  sternum  in  front  to  the  vertebral  column  behind,  and  contains  all 
the  thoracic  viscera  excepting  the  lungs.  The  mediastinum  may  be  divided  for 
purposes  of  description  into  two  parts — an  upper  portion,  above  the  upper  \e\e\ 

'  Annals  of  Surgery,  April,  1899. 

7.5 


1186 


THE  ORGANS  OF  VOICE  AND  BESPIBATION 


of  the  pericardium,  which  is  named  the  superior  mediastinum;  and  a  lower  portion, 
below  the  upper  level  of  the  pericardium.  This  lower  portion  is  again  subdivided 
into  three — that  part  which  contains  the  pericardium,  its  contents,  and  other 
structures  below  this  plane:  the  middle  mediastinum;  that  part  which  is  in  front  of 
the  pericardium,  the  anterior  mediastinum;  and  that  part  which  is  behind  the  peri- 
cardium, the  posterior  mediastinimi. 

The  superior  mediastinum  (Fig.  911)  is  that  portion  of  the  interpleural  space 
which  lies  between  the  manubrium  sterni  in  front  and  the  upper  thoracic  vertebrae 
behind.  It  is  bounded  below  by  a  plane  passing  backward  from  the  junction 
of  the  manubrium  and  gladiolus  sterni  to  the  lower  part  of  the  body  of  the  fourth 
thoracic  vertebra,  and  laterally  by  the  lungs  and  pleurae.  It  contains  the  origins 
of  the  Sternohyoid  and  Sternothyroid  muscles  and  the  lower  ends  of  the  Longus 
colli  muscles;  the  arch  of  the  aorta;  the  innominate,  the  thoracic  portion  of  the 
left  carotid  and  subclavian  arteries ;  the  upper  half  of  the  superior  vena  cava  and 


Left  Innom-     Left  Carotid 
mate  Vein.  Artery. 


Vagus  Nerve.-y^ 


Vertebral  ///!' 

Artet  y ■    -'^^^y 

heft  Sublcavian 
Ariel  y  ^;^^ 


Internal  Mammary 
Artery. 


y/2nd  Eib. 


Fig.  911. — Transverse  section  through  the  second  tho 


3rd  Bib 
ertebra      (Braune.) 


the  innominate  veins,  and  the  left  superior  intercostal  vein;  the  vagus,  cardiac, 
phrenic,  and  left  recurrent  laryngeal  nerves ;  the  trachea,  oesophagus,  and  thoracic 
duct;  the  remains  of  the  thymus  gland  and  some  lymph  nodes. 

The  anterior  mediastinum  (Fig.  907)  is  bounded  in  front  by  the  sternum, 
laterally  by  the  pleurae,  and  behind  by  the  pericardium.  It  is  narrow  above, 
but  widens  out  a  little  below,  and,  owing  to  the  oblique  course  taken  by  the  left 
pleura,  it  is  directed  from  above  obliquely  downward  and  to  the  left.  Its  anterior 
wall  is  formed  by  the  left  Triangularis  sterni  muscle  and  the  fifth,  sixth,  and  seventh 
left  costal  cartilages.  It  contains  a  quantity  of  loose  areolar  tissue,  some  lym- 
phatic vessels  which  ascend  from  the  convex  surface  of  the  liver,  two  or  three 
lymph  nodes  (anterior  mediastinal  glands),  and  the  small  mediastinal  branches 
of  the  internal  mammary  artery. 

The  middle  mediastinum  (Fig.  907)  is  the  broadest  part  of  the  interpleural 
space.  It  contains  the  heart  enclosed  in  the  pericardium,  the  ascending  aorta, 
the  lower  half  of  the  superior  vena  cava,  with  the  vena  azygos  major  opening  into 


THE  MEDIASTINUM,    OR  INTERPLEURAL  HI' ACE 


1187 


it,  the  bifurcation  of  the  trachea  and  the  two  bronchi,  the  pulmonary  artery  divid- 
ing into  its  two  branches  and  the  right  and  left  pulmonary  veins,  the  phrenic 
nerves,  and  some  broneiiial  lymph  nodes. 

The  posterior  mediastiniun  (Figs.  907  and  912)  is  an  irreguhir  triangular  space 
running  parallel  with  the  vertebral  column;  it  is  bounded  in  jront  by  the  peri- 


FiG.  912. — The  posterior  mediastinum. 

cardium  above,  and  by  the  posterior  surface  of  the  Diaphragm  below,  behind 
by  the  ^'ertebral  column  from  the  lower  border  of  the  fourth  to  the  twelfth  thoracic 
vertebra,  and  on  either  side  by  the  pleura.  It  contains  the  descending  thoracic 
aorta,  the  venae  azygos  major  and  minor,  the  vagus  and  splanchnic  nerves,  the 
oesophagus,  the  thoracic  duct,  and  some  lymph  nodes. 


1188 


THE  ORGANS  OF  VOICE  AND  BESPIBATION 


Applied  Anatomy. — Primary  tumors  of  the  mediastinum  are  usually  lymphomata  or  lympho- 
sarcomata  arising  from  the  thymus  or  from  the  bronchial  or  posterior  mediastinal  lymph  nodes; 
sarcomata,  dermoid  cysts,  and  embryomata,  occur  more  rarely.  These  tumors  give  rise  to  pain, 
deformity  of  the  thorax,  and  symptoms  of  pressure  on  the  various  nerves,  bloodvessels,  air 
passages,  lymphatics,  and  on  the  oesophagus,  as  these  various  structures  pass  through  the  thorax. 
They  may  produce  physical  signs  very  much  like  those  of  an  aortic  aneiu^ism,  so  that  diagnosis 
between  the  two  is  often  difficult.  The  prognosis  is  bad,  life  usually  ending  within  a  few  months 
or  a  year  of  the  onset  of  the  symptoms. 

Inflammation  of  the  mediastinum  due  to  wounds,  or  to  the  spread  of  inflammation  from  ad- 
jacent parts  {e.  g.,  the  oesophagus,  the  pericardium),  is  sometimes  acute,  leading  to  abscess 
formation.  A  more  chronic  form  associated  with  adhesions  and  inflammation  of  the  pericar- 
dium— the  so-called  chronic  adhesive  mediastinopericarditis — gives  rise  to  obscure  symptoms 
suggesting  gradual  heart  failure,  and  leads  to  death  slowly  but  surely. 


THE  LUNGS  (PULMONES)  (Figs.   913,  914). 

The  lungs  are  the  essential  organs  of  respiration;  they  are  two  in  number, 
placed  one  on  each  side  of  the  thorax,  separated  from  each  other  by  the  b^art  and 
other  contents  of  the  mediastinum.  A  heaUhy  lung  hangs  free  within  the  pleural 
cavity.     It  is  suspended  by  the  root  and  by  the  ligamentum  pulmonale.     In  many 


Groove  foi  innominate 
aiteiy 


Groove  for  supet  ior_ 
vena  cava 


G)  oove  for  vena 
azygos  major 

Eparterial  bronchus 

Hyparterial  broyichus 
Pulmonary  veins 


Groove  for  oesophagus 


Ligamentum  latum 
pulmonis 


Fig.  913. — Mediastinal  surface  of  right  lung. 


cases  examined  the  lung  does  not  hang  free,  but,  as  a  result  of  former  pleurisy, 
an  area  of  the  pulmonary  pleura  is  adherent  to  the  parietal  pleura.  Each  lung 
is  conical  in  shape,  and  presents  for  an  examination  an  apex,  a  base,  three  bor- 
ders, and  three  surfaces. 

The  apex  {apex  pulmonis)  is  rounded,  and  extends  into  the  root  of  the  neck 
about  an  inch  to  two  inches  (2.5  to  5  cm.)  above  the  level  of  the  anterior  end  of  the 
first  rib.  A  furrow  produced  by  the  subclavian  artery  as  it  curves  outward  in  front 
of  the  pleura  runs  upward  and  outward  immediatelj'  below  the  apex.  The 
brachial  plexus  is  in  close  proximity  to  this  portion  of  the  lung. 

The  base  [basis  pulmonis)  or  diaphragmatic  surface  is  broad,  concave,  and 
rests  upon  the  convex  surface  of  the  Diaphragm,  which  separates  the  right  lung 
from  the  upper  surface  of  the  right  lobe  of  the  liver  and  the  left  lung  from  the 


THE  LUNGS 


1189 


upper  surface  of  the  left  lobe  of  the  liver,  the  fundus  of  the  stomach,  and  the 
spleen.  Since  the  Diaphragm  extends  higher  on  the  right  than  on  the  left  side, 
it  follows  that  the  concavity  on  the  base  of  the  right  lung  is  deeper  than  that  of 
the  left.  Laterally  and  behind,  the  base  is  bounded  by  a  thin,  sharp  margin 
which  projects  for  some  distance  into  the  costophrenic^  sinus  of  the  pleura, 
between  the  lower  ribs  and  the  costal  attachment  of  the  Diaphragm.  The  base 
of  the  lung  descends  during  inspiration  and  ascends  during  expiration;  its  rela- 
tion to  the  thoracic  wall  is  indicated  in  Figs.  919  and  920. 


Grooiefni  left  mhclavinii  artery 
Grooie  for  left  innominate  vein 


Pulmonary  artery 
Pulmonary  veins 


Incisura  cardiaca 


Fig.  9U.— Mediastinal  surface  of  left  lung. 


Surfaces. — The  external,  costal,  or  thoracic  surface  (fades  costalis)  (Figs.  917 
and  918)  is  smooth,  convex,  of  considerable  extent,  and  corresponds  to  the  form 
of  the  cavity  of  the  thorax,  being  deeper  behind  than  in  front.  It  is  in  contact 
with  the  costal  pleura,  and  presents,  in  a  hardened  specimen,  slight  grooves 
corresponding  to  the  overlying  ribs. 

The  inner  or  mediastinal  surface  (fades  viediastinalis)  (Figs.  913  and  914)  is 
in  contact  with  that  portion  of  the  pleura  which  forms  the  lateral  boundary  of 
the  mediastinal  space.  It  presents  a  deep  concavity  which  accommodates  the 
pericardial  sac;  this  is  larger  and  deeper  on  the  left  than  on  the  right  lung,  on 
account  of  the  heart  projecting  farther  to  the  left  than  to  the  right  of  the  mesal 
plane.  Above  and  behind  this  concavity  is  a  triangular  depression  named  the 
hilum  (kilm  pulmonis),  where  the  structures  which  form  the  root  of  the  lung  enter 
and  leave  the  viscus. 

Oti  the  right  lung  (Fig.  915),  immediately  above  the  hilum,  is  an  arched  furrow 
which  accommodates  the  vena  azygos  major,  while  running  upward,  and  then 
arching  outward  some  little  distance  below  the  apex,  is  a  wide  groo\-e  for  the  supe- 
rior vena  cava  and  right  innominate  vein ;  and  behind  this,  nearer  the  apex,  is  a  sec- 
ond furrow  for  the  innominate  artery.  x\long  the  back  part  of  the  inner  surface 
is  a  vertical  groove  for  the  oesophagus;  this  groove  becomes  less  distinct  below, 
owing  to  the  inclination  of  the  lower  part  of  the  oesophagus  to  the  left  of  the  middle 
line.  In  front  and  to  the  right  of  the  lower  part  of  the  oesophageal  groove,  the 
inner  surface  is  applied  to  the  pleural  covering  of  the  right  and  posterior  aspects 


1190 


THE  ORGANS  OF  VOICE  AND  RESPIRATION 


of  the  thoracic  parts  of  the  inferior  vena  cava;  this  vessel  being  accommodated 
in  a  deep  concavitj'. 

On  the  left  lung  (Fig.  914),  immediately  above  the  hilum,  is  a  well-marked 
curved  furrow  produced  by  the  arch  of  the  aorta,  and  running  upward  from  this 
toward  the  apex  is  a  groove  accommodating  the  subclavian  artery;  a  slight  impres- 
sion in  front  of  the  latter  and  close  to  the  margin  of  the  lung  lodges  the  left  in- 
nominate vein.  Behind  the  hilum  and  pericardial  depression  is  a  vertical  furrow 
produced  by  the  descending  thoracic  aorta,  and  in  front  of  this,  near  the  base 
of  the  lung,  the  lower  part  of  the  oesophagus  causes  a  shallow  depression. 


Fig.  915.— Front 


of  the  heart  and  lungs. 


Borders. — The  posterior  border  (margo  posterior)  is  broad  and  rounded,  and 
is  received  into  the  deep  concavity  on  either  side  of  the  vertebral  column.  It  is 
much  longer  than  the  anterior  border. 

The  inferior  border  (margo  inferior)  is  the  sharp  margin  of  the  base  separating 
the  costal  and  diaphragmatic  surfaces.  It  projects,  below,  into  the  upper  part  of 
the  costophrenic  sinus. 

The  anterior  border  (margo  anterior)  is  thin  and  sharp,  overlaps  the  front  of  the 
pericardium,  and  is  projected  into  the  costomediastinal  sinus  of  the  pleura.  The 
anterior  border  of  the  right  lung  is  almost  vertical;  that  of  the  left  presents,  below, 
an  angular  notch,  the  incisura  cardiaca,  into  which  the  heart  and  pericardium  are 
received.  A  projection  from  the  upper  lobe  comes  forward  beneath  the  cardiac 
notch;  it  is  called  the  lingula  pulmonis. 

Fissures  and  Lobes  of  the  Lung.— The  left  lung  is  divided  into  two  lobes,  an 
upper  and  a  lower,  by  an  oblique  fissure  (incisura  interlobaris) ,  which  extends 
from  the  outer  to  the  inner  surface  of  the  lung  both  above  and  below  the  hilum. 


THE  LUNGS 


1191 


As  seen  on  the  surface,  this  fissure  commences  on  the  inner  aspect  of  the  hnig 
at  the  upper  and  posterior  part  of  the  hihim,  and  runs  backward  and  upward 


ANCE    OF 
AZYGOS 
CH    OF    PUL- 
RY    ARTERY 


Fig.  916. — Pulmonary  veins,  seen  in  a  dorsal  view  of  the  heart  and  lun^.     The  lungs  have  been  pulled  away 
from  the  median  line,  and  a  part  of  the  right  lung  has  been  cut  away  to  display  the  air  ducts  and  bloodvessels. 

(Testut.) 


to  the  posterior  border,  which  it  crosses  about  two  and  a  half  inches  (6.5  cm.)  be- 
low the  apex.     It  then  extends  downward  and  forward  over  the  outer  surface  and 


1192 


THE  ORGANS  OF  VOICE  AND  RESPIRATION 


reaches  the  lower  border  a  little  behind  its  anterior  inferior  extremity,  and  its 
further  course  can  be  followed  upward  and  backward  across  the  inner  surface  as  far 
as  the  lower  part  of  the  hilum.  The  upper  lobe  {lohus  superior)  lies  above  and  in 
front  of  this  fissure,  and  includes  the  apex,  the  anterior  border,  and  a  considerable 
part  of  the  outer  surface  and  the  greater  part  of  the  inner  surface  of  the  lung.  The 
lower  lobe  {lobus  inferior),  the  larger  of  the  two,  is  situated  below  and  behind 
this  fissure,  and  comprises  almost  the  whole  of  the  base,  a  large  portion  of  the 
outer  surface,  and  the  greater  part  of  the  posterior  border. 

The  right  lung  is  divided  into  three  lobes,  upper,  middle,  and  lower,  by  an  oblique 
and  a  horizontal  fissure.     The  oblique  fissure  separates  the  lower  from  the  middle 


Fig.  919. — Front  view  of  thorax,  showing  relations  of  pleurae  and  lungs  to  the  thoracic  wall.     The  blue  lines  indicate 
the  lines  of  the  reflection  of  the  pleurae;  the  red,  the  outlines  of  the  lungs  and  their  fissures. 


and  upper  lobes,  and  corresponds  closely  with  the  fissure  of  the  left  lung.  Its 
direction  is,  however,  more  vertical,  and  it  cuts  the  lower  border  about  three  inches 
from  the  anterior  margin.  The  horizontal  fissure  separates  the  upper  from  the 
middle  lobe.  It  begins  in  the  oblique  fissure  near  the  posterior  border  of 
the  lung  and,  running  horizontally  forward,  cuts  the  anterior  border  at  the  level  of 
of  the  sternal  end  of  the  fourth  costal  cartilage ;  on  the  inner  surface  it  may  be  traced 
backward  to  the  hilum.  The  middle  lobe  (lobiis  mediiis),  the  smallest  of  the 
lobes  of  the  right  lung,  lies  between  the  horizontal  fissure  and  the  lower  part  of 
the  oblique  fissure;  it  is  wedge-shaped  and  includes  the  lower  part  of  the  anterior 
border  and  the  anterior  part  of  the  base  of  the  lung. 

The  right  lung  is  the  larger  and  heavier;  it  is  broader  than  the  left,  owing  to 


THE  LUNGS 


1193 


the  inclination  of  the  heart  to  the  left  side;  it  is  also  shorter  by  an  inch,  in 
consequence  of  the  Diaphragm  risuig  higher  on  the  right  side  to  accommodate 
the  liver. 

The  Root  of  the  Lung  {radix  jndnwnis)  (Figs.  913  and  914). — A  little  above  the 
middle  of  the  inner  surface  of  each  lung,  and  nearer  its  posterior  than  its  anterior 


Fig.  920. — Lateral  view  of  thorax,  showing  relations  of  right  pleura  and  lung  to  the  thoracic  wall.    The  blue  line  in- 
dicates the  line  of  pleural  reflection;  the  red  lines,  the  outline  of  the  lung  and  its  fissures. 

border,  is  its  root,  by  which  the  lung  is  connected  to  the  heart  and  the  trachea. 
The  root  is  formed  by  the  bronchial  tube,  the  pulmonary  artery,  the  pulmonary 
veins,  the  bronchial  arteries  and  veins,  the  pulmonary  plexus  of  nerves,  lymphatics, 
bronchial  lymph  nodes,  and  areolar  tissue,  all  of  which  are  enclosed  by  a  reflection 
of  the  pleura.  The  root  of  the  right  lung  lies  behind  the  superior  vena  cava  and 
ascending  portion  of  the  aorta,  and  below  the  vena  azygos  major.  The  root  of 
the  left  lung  lies  beneath  the  arch  of  the  aorta  and  in  front  of  the  descending 
aorta;  the  phrenic  nerve  and  the  anterior  pulmonary  plexus  lie  in  front  of  each, 
and  the  vagus  and  posterior  pulmonary  plexus  behind  each;  below  each  is  the 
broad  pulmonary  ligament. 

The  chief  structures  composing  the  root  of  each  lung  are  arranged  in  a  similar 
manner  from  before  backward  on  both  sides — viz.,  the  two  pulmonary  veins  in 
front,  the  pulmonary  artery  in  the  middle,  and  the  bronchus,  together  with  the 
bronchial  vessels,  behind.  From  above  downward,  on  the  two  sides,  their 
arrangement  differs,  thus: 


1194  THE  ORGANS  OF  VOICE  AND  RESPIRATION 

On  the  right  side  their  position  is — bronchus,  pulmonary  artery,  pulmonary 
veins;  but  on  the  left  side  their  position  is — pulmonary  artery,  bronchus,  pulmo- 
nary veins.  It  should  be  noted  that  the  entire  right  bronchus  does  not  lie  above 
the  right  pulmonary  artery,  but  only  its  eparterial  branch  (see  p.  1177),  which 
passes  to  the  upper  lobe  of  the  right  lung;  the  divisions  of  the  bronchus  for  the 
middle  and  lower  lobes  lie  below  the  artery. 

Divisions  of  the  Bronchi. — Just  as  the  lungs  differ  from  each  other  in  the 
number  of  their  lobes,  so  the  bronchi  differ  in  their  mode  of  subdivision. 

The  right  bronchus  gives  off,  about  an  inch  from  the  bifurcation  of  the  trachea, 
a  branch  for  the  upper  lobe.  This  branch  arises  above  the  level  of  the  pulmonary 
artery,  and  is  therefore  named  the  eparterial  bronchus.  All  the  other  branch 
bronchi  come  off  below  the  pulmonary  artery,  and  consequently  are  termed 
hyparterial  bronchi.  The  first  of  these  is  distributed  to  the  middle  lobe,  and  the 
main  tube  then  passes  downward  and  backward  into  the  lower  lobe,  giving  off 
in  its  course  a  series  of  large  ventral  and  small  dorsal  branches.  The  ventral 
and  dorsal  branches  arise  alternately,  and  are  usually  eight  in  number — four  of 
each  kind.  The  branch  to  the  middle  lobe  is  regarded  as  the  first  of  the  ventral 
series. 

The  left  bronchus  passes  below  the  level  of  the  pulmonary  artery  before  it 
divides,  and  hence  all  its  branches  are  hyparterial;  it  may  therefore  be  looked 
upon  as  equivalent  to  that  portion  of  the  right  bronchus  which  lies  on  the  distal 
side  of  its  eparterial  branch.  The  first  branch  of  the  left  bronchus  arises  about 
two  inches  from  the  bifurcation  of  the  trachea,  and  is  distributed  to  the  upper  lobe. 
The  main  stem  then  enters  the  lower  lobe,  where  it  divides  into  ventral  and  dorsal 
branches  similar  to  those  in  the  right  lung.  The  branch  to  the  upper  lobe  of  the 
left  lung  is  regarded  as  the  first  of  the  ventral  series. 

The  true  weight  of  the  human  lungs  as  ascertained  in  the  bodies  of  criminals  executed  by 
electricity,  in  which  the  mode  of  death  is  attended  by  a  nearly  bloodless  condition  of  the  lungs,, 
is  215  grams  (7^  ounces)  for  the  left  lung  and  240  grams  (8i  ounces)  for  the  right  lung  (E.  A. 
Spitzka,  Amer.  Jour,  of  Anat.,  iii,  1,  p.  v)-  Ordinarily,  with  the  vascular  channels  more  or  less 
filled  with  blood  and  serum,  the  two  lungs  together  weigh  about  42  ounces,  the  right  lung  being 
2  ounces  heavier  than  the  left,  but  much  variation  is  met  with  according  to  the  amount  of  blood 
or  serous  fluid  they  may  contain.  The  lungs  are  heavier  in  the  male  than  in  the  female.  The 
specific  gravity  of  the  lung  tissue  varies  from  0..345  to  0.746. 

The  color  of  the  lungs  at  birth  is  a  pinkish  white;  in  adult  life  a  dark  slate-color,  mottbd  in 
patches;  and  as  age  advances  this  mottling  assumes  a  black  color.  The  coloring  matter  con- 
sists of  granules  of  carbonaceous  substance  deposited  in  the  areolar  tissue  near  the  surface  of  the 
organ.  It  increases  in  quantity  as  age  advances,  and  is  more  abundant  in  males  than  in  females. 
The  posterior  surface  of  the  lung  is  usually  darker  than  the  anterior. 

The  surface  of  the  lung  is  smooth,  shining,  and  marked  out  into  numerous  polyhedral  spaces, 
indicating  the  lobules  of  the  organ;  the  area  of  each  of  these  spaces  is  crossed  by  numerous  lighter 
lines. 

The  substance  of  the  lung  is  of  a  light,  porous,  spongy  texture;  it  floatsin  water  and  crepi- 
tates when  handled,  owing  to  the  presence  of  air  in  the  tissue;  it  is  also  highly  elastic;  hence 
the  collapsed  state  of  these  organs  when  they  are  removed  from  the  closed  cavity  of  the  thorax. 

The  Fetal  Lung. — After  respiration  has'  been  established,  the  lung  fills  the  pleural  cavity. 
In  the  stillborn  fetus,  as  the  lung  has  never  been  distended  with  air  and  has  never  received  a  large 
amount  of  blood,  it  is  gathered  into  a  small  mass  at  the  back  of  the  thorax.  It  will  sink  in  water 
and  feels  solid  to  the  touch. 

Structure. — The  structm-e  of  the  lung  is  such  that  the  blood  brought  by  the  pulmonary 
artery  comes  into  close  relation  with  the  air  which  enters  from  the  bronchioles.  The  blood 
gives  materials  to  the  air,  and  the  air  gives  elements  to  the  blood,  and  the  process  of  respiration 
causes  the  dark  blood  brought  from  the  heart  by  the  pulmonary  artery  to  retiu-n  to  the  heart  as 
red  blood  in  the  pulmonary  veins.  The  lungs  are  composed  of  an  external  serous  coat,  a  sub- 
serous areolar  tissue,  and  the  pulmonary  substance  or  parenchyma. 

The  serous  coat  is  thin,  transparent,  and  invests  the  entire  organ  as  far  as  the  root.  It  is 
composed  of  a  layer  of  endothelial  cells  resting  upon  a  thin  layer  of  fibroelastic  tissue,  and  is 
continuous  with  the  subserous  tissue.     It  is  known  as  the  pulmonary  plem-a  (p.  1181). 


THE  LUNGS  1195 

The  subserous  areolar  tissue  contains  a  large  proportion  of  elastic  fibres;  it  invests  the 
entire  surface  of  the  lung,  and  extends  inward  between  the  lobules. 

The  parenchyma  is  composed  of  lobules  which,  although  closely  connected  by  an 
interlobular  areolar  tissue,  are  quite  distinct  from  one  another.  The  lobules  vary  in  size  from 
0.3  cm.  to  .3  cm.  (5  inch  to  U  inches);  those  on  the  surface  are  large,  of  pyramidal  form,  with 
the  bases  turned  toward  the  surface;  those  in  the  interior  are  smaller  and  of  variou.s  forms. 
Each  lobule  is  composed  of  one  of  the  ramifications  of  a  bronchiole  (about  1  mm.  in  diameter) 
and  its  terminal  air  cells,  and  of  the  ramifications  of  the  pulmonary  and  bronchial  vessels,  lym- 
phatics, and  nerves,  all  of  these  structures  being  connected  by  fibroelastic  tissue. 

The  bronchus  upon  entering  the  lung  divides  like  the  ducts  of  a  gland,  the  terminal  tubules, 
about  I  mm.  in  diameter,  constituting  the  bronchioles.  Each  bronchiole  forms  a  lol^ule  that  is 
separated  and  closed  from  its  neighbor.  The  bronchiole  diminishes  in  (liamctcr  \><  about  0..5  mm. 
and  divides  into  several  tubules  (0.3  to  0.4  ram.  in  diameter),  the  respiratory  bronchioles,  upon 
the  sides  of  which  some  minute  depressions,  alveoli,  may  be  seen.  Each  respiratory  bronchiole 
further  subdivides  into  several  alveolar  ducts  (0.2  mm;  in  diameter),  along  which  alveoli  are 
numerous.  The  alveolar  ducts  lead  into  individual  dilated  spaces,  the  alvei,  air  sacs,  or  infun- 
dibula  (0.3  to  5  mm.  in  diameter),  upon  the  sides  of  which  are  alveoli  or  saccules  (0.0.5  to  0.1  mm. 
in  diameter).  The  alveoli  are  partially  separated  from  one  another  by  low  partitions  or  septa, 
of  the  same  structure  as  the  alveolar  wall. 

Changes  in  Stracture  of  the  Bronchus  and  Its  Divisions.— Each  main  bronchus  resembles 
the  trachea  in  structure.  Within  the  lung  the  bronchial  tubes  are  circular  in  outline.  As  the 
bronchus  divides  and  redivides  monopodially,  changes  occur  in  the  various  coats.  The  mucous 
coat  presents  a  corrugated  appearance  and  the  cartilage  in  the  submucosa  changes  to  a  com- 
plete investing  layer  composed  of  a  number  of  individual  plates.  With  this  change  the  smooth 
muscle  tissue,  internal  to  the  cartilage,  increases  so  as  to  form  a  complete  layer.  As  the  smaller 
tubes  are  approached  the  cartilage  decreases  in  amount,  while  the  muscle  increases  relatively. 
The  mucous  glands  in  mucosa  disappear  in  those  tubules  of  1  mm.  in  diameter,  while  the  car- 
tilage persists  until  a  diameter  of  about  0.5  mm.  is  reached. 

Each  bronchiole  consists  of  a  layer  of  simple  columnar  and  goblet  epithelial  cells  resting  upon 
a  basement  membrane  and  a  fibroelastic  tunica  propria;  external  to  this  is  found  a  layer  of 
smooth  muscle  tissue,  and  beyond  this  a  layer  of  white  fibrous  tissue  containing  the  main  vessels 
and  nerves  of  the  tubules.  The  respiratory  bronchiole  is  lined  by  simple  ciliated  cells,  that 
gradually  give  way  to  nonciliated  columnar  and  cuboidal  cells,  and  lastly  flattened  epithelium 
(the  respiratory  epithelium).  Some  muscle  tissue  is  still  present,  and  the  elastic  tissue  increases 
in  quantity.  The  alveolar  ducts  are  lined  by  simple  epithelial  plates  resting  upon  a  basement 
membrane  supported  by  elastic  tissue.  At  the  end  of  this  tubule  the  muscle  tissue  disappears. 
The  air  sacs  are  composed  of  the  alveoli  or  saccules  lined  by  respiratory  epithelium  that  rests 
upon  a  basement  membrane  supported  by  a  meshwork  of  elastic  tissue  containing  the  densest 
capillary  plexus  of  the  body.  This  elastic  tissue  allows  the  alveoli  to  increase  from  two  to  three 
times  their  ordinary  diameters.  Separating  one  alveolus  from  another  is  a  low  septum  that 
has  the  same  structure  as  the  alveolar  wall. 

Vessels  of  the  Lungs. — The  pulmonary  artery  (Figs.  915  and  916)  conveys  the  venous 
blood  to  the  lungs;  it  divides  into  branches  which  accompany  the  bronchial  tubes,  and  terminates 
in  a  dense  capillary  network  upon  the  walls  of  the  air  cells.  In  the  lung  the  branches  of  the 
pulmonary  artery  are  usually  above  and  in  front  of  a  bronchial  tube,  the  vein  below.  The 
pulmonary  artei-ics  are  the  nutrient  vessels  of  the  respiratory  epithelium. 

The  pulmonary  capillaries  form  plexuses  which  lie  immediately  beneath  the  epithelium  of  the 
walls  and  septa  of  the  air  cells  and  of  the  alveoli.  In  the  septa  between  the  air  cells  the  capillary 
network  forms  a  single  layer.  The  capillaries  form  a  very  minute  network,  the  meshes  of  which 
are  smaller  than  the  vessels  themselves;^  their  walls  are  also  exceedingly  thin.  The  arteries 
of  neighboring  lobules  are  independent  of  one  another,  but  the  veins  freely  anastomose. 

The  pulmonary  veins  commence  in  the  pulmonary  capillaries,  the  radicles  coalescing  into 
larger  branches,  wiiich  run  along  through  the  substance  of  the  lung,  independently  from  the 
minute  arteries  and  bronchi.  After  freely  communicating  with  other  branches  they  form  large 
vessels,  which  ultimately  come  into  relation  with  the  arteries  and  bronchial  tubes,  and  accom- 
pany them  to  the  hilum  of  the  organ.  Finally,  they  open  into  the  left  auricle  of  the  heart,  con- 
veying oxygenated  blood  to  be  eventually  distributed  to  all  parts  of  the  body  by  the  aorta. 

The  bronchial  arteries  supply  blood  for  the  nutrition  of  bronchial  tubes  and  vessels  of  the 
lung.  The  thoracic  aorta  usually  gives  off  two  left  bronchial  arteries.  The  single  right  bron- 
chial artery  usually  arises  from  the  first  right  aortic  intercostal,  but  sometimes  from  the  superior 
left  bronchial  artery,  or  from  the  aorta.  In  the  root  of  the  lung  they  are  posterior  to  the  bron- 
chus, they  accompany  the  bronchial  tubes,  supply  the  bronchial  tubes  and  surrounding  inter- 
lobular tissue,  and  give  branches  to  the  walls  of  the  larger  pulmonary  vessels,  the  oesophagus, 
pericardium,  and  bronchial  lymph  nodes.  Those  supplying  the  bronchial  tubes  form  a  capil- 
lary plexus  in  the  muscular  coat,  from  which  branches  are  given  oft"  to  form  a  second  plexus  in 
the  mucous  coat.     This  plexus  anastomoses  with  branches  of  the  pulmonary  artery,  and  empties 


1196 


THE  ORGANS  OF   VOICE  AND  RESPIRATION 


into  the  pulmonary  vein.  Others  are  distributed  in  the  interlobular  areolar  tissue,  and  terminate 
partly  in  the  deep,  partly  in  the  superficial,  bronchial  veins.  Lastly,  some  ramify  upon  the 
surface  of  the  lung  beneath  the  pleura,  where  they  form  a  capillary  network.  There  may  be 
but  one  bronchial  artery;  there  may  be  three  or  four. 

The  bronchial  veins  are  not  found  in  the  walls  of  the  very  small  bronchi.  The  small  bronchial 
veins  run  along  by  the  front  and  back  of  the  medium  sized  and  larger  tubes,  and  form  two  trunks 
at  the  root  of  each  lung.  These  vessels  terminate  on  the  right  side  in  the  vena  azygos  major, 
and  on  the  left  side  in  the  superior  intercostal  or  left  upper  azygos  vein.  Tracheal  and  posterior 
mediastinal  veins  open  into  the  bronchial  veins.  The  venous  blood  from  the  smaller  tubes 
passes  to  the  pulmonary  veins. 


BRONCHIOLe 


-A  pulmonary  lobule, 
and  Charpy.) 


Fig.  922.^ — The  terminal   bronchial  tubes.     The  respiratory 
bronchiole  and  alveoli.      (Poirier  and  Charpy.) 


The  lymphatics  begin  in  networks  about  the  lobules  and  form  networks  about  the  bronchi 
and  beneath  the  bronchial  mucous  membrane.  The  superficial  collecting  trunks  arise  about 
the  lobules  and  beneath  the  pleura.  According  to  Sappey,  the  superficial  trunks  from  the  upper 
lobe  begin  on  the  costal  surface;  one  set  passes  around  the  anterior  border,  another  set  around 
the  posterior  border,  and  a  third  into  the  incisura  interlobaris.  The  same  observer  says  that 
the  superficial  trunks  from  the  middle  lobe  unite  with  the  trunks  from  the  upper  and  lower  lobes; 
and  the  superficial  trunks  from  the  lower  lobe,  like  those  of  the  upper  lobe,  are  in  three  sets. 
One  set  passes  around  the  posterior  margin,  one  around  the  anterior  margin,  and  one  into  the 
interlobar  fissure.  All  of  the  superficial  trunks  convey  lymph  to  the  nodes  of  the  hilum.  Some 
of  the  deep  collecting  trunks  begin  by  the  side  of  the  small  bronchi;  others  course  along  by  the 
pulmonary  veins  or  pulmonary  arteries.  All  of  them  pass  to  the  nodes  of  the  hilum.  The 
nodes  of  the  hilum  are  in  communication  with  the  peritracheobronchial  nodes. 

Nerves. — The  lungs  are  supplied  from  the  anterior  and  posterior  pulmonary  plexuses,  formed 
chiefly  by  branches  from  the  sympathetic  and  vagus.  The  filaments  from  these  plexuses  accom- 
pany the  bronchial  tubes,  and  are  lost  upon  them.     Small  ganglia  are  found  upon  these  nerves. 

Surface  Form. — The  apex  of  the  lung  is  situated  in  the  neck,  behind  the  interval  between  the 
two  heads  of  origin  of  the  Sternomastoid  muscle.  The  height  to  which  it  rises  above  the  clavicle 
varies  very  considerably,  but  is  generally  about  one  inch.  It  may,  however,  extend  as  much  as 
an  inch  and  a  half  or  an  inch  and  three-quarters,  or,  on  the  other  hand,  it  may  scarcely  project 
above  the  level  of  this  bone.  In  order  to  mark  out  the  anterior  margin  of  the  lung,  a  line  is 
to  be  drawn  from  the  apex  point,  one  inch  above  the  level  of  the  clavicle,  and  rather  nearer  the 
posterior  than  the  anterior  border  of  the  Sternomastoid  muscle,  downward  and  inward  across 
the  sternoclavicular  articulation  and  first  piece  of  the  sternum  until  it  meets,  or  almost  meets, 
its  fellow  of  the  other  side  opposite  the  articulation  of  the  manubrium  and  gladiolus.  From  this 
point  the  two  lines  are  to  be  drawn  downward,  one  on  either  side  of  the  mesal  line  and  close  to 
it,  as  far  as  the  level  of  the  articulation  of  the  fourth  costal  cartilages  to  the  sternum.  From 
here  the  two  lines  diverge;  the  left  is  to  be  drawn  at  first  passing  outward  with  a  slight  inclina- 
tion downward,  and  then  taking  a  bend  downward  with  a  slight  inclination  outward  to  the  apex 


THE  LUNGS  1107 

of  the  heart,  and  thence  to  the  sixth  sternochondral  articulation.  The  direction  of  the  anterior 
border  of  this  part  of  the  left  lung  is  denoted  with  sufficient  accuracy  by  a  curved  line  with  its 
convexity  directed  upward  and  outward  from  the  articulation  of  the  fourth  right  costal  cartilage 
of  the  sternum  to  the  fifth  intercostal  space,  an  inch  and  a  half  l^elow  and  three-(|uartcrs  of  an 
inch  internal  to  the  left  nipple  in  the  male.  The  continuation  of  the  anterior  border  of  the 
right  lung  is  marked  by  a  prolongation  of  its  line  from  the  level  of  the  fourth  costal  cartilages 
vertically  downward  as  far  as  the  sixth,  when  it  slopes  off  along  the  line  of  the  sixth  costal  cartilage 
to  its  articulation  with  the  rib. 

The  lower  border  of  the  lung  is  marked  out  by  a  slightly  curved  line  with  its  convexity  down- 
ward from  the  articulation  of  the  sixth  costal  cartilage  to  its  rib  to  the  spinous  process  of  the 
tenth  thoracic  vertebra.  If  vertical  lines  are  drawn  downward  from  the  middle  of  the  clavicle, 
from  the  deepest  part  of  the  axilla,  and.  from  the  apex  of  the  scapula,  while  the  arms  are  raised 
from  the  sides,  they  should  intersect  this  convex  line,  the  first  at  the  sixth,  the  second  at  the 
eighth,  and  the  third  at  the  tenth  rib.  It  will  thus  be  seen  that  the  pleura  extends  farther  down 
than  the  lung,  so  that  it  may  be  wounded,  and  a  wound  may  pass  through  its  cavity  into  the  Dia- 
phragm, and  the  abdominal  viscera  may  be  injured  without  the  lung  being  involved. 

The  posterior  border  of  the  lung  is  indicated  by  a  line  drawn  from  the  level  of  the  spinous 
process  of  the  seventh  cervical  vertebra,  doAvn  either  side  of  the  vertebral  column,  correspond- 
ing to  the  costovertebral  joints  as  low  as  the  spinous  process  of  the  tenth  thoracic  vertebra. 
The  trachea  bifurcates  opposite  the  spinous  process  of  the  fourth  thoracic  vertebra,  and  from  this 
point  the  two  bronchi  are  directed  outward. 

"The  position  of  the  great  fissure  of  the  lungs  may  be  indicated  by  a  line  drawn  from  the  third 
thoracic  spine  obliquely  downward  in  such  a  manner  as  to  reach  the  sixth  rib  close  to  the  mid- 
clavicular line.  The  interlobar  fissure  between  the  upper  and  middle  lobes  of  the  right  lung 
corresponds  to  a  line  drawn  from  the  apex  of  the  axilla  almost  horizontally  to  the  sternum, 
reaching  the  latter  at  about  the  level  of  the  fourth  costal  cartilage"  (Ehrendrath). 

Applied  Anatomy. — The  lungs  may  be  wounded  or  torn  in  three  ways:  (1)  By  compression 
of  the  thorax,  without  any  injury  to  the  ribs.  (2)  By  a  fractured  rib  penetrating  the  lung.  (3) 
By  stabs,  giuishot  wounds,  etc. 

The  first  form,  where  the  lung  is  ruptured  by  external  compression  without  any  fracture  of 
the  ribs,  is  very  rare,  and  usually  occurs  in  young  children,  and  affects  the  root  of  the  lung — 
i.  e.,  the  most  fixed  part — and  thus,  implicating  the  great  vessels,  is  frecjuently  fatal.  It  would 
seem  to  be  a  most  unusual  injury,  and  the  exact  mode  of  its  causation  is  difficult  to  understand. 
The  probable  explanation  is  that  immediately  before  the  compression  is  applied  a  deep  inspira- 
tion is  taken  and  the  lungs  are  fully  iriflated;  owing  then  to  spasm  of  the  glottis  at  the  moment 
of  compression,  the  air  is  unable  to  escape  from  the  lung,  the  lung  is  not  able  to  recede,  and 
consequently  gives  way. 

In  the  second  variety,  when  the  wojind  in  the  lung  is  produced  by  the  penetration  of  a  broken 
rib,  both  the  pleura  costalis  nnd  the  pleura  pulmonalis  must  necessarily  be  injured,  and  conse- 
quently the  air  taken  into  the  wounded  air  cells  may  find  its  way  through  these  wounds  into  the 
cellular  tissue  of  the  parietes  of  the  thorax.  This  it  may  do  without  collecting  in  the  pleural 
cavity;  the  two  layers  of  the  pleura  are  so  intimately  in  contact  that  the  air  may  pass  straight 
through  from  the  wounded  lung  into  the  subcutaneous  tissue.  Emphysema  constitutes,  there- 
fore, an  important  sign  of  injury  to  the  lung  in  cases  of  fracture  of  the  ribs.  Pneumothorax,  or  air 
in  the  pleural  cavity,  is  much  more  likely  to  occur  in  injuries  to  the  lung  of  the  third  variety;  that 
is  to  say,  from  external  wounds,  from  stabs  and  gunshot  injuries,  in  which  cases  air  passes  either 
from  the  wound  of  the  lung  or  from  an  external  wound  into  the  cavitv  of  the  pleura  during  the 
respiratory  movements.  In  these  cases  there  is  generally  no  emphysema  of  the  subcutaneous 
tissue  unless  the  external  wound  is  small  and  valvular,  so  that  the  air  drawn  into  the  wound 
during  inspiration  is  then  forced  into  the  cellular  tissue  during  expiration  because  it  cannot 
escape  from  the  external  wound.  Occasionally  in  wounds  of  the  parietes  of  the  thorax  no 
air  finds  its  way  into  the  cavity  of  the  pleura,  because  the  lung  at  the  time  of  the  accident 
protrudes  through  the  wound  and  blocks  the  opening.  This  occurs  where  the  wound  is  large, 
and  constitutes  a  so-called  hernia  of  the  lung.  True  hernia  of  the  lung  occurs,  though  very 
rarely,  after  wounds  of  the  thoracic  wall,  when  the  wound  has  healed  and  the  cicatrix  subse- 
quently yields  from  the  pressure  of  the  viscus  behind.  It  forms  a  globular,  elastic,  crepitating 
swelling,  which  enlarges  during  expiratory  efforts,  falls  during  inspiration,  and  disappears  on 
holding  the  breath.  Wounds  of  the  lung  may  produce  dangerous  or  fatal  hemorrharje  into  the 
pleural  sac.  In  many  cases  the  bleeding  is  spontaneously  arrested;  in  others  the  surgeon  must 
interfere  to  save  life.  In  some  cases  air  has  been  admitted  by  intercostal  incision  and  the  inser- 
tion of  a  tube,  and  pulmonary  collapse  has  arrested  bleeding.  In  other  cases  it  is  necessary  to 
resect  portions  of  several  ribs,  and  stop  bleeding  by  ligatures  or  suture  ligatm'es.  J.  Chalmers 
Da  Costa  reports  a  case  in  which  a  furious  secondary  hemorrhage  followed  a  gunshot  wound. 
He  resected  several  ribs,  packed  the  plem-al  cavity  about  the  lung  with  sterile  gauze,  to  oljtain 
a  base  for  support,  and  then  arrested  the  bleeding  by  packing  iodoform  gauze  against  the  firmly 
supported  lung.     This  patient  recovered. 


1198  THE  ORGANS  OF  VOICE  AND  RESPIRATION 

Incision  of  the  lung  (pneumotomy)  is  performed  for  pulmonary  abscess  (either  tuberculous  or 
pyogenic),  pulmonary  gangrene,  hydatid  cysts,  and  bronchiectasis.  In  pulmonary  abscess, 
locate  the  area  by  physical  signs  and  the  -r-rays,  resect  a  portion  of  a  rib  over  it,  and  note  if  the 
pleura  is  adherent.  If  it  is  adherent,  continue  the  operation.  If  it  is  not  adherent,  insert  stitches 
of  catgut  through  the  two  layers  of  pleura  and  the  superficial  part  of  the  lung,  so  as  to  encircle 
a  considerable  area,  and  then  wait  several  days  for  adhesions  to'form.  Adhesions  protect  the 
pleura  from  infection,  and,  by  keeping  air  from  the  pleural  sac,  prevent  pneumothorax.  ^Vhen 
ready  to  continue  the  operation,  locate  the  abscess  with  an  aspirating  needle  and  syringe,  open 
it  with  a  cautery  at  a  dull  red  heat,  and  drain  by  means  of  a  tube. 

Pneumotom}'  is  very  unsatisfactory  in  tuberculous  cavities  and  bronchiectasis.  In  tubercu- 
losis, excision  of  the  diseased  area  (pneumectomy)  has  been  emploj'ed,  but  it  is  not  to  be  advised. 

Operations  upon  the  lungs  can  be  most  safely  performed  with  the  patient  in  a  Sauerbruch 
chamber.     The  danger  of  collapse  of  the  lung  is  thus  eliminated. 

The  routine  methods  of  physical  examinations — inspection,  palpation,  percussion,  and  aus- 
cultation— are  nowhere  more  important  than  they  are  in  the  diagnosis  of  diseases  of  the  lungs. 
It  is  essential,  too,  that  in  every  case  the  two  sides  of  the  thorax  should  be  compared  with  each 
other,  and  that  the  wide  variations  that  may  be  met  with  under  normal  conditions  in  different 
persons  and  at  different  ages  should  be  kept  in  mind  when  the  thorax  is  being  examined. 

On  iivspection  the  thorax  will  be  seen  to  be  enlarged  and  barrel-shaped  in  emphysema,  in 
which  the  volume  of  the  lungs  is  increased  by  dilatation  of  their  alveoli,  or  in  an  acute  attack  of 
asthma,  or  when  a  large  pleural  effusion  or  mediastinal  tumor  is  present.  The  thoracic  wall  will 
be  flattened  or  sunken,  on  the  other  hand,  over  an  area  of  lung  that  has  collapsed  or  become 
fibrosed,  as  often  happens  in  chronic  pulmonary  tuberculosis.  The  respiratory  movements  of 
the  thoracic  wall  will  be  lessened,  or  even  absent,  over  a  part  or  the  whole  of  the  affected  side  in 
such  acute  disorders  as  pleurisy,  pneumonia,  or  pleural  effusion,  or  in  more  chronic  disease  where 
the  underlying  lung  is  fibrosed,  or  is  crushed  to  one  side  by  a  mediastinal  tumor;  and  by  the  use 
of  the  .r-rays  a  corresponding  loss  of  movement  or  displacement  of  the  Diaphragm  on  the  affected 
side  can  often  be  observed.  Under  normal  conditions  the  intercostal  spaces  are  a  little  depressed; 
but  they  may  be  obliterated  or  even  bulging  on  that  side  when  a  large  effusion  or  newgrowth 
fills  up  one  of  the  pleural  cavities. 

On  palpation,  the  hand  can  be  used  to  verify  the  eye's  impressions  as  to  the  degree  of  move- 
ment on  respiration  of  any  part  of  the  thoracic  wall.  The  facility  with  which  the  vibrations 
produced  by  the  voice  are  conducted  from  the  larynx  by  the  underlying  lung  to  the  hand  (in  the 
form  of  vocal  fremitus)  can  also  be  tested.  The  vocal  fremitus  is  commonly  much  increased 
over  the  consolidated  area  in  pneumonia  or  in  fibrosis  of  the  lung,  and  much  diminished  over  a 
pleural  effusion  when  the  lung  is  pushed  up  by  the  fluid  toward  the  top  of  the  pleural  cavity. 
It  is  also  diminished,  but  to  a  less  extent,  in  emphysema,  and  in  bronchitis  when  the  bronchi 
are  blocked  by  secretion.  In  bronchitis  the  bubbling  of  the  secretion  in  the  tubes  can  often  be 
felt  by  a  hand  placed  on  the  thoracic  wall  as  the  patient  breathes;  and  in  chronic  pleurisy  the 
friction  of  the  two  roughened  pleural  surfaces  against  each  other  can  sometimes  be  felt  in  the 
same  way. 

On  percussion,  the  normal  resonance  of  the  pulmonary  tissue  is  found  to  be  increased  in  em- 
physema, and  in  pneumothorax  this  hyperresonance  may  be  still  further  increased.  The 
resonance  is  lessened  in  any  condition  causing  collapse  or  solidification  of  the  lung  tissue,  or 
when  its  place  is  taken  by  fluid  (pleural  efl^usion)  or  some  solid  growth  (mediastinal  tumor). 
Thus,  dulness  on  percussion  at  the  bases  of  the  lungs  is  common  in  the  hypostatic  congestion  of 
the  bases  seen  in  heart  failure;  dulness  at  the  right  base  is  often  due  to  compression  of  the  lung 
by  enlargement  of  the  liver;  some  dulness  at  the  apex  of  a  lung  is  frequently  met  with  in  tuber- 
culosis of  that  part,  before  the  disease  has  progressed  very  far.  Complete  dulness  over  one  side 
of  the  thorax,  back  and  front  alike,  except  at  the  apex,  is  common  when  a  large  pleural  effusion 
has  taken  the  lung's  place.  Von  Koranyi,  Grocco,  and  others,  have  dra\\n  attention  to  a  tri- 
angular patch  of  dulness  along  the  vertebral  column  (the  paravertebral  triangle  of  dulness)  on 
the  unaffected  side  in  pleural  efl^usion;  this  triangle  of  dulness  is  said  to  be  absent  in  other  con- 
ditions causing  loss  of  pulmonary  resonance  on  percussion,  and  is  due  to  shifting  over  of  the 
contents  of  the  posterior  mediastinum  toward  the  sound  side.  The  apex  of  this  triangle  is  in 
the  middle  line  at  the  upper  level  of  the  fluid  effusion;  its  base,  some  two  to  four  inches  in  length, 
runs  horizontally  outward  from  the  middle  line  at  the  level  where  the  pulmonary  resonance 
normally  comes  to  an  end. 

On  auscultation  of  the  lungs,  both  in  health  and  disease,  the  variety  of  sounds  to  be  heard  is 
very  great.  It  is  impossible  to  give  adequate  consideration  to  them  here,  and  for  further  infor- 
mation reference  should  be  made  to  the  text-books  dealing  with  the  subject. 


THE  OEGANS  OF  DIGESTION. 


THE  Apparatus  for  tlie  Digestion  of  the  Food  (apparatus  digesiorius)  consists 
of  the  alimentary  canal  and  of  certain  accessory  organs. 
The  alimentary  canal  is  a  musculomembranous  tube,  about  thirty  feet,  or  nine 
meters,  in  length,  extending  from  the  mouth  to  the  anus,  and  Hned  throughout  the 
entire  extent  by  mucous  membrane.  It  has  received  difi'erent  names  in  the  various 
parts  of  its  course;  at  its  commencement,  the  mouth,  we  find  provision  made  for 
the  mechanical  division  of  the  food  (mastication),  and  for  its  admixture  with  a  fluid 
secreted  by  the  salivary  glands  (insalivation);  beyond  this  are  the  pharynx  and 
the  oesophagus,  the  organs  which  convey  the  food  (deglutitioii)  into  that  part  of 
the  alimentary  canal,  the  stomach,  in  which  the  principal  chemical  changes  occur, 
and  in  which  the  reduction  and  solution  of  the  food  take  place  in  digestion ;  in  the 
small  iijtestine  the  nutritive  principles  of  the  food  are  separated,  by  its  admixture 
with  the  Ijile,  pancreatic  and  intestinal  fluids,  from  that  portion  which  passes  into 
the  large  intestine,  most  of  which  is  expelled  from  the  system  through  the  rectum 
and  anal  canal. 

Alimentary  Canal. 


Mouth. 
Pharynx. 
(Esophagus. 
Stomach. 


f  Duodenum. 
Small  intestine  \  Jejunum. 
L  Ileum. 

[  Cecum  and  appendix. 
Colon. 
Rectum. 
.  Anal  canal. 


Large  intestine  • 


Accessory  Organs. 
Teeth. 
Tongue. 

f  Parotid. 
Salivary  glands  ]  Submaxillary. 


Sublingual. 


Liver. 
Pancreas. 


THE  MOUTH,  ORAL  OR  BUCCAL  CAVITY  (CAVUM  ORIS). 

The  mouth  is  placed  at  the  commencement  of  the  alimentary  canal;  it  is  a 
nearly  oval-shaped  cavity,  in  which  the  mastication  and  insalivation  of  the  food 
take  place  (Figs.  923  and  924). 

The  aperture  of  the  mouth  (rima  oris)  is  bounded  by  the  lips.  The  angle  of  the 
mouth  (angulus  oris)  is  formed  on  each  side  by  the  meeting  of  the  upper  and 
lower  lips  {commissura  labiorum).  Wien  at  rest  with  the  lips  in  contact,  the  runa 
is  a  slighdy  curved  line.  Every  movement  which  the  lips  make  alters  the  shape 
of  the  rima.  When  the  mouth  is  closed  the  floor  and  roof  are  usually  in  contact 
and  its  sides  are  approximated  to  the  dental  arches.  The  mouth  consists  of  two 
parts — an  outer,  smaller  portion,  the  vestibule,  and  an  inner,  larger  part,  the  cavity 

proper  of  the  mouth. 

ai99) 


1200 


THE  ORGANS  OF  DIGESTION 


The  Lips  (labia  oris)  are  two  fleshy  folds  which  surround  the  orifice  of  the  mouth 
formed  externally  by  integument  and  internally  by  mucous  membrane,  between 
which  are  found  the  Orbicularis  oris  muscle  (Fig.  292),  the  labial  vessels,  some 
nerves  (Fig.  439),  areolar  tissue,  and  fat,  and  numerous  small  labial  glands.  The 
upper  lip  is  called  the  labium  superius;  the  lower  lip  is  called  the  labium  inferius. 
The  inner  surface  of  each  lip  is  connected  in  the  middle  line  to  the  gum  of  the 
corresponding  jaw  by  a  fold  of  mucous  membrane,  the  frenulum  {frenulum  labii 
superioris  and  frenuluvi  labii  inferioris) ,  the  upper  being  the  larger  of  the  two. 

The  labial  glands  (glandulae  labialis)  (Fig.  439)  are  situated  between  the  mucous 
membrane  and  the  Orbicularis  oris  muscle  around  the  orifice  of  the  mouth.  They 
are  circular  in  form  and  of  small  size;  their  ducts  open  by  minute  orifices  upon  the 
surface  of  the  mucous  membrane.  In  structure  they  resemble  the  salivary  glands. 
The  vestibule  {vestibulum  oris)  is  a  slit-like  space,  bounded  in  front  and  later- 
ally by  the  lips  and  cheeks;  behind  and  internally  by  the  gums  and  teeth.     Above 

and  below  it  is  limited  by  the  reflection  of 
the  mucous  membrane  from  the  lips  and 
cheeks  to  the  gum  covering  the  upper  and 
lower  alveolar  arch  respectively.  It  re- 
ceives the  secretion  from  the  parotid,  buc- 
cal, molar,  and  labial  glands,  and  commu- 
nicates, when  the  jaws  are  closed,  w;ith  the 
cavum  oris  by  an  aperture  on  each  side  be- 
hind the  wisdom  teeth,  and  by  narrow  clefts 
between  opposing  teeth  (interdental  spaces). 
The  Cheeks  (buccae)  form  the  sides  of  the 
face  and  are  continuous  in  front  with  the 
lips.  They  are  composed  externally  of 
integument,  internally  of  mucous  mem- 
brane, and  between  the  two  of  a  layer  of 
muscle,  besides  a  large  quantity  of  fat, 
areolar  tissue,  vessels,  nerves,  and  buccal 
glands. 

The  Mucous  Membrane. — The  mucous  mem- 
brane lining  the  cheek  is  reflected  above  and  below 
upon  the  gums,  where  its  color  becomes  lighter;  it 
is  continuous  behind  with  the  lining  membrane  of 
the  soft  palate.  It  is  composed  of  stratified  squa- 
mous epithelial  cells  that  rest  upon  a  basement 
membrane  and  papillated  tunica  propria  that  con- 
sists of  fibroelastic  tissue  supporting  the  smaller 
vessels  and  nerves.  Opposite  the  second  molar 
tooth  of  the  upper  jaw  is  a  papilla,  the  summit  of 
which  presents  the  aperture  of  the  parotid  duct 
{ductus  parotideus  [Stenonis\}  (Fig.  958).  The 
principal  muscle  of  the  cheek  is  the  Buccinator,  but  mmierous  other  muscles  enter  into  its 
formation — viz.,  the  Zygomatic!,  Risorius,  and  Platj'sma. 

The  Buccal  Glands  {glandulae  buccales). — The  buccal  glands  are  placed  in  the  submucous 
tissue  between  the  mucous  membrane  and  Buccinator  muscle;  they  are  similar  in  structure  to 
the  labial  glands,  but  smaller.  Foiu-  or  five  glands  of  larger  size  than  the  pre\'iously  mentioned 
glands  are  placed  beneath  the  mucous  membrane  in  the  neighborhood  of  the  last  molar  tooth. 
They  are  called  the  molar  glands  {glandulae  molares).  Their  ducts  open  into  the  mouth  opposite 
the  last  molar  tooth  The  fat  pad  of  the  cheek  {corpus  adiposum  buccae)  has  been  described  on 
page  376. 

The  Glims  {gingivae)  are  composed  of  a  dense  fibrous  tissue,  closely  connected 
to  the  periosteum  of  the  alveolar  processes  and  surrounding  the  necks  of  the  teeth. 
Thev  are  covered  bv  smooth  and  vascular  mucous  membrane,  which  is  remarkable 


SMALL 
INTESTINE 


ANJJS 
Fig.  923. — Diagram  of  the  alimentary  tube  and 
its  appendages.     (Testut.) 


THE  ilOUril,    ORAL   OB  BUCCAL   CAVITY 


1201 


for  its  limited  sensibility.  Around  the  necks  of  the  teeth  the  fibroelastic  portion 
presents  numerous  fine  papilhe;  from  here  it  is  reflected  into  each  alveolus,  where 
it  is  continuous  with  the  periosteal  membrane  lining  that  cavity. 

The  cavity  of  the  mouth  proper  (camm  oris  propriiim)  is  bounded  laterally 
and  in  front  by  the  alveolar  arches  with  their  contained  teeth;  hrhind,  it  ('f)mmuni- 
cates  with  the  pharynx  by  a  constricted  aperture  termed  the  isthmus  faucium.  It 
is  roofed,  in  by  the  hard  and  soft  palate.  The  greater  part  of  the  floor  is  formed 
by  the  tongue,  the  remainder  being  completed  by  the  reflection  of  the  mucous 
membrane  from  the  sides  and  under  surface  of  the  tongue  to  the  gum  lining  the 
inner  aspect  of  the  mandible.  It  receives  the  secretion  from  the  submaxillary, 
sublingual,  and  lingual  glands. 

Floor  of  the  Mouth. — If  the  tongue  be  lifted  out  of  its  resting-place,  the  true 
floor  of  the  mouth,  or  sublingual  region,  may  be  examined.     In  the  middle  a  fold 


Fig.  924. — Antpro-infc 


that  che  pharyngeal  istbu 


of  mucous  membrane,  the  frenum  linguae,  extends  from  the  under  surface  of  the 
tongue  to  the  floor.  On  each  side  of  the  frenum  is  a  papilla ,  the  caruncula  sublingu- 
alis, on  the  summit  of  which  is  the  small  orifice  of  the  submaxillary  (^Yharton's) 
duct.  Extending  backward  from  these  caruncles,  between  the  tongue  and  the  al- 
veolar arches  on  each  side,  is  a  carunculated  fold,  the  plica  sublingualis,  ^^■hich 
becomas  lost  posteriorly.  The  carunculated  elevations,  of  variable  number, 
present  the  orifices  of  the  sublingual  ducts. 

Structure. — The  mucous  mevihranc  lining  the  mouth  is  continuous  with  tlie  integument  at 
the  free  margin  of  the  lips  and  with  the  mucous  lining  of  the  pharynx  behind;  it  is  of  a  rose- 
pink  tinge  during  life,  and  very  thick  where  it  covers  the  hard  parts  bounding  the  cavity.  It 
is  covered  by  stratified  squamous  epithelium.  In  the  subepithelial  fibroelastic  tissue  are  seen 
many  small  accessory  salivary  glands. 


1202 


THE  ORGANS  OF  DIGESTION 


The  Palate  (palatum)  forms  the  roof  of  the  mouth;  it  consists  of  two  portions: 
the  hard  palate,  about  two-thirds  in  front;  the  soft  palate,  about  one-third  behind. 

The  hard  palate  {palatum  durum)  (Figs.  924  and  925)  is  bounded  in  front 
and  at  the  sides  by  the  upper  alveolar  arches  and  gums;  behind,  it  is  continuous 
with  the  soft  palate.  It  is  formed  by  the  palate  processes  of  the  maxillae  and  the 
palate  processes  of  the  palate  bones  (Fig.  72).  It  is  covered  by  a  dense  structure 
formed  by  the  periosteum  and  mucous  membrane  of  the  mouth,  which  are  inti- 
mately adherent,  particularly  to  the  front  and  sides,  by  means  of  a  layer  of  fibrous 


DESCENDING 

PALATINE 

ARTERY 


the  right  side  of  the  mucous  membrane  has  been  removed, 
membrane  and  the  glandular   layer.      (Poirier  and  Charpy.) 


left  side  shows 


tissue.  Along  the  middle  hne  is  a  linear  ridge  or  raphe  (raphe  palati),  which 
terminates  anteriorly  in  a  small  papilla,  the  incisive  papilla  {papilla  incisiva), 
corresponding  with  the  inferior  opening  of  the  anterior  palatine  fossa.  On  either 
side  and  in  front  of  the  raphe  the  mucous  membrane  is  thick,  pale  in  color,  and 
corrugated;  these  corrugations,  which  are  composed  of  fibrous  tissue,  are  the 
palatine^  rugae  (plicae  palatinae  transversae) .  In  very  young  children  the  rugae 
are  distinct  and  definite.  In  the  aged  they  are  indistinct.  Behind,  it  is  thin, 
smooth,  and  of  a  deeper  color;  it  is  covered  with  stratified  squamous  epithelium 
and  the  fibrous  tissue  beneath  it  contains  many  mucous  glands,  the  palatine  glands 
(glandulae  palatinae).  The  palatine  vessels  and  nerves  lie  in  the  fibrous  tissue 
beneath  the  mucous  membrane. 

The  soft  palate  (palatum  molle)  (Figs.  924  and  925)  is  a  movable  slanting  fold 
suspended  from  the  posterior  border  of  the  hard  palate,  and  forming  an  incomplete 
septum  between  the  mouth  and  pharynx.    It  consists  of  a  fold  of  mucous  mem- 


'  Concerning  the  etymology  O'   palatal  and  palatii 


i  footnote  on  page  109. 


THE  MOUTH,    ORAL   OR  BUCCAL   CA  V'lTY  1203 

brane  enclosing  muscle  fibres,  an  aponeurosis,  vessels,  nerves,  lymphoid  tissnc,  and 
mucous  glands.  When  occupying  its  usual  position  it  is  relaxed  and  pendent, 
and  its  oral  surface  is  concave,  continuous  with  the  roof  of  the  mouth,  and  marked 
by  a  median  ridge  or  raphe,  which  indicates  its  original  separation  into  two  lateral 
halves.  Its  pharyngeal  surface  is  convex,  and  continuous  with  the  mucous  mem- 
brane covering  the  floor  of  the  posterior  nares.  Its  anterior  or  upper  border  is 
attached  to  the  posterior  margin  of  the  hard  palate,  and  its  sides  are  blende>d  witli 
the  pharynx.  Its  posterior  or  lower  border  is  free.  The  posterior  portion  of  the 
soft  palate  (velum  palatiimm)  terminates  posteriorly  and  externally  on  eacii  side 
in  a  free  margin,  the  posterior  arch  of  the  palate,  and  bounds  the  isthmus  of  the 
pharynx. 

Hanging  from  the  middle  of  its  lower  border  is  a  small,  cone-shaped,  pen- 
dulous process,  the  uvula  {uvula  falatind).  The  uvula  varies  greatly  in  length  in 
different  individuals.  It  is  composed  of  glands  and  connective  tissue,  contains 
a  prolongation  of  the  Azygos  uvulre  muscle  and  is  covered  with  mucous  membrane, 
and  arching  outward  and  downward  from  the  base  of  the  uvula  on  each  side  are 
two  curved  folds  of  mucous  membrane,  containing  muscle  fibres,  called  the 
arches  or  pillars  of  the  soft  palate  or  pillars  of  the  fauces  {anus  'palatini). 

The  anterior  pillar  (arms  glossopalatinus)  (Fig.  924)  on  each  side  runs  downward, 
outAA'ard,  and  forward  to  the  side  of  the  base  of  the  tongue,  and  is  formed  by  the 
projection  of  the  Palatoglossus  muscle,  covered  by  mucous  membrane. 

The  posterior  pillar  (arcus  pharyngopalatmus)  (Fig.  924)  is  larger  and  projects 
farther  inward  than  the  anterior;  it  runs  downward,  outward,  and  backward 
to  the  sides  of  the  pharynx,  and  is  formed  by  the  projection  of  the  Palatopharyn- 
geus  muscle,  covered  by  mucous  membrane.  The  anterior  and  posterior  pillars 
are  separated  below  by  a  triangular  interval  {tonsillar  sinus),  in  which  the  tonsil 
is  lodged. 

The  aperture  by  which  the  mouth  communicates  with  the  pharynx  is  called  the 
isthmus  of  the  fauces  {isthimis  faucium) .  It  is  boui'^ded,  above,  by  the  free  margin 
of  the  soft  palate;  helow,  by  the  back  of  the  tongue;  and  on  each  side,  by  the  pillars 
of  the  fauces  and  the  tonsils. 

The  aponeurosis  of  the  soft  palate  is  a  thin  but  firm  fibrous  layer  attached  above  to  the  pos- 
terior border  of  the  hard  palate,  and  becoming  thinner  toward  the  free  margin  of  the  soft  palate. 
Laterally,  it  is  continuous  with  the  pharyngeal  aponeurosis.  It  forms  the  framework  of  the 
anterior  half  of  the  soft  ]ialate,  and  is  joined  by  the  tendons  of  the  Tensor  palati  nuiscles. 

The  muscles  of  the  soft  palate  arc  found  in  its  posterior  h:df,  and  arc  six  on  cac-h  side — the 
Levator  palati,  Tensor  palati,  Azygos  uvulae,  Palatoglossus,  Palatopharyngeus,  and  Sal- 
■pingopharyngeus  (see  p.  397).  The  following  is  the  relative  position  of  these  structures  in  a 
dissection  of  the  soft  palate  from  the  posterior  or  nasopharyngeal  to  the  anterior  or  oral  surface: 
Immediately  beneath  the  jiharyngeal  mucous  membrane  is  a  thin  stratum  of  muscle  tissue,  the 
posterior  fasciculus  of  the  Palatopharyngeus  muscle,  joining  with  its  fellow  of  the  opposite  side 
in  the  middle  line.  This  posterior  fasriculus  is  joined  by  the  Salpingopharyngeus  muscle. 
Beneath -this  arc  the  Azygos  uvulas  and  Salpingopharsmgeus  muscles,  consisting  of  two  rounded 
fleshy  fasciculi,  placed  side  by  side  in  the  niciliau  line  of  the  soft  jjalate.  Next  comes  the  apo- 
neurosis of  the  Levator  palati,  joining  with  the  muscle  ;)f  tlie  opposite  side  in  the  middle  line. 
Fourthly,  the  anterior  fasciculus  of  the  Palatopharyngeus,  thicker  than  the  posterior,  and  sepa- 
rating the  Levator  palati  from  the  next  muscle,  the  Tensor  palati.  This  muscle  terminates  in  a 
tendon  which,  after  winding  around  the  hamular  process  of  the  internal  pterygoid  plate  of  the 
sphenoid  bone,  expands  into  a  broad  aponeurosis  in  the  soft  palate,  anterior  to  the  other  muscles 
so  far  enumerated.  Finally,  we  have  a  thin  muscular  stratum,  the  Palatoglossus  muscle,  placed 
in  front  of  the  aponeurosis  of  the  Tensor  palati,  and  separated  from  the  oral  mucous  membrane  by 
lymphoid  tissue. 

The  mucous  membrane  of  the  soft  palate  is  thin,  and  covered  with  stratified  squamous  epi- 
thelium on  both  surfaces,  excepting  near  the  orifice  of  the  Eustachian  tube,  where  its  epithelium 
is  stratified  and  ciliated.'     Beneath  the  mucous  membrane  on  the  oral  siu-face  of  the  soft  palate 

'  According  to  Klein,  the  mucous  membrane  on  tlie  nasal  surface  of  the  soft  palate  in  the  fetus  is  covered  through- 
out by  columnar  ciliated  epithelium,  which  subsequentb'  becomes  squamous;  and  some  anatomists  state  that  it  is 
covered  with  columnar  ciliated  epithelium,  except  at  its  free  margin,  throughout  life. 


1204 


THE  ORGANS  OF  DIGESTION 


is  a  considerable  amount  of  lymphoid  tissue.  The  palatine  glands  form  a  continuous  layer 
on  the  pharyngeal  surface  and  around  the  uvula. 

The  arteries  supplying  the  palate  are  the  descending  palatine  branch  of  the  internal  maxil- 
lary artery  (a.  palatina  descendens) ,  the  ascending  or  palatine  branch  of  the  facial  artery  (a. 
palatina  ascendens),  and  sometimes  a  palatine  branch  of  the  ascending  pharyngeal.  The 
■veins  terminate  chiefly-  in  the  pterygoid  and  tonsillar  plexuses.  The  lymphatic  vessels  pass  to 
the  superior  deep  cervical  nodes. 

The  motor  nerves  are  chiefly  derived  from  the  pharjoigeal  plexus,  the  Tensor  palati,  however, 
receiving  a  special  branch  from  the  otic  ganglion.  The  sensor  nerves  are  derived  from  the  de- 
scending palatine,  nasopalatine,  and  from  the  glossopharyngeal. 

Development  of  the  Mouth. — The  mouth  is  developed  partly  from  the  stomodeum,  the 
depression  between  the  head  end  of  the  embryo  and  the  pericardial  area,  and  partly  from  the 
floor  of  the  extreme  end  of  the  foregut.  The  floor  of  the  stomodeum  is  the  thin,  buccopharyngeal 
membrane,  formed  by  the  apposition'of  ectoderm  and  entoderm;  this  membrane  wholly  disap- 
pears after  the  second  week  of  embryonic  life,  and  a  communication  is  established  between  the 
mouth  and  future  pharynx.  With  the  development  of  the  face  the  nasal  passages  are  separated 
from  the  mouth  proper  by  the  coalescence  of  the  maxillary  and  palatal  processes  of  the  first 
visceral  arch  with  the  lateral  nasal  and  globular  proce.sses  forming  the  maxilte  and  palate. 

The  development  of  the  teeth  is  described  on  page  1212. 

Applied  Anatomy. — Cleft  palate  is  by  no  means  a  rare  congenital  deformity,  and  may  be 
partial  or  complete.  Most  of  the  cleft  is  in  the  middle  line.  It  may  be  a  mere  cleft  of  the 
uvula,  it  may  be  limited  to  the  soft  palate,  or  it  may  involve  the  hard  palate  to  but  not  include 
the  alveolus'.  It  may  pass  through  the  alveolus,  but  if  it  does  so  it  ceases  to  be  median  at  this 
point,  and  follows  the  line  of  suture  between  the  incisive  bone  and  the  maxilla  (pp.  106  and 
152).  Complete  cleft  palate  is  likely  to  be  accompanied  by  harelip.  This  cleft  in  the  lip  is 
not  median,  but  is  at  the  termination'  of  the  palate  cleft.  If  the  cleft  of_  a  cleft  palate  runs 
along  each  side  of  the  incisive  bone,  the  bone  is  isolated  from  the  maxilla  and  the  cleft  is 
Y-shaped.     In  such  a  case  double  harelip  is  present. 

The  Teeth  {denies).— ^he  human  subject  is  provided  with  two  sets  of  teeth, 
which  make  their  appearance  at  different  periods  of  life. 

Those  of  the  first  set  appear  in  childhood,  and  are  called  the  temporary,  decidu- 
ous, or  milk  teeth.  Those  of  the  second  set  are  named  permanent  or  succedaneous 
teeth. 

The  temporary  teeth  are  twenty  in  number — four  incisors,  two  canines,  and  four 
molars  in  each  jaw  (Figs.  926  and  947). 

The  permanent  teeth  are  tliirty-two  in  number — four  incisors  (two  central  and 
two  lateral),  two  canines,  four  bicuspids,  and  six  molars  in  each  jaw  (Figs.  928  and 
932). 

The  dental  formulae  may  be  represented  as  follows: 


Temporary  Teeth. 


Upper  jaw     . 


Molar.       Canine.       Incisor. 
.2  1  2 


Lower  jaw 


Incisor.       Canine.       Molar. 
2  1  2 


Total,  20. 


Permanent  Teeth. 


Molar.     Bicuspid.     Canine.     Incisor. 
Upper  jaw    .3  2  1  2 


Incisor.     Canine.     Bicuspid.     Molar 

2  12  3 


Total,  32. 


Lower  jaw    .3  2  1  2 

General  Characters  (Fig.  933). — ^Each  tooth  consists  of  three  portions — the 
crown  or  body  (corona  dentis),  projecting  above  the  gums;  the  root  or  fang  {radix 
dentis),  entirely  concealed  within  the  alveolus;  and  the  neck  (collum  dentis),  the 
constricted  portion  between  the  root  and  crown,  covered  by  the  gum. 

The  roots  of  the  teeth  are  firmly  implanted  within  the  sockets  or  alveoli  of  the 
jaws  (alveoli  dentalc^;  (see  pp.  104  and  117).  These  depressions  are  lined  with 
periosteum,  which  is  reflected  on  to  the  tooth  at  the  apex  of  the  root  and  covers 


1  According  to  Klein,  the  mucous  membrane  on  the  nasal  surface  of  the  soft  palate  in  the  fetus  is  covered 
throughout  by  columnar  ciliated  epithelium,  which  subsequently  becomes  squamous;  and  some  anatomists 
state  that  it  is  covered  with  columnar  ciliated  epithelium,  except  at  its  free  margin,  throughout  hfe. 


THE  MOUTH,    ORAL  OH  BUCCAL  CAVITY 


1205 


it  as  far  as  the  neck.  This  is  the  root-,  or  pericemental  membrane  (periosteum  alve- 
olare).  At  the  margin  of  the  alveoki.s  the  periosteian  l)econies  continuous  with 
the  fil)rous  structure  of  the  gums. 

Surfaces. — In  consequence  of  the  curve  of  the  dental  arch,  such  terms  as  anterior, 
posterior,  internal,  and  external,  as  applied  to  the  teeth,  are  misleading  and  con- 
fusing. Special  terms  are  therefore  applied  to  the  different  surfaces  of  a  tootii: 
That  which  looks  toward  the  lips  and  cheek  is  the  labial  or  buccal  surface  (fades 


Fig.  026. — Deciduous  teetli  of  left  side.     Labial  view. 


Fig.  927. — Deciduous  teeth.     Lingual  view. 


lahialis);  that  toward  the  tongue  is  the  lingual  surface  { fades  lingualis);  that 
surface  which  is  directed  toward  the  mesal  plane,  supposing  the  teeth  were  arranged 
in  a  straight  line  outward  from  the  central  incisor,  is  known  as  the  proximal 
surface,  looks  toward  predecessor;  while  that  directed  away  from  the  mesal  plane 
is  called  the  distal  surface,  looks  toward  successor.  The  surface  which  comes  in 
contact  with  the  teeth  of  the  opposite  jaw  is  the  grinding,  masticating,  or  occlusal 
surface  (fades  masticator ia^. 


Fig.  928. — Permanent  teeth,  right  side.      (Burehard.) 

The  Temporary,  Deciduous,  or  Milk  Teeth  (dentes  decidui)  (Figs.  926  and  927) 
are  smaller,  but  resemble  in  form  those  of  the  permanent  set.  The  neck  is  more 
marked,  owing  to  the  greater  degree  of  convexity  of  the  labial  and  lingual  surfaces 
of  the  crown.  The  last  of  the  two  temporary  molars  is  the  largest  of  all  the 
deciduous  teeth,  and  is  succeeded  by  the  second  bicuspid.  The  first  upper  molar 
has  only  three  cusps — two  labial,  one  lingual;  the  second  upper  molar  has  four 
cusps.     The  first  lower  molar  has  four  cusps;  the  second  lower  molar  has  five. 


1206 


THE  ORGANS  OF  DIGESTION 


The  roots  of  the  temporary  molar  teeth  are  smaller  and  more  diverging  than 
those  of  the  permanent  set,  but  in  other  respects  bear  a  strong  resemblance  to  them. 

Permanent  Teeth  {denies  permanentes)  (Fig.  928). — ^The  incisors  or  cutting  teeth 
{denies  incisivi)  are  so  named  from  their  presenting  a  sharp  cutting  edge,  adapted 
for  incising  the  food.  They  are  eight  in  number,  and  comprise  the  four  front 
teeth  in  each  jaw. 

The  crown  is  directed  vertically  and  is  chisel-shaped,  being  bevelled  at  the 
expense  of  its  lingual  surface,  so  as  to  present  a  sharp  horizontal  cutting  edge. 
Before  being  subjected  to  attrition  this  edge  presents  three  small  elevations.  The 
labial  surface  is  convex,  smooth,  and  highly  polished.  The  lingual  surface  is  con- 
cave, and  is  marked  by  two  marginal  ridges  extending  from  an  encircling  ridge 
at  the  neck  to  the  angles  of  the  cutting  edge  of  the  tooth.  The  ridge  at  the  neck 
is  termed  the  cingulum  or  basal  ridge.  The  neck  of  the  tooth  is  constricted.  The 
root  is  long,  single,  conical,  transversely  flattened,  thicker  before  than  behind, 
and  slightly  grooved  on  either  side  in  the  longitudinal  direction.  The  root  may 
be  curved. 


Fig.  929. — Right  half  of  upper  jaw  (from  below), 
with  the  corresponding  teeth.  The  letters  and 
numbers  point  to  the  classes  of  teeth  and  the  numbers 
in  classes. 


Fig.  930.— Right  half  of  lower  jaw.  with  the  cor- 
responding teeth.  The  letter  and  numbers  point  to 
the  various  cusps  or  their  modifications  on  the  differ- 
ent teeth.     (Burchard.) 


The  incisors  of  the  upper  jaw  are  altogether  larger  and  stronger  than  those  of 
.  the  lower  jaw,  the  central  incisors  being  larger  and  flatter  than  the  lateral  incisors. 
They  are  directed  obliquely  downward  and  forward. 

The  incisors  of  the  lower  jaw  are  smaller  and  flatter  than  the  upper,  and  the 
elevations  upon  their  lingual  faces  are  not  marked.  The  two  central  are  smaller 
than  the  two  lateral  incisors,  being  the  smallest  of  all  the  teeth.  The  roots  of  these 
teeth  are  flattened  laterally. 

The  Canine  Teeth  {denies  canini)  are  four  in  number,  two  in  the  upper,  two  in 
the  lower  jaw — one  being  placed  distal  to  each  lateral  incisor.  They  are  larger  and 
stronger  than  the  incisors,  especially  in  the  roots,  which  are  deeply  implanted 
and  each  causes  a  well-marked  prominence  of  the  process  at  the  place  of  inser- 
tion. 

The  crown  is  large,  of  spear-head  form,  and  its  very  convex  labial  surface  is 
marked  by  three  longitudinal  ridges.  The  concave  lingual  surface  is  also  marked 
by  three  ridges  which  unite  at  a  basal  ridge.  The  point  or  cusp  is  longer  than  in 
the  other  teeth,  and  is  the  point  of  division  between  a  short  proximal  and  a  long 
distal  cutting  edge.     These  two  edges  form  an  obtuse  angle  with  each  other. 


TH?:  MOUTH,    ORAL  OR  BUCCAL   CAVfTY  ]  207 

The  root  is  single,  oval,  or  elliptical  on  transverse  section,  and  is  lonf;er  and  more 
prominent  than  the  roots  of  the  incisors. 

The  upper  canines,  popularly  called  the  eye  teeth,  are  larger  and  longer  than  the 
two  lower,  and  in  occlusion  are  distal  to  them  to  the  extent  of  half  the  width  of  the 
crown. 

The  lower  canines,  popularly  called  the  stomach  teeth,  have  the  general  form  of 
the  upper  canines,  but  their  lingual  surfaces  are  much  more  flattened,  owing  to 
the  absence  of  the  elevations  marking  the  upper  teeth.  Their  roots  are  more 
flattened  and  may  be  bifid  at  their  apices. 

The  bicuspid  teeth,  or  the  premolars  {dentes  'premolares)  are  eight  in  number, 
four  in  each  jaw;  they  are  placed  distal  to  the  canine  teeth,  two  upon  each  side 
of  the  jaw. 

The  crown  is  surmounted  by  two  cusps,  one  buccal  and  one  lingual,  separated 
by  a  groove,  the  buccal  being  more  prominent  and  larger  than  the  lingual.  The 
lower  bicuspids  are  not  truly  bicuspid,  the  first  having  but  a  primitive  lingual 
cusp,  the  second  having  the  lingual  cusp  divided  into  two  sections — /.  e.,  it  is 
usually  tricuspid.  The  necks  of  the  teeth  are  ovaX;  the  roots  are  single  and  later- 
ally compressed,  that  of  the  first  upper  bicuspid  being  frequently  bifid.  The 
first  upper  bicuspid  is  usually  the  largest  of  the  series.  The  roots  of  the  lower 
bicuspids  are  less  compressed  and  more  rounded. 

The  Molar  Teeth  {dentes  molares)  are  the  largest  and  strongest  teeth  of  the  per- 
manent set,  and  are  adapted  by  their  forms  for  the  crushing  and  grinding  of  the 
food.  They  are  twelve  in  number,  six  in  each  jaw,  three  being  placed  posterior 
to  each  second  bicuspid. 

The  crowns  are  cuboidal  in  form,  are  convex  bucally  and  lingually;  they  are 
flattened  proximally  and  distally.  They  are  formed  by  the  fusion  of  three  primi- 
tive cuspids  in  the  upper  and  four  in  the  lower.  To  these  are  added  in  the  first 
and  second  upper  molars  a  distolingual  tubercle,  and  in  the  first  and  third 
molars  of  the  lower  jaw  a  distobuccal  tubercle.  The  unions  of  the  primitive 
forms  are  marked  by  sulci.  The  necks  of  these  teeth  are  large  and  rhom- 
boidal  in  form.  The  roots  of  the  upper  molars  are  three  in  number — one  large 
lingual  or  palatal  root,  and  two  smaller  buccal  roots.  In  the  lower  molars,  two  roots 
are  found,  a  proximal  and  a  distal,  each  of  which  is  much  flattened  from  before 
backward. 

The  first  molar  teeth  are  the  largest  of  the  dental  series;  they  have  four  cusps 
on  the  upper  and  five  in  the  lower — three  buccal  and  two  lingual.  The  second 
molars  are  smaller;  the  crowns  of  the  upper  are  compressed  until  the  distolingual 
cusp  is  reduced.  The  crowns  of  the  lower  are  almost  rectangular,  with  a  cusp 
at  each  angle.  The  third  molars  are  called  the  wisdom  teeth,  or  dentes  sapientiae 
(denies  serotini) ,  from  their  late  eruption ;  they  have  three  cusps  upon  the  upper  and 
five  upon  the  lower.  The  three  roots  of  the  upper  are  frequently  fused  together, 
forming  a  grooved  cone,  which  is  usually  curved  backward.  The  roots  of  the  lower, 
two  in  number,  are  compressed  together,  and  curve  backward. 

Of  the  permanent  teeth,  all  but  the  molars  represent  succedaneous  teeth, 
that  is,  teeth  that  succeed  those  of  the  temporary  set.  The  molars  are  primary 
teeth,  as  they  possess  no  predecessors  in  the  temporary  set. 

Arrangement  of  the  Teeth.i — The  human  teeth  are  arranged  in  two  parabolic 
arches,  the  upper  row  or  arch  {amis  dentalis  sirperior)  being  larger,  its  teeth  over- 
lapping the  lower  row  or  arch  {arms  dentalis  inferior).  The  a^'erage  distance 
between  the  centres  of  the  condyles  of  the  mandible  is  about  four  inches,  which 
is  also  the  distance  from  either  of  these  points  to  the  line  of  junction  between  the 
lower  incisor  teeth.    Whether  the  jaw  be  large  or  small,  the  equilateral  triangle 

1  After  Dr.  W.  G    A.  Bonwill. 


1208 


THE  ORGANS  OF  DIGESTION 


indicated  is  included  in  it;  the  range  of  size  is  between  three  and  one-half  and  four 
and  one-half  inches. 


Fig.  931. — View  of  teeth  in  situ,  with  the  external  plates  of  the  alveolar  processes  removed.     tCryer.) 

Owing  to  the  smaller  sizes  of  the  lower  incisors,  the  teeth  of  the  mandible  are 
each  one-half  a  tooth  in  advance  of  its  upper  fellow,  so  that  each  tooth  of  the  dental 


Fig.  932. — Front  and  side  views  of  the  teeth  and  jaws.     (Cryer.) 


series  has  two  antagonists,  with  the  exception  of  the  lower  central  incisors  and 
upper  third  molars  (Figs.  931  and  932). 


THE  MOUTH,    ORAL  OR  BUCCAL   CAVITY 


12U9 


The  grinding  faces  of  the  upper  bicuspids  and  molars  curve  progressively  upward 
and  point  outward,  the  first  molar  being  at  the  lowest  point  of  the  curve,  the  third 
molar  at  the  highest.  The  curve  of  the  lower  dental  arch  is  the  reverse,  the  first 
molar  at  its  deepest  part,  the  third  molar  at  its  extremity.  The  greater  the  depth 
to  which  the  upper  incisors  overlap 
the  lower,  the  more  marked  this 
curve  and  the  more  pointed  are  the 
cusps  of  the  grinding  teeth. 

The  movement  of  the  human 
mandible  is  forward  and  downward, 
the  resultant  of  these  directions 
being  an  oblique  line,  upon  an 
average  of  35  degrees  from  the 
horizontal  plane.' 

When  the  mandible  is  advanced 
until  the  cutting  edges  of  the  in- 
cisors are  in  contact,  the  jaws  are 
separated,  but  at  the  highest  point 
of  the  lower  arch  its  third  molar 
advances,  and  meets  and  rests  upon 
a  high  point,  the  second  molar  of 
the  upper  arch,  and  thus  undue 
strain  upon  the  incisors  is  obviated. 

In  the  lateral  movements  of  the 
mandible  but  one  side  is  in  effective 
action  at  one  time;  the  oblique 
positions  of  the  cusps  of  the  oppo- 
site teeth  are  such  that  when  either 
side  is  in  action  the  other  is  balanced 
at  two  or  more  points. 


I'ulp  Cavity. 


Fig.  934. — Vertical  section  of  a  tooth  in  situ  (15  diam- 
eters), c  is  placed  in  the  pulp  cavity,  opposite  the  cervix, 
or  neck  of  the  tooth;  the  part  above  is  the  crown,  that  below 
is  the  root  (fang).  1.  Enamel  with  radial  and  concentric 
markings.  2.  Dentin  with  tubules  and  incremental  lines.  3. 
Cementum  or  crusta  petrosa,  ^\-ith  bone  corpuscles.  4.  Perice- 
FlG.  933. — Vertical  section  of  molar  tooth.  mental  membrane.     5.  Bono  of  mandible. 


There  is  an  anatomical  correspondence  between  the  forms  and  arrangement 
of  the  teeth,  the  form  of  the  condyle  of  the  mandible,  and  the  muscular  arrange- 
ment. Individuals  who  have  teeth  with  long  cusps  have  the  head  of  the  bone  much 
rounded  from  before  backward,  and  have  a  preponderance  of  the  direct  over  the 
oblique  muscles  of  mastication,  and  vice  versa;  teeth  with  short  or  no  cusps  are 
associated  with  a  flattened  condyle  and  strong  oblique  muscles. 

Very  great  aberrations  in  the  dental  arrangement  are  frequently  followed  by 
accommodative  changes  in  the  condyles  of  the  mandible. 

Structure  of  the  Teeth.— A  longitudinal  section  of  a  tooth  will  show  the  presence  of  a  central 
chamber  having  the  general  form  of  the  crown  of  the  tooth,  and  called  the  pulp  chamber  or 
pulp  cavity  {camim  dentis).    The  solid  jiortion  of  the  tooth  exhibits  three  hard  tissues:  one,  the 


1  W.  E.  W.alker,  Dental  Cosmos,  1896. 


1210 


THE  ORGANS  OF  DIGESTION 


proper  dental  substance,  called  dentin  or  ivory  sheathed  upon  the  exposed  crown  by  a  layer 
called  the  enamel,  while  the  dentin  of  the  root  is  enclosed  in  a  distinct  tissue,  the  cementum  or 
crusta  petrosa.  Both  enamel  and  cementum  are  thinnest  at  the  neck  and  thickest  upon  their 
distal  portions. 

The  enamel  {substantia  adamantina)  (Figs.  934,  935,  and  938)  is  the  hardest  and  most  com- 
pact part  of  a  tooth,  and  forms  a  thin  crust  over  the  e.xposed  part  of  the  crown,  as  far  as  the 
commencement  of  the  root.  It  is  thickest  on  the  grinding  surface  of  the  crown  until  worn  away 
by  attrition,  and  becomes  thinner  toward  the  neck.  It  consists  of  a  congeries  of  minute  hex- 
agonal rods,  columns,  or  prisms,  known  as  enamel  fibres  or  prisms  (prismata  adamantina) 
(Fig.  938).  In  general  they  lie  parallel  with  one  another,  resting  by  one  extremity  upon  the 
dentin,  which  presents  a  number  of  minute  depressions  for  their  reception,  and  forming  the 
free  surface  of  the  crown  by  the  other  extremity.  There  are  additional  shorter  (supplemental) 
prisms  filling  in  the  spaces  between  the  long  diverging  prisms.  There  are  occasional  collections 
of  prisms  which  run  diagonally.  The  prisms  are  directed  vertically  on  the  summit  of  the 
crown,  horizontally  at  the  sides;  they  are  about  tttVu  inch  in  diameter,  and  pursue  a  more  or 
less  wavy  course.  By  reflected  light  radial  striations  are  visible,  best  marked  near  the  dentin. 
These  are  Schreger's  lines  and  are  due  to  the  fact  that  the  prisms  take  an  undulatory  course 


'/ 


Fig.  935. — Longitudinal  ground  section  through  the  apex  of  a  canine  tooth  from  a  three-and-a-half-year-( 
boy.  The  entrance  of  the  dental  canaliculi  between  the  enamel  prisms  and  the  course  taken  by  the  latter  i 
shown.     X  135.      (Szymonowicz.) 


and  those  of  two  layers  may  have  opposite  directions.  Another  series  of  lines,  having  a  brown 
appearance  from  pigmentation,  and  denominated  the  parallel  striae  or  brown  striae  of  Betzius, 
or  the  colored  lines,  are  seen  on  a  section  of  the  enamel.  These  lines  are  concentric,  and  cross 
the  enamel  rods.  They  are  caused  by  the  mode  of  enamel  deposition.  Inasmuch  as  the  enamel 
columns,  when  near  the  dentin,  cross  each  other  and  only  become  parallel  farther  away,  a 
series  of  radial  markings,  light  and  dark  alternately,  is  obtained  (Fig.  934).  The  enamel  prisms 
are  themselves  calcified  and  are  fixed  to  each  other  by  a  very  small  amount  of  cement  substance. 
Numerous  minute  interstices  intervene  between  the  enamel  fibres  near  their  dentinal  surface. 
It  is  noted  that  some  of  the  dentinal  canals  at  the  crown  penetrate  a  certain  distance  between 
the  rods  of  the  enamel;  this  is  considered  pathological  by  some  (Fig.  935).  No  nutritive  canals 
exist  in  the  cniunpl,  except  the  very  few  dentinal  canals  which  at  the  crown  penetrate  a  short 
distance,  mikI  llicsc  are  found  only  in  a  small  area. 

Chemical  Composition. — According  to  Bibra,  enamel  consists  of  96.5  per  cent,  of  earthy 
matter  and  3.5  per  cent,  of  animal  matter.     The  earthy  matter  consists  of  the  phosphate  and 


THE  MOUTH,    ORAL   OR  BUCCAL   CAVITY 


1211 


the  carbonate  of  calcium,  with  traces  of  fluoride  of  calcium,  phosphate  of  magnesia   ami  other 
salts.  ' 

The  enamel  of  a  recently  erupted  tooth  is  covered  by  a  membrane,  tiie  thickness  of  which 
IS  20^0  mch  It  is  known  as  enamel  cuticle  oi-  Nasmyth's  membrane  (ciillnila  deniia)  It 
IS  probably  the  remains  of  the  enamel  organ,  though  some  consider  it  the  contiruiation  of  the 
cementum. 

The  dentin  or  ivory  (substantia  eburnca)  (Fig.  937)  forms  the  principal  mass  of  the  tooth. 
It  represents  modified  bone,  but'  differs  from  the  latter  in  that  its  cells  are  upon  the  siu^ace  of 
the  pulp  and  not  In  the  substance  of  the  dentin.  The  important  parts  are:  dentinal  tubules 
denlMKil  shcntiis,  matrix,  and  dentinal  fibres. 

Till'  dentinal  tubules  are  minute  canals  which  have  a  spiral  course,  more  or  less  perpendicular 
to  the  pulp  cavity,  and  extending  from  this  cavity  to  the  enamel  or  to  the  cementum.  The 
diameter  at  the  pulpal  end  is  about  ^niVs  of  an  inch,  and  this  diminishes  as  the  tubules  branch. 
The  tubules  usually  end  blindly  near  the  enamel;  some,  however,  terminate  in  the  interglobular 

spaces  or  anastomose  with  other 
tubules.  The  dentinal  tubules  contain 
the  dentinal  fibres,  which  represent 
the  pcriplK'iul  prijfcsses  of  the  odonto- 
blastic cells,  and  their  branches  follow 
the  divisions  of  the  tubules.  The 
tubule  branches  are  most  numerous 
near  the  enamel  or  the  cementum. 


Fig.  936. — Ground  section  through  the  root  of  a  human  pre- 
molar. D.  Dentin.  K.  Cement  corpuscles.  O.  Osteoblasts, 
Ep.  Remains  of  Hertwig's  epithelial  sheath,  200  diameters.  -A 
Interglobular  spaces.     (Rose.) 


Fig.  937. — From  a  ground  section  through 
the  parts  of  a  dentin,  near  the  pulp,  of  a  human 
canine  tooth  which  lias  been  impregnated  with 
pigment.  The  dental  canaliculi  are  cut  across 
and  are  joined  together  by  side  branches. 
X  400. 


The  dentinal  sheaths,  or  Netmiann's  sheaths,  are  tubes  of  markedly  resistant  dentin  sur- 
rounding and  bounding  the  dentinal  tnlinlcs.     They  branch  and  curve  as  do  the  tubules. 

Tlie  matrix,  or  intertubular  dentin,  is  less  dense  than  that  of  the  sheaths.  It  fills  the  spaces 
between  the  sheaths,  and  seems  to  be  composed  of  lamellae  that  run  parallel  to  the  pulp  chamber. 
Fibrils  have  been  found  in  the  matrix.  Scattered  in  the  matrix,  and  especially  near  the  enamel, 
are  numerous  spaces  filled  with  a  gelatinous  substance;  these  are  the  interglobular  spaces 
(spatia  interglobulares) ,  representing  areas  of  incomplete  calcification.  Between  the  dentin  and 
cementum  the  spaces  are  very  numerous,  but  small;  these  constitute  Tomes'  granular  layer. 

In  a  dry  tooth  a  section  of  dentin  often  displays  a  series  of  lines — the  incremental  lines  oi 
Salter — which  are  parallel  with  the  laminae  above  mentioned.  These  lines  are  caused  by  two 
facts:  (1)  The  imperfect  calcification  of  the  dentinal  laminae  immediately  adjacent  to  the  line. 
(2)  The  drying  process,  which  reveals  these  defects  in  the  calcification.  These  lines  are  wide 
or  narrow  according  to  the  number  of  laminae  involved,  and  along  their  coiu'se,  in  consequence  of 
the  imperfection  in  the  calcifying  process,  little  irregular  cavities  are  left,  which  are  the  inter- 
globular spaces  already  referred  to.  They  have  received  their  name  from  the  fact  that  they  are 
smrounded  by  minute  nodules  or  globules  of  dentin.  Other  curved  lines  may  be  seen  ]>arallel 
to  the  surface.  These  are  the  concentric  lines  of  Schreger,  and  are  due  to  the  optical  effect  of 
simultaneous  ciu'vature  of  the  dentinal  tubules. 


1212 


THE  ORGANS  OF  DIGESTION 


Chemical  Composition. — According  to  Berzelius  and  Bibra,  dentin  consists  of  twenty-eight 
parts  of  animal  and  seventy-two  of  earthy  matter.  The  animal  matter  is  resolvable  by  boiling 
into  gelatin.  The  earthy  matter  consists  of  phosphate  and  carbonate  of  calcium,  with  a  trace  of 
fluoride  of  calcium,  phosphate  of  magnesia,  and  other  salts. 

The  cementum,  or  crusta  petrosa  (substantia  ossea)  (Fig.  934).  is  disposed  as  a  thin  layer 
on  the  roots  and  neck  of  a  tooth,  from  the  termination  of  the  enamel  as  far  as  the  apex  of 
the  root,  where  it  is  usually  very  thick.  At  the  neck  it  overlies  a  slight  margin  of  enamel.  In 
structure  and  chemical  composition  it  is  true  bone.  It  consists  of  a  number  of  lamella;  that  are 
thicker  near  the  apex  than  the  neck  of  the  tooth  in  young  teeth.  In  older  teeth  there  are  addi- 
tional shorter  supplemental  lamellae  at  the  apex.  Between  the  lamellae  are  the  lacunae  and 
canaliculi,  and  it  is  claimed  that  in  thick  cementum  even  Haversian  systems  may  be  found. 
It  is  composed  of  about  66  per  cent,  organic  matter  and  34  per  cent,  inorganic  matter.  The 
teeth  of  the  young  usually  contain  Haversian  systems  in  the  thicker  portions  of  the  cementum. 
The  neck  of  the  tooth  does  not  contain  lacunje.  Sharpey's  fibres  (p.  38)  are  very  numerous. 
Some  of  the  lacunae  of  the  cementum  receive  dentinal  tubes  from  the  dentine. 

As  age  advances  the  cement  increases  in  thickness,  and  gives  rise  to  those  bony  growths,  or 
exostoses,  so  common  in  the  teeth  of  the  aged;  the  pulp  cavity  becomes  also  partially  filled 
by  a  hard  substance  intermediate  in  structure  between  dentin  and  bone  (the  osteodentin  of 
Owen;  the  secondary  dentin  of  Tomes).  It  is  formed  by  the  odontoblasts,  the  dental  pulp 
lessening  in  volume. 


Fig.  938.' — Enamel  prisms  (350  diameters).     A.  Fragments  and  single  fibres  of  the  enamel  isolated  by  the  action 
of  hydrochloric  acid.    B.  Sm-face  of  a  small  fragment  of  enamel,  showing  the  hexagonal  ends  of  the  fibres. 


The  pulp  ipulpa  dentis)  occupies  the  pulp  cavity  or  chamber.  This  chamber  communicates 
with  the  outside  through  a  minute  canal  in  the  apex  of  each  fang,  called  the  root  canal  (canalis 
radicis  dentis).  The  foramen  at  the  apex  is  called  the  apical  foramen  (foramen  apieis  dentis). 
The  pulp  is  a  highly  vascular  and  sensitive  mass  of  mucous  connective  tissue  connected  with 
the  nutrition  and  sensitiveness  of  the  tooth.  It  consists  of  a  network  of  delicate  fibrils  sup- 
porting spindle-shape,  stellate,  and  spheroidal  cells,  and,  lastly,  the  odontoblasts,  which  are 
arranged  in  a  single  row  upon  the  surface  of  the  pulp;  each  odontoblast  is  a  cylindrical  or  flask- 
shaped  cell  possessing  several  processes,  of  which  the  peripheral  becomes  the  dentinal  fibre. 
The  bloodvessels  of  the  pulp  break  up  into  innumerable  capillary  loops  which  lie  beneath  the 
layer  of  odontoblasts.  The  nerve  fibrils  break  up  into  numberless  amyelinic  filaments,  which 
spread  out  beneath  the  odontoblasts,  and  probably  send  terminal  filaments  to  the  extreme 
periphery  of  the  pulp  outside  the  odontoblasts.  The  matrix  cells  and  their  processes  are  irregu- 
larly arranged  in  the  body  of  the  pulp,  but  in  the  canal  portion  the  fibrillae  are  in  the  direction  of 
the  axis  of  the  root. 

The  peridental  membrane  (perieementum)  is  a  vascular  and  sensitive  fibrous  tissue  membrane 
that  holds  the  tooth  in  place.  Upon  its  internal  surface  it  forms  cementum,  while  upon  its  outer 
surface  it  forms  the  bone  of  the  alveolar  process  of  maxilla  or  mandible.  It  is  thickest  at  the 
apical  and  gingival  regions  of  the  tooth  and  thin  in  the  middle.  Upon  its  inner  surface  are. 
seen  cementoblasts,  and  upon  its  outer  surface  are  found  osteoblasts.  The  arteries  are  derived 
from  the  apical  artery,  and  ultimately  form  a  capillary  plexus  beneath  the  cemental  and  alveolar 
surfaces  of  the  membrane.  The  venous  channels  converge  at  the  apex  to  empty  into  the 
apical  vein. 

Lymphatics  are  said  to  be  absent. 

Development  of  the  Teeth  (Figs.  939  to  945). — The  teeth  are  an  evolution  from  the 
dermoid  system,  and  not  of  the  bony  skeleton;  they  are  developed  from  two  of  the  blasto- 


THE  MOUTH,    ORAL   OR  BUCCAL   CA  VfTY 


1213 


dermic  layers,  the  ectoderm  and  mesoderm.  From  the  former  the  enamel  is  developed;  from 
the  latter  the  dentinal  pulp,  dentin,  cementum,  and  peridental  membrane.  It  is  customary  to 
view  the  development  of  the  permanent  and  temporary  teeth  as  separate  studies. 

The  earliest  evidence  of  tooth  formation  in  the  human  embryo  is  observed  about  the  sixth 
week.  The  epithelium  covering  the  embryonic  jaws  is  seen  to  rise  as  a  ridge  along  the  summit 
of  each  jaw.  This  ridge  is  the  maxillary  rampart  of  Kblliker  and  Waldeyer.  A  transverse 
section  through  the  jaw  will  show  the  clcwiiidii  in  lie  due  lo  a  liiii-ar  and  miilincd  activity  of  the 
germinal  epithelial  layer;  a  corresponding  c|iithclial  growth  is  seen  lo  .sink  as  a  liand  into  the 
mesodermal  tissue  beneath.     This  band  is  called  the  dental  lamina  (jr  dental  shelf.     The  local 


■^. 


Enamel  pidp 
Superficial  cells 
of  enamel  organ 


..Epithelium  of 
oral  cavity 

Basal  layer 

Superficial  cells  of 
eitatnel  organ 

'Enamel  pulp 
-Dentinal  papilla 


Fic  939  — \nlage  of  the  enamel  germ  con- 
nected ^ith  the  oral  epithelium  by  the 
enamel  ledge       \  110 


Fig.  940.— First  trace  of  the  dentinal  papilla.      X  110. 


Epithelium  of 
~ —  oral  cavity 
s^ Basal  layer 


Part  of  enamel  ledge 
of  a  permanent  tooth 
Enamel  germ  of 
ane)it  toolh 
cl  pulp 
Dentinal  papilla 
Odontoblasts 
Enamel  cells 


Fig.  941. — Advanced  stage  with  larger  papilla  and 
differentiating  enamel  pulp.      X  110. 


Fig.  942. — Budding  from  the  enamel  ledge  of 
the  anlage  of  tlie  enamel  germ,  which  later  goes 
to  form  the  enamel  of  a  permanent  tooth;  at  the 
periphery  of  the  papilla  the  odontoblasts  are  be- 
ginning to  differentiate.      X  40. 


Figs.  939  to  942.— Four  stage; 


1  the  development  of  a  tooth  in  a  sheep  i 
(From  Bohm  and  Davidoff.) 


iibryo  (from  the  lower  jaw) 


cell  activity  continues,  and  in  its  descent  the  band  appears  to  meet  with  a  resistance  which  causes 
a  flattening  of  its  extremity  into  a  continuous  lamina.  From  the  outer  or  labial  surface  of  the 
shelf  epithelial  buds  are  given  off  successively,  ten  in  number,  one  for  each  temporary  tooth; 
the  earliest  (central  incisors)  appear  about  the  seventh  to  the  eiijhth  week. 

The  growth  of  each  bud  continues,  and  each  expands  into  a  flask-like  form,  the  walls  covered 
by  a  layer  of  germinal  cells,  its  interior  composed  of  stellate  cells.  The  bulb  is  now  seen  to  flatten 
upon  its  deep  surface,  as  though  it  had  met  with  an  outlined  resistance  from  the  mesodermal 


1214 


THE  ORGANS  OF  DIGESTION 


tissue  beneath.  The  mesoderm  at  the  base  of  each  enamel  organ  condenses,  and  seems  to 
force  the  adjacent  part  of  the  enamel  germ  toward  the  apex  of  the  organ,  producing  thus  a  sac- 
like structure,  the  enamel  organ;  the  latter  now  consists  of  three  layers,  outer  columnar  layer, 
middle,  stellate  reticulum,  and  inner,  enamel-forming  cells,  the  membrana  adamantina.  The 
papilla-like  mass  of  mesoderm  that  extends  into  the  enamel  organ  is  called  the  dental  papilla. 


Dental  furiow 


Remains  of  ' '  nech  '  of 
enamel  organ,  or  of  the— 
common  dental  shelf 


Permanent  special 
dental  germ 


Meckel's  cartilage. 


Fig.  943. — Vertical  sestioa  of  the  mandibl 


lute}  nal  enamel  layer, 
0)  ada  lantohlasts 

De  ital  sac 

»v»     E  lai  lel  palp 

Exte  nal  enamel 
layei 
Papiha 


early  human  fetus.     (Magnified  25  diameters.) 


The  mesoderm  peripheraii  to  the  enamel  organ  condenses  to  form  a  sheath  called  the  dental  sac 
or  follicle.  In  the  meantime  the  dental  shelf  becomes  attenuated  and  tends  to  disappear,  and 
bone  is  being  deposited  in  the  intervals  around  and  between  the  teeth,  so  that  the  latter  soon  lie 
in  a  gutter  of  bone. 

The  cells  of  the  enamel  organ  now  undergo  a  series  of  differentiations.     The  inner  layer, 
arranged  as  columnar  epithelium,  are  the  enamel  cells,  or  ameloblasts.    The  layer  is  called" the 


Dentine    c. 


Fig.  944. — Section  through  tooth  follicle 
^— human  canine  seven  and  one-half  months. 
A,  Follicular  wall.  B.  Outer  epithelial  coat. 
C.  Stellate  reticulum.  Z>.  Stratum  inter- 
medium. E.  .\meloblasts.  F.  Odontoblasts. 
G.  Pulp. 


Fig.  945. — Diagram  after  Williams  (Dental  Cosmos,  1896), 
mode  of  enamel  deposition.  A.  Blood  supply  to  B,  secreting 
papilla;.  C  Layer  of  ameloblasts  containing  enamel  globules 
and  droplets  of  calcoglobulin.  D.  Enamel  globules  deposited. 
E.  Formed  dentin.  F.  Forming  dentin.  G.  Layer  of  odonto- 
blasts.    H.  Blood  supply  to  odontoblastic  layer. 


ameloblastic  or  enamel-forming  layer  (Figs.  944,  94.5,  and  946).  The  cells  of  the  outer  wall 
remain  cuboidal;  the  cells  which  lie  between  become  much  distended,  and  on  account  of  their 
appearance  when  seen  in  section  this  portion  of  the  organ  is  called  the  enamel  jelly  or  the 
stellate  reticulum.  The  layer  of  cells  immediately  contiguous  to  the  ameloblasts  forms  a  layer 
called  the  stratimi  intermedium  (Fig.  944,  D). 


THE  MOUTH,   ORAL  OR  BUCCAL  CAVITY  1215 

The  enclosed  mesoblastic  papilia  (tlie  fiittire  dental  pulp)  has  its  peripheral  cells,  whieh  are 
called  odontoblasts,  differentiated  into  columnar  bodies  disposed  as  a  layer,  each  cell  iKiving 
8  large  nucleus.  The  vascular  supply  of  the  pulp  is  now  well  marked.  A  section  of  a  follicle 
at  this  period  will  exhibit  the  follicular  wall  springing  from  the  base  of  the  dental  papilla  and 
having  a  well-marked  blood  supply.  The  bony  alveolar  walls  are  well  outlined,  and  e\idences  of 
a  periosteum  appear  (Figs.  943,  944,  and  945). 

Development  of  Enamel  (Fig.  945). — In  point  of  time,  the  deposition  of  dentin  actually 
begins  before  that  of  enamel,  so  that  the  first-formed  layer  of  enamel  is  deposited  against  a  layer 
of  immature  dentin,  and  is  formed  from  within  outward,  so  that  the  youngest  enamel  is  ■upon 
the  sm-face  of  the  tooth .  The  enamel  is  built  up  of  two  distinct  substances — globules  of  uniform 
size  which  are  formed  by  the  ameloblasts,  and  a  cementing  substance,  probably  an  albuminate 
of  calcium  (caleoglobulin),  the  basis  of  all  the  calcified  tissues.  In  the  ends  of  the  ameloblasts, 
next  to  the  dentin,  the  secretion  of  caleoglobulin  is  deposited,  and  into  the  plastic  mass  the 
enamel  globules  are  extruded,  each  globule  remaining  connected  with  the  ameloblasts  by  plasmic 
strings,  which  also  join  the  globules  laterally.' 

The  first  deposit  of  enamel  begins  in  the  tips  of  the  cusps,  and  is  quickly  followed  by  a  disap- 
pearance of  the  stellate  reticulum  at  that  point;  the  stellate  reticulum  appears  to  atrophy,  so  that 
the  vascular  follicular  wall  is  brought  into  direct  apposition  with  the  stratum  intermedium,  which 
becomes  differentiated  into  a  glandular  (secreting) 
tissue  which  elaborates  the  calcic  albuminous  basis 
of  the  enamel.  The  secretion  passes  from  the  cells 
of  the  stratum  intermedium  through  a  membrane  into 
the  ameloblasts,  where  it  is  in  part  combined  with 
the  cellular  globules,  and  irregular  masses  of  it  are 
extruded  as  cementing  substance.  The  deposition 
continues  until  the  enamel  cap  has  its  typical  form. 
The  deposition  of  the  layers  of  globules  is  indicated 
by  parallel  lines  transverse  to  the  axes  of  the  enamel 
rods.  At  the  completion  of  amelification  the  ameloblasts 
are  partially  calcified  and  form  the  enamel  cuticle  or 
Nasmyth's  membrane  (cuticii/a  deniis).  Fig.  946.— Part  of  section  of  developing 

Formation    of    Dentin. — The     layer     of     columnar      tooth  of    young    rat,  showing    the    mode    of 

11     1  1-^1  .1  p  .1  1        .1  J      J.  deposition  of  the  dentin  (highly  magnified). 

cells  bounding  the  periphery  of  the  pulp,  the  OdontO-      a.  Outer   layer  of  fully  calcified    dentin,      b. 

blasts,  are  in  apposition  with  the  olexus  of  capillary     Uncalcified  matri.i  with  a  few  nodules  of  cal- 

1     /T-<-      ^  i/i\        T-t      1         11  •  ,•        I      11*1       careous  matter,     c.  Odontoblasts  with  proc- 

vessels  (I'lg.  946).      iiach  cell  is  a  secreting  body  which      esses    extending    into    the    dentin,      d.   Pulp. 


selects  the  material  for  dentin  building.     Against  the    The  section  is  stained 

,  p  111., I  7  T-  -,i  colors  the  uncalcifaed  matrix,  but  not  the  cal- 

layer  ot  ameloblasts,  the  membrana  ebons,  covering  the     cified  part. 

dental  papilla,  the  odontoblasts  deposit  globules  of  the 

calcium  albuminate,  and  receding  as  the  deposits  are  made,  leave  one  or  more  protoplasmic  proc- 
esses in  the  calcic  deposit.  These  are  known  as  Tomes'  or  dentinal  fibres.  The  process  contin- 
ues until  the  normal  dentin  thickness  is  formed.  The  deposit  is  laid  down  in  a  scaffolding  of  finely 
fibrillated  tissue,  and  begins  about  the  sixteenth  week.  The  layer  of  formative  cells  remains 
constant.  The  remains  of  the  dentinal  papilla  constitute  the  pulp  and  lie  in  the  pulp  cavity 
(p.  1212). 

Formation  of  Cementum. — Aa  the  enamel  organ  continues  to  grow  the  dental  follicle  cov- 
ering atrophies,  while  that  over  the  future  root  region  continues  to  grow.  Upon  its  dentinal 
surface  the  stellate  cells  constitute  the  cementoblasts.  Upon  its  outer  surface  the  stellate  cells 
are  osteoblasts  that  form  the  alveolar  bone.  The  cementum  of  the  tooth  is  not  formed  until 
the  dentin  has  extended  below  the  enamel  cap,  while  the  cementum  of  the  apex  is  usually  not 
completed  until  after  the  eruption  of  the  tooth. 

Formation  of  Alveoli. — By  the  time  the  crowns  of  the  teeth  have  formed,  each  is  enclosed 
in  a  loeulus  of  bone  which  has  developed  around  it  and  at  some  distance  from  it;  the  developing 
permanent  tooth  is  contained  in  the  same  loeulus,  but  is  later  separated  from  the  temporary 
tooth  by  a  growth  of  bone.  The  alveolar  process  is  not  completed  until  after  the  eruption  of 
the  teeth.  During  eruption  that  portion  of  the  process  overlying  the  crown  undergoes  absorp- 
tion, and  as  soon  as  the  immature  tooth  is  erupted  the  alveolar  process  has  developed  about  the 
root,  whose  formation  is  also  completed  after  eruption. 

Development  of  the  Permanent  Teeth. — The  permanent  teeth  as  regards  their  develop- 
ment may  be  divided  into  two  sets:  (1)  Those  which  replace  the  temporary  teeth,  and  which, 
like  them,  are  ten  in  number;  these  are  the  successional  permanent  teeth;  and  (2)  those  which 
have  no  temporary  predecessors,  but  are  superadded  at  the  back  of  the  dental  series.  These 
are  three  in  number  on  either  side  in  each  jaw,  and  are  termed  the  superadded  permanent 
teeth.  They  are  the  three  molars  of  the  permanent  set,  the  molars  of  the  temporary  set  being 
replaced  by  the  premolars  or  bicuspids  of  the  permanent  set. 

I  J.  L.  Williams,  Dental  Cosmos,  1S06. 


1216 


THE  ORGANS  OF  DIGESTION 


The  Development  of  the  Successional  Permanent  Teeth — the  ten  anterior  ones  in  either 
jaw — will  be  first  considered.  The  germs  for  these  teeth  are  developed  from  the  lingual  side 
of  the  dental  shelf,  opposite  to  the  corresponding  temporary  teeth.  The  germ  for  the  central 
incisor  appears  at  about  the  serenieenth  week,  and  the  others  follow  successively  in  order  of  their 
eruption.  The  deposition  of  enamel,  dentin,  and  cementum  occurs  as  in  the  temporary  teeth. 
The  sac  of  each  permanent  tooth  is  also  connected  with  the  fibrous  tissue  of  the  gum  by  a 
slender  band  of  the  gubemaculum,  which  passes  to  the  margin  of  the  jaw  behind  the  corre- 
sponding milk  tooth  (see  above). 

The  Superadded  Permanent  Teeth — three  on  each  side  in  each  jaw — develop  as  primary 
teeth.  The  enamel  germ  for  the  first  molar  tooth  appears  during  the  sixteenth  week  from  the 
end  of  the  dental  shelf.  The  enamel  germ  for  the  second  molar  tooth  appears  about  the  fourth 
month  after  birth  from  the  neck  of  the  enamel  sac  of  the  first  molar  tooth,  while  that  for  the 
third  molar  or  wisdom  tooth  does  not  appear  until  the  third  year  after  birth,  from  the  enamel  sac 
of  the  second  molar  tooth. 

Eruption. — When  the  teeth  are  ready  to  erupt  the  bone  between  them  and  the  gum  is  absorbed 
as  well  as  that  covering  the  labial  surface  of  the  crown,  until  one-half  of  the  enamel  is  exposed. 
The  bone  covering  the  lingual  surface  is  more  slowly  absorbed,  as  it  protects  the  permanent 
tooth  germ  beneath.  As  a  result  of  this  process  the  tooth  is  exposed  chiefly  by  the  removal  of  the 
bone  around  the  crown,  and  not  by  a  growth  upward  of  the  tooth  itself.  In  the  replacement  of 
the  temporary  teeth  by  the  permanent  set  the  roots  of  the  temporary  teeth  are  gradually  absorbed 
until  merely  the  enamel  cap  and  contained  dentin  remain.  The  hold  of  the  tooth  upon  the  jaw 
is  weakened  so  that  it  mav  readilv  be  remox-ed  or  lost. 


Fig.  947.— The  milk  teeth  in  a  child  aged  about  four  years.  The  permanent  teeth  are  seen  in  their  alveoli.   (Cryer.) 

Calcification  of  the  permanent  teeth  proceeds  in  the  following  order:  First  molar,  soon  after 
birth;  the  central  incisor,  lateral  incisor,  and  canine,  about  six  months  after  birth;  the  bicuspids, 
at  the  second  year  or  later;  second  molar,  end  of  second  year;  third  molar,  about  the  twelfth 

The  Eruption  of  the  Temporary  Teeth  commences  at  the  seventh  month,  and  is  complete 
about  the  end  of  the  second  year. 
The  periods  for  the  eruption  of  the  temporary  set  are  (C.  S.  Tomes) : 

Lower  central  incisors 6  to    9  months. 

Upper  incisors 8  to  10        ^^ 

Lower  lateral  incisors  and  first  molars 1.5  to  21 

Canines l^  ^°  II       « 

Second  molars -0  to  -4 


THE  TONGUE  1217 

The  Eruption  of  the  Permanent  Teeth  takes  place  at  the  follo\\in<;  periods,  the  teeth  of  the 
lower  jaw  preceding  those  of  tlie  upper  by  a  short  interval: 

6i  years,  first  molars.  10th  year,  second  bicuspid. 

7th  year,  two  middle  incisors.  11th  to  12th  year,  canine. 

8th  year,  two  lateral  incisors.  12th  to  13th  year,  second  molars. 

9th  year,  first  bicuspid.  17th  to  21st  year,  third  molars. 

THE  TONGUE  (LINGUA)  (Fig.  948). 

The  tongue  is  a  very  mobile  muscular  organ,  undergoing  changes  in  length  and 
width  at  every  contraction  of  its  muscle.  It  is  one  of  the  organs  of  the  special 
sense  of  taste,  and  is  also  an  organ  of  speech,  and  assists  in  insalivation,  masti- 
cation, and  deglutition.  It  is  situated  in  the  floor  of  the  mouth,  in  the  interval 
between  the  two  lateral  portions  of  the  body  of  the  mandible,  and  when  at  rest 
is  about  three  and  one-half  inches  (8.75  cm.)  in  length.  We  describe  the  body, 
base,  apex,  dorsum,  margin,  and  inferior  surface. 

The  body  {corpus  linguae)  forms  the  great  bulk  of  the  organ  and  is  composed 
of  striated  muscle. 

The  base  or  root  (radix  linguae)  is  directed  backward  and  connected  with  the 
hyoid  bone  by  the  Hyoglossi  and  Geniohyoglossi  muscles  and  the  hyoglossal  mem- 
brane; with  the  epiglottis  by  three  folds,  glossoepiglottic  folds,  of  raucous  membrane; 
with  the  soft  palate  by  means  of  the  anterior  pillars  of  the  fauces;  and  with  the 
pharynx  by  the  Superior  constrictor  muscles  and  the  mucous  membrane. 

The  apex  or  tip  (apex  linguae)  is  free,  thin,  and  narrow,  and  is  directed  forward 
against  the  inner  surface  of  the  lower  incisor  teeth. 

The  dorsum  of  the  tongue  {dorsum  linguae)  of  a  living  person,  when  at 
rest,  is  markedly  arched  from  before  backward.  On  the  dorsum  is  a  median 
longitudinal  raph^  {sulcus  medianus  linguae).  This  slight  depression  terminates 
posteriorly  in  the  depression  known  as  the  foramen  cecum  (foramen  caecum  linguae 
[Morgagnii]),  from  which  a  shallow,  V-shaped  groove,  the  sulcus  terminalis  of  His, 
runs  outward  and  forward  on  each  side  to  the  lateral  margin  of  the  tongue.  The 
part  of  the  dorsum  of  the  tongue  in  front  of  this  groove,  known  as  the  anterior, 
apical,  or  oral  part,  forming  about  two-thirds  of  its  upper  surface,  looks  upward, 
is  practically  horizontal,  and  is  rough  and  covered  with  papilla?;  the  posterior  or 
basal  third  of  the  dorsum  is  vertical  and  looks  backward,  is  smoother,  and  contains 
numerous  muciparous  glands  and  lymphoid  nodules. 

The  margin  of  the  tongue  (jnargo  lateralis  linguae)  is  free  in  front  of  the  anterior 
arch  of  the  palate.  Just  in  front  of  the  arch  are  several  vertical  folds,  the  folia 
linguae . 

The  under  or  inferior  surface  {fades  inferior  linguae)  of  the  tongue  is  connected 
with  the  mandible  by  the  Geniohyoglossi  muscles;  from  its  sides  the  mucous  mem- 
brane is  reflected  to  the  inner  surface  of  the  gums,  and  from  its  under  surface 
on  to  the  floor  of  the  mouth,  where,  in  the  middle  line,  it  is  elevated  into  a  distinct 
vertical  fold,  the  frenum  linguae  (frenulum  linguae).  To  each  side  of  the  frenum 
is  a  slight  fold  of  the  mucous  membrane,  the  plica  fimbriata,  the  free  edge  of  which 
exhibits  a  series  of  fringe-like  processes. 

The  tip  of  the  tongue,  part  of  the  under  surface,  its  sides,  and  dorsum  are  free. 

Structure  of  the  Tongue. — The  tongue  is  partly  invested  by  mucous  membrane  and  a  sub- 
mucous fibrous  layoT  surrounding  the  central  muscle  tissue.  It  consists  of  symmetrical  halves, 
separated  from  each  other,  in  the  middle  line,  by  an  incomplete  fibrous  septum.  Each  half  is 
composed  of  muscle  fibres  arranged  in  various  directions  (p.  393),  containing  many  glands  and 
much  interposed  fat,  and  supplied  by  vessels  and  nerves. 

The  mucous  membrane  {tunica  mucosa  linguae)  invests  the  entu-e  e.xtent  of  the  free  surface 
of  the  tongue.     On  the  dorsum  it  is  thicker  behind  than  in  front,  and  is  continuous  with  the 


1218 


THE  ORGANS  OF  DIGESTION 


sheath  of  the  muscles  attached  to  it,  through  the  submucous  fibrous  layer.  On  the  under  surface 
of  the  organ,  where  it  is  thin  and  smooth,  it  can  be  traced  on  each  side  of  the  frenum  through 
the  ducts  of  the  submaxillary  and  the  sublingual  glands.  As  it  passes  over  the  borders  of  the 
organ  it  gradually  assumes  a  papillary  character.  That  covering  the  under  surface  of  the 
organ  is  thin,  smooth,  and  identical  in  structure  with  that  lining  the  rest  of  the  oral  cavity. 
The  mucous  membrane  covering  the  tongue  behind  the  foramen  cecum  and  sulcus  terminalis 
is  thick  and  freely  movable  over  the  subjacent  parts. 

The  mucosa  consists  of  stratified  squamous  epithelial  cells  resting  upon  a  basement  mem- 
brane, and  this  upon  a  papillated  tunica  propria  of  fibroelastic  tissue  containing  the  capillary 
loops  and  nerves.  Upon  the  apical  two-thirds  of  the  dorsum  of  the  tongue  the  projections  of 
the  mucosa  are  seen,  and  these  are  the  papillse.  They  vary  in  number,  size,  form.,  and  location; 
they  are  the  filiform  papillae,  fungiform  papillae,  and  circumvallate  papillae. 


EPIGLOTTIS 


IRCUM- 
VALLATE 
PAPILUC. 


Fig.  94S. — Upper  surface  of  the  tongue. 

The  filiform  or  conical  papillae  {papillae  filiformes)  are  small  and  scattered  over  the  apical 
two-thirds  (dorsum  and  margin)  of  the  tongue,  and  are  arranged  in  parallel  lines  that  are  directed 
outward  and  forward,  especially  posteriorly.  Minute  secondary  papillae  of  a  whitish  color  pro- 
ject from  these  filiform  structures. 

The  fvingiform  papillae  (papillae  fungiformes)  (Fig.  949)  are  scattered  sparingly  over  the 
dorsum  of  the  tongue,  and  are  more  numerous  at  the  sides  and  apex.  They  are  largjer  in  size 
but  less  numerous  than  the  preceding,  and  are  readily  recognized  by  their  large  size  and  deep 
red  color.  Their  bases  are  narrow  and  constricted,  while  the  free  ends  are  large  and  blunt; 
the  whole  papilla  is  above  the  general  epithelial  surface  of  the  tongue.  These  papillae  possess 
secondary  papillee,  and  in  their  epithelium  taste  buds  are  at  times  seen. 

The  circumvallate  papillae  (papillae  vallatae)  (Fig.  949)  are  of  large  size,  but  only  eight  to 
twelve  in  number.  They  are  arranged  like  a  letter  V  at  the  junction  of  the  apical  two-thirds  and 
basal  one-third  of  the  dorsum,  with  the  apex  at  the  foramen  cecum  and  the  arms  directed  out- 


THE  TONGUE 


1219 


ward  and  forward  just  in  front  of  the  sulcus  terrainalis.  These  papillse  are  partially  or  wholly 
submerged,  that  is,  lie  in  depressions.  Each  consists  of  a  narrow  base,  attached  at  the  bottom 
of  the  depression,  while  the  remainder  is  surrounded  by  the  vallum  or  ditch.  Kach  papilla  is 
from  jV  to  iV  inch  in  width  and  possesses  secondary  papillfe.  In  the  epithelium  of  the  sides 
are  found  the  taste  buds. 

The  foramen  cecum,  accordinj;  to  His,  represents  the  remains  of  ilic  cva<,'inatlon  that  formed 
the  middle  lobe  of  the  thyroid  body  and  the  upper  end  of  the  supposed  thyrnirlossal  duct  {ductus 
thi/roglossus).    This  may  exist  as  a  canal,  at  times  e.xtending  toward  the  hyuid  bone. 


Filiform. 


Circnmvallate, 


Fig.    949. — Filiform    papillse,    Fig.  950. — Fungiform  papillae,  magni-    Fig.    951. — Circumvallate    papillae,     mag- 
magnified,  fied.  ■  nified. 


Upon  the  posterior  or  basal  one-third  of  the  dorsum  of  the  tongue  papillse  are  not  found. 
The  surface  is  irregular,  however,  due  to  the  presence  of  nodular  collections  of  lymphoid  tissue, 
that  produce  rounded  elevations  of  the  mucosa.  Each  nodule  possesses  a  little  pit  or  crypt,  and 
collectively  the  follicles  are  termed  the  lin§rual  tonsil  {tonsilla  lingiialis).  Each  crypt  is  lined 
by  stratified  sciuamous  epithelial  cells  upon  basement  membrane  and  timica  propria;  in  the  latter 
are  numerous  solitary  nodules  arranged  aroimd  the  pit,  and  each  group  is  isolated  from  the 
neighboring  collection.     These  groups  constitute  the  hngual  tun  l1 

Beneath  the  tunica  propria  of  the  mucosa  is  the 
muscle  tissue  of  the  tongue.  This  muscle  tissue 
is  of  the  voluntary  striated  variety  and  is  divided 
into  two  sets  of  muscles — Intrinsic  and  Extrinsic 
(described  on  p.  393). 

Scattered  throughout  the  tongue,  but  especially 
located  in  definite  areas,  are  glands  of  a  mucous 
and  serous  character.  The  mucous  glands  are 
found  behind  the  circumvallate  papillie  and  along 
the  margins,  and  an  especial  group  at  the  apex, 
called  the  apical  glands  or  glands  of  Nuhn  and 
Blandin  (glnmlular  liiir/uales  anteriores  of  Nuhn 
and  Blandin)  (Fig.  953)  Each  gland  is  situated 
at  the  side  of  the  frenulum  and  is  covered  by  a 
fasciculus  of  muscle  fibres  derived  from  the  Stylo- 
glossus and  Inferior  lingualis  mu.scles.  Each  gland 
is  from  one-half  inch  to  nearly  an  inch  in  length 
(1  to  2  cm.)  and  about  one-third  of  an  inch  broad 
(S  mm.).  Each  gland  has  from  four  to  six  ducts, 
which  open  on  the  under  surface  of  the  apex. 
The  serous  glands,  or  glands  of  von  Ebner,  occur 
in  the  basal  part  of  the  tongue,  the  ducts  opening 
chiefly  into  the  fossre  around  the  circiuiivallate 
papillfe.  Both  mucous  ami  serous  glaud.s  resemble 
the  other  salivary  gl.-imls  in  stniciure  (p.  122(>). 

The  Vessels  of  the  Tongue.  -The  arteries  of  the  tongue  are  derived  from  the  lingual,  the 
facial,  and  ascending  pharyngeal.     The  veins  of  the  tongue  open  into  the  internal  jugular. 

The  lingual  artery  (Fig,  0.5.5)  on  each  side  passes  forward  beneath  the  Kyoglossiis  muscle 
and  courses  to  the  apex  of  the  tongue,  between  the  Genioglossus  and  the  Inferior  lingual  mu.scles, 
about  one-eighth  of  an  inch  from  the  surface.     It  divides  into  the  ranine  (Fig.  953)  and  sub- 


'; 


\\       !.>. 


Frc  0o2  — Circum-\  \lHte  papilla?  of  tongue  of 
rihbit  snoring  po-sition  ot  t  iste  goblets  a. 
DuctofgUnd  rl  SeiousgHnd  n  Tai,te  buds. 
/  Prim  ir\  s^pf  i  nd  I  second  ir>  septn.  of 
papillp  »  Mvtlmited  ner^e  V  Vubck  hbres. 
(.stohr  ) 


1220 


THE  ORGANS  OF  DIGESTION 


lingual  (Fig.  955).  Near  the  apex  a  branch  is  given  off  from  the  ranine  artery,  which  pene- 
trates the  septum  and  joins  a  like  branch  from  the  other  side.  The  dorsalis  linguae  is  a  branch  of 
the  lingual  supplying  the  posterior  part  of  the  tongue,  and  rami  from  the  tonsillar  branch  of 
the  facial  go  to  the  same  region.  A  network  of  capillary  vessels  is  placed  beneath  the  epithelium. 
The  ranine  veins  lie  to  the  side  of  the  frenum  underneath  the  mucous  membrane.  Each 
ranine  vein  runs  backward,  superficial  to  and  upon  the  Hyoglossus  muscle  and  near  to  the 


Lingual  nerve,        Sanine  artery. 


Fig.  953. — Under  surface  of  tongue,  showing  position  and  relations  of  gland  of  Blandin  or  Nuhn.     (From 
a  preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 

hypoglossal  nerve.  The  venae  comites  of  the  lingual  artery  usually  join  the  ranine  vein,  and 
the  trunk  opens  into  the  internal  jugular  vein,  but  the  vessels  may  open  separately  into  the 
jugular  vein  (Fig.  496). 

The  Lymphatic  Vessels  of  the  Tongue  (Fig.  559). — The  lymphatic  vessels  from  the  anterior 
half  of  the  tongue  pass  to  the  submaxillary  lymph  nodes. 

Lymph  vessels  from  the  posterior  half  of  the  tongue  are  connected  with  satellite  nodes  on 
the  Hyoglossus  muscle  and  terminate  in  the  deep  cervical  nodes.  The  last-named  lymph 
vessel  "accompanies  the  ranine  vein.     The  lingual  lymphatics  arise  from  a  network  beneath  the 


LONGITU 

VEBTICALIS. 


JALIS.— fe-^gg^i^,  '  f  ^^^\im-^>^ 

LINGU/E  MUSCLE        |3>^5^^ 

TRAHSVERSUS    ^J^f^^^^&^Z^  —    \ 

LINGU>E  MUSCLE^       V, VjfyW^M^*?.'       '      ~ 


INFERIOR 
LONCITUDINALIS 
MUSC 


'•^^.         STYLOGLOSSUS 
afli         MUSCLE 


SUBLINGUAL 


Fig.  954. — Frontal  section  through  the  body  of  the  tongue  of  ; 


vborn  babe.     X  3.     (Spalteholz.) 


epithelium.  Across  the  anterior  two-thirds  of  the  tongue  there  is  little  or  no  lymphatic  con- 
nection between  the  two  sides;  in  the  posterior  one-third  there  is  free  connection,  due  to  absence 
of  septum  here. 


THE  TONGUE 


1221 


The  Nerves  of  the  Tongue  (Fig.  Ooo).— Tlie  nerves  of  the  tonRne  are  five  in  nnmhcr  in  each 
half — the  lingual  branch  of  the  Inferior  maxillary  division  of  the  trigeminal,  whicli  is  distributed 
to  the  papillae  at  the  fore  part  and  sides  of  the  tongue,  and  forms  the  nerve  of  ordinary  sensibilitv 
for  its  anterior  two-thirds;  the  chorda  tsrmpani,  which  runs  in  the  sheath  of  the  lingual,  is  gen- 
erally regarded  as  the  nerve  of  taste  for  the  same  area  (p.  997);  the  lingual  branch  of  the  glosso- 
pharyngeal, ■whicii  is  disiiilnited  to  the  mucous  membrane  at  the  ba.se  and  sides  of  the  tongue, 
and  to  the  |>a|)illae  lircunnallatae,  and  which  supplies  both  sensor  and  gustatory  filaments  to 
this  region;  the  hypoglossal  nerve,  which  is  the  motor  nerve  to  the  muscular  substance  of  the 
tongue;  and  the  internal  laryngeal  branch  of  the  superior  laryngeal,  which  sends  some  fine 
branches  to  the  root  near  to  the  epiglottis.  Sympathetic  filaments  also  pass  to  the  tongue  from 
the  nervi  mollcs  on  the  lingual  and  other  arteries  supplying  it.  Some  of  the  nerves  end  free 
between  the  cells  of  epithelium;  others  terminate  as  end  organs  (Meissner's  corpuscles  and 
the  end-bulbs  of  Krause),  and  in  taste  buds  as  sensor  dendrites  (p.  1149). 


Jntet  nal  lai  ynqeal 

blanch  of  the 

superior  laryngeal. 


-Under  surface  of  tongue,  showing  the  distribution  of  nerves  to  this  organ, 
in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 


(From  a  prei  aration 


The  Development  of  the  Tongue  (Figs.  956  and  957). — The  tongue  is  developed  in  the  floor 
of  the  pharynx.  The  rudiment  of  the  anterior  or  buccal  portion  appears  during  the  third  week 
as  a  rounded  elevation,  immediately  behind  the  ventral  ends  of  the  mandibular  arches.  This 
elevation  is  named  the  tuberculum  impar  (Figs.  956  and  957);  it  extends  forward  on  the  oral 
surface  of  the  mandibular  arch,  and  increases  markedly  in  size  by  the  development  of  a  pair  of 
lateral  tongue  elevations,  which  raise  themselves  from  the  inner  surfaces  of  the  mandibular 
arches,  ancl,  blending  with  the  tuberculum  impar,  form  the  tip  and  greater  portion  of  the  buccal 
part  of  the  tongue.  These  lateral  growths  correspond  with  similar  structures  which  were  de- 
scribed by  E.  Kallius  in  the  development  of  the  tongue  of  the  lizard.  From  the  ventral  ends  of  the 
fourth  arch  there  arises  a  second  and  larger  elevation,  in  the  centre  of  which  is  a  median  groove 
or  furrow.     This  elevation  is  named  the  furcula  (Fig.  956),  and  is  at  first  separated  from  the 


1222 


THE  ORGANS  OF  DIGESTION 


tuberculum  impar  by  a  depression,  but  later  by  a  ridge  formed  by  the  forward  growth  and  fusion 
of  the  ventral  ends  of  the  second  and  third  arches.  The  posterior  or  pharyngeal  part  of  the 
tongue  is  developed  from  this  ridge,  which  extends  forward  in  the  form  of  a  V,  so  as  to  embrace 
between  its  tv%'0  limbs  the  tuberculum  impar  (Figs.  956  and  957).  At  the  apex  of  the  V  a  pit- 
like invagination  occurs,  to  form  the  middle  thyroid  rudiment,  and  this  depression  is  represented 
in  the  adult  by  \he  foramen,  cecum  of  the  tongue.  In  the  adult  the  union  of  the  anterior  and  pos- 
terior parts  of  the  tongue  is  marked  by  a  V-shaped  depression  (sulcus  terminalis),  the  apex  of 
which  is  at  the  foramen  cecum,  while  the  two  limbs  run  outward  and  forward,  parallel  to,  but  a 
little  behind,  the  circumvallate  papillse.  The  prominent  anterior  part  of  the  furcula  forms  the 
epiglottis;  the  furrow  behind  it  is  the  entrance  to  the  larynx;  and  the  anterior  parts  of  its  lateral 
margins  constitute  the  arytenoepiglottidean  folds. 


Tnbermlum  impar 
(papillary  part  of  tongue) 


Posterior  part  of  tongue. 


Mandibular  arch. 


■Hyoid  arch. 


Entrance  to  larynx. 


Fig.  956. — The  floor  of  the  pharynx  of  a  human  embryo  about  twenty-three  days  old.     X  30.     (From  His.) 

Applied  Anatomy. — The  diseases  to  which  the  tongue  is  liable  are  numerous,  and  its  ap- 
plied anatomy  is  of  importance,  since  any  or  all  the  structures  of  which  it  is  composed — muscles, 
connective  tissue,  mucous  membrane,  glands,  vessels,  nerves,  and  lymphatics — may  be  the  seat 
of  morbid  changes.  It  is  not  often  the  seat  of  congenital  defects,  though  a  few  cases  of  vertical 
cleft  have  been  recorded,  and  it  is  occasionally,  though  much  more  rarely  than  is  commonly  sup- 
posed, the  seat  of  tongue-tie,  from  shortness  of  the  frenum. 

There  is,  however,  one  condition  which  must  be  regarded  as  congenital,  though  not  uncom- 
monly it  does  not  exhibit  the  significant  changes  until  a  year  or  two  after  birth.  This  is  an 
enlargement  of  the  tongue  which  is  due  primarily  to  a  dilatation  of  the  lymph  channels  and  a 
greatly  increased  development  of  the  lymphatic  tissue  throughout  the  tongue  (macroglossia) .  This 
is  often  aggravated  by  inflammatory  changes  induced  by  injury  or  exposure,  and  the  tongue  may 


Papillary  portion  of  tongue. 


Mandibular  arch. 


Syoid  arch. 


Foramen  cxcum.    Posterior  part    Third  arch, 
of  tongue. 
Fig.  957. — Floor  of  mouth  of  an  embryo  slightly  older  than  that  shown  in  Fig.  956.     X  16.     (From  His.) 

assume  enormous  dimensions  and  hang  out  of  the  mouth,  giving  the  child  an  imbecile  expression. 
The  treatment  consists  in  excising  a  V-shaped  portion  and  bringing  the  cut  surfaces  together 
with  deeply  placed  silver  sutures.  Acute  inflammation  of  the  tongue  (acute  glossitis)  may 
be  caused  by  injury  or  the  introduction  of  some  septic  or  irritating  matter,  and  it  is  attended 
by  great  swelling  from  infiltration  of  the  connective  tissue  of  the  tongue;  this  connective  tissue 
is  present  in  considerable  quantity.  The  great  swelling  renders  the  patient  incapable  of  swal- 
lowing or  speaking,  and  may  seriously  impede  respiration.     The  condition  may  eventuate  in 


THE  SALIVARY  GLANDS  1223 

suppuration  and  the  formation  of  an  ai'iilc  ah.^irxx.  Chronic  absce.is,  which  has  been  mistaken 
for  cancer,  may  also  occur  in  the  sul)>t:iiiir  df  the  tongue. 

The  mucous  membrane  of  the  tongue  ina\-  hceonic  chronically  inflamed,  and  presents  different 
appearances  in  different  stages  of  the  disease,  to  which  the  terms  leukoplakia,  ■psoriasis,  and 
ichthyosis  have  been  given. 

The  tongue,  being  very  vascular,  is  often  the  seat  of  nevoid  growths,  and  these  have  a  tendency 
to  grow  rapidly. 

The  tongue  is  frequently  the  seat  of  ulceration,  which  may  arise  from  many  causes,  as  from 
the  irritation  of  jagged  teeth,  dyspepsia,  tuberculosis,  syphilis,  and  cancer.  Of  these,  the  cancerous 
ulcer  is  the  most  important,  and  probably  also  the  most  common.  The  variety  is  the  squamous 
epithelioma,  which  soon  develops  into  an  ulcer  with  an  indurated  base.  It  produces  great  pain 
which  speedily  extends  to  all  parts  supplied  with  sensation  by  the  trigeminal  nerve,  especially  to 
the  region  of  the  ear.  The  pain  in  these  cases  is  conducted  to  the  ear  and  temporal  region  by 
the  lingual  nerve,  and  from  this  nerve  pain  radiates  to  the  other  branches  of  the  inferior  ma.xii- 
lary  nerve,  especially  the  auriculotemporal.  Possibly  pain  in  the  ear  itself  may  be  due  to  impli- 
cation of  the  fibres  of  the  glossopharyngeal  nerve,  which  by  its  tympanic  branch  reaches  the 
tympanic  plexus.  Cancer  of  the  tongue  spreads  through  the  organ  very  rapidly  because  of  the 
almost  constant  muscular  movements. 

Cancer  of  the  tonejue  may  necessitate  removal  of  a  part  or  the  whole  of  the  organ,  and  many 
different  methods  have  been  adopted  for  its  excision.  The  better  method  is  by  the  scissors, 
usually  known  as  Whitehead's  method.  The  mouth  is  widely  opened  with  a  gag,  the  tongue  is 
transfixed  with  a  stout  silk  ligature,  by  which  to  hold  and  make  traction  on  it  and  the  reflection 
of  mucous  membrane  from  the  tongue  to  the  jaw,  and  the  insertion  of  the  Geniohyoglossi  first 
divided  with  a  pair  of  curved  blunt  scissors.  The  Palatoglossi  are  also  divided.  The  tongue 
can  now  be  pulled  well  out  of  the  mouth.  The  base  of  the  tongue  is  cut  through  by  a  series  of 
short  snips,  each  bleeding  vessel  being  dealt  with  as  soon  as  divided,  until  the  situation  of  the 
ranine  artery  is  reached.  The  remaining  undivided  portion  of  tissue  is  to  be  seized  with  a  pair  of 
Wells'_  forceps,  the  tongue  removed,  and  the  vessel  secured.  In  the  event  of  the  ranine  arterv 
being  accidentally  injured  early  in  the  operation,  hemorrhage  can  be  at  once  controlled  by 
passing  two  fingers  over  the  dorsum  of  the  tongue  as  far  as  the  epiglottis  and  dragging  the  root  of 
the  tongue  forcibly  forward. 

In  cases  where  the  disease  is  confined  to  one  side  of  the  anterior  portion  of  the  tongue  this 
operation  may  be  modified  by  splitting  the  tongue  down  tb^  centre  and  removing  only  the  affected 
half.  If  the  posterior  portion  of  the  tongue  is  attacked  by  cancer  the  entire  tongue  must  be 
removed,  even  if  but  one  side  of  the  organ  is  apparently  involved.  The  exchange  of  lymph 
between  the  halves  of  the  posterior  portion  of  the  tongue  makes  it  certain  that  the  opposite  half 
becomes  involved  soon  after  the  origin  of  the  disease.  Whatever  operation  is  performed  for 
cancer  of  the  tongue,  the  lymph  nodes  must  be  removed  from  both  sides  of  the  neck.  This  is  to 
be  done,  even  if  but  one  side  of  the  tongue  is  removed. 

Finally,  where  both  sides  of  the  floor  of  the  mouth  are  involved  in  the  disease,  or  where  very 
free  access  is  required  on  account  of  the  extension  backward  of  the  disease  to  the  pillars  of  the 
fauces  and  the  tonsil,  or  where  the  mandible  is  involved,  the  operation  recommended  by  Syme 
must  be  performed.  This  is  done  by  an  incision  through  the  central  line  of  the  lip,  across  (he 
chin,  and  down  as  far  as  the  hyoid  bone.  The  mandible  is  sawed  through  at  the  symphysis,  and 
the  two  halves  of  the  bone  forcibly  separated  from  each  other.  The  mucous  membrane  is  sepa- 
rated from  the  bone,  the  Geniohyoglossi  detached  from  the  bone,  and  the  Hyoglossi  divided. 
The  tongue  is  then  drawn  forward  and  removed  close  to  its  attachment  to  the  hyoid  bone.  Ad- 
jacent lymph  nodes  can  be  removed,  and  if  the  bone  is  implicated  in  the  disease,  it  can  also'  be 
removed  by  freeing  it  from  the  soft  parts  externally  and  internally,  and  making  a  second  section 
with  the  saw  beyond  the  diseased  part. 


THE  SALIVARY  GLANDS  (Fig.  95S) 

The  principal  salivary  glands  communicating  with  the  mouth,  and  pouring 
their  secretion  into  its  cavity,  are  the  parotid,  submaxillary,  and  sublingual. 

The  Parotid  Gland  (glcndida  parotis)  is  the  largest  of  the  three  salivary  glands, 
varying  in  weight  from  half  an  ounce  to  an  ounce.  It  lies  upon  the  side  of  the  face, 
immediately  below  and  in  front  of  the  external  ear.  The  main  portion  of  the  gland 
is  superficial,  somewhat  flat  and  quadrilateral  in  form,  and  is  placed  between 
the  ramus  of  the  mandible  in  front  and  the  mastoid  process  and  Sternomastoid 
muscle  behind,  overlapping,  however,  botli  boiuidaries.  Above,  it  is  limited  by 
the  zygoma;  beloiv,  it  extends  to  about  the  level  of  a  line  joining  the  tip  of  the  mas- 


1224 


THE  ORGANS  OF  DIGESTION 


toid  process  to  the  angle  of  the  mandible.  The  remainder  of  the  gland  is  wedge- 
shaped,  and  extends  deeply  inward  toward  the  pharyngeal  wall. 

The  gland  is  enclosed  within  a  capsule  continuous  with  the  deep  cervical  fascia; 
the  layer  covering  the  outer  surface  is  dense  and  closely  adherent  to  the  gland; 
a  portion  of  the  fascia,  attached  to  the  styloid  process  and  the  angle  of  the  mandible, 
is  thickened  to  form  the  stylomandibular  ligament  which  intervenes  between  the 
parotid  and  submaxillary  glands. 

The  anterior  surface  of  the  gland  is  moulded  on  the  posterior  border  of  the  ramus 
of  the  mandible  with  the  attached  Internal  pterygoid  and  Masseter  muscles,  and 
advances  forward  between  the  two  Pterygoid  muscles  and  overlaps  the  Masseter. 
A  part  of  the  overlapping  portion,  immediately  below  the  zygoma,  is  usually 
detached,  and  is  named  the  socia  parotidis  {gl.  paroiis  accessoria). 

The  outer  or  superficial  surface,  slightly  lobulated,  is  covered  by  the  integument, 
the  superficial  fascia  containing  the  facial  branches  of  the  great  auricular  nerve 
and  some  small  lymph  nodes,  and  the  fascia  which  forms  the  capsule  of  the  gland. 


Pig.  958. — The  salivary  glands.     (Note  that  the  deep  process  of  the  submaxillary  gland  lies  upon  the  deep  surface 

of  the  Mylohyoid.) 


The  inner  or  deep  surface  extends  inward  by  means  of  two  processes,  one  of 
which  lies  on  the  styloid  process  and  the  styloid  group  of  muscles  and  projects 
under  the  mastoid  process  and  Sternomastoid  muscle;  the  other  is  situated  in 
front  of  the  styloid  process  and  passes  into  the  posterior  part  of  the  glenoid  fossa 
behind  the  temporomandibular  joint.  The  deep  surface  is  in  contact  with  the 
internal  and  external  carotid  arteries,  the  internal  jugular  vein,  and  the  vagus 
and  glassopharyngeal  nerves. 

The  anterior  harder  lies  on  the  superficial  surface  of  the  Masseter;  the  j>osterior 
abuts  on  the  external  auditory  canal  and  the  mastoid  process,  and  overlaps 


THE  HA  LIVA  R  Y  GLA NDS  1 225 

the  anterior  edge  of  the  Sternomastoid.  The  superior  border  is  in  contact  with 
the  zygomatic  arch,  and  the  inferior  overlaps  the  posterior  belly  of  the  Digastric. 
The  inner  border  at  the  junction  of  the  anterior  and  inner  surfaces  is  in  relation 
with  the  styloid  process  and  styloid  muscles,  and  is  separated  from  the  pharyngeal 
wall  by  some  loose  connective  tissue. 

Structures  within  the  Gland. — The  external  carotid  arteri/  lies  at  first  in  contact 
with  the  deep  surface,  and  then  in  the  substance  of  the  gland.  The  artery  gives 
off  its  posterior  auricular  branch  which  emerges  from  the  gland  behind;  it  then 
divides  into  its  terminal  branches,  the  internal  maxillary  and  superficial  temporal; 
the  former  runs  inward  behind  the  neck  of  the  mandible;  the  latter  runs  upward 
across  the  zygoma  and  gives  off  its  transverse  facial  branch  which  emerges  from 
the  front  of  the  gland.  Superficial  to  the  arteries  are  the  temporal  and  internal 
maxillary  veins,  uniting  to  form  the  temporomaxillary  vein;  in  the  lower  part  of 
the  gland  this  vein  divides  into  anterior  and  posterior  divisions.  The  anterior 
division  emerges  from  the  gland  to  join  the  facial  vein;  the  posterior  unites  in  the 
gland  with  the  posterior  auricular  vein  to  form  the  external  jugular  vein  (Fig.  495). 
On  a  still  more  superficial  plane  is  the  facial  nerve,  the  branches  of  which  emerge  at 
the  upper  and  anterior  borders  of  the  gland.  Branches  of  the  great  auricular 
nerve  pierce  the  gland  to  join  the  facial,  and  the  auriculotemporal  branch  of  the 
inferior  maxillary  nerve  emerges  from  the  upper  part  of  the  gland. 

Lymph  nodes,  known  as  the  parotid  nodes,  are  in  and  about  the  parotid  gland, 
some  Ijeing  embedded  in  the  outer  surface  of  the  parotid  fascia,  others  being  in 
the  inner  surface  of  the  fascia,  others  in  the  gland  itself,  particularly  along  the 
temporomaxillary  vein  and  external  carotid  artery  (see  p.  775). 

The  Duct  of  the  Parotid  Gland,  or  Stenson's  Duct  (ductus  jmrotideus  [Ste7207iis]) 
(Fig.  958),  is  about  two  inches  and  a  half  (5  to  6  cm.)  in  length.  It  commences  by 
numerous  branches  from  the  anterior  part  of  the  gland,  crosses  the  Masseter 
muscle,  and  at  its  anterior  border  turns  inward  nearly  at  a  right  angle  and  passes 
into  the  substance  of  the  Buccinator  muscle,  which  it  pierces;  it  then  runs  for  a 
short  distance  obliquely  forward  between  the  Buccinator  muscle,  and  the  mucous 
membrane  of  the  mouth,  and  opens  upon  the  inner  surface  of  the  cheek  by  a  small 
orifice,  opposite  the  second  upper  molar  tooth  (Fig.  936).  While  crossing  the 
Masseter  it  receives  the  duct  of  the  socia  parotidis.  In  this  position  it  has  the 
transverse  facial  artery  above  it  and  some  branches  of  the  facial  nerve  below  it. 

The  parotid  duct  is  dense,  it  is  of  considerable  thickness,  and  its  canal  is  about 
the  size  of  a  crowquill;  but  at  its  orifice  on  the  inner  aspect  of  the  cheek  its  lumen 
is  greatly  reduced  in  size.  The  duct  corresponds  to  the  middle  third  of  a 
line  drawn  across  the  face  from  the  lower  margin  of  the  external  auditory  meatus 
to  midway  between  the  red  margin  of  the  upper  lip  and  the  columella  of  the  nose. 

Vessels  and  Nerves. — The  arteries  supplying  the  parotid  gland  are  derived  from  the  ex- 
ternal carotid,  and  from  the  branches  given  oflF  by  that  vessel  in  or  near  its  substance.  The 
veins  empty  into  the  external  jugular  thi-ough  some  of  its  tributaries.  The  l3nmphatics  terminate 
in  the  superficial  cervical  and  the  deep  cervical  nodes,  passing  in  their  course  through  two  or 
three  lymph  nodes  placed  on  the  surface  and  in  the  substance  of  the  parotid.  The  nerves 
are  derived  from  the  plexus  of  the  sympathetic  on  the  external  carotid  artery,  the  nervus  inter- 
medius,  the  auriculotemporal,  ami  the  great  auricular  nerves,  ll  is  probable  that  the  branch 
from  the  auriculotemporal  nerve  is  ilcri\ed  from  the  glossopharyngeal  through  the  otic  gan- 
glion. At  all  events,  in  some  of  the  lower  animals  this  has  been  proved  experimentally  to  be 
the  case. 

The  Submaxillary  Gland  (glandula  submaxillar  is)  (Fig.  958)  is  irregular  in 
form  and  weighs  about  two  drams  (eight  to  ten  grams).  A  considerable  part 
of  it  is  situated  in  the  submaxillary  triangle,  reaching  forward  to  the  anterior 
belly  of  the  Digastric  and  backward  to  the  stylohyoid  ligament  which  intervenes 


1226  THE  ORGANS  OF  DIGESTION 

between  it  and  the  parotid  gland.  Above,  it  extends  under  cover  of  the  body 
of  the  mandible ;  heloic,  it  usually  overlaps  the  intermediate  tendon  of  the  Digastric 
and  the  insertion  of  the  Stylohyoid,  while  from  its  deep  surface  a  tongue-like 
deep  process  extends  forward  and  inward  above  the  Mylohyoid  muscle. 

The  deep  surface  is  in  relation  with  the  Mylohyoid,  Hyoglossus,  Styloglossus, 
Stylohyoid,  and  posterior  belly  of  the  Digastric  muscles;  in  contact  with  it  are  the 
mylohyoid  nerve  and  the  mylohyoid  and  submental  vessels. 

The  facial  artery  is  embedded  in  a  groove  in  the  posterior  border  of  the 
gland. 

The  deep  process  of  the  gland  extends  forward  and  inward  between  the  Mylo- 
hyoid below  and  externally,  and  the  Hyoglossus  and  Styloglossus  internally; 
above  it  is  the  lingual  nerve;  below  it,  the  hypoglossal  nerve  and  ranine  vein. 

The  duct  of  the  submajcillary  gland,  or  Wharton's  duct  (ductus  sitbmaxiUaris  [U'hartoni]),  is 
about  two  inches  (5  cm.)  in  length,  and  its  wall  is  much  thinner  than  that  of  the  parotid  duct.  It 
begins  by  numerous  branches  from  the  deep  portion  of  the  gland  which  lies  on  the  upper  surface 
of  the  Mylohyoid  muscle,  and  runs  forward  and  inward  between  the  Mylohyoid  and  the  Hyoglos- 
sus and  Geniohyoglossus  muscles,  then  between  the  sublingual  gland  and  the  Geniohyoglossus 
muscle,  and  opens  by  a  narrow  orifice  on  the  summit  of  a  small  papilla  [caruncula  sidilingvalu) 
at  the  side  of  the  frenum  linguae.  On  the  Hyoglossus  muscle  it  lies  between  the  lingual  and 
hypoglossal  nerves,  but  at  the  anterior  border  of  the  muscle  it  is  crossed  by  the  lingual  nerve. 

Vessels  and  Nerves. — The  arteries  supplying  the  submaxillary  glands  are  branches  of  the 
facial  and  lingual.  Its  veins  follow  the  course  of  the  arteries.  The  lymphatics  drain  into  the 
submaxillary  lymph  nodes.  The  nerves  are  derived  from  the  submaxillary  ganglion,  through 
which  it  receives  filaments  from  the  chorda  tympani  and  from  the  lingual  branch  of  the  inferior 
maxillary,  sometimes  from  the  mylohyoid  branch  of  the  inferior  dental  and  from  the  S3mipa- 
1:hetic. 

The  Sublingual  Gland  (glandida  sublingiuilis)  (Fig.  958)  is  the  smallest  of  the 
salivary  glands.  It  is  situated  beneath  the  mucous  membrane  of  the  floor  of 
the  mouth,  at  the  side  of  the  frenum  linguae,  in  contact  with  the  inner  surface 
of  the  mandible,  close  to  the  symphysis.  It  is  narrow,  flattened,  in  shape  some- 
what like  an  almond,  and  weighs  about  a  dram.  It  is  in  relation,  above,  with  the 
mucous  membrane;  beloiv,  with  the  Mylohyoid  muscle;  in  front,  with  the  mandible 
and  its  fellow  of  the  opposite  side;  behind,  with  thd  deep  part  of  the  submaxillary 
gland;  and  internally,  with  the  Geniohyoglossus,  from  which  it  is  separated  by 
the  lingual  nerve  and  submaxillary  duct.  Its  excretory  ducts  or  ducts  of  Rivinus 
{ductus  sublingualis  minores)  are  from  eight  to  twenty  in  number;  some  join  the 
submaxillary  duct,  others  open  separately  into  the  mouth,  on  the  elevated  crest 
of  mucous  membrane  {plica  sublingualis)  caused  by  the  projection  of  the  gland 
on  either  side  of  the  frenum  linguse.  One  or  more  join  to  form  a  tube  which  opens 
into  the  submaxillary  duct;  this  is  called  the  duct  of  Bartholin  {ductus  sublingualis 
major). 

Vessels  and  Nerves. — The  sublingual  gland  is  supplied  with  blood  from  the  sublingual  and 
submental  arteries.     Its  nerves  are  derived  from  the  lingual. 

Structure  of  Salivary  Glands  (Fig.  959). — The  salivary  glands  are  compound  tubulorace- 
mose  or  racemose  glands,  surrounded  by  a  capsule  of  white  fibrous  connective  tissue  that  divides 
the  gland  into  numerous  lobes  and  lobules.  The  tissue  between  the  lobules  supports  blood- 
vessels, nerves,  lymphatics,  and  ducts.  Each  lobule  consists  of  the  ramifications  of  a  single 
duct,  dividing  frequently  like  the  branches  of  a  tree,  the  branches  terminating  in  either  rounded 
or  tubular  ends,  the  acini  or  alveoli,  around  which  the  capillaries  are  distributed.  Each  alveolus 
or  acinus  consists  of  a  single  layer  of  columnar  or  pyramidal  epithelial  cells  resting  upon  a  6a.se- 
ment  membrane,  further  supported  by  the  fibroelastic  fiinira  propria,  in  which  the  capillaries  and 
nerves  are  found.  Within  the  lobide  are  found  intralobular  ducts  that  collect  the  secretion 
from  the  alveoli  and  empty  it  into  the  interlobular  ducts  between  the  lobules.  The  latter  join, 
to  ultimately  form  the  excretory  duct  of  the  gland. 

The  main  or  excretory  duct  of  each  gland  consists  of  mucous,  muscle,  and  fibrous  coats. 
The  mucous  coat  is  composed  of  either  simple  columnar  or  stratified  columnar  epithelial  cells 


THE  FiALIVARY  GLANDS 


1227 


that  rest  upon  a  basement  membrane,  and  fibroelastic  tunica  [iropria.  Tlie  muscle  coat 
consists  of  circularly  arrancred  smooth  muscle  tissue.  The  fibrous  coat  consists  of  fibrmlaslic 
tissue  and  serves  to  support  the  other  coats. 

The  salivary  glands  are  mucous,  serous,  and  mixed.  The  mucous  glands  secrete  a  thick 
viscid  fluid  and  the  cells  of  the  acini  stain  lightly.  The  alveoli  arc  tubular  in  form  and  the  cells 
large  and  of  a  columnar  shape,  cloudy  to  transparent,  and  may  even  he  striated  in  appearance. 
At  intervals  peculiar,  darkly  staining  crescent-shaped  cells  or  cell  groups  arc  seen  lielwccn  the 
above  epithelium  and  the  basement  membrane;  these  are  the  demilunes  of  Heidenhain  or 
crescents  of  Gianuzzi  (Fig.  959),  by  some  regarded  as  mucous  cells  in  the  resting  stage,  and  by 
others  as  distinctly  separate  cells.  These  glands  are  the  small  unnamed  glands  of  lips,  cheek, 
pharynx,  cesophagus,  and  tongue  (especially  the  glands  of  Nuhn  and  Blandin). 

Serous  glands  are  those  that  secrete  a  thin,  watery  fluid,  anrl  the  cells  of  the  acini  stain  darkly. 
The  acini  arc  grape-like  and  the  cells  are  somewhat  pyramidal  in  form,  smaller  than  mucous 
cells,  and  possess  richly  granular  protoplasm.  These  glands  are  the  parotid  and  many  small 
unnamed  glands  in  the  tongue  and  lips. 

Mixed  glands  are  those  in  which  some  of  the  alveoli  are  tubular  (mucous)  and  others  grape- 
like (serous),  representing  both  of  the  above  varieties  in  one  capsule.  Here  belong  the  sub- 
lingual and  submaxillary  glands. 

The  arteries  enter  the  capsule  and  divide  into  branches  that  enter  the  interlobular  tissues; 
from  these  vessels  branches  enter  the  lobules  and  form  capillary  plexuses  around  the  alveoli  in 
close  proximity  to  the  basement  membrane.  The  veins  return  the  blood  in  vessels  parallel  to 
the  arteries. 

The  nerves  enter  with  the  vessels  and  ultimately  form  plexuses  in  the  interlobular  and  intra- 
lobular tissue,  the  latter  sending  filaments  that  end  in  relation  to  the  epithelial  cells  and  blood- 
vessels. In  the  submaxillary  gland  small  ganglia  are  found  in  connection  with  the  interlobular 
nerve  plexus. 

Development  of  the  Salivary  Glands. — The  salivary  glands  arise  as  diverticula  from  the 
epithelial  lining  of  the  mouth,  and  their  rudiments  appear  in  the  following  order — viz.,  the 
parotid  during  the  fourth  week,  the  submaxillary  in  the  sixth  week,  and  the  sublingual  during 
the  ninth  week  (Hammar). 


( lescent  of  Gianazsi. 


Urary  duct. 


-A  highly  magnified  section  of  the  submaxillary  gland  of  the  dog,  stained  with  carmine.     (Koliiker.) 


Surface  Form. — The  orifice  of  the  mouth  is  bounded  by  the  lips,  two  thick,  fleshy  folds 
covered  externally  by  integument  and  internally  by  mucous  membrane,  and  consisting  of  muscles, 
vessels,  nerves,  areolar  tissue,  and  numerous  small  glands.  The  size  of  the  orifice  of  the  mouth 
varies  considerably  in  different  individuals,  but  seems  to  bear  a  close  relation  to  the  size  and 
prominence  of  the  teeth.  Its  corners  correspond  pretty  accurately  to  the  outer  border  of  the 
canine  teeth.  In  the  Ethiopian  tribes  the  front  teeth  are  large  and  inclined  forward,  the  mouth 
is  large;  and  this,  combined  with  the  thick  and  everted  lips  which  appear  to  be  associated  with 
prominent  teeth,  gives  to  the  negro's  face  much  of  the  peculiarity  by  which  it  is  characterized. 
The  smaller  teeth  and  the  slighter  prominence  of  the  alveolar  arch  of  the  more  highly  civilized 
races  render  the  orifice  of  the  mouth  much  smaller,  and  thus  a  small  mouth  is  an  indication 
of  intelligence,  and  is  regarded  as  an  evidence  of  the  higher  civilization  of  the  individual. 

Upon  looking  into  the  mouth,  the  first  thing  we  may  note  is  the  tongue,  the  upper  surface  of 
which  will  be  seen  occupying  the  floor  of  the  cavity.  This  surface  is  convex,  and  is  marked 
along  the  middle  line  by  a  raph^  which  divides  it  into  two  symmetrical  portions.  The  anterior 
two-thirds  is  rough  and  studded  with  papillae;  the  posterior  third,  smooth  and  tuberculated, 
contains  numerous  lymphoid  structures  which  proiect  from  the  surface.     Upon  raising  the 


1228  THE  ORGANS  OF  DIGESTION 

tongue  the  mucous  membrane  which  invests  the  upper  surface  may  be  traced  covering  the  sides 
of  the  under  surface,  and  then  reflected  over  the  luoor  of  the  mouth  on  to  the  inner  surface  of 
the  mandible,  a  part  of  which  it  covers.  As  it  passes  over  the  borders  of  the  tongue  it  changes 
its  character,  becoming  thin  and  smooth  and  losing  the  papillae  which  are  to  be  seen  on  the 
upper  surface.  In  the  middle  line  the  mucous  membrane  on  the  under  surface  of  the  tip  of  the 
tongue  forms  a  distinct  fold,  the  freiium.  linguw,  by  which  this  organ  is  connected  to  the  sym- 
physis of  the  mandible.  Occasionally  it  is  found  that  this  frenum  is  rather  shorter  than  natural, 
and,  acting  as  a  bridle,  prevents  the  complete  protrusion  of  the  tongue.  When  this  condition 
exists  and  an  attempt  is  made  to  protrude  the  organ,  the  tip  will  be  seen  to  remain  buried  in  th^ 
floor  of  the  mouth,  and  the  dorsum  of  the  tongue  is  rendered  very  convex,  and  more  or  lesp 
extruded  from  the  mouth;  at  the  same  time  a  deep  furrow  will  be  noticed  to  appear  in  the  middle 
line  of  the  anterior  part  of  the  dorsum.  Sometimes,  a  little  external  to  the  frenum,  the  ranine 
vein  may  be  seen  immediately  beneath  the  mucous  membrane.  The  corresponding  artery, 
being  more  deeply  placed,  does  not  come  into  view,  nor  can  its  pulsation  be  felt  with  the  fin- 
ger. On  either  side  of  the  frenum,  in  the  floor  of  the  mouth,  is  an  elevation  or  ridge,  pro- 
duced by  the  projection  of  the  sublingual  gland,  which  hes  immediately  beneath  the  mucous 
membrane.  And  close  to  the  attachment  of  the  frenum  to  the  tip  of  the  tongue  may  be  seen 
on  either  side  the  slit-like  orifices  oi  the  submaxillary  duds,  into  which  a  fine  probe  may  be  passed 
without  much  difficulty.  By  everting  the  lips  the  smooth  mucous  membrane  lining  them  may 
be  examined,  and  may  be  traced  from  them  on  to  the  outer  surface  of  the  alveolar  arch.  In  the 
middle  line,  both  of  the  upper  and  lower  lip,  a  small  fold  of  mucous  membrane  passes  from  the 
lip  to  the  bone,  constituting  the  frena ;  these  are  not  so  large  as  the  frenum  linguae.  By  pulling 
outward  the  angle  of  the  mouth,  the  mucous  membrane  lining  the  cheeks  can  be  seen,  and  on  it 
may  be  perceived  a  little  papilla  which  marks  the  position  of  the  orifice  of  the  parotid  duct.  The 
exact  position  of  the  orifice  of  the  duct  will  be  found  to  be  opposite  the  second  upper  molar 
tooth.  The  introduction  of  a  probe  into  this  duct  is  attended  with  considerable  difficulty. 
The  teeth  are  the  next  objects  which  claim  our  attention  upon  looking  into  the  mouth.  These, 
are,  as  stated  above,  ten  ia  either  jaw  in  the  temporary  set,  and  sixteen  in  the  permanent  set. 
The  gums,  in  which  they  are  implanted,  are  dense,  firm,  and  vascular. 

At  the  back  of  the  mouth  is  seen  the  isthmus  of  the  fauces,  or,  as  it  is  popularly  called,  "the 
throat;"  this  is  the  space  between  the  pillars  of  the  fauces  on  either  side,  and  is  the  means  by 
which  the  mouth  communicates  with  the  pharynx.  Above,  it  is  bounded  by  the  soft  palate, 
the  anterior  surface  of  which  is  concave  and  covered  with  mucous  membrane,  which  is  con- 
tinuous with  that  lining  the  roof  of  the  mouth.  Projecting  downward  from  the  middle  of  its 
lower  border  is  a  conical-shaped  projection,  the  uvula.  On  either  side  of  the  isthmus  of  the 
fauces  are  the  anterior  and  posterior  pillars,  formed  by  the  Palatoglossus  and  Palatopharyngeus 
muscles,  respectively,  covered  over  by  mucous  membrane.  Between  the  two  pillars  on  either 
side  is  situated  the  tonsil. 

When  the  mouth  is  wide  open  a  prominent  tense  fold  of  mucous  membrane  may  be  seen  and 
felt,  extending  upward  and  backward  from  the  position  of  the  fang  of  the  last  molar  tooth  to 
the  posterior  part  of  the  hard  palate.  This  is  caused  by  the  pterygoma.xillanj  ligament,  which 
is  attached  by  one  extremity  to  the  apex  of  the  internal  pterygoid  plate,  and  by  the  other  to  the 
posterior  extremity  of  the  mylohyoid  ridge  of  the  lower  jaw.  It  connects  the  Buccinator  with 
the  Superior  constrictor  of  the  pharynx.  The  fang  of  the  last  molar  tooth  indicates  the  position 
of  the  lingual  nerve  where  it  is  easily  accessible,  and  can  with  readiness  be  divided  in  cases 
of  cancer  of  the  tongue  (see  p.  993).  On  the  inner  side  of  the  last  molar  tooth  we  can  feel 
the  hamular  process  of  the  internal  pterygoid  plate  of  the  sphenoid  bone,  around  which  the 
tendon  of  the  Tensor  palati  plays.  The  exact  position  of  this  process  is  of  importance  in  per- 
forming the  operation  of  staphylorrhaphy.  About  one-third  of  an  inch  (8  mm.)  in  front  of  the 
hamular  process,  and  the  same  distance  directly  inward  from  the  last  molar  tooth,  is  the  situation 
of  the  opening  of  the  posterior  palatine  canal,  through  which  emerges  the  posterior  or  descend- 
ing palatine  branch  of  the  internal  maxillary  artery  and  one  of  the  descending  palatine  nerves 
from  Meckel's  ganglion.  The  exact  position  of  the  opening  on  the  subject  may  be  ascertained 
by  driving  a  needle  through  the  tissues  of  the  palate  in  this  situation,  when  it  will  be  at  once 
felt  to  enter  the  canal.  The  artery  emerging  from  the  opening  runs  forward  in  a  groove  in 
the  bone  just  internal  to  the  alveolar  border  of  the  hard  palate,  and  may  be  wounded  in  the 
operation  for  the  cure  of  cleft  palate.  Under  these  circumstances  the  palatine  canal  may  require 
plugging.  By  introducing  the  finger  into  the  mouth  the  anterior  border  of  the  coronoid  process 
of  the  mandible  can  be  felt,  and  it  is  especially  prominent  when  the  jaw  is  dislocated.  By  throw- 
ing the  head  well  back  a  considerable  portion  of  the  posterior  wall  of  the  pharynx  may  be  seen 
through  the  isthmus  faucium,  and  on  introducing  the  finger  the  anterior  surface  of  the  bodies 
of  the  upper  cervical  vertebrae  may  be  felt  iminediately  beneath  the  thin  muscular  stratum  form- 
ing the  wall  of  the  pharynx.  The  finger  can  be  hooked  around  the  posterior  border  of  the  soft 
palate,  and  by  turning  it  forward  the  posterior  nares,  separated  by  the  septum,  can  be  felt,  or 
the  presence  of  any  adenoid  or  other  growths  in  the  nasopharynx  can  be  ascertained. 


THE  PHARYNX  1229 

Applied  Anatomy. — The  duct  of  a  salivary  gland  may  be  blocked  by  a  ciilculii.i,  and  the 
condition  is  often  productive  of  severe  pain. 

A  wound  of  the  parotid  duct  or  of  the  parotid  gland  may  be  followed  liy  a  .wlitary  fistula. 

The  parotid  recess  is  completely  linefl  Ijy  fascia,  except  above.  "  Between  the  anterior  edge 
of  the  styloid  process  and  the  posterior  border  of  the  External  pterygoid  muscle  there  is  a  gap 
in  the  fascia,  through  which  the  parotid  space  communicates  with  the  connective  tissue  about 
the  pharynx." 

This  explains  why  there  is  frequently  swelling  of  the  parotid  region  in  postpharyngeal  abscess. 
A  'parotid  abscess  rarely  bm'sts  through  the  skin;  it  may  pass  into  the  temporal  fossa,  may  enter 
the  zygomatic  fossa,  may  advance  toward  the  mouth,  pharynx,  or  neck.  Because  of  the  situa- 
tion of  the  gland,  a  parotid  abscess  may  cause  inflammation  of  the  temporomandibular  joint  or 
periostitis  of  the  bone  about  the  canal,  and  may  even  burst  into  the  external  auditory  canal 
(Treves). 

The  facial  nerve  passes  through  the  gland,  and  inflammation  or  tuberculosis  of  the  gland 
may  cause  facial  palsy.  Some  enlargements  of  the  parotid  region  are  due  to  inflammation  of 
the  parotid  lymph  nodes,  and  these  nodes  may  become  tuberculous. 

Mumps  is  characterized  by  acute  inflammation  of  the  parotid  gland. 

Various  tumors  occur  in  the  parotid  (fibroma,  sarcoma,  carcinoma,  enchondroma,  etc.). 
Most  parotid  tumors  contain  more  or  less  cartilage.  Complete  extirpation  of  the  parotid  gland 
surgically  is  certainly  extremely  difficult,  and  Treves  and  others  maintain  that  it  is  impossible. 


THE  PHARYNX  (Figs.  964,  965). 

The  pharynx  is  that  part  of  the  ahmentary  canal  which  is  placed  behind,  and 
communicates  with  the  nose,  mouth,  and  larynx.  It  is  a  musculomembranous 
tube,  somewhat  conical  in  form,  with  the  base  upward  and  the  apex  downward, 
extending  from  the  under  surface  of  the  skull  to  the  level  of  the  cricoid  cartilage 
in  front  and  that  of  the  sixth  cervical  vertebra  behind. 

The  cavity  of  the  pharynx  {camim  -pharynqis)  is  about  five  inches  in  length,  and 
broader  in  the  transverse  than  in  the  antero-posterior  diameter.  Its  greatest 
breadth  is  immediately  below  the  base  of  the  skull,  where  it  projects  on  either  side, 
behind  the  orifice  of  the  Eustachian  tube,  as  a  recess  termed  the  fossa  of  Rosen- 
miiller;  its  narrowest  part  is  at  its  termination  in  the  oesophagus.  It  is  limited 
above  by  the  body  of  the  sphenoid  as  well  as  by  the  basilar  process  of  the  occipital; 
helow,  it  is  continuous  with  the  oesophagus;  posteriorly,  it  is  connected  by  loose  are- 
olar tissue  with  the  cervical  portion  of  the  vertebral  column  and  the  Longus  colli 
and  Rectus  capitis  anticus  muscles ;  this  areolar  tissue  is  contained  in  what  is  called 
the  retropharyngeal  space;  anteriorly,  it  is  incomplete,  and  is  attached  in  succession 
to  the  Eustachian  tube,  the  internal  pterygoid  plate,  the  pterygomandibular  liga- 
ment, the  posterior  termination  of  the  mylohyoid  ridge  of  the  mandible,  the 
mucous  membrane  of  the  mouth,  the  base  of  the  tongue,  hyoid  bone,  the  thy- 
roid and  cricoid  cartilages;  laterally,  it  is  connected  to  the  styloid  processes  and 
their  muscles,  and  is  in  contact  with  the  common  and  internal  carotid  arteries, 
the  internal  jugular  veins,  and  the  glossopharyngeal,  vagus,  hypoglossal,  and 
sympathetic  nerves,  and  above  with  a  small  part  of  the  Internal  pterygoid 
muscles.  Seven  openings  communicate  with  it — viz.,  the  two  posterior  nares, 
the  two  Eustachian  tubes,  the  mouth,  larynx,  and  oesophagus.  The  cavity  of 
the  pharynx  may  be  subdivided  from  above  downward  into  three  parts — nasal, 
oral,  and  laryngeal. 

The  Nasal  Part,  or  Nasopharynx  {pars  nasalis  pharyngis)  (Fig.  964),  lies  behind 
the  nose  and  above  the  level  of  the  soft  palate;  it  differs  from  the  two  lower  parts 
of  the  tube  in  that  its  cavity  always  remains  patent.  In  front  it  communicates 
through  the  posterior  nares  (ehoanae)  (Fig.  965)  with  the  nasal  fossa.  On  its 
lateral  wall  is  the  pharyngeal  orifice  of  the  Eustachian  tube  {p.stium  pharyngeum 
tubae  auditivae)  (Figs.  960  and  961),  somewhat  triangular  in  shape  and  bounded 
behind  by  a  firm  prominence,  the  Eustachian  cushion  {torus  tubarius),  caused  by 


1230 


THE  ORGANS  OF  DIGESTION 


the  inner  extremity  of  the  cartilage  of  the  tube  which  elevates  the  mucous  mem- 
brane (Fig.  961).  At  the  pharyngeal  end  of  the  tube  is  a  collection  of  lymphoid 
tissue  called  by  Gerlach  the  tubal  tonsil.  The  orifice  is  about  one-third  to  one-half 
inch  behind  the  inferior  turbinated  bone.  A  vertical  fold  of  mucous  membrane,  the 
salpingopharsmgeal  fold  {-plica  salpingopharyngea)  (Fig.  961),  stretches  from  the 
lower  part  of  the  cushion  to  the  pharynx;  it  contains  the  Salpingopharyngeus 
muscle.  A  second  and  smaller  fold,  the  salpingopalatine  fold  (plica  salpingo palatina) 
(Fig.  949) ,  stretches  from  the  upper  part  of  the  cushion  to  the  palate.  Behind  the 
orifice  of  the  Eustachian  tube  is  a  deep  recess,  the  lateral  recess  or  fossa  of  Rosenmiil- 
ler  {recessus  pJiaryngeus)  (Fig.  961),  which  represents  the  remains  of  the  upper  part 
of  the  second  inner  branchial  cleft.  The  posterior  wall  of  the  nasopharynx  is 
directed  upward  and  forward,  and  it  meets  the  superior  wall  at  an  angle  constituting 
the  vault  of  the  pharynx  (fornix  pharyngis) .  On  the  posterior  wall,  above  the  level 
of  the  orifices  of  the  Eustachian  tubes,  is  a  prominence,  best  marked  in  childhood, 
produced  by  a  mass  of  lymphoid  tissue  which  is  known  as  the  phar3mgeal  tonsil 
(tonsilla  pharyngea)  (Fig.  960).  In  the  pharyngeal  vault,  in  the  middle  line, 
an  irregular  flask-shaped  depression  of  the  mucous  membrane  is  sometimes  seen 
extending  up  as  far  as  the  basilar  process  of  the  occipital  bone.  It  is  known  as 
the  pharyngeal  bursa,  a  possible  vestige  of  the  pharyngeal  tonsil.  The  floor  of  the 
nasopharynx  is  formed  by  the  upper  surface  of  the  sloping  soft  palate;  in  front 
the  floor  is  continuous  with  that  of  the  nasal  cavities,  while  behind  it  ends  at  the 
free  margin  of  the  soft  palate,  which  bounds  the  isthmus  of  the  phar3mx  (isthmus 
pharyngonasalis). 

The  Oral  Part  (pars  oralis  pharyngis)  of  the  pharynx  reaches  from  the  under 
surface  of  the  soft  palate  to  about  the  level  of  the  hyoid  bone.  It  opens  ante- 
riorly, through  the  isthmus  faucium,  into  the  mouth,  while  in  its  lateral  wall, 
between  the  two  pillars  of  the  fauces,  is  the  tonsil. 


SALPINGO- 

NASAL  FOLD 

EUSTACHIAN 

CUSHION 


-Pharyngeal  tonsil  in  an  adult. 
(Escat.) 


GEAL  FOLD 

Fig.  961. — The  posterior  lateral  cavity  of  the  naso- 
pharynx.    (Escat.) 


The  Tonsils  (tonsilla  palatina)  (Figs.  963  and  964)  are  two  lymphoid  bodies 
situated  one  on  each  side  of  the  fauces,  between  the  anterior  and  posterior  pillars 
of  the  soft  palate,  corresponding  in  position  externally  to  the  angle  of  the  mandible. 
They  are  usually  of  an  oval  form  as  viewed  from  their  oral  aspect,  and  vary  con- 
siderably in  size  in  different  individuals.  As  seen  in  horizontal  sections  in  hard- 
ened heads,  the  form  of  each  tonsil  is  rather  that  of  a  Brazil  nut,  with  antero- 
internal,  lateral,  and  posterior  surfaces,  and  an  upjxr  and  a  loiver  pole}     A  recess, 


'  Cf.  George  Fetterolf'a  article:  "The  Anatomy  and  Relations  of  the  Tonsil  i 
can  Journal  of  the  Medical  Sciences,  July,  1912. 


I  the  Hardened  Body, 


THE  PHARYNX  1231 

the  supratonsillar  fossa  {fossa  supmtonsillaris)  may  be  seen,  directed  upward, 
outward,  and  liackward  above  the  tonsil,  the  recess  being  the  remains  of  the 
second  inner  visceral  cleft.  The  space  below  the  tonsil,  between  the  tongue  in 
front  and  the  posterior  pillar  behind,  is  called  the  tonsillar  sinus.  The  tonsil  is 
encased  within  a  thin  fibrous  capsule  over  its  lateral  and  posterior  surfaces.  An 
extension  of  the  tonsillar  capsule,  inward  and  backward  beyond  the  anterior 
pillar  of  the  fauces,  with  its  free  surface  covered  by  mucous  membrane  and  partly 
coA'ering  the  antero-internal  surface  of  the  tonsil  is  called  the  plica  triangularis. 
"Of  its  three  sides  the  anterior  is  attached  apparently  to  the  anterior  pillar,  the 
posterior  runs  downward  and  backward  over  the  tonsil,  and  the  inferior  either  is 
inserted  into  the  side  of  the  tongue,  or,  in  the  case  of  a  small  tonsil'and  a  large 
fossa,  fades  away  in  the  lower  part  of  the  tonsillar  sinus. "^ 

The  fibrous  capsule  covering  the  lateral  and  posterior  surfaces  of  the  tonsil 
lies  in  contact  with  the  aponeurosis  of  the  Superior  constrictor  muscle  of  the 
pharynx;  external  to  this  is  a  mass  of  areolar  tissue  with  the  ascending  palatine 
arterj'  and,  more  laterally,  the  Internal  pterygoid  muscle.  The  internal  carotid 
artery  lies  behind  and  to  the  outer  side  of  the  tonsil,  and  nearly  an  inch  (20  to  25 
mm.)  distant  from  it.  The  Palatoglossus  courses  along  the  anterior  margin, 
while  the  Palatopharyngeus  is  in  contact  with  the  capsule  investing  the  posterior 
surface  of  the  tonsil. 

The  free  or  antero-internal  surface  of  the  tonsil  is  directed  toward  the  cavity 
of  the  oropharynx  and  presents  from  twelve  to  fifteen  orifices,  each  leading  into 
small  recesses  or  crypts  {fossulae  tonsillares) .  From  the  crypts  numerous  follicles 
branch  out  into  the  substance  of  the  tonsil  by  means  of  very  irregular  channels. 
As  indicated  above,  this  surface  of  the  tonsil  is  partially  covered  by  the  plica 
triangularis,  which  may  be  free  or  attached. 

Structure. — The  tonsil  is  covered  externally  by  a  capsule  of  white  fibrous  tissue  that  separates 
it  from  the  siurounding  organs  and  tissues,  and  is  continued  into  the  plica  triangularis.  This 
capsule  sends  in  trabeculae  that  divide  the  organ  into  irregular  compartments.  Within  the 
compartments  is  the  delicate  framework  and  reticulum  in  the  meshes  of  which  are  found  dififuse 
lymphoid  tissue  and  solitary  nodules  or  follicles.  The  internal  svu'face  presents  twelve  to  fifteen 
depressions  or  crypts  that  extend  into  the  organ  in  the  form  of  irregular,  blindly  ending,  tortuous 
channels  or  follicles.  The  internal  sitfface  of  the  tonsils  and  the  crypts  and  follicles  are  lined 
by  stratified  squamous  cells,  exhibiting  in  places  marked  degenerative  changes,  and  in  others 
leukocytes  that  are  passing  through  the  epithelial  layer  to  the  crypts. 

The  arteries  supplying  the  tonsil  are  all  derived  from  branches  of  the  external  carotid.  Accord- 
ing to  the  observations  of  J.  Leslie  Davis,'  they  usually  enter  the  tonsil  at  what  is  commonly 
called  the  hilum,  just  behind  and  about  a  quarter  of  an  inch  from  the  margin  of  the  anterior 
pillar,  about  midway  between  the  upper  and  lower  poles.  Fetterolf^  enumerates:  (1)  an 
anterior  tonsillar  artery,  a  branch  from  the  dorsalis  linguae;  (2)  the  superior  tonsillar  artery,  from 
the  descending  palatine;  (3)  the  posterior  tonsillar  artery,  a  branch  of  the  ascending  pharyngeal, 
and  (4)  three  inferior  tonsillar  arteries,  of  which  one  is  a  branch  of  the  dorsalis  linguae,  while 
the  other  two  are  offshoots  from  the  tonsillar  branches  of  the  facial. 

The  veins  of  the  tonsil  terminate  in  the  tonsillar  plexus  on  the  lateral  and  posterior  surfaces 
of  the  tonsil,  and  the  tonsillar  plexus  joins  the  pharyngeal  plexus  which  communicates  with 
the  pterygoid  plexus  of  the  internal  jugular  or  the  facial  vein.  While  most  of  the  veins  leave 
at  the  hilum,  there  is  usually  a  large  vein  com-sing  downward  along  the  posterior  siu-face  of  the 
tonsil,  to  the  outer  side  of  the  Palatopharyngeus. 

Surrounding  each  follicle  is  a  close  plexus  of  lymphatic  vessels.  From  these  plexuses  the 
lymphatic  vessels  pass  to  the  submaxillary  lymph  nodes  below  the  angle  of  the  mandible.  From 
the  submaxillary  nodes  lymph  passes  to  the  deep  cervical  nodes. 

The  Nerves  of  the  Tonsil. — A  branch  from  the  glossopharyngeal  nerve  by  uniting  with 
branches  from  the  middle  and  posterior  palatine  branches  from  the  sphenopalatine  ganglion 
forms  the  tonsillar  plexus. 

1  G.  Fetterolf,  loc.  cit. 

2  "Tonsillectomy,  Why,  When,  and  How,"  etc.,  Pennsylvania  Medical  .lournal,  November,  1911. 

3  G.  Fetterolf,  loc.  cit. 


1232 


THE  ORGANS  OF  DIGESTION 


Development. — The  tonsils  are  developed  from  the  lower  parts  of  the  second  inner  visceral 
clefts,  immediately  behind  the  anterior  pillars  of  the  fauces.     The  entoderm  wliich  lines  these 


Fig.  962. — Diagrams  of  horizontal  sections  of  left  tonsillar  region,  viewed  from  above,  the  upper  one  showing  the 
attached  form  of  plica  and  the  lower  one  the  free  form:  T,  Tonsil;  C,  capsule;  PT,  pHca  triangularis;  M,  M,  mucous 
membrane;  L,  L,  lacunae;  AF,  anterior  tonsillar  fossa;  SC,  superior  constrictor;  A,  Palato-glossus;  P,  Palato-pharyn- 
geus;  y,  V,  main  veins  of  tonsillar  plexus.      (Fetterolf.) 


Fig.  963. — Actual  shape  of  (left)  tonsil,  with  arterial  supply:  1,  Mesa!  aspect;  2,  postero- lateral  aspect;  E,  lateral 
surface;  B,  posterior  surface;  G,  groove  for  Palato-pharyngeus;  T,  tonsil  tissue;  PT,  plica  triangularis;  C,  capsule; 
A  A,  anterior  tonsillar  artery;  PA,  posterior  tonsillar  artery;  SA,  superior  tonsillar  artery;  I  A,  inferior  tonsillar  arteries. 
iFetterolf.) 


THE  PHARYNX  1233 

clefts  grows  in  the  form  of  a  number  of  solid  burls  into  the  siirrounrling  mesoderm.  These 
buds  become  hollowed  out  by  the  degeneration  and  casting  oH'  of  their  central  cells,  and  by  this 
means  the  tonsillar  crypts  are  formed.  Lymphoid  cells  accumulate  around  the  crypts,  and 
become  grouped  to  form  the  lymphoid  follicles;  the  latter,  however,  are  not  well  defined  until 
after  birth. 

Applied  Anatomy. — ^The  tonsils  can  be  easily  inspected  by  instructing  the  patient  to  throw 
the  head  back  with  mouth  wide  open,  the  tongue  being  depressed  by  a  spatula  or  tongue 
depressor.  The  normal  tonsil  should  not  project  inward  beyond  the  plane  of  the  anterior 
pillar  of  the  fauces.  When  enlarged  they  make  deglutition  and  respiration  troublesome. 
The  deafness  which  so  often  attends  hypertrophy  of  the  tonsil  is  not  due  to  blocking  of  the 
Eustachian  orifice  by  the  tonsil,  but  is  due  to  the  attendant  thickening  of  the  mucous  mem- 
brane lining  the  tube  itself.  The  tonsils  may  be  the  seat  of  acute  Inflammation,  which  may  run 
on  to  suppuration,  reciuiring  evacuation  of  the  pus.  The  incision  into  the  tonsil  should 
always  be  made  from  in  front  backward  and  inward.  Another  form  of  acute  inflammation 
of  the  tonsil  is  follicular  tonsillitis,  due  to  the  lodgment  of  micro-organisms  in  the  tonsillar 
crypts. 

Tonsillectomy  is  the  complete  enucleation  of  the  gland.  In  this  operation,  profuse  bleeding 
may  be  avoided  by  the  use  of  dis.sectors  designed  to  keep  to  the  outer  surface  of  the  capsule 
and  by  the  use  of  the  snare  and  tenaculum.  Successful  methods  are  those  of  Fetterolf  and 
Davis,^  whereby  enucleation  is  complete  without  inflicting  damage  upon  surrounding  structures, 
such  as  the  faucial  pillars,  which,  if  injured,  may  cause  discomfort  and  affect  the  voice,  and  also 
avoiding  injiuy  to  the  ascemting  pharyngeal  artery  or  one  of  the  palatine  arteries  lying  without 
the  capsule  of  the  tonsil. 

The  tonsil  may  be  the  seat  of  malignant  growth,  either  an  epithelioma  or  a  lymphosarcoma. 

The  Laryngeal  Part  of  the  pharynx  {fars  laryugea  fharyngis)  i.s  that  division 
which  lies  behind  the  larynx;  it  is  wide  above  where  it  is  continuous  with  the  oral 
portion,  while  below  at  the  lower  border  of  the  cricoid  cartilage  it  becomes  continu- 
ous with  the  oesophagus.  In  front  it  presents  the  triangular  aperture  of  the  larynx, 
the  base  of  which  is  directed  forward  and  is  formed  by  the  epiglottis,  while  its 
lateral  boundaries  are  constituted  by  the  arytenoepiglottic  folds.  On  either  side 
of  the  laryngeal  orifice  is  a  recess,  termed  the  sinus  pyriformis  (rccessus  pyriformis) 
(Fig.  964);  it  is  bounded  internally  by  the  arytenoepiglottic  fold,  externally  by 
the  thyroid  cartilage  and  thyrohyoid  membrane.  In  the  anterior  part  of  the  sinus 
pyriformis  is  a  fold  (plica  nervi  laryngei),  which  passes  downward  and  inward. 
Extending  outward  from  the  epiglottis  on  each  side  is  a  fold,  the  pharjmgoepiglottic 
fold  {plica  pharyngoepiglottica).  This  ascends  in  the  lateral  wall  of  the  pliaiynx, 
nearly  to  the  posterior  arch  of  the  fauces. 

Structure.  —The  pharynx  i.s  composed  of  mucous,  fibrous,  and  muscular  coats. 

The  mucous  coat  {tunica  mucosa)  is  continuous  with  thai  liiiini;-  ilic  iMislarhian  tubes,  the 
nasal  fo.ssje,  the  mouth,  and  the  larynx.  In  the  nasopharynx  it  is  covered  by  stratified  ciliated 
epithelium;  in  the  buccal  and  laryngeal  portions  the  epithelium  is  of  the  stratified  squamous 
variety.  In  the  tunica  propria  considerable  difl^use  lymphoid  tissue,  pharyngeal  tonsil,  and 
mucous  glands  (ghiudu/ar  plinrtpir/eae)  are  found;  the  latter  are  especially  numerous  at  the  upper 
part  of  the  |iharviix  around  the  orifices  of  the  Eustachian  tubes. 

The  pharyngeal  aponeurosis  or  fibrous  coat  is  situated  between  the  mucous  and  the  muscle 
layers,  and  consists  of  large  bundles  of  white  fibrous  connective  tissue.  It  is  thick  above,  where 
the  muscle  fibres  are  wanting,  and  is  firmly  connected  to  the  periosteum  of  the  basilar  process  of 
the  occipital  and  petrous  portion  of  the  temporal  bones.  As  it  descends  it  diminishes  in  thick- 
ness, and  is  gradually  lost.  It  is  strengthened  posteriorly  by  a  strong  fibrous  band,  which  is 
attached  above  to  the  pharyngeal  spine  on  the  under  surface  of  the  basilar  portion  of  the  occipital 
bone,  and  passes  downward,  forming  a  median  raphe,  which  gives  attachment  to  the  Constrictor 
muscles  of  the  pharynx. 

The  muscular  coat  has  been  already  described  (pp.  .394  to  397). 

The  motor  nerves  are  derived  chiefly  from  the  pharyngeal  ])lexus;  the  Tensor  palati,  however, 
receives  a  special  branch  from  the  otic  ganglion.  The  sensor  filaments  are  derived  from  the 
descending  palatine,  nasopalatine,  and  from  the  glossopharyngeal  nerve. 

'  G.  Fetterolf,  loc.  cit.  ^  J.  Leslie  Davis,  loo.  cit. 


1234 


THE  ORGANS  OF  DIGESTION 


The  Lymphatic  Pharyngeal  Ring. — This  name  was  applied  by  Waldeyer  to  the  lymphatic 

■  structures  gathered  into  a  sort  of  ring  about  the  pharynx.     There  are  foiu-  chief  collections  of 

this  tissue  on  each  side.     The  first  is  known  as  the  lingual  tonsil  (p.  1219);  the  second  as  the 

palatal  tonsil  (p.  1230);  the  third  as  the  pharyngeal  tonsil  (p.  1230);  and  the  fourth  as  the  tubal 

tonsil  (pp.  112S,  1230). 

Development  of  the  Pharjmx  (Figs.  956,  957). — The  pharynx  develops  from  the  cephalic 
portion  of  the  foregut,  flanked  by  the  five  branchial  (visceral)  arches,  with  four  intervening  bran- 
chial clefts  (visceral  pouches).     These  have  become  retrogressively  modified  in  that  they  have 


GENIO- 

HYOGLOSSUS 

MUSCLE 


SOFT    PALATE 
NASOPHARYNX 


ANTERIOR   PALA- 
TINE ARCH 
POSTERIOR  PALA- 

ARCH 
TONSIL 
CAVITY  OF 
PHARYNX 
TONSILLAR 
SINUS 


EPIGLOTTIS 


EPIGLOTTIC 
FOLD 

CUNEIFORM 
CARTILAGE 


Fig.  964. — Sagittal  median  section  of  the  head  and  neck.    The  head  is  thrown  backward  into  complete  extension, 
which  explains  the  relations  between  the.  lower  jaw  and  the  hyoid  bone  as  seen  in  the  figure.     (Luschka.) 


lost  their  respiratory  function  (as  gills),  but  recur  in  the  development  of  each  individual  for  the 
purpose  of  forming  organs  not  entirely  vestigial.  Thus,  the  first  or  most  cephalic  branchial 
arch  assists  in  the  formation  of  the  jaws,  the  malleus,  incus,  sphenomandibular  ligament,  and 
part  of  the  external  ear.  The  second  arch  forms  the  styloid  process,  lesser  cornu  of  hyoid  and 
the  intervening  stylohyoid  ligament,  the  stapes,  a  part  of  the  external  ear,  and  a  part  of  the 
posterior  one-third  of  the  tongue.  From  the  third  arch  are  formed  the  body  and  greater  cornu 
of  the  hyoid  bone,  and  part  of  the  posterior  one-third  of  the  tongue.  The  foiu-th  and  fifth  arches 
share  in  forming  the  thjToid  cartilage.  The  inner  furrows  or  clefts,  lined  by  entoderm,  contribute 
to  the  formation  of  important  structures.  Thus,  the  first  inner  furrow  becomes  the  middle- 
ear  cavity  and  Eustachian  tube,  the  "closing  membrane"  persisting  as  the  tympanic  membrane 


THE  PHARYNX 


1235 


separating  the  inner  from  the  outer  furrow,  whioh  becomes  the  external  auditory  meatus. 
The  second  inner  furrow  becomes  the  lateral  recess  of  the  pharynx,  and  its  entodcrmal  lining 
gives  rise  to  the  tonsil.  From  the  third  inner  furrow  are  developed  the  thymus  and  the 
inferior  parathyroid  gland,  while  the  fourth  gives  rise  to  the  lateral  lobes  of  the  thyroid 
and  the  superior  parathyroid  glands.  The  isthmus  of  the  thyroid  is  derived  by  a  median 
ventral  evagination  of  the  entoderm  arising  between  the  tuberculum  impar  and  the  second 
visceral  bar.  Another  median  ventral  evagination  occiu-s  at  the  level  of  the  fourth  visceral 
arch  to  form  the  respiratory  apparatus.  The  tuberculum  impar  forms  the  papillary  portion  of 
the  tongue. 

Applied  Anatomy. — The  internal  carotid  arteri/  is  in  close  relation  with  the  pharynx,  so  that 
its  pulsations  can  be  felt  through  the  mouth.  It  has  been  occasionally  wounded  by  sharp- 
pointed  instruments  introduced  into  the  mouth  and  thrust  through  the  wall  of  the  pharynx. 


Fig.  965. — The  anterior  surface  of  the  pharynx.     (Sappey.) 


In  aneurism  of  this  vessel  in  the  neck  the  tumor  necessarily  bulges  into  the  pharynx,  as  this  is 
the  direction  in  which  it  meets  with  the  least  resistance,  nothing  lying  between  the  vessel  and  the 
mucous  membrane  except  the  thin  Constrictor  muscle,  whereas  on  the  outer  side  there  is  the 
dense  cervical  fascia,  the  muscles  descending  from  the  styloid  process,  and  the  margin  of  the 
Sternomastoid  muscle. 

The  mucous  membrane  of  the  pharynx  is  very  vascular,  and  is  often  the  seat  of  infiammation, 
frequently  of  a  septic  character,  and  dangerous  on  account  of  its  tendency  to  spread  to  the  larynx. 
On  account  of  the  tissue  which  surrounds  the  pharyngeal  wall  being  loose  and  lax,  the  inflam- 
mation is  liable  to  spread  through  it  far  and  wide,  extending  downward  into  the  posterior  medi- 
astinum along  the  oesophagus.  Abscess  may  form  in  the  connective  tissue  behind  the  pharynx, 
between  it  and  the  vertebral  column,  constituting  what  is  known  as  retropharyngeal  abscess. 
This  is  most  commonly  due  to  caries  of  the  cervical  vertebrfe,  but  may  also  be  caused  by  sup- 
puration of  a  lymph  node  which  is  situated  in  this  position  opposite  the  axis,  and  which  receives 
lymphatics  from  the  nares,  or  by  gumma  or  by  acute  pharyngitis.  In  these  cases  the  pus  may 
be  easily  evacuated  by  an  incision,  with  a  gtiarded  bistoury,  through  the  mouth,  but,  for  aseptic 


1236 


THE  ORGANS  OF  DIGESTION 


reasons,  it  is  desirable  that  the  abscess  should  be  opened  from  the  neck.  In  some  instances  this  is 
perfectly  easy;  the  abscess  can  be  felt  bulging  at  the  side  of  the  neck  and  merely  requires  an  inci- 
sion for  its  relief;  but  this  is  not  always  so,  and  then  an  incision  should  be  made  along  the  posterior 
border  of  the  Sternomastoid  and  the  deep  fascia  should  be  divided.  A  director  should  now 
be  inserted  into  the  wound,  the  forefinger  of  the  left  hand  being  introduced  into  the  mouth  and 
pressm-e  made  upon  the  swelling.     This  acts  as  a  guide,  and  the  director  is  to  be  pushed  onward 

until  pus  appears  in  the  groove.     A  pair  of  sinus  forceps 
are  now  inserted  along  the  director  and  the  opening  into 
the  cavity  dilated. 
Foreign  bodies  not  infrequently  become  lodged  in  the 

U  mm      pharynx  and  most  usually  at  its  termination  at  about 

the  level  of  the  cricoid  cartilage,  just  beyond  the  reach 
of  the  finger,  as  the  distance  from  the  arch  of  the  teeth 
to  the  commencement  of  the  cssophagus  is  about  six 
inches. 

Hypertrophy  of  the  lymphoid  tissue  of  the  naso- 
pharynx produces  groups  of  hypertrophic  masses  known 
as  adenoids.     A  child  with  adenoids  has  a  cough,  and 

19  mm      when  awake  or   asleep,  breathes  noisily  and  with   the 

mouth  open.  The  voice  is  muffled,  the  hearing  is  im- 
paired, the  expression  is  vacant,  the  mind  is  dull,  and 
the  tonsils  are  enlarged. 


THE  (ESOPHAGUS  (Figs.  966,  967). 

The  (esophagus,  or  gullet,  is  a  musculomembra- 
nous  canal,  about  nine  or  ten  inches  in  length, 
extending  from  the  pharynx  to  the  stomach. 
It  commences  at  the  upper  border  of  the  cricoid 
cartilage,  opposite  the  sixth  cervical  vertebra, 
descends  along  the  front  of  the  vertebral  column 
through  the  posterior  mediastinum,  passes 
through  the  Diaphragm,  and,  entering  the  abdo- 
men, terminates  at  the  cardiac  orifice  of  the 
stomach,  opposite  the  eleventh  thoracic  verte- 
bra, about  an  inch  (2.5  cm.)  to  the  left  of  the  me- 
dian plane.  The  general  direction  of  the  oesopha- 
gus is  vertical,  but  it  presents  two  or  three  slight 
curves  in  its  course.  At  its  commencement  it  is 
placed  in  the  median  line,  but  it  inclines  to  the 
left  side  as  far  as  the  root  of  the  neck,  gradually 
passes  to  the  middle  line  again,  and  finally 
deviates  to  the  left  as  it  passes  forward  to  the 
oesophageal  opening  of  the  Diaphragm  (Jiiatus 
oesophageus).  The  oesophagus  also  presents 
antero-posterior  flexures,  corresponding  to  the 
curvature  of  the  cervical  and  thoracic  portions 
of  the  vertebral  column.  It  is  the  narrowest 
part  of  the  alimentary  canal,  being  most  con- 
tracted at  its  commencement,  at  about  the  level 
of  the  third  thoracic  vertebra,  and  at  the  point 
where  it  passes  through  the  Diaphragm  (Fig. 
966). 

When  empty,  the  oesophagus  is  contracted  so  that  its  anterior  and  posterior  walls 
come  in  contact  and  the  lumen  is  stellate  on  account  of  the  longitudinal  foldings 
of  the  inelastic  mucous  membrane  loosely  held  by  the  submucosa.     The  calibre 


lS-14  mm 


L^O 


Fig.  966. — Contour  of  the  CESophagus. 
On  the  left  the  distances  of  the  co  istric- 
tions  from  the  incisor  teeth  are  given  in 
centimeters:  on  the  right  are  given  the 
diameters  in  millimeters.  (Half  natural 
size.) 


THE  (ESOPHAGUS 


1237 


of  the  lumen  varies  between  half  an  inch  to  an  inch  or  more,  dependintr  upon  the 
absence  or  presence  of  swallowed  substances.  The  average  distance  from  the 
upper  incisor  teeth  to  the  beginning  of  the  gullet  is  about  six  inches  (15  cm.); 
the  average  distance  from  the  incisor  teeth  to  the 
cardiac  opening  of  the  stomach  is  fifteen  or  sixteen 
inches  (40  cm.).  The  portion  of  the  a\sophagus 
which  is  in  the  neck  is  called  the  cervical  portion 
ipcn-s  ccrvicalis);  the  portion  in  the  thorax,  the 
thoracic  portion  {pars  thoracalis);  and  the  portion 
which  lies  in  the  oesophageal  groove  of  the  liver, 
and  therefore  below  the  Diaphragm,  is  the  abdom- 
inal portion.  The  abdominal  portion  of  the  oesopha- 
gus {pars  ahdominalis)  is  not  over  half  an  inch  in 
length,  and  is  limited  to  the  small  portion  of  the 
anterior  and  left  lateral  surface  observed  when  a 
stomach  which  is  completely  empty  is  drawn 
downward  with  considerable  force.  The  abdominal 
portion  of  the    oesophagus   is  covered  by  perito- 


Mirr""' 


PULMONARY 


OESOPHAGUS 


-DIAPHRAGM 


Fig.   968. — The   relations  of  cesopha- 
FlG.   967. — Pleural  cul-de-sac  of  the  posterior  mediastinum.     Level         gus,    trachea,    and    aorta    in    an    infant, 
of  sixth  thoracic  vertebra.  (Poirier  and  Charpy.) 


neum  only  on  its  ventral  and  left  aspects.      It  is  somewhat  conical,  with  its 
base  toward  the  stomach,  and  is  known  as  the  antrum,  cardiacum. 

Relations. — The  cervical  portion  of  the  oesophagus  is  in  relation,  in  front,  with  the  trachea, 
and  at  the  lower  part  of  the  neck,  where  it  projects  to  the  left  side,  with  the  thjToid  _  gland ; 
behind,  \i  rests  upon  the  vej-tebral  column  and  Longus  colli  muscles;  on  either  side,  it  is  in 
relation  with  the  common  carotid  artery  (especially  the  left,  as  it  inclines  to  that  side)  and 
part  of  the  lateral  lobe  of  the  thyroid  gland;  the  recurrent  laryngeal  .nerves  ascend  between 
it  and  the  trachea;  to  its  left  side  is  the  thoracic  duct. 

The  thoracic  portion  of  the  cesophaguis  is  at  first  situated  a  litde  to  the  left  of  the  median 
line;  it  then  passes  behind  the  aortic  arch,  separated  from  it  by  the  trachea,  and  descends  in  the 
posterior  mediastinum,  along  the  right  .side  of  the  aorta,  then  runs  in  front  and  a  little  to  the  left 
of  the  aorta,  and  enters  the  abdomen  through  the  Diaphragm  at  the  level  of  the  tenth  thoracic 
vertebra.  Just  before  it  passes  through  the  Diaphragm  it  presents  a  distinct  dilatation  or  bidb. 
It  is  in  relation,  in  front,  with  the  trachea,  the  left  bronchus,  the  pericardium,  and  the  Diaphragm; 
behind,  it  rests  upon  the  vertebral  column,  the  Longus  colli  muscles,  the  right  intercostal  arteries, 
the  thoracic  duct,  and  the  vena  azygos  minor  veins;  and  beloiv,  near  the  Diaphragm,  upon  the 


1238 


THE  ORGANS  OF  DIGESTION 


front  of  the  aorta.  On  its  lejt  side,  in  the  superior  mediastinum,  p.re  the  terminal  part  of  the 
arch  of  the  aorta,  the  left  subclavian  artery,  the  thoracic  duct,  and  left  pleiua,  while  running 
upward  in  the  angle  between  it  and  the  trachea  is  the  left  recurrent  laryngeal  nerve;  below,  it 
is  in  relation  with  the  descending  thoracic  aorta.  On  its  right  side  are  the  right  pleura  and  the 
vena  azygos  major,  which  it  overlaps.  The  vagus  nerves  descend  in  close  contact  with  it,  the 
right  nerve  passing  down  behind,  and  the  left  nerve  in  front  of  it;  the  two  nerves  uniting  to  form 
a  plexus  {plexus  oesophageus  s.  gulae)  aroimd  the  tube. 

In  the  lower  part  of  the  posterior  mediastinum  the  thoracic  duct  lies  to  the  right  side  of  the 
oesophagus;  higher  up,  it  is  placed  behind  it,  and,  crossing  about  the  level  of  the  fourth  thoracic 
vertebra,  is  continued  upward  on  its  left  side. 


LEFT 

PULMONARY 

ARTERY 

LEFT  LUNG 

LEFT  BR 

THORACIC   DUCT 


VAGUS  NERVE 
PLEURA 


AZYGOS  VEI 


:::z:iM^ 


DIAPHRAGM 


1  the  cervical  region  and  i 
(Poirier  and  Charpy.) 


the  posterior  mediastinum. 


Structure. — The  cesophagus  has  four  coats — an  external  or  fibrous,  a  muscular,  a  sub- 
mucous, and  an  internal  or  mucous  coat. 

The  fibrous  coat  consists  of  white  fibrous  connective  tissue  tha,t  supports  the  other  coats  and 
assists  in  connecting  the  oesophagus  to  the  surrounding  tissues  or  organs. 

The  muscular  coat  (tutuca  muscularis)  is  composed  of  two  planes  of  considerable  thickness, 
an  external  longitudinal  and  an  internal  circular. 

The  longitudinal  fibres  are  arranged,  at  the  commencement  of  the  tube,  in  three  fasciculi — 
one  in  front,  which  is  attached  to  the  vertical  ridge  on  the  posterior  surface  of  the  cricoid  car- 
tilage, and  one  at  each  side,  which  is  continuous  with  the  fibres  of  the  Inferior  constrictor  of 
the  pharynx;  as  they  descend  they  blend  together  and  form  a  uniform  layer,  which  covers  the 
outer  surface  of  the  tube. 

Accessory  slips  of  muscle  tissue  pass  between  the  oesophagus  and  the  left  pleura,  where 
the  latter  covers  the  thoracic  aorta,  or  the  root  of  the  left  bronchus,  or  the  back  of  the  peri- 
cardium (Fig.  970). 


THE  (ESOPHAGUS 


1239 


The  circular  fibres  are  continuous  above  with  the  Inferior  constrictor  of  the  pharynx;  their 
direction  is  transverse  at  the  upper  and  lower  parts  of  the  tube,  but  oblique  in  the  intermediate 
part.     Below,  the  circular  fibres  pass  iiiiu  ihc  circular  and  oblique  fibres  of  the  stomach. 

The  muscle  fibres  in  the  upper  part  "f  ilic  u-^cijihagus  are  of  a  red  color,  and  consist  chiefly  of 
the  striped  variety,  but  below  they  con.si.^l  for  the  must  part  of  involuntary  muscular  fibres. 

The  submucous  coat  {tela  submucosd)  connects  loosely  the  mucous  and  muscular  coats. 

The  mucous  coat  (limica  mucosa)  is  thick,  of  a  reddish  color  above  and  pale  below.  It  is 
disposed  in  longitudinal  folds,  which  disappear  on  distention  of  the  tube.  Its  surface  is  studded 
with  minute  papilla;,  and  is  covered  throughout  with  a  thick  layer  of  stratified  pavement  epi- 
thelium. Beneath  the  mucous  membrane,  between  it  and 
the  submucous  coat,  is  a  layer  of  lonoiliidiiKilly  arranged 
nonstriped  muscle  tissue.  This  is  the  muscularis  mucosae 
{lamina  muscularis  mucosae).  At  the  coinnieiiccincnt  of  the 
oesophagus  it  is  absent,  or  only  represented  by  a  few  scattered 
bundles;  lower  down  it  forms  a  considerable  stratum. 

The  oesophageal  glands  are  small  compound  racemose 
glands  of  the  mucous  type;  they  are  lodged  in  the  submucous 
tissue  and  each  opens  upon  the  mucous  surface  by  a  long 
excretory  duct. 

Vessels  and  Nerves. — The  larger  vessels  are  in  the 
submucosa  and  send  branches  to  the  mucosa  and  muscularis. 
The  arteries  supplving  the  rjesophagus  are  derived  from  the 
inferior  thyroid  branch  of  the  thyroid  axis  of  the  subclavian, 
from  the  descending  thoracic  aorta  and  the  bronchial  arte- 
ries, and  from  the  gastric  branch  of  the  coeliac  axis,  and  from 
the  left  inferior  phrenic  of  the  abdominal  aorta.  They  have 
for  the  most  part  a  longitudinal  direction.  The  veins  are 
gathered  into  a  plexus  on  the  outer  surface  of  the  oesopha- 
gus. This  plexus  receives  the  venous  blood  from  the  walls 
of  the  tube.  From  the  lower  portion  of  tlie  plexus  branches 
go  to  the  coronary  vein  of  the  stomach.  Higher  up  branches 
go  to  the  azygos  veins  and  thyroid  veins.  In  this  manner 
a  communication  is  opened  between  the  portal  vein  and  the 
systemic  veins. 

The  lymphatics  drain  into  the  inferior  deep  cervical  nodes 
and  the  nodes  of  the  posterior  mediastinum. 

The  nerves  are  derived  from  the  vagus  and  from  the 
sympathetic;  they  form  a  plexus  in  which  are  groups  of 
ganglion  cells  between  the  two  layers  of  the  muscular  coat. 
From  this  fibres  pass  to  supply  the  muscle,  and  others  go  to 
the  submucous  tissue  to  form  a  secondary  plexus.  It  is 
usual  to  regard  the  plexus  as  consisting  of  two  parts,  an 
anterior  oesophageal  plexus,  derived  from  the  left  vagus, 
and  a  posterior  oesophageal  plexus,  derixed  from  the  right 
vagus.  These  two  plexuses  are  in  the  posterior  mediasti- 
num ;  they  communicate  with  each  other  and  contain  sym- 
pathetic fibres. 

Applied  Anatomy. — The  relations  of  the  oesophagus  are  of  considerable  practical  interest 
to  the  surgeon,'as  he  is  frequently  required,  in  cases  of  stricture  of  this  tube,  to  dilate  the  canal 
by  a  bougie,  when  it  is  of  importance  that  the  direction  of  the  oesophagus  and  its  relations  to 
surrounding  parts  should  be  remembered.  In  cases  of  malignant  disease  of  the  oesophagus, 
where  its  tissues  have  become  softened  from  infiltration  of  the  morbid  deposit,  the  greatest 
care  is  requisite  in  directing  the  bougie  through  the  strictured  part,  as  a  false  passage  may  easily 
be  made,  and  the  instrument  may  pass  into  the  mediastinum,  or  into  one  or  the  other  pleural 
cavity,  or  even  into  the  pericardium. 

One  should  also  remember  that  obstruction  of  the  oesophagus,  and  consequent  symptoms  of 
stricture,  are  occasionally  produced  by  aneurism  of  some  part  of  the  aorta  pressing  upon  the 
tube.     In  such  a  case  the  passage  of  a  bougie  could  only  hasten  the  fatal  issue. 

In  passing  a  bougie  the  left  forefinger  should  be  introduced  into  the  mouth  and  the  epiglottis 

felt  for,  care  being  taken  not  to  throw  the  head  too  far  backward.     The  bougie  is  then  to  be 

passed  beyond  the  finger  until  it  touches  the  posterior  wall  of  the  pharynx.     The  patient  is 

now  asked  to  swallow,  and  at  the  moment  of  swallowing  the  bougie  is  passed  gently  down- 

,  ward,  all  violence  being  carefully  avoided. 

It  occasionally  happens  that  "a  foreign  body  becomes  impacted  in  the  oesophagus  and  can 
neither  be  brought  upward  nor  moved  downward.  When  all  ordinary  means  for  its  removal 
have  failed,  and  the  body  is  lodged  above  the  lower  one-third  of  the  gullet,  external  wsopha- 


FlG.  970. — Accessory  muscle  slips 
between  the  CESophagus  and  pleura, 
and  cesophagus  and  trachea.  (From 
a  preparation  in  the  Museum  of  the 
Royal  College  of  Surgeons  of  England.) 


1240  THE  ORGANS  OF  DIGESTION 

gotomy  is  performed.  If  the  foreign  body  is  lodged  in  the  lower  one-third  of  the  gullet,  the 
stomach  is  opened  (gastrotomy)  and  the  foreign  body  is  extracted.  If  the  foreign  body  is  allowed 
to  remain  lodged  in  the  oesophagus,  extensive  inflammation  and  ulceration  may  ensue.  In  one 
case  the  foreign  body  ultimately  penetrated  the  intervertebral  substance,  and  destroyed  life 
by  inflammation  of  the  membranes  and  substance  of  the  spinal  cord. 

The  operation  of  cesophagotomy  is  thus  performed:  The  patient  being  placed  upon  his  back, 
with  the  head  and  shoulders  slightly  elevated,  an  incision,  aljout  four  inches  in  length,  should 
be  made  on  the  left  side  of  the  trachea,  from  the  thyroid  cartilage  downward,  dividing  the  skin, 
Platysma,  and  deep  fascia.  The  edges  of  the  wound  being  separated,  the  Omohyoid  muscle 
should,  if  necessary,  be  divided,  and  the  fibres  of  the  Sternohyoid  and  Sternothyroid  muscles 
drawn  inward;  the  sheath  of  the  carotid  vessels,  being  exposed,  must  be  drawn  outward,  and 
retained  in  that  position  by  retractors;  the  cesophagus  will  now  be  exposed,  and  should  be  divided 
over  the  foreign  body,  which  can  then  be  removed.  Great  care  is  necessary  to  avoid  wounding 
the  thyroid  vessels,  the  thyroid  gland,  and  the  laryngeal  nerves. 

The  oesophagus  may  be  obstructed  not  only  by  foreign  bodies,  but  also  by  changes  in  its  coats, 
producing  siridure,  or  by  pressure  on  it  from  without  of  new  growths  or  aneurisms,  etc. 

The  different  forms  of  stricture  are:  (1)  the  spasmodic,  occurring  in  neurotic  individuals,  and 
intermittent  in  character,  so  that  the  dysphagia  is  not  constant.  Spasmodic  stricture  of  the 
oesophagus  sometimes  occurs  incases  of  cancer  of  the  stomach  and  cancer  of  the  liver;  (2) 
fibrous,  due  to  cicatrization  after  injuries,  such  as  swallowing  corrosive  fluids  or  boiling  water; 
and  (3)  maligtiant,  usually  epitheliomatous  in  its  nature.  Cancer  is  most  common  either  at 
the  upper  end  of  the  tube,  opposite  to  the  cricoid  cartilage,  or  at  its  lower  end  at  the  cardiac 
orifice.  Cicatricial  stricture  may  be  treated  by  gradual  dilatation.  If  a  stricture  is  impassable 
from  above,  the  stomach  may  be  opened,  an  instrument  passed  from  below,  and  a  string  used 
to  divide  the  stricture.  The  operation  of  (B.?o;:i/i090«fomi/ has  occasionally  been  performed,  but 
if  any  operative  interference  is  undertaken  for  stricture,  with  the  idea  of  forming  an  orifice  for 
the  introduction  of  food,  it  is  better  to  perform  gastrostomy.  In  malignant  stricture,  gastrostomy 
is  the  only  operation  to  be  thought  of. 

THE  ABDOMEN. 

The  abdomen  is  that  portion  of  the  trunk  which  lies  below  the  Diaphragm,  and 
it  contains  the  largest  cavity  in  the  body.  It  is  of  an  oval  form,  the  extremities 
of  the  oval  being  directed  upward  and  downward;  the  upper  one  is  formed 
by  the  under  surface  of  the  Diaphragm,  the  lower  end  is  limited  by  the  structures 


Male  Type 


Fig.  971. — Schematic  outlines  of  the  abdomen. 

which  clothe  the  inner  surface  of  the  bony  pelvis,  principally  the  Levatores  ani 
and  the  Coccygei  muscles  on  either  side.  These  muscles  are  sometimes  termed 
the  Diaphragm  of  the  pelvis.  In  order  to  facilitate  description,  it  is  artificially 
divided  into  two  parts,  an  upper  and  larger  part,  the  abdomen  proper,  and  a  lower 
and  smaller  part,  the  pelvis.  The  cavities  of  these  divisions  are  not  separated 
from  each  other,  but  the  limit  between  them  is  marked  by  the  brim  of  the  true 
pelvis.  The  cavity  is  wider  above  than  below,  and  measures  more  in  the  vertical 
than  in  the  transverse  diameter. 

The  abdomen  proper  differs  from  the  other  great  cavities  of  the  body  in  being 
bounded  for  the  most  part  by  muscles  and  fascise,  so  that  it  can  vary  in  capacity 
and  shape  according  to  the  condition  of  the  viscera  which  it  contains;  but,  in 


THE  ABD03IEN 


1241 


addition  to  this,  the  abdomen  varies  in  form  and  extent  with  age  and  sex  (Fig. 
971).  In  the  adult  male,  with  moderate  distention  of  the  viscera,  it  is  oval  or 
barrel-shaped,  but  at  the  same  time  flattened  from  before  backward.  In  the 
adult  female,  with  a  fully  developed  pelvis,  it  is  conical  with  the  apex  above,  and 
in  young  children  it  is  conical  with  the  apex  below. 


Heart  contoitr 


/-.  Small  intestine 


Peritoneum  — 


Fig.  972. — Topography  of  thoracic  and  abdominal  viscera. 


Boundaries.— The  boundary  between  the  thorax  and  abdomen  is  the  Dia- 
phragm, which  extends  as  a  dome  over  the  abdomen,  so  that  the  cavity  extends 
high  into  the  bony  thorax,  reaching  on  the  right  side,  in  the  midclavicular  line, 
to  the  upper  border  of  the  fifth  rib;  on  the  left  side  it  falls  below  this  level  by 
about  half  an  inch  or  more.  The  abdomen  proper  is  bounded  in  front  and  at  the 
sides  by  the  lower  ribs,  the  abdominal  muscles,  and  the  iliac  fossa?;  behind,  by  the 
vertebral  column  and  the  Psoas  and  Quadratus  lumborum  muscles;  above,  by  the 
Diaphragm;  below,  by  the  plane  of  the  inlet  or  brim  of  the  pelvis.  The  muscles 
forming  the  boundaries  of  the  cavity  are  lined  upon  their  inner  surface  by  a  layer 
of  fascia,  differently  named,  according  to  the  part  which  it  covers. 


1242 


THE  ORGANS  OF  DIGESTION 


The  abdomen  contains  (Fig.  972)  the  greater  part  of  the  ahmentary  canal ; 
some  of  the  accessory  organs  to  digestion — viz.,  the  liver  and  pancreas;  the  spleen, 
the  kidneys,  and  adrenals,  or  suprarenal  capsules.  Most  of  these  structures, 
as  well  as  the  wall  of  the  cavity  in  which  they  are  contained,  are  covered  by  an 
extensive  and  complicated  serous  membrane,  the  peritoneum  (Fig.  1004). 

The  Apertures  in  the  Walls  of  the  Abdomen. — ^The  apertures  found  in  the  walls  of 
the  abdomen,  for  the  transmission  of  structures  to  or  from  it,  are  the  umbilicus,  for 
the  transmission  (in  the  fetus)  of  the  umbilical  vessels;  the  caval  opening  in  the 
Diaphragm,  for  the  transmission  of  the  inferior  vena  cava;  the  aortic  opening, 
for  the  passage  of  the  aorta,  vena  azygos  major,  and  thoracic  duct;  and  the 
oesophageal  opening,  for  the  oesophagus  and  vagus  nerves.  Below,  there  are  two 
apertures  on  each  side ,  one  for  the  passage  of  the  femoral  vessels,  and  the  other 
for  the  transmission  of  the  spermatic  cord  in  the  male,  and  the  round  ligament 
in  the  female. 


Limit 


i^iiiLsc^, 


Fig.  973. — The  regions  of  the  abdomen  and  their  contents.     Edges  of  costal 


Regions  (Fig.  973). — For  convenience  of  description  of  the  viscera,  as  well  as 
of  reference  to  the  morbid  conditions  of  the  contained  parts,  the  abdomen  is  arti- 
ficially divided  into  nine  regions  by  imaginary  planes,  two  horizontal  and  two 
sagittal,  passing  through  the  cavity,  the  edges  of  the  planes  being  indicated  by 
lines  drawn  on  the  ventral  surface  of  the  body.  Of  the  horizontal  planes,  the  upper 
or  infracostal  is  indicated  by  a  line  encircling  the  body  at  the  level  of  the  lowest 
points  of  the  tenth  costal  cartilages,  the  lower  by  a  line  carried  around  the  trunk 
at  the  level  of  the  summits  of  the  iliac  crests.  The  lower  plane  closely  corre- 
sponds to  the  intertubercular  plane  passing  through  the  trunk  at  the  level  of  the 
prominent  and  easily  defined  tubercle  on  the  iliac  crest  about  two  inches  behind 


THE  ABDOMEN 


1243 


the  anterior  superior  iliac  spine.  By  means  of  these  imaginary  planes  the  abdomen 
is  divided  into  three  zones,  which  are  named,  from  above  downward,  ■mbcostal, 
umbilical,  and  hypogastric  zones.  Each  of  these  is  furtlier  sul)divided  by  two 
sagittal  planes,  which  are  indicated  on  the  surface  by  lines  drawn  vertically  through 
points  half  way  between  the  anterior  superior  iliac  spines  and  tlie  symphysis  pu\ns. 
The  regions  as  outlined  by  the  BNA  Commission  are  shown  in  Fig.  974.' 

The  middle  region  of  the  upper  zone  is  called  the  epigastric,  and  the  two  lateral 
reo-ions,  the  right  and  left  hypochondriac.  The  central  region  of  the  middle  zone  is 
the  umbilical;  and  the  two  lateral  regions,  the  right  and  left  lumbar.  The  middle 
region  of  the  lower  zone  is  tlie  hypogastric  or  pubic  region;  and  the  lateral  regions 
are  the  right  and  left  iliac  or  inguinal. 


REGIO  INGUINAUIS- 


The  pelvic  cavity  is  that  part  of  the  abdominal  cavity  which  lies  below  and  behind 
a  plane  passing  through  the  promontory  of  the  sacrum,  the  iliopectineal  lines  and 
the  pubic  crests.  It  is  bounded  behind  by  the  sacrum,  coccyx,  Pyriformis  muscles, 
and  the  great  sacrosciatic  ligaments;  in  front  and  laterally  by  the  pubes  and  ischia 
and  Obturator  internus  muscles;  above,  it  communicates  with  the  cavity  of  the 
abdomen;  beloiv,  it  is  closed  by  the  Leva  tores  ani  and  Coccygei  muscles  and  the 
triangular  ligament.  The  pelvic  cavity  contains  the  urinary  bladder,  the  sigmoid 
colon,  the  rectum,  a  few  coils  of  small  intestine,  and  some  of  the  generative  organs. 

If  the  anterior  abdominal  wall  is  reflected  in  the  form  of  four  triangular  flaps 
by  means  of  vertical  and  transverse  incisions — the  former  from  the  ensiform  car- 
tilage to  the  symphysis  pubis,  the  latter  from  flank  to  flank  at  the  level  of  the 
umbilicus — the  abdominal  or  peritoneal  cavity  is  freely  opened  and  the  contained 

^  Anatomists  are  far  from  agreed  as  to  the  best  method  of  subdividing  the  abdooainal  cavity,  .\ddison  (Jour- 
nal of  Anatomy  and  Physiology,  vols,  xxxiv  and  xxxv),  in  a  careful  analysis  of  the  abdominal  viscera  in  forty 
subjects,  adopts  the  following  lines:  (1)  a  median,  from  the  symphysis  pubis  to  the  ensiform  cartilage:  C2)  two 
lateral  lines  drawn  vertically  through  a  point  midway  between  the  anterior  superior  iliac  spine  and  the  sjTnphysis 
pubis:  (3)  an  upper  transverse  line  half  way  between  the  symphysis  pubis  and  the  suprasternal  notch:  and 
(4)  a  lower  transverse  line  midway  between  the  last  and  the  upper  border  of  the  symphysis  pubis.  The  upper 
transverse  line  corresponds  with  what  he  has  termed  the  transpylonc  plane,  from  the  fact  that  in  most  cases 
this  plane  traverses  the  pylorus. 


1244  THE  ORGANS  OF  DIGESTION 

viscera  are  in  part  exposed.  Above  and  to  the  right  side  is  the  liver,  situated 
chiefly  under  the  shelter  of  the  right  ribs  and  their  cartilages,  but  extending  across 
the  middle  line,  and  reaching  for  some  distance  below  the  level  of  the  ensiform 
cartilage.  To  the  left  of  the  liver  is  the  stomach,  from  the  lower  border  of  which 
an  apron-like  fold  of  peritoneum,  the  greater  omentum,  descends  for  a  varying 
distance,  and  obscures,  to  a  greater  or  less  extent,  the  other  viscera  (Fig.  1002). 
Below  it,  however,  some  of  the  coils  of  the  small  intestine  can  generally  be  seen, 
while  in  the  right  and  left  iliac  regions  respectively  the  cecum  and  the  sigmoid 
flexure  of  the  colon  are  exposed.  The  bladder  occupies  the  anterior  part  of  the 
pelvis,  and,  if  distended,  will  project  above  the  symphysis  pubis;  the  rectum  lies 
in  the  concavity  of  the  sacrum,  but  is  usually  obscured  by  the  coils  of  the  small 
intestine.     The  sigmoid  colon  lies  between  the  rectum  and  the  bladder. 

If  the  stomach  is  followed  from  left  to  right  it  will  be  found  to  be  continuous 
with  the  first  part  of  the  small  intestine,  or  duodenum,  the  point  of  continuity 
being  marked  by  a  thickened  ring  which  indicates  the  position  of  the  pyloric 
sphincter.  The  duodenum  passes  toward  the  under  surface  of  the  liver,  and  then, 
curving  downward,  is  lost  to  sight.  If,  however,  the  great  omentum  be  thrown 
upward  over  the  thorax,  the  terminal  part  of  the  duodenum  will  be  observed 
passing  across  the  vertebral  column  toward  the  left  side,  where  it  becomes  con- 
tinuous with  the  coils  of  the  small  intestine.  These  measure  some  twenty  feet  in 
length,  and  if  followed  downward  will  be  seen  to  end  in  the  right  iliac  fossa  by 
opening  into  the  cecum,  the  commencement  of  the  large  intestine.  From  the 
cecum  the  large  intestine  takes  an  arched  course,  passing  at  first  upward  on  the 
right  side,  then  across  the  middle  line  and  downward  on  the  left  side,  and  forming 
respectively  the  ascending,  transverse,  and  descending  parts  of  the  colon.  In  the 
left  iliac  region  it  assumes  the  form  of  a  loop,  the  sigmoid  flexure,  then  follows  the 
curve  of  the  sacrum  and  terminates  in  the  rectum  and  anal  canal. 

The  spleen  lies  behind  the  stomach  in  the  left  hypochondriac  region,  and  may 
be  in  part  exposed  by  pulling  the  stomach  over  toward  the  right  side. 

The  glistening  appearance  of  the  deep  surface  of  the  abdominal  wall  and  of 
the  exposed  viscera  is  due  to  the  fact  that  the  former  is  lined  and  the  latter  more 
or  less  completely  covered  by  a  serous  membrane,  the  peritoneum. 


THE  PERITONEUM  (TUNICA  SEROSA). 

The  peritoneum  is  the  largest  serous  membrane  in  the  body,  and  consists,  in 
the  male,  of  a  closed  sac,  a  part  of  which  is  applied  against  the  abdominal  parietes, 
while  the  remainder  is  reflected  more  or  less  completely  over  the  contained  viscera. 
In  the  female  the  peritoneum  is  not  a  closed  sac,  since  the  free  extremities  of  the 
Fallopian  tubes  open  directly  into  the  peritoneal  cavity.  The  part  which  lines  the 
parietes  is  named  the  parietal  peritoneum;  that  which  is  reflected  over  the  viscera, 
the  visceral  peritoneum.  The  free  surface  of  the  membrane  is  smooth,  covered  by  a 
layer  of  flattened  endothelium,  and  lubricated  by  a  smafl  quantity  of  serous  fluid. 
Hence  the  viscera  can  glide  freely  against  the  wall  of  the  cavity  or  upon  one  another 
with  the  least  possible  amount  of  friction.  The  attached  surface  is  rough,  being 
connected  to  the  viscera  and  inner  surface  of  the  parietes  by  means  of  areolar 
tissue  termed  the  subserous  areolar  tissue  [tela  subserosa).  The  parietal  portion 
is  loosely  connected  with  the  fascia  lining  the  abdomen  and  pelvis,  but  more 
closely  to  the  under  surface  of  the  Diaphragm  and  also  in  the  middle  line  of  the 
abdomen. 

The  space  between  the  parietal  and  visceral  layers  of  the  peritoneum  is  named 
the  peritoneal  cavity;  but  it  must  be  remembered  that  under  normal  conditions  this 
cavity  is  a  potential  one,  since  the  parietal  and  visceral  layers  are  in  contact. 


THE  PERITONEUM 


1245 


The  peritoneal  "cavity"  is  subdivided  into  a  greater  and  a  lesser  cavity  or  sac,  wliicii 
communicate  through  the  foramen  of  Winslow  {foramen,  eplplolcwii).  I'he 
greater  sac  is  opened  wiien  tlie  ventral  abdominal  wall  is  pierced;  the  lesser  is 
situated  behind  tiie  stomacli  and  adjoining  structures,  and  may  be  regarded  as  a 
diverticulum  of  the  greater  sac. 

The  disposition  of  the  peritoneum  as  it  is  applied  to  the  parietes  and  also 
reflected  over  the  viscera  contained  in  the  abdominal  cavity  is  best  vndersfood 
after  tracing  the  developmental  (enibrijolorjic)  history  of  the  peritoneum  and  the 
alimentary  tract. 

Development  of  the  Peritoneum  and  Alimentary  Tract/ — ^The  segment- 
ing ovum,  at  an  early  stage,  becomes  a  blastodermic  vesicle  with  two  layers 
of  cells  composing  its  wall,  named,  from  without  inward,  ectoderm  and  ento- 
derm. The  cavity  of  the  vesicle  is  filled  with  the  nutritive  yolk  {vitellus).  Only 
a  part  of  the  ovum  is  destined  to  form  the  embryo,  the  remainder  being  used 
up  in  the  formation  of  membranes  and  other  appendages  which  are  concerned 
in  protection  and  nutrition;  the  ovum  may,  therefore,  be  divided  into  its  embryonic 
area  and  extra-embryonic  portion.  In  the  embryonic  area,  in  its  caudal  part, 
appears  the  transitory  primitive  streak  and  groove  produced  by  an  axial  thickening 
of  the  ectoderm.  From  the  head  process  of  the  primitive  streak  a  third  layer  of 
cells,  the  mesoderm,  extends  in  all  directions  between  ectoderm  and  entoderm,  ex- 
tending alongside  the  neural  tube  and  notochord.  The  extension  of  the  mesoderm 
takes  place  throughout  the  whole  of  the  embryonic  and  extra-embryonic  areas  of 
the  ovum  except  in  certain  regions.     One  such  area,  devoid  of  mesoderm,  is  seen 


Fig.  975. — Diagrammatic  outline  of  a  longitudinal  vertical  section  of  the  chick  on  tte  fourth  day.  ep.  Ecto- 
derm, sm.  Somatic  mesoderm,  hit.  Entoderm,  vm.  Visceral  mesoderm,  af.  Cephalic  fold,  vt-  Caudal  fold, 
am.  Cavity  of  true  amnion,  ys.  Yolk  sac.  i.  Intestine,  s.  Foregut.  a.  Future  anus,  still  closed,  m.  The 
mouth,  me.  The  mesentery,  al.  The  allantoic  vesicle,  pp.  Space  between  inner  and  outer  folds  of  amnion. 
(From  Quain's  Anatomy,  Alien  Thomson.) 


immediately  cephalad  of  the  neural  tube.  This  is  named  the  buccopharyngeal 
area,  since  it  afterward  forms  the  temporary  septum  between  the  primitive  mouth 
and  primitive  pharynx.  This  membrane  extends  from  the  head  to  the  peri- 
cardial area.  A  similar  area  devoid  of  mesoderm  is  seen  immediately  caudad  of 
the  embryonic  area,  and  is  named  the  cloacal  membrane,  since  it  afterward  forms 
the  temporary  septum  between  the  anal  pit  and  the  primitive  hindgut. 

While  the  paraxial  mesoderm  extends  along  the  neural  tube  and  notochord 
and  in  all  directions,  its  lateral  portion  splits  into  two  concentric  layers;  the  outer 
or  somatic  layer  becomes  applied  to  the  ectoderm,  and  with  it  forms  the  somato- 
pleure  or  body  wall;  the  inner  or  splanchnic  layer  adheres  to  the  entoderm,  and 
with  it  forms  the  splanchnopleure,  from  which  the  greater  portion  of  the  digestive 
tract  is  formed.  The  space  created  between  the  layers  of  the  mesoderm  is 
termed  the  coelom  or  body  cavity.  A  portion  of  this  space  is  later  enclosed  within 
the  embryo,  and  is  called  the  embryonic  coelom,  while  the  portion  of  the  coelomic 


1  In  the  preparation  of  this  chapter  the  editor  has  consulted  several  original  treatises,  i 
ton's  "Anatomy  of  the  Human  Peritoneum  and  Abdominal  Cavity,"  1903. 


atably  G.  S.  Huntingr 


1246 


THE  OB&ANS  OF  DIGESTION 


cavity  left  outside  the  embryo,  the  extra-embryonic  coelom,  envelops  the  vitelline 
or  yolk  sac. 


-Diagram  of  a  longitudinal  section  of  a 


bryo.     Very  early,      (After  Quain.) 


The  relatively  slow  growth  of  the  margin  of  the  embryonic  area  and  the  relati-\'ely 
rapid  growth  of  the  axial  parts  soon  come  to  form  a  ring  of  constriction  between 
the  embryo  and  the  yolk  sac,  and  a  part  of  the  latter — that  is,  a  part  of  its  splanch- 
*  nopleural   wall    and    part    of    the 

cavity — becomes  enclosed  within 
the  embryo  to  form  the  primitive 
alimentary  canal  (Fig.  976).  At 
the  same  time  a  part  of  the  coelom 
becomes  enclosed  within  the  em- 
bryo by  the  relative  approximation 
of  the  lateral,  cephalic,  and  caudal 
folds,  and  the  embryonic  coelom 
cavity  forms  the  rudiment  of  the 
pleural,  pericardial,  and  peritoneal 
cavities.  The  abdominal  cavity  is 
separated  from  the  other  cavities 
by  the  septum  transversum,  the 
proton  of  the  Diaphragm.  The 
embryo  grows  more  rapidly  in 
length  than  in  width,  and  its 
cephalic  and  caudal  extremities 
are  bent  ventrad;  the  forward 
growth  of  the  head  tilts  the  areas 
situated  cephalad  so  that  the  posi- 
tions of  the  buccopharyngeal  and 
pericardial  areas  become  reversed;  the  same  inversion  takes  place  with  regard  to 
the  cloacal  membrane. 


Figs.  977  and  978. — Early  form  of  the  alimentary  canal.  In 
Fig.  977  a  front  view,  and  in  Fig.  978  an  antero-posterior  sec- 
tion are  represented,  a.  Four  pharyngeal  or  visceral  pouches. 
h  The  pharynx,  c,  c.  The  commencing  lungs,  d.  The  stom- 
ach. /,  /.  The  diverticula  connected  with  the  formation  of  the 
liver,  g.  The  yolk  sac,  into  which  the  middle  intestinal 
groove  opens.  h.  The  hind  gut.  (From  Kolliker,  after 
Bischoff.) 


THE  PERITONEUM 


1247 


The  alimentary  tube,  now  in  its  simplest  form,  is  nearly  straight  and  may  he 
divided  into  three  portions:  (a)  the  foregid  between  the  pericardium  and  noto- 


Bitccopharynqeal 
membrane 

Pharynx  - 
Auditory  pit 

Aortic  bulb 


Cloacal  dilataiwn- 
of  hindgut 


Allantoic  stall 
Umbilical  vein 


lOplic  vesicle. 


Stomach  -+-- 


_Mid(jut  and  yolk 


^Hindgut, 


illantois 
Umbilical  aiteiy 


Fig.  979. — Human  emoryo,  about  fifteen  days  old.     Brain  and  heart  represented  from  right  side;  alimentarji 
canal  and  yolk  sac  in  mesal  section.      (After  His.) 

chord;  (b)  the  midgut,  opening  directly  into  the  yolk  sac;  and  (c)  the  hindgut, 
contained  within  the  caudal  fold.     The  passage  between  the  midgut  and  the 


(Esophagus. 


V-shaped  loop 

of  hindgut.' 

Vitello-intestinal  duct. 

Cloaca. 


Figs.  9S0  and  9S1. — Front 


(Esophagus, 


stages  in  the  development  of  the  alimentary  canal.     (His.) 


yolk  sac  is  at  first  relatively  wide,  but  it  is  subsequently  narrowed  and  lengthened 
to  become  the  tubular  vitelline  duct  (to  wholly  disappear  eventually). 


1248 


THE  ORGANS  OF  DIGESTION 


In  its  course  from  the  head  to  the  tail  the  primitive  alimentary  canal  is  held  to 
the  body  axis  (notochord)  by  a  broad  mass  of  mesoderm,  from  which  the  common 


Bathke's  pouch 
{pituitary  invagination). 


Median  rudiment  of 
I  thyroid  gland. 

Mandibular  arch. 
Notochord. 


Rathke's 

~~ pouch 
{pituitary 
invagination). 


Omphalo- 
mesenteric 
duct. 

AUantois.-'\ 


Terminal  portion  of 
~   hindgut. 


-Wolffian  duct. 


Figs.  982  and  983. — Sketches  in  profile  of  two  stages  in  the  development  of  the  human  alimentary  canal.     Fig.  982, 
A  X  30.    Fig.  983.  B  X  20.     (His.) 

mesentery  of  the  gut  is  subsequently  developed.  The  foregut^  is  also  held  by 
a  ventral  mesentery,  the  thoracic  portion  of  which  becomes  modified  by  the  de- 
velopment of  the  heart  and  lungs,  while  the  abdominal  portion  serves  as  a  matrix 
for  the  developing  liver,  and  ultimately  becoming  the  falciform  ligament  and  gastro- 

'  The  junction  of  the  foregut  with  the  midgut  is  generally  understood  to  be  at  the  level  of  the  orifice  of  the  com- 
mon bile  duct,  or  site  of  origin  of  the  liver  diverticulum. 


THE  PEBITOJS-EUM 


1249 


hepatic  omentum.  The  mesoderm  lining  the  body  cavity  as  well  as  the  free 
surfaces  of  the  mesenteries  soon  assumes  the  character  of  a  serous  membrane, 
and  is  then  called  the  peritoneum.  Topographically,  this  membrane  may  be  sul)- 
divided  into:  (a)  Parietal  peritoneum,  investing  the  inner  surface  of  the  abdominal 
cavity;  (6)  visceral  peritoneiun,  investing  the  alimentary  tube  and  its  derivatives; 
(c)  mesenteric  peritoneum,  connecting  the  two  former,  as  a  suspensory  support 
for  the  alimentary  tract,  and  carrying  the  vessels  and  nerves  to  it. 

The  pharynx,  oesophagus,  stomach,  and  part  of  the  duodenimi  are  developed 
from  the  foregut;  the  descending  and  sigmoid  parts  of  the  colon,  the  rectum,  and 
the  tubular  diverticulum  of  the  allantois  are  developed  from  the  hindgut;  the 
midgut  gives  origin  to  the  remainder  of  the  alimentary  tube. 


Point  where 
J        intei<tinal 
'         loops  cross 
each  other. 

Mesocolon. 

Large  intes- 
tine. 
Small  inieS' 
tine. 


Figs.  9S4  and  985. — Illustrating  two  stages  in  the  development  of  the  human  alimentary  canal  and  its  mesentery. 
The  arrow  indicates  the  entrance  to  the  bursa  omentalis.     (Hertwig.j 

The  upper  part  of  the  foregut  becomes  dilated  in  the  form  of  branchial  pouches 
to  form  the  pharynx;  the  succeeding  part  remains  tubular'  and  with  the  descent 
of  the  stomach  becomes  elongated  to  form  the  oesophagus.  About  the  fifth  week 
a  fusiform  dilatation,  the  future  stomach,  makes  its  appearance.  The  stomach, 
together  with  a  succeeding  part  of  the  duodenum,  has  a  ventral  mesentery,  called 
the  ventral  mesogastrium,  in  addition  to  its  dorsal  attachment,  the  dorsal  meso- 
gastrium.  In  the  base  of  the  dorsal  mesogastrium  courses  the  aorta  which  sup- 
plies a  series  of  branches,  embedded  in  the  mesoderm,  to  the  alimentary  tube. 
The  stomach  undergoes  a  further  dilatation,  and  its  two  curvatures  can  be  recog- 
nized, the  greater  directed  dorsad  and  the  lesser  ventrad,  while  its  two  surfaces 
look  to  the  right  and  left  respectively.  The  midgut  undergoes  great  elongation 
and  forms  a  loop  which  projects  downward  and  forward;  from  the  arch  of  the  loop 
the  vitelline  duct  passes  to  the  umbilicus.  For  a  time  a  part  of  the  loop  extends 
beyond  the  abdominal  cavity  into  the  umbilical  cord,  but  is  withdrawn  into  the 
cavity  by  the  end  of  the  third  month. 

About  the  sixth  week  a  lateral  diverticulum  makes  its  appearance  on  the  caudal 
part  of  the  loop  a  short  distance  from  the  vitelline  duct,  and  indicates  the  future 
cecum  and  appendix.  The  part  of  the  loop  on  the  distal  side  of  the  cecal  diver- 
ticulum increases  in  diameter  and  forms  the  future  ascending  and  transverse 
portions  of  the  large  intestine.  The  cecal  diverticulum  shares  only  partially  in 
this  increase  in  calibre,  its  pendant  portion  remaining  rudimentary  and  forming 
the  appendix. 

The  stomach  and  intestine,  with  their  mesenteries,  undergo  changes  of  position 
determined  by  several  growth  factors,  such  as  the  elongation  of  the  intestine,  and 

1  The  epithelium  of  the  cesophagus  and  certain  other  portions  of  the  gut  increases  so  greatly  in  thickness  by  active 
proliferation  of  the  cells  that  the  lumen  is  nearly  or  wholly  closed  during  the  second  month,  to  be  restored  about  one 
jnonth  later  (Congenital  stenosis). 


1250 


THE  ORGANS  OF  DIGESTION 


the  development  of  such  organs  as  the  liver,  pancreas,  and  spleen.  Such  devel- 
opmental changes,  with  subsequent  displacements,  adhesions,  and  absorptions, 
serve  to  form  all  the  mesenteries,  omenta,  and  peritoneal  folds  of  the  adult,  so 
that,  while  in  the  primitive  condition  the  intestinal  tube  is  suspended  by  a  dorsal 
mesentery  and  freely  movable,  certain  portions  of  it  become  later,  by  secondary 
adhesion,  firmly  connected  with  the  parietes  (retroperitoneal)  or  with  other  por- 
tions of  the  tract. 

Rotation  of  Stomach  and  Intestine. — ^The  stomach  rotates  so  that  its  greater 
(dorsal)  curvature  with  the  attached  dorsal  mesogastrium  is  carried  downward 
and  to  the  left,  so  that  the  right  surface  of  the  stomach  is  now  directed  backw'ard 
and  the  left  surface  forward  (ventrad) — a  change  in  position  which  explains 
why  the  left  vagus  nerve  is  found  on  the  front  of  the 
stomach  and  the  right  vagus  on  the  back  of  it.  As  the 
stomach  rotates,  the  dorsal  mesogastrium  is  necessarily 
elongated;  this  elongation  is,  however,  augmented  in 
further  development,  so  that  a  large  pouch,  the  bursa 
omentalis  or  lesser  sac  is  formed.  The  entrance  to  this 
pouch  constitutes  the  future  foramen  of  Winsloiv. 
The  duodenum,  developed  from  that  part  of  the  tube 
which  immediately  succeeds  the  stomach,  undergoes 

S"  pt  tm  ti  ansi  ersiim. 


Fig.  987.— Final  disposition 
of  the  intestines  and  their  vas- 
cular relations,  A.  .\orta.  H, 
Hepatic  artery.  5.  Splenic  ar- 
tery. M ,  Col.  Branches  of  supe- 
rior mesenteric  artery,  vi,  m'. 
Branches  of  inferior  mesenteric 
artery.     (Jonnesco.) 


Intcsth 

y -shaped  loop, 
Mesente 


little  elongation.  It  is  at  first  suspended  by  a  mesentery  (mesoduodenum)  and 
projects  forward  in  the  form  of  a  loop.  The  loop  is  subsequently  displaced 
backward  by  the  transverse  colon,  so  that  the  right  surface  of  the  mesoduodenum 
is  swung  back,  and,  adhering  to  the  parietal  peritoneum  pardy  in  front  of  the 
right  kidney,  is  obliterated;  in  this  way  the  duodenum,  together  with  the  pancreas 
which  has  invaded  the  dorsal  mesoduodenum,  become  retroperitoneal.  It  is 
further  fixed  in  position  by  the  liver  and  pancreas  which  arise  as  diverticula  from 
it.  The  liver,  developing  between  the  layers  of  the  ventral  mesogastrium,  comes 
to  occupy  the  upper  right  portion  of  the  abdominal  cavity,  and  thus  reduces  the 
entrance  to  the  omental  bursa  to  the  small  foramen  of  Winslow. 

The  remainder  of  the  alimentary  canal  becomes  elongated,  and  as  a  consequence 
the  tube  becomes  complexly  coiled  on  itself,  and  this  elongation  demands  a 
corresponding  increase  in  the  width  of  the  intestinal  attachment  of  the  mesentery, 
which  becomes  folded. 

Rotation  of  the  Intestine. — At  an  early  stage  the  small  and  large  intestines  are 
attached  to  the  dorsal  wall  of  the  abdomen  by  a  common  mesentery,  the  coils 


THE  PERITONEUM 


1251 


of  the  small  intestine  falling  to  the  right,  while  the  large  intestine  lies  on  the  left 
side.^ 

The  gut  now  becomes  rotated  upon  itself,  so  that  the  large  intestine  is  carried 
over  in  front  of  the  small  intestine,  and  the  cecum  is  placed  immediately  below 
the  liver;  about  the  sixth  month  the  cecum  descends  into  the  right  iliac  fossa,^ 
and  the  large  intestine  now  forms  an  arch  consisting  of  the  ascending,  transverse, 
and  descending  portions  of  the  colon — the  transverse  portion  crossing  in  front  of 
the  duodenum  and  lying  just  below  the  greater  curvature  of  the  stomach ;  within 
this  arch  the  coils  of  the  small  intestine  are  disposed  (Figs.  984  and  985).  The 
intestine  in  its  rotation  twists  the  mesentery  in  a  funnel-shaped  manner,  so  that 


Fig.  988. — Torsion  of  the  umbilical  loop. 
Initial  position.     (Jonnesco.) 


Fig.  989.— Torsion  of  the  umbilical  loop. 
Acquired  position.     (Jonnesco.) 


the  original  right  leaf  of  the  mesentery  of  the  small  intestine  has  become  the  left, 
and  vice  versa.  The  mesentery  of  the  small  intestine  assumes  the  oblique  attach- 
ment characteristic  of  its  adult  conditions.  All  divisions  of  the  large  intestine 
are  at  first  freely  movable,  being  suspended  by  a  free  mesocolon;  but  subsequently 
the  ascending  and  descending  portions  become  fixed  retroperitoneal  structures 
in  consequence  of  adhesion  of  the  opposed  surfaces  of  the  ascending  and  descending 
mesocolons  and  of  the  dorsal  parietal  peritoneum.  Occasionally  the  descending 
mesocolon,  more  rarely  the  ascending,  persists  so  that  the  bowel  is  more  or  less 
movable  in  these  divisions.  The  sigmoid  colon  usually  remains  mo^'able  through- 
out life. 

The  omental  bursa,  which  at  first  reaches  only  as  far  as  the  greater  curvature 
of  the  stomach,  grows  downward  as  a  double-layered,  pouch-like  fold,  the  interior 
layer  derived  from  the  right  leaf  of  the  primitive  mesogastrimn,  its  exterior  layer 
from  the  left  leaf.  This  omental  sac  or  greater  omentum  extends  downward  as  an 
apron-like  fold  in  front  of  the  transverse  colon  and  the  coils  of  the  small  intestine. 
The  anterior  layer  of  the  transverse  mesocolon  is  at  first  quite  distinct  from  the 

1  Sometimes  this  condition  persists  throughout  life,  and  it  is  then  found  that  the  duodenum  does  not  cross  from 
the  right  to  the  left  side  of  the  vertebral  column,  but  lies  entirely  on  the  right  side  of  the  mesal  plane,  where  it  is 
continued  into  the  jejunum;  the  arteries  to  the  small  intestine  (rami  intestini  tenuis)  also  arise  from  the  right  instead 
of  the  left  aide  of  the  superior  mesenteric  artery. 

2  Sometimes  the  downward  progress  of  the  cecum  is  arrested,  so  that  in  the  adult  it  may  be  found  lying  imme- 
diately below  the  liver  instead  of  m  the  right  iliac  region. 


5252 


THE  ORGANS  OF  DIGESTION 

Diaphragm 


Greater  curvature 
Anterior  lamella  of  greater  omentum . 
Posterior  lamella  of  greater  omentum 

2Ya7isverse  colon 


Greater  omentum 


'se  mesocolon 
Duodenum 


Small  intestine 


Fig.  990. — Illustrating  the  development  of  the  bursa  omentaHs,  cavity  of  the  greater  omentum  or  lesser  sac. 
Fetal  stage.     *  Lesser  sac.     (Hertwig.) 


Stomach 

Greater  curvature 

Posterior  lamella  of  greater  omentum 

Transverse  colon 


Greater  omentuv. 


Lesser  omentum 


Pancreas 

Part  of  omentum  enclosing  pane 

Transverse  mesocolon 

Duodenum 


Small  intestine 


Fig.  991- — Development  of  bursa  omentalis.     Infantile  stage.     Greater  omentum  covers  the  intestines  and  ha 
fused  with  the  transverse  mesocolon.     Pancreas  is  free  from  peritoneum  posteriorly.     (Hertwig.) 


^  I        Bursa  omentalis. 


Border  of  the 


Dorsal 
mesogastrium- 

2- Duodenum. 


Greater  omentum. 


Transverse  colon. 


Fig.  992. — Schematic  figure  of  the  bursa  omentalis.  etc.     Human  embryo  of  eight  weeks.     (Kollmann.l 


THE  PERITONEVM 


1253 


posterior  layer  of  the  bursa  omentalis,  but  ultimately  the  two  l)leiK],  and  hence  the 
greater  omentum  appears  as  if  attached  to  the  transverse  colon  (Figs.  990,  991, 
and  992). 

The  lesser  omentum  is  formed  by  a  thinning  of  the  mesoderm  (jf  the  ventral 
mesogastrium  which  attaches  the  stomach  and  part  of  the  duodenum  to  the  ventral 
abdominal  wall.  By  the  subsequent  growth  of  the  liver  this  leaf  is  divided  into 
two  parts — viz.,  the  falciform  and  coronary  ligaments  between  the  liver  and  the 
abdominal  wall  and  Diaphragm;  and  the  lesser  or  gastrohepatic  omentum,  be- 
tween the  liver  and  the  stomach. 


Ventral  mesofjasti  u( 


Fig,  093. — Abdominal  part  of  al 


uperior  mesenteric 
artery. 


Mesentery. 


mesenteric  artery. 


r:iTi:il  ;iiid  its  attachment  to  the  primitive  or  common  mesentery. 
il.iiu  (jf  six  weelcs.     (Kollmann.) 


Vertical  Disposition  of  the  Greater  Sac  (Fig.  995). — It  is  convenient  to  trace  the 
greater  sac  from  the  back  of,  the  abdominal  wall  at  the  level  of  the  umbilicus. 

On  following  the  parietal  peritoneum  upward  from  this  level  it  is  seen  to  be 
reflected  around  a  fibrous  cord,  the  ligamentum  teres  or  impervious  umbilical  vein 
(Figs.  998  and  1087),  which  reaches  from  the  umbilicus  to  tlie  under  surface  of 
the  liver.  This  reflection  forms  a  somewhat  triangular  fold,  the  falciform  or 
suspensory  ligament  of  the  liver  (ligamentum  falciforme  hepatis),  attaching  the 
upper  and  anterior  surfaces  of  the  liver  to  the  Diaphragm  and  abdominal  wall. 
With  the  exception  of  the  line  of  attachment  of  this  ligament  the  peritoneum 
covers  the  whole  of  the  under  surface  of  the  anterior  part  of  the  Diaphragm  and 
is  continued  from  it  on  to  the  upper  surface  of  the  right  lobe  of  the  liver  as  the 
superior  layer  of  the  coronary  ligament,  and  on  to  the  upper  surface  of  the  left 
lobe  as  the  superior  layer  of  the  left  lateral  ligament  of  the  liver.  Covering  the 
upper  and  anterior  surfaces  of  tiie  liver  it  is  continued  around  i^"  sharp  margin 
on  to  its  under  surface,  where  it  presents  the  following  relations:  (a)  It  covers 
the  under  surface  of  the  right  lobe  and  is  reflected  from  the  back  part  of  this  to 
the  upper  extremity  of  the  right  kidney,  forming  in  this  situation  die  inferior 
layer  of  the  coronary  ligament;  from  the  kidney  it  is  carried  downward  to  the  tluo- 
denum  and  hepatic  flexure  of  the  colon  and  inward  to  the  inferior  vena  cava. 


1254 


THE  ORGANS  OF  DIGESTION 


where  it  is  continuous  with  the  posterior  wall  of  the  lesser  sac.  Between  the  two 
layers  of  the  coronary  ligament"  there  is  a  triangular  surface  of  the  liver  which 
is  devoid  of  peritoneal  covering;  this  is  named  the  bare  area  of  the  liver,  and  is 
attached  to  the  Diaphragm  by  areolar  tissue.  Toward  the  right  margin  of  the 
liver  the  two  layers  of  the  coronary  ligament  gradually  approach  each  other,  and 
ultimately  fuse  to  form  a  small  triangular  fold  connecting  the  right  lobe  of  the 
liver  to  the  Diaphragm,  and  named  the  right  lateral  ligament  of  the  liver.     The 


Intel  lud  iiKimiicu 


OTll 

^upenoi  ^et,ital 
ai  te)  y 
(Idle  mgutiial, 
fossa 


Fig,  994. — Posterior  view  of  the  anterior  abdominal  wall  in  its  lower  half.     The  peritoneum  is  in  place, 
and  the  various  cords  are  shining  through.     (After  Joessel.) 

apex  of  the  triangular  bare  area  corresponds  to  the  point  of  meeting  of  the  two 
layers  of  the  coronary  ligament,  its  base  with  the  fossa  of  the  inferior  vena  cava. 
(b)  It  covers  the  lower  surface  of  the  quadrate  lobe,  the  under  and  lateral  surfaces 
of  the  gall-bladder,  and  the  under  surface  of  the  posterior  border  of  the  left  lobe; 
it  is  then  reflected  from  the  upper  surface  of  the  liver  to  the  Diaphragm  as  the 
inferior  layer  of  the  left  lateral  ligament,  and  from  the  transverse  fissure  and 
the  fissure  for  the  ligamentum  venosum  to  the  lesser  curvature  of  the  stomach  as 
the  anterior  layer  of  the  gastrohepatic,  or  lesser  omentum.  If  this  layer  of  the  lesser 
omentum  be  followed  to  the  right  it  will  be  found  to  turn  around  the  hepatic 
artery,  bile  duct,  and  portal  vein  and  become  continuous  with  the  anterior  wall  of 
the  lesser  sac,  forming  a  free  folded  edge  of  peritoneum. 

Traced  downward  it  covers  the  antero-superior  surface  of  the  stomach  and  the 
commencement  of  the  duodenum,  and  is  carried  down  from  the  greater  curvature 
of  the  stomach  into  a  large  free  fold,  the  gastrocolic  or  greater  omentum  (Figs.  996 
and  1002).  Reaching  the  free  edge  of  this  fold,  it  is  reflected  upward  to  cover 
the  under  and  posterior  surfaces  of  the  transverse  colon,  and  thence  to  the  pos- 


THE  PERITONEUM 


1 255 


terior  abdominal  wall  as  the  inferior  layer  of  the  transverse  mesocolon  fFif;.  995). 
It  reaches  the  abdominal  wall  at  the  upper  border  of  the  tliird  part  of  the  duo- 
denum, and  is  then  carried  down  on  the  superior  mesenteric  v-essels  to  the  small 
intestine  as  the  anterior  layer  of  the  mesentery.     It  encircles  the  intestine,  and 


Fig.  995. — Diagram  showing  the  vertical  disposition  of  the  peritoneum.     Lesser  sac  in  red;  greater 


subsequently  may  be  traced,  as  the  posterior  layer  of  the  mesentery,  upward  and 
backward  to  the  abdominal  wall.  From  this  it  sweeps  down  o^'er  the  aorta  into 
the  pelvis,  where  it  invests  the  sigmoid  colon,  its  reduplication  forming;  the  sigmoid 
mesocolon  (Fig.  1004).  Leaving  first  the  sides  and  then  the  front  of  the  rectum, 
it  is  reflected  on  to  the  base  of  the  bladder,  and,  after  covering  the  upper  surface 
of  that  viscus,  is  carried  along  the  urachus  and  impervious  hypogastric  arteries 
to  the  back  of  the  abdominal  wall,  from  which  a  start  was  made. 

Between  the  rectum  and  the  bladder  the  peritoneum  forms,  in  the  male,  a  pouch, 
the  rectovesical  pouch  (excavatio  rectovesicalis),  bounded  on  the  sides  by  two 
crescentic  or  semilunar  folds  (plicae  rectovesicales),  which  pass  from  the  posterior 
surface  of  the  bladder  to  the  sides  of  the  rectum;  the  bottom  of  this  pouch  is  about 
on  a  \e\e\  with  the  middle  of  the  seminal  vesicles — /.  e.,  three  inches  or  so  from 
the  orifice  of  the  anus.  When  the  bladder  is  distended  the  peritoneum  is  carried 
up  with  the  expanded  viscus,  so  that  a  considerable  part  of  the  anterior  surface 
of  the  latter  lies  directlv  against  the  abdominal  wall  without  the  intervention  of 


1256  THE  ORGANS  OF  DIGESTION 

the  peritoneal  membrane.  When  the  bladder  is  empty  the  peritoneum  forms 
a  transverse  fold  over  its  upper  surface  (plica  vesicalis  transversa). 

In  the  female  the  peritoneum  is  reflected  from  the  rectum  to  the  upper  part 
of  the  posterior  vaginal  wall,  forming  the  rectovaginal  pouch  or  pouch  of  Douglas 
(excavatio  rectouterina)  (Fig.  996) .  It  is  continued  over  the  posterior  surface 
and  fundus  of  the  uterus  on  to  its  anterior  surface,  which  it  covers  as  far  as 
the  junction  of  the  body  and  cervix  uteri,  forming  here  a  second  but  shallower 
depression,  the  uterovesical  pouch  (excavatio  vesicouferina).  It  is  also  reflected 
from  the  sides  of  the  uterus  to  the  lateral  wall  of  the  pelvis  on  each  side  as  two 
expanded  folds,  the  broad  ligaments  of  the  uterus  (ligamenta  lata  uteri),  in  the 
free  margin  of  each  of  which  is  the  Fallopian  tube. 

Vertical  Disposition  of  the  Lesser  Sac  (Fig.  995). — A  start  may  be  made  in  this 
case  on  the  posterior  abdominal  wall  above  the  pancreas.  From  this  region 
the  peritoneum  may  be  followed  upward  on  to  the  inferior  surface  of  the  Dia- 
phragm, and  thence  on  to  the  Spigelian  and  caudate  lobes  of  the  liver  to  the  fissure 
for  the  ligamentum  venosum  and  the  transverse  fissure;  this  cul-de-sac  is  the  Spige- 
lian recess.  Traced  laterally,  it  is  continuous  over  the  inferior  vena  cava  with  the 
posterior  wall  of  the  greater  sac.  From  the  liver  it  is  carried  downward  to  the 
lesser  curvature  of  the  stomach  as  the  posterior  layer  of  the  gastrohepatic  omentum, 
and  is  continuous  on  the  right,  around  the  hepatic  artery,  bile  duct,  and  portal  vein, 
with  the  greater  sac.  The  posterior  layer  of  the  gastrohepatic  omentum  is  carried 
down  to  the  greater  curvature  of  the  stomach  as  a  covering  for  the  postero-inferior 
surface  of  this  viscus,  and  from  the  greater  curvature  is  continued  downward 
as  the  deep  layer  of  the  greater  or  gastrocolic  omentum.  From  the  free  margin 
of  this  fold  it  is  reflected  upward  on  itself  to  the  anterior  and  superior  surfaces  of 
the  transverse  colon  and  thence  as  the  superior  layer  of  the  transverse  mesocolon 
to  the  upper  border  of  the  third  part  of  the  duodenum,  from  which  it  may  be 
followed  over  the  front  of  the  pancreas  to  the  level  at  which  a  start  was  made. 
It  will  be  seen  that  the  loop  formed  by  the  wall  of  the  lesser  sac  below  the  transverse 
colon  follows,  and  is  closely  applied  to,  the  deep  surface  of  that  formed  by  the 
greater  sac,  and  that  the  greater  omentum  or  large  fold  of  peritoneum  which  hangs 
in  front  of  the  small  intestine  therefore  consists  of  four  layers,  two  anterior  and 
two  posterior,  separated  by  the  potential  cavity  of  the  lesser  sac  though  inseparably 
blended,  as  a  rule,  in  the  adult. 

Horizontal  Disposition  of  the  Peritoneum. — Below  the  transverse  colon  the 
arrangement  is  extremely  simple,  as  it  includes  only  the  greater  sac  (Fig.  997) ; 
above  the  level  of  the  transverse  colon  it  is  more  complicated  on  account  of  the 
existence  of  the  two  sacs.  Below  the  transverse  colon  it  may  be  considered  in 
in  three  regions — ^viz.,  in  the  pelvis  and  in  the  abdomen  proper,  upper  and  lower 
portions. 

1.  7/1  the  Pelvis. — ^The  peritoneum  here  follows  closely  the  surfaces  of  the  pelvic 
viscera  and  the  irregularities  of  the  pelvic  walls  and  presents  important  differences 
in  the  two  sexes:  (a)  In  the  male  it  encircles  the  sigmoid  flexure,  from  which 
it  is  reflected  to  the  posterior  wall  as  a  fold,  the  sigmoid  mesocolon.  It  then 
leaves  the  sides  and,  finally,  the  front  of  the  rectum,  and  is  continued  to  the  bladder; 
on  either  side  of  the  rectum  it  forms  a  fossa,  the  pararectal  fossa,  which  varies  in 
size  with  the  distention  of  the  rectum.  In  front  of  the  rectum  the  peritoneum 
forms  the  rectovesical  pouch,  which  is  limited  laterally  by  peritoneal  folds  extending 
from  the  sides  of  the  bladder  to  the  rectum  and  sacrum.  These  folds  are  known 
from  their  position  as  the  rectovesical  or  sacrogenital  folds.  The  peritoneum  of 
the  anterior  pelvic  wall  covers  the  superior  surface  of  the  bladder,  and  on  either 
side  of  this  viscus  forms  a  depression,  termed  the  paravesical  fossa,  and  limited 
externally  by  the  fold  of  peritoneum  covering  the  vas  deferens.  The  size  of  this 
fossa  is  dependent  on  the  state  of  distention  of  the  bladder;  when  the  bladder  is 
empty,  a  variable  fold  of  peritoneum,  the  plica  vesicalis  transversa,  divides  the 


THE  PERITONEUM 


1257 


fossa  into  two  portions.  On  the  peritoneum  between  the  paravesical  and  para- 
rectal fossffi  the  only  elevations  are  those  produced  by  the  ureters  and  the  internal 
iliac  vessels.  (6)  In  the  female,  pararectal  and  paravesical  fosstB  similar  to  those 
in  the  male  are  present;  the  outer  limit  of  the  paravesical  fossa  is  the  peritoneum 
investing  the  round  ligament  of  the  uterus.     The  rectovesical  pouch  is,  however, 


LESSER  SSC 

-FORAMEN   OF 

WINSLOW 

WITH  ARROW 

PASSED 

Fig.  996. — Diagrammatic  mesal  section  of  the  female  body,  to  show  the  peritoneum  on  vertical  tracing.^  The 
greater  sac  of  the  peritoneum  is  black  and  is  represented  as  being  much  larger  than  in  nature;  the  lesser  sac  is  very 
darkly  shaded;  the  peritoneum  on  section  is  shown  as  a  white  line,  and  a  white  arrow  is  passed  through  the  fora 
men  of  Winslow  from  the  greater  into  the  lesser  sac.      (Cunningham.) 


divided  by  the  uterus  and  vagina  into  a  small  anterior  uterovesical  and  a  large, 
deep,  posterior  rectovaginal  pouch  or  pouch  of  Douglas.  The  sacrogenital  folds 
form  the  margins  of  the  latter,  and  are  continued  on  to  the  back  of  the  uterus  to 
form  a  transverse  fold,  the  torus  uterinus.  The  broad  ligaments  extend  from  the 
sides  of  the  uterus  to  the  lateral  walls  of  the  pelvis ;  they  contain  in  their  free  margins 
the  Fallopian  tubes,  and  on  their  posterior  surface  the  ovaries  attached  by  the 
mesovaria.  Below,  the  broad  ligaments  are  continuous  witn  the  peritoneum  on 
the  lateral  walls  of  the  pelvis.  On  the  lateral  pelvic  wall  behind  the  attachment 
of  the  broad  ligament,  in  the  angle  between  the  elevations  produced  by  tlie 
diverging  internal  and  external  iliac  vessels,  is  a  slight  if>ssa,  the  ovarian  fossa, 
in  which  the  ovary  normally  lies. 

2.  In  the  Lower  Abdomen  (Fig.  997). — Starting  from  the  linea  alba,  below  the 
level  of  the  transverse  colon,  and  tracing  the  continuity  in  a  horizontal  direction 
to  the  right,  the  peritoneum  covers  the  inner  surface  of  the  abdominal  wall  almost 
as  far  as  the  outer  border  of  the  Quadratus  lumborum;  it  encloses  the  cecum  and 
appendix,  and  is  reflected  over  the  sides  and  aiiterior  surface  of  the  ascending 
colon;  it  may  then  be  traced  over  the  Psoas  muscle  and  the  inferior  vena  cava 
toward  the  middle  line,  whence  it  passes  along  the  mesenteric  vesiels  to  invest 
the  small  intestine,  and  back  asain  to  the  laro-e  vessels  in  front  of  the  vertebral 


1258 


THE  ORGANS  OF  DIGESTION 


column,  forming  the  mesentery,  between  the  layers  of  which  are  contained  the 
mesenteric  bloodvessels,  nerves,  lacteals,  and  lymph  nodes.  It  is  then  continued 
over  the  left  Psoas  muscle;  it  covers  the  sides  and  anterior  surface  of  the  descending 
colon,  and,  reaching  the  abdominal  wall,  is  continued  on  it  to  the  middle  line. 
3.  In  the  Upper  Abdomen  (Fig.  998). — Above  the  transverse  colon  the  peri- 
toneum can  be  traced,  forming  the  greater  and  lesser  sacs,  and  their  communication 
through  the  foramen  of  Winslow  can  be  demonstrated. 


Mesentery   Aorta 


Mesocolon 
(imperject) 


Fig.  997. — Peritoneal  reflection  in  transverse  section  of  lumbar  region  below  the  tr; 
from  above.     Schematic.     (Tillaux.) 


(a)  Greater  Sac. — Commencing  on  the  posterior  abdominal  wall  at  the  inferior 
vena  cava,  the  membrane  may  be  followed  to  the  right  over  the  front  of  the  upper 
part  of  the  right  kidney  on  to  the  antero-lateral  abdominal  wall.  From  the  middle 
of  the  anterior  wall  a  backwardly  directed  fold  encircles  the  impervious  umbilical 
vein  and  forms  the  falciform  ligament  of  the  liver.  Continuing  to  the  left,  the 
peritoneum  lines  the  lateral  abdominal  wall  and  covers  the  outer  part  of  the  front 
of  the  left  kidney,  and  is  reflected  to  the  posterior  border  of  the  hilus  of  the  spleen 
as  the  posterior  layer  of  the  lienorenal  ligament  (Fig.  1001).  It  can  then  be  traced 
over  the  surface  of  the  spleen  to  the  front  of  the  hilus,  and  thence  to  the  cardiac 
extremity  of  the  stomach  as  the  anterior  layer  of  the  gastrosplenic  omentum.  It 
covers  the  antero-superior  surface  of  the  stomach  and  first  part  of  the  duodenum 
and  extends  up  from  the  lesser  curvature  of  the  stomach  to  the  liver,  the  latter 
portion  forming  the  anterior  layer  of  the  gastrohepatic  omentum. 

(b)  Lesser  Sac. — On  the  posterior  abdominal  wall  the  peritoneum  of  the  greater 
sac  is  continuous  with  that  of  the  lesser  sac  in  front  of  the  inferior  vena  cava. 
Starting  from  here,  the  lesser  sac  maybe  traced  across  the  aorta  and  over  the  inner 
part  of  the  front  of  the  left  kidney  to  the  hilus  of  the  spleen  as  the  anterior  layer 
of  the  lienorenal  ligament.  From  the  spleen  it  is  reflected  to  the  stomach  as  the 
posterior  layer  of  the  gastrosplenic  omentum.  It  covers  the  postero-inferior 
surfaces  of  the  stomach  and  commencement  of  the  duodenum,  and  from  the 
lesser  curvature  of  the  stomach  extends  upward  to  the  liver  as  the  posterior  layer 
of  the  gastrohepatic  omentum;  the  right  margin  of  this  layer  is  continuous  around 
the  hepatic  artery,  bile  duct,  and  portal  vein  with  the  wall  of  the  greater  sac. 

The  foramen  of  Winslow  (foramen  epiploicum)  is  the  passage  of  communication 


THE  PERITONEUM 


1259 


between  the  greater  and  lesser  sacs.  It  is  bounded  in  front  by  the  free  border 
of  the  gastrohepatic  omentum,  with  the  hepatic  artery,  common  bile  duct,  and 
portal  vein  between  its  two  layers;  behind  by  the  peritoneum  covering  the  inferior 
vena  cava;  above  by  the  peritoneum  on  the  caudate  lobe  of  the  liver,  and  heloio 
by  the  peritoneum  covering  the  commencement  of  the  duodenum  and  the  hepatic 
artery,  the  latter  passing  forward  below  the  foramen  before  ascending  between  the 
two  layers  of  the  gastrohepatic  omentum  (Fig.  998). 


Lig.  teres 


Common  bite  duct 


Inferior  Vena  Cava 


Fig.  998.^ — Transverse  section  of  peritoneum  above  the  transverse  colon.     The  arrow  points  to  the  lesser 
sac  and  passes  through  the  foramen  of  Winslow. 


The  boundaries  of  the  lesser  sac  will  now  be  evident.  It  is  bounded  in  front, 
from  above  downward,  by  the  Spigelian  lobe  of  the  liver,  the  gastrohepatic  omen- 
tum, the  stomach,  and  the  anterior  two  layers  of  the  greater  omentum;  behind,  it 
is  limited,  from  below  upward,  by  the  two  posterior  layers  of  the  greater  omentum, 
the  transverse  colon,  and  the  ascending  layer  of  the  transverse  mesocolon,  the 
upper  surface  of  the  pancreas,  the  left  suprarenal  gland,  and  the  upper  end  of 
the  left  kidney.  Laterally,  the  lesser  sac  extends  from  the  foramen  of  Winslow 
to  the  spleen  {recessus  lienalis)  (Fig.  1001),  where  it  is  limited  by  the  lienorenal 
ligament  and  the  gastrosplenic  omentum. 

In  the  fetus  the  lesser  sac  reaches  as  far  as  the  free  margin  of  the  great  omentum, 
but  in  the  adult  its  vertical  extent  is  usually  more  limited,  owing  to  adhesions 
between  the  layers  of  the  omentum.  It  should  be  stated  that  during  a  consider- 
able part  of  fetal  life  the  transverse  colon  is  suspended  from  the  posterior  abdomi- 
nal wall  by  a  mesentery  of  its  own — the  two  posterior  layers  of  the  greater  omen- 
tum passing,  at  this  stage,  in  front  of  the  colon  (Fig.  990).  This  condition  some- 
times persists  throughout  adult  life,  but,  as  a  rule,  adhesion  occurs  between  the 
mesentery  of  the  transverse  colon  and  the  posterior  layer  of  the  greater  omentum, 
with  the  result  that  the  colon  appears  to  receive  its  peritoneal  co\ering  by  the 
splitting  of  the  two  posterior  layers  of  the  latter  fold.  In  the  adult  the  lesser  sac 
intervenes  between  the  stomach  and  the  structures  on  which  that  viscus  lies,  and 
performs,  therefore,  the  functions  of  a  serous  bursa  for  the  stomach. 

Numerous  peritoneal  folds  extend  between  the  various  organs  or  connect  them 
to  the  parietes.     They  serve  to  hold  them  in  position,  and,  at  the  same  time, 


1260 


THE  ORGANS  OF  DIGESTION 


enclose  the  vessels  and  nerves  proceeding  to  them.  Some  of  these  folds  which 
connect  certain  viscera  with  the  parietes  are  called  ligaments,  such  as  the  ligaments 
of  the  liver  and  the  false  ligaments  of  the  bladder.  Others,  which  connect  certain 
parts  of  the  intestine  with  the  abdominal  wall,  constitute  the  mesenteries;  and 
lastly,  those  which  proceed  from  the  stomach  to  certain  viscera  in  its  neighborhood 
are  called  omenta. 

The  ligaments,  formed  by  folds  of  the  peritoneum,  include  those  of  the  liver, 
spleen,  bladder,  and  uterus.  They  will  be  found  described  with  their  respective 
organs. 

The  omenta  are  the  lesser  omentum,  the  greater  omentum,  and  the  gastrosplenic 
omentum. 

The  lesser  or  gastrohepatic  omentum  (omentum  minus)  (Figs.  996  and  999)  is 
the  duplicature  which  extends  between  the  transverse  fissure  of  the  liver  and  the 
right  side  of  the  abdominal  portion  of  the  oesophagus,  the  lesser  curvature  of  the 
stomach,  and  the  upper  portion  of  the  superior  surface  of  the  duodenum. 


Papillayy  tubercle 


Cut  edge  of  peritoneum 


Cut  edge  of  pei  itoneum 


Fig.  999. — Bursa  omentalis,  or  lesser  sac,  opened  from  the  front  by  an  incision  through  the  gastrocolic  omen- 
tum.    A  probe  passes  through  the  foramen  of  Winslow  and  rests  on  the  gastropancreatic  fold.     (Hecle.) 


The  portion  going  to  the  oesophagus  and  stomach  is  called  the  hepatogastric  ligament  (/1,9a- 
mentum  hepatogastricum) .  The  division  of  the  ligament  which  goes  to  the  oesophagus  is  strong 
and  dense;  the  division  which  goes  to  the  lesser  curvature  of  the  stomach  is  thin  and  relaxed. 
The  portion  of  the  lesser  omentum  which  goes  to  the  duodenum  is  continuous  with  the  first- 
named  portion.  It  is  called  the  hepatoduodenal  ligament  (Hgamentinn  hcpatoditodenale). 
The  right  margin  of  this  ligament  is  free  and  concave.  The  hepatocolic  Ugament  (ligavientwn 
hepatocolicum  is  not  invariably  present.  It  is  a  fold  of  the  hepatoduodenal  ligament  and  runs 
from  the  posterior  surface  of  the  gall-bladder  to  the  descending  portion  of  the  duodenum  or 
possibly  to  the  transverse  colon. 

The  lesser  omentum  is  thin,  and  is  continuous  with  the  two  layers  which  cover 
respectively  the  anterior  and  posterior  surfaces  of  the  stomach.  ^Vhen  the  two 
layers  reach  the  lesser  curvature  of  the  stomach,  they  join  and  ascend  as  the  double 


THE  PERITONEUM 


1261 


fold  to  the  transverse  or  portal  fissure  of  the  liver;  to  the  left  of  this  fissure  the  double 
fold  is  attached  to  the  bottom  of  the  fissure  for  the  ligamentum  venosum,  along 
which  it  is  carried  to  the  Diaphragm,  where  the  two  layers  separate  to  embrace  the 
end  of  the  oesophagus.  At  the  right  border  the  two  layers  are  continuous  and  form 
a  free  margin  which  constitutes  the  anterior  boundary  of  the  foramen  of  Winslow. 
Between  the  two  layers,  close  to  this  free  margin,  are  the  hepatic  artery,  the  com- 
mon bile  duct,  the  portal  vein,  lymphatics,  and  the  hepatic  plexus  of  nerves  (Fig.  1000) 
— all  these  structures  being  enclosed  in  loose  areolar  tissue  which  is  continuous 
with  Glisson's  capsule.  Between  the  layers  where  they  are  attached  to  the 
stomach  lie  the  gastric  artery  and  the  pyloric  branch  of  the  hepatic  artery. 

The  greater  or  gastrocolic  omentum  {omentum  majtis)  (Figs.  996  and  1002)  is  the 
largest  peritoneal  fold.  It  consists  of  a  double  sheet  of  peritoneum,  folded  on 
itself  so  that  it  is  made  up  of  four  layers.  The  two  layers  which  descend  from  the 
stomach  pass  in  front  of  the  small  intestines,  sometimes  as  low  down  as  the  pelvis; 
they  then  turn  upon  themselves,  and  ascend  again  as  far  as  the  transverse  colon, 
where  they  separate  and  enclose  that  part  of  the  intestine.  These  separate  layers 
may  be  easily  demonstrated  in  the  young  subject,  but  in  the  adult  they  are  morev 


CYSTIC  DUCT 


FREE  EDG 
OF  LESSE 
OMENTU 


PANCREATIC  DUCT 


IGHT  GASTRO- 
PIPLOIC  ARTERY 
SUPERIOR  PANCREATICO' 
DUODENAL  ARTERY 


Fig.  1000. — Structures  between  the  layers  of  the  lesser  omentum.     The  liver  has  been  raised  up,  and  the  anterior 
layer  of  the  omentum  removed.     Semidiagrammatic.     (Cunningham.) 


or  less  inseparably  blended.  The  left  border  of  the  greater  omentum  is  continuous 
with  the  gastrosplenic  omentum;  its  right  border  extends  only  as  far  as  the  duo- 
denum. The  greater  omentum  is  usually  thin,  presents  a  cribriform  appearance, 
and  always  contains  some  adipose  tissue,  which  in  fat  persons  accumulates  in 
considerable  quantity.  Between  its  two  anterior  layers  is  the  anastomosis 
between  the  right  and  left  gastroepiploic  arteries.  In  opening  the  abdomen  the 
greater  omentum  is  rarely  found  spread  out  evenly  over  the  intestines.  It  often 
projects  between  intestinal  coils,  or  is  largely  gathered  in  some  one  region,  or  is 
pushed  in  front  of  the  stomach  by  distention  of  the  colon. 

The  gastrosplenic  omentimi  is  the  fold  which  connects  the  margins  of  the  hilum 
of  the  spleen  to  the  stomach,  being  continuous  by  its  lower  border  with  the  greater 
omentum.     It  contains  the  vasa  brevia. 


1262 


THE  ORGANS  OF  DIGESTION 


RENAL  SURFACE 

POUCH   OF  GREATER  SAC 

LIENORENAL    L'.GAWENT 

PHRENIC  SURFACE 

GASTROSPLENIC 

OMENTUM 

POUCH   OF  GREATEP  SAC 

GASTRIC  S'iRFACE 


Fig.  1001.— Horizontal  section  through  the  stomach,  pancreas,  spleen,  and  the  left  kidney  to  show  peritoneal  reflec- 
tions at  the  hilum  of  the  spleen.     (G.  S.  H.) 


Fig.  1002. — The  greater  omentum  as  seen  from  the  front.     (Testut.) 


THE  PERITONEUM 


1263 


mesocolon,  and  the  mesentery  of  the  vermiform  appendix.     In  addition  to  these 
there  are  sometimes  present  an  ascending  and  a  descending  mesocolon. 

The  mesentery  (mesenterium)   (Figs.  1003  and  1004),  is  the  broad,  fan-shaped 
fold  of  peritoneum  which  connects  the  convolutions  of  the  jejunum  and  ileum  with 


^Duodenum 


Soot  of  meseii    ^ 

tery  ^   t- 


Sigmoid  Jiexin  r 
Ceciim 


Fig.  1003. — Mesentery.     Small  intestine  pushed  upward  to  the  right      l,Tiilau\ ) 

the  posterior  wall  of  the  abdomen.  Its  root  (radix  mesenterii),  the  part  connected 
with  the  structures  in  front  of  the  vertebral  column,  is  narrow,  about  six  inches 
in  length,  and  directed  obliquely  from  the  left  side  of  the  second  lumbar  vertebra 
to  the  right  iliac  fossa  (Fig.  1004).  Its  intestinal  border  is  about  twenty  feet  in 
length,  and  here  the  two  layers  separate  so  as  to  enclose  the  intestine  and  form  its 
peritoneal  coat.  Its  breadth,  between  its  vertebral  and  intestinal  border,  is  about 
eight  inches.  Its  upper  border  is  continuous  with  the  under  surface  of  the  trans- 
verse mesocolon;  its  lower  border,  with  the  peritoneum  covering  the  cecum  and 
ascending  colon.  It  serves  to  retain  the  small  intestines  in  their  position,  and 
contains  between  its  layers  the  mesenteric  vessels  and  nerves,  the  lymphatic  vessels, 
and  mesenteric  lymph  nodes.  These  nodes  number  from  50  to  150.  The  mesentery 
is  somewhat  translucent,  particularly  at  its  upper  part,  but  in  stout  individuals 
it  becomes  opaque  on  account  of  the  fat  deposited  between  its  layers. 

In  most  cases  the  peritoneum  covers  only  the  front  and  sides  of  the  ascending 


1264 


THE  ORGANS  OF  DIGESTION 


and  descending  parts  of  the  colon.  Sometimes,  however,  these  are  surrounded  by 
the  serous  membrane  and  attached  to  the  posterior  abdominal  wall  by  an  ascending 
mesocolon  {mesocolon  ascendens)  and  a  descending  mesocolon  {mesocolon  descendens) 
respectively.  At  the  place  where  the  transverse  colon  turns  downward  to  form  the 
descending  colon,  a  fold  of  peritoneum  is  continued  to  the  under  surface  of  the 
Diaphragm  opposite  the  tenth  and  eleventh  ribs.  This  is  the  phrenocolic  ligament 
{ligamenhim  lihrenicocolicum) ;  it  passes  below  the  spleen,  and  serves  to  support 
this  organ,  and  therefore  it  has  received  the  name  of  sustentaculum  lienis. 


Peritoneum. 
Extraperitoneal  t 


Diaphragmatic  end  of 
gastrohepatic  omeittun 
Gastrophrenic  ligament. 


5  Bare  surface  for  2nd  pan 
5  Left  lateral  false  liga- 


leaves  the  wall  of  the 


The  transverse  mesocolon  {mesocolon  transversum)  (Fig.  1004)  is  a  broad  fold 
which  connects  the  transverse  colon  to  the  posterior  wall  of  the  abdomen.  It  is 
formed  by  the  two  posterior  layers  of  the  greater  omentum,  which,  after  separating 
to  surround  the  transverse  colon,  join  behind  it,  and  are  continued  backward  to  the 
vertebral  column,  where  they  diverge  in  front  of  the  anterior  border  of  the  pancreas. 
This  fold  contains  between  its  layers  the  vessels  which  supply  the  transverse  colon. 

The  sigmoid  mesocolon  {mesocolon  sigmoidciim)  (Fig.  1004)  is  the  fold  of  peri- 
toneum which  retains  the  sigmoid  flexure  in  connection  with  the  pelvic  wall. 
Its  line  of  attachment  forms  a  V-shaped  curve,  the  apex  of  the  curve  being  placed 


THE  PERITONEUM 


1265 


about  the  point  of  division  of  the  left  common  iliac  artery.  The  curve  begins 
on  the  inner  side  of  the  left  Psoas,  and  runs  upward  and  backward  to  the  apex, 
from  \\hich  it  bends  sharply  downward  and  inward,  and  ends  in  the  mesal  ]5lane 
at  the  level  of  the  third  sacral  segment.  Between  the  two  layers  of  this  fold  run 
the  sigmoid  and  superior  hemorrhoidal  vessels. 


Fig.  1005. — Superior  and  inferior  duodenal  fossse.     (Po 


»RTEHy 

■  and  Cliarpy.) 


The  mesoappendix  or  mesentery  of  the  vermiform  appendix  (mesenteriolmn  pro- 
cessus vermiformis)  (Fig.  1008)  is  a  double  fold  of  peritoneum  derived  from  the 
left  leaf  of  the  mesentery.  In  the  majority  of  cases  it  is  triangular  in  shape  and 
usually  extends  along  the  entire  length  of  the  appendix.  Between  its  two  layers 
lie  the  appendicular  artery  (Fig.  1055),  a  branch  of  the  ileocolic  artery,  some 
connective  tissue,  and  lymph  vessels  and  nerves. 

The  appendices  epiploicae  are  small  pouches  of  the  peritoneum  filled  with  fat 
.and  situated  along  the  colon  and  upper  part  of  the  rectum.  They  are  chiefly 
appended  to  the  transverse  colon. 

Retroperitoneal  Fossae. — In  certain  parts  of  the  abdominal  cavity  there  are 
recesses  of  peritoneum  forming  culs-de-sac  or  pouches,  which  are  of  surgical  inter- 
est in  connection  with  the  possibility  of  the  occurrence  of  retroperitoneal  hernia. 
One  of  these  is  the  lesser  sac  of  the  peritoneum  (Figs.  996  and  998),  which  may  be 
regarded  as  a  recess  of  peritoneum  through  the  foramen  of  Winslow,  in  which 
a  hernia  may  take  place,  but  there  are  several  others,  of  smaller  size,  which  require 
mention. 

These  recesses,  or  fossse,  may  be  divided  into  three  groups — viz. :  (1)  the  duodenal 
fossae;  (2)  pericecal  fossae;  and  (3)  the  intersigmoid  fossa. 

1.  Duodenal  Folds  and  Fossse. — Moynihan  has  described  no  less  than  nine  fossae 
as  occurring  in  the  neighborhood  of  the  duodenum.  Three  of  these  are  fairly 
constant.  Five  of  the  fossae  are  here  considered:  (a)  The  inferior  duodenal 
fossa,  or  fossa  of  Treitz  (Fig.  1005),  is  the  most  constant  of  all  the  peritoneal  fossse 
in  this  region,  being  present  in  from  70  to  75  per  cent,  of  cases.  It  is  situated 
opposite  the  third  lumbar  vertebra  on  the  left  side  of  the  ascending  portion  of  the 
duodenum.  Its  opening  is  directed  upward,  and  is  boimded  by  a  thin,  sharp 
fold  of  peritoneum  with  a  concave  free  upper  margin,  called  the  inferior  duodenal 
fold  {plica  duodenomesocolica) .  The  tip  of  the  index  finger  introduced  into  the 
fossa  under  the  fold  passes  some  little  distance  behind  the  ascending  or  fourth 
portion  of  the  duodenum,  (b)  The  superior  duodenal  fossa  (Fig.  1005)  is  the  next 
most  constant  pouch  or  recess,  being  present  in  from  40  to  50  per  cent,  of  cases. 
It  often  coexists  with  the  inferior  one,  and  its  orifice  looks  downward,  in  the  oppo- 
site direction  to  the  preceding  fossa.     It  lies  to  the  left  of  the  ascending  portion 


1266 


THE  ORGANS  OF  DIGESTION 


of  the  duodenum.     It  is  bounded  by  the  free  edge  of  the  superior  duodenal  fold 

(plica  duodenojejunalis),  which  presents  a  semihinar  margin;  to  the  right  it  is 
blended  with  the  peritoneum  covering  the  ascending  duodenum,  and  to  the  left 
with  the  peritoneum  covering  the  perirenal  tissues.  The  fossa  is  bounded  in 
front  by  the  superior  duodenal  fold;  behind  by  the  second  lumbar  vertebra;  to 
the  right  by  the  duodenum,  (c)  The  duodenojejunal  fossa  or  mesocolic  fossa 
(recessus  duodenojejunalis)  is  formed  where  the  duodenojejunal  angle  enters  the 
root  of  the  transverse  mesocolon.  There  are  two  forms:  (1)  a  single  fossa  and  (2) 
a  double  fossa.  It  can  be  seen  by  pulling  the  jejunum  downward  and  to  the  right 
after  the  transverse  colon  has  been  pulled  upward.  It  will  appear  as  an  almost 
circular  opening,  looking  downward  and  to  the  right,  and  bounded  by  two  free 
borders  or  folds  of  peritoneum,  the  duodenomesocolic  ligaments.     The  opening 


DUODENUM- 


RIGHT  DUODENO- 

MESOCOLrC 

LIGAMENT 


INFERIOR   MESEN- 
TERIC ARTERY 

Fig.  1006. — Duodenojejunal  fossa.     (Poirier  and  Charpy.) 

admits  the  little  finger  into  the  fossa  to  the  depth  of  from  four-fifths  to  one  and  one- 
fifth  inches,  or  2  to  3  cm.  The  fossa  is  bounded  above  by  the  pancreas,  to  the  right 
by  the  aorta,  and  to  the  left  by  the  kidney;  beneath  is  the  left  renal  vein.  The 
fossa  exists  in  from  15  to  20  per  cent,  of  cases,  and  has  never  yet  been  found 
in  conjunction  with  any  other  form  of  duodenal  fossa,  (d)  Paraduodenal  fossa  or 
the  fossa  of  Landzert  (recessus  duodenojejunalis)  is  most  distinct  in  the  infant, 
and  is  to  the  left  of  the  ascending  portion  of  the  duodenum.  The  fold  of  peri- 
toneum to  its  outer  side  and  above  is  produced  by  the  inferior  mesenteric  vein. 
Its  lower  limit  is  a  fold  called  the  mesentericomesocolic  fold,  (e)  The  retro- 
duodenal  fossa  (Fig.  996)  was  described  in  1893  by  Jonnesco.  It  is  a  peritoneal 
cul-de-sac,  sometimes  found  behind  the  horizontal  and  ascending  portions  of  the 
duodenum. 

2.  Pericecal  Folds  and  Fossae. — There  are  at  least  three  pouches  or  recesses  to  be 
found  in  the  neighborhood  of  the  cecum,  which  are  termed  pericecal  fossae.  (1) 
The  ileocolic  fossa  or  superior  ileocecal  {recessus  ileocecalis  superior)  (Fig.  1007) 
is  formed  by  a  fold  of  peritoneum,  the  ileocolic  fold,  arching  over  the  branch  of 
the  ileocolic  artery  which  supplies  the  ileocolic  junction.     The  fossa  is  a  narrow 


THE  PERITONEUM 


1267 


chink  situated  between  the  ileocolic  fold  in  front,  and  the  mesentery  or  the  small 
intestine,  the  ileum,  and  a  small  portion  of  the  cecimi  behind.  (2)  The  ileocecal 
or  ileoappendicular  fossa  {recessiis  ileocecalis  inferior)  (Fig.  1007)  is  situated  behind 
the  angle  of  junction  of  the  ileum  and  cecum.  It  is  formed  by  a  fold  of  peri- 
toneum, the  ileocecal  fold  (plica  ileocecalis),  or  "bloodless  fold"  of  Treves,  the 
upper  border  of  which  is  attached  to  the  ileum,  opposite  its  mesenteric  attach- 
ment, while  the  lower  border,  passing  over  the  ileocecal  junction,  joins  the 
mesentery  of  the  appendix,  and  sometimes  the  appendix  itself;  hence  this  fold 
is  sometimes  called  the  ileoappendicular  fold.  Between  this  fold  and  the  mesen- 
tery of  the  vermiform  appendix  is  the  inferior  ileocecal  fossa.  It  is  bounded  above 
by  the  posterior  surface  of  the  ileum  and  the  mesentery;  in  front  and  below  by  the 
ileocecal  fold  and  behind  by  the  upper  part  of  the  mesentery  of  the  appendix. 
(3)  The  retrocecal  or  subcecal  fossa  {recessns  retrocecalis)  (Fig.  1008)  is  situated 


^fcs&    \%        ^Epiploic  appendages. 

/Ileocolic  fold. 

Superior  ileocecal 
recess. 

Inf(7ior  ileocecal 
Jossa 


Cecal  fold 


Retrocecal  recess.        Ileocecal  fold. 

Fia.  1007.— The  pericecal  folds  and  foss: 


behind  the  cecum,  which  has  to  be  raised  to  bring  the  fossa  into  view.  It  varies 
much  in  size  and  extent.  In  some  cases  it  is  sufficiently  large  to  admit  the  index 
finger  and  extends  upward  behind  the  ascending  colon  in  the  direction  of  the  kidney ; 
in  others  it  is  merely  a  shallow  depression.  It  is  bounded  and  formed  by  two  folds: 
one,  the  external  parietocolic  fold,  or  the  superior  cecal  fold,  which  is  attached  by 
one  edge  to  the  abdominal  wall  from  the  lower  border  of  the  kidney  to  the  iliac 
fossa  and  by  the  other  to  the  postero-external  aspect  of  the  colon;  and  the  other, 
the  inferior  cecal  or  mesentericoparietal  fold,  which  is  in  reality  the  insertion  of  the 
mesentery  into  the  iliac  fossa.  In  some  instances  the  subcecal  fossa  is  double. 
3.  The  intersigmoid  fossa  {recessns  intersigmoideus)  is  constant  in  the  fetus 
and  common  during  infancy,  but  disappears  in  a  large  percentage  of  cases  as  age 
advances.  Upon  drawing  the  sigmoid  flexure  upward,  the  left  surface  of  the  sig- 
moid mesocolon  is  exposed,  and  on  it  will  be  seen  a  funnel-shaped  recess  of  the 
peritoneum,  lying  on  the  external  iliac  vessels,  in  the  interspace  between  the 
Psoas  and  Iliacus  muscles.  This  is  the  orifice  leading  to  the  fossa  intersigmoidea, 
which  lies  behind  the  sigmoid  mesocolon,  and  in  front  of  the  parietal  peritoneum. 
The  fossa  varies  in  size;  in  some  instances  it  is  a  mere  dimple,  whereas  in  others 
it  will  admit  the  whole  of  the  index  finger. 


1268 


THE  ORGANS  OF  DIGESTION 


Any  of  these  fossse  may  be  the  site  of  a  retroperitoneal  hernia.  The  pericecal 
fossae  are  of  especial  interest,  because  hernia  of  the  vermiform  appendix  frequently 
takes  place  into  one  of  them,  and  may  there  become  strangulated.  The  presence 
of  these  pouches  also  explains  the  course  which  pus  has  been  known  to  take  in 
cases  of  perforation  of  the  appendix,  where  it  travels  upward  behind  the  ascend- 
ing colon  as  far  as  the  Diaphragm.^ 

Applied  Anatomy. — Study  of  the  peritoneum  by  Robinson  and  others  shows  that  absorption 
takes  place  more  rapidly  from  the  region  of  the  Diaphragm,  less  rapidly  but  still  very  actively  from 
the  region  of  the  small  intestine,  slowly  from  the  pelvic  region.     Clinically  we  know  that  pelvic 


ILEO -APPENDICULAR 
MESO-APPENDIX 


Fig.  1008.— The  retr. 


al  fossa.     The  ileum  and  i 


'.  drawn  backward  and  upward.     (Souligoux.) 


peritonitis  is  not  nearly  so  dangerous  as  peritonitis  in  the  small  intestine  or  Diaphragm  areas,  and 
that  peritonitis  in  the  region  of  the  Diapliragm  is  the  most  fatal  form  of  the  infection.  After 
abdominal  operations  in  infected  cases,  it  is  well  to  elevate  the  head  of  the  bed  (Fowler's  position), 
so  as  to  obtain  the  aid  of  gravity  in  draining  septic  fluids  away  from  the  dangerous  region  and 
toward  the  safer  region.'  In  areas  in  which  absorption  is  rapid,  protective  exudation  is  not  apt  to 
form.  In  areas  in  which  absorption  is  slow,  inflammatory  exudation  is  apt  to  circumscribe  the 
area  and  prevent  diffusion.  After  an  operation  in  a  noninfected  case,  if  salt  solution  has  been 
left  in  the  abdominal  cavity  because  of  shock  or  hemorrhage,  raising  the  foot  of  the  bed  will  aid 
rapid  absorption  of  the  fluid  by  favoring  the  natural  current  toward  the  Diaphragm  and  hurrying 
the  fluid  to  a  region  in  which  absorption  is  rapid.  Dr.  John  B.  Murphy's  plan  of  treating  general 
peritonitis  has  proved  remarkably  successful.  He  does  not  remove  the  exudation  of  lymph  which 
is  seen  upon  the  peritoneum.  This  exudation  is  conservative,  blocks  up  lymph  spaces,  and  lessens 
the  absorption  of  dangerous  toxins.  He  inserts  a  drainage  tube  into  the  peritoneal  cavity  above 
the  pubes,  puts  the  patient  erect  or  semierect  in  bed  (Fowler's  position),  and  administers  salt 
solution  continuously  by  low  pressure  proctolysis.  According  to  Murphy,  the  lymph  circulation 
is  reversed  and  the  peritoneum  becomes  a  secreting  surface.  Certain  it  is  that  the  salt  solution 
absorbed  from  the  rectum  reaches  the  peritoneal  cavity  in  large  amounts  and  flows  out  of  the 
drainage  tube. 

The  greater  omentum  stores  up  fat,  and,  being  movable,  it  is  able  to  pass  to  diff'erent  parts  ot 
the  peritoneal  cavity.  Dr.  Robinson,  in  his  work  on  the  Peritoneum,  describes  its  functions  as 
follows:  "The  omentum  is  the  great  protector  against  peritoneal  infectious  invasions.  It  builds 
barriers  of  exudates  to  check  infection.  It  is  like  a  man-of-war,  ready  at  a  moment's  notice  to 
move  to  invaded  parts.     It  circumscribes  abscesses,  it  repairs  visceral  wounds,  and  prevents 


1  On  the  anatomy  of  these  fossae,  see  the  Arris  and  Gale  Lecturi 

2  George  R.  Fowler,  in  Medical  Record,  April  14,  1900. 


i  by  Moynihan.  1899. 


THE  PERITONEUM  1269 

adhesions  of  mobile  viscerca  to  the  anterior  abdominal  wall.  It  resists  infectious  invasions  by 
typical  peritoneal  exudates,  and  not  by  succumbing  to  absorbed  sepsis.  It  is  a  director  of  peri- 
toneal fluids,  a  peritoneal  drain." 

In  abdominal  wounds  the  greater  omentum  often  protrudes.  This  structure  frequently  con- 
stitutes or  is  part  of  a  hernia,  and  is  almost  invariably  present  in  umbilical  hernia.  As  a  result 
of  inflammation,  it  may  become  adherent  to  adjacent  structures.  Adhesions  may  be  of  service 
by  matting  together  the  intestines  and  circumscribing  infections.  They  may  be  harmful  by 
constricting  the  bowels  and  producing  oljstruction.  A  portion  of  the  omentum  may  become 
adherent  to  some  other  part  and  form  a  band,  and  under  this  band  the  gut  may  be  caught  and 
stranqidated.  The  omentum  may  adhere  to  and  plug  a  perforation  in  a  hollow  viscus,  and  the 
surgeon  may  utilize  it  for  the  same  purpose,  or  to  cover  a  raw  surface  or  overlie  a  suture  line. 
The  omentum  may  be  in  the  sm-geon's  way  while  operating.  If  it  is,  the  patient  is  placed  in 
the  Trendelenburg  position  (pelvis  elevated). 

Any  tear  or  opening  found  by  the  surgeon  in  the  greater  omentum  must  be  closed  with  sutures, 
because  of  the  danger  that  intestine  might  enter  and  be  caught  in  such  an  opening.  A  tumor 
cut  off  from  its  proper  blood  supply,  for  instance,  an  ovarian  cyst  with  a  twisted  pedicle,  may 
continue  to  receive  nourishment  from  adherent  omentum,  and  gangrene  may  thus  be  prevented. 

The  lax  character  and  sliiriing  Icndency  of  the  subserous  tissue  explains  the  occurrence  of 
■ptosis  of  the  abdominal  viscera  and  kiihieijs. 

The  vast  number  of  nerves  in  the  peritoneum  accounts  for  the  profound  shock  which  follows 
a  wound,  attends  an  intraperitoneal  calamity,  or  which  develops  from  infection.  An  infective 
process  of  any  portion  of  the  peritoneum  produces  pain  and  reflex  symptoms  (vomiting,  ab- 
dominal rigidity,  intestinal  paresis,  etc.). 

The  parietal  peritoneum  is  very  sensitive  to  pain,  but  not  to  touch;  hence,  after  injecting  a 
local  anesthetic  and  opening  the  abdomen,  a  fairly  satisfactory  exploration  can  be  made  with 
the  finger. 

The  intestine,  the  mesentery,  the  stomach,  the  anterior-  margin  of  the  liver,  and  the  gall-bladder 
are  insensitive,  and  may  be  cut  or  even  burned  without  pain.i  Viscera  which  obtain  their  inner- 
vation purely  from  visceral  nerves  are  insensitive;  those  which  receive  branches  from  somatic 
nerves  are  sensitive  (Lennander). 

The  oblique  origin  of  the  mesentery  causes  this  structure  to  form  a  sort  of  shelf.  A  hemor- 
rhage or  extravasation  into  the  abdomen,  to  the  right  of  the  mesentery,  tends  to  flow  into  the 
right  iliac  fossa;  one  occurring  on  the  left  side  flows  into  the  pelvis.  Monks  shows  how  the 
mesentery  can  be  utilized  to  determine  the  direction  of  an  intestinal  loop: 

"Now,  let  us  suppose  that  the  surgeon  has  between  his  fingers  a  loop  of  bowel,  and  wishes 
to  determine  its  direction.  He  knows  that  one  side  of  the  loop  is  the  left  side  of  the  intestine, 
and  that  the  corresponding  side  of  the  mesentery,  if  closely  followed  down  to  the  mesenteric 
root,  will  conduct  him  into  the  left  fossa;  he  also  knows  that  the  other  side  of  the  bowel  is  its 
right  side,  and  that  the  mesentery  on  that  side  will  conduct  him  into  the  right  fossa.  Now, 
if  his  finger  goes  into  the  great  fossa  on  the  left  side  of  the  abdomen,  after  having  closely  fol- 
lowed the  mesentery  down  to  its  root  and  arranged  his  loop  to  be  parallel  with  that  root,  he  then 
knows  that  the  left  and  right  sides  of  the  intestine  face  to  the  left  and  right  sides  of  the  abdomen 
respectively,  and  that  the  end  of  the  loop  which  points  downward  is  the  end  nearest  the  ileo- 
cecal valve.  He  can  determine  the  direction  of  the  gut  in  a  similar  way  in  case  his  finger  enters 
the  right  fossa.  All  this  would  seem  very  simple  were  it  not  for  the  twists  in  mesentery  and 
intestine,  which  tend  to  mislead  one.  A  little  practice  will  usually  enable  one  to  recognize  a  twist 
in  the  mesentery.  This  should  be  untwisted  by  rotation  of  the  gut,  after  which  the  direction  is 
determined  by  another  palpation  of  the  mesenteric  root."* 

The  studies  made  of  the  arrangement  and  variations  of  the  loops  of  the  mesenteric  vessels  by 
Dr.  Thomas  Dwight'have  been  utilized  and  expanded  by  Dr.  George  H.  Monks  in  laj'ing  down 
rules  for  the  determination  of  the  exact  portion  of  small  intestine  which  may  be  in  the  surgeon's 
hand.*    His  views  are  as  follows: 

"General  Vascularity  of  the  Mesentery  near  the  Bowel. — Opposite  the  upper  part  of  the  bowel 
the  mesenteric  vessels  are  distinctly  larger  than  opposite  any  other  part  of  it.  These  vessels  grow 
smaller  and  smaller  as  we  pass  downward  until  the  lower  third  of  the  gut  is  reached,  where  they 
remain  about  the  same  size  as  far  as  the  ileocecal  valve.  The  arrangement  of  the  mesenteric 
vessels  has  some  features  which  iiiliinatcly  concern  the  subject  in  hand,  and  which  I  shall  describe 
with  some  detail.  Diagranuiiaiically  speaking,  the  main  branches  of  the  superior  mesenteric 
artery  unite  with  each  other  by  means  of  loops,  which  are  called  for  convenience  'primary  loops;' 
in  some  parts  of  the  tube,  'secondary  loops,'  and  even,  occasionally,  'tertiary  loops,'  are  super- 
imposed upon  these.  From  these  loops  little  straight  vessels — the  vasa  recta  already  referred  to 
— run  to  the  bowel,  upon  which  they  ramify,  alternating,  as  a  rule,  as  to  the  side  of  the  intestine 
which  they  supply.  The  mesenteric  veins  are  arranged  in  a  manner  somewhat  similar  to  the 
arteries. 

'  Dr.  K.  E.  L.  Lennander,  in  Mittheilungen  aus  dem  Grenzgebieten  der  Medicin  und  Chirurgie,  Band  x,  Heft,  1,  2. 

2  Intestinal  Localization,  by  George  H.  Monks,  Annals  of  Surgery,  October,  1903. 

3  Reports  of  tiie  Meeting  of  American  Anatomists,  1S97. 
■*  Annala  of  Surgery,  1903. 


1270  THE  ORGANS  OF  DIGESTION 

"  The  Loops  of  the  Mesenteric  FesseZs.— Opposite  the  upper  part  of  the  bowel  there  are  only 
primary  loops.  Occasionally  a  secondary  loop  appears,  but  it  is  small  and  insignificant  as  com- 
pared with  the  primary  loops,  which  are  large  and  quite  regular.  As  we  proceed  down  the 
bowel,  secondary  loops  become  more  numerous,  larger,  and  approach  nearer  to  the  bowel  than 
the  primary  loops  in  the  upper  part.  As  a  rule,  secondary  loops  become  a  prominent  feature 
at  about  the  fourth  foot.  As  we  continue  farther  downward,  the  secondary  loops  (and,  possibly, 
tertiary  loops)  become  still  more  numerous  and  the  primary  loops  smaller,  the  loops  all  the  time 
getting  nearer  and  nearer  to  the  gut.  Opposite  the  lower  part  of  the  gut  the  loops  generally 
lose  their  characteristic  appearance,  and  are  represented  by  a  complicated  network. 

"The  Vasa  Recta. — Opposite  the  upper  part  of  the  intestine  the  vasa  recta  are  from  three  to 
five  centimetres  long,  when  the  loop  of  small  intestine  to  which  they  run  is  lifted  up  so  as  to  put 
them  gently  on  the  stretch.  They  are  straight,  large,  and  regular,  and  rarely  give  off  branches 
in  the  mesentery.  In  the  lower  third  they  are  very  short,  being  generally  less  than  1  cm.  in 
length.  Here  they  are  less  straight,  smaller,  less  regular,  and  have  frequent  branches  in  the 
mesentery. " 


THE   STOMACH    (GASTER;   VENTRICULUS)    (Figs.  972,  1010). 

The  stomach  is  one  of  the  principal  organs  of  digestion,  and  serves  as  a  tem- 
porary receptacle  for  food.  It  is  the  most  dilated  part  of  the  alimentary  canal 
and  is  situated  between  the  termination  of  the  oesophagus  (cardia)  and  the 
commencement  of  the  small  intestine. 

It  lies  more  or  less  obliquely  or  horizontally  in  the  epigastric,  umbilical,  and  left 
hypochondriac  regions  of  the  abdomen,  and  occupies  a  recess  or  chamber  called 
the  stomach  chamber  (Fig.  999).  When  distended  the  viscus  completely  fills  the 
space.  \Yhen  the  stomach  is  empty  it  lies  upon  the  floor  of  the  chamber,  and  the 
portion  it  has  vacated  is  occupied  by  the  transverse  colon,  which  ascends  in  front 
of  the  stomach  and  finally  gets  above  it.  The  anterior  and  left  wall  of  the  stomach 
chamber  is  formed  by  the  anterior  abdominal  wall  and  Diaphragm.  The  roof 
is  formed  by  the  under  surface  of  the  Diaphragm  and  the  under  surface  of  the  left 
lobe  of  the  li^'er.  The  floor  is  formed  by  the  left  suprarenal  gland  and  the  summit 
of  the  left  kidney,  the  gastric  surface  of  the  spleen,  the  upper  surface  of  the 
pancreas,  the  transverse  mesocolon,  and  the  colon. 

The  shape  and  position  of  th^  stomach  are  so  greatly  modified  by  changes 
within  itself  and  in  the  surrounding  organs  that  no  one  form  can  be  described 
as  typical.  The  chief  modifications  are  determined  by  (1)  the  amount  of  the 
stomach  contents,  (2)  the  stage  which  the  digestive  process  has  reached,  (3)  the 

degree  of  development  or  functional  power 
of  the  gastric  musculature,  and  (4)  the  con- 
dition of  the  adjacent  intestines. 

When  empty  and  contracted,  as  after  a 

iith  Thoracic  V. -^    Z    ~{\  ,'    pcrlod  of  Tcst,^  thc  stomach  is  sickle-  or 

sausage-shaped,  as  shown  in  Fig.  1009.     At 

an    early   stage    of  gastric   digestion   the 

stomach  commonly  consists   of   two   seg- 

^  ments — (a)  a  large  globular  portion  on  the 

fst  Lumbar  V.  /  /  L       \        ^^i^^^  gnd  (6)  a  narrow  tubular  portion  on 

the  right,  corresponding  to  the  fundus  and 
pyloric   portions,   and   forming   an   angle 
with  each  other,  the  axis  of  the  fundus 
Fig.  1009.— Form  and  topography  of  the  stem-     being  directed  dowuward  and  inward  while 
S?aU^™terd';Sh''lnr:S?ufedl^j:^dur°"     the  pyloric  portiou  curvcs  upward  and  to 

the  right. 
The  stomach  presents  two  openings,  two  borders  or  curvatures,  and  two  sur- 
faces. 

;  given  by  the  immediate  examination  of  the  organ  in  situ  in  executed 


THE  STOMACH 


nil 


Antrum  cardiacum 


Pyloric  vestibule 


Openings. — The  opening  by  which  the  oesophagus  communicates  with  the 
stomach  is  known  as  the  cardiac  orifice,  and  is  situated  at  the  level  of  the  eleventh 
thoracic  vertebra,  nearly  an  inch  from  the  midline,  corresponding  to  the  seventh 
left  chondrosternal  junction.  The  short  intra-abdominal  portion  of  the  oesopha- 
gus (anfntm  cardiacum)  is  conical  in  shape  and  curved  sharply  to  the  left,  the  base  of 
the  cone  being  continuous  with  the  cardiac  orifice  of  the  stomach.  The  right  mar- 
gin of  the  oesophagus  is  continuous  with  the  lesser  curvature  of  the  stomach,  while 
the  left  margin  joins  the  greater  curvature  at  an  acute  angle,  the  incisura  cardiaca. 

The  pyloric  orifice  communicates  with  the  duodenum,  and  its  position  is  indi- 
cated on  the  surface  by  a  circular  g^oo^•e,  the  duodenopyloric  constriction.  This 
orifice  lies  to  the  right  of  the  middle  line 
at  the  le^'el  of  the  first  lumbar  -vertebra ; 
it  may  be  from  one  to  two  inches  to 
the  right  of  the  middle  line,  depending 
upon  the  degree  of  distention  of  the 
stomach.  Its  position  on  the  ventral 
surface  of  the  body  would  be  indicated 
by  a  point  in  the  transpyloric  plane  (see 
p.  1243)  about  one  inch  to  the  right  of 
the  middle  line. 

Curvatures. — The  lesser  ciurature  {cur- 
xatura  reniricidi  minor),  extending  be-  sulcus intermediis 
tween  the  cardiac  and  pyloric  orifices, 
forms  the  right  or  posterior  border  of  the 
stomach.  It  descends  as  a  continuation 
of  the   right  margin  of  the   oesophagus 

in  front  of  the  left  crus  of  the  Diaphragm,  and  then,  turning  to  the  right,  it  crosses 
the  first  lumbar  vertebra  and  ends  at  the  pylorus.  Nearer  its  pyloric  than  its 
cardiac  end  is  a  well-marked  notch,  the  incisura  angularis,  which  varies  somewhat 
in  position  with  the  state  of  distention  of  the  viscus,  it  serves  to  separate  the 
stomach  into  a  right  and  left  portion.  The  lesser  curvature  gives  attachment  to 
the  two  layers  of  the  gastrohepatic  omentum,  and  between  these  two  layers  are 
the  gastric  artery  and  the  pyloric  branch  of  the  hepatic  artery.  It  is  from  three 
to  four  inches  (S-10  cm.)  in  length. 

The  greater  curvature  {curvatura  ventrictili  major)  is  directed  mainly  forward 
and  to  the  left,  and  is  three  or  four  times  as  long  as  the  lesser  curvature  (twelve  to 
sixteen  inches,  or  30  to  40  cm.);  starting  from  the  cardiac  orifice  at  the  incisura 
cardiaca  it  forms  an  arch  backward,  upward,  and  to  the  left;  the  highest  point 
of  the  convexity  is  on  a  le\  el  with  the  sixth  left  costal  cartilage  or  tenth  thoracic 
^"ertebra.  From  this  level  it  may  be  followed  downward  and  forward  with 
a  slight  convexity  to  the  left  as  low  as  the  cartilage  of  the  ninth  rib ;  it  then  turns 
to  the  right  to  end  at  the  pylorus.  Directly  opposite  the  incisura  angularis  of  the 
lesser  curvature  the  greater  cur\"ature  presents  a  dilatation,  the  pyloric  vestibule  or 
anirum,  which  is  limited  on  the  right  by  a  slight  groove,  the  sulcus  intermedins;  this 
sulcus  is  about  an  inch  from  the  duodenopyloric  constriction.  The  portion  between 
the  sulcus  intermedins  and  the  duodenopyloric  constriction  is  termed  the  pyloric 
canal.  At  its  commencement  the  greater  curvature  is  covered  by  peritoneum  con- 
tinuous 'sv'ith  that  covering  the  front  of  the  organ.  The  left  part  of  the  curvature 
gives  attachment  to  the  gastrosplenic  omentum,  while  to  its  anterior  portion  are 
attached  the  two  anterior  layers  of  the  great  omentum,  separated  from  each  other 
by  the  gastroepiploic  vessels. 

Surfaces. — \\\\en  the  stomach  is  in  the  slightly  dilated  condition,  its  surfaces 
are  directed  more  upward  and  downward  respectively,  but  when  the  viscus  is  dis- 
tended they  are  directed  more  forward  and  backward.  They  may,  therefore, 
be  described  as  antero-superior  and  postero-inferior. 


1272  THE  ORGANS  OF  DIGESTION 

Antero-superior  Surface. — The  left  half  of  this  surface  is  in  contact  with  the  Dia- 
phragm, which  separates  it  from  the  base  of  the  left  lung,  the  pericardium,  the 
seventh,  eighth,  and  ninth  ribs,  and  intercostal  spaces  of  the  left  side.  The  right 
half  is  in  relation  with  the  left  and  quadrate  lobes  of  tlie  liver  and  with  the  ventral ' 
abdominal  wall.  When  the  stomach  is  empty  the  transverse  colon  may  be  found 
lying  on  the  front  part  of  this  surface.  The  whole  surface  is  covered  by  peri- 
toneum. 

The  Postero-inferior  Surface  {paries  posterior)  is  in  relation  with  the  Diaphragm, 
the  gastric  surface  of  the  spleen,  the  left  suprarenal  gland,  the  upper  part  of  the 
front  of  the  left  kidney,  the  anterior  surface  of  the  pancreas,  the  splenic  flexure 
of  the  colon,  and  the  upper  layer  of  the  transverse  mesocolon.  These  structures 
form  a  shallow  concavity  (^'stomach  bed"),  on  which  the  stomach  rests.  The 
transverse  mesocolon  intervenes  between  the  stomach  and  the  duodenojejunal 
flexure  and  small  intestine.  The  postero-inferior  surface  is  covered  with  peri- 
toneum, except  over  a  small  area  close  to  the  cardiac  orifice;  this  area  is  limited 
by  the  lines  of  attachment  of  the  gastrophrenic  ligament,  and  lies  in  contact  with 
the  Diaphragm  and  frequently  with  the  upper  portion  of  the  left  adrenal  gland. 

Component  Parts  of  the  Stomach. — The  stomach  may  be  divided  into  a  left 
portion  or  body  and  a  right  or  pyloric  portion  or  antrum  by  a  plane  passing  through 
the  incisura  angularis  and  the  left  limit  of  the  opposed  dilatation  (pyloric  vestibule) 
on  the  greater  curvature.  The  left  portion  of  the  body  (corpus  ventriculi)  is  known 
as  the  fundus,  while  that  which  is  adjacent  to  the  cardiac  orifice  is  known  as  the 
cardiac  antrum.  The  pyloric  antrum  is  divided  into  a  right  part,  the  pyloric  canal, 
and  a  left,  the  pyloric  vestibule,  by  a  plane  passing  through  the  sulcus  intermedius 
at  right  angles  to  the  axis  of  this  portion  (Fig.  1010). 

The  size  of  the  stomach  varies  considerably  in  diflFerent  subjects.  WTien  mod- 
erately distended  its  greatest  length,  from  the  top  of  the  fundus  to  the  lowest  part 
of  the  greater  curvature,  is  from  ten  to  twelve  inches  and  its  diameter  at  the 
widest  part  from  four  to  five  inches.  The  distance  between  the  two  orifices, 
when  the  stomach  is  in  situ,  is  three  to  four  inches,  and  the  measurement  from  the 
anterior  to  the  posterior  wall  three  and  one-half  inches.  Its  weight,  according 
to  Clendinning,  is  about  four  ounces  and  a  half,  and  its  capacity  in  the  adult  male 
is  five  to  eight  pints.     The  stomach  of  a  newborn  child  holds  about  one  ounce. 

Alterations  in  Position, — There  is  no  organ  in  the  body  the  position  and  connections  of 
which  present  such  frequent  aUerations  as  the  stomach.  When  empty,  it  lies  at  the  back  part 
of  the  abdomen,  some  distance  from  the  ventral  abdominal  wall,  and  is  in  the  left  hypochondriac 
region  and  the  left  portion  of  the  epigastric  region.  Its  fundus  is  directed  upward  and  backward 
toward  the  Diaphragm.  The  long  axis  of  the  viscus  is  quite  oblique.  Its  pyloric  end  is  directed 
toward  the  right,  covered  in  front  by  the  left  lobe  of  the  liver,  and  on  a  level  with  the  first  lumbar 
vertebra.  When  empty  and  contracted  the  stomach  assumes  a  more  or  less  cyhndrical  form, 
especially  noticeable  at  its  pyloric  end,  and  resembles  a  piece  of  thick-walled  intestine.  When 
the  stomach  is  distended,  its  surfaces  become  convex  and  the  shape  becomes  pyriform,  its  long 
axis  being  downward,  forward,  and  to  the  right.  The  greater  curvature  is  elevated  and  carried 
forward,  so  that  the  anterior  surface  is  turned  more  or  less  upward  and  the  posterior  surface 
downward,  and  the  stomach  is  brought  well  against  the  anterior  wall  of  the  abdomen.  Its 
fundus  expands  and  rises  considerably  above  the  level  of  the  cardiac  orifice;  in  doing  this  the 
Diaplu'agm  is  forced  upward,  contracting  the  cavity  of  the  thorax;  hence  the  dyspnea  complained 
of  as  inspiration  is  impeded.  The  apex  of  the  heart  is  also  tilted  tipward;  hence  the  oppression 
in  this  region  and  the  palpitation  experienced  in  extreme  distention  of  the  stomach.  The  left 
lobe  of  the  liver  is  pushed  toward  the  right.  When  the  stomach  becomes  distended  the  change 
in  the  position  of  the  pylorus  may  be  considerable;  it  is  shifted  to  the  right  as  much  as  two 
inches  from  the  median  line,  and  lies  under  cover  of  the  liver,  near  the  neck  of  the  gall- 
bladder. In  consequence  of  the  distention  of  the  stomach  the  pyloric  antrum  bulges  in  front 
of  the  pylorus,  concealing  it  from  view,  and  causing  it  to  undergo  a  rotation,  so  that  its  orifice  is 
directed  backward.  When  the  stomach  is  greatly  distended  its  lower  border  may  enter  the  um- 
bilical and  the  left  lumbar  regions.  During  inspiration  the  stomach,  is  displaced  downw-ard  by 
the  descent  of  the  Diaphragm,  and  it  is  elevated  by  the  pressure  of  the  abdominal  muscles  during 
expiration.  Pressure  from  witlwut,  as  from  tight  lacing,  pushes  the  stomach  down  toward  the 
pelvis.     In  fact,  in  the  female,  because  of  tight  lacing,  the  body  of  the  stomach  may  be  to  the  left 


THE  STOMA  CH 


vm 


side  of  the  vertebral  column  and  nearly  vertical  in  direction,  the  pyloric  portion  being  sharply 
angled  upward  toward  the  pylorus,  which  lies  underneath  the  liver..  Besides  the  anfjulation, 
the  stomach  may  have  a  median  constriction,  and  there  may  even  be  an  hour-fjlaxn  sttnitacli. 
In  disease  the  position  and  connection  of  the  stomach  may  be  greatly  changed,  from  the  accumu- 
lation of  fluid  in  the  thoracic  cavity  or  abdomen,  or  from  alteration  in  size  of  any  of  the  surround- 
ing viscera. 

Variations  According  to  Age. — In  an  early  period  of  development  the  stomach  is  vertical,  and  in 
the  newborn  child  it  is  more  vertical  than  later  on  in  life,  as  owing  to  the  large  size  of  the  liver 
it  is  pushed  over  more  to  the  left  side  of  the  abdomen,  and  the  whole  of  the  anterior  surface  is 
covered  by  the  left  lobe  of  this  organ. 

Interior  of  the  Stomach. — When  examined  after  death,  the  stomach  i.s  usually 
fixed  at  some  temporary  stage  .of  the  digestive  process.  A  common  form  is  that 
shown  in  Fig.  1011.  If  the  viscus  be  laid  open  by  a  section  through  the  plane  of 
its  two  curvatures,  it  is  seen  to  consist  of  the  two  segments  aheady  described — 
viz.,  a  large  globular  portion  to  the  left,  comprising  the  body  and  fundus,  and  the 
tubular  pyloric  portion  to  the  right.  The  mucous  membrane  lining  the  interior 
is  soft  and  velvety,  red  or  reddish  brown  in  the  body  and  fundus,  and  of  a  pinkish 
tinge  at  the  pyloric  end.  It  is  thrown  into  numerous  folds  or  nigae,  chiefly  longi- 
tudinal in  direction  and  most  marked  toward  the  pyloric  end  and  along  the  greater 
curvature.  To  the  left  of  the  cardiac  orifice  is  the  incisura  cardiaca;  the  projec- 
tion of  this  notch  into  the  cavity  of  the  stomach  increases  as  the  organ  distends, 
and  has  been  supposed  to  act  as  a  valve  preventing  regurgitation  into  the  oesopha- 
gus. In  the  pyloric  portion  are  seen  (a)  the  elevation  corresponding  to  the 
incisura  angularis,  and  (6)  the  circular  projection  from  the  duodenopyloric  con- 
striction which  forms  the  pyloric  valve.  The  separation  of  the  pyloric  vestibule 
from  the  pyloric  canal  is  scarcely  indicated,  but  the  manner  in  which  the  pylorus 
is  invaginated  into  the  duodenum  is  evident. 

The  pyloric  valve  (vahnda  jpylori)  (Fig.  1013)  is  formed  by  a  reduplication  of 
the  mucous  membrane  of  the  stomach,  containing  numerous  circular  fibres,  which 
are  aggregated  into  a  thick  circular  ring,  the  Pyloric  Sphincter  (m.  sphincter  pylori) ; 
some  of  the  deeper  longitudinal  fibres  turn  in  and  interlace  with  the  circular  fibres 


Pijloi  as 
Pylonc  canal. 


Fig.  1011. — Interior  of  the  stomach. 


of  the  valve.  The  pylorus  is  normally  kept  closed  by  the  action  of  this  Sphincter 
muscle.  During  the  early  stage  of  digestion  it  remains  closed,  but  after  a  time 
opens  now  and  then,  this  relaxation  becoming  more  frequent  and  the  period  of 
patency  more  prolonged  as  digestion  advances. 


1274 


THE  ORGANS  OF  DIGESTION 


Structure. — The  wall  of  the  stomach  consists  of  four  coats — serous,  muscular,  submucous, 
and  mucous,  together  with  vessels  and  nerves. 

The  serous  coat  {tunica  serosa)  is  derived  from  the  peritoneum,  and  covers  the  entire  surface 
of  the  organ,  excepting  along  the  greater  and  lesser  curvatures,  at  the  points  of  attachment  of 
the  greater  and  lesser  omenta;  here  the  two  layers  of  peritoneum  leave  a  small  triangular  space 
uncovered  by  peritoneum  along  which  the  nutrient  vessels  and 
nerves  pass.  On  the  posterior  surface  of  the  stomach,  close  to  the 
cardiac  orifice,  there  is  also  a  small  triangular  ai'ea  uncovered  by 
peritoneum,  where  the  organ  is  in  contact  with  the  under  surface 
of  the  Diaphragm. 

The  muscular  coat  {tunica  viuscularis)  (Figs.  1014  and  1015)  is 
situated  immediately  beneath  the  serous  covering,  to  which  it  is 
closely  connected.  It  consists  of  three  sets  of  smooth  muscle 
tissue — longitudinal,  circular,  and  oblique,  from  without  inward, 
in  the  order  named. 

The  longitudinal  fibres  {stratum,  longitudinale)  are  the  most 
superficial,  and  are  arranged  in  two  sets.  The  first  set  consists  of 
fibres  continuous  with  the  longitudinal  fibres  of  the  oesophagus; 
they  radiate  in  a  stellate  manner  from  the  cardiac  orifice  and  are 
practically  all  lost  before  the  pyloric  portion  is  reached.  The 
second  set  commences  on  the  body  of  the  stomach  and  passes  to 
the  right,  its  fibres  becoming  more  closely  collected  as  they  approach  the  pylorus.  Some  of 
the  more  superficial  fibres  of  this  set  pass  on  to  the  duodenum,  but  the  deeper  fibres  dip  in  and 
interlace  with  ,the  circular  fibres  of  the  pyloric  valve  Sphincter.     The  bundles  of  longitudinal 


lagrami 


Fig.  1012, 
view  of  the  coats  of  the  stom- 
ach, duodenum,  and  pylorus. 
The  ridge  is  the  pyloric  valve, 
(Allan  Thomson.) 


Fig.  1013. — The  superficial  muscular  layer  of  the  stomach. 


s'ed  from  above  and  in  front.     (Spalteholz.) 


muscle  fibre  on  the  upper  and  lower  surfaces  of  the  pylorus  are  particularly  firm  and  distinct, 
and  are  called  the  pyloric  ligaments  {!ir/amcnta  pylori). 

The  circular  fibres  {stratum  circulare)  form  a  uniform  layer  throughout  the  whole  extent  of 
the  stomach  internal  to  the  longitudinal  fibres.     They  begin  as  tiny  rings  at  the  left  extremity  of 


THE  STOMACH 


1275 


the  fundus  and  pass  over  into  larger  and  larger  rings  to  encircle  the  entire  organ.  At  the  pylorus 
they  are  most  abundant,  and  are  aggregated  into  a  circular  ring  or  Sphincter,  which  projects  into 
the  cavity,  and  forms,  with  the  fold  of  mucous  membrane  covering  its  surface,  the  pyloric  valve 
(Fig.  1012).  The  circular  fibre  stratum  is  continuous  with  the  circular  layer  of  the  oesophagus, 
the  fibres  being  interlaced  at  the  transition. 

The  oblique  fibres  ( jibrae  obliquae)  arise  at  the  left  side  of  the  cardia  from  the  circular  fibres 
of  the  cesophagus.  The  fibres  pass  down  in  the  anterior  and  posterior  walls,  and  almost  reach 
the  pylorus.  Certain  oblique  muscular  fibres  encircle  the  fundus  of  the  stomach  in  a  series  of 
rings. 

The  submucous  coat  {tela  submucosa)  consist  of  loose  areolar  tissue,  connecting  the  mucous 
and  muscular  coats.  It  supports  the  large  bloodvessels  previous  to  their  distribution  to  the 
mucous  membrane;  hence  it  is  sometimes  called  the  vascular  coat. 


Fig.  lOH. — 1'he  middle  and  deep  muscular  layer  of  the  stomach,  viewed  from  above  and  in  front.     (Spalteholz.) 


The  mucous  membrane  (tunica  mucosa)  (Figs.  1015,  1016,  1017,  and  lOlS)  is  thick,  its  surface 
smooth,  soft,  and  velvety.  In  the  fresh  state  it  is  of  a  pinkish  tinge  at  the  pyloric  end,  and  of  a 
red  or  reddish-brown  color  over  the  rest  of  the  surface.  In  infancy  it  is  of  a  brighter  hue,  the 
vascular  redness  being  more  marked.  It  is  thin  at  the  cardiac  extremity,  but  thicker  toward 
the  pylorus.  During  the  contracted  state  of  the  organ  it  is  thrown  into  numerous  folds  or 
rugae  [plicae  mucosae)  (Figs.  1015  and  1016),  which  for  the  most  part  have  a  longitudinal  du-ection, 
and  are  most  marked  toward  the  pyloric  end  of  the  stomach  and  along  the  greater  curvature. 
These  folds  consist  of  mucous  and  submucous  coats,  and  are  entirely  obliterated  when  the  organ 
becomes  fully  distended. 

Structure  of  the  Mucous  Membrane. — When  examined  with  a  lens  the  inner  surface  of  the 
mucous  membrane  presents  a  peculiiir  lujncycomb  appearance,  from  being  covered  with  small 
shallow  depressions,  the  gastric  crypts  or  pits  (foirokie  gastricae)  (Figs.  1015  and  lOlS)  of  a  poly- 
gonal or  hexagonal  form,  \\hich  vary  from  [J;]  to  ^hi  of  an  inch  in  diameter,  and  are  separated 
by  slightly  elevated  ridges  (plicae  villosae).  The  pits  in  the  cardiac  and  fundal  portions  of 
the  stomach  extend  tlirough  about  one-sixth  the  thickness  of  the  mucosa,  while  in  the  pj'loric  end 
they  extend  through  about  one-half  the  mucous  coat.  In  the  bottom  of  the  crypts  are  seen 
three  to  seven  orifices  of  minute  tubes,  the  gastric  glands  (Fig.  1018),  which  are  placed  per- 


1276 


THE  ORGANS  OF  DIGESTION 


pendicularly  side  by  side  throughout  the  entire  substance  of  the  mucous  membrane.  The  sur- 
face of  the  mucous  membrane  of  the  stomach  is  covered  by  a  single  layer  of  columnar  epithe- 
lium and  a  few  goblet  cells;  it  lines  the  crypts,  and  also  for  a  certain  distance  the  mouths  of  the 
gastric  glands;  in  the  glands  the  character  of  the  epithelium  changes.     This  epithelium  com- 


Gaatric  Areas.  Bugte. 


Fig.   1015. — Mucous  membri 


of  the  atoraaou,  from  the  pars  pylo 
(Spalteholz.) 


viewed  from  the  surface.      X  5. 


Midges  beticecn  the  alveoli. 


Gastric  alveoli. 

Fig.     1016. — Mucous     membrane    of 
etomach,    from    the    pars    pylorica,    \'iei 
from  the  surface.     X  16.     (Spalteholz.) 


mences  very  abruptly  at  the  cardiac  orifice,  where  the 
cell.i  suddenly  change  in  character  from  the  stratified 
epithelium  of  the  n'.sophagus. 

The  Gastric  Glands. — The  gastric  glands  are  of 
three  kinds — the  true  gastric  glands,  the  pyloric 
glands,  and  the  cardiac  glands. 

The  true  gastric  glands  (Fig.  1020)  are  called  also 
the  oxyntic  glands,  the  fundus  glands,  and  the  peptic 
glands  (iilu)uhdae  gaslricae  propriae).  They  are  dis- 
tributed throughout  the  entire  fundus  and  body,  and 
may  be  found  even  at  the  pylorus.  They  are  mainly 
of  the  simple  tubular  variety,  and  are  lined  by  simple 
epithelial  cells  resting  upon  a  delicate  basement  mem- 
brane supported  by  the  tunica  propria.  The  duct,  or 
mouth,  however,  in  these  glands  is  shorter  than  in  the 
other  variety,  sometimes  not  amounting  to  more  than 
one-sixth  of  the  whole  length  of  the  gland;  it  is  lined 
throughout  by  columnar  epithelium.  ."Vt  the  point 
where  the  terminal  tubes  open  into  the  mouth,  and 
which  is  termed  the  neck,  the  epithelium  alters,  and 
consists  of  short  columnar  or  polyhedral,  granular 
cells,  which  almost  fill  the  tube,  so  that  the  lumen 
becomes  suddenly  constricted,  and  is  continued  down 
as  a  very  fine  channel.  They  are  known  as  the  chief 
or  the  peptic  or  the  central  cells  of  the  glands,  and 
furnish  pepsin.  Between  these  cells  and  the  basement 
memlirane  are  found  other  darker  granular-looking 
cells,  studded  throughout  the  tubes  at  intervals,  and 
giving  it  a  beaded  or  varicose  appearance.  The  fun- 
dus is  the  blind  extremity  of  the  gland,  and  here  the 
chief  cells  predominate.  These  are  known  as  the 
acid,  parietal,  or  oxyntic  cells.     Some  of  the  parietal 


THE  STOMA  CH 


1277 


cells  empty  directly  into  the  lumen  of  the  crland  by  secretory  capillaries;  others  empty  by  a 
channel  which   divides    into   secretory   capillaries.     The  parietal  cells  secrete  the  acid  of  the 


^   lA.  S^-^  --v-^  ^'kU 


V. 


w.. 


TWO   MAMMILL/E      L 


Figs.  1017  and  1018.— The  mucous  membrane  of  the  stomach.  Fig.  1017.  Natural  size.  Fig.  1018.  Magnified  25 
diameters.  In  Fig.  1017  the  rugae  and  the  mamillated  surfaces  are  shown  In  Fig  1018  the  glind  mouth'^  (foveolae 
gastricae),  with  the  gland  tubes  leading  from  some  of  them,  and  the  r  dges  separat  ng  the  n  ou  h  (p  ae  villosae) 
are  seen.     (Cunningham.) 


Fig.    1019.- Pyloric  gland. 


Fig.    1020.— Peptic  gastric  gland. 


gastric  juice.  Between  the  glands  the  tunica  propria  consists  of  fibroelastic  connective-tissue 
framework  with  lymphoid  tissue  and  a  rich  capillary  plexus.  In  places  this  latter  tissue, 
especially  in  early  life,  is  collected  into  little  masses,  which  to  a  certain  extent  resemble  the 


1278 


THE  ORGANS  OF  DIGESTION 


PLEXUS 

BENEATH  THE 

EPITHELIUM 


solitary  nodules  of  the  intestine,  and  are  by  some  termed  the  lenticular  follicles  of  the  stom- 
ach.    They  are  not,  however,  so  distinctly  circumscribed  as  the  solitary  follicles. 

The  pyloric  glands  {glandulae  pyloricae)  (Fig.  1019)  are  the  branched  tubular  glands,  and 
secrete  mucus  and  pepsin. 

They  are  placed  most  plentifullj^  about  the  pylorus,  but  between  the  fundus  and  pylorus,  in 
the  region  known  as  the  transitional  or  intermediate  zone,  both  true  gastric  glands  and  pyloric 
glands  are  found.  Each  pyloric  gland  consists  of  two  or  three  short  tubes  opening  into  a  com- 
mon mouth  or  duct,  the  external  orifice  of  which 
is  situated  at  the  bottom  of  a  ervpt.  The  tubes 
are  wavy,  and  are  of  about  equal  length  with  the 
duct.  The  tubes  and  duct  are  lined  throughout 
with  simple  epithelium,  the  duct  being  lined  by 
columnar  cells  continuous  with  the  epithelium 
lining  the  surface  of  the  mucous  membrane  of 
the  stomach,  the  tubes  with  tall,  broad,  and 
pale-staining  cells,  which  are  finely  granular. 
The  pyloric  glands  branch  more  frequently,  are 
more  curved  in  direction,  and  open  into  deeper 
foveolae  than  the  true  gastric  glands  (Szymono- 
wicz).  They  contain  only  chief  or  peptic  cells 
and  do  not  possess  parietal  cells.  These  glands, 
at  times,  extend  into  the  submucous  coat. 

The  cardiac  glands  are  found  about  the  oeso- 
phageal orifice.  They  resemble  the  glands  of  the 
oesophagus  and  are  mucous  in  character. 

External  to  the  tunica  propria  of  the  mucous 
membrane,  and  between  it  and  the  submucous 
coat,  is  a  thin  stratum  of  involuntary  muscle  tis- 
sue {muscularw  mucosae),  which  in  some  parts 
consists  only  of  a  single  longitudinal  layer;  in  others,  of  two  layers,  an  irmer  circular,  and  an 
outer  longitudinal. 

Vessels  and  Nerves. — The  arteries  supplying  the  stomach  are  the  gastric,  the  pyloric. 
and  the  right  gastroepiploic  branch  of  the  gastroduodenal,  the  left  gastroepiploic  and  vasa 
brevia  from  the  splenic.  The  gastric  artery  passes  to  the  lesser  curvature  just  below  the  cardia 
It  gives  off  the  oesophageal  branch,  and  passes  from  left  to  right  along  the  lesser  curvature  of  the 
stomach  beneath  the  peritoneum  between  the  two  layers  of  the  lesser  omentum  and  upon  the 
wall  of  the  stomach.     It  may  in  this  course  be  a  single  vessel,  or  may  divide  into  two  branches. 


PLEXUS  OF 

BLOODVESSELS 

IN  SUBMUCOUS 

TISSUE 


Fig.  1021. — Terminations  of  the  bloodvessels  in 
the  mucous  membrane  of  the  stomach.  (Poirier 
and  Charpy.) 


(Poirier  and  Charpy.) 


which  run  along  each  side  of  the  lesser  curvature  (Fig.  1022).  If  there  is  a  single  artery,  it  gives 
off  six  or  seven  descending  branches  to  the  anterior  wall  and  about  the  same  number  to  the  pos- 
terior wall  of  the  stomach.  It  also  gives  branches  to  the  lesser  omentum.  If  two  vascular 
arches  form,  one  gives  branches  to  the  anterior  wall  of  the  stomach,  the  other  to  the  posterior 


THE  STOMACH  1279 

wall,  and  both  to  the  lesser  omentum.  The  termination  of  the  gastric  anastomoses  with  the 
pyloric  liranch  or  two  rami  of  the  pyloric  branch  of  the  hepatic  artery.  From  each  arch  si.x  or 
seven  descending  branches  come  off  to  the  anterior  and  posterior  walls  of  the  stomach.  The 
gastroduodenal  artery  is  given  off  by  the  hepatic.  From  the  gastroduodenal  comes  the  right 
gMstrucpiploic.  The  left  gastroepiploic  comes  from  the  splenic.  The  right  gastroepiploic 
artery  passes  from  right  to  left  in  the  gastrocolic  omentum  below  the  greater  curvature  of  the 
stomach.  The  left  gastroepiploic  artery  iiasses  forward  in  the  gastrosplenic  omentum  to 
below  the  greater  curvature  of  tlic  .stomach,  and  pas.ses  from  left  to  right  along  that  curvature 
in  the  greater  omentum,  and  joins  the  right  gastroepiploic  artery.  The  gastroepiploic  arteries 
are  not  upon  but  are  distinctly  below  the  stomach  wall.  From  them  numerous  gastric  branches 
are  sent  to  the  anterior  and  posterior  walls  of  the  stomach,  and  they  anastomose  with  branches 
of  the  gastric  and  pyloric.  Vasa  brevia,  four  or  five  in  number,  arise  from  the  splenic,  pass 
forward  in  the  gastrosplenic  omentum,  and  supply  the  fundus.  The  arteries  of  the  stomach  lie 
first  beneath  the  peritoneum,  but  soon  enter  the  muscular  coat,  supply  it,  pierce  it,  ramify  in  the 
submucous  coat,  and  are  finally  distributed  to  the  mucous  membrane.  The  arrangement  of  the 
vessels  in  the  mucous  membrane  is  somewhat  peculiar  (Fig.  1021).  The  arteries  break  up 
at  the  base  of  the  gastric  tubules  into  a  plexus  of  fine  capillaries  which  run  upward  between 
the  tubules,  anastomosing  with  each  other,  and  ending  in  a  plexus  of  larger  capillaries,  which 
surround  the  mouths  of  the  tubes  and  also  form  hexagonal  meshes  around  the  crypts. 

The  capillarv  network  about  the  glands  gives  origin  to  the  veins.  The  various  small  veins 
unite  and  form  a  plexus  in  the  submucous  tissue  (Fig.  1021).  From  this  plexus  come  branches 
which  pass  through  the  muscular  coat  and  terminate  in  the  right  gastroepiploic  branch  of  the 
superior  mesenteric,  the  left  gastroepiploic  branch  of  the  splenic,  the  veins  to  the  siilcnic  which 
correspond  to  the  vasa  brevia  arteries,  and  the  gastric  or  coronary  branch  of  the  portal. 

The  lymphatics  (Figs.  570  and  .571)  arise  in  the  mucous  membrane  and  terminate  in  a  net- 
work in  the  submucous  tissue.  From  this  network  trunks  arise  which  perforate  the  muscular 
coat  in  the  regions  of  the  curvatures  and  terminate  in  the  seromuscular  collecting  trunks.  The 
details  of  the  lymphatic  drainage  of  the  stomach  are  given  on  page  792. 

The  nerves  of  the  stomach  come  from  the  right  and  left  vagi  and  from  the  solar  plexus  of 
the  sympathetic.  The  left  \agus  ])asses  to  the  front  of  the  stomach,  and  the  right  nerve  passes 
to  the  back,  and  thev  unite  with  the  fibres  of  the  sympathetic.  The  fibers  thus  formed  are  mostly 
amvelinic.  Thev  form  Auerbach's  plexus  in  the  muscular  coat  between  the  circular  and  longi- 
tudinal fibres  and  Meissner's  plexus  in  the  submucous  coat,  the  latter  plexus  being  formed  by 
fibres  from  the  former.  Auerbach's  ])lexus  supplies  the  muscular  coat  of  the  stomach,  while 
fibres  from  Meissner's  plexus  ramify  in  the  submucous  coat  and  terminate  in  the  muscularis 
mucosae  and  the  mucous  membrane,  branches  passing  to  the  gastric  glands  and  to  just  beneath 
the epithehum.     (See  nerve  supply  of  small  intestine,  p.  1295). 

Relations  of  the  Stomach. — The  antero-superior  surface  is  in  relation  with  the  left 
and  quadrate  lobes  of  the  liver,  the  ventral  abdominal  parietes,  and  the  costal  portion  of  the 
Diaphragm.  The  postero-inferior  surface  is  in  relation  with  the  lumbar  portion  of  the  Dia- 
phragm, the  pancreas,  and  the  transverse  mesocolon,  while  the  fundus  may  come  into  contact 
with  the  left  kidney  and  suprarenal  gland,  the  spleen,  and  splenic  fiexure  of  the  colon.  The  lesser 
curvature  is  directed  toward  the  transverse  fissure  of  the  liver,  while  the  greater  curvature  may 
be  in  contact  with  the  transverse  colon. 


Movements  and  Innervation  of  the  Stomach, 

Movements. — It  has  apparently  been  demonstrated  that  the  stomach  "consists  of  two  parts 
physiologically  distinct."'  The  cardiac  portion  of  the  stomach  is  a  food  reservoir  in  which 
salivary  digestion  continues;  the  pyloric  portion  is  the  seat  of  active  gastric  digestion.  Cannon 
affirms  that  there  are  no  peristaltic  waves  in  the  cardiac  portion,  but  that  as  the  food  passes  from 
the  pyloric  portion  into  the  intestines,  tonic  contraction  of  the  muscles  of  the  fundus  squeezes  the 
contents  of  the  pyloric  portion.  Moritz,  Levan,  and  Cannon  assert  that  muscular  activity  is 
chiefly  manifested  in  the  pyloric  portion.  In  this  portion  during  digestion  there  is  a  succes- 
sion of  peristaltic  waves,  which  waves  in  the  human  being  pass  at  the  rate  of  three  per  minute 
(Moritz).  Cannon  points  out  that  the  efficiency  of  peristalsis  in  mixing  the  food  depends 
upon  the  contraction  of  the  pyloric  sphincter.  So  long  as  the  sphincter  holds,  each  constric- 
tion ring  coursing  from  the  middle  to  the  end  of  the  stomach  presses  the  food  into  a  blind  pouch; 
the  tood,  unable  to  escape  through  the  pyloric  opening,  has  as  its  only  outlet  the  opening  in 
the  advancing  ring.  This  is  an  admirable  device  for  bringing  the  food  under  the  influence  of 
the  glandular  secretions  of  the  pyloric  region.  For,  as  a  constriction  occurs,  the  secreting  sur- 
face enclosed  by  the  narrowed  muscular  ring  is  pressed  close  around  the  food  within  the  ring. 
As  the  constriction  advances  it  continually  presses  inward  fresh  glandular  surfaces,  and  further- 

1  Walter  B.  Cannon, .  Medical  News,  May  20,  1905. 


1280  THE  ORGANS  OF  DIGESTION 

more,  as  the  constriction  advances,  a  thin  stream  of  food  is  continuously  forced  back  through 
the  ring  and  thus  past  the  moutlis  of  the  glands.  The  old  view  that  the  pyloric  sphincter  only 
opens  after  several  hours'  continuance  of  the  process  of  digestion,  and  that  then  the  stomach 
empties  at  once,  is  incorrect.  It  is  emptied  in  small  amounts,  which  escape  at  frequent  intervals 
because  of  the  intermittent  opening  of  the  pylorus.  When  the  pylorus  is  open  a  wave  of  peri- 
stalsis forces  some  of  the  material  from  the  stomach  into  the  duodenum  (Cannon). 

Cannon  is  of  the  opinion  that  the  pyloric  sphincter  is  caused  to  relax  by  the  presence  of  free 
hvdrochloric  acid  in  the  pyloric  portion  of  the  stomach.  When  the  pylorus  is  open  acid  chyme 
passes  into  the  duodenum,  and  acid  in  the  duodenum  causes  the  pylorus  to  close.  The  acid 
in  the  duodenum  causes  a  flow  of  alkaline  pancreatic  juice  and  the  acid  is  neutralized.  "As 
the  neutralizing  proceeds,  the  stimulus  closing  the  pylorus  is  weakened  until  the  acid  in  the 
stomach  again  opens  the  sphincter."' 

Innervation. — The  stomach,  as  previously  shown,  has  nerve  plexuses  in  its  walls  and  is 
connected  to  the  cerebrospinal  and  sympathetic  systems.  It  is  probable  that  gastric  peristalsis 
is  due  to  a  local  reflex  from  Auerbach's  plexus  (Magnus),  the  local  reflex  being  inaugurated  by 
local  stimulation,  which  stimulation,  in  the  words  of  Bayliss  and  Starling,  "produces  excitation 
above  and  inhibition  below  the  excited  spot."^  Reversed  peristalsis  cannot  occur  if  "the  reflex 
mechanism  is  intact"  (Cannon).  Cannon  in  the  previously  quoted  article  states  that  cutting 
the  vagi  or  splanchnic  nerves  does  not  destroy  the  reflex  mechanism  of  the  pylorus,  but,  never- 
theless, it  is  markedly  affected  by  the  central  nerve  system. 

Surface  Form  (see  p.  1241). — The  cardiac  orifice  corresponds  to  the  articulation  of  the  seventh 
left  costal  cartilage  with  the  sternum.  The  pyloric  orifice  of  the  empty  stomach  is  about  an  inch 
to  the  right  of  the  midline  in  the  transpyloric  line.  According  to  Braune,  when  the  stomach  is 
distended,  the  pylorus  moves  considerably  to  the  right,  sometimes  as  much  as  three  inches. 
The  fundus  of  the  stomach  reaches,  on  the  left  side,  as  high  as  the  level  of  the  sixth  costal  car- 
tilatre  of  the  left  side,  being  a  little  below  and  behind  the  apex  of  the  heart.  The  portion  of  the 
distended  stomach  which  is  in  contact  with  the  abdominal  walls,  and  is  therefore  accessible  for 
opening  in  the  operations  of  gastrotomy  and  gastrostomy,  is  represented  by  a  triangular  space, 
the  base  of  which  is  formed  by  a  line  drawn  from  the  tip  of  the  tenth  costal  cartilage  on  the  left 
side  to  the  tip  of  the  ninth  costal  cartilage  on  the  right,  and  the  sides  by  two  lines  drawn  from 
the  extremity  of  the  eighth  costal  cartilage  on  the  left  side  to  the  end  of  the  base  line.  What>  is 
commonly  termed  the  semilunar  space  of  Traube  is  that  portion  of  the  stomach  which  is  not 
covered  by  neighboring  viscera.  It  is  bounded  above  by  the  left  lobe  of  the  liver  and  the  inferior 
margin  of  the  left  lung,  posteriorly  and  to  the  left  by  the  spleen;  on  percussion,  this  area  is  nor- 
mally tympanitic. 

Applied  Anatomy. — Operations  on  the  stomach  are  frequently  performed,  ulcers  are  excised, 
malignant  growths  are  removed  with  the  associated  lymphatic  involvement,  the  entire  stomach 
may  be  removed  for  cancer,  etc.  By  "gastrotomy"  is  meant  an  incision  into  the  stomach  for  the 
removal  of  a  foreign  body,  or  the  arrest  of  hemorrhage,  or  for  exploration,  the  opening  being 
immediately  afterward  closed — in  contradistinction  to  "gastrostomy,"  the  making  of  a  more  or 
less  permanent  fistulous  opening.  Gastrotomy  is  probably  best  performed  by  an  incision  in  the 
linea  alba,  especially  if  the  foreign  body  is  large.  The  cut  may  reach  from  the  ensiform  car- 
tilage to  the  umbilicus.  The  incision  may  be  made  over  the  foreign  body  itself,  where  this  can  be 
felt,  or  by  one  of  the  incisions  for  gastrostomy,  to  be  mentioned  shortly.  The  peritoneal  cavity 
is  opened,  and  the  point  at  which  the  stomach  is  to  be  incised  decided  upon.  This  portion  is 
then  brought  out  of  the  abdominal  wound  and  sponges  carefully  packed  around.  The  stomach 
is  now  opened  by  a  transverse  incision  and  the  foreign  body  extracted.  The  wound  in  the 
stomach  is  then  "closed  by  Lembert  sutures — i.  e.,  by  sutures  passed  through  the  peritoneal, 
muscular,  and  submucous  coats  in  such  a  way  that  the  peritoneal  surfaces  on  each  side  of  the 
wound  are  brought  into  apposition.  Gastrostomy  was  formerly  done  in  two  stages  by  the  direct 
method.  The  first  stage  consisted  in  opening  the  abdomen,  drawdng  up  the  stomach  into  tht 
external  wound,  and  fixing  it  there;  and  the  second  stage,  performed  from  two  to  four  days 
afterward,  consisted  in  opening  the  stomach.  The  operation  is  now  done  by  a  valvular  method. 
The  following  plan  is  known  as  the  Ssabanejew-Frank  operation.  An  incision  is  commenced 
opposite  the  eighth  intercostal  space,  two  inches  to  the  left  of  the  median  line,  and  carried  down- 
ward for  three  inches.  By  this  incision  the  fibres  of  the  Rectus  muscle  are  exposed  and  these 
are  separated  from  one  another  in  the  same  line.  The  posterior  layer  of  the  sheath,  the  trans- 
versalis  fascia,  and  the  peritoneum  are  then  divided,  and  the  peritoneal  cavity  is  opened.  In- 
stead of  the  above  incision,  the  curved  incision  of  Fenger  can  be  made  at  the  margin  of  the  left 
costal  cartilages.  The  anterior  wall  of  the  stomach  is  now  seized  and  drawn  out  of  the  wound 
and  a  silk  suture  passed  through  its  submucous,  muscular,  and  serous  coats  at  the  point  selected 
for  opening  the  viscus.  This  is  held  by  an  assistant  so  that  a  long  conical  diverticulum  of  the 
stomach  protrudes  from  the  external  wound,  and  the  parietal  peritoneum  and  the  posterior  layer 
of  the  sheath  of  the  Rectus  are  sutured  to  the  base  of  the  cone.    A  second  incision  is  made  through 

»  Walter  B.  Cannon,  Medical  News,  May  20,  1905.  ^  Ibid. 


THE  SMALL  INTESTINE  1281 

the  skin,  over  the  margin  of  the  costal  cartilage,  above  and  a  little  to  the  outer  side  of  the  first 
incision.  If  Fenger's  incision  were  used,  the  second  incision  should  be  above  the  margin  of  the 
cartilages.  With  a  pair  of  dressing  forceps  a  track  is  made  under  the  skin  through  the  subcu- 
taneous tissue  from  the  one  opening  to  the  other  and  the  diverticulum  of  the  stomach  is  drawn 
along  this  track  bv  means  of  this  suture  inserted  into  it;  so  that  its  apex  appears  at  the  second 
opening.  A  small  perforation  is  now  made  into  the  stomach  through  this  protruding  ape.x  and 
its  margin  carefully  and  accurately  sutured  to  the  margin  of  the  external  wound.  The  remainder 
of  this  incision  and  the  whole  of  the  first  incision  are  then  closed  in  the  ordinary  way  and  the 
wound  dressed. 

In  cases  of  gastric  ulcer,  perforation  sometimes  takes  place,  and  this  was  formerly  rewarded 
as  an  almost  fatal  complication.  In  the  present  day,  by  opening  the  abdomen  and  closing 
the  perforation,  which  is  generally  situated  on  the  anterior  surface  of  the  stomach,  a  consider- 
able percentage  of  cases  are  cured,  provided  the  operation  is  undertaken  within  twelve  to  fifteen 
hours  after  the  perforation  has  taken  place.  The  opening  is  best  closed  by  bringing  the  peri- 
toneal surfaces  on  either  side  into  apposition  by  means  of  Lembert  sutures. 

Pylorectomy  or  excision  of  the  pylorus  is  performed,  particularly  for  early  cancer,  but  is  also 
done  for  cicatricial  stricture  and  for  ulcer.  The  mortality  after  operation  for  cancer  was,  until 
recently,  very  great,  but  of  late  years  it  has  been  notably  reduced,  though  it  is  still  much  higher 
than  that  which  follows  operations  for  any  non-malignant  condition. 

In  operating  for  cancer,  bear  in  mind  Cuneo's  study  of  the  lymphatics  (p.  792).  These 
observations  indicate  that  the  fundus  and  two-thirds  of  the  greater  curvature  are  free  from 
lymphatic  involvement  in  pyloric  cancer.'  In  every  operable  case  of  cancer  of  the  pylorus 
the  entire  lesser  curvature  must  be  removed  up  to  the  gastric  artery  (Mikulicz's  point),  and 
the  greater  curvature  must  be  removed  to  the  left  of  the  involved  lymph  nodes  (Hartmann's 
rule). 

Gastroenterostomy  is  an  operation  which  establishes  a  fistulous  communication  between  the 
stomach  and  jejunum.  The  operation  is  often  called  gastrojejunostomy.  The  opening  may  be 
made  upon  either  the  anterior  or  the  posterior  wall  of  the  stomach,  between  the  cardia  and  the 
seat  of  pyloric  disease.  The  operation  is  employed  for  stricture  of  the  pylorus  (benign  or  malig- 
nant), and  occasionally  for  ulcer  of  the  stomach. 

Hypertrophy  and  spasm  of  the  circumferential  muscular  coat  of  the  pylorus  coming  on 
during  the  first  few  weeks  of  life,  and  somewhat  erroneously  described  as  congenital  hyper- 
trophic stenosis  of  the  pylorus,  is  a  rare  but  serious  disorder  of  infancy.  It  is  characterized  by 
abdominal  pains  and  obstinate  vomiting  coming  on  after  food  has  been  given,  and  gastric 
peristalsis  can  be  observed  by  inspection  of  the  child's  epigastrium  after  it  has  been  fed  and 
before  vomiting  has  occurred.  Progressive  wasting  for  want  of  nourishment  and  death  from 
exhaustion  tend  to  ensue.  Treatment  should  be  by  washing  out  the  stomach,  and  the  admin- 
istration at  frequent  intervals  of  small  quantities  of  easily  digested  food.  Surgical  interference 
— pyloroplasty  or  pylorectomy — entailing  a  severe  operation,  gives  less  favorable  result. 

Total  gastrectomy  is  the  removal  of  the  entire  stomach.  It  is  only  used  for  cancer.  It  was  first 
performed  by  Conner,  of  Cincinnati.  The  first  successful  operation  was  done  by  Schlatter,  of 
Zurich,  in  1898.  A  number  of  successes  have  been  reported.  It  is  a  justifiable  operation  onlv  in 
a  case  in  which  almost  the  entire  stomach  is  cancerous,  in  which  the  viscus  is  movable,  in  which 
there  are  no  secondary  deposits,  and  no  irremovable  diseased  lymph  nodes. 

Gastrogastrostomy  is  an  operation  employed  in  hour-glass  stomach.  In  this  operation  an 
anastomosis  is  made  between  the  pyloric  and  cardiac  ends  of  the  stomach. 

Gastroplication  is  the  operation  of  suturing  the  stomach  wall  into  folds  or  reefs,  in  order  to 
lessen  its  size.     It  is  employed  in  some  cases  of  gastric  dilatation. 

Gastroptosis  is  a  condition  in  which  the  stomach  is  displaced  downward.  In  some  of  these 
cases  the  greater  curvature  almost  reaches  the  level  of  the  symphysis  pubis,  and  the  lesser  curva- 
ture is  midway  between  the  umbilicus  and  ensiform  cartilage.  The  condition  is  usually  associated 
with  enteroptosis  and  movable  kidney  (nephroptosis).  In  this  condition  the  gastrohepatic  omen- 
tum is  pulled  upon  and  lengthened.  The  best  operation  for  gastroptosis  was  devised  by  Beyea. 
He  applies  sutures  so  as  to  make  folds  in  and  thus  shorten  the  stretched  omentum.  Thus'  the 
stomach  is  elevated  to  its  proper  position,  and  its  mobility  is  not  lessened,  as  it  is  in  other  opera- 
tions which  suture  it  to  the  abdominal  wall. 


THE  SMALL   INTESTINE  (INTESTINUM  TENUE). 

The  small  intestine  is  a  convoluted  tube,  extending  from  the  pylorus  to  the 
ileocecal  valve,  where  it  terminates  in  the  large  intestine.     It  is  about  twenty  feet 

'  Willium  J.  Mayo,  .\nnals  of  Surgery,  March,  1904. 

81 


1282  THE  ORGANS  OF  DIGESTION 

(6  m.)  in  length,'  and  gradually  diminishes  in  size  from  its  commencement 
to  its  termination.  It  is  contained  in  the  central  and  lower  part  of  the  abdominal 
cavity,  and  is  surrounded  above  and  at  the  sides  by  the  large  intestine;  a  portion 
of  it  extends  below  the  brim  of  the  pelvis  and  lies  in  front  of  the  rectum. 
It  is  in  relation,  in  front,  with  the  great  omentum  and  abdominal  parietes,  and 
the  greater  part  of  it  is  connected  to  the  vertebral  column  by  a  fold  of  peritoneum, 
the  mesentery  (p.  1263).  The  small  intestine  is  divisible  into  three  portions — 
the  duodenum,  the  jejunum,  and  the  ileum. 


The  Duodenum  (Figs.  1023,  1030). 

The  duodenum  has  received  its  name  from  being  about  equal  in  length  to  the 
breadth  of  twelve  fingers  (ten  inches).  It  is  the  shortest,  the  widest,  and  the  most 
fixed  part  of  the  small  intestine,  and  has  no  mesentery,  being  only  partially  in- 
vested by  peritoneum.  Somewhat  more  than  the  upper  half  of  the  duodenum  is 
placed  in  the  epigastric  region;  the  remainder  is  in  the  umbilical  region.  Its 
course  prevents  a  remarkable  curve,  somewhat  of  the  shape  of  an  incomplete  circle, 
so  that  its  termination  is  not  far  removed  from  its  beginning. 

In  the  adult  the  course  of  the  duodenum  is  as  follows:  Commencing  at  the 
pylorus  it  passes  backward,  upward,  and  to  the  right,  beneath  the  quadrate  lobe 
of  the  liver  to  the  neck  of  the  gall-bladder,  varying  slightly  in  direction  according 
to  the  degree  of  distention  of  the  stomach;  it  then  takes  a  sharp  curve  and  descends 
along  the  right  margin  of  the  head  of  the  pancreas,  for  a  variable  distance,  gener- 
ally to  the  level  of  the  upper  border  of  the  body  of  the  fourth  lumbar  vertebra. 
It  now  takes  a  second  bend,  and  passes  from  right  to  left  across  the  front  of  the 
vertebral  column,  having  a  slight  inclination  upward;  and  to  the  left  side  of  the 
vertebral  column  it  ascends  for  about  an  inch,  and  then  terminates  opposite  the 
second  lumbar  vertebra  in  the  jejunum.  As  it  unites  with  the  jejunum  it  turns 
abruptly  forward,  forming  the  duodenojejimal  flexure.  From  the  above  descrip- 
tion it  will  be  seen  that  the  duodenum  may  be  divided  into  four  portions — superior, 
descending,  transverse,  and  ascending. 

The  first  or  superior  portion  {pars  superior)  (Figs.  1023  and  1024)  is  about 
two  inches  (5  cm.)  in  length.  Beginning  at  the  pylorus,  it  ends  at  the  level  of  the 
neck  of  the  gall-bladder.  It  is  the  most  movable  of  the  four  portions.  It  is  almost 
completely  covered  by  peritoneum  derived  from  the  two  layers  of  the  lesser  omen- 
tum, but  a  small  part  of  its  posterior  surface  near  the  neck  of  the  gall-bladder 
and  the  inferior  vena  cava  is  uncovered  (Fig.  1024).  It  is  in  such  close  relation 
with  the  gall-bladder  that  it  is  usually  found  to  be  stained  by  bile  after  death, 
especially  on  its  anterior  surface.  It  is  in  relation  above  and  in  front  with  the 
quadrate  lobe  of  the  liver,  lying  in  a  slight  concavity,  the  impressio  duodenalis,  and 
the  gall-bladder;  behind,  with  the  gastroduodenal  artery,  the  common  bile  duct, 
and  the  portal  vein;  and  below,  with  the  head  of  the  pancreas. 

The  second  or  descending  portion  (pars  descendens)  (Figs.  1023  and  1025)  is 
between  three  and  four  inches  (7.5  to  10  cm.)  in  length,  and  extends  from  the  neck 
of  the  gall-bladder  on  a  level  with  the  first  lumbar  vertebra  along  the  right  side 
of  the  vertebral  column  as  low  as  the  body  of  the  fourth  lumbar  vertebra.  It  is 
crossed  in  its  middle  third  by  the  transverse  colon,  the  posterior  surface  of  which 
is  uncovered  by  peritoneum  and  is  connected  to  the  duodenum  by  a  small  quantity 
of  connective  tissue.  The  portions  of  the  descending  part  of  the  duodenum  above 
and  below  this  interspace  are  named  the  supracolic  and  infracolic  portions,  and  are 

*  Treves  states  that  m  one  hundred  cases  the  average  length  of  the  small  intestine  in  the  adult  male  was  22 
feet  6  inches,  and  in  the  adult  female  23  feet  4  inches;  but  that  it  varies  very  much,  the  extremes  in  the  male 
being  31  feet  10  inches  in  one  case  and  15  feet  6  inches  in  another,  a  difference  of  over  15  feet.  He  states  that 
he  has  convinced  himself  that  the  length  of  the  bowel  is  independent,  in  the  adult,  of  age,  height,  and  weight. 


THE  DUODENUM 


1283 


covered  in  front  by  peritoneum  (Fig.  1025).     Tlie  infracolic  part  is  covered  by  the 
right  leaf  of  the  mesentery.    Posteriorly  the  descending  portion  of  the  duodenum 


Trihntary  to 


Hepatic  artery,  portal 
vein,  and  bile  duct. 


Supra  leual 
oupiiic! 


tira  of  Diaphragm. 
Gast}  ic  a}tei  y 


Fig.  1023. — Relations  of  duodenum,  pancreas,  and  spleen.     (From  a  cast  by  Professor  Birmingham.')     The  broken 
line  represents  the  line  of  attachment  of  the  transverse  ] 


is  not  covered  by  peritoneum.     It  is  in  relation,  in  front,  with  the  transverse  colon, 
and  above  this  with  the  right  lobe  of  the  liver,  where  it  lies  in  the  impressio  duo- 


^  In  the  subject  from  which  the  east  was  taken  the  left  kidney  i 


1284 


THE  ORGANS  OF  DIGESTION 


denalis  for  the  second  part  of  the  duodenum ;  behind,  with  the  inner  part  of  the  right 
kidney,  to  which  it  is  connected  by  loose  areolar  tissue,  the  right  renal  vessels,  and 
the  inferior  vena  cava;  at  its  inner  side  is  the  head  of  the  pancreas  and  the  common 
bile  duct;  to  its  outer  side  is  the  hepatic  flexure  of  the  colon.  The  common  bile 
duct  passes  downward  behind  the  first  portion  of  the  duodenum,  descends  to  the 


Lesser  omentum 


Hepatic  Artery 


Portal  Vein 


/■'     ^      .'.-'Greater' 
t  --'.-•         Sac 

omentum     Transverse  Mesocolon  E.  A.  S. 

Fig.  1024. — Diagram  of  cross-section  of  the  first 
part  of  tile  duodenum,  to  sliow  its  peritoneal  rela- 
tions.    (Gerrisli.) 


Fig.  1025. — Diagram  of  cross-section  of  the  second 
part  of  the  duodenum,  to  show  its  peritoneal  rela- 
tions.    (Gerrish.) 


inner  side  of  the  second  portion,  is  joined  by  the  pancreatic  duct,  and  the  two  to- 
gether perforate  the  inner  side  of  this  portion  of  the  intestine  obliquely,  and  empty 
into  the  duodenum  by  a  common  opening  or  by  two  openings  at  the  summit  of  a 
papilla,  some  three  and  a  half  or  four  inches  (9  to  10  cm.)  beyond  the  pylorus. 


.^J^il:::;--. 


Fig.  1026. — Diagram  of  the  third  jjart  of  the 
duodenum,  to  show  its  peritoneal  relations.  (Ger- 
rish.) 


Fig.  1027. — Diagram  of  the  fourth  part  of  the  duode- 
num, to  show  its  peritoneal  relations.      (Gerrish.)  ' 


The  relations  of  the  second  part  of  the  duodenum  to  the  right  kidney  present  con- 
siderable variations. 

The  third,  preaortic,  or  transverse  portion  {pars  horizonialis  inferior)  (Figs. 
1023  and  1026)  is  from  two  to  three  inches  in  length.  It  commences  at  the 
right  side  of  the  upper  border  of  the  fourth  lumbar  vertebra  and  passes  from  right 


THE  DUODENUM 


1285 


to  left,  with  a  slight  indination  upward,  in  front  of  the  great  vessels  and  crura 
of  the  Diaphragm,  and  ends  in  the  fourth  portion  in  front  of  or  just  to  the  left 
of  the  abdominal  aorta.  It  is  crossed  by  the  superior  mesenteric  vessels  and  the 
mesentery.  Its  ventral  surface  is  co\'ered  by  peritoneum,  except  near  the  middle 
line,  where  it  is  crossed  by  the  superior  mesenteric  vessels  (Fig.  1026).  Its  posterior 
surface  rests  upon  the  aorta,  the  inferior  vena  cava,  and  the  crura  of  the  Dia- 
phragm.    Its  upper  surface  is  in  relation  with  the  head  of  the  pancreas. 

The  fourth  or  ascending  portion  of  the  duodenum  (pars  ascendens)  (Figs.  1023 
and  1027)  is  about  an  inch  (2.5  cm.)  long.  It  ascends  on  the  left  side  of  the 
vertebral  column  and  aorta,  as  far  as  the  level  of  the  upper  border  of  the  second 
lumbar  vertebra,  where  it  turns  abruptly  forward  to  become  the  jejunum,  forming 
the  duodenojejunal  flexure  {flexura  diiodenojejunalis)  (Fig.  1028).  It  lies  in  front 
of  the  left  Psoas  muscle  and  left  renal  vessels,  and  is  covered  in  front  and  partly 
at  the  sides  by  peritoneum,  continuous  with  the  left  portion  of  the  mesentery 
(Fig.  1027).  The  left  side  of  the  termination  of  the  ascending  portion  is  also 
covered  by  peritoneum,  and  in  this  region  some  of  the  duodenal  fossae  are  found 
(p.  1265). 


DIAPHRAGM 


CCELIAC  AXIS 


GANGLION  OF 
CCELIAC  PLEXUS 
SUPERIOR    MESEA 
TERIC  ARTERY 
SUSPENSORY 
MUSCLE  OF 
DUODENUM 


CELLULAR  MEMBRANE 
3NNECTINGTHE  PARTS 
'FTHE  DUODENALRING 
BEHIND  THE  PANCREAS 


Fia.  1028. — Suspensory  muscle  of  the  duodenu 


■  muscle  of  Treitz,      (Po 


and  Charpy.) 


The  first  part  of  the  duodenum,  as  stated  above,  is  somewhat  movable,  but 
the  rest  is  practically  fixed  and  is  bound  down  to  neighboring  viscera  and  the 
posterior  abdominal  wall  by  the  peritoneum.  In  addition  to  this,  the  fourth  part 
of  the  duodenum  and  the  duodenojejunal  flexure  is  further  bound  down  and  fixed 
by  a  structure  called  the  Suspensory  muscle  of  the  duodenum  or  the  suspensory 
ligament  of  Treitz  {m.  suspensorius  duoden  i)  (Fig.  1 028) .  This  structui-e  com  niences 
in  the  connective  tissue  around  the  CQ?liac  axis  and  left  crus  of  the  Diaphragm, 
and  passes  downward  to  be  inserted  into  the  superior  border  of  the  duodenojejunal 
curve  and  a  part  of  the  ascending  duodenum,  and  from  this  it  is  continued  into  the 
mesentery.  It  possesses,  according  to  Treitz,  some  few  nonstriated  muscle  fibres 
mixed  with  the  fibrous  tissue,  of  which  it  is  principally  made  up.  It  is  of  little 
importance  as  a  muscle,  but  acts  as  a  suspensory  ligament. 


1286 


THE  ORGANS  OF  DIGESTION 


Interior  of  the  Duodenum  (Fig.  1029).— The  proximal  part  of  the  duodenum  is 
comparatively  smooth.     Valvulae  conniventes  begin  to  appear  in  the  distal  half 


COMMON   BILE    DUCT 

Fig.  1029.— The  interior  of  the  duodenum.      (Spalteholz.) 


Gastric  artery 


Hepatic  fiuct-^rr^—^^^ 
Cystic  duct    ^°-  ^      ^^^- 
Hepatic  artery- 
liigfd  sjiprarenal, 
gland 
Pyloric  orifice- 
HigfU  gastro-epiploLC 
artery 


'  ""'¥^ ' '  '/111  ni^B'  I K '  .l""" '" ' 

Spermatic  veisels  ^Spermatic  vessels 

Ivjerior  viesenteric  artery 

Via.  1030.— The  duodenum,  its  four  parts  marked  a,  6,  c,  d.     The  Hver  is  hfted  up;  the  greater  part  of  the 
stomach  is  removed,  broken  hues  indicating  its  former  position.     (Testut.) 


THE  JEJUNUM  AND  ILEUM 


1287 


of  the  first  portion,  being  at  first  trivial  elevations  irregularly  placed.  They 
become  higher,  regular,  and  more  numerous  farther  on,  and  near  the  termination 
of  the  duodenum  are  strongly  marked  and  closely  placed  transverse  or  spiral  folds 
(Fig.  1029  and  p.  1289).  In  the  descending  portion  (Fig.  1029),  to  the  side  and 
rear,  is  a  longitudinal  fold  {plica  longitvdinalis  duodeni),  which  is  formed  by  the 
projection  of  the  bile  duct  and  pancreatic  duct  beneath  the  mucous  membrane. 

The  caruncula  major  of  Santorini  or  the  bile  papilla  is  a  projection  in  the  lower 
part  of  the  longitudinal  fold.  At  the  summit  of  this  papilla  the  bile  duct  and  pan- 
creatic duct  empty  into  the  duodenum.  One  inch  above  and  half  an  inch 
or  more  in  front  of  the  bile  papilla  is  a  much  smaller  papilla,  the  caruncula 
minor  of  Santorini  {papilla  duodeni  [Santoriai'\),  on  the  summit  of  which  the  acces- 
sory pancreatic  duct  of  Santorini  opens  when  present. 


ANASTOMOSIS    OF  THE 
TWO   PANCREATICO- 
DUODENAL ARTERIES 


Fig.  1031.' — The  bloodvessels  of  the  duodenum.     (Poirier  and  Charpy.) 

Structure  of  the   Duodenum.— (See  Structure  of  the  Small  Intestine,  p.  1289.) 

Vessels  and  Nerves. — The  arteries  (Fig.  1031)  supplying  the  duodenum  are  the  pyloric  and 
pancreaticoduodenal  branches  of  the  hepatic,  and  the  inferior  pancreaticoduodenal  branch 
of  the  superior  mesenteric.  The  veins  (Fig.  1031)  correspond  to  the  arteries.  The  superior 
duodenal  vein  passes  into  the  superior  mesenteric,  and  the  inferior  duodenal  vein  passes  into 
the  portal.  The  Ijrmphatics  pass  along  with  the  pancreaticoduodenal  arteries,  lymph  nodes 
being  present  here  and  there,  and  terminate  in  the  nodes  about  the  coeliac  axis.  The  nerves 
are  derived  from  the  solar  plexus. 

Applied  Anatomy. —  Ulcer  oftlie  duodenum  is  more  common  than  used  to  be  thought.  The 
portion  of  the  duodenum  between  the  pylorus  and  the  bile  papilla  is  about  four  inches  in  length, 
and  is  called  by  the  Mayo  brothers  the  vestibule  of  the  duodtnum.  Here  the  acid  gastric  juice 
enters  and  may  produce  an  ulcer.  The  portion  of  the  duodenum  beldvv  the  vestibule  is  not 
liable  to  ulcer,  because  it  is  protected  by  the  alkaline  bile  and  pancreatic  juice. 

A  duodenal  ulcer  may  perforate  a  large  duodenal  vessel  and  cause  death  from  hemorrhage, 
or  may  perforate  the  intestine  and  produce  septic  peritonitis.  A  perforated  ulcer  is  treated 
by  laparotomy  and  closure  of  the  perforation.  Occasionally  ulceration  of  the  duodenal  glands 
(Curling's  ulcer)  may  occur  in  cases  of  extensive  burns  of  the  skin,  but  is  not  a  very  common 
complication. 


The  Jejunum  and  Ileum  (Figs.  972,  1003). 

The  remainder  of  the  small  intestine  from  the  termination  of  the  duodenum 
comprises  the  jejunum  and  ileum ;  the  former  name  being  given  to  the  upper  two- 
fifths  and  the  latter  to  the  remaining  three-fifths.  Spalteholz  and  others  call  all  of 
the  small  intestine  below  the  duodenum  the  intestinum  tenue  mesenterial.     There 


1288  THE  ORGANS  OF  DIGESTION 

is  no  morphological  line  of  distinction  between  the  jejunum  and  ileum,  and  the 
division  is  arbitrary;  but  at  the  same  time  it  must  be  noted  that  the  character  of 
the  intestine  gradually  undergoes  a  change  from  the  commencement  of  the  jeju- 
num to  the  termination  of  the  ileum,  so  that  a  portion  of  the  bowel  taken  from 
these  two  situations  would  present  characteristics  and  marked  differences.  These 
are  briefly  as  follows : 

Jejunum.  Ileum. 

Calibre larger  (1|  inches).  smaller  (1  inch). 

Wall thicker,  heavier.  thinner,  lighter. 

Color red,  more  vascular.  pale,  less  vascular. 

Valvulae  conniventes        .      .  prominent.  smaller  and  fewer. 

Lymphoid  tissue  ....  diffuse  and  few  nodules.  diffuse  and  manj'  Peyer's  patches. 

Villi numerous,  short,  and  broad,    fewer,  slender,  filiform. 

Intestinal  glands  ....  more  numerous.  less  numerous. 

The  Jejunum  (intestinum  jejununi). — The  jejunum  is  wider,  its  diameter  being 
about  one  inch  and  a  half  (3.75  cm.),  and  is  thicker,  more  vascular,  and  of  a  deeper 
color  than  the  ileum,  so  that  a  given  length  weighs  more.  Its  valvulae  conniventes 
are  large  and  thickly  set  and  its  villi  are  larger  than  in  the  ileum.  The  patches  of 
Peyer  are  almost  absent  in  the  upper  part  of  the  jejunum,  and  in  the  lower  part 
are  less  frequently  found  than  in  the  ileum,  and  are  smaller  and  tend  to  assume 
a  circular  form.  Brunner's  glands  are  only  found  in  the  duodenum.  By  grasping 
the  jejunum  between  the  finger  and  thumb  the  valvulae  conniventes  can  be  felt 
through  the  walls  of  the  gut;  these  being  absent  in  the  lower  part  of  the  ileum, 
it  is  possible  in  this  way  to  distinguish  the  upper  from  the  lower  part  of  the  small 
intestine. 

The  Ileum  (intestinum  ilewni). — The  ileum  is  narrower,  its  diameter  being 
one  inch  (2.5  cm.)  or  a  little  more,  and  its  coats  are  thinner  and  less  vascular 
than  those  of  the  jejunum.  It  possesses  but  few  valvulae  conniventes,  and  they 
are  small  and  disappear  entirely  toward  its  lower  end,  but  Peyer's  patches  are 
larger  and  more  numerous.  The  jejunum  for  the  most  part  occupies  the  umbilical 
and  left  iliac  regions,  while  the  ileum  occupies  chiefly  the  umbilical,  hypogastric, 
right  iliac,  and  pelvic  regions,  and  terminates  in  the  right  iliac  fossa  by  opening 
into  the  inner  side  of  the  commencement  of  the  large  intestine.  The  jejunum 
and  ileum  are  attached  to  the  posterior  abdominal  wall  by  an  extensive  fold  of 
peritoneum,  the  mesentery  (p.  1263),  which  allows  the  freest  motion,  so  that  each 
coil  can  accommodate  itself  to  changes  in  form  and  position.  The  mesentery  is 
fan-shaped;  its  posterior  border  or  root,  about  six  inches  (15  cm.)  in  length,  is 
attached  to  the  posterior  abdominal  wall  from  the  left  side  of  the  body  of  the 
second  lumbar  vertebra  to  the  right  iliac  fossa,  crossing  successively  the  third  part 
of  the  duodenum,  the  aorta,  the  inferior  vena  cava,  the  right  ureter,  and  the 
right  Psoas  muscle  (Fig.  1004).  Its  breadth  between  its  vertebral  and  intestinal 
borders  is  about  eight  inches  (20  cm.)  from  its  commencement  to  its  termination 
at  the  intestine,  and  it  is  greater  in  the  middle  than  at  either  end  of  the  bowel. 
According  to  Lockwood,  it  tends  to  increase  in  length  as  age  advances.  Between 
the  two  layers  of  which  it  is  composed  are  contained  bloodvessels,  nerves,  lacteals, 
and  lymph  nodes,  together  with  a  variable  amount  of  fat. 

Meckel's  Diverticulum  (diverticulum  ilei). — ^This  consists  of  a  pouch  which  pro- 
jects from  the  lower  part  of  the  ileum  in  about  2  per  cent,  of  subjects.  Its  average 
position  is  about  three  feet  from  the  ileocolic  junction,  and  its  average  length  about 
two  inches.  Its  calibre  is  generally  the  same  as  that  of  the  ileum.  Sometimes 
only  a  portion  of  the  proximal  end  has  a  lumen  and  the  balance  of  the  structure 
is  impervious  and  shrunk  to  a  fibrous  cord.  In  other  cases  the  diverticulum  is 
actually  of  greater  diameter  than  the  intestine.  It  usually  is  at  a  right  angle 
to  the  intestine,  but  may  take  almost  any  direction.  Its  blind  extremity  may  be 
unattached  or  may  be  connected  with  the  abdominal  wall  or  with  some  other 


THE  JEJUNUM  AND  ILEUM 


1289 


portion  of  the  intestine  by  a  fibrous  .band.  It  represents  the  remains  of  the 
vitelline  or  omphalomesenteric  duct,  the  duct  of  communication  between  the 
umbilical  vesicle  and  the  alimentary  canal  in  early  fetal  life. 

Structure  of  the  Small  Intestine,  Including  the  Duodenum. — The  wall  of  the  small 
intestine  is  composed  of  four  coats — serous,  muscular,  subm.ucous,  and  mucous. 

The  Serous  Coat  {tunica  serosa). — The  relation  of  the  jieritoneum  to  the  duodenum  has  been 
described.  The  remaining  portion  of  the  small  intestine  is  surrounded  by  the  peritoneum, 
excepting  along  its  attached  or  mesenteric  border;  here  a  space  is  left  for  the  vessels  and  nerves 
to  pass  to  the  gut. 

The  muscular  coat  {tunica  muscularis)  consists  of  two  layers  of  fibres,  an  external  or  longi- 
tudinal layer  and  an  internal  or  circular  layer. 

The  longitudinal  fibres  {stratum  longitudinale)  are  thinly  scattered  over  the  surface  of  the 
intestine,  and  are  more  distinct  along  its  free  border. 

The  circular  fibres  {stratum  circulare)  form  a  thick,  uniform  layer;  they  siuround  the  cylinder 
of  the  intestine  in  the  greater  part  of  its  circumference,  and  are  composed  of  smooth  muscle  cells 
of  considerable  length.  The  muscular  coat  is  thicker  at  the  upper  than  at  the  lower  part  of  the 
small  intestine. 

The  submucous  coat  (fcla  subinucosa)  connects  the  mucous  and  muscular  layers.  It  con- 
sists of  loose,  filamentous  areolar  tissue,  which  forms  a  bed  for  the  subdivisions  of  the  nutrient 
vessels,  previous  to  their  distribution  to  the  mucous  surface,  also  for  the  lymph  channels  and 
nerves. 

The  submucous  coat  contains  lymph  nodules  {noduli  lymphatici).  Each  nodule  is  pyramidal 
or  pear-shaped,  and  the  apex  lies  in  the  mucous  membrane  and  forms  a  rounded  elevation. 
These  rounded  elevations  mark  the  solitary  follicles  and  Peyer's  patches  (Figs.  1033  and 
1040),  and  nowise  resemble  villi.  In  the  duodenum  the  submucous  tissue  contains  the  duo- 
denal glands.  The  submucous  tissue  is  prolonged  into  the  valvulae  conniventes.  It  contains 
bloodvessels,  Meissner's  plexus  of  nerves,  and  lymph  vessels. 

The  mucous  membrane  {tunica  mucosa)  is  thick  and  highly  vascular  at  the  upper  part  of  the 
small  intestine,  but  somewhat  paler  and  thinner  below.  It  consists  of  the  following  structures: 
next  the  areolar  or  submucous  coat  is  a  layer  of  unstriped  muscle  tissue,  the  muscularis  mucosae; 
internal  to  this  is  a  quantity  of  retiform  tissue,  enclosing  in  its  meshes  lymph  corpuscles  (diffuse 
lymphoid  tissue),  and  in  which  the  bloodvessels  and  nerves  ramify.  Lastly,  a  basement  mem- 
brane, supporting  a  single  layer  of  columnar  epithelial  and  goblet  cells.  They  are  granular 
in  appearance,  and  each  possesses  a  clear,  oval  nucleus.  At  their  superficial  or  unattached 
end  they  present  a  distinct  layer  of  highly  refracting  material,  the  cuticiilar  border,  marked  by 
vertical  striae. 

The  mucous  membrane  presents  for  examination  the  following  structures  contained  within  it 
or  belonging  to  it: 


Valvulae  conniventes. 

Villi. 

Intestinal  glands. 


Lymphatic  nodules   i  „        ,•'  •'    ^  j  r  n-  i 

■'     '^  I  reyer  s  or  agmmated  follicles. 


The  valvulae  conniventes  or  the  valves  of  Kerkring  {plicae  circulares  [Kerkringi])  (Fig.  1032) 
are  large  folds  or  valvular  flaps  projecting  into  the  lumen  of  the  bowel.  They  are  composed  of 
reduplications  or  folds  of  the  mucous  membrane,  the  two  layers  of  the  fold  being  bound  together 
by  submucous  tissue;  they  contain  no  muscular 
fibres,  and,  unlike  the  folds  in  the  stomach,  they 
are  permanent,  and  are  not  obliterated  when 
the  intestine  is  distended.  The  majority  ex- 
tend transversely  across  the  cylinder  of  the 
intestine  for  about  one-half  or  two-thirds  of  its 
circumference,  but  some  form  complete  circles, 
and  others  have  a  spiral  direction;  the  latter 
usually  extend  a  little  more  than  once  around 
the  bowel,  but  occasionally  two  or  three 
times.  The  larger  folds  are  about  one-third 
of  an  inch  in  depth  at  the  broadest  part;  but 
the  greater  number  are  of  smaller  size.  The 
larger  and  smaller  folds  alternate  with  each 
other.  They  are  not  found  at  the  commence- 
ment of  the  duodenum,  but  begin  to  appear 
about  one  or  two  inches  beyond  the  pylorus.     „      ,.„„     •,,  ,    ■  ..  *i. 

T       ,1       1  p     ,         1  !•  •  Fig.    1032. — Valvulae  conniventes    in  the  upper  part 

In   the   lower  part  of  the  descending  portion,  of  the  small  intestine.     (Poirier  and  Charpy.) 


1290 


THE  ORGANS  OF  DIGESTION 


LA   ,,R  Of  LONCJtUI^WAl,  J^tPf^fQ 


COUS    C0A4 


Fig.  1033. — Mucosa  of  small  intestine  in  ideal  vertical  cross-section.     (Testut,  after  Heitzmann.) 

'C  tic  la)  In  del 


Tunica  pyopi  a       / 


Lpitheliiim 


Blood  capilla  les^ _^  ■>        "         ^o      «    ^   3  "="  H    """'*'  "'S  ««^' 


>v 


*  1  -^  ~"^ 


\     Je  ts  of  smooth 
I  iscle  cell 


t  al  lymph 
6pace 


.4f 

« 

i.%  s^ 

^1 

-ki C  '^li.rarl^,   _-l 


Fig.  1034. — Longitudinal  section  through  the  end  of  a  villus  from  the  small  intestine  of  a  cat.     X  450. 


THE  JEJUNUM  AND  ILEUM 


1291 


below  the  point  where  the  bile  and  pancreatic  ducts  enter  the  intestine,  they  are  very  large  and 
closely  approximated.  In  the  transverse  portion  of  the  duodenum  and  upper  half  of  the  jejunum 
they  are  large  and  numerous;  and  from  this  point,  down  to  the  middle  of  the  ileum,  they  diminish 
considerably  in  size.  In  the  lower  part  of  the  ileum  they  almost  entirely  disappear;  hence  the 
comparative  thinness  of  this  portion  of  the  intestine  as  compared  with  the  duodenum  and  jeju- 
num. The  valvulae  conniventes  retard  the  passage  of  the  food  along  the  intestine,  and  afford  a 
more  extensive  surface  for  absorption. 

The  villi  (villi  intestinalis)  (Figs.  1034  and  10.35)  are  minute,  highly  vascular  processes, 
never  larger  than  1  millimeter,  projecting  from  the  mucous  membrane  of  the  small  intestine 
throughout  its  whole  extent,  and  giving  to  its  surface  a  velvety  appearance.  They  spring 
from  the  valvulae  conniventes  and  also  from  the  sjiaces  between  them.  In  shape,  according 
to  Rauber,  they  are  short  and  leaf-shaped  in  the  duodenum,  tongue-shaj)ed  in  the  jejunum, 
and  filiform  in  the  ileum.  They  are  largest  and  most  numerous  in  the  duodenum  and  jejunum, 
and  become  fewer  and  smaller  in  the  ileum.  Kraus  estimates  their  number  in  the  upper  part 
of  the  small  intestine  at  from  fifty  to  ninety  in  a  sc[uare  line;  and  in  the  lower  part  from  forty  to 
seventy,  the  total  number  for  the  whole  length  of  the  intestine  being  about  four  millions. 


F^ymph  trunk. 


CapUiaries. 


Lymphatic  plexus. 
testine.      (Cadiat.) 


Structure  of  the  Villi  (Figs.  1034  and  1035).— The  structure  of  the  villi  has  been  studied  by 
many  eminent  anatomists.  We  shall  here  follow  the  description  of  Watney,'  whose  researches 
have  a  most  important  bearing  on  the  physiology  of  that  which  is  the  peculiar  function  of  this 
part  of  the  intestine,  the  absorption  of  fat. 

The  essential  parts  of  a  villus  are  the  lacteal  vessel,  the  bloodvessels,  the  epithelium,  the 
basement  membrane,  and  muscle  and  lymphoid  tissues  of  the  mucosa,  these  structures  being 
supported  and  held  together  by  retiform  tissue. 

These  structures  are  arranged  in  the  following  manner:  Situated  in  the  centre  of  the  villus 
is  a  space,  the  lacteal,  terminating  near  the  summit  in  a  blind  extremity;  running  beside  this 
vessel  are  unstriped  muscle  fibres;  surrounding  it  is  a  meshwork  of  fibroelastic  tissue  supporting 
a  plexus  of  capillary  vessels  and  diffuse  lymphoid  tissue,  the  whole  being  enclosed  by  a  basement 
membrane,  and  covered  by  simple  columnar  epithelium  and  goblet  cells.  Nerve  fibres  are  con- 
tained within  the  villi;  they  form  ramifications  throughout  the  reticulum. 

The  lacteals  are  in  some  cases  double,  and  in  some  animals  mult i pic.  Situated  in  the  axis  of  a 
villus,  each  commences  by  a  dilated  cecal  extremity  near  to,  but  not  quite  at,  the  summit  of  the 
villus.  The  walls  are  composed  of  a  single  layer  of  endothelial  cells,  the  interstitial  substance 
between  the  cells  being  continuous  with  the  reticulum  of  the  matrix.  The  muscle  fibres  are 
derived  from  the  muscularis  mucosae,  and  are  arranged  in  bundles  around  the  lacteal  vessel. 


1  Phil.  Trans.,  vol.  clxv,  part  i 


1292 


THE  ORGANS  OF  DIGESTION 


extending  from  the  base  to  the  summit  of  the  villus,  and  giving  off  laterally  individual  muscle 
cells,  which  are  enclosed  by  the  reticulum,  and  by  it  are  attached  to  the  basement  membrane. 

The  bloodvessels  form  a  plexus  between  the  lacteal  and  the  basement  membrane,  and  are 
enclosed  in  the  reticular  tissue;  in  the  interstices  of  the  capillary  plexus,  which  they  form,  are 
contained  the  cells  of  the  villus. 

The  intestinal  glands,  crypts  or  glands  of  Lieberkiihn  (glandidae  intestinales  [Liebrkuhni]) 
(Figs.1036  and  1040),  are  found  in  considerable  numbers  over  every  part  of  the  mucous  membrane 
of  the  small  intestine.  They  consist  of  minute  simple  tubular  depressions  of  the  mucous  mem- 
brane, arranged  perpendicularly  to  the  surface,  upon  which  they  open  by  small  circular  aper- 
tures. They  may  be  seen  with  the  aid  of  a  lens,  their  orifices  appearing  as  minute  dots  seen  at 
iDe  base  of  the  villi.  Their  walls  are  thin,  consisting  of  a  basement  membrane  lined  by  simple 
columnar  epithelium  and  goblet  cells,  and  are  surrounded  by  capillary  vessels.  In  the  glands  of 
the  ileum  and  also  to  a  certain  extent  those  of  the  jejunum  are  seen  some  coarsely  granular  cells, 
the  cells  of  Faneth.     They  seem  to  be  cells  of  special  secretion. 

The  duodenal  or  Brimner's  glands  (glandulae  duodenales  [Brumieri])  are  limited  to  the  duode- 
num. They  are  small,  branched,  tubular  glands  in  the  submucous  coat,  and  open  upon  the 
surface  of  the  mucous  membrane  by  minute  excretory  ducts.  They  are  most  numerous  and 
largest  near  the  pylorus.  They  resemble  the  pyloric  glands  in  appearance,  and  are  believed  to 
be  a  direct  continuation  of  those  glands.  The  cells  are  clear  and  pale  staining,  and  Stohr  states 
that  cells  resembling  parietal  ceils  are  occasionally  seen. 


d  of  Lieberkiihn  in  the 
(Paneth.) 


Fig.  1037. — Transverse   section    of    crypts  of 
Lieberkiihn.     (Klein  and  Noble  Smith.) 


The  lymph  nodules  (noduli  lymphaiici)  are  small  pyriform  structures.  The  bodies  of  the  nodes 
are  in  the  submucous  coat;  the  apices  are  in  the  mucous  membrane,  which  is  thrown  by  them 
into  rounded  elevations.     They  are  divided  into  solitary  follicles  and  Peyer's  patches. 

The  solitary  foUicles  (noduli  lymphatici  solitarii)  (Fig.  1033)  are  found  scattered  throughout 
the  mucous  and  submucous  coats  of  the  small  intestine  and  the  large  intestine.  In  the  small 
intestine  they  are  most  numerous  in  the  lower  part  of  the  ileum,  upon  and  between  the  valvulae 
cormiventes.  They  are  small,  round,  whitish  bodies,  from  one-twenty-fourth  of  an  inch  to  one- 
quarter  of  an  inch  (1  to  6  mm.)  in  diameter.  Their  free  surface  is  free  of  villi,  and  each 
follicle  is  surrounded  by  the  openings  of  the  glands  of  Lieberkiihn.  They  are  now  recognized 
as  lymph  nodules.  They  consist  of  a  dense  interlacing  retiform  tissue  closely  packed  with 
lymph  corpuscles  and  permeated  with  an  abundant  capillary  network.  The  interspaces  of  the 
retiform  tissue  are  continuous  with  larger  lymph  spaces  at  the  base  of  the  nodule,  through  which 
they  communicate  with  the  lacteal  system.  Each  consists  of  a  lighter  central  area,  the  germinal 
centre,  where  the  leukocytes  are  reproducing,  and  a  peripheral  darker  zone,  where  the  cells  are 
more  numerous  and  closely  packed. 

Peyer's  patches,  the  agminated  foUicles,  or  the  tonsillae  intestinales  {noduli  lymphatici 
aggregati[Peyeri])  (Figs. 1038,  1039,  and  1040) may  be  regarded  as  aggregations  of  solitary  follicles, 
forming  circular  or  oval  patches  from  ten  to  sixty  in  number,  and  varying  in  length  from  half  an 
inch  to  four  inches  (1.2.5  to  10  cm.).  Thev  are  largest  and  most  numerous  in  the  ileum.  In 
the  lower  part  of  the  jejunum  they  are  small,  of  a  circular  form,  and  few  in  number.  They  are 
occasionally  seen  in  the  duodenum.  They  are  placed  lengthwise  in  the  intestine,  and  are  situated 
in  the  portion  of  the  tube  most  distant  from  the  attachment  of  the  mesentery.  Each  patch  is 
formed  of  a  group  of  the  above-described  solitary  follicles  covered  with  mucous  membrane,  and 
in  almost  every  respect  are  similar  in  structure  to  them.     They  do  not,  however,  as  a  rule. 


THE  JEJUNUM  AND  ILEUM 


1293 


possess  villi  on  their  free  surface  nor  glands.  Each  patch  is  surrounded  by  a  circle  of  the  crypts 
of  Lieberkuhn.  They  are  best  marked  in  the  young  subject,  becoming  indistinct  in  middle  age 
and  sometimes  altogether  disappearing  in  advanced  life.     They  are  largely  supplied  with  blood 


^..■•Capillary  uetwoyTc. 


Fig.  1038. — Transverse  section  through  the  equatorial  plane 
of  three  of  Peyer's  follicles  from  the  rabbit. 


Fig.    1039. — Free  surface  of  a  Peyer' 
patch.     (After  Quain.) 


vessels,  which  form  an  abundant  plexus  around  each  follicle  and  give  off  fine  branches  which 
permeate  the  lymphoid  tissue  in  the  interior  of  the  follicle.  The  lacteal  plexuses  which  are 
found  throughout  the  small  intestine  are  especially  abundant  around  these  patches:  here  they 
form  rich  plexuses  with  sinuses  around  the  glands  (Fig.  1024).  In  typhoid  fever  there  is  ulcera- 
tion of  Peyer's  patches. 


CHYLI  FERGUS 


Fig.  1040. — Vertical  section  of  a  Peyer's  patch 


with  the  lymphatic  vessels  injected.     (Frey.) 


Vessels  and  Nerves. — The  arteries  {vasa  intestini  tenuis  (are  branches  of  the  superior 
mesenteric  (Fig.  470)  and  course  within  the  mesentery,  forming  single,  double,  or  even  tertiary 
loops  (Figs.  1041,  1042, 1043, 1044,  1045,  and  1046).  The  terminal  branches  reach  the  intestine, 
and  each  branch  divides  into  two,  one  going  to  each  side  of  the  intestine  and  passing  transversely 
around  it.     At  first  they  are  directly  beneath  the  peritoneum,  but  after  a  time  they  pass  to  the 


1294 


THE  ORGANS  OF  DIGESTION 


submucosa  and  form  a  plexus,  from  which  branches  go  to  the  mucous  membrane  Some  of 
these  enter  the  villi;  others  form  plexuses  about  the  glands  of  Lieberkuhn  (Birmingham).  The 
details  of  the  arterial  blood  supply  of  the  small  intestines  are  given  on  page  663. 


Seventeen  feet. 


Twenty  feet. 


Figs.  1041,  1042,  104.3,  1044,  1045,  1046. — Diagrams  showing  the  arrangement  and  variations  of  the  loops  of 
the  mesentenc  vessels  for  various  segments  of  the  small  intestine  of  average  length.  Nearest  the  duodenum  the 
mesenteric  loops  are  primary,  the  rasa  recta  are  long  and  regular  in  distribution,  and  the  translucent  spaces  (lunettes) 
are  extensive.  Toward  the  ileocolic  junction,  secondare  and  tertiary  loops  are  observed,  the  vessels  are  smaller 
and  become  obscured  by  numerous  fat-tabs.     (After  ilonts.)     (See  p.  1269  for  detailed  description.) 


THE  JEJUNUM  AND  ILEUM 


1295 


The  veins  correspond  to  the  arteries,  and  the  venous  blood  passes  to  the  superior  mesenteric 
vein,  which,  it  will  he  remembered,  unites  with  the  splenic  vein  to  form  the  portal  vein.  The 
mesenteric  veins  are  devoid  of  valves. 

The  lacteals  are  lymphatics  (Figs.  1033  and  1040)  which  arise  in  the  villi.  Lymphatics  also 
becin  in  sinuses  at  the  base  of  the  solitary  follicles  and  in  Peyer's  patches.  There  is  an  extensive 
lymphatic  jilexus  in  the  submucous  coat,  another  in  the  muscular  coat,  another  under  the  peri- 
toneum. The  submucous  plexus  is  formed  by  lymphatics  from  the  villi  and  mucous  membrane. 
This  plexus  is  joined  by  lymphatics  from  the  bases  of  the  solitary  follicles,  and  the  lymph  passes 
oy  vessels  to  larger  vessels  at  the  mesenteric  border  of  the  gut.  The  muscular  lymphatics  are 
placed  between  the  two  muscular  layers.  They  form  a  plexus  and  communicate  freely  with 
the  lymphatics  from  the  mucous  membrane,  and  empty  themselves  in  the  same  manner  into  the 
commencement  of  the  lacteal  vessels  at  the  attached  border  of  the  gut.  The  vessels  from  all 
sources  of  lymphatic  supply  pass  up  between  the  two  layers  of  the  mesentery,  being  connected 
with  the  mesenteric  nodes  (Fig.  572),  and  unite  to  form  a  trunk,  the  intestinal  lymphatic 
txunk,  which  opens  into  the  receptaculum  chyli,  or  the  vessels  unite  to  form  several  trunks, 
which  open  separately  into  the  receptaculum  chyli. 


.  1047.— lleissn 


i  plexi 


( Ramon  y  Cajal.) 


The  nerves  of  the  small  intestine  (Fig.  1047)  are  derived  from  the  coeUac  plexus  about 
the  superior  mesenteric  artery.  They  pass  along  within  the  mesentery  with  the  superior 
mesenteric  artery  and  reach  the  intestine.  They  pass  to  the  plexus  of  nerves  and  ganglia  situated 
between  the  circular  and  longitudinal  muscular  fibres  (Auerbach's  plexus),  from  which  the  nerve 
branches  are  distriliuicd  to  the  muscular  coats  of  the  intestine.  From  this  plexus  a  secondary 
plexus  is  derived  (Meissner's  plexus).  It  is  formed  by  branches  which  have  perforated  the  cir- 
cular muscular  fibres.  This  plexus  lies  in  the  submucous  coat.  It  is  also  gangliated,  and  from 
it  the  ultimate  fibres  pass  to  the  muscularis  mucosae,  to  the  villi,  and  to  the  mucous  membrane. 
The  nerves  of  the  intestine  are  amyelinic,  and  some  of  the  fibres  are  derived  from  the  vagus. 

Applied  Anatomy. — The  applied  anatomy  of  the  small  intestine,  especially  the  surgical 
anatomy  of  the  hernias,  is  given  on  page  1315. 


THE  LARGE  INTESTINE  (INTESTINUM  CRASSUM)  (Figs.  977,  1078). 

The  large  intestine  extends  from  the  termination  of  the  ileum  to  the  anus.  It 
is  about  five  feet  or  more  in  length,  being  one-fifth  of  the  whole  extent  of  the 
intestinal  canal.     It  is  largest  at  its  commencement  at  the  cecum,  and  gradually 


1296 


THE  ORGANS  OF  DIGESTION 


diminishes  as  far  as  the  rectum,  where  there  is  a  dilatation  of  considerable  size 
just  above  the  anal  canal.  It  differs  from  the  small  intestine  in  its  greater  size, 
its  more  fixed  position,  its  sacculated  wall,  and  in  possessing  certain  appendages 
to  its  external  coat,  the  appendices  epiploicae  (Fig.  1048),  little  peritoneal  pouches 
containing  fat. 


ACCULATIONS 


PENDtCES  EPIF 


MUSCULAR    BAND 


Fig.  104S. — Large  intestine.     A  piece  of  transverse  colon  from  a  child  two  years  old.     The  three  chief  character- 
istics of  the  large  intestine — sacculations,  taenite,  and  appendices  epiploicae — are  shown.     (Cunningham.) 

Further,  the  longitudinal  muscle  fibres  of  the  large  intestine  do  not  form  a  con- 
tinuous layer  around  the  gut,  but  are  arranged  in  three  longitudinal  bands  or  taeniae 
{taeniae  coli)  (Fig.  104S).  The  large  intestine,  in  its  course,  describes  an  arch 
which  surrounds  the  convolutions  of  the  small  intestine.  The  segment  of  the 
intestinal  tract  where  the  small  intestine  joins  the  large  is  termed  the  ileocecal 
or  ileocolic  junction.     The  large  intestine  commences  in  the  right  inguinal  region, 

in  a  dilated  part,  the  cecum,  together  with 
a  rudimentary  structure,  the  appendix. 
It  ascends  through  the  right  lumbar  and 
right  hypochondriac  regions  to  the  under 
surface  of  the  liver;  here  it  takes  a  bend 
to  the  left  (hepatic  flexure),  and  passes 
trans^'ersely  across  the  abdomen  on  the 
confines  of  the  epigastric  and  umbilical 
regions,  to  the  left  hypochondriac  re- 
gion; it  then  bends  again  (splenic  flexure), 
and  descends  through  the  left  lumbar  re- 
gion to  the  left  iliac  fossa,  where  it  be- 
comes convoluted,  and  forms  the  sigmoid 
flexure;  finally  it  enters  the  pelvis  and 
descends  along  its  posterior  wall  to  the 
anus.  The  large  intestine  is  divided  into 
the  cecum,  colon,  rectum,  and  anal  canal. 


The  Cecum. 

The  cecum  {iniesiinum  cecum)  (Figs.  1050  and  1051-1054),  the  commencement 
of  the  large  intestine,  is  the  large  blind  pouch  situated  below  the  ileocecal  valve. 
Its  blind  end  or  fundus  is  directed  downward,  and  its  open  end  upward,  communi- 
cating directly  with  the  colon,  of  which  this  blind  pouch  appears  to  be  the  beginning 
or  head,  and  hence  the  old  name  caput  cecum  coli  was  applied  to  it.  Its  size  is 
variously  estimated  by  different  authors,  but  on  an  average  it  may  be  said  to  be 
two  and  one-half  inches  (6.25  cm.)  in  length  and  three  (7.5  cm.)  in  breadth.* 


1  In  435  careful  autopsies,  Robinson  found  the  cecum  and  appendix  congenitally  absent  in  one  case  (St. 
Louis  Courier  of  Medicine,  October-December.  1902).  Sometimes  a  very  large,  sometimes  an  exceedingly 
small,  cecum  is  encountered.  A  large  cecum  maybe  four  inches  in  width,  entirely  surrounded  by  peritoneurn, 
and  usually  is  excessively  mobile.  An  adult  cecum  may  be  only  one  inch  in  width  and  one-half  an  inch  in 
length,  and  it  is  usually  devoid  of  mobility. 


THE  CECUM 


1297 


It  is  situated  in  the  right  iliac  fossa,  above  the  outer  half  of  Poupart's  ligament; 
it  rests  on  the  Iliopsoas  muscle,  and  lies  immediately  behind  the  abdominal  wall. 
As  a  rule,  it  is  entirely  enveloped  on  all  sides  by  peritoneum,  but  in  a  certain  number 
of  cases  (6  per  cent. ,  according  to  Berry)  the  peritoneal  covering  is  not  complete, 
so  that  a  small  portion  of  the  upper  end  of  the  posterior  surface  is  uncovered  and 
connected  to  the  iliac  fossa  by  connective  tissue.  The  cecum  lies  quite  free  in 
the  abdominal  cavity  and  is  capable  of  a  considerable  amount  of  movement, 
so  that  it  may  become  herniated  down  the  right  inguinal  canal,  and  has  occasion- 
ally been  found  in  an  inguinal  hernia  on  the  left  side.' 

The  cecum  varies  in  shape,  but,  according  to  Treves,  in  man  it  may  be  classified 
under  one  of  four  types  (Figs.  1051-1054).  In  early  fetal  life  it  is  short,  conical, 
and  broad  at  the  base,  with  its  apex  turned  upward  and  inward  toward  the  ileocecal 
junction.  It  then  resembles  the  cecum  of  some  of  the  monkey  tribe,  e.  </.,  j\Ian- 
gabey  monkey.  As  the  fetus  grows  the 
cecum  increases  in  length  more  than  in 
breadth,  so  that  it  forms  a  longer  tube  than 
in  the  primitive  form  and  without  the  broad 
base,  but  with  the  same  inclination  inward 
of  the  apex  toward  the  ileocecal  junction. 
This  form  is  seen  in  others  of  the  monkey 
tribe,  e.  g.,  the  spider  monkey.  As  develop- 
ment goes  on,  the  lower  part  of  the  tube 
ceases  to  grow  and  the  upper  part  becomes 
greatly  increased,  so  that  at  birth  there  is  a 
narrow  tube,  the  vermiform  appendix,  hang- 
ing from  a  conical  projection,  the  cecum. 
This  is  the  infantile  form,  and  as  it  persists 
throughout  life,  in  about  2  per  cent,  of  cases 
it  is  regarded  by  Treves  as  the  first  of  his 
four  types-  of  human  ceca.  The  cecum  is 
conical  and  the  appendix  rises  from  its 
apex.  The  three  longitudinal  bands  start 
from  the  appendix  and  are  equidistant 
from  each  other.  In  the  second  type,  the 
conical  cecum  has  become  quadrate  by  the 
growing  out  of  a  saccule  on  either  side  of  the 
anterior  longitudinal  band.    These  saccules 

are  of  equal  size,  and  the  appendix  arises  from  between  them  instead  of  from  the 
apex  of  a  cone.  This  t}'pe  is  found  in  about  3  per  cent,  of  cases.  The  third  type 
is  the  normal  type  of  man.  Here  the  two  saccules,  which  in  the  second  type  were 
uniform,  have  grown  at  unequal  rates,  the  right  with  greater  rapidity  than  the  left. 
In  consequence  of  this  an  apparently  new  apex  has  been  formed  by  the  growing 
downward  of  the  right  saccule,  and  the  original  apex,  with  the  appendix  attached, 
is  pushed  over  to  the  left  toward  the  ileocecal  junction.  The  three  longitudinal 
bands  still  start  from  the  base  of  the  appendix,  but  they  are  now  no  longer  equi- 
distant from  one  another,  because  the  right  saccule  has  grown  between  the  anterior 
and  postero-external  bands,  pushing  them  over  to  the  left.  This  type  occurs  in 
about  90  per  cent,  of  cases.  The  fourth  type  is  merely  an  exaggerated  condition 
of  the  third;  the  right  saccule  is  still  larger,  and  at  the  same  time  the  left  saccule 
has  been  atrophied,  so  that  the  original  apex  of  the  cecum,  with  the  appendix, 
is  close  to  the  ileocecal  junction,  and  the  anterior  band  courses  inward  to  the 
same  situation.     This  type  is  present  in  about  4  per  cent,  of  cases. 


Fig.  1050.— The  ^ 


show  the  ileocecal  ■ 


Tnd   colon   laid   open   to 


^  In  310  adult  males,  Robinson  found  8  per  cent,  with  undescended  cecum  and  appendix.     Nondescent  was 
found  in  less  than  4  per  cent,  of  females,     A  partly  descended  cecum  usually  lies  upon  the  right  kidney. 


1298 


THE  ORGANS  OF  DIGESTION 


The  Interior  of  the  Cecum. — Corresponding  to  the  surface  sacculations  are  seen 
the  pouch-Hke  depressions  (haustra)  bounded  by  the  semilunar  folds  (plicae  semi- 
lunares  coli)  (Fig.  1050),  corresponding  to  the  surface  constrictions  which  mark 
off  the  saccules.  The  interior  of  the  cecum  is  continued  into  the  colon  above, 
and  the  orifice  of  the  ileum  and  of  the  appendix  open  into  it.  These  orifices, 
guarded  respectively  by  the  ileocecal  valve  and  by  the  valve  of  Gerlach,  are 
described  on  pages  1299  and  1301. 

Pericecal  Folds  and  Fossae. — See  page  1266,  and  Figs.  1007  and  1008. 

Ttpe  III.  Type  II. 


90% 


Ttpe  I  (Treves). 


Figs.  1051  to  105-1. — The  four  t\-pes  of  cecum. 

The  Vermiform  Appendix  {process7is  vermiformis)  (Figs.  1056  and  1062). — The 
vermiform  appendix  is  found  only  in  man,  the  higher  apes,  and  the  wombat, 
although  in  certain  rodents  a  somewhat  similar  arrangement  exists.  In  carnivo- 
rous animals  the  cecum  is  very  slightly  developed;  in  herbivorous  animals  (with 
a  simple  stomach)  it  is,  as  a  rule,  extremely  large.  It  has  been  suggested  that  the 
vermiform  process  in  man  is  the  degenerated  remains  of  the  herbivorous  cecum, 
which  has  been  replaced  by  the  carnivorous  form.  The  vermiform  appendix  is 
a  long,  narrow,  worm-shaped,  musculomembranous  tube,  which  starts  from  what 
was  originally  the  apex  of  the  cecum.  After  development  has  advanced  the  vermi- 
form appendix  comes  off,  as  a  rule,  from  the  inner  side  of  the  posterior  wall  of  the 
cecum,  below  and  behind  the  termination  of  the  ileum.  This  origin  usually  cor- 
responds to  McBumey's  point  on  the  abdominal  wall,  two  to  three  inches  from  the 
anterior  superior  iliac  spine  on  a  line  from  this  process  to  the  umbilicus,  and  which 
is  the  usual  seat  of  the  greatest  tenderness  in  appendicitis.     The  origin  of  the 


THE  CECUM 


1299 


appendix  varies  with  the  type  of  cecum  present.  These  variations  are  shown  in 
Figs.  1051-1054.  The  movable  portion  of  the  appendix  may  be  met  with  in  dif- 
ferent situations.  It  may  pass  upward  and  in  front  of  the  cecum  and  colon, 
upward  and  behind  the  cecum,  and  even  behind  the  colon  betwe>rn  the  two 
layers  of  the  mesocolon;  upward  and  to  the  inner  side  or  upward  and  to  the 
outer  side  of  the  cecum  and  colon.  It  may  pass  to  the  left  under  the  ileum 
and  mesentery,  upward  and  to  the  left  or  downward  and  to  the  left  into  the 
true  pelvis.  It  may  pass  directly  downward  under  the  cecum.  It  may  pass  to  the 
right  in  front  of  or  back  of  the  cecum.  It  may  occupy  any  one  of  the  peri- 
cecal fossff  (p.  1266),  but  most  often  enters  the  ileocecal  fossa.  When  the  cecum 
is  mobile  the  appendix  may  be  found  almost  anywhere  within  the  abdomen. 
When  the  cecum  is  undescended,  the  appendix  of  course  shares  in  the  failure  to 
descend,  and  may  be  below  the  gall-bladder  or  in  front  of  the  right  kidney,  and  may 
pass  in  several  directions — upward  behind  the  cecum,  to  the  left  behind  the  ileum 
and  mesentery;  or  downward  and  inward  into  the  true  pelvis.     It  varies  from  one- 


FlG,   1055. — Arteries  of  the  cecum  and  of  the  appendix  venniformis  and  of  the  terminal  porti( 
(Poirier  and  Charpj'.) 


half  an  inch  to  nine  inches  in  length  (1.25  to  22.5  cm.)  its  average  being  about 
three  inches  (7.5  cm.).  Its  diameter  is  from  one-eighth  inch  to  one-quarter  inch 
(3  to  6  mm.).  The  operating  surgeon  may  occasionally  fail  to  find  an  appendix 
buried  in  one  of  the  cecal  fossae,  and  may  conclude  that  the  diverticulum  is  absent. 
In  rare  instances  the  appendix  has  been  found  absent.  It  is  retained  in  position 
by  a  fold  of  peritoneum  derived  from  the  left  leaf  of  the  mesentery,  which  forms 
a  mesentery  for  it,  and  is  called  the  mesoappendix  (p.  1265  and  Figs.  1007  and 
1008).  This  fold,  in  the  majority  of  cases,  is  more  or  less  triangular  in  shape,  and, 
as  a  rule,  extends  along  the  entire  length  of  the  tube.  In  color  the  healthy  ap- 
pendix is  yellowish-pink  and  is  soft  and  smooth  to  the  touch.  The  canal  of  the 
appendix  is  small  and  extends  throughout  the  whole  length  of  the  organ.  The  walls 
of  the  healthy  di\'erticulum  are  thick,  and  the  diameter  of  the  lumen  is  usually  triv- 
ial as  compared  with  the  diameter  of  the  appendix  itself.  The  lumen  of  the  ap- 
pendix communicates  with  the  cecum  by  an  orifice  wliich  is  placed  below  and 
behind  the  ileocecal  opening  (Fig.  1060).  It  is  sometimes  guarded  above  and  to 
the  left  side  by  a  semilunar  fold  of  mucous  membrane,  the  valve  of  Gerlach  (valvula 
processus  vermiform  is).  The  valve  is  inconstant,  and  is  never  perfect.  It  is  stated 
that  the  lumen  of  the  appendix  tends  to  undergo  obliteration  in  advanced  age  as 
an  involution  change  in  a  supposedly  functionless  organ.  The  lumen  rarely 
contains  foreign  bodies  after  death,  but  often  contains  fecal  concretions.  Certain 
it  is  that  in  25  per  cent,  of  necropsies  upon  adults  or  elderly  persons  the  lumen 
is  foimd  to  be  partially  or  completely  occluded. 


1300 


THE  ORGANS  OF  DIGESTION 


Structure  of  the  Appendix  (Fig.  105S).— The  coats  of  the  appendix  correspond  to  the  coats 
of  the  bowel — serous,  muscular  (the  outer  layer  of  longitudinal,  the  inner  of  circular  fibres), 
submucous,  and  mucous. 

The  outer  or  serous  coat  forms  a  complete  investment  for 
the  appendix  except  al<jni;;  the  narrow  line  of  attachment  of  its 
mesentery  in  its  pi-oximal  two-thirds  or  more. 

The  longitudinal  muscle  layer  is  thin  and  irregularly  distrib- 
uted, and  in  certain  regions  may  be  exceedingly  thin  or  actually 
absent,  so  that  the  peritoneal  and  submucous  coats  are  contiguous 
over  small  areas. 

The  circular  muscle  layer  is  a  much  thicker  layer  than  the 
preceding,  and  at  the  blind  extremity  forms  a  dome-like  col- 
lection of  interlacing  fibres.  Both  layers  have  openings  at  in- 
tervals for  the  passage  of  bloodvessels. 

The  submucous  coat  varies  greatly  in  thickness.  It  contains 
bloodvessels,  nerves,  and  lymphatics,  and  a  large  number  of 
lymphoid  follicles  (.300  to  400)  and,  at  times,  adipose  tissue. 

The  mucous  membrane  (Fig.  10.56)  is  lined  by  columnar 
epithelium  and  contains  numerous  solitary  lymph  follicles,  glands 
of  Lieberkiihn  (about  25,000),  surrounded  by  diffuse  lymphoid 
tissue,  bloodvessels,  lymphatics,  and  nerves. 

The  muscularis  mucosae  may  be  absent,  may  be  scanty,  or 
may  be  distinct.  The  lymphoid  foUicles  are  visible  to  the  naked 
eye  (Fig.  1056).  Some  of  them  are  in  the  submucosa,  some  of 
them  chiefly  in  the  mucosa,  the  bases  of  the  latter,  however,  being 
in  the  submucosa. 

The  ajteries  of  the  cecum  and  appendix  are  derived  from  the 
ileocolic  branch  of  the  superior  mesenteric  artery.  Close  to  the 
ileocecal  junction  the  ileocolic  artery  gives  off  anterior  and  pos- 
terior ileocecal  branches  to  the  terminal  part  of  the  ileum  and 
beginning  of  the  large  intestine.  The  terminal  branches  to  the 
cecum  are  called  anterior  and  'posterior  cecal  arteries.  The  appendix  is  supplied  by  the 
appendicular  artery,  a  branch  of  the  posterior  ileocecal  artery  (see  p.  664). 

The  veins  of  the  appendix  are  numerous,  thin  walled,  and  large.  Veins  from  the  submucous 
plexus  pass  through  the  muscular  gaps  and  enter  the  subperitoneal  plexus.  Veins  from  the  sub- 
peritoneal plexus  pass  into  the  veins  in  the  mesoappendix  which  correspond  to  but  do  not  really 


Fig.  1056.— The  internal  sur- 
face of  the  vermiforin  appendix, 
(Bonamy  and  Broca.) 


ILEOCOLIC  ARTERY 


POSTERIOR 

ILEOCECAL 

ARTERY 

AND    VEIN 


Fig.  1057. — Arteries  and  veins  of  the  cecum  and  vermiform  appendix  seen  from  behind.     (Poirier  and  Charpy.) 


accom]5any  the  arteries  (Lockwood).  Most  of  the  veins  of  the  mesoappendix  pass  to  the  pos- 
terior ileocecal  vein,  though  some  pass  directly  to  the  cecal  vein.  These  veins  are  radicles  of 
the  portal  system. 

The  lymphatics  of  the  cecum  and  appendix  are  described  on  page  794. 


THE  CECUM 


1301 


The  Ileocecal  Valve  (valvuli  coli)  (Figs.  1060  and  1061). — The  lower  end  of  the 
ileum  terminates  by  opening  into  the  inner  and  back  part  of  the  large  intestine, 
at  the  point  of  junction  of  the  cecum  with  the  colon.  The  opening  is  guarded 
by  a  valve,  consisting  of  two  semilunar  segments,  an  upper  or  colic  segment  {labium 
s-uperius)  and  a  lower  or  cecal  segment  {labium  iiiferius),  which  project  into  the 


EPITHELIUM 


MUSCULAR  LAYER 


Fig.  1058. — Transverse  section  of  the  vermiform  appendix  of  i 


lumen  of  the  large  intestine.  The  upper  one,  nearly  horizontal  in  direction,  is 
attached  by  its  convex  border  to  tlie  point  of  junction  of  the  ileum  with  the  colon; 
the  lower  segment,  which  is  more  concave  and  longer,  is  attached  to  the  point  of 
junction  of  the  ileum  with  the  cecum.    At  each  end  of  the  aperture  the  two  segments 


ANTERIOR 
LYMPHATICS 
OF  CECUM 


Fig.  1039. — Lymph.itica  of  tlie  cecum  and  appendix,  anterior  view.      (Poirier  and  Charpy.) 

of  the  valve  coalesce,  and  are  continued  as  a  narrow  membranous  ridge  around 
the  canal  for  a  short  distance.  Each  ridge  is  known  as  the  frenulum  of  the  valve 
(frenulum  valvulae  coli).  The  left  or  anterior  part  of  the  aperture  is  rounded; 
the  right  or  posterior  is  narrow  and  pointed.  In  the  formation  of  the  valve  the 
termination  of  the  small  intestine  invaginates  for  a  short  distance  into  the  lumen 


1302 


THE  ORGANS  OF  DIGESTION 


of  the  large  intestine  (Fig.  1061),  the  invaginated  portion  of  the  wall  of  the  small 
intestine  uniting  with  a  corresponding  portion  of  the  wall  of  the  large  intestine. 
Each  segment  of  the  valve  is  formed  by  a  reduplication  of  the  mucous  membrane 
and  of  the  circular  muscle  fibres  of  the  intestine,  the  longitudinal  fibres  and  peri- 
toneum being  continued  uninterruptedly 
across  the  one  portion  of  the  intestine  to 
the  other. 

The  surface  of  each  segment  of  the 
valve  directed  toward  the  ileum  possesses 
villi,  and  presents  the  characteristic 
structure  of  the  mucous  membrane  of  the 


ORIFICE   O 


Fig.  lOGO. — Ileocecal  valve  of  the  circula 
(Poirier.) 


Fig,  1061. — Vertical  section  througli  the  cecum  and 
ileocecal  valve.     (Gegenbaur.) 


small  intestine;  while  that  turned  toward  the  large  intestine  is  destitute  of  villi, 
and  marked  with  the  orifices  of  the  numerous  tubular  glands  peculiar  to  the  mucous 
membrane  of  the  large  intestine. '  These  differences  in  structure  continue  as  far 

as  the  free  margins  of  the 
valve.  ^^Tien  the  cecum  is 
distended  it  is  supposed  that 
the  margins  of  the  opening 
are  approximated  so  as  to 
pr€;vent  reflux  into  the  ileum. 
It  is  known,  however,  that  a 
very  large  enema  which  dis- 
tends the  cecum  and  colon 
may  in  part  enter  the  ileum, 
being  driven  there  by  waves 
of  reversed  peristalsis.  The 
valve  resists,  but  a  certain 
amount  of  pressure  over- 
comes it.  Some  believe  that 
the  so-called  ileocecal  valve 
is  not  a  valve,  but  a  distinct 
sphincter.  This  has  been 
demonstrated  to  be  true  in 
cats  and  dogs,  but  lacks  dem- 
onstration in  man  (p.  1.313). 

AppUed  Anatomy. — The  vermiform  appendix  is  very  liable  to  become  inflamed,  the  condi- 
tion being  known  as  appendicitis.  The  condition  may  be  set  up  by  a  catarrhal  inflammation 
arising  in  the  appendix  or  derived  from  the  colon.  It  may  remain  catarrhal  and  then  subside. 
It  may  become  purulent  or  may  be  purulent  from  the  beginning.     Anything  which  lessens  vital 


LONG  MUSCU- 
LAR FIBRES 
FROM    ILEUM 


Fig.   1062.^ — Cecum  and 


•ermiform  appendix;  ileum  cut  through. 
(Sappey.) 


THE  COLON 


1.303 


resistance  makes  the  appendix  a  read.y  prey  to  bacteria.  Among  causes  which  lessen  resistance 
are  fecal  concretions,  twists  of  tlie  mesoappendix  cutting  off  the  lilood  supply,  bruises  inflicted 
by  the  Psoas  muscle  (Byron  Robinson),  blocking  of  tlie  outlet  of  the  apjiendix  by  catarrhal 
exudate,  concretions,  proliferated  lymphoid  tissue,  or  adhesions.  Appendicitis  may  arise  by  the 
appendix  becoming  twisted,  owing  to 
the  shortness  of  its  mesentery,  in  con- 
sequence of  distention  of  the  cecum. 
As  the  result  of  inflammation,  its 
blood  supply,  which  is  mainly  through 
one  large  artery  running  in  the  meso- 
appendix, becomes  interfered  with. 
Again,  in  rarer  cases,  the  inflamma- 
tion is  set  up  by  the  impaction  of  a 
solid  mass  of  feces  or  a  foreign  body 
in  the  appendix.  The  inflammation 
may  result  in  ulceration  and  perforation, 
or  in  gangrene  of  the  appendix  the  ap- 
pendix may  be  blocked  and  full  of  pus, 
or  abscess  may  form  outside  of  it  (appen- 
dicular abscrss).  These  conditions  re- 
quire prompt  operative  interference, 
and  in  cases  of  recurrent  attacks  of 
appendicitis  it  is  advisable  to  remove 
this  diverticulum  between  the  attacks. 
The  cecum  and  appendix  may  be 
implicated  in  cases  of  strangulated 
hernia,  giving  rise  to  serious  symptoms 
of  obstruction.     An  obstruction   in   the 

distal  part  of  the  large  bowel  causes  distention,  particularly  of  the  cecum,  which  sometimes 
assumes  enormous  dimensions,  and  has  been  known  to  rupture,  causing  fatal  peritonitis. 


Fig.  1063.  — Ileocecal  valve.     ( Sappey.) 


The  Colon. 

The  colon  is  divided  into  four  parts — the  ascending,  transverse,  and  descending 
colon  and  the  sigmoid  flexure. 

The  ascending  colon  {colon  ascendens)  is  smaller  than  the  cecum,  with  which 
it  is  continuous.  It  passes  upward,  from  its  commencement  at  the  cecum,  oppo- 
site the  ileocecal  valve,  to  the  under  surface  of  the  right  lobe  of  the  liver,  on  the 
right  of  the  gall-bladder,  where  it  is  lodged  in  a  shallow  depression  on  the  liver, 
the  impressio  colica;  here  it  bends  abruptly  forward  and  inward  to  the  left,  forming 
the  hepatic  flexure  (flexura  coli  dextra).  It  is  retained  in  contact  with  the  pos- 
terior wall  of  the  abdomen  by  the  peritoneum,  which  covers  its  anterior  surface 
and  sides,  its  posterior  surface  being  connected  by  loose  areolar  tissue  with  the 
Quadratus  lumborum  muscle,  and  with  the  front  of  the  lower  and  outer  part 
of  the  right  kidney  (Fig.  1064).  Sometimes  the  peritoneum  almost  completely 
invests  it,  and  forms  a  distinct  but  short  mesocolon'  (p.  1251).  It  is  in  relation, 
in  front,  with  the  convolutions  of  the  ileum  and  the  abdominal  parietes. 

The  transverse  colon  {colmi  transversum)  (Fig.  999),  the  longest  and  most 
movable  part  of  the  large  intestine,  passes  transversely  from  the  right  hypo- 
chondriac region  across  the  abdomen,  within  the  confines  of  the  epigastric  and 
umbilical  zones,  into  the  left  hypochondriac  region,  where  it  ciir\-es  downward 
beneath  the  lower  end  of  the  spleen,  forming  the  splenic  flexure  {flexiira  coli 
sinistra).     In  its  course  the  transverse  colon  describes  an  arch,  the  concavity  of 


1  Treves  states  that  after  a  careful  examination  of  one  hundred  subjects,  he  found  that  in  fifty-two  there  was 
neither  an  ascending  nor  a  descending  mesocolon.  In  twenty-two  there  was  a  descendmg  mesocolon,  but  no 
trace  of  a  corresponding  fold  on  the  other  side.  In  fourteen  subjects  there  was  a  mesocolon  to  both  the  ascend- 
ing and  the  descending  segments  of  the  bowel;  while  in  the  remaining  twelve  there  wa^  an  ascending  mesocolon, 
but  no  corresponding  fold  on  the  left  side.  It  follows,  therefore,  that  in  performing  lumbar  colostomy  a  meso- 
colon may  be  expected  on  the  left  side  in  36  per  cent,  of  all  cases,  and  on  the  right  in  26  per  cent.  (The  Anatomy 
of  the  Intestinal  Canal  and  Peritoneum  in  Man,  1885,  p.  55.) 


1304 


THE  OBGAXS  OF  DIGESTION 


which  is  directed  backward  toward  the  vertebral  column  and  a  little  upward. 
It  is  almost  completely  invested  by  peritoneum,  and  connected  to  the  posterior 


Fig  1064  — Diagram  of  the  relations  of  the  large  mtestme  and  kidnej  s  from  behind 


abdominal  wall  by  a  large  and  vade  duplicature  of  that  membrane,  the  transverse 
mesocolon  (Fig.  1013).  The  transverse  colon  is  in  relation,  by  its  upper  surface, 
■with  the  hver  and  gall-bladder,  the  greater  curvature  of  the  stomach,  and  the  lower 


THE  COLON 


]  :105 


DESCENDING  COLON 


end  of  the  spleen;  by  its  under  surface,  with  the  small  intestines;  by  its  anterior 
surface,  with  the  anterior  layers  of  the  greater  omentum  and  the  abdominal 
parietes;  its  posterior  surface  on  the  right  side 
is  in  relation  with  the  second  portion  of  the  duo- 
denum, and  on  the  left  side  is  in  contact  with 
some  of  the  con\'oIutions  of  the  jejunum  and 
ileum. 

The  splenic  flexure  is  in  relation  with  the  lower 
end  of  the  spleen  and  the  tail  of  the  pancreas.  It 
lies  at  a  higher  level  than,  and  on  a  plane  posterior 
to,  the  hepatic  flexure,  and  is  attached  to  the  Dia- 
phragm opposite  the  tenth  and  eleventh  ribs,  by 
a  peritoneal  fold,  the  phrenocolic  ligament  (see 
p.  1264). 

The  descending  colon  {colon  descendens)  passes 
downward  through  the  left  hypochondriac  and 
lumbar  regions  along  the  outer  border  of  the  left 
kidney.     At  the  lower  end  of  the  kidney  it  turns 


.  1066. — Sigmoid  colon  and  rectum,  front  vie 
of  the  sigmoid  colon.     The  small  intestine  i 


'.    The  broken  lines  indicate  the  situation  of  the  concealed  part 
drawn  away,  and  the  anus  is  turned  forward.     (Testut.) 


inward  toward  the  outer  border  of  the  Psoas  muscle,  along  which  it  descends  to 
the  crest  of  dae  ilium,  where  it  terminates  in  the  sigmoid  flexure.     It  is  retained 


1306  THE  ORGANS  OF  DIGESTION 

in  position  by  the  peritoneum,  which  covers  its  anterior  surface  and  sides,  its 
posterior  surface  being  connected  by  areolar  tissue  with  the  outer  border  of 
the  left  kidney,  and  the  Quadratus  lumborum  muscle  (Fig.  1004).  It  is  smaller 
in  calibre  and  more  deeply  placed  than  the  ascending  colon,  and  is  more  fre- 
quently covered  with  peritoneum  on  its  posterior  surface  than  the  ascending 
colon  (Treves). 

The  sigmoid  flexure,  pelvic  colon,  or  sigmoid  colon  {colon  sicjmoideum)  (Figs. 
1065  and  1066)  is  the  narrowest  part  of  the  colon;  it  is  situated  in  the  left  iliac  fossa, 
commencing  from  the  termination  of  the  descending  colon,  at  the  margin  of  the 
crest  of  the  ilium,  and  then  forming  a  loop,  which  varies  in  length  and  position, 
and  which  terminates  in  the  rectum  at  the  level  of  the  attachment  of  the  mesen- 
tery upon  the  front  of  the  third  sacral  vertebra.  It  passes  downward  about 
two  inches  (5  cm.)  parallel  to  the  outer  border  of  the  Psoas  muscle,  then  taking  a 
transverse  direction  enters  the  cavity  of  the  pelvis,  crosses  this  cavity  from  left  to 
right  and  a  little  upward  to  the  lower  margin  of  the  right  iliac  fossa;  thence  it 
passes  downward,  backward,  and  inward  along  the  anterior  surface  of  the  sacrum 
to  its  junction  with  the  rectum.  It  is  surrounded  by  the  peritoneum  and  is 
attached  to  the  posterior  abdominal  wall  by  the  mesosigmoid.  "When  the  sigmoid 
is  lifted  upward  and  to  the  right  and  the  mesosigmoid  is  put  slightly  on  the  stretch 
the  intersigmoid  fossa  (p.  1267)  is  brought  into  view.  When  the  sigmoid  flexure 
is  empty  most  of  it  falls  into  the  rectovesical  or  rectovaginal  space  (Fig.  1066). 
When  distended  it  mounts  up  into  the  abdomen,  reaching  to  or  even  above  the 
umbilicus.  The  sigmoid  flexure  is  in  relation  in  front  with  the  small  intestine 
and  abdominal  parietes.  The  sigmoid  mesocolon  is  attached  to  a  line  running 
downward  and  inward  from  the  crest  of  the  ilium,  across  the  left  Psoas  muscle, 
left  external  iliac  artery  and  vein,  left  spermatic  or  ovarian  vessels,  and  the  left 
ureter  (Fig.  1004). 

Applied  Anatomy. — The  diameter  of  the  large  intestine  gradually  diminishes  from  the 
cecum,  which  has  the  greatest  diameter  of  any  part  of  the  bowel,  to  the  point  of  junction  of  the 
sigmoid  flexure  with  the  rectum,  at  or  a  little  below  which  point  stricture  most  commonly  occurs 
and  diminishes  in  frequency  as"  one  proceeds  upward  to  the  cecum.  When  distended  by  some 
obstruction  low  down,  the  outline  of  the  large  intestine  can  be  defined  throughout  nearly  the 
whole  of  its  course — all,  in  fact,  except  the  hepatic  and  splenic  flexures,  which  are  more  deeply 
placed;  the  distention  is  most  obvious  in  the  two  flanks  and  on  the  front  of  the  abdomen  just 
above  the  umbilicus.  The  cecum,  however,  is  that  portion  of  the  bowel  which  is,  of  all,  most 
distended  (see  p.  1297).  The  hepatic  flexure  and  the  right  extremity  of  the  transverse  colon  are 
in  close  relationship  with  the  liver,  and  abscess  of  this  viscus  sometimes  bursts  into  the  gut  in  this 
situation.  The  gall-bladder  may  become  adherent  to  the  colon,  and  gallstones  may  find  their 
way  through  into  the  gut,  where  they  may  become  impacted  or  may  be  discharged  per  anum. 
The  mobihty  of  the  sigmoid  flexure  renders  it  more  liable  to  become  the  seat  of  a  volvulus  or 
twist  than  any  other  part  of  the  intestine.  It  generally  occurs  in  patients  who  have  been  the 
subjects  of  habitual  constipation,  and  in  whom,  therefore,  the  mesosigmoid  is  elongated.  The 
gut  at  this  part  being  loaded  with  feces,  from  its  weight  falls  over  the  gut  below,  and  so  gives 
rise  to  the  twist. 


The  Rectum  (Intestinum  Rectum)  (Figs.  1067,  1068). 

The  rectum  is  continuous  with  the  sigmoid  flexure,  while  below  it  ends  in  the 
anal  canal.  From  its  origin  at  the  level  of  the  third  sacral  vertebra  it  passes 
downward,  lying  in  the  sacrococcygeal  curve,  and  extends  for  about  an  inch  (2.5 
cm.)  in  front  of,  and  a  little  below,  the  tip  of  the  coccyx,  as  far  as  the  apex  of 
the  prostate  gland.     It  then  bends  sharply  backward  to  continue  as  the  anal  canal. 

It  therefore  presents  two  antero-posterior  curves.  An  upper,  with  its  convexity 
backward,  is  due  to  the  conformation  of  the  sacrococcygeal  column.  The  lower 
one  has  its  convexity  forward,  and  is  angular.  Two  lateral  curves  are  also 
described — the  one  to  the  right,  opposite  the  junction  of  the  third  and  fourth  sacral 


TIIl^  RECTUM 


1307 


I      GLAND 

L TRANSVERSA 


Fig.  1067.— Sagittal  section  in  tVie  median  line  of  the  male  pelvis.     Rectum  distended.      (Poirier  and  Charpy.) 


BECTAL  FOLD 


Fig.  106S.— Jlcdian  sagittal  section  of  the  female  pelvis.     Rectum  distended.     (Luschka.) 


1308 


THE  ORGANS  OF  DIGESTION 


vertebrae;  the  other  to  the  left,  opposite  the  sacrococcygeal  articulation.    They 
are,  however,  of  little  importance. 

The  adult  rectum  measures  about  five  inches  (12.5  cm.)  in  length,  and  at  its 
commencement  its  calibre  is  similar  to  that  of  the  sigmoid  flexure,  but  near  its 
termination  it  is  dilated  to  form  the  rectal  ampulla.  The  rectum  has  no  saccu- 
lations comparable  to  those  of  the  colon,  but  a  sacculated  condition,  due  to  the 
presence  in  its  interior  of  valves  (shortly  to  be  described),  is  sometimes  seen. 

The  peritoneum  is  related  to  the  upper  two-thirds  of  the  rectum,  covering  at 
first  its  front  and  sides,  but  lower  down  its  front  only;  from  the  latter  it  is  reflected 
on  to  the  seminal  vesicles  in  the  male  and  the  posterior  vaginal  wall  in  the  female, 
forming  the  vesico-uterine  cul-de-sac  of  Douglas. 

The  level  at  which  the  peritoneum  leaves  the  anterior  wall  of  the  rectum  to  be 
reflected  on  to  the  viscus  in  front  of  it  is  of  considerable  importance  from  a  surgical 
point  of  view,  in  connection  with  removal  of  the  lower  part  of  the  rectum.     It  is 

.higher  in  the  male  than  in  the  female.  In 
the  former  the  height  of  the  rectovesical 
pouch  is  about  three  inches  (7.5  cm.) ;  that  is 
to  say,  the  height  to  which  an  ordinary  index 
finger  can  reach  from  the  anus.  In  the 
female  the  height  of  the  rectovaginal  pouch 
is  about  two  and  a  quarter  inches  (5.2 
cm.)  from  the  anal  orifice.  The  rectum 
is  surrounded  by  a  dense  tube  of  fascia  de- 
rived from  the  fascia  endopehina ,  but  fused 
behind  with  the  fascia  covering  the  sacrum 
and  coccyx.  The  fascial  tube  is  loosely 
attached  to  the  rectal  wall  by  areolar  tissue 
in  order  to  allow  the  viscus  to  distend. 


Fig.  1069. — Diagram   of  rectum,  showing  Hous- 
ton's valves  in  the  interior.     (Cunningham.) 


Relations  of  the  Rectum. — The  upper  part 
of  the  rectum  is  in  relation,  hehind,  with  the 
superior  hemorrhoidal  vessels,  the  left  PjTiformis 
muscle,  and  left  sacral  plexus  of  nerves,  which 
separate  it  from  the  anterior  surfaces  of  the  sacral  vertebra;  in  its  lower  part  it  lies  directly 
on  the  sacrum,  coccyx,  and  Levatores  ani,  a  dense  fascia  alone  intervening;  in  front,  it  is  sep- 
arated above,  in  the  male,  from  the  posterior  surface  of  the  bladder;  in  the  female,  from  the 
posterior  surface  of  the  uterus  and  its  appendages  by  some  convolutions  of  the  small  intestine 
(Fig.  1068).  To  the  sides  below  the  peritoneal  reflections,  the  rectum  is  sm'rounded  by  cellular 
tissue  in  wliich  on  each  side  lie  the  lateral  sacral  artery  and  the  bifurcated  hypogastric  plexus  of 


RECTAL  VALVES 


Fig.  1070.  Fig.  1071.  Fig.  1072. 

Figs.  1070-1072. — The  anal  canal  and  lower  part  of  the  rectum  in  the  fetus.  Fig.  1070.  Aged  four  to  five  months. 
Pig.  1071.  Six  months.  Fig.  1072.  Nine  months.  In  each  the  anal  canal  is  distinctly  marked  off  from  the  rectum 
proper;  the  columns  of  Morgagni  and  the  rectal  valves  are  distinct.     (Cunningham.) 


the  sympathetic.  This  portion  of  the  rectum  is  separated  from  the  sacrum  and  coccyx  by  an 
interval,  the  retrorectal  space,  which  is  filled  with  cellular  tissue.  The  lower  or  prostatic  portion 
in  the  male  is  in  relation  anteriorly  with  the  triangular  portion  of  the  base  of  the  bladder,  the 
seminal  vesicles,  vasa  deferentia,  and,  more  anteriorly,  with  the  prostate  gland;  in  the  female, 
with  the  posterior  wall  of  the  vagina. 


THE  RECTUM 


1309 


The  Anal  Canal  {pars  analis  recti)  (Figs.  1070-1073).— The  anal  canal  is 
the  terminal  portion  of  the  large  intestine.  It  begins  at  the  level  of  the  apex  of 
the  prostate,  is  directed  downward  and  backward,  and  ends  at  the  anus.  It  forms 
an  ano-le  with  the  lower  part  of  the  rectum  and  measures  an  inch  to  an  inch  and 
a  half''(2.5  to  3.75  cm.)  in  length.  It  has  no  peritoneal  covering,  but  is  invested 
b\  the  Internal  sphincter,  supported  by  the  Levatores  ani  muscles,  and  surrounded 
at  its  termination  by  the  External  sphincter;  in  the  empty  condition  it  presents 
the  appearance  of  a  longitudinal  slit.  Behind  is  a  mass  of  muscle  and  fibrous 
tissue,  the  anococcygeal  body;  in  front  of  it,  in  the  male,  are  the  membranous  por- 
tion and  bulb  of  the  urethra,  and  the  base  of  the  triangular  ligament,  and  in  the 
female  it  is  separated  from  the  lower  end  of  the  vagina  by  a  mass  of  muscle  and 
fibrous  tissue,  named  the  perineal  body. 


PART  OF  H 

LEVATOR  ANI  ( 
INTERNAL 
SPHINCIER" 


ANALCANALC      hi  ,^ 


ANAL  VALVES 


Fig.  1073.  — The  interior  of  the  anal  canal  and  lower  part  of  the  rectum,  showing  the  columns  of  Morgagni  and 
the  anal  valves  between  their  lower  ends.  The  columns  were  more  numerous  in  the  specimen  than  usual. 
(Cunningham.) 

The  Anal  Orifice  or  Anus  is  the  external  opening  of  the  anal  canal,  formed 
by  pigmented  skin  containing  numerous  sebaceous  and  sudoriparous  glands 
glaudulae  circumanales)  and  furnished  with  hairs.  "i-VTiile  the  anus  is  closed, 
the  skin  around  it  is  thrown  into  radial  folds  by  the  contraction  of  the  External 
sphincter. 

Structure  of  Large  Intestine.— The  large  intestine  has  four  coats— serous,  muscular,  sub- 
mucous, and  mucous.  The  serous  coat  is  derived  from  the  peritoneum,  and  invests  the  different 
portions  of  tiie  large  intestine  to  a  variable  extent.  The  cecum  is  completely  covered  by  the 
serous  membrane,  except  in  a  small  percentage  of  cases  (5  or  6  per  cent.),  where  a  small  portion 
of  the  upper  end  of  the  posterior  surface  is  uncovered.  The  ascending  and  descending  colon 
are  usually  covered  only  in  front  and  at  the  sides;  a  variable  amount  of  the  posterior  surface 
is  uncovered.'  The  transverse  colon  is  almost  completely  invested,  the  parts  corresponding  to 
the  attachment  of  the  great  omentum  and  transverse  mesocolon  being  alone  excepted.  The 
sigmoid  flexure  is  completely  surrounded,  except  along  the  line  to  which  the  sigmoid  mesocolon 
is  attached.  The  upper  two-thirds  of  the  rectum  is  covered  in  front  and  laterally  by  the  peri- 
toneum, but  not  posteriorly,  between  the  two  posterior  folds  of  peritoneum,  the  so-called  meso- 
rectiim;  later  it  is  covered  only  on  its  anterior  surface;  and  the  lower  portion  is  entirely  devoid 
of  any  serous  covering.  In  the  course  of  the  colon  the  peritoneal  coat  is  thrown  into  a  number  of 
small  pouches  filled  with  fat,  called  appendices  epiploicae.  They  are  chiefly  appended  to  the 
transverse  colon,  and  are  particularly  numerous  along  the  anterior  band. 

The  muscular  coat  consists  of  an  external  longitudinal  and  an  internal  circular  layer  of  smooth 
muscle  tissue. 

The  longitudinal  fibres  do  not  form  a  uniform  layer  over  the  whole  surface  of  the  large  intes- 
tine.    In  the  cecum  and  colon  they  are  especially  collected  into  three  flat  longitudinal  bands 


1  See  footnote,  page  1303. 


];310  THE  ORGANS  OF  DIGESTION 

or  taeniae  {taenicB  coli)  (Figs.  104S  and  1049),  each  being  about  half  an  inch  (12  mm.)  in  width, 
and  named,  respectively,  the  mesocolic,  omental,  and  free  longitudinal  bands  or  tseniee.  These 
bands  commence  at  the  base  of  the  vermiform  appendix,  which  structure  is  surrounded  bv  a 
uniform  layer  of  longitudinal  muscular  fibres.  The  bands  pass  from  the  base  of  the  appendix 
to  the  rectum.  At  this  point  they  broaden,  fuse,  and  surround  the  rectum.  On  the  ascending, 
descending,  and  sigmoid  colon  the  mesocolic  band  {taenia  mesocolica)  is  posterior  and  internal; 
the  omental  band  {taenia  omentalis)  is  posterior  and  external;  the  free  band  {taenia  libera)  is 
anterior.  On  the  transverse  colon  the  taenia  Ubera  is  inferior;  the  taenia  mesocolica  is  poste- 
rior; the  taenia  omentalis  is  anterior  and  superior.  These  bands  are  one-sixth  shorter  than  the 
other  coats  of  the  intestine  to  which  they  are  applied,  and  serve  to  produce  the  sacculi  (Fig. 
1049),  which  are  characteristic  of  the  cecum  and  colon;  accordingly,  when  they  are  dissected  off, 
the  tube  can  be  lengthened,  and  its  sacculated  character  becomes  lost.  There  are  three  rows  of 
the  sacculations  separated  from  each  other  by  the  longitudinal  bands.  These  pouches  are  also 
subdivided  by  transverse  furrows  which  correspond  to  concave  folds  of  mucous  membrane, 
called  semilunar  folds  {plicae  semilunares  coli).  In  the  sigmoid  flexure  the  longitudinal  fibres 
become  more  scattered,  and  around  the  rectum  they  spread  out  and  form  a  layer  which  com- 
pletely encircles  this  portion  of  the  gut,  but  is  thicker  on  tlie  anterior  and  posterior  surfaces  than 
on  the  lateral  surfaces.  In  addition  to  the  muscular  fibres  of  the  bowels,  two  bands  of  smooth 
muscle  fibres  arise  from  the  second  and  third  coccygeal  vertebrae,  and  pass  downward  and  for- 
ward to  blend  with  the  longitudinal  muscle  tissue  on  the  posterior  wall  of  the  anal  canal.  They 
are  known  as  the  rectococcygeal  muscles  {m.  rectococcygeus). 

The  circular  fibres  form  a  thin  layer  over  the  cecum  and  colon,  being  especially  accumulated 
in  the  intervals  between  the  sacculi.  In  the  rectum  the  circular  fibres  constitute  a  thick  layer, 
and  in  the  anal  canal  they  become  numerous  and  constitute  the  Internal  sphincter. 

The  submucous  coat  {tela  submucosa)  connects  the  muscular  and  mucous  layers  closely 
together.     Solitary  follicles  are  quite  numerous  here. 

The  mucous  membrane,  in  the  cecum  and  colon,  is  pale,  smooth,  destitute  of  villi,  and  raised 
into  numerous  crescentic  folds  which  correspond  to  the  intervals  between  the  sacculi.  In  the 
rectum  it  is  thicker,  of  a  darker  color,  more  vascular,  and  connected  loosely  to  the  muscular 
coat,  as  in  the  oesophagus.  It  consists  of  simple  columnar  and  goblet  cells  resting  upon  a  base- 
ment membrane,  beneath  which  is  seen  the  tunica  propria,  which  contains  the  capillaries  and  a 
considerable  amount  of  diffuse  lymphoid  tissue.  Externally,  is  seen  the  muscularis  mucosae. 
Simple  tubular  glands,  lined  chiefly  by  goblet  cells,  are  present.  They  are  much  broader  than 
those  of  the  small  intestine. 

Wlien  the  lower  part  of  the  rectum  is  contracted,  its  mucous  membrane  is  thrown  into  a  num- 
ber of  folds,  which  are  longitudinal  in  direction  and  are  effaced  by  the  distention  of  the  gut. 
Besides  these,  are  certain  permanent  horizontal  folds,  of  a  semilunar  shape,  known  as  the  rectal 
or  Houston's  valves  (Figs.  1070  to  1072).  They  are  usually  three  in  number;  sometimes  a  fourth 
is  found,  and  occasionally  only  two  are  present.'  One  is  situated  near  the  commencement  of  the 
rectum,  on  the  right  side;  a  second  extends  inward  from  the  left  side  opposite  the  middle  of  the 
sacrum;  a  third,  the  largest  and  most  constant,  projects  backward  from  the  forepart  of  the 
rectum,  opposite  the  base  of  the  bladder.  When  a  fourth  is  present,  it  is  situated  nearly  an  inch 
(2. .5  cm.)  above  the  anus  on  the  left  and  posterior  wall  of  the  tube.  These  folds  are  about  half 
an  inch  (12  mm.)  in  width  and  contain  some  of  the  circular  fibres  of  the  gut.  In  the  empty 
state  of  the  intestine  they  overlap  each  other  so  effectually  that  they  render  the  introduction  of 
a  bougie  or  the  finger  somewhat  difficult,  and  their  use  seems  to  be  "to  support  the  weight  of 
fecal  matter,  and  prevent  its  urging  toward  the  anus,  where  its  presence  always  excites  a  sensa- 
tion demanding  its  discharge." 

The  lumen  of  the  anal  canal  presents,  in  its  upper  half,  a  number  of  vertical  folds,  produced 
by  an  infolding  of  the  mucous  membrane  and  some  of  the  muscle  tissue.  They  ai-e  known  as 
the  columns  of  Morgagni  or  anal  columns  (columnae  rectales  [Morgagni])  (Figs.  1073  and  1074). 
There  are  from  five  to  ten  of  these  folds,  each  of  which  is  about  half  an  inch  long.  They  are 
most  prominent  when  the  Sphincter  contracts.  The  outer  angle  of  each  column  below  passes 
into  a  semilunar  valve.  The  grooves  between  the  columns  are  shallow  above  and  deeper  below, 
and  end  in  the  anal  valves.  The  valves  of  Morgagni  or  anal  valves  (Figs.  1073  and  1074) 
are  folds  wliich  stretch  from  the  base  of  one  column  to  another,  and  form  the  anal  pockets 
or  crypts  of  Morgagni  {ximix  rectales).  Just  below  the  anal  valves  is  the  junction  of  the  mucous 
memljrane  of  the  anal  canal  with  the  skin;  this  is  indicated  by  the  so-called  white  line  of  Hilton 
or  anocutaneous  line  of  Hermann  (Fig.  1074). 

Vessels  and  Nerves  of  the  Large  Intestine. — The  arteries  (see  also  p.  664)  supplying  the 
large  intestine  give  off  large  branches,  which  ramify  between  the  muscular  coats  supplying  them, 
and,  after  dividing  into  small  vessels  in  the  submucous  tissue,  pass  to  the  mucous  membrane. 
The  cecum,  the  appendix,  and  the  ileocecal  valve  are  supplied  by  the  branches  from  the  anasto- 
motic loops  between  the  right  coUc  and  ileocolic  branches  of  the  superior  mesenteric  artery 

^  Dublin  Hospital  Reports,  vol.  v,  p.  163. 


THE  RECTUM 


1311 


(Fig.  1075).     The  ascending  colon  is  supplied  by  the  right  colic,  and  the  transverse  colon  by 
the  middle  colic  branch  of  the  superior  mesenteric.     The  descending  colon  is  supi^lied  by  the 


^^\.Ly.  \\%;^^^ 


LULAH  TISSUE 


Fig.  1074. — Inner  wall  ot  the  lower  end  of  the  rectum  and  anus.  On  the  right  the  mucous  membrane  has 
been  removed  to  show  the  dilatation  of  the  veins  and  how  they  pass  through  the  muscular  wall  to  anastomose 
with  the  external  hemorrhoidal  plexus.     (Luschka.) 


Fig.  1075. — The  arterial  blood  supply  of  the  anterior  (ventral)  surface  of  the  cecum  and  appendix:  .4.  Ileo- 
colic artery.  B.  Cecal  appendicular  artery.  D.  Anterior  cecal  artery.  F  and  G.  Appendicular  artery.  Note 
that  the  cecal  and  appendicular  arteries  anastomose  by  fine  capillaries,  both  ventrally  and  dorsally.  C.  Iliac 
artery.  1.  Right  colon.  2.  External  sac  cuius  of  cecum  (to  right  of  taenium  coli).  3.  Appendix.  4.  Iliac 
muscle.     5.  Psoas  muscle,     (Robinson.) 


1312 


THE  ORGANS  OF  DIGESTION 


left  colic  branch  of  the  inferior  mesenteric,  and  the  sigmoid  flexure  by  the  sigmoid  branches 
of  the  inferior  mesenteric.  The  rectum  (Fig.  1076)  is  supplied  mainly  bj-  the  superior  hemor- 
rhoidal branch  of  the  inferior  mesenteric,  but  also  at  its  lower  end  by  the  middle  hemorrhoidal 

from  the  internal  Uiac,  and  the 
inferior  hemorhoidal  from  the 
internal  pudic  artery.  The 
superior  hemorrhoidal,  the  con- 
tinuation of  the  inferior  mesen? 
teric,  divides  into  two  branches, 
which  run  down  either  side  of  the 
rectum  to  within  about  five  inches 
(12.5  cm.)  of  the  anus;  they  here 
split  up  into  about  six  branches, 
which  pierce  the  muscular  coat 
and  descend  between  it  and  the 
mucous  membrane  in  a  longitu- 
dinal direction,  parallel  with  each 
other  as  far  as  the  Internal 
sphincter,  where  they  anastomose 
with  the  other  hemorrhoidal  arte- 
ries and  form  a  series  of  loops 
around  the  anus.  The  veins  of 
the  large  intestine  correspond  to 
the  arteries  and  join  the  superior 
and  inferior  mesenteric  veins 
which  join  the  portal  vein.  The 
veins  of  the  rectum  (Fig.  1076) 
commence  in  a  plexus  of  vessels 
which  surrounds  the  lower  ex- 
tremity of  the  intestinal  canal. 
In  the  vessels  forming  this 
plexus  are  small  saccular  dilata- 
tions just  within  the  margin  of 
the  anus  (Figs.  1074  and  1076); 
from  it  about  six  vessels  of  con- 
siderable size  are  given  off. 
These  ascend  between  the  mus- 
cular' and  mucous  coat  for  about 
five  inches  (12.5  cm.),  running 
parallel  to  each  other;  they  then 
pierce  the  muscular  coat,  and, 
by  their  union,  form  a  single 
trunk,  the  superior  hemorrhoidal 
vein,  which  empties  into  the 
inferior  mesenteric  tributary  of 
the  portal  vein.  This  arrange- 
ment is  termed  the  hemorrhoidal 
plexus  (Fig.  523);  it  communi- 
cates with  the  tributaries  of  the 
middle  and  inferior  hemorrhoidal 
veins  at  its  commencement,  and  thus  a  communication  is  established  between  the  systemic 
and  portal  circulations.  The  inferior  hemorrhoidal  veins  empty  into  the  internal  pudic 
veins,  and  the  middle  hemorrhoidal  veins  empty  into  the  internal  iliac  veins. 
The  lymphatics  of  the  large  intestine  are  described  on  page  794. 

The  nerves  are  derived  from  the  sympathetic  plexuses  around  the  branches  of  the  superior 
and  inferior  mesenteric  arteries.  They  are  distributed  in  a  similar  way  to  those  found  in  the 
small  intestine.  The  spinal  centre  for  the  nerves  of  the  anus  and  rectum  is  situated  in  the  first 
and  second  sacral  segments  of  the  spinal  cord. 


Fig.  1076.  — The  bloodvessels  of  the  rectum  and  anus,  showing  the 
distribution  and  anastomosis  on  the  posterior  surface  near  the  termi- 
nation of  the  gut.     (Poirier  and  Charpy.) 


Movements  and  Innervation  of  the  Intestines. 


Movements. — As  the  small  intestine  is  devoid  of  any  sphincter  arrangement,  peristalsis  cannot 
mix  the  food  as  it  does  in  the  pyloric  portion  of  the  stomach.  The  process  by  which  the  food  is 
mixed  with  the  secretions  and  is  brought  against  the  intestinal  wall  for  absorption  is  called  by 
Cannon  "rhythmic  segmentation."     Rhythmic  motions  "mix  the  food  and  expose  it  to  the 


MOVEMENTS  AND  INNERVATION  OE  THE  INTESTINES      V.Mi 


Gland  of  Lieierkuhn 


A//^B 


~!l2^^i0!SiM^^iS^^&l^^^<h    SoUtary  gland 


mucosa  without  advancing  it  apprcriativdij  along  the  canal."'  In  this  process  constrictions  occur 
in  the  circular  fibres,  with  the  result  that  a  collection  of  stationary  food  is  divided  into  a  number 
of  segments.  In  the  middle  of  each  segment  constrictions  appear  and  the  earlier  constrictions 
relax.  Then  the  latter  constrictions  relax  and  the  earlier  reappear,  and  so  on  until  the  food  is 
thoroughly  mixed  with  digestive  secretions.  Finally,  the  food  is  driven  on  by  peristalsis,  coming 
again  to  rest,  and  being  again  subjected  to  "rhythmic  segmentation."  Cannon  says  that  in  the 
duodenum  "rhythmic  segmentation"  lasts  for  several  minutes,  but  in  other  parts  of  the  intestine 
it  may  continue  for  half  an  hour  or  more,  the  food  which  is  being  subjected  to  it  scarcely  moving 
aloncr  the  canal.  It  is  probable  that  in  man  there  are  from  seven  to  eight  segmentations  per 
minute  in  a  given  area.     It  is  also  probable  that  there  is  a  sphincter  action  at  the  ileocecal  opening. 

Cannon  divides  the  large  intestine  into  two  parts — a  distal  part,  in  which  the  material  is  hard 
and  lumpy  and  is  "advanced  by  rings  of  tonic  contraction,"  and  a  proximal  part,  in  which  the 
material  is  soft.     In  this  part  "  the  common  movements  are  waves  of  constriction  running  back- 
ward toward  the  cecum."    The  resistance  of 
the  valve  or  sphincter  enables  reversed  peri- 
stalsis   or    antiperistalsis   to   mix    the   food. 
When  more  food  enters  from  the  small  intes- 
tine, antiperistalsis  ceases,  tonic  contraction  of 
the  cecum  and  proximal  portion  of  the  colon 
occurs,  some  of  the  food  is  merged  into  the 
transverse    colon,    and    antiperistalsis    again 
begins  to  act  on  what  remains.     The  above 
facts  have  been  observed  in  animals  and  are 
probably  true  in  man. 

Innervation. — The  vagus  fibres  of  the 
small  intestine  seem  to  excite  contraction  of 
the  circular  fibres  after  a  brief  preliminary 
period  of  inhibition.^  Some  observers  main- 
tain that  the  splanchnic  fibres  are  inhibitory, 
but  others  claim  that  they  are  also  motor. 
The  local  reflex  of  the  small  intestine  is  in 
Auerbach's  plexus.  Cannon  quotes  Bayliss 
and  Starling  to  the  effect  that  the  pelvic  visceral 
nerves  to  the  large  intestine,  "arising  like 
the  vagus  from  the  central  nerve  system,  are 
augmentary  nerves,  whereas  the  supply  from 
the  sympathetic  system  is  purely  inhibitory 
in  its  action."  It  is  further  contended  that 
the  pelvic  visceral  nerves  are  distributed  to 

the  distal  colon  only.     "The  region  of  anti-    _  .„  ,  . 

..T'j  ^^1,       s  •        --„i         Fig.   1077. — Transverse  section  of  wall  of  large  intestine. 

peristalsis  does  not,  tneretore,  receive  motor 
imjiulses  from  the  pelvic  nerves." 

Surface  Form.— The  coils  of  the  small  intestine  occupy  the  front  of  the  abdomen  below  the 
transverse  colon,  and  are  covered  more  or  less  completely  by  the  great  omentum.  For  the  most 
part  the  coils  of  the  jejunum  occupy  the  left  side  of  the  abdominal  cavity— i.  e.,  the  left  lumbar 
and  inguinal  regions  and  the  left  half  of  the  umbilical  region— while  the  coils  of  the  ileum  are 
situated  to  the  right,  in  the  right  lumbar  and  inguinal  regions,  in  the  right  half  of  the  umbilical 
region,  and  also  in  the  hypogastric  region.  The  cecum  is  situated  in  the  right  inguinal  region. 
Its  position  varies  slightly,  but  the  mid-point  of  a  line  drawn  from  the  anterior  superior  spinous 
process  of  the  ilium  to  the  symphysis  pubis  will  about  mark  the  middle  of  its  lower  border.  It  is 
comparatively  superficial.  "  From  it  the  ascending  colon  passes  upward  through  the  right  lumbar 
and  hypochondriac  regions,  and  becomes  more  deeply  situated  as  it  ascends  to  the  hepatic  flexure, 
which  is  deeply  placed  under  cover  of  the  liver.  The  transverse  colon  crosses  the  belly  trans- 
versely on  the  confines  of  the  umbilical  and  epigastric  regions,  its  lower  border  being  on  a  level 
slightly  above  the  umbilicus,  its  upper  border  just  below  the  greater  curvature  of  the  stomach. 
The  splenic  flexure  of  the  colon  is  situated  behind  the  stomach  in  the  left  hypochondrium,  and 
is  on  a  higher  level  than  the  hepatic  flexure.  The  descending  colon  is  deeply  seated,  passing 
down  through  the  left  hvpochondriac  and  lumbar  regions  to  the  sigmoid  flexure,  which  is  situ- 
ated in  the  left  inguinal' region,  and  which  can  be  felt  in  thin  persons,  with  relaxed  abdominal 
walls,  rolling  under  the  fingers  when  empty,  and  when  distended  forming  a  distinct  bulge.  The 
usual  position  of  the  base  of  the  vermiform  appendix  is  indicated  by  a  point  on  the  cutaneous 
surface  two  to  three  inches  (.5-7.5  cm.)  from  the  anterior  superior  spinous  process  of  the  ilium,  on- 
a  line  drawn  from  tliis  process  to  the  umbilicus.  This  is  known  as  McBumey's  point.  Another 
mode  of  defining  the  position  of  the  base  of  the  appendix  is  to  draw  a  line  between  the  anterior 
superior  spines  of  the  ilia  and  marking  the  point  where  this  line  intersects  the  right  semilunar 
line. 


tudinal  muscle 
jlbres 


'  Medical  Newa,  May  20.  1905. 


2  Bayliss  and  Starling,  Journal  of  Physiology,  1899. 


1314  THE  ORGANS  OF  DIGESTION 

Upon  introducing  the  finger  into  the  rectum,  the  membranous  portion  of  the  urethra  can 
be  felt,  if  an  instrument  has  been  introduced  into  the  bladder,  exactly  in  the  middle  line;  behind 
and  above  this  the  prostate  gland  can  be  recognized  by  its  shape  and  hardness  and  any  enlarge- 
ment detected;  above  the  prostate  the  fluctuating  wall  of  the  bladder  when  full  can  be  felt, 
and  if  thought  desirable  it  can  be  tapped  in  this  situation;  on  either  side  and  behind  the  prostate 
the  seminal  vesicles  can  be  readily  felt,  especially  if  enlarged  by  tuberculous  disease.  Behind, 
the  coccyx  is  to  be  felt,  and  on  the  mucous  membrane  one  or  two  of  Houston's  folds.  The 
ischiorectal  fossae  can  be  explored  on  either  side,  with  a  view  to  ascertaining  the  presence  of 
deep-seated  collections  of  pus.  Finally,  it  will  be  noted  that  the  finger  is  firmly  gripped  by  the 
sphincter  for  about  an  inch  (2.5  cm.)  up  the  bowel. 

Applied  Anatomy. — The  small  intestine  is  much  exposed  to  injury,  but,  in  consequence 
of  its  elasticity  and  the  ease  with  which  one  fold  glides  over  another,  it  is  not  so  frequently  rup- 
tured as  would  otherwise  be  the  case.  Any  part  of  the  small  intestine  may  be  ruptured,  but 
probably  the  most  common  situation  is  the  transverse  duodenum,  on  account  of  its  being  more 
fixed  than  other  portions  of  the  bowel,  and  because  it  is  situated  in  front  of  the  bodies  of  the 
vertebrae,  so  that  if  this  portion  of  the  intestine  is  struck  a  sharp  blow,  as  from  the  kick  of  a 
horse,  it  is  unable  to  glide  out  of  the  way,  but  is  compressed  against  the  bone  and  lacerated. 
Wounds  of  the  intestine  sometimes  occur.  If  the  wound  is  a  small  puncture,  under,  it  is  said, 
eie-quarter  of  an  inch  (6  mm.)  in  length,  there  may  be  no  extravasation  of  the  contents  of  the 
bowel.  The  mucous  membrane  becomes  everted  and  perhaps  plugs  the  little  opening.  The 
bowels,  therefore,  may  be  punctured  with  a  fine  capillary  trocar,  in  cases  of  excessive  distention 
of  the  intestine  with  gas,"  without  much  danger  of  extravasation.  A  longitudinal  wound  gapes 
mOre  than  a  transverse  wound,  owing  to  the  greater  thickness  of  the  circular  muscular  coat.  In 
closing  a  wound  of  the  intestine,  use  Lembert's  inversion  sutures,  which  bring  the  peritoneal 
surfaces  in  contact.  Halsted  showed  that  these  sutures  must  include  the  tough  submucous 
coat.  The  portions  of  intestine  which  lie  in  the  pelvis  are  inflamed  in  pelvic  peritonitis  and 
become  embedded  in  adhesions.  The  portions  of  intestine  which  may  be  present  are  the  termi- 
nation of  the  ileum,  the  portion  of  small  intestine  with  the  largest  mesentery  (Treves),  the  rectum, 
and  the  pelvic  colon.  The  small  intestine,  and  most  frequently  the  ileum,  may  become  strangu- 
lated by  internal  bands,  or  through  apertures,  normal  or  abnormal.  The  bands  may  be  formed  in 
several  different  ways:  they  may  be  old  peritoneal  adhesions  from  previous  attacks  of  peritonitis; 
or  adherent  omentum  from  the  same  cause;  or  the  band  may  be  formed  by  Meckel's  diverticulum, 
which  has  contracted  adhesions  at  its  distal  extremity;  or  the  band  may  be  the  result  of  the 
abnormal  attachment  of  some  normal  structure,  as  the  adhesion  of  two  appendices  epiploicae, 
or  an  adherent  vermiform  appendix  or  Fallopian  tube.  Intussusception  or  invagination  of  the 
small  intestine  may  take  place  in  any  part  of  the  jejunum  and  ileum,  but  the  most  frequent  situa- 
ation  is  at  the  ileocecal  valve,  the  valve  forming  the  apex  of  the  entering  tube.  This  form  may 
attain  great  size,  and  it  is  not  uncommon  in  these  cases  to  find  the  valve  projecting  from  the  anus. 
Stricture,  the  impaction  of  foreign  bodies,  and  twisting  of  the  gut  (volvulus)  may  lead  to  intestinal 
obstruction.  Volvulus  is  most  common  in  the  sigmoid  flexure.  Meckel's  diverticulum  may 
itself  become  twisted  and  strangulated. 

Resection  of  a  portion  of  the  intestine  may  be  required  in  cases  of  gangrene  of  the  bowel;  in 
cases  of  intussusception;  for  the  removal  of  a  newgrowth  in  the  bowel;  in  dealing  with  artificial 
anus;  and  in  cases  of  rupture.  The  operation  is  termed  enterectomy,  and  is  performed  as  follows: 
The  abdomen  having  been  opened  and  the  amount  of  bowel  requiring  removal  having  been  deter- 
mined upon,  the  gut  must  be  clamped  on  either  side  of  this  portion  in  order  to  prevent  the  escape 
of  any  of  the  contents  of  the  bowel  during  the  operation.  The  portion  of  bowel  is  then  separated 
above  and  below  by  means  of  scissors.  If  the  portion  removed  is  small,  it  may  be  simply  removed 
from  the  mesentery  at  its  attachment  and  the  bleeding  vessels  tied ;  but  if  it  is  large,  it  will  be 
necessary  to  remove  also  a  triangular  piece  of  the  mesentery,  and  having  secured  the  vessels, 
suture  the  cut  edges  of  this  structure  together.  The  surgeon  then  proceeds  to  unite  the  cut 
ends  of  the  bowel.  He  may  do  it  by  the  operation  termed  end-to-end  ana^tomosk.  There 
are  many  ways  of  doing  this,  which  may  be  divided  into  two  classes — one,  where  the  anastomosis 
is  made  by  means  of  some  mechanical  appliance,  such  as  Murphy's  button,  or  one  of 
the  forms  of  decalcified  bone  bobbins;  and  the  other,  where  the  operation  is  performed  by 
simply  suturing  the  ends  of  the  bowel  in  such  a  manner  that  the  peritoneum  covering  the  free 
divided  ends  of  the  bowel  is  brought  into  contact,  so  that  speedy  union  may  ensue. 

In  some  cases  after  resection  each  open  end  of  the  gut  is  closed,  the  side  of  the  terminal  portion 
is  sutured  to  the  side  of  the  initial  portion,  a  fistula  is  made  in  each,  and  the  suturing  is  com- 
pleted so  as  to  cause  the  two  flstulse  to  correspond.  A  permanent  side-to-side  opening  is  thus 
made.  Lateral  anastomosis  without  resection  may  be  practised  between  two  pieces  of  intestine, 
-in  order  to  side-track  an  intervening  portion,  which  is  the  seat  of  malignant  disease  or  of  an 
artificial  anus.  Complete  exclusion  of  a  portion  of  intestine  is  performed  for  irremovable  tumors 
or  persistent  fecal  fistulse  of  the  large  intestine.  The  intestine  is  cut  through  above  and  below 
the  diseased  area  and  the  ends  of  the  healthy  gut  are  united  to  each  other,  or  the  larger  end  is 
closed,  an  opening  is  made  into  the  side  of  the  larger  end  and  the  smaller  end  is  implanted  in  it 


MOVEMENTS  AND  INNERVATION  OF  THE  INTESTINES      1315 

{lateral  implantation).  The  two  ends  of  the  excluded  portion  are  fastened  to  the  skin  and  are 
left  open. 

In  ascites  resultinfi  from  cirrhosis  of  the  hver,  benefit  occasionally  follows  the  performance  of 
Talma's  operation  [rpijdiiprxii).  The  abdomen  is' ojjened  and  the  omentum  is  sutured  to  the 
anterior  abdominal  wall  or  in  the  abdominal  wound,  in  the  hope  of  establishing  a  more  free 
communication  between  the  portal  and  systemic  circulations,  thus  lowering  portal  pressure. 

Hernia. — The  two  chief  sites  at  which  e.xternal  hernia  may  take  place  are  the  inguinal  region 
and  the  crural  canal.  The  description  of  the  inguinal  canal  and  its  relations  will  be  found  on 
pages  437  to  439  and  that  of  the  crural  canal  on  pages  503  and  684.  Some  points  in  regard 
to  the  disposition  of  the  peritoneum  in  these  regions  may,  however,  be  recapitulated  here. 

Between  the  upper  margin  of  the  front  of  the  pelvis  and  the  umbilicus,  the  peritoneum, 
when  viewed  from  behind,  will  be  seen  to  be  raised  into  fine  folds  with  intervening  depressions, 
by  more  or  less  prominent  bands  which  converge  to  the  umbilicus.  The  urachus,  situated  in 
the  middle  line,  is  covered  by  a  fold  of  peritoneum  known  as  the  plica  urachi.  On  either  side  of 
this  a  fold  of  peritoneum  around  the  impervious  hypogastric  artery  forms  the  plica  hypogastrica. 
To  either  side  of  these  three  cords  is  the  deep  epigastric  artery  covered  by  the  plica  epigastrica. 
Between  these  raised  folds  are  depressions  constituting  the  so-called  fossae.  The  most  internal, 
between  the  plica  urachi  and  plica  hypogastrica,  is  known  as  the  internal  inguinal  fossa  {fovea 
supravesicalis).  The  middle  one  is  situated  between  the  plica  hyjiogastrica  and  plica  epigas- 
trica, and  is  termed  the  middle  inguinal  fossa  {fovea  iinjiiiiintix  iiinliiilix).  The  external  one  is 
external  to  the  plica  epigastrica  and  is  known  as  the  external  inguinal  fossa  {fovea  inguinalis 
lateralis).  Occasionally  the  deep  epigastric  artery  corresponds  in  position  to  the  impervious 
hypogastric  artery,  and  then  there  is  but  one  fold  on  each  side  of  the  middle  line.  In  the  usual 
position  of  the  parts  the  floor  of  the  external  inguinal  fossa  corresponds  to  the  internal  abdominal 
ring,  and  into  this  fossa  an  oblique  inguinal  hernia  descends.  To  the  inner  side  of  the  plica 
epigastrica  are  the  two  internal  fossae,  and  through  either  of  these  a  direct  hernia  may  descend. 
The  whole  of  the  space  between  the  deep  cpii^astric  artery,  the  margin  of  the  Rectus  and  Pou- 
part's  ligament,  is  known  as  Hesselbach's  triangle.  Below  the  level  of  Poupart's  ligament 
is  a  small  depression  corresponding  to  ihe  jiosiiion  of  the  crural  ring.  It  is  known  as  the  femoral 
fossa,  and  into  it  a  femoral  hernia  descends. 

Inguinal  Hernia. — Inguinal  hernia  is  that  form  of  protrusion  which  makes  its  way  through 
the  abdomen  in  the  inguinal  region.  There  are  two  principal  varieties  of  it — external  or  oblique, 
and  internal  or  direct. 

In  oblique  inguinal  hernia  the  intestine  escapes  from  the  abdominal  cavity  at  the  internal  ring, 
pushing  before  it  a  pouch  of  peritoneum  which  forms  the  hernial  sac.  As  it  enters  the  inguinal 
canal  it  receives  an  investment  from  the  extraperitoneal  tissue  and  is  enclosed  in  the  infun- 
dibuliform  fascia.  In  passing  along  the  inguinal  canal  it  displaces  upward  the  arched  fibres 
of  the  Transversalis  and  Internal  oblique,  and  receives  a  covering  of  Cremaster  muscle  and 
cremasteric  fascia.  It  then  passes  along  the  front  of  the  spermatic  cord  and  escapes  frCm  the 
inguinal  canal  at  the  external  ring,  becoming  invested  by  intercolumnar  fascia.  Lastly,  it 
descends  into  the  scrotum,  receiving  coverings  from  the  superficial  fascia  and  the  integument. 

The  seat  of  stricture  in  oblique  inguinal  hernia  is  at  either  the  external  or  internal  abdominal 
ring;  most  frequently  in  the  latter  situation.  If  it  is  situated  at  the  external  ring,  the  division  of 
a  few  fibres  at  one  point  of  the  circumference  is  all  that  is  necessary  for  the  replacement  of  the 
hernia.  If  at  the  internal  ring,  it  is  necessary  to  divide  the  aponeurosis  of  the  External  oblique 
so  as  to  lay  open  the  inguinal  canal;  in  dividing  the  aponeurosis  the  incision  should  be  directed 
parallel  to  Poupart's  ligament,  and  the  constriction  at  the  internal  ring  should  then  be  divided 
directly  upward. 

When  the  intestine  passes  along  the  inguinal  canal  and  escapes  from  the  external  ring  into  the 
scrotum,  it  is  called  complete  oblique  inguinal  or  scrotal  hernia.  If  the  intestine  does  not  escape 
from  the  external  ring,  but  is  retained  in  the  inguinal  canal,  it  is  called  incomplete  inguinal 
hernia  or  bubonocele.  In  each  of  these  cases  the  coverings  which  invest  it  will  depend  upon 
the  extent  to  which  it  descends  in  the  inguinal  canal. 

There  are  some  other  varieties  of  oblique  inguinal  hernia  (Figs.  1078  to  1082)  depending 
upon  congenital  defects  in  the  processus  vaginalis,  the  pouch  of  peritoneum  which  precedes 
the  descent  of  the  testis.  Normally  this  pouch  is  closed  before  birth,  closure  commencing  at 
two  points — viz.,  at  the  internal  abdominal  ring  and  at  the  top  of  the  epididymis,  and  gradually 
extending  until  the  whole  of  the  intervening  portion  is  converted  into  a  fibrous  cord.  From 
failure  in  the  completion  of  this  process,  variations  in  the  relation  of  the  hernial  protrusion  to 
the  testis  and  tunica  vaginalis  are  produced;  these  constitute  distinct  varieties  of  inguinal 
hernia — viz.,  congenital,  infantile,  encysted,  and  hernia  of  the  funicular  process. 

Where  the  processus  vaginalis  remains  patent  throughout,  the  cavity  of  the  tunica  vaginalis 
communicates  directly  with  that  of  the  peritoneum.  The  intestine  det":ends  along  this  pouch 
into  the  cavity  of  the  tunica  vaginalis  which  constitutes  the  sac  of  the  hernia,  and  the  gut  lies  in 
contact  with  the  testis.  Though  this  form  of  hernia  is  termed  congenital,  the  term  does  not  imply 
that  the  hernia  existed  at  birth,  but  merely  that  a  condition  is  present  which  may  allow  of  the 


1316 


THE  ORGANS  OF  DIGESTION 


descent  of  the  hernia  at  any  moment.    As  a  matter  of  fact,  congenital  hernise  frequently  do  not 
appear  until  adult  life. 

Where  the  processus  vaginalis  is  occluded  at  the  internal  ring  only  and  remains  patent  through- 
out the  rest  of  its  extent,  two  varieties  of  oblique  inguinal  hernia  may  be  produced — viz.,  infantile 


Fig,  1078. — Commoii  scrotal  hernia. 


Fig,  1079. — Congenital  hernia 


Fig.  10S2, — Hernia  into  the  funicular  process. 
Figs.  1078  to  1082. — Varieties  of  oblique  inguinal  hernia. 


and  encysted  hernite.  In  the  infantile  form  (Fig.  1080)  the  bowel  pressing  upon  the  septum  and 
the  peritoneum  in  its  immediate  neighborhood  causes  it  to  yield  and  form  a  sac  which  descends 
behind  the  tunica  vaginalis;  so  that  in  front  of  the  bowel  there  are  three  layers  of  peritoneum. 


MOVEMENTS  AND  INNERVATION  OF  THE  INTESTINES      1317 

the  two  layers  of  the  tunica  vaginalis  and  its  own  sac.  In  the  encysted  form  (Fig.  1060)  pressure 
at  the  occkided  spot  causes  the  septum  to  yield  and  form  a  sac  which  projects  into  the  tunica 
vaoinalis,  forming  thus  a  sac  within  a  sac,  so  that  in  front  of  the  bowel  there  are  two  layers  of 
peritoneum,  one  from  the  tunica  vaginalis  and  one  from  its  own  sac. 

Where  the  processus  vaginalis  is  occluded  at  the  lower  point  only,  i.  e.,  just  above  the  testis, 
the  intestine  descends  into  the  pouch  of  peritoneum  as  far  as  the  testis,  but  is  prevented  from 
enterincf  the  sac  of  the  tunica  vaginalis  by  the  septum  which  has  formed  between  it  and  the 
pouch. "^  This  is  Icnown  as  hernia  into  the  funicular  jrrocess;  it  resembles  the  congenital  form 
e.Kcejjt  that  instead  of  envelo|)ing  the  testis  it  lies  above  it. 

In  direct  inguinal  hernia  the  protrusion  makes  its  way  through  some  part  of  Hesselbach's 
triangle,  either  through  {a)  the  outer  part,  where  only  extraperitoneal  tissue  and  transversalis 
fascia  intervene  between  the  peritoneum  and  the  aponeurosis  of  the  External  oblique;  or  through 
(i)  the  conjoined  tendon  which  stretches  across  the  inner  two-thirds  of  the  triangle  between  the 
artery  and  the  middle  line.  In  the  former  the  hernial  protrusion  escapes  from  the  abdomen  on 
the  outer  side  of  the  conjoined  tendon,  pushes  before  it  the  peritoneum,  extraperitoneal  tissue, 
and  transversalis  fascia,  and  enters  the  inguinal  canal.  It  passes  along  nearly  the  whole  length 
of  the  canal  and  finally  emerges  from  the  external  ring,  receiving  an  investment  from  the  inter- 
columnar  fascia.  The  coverings  of  this  form  of  hernia  are  similar  to  those  of  the  oblique  form, 
except  that  a  portion  derived  from  the  general  layer  of  transversalis  fascia  replaces  the  infun- 
dibuliform  fascia. 

In  the  second  form,  which  is  the  more  frequent,  the  hernia  is  either  forced  through  the  fibres 
of  the  conjoined  tendon,  or  the  tendon  is  gradually  distended  in  front  of  it  so  as  to  form  a  com- 
plete investment  for  it.  The  intestine  then  enters  the  lower  end  of  the  inguinal  canal,  escapes  at 
the  external  ring  lying  on  the  inner  side  of  the  cord,  and  receives  additional  coverings  from  the 
external  spermatic  fascia,  the  superficial  fascia,  and  the  integument.  The  coverings  of  this  form, 
therefore,  differ  from  those  of  the  oblique  form  in  that  the  conjoined  tendon  is  substituted  for  the 
cremaster,  and  the  infundibuliform  fascia  is  replaced  by  a  portion  of  the  general  layer  of  the 
transversalis  fascia. 

The  seat  of  stricture  in  both  varieties  of  direct  hernia  is  usually  found  either  at  the  neck  of  the 
sac  or  at  the  external  ring.  In  that  form  which  perforates  the  conjoined  tendon  it  not  infre- 
quently occurs  at  the  edges  of  the  fissure  through  which  the  gut  passes.  In  all  cases  of  inguinal 
hernia',  whether  direct  or  oblique,  it  is  proper  to  divide  the  stricture  directly  upward;  by  cutting 
in  this  direction  the  incision  is  made  parallel  to  the  deep  epigastric  artery — external  to  it  in  the 
oblique  variety,  internal  to  it  in  the  direct  form  of  hernia;  all  chance  of  wounding  the  vessel  is 
thus  avoided.  Direct  inguinal  hernia  is  of  much  less  frequent  occurrence  than  the  oblique,  and 
is  found  more  often  in  men  than  in  women.  The  main  differences  in  position  between  it  and 
the  oblique  form  are:  (o)  it  is  placed  over  the  pubis  and  not  in  the  course  of  the  inguinal  canal; 
(&)  the  deep  epigastric  artery  runs  on  the  outer  or  iliac  side  of  the  neck  of  the  sac;  and  (c)  the 
spermatic  cord  lies  along  its  external  and  posterior  sides,  not  directly  behind  it,  as  in  oblique 
inguinal  hernia. 

Femoral  Hernia. — In  femoral  hernia  the  protrusion  of  the  intestine  takes  place  through 
the  crural  ring.  As  already  described  (p.  503),  this  ring  is  closed  by  the  septum  crurale,  a 
partition  of  modified  extraperitoneal  tissue;  it  is,  therefore,  a  weak  spot  in  the  abdominal  wall, 
and  especially  in  the  female,  where  the  ring  is  larger  and  where  profound  changes  are  produced 
in  the  tissues  of  the  abdomen  by  pregnancy.  Femoral  hernia  is,  therefore,  more  common  in 
women  than  in  men. 

When  a  portion  of  intestine  is  forced  through  the  femoral  ring  it  carries  before  it  a  pouch  of 
peritoneum  which  forms  the  hernial  sac.  It  receives  an  investment  from  the  extraperitoneal 
tissue  or  septum  crurale  and  descends  along  the  femoral  canal,  or  inner  compartment  of  the 
sheath  of  the  femoral  vessels,  as  far  as  the  saphenous  opening ;  at  this  point  it  changes  its  course, 
being  prevented  from  extending  farther  down  the  sheath  on  account  of  the  narrowing  of  the 
latter,  and  its  close  contact  with  the  vessels,  and  also  from  the  close  attachment  of  the  superficial 
fascia  and  femoral  sheath  to  the  lower  part  of  the  circumference  of  the  saphenous  opening. 
The  tumor  is  consequently  directed  forward,  pushing  before  it  the  cribriform  fascia,  and  then 
curves  upward  over  Poupart's  ligament  and  the  lower  part  of  the  External  oblique,  being  covered 
by  the  superficial  fascia  and  integument.  While  the  hernia  is  contained  in  the  femoral  canal  it  is 
usually  of  small  size  owing  to  the  resisting  nature  of  the  surrounding  parts,  but  when  it  escapes 
from  the  saphenous  opening  into  the  loose  areolar  tissue  of  the  groin  it  becomes  considerably 
enlarged.  The  direction  taken  by  a  femoral  hernia  in  its  descent  is  at  first  downward,  then  for- 
ward and  upward;  in  the  application  of  taxis  for  the  reduction  of  a  femoral  hernia,  therefore, 
pressure  should  be  directed  in  the  reverse  order. 

The  coverings  of  a  femoral  hernia,  from  within  outward,  are  peritoneum,  septum  crurale, 
femoral  sheath,  cribriform  fascia,  superficial  fascia,  and  integument.  Sir  Astley  Cooper  has 
described  an  investment  for  femoral  hernia  under  the  name  of  fascia  propria,  lying  immediately 
external  to  the  peritoneal  sac  but  frequently  separated  from  it  by  some  adipose  tissue.  Surgi- 
cally it  is  important  to  remember  the  frequent  existence  of  this  layer  on  account  of  the  ease  with 


1318  THE  ORGANS  OF  DIGESTION 

which  an  inexperienced  operator  may  mistake  the  fascia  for  the  peritoneal  sac  and  the  contained 
fat  for  omentum,  as  there  is  often  a  great  excess  of  subperitoneal  fatty  tissue  enclosed  in  the 
"fascia  propria."  In  many  cases  it  resembles  a  fatty  tumor,  but  on  further  dissection  the  true 
hernial  sac  will  be  found  in  the  centre  of  the  mass  of  fat.  The  fascia  propria  is  merely  modified 
extraperitoneal  tissue  which  has  been  thickened  to  form  a  membranous  sheet  by  the  pressure  of 
the  hernia. 

When  the  intestine  descends  along  the  femoral  canal  only  as  far  as  the  saphenous  opening  the 
condition  is  known  as  incomplete  femoral  hernia.  The  small  size  of  the  protrusion  in  this  form 
of  hernia,  on  account  of  the  firm  and  resisting  nature  of  the  canal  in  which  it  is  contained,  ren- 
ders it  an  exceedingly  dangerous  variety  of  the  disease  from  the  extreme  difficulty  of  detecting 
the  existence  of  the  swelling,  especially  in  corpulent  subjects.  The  coverings  of  an  incomplete 
femoral  hernia  would  be,  from  without  inward,  integument,  superficial  fascia,  superior  falciform 
process  of  fascia  lata,  femoral  sheath,  septum  crurale,  and  peritoneum. 

The  seat  of  stricture  of  a  femoral  hernia  varies ;  it  may  be  in  the  peritoneum  at  the  neck  of  the 
hernial  sac;  in  the  greater  number  of  cases  it  is  at  the  point  of  junction  of  the  superior  falciform 
process  with  the  free  edge  of  Gimbernat's  ligament;  or  it  may  be  at  the  margin  of  the  saphenous 
opening.  The  stricture  should  in  every  case  be  divided  in  a  direction  upward  and  inward  for  a 
distance  of  about  one-sixth  to  one-quarter  of  an  inch.  All  vessels  or  other  structures  of  impor- 
tance in  relation  to  the  neck  of  the  sac  will  thus  be  avoided. 

The  spine  of  the  pubis  forms  an  important  landmark  in  serving  to  differentiate  the  inguinal 
from  the  femoral  variety  of  hernia.  The  inguinal  protrusion  is  above  and  to  the  inner  side  of 
the  spine,  while  the  femoral  is  below  and  to  its  outer  side. 

By  the  term  internal  hernia,  we  mean  hernia  into  the  foramen  of  Winslow,  into  the  retro- 
duodenal  fossa,  into  the  retrocecal  fossa,  or  into  the  intersigmoid  fossa.  Such  a  hernia  produces 
the  symptoms  of  acute  strangulation  of  the  intestine. 

In  typhoid  fever  there  is  ulceration  of  Peyer's  patches.  One  of  these  ulcers  may  perforate. 
The  only  chance  for  life  is  immediate  laparotomy  and  closure  of  the  perforation.  This  saves 
one-fifth,  or  possibly  one-third,  of  the  cases.  The  incision  is  made  to  expose  the  lower  ileum,  as 
in  the  vast  majority  of  cases  the  perforation  is  in  this  portion  of  the  gut. 

The  surgical  anatomy  of  the  rectum  is  of  considerable  importance.  There  may  be  congenital 
malformation  due  to  arrested  or  imperfect  development.  Thus,  there  may  be  no  invagination  of 
the  ectoderm,  and  consequently  a  complete  absence  of  the  anus;  or  the  hind  gut  may  be  imper- 
fectly developed,  and  there  may  be  an  absence  of  the  rectum,  though  the  anus  is  developed; 
or  the  invagination  of  the  ectoderm  may  not  communicate  with  the  termination  of  the  hind  guf 
from  want  of  solution  of  continuity  in  the  septum  which  in  early  fetal  life  exists  between  the 
two.  The  mucous  membrane  is  thick  and  but  loosely  connected  to  the  muscular  coat  beneath 
and  thus  favors  prolapse,  especially  in  children.  The  vessels  of  the  rectum  are  arranged  as 
mentioned  above,  longitudinally,  and  are  contained  in  the  loose  cellular  tissue  between  the 
mucous  and  muscular  coats,  and  receive  no  support  from  surrounding  tissues,  and  this  favors 
varicosity.  Moreover,  the  veins,  after  running  upward  in  a  longitudinal  direction  for  about  five 
inches  in  the  submucous  tissue,  pierce  the  muscular  coats,  and  are  liable  to  become  constricted 
at  this  point  by  the  contraction  of  the  muscular  wall  of  the  gut.  In  addition  to  this  there  are  no 
valves  in  the  superior  hemorrhoidal  veins,  and  the  vessels  of  the  rectum  are  placed  in  a  dependent 
position,  and  are  liable  to  be  pressed  upon  and  obstructed  by  hardened  feces.  The  anatomical 
arrangement,  therefore,  of  the  hemorrhoidal  vessels  explains  the  great  tendency  to  the  occurrence 
of  piles.  The  presence  of  the  Sphincter  ani  is  of  surgical  importance,  since  it  is  the  constant 
contraction  of  this  muscle  which  prevents  an  ischiorectal  abscess  from  healing  and  tends  to 
cause  a  fistula.  Also,  the  reflex  contraction  of  this  muscle  is  the  cause  of  the  severe  pain  com- 
plained of  in  fissure  of  the  anus.  The  relations  of  the  peritoneum  to  the  rectum  are  of  impor- 
tance in  connection  with  the  operation  of  removal  of  the  lower  end  of  the  rectum  for  malignant 
disease.  The  membrane  gradually  leaves  the  rectum  as  it  descends  into  the  pelvis ;  first  leaving 
its  posterior  surface,  then  the  sides,  and  then  the  anterior  surface,  to  become  refiected  in  the 
male  on  to  the  posterior  wall  of  the  bladder,  forming  the  rectovesical  pouch,  and  in  the  female 
on  to  the  posterior  wall  of  the  vagina,  forming  Douglas'  pouch.  The  rectovesical  pouch  of 
peritoneum  extends  to  within  three  inches  (7.5  cm.)  from  the  anus,  so  that  it  is  not  desirable 
to  remove  more  than  two  and  a  half  inches  (6.25  cm.)  of  the  entire  circumference  of  the  bowel,  for 
fear  of  the  risk  of  opening  the  peritoneum.  When,  however,  the  disease  is  confined  to  the  poste- 
rior surface  of  the  rectum,  or  extends  farther  in  this  direction,  a  greater  amount  of  the  posterior 
wall  of  the  gut  may  be  removed,  as  the  peritoneum  does  not  extend  on  this  surface  to  a  lower 
level  than  five  inches  from  the  margin  of  the  anus.  The  rectovaginal  or  Douglas'  pouch  in  the 
female  extends  somewhat  lower  than  the  rectovesical  pouch  of  the  male,  and  therefore  it  is 
advisable  to  remove  a  less  length  of  the  tube  in  this  sex.  Of  recent  years,  however,  much  more 
extensive  operations  have  been  done  for  the  removal  of  cancer  of  the  rectum,  and  in  these  the 
peritoneal  cavity  has  necessarily  been  opened.  If,  in  these  cases,  the  opening  is  plugged  with 
iodoform  gauze  until  the  operation  is  completed,  and  then  the  edges  of  the  wound  in  the  peri- 
toneum are  accurately  brought  together  with  sutures,  no  evil  result  appears  to  follow.    For  cases 


THE  LIVER  1319 

of  cancer  of  the  rectum  which  are  too  low  to  be  reached  by  abdominal  section,  and  too  high  to  be 
removed  by  the  ordinary  operation  from  below,  Kraske  has  devised  an  operation  which  goes  by 
his  name.  The  patient  is  placed  on  his  right  side  and  an  incision  is  made  from  the  second  sacral 
spine  to  the  anus.  The  soft  parts  are  now  separated  from  the  back  of  the  left  side  of  the  sacrum 
as  far  as  its  left  margin,  and  the  greater  and  lesser  sacrosciatic  ligaments  are  divided.  A  portion 
of  the  lateral  mass  of  the  sacrum,  commencing  on  the  left  border  at  the  level  of  the  third  poste- 
rior sacral  foramen,  and  running  downward  and  inward  through  the  fourth  foramen  to  the  cornu, 
is  now  cut  away  with  a  chisel.  The  left  side  of  the  wound  being  now  forcibly  drawn  outward, 
the  whole  of  the  rectum  is  brought  into  view,  and  the  diseased  portion  can  be  removed,  leaving 
the  anal  portions  of  the  gut,  if  healthy.  The  two  divided  ends  of  the  gut  can  perhaps  then  be 
approximated  and  sutured  together.  Kraske's  operation  is  in  many  cases  preceded  by  the  per- 
formance of  iliac  colostomy.  In  cancer  high  up  in  the  rectum  removal  of  the  growth  through 
the  abdomen  is  sometimes  practised,  the  divided  lower  end  of  the  rectum  being  sutured  to  the 
divided  upper  end  (Weir's  operation). 

The  colon  frequently  reciuires  opening  in  cases  of  intestinal  obstruction,  and  by  some  sur- 
geons this  operation  is  performed  in  cases  of  cancer  of  the  rectum,  as  soon  as  the  disease  is  recog- 
nized, in  the  hope  that  the  rate  of  growth  may  be  retarded  by  removing  the  irritation  produced 
by  the  passage  of  fecal  matter  over  the  diseased  surface.  The  operation  of  colostomy  may  be 
performed  either  in  the  inguinal  or  lumbar  region;  but  inguinal  colostomy  (Maydl's  operation) 
has  at  the  present  day  superseded  the  lumbar  operation.  The  main  reason  for  preferring  this 
operation  is  that  a  spur-shaped  process  of  the  mesocolon  can  be  formed,  which  prevents  any  fecal 
matter  finding  its  way  past  the  artificial  anus  and  becoming  lodged  on  the  diseased  structures 
below.  The  sigmoid  flexure  being  surrounded  by  peritoneum,  a  coil  can  be  drawn  out  of  the 
wound,  and  when  it  is  opened  transversely  a  spur  is  formed,  and  this  prevents  any  fecal  matter 
finding  its  way  from  the  gut  above  the  opening  into  that  below.  The  operation  is  performed 
by  making  an  incision  two  or  three  inches  in  length  from  a  point  one  inch  internal  to  the  anterior 
superior  spinous  process  of  the  ilium,  parallel  to  Poupart's  ligament.  The  various  layers  of 
abdominal  muscles  are  cut  through,  and  the  peritoneum  opened  and  sewed  to  the  external 
skin.  The  sigmoid  flexure  is  now  sought  for,  and  pulled  out  of  the  wound  and  fixed  by  pushing 
a  glass  bar  through  a  slit  in  the  mesocolon.  The  two  parts  of  the  loop  are  sutured  together. 
The  intestine  is  now  sutured  to  the  parietal  peritoneum.  The  wound  is  dressed,  and  either 
immediately  or  between  the  second  to  the  fourth  day,  according  to  the  requirements  of  the  case, 
the  protruded  coil  of  intestine  is  opened.     It  is  opened  transversely  with  the  Paquelin  cautery. 

The  loose  connective  tissue  around  the  rectum  is  occasionally  the  site  of  an  abscess,  the  active 
focus  of  which,  however,  may  be  located  elsewhere.  This  form  of  abscess  may  be  described  as 
the  superior  pelvic  rectal;  it  is  placed  above  the  pelvic  diaphragm,  but  beneath  the  peritoneum. 
The  acute  variety  is  generally  due  to  ulceration  or  perforation  of  the  bowel  (possibly  produced  by 
a  foreign  body)  above  the  level  of  the  attachment  of  the  Levator  ani.  The  abscess  may  also  occur 
above  a  stricture  (simple  or  malignant)  of  the  rectum;  occasionally  it  arises  from  suppuration 
around  the  prostate,  and  more  rarely  follows  abscess  of  the  seminal  vesicles.  Chronic  abscesses 
also  appear  in  the  same  region  either  from  caries  of  the  anterior  surface  of  the  sacrum  or  from 
caseation  of  the  presacral  lymph  nodes,  while  in  other  cases  an  abscess  finds  its  way  down  into 
the  pelvis  from  disease  of  the  anterior  surfaces  of  the  bodies  of  the  lumbar  vertebral. 


THE  LIVER  (HEPAR)  (Figs.  1083,  1084). 

The  liver  is  the  largest  gland  in  the  body  and  is  situated  in  the  upper  and 
right  part  of  the  abdominal  cavity,  occupying  almost  the  whole  of  the  right  hypo- 
chondrium,  the  greater  part  of  the  epigastrium,  and  not  uncommonly  extending 
into  the  left  hypochondrium  as  far  as  the  midclavicular  line.  In  the  male  it  weighs 
from  fifty  to  sixty  ounces;  in  the  feinale,  from  forty  to  fifty.  It  is  relatively 
much  larger  in  the  fetus  than  in  the  adult,  constituting,  in  the  former,  about  one- 
eighteenth,  and  in  the  latter,  about  one-thirty-sixth  of  the  entire  body  weight. 
Its  greatest  transverse  measurement  is  from  eight  to  nine  inches  (20  to  22  cm.). 
Vertically,  near  its  lateral  or  right  surface,  it  measures  about  six  or  seven  inches 
(15  to  IS  cm.),  while  its  greatest  antero-posterior  diameter  is  on  a  level  with  the 
upper  end  of  the  right  kidney  and  is  from  four  to  five  inches  (10  to  12  cm.).  Op- 
posite the  vertebral  column  its  measurement  from  before  backward  is  reduced 
to  about  three  inches  (7.5  cm.).  Its  consistence  is  that  of  a  soft  solid;  it  is,  how- 
ever, friable  and  easily  lacerated;  its  color  is  a  dark  reddish  brown,  and  its 
specific  gravity  is  1.05. 


1320 


THE  ORGAKS  OF  DIGESTION 


To  obtain  a  correct  idea  of  its  shape,  it  must  be  hardened  in  situ,  and  it  will 
then  be  seen  to  present  the  appearance  of  a  wedge,  the  base  of  which  is  directed 
to  the  right  and  the  thin  edge  toward  the  left.  Symington  describes  its  shape  as 
that  "of  a  right-angled  triangular  prism  with  the  right  angles  rounded  off." 

Surfaces. — The  liver  possesses  five  surfaces — viz.,  a  superior,  inferior,  anterior, 
posterior,  and  a  right  lateral  surface.  A  sharp,  well-defined  margin  divides  the 
inferior  from  the  anterior  and  lateral  surfaces,  but  the  other  surfaces  are  separated 
from  one  another  by  thick,  rounded  borders.  The  superior  and  anterior  surfaces 
are  separated  from  each  other  by  a  thick  rounded  border,  and  are  attached  to  the 
Diaphragm  and  anterior  abdominal  wall  by  a  triangular  or  falciform  fold  of  peri- 
toneum, the  suspensory  or  falciform  ligament,  in  the  free  margin  of  which  is  a  rounded 
cord,  the  ligamentum  teres  or  impervious  umbilical  vein.  The  line  of  attachment 
of  the  falciform  ligament  divides  the  liver  into  two  unequal  parts,  termed  the 
right  and  left  lobes,  the  right  being  much  the  larger.  The  inferior  and  posterior 
surfaces  are  divided  into  five  lobes  by  five  fissures,  which  are  arranged  in  the  form 


T    LATERAL 


Fig.   1083.— The  liver.     Upper  surface.     (Drawn  from  His'  model.) 


of  the  letter  H.  The  left  limb  of  the  H  marks  on  these  surfaces  the  division  of 
the  liver  into  right  and  left  lobes;  it  is  known  as  the  longitudinal  fissure,  and  con- 
sists of  two  parts — viz.,  the  umbilical  fissure  in  front  and  the  fissure  for  the  ductus 
venosus  behind.  The  right  limb  of  the  H  is  formed  in  front  by  the  fissure  or 
fossa  for  the  gall-bladder,  and  behind  by  the  fissure  for  the  inferior  vena  cava ;  these 
two  fissures  are  separated  from  one  another  by  a  band  of  liver  substance,  termed 
the  caudate  lobe.  The  bar  connecting  the  two  limbs  of  the  H  is  the  transverse 
or  portal  fissure;  in  front  of  it  is  the  quadrate  lobe,  behind  it  is  the  Spigelia)i  lobe. 

The  superior  surface  (fades  superior)  (Fig.  1083)  comprises  a  part  of  both 
loljes,  and,  as  a  whole,  is  convex,  and  fits  under  the  vault  of  the  Diaphragm;  its 
central  part,  however,  presents  a  shallow  depression,  the  cardiac  depression  (im- 
pressiocardiaca),  which  corresponds  with  the  position  of  the  heart  on  the  upper 
surfaces  of  the  Diaphragm.  It  is  separated  from  the  anterior,  posterior,  and  lateral 
surfaces  by  thick,  rounded  borders.  Its  left  extremity  is  continued  into  the  under 
surface  by  a  prominent  sharp  margin.  Except  along  the  lines  of  attachment 
of  the  falciform  ligament  this  surface  is  completely  covered  by  peritoneum. 

The  anterior  surface  is  large,  triangular  in  shape,  and  comprises  also  a  part  of 
both  right  and  left  lobes.     It  is  directed  forward,  and  the  greater  part  of  it  is  in 


THE  LIVER  1321 

contact  with  the  Diaphragm,  which  separates  it  on  the  right  from  the  sixth  to 
the  tenth  ribs  and  their  cartilages,  and  on  the  left  from  the  seventh  and  eighth 
costal  cartilages.  In  the  middle  line  it  lies  behind  the  ensiform  cartilage,  and  in 
the  angle  between  the  diverging  rib  cartilages  of  opposite  sides  the  anterior  sur- 
face is  in  contact  with  the  abdominal  wall.  It  is  separated  from  the  inferior 
surface  by  a  sharp  margin,  and  from  the  superior  and  lateral  surfaces  by  thick 
rounded  borders.  It  is  completely  covered  by  peritoneum  except  along  the  line 
of  attachment  of  the  falciform  ligament. 

The  lateral  or  right  surface  (Figs.  1083  and  1084)  is  convex  from  before  back- 
ward and  slightly  so  from  above  downward.  It  is  directed  toward  the  right  side, 
forming  the  base  of  the  wedge,  and  lies  against  the  lateral  portion  of  the  Dia- 
phragm, which  separates  it  from  the  lower  part  of  the  right  pleura  and  lung,  outside 
which  are  the  right  costal  arches  from  the  seventh  to  the  eleventh  inclusive. . 

The  inferior  or  visceral  surface  {fades  inferior)  (Figs.  1084  and  1085)  is  uneven, 
concave,  directed  downward,  backward,  and  to  the  left,  and  is  in  relation  with  the 
stomach  and  duodenum,  the  hepatic  flexure  of  the  colon,  and  the  right  kidney 
and  suprarenal  glands.  The  surface  is  divided  by  a  longitudinal  fissure  into  a  right 
and  a  left  lobe,  and  is  almost  completely  invested  by  peritoneum;  the  only  parts 
where  this  covering  is  absent  are  where  the  gall-bladder  is  attached  to  the  liver 
and  at  the  transverse  fissure,  where  the  two  layers  of  the  lesser  omentum  are  sepa- 
rated from  each  other  by  the  bloodvessels  and  duct  of  the  viscus.  The  under 
surface  of  the  left  lobe  presents  to  the  right  and  near  the  centre  a  rounded  emi- 
nence, the  omental  tuberosity  (tuber  omentale)  (Fig.  1084),  which  is  in  contact  with 
the  lesser  omentum.  It  is  surrounded  by  a  broad  depression,  the  gastric  surface 
or  impression  {impressio  gasf.rica),  with  which  the  stomach  is  in  contact.  Between 
the  gall-liladder  and  the  left  lobe  is  the  quadrate  lobe.  The  quadrate  lobe  is 
bounded  to  the  left  by  the  umbilical  fissure  or  the  fissure  for  the  umbilical  vein  (fossa 
venae  umbiUcalis),  which  is  the  anterior  portion  of  the  longitudinal  fissure  and 
lodges  the  round  ligament.  The  under  surface  of  the  right  lobe  is  divided  into  two 
unequal  portions  by  a  fossa,  which  lodges  the  gall-bladder  and  is  called  the  fossa 
vesicalis  [fossa  vesicae  felleae).  The  portion  to  the  left,  the  smaller  of  the  two, 
is  the  quadrate  lobe,  and  is  in  relation  with  the  pyloric  end  of  the  stomach  (impressio 
pylorica)  and  the  first  portion  of  the  duodenum.  The  portion  of  the  under  sur- 
face of  the  right  lobe  to  the  right  of  the  fossa  vesicalis  presents  two  shallow  concave 
impressions,  one  situated  behind  the  other,  the  two  being  separated  by  a"  ridge. 
The  anterior  of  these  two  impressions,  the  colic  impression  (impressio  colica), 
is  produced  by  the  hepatic  flexure  of  the  colon ;  the  posterior,  the  renal  impression 
(impressio  reualis),  is  occupied  by  the 'upper  end  of  the  right  kidney  and  lower  part 
of  the  suprarenal  gland  (Fig.  1084).  To  the  inner  side  of  the  renal  impression  is  a 
third  and  slightly  marked  impression,  lying  between  it  and  the  neck  of  the  gall- 
bladder. This  is  caused  by  the  second  portion  of  the  duodenum,  and  is  known 
as  the  duodenal  impression  (impressio  duodenalis).  Just  in  front  of  the  inferior 
vena  cava  is  a  narrow  strip  of  liver  tissue,  the  caudate  lobe,  which  connects  the 
right  inferior  angle  of  the  Spigelian  lobe  to  the  under  surface  of  the  right  lobe. 
It  forms  the  upper  boundary  of  the  foramen  of  Winslow. 

The  posterior  surface  (fades  posterior)  (Fig.  1085)  is  rounded  and  broad  behind 
the  right  lobe,  but  narrow  on  the  left.  Over  a  large  part  of  its  extent  it  is  not 
covered  by  peritoneum;  this  uncovered  area  (Fig.  1084)  is  about  three  inches  (7.5 
cm.)  broad,  and  is  in  direct  contact  with  the  Diaphragm,  being  united  to  it  by 
areolar  tissue.  It  is  marked  off  from  the  upper  surface  by  the  line  of  reflection  of 
the  upper  or  anterior  layer  of  the  coronary  ligament  and  from  the  under  surface 
of  the  liver  by  the  line  of  reflection  of  the  lower  layer  of  the  coronary  ligament 
(Fig.  1086).  The  central  part  of  the  posterior  surface  presents  a  deep  concavity 
which  is  moulded  on  the  vertebral  column  and  crura  of  the  Diaphragm.     To  the 


1322 


THE  ORGANS  OF  DIGESTION 


right  of  this  the  inferior  vena  cava  is  lodged  in  an  indentation  in  the  hver  substance, 
lying  between  the  uncovered  area  and  the  Spigelian  lobe.  Close  to  the  right  of 
this  indentation  and  immediately  above  the  renal  impression  is  a  small  triangular 
depressed  area,  the  suprarenal  impression  {impressio  siqyrarenalis)  (Fig.  1084), 
the  greater  part  of  which  is  devoid  of  peritoneum;  it  lodges  the  right  suprarenal 
gland,  which  is  inserted  between  the  liver  and  Diaphragm.  To  the  left  of  the 
fossa  for  the  inferior  vena  cava  is  the  Spigelian  lobe,  which  lies  between  the  fissure 
for  the  inferior  vena  cava  and  the  fissure  for  the  ductus  venosus.  Below  and  in 
front  it  projects  and  forms  part  of  the  posterior  boundary  of  the  transverse  fissure. 
Here,  to  the  right,  it  is  connected  with  the  under  surface  of  the  right  lobe  of  the 
liver  by  the  caudate  lobe,  and  to  the  left  it  presents  a  tubercle,  the  tuberculum 
papillare  (Fig.  1084).  It  is  opposite  the  tenth  and  eleventh  thoracic  vertebrse, 
and  rests  upon  the  aorta  and  crura  of  the  Diaphragm,  being  covered  by  the  peri- 
toneum of  the  lesser  sac.  On  the  posterior  surface  to  the  left  of  the  Spigelian 
lobe  is  a  groove,  the  oesophageal  groove  (impressio  oesophagea)  ,^  indicating  the 
position  of  the  abdominal  portion  of  the  oesophagus  (Fig.  1084). 


Umbilical  jisstire.  li  i  li     nt 

1084. — The  liver.     Posterior  and  inferior  surfaces. 


from  His'  model.) 


The  inferior  border  or  margin  (margo  inferioris)  is  thin  and  sharp,  and  marked 
opposite  the  attachment  of  the  falciform  ligament  by  a  deep  notch,  the  umbilical 
notch  (incisura  umbilicalis),  and  opposite  the  cartilage  of  the  ninth  rib  by  a  second 
notch  for  the  fundus  of  the  gall-bladder  (incisura  vesicae  felleae).  In  adult  males 
this  border  generally  corresponds  with  the  lower  margin  of  the  thorax  in  the  right 
midclavicular  line;  but  in  women  and  children  it  usually  projects  below  the  ribs. 

The  left  extremity  of  the  inferior  margin  of  the  liver  is  thin  and  flattened  from 
above  downward. 

Fissures. — ^Five  fissures  are  seen  upon  the  under  and  posterior  surfaces  of  the 
liver,  which  serve  to  divide  it  into  its  five  lobes.  They  are:  the  umbilical  fissure, 
the  fissure  for  the  ductus  venosus  (forming  together  the  longitudinal  fissure),  the 
transverse  fissiu'e,  the  fissure  for  the  gall-bladder,  and  the  fissure  for  the  inferior 
vena  cava. 

The  longitudinal  fissure  (fossa  longitvdinalis  sinistra)  is  a  deep  groove,  which 
extends  from  the  notch  on  the  anterior  margin  of  the  liver  to  the  upper  border  of 
the  posterior  surface  of  the  organ.  It  separates  the  right  and  left  lobes,  the 
transverse  fissure  (Fig.  1084)  joins  it,  at  right  angles,  and  divides  it  into  two  parts. 
The  anterior  part,  or  umbilical  fissure  (fossa  venae  imibilicalis),  lodges  the  umbilical 


THE  LIVER 


1323 


vein  in  the  fetus,  and  its  remains  {ligamentum  teres)  in  the  adult;  it  h'ts  between 
the  quadrate  lobe  and  the  left  lobe  of  the  liver,  and  is  often  partially  bridged 
over  by  a  prolongation  of  the  liepatic  substance,  the  pons  hepatis.  The  posterior 
part  or  fissure  for  the  ductus  venosus  {fossa  ductus  veiiosi.)  lies  Ijetween  the  left 
lobe  and  the  Spigelian  lobe;  it  lodges  in  the  fetus  the  ductus  venosus,  and  in  the 
adult  a  slender  fibrous  cord  (lig.  venosum)  the  impervious  remains  of  that  vessel. 
The  transverse  or  portal  fissure  (porta  hepatis)  (Fig.  1084)  is  a  short  but  deep 
fissure,  about  two  inches  (5  cm.)  in  length,  extending  transversely  across  the  under 
surface  of  the  left  portion  of  the  right  lobe,  nearer  to  its  posterior  surface  than 
its  anterior  border.  It  joins,  nearly  at  right  angles,  with  the  longitudinal  fissure, 
and  separates  the  quadrate  lol^e  in  front  from  the  caudate  and  Spigelian  lobes 
behind.  By  the  older  anatomists  this  fissure  was  considered  the  gateway  (porta) 
of  the  liver;  hence  the  large  vein  which  enters  at  this  fissure  was  called  the  portal 
vein  (Fig.  1085).  Besides  this  vein,  the  fissure  transmits  the  hepatic  artery  and 
nerves,  and  the  hepatic  duct  and  lymphatics.  At  their  entrance  into  the  fissure, 
the  hepatic  duct  lies  in  front  and  to  the  right,  the  hepatic  artery  to  the  left,  and 
the  portal  vein  behind  and  between  the  duct  and  artery. 

iV'snn'haqeal  qroove.         Portal  vein.         Suprarenal  impreasmn. 

^';Ar(5^£RED"~§P>^      RIGHT    LATERAL 
-Ti^^    /      PER/rn..^>^   LIGAMENT 


Hepatic  aiteiy,       I 

Common  Oile  duct. 
Fir,,  loss.— Posterior  and  under  surfaces  of  the  liver.      (Drawn  from  His'  model.) 

The  fossa  or  fissure  for  the  gall-bladder  (fossa  vesicae  felleae)  is  a  shallow,  oblong 
fossa,  placed  on  the  under  surface  of  the  right  lobe,  parallel  with  the  longitudinal 
fissure.  It  extends  from  the  anterior  free  margin  of  the  liver,  which  is  notched 
for  its  reception,  to  the  right  extremity  of  the  transverse  fissure. 

The  fissure  for  the  inferior  vena  cava  (fossa  venae  cavae)  (Fig.  1084)  is  a  short, 
deep  fissure,  in  some  cases  a  complete  canal,  in  consequence  of  the  substance 
of  the  liver  occasionally  surrounding  this  vessel.  It  extends  obliquely  upward 
from  the  lobus  caudatus,  which  separates  it  from  the  transverse  fissure  on  the 
posterior  surface  of  the  liver,  and  is  situated  between  the  Spigelian  lobe  and  the 
bare  area  of  the  liver.  On  slitting  open  the  inferior  vena  cava  the  orifices  of 
the  hepatic  veins  will  be  seen  opening  into  this  vessel  at  its  upper  part,  after 
perforating  the  floor  of  this  fissure. 

Lobes. — ^The  lobes  of  the  liver,  like  the  ligaments  and  fissures,  are  five  in 
number — the  right  lobe,  the  left  lobe,  the  lobus  quadratus,  the  lobus  Spigelii,  and 
the  lobus  caudatus,  the  last  three  being  merely  parts  of  the  right  lobe. 


1324  THE  ORGANS  OF  DIGESTION 

The  right  lobe  (lohiis  hepatis  dexter)  (Figs.  1083  and  1084)  is  much  larger  than 
the  left,  the  proportion  between  them  being  as  six  to  one.  It  occupies  the  right 
hypochondrium,  and  is  separated  from  the  left  lobe,  on  its  upper  and  anterior  sur- 
faces, by  the  falciform  ligament;  on  its  under  and  posterior  surfaces  by  the  longi- 
tudinal fissure;  and  in  front  by  the  umbilical  notch.  It  is  of  a  somewhat  quadri- 
lateral form,  its  under  and  posterior  surfaces  being  marked  by  three  fissures — the 
transverse  fissure,  the  fissure  for  the  gall-bladder,  and  the  fissure  for  the  inferior 
vena  cava,  which  separate  its  left  part  into  three  smaller  lobes — the  lobus  Spigelii, 
lobus  quadratus,  and  lobus  caudatus.  On  it  are  seen, four  shallow  impressions — one 
in  front,  for  the  hepatic  flexure  of  the  colon;  a  second  behind,  for  the  right  kidney; 
a  third  internal,  between  the  last-named  and  the  gall-bladder,  for  the  second  part 
of  the  duodenum;  and  a  fourth  on  its  posterior  surface,  for  the  suprarenal  gland. 

The  lobus  quadratus  (Figs.  1084  and  1085)  is  situated  on  the  under  surface  of 
the  right  lobe,  is  bounded  in  front  by  the  inferior  margin  of  the  liver;  behind, 
by  the  transverse  fissure;  on  the  right,  by  the  fissure  of  the  gall-bladder;  on  the 
left,  by  the  umbilical  fissure.  It  is  oblong  in  shape,  its  antero-posterior  diameter 
being  greater  than  its  transverse. 

The  lobus  Spigelii  Qob^ts  caudatus  \Spigelii\)  (Figs.  1084  and  1085)  is  situated 
upon  the  posterior  surface  of  the  right  lobe  of  the  liver.  It  looks  directly  back- 
ward, and  is  nearly  vertical  in  direction.  It  is  bounded  below  by  the  transverse 
fissure,  on  the  right  by  the  fissure  for  the  inferior  vena  cava,  and  on  the  left  by 
the  fissure  for  the  ductus  venosus.  It  is  longer  from  above  downward,  and  is 
somewhat  concave  in  the  transverse  direction.  Its  lower  end  usually  projects  in 
the  form  of  a  rounded  process,  the  tuber  papillare  (processus  papiUaris). 

The  lobus  caudatus  {processus  caudatus)  (Fig.  1084),  or  tailed  lobe,  is  a  small 
elevation  of  the  hepatic  substance  extending  obliquely  outward,  from  the  lower 
extremity  of  the  Spigelian  lobe  to  the  under  surface  of  the  right  lobe.  It  is  situ- 
ated behind  the  transverse  fissure,  and  separates  the  fissure  for  the  gall-bladder 
from  the  commencement  of  the  fissure  for  the  inferior  vena  cava. 

The  left  lobe  (lohis  hepatis  sinister)  (Figs.  1083  and  1084)  is  smaller  and  more 
flattened  than  the  right.  It  is  situated  in  the  epigastric  and  left  hypochondriac 
regions.  Its  upper  surface  is  slightly  convex;  its  under  surface  is  concave, 
and  presents  a  shallow  depression  for  the  stomach,  the  gastric  impression.  This 
is  situated  in  front  of  the  groove  for  the  oesophagus,  and  is  separated  from  the  lon- 
gitudinal fissure  by  the  omental  tuberosity,  which  lies  against  the  small  omentum 
and  lesser  curvature  of  the  stomach.  The  posterior  end  of  the  left  lobe  frequently 
exhibits  a  flat  projection,  composed  of  connective  tissue,  and  called  the  appendix 
fibrosus  hepatis.  In  the  adult,  portions  only  of  bile  ducts  are  present  in  it.  In 
the  newborn  it  is  a  definite  portion  of  secreting  liver  substance,  which  later  under- 
goes connective-tissue  transformation. 

Ligaments. — The  liver  is  connected  to  the  under  surface  of  the  Diaphragm 
and  the  anterior  walls  of  the  abdomen  by  five  ligaments,  four  of  which  are  peri- 
toneal folds;  the  fifth  is  round,  fibrous  cord,  resulting  from  the  occlusion  of  the 
umbilical  vein.  These  ligaments  are  the  falciform,  two  lateral,  coronary,  and 
round.  It  is  also  attached  to  the  lesser  curvature  of  the  stomach  by  the  gastro- 
hepatic  or  small  omentum  (p.  1260). 

The  falciform  ligament  (ligameniuvi  falciforvie  hepatis)  (Figs.  1086  and  1087) 
is  a  broad  and  thin  antero-posterior  peritoneal  fold,  falciform  in  shape,  its  base 
being  directed  downward  and  backward,  its  apex  upward  and  backward.  It  is 
attached  by  one  margin  to  the  under  surface  of  the  Diaphragm,  and  the  posterior 
surface  of  the  sheath  of  the  right  Rectus  muscle  as  low  down  as  the  umbilicus; 
by  its  hepatic  margin  it  extends  from  the  notch  on  the  anterior  margin  of  the  liver, 
as  far  back  as  its  posterior  surface.  It  is  composed  of  two  layers  of  peritoneum 
closely  united.     Its  free  edge  contains  the  round  ligament  of  the  liver. 


THE  LIVER 


1325 


The  coronary  ligament  {\u\mnenium.  coronarium.  hepatis)  (Figs.  1083  and  1086) 
connects  the  posterior  surface  of  the  liver  to  the  Diaphragm.  It  consists  of  tMo 
layers.  The  upper  layer  is  formed  by  the  reflection  of  the  peritoneum  from 
the  upper  margin  of  the  bare  area  of  the  liver  to  the  under  surface  of  the  Diaphragm, 
and  is  continuous  with  the  right  layer  of  the  falciform  ligament.  The  loner 
layer  is  reflected  from  the  lower  margin  of  the  bare  area  on  to  the  right  kidney 
and  suprarenal  gland. 


RrGHT 

LATERAL / 

LIGAMENT 


Fig.  1086. — The  peritoneal  ligaments  of  the  ii" 


(Schematic.)     (Poirier  and  Charpy.) 


The  lateral  ligaments  (Figs.  1083  and  1086)  are  two  in  number,  and  are  called 
the  right  and  left  lateral  ligaments. 

The  right  lateral  ligament  {ligaynentum  triangulare  de.rtrum)  (Figs.  1083  and 
1086)  is  in  reality  the  right  extremity  of  the  coronary  ligament.  This  ligament 
is  triangular  in  form,  runs  from  the  liver  to  the  Diaphragm,  and  is  formed  by 
the  apposition  of  the  upper  and  lower  layers  of  the  coronary  ligament. 

The  left  lateral  ligament  {liganien- 
tum  triangulare  sinistrum)  (Figs. 
1083  and  1086)  is  a  fold  of  some 
considerable  size,  which  connects 
the  posterior  part  of  the  upper  sur- 
face of  the  left  lobe  to  the  Dia- 
phragm; its  anterior  layer  \h  con- 
tinuous with  the  left  layer  of  the 
falciform  ligament. 

The  round  ligament  {ligamentmn 
teres  hepatis)  (Figs.  1085  and  1087) 
is  a  fibrous  cord  resulting  from  the 
occlusion  of  the  fetal  umbilical  vein. 
It  ascends  from  the  umbilicus,  in 
the  free  margin  of  the  falciform 
ligament,  to  the  notch  in  the  ante- 
rior border  of  the  liver,  from  which 
it  may  be  traced  along  the  umbilical 
fissure  on  the  inferior  surface  of  the 
liver;  on  the  posterior  surface  it  is  continued  upward  as  the  impervious  ductus 
venosus  (Jig.  venosiim)  as  far  as  the  inferior  vena  cava. 

Support  and  Movability  of  the  Liver. — The  liver  is  movable  within  certain 
narrow  limits.  It  moves  with  respiration.  On  inspiration  it  moves  down  with 
the  Diaphragm  to  distinctly  below  the  costal  arch  in  the  right  midclavicular  line. 
Its  fixation  to  the  under  surface  of  the  Diaphragm  by  means  of  Qonnective  tissue 
gives  it  its  strongest  support. 

The  surface  relations  of  the  liver  are  given  on  page  1334. 


Fig.  1087. — Diagram  to  show  the  relations  of  the  falciform 
or  suspensorj'  and  round  ligaments  to  the  liver  and  the  ab- 
dominal wall.     (Gerrish.) 


1326 


THE  ORGANS  OF  DIGESTION 


Abnormalities  of  the  Liver. — The  liver  may  be  divided  into  many  lobules,  and  such  lobu- 
lation is  most  evident  on  the  parietal  surface  of  the  right  lobe.  Lobulation  is  probably  a  patho- 
logical change.     Occasionally  the  right  lobe  is  small  and  the  left  large. 

Accessory  Livers  are  fragments  of  hepatic  tissue  or  vestiges,  which  are  entirely  separated  from 
the  liver.  They  are  seldom  met  with.  When  they  do  exist  their  most  common  situation  is  in 
the  suspensory  ligament,  but  they  have  been  found  in  the  great  omentum,  in  the  peritoneum, 
wall  of  the  gall-bladder,  and  in  other  situations.  They  may  be  congenital  or  may  be  due  to 
atrophy  of  the  pedicle  of  an  accessory  lobe  or  of  a  pedunculated  lobe.  Tight  lacing  alters  the 
shape  and  position  of  the  liver  (Fig.  10S8)  It  may  flatten  the  dome  and  increase  the  length  of 
the  anterior  surface,  this  change  being  especially  obvious  in  the  right  lobe,  and  a  costal  groove 
may  be  formed  by  the  pressure  of  a  rib.  "When  the  elongated  right  lobe  passes  over  the  right 
kidney,  there  is  atrophy  of  the  hepatic  substance  and  thickening  of  the  capsule,  which  is  opaque 
and  forms  a  hinge-like  ligament  between  the  main  part  of  the  right  lolie  above  the  constricted 
lower  portion.  This  lobe  is  variously  termed  partial  hepatoptosis,  constriction  lobe,  or  the 
sustentacular  formation  of  the  right  lobe  (Hertz).  The  constriction  furrow  is  produced  by 
the  pressure  of  the  corset  in  front  and  the  resistance  of  the  kidney  behind.  The  constriction  lobe 
tapers  to  a  point,  so  that  the  shape  of  the  liver,  as  seen  from  the  front,  is  that  of  a  right-angled 
triangle,  with  the  ape.x  downward."'  Such  a  constriction  lobe  is  known  as  Riedel's  lobe.  The 
left  lobe  may  also  project  down,  but  not  so  markedly.     Tight  lacing  may  cause  the  entire  organ 


Fig.  loss. — Deformed  female  lii 


(Poirier  and  Charpy.) 


to  occupy  a  level  higher  than  normal.  Such  a  liver  is  thick  and  excessively  convey  above  and  thin 
below,  and  reaches  to  or  laps  over  the  spleen.  In  severe  cases  the  superior  surface  is  thrown  into 
antero-posterior  creases  or  folds.  Riedel's  lobe  (Fig.  1088)  may  be  congenital,  may  be  due  to 
tight  lacing,  or  may  arise  in  cholelithiasis  or  cholecystitis  from  the  traction  of  adhesions.  Such 
a  lobe  comes  off  from  the  right  lobe.  It  may  be  a  tapering  mass  of  liver  tissue,  it  may  have  a  thin 
pedicle  of  liver  tissue,  or  its  pedicle  may  be  merely  a  double  fold  of  peritoneum.  The  gall- 
bladder may  lie  upon  its  under  surface,  or  may  be  placed  to  the  left  of  it. 

Vessels. — The  bloodvessels  connected  with  the  liver  are  the  hepatic  artery,  the  portal  vein, 
and  the  hepatic  veins. 

The  hepatic  artery  and  portal  vein  (Figs.  467,  468,  557,  and  1089),  accompanied  by  numerous 
lymphatics  and  nerves,  ascend  to  the  transverse  fissure  between  the  layers  of  the  gastrohepatic 
omentum,  and  in  front  of  the  foramen  of  Winslow.  The  hepatic  duct,  lying  in  company  with 
them,  descends  from  the  transverse  fissure  between  the  layers  of  the  same  omentum.  The  rela- 
tive position  of  the  three  structures  in  the  lesser  omentum  (Fig.  1000)  is  as  follows :  The  hepatic 


of  the  Liver. 


THE  LIVER 


1327 


duct  lies  to  the  right,  the  hepatic  artery  to  the  left,  and  the  portal  ye.n  behind  and  between  1  e 
other  two  They  e  iter  the  transverse  fissure  in  the  above-desxT.bcc  order,  but  in  tha  fissure 
u  Icr.  --earnuZMncnt,  the  duct  being  in  front,  the  artery  in  the  middle,  and  the  vein  behind. 
T  '  r  .  V  he  ^'in,  and  the  duct  divide  into  a  right  and  left  branch  and  several  smaller  branches 
and  wi  h  n  the  or<.an  the  vessels  from  the  three  sources  accompany  each  other  and  divide  at  the 


Fig.  1089.-Scheraatic  section  o£  the  liver.     The  fibrous  tunic  is  shown  in  black  and  the  capsule  of  Glisson  in  rect 


same  points;  so  each  branch  of  the  portal  vein  is  accompanied  by  a  branch  o  the  hepatic  artery 
and  of  the  duct.  They  are  enveloped  in  a  loose  areolar  tissue,  the  capsule  of  Ghsson  (Fig 
^0S9)    which  accompanies  the  vessels  in  their  course  through  the  fortal  canals  in  the  interior  of 

*The"hepatic  veins  (Fig.  471)  convey  the  blood  from  the  liver.  They  commence  in  the  sub- 
st'ince  of  the  liver,  in  the  capillary  terminations  of  the  portal  vein  and  hepatic  artery;  tiiese 
tributaries  o-radually  uniting,  usually  form  three  veins,  which  converge  toward  the  posterior 
surface  of  the  liver  and  open  into  the  portion  of  the  inferior  vena  cava  situated  in  the  groove  a 
t  e  back  part  of  this  organ.  Of  these  three  veins,  one  from  the  right  and  another  from  the^  e 
lobe  open  obliquely  intS  the  inferior  vena  cava,  that  from  the  middle  of  the  organ  and  lobus 
Spigelii  having  a  straight  course. 


COMMON    D' 


DUODENUM 


-The  relations  of  the  vessels  as  they  pass  into  the  transverse  fissure  of  the  liver.     (Poirier  and  Charpy.; 


The  hepatic  veins  have  very  little  cellular  investment;  what  there  is  binds  their  parietes 
closely  to  the  walls  of  the  canals  through  which  they  run;  so  that,  on  section  of  the  organ, 
these'veins  remain  widely  open  and  solitary  (Fig.  1092),  and  may  be  easily  d-tmgu^^d  from 
the  branches  of  the  portal  vein  (Fig.  1093),  which  are  more  or  less  col  apsed,  and  always  ac- 
companied by  an  artery  and  duct;  the  hepatic  veins  are  destitute  of  valves. 


1328 


THE  ORGANS  OF  DIGESTION 


Structure.  —The  substance  of  the  hver  is  composed  of  lobules  held  together  by  extremely 
fine  areolar  tissue,  and  of  the  ramifications  of  the  portal  vein,  hepatic  duct,  hepatic  artery,  hepatic 
veins,  lymphatics,  and  nerves,  the  whole  being  invested  by  a  serous  and  fibrous  coat. 

The  serous  coat  {tunica  serosa)  is  derived  from  the  peritoneum,  and  invests  the  greater  part 
of  the  surface  of  the  organ.     It  is  intimately  adherent  to  the  fibrous  coat. 

The  axeolar  or  fibrous  coat  (capsula  fibrosa  [Olissoni])  lies  beneath  the  serous  investment  and 
covers  the  entire  surface  of  the  organ;  it  is  called  the  capsule  of  Glisson;  the  latter  term  has  also 
been  retained  for  the  heavy  fibrous  tissue,  at  the  portal  fissure,  that  envelops  and  accompanies 
the  vessels  into  the  liver.  It  is  difficult  of  demonstration,  excepting  where  the  serous  coat  is 
deficient.  The  areolar  tissue  which  surrounds  and  binds  together  the  liver  lobules  is  continuous 
with  the  areolar  coat. 

The  Lobules'  (lobuli  hepatis)  (Fig.  1096).— The  lobules  form  the  chief  mass  of  the  hepatic 
substance;  they  may  be  seen  either  on  the  surface  of  the  organ  or  by  making  a  section  through 
the  gland.  They  are  small  granular  bodies  about  the  size  of  a  millet  seed,  measuring  from  one- 
twentieth  to  one-tenth  of  an  inch  in  diameter.  In  the  human  subject  their  outline  is  very  irreg- 
ular, but  in  some  of  the  lower  animals  (for  example,  the  pig)  they  are  well  defined,  and  when 
divided  transversely  have  a  polygonal  outline.  If  divided  longitudinally  they  are  more  or  less 
foliated  or  oblong.  The  bases  of  the  lobules  are  clustered  around  the  smallest  radicles  of  the 
hepatic  veins  {sublobular  veins),  to  which  each  is  connected  by  means  of  a  small  branch  which 
issues  from  the  centre  of  the  lobule  {intralobular  vein).  The  remaining  part  of  the  surface  of 
each  lobule  is  imperfectly  isolated  from  the  surrounding  lobules  by  a  thin  stratum  of  areolar  tissue 
in  which  are  ducts  and  a  plexus  of  vessels,  the  interlobular  plexus  (Figs.  1094  and  1095).  In 
some  animals,  as  the  pig,  the  lobules  are  completely  isolated  from  one  another  by  this  interlobular 
areolar  tissue. 

If  one  of  the  sublobular  veins  be  laid  open,  the  bases  of  the  lobules  may  be  seen  through  the 
thin  wall  of  the  vein  on  which  they  rest,  arranged  in  the  form  of  a  tesselated  pavement,  the 
centre  of  each  polygonal  space  presenting  a  minute  aperture,  the  mouth  of  an  intralobular  vein 
(Fig.  1092). 


Fig.  1091. — The  hepatic  cells  at  different  stages  of  digestion.     (Heidenhain.) 

Microscopic  Appearance. — Each  lobule  is  composed  of  irregular,  anastomosing  chains  of  cells, 
hepatic  ceUs  (Fig.  1091),  surrounded  by  a  dense  capillary  plexus,  composed  of  vessels  which 
penetrate  from  the  circumference  to  the  centre  of  the  lobule,  and  terminate  in  a  single  straight 
central  vein,  which  runs  through  its  centre,  to  open  at  its  base  into  one  of  the  radicles  of  the 
hepatic  vein.  These  structures  are  supported  by  a  delicate  meshwork  of  retiform  connective 
tissue.  Within  the  chains  of  the  cells  are  the  minute  commencements  of  the  bile  ducts.  There- 
fore, in  the  lobule  we  have  all  the  essentials  of  a  secreting  gland;  that  is  to  say,  (1)  cells,  by 
which  the  secretion  is  formed;  (2)  bloodvessels,  in  close  relation  with  the  cells,  containing  the 
blood  from  which  the  secretion  is  derived;  and  (3)  ducts,  by  which  the  secretion,  when  formed, 
is  carried  away.     Each  of  these  structures  will  have  to  be  further  considered. 

1.  The  hepatic  cells  are  epithelial  in  nature  and  of  more  or  less  cuboidal  or  polygonal  form. 
They  vary  in  size  from  the  xt/to  to  the  yjyVff  "f  ^^  mch  in  diameter;  they  consist  of  a  granular 
protoplasm  without  any  cell  wall,  and  contain  one  or  sometimes  two  distinct  nuclei.  In  the  nu- 
cleus is  a  highly  refracting  nucleolus  with  granules.  Embedded  in  the  protoplasm  are  niunerous 
brownish  particles,  the  coloring  matter  of  the  bile,  oil  globules,  and  glycogen  granules  in  varying 
quantities.  Secretory  capillaries  are  to  be  found  in  the  cells.  The  cells  adhere  together  by 
their  surfaces  so  as  to  form  rows,  which  radiate  from  the  centre  to  the  circumference  of  the 
lobules.      .\s  stated  above,  they  are  the  chief  agents  in  the  secretion  of  the  bile. 

2.  The  Bloodvessels. — The  blood  in  the  capillary  plexus  around  the  liver  cells  is  brought 
to  the  liver  principally  by  the  portal  vein,  but  also  to  a  certain  extent  by  the  hepatic  artery.  For 
the  sake  of  clearness  the  distribution  of  the  blood  derived  from  the  hepatic  artery  may  be  con- 
sidered first. 

The  hepatic  artery,  entering  the  liver  at  the  transverse  fissure  with  the  portal  vein  and  hepatic 
duct,  ramifies  with  these  vessels  through  the  portal  canals.     It  gives  ofT  vaginal  branches  which 


^  According  to  Mall  (Jour,  of  Anat.,  vol.  v,  No.  3),  the  lobule  as  here  described  is  not  his  structural  unit, 
refers  to  all  the  tissue  surrounding  each  terminal  branch  of  the  portal  vein. 


THE  LIVER 


1329 


raniifv  in  the  interlobular  tissue,  and  appear  to  be  destined  chiefly  for  the  nutrition  of  the  coats 
of  the  large  vessels,  the  ducts,  and  the  investing  membrane  of  the  liver.  It  also  gives  nlf  capsular 
branches  which  reach  the  surface  of  the  organ,  terminating  in  the  fibrous  coat  in  stellate  ])lcxuscs. 
Finally,  it  gives  off  interlobular  branches  (rami  artcriosi  interlobulares)  which  form  a  plexus  of 
capillaries  {interlobular  capi/lariix)  on  the  outer  side  of  each  lobule,  to  supply  its  wall  and  the 
accompanying  bile  ducts.  From  this  plexus  some  lobular  branches  enter  the  lobule  and  end  in 
the  capillary  network  between  the  cells. 


OHJices  of  intralohular  i 


.  1092. — Longitudinal  section  of  an  hepatic 
vein.     (After  Kiernan.) 


Fig.  1093. — Longitudinal  section  of  a  small  portal  vein 
and  canal.     (After  Kiernan.) 


Theportal  vein  also  enters  at  the  transverse  fissure  and  runs  through  the  portal  canals,  dividing 
into  branches  in  its  course,  which  finally  break  up  into  a  plexus,  the  interlobular  plexus,  in 
the  interlobular  connective  tissue.  In  their  course  these  branches'  receive  the  vaginal  and 
capsular  veins,  corresponding  to  the  vaginal  and  capsular  branches  of  the  hepatic  artery  (Fig. 
1094).    Thus  it  will  be  seen  that  all  the  blood  carried  to  the  liver  by  the  portal  vein  and  hepatic 


Intralobular 


Trunk  of  intralobular 
vein. 


Fig.  1094. — Horizontal  section  of  injected  liver  (dog). 


artery,  except  perhaps  that  derived  from  the  interlobular  branches  of  the  hepatic  artery,  directly 
or  indirectly  finds  its  way  into  the  interlobular  plexus.  From  this  plexus  the  blood  is  carried 
into  the  lobule  by  fine  branches  which  pierce  its  wall  and  then  converge  from  the  cu-cumference 
to  the  centre  of  the  lobule,  forming  a  number  of  converging  vessels,  intralobular  capillaries,  wliich 
are  connected  by  transverse  branches  (Figs.  109.5  and  1096).     In  the  interstices  of  the  network 

S4 


1330 


THE  ORGANS  OF  DIGESTION 


of  vessels  thus  formed  are  situated,  as  before  said,  the  liver  cells;  and  here  it  is  that  the  blood  is 
brought  into  intimate  connection  with  the  liver  cells  and  the  bile  is  secreted.  The  endothelium  of 


Fig.  1095. — Magnified  section  of  a  human  liver,  placed  in  preservative  a  few  minutes  after  death  (electro- 
cution). The  sinusoidal  endotlielium  is  seen  closely  applied  to  the  hepatic  epithelial  cells.  The  cell  elements 
of  the  blood  in  the  sinusoids  have  been  omitted,  but  in  this  as  in  other  similarly  obtained  preparations 
numerous  bell-shaped  forms  of  red  blood'cells  were  seen. 


ranch  of  portal  vein. 


Small  Hie  dnct. 

y  Branch  of 

/         hepatic  artefy. 


'11 

Small  hile     f'^'r 
duct.  ',    V.  ~ 

Branch  of     • '  • 

hepatic  artery.  '>"■ 

Branch  of. 

portal  vein. 


Fig.  1096. — A  lobule  of  human  liver.     (After  Eauber-Kopsch.) 


the  capillaries  and  the  epithelial  cells  are  closely  adherent  to  each  other,  forming  sinusoids. 
Arrived  at  the  centre  of  a  lobule,  all  these  minute  vessels  empty  themselves  into  one  vein,  of 


THE  EXCRETORY  APPARATUS  OF  THE  LIVER  1331 

considerable  size,  which  runs  down  the  eentre  of  the  lobule  from  apex  to  base  and  is  called  the 
intralobular  or  central  vein  (rciid  iiitrdldlnilnnx)  (Fig.  1096).  At  the  base  of  the  lobule  this  vein 
opens  direetly  into  the  sublobular  vein,  with  which  the  lobule  is  connected,  and  which,  as  before 
mentioned,  is  a  radicle  of  the  hepatic  vein.  The  sublobular  veins,  uniting  into  larger  and  larger 
trunks,  end  at  last  in  the  hepatic  veins,  which  do  not  receive  any  intralobular  veins  directly. 
Finally,  the  hepatic  veins,  as  mentioned  on  page  751,  converge  to  form  three  large  trunks  which 
open  into  the  inferior  vena  cava,  while  that  vessel  is  situated  in  the  fissure  appropriated  to  it  at 
the  back  of  the  liver.  The  portal  vein  is  the  nutrient  vessel  of  the  parenchyma  of  the  liver, 
while  the  hepatic  artery  nourishes  the  vessels,  ducts,  and  interlobular  connective  tissue. 

3.  The  Ducts. — Having  shown  how  the  blood  is  brought  into  intimate  relation  with  the 
hepatic  cells  in  order  that  the  bile  may  be  secreted,  it  remains  now  only  to  consider  (he  way  in 
which  the  secretion,  having  been  formed,  is  carried  away.  Several  views  have  pre\aile(l  as  to 
the  mode  of  origin  of  the  hepatic  ducts;  it  seems,  however,  to  be  clear  that  they  eomnienee  by 
little  passages,  which  are  formed  between  the  cells  and  which  have  been  termed  intercellular 
biliary  passages,  bile  capillaries,  or  bile  canalicuU  {ductus  biliferi).  These  passages  are  merely 
little  channels  or  spaces  left  between  the  contiguous  surfaces  of  two  cells  or  in  the  angle  where 
three  or  more  liver  cells  meet,  and  it  seems  doubtful  whether  there  is  any  delicate  membrane 
forming  the  wall  of  the  channel.  Heidenhain,  however,  thinks  they  have  coats.  The  channels 
thus  formed  radiate  to  the  circumference  of  the  lobule,  and  empty  into  small  interlobular  ducts 
between  the  lobules.  These- are  lined  by  low  epithelial  cells  supported  by  a  basement  mem- 
brane and  a  little  fibrous  tissue.  The  interlobular  ducts  pass  into  the  portal  canals,  become 
enclosed  in  Glisson's  capsule,  and,  accompanying  the  portal  vein  and  hepatic  artery  (Fig.  1096), 
join  with  other  ducts  to  form  two  main  trunks,  the  right  and  left  branches  of  the  hepatic  duct, 
which  leave  the  liver  at  the  transverse  or  portal  fissure,  and  by  their  union  form  the  hepatic 
duct.  The  larger  interlobular  ducts  possess  some  circularly  arranged  smooth  muscle  tissue, 
while  the  main  ducts  possess  three  coats — mucous,  muscular,  and  fibrous.  The  mucous  coat 
consists  of  tall  columnar  epithelial  cells,  basement  membrane,  and  tunica  propria.  The  mus- 
cular coat  consists  of  smooth  muscle  tissue  circularly  arranged.  The  fibrous  coat  consists  of 
loose  white  fibrous  tissue  supporting  the  other  coats. 

The  lymphatics,  in  the  substance  of  the  liver  (Fig.  569),  commence  in  lymphatic  spaces 
around  the  capillaries  of  the  lobules;  they  accompany  the  vessels  of  the  interlobular  plexus,  often 
enclosing  and  surrounding  them.  These  unite  and  form  larger  vessels,  which  run  in  the  portal 
canals,  enclosed  in  Glisson's  capsule,  and  emerge  at  the  portal  fissure  to  be  distributed  in  the 
manner  described.  Other  superficial  lymphatics  arise  from  the  superficial  lobules,  pass  under 
the  peritoneum,  and  form  a  close  plexus,  where  this  membrane  covers  the  liver.  The  first- 
named  group  of  lymphatics  gives  origin  to  the  deep  collecting  trunks,  the  second  to  the  superficial 
collecting  trunks.  One  group  of  deep  collecting  trunks  accompanies  the  portal  vein,  there  being 
fifteen  to  eighteen  of  them  emerging  from  the  transverse  fissure.  They  empty  into  the  lymph 
nodes  of  the  hilum.  Another  group  -accompanies  the  hepatic  veins.  There  are  five  or  six 
trunks  which  pass  through  the  Diapfiragm  and  terminate  in  the  lymph  nodes  about  the  inferior 
vena  cava  (intrathoracic  nodes).  The  superficial  trunks  of  the  superior  surface  are  divided 
into  posterior,  anterior,  and  superior  trunks.  Some  of  the  posterior  trunks  terminate  in  the 
nodes  about  the  coeliac  axis,  others  in  the  nodes  about  the  lower  portion  of  the  inferior  vena  cava 
in  the  thorax;  others  in  the  nodes  about  the  abdominal  portion  of  the  oesophagus.  The  anterior 
trunks  which  are  limited  to  the  right  lobe  pass  to  the  nodes  of  the  hilum.  The  superior  trunks 
ascend  in  the  suspensory  ligament.  Some  pass  to  the  nodes  about  the  inferior  vena  cava,  just 
above  the  Diaphragm;  others  to  the  hepatic  nodes.  The  balance  unite  to  form  a  very  large 
trunk,  which  passes  through  the  Diaphragm  and  divides  into  branches  which  enter  the  nodes 
back  of  the  base  of  the  ensiform  cartilage. 

The  nerves  of  the  liver  are  derived  from  the  left  vagus  and  sympathetic.  The  branches  of  the 
left  vagus  ascend  from  in  front  of  the  stomach  within  the  lesser  omentum.  The  sympathetic  nerves 
pass  along  the  hepatic  artery,  enter  the  liver  at  the  transverse  fissure,  and  accompany  the  vessels 
and  ducts  to  the  interlobular  spaces.  Here,  according  to  Korolkow,  the  myelinic  fibres  are  dis- 
tributed almost  exclusively  to  the  coats  of  the  bloodvessels,  while  the  amyelinic  fibres  enter  the 
lobides  and  ramify  between  the  cells. 

The  Excretory  Apparatus  of  the  Liver. 

The  excretory  apparatus  of  the  liver  consi.st.s  of  (1)  the  hepatic  duct,  formed,  as 
we  have  seen,  by  the  junction  of  the  two  main  ducts,  which  pass  out  of  the  liver 
at  the  transverse  fissure;  (2)  the  gall-bladder,  which  serves  as  a  ^eser^■oir  for  the 
bile;  (3)  the  cystic  duct,  or  the  duct  of  the  gall-bladder;  and  (4)  the  common 
bile  duct,  formed  by  the  junction  of  the  hepatic  and  cystic  ducts. 


1332 


THE  ORGANS  OF  DIGESTION 


The  Hepatic  Duct  (ductus  hepaticus)  (Figs.  1097  and  1098). — T-no  main  trunks 
of  nearly  equal  size  issue  from  the  liver  at  the  transverse  fissure,  one  from  the 
right,  the  other  from  the  left  lobe;  these  unite  to  form  the  hepatic  duct,  which 
then  passes  downward  and  to  the  right  for  about  an  inch  and  a  half  or  two 
inches  (3.75  to  5  cm.),  between  the  layers  of  the  lesser  omentum,  where  it  is 
joined  at  an  acute  angle  by  the  cystic  duct,  and  so  forms  the  common  bile  duct 
(ductus  communis  choledochus) .  The  hepatic  duct  is  accompanied  by  the  hepatic 
artery  and  portal  vein  (Fig.  1090). 

The  Gall-bladder  {vesica  fellea)  (Figs. 
1084  and  1097).— The  gall-bladder  is  the 
reservoir  for  the  bile;  it  is  a  conical  or  pear- 
shaped  musculomembranous  sac,  lodged  in  a 
fossa  on  the  under  surface  of  the  right  lobe  of 
the  liver,  and  fixed  in  it  by  connective  tissue, 
and  extending  from  near  the  right  extremity 
of  the  transverse  fissure  to  the  anterior  border 
of  the  organ.  It  is  from  three  to  four  inches 
(7.5  to  10  cm.)  in  length,  one  inch  (2.5  cm.) 
,  in  breadth  at  its  widest  part,  and  holds  from 
eight  to  ten  drams  (30  to  40  c.c).  It  is 
divided  into  a  fundus,  body,  and  neck.  The 
fundus  (fundus  vesicae  felleae),  or  broad  ex- 
tremity, is  directed  downward,  forward,  and 
to  the  right,  and  projects  beyond  the  anterior 
border  of  the  liver;  the  body  (corpus  vesicae 
felleae)  and  neck  (collum  vesicae  felleae)  are 
directed  upward  and  backward  to  the  left.. 
The  neck  of  the  gall-bladder  is  on  a  slightly 
higher  level  than  the  lowest  point  of  the  gall- 
bladder; thus  the  weight  of  the  bile  is  away 
from  rather  than  toward  the  outlet.  The 
upper  surface  of  the  gall-bladder  is  attached 
to  the  liver  by  connective  tissue  and  vessels. 
The  under  surface  is  covered  by  peritoneum, 
which  is  reflected  on  to  it  from  the  surface  of  the 
liver.  Occasionally  the  whole  of  the  organ  is 
invested  by  the  serous  membrane,  and  is  then 
Fig.  io97.-The^  ^'.'"''(st'iHehoil)''"''  '^"""'     Connected  "to  the  liver  by  a  kind  of  mesentery. 

Relations. — Tiie  body  of  the  gall-bladder  is  in  relation,  hy  its  upper  surface,  with  the  hver, 
to  which  it  is  connected  by  areolar  tissue  and  vessels;  by  its  under  surface,  with  the  commence- 
ment of  the  transverse  colon;  and  farther  back,  with  the  upper  end  of  the  descending  portion 
of  the  duodenum  or  sometimes  with  the  pyloric  end  of  the  stomach  or  the  first  portion  of  the 
duodenum.  The  fundus  is  completely  invested  by  peritoneum;  it  is  in  relation,  in  front,  with 
the  abdominal  parietes,  immediately  below  the  ninth  costal  cartilage;  behind,  with  the  trans- 
verse arch  of  the  colon.  The  neck  is  narrow,  and  curves  upon  itself  like  the  letter  S;  at  its  point 
of  connection  with  the  cystic  duct  it  presents  a  well-marked  constriction. 

When  the  gall-bladder  is  distended  with  bile  or  filled  with  calculi,  the  fundus  may  be  felt 
through  the  abdominal  parietes,  especially  in  an  emaciated  subject;  the  relations  of  this  sac  will 
also  serve  to  explain  the  occasional  occurrence  of  abdominal  biliary  fistulse,  through  which  biliary 
calculi  may  pass  out,  and  of  the  passage  of  calculi  from  the  gall-bladder  into  the  stomach,  duo- 
denum, or  colon,  which  occasionally  happens. 

Structure.— The  gall-bladder  consists  of  three  coats— serofibrous,  muscular,  and  mucous. 

The  external  or  serofibrous  coat  (timica  serosa  vesicae  felleae)  consists  of  white  fibrous  tissue 
that  surrounds  the  muscle  coat;  the  fundus  is  completely  covered  by  peritoneum,  while  the  body 
and  neck  are  covered  on  their  under  surfaces  only. 

The  muscular  coat  (tunica  muscularis  vesicae  felleae)  is  a  thin  but  strong  la.Ter  which  forms 


GALL-.^ ay* 

»DDER'         .     S»,fU. 


THE  EXCRETORY  APPARATUS  OF  THE  LIVER 


1333 


the  framework  of  the  sac,  consisting  of  dense  fibrous  tissue  which  interlaces  in  all  directions  and 
is  mixed  with  plain  muscle  fibres  which  are  disposed  chiefly  in  a  longitudinal  direction,  a  few 
running  transversely. 

The  internal  or  mucous  coat  {tunica  mucosa  vesicae  felleae)  is  loosely  connected  with  the 
fibrous  portion  of  the  preceding  coat.  It  is  generally  tinged  with  a  yellowish-brown  color,  and 
is  everywhere  elevated  into  minute  rugae,  by  the  union  of  which  numerous  meshes  are  formed, 
the  depressed  intervening  spaces  having  a  polygonal  outline.  The  meshes  are  smaller  at  the 
fundus  and  neck,  being  most  developed  about  the  centre  of  the  sac.  Opposite  the  neck  of  the 
gall-bladder  the  mucous  membrane  projects  inward  in  the  form  of  oblique  ridges  or  folds,  forming 
a  spiral  valve  (Fig.  1097). 

The  mucous  membrane  is  covered  with  columnar  epithelium,  and  secretes  an  abundance  of 
thick  viscid  mucus;  it  is  continuous  through  the  hepatic  duct  with  the  mucous  membrane  lining 
the  ducts  of  the  liver,  and  through  the  ductus  communis  choledochus  with  the  mucous  membrane 
of  the  duodenum.  Mucous  glands  may  be  found  in  this  coat,  as  well  as  diffuse  lymphoid  tissue 
and  solitary  follicles. 


The  Cystic  Duct  (ductus  cysticus). — The  cystic  duct,  the  smallest  of  the  three 
biliary  ducts,  is  about  an  inch  and  a  half  (3.75  cm.)  in  length.  It  passes  obliquely 
downward  and  to  the  left  from  the  neck  of  the  gall-bladder,  and  joins  the  hepatic 
duct  to  form  the  common  bile  duct.  It  lies  in  the  gastrohepatic  omentum  in 
front  of  the  portal  vein,  the  hepatic  artery  lying  to  its  left  side.  The  mucous 
membrane  lining  its  interior  is  thrown  into  a  series  of  crescentic  folds,  from  five 
to  twelve  in  number,  similar  to  those  found  in  the  neck  of  the  gall-bladder.  They 
project  into  the  duct  in  regular  succession,  and  are  directed  obliquely  around  the 
tube,  presenting  much   the  appearance  of  a   continuous  spiral   valve   (yalvula 

spiralis  [Heisteri])  (Fig.  1097).  When  the 
duct  is  distended,  the  spaces  between  the 
folds  are  dilated,  so  as  to  give  to  its  exte- 
rior a  twisted  appearance. 
The  common  bile  duct  {ductus  cJiole- 
PATic  dochus)  (Figs.  1097  and  1098),  the  largest 

''^  of  the  three,  is  the  common  excretory  duct 

of  the  liver  and  gall-bladder.     It  is  about 
three  inches  in  length,  is  of  the  diameter 
;t  of  a  goose-quill,  and  is  formed  by  the 

junction  of  the  cystic  and  hepatic  ducts. 
It  descends  along  the  right  border  of  the 
lesser  omentum  behind  the  first  portion  of 
the  duodenum,  in  front  of  the  portal  vein, 
""°'*  and  to  the  right  of  the  hepatic  artery 

(Fig.  1000);   it  then  passes  between  the 
head    of    the    pancreas    and    descending 


I'IG.  1098. — The  biliary   ducts.     (Schematic.) 
(Poirier  and  Charpy.) 


Fig.  1099. — The  sphincter  of  the  common  bile  duct. 
(Poirier  and  Charpy.) 


portion  of  the  duodenum,  and,  running  for  a  short  distance  along  the  right  side 
of  the  terminal  part  of  the  pancreatic  duct,  passes  ^^^th  it  obliquely  through  the 
wall  of  the  descending  portion  of  the  duodenum  between  the  mucous  and  muscular 


1334  THE  ORGANS'  OF  DIGESTION 

coats  in  the  submucous  tissue  for  one-half  to  three-quarters  of  an  inch  (1.25  to 
2  cm.).  The  two  ducts  usually  unite  just  before  opening  into  the  duodenum 
(Figs.  1098  and  1099),  but  may  remain  independent  throughout  (in  about  10  per 
cent,  of  individuals).  The  ampulla  of  Vater  (Fig.  1098)  is  the  conical  cavity 
formed  by  the  fusion  of  the  two  ducts,  and  is  much  larger  than  the  opening  on 
the  bile  papilla.  It  averages  9.3  mm.  in  length.  The  average  diameter  of  the 
orifice  is  2.5  mm.  (Opie).  The  two  ducts  open  by  a  common  orifice  if  there  is 
an  ampulla,  or  by  two  separate  orifices  if  there  is  no  ampulla,  upon  the  summit 
of  a  papilla,  situated  at  the  inner  side  of  the  descending  portion  of  the  duodenum, 
a  little  below  its  middle  and  about  three  or  four  inches  (7.5  to  10  cm.)  below 
the  pylorus.  Circular  muscle  fibres,  continuous  with  the  longitudinal  fibres  of 
the  ducts,  surround  the  termination  of  the  two  ducts  in  the  ampulla.  These 
fibres  constitute  the  so-called  sphincter  of  Oddi  (Fig.  1099). 

Structure.— The  coats  of  the  large  bihary  ducts  are  an  external  or  fibrous,  a  middle  or  mus- 
cular, and  an  internal  or  mucous.  The  fibrous  coat  is  composed  of  strong  fibroareolar  tissue. 
The  muscular  coat  consists  chiefly  of  circularly  arranged  smooth  muscle  tissue.  The  mucous 
coat  is  continuous  with  the  lining  membrane  of  the  hepatic  ducts  and  gall-bladder,  and  also  with 
that  of  the  duodenum;  and,  like  the  mucous  membrane  of  these  structures,  its  epithelium  is  of 
the  simple  columnar  variety.  It  is  provided  with  numerous  mucous  glands,  which  are  lobu- 
lated  and  open  by  minute  orifices  scattered  irregularly  in  the  larger  ducts.  It  is  questionable 
if  the  smallest  biliary  ducts,  which  lie  in  the  interlobular  spaces,  have  any  coats.  Heidenhain 
thinks  they  have  a  connective-tissue  coat,  in  which  are  muscle  cells  arranged  both  circularly  and 
longitudinally,  and  an  epithelial  layer,  consisting  of  short  columnar  cells. 

Dimensions  of  the  Bile  Ducts. — The  hepatic  duct  is  about  two  inches  (5  cm.)  in  length,  and 
its  lumen  is  one-sixth  of  an  inch  (4  mm.)  in  diameter.  The  cystic  duct  is  about  one  and  one- 
half  inched  (3.75  cm.)  in  length,  and  its  lumen  is  one-twelfth  of  an  inch  (2  mm.)  in  diameter. 
The  common  duct  is  aibout  three  inches  (7.5  cm.)  in  length,  and  its  lumen  is  one-quarter  of  an 
inch  (6  mm.)  in  diameter.  The  duodenal  opening  is  smaller  than  the  common  duct.  The 
ducts  are  capal^le  of  considerable  distention,  but  the  duodenal  opening  cannot  be  dilated  (HjTtl). 

Bloodvessels,  Lymphatics,  and  Nerves  of  the  Gall-bladder  and  Bile  Ducts. —The  cystic 
artery  (Fig.  4G7),  a  branch  from  the  right  division  of  the  hepatic,  supplies  the  gall-bladder  and 
cystic  duct  with  blood.  It  passes  along  the  cystic  duct,  and  on  reaching  the  gall-bladder  divides 
into  an  upper  branch  and  a  lower  branch.  The  upper  branch  lies  between  the  gall-bladder  and 
the  liver  and  sends  branches  to  each.  The  lower  branch  is  between  the  peritoneum  and  the  wall 
of  the  gall-bladder.  The  cystic  veins  empty  into  the  portal  vein.  The  common  duct  receives 
branches  from  the  superior  pancreaticoduodenal  artery.  There  is  a  submucous  lymphatic 
network  and  a  muscular  lymphatic  network.  The  lymphatics  are  much  less  numerous  at  the 
fundus  of  the  gall-bladder  than  at  the  neck  or  in  the  extrahepatic  ducts.  The  collecting  trunks 
end  in  lymph  nodes  along  the  cystic  and  common  ducts,  and  these  glands  are  in  communication 
with  the  duodenal  lymphatics  and  the  lymphatics  from  the  head  of  the  pancreas.  The  nerves 
of  the  gall-bladder  and  bile  ducts  come  from  the  coeliac  plexus  of  the  sympathetic. 

The  Bile  (fel). — The  bile  is  a  reddish-brown  or  greenish  fluid.  It  contains  pigments  (bili- 
rubin and  biliverdin),  fats  and  soaps,  cholesterin,  sodium  salts  of  glycocholic  and  taurocholic 
acid,  lecithin,  and  nucleoalbumin  furnished  by  the  mucous  membrane.  There  are  also  present 
CO2;  chlorides,  carbonates,  phosphates,  and  sulphates  of  the  alkalies  and  of  calcium,  and  iron. 
The  aiiKiuiit  iKjnnally  secreted  is  from  one  pint  to  one  and  one-half  pints  in  the  twenty-four  hours. 

Surface  Relations. — The  liver  is  situated  in  the  right  hypochondriac  and  the  epigastric 
regions,  and  is  moulded  to  the  arch  of  the  Diaphragm.  In  the  greater  part  of  its  extent  it  lies 
under  cover  of  the  lower  ribs  and  their  cartilages,  but  in  the  epigastric  region  it  comes  in  con 
tact  with  the  abdominal  wall,  in  the  subcostal  angle.  The  upper  limit  of  the  right  lobe  of  the 
liver  may  be  defined  in  the  middle  line  by  the  junction  of  the  mesosternum  with  the  ensiform 
cartilage;  on  the  right  side  the  line  must  be  carried  upward  as  far  as  the  fifth  rib  cartilage  in  the 
midclavicular  line  and  then  downward  to  reach  the  seventh  rib  at  the  side  of  the  thorax.  The 
upper  limit  of  the  left  lobe  may  be  defined  by  continuing  this  line  to  the  left  with  an  inclination 
downward  to  a  point  about  7  cm.  to  the  left  of  the  mesal  plane  on  a  level  with  the  sixth  left  costal 
cartilage.  The  lower  limit  of  the  liver  may  be  indicated  by  a  line  drawn  half  an  inch  below  the 
lower  border  of  the  thorax  on  the  right  side  as  far  as  the  ninth  right  costal  cartilage,  and  thence 
obliquely  upward  across  the  subcostal  angle  to  the  eighth  left  costal  cartilage.  A  slight  curved 
line  with  its  convexity  to  the  left  from  this  point — i.  e.,  the  eighth  left  costal  cartilage — to  the 
termination  of  the  line  indicating  the  upper  limit  will  denote  the  left  margin  of  the  liver.  The 
fundus  of  the  gall-bladder  approaches  the  surface  behind  the  anterior  extremity  of  the  ninth 
costal  cartilage,  close  to  the  outer  margin  of  the  right  Rectus  muscle. 


THE  EXCRETORY  APPARATUS  OF  THE  LIVER  1335 

It  must  be  remembered  that  the  liver  is  subject  to  considerable  alterations  in  position,  and 
the  student  should  make  himself  acquainted  with  the  different  circumstances  under  which  this 
occurs,  as  they  are  of  importance  in  determining  the  existence  of  enlargement  or  other  diseases 
of  the  organ. 

Its  position  varies  according  to  the  posture  of  the  body.  In  the  erect  position  in  the  adult  male 
the  edge  of  the  liver  projects  about  half  an  inch  below  the  lower  edge  of  the  right  costal  car- 
tilages, and  its  anterior  border  can  be  often  felt  in  this  situation  if  the  abdominal  wall  is  thin. 
In  the  supine  position  the  liver  gravitates  backward  and  recedes  above  the  lower  margin  of  the 
ribs,  and  cannot  then  be  detected  by  the  finger.  In  the  prone  position  it  falls  forward,  and  can 
then  generally  be  felt  in  a  patient  with  loose  and  lax  abdominal  walls.  Its  position  varies  also 
with  the  ascent  or  descent  of  the  Diaphragm.  In  a  deep  inspiration  the  liver  descends  below 
the  ribs;  in  expiration  it  is  raised  behind  them.  Again,  in  emphysema,  where  the  lungs  are 
distended  and  the  Diaphragm  descends  very  low,  the  liver  is  pushed  down;  in  some  other  dis- 
eases, as  phthisis,  where  the  Diaphragm  is  much  arched,  the  liver  rises  very  high  up.  Pressure 
from  without,  as  in  tight  lacing,  by  compressing  the  lower  part  of  the  thorax,  displaces  the  liver 
considerably,  its  anterior  edge  often  extending  as  low  as  the  crest  of  the  ilium;  and  its  convex 
surface  is  often  at  the  same  time  deeply  indented  from  the  pressure  of  the  ribs.  Again,  its  posi- 
tion varies  greatly  according  to  the  greater  or  less  distention  of  the  stomach  and  intestines. 
\\Tien  the  intestines  are  empty  the  liver  descends  in  the  abdomen,  but  when  they  are  distended 
it  is  pushed  upward.  Its  relations  to  surrounding  organs  may  also  be  changed  by  the  growth  of 
tumors  (ir  liy  (•(illcctions  of  fluid  in  the  thoracic  or  abdominal  cavities. 

Applied  Anatomy. — Movable  liver  or  hepatoptosis  is  a  rare  condition,  in  which  the  liver 
moves  or  can  be  moved  from  its  normal  position.  It  is  due  to  lessened  tone  of  the  abdoininal 
muscles  and  relaxation  of  the  liver  supports.  In  movable  liver  the  organ  may  be  rotated  on  its 
vertical  axis  or  on  its  transverse  axis.  Tongue-lLke  lobes  have  been  referred  to.  On  account  of  its 
large  size,  its  fixed  position,  and  its  friability,  the  liver  is  more  frequently  ruptured  than  any  other 
of  the  abdominal  viscera.  The  rupture  may  vary  considerably  in  extent,  from  a  slight  scratch 
to  an  extensive  laceration  completely  through  its  substance,  dividing  it  into  two  parts.  Some- 
times an  internal  rupture  without  laceration  of  the  peritoneal  covering  takes  place,  and  such 
injuries  are  most  susceptible  of  repair;  but  small  tears  of  the  surface  may  also  heal;  when,  how- 
ever, the  laceration  is  extensive,  death  usually  takes  place  from  hemorrhage,  on  account  of  the 
fact  that  the  hepatic  veins  are  contained  in  rigid  canals  in  the  liver  substance  and  are  unable 
to  contract,  and  are,  moreover,  unprovided  with  valves.  The  liver  may  also  be  torn  by  the  end 
of  a  broken  rib  perforating  the  Diaphragm.  The  liver  may  be  injured  by  stahs  or  other  punc- 
tured vjounds,  and  when  these  are  inflicted  through  the  chest  wall  both  pleural  and  peritoneal 
cavities  may  be  opened  up  and  both  lung  and  liver  be  wounded.  In  cases  of  wound  of  the  liver 
from  the  front,  protrusion  of  a  part  of  this  viscus  may  take  place,  but  can  generally  easily  be 
replaced.  In  cases  of  laceration  of  the  liver,  when  there  is  evidence  that  bleeding  is  going  on, 
the  abdomen  must  be  opened,  the  laceration  sought  for,  and  the  bleeding  arrested.  This  may 
be  done  temporarily  by  introducing  the  forefinger  into  the  foramen  of  Winslow  and  placing  the 
thumb  on  the  gastrohepatic  omentum  and  compressing  the  hepatic  artery  and  portal  vein  between 
the  two.  Any  bleeding  points  can  then  be  seen.  Bleeding  is,  if  possible,  arrested  by  suture 
hgatures.  The  edges  of  a  small  laceration  are  simply  brought  together  and  sutured  by  means 
of  a  blunt,  curved,  round  needle  passed  from  one  side  of  the  wound  to  the  other.  "All  sutures 
must  be  passed  before  any  are  tied,  and  this  must  be  done  with  the  greatest  gentleness,  as  the  liver 
substance  is  very  friable.  If  suture  fails  the  actual  cautery  may  succeed.  When  the  laceration  is 
extensive,  the  liver  is  sutured  to  the  abdominal  wall  to  hold  it  firm  when  pressure  is  applied,  and 
then  the  laceration  is  packed  with  a  piece  of  iodoform  gauze,  the  end  of  which  is  allowed  to  hang 
out  of  the  external  wound.  Abscess  of  the  liver  is  of  not  infrequent  occurrence,  and  may  open  in 
many  different  ways  on  account  of  the  relations  of  this  viscus  to  other  organs.  Thus,  it  may  burst 
into  the  lung,  the  pus  being  coughed  up,  or  into  the  stomach,  the  pus  perhaps  being  vomited;  it 
may  burst  into  the  colon  or  into  the  duodenum,  or,  by  perforating  the  Diaphragm,  it  mav  empty 
itself  into  the  pleural  cavity.  Frequently  it  makes  its  way  forward,  and  points  on  the  anterior 
abdominal  wall,  and  finally  it  may  burst  into  the  peritoneal  or  pericardiac  cavity.  Abscesses 
of  the  liver  require  opening,  and  this  must  be  done  by  an  incision  in  the  abdominal  wall,  in  the 
thoracic  wall,  or  in  the  lumlsar  region,  according  to  the  direction  in  which  the  abscess  is  tracking. 
The  incision  through  the  abdominal  wall  is  to  be  preferred  when  possible.  The  abdominal  wall 
is  incised  over  the  swelling,  and  unless  the  peritoneum  is  adherent,  gauze  is  packed  all  around 
the  exposed  liver  surface  and  the  abscess  opened,  if  deeply  seated,  preferably  by  the  thermo- 
cautery. Hydatid  cysts  are  more  often  found  in  the  liver  than  in  any  other  of  the  viscera.  The 
reason  of  this  is  not  far  to  seek.  The  embryo  of  the  egg  of  the  tenia  echinococcus  being  liberated 
in  the  stomach  by  the  disintegration  of  its  shell,  bores  its  way  through  the  gastric  walls  and 
usually  enters  a  bloodvessel,  and  is  carried  by  the  blood  stream  to  the  hepatic  capillaries,  where 
its  onward  course  is  arrested,  and  where  it  undergoes  development  into  the  fully  formed  hydatid. 
Tumors  of  the  liver  have  recently  been  subjected  to  surgical  treatment  by  removal  of  a  portion 
of  the  organ.     The  abdomen  is  opened  and  the  diseased  portion  of  liver  exposed;  the  circula- 


1336  THE  ORGANS  OF  DIGESTION 

tion  is  controlled  by  compressing  the  portal  vein  and  the  hepatic  artery  in  the  gastrohepatic 
omentum  and  a  wedge-shaped  portion  of  liver  containing  the  tumor  removed;  the  divided 
vessels  are  ligated,  and  the  cut  siu-faces  brought  together  and  sutured  in  the  manner  directed 
on  page  1333. 

When  the  gall-bladder  or  one  of  its  main  ducts  is  ruptured,  which  may  occur  independently 
of  laceration  of  the  liver,  death  usually  occurs  from  peritonitis.  If  the  symptoms  have  led  to 
the  performance  of  a  laparotomy  and  a  small  rent  is  found,  it  should  be  sutured;  if  an  extensive 
opening  is  found  the  gall-bladder  should  be  removed.  If  the  cystic  duct  is  torn,  its  distal 
end  must  be  closed  and  the  gall-bladder  removed.  In  rupture  of  either  of  the  other  ducts, 
simply  provide  for  free  drainage. 

The  gall-bladder  may  become  distended  with  bile  in  cases  of  obstruction  of  its  duct  or  of  the 
common  bile  duct,  or  it  may  become  distended  from  a  collection  of  gallstones  within  its  interior, 
thus  forming  a  large  tumor.  The  swelling  due  to  distention  with  bile  is  pear-shaped,  and  pro- 
jects downward  and  forward  to  the  umbilicus.  It  moves  with  respiration,  since  it  is  attached  to 
the  liver.  To  relieve  a  patient  of  gallstones,  the  gall-bladder  must  be  opened  and  the  gallstones 
removed.  The  operation  is  performed  by  an  incision  two  or  three  inches  long  in  the  right  semi- 
lunar line,  commencing  at  the  costal  margin.  The  peritoneal  cavity  is  opened,  and,  the  tumor 
having  been  found,  gauze  pads  are  packed  around  it  to  protect  the  peritoneal  cavity,  and  it  is 
aspirated.  When  the  contained  fluid  has  been  evacuated  the  flaccid  bladder  is  drawn  out  of 
the  abdominal  wound  and  its  wall  incised  to  the  extent  of  an  inch;  any  gallstones  in  the  bladder 
are  now  removed  and  the  interior  of  the  sac  sponged  dry.  If  the  case  is  one  of  obstruction  of 
the  duct,  an  attempt  must  be  made  to  dislodge  the  stone  by  manipulation  through  the  wall  of 
the  duct;  or  it  may  be  crushed  from  without  by  the  fingers  or  carefully  padded  forceps.  If  this 
does  not  succeed,  the  safest  plan  is  to  incise  the  duct,  extract  the  stone,  close  the  incision  in  the 
duct  by  fine  sutures  in  two  layers,  and  employ  drainage.  After  all  obstruction  has  been  removed, 
four  courses  are  open  to  the  surgeon:  (1)  The  wound  in  the  gall-bladder  may  be  at  once  sewed 
up,  the  organ  returned  into  the  abdominal  cavity,  and  the  external  incision  closed.  (2)  The 
edges  of  the  incision  in  the  gall-bladder  may  be  sutured  to  the  fascia  of  the  external  wound, 
and  a  fistulous  communication  established  between  the  gall-bladder  and  the  exterior;  this 
fistulous  opening  usually  closes  in  the  course  of  a  few  weeks.  (3)  The  gall-bladder  may  be 
connected  with  the  intestinal  canal,  preferably  the  duodenum,  by  means  of  a  lateral  anastomosis; 
this  is  known  as  cholecystenterostomy.  (4)  The  gall-bladder  may  be  completely  removed 
(cholecystectomy) . 

If  a  stone  blocks  the  ampulla  of  Vater  and  if  the  common  bile  duct  and  the  pancreatic 
duct  empty  into  the  diverticulum,  it  is  evident  that  both  ducts  will  be  blocked.  It  has  been 
demonstrated  that  in  such  a  case  the  pressure  urging  the  bile  onward  is  sufficient  to  overcome 
the  pressure  in  the  pancreatic  duct  and  drive  bile  into  the  ducts  of  the  pancreas,  the  result, 
perhaps,  being  disastrous  inflammation  of  the  pancreas. 

Septic  trouble  arises  more  rapidly  when  a  stone  is  blocked  in  the  duct  than  when  stones  merely 
block  the  gall-bladder,  because  the  first-named  part  is  richer  in  lymphatics  (Murphy). 


THE  PANCREAS  (Figs.  1100,  1102). 

Dissection. — -The  pancreas  may  be  exposed  for  dissection  in  three  different  ways:  (1)  By 
raising  the  liver,  drawing  down  the  stomach,  and  tearing  through  the  gastrohepatic  omentum 
and  the  ascending  layer  of  the  transverse  mesocolon.  (2)  By  raising  the  stomach,  the  arch  of 
the  colon,  and  greater  omentum,  and  then  dividing  the  inferior  layer  of  the  transverse  mesocolon 
and  raising  its  ascending  layer.  (3)  By  dividing  the  two  layers  of  peritoneum,  which  descend 
from  the  greater  curvature  of  the  stomach  to  form  the  greater  omentum;  turning  the  stomach 
upward,  and  then  cutting  through  the  ascending  layer  of  the  transverse  mesocolon  (see  Fig.  996). 

The  pancreas  is  a  compound  racemose  gland,  analogous  in  its  structure  to  the 
salivary  glands,  though  softer  and  less  compactly  arranged  than  those  organs. 
It  is  long  and  irregularly  prismatic  in  shape,  and  of  a  reddish-white  color.  Its 
right  extremity,  being  broad,  is  called  the  head,  and  is  connected  to  the  main 
portion  of  the  organ,  the  body,  by  a  slight  constriction,  the  neck;  while  its  left 
extremity  gradually  tapers  to  form  the  tail.  It  is  situated  transversely  across  the 
posterior  wall  of  the  abdomen,  at  the  back  of  the  epigastric  and  left  hypochondriac 
regions.  Its  length  varies  from  five  to  six  inches  (12.5  to  15  cm.),  its  breadth 
is  an  inch  and  a  half  (3.75  cm.),  and  its  thickness  from  half  an  inch  to  an  inch 
(1.25  to  2.5  cm.),  being  greater  at  its  right  extremity  and  along  its  upper  border. 
Its  weight  varies  from  two  to  three  and  one-half  ounces  (60  to  100  grams). 


THE  PANCREAS 


1337 


The  head  {caput  pancreatis)  (Fig.  1100)  is  flattened  from  before  backward,  and 
is  lodged  within  the  curve  of  the  duodenum.  The  upper  border  is  in  contact 
with  the  first  part  of  the  duodenum,  and  its  lower  overlaps  the  third  part;  its  right 


HEPATIC  DUCT — Iflt,  , 

CYSTIC  DUCT — SW] 


SUPERIOR  MESENTERIC  VEIN 

Fig.  1100. — Position  and  relations  of  pancreas. 


p.    MESENTERIC  ARTERY. 


AREA   FOR 


Fig.  1101. — The  pancreas  and  duodenum  from  behind.     (Drawn  from  His'  model.) 

and  left  borders  overlap  in  front,  and  insinuate  themselves  behind,  the  second 
and  fourth  parts  of  the  duodenum  respectively.  The  angle  of  junction  of  the  lower 
and  left  lateral  borders  forms  a  prolongation,  termed  the  processus  uncinatus. 
In  the  groove  between  the  duodenum  and  the  right  lateral  and  lower  borders  in 


1338 


THE  ORGANS  OF  DIGESTION 


front  are  the  anastomosing  superior  and  inferior  pancreaticoduodenal  arteries; 
the  common  bile  duct  descends  behind,  along  the  right  border,  to  its  termination 
in  the  second  part  of  the  duodenum. 

The  greater  part  of  the  right  half  of  the  anterior  surface  is  in  contact  with  the 
transverse  colon,  only  areolar  tissue  intervening.  From  its  upper  part  the  neck 
originates,  its  right  limit  being  marked  by  a  groove  for  the  gastroduodenal  artery. 
The  lower  part  of  the  right  half,  below  the  transverse  colon,  is  covered  by  peri- 
toneum continuous  with  the  inferior  layer  of  the  transverse  mesocolon,  and  is 

in  contact  with  the  coils  of  the  small  in- 
testine. The  superior  mesenteric  artery 
passes  down  in  front  of  the  left  half 
across  the  uncinate  process;  the  superior 
mesenteric  vein  runs  upward  along  the 
right  side  of  the  artery,  and,  behind  the 
neck  of  the  pancreas,  joins  with  the 
splenic  vein  to  form  the  portal  vein. 

The  posterior  surface  is  in  relation  with 
the  inferior  vena  cava,  the  renal  veins, 
the  right  crus  of  the  Diaphragm,  and 
the  aorta. 

The  neck  springs  from  the  right  upper 
portion  of  the  front  of  the  head.  It  is 
about  an  inch  (2.5  cm.)  long,  and  is 
directed,  at  first,  upward  and  forward, 
and  then  upward  and  to  the  left  to  join  the  body;  it  is  somewhat  flattened  from 
above  downward  and  backward.  Its  antero-superior  surface  supports  the 
pylorus;  its  postero-inferior  surface  is  in  relation  with  the  commencement  of  the 
portal  vein;  on  the  right  it  is  grooved  by  the  gastroduodenal  artery. 

The  body  {corpus  pancreatis)  is  somewhat  prismatic  in  shape,  and  has  three 
surfaces — anterior,  posterior,  and  inferior. 

The  anterior  surface  (fades  anterior)  is  somewhat  concave,  and  is  directed  for- 
ward and  upward;  it  is  covered  by  the  postero-inferior  surface  of  the  stomach 
which  rests  upon  it,  the  two  organs  being  separated  by  the  lesser  sac  of  the  peri- 
toneum. Where  it  joins  the  neck  extremity  there  is  a  well-marked  prominence, 
called  the  omental  tuberosity  (tuber  omentale),  which  abuts  against  the  posterior 
surface  of  the  small  omentum. 

The  posterior  surface  (fades  posterior)  (Fig.  1101)  is  devoid  of  peritoneum,  and 
is  in  contact  with  the  aorta,  the  splenic  vein,  the  left  kidney  and  its  vessels,  the 
left  suprarenal  gland,  the  crura  of  the  Diaphragm,  and  the  origin  of  the  superior 
mesenteric  artery. 

The  inferior  surface  (fades  inferior)  (Fig.  1101)  is  narrow  on  the  right,  but 
broader  on  the  left,  and  is  covered  by  peritoneum ;  it  lies  upon  the  duodenojejunal 
flexure  and  on  some  coils  of  the  jejunum;  its  left  extremity  rests  on  the  splenic 
flexure  of  the  colon. 

The  superior  border  (margo  superior)  of  the  body  is  blunt  and  flat  to  the  right; 
narrow  and  sharp  to  the  left,  near  the  tail.  It  commences  to  the  right  in  the 
omental  tuberosity,  and  is  in  relation  with  the  coeliac  axis,  from  which  the  hepatic 
artery  courses  to  the  right  just  above  the  gland,  while  the  splenic  branch  runs 
toward  the  left  in  a  groove  along  this  border. 

The  anterior  border  (margo  anterior)  separates  the  anterior  from  the  inferior 
surface,  and  along  this  border  the  two  layers  of  the  transverse  mesocolon  diverge 
from  each  other;  one  passing  upward  over  the  anterior  surface,  the  other  back- 
ward over  the  inferior  surface. 

The  inferior  border  (margo  inferior)  separates  the  posterior  from  the  inferior 
surface;  the  superior  mesenteric  vessels  emerge  under  its  right  extremity. 


THE  PANCREAS 


13.39 


Tlie  tail  (caiida  paucreatis)  is  narrow;  it  extends  to  the  left  as  far  as  the  lower 
part  of  tlie  gastric  surface  of  the  spleen,  and  it  is  in  contact  with  the  splenic  flexure 
of  the  colon. 

Birmingham  describes  the  body  of  the  pancreas  as  projecting  forward  as  a 
prominent  ridge  into  the  abdominal  cavity  and  forming  a  sort  of  shelf  on  whicli 
the  stomach  lies.  He  says:  "The  portion  of  the  pancreas  to  the  left  of  the  middle 
line  has  a  very  considerable  antero-posterior  thickness;  as  a  result  the  anterior 
surface  is  of  considerable  extent,  it  looks  strongly  upward,  and  forms  a  large 
and  important  part  of  the  shelf.  As  the  pancreas  extends  to  the  left  toward  the 
spleen  it  crosses  the  upper  part  of  the  kidney,  and  is  so  moulded  on  to  it  that  the 
top  of  the  kidney  forms  an  extension  inward  and  backward  of  the  upper  surface 
of  the  pancreas  and  extends  the  bed  in  this  direction.  On  the  other  hand,  the 
extremity  of  the  pancreas  comes  in  contact  with  the  spleen  in  such  a  way  that  the 
plane  of  its  upper  surface  runs  with  little  interruption  upward  and  backward  into 
the  concave  gastric  surface  of  the  spleen,  which  completes  the  bed  behind  and  to 


RECTUS    MUSCLE 


/th  Costal  Caihlane 

nil  Costal  Cai  tilage. 


,,'Sih  Rib. 


Fig.  1103. — Transver; 


Abdominal  Aorta. 

section  through  the  middle  of  the  first   lumbar 
pancreas.     (Braune.) 


11th  Rib. 
vertebra,  showing   the   relations  of  the 


the  left,  and,  running  upward,  forms  a  partial  cap  for  the  wide  end  of  the 
stomach. 

The  principal  excretory  duct  of  the  pancreas,  called  the  pancreatic  duct  or  canal 
of  Wirsung  (duchi^  paiwreaticus  [Wirsungi])  (Figs.  1100  and  1102),  extends  trans- 
versely from  left  to  right  through  the  substance  of  the  pancreas.  In  order  to  expose 
it,  the  superficial  portion  of  the  gland  must  be  removed.  It  commences  by  the 
junction  of  the  small  ducts  of  the  lobules  situated  in  the  tail  of  the  pancreas,  and, 
running  from  left  to  right  through  the  body,  it  constantly  receives  the  ducts  of 
the  various  lobules  composing  the  gland.  Considerably  augmented  in  size,  it 
reaches  the  neck,  and,  turning  obliquely  downward,  backward,  and  to  the  right, 
it  comes  into  relation  with  the  common  bile  duct,  lying  to  its  left  side;  leaving  the 
head  of  the  gland,  it  passes  very  obliquely  through  the  mucous  and  muscular  coats 
of  the  duodenum,  and  usually  terminates  by  an  orifice  common  to  it  and  the 


1340 


THE  ORGANS  OF  DIGESTION 


common  bile  duct  upon  the  summit  of  an  elevated  papilla,  situated  at  the  inner 
side  of  the  descending  portion  of  the  duodenum,  three  or  four  inches  (7.5  to  10 
cm.)  below  the  pylorus  (Figs.  1098  and  1099). 

Sometimes  the  pancreatic  duct  and  common  bile  duct  open  separately  into  the 
duodenum  (Fig.  1029).  Frequently  there  is  an  accessory  duct,  which  is  given  off 
from  the  canal  of  Wirsung  in  the  neck  of  the  pancreas  and  passes  horizontally 
to  the  right  to  open  into  the  duodenum  about  an  inch  above  the  orifice  of  the 
main  duct.  This  is  known  as  the  duct  of  Santorini  {dudm  pancreatic-m  accessorius 
[Santorini])  (Fig.  1102). 

The  pancreatic  duct,  near  the  duodenum,  is  about  the  size  of  an  ordinary  quill ; 
its  walls  are  thin,  consisting  of  three  coats,  an  external  fibrous,  a  middle  muscular, 
and  an  internal  mucous;  the  latter  is  smooth,  and  furnished  near  its  termination 
with  a  few  scattered  follicles. 

Structure. — In  structure,  the  pancreas  resembles  the  salivary  glands.  It  differs  from  them, 
however,  in  certain  particulars,  and  is  looser  and  softer  in  its  texture.  It  is  not  enclosed  in  a 
distinct  capsule,  but  is  surrounded  by  areolar  tissue,  which  dips  into  its  interior,  and  connects 
the  various  lobules  of  which  it  is  composed.  Each  lobule,  like  the  lobules  of  the  salivary 
glands,  consists  of  one  of  the  ultimate  ramifications  of  the  main  duct,  terminating  in  a  number 
of  cecal  pouches  or  alveoli,  which  are  mainly  grape-like.  The  minute  ducts  connected  with  the 
alveoli  are  narrow  and  lined  with  flattened  cells.  The  alveoli  are  almost  completely  filled  with 
secreting  cells,  so  that  scarcely  any  lumen  is  visible.  In  the  centre  of  the  end-tubules  flat  cells 
are  frequently  found.  They  are  continuations  into  the  tubules  of  the  duct  epithelium.  These 
cells  are  known  as  the  centro-acinar  cells  of  Langerhans.  The  true  secreting  cells  which  line 
the  wall  of  the  alveolus  are  very  characteristic.  They  are  pyramidal  or  rounded  in  shape  and 
present  two  zones — an  outer  one  clear  and  finely  striated  next  the  basement  membrane,  and  an 
inner  granular  one  next  the  lumen.  The  highly  refracting  granules  are  known  as  zsrmogen 
granules.  During  digestion  the  granules  gradually  disappear  and  the  cells  become  clear.  Dur- 
ing fasting  the  granular  zone  occupies  more  than  one-half  of  the  cell  (Szymonowicz).  In  some 
secreting  cells  of  the  pancreas  is  a  spherical  mass,  staining  more  easily  than  the  rest  of  the  cells; 


Interlobular  duct. 


this  is  termed  the  paranucleus,  and  it  is  believed  to  be  an  extension  from  the  nucleus.  The  con- 
nective tissue  among  the  gland  tubules  and  alveoli  presents  in  certain  parts  collections  of  cells, 
which  are  termed  interalveolar  cell  islets,  or  islands  of  Langerhans.  Opie  points  out  that  they 
are  most  common  in  the  splenic  end  of  the  pancreas.  The  cells  of  the  islands  are  smaller  and 
paler  than  the  secretmg  cells  of  tlie  alveoli,  and  are  arranged  in  layers  with  intervening  spaces. 
Tlie  islands  are  sharply  demarcated  from  the  alveoli,  are  much  larger  than  the  latter,  and  are 


THE  PANCREAS  1341 

very  vnsciifiir.     There  are  no  duels  in  the  ishxnds  of  Langerhans.     Their  function  is  to  furnish 

the  iiiliTHiil  sccreliciii  of  ihe  ]ian(rea.s. 

Bloodvessels,  Lymphatics,  and  Nerves.— The  arteries  of  the  pancreas  come  from  the 
superior  pancreaticoduodenal  branch  of  the  gastroduodenal ;  1  he  inferior  pancreaticoduodenal 
branch  of  the  superior  mesenteric;  the  inferior  pancreatic  branch  of  the  superior  mesenteric; 
pancreatic  branches  of  the  hepatic  and  pancreatic  branches  of  the  splenic.  In  a  fe«  cases  a 
large  artery,  the  pancreatica  magna,  aceom))anies  the  pancreatic  duel.  In  mcjst  cases  fiiere  is 
no  such  vessel.  The  veins  are  the  anterior  pancreaticoduodenal  branch  of  the  superior  mes- 
enteric; the  posterior  pancreaticoduodenal  branch  and  olher  pancreatic  branches  of  the 
portal;  and  pancreatic  branches  of  the  splenic.  The  lymphatics  arise  in  a  network  al)ont  the 
lobules.  Numerous  collecting  trunks  jiass  to  the  surface  of  the  pancreas,  anastomose  with  each 
other,  and  enter  into  nodes  about  the  pancreas.  The  splenic  nodes  receive  most  of  the  trunks. 
Others  are  received  by  nodes  along  the  aorta  (Sappey),  nodes  at  the  origin  of  the  superior 
mesenteric  artery,  and  nodes  along  the  pancreaticoduodenal  vessels.  The  nerves  eome  from 
the  coeliac,  superior  mesenteric,  and  splenic  plexuses. 

The  Pancreatic  Juice. — The  pancreatic  juice  is  a  clear,  somewhat  viscid  alkaline  liquid. 
Its  speeifie  gravity  is  about  1 .0.30.  The  solid  matter  consists  chiefly  of  proteids,  and  amounts 
to  about  10  per  cent,  of  a  sample  of  the  juice.  The  juice  contains  a  ferment  which  breaks  up 
fat,  a  ferment  which  converts  starch  into  sugar,  and  a  fermeht  which  digests  proteid  material. 

Surface  Form. — The  pancreas  lies  in  front  of  the  second  lumbar  vertebra,  and  can  some- 
times be  felt,  in  emaciated  subjects,  when  the  stomach  and  colon  are  empty,  by  making  deep' 
pressure  in  the  middle  line  about  three  inches  above  the  umbilicus. 

Applied  Anatomy. — Of  late  years  our  knowledge  of  the  structure,  functions,  and  diseases 
of  the  pancreas  has  been  notably  increased,  and  surgeons  have  begun  to  operate  for  certain  pan- 
creatic diseases.  It  is  occasionally  the  seat  of  cancer,  which  usually  affects  the  head  or  duodenal 
end,  and  therefore  often  speedily  involves  the  common  bile  duct,  leading  to  persistent  jaundice. 
Cancer  of  the  pancreas  may  be  primary  or  secondary.  Primary  sarcoma  is  very  unusual;  sec- 
ondary sarcoma  is  more  common,  but  cancer  is  far  commoner  than  either  form  of  sarcoma. 
Adenoma  may  also  occur.  Cases  are  on  record  of  the  successful  removal  of  tumors  of  the  pan- 
creas, but  the  operations  are  very  dangerous,  are  extremely  difficult,  and  are  seldom  attempted. 
The  pancreas  may  be  the  seat  of  syphilitic  or  tuberculous  disease.  As  a  result  of  pancreatic 
injury,  there  may  be  effusion  into  the  lesser  peritoneal  cavity.  The  lesser  cavity  becomes  distended, 
and  the  fluid  of  this  pseudocyst  may  contain  pancreatic  juice  (.lordan  Lloyd).  True  cysts  of 
the  pancreas  are  occasionally  found.  Pancreatic  cysts  may  result  from  blocking  of  the  duct, 
from  epithelial  proliferation,  from  traumatism  and  hemorrhage,  or  from  hydatid  disease.  Con- 
genital cysts  may  occur,  and  cystic  carcinoma  is  sometimes  encountered.  Cysts  of  the  pancreas 
may  present  in  the  epigastric  region  above  and  to  the  right  of  the  umbilicus.  The  fluid  in  these 
cysts  contains  some  of  the  pancreatic  secretion.  A  pancreatic  cyst  is  best  treated  by  opening 
the  abdomen,  suturing  the  cyst  to  the  skin,  opening  the  cyst,  and  providing  for  drainage.  Com- 
plete extirpation  of  the  cyst  is  invariably  difficult  and  is  usually  impossible.  It  has  been  said 
that  the  pancreas  is  the  only  abdominal  viscus  which  has  never  been  found  in  a  hernial  protru- 
sion; but  even  this  organ  has  been  found,  in  company  with  otlier  viscera,  in  rare  cases  of  dia- 
phragmatic  hernia.  The  pancreas  has  been  known  to  become  invaginated  into  the  intestines 
and  portions  of  the  organ  have  sloughed  off.  In  cases  of  excision  of  the  pylorus  great  eare  must 
be  exercised  to  avoid  wounding  the  pancreas,  as  the  escape  of  the  pancreatic  fluid  may  be  attended 
with  serious  and  even  with  fatal  results,  peritonitis  and  fat  necrosis,  and  gangrene  being  caused. 

Rupture  of  the  pancreas  as  a  solitary  result  of  traumatism  is  very  unusual,  but  is  more  common 
in  violent  injuries  which  rupture  the  liver  and  spleen  as  well.  An  injury  which  lacerates  the 
pancreas  and  permits  blood  and  pancreatic  juice  to  flow  into  the  lesser  peritoneal  cavity  is  usually 
rapidly  fatal,  but  may  not  be.  The  foramen  of  Winslow  may  be  occluded  by  inflammation,  and 
a  pseudocyst  may  form.  In  severe  laceration  of  the  pancreas  alone  it  would  be  proper  to  open 
the  abdomen,  ligate  bleeding  vessels,  suture  the  pancreas,  and  drain  the  lesser  peritoneal  cavity 
posteriorly.  A  gunshot  wound  of  the  pancreas  requires  posterior  drainage.  Every  effort  must 
be  made  in  a  pancreatic  wound  to  rapidly  get  rid  of  pancreatic  fluid  by  drainage  from  the  wound 
area,  as  this  fluid  is  extremely  irritant  and  may  cause  gangrene. 

Inflammation  of  the  pancreas  is  due  to  infection.  Occasionally  it  seems  to  follow  the  entrance 
of  bile  into  the  pancreatic  duct,  because  of  plugging  of  the  amjjulla  with  a  calculus  (Halsted, 
Opie).  Hemorrhage  into  the  pancreas  is  frequent  in  acute  pancreatitis,  and  fat  necrosis  is  com- 
mon in  the  fat  of  the  naesentery,  subperitoneal  tissue,  omentum,  and  other  parts.  Acute  pan- 
creatitis may  be  recovered  from  if  the  abdomen  is  opened,  the  pancreas  incised,  and  drainage 
employed. 

In  chronic  interstitial  pancreatitis  of  the  head  of  the  pancreas  the  bile  duct  is  apt  to  become 
blocked,  and  the  disease  is  frequently  mistaken  for  cancer.  Cure  may  follow  opening  and 
drainage  of  the  gall-bladder. 

Extensive  fibrosis  of  the  islands  of  Langerhans  is  one  of  the  commonest  lesions  found  post 
mortem  in  cases  of  diabetes  meUitus. 


THE  UEINOGENITAL  OEGANS.' 


THE  urinogenital    organs  (apparatus  itrogenitalis)  consist  of   (a)  the  urinary 
organs  for  the  excretion  of  the  urine,  and  (b)  the  genital  organs  which  are 
concerned  with  the  process  of  reproduction. 


THE  URINARY  ORGANS. 

The  urinary  organs  comprise  the  kidneys,  which  secrete  the  urine;  the  ureters 
or  ducts  wliich  convey  it  to  the  bladder,  where  it  is  for  a  time  retained;  and  the 
urethra,  through  which  it  is  discharged  from  the  body. 


THE  KIDNEYS  (RENES)  (Figs.  1105,    1107). 

The  kidneys  are  situated  in  the  posterior  part  of  the  abdomen,  one  on  each  side 
of  the  vertebral  column,  behind  the  peritoneum,  and  are  surrounded  by  a  mass 
of  fat  and  loose  areolar  tissue.  Their  upper  extremities  are  on  a  level  with  the 
upper  border  of  the  twelfth  thoracic  vertebra,  the  lower  extremity  on  a  level 
with  the  third  lumbar  vertebra.  The  right  kidney  is  usually  on  a  slightly  lower 
level  than  the  left,  probably  on  account  of  the  vicinity  of  the  liver.  In  the  female 
the  kidneys  are  a  little  lower  than  in  the  male.  The  long  axis  of  each  kidney 
is  directed  from  above  downward  and  outward,  the  transverse  axis  from  within 
backward  and  outward. 

Each  kidney  is  about  four  and  one-half  inches  (11.5  cm.)  in  length,  two  to  two  and 
one-half  inches  (5.5  cm.)  in  breadth,  and  about  one  and  one-half  inches  (3.7  cm.)  in 
thickness.  The  left  is  somewhat  longer  and  narrower  than  the  right.  The  weight 
of  the  kidney  in  the  adult  male  varies  from  four  and  one-half  ounces  to  six  ounces 
(130  to  170  grams);  in  the  adult  female,  from  four  ounces  to  five  and  one-half 
ounces  (115  to  155  grams).  The  specific  gravity  is  about  1.052.  The  kidney  has  a 
characteristic  form,  resembling  that  of  a  lima  bean,  and  presents  for  examination 
two  surfaces,  two  borders,  and  an  upper  and  a  lower  extremity.  The  combined 
weight  of  the  two  kidneys  in  proportion  to  the  body  is  about  1  to  240. 

Relations. — The  anterior  surface  (fades  anterior)  of  each  kidney  is  convex,  and  looks  for- 
ward and  outward.  Its  relations  to  adjacent  viscera  differ  so  completely  on  the  two  sides  that 
separate  descriptions  are  necessary. 

(a)  Anterior  Surface  of  Right  Kidney. — ^A  narrow  portion  at  the  upper  extremity 
is  in  relation  with  the  suprarenal  gland.  Immediately  below  this  a  large  area, 
involving  about  three-fourths  of  the  surface,  lies  in  the  renal  impression  on  the 
inferior  surface  of  the  liver,  and  a  narrow  but  somewhat  variable  area  near  the 
inner  liorder  is  in  contact  with  the  second  part  of  the  duodenum.  The  lower 
part  of  the  anterior  surface  is  in  contact  externally  with  the  hepatic  flexure  of  the 

1  Usage  has  sanctioned  the  employment  of  urogenital  as  the  equivalent  of  urinogenital,  although  the  latter 
form  only  is  philologically  correct. 

(1343) 


1344 


THE  URINOGENITAL   ORGANS 


colon,  and  internally  with  the  small  intestine.  The  areas  in  relation  with  the 
liver  and  intestine  are  covered  by  peritoneum;  the  suprarenal,  duodenal,  and  colic 
areas  are  devoid  of  peritoneum. 

licriplndilitin 


Great  splanchnic 
nerve  piercing 


chyh. 


(!)  eat  splanchnic 
lUlK  pu't( 


Semilunar 
ganglion. 


Fig.  1105. — The  relations  of  the  viscera  and  large  vessels  of  the  abdomen.     (Seen  from  behind,  the  last  thoracic 
vertebra  being  well  raised.) 

(6)  Anterior  Surface  of  Left  Kidney. — ^A  small  area  along  the  upper  part  of  the 
inner  border  is  in  relation  with  the  suprarenal  gland,  and  close  to  the  outer  border 
is  a  narrow  strip  in  contact  with  the  renal  impression  on  the  spleen.     A  broad. 


THE  KIDNEYS 


1345 


somewhat  quadrilateral  field,  at)out  the  middle  of  the  anterior  surface,  marks 
the  site  of  contact  with  the  body  of  the  pancreas,  on  the  deep  surface  of  which  are 
the  splenic  vessels.  Above  this  is  a  small  triangular  portion,  between  the  suprarenal 
and  splenic  areas,  in  contact  with  the  postero-inferior  surface  of  the  stomach. 
Below  the  pancreatic  area  the  outer  part  is  in  relation  with  the  splenic  flexure  of 
the  colon,  the  inner  with  the  small  intestine.  The  area  in  contact  with  the  stomach 
is  covered  by  the  peritoneum  of  the  lesser  sac,  while  that  in  relation  to  the  small 
intestine  is  covered  by  the  peritoneum  of  the  greater  sac;  behind  the  latter  are  some 
liranches  of  the  left  colic  vessels. 


SUPERIOR 
MCSCI 

ARTERY 


INFERrOR 

MESENTERIC 

ARTERY 


Fig.  1106.— Poster! 


■  abdominal  wall,  after  removal  of   the  peritoneum,  showing  kidneys,  suprarena 
and  great  vessels.     (Corning.) 


The  Posterior  Surface  {fades  posterior)  (Fig.  1108).^ — ^The  posterior  surface  of  the 
kidney  is  flatter  than  the  anterior  and  is  directed  backward  and  inward.  It 
is  entirely  devoid  of  peritoneal  covering,  being  embedded  in  areolar  and  fatty 
tissues.  It  lies  upon  the  Diaphragm,  the  anterior  layer  of  the  lumbar  aponeuro- 
sis, the  external  and  internal  arcuate  ligaments,  the  Psoas  andTransversalis  muscles, 
one  or  two  of  the  upper  lumbar  arteries,  the  last  thoracic,  iliohypogastric,  and 
ilioinguinal  nerves.  The  lumbocostal  ligaments  overlie  the  posterior  surface  of 
the  kidney  (Fig.  993).  The  right  kidney  rests  upon  the  twelfth  rib  (Fig.  993), 
the  left  usually  on  the  eleventh  and  twelfth  ribs.     The  Diaphragm  separates  the 

85 


1346 


THE   URINOGENITAL   ORGANS 


kidney  from  the  pleura  as  the  pleura  dips  down  to  form  the  phrenicocostal  sinus 
(Fig.  910),  but  frequently  the  muscle  fibres  of  the  Diaphragm  are  defective  or 


Fig.   1107. — Right  kidney.     Anterior  ' 


Fig.  1108.— Left  kidney.     Posterior  ' 


absent  over  a  triangular  area  immediately  above  the  external  arcuate  ligament, 
and  when  this  is  the.  case  the  perirenal  areolar  tissue  is  in  immediate  apposition 


SUPRARENAL  AREA 


Fig.    1109. — The  anterior  surfaces  of  the  kidneys,  showing  areas  of  contact  of  neighboring  viscera. 


with  the  diaphragmatic  pleura.     In  the  lower  part  of  the  posterior  surface  of  the 
kidney  is  an  impression  produced  by  the  Quadratus  lumborum  muscle  and  called 


THE  KIDNEYS 


1347 


the  impressio  muscularis.     A  little  internal  to  this  a  flattening,  caused  by  the  Psoas 
muscle,  is  often  recognizable. 


Fig.  1110. — The  posterior  surfaces  of  the  kidneys,  showing  areas  of  relation  to  the  parietes. 


Fig.  1111 — Longitudinal  section,  showing 
the  arrangement  of  the  renal  fascia.  (After 
Gerota.) 


RARENAL 
FAT 
QUADRATUS  LUM" 
SACROLUMBALIS    BORUM   MUSCUE 
GROUP 

Fig.  1112. — Transverse  section,  showing  the  relations 
of  the  renal  fascia  and  the  two  layers  of  fat.  (After 
Gerota.) 


Borders.— The  external  border  {marcio  lateralis)  (Figs.  1107  and  1108)  is  convex, 
and  is  directed  outward  and  backward,  toward  the  posterolateral  wall  of  the 


1348 


THE   URINOOENITAL   ORGANS 


abdomen.     On  the  left  side  it  is  in  contact,  at  its  upper  part,  with  the  spleen 
(Fig.  llOfi). 

The  internal  border  {margo  7nedialis)  (Figs.  1107  and  1108)  is  concave,  and  is 
directed  forward,  inward,  and  a  little  downward.  It  presents  a  deep  longitudinal 
fissure,  bounded  by  a  prominent  overhanging  anterior  and  posterior  lip.  This 
fissure  is  named  the  hilum  {hilus  renalis)  (Fig.  1108),  and  allows  of  the  passage 
of  the  vessels,  nerves,  and  ureter  into  and  out  of  the  kidney. 

At  the  hilum  of  the  kidney  the  relative  position  of  the  main  structures  passing 
into  and  out  of  the  kidney  is  as  follows :  The  vein  is  in  front,  the  artery  in  the 
middle,  and  the  duct  or  ureter  behind  and  toward  the  lower  part  (Fig.  1107). 
By  a  knowledge  of  these  relations  the  student  may  distinguish  between  the  right 
and  left  kidney.  The  kidney  is  to  be  laid  on  the  table  before  the  student  on  its 
posterior  surface,  with  its  lower  extremity  toward  the  observer — that  is  to  say, 
with  the  ureter  behind  and  beloio  the  other  vessels;  the  hilum  will  then  be  directed 
to  the  side  to  which  the  kidney  belongs.  Frequently,  however,  the  branches  of 
both  artery  and  vein  are  placed  behind  the  ureter. 

Extremities. — The  superior  extremity  {extremitas  superior)  (Figs.  1107  and 
1108)  is  directed  slightly  inward  as  well  as  upward,  being  situated  about  4  cm. 
from  the  mesal  plane.     It  is  thick,  broad,  bulky,  and  rounded,  and  is  surmounted 

by  the  suprarenal  gland  (Fig.  1113),  which 
covers  also  a  small  portion  of  the  anterior 
surface. 

The  inferior  extremity  {extremitas  inferior) 
(Figs.  1107  and  1108),  directed  a  little  out- 
ward as  well  as  downward,  is  smaller  and 
thinner  and  usually  more  pointed  than  the 
superior.  It  is  situated  about  6  cm.  from  the 
mesal  plane,  and  extends  to  within  two  inches 
(5  cm.)  of  the  crest  of  the  ilium. 

Fixation  of  the  Kidney  (Figs.  1111  and 
1112). — The  kidney  and  its  vessels  are  em- 
bedded in  a  mass  of  fatty  tissue  termed  the 
perirenal  fat  (capsida  adiposa),  which  is  thickest 
at  the  margins  of  the  kidney  and  is  prolonged 
through  the  hilum  into  the  renal  sinus.  The 
kidney  and  the  capsula  adiposa  are  enclosed  in 
a  sheath  of  fibrous  tissue  continuous  with  the 
subperitoneal  fascia,  and  named  the  fascia 
renalis.  At  the  outer  border  of  the  kidney  the 
fascia  renalis  splits  into  an  anterior  and  a  pos- 
terior layer.  The  anterior  layer  is  carried  in- 
ward in  front  of  the  kidney  and  its  vessels,  and 
is  continuous  over  the  aorta  with  the  corre- 
sponding layer  of  the  opposite  side.  The  pos- 
terior layer  extends  inward  behind  the  kidney 
and  blends  with  the  fascia  on  the  Quadratus  lumborum  and  Psoas  muscles  and 
through  this  fascia  is  attached  to  the  vertebral  column.  At  the  upper  margin  of 
the  suprarenal  gland  the  two  layers  of  the  fascia  renalis  fuse,  and  imite  with  the  fas- 
cia of  the  Diaphragm;  below  they  remain  separate,  and  are  gradually  lost  in  the 
subperitoneal  fascia  of  the  iliac  fossa  (Fig.  1 1 1 1 ) .  The  fascia  renalis  is  connected  to 
the  fibrous  capsule  of  the  kidney  by  numerous  trabeculse,  which  traverse  the  adipose 
capsule  and  are  strongest  near  the  lower  end  of  the  organ.  The  perirenal  fat  does  not 
look  like  the  fat  in  other  regions,  but  is  soft,  delicate,  and  of  a  canary-yellow  color. 
Behind  the  fascia  renalis  is  a  considerable  quantity  of  fat  which  constitutes  the 


Fig.  1113. — Vertical  section  of  kidney. 


THE  KIDNEYS 


1349 


WALL  OF  RENAL  CALIX 


Fig.  1114. — Area  cribrosa  of  renal  papilla.      (Toldt.) 


pararenal  or  Transversalis  fat.     The  kidney  is  held  in  position  throngh  the  at- 
tachments of  the  fascia  renahs  and  by  the  apposition  of  the  neighboriiis  viscera. 

General  Structure  of  the  Kidney.—  ^„e:a  chibhosa 

The  Uiilncy  is  invested   by  a  capsule  of 

interlacing  bundles  of  fibrous  connective 

tissue  (tunica  fibrosa),  which  forms  a  firm, 

smooth  covering  for  the  organ.    The  cap- 
sule can  be  easily  stripped  off,  but  in  doing 

so,  numerous  fine  processes  of  connective 

tissue   and    .small   bloodvessels   are   torn 

through.     Beneath  this  coat,  a  thin  wido- 

meshed  network  of  unstriped  muscle  fibres 

forms  an  incomplete  covering.     When  the 

capsule  is   removed,  the   surface  of  the 

kidney  is  found  to  be  smooth  and  even, 

and  of  a  very  deep  red  color.     In  infants, 

fissures  extending  for  some  depth  may  be 

seen  on  the  surface  of  the  organ,  a  remnant 

of  the  lobular  construction  of  the  gland 

(Fig.    1105).      The   kidney   is   dense   in 

texture,  but  is  easily  lacerable  by  mechan- 
ical force.     If  a  vertical  section  of  the 

kidney  be  made  from  its  convex  to  its 

concave  border,  and  the  loose  tissue  and 

fat  removed  from  around  the  vessels  and 

the  excretory  duct,  it  will  be  seen  that  the  organ  consists  of  a  central  cavity  surrounded,  except 

at  the  hilum,  by  the  proper  kidney  substance  (Fig.  1113).     This  central  cavity  is  called  the 

renal  sinus  (sinus  renalis)  and  is 
SUPERIOR  lined  by  a  prolongation  of  the  cap- 

sule, which  is  continued  around 
the  lips  of  the  hilum.  Through 
the  hilum  the  bloodvessels  of  the 
kidney  and  its  excretory  duct  pass, 
and  therefore  these  structures,  upon 
entering  the  kidney,  are  contained 
within  the  sinus. 

The  excretory  duct  or  ureter 
begins  as  a  funnel-shaped  sac,  the 
pelvis  of  the  ureter  (pelvis  ureter- 
iciis  s.  renalis).  The  pelvis  begins 
at  the  renal  papillfe  in  the  form  of 
a  number  of  truncated  cup-shaped 
infundibular  divisions,  the  calices 
minores,  into  each  of  which  usually 
one  papilla  projects.  These  minor 
calices  vary  from  ten  to  twenty  in 
number.  Several  minor  calices 
unite  to  form  larger  divisions,  the 
calices  majores  (Fig.  1115),  which 
are  usually  two  in  number,  though 
more  may  be  present.  These 
major  calices  unite  to  form  the 
main  compartment  of  the  pelvis, 
which  becomes  narrowed  below  at 
the  le\'el  of  the  second  lumbar  ver- 
tebra to  be  continued  as  the  ureter 
proper  (Fig.  1115). 

The  kidney  substance  or  paren- 
chyma consists  of  very  irregular 
tubules,  the  uriniferous  tubules, 
which  are  supported  by  a  frame- 
work of  retiform  connective  tissue 

and  surrounded  by  blood-  and  lymph  vessels  and  nerves.  It  is  readily  divisible  into  an  outer 
third,  the  cortex,  about  one-third  to  one-half  of  an  inch  (8  to  12  mm.)  in  thickness,  and  an  inner 
two-thirds,  the  medulla,  two-thirds  to  three-quarters  of  an  inch  (16  to  20  mm.)  in  thickness. 


Fig.  1115. — The  right  kidney  with  the  pelvis  of  the  ureter  exposed, 
and  showing  dorsal  branch  of  the  renal  artery,  viewed  from  behind. 
(Spalteholz.) 


1350 


THE  VRINOGENITAL  ORGANS 


The  cortex  is  reddish  brown  in  color  and  soft  and  granular  in  consistence.  It  lies  imme- 
diatel}-  beneath  the  capsule,  arches  over  the  bases  of  the  pyramids,  and  dips  in  between  adjacent 
pyramids  toward  the  renal  sinus  in  the  form  of  renal  columns  {columnae  renales  [Bertini]).  If 
a  section  of  the  cortex  be  examined  with  a  lens,  it  will  be  seen  to  consist  of  a  series  of  liwhter 
colored,  ray-like  prolongations  of  straight  tubules  from  the  medulla,  called  the  medullary  rays 
{pars  radiata).  The  darker  colored  intervening  substance  composing  the  remainder  of  the 
cortex,  from  the  complexity  of  its  structure,  is  called  the  labyrinth  {pars  convoluta),  and  contains 
the  convoluted  portions  of  the  uriniferous  tubules  and  the  Malpighian  corpuscles.  The  medul- 
lary rays  gradually  taper  toward  the  circumference  of  the  kidney,  but  do  not  reach  the  capsule. 

The  meduUa  consists  of  reddish,  striated,  conical  masses,  the  medullary  psrramids  (pijramides 
renales  [Malpighii]),  the  number  of  which,  varying  from  ten  to  twinty,  corrrsiionds  to  the  number 
of  lobes  of  which  the  organ  is  composed  in  the  fetal  state.  The  pyramids  are  composed  of 
straight  tubes  which  pass  from  the  base  to  the  apex.  The  sides  of  the  pyramids  are  contiguous 
with  the  renal  columns,  while  the  apices,  known  as  the  renal  papillae,  project  into  the  minor 
calices  of  the  ureteral  pelvis,  each  calix  receiving  one,  two,  or  three  papillae.     Each  papilla  shows 


Fig.  1116. — A  section  through  the  cortex  of  an  ape's  kidney. 


beginning  of  the  tubule,  is  shown.     X  350.     (Szymonowicz.) 


upon  its  apex  a  number  (16  to  20)  of  minute  orifices  of  the  excretory  ducts  of  the  pyramid;  this 
perforated  area  of  the  apex  is  called  the  area  ciibrosa  (Fig.  1114). 

The  renal  colimms  (of  Berlin)  separate  the  pyramids  from  one  another  and  consist  of  cortical 
masses  extending  toward  the  renal  sinus.  At  the  sinus  ends  they  contain  a  considerable  amount 
of  white  fibrous  and  adipose  tissue.  They  serve  as  a  passageway  for  the  main  bloodvessels, 
lymphatics,  and  nerves  to  and  from  the  parenchyma  of  the  organ. 

Minute  Anatomy. — The  uriniferous  tubules  {tiibuli  renales)  are  in  part  very  convoluted 
and  in  part  straight  and  regular.  They  arise  in  the  cortex,  pass  into  the  medulla,  return  to  the 
cortex,  and  end  at  the  area  cribrosa  of"  the  renal  papilla.  Each  tubule  starts  at  the  glomerulus 
or  renal  corpuscle  {Malpighian  body),  a  small,  round,  reddish  mass,  which  measurerT20  to 
200 /i.  "Elaclrorthese  ITTrtrTJbdies  is  composed  of  two  parts,  a  central  glomerulus  of  vessels, 
called  a  Malpighian  tuft  and  a  membranous  envelope,  the  Malpighian  capsule,  or  capsule  of 
Boumian,  which  is  the  small  pouch-like  commencement  of  a  uriniferous  tubule. 

The  Malpighian  tuft,  or  vascular  glomerulus,  is  a  network  of  convoluted  capillary  bloodvessels, 
held  together  by  scanty  connective  tissue.  This  capillary  network  is  derived  from  a  small  arterial 
twig,  the  afferent  vessel,  which  pierces  the  wall  of  the  capsule,  generally  at  a  point  opposite  to 
that  at  which  the  latter  is  connected  with  the  tube;  and  the  resulting  vein,  the  efferent  vessel. 


THE  KIDNEYS 


1351 


that  at  which  the  latter  Is  connected  with  tlie  tube;  and  the  resulting  arteriole,  the  efferent  vessel, 
emerges  from  the  capsule  at  the  same  point.  The  afferent  vessel  is  usually  the  larger  of  the  two 
(Fig.  1116).  The  Malpighian  or  Boivman's  capsule,  wliich  surrounds  the  glomerulus,  is  formed 
of  a  hyaline  membrane,  supported  by  a  small  amount  of  connective  tissue,  which  is  continuous 
with  the  connective  tissue  of  the  tube.  It  is  lined  on  its  inner  surface  by  a  single  layer  of  squam- 
ous epithelial  cells,  which  ai-e  reflected  from  the  lining  membrane  to  the  glomerulus,  at  the  point 
of  entrance  or  exit  of  the  afferent  and  efferent  vessels.  The  whole  surface  of  the  glomerulus  is 
co\-ered  with  a  continuous  layer  of  the  same  cells,  which  rests  on  a  delicate  supporting  membrane 
(Fig.  1116).  Thus,  between  the  glomerulus  and  the  capsule  a  space  is  left,  forming  a  cavity  lined 
by  a  continuous  layer  of  squamous  cells;  this  cavity  varies  in  size  according  to  the  state  of 
secretion  and  the  amount  of  fluid  present  in  it.  In  the  fetus  and  young  subject  the  cells  are 
polyhedral  or  even  columnar. 

At  the  junction  of  a  tubule  with  the  Malpighian  capsule  there  is  a  somewhat  constricted  por- 
tion which  is  termed  the  neck  (Fig.  1118).  Beyond  tliis  the  tubule  becomes  convoluted,  and 
])uiMi('s  i\  considerable  course  in  the  cortical  structiu-e,  constituting  the  proximal  or  first  convo- 
luted tubule  (Figs.  1118  and  1121).  After  a  time  the  convolutions  disappear,  and  the  tubule 
approaches  the  medullary  portion  of  the  kidney  in  a  more  or  less  spiral  manner.  This  section 
of  the  tubule  has  been  called  the  spiral  tube  of  Schachowa.  Throughout  this  portion  of 
their  course  the  tubuli  uriniferi  are  contained  entirely  in  the  cortical  structure,  and  present  a 
fairly  uniform  calibre.     They  now  enter  the  medullary  portion,  suddenly  become  much  smaller, 


MEDULLAR 


MEDUL 

Fig.  1117.— Part  of  a  section  through  the  cortex  of  the  kidney  in  the  direction  of  the  straight  tubules.     (Toldt.) 


quite  straight  in  du-ection,  and  dip  down  for  a  variable  depth  into  the  pjTamids,  constituting  the 
descending  hmb  of  Henle's  loop.  Bending  on  themselves,  they  form  what  is  termed  the  loop  of 
Henle,  and  re-ascending,  they  become  suddenly  enlarged  and  again  spiral  in  direction,  forming 
the  ascending  Umb  of  Henle's  loop,  and  reenter  the  cortical  structiu-e.  In  the  cortex  the  tubule 
again  becomes  slightly  convoluted,  and  is  called  the  distal  or  second  convoluted  tubule  (Fig. 
1116).  This  terminates  in  a  narrow  arched  collecting  or  junctional  tubule,  which  enters  the 
straight  collecting  tubule. 

Each  straig'ht  collecting  tubule  {iuhulus  renalis  recta)  passes  from  the  cortex  into  the  medulla, 
receiving  at  various  intervals  in  the  cortical  part  of  its  course  several  arched  collecting  tubules. 
In  the  medullary  pyramid,  several  straight  collecting  tubules  unite  to  form  from  sixteen  to 
twenty  papillary  or  excretory  ducts,  which  empty  at  the  area  cribrosa  of  the  renal  papilla.  As 
they  approach  the  papilla,  their  diameter  gradually  increases. 

It  will  be  seen  from  the  above  description  that  there  is  a  continous  series  of  tubes  from  their 
commencement  in  the  Malpighian  bodies  to  their  termination  at  the  orifices  on  the  apices  of 
the  pyramids  of  Malpighi,  and  that  the  urine,  the  excretion  of  which  commences  in  Bowman's 
capsule,  finds  its  way  through  these  tubes  into  the  calices  of  the  ureter. 

Structure  of   the  Uriniferous  Tubule. — The  uriniferous  tubule  consists  throughout  of 


1352 


THE  UBINOGENITAL  ORGANS 


a  single  layer  of  epithelial  cells  resting  upon  a  basement  membrane  which  is  supported  by  a 
delicate  meshwork  of  retiform  connective  tissue.  The  tissue  contains  the  vessels,  nerves,  and 
lymphatics.  The  diameter  of  the  tubule  and  the  size  of  the  cells  vary  in  the  different  portions. 
The  capsule  of  Bowman  is  lined  with  simple  squamous  cells,  and  the  renal  corpuscle  has  a  diameter 
of  120  to  200  microns;  the  neck  is  lined  by  simple  squaraous  cells,  and  has  a  diameter  of  about 
15  microns;  the  proximal  convoluted  and  spiral  tubules  are  lined  with  irregular  columnar  cells; 

the  lumen  of  the  tubule  is  irregular  and  the 
diameter  averages  about  40  microns;  the  descend- 
ing limb  ofHenle's  loop  is  lined  with  simple  squa- 
mous cells,  and  the  diameter  is  from  10  to  1.3 
microns;  the  loop  and  ascending  limb  are  lined 
with  regular  cuboidal  cells,  and  the  diameter 
averages  from  23  to  28  microns;  the  distal  con- 
voluted tubule  is  lined  with  irregular  columnar 
cells,  the  lumen  is  irregular,  and  the  diameter 
about  45  microns;  the  arched  connecting  tubule 
is  lined  with  simple  cuboidal  cells,  and  the 
diameter  is  about  45  microns;  the  straight  col- 
lecting tubule  is  lined  by  columnar  cells,  and  the 
diameter  increases  from  45  to  75  microns;  the 
papillary  ducts  are  lined  with  tall  columnar  cells, 
and  the  diameter  reaches  200  to  300  microns. 
The  protoplasm  of  these  cells  is  granular  at  the 
basal  end,  while  the  luminal  end  is  striated. 

The  parts  of  the  kidney  in  which  the  various 
portions  of  the  uriniferous  tubules  lie  are  as 
follows: 

Cortex. — In  the  labyrinth  are  found  the  renal 
corpuscles,  the  neck,  and  the  proximal  and  distal 
convoluted  tubules. 

In  the  medullary  rays  are  found  the  upper 
ends  of  the  descending  and  ascending  limbs  of 
Henle's  loop,  the  arched  collecting  tubules,  and 
the  upper  ends  of  the  straight  collecting  tubules. 
Medulla. — Here  are  found  the  lower  ends  of 
the  descending  and  ascending  limbs  of  Henle's 
loop,  the  loop,  the  straight  collecting  tubules,  and 
the  papillarii  ducts. 

The  Renal  Bloodvessels. — The  kidney  is 
plentifully  supplied  with  blood  by  the  renal  artery 


Fig.  1118. — Diagram  of  three  uriniferous  tubules 
and  tlieir  relation  to  a  collecting  tubule.  A.  Of  a 
tubule,  the  Malpighian  corpuscle  of  which  is  situated  • 
in  the  lowermost  portion  of  the  cortex.  B.  About 
the  middle  of  tlie  cortex.  C.  In  the  outer  portion 
of  the  cortex,  tii.  Malpighian  corpuscle,  v.  Vessel 
porta,  n.  Neck.  p(:.  Proximal  convoluted  portion. 
es.  End  segment,  dl.  Descending  limb.  al.  As- 
cending limb  of  tile  loop  of  Henle.  dc.  Distal 
convoluted  portion.  j.  Junctional  tubule.  c. 
Collecting  tubule.     (Huber.) 


Fig.  1119.  —  Longitu- 
dinal section  of  Henle's 
descending  Umb.  a. 
Membrana  propria,  b. 
Epithelium. 


Fig.  1120. —  Longitudiniil 
section  of  straight  tube.  a. 
Cylindrical  or  cubical  epi- 
thelium, b.  Membrana  pro- 
pria. 


(Figs.  1107  and  1115);  a  large  branch  of  the  abdominal  aorta  given  off  at  the  level  of  the  articular 
disk  between  the  first  and  second  lumbar  vertebrje.    The  importance  of  the  kidney  as  an  excre- 


THE  KIDNEYS 


1353 


tory  organ  is  evidenced  by  the  fact  that  the  artery  is  three  times  as  large  as  is  necessary  for  the 
nutrition  of  an  organ  of  the  size  of  the  kidney.  Previously  to  entering  tiie  kidney,  each  artery 
divides  into  four  or  five  branches,  which  are  distributed  to  its  substance.  At  the  hilum  these 
branches  He  between  the  renal  vein  and  ureter,  the  vein  lieing  in  front,  the  ureter  behind.  Each 
vessel  gives  off  a  small  branch  to  the  suprarenal  glands,  the  ureter,  and  the  surrounding  tissue  and 
nniscles.  It  has  been  pointed  out  by  Hyrtl  (p.  665)  that  the  renal  artery  gives  off  a  branch  which 
Hivides  and  supplies  the  dorsal  portion  of  the  kidney  and  a  larger  branch  which  divides  and  sup- 
plies the  ventral  portion  of  the  kidney.     Between  these  two  vascular  systems  is  a  nonvascular 


Interlobular 
riery  and  cein 


Fig.  1121. — Diagrammatic  representation  of  the  course  of  the  uriniferous  tubules  (left)  and  the  kidney  vessels 
(right).  The  arteries  are  red.  the  veins  blue;  capsules  of  Bowman,  convoluted  tubules  I  order  and  loops  of 
Henle  are  black;  convoluted  tubules  II  order  and  collecting  tubules  gray.  I,  II,  III,  IV.  Four  kidney  lobules, 
a.  Vas  alTerens.  e.  Vas  efferens.  1.  Bowman's  capsule.  2.  Convoluted  tubule  I  order.  3.  Descending  limb 
of  loop  of  Henle.  4.  .\scending  limb  of  loop  of  Henle.  5.  Convoluted  tubule  II  order.  6,  7.  (Collecting 
tubules.     S.  Papillary  duct.     (Szymonowicz.) 


zone,  called  by  Robinson  the  exsanguinated  renal  zone  of  Hyrtl.  It  "is  one-half  inch 
dorsal  to  the  external  border  of  the  kidney."  Frequently  there  is  a  second  renal  artery, 
which  is  given  off  from  the  abdominal  aorta  at  a  lower  leveh  and  supplies  the  lower  portion  of  the 


1354 


THE   UBINOGENITAL   ORGANS 


'""X 


kidney.  It  is  termed  the  accessory  renal  artery.  Within  the  sinus  the  renal  artery  divides 
into  foiu-  or  five  branches,  about  tlxree-foiu'ths  of  the  blood  going  to  the  anterior  pyramids  and 
the  remainder  to  the  posterior  pyramids.  Each  extremity  of  the  kidney  is  supplied  by  a  branch 
which  divides  into  anterior,  middle,  and  posterior  branches,  which  do  not  anastomose  with  each 
other.  The  branches  of  the  renal  arteries  pass  to  the  kidney  substance  between  the  pyramids 
and  are  known  as  interlobar  arteries  (arteriae  interlohares  rents)  (Fig.  1117).  At  the  junction 
of  the  cortical  and  medullary  portions  (the  boundary  zone)  these  vessels  tiu-n  and  for  a  short 
distance  piusue  a  course  parallel  to  the  kidney  surface.  There  are  thus  formed  a  series  of 
incomplete  vascular  arches  across  the  bases  of  the  pyramids,  the  arcuate  arteries  (arteriae  arci- 
formes)  (Figs.  1113  and  1121).  From  these  arches  two  sets  of  vessels  come.  The  vessels  of  one 
set  go  to  the  periphery  and  enter  the  cortex,  the  intralobular,  or  cortical  arteries,  those  of  the  other 
set  pass  toward  the  sinus  and  enter  the  medulla.  These  last  vessels  are  the  arteriolae  recti 
(Figs.  1117  and  1121).  As  the  intralobular  arteries  pass  toward  the  capsule  they  give  off 
branches  to  each  renal  corpuscle,  the  vasa  afEerentia  or  afferent  arterioles.  As  the  arteriole 
enters  the  corpuscle  it  divides  into  several  branches,  each  of  which  forms  a  capillary  plexus. 
The  blood  from  each  plexus  is  collected  by  a  small  branch  which  joins  with  its  fellows  to  form 
the  vas  eflerens  or  efferent  arteriole.  These  various  plexuses  constitute  a  glomerulus  or  Mal- 
pighian  Tuft  (Fig.  1116).  On  leaving  the  glomerulus  the  arteriole  forms  a  capillary  network 
around  the  adjacent  portions  of  the  imniferous  tubule.  The  blood  is  collected  by  various 
channels  and  emptied  into  the  intralobular  vein,  which  starts  in  the  venae  stellatae,  beneath 
the  capsule,  and  empties  its  blood  into  the  arcuate  vein. 

The  arteriolae  rectae  supply  the  medulla  and  are  smaller  in  diameter  than  the  intralobular 
arteries,  and  soon  form  a  rich  capillary  plexus  around  the  tubules  of  the  medulla.  The  blood  is 
collected  by  the  venae  rectae,  which  empty  into  the  arcuate  vein  {vena  arciformis)  at  the  boun- 
dary zone.  The  blood  is  carried  to  the  cohunns  of  Bertin,  where  it  continues  toward  the  sinus 
in  the  interlobular  veins.  In  the  sinus  these  veins  unite  to  form  the  renal  vein  {vena  renali^) 
(Fig.  1107). 

The  nerves  of  the  kidney,  although  small,  are  about  fifteen  in  number.  They  have  small 
ganglia  developed  upon  them,  and  are  derived  from  the  renal  plexus,  which  is  formed  by  branches 
from  the  solar  plexus,  the  lower  and  outer  part  of  the  semilunar 
ganglion  and  aortic  plexus,  and  from  the  lesser  and  smallest 
splanchnic  nerves.  They  communicate  with  the  spermatic 
plexus,  a  circumstance  which  may  explain  the  occurrence  of  pain 
in  the  testicle  in  affections  of  the  kidney.  So  far  as  they  have 
been  traced,  they  seem  to  accompany  the  renal  artery  and  its 
branches,  and  they  have  been  traced  to  the  epithelium,  but  their 
exact  mode  of  termination  is  not  known. 
The  Lsrmphatics  are  described  on  page  796. 
Variations  and  Abnormalities. — Congenital  absence  of  the 
kidney  has  licrii  iil>served.  Not  unusually  one  kidney  is  con- 
siderably larger  than  the  other;  occasionally  one  is  very  large 
and  the  other  is  very  small,  from  atrophy,  the  large  organ  having 
become  large  in  response  to  a  functional  need,  which  causes  it  to 
compensate  for  the  insufficiency  of  the  small  kidney.  If  a  kidney 
is  removed  surgically,  the  other  kidney  enlarges.  As  previously 
stated,  the  kidneys  of  the  fetus  and  of  the  young  child  show 
distinct  fissures  which  make  each  organ  lobulated  (Fig.  1122). 
The  aihilt  kiiliicys  frequently  exhibit  remains  of  these  fissures. 
A  horseshoe  kidney  is  a  condition  in  which  the  lower  extremi- 
ties of  the  two  kidneys  are  united  by  kidney  structure,  the  bond 
of  union  crossing  the  middle  line.  The  strip  of  kidney  tissue  which  effects  the  junction  may  be 
slight,  considerable,  or  extensive  in  amount.  Sometimes  the  two  kidneys  are  completely  fused 
together  into  one  large  organ  with  two  ureters. 

Surface  Form. — The  kidneys,  being  situated  at  the  back  part  of  the  abdominal  cavity  and 
deeply  situated,  cannot  be  felt  unless  enlarged  or  misplaced.  They  are  situated  on  the  confines 
of  the  epigastric  and  umbilical  regions  internally,  with  the  hypochondriac  and  lumbar  regions 
externally.  The  left  is  somewhat  higher  than  the  right.  According  to  Morris,  the  position  of 
the  kidney  may  be  thus  defined:  Anteriorly:  "(1)  A  horizontal  line  through  the  umbilicus  is 
below  the  lower  edge  of  each  kidney.  (2^  A  vertical  line  carried  upward  to  the  costal  arch  from 
the  middle  of  Poupart's  ligament  has  one-third  of  the  kidney  to  its  outer  side  and  two-thirds  to 
its  inner  side — i.  e.,  between  this  line  and  the  median  line  of  the  body."  In  adopting  these  lines 
it  must  be  borne  in  mind  that  the  axes  of  the  kidneys  are  not  vertical,  but  oblicfue,  and  if  con- 
tinued upward  would  meei  aDout  the  ninth  thoracic  vertebra.  Posteriorly:  The  upper  end  of  the 
left  kidney  would  be  defined  by  a  line  drawn  horizontally  outward  from  the  spinous  process  of  the 
eleventh  thoracic  vertebra,  and  its  lower  end  by  a  point  two  inches  (5  cm.)  above  the  iliac  crest. 


Fig.  1122. — Peta!  kidney,  showing 
lobulation,     (Testut.) 


THE  KIDNEYS  1355 

The  right  kichit-y  would  be  half  to  three-quarters  of  an  inch  lower.  Morris  lays  clown  the  fol- 
lowini'  rules  for  indicating  the  position  of  the  kidney  on  the  posterior  surface  of  the  body:  •'(1) 
A  line  parallel  with,  and  one  inch  from,  the  vertebral  column,  between  the  lower  edge  of  the  tip 
of  the  spinous  process  of  the  eleventh  thoracic  vertebra  and  the  lower  edge  of  the  spinous 
process  of  the  third  lumbar  vertebra.  (2)  A  line  from  the  top  of  this  first  line  outward  at  right 
angles  to  it  for  two  and  three-quarter  inches.  (3)  A  line  from  the  lower  end  of  the  first  trans- 
versely outward  for  two  and  three-c[uarter  inches.  (4)  A  line  parallel  to  the  first  and  connecting 
the  outer  extremities  of  the  second  and  third  lines  just  described." 

The  hilum  of  the  right  kidney  is  two  inches  from  the  mesal  plane;  the  hilum  of  the  left  one 
and  one-half  inches  from  the  mesal  plane.  A  line  joining  the  two  hili  crosses  the  vertebral 
column  op]50site  the  disk  between  the  first  and  second  lumbar  vertebrae. 

Applied  Anatomy. — Cases  of  congenital  absence  of  a  kidney,  of  atrophy  of  a  kidney,  and 
a  liiir.s-islinr  L-i:liini  are  of  great  importance,  and  must  be  duly  taken  into  account  when  neph- 
rectum)-  is  c()nlein|)iated.  A  more  common  malformation  is  where  the  two  kidneys  are  fused 
together.  They  may  be  only  joined  together  at  their  lower  ends  by  means  of  a  thick  mass  of 
renal  tissue,  so  as  to  form  a  horseshoe-shaped  body,  or  they  may  be  completely  united,  forming 
a  disk-like  kidney,  from  which  two  ureters  descend  into  the  bladder.  These  fused  kidneys  are 
generally  situated  in  the  middle  line  of  the  abdomen,  but  may  be  misplaced  as  well. 

One  or  both  kidneys  may  be  misplaced  as  a  congenital  condition,  and  remain  fixed  in  this 
abnormal  position.  They  are  then  very  often  misshapen.  They  may  be  situated  higher  or  lower 
than  normal  or  removed  farther  from  the  spine  than  usual  or  they  may  be  displaced  into  the 
iliac  fossa,  over  the  sacroiliac  joint,  on  to  the  promontory  of  the  sacrum,  or  into  the  pelvis  be- 
tw-een  the  rectum  and  bladder  or  by  the  side  of  the  uterus.  In  these  latter  cases  they  may  give 
rise  to  very  serious  trouble.  The  kidney  may  also  be  misplaced  as  a  congenital  condition,  but 
may  not  be  fixed.  It  is  then  known  as  a  floating  kidney.  It  is  believed  to  be  due  to  the  fact 
that  the  kidney  is  completely  enveloped  by  peritoneum,  which  then  passes  backward  to  the 
vertebral  column  as  a  double  layer,  forming  a  -mesonephron,  which  permits  of  movements  taking 
place.  The  kidney  may  also  be  misplaced  as  an  acquired  condition;  in  these  cases  the  kidney  is 
mobile  in  the  tissues  by  which  it  is  surrounded,  either  moving  in  or  moving  with  its  fatty  capsule. 
This  condition  is  known  as  movable  kidney  {nephroptosis),  and  is  more  common  in  the  female 
than  in  the  male,  and  on  the  right  than  the  left  side.  If  a  displaced  kidney  becomes  fixed  in  an 
abnormal  position,  it  is  said  to  be  dislocated.  Movable  kidney  cannot  be  distinguished  from 
floating  kidney  until  the  kidney  is  exposed  by  incision.  Other  malformations  are  the  persist- 
ence of  the  fetal  lobulation;  the  presence  of  two  pelves  or  two  ureters  to  the  one  kidney.  In 
some  rare  instances  a  third  kidney  may  be  present. 

The  kidney  is  embedded  in  a  large  quantity  of  loose  fatty  tissue,  and  is  but  partially  covered 
by  peritoneum;  hence  rupture  of  this  organ  is  not  nearly  so  serious  an  accident  as  rupture  of 
the  liver  or  spleen,  since  the  extravasation  of  blood  and  urine  which  follows  is,  in  the  majority 
of  cases,  outside  the  peritoneal  cavity.  Occasionally  the  kidney  may  be  bruised  by  blows  in  the 
loin  or  by  being  compressed  between  the  lower  ribs  and  the  ilium  when  the  body  is  violently 
bent  forward.  This  is  followed  by  a  little  transient  hematuria,  which,  however,  speedily  passes 
off.  Occasionally,  when  rupture  involves  the  pelvis  of  the  ureter  or  the  commencement  of  the 
ureter,  this  duct  may  become  blocked,  and  hydroiiephrosis  follows. 

The  loose  cellular  tissue  around  the  kidney  may  be  the  seat  of  suppuration,  constituting 
perinephritic  abscess.  This  may  be  due  to  injury,  to  disease  of  the  kidney  itself,  or  to  extension 
of  inflammation,  from  neighboring  parts.  The  abscess  may  burst  into  the  pleura,  causing 
empyema ;  into  the  colon  or  bladder ;  or  may  point  externally  in  the  groin  or  loin.  Tumors  of  the 
kidney,  of  w-hich,  perhaps,  sarcoma  in  children  is  the  most  common,  may  be  recognized  by  their 
position  and  fixity;  by  the  resonant  colon  lying  in  front  of  it;  by  their  not  moving  with  respira- 
tion; and  by  their  rounded  outline,  not  presenting  a  notched  anterior  margin  like  the  spleen,  with 
which  they  are  most  likely  to  be  confounded.  The  examination  of  the  kidney  should  be  bimanual; 
that  is  to  say,  one  hand  should  be  placed  in  the  flank  and  firm  pressure  made  forward,  while 
the  other  hand  is  buried  in  the  abdominal  wall,  over  the  situation  of  the  organ.  Manipulation 
of  the  kidney  frequently  produces  a  peculiar  sickening  sensation  and  some  faintness. 

The  kidney  is  frequently  attacked  surgically.  It  may  be  exposed  and  opened  for  exploration 
or  the  evacuation  of  pus  {nephrotomy);  it  may  be  incised  for  the  removal  of  stone  {nephro- 
lithotomy); it  may  be  sutured  when  wounded  {nephrorrhaphy);  it  may  be  fixed  in  place  by 
sutures  {nephropexy)  or  gauze  pads  when  movable  or  floating;  or  it  may  be  removed  {nephreo- 
tomy). 

The  kidney  may  be  exposed  either  by  a  lumbar  or  abdominal  incision.  The  operation  is 
best  performed  by' a  lumbar  incision,  except  in  a  case  of  very  large  tumor  or  of  wandering  kid- 
ney with  a  loose  "mesonephron,  on  account  of  the  advantages  which  it  possesses  of  not  opening 
the  peritoneum  and  of  aft'ording  admirable  drainage.  It  may  be  performed  either  by  an  olslique, 
a  vertical,  or  a  transverse  incision.  A  common  incision  for  exposing  the  kidney  begins  an  inch 
below  the  twelfth  rib,  at  the  margin  of  the  Erector  spinae  muscle,  and  passes  obliquely  down- 


1356  THE   VRINOQENITAL   ORGANS 

ward  and  forward,  exposing  the  anterior  border  of  the  Latissimus  dorsi  and  the  posterior  border 
of  the  Internal  oblique.  The  surgeon  divides  the  posterior  leaflet  of  the  lumbar  fascia,  dra^s 
aside  or  incises  the  Quadratus  lumborum,  and  cuts  the  anterior  leaflet  of  the  lumbar  fascia  and 
also  the  transversalis  fascia.  He  opens  the  fatty  capsule  down  to  the  kidney  and  strips  it  from 
the  true  capsule,  bringing  the  kidney  outside  of  the  body  for  inspection.  The  vertical  incision 
at  the  edge  of  the  Erector  spinae  muscle  is  frequently  used.  A  gridiron  or  muscle-splitting 
operation  is  used  by  some  in  order  to  avoid  the  division  of  nerves,  vessels,  and  muscle  fibres. 

The  abdominal  operation  is  best  performed  by  an  incision  in  the  linea  semilunaris  on  the 
side  of  the  kidney  to  be  removed,  as  recommended  by  Langenbuch;  the  kidney  is  then  reached 
from  the  outer  side  of  the  colon,  ascending  or  descending,  as  the  case  may  be,  and  the  vessels 
of  the  colon  are  not  interfered  with.  If  the  incision  were  made  in  the  linea  alba,  the  kidney 
would  be  reached  from  the  inner  side  of  the  colon,  and  the  vessels  running  to  supply  the  colon 
would  necessarily  be  interfered  with.  The  incision  is  made  of  varying  length  according  to  the 
size  of  the  kidney,  and  commences  just  below  the  costal  arch.  The  abdominal  cavity  is  opened. 
The  intestines  are  held  aside,  and  the  outer  layer  of  the  mesocolon  incised,  so  that  the  fingers 
can  be  introduced  behind  the  peritoneum  and  the  renal  vessels  are  sought  for.  These  vessels 
are  then  to  be  ligated;  if  tied  separately,  care  must  be  taken  to  ligate  the  artery  first.  The 
kidney  must  now  be  enucleated,  and  the  vessels  and  the  ureter  divided,  and  the  latter  disinfected 
and  tied,  and,  if  it  is  thought  necessary,  stitched  to  the  edge  of  the  wound. 


THE   URETERS    (Figs.    1106,    1115). 

The  ureters  are  the  two  tubes  which  convey,  the  urine  from  the  kidneys  into 
the  bladder.  Each  ureter  commences  within  the  sinus  of  the  corresponding 
kidney  by  a  number  of  short  cup-shaped  branches,  the  minor  caUces  or  infun- 
dibula,  which  unite  either  directly  or  indirectly  to  form  a  dilated  pouch,  the 
pelvis  (Fig.  1115),  from  which  the  ureter,  after  passing  through  the  hilum 
of  the  kidney,  descends  to  the  bladder.  The  minor  caMces  encircle  the  apices 
of  the  renal  papillse;  but  inasmvich  as  one  calix  may  include  two  or  even  more 
papillae,  their  number  is  generally  less  than  the  pyramids  themselves.  The 
minor  calices  vary  in  number  from  ten  to  twenty  or  more.  These  calices  con- 
verge into  two  or  three  tubular  di\'isions,  the  major  calices,  which  by  their 
junction  form  the  pelvis  or  dilated  portion  of  the  ureter,  which  is  situated  be- 
hind the  renal  vessels  and  which  lies  partly  within  and  partlj'  outside  the  renal 
sinus.  It  is  usually  placed  on  a  level  with  the  spinous  process  of  the  first  lumbar 
vertebra. 

The  ureter  proper  is  a  cylindrical  membranous  tube,  about  ten  to  twelve 
inches  (25  to  30  cm.)  in  length  and  about  one-sixth  inch  (4  mm.)  in  diameter, 
directly  continuous  near  the  lower  end  of  the  kidney  with  the  tapering  extrem- 
ity of  the  pelvis.  Its  walls  are  from  1  to  2  mm.  thick,  and  its  calibre  va- 
ries. It  exhibits  four  main  constrictions — (1)  at  its  junction  with  its  pelvis; 
(2)  as  it  passes  over  the  brim  of  the  pelvis;  (3)  as  it  enters  the  bladder;  (4)  at 
its  termination.  Its  course  is  obliquely  downward  and  inward  through  the 
lumbar  region  {fars  abdoniinalis)  (Fig.  1106),  into  the  cavity  of  the  pelvis  {pars 
■pelvina)  (Fig.  1124),  where  it  passes  downward,  forward,  and  inward  across 
that  cavity  to  the  base  of  the  bladder,  into  which  it  then  opens  by  a  constricted 
orifice  {orificium  ureterw)  (Fig.  1134),  after  having  passed  obliquely  for  nearly 
an  inch  between  the  vesical  muscular  and  mucous  coats  (Fig.  1123).  The 
lower  part  of  the  abdominal  portion  of  the  ureter  exhibits  a  spindle-shaped 
dilatation. 

Relations  (Fig.  1124). — The  ahiominal  -part  lies  behind  the  peritoneiun  on  the  inner  part  of 
the  Psoas  muscle,  and  is  crossed  obliquely  by  the  spermatic  or  ovarian  vessels.  It  enters  the 
pelvic  cavity  by  crossing  either  the  termination  of  the  common,  or  the  commencement  of  the 
external,  iliac  vessels. 

At  its  origin  the  right  ureter  is  usually  covered  by  the  second  part  of  the  duodenum,  and  in  its 


THE   URETERS 


1357 


course  downward  lies  to  the  right  of  the  inferior  vena  cava  and  is  crossed  by  the  right  colic  artery, 
while  near  the  pelvic  brim  it  passes  behind  the  lower  part  of  the  mesentery  and  the  terminal 
part  of  the  ileum.     The  left  ureter  is  crossed  by  the  left  colic 
artery,  and  near  the  brim  of  the  pelvis  passes  behind  the  sig- 
moid colon  and  its  mesentery. 

The  pelvic  part  runs  at  first  downward  on  the  lateral  wall 
of  the  pelvic  cavity  under  cover  of  the  peritoneum,  lying  in 
front  of  the  internal  iliac  vessels  and  on  the  inner  side  of  the 
impervious  part  of  the  hypogastric  artery  and  the  obturator 
nerve  and  vessels.  Opposite  the  lower  part  of  the  great 
sacrosciatic  foramen  it  inclines  inward  behind  the  vas  def- 
erens (which  crosses  to  its  inner  side)  and  reaches  the  base 
of  the  bladder,  where  in  the  male  it  is  situated  in  front  of  the 
up[)er  end  of  the  seminal  vesicle  and  at  a  distance  of  about 
two  inches  from  the  opposite  ureter.  Finally,  the  ureters  run 
obliquely   for   about   three-quarters  of   an    inch  through  the 

wall  of  the  bladder  and  open   by  sht-like   apertures  into  the  " 

ca\-ity  of  that  viscus_  at  the  lateral   angles  of  the   trigone.     „eft°od  oVentri;c?rf''thTurlterT^to 
When  the  bladder  is  distended  the  openings  of  the  ureters  are    the  bladder.    (F.  H.  Gerrish.) 
about  two  inches  apart,  but  when  it  is  empty  and  contracted 

the  distance  between  them  is  diminished  by  one-half.  Owing  to  their  oblique  course  through 
the  coats  of  the  bladder,  their  upper  and  lower  walls  become  closely  applied  to  each  other  when 
the  viscus  is  distended,  and,  acting  as  a  valve,  prevent  regurgitation  of  urine  from  the  bladder. 

In  the  female,  the  ureter  forms,  as  it  lies  in  relation  to  the  wall  of  the  pelvis,  the  posterior  boun- 
dary of  a  shallow  depression  named  the  ovarian  fossa,  in  which  the  ovary  is  situated.  It  then 
rims  inward  and  forward  on  the  lateral  aspect  of  the  cervix  of  the  uterus  and  of  the  upper  part 
of  the  vagina  to  reach  the  base  of  the  bladder.     In  this  part  of  its  course  it  is  accompanied  for 


RIGHT  URET 


APPENDIX  (drawn 
up  under) 


il\^) 


Fig.  H24  — The  relations  of  the  pelvic  mesocolon  with  the  wall    the  iliac   sigmoid 
arteries,  and  the  ureter      (Poirier  and  Charp>  ) 


nd  superior  hemorrhoidal 


about  an  inch  by  the  uterine  artery,  which  then  crosses  in  front  of  the  ureter  and  ascends  between 
the  two  layers  of  the  broad  ligament.  The  ureter  is  distant  about  three-quarters  of  an  inch 
from  the  lateral  aspect  of  the  neck  of  the  uterus. 

The  ureter  is  sometimes  double,  and  the  two  tubes  may  remain  distinct  as  far  as  the  base  of 
the  bladder.     On  rare  occasions  they  open  separately  into  the  bladder  cavity. 


1358  THE  URINOGENITAL  0RGA2s^S 

Structure. — The  ureter  is  composed  of  three  coats — fibrous,  muscular,  and  mucous. 

The  fibrous  coat  (tunica  adventitia)  is  the  same  throughout  the  entire  length  of  the  duct,  being 
continuous  at  one  end  with  the  fibrous  capsule  of  the  kidney  at  the  floor  of  the  sinus,  while  at  the 
other  it  is  lost  in  the  fibrous  structure  of  the  bladder. 

In  the  pelvis  of  the  ureter  the  muscular  coat  (tunica  muscularis)  consists  of  tw-o  layers,  an 
internal  longitudinal  and  an  external  circular;  the  longitudinal  fibres  become  lost  upon  the 
sides  of  the  papillae  at  the  extremities  of  the  calices;  while  the  circular  fibres  become  more  prom- 
inent and  resemble  a  small  sphincter.  In  the  ureter  proper  the  muscle  layers  are  very  distinct, 
and  are  three  in  number — an  external  longitudinal  (stratum  externum),  a  middle  circular 
(stratum  medium),  and  an  internal  longitudinal  layer  (stratum  internum).  The  external  longi- 
tudinal layer  is  found  more  prominent  in  the  lower  half  or  lower  third  of  the  ureter. 

The  mucous  coat  (tunica  mucosa)  is  smooth,  and  presents  a  few  longitudinal  folds  which  be- 
come effaced  by  distention.  It  is  continuous  with  the  mucous  membrane  of  the  bladder  below, 
while  above  it  is  prolonged  over  the  papillie  of  the  kidney.  Its  epithelium  is  of  a  peculiar  char- 
acter, and  resembles  that  found  in  the  bladder.  It  is  known  by  the  name  of  transitional  epi- 
thelium. It  consists  of  several  layers  of  cells,  of  which  the  innermost — that  is  to  say,  the  cells  in 
contact  with  the  urine — are  quadrilateral  in  shape,  with  concave  margins  on  their  outer  surface, 
into  which  fit  the  rounded  ends  of  the  cells  of  the  second  layer.  These,  the  intermediate  cells, 
more  or  less  resemble  columnar  epithelium,  and  are  pear-shaped,  w-ith  a  rounded  internal  ex- 
tremity, which  fits  into  the  concavity  of  the  cells  of  the  first  layer,  and  a  narrow  external  extremity 
which  is  wedged  in  between  the  cells  of  the  third  layer.  The  external  or  third  layer  consists  of 
conical  or  oval  cells  varying  in  number  in  different  parts,  and  presenting  processes  which  extend 
down  into  the  basement  membrane.  A  few  racemose  glands  are  at  times  seen  in  the  mucous 
coat. 

Vessels  and  Nerves. — The  arteries  supplying  the  ureter  are  branches  from  the  renal,  sper- 
matic, internal  iliac,  and  inferior  vesical. 

The  nerves  are  derived  from  the  inferior  mesenteric,  spermatic,  and  pelvic  plexuses. 

Applied  Anatomy. — Subcutaneous  rupture  of  the  ureter  is  not  a  common  accident,  but  occa- 
sionally occurs  from  a  sharp  direct  blow  on  the  abdomen,  as  from  the  kick  of  a  horse.  The  ureter 
may  be  either  torn  completely  across,  or  only  partially  divided,  and,  as  a  rule,  the  peritoneum 
escapes  injury.  If  torn  completely  across,  the  urine  collects  in  the  retroperitoneal  tissues;  if  it 
is  not  completely  divided,  the  lumen  of  the  tube  may  become  obstructed  and  hydronephrosis  or 
pyonephrosis  results.  The  ureter  may  be  accidentally  wounded  in  some  abdominal  operations; 
if  this  should  happen,  the  divided  ends  must  be  sutured  together,  or,  failing  to  accomplish  this, 
the  upper  end  must  be  implanted  into  the  bladder  or  the  intestine. 

Stones  (calculi)  not  uncommonly  become  impacted  in  the  ureter.  This  may  occur  at  any 
part,  but  most  commonly  either  at  the  point  where  the  tube  is  crossing  the  pelvic  brim  or  at  the 
termination,  where  it  is  passing  obliquely  through  the  muscular  wall  of  the  bladder.  In  the 
former  case,  an  incision  with  its  centre  opposite  and  one  inch  internal  to  the  anterior  superior 
spine  of  the  ilium  dividing  all  the  structiu'es  down  to  the  peritoneum,  enables  the  operator  to 
reach  the  ureter  by  pushing  the  unopened  peritoneum  inward;  the  stone  can  then  be  felt  in  the 
ureter,  the  wall  of  which  is  incised,  and  the  stone  extracted,  free  drainage  being  provided  for  the 
escaping  urine.  ^Vhen  the  stone  is  impacted  at  the  vesical  end  of  the  tube  a  preliminary  incision 
into  the  bladder  is  required,  and  by  scratching  through  the  mucous  membrane  overlying  it  the 
calculus  can  then  be  removed. 

The  diagnosis  of  ureteral  calculus  is  sometimes  made  by  an  a;-ray  examination.  In  identifying 
any  shadows  in  the  picture  thus  secured,  caution  must  be  exercised  not  to  mistake  similar  shadows 
thrown  by  ■periureteral  phleboliths  in  the  pelvic  veins  as  ureteral  calculi.' 


THE   URINARY   BLADDER    (VESICA   URINARIA)    (Figs.    1127,   1128). 

The  urinary  bladder  is  a  musculomembranous  sac  situated  in  the  pelvis,  behind 
the  pubes,  and  in  front  of  the  rectum  in  the  male,  the  cervix  uteri  and  vagina 
intervening  between  it  and  that  intestine  in  the  female.  The  shape,  position, 
and  relations  of  the  bladder  are  greatly  influenced  by  age,  sex,  and  the  degree  of 
distention  of  the  organ.  During  infancy  it  is  conical  in  shape,  and  projects 
above  the  symphysis  pubis  into  the  hypogastric  region.  In  the  adxdt  cadaver, 
when  quite  empty  and  collapsed  (Figs.  1125  and  1126),  it  is  cup-shaped,  and  on 
vertical  median  section  its  cavity,  with  the  adjacent  portion  of  the  urethra,  presents 
a  Y-shaped  cleft,  the  stem  of  the  Y  corresponding  to  the  urethra.     It  is  placed 

1  Consult  article  by  George  O.  Clark  in  Annals  of  Surgery,  1909.  p.  913. 


THE   URINARY  BLADDER 


1359 


deeply  in  the  pelvis,  flattened  from  before  backward,  and  reaches  as  high  as 
the  upper  border  of  the  symphysis  pubis.  When  empty  and  contracted,  and  as 
seen  immediately  after  death  (as  after  electrocution) ,  the  bladder  is  nearly  spher- 
ical in  shape.  When  slightly  distended,  it  has  a  rounded  form,  and  is  still  con- 
tained within  the  pelvic  cavity  (Fig.  1126),  and  when  greatly  distended  (Figs.  1126 
and  1182),  it  is  ovoid  in  shape,  rising  into  the  abdominal  cavity,  and  often  extend- 


FlG.  1125. — The  empty  bladder.     (Poirier  and  Charpy.) 


Fig.  1126.— Modifications  of  form  of  the 
bladder  during  distention.  (Poirier  and 
Charpy.) 


ing  nearly  as  high  as  the  umbilicus.  It  is  larger  in  its  vertical  diameter  than  from 
side  to  side,  and  its  long  axis  is  directed  from  above  obliquely  downward  and 
backward,  in  a  line  directed  from  some  point  between  the  symphysis  pubis  and 
umbilicus  (according  to  its  distention)  to  the  end  of  the  coccyx.  The  bladder, 
when  distended,  is  slightly  curved  forward  toward  the  anterior  wall  of  the  abdo- 
men, so  as  to  be  more  convex  behind  than  in  front.  When  moderately  distended, 
it  measures  about  five  and  one-half 
inches  (14  cm.)  in  the  vertical  di- 
ameter, four  and  one-half  inches 
(12  cm.)  across,  and  three  inches 
(10  cm.)  antero-posteriorly.  In  the 
female  it  is  larger  in  the  transverse 
than  in  the  vertical  diameter,  and 
its  capacity  is  said  to  be  greater 
than  in  the  male.  The  ordinary 
amount  which  it  can  contain  with- 
out serious  discomfort  is  about  a 
pint. 

The  bladder  is  divided  for  pur- 
poses of  description  into  a  superior, 
an  antero-inferior,  and  two  lateral 
surfaces,  a  base  or  fundus,  and  a 
summit  or  apex. 

Surfaces. — The  superior  or  ab- 
dominal surface  (Figs.  994  and  1106)  is  entirely  free,  and  is  invested  throughout 
by  peritoneum.  It  looks  almost  directly  upward  into  the  abdominal  cavity, 
and  extends  in  an  antero-posterior  direction  from  the  apex  to  the  base  of  the 
bladder.  It  is  in  relation  with  the  small  intestine  and  sometimes  with  the  sig- 
moid flexure,  and,  in  the  female,  with  the  uterus.  On  each  side,  in  the  male, 
a  portion  of  the  vas  deferens  is  in  contact  with  the  hinder  part  of  this  surface, 
lying  beneath  the  peritoneum.  In  the  relaxed  and  empty  condition  of  the  blad- 
der a  transverse  fold  of  peritoneum  {plica  vesicalis  transversa)  is  formed  on  this 
surface. 


Fig.  1127.— Mesal 


1360 


THE   UBINOGENITAL   ORGANS 


The  antero-inferior  or  pubic  surface  (Figs.  337  and  1128)  looks  downward  and 
forward.  In  the  undistended  condition  it  is  uncovered  by  peritoneum,  and  is 
in  relation  with  the  Obturator  internus  muscle  on  each  side,  with  the  rectovesical 
fascia,  and  anterior  true  ligaments  of  the  bladder.  It  is  separated  from  the  body 
of  the  pubis  by  a  triangular  interval,  occupied  by  fatty  tissue,  the  pubovesical 
space  of  Retzius.  As  the  bladder  ascends  into  the  abdominal  cavity  during  dis- 
tention the  distance  between  its  apex  and  the  umbilicus  is  necessarily  diminished, 
and  the  urachus  (Figs.  994  and  1128)  is  thus  relaxed;  so  that,  instead  of  passing 
directly  upward  to  the  umbilicus,  it  descends  first  on  the  upper  part  of  the  anterior 
surface  of  the  bladder,  and  then  curving  upward,  ascends  on  the  back  of  the 
abdominal  wall.  The  peritoneum,  which  follows  the  urachus,  thus  comes  to 
form  a  pouch  of  varying  depth  between  the  anterior  surface  of  the  viscus  and  the 


Prostatic  plexxis 
of  veins. 


Prepuce.- 
FiG.  112S. — Vertical  section  of  bladder,  penis,  and  urethra. 

abdominal  wall  (Fig.  337) .  The  pouch  passes  to  the  neighborhood  of  the  internal 
abdominal  rings.  Thus,  when  the  bladder  is  distended,  the  upper  part  of  its 
anterior  surface  is  in  relation  with  the  urachus  and  is  covered  by  peritoneum. 
The  lower  part  of  its  anterior  surface,  for  a  distance  of  about  two  inches  above 
the  symphysis  pubis,  is  devoid  of  peritoneum,  and  is  in  contact  with  the 
abdominal  wall. 

The  lateral  surfaces  are  invested  behind  and  above  by  peritoneum,  which  extends 
as  low  as  the  level  of  the  impervious  hypogastric  artery;  below  and  in  front  of  this, 
these  surfaces  are  uncovered  by  peritoneum,  and  are  separated  from  the  Levatores 
ani  muscles  and  the  walls  of  the  pelvis  by  a  quantity  of  loose  areolar  tissue  contain- 
ing fat.  In  front  this  surface  is  connected  to  the  rectovesical  fascia  by  a  broad 
expansion  on  either  side,  the  lateral  true  ligaments.     The  vas  deferens  crosses  the 


THE  URINARY  BLADDER  1361 

hinder  part  of  the  lateral  surface  obliquely,  and  passes  between  the  ureter  and  the 
bladder.  When  the  bladder  is  emjity  the  peritoneum  descends  on  the  pelvic 
wall  as  low  as  the  lateral  border  of  the  bladder  and  enters  a  groove  known  as  the 
paravesical  fossa.  The  lateral  surfaces,  the  pubic  surface,  and  the  abdominal 
surface  together  constitute  the  body  of  the  bladder  (corjms  vesicae). 

The  fundus  or  base  {fundus  vesicae)  (Figs.  1128  and  1152)  is  directed  downward 
and  backward,  and  is  partly  covered  by  peritoneum.  In  the  male  the  upper  por- 
tion, to  within  about  an  inch  and  a  half  of  the  prostate,  is  covered  by  the  recto- 
vesical pouch  of  peritoneum  (Fig.  998).  The  lower  part  is  in  direct  contact  with 
the  anterior  wall  of  the  second  part  of  the  rectum,  the  seminal  vesicles,  and  the 
vasa  deferentia  (Figs.  1 128  and  1 135) .  The  ureters  enter  the  bladder  at  the  upper 
part  of  its  base,  about  an  inch  and  a  half  above  the  base  of  the  prostate  gland 
(Fig.  1128). 

The  portion  of  the  bladder  in  relation  with  the  rectum  corresponds  to  a  tri- 
angular space,  bounded  helow,  by  the  prostate  gland;  above,  by  the  rectovesical 
fold  of  the  peritoneum;  and  on  each  side,  by  the  seminal  vesicles  and  the  vas  de- 
ferens. It  is  separated  from  direct  contact  with  the  rectum  by  the  rectovesical 
fascia.  When  the  bladder  is  very  full,  the  peritoneal  fold  is  raised  with  it,  and  the 
distance  between  its  reflection  and  the  anus  is  about  four  inches;  but  this  distance 
is  much  diminished  when  the  bladder  is  empty  and  contracted.  In  the  female, 
the  base  of  the  bladder  is  connected  to  the  anterior  aspect  of  the  cervix  uteri 
by  areolar  tissue,  and  is  adherent  to  the  anterior  wall  of  the  vagina  (Fig.  996). 
Its  upper  surface  is  separated  from  the  anterior  surface  of  the  body  of  the  uterus 
by  the  uterovesical  pouch  of  the  peritoneum  (Fig.  996). 

The  so-called  neck  or  cervix  of  the  bladder  {collum  vesicae),  the  fixed  portion  of 
this  viscus,  is  the  point  of  commencement  of  the  urethra;  there  is,  however,  no 
tapering  part,  which  would  constitute  a  true  neck,  but  the  bladder  suddenly 
contracts  to  the  opening  of  the  urethra  (Fig.  337).  In  the  male  it  is  surrounded 
by  the  prostate  gland  and  its  direction  is  oblique  when  the  individual  is  in  the  erect 
posture  (Figs.  337  and  1128).  In  the  female  its  direction  is  obhquely  downward 
and  forward.  The  so-called  neck  is  the  most  fixed  portion  of  the  bladder,  and  is 
located  one  inch  (2.5  cm.)  behind  the  junction  of  the  inferior  and  middle  thirds 
of  the  symphysis  pubis;  or  two  inches  (5  cm.)  behind  and  below  the  superior  border 
of  the  symphysis. 

The  sumniit  or  apex  (vertex  vesicae)  is  the  portion  of  the  bladder  which  when 
that  organ  is  empty  or  nearly  empty  is  nearest  to  the  upper  border  of  the  symphysis. 
It  is  directed  upward  and  forward.  In  a  distended  bladder  the  apex  is  well  above 
the  pubes  in  the  abdominal  cavity. 

The  urachus  or  middle  umbilical  ligament  (Ugamentum  umbilicale  medium) 
(Fig.  994)  is  the  impervious  remains  of  the  tubular  canal  of  the  allantois,  which 
existed  in  the  embryo,  and  a  portion  of  which  expanded  to  form  the  bladder. 
It  passes  upward,  from  the  apex  of  the  bladder,  between  the  transversalis  fascia 
and  peritoneum,  to  the  umbilicus,  becoming  thinner  as  it  ascends.  It  is  composed 
of  fibrous  tissue,  mixed  with  plain  muscle  fibres. 

■  The  urachus  causes  the  formation  of  a  peritoneal  fold,  the  phca  umbiUcalis  media  (Fig.  V)94). 
On  each  side  of  it  is  placed  a  fibrous  cord,  the  imperious  portion  of  the  hypogastric  artery, 
which,  passing  upward  from  the  side  of  the  bladder,  approaches  the  urachus  above  its  summit. 
Over  each  cord  is  the  fold  known  as  the  plica  umbihcahs  lateraUs  (Fig.  994).  In  the  infant,  at 
birth,  the  urachus  is  occasionally  found  pervious,  so  diat  the  urine  escapes  at  the  umbilicus,  and 
calculi  have  been  found  in  its  canal. 

Ligaments. — ^The  bladder  is  retained  in  its  place  by  ligaments,  which  are  divided 
into  true  and  false.  The  true  ligaments  are  five  in  number — two  anterior,  two 
lateral,  and  the  urachus.  The  false  ligaments,  also  five  in  number,  consist  of 
folds  of  the  peritoneum. 


1362 


THE  URINOGENriAL  ORGANS 


The  two  anterior  true  ligaments  or  puboprostatic  ligaments  (ligamenta  pubo' 
prostaiica)  extend  from  the  back  of  the  ossa  pubis,  one  on  each  side  of  the  sym- 
physis, to  the  front  of  the  neck  of  the  bladder,  over  the  anterior  surface  of  the 
prostate  gland. 

The  two  lateral  true  ligaments,  formed  by  expansions  from  the  fascia  lining  the 
lateral  wall  of  the  pelvis,  are  broader  and  thinner  than  the  preceding.  They 
are  attached  to  the  lateral  parts  of  the  prostate  gland  and  to  the  sides  of  the  base 
of  the  bladder. 

The  urachus  or  middle  umbilical  ligament  is  the  fibromuscular  cord  already  men- 
tioned, extending  between  the  summit  of  the  bladder  and  the  umbilicus. 

The  two  posterior  false  ligaments  pass  forward,  in  the  male,  from  the  sides  of 
the  rectum  (plicae  rectovesicales) ;  in  the  female,  from  the  sides  of  the  uterus  {plicae 
vesicouterinae),  to  the  posterior  and  lateral  aspect  of  the  bladder;  they  form  in 
the  male  the  lateral  boundaries  of  the  rectovesical  pouch  (excavatio  rectovesicalis 
(Figs.  337  and  1067) ;  in  the  female  the  peritoneum  is  reflected  from  the  rectum 
to  tlie  upper  part  of  the  posterior  vaginal  wall,  forming  the  rectovaginal  pouch 


Fig.  1129.— Fibn 
longitudinal  layer, 
Charpy . ) 


!  of  the  external 
(Poirier    and 


Fig,  1130.— Fibres  of  the  middle  Fig.  1131.— Fibres  of  the  inter- 

or    circular     layer.       (Poirier    and     nal    longitudinal    \ayer.       (Poirier 
Charpy.)  and  Charpy.) 


or  pouch  of  Douglas  (Fig.  1068).  It  is  continued  over  the  posterior  surface  and 
fundus  of  the  uterus  on  to  its  anterior  surface  and  then  to  the  bladder,  forming 
here  a  second  but  shallower  pouch,  the  uterovesical  pouch,  bounded  on  either 
side  by  the  uterovesical  or  posterior  false  ligaments  of  the  bladder.  The  poste- 
rior false  ligaments  contain  the  impervious  hypogastric  arteries  and  the  ureters, 
together  with  vessels  and  nerves.  In  the  base  of  each  fold  is  smooth  muscle 
fibre,  the  Rectovesical  muscle  (m.  rectovesicalis). 

The  two  lateral  false  ligaments  are  reflections  of  the  peritoneum,  from  the 
iliac  fossfe  and  lateral  walls  of  the  pelvis  to  the  sides  of  the  bladder.  Each  lateral 
false  ligament  (ligameutum  umhilicale  laterale)  passes  in  front  into  the  pUca 
umbilicalis  lateralis  over  the  corresponding  hypogastric  artery.  The  two  lateral 
reflections  of  peritoneum  are  continuous  in  front  of  the  apex  of  the  bladder,  at 
which  point  the  peritoneum  passes  upon  the  urachus. 

The  superior  or  anterior  false  ligament  (plica  umbilicus  media;  suspensory  liga- 
ment) is  the  prominent  fold  of  peritoneum  extending  from  the  summit  of  the 
bladder  to  the  umbilicus.     It  is  carried  off  from  the  bladder  by  the  urachus.     The 


THE  VBINARY  BLADDER  1363 

peritoneal  fold  over  each  imper\ious  hypogastric  artery  is  called  the  plica  umbili- 
calis  lateralis  (Fig.  994),  and  is  the  prolongation  forward  of  the  ligamentum  nmbil- 
icale  laterale.  Besides  the  true  and  false  ligaments,  the  bladder  receives  support 
from  the  fibrous  tissue  and  unstriated  muscle  about  the  seminal  vesicles,  and  ter- 
minations of  the  ureters  and  vasa  deferentia.  In  the  female  the  connection  with 
the  anterior  vaginal  wall  supports  the  base  of  the  bladder.  In  both  sexes  the  most 
solidly  fixed  part  of  the  bladder  is  about  the  internal  orifice  of  the  urethra. 

Structure. — The  bladder  is  composed  of  tliree  coats — fibrous,  muscvilar,  and  mucous. 

Tlie  fibrous  coat  (tunica  fi})r(tsa)  consists  of  white  fibrous  tissue,  which  supports  the  other 
coats.     It  is  partially  in\fsted  by  peritonevim. 

The  muscular  coat  {tunica  niuscularis)  (Figs.  1129,  1130,  and  1131)  consists  of  three  incom- 
pletely differentiated  layers  of  unstriped  muscular  fibre — an  external  layer,  composed  of  fibres 
having  for  the  most  part  a  longitudinal  arrangement;  a  middle  layer,  in  which  the  fibres  are 
arranged,  more  or  less,  in  a  circular  manner;  and  an  internal  layer,  in  which  the  fibres  have  a 
general  longitudinal  arrangement. 

The  fibres  of  the  external  longitudinal  layer  (stratum  externum)  arise  from  the  posterior  sur- 
face of  the  body  of  the  os  pubis  in  both  sexes  (m.  pubovesicalis),  and  in  the  male  arise  also  from 
the  adjacent  part  of  the  prostate  gland  and  its  capsule.  They  pass,  in  a  more  or  less  longitudinal 
manner,  up  the  anterior  surface  of  the  bladder,  over  its  apex,  and  then  descend  along  its  pos- 
terior surface  to  its  base,  where  they  become  attached  to  the  prostate  in  the  male  ami  to  ihe  front 
of  the  vagina  in  the  female.  At  the  sides  of  the  bladder  the  fibres  are  arranged  iibii(|iicly  and 
intersect  one  another.  The  external  longitudinal  layer  has  been  named  the  Detrusor  urinae 
muscle. 

The  middle  circular  layers  (stratum  medium)  are  very  thinly  and  irregularly  scattered  on  the 
body  of  the  organ,  and,  though  to  some  extent  placed  transversely  to  the  long  axis  of  the 
bladder,  are  for  the  most  part  arranged  obliquely.  Toward  the  lower  j)art  of  the  bladder, 
around  the  neck  and  the  commencement  of  the  urethra,  they  are  disposed  in  a  thick  circular 
layer,  forming  the  sphincter  vesicae,  which  is  continuQus  with  the  muscle  fibres  of  the  prostate 
gland. 

The  internal  longitudinal  layer  (stratum  internum)  is  thin,  and  its  fasciculi  have  a  reticular 
arrangement,  but  with  a  tendency  to  assume  for  the  most  part  a  longitudinal  direction.  Two 
bands  of  oblique  fibres,  originating  behind  the  orifices  of  the  ureters,  converge  to  the  back  part 
of  the  prostate  gland,  and  are  iusrrtnJ,  by  means  of  a  (ibroiis  process,  into  the  so-called  middle 
lobe  of  that  organ.  They  are  the  muscles  of  the  ureters,  described  by  Sir  C.  Bell,  who  supposed 
that  during  the  contraction  of  the  bladder  they  served  to  retain  the  oblique  direction  of  the  ureters, 
and  so  prevent  the  reflux  of  the  urine  into  them. 


Fig.  1132. — Superficial  layer  of  the    epitfielium  of  Fig.  1133. — Deep  layers  of  epithelium  of  bladder, 

the  bladder.     Composed  of  polyhedral  cells  of  vari-  showing  large  club-shaped  cells  above,  and  smaller, 

ous  sizes,  each  with  one,  two,  or  three  nuclei.    (Klein  more  spindle-shaped  cells  below,  each  with  an  oval 

and  Noble  Smith.)  nucleus.      (Klein  and  Noble  Smith.) 

The  mucous  coat  (tunica  mucosa)  is  thin,  smooth,  and  of  a  pale  rosefolor.  It  is  continuous 
above  through  the  ureters  with  the  lining  membrane  of  the  uriniferous  tubes,  and  below  with 
that  of  the  urethra.  Except  at  the  trigone,  it  is  connected  very  loosely  to  the  muscular  coat  by  a 
layer  of  areolar  tissue,  and  is  therefore  thrown  into  folds  or  rugfe  when  the  bladder  is  empty  (Fig. 
1135).  The  epitheliiim  covering  it  is  of  the  transitional  variety,  consisting  of  a  superficial  layer 
of  polyhedral  flattened  cells,  each  with  one,  two,  or  three  nuclei  (Fig.  1132);  beneath  these  is  a 
stratum  of  large  club-shaped  cells  with  the  narrow  extremity  of  each  cell  du-ected  downward  and 
wedged  in  between  smaller  spindle-shaped  cells,  each  with  an  oval  nucleus  (Fig.  1133).  There 
are  no  true  glands  in  the  mucous  membrane  of  the  bladder,  though  certain  mucous  follicles 


1364 


THE  VBINOGENITAL  ORGANS 


which  exist,  especially  near  the  neck  of  the  bladder,  have  been  regarded  as  such.  The  epithelial 
cells  rest  upon  a  basement  membrane,  beneath  which  is  the  fibroelastic  tunica  propria,  which 
contains  diffuse  lymphoid  tissue,  and  in  which  solitary  nodules  have  been  found. 


\     BIDGE  FORMED  BV 
INTERURETEHAL 
MUSCLE 


UVULA    VESICAE 


Fig.  1134.— The  interior  of  the  bl 


wing  the  vesical  trigone.     (Poirier  and  Charpy.) 


The  Interior  of  the  Bladder. — Upon  the  inner  surface  of  the  bladder  are  seen 
the  mucous  membrane,  orifices  of  the  ureters,  the  trigone,  and  the  commencement 
of  the  urethra. 


~'  -l4jj       FIBRES 
W       OR,F,CEOF 


CIRCULAR 


-TRIGONE 
TRANSVERSE 
RES  OF 


LONGITUOINAl 
FIBRES  OF 
TRIGONE 


Fig.  1135. — The  internal  surface  of  the  bladder.     (Poirier  and  Charpy.) 


The  mucous  membrane  of  the  empty  bladder  is  thrown  into  folds  or  ruga,  except 
over  the  trigone,  where  it  is  firmly  adherent  to  the  muscular  coat  and  is  smooth 
(Figs.  1134  and  1135).     The  folds  disappear  when  the  bladder  is  distended. 


THE  URINARY  BLADDER  1365 

The  vesical  trigone  or  the  trigonum  vesicae  (Fig.  1135)  Is  a  smooth,  triangular 
surface,  with  the  apex  directed  forward,  situated  at  the  base  of  the  bladder,  imme- 
diately behind  the  urethral  orifice.  It  represents  an  equilateral  triangle,  the  sides 
measuring  about  one  inch  in  the  empty  bladder  and  increasing  to  about  one  and 
one-half  inches  in  the  distended  bladder.  It  is  paler  in  color  than  the  rest  of  the 
interior,  and  never  presents  anj'  rugae,  even  in  the  contracted  condition  of  the  organ, 
owing  to  the  intimate  adhesion  of  its  mucous  membrane  to  the  subjacent  tissue. 
It  is  bounded  at  each  basal  angle  by  the  orifice  of  a  ureter,  and  at  its  apex  by  the 
orifice  of  the  urethra.  Projecting  from  the  lower  and  anterior  part  of  the  bladder, 
and  reaching  to  the  orifice  of  the  urethra,  is  a  slight  elevation  of  mucous  membrane, 
particularly  prominent  in  old  persons,  called  the  uvula  vesicae. 

Stretching  from  one  ureteral  opening  to  the  other  is  a  smooth,  slightly  curved 
ridge  (torus  interuretericus),  the  convexity  of  which  is  toward  the  urethra.  It  is 
produced  by  transverse  muscle  fibres  beneath  the  mucous  membrane.  The  outer 
prolongations  of  this  ridge  beyond  the  ureteral  orifices  are  called  the  ureteral  folds 
{plicae  uretericae).  They  are  formed  by  the  ureters  as  they  traverse  the  bladder 
wall.  About  the  urethral  orifice  are  slight  radial  folds  of  mucous  membrane, 
which  are  continuous  with  the  longitudinal  folds  of  the  prostatic  urethra. 

The  internal  urethral  orifice  (orificium  urethrae  internum)  is  sickle-shaped  and 
is  surrounded  by  a  circular  prominence  {annulus  urethralis),  which  is  most  dis- 
tinct in  the  male. 

Vessels  and  Nerves. — The  arteries  (Fig.  472)  supplying  the  bladder  are  the  superior, 
middle,  and  inferior  vesical  in  the  male,  with  additional  branches  from  the  uterine  and  vaginal 
in  the  female.  They  are  all  derived  from  the  anterior  trunk  of  the  internal  iliac.  The  obturator 
and  sciatic  arteries  also  supply  small  visceral  branches  to  the  bladder.  The  veins  form  a  com- 
pllraicd  plexus  around  the  neck,  sides,  and  base  of  the  bladder  (Fig.  524).  The  veins  communi- 
cate below  with  tlie  plexus  about  the  prostate  and  terminate  in  the  internal  iliac  vein. 

The  lymphatics  are  few  in  number;  they  form  two  plexuses,  one  in  the  muscular  and  another 
in  the  deep  tissue  of  the  mucous  coat,  and  accompany  the  bloodvessels.  The  subepithelial  portion 
of  the  mucous  membrane  of  the  bladder  contains  no  lymphatics  whatever  (Sappey).  The  mus- 
cular tissue  contains  a  few  lymphatics.  The  subperitoneal  tissues  contain  the  usual  number. 
The  collecting  trunks  from  the  anterior  surface  terminate  in  the  external  iliac  nodes.  The 
trunks  from  the  posterior  surfa>:'e  terminate  in  tlie  internal  iliac  nodes,  the  hjrpogastric  nodes, 
and  the  nodes  in  front  of  the  sacral  promontory. 

The  nerves  are  derived  from  the  pelvic  plexus  of  the  sympathetic  and  from  the  third  and 
fourth  sacral  nerves ;  the  former  supplying  the  upper  part  of  the  organ,  the  latter  its  base  and 
neck.  According  to  F.  Darwin,  the  sympathetic  fibres  have  ganglia  connected  with  them,  which 
send  branches  to  the  vessels  and  to  the  muscular  coat. 

Surface  Form. — The  surface  form  of  the  bladder  varies  with  its  degree  of  distention  and 
under  other  circumstances.  In  the  young  child  it  is  represented  by  a  conical  figure,  the  apex 
of  which,  even  when  the  viscus  is  empty,  is  situated  in  the  hypogastric  region,  about  an  inch 
above  the  level  of  the  symphysis  pubis.  In  the  adult,  when  the  bladder  is  empty,  its  apex  does 
not  reach  above  the  level  of  the  upper  border  of  the  symphysis  pubis,  and  the  whole  organ  is 
situated  in  the  pelvis;  the  neck,  in  the  male,  corresponding  to  a  line  drawn  horizontally  backward 
through  the  symphysis  a  little  below  its  middle.  As  the  bladder  becomes  distended,  it  gradually 
rises  out  of  the  pelvis  into  the  abdomen,  and  forms  a  swelling  in  the  hypogastric  region,  which  is 
jierceptible  to  the  hand  as  well  as  to  percussion.  In  extreme  distention  it  reaches  into  the  umbili- 
cal region.  Under  these  circumstances  the  lower  part  of  its  anterior  surface,  for  a  distance  of 
about  two  inches  above  the  symphysis  pubis,  is  closely  applied  to  the  abdominal  wall,  without 
the  intervention  of  peritoneum,  so  that  it  can  be  tapped  by  an  opening  in  the  middle  line  just 
above  the  symphysis  pubis,  without  any  fear  of  wounding  the  peritoneum.  When  the  rectum 
is  distended,  the  prostatic  portion  of  'the  urethra  is  elongated  and  the  bladder  lifted  out  of 
the  pelvis  and  the  peritoneum  pushed  upward.  Advantage  is  taken  of  this  by  some  sur- 
geons in  performing  the  operation  of  suprapubic  oystotomy.  The  rectum  is  distended  by  a 
rubber  bag,  which  is  introduced  into  this  cavity  empty,  and  is  then  filled  with  ten  or  twelve 
ounces  of  water.  If,  now,  the  bladder  is  injected  with  about  half  a  pint  of  some  antiseptic  fluid 
it  will  appear  above  the  pubes  plainly  perceptible  to  the  sight  and  touch.  The  peritoneum  will 
be  pushed  out  of  the  way,  and  an  incision  three  inches  lotig  may  be  made  in  the  hnea  alba, 
from  the  symphysis  pubis  upward,  without  any  great  risk  of  wounding  the  peritoneum.    Other 


1366  THE  UBINOGENITAL  ORGANS 

surgeons  object  to  the  employment  of  this  bag,  as  its  use  is  not  unattended  with  risk,  since  it  causes 
pressure  on  the  prostatic  veins  and  hence  produces  congestion  of  the  vessels  over  the  bladder 
and  a  good  deal  of  venous  hemorrhage. 

When  distended,  the  bladder  can  be  felt  in  the  male,  from  the  rectum,  behind  the  prostate, 
and  fluctuation  can  be  perceived  by  a  bimanual  examination,  one  finger  being  introduced  into  the 
rectum  and  the  distended  bladder  being  tapped  on  the  front  of  the  abdomen  with  the  finger  of 
the  other  hand.  This  portion  of  the  bladder — that  is,  the  portion  felt  in  the  rectum  by  the 
finger — is  uncovered  by  peritoneum. 

Applied  Anatomy. — A  certain  defect  of  development  in  which  the  bladder  is  implicated  is 
known  under  the  name  of  extroversion  of  the  bladder.  In  this  condition  the  lower  part  of  the 
abdominal  wall  and  the  anterior  wall  of  the  bladder  are  wanting,  so  that  the  posterior  surface 
of  the  bladder  presents  on  the  abdominal  surface,  and  is  pushed  forward  by  the  pressure  of  the 
viscera  within  the  abdomen,  forming  a  red,  vascular  protrusion,  on  which  the  openings  of  the 
ureters  are  visible.  The  penis,  except  the  glans,  is  rudimentary,  and  is  cleft  on  its  dorsal  sur- 
face, exposing  the  floor  of  the  urethra — a  condition  known  as  epispadias.  The  pelvic  bones 
are  also  arrested  in  development  (see  p.  220). 

The  bladder  may  be  ruptured  by  violence  applied  to  the  abdominal  wall  when  the  viscus  is 
distended  without  injury  to  the  bony  pelvis,  or  it  may  be  torn  in  case  of  fracture  of  the  pelvis. 
The  rupture  may  be  either  intraperitoneal  or  extraperitoneal,  that  is — may  implicate  the  superior 
surface  of  the  bladder  in  the  former  case,  or  one  of  the  other  surfaces  in  the  latter.  Rupture 
of  the  antero-inferior  surface  alone  is,  however,  very  rare.  Until  recently  intraperitoneal  rupture 
was  uniformly  fatal,  but  now  abdominal  section  and  suturing  the  rent  with  Lembert  sutures 
often  saves  the  patient.  The  sutures  are  inserted  only  through  the  peritoneal  and  muscular 
coats  in  such  a  way  as  to  bring  the  serous  surfaces  at  the  margin  of  the  wound  into  apposition, 
and  one  is  also  inserted  just  beyond  each  end  of  the  wound.  The  bladder  should  be  tested  as  to 
whether  it  is  water-tight  before  closing  the  external  incision. 

The  muscular  coat  of  the  bladder  undergoes  hypertrophy  in  cases  in  which  there  is  any  per- 
sistent obstruction  to  the  flow  of  urine.  Under  these  circumstances  the  bundles  of  which  the 
muscular  coat  consists  become  much  increased  in  size,  and,  interlacing  in  all  directions,  give  rise 
to  what  is  known  as  \he  fasciculated  bladder.  Between  these  bundles  of  muscle  fibres  the  mucous 
membrane  may  bulge  out,  forming  sacculi,  constituting  the  sacculated  bladdfr,  and  in  these  little 
pouches  phosphatic  concretions  may  collect,  forming  encysted  calculi.  The  mucous  membrane  is 
very  loose  and  lax,  except  over  the  trigone,  to  allow  of  the  distention  of  the  viscus. 

Various  forms  of  tumors  have  been  found  springing  from  the  wall  of  the  bladder.  The  inno- 
cent tumors  are  the  papilloma  and  the  mucous  polypus,  arising  from  the  mucous  membrane;  the 
fibrous  tumor,  from  the  deep  mucous  tissue;  and  the  myoma,  originating  in  the  muscle  tissue; 
and,  very  rarely,  dermoid  tumors,  the  exact  origin  of  which  it  is  difficult  to  explain.  Of  the 
malignant  tumors,  epitheliomata  are  the  most  common,  but  sarcomata  are  occasionally  found  in 
the  bladders  of  children. 

Puncture  of  the  bladder  is  performed  above  the  pubes  without  wounding  the  peritoneum. 
Suprapubic  cystotomy  is  considered  above  under  the  heading  of  Surface  Form.  This  operation 
may  be  employed  to  permit  of  the  removal  of  a  calculus,  and  is  then  called  suprapubic  lithotomy. 

THE   MALE   URETHRA    (URETHRA   VIRILIS)    (Figs.  1136,  1137). 

The  urethra  in  the  male  extends  from  the  neck  of  the  bladder  at  the  internal 
orifice  of  the  urethra  {orificmm  urethrae  internum)  to  the  meatus  urinarius,  the 
external  orifice  of  the  urethra  {orificium  urethrae  externum),  at  the  end  of  the  penis. 
The  internal  orifice  has  been  described  (p.  1363).  The  urethra  presents  a  double 
curve  in  the  flaccid  state  of  the  penis  (Fig.  1128),  but  in  the  erect  state  of  this 
organ  it  forms  only  a  single  curve,  the  concavitj^  of  which  is  directed  upAvard. 
It  presents  three  important  constrictions — (1)  at  the  beginning,  (2)  in  the  mem- 
branous portion,  (3)  at  the  end.  Its  length  varies  from  seA'en  to  eight  inches 
(17  to  20  cm.);  and  it  is  divided  into  three  portions,  the  prostatic,  membranous, 
and  spongy,  the  structure  and  relations  of  which  are  essentially  different.  Except 
during  the  passage  of  the  urine  or  semen,  the  urethra  is  a  mere  transverse,  T- 
shaped,  or  crescentic  cleft  or  slit  (Fig.  1137),  with  its  upper  and  under  surfaces  in 
contact.  At  the  meatus  urinarius  the  slit  is  vertical,  and  in  the  prostatic  portion 
somewhat  arched  (Fig.  1137). 

The  prostatic  portion  (jmrs  prostatica)  (Figs.  1136  and  1171),  the  AA-idest 
part  of  the  canal,  is  about  an  inch  in  length.     It  is  between  the  internal  orifice 


THE  MALE   URETHRA 


1.367 


of  the  urethra  and  the  deep  layer  of  the  triangular  ligament  and  lies  within 
the  pelvic  cavity.  It  passes  almost  vertically  through  the  prostate  gland  from 
its  base  to  its  apex,  lying  nearer  its  anterior  than  its  posterior  surface.  The 
gland  seeTus  to  completely  surround  this  portion  of  the  urethra  (Fig.  1166),  but 
the  glandular  substance  proper  does  not  (Fig.  1169).  The  gland  is  like  a  clasp 
open  in  front,  and  the  open  part  of  the  clasp  is  closed  by  the  prostatic  muscle. 
The  form  of  the  canal  is  spindle-shaped,  being  wider  in  the  middle  than  at  either 
extremity,  and  narrowest  below,  where  it  joins  the  membranous  portion.  Except 
during  the  passage  of  fluid,  the  canal  is  in  a  collapsed  state  and  is  horseshoe-shaped 
on  trans-section,  the  anterior  M'all  resting 
upon  the  posterior  wall  (Fig.  1137),  and 
the  mucous  membrane  exhibiting  longi- 
tudinal folds.  When  distended,  the  largest 
portion  of  the  prostatic  urethra  in  the  ca- 
daver has  a  diameter  of  about  one-half  inch 
(12  mm.). 

Upon  the  posterior  wall  or  floor  of  the 
canal  is  a  narrow  longitudinal  ridge,  the 
verumontanum  or  caput  gallinaginis  (Figs. 
1136  and  1171)  {crista  iirethralis),  formed 
by  an  elevation  of  the  mucous  membrane 
and  its  subjacent  tissue  (Fig.  1170).  It  is 
about  16  mm.  in  length  and  about  3  mm. 
in  height,  and  contains,  according  to  Kobelt, 
muscle  and  erectile  tissues.  On  either 
side  of  the  verumontanum  is  a  slightly 
depressed  fossa,  the  prostatic  sinus,  the  floor 
of  which  is  perforated  by  numerous  aper- 
tures, the  orifices  of  the  prostatic  ducts 
(Figs.  1136  and  1171),  from  the  lateral  lobes 
of  the  glands;  the  ducts  of  the  middle  lobe 
open  behind  the  verumontanum.  At  the 
forepart  of  the  verumontanum,  in  the 
middle  line,  is  a  depression,  the  sinus 
pocularis  {idriculus  prostaticus)  (Figs.  337 
and  1171),  upon  the  margins  of  which  are 
the  slit-like  openings  of  the  ejaculatory  ducts 
(Fig.  1171).  The  sinus  pocularis  forms  a 
cul-de-sac  about  a  quarter  of  an  inch  in 
length,  which  runs  upward  and  backward 
in  the  substance  of  the  prostate  into  the 
so-called  middle  lobe;  its  prominent  ante- 
rior wall  partly  forms  the  verumontanum. 
Its  walls  are  composed  of  fibrous  tissue, 

muscle  fibres,  and  mucous  membrane,  and  numerous  small  glands  open  on  its 
inner  surface.  It  has  been  called  the  uterus  masculinus,  because  it  is  developed 
from  the  united  lower  ends  of  the  atrophied  JMiillerian  ducts,  and  therefore  is 
homologous  with  the  uterus  and  vagina  in  the  female. 

The  membranous  portion  {fars  memhranacea)  (Figs.  1128  and  1136)  lies 
between  the  two  layers  of  the  triangular  ligament,  and  extends  downward  and  for- 
ward between  the  apex  of  the  prostate  and  the  bulb  of  the  corpus  spongiosum. 
It  is  the  narrowest  part  of  the  canal  (excepting  the  meati),  has  a  calibre  of  about 
one-third  of  an  inch  (8  mm.),  and  measures  about  half  an  inch  (10  to  12  mm.) 
in  length.     Its  anterior  concave  surface  is  placed  about  an  inch  below  and  behind 


Fossa 
name. 


rethra,  laid  open 
rface).     (Testut.) 


1368 


THE  UBINOGENITAL   ORGANS 


the  pubic  arch,  from  which  it  is  separated  by  the  dorsal  vessels  and  nerve  of  the 
penis,  and  some  muscle  fibres.  Its  posterior  convex  surface  is  separated  from 
the  rectum  by  a  triangular  mass  of  tissue  which  constitutes  the  perineal  body. 
As  it  pierces  the  superficial  layer  of  the  triangular  ligament  the  fibres  around  the 
opening  are  prolonged  over  the  tube  and  fix  the  two  structures  firmly  to  each  other. 
The  membranous  urethra  is  surrounded  ,by  cavernous  tissue  and  by  the  Compres- 
sor urethrae  muscle  {in.  sphincter  urethrae  membranaceae)  (Fig.  .338).  On  the  floor 
of  the  membranous  urethra  is  the  anterior  extremity  of  the  verumontanum. 
Behind  this  part  of  the  urethra,  on  each  side  of  the  middle 
a.  .«■.  line,  are  Cowper's  glands  (Figs.  334  and  1128).     When  the 

urethra  is  empty  the  mucous  membrane  of  this  part  is 
thrown  into  longitudinal  folds,  which  are  obliterated  by  dis- 
tention. 

The  penile  or  spongy  portion  (pars  cavernosa)  (Figs. 
1136  and  1138)  is  the  longest  part  of  the  urethra,  and  is 
contained  in  the  corpus  spongiosum.  It  is  about  six  inches 
(15  cm.)  in  length,  and  extends  from  the  termination  of  the 
membranous  portion  to  the  meatus  urinarius.  Its  proximal 
end  is  fixed  in  position  and  unchangeable  in  direction.  Its 
distal  end  is  movable  and  changeable  in  direction.  Com- 
mencing just  below  the  triangular  ligament  it  is  first  directed 
forward  through  the  bulb;  it  then  passes  downward  and  for- 
ward, the  turn  beginning  at  the  point  of  attachment  of  the 
suspensory  ligament  of  the  penis  (Fig.  1128).  The  direction 
of  the  spongy  portion  of  the  urethra  is  changed  by  altera- 
tions in  the  position  of  the  penis.  When  the  canal  is  closed 
the  anterior  and  posterior  walls  are  in  contact  (roof  and 
floor),  except  in  the  glans  penis,  where  the  lateral  walls 


,{«SI.. 


i^ 


MM 


Fig.  1137.  —  Cross-sec- 
tion of  ihe  male  urethra 
at  various  distances  from 
its  free  end,  showing 
marked  alterations  of 
form.     (Testut.) 


Fig.  1138.— The  distal  port  on  of  the  male  urethra,  laid  open  on  its 
posterior  (under)  surface,  showing  the  lacunte.     (Testut.) 


come  together.  The  calibre  of  the  spongy  urethra  varies  in  different  por- 
tions of  the  tube.  It  is  narrow  and  of  uniform  size  in  the  body  of  the  penis, 
measuring  about  one-third  of  an  inch  (9  mm.)  in  diameter;  it  is  dilated  behind, 
within  the  bulb  (13  to  14  mm.),  and  again  anteriorly  within  the  glans  penis  (12 
to  14  mm.),  where  it  forms  the  fossa  navicularis  (fossa  navicularis  urethrae).  In 
the  roof  of  the  fossa  navicularis  there  is  a  transverse  fold  of  mucous  membrane, 


THE  MALE  VB.ETHBA  1369 

the  valve  of  Guerin  (valvtilae  fossae  navicularis),  g'uarding  a  recess,  the  lacuna 
magna.     The  urethra  opens  anteriorly  by  the  meatus  urinarius. 

The  bulbous  portion  is  a  name  sometimes  given  to  the  posterior  part  of  the  spongy 
portion  contained  within  the  bulb. 

The  meatus  urinarius  or  external  orifice  of  the  urethra  {orificiiim  urethrae  e.rtermnn) 
(Figs.  1136  and  113S)  is  the  most  contracted  part  of  the  urethra.  Its  calibre 
averages  about  7  mm.  It  is  a  vertical  slit  (Fig.  1137),  bounded  on  each  side  by 
a  small  lip  or  labium. 

The  inner  surface  of  the  lining  membrane  of  the  urethra,  especially  on  the  floor 
of  the  spongy  portion,  presents  the  orifices  of  numerous  mucous  glands  (Fig.  1138) 
situated  in  the  subepithelial  tissue,  and  named  the  glands  of  Littre  (gla?uhilae 
urethrales).  Besides  these  there  are  a  number  of  little  recesses  or  follicles,  of 
varying  sizes,  called  lacunae  {lacunae  urethrales).  Their  orifices  are  directed  for- 
ward, so  that  they  may  easily  intercept  the  point  of  a  catheter  in  its  passage  along 
the  canal.  One  of  these  lacunae,  larger  than  the  rest,  is  situated  in  the  upper  sur- 
face of  the  fossa  navicularis,  about  half  an  inch  from  the  orifice;  it  is  called  the 
lacuna  magna  (Fig.  1138).  Into  the  bulbous  portion  are  found  opening  the  ducts 
of  Cowper's  glands. 

Structure. — ^The  male  urethra  is  composed  of  three  coats — mucous,  muscular,  and  fibrous. 

The  mucous  coat  forms  part  of  the  urinogenital  mucous  membrane.  It  is  continuous  with 
the  mucous  membrane  of  the  bladder,  ureters,  and  kidneys;  externally  with  the  integument 
covering  the  glans  penis;  and  is  prolonged  into  the  ducts  of  the  glands  which  open  into  the 
urethra — viz.,  Cowper's  glands  and  the  prostate  gland — into  the  vasa  deferentia  and  the  seminal 
vesicles  through  the  ejaculatory  ducts.  The  mucous  membrane  is  arranged  in  longitudinal 
folds  when  the  tube  is  empty.  Small  papillae  are  found  upon  it  near  the  orifice,  and  its  epithelial 
lining  varies  in  the  different  divisions.  The  prostatic  portion  is  lined  by  transitional  cells,  con- 
tinued from  the  bladder,  the  membranous  portion  by  stratified  columnar  cells,  and  the  penile 
portion,  by  simple  columnar  epithelium,  except  in  the/oraa  navicularis,  where  stratified  squamous 
cells  are  found.  The  cells  rest  upon  a  basement  membrane  supported  by  the  tunica  propria, 
composed  of  fibroelasiic  tissue.  In  the  latter  are  found  diffuse  lymphoid  tissue  and  racemose 
glands,  the  urethral  glands  (glands  of  Littre). 

The  muscular  layer  is  continuous  with  the  muscle  of  the  prostate  and  bladder,  and  lies  external 
to  the  mucous  coat.  It  is  composed  of  nonstriated  muscle  arranged  in  an  outer  layer  of  circular 
fibres  (stratum  eirculare)  and  an  inner  layer  of  longitudinal  fibres  (stratum  longitudinale).  These 
layers  are  prominent  in  the  prostatic  urethra,  less  so  in  the  membranous  portion,  and  ultimately 
disappear  in  the  spongy  part.  The  longitmlinal  fibres,  when  contracted,  shorten  the  urethra 
and  increase  its  diameter.  The  cii'cular  fibres  are  in  a  state  of  tonic  contraction  and  close  the 
urethra,  constituting,  ap])arently,  a  real  sphincter  (ZeissI,  Zuckerkandl).  The  so-called  sphincter 
of  the  urethra,  the  Accelerator  uiinae,  is  a  voluntary  muscle  and  is  not  the  real  sphincter.  Out- 
side of  the  muscle  layer  of  tl>e  urethi-a  is  the  tissue  of  the  corpus  spongiosum. 

The  fibrous  coat  (tunica  fibrosa)  consists  chiefly  of  white  fibrous  tissue  supporting  the  pre- 
ceding coats. 

Applied  Anatomy. — The  urethra  may  be  ruptured  by  the  patient  falling  astride  of  any  hard 
substance  and  striking  his  perineum,  so  that  the  urethra  is  crushed  against  the  pubic  arch. 
Bleeding  will  at  once  take  place  from  the  urethra,  and  this,  together  with  the  bruising  in  the 
perineum  and  the  history  of  the  accident,  will  at  once  point  to  the  nature  of  the  injury. 

Rupture  of  the  urethra  leads  to  extrava^sation  of  urine.  In  rupture  back  of  the  superior  layer 
of  the  triangular  ligament  the  urine  usually  follows  the  rectum  and  reaches  the  margin  of  the 
anus.  Rupture  of  the  membranous  part  liberates  urine  between  the  two  layers  of  the  triangular 
ligaipent,  where  it  remains  until  a  path  of  exit  is  made  by  suppuration  or  the  surgeon's  knife. 
In  rupture  superficial  to  the  anterior  layer  of  the  ligament  the  urine  passes  into  the  scrotum  and 
may  mount  up  to  the  abdomen  between  the  symphysis  and  the  pubic  spine,  between  which 
points  the  deep  layer  of  the  superficial  fascia  is  not  attached.  It  cannot  pass  to  the  thigh  nor 
cross  the  midline,  because  the  fascia  is  attached  to  the  fascia  lata  and  at  the  midline. 

The  applied  anatomy  of  the  urethra  is  of  considerable  importance  in  connection  with  the 
passage  of  instruments  into  the  bladder.  Otis  was  the  first  to  point  out  that  the  urethra  is 
capable  of  great  dilatation,  so  that,  excepting  through  the  external  meatus,  an  instrument  corre- 
sponding to  20  to  28  French  gauge  can  usually  be  passed  without  damage.  The  orifice  of 
the  lu'etlira  is  not  so  dilatable,  and  therefore  may  require  slitting,  although  the  introduction 
of  the  Oberlander  dilator,  which  is  expanded  after  introduction,  renders  slitting  of  the  meatus 
seldom  necessary  in  cases  of  clu-onic  gonorrhoea.     A  recognition  of  this  dilatability  caused  Bige- 


1370  THE  VBINOGEXITAL  ORGANS 

low  to  very  considerably  modify  the  operation  of  lithotrity  and  introduce  that  of  litholaiiaxy. 
In  passing  a  fine  catheter,  the  point  of  the  instrument  after  it  has  passed  the  lacuna  magna  should 
be  kept  as  far  as  possible  along  the  upper  wall  of  the  canal,  as  the  point  is  otherwise  verv  liable 
to  enter  one  of  the  lacunae.  Stricture  of  the  urethra  is  a  disease  of  very  common  occurrence,  and 
is  generally  situated  in  the  spongy  portion  of  the  urethra,  most  commonly  in  the  bulbous  portion 
just  in  front  of  the  membranous  urethra,  but  in  a  very  considerable  number  of  cases  in  the  penile 
part  of  the  canal.  Even  in  a  normal  urethra,  and  very  markedly  in  an  inflamed  urethra,  a 
bougie  encounters  resistance  behind  the  bulb.  This  is  usually  supposed  to  be  due  to  spasm  of 
the  Compressor  urethrse  muscle. 

In  irrigation  of  the  urethra  by  gravity  fluid  tends  to  block  at  the  same  point,  especially  if  it  is 
thrown  in  suddenly  or  forcibly.  If  a  reservoir  is  raised  seven  and  one-half  feet  from  the  floor, 
and  if  a  patient  sits  on  a  chair  or  lies  upon  a  bed,  fluid  can  be  readily  made  to  pass  by  hydraulic 
pressure  from  the  meatus  to  the  bladder.  Spasm  may  temporarily  prevent  the  inflow,  but  the 
weight  of  the  column  of  fluid  soon  tires  out  the  muscle  and  causes  it  to  relax.  Relaxation  is 
favored  by  having  the  patient  take  slow,  deep  breaths,  and  make  efforts  at  urination  (Valentine). 

Chronic  gonorrhea  is  frequently  kept  up  by  persistent  inflammation  of  the  ducts  and  follicles 
in  the  mucous  membrane.  This  condition  is  known  as  chronic  glandular  urethritis  or  para- 
urethritis. In  these  crypts  and  glands  gonococci  may  remain  when  gonorrhea  appears  to  have 
passed  away,  and  from  time  to  time  reinfection  of  the  urethra  may  arise  from  such  a  source. 

Median  urethrotomy  or  perineal  section  is  opening  of  the  membranous  urethra.  Through  such 
an  opening  the  bladder  can  be  drained  and  explored,  and  the  operation  is  sometimes  called 
median  cystotomy. 

In  lateral  lithotomy  the  knife  enters  the  membranous  urethra  and  strikes  the  groove  of  the 
staff.  Its  edge  is  then  turned  toward  the  left  ischial  tuberosity  and  is  carried  along  the  groove 
into  the  bladder,  dividing  the  membranous  urethra,  the  prostatic  urethra,  the  posterior  layer  of 
the  triangular  ligament,  the  Compressor  urethrse  muscle,  anterior  fibres  of  the  Levator  ani 
muscle  and  the  left  lobe  of  the  prostate  gland. 


THE  FEMALE  URETHRA  (URETHRA  MULIEBRIS). 

The  female  urethra  is  a  narrow  membranous  canal,  about  an  inch  and  a  half  in 
length,  extending  from  the  internal  urethral  orifice  at  the  neck  of  the  bladder  to 
the  meatus  urinarius.  It  is  placed  behind  the  symphysis  pubis,  embedded  in  the 
anterior  wall  of  the  vagina,  and  its  direction  is  obliquely  downward  and  forward; 
its  course  is  slightly  curved  and  the  concavity  directed  forward  and  upward. 
Ordinarily  the  wall  is  collapsed  so  that  the  lumen  is  of  stellate  outline;  the  urethra 
may  be  dilated  to  about  a  quarter  of  an  inch  (6  to  8  mm.);  toward  the  bladder 
the  calibre  increases  slightly.  The  urethra  perforates  both  layers  of  the  tri- 
angular ligament,  and  its  external  orifice  is  situated  directly  in  front  of  the  vaginal 
opening  and  about  an  inch  behind  the  glans  clitoridis. 

Structure. — The  female  urethra  consists  of  three  coats — mucous,  muscular,  and  fibrous. 

The  mucous  coat  (tunica  mucosa^  is  pale,  continuous  externally  with  that  of  the  vulva,  and 
internally  with  that  of  the  bladder.  It  is  thrown  into  longitudinal  folds,  one  of  which,  placed 
along  the  floor  of  the  canal,  extends  from  the  vesical  trigone  almost  to  the  external  orifice  of  the 
urethra.  It  is  called  the  crest  (crista  urethralis).  The  outline  of  the  urethra  is  stellate  when 
collapsed,  because  of  the  formation  of  numerous  longitudinal  folds.  It  is  lined  by  laminated 
epithelium,  which  becomes  transitional  near  the  bladder.  Many  mucous  glands  open  into  the 
urethra,  and  there  are  numerous  lacunfe.  On  either  side  of  the  terminal  portion  of  the  urethra 
lie  a  group  of  mucous  glands  (glandulae  paraurethrales),  each  lateral  group  opening  into  the  vesti- 
bule by  a  common  duct  (ductus  paraurethralis)  at  the  side  of  the  urinary  meatus.  These  glands 
are  regarded  as  being  homologous  with  the  prostate  in  the  male. 

The  mucous  coat  is  lined  by  .stratified  .irpiamous  cells  resting  upon  a  basement  membrane  and 
by  papillated  tunica  propria;  the  latter  consists  of  fibroelastic  tissue  containing  the  smaller 
vessels,  some  lymphoid  tissue,  and  a  few  racemose  glands.  In  the  deeper  portion  of  the  tunica 
propria  the  structure  is  very  vascular,  is  of  a  spongy  nature,  and  constitutes  the  erectile  tissue. 

The  muscular  coat  (tunica  wuseularis)  is  continuous  with  that  of  the  bladder;  it  extends  the 
whole  length  of  the  tube,  and  consists  of  an  internal  layer  of  nonstriated  longitudinal  fibres 
(stratum  longitudinale)  and  an  external  layer  of  nonstriated  circular  fibres  (stratum,  circulare). 
In  addition  to  these,  between  the  two  layers  of  the  triangular  ligament,  the  female  urethra  is  sur- 
rounded by  the  Compressor  urethrse  muscle,  as  in  the  male. 


THE  TEfiTICLES  AND   THEIR   COVERINGS 


1371 


The  fibrous  coat  consists  of  \Yhite  fibrous  tissue  which  supports  the  other  coats. 

The  urethra,  because  it  is  not  surrounded  by  dense  resisting  structures,  as  in  the  male,  aduiite 
of  creat  dilatation,  which  enables  the  surgeon  to  remove  with  considerable  facility  calculi  or 
other  foreign  bodies  from  the  cavity  of  the  bladder. 


Fig.  1139. — Mesal  section  through  the  pelv 


5  of  a  woman,  aged  twenty-one  years. 
(Corning.) 


Peritoneum  in  blue. 


THE  MALE  REPRODUCTIVE  ORGANS. 

The  male  reproductive  organs  (ore/ana  genitalia  virilia)  include  the  testes,  the 
vasa  deferentia,  the  seminal  vesicles,  the  ejaculatory  ducts,  and  the  penis,  together 
with  the  following  accessory  structures — viz.,  the  prostate  and  Cowper's  glands. 


THE  TESTICLES  (TESTES)  AND  THEIR  COVERINGS  (Figs.   1140,    1141). 

The  testes  are  two  glandular  organs,  which  secrete  the  spermatozoa;  they  are 
situated  in  the  scrotum,  being  suspended  by  the  spermatic  cords.  At  an  early 
period  of  fetal  life  the  testes  are  contained  in  the  abdominal  cavity,  behind  the 
peritoneum.  Before  birth  they  descend  to  the  inguinal  canal,  along  which  they 
pass  with  the  spermatic  cord,  and  emerging  at  the  external  abdominal  ring,  they 
descend  into  the  scrotum,  becoming  invested  in  their  course  by  coverings  derived 


1372 


THE  VRINOGENITAL  ORGANS 


from  the  serous,  muscular,  and  fibrous  layers  of  the  abdominal  parietes  as  well 

as  by  the  scrotum  proper. 

The  coverings  of  the  testis  are  the  following: 

Skin       )  o      . 

bcrotum. 


Dartos 

Intercolumnar  or  External  spermatic  fascia. 

Cremasteric  fascia. 

Infundibuliform  or  Internal  spermatic  fascia. 

Tunica  vaginalis. 


^IGUINAL   CA 


CREMASTERIC 

AND    FASC 

INTEHCO 

FASC 


4LF   OF  SCF 


Fig.  1140.— The  scrotum.     On  the  left  side  the  cavity  of  the  tunica  vaginalis  has  been  opened;  on  the 
right  side  only  the  layers  superficial  to  the  Cremaster  have  been  removed.     (Testut.) 

The  scrotum'  (Figs.  1140  and  1141)  is  a  cutaneous  pouch  which  contains 
the  testes  and  part  of  the  spermatic  cords.  It  is  divided  on  its  surface  into  two 
lateral  portions  by  a  median  line  or  raphe  (raphe  scrofi),  which  is  continued 
forward  to  the  under  surface  of  the  penis  and  backward  along  the  middle  line 
of  the  perineum  to  the  anus.  Of  these  two  lateral  portions,  the  left  is  usually 
longer  than  the  right,  to  correspond  with  the  usual  greater  length  of  the  left  sper- 
matic cord.  Its  external  aspect  varies  under  different  circumstances;  thus,  under 
the  influence  of  warmth  and  in  old  and  debilitated  persons  it  becomes  elongated 
and  flaccid  but  under  the  influence  of  cold  or  sexual  excitement  and  in  the  young 


.  bag  of  leather  or  skin;  through  a  blunder  two  of  the  letters  in  the  word  have  become 


THE  TESTICLES  AND  THEIR  CO  VEHINGS 


i;i7: 


and  robust  it  is  siiort,  corrugated,  and  closely  applied  to  the  testes.  The  wrinkles 
in  the  scrotum  are  called  rugae. 

The  scrotum  consists  of  two  layers,  the  integument  and  the  dartos. 

The  integument  is  very  thin,  of  a  brownisli  color,  and  generally  thrown  into  folds 
or  ruo-re.  It  is  provided  with  sebaceous  follicles,  the  secretion  of  which  has  a 
peculiar  odor,  and  is  beset  with  thinly  scattered,  crisp  hairs,  the  roots  of  which 
may  be  seen  through  tlie  skin. 


ACCESSORY 

SLIP  OF 

ORIGIN  OF 

CREMASTER 

MUSCLE 


RVE   FILAMENTS 
SPERMATIC 
EXUS 


Fig.  1141. — The  scrotum.  The  penis  has  been  turned  upward,  and  the  anterior  wall  of  the  scrotum  has  been 
removed.  On  the  right  side,  the  spermatic  cord,  the  jnfundibuliform  fascia,  and  the  Cremaster  muscle  are  dis- 
played; on  the  left  side,  the  infundibuliform  fascia  has  been  divided  by  a  longitudinal  incision  passing  along  the 
front  of  the  cord  and  the  testicle,  and  a  portion  of  the  parietal  layer  of  the  tunica  vaginalis  has  been  removed  to 
disjjlay  the  testicle  and  a  portion  of  the  head  of  "the  epididymis,  which  are  covered  by  the  visceral  layer  of  the 
tunica  vaginalis.     (Toldt.) 

The  dartos  {tunica  dartos)  (Figs.  1140  and  1142)  is  a  thin  layer  of  loose  vascular 
tissue,  containing  smooth  muscle  tissue,  but  no  fat;  it  forms  the  proper  tunic  of 
the  scrotum,  is  continuous  around  the  base  of  the  scrotum,  with  the  two  layers  of 
the  superficial  fascia  of  the  groin  and  perineum,  and  sends  inward  a  distinct 
mesal  septum,  the  septum  of  the  scrotum  {septum  scroti)  (Fig.  1140),  which  dn'ides 
it  into  two  cavities  for  the  two  testes,  the  septum  extending  between  the  raph^ 
and  the  under  surface  of  the  penis  as  far  as  its  root. 


1374 


THE   UBINOGENITAL   ORGANS 


The  dartos  is  closely  united  to  the  skin  externally,  but  connected  with  the 
subjacent  parts  by  delicate  areolar  tissue,  upon  which  it  glides  with  the  greatest 
facility. 

The  intercolumnar  or  external  spermatic  fascia  (Fig.  1140)  is  a  thin  membrane 
de^i^'ed  from  the  margin  of  the  pillars  of  the  external  abdominal  ring,  during 
the  descent  of  the  testis  in  the  fetus,  which  is  prolonged  downward  around  the 
surface  of  the  cord  and  testis.  It  is  separated  from  the  dartos  by  loose  areolar 
tissue,  which  allows  of  considerable  moA'ement  of  the  latter  upon  it,  but  is  inti- 
mately connected  with  the  succeeding  layers. 

The  cremasteric  fascia  {fascia  cremasterica)  (Figs.  1140  and  1141)  consists 
of  scattered  bundles  of  muscle  fibres,  the  Cremaster  muscle  (m.  cremaster)  (Figs. 
1140  and  1141)  derived  from  the  lower  border  of  the  Internal  oblique  and  collected 
within  a  continuous  covering  by  intermediate  areolar  tissue. 

Shin  - 

Dartos 

Intercolumnar  fascia 

Cremasteric  fascia 

InfundibiUiform  fascia 

Parietal  tunica  vaginalis 

Visceral  tunica  vaginalis 

Tunica  alimginea  ~ 
Tunica  vasevlosa 

A  lobule  of  the  testicle  ^ 


A  septum 

Mediastinum  testi': 

Digital  fossa 

Spermatic  vein 

Epididymis 

Vas  deferens 

Artery  to  vas 

Spei-matic  artery 

Internal  muscle 

tunic  of  Kolliker 


Fig.  1 142. — Transverse  section  through  the  left  side  of  the  scrotum  and  the  left  testis.     The  sac  of  the  tunica  vagi- 
nalis is  represented  in  a  distended  condition.     (Del^pine.) 

The  infundibuliform  fascia  {tunica  vaginalis  communis  [testis  et  funiculi  sper- 
matid]) (Figs.  1140  and  1141)  is  a  thin  membranous  layer,  which  loosely  invests 
the  surface  of  the  cord.  It  is  a  continuation  downward  of  the  fascia  transversalis. 
Beneath  it  is  a  quantity  of  loose  connective  tissue  which  connects  this  layer  of 
fascia  with  the  spermatic  cord  and  posterior  parts  of  the  testicle.  This  connective 
tissue  is  continuous  above  with  the  subserous  areolar  tissue  of  the  abdomen. 
These  two  layers,  the  infundibuliform  fascia  and  the  tissue  beneath  it,  are  known 
collectively  as  the  fascia  propria.  The  infundibuliform  fascia  completely  encloses 
the  testicle  and  epididymis  and  is  fused  witl^  the  parietal  lamina  of  the  tunica 
vaginalis  propria  testis. 

'The  tunica  vaginalis  (tunica  vaginalis  propria  testis)  is  described  with  the 
testis  (p.  1.379). 

Vessels  and  Nerves. — The  arteries  supplying  the  coverings  of  the  testis  are  the  superficial 
and  deep  external  pudic,  from  the  femoral;  the  superficial  perineal  branch  of  the  internal  pudic; 
and  the  cremasteric  branch  from  the  deep  epigastric.  The  veins  follow  the  course  of  the  corre- 
sponding arteries.  The  lymphatics  terminate  in  the  inguinal  nodes.  The  nerves  are  the 
ilioinguinal  and  genital  branch  of  the  genitofemoral  nerve  and  of  the  lumbar  plexus,  the  tn-o 
superficial  perineal  branches  of  the  internal  pudic  nerve,  and  the  inferior  pudendal  branch  of  the 
small  sciatic  nerve. 


THE  TESTICLES  AND   THEIR   COVERINGS 


1375 


ANTERIOR 

GROUP  OF 

VEINS 


The  inguinal  or  spermatic  canal  {canalis  ing^dnalis)  (Figs.  330  and  1124) 
contains  tlie  spermatic  cord  in  tlie  male  and  the  round  ligament  in  the  female. 
It  is  an  ol)lique  canal,  about 
an  inch  and  a  half  in  lengdi, 
directed  downward  and  in- 
ward and  placed  parallel 
with,  and  a  little  above, 
Poupart's  ligament.  It  com- 
mences above  at  the  internal 
or  deep  alidominal  ring,  which 
is  the  point  where  the  cord 
enters  the  inguinal  canal,  and 
terminates  below  at  the  ex- 
ternal or  superficial  ring.  It 
is  bounded,  in  front,  by  the 
integument  and  superficial 
fascia,  by  the  aponeurosis  of 
the  External  oblique  through- 
out its  whole  length,  and  by 
the  Internal  oblique  for  its 
outer  third;  behind,  by  the 
triangular  fascia,  the  conjoined 
tendon  of  the  Internal  oblique 
and  Trans versalis,  transver- 
salis  fascia,  and  the  subperi- 
toneal fat  and  peritoneum; 
above,  by  the  arched  fibres  of  the  Internal  oblique  and  Transversalis;  below, 
by  the  imion  of  the  transversalis  fascia  with  Poupart's  ligament. 


FiQ.  1143.— The  arteries  of  the  testis  : 
Charpy.) 


id  the  cord.       (Poirier  and 


TRANSVERSALIS 


DEEP 

EPIGASTRIC 

ARTERY 


SPERMATIC 


Fig.  1144. — The  spermatic  cord  and  the  ligament  of  Cloquet.     (Poirier  and  Charpy.) 

The  spermatic  cord  (funicuhis  spermaiicms)   (Figs.   1140  and  1144)  extends 
from  the  internal  abdominal  ring,  where  the  structures  of  which  it  is  composed 


1376 


THE  URINOQEXITAL   ORGANS 


converge,  to  the  back  part  of  the  testicle.  In  the  abdominal  wall  the  cord  passes 
obliquely  along  the  inguinal  canal,  lying  at  first  beneath  the  Internal  oblique  muscle 
and  upon  the  fascia  transversalis;  but  nearer  the  pubes  it  rests  upon  Poupart's 
ligament,  having  the  aponeurosis  of  the  External  oblique  in  front  of  it  and  the 
conjoined  tendon  behind  it.  It  then  escapes  at  the  external  ring,  and  descends 
nearly  vertically  into  the  scrotum.  The  left  cord  is  usually  rather  longer  than  the 
right,  consequently  the  left  testis  generally  hangs  somewhat  lower  than  its  fellow. 


DEFERENS 


.SPERMATIC 

^         CORD 


INTERNAL 

SAPHENOUS 

VEIN 


Fig,  1145.^ — The  spermatic  cord  in  the  inguinal  canal.     (Poirier  and  Charpy.) 

Structure. — The  spermatic  cord  contains  the  spermatic  duct  or  vas  deferens,  the  deferential 
artery  and  veins,  the  spermatic  artery,  the  pampiniform  plexus  of  veins,  the  spermatic  plexus, 
and  the  deferential  plexus  of  the  symjiathetic  nerve,  lymphatics,  and  the  cord-like  remnant  of  the 
funicular  process  of  peritoneiun  called  the  ligament  o£  Cloquet  (Fig.  1144).  All  the  above 
structures  are  held  together  by  connective  tissue.  These  structures  are  ensheathed  by  the 
infundibuliform  process  of  the  transversalis  fascia  (Fig.  1144  and  p.  1374).  This  fascia  is  thin 
above  and  tliicker  below,  and  encloses  the  testicle  and  epididymis,  as  well  as  the  cord,  being 
firmly  adherent  to  the  parietal  layer  of  the  vaginal  tunic  of  the  testicle  and  with  the  posterior  por- 
tion of  the  testicle  and  epididymis.  Upon  this  fascia  are  the  fibres  of  the  Cremaster  muscle, 
which  spring  from  the  Internal  oblique,  and  in  this  fascia  are  the  cremasteric  artery,  the  genital 
branch  of  the  genitofemoral  nerve,  and  external  spermatic  veins.  This  fascia  is  surrounded  by 
the  intercolumnar  or  spermatic  fascia,  which  is  distinct  above,  but  not  below. 

Vessels  and  Nerves  of  the  Spermatic  Cord. — The  arteries  (Figs.  1141  and  1J143)  of  the  cord 
are  the  spermatic,  from  the  aorta;  the  artery  of  the  vas  deferens,  from  the  superior  vesical;  the 
cremasteric,  from  the  deep  epigastric. 

The  spermatic  artery  {a.  spermatica  interna)  arises  from  the  abdominal  aorta  below  the  renal 
artery,  descends  l)y  the  Psoas  muscle,  crosses  the  ureter  and  external  iliac  vessels,  meets  the  vas 
deferens  at  the  internal  abdominal  ring,  escapes  from  the  abdomen  at  the  internal  or  deep  ab- 
dominal ring,  and  lying  in  front  of  the  vas  deferens  accompanies  the  other  constituents  of  the 
spermatic  cord  along  the  inguinal  canal  and  through  the  external  abdominal  ring  into  the  scrotum. 
It  then  descends  to  the  testis,  and,  becoming  tortuous,  divides  into  several  branches,  two  or  three 
of  which,  the  epididymal  branches,  accompany  the  vas  deferens  and  supply  the  epididymis, 
anastomosing  with  the  artery  of  the  vas  deferens  and  the  cremasteric  artery;  others,  the  glandular 
branches,  pierce  the  back  of  the  tunica  albuginea  and  supply  the  substance  of  the  testis. 

The  artery  of  the  vas  deferens  (a.  deferentialis),  a  branch  of  the  superior  vesical,  is  a  long 
slender  vessel  which  accompanies  the  vas  deferens,  ramifying  upon  the  coats  of  that  duct,  and 
anastomosing  with  the  spermatic  artery  and  the  cremasteric  artery  near  the  testis. 


THE  TESTICLES  AND   THEIR   COVERINGS 


J  377 


The  cremasteric  artery  {a.  spermatica  externa)  is  a  branch  of  the  deep  epigastric  artery.  It 
accorapjinics  the  s|]erniiitic  cord  and  supplies  the  Cremaster  muscle  and  other  coverings  of  the 
cord,  aiiMstoiiinsiiii;  with  the  spermatic  and  deferential  arteries. 

The  spermatic  veins  (Figs.  523  and  1146)  emerge  from  the  back  of  the  testis  and  receive 
tributaries  from  the  epididymis;  they  unite  and  form  a  convoluted  plexus,  the  pampiniform 
plexus  (plexus  pampiniformis),  which  forms  the  chief  mass  of  the  cord;  the  ves.sels  composing 
this  plexus  are  very  numerous,  and  ascend  along  the  cord  in  front  of  the  vas  deferens;  below  the 
external  or  superficial  abdominal  ring  they  unite  to  form  three  or  four  veins,  which  pass  along  the 
inguinal  canal,  and,  entering  the  abdomen  through  the  internal  or  deep  abdominal  ring,  coalesce 
to  form  two  veins.  These  again  unite  to  form  a  single  vein,  which  opens  on  the  right  side  into 
the  inferior  vciki  cava  at  an  acute  angle,  and  on  the  left  side  into  the  left  renal  vein  at  a  right  angle. 

The  lymphatic  vessels  of  the  scrotum  terminate  in  the  superficial  inguinal  nodes.  The  lym- 
phatics of  the  testicle  join  the  lymphatics  of  the  epididymis  and  of  the  visceral  layer  of  the  vaginal 
tunic  of  the  testicle,  and  ascend  in  the  spermatic  cord.  They  reach  the  lumbar  region  along  the 
spermatic  bloodvessels  and  terminate  in  the  lateral  aortic  nodes,  and  sometimes  in  the  nodes  in 
front  of  the  aorta.     The  lymphatics  of  the  seminal  duct  pass  to  the  external  iliac  nodes. 

The  nerves  are  the  spermatic  plexus  from  the  sympathetic,  joined  by  filaments  from  the 
pelvic  plexus  which  accompany  the  artery  of  the  vas  deferens. 


Fig.  114G. — Spermatic  veins.      (Testut.) 

The  testes  (Figs.  1 141  and  1146)  are  suspended  in  the  scrotum  by  the  spermatic 
cords,  the  left  testis  hanging  somewhat  lower  than  its  fellow.  The  average  dimen- 
sions of  this  gland  are  from  one  and  a  half  to  two  inches  (4  cm.)  in  length,  one 
inch  (2.5  cm.)  in  breadth,  and  an  inch  and  a  quarter  (3  cm.)  in  the  antero-posterior 
diameter,  and  the  weight  varies  from  six  to  eight  drams  (25  to  30  grams) .  It  is 
of  a  grayish-white  color,  and  of  resilient  consistency.     Each  gland  is  of  an  oval 

87 


1378 


THE   VRINOGENITAL   ORGANS 


form,  compressed  laterally,  and  having  an  oblique  position  in  the  scrotum,  the 
upper  extremity  {e.xtreviitus  superior)  being  directed  forward  and  a  little  outward, 
the  lower  extremity  {extremitus  inferior),  backward  and  a  little  inward;  the  an- 
terior convex  border  looks  forward  and  downward;  the  posterior  or  straight  border 
{margo  posterior),  to  which  the  cord  is  attached,  backward  and  upward. 

The  anterior  border  {margo  anterior)  and  lateral  surfaces  {fades  lateralis  et  fades 
medialis),  as  well  as  both  extremities  of  the  organ,  are  convex,  free,  smooth,  and 
invested  by  the  visceral  layer  of  the  tunica  vaginalis.  The  posterior  border, 
to  which  the  cord  is  attached,  receives  only  a  partial  investment  from  that  mem- 
brane. To  the  inferior  part  of  the  posterior  border  is  attached  the  gubemaculum 
testis  (see  p.  1424),  which  anchors  the  testis  firmly  to  the  scrotum.  Lying  upon 
the  outer  edge  of  this  posterior  border  is  a  long,  narrow,  flattened  body,  named, 
from  its  relation  to  the  testis,  the  epididymis  (Figs.  1147  and  1148),  which  curves 
outward  and  backward. 


Spet  maiic  cord 


■ll^Pi  II  of 

LO}d. 


Tunica  rafjnialis, 
parietal  lat/er.  '\ 
Kon-pcdimcnlated 
hydatid. 
Digital 
foasa. 


Fig.  1147. — The  left  testis  in  situ,  the  tunica  vagi- 
nalis having  been  laid  open. 


ALBUGINEA 


Fig.  1148. — Frontal  section  of  the  testis  and  epi- 
didymis.    (Poirier  and  Charpy. ) 


The  epididymis  consists  of  a  central  portion  or  body  (corpus  epididymidis);  an 
upper  enlarged  extremity,  the  head  or  globus  major  {caput  epididymidis);  and  a 
lower  pointed  extremity,  the  tail  or  globus  minor  {caiida  epididymidis').  The 
globus  major  is  directed  inward  and  is  intimately  connected  with  the  upper  end 
of  the  testicle  by  means  of  its  efferent  ducts,  and  the  globus  minor  is  connected 
with  its  lower  end  by  cellular  tissue  and  a  reflection  of  the  tunica  vaginalis.  The 
globus  minor  bends  suddenly  and  passes  into  the  seminal  duct,  the  direction  of 
which  is  upward  and  backward.  The  outer  surface  and  upper  and  lower  ends  of 
the  epididymis  are  free  and  covered  by  serous  membrane;  the  body  is  also  com- 
pletely invested  by  it,  excepting  along  its  inner  border,  and  between  the  body  and 
the  posterior  part  of  the  outer  surface  of  the  testis  is  a  pouch  or  cul-de-sac,  named 
the  digital  fossa  (sinus  epididymidis).  Above  this  fossa  is  a  fold  of  the  tunica 
vaginalis,  which  is  called  the  Ugamentum  epididymidis  superior,  and  below  it  is 
another  fold,  the  Ugamentum  epididymidis  inferior.  The  epididymis  is  con- 
nected to  the  back  of  the  testis  by  a  fold  of  the  serous  membrane.  Attached  to 
the  upper  end  of  the  testis,  close  to  the  globus  major,  is  a  small  body;  it  is  oblong 
in  shape  and  has  a  broad  base,  and  is  called  the  sessile  hydatid  {appendix  testis 
[Morgagni])  (Figs.  1140  and  1147).     Attached  to  the  globus  major  of  the  epi- 


THE  TESTICLES  AND  THEIR  CO  VERINOS 


1379 


didymis  is  another  small,  pear-shaped  body — the  pedunculated  hydatid  {appendix 
epididymidis).  These  bodies  are  the  remains  of  embryonic  structures.  When 
the  testis  is  removed  from  the  body,  the  position  of  the  vas  deferens,  on  the  pos- 
terior surface  of  the  testis  and  inner  side  of  die  epididymis,  marks  the  side  to  which 
the  eland  has  belonged. 


Structure  of  the  Epididymis. — The  epididymis  is  surrounded  by  a  capsule  of  white  fibrous 
tissue.  The  globus  major  consists  of  from  ten  to  fifteen  tubules,  which  are  convoluted  and  lined 
by  stratified  ciliated  epithelial  cells.  The  body  and  globus  minor  are  composed  of  the  convolu- 
tions of  a  single  tubule,  which  if  straightened  would  measure  upward  of  twenty  feet.  These 
parts  are  lined  by  stratified  ciliated  cells  and  continue  as  the  vas  deferens. 

The  Tunics  of  the  Testicle. — l''he  testis  is  invested  by  two  tunics — the  tunica 
vaginalis  and  the  tunica  albuginea 

Tlie  tunica  vaginalis  (tunica  vaginalis  propria  testis)  (Figs.  1147  and  11.50) 
is  the  serous  covering  of  the  testis  and  epididymis.  It  is  a  pouch  of  serous  mem- 
brane, derived  from  the  peritoneum  (processus  vaginalis  peritonaei)  during  the 
descent  of  the  testis  in  the 
fetus  from  the  abdomen  into 
the  scrotum.  After  its  descent 
that  portion  of  the  pouch 
which  extends  from  the  internal 
ring  to  near  the  upper  part  of 
the  gland,  the  funicular  process, 
becomes  obliterated,  the  lower 
portion  remaining  as  a  shut 
sac,  which  invests  the  outer 
surface  of  the  testis,  and  is  re- 
flected to  the  internal  surface 
of  the  scrotum;  hence  it  may 
be  described  as  consisting  of  a 
visceral  and  parietal  portion. 

The  visceral  portion  (lamina 
visceralis)  of  the  timica  vagi- 
nalis propria  covers  the  outer 
surface  of  the  testis,  as  well  as 
the  epididymis,  connecting  the 
latter  to  the  testis  by  means 
of  a  distinct  fold.  From  the 
posterior  border  of  the  gland 
it  is  reflected  to  the  internal 
surface  of  the  infundibuliform  process  of  the  transversalis  fascia,  and  between  the 
tunic  and  the  fascia  is  a  layer  of  unstriated  muscle  fibres,  the  Internal  cremaster 
muscle  (Fig.  1142). 

The  parietal  portion  (lamina  parietalis)  of  the  tunica  vaginalis  propria  is  the 
reflected  portion.  It  is  far  more  extensive  than  the  visceral  portion,  extending 
upward  for  some  distance  in  front  and  on  the  inner  side  of  the  cord,  and  reaching 
below  the  testis.  The  inner  surface  of  the  tunica  vaginalis  is  free,  smooth,  and 
covered  by  a  layer  of  endothelial  cells.  The  interval  between  the  visceral  and 
parietal  layers  of  this  membrane  constitutes  the  cavity  of  the  timica  vaginalis  and 
contains  a  small  amount  of  serous  fluid. 

The  obliterated  portion  of  the  pouch  may  generally  be  seen  as  a  fibrocellular 
thread,  the  ligament  of  Cloquet  (rudimentum  processus  vaginalis)  (Fig.  1144), 
lying  in  the  loose  areolar  tissue  around  the  spermatic  cord;  sometimes  this  may  be 
traced  as  a  distinct  band  from  the  upper  end  of  the  inguinal  canal,  where  it  is 


the   arrange- 


1380  THE  URINOGENITAL  ORGANS 

connected  with  the  peritoneum,  down  to  the  tunica  vaginalis;  sometimes  it  gradu- 
ally becomes  lost  on  the  spermatic  cord.  Occasionally  no  trace  of  it  can  be  de- 
tected. In  some  cases  it  happens  that  the  pouch  of  peritoneum  does  not  become 
obliterated,  but  the  peritoneal  cavity  communicates  with  the  tunica  vaginalis. 
This  may  give  rise  to  one  of  the  varieties  of  oblique  inguinal  hernia  or  hydrocele; 
or  in  other  cases  the  pouch  may  contract,  but  not  become  entirely  obliterated; 
it  then  forms  a  minute  canal  leading  from  the  peritoneum  to  the  tunica  vaginalis. 

The  tunica  albuginea  (Figs.  1148  and  1149)  is  the  fibrous  covering  of  the  testis. 
It  is  a  dense  fibrous  membrane,  of  a  bluish-white  color,  composed  of  bundles 
of  white  fibrous  tissue,  which  interlace  in  every  direction.  Its  outer  surface  is 
covered  by  the  tunica  vaginalis,  except  at  the  points  of  attachment  of  the  epididy- 
mis to  the  testis,  and  along  its  posterior  border,  where  the  spermatic  vessels  enter 
the  gland.  It  consists  of  two  portions,  the  tunica  fibrosa  and  the  tunica  vasculosa ; 
the  former  is  the  thicker  of  the  two  and  contains  few  vessels,  while  the  latter  con- 
tains many  small  vessels.  The  tunica  vasculosa  sends  septa  into  the  organ 
which  divide  it  into  compartments.  These  septa  converge  and  end  at  the 
mediastinum.  This  membrane  surrounds  the  glandular  structure  of  the  testis, 
and  at  its  posterior  border  forms  a  projection,  triangular  in  shape  and  cellular 
in  structure,  which  is  reflected  into  the  interior  of  the  gland,  forming  an  incomplete 
vertical  septum,  called  the  mediastinum  testis. 

The  mediastinum  testis  (corpus  Highmori)  (Figs.  1148  and  1149)  extends 
from  the  upper,  nearlv  to  the  lower,  extremity  of  the  gland,  and  is  wider  above 
than  below.  From  the  front  and  sides  of  this  septum  numerous  slender  fibrous 
cords  and  imperfect  septa — septv.la  testis  (Fig.  1149) — are  given  off,  which  radiate 
toward  the  surface  of  the  organ,  and  are  attached  to  the  inner  surface  of  the  tunica 
albuginea.  This  scaffolding  of  connective  tissue  divides  the  parenchyma  {'paren- 
chyma testis)  of  the  organ  into  a  number  of  incomplete  spaces,  which  are  somewhat 
cone-shaped,  being  broad  at  their  bases  at  the  surface  of  the  gland,  and  becoming 
narrower  as  they  converge  to  the  mediastinum.  The  mediastinum  supports 
the  bloodvessels,  lymphatics,  and  ducts  of  the  testis  in  their  passage  to  and  from 
the  substance  of  the  gland,  and  contains  numerous  fine  canals,  into  which  open 
the  very  small  tubules  of  the  proper  substance  of  the  testis. 

Structure  of  the  Testis  (Fig.  1149).— The  glandular  structure  of  the  testis  consists  of 
numerous  lobules  (lobuli  testis).  Their  number,  in  a  single  testis,  is  estimated  to  be  about  200. 
They  differ  in  size  according  to  their  position,  those  in  the  middle  of  the  gland  being  larger  and 
longer.  The  lobules  are  pyramidal  in  shape,  the  base  of  each  being  directed  toward  the  circum- 
ference of  the  organ,  the  apex  toward  the  mediastinum.  Each  lobule  is  contained  in  one  of  the 
intervals  between  the  fibrous  cords  and  vascular  processes  which  extend  between  the  medias- 
tinum testis  and  the  tunica  albuginea,  and  consists  of  from  one  to  three  or  more  minute  convo- 
luted tubes  2{  feet  in  length  and  140  to  200  ft  in  diameter,  the  tubuli  seminiferi  contorti,  which 
usually  end  blindly  beneath  the  tunica  albuginea.  The  contorted  tubes  unite  at  the  apex  of 
the  lobules  and  form  several  straight  tubes  (tiihuli  recti),  which  pass  into  the  mediastinum  testis 
and  form  the  network  known  as  the  rate  testis  (Fig.  1149).  The  efferent  ducts  (ductuli  effer- 
entes  testis)  (Fig.  1149),  about  twelve  to  fifteen  in  number,  arise  from  the  rete  and  continue  into 
the  globus  major  as  the  coni  vasculosi.  The  total  number  of  tubes  is  considered  by  Lauth  to 
be  about  840.  The  tubuli  recti  and  rete  testes  are  lined  by  simple  squamous  or  cuboidal  cells, 
while  the  vasa  efferentia  are  lined  by  simple  columnar  cells  which  are  either  ciliated  or  non- 
ciliated.  The  convoluted  tubules  are  pale  in  color  in  early  life,  but  in  old  age  they  acquire  a 
deep  yellow  tinge  from  containing  much  fatty  matter.  Each  tube  consists  of  a  basement  layer, 
formed  of  epithelial  cells  united  edge  to  edge,  outside  of  which  are  other  layers  of  flattened  cells 
arranged  in  interrupted  laminse,  which  give  to  the  tube  an  appearance  of  striation  in  cross- 
section.  The  cells  of  the  outer  layers  gradually  pass  into  the  interstitial  tissue.  Within  the  base- 
ment membrane  are  epithelial  cells  arranged  in  several  irregular  layers,  which  are  not  always 
clearly  separated,  but  which  may  be  arranged  in  different  groups  that  do  not  form  clearly  defined 
layers.  The  various  groups  cannot  be  seen  in  a  single  cross-section,  but  may  be  discerned  in 
successive  sections.  Among  these  cells  may  be  seen  the  spermia  in  different  stages  of  develop- 
.raent.  (1)  Lining  the  basement  membrane  and  forming  the  outer  zone  is  a  layer  of  cubical 
cells,  spermatogonia,  containing  small  nuclei  and  pyramidal  cells,  the  columns  of  Sertoli.     The 


THE  TESTICLES  AND  THEIR  CO  VEBINGS 


1381 


nucleus  of  the  former  may  be  seen  to  be  in  the  process  of  indirect  division  (karyokinesis),  and  in 
consequence  of  this  daufj;li(or  cells  arc  I'urmcd,  which  constilulc  ihc  second  zone.  (2)  Within  this 
first  layer  is  to  be  seen  a  nuiiilicr  cif  lar;;cr  cells  wiili  clear  nuclei,  arranged  in  two  or  three  strata; 
these  are  the  spermatocytes  of  the  first  order,  or  mother  cells.  Most  of  the  cells  are  in  a  con- 
dition of  karyokinctic  division,  and  the  cells  which  result  from  this  division  form  those  of  the  next 
layer,  the  spermatocytes  of  the  second  order,  or  daughter  cells.  (.3)  The  latter  by  division 
give  rise  to  the  spermids,  which  change  into  the  spermia  or  spermatozoa.  In  addition  to  these 
three  layers  of  cells,  others  are  seen,  which  are  termed  the  supporting  cells,  or  cells  of  Sertoli. 
They  are  elongated  and  columnar,  and  project  inward  from  the  basement  membrane  toward 
the  lumen  of  the  tube.  They  give  off  numerous  lateral  branches,  which  form  a  reticulum  for  the 
support  of  the  three  groups  of  cells  just  described.  As  development  of  the  spermia  proceeds,  the 
latter  group  themselves  around  the  inner  extremities  of  the  supporting  cells.  The  nuclear  part  of 
the  spermid,  which  is  partly  embedded  in  the  supporting  cell,  is  differentiated  to  form  the  head 
of  the  spermium,  while  the  cell  protoplasm  becomes  lengthened  out  to  form  the  middle  piece 
and  tail,  the  latter  projecting  into  the  lumen  of  the  tube.  Ultimately  the  heads  are  separated 
from  the  column  of  Sertoli  and  the  spermia  are  set  free. 

The  process  of  spermatogenesis  bears  a  close  relation  to  that  of  matiffation  of  the  ovum. 
The  spermatocyte  is  equivalent  to  the  immature  ovum.  It  undergoes  subdivision,  and  ulti- 
mately gives  origin  to  fom'  spermia,  each  of  which  contains,  therefore,  only  one-fourth  of  the 
chromatin  elements  of  the  nucleus  of  the  spermatocyte  (see  Ovum,  p.  1400). 


EPIDIDYMIS 


Tig.  1150. — Vaginal  tunics  of  the  rigiit  testicle.     (Poir- 
ier  and  Charpy.) 


Fig.  1151. — Ligament  of  the  scrotum  or  gube 
naculum  testis.     (Poirier  and  Charpy.) 


The  tubules  are  enclosed  in  a  delicate  plexus  of  capillary  vessels,  and  are  held  together  by  an 
intertubular  connective  tissue,  which  presents  large  interstitial  spaces  lined  by  endothelium, 
which  are  believed  to  be  the  rootlets  of  lymphatic  vessels  of  the  testis.  In  this  interstitial  tissue 
are  groups  of  large  granular  cells,  the  interstitial  cells.  These  contain  pigment,  fat,  and  crystal- 
loids, and  are  more  numerous  before  and  after  sexual  activity. 

The  aberrant  ducts  of  the  epididymis  (ductidi  aberrantes)  are  tortuous  and  end  in  blind  ex- 
tremities. The  superior  aberrant  duct  (ductus  aberrans  superior)  is  in  the  globus  major  and 
joins  the  rete  testis.  The  inferior  aberrant  duct  (ductus  aberrans  inferior)  (Fig.  1149).  is  in  the 
tail  of  the  epididymis,  and  lakes  origin  from  the  duct  of  the  epididymis  or  the  seminal  duct.  It 
is  a  persi-stent  canal  of  the  Wiilffian  body.  It  extends  up  the  cord  for  two  or  three  inches  and 
terminates  liy  a  blind  exlrcniity,  which  is  occasionally  bifurcated.  It  may  be  as  much  as  fourteen 
inches  in  length  when  uin'avellc<l.     Its  structure  is  similar  to  that  of  the  vas  deferens. 

The  descent  of  the  testis  will  be  described  on  page  1424. 

The  Semen. — The  semen  is  the  viscid,  whitish,  or  opalescent  fluid,  of  alkahne 
reaction  and  characteristic  odor,  which  is  secreted  by  the  testes,  prostate,  seminal 
vesicles,  and  Cowper's  glands.  It  contains  water  artd  about  IS  per  cent,  of  solid 
matter,  chiefly  consisting  of  proteids,  salts,  and  nitrogenous  substances.  The 
semen  serves  to  convey  and  maintain  the  vitality  of  the  spermia  in  their  course 
along  the  seminal  passages. 

The  Spermatozoa,  or  Spermia,  are  present  in  enormous  numbers  in  the  seminal 
fluid.     Each  consists  of  a  head,  neck,  body,  and  tail. 


1382 


THE  UBINOGENITAL  ORGANS 


■  The  head  is  oval,  but  flattened  so  that  when  viewed  in  profile  it  is  pear-shaped. 
Its  anterior  part  is  covered  by  a  layer  of  modified  tissue  called  the  head-cap  or 
'perforator. 

The  neck  and  body  together  form  a  cylindric  or  rod-like  segment,  the  neck 
containing  the  two  centrosomes.  From  the  posterior  centrosome  proceeds  the 
axial  filament,  which  in  the  body  of  the  spermium  is  encircled  by  a  spiral  thread. 

The  tail  is  about  four  limes  the  combined  length  of  the  head  and  body,  and 
consists  of  the  axial  filament  surrounded  by  a  delicate  sheath  of  protoplasm. 
The  terminal  portion  of  the  tail  is  named  the  end  piece,  and  consists  of  the  axial 
filament  only. 

Bv  virtue  of  their  tails,  which  act  as  propellers,  the  spermia,  in  the  fresh  con- 
dition, are  capable  of  free  movement,  and  if  placed  in  favorable  surroundings 
(e.  g.,  in  the  female  passages)  may  retain  their  vitality  forseveral  days. 


w- 


Middle 
'  piece 


'  Main  pit 


Middle  _ 
piece 


■of 
the 
tail 


Applied  Anatomy. — The  scrotum  forms  an  admirable 
covering  for  the  protection  of  the  testicle.  This  body,  lying 
suspended  and  loose  in  the  cavity  of  the  scrotum,  and  sur- 
rounded by  a  serous  membrane,  is  capable  of  great  mobility, 
and  can  therefore  easily  slip  about  within  the  scrotum,  and 
thus  avoid  injuries  from  blows  or  squeezes.  The  skin  of  the 
scrotum  is  very  elastic  and  capable  of  great  distention,  and 
on  account  of  the  looseness  and  amount  of  subcutaneous 
tissue,  the  scrotum  becomes  greatly  enlarged  in  cases  of 
edema,  to  which  this  part  is  especially  hable  on  account  of 
its  dependent  position.  The  scrotum  is  frequently  the  seat 
of  epithelioma;  this  is  no  doubt  due  to  the  rugse  on  its  surface, 
which  favor  the  lodgement  of  dirt,  and  this,  causing  irritation, 
is  the  exciting  cause  of  the  disease.  Cancer  was  especially 
common  in  chimney-sweeps  from  the  lodgement  of  soot. 
The  scrotum  is  also  the  part  most  frequently'  affected  by 
elephantiasis. 

On  account  of  the  looseness  of  the  subcutaneous  tissue 
considerable  extravasations  of  blood  may  take  place  from  very 
slight  injuries.  It  is  therefore  generally  recommended  never 
to  apply  leeches  to  the  scrotum,  since  they  may  lead  to 
considerable  ecchytnosis,  but  rather  to  puncture  one  or  more 
of  the  superficial  veins  of  the  scrotum  in  cases  where  local 
bloodletting  from  this  part  is  judged  to  be  desirable.  The 
muscle  tissue  in  the  dartos  causes  contraction  and  consider- 
able diminution  in  the  size  of  a  wound  of  the  scrotum,  as 
after  the  operation  of  castration,  and  is  of  assistance  in  keep- 
ing the  edges  together  and  covering  the  exposed  parts. 
Abnormalities  in  the  formation  and  in  the  descent  of  the  testes  may  occur.  The  testis  may 
fail  to  be  developed,  or  it  may  be  fully  developed  and  the  vas  deferens  may  be  undeveloped  in 
whole  or  in  part;  or,  again,  both  testes  and  vas  deferens  may  be  fully  developed,  but  the  duct  may 
not  become  connected  to  the  gland.  The  testis  may  fail  in  its  descent  (cryptorchismus)  or  it  may 
descend  into  some  abnormal  position  (ectopia  testis).  Thus,  it  may  be  retained  in  the  position 
where  it  was  primarily  developed,  below  the  kidney;  or  it  may  descend  to  the  internal  abdominal 
ring,  but  fail  to  pass  through  this  opening;  it  may  be  retained  in  the  inguinal  canal,  which  is, 
perhaps,  the  most  common  position;  or  it  may  pass  through  the  external  abdominal  ring  and 
remain  just  outside  it,  failing  to  pass  to  the  bottom  of  the  scrotum.  On  the  other  hand,  it  may 
get  into  some  abnormal  position;  it  may  pass  the  scrotum  and  reach  the  perineum,  or  it  may 
fail  to  enter  the  inguinal  canal,  and  may  find  its  way  through  the  femoral  ring  into  the  crural 
canal,  and  present  itself  on  the  thigh  at  the  saphenous  opening.  Ectopia  testis  is  due  to  the 
absence,  overdevelopment,  or  malposition  of  some  portion  of  the  gubernaculum.  There  is  still 
a  third  class  of  cases  of  abnormality  in  the  position  of  the  testis,  where  the  organ  has  descended  in 
due  course  into  the  scrotum,  but  is  malplaced.  The  most  common  form  of  this  is  where  the  testis 
is  inverted;  that  is  to  say,  the  organ  is  rotated,  so  that  the  epididymis  is  connected  to  the  front  of 
the  scrotum,  and  the  body,  surrounded  by  the  tunica  vaginalis,  is  directed  backward.  In  these 
cases  the  vas  deferens  is  to  be  felt  in  the  front  of  the  cord.  The  condition  is  of  importance  in 
connection  with  hydrocele  and  hematocele,  and  the  position  of  the  testis  should  always  be  care- 
fully ascertained  before  performing  any  operation  for  these  affections.  Again,  more  rarely,  the 
testis  may  be  reversed.     This  is  a  condition  in  which  the  top  of  the  testis,  indicated  by  the  globus 


-End  pie 


Fig.  1152. — Spermium  of  man.  A1 
the  left  a  surface  view  is  shown; 
at  the  right  a  lateral  view.  X  1200 
(Szymonowicz,  after  Retzius.) 


THE    VA8  DEFERENS  1383 

major  of  the  epididymis,  is  at  the  bottom  of  the  scrotum,  and  the  vas  deferens  comes  ofT  from  the 
summit  of  the  organ. 

The  testis  may  require  removal  for  malitfnani,  disease,  tuberculous  disease,  cystic  disease,  in 
cases  of  large  hernia  testis,  and  in  some  instances  of  incom-pletely  descended  or  misplaced  testes. 
The  operation  of  castration  is  a  comparatively  simple  one.  An  incision  is  made  into  the  cavity 
of  the  tunica  vaginalis  from  the  external  ring  to  the  bottom  of  the  scrotuni.  The  coverings  are 
shelled  off  the  organ,  and  the  mesorchium,  stretching  between  the  back  of  the  testis  and  the 
scrotum,  divided.  The  cord  is  then  isolated,  and  an  aneurism  needle,  armed  with  a  double 
ligature,  passed  under  it,  as  high  as  is  thought  necessary,  and  the  cord  tied  in  two  places,  and 
divided  between  the  ligatures.  Sometimes,  in  cases  of  malignant  disease,  it  is  desirable  to 
open  the  inguinal  canal  arid  tie  the  cord  as  near  the  internal  abdominal  ring  as  possible. 

A  collection  of  serous  fluid  in  the  sac  of  the  vaginal  tunic  of  the  testicle  is  known  as  an  ordinary 
or  testicular  hydrocele.  In  congenital  hydrocele  a  communication  remains  between  the  tunica 
vaginalis  testis  and  the  peritoneal  cavity.  This  communication  should  have  closed  during 
development.  In  infantile  hydrocele  the  tunica  vaginalis  and  part  of  the  funicular  process  are 
distended  with  fluid,  but  the  funicular  process  is  closed  above  and  the  cavity  of  the  hydrocele 
does  not  communicate  with  the  peritoneal  cavitj'.  In  encysted  hydrocele  of  the  cord  the  funicular 
process  is  closed  above  and  below,  but  between  these  points  is  not  obliterated.  In  funicular 
hydrocele  the  funicular  process  is  closed  below  and  open  above.  Congenital  hydrocele  can 
usually  be  cured  by  the  application  of  a  truss.  This  obliterates  the  upper  end  of  the  funicular 
process,  and  the  obliteration  once  begun  may  proceed  to  completion.  If  it  does  not,  the  condi- 
tion has  become  an  infantile  hydrocele.  An  infantile  hydrocele  can  usually  be  cured  bj'  multiple 
puncture  or  tapping.  The  same  is  true  of  encysted  hydrocele  of  the  cord.  In  hydrocele  of  the 
funicular  process  a  truss  should  be  worn  for  a  time  and  the  fluid  then  evacuated  by  ta|)ping. 
In  ordinary  testicular  hydrocele  incise  and  pack,  or  incise  and  suture  the  cut  edge  of  the  parietal 
layer  of  the  tunic  to  the  skin,  or  extirpate  the  parietal  layer  of  the  tunic.  A  successful  method 
is  that  of  Longuet.  He  makes  an  incision,  pulls  out  the  testis,  and  allows  all  the  coats  except  the 
skin  to  fall  behind  and  make  a  sheath  for  the  cord.  These  coats  are  held  behind  by  one  catgut 
suture.  A  bed  is  made  for  the  testis  beneath  the  skin  toward  the  septum  of  the  scrotum.  The 
testicle  is  rotated  on  its  long  axis,  and  placed  in  the  bed,  and  the  skin  is  sutured  above  it.  This 
operation  is  known  as  cvtraserous  transposition.  If  a  portion  of  bowel  enters  an  open  vaginal 
process  the  condition  is  congenital  hernia. 

In  infantile  hernia  the  funicular  process  is  closed  above  but  not  below,  and  the  hernia  descends 
in  a  special  sac  back  of  the  vaginal  tunic.  If  the  hernia  pushes  down  on  the  vaginal  process  and 
causes  it  to  double  on  itself  the  condition  is  encysted  infantile  hernia. 


THE  VAS  DEFERENS  (DUCTUS  DEFERENS)  (Figs.  1145,  1153). 

The  vas  deferens,  or  seminal  duct,  the  excretory  duct  of  the  testis,  is  the  con- 
tinuation of  the  epididymis.  Commencing  at  the  lower  part  of  tlie  globus  minor, 
it  ascends  along  the  posterior  border  of  the  testis  and  inner  side  of  the  epididymis, 
and  along  the  back  pa'rt  of  the  spermatic  cord,  through  the  inguinal  canal  to 
the  internal  or  deep  abdominal  ring.  From  the  ring  it  curves  around  the  outer 
side  of  the  deep  epigastric  artery,  and  ascends  for  about  an  inch  in  front  of  the 
external  iliac  artery.  It  is  next  directed  backward  and  slightly  downward,  and, 
crossing  the  external  iliac  vessels  obliquely,  enters  the  pelvic  cavity,  where  it  lies 
between  the  peritoneal  membrane  and  the  lateral  wall  of  the  pelvis,  and  passes 
on  the  inner  side  of  the  impervious  hypogastric  artery  and  the  obtm-ator  ner\'e 
and  vessels.  It  then  crosses  in  front  of  the  ureter,  and,  reaching  the  inner  side 
of  this  tube,  bends  at  an  acute  angle,  and  runs  inward  and  sliglitly  forward 
between  the  base  of  the  bladder  and  the  upper  end  of  the  seminal  ^•esicle.  Reach- 
ing the  inner  side  of  the  seminal  vesicle,  it  is  directed  downward  and  inward 
in  contact  with  this  structure  and  gradually  approaches  the  vas  of  the  opposite 
side.  Here  the  vas  deferens  lies  between  the  base  of  the  bladder  and  the  rectinn, 
where  it  is  enclosed,  together  with  the  seminal  vesicle,  in  a  sheath  derived  from  the 
rectovesical  fascia. 

At  the  base  of  the  bladder  it  becomes  enlarged  and  sacculated,  forming  the 
ampulla  (ampulla  ductus  deferentis)  (Fig.  1153),  and  tlien,  becoming  narrowed 
at  the  base  of  the  prostate,  it  is  joined  by  tiie  duct  of  the  seminal  vesicle  to  form 


1384 


THE  URINOGENITAL  ORGANS 


the  ejaculatory  duct  (Fig.  1154).  The  vas  deferens  offers  a  hard  and  cord-hke 
sensation  to  the  fingers;  it  is  about  two  feet  in  length  if  unravelled,  of  cylindrical 
form,  and  about  3  mm.  in  diameter.  Its  walls  are  dense,  measuring  0.7  mm., 
and  its  canal  is  extremely  small,  measuring  about  0.5  mm. 

Structure. — The  vas  deferens  consists  of  three  coats:  (1)  An  external  or  areolar  coat  {tunica 
adrentitia).  (2)  A  muscular  coat  {tunica  muscularis),  which  in  the  greater  part  of  the  tube 
consists  of  three  layers  of  unstriped  muscle  tissue,  an  inner  layer  of  thin  longitudinal  fibres 
{stratum  internum),  a  thick  middle  layer  of  circular  fibres  {stratum  medium),  and  a  thick  external 
layer  of  longitudinal  fibres  {stratum  externum).  (3)  An  internal  or  mucous  coat  {tunica  mucosa), 
which  is  pale,  and  arranged  in  longitudinal  folds;  its  epithelial  cells  are  chiefl)'  of  the  stratified 
columnar  variety  of  which  the  superficial  layer  is  ciliated. 

Organ  of  Giraldes  (paradidymis). — ^This  term  is  applied  to  a  small  body  of 
rounded  shape  in  the  lower  end  of  the  spermatic  cord,  in  front  of  the  bloodvessels. 
It  consists  of  a  small  collection  of  minute  vesicles  and  a  small  collection  of  con- 
voluted tubules.  These  tubes  are  lined  with  columnar  ciliated  epithelium,  and 
probably  represent  the  remains  of  a  part  of  the  Wolffian  body. 


MUSCULAR 


THE  SEMINAL  VESICLES  (VESICULAE  SEMINALES)  (Figs.   1152,   1153). 

The  seminal  vesicles  are  two  convoluted  membranous  pouches  placed  between 
the  base  of  the  bladder  and  the  rectum,  serving  as  reservoirs  for  the  spermia,  and 
secreting  a  fluid  to  be  added  to  the  secretion  of  the  testes.  Each  sac  is  some- 
what pyramidal  in  form,  the 
broad  end  being  directed 
backward  and  the  narrow 
end  forward  toward  the 
prostate.  It  measures  about 
two  and  a  half  inches 
(6.25  cm.)  in  length,  about 
10  mm.  in  breadth,  and  4  to 
6  mm.  in  thickness.  They 
vary,  however,  in  size,  not 
only  in  different  individ- 
uals, but  also  in  the  same 
individual  on  the  two  sides. 
The  anterior  surface  is  in 
contact  with  the  base  of 
the  bladder,  extending  from 
near  the  termination  of 
the  ureters  to  the  base  of 
the  prostate  gland.  The 
posterior  surface  rests  upon 
the  rectum,  from  which  it 
is  separated  by  the  recto- 
vesical fascia.  Their  upper 
extremities  diverge  from 
each  other.  Their  lower 
extremities  are  pointed,  and 
converge  toward  the  base 
of  the  prostate  gland,  where  each  joins  with  the  corresponding  vas  deferens  to 
form  the  ejaculatory  duct.  Along  the  inner  margin  of  each  vesicle  runs  the 
ampulla  of  the  vas  deferens.     The  inner  border  of  the  vesicle  and  the  correspond- 


FiG.  1153. — The  urinary  bladder,  distended,  with  surrounding 
structures,  viewed  from  behind.     (Spalteholz.l 


THE  EJACULATOBV  DUCTS 


1385 


in"  vas  deferens  form  the  lateral  boundaries  of  a  triangular  space,  limited  behind 
by  the  rectovesical  peritoneal  fold;  the  portion  of  the  l)ladder  included  in  this  space 
rests  on  the  rectum. 

Each  vesicle  consists  of  a  single  tube,  coiled  upon  itself  and  giving  oft'  several 
irregular  cecal  diverticula  (Fig.  1154),  the  separate  coils,  as  well  as  the  diverticula, 
beino-  connected  by  fibrous  tissue.  Wien  uncoiled  this  tube  is  about  the  diameter 
of  a  quill,  and  varies  in  length  from  four  to  six  inches  (10  to  15  cm.);  it  terminates 
above  in  a  cul-de-sac;  its  lower  extremity  becomes  constricted  into  a  narrow 
straight  duct,  the  excretory  duct  (ductus  excretorius)  (Fig.  1154),  which  joins  with 
the  corresponding  vas  deferens  to  form  the  ejaculatory  duct. 


VERUMONTANUM 


URETHRA 

IlG,    1154. — The  ejaculatory  ducts  viewed  from  in  front  and  above.     (Spalteholz.) 

Structure. — The  semina!  vesicles  are  composed  of  three  coats — an  external  or  fibrous 
{tunica  adve.ntitia) ;  a  middle  or  muscular  coat  (tunica  muscularis),  which  is  thinner  than  in  the 
seminal  duct,  and  is  arranged  in  two  layers,  an  outer,  longitudinal,  and  an  inner,  circular;  an 
internal  or  mucous  coat  (tunica  mucosa),  which  is  usually  thrown  into  waves  or  folds,  and  which 
is  pale,  of  a  whitish-brown  color,  and  of  a  delicate  reticular  structure,  like  that  seen  in  the  gall- 
bladder. The  epithelium  is  of  the  columnar  variety,  and,  in  the  diverticula,  goblet  cells  are 
present,  the  secretion  of  which  increases  the  bulk  of  the  seminal  fluid. 

Vessels  and  Nerves. — The  arteries  supplying  the  seminal  vesicles  are  derived  from  the 
middle  and  inferior  vesical  and  middle  hemorrhoidal.  The  veins  and  lymphatics  accompany 
the  arteries.  The  lymphatics  anastomose  on  the  surface  of  the  vesicle.  The  trunks  from  this 
network  anastomose  with  the  lymphatics  of  the  bladder  and  prostate,  and  pass  to  the  external 
and  internal  iUac  nodes.     The  nerves  are  derived  from  the  pelvic  plexus. 

Applied  Anatomy. — The  seminal  vesicles  are  often  the  seat  of  an  extension  of  the  diseaSS" 
in  cases  of  tiil)rrruIosis  of  the  testis,  and  should  always  be  examined  through  the  rectum  before 
coming  to  a  decision  with  regard  to  castration  in  this  affection.  The  vesicles  have  been  deliber- 
ately extirpated  for  local  tuberculosis.  In  gonorrhea  the  seminal  vesicles  may  become  acutely 
inflamed  {acute  seminal  vesiculitis).  Chronic  seminal  vesiculitis  may  follow  the  acute  form  or 
may  arise  insidously  during  gonorrhea. 


THE  EJACULATORY  DUCTS  (DUCTUS  EJACULATORII)  (Fig.  1154). 

The  eiaculatory  ducts  are  two  in  number,  one  on  each  side.  Each  duct  is  formed 
by  the  junction  of  the  duct  of  the  seminal  vesicle  with  the  vas  deferens.  Each  duct 
is  about  three-quarters  of  an  inch  (2  cm.)  in  length;  it  commences  at  the  base  of 
the  prostate,  and  runs  forward  and  downward  between  the  middle  and  lateral 


1386  THE  URINOGENITAL  ORGANS 

lobes  of  that  gland,  and  along  the  side  of  the  sinus  pocularis,  to  terminate  by  a 
separate  slit-like  orifice  close  to  the  margins  of  the  sinus.  The  ducts  diminish 
in  size  and  also  converge  toward  their  terminations. 

Structure. — The  coats  of  the  ejaculatory  ducts  are  extremely  thin.  They  are  an  outer 
fibrous  layer,  which  is  almost  entirely  lost  after  the  entrance  of  the  duct  into  the  prostate; 
a  layer  of  muscle  fibres,  consisting  of  an  oider  thin  circular  and  an  inner  longitudinal  layer;  and 
the  mucous  membrane,  lined  by  simple  columnar  epithelial  cells. 


THE   PENIS    (Figs.  1155,  1156). 

The  penis  is  a  pendulous  organ  suspended  from  the  front  andsides  of  the  pubic 
arch  and  containing  the  greater  part  of  the  urethra.  In  the  flaccid  condition 
it  is  cylindrical  in  shape,  but  when  erect  assumes  the  form  of  a  triangular  prism 
with  rounded  sides,  one  side  of  the  prism  forming  the  dorsum.  It  is  composed  of 
three  cylindrical  masses  of  erectile  tissue  bound  together  by  fibrous  tissue  and 
covered  with  skin.  Two  of  the  masses  are  lateral,  and  are  known  as  the  corpora 
cavernosa;  the  third  is  median,  and  is  termed  the  corpus  spongiosum  (Figs.  1155 
and  1163). 

The  two  corpora  cavernosa  (corpora  cavernosa  penis)  (Figs.  1155  and  1156) 
form  the  greater  part  of  the  body  of  the  penis.  They  consist  of  two  fibrous 
cylindrical  tubes,  placed  side  by  side,  and  intimately  connected  along  the  median 
line  for  their  anterior  three-fourths,  while  at  their  back  part  they  separate  from 
each  other  to  form  the  crura  penis,  which  are  two  strong  tapering  fibrous  processes 
or  roots  firmly  connected  to  the  rami  of  the  os  pubis  and  ischium  (Figs.  1155  and 
1156).  Each  cms  commences  by  a  blunt-pointed  process  in  front  of  the  tuberosity 
of  the  ischium,  and  before  its  junction  with  its  fellow  to  form  the  body  of  the  penis 
it  presents  a  slight  enlargement,  named  by  Kobelt  the  bulb  of  the  corpus  cavemosum. 
Just  beyond  this  point  they  become  constricted,  and  retain  an  ecjual  diameter 
to  their  anterior  extremity,  where  they  form  a  single  rounded  end  (digital  pro- 
cess) which  is  received  into  a  fossa  in  the  base  of  the  glans  penis  (Fig.  1155). 
A  median  groove  on  the  upper  surface  lodges  the  dorsal  arteries,  nerves,  and  veins 
of  the  penis  (Figs.  1161  and  116.3),  and  the  groove  on  the  under  surface  receives 
the  corpus  spongiosum  (Fig.  1155). 

The  corpora  cavernosa  are  surrounded  by  a  strong  fibrous  envelope  (hmica 
albuginea^  consisting  of  superficial  and  deep  fibres.  The  superficial  fibres  are 
longitudinal  in  direction,  being  common  to  the  two  corpora  cavernosa,  and  in- 
vesting them  in  a  common  covering;  the  other,  deep,  circular  in  direction,  and 
being  proper  to  each  corpus  cavernosum.  The  internal  circular  fibres  of  the  two 
corpora  cavernosa  form,  by  their  junction  in  the  mesal  plane,  an  incomplete 
partition  or  septum  (septum  penis)  between  the  two  bodies.  This  is  thick  and 
complete  behind,  but  in  front  it  is  incomplete,  and  consists  of  a  number  of  vertical 
bands,  which  are  arranged  like  the  teeth  of  a  comb.  It  is  therefore  named  the 
septum  pectiniforme.  These  bands  extend  between  the  dorsal  and  the  urethral 
surface  of  the  corpora  cavernosa.  The  fibrous  investment  of  the  corpora  cavernosa 
is  extremely  dense,  of  considerable  thickness,  and  consists  of  bundles  of  shining 
white  fibres,  with  an  admixture  of  well-developed  elastic  fibres,  so  that  it  is 
possessed  of  great  elasticity. 

The  corpus  spongiosum  (corpus  cavernosum  urethrae)  (Figs.  1155  and  1156) 
contains  the  urethra,  and  is  situated  in  the  groove  on  the  under  surface  of  the 
corpora  cavernosa  penis.  Behind,  it  is  expanded  to  form  the  urethral  bulb  (bidhus 
urethrae)  and  lies  in  apposition  with  the  superficial  layer  of  the  triangular  ligament, 
from  which  it  receives  a  fibrous  investment.  The  urethra  enters  the  bulb  nearer 
to   the  upper   than  to   the  lower  surface.     On  the  latter   there  is  a  depressed 


THE  PKNLS 


1387 


median  raphe  (sulcus  bulbi),  from  wliich  a  thin  fibrous  septum  projects  into  the 
substance  of  the  bulb  and  divides  it  imperfectly  into  two  lateral  lobes  or  hemi- 
spheres {liemisphaeria  bulbi  urethrae). 

Tiie  portion  of  the  corpus  spongiosum  '^"o^ure'thra 

in  front  of  the  bulb  lies  in  a  groove  on 
the  under  surface  of  the  conjoined  corpora 
cavernosa.  It  is  cylindrical  in  form  and 
tapers  slightly  from  behind  forward.  Its 
anterior  extremity  is  expanded  in  the 
form  of  an  obtuse  cone,  flattened  from 
above  downward.     This  expansion,  termed 


URETHRA 

'j- — The  penis,  with    the  pubic  bone: 
from  before  and  below.     (Toldt.) 


Fig.  1156. — The  penis,  with  the  urethra,  Cowper's 
glands,  the  prostate  gland,  and  the  seminal  vesicles 
seen  from  below  and  behind.     (Toldt.) 


the  glans  penis,  is  moulded  on  the  rounded  ends  of  the  corpora  cavernosa,  extending 
farther  on  their  upper  than  on  their  lower  surfaces.     At  the  summit  of  the  glans 


1388 


THE   URINOGENJTAL   OBGAXS 


is  the  vertical,  slit-like  urethral  orifice  or  meatus.  The  circumference  of  the  base 
of  the  glans  forms  a  rounded  projecting  border,  the  corona  glandis,  overhanging 
a  deep  sulcus  (sulcus  retrocjlandularis),  behind  which  is  the  neck  of  the  penis 
(collum  fenis). 

For  descriptive  purposes  it  is  convenient  to  divide  the  penis  into  three  parts — 
the  root,  the  body,  and  the  extremity. 

The  root  (radix  penis)  of  the  penis  is  triradiate  in  form,  consisting  of  the  di- 
verging crura,  one  on  either  side,  and  the  mesal  bulb  of  the  corpus  spongiosum. 
Each  crus  is  covered  by  the  Erector  penis  muscle,  v^'hile  the  bulb  is  surrounded 
by  the  Accelerator  urinse  muscle.  The  root  of  the  penis  lies  in  the  perineum 
between  the  superficial  layer  of  the  triangular  ligament  and  the  fascia  of  Colles. 
In  addition  to  being  attached  to  the  pubic  rami  and  to  the  triangular  ligament, 
the  root  is  bound  to  the  front  of  the  symphysis  pubis  by  the  suspensory  ligament 
(lig.  suspensorium  penis).  The  upper  fibres  of  this  ligament  pass  downward  from 
the  lower  end  of  the  linea  alba,  and  the  lower  fibres  from  the  symphysis  pubis; 
together  they  form  a  strong,  fibrous  band  which  extends  to  the  upper  surface  of 
the  root,  where  it  splits  into  two  fasciculi  and  blends  with  the  fascial  sheath  of 
the  orffan. 


.-MEDIAN    GROOVE 


Fig.  11.58.— Glans  penis,  under  surface.      (Testut.) 


The  body  of  the  penis  (corpus  penis)  extends  from  the  root  to  the  ends  of  the 
corpora  cavernosa  between  the  root  and  extremity.  In  the  flaccid  condition 
of  the  organ  it  is  cylindrical,  but  when  erect  it  has  a  triangular  prismatic  form 
with  rounded  angles,  the  broadest  side  being  turned  upward,  and  called  the  dorsum 
penis.  The  lower  surface  of  the  body  of  the  penis  is  called  the  urethral  surface 
(fades  urethralis).  The  body  is  covered  by  integument,  and  contains  in  its 
interior  a  large  portion  of  the  urethra. 

The  extremity  is  formed  by  the  glans  penis,  the  expanded  anterior  (distal)  end 
of  the  corpus  spongiosum.  It  is  separated  from  the  body  by  the  constricted  neck, 
which  is  surmounted  by  the  corona  glandis. 

The  integument  covering  the  penis  is  remarkable  for  its  thinness,  its  dark  color, 
its  looseness  of  connection  with  the  deeper  parts  of  the  organ,  and  for  the  absence 
of  adipose  tissue.  At  the  root  of  the  penis  the  integument  is  continuous  with 
that  upon  the  pubes,  scrotum,  and  perineum.  At  the  neck  of  the  glans  it  leaves 
the  surface  and  becomes .  folded  upon  itself  to  form  the  prepuce  (praeputium) 
(Fig.  1161).  The  internal  layer  of  the  prepuce  is  directly  continuous,  along  the 
line  of  the  neck,  with  the  integument  over  the  glans.     Immediatelv  behind  the 


THE  PENIS 


1389 


urinary  meatus  it  forms  a  small,  secondary  reduplication,  attached  along  the 
bottom  of  a  depressed  median  raphe,  which  extends  from  the  meatus  to  the  neck; 
this  fold  is  termed  the  frenulum  {frenulum  praefutii).  The  integument  covering 
the  glans  is  continuous  with  the  urethral  mucous  membrane  at  the  meatus;  it  is 
devoid  of  hairs,  but  projecting  from  its  free  surface  are  a  number  of  small, 


Fig.  1159. — a.  Capillary  network.  Fk 

b.  Cavernous  spaces. 
Figs.  1159  and  1160. — From  the  peripheral  portion  of  the  corpus 

(Copied  from  Langer.) 


Connection  of  the  arterial  twigs  (a)  wit 
penis  under  a  low  magnifying  powe 


LACUNA    MAGNA 


highly  sensitive  papillfe.  In  the  retroglandular  sulcus  numerous  small  glands,  the 
glandulae  Tysonii  odoriferae  (glandidae  praeputii)  have  been  described.  They 
secrete  a  sebaceous  material  of  very  peculiar  odor,  called  smegma  praepufii,  which 
probably  contains  casein,  and  readily  undergoes  decomposition. 

The  prepuce  covers  a  variable  amount  of  the  glans  and  is  separated  from  it 
by  a  potential  sac — the  preputial  sac — which  presents  two  shallow  recesses  {fossae 
frenuli),  one  on  either  side  of  the  frenuluni. 

Structure.— From  the  internal  meatus 

surface  of  the  fibrous  envelope  of 
the  corpora  cavernosa,  as  well  as 
from  the  sides  of  the  septum,  are 
given  off  a  number  of  band.s  or 
cords  which  cross  the  interior  of 
each  crus  in  all  directions,  subdi- 
viding it  into  a  number  of  separate 
compartments,  and  giving  the  entire 
structure  a  spongy  appearance. 
These  bands  and  cords  are  called 
trabeculae  corporum  cavemosum, 
and  consist  of  white  fibrous  tissue, 
elastic  fibres,  and  smooth  muscle 
tissue.  In  them  are  continued 
numerous  arteries  and  nerves. 

The  component  fibres  of  which 
the  trabecula;  are  composed  are 
larger  and  stronger  around  the 
circumference  than  at  the  centre  of 
the  corpora  cavernosa;  they  are 
also  thicker  behind  than  in  front. 
The  interspaces,  on  the  contrary, 
are  larger  at  the  centre  than  at  the 
circumference  their  long  diameter 
being  directed  tninsversely;  they 
are    largcsl    aiikTinrly.     They    are 

called  cavernous  spaces  and  are  occupied  by  blood  during  erection,  and  are  lined  by  a  layer  of 
flattened  endothelial  cells  (Fig.  1159). 

The  arteries  bringing  the  blood  to  these  spaces  are  the  arteries  of  the  corpora  cavernosa 
and  branches  from  the  dorsal  artery  of  the  penis,  which  perforate  the  fibrous  capsule,  along 
the  upper  surface,  especially  near  the  fore  part  of  the  organ. 


CAVERNOSUM 


I  sagittnl  sectic 
(Testut.) 


1390 


THE  URINOGENITAL   ORGANS 


On  entering  the  cavernous  structure  the  arteries  divide  into  branches  which  are  supported  and 
enclosed  by  the  trabecule.  Some  of  these  terminate  in  a  capillary  network,  the  branches  of 
which  open  directly  into  the  cavernous  spaces  (Fig.  1160);  others  assume  a  tendril-like  ajjpear- 
ance,  and  form  convoluted  and  somewhat  dilated  vessels,  which  were  named  by  Muller  helicine 
arteries  (arteriae  helicinae).  They  project  into  the  spaces,  and  from  them  are  given  off  small 
capillary  branches  to  supply  the  trabecular  structure.  They  are  bound  down  in  the  spaces  by 
fine  fibrous  processes,  and  are  more  abundant  in  the  back  part  of  the  corpora  cavernosa. 


Fig.  1162. — Diagram  of  the  arteries  of  the  penis.     (Testut.) 


The  blood  from  the  cavernous  spaces  is  returned  by  a  series  of  vessels,  some  of  which  emerge 
in  considerable  numbers  from  the  base  of  the  glans  penis  and  converge  on  the  dorsum  of  the 
organ  to  form  the  deep  dorsal  vein;  others  pass  out  on  the  upper  surface  of  the  corpora  cavernosa 
and  join  the  dorsal  vein;  some  emerge  from  the  under  surface  of  the  corpora  cavernosa, 
and,  receiving  branches  from  the  corpus  spongiosum,  wind  around  the  sides  of  the  penis  to  ter- 
minate in  the  dorsal  vein;  but  the  greater  number  pass  out  at  the  root  of  the  penis  and  join  the 
prostatic  plexus. 

The  fibrous  envelope  of  the  corpus  spongiosum  is  thinner,  whiter  in  color,  and  more  elastic 
than  that  of  the  corpora  cavernosa.  The  trabecule  are  more  delicate,  more  nearly  uniform  in 
size,  and  the  meshes  between  them  smaller  than  in  the  corpora  cavernosa,  their  long  diameter, 
for  the  most  part,  corresponding  with  that  of  the  penis.    The  external  envelope  or  outer  coat  of 

the  corpus  spongiosum  is  formed  partly 
of  unstriped  muscle  tissue,  and  a  layer 
of  the  same  tissue  immediately  surrounds 
the  canal  of  the  urethra.  The  corpus 
spongiosum  receives  its  blood  through  the 
bulbourethral  branch  of  the  internal  pudic 
artery. 

The  lymphatics  of  the  skin  of  the  penis 
terminate  in  the  inguinal  nodes.  The 
lymphatics  of  the  penile  portion  of  the 
urethra  accompany  those  of  the  glans 
penis  and  terminate  with  them  in  the  deep 
inguinal  and  external  iliac  nodes.  Those 
of  the  membranous  and  prostatic  portions 
pass  to  the  internal  iliac  nodes. 

The  nerves  are   derived  from  the  in- 
ternal pudic  nerve  and   the  pelvic  plexus. 
On  the  glans  and  bulb  some  filaments  of 
the  cutaneous  nerves  have  Pacinian  bodies   connected  with   them,  and,  according  to  Krause, 
many  of  them  terminate  in  peculiar  end-bulbs  (see  p.  817). 

Applied  Anatomy. — It  is  occasionally  necessary  to  remove  a  penis  for  malignant  disease. 
Usually,  removal  of  the  antescrotal  portion  is  all  that  is  necessary,  but  sometimes  it  is  requisite 
to  remove  the  whole  organ  from  its  attachment  to  the  rami  of  the  ossa  pubis  and  ischia.  The 
former  operation  is  performed  either  by  cutting  off  the  whole  of  the  anterior  part  of  the  penis 
with  one  sweep  of  the  knife,  or,  what  is  better,  cutting  through  the  corpora  cavernosa  from  the 
dorsum,  and  (^hen  separating  the  corpus  spongiosum  from  them,  dividing  it  at  a  level  nearer  the 
glans  penis.  The  mucous  membrane  of  the  urethra  is  then  slit  up,  and  the  edges  of  the  flap 
attached  to  the  external  skin,  in  order  to  prevent  contraction  of  the  orifice,  which  would  other- 


SULBOCAVERNOUS  ARTERY/ 

—  ANTERIOR  BRANCH        (   "RET 
CORPUS 
SPONGIOSUM 


THE  PROSTATE 


1391 


wise  take  place.  The  vessels  which  re(|uire  ligation  are  the  two  dorsal  arteries  of  the  jjenis,  ihu 
arteries  of  the  corpora  cavernosa,  and  the  artery  of  the  septum.  VVhen  the  entire  organ  requires 
removal  the  patient  is  placed  in  the  lithotomy  position,  and  an  incision  is  made  through  the 
skin  and  subcutaneous  tissue  around  the  root  of  the  penis,  and  carried  down  the  median  line  of 
the  scrotum  as  far  as  the  perineum.  The  two  halves  of  the  scrotum  are  then  separated  from 
each  other,  and  a  catheter  having  been  introduced  into  the  bladder  as  a  guide,  the  spongy  ])or- 
tion  of  the  urethra  below  the  triangular  ligament  is  separated  from  the  corjiora  cavernosa  and 
divided,  the  catluicr  hiiving  been  with- 
drawn just  behind  the  l)ulb.  The  sus- 
pensory ligament  is  now  severed,  and  the 
crura  separated  from  the  bone  with  a 
periosteum  scraper,  and  the  whole  penis 
removed.  The  membranous  portion  of 
the  urethra,  which  has  not  been  removed, 
is  now  to  be  attached  to  the  skin  at  the 
posterior  extremity  of  the  incision  in  the 
perineum.  The  remainder  of  the  wound 
is  to  be  brought  together,  free  drainage 
being  provided  for. 


THE  PROSTATE  GLAND   (PROS- 
TATA) (Figs.  1153,  1156, 
1166). 

The  prostate  gland  is  a  structure 
accessory  to  the  true  generative 
organs  and  secretes  a  viscid,  opal- 
escent secretion  in  which  spermia 
will  live  and  which  furnishes  a 
medium  "in  which  they  maintain 
the  motile  activity  necessary  to 
carry  them  to  their  destination. 
It  is  a  pale,  firm,  partly  glandular 
and  partly  muscular  body,  which  is 
placed  immediately  belov  the  neck 
of  the  bladder  and  about  the  com- 
mencement  of   the    urethra. 

It  is  situated  in  the  pelvic  cavity  below  the  lower  part  of  the  symphysis  pubis, 
above  the  deep  layer  of  the  triangular  ligament,  and  in  front  of  the  rectum,  through 
which  it  may  be  distinctly  felt,  especially  when  enlarged.  It  is  about  the  size 
of  a  horse  chestnut  and  somewhat  conical  in  shape,  and  presents  for  examination 
a  base,  an  apex,  an  anterior,  a  posterior,  and  two  lateral  surfaces. 

The  base  (basis  prostatae)  is  directed  upward,  and  is  applied  to  the  under 
surface  of  the  bladder.  The  greater  part  of  this  surface  is  directly  continuous 
with  the  bladder  wall;  the  urethra  penetrates  it  nearer  to  its  anterior  than  to  its 
posterior  border. 

The  apex  (apex  prostatae)  is  directed  downward  and  rests  upon  the  deep  layer 
of  the  triangular  ligament.  The  apex  is  fixed,  except  for  the  slight  mobility  of 
the  triangular  ligament;  the  rest  of  the  gland  is  somewhat  movable. 

Surfaces. — The  posterior  surface  (fades  posterior)  is  flattened  from  side  to  side 
and  convex  from  above  downward;  it  rests  on  the  rectum,  and  is  distant  about 
an  inch  and  a  half  from  the  anus.  Near  its  upper  border  there  is  a  depression 
through  which  the  two  common  ejaculatory  ducts  enter  the  prostate.  Tliis  de- 
pression serves  to  divide  the  posterior  surface  into  a  lower  larger  and  upper  smaller 
part.  The  upper  smaller  part  constitutes  the  so-called  "middle  lobe"  of  the  pros- 
tale  and  intervenes  between  the  ejaculatory  ducts  and  the  urethra;  it  varies  greatly 


SUPERFICIAL   DORSAL  VEIN 

EXTERNAL   PUDIC    VEIN 
.—  OBTURATOR    VEIN 


Fig,  11G4.— Veins  of  the  penis.      (Testut.) 


1392 


THE  URINOQENITAL  ORGANS 


in  size  and  in  some  subjects  is  destitute  of  glandular  tissue.  The  lower  larger 
portion  sometimes  presents  a  shallow  median  furrow  which  imperfectly  separates 
it  into  a  right  and  a  left  lateral  lobe ;  these  form  the  main  mass  of  the  gland  and  are 


BULBO- 

CAVERNOSU 

MUSCLE 


Fig,  1165. — Male  pelvic  organs  seen  from  right  side.     Bladder  and  rectum  distended;  relations  of  peritoneum 
to  the  bladder  and  rectum  shown  in  blue.     The  arrow  points  to  the  rectovesical  pouch.     (Corning.) 


DEFERENS 


PROSTATE 

Fig.  1166. — Prostate  -with  seminal  vesicles  and  seminal  duets,  viewed  from  in  front  and  above.     (Spalteholz.) 


THE  PROSTA  TE 


i;593 


directly  continuous  with  each  otlier  behind  the  urethra.  In  front  of  tiie  urethra 
tliey  are  connected  by  a  band  which  is  named  tiie  anterior  commissure;  tliis  consists 
of  the  same  tissues  as  tiie  capsule  and  is  devoid  of  glandular  suljstance. 

The  anterior  surface  (fades  anterior)  measures  about  one  inch  (2.5  cm.)  from 
above  downward,  l)ut  is  narrow  and  convex  from  side  to  side.  It  is  placed 
about  three-fourths  of  an  inch  behind  the  pubic  symphysis,  from  which  it  is  .sepa- 
rated by  a  plexus  of  veins  and  a  quantity  of  loo.se  fat.  It  is  connected  to  die  pubic 
hone  on  either  side  by  the  puboprostatic  ligaments.  The  urethra  emerges  from  this 
surface  a  little  above  and  in  front  of  tlie  apex  of  the  gland. 

The  lateral  surfaces  are  prominent,  and  are  covered  by  the  anterior  portions  of 
the  Leva  tores  ani  muscles,  which  are,  however,  separated  from  the  gland  by  a 
plexus  of  veins. 


PERITONEUM 


EJACULATORY 


CAVERNOSUM 


Fig.  1167. — Diagrammatic  representation  of  the  male  organs  of  reproduction  and  their  i 
the  urethra.     Lateral  view.     (Toldt.) 


ilations  to  the  bladder  and 


The  prostate  measures  about  an  inch  and  a  half  (3.75  cm.)  transversely  at  the 
base,  three-quarters  of  an  inch  (1.8  cm.)  in  its  antero-posterior  diameter,  and  an 
inch  and  a  quarter  (3  cm.)  in  its  vertical  diameter.  Its  weight  is  about  four  and 
a  half  drams  (18  grams).  It  is  held  in  position  by  the  anterior  ligaments  of  the 
bladder  {Ugamenta  jmboprostatica) ;  by  the  deep  layer  of  the  triangular  ligament, 
which  invests  the  commencement  of  the  membranous  portion  of  the  urethra  and 
prostate  gland;  and  by  the  anterior  portions  of  the  Levatores  ani  muscles,  which 
pass  backward  from  the  os  pubis  and  embrace  the  sides  of  the  prostate.  These 
portions  of  the  Levatores  ani,  from  the  support  they  afford  to  the  prostate,  are 
named  the  Levatores  prostatae. 

The  prostate  gland  is  perforated  by  the  urethra  and  the  ejaculatory  ducts. 
The  urethra  usually  lies  along  the  junction  of  its  anterior  with  its  middle  third. 
The  ejaculatory  ducts  pass  obliquely  downward  and  forward  through  the  posterior 
part  of  the  prostate,  and  open  into  the  prostatic  portion  of  the  urethra. 

Structure. — The  prostate  is  immediately  enveloped  by  a  thin  but  firm  musculofibrous  capsule, 
distinct  from  the  prostatic  fascia  derived  from  the  rectovesical  fascia,  and  separated  from  it  by 
a  plexus  of  veins.  The  capsule  is  firmly  adherent  to  the  prostate  and  is  structurally  continuous 
with  the  stroma  of  the  gland,  being  composed  of  the  same  tissues — viz.,  smooth  muscle  and 
fibrous  tissue.     The  prostatic  fascia,  distinct  and  dense,  does  not  cover  the  apex  and  at  the 


1394 


THE  UBINOGENITAL  ORGANS 


attachment  of  the  base  to  the  under  surface  of  the  bladder.  The  substance  of  the  prostate  is  of 
a  pale,  reddish-gray  color,  of  great  densitj',  and  not  easily  torn.  It  consists  of  glandular  sub- 
stance and  muscle  tissue. 

The  muscle  tissue,  according  to  KoUiker,  constitutes  the  proper  stroma  of  the  prostate,  the 
connective  tissue  being  very  scanty,  and  simply  forming  thin  trabeculse  between  the  muscle  fibres, 
in  which  the  vessels  and  nerves  of  the  gland  ramify.  The  muscle  tissue  is  arranged  as  follows: 
Immediately  beneath  the  fibrous  capsule  is  a  dense  layer,  which  forms  an  investing  sheath  for 
the  gland;  secondly,  around  the  urethra,  as  it  lies  in  the  prostate,  is  another  dense  layer  of  cir- 
cular fibres,  continuous  above  with  the  internal  layer  of  the  muscle  coat  of  the  bladder,  and  heloic 
blending  with  the  fibres  surrounding  the  membrcinous  portion  of  the  urethra.     Between  these 


LEFT    COMMON 


Fig.  116S. — Sagittal  section  of  the  lower  part  of  a  male  trunk,  the  right  segment.     (Testut.) 


two  layers  strong  bands  of  muscle  tissue,  which  decussate  freely,  form  meshes  in  which  the 
glandular  structure  of  the  organ  is  embedded.  In  that  part  of  the  gland  which  is  situated  in 
front  of  the  urethra  the  muscle  tissue  is  especially  dense,  and  there  is  here  little  or  no  gland  tissue; 
while  in  that  part  which  is  behind  the  urethra  the  muscle  tissue  presents  a  wide-meshed  structure, 
which  is  densest  at  the  base  of  the  gland — that  is,  near  the  bladder — and  becomes  looser  and 
more  sponge-like  toward  the  ape.x  of  the  organ. 

The  glandular  substance  is  composed  of  lobules  containing  numerous  branched  tubular 
glands  opening  into  elongated  canals,  which  join  to  form  from  twelve  to  twenty  small  excretory 
ducts.  The  glands  are  held  together  by  areolar  tissue,  supported  by  prolongations  from  the 
fibrous  capsule  and  muscle  stroma,  and  enclosed  in  a  delicate  capillary  plexus.  The  epithelium 
which  lines  the  canals  and  the  terminal  tubules  is  of  the  columnar  variety.     The  prostatic  ducts 


THE  PROSTATE 


1395 


open  into  the  floor  of  the  prostutii-  portion  of  the  urethra,  and  are  lined  by  two  layers  of  epithe- 
liviiii,  the  inner  layer  consisiinfj;  of  ((jluniiiar  and  the  outer  of  small  eubical  cells. 

Vessels  and  liferves.— Tiie  arteries  .supplyino;  the  prostate  are  derived  from  the  internal 
pudic,  inferior  vesical,  and  middle  hemorrhoidal.  Branches  of  the  vessels  enter  the  gland  in 
the   septa   between   the    lobules   and   send   off 

minute  branches  to  the  lobules  (Walker).     The  =,=„.=T.x,r 

veins  form  a  plexus  around  the  sides  and  base 
of  the  gland  between  the  layers  of  the  fascial 
sheath;  they  receive  in  front  the  dorsal  vein  of 
the  penis,  and  terminate  in  the  internal  Uiac 
vein.  The  lymphatics  of  the  prostate  are  de- 
scribed on  ]5age  796.  The  nerves  are  derived 
from  the  pelvic  plexus. 

Applied  Anatomy,  —  The  relation  of  the 
■prostate  to  the  rectum  should  be  noted;  by  means 
of  the  finger  introduced  into  the  rectum  the 
surgeon  detects  enlargement  or  other  disease  of 
the  prostate;  he  can  fee!  the  apex  of  the  gland, 
which  is  the  guide  to  Cock's  operation  for  stric- 
tm-e;  he  is  enabled  also  by  the  same  means  to 
direct  the  point  of  a  catheter  when  its  introduc- 
tion is  attended  with  difficulty  either  from  injury  or  disease  of  the  membranous  or  prostatic  portions 
of  the  urethra.  When  the  finger  is  introduced  into  the  bowel  the  surgeon  may,  in  some  cases,  espe- 
cially in  boys,  learn  the  position,  as  well  as  the  size  and  weight,  of  a  calculus  in  the  bladder.  In 
the  operation  for  the  removal  of  a  calculus,  if,  as  is  not  infrequently  the  case,  the  stone  should  be  , 
lodged  behind  an  enlarged  prostate,  it  may  be  displaced  from  its  position  by  pressing  upward  the 
base  of  the  bladder  from  the  rectum.     The  prostate  gland  is  occasionally  the  seat  of  suppuration, 


Fir.  1169.— Section  of  the  prostate.     (.Jarjavay.) 


Fig.  1170 — Transverse  section  of  normal  prostate  through  the  middle  of  the  verumontanum,  from  a  subject 
aged  nineteen  years;  a.  Longitudinal  section  of  ducts  leading  from  the  lobules  of  the  prostatic  glands.  6. 
Verumontanum.  c.  Sinus  pocularis.  d.  Urethra,  c.  Ejaculatory  ducts,  f.  Arteries,  veins,  and  venous 
sinuses  in  sheath  of  prostate,  ff.  Nerve  trunks  in  sheath,  h.  Point  of  origin  of  fibromuscular  bands  encircling 
urethra,  i.  Zone  of  striated  voluntary  muscle  on  superior  surface.  (Drawn  with  Edinger  projection  appa- 
ratus.)    (Taylor.) 


either  due  to  injury,  gonorrhea,  or  tuberculous  disease.  The  gland  is  enveloped  in  a  dense  un- 
yielding capsule,  which  determines  the  course  of  an  abscess,  and  also  explains  the  great  pain  which 
is  present  in  acute  inflammation.  The  abscess  most  frequently  bursts  into  the  urethra,  the  direc- 
tion in  which  there  is  least  resistance,  but  may  occasionally  burst  into  the  rectum,  or  more  rarely 
in  the  perineum.  In  advanced  life  the  prostate  often  becomes  considerably  enlarged,  and  may 
project  into  the  bladder  so  as  to  impede  the  passage  of  the  urine.     According  to  Dr.  Messer's 


1396 


THE  UBINOGENITAL  ORGANS 


researches,  conducted  at  Greenwich  Hospital,  it  would  seem  that  such  obstruction  exists  in  20 
per  cent,  of  all  men  over  sixty  years  of  age.  The  prostate  may  be  enlarged  by  the  growth  of 
innocent  tumors,  adenomata,  fibromata,  myomata,  and  myofibromata.  The  entire  gland  may 
be  hypertrophied.  A  tumor  may  be  encapsulated,  but  often  is  surrounded  by  an  area  of  hyper- 
plasia of  prostatic  tissues,  and  usually  the  area  of  hyperplasia  is  much  more  extensive  than  the 
tumor.  A  tumor  may  be  beneath  the  mucous  membrane,  deep  in  the  gland,  or  beneath  the 
sheath.  The  growth  called  the  third  lobe  is  submucous.  In  some  cases  the  enlargement  affects 
principally  the  lateral  lobes,  which  may  undergo  considerable  enlargement  without  causing  much 
inconvenience.  In  other  cases  it  would  seem  that  the  nodule  forms  the  so-called  middle  lobe, 
and  even  a  small  enlargement  of  this  character  may  act  injuriously,  by  forming  a  sort  of  valve 
over  the  urethral  orifice,  preventing  the  passage  of  the  urine,  and  the  more  the  patient  strains, 
the  more  completely  will  it  block  the  opening  into  the  urethra.  In  consequence  of  the  enlarge- 
ment of  the  prostate  a  pouch  is  formed  at  the  base  of  the  bladder  behind  the  projection,  in  which 
urine  collects  and  cannot  be  entirely  expelled.  The  urine  becomes  decomposed  and  ammoniacal, 
and  leads  to  cystitis.  If  the  prostate  enlarges  the  urethra  is  lengthened,  often  dilated,  altered  in 
shape,  or  distorted. 

The  relation  of  the  enlarged  prostate  to  the  neck  of  the  bladder  is  greatly  altered  from  the 
relation  of  the  normal  prostate.  Normally,  it  is  extravesical;  when  enlarged  it  may  encapsule 
"the  neck  of  the  bladder  in  a  cuff -like  manner,  extending  several  inches  upward  on  its  wall," 
and  often  it  protrudes  "into  the  vesical  cavity,  carrying  on  its  surface  the  mucosa  vesicae."  In 
many  cases  of  prostatic  enlargement  the  gland  should  be  removed  (prostatectomy).  One  method 
is  enucleation  through  a  suprapubic  incision;  another  method  is  enucleation  through  a  perineal 
incision;  another  method  is  carried  out  by  both  incisions  (the  combined  method). 

In  elderly  individuals  the  gland  tubules  may  form  round,  indurated,  and  sometimes  calcified 
masses,  about  1  mm.  in  diameter,  and  called  prostatic  stones. 


A    RIDGE    OF 
MUCOSA 
ULBOUS 
RETHRA 


Fig.  1171. — Proximal  portion  of  the  urethra,  laid  open  by  a  median,  anterior  cut.     (Testut.) 


COWPER'S  GLANDS  (GLANDULAE  BULBOURETHRALES)  (Fig.    1171). 

Cowper's  glands  are  two  small,  rounded,  and  somewhat  lobulated  bodies  of 
a  yellow  color,  about  the  size  of  peas,  placed  behnid  the  fore  part  of  the  mem- 
branous portion  of  the  urethra,  between  the  two  layers  of  the  triangular  ligament. 


THE  OVARIES 


1397 


They  lie  close  above  the  bulb,  and  are  enclosed  by  the  transverse  fibres  of  the 
Compressor  iirethrae  muscle.  Their  existence  is  said  to  be  constant;  they  gradu- 
ally diminish  in  size  as  age  advances. 

The  excretory  duct  of  each  gland,  nearly  an  inch  in  length,  passes  obliquely 
forward  beneath  the  mucous  membrane,  and  opens  by  a  minute  orifice  on  the 
floor  of  the  bulbous  portion  of  the  urethra. 

Structure. — Each  gland  consists  of  several  lobules  held  together  by  a  fibrous  investment. 
Each  lobule  consists  of  a  number  of  acini  lined  by  columnar  epithelial  cells,  opening  into  one 
duct,  which,  joining  with  the  ducts  of  other  lobules  outside  the  gland,  form  the  single  excretory 
duct. 

THE  FEMALE  REPRODUCTIVE  ORGANS. 

The  female  reproductive  organs  (organa  genitalia  muliebria)  consist  of  an  internal 
and  an  external  group.  The  internal  organs  are  situated  within  the  pelvis,  and 
consist  of  the  ovaries,  the  Fallopian  tubes  or  oviducts,  the  uterus,  and  the  vagina. 
The  external  organs  are  placed  superficial  to  the  triangular  ligament  of  the  urethra 
and  below  and  in  front  of  the  pubic  arch.  They  comprise  the  mons  veneris, 
the  labia  majora  et  minora,  the  clitoris,  the  bulbi  vestibuli,  and  the  glands  of 
Bartholin. 

THE   OVARIES   (OVARIA)    (Figs.   1172,  1177). 

The  ovaries  are  homologous  with  the  testes  in  the  male.  They  are  two  nodular, 
oval-shaped  bodies  of  an  elongated  form,  situated  one  on  either  side  of  the  uterus, 
in  the  posterior  layer  of  the  broad  ligament  behind  and  below  the  Fallopian  tube. 


f 


'   ^   Ligament  of  ovary. 
Fallopian  tube. 
Hound  ligament 
of  uterifi. 

Fig.  1172. — Female  pelvis  and  its  contents,  seen  from  above  and  in  front. 

The  ovaries  are  of  a  grayish-pink  color,  and  present  either  a  smooth  or  a  puckered, 
inieven  surface.  They  are  each  about  an  inch  and  a  half  (3.75  cm.)  in  length 
three-quarters  of  an  inch  (2  cm.)  in  width,  and  about  a  third  of  an  inch  (8  mm.) 
thick,  and  weigh  from  one  to  two  drams  (4  to  8  grams). 


1398 


TFIE  UBINOGENITAL   ORGANS 


Each  ovary  {ovarium)  presents  an  outer  and  an  inner  surface,  an  upper  and 
a  lower  extremity,  and  an  anterior  and  a  posterior  border.  It  lies  in  a  shallow 
depression,  named  the  fossa  ovarii,  on  the  lateral  wall  of  the  pelvis;  this  fossa  is 
bounded  above  by  the  external  iliac  vessels,  in  front  by  the  impervious  hypogastric 
artery,  and  behind  by  the  ureter.  The  exact  position  of  the  ovary  has  been  the 
subject  of  considerable  difference  of  opinion,  and  the  description  here  given 
applies  to  the  nulliparous  woman.  The  ovary  becomes  displaced  during  the 
first  pregnancy  and  probably  never  again  returns  to  its  original  position. 

In  the  erect  posture  the  long  axis  of  the  ovary  is  nearly  vertical.  The  uffer 
or  tubal  extremity  is  near  the  external  iliac  vein;  to  it  is  attached  the  ovarian 
fimbria  of  the  Fallopian  tube  and  a  fold  of  peritoneum,  the  suspensory  ligament 
of  the  ovary,  which  is  directed  upward  over  the  iliac  vessels  and  contains  the 
ovarian  vessels.     The  lower  or  uterine  end  is  directed  toward  the  pelvic  floor;  it 


Fig.  1173. — Female  pehic  organs  t«  sztu,  seen  from  above      (Bardeleben.) 


is  usually  narrower  than  the  upper  end  and  is  attached  to  the  lateral  angle  of  the 
uterus,  immediately  behind  the  Fallopian  tube,  by  a  rounded  cord  termed  the 
ligament  of  the  ovary,  which  lies  within  the  broad  ligament  and  contains  some  non- 
striated  muscle  fibres.  The  outer  surface  is  in  contact  with  the  parietal  peritoneum 
which  lines  the  fossa  ovarii,  the  inner  surface  is  to  a  large  extent  covered  by  the 
fimbriated  extremity  of  the  Fallopian  tube.  The  anterior  or  straight  border  is 
directed  toward  the  impervious  hypogastric  artery,  and  is  attached  to  the  back 
of  the  broad  ligament  by  a  short  fold  named  the  mesovarium.  Between  the  two 
layers  of  this  fold  the  bloodvessels  and  nerves  pass  to  enter  the  hilum  of  the 
ovary.  The  posterior  or  convex  border  is  free  and  is  directed  toward  the  ureter. 
The  Fallopian  tube  arches  over  the  ovary,  running  upward  in  relation  to  its  anterior 
border,  then  curving  over  its  upper  or  tubal  pole,  and  finally  passing  downward 
on  its  posterior  border  and  inner  surface. 
The  Descent  of  the  Ovary  is  described  on  page  1425. 


THE  OVARIES 


1399 


The  Ovary  at  Different  Ages. — The  ovary  of  childhood  is  smooth  and  even.  The  scars 
of  many  ruptured  Graafian  follicles  cause  this  surface  of  the  ovary  to  become  pitted,  puckered, 
fibrous,  and  uneven  in  old  age.  The  surface  of  the  ovary  is  grayish  red  in  color.  The  corpus 
luteum  of  a  nonpregnant  woman  slowly  degenerates  and  disappears.  The  corpus  luteum  of 
an  impregnated  woman  enlarges  during  pregnancy. 


Fig.  1174. — Diagrammatic  representation  of  the  female  reproductive  organs  and  their  relations  to  the  bladder  and 
urethra,  lateral  view.     (Toldt.) 


Structure  (Figs.  1175,  1176,  and  1184). — The  ovary  consists  of  the  cortex  and  medulla, 
in  the  former  of  which  are  founi)  the  Graafian  follicles  and  theu-  remains  and  the  hilum  of  the 
ovary.  The  cortex  consists  of  stroma  and 
Graafian  follicles.  Peripherally,  the  stroma 
is  condensed  to  form  a  capsule,  the  tunica 
albuginea,  which  is  covered  by  a  layer  of 
cuboidal  epithelial  cells  called  the  germinal 
epithelium,  and  is  often  referred  to  as  the 
serous  covering  of  the  organ.  These  cells 
are  sharply  marked  off  by  a  whitish  line, 
at  the  hilum  of  the  ovary,  from  the  endo- 
thelium of  the  peritoneum.  The  stroma 
consists  of  a  delicate  white  fibrous  tissue 
meshwork,  containing  many  small  blood- 
vessels and  groups  of  large  polygonal  epi- 
thelial cells  called  interstitial  ceils. 

In  the  stroma  are  foimd  the  Graafian 
follicles  (Fig.  1175)  and  their  remains. 
The  follicles  are  of  different  sizes;  the 
smallest  are  beneath  the  tunica  a;lbuginea, 
the  medium-sized  follicles  are  found  toward 
the  medulla,  while  the  largest  extend  from 
the  innermost  part  of  the  cortex  and  beyond 
its  ordinary  limit,  thus  causing  the  nodular 
appearance  of  the  surface  of  the  ovary.     A 

large  follicle  consists  of  a  sheath  of  stroma  called  the  theca  foUiculi,  the  inner  portion  of  which 
is  quite  vascular.  Lining  the  theca  are  several  layers  of  granular  cells,  the  zona  granulosa. 
The  greater  part  of  the  follicle  is  devoid  of  cells,  but  contains  a  licjuid,  the  liquor  foUiculi,  and  the 


Fig.  1175. — Section  of  the  ovary:  1.  Outer  covering. 
1'.  Attached  border.  2.  Central  stroma.  3.  Peripheral 
stroma.  4.  Bloodvessels.  5.  Graafian  follicles  in  their 
earliest  stage.  6,  7,  8.  More  advanced  follicles.  9.  An 
almost  mature  follicle.  9'.  Follicle  from  which  the  ovum 
has  escaped.     10.  Corpus  luteum.     (.\fter  Schron.) 


1400 


THE   UBINOGENITAL   ORGANS 


space  occupied  by  this  is  termed  the  antrum.  At  one  point  the  zona  granulosa  forms  a  mass 
which  projects  into  the  antrum;  this  mass,  the  discus  proligerus,  contains  the  ovum  and  its 
membrane.  Beneath  the  granular  cells  of  the  discus  is  a  layer  of  radially  placed  tall  columnar 
cells,  the  corona  radiata,  within  which  lies  a  broad  clear  membrane,  the  zona  pellucida,  or  zona 
radiata.  Between  the  zona  pellucida  and  the  ovum,  which  lies  within  it,  is  said  to  exist  a  narrow 
space,  the  perivitelline  space. 

The  ovum  consists  of  an  outer  membrane,  the  vitelline  membrane,  internal  to  which  is  the 
protoplasm  or  vitellus.  Embedded  in  the  latter  is  a  large,  pale-staining,  eccentrically  placed 
nucleus,  the  germinal  vesicle,  which  contains  a  large,  deeply  staining  nucleolus,  or  germinal 
spot.  Although  the  ovum  is  usually  described  as  a  typic  cell,  the  matured  ovum,  since  it  does 
not  contain  a  centrosome,  cannot  be  so  designated. 

When  a  follicle  enlarges  it  ruptures  and  the  ovum  usually  escapes  into  the  oviduct.  This 
process  constitutes  ovulation.  When  the  ovum  escapes,  the  vessels  of  the  follicle  rupture  and  fill 
the  antrum  with  blood  and  form  thus  the  corpus  hemorrhagicum.  As  this  becomes  organized,  the 
hemoglobin  is  absorbed  and  this  body  becomes  yellowish,  due  to  the  presence  of  a  great  number 
of  large  yellow  ekments,  the  lutein  cells,  and  thus  the  corpus  luteum  is  formed.    If  pregnancy 


{fibre 


Tkecn 
follkuir 


3Iemhrana^ 
granulosa 


Fig.  1176. — Section  through  a  Graafian  foUicle  from  an  ape's  ovary.     X  90.     (Szymonowicz.) 


supervenes,  this  body  persists  almost  the  entire  period  of  gestation;  if  the  ovum  is  not 
impregnated,  the  corpus  luteum  soon  becomes  contracted  and  whitish,  and  forms  the  corpus 
albicans. 

The  medulla  consists  of  a  loose  network  of  coarse  bundles  of  white  fibrous  tissue,  which  sup- 
ports many  large  bloodvessels;  here  are  also  seen  smooth  muscle  tissue  and  interstitial  cells. 

The  hiliim  is  a  scar-like  depression  at  which  the  medulla  comes  to  the  surface;  here  the  vessels, 
nerves,  and  lymphatics  enter  and  emerge. 

Each  ovum,  before  it  can  be  fertilized,  must  undergo  maturation.  In  this  process  the  oocyte 
undergoes  two  divisions,  resulting  in  four  cells,  each  of  which  contains  one-fourth  the  amount 
of  chromatin  in  the  form  of  one-half  the  number  of  chromosomes.  Three  of  these,  the  polar 
bodies,  are  small  and  unimportant  and  disappear.     The  fourth  is  the  large  matured  ovum. 

The  development  and  maturation  of  the  Graafian  vesicles  and  ova  continue  uninterruptedly 
from  puberty  to  the  end  of  the  fruitful  period  of  woman's  life,  while  their  formation  commences 
before  birth.  Before  puberty  the  ovaries  are  small,  the  Graafian  vesicles  contained  in  them  are 
disposed  in  a  comparatively  thick  layer  in  the  cortical  substance;  here  they  present  the  appear- 
ance of  a  large  number  of  minute  closed  vesicles,  constituting  the  early  condition  of  the  Graafian 
vesicles;  many,  however,  never  attain  full  development,  but  shrink  and  disappear.  At  puberty 
the  ovaries  enlarge  and  become  more  vascular,  the  Graafian  vesicles  are  developed  in  greater 
abundance,  and  their  ova  are  capable  of  fecundation. 


THE  FALLOPIAN  TUBE,   OR  OVIDUCT  1401 

Vessels  and  Nerves. — The  arteries  of  the  ovaries  (Figs.  118.5  and  1187)  are  the  ovarian 
from  the  aorta,  corresponding  to  the  spermatic  arteries  in  the  male.  The  ovarian  artery  on  each 
side  enters  the  pelvis  in  the  fold  of  broad  ligament  known  as  the  suspensory  ligament  of  the  ovary 
and  enters  the  attached  border,  or  hilum,  of  the  ovary.  The  ovarian  vessels  anastomose  about 
the  hilum  with  branches  of  the  uterine  artery.  The  veins  follow  the  course  of  the  arteries; 
they  form  a  plexus  near  the  ovary,  the  pampiniform  plexus,  corresponding  to  a  like  structure 
near  tlie  testis  of  the  male.  The  lymphatics  (Pis-  llSd)  terminate  in  the  nodes  to  the  corre- 
sponding side  of  tiie  aorta,  and  tiiey  anasloniosi-  in  their  cdurse  with  trunks  from  the  uterine 
fundus  and  oviduct.  The  nerves  come  from  the  ovarian  plexus,  which  is  a  continuation  of  the 
renal  plexus  along  the  ovarian  artery,  anti  from  the  aortic  plexus. 

The  epobphoron,  parovarium  or  organ  of  Rosenmiiller  (Figs.  1177,  1180,  and  1181)  is  placed 
in  the  meso.salpinx,  between  the  ovary  and  tube.  It  consists  of  a  number  of  epithelial-lined 
closed  tubes.  This  structure  can  be  readily  seen  if  the  mesosalpinx  is  stretched  and  held  in 
front  of  the  light.  One  of  these  tubes  runs  parallel  to  the  Fallopian  tube,  and  is  called  Gartner's 
duct  {(hictiis  cpuopjinri  Iniii/itiiilhtalis).  A  number  of  tubes  (duduli  trarwversi)  ascend  from  near 
the  (>v;irv  and  each  enipiies  into  diirtner's  duct  at  a  right  angle.  Gartner's  duct  is  a  portion  of 
the  \\'(ilftian  duet,  which  has  jiersisted  and  is  represented  in  the  male  by  the  canal  of  the  epi- 
didymis. The  tubules  which  join  the  duct  are  persistent  mesonephric  tubules  and  are  the 
homologues  of  the  vasa  eiferentia  and  coni  vasculosi  of  the  testis,  and  probably  also  the  aberrant 
ducts  of  the  canal  of  the  epididymis. 

The  paroophoron  is  within  the  mesosalpinx,  but  is  nearer  to  the  uterus  than  is  the  epoophoron. 
It  consists  of  several  small  tubules,  which  can  be  seen  in  an  adult  only  by  the  aid  of  a  pocket 
lens.  They  are  visible  to  the  naked  eye  in  a  child  at  birth.  It  represents  the  organ  of  Giraldes 
in  the  male  and  is  derived  from  the  mesonephros. 

Applied  Anatomy. — An  ovary  may  fail  to  descend  and  remain  well  above  the  pelvic 
brim;  it  may  prolapse  into  Douglas'  pouch;  it  may  enter  the  sac  of  a  hernia;  it  may  inflame;  a 
tumor  or  cyst  may  arise  from  it.  A  solid  tumor  of  the  ovary  may  be  a  fibroma,  a  sarcoma,  or  a 
carcinoma.  "Cysts  may  originate  in  any  part  of  the  tuboovarian  structure;  as  the  cortical, 
medullary,  or  parenchymatous  portions  of  the  ovary;  in  the  structure  between  the  tube  and 
ovary  known  as  the  Rosenmiiller  organ  or  parovarian  structures;  and  in  the  hydatid  of 
JMorgagni."  Cysts  may  be  simple,  proliferating,  or  dermoid;  unilocular  or  multilocular. 
Glandular  proliferous  cysts,  papillary  proliferous  cysts,  dermoid  cysts,  and  parovarian  cysts 
may  attain  a  large  or  even  an  enormous  size.  The  operation  for  the  removal  of  an  ovarian 
cyst  is  one  of  the  most  successful  of  the  major  procedures  of  surgery. 


THE    FALLOPIAN    TUBE,    OR    OVIDUCT    (TUBA   UTERINA   [FALLOPII]) 

(Figs.  1177,  1178). 

The  Fallopian  tubes  or  oviducts  convey  the  ova  from  the  ovaries  to  the  cavity 
of  the  uterus.  They  are  two  in  number,  one  on  each  side,  situated  in  the  upper 
margin  of  the  broad  hgament,  extending  from  each  superior  angle  of  the  uterus  to 
the  side  of  the  pelvis.  Each  tube  is  about  four  inches  (10  cm.)  in  length,  and 
is  described  as  consisting  of  three  portions — (1 )  the  isthmus  {isthvius  tuhae  uterinae) 
(Fig.  1177),  or  inner  constricted  third;  (2)  the  ampulla  {ampulla  tuhae.  uterinae) 
(Fig.  1177),  or  outer  dilated  portion,  which  curves  over  the  ovary;  and  (.3)  the 
infundibulum  (infimdibuhim  tubae  uterinae),  the  funnel-hke  expansion  of  the  tube, 
at  the  bottom  of  which  is  the  abdominal  orifice  or  pavilion  (ostium  abdominale 
tubae  uterinae)  (Fig.  1177).  The  abdominal  orifice  has  a  small  diameter  (2  mm. 
when  relaxed  to  its  full  extent).  The  margin  of  the  infundibulum  is  rendered 
irregular  by  the  presence  of  numerous  small  processes,  the  fimbriae  (fimbriae 
tubae).  This  end  of  the  tube  is  called  the  fimbriated  extremity  (Fig.  1177),  because 
of  these  processes.  The  surfaces  of  the  fimbriae  looking  into  the  cavity  of  the 
infundibulum  are  covered  with  mucous  membrane  continuous  with  the  tubal 
mucous  membrane.  The  outer  surfaces  are  covered  with  peritoneum.  One  of 
the  fimbriae  is  attached  to  the  ovary  and  is  called  the  ovarian  fimbria  (fimbria 
ovarica)  (Fig.  1177).  The  uterine  opening  (ostium  uterinum  tubae)  is  even  smaller 
than  the  abdominal  opening,  and  will  admit  only  a  small  bristle.  In  connection 
with  the  fimbriae  of  the  Fallopian  tube  or  with  the  broad  ligament  close  to  them 


1402 


THE  UBINOGENITAL  ORGANS 


there  are  frequently  one  or  more  small  pedunculated  vesicles.     These  are  termed 
the  hydatids  of  Morgagni  {appendices  vesicidosi). 

The  course  pursued  by  the  Fallopian  tube  has  been  given  in  its  relations  to  the 
ovary  on  page  1398. 

Structure. — The  Fallopian  tube  consists  of  three  coats — serous,  muscular,  and  mucous. 

The  external  or  serous  coat  (tunica  serosa)  is  peritoneal.  Beneath  this  lies  the  tunica 
adventitia,  composed  of  lax  connective  tissue. 

The  middle  or  muscular  coat  (tunica  muscularis)  consists  of  an  external  longitudinal  layer 
(stratum  longitudinale),  and  an  internal  circular  layer  [stratum  circulare)  of  smooth  muscle  fibres 
continuous  with  those  of  the  uterus;  near  the  uterine  end  of  the  tube  an  inner  longitudinal  la\'er 
is  found. 

The  internal  or  muocus  coat  (tunica  mucosa)  is  continuous  with  the  mucous  lining  of  the 
uterus  and,  at  the  free  extremity  of  the  tube,  with  the  peritoneum.  It  is  thrown  into  branched 
longitudinal  folds  or  villi  (plicae  iubariae),  which  in  the  outer,  larger  part  of  the  tube  or  ampulla 
(plicae  ampullare.s)  are  much  more  extensive  than  in  the  narrow  canal  of  the  isthmus  (plicae 
isthmicae).  The  lining  epithelium  is  simple  ciliated.  This  form  of  epithelium  is  also  found  on 
the  inner  surface  of  the  fimbriae,  while  on  the  outer  or  serous  surfaces  of  these  processes  the  epi- 
thelium gradually  merges  into  the  endothelium  of  the  peritoneum. 


Fimbria  ucarica. 
Fig.  1177. — Dissection  of  uterine  appendages, 


L  from  behind.     (Henle.) 


Vessels  and  Nerves. — The  cliief  artery  of  the  tube  is  the  tubal  branch  of  the  uterine  artery 

(ramus  tuharius)  (Fig.  1185).  It  also  receives  branches  from  the  ovarian  (Fig.  llSo).  Some 
of  the  tubal  veins  empty  into  the  uterine  veins,  some  into  the  ovarian  veins.  The  lymphatics 
(Fig.  1186)  coming  from  the  tube  unite  with  the  trunks  coming  from  the  uterus  and  ovary  and 
terminate  in  the  lateral  aortic  nodes.  The  nerves  come  from  the  same  plexuses  that  send 
branches  to  the  uterus  and  ovary. 

Applied  Anatomy. — Extrauterine  pregnancy  most  commonly  occurs  in  the  ampulla  of  the 
tube.  The  product  of  the  conception  may  escape  tlirough  the  ostium  abdominale  or  the  walls 
of  the  tube  may  rupture,  a  violent  hemorrhage  resulting.  Pelvic  peritonitis  is  a  not  uncommon 
sequence  of  tubal  disease.  Salpingitis  is  inflammation  of  the  mucous  coat  of  the  tube — inter- 
stitial salpingitis  of  the  middle  coat;  perisalpingitis  of  the  peritoneal  coat.  If  inflammation 
closes  the  uterine  and  the  abdominal  ends  of  the  tube,  mucus  gathers  and  distends  the  tube 
(hydrosalpinx).     If  purulent  matter  gathers,  the  condition  is  known  as  pyosalpiivx. 


THE  UTERUS,   OR  WOMB  (Figs.  1178,  1181). 

The  uterus  is  the  organ  of  gestation,  receiving  the  fecundated  ovum  in  its  cavity, 
retaining  and  supporting  it  during  the  development  of  the  fetus,  and  becoming 
the  principal  agent  in  its  expulsion  at  the  time  of  parturition.     It  is  a  hollow 


THE   UTERUS,    OR    WOMB 


1403 


muscular  organ.  The  nonpregnant  uterus  is  contained  in  the  cavity  of  the  pelvis 
between  the  bladder  and  the  rectum  (Figs.  1183  and  11S8).  It  is  rarely  placed 
exactly  in  the  midline,  but  inclines  to  one  side  or  the  other,  more  often  to  the 
left  than  to  the  right.  The  walls  of  the  organ  are  extremely  thick.  The  uterus 
is  movable  as  a  whole,  and  the  body  of  the  uterus  is  movable  upon  the  neck. 
Its  position  varies  with  the  condition  of  adjacent  parts,  especially  of  the  bladder 
and  rectum.  The  cervix  is  more  firmly  fixed  than  the  body  and  fundus,  and  hence 
the  latter  vary  more  in  position  than  the  former.  Normally,  in  an  erect  indi- 
vidual, with  the  bladder  and  rectum  empty,  the  external  os  is  at  the  level  of  the 
upper  surface  pf  the  pubic  symphysis  (Fig.  1174)  and  in  a  frontal  plane  passing 
through  the  ischiatic  spines.  The  long  axis  of  the  uterus  is  directed  forward  and 
upward  (Fig.  1174)  and  is  angled  where  the  body  and  cervix  join.  Hence,  nor- 
mally, with  the  bladder  empty,  the  uterus  is  anieverted  and  anieflexed.  When 
the  bladder  fills,  the  anteversion  and  anteflexion  are  almost  aboli.shed.  If  the 
bladder  is  overdistended  and  the  rectum  is  empty,  the  uterus  is  pushed  strongly 
backward;  so  that  its  long  axis  corresponds  to  the  long  axis  of  the  vagina;  in 
other  words,  it  is  retroverted. 


MESOVARI 


MESOSALPINX 


TUBAL 

EXTREMITY 

OF  OVAH^ 


FALLOPIAN 


OUND 
LIGAMENT 
F  UTERUS 


POST. 
FORNIX  OF 
VAGINA 


VAGINAL 

RTION  OF 
RVIX 


Fig.  1178. — The  uterus,  the  left  Fallopian  tube,  and  the  left  ovary  in  their  connection  with  the  broad  ligament  of 
the  uterus,  which  has  been  fully  unfolded.    Seen  from  behind.     From  a  virgin,  aged  nineteen  jjears.     (Toldt.) 

In  the  virgin  state  it  is  pear-shaped,  flattened  from  before  backward,  and  is 
retained  in  its  position  by  the  round  and  broad  ligaments  on  each  side,  and 
projects  into  the  upper  end  of  the  vagina  below  (Figs.  1178  and  1179).  Its  upper 
end,  or  base,  is  directed  upward  and  forward;  its  lower  end,  or  apex,  downward 
and  backward,  in  the  line  of  the  axis  of  the  inlet  of  the  pelvis.  It  therefore  forms 
an  angle  of  about  110  degrees  with  the  vagina,  since  the  direction  of  the  vagina 
corresponds  to  the  axis  of  the  cavity  and  outlet  of  the  pelvis.  The  nonpregnant 
adult  uterus  measures  about  three  inches  (7.5  cm.)  in  length,  two  inches  (5  cm.) 
in  breadth  at  its  upper  part,  and  nearly  an  inch  (2.5  cm.)  in  thickness,  and  it 
weighs  from  an  ounce  to  an  ounce  and  a  half  (30  to  45  grams). 

It  consists  of  two  parts  (Fig.  1178):  (1)  An  upper  and  larger  portion,  consists 
ing  of  the  body  and  fundus.  This  portion  is  flattened  from  before  backward, 
(2)  A  lower,  smaller,  and  cylindrical  portion,  the  cervix. 

On  the  surface,  about  midway  between  the  base  and  apex,  a  slight  constriction, 
known  as  the  isthmus  uteri,  and  a  corresponding  narrowing  of  the  uterine  cavity, 
the  internal  os,  serve  to  demarcate  the  two  portions. 


1404 


THE  UBINOQENITAL  ORGANS 


The  fundus  {fundus  uteri)  (Fig.  1 178)  is  the  upper  broad  extremity  of  the  uterus. 
If  a  Hue  is  drawn  from  the  uterine  opening  of  one  Fallopian  tube  to  the  other, 
the  portion  above  the  line  is  the  fundus.  The  fundus  is  directly  continuous  with 
the  body. 

The  body  of  the  uterus  {corpus  uteri)  (Fig.  1178)  gradually  narrows  from  the 
fundus  to  the  isthmus.  In  outline,  when  seen  from  in  front  or  laehind,  it  resembles 
a  triangle,  the  base  being  above  and  the  apex  being  absent.  The  anterior  surface 
{fades  vesicales)  is  so  slightly  rounded  as  to  appear  flattened.     It  is  covered  by 


eXTCRNAL 
ORIFICE  OF 
URETHRA 


RAVAGI^ 
PORTION 

CERVIX 


Fig.  1179, — The  external  genital  organ  of  a  virgin  attached  to  the  vagina,  which  has  been  isolated  and  opened,  and 
a  portion  of  the  cervix  uteri.     (Toldt.) 

peritoneum  (Fig.  1178),  which  becomes  reflected  from  it  at  its  isthmus  to  form  the 
uterovesical  pouch,  which  lies  between  the  uterus  and  bladder  (Fig.  1182).  Its 
posterior  surface  is  more  rounded  than  the  anterior,  being  convex  transversely. 
It  is  covered  by  peritoneum  throughout  except  along  the  attachments  of  the 
layers  of  the  broad  ligament  (Fig.  1183),  and  is  separated  from  the  rectum  by 
some  convolutions  of  the  small  intestine  (Fig.  1182).     The  peritoneum  which 


THE  UTERUS,   OB   WOMB 


1405 


covers  the  posterior  surface  forms  most  of  the  anterior  wall  of  Douglas'  cul-de-sac 
(Figs.  1181  and  1182,  and  p.  1407).  Its  lateral  margins  (Figs.  1178  and  1181) 
are  slightly  convex.  At  the  upper  angle  the  Fallopian  tube  joins  the  body  of 
the  uterus;  immediately  below  this  the  round  ligament  is  attached,  and  be- 
hind the  latter  is  the  attachment  of  the  ligament  of  the  ovary;  behind  both  of 


Fig.  1180. — The  parovarium.    The  mesoaalpinx  is  partly  removed.     (Poirier  and  Charpy.) 

these  structures,  and  from  the  side  of  the  womb  the  broad  ligament  passes.  The 
division  between  the  body  and  the  cervix  is  indicated  externally  by  the  isthmus 
and  by  the  reflection  of  the  peritoneum  from  the  anterior  surface  of  the  uterus 
on  tp  the  bladder,  and  internally  by  a  narrowing  of  the  canal  called  the  internal 
OS  (Fig.  1181). 

The  neck  or  cervix  uteri  (Figs.  1178  and  1181)  is  the  lower  constricted  segment 
of  the  uterus;  around  its  circumference  is  attached  the  upper  end  of  the  vagina 
(Figs.  1178  and  1182),  which  extends  upward  a  greater  distance  behind  than  in 
front.  The  neck  is  spindle-shaped  in  the  nulliparous  and  cylindrical  in  parous 
women. 


UTEnmc 

ORIFICE   OF 
FALLOPIAN  TUBE 


EPOOPHOHON 


UTEROVAGINAL 

VENOUS 

PLEXUS 


Fig.  1181.— The  uterus  and  the  right  Fallopian  tube  opened  from  behind.     (Toldt.) 

The  supravaginal  portion  {poiiio  S2ipravaginalis  [cervicis])  (Figs.  1178  and  1182) 
is  not  covered  by  peritoneum  in  front;  a  pad  of  cellular  tissue  is  interposed  between 
it  and  the  bladder.     Behind,  the  peritoneum  is  ex-tended  over  it. 

The  vaginal  portion  (portio  vaginalis  [cervicis])  (Figs.  1178  and  1182)  is  the  lower 
end  projecting  into  the  vagina.     It  is  circular  or  elliptical,  the  long  axis  of  the 


1406 


THE   imiNO GENITAL   ORGANS 


CTAL   PERITONEUM 

CTOVAGrNAL    POUCH 

NTERIOR    AND    POS- 
TERIOR   LAYERS    OF 


ellipse  being  transversely  placed.  On  its  surface  is  a  small  aperture,  the  ex- 
ternal OS  or  OS  uteri  {orificium  externum  uteri)  (Figs.  1178  and  1181),  gener- 
ally linear  in  shape,  but  sometimes  oval 
or  almost  circular.  If  a  woman  has 
borne  children,  the  opening  is  trans- 
verse and  the  margins  are  irregular. 
The  margin  of  the  opening  is,  in  the 
absence  of  parturition  or  di-sease, 
quite  smooth.  This  aperture  divides 
the  vaginal  portion  of  the  cervix  into 
two  lips,  an  upper  or  posterior  lip 
(labium  posterius)  and  an  anterior  lip 
(labium  anterius).  On  each  side  of 
the  cervix  and  upper  portion  of  the 
vagina  there  is  a  space  containing 
bloodvessels  and  filled  with  loose 
cellular  tissue.  This  loose  tissue 
passes  upward  between  the  layers  of 
the  broad  ligament,  and  is  called  parametrium.  On  each  side  of  the  cervix  and 
three-quarters  of  an  inch  away  is  the  terminal  portion  of  the  corresponding  ureter. 


Fii  lis-  I  he  re 
\agina,  fanow  in^  thei 
grammatic       (Te^tut 


\  IX   uteri  and   tipper  end  of   the 
relationb  to  the  peritoneum.    Dia- 


Fig.  llS3._Douglas' pouch.    (From  a  preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  England. 

Folds  and  Ligaments.— The  ligaments  of  the  uterus  are  eight  in  number. 
Some  are  simple  folds  of  peritoneum;  others  contain  connective  tissue  and  muscle. 
The  ligaments  are  as  follows:  one  anterior,  one  posterior,  two  lateral  or  broad, 


ous 

ABRANC 


THE  UTERUS,   OR    WOMB  1407 

two  sacrouterine — all  these  being  formed  of  peritoneum — and,  lastly,  two  round 
ligaments. 

The  anterior  ligament  or  the  uterovesical  fold  is  reflected  on  to  the  bladder  from 
the  front  of  the  uterus,  at  the  junction  of  the  cervix  and  body.  It  forms  the  utero- 
vesical pouch  {excavatio  vesicoiderina)  (Figs.  1182  and  1183). 

The  posterior  ligament  or  the  rectovaginal  fold  passes  from  the  posterior  wall 
of  the  uterus  over  the  upper  fourth  of  the  vagina,  and  thence  on  to  the  rectum  and 
sacrum.  It  thus  forms  a  pouch,  called  the  rectovaginal  pouch  or  Douglas'  pouch 
(Figs.  1182  and  1183),  the  boundaries  of  which  are,  in  front,  the  posterior  wall 
of  the  uterus,  the  supra\'aginal  portion  of  the  cervix,  and  the  upper  fourth  of  the 
vagina;  behind,  the  rectum  and  sacrum;  above,  the  small  intestine;  and  laterally, 
the  folds  of  Douglas  or  rectouterine  folds,  which  contain  the  sacrouterine  ligaments. 

The  broad  ligament  {ligamentwn  latum  uteri)  (Figs.  1183  and  1184)  is  a  peri- 
toneal fold  which  passes  from  each  side  of  the  uterus  to  the  lateral  wall  of  the 
pelvis  as  high  as  the  external  iliac  vein.  From  this  region  comes  the  peritoneal 
fold  called  the  suspensory  ligament  of  the  ovary  (Fig.  1173).  The  two  broad 
ligaments  form  a  septum  across  the  pelvis,  which  divides  that  cavity  into  two  por- 
tions. In  the  anterior  part  are  contained  the  bladder,  urethra,  and  vagina; 
in  the  posterior  part,  the  rectum.  With  the  uterus  normally  placed  the  anterior 
surface  of  the  broad  ligament  faces  forward  and  downward,  and  the  posterior 
surface  faces  upward  and  backward.  The  ligament  is  more  nearly  vertical 
at  its  pelvic  attachment.     The  two  layers  of 

the  broad  ligament  are  mostly  near  to  each  ^-^Sn    mesosalpinx 

other,  to  the  side  and  below  they  separate 
and  pass  into  the  peritoneum  of  the  lateral 
pehic  wall,  the  bladder,  and  the  rectum. 
Between  the  two  layers  of  each  broad  liga- 
ment are  contained  (1)  the  Fallopian  tube 
superiorly;  (2)  the  round  ligament;  (3)  the 
ovary  and  its  ligament;  (4)  the  parovarium 
or  organ  of  Rosenmiiller,  and  the  paroopho- 
ron; (5)  loose  connective  tissue,  which  is 
called  parametrium;  (6)  unstriped  muscle 
tissue;  and  (7)  bloodvessels  and  nerves.  The 
Fallopian   tube  is    in    the    free    edge  of   the        ^       i,q,    -yu    u     j  ,•         *    <•    *w 

,  \..  .        ,    .    °  .    ,  Fig.     1184.— The    broad    ligament    of     the 

broad  hgament,  and  is  contained  in  a  special     uterus,  wuh  the  mesovarium,  the  mesosai- 

n   ,  I  ....         ,,       1       I     ,        ,1  ,      V     ,1  pinx,  the  ovary,   and   the   Fallopian  tube   in 

lOlcl,    which    IS    attached    to    the    part   or     the      transverse  section.     (Toldt.) 

ligament  near  the  ovary,  and  is  known  by  the 

name  of  the  mesosalpinx  (Figs.  1181  and  1184).  If  the  mesosalpinx  is  spread 
out,  it  is  seen  to  be  roughly  triangular;  the  base  of  the  triangle  is  outward,  the 
apex  at  the  upper  and  outer  angle  of  the  uterus ;  the  upper  boundary  is  the  Fallo- 
pian tube,  and  the  lower  boundary  is  the  ovary  and  its  ligament.  Between  the 
two  layers  of  the  mesosalpinx  are  the  parovarium  and  the  paroophoron.  Between 
the  fimbriated  extremity  of  the  tube  and  the  lower  attachment  of  the  broad 
ligament  is  a  concave  rounded  margin,  called  the  infundibulopelvic  ligament 
(Fig.  1177). 

The  mesovarium  passes  upward  from  the  posterior  surface  of  the  broad  liga- 
ment (Fig.  1184).  Beneath  the  mesovarium  is  a  larger  and  thicker  portion  of 
the  broad  ligament,  called  the  mesometrium  (Fig.  1184). 

The  sacrouterine  or  rectouterine  ligaments  {plicae  rectouterinae)  are  contained 
in  the  peritoneal  folds  of  Douglas.  They  pass  from  the  second  and  third  segments 
of  the  sacrum,  downward  and  forward  on  the  lateral  aspects  of  the  rectum,  to  be 
attached  one  on  each  side  of  the  uterus  at  the  junction  of  the  supravaginal  cervix 
and  the  body,  this  point  corresponding  internally  to  the  position  of  the  os  internum. 


1408  THE  URINOGENITAL  ORGANS 

They  contain  fibrous  tissue  and  unstriated  muscle  fibre.  Muscle  fibres  from  the 
uterine  wall  to  the  rectal  wall  constitute  the  Rectouterinus  muscle  {miisculus  recto- 
uterinus).     This  muscle  is  part  of  the  sacrouterine  ligaments. 

A  round  ligament  (ligamentiim  teres  uteri)  (Figs.  1178  and  1183)  is  attached  on 
each  side  of  the  uterus.  The  two  ligaments  are  rounded  cords  between  four  and 
five  inches  in  length,  each  situated  between  the  layers  of  the  broad  ligament 
in  front  of  and  below  the  Fallopian  tube.  Commencing  at  the  superior  angle 
of  the  uterus,  this  ligament  passes  forward,  upward,  and  outward  through  the 
internal  abdominal  ring,  along  the  inguinal  canal,  to  the  labium  majus,  in  which 
it  becomes  lost.  The  round  ligament  consists  principally  of  muscle  tissue  pro- 
longed from  the  uterus;  also  of  some  fibrous  and  areolar  tissue,  besides  bloodvessels 
and  nerves,  enclosed  in  a  duplicature  of  peritoneum,  which  in  the  fetus  is  pro- 
longed in  the  form  of  a  tubular  process  for  a  short  distance  into  the  inguinal 
canal.  This  process  is  called  the  canal  of  Nuck.  It  is  generally  obliterated  in 
the  adult,  but  sometimes  remains  pervioUs  even  in  advanced  life.  It  is  analogous 
to  the  peritoneal  pouch  which  precedes  the  descent  of  the  testis. 

The  cavity  of  the  uterus  (cavum  uteri)  (Fig.  1181)  is  small  in  comparison  with 
the  size  of  the  organ,  because  of  the  great  thickness  of  the  wall.  That  portion 
of  the  cavity  which  corresponds  to  the  body  is  triangular,  flattened  from  before 
backward,  so  that  its  anterior  and  posterior  walls  are  closely  approximated, 
and  having  its  base  directed  upward  toward  the  fundus.  At  each  superior 
angle  is  the  minute  orifice  of  the  Fallopian  tube.  At  the  inferior  angle  of  the 
uterine  cavity  is  a  small  constricted  opening,  smaller  and  more  nearly  circular 
than  the  external  os  uteri,  the  internal  os  uteri  (orificium  internum  uteri)  (Fig. 
1181),  which  leads  into  the  cavity  of  the  cervix. 

The  cavity  of  the  cervix  (canalis  cervicis  uteri)  (Fig.  1181)  extends  from  the 
internal  os  uteri  to  the  external  os  uteri.  It  is  somewhat  fusiform,  flattened  from 
before  backward,  broader  at  the  middle  than  at  either  extremity,  and  communicates 
below  with  the  vagina.  The  wall  of  the  canal  presents,  anteriorly  and  posteriorly, 
a  longitudinal  column,  from  which  proceed  a  number  of  small  oblicjue  columns, 
giving  the  appearance  of  branches  from  the  stem  of  a  tree;  and  hence  the  name 
uterine  arbor  vitae  (plicae  palmatae)  applied  to  it.  The  longitudinal  ridges  are  not 
exactly  apposed,  but  fit  against  each  other  so  as  to  close  the  cervical  canal.  These 
folds  usually  become  very  indistinct  after  the  first  labor.- 

The  total  length  of  the  uterine  cavity  from  the  external  os  to  the  fundus  is  about 
two  and  a  half  inches. 

The  Uterus  at  Different  Ages.— The  uterus  of  the  fetus  is  in  the  abdominal  cavity  pro- 
jecting above  the  brim  of  the  pelvis.  The  cervix  is  considerably  larger  than  the  body.  At 
birth  the  cervix  is  larger  relatively  than  in  the  adult ;  there  is  no  distinct  internal  os  distinguishing 
the  cavity  of  the  body  of  the  uterus  from  the  cavity  of  the  cervix.  The  arbor  vitse  is  distinct  and 
extends  to  the  upper  part  of  the  cavity  of  the  organ.  The  growth  of  the  uterus  is  slow  until 
puberty  is  almost  reached,  vi'hen  for  a  time  the  growth  is  rapid.  The  growth  of  the  uterine  body 
causes  the  mucous  membrane  of  this  part  to  lose  its  folds,  hence  the  arbor  vitse  disappears  from 
the  body.  In  a  woman  who  has  had  children  the  uterine  cavity  is  larger  than  in  a  woman  who 
has  never  borne  a  child.  In  advanced  years  the  uterine  wall  becomes  paler  and  hard  and  rigid 
from  atrophic  fibrous  changes.  A  more  distinct  constriction  separates  the  body  and  cervix. 
The  internal  os  frequently  and  the  external  os  occasionally  are  obliterated  in  old  age. 

Abnormalities. — Very  rarely  the  uterine  cavity  is  divided  into  two  by  a  septum.  Occasionally 
the  condition  known  as  bicomate  uterus  exists.  In  this  condition  each  lateral  angle  is  pro- 
longed into  a  horn  or  cornu.  The  uterus  is  formed  by  the  union  of  the  two  ducts  of  Muller,  and 
failure  of  fusion  of  these  ducts  makes  a  double  uterus  or  a  bicornate  uterus. 

Changes  at  a  Menstrual  Period.— For  several  days  before  the  menstrual  flow  begins  the 
mucous  membrane  increases  in  thickness  and  vascularity  and  its  surface  is  cast  into  folds.  After 
these  preparatory  changes  the  superficial  portions  of  the  mucous  membrane  break  down  and  are 
cast  off,  and  bleeding  begins.  At  the  termination  of  menstruation  the  mucous  membrane 
rapidly  regenerates.  At  each  menstrual  period  from  four  to  five  fluidounces  of  blood  are  dis- 
charged.    The  meaning  of  menstruation  is  uncertain.     Pfliiger  believes  the  wall  of  the  uterus 


THE  UTERUS,   OB   WOMB  1409 

is  made  raw,  so  that  if  an  impregnated  ovum  arrives  it  will  adhere.  Reichert  believes  that 
menstruation  means  that  no  impregnated  ovum  has  arrived  in  the  womb,  and  hence  no  bed  is 
needed  for  one. 

Changes  Induced  by  Pregnancy .^The  muscle  fibres  hypertrophy  enormously  and  be- 
come vastly  longer  and  broader.  There  is  a  great  increase  in  connective  tissue,  and  new 
connective-tissue  fibres  pass  between  bundles  of  muscle.  The  peritoneal  coat  undergoes  hyper- 
plasia. It  remains  closely  adherent  to  the  uterus,  except  over  the  lower  segment,  from  which 
region  it  can  be  easily  stripped.  The  bloodvessels  become  large  and  tortuous.  The  nerves  are 
increased  in  length  and  new  filaments  form.  The  lymphatics  undergo  hypertrophy  and  hyper- 
plasia. The  uterus  becomes  spherical,  and  after  the  fourth  month  ovoidal.  Early  in  pregnancy 
the  increase  in  weight  causes  the  uterus  to  descend  in  the  pelvis.  After  the  third  month  it  rises 
progressively,  and  during  the  ninth  month  the  fundus  reaches  the  epigastrium.  "Before  term 
(four  weeks  in  primiparse,  ten  days  or  one  week  in  multiparae)  the  fundus  sinks  again,  as  the 
presenting  part  and  lower  uterine  segment  become  engaged  in  the  pelvic  cavity.  This  phenome- 
non is  explained  by  contraction  of  the  overstretched  abdominal  walls."'  The  womb  is  acutely 
antetlexed  during  the  first  three  months  of  pregnancy.  After  this  period,  as  the  womb  rises, 
the  anteflexion  is  diminished,  but  some  degree  remains,  because  the  abdominal  walls  are  too  lax 
to  hold  the  organ  straight.  The  uterus  passes  somewhat  to  the  right  side  and  undergoes  a  rota- 
tion on  its  longitudinal  axis,  so  that  the  anterior  surface  looks  front  and  to  the  right.  These 
changes  in  position  are  caused  by  fecal  distention  of  the  sigmoid.  The  intestines  are  above  and 
back  of  the  uterus.  During  the  first  four  months  the  cervix  softens  and  enlarges  somewhat. 
The  length  of  the  cervical  canal  is  not  altered  during  pregnancy,  and  the  canal  does  not  dilate 
until  labor  begins.  During  pregnancy  the  cervical  glands  secrete  thick  mucus,  which  coagulates 
and  occludes  the  cervical  canal;  the  round  ligaments  become  stronger,  and  the  layers  of  the 
broad  ligaments  are  separated  toward  their  inner  portions  by  the  enlarging  womb. 

After  parturition  the  uterus  nearly  regains  its  former  size,  usually  weighing  something  over 
one  and  a  half  ounces;  but  its  cavity  is  larger  than  in  the  virgin  state,  the  external  orifice  is  more 
marked,  its  edges  present  a  fissured  surface,  its  vessels  are  very  tortuous,  and  its  muscle  layers 
are  more  defined. 

Structure. — The  uterus  is  composed  of  three  coats — an  external  or  serous  coat,  a  middle 
or  muscular  coat,  and  an  internal  or  mucous  coat. 

Tlie  serous  coat  or  perimetrium  ilniiini  .vrni.va)  is  derived  from  the  peritoneum;  it  invests 
the  fundus  and  the  whole  of  the  posterior  surface  of  the  uterus;  but  covers  the  anterior  surface 
only  as  far  as  the  junction  of  the  body  and  cervix.  In  the  lower  fourth  of  the  posterior  surface 
the  peritoneum,  though  covering  the  uterus,  is  not  closely  connected  with  it,  being  separated 
from  it  by  a  layer  of  loose  cellular  tissue  and  some  large  veins.  At  the  lateral  margins  of  the 
uterus  the  serous  coat  passes  on  to  the  broad  ligaments.  The  serous  coat  adheres  closely  to  the 
uterus,  and  it  is  very  difficult  to  separate  _it  from  the  muscle. 

The  muscular  coat  {tiinicn  vuiscularis)  (Fig.  1181)  forms  the  chief  bulk  of  the  substance  of  the 
uterus.  In  the  unimprcgnated  -tate  it  is  dense,  firm,  of  a  grayish  color,  and  cuts  almost  like 
cartilage.  It  is  thick  opposite  the  middle  of  the  body  and  fundus,  and  thin  at  the  orifices  of  the 
Fallopian  tubes.  It  consists  of  bundles  of  unstriped  muscle  tissue,  disposed  in  layers,  intermixed 
with  areolar  tissue,  bloodvessels,  lymphatic  vessels,  and  nerves.  The  muscle  tissue  is  disposed 
in  three  layers — external,  middle,  and  internal. 

The  external  layer  is  placed  beneath  the  peritoneum,  disposed  as  a  thin  plane  on  the  anterior 
and  posterior  surfaces.  It  consists  of  fibres  which  pass  transversely  across  the  fundus,  and,  con- 
verging at  each  superior  angle  of  the  uterus,  are  continued  on  the  Fallopian  tube,  the  round 
ligament,  the  ligament  of  the  ovary;  some  passing  at  each  side  of  the  broad  ligament,  and  others 
running  backward  from  the  cervix  into  the  sacrouterine  ligaments.  The  fibres  of  the  external 
portion  of  the  outer  layer  {stratum  subserosum)  are  longitudinal.  The  fibres  of  the  inner  portion 
of  the  outer  layer  {stratum  supravasculare)  are  partly  circular  and  partly  longitudinal. 

The  middle  layer  of  fibres  {stratum  vasculare),  which  is  thickest,  presents  bundles  of  circular 
fibres  closely  connected  with  bloodvessels.  In  this  layer  are  most  of  the  large  bloodvessels. 
The  circular  fibres  about  the  internal  os  form  a  distinct  sphincter.  Those  which  surround  the 
orifices  of  the  Fallopian  tubes  are  arranged  in  the  form  of  two  hollow  cones,  the  apices  of  which 
surround  the  orifices  of  the  Fallopian  tubes,  their  bases  intermingling  with  one  another  on  the 
middle  of  the  body  of  the  uterus. 

The  internal  or  deep  layer  {stratum  mucosum)  consists  of  longitudinal  fibres.  Some  consider 
the  deeper  portion  of  the  muscle  tissue  of  the  uterus  to  be  the  muscularis  mucosae.  But  the  deep 
portion  of  the  muscle  substance  is  continuous  with  the  more  superficial  portion,  and  there  is  no 
submucous  coat  between  the  muscle  and  the  mucous  membrane.  The  deeper  layer  of  muscle 
fibres  of  the  uterus  contains  connective  tissue  and  elastic  fibres.  The  muscle  tissue  of  the 
cervix  contains  more  connective  and  elastic  tissue  than  does  the  body  of  the  uterus;  hence,  the 
cervix  is  harder  and  stiffer  than  the  body. 

>  A  Text-book  of  Obstetrics.     By  Prof.  Barton  Cooke  Hirst. 


1410 


THE   UBINOGENITAL   ORGANS 


The  mucous  membrane  (tunica  jiuicosa)  (Fig.  IISI)  is  thin,  smooth,  and  closely  adherent  to  the 
subjacent  muscle  tissue.  It  is  continuous,  through  the  fimbriated  extremity  of  the  Fallopian 
tubes,  with  the  peritoneum,  and  through  the  os  uteri  with  the  lining  of  the  vagina. 

In  the  body  of  the  uterus  it  is  smooth,  soft,  of  a  pale  red  color,  lined  with  simple  ciliated  epi- 
thelium, and  presents,  when  viewed  with  a  lens,  the  orifices  of  numerous  tubular  glands  arranged 
perpendicularly  to  the  surface.  It  is  not  provided  with  any  submucosa,  but  is  intimately  con- 
nected with  the  innermost  layer  of  the  muscular  coat.  In  structure  its  tunica  propria  difi^ers 
from  ordinary  mucous  membrane,  consisting  of  an  embryonic  nucleated  and  highly  cellular 
form  of  connective  tissue,  in  which  run  numerous  large  lymphatics.  In  it  are  the  tube-like 
uterine  glands  (glandidae  iderinae),  which  are  of  small  size  in  the  unimpregnated  uterus, 
but  shortly  after  impregnation  become  enlarged  and  elongated,  presenting  a  contorted  or  waved 
apjiearance  toward  their  closed  extremities,  which  reach  into  the  muscularis,  and  may  be  single 
or  bifid.  The  uterine  glands  consist  of  a  delicate  membrane,  lined  with  epithelium,  which 
becomes  ciliated  toward  the  orifices. 

In  the  cervix  the  mucous  membrane  is  sharply  differentiated  from  that  of  the  uterine  cavity. 
It  is  thrown  into  numerous  oblique  ridges,  which  diverge  from  an  anterior  and  posterior  longi- 
tudinal raphe,  presenting  an  appearance  which  has  received  the  name  of  arbor  vitae  {plicae 


Branches  to  tube. 


nal  arteries. 
Fig,  1185.^ — The  arteries  of  the  internal  reproductive  organs  of  the  female,  seen  from  behind.     (After  Hyrtl.) 

pahnatae).  In  the  upper  two-thirds  of  the  canal  the  mucous  membrane  is_ provided  with  numer- 
ous deep  glands  (glandidae  cervicales  uteri),  which  secrete  a  clear  viscid  alkaline  mucus;  and 
in  addition,  extending  through  the  whole  length  of  the  canal,  are  a  variable  number  of  little  cysts, 
presumably  glands,  which  have  become  occluded  and  distended  with  retained  secretion.  They 
are  called  the  ovules  of  Naboth.  The  mucous  membrane  covering  the  lower  half  of  the  cervical 
canal  presents  numerous  papillae.  The  epithelium  of  the  upper  two-thirds  is  ciliated,  but  below 
this  it  loses  its  cilia,  and  close  to  the  external  os  gradually  changes  to  squamous  epithelium. 

Vessels  and  Nerves  (Fig.  11S5).— The  arteries  of  the  uterus  are  the  uterine,  from  the  inter- 
nal iliac,  and  the  ovarian,  from  the  aorta.  They  are  remarkable  for  their  tortuous  course  in  the 
substance  of  the  organ  and  for  their  frequent  anastomoses.  The  uterine  artery  reaches  the  lower 
part  of  the  uterus  at  the  side  and  is  prolonged  as  a  large  artery  to  the  body  and  fundus,  which 
ascends  between  the  layers  of  the  broad  ligament.  The  uterine  artery  gives  off  a  smaller  branch, 
the  cervical,  which  descends  to  supply  the  cervix  and  sends  cervicovaginal  branches  to  the 
vagina.  The  azygos  arteries  of  the  vagina  come  from  the  cervicovaginal  reenforced  by  branches 
of  the  vaginal  arteries  (Fig.  1187).  A  median  longitudinal  vessel  is  formed  in  front  and  behind, 
which  descends  in  the  vaginal  wall.  The  termination  of  the  ovarian  artery  meets  the  termination 
of  the  uterine  artery,  and  forms  an  anastomotic  trunk  from  which  branches  are  given  off  to 


THE   UTERUS,    OR    WOMJS 


1411 


supply  the  uterus.  Dr.  Robinson,  instead  of  describing  the  uterine  and  ovarian  arteries  as  two 
vessels,  describes  them  as  parts  of  one  vessel,  the  arteria  uterina  ovarica  {\t.  673).  The  veins 
are  of  large  size,  and  correspond  with  the  arteries.  In  tlic  iiii])rct;natcil  ut(T\is  these  vessels  form 
the  uterine  sinuses,  consisting  of  the  lining  membrane  of  the  \eins  adhering  to  the  walls  of  the 
canals  channelled  through  the  substance  of  the  uterus.  They  terminate  in  the  uterine  plexuses, 
which  empty  into  the  internal  iliac  veins.  The  lymphatics  (Fig.  1 186)  are  descrilied  on  page 
797.  The  nerves  come  chiefly  from  the  uterovaginal  plexus,  which  continues  into  the  hypo- 
gastric plexus  and  receives  filaments  from  the  third  and  fourth  sacral  nerves.  The  uterus 
also  receives  direct  fibres  from  the  hypogastric  plexus  and  from  the  vesical  plexus. 


VESSELS    FROM 

NECK  OF  UTERUS 

TO  LATERAL 

SACRAL  NODE 

VESSELS    FROM 

NECK  OF  UTERUS 


Fig.  1186. — The  lymphatics  of  the  internal  organs  of  generation  in  the  female.     (Poirier  and  Charpy.) 


AppUed  Anatomy. —Pftoic  cellulitis  {-parametritis)  is  inflammation  of  the  pelvic  cellular 
tissue.  It  is  due  to  sepsis,  and  its  usual  antecedent  is  uterine  sepsis.  A  laceration  of  the  cervix 
may  admit  bacteria.  An  abscess  may  form.  If  it  points  in  the  vagina  it  should  be  incised  through 
the  vaginal  wall.  The  uterus  may  require  removal  (hysterectomy)  in  cases  of  malignant  disease 
or  for  fibroid  tumors.  Carcinoma  is  the  most  common  form  of  malignant  disease  of  the  uterus, 
though  cases  of  sarcoma  do  occur.  Carcinoma  may  show  itself  either  as  a  columnar  carcinoma 
or  as  a  squamous  carcinoma,  the  former  commencing  either  in  the  cervix  or  body  of  the  uterus, 
the  latter  always  commencing  in  the  epithelial  cells  of  the  mucous  membrane  covering  of  the 
vaginal  surface  of  the  cervix.  The  columnar  form  may  be  treated  in  the  early  stage,  before  fixation 
has  taken  place,  by  removal  of  the  uterus,  either  through  the  vagina  or  by  means  of  abdominal 
section.     The  former  operation  is  attended  by  the  smaller  death  rate.     Vaginal  hysterectomji 


1412 


THE  UBINOGENITAL  ORGANS 


may  be  performed  in  any  case  in  which  the  uterus  or  the  uterus  and  tumor  are  not  too  large  to  be 
withdrawn  through  the  vagina.  It  is  difficult  in  this  operation  to  deal  with  adhesions  and  other 
complications  in  the  upper  part  of  the  pelvis,  and  for  this  reason  many  surgeons  prefer  the  abdom- 

FimirinteA  extremity 
of  t  (he 
/rw>  Fallopian  tube  '^ 


I  ugma,  aiae 

Fig.  11S7. — The  uterus  and  its  appendages.  Posterior  ^-iew.  The  parts  have  been  somewhat  displaced  from 
their  proper  position  in  the  preparation  of  the  specimen;  thus,  the  right  ovary  has  been  raised  aboA'e  the  Fal- 
lopian tube,  and  the  fimbriated  extremities  of  the  tube  have  been  turned  upward  and  outward.  (From  a  prepa- 
ration in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 

inal  operation.  Vaginal  hysterectomy  is  performed  by  placing  the  patient  in  the  lithotomy  posi- 
tion and  introducing  a  large  duckbill  speculum  into  the  vagina.  The  cervix  is  then  seized  with  a 
volsellum  and  pulled  down  as  far  as  possible  and  the  mucous  membrane  of  the  vagina  incised 
around  the  cervix  as  near  to  it  as  the  disease  will  allow,  especially  in  front,  where  the  ureters  are 
in  danger  of  being  wounded.     A  pair  of  dressing  forceps  are  then  pushed  through  into  Douglas' 

pouch  and  opened  sufficiently  to  allow  of  the 
introduction  of  the  two  forefingers,  by  means 
of  which  the  opening  is  dilated  laterally  as 
far  as  the  sacrouterine  ligaments.  A  some- 
what similar  proceeding  is  adopted  in  front, 
but  here  the  bladder  has  to  be  separated 
from  the  anterior  wall  of  the  uterus  for  about 
an  inch  before  the  vesicouterine  fold  of 
peritoneum  can  be  reached.  This  is  done 
by  carefully  burrowing  upward  with  a  director 
and  stripping  the  tissues  from  the  anterior 
uterine  wall.  When  the  vesicouterine  pouch 
has  been  opened  and  the  opening  dilated 
laterally,  the  uterus  remains  attached  only 
•by  the  broad  ligaments,  in  which  are  con- 
tained the  vessels  that  supply  the  uterus. 
Before  division  of  the  ligaments  these  vessels 
have  to  be  dealt  with.  The  forefinger  of  the 
left  hand  is  introduced  into  Douglas'  pouch 
and  an  aneurism  needle,  armed  with  a  long 
silk  ligature,  is  inserted  into  the  vesicouterine 
pouch,  and  is  pushed  through  the  broad  liga- 
ment of  one  side  about  an  inch  above  its  lower 
level  and  at  some  distance  from  the  uterus. 
One  end  of  the  ligature  is  now  pulled  through 
the  anterior  opening,  and  in  this  way  we 
have  the  lowest  inch  of  the  broad  ligament. 
in  which  is  contained  the  uterine  artery, 
enclosed  in  a  ligature.  This  is  tied  tightly,  and  the  operation  is  repeated  on  the  other  side.  The 
broad  ligament  is  then  divided  on  either  side,  between  the  ligature  and  the  uterus,  to  the  extent 
to  which  it  has  been  constricted.     By  traction  on  the  volsellum  which  grasps  the  cervix,  the  uterus 


Fig.  IISS. — Relations  between  uterus,  ureter,  and 
uterine  artery.     (Schematic.) 


THE  VAGiy^A  >  1413 

can  be  pulled  considerably  farther  down  in  the  vagina,  and  a  second  inch  of  the  broad  ligament 
is  treated  in  a  similar  way.  This  second  ligature  will  embrace  the  pampiniform  plexus  of  veins, 
and,  when  the  broad  ligament  has  been  divided  on  either  side,  it  will  be  found  that  a  third  liga- 
ture can  be  made  to  pass  over  the  Fallopian  tube  and  top  of  the  broad  ligament,  after  the  uterus 
has  been  dragged  down  as  far  as  ]Jossible.  After  the  third  ligature  has  been  tied  and  the  struc- 
ture between  it  and  the  uterus  divided,  this  organ  will  be  freed  from  all  its  connections  and  can 
be  removed  from  the  vagina.  This  canal  is  then  sponged  out  and  lightly  dressed  with  gauze, 
no  sutures  being  used.  The  gauze  may  be  removed  at  the  end  of  the  second  day.  In  squamous 
epithelioma,  amputation  of  the  cervix  is  done  by  some  in  those  cases  where  the  disease  is  recog- 
nized before  it  has  invaded  the  walls  of  the  vagina  or  the  neighboring  broad  ligaments.  The 
operation  consists  in  removing  a  wedge-shaped  piece  of  the  uterus,  including  the  cervix,  through 
the  vagina  and  attaching  the  cut  surface  of  the  stump  to  the  anterior  and  posterior  vaginal  walb, 
so  as  to  prevent  retraction.  In  view,  however,  of  the  continuity  of  the  lymphatic  network  of  the 
cervix  with  the  lymphatics  of  the  body,  the  operation  is  insufficient  and  should  be  condemned. 
Complete  abdominal  hysterectomy  is  rarely  necessary,  except  for  malignant  disease.  In  this  opera- 
tion the  entire  uterus  is  removed.  The  preliminary  introduction  of  bougies  into  the  ureters  as 
practised  by  Kelly  and  Clark  enables  the  surgeon  to  readily  recognize  the  situations  of  these  tubes. 
After  the  abdomen  has  been  opened  the  uterine  vessels  are  secured  and  the  broad  ligaments 
divided  in  a  similar  manner  to  that  employed  in  vaginal  hysterectomy,  except  that  the  proceeding 
is  commenced  from  above.  When  the  first  two  ligatures  have  been  tied  and  the  broad  ligament 
divided,  it  will  be  found  that  the  uterus  can  be  raised  out  of  the  pelvis.  A  transverse  incision 
is  now  made  through  the  peritoneum,  where  it  is  reflected  from  the  anterior  surface  of  the  uterus 
on  to  the  back  of  the  bladder  and  the  serous  membrane  peeled  from  the  surface  of  the  uterus 
until  the  vagina  is  reached.  The  anterior  wall  of  this  canal  is  cut  across.  The  uterus  is  now 
turned  forward  and  the  peritoneum  at  the  bottom  of  Douglas'  pouch  incised  transversely,  and 
the  posterior  wall  of  the  vagina  cut  across  until  it  meets  the  incision  on  the  anterior  wall.  The 
uterus  is  now  almost  free,  and  is  held  only  by  the  lower  part  of  the  broad  ligament  on  either 
side,  containing  the  uterine  artery.  A  third  ligature  is  made  to  encircle  this,  and,  after  having 
been  tied,  the  structures  are  divided  between  the  ligature  and  the  uterus.  The  organ  can  now 
be  removed.  The  vagina  is  plugged  with  gauze,  and  the  external  wound  closed  in  the  usual 
way.  The  vagina  acts  as  a  drain,  and  therefore  the  opening  into  it  is  usually  left  unsutured.  In 
some  cases  of  uterine  fibroid  the  abdomen  is  opened  and  the  tumor  is  removed,  but  the  uterus  is 
not  taken  away.  This  operation  is  called  myomectomy.  This  operation  is  suited  only  to  solitary 
subperitoneal  or  interstitial  tumors  (Penrose). 

The  common  operation  for  uterine  fibroids  is  supravaginal  amputation.  The  uterus  is  cut 
away  and  the  cervical  flaps  are  sutured.  Before  the  technique  of  hysterectomy  was  perfected 
and  before  myomectomy  was  devised  the  favorite  operation  for  uterine  fibroids  was  sal  pin  (jo- 
oophorectomy,  and  by  it  a  large  majority  of  cases  operated  upon  were  cured.  When  it  succeeds, 
a  premature  menopause  is  induced  and  the  tumor  shrinks.  The  operation  is  useless  if  a  woman 
is  past  the  menopause,  and  is  likely  to  fail  if  the  turnor  is  very  soft  or  very  large. 


THE  VAGINA  (Figs.  1174,  1192). 

The  vagina  {indvouterine  canal)  is  a  musculomembranous  passage,  which 
extends  from  the  vulva  to  the  uterus.  It  is  situated  in  the  cavity  of  the  pelvis, 
behind  the  bladder  and  in  front  of  the  rectum.  Its  direction  is  curved  upward  and 
backward,  at  first  in  the  line  of  the  pelvic  outlet,  and  afterward  in  that  of  the  axis 
of  the  cavity  of  the  pelvis.  Its  walls  are  ordinarily  in  contact,  and  its  usual  shape 
on  transverse  section  is  that  of  an  H,  the  transverse  limb  being  slighdy  curved 
forward  or  backward,  while  the  lateral  limbs  are  somewhat  convex  toward  the 
median  line.  Its  length  is  about  two  and  a  half  inches  (6.25  cm.)  along  its  anterior 
wall  (paries  anterior),  and  three  and  a  half  inches  (8.75  cm.)  along  its  posterior 
wall  {paries  posterior),  and  its  wall  is  about  2  mm.  thick.  It  is  constricted  at 
its  commencement,  and  becomes  dilated  medially,  and  narrowed  near  its  uterine 
extremity;  it  surrounds  the  vaginal  portion  of  the  cervix  uteri,  a  short  distance 
from  the  os,  its  attachment  extending  higher  up  on  the  posterior  than  on  the 
anterior  wall  of  the  uterus  (Fig.  1182).  To  the  recess  behind  the  cervix  the  term 
posterior  fornix  is  applied,  while  the  smaller  recess  in  front  is  termed  the  anterior 
fornix. 


1414 


THE   UBINOGENITAL   ORGANS 


Relations  (Figs.  1174  and  1192). — The  upper  part  of  the  anterior  wall  of  the  vagina  is  in 
relation  with  the  base  of  the  bladder,  being  separated  from  that  viscus  by  lax  connective  tissue. 
Lower  down  the  middle  line  of  the  anterior  wall  and  closely  joined  to  it  is  the  urethra.  The  upper 
part  of  the  posterior  wall,  near  the  middle  line,  is  covered  for  a  quarter  of  an  inch  or  more  with 
peritoneum,  which  forms  the  anterior  wall  of  the  depths  of  the  rectovaginal  pouch  of  peritoneum 
or  pouch  of  Douglas  {excavatio  rectoiiterina  [Doriglasi])  (Fig.  11S2),  between  the  uterus  and 
vagina  and  the  rectum.  The  portion  of  the  posterior  wall  below  the  level  of  the  pouch  of 
Douglas  is  placed  close  to  the  rectum,  a  layer  of  pelvic  fascia  intervening.  As  the  vaginal  orifice 
is  approached,  the  rectum  and  vagina  separate,  and  interposed  between  them  is  a  mass  of  fibro- 
fatty  tissue  called  the  peiineum  or  perineal  body.  Its  sides  are  enclosed  between  the  Levatores 
ani  muscles.  The  lu-eter  toward  its  termination  (Fig.  1183)  lies  near  the  lateral  wall  of  the 
vagina,  passing  at  this  point  in  a  direction  downward,  inward,  and  slightly  forward  to  reach  the 
bladder.  The  vagina  near  its  termination  passes  through  the  triangular  hgament,  and  upon  its 
sides  are  the  bulbs  of  the  vestibule,  the  glands  of  Bartholin,  and  the  Bulbocavernous  muscle. 

Structure. — The  vagina  consists  of  an  internal  mucous  lining,  a  muscular  coat,  and  a 
fibrous  coat;  between  the  first  two  is  found  a  layer  of  erectile  tissue. 


AFFERENTS 
TO  EXTERNAL 
ILIAC  NODES 


Fig.  1189. — The  lymphatics  of  the  vagina.     Schematic.     (Poirier  and  Charpy.) 


The  mucous  membrane  (tunica  mucosa)  (Fig.  1179)  is  continuous  above  with  that  lining  the 
uterus.  Its  inner  surface  presents,  along  the  anterior  and  posterior  walls,  a  longitudinal  ridge 
or  raph^,  called  the  rugous  columns  of  the  vagina  (colvmna  ruganim  anterior  et  posterior). 
The  anterior  column  extends  downward  as  far  as  the  external  orifice  of  the  urethra,  forming  the 
carina  urethralis  vaginae.  Numerous  transverse  ridges  or  rugse  (rngae  vaginales)  extend  out- 
ward from  the  raphe  on  either  side.  These  rugse  are  separated  by  furrows  of  variable  depth, 
giving  to  the  mucous  membrane  the  appearance  of  being  studded  over  with  conical  projections 
or  papillae;  they  are  most  numerous  near  the  orifice  of  the  vagina,  especially  in  women  before 
parturition.  The  epithelium  covering  the  mucous  ibembrane  is  of  the  stratified  squamous 
variety.  The  subepithelial  tissue  is  very  loose  and  contains  numerous  large  veins,  which  by 
their  anastomoses  form  a  plexus,  together  with  smooth  muscle  fibres  from  the  muscular  coat;  it  is 
regarded  by  Gussenbauer  as  an  erectile  tissue.  It  contains  a  number  of  mucous  crypts,  but  no 
true  glands. 

The  muscular  coat  {tunica  muscularis)  consists  of  two  layers,  an  external  longitudinal,  which 
is  far  the  stronger,  and  an  internal  circular  layer.  The  longitudinal  fibres  are  continuous  with 
the  superficial  muscle  fibres  of  the  uterus.  The  strongest  fasciculi  are  those  attached  to  the  recto- 
vesical fascia  on  each  side.     The  two  layers  are  not  distinctly  separable  from  each  other,  bu; 


THE  EXTERNAL  ORGANS  1415 

are  connected  by  oblique  decussating  fasciculi  which  pass  from  the  one  layer  to  the  other.  Above 
the  triangular  ligament  the  fibres  are  nonstriated;  in  the  region  of  the  ligament  they  show  stria- 
tions.  In  addition  to  this,  the  vagina  at  its  lower  end  is  surrounded  by  a  band  of  striped  muscle 
tissue,  the  Sphincter  vaginae  (p,  445). 

Tile  fibrous  coat  is  composed  of  dense  white  fibrous  connective  tissue,  which  connects  the 
vagina  to  (he  surrounding  organs.     It  contains  a  large  plexus  of  bloodvessels. 

The  erectile  tissue  consists  of  a  layer  of  loose  connective  tissue  situated  between  the  mucous 
membrane  and  the  muscular  coat;  embedded  in  it  is  a  plexus  of  large  veins,  and  numerous 
bundlt-s  of  unstripcd  muscular  fibres  derived  from  the  circular  muscular  layer.  The  arrange- 
ment of  the  veins  is  similar  to  that  found  in  other  erectile  tissues. 

Bloodvessels,  Nerves,  and  Lymphatics. — The  arteries  of  the  vagina  are  branches  of  the 
vesicovaginal  artery,  ihc  vaginal  branch  of  the  uterine  artery  f|),  672)  and  branches  of  the 
internal  pudic  and  middle  hemorrhoidal.  The  veins  form  an  alnuulant  plexus  around  the  wall 
of  the  vaginii  and  pass  to  ihc  internal  iliac  veins.  The  lymphatics  (Fig.  1189)  arise  from  two 
communicating  networks,  one  of  which  is  beneath  the  mucous  incniljrane,  the  other  in  the  muscu- 
lar wall.  There  is  a  third  network  around  the  vaginal  wall,  from  w  hicli  the  collectors  arise.  The 
trunks  from  the  upper  third  of  the  vagina  pass  to  the  external  Uiac  nodes;  those  from  the  middle 
third  pass  to  the  internal  iliac  nodes;  those  from  the  lower  third  terminate  in  the  nodes  at  the 
promontory  of  the  sacrum  or  in  the  lateral  sacral  nodes.  The  nerves  come  from  the  third  and 
fourth  sacral  nerves  and  from  the  uterovaginal  and  vesical  plexuses  of  the  sympathetic. 

THE  EXTERNAL  ORGANS  (PARTES  GENITALES  EXTERNAE  MULIEBRES). 

The  external  reproductive  organs  in  the  female  are  the  mens  Veneris,  the  labia 
majora  and  minora,  the  vestibule,  the  clitoris,  the  vaginal  bulb,  and  tiie  glands  of 
Bartholin.  The  term  vulva  {pudendum,  midiebre),  as  generally  appHed,  includes 
all  of  these  parts.  In  examining  the  structures  entering  into  the  formation  of 
the  vulva  we  find  the  homologues  of  most  of  the  structures  which  make  up  the 
male  genitals. 

Labia  majora  =  Scrotum. 

Clitoris  =  Corpora  cavernosa. 

Bulbus  vestibuli  =  Corpus  spongiosum. 

Vestibular  glands  =  Bulbourethral  glands 
(of  Bartholin).                                                (of  Cowper). 

The  mons  Veneris  (commissura  lahiorum  anterior)  is  the  rounded  eminence 
in  front  of  the  pubic  symphysis  formed  by  a  collection  of  fatty  tissue  beneath  the 
integument.     It  becomes  covered  with  hair  at  the  time  of  puberty. 

The  labia  majora  (labia  majora  imdendi)  (Figs.  1190  and  1191)  are  two  promi- 
nent longitudinal  cutaneous  folds,  narrow  behind,  but  fuller  and  larger  toward  the 
mons  Veneris,  and  bounding  the  pudendal  slit  {rima  inidendi)  or  common  urinogeni- 
tal  opening.  Each  labium  majus  has  two  surfaces,  an  outer,  which  is  covered  by 
pigmented  skin  with  numerous  sebaceous  glands  and  strong,  crisp  hairs,  and  an  in- 
ner, which  is  smooth  and  moist  and  is  continuous  with  the  genitourinary  mucous 
tract.  In  the  subcutaneous  areolofatty  tissue  of  each  labium  majus  the  round 
ligament  of  the  uterus  ends.  The  labia  are  joined  with  each  other  anteriorly 
by  the  mons  Veneris  or  anterior  commissure.  Posteriorly  they  appear  to  become 
lost  in  the  neighboring  integument,  although  sometimes  connected  by  a  slight 
transverse  fold  in  front  of  the  anus,  the  posterior  commissvure  (commissura  labioriim 
-posterior),  or  posterior  l)oundary  of  the  vulvar  orifice.  The  interval  between 
the  posterior  commissure  and  the  anus,  about  an  inch  in  length,  constitutes  the 
obstetric  perineum. 

Bloodvessels,  Nerves,  and  Lymphatics.— The  arteries  of  the  labia  majora  are  derived  from 
the  superficial  external  pudic  arteries  ami  from  iicriiual  branches  of  the  internal  pudic  arteries. 
Homologous  with  the  scrotum,  tlie  nerve  supply  is  ilcrivcil  from  branches  of  the  ilioinguinal, 
internal  pudic,  and  perineal  branches  of  the  small  sciatic.  The  lymphatics  drain  into  the 
superficial  inguinal  and  internal  iliac  lymph  nodes. 


1416 


THE  URINOGENITAL  ORGANS 


The  labia  minora,  or  nymphse  {labia  minora  pvdendi)  (.Figs.  1191,  1192),  are 
two  smaller,  narrower  longitudinal  folds,  with  a  delicate  covering  of  modified 
skin,  and  usually  hidden  from  view  unless  the  labia  majora  are  separated.  They 
end  posteriorly  by  gradually  joining  the  labia  majora,  although  in  the  young 
there  is  usually  a  transverse  fold,  the  fourchette  or  frenulum  (Jreimluvi  labiorum 
fiidendi).  Traced  forward  each  labium  minus  divides  into  an  outer  and  an  inner 
portion  or  limb.  The  outer  parts  of"  the  two  labia  unite  over  the  glans  clitoridis 
to  form  the  prepuce  of  the  clitoris  ipraeputium  clitoridis)  (Fig.  1191).  The  internal 
limbs  unite  at  an  acute  angle  beneath  the  glans  clitoris  and  are  attached  to  the 
under  surface  of  the  glans  to  form  the  frenulum  clitoridis.  The  two  labia  minora 
are  in  contact,  flanked  by  the  labia  majora,  and  are  covered  by  modified  skin, 


MONS  VENERIS 


POSTERIOR 

COMMISSURE 

OF  VULVA 


NTERIOR 
OMMISSUDE 
F  VULVA 


1190.^ — The  female  pudendum  or  A-ulva  with  the  labia  majora.     (Toldt.) 


with  numerous,  sebaceous  glands  (glwidulae  vestibidares  minores),  resembling 
the  smooth,  moist,  pink-colored  integument  of  the  inner  surface  of  the  labia  majora. 
The  cleft  between  the  labia  minora  is  called  the  vestibule,  the  structures  of  which 
are  seen  only  on  separating  the  labia. 

The  vestibule  (vestibidum  vaginae)  (Figs.  1174  and  1191)  is  the  cleft  between 
the  labia  minora,  between  the  glans  clitoridis  in  front  and  the  fourchette  behind. 
On  separating  the  labia  minora  the  following  structures  in  the  vestibule  are  seen: 
(1)  The  external  urethral  orifice  and  the  minute  openings,  one  on  each  side,  of 
the  paraurethral  ducts;  (2)  the  vaginal  orifice;  and  (3)  the  openings  of  the  ducts 
of  the  vestibular  glands  (of  Bartholin).  The  recess  between  the  fourchette  and 
the  vaginal  orifice  is  called  the  fossa  navicularis. 


THE  EXTERNAL   ORGANS 


1417 


The  external  orifice  of  the  urethra,  or  urinary  meatus  (orificimn  7irrthrac  c.vicrnum) 
(Figs.  1191  and  1194),  is  situated  immediately  in  front  of  tlie  vaginal  orifice  and 
about  an  inch  behind  the  glans  clitoridis.  The  orifice  usually  presents  the 
appearance  of  a  vertical  slit,  and  is  surrounded  by  a  prominent  elevation  of  the 
mucous  membrane.  On  each  side  of  the  urinary  meatus  there  may  sometimes 
be  seen  the  minute  orifice  of  the  duct  of  the  paraurethral  glands,  supposed  to  be 
the  homologues  of  the  prostate. 


vAON 


5     VENERIS 


1191. — The  vulva.     External  female  organs  of  generation. 


The  vaginal  opening  is  situated  behind  the  urethral  orifice,  and  its  appearance 
varies  with  the  condition  of  the  hymen,  a  membranous  fold  which  more  or  less 
closes  the  aperture  in  the  virgin. 

The  hymen  varies  much  in  shape.  Its  commonest  form  is  that  of  a  ring,  gener- 
ally broadest  posteriorly;  sometimes  it  is  represented  by  a  .semilunar  or  crescentic 
fold,  with  its  concave  margin  turned  toward  the  pubes.  A  complete  septum 
stretched  across  the  lower  part  of  the  vaginal  orifice  is  called  an  imperforate  hymen. 
Occasionally  the  hymen  is  cribriform,  or  its  free  margin  forms  a  mcmhrantnis 
fringe,  or  it  may  be  entirely  absent.  It  may  persist  after  copulation,  so  that  it 
cannot  be  considered  as  a  test  of  virginity.     After  rupture  of  the  hymen  the  small 


1418 


THE   UBINOGENITAL   ORGANS 


rounded   nodular   elevations   known  as  the  carunculae  myrtiformes   (canmculae 
hymenales)  are  found  as  the  remains  of  the  structure. 

The  clitoris  (Figs.  1191,  1192)  is  an  erectile  structure  which  is  the  morpho- 
logic homologue  of  the  penis;  unlike  the  penis,  however,  it  is  not  traversed  by  the 
urethra.  It  is  situated  beneath  the  anterior  commissure  (or  mons  Veneris)  and 
is  partly  hidden  between  the  anterior  extremities  of  the  labia  minora.  It  is  com- 
posed of  a  body  and  two  crura;  the  extremity  of  the  body  is  surmounted  by  a  small 
glans. 


-Sagittal  section  of  the  lower  part  of  a  female  trunk,  right  segment.     SM,  INT.  Small  intestine. 
(Testut.) 


The  body  of  the  clitoris,  composed  of  erectile  tissue,  is  about  an  inch  and  a 
quarter  in  length  (3  cm.),  and  is  bent  upon  itself  so  that  the  angle  opens  downward. 
It  tapers  toward  the  glans,  is  enclosed  by  a  dense  fibrous  coat,  and  is  divided  by 
an  incomplete  septum  corporum  cavemosorum  into  two  semicylindrical  corpora 
cavernosa  clitoridis,  homologous  with  the  corpora  cavernosa  of  the  male.  A  sus-  ■ 
pensory  ligament  passes  from  the  pubic  symphysis  to  the  fibrous  coat  of  the 
body  of  the  clitoris.  Each  corpus  cavernosum  diverges  from  its  fellow  to  form 
the  eras  clitoridis.  Each  crus  is  attached  to  the  pubic  arch  (pubis  and  ischium) 
and  is  covered  by  the  Ischiocavernosus  muscle  (in.  erector  clitoridis). 


THE  EXTERNAL  ORGANS 


1419 


The  glans  clitoridis  is  a  minute  mass  of  erectile  tissue,  surmounting  tiie  tapering 
apex  of  the  Ijody  of  the  chtoris.  It  is  covered  by  a  very  sensitive  epitheUum,  and 
its  erectile  tissue,  like  that  of  the  glans  penis,  is  continuous  with  the  erectile  tissue 


CRESCENTIC  FRINGED  BILABIAL  Bl  PERFORATE  CRIBRIFORM 

Fig.   1193. —Varieties  of  hymen.     (Testut,  after  Rose.) 


SPHINCTER 
VAGINAE 
MUSCLE 


MUSCLE 

ORIFICE    OF 

URETHRA 


TRANSVERSE 

PEHINEI 
MUSCLE 


j|;.^>fyi^=^ 


EXCRETORY 


Fig.  H94. — The  female  external  organs  of  generation  dissected.     (Spalteholz.) 


1420  THE   VRINOGENITAL   ORGANS 

of  the  bulbus  vestibuli,  the  homologue  of  the  corpus  spongiosum  of  the  male. 
The  praeputium  clitoridis  and  the  frenulum  clitoridis  have  already  been  described 
(p.  1416)  as  divisions  of  the  labia  minora. 

Arteries  and  Nerves  of  the  Clitoris. — The  body  and  the  crura  of  the  clitoris  derive  their 
blood  supply  from  the  deep  artery  of  the  clitoris  (arteria  profunda  clitoridis),  a  branch  of  the 
internal  pudic  artery.  Another  branch  of  this  artery,  the  dorsal  artery  of  the  clitoris  (arteria 
dorsiili.s  clitoridis)  supplies  the  glans.  The  nerve  supply  is  derived  from  the  dorsal  nerve  of  the 
clitoris,  from  the  internal  pudic,  and  from  the  h3rpogastric  sympathetic" plexus. 

The  vaginal  bulb  (bulbus  vestibuli)  (Fig.  1194)  may  be  regarded  as  the  homo- 
logue of  the  bulb  portions  of  the  corpus  spongiosum  of  the  male.  The  principal 
morphological  difference  lies  in  the  fact  that  the  two  halves  are  fused  in  the  male, 
but  remain  separated  in  the  female.  The  bulbus  vestibuli  consists  of  a  mass  of 
minute  convoluted  bloodvessels,  of  such  plexiform  arrangement  as  to  be  often 
called  erectile  tissue,  arranged  in  two  halves,  one  on  either  side  of  the  vaginal  and 
urethral  orifices.  Each  half  is  thicker  or  more  massive  posteriorly,  while  anteriorly 
it  is  attenuated  and  joins  its  fellow  of  the  opposite  side  to  form  the  pars  intermedia, 
continuous  with  the  erectile  tissue  of  the  glans  clitoridis.  Each  half  of  the  bulbus 
vestibuli  rests  against  the  lateral  wall  of  the  vagina  and  lies  superficial  to  the 
triangular  ligament.  Externally  and  inferiorly  it  is  covered  by  the  Bulbocaver- 
nosus  muscle. 

Arteries  and  Nerves  of  the  Bulbus  Vestibuli. — The  blood  is  supplied  by  the  artery  to  the 
bulb  (arteria  hulbi  vestibuli),  a  branch  of  the  internal  pudic  artery.  The  nerve  supply  is  by 
branches  of  the  hypogastric  sympathetic  plexus. 

The  Glands  of  "BdiXtho^ni^glandula  vestibularis  major  [Bartholini])  (Fig.  1194). — 
On  each  side  of  the  posterior  part  of  the  commencement  of  the  vagina  is  a  round 
or  oblong  body,  of  a  reddisli-yellow  color,  and  of  the  size  of  a  horse-bean,  analo- 
gous to  Cowper's  gland  in  the  male.  It  is  called  the  gland  of  Bartholin,  the  gland 
of  Duvemey,  the  vulvovaginal  gland,  or  the  suburethral  gland.  Bartholin's  gland 
lies  partly  in  the  inferior  or  anterior  leaf  of  the  triangular  ligament.  The  pos- 
terior portion  of  the  bulbus  vestibuli  and  the  Bulbocavernous  muscle  partly  cover 
it.  Each  gland  opens  by  means  of  a  long  single  duct  immediately  external  to 
the  hymen,  in  the  angle  or  groove  betw^een  it  and  the  nympha  (Fig.  1193). 


DEVELOPMENT  OF  THE  URINARY  AND  GENERATIVE  ORGANS. 

The  permanent  organs  of  the  adult  are  preceded  by  a  set  of  purely  embryonic  structures  which, 
with  the  exception  of  their  ducts,  almost  entirely  disappear  before  birth.  These  embryonic 
structures,  all  developed  from  the  intermediate  cell  mass  of  mesodermal  tissue,  are  on  either 
side;  the  pronephros,  the  mesonephros,  the  Wolffian  (mesonephric)  duct,  and  the  Miillerian 
duct  (oviduct).  The  pronephros  disappears  very  early;  the  structural  elements  of  the  meso- 
nephros mostly  atrophy,  but  in  their  place  is  developed  the  genital  gland,  in  association  with 
which  the  mesonephric  duct  remains  as  the  duct  of  the  male  genital  gland,  the  oviduct  as  that  of 
the  female. 

The  pronephros  is  an  early  embryonic  structure  in  all  vertebrates.  It  develops  at  about  the 
level  of  the  heart  by  a  proliferation  of  the  mesodermal  cells  of  the  intermediate  cell  mass.  In  it 
appear  (a)  a  longitudinal  cord  of  cells,  which  later  acquires  a  lumen  to  form  the  pronephric 
duct;  (6)  two  transverse  pronephric  tubules  develop  as  invaginations  of  the  coelomic  meso- 
thelium.  Of  these,  the  cephalic  one  acquires  a  lumen  and  opens  into  the  coelomic  cavity;  the 
other  remains  a  solid  cord  of  cells.  Neither  tubule  becomes  connected  with  the  pronephric  duct. 
The  pronephric  duct  remains  to  become  the  Wolffian  duct  of  the  next  stage,  while  the  tubules 
are  represented,  in  the  adult,  by  t'le  hydatids  at  the  fimbriated  end  of  the  Fallopian  tube  in  the 
female,  and  by  the  stalked  hydatid  at  the  upper  end  of  the  testis  in  the  male. 

The  Mesoiiephros,  Miillerian  Duct,  and  Genital  Gland. — On  the  inner  side  of  the  Wolffian 
duc't  a  series  of  tubules,  the  Wolffian  tubules,  are  developed.  Each  tubule  opens  laterally  into 
the  duct,  while  its  middle  part  is  invaginated  by  a  tuft  of  capillary  bloodvessels  to  form  a  glom- 


DEVELOPMENT  OF   UBINARY  AND   GENERATIVE  ORGANS      1421 

erulus.  These  tubules  increase  in  number,  and  collectively  constitute  the  mesonephros  or 
Wolffian  body  (Figs.  1195,  1196).  At  the  beginning  of  the  second  month  this  body  forms  an 
elongated  spindle-shaped  structure,  which  projects  into  the  ccelomic  cavity  at  the  side  of  the  dor- 
sal mesentery,  and  reaches  from  the  septum  transversum  cephalad  to  the  fifth  lumbar  somite 
caudad.     The  Wolffian  body  persists  and  forms  the  permanent  kidney  in  fishes  and  amphibians, 


Iffian  duct. 
^.MilUerJan  duct. 


(  Stroma 
Genital  J      of  ovary, 
ridge.  |  Pr' 

[^      ova. 


-Body  wall. 

\]\\m\    ^^^s/      i 

Mesentery.- 
Fig.  1195. — Section  of  the  urinogenital  area  of  a  chick  embryo  of  the  fourth  day.     (Waldeyer.) 

but  in  reptiles,  birds,  and  mammals  it  is  superseded  by  the  metanephros,  which  forms  the  perma- 
nent kidney  in  these  animals.  The  cephalic  tubules  of  the  Wolffian  body  become  attached  to  the 
sexual  eminence  or  genital  ridge,  from  which  the  ovary  in  the  female  and  the  testicle  in  the  male 
are  developed.  Diu-ing  the  development  of  the  permanent  kidneys  the  Wolffian  bodies  atrophj', 
and  this  process  proceeds  to  a  much  greater  extent  in  the  female  than  in  the  male. 


Mullerian  ducts. 


Fig.  1196.— Enlarged  view  from  the  front  of  the  left 
Wolffian  body  before  the  establishment  of  the  distinc- 
tion of  sex.  o.  b,  c.  d.  Tubular  structure  of  the  Wolf- 
fian body.  e.  Wolffian  duct.  /.  Its  upper  extremity, 
ff.  Its  termination  in  x,  the  urinogenital  sinus,  h.  The 
duct  of  Miiller.  t.  Its  upper,  funnel-shaped  extremity. 
k.  Its  lower  end,  terminating  in  the  urinogenital  sinus. 
I.  The  mass  of  blastema  for  the  reproductive  organ, 
ovary,  or  testicle.     (From  Farre,  after  Kobelt.) 


Fig.  1197.— Urinogenital  sinus  of  female 
,uman  embryo  of  eight  and  a  half  to  nine 
i^eeks  old. 


In  the  male,  the  Wolffian  duct  persists,  and  forms  the  tube  of  the  epididymis,  the  vas  deferens, 
and  common  ejaculatory  duct,  while  the  seminal  vesicle  arises  as  a  lateral  diverticulum  from  its 
caudal  end.  The  cephalic  Wolffian  tubules  form  the  rete  testis,  vasa  efferentia,  and  coni  vas- 
culosi  of  the  testis;  while  the  caudal  tubules  atrophy  or  are  represented  by  the  occasional  vasa 
aberrantia  of  the  globus  minor  and  by  the  paradidymis. 

In  the  female,  the  Wolffian  bodies  and  ducts  atrophy.  The  remains  of  the  Wolffian  tubules 
are  represented  by  the  epobphoron  and  the  paroophoron  (p.  1407),  while  the  cephalic  portion  of 
the  Wolffian  duct  sometimes  persists  as  the  functionless  duct  of  Gartner  (Fig.  IISI). 


1422: 


THE  UBINOGENITAL   0BGAN8 


Fig.  1198. — Diagram  of  the  primitive 
urinogenital  organs  in  the  embryo  pre- 
vious to  sexual  distinction.  3.  Ureter. 
4.  Urinary  bladder.  5.  Uraehus.  cl. 
Cloaca,  cp.  Elevation  which  becomes 
clitoris  or  penis,  i.  Lower  part  of  in- 
testine. Is.  Fold  of  integument  from 
which  the  labia  majora  or  scrotum  are 
formed,  m,  m.  Right  and  left  Miillerian 
ducts  uniting  and  running  with  the 
WoIflHan  ducts  in  gc,  the  genital  cord. 
ot.  The  genital  ridge  from  which  either 
the  ovary  or  testicle  is  formed,  ug. 
Sinus  urogenital!.  TF.  Left  Wolffian 
body,  w,  w.  Kight  and  left  Wolffian 
ducts. 


Fig.  1199. — Diagram  of  the  female 
type  of  sexual  organs.  c.  Gland  of 
Bartholin,  and  immediately  above  it 
the  urethra.  cc.  Corpus  cavernosum 
clitoridis.  dG.  Remains  of  the  left 
Wolffian  duct,  such  as  give  rise  to  the 
duct  of  Gartner,  represented  by  dotted 
lines;  that  of  the  right  side  is  marked 
w.  f.  The  abdominal  opening  of  the 
left  Fallopian  tube.  g.  Round  liga- 
ment corresponding  to  gubernaculum. 
k.  Situation  of  the  hymen,  i.  Lower 
part  of  the  intestine.  /.  Labium,  n. 
Nympha.  o.  The  left  ovary.  po. 
Parovarium  (epoophoron  of  Waldeyer). 
sc.  Vascular  bulb  or  corpus  spongiosum. 
u.  Uterus.  The  Fallopian  tube  of  the 
right  side  is  marked  m.  v.  Vulva,  va. 
Vagina.  W.  Scattered  remains  of 
Wolffian  tubes  near  it  (paroophoron 
of  Waldeyer). 


Fig.  1200. — Diagram  of  the  male 
type  of  sexual  organs.  C.  Cowper's 
gland  of  one  side.  cp.  Corpora  cav- 
ernosa penis  cut  short,  e.  Caput  epi- 
didymis, g.  The  gubernaculum.  i. 
Lower  part  of  the  intestine,  ni.  Miil- 
lerian duct,  the  upper  part  of  which 
remains  as  the  hydatid  of  Morgagni; 
the  lower  part,  represented  by  a  dotted 
line  descending  to  the  prostatic  vesicle, 
constitutes  the  occasionally  existing 
cornu  and  tube  of  the  uterus  mascu- 
iinus.  pr.  The  prostate  gland.  $. 
Scrotum.  sp.  Corpus  spongiosum 
urethrae.  t.  Testicle  in  the  place  of 
its  original  formation.  t'.  Together 
with  the  dotted  lines  above,  indicates 
the  direction  in  which  the  testicle  and 
epididymis  descend  from  the  abdomen 
into  the  scrotum.  vd.  Vas  deferens. 
vh.  Vas  aberrans.  7'S.  The  vesicula 
seminalis.  TF.  Scattered  remains  of 
the  Wolffian  body,  constituting  the 
organ  of  Giraldes,  or  the  paradidymis 
of  Waldeyer. 


Figs.  119S  to  1200. — Diagrams  to  show  the  development  of  the  male  and  female  generative  organs  from  ; 
ent  type.     (Allen  Thomson.) 


DEVELOPMENT  OF  URINARY  AND  GENERATIVE  ORGANS      1423 


Wolffian  body 
Milllermn  duct 
Wolffian  duct 


The  Miillerian  Ducts. — Shortly  after  the  formation  of  the  Wolffian  ducts  a  second  pair  of 
ducts  is  developed.  These  are  named  the  Miillerian  ducts.  Each  arises  on  the  outer  aspect  of 
the  corresponding  Wolffian  body  as  a  tubular  invagination  of  the  cells  lining  the  coelom  (Fig. 
1194).  The  orifice  of  the  invagination  remains  patent,  and  undergoes  enlargement  and  modi- 
fication to  form  the  abdominal  ostium  of  the  Fallopian  tube.  The  ducts  pass  caudad  on  the 
outer  aspects  of  the  Wolffian  bodies,  but  toward  the  posterior  end  of  the  embryo  they  cross  to  the 
inner  side  of  the  Wolffian  ducts,  and  thus  come  to  lie  side  by  side  between  and  behind  the  latter 
— the  four  ducts  forming  what  is  termed  the  (jcnital  cord  (Fig.  1197). 

Ultimately,  the  Miillerian  ducts  open  into  the  ventral  part  of  the  cloaca  between  the  orifices  of 
the  Wolffian  ducts,  and  terminate  on  an  elevation  named  the  Mullerian  eminence  (Fig.  1197). 

In  the  male  the  Mullerian  ducts  atrophy,  but  traces  of  their  cephalic  ends  are  represented  by 
the  sessile  hydatids  of  the  epididymis,  while  their  terminal  fused  portions  form  the  uterus  mascu- 
linus  or  sinus  pocularis  in  the  floor  of  the  prostatic  portion  of  the  uretlira  (Fig.  1200). 

In  the  female,  the  Mullerian  ducts  persist  and  undergo  further  development.  The  portions 
which  lie  in  the  genital  cord  fuse  to  form  the  uterus  and  vagina;  the  parts  cephalad  of  this  cord  re- 
main separate,  and  each  forms  the  correspond- 
ing Fallopian  tube — the  abdominal  ostium  of 
which  is  developed  from  the  anterior  extremity 
of  the  original  tubular  invagination  from  the 
ca?lom  (Fig.  1199),  The  fusion  of  the  Muller- 
ian ducts  begins  in  the  third  month,  and  the 
septum  formed  by  their  fused  mesal  walls 
disappears  from  below  upward,  and  thus  the 
cavities  of  the  vagina  and  uterus  are  produced. 
About  the  fifth  month  an  annuMr  constriction 
marks  the  position  of  the  neck  of  the  uterus, 
and  after  the  si.xth  month  the  walls  of  the  uterus 
begin  to  thicken.  The  development  of  the 
vagina  in  the  manner  just  described  would 
necessitate  the  growth  of  a  septum  between  it 
and  the  urethra;  but  Wood-.Jones  maintains 
that  no  such  septum  exists,  and  that  "the 
vagina  is,  for  a  great  part  of  fetal  life,  a  solid 
rod,  and  not  an  open  canal  at  all."  He  says: 
"Early  in  the  history  of  the  embryo  the 
Mullerian  ducts  open  into  the  urogenital 
sinus  at  its  upper  part;  late  in  its  history 
they  open  at  the  hind-end  of  the  vagina,  and 

for 'a  considerable  interval  they  have  no  open-        j,^^    I201.-Transverse  section  of  human  embryo  of 
ing  at  all — the  old  one  being  losi  and  the  new    eight  and  a  half  to  nine  weeks  old.     (From  model  by 
one   not  yet  formed.      No  septal  division  is    K^ibel.) 
employed  in  this  change;  but  as  the  hindgut, 

when  its  cloacal  opening  is  lost,  reestabhshes  communication  with  the  exterior  by  a  new 
downgrowth,  so  the  Miillerian  ducts,  when  their  cloacal  opening  becomes  obliterated,  tunnel 
a  new  passage  to  the  hind  end." 

Genital  Gland. — The  first  appearance  of  the  genital  gland  is  essentially  the  same  in  the  two 
sexes,  and  consists  in  a  thickening  of  the  epithelial  layer  which  lines  the  jieritoneal  or  body  cavity 
on  the  inner  side  of  the  Wolffian  ridge.  Beneath  the  thickened  epithelium  an  increase  in  the 
mesoderm  takes  place,  forming  a  distinct  projection.  This  is  termed  the  (jcnital  ridge  (Fig.  1135), 
and  from  it  the  testis  in  the  male  and  the  ovary  in  the  female  are  developed.  At  first  the  Wolf- 
fian body  and  genital  ridge  are  suspended  by  a  common  mesentery,  but  as  the  embryo  grows  the 
genital  ridge  gradually  becomes  pinched  off  from  the  Wolffian  body,  with  which  it  is  at  first  con- 
tinuous, though  it  still  remains  connected  to  the  remnant  of  this  body  by  a  fold  of  peritoneum, 
the  mesorchium  or  mesovarium  (Fig.  1201).  About  the  seventh  week  the  distinction  of  sex  in 
the  genital  ridge  begins  to  be  perceptible. 

The  ovary,  thus  formed  from  the  genital  ridge,  consists  of  a  central  part  of  connective  tissue 
covered  by  a  layer  of  epithelium,  the  germinal  epithelium.  Between  the  cells  of  the  germinal 
epithelium  a  number  of  larger  cells,  the  primitive  ova,  are  found,  and  these  are  carried  into  the 
subjacent  sti'oma  by  bud-like  ingrowths  of  the  germinal  epithelium,  the  cells  of  which  surround  the 
primitive  ova;  in  this  manner  the  primitive  Graafian  follicles  are  formed.  The  rest  of  the  ger- 
minal epithelium  on  the  surface  of  the  ovary  forms  the  permanent  epithelial  covering  of  this 
organ  (Fig.  1202).  According  to  Beard,  the  primitive  ova  are  early  set  apart  during  the  segmen- 
tation of  the  ovum  and  migrate  into  the  germinal  ridge. 

Waldeyer  taught,  and  for  many  years  his  views  have  been  accepted,  that  the  primitive  germ 
ci;lls  are  derived  from  the  "germinal  epithelium"  covering  the  genital  ridge.     Beard,'  on  the 

1  Journal  of  Anatomy  and  Physiology,  vol.  x.>Lxviii, 


-^Svinal  ™''''- 


Spinal  ganglion, 

Nolochord. 

■Sympathetic  ganglion. 
Inferior  vena  cava. 
■Common  iliac  criery. 
Ureter. 
Mesovarium. 

^Intestine. 


Bladder. 
*f-  -  Umbilical  artery. 


1424 


THE  URINOGENITAL  ORGANS 


other  hand,  maintains  that  in  the  skate  they  are  not  derived  from  this  epithehum,  but  arc  probably 
formed  during  the  later  stages  of  cell  cleavage,  before  there  is  any  trace  of  an  embiyo;  and  a 
similar  view  was  advanced  by  Nussbaum  as  to  their  origin  in  amphibia.  Beard  says:  "At  the 
close  of  segmentation  many  of  the  future  germ  cells  lie  in  the  segmentation  cavity  just  beneath 
the  site  of  the  future  embryo,  and  there  is  no  doubt  they  subsequently  wander  into  it."  The 
germ  cells,  "after  they  enter  the  resting  phase,  are  sharply  marked  off  from  the  cells  of  the  em- 
bryo by  entire  absence  of  mitoses  among  them."  They  can  be  further  recognized  by  their 
irregular  form  and  amoeboid  processes,  and  by  the  fact  that  their  cytoplasm  has  no  affinity  for 
ordinary  stains,  but  assumes  a  brownish  tinge  when  treated  by  osmic  acid.  The  path  along 
which  they  travel  into  the  embryo  is  a  very  definite  one — viz.,  "from  the  yolk  sac  upward  between 
the  splanchopleure  and  gut  in  the  hinder  portion  of  the  embryo."  This  pathway,  named  by 
Beard  the  germinal  path,  "leads  them  directly  to  the  position  which  they  ought  finally  to  take 
up  in  the  'germinal  ridge.' "  A  considerable  number  apparently  never  reach  their  proper  desti- 
nation, since  "vagrant  germ  cells  are  found  in  all  sorts  of  places,  but  more  particularly  on  the 
mesentery."  Some  of  these  may  possibly  find  their  way  into  the  germinal  ridge;  some  probably 
undergo  atrophy,  while  others  may  persist  and  become  the  seat  of  dermoid  tumors. 


Ovarian  tube  of  epithelium. 


Blood-v 
Graafian  follicle. 


— Germinal  epithelium. 


Primitive  ova. 
-Cell  nest. 


Fig.  1202. — Section  of  the  ovary  of  i 


vborn  child.     (Waldeye 


The  testis  is  developed  in  a  very  similar  way  to  the  ovary.  Like  the  ovary,  in  its  earliest 
stages  it  consists  of  a  central  mass  of  connective  tissue  covered  by  germinal  epithelium,  among 
which  larger  cells,  the  primitive  sperm  cells,  are  seen.  These  are  carried  into  the  subjacent  stroma 
by  tubes  of  germinal  epithelium,  which  form  the  lining  of  the  seminiferous  tubules,  while  the 
primitive  sperm  cells  form  the  spermatogonia.  The  seminiferous  tubules  become  connected 
with  outgrowths  from  the  Wolffian  body,  which,  as  before  mentioned,  form  the  rete  testis  and 
vasa  efFerentia. 

Descent  of  the  Testes. — The  testes,  at  an  early  period  of  fetal  life,  are  placed  at  the  back  part 
of  the  abdominal  cavity,  behind  the  peritoneum  and  a  little  below  the  kidneys;  their  anterior 
surfaces  and  sides  are  invested  by  peritoneum.  About  the  third  month  of  intrauterine  life  a 
peculiar  structure,  the  gubemaculum  testis,  makes  its  appearance.  This  is  at  first  a  slender 
band,  extending  from  that  part  of  the  skin  of  the  groin  which  afterward  forms  the  scrotum 
through  the  inguinal  canal  to  the  body  and  epididymis  of  the  testis,  and  is  then  continued  upward 
in  front  of  the  kidney  toward  the  Diaphragm.  As  development  advances,  the  peritoneum  cover- 
ing the  testis  encloses  it  and  forms  a  mesentery,  the  mesorchium,  which  encloses  also  the  guber- 
naculum  and  forms  two  folds,  one  above  the  testis  and  the  other  below  it.  The  one  above  the 
testis  is  the  plica  vascularis,  and  contains  ultimately  the  spermatic  vessels;  the  one  below,  the 
plica  gubernatrix,  contains  the  lower  part  of  the  gubernaculum,  which  has  now  grown  into  a 
thick  cord;  it  terminates  below  at  the  internal  ring  in  a  tube  of  peritoneum,  the  processus  vagi- 
nalis, which  protrudes  itself  down  the  inguinal  canal.  The  lower  part  of  the  gubernaculum  by 
the  fifth  month  has  become  a  thick  cord,  while  the  upper  part  has  disappeared.  The  lower  part 
can  now  be  seen  to  consist  of  a  central  core  of  unstriped  muscle  fibre,  and  outside  this  of  a  firm 
layer  of  striped  elements,  connected,  Ijehind  the  peritoneum,  with  the  abdominal  wall.  As  the 
scrotum  develops,  the  main  portion  of  the  lower  end  of  the  gubernaculum  is  carried  with  the 
skin  to  which  it  is  attached  to  the  bottom  of  this  pouch;  other  bands  are  carried  to  the  inner  side 
of  the  thigh  and  to  the  perineum.  The  fold  of  peritoneum,  constituting  the  processus  vaginalis, 
projects  itself  downward  into  the  inguinal  canal,  and  emerges  at  the  external  abdominal  ring, 


DEVELOPMENT  OF  URINARY  AND  GENERATIVE  ORGANS     1425 

pushing  before  it  a  part  of  the  Internal  oblique  and  the  aponeurosis  of  the  External  oblique, 
which  form,  respectively,  the  Cremaster  muscle  and  the  external  spermatic  fascia.  It  forms  a 
gradually  elongating  pouch  or  cul-de-sac,  which  eventually  reaches  the  bottom  of  the  scrotum, 
and  behind  this  the  testis  is  drawn  by  the  growth  of  the  body  of  the  fetus,  for  the  gubernaculum 
does  not  grow  commensiu'ately  with  the  growth  of  other  parts,  and  therefore  the  testis,  being 
attached  by  the  gubernaculum  to  the  bottom  of  the  scrotum,  is  prevented  from  rising  as  the  body 
grows,  and  is  drawn  first  into  the  inguinal  canal  and  eventually  into  the  scrotum.  It  seems  cer- 
tain also  that  the  gubernacular  cord  becomes  shortened  as  development  proceeds,  and  this  assists 
in  causing  the  testis  to  reach  the  bottom  of  the  scrotum.  By  the  eighth  month  the  testis  has 
reached  the  scrotum,  preceded  by  the  lengthened  pouch  of  peritoneum,  the  processus  vaginalis, 
which  communicates  by  its  upper  extremity  with  the  peritoneal  cavity.  Just  before  birth  the 
upper  part  of  the  pouch  usually  becomes  closed,  and  this  obliteration  extends  gradually  down- 
ward to  within  a  short  distance  of  the  testis.  The  process  of  peritoneum  surrounding  the  testis 
is  now  entirely  cut  off  from  the  general  peritoneal  cavity  and  constitutes  the  tunica  vaginalis.^ 

In  the  female  there  is  also  a  gubernaculum,  which  effects  a  considerable  change  in  the  position 
of  the  ovary,  though  not  so  extensive  a  change  as  in  that  of  the  testis  in  the  male.  The  guber- 
naculum in  the  female,  as  it  lies  on  either  side  in  contact  with  the  fundus  of  the  uterus,  contracts 
adhesions  to  this  organ,  and  thus  the  ovary  is  prevented  from  descending  below  this  level.     The 


UmbllnnI  <  o,  d 


MSllerian 
duct 

Kidney  dU  ei  tn  iihim. 


Fig.  1203.— Tail  end  of  human  embryo  of  twenty-  Fig.  1204.— Tail  end  of  human    embryo  of    thirty- 

five  to  twenty-nine  days  old.  (From  model  by  two  to  thirty-three  days  old.  (From  model  by 
Keibel.)  Keibel.) 

upper  part  of  the  gubernaculum,  i.  e.,  the  part  between  the  ovary  and  the  uterus,  becomes  ulti- 
mately the  rounded  ligament  of  ihe  ovary,  while  the  lower  part,  i.  e.,  the  part  between  the  attach- 
ment of  the  cord  to  the  uterus  and  its  termination  in  the  labium  majus,  ultimately  forms  the  round 
ligament  of  the  uterus.  A  pouch  of  peritoneum  accompanies  it  along  the  inguinal  canal,  analogous 
to  the  processus  vaginalis  in  the  male;  it  is  called  the  canal  of  Nuck.  In  rare  cases  the  guber- 
naculum may  fail  to  contract  adhesions  to  the  uterus,  and  then  the  ovary  descends  through  the 
inguinal  canal  into  the  labium  majus,  extending  down  the  canal  of  Nuck,  and  under  these 
circumstances  its  position  resembles  that  of  the  testis  in  the  male. 

The  Metanepnros  or  Permanent  Kidney. — The  rudiments  of  the  permanent  kidneys  make 
their  appearance  about  the  end  of  tiie  first  or  beginning  of  the  second  month.  Each  arises  as  a 
diverticulum  from  the  hind  end  of  the  Wolffian  duct,  close  to  where  the  latter  opens  into  the 
cloaca  (Figs.  1203,  1204).  This  diverticulum  grows  cephalad  into  the  posterior  part  of  the 
intermediate  cell  mass,  where  its  blind  or  cephalic  extremity  becomes  dilated  and  subsequently 
divides  into  several  buds,  which  form  the  rudiments  of  the  pelvis  and  calices  of  the  lu-eter. 
By  fiu'ther  subdivisions  it  gives  rise  to  the  collecting  tubules  of  the  kidney  The  secretory 
tubules  are  developed  from  condensations  of  the  nephrogenic  tissue.  At  first  these  are  spher- 
ical masses  of  cells  which  become  hollowed,  forming  the  renal  vehicles.  These  become  elon- 
gated and  S-shaped;  one  end  of  the  S-shaped  tube  becomes  continuous  with  the  lumen  of  a 
renal  diverticular  branch,  the  other  end  becomes  cup-shaped  and  then  spherical,  being  invagi. 
nated  by  a  tuft  of  capillaries  derived  from  the  renal  artery  to  form  a  glomerulus.  The  inter- 
vening portions  of  the  tube  become  convoluted  and  looped  to  form  the  uriniferous  tubule.  The 
mesoderm  around  the  subdivisions  of  the  diverticulum  becomes  condensed  to  form  the  connec- 
tive tissue  and  vessels  of  the  kidney.  The  diverticulum  is  elongated  to  form  the  ureter,  the 
posterior  extremity  of  which  opens  at  first  into  the  hind  end  of  the  Wolffian  duct;  after  the 
sixth  week  it  separates  from  the  Wolffian  duct,  and   opens  independently,  into  the  part  of  the 


I  The  obliteration  of  the  process  of  peritoneum  which  accompanies  the  < 
process,  is  often  incomplete. 


)rd,  and  is  hence  called  the  fu 


1426 


THE  UBINOGENITAL  ORGANS 


Ureter, 


Wolffian  duct 
MiWei  lan  duct 
Bladder 
Symphysis  pvt)^''^^^ 


cloaca  which  ultimately  becomes  the  bladder  (Fig.  1205).     The  manner  in  which  this  separation 
is  brought  about  is  not  fully  known.' 

The  secretory  tubules  of  the  kidney  become  arranged  into  pyramidal  masses  or  lobules,  and 
the  lobulated  condition  of  the  kidneys  exists  for  some  time  after  birth,  while  traces  of  it  may  be 
found  even  in  the  adult.  The  kidney  of  the  ox  and  many  other  animals  remains  lobulated 
throughout  life. 

The  Urethra. — In  the  female  the  lu-ethra  is  formed  from  the  upper  part  of  the  urinogenital 
sinus — viz.,  that  part  which  lies  above  the  openings  of  the  Wolffian  and  INIiillerian  ducts.  The 
portion  of  the  sinus  below  these  openings  becomes  gradually  shortened,  and  it  is  ultimately  opened 
out  to  form  the  vestibule,  and  in  this  manner  the  lu-ethra  and  vagina  come  to  open  separately  on 
the  surface.  Wood-Jones  regards  the  female  uretlira  as  "the  cloacal  remnant  in  its  simplest 
form,"  and  points  out  that  "it  does  not  remain  tubular  throughout  fetal  life,  but  is  for  a  time 
obliterated  more  or  less  completely  by  the  proliferation  of  the  vaginal  bulbs."  Developmentally 
considered,  the  male  urethra  consists  of  two  parts — (1)  the  prostatic  and  membranous  portions, 
which  are  derived  from  the  iffinogenital  sinus,  and  correspond  to  the  whole  of  the  female  urethra; 
(2)  the  penile  portion,  which  is  formed  by  the  fusion  of  the  inner  genital  folds. 

The  prostate  gland  originally  consists  of  two  separate  portions,  each  of  which  arises  as  a 
series  of  diverticular  buds  from  the  epithelial  lining  of  the  urinogenital  sinus,  between  the  third 
and  fourth  months.     These  buds  become  tubular,  and  form  the  glandular  substance  of  the  two 

lobes,  which  ultimately  meet  and  fuse  behind 
the  uretlira  and  also  extend  on  to  its  ventral 
aspect.  The  third  or  middle  lobe  is  formed 
as  an  extension  of  the  lateral  lobes  between 
the  common  ejaculatory  ducts  and  the  blad- 
der. Skene's  ducts  in  the  female  urethra 
are  regarded  as  the  homologues  of  the  pros- 
tatic glands. 

The  glands  of  Coicper  in  the  male,  and 
of  Bartholin  in  the  female,  also  arise  as 
diverticula  from  the  epithelial  lining  of  the 
(Urogenital  sinus. 

The  Urinary  Bladder. — The  trigone  of 
the  bladder  is  formed  from  the  upper  part 
of  the  urinogenital  sinus;  the  remainder  of 
the  viscus  is  developed  from  the  part  of  the 
cloaca  which  lies  above  the  sinus  (Fig.  1204). 
The  bladder  is  at  first  tubular  in  shape,  its 
canal  being  continuous  with  that  of  the  allan- 
tois,  but  after  the  second  month  its  cavity 
expands  to  form  a  sac,  from  the  summit  of 
which  the  tube  of  the  allantois  extends  to 
the  umbilicus;  this  tube  undergoes  obliteration  to  form  the  fibrous  cord  of  the  urachus.  In  some 
cases  the  allantoic  canal  remains  patent,  and  urine  may  escape  by  it  at  the  umbilicus.  If  the 
urethra  be  looked  upon  as  the  remnant  of  the  cloaca,  then  the  bladder,  with  the  exception  of 
the  trigone,  must  be  regarded  as  being  developed  by  a  dilatation  of  the  proximal  part  of  the 
allantois. 

The  external  organs  of  generation  (Fig.  1206),  like  the  internal,  pass  during  development 
through  an  indifferent  stage  in  which  there  is  no  distinction  of  sex.  It  is  therefore  necessary  to 
describe  this  stage,  and  then  follow  the  development  of  the  female  and  male  organs, 
respectively. 

The  cloacal  membrane,  which  is  composed  of  ectoderm  and  entoderm,  originally  extends 
from  the  umbilicus  to  the  tail.  The  mesoderm  around  the  cloacal  chamber  gradually 
extends  between  the  layers  of  the  membrane,  stopping  short,  however,  around  the  margins  of  the 
entodermal  cloaca,  so  that  the  bilaminar  cloacal  membrane  is  limited  to  this  part.  About  the 
fifth  week  a  prominence,  the  genital  tubercle,  arises  in  front  of  the  cloacal  membrane,  while  at  the 
sides  the  edges  of  the  mesoderm  are  elevated  to  form  the  lahioscrotal  or  outer  genital  folds. 

Along  the  under  surface  of  the  genital  tubercle  the  ectoderm  is  thickened,  and  at  the  apex  of 
the  tubercle  projects  forward  as  an  epithelial  horn.     In  this  ectodermal  thickening  a  longitudinal 


Glans  perns 

lietlua. 


Vertebral  culuinn. 


Fig.  1205. — Tail  end  of  human  embryo,  from  eight  and  a 
half  to  nine  weelis  old.     (From  model  by  Keibel.) 


1  The  separation  of  the  uterus  from  the  Wolffian  duct  may  be  brought  about  by  the  absorption  of  the  hinder 
end  of  the  latter  into  the  genitourinary  chamber,  and  by  the  growth  of  the  wall  of  this  chamber  between  the 
openings.  Robinson  (Proceedings  of  the  Anatomical  Society  of  Great  Britain  and  Ireland,  May,  1903,  p.  63) 
states,  regarding  an  embryo  of  about  seven  weeks,  that  '  'from  the  posterior  or  lower  opening  of  the  WolflBan 
duct  a  grooved  ridge,  the  Wolffian  ledge,  runs  caudally  on  the  wall  of  the  genitourinary  chamber  and  gradually 
disappears  at  the  junction  of  the  Wolflian  angle  with  the  body  of  the  chamber.  The  lateral  margins  of  the 
groove  are  continuous  anteriorly  with  the  lateral  margins  of  the  Wolffian  duct,  and  apparently  fuse  together 
to  form  the  ventral  wall  of  the  lower  part  of  the  duct.  .  .  .  Obviously,  if  the  lateral  margins  of  the  groove 
were  to  fuse  from  before  backward,  the  aperture  of  the  Wolffian  duct  would  be  carried  farther  backward  in  the 
chamber,  and  its  distance  from  the  opening  of  the  ureter  increased." 


DEVELOPMENT  OF  URINARY  AND  GENERATIVE  ORGANS      1427 

groove,  the  genital  groove,  appears,  and  into  its  lips  the  mesoderm  extends  to  form  the  inner 
genital  folds.  After  the  ruptiu-e  of  the  cloaca!  membrane  this  groove  becomes  continuous  with 
the  urogenital  sinus.  With  the  formation  of  these  parts  the  indifferertt  stage  of  the  external 
genital  organs  is  reached. 

In  the  female  this  stage  is  largely  retained;  the  lower  part  of  the  urinogenital  sinus  persists  as 
the  vestibule,  the  genital  tubercle  forms  the  clitoris,  the  labioscrotal  folds  the  labia  majora,  and 
the  inner  genital  folds  the  labia  minora. 


Heal  cord, 
nilal  tubercle. 


1  .     L 


^ Genital  tubercle. 

A     V Labioscrotal  fold. 

1      } Inner  oenital  fold* 

Genital  groove. 


Labioscrotal  fold. 
Inner  genital  fold. 
Genital  f^roove. 
Perineum. 


J  J 


T' 


-Glans  clitoridis. 
-Labioscrofal  fold. 
-Inner  genital  fold, 
"Genital  groove. 


j!  ,wniia,v\v\\.xw-^^^ 


1/ 


Raphe. 


Vaginal  orifice. 


s- 


-Stages  in  the  development  of  the  external  sexual  orsan; 
the  Ecker-Ziegler  models.) 


the  male  and  female 


In  the  male  the  changes  are  greater  on  account  of  the  development  of  the  penile  portion  of  the 
urethra.  The  genital  tubercle  enlarges  to  form  the  corpora  cavernosa  and  glans  penis.  The 
lips  of  the  inner  genital  folds  meet  and  fuse  from  behind  forward  to  form  the  penile  urethra, 
the  bulb,  and  the  corpus  spongiosum.  The  part  of  the  urethral  groove  on  the  glans  penis  is 
closed  independently,  and  the  last  part  of  the  urethral  tube  to  be  completed  is  that  at  the  junction 
of  the  glans  and  body  of  the  penis.  If  the  lips  of  the  groove  fail  to  close,  the  condition  known  as 
hi/pospadias  results. 

The  labioscrotal  folds  meet  and  unite  in  the  middle  line  to  form  the  scrotum,  their  line  of 
union  being  indicated  by  the  median  raph^. 


1428 


THE   URINOGENITAL   ORGANS 


The  prepuce  is  formed  by  the  growth  of  a  sohd  plate  of  ectoderm  into  the  superficial  part  of 
the  genital  tubercle;  on  coronal  section  this  plate  presents  the  shape  of  a  horseshoe.  By  the 
breaking-down  of  its  more  centrally  situated  cells  this  plate  is  split  into  two  lamellae  and  a 
cutaneous  fold,  the  prepuce/  is  liberated  and  forms  a  hood  over  the  glans.  "Adherent  prepuce 
is  not  an  adhesion  really,  but  a  hindered  central  desquamation"  (Berry  Hart,  op.  cit.). 

The  homologies  of  the  different  parts  of  the  sexual  organs  may  be  stated  in  tabular  form  as 
follows: 


Indifferent  Stage. 

Male. 

Female, 

Genital  Ridge. 

Testis  (secretory  portion). 

Ovary. 

Wolffian  body. 

Rete  testis,   vasa   efferentia,   coni 
vasculosi,  paradidymis. 

Epoophoron   or   organ   of   Rosen- 
miiller.     Paroophoron. 

AYolffian  duct  . 

Canal  of  epididymis,  vas  deferens, 
common  ejaculatory  duct.     Sem- 
inal vesicle. 

Hydatid  of   Morgagni.      (Duct  of 
Gartner.) 

Miillerian  ducts    . 

Sessile    hydatids    of    epididymis. 
Uterus  masculinus. 

Fallopian  tubes,  uterus,  vagina. 

Genital  tubercle   . 

Corpora  cavernosa  and  glans  penis. 

Prostatic  and  membranous  parts  of 
urethra. 

Clitoris. 

Urethra.     Vestibule. 

Urinogenital  sinus 

Inner  genital  folds 

Penile  urethra,  bulb,  and  corpus 
spongiosum. 

Labia  minora. 

Labioscrotal  folds 

Scrotum. 

Labia  majora. 

THE  MAMMARY  GLAND  (MAIMMA)  (Figs.  1208,  1210). 

The  breasts,  mammary  glands  or  mammae,  secrete  the  milk,  and  are  accessory 
glands  to  the  organs  of  reproduction.  They  develop  fully  in  the  female,  but 
usually  remain  rudimentary  in  the  male.  There  are  two  of  these  glands,  and 
they  are  situated  in  the  superficial  fascia  of  the  anterior  portion  of  the  thorax. 

Description  of  a  Well-developed  Breast. — ^Each  gland  appears  as  a  hemispher- 
ical body  projecting  from  the  front  of  the  thorax  beneath  the  skin  and  lying  over 
a  portion  of  the  Pectoralis  major  muscle  and  a  smaller  portion  of  the  Serratus 
magnus  muscle.  The  hemispherical  projection  extends  usually  from  the  margin 
of  the  sternum  to  the  axilla  and  from  the  level  of  the  second  rib  to  the  level  of  the 
sixth  rib,  or  from  the  third  rib  to  the  seventh  rib,  but  this  does  not  represent 
the  real  size  of  the  gland.  The  gland  is  much  larger  than  this,  being  rendered 
so  by  tails  or  prolongations  of  breast  tissue,  which  will  be  described  later  (p.  1430). 

The  nipple  {papilla  mammae)  (Figs.  1207  and  1210)  projects  from  a  little 
below  and  to  the  median  side  of  the  summit  of  the  hemisphere  at  or  above  the 
level  of  the  fifth  rib,  and  is  covered  with  thin  skin.  The  right  nipple  may  not 
exactly  correspond  in  situation  and  direction  to  the  left  nipple.  The  nipple 
varies  considerably  in  height  and  shape.  In  the  virgin  it  is  usually  cylindrical 
and  is  directed  forward  and  slightly  upward  and  outward.     The  apex  of  the 


1  Spicer  (Journal  of  Anatomy  and  Physiology,  vol.  xliii,  1909)  describes  the  prepuce  as  arising  in  the  form 
of  an  annular  hood  of  niesoblastic. tissue  which  proceeds  forward  wiihin  the  substance  of  the  surrounding  epithe- 
lium. ^  ','The  main  portion  of  this  hood  springs  from  mesoblastic  tissue  considerably  posterior  to  the  cervix 
glandis,  is  in  the  form  of  a  crescentic  swelling,  or  collar,  and  this  creeps  forward,  burrowing  always  in  the  epithelial 
layers,  bridging  over  the  groove  of  the  cervix  which  is  filled  with  epidermal  cells,  and  finally  overlaps  the  body 
of  the  glans.     This  hood  is  the  prepuce." 

'  'The  epidermis  covering  the  glans  thuis  becomes  divided  into  two  layers — an  outer,  which  forms  the  super- 
ficial covering  of  the  prepuce,  and  an  inner,  which  remains  as  a  more  or  less  solid  layer  between  the  prepuce  and 
the  glans  until  after  birth.  From  it  is  differentiated  a  basal  layer  of  cubical  or  cylindrical  epithelium  to  line  the 
inner  aspect  of  the  prepuce,  and  another  to  cover  the  surface  of  the  glans,  while  central  desquamation  ensues 
later  and  prepares  the  way  for  a  movable  prepuce." 


THE  MAMAfARY  GLAND 


1429 


nipple  is  rendered  rough  by  fissures  (Fig.  1207),  it  exhibits  a  depression  in  which 
are  the  openings  of  the  milk  ducts  (Fig.  1209),  and  its  circumference  is  thrown 
into  concentric  ridges  (Fig.  1209).  The  nipple  is  surrounded  by  a  darker  circular 
wrinkled  area,  the  areola  (areola,  mammae)  (Figs.  1207  and  1208),  which  contains 
sweat  glands  and  on  which  are  twelve  or  fifteen  small  rounded  elevations.  These 
ele\'ations  are  caused  by  cutaneous  sebaceous  glands  which  in  structure  represent 
a  transition  between  sebaceous  and  mammary  glands.  They  are  probably 
rudimentary  portions  of  the  mammary  gland  and  are  known  as  the  glands  of 
Montgomery  {glandulae  areolares)  (Fig.  1209).  The  color  of  the  nipple  and  areola 
varies  with  the  complexion  of  the  individual.  In  brunettes  it  is  darker  than  in 
blondes.  The  usual  color  of  the  nipple  in  a  young  woman  is  rosy  pink,  the  areola 
being  of  a  darker  shade.  During  the  early  months  of  pregnancy  the  nipple 
and  areola  become  dark  brown  in  color,  the  areola  becomes  larger  in  circumference, 
and  the  glands  of  Montgomery  increase  in  size  (Fig.  1210).  The  nipple  contains 
nonstriated  muscle,  and  mechanical  irritation  or  sexual  excitement  makes  it  stiff 
and  erect.  The  skin  covering  the  breast  is  clear,  soft,  and  delicate,  and  sub- 
cutaneous veins  are  often  visible.  The  skin  of  the  nipple  and  areola  is  particularly 
delicate. 


Lactiferous 
duct. 


Lobnh  unravelled 


1  mpulla. 


[  ni  nil  m  tounectwe  iiasne. 


Fig.  1207. — Dissection  of  the  lower  half  of  the  female  breast  during  the  period  of  lactation.     (From  Luschka.) 


Variations  in  the  Mammae. — Before  puberty  the  glands  are  small,  are  of  the 
infantile  type,  grow  slowly,  and  differ  but  slightly  from  the  male  organs.  The 
nipple  is  small,  flat,  and  pale.  At  puberty  the  increase  in  the  size  of  the  breast 
is  rapid  and  considerable,  due  to  growth  of  gland  tissue  and  of  subcutaneous 
fat.  In  the  young  virgin  the  breasts  are  of  hemispherical  form  and  of  firm  con- 
sistency. During  pregnancy  the  breasts  enlarge  greatly  and  remain  very  large 
throughout  lactation.  This  enlargement  is  due  to  new  gland  tissue  and  increased 
vascularity.  Numerous  blue  veins  are  visible  in  the  skin,  the  areola  darkens, 
and  the  glands  of  Montgomery  enlarge  (Fig.  1210).  After  the  termination 
of  lactation  the  breasts  diminish  in  size.  They  do  not  become  as  small  as  the 
virgin  breast,  are  apt  to  lose  their  hemispherical  outlines,  and  become  soft  and 


1430  THE  URINOGENITAL  ORGANS 

flabby.  They  droop  as  flaccid  pendulous  masses,  the  subcutaneous  fat  is  largely 
gone,  and  the  oudines  of  the  lobular  breast  tissue  can  be  seen  and  felt.  The 
nipple  is  long  and  hangs  down  like  a  teat.  At  the  menopause  the  breast  usually 
shrinks.  In  some  cases,  however,  it  actually  increases  in  size.  In  such  a  case, 
although  the  gland  atrophies,  there  is  an  extensive  deposit  of  fat.  In  old  age  the 
glands  undergo  atrophy  and  largely  disappear,  the  skin  is  flabby  and  thrown 
into  wrinkles,  and  the  breasts  contain  very  little  glandular  structure,  and  are  hard 
from  the  presence  of  fibrous  tissue.  The  nipples  become  pigmented  and  corru- 
gated. Women  vary  greatly  in  the  development  of  the  breasts.  In  some  women 
they  are  large,  firm,  and  well  proportioned;  in  others  they  are  small,  flat,  or 
atrophy  occurs  in  the  course  of  certain  bodily  diseases,  as  in  phthisis,  and  in 
certain  mental  diseases,  as  melancholia.  If  the  ovaries  are  ill-developed  the 
breasts  remain  flat  and  small.  The  outline  and  direction  of  the  breast  and  also 
of  the  nipple  may  be  altered  by  corsets.  The  left  mamma  is  usually  somewhat 
larger  than  the  right. 

One  gland  or  both  glands  may  be  entirely  absent,  the  nipple  being  also  absent.  One  or  both 
glands  may  be  absent,  one  or  both  nipples  being  present.  When  there  is  only  one  nipple,  it  is 
apt  to  be  the  left.  The  term  polsrmazia  {mammae  accessonde  muliebris)  means  the  presence  of 
supernumerary  breasts,  with  or  without  nipples.  Polythelia  means  the  presence  of  supernu- 
merary nipples,  the  associated  glandular  structure  being  rudimentary.  There  may  be  one,  two, 
or  several  supernumerary  breasts,  and  when  more  than  one  exists,  are  usually  asymmetrical. 
If  one  is  functionally  active,  it  enlarges  during  pregnancy  and  furnishes  milk. 

Supernumerary  mammfe  may  secrete  milk  or  may  be  without  function.  The  most  common 
situation  is  on  the  part  of  the  chest  below  and  to  the  inner  side  of  the  normally  placed  gland. 
They  may  also  exist  in  the  axilla,  the  abdomen,  the  groin,  the  back  and  the  thigh.  Many  cases 
of  supposed  supernumerary  glands  have  been  really  instances  in  which  moles,  warts,  or  sebaceous 
cysts  have  been  mistaken  for  nipples,  but  some  cases  are  undoubted. 

Prolongations  of  Mammary  Tissue. — As  previously  stated,  the  outlines  of  the 
breast  are  not  regular,  but  here  and  there  tails,  prolongations,  or  cusps  come  off 
from  and  are  true  portions  of  the  gland.  Two  or  even  more  prolongations  pass  to 
the  edge  of  the  sternum ;  others  pass  toward  the  axilla,  the  clavicle,  and  the  origin 
of  the  External  oblique  muscle  from  the  ribs.  Underneath  the  mammary  gland 
prolongations  of  mammary  tissue  penetrate  the  pectoral  fascia  (Heidenhain).  If 
one  of  the  glandular  cusps  is  of  considerable  size  it  is  called  an  outlying  lobule. 

Structure  of  Mammary  Gland  and  Nipple  (Figs.  1207  and  1208).— The  glands  of  the 
breast  (corpus  mammae)  rest  by  a  smooth  posterior  surface  upon  the  loose  pectoral  fascia,  which 
fastens  the  breast  to  the  muscle  beneath,  but  so  loosely  that  the  breast  is  movable.  The  mamma 
consists  of  gland  tissue;  of  fibrous  tissue,  connecting  its  lobes,  of  fatty  tissue  in  the  intervals 
between  the  lobes,  of  retinacula,  and  of  skin.  The  gland  tissue,  when  freed  from  fibrous  tissue 
and  fat,  is  of  a  pale  reddish  color,  firm  in  texture,  generally  globular  in  form,  with  prolongations 
here  and  there,  flattened  from  before  backward,  thicker  in  the  centre  than  at  the  circumference, 
and  presenting  several  inequalities  on  its  surface,  especially  in  front.  On  the  anterior  surface 
there  are  many  irregular  elevated  processes  with  deep  spaces  between  them.  From  the  summits 
of  the  elevations  connective-tissue  strands  {redinacula  cutis)  pass  to  the  true  skin.  The  glandular 
structure  consists  of  numerous  glands  divided  into  lobes  (/o6i  mammae),  and  these  are  composed 
of  lobules  {lobuli  mammae),  connected  by  areolar  tissue,  which  contains  the  bloodvessels  and 
ducts.  The  smallest  lobules  consist  of  a  cluster  of  rounded  alveoli  (Fig.  1207),  which  open  into 
the  smallest  branches  of  the  excretory  ducts;  these  ducts,  uniting,  form  larger  ducts,  which 
terminate  in  single  canals.  Each  canal  is  called  a  lactiferous,  galactophorous,  or  mammillary 
duct  {ductus  lactiferus)  (Fig.  1207).  The  alveoli  are  tubular  in  form  and  are  lined  by  low 
columnar  epithelial  cells  which  rest  upon  a  basement  membrane.'  Each  glandular  area  possesses 
one  lactiferous  duct.  This  passes  to  the  apex  of  the  lobe  and  then  into  the  nipple.  The  lactif- 
erous ducts  are  white  and  cord-like,  and  contrast  with  the  yellowish-red  tissue  of  the  gland  itself. 
The  number  of  excretory  ducts  varies  from  fifteen  to  twenty,  each  representing  an  individual 
gland.     They  converge  toward  the  areola,  beneath  which  each  duct  possesses  a  spindle-shaped 

1  According  to  Lacroix  and  Benda,  there  is  a  thin  layer  of  noDstriated  muscle  between  the  basement  mem- 
brane and  the  secreting  cell. 


THE  MAMMARY  GLAND 


14-Sl 


dilatation,  the  ampulla  (sinus  lactiferans)  (Fig.  1207).  The  ampullse  serve  as  reservoirs  for  the 
milk.  At  the  base  of  the  nipple  the  ducts  become  contracted  and  pursue  a  straight  course  to  its 
summit,  perforating  it  by  separate  orifices  considerably  narrower  than  the  ducts  themselves. 
Each  orifice  (poms  lactiferus)  is  the  orifice  of  a  tube  which  drains  an  individual  gland.  The 
ducts  are  composed  of  areolar  tissue,  with  longitudinal  and  transverse  elastic  fibres  and  some 
muscle  tissue  derived  from  that  of  the  nipple;  their  mucous  lining  is  continuous,  at  the  point 
of  the  nipple,  with  the  integument.  The  epithelium  of  the  mammary  gland  difi^ers  according 
,to  the  state  of  activity  of  the  organ.  In  the  gland  of  a  woman  who  is  not  pregnant  or  nursing 
the  alveoli  are  very  small,  few  in  number,  solid,  and  filled  with  a  mass  of  granular  polyhe- 
dral cells.  During  pregnancy  the  alveoli  increase  in  number  and  enlarge  and  the  cells  undergo 
rapid  multiplication.  At  the  commencement  of  lactation  the  cells  in  the  centre  of  an  alveolus 
undergo  fatty  degeneration,  and  are  eliminated  in  the  first  milk  as  colostrum  corpuscles.  The 
peripheral  cells  of  the  alveolus  remain,  and  form  a  single  layer  of  granular,  short  columnar  cells 
lining  the  limiting  membrana  propria.     The  single  nucleus  of  each  cell  divides  and  forms  two. 


Fig.   120S. — Right  breast  in  sagittal  section,  inner  surface  of  outer  segment.     (Testut.) 

In  the  protoplasm,  especially  in  the  end  of  the  cells  toward  the  alveolus,  drops  of  fat  appear 
and  the  nucleus  toward  this  end  of  the  cell  also  becomes  fatty. 

The  end  of  the  cell  toward  the  alveolus  breaks  down,  and  the  liberated  material  constitutes 
"  the  albuuiinous  ingredients  of  the  milk,  while  the  drops  of  fat  become  the  milk  globules.  The 
portion  of  the  cell  which  remains  forms  new  cytoplasm,  and  the  same  process  is  repeated  over  and 
over  again.     The  cells  also  secrete  water  and  the  salts  which  are  found  in  the  milk."' 

After  lactation  a  number  of  the  alveoli  atrophy  and  disappear,  while  the  remainder  become 
much  reduced  in  size.     The  gland  then  consists  mainly  of  adipose  and  fibrous  tissues. 

Tiie  fibrous  tissue  (Fig.  1208)  invests  the  entire  surface  of  the  breast,  and  sends  down  septa 
between  its  lobes,  which  serve  to  hold  them  together. 

The  fatty  tissue  (Figs.  1207  and  1208)  siurounds  the  surface  of  the  gland  and  occupies  the 
intervals  between  its  lobes.  It  usually  exists  in  considerable  abundance,  and  determines  the 
form  and  size  of  the  gland.     There  is  no  fat  immediately  beneath  the  areola  and  nipple. 

'  Human  Physiology.    By  Joseph  Howard  Raymond. 


1432  THE  URINOGENTTAL  ORGANS 

Vessels  and  Nerves. — The  arteries  supplying  the  mammary  gland  are  derived  from  the 
perforating  branches  of  the  iatemal  mammary,  the  long  thoracic  branches  of  the  axUlary, 
and  branches  from  the  intercostals.  The  veins  describe  an  anastomotic  circle  around  the  base 
of  the  nipple,  called  by  Haller  the  circulus  venosus.  From  this  large  branches  transmit  the  blood 
to  the  circumference  of  the  gland  and  end  in  the  axillary  and  internal  mammary  veins.  The 
lymphatics  of  the  mammary  gland  (Fig.  562)  and  mammary  region  have  been  previously 
described  (pp.  782  and  797).  The  nerves  are  derived  from  the  fourth,  fifth,  and  sixth  inter- 
costal nerves,  and  sympathetic  filaments  from  the  thoracic  cord  pass  to  the  breast  along  the 
branches  of  the  intercostal  nerves. 

Applied  Anatomy. — Occasionally  the  mammary  gland  undergoes  enormous  hypertrophy. 
This  may  occur  in  any  age,  even  in  the  virgin.  The  physiological  enlargement  of  puberty  may 
become  excessive  or  the  physiological  enlargement  of  pregnancy  and  lactation  may  continue 
and  increase  after  the  termination  of  lactation.  The  chief  elements  in  lie  enlargement  are  fat 
and  connective  tissue,  and  it  is  doubtful  if  there  is  extensive  reproduction  of  glandular  tissue. 

Abscess  of  the  breciM  may  occur  at  any  age,  but  is  most  common  by  far  in  nursing  women. 
The  portals  are  opened  to  infection  by  a  crack  in  the  nipple  and  bacteria  are  carried  inward 
by  the  lymph  vessels.  In  some  cases  the  pus  gathers  beneath  the  skin  (supramanmiary  abscess), 
in  others  in  the  breast  tissue  {intramammary  abscess).  In  rare  cases  pus  gathers  beneath  the 
breast  (retromammary  abscess).  In  intramammary  abscess  the  pus  burrows  through  the  fibrous 
septa  or  fascia  and  forms  numerous  channels,  and  such  a  channel  is  constricted  in  hour-glass 
shape  at  the  point  where  it  passes  through  fascia  or  a  fibrous  septum. 


AREOLA  — 


LARGE 

5EBACEOU: 

GLANDS 


CONCENTRIC 


Fig.    1209.^ — Nipple  and  areola  of  a  virgin,     (Testut.)  Fig.   1210. — Nipple  and  areolae  of  a  preg- 

nant woman.      (Testut.) 


In  every  patient  suffering  from  abscess  the  nipple  should  be  examined  for  a  sore  or  crack,  and 
the  area  when  found  should  be  treated  antiseptically.  A  supramammary  abscess  should  be 
opened  by  an  incision  radiating  from  the  nipple.  • 

In  intramammary  abscess  follow  the  advice  of  Sheild:  Open  the  abscess  by  an  incision  radi- 
ating from  the  nipple,  insert  the  index  finger,  and  when  possible  pass  it  to  the  bottom  of  the 
abscess  and  carry  the  tip  from  the  depths  of  the  abscess  to  as  near  the  surface  as  possible.  At  this 
point  make  a  counter  opening.  The  finger  breaks  down  septa  which  cause  constriction  and  thus 
converts  the  tracking  sinuses  into  one  large  cavity.'     Drain  by  tubes. 

A  retromammary  abscess  is  opened  by  an  incision,  following  the  outline  of  the  breast  at  the 
thoracomammary  junction,  the  finger  being  pushed  through  the  incision  and  up  under  the  gland. 

Tuberculosis  of  the  breast  may  occur,  and  if  it  does,  cold  abscess  is  apt  to  form.  The  best 
treatment  is  removal  of  the  gland  and  the  associated  lymph  nodes. 

Chronic  mastitis  is  a  condition  of  mammary  fibrosis,  most  common  in  neurotic  single  women, 
and  apt  to  be  associated  with  ovarian  or  uterine  disease. 

Malignant  dermatitis  or  Paget's  disease  of  the  nipple  is  a  chronic  condition  consisting  of  epi- 
thelial proliferation,  induration,  desquamation,  and  ulceration,  and  it  is  apt  to  be  followed  by 
epithelioma. 

Chancre  of  the  nipple  is  occasionally  met  with. 

Secondary  and  tertiary  syphilitic  lesions  are  seen  upon  the  skin  of  the  breast,  the  nipple,  and 
the  areola. 

Cysts  and  tumors  are  common  in  the  breast.  There  may  be  cystic  degeneration  of  the  gland 
m  women  near  the  menopause  (involution  cysts);  a  lacteal  cyst;  a  hydatid  cyst;  an  adenoma 

^  Diseases  of  the  Breast.     By  A.  Marmaduke  Sheild. 


THE  MAMMARY  GLAND  1433 

may  become  cystic.  The  nipple  may  suffer  from  epithelioma,  myoma,  myxoma,  angioma,  papil- 
loma, or  fibroma.  The  innocent  tumors  of  the  breast  are  fibroadenoma,  cystic  adenoma,  myxoma, 
and  angioma.  The  skin  of  the  breast  may  suffer  from  any  form  of  growth  or  cyst  which  could 
arise  from  the  skin  of  another  ])art.  Malignant  tumors  of  the  glandular  structure  are  ten  times 
as  frequent  as  innocent  tumors.     Sdraima  is  rare;  carcinoma  is  very  common. 

Carcinoma  of  the  breast  has  occupicii  much  of  the  attention  of  surgeons  during  recent  years. 
The  old  operation  was  uniformly  followed  by  recurrence.  The  modern  radical  operation  has 
been  evolved  from  the  studies  of  Moore,  the  younger  Gross,  Heidenhain,  Stiles,  Banks,  Halsted, 
and  others.  The  modern  operation  always  removes  at  least  the  skin  and  subcutaneous  tissue 
over  the  hemispherical  portion  of  the  breast,  the  outlying  lobules  of  the  breast,  the  ]5ectoral  fascia, 
and  the  sternal  portion  of  the  great  Pectoral  muscle,  the  lymphatic  tracts  from  the  breast,  the 
lymphatic  nodes  and  cellular  tissue  from  the  axilla,  and  from  beneath  the  Latissimus  dorsi 
muscle.  The  pectoral  fascia  and  the  sternal  portion  of  the  great  Pectoral  muscle  must  come  away 
in  every  case,  because  breast  tissue  may  pass  through  the  fascia.  The  entire  breast  must  be  re- 
moved, because  even  in  a  recent  case  the  entire  breast  is  regarded  as  infected.  The  clavicular 
portion  of  the  great  Pectoral  muscle  is  anatomically  distinct  from  the  sternal  portion  and  its 
removal  is  not  imperative.  Some  operators  remove  the  lesser  Pectoral  muscle.  To  leave  it  is 
of  no  value  to  the  arm,  and  it  frequently  causes  an  annoying  rigid  band  anterior  to  the  axilla.  To 
take  it  away  gives  ready  access  to  the  axillary  vessels  at  a  desirable  point  above.  The  sheath  of 
the  axillary  vein  should  be  removed  with  the  nodes  and  cellular  tissue  of  the  axilla.  The  nodes 
receiving  lymph  from  the  cancerous  area  must  be  removed,  of  course.  In  view  of  the  fact  that  in 
an  undetermined  percentage  of  cases  a  lymph  tract  passes  direct  to  the  subclavian  nodes,  it  is 
evident  that  these  nodes  may  become  infected  by  this  route  instead  of,  as  is  more  usual,  secondarily 
to  axillary  infection;  hence  it  seems  wiser  in  every  case  to  remove  the  cellular  tissue  and  nodes 
from  the  subclavian  triangle.  All  of  these  structures  should  be  removed  as  one  piece,  in  order 
to  avoid  cutting  across  lymph  tracts  and  flooding  the  wound  with  carcinoma  cells  which  might 
adhere,  grow,  and  reproduce  cancer. 

Halsted's  operation  is  the  method  adopted  by  most  surgeons.  The  wound  cannot  be  com- 
pletely closed,  and  the  raw  spot  is  covered  at  once  or  later  with  Thiersch's  skin  grafts.  (For 
surgical  considerations  regarding  the  lymphatics  in  mammary  carcinoma  see  page  804). 

The  male  breast  (mamma  virilis)  is  a  small,  flat  structure,  consisting  chiefly 
of  connective  tissue,  but  containing  some  branched  tubules.  Under  normal 
circumstances  it  remains  permanently  of  the  infantile  type.  It  possesses  a  nipple 
which  is  much  smaller  than  that  of  the  female  breast,  and  which  usually  lies 
over  the  fourth  intercostal  space,  but  may  lie  over  the  fourth  or  fifth  rib.  The 
nipples  of  the  two  sides  are  rarely  placed  quite  symmetrically.  Accessory  glands 
and  accessory  nipples  are  as  common  among  males  as  females.  The  male 
breast  may  exhibit  some  evidence  of  temporary  functional  activity  at  birth  and 
at  puberty.     Cases  have  been  recorded  of  actual  lactation  by  the  male  breast. 

Applied  Anatomy. — The  male  breasts  may  undergo  enormous  hypertrophy  (gynecomazia). 
In  these  cases  the  penis  is  often  small  and  the  testicles  may  be  atrophied.  The  breasts  may  be 
absent  in  the  male.  Disease  of  the  male  breast  is  not  nearly  so  frequent  as  disease  of  the  female 
breast.  The  organ  may  be  the  seat  of  syphilis,  tuberculosis,  acute  or  chronic  mastitis,  abscess 
or  tumor.     A  number  of  cases  of  cancer  of  the  male  breast  have  been  recorded. 


THE  DUCTLESS  GLANDS. 


THERE  are  certain  organs,  in  various  situations,  which  are  very  similar  to 
secreting  glands,  but  differ  from  them  in  one  essential  feature — viz.,  they  do 
not  possess  any  ducts  by  which  their  secretion  is  discharged.  These  organs 
are  known  as  the  ductless  glands.  They  are  capable  of  internal  secretion — that 
is  to  say,  of  forming,  from  materials  brought  to  them  by  the  blood,  substances 
which  have  a  certain  influence  upon  the  nutritive  and  other  changes  going  on 
in  the  body.  This  secretion  is  carried  into  the  blood  stream,  either  directly  by 
the  veins  or  indirectly  through  the  medium  of  the  lymphatics. 

These  glands  include  the  thyroid  and  the  parathyroids,  the  thymus,  the  spleen, 
the  suprarenal  glands,  and  the  small  carotid,  coccygeal,  and  parasympathetic 
bodies,  which  will  be  described  in  this  section.  They  also  include  the  lymph 
and  hemolymph  nodes  (or  glands)  which  have  already  been  described  on  pages 
76S  to  802 ;  and  the  epiphysis  (pineal  gland)  and  hypophysis  (pituitary)  described 
with  the  brain  on  pages  906  and  909.  Certain  isolated  cell  masses  in  the  pancreas, 
the  testicle,  and  ovary,  apparently  engaged  in  internal  secretion,  are  described 
with  those  organs. 

THE    THYROID   GLAND    OR   BODY    (GLANDULA    THYREOIDEA) 

(Fig.  1211). 

The  thyroid  gland  is  a  highly  vascular  organ,  situated  at  the  front  and  sides  of 
the  neck,  and  extending  upward  upon  each  side  of  the  larynx;  it  consists  of  two 
lateral  lobes  connected  across  the  middle  line  by  a  narrow  transverse  portion, 
the  isthmus. 

The  weight  of  the  gland  is  somewhat  variable,  but  is  usually  about  one  ounce. 
It  is  somewhat  heavier  in  the  female,  in  whom  it  becomes  enlarged  during  men- 
struation and  pregnancy. 

The  lateral  lobes  are  conical  in  shape,  the  apex  of  each  being  directed  upward 
and  outward  as  far  as  the  junction  of  the  middle  with  the  lower  third  of  the  thy- 
roid cartilage;  the  base  looks  downward,  and  is  on  a  level  with  the  fifth  or  sixth 
tracheal  ring.  Each  lobe  is  about  two  inches  (5  cm.)  in  length,  its  greatest  width 
is  about  one  inch  and  a  quarter  (3  cm.),  and  its  thickness  about  three-quarters 
(2  cm.)  of  an  inch.  The  summit  of  the  lateral  lobe  is  not  unusually  pointed  and 
reaches  to  the  level  of  the  oblique  line  upon  the  ala  of  the  thyroid  cartilage  or  even 
higher.  The  right  lobe  is,  as  a  rule,  somewhat  larger  than  the  left.  The  lower 
portion  of  the  gland,  when  the  head  is  extended,  is  about  one  inch  above  the 
upper  margin  of  the  sternum;  when  the  head  is  flexed,  it  is  at  the  level  of  the 
upper  border  of  the  sternum  or  even  below  and  behind  it. 

The  external  or  superficial  surface  is  convex,  and  covered  by  the  skin,  the  super- 
ficial fascia,  the  deep  fascia,  the  Sternomastoid,  the  anterior  belly  of  the  Omo- 
hyoid, the  Sternohyoid,  and  Sternothyroid  muscles,  and  beneath  the  last-named 
muscles  by  the  pretracheal  layer  of  the  deep  fascia,  which  forms  a  capsule  for 
the  gland  (Fig.  297). 

The  deep  or  internal  surface  is  moulded  over  the  underlying  structures — \\z., 
the  thyroid  and  cricoid  cartilages,  the  trachea,  the  Inferior  constrictor  and  pos- 

14.35 


1436  THE  DUCTLESS  GLANDS 

terior  part  of  the  Cricothyroid  muscles,  the  oesophagus  (particularly  on  the  left 
side  of  the  neck),  the  superior  and  inferior  thyroid  arteries,  and  the  recurrent 
laryngeal  nerves. 

The  deep  surface  of  each  lobe  is  fixed  by  bands  of  fibrous  tissue  passing  from 
the  capsule  of  the  isthmus  and  lateral  lobes  to  the  sides  of  the  cricoid  cartilage 
and  the  posterior  fascia  of  the  trachea.     These  bands  are  called  the  lateral  or 

suspensory  ligaments.     Because  of  this  fixation 
to  the  larynx  and  trachea  by  the  capsule  and 
fT^  J        by   the  lateral    ligaments,    the   thyroid   gland 

R  m         moves  with   the  trachea  and   ascends  during 

the  act  of  swallowing.  The  recurrent  laryn- 
geal nerve  on  each  side  is  in  contact  with 
the  outer  and  posterior  surface  of  the  sus- 
pensory ligament. 

The  anterior  border  is  thin,  and  inclines 
obliquely  from  above  downward  and  inward 
toward  the  middle  line  of  the  neck,  while  the 
posterior  border  is  thick  and  overlaps  the  com- 
mon carotid  artery. 

The  isthmus  (isthmus  cjlaudidae  thyroidea) 
connects  the  lower  two-thirds  of  the  two  lat- 
eral lobes;  it  measures  about  half  an  inch  in 
breadth  and  the  same  in  depth,  and  usually 
covers  the  second  and  third  rings  of  the  trachea, 
but  sometimes  also  the  first  and  fourth  rings. 
Its  situation  and  size  present,  however,  many 
variations,  a  point  of  importance  in  the  oper- 
ation of  tracheotomy.  In  the  middle  line  of 
the  neck  it  is  covered  by  the  skin  and  fascia, 
and  close  to  the  middle  line,  on  either  side,  by 
the  Sternohyoid  muscle.  Across  its  upper 
border  run  branches  of  the  superior  thyroid 
artery  and  vein;  at  its  lower  border  is  a 
branch  of  the  inferior  thyroid  veins.  Some- 
times the  isthmus  is  altogether  wanting. 
The  third,  pyramidal  or  middle  lobe  frequently 
Fig.  12H. -The  thyroid  gland.  (Spaitehoiz.)     arises  from  the  upper  part  of  the  isthmus,  or 

from  the  adjacent  portion  of  either  lobe,  but 
most  commonly  from  the  left  lobe,  and  ascends  in  front  of  the  thyroid  cartilage 
in  the  direction  of  the  middle  of  the  hyoid  bone.  It  may  reach  the  bone  or 
may  not  reach  it.  If  it  reaches  the  bone  it  is  attached  to  it.  If  it  does  not 
reach  the  bone,  fibrous  tissue,  which  often  contains  muscle,  is  prolonged  from  the 
tip  of  the  pyramid  to  the  back  of  the  bone  or  to  the  thyrohyoid  membrane.  The 
pyramid  is  occasionally  quite  detached,  or  divided  into  two  or  more  parts. 

A  few  muscle  bands,  derived  from  the  Thyrohyoid  muscles,  are  occasionally 
found  attached,  above,  to  the  body  of  the  hyoid  bone,  and  below  to  the  isthmus 
of  the  gland  or  its  pyramidal  process.  These  form  a  muscle,  which  was  named 
by  Soemmerring  the  Levator  glandulae  thyreoideae. 

Accessory  Thjrroids  {glandulae  thyreoideae  accessoriae). — ^Frequently  small 
isolated  masses  of  thyroid  tissue  exist.  They  are  found  particularly  about  the 
lateral  lobes  of  the  thyroid  gland  in  the  sides  of  the  neck  or  just  above  the  hyoid 
bone,  and  are  called  accessory  thyroids. 

Structure  of  the  Thyroid  (Fig.  1212).— The  thyroid  body  is  invested  by  a  capsule  of  con- 
nective tissue  which  projects  into  its  substance  as  a  framework  and  imperfectly  divides  it  into 


THE  THYROID  GLAND  OR  BODY 


1437 


masses  of  irregular  form  and  size,  known  as  lobes  and  lobules.  More  slender  septa  separate 
the  secretory  alveoli  from  one  another.  While  the  anterior  portion  of  the  capsule  is  thin  and 
easily  torn,  the  posterior  portion  is  thick  and  dense.  When  the  organ  is  cut  into,  it  is  of  a 
brownish-red  color,  and  is  seen  to  be  made  up  of  a  number  of  closed  vesicles  or  alveoli  con- 
taining a  yellow  glairy  fluid  and  separated  from  each  other  by  intermediate  connective  tissue. 

It  is  a  compound  tubular  gland,  each  lobule  of  which  consists  of  a  number  of  short  closed 
tubules  or  alveoli,  which  are  surrounded  by  the  interstitial  reticulum. 

According  to  Baber,  who  has  published  some  important  observations  on  the  minute  structure 
of  the  thyroid,  the  vesicles  of  the  thyroid  of  the  adult  animal  are  generally  closed  cavities;  but  in 
some  young  animals  (e.  g.,  young  dogs)  the  vesicles  are  more  or  less  tubular  and  branched.  This 
appearance  he  supposes  to  be  due  to  the  mode  of  growth  of  the  gland,  and  merely  indicating  that 
an  increase  in  the  number  of  vesicles  is  taking  place.  Each  vesicle  is  lined  by  a  single  layer  of 
cuboidal  epithelial  cells  which  rest  upon  a  delicate  basement  membrane.  Between  the  tubules 
exists  a  delicate  reticulum.  The  vesicles  are  of  various  sizes  and  shapes,  and  contain  as  a  normal 
product  a  viscid,  homogeneous,  semifluid,  slightly  yellowish  material  which  frequently  contains 
red  corpuscles  in  various  stages  of  disintegration  and  deeolorization,  the  yellow  tinge  being 
probably  due  to  the  hemoglobin,  which  is  thus  set  free  from  the  colored  corpuscles.  This  normal 
product  is  known  as  colloid  material,  and  it  is  secreted  by  the  epithelium.     What  part  if  any  the 


Li/n  il  U      eisel 


Wall  of  gland  le^  cle 


-om  a  transverse  section  of  the  thyroid  of  a  dog.     Semi- 
tlatic.      (Baber.) 


colloid  plays  in  the  formation  of  the  internal  secretion  of  the  gland  is  not  known.  It  is  quite 
possible  that  the  colloid  corresponds  to  the  external  secretion  of  glands  with  ducts  and  that  the 
true  internal  secretion  passes  directly  into  the  capillaries  which  form  a  network  about  the  alveoli 
(Szymonowicz),  or  passes  into  the  lymphatics.  In  the  thyroid  gland  of  the  dog,  Baber  has 
found  large  round  cells,  parenchymatous  cells,  each  provided  with  a  single  oval-shaped  nucleus, 
which  migrate  into  the  interior  of  the  gland  vesicles.  Between  the  thyroid  vesicles  in  the  human 
being  are  collections  of  round  cells.  They  are,  in  reality,  miniature  immature  vesicles,  and  are 
much  more  numerous  in  youth  than  in  old  age. 

The  capillary  bloodvessels  form  a  dense  plexus  in  the  connective  tissue  around  the  vesicles, 
between  the  epithelium  of  the  vesicles  and  the  endothelium  of  the  lymph  spaces,  which  latter 
surround  a  greater  or  smaller  part  of  the  circumference  of  the  vesicles.  These  lymph  spaces 
empty  themselves  into  lymphatic  vessels  which  run  in  the  interlobular  connective  tissue,  not 
uncommonly  surrounding  the  arteries  which  they  accompany,  and  communicate  with  a  network 
in  the  capsule  of  the  gland.  Small  glands  may  be  connected  with  this  network.  Baber  has 
found  in  the  lymphatics  of  the  thyroid  a  viscid  material  which  is  morphologically  identical  with 
the  normal  constituent  of  the  vesicle. 

Vessels  and  Nerves.— The  arteries  (Figs.  444  and  499;  see  also  p.  592)  supplying  the  thy- 
roid are  the  superior  thjrroid  from  the  external  carotid,  and  the  inferior  thjrroid  from  the  thyroid 
axis  of  the  first  ])art  of  the  subclavian.  Sometimes  there  is  an  atlditional  vessel,  the  thjrroidea 
media  or  ima,  usually  arising  from  the  innominate  artery,  but  sometimes  from  the  arch  of  the 
aorta  or  the  common  carotid.     It  ascends  upon  the  front  of  the  trachea.     The  superior  thjToid 


1438  THE  DUCTLESS  GLANDS 

artery  reaches  the  summit  of  the  upper  horn  of  the  gland,  and  usually  at  this  point  gives  off  a 
vessel  which  courses  down  the  posterior  surface  of  the  gland.  The  main  trunk  passes  down- 
ward and  inward  at  the  junction  of  the  inner  and  anterior  border  of  the  upper  horn,  giving 
branches  to  adjacent  srructiu'es  and  sending  branches  over  the  anterior  siu^ace  of  the  th^Toid 
gland.  It  reaches  the  isthmus  and  crosses  the  isthmus  at  its  upper  border  to  anastomose  with 
the  artery  from  the  other  side.  The  inferior  th\Toid  artery,  which  is  usually  larger  than  the  supe- 
rior, after  it  has  passed  posterior  to  the  sheath  of  the  carotid  and  the  sympathetic  nerve,  reaches 
the  posterior  surface  of  the  gland.  At  this  point  branches  are  given  off;  some  pass  into  the  hilum ; 
the  others  go  to  the  posterior  surface  of  the  gland.  The  relation  of  the  artery  to  the  recurrent 
laryngeal  nerve  is  very  important  to  the  sm-geon.  "Usually  the  main  trunk  of  the  artery  passes 
behind  the  nerve;  sometimes  the  artery  breaks  up  before  reaching  the  nerve;  in  this  case  one  or 
more  of  the  branches  may  pass  in  front  of  it.  Aluch  less  commonly  the  main  trunk  or  all  its 
branches  will  be  found  to  lie  in  front  of  the  nerve."'  If  the  th_\Toidea  ima  is  present  it  goes  to 
the  lower  part  of  the  gland.  The  larger  branches  of  the  th\Toid  arteries  are  beneath  the  capsule 
and  upon  the  sm-face  of  the  gland;  smaller  branches  pass  to  the  interior  of  the  gland  (Berri-). 
The  arteries  are  remarkable  for  their  large  size  and  frequent  anastomoses. 

The  thjrroid  veins  (Figs.  49S  and  499;  see  also  p.  715J  form  a  plexus  upon  the  surface  of  the 
gland  and  beneath  the  capsule.  Here  and  there  veins  pass  through  the  capsule  and  go  to  adja- 
cent venous  trunks.  Berry,  accepting  Kocher"s  description,  notes  the  following  veins:  The 
superior  thyroid  vein  runs  with  the  superior  th^Toid  artery  and  passes  to  the  internal  jugular 
vein.  A  transverse  vein  of  the  upper  border  of  the  isthmus  joins  the  two  superior  thvToid  veins. 
A  single  vein,  the  middle  thyroid,  sometimes  emerges  from  the  side  of  the  gland  and  passes  to 
the  internal  jugular.  Usually,  however,  instead  of  this  single  vein  there  are  two  veins,  the  supe- 
rior and  inferior  a;Ccessory  tiyroids.  The  superior  accessory  thyroid  emerges  from  the  outer 
side  of  the  upper  horn,  below  the  apex,  and  passes  to  the  internal  jugular.  The  inferior 
accessory  thyroid  emerges  from  the  posterior  and  inferior  portion  of  the  gland  and  passes  to 
the  internal  jugular.  The  veins  from  the  lower  border  of  the  gland  vary  greatly.  A  vein  passes 
vertically  down  on  each  side  in  front  of  the  trachea  from  the  isthmus  and  from  the  inner  side  of 
the  inferior  horn.  It  is  called  by  Kocher  the  thyroidea  ima.  The  vein  of  the  left  side  passes  to 
the  left  innominate;  the  vein  of  the  right  side  passes  to  the  right  innominate  or  left  innominate. 
As  Berry  points  out,  the  vein  of  one  side  may  be  small  or  may  be  absent,  or  the  two  veins  may 
unite  and  form  one  vein  which  enters  the  left  innominate.  An  inferior  thyroid  vein  is  often 
present.  It  is  of  small  size,  emergen  at  the  inferior  and  external  part  of  the  gland,  and  passes  to 
the  corresponding  innominate  vein." 

The  Ismiphatics  are  numerous  and  of  large  size.  Collecting  trunks  arise  from  a  network  within 
the  capsule.  Some  trunks  ascend  from  the  upper  margin  of  the  isthmus  and  reach  the  node  in 
front  of  the  larynx;  others  ascend  along  the  superior  th}Toid  artery  and  reach  the  nodes  at  the 
bifurcation  of  the  carotid.  Descending  trunks  from  the  lower  margin  of  the  isthmus  reach  the 
nodes  in  front  of  the  trachea;  trunks  from  the  side  of  the  gland  descend  to  the  nodes  about  the 
recurrent  laryngeal  nerve.' 

The  nerves  of  the  thjToid  are  amyelinic  and  are  derived  from  the  middle  and  inferior  ganglia 
of  the  sympathetic.     They  reach  the  gland  by  following  the  thjToid  arteries.^ 

Applied  Anatomy. — The  th\Toid  gland  may  be  congenitally  absent,  and  when  it  is  the  indi- 
vidual suffers  from  the  worst  form  of  crdinixm.  One  lobe  may  be  congenitally  absent,  but 
this  will  provoke  no  trouble  unless  the  other  lobe  undergoes  atrophy. 

Complete  removal  of  the  th\Toid  and  parath\Toids  will  produce  operative  myxedema  (cachexia 
sfrumipriva),  unless  accessory  th\Toids  enlarge  and  perform  the  functions  of  the  thvToid. 

The  th\Toid  gland  may  be  congenitally  enlarged.  The  gland  tends  to  atrophy  in  old  age. 
It  is  atrophied  in  m_\-xedema  and  cretinism.  Some  forms  of  th^Toid  enlargement  are  called 
goitre. 

^Vhen  all  parts  of  the  gland  enlarge  the  condition  is  known  as  parenchymatous  goitre. 

Adenomatous  goitre  consists  of  an  adenoma  or  of  adenomata.  In  cystic  goitre  there  are  one 
or  more  cysts  due  to  cystic  degeneration  of  adenomata  or  to  fusion  of  adjacent  tubules. 

A  pulsating  goitre  is  one  which  receives  impulses  from  the  carotid  pulsations.  In  a  fibroid 
goitre  there  is  increase  of  interstitial  connective  tissue.  A  goitre  which  passes  back  of  the  sternum 
is  known  as  substernal  or  intrathoracic.  A  goitre  may  extend  back  of  the  trachea  or  back  of  the 
oesophagus. 

Exophthalmic  goitre,  Graves'  disease  or  Basedow's  disease,  is  a  remarkable  disease.  Its  three 
chief  symptoms  are  enlargement  of  the  th^Toid,  or  goitre;  prominence  of  the  eyeballs,  or  exoph- 
thalmos (see  p.  372);  and  very  rapid  pulse,  or  tachycardia.  Dyspnea,  tremor,  and  various  other 
symptoms  are  usually  found.  The  th\Toid  gland  may  be  the  seat  of  a  carcinoma  or  sarcoma 
{mahgnant  goitre),  syphilitic  or  tuberculous  disease,   ordinary   inflammation,   suppuration,   or 

1  Diseases  of  the  Th\Toid  Gland.    By  James  Berr>'.  -  Ibid. 

^  The  LjTuphatics.    By  Poirier,  Cun^o,  and  Delamere.    Translated  and  edited  bv  Cecil  H.  Leaf. 
'  D.  A.  Rhinehart:  Amer.  Jour,  of  .Anat.,  vol.  xiii,  Mav  15,  1912. 


THE  PARATHYROID  GLANDS 


1439 


hydatid  disease.  For  the  relief  of  ordinary  goitre  various  methods  have  been  employed.  Tap- 
ping, injection  of  astringents,  simple  incision,  and  the  seton  are  obsolete.  Ligation  of  the  thy- 
roid arteries  is  rarely  performed  as  a  curative  measure.  The  superior  and  inferior  thyroids  of 
one  side  have  been  tied  in  some  cases;  all  four  thyroids  in  other  cases.  Jaboulay  has. performed 
exothyropcxy.  In  this  operation  the  gland  is  dislocated  from  its  bed,  brought  out  of  the  vvfound, 
and  left  exposed,  in  hope  that  it  will  atrophy. 

Diviidon.  of  the  isthmus  is  occasionally  practised  to  relieve  dyspnea.  The  operation  some- 
times succeeds,  but  often  fails. 

Extirpation  of  one-half  or  two-thirds  of  the  gland  is  a  very  successful  operation.  Removal  of 
the  entire  gland  will  be  followed  by  operative  myxedema.  Removal  or  injury  of  the  parathyroids 
causes  tetany. 

In  extirpating  a  lobe  of  the  thyroid  by  the  method  until  recently  in  vogue,  great  care  must  be 
taken  to  avoid  tearing  the  capsules,  as  if  this  happens  the  gland  tissue  bleeds  profusely.  The 
thyroid  arteries  should  be  ligated  on  the  diseased  side  before  an  attempt  is  made  to  remove  the 
mass,  and  in  ligating  the  inferior  thyroid  the  position  of  the  recurrent  laryngeal  nerve  must  be 
borne  in  mind,  so  as  not  to  include  it  in  the  ligature.  In  order  to  preserve  the  parathyroids  from 
injury,  C.  H.  Mayo  recommends  that  after  the  vessels  entering  and  leaving  the  thyroid  have  been 
double  clamped  and  divided,  the  entire  lobe  should  be  elevated,  the  capsule  split  along  the  side 
of  the  gland  and  pushed  back  with  gauze,  and  the  gland  lifted  and  removed  without  disturbing 
the  posterior  portion  of  the  capsule.  As  pointed  out  before,  the  posterior  portion  of  the  capsule 
is  so  thick  and  strong  that  it  is  easier  to  leave  it  in  situ  than  to  bring  it  out  of  the  wound  with  the 
gland. 

A  cystic  or  solid  tumor  of  the  thyroid  may  be  removed  by  iiiiraglandular  enucleation.  If  opera- 
tion becomes  necessary  in  exophthalmic  goitre,  partial  extirjiation  is  usually  preferred.  Bilateral 
extirpation  of  the  cervical  ganglia  of  the  sympathetic  (syiiipafhcrtoiny  or  Jonnesco's  operation) 
has  been  practised  by  some  surgeons  for  exophthalmic  goitre.  The  value  of  the  procedure  is 
uncertain. 

THE    PARATHYROID    GLANDS    (Fig.    1213). 


The  parathyroid  glands  are  small,  brownish-red  bodies,  situated  near  the  thy- 
roid gland,  but  differing  from  it  in  structure,  being  composed  of  masses  of  cells 
arranged  in  a  more  or  less  reticular  fashion  with  numerous  intervening  bloodvessels. 
They  measure  on  an  average  about  a  quarter  of 
an  inch  (6  mm.)  in  length,  and  from  an  eighth 
to  a  sixth  of  an  inch  (3  to  4  mm.)  in  breadth, 
and  usually  present  the  appearance  of  flat  oval 
disks.  They  are  classified  according  to  their 
position  into  superior  and  inferior.  The  supe- 
rior, usually  two  in  number,  are  the  more  con- 
stant in  position,  and  are  situated,  one  on  either 
side,  at  the  level  of  the  lower  border  of  the 
cricoid  cartilage,  behind  the  junction  of  the 
pharynx  and  oesophagus,  and  in  front  of  the 
prevertebral  fascia.  The  inferior,  also  usually 
two  in  number,  may  be  applied  to  the  lower 
edge  of  the  lateral  lobe,  or  may  be  placed  at 
some  little  distance  below  the  thyroid  body,  or 
may  be  found  in  relation  with  one  of  the  inferior 
thyroid  veins.  Although  there  are  usually  four 
parathyroids,  there  may  be  but  three,  or  there 
may  be  six  or  even  eight.  Parathyroid  tissue 
may  exist  within  the  thyroid  gland  even  when 
the  superior  parathyroids  are  present.  Acces- 
sory parathyroids  may  be  found  over  a  wide 
area.  Rogers  and  Fergusson  found  one  in  the 
middle  of  the  posterior  portion  of  the  pharynx. 
Ogle  found  a  gland  in  the  thorax  which  was  partly 
parathyroid. 


Fig.  1213.  -The  position  of   the 


thyroid    glands 
(Zuckerkandl.) 


1440 


THE  DVCrLESS  GLANDS 


Structure. — The  structure  of  the  parathyroids  is  different  frora  that  of  the  thyroid.  They 
are  composed  of  groups  of  epithehal  ceils  arranged  in  a  chain-Iilie  fasliion  with  numerous  inter- 
vening capillaries.  There  is  a  certain  type  of  cell,  but  the  form  varies.  These  variations  result 
from  changes  due  to  episodes  of  rest  and  activity  (Verebely).  MacCallum's  studies  seem  to 
lead  to  the  same  conclusion.  Thomson'  states  that  he  finds  only  one  type  of  cell  in  the  infant 
gland,  and  that  in  the  adult  there  is  primarily  but  one  type  of  cell,  the  other  cells  noted  being 
modifications  of  the  principal  cell  due  to  degeneration  or  hyperfunction.  There  is  much  lym- 
phoid tissue  in  the  interstitial  connective  tissue.  The  capillaries  are  of  the  sinusoidal  variety. 
The  nerves  of  the  parathyroids  are  derived  from  the  sympathetic  system.  Each  parathyroid 
gland  is  supplied  by  a  parathyroid  artery.  The  inferior  parathyroid  artery  is  always  a  branch 
of  the  inferior  thyroid  artery  or  of  the  anastomosing  channel  between  the  superior  and  inferior 
thyroid  arteries  of  one  side  (Geist).  The  superior  parathyroid  artery  may  be  a  branch  of  the 
superior  thyroid  (Poole),  but  it  is  usually  a  branch  of  the  inferior  thyroid  or  of  the  anasto- 
mosing channel.  Ginsburg'  has  shown  that  each  of  the  glands  has  an  accessory  blood  supply, 
by  anastomotic  channels  from  the  opposite  side. 

Embryology. — The  parathyroids  develop  chronologically  in  advance  of  the  thyroid.  They 
are  derived  from  the  third  and  fourth  branchial  clefts  of  each  side.  An  independent  accessory 
parathyroid  may  develop  from  the  fifth  cleft  (Getzowa,  Michand).  Some  have  regarded  the  para- 
thyroids as  embryonic  portions  of  the  thyroid,  but,  as  MacCallum  says,  "  there  is  no  histological 
proof  that  parathyroid  tissue  can  ever  become  converted  into  thyroid  tissue."  Most  observers 
regard  the  parathyroids  as  distinct  glands  possessed  of  a  special  function.  Certain  it  is,  as 
Gley  '  and  others  have  shown,  removal  of  the  parathyroids  from  herbivora,  leaving  the  thyroid 
intact,  is  followed  by  spasms,  tetany,  etc.,  just  as  complete  thyroidectomy  is  followed  by  such 
symptoms  in  carnivora. 

Applied  Anatomy. — Surgeons  have  become  convinced  that  removal  of  the  parathyroids  in 
man  causes  tetany,  and  that  damage  to  them  may  produce  serious  symptoms.  Because  of  this 
danger  most  surgeons  now  prefer  to  remove  a  goitre  from  within  the  capsule  of  the  thyroid  gland, 
after  the  plan  of  the  Mayos,  and  thus  avoiding  the  parathyroids. 


THE  THYMUS  GLAND  (Fig.  1214). 

The  thymus  gland  is  a  temporary  organ,  attaining  its  full  size  at  the  end  of  the 
second  year,  when  it  ceases  to  grow  and  remains  practically  stationary  until 
puberty,  at  which  period  it  rapidly  degenerates.     It  does  not  entirely  disappear, 


Trachea 
Thyroid  veins 

Right  vagus 
Superior  vena  cava 


Ihi/ioid  body 

I  eft  common  carotid  artery. 
.Left  ijitet  nal  jugular  vein. 

Left  subclavian  vessels. 


Fig.  1214. — The  thymus  gland  of  a  full-time  fetus  exposed  in  situ, 

for  the  shrunken  and  degenerated  mass,  even  later  in  life,  maintains  a  likeness  to 
the  original  form  and  retains  within  its  substance  small  portions  of  thymus  tissue 
(Waldeyer).     If  examined  when  its  growth  is  most  active,  it  will  be  found  to  con- 


'  Internal  Secretions.     By  William  Hanna  Thomson.     New  York  Medical  Journal,  November  19,  1904. 

^  University  of  Pennsylvania  Medical  Bulletin,  January,  1908. 

^  American  Journal  of  the  Medical  Sciences,  1907,  n.  s.,  cxxxiv,  p.  562. 


THE  THYMUS  GLAND 


1441 


sist  of  two  lateral  lobes  placed  in  close  contact  along  the  middle  line,  situated 
partly  in  the  superior  mediastinum,  partly  in  the  neck,  and  extending  from  the 
level  of  the  fourth  costal  cartilage  upward  as  high  as  the  lower  border  of  the  thy- 
roid gland.  It  is  covered  by  the  sternum  and  by  the  origins  of  the  Sternohyoid 
and  Sternothyroid  muscles.  Belotv,  it  rests  upon  the  pericardium,  being  separated 
from  the  arch  of  the  aorta  and  great  vessels  by  a  layer  of  fascia.  In  the  neck 
it  lies  on  the  front  and  sides  of  the  trachea,  behind  the  Sternohyoid  and  Sterno- 
thyroid muscles.  The  two  lobes  generally  differ  in  size;  they  are  occasionally 
united  so  as  to  form  a  single  mass,  and  are  sometimes  separated  by  an  intermediate 
lobe.  The  thymus  is  of  a  pinkish-gray  color,  is  soft,  and  is  lobulated  on  its  sur- 
faces. It  is  about  two  inches  (5  cm.)  in  length,  one  and  a  half  inches  (3.75  cm.) 
in  breadth  below,  and  about  a  quarter  of  an  inch  (6  mm.)  in  thickness.  At  birth 
it  weighs  about  half  an  ounce. 


'^^■IM'  -i  - 


Fig.  1215. — A  lobule  of  the  thymus  of  a  child,  as  seen  under  low  power.  C. 
Cortex,  c.  Concentric  corpuscles  within  medulla,  b.  Bloodvessels,  tr.  Tra- 
beculse.     (Schiifer.) 


Fig.  1216.— Elements 
of  the  thymus.  ;■,  300. 
a.  Lymph  corpuscles,  b. 
Concentric  corpuscle. 
(Schiifer,  after  Cadiot.) 


Structure  (Figs.  1195  and  1197). — Each  lateral  lobe  is  composed  of  numerous  lobules 
held  together  by  deHcate  areolar  tissue,  the  entire  gland  being  enclosed  in  an  investing  capsule 
of  a  similar  but  denser  structure.  The  primary  lobules  vary  in  size  from  a  pin's  head  to  a 
small  pea,  and  are  made  up  of  a  number  of  small  nodules  which  are  irregular  in  shape  and 
are  more  or  less  fused  together,  especially  toward  the  interior  of  the  gland.  Each  lobule  consists 
of  a  cortical  and  medullary  portion,  which  differ  in  many  essential  particulars  from  each  other. 
The  cortical  portion  is  mainly  composed  of  dense  lymphoid  tissue,  consisting  chiefly  of  lympho- 
cytes and  hyaline  cells  supported  by  a  delicate  reticulum.  In  addition  to  this  reticulum,  of  which 
traces  only  are  found  in  the  medullary  portion,  there  is  also  a  network  of  finely  branched  cells 
which  is  continuous  with  a  similar  network  in  the  medullary  portion.  This  network  forms  an 
adventitia  to  the  bloodvessels.  The  medullary  portion  consists  of  difiEuse  Isrmphoid  tissue 
(granular  cells)  and  concentric  corpuscles  (cnriui.-^cles  of  Hassal).  The  granular  cells  are 
rounded  or  flask-shaped  masses  attached  (often  by  fibrillated  extremities)  to  bloodvessels  and 
to  newly  formed  connective  tissue.  The  concentric  corpuscles  are  composed  of  a  central  mass 
consisting  of  one  or  more  granular  cells,  and  of  a  capsule  which  is  formed  of  concentrically 
arranged  epithelioid  cells  which  seem  to  be  continuous  with  the  branched  cells  forming  the  net- 
work mentioned  above. 

Each  lobule  is  surrounded  by  a  capillary  plexus  from  which  vessels  pass  into  the  interior 
and  radiate  from  the  periphery  toward  the  centre,  and  form  a  second  zone  just  within  the 
margin  of  the  medullary  portion.  In  the  centre  of  the  medulla  there  are  ver}'  few  vessels,  and 
they  are  of  minute  size. 

Watney  has  made  the  important  observation  that  hemoglobin  is  found  in  the  thymus  either 
in  cysts  or  in  cells  situated  near  to  or  forming  part  of  the  concentric  corpuscles;  This  hemo- 
globin varies  from  granules  to  masses  exactly  resembling  colored  blood  corpuscles,  oval  in  the 
bird,  reptile,  and  fish;  circular  in  all  mammals  except  in  the  camel.  Dr.  Watney  has  also  dis- 
covered in  the  lymph  issuing  from  the  thymus  similar  cells  to  those  found  in  the  gland,  and, 
like  them,  containing  hemoglobin  either  in  the  form  of  granules  or  masses.     From  these  facts 


1442 


THE  DUCTLESS  GLANDS 


he  arrives  at  the  physiological  conclusion  that  the  thymus  is  one  source  of  the  colored  blood 
eor|5uscles. 

Vessels  and.  Nerves. — The  arteries  supplying  the  thymus  are  derived  from  the  interna] 
mammary  and  from  the  superior  and  inferior  thyroid.  The  veins  terminate  in  the  two  innom- 
inate veins,  and  in  the  internal  mammary  and  the  thyroid  veins.  The  Ijrmphatics  are  of  large 
size,  arise  in  the  substance  of  the  gland,  and  are  said  to  terminate  in  the  internal  jugular  vein. 
The  nerves  are  exceedingly  minute;  they  are  derived  from  the  vagus  and  sympathetic. 
Branches  from  the  descendens  hjrpoglossi  and  phrenic  reach  the  investing  capsule,  but  do  not 
penetrate  into  the  substance  of  the  gland. 


Fig,  1217. — Minute  structure  of  the  thymus  gland.  Lobule  of  injected  thymus  from  a  calf,  four  days  old, 
slightly  diagrammatic,  magnified  about  50  diameters.  The  large  vessels  are  disposed  in  two  rings,  one  of  which 
surrounds  the  lobule,  the  other  lies  just  within  the  margin  of  the  medulla,  A  and  B.  From  thymus  of  camel,  ex- 
amined without  addition  of  any  reagent.  Magnified  about  400  diameters.  A.  Large,  colorless  cells  containing 
small  oval  masses  of  hemoglobin.  Similar  cells  are  found  in  the  Ijonph  nodes,  spleen,  and  medulla  of  bone. 
B.  Colored  blood  corpuscles,     (Watney.) 

Applied.  Anatomy. — Sudden  death — "thymus  death" — with  heart  failure,  and  with  or 
without  acute  respiratory  embarrassment,  has  been  recorded  in  a  number  of  infants  and  children 
in  whom  the  thymus  was  enlarged,  and  the  lymphatic  tissues  throughout  the  body  showed 
general  hypertrophy,  but  who  showed  no  other  evidence  of  disease.  Such  deaths  have  often 
occurred  during  the  administration  of  anesthetics. 

Primary  tumors  of  the  thymus  are  rare  forms  of  mediastinal  newgrowth,  and  are  usually 
dermoids  or  lymphosarcomas. 


THE  SPLEEN  (LIEN)  (Figs.  1218,  1219). 

The  spleen  is  situated  principally  in  the  posterior  portion  of  the  left  hypoclion- 
driac  region,  its  upper  and  inner  extremity  e.xtending  into  the  epigastric  region; 
it  hes  between  the  fundus  of  the  stomach  and  the  Diaphragm.  It  is  obliquely 
placed,  its  long  axis  following  the  obliquity  of  the  tenth  rib.     If  the  abdomen  is 


THE  SPLEEN 


1443 


opened  a  spleen  of  ordinary  size  is  not  visible  from  tlie  front,  as  it  is  placed 
between  the  left  kidney,  Diaphragm,  and  stomach.     It  moves  with  the  respiratory 


OMENTUM 


Fig.  121S. — The  spleen.     Internal  or  visceral  .surfact 


I'li;.  1219. — The  splei 


Diapuragmatic  surface. 


movements  and  with  the  movements  of  the  stomach.     It  is  the  largest  of  the  so- 
called  ductless  glands,  and  varies  greatly  in  size.     Usually  it  measures  some  five 


1444  THE  DUCTLESS  GLANDS 

inches  in  length.      It  is  of  an  oblong,  flattened,  tetrahedral  form,  soft,  of  very 
friable  consistence,  highly  vascular,  and  of  a  dark-purplish  color. 

Relations. — The  external  or  phrenic  surface  (fades  diphragmatica)  is  convex,  smooth,  and 
is  directed  upward,  backward,  and  to  the  left,  except  at  its  upper  end,  where  it  is  directed  snghtly 
inward.  It  is  in  relation  with  the  under  surface  of  the  Diaphragm,  which  separates  it  from 
the  nhith,  tenth,  and  eleventh  ribs  of  the  left  side,  and  the  intervening  lower  border  of  the  left 
lung  and  pleura. 

The  internal  surface  is  concave,  and  divided  by  a  ridge  into  an  anterior  or  gastric,  and  a 
posterior  or  renal  portion. 

The  gastric  surface  (fades  gastrica),  which  is  directed  forward  and  inward,  is  broad  and 
concave,  and  is  in  contact  with  the  posterior  wall  of  the  fundus  of  the  stomach;  and  below  this 
with  the  tail  of  the  pancreas.  It  presents  near  its  inner  border  a  long  fissure,  termed  the  hiltun 
(hilus  lienis),  in  which  are  several  irregular  apertures,  for  the  entrance  and  exit  of  vessels  and 
nerves. 

The  renal  surface  (fades  renalis)  is  directed  inward  and  downward.  It  is  somewhat  flattened, 
is  considerably  narrower  than  the  gastric  surface,  and  is  in  relation  with  the  upper  part  of  the 
outer  surface  of  the  left  kidney  and  occasionally  with  the  left  suprarenal  gland. 

The  upper  end  of  the  spleen  (extremitas  superior)  is  directed  inward,  toward  the  vertebral 
column,  where  it  lies  on  a  level  with  the  eleventh  thoracic  vertebra,  within  one  and  one-half  to 
two  inches  of  the  midline.  The  lower  end  (extremitas  inferior),  sometimes  termed  the  basal 
surface,  is  flat,  triangular  in  shape,  and  rests  upon  the  splenic  flexure  of  the  colon  and  the 
phrenocolic  ligament,  and  is  generally  in  contact  with  the  tail  of  the  pancreas.  The  anterior 
loorder  (margo  anterior)  is  free,  sharp,  and  thin,  and  is  often  notched,  especially  below;  it  sepa- 
rates the  phrenic  surface  from  the  gastric  surface.  The  posterior  border  (margo  posterior), 
more  rounded  and  blunter  than  the  anterior,  separates  the  renal  from  the  phrenic  surface; 
it  corresponds  to  the  lower  border  of  the  eleventh  rib  and  lies  between  the  Diaphragm  and 
left  kidney.  The  internal  border,  or  intermediate  margin,  is  the  ridge  which  separates  the 
renal  and  gastric  portions  of  the  internal  surface. 

The  spleen,  with  the  exception  of  its  hilum,  is  completely  invested  with  peritoneum,  which 
is  firmly  adherent  to  the  capsule  of  the  organ.  Two  folds  of  peritoneal  tissue — the  lienorenal 
Ugament  and  the  gastrosplenic  omentum — serve  to  hold  the  organ  in  position.  The  lienorenal 
ligament  (Figs.  998  and  1001)  is  derived  from  the  layers  of  the  peritoneum  forming  the  greater 
and  lesser  sacs  where  they  come  into  contact  between  the  left  kidney  and  the  spleen.  Between 
these  two  layers  the  splenic  vessels  pass.  The  gastrosplenic  omentum  (ligamentum  gastro- 
lienale)  is  also  formed  of  two  layers,  derived  from  the  greater  and  lesser  sacs,  respectively,  where 
they  meet  between  the  spleen  and  the  fundus  of  the  stomach  (Fig.  1001).  Between  these  two 
layers  run  the  vasa  brevia  and  the  left  gastroepiploic  branches  of  the  splenic  artery  and  vein. 
The  spleen  is  also  supported  by  the  phrenocolic  Ugament  (see  p.  1263). 

The  size  and  weight  of  the  spleen  are  liable  to  extreme  variations  at  different  periods  of  life  in 
different  individuals,  and  in  the  same  individual  under  different  conditions.  In  the  adult,  in  whom 
it  attains  its  greatest  size,  it  is  usually  about  five  inches  (12  cm.)  in  length,  tliree  inches  (7.5  cm.) 
in  breadth,  and  an  inch  or  an  inch  and  a  cjuarter  (3  cm.)  in  thickness,  and  weighs  about  six  and 
one-half  ounces  (195  gm.)  At  birth  its  weight,  in  proportion  to  the  entire  body,  is  almost  equal  to 
what  is  observed  in  the  adult,  being  as  1  to  350;  while  in  the  adult  it  varies  from  1  to  320  to  1  to 
400.  In  old  age  the  organ  not  only  decreases  in  weight,  but  decreases  considerably  in  proportion 
to  the  entire  body,  being  as  1  to  700.  The  size  of  the  spleen  is  increased  during  and  after 
digestion,  and  varies  considerably  according  to  the  state  of  nutrition  of  the  body,  being  large 
in  well-fed,  and  small  in  starved  animals.  In  intermittent  and  other  fevers  it  becomes  much 
enlarged,  weighing  occasionally  from  eighteen  to  twenty  pounds. 

Frequently  in  the  neighborhood  of  the  spleen,  and  especially  in  the  gastrosplenic  and  great 
omenta,  small  nodules  of  splenic  tissue  may  be  found,  either  isolated,  or  connected  to  the  spleen 
by  thin  bands  of  splenic  tissue.  Every  such  nodule  is  known  as  a  supernumerary  or  accessory 
spleen  (lien  accessorius).     Accessory  spleens  vary  in  size  from  that  of  a  pea  to  that  of  a  plum. 

Support  and  Mobility  of  the  Spleen. — The  spleen  is  normally  movable  within  certain 
narrow  limits.  It  moves  with  respiration  and  with  the  stomach  movements.  It  is  supported  by 
ligaments  (p.  1258).  An  unduly  mobile  spleen  is  called  a  movable  spleen.  In  order  that  a 
spleen  shall  become  unduly  movable,  the  ligaments  must  stretch,  and  this  stretching  is  often 
effected  when  the  organ  is  greatly  enlarged,  but  even  an  apparently  normal  spleen  may  become 
movable.     Movable  spleen  is  usually  associated  with  movable  left  kidney. 

Structure. — The  spleen  is  invested  by  a  capsule  consisting  of  an  external  serous  and  an 
internal  fibromuscular  layer. 

The  external  or  serous  layer  (tunica  serosa)  is  derived  from  the  peritoneum ;  it  is  thin,  smooth, 
and  in  the  hiunan  subject  is  intimately  adherent  to  the  fibromuscular  layer.  It  invests  the 
entire  organ,  except  at  the  places  of  its  reflection  on  to  the  stomach  and  Diaphragm  and  at 
the  hilura. 


THE  SPLEEN 


1445 


The  flbromuscular  layer  (tunica  albuginca)  forms  the  framework  of  the  spleen.  It  is  com- 
posed of  white  fibrous  connective  tissue  containing  smooth  muscle  cells  and  elastic  fibres,  and 
it  invests  the  organ  as  a  capsule,  and  at  the  hilum  is  reflected  inward  upon  the  vessels  in  the  form 
of  sheaths.     From  these  sheaths,  as  well  as  from  the  inner  surface  of  the  flbromuscular  layer. 


numerous  small  fibrous  bands,  trabeculae  (trabecidae  lienis)  (Figs.  1220  and  1221).  are  given 
oft'  in  all  directions;  these  uniting  with  the  bands  from  the  vessel  sheaths  constitute  the  frame- 
work of  the  spleen.  This  framework  resembles  a  sponge-like  material,  consisting  of  a  number 
of  small  spaces  or  areolae.  The  spaces  of  the  areolee  contain  the  lymphoid  material  known 
as  splenic  pulp  (pulpa  lienis). 


Fig.  1221. — Transverse  section  of  the  hu 


Within  the  capsule  is  the  parenchjona,  consisting  of  the  splenic  pulp  and  splenic  ( Malpighian) 
corpuscles.  The  splenic  pulp  is  dark  reddish  brown  in  color  and  consists  of  a  delicate  niinihim, 
ujion  the  fibres  of  which  arc  seen  stellate  connective-tissue  cells.  In  the  meshes  of  the  reticulum 
are  diffuse  lymphoid  tissue,  erythrocytes,  ervthroblasts,  disintegrating  erythrocytes,  pigment 
granules,  branched  cells,  and  certain  large  polynuclear  elements,  splenic  cells.  The  lymphoid 
tissue  consists  of  leukocytes,  mainly  lymphocytes,  and  hyaline  cells  scattered  throughout  the 
reticulum.    The  erythrocytes  are  on  their  way  to  or  from  the  blood  current;  the  erythroblasts 


1446 


THE  DUCTLESS  GLANDS 


are  newly  formed  red  blood  cells  that  have  as  yet  not  lost  their  nuclei.  The  disintegrating 
red  cells  are  useless  cells  that  by  their  disintegration  contribute  the  coloring  matters  to  the  bile. 
The  branched  cells  are  large,  flattened,  stellate  elements,  the  processes  of  which  seem  to  anas- 
tomose to  assist  in  forming  the  reticular  substance,  and  also  seem  to  connect  with  the  endo- 
thelial cells  of  the  capillaries.  The  splenic  cells  are  large  polynuclear  elements  possessing 
the  power  of  ameboid  movements.  They  often  contain  pigment  granules  and  red  cells  in  their 
protoplasm,  thus  indicating  phagocyiosin.  The  trabeculse  are  continuations  of  the  capsule, 
and  consist  of  white  iibrous  connective  tissue  and  smooth  muscle  tissue. 

The  splenic  (Malpighian)  corpuscles  are  dense,  spherical  or  cylindrical  collections  of  lym- 
phoid tissue  (solitary  nodules)  surrouiiding  an  arteriole.  Each  corpuscle  shows  a  lighter  genninal 
centre  and  a  darker  peripheral  zone  where  the  leukocytes  are  more  numerous  and  more  closely 
packed.  Each  corpuscle  usually  exhibits  an  excentrically  placed  arteriole,  as  the  lymphoid 
tissue  is  collected  in  the  adventitial  sheath  of  the  vessel.  These  bodies  are  visible  to  the  naked 
eye,  and  appear  as  whitish  dots. 

Bloodvessels  of  the  Spleen.' — The  splenic  artery  enters  the  hilum  and  divides  into  branches 
that  follow  the  trabeculse.  Of  these,  some  quickly  pass  to  the  pulp,  while  others  follow  the 
trabecule  to  their  smallest  divisions.  The  external  coats  of  these  arterioles,  at  first  consisting  of 
ordinary  connective  tissue,  undergo  a  transformation,  becoming  much  thickened  and  converted 
into  lymphoid  tissue.  The  spleen  is  divided  into  circulatory  lobules  about  1  mm.  in  diameter, 
each  of  which  is  divided  into  histological  units,  one  for  each  terminal  vessel,  or  ampulla.  These 
terminal  vessels  are  large  endothelial  channels  surrounded  by  lymphoid  tissue,  called  the  ellip- 
soidal sheath.  These  terminal  ampullae  are  porous  and  continue  as  veins,  that  collect  the  blood 
and  empty  it  into  the  splenic  vein  at  the  hilum. 


I  esse;  undergoing  lymphoid  change. 


ssel  continuous 
jfe>v         with  processes  of 
Jl       supporting  cells. 


Supporting  cell. 


Fig.    1222.- Section  of  spleen,  showing  the  termination  of  the  small  bloodvessels. 


The  spleen  is  subject  to  rhythmical  contractions,  one  per  minute;  during  a  contraction  the 
organ  is  reduced  about  18  per  cent,  in  volume.  These  contractions  are  produced  by  the  con- 
tractions of  the  smooth  muscle  tissue  in  the  capsule  and  trabeculse  of  the  pulp.  When  the 
cardiac  impulse  sends  the  blood  into  the  arterial  channels  the  blood  passes  through  the  porous 
walls  of  the  ampulla  into  the  pulp.  When  the  rhythmical  contractions  occur  the  blood  is  forced 
into  the  veins  through  the  pores  of  the  ampullae,  and  at  the  same  time  the  arteries  are  closed. 

The  lymphatics  originate  in  two  ways — {.  e.  from  the  sheath  of  the  arteries  and  in  the 
trabeculfe.  The  former  trunks  are  the  deep  collecting  trunks,  and  accompany  the  blood- 
vessels; the  latter  pass  to  the  superficial  Ijrmphatic  plexus,  which  may  be  seen  on  the  surface 
of  the  organ.  Lymphatic  channels  do  not  exist  in  the  pulp.  The  deep  trunks  at  the  hilum 
number  from  five  to  ten,  and  terminate  in  the  splenic  nodes.  The  superficial  trunks  also  pass 
to  the  hilum  and  terminate  in  the  .splenic  nodes. 

The  nerves  are  derived  from  the  splenic  plexus,  which  is  a  part  of  or  connected  with  the 
solar  plexus.     The  nerves  enter  the  spleen  with  the  vessels. 

Surface  Form. — The  spleen  is  situated  under  cover  of  the  lower  ribs  of  the  left  side,  being 
separated  from  them  by  the  Diaphragm,  and  above  by  a  small  portion  of  the  lower  margin  of 
the  left  lung  and  pleura.  Its  position  corresponds  to  the  ninth,  tenth,  and  eleventh  ribs.  It  is 
placed  very  obliquely.  "  It  is  oblique  in  two  directions — viz.,  from  above  downward  and  outward, 
and  also  from  above  downward  and  forward"  (Cunningham).  "Its  highest  and  lowest  points 
are  on  a  level  respectively  with  the  ninth  thoracic  and  first  lumbar  spines;  its  inner  end  is  dis- 


'F.  P.  Mall,  Amer.  .Jour,  of  .\nat.,  1903,  vol.  ii.  No.  3. 


THE  SUPRARENAL   GLANDS,   OR  ADRENAL  CAPSULES    1447 

tant  about  an  inch  and  a  half  from  the  median  plane  of  the  body,  and  its  outer  end  about  reaches 
the  niidaxillary  line"  (Quain). 

Applied  Anatomy. — Injury  of  the  spleen  is  less  common  than  that  of  the  liver,  on  account 
of  its  protected  situation  and  connections.  It  may  be  ruptured  by  direct  or  indirect  violence, 
torn  by  a  broken  rib,  or  injured  by  a  punctured  or  gunshot  wound.  When  the  organ  is  enlai'ged 
the  chance  of  rupture  is  increased.  The  great  risk  is  hemorrhage,  owing  to  the  extreme  vascu- 
larity of  the  organ,  and  the  absence  of  a  proper  system  of  capillaries.  The  injurv  is  not,  how- 
ever, necessarily  fatal,  and  this  would  appear  to  be  due  in  a  great  measure  to  the  contractile 
power  of  its  capsule,  which  narrows  the  wound  and  thus  antagonizes  the  escape  of  blood.  In 
cases  in  which  the  symptoms  suggest  such  an  injury  and  indicate  danger  to  life,  laparatomy  must 
be  performed;  and  if  the  hemorrhage  cannot  be  arrested  by  ordinary  surgical  methods  the 
spleen  must  be  removed.  The  spleen  may  become  displaced,  producing  great  pain  from  stretch- 
ing of  the  vessels  and  nerves,  and  this  dislocation  may  render  necessary  removal  of  the  organ. 
The  spleen  may  become  enormously  enlarged  in  certain  diseased  conditions,  such  as  ague,  leu- 
kemia, syphilis,  valvular  disease  of  the  heart,  or  without  any  obtainable  history  of  previous 
disease.  It  may  also  become  enlarged  in  lymphadenoma  as  a  part  of  a  general  blood  disease. 
In  these  cases  the  mass  may  fill  the  abdomen  and  extend  into  the  pelvis,  and  may  be  mistaken 
for  ovarian  or  uterine  disease. 

The  spleen  is  sometimes  the  seat  of  cystic  tumors,  especially  hydatids,  and  of  abscess.  These 
cases  require  treatment  by  incision  and  drainage;  and  in  abscess  great  care  must  be  taken 
if  there  are  no  adhesions  between  the  spleen  and  abdominal  cavity,  to  prevent  the  escape  of 
any  of  the  pus  into  the  peritoneal  cavity.  If  possible,  the  operation  should  be  performed  in 
two  stages.  Sarcoma  and  carcinoma  are  occasionally  found  in  the  spleen,  but  very  rarely  as 
a  primary  disease.  In  movable  spleen,  if  the  organ  is  normal,  follow  the  advice  of  Rvdvgier 
and  loosen  the  parietal  peritoneum  to  make  a  pocket,  place  the  spleen  in  the  pocket,  and  pass 
sutures  through  the  parietal  peritoneum  and  splenic  ligaments.  A  movable  diseased  spleen 
should  be  removed. 

Extirpation  of  the  spleen  has  been  performed  for  wounds  or  injuries,  floating  spleen,  simjjle 
hypertrophy,  and  leukemic  enlargement;  but  in  the  latter  case  the  operation  is  now  regarded 
as  unjustifiable,  as  it  is  practically  certain  to  terminate  fatally.  The  incision  is  best  made  in 
the  left  semilunar  line:  the  spleen  is  isolated  from  its  surroundings,  and  the  pedicle  transfixed 
and  ligated  in  two  portions,  before  the  tumor  is  turned  out  of  the  abdominal  cavity,  if  this  is 
possible,  so  as  to  avoid  any  traction  on  the  pedicle,  which  may  cause  tearing  of  the  splenic  vein 
and  which  inevitably  induces  grave  shock.  In  applying  the  ligatures  the  surgeon  must  not 
include  the  tail  of  the  pancreas,  and  in  lifting  out  the  organ  care  must  be  taken  to  avoid 
rupturing  the  capsule. 


THE   SUPRARENAL  GLANDS,  OR  ADRENAL  CAPSULES  (GLANDULAE 
SUPRARENALIS)    (Figs.  122.3,  1224). 

The  suprarenal  glands  are  two  small  flattened  bodies,  of  a  yellowish  color, 
situated  at  the  back  part  of  the  abdomen,  behind  the  peritoneum,  and  immedi- 
ately above  and  in  front  of  the  upper  extremity  of  each  kidney ;  hence  their  name. 
The  right  one  (Fig.  122.3)  is  somewhat  triangular  in  shape,  bearing  a  resemblance 
to  a  cocked  hat;  the  left  (Fig.  1224)  is  more  semilunar,  usually  larger  and  placed 
at  a  higher  level  than  the  right.  They  vary  in  size  in  different  indi\iduals, 
being  sometimes  so  small  as  to  be  scarcely  detected;  their  usual  size  is  from 
an  inch  and  a  quarter  to  nearly  two  inches  (3  to  5  cm.)  in  length,  rather  less  in 
width,  and  one-quarter  of  an  inch  (6  mm.)  in  thickness.  Their  average  weight 
is  from  one  to  one  and  one-half  drams  (6  grams)  each. 

Relations. — The  relations  of  the  suprarenal  glands  differ  on  the  two  sides  of 
the  body. 

The  right  suprarenal  (Fig.  1223)  is  situated  behind  the  inferior  vena  cava  and  the 
right  lobe  of  the  liver,  and  in  front  of  the  Diaphragm  and  the  upper  end  of  the 
right  kidney.  It  is  roughly  triangular  in  shape,  and  its  base,  directed  downward,  is 
in  contact  with  the  inner  and  anterior  aspects  of  the  upper  end  of  the  right  kidney. 
It  presents  two  surfaces  for  examination,  an  anterior  and  a  posterior.  The 
anterior  surface  (fades  anterior)  presents  two  areas,  separated  by  a  furrow,  the 
hilum  (hilus  gla7idulae  suprarenalis) ;  one  area,  occupying  about  one-third  of  the 


1448 


THE  DUCTLESS  GLANDS 


whole  surface,  is  situated  above  and  internally;  it  is  depressed,  uncovered  by 
peritoneum,  and  is  in  contact  in  front  with  the  posterior  surface  of  the  right  lobe 
of  the  liver,  and  along  its  inner  border  with  the  inferior  vena  cava;  the  remain- 
ing area  is  elevated,  and  is  divided  into  a  nonperitoneal  portion,  in  contact  with 
the  hepatic  flexure  of  the  duodenum,  and  a  portion  covered  by  peritoneum  forming 
the  hepatorenal  fold.  The  posterior  surface  [fades  'posterior)  is  divided  into  an 
upper  and  a  lower  part  by  a  curved  ridge;  the  upper,  slighdy  concave,  rests  upon 
the  Diaphragm;  the  lower,  or  base  (basis  glandulae  suprarenalis)  is  concave, 
and  is  in  contact  with  the  upper  end  and  the  adjacent  part  of  the  anterior  surface 
of  the  kidney. 

The  left  suprarenal  (Fig.  1224),  slighdy  larger  than  the  right,  is  crescentic  in 
shape,  its  concavity  being  adapted  to  the  inner  border  of  the  upper  extremity 
of  the  left  kidney.  It  presents  an  inner  border  which  is  convex,  and  an  outer 
which  is  concave;  its  upper  border  is  narrow;  and  its  lower  rounded.     Its  anterior 


•^* 


HILUM-^Srf*'  SB 

^r  li»     SUPRARENftl 
r        V        ARTERY 

1                    SUPRARENAl- 

PRARENAL     (IBFTJI 

«■                   ARTERY 

VEIN                   HI 

G.  1223.— The  right  s 
(Spaltehol 

luprarenal  gland. 

z.) 

Fig.  1224. — The  left  suprarenal  gland. 
(Spalteholz.) 


surface  presents  two  areas — an  upper  one,  covered  by  the  peritoneum  forming 
the  lesser  sac,  which  separates  it  from  the  cardiac  end  of  the  stomach  and  to  a 
small  extent  from  the  superior  extremity  of  the  spleen;  and  a  lower  one,  which 
is  in  contact  with  the  pancreas  and  splenic  artery,  and  is,  therefore,  not  covered 
by  the  peritoneum.  A  hilum  is  present,  as  in  the  right  suprarenal.  Its  posterior 
surface  presents  a  vertical  ridge,  which  divides  it  into  two  areas.  The  ridge  lies 
in  the  sulcus  between  the  kidney  and  crus  of  the  Diaphragm,  while  the  area  on 
either  side  of  it  lies  on  these  parts  respectively;  the  outer  area,  which  is  thin,  rest- 
ing on  the  kidney,  and  the  inner  and  smaller  area  resting  on  the  left  crus  of  the 
Diaphragm. 

The  surface  of  the  suprarenal  gland  is  surrounded  by  areolar  tissue  containing 
much  fat,  and  closely  invested  by  a  thin  fibrous  coat,  which  is  difficult  to  remove, 
on  account  of  numerous  fibrous  processes  and  vessels  which  enter  the  organ 
through  the  furrows  on  its  anterior  surface  and  base. 

Accessory  suprarenal  glands  (glandulae  suprarenales  accessoriae)  are  often 
to  be  found  in  the  connective  tissue  around  the  suprarenals.  The  smaller  of 
these,  on  section,  show  a  uniform  surface,  but  in  some  of  the  larger  a  distinct 
medulla  can  be  made  out. 


Structure  (Fig.  1225). — On  making  a  perpendicular  section,  the  suprarenal  gland  is  seen 
to  consist  of  two  substances — surrounded  by  a  capsule — the  external  or  cortical  and  the 
internal  or  medullary.     The  former,  which  constitutes  the  chief  part  of  the  organ,  is  of  a  deep- 


THE  SUPRARENAL  GLANDS,   OR  ADRENAL  CAPSULES     1449 

yellow  color.  The  medullary  substance  is  soft,  pulpy,  and  of  a  dark-brown  color.  In  the 
centre  is  often  seen  a  space,  not  natural,  but  formed  after  death  by  the  disintegration  of  the 
medullary  substance. 

The  capsule  consists  of  white  fibrous  connective  tissue  in  which  some  smooth  muscle  tissue 
is  seen.     From  the  capsule  and  vessel  sheaths  the  framework  of  the  organ  is  derived. 

The  cortical  portion  consists  of  epithelial  cells  arranged  in  three  zones.  The  zona  glomer- 
ulosa — the  outermost — consists  of  oval  or  round  cell  groups  surrounded  by  capillary  plexuses  and 
reticulum.  The  cells  are  polyhedral  in  .sluipc  \\iili  clear  nuclei;  the  protoplasm  is  granular  and 
contains  many  fat  globules.  The  zona  fasciculata — or  middle  zone — consists  of  columns  of 
ejiithelial  cells  (usually  two  cells  wide)  supported  by  reticulum  containing  bloodvessels  and  lym- 
phatics. These  cells  resemble  the  above,  but  the  nuclei  are  in  the  peripheral  portion  of  the  cells. 
The  zona  reticularis,  the  innermost  of  the  three,  consists  of  anastomosing  columns  or  chains 
of  cells.  Tliese  cells  are  smaller  than  the  preceding,  are  distinct  in  outline,  and  possess  a 
granular  and  pigmented  protoplasm. 


'MeduUary  vein. 


3  i.  CJ:-<^ 


F  G    1'25  — Sect  on  of  human    up  a  enal  gl  nd        Rada    h  ) 


The  medullary  portion  {substantia  medullaris)  (Fig.  1225).  is  usually  separated  from  the 
cortex  by  a  layer  of  large  smooth  cells.  Beneath  this  layer  the  epithelial  cells  are  arranged 
in  irregular  groups  and  chains,  surrounded  by  reticulum  and  capillaries.  The  cells  are  small 
and  their  outlines  are  indistinct.  They  color  deeply  with  chromium  salts,  and  are  called 
chromaffin  ciUn.     Many  sympathetic  nerve  cells  are  present. 

Vessels  and  Nerves. — The  numerous  arteries  which  enter  the  suprarenal  bodies  from  the 
sources  mentioned  below  form  plexuses  in  the  capsule  and  penetrate  the  cortical  part  of  the 
gland,  where  they  break  up  into  capillaries  in  the  fibrous  septa,  and  these  converge  to  the  very 
numerous  thin-walled  veins  of  the  medullary  portion.  These  veins  usually  empty  directly 
into  the  large  central  veins.  The  medullary  vessels  are  derived  from  the  cortical  vessels,  and 
pass  to  the  medulla  without  branching  to  form  plexuses  of  capillaries  around  the  cells.  The 
veins  in  this  region  converge  to  form  from  two  to  four  central  veins,  which  unite  to  become 
the  suprarenal  vein,  which  in  tm-n  emerges  as  a  single  vessel  from  the  centre  of  the  gland. 

The  arteries  supplying  the  suprarenal  glands  are  three  in  number  and  of  large  size;  they 
are  derived  from  the  aorta,  the  phrenic,  and  the  renal;  they  subdivide  into  numerous  minute 
branches  previous  to  entering  the  substance  of  the  gland. 

The  suprarenal  vein  returns  the  blood  from  the  medullary  venous  plexus,  and  receives  several 
branches  from  the  cortical  substance;  it  emerges  from  the  hilum  and  opens  on  the  right  side 
into  the  inferior  vena  cava,  on  the  left  side  into  the  renal  vein. 

The  lymphatics  form  several  collections  which  are  about  the  beginning  of  the  suprarenal 
vein.     They  terminate  in  the  noiles  at  the  corresponding  sid'e  of  the  aorta. 

The  nerves  arc  myelinated  and  amyelinated,  are  exceedingly  numerous,  and  are  derived 
from  the  solar  and  renal  plexuses,  and,  according  to  Bergmann,  from  the  phrenic  and  vsigus 
nerves.  They  enter  the  lower  and  inner  part  of  the  gland.  A  plexus  in  the  gland  sends 
branches  into  the  cortex,  where  plexuses  are  formed  around  the  vessels.  Branches  are  also 
sent  to  the  medulla,  where  rich  plexuses  are  formed  around  the  cells  and  vessels.  Many  sym- 
pathetic ganglia  are  seen  there. 


1450  THE  DUCTLESS  GLANDS 

THE   CAROTID   GLANDS,   OR  CAROTID  BODIES    (GLOMUS 
CAROTICUM). 

The  carotid  bodies,  two  in  number,  are  situated  one  on  either  side  of  the  neck, 
behind  the  common  carotid  artery  at  its  point  of  bifurcation  into  the  internal  and 
external  carotid  trunks.  They  are  reddish  brown  in  color  and  oval  in  shape, 
the  long  diameter  measuring  about  one-fifth  of  an  inch  (5  mm.)  Each  is  invested 
by  a  fibrous  capsule  and  consists  of  spherical  or  irregular  masses  of  cells — the 
masses  being  more  or  less  isolated  from  each  other  by  septa  which  extend  inward 
from  the  capsule.  A  network  of  large  capillaries  from  tlie  carotid  artery  ramifies 
among  the  cell  masses,  together  with  numerous  sympathetic  nerve  fibres.  The 
cells  are  polyhedral  in  shape,  and  each  contains  a  large  nucleus  embedded  in 
finely  granular  protoplasm  which  is  stained  yellow  by  chromic  salts. 

Applied  Anatomy. —  Tumors  may  arise  in  this  structure.  Such  a  tumor  is  apt  to  be  above 
the  level  of  the  upper  margin  of  the  thyroid  cartilage,  and  in  most  cases  it  moves  with  each 
arterial  beat. 


THE   COCCYGEAL   GLAND   OR  BODY,  OR  LUSOHKA'S   GLAND 
(GLOMUS   COCCYGEUM). 

Lying  near  the  tip  of  the  coccyx  in  a  small  tendinous  interval  formed  by  the 
union  of  the  Levator  ani  muscles  and  just  above  the  coccygeal  attachment  of  the 
Sphincter  ani  is  a  small  conglobate  body  about  as  large  as  a  millet  seed,  first 
described  by  Luschka,  and  named  by  him  the  coccygeal  gland.  Its  most  obvious 
connections  are  with  the  middle  sacral  artery. 

Structure. — It  consists  of  a  congeries  of  small  arteries  with  little  aneurismal  dilatations 
derived  from  the  middle  sacral  and  freely  communicating  with  each  other.  The  gland  is  sur- 
rounded by  a  capsule  of  white  fibrous  connective  tissue  which  sends  in  septa  to  form  the  frame- 
work of  the  organ  and  to  divide  it  into  spaces  which  contain  groups  of  polyhedral  cells.  Each 
cell  contains  a  large  round  or  oval  nucleus,  the  protoplasm  surrounding  which  is  clear  and  is 
not  stained  by  chromic  salts.'  Nerves  pass  into  this  little  body  from  the  sympathetic,  but 
their  mode  of  termination  is  unknown.  Macalister  believes  the  glomerulus  of  the  vessels  "con- 
sists of  the  condensed  and  convoluted  metameric  dorsal  arteries  of  the  caudal  segments  em- 
bedded in  tissue  which  is  possibly  a  small  persisting  fragment  of  the  neurenteric  canal." 


THE  PARASYMPATHETIC  BODIES  (ORGANA  PARASYMPATHETICA ; 
PARAGANGLIA  LUMBALE). 

The  parasympathetic  bodies  were  discovered  in  1901  by  Zuckerkandl.  They  are 
from  one  to  four  in  number,  situated  retroperitoneally,  ventrad  of  the  abdominal 
aorta  at  the  level  of  the  third  and  fourth  lumbar  vertebrae.  Each  parasympathetic 
body  is  from  6  to  10  mm.  in  length  and  from  2  to  4  mm.  in  width,  and  is  surrounded 
by  a  capsule  of  fibrous  tissue.  In  the  meshes  of  the  reticulum  are  found  groups 
of  polyhedral  or  cuboidal  epithelial  cells,  closely  packed  and  of  the  chromaiEn 
type.  These  bodies  are  usually  supplied  by  fine  arterial  twigs  from  the  aorta. 
They  are  best  developed  in  the  fetus  and  in  infancy,  apparently  being  absent  in 
the  adult. 

1  Consult  J.  W.  T.  Walker,  "Ueber  die  menschliche  Steissdriise,"  Arck.  f .  mikr.  Anat.  u.  Entwickgesch.,  1904- 


INDEX 


Abdomen,  1240 

boundaries  of,  1241 
•  fascite  of,  424 

triangular,  425,  428 
lymphatic  vessels  of,  789,  790 
lymphatics  of,  787 
muscles  of,  423 
regions  of,  1242 
veins  of,  739 

walls  of,  apertures  in,  1242 
Abdominal  aorta,  657 

applied  anatomy  of,  658 
surface  marking  of,  657 
aortic  plexus  of  nerves,  1076 
furrow,  439 
ring,  426,  436,  437 
xascera,  lymphatic  vessels  of, 
792 
Abdominothoracic  arch,  166 
Abducent  nerve,  993 

applied  anatomy  of,  994 
nucleus,  883 
Abduction,  267 
Abductor  hallucis  muscle,  538 
indicis  muscle,  494 
minimi  digiti  muscle,  foot,  539 
surface  form  of,  544 
hand,  493 
pollicis  longus  muscle,  485 
muscle,  489 
Aberrant  ganglion,  1014 
Accelerator  urinae  muscle,  443 
Accessory  cephalic  vein,  731 
ganglion,  1014 
ligament.  275 
liver,  1326 

obturator  nerve,  1049 
olivary  nuclei,  873 
posterior  palatine  canals,  110, 

128 
pudic  artery,  675 
suprarenal  glands,  1448 
thyroid  gland,  1436 
veins,  717 
Acervus  cerebri,  906 
Acetabulum,  213 
fossa,  of,  213 

transverse  ligament  of,  325 
Acid  cells,  1276 
Acoustic  nerve,  1000 

applied  anatomy  of,  1001 
nuclei,  881 
Acromial  angle,  177 
artery,  638 
bursa,  303 
nerve,  1022 
region,  muscles  of,  462 
Acromioclavicular     articulation, 
297 
applied  anatomy  of,  299 
surface  form  of,  299 
ligaments,  297 
Acromion,  175 
angle,  177 
process,  175 
Acromiothoracic  artery,  638 
Adduction,  267 
Adductor  brevis  muscle,  514 
canal,  685 
longus  muscle,  513 


Adductor  longus  muscle,  applied 

anatomy  of,  515 

surface  form  of,  543 

magnus  muscle,  514 

applied  anatomy  of,  515 
surface  form  of,  543 

minimus  muscle,  514 

obliquus  hallucis  muscle,  541 
pollicis  muscle,  492 

transversus    hallucis    muscle, 
541 
polHcis  muscle,  492 

surface  form  of,  497 

tubercle,  225 
Aditus  laryngis,  1169 
Adminiculum  linae  albae,  428 
Adrenal  capsule,  1447 
Aequator  leniis,  1107 
Afferent  lymphatic  vessels,  768 

root  of  spinal  cord,  823 
Agger  nasi,  1082 
Agminated  follicles,  1292 
Air  sacs,  1195 

sinus,  frontal,  79 
Ala  cinerea,  866 

lobuli  centralis  cerebelli,  886 

nasi,  1079 

sacralis,  61 
Alae  of  ethmoid,  96 

magna,  92 

parvae,  93 

of  sphenoid,  92 

of  vomer,  114,  138 
Alar  cartilage.  1080 

thoracic  artery,  639 
Alcock's  canal,  450,  675 
Alimentary  canal,  1199 

tract,  development  of,  1245 
Alisphenoids,  95 
Alveolar  artery,  601 

index  of  skull,   147 

point  of  skull,  146 

process  of  maxilla;,  104 
Alveoli  dentales,   104,  117,  1204 

of  lungs,  1195 
Alveus,  929,  942 
Ameloblasts,  1214 
Amphiarthrosis,  264,  266 
Ampulla  ductus  deferentis,  1383 
lacrimalis,  1116 

of  Fallopian  tube,  1401 

of  lacrimal  canal,  1116 

of  rectum,  1308 

tubae  uierinae,  1401 

of  vas  deferens,  1383 

of  Vater,  1334 
Ampullae  Tuembranaceae,  1142 

ossea,  1137 
Ampullar  nerve,  1001 
Amygdala,  887,  948 
Amygdaline  fissure,  924 

nucleus,  948 
Amygdaloid  tubercle,  939,  948 
Anal  canal,  1309 

fascia,  446,  454 

oriBce,  1309 

pockets,  1310 

valves,  1310 
Anastomosis  of  arteries,  572 
circumpatellar,  696 

between   portal  and   systemic 
veins,  754 


Anastomosis,  crucial,  678,  690 

of  veins,  706 
Anastomotic  vein  of  Trolard,  720 
Anastomotica  magna  of  brachial, 
643 
of  femoral,  691 
Anatomical    neck    of    humerus, 

178 
Anconeus  muscle,  482 

surface  form  of,  496 
Andersch,  ganglion  of,  1002 
Angiology,  definition  of,  34 
Angle,  acromial,   177 

filtration,  1105 

of  jaw,  lis 

lateral,  inferior,  60 

of  Ludwig,  157,  166 

nasal,  100 

of  pubis,  212 

of  ribs,   163 

Rolandic,  918 

sacrovertebral,  58 

subcostal,  156 

subscapular,  172 
Angular  gyre,  923 

processes,  77,  135 

vein,  710 
Angulu^  costae,  163 

frontalis,  76 

inferior,  176 

infra^ternalis,  156 

iridis,  1105 

lateralis,  176 

Ludovici,  157,  166 

mandibulae,  118 

mastoideus,  76 

medialis,  176 

occipitalis,  76 

oris,  1199 

sphenoidalis,  76 
Anfde  bone,  244 
Ankle-joint,  342 

applied  anatomy  of,  346 

surface  form  of,  346 
Anlage  of  cerebellum,  855 
Annuli  fibrosi,  562 
Annulus  femoralis,  428,  503,  685 

fibrosus,  270,  558 
dexter,  558 
sinister,  560 

inguinalis  abdominis,  437 
subcutaneous,  426 
cru^  inferius,  427 
superius,  427 

ovalis,  557 

tendineus  communis,  370 

tympanicus,  1123 

urethralis,  1365 
Anococcygeal  body,  1309 

nerves,  1062 

raph6,  451,  453 
Ansa  ceniicalis,  1024 

hypoglossi,  1024 

lenticularis,  905,  9.51 

peduncularis,  905,  951 

subclavii  [Vieussenii],  1069 
Antecubital  fossa,  641 

lymph  nodes,  781 
Antihelix  of  ear,  1120 
Antitragicus  muscles,  1121 
Antitragus  of  ear,  1120 
Antrum  cardiacum,  1237,  1271 

( 14.-,!  ! 


1452 

Antrum  of  Highmore,  101,  103 
mastoid,  83 
opening  of,  1126 
iy?npanicum,  1126 
Anus,  1309 

lymphatic  vessels  of,  794 
Aorta,  57.5 

abdominal,  657 
abdominalis,  657 
arch  of,  579 

applied  anatomy  of,  580 
development  of,  761 
ascendens,  576 
ascending,  576 
descending,  653 
dorsal,  762 
primitive,  755 
surf-line  of,  580 
thoracalis,  653 

rami  mediastinales,  654 
pericardiaci,  654 
thoracic,  653 
transverse,  579 
ventral,  761 
Aortenspindel,  580 
Aortic  arches,  761 
bulb,  757,  759 
isthinus,  762 
lymph  nodes,  788 
opening  of  diaphragm,  419 
septum,  759,  760 
spindle,  762 

stem,  primitive,  757,  759 
valve,  560 
Aorticorenal  ganglion,  1073 
Apertura     externa      aquaeducti 


canaliculi  cochleae,  86 
lateralis  [ventriculi  quarii\,  867, 
969 
■    medialis  [ventriculi  quarti],  867, 
969 
pelvis  [minoris]  inferior,  217 

superior,  215 
pyriformis,  135,  138,  1081 
scalae  vestibuli  cochlece,  1137 
sinus  sphenoidalis,  91,  95 
superior  canaliculi  tympanici. 

84 
thoracis  inferior,  156 
superior,  155 
Apex  capituli  fibulae,  236 
linguae,  1217 
nasi,  1079 
OSS.  sacri,  61 
patellae,  231 
prostatae,  1391 
pulmonis,  1188 


Apical  foramen,  1212 

glands,  1219 
Aponeuroses,  360 

epicranial,  363 

of  external  obUque,  425 

gluteal,  516 

of  internal  oblique,  428 

lumbar,  409 

palatal,  397 

pharyngeal,  395 

of  soft  palate,  1203 

suprahyoid,  389 

vertebral,  404,  408 
Aponeurosis  palmaris,  488 

plantaris,  537 
Aponeurotic  fascia,  361 
Apophysis  of  bone,  37 
Apparatus  digestorius,  1199 

lacrimalis,^  1115 

respiratorius,  1163 
Appendices   epiploicae,    1265, 
1296,  1309 

vesiculosi,  1402 
Appendicular  artery,  664 

lymph  nodes,  791 

planes  of  body,  34 


INDKX 

Appendix,  ensiform,  159 
epididymidis,  1379 
testis  [Morgagni],  1378 
ventriculi,  1171 
vermiform,  1298 
xiphoid,  159  ,       .     , 

Applied  anatomy  of  abdommal 
aorta,  658 
of  abducent  nerve,  994 
of  acoustic  nerve,  1001 
of  acromiocla^acular  articu- 
lation, 299 
of  adductor  longus  muscle, 
515 
magnus  muscle,  515 
of  ankle-joint,  346 
of  anterior  tibial  artery,  697 
of  arch  of  aorta,  580 
of    articulations    of    elbow- 
joint,  309 
of  hip-joint,  329 
of  phalanges  of  foot,  256 
of  shoulder-joint,  304 
of  tarsus,  351 
of  vertebral  column,  278 
of  wrist-joint,  315 
of      ascending      pharyngeal 

artery,  597 
of  auditory  canal,  1124 
of  axilla,  634 
of  axillary  artery,  637 

veins,  732 
of  azygos  veins,  737 
of  bladder,  1366 
of  bone,  46 
of  bones  of  foot,  256 
of  brachial  artery,  641 

plexus  of  nerves,  1039 
of  carotid  glands,  14.50 
of  carpal  bones,  205 
of  cavernous  sinuses,  724 
of  cervical  fascia,  384 
ganglion,  1069 
lymph  nodes,  780 
of  choroid,  1110 
of  clavicle,  172 
of  colon,  1306 
of  common   carotid   artery, 
586 
iliac  arteries,  669 
of  conjunctiva,  1118 
of  cornea,  1109 
of  coronary  artery,  578 
of  costal  cartilages,  167 
of  crystalUne  lens,  1111 
of    deep    epigastric    artery, 

681 
definition  of,  33 
of  deltoid  muscle,  463 
of   descending   palatine    ar- 
tery, 602 
of  dorsalis  pedis  artery,  699 
of  duodenum,  1287 
of  emissary  veins,  727 
of  external  abdominal  ring, 
427 
carotid  artery,  588 
iliac  artery,  680 
of  eyelids,  1118 
of  facial  artery,  595 

nerve,  999 
,     veins,  711 
of  femoral  artery,  687 
of  femur,  229 
of  fibula,  239 
of    glossopharyngeal    nerve, 

1003 
of  hamstring  muscles,  525 
of  heart,  568 
of    hemorrhoidal    plexus    of 

veins,  745 
of  humerus,  184 
of  hyoid  bone,  154 
of  hypoglossal  nerve,  1012 
of  ilio  tibial  band,  508 


Applied      anatomy     of     inferior 
ealcaneoscaphoid     liga- 
ment, 349 
vena  cava,  748 
of  innominate  artery,  582 
of  intercostal  arteries,  657 
of  internal  ealcaneoscaphoid 
ligament,  349 
carotid  artery,  608_ 
iliac  artery,  671,  679 
jugular  vein,  717 
of  intestines,  1295,  1314 
of  iris,  1110 
of  kidneys,  1355 
of  knee-joint,  338 
of  lacrimal  gland,  1118 

sac,  1119 
of  lateral  sinus,  724 
of  hver,  1335 
of  lumbar  plexus  of  nerves, 

1062 
of   lymph    nodes    of    lower 
extremity,  786 
of  upper  extremity,_7S4 
of  lymphatic  vessels,  770 
of  diaphragm,  799 
of  stomach,  793 
of  male  breast,  1433 

urethra,  1369 
of  mammary  gland,^  1432 
of  mediastinum,  1188 
of  middle  meningeal  artery, 

600 
of  mouth,  1204 
of  muscles,  359 
of  back,  416 
of  cranial  region,  365 
of  femoral  region,  512,  515 
of  leg.  535 

of  lower  extremity,  544 
of  orbital  region,  371 
of  palatal  region,  399 
of  radioulnar  region,  478, 

485 
of  tongue,  394 
of  upper  extremity,  497 
of  nasal  duct,  1119 
of  nose,  1084 
of  oculomotor  nerve,  977 
of  oesophagus,  1239 
of  olfactory  nerve,  974 
of  optic  nerve,  975 
of  ovaries,  1401 
of  palmar  fascia,  489 
of  pancreas,  1341 
of  parathyroid  glands,  1440 
of  patella,  231 
of  pelvis,  220 
of  penis,  1390 
of  pericardium,  550 
of  peritoneum,  1268 
of  pharynx,  1235 
of  phrenic  nerve,  1025 
of  plantar  arch,  704 
of  pleurae,  1185 
of  pophteal  artery,  693 
of  portal  veins,  754 
of  posterior  tibial  artery,  701 
of    pronator    teres    muscle, 

473 
of  prostate  gland,  1395 
of  psoas  magnus  musclej__505 
of  pulmonary  artery,  575 

veins,  708 
of  pyloric  artery,  662 
of       quadriceps       extensor 

muscle,  512 
of  radial  artery,  646 
of  radius,  192 
of  rectus  femoris  muscle,  512 
of  retina,  1111 
of  ribs,  167 

of  salivary  glands,  1229  • 
of  saphenous  veins,  741 
of  scapula,  178 


INDEX 


1453 


Applied  anatomy  of  sclera,  1110 
of  scrotum,  1382 
of  seminal  vesicles,  1385 
of  serratus  magnus  muscle, 

461 
of  skull,   149 
of  spermatic  veins,  750 
of    spinal    accessory    nerve, 
1009 
arteries,  621 
cord,  842 
pia,  846 
of  spleen,  1447 
of  sternoclavicular  articula- 
tion, 297 
of  sternomastoid  muscle,  386 
of  sternum,  167 
of  stomach,  1280 
of  subclavian  artery,  627 
of   superficial   palmar   arch, 

652 
of        superior        mesenteric 
lymph  nodes,  791 
radioulnar       articulation, 

311 
thyroid  artery,  590 
of   synovial   membranes   of 

wrist,  487 
of  temporal  artery,  598 
of    temporomandibular    ar- 
ticulation, 281 
of  testes,  1383 
of  thoracic  aorta,  654 

duct,  774 
of  thorax,  167 
of  thymus  gland,  1442 
of  thyroid  gland,  1438 
of  tibia,  239 
of  tongue,  1222 
of  tonsil,  1233 
of  trachea,  1180 
of    tracheobronchial    lymph 

nodes,  802 
of  triceps  muscles,  471 
of  trigeminal  nerve,  991 
of  trochlear  nerve,  978 
of  tympanum,  1135 
of  ulna,  192 
of  ulnar  artery,  649 
of  ureters,  1358 
of  uterus,  1411 
of  vaginal  artery,  673 
of  vagus  nerve,  1008 
of  vermiform  appendix,  1302 
of  vertebral  artery,  620 
column,  68 
Aquaeductus    cochleae,    86,    131, 
1140 
Fallopii,  85 
vestibuli,  86,  128,  1137 
Aqueduct  of  midbrain,  896 
Aqueous  chamber,  1105 

humor,  1105 
Arachnoid  of  brain,  968 
■villi  of,  970 
spinal,  844 
Arachnoidea  encephali,  968 

spinalis,  844 
Arbor  vitae  cerebelli,  886 
Arboriform  nerve  cells,  808 
Arch,  abdominothoracic,  166 
of  aorta,  579 
of  atlas,  50,  51 
axillary,  407 
crural,  684 
femoral,  436 
nasal,  of  veins,  710 
palmar,  645,  652 
plantar,  704 
pubic,  217 
supraorbital,  77 
tarsal,  612 
Arches,  aortic,  761 
Arcuate  fibres,  873 

of  medulla  oblongata,  863 


Arcuate  ligaments,  419 
Arcus  aortae,  579 

cartilaoinis  cricoideae,  1165 
dentalis  inferior,  1207 

superior,  1207 
glossopalatiniis,  1203 
lumbocostalis  lateralis,  419 

medialis,  419 
palatini,   1203 
pharyng'opalalinus,  1203 
planiaris,  704 

rami  perforantes   anteriores, 
704 
posteriores,  704 
pubis,  217 
superciliares,  77,  79 
tarseus  inferior,  612 

superior,  612 
iendineus,  449,  450 
venosi  digitales,  728,  729 
venosus  dorsalis  pedis,  739 

plantaris,  741 
vertebrae,  48 
volaris  profundus,  645 
superficialis,  652 
Area  acustica,  866 
cribrosa,  85 
media,  85 
superior,  85 
plumiformis,  873 
■vestibularis  inferior,  1147 
posterior,   1147 
Areola  mammae,   1429 

of  mammary  gland,   1429 
Areolar     tissue,      subcutaneous, 

1154 
Arm,  bones  of,  178 
fascia  of,  461,  467 
muscles  of,  461,  467 
Arnold,  bundle  of,  957 
nerve  of,   1005 
ponticulus  of,  863 
Arrectores  pilorum,  1161 
Arteria  aheolaris  inferior,  601 
rainus  ^nylohyoideus,  601 
superior  posterior,  601 
angularis,  594 
anonyma,  582 
appendicularis,  664 
arcuata,  699 
auditiva  interna,  622 
auricularis  posterior,  596 
ramus  auricularis,  596 
mastoideus,  596 
profunda,  600 
axillaris,  635 

rami  pectorales,  638 
ramus  acromialis,  638 
clavicularis,  638 
deltoideus,  638 
basilaris,  622 

rami  ad  pontem,  622 
brachialis,  640 
buccinatoria,  601 
bulbi  urethrae,  675 

vestibuli,  1420 
canalis  pterygoidei,  602 
carQ^is  communis,  583 
dextra,  583 
sinistra,  583 
externa,  588 
interna,  606 

ramus  caroticotympanicus, 
609 
centralis     retinae,     613,     1090, 

1105 
cerebelli  inferior  anterior,  622 
posterior,  621 
superior,  622 
cerebri  anterior,  614 
media,  616 
posterior,  622 
cenicalis  ascendens,  629 

profunda,  633 
chorioidea,  617 


Arteria  ciliares,  613 

circumflexa    femoris    lateralis, 
690 
medialis,  690 

ramus  acetabuli,  690 

profundus,  690 
superficialis,  690 
humeri  anterior,  639 

posterior,  639 
ilium  profunda,  682 

superficialis,  689 
scapulae,  639 
coeliaca,  659 
colica  dextra,  664 
media,  664 
sinistra,  666 
coUateralis  ulnaris  inferior,  643 

superior,  643 
comes  nervi  phrenici,  1024 
comitans  nervi  ischiadici,  677 
communicans  anterior,  615 

posterior,  617 
coronoria  [cordis]  dextra,  578 

sinistra,  578 
cystica,  661 
deferentalis,  1376 
dorsalis  clitoridis,  676,  1420 
hallucis,  700 
nasi,  612 
pedis,  698 
penis,  676 
epigastrica  inferior,  680 
ramus  pubicus,  681 
superficialis,  689 
superior,  633 
ethmoidalis  anterior,  611 

posterior,  611 
femoralis,  683 
frontalis,  612 
gastrica  dextra,  661 
sinistra,  660 

roTni  oesophagei,  661 
gastroduodenalis,  661 
gastroepiploica  dextra,  661 
rami  epiploici,  661 
sinistra,  662 
{7e7iu  inferior  lateralis,  695 
medialis,  695 
media,  695 
superior  lateralis,  695 
.  medialis,  694 
suprema,  691 

ramus   musculoarticularis, 
691 
saphenus,  691 
glutaea  inferior,  677 
superior,  678 

ramus  inferior,  678 
superior,  678 
hemorrhoidalis  inferior,  675 
media,  672 
superior,  667 
hepatica,  661 
hypogastrica,  669 
ileocolica,  664 
iliaca  externa,  679 
iliolumbalis,  678 
ramus  iliacus,  678 
lumbalis,  678 
spinalis,  678 
infraorbitalis,  602 
interossea  communis,  650 
dorsales,  650 
recurrens,  651 
volaris,  650 
labialis  inferior,  593 

superior,  594 
lacrimalis,  610 
laryngea  superior,  590 
lienalis,  661 

rami  pancreatica,  662 
ligamenti  teretis  uteri,  680 
lingualis,  590 

ramus  hyoidews,  591 
dorsalis  linguae,  591 


1454 


INDEX 


Arteria  magna,  575 
hallucis,  700 
malleolaris    anterior 


posterior  medialis,  703 
■mammaria  interna,  631 
rami  intercostales,  632 
perforantes,  632 
stemales,  632 
masseterica,  601 
maxillaris  externa,  592 

rami  glandulares,  593 
ramus  tonsillaris,  593 
interna,  598 
mediana,  650 
Tneningea  anterior,  609 
media,  600 
posterior,  597 
mentalis,  601 
■mesenlerica  inferior,  666 

superior,  663 
musculophrenica,  632 
nutrida  fibulae,  702 
humeri,  643 
iifoiae,  702 

ramus  communicoTis,  703 
ohturatoria,  673 

ramus  anterior,  674 
iliacus,  673 
posterior,  674 
pvhieus,  673 
vesicalis,  673 
occipitalis,  595 

ramt  muscidares,  595 

occipitales,  596 
ramus  auricularis,  596 
descendens,  596 
meningeus,  596 
7nastoideu3,  596 
ophthalmica,  610 
ovaricae,  665 
palatina  ascendens,  593,  1204 

descendens,  602,  1204 
pancreaticoduodenalis   inferior, 
663 
superior,  661 
perforans  prima,  691 
secunda,  691 
tertia,  691 
pericardiacophrenica,  632 
perinei,  675 
peronaea,  701 

ramus  calcaneus  lateralis,  702 
comir.unicans,  702 
perforans,  702 
pharyngea  ascendens,  597 
rami  pharyngei,  597 
plantaris  lateralis,  703 
medialis,  703 

ramus  superficialis,  703 
poplitea,  691 
princeps  cervicis,  596 
hallucis,  700 
poinds,  647 
profunda  brachii,  641 

rami  musculares,  644 
clitoridis,  676,  1420 
femoris,  689 

ram/as  ascendens,  690 
descendens,  690 
linguae,  591 
penis,  676 
pudenda  externa  profunda,  689 
superficialis,  689 
interna,  674 
pulmonalis,  574 
ramus  dexter,  575 
sinister,  575 
radialis,  644 

rami  musculares,  646 

perforantes,  648 
ramus  carpeiis  dorsalis,  647 
volaris,  647 
volaris  superficialis,  647 


Arteria  recurrens  radialis,  646 
tibialis  anterior,  698 
posterior,  698 
recurrentes  ulnaris  anterior,  650 

posterior,  650 
sacralis  lateralis,  678 

rami  spinales,  678 
sigmoideae,  667 
spermatica  externa,  680,  1377 

interna,  665,  1376 
sphenopalatina,  602 
spinalis  anterior,  621 

posterior,  621 
sternocJeidomastoidea,  595 
siylomastoidea,  596 
subdavia,  623 
sublingualis,  591 
submentalis,  593 
subscapularis,  639 
supraorbitalis,  610 
suprarenalis  inferior,  665 

media,  662 
larsea  lateralis,  699 
temporalis  media,  598 
profunda  anterior,  601 

posterior,  601 
superficialis,  597 

rami    auriculares    anierio- 

res,  598 
ramus  frontalis,  598 
parietalis,  598 
thoracalis  lateralis,  638 

suprema,  638 
thyreoidea  ima,  582 
inferior,  629 

rami  oesophagi,  629 
tracheales,  629 
superior,  589 

rami  glandulares,  590 
ramus  anterior,  589 
cricnthyroideus,  590 
hyoideus,  590 
posterior,  589 
siernocleidonvistoideus, 
590 
tibialis  anterior,  696 

posterior,  700 
transversa  colli,  630 

ramus  ascendens,  630 
descendens,  630 
faciei,  598 
scapulae,  629 

ram.us  acromialis,  630 
tympanica  anterior,  600 
inferior,  597 
superior,  600 
ulnaris,  648 

rami  musculares,  651 
ramus  carpeus  dorsalis,  651 
volaris,  651 
volaris  profundu^s,  651 
urethralis,  676 
uterina,  672 

ramus  ovarii,  672 
vaginalis,  672 
vertebralis,  619 

rami  spinales,  620 
ramu^  meningeus,  621 
vesiculis  inferior,  672 
medialis,  672 
superior,  671 
volaris  indicts  radialis,  647 
zygomaticoorbitalis,  598 
Arteriae  alveolares  superiores  an- 
teriores,  602 
arciformes,  1354 
bronchiales,  654 
ciliares  anteriores,  613 
posteriores  breves,  613 
longae,  613 
digitales  dorsales,  647,  699 
plantares,  704 
volar es  communes,  652 
propriae,  652 
gastricae  breves,  662 


Arteriae  ileae,  663 

iliacae  communes,  668 
intercostales,  655 

rami  cutanei  laferales,  656 
musculares,  656 

ramus  posterior,  655 
interlobares  rents,  1354 
inlestinales,  663 
jejunales,  663 
lumbales,  662 

ramus  dorsalis,  663 
spinalis,  663 
mediastinales  anteriores,  632 
metacarpeae  dorsales,  647 

volares,  648 
metatarseae  dorsales,  699 

plantares,  704 
oesophageae,  654 
palpebrales  laterales,  610 

mediates,  612 
phrenicae  inferiores,  658 

rami  suprarenales  supe- 
rior, 659 
receptaculi,  609 
renales,  665 
surales,  694 
tunica  adventitia,  573 

inlima,  573 

media,  573 
Arterial  sheath,  574 
Arteriolae  recti,  1354 
Arterioles,  547 

precapillary,  573 
Artery  or  Arteries,  572 
acromial,  638 
acromiothoracic,  638 
of  ala,  574 
alveolar,  601 
anastomosis  of,  572 

around  elbow-joint,  644 

circumpatellar,  696 

crucial,  678,  690 
anastomotica   magna   of    bra- 
chial, 643,  644 
of  femoral,  691 
angular,  592,  594 
of  ankle-joint,  345 
antero-lateral  ganglionic,  617 
antero-median  ganglionic,  614 
aorta,  57,5 

abdominal,  657 

arch  of,  579 

ascending,  576 

descending,  653 

thoracic,  653 
appendicular,  664 
articular,  694,  695 
of  auditorj^  canal,  1123 

internal,  622 
auricular,  596 

anterior,  598 

deep,  600 

posterior,  596 
axiUary,  635 
azygos,  articular,  695 

of  vagina,  672 
basilar,  622 
of  bile  ducts,  1336 
of  bladder,   1365 
brachial,  640 
bracliiocephalic,  582 
of  brain,  617 
bronchial,  582,  654 
buccal.  601 
of  bulb,  675 
bulbar,  622 
calcaneal,  702,  703 
capsular,  662 
carotid,  common,  583 

external,  588 

internal,  609 
of  cecum,  664,   1300 
central   ganglionic   system   of, 
618 

of  retina,  613 


INDEX 


1455 


Artery    or    Arteries,    cerebellar, 

621,  622 
cerebral,  anterior,  614 

hemorrhage,  617 

middle,  616 

posterior,  622 
cervical,  629,  630 
cervicouterine,  672 
cervicovaginal,  672 
choroid,  617,  622,  1099 
ciliary,  613 
circle  of  Willis,  617 
circumflex,  639,  690 
circumpatellar,  anastomosis  of, 

696 
clavicular,  638 
of  clitoris,  1420 
coats  of,  573 
coccygeal,  677 
cceliac,  659 
colic,  664,  666 

communicating,  anterior,  614, 
650 

of  dorsalis  pedis,  700 

of  peroneal,  702 

posterior,  617 
of  cornea,  1092 
coronary,  578,  660 
of  corpus  cavernosum,  676 
cortical  system  of,  619 
cranial,  from  occipital,  596 
cremasteric,  680 
cricothyroid,  590 
cystic,  661 
dental,  601,  602  ^ 
development  of,  761 
digital,  652 

collateral,  652 

plantar,  704 

ulnar,  652 
dorsal,  of  penis,  676 
dorsalis  hallueis,  700 

indicis,  647 

hnguae,  591 

nasi,  613 

pedis,  698 

polhcis,  647 

scapulse,  639 
of  duodenum,  1287 
dural,  from  ascending  pharyn- 
geal, 597 

from  occipital,  596 
of  elbow-joint,  308 
epigastric,  deep,  680 

superficial,  689 

superior,  633 
ethmoidal,  611 
facial,  592 

transverse,  598 
of  Fallopian  tube,  1402 
femoral,  683,  689 
fibular,  698 

frontal.  598,  612.  615,  617 
of  gall-ljladder,  1335 
ganglionic,  614,  617,  618 
gastric,  660 
gastroduodenal,  661 
gastroepiploic,  661 
glandular,  593 
of  globe  of  eye,  1108 
gluteal,  678 
of  head,  583 
of  heart,  565 
hemorrhoidal,  672,  675 
hepatic,  661 
of  hip-joint,  327 
histology  of,  573 
humeral,  63S 
hypogastric,  570,  669,  763 

imperious,  671 
ileal,  664 
ileocecal,  664 
ileocolic,  664 
iliac,  common,  668 

deep  circumflex,  682 


Artery  or  Arteries,  iliac,  external, 
679 

internal,  669 

superficial   circumflex,   689 
iliolumbar,  678 
infrahyoid,  590 
infraorbital,  602 
infrascapular,  639 
innominate,  582 
inosculation  of,  572 
intercostal,  632,  655 
interosseous,  foot,  699,  700 

hand,  647,  64S 

recurrent,  651 

ulnar,  650 
of  iris,  1099 
of  Iddneys,  1352 
of  knee-joint,  337 
of  labia  majora,  1415 
labial  coronary,  593,  594 
lacrimal,  610 
of  large  intestines,  1310 
laryngeal,  590,  629,  1174 
lateralis  nasi,  594 
lenticulostriate,  617 
lingual,  590,  591,  601 
of  liver,  1326 
of  lower  extremity,  682 
lumbar,  662 
lymphatics  of,  574 
malar,  610 
malleolar,  698,  703 
mammary,  631,  638 
masseteric,  601 
mastoid,  from  occipital,  596 

from  posterior  auricular,  596 
maxillary,  598 
mediastinal,  632,  654 
medidural,  600 
medullary,  619 
of  membrana  tympani,  1131 
meningeal,  anterior,  609 

from  ascending  pharyngeal, 
597 

from  occipital,  596 

middle,  600 

posterior,  597,  621 

small,  600 
mental,  601 
mesenteric,  663,  666 
metatarsal,  699 
musculophrenic,  632 
mylohyoid,  601 
nasal,  612,  613 
nasopalatine,  602 
of  neck,  583 
nerves  of,  574 
of  nose,  1081 
nutrient,  of  fibula,  702 

of  humerus,  643 

of  tibia,  702 
obturator,  673 
occipital,  595,  623 
oesophageal,  629,  654,  1239 
ophthalmic,  610 
orbital,  598 
ovarian,  665,  1401 
palatine,  596,  597,  602,  1204 
palpebral,  610,  612 
pancreatic,  662,  1341 
pancreaticoduodenal,  661,  663 
parietal,  617 
of  parotid  gland,  1225 
par\ddural,  600 
of  penis,  1389 
perforating,  690 

of  foot,  704 

fourth,  689 

of  hand,  648 
pericardiac,  632,  654 
perineal,  675 
perirenal,  665 
peroneal,  701,  702 
petrosal,  600 
pharyngeal,  597 


Artery  or  Arteries,  phrenic,  658 
of  pia  of  brain,  972 

of  spinal  cord,  846 
of  pinna  of  ear,  1121 
plantar,  700,  703 
of  pleura;,  1185 
pontile,  622 
popliteal,  691 
postdural,  597 

postero-median  ganglionic,  617 
prevertebral,  597 
princeps  hallueis,  700 

polhcis,  647 
profunda  femoris,  689 

inferior,  643 

superior,  642 

of  ulnar,  651 
of  prostate  gland,  1395 
pterygoid,  601 
pterygopalatine,  602 
pubic,  681 
pudic,  accessory,  675 

external,  689 

internal,  674,  676 
pulmonary,  574 
pyloric,  661 
radial,  644 

carpal,  647 
radialis  indicis,  647 
ranine,  591 
recurrent,  radial,  646 

tibial,  698 

ulnar,  650 
renal,  665 
sacral,  669,  678 
of  salivary  glands,  1227 
scapular,  630 
sciatic,  677 

of  seminal  vesicles,  1385 
of  septum,  594,  602 
of  shoulder-joint,  303 
sigmoid,  667 
of  skin,  1156 
of  small  intestine,  1293 
spermatic,  665,  1376 
spinal,  620,  621 
splenic,  661,  1446,  1449 
splenopalatine,  602 
sternal,  632 

sternomastoid,  590,  595 
of  stomach,  1278 
stylomastoid  of  posterior  au- 
ricular, 596 
subclavian,  623 
sublingual,  591 
submaxillary,  593,  1226 
submental,  593 
subpleural,  mediastinal  plexus 

of,  632 
subscapular,  630,  639 
superficialis  volae,  647 
supra-acromial,  6.30 
suprahyoid,  591 
supraorbital,  610 
suprarenal,  662 
suprascapular,  629 
suprasternal,  629,  630 
sural,  694 
tarsal,  699 
temporal,  600,  617 

anterior,  598,  623 

deep,  601 

middle,  598 

posterior,  598,  623 

superficial,  597 
of  temporomandibular  articu- 
lation, 281 
terminal,  definition  of,  573 
thoracic,  638,  639 
thymic,  582,  1442 
thyroid  axis,  628 

inferior,  629 

superior,  589 
thyroidea  ima,  582 
tibial,  696,  700 


1456 


INDEX 


Artery  or  Arteries,  of  tongue,  1219 
tonsillar,  593,  1231 
tracheal,  629,  1179 
of  trunk,  653 
tympanic,  609 

anterior,  600 

from  ascending  pharyngeal, 
597 

superior,  600 
ulnar,  648,  651 
umbilical,  570 
of  upper  extremity,  623 
ureteral,  665,  1358 
urethral,  676 
uterine,  672,  1410 
vaginal,  672,  1415 

bulb,  1420 
of  vas  deferens,  671 
vasa  brevia,  662 

intestini  tenuis,  663 
of  vermiform  appendix,  1300 
vertebral,  619,  628 
vesical,  671,  672 
Vidian,  602,  609 
of  voluntary  muscles,  356 
of  wrist-joint,  315 
Arthrodia,  264,  265,  266 
Articular  arteries,  694,  695 
cartilage,  260 
disks,  260 

triangular,  312 
eminence  of  zygomatic  process 

of  temporal  bone,  81 
facet  of  clavicle,  171 
fibrocartilage,  260 
lamella  of  bone,  259 
meniscus,  280 
nerve  corpuscles,  817 
processes  of  atlas,  51 
surfaces  of  axis,  52 

of  sacrum,  60 
synovial  membrane,  261 
ArticulatioacromioclavicularisfiQ? 
atlantoepislTophica,  273 
atlantooccipitalis,  275 
calcaneocuboidea,  347 
carpometacarpeae  pollicis,   317 
coxae,  322 
citbiti,  306 

cuboideonavicularis,  350 
genu,  331 
humeri,  301 
intercarpea,  315 
mandihidaris,  279 
radiocarpea,  314 
radioulnaris,  310 

distalis,  312 
sacroiliaca,  290 
stemoclavicularis,  295 
talocalcanea,  347 
talocruralis,  342 
tarsi  transversa  [Choparti],  349 
iibiofibularis,  340 
Ariiculationes  capitulorum,  282 
carpometacarpeae,  317,  318 
costotransversariae,  284 
costovertehrales,  282 
digitorum  manus,  321 

pedis,  354 
interchondrales,  288 
intermetacarpeae,  319 
intermetatarseae,  352 
intertarseae,  347 
metacarpophalangeae,   320 
metatarsopkalangeae,  353 
ossiculorum  auditus,  1133 
stemocostales,  286 
tarsometatarseae,  351 
Articulations,  259 

acromiocla^dcular,  297 

of  astragalus  with  scaphoid,  349 

of  atlas  with  axis,  273 

with  occipital  bone,  275 
of  axis  mth  occipital  bone,  277 
biaxial,  264,  265 


Articulations,   calcaneo-astragal- 
oid,  347 

calcaneocuboid,  347 

calcaneoscaphoid,  348 

carpometacarpal,  318 

of  carpus,  315 

of  cartilages  of  ribs  with  each 
other,  288 

costocentral,  282,  285 

costosternal,  286 

costotransverse,  284,  285 

costovertebral,  2S2 

of  cuneiform  bones  with  each 
other,  350 

of  elbow-joint,  306 

of    external    cuneiform    bone 
with  cuboid,  351 

of  hip-joint,  322 

immovable,  263 

intercuneiform,  350 

interneural,  271 

of  knee-joint,  331 

of  lower  extremity,  322 

mediotarsal,  349 

metacarpophalangeal,  320 

of  metatarsal  bones  with  each 
other,  352 

metatarsophalangeal,  353 

mixed,  264 

movable,  264 

of  ossicles  of  tympanum,  1133 

of  pelvis,  290 

of  phalanges  of  foot,  354 
of  hand,  321 

polyaxial,  264 

of  pubic  bones,  294 

radiocarpal,  314 

radioulnar,  310 

of   ribs   with   their  cartilages, 
288 
with  vertebrae,  282 

sacroihac,  290 

of  sacrum  and  coccyx,  292 
and  ilium,  290 

of  scaphoid  with  cuboid,  350 
with  cuneiform,  349 

of  scapula,  299 

scapulocla"\acular,  297 

of  shoulder-joint,  301 

sternoclavicular,  295 

of  sternum,  288 

tarsometatarsal,  351 

of  tarsus,  347 

temporomandibular,   133,   279 

tibiofibular,  340 

tibiotarsal,  342 

transverse  tarsal,  349 

of  trunk,  268 

of  upper  extremity,  295 

of  vertebral  column,  268 
with  cranium,  275 
with  pelvis,  289 

of  wrist-joint,  314 
Aryepiglottic  muscles,   1173 
Arytenoepiglottic      fold,      1167, 

1170 
Arytenoid  cartilage,  1166 
Arytenoideus  muscles,   1172 
Ascending  aorta,  576 

colon,  1303 

mesacolon,  1264 
Association  nerve  fibers,  954 
Asterion,  133,  146 
Astragaloscaphoid  ligament,  349 
Astragalus,  244 

articulation  of  calcaneus  and, 
347 
of  scaphoid  mth,  349 
Astrocytes,  818 
Atlanto-axial  ligaments,  274 
Atlanto-odontoid  joint,  274 
Atlas,  50 

accessory  ligament  of,  275 

articulation  of,  -with  axis,  273 
with  occipital  bone,  275 


Atlas,  development  of,  63 

transverse  ligament  of.  274 
Atrium,  1125 
dextrum,  554 
maxillary,  orifice  of,  141 
meatus  medii,  141 

nasi,  1082 
of  nasal  meatus,  141 
sinistrum,  559 
Attic,  1125 

Attollens  aurem  muscle,  366 
Attrahens  aurem  muscle,  366 
Auditory  artery,  internal,  622 
canal,  1122 

applied  anatomy  of,  1124 
arteries  of,  1123 
cartilaginous      portion      of, 

1122 
lymphatics  of,  1123 
nerves  of,  1123 
osseous  portion  of,  1122 
skin  of,  1123 
veins  of,  1123 
hair,   1143 
meatus,  1122 

external,  88,  133,  1122 

lymphatic  vessels  of,  777 
internal,  85,  128 
nerve,  1000 

nuclei,  881 
teeth,  1144 
vesicles,  142 
Auerbach's  plexus  of  nerves,  1279 
Aula,  908 
Aulix,  908 

Auricles  of  ear,  1119 
of  heart,  fibres  of,  562 
left,  559 
right,  554 
primitive,  757 
Atiricula,  1119 
dextra,  554 
sinistra,  559 
Auricular  appendix,  554,  559 
artery,  596,  598,  600 
canal,  757 
fissure,  131 
IjTnph  nodes,  774 
nerve,  anterior,  988 
from  vagus,  1005 
great,  1020 
posterior,  997 
point  of  skull,  146 
region,  muscles  of,  365 
systole,  565 
vein,  712 
Auriculotemporal  nerves,  988 
Auriculoventricular     bundle     of 
His,  564 
opening,  557,  559 
Auris  interna,  1136 
Avalanche  conduction  of  Ramon 

y  Cajal,  815 
Axes  of  pehas,  218 
Axial  planes  of  body,  34 
Axilla,  633 

applied  anatomy  of,  634 
dissection  of,  455 
ligaments  of,  456 
Axillary  arch,  407 
artery,  635 

applied  anatomy  of,  637 
fascia,  456,  633 
lymph  nodes,  782 
sheath,  636 
veins,  731 

applied  anatomj-  of,  732 
Axis,  52 

articulation  of,  with  occipital 

bone,  277 
coeliac,  659 

of  crystalline  lens,  1107 
development  of,  64 
optic,  1088 
sagittal,  1088 


INDEX 


1457 


.Vxis,  thyroid,  628 

vi.su ill,  loss 
Axia  Icntis,  1107 

oinica,  loss 

pdms,  218  ■ 
Axis-cvliiider  process,  807,  811 
Axones.'SlO 

amyelinic,  S12 

myelinic,  811 

of  spinal   cord,   myelinization 
of,  S40 
Azygos  arteries  of  vagina,  672 

articular  arterj',  695 

uvulae  muscle,  398 

veins,  736 

applied  anatomy  of,  737 


Back,  fascia  of,  404 
muscles  of,  403 

applied  anatomy  of,  416 
fifth  layer,  413 
first  layer,  404 
fourth  layer,  410 
second  layer,  407 
surface  form  of,  416 
third  layer,  408 
Baillarger,  fibre  band  of,  953 
Ball-and-socket  joint,  264 
Band  of  Vicq  d'Azyr,  932 
Barha,  1159 
Bartholin,  duct  of,  1226 

glands  of,  1420 
Basihyal,  153 
Basilar  artery,  622 
groove,  73 

of  pons,  864 
membrane,  1143 
process,  71 
sinus,  727 
suture,  122 
vein,  720 
Basilic  vein,  730 
Basion,  131,  146 
Basis  cochleae,  1138 
cordis,  551 

glandulae  suprarenalis,  1448 
mandibulae,  117 
modioli,  1138 
nasi,  1079 

ossa  metacarpalia,  201 
metatarsalia,  250 
sacri,  61 
patellae,  231 
phalangis,  204 
prostatae,  1391 
pulmonis,  1188 
Basisvlvian  fissure,  917 
Basket  cells,  892 
Basophiles,  40 

Bechterew,  fibre  band  of,  953 
Bell,  respiratory  nerve  of,  exter- 
nal, 1029 
internal,  1024 
Bertin,  ligament  of,  323 
Biaxial  articulations,  264 
Biceps  brachii  muscles,  469 
femoris  muscle,  522 

applied  anatomy  of,  525 
bursa  of,  524 
surface  form  of,  543 
flexor  cubiti  muscle,  469 
muscle,  469 

surface  form  of,  495 
Bichat,  fissure  of,  940 
Bicipital  fascia,  469,  730 
groove,  180 
tuberosity,  191 
Bicornate  uterus,  1408 
Bicuspid  teeth,  1207 

valve,  561 
Bifurcatio  tracheae,  1175 
Bigelow,  ligament  of,  324 
92 


Bile,  1334 

duct,  1333 

arteries  of,  1334 
lymphatics  of,  796,  1334 
nerves  of,  1334 
veins  of,  1334 

papilla,  1287 
Bipolar  nerve  cells,  SOS,  1102 
"Bird's  nest"  of  cerebellum,  888 
Biventer  cervicis  muscles,  413 
Biventral  lobes,  887 

muscle,  358 
Bladder,  1358 

applied  anatomy  of,  1366 

arteries  of,  1365 

cervix  of,  1361 

development  of,  1426 

interior  of,  1364 

ligaments  of,  1361 
true,  1362 

lymphatics  of,  796,  1365 

mucous  membrane  of,  1364 

nerves  of,  1365 

rugae  of,  1364 

surface  form  of,  1365 

trigone  of,  1365 

veins  of,  1365 
Blind  spot,  1101 
Blood  cells,  40 

circulation  of,  547 

islands,  755 
Blood-vascular  system,  547 

development  of,  755 
Bloodvessels  of  bone,  40 

of  nerves,  813 
BNA,  definition  of,  33 
Bochdalek,  ganglion  of,  984 
Bodies,  carotid,  1450 

Nissl,  809 

parasympathetic,  1450 

quadrigeminal,  894 

tigroid,  809 
Body,  ciliary,  1094 

coccygeal,  1450 

geniculate,  external,  905 
internal,  895 
lateral,  910 

of  Luys,  905 

pineal,  906 

pituitary,  909 

thyroid,  1435 

vitreous,  1105  ! 

Bone  or  Bones,  acetabulum,  213  i 

ankle,  244 

apophysis  of,  37 

appUed  anatomy  of,  46 

of  arm,  178 

astragalus,  244 

atlas,  50 

axis,  52 

bloodvessels  of,  40 

breast,  157 

calcaneus,  239 

calcification  of,  44 

calf,  236 

cambium  layer  of,  46 

canaliculi  of,  39 

cancellous,  40 

carpus,  195 

of  cerebral  cranium,  70 

chemical  composition  of,  41 

of  chest,  154 

clavicle,  169 

coccyx,  61 

colhir,  169 

compact,  38 

covering,  142 

of  cranium,  70 

cuboid,  245 

cuneiform,  of  foot,  247 
of  hand,  197 

dense,  38 

dermal,  142 

destroyers,  44 

diaphysis  of,  35 


Bone  or  Bones,  of  elbow,  185 
cndosteuni  of,  39 
epactal,  144 
ei)ii)hyses  of,  35 
epiptcric,  144 
ethmoid,  96 
extremities  of,  35 
of  face,  99 
femur,  221 
fibers  of,  38 
fibula,  236 
flat,  36 
of  foot,  239 
of  forearm,  185 
formers,  44 
frontal,  76 
growth  of,  42 
of  hand,  194 

lower  row,  198 

upper  row,  196 
heel,  239 
liip,  207 
humerus,  178 
hvoid,  153 
ilium,  207 
interparietal,  74 
irregular,  36 
ischium,  210 
knee-cap,  230 
lacrimal,  106 

lesser,  107 
lacuna  of,  39,  259 
lamellce  of,  39 

articular,  259 
of  leg,  230 
lingual,  153 
long,  35 
of  lower  extremity,  207 

jaw,  115 
lymphatics  of,  41 
malar,  107 
mandible,  115 
marrow  of,  40 
maxillte,  100 
medullary  canal  of,  35 
metacarpus,  201 
metatarsal,  249 
nasal,  99 
navicular,  of  foot,  246 

of  hand,  196 
nerves  of,  41 
occipital,  70 
OS  calcis,  239 

coxae,  207 

innominatum,  207 

magnum,  199 

pubis,  207,  212 

trigonum,  245 
osseous  tissue  of,  38 
ossification  of,  42 
palate,  109 
parietal,  74 
patella,  230 
of  pelvis,  215 
periosteum  of,  38 
phalanges  of  foot,  252 

of  hand,  204 
pisiform,  198 
premaxillary,  105 
proliferation  of,  44 
pubis,  212 
radius,  190 
ribs,  161 

rider's,  229,  360,  515 
sacrum,  58 
scaphoid,  of  foot,  246 

of  hand,  196 
scapula,  172 
semilunar,  197 
sesamoid,  257 
shaft  of,  35 
shin,  231 
short,  36 
shoulder  blade,  172 

girdle,  169 


1458 


INDEX 


Bone  or  Bones,  of  skull,  69 
sphenoid,  S9 
spine,  48 
sternum,  157 
supernumerary,  144 
sutural,  144 
tarsus,  239 
temporal,  80 
thigh,  220 
of  thorax,  154 
tibia,  231 
trapezium,  198 
trapezoid,  199 
turbinated,  113,  139 
ulna,  185 
unciform,  200 
of  upper  extremity,  168 

jaw,  100 
vascularization  of,  45 
vertebrse,  48 

cervical,  49 

coccygeal,  58 

lumbar,  56 

sacral,  58 

thoracic,  53 
vomer,  114 
wedge,  247 
Wormian,  144 
Bony  semicircular  canals,  1137 
Born,  ostium  primum  of,  759 

secundum  of,  759 
Bowman,  capsule  of,  1350,  1351 

membrane  of,  1091 
Brachia  conjunctiva,  891 


Bracliial  artery,  640 

applied  anatomy  of,  641 
surface  marking  of,  641 

fascia,  467 

plexus  of  nerves,  1026 

applied  anatomy  of,  1039 

veins,  731  . 
Brachialis  anticus  muscle,  469 

surface  form  of,  496 
Brachiocephalic  artery,  582 

veins,  733 
Brachioradialis  muscle,  479 

surface  form  of,  496 
Brachium    quadrigeminuTn    infe- 
rius,  895 
superius,  895 
Brachy cephalic  cranium,  146 
Brain,  846 

adult  human,  860 

arachnoid  of,  968 
■idlli  of,  970 

areas  of,  959 

arteries  of,  617 

cerebellum,  884 

development  of,  850 

dimensions  of,  849 

dura  of,  964 

fourth  ventricle  of,  864 

hind,  861 

isthmus,  860  (note) 

laminse  of,  855 

localization  of  function  of,  959 

medulla  oblongata,  861 

meninges  of,  964 

nuclei  of,  857 

Pacchionian  bodies  of,  970 

pia  of,  972 

pons,  864 

structure  of,  plan  of,  858 

topography  of,  847 

tube,  development  of,  852 
flexures  of,  855 

vesicle,  primary,  851 

weight  of,  849 

zones  of,  855 
Breast  bone,  157 

female,  1428 

male,  1433 
Bregma,  76,  123,  146 
Bregmatic  fontanelle,  143 


Brim  of  pelvis,  215 

Broad  ligament  of  lung,  1183 

of  uterus,  1407 
Broca's  cap,  917 

diagonal  band,  928 
Bronchi,  1175 

left,  1177 

right,  1176 
Bronchial  artery,  582,  654 

veins,  737 
Bronchioles,  respiratory,  1195 
Bronchiomediastinal  lymph 

nodes,  801 
Bronchus  dexter,  1176 

ramus  hronchialis  eparteria- 
lis,  1177 
hyparterialis,  1177 

sinister,  1177 
Bruce  and  Campbell,  intermedio- 

lateral  tract  of,  839 
Bruch,  membrane  of,  1093 
Bruns,  falciform  margin  of,    508 
Bryant's  triangle,  329 
Buccae,  1200 
Buccal  artery,  601 

cavitv,  1199 

glands,  1200 

lymph  nodes,  776 

nerve,  987,  998 

region,  muscles  of,  374 
Buccinator  muscle,  375 

nerve,  987 
Buccopharyngeal      fascia,      377, 

394 
Bulb,  aortic,  759 

artery  of,  675 

of  corpora  cavernosa,  1386 

of  internal  jugular  vein,  714 

occipital,  939 

olfactory,  927 

urethral,  1386 
Bulbar  arteries,  622 
Bulboid  corpuscles,  817 
Bulbous  aortae,  576 
Bulbus  cordis,  757,  759 

cornu  posterioris,  939 

oculi,  1086 

olfactorius,  927 

jnli,  1159 

urethrae,  1386 

vena  jugularis  inferior,  714 
superior,  714 

vestibuli,  1420 
Bulla  ethmoidalis,  1082 
Burdach,  column  of,  827 
Bursa  or  BursEe,  about  knee-joint, 
336 

of  biceps  femoris  muscle,  524 

deep  infrapatellar,  336 

of  elbow-joint,  308 

gluteofemoral,  327 

of    gluteus    maximus    muscle, 
516 
medius  muscle,  517 

of  greater  trochanter,  327 

of  hand,  487 

of  hip-joint,  327 

iliopectineal,  327 

infrapatellar,  deep,  336 

infraspinatus,  303 

ischiogluteal,  327 

of  knee-joint,  336 

obturator,  327,  518 

olecranon,  308 

patellar,  deep,  512 

prepatellar,  336,  512 

of  pjTiformis  muscle,  517 

of  quadriceps  femoris  muscle, 
521 

of  shoulder-joint,  303 

subacromial,  303,  462 

subcutaneous  acromial,  303 
tibial,  336 
trochanteric,  327 

subdeltoid,  ,303,  462 


Bursa  or  Burste,  subscapular,  303 
subtendinous  iliac,  327 
suprapatellar,  336,  511 
synovial,  subcutaneous,  262 

subtendinous,  262 

thecal,  262 
of  tendo  Achillis,  530  • 
tensoris  veil  palati,  397 
of  tibialis  anticus  muscle,  526 
of  wrist,  487 
Bursa  or  Bursae,  anserina,  513, 

524 
hicipitogastrocnemialis,  524 
bicipitoradialis,  308 
glutaeofemorales,  327,  516 
iliaca  subtendinea,  327,  .504 
iliopectinea,  327,  504 
infrapatellaris    profunda,    336, 

512 
intermetacarpophalangeae,  487 
intratendinea  olecrani,  308 
ischiadica     musculus      ghdaei 

maximi,  327,  516 
mucosae  subcutaneae,  262 

subtendineae,  262 
tnuscidi  poplitei,  337 
m.usculus    bicipitis  femoris  in- 
ferior, 524 

infraspinati,  465 

obiuratorii  interni,  327,  518 

peciinei,  513 

pisiformis,  517 

recti  femoris,  510 

sartorii  propria,  509 

sternohyoidei,  1167 

subscapularis,  464 

tensoris  veli  palati,  397 

teretis  majoris,  466 
praepatellaris  subcutanea,  336, 
506,  512 

subfacialis,  336 

svhtendinea,  336 
sternohyoidii,  387 
suhacromialis,  462 
subcutanea  calcanea,  530 

digitorum  dorsales,  487 

epicondyli    humeri    lateralis, 
308 
medialis,  308 

olecrani,  308 

prominentiae  laryngeae,  1164 

tuberositatis  tibiae,  336 
subdeltoidea,  462 
subtendinea    musculus    tibialis 
anterioris,  526 

olecrani,  308 
suprapatellaris,  336,  511 
tendinis  calcanei,  530 
trochanterica   musculus   glutaei 
maximi,  516 
medii  anterior,  517 

posterior,  517 
minimi,  517 

subcutanea,  327,  506 
Bursal  synovial  membrane,  262 


Cacuminal  lobes,  886 
Cajal,  nerve  cells  of,  1102 
Calcaneal  arteries,  702,  703 

nerves,  1057 
Calcaneo-astragaloid       articula- 
tion, 347 
ligaments,  347 
Calcaneocuboid  articulation,  347 

ligamients,  348 
Calcaneoscaphoid      articulation, 
348 
ligaments,  348 
Calcaneus,  239 

articulation  of  astragalus  and, 
347 
of  scaphoid  and,  348 


INDEX 


1459 


Calcaneus,  articulation  with  cu- 
boid, 347 
Calcar,  939 

avis,  939 

femorale,  227 
Calcarine  fissure,  919 
Calf  bono,  536 
Calices  majores,  1349 

minor  es,  1349 

of  ureters,  1356 
Callosal  eminence,  939 

gyre.  920,  921 
Calyculi  gualaiorii,  1148 
Catncra  oculi  anterior,  1105 

posterior,  1105 
Camper,  fascia  of,  424 
Canal  or  Canals,  adductor,  685 

Alcock's,  450,  675 

alimentary,  1199 

anal,  1309 

auditory,  1122 

auricular,  757 

carotid,  131 

of  Corti,  1145 

crural,  684 

dental,  102,  117 

diploic,  718 

ethmoidal,  79,  98 

for  Eustachian  tube,  1127 

femoral,  503,  684 

Haversian,  39 

of  Huguier,  84,  88,  997,  1126 

Hunter's,  511,  515,  685 

hyaloid,  1106 

incisor,  105 

infraorbital,  102,  136 

inguinal,  437,  1375 

lacrimal,  1116 

malar,  108 

medullary,  of  bone,  35 

membranous,  of  cochlea,  1144 

for  nasal  duct,  orifice  of,  141 

nasopalatine,  114 

of  Nuck,  1408 

nutrient,  of  fibula,  237 
of  metacarpal  bones,  201 
of  radius,  191 
of  ulna,  189 

obturator,  517 

palatine,  anterior,  139 
posterior,  102,  110,  134 
accessory,  1 10,  128 

palatomaxillary,  102 

of  Petit,  1106 

pterygoid,   130 

pterygopalatine,  92,  130,  134 

pyloric,  1272 

sacral,  61 

of  Schlemm,  1092 

semicircular,  bony,  1137 
membranous,  1142 

spermatic,  437,  1375 

of  spinal  cord,  central,  831 

for  tensor  tympani,  1127 

of  vermiform  appendix,  1299 

vertebral,  49,  67 

Vidian,  93,  130,  134 

Volkmann's,  39 

of  Wirsung,  1339 
Canales  diploid  [Brescheli\,  718 

palatini,  110 

semicirculares  ossei,  1137 

lateralis,  ,1138 

posterior,  1137 

superior,  1137 

Canaliculi  of  bone,  39 

caroticotympanici,  86 
Canaliculus  chordae  tympani,  88, 
1126 

innominatum,  92,  127,  1135 

tympanicus,  87,  1125 
Canalis     adductorius     [Hunteri], 
511,  515,  685 

centralis  cochleae,  85 
medullae  spinalis,  831 


Canalis  ccrviris  uteri,  1408 

COIIillllni,l,„x.    71 

ethiii,n,hilr  .inlrrias,  98 

/«/,v/.  /•,«,s-,    '.IS 

faeiaUs,  S5 

femoralis,  503,  684 

hyaloideus,  1106 

hypoglossi,  71 

inguinalis,  437,  1375 

iayr'.nialis,  104 

mandihulae,  117 

niuscidotid}arius,  87 

nasolacrivialis,  102 

ohturatorius,  517 

pteryfjoideus,  93 

pterygopalatirtus,   110 

radicis  dentis,  1212 

reuniens  of  Hensen,  1142 

sacralis,  61 

spiralis  cochleae,  1140 
modioli,   1139 

vertebralis,  49 
Cancellous  bone,  40 
Canine  eminence,  101 

fossa,  101,  135 

teeth,  1206 
Canthi  of  eyelids,  1113 
Capillaries,  547,  573 
Capilli.  1159 
Capitellum,   182 
Capitulum  costae,  162 

fibulae,  236 

humeri,  182 

mallei,  1131 

mandihulae,  118 

ossa  yneiacarpalia,  201 
metata.rsalia,  250 

radii,  190 

stapedis,  1133 

ulnae,  189 
Capsula  adiposa,  1348 

articularis       cricoarytaenoidea, 
1168 

extrema,  948 

lentis,  1107. 
Capsulae  articulares.      See  Indi- 
vidual joints. 
Capsular  artery,  662 

ligaments.  See    Individual 

joints. 
Capsule,  adrenal,  1447 

of  Bowman,  1350,  1351 

of  crystalline  lens,  1107 

external,  951 

internal,  948 

Malpighian,  13.50,  1351 

of  Ti5non,  371,  1086 
Caput  cecum  coli,  1297 

epididymidis,  1378 

femoris,  221 

gallinaginis,  1367 

gelatinosa  Rolandi,  830 


humeri,  178 

obliguum   musculus   adductoris 
hallucis,  541 

panereatis,  1337 

transversuirt  musculus  adducto- 
ris hallucis,  541 
Cardiac  cycle,  565 

ganglion  of  Wrisberg,  1072 

glands,  1278 

muscle  fibers,  355,  357 

muscles,  355 

nerves,  cervical,  1007 
inferior,   1069 
superior,  1068 
thoracic,  1007 

orifice,  1271 

plexus  of  nerves,  1072 

revolution,  565 

veins,  708 
anterior,  556 
Carina  urcthralis  vaginae,   1414 
Caroticotympanic  nerve,  1066 


Carotid  arteries,  common,  583 
applied  anatomy  of,  586 
left,  583 
right,  583 

surface  marking  of,  586 
external,  588 

applied  anatomy  of,  .588 
surface  marking  of    588 
internal,  606 

applied  anatomy  of,  608 
cavernous  portion  of,  608 
cerebral  portion  of,  60S 
cervical  portion  of,  607 
petrous  portion  of,  607 
bodies,  1450 

canal,  131  , 

foramen,  84,  86 
ganglion,  1066 
glands,  586,  1450 
groove,  126 
nerve,  1003 

plexus  of,  1069 
sheath,  383 
triangle,  388,  603,  604 
Carpal  arch,  647 
artery,  radial,  647 

ulnar,  651 
bones,  195 

applied  anatomy  of.  205 
common  characters  of,  196 
surface  form  of,  205 
meniscus,  317 
Carpometacarpal     articulations, 

317 
Carpus,  195 

articulations  of,  315 
Ugaments  of,  315 
Cartilage,  259 
alar,  lesser,  1080 
articular,  260 
arytenoid,  1166 
costal,  165 
cricoid,  1165 
cuneiform,  1166 
elastic,  261 
epiphyseal,  44 
hyaline,  260 
intrathyroid,  1165 
of  Jacobson,  1080,  1083 
of  larynx,  1163 
matrix,  260 
Meckel's,  118 
of  nose,  1079 
parachordal,  141 
of  pinna  of  ear,  1120 
of  Santorini,  1166 
sesamoid,  1080 
thyroid,  1163 
of  trachea,  1177 
vomerine,  1080 
of  Wrisberg,  1166 
Cartilagincs  alares  mitwres,  1080 
arytenoideae,  1166 
basis,  1166 
crista  arcuata,  1166 
fm>ea  oblonga,  1166 
triangularis,  1166 
processus  muscularis,   1166 
voealis,  1166 
corniculatae,  1166 
cuneiformes,  1166 
laryngis,  1163 
nasi,  1079 
Cartilaginous  ear  capsules,  141 
Cartilago  alaris  major,  1079 
cru^  laterale,  1070 
mediate,  1079 
auriculae,  1120 
costalis,  165 
cricoidea,  1165 
epiglottica,  1167 
nasi  lateralis,  1079 
septi  nasi,  1080 
thyreoidea,  1163 
triticea,  1168 


1460 


INDEX 


Cartilago  tubae  auditivae,  1128 
lamina  lateralis,  1128 
medialis,  1128 

■vomeronasalis,  1080 
Caruncula  lacrimalis,  1115 

sublingualis,  1201,  1226 
Carunculae  hymenales,  1418 

myrtiformes,  1418 
Cauda  epididymidis,  1378 

equina,  823,  845 

helicis,  1120 

pancreatis,  1339 
Caudate  lobe  of  liver,  1324 

nucleus,  937,  946 
Caudatum,  854,  937,  946 
Cavernous  groove,  91 

nerves,  1077 
plexus  of,  1066 

sinuses,  724 
Cavitas  glenoi'dalis,  176 
Cavity  or  Cavities,  cotyloid,  213 

glenoid,  176 

of  heart,  553 

of  mouth,  138 

nasal,  138 

of  pelvis,  216 

pulp,  1212 

sigmoid,  of  radius,  192 
of  ulna,  187 

of  thorax,  157 

tjTiipanic,  1125 

Cavum  ariiculare,  294 

\genu],  336 

conchae,  1120 

dentis,  1209 

epidurale,  843 

laryngis,  1169 

mediastinale  posterius,  1183 

nasi,  138,  1081 

regio  olfactoria,  1082 
respiratoria,  1082 

oris,  1199 

proprium,  1201 

pharyngis,  1229 

pleurae,  1181 

septi  pellucidi,  913,  945 

subarachnoideale,  845,  969 

thoracis,  154,  157 

tympani,  1125 

paries  carotica,  1127 
jugularis,  1125 
labyrinthica,  1126 
mastoidea,  1126 
tegmentalis,  1125 

irfen',  1408 
Cecal  arteries,  664,  1300 

fold,  1267 
Cecum,  1296 

arteries  of,  664,  1300 

interior  of,  1298 

lymphatics  of,  1300 

miicous  membrane  of,  1300 

veins  of,  1300 
Cell  or  Cells,  acid,  1276 

air,  mastoid,  1127 

basket,  892 

centro-acinar,   of  Langerhans, 
1340 

of  Claudius,  1147 

commissural,  of  cord,  841 

of  Deiters,  1146 

enamel,  1214 

ependymal,  818 

ethmoidal,  79,  97,  98,  141 

ganglion,  807 

of  Golgi,  952 

gustatory,  1149 

hair,  1143    ' 
outer,  1146 

of  Hensen,  1147 

interstitial,  1399 

islets,  interalveolar,  1340 

of  lateral  ventricles,  936 

lutein,  1400 

of  Martinotti,  952,  953 


Cell  or  Cells,  mastoid,  S3 
nerve,  arboriform,  80S 
bipolar,  808,  1102 
of  cerebral  cortex,  952 
ciliated  ependymal,  806 
germinal,  806 
gUa,  818 
Golgi,  808 
multipolar,  808 
of  spinal  cord,  832 
stellate,  808 
unipolar,  808 
oxyntic,  1276 
parenchymatous,  1437 
parietal,  1276 
polymorphous,  952 
Purkinjean,  892 
pyramidal,  952 
splenic,  1445 
Cellulae  eihmoidales,  97 
mastoideae,  83,  1123 
Cementum  of  teeth,  1212 
Centripetal  nerve  fiber,  810 
Centro-acinar    cells    of    Langer- 
hans, 1340 
Centrum  semiovale,  932 

lendineum,  [diaphragma],  419 
Cephalic  fixture  of  brain,  855 
index  of  skull,  146 
vein,  730 

accessory,  731 
Ceratohyals,  154 
Cerebellar    artery,    anterior    in- 
ferior, 622 
posterior  inferior,  621 
superior,  622 
hemispheres,  S85 
tract  of  spinal  cord,  838 
veins,  720 
Cerebello-olivary  fibers,  873 
Cerebellospinal  tract  of  cord,  839 
Cerebellum,  884 
anlage  of,  855 
"bird's  nest"  of,  888 
cortex  of,  microscopic  appear- 
ance of,  892 
fibers  of,  891 
fissures  of,  885 
flocculus  of,  888 

peduncles  of,  888 
folia  of,  884 
frenulum  of,  891 
furrowed  band  of,  888 
gray  masses  of,  888 
lingula  of,  886 
lobes  of,  885 
nuclei  of,  888 
peduncles  of,  889 
peduncular  sulcus  of,  885 
postramus  of,  888 
preramus  of,  888 
proton  of,  855 
ramus  of,  888 
vermis  of,  885 
weight  of,  883 
worm  of,  885 
Cerebral  artery,  anterior,  614 
middle,  616 
posterior,  622 
cortex,  932 

nerve  cells  of,  952 
fibres  of,  952 
cranium,  bones  of,  70 
fibre  systems,  summarj^  of,  954 
fissures,  915 
gyres,  915 
hemispheres.  912 

configuration  of,  914 
gray  masses  in,  946 
hemorrhage,  arterv  of,  617 
lobes,  916 
veins,  719 
Cerebrospinal  fluid,  845,  970 

tract,  ventral,  840 
Cerebrum,  912 


Cerumen,  1123 

Cervical  arteries,  629,  630 

cardiac  nerve,  1007 

curve  of  vertebral  column,  66 

enlargement  of  spinal  cord,  823 

fascia,  applied  anatomy  of,  384 

flexure  of  brain,  855 

ganglion,  1066,  1069 

lymph  nodes,  777,  779 

nerves,  di\'ision  of,  1016 

nucleus  of  spinal  cord,  833 

pleura,  1183 

plexus  of  nerves,  1018,  1020 
applied  anatomy  of,  1026 

rib,  53,  64 

veins,  717,  718 

vertebrae,  49 
seventh,  53 
Cer^^calis  ascendens  muscle,  412 
Cer\icofacial  nerve,  996 
Cervicouterine  artery,  672 
Cervicovaginal  artery,  672 
Cervix  uteri,  1405 

portio  supravaginalis,  1405 
vaginalis,  1405 
Chassaignac's  tubercle,  68 
Check  ligaments,  1087 
Cheeks,  1200 
Chemoprosope  skull,  146 
Chest,  154.     See  Thorax. 
Chiasma  opticum,  974 
Choanae,  138,  1081,  1229 
Chondrin,  260 
Chondroblasts,  259 
Chondroglossus  muscle,  392,  393 
Chondrosternal   ligaments,    286, 

287 
Chondroxiphoid  ligaments,  288 
Chorda  obliqua,  311 

tympani,  877,  882,  997 
Chordae  tendineae,  558,  561 

Willisii,  721 
Chorioidea,  1093 
Choroid,  1093 

applied  anatomy  of,  1110 

artery  of,  617,  1099 

fissure,  940 

nerves  of,  1099 

plexuses    of   fourth    ventricle, 
867 
of  lateral  ventricles,  940 
of  third  ventricle,  940 

vein,  720 
Chromatophiles,  809 
Chyle,  767 

Chyliferous  vessels,  767 
Cilia,  1113,  1159 
Ciliary  arteries,  613 

body,  1094 

ganglion,  982 

glands,  1162 

ligament,  1096  " 

muscle,  1095 

nerves,  981,  982 

processes,  1094 
Ciliated  ependymal  nerve  cells, 

806 
Cinerea,  819 
Cingulum,  955,  1206 
Circle  of  Willis,  617,  618 
Circular  sinus,  726 
Circulation  of  blood,  547 

fetal,  568 

placental,  755,  756 

pulmonary,  548 

systemic,  548 

umbilical,  756 

vitelline,  755 
Circulus  arteriosus,  617 

iridis  major,  1099 
minor,  1099 

tonsillaris,  1003 
Circumanal  glands,  1162 
Circumduction,  267 
Circumference  of  pehfis,  215,  217 


INDEX 


1461 


Circumfereniia  articularis,  191 
Circumferential  lamella  of  bone, 

39 
Circumflex  arteries,  639,  690 

iliac  vein,  742 

nerve,  1030 
Circuminsular  fissure,  925 
CirciiiiipaliHai  imastomosis,  696 
Cish  ni.i  l.n^.ilis.  969 

c-'nl„li,,ni,'hillnns,  969 

L..DU,  77U,  772 

interpeduncularis,  970 

ponlis,  969 
Cisternae  subarachnoidales,  969 
Clarke's  column,  830,  833 
Claudius,  cells  of,  1147 
Claustrum,  948,  954 
Clam,  863 
Clavicle,  169 

applied  anatomy  of,  172 

surface  form  of,  171 
Clavicula,  169 
Clavicular  artery,  638 

facet,  157 

nerve,  1022 
Clavipectoral  fascia,  456,  459 
Cleavage  lines  of  Langer,  1150 
Cleft  palate,  151 
Clinoid  processes,  90,  94,  126 
Clitoris,  1418 

arteries  of,  1420 

frenulum  of,  1416 

nerves  of,  1420 

prepuce  of,  1416 
Clival  lobes,  886 
Clivus,  73,  90 
Cloquet,  ligament  of,  1376,  1379 

lymph  nodes  of,  786 

septum  crurale  of,  504 
Club  foot,  256 
Coaptation,  267 
Coccygeal  artery,  677 

body,  1450 

ganglion,  1072 

gland,  1450 

ligament,  843,  845 

nerves,  1019 

divisions  of,  1051 
plexus  of,  1062 

vertebra,  58 
Coccygeus  muscle,  453 
Coccyx,  61 
Cochlea,  1138 

bony  canal  of,  1138,  1140 

membranous  canal  of,   1144 
Cochlear  nerve  nuclei,  881 
Coelileariform  process,  1127 
Coeliac  artery,  659 

axis,  659 

plexus  of  nerves,  1008,  1073 
Coeliolympha,  970 
Coelom,  1245 
Cohnheim's  fields,  356 
Colic  arteries,  664,  666 

impression  of  liver,  1321 

lymph  nodes,  791 

olexus  of  nerves,  1076 
Co'llar  bone,  169 
Collateral  circulation,  definition 
of,  573 

eminence,  938 

CoUes,  fascia  of,  424,  441 
fracture,  193 

passive  motion  after,  268 
CoUieuli  inferiores  [corpora  quad- 
rigemini],  894 
superiores  [corpora,  quadrigem- 
ini],  894 
Colliculus  nervi  opHci,  1101 
Collum  anatomicum,  178 
chirurgicum,  178 
costae,  162 
dentis,  1204 
femoris,  221 


Collum  mallei,  1131 
viandibulae,  118 
radii,  191 
scapulae,  176 
tali,  245 
vesicae,  1361 
felleae,  1332 
Colon,  1303 

applied  anatomy  of,  1306 
aseendens,  1303 
descende^is,  130.5 
hepatic  flexure  of,  1303 
mucous  membrane  of,  1310 
sigmoid  flexure  of,  1300 
sigmoideum,  1306 
splenic  flexure  of,  1303 
transversum,  1303 
Colostrum  corpuscles,  1431 
Column  of  Burdaeh,  827,  835 
Clarke's,  830,  833 
of  Goll,  827,  835 
of  Sertoli,  1380 
of  spinal  cord,  826 
Columna  rugarum  anterior,   1414 
posterior,  1414 
vertebralis,  48,  66 
Columnae  carneae,  558,  561 
renales  [Bertini],  1350 
pars  convoluta,  1350 
radiata,  1350 
Comes    nervi    iscliiadiei    artery, 
677 
mediana  artery,  650 
phrenici  artery,  632 
Comma  tract  of  Schultze,  835 
Commissura  anterior  alba,  840 
cinerea  [grisea],  830 
inferior  [Gitddeni],  895 
labiorum,  1199 
anterior,  1415 
posterior,  1415 
maxima,  933 
palpebrarum  lateralis,  1113 

medialis,  1113 
ventralis  alba,  830 
Commissural  cells  of  cord,  841 
Commissure,  anterior,  946 
of  Gudden,  895 
habenular,  906 
hippocampal,  944 
middle,  ?03 
posterior,  906 

of  spinal  cord,  gray,  830,  831, 
white,  834 
Communicantes  hypoglossi 

^  nerve,  1023 
Communicating  artery,  anterior, 
614,  650 
of  dorsalis  pedis,  700 
of  peroneal,  702 
posterior,  617 
of  tibia,  703 
peroneal  nerve,  1059 
Complexus  muscle,  412 
Compressor  narium  minor  mus- 
cle, 372 
urethrae  muscle,  448 
Concentric  corpuscles,  1441 

lamella  of  bone,  39 
Concha  auriculae,  1120 
nasalis  inferior,  113 
media,  98 
superior,  98 
Conchae  sphenoidales,  91,  95 
Conductor  sonorus,  866 
Condylar  foramen,  71,  127,  128, 
132 
fossa,  132 
Condyle,  external,  182 

internal,  182 
Condyles  of  liones.     See  Bones. 
Condyloid  joint,  264,  265 

process  of  mandible,  118 
ConAylus  lateralis  femoris,  225 
tibiae,  233 


Condylus  medialis  fem.oris,  225 
tibiae,  233 
occipitalis,  71 
Confluence  of  sinuses,  72,  724 

I  ( 'niijhu  „»  .sinuum,  72,  724 
( 'u]i|iil;:i1  ligaments,  271 

r„i:j:,,,aln,   215 

Conjugate  diameter  of  pelvis,  215 
Conjunctiva,  1114 

applied  anatomy  of,  1118 

fornices  of,  1115 

glands  of,  1115 

nerves  of,  1115 
Conoid  ligament,  298 

tulierelo,  169 
Constriction  lobe  of  liver,  1326 
Constrictions  of  Ranvier,  811 
Constrictor  isthmi  faueium  mus- 
cle, 391  (note) 

muscles,  394,  395 

urethrae  muscle,  448 
Contralateral  tract  cells  of  cord, 

841 
Conus  arteriosus,  557,  574 

elasticus,  1168 

medullaris,  823 
Cooper,  ligament  of,  428,  456 
Cor,  551 

fades  diaphragmatica,  552 
sternocostalis,  551 

margo  acutua,  552 
obtusus,  552 

sulci  longitudinales,  553 

sulcus  coronarius,  553 

longitudinalis  anterior,  553 
posterior,  553 
Coracoaeromial  ligament,  299 
Coracobrachialis  muscle,  468 

surface  form  of,  495 
Coracoclavicular  ligament,  298 
Coracohumeral  ligament,  302 
Coracoid  process,  176 
Cord,  gangliated,  1066 

spermatic,  437,  1375 

spinal.     See  Spinal  cord. 
Corium  of  skin,  1153 

stratum  papillare,  1153 
reticular  e,  1154 
Cornea,  1090 

applied  anatorav  of,  1109 

arteries  of,  1092 

dissection  of,  1092 

nerves  of,  1092 
Corneal  corpuscle,  1091 

spaces,  1091 
Corniculum  laryngis,  1166 
Cornu  ammonis,  929 
Cornua  coccygea,  62 

of  coccyx,  62 

of  lateral  ventricles,  936 

majora  ossei  hyoidei,  154 

minora  ossei  hyoidei,  154 

sacral,  59 

of  spinal  cord,  830 
Cornucommissural  tract,  g37 
Corona  ciliaris,  1094 

dentis,  1204 

glandis,  1388 

radiata,  905,  949 
Coronal  planes  of  body,  34 

suture,  76,  121 
Coronary  arteries,  578.  660 

ligament  of  knee-joint,  336 

plexus  of  nerves,  1073,  1076 

sinus,  555,  708 

valve,  555,  708 

veins.  709 
Coronoid  fossa,  182 

process  of  mandible,  118 
Corpora  albicaniia,  907 

Arantii,  561 

cavernosa,  1386 
bulb  of,  1386 
clitoridis,  1418 
penis,  1386 


1462 


INDEX 


Corpora  mammillaria,  847 
guadrigemina,  894,  897 
Corpus    adiposum    biiccae,    376, 

1200 
albicans,  1400 
Arantii,  559 
callosum,  912,  933 

development  of,  934 

genu  of,  934 

peduncle  of,  928 

rostrum  of,  934 

splenium  of,  934 

tapetuni  of,  938 
cavernosun;!,  artery  of,  676 

urethrae,   13S6 
ciliare,  1094 
costae,  163 
epididymidis,  1378 
femoris,  224 
fibulae,  236 


geniculatum  laterale,  904,  905 


hemorrhagicum,  1400 
Highmori,  1380 
humeri,  ISO 
hypothalamicus,  905 
incudis,  1132 
linguae,  1217 
luteum,  1400 
mammae,  1430 
mandibulae,  115 
maxillare,  101 
■medullare,  888 
OS  sphenoidale,  90 
ossa  metacarpalia,  201 

metatarsalia,  250 
ossei  hyoidei,  153 
ossi's  ischii,  210 

pubis,  212 
pancreaiis,  1338 
phalangii,  204 
resiiformc,  864,  889 
spongiosum,   1386 
sterni,  157 
striatum,  946 
fe'biae,  234 
ulnae,  187 
unguis,  1156 
Mteri,  1404 

fades  vesicles,  1404 
ventriculi,  1272 
vertebrae,  48 
vesicae,  1361 

felleae,  1332 
vitreum,  1105 
Corpuscles,  articular,  817 
bulboid,  817 
colostrum,  1431 
concentric,  1441 
corneal,  1091 
genital,  817 
of  Hassal,  1441 
Herbst's,  816 
■  lamellated,  816 
Malpighian,  1445 
Pacinian,  816 
renal,  1350 
splenic,  1445 
tactile,  816 
touch,       of       Meissner       and 

Wagner,  816 
Vater's,  816 
Corpuscula  bulboidea,  817 
lamellosa,  816 
nervorum  articularia,  817 

genitalia,  817 
tactus,  816 
Corrugator     cutis     ani     muscle, 

453 
supercilii  muscle,  367 
Cortex,  cerebral.  932 

of  kidneys,  1349 

Corti,  canal  of,  1145 

ganglion  of,  1148 


Corti,  ganglion  of,  spirale  of,  1139 

membrane  of,  1147 

organ  of,  1144 

rods  of,  1145 
Cortical  arterial  system,  619 
Corticopontile  tract,  900 
Corticothalamic  fibers,  905 
Costae,  161 

spuriae,  161 

verae,   161 
Costal  cartilages,  165 

pleura,  1183 

process,  50 
Costoaxillary  veins,  732 
Costocentral  articulations,  285 
Costoclavicular  ligament,  296 
Costocoracoid  ligament,  460 

membrane,  459 
Costomediastinal  sinus,  1184 
Costophrenic  sinus,  1184 
Costosternal  articulations,  286 
Costotransverse       articulations, 
284 

ligaments,  284,  285 

foramen,  50 
Costovertebral  articulations,  282 

ligament,  282 
Cotyloid  cavity,  213 

ligament,  325 

notch,  213 
Cowper's  glands,  1396 

development  of,  1426 
Cranial     branches    of    occipital 
artery,  596 

fossa,  138 

indices,  146 

nerves,  972 

periosteum,  364 

region,  fascia  of,  363 
muscles  of,  362 

applied  anatomy  of,  365 
Craniocerebral  topography,  962 
Craniology,  144 

Cranium,  articulations  of  verte- 
bral column  with,  275 

bones  of,  70 

brachycephalic,  146 

cerebrate,  70 

dolichocephalic,  146 

muscles  of,  362 

membranous,   primordial,   141 
Cremaster  muscle,  430 
Cremasteric  arteries,  680 

fascia,  430,  1374 
Crescentic   lobes   of   cerebellum, 

886 
Crest,  ethmoidal,  91 

falciform,  85 

frontal,  78,  124 

of  ilium,  210 

incisor,  105 

of  lacrimal  bone,  137 

nasal,  105,  110^ 

neural,  805 

obturator,  213 

occipital,  70,  72,  132 

of  pubis,  212 

supramastoid,  81 

temporal,  74 

of  tibia,  234 

turbinated,  102,  104,  110 
Cribriform  fascia,  506,  508 

lamina,  1090 

plate  of  ethmoid,  96 
Cricoarytenoid  ligaments,  1169 

muscles,  1172 
Cricoid  cartilage,  1165 
Cricothyroid  artery,  590 

membrane,  1165,  1168 

muscles,  1172 
Cricotracheal  ligaments,   1168 
Crista  anterior  corpus  fibulae,  237 
,  tibiae,  234 

\basilaris,  1144 

T 


Crista  colli  costae,  162 
conchalis,  102,  110 
ethTnoidalis,  104,  110 
fenestrae  cochleae,  1126 
frontalis,  78 
iliaca,  210 
infratemporalis,  92 
interossea,  189 

corpus  fibulae,  237 
radii,  191 
tibiae,  234 
intertrochanterica,  224 
lacrimalis  posterior,  107 
lateralis  corpus  fibulae,  237 
mallei,  1131 

medialis  corpus  fibidae,  237 
nasalis,  105,  110 
obturatoria,  213 
occipitalis  externa,  70 

interna,  72 
sacralis  media,  59 
sphenoidalis,  91 
spiralis,  1145 
supraventricularis,  557 
terminalis  [His],  758 

atrii  dextri,  554,  551,  557 
transversa,  85 
ureihralis,  1370 
vesiibidi,  1137 
Cristae  cutis,  1150 
matricis  unguis,  1157 
sacrales  articulares,  59 
laterales,  60 
Cristi  gaUi,  96,  124 
Crucial  anastomosis,  678,  690 
ligaments,  333 
ridge,  71 
Cruciform  ligament,  275 
Crura  anlhelicis,  1120 
cerebri,  847,  895 
of  diaphragm,  419 
of  ear,  1120 
fornicis,  944 
of  penis,  1386 
Crural  arch,  684 
canal,  684 
cisterna,  969 
nerve,  1049 
ring,  428,  685 
sheath,  683 
Crureus  muscle,  511 

surface  form  of,  543 
Crus  clitoridis,  1418 

kelicis,  1120 
Crusta  of  midbrain,  900 

petrosa,  1212 
Cruveilheir,  glenoid  ligament  of, 

321 
Crypts  of  Lieberkiihn,  1292 
of  Morgagni,  1310 
of  tonsils,  1231 
Crystalline  lens,  1106 

applied  anatomy  of,  1111 
Cuboid  bone,  245 

articulation     of      calcaneus 
with,  347 
of  scaphoid  with,  350 
Culrainal  lobes,  886 
Cuneal  fissure,  924 
Cuneate  columns  of  spinal  cord, 

826 
Cuneiform     bones,     articulation 
of  scaphoid  with,  349 
of  foot,  247,  248 
of  hand,  197 
cartilage,  1166 
Cupola,  1140 
Cupula.  1138,  1140 

pleurae,  1183 
Curvatura  ventriculi  major,  1271 

minor,  1271 
Cusps  of  mitral  valve,  561 
Cutaneous  nerve,  external,  1045 
femoral,  1055 
from  external  popliteal,  1059 


INDEX 


1463 


Cutaneous  nei-ve,  gluteal,  1055 
internal,  1032,  1050 

lesser,  1034 
lateral,  1045 
middle,  1050 
perforating,  1060 
perineal,  1055 
postfemoral,  1054 
Cuticle  of  skin,  1151 
Cuiicula  dentis,  1211 

pili.  1161 
Cutis  vera,  1153 
Cuvirr,  duct  of,  S.W,  764 
Cijmba  conchav,  1120 
Cystic  artery,  661 
duct,  1333 
lymph  nodes,  790 
plexus  of  nerves,  1076 
vein,  754 


Dacryon,  137,  146 
Dartos  of  scrotum,  1373 
Darwin,  tubercle  of,  1120 
Deciduous  t«eth,  1205 
Decussaiio  pyramidiim,  863,  869 
Decussation  of  lemnisei,  870 

of   pyramids   of   medulla   ob- 
longata, 869 
Deglutition,  muscles  of,  397,  399 
Deiters'  cells,  1146 

nucleus,  839 
Deltoid  impression,  180,  181 

ligament,  343 

muscle,  462 

applied  anatomy  of,  463 
surface  form  of,  495 

tubercle,  169 
Demours,  membrane  of,  1091 
Dendraxones,  811 
Dendrites,  804,  809 
Dense  bone,  38 
'Dental  arteries,  601,  602 

canal,  anterior,  102 
inferior.  117 
posterior,  102 

follicle,  1214 

lamina,  1213 

nerves,  984,  989 

papilla,  1214 

sac,  1214 

shelf,  1213 
Dentate  fascia,  930 

gyre,  930 

gray  substance  of,  953 

ligament,  846 
Dentatofasciolar  groove,  930 
Denies,  1204 

canini,  1206 

deddui,  1205 

fades  labialis,  1205 
lingualis,  1205 
masticatoria,  1205 

incisivi,  1206 

molarcs,  1207 

permanentes,   1206 

premolares,  1207 

serotini,  1207 
Dentin,  intertubular,  1211 

of  teeth,  1211 
Dentinal  fibres,  1211 

sheaths,  1211 

tubules,  1211 
Depression,  infrasternal.  166 

Pacchionian,  74 

pterygoid,  118 

trigeminal,  84 
Depressor  alae  nasi  muscle,  372 

anguli  oris  muscle,  374 

labii  inferioris  muscle,  374 
Dermal  bones,  142 
Dermis,  1153 
Descemet,  membrane  of,  1091 


Descendens     hvpoglossi     nerve, 

1014 
Descending  aorta,  653 
colon,  1305 
mesocolon,  1264 
Detrusor  urinee  muscle,  1363 
Development  of  alimentary  tract, 

1245 

aortic  arches,  761 

arteries,  761 

atlas,  63 

axis,  64 

bladder,  1426 

blood-vascular  system,  755 

brain,  850 

carpal  bones,  206 

clavicle,  171 

coccyx,  65 

common  iliac  veins,  764 

corpus  callosum,  934 

Cowper's  glands,  1426 

dorsal  aorta,  762 

ductus  venosus,  764 

ethmoid  bone,  99 

femur,  228 

fibula,  238 

frontal  bone,  80 

generative  organs,  1420 

heart,  755,  760 

humerus,  183 

hyoid  bone,  154 

ilium,  214 

inferior  vena  cava,  765 

ischium,  214 

island  of  Reil,  917 

jugular  veins,  764 

lacrimal  bone,  107 

lymphatic  vessels,  769 

malar  bone,  109 

mandible,  118 

maxilliE,  105 

metacarpal  bones.  206 

metatarsal  bones,  254 

mouth,  1204 

nerve  system,  804 

tissue,  806 

occipital  bone,  73 

OS  innominatum,  214 

palate  bone,  112 

parathyroid  glands,  1440 

parietal  bone,  76 

veins,  764 

patella,  231 

peritoneum,  1245 

phalanges  of  foot,  254 

of  hand,  207 

pharynx,  1234 

portal  veins,  764 

prostate  gland,  1426 

pubis,  214 

radius,  192 

ribs,  165 

sacrum,  65 

salivary  glands,  1227 

scapula,  176 

skeletal  muscles,  361 

skull,  141 

sphenoid  bone.  95 

spinal  cord,  827 

sternum,  159 

sylvian  cleft,  917 

tarsal  bones,  254 

teetli,  1212 

temporal  bone,  88 

tibia,  235 

tongue.  1221 

tonsil,  1232 

turbinated  bone,  114 

ulna,  190 

urethra,  1426 

urinary  organs,  1420 

valves  of  heart,  760 

veins,  763 

ventral  aorta,  761 

vertebrse,  63 


Diii-InpiiicMt  of  vomer,  115 
I)i:m..iK,l  fissures,  920 
l),n,n,i'r  niiliqua  pclvis  niinoHs, 
21G 
transverse  pelvis  minoris,  215 
Diameters  of  pelvis,  215,  216 
Diaphragm,  418 
crura  of,  419 
ligaments  of,  419 
lymphatic  vessels  of,  799 
openings  of,  419,  421 
of  pelvis,  1240      • 
Diaphragma,  418 
scllae,  967 
iirogenitale,  446 
Diaphragmatic  lymph  nodes,  798 

pleura,  1183 
Diaphysis  of  bone,  35 
Diaplexus,  940 
Diarthrosis,  264,  266 
Diastole,  ventricular,  565 
Diaxonic  neurones,  810 
Dieneephalon,  902 
Digastric  fossa,  82,  117,  131 
muscle,  388 
nerve  from  facial,  998 
Digital  arteries  of  foot,  704 
of  hand,  652 
fossa,  223,  1376 
veins,  dorsal,  728,  739 
plantar,  741 
Dilator  naris  muscles,  372 
Diploe,  36 

veins  of,  718 
Diploic  canals,  718 
Discus  arlicularis,  280,  296,  298, 
312 
proligerus,  1400 
Disks,  articular,  260 
interpubic,  294 
optic,  1100 
Dissection  of  axilla,  455 
of  ciliary  body,  1093 
of  cornea,  1092 
of    costocoracoid    membrane, 

459 
of   deep   layer   of   muscles   of 

forearm,  476 
of  inferior  mesenteric   artery, 

666 
of    internal    oblique    muscle, 

428 
of  left  auricle  of  heart,  559 

ventricle  of  heart,  560 
of  meninges  of  brain,  964 
of  muscles  of  abdomen,  423 
of  anterior  femoral   region, 
505 
humeral  region,  467 
scapular  region,  463 
tibiofibular  region,  525 
of  arm,  461 

of  auricular  region,  366 
of  back,  404,  407,  408,  410, 

413 
of  buccal  region,  374 
of  cranial  region,  362 
of  fibular  region,  534 
of  forearm,  471 
of  gluteal  region,  515,  516 
of  hand,  486 
of  infrahyoid  region,  386 
of   internal   femoral   region, 

512 
of  larynx,  1172 
of  lingual  region,  391 
of  mandibular  region,  374 
of  orbital  region,  368 
of  palatal  region,  397 
of  palpebral  region,  366 
of  pectoral  region,  455 
of  pharyngeal  region,  394 
of  plantar  region,  538,  539 
of  posterior  femoral  region, 
522 


1464 


INDEX 


Dissection  of  muscles  of  posterior 
scapular  region,  464 
tibiofibular  region,  528 
of     pterygomandibular     re- 
gion, 379 
of  radial  region,  479 
of  shoulder,  461 
of  superficial  cervical  region, 

381 
of  suprahyoid  region,  388 
of  mylohyoid  muscle,  390 
of  pancreas,  1336 
of  pectoralis  muscles,  459 
of  popliteal  space,  691 
of    rectus    abdominis    muscle, 

433 
of  right  auricle  of  heart,  555 

ventricle  of  heart,  557 
of  spinal  cord,  842 
of  superior  mesenteric  artery, 

663 
of  temporal  nmscle,  378 
of  transversalis  muscle,  432 
Distobuccal  tubercle,  1207 
Distolingual  tubercle,  1207 
Diverticulum  ilei,  1288 

Meckel's,  1288 
Dobies'  line,  356 
Dolichocephalic  cranium,   146 
Dolichofacial  skull,  146 
Dorsal     artery    of     penis,     676, 
1463 
nerve  of  penis,  1061 
region  of  foot,  fascia  of,  537 

muscle  of,  537       ^ 
root  of  spinal  cord,  S23 
veins  of  penis,  746 
Dorsales  poUicis  arteries,  647 
Dorsalis  hallucis  artery,  700 
indicis  artery,  647 
linguae  artery,  591 
nasi  artery,  613 
pedis  artery,  698 

applied  anatomy  of,  699 
surface  marking  of,  699 
scapulae  artery,  639 
Dorso-epitrochlearis  muscle,  407 
Dorsolateral   fissure   of   medulla 
oblongata,  862 
of  spinal  cord,  825 
spinocerebellar  tract  of   cord, 
838 
Dorsomediales  Sakralfeld  [Ober- 

steiner],  836 
Dorsomedian  fissure  of  medulla 

oblongata,  862 
Dorsoparamedian       fissure       of 
spinal  cord,  826 
furrow  of  medulla  oblongata, 
863 
Dorsum  ilii,  207 
linguae,  1217 
nasi,  1079 
sellae,  90,  126 
Douglas,   pouch  of,    1256,    1362, 
1407 
semilunar  fold  of,  430 
Drum  of  ear,  1124 
Duct  of  Bartholin,  1226 
bile,  1333 

of  Cuvier,  550,  764 
cystic,  1333 
ejaculatory,  1385 
excretory,  1385 
galactophorous,  1430 
Gartner's,  1401 
hepatic,  1332 
interlobular,   1226 
intralobular,   1226 
lactiferous,  1430 
lymphatic,  right,  773 
mammillary,  1430 
Miillerian,  1423 
nasal,  1117 

canal  for  orifice  of,  141 


Duct,  pancreatic,  1339 
parotid,   1200 

gland,  1225 
pronephric,  1420 
of  Rivinus,  2261 
of  Santorini,  1340 
seminal,  1383 
Stenson's,  1225 
of  submaxillary  gland,  1226 
thoracic,  771 
thyroglossal,  1219 
Wharton's,  1226 
Ductless  glands,  1435 
Ductuli  aberrantes,  1381 
efferentes  testis,  1380 
Ductus  aberrans  inferior,  1381 

superior,  1381 
arteriosus,  569,  575 
cochlearis,  1144 
coledochus,  1333 
cysticus,  1333 
deferens,  1383 

stratum  externum,  1384 
internum,  1384 
medium,  1384 

tunica  adventitia,  1384 
mucosa,  1384 
niuscularis,  1384 
ejaculaforii,   1385 
endolymphaticus,       86,       1137, 

1141 
excretorius,  1385 
hepaticus,  1332 
lacrimalis  inferior,  1116 

superior,  1116 
lactiferus,  1430 
lymphaticus  dexter,  773 
nasolacrimalis,  1117 
pancreaticus    [Wirsunoi\,    1339 

accessorius,  1339 
paraurethralis,  1370 
parotideus       [Stenonis],    1200, 

1225 
reuniens  [Henseni],  1142 
semicirculares,  1142 
sublingualis  major,  1226 

minores,  1226 
snhmaxillaris  [Whartoni\,  1226 
sudoriferus,  1162 
thoracic-US,  771 
thyroglossus,  1219 
-oenosus,  764 
Duodenal  fossae,  1265 
glands,  1289 
impression  of  liver,  1321 
Duodenojejunal     flexure,     1282, 

1285 
fossaj,  1265 
Duodenomesocolic        ligaments, 

1265 
Duodenopylorio         constriction, 

1270 
Duodenum,  1282 

applied  anatomy  of,  1287 

arteries  of,  1287 

interior  of,  1286 

lymphatic     vessels     of,     793, 

1287 
nerves  of,  1287 
pars  ascendens,  1285 

descendens,  1282 

horizontalis  inferior,   1284 

superior,  1282 
suspensory  muscle  of,  1285 
Dura  of  brain,  964 

arteries  of,  967 

nerves  of,  968 

veins  of,  967 
m.ater  encephali,  964 

spinalis,  843 
of  spinal  cord,  843 
Dural  artery,  596,  597 
nerves,  983,  1005,  1011 
veins,  719 
Duverney,  glands  of,  1420 


E 

Ear,  1119 

antihelix  of,  1120 
fossa  of,  1120 

antitragus  of,  1120 

auditory  canal,  1122 
meatus,   1122 

auricula  of,  1119 

capsules,  cartilaginous,  141 

cochlea  of,  1138 

crura  of,  1120 

drum  of,  1124 

external,  1119 

helix  of,  1119 

incus  of,  1132 

internal,  1136 

labyrinth  of,   1136 

malleus  of,  1131 

membrana  tvnipani,  1128 

middle,  1124 

modiolus  of,  1138 

pinna  of,  1119 

saccule  of,  1141 

semicircular   canals   of,   bonv. 
1137 
membranous,  1142 

stapes  of,  1133 

tragus  of,  1120 

tympanum,  1124 

utricle  of,  1140 

vestibule  of,  1136 
Ectal  arcuate  fibres  of  medulla 

oblongata,  863 
Efferent  root  of  spinal  cord,  823 
Eighth  nerve,  1000 
Ejaculatory  ducts,  1385 
Elastic  cartilage,  ^61 

lamina,  573 

tissue,  vellow,  261 
Elbow,  bend  of,  641 

bones  of,  185 

joint,   anastomosis  of  arteries 
around,  644 
articulation  of,  306 

applied  anatomy  of,  309 
surface  form  of,  309 
bursas  of,  308 
Eleventh  nerve,  1009 

thoracic  vertebra,  55 
Elliptical  recess,  1137 
Embryology,  definition  of,  33 
Eminence,  callosal,  939 

canine,  101 

collateral,  938 

frontal,  76 

hypothenar,  486 

iliopectineal,  210,  213 

of  Jacobson,  1083 

olivary,  90 

parietal,  74 

thenar,  486 
Eminentia  abducentis,  866,  994 

arcuata,  84 

articularis,  81,  131 

conchae,   1120 

fossae  triangularis,  1120 

iliopectinea,  210,  213 

intercondyloidea,  233 

m,edialis,  866 

pyramidalis.  1127 

teres,  866,  994 
Emissaria,  727 
Emissarium  condyloideum,   727 

mastoideum,  727 

occipitale,  727 

parietale,  727 
Emmissary  speech  tract,  957 

veins,  727 
Enamel  cells,  1214 

jeUy,  1214 

of  teeth,  1210 
Enarthrosis,  264,  265,  266 
Encephalocele,  149 
Encephalon,  846 


INDEX 


1465 


End-bulbs  of  Krause,  813,  817 
Endocardial  cushions,  758 
Endocardium,  562 
Endognathion,  106 
Endolympli,   1140 
Endomysium,  355 
Endoneurium,  812 
Endoskeleton,  35 
Endosteum  of  bone,  39 
Endothelium   camerae   anlerioris, 

1092 
Ensiform  appendix,  159 
Entocinerea,  829 
Eosinophiles,  40 
Epactal  bones,  145 
Eparterial     branch       bronchus, 

1177 
Ependymal  cells,  818 
EpicarcHum,  549,  565 
Epicondylus  lateralis,  182,  226 

medians,  182,  226 
Epicranial  aponeurosis,  363 
Epidermis,  1151 

siratuTTi  corneum,  1151 

germinativum       [Malphigii] , 
1152 
Epididymis,  1378 
Epidural  space,  843 
Epigastric  artery,  deep,  680 

applied  anatomy  of,  681 
superficial,  689 
superior,  633 

vein,  742 
Epiglottis,  1167 
Epdmysium.  355 
Epineurium,  812 
Epiotic  portion  of  temporal  bone, 

88 
Epiphyseal  cartilage,  44 

recess,  906 
Epiphyses  of  bone,  35 
Epiphysis,  906 
Epipteric  bone,  145 
Episternal  centres,  160 
Epistropheus,  52 
Episylvian  ramus,  917 
Epithalamus,  907 
Epithelium  corneae,  1091 

germinal,  1399 

lends,  1108 

respiratory,  1195 
Epitrochlear  lymph  nodes,  782 
Epitympanic  recess,  1125 
Eponychium,  1157 
Epoophoron,  1401 
Erector  clitoridis  muscle,  446 

penis  muscle,  444 

spinae  aponeurosis,  410 
muscle,  410 

surface  form  of,  416 
Erythroblasts,  40,  755 
Ethmoid  bone,  96 
Ethmoidal  arteries,  611 

canals,  79,  98 

cells,  79,  97,  98,  139 

crest,  91 

foramen,      structures      trans- 
mitted by,  125,  137 

infundibulum,  99 

notch,  79 

process,  114 


spine,  90,  12.5 
Eustachian  cushion,   1229 
tube,  1127 

canal  for,  1127 
valve,  555 
Excavatio    papillae    nerni    optici, 
1101 
reclouterina     [Douolasi],     1256, 

1414 
rectovesicalis,  1255,  1362 
vesicouterina,  1256,  1407 
Excitoglandular  neurones,  804 
Excitomotor  neurones,  804 


Excretory    apparatus"   of    liver, 
1331 
duct,  1385 
Exognathion,  106 
Exoskeleton,  35 
Expression,  muscles  of,  380 
Exsanguinated    renal    zone    of 

Hyrtl,  665 
Extensor         brevis        digitorum 
muscle,  537 
poUicis  muscle,  483 
carpi  radialis  brevior  muscle, 
479 
longior  muscle,  479 
ulnaris  muscle,  482 
coccygis  muscle,  414 
communis    digitorum    muscle, 

480 
indicis  muscle,  484 
longus  digitorum  muscle,  527 
surface  form  of,  544 
pollicis  muscle,  484 
minimi  digiti  muscle,  481 
ossis  metacarpi  pollicis  muscle, 

482 
proprius  hallucis  muscle,   527 
surface  form  of,  544 
Extracranial  lymphatics,  774 
Extravertebral  veins,  737 
Extremitas  acromialis,  171 

sternalis,  171 
Extrinsic    ligaments    of    larynx, 
1167 
muscles  of  tongue,  393 
Eye,  1086 

appendages  of,  1112 
aqueous  humor  of,  1105 
choroid,   1093 
ciliary  body,  1094 
cornea  of,  1090 
crystalline  lens  of,  1106 
globe  of,  arteries  of,  1108 
lymphatics  of,  1109 
nerves  of,  1 109 
veins  of,  1109 
iris,  1096 

refracting  media  of,  1105 
retina  of,  1100 
sclera  of,  1090 

suspensory  ligament  of,  1087 
tunics  of,  1089 
vitreous  body  of,  1105 
EyebaU,  1086 

fascia  of,  371 
Eyebrows,  1112 
Eyelashes,  1113 
Eyelids,  1112 

applied  anatomy  of,  1118 
canthi  of,  1113 
structure  of,  1113 
surface  form  of,  1117 


F 

Face,  bones  of,  69,  99 
exterior  of,  veins  of,  710 
lymph  nodes  of,  777 
Ij^mphatic  vessels  of,  777 
muscles  of,  362 

surface  form  of,  380 
Facet,  acromial,  of  clavicle,  171 
articular,  of  clavicle,  171 
costal,  171 
Facial  artery,  592 

applied  anatomy  of,  595 

transverse,  598 
nerve,  994 

applied  anatomy  of,  999 

nucleus,  882 
suture,  transverse,  121 
vein,  710 

applied  anatomy  of,  711 

common,  710 

deep,  712 


Facial  vein,  transverse,  712 
Fades  anterior,  101 

corpus  fibulae,  237 

lateralis,  181 

medialis,  181 
articularis  acromialis,   171 

anterior,  52 

calcanei  anterior,  242,  245 
media,  242,  245 
posterior,  239,  245 

carpea,  192 

cuboidea,  243 

fibularis,  233 

inferior,  51,  235 

malleoli,  238 

navicularis,  245 

patellae,  230 

posterior,  52 

sternalis,  171 

superior,  52,  233 

tuberculi  costae,  162 
auricularis,  60,  210 
cerebralis,  74,  78,  79,  92 
convexa  cerebri,  914 
costalis,  172 

diaphragmatica  cordis,  552 
dorsalis,  59,  172,  189 

corpus  radii,  191 
frontalis,  76 
infralemporalis,  101 
lateralis  corpus  fibulae,  237 
radii,  191 
tibiae,  234 
lunata,  213 
malaris,  107 
malleolaris  lateralis,  245 

medialis,  245 
maxillaris.  111 
medialis,  189 

cerebri,  914 

corpus  fibulae,  237 
tibiae,  234 
nasalis,  102,  109,  110 
orbitalis,  79,  102,  108 
palatina,  109 
parielalis,  74 
patellaris,  225 
pelvina,  58 
posterior,  181 

corpus  fibulae,  237 
tibiae,  234 
sternocostalis  cordis,  551 
temporalis,  107 
ureihralis,  1388 
volaris,  189 

corpus  radii,  191 
Falciform  crest,  85 
ligament,  1320,  1324 
margin  of  Bruns,  508 
process  of  fascia  lata,  508 

of  sacrosciatic  ligament,  291 
Falcula,  967 
Fallopian  tube,  1401 

ampulla  of,  1401 

applied  anatomy  of,  1402 

arteries  of,  1402 

fimbria  of,  1401 

infundibulum  of,   1401 

isthmus  of,  1401 

lymphatic    vessels    of,    797, 
1402 

nerves  of,  1402 

pa^dliou  of,  1401 

structure  of,  1402 

veins  of,  1402 
False  pelvis,  215 

suture,  264 
Falx  cerebelli,  967 
cerebri,  914,  966 
Fascia  or  Fascise,  355,  360 
of  abdomen,  424,  428 
anal,  446,  450 
antebrachial,  471 
aponeurotic,  361 
of  arm,  461,  467 


14G6 


INDEX 


Paseia  or  Fascise,  axillary,  456, 

633 
of  back,  404 
bicipital,  469,  730 
brachial,  467 

buccopharyngeal,  377,  394 
of  Camper,  424 
cervical,  382,  383 
clavipectoral,  459 
of  CoUes,  425,  441 
covering  quadratus  lumborum, 

439 
of  cranial  region,  363 
cremasteric,  430,  1374 
cribriform,  506,  508 
deep,  361 
dentate,  930 
endopelvina,  450 
of  eyeball,  371 
of  foot,  536 

dorsal  region,  537 
of  forearm,  471 
of  hand,  486 
of  hip,  515 
iliac,  592 
infraspinatus,  464 
infundibuliform,  436,  1374 
intercolumnar,  427,  1374 
intercostal,  417 
ischiorectal,  446 
of  leg,  525 

of  lower  extremity,  501 
lumbar,  409 
masseteric,  377 
of  neck,  380 
nuchse,  406 
obturator,  448 
orbital,  371 
palmar,  488 
parotid,  377 
pectoral,  456 
pelvic,  448 
of  pelvic  outlet,  440 
plantar,  537 
pretracheal,   384 
prevertebral,  384 
propria,   1374 
of  pyriformis,  448 
rectovesical,  1361 
renal,  1348 
of  Scarpa,  424 
of  shoulder,  461 
Sibson's,  1183 
spermatic,  427,  437,  1374 
subscapular,  463 
superficial,  360 
supraspinatus,  464 
temporal,  378 
of  thigh,  506 

of  thoracic  region,  455,  456 
of  thorax,  416 
triangular,  425,  428 
of  trunk,  403 
of  upper  extremity,  454 
Fascia  or  Fasciae,  antibrachii,  471 
axillaris,  456,  633 
brachii,  467 

buccopharyngea,  377,  394 
bulbi  [Tenoni],  1086 
colli,  382 

coracoclavicularis,  459 
cremasterica,  430,  1374 
cribrosa,  506 
cruris,  503 

diaphragmaiis  urogenitalis  in- 
ferior, 446 
superior,  449 
dorsalis  pedis,  537 
iliaca,  502 
inferior    diaphragmaiis    pelvis, 

454 
infraspinata,  464 
lata,  506 

parotideomasseterica,  377 
■praeoertebralis,  384 


Fascia  or  Fasciae,  subscapularis, 
463 

supraspinata,  464 

temporalis,  378 

transversalis,  436 
Fasciculus  albicantiothalami,  905 

anterolateralis  superficialis 

[Gowersi],  838    * 

atrioventricularis,  564 

cerebellospinalis,  838 

cerebrospinalis  anterior,  839. 
lateralis,  838 

cunealus  [Burdachi\,  835 

gracilis  [Golli],  835 

intermedins  of  Lowenthal  and 
Bechterew,  839 

lateralis  proprius,  839 

longitudinalis  inferior,  955 
superior,  955 

marginalis,  835 

pedunculomammillaris,  907 

perpendicular,  955 

rectus,  955 

retroflexus,  898,  906 

ihalamomammillaris,  905,   907 

uncinafus,  955 
Fasciola  cinerea,  930 
Fat  collagen,  42  »> 
Fauces,  isthmus  of,  1203 

pillars  of,  1203 
Female  breast,  1428 

reproductive  organs,  1397 

urethra,  1370 
Femoral  arches,  427,  436 

artery,  683 

applied  anatomy  of,  687 

deep,  689 

surface  marking  of,  687 

canal,  503,  684 

fossa,  1315 

hernia,  1317 

ligament,  508 

nerves,  cutaneous,  1055 

region,    anterior,    muscles    of, 
505 
applied  anatomy  of,  512 
internal,  muscles  of,  512 

applied  anatomy  of,  515 
posterior,  muscles  of,  522 

ring,  428,  685 

sheath,  503,  683 

spur,  227 

vein,  742 
Femur,  221 

applied  anatomy  of,  229 

condyles  of,  225 

distal  extremity  of,  225 

linea  aspera,  224 
quadrati,  224 

popliteal  surface  of,  224 

proximal  extremity  of,  221 

ridges  of,  224 

shaft  of,  224 

spiral  line  of,  224 

surface  form  of,  228 

trochanters  of,  222 

trochlea  of,  225 

tubercle  of,  224 

tuberosities  of,  226 
Fenestra  cochleae,  1126 

ovalis,  1126,  1137 

rotunda,  85,  1126,  1140 

vestibuli,  85,  1126,  1137 
Fenestrated  membrane  of  Henle, 

573 
Fetal  circulation,  570 

left  superior  vena  cava,  550 

lungs,  1194 
Fetus,     hypogastric     artery     in, 
670 

pelvis  in,  219 

vascular    system    in,     peculi- 
arities of,  568 
Fibrae  arcuatae,  1091 
externae,  863,  864 


Fibrae  arcuatae  internae,  864 

cerebello-olivares,  873 

intercrurales,  427 

lentis,  1107 
Fibres,  arcuate,  873 

of  medulla  oblongata,  863 

of  auricles  of  heart.  562 

cerebello-olivary,  873 

of  cerebellum,  891 

corticothalamic,  905 

dentinal,  1211 

frontothalamic,  950 

intercolumnar,      of      external 
abdominal  ring,  427 

muscle,  cardiac,  355 
plain,  355 
unstriped,  355 

nerve,  centripetal,  810 
of  cerebral  cortex,  952 
glia,  818 
of  spinal  cord,  832,  834 

olivocerebellar,  873 

osteogenetic,  42 

Purkinje's,  357,  565 

Remak's,  812 

striatothalamic,  950 

thalamocortical,  905 

thalamofrontal,  950 

thalamostriate,  950 

tracts  of  midbrain,  900 

in  pars  dorsalis  pontis,  876 
in  tegmentum  of  midbrain, 
898^ 

of  ventricles  of  heart,  563 
Fibrillae,  356 

peripheral,  816 

terminal,  816 
Fibrocartilages,  259,  260 

articular,  260 

circumferential,  261 

connecting,  261 

intervertebral,  269 

semilunar,  334,  335 
Fibrocartilagines    interoerlebrales, 

269 
Fibroelastic   tissue,   subendothe- 

lial,  573 
Fibrous  pericardium,  548 

sheaths  of  flexor  tendons,  539 
Fibula,  236 

applied  anatomy  of,  239 

nutrient  artery  of,  702 
canal  of,  237 
foramen  of,  237 

surface  form  of,  238 
Fibular  artery,  698 

region,  muscles  of,  534 
Fifth  lumbar  vertebra,  57 
-  nerve,  978 

ventricle,  934,  945 
Fila  olfactoria,  927 

radicularia,  1013 
Filaments,  temporomalar,  109 
Filtration  angle,  1105 
Filum  durae  spinalis,  843,  845 

externuTn,  825 

internum,  825 

terminale,  825 
Fimbria,  929,  930,  943 

ovarica,  1401 

tubae,   1401 
First  nerve,  973 

thoracic  vertebra,  54 
Fissura  antitragohelicina,    1 120 

calcarina,  919 

cerebri  lateralis  [Sylvii],  916 

collateralis,  924 

ectorhinalis,  924 

inflexa,  920 

longitudinalis  cerebri,  847,  914 

mediana  anterior  [medullae  ob- 
longatae],  861 
[medullae  spinalis] ,  825     , 
'  T  [medulla  oblongata] , 


INDEX 


1467 


Fii^snm  urripilaUs,  91S 
url.,l.:hs  ,„hi;,.i;  134 
p„r:M„n,.,l:,l,   1123 

IP  I, r,,.,!,,!,...   122 

p,lruii/„ii"",ir„  laiaseri],  1126 
I,(,>lii,iiKili>,  '.f2i 

rliiiii.':i,  :ar, 

SI,h,„.,„rr,i„l„IU,    122 

»;./,.„. .,„/,.;n-/.    122 

<™„.s,,,.s»  r,/t/»-i,  847 

iymjiiinninn^ituidea,  87 

vestibuli,  1137,  1140 
Fissure  or  Fissures,  amygdaline, 
924 

antitragohelicina,   1120 

auricular,  131 

basisylvian,  917 

of  Bichat,  940 

calcarine,  919 

central,  918 

of  cerebellum,  885 

cerebral,  915 

choroid,  940 

cireuminsular,  917,  925 

collateral,  924 

cuneal,  924 

diagonal,  920 

of  frontal  lobe,  919 

Glaserian,  88,  1126 

inflected,  920 

interlobar,  916 

intermedial,  923  ' 

intraprecuneal,  924 

of  liver,  1322 

of  lungs,  1190 

medifrontal,  919 

meditemporal,  924 

of  medulla  oblongata,  861 

occipital,  918,  924 

olfactory,  920 

orbital,  93 

orbitofrontal,  919 

paracentral,  920 

paramesal,  919 

parietal,  923 

petrosphenoidal,   122 

petrotympanic,  88,  1126 

postcalcarine,  919 

postcentral,  923 

postinsular,  925 

postrhinal,  925 

precentral,  919  ■ 

precuneal,  923 

preinsula,  925 

pterygomaxillary,  134 

radiate,  920 

rhinica,  925 

of  Rolando,  918 

rostral,  920 

of  Santorini,  1122 

sphenoidal,  93,  126,  134 

sphenomaxillary,  109,  134,  137 

of  spinal  cord,  825 

sternal,  161 

subcentral,  923 

subfrontal,  919 

subrostral,  920 

subtemporal,  924 

supercentral,  919 

superfrontal,  919 

sylvian,  916 

of  temporal  lobe,  924 

of  tragus  of  car,  1121 

transinsular,  925 

transorbital,  921 

transparietal,  923 

transprecentral,  920 

transtemporal,  924 

tympanomastoid,   87 
Fixation  muscles,  359 
Flat  bones,  36 

Flechsig,  nucleus  semilunaris  of, 
905 

oval  bundle  of,  836 
Flexor  accessorius  muscle,  539 


Flexor  brevis  digitorum  muscle, 
538 
surface  form  of,  544 
haUucis  muscle,  541 
minimi    digiti  muscle,  foot, 
541 
hand, 494 
poUicis     muscle,     490,     492 
(note) 
carpi  radialis  muscle,  473 
surface  form  of,  496 
ulnaris  muscle,  474 

surface  form  of,  496 
longus  digitorum  muscle,  533 
hallucis  muscle,  532 
poUicis  muscle,  476 
profundus    digitorum    muscle, 

476 
sublimis     digitorum     muscle, 
475 
surface  form  of,  496 
tendons,    fibrous    sheaths,  of, 
539 
at     wrist,     synovial     mem- 
branes of,  486 
Flexura  coli  dextra,  1303 
sinistra,  1303 
duodenojejunalis,  1285 
Flexures  of  brain  tube,  855 
of  colon,  1303 
hepatic,  1296,  1303 
sigmoid,  1296,  1303 
Floating  ribs,  161 
Floccular  fossa,  86,  128 
Flocculi  secundarii,  888 
Flocculus  of  cerebellum,  888 

peduncles  of,  888 
Flood's  ligament,  302 
Floor     of    fourth     ventricle     of 

brain,  865 
Flumina  pilorum,  1159 
Folia,  884 

linguae,   1217 
Folium  vermis,  886 
Follicles,  agminated,  1292 

solitary,  1292 
Folliculus  pili,  1159 
Fontana,  spaces  of,  1092,  1097 
Fontanelles,  143 
anterior,  76,  142 
bregmatie,  143 
lateral,  144 
posterior,  76,  143 
Foot,  arch  of,  longitudinal,  254 
transverse,  255 
arteries  of,  699,  703 
bones  of,  239 

applied  anatomy  of,  256 
surface  form  of,  255 
club,  256 
construction    of,    as   a   whole, 

254 
fascia  of,  536 
flat,  255 
muscles  of,  536 
phalanges  of,  252 

articulations  of,  354 
veins  of,  739,  741 
Foramen,  apical,  1212 
caroticum  externum,  86 

internum,  84 
carotid,  84,  86 

cecum,  7S,  96.  124,  862,  1217 
condylar,  71,  127.  12S,  132 
costot^ans^'er^e,  50 
ethmoidal.   137 
of  Husclike,  89 
incisor,  105 
infraorbital,   101,  136 
intervertebral,  49 
jugular,  71,  131 
of  Key  and  Retzius,  845,  969 
of  Langer,  783 
of  Luschka,  867,  969 
of  Majendie,  845,  867,  969 


Foramen,  malar,  107,  136 
of  mandible,  117 
mastoid,  82,  128,  133 
mental,  116,  136 
of  Monro,  936 
nasal,  99 
nutrient,  of  clavicle,  170 

of  fibula,  237 

of  metacarpal  bones,  201 

of  radius,  191    . 

of  tibia,  234 

of  ulna,  189 
obturator,  213 
olfactory,  138,  139 
optic,  90,  94,  126 
palatine,  121 
parietal,  74 
pterygospinous,  383 
sacral,  59 
sacrosciatic,  great,  211,  292 

lesser,  211,  292 
of  Scarpa,  105,  128 
sphenopalatine,  112,  134,  138, 

140 
spinal,  49 

of  Stenson,  105,  128 
sternal,  159,  161 
stylomastoid,  87,  131 
supracondyloid,  181  (note) 
supraorbital,  135 
supratrochlear,  182 
temporomalar,  109 
thyroid,  213 
transverse,  50 
vertebral,  49 
vertebrarterial,  50 
Vesalii,  92,  127 
of  Win.slow,  1259 
Foramen  apicis  dentis,  1212 
caecum     linguae     [Morgagnii\, 

1217 
cecum,  78,  96,   124,  862,   1217 
diaphragmatis  sellae,  967 
epiploicum,  1245,  1258 
ethmoidale  anterius,  79 

posterius,  79 
infraorhitale,  101 
ischiadicum  majus,  211,  292 

minus,  211,  292 
jugulare,  127 
lacerum,  127 

anterius,  93,  126 

medium.,  127,  131 

pOsteriv^,  71,  73,  127 
magnum,  71,  127,  131 
mandihulare,  117 
mastoideum.,  82 
mentale,  116 


obturalum,  213 

occipitale  magnum,  71 

opticum,  90 

ovale,  92,  127,  131,  557,  759 

parietale,  74 

rotundum,  92,  127,  134 

singulare,  85,  1148 

sphenopalatinum,  112 

spinosum,  92,  127,  131 

stylomastoideuni,  87 

transversarium,  50 

venae  cavae,  421 

verlehrnU,  49 

zygomnlii-iilrmpnrak;  108 
Fornmuin  ,,h,nlu,-;,i.  102 

intern  rlrhr.il in.    Is,  49 

sacraliii  anicriosa,  59 
posteriosa,  60 

venarum minimarum  [Thebesii], 
555 
Forearm,  bones  of,  185 

fascia  of,  471 

muscles  of.  471 
Forebrain,  902 

development  of,  852 

structure  of,  902 


1468 


INDEX 


Forebrain,  thalami  of,  902 
Foregut,  1247 

Formalio  reticularis,  872,  897 
alba,  872 
grisea,  872 
Fornices  conjunctivae,  1115 
Fornicolumns,  954 
Fornix,  913,  942 
body  of,  942 
periphericus,  959 
pharyngis,  1230 
pillars  of,  943,  944 
Fossa  of  acetabulum,  213 
antecubital,  641 
of  antihelix  of  ear,  1120 
canine,  101,  136 
condylar,  131 
coronoid,  182 
cranial,  138 
digastric,  82,  117,  131 
digital,  223,  1376 
duodenal,  1265 
duodenojejunal,  1266 
femoral,  1315 
floccular,  86,  128 
glenoid,  87,  137 
hyaloidea,  1105 
hypophyseos,  90,  909 
iliac,  209 

ileoappendicular,  1267 
ileocecal,  1267 
iliocolic,  1266 
incisive,  101,  135 
incisor,  116 
incudis,  1127 
infraspinous,  172 
inguinal,  1315 
intersigmoid,  1267 
ischiorectal,  454 
jugular,  86,  87 
lacrimal,  79 
of  Landzert,  1266 
mesocolic,  1266 
nasal,  138,  1081 
occipital,  128 
olecranon,  182 
orbital,  138 
palatine,  105,  128 
paraduodenal,  1266 
pararectal,  1256 
paravesical,  1361 
pericecal,  1266 
pterygoid,  94,  109 
radial,   182 
retroduodenal,   1266 
retroperitoneal,   1265 
rhomboidal,  865 
of  Rosenmiiller,  1230 
scaphoid,  94,  130,  1120 
sigmoid,  82 
of  skull,  anterior,  123 
inferior  occipital,  128 
middle,  125 
posterior,  127 
sphenomaxillary,  109,  134 
subcecal,  1267 
sublingual,  117 
submaxillary,   117 
subscapular,  172 
supraspinous,   172 
supratonsUlar,  1231 
temporal,  92,  134 
of  Treitz,  1265 
trochanteric,  223 
trochlear,  79 
vesicalis,  1321 

zygomatic,  92,  101,  130,  134 
Fossa  acetabuli,  213 
cdnina,  101 


coronoidea,  182 
cranii  anterior,  123 
media,  125 
posterior,  127 
dinastrica,  117 


Fossa  ductus  venosi,  1323 

glandulae  lacrimalis,  79 

iliaca,  209 

infraspinata,  172 

infratemporalis,  133 

intercondyloidea,  225 
anterior,  233 
posterior,  233 

ischiorectalis,  454 
jugularis,  86,  87 

longitudinalis  sinistra,  1322 

mandibularis,  87 

mastoidea,  82 

navicularis,  1368,  1416 
urethrae,  1368 

olecrani,  182 

ovalis,  508,  557 

margo  falciformis,  508 

ovarii,  1398 

pterygopalatina,  134 

radialis,  182 

rhomboidea,  865 

sacci  lacrimalis,  107 

scaphoidea,  94 

subarcuata,  86 

subscapularis,  172 

supraspinMa,  172 

supratonsillaris,  1231 

temporalis,  92,  134 

triangularis  [auriculae],  1120 

trochanterica,  223 

venae  cavae,  1323 
umbilicalis,  1321 

vesicae  felleae,  1321 
Fossae  frenuli,  1389 
Fossulae  tonsillares,  1231 
Fountain  decussation,  900 
Fourchette,   1416 
Fourth  nerve,  977 

ventricle  of  brain,  864 
Fovea  articularis  superior,  51 

capitis  femoris,  221 

capituli  radii,  190 

centralis,  1100,  1104 

costalis  inferior,  53 
superior,  53 
transversalis,  54 

dentis,  50 

hemieUiptica,  1137 

inferior,  866 

inguinalis  lateralis,  1315 
Tnedialis,  1315 
supravesicalis,  1315 

mediana,  866 

pterygoidea,  118 

sublingualis,  117 

submaxillaris,  117 

superior,  866 

trigemini,  866 

trochlearis,  79 
Foveola     grannlaris     [Pacchioni\, 

970 
Foveolae  gastricae,  1275 

granulares  [Pacchio7ii\,  74 
Frankfort,  horizontal  line  of,  146 
Frenulum  of  cerebellum,  891 

clitoridis,  1416 

of  clitoris,  1416 

Giacomini,  930 

of  ileocecal  valve,  1301 

labii  inferioris,  1200 
superioris,  1200 

labiorum  pudendi,  1416 

linguae,  1217 

of  penis,  1389 

praeputii,  1389 

valvulae,  895 
coli,  1301 
Frenum  linguae,  1201,  1217 
Frontal  air  sinus,  79 

artery,  598,  612 

anterior  internal,  615 
ascending,  617 
inferior  external,  617 
internal,  615 


Frontal  artery,  middle  internal, 
615 
posterior  internal,  615 

bone,  76 

crest,  78,  124 

diploic  vein,  718 

eminence,  76 

lobe,  919 

fissures  of,  919 
gyre  of,  921 

nerve,  980 

planes  of  body,  34 

process  of  malar  bone,  108 

suture,  121 

vein,  710 
Frontalis  muscle,  363 
Frontoethmoidal  suture,   122 
Frontolacrimal  suture,  122 
Frontomalar  suture,  121 
Frontomaxillary  suture,  122 
Frontoparietal  operculum,  917 

suture,  121 
Frontopontile    tract,    900,    950,. 

957 
Frontosphenoidal  suture,  121 
Frontothalamic  fibers,  950 
Fundiform  ligament  of  Retzius, 

536 
Fundus  folliculi  pili,  1159 

glands,  1276 

tympani,  1125 

uteri,  1404' 

vesicae,  1361 
felleae,   1332 
Funicular  process,  1379 
Funiculi  niedullae  sjnnalis,  826 
Funiculus  anterior,  827 

cuneaius,  827,  835,  863 

gracilis,  827,  835,  863 

lateralis,  817,  835,  864 
[Rolandi],  872 

separans,  866 

spermaticus,  437,  1375 
Furcula,  1221 
Fusiform  muscles,  358 


G 

Galactophoeotjs  duct,  1430 
Galea  aponcurotica,  363 
Galen,  veins  of,  720,  943 
Gall-bladder,  1332 

arteries  of,  1334 

lymphatic     vessels     of,     795, 
1334 

nerves  of,  1334 

veins  of,  1334 
Ganglia  aberrantia,  1014 

coeliaca,  1073 

trunci  sympathici,  1063 
Gangliated  cord,  1066 
cervicocephalic,  1066 
lumbar,  1071 
thoracic,  1070 
Ganglion,  aberrant,  1014 

accessory,  1014 

of  Andersch,  1002 

aorticorenal,   1073 

of  Bochdalek,  984 

cardiac,  of  Wrisberg,  1072 

carotid,   1066 

cell,  807 

cervical,  1066,  1069 

ciliary,  982 

coccygeal,  1072 

of  Corti,  1148^ 

Gasserian,  978 

geniculate,  996 

inferior,   1002 

interpeduncular,  906 

jugular,  1002 

lenticular,  982 

Meckel's,  984 

ophthalmic,  982 


INDEX 


1469 


Ganslion,  otic,  989 
petrous,   1002 
phrenic,   1074 
of  Scarpa,  1000,  1147 
semilunar,  978,  1073 
of  Sonimering,  896 
sphenopalatine,       982,       984, 

986 
spinal,  1016 
spiral,  1000,  1148 

of  Corti,  1139 
submaxillary,  990 
superior,  1002 
of  Valentin,  984 
vestibular,  1000 
Ganylion  cardiacum    [WrisberOil, 
1072 
cervicale  inferius,  1069 
viedium,  1069 
supcrius,  1066 
ciliarc,  982 

radix  brevis  ganglii  ciliaris, 
982 
longa  ganglii  ciliaris,  981, 

982 
sympathetica  ganglii  cilia- 
ris, 982 
coccijgcum  impar,   1063,   1072 
gcnicuH,  996 
habenulae,  906 
Jugulare,  1005 
itiesentericuin  superius,  1076 
nodosum,  880,  1005 
oticum,  989 

ramus  anastomoticus  cum  n. 
auriculotemporali,  990 
pcirosum,  880 
phrenicum,  1074 
semilunare  [Gasseri],  978 
sphenopalatinum,  984 

ratni  nasales  posterioris  in- 

feriores,  986 

superiores,  986 


spirale,  1148 
cochleae,  1139 

splanchnicimi,  1071 

submaxillare,  990 

rami  coniynunicanies  cum.  n. 
linguali,  990 
submaxillares,  990 

superius,  880 

vestibulare,  1147 
Ganglionic    arteries,     614,     617, 

618 
Gartner's  duct,  1401 
Gasserian  ganglion,  978 
Gaster,  1270 
Gastric  artery,  660 

crypts,  1275 

glands,  1276 

impression  of  liver,  1321 

lymph  nodes,  790 

nerve,  1007 

pits,  1275 

plexus  of  nerves,  1076 

veins,  753 
Gastrocnemius  muscle,  528 

surface  form  of,  544 
Gastrocolic      omentum,       1254, 

1261 
Gastroduodenal  artery,  661 

plexus  of  nerves,  1076 
Gastroepiploic  arteries,  661 

lymph  nodes,  790 

plexus  of  nerves,  1076 

A'eins,  753 
Gastrohepatic    omentum,    1254, 

1260 
Gastrosplenic  omentum,  1261 
Gelaiinosa  centralis,  829,  831 

Rolandi,  829,  833 
Gemellus  inferior  muscle,  520 

superior  muscle,  520 
Gcmmules,  810 


Generative  organs,  development 

of,  1420 
Genial  tubercles,  117 
Geniculate   body,    external,    905 
internal,  895 
lateral,  910 

ganglion,  996 

tract,  950 
Geniculum  n.  facialis,  996 
Geniohyoglossus  muscle,  391 
Geniohyoid  muscle,  390 
Genital  corpuscles,  817 

gland,  1423 

ridge,  1423 
Genitals,      external,     lymphatic 

vessels  of,  790 
Gennari,  fiber  band  of,  953 
Genu  corporis  callosi,  934 

facialis  internum,  882 
Gerlach,  valve  of,  1299 
Germinal  centre,  1292 

epithelium,  1399 

nerve  cells,  806 

spot,  1400 

vesicle,  1400 
Gianuzzi,  crescents  of,   1227 
Gimbernat's  ligament,  426,  428 
Gingivae,  1200 
Ginglymus,  264,  265 
Girald(5s,  organ  of,  1384 
Glabella,  77,  134,  146 
Gladiolus,  159 
Glands,  apical,  1219 

of  Bartholin,  1420 

buccal,  1200 

cardiac,   1278 

carotid,  586,  1450 

ciliary,  1162 

circumanal,  1162 

coccygeal,  1450 

of  conjunctiva,  1115 

Cowper's,  1396 

ductless,  1435 

duodenal,  1289 

of  Duverney,  1420 

fundus,  1276 

gastric,  1276 

genital,  1423 

intestinal,  1292 

labial,  1200 

lacrimal,  1115 

of  larynx,  1174 

of  Lieberkiihn,  1292 

of  Littr^,  1369 

Luschka's,  1450 

lymphatic.    See  Lymph  nodes. 

mammary,  1428 

Meibomian,  1114 

molar,  1200 

of  Moll,  1113 

of  Montgomery,  1429 

of  Nuhn  and  Blandin,  1219 

oesophageal,  1239 

oxyntic,  1276 

palatine,  1202 

parathyroid,  1439 

parotid,   1223 

peptic,  1276 

prostate,  1391 

pyloric,  1278 

salivary,  1223 

sebaceous,  1113,  1161 

serous,  1219 

sublingual.  1226 

submaxillary,  1225 

suburethral,  1420 

sudoriferous,   1161 

suprarenal,  1447 

sweat,  1161 

tarsal,  1114 

thymus,  1440 

thyroid,  1435 

of  trachea,  1178 

trachoma,  1115 

of  von  Ebner,  1219 


Glands,  vulvovaginal,  1420 
Glandula  lacrimalis,  1115 
inferior,  1116 
superior,  1116 

parotis,  1223 
accessoria,  1224 

sublingualis,  1226 

submaxillaris,  1225 

thyreoidea,  1435 
accessoriae,  1436 

vestibularis  major   [BarthoKni\, 
1420 
Glandulae  areolares,  1429 

buccales,  1200 

bulbourethralis,  1396 

ceruminosae,  1123 

cervicales  uteri,  1410 

ciliares  [Molh'\,  1113,   1162 

circumanales,  1162,  1309 

duodenales  [Brunneri],  1292 

gastricae  propriae,  1276 

inlestinales  [LieberkUhni\,  1292 

labialis,  1200 

linguales  anieriores,  1219 

tnolares,  1200 

mucosae  [Krausei],  1115 

olfactoriae,  1085 

palatinae,  1202 

paraurethrales,  1370 

pharyngeae,   1233 

praeputii,  1389 

pyloricae,  1278 

sebaceae,  1113,  1161 

sudoriferae,  1161 

suprarenaies  accessoriae,  1448 
fades  anterior,  1447 
posterior,  1448 

suprarenalis,  1447 

tar  sales  [Meibomi\,  1114 

tracheales,  1178 

Tysonii  odoriferae,  1389 

urethrales,  1369 

uterinae,  1410 

vestibulares  minores,  1416 
Glandular  artery,  593 
Glans  clitoridis,  1419 

penis,  1387 
Glaserian  fissure,  88,  1126 
Glenohumeral  ligament,   .302 
Glenoid  fossa,  87,  131 

ligament,  176,  303 
of  Cruveilheir,  321 

surface  of  scapula,  176 
GHa  cells,  818 

fibers,  818 
Ghding  joints,  264 
Gliosa  centralis,  829 

cornualis,  829,  833,  870 
Globus  pallidus,  948 
Glomus  carotic.um,  1450 

coccygeum,  1450 
Glossoepiglottic  fold,  1167 
Glossopharyngeal  nerve,  1001 
applied  anatomy  of,  1003 
nucleus,  880 
Gluteal  aponeurosis,  516 

artery,  678 

nerves,  1054,  1055 

region,  muscles  of,  515 

ridge,  224 

veins,  743 
Gluteofemoral  bursse,  327 
Gluteus  maximus  muscle,  515 
bursse  of,  516,  517 
surface  form  of,  543 

medius  muscle,  516 

surface  form  of,  543 
Gnathic  index  of  skull,  147 
Golgi,  cells  of,  808,  952 

organs  of,  817 
Goll,  column  of,  827,  835 
Gomphosis,  264 
Gonion,  146 
Gower's,  tract  of,  838 
Graafian  folhcles,  1399 


1470 


INDEX 


Gracile   column   of   spinal   cord, 
826 

lobes,  887 
Gracilis  muscle,  512 
bursa  of,  513 
surface  form  of,  543 
Granulationes  arachnoidales  [Pac- 

chioni],  721,  970 
Gray  commissure  of  spinal  cord, 
830 

masses  of  cerebellum,  888 

substance  of  spinal  cord,  829 
Grooves,  auriculoventricular,  553 

basilar,  73 
of  pons,  864 

bicipital,   180 

carotid,  126 

cavernous,  91 

dentatofasciolar,  930 

infraorbital,  102,  136 

interauricular,  553 

interventricular,  553 

lacrimal,    102,    104,    107,    137, 
138 

musculospiral,  180 

mylohyoidean,  117 

nasopalatine,  114 

obturator,  211,  213,  214 

occipital,  82,  131 

oesophageal,  421 

optic,  90,  126 

peroneal,  246 

popliteal,  226 

pterygopalatine,  110,  111 

pyramido-olivary,  863 

sacral,  60 

of  spinal  cord,  825 

subclavian,   171 

subcostal,  163 

ulnar,  182 

vertebral,  67 
Growth  of  bone,  42 
Guhernaculum  testis,  1378 
Gudden,  infracommissure  of,  895 

tractus  peduncularis  transver- 
sus,  895 
Guerin,  valve  of,  1369 
Gullet,  1236 
Gums,  1200 
Gustatory  areas  of  brain,  960 

cells,  1149 

hair,  1149 

path,  1003 
Gyre,  angular,  923 

callosal,  920,  921 

cerebral,  915 

dentate,  930 

hippocampal,  925 

marginal,  923 

medifrontal,  921 

meditemporal,  924 

mesorbital,  920,  922 

olfactory,  928 

paracentral, '921 

paraoccipital,  923 

parietal,  923 

postcentral,  923 

postparietal,  923 

precentral,  921 

preinsular,  926 

subcalcarine,  925 

subcallosal,  928 

subcollateral,  925 

subfrontal,  921 

subtemporal,  925 

superfrontal,  920,  921 

supertemporal,  924 

transtemporal,  924 

uncinate,  925 
Gyri  Andreae  Retzii,  930 
Gyrus  ambiens,  928 

angularis,  923 

breves  insulae,  926 

centralis  anterior,  921 
posterior,  923 


Gyrus  dentatus,  929 
epicallosus,  930 
fasciolaris,  930 
fornicatus,  921 
frontalis  inferior,  921 

medius,  921 

superior,  921 
fusiformis,  925 
hippocampi,  925 
lingualis,  925 
longus  insulae,  915 
occipitotemporalis,  925 
rectus,  922 
semiluTmris,  928 


supracallosus,  931 
supramarginalis,  923 
temporalis  inferior,  925 

medius,  925 

superior,  925 


Habenulah  commissure,   906 
Hairs,  1159 

auditory,  1143 

bulb,  1159 

cells, '1143 
outer,  1146 

follicle,  1159 

fundus  of,  1159 

gustatory,  1149 

papilla,  1159 

root  of,  1159 

sheaths  of,  1160 

streams,  1159 

whirlpools,  1159 
Hallucis,  etymology  of,  525 
Hamstring  muscles,  522 

applied  anatomy  of,  525 
Hamular  process,  94,  107,  130 
Hamulus,  1140 

lacrimalis,  107 

laminae  spiralis,  1140 

ossis  hamati,  200 

pterygoideus,  94 
Hand,  arteries  of,  647 

bones  of,  194 
lower  row,  198 
upper  row.  196 

bursce  of,  487 

fasciae  of,  486 

ligaments  of,  315 

muscles  of,  486 

phalanges  of,  204 
articulations  of,  321 

veins  of,  plexus  of,  729 
superficial,  728 
Hard  palate,  1202 
Harelip,  151 
Hasner,  valve  of,  1117 
Hassal,  corpuscles  of,  1441 
Haversian  canal,  39 

lamella  of  bone,  39 
Head,  arteries  of,  583 

lymph  nodes  of,  774 

muscles   of,    surface   form   of, 
380 

veins  of,  710 
Heart,  551 

apex  of,  551 

applied  anatomy  of,  565 

arteries  of,  565 

auricles  of,  fibers  of,  562 
left,  559 
right,  554 

base  of,  551 

beat,  myogenic  theory  of,  566 
neurogenic  theory  of,  566 

cavities  of,  553 
capacity  of,  561 

component  parts  of,  553 

development  of,  755,  760 

endocardium',  562 


Heart,  grooves   of,   auriculoven- 
tricular, 553 
interauricular,  553 
interventricular,  553 
infundibulum  of,  557 
left,  553 

lymphatic  vessels  of,  5C5,  802 
margins  of,  552 
muscular  fibers  of,  562 
myocardium,  562 
nerves  of,  565 
position  of,  551 
pulmonary,  553 
right,  553 
rudiments  of,  755 
size  of,  552 
surface  form  of,  567 
surfaces  of,  551 
systemic,  553 
valves  of,  action  of,  565 

development  of,  760 
veins  of,  565 

ventricles  of,  fibers  of,  563 
left,  560 
right,  557 
weight  of,  552 
Hebenula,  906 
Heel  bone,  239 

Heidenhain,  demilunes  of,  1227 
Helicis  major  muscle,  1121 

minor  muscle,  1121 
Helicolrema,  1138,  1140 
Hehx  of  ear,  1119 
Helweg,  olivospinal  tract  of,  8391 
Hemicerebra,  847 
Hemiseptum,  934 
Hemisphaeria  bulbi  urethrae,  1387 
Hemispheres,  cerebral,  912 
Hemolymph  nodes,  768 
Hemorrhoidal     artery,     inferior, 
675 
middle,  672 
superior,  667 
nerve,  inferior,  1061 
plexus  of  nerves,  1077 
veins,  744,  753 
plexus  of,  745 
Henle,  fenestrated  memljrane  of, 
573 
layer  of  nerve  fiber  of,   1103, 

1160 
ligament  of,  433 
loop  of,  1351 
sheath  of,  812 
spine  of,  81 
Hensen,     canalis     reuniens     of, 
1142,  1147 
cells  of,  1147 
membrane  of,  356 
stripe  of,  1147 
Hepar,  1319 

capsula  fibrosa  [Glissoni],  132S 
fades  inferior,  1321 
posterior,  1321 
superior,  1320 
impressio  cardiaca,  1320 
colica,  1321 
duodenalis,  1321 
gastrica,  1321 
oesophagea,  1322 
pylorica,  1321 
renalis,  1321 
suprarenalis,   1322 
■margo  inferioris,  1322 
tunica  serosa,  1328 
Hepatic  artery,  660 
duct,  1332 

flexure  of  colon,  1296 
lymph  nodes,  790 
plexus  of  nerves,  1076 
veins,  751 
Hepatocolic  ligaments,  1260 
Hepatoduodenal  ligaments,  1260 
Hepatogastric  ligaments,  1260 
Herbst's  corpuscles,  816 


INDEX 


1471 


Hernia,  1315 
femoral,  1317 
inguinal,  1315 
Hesselbach,  ligament  of,  433 

triangle  of,  437,  1315 
Hey,  ligament  of,  508 
Hiatus  aorticus  diaphragma,  419 
canalalis  facialis,  84 
Fallopii,  84 
maxillaris,  102,  103 
oesophageiis,  1236 

diaphragma,  421 
sacralis,  59,  01 
semilunaris,  1081 
tentorial,  847 
Highmore,  antrum  of,  101,  103 
Hilura  of  kidneys,  1348 
of  nucleus  dentatus,  888 
of  suprarenal  glands,  1448 
Hilus     alandulae     suprarenahs, 
1448 
lienis,  1444 
nuclei  dentati,  888 
pulmonis,  1189 
renalis,  1348 
Hindbrain,  861 

development  of,  855 

structure  of,  861 

Hindgut,  1247 

Hinge-joint,  264,  205 

Hip  bone,  207 

fasciEe  of,  515 

-joint,  arteries  of,  327 

articulations  of,  322 

applied  anatomy  of,  329 
surface  form  of,  329 
bursEB  of,  327 
movements  of,  328_ 
muscles  of,  326,  515 
nerves  of,  327 
synovial  membrane  of,  326 
Hippocampal  commissure,   944 

gyre,  925 
Hippocampus,  942 

gray  substance  of,  953 
Hirci,  1159 

His,  auriculoventricular    bundle 
of,  564 
crista  terminalis  of,  758 
spina  vestibuli  of,  758 
sulcus  terminalis  of,  1217 
Histology,  definition  of,  33 
Homolateral  tract  cells  of  cord, 

841 
Homologies     of     sexual    organs, 

1428 
Horner's  muscle,  367 
Horns  of  spinal  cord,  830 
Horny  layer  of  skin,  1151 
Horseshoe  kidney,  1354 
Houston's  valves,  1310 
Howship's  foveolEe,  39 
Huguier,  canal  of,  88,  997,  1126 
Humeral  artery,  638 
ligament,  303 
lymph  nodes,  782 
region,  muscles  of,  467,  470 
Humerus,  178 

applied  anatomy  of,  184 
development  of,  183 
head  of,  178 
neck  of,  anatomical,  178 

surgical,  178 
shaft  of,  180 
surface  form  of,  184 
tuberosities  of,  180 
Humor  aqueus,  1105 

vitreus,  1105 
Hunter's  canal,  511,  515,  685 
Huschke,  foramen  of,  89 
Huxley's  layer,  1160 
Hyaline  cartilage,  260 
Hyaloid  canal,  1106 

membrane,  1106 
Hydatids  of  Morgagni,  1402 


Hydatids,  pedunculated,  1379 

sessile,  1378 
Hydrenccphalocele,  149 
Hymen,  1417 

imperforate,  1417 
Hyoepiglottic  ligaments,  1167 
Hyoglossus  muscle,  391 
Hyoid  bone,  153 

applied  anatomy  of,  154 
development  of,  154 
elevators  of,  388 
surface  form  of,  154 
Hyparterial     branch     bronchus, 

1177 
Hypogastric   arteries,    570,    669 
763 
in  fetus,  670 
impervious,  671 
lymph  nodes,  787 
plexus  of  nerves,  1077 
vein,  743 
Hypoglossal  nerve,  1010 

applied  anatomy  of,  1012 
nucleus,  878 
Hypophysis,  909 
Hyposylvian  ramus,  917 
Hypothalamic     tegmental     sub- 
stance, 905 
Hypothalamus,  structure  of,  908 
Hypothenar  eminence,  486 
Hyrtl,  exsanguinated  renal  zone 
of,  665 


Ileal  artery,  664 

lymph  nodes,  791 
Ileoappendicular  fold,  1267 

fossa,  1267 
Ileocecal  arteries,  664 
fossa,  1207 
junction,  1296 
valve,  1301 
Ileocolic  fold,  1266 
fossa,  1266 
junction,  1296 
lymph  nodes,  791 
plexus  of  nerves,  1076 
Ileum,  1288 
Iliac  arteries,  common,  668 

applied  anatomy  of,  669 
surface  marking  of,  669 
deep  circumflex,  682 
'  external,  079 

applied  anatomy  of,  680 
surface  marking  of,  680 
internal,  069 

applied  anatomy  of,  671 

679 
surface  marking  of,  679 
superficial  circumflex,  689 
bursa,  subtendinous,  327 
fascia,  502 
fossa,  209 
furrow,  219,  439 
lymph  nodes,  787,  788 
region,  muscles  of,  502 
veins,  common,  747 

development  of,  704 
deep  circumflex,  742 
external,  742 
internal,  743 
Iliacus  muscle,  504 
Iliococcygeus  muscles,  452 
Iliocolic  arteries,  004 
Iliocostalis  muscle,  410 
Iliofemoral  ligament,  323 
Iliolumbar  artery,  078 
ligament,  290 
veins,  748 
Iliopectineal  bursa,  327 
eminence,  210,  213 
ligament,  503 
hne,  209,  212 
Iliopsoas  muscle,  504  (note) 


Iliosacralis  muscles,  452 
Iliotibial  band,  507 

applied  anatomy  of,  508 
Iliotrochanteric  ligament,  324 
Ilium,  207 
crest  of,  210 
curved  lines  of,  207,  208 
spinous  processes  of,  210 
lips  of,  210 

intermediate  space  of,  210 
Impervious   hypogastric    artery, 

671 
Impressio  Irigemini,  84,  85 
Impression,  deltoid,  180,  181 

rhomboid,  171 
Incisive  fossa,  101,  135 

papilla,  1202 
Incisor  canal,  105 
crest,  105 
foramina,  105 
fossa,  116 
Incistira  acetabuli,  213 
cardiaca,  1190 
cerebelli  posterior,  884 
clavicularis,  157 
costalis  I,  157 
//,  159 
VII,  159 
ethmoidalis,  79 
frontalis,  77 
interlobaris,  1190 
intertragica,  1120 
ischiadica,  minor,  211 
jugularis,  71,  157 
lacrimalis,  102 
mandibulae,  118 
mastoidea,  82 
poplitea,  233 
radialis,  187 
scapiilae,  175 
semilunaris,  187 
sphenopalatine,  112 
supraorbitalis,  77 
tentorii,  893 
terminalis  auris,  1120 
thyreoidea  superior,  1164 
tympanica  [Rivini],  1125 
ulnaris,  192 
umbilicalis,  1322 
vertebralis  inferior,  49 

superior,  49 
resicae  felleae,  1322,  1323 
Incisurae      cartilaginis      meatus 
acustici  externi  [Santorinil,  1122 
Incisures     of      Sohmidt-Lanter- 

mann,    811 
Incus,  1132 
crus  breve,  1133 
longum,  1133 
processus  lenlicularis,  1133 
Indices,  cranial,  140 
Indusium.  930,  931,  934 
Inflected  fissures,  920 
Infraclavicular  lymph  nodes,  782, 
783 
nerve,  1029 
Infracommissure  of  Gudden,  895, 

910 
Infracostales  muscles,  417 
Infraglenoid  tubercle,  175 
Infrahyoid  artery,  590 

region,  muscles  of,  380 
Infraorbital  artery,  002 
canal,  102.  136 
foramen,  101,  130 
groove,  102 
nerve,  982  (note),  998 
plexus  of  nerves,  984,  998 
Infrapatellar  bursa,  336 
I      pad,  336 

\  Infraseapular  arteries,  639' 
I  Infraspinatus  bursa,  303 
fascia,  464 
muscle,  465 
I  Infraspinous  fossa,  172 


1472 


INDEX 


Infrasternal  depression,  166 
Infratioehlear  nerve,  981 
Infundibula  of  lungs,  1195 

of  ureters,  1356 
Infundibuliform  fascia,  436,  437, 

1374 
Infundibulopelvic  ligament,  1407 
Infundibulum,  141,  760,  909 

ethmoidal,  99 

elhmoidale,  99 

of  Fallopian  tube,  1401 

of  heart,  557 

iuher  uterinae,   1401 
Inguinal  canal,  437,  1375 

fossae,  1315 

hernia,  1315 

lymph  nodes,  785 
Inion,  146 
Inlet  of  pelvis,  215 

of  thorax,  155 
Innervation  of  intestines,  1313 

of  stomach,  1280 
Innominate  artery,  582 

veins    733 
Inosculation  of  arteries,  572 
Inscriptiones  tendineae,  433 
Insula,  925 
Integument  of  nose,  1081 

of  scrotum,  1373 
Integumentum  commune,  1149 
Interalveolar  cell  islets,  1340 
Interauricular  groove,  553 

septum,  559 
Interbronchial  lymph  nodes,  801, 

1179 
Intercalatum  of  midbrain,  897 
Intercavernous  sinuses,  726 
Intercellular  lymph  spaces,  767 

substance  of  bone,  39 
luterchondral  ligaments,  288 
Interclavicular  ligament,  296 
Intercolumnar  fascia,  427,  1374 

fibers   of    external    abdominal 
.      ring,  427 
Intercondyloid  notch,  225 
Intercostal  arteries,  655 
anterior,  632 
applied  anatomy  of,  657 
superior,  633 

fascia,  417 

lymph  nodes,  798 

lymphatic  vessels,  799 

muscles,  417 

nerves,  1040 

applied  anatomy  of,  1043 

space,  155 

veins,  735,  736 
Intercostobrachial  nerve,  1042 
Intercostohumeral  nerves,  1042 
Intercuneiform  articulations,  350 
Interdigital  veins,  739 
Interglobular  spaces,  1211 
Interlobar  fissures,  916 
Interlobular  duets,  1226 
Intermaxillary  suture,  135 
Intermedial  fissures,  923 
Intermediate  lamella  of  bone,  39 

space  of  ilium,  210 
Intermediolateral  tract  of  Bruce 

and  Campbell,  839 
Intermiiscular    septum    of    arm, 
467 
of  thigh,  507,  508 
Internasal  suture,  135 
Interneural   articulations,   271 
Interossei  muscles,  foot,  541 
hand,  494 

surface  form  of,  497 
Interosseous  arteries,  foot,   699, 
700 
hand,  647,  650 

recurrent  artery,  651 

veins,  729 
Interpalpebral  slit,  1112 
Interparietal  bone,  74 


Interparietal  suture,  121 
Interpeduncular  gangUon,  906 

nucleus,  898 
Interpleural  space,  1185 
Interpubic  disk,  294 
Intersigmoid  fossa,  1268 
Interspinales  muscle,  414 
Interspinous  ligament,  272 
Intersternal  ligaments,  288 
Interstitial  cells,  1399 
lamella  of  bone,  39 
Intertransversales  laterales  mus- 
cle, 414 
mediales  muscle,  414 
Intertransverse   ligaments,    272, 

293 
Intertrochanteric  line,  224 
Intertubular  dentin,  1211 
Interventricular  grooves,  553 

septum,  557,  561 
Intervertebral  fibrocartilage,  269 
foramina,  49 
notches,  49 

substance,  structure  of,  270 
veins,  738 
Intestinal  glands,  1292 
lymphatic  trunks,  772 
plexus  of  nerves,  1076 
Intestines,   applied  anatomy  of, 
1314 
innervations  of,  1313 
large,  1295 

arteries  of,  1310 
lymphatic    vessels    of,    794, 

1312 
nerves  of,  1312 
veins  of,  1312 
movements  of,  1312 
relations  of,  1250 
small,  1281 

applied  anatomy  of,  1314 
arteries  of,  1293 
lymphatic    vessels    of,    793, 

1295 
mucous  membrane  of,  1289 
nerves  of,  1295 
veins  of,  1295 
vilU  of,  1291 

structure  of,  1291 
surface  form  of,  1313 
Intestinum  cecum,  1296 
crCLSsum,  1295 
ileum,  1288 
jejunum,  1288 
rectum,  1306 

pars  analis  recti,  1309 
tenue,  1281 

mesenteriale,  1287 

plicae   circular es   [Kerkri?igi], 

1289 
tela  submucosa,   1289 
tunica  mucosa,  1289 
muscularis,  1289 

stratum   circulare,    1289 
longitudinale,    1289 
serosa,   1289 
Intra-articular  ligament,  283 
Intracartilaginous  ossification,  42 
Intracranial  lymphatics,  774 
Intraiugular  process,  73 
Intralobular  ducts,  1226 

veins,  751 
Intramembranous  ossification,  42 
Intraparietal   sulcus   of   Turner, 

922 
Intraprecuneal  fissure,  924 
Intrathyroid  cartilage,  1165 
Intravertebral  veins,  738 
Intrinsic    ligaments    of    larynx, 
1168 
muscles  of  tongue,  393 
Intumescentia  cervicalis,  823 
ganglioformis,  996 
lumbalis,  823 
Involuntary  muscles,  355,  357 


Iris,  1096 

applied  anatomy  of,  1110 

arteries  of,  1099 

epithelium  of,  pigmented,  1099 

muscle  fibers  of,  1099 

nerves  of,  1099 

stroma  of,  1098 

structure  of,  1098 
Irregular  bones,  36 
Ischiobulbosus  muscle,  444 
Ischiocapsular  ligament,  323 
Ischiogluteal  bursa,  327 
Ischiorectal  fascia,  446 

fossa,  454 

region,  muscles  of,  453 
Ischium,  210 

obturator  groove  of,  211 

ramus  of,  212 

spine  of,  211 

tuberosity  of,  211 
Islands  of  Langerhans,  1340 

of  Reil,  925 

development  of,  917 
Isthmus  aortae,  580 

cartilaginis  auris,  1121 

of  Fallopian  tube,  1401 

of  fauces,  1201,  1203 

faucium,  1201,  1203 

glandulae  thyroidea,  1436 

gyri  hippocampi,  925 

pharyngonasalis,  1230 

of  pharynx,  1230 

rhombencephali,  855 

tubae  audilivae,  1128 
uterinae,  1401 
Iter  chordae,  1126 
Ivory  of  teeth,  1211 


Jacob's  membrane,  1103 
Jacobson,     cartilage     of,     1080, 
1083 

eminence  of,  1083 

nerves  of,  1002 
Jaw,  angle  of,  118 

lower,  bones  of,  115 

upper,  bones  of,  100 
Jejunum,  1288 
Joints.     See  Articulations. 
Jugular  foramen,  71,  131 

fossa,  86 

ganglion,  1002 

lymph  nodes,  778 

process,  71,  131 

sinus,  713 

tubercle,  73 

veins,  713 

development  of,  764 


Keekeing,  valves  of,  1289 
Key   and   Retzius,    foramen   of, 

845,  969 
Kidneys,  1343 

abnormalities  of,   1354 

applied  anatomy  of,  1355 

arteries  of,  1352 

columns  of,  1349 

convolutions  of,  1351 

cortex  of,  1349 

fixation  of,  1348 

glomerulus  of,  1350 

hilum  of,  1348 

horsehsoe,   1349 

labyrinth  of,  1349 

lymphatic  vessels  of,  796,  1354 

medulla  of,  1349 

minute  anatomy  of,  1350 

nerves  of,  1354 

parenchyma  of,  1349 


INDEX 


1473 


liidncys,  permanent,  1425 

relations  of,  1343 

structure  of,  1349 

substance,  1349 

surface  form  of,  1354 

tubules  of,  1351 

^'eins  of,  1354 
Kneecap,  230 

Knee-joint,  applied  anatomy  of, 
338 

arteries  of,  337 

hursce  of,  336 

lijiaments  of,  331 

nio\'enients  of,  337 

ner\-es  of,  337 

structiu'es  around,  337 

surface  form  of,  338 

synovial  memlirane  of,  336 
Krause,  end-bulbs  of,  813,  817 

membrane  of,  356 
Kiihne,  muscle  spindles  of,  817 


Labia  majora,  1415 
minora,  1416 

pudendi,  1416 
oris,  1200 
Labial  artery,  593 

coronarv  arteries,  594 
glands,  1200 
nerves,  984 
Labium  externum  cristi  iliaca,  210 
qUnoidale,  303,  325 
inferius,  1200 
internum  crista  iliaca,  210 
lalerale  [linea  aspera],  224 
mediate  [linea  aspero\,  224 
superius,  1200 
tympanicutn,  1144 
vestibulare,  1144 
Labyrinth  of  ear,  1136 
membranous,  1140 

structure  of,  1142 
osseous,  1136 
of  ethmoid,  97 
of  kidneys,  1349 
LabyrinthuJi  ethmoidalis,  97 
membranaceus,  1140 
osseus,  1136 
Lacertus  fibrosus,  469 
Lachrymal.     See  Lacrimal. 
Lacrimal  apparatus,  1115 
artery,  610 
bone,  106 
crests  of,  137 
lesser,  107 
canal,  104,  107,  1116 

ampulla  of,  1116 
fossa,  79 
gland,  1115 

applied  anatomy  of,  11  IS 
groove,  102,  104,  137,  138 
nerve,  980 
notch,  102 
papilla,  1113,  1116 
process,  114 
sac,  1116 

applied  anatomy  of,  1119 
sulcus,  107 
tubercle,  104 
Lacteals.  767 
Lactiferous  duct,  1430 
Lacuna  of  bone,  39,  259 
magna,  1369 
musculorum,  503 
vasorum.  503 
Lacunae,  39 
laterales,  721 
urethrales,  1369 
Lacus  lacrimalis,  1113,  1115 
Lagena,  1 147 
Lambda,  76,  123,  146 
Lambdoid  suture,  73,  76,  121        j 
93 


Lamella  of  bone,  39 
Lamellated  corpu.scles,  816 
Lamina  basalis,  1093 
of  brain,  885 

cartilaginis  cricoideae,  1165 
choriocapillaris,  1093 
cribriform,  1090 
cribrosa,  85 

sclerae,  1090 
elaslica  anterior,  1091 

posterior,  1091 
fibrocartilaginea       interpubica, 

294 
fusca,  1090 

horizontal,  of  ethmoid,  96 
lateralis   processus  pterygoidei, 

94 
Tnedialis  processus  pterygoidei, 

94 
medullaris  interna,  905 
papyracea,  98 
periclaustral,  948 
perpendicularis,  97 
reticular,  1147 
reticularis,  1147 
rostralis,  913 
spiralis  ossea,  1138,  1140,  1144 

secundaria,  1137,  1140 
suprachoroidea,  1093, 
terminalis,  847,  908,  909 
vasculosa,  1093 
Landzert,  fossa  of,  1266 
Langer,  cleavage  lines  of,  1150 

foramen  of,  783 
Langerhans.    centro-acinar    cells 
of,  1340 
islands  of,  1340 
Lanugo,  1159 

Laryngeal  artery,  inferior,  629 
superior,  590 
nerve,  1078 
inferior,  1007 
recurrent,  1007 
superior,  1006 
sinus,  1170 
veins,  735 
Larynx,  1163 
arteries  of,  1174 
cartilages  of,  1163 
glands  of,  1174 
interior  of,  1169 
ligaments  of,  1167 
movements  of,  1169 
mucous  membrane  of,  1174 
muscles  of,  1172 
nerves  of,  1174 
veins  of,  1174 
ventricles  of,  1170 
Lateralis  nasi  artery,  594 
Latissimus  dorsi  muscle,  406 

surface  form  of,  416 
Leg,  bones  of,  230 
fasciae  of,  525 
muscles  of,  525 

applied  anatomy  of,  535 
Lemnisci,  decussation  of,  870 
Lemniscus  lateralis,  876 

medialis,  876 
Lens  crystallina,  1106 
crystalHne,  1106 
ligament  of,  suspensory,  1106 
Lenticula,  854,  947 
Lenticular  ganglion,  982 

nucleiis,  947 
Lenticulostriate  arteries,  617 
Leptoprosope  skull,  146 
Lesser's  triangle,  591,  1012 
Leukocytes,  40 

Levator  anguli  oris  muscle,  373 
scapulae  muscle,  407 

surface  form  of,  416 
ani  muscle,  450 
costarum  muscle,  417 
glandulae   thyroideae   muscle, 
1436 


Levator  labii  superioris  alaoque 
nasi  muscle,  372 
muscle,  373 
menti  mu.scle,  374 
palati  muscle,  397 
palpebrae    superioris    muscle, 

369 
prostatae  muscle,  452 
Lieberkiihn,  crypts  of,  1292 

glands  of,  1292 
Lien,  1442 

exiremitas  inferior,  1444 

superior,  1444 
fades  diaphrdgmatica,  1444 
gastrica,  1444 
renalis,  1444 
margo  anterior,  1444 

posterior,  1444 
tunica  albuginea,  1445 
serosa,  1444 
Ligamenta    accessoria    plantaria, 
354 
alaria,  277,  336 
basium   ossis  metacarp.  dorsa- 
Ha,  319 
interossea,  319 
volaria,  319 
metatars.  dorsalia,  352 
interossea,  352 
plantaria,  352 
brevia,  476 
carpometacarpeae  dorsalis,  SIS 

volaria,  318 
collatcralia,  321 

articulationes    digitorum    pe- 
dis, 354 
metatarsophalangeae,  354 
columnae  vertebralis,  268 
cruciata  genu,  333 
cuneometatarsea  interossea,  352 
intercarpea  dorsalia,  315,  316, 
317 
interossea,  315,  316 
volaria,  315,  316 
intercostalia  externa,  288 

interna,  288 
intercruralia,  271 
intercuneiformia  dorsalia,  350 
interossea,  3.50 
plantaria,  350 
interspinalia,  272 
intertransversariu,  272 
Inbyrinthi  canaliculorum,   1142 
lata  uteri,  1256 
longa,  476 

navicnlaricuneiformia  dorsalia, 
350 
plantaria,  350 
puboprostatica,  1362,  1393 
pylori,  1274 

sacroiliaca  anteriora,  290 
subflava,  271 

tarsometatarsea  dorsalia,  352 
plantaria,  352 
Ligamenti     auricularia     [Valsal- 
vae], 1121 
Ligamentous  action  of  muscles, 

267 
Ligaments,  259,  261 
accessory.  275 
acromioclavicular,   297 
annular,  anterior,  486,  536 
external,  537 
internal,  536 
posterior,  487 
of  radius,  310 
arcuate,  419 
astragaloscaphoid,  349 
atlanto-axial,  274 
of  axilla,  suspensory,  456 
of  Bertin,  323 
of  Bigelow,  324 
of  bladder,  1361 

true,  450 
broad,  11S3,  1407 


1474 


INDEX 


Ligaments,  calcaneo-astragaloid, 

347 
calcaneocuboid,  348 
calcaneoscaphoid,  348 
cat>sular.         See       Individual 

joints, 
of  carpus,  315 
check,  1087 

chondrosternal,  286,  287 
chondroxiphoid,  288 
ciliary,  1096 
of  Cloquet,  1376,  1379 
coccygeal,  843,  845 
common,  anterior,  268 

posterior,  269 
conjugal,  271 
conoid,  298 
of  Cooper,  428 
coracoaeromial,  299 
coracoclavicular,  298 
coracohumeral,  302 
coronary,  of  knee-joint,  336 
eostocla-sdcular,  296 
costocoracoid,  460 
costotransverse,  284,  285 
costovertebral,  282 
cotyloid,  325 
cricoarytenoid ,   1 1 69 
cricotracheal,  1168 
crucial,  333 
cruciform,  275 
deltoid,  343 
dentate,  846 
of  diaphragm,  419 
duodenomesocolic,  1266 
falciform,  1320,  1324 
femoral,  50S 
of  fingers,  319 
Flood's,  302 

fundiform,  of  Retzius,  536 
Gimbernat's,  426,  428 
glenohumeral,  302 
^        glenoid,  176,  303 

of  Cruveilheir,  321 
of  hand,  315 
of  Henle.  433 
hepatocolic,  1260 
hepatoduodenal,    1260 
hepatogastric,  1260 
of  Hesselbach,  433 
of  Hey,  508 
of  hip,  322 

hyoepiglottic,  1167,  1168 
iliofemoral,  323 
iliolumbar,  290 
iliopectineal,  503 
iliotrochanteric,  324 
of  incus,  1133 
infundibulopeh-ic,   1407 
interchondral,  288 
intercla"\'icular,  296 
interosseous.      See  Individual 

joints, 
interspinous,  272 
iutersternal,  288,  289 
intertransverse,  272,  293 
intra-articular,  283 
ischiocapsular,  323 
of  knee-joint,  331 
lateral.     See  Individual  joints, 
of  liver,  1324 
lumbosacral,  289,  1345 
malleus,  1133 
oblique,  311 
obturator,  295 
occipito-atlantal,   275,   276 
oecipito-axial,  277 
odontoid,  277,  278 
orbicular,  310 
of  patella,  331 
phrenocolic,   1305 
of  pinna  of  ear,  1121 
Poupart's,  426,  427 
pterygomandibular,  376,  383 
pterygospinous,  383 


Ligaments,  pubic,  294 
pubofemoral,  323 
puboprostatic,  450 
pyloric,  1274 
radioulnar,  312 
rhomboid,  296 
round,  437 
sacrococcygeal,  293 
sacroiliac,  290 
sacrosciatic,  291,  292 
sacrouterine,  1407 
of  scapula,  299,  300,  301 
Schlemm's,  302 
spinal,  268 
spinoglenoid,  301 
of  stapes,  1133 
stellate,  282 
sternoclavicular,  296 
sternocostal,  286 
stylohyoid,  389 
stylomandibular,  280,  382 
superficial    transverse,  of    fin- 
gers, 489 
suprascapular,  .300 
supraspinous,  272 
suspensory,  of  Ijladder,  1362 

of  Cooper,  456 

of  eve,  1087 

of  lens,  1106 

of  penis,  424 

of  Treitz,  1285 
sutural,  121,  259 
syno^dal,  262 
tarsal,  366 

thjToarytenoid,    1170 
thyroepiglottic,  1167,  1169 
thyrohyoid,  1167 
tibiotarsal,  343 

transverse','of  acetabulum,  325, 
326 

of  atlas,  274 

humeral,  303 

of  knee-joint,  336 

metatarsal,  353 

pelvic,  446 
trapezoid,  298 
triangular,  deep  layer  of,  449 

in  female,  446 

in  male,  446 
true,  of  bladder,  450 
umbilical,  1361 
uterosacral,  1407 
of  uterus,  1406 
of  vertebral  bodies,  268 
volar,  315 
of  Winslow,  332 
of  Wrisberg,  336 
of  wTist-joint,  314 
Y,  324 
of  Zinn,  370 
LigameTUum     acromioclamculare, 

297 
annulare  baseos  stapedius,  1133 

radii,  310 
apicis  dentis,  278 
arcuatum  externum,  439 

pubis,  294 
arteriosum,  570,  575 
auriculare  anterius,  1121 

posterius,  1121 

superiu^,  1121 
bifurcatum,  348 
calcaneocuhoideum  dorsale,  348 

plantare,  348 
calcaneofibulare,  344 
calcaneonavicular'e  plantare,  348 
calcaneotibiale,  343 
capituli    costae    interarticulare, 
283 
radiatum,  282 
capitulorum-     ossis   metacarpa- 

liuTTi  transversum,  320 
carpi  dorsale,  487 

fasciculi  transversi,  489 

transversum,  486 


Ligamentum  collaterale  carpi  radi- 
ate, 314 
ulnare,  314 

fihulare,  333 

radiate,  308 

tibiale,  332 

ulnare,  307 
colli  costae,  284 
conoideum,  298 
coracoacromiale,  299 
coracoclavicularc,  298 
coracohuinerale,  302 
coronarium  hepatis,  1325 
costoclamculare,  296 
costotransDersarium       anterius, 
284 

posterius,  285 
costoxiphoideum  anterius,  288 
cricoaryteTioideum        posterius, 

1168 
cricothyrqideum  medium,  1168 
cricotracheale,  1168 
cruciatum  anterius,  333 

atlantis,  275 

cruris,  536 

posterius,  333 
cuboideona\aculare       dorsale, 
350 

plantare,  350 
cuneocuboideum  dorsale,  351 

interosseum,  350,  351 

plantare,  351 
deltoideum,  343 
denticulatum,    821,    S45,    846, 

1013 
epididytnidis  inferior,  1378 

superior,  1378 
falciforme  hepatis,  1253,  1324 
gastrolienale,  1444 
hepatocolicum,  1260 
hepatodv^denale,  1260 
hepatogastricum,  1260 
hyoepigloiticum,  1168 
kyotkyreoideum  laterale,  1167 

medium,  1167 
iliofemorale,  323 
iliolunibale,  290 
incudis  posterius,  1133 

superius,  1133 
inguinale,  427 

rejlexum,  428 
inter  clavicular  e,  296 
iiiterfoveolare,  433 
ischiocapsulare,  323 
laciniatum,  536 
lacunare,  428 
laterale     externum     breve     seu 

posticum,  333 
latum  pulmonis,  1184 

uteri,  1407 
longitudinale  anterius,  268 

posterius,  269 
mallei  anterius,  1133 

laterale,  1153 

sup^ius,  1153 
malleoli  lateralis  anterius,  341 

posteriu^s,  342 
mucosum,  336 
nuchae,  272,  406 
ossiculorum  auditus,  1133 
palpebrale  mediate,  367,  1114 
patellae,  331 

pectinatum  iridis,  1092,  1096 
phrenicocolicum,  1264 
pisohamatum,   316 
pisometacarpeum,  316 
plantare  Ionium,  348 
popliteum  obliquum,  332 
pubicum  superius,  294 
pubocapsulare,  323 
pulmonale,  1184 
radiocarpeum  dorsale,  314 

volare,  314 
sacrococcygeum  anterius,  293 

posterius,  293 


INDEX 


1475 


Ligamentum  sacrococcygeum  pos- 
tcrius  profundum,  293 
supcrficiale,  293 
sacroiliacum  posterius,  290 
breve,  290 
longum,  290 
sacrosjnnosufn,  292 
sacrotuberosum,  291 
splienomanflibidare,  279 
spirale  cochleae,  1144 
sternoclavipularc,  296 
sternocosiale  inlerariiculare,  287 

radiatum,  286 
siernopericardica,  548 
siylohyoideus,  389 
stylomandibulare,  280 
supraspincde,  272 
suspensorium  penis,  13SS 
talocalcaneum  anterius,  Si? 

interosseum,  347 

laterale,  347 

mediale,  347 

posterius,  347 
talofibulare  anterius,  344 

posterius,  344 
ialotibiale  anterius,  343 

posterius,  343 
temporomandibulare,  279 
teres,  324,  752,  764 

femoris,  324 

hepatis,  1325 

Mteri,  437,  1408 
thyreoepiglotticum ,  1169 
tibionaviculare,  343 
transversum  acetabuli,  326 

atlantis,  274 

cruris,  536 

genu,  336 

pelvis,  446 

scapulae  inferius,  301 
superius,  300 
trapezoideum,  298 
triangulare  dextruni,  1325 

sinistrum,  1325 
unibilicale  laterale,  671,  1362 

medium,  1361 
vaginale,  321 
jieraa  ca»ae  sinistrae,  550 
venosum,  752,  1325 
Light  stimuli,  path  of,  1104 
Limbic  lobe,  929 
lAmhus  fossae  ovalis  [Vieussenii\, 

557 
laminae  spiralis,  1144 
tnembranae  iympanae,  1130 
Limen  insulae,  925 

nasi,  1082 
Line,  iliopectineal,  209 
intertrochanteric,  224 
spiral,  of  femur,  224 
iinea  aibo,  426,  435,  439 
arcuata,  209,  212 
aspera,  224 
glutaea  anterior,  207 

inferior,  208 

posterior,  207 
intercondyloidea,  226 
intermedia  crista  iliaca,  210 
intertrochanterica,  224 
mylohyoidea,  117 
nuchae  inferior,  70 

superior,  70 

suprema,  70 
obliqua,  117,  1164 
pectineal  224 
poplitea,  234 
quadrati,  224 
semicircularis,  430,  435 
semilunaris,  439 

of  abdomen,  436 
splendens,  845 
temporalis  inferior,  74 

superior,  74 
transversae,  439 
m'sus,  1088 


Lineae  musculares,  172 

semilunares,  436 

transversae,  58 
Lingua,  1217 

fades  inferior,  1217 

margo  lateralis,  1217 

tunica  mucosa,  1217 
Lingual   arteries,  590,   591,  601, 
1219 

bone,  153 

lymph  nodes,  776 

muscles,  393 

nerves,  988 

from  glossopharyngeal,  1003 

region,  muscles  of,  391 

septum,  393 

tonsil,  1219 

veins,  715 
Lingula,  91,  117,  867,  886 

cerehelli,  SS6 

mandibulae,  117 

pulmonic,  1190 

sphrnoidalis,  91 
Lips,  1200 
Liquor  cerebrospinalis,  970 

folliculi,  1400 
Littr(5,  glands  of,  1369 
Liver,  1319 

abnormalities  of,  1326 

accessory,  1326 

applied  anatomy  of,  1335 

arteries  of,  1326 

colic  impression  of,  1321 

constriction  lobe  of,  1326 

duodenal  impression  of,  1321 

excretory  apparatus  of,  1331 

fissures  of,  1322 

gastric  impression  of,  1321 

Egaments  of,  1324 

ligamentum  venosum  of,  764 

lobes  of,  1323 

lobules  of,  1328 

lymphatic  vessels  of,  794,  1331 

movability  of,  1325 

nerves  of,  1331 

omental  tuberosity  of,  1321 

renal  impression  of,  1321 

Riedel's  lobe  of,  1326 

structure  of,  1328 

support  of,  1325 

suprarenal  impression  of,  1322 

surface  relations  of,  1334 

surfaces  of,  1320 

veins  of,  1327 
Lobe  or  Lobes,  biventral,  887 

cacuminal,  886 

central,  886 

of  cerebellum,  885 

cerebral,  915 

clival,  886 

crescentic,  886 

culminal,  886 

frontal,  919 

gracile,  887 

limbic,  929 

of  lungs,  1190 

nodular,  888 

occipital,  924 

olfactory,  926 

parietal,  922 

pyramidal,  887 

quadrate,  886 

semilunar,  887 

temporal,  924 

tuberal,  887 

uvular,  887 
Lobi  m,ammae,  1430 
Lobules  of  liver,  1328 

of  lungs,  1195 
Lobuli  hepatis,  1328 

mamm.ae,  1430 

testis,  1380 
Lobulus  auriculae,  1120 

biventer  cerebelU,  887 

centralis  cerebclli,  886 


Lobulus  paracentralis,  921 

parieialis  inferior,  923 
superior,  923 

semilunaris  inferior   {cerebelli\, 
887 
Lobus  caudatus  [Spigelii],  1324 

frontalis,  921 

hepatis  dexter,  1324 
sinister,  1324 

occipitalis,  924 

olfactorius,  926 

parietalis,  922 

temporalis,  924 
Lockwood,  tendon  of,  370 
Locus  caeruleus,  866 
Longissimus  dorsi  muscle,  412 
Longitudinal  fasciculus,  955 
-  vertebral  veins,  738 

zones  of  brain,  855 
Longus  colli  muscle,  401 
Lowenthal  and   Bechterew,   fas- 
ciculus intermedins  of,  fS39 

tract  of  cord,  840 
Lower,  tubercle  of,  557 
Ludwig,  angle  of,  157,  166 
Lumbar  aponeurosis,  409 

arteries,  662 

curve  of  vertebral  column,  66 

enlargement  of  spinal  cord,  823 

fascia,  409 

lymph  nodes,  788 

lymphatic  trunks,  772 

nerves,  1019 

divisions  of,  1018,  1044 

plexus  of  nerves,  1044 

applied  anatomy  of,  1062 

portion    of    gangliated    cord, 
1071 

puncture,  68 

veins,  749 

ascending,  736,  749 

vertebrae,  56 
fifth,  57 
Lumbosacral  ligament.  289.  1345 

plexus  of  nerves,  1044 
Lumbricales  muscle,  foot,  540 

hand,  493 
Lungs,  1188 

alveoli  of,  1195 

applied  anatomy  of,  1197 

arteries  of,  1195 

borders  of,  1190 

broad  Ugamcnt  of,  1183 

color  of,  1194 

fetal,  1194 

fis.sures  of,  1190 

infundibula  of,  1195 

lobes  of,  1190 

lobules  of,  1195 

lymphatic  vessels  of,  802,  1196 

nerves  of,  1196 

parenchvma  of,  1195 

root  of,  1193 

saccules  of,  1195 

septa  of,  1195 

structure  of,   1194 

substance  of,  1194 

surface  form  of,  1196 

surfaces  of,  1189 

veins  of,  1195 

weight  of,  1194 
Lunula,  1157 

of  nails,  1157 
Lunulae     valvularum     sem  iluna- 

rium,  559,  561 
Luschka,  foramen  of,  867,  969 

gland  of,  1450 
Lutein  cells,  1400 
Luys,  body  of,  905 

centrum  medium  of,  905 
Lymph,  767 

nodes,  antecubital,  781 
aortic,  788 
appendicular,  791 
auricular,  posterior,  774 


1476 


INDEX 


Lymph  nodes,  axillary,  782 

bronchiomediastinal,  801 

buccal,  776 

cervical,  777,  779 

of  Cloquet,  786 

colic,  791 

cystic,  790 

definition  of,  768 

diaphragmatic,  798 

epitrochlear,  782 

of  face,  774,  776 

gastric,  790 

gastroepiploic,  790 

of  head,  774 

hepatic,  790 

humeral,  782 

hypogastric,  787 

ileal,  791 

ileocolic,  791 

ihac,  787,  788 

infraclavicular,  782,  783 

inguinal,  785,  786 

interbronchial,  801,  1179 

intercostal,  798 

jugular,  778 

Ungual,  776 

of  lower  extremity,  784 

lumbar,  788 

mammary,  798 

mandibular,  776 

mastoid,  774 

maxillary,  776 

mediastinal,  SCO 

mesenteric,  790,  791 

mesocolic,  791 

middle,  of  Stahr,  778 

of  neck,  774,  777 

obturator,  787 
, occipital,  774 

pancreaticoduodenale,  793 

paracardial,  790 

parietal,  787,  798 

parotid,  774 

pectoral,  782 

peritracheobronehial,    1179 

popliteal,  784 

preaortic,  789 

preauricular,  774 

prelaryngeal,  779 

pretracheal,   779 

retroaortic,  789 

retropharyngeal,  776 

retropyloric,  790 

of  RosenniiiUer,  786 

sacral,  788 

splenic,  790 

subclavian,  783 

submaxillary,  778 

submental,  779 

subparotid,  776 

subpyloric,  790 

subscapular,  783 

substernomastoid,  779 

supracla'vicular,  779 

suprahj'oid,    779 

supratrochlear,  782 

of  thorax,  798 

tibial,  784 

of  trachea,  1179 

tracheobronchial,  800 

of  upper  extremitj^  781,  782 

visceral,  790,  800 
sinuses,  768 
spaces,  767 

periscleral,  1086 

perivascular,  707 

suprascleral,  1086 
-vascular  system,  547 
Lymphatic  or  Lymphatics,  767 
applied  anatomy  of,  770 
duct,  right,  773 
extracranial,  774 
glands.     See  Lymph  nodes, 
intracranial,  774 
origin  of,  769 


Lymphatic  or  Ljonphatics,  pas- 
sages of  eyeball,  1109 
pharyngeal  ring,  1234 
sacs,  primary,  770 
structure  of,  769 
terminations  of,  769 
trunks,  intestinal,  772 

lumbar,  772 
vessels  of  abdomen,  787,  789, 
790 

of  abdominal  viscera,  792 

afferent,  768 

of  anus,  794 

of  arteries,  574 

of   auditory  meatus,    exter- 
nal, 777 

of  bladder,  796 

of  bone,  41 

of  cecum,  1300 

of  common  bile-duct,  796 

development  of,  769 

of  diaphragm,  799 

of  duodenum,  793 

efferent,  768 

of  external  genitals,  790 

of  face,  774,  777 

of  Fallopian  tube,  797 

of  gall-bladder,  795 

of  head,  774 

of  heart,  802 

intercostal,  799 

of  intestine,  large,  794 
small,  793 

of  kidney,  796 

of  labia  majora,  1415 

of  liver,  794 

of  lower  extremity,  786,  787 

of  lungs,  802       ■ 

of  mammary  gland,  798 

of  membrana  tympani,  1131 

of  mouth,  777 

of  muscles  of  neck,  780 

of  nasal  fossae,  777 

of  neck,  774,  780 

of  nose,  1081 

of  oesophagus,  802 

of  ovaries,  797 

of  pancreas,  796 

of  parotid  gland,  1225 

of  pelvic  viscera,  792 

of  pelvis,  789,  790 

of  penis,  1390 
j  of  perineum,  790 

of  pinna,  777 

of  pleura,  802 

of  prostate,  796 

of  rectum,  794 

of  reproductive  organs,  796 

of  scalp,  776 

of  seminal  vesicles,  797 

of  skin,  1156 

of  spermatic  cord,  1377 

of  spleen,  796,  1446 

of  stomach,  792,  1279 

of  submaxillary  gland,  1226 

of    suprarenal    glands,    796, 
1449 

of  testes,  796 

of  thoracic  viscera,  802 
wall,  798 

of  thorax,  798 

of  thymus  gland,  802 

of  thyroid  gland,  1438 

of  tongue,  777 

of  tonsil,  1231 

of  upper  extremity,  783,  784 

of  ureter,  796 

of  urethra,  796 

of  urinary  organs,  796 

of  uterus,  797 

of  vagina,  797 

of  vas  deferens,  797 

of  vermiform  appendix,  1300 
Lymphoglandulae,  768 

auriculares  anteriores,  775 


Lymphoglandulae  auriculares  pos- 

ieriores,  774 
axillares,  782 
bronchiales,  801,  1179 
cervicales  profundae,  779 
inferiores,  779 
superficiales,  777 
superiores,  779 
coeliacae,  795 
faciales  profundae,  776 
gastricae  inferiores,,  790 

superiores,  790 
hepaticae,  790 
hypogastricae,  787 
inguinales,  785 
intercostales,  798 
linguales,  776 
lumbales,  788 
mediastinales  anteriores,  800 

posteriores,  800 
mesentericae,  790 
occipitales,  774 
pancreaticolienales,  790 
parotideae,  774 
pectorales,  782 
popliteae,  784 
suhinguinales,  785 

profundae,  786 
suhniaxillares,  778 
tibialis  anterior,  784 
tracheales,  801,  1179 


M 

McBdrney's  point,  1298,  1313 
Macewen's  suprameatal  triangle, 

81,  151 
Macula  acustica  sacculi,  1141 
lutea,  1100,  1104 
utriculi,  1141 
Majendie,  foramen  of,  845,  867, 

969 
Malar  arteries,  610 
bone,  107 
canal,  108 
foramen,  107,  136 
nerve,  998 

of  superior  maxillary,  983 
process  of  maxillae,  101,  104 
Male  breast,  1433 

reproductive  organs,  1371 
urethra,  1366 
Malleolar  arteries,  698,  703 
folds,  1130 
sulcus,  238 
Malleolus,  external,  237 
internal,  235 
lateralis,  237 
Tnedialis,  235 
Malleus,  1131 

ligaments  of,  1133 
processus  anterior  [Foliii,  1132 
lateralis,  1132 
Malpighian  body,  1350 
capsule,  1350 
corpuscles,  1445 
layer  of  skin,  1152 
tuft,  1350 
Mamma  virilis,  1433 
Mammae   accessoridae  muliebris, 

1430 
Mammary  artery,  external,    638 
internal,  631 
gland,  1428 

applied  anatomy  of,  1432 
areola  of,  1429 
arteries  of,  1432 
lymphatic    vessels    of,    798, 

1432 
nerves  of,  1432 
prolongation  of,  1430 
variations  in,  1429 
veins  of,  1432 
lymph  nodes,  internal,  798 


INDEX 


1477 


Mammary  veins,  734 
Mammillary  duct,  1430 
Mandible,  115 

changes  produced  in,   by  age, 
119 

condyle  of,  118 

condyloid  process  of,  118 

coronoid  process  of,  118 

depressors  of,  388 

olilique  line  of,  117 

perpendicular      portions      of, 
117 

side    views    of,     at    different 
periods  of  life,  119 

symphysis  of,  115 
MntuHbuln,   115 
Mandiliular  lymph  nodes,  776 

nerve,  987 

from  facial,  998 

region,  muscles  of,  374 
Manubrium  mallei,  1131 

stemi,  157 
Marclii's  tract  of  cord,  839 
Margin  of  orbit,  101 
Marginal  cusp   of  mitral   valve, 
561 

gyre,  923 

tract  of  spinal  cord,  836 

veins,  709 
MarQO  acutus,  552 

axillaris,  175 

ciliaris,  1096 

dorsalis  corpus  radii,  191 
ulnae,  187 

frontalis,  76 

infraorhitalis,  101,  137 

loTubdoideus,  73 

lateralis,  180 

ma^toideus,  73 

mcdialis,  180 

corpus  tibiae,  234 

nasi,  1079 

obiiisus,  552 

occipitalis,  76 

pupillaris,  1097 

sagittalis,  76 

squamosus,  76 

supraorbitalis,  77,  137 

vertebralis,  175 

volaris  corpus  radii,  191 
ulnae,  187 
Marrow,  bone,  40 

cells,  40 
Marshall,  oblique  vein  of,   550, 
709 

vestigial  fold  of,  550 
Martinotti,  cells  of,  952,  963 
Massae  laterales,  51 
Masseter  muscle,  377 

surface  form  of,  380 
Masseteric  artery,  601 

fascia,  377 

nerve,  987 
Mastoid  air  cells,  1127 

antrum,  83  • 

artery,  596 

bone,  sigmoid  fossa  of,  82 

cells,  83 

foramen,  82,  128,  133 

lymph  nodes,  774 

portion  of  temporal  bone,  82 

process  of  temporal  bone,  82 
Masto-occipital  suture,  73,  122 
Mastoparietal  suture,  122 
Matrix  of  nails,  1157 

unguis,  1157 
Maxilla;,  100 

alveolar  process  of,  104 

malar  process  of,  104 

nasal  process  of,  104 

palatal  process  of,  104 
Maxillary  artery,  59S 

atrium,  orifice  of,  141 

hiatus,  102 

IjTiiph  nodes,  776 


Maxillary  nerve,  982,  9S7 
process  of  palate  bone.  111 
of  turbinated  bone,  114 
region,  muscles  of,  373 
sinus,  101,  103 
tuljerosity,  102 
vein,  712 
Meatus  acuslicus  externus,  1122 
carlilagineus,  1122 
osseous,  1122 
pars  externa,  1122 
interna,  1122 
media,  1122 
interjius,  85 
auditory,  1122 
external,  88,  133 
internal,  85,  128 
nasi  inferior,  1082 
medius,  1082 
superior,  1082 
of  nose,  98,  110 
atrium  of,  141 
urinarius,  1369 
Meckel's  cartilage,  118 
diverticulum,  1289 
ganglion,  984 
Median  nerves,  1034 

veins,  730 
Mediastinal  arteries,  632,  654 
lymph  nodes,  800 
pleura,  1183 
plexus,  subpleural,  632 
Mediastinum,  1185 

applied  anatomy  of,  1188 
testis  [corpus  Highmoi'i],  1380 
Medicommissure,  903 
Medicornu,  938 
Medidural  artery,  600 
Medifrontal  fissures,  919 

gyre,  921 
Mediotarsal   articulation,   349 
Medipedunculi,  890 
Meditemporal  fissure,  924 

gyre,  924 
Medulla  of  kidneys,  1349 
oblongata,  861 
areas  of,  862 
fissures  of,  861 
funiculus  of,  863 
olive  of,  863 
pyramids  of,  863,  869 
restis  of,  864 

tuberculum  cinereum  of,  864 
veins  of,  721 
ossium  rubra,  40 
spinalis,  820 
Medullary  arteries,  619 
body,  888 
canal  of  bone,  35 
cavity,  formation  of,  45 
pyramids,  1349 
rays,  1349 

sheath  of  Schwann,  811 
velum,  inferior,  884,  891 
posterior,  888 
superior,  884,  891 
Medullated    axis-cyhnder    proc- 
esses, 811 
Megacephalic  skiUls,  145 
Meibomian  glands,  ill4 
Meissner    and    Wagner,     touch 

corpuscles  of,  816 
Meissner's  plexus  of  nerves,  1279 
Membrana  adamantina,  12l4 
atlantooccipitalis  anterior,  275 

posterior,  276 
basilaris,  1138,  1143 
cricothyroidea,  1165 
flaccida  of  Shrapnell,  1130 
hyaloidea,  1105 
hyothyreoidea,  1167 
interossea  antebrachii,  312 

cruris,  341 
mucosa  nasi,  1083 
nictitans,  lil5 


Membrana  obluratoria,  517 
stapedis,  1133 
pupillaris,  1100 
sacciformis,  318 
slerni,  286 
tectoria,  277,  1147 
tympani,  87,  1122,  1128 
artei'ies  of,   1131 
lymphatics  of,  1131 
nerves  of,  1131 
secundaria,  1126,  1140 
stratum  circulare,  1131 
mucos'um,  1130 
radiatum,  1131 
veiris  of,  1131 
vestibularis  [Reissneri],  1144 
Membrane,  basilar,  1143 
Bowman's,  1091 
of  brain,  964 
of  Bruch,  1093 
of  Corti,  1147 
costocoracoid,  459 
cricothyroid,  1165,  1168 
of  Demours,  1091 
of  Descemet,  1091 
of  Henle,  fenestrated,  573 
of  Hensen,  356 
hyaloid,  1106 
intercostal,  417 
of  KoUiker,  1147 
of  Krause,  356 
Nasmyth's,  1211 
otolith,  1143 
peridental,  1212 
of  Reissner,  1144 
of  Ruysch,  1093 
Schneiderian,  1083 
serous,  of  diaphragm,  421 
of  spinal  cord,  842  - 

sutural,  263 
synovial,  259,  261 
thyrohyoid,  1164,  1167 
tympanic,   1128 
vitelhne,   1400 
Membranous    canal    of   cochlea, 
1144 
labyrinth  of  ear,  1140 
primordial  cranium,  141 
semicircular  canals,  1142 
Meningeal  artery,  596,  597 
anterior,  609 
middle,  600 
posterior,  597,  621 
small,  600 
nerve,  983 

from  hypoglossal,  1011 
from      internal     maxillary, 

987 
from  vagus,  1005 
veins,  719 
Meninges  of  brain,  964 

encephali,  964 
Meningocele,  149 
Meningorachidian  veins,  843 
Menisci,  334 

articidares,  260 
Meniscofemoral  joint,  338 
Meniscotibial  joint,  338 
Meniscus  lateralis,  335 

niedialis,  334 
Mental  artery,  601 
foramen  li6,  136 
point  of  skull,  146 
process,  116,  135 
tubercles,  ll6 
Mesal  plane  of  skull,  146 
Mesencephalic  root  nuclei,  884 
Mesencephalon,  893 
Mesenteric  arteries,  663,  666 
lymph  nodes,  790 
peritoneum,  1249 
plexus  of  nerves,  1076 
veins,  753 
Mesentericomesocolic  fold,  1266 
Mesentericoparietal  fold,  1267 


1478 


INDEX 


Mesenteriolum    processus    vermi- 

formis,  1265 
Mesenterium,  1263 
Mesentery,  1263 

of  vermiform  appendix,  1265 
Masoappendix,  1265,  1299 
Mesocele,  897 
Mesocephalic  skull,  145 
Mesooolic  band,  1310 
fossae,  1266 
lymph  nodes,  791 
Mesocolon,  ascending,  1264 
descending,  1264 
sigmoid,  1264 
transverse,  1264 
Mesocolon  ascendens,  1264 
descendens,  1264 
sigmoideum,  1264 
transversum,  1264 
Mesogastrium,  1249 
Mesognathion,  106 
Mesometrium,   1407 
Meson  planes  of  body,  34 
Mesonephros,  1420 
Mesorbital  gyre,  920,  922 
Mesorchium,  1423 
Mesosigmoid,  1306 
Mesosteruum,  157 
Mesovariuin,  139S,  1407,  1423 
Metacarpal  bones,  201 
of  index  finger,  202 
of  little  finger,  203 
of  middle  finger,  203 
nutrient  canal  of,  201 

foramen  of,  201 
peculiar  characters  of,  202 
of  ring  finger,  203 
of  thumb,  202 
spaces,  202 
Metacarpophalangeal      articula- 
tions, 320 
surface  form  of,  321 
Metacarpus,  201 
Metanephros,  1425 
Metapore,  845,  867,  969 
Metasternum,  157 
Metatarsal  artery;  699 

articulation,     synovial     mem- 
brane in,  353 
;     bones,  249 

articulations  of,  252,  352 
common  characters  of,  250 
fifth,  252 
first,  250 
fourth,  251 

peculiar  characters  of,  250 
second,  251 
third,  251 
ligament,  transverse,  353 
veins,  741 
Metatarsophalangeal       articula- 
tions, 353 
Metopic  suture,  121 
Meynert,    fasciculus    retroflexus 

of,  906 
Microcephalic  skulls,  145 
Midbrain,  893 
aqueduct  of,  S97 
central  aqueduct  gray,  897 
crusta  of,  900 
development  of,  855 
fiber  tracts  of,  899,  900 
gray  masses  in,  summary  of, 

900 
intercalatum  of,  897 
pes  of,  900 
structure  of,  894,  896 
substantia  nigra  of,  897 
tegmentum  of,  89^6 
Midgut,  1247 
Milk  teeth,  1205 
Mitral  orifice,  560 

valve,  561 
Mixed  articulation,  264 
Moderator  band,  558 


Modiolus,  1138,  1139 
Molar  glands,  1200 

teeth,  1207 
Moll,  glands  of,  1113 
Monakow's  tract  of  cord,  839 
Monaxonic  neurones,  810 
Monro,  foramen  of,  936 
Mons  Veneris,  1415 
Montgomery,  glands  of,  1429 
Monticulus  cercbelli,  885 
Morgagni,  crypts  of,  1310 
hydatids  of,  1402 
sinus  of,  395 
valves  of,  1310 
Moss  fibers  of  Ramon  y  Cajal, 

893 
Motor  area  of  brain,  959 
end  plates,  816 
neurones,  804 
root  of  spinal  cord,  823 
Mouth,  1199 
angle  of,  1199 
aperture  of,  1199 
applied  anatomy  of,  1204 
cavity  of,  138,  1201 
development  of,   1204 
floor  of,  1201 
lymphatic  vessels  of,  777 
structure  of,  1201 
vestibule  of,  1200 
Movable  articulations,  264 
Mucous    membrane   of   bladder, 
1364 
of  cecum,  1310 
of  cheeks,  1200 
of  colon,  1310 
of  larynx,  1174 
of  nasal  fossae,  1083 
of  nose,  1081 
of  small  intestine,  1289 
of  soft  palate,  1203 
of  stomach,  1275 
of  tongue,  1217 
of  trachea,  1178 
of  tympanum,  1134 
of  uterus,  1410 
of  vagina,  1414 
Miiller,  muscle  of,  371 
nerve  fibers  of,  1104 
ring  muscle  of,  1096 
Miillerian  duct,  1423 
Multifidus  spinae  muscle,  413 
Multipenniforni  muscle,  358 
Multipolar  nerve  cells,  808 
Muscle  or  Muscles,  355 

of    abdomen,     anterio-lateral, 
423 
posterior,  439 
abductor  hallucis,  538 
indicis,  494 
minimi  digiti,  foot,  539 

hand,  493 
polUcis,  489 
longus,  485 
accelerator  urinae,  443 
of  acromial  region,  462 
adductor  brevis,  514 
longus,  513 
magnus,  514 
minimus,  514 
obliquus  hallucis,  541 

poUicis,  492 
transversus  hallucis,  541 
poUicis,  492 
anconeus,  482 
anomalous,  361 
antitragicus,   1121 
applied  anatomy  of,  359 
of  arm,  461,  467 
arrectores  pilorum,  1161 
of  articulations  of  elbow-joint 
308 
of  shoulder-joint,  303 
aryepiglottic,  1173    ■ 
arytenoideus,  1172 


Muscle  or  Muscles,   attachment 

of,  357 
attoUens  aurem,  366 
attrahans  aurem,  366 
of  auricular  region,  365 
azygos  uvulae,  398 
of  back,  403 
biceps,  469 

femoris,  522 

flexor  cubiti,  469 
biventer  cervices,  413 
biventral,  358 
brachialis  anticus,  469 
brachioradialis,  479 
of  buccal  region,  374 
buccinator,  375 
cardiac,  355 

cervicalis  ascendens,  412 
chondroglossus,  393 
ciliary,  1095 
coccygeus,  453 
complexus,  412 
compressor  bulbi,  444 

hemisphaerium  bulbi,  444 

naris,  372 

narium  minor.  372 

urethrae,  448 
constrictor,  inferior,  394 

middle,  395 

radicis  penis,  444 

superior,  395 

urethrae,  448 
coracobrachialis,  468 
ccrrugator  cutis  ani,  453 

supercilii,  367 
of  cranial  region,  362 
of  cranium,  362 
cremaster,  430 
cricoarytenoid,  1172 
cricothyroid,  1172 
crureus,  511 
of  deglutition,  397 
deltoid,  462 
depressor  alae  nasi,  372 

anguU  oris,  374 

labii  inferioris,  374 
detrusor  urinae,  1363 
development  of,  361 
of  diaphragm,  418 
digastric,  388 
dilator  naris,  anterior,  372 

posterior,  372 
of  dorsal  region,  537 
erector  clitoridis,  446 

penis,  444 

spinae,  410 
of  expression,  380 
extensor  brevis  digitorum,  537 
polUcis,  483 

carpi  radialis  brevior,  479 
longior,  479 
ulnaris,  482 

coccj'gis,  414 

communis  digitorum,  480 

indicis,  484 

longtis  digitorum,  527 
poUicis,  484 

minimi  digiti,  481 

ossis  metacarpi  poUicis,  482 

proprius  hallucis,  527 
of  face,  362 

of  femoral  region,  anterior,  505 
internal,  512 
posterior,  522 
fibers,  355 

of  fibular  region,  534 
fixation,  359 
flexor  accessorius,  539 

brevis  digitorum,  538 
hallucis,  541 
minimi  digiti,  foot,  541 

hand,  493 
poUicis,  490,  492  (note) 

carpi  radialis,  473 
ulnaris,  474 


INDEX 


1479 


Muscle  or  Muscles,  flexor  longus 
digitorum,  533 
hallucis,  532 
pollicis,  476 

profundus  digitorum,  476 

sublimis  digitorum,  475 
of  foot,  536 
■     of  forearm,  471 
form  of,  357 
frontalis,  364 
fusiform,  358 
gastrocnemius,  528 
geraelli,  520 
geniohyoglossus,  391 
geniohyoid,  390 
of  gluteal  region,  515 
gluteus  maximus,  515 

medius,  516 

minimus,  517 
gracilis,  512 
hamstring,  522 
of  hand,  486 
hclicis  major,  1121 

minor,  1121 
of  hip,  515 
Horner's,  367 
of  humeral  region,  467,  470 
hyoglossus,  391 
of  iliac  region,  502 
iliacus,  504 
iliococcygeus,  452 
iliocostalis,  410 
iliopsoas,  504  (note) 
iliosacralis,  452 
incisivus,  375 
inferior  oblique,  370 
infracostales,  417 
of  infrahyoid  region,  386 
infraspinatus,  465 
insertion  of,  definition  of,  359 
intercostal,  417 
interossei,  foot,  541 

of  hand,  494 
interspinales,  414 
intertransversales,  414 
involuntary,  355 

nonstriated,  bloodvessels  of, 
357 
nerves  of,  357 
ischiobulbosus,  444 
of  ischiorectal  region,  453 
of  larynx,  1172 
latissimus  dorsi,  406 
of  leg,  525 

levator  anguli  oris,  373 
scapulae,  407 

ani,  450 

glandulae  thyroideae,  1436 

labii  superioris,  373 
alaeque  nasi,  372 

menti,  374 

palati,  397 

palpebrae  superioris,  369 

penis,  444 

prostatae,  452 
levatores  costarum,  417 
ligamentous  action  of,  367 
of  lingual  region,  391 
lingualis,  393 
longissimus  dorsi,  412 
longus  colli,  401 
of  lower  extremity,  501 
lumbricales,  foot,  540 

hand,  493 
of  mandibular  region,  374 
masseter,  377 
of  maxillary  region,  373 
Miiller's,  371 
nuiltifidus  spinae,  413 
multipennate,  358 
mylohyoid,  389 
of  nasal  region,  372 
nasolabialis,  375 
of  neck,  380 
of  nose,  1081 


oblique. 


l_'l 


exUTiial,  4:14 

internal,  428 
obliquus  auriculae,  1121 

inferior,  415 

superior,  415 
obturator  externus,  521 

internus,  518 

occipitalis,  363 
occipitofrontalis,  363 
omohyoid,  388 

opponens  minimi  digiti,  foot, 
541 
hand,  493 

pollicis,  490 
orbicular,  358 
orbicularis  oris,  374 

palpebrarum,  366 
orbital,  368,  371 
origin  of,  definition  of,  359 
of  palatal  region,  397 
palatoglossus,  398 
palatopharyngeus,  398 
of  palmar  region,  493 
palmaris  brevis,  492 

longus,  474 
of  palpebral  region,  366 
papillary,  558 
pectineus,  513 
pectoralis  major,  456 

minor,  460 
of  pelvic  outlet,  440 
penniform,  358 
of  perineum  in  female,  445 

in  male,  442 
peronelis  brevis,  535 

longus,  534 

tertius,  527 
of  pharyngeal  region,  394 
of  pinna  of  ear,  1121 
of  plantar  region,  537 
plantaris,  530 
platysraa,  381 
popliteus,  531 
pronator  quadratus,  478 

teres,  472 
psoas  magnus,  504 

parvus,  504 
pterygoid,  379,  380 
of  pterygomandibular  region, 

379 
pubocavernosus,  444 
pubococcygeus,  452 
puboreotalis,  452 
pyramidalis,  435 

nasi,  372 
pyriformis,  517 
quadratus  femoris,  520 

lumborum,  439 

menti,  374 
quadriceps  extensor,  509 
quadrilateral,  358 
of  radi.al  region,  479,  489 
of  radioulnar  region,  472,  480 
recti,  370 

rectoeoecygeal,  1311 
rectouterinus,  1408 
rectOA'esieal,  1362 
rectus  abdominis,  433 

capitis  anticus,  400 
lateralis,  400 
posticus,  414 

femoris,  510 
retrahens  aurera,  366 
rhomboideus,  407 
ring,  of  Muller,  1096 
risorius,  377 
rotatores  spinae,  413 
salpingopharyngeus,  399 
sartorius,  508 
scalenus  anticus,  401 

medius,  401 

posticus,  402 


Muscle  or  Muscles  of  scapular 

region,  463,  464 
semimembranosus,   524 
semispinalis  colli,  413 

dorsi,  413 
semitendinosus,  524 
serratus  magnus,  461 

posticus,  408 
of  shoulder,  461 
skeletal,  355 
of  soft  palate,  1203 
soleus,  529 
spinalis  colli,  412 

dorsi,  412 
sphincter,  358 

ani,  453,  454 

recti,  452 

urethrae  memliranaceae,  448 

vaginae,  445 
spindle,  357 
spindles  of  Kuhne,  817 
splenius  capitis,  409 

colli,  409 
stapedius,  1134 
sternalis,  459 
sternohyoid,  386 
sternomastoid,  385 
sternothyroid,  387 
striated,  355 
striations  of,  cross,  356 

longitudinal,  356 
striped,  355 
styloglossus,  392 
stylohyoid,  389 
stylopharyngeus,  396 
subanconeus,  471 
subclavixis,  460 
subcrureus,  512 
subsoapvilaris,  464 
substance,  356 
of   superficial   cervical   region, 

381 
superior  oblique,  370 
supinator  [brevis],  482 

longus,  479 
of  suprahyoid  region,  388 
supraspinales,  414 
supraspinatus,  464 
suspensory,  of  duodenum,  1285 
synergic,  359 
tarsal,  369,  370 
temporal,  378 
of  temporomandibular  region, 

377 
tensor  fasciae  femoris,  508 

palati,  397 

tarsi,  367 
teres  major,  466 

minor,  466 
of  thigh,  505 

of  thoracic  region,  455,  461 
of  thorax,  416 
thyroarytenoid,  1173 
thyroepiglotticus,  1173 
thyrohyoid,  387 
tibialis  anticus,  526 

posticus,  533 
of  tibiofibular  region,  anterior, 
525 
posterior,  528 
of  tongue,  393 

traehealis,  of  Todd  and  Bow- 
man, 1178 
trachelomasfoid,  412 
tragicus,  1121 
transversalis,  432 

capitis,  412  (note) 

cervicis,  412 
transverse  perineal,  442,  44.5 
transversus  auriculae,  1121 

perinei  profundus,  448 
trapezius,  404 
triangular,  358 
triangularis  sterni,  417 
triceps,  470 


1480 


INDEX 


Muscle  or   Muscles,   triceps  ex- 
tensor cubiti,  470 
ot  trunk,  403 
of  tympanum,  1134 
ot  ulnar  region,  492 
unstriped,  355 
of  upper  extremity,  454 
of  ureters,  1363 
variable,  361 
vastus  externus,  510 

internus,  511 
vegetative,  355 
of  vertebral  region,  400,  401 
voluntary,  355 

arteries  of,  356 

nerves  of,  357 

veins  of,  357 
zygomaticus  major,  373 

minor,  373 
Musculi  airectores  pilorum,  1161 
intercoslales  externi,  417 

interni,  417 
interossei,  493 

dorsales,  494 

volares,  494 
interspinales,  414 
intertraTisversarii,  414 
laxator  tympani  major  et  mi- 
nor, 1134 
levatores  costarum,  417 
lumbricales,  493 
papillares,  558,  561 
pectinati,  554,  557,  559 
rotatores,  413 
subcoslales,  417 
supraspinalcs,  414 
Musculocutaneous  nerve,   1060 
Musculophrenic  artery,  632 
Musculospiral  groove,  180 

nerve,  1037 
Musoulus  abductor  digili  quinti, 
492,  539 
brevis,  493 

hallucis,  538 

pollidis  brevis,  489 
longus,  482 
accessorius,  410 
adductur  brevis,  514 

longiis,  613 

magThUS,  514 

mininiuc,  514 

poUicis,  490 

transvernus  pollicis,  492 
anconaeus,  482 
antitragicuj,  1121 
articularis  genu,  512 
auricularis  anterior,  366 

posteriori',  366 

superior,  366 
arytenoideas  obliquus,  1172 

iransversus,  1173 
biceps  brachii,  469 
caput  breve,  469 
Imifjum,  469 

femoris,  522 

capwj  fereae,  523 
longum,  522 
bipennatus,  358 
biventer  cerncis;  413 
brachialis,  469 
brachiorddialis,  479 
buccinator,  375 

bulbocavernosus,  443,  445,  675 
caninus,  373 
capitis  posterior  major,  414 

Tninor,  414 
chondroglossus,  392 
ciliaris,  1095 

fibrae  circiilares,  1096 
meridianales,  1095 
coccygeiis,  453 
compressor  bulbi,  444 

hemisphaerium  bulbi,  444 
constrictor  isthi  faucium,    391 

(note) 


Musculus    constrictor    pharyngis 
inferior,  394 
medius,  395 
superior,  395 
radicis  penis,  444 
coracobra-chialis,  468 
cremaster,  430,  1374 
cricoarytenoideus  lateralis,  1172 

posterior,  1172 
cricotkyreoideus,  1172 
deltoideus,  462 
depressor  septi,  372 
digastricus,  388 
dilatator  pupillae,  1099 
epicranius,  363 
erector  clitoridis,  1418 
extensor   carpi   radialis    brevis, 
479 
longus,  479 
digiti  quinti  proprius,  481 
digitorum  brevis,  537 
communis,  480 
longus,  527 
hallucis  longus,  527 
indicis  proprius,  484 
pollicis  brevis,  483 
longus,  484 
flexor  carpi  radialis,  473 
ulnaris,  474 

caput  humerale,  474 
ulnare,  474 
digiti  quinti  brevis,  541 
digitorum  brevis,  538 
longus,  533 
profundus,  476 
sublimis,  475 

caput  humerale,  475 
radiate,  475 
ulnare,  475 
pollicis  brevis,  490 
longus,  476 
frontalis,  363 
gastrocnemius,  528 
caput  laterale,  528 
mediale,  528 
gemellus  inferior,  520 

superior,  520 
genioglossus,  391 
geniohyoideus,  390 
glossopalatinus,  398 
glutaeus  maximus,  515 
medius,  516 
minimus,  517 
gracilis,  512 
hallucis  longus,  532 
helicis  major,  1121 

m.inor,  1121 
hyoglossus,  391 
iliacus,  504 
iliococcygeus,  452 
iliocostalis  ceroids,  412 
dorst,  410 
lumborum,  410 
iliosacralis,  452 
incisivus  inferior,  375 

superior,  375 
infraspinatus,  465 
interossei,  541 
dorsales,  541 
plantar es,  542 
ischiobulbosus,  444 
ischiocavernosus,  444,  446,  675 
latissimus  dorsi,  406 
levator  scapulae,  407 

jicH  palatini,  397 
longissimus  cdpitis,  412 
cervicis,  412 
dorsi,  412 
longitudinalis  inferior,  393 

superior,  393 
longus  capitis,  400 

coiZi,  401 
lumbricales,  540 
masseter,  377 
mentalis,  374 


Musculus  multifidus,  413 
mylohyoideus,  389 
nasalis,  372 
nasolabialis,  375 
obliquus  auriculae,  1121 

capitis  inferior,  415 
superior,  415 

externus  abdominis,  424 

internus  abdominis,  428 

ocuZi  inferior,  370 

superior,  370 

obturator  externus,  521 

internus,  518 
occipitalis,  363 
omohyoideus,  388 
opponens  digiti  quinti,  493 

pollicis,  490 
orbicularis  oculi,  366 

oris,  374 
orbitale,  371 

ossiculorum  auditus,  1134 
palmaris  brevis,  492 

longus,  474 
pectineus,  513 
pecioralis  major,  456 

minor,  460 
peronaeus  brevis,  535 

longus,  534 

tertiv^,  527 
pharyngopalatinus,  398 
piriformis,  517 
plantaris,  530 
platysma,  381 
popliteus,  531 
procerus,  372 
pronator  quadratus,  478 

ieres,  472 

caput  humerale,  472 
ulnare,  472 
psoas  major,  504 

mino)-,  504 
pterygoideus  externus,  379 

internus,  380 
ptibocajjerraostts,  444 
pubococcygeus,  452 
puborectalis,  452 
pubovesicalis,  1363 
pyramidalis,  435 
quadratus  femoris,  520 

Zo&ii  inferioris,  374 

lumborum,  439 

plantae,  539 
quadriceps  femoris,  509 
rectococcygeus,  1310 
rectouterinus,  1408 
rectovesicalis,  1362 
rectus  abdominis,  433 

capitis  anterior,  400 
lateralis,  400 

femoris,  510 
rhomboideu^  major,  407 

minor,  407 
risorius,  377 
sacrospinalis,  410 
salpingopharyngeus,  399 
sartorius,  508 
scalenus  anterior,  401 

medius,  401 

posterior,  402 
semimembranosis,  524 
semispinalis  capitis,  412 

cervicis,  413 

dorsi,  413 
semitendinosus,  524 
serratus  anterior,  461 

posterior  inferior,  408 

superior,  408 
solcus,  529 

sphincter  ani  externus,  453 
internus,  454 

papillae,  1099 

pylori,  1273 

recti,  452 

urethrae  membranacea,   448, 
1368 


INDEX 


1481 


Musculus  spinalis  ccrmcis,  412 

dorsi,  412 
splenius  capitis,  409 

ceroids,  409 
sta,pedius,  1134 
sternoclcidomastoideus,  385 
sternohyoideus,  386 
slernothyreoideus,  387 
styloglossus,  392 
stylohyoidcus,  389 
slylopharyngeus,  396 
suhclavius,  460 
subscapularis,  464 
supinator,  482 
supraspinatus,  464 
suspensoriiis  duodenum,  1285 
temporalis,  378 
tensor  fasciae  laiae,  508 

iieZi  palatini,  397 
ieres  major,  466 

minor,  466 
thyreoarytenoideus ,  1173 
thyreoepiglotticus,  1173 
Ihyreohyoideus,  387 
tibialis  anterior,  526 

posterior,  533 
transversalis  capitis,  412  (note). 
transversus  ahdomiriis,  432 

auriculae,  1121 

linguae,  393 

menti,  374  (note) 

perinei  superficialis,  442,  445 

thoracis,  417 
trapezius,  405 
triangularis,  374 
triceps  brachii,  470 

caput  laterale,  470 

longum,  470 

mediate,  470 

unipennatus,  358 

uvulae,  398 

vastus  intermedius,  511 

lateralis,  510 

medialis,  511 
verticalis  liTi/juae,  393 
vocalis,  1173 
zygomaticus,  373 
Myelencephalon,  861 
Myelin  sheath,  811 
Myelocele,  831 
Myelocytes,  40 
Mylohyoid  artery,  601 
muscle,  389 
nerves,  989 
ridge,  117 
Mylohyoidean  groove,  117 
Myocardium,  562 
Myogenic  theory  of  heart  beat, 

566 
Myology,  definition  of,  34 


N 

Nails,  1156 

lunula  of,  1157 

matrix  of,  1157 
Nares,  1081 

anterior,  1081 

posterior,  138,  1081 
Nasal  angle,  100 

aperture,  anterior,  138 

arch  of  veins,  710 

artery,  612 

transverse,  613 

bones,  99 

cavity,  138 

crest,  105,  110 

duct,  1117  ■ 

applied  anatomy  of,  1119 
canal  for  orifice  of,  141 

foramen,  99 

fossa;,  1081' 

arteries  of,  1085 
inner  wall  of,  1083 


Nasal   fossae,    lymphatic   vessels 
of,  777,  1085 

mucous  membrane  of,  1083 

nerves  of,  1085 

outer  wall  of,  1082 

veins  of,  1085 
index  of  skull,  146 
meatus,  atrium  of,  141 

inferior,  141 

middle,  140 

superior,  139 
nerve,  980,  984 
process  of  maxillas,  104 
region,  muscles  of,  372 
sinus,  septum  of,  139 
slit,  139 
spine,  79 

anterior,  135,  139 

posterior,  129,  139 
surface  of  maxillae,  102 
Nasion,  134,  146 
Nasmyth's  membrane,  1211 
Nasofrontal  suture,  122 

vein,  725 
Nasomaxillary  suture,  135 
Nasopalatine  arterj',  602 
canal,  114 
groove,  114 
nerve,  986 
Nasopharynx,  1229 
Nasus  externus,  1079 
Navicular  bone,  foot,  246 

hand,  196 
Neck,  arteries  of,  583 
fascia  of,  380 
lymphatics  of,  774 
muscles  of,  380 

lymphatic  vessels  of,  780 

surface  form  of,  402 
sldn  of,  lymphatic  vessels  of, 

780 
triangles  of,  385,  602 
veins  of,  710,  713 
N^laton's  line,  229,  329 
Nerve  or  Nerves,  812 
abducent,  993 
acoustic,  1000 
acromial,  1022 
ampullar,  1001 
of  ankle-joint,  345 
anococcygeal,  1062 
Arnold's,  1005 
of  arteries,  574 

articular,   from   external   pop- 
liteal, 1059 

from  great  sciatic,  1055 

from  internal  popliteal,  1057 

from  posterior  tibial,  1057 

from  ulnar,  1036 
of  articulations  of  elbow-joint, 
308 

of  shoulder-joint,  303 
auditory,  1000 
of  auditory  canal,  1123 
auricvilar,  anterior,  988 

from  vagus,  1005 

great,  1020 

posterior,  997 
auriculotemporal,  988 
beginnings,  peripheral,  815 
of  bile  ducts,  1334 
of  bladder,  1365 
bloodvessels  of,  813 
of  bone,  41 
buccal,  987,  998 
buccinator,  987 
calcaneal,  1057 
cardiac,  cervical,  1007 

great,  1069 

inferior,  1069 

middle,  1069 

superior,  1068 

thoracic,  1007 
of  cardiac  muscle,  357 
caroticotympanic,  1066 


Nerve  or  Nerves,  carotid,  1003 
cavernous,  1077 
cell,  bipolar,  1102 

body,  807 

arboriform,  SOS 
bipolar,  808 

central    endoplastic    por- 
tion, 809 
Golgi,  808 

peripheral       exoi:)lastic 
portion,  809 
multipolar,  808 
stellate,  808 
unipolar,  808 

of  cerebral  cortex,  952 

ciliated  ependymal,  806 

germinal,  806 

glia,  818 

nidi,  S12 

nuclei,  812 

of  spinal  cord,  832 
cervical,  1021 
cervicofacial,  998 
chemical  composition  of,  819 
chorda  tympani,  997 
of  choroid,  1099 
ciliary,  981,  982 
circumflex,  1030 
clavicular,  1022 
of  clitoris,  1420 
coccygeal,  1019 
cochlear,  1000 
communicans  tibialis,  1057 
communicantes        hypoglossi, 

1023 
of  conjunctiva,  1115 
of  cornea,  1092 
corpuscles,  816,  817 
cranial,  972 
crural,  anterior,  1049 
cutaneous,  of  abdomen,  1043 

external,  1047 

femoral,  1055 

from  external  popliteal,  1059 

from  musculospinal,  1038 

gluteal,  1055 

internal,  1032,  1050 
lesser,  1034 

lateral,  1047 

middle,  1050 

palmar,  1036 

perforating,  1060 

perineal,  1055 

postfemoral,   1054 
dental,  984,  989 
descendens  hypoglossi,  1011 
digastric,  from  facial,  998 
digital  dorsal,  1060 
dorsal,  of  clitoris,  1061 

of  penis,  1061 
of  duodenum,  12S7 
of  dura  of  brain,  968 
dural,  983 

from  hypoglossal.  1041 

from  vagus,  1005 
eighth,  1000 
eleventh,  1009 
facial,  994 

of  Fallopian  tube,  1402 
femoral,  1049 
fibers,  812 

association,  954 

centripetal,  810 

of  cerebral  cortex,  952 

commissural,  955 

glia,  818 

projection,  956 

radiating,  1104 

of  spinal  cord,  832,  834 

supporting,  of  Miiller,  1104 

sympathetic,  812 

vasomotor,  813 
fifth,  978 
first,  973 
fourth,  977 


14S 


IXDEX 


Keire  or  Xerves,  frontal,  9S0 
of  gall-bladder,  13.3-4 
gauglion  of,  of  Andersch,  1002 

aorticorenal,  1073 

of  Bochdalek.  9S4 

cardiac,  of  Wrisberg,  1072 

carotid,  1066 

cer\-ical,  1069 

ciliary,  9S2 

coccygeal,  1072 

Gasserian.  978 

geniculate.  996 

inipar.  1072 

inferior,  1002,  1005 

jugular,  1002,  1005 

lenticular,  9S2 

Meckel's.  984 

ophthalmic,  982 

otic.  989 

petrous.  1002 

of  Scarpa.  1000 

semilunar,  978,  1073 

sphenopalatine,     982,     984, 
986 

spiral,  1000 

submasillarj-,  990 

superior,  1002 

of  Valentin,  984 

vestibular,  1000 
gastric,  1007 
genitocrural.  1047 
genitofemoral.  1047 
gingival,  95>4 
glossopharj-ngeal,  1001 
gluteal,  1054 
granules.  1103 
of  heart,  565 

hemorrhoidal,  inferior,  1061 
of  hip-joint.  327 
h\-pogastric,  1046 
h\-poglossal,  1010 
ffiae,  1046 

iliohj-pogasmc.  1045 
ilioinguinal,  1046 
infraclaricular.  1029 
infraorbital.  982  (note),  998 
infratrochlear,  981 
intercostal.  1040 
intercostobrachial,  1042 
intercostohunieral,  1042 
interosseous,  anterior,   1036 

volar.  1036 
of  involuntar\"  striated  muscle, 

357 
of  iris,  1099 
Jacobson's,  1002 
of  kidneys,  1354 
of  knee-joint,  337 
of  labia  majora,  1415 
labial,  984 
lacrimal,  980 
of  large  intestine,  1312 
larj-ngeal.  1068 

inferior,  1007 

recurrent,  1007 

superior,  1006 
of  larj-ns,  1174 
lingual,  988 

from  elossophar\Tigeal,  1003 
of  liver.  1-331 
lumbar,  1020 
lumboinguinal,  1047 
of  lungs.  1196 
malar,  998 

of  superior  mavillary,  983 
from  facial,  998 
of  mammarj-  gland,  1432 
mandibular.  987 

from  facial.  998 
masseteric.  9s>< 
maxillarj-.  inferior,  987 

superior.  982 
median,  1034 

of  membranan  tjTnpani,  1131 
meningeal.  9S3 


Nerve    or     Nerves,    meningeal, 
from  hjTxiglossal,  1011 

from  inferior  maxfUarj-,  987 

from  vagus,  1005 
muscular,  of   brachial   plexus, 
1028 

from  glossopharjiigeal,  1003 

from  great  sciatic,  1055 

from  hj-poglossal,  1012 

from  internal  plantar,  1059 
popliteal,  1057 

from  median,  1035 

from  musculospinal,  1037 

from  posterior  tibial,  1057 

from  ulnar,  10-36 
musculocutaneous.  1031,  1060 
musculospiral,  1037 
mylohyoid,  989 
nasal,  980,  984 

fossiB.  1085 
nasopalatine,  986 
ninth,  1001 
of  nose,  1081 
obturator,  104* 

accessory".  1049 
occioital.  great,  1017 

small.  1020 

third,  1017 
oculomotor,  976 
of  oesophagus,  1239 
olfactorj-.  973 
ophthalmic,  979 
optic,  974 
orbital,  983 
origin  of,  814 
of  ovaries,  1-401 
palatine,  986 
palpebral,  984 
of  pancreas,  1-341 
papiUse,  1154 
parotid.  988 
of  parotid  glands,  1225 
patellar,  1051 
of  penis,  1390 
pericranial.  9b0 
perineal,   1061 
peroneal,  1057,  1059 
petrosal,  98-5 

deep,  1066 

superficial,  989,  996 
phar\-ngeal.   986,    1003,    1006, 

1068 
phrenic.   1024 
of  pia  of  brain,  970 
plantar,  1057,  1058 
of  pleura,  1185 

plexus    of    abdominal    aortic, 
1076 

Auerbach's,  1279 

brachial,  1026 

cardiac.  1072 

carotid.  1066 

cavernous,  1066 

cervical.  1018.  1020 

coccygeal.  1062 

coeliac.  1008,  1073 

coUc,  1076 

coronar\-.  1073,  1076 

cvstic,  1076 

gastric,  1076 

gastroduodenal,  1076 

gastroepiploic,  1076 

hemorrhoidal,  1077 

hepatic,  1076 

hj-pogastric.  1077 

ileocolic,  1076 

infraorbital,  984,  998 

intestinal.  1076 

lumbar,  1044 

lumbosacral.  1044 

ileissner's.  1280 

mesenteric,  1076 

oesophageal.      1007,       1073, 
1075 

ovarian,  1076 


Nerve  or   Nerves,   plextis,   pan- 
creatic, 1076 

pancreaticoduodenal,  1076 

patellar,  1051 

peh-ic,  1077 

pharj-ngeal,  1003,  1006 

phrenic,  1074 

prostatic.  1077 

pudendal,  1060 

pulmonarj-,  1073 
posterior,  1005 

pvloric.  1076 

renal,  1008^  1075 

sacral-  1053 

sigmoid,  1076 

solar,  1073 

spermatic.  1076 

splenic,  1008,  1076 

suprarenal.  1074 

thjToid,  1069 

tjTnpanic,  1002 

uterine.  1077 

vaginal-  1077 

vertebraUs^  1069 

vesical,  10 1  7 
pnevunogastric,  1003 
pophteal,  1055,  1059 
of  prostate  eland,  1395 
pterj-goid,  987,  988 
pterj-gopalatine,  986 
pudendal,  1055 
pudic.  1061 
pulmonary,  1007 
radial.  1038 
recurrent.  987 

respirator^-,  of  Bell,  1024,  1029 
sacral,  1019 

of  salivary'  glands,  1226 
saphenous.  1056,  1057 
scapular,  posterior,  1029 
sciatic,  1054,  1055 
scrotal,  long.  1055 
second,  974 

of  seminal  vesicles,  1385 
seventh,  994 
sheath  of.  812 
sixth,  993 
of  skin,  1156 
of  small  intestine,  1295 
spermatic,  1047 
sphenoidal,  990 
sphenopalatine,  983 
spinal,  1012 

accessorj-,  1009 
spindles.  817 
splanchnic.  1071 
of  spleen.  1446,  1449 
sternal.  1022 
of  stomach,  1279 
structure  of,  812 
stj-lohyoid,  998 
subcutaneus  malae,  983 
of  submaxillary  gland,  1226 
subscapular.  1030 
supracla^-icular,  1022 
supraorbital.  980 
suprascapular,  1029 
supratrochlear,  980 
system,  803 

central,  819 

development  of,  804 

structure  of,  80/ 

supporting    tissue    elements 
of,  818 

sympathetic.  1063 
tarsal,  1059 
of  taste,  1149 
temporal,  from  facial,  998 

from  internal  maxillary,  987 

from  superior  masHlarj-,  983 
temporofacial,  998 
temporomalar,  983 
of  temporomandibular  articu- 
lation, 281 
tenth,  1003 


INDEX 


1483 


Nerve  or  Nerves,  termination  of, 

«17 
third,  976 
thoracic,  1018 

anterior,  1030 

long,  1029 

posterior,  1029 
thoraeicolumlsar,   1043 
thoracoabdominal   intercostal, 

1043 
of  thymus  gland,  1440 
thyrohyoid,  1011 
thyroid,  1069' 
of  thyroid  gland,  1438 
tibial,  1055 

anterior,  1059 

posterior,  1057 
tissue,  development  of,  800 
of  tongue,  1221 
of  tonsil,  1231 
tonsillar,  1003 
tract,  cerebellospinal,  838 

Lowenthal's,  840 

ventral  cerebrospinal,  840 

Monakow's,  839 

prepvramidal,  839 
tirifacial,  978 
trigeminal,  978 
trochlear,  977 
twelfth,  1010 
tympanic,  from  facial,  997 

from  glossopharyngeal,  1002 
of  tympanum,  1135 
ulnar,  1036 
of  ureters,  1358 
of  uterus,  1411 
utricular,  1000 
utriculoampullar,  1000 
of  vagina,  1415 
of  vaginal  bulb,  1420 
vagus,  1003 
vestibular,  1000 
Vidian,  985,  1066 
of  voluntary  muscles,  357 
of  >  Wrisberg,  1034 
of  wrist-joint,  315 
Nirm  anococcygei,  1062 
miriculares  anteriores,  988 
rami  parotidei,  988 

temporales  superficiales, 
9SS 
carotid  externi,  1068 
■cavernosi  penis  ininores,  1077 
■cerebrales,  972 
ciliares  breves,  982 

longi,  981 
cluniwm.    inferiores    [latcrales], 

1055 
■digitales  dorsales  hallucis  later- 
alis, 1060 
pedis,  1060 

plantares  communes,  1057 
proprii,  1058 

wlares  communes,  1035 
proprii,  1035 
■digiti  secundi  medialis,  1060 
intercostales,  1041 

rami  anteriores,  1042 
cutanei  laterales,  1042 
musculares,  1042 
posteriores,  1042 
labiales  anteriores,  1047 

posteriores,  1061 
nervorum, '813 
palatini,  986 
palatinus  anterior,  986 

medius,  986 

posterior,  986 
scrotales  anteriores,  1047 

posteriores,  1061 
sphenopalatini,  983 
spinales,  1012 

radix  anterior,  1013 
posterior,  1013 

rami  anteriores,  1015 


Nervi  spinales   rami  posteriores, 
1014 
rainus  communicans,  1015 
meninocus,  1014 
sutjscapiilfireii,  1030 
supraclavicularcs,   1022 
anteriores,  1022 
nicdii,  1022 
posteriores,  1022 
temporalis  profundi,  987 
ihoracales  anteriores,  1030 
Nervus  abducens,  993 
accessorius,  1009 

ramus  externus,  1009 
internus,  1009 
acusiicus,  1000,  1147 
radix  cochlearis,  1000 
vestibularis,  1000 
aheolaris  inferior,  989 
auricularis  magnus,  1020 
posterior,  997 

ramus  occipitalis,  998 
auriculotemporalis,  988 

rami    anastomotica    cum    n. 
faciali,  988 
axillaris,  1030 
buccinatorius,  987 
canalis  pterygnidei,  985 
cardiacu-s  inferior,  1069 
medius,  1069 
superior,  1068 
caroticotyinpanicus        inferior, 
1003 
superior,  1003 
caroticus  internus,  1066 
cavernous  penis  major,  1077 
cochlearis,  1147 
CMtanetts    antebrachii    dorsalis, 
1038 
lateralis,  1031 
Tnedialis,  1032 
hrachii  lateralis,  1030 
medialis,  1034 
posterior,  1038 
coZii,  1021 

rami  inferiores,  1021 

ramus  superior,  1021 

dorsalis  intermedius,  1060 

medialis,  1060 
femoris  lateralis,  1047 
posterior,  1054 

rami  perineales,  1055 
SMrac  lateralis,  1059 

ramus  anastomoticus  pe- 
ronaeus,  1059 
medialis,  1057 

ramus  anastoinoticus  pe- 
ronaefiLS,   1057 
dorsalis  clitoridis,  1061 
penis,  1061 
scapulae,   1029 
facialis,  994 

gewM  internum,  994 
rami  buccales,  998 
temporales,  998 
zygomatici,  998 
ramus  coiZi,  999 
digastricus,  998 
marginalis        mandibulae, 

998 
stylohyoideus,  998 
femoralis,  1049 
frontalis,  980 
genitofemoralis,  1047 
glossopharyngeus,  1001 
ganglion  inferius,  1002 
superius,  1002 
glutaeus  inferior,  1054 

superior,  1054 
hemorrhoidalis  inferior,  1061 
hyoglossus,  1010 

rami  linguales,  1012 
ramus  descendens,  1011 
thyreohyoideus,   1011 
iliohypogastricus,  1045 


Nervus     iliohypogastricus     rami 
musculares,  1045 
ramus     cutaneus      anterior, 
1046 
lateralis,  1046 
ilioinguinalis.  1046 

rami  musculares,  1046 
infratrochlearis,  981 
intercostalis  I,  1040 

ramus     cutaneus      anterior, 
1041 
intercostobrachialis,  1042 
intermedius,  877,  882,  955,  995 
interosseus     [antebrachii]     dor- 
salis, 1039 
DoZoris,  1035 
,  ischiadicus,  1055 

rami  arliculares,  1055 
musculares,  1055 
jugularis,  1068 
lacrimalis,  980 
laryngeus  superior,  1006 
ramus  externus,  1006 
internus,  1006 
lingualis,  988 
lumboinguinalis,  1047 
mandibularis,  987 


maxillaris,  982 

rami     alvcolares     superiores 
posteriores,  984 
ra»ni  gingivales  supe- 
riores, 984 
lahialis  superiores,  984 
nasales  inierni,  984 
palpebrales  inferiores,  984 
ramus     alveolaris     superior 
anteriores,  984 
medius,  984 
meatus  auditorii  externi,  988 

ramus  membranae  tym- 
pani,  988 
mediamts,  1034 

rami  musculares,  1035 
ramus  cutaneus  palmaris  n. 
mcdiani,  1035 
meninqeus  medius,  983 
menialis,  989 
mtisculocutaneus,  1031 
mylohyoideus,  989 

rami  deniales  inferiores,  989 
gingivales  inferiores,  989 
nasociliaris,  980 

rami  nasales  laterales,  981 
mediales,  981 
nasopalatimis,  986 
obfuratorius,  1047 
accessorius,  1049 
ramus  anterior,  1049 
cutaneus,  1049 
posterior,  1049 
occipitalis  major,  1017 
minor,  1020 
tertius,  1017 
oculomotorius,  976 

ra(ii.i;  hreois  ganglii  ciliaris, 

977 
ramus  inferior,  976 
superior,  976 
olfactorius,  97.3 
ophthalmicus,  979 
opticus,  974 
perinei,  1061 

peronaeus  communis,  1059 
rami  arliculares,  1059 
profundus,  1059 

rami  m2isculares,  1059 
super ficialis,  1060 
petrosus  profundus,  985,  1135 
super  ficialis.  1135 
major,  985 
phrenicv^,  1024 
plantaris  lateralis,  1058 

ramus  profundiis,  1059 
superficialis,  1058 


1484 


INDEX 


Nenus  plantaris  medialis,  1057 
pterygoideus  externus,  988 

internus,  987 
pudendus,  1061 
radialis,  1037 

Tami  musculares,  1037 

ramus  superficialis,  1038 

nn.     digitali 

1039 

recurrens,  1007 

ra?ni  cardiaci  inferiores,  1007 
superiores,  1007 
saphenus,  1050 

ramus  infrapatellaris,  1051 
spermaticus  externus,  1047 
spinosu^,  987 

splanchnicus  imus,  1071  , 

mujor,  1071 
minor,  1071 
stapedius,  997 
subclavius,  1029 
subscapularis,  1029 
supraorbitalis,  980 
supratrochlearis,  980 
temporalis  profundus  anterior, 
987 
posterior,  987 
thoracalis  longus,  1029 
thoracodorsalis,  1030 
tibialis,  1055 

rami  articulares,  1057 
m,usculares,  1057 
calcanei  laterales,  1057 
mediales,  1057 
ramtts  articularis  ad  articula- 
tionem  talocruralem,   1057 
trigeminus,  978 
irochlearis,  977 
tyTnpanicus,  1002,  1125,  1135 
romi  linguales,  1003 
pharyngei,  1003 
tonsillares,  1003 
ramus  stylopharyngetis,  1003 
ulnaris,  1036 

rami  Tnusculares,  1036 
ramus     cutaneus     palmaris, 
1036 
dorsalis  manus,  1036 

nn.  digitales  dorsales, 
1036 
profundus,  1037 
superficialis,  1037 
Bogtis,  1003 

rami  coeliaci,  1008 
gastrici,  1007 
hepatica,  1008 
lienales,  1008 
oesophagei,  1007 
renales,  lOOS 
ramus  aurieularis,  1005 
meningewi,  1005 
pharyngeus,  1006 
vestibularis,  1147 
zygomaticus,  983 

ramus  zygomaticofacialis,  983 
zygomaticotemporalis,    983 
Neumann's  sheaths,  1211 
Neural  crest,  805 

segments,  851 
Neuraxone,  807 
Neurilemma,  811 
nucleus  of,  812 
Neuroblasts,  806 
Neuroeentral  suture,  63 
Neuroepithelium,  1143 
Neurofibrils,  809 
Neurogenic  theory  of  heart  beat, 

566 
Neuroglia,  806,  818 
Neurology,  definition  of,  34 
Neuromeres,  851 
Neuromuscular  spindles,  817 
Neurones,  803,  807 

centripetal,    peripheral    nerve 
beginnings  of,  816 


Neurones,  diaxonic,  810 

excitoglandular,  804 

excitomotor,  804 

monaxonic,  810 

motor,  804 

polyaxonic,  810 

sensor,  804 

theory  of,  818 

varied  forms  of,  807 
Neurotendinous  spindles,   817 
iVicZi,  832 
Nidus  avis,  888 

habenulae,  906 

laryngoi,  879 

pharyngei,  879,  881 
Ninth  nerve,  1001 

thoracic  vertebra,  54 
Nipple,  1428 
Nissl  bodies,  809 
Nodes,  hemolymph,  768 

lymph,  768 

Parrot's,  151 

of  Ranvier,  811 

of  Tawara,  564 
Noduli  lymphatici  aggregati  [Pey- 
cri],  1292 
solitarii,  1292 
Nodulus,  888 

valvulae  semilunaris  [Arantii] 
559,  561 

vermis,  888 
Norma  basalis,  128 

frontalis,  134 

lateralis.  132 

verticalis,  123 
Nose,  1079 

apphed  anatomy  of,  1085 

arteries  of,  1081 

cartilage  of,  1079 

framework  of,  liony,  1079 
cartilaginous,  1079 

integument  of,  1081 

lymphatics  of,  1081 

meatus  of,  110 

mucous  membrane  of,  1081 

muscles  of,  1081 

nerves  of,  1081 

septum  of,  138 
artery  of,  602 
cartilage  of,  1080 

veins  of,  1081 
Nostrils,  1081 
Notch,  cotyloid,  213 

ethmoidal,  79 

intercondyloid,  225 

intervertebral,  49 

lacrimal,  102 

popliteal,  233 

preoccipital,  914 

presternal,  157,  166,  171 

pterygoid,  94 

of  Rivinus,  1130 

sacrosciatic,  210,  211 

sigmoid,  118 

sphenopalatine,  112 

supraorbital,  77,  135 

suprascapular,  175 

suprasternal,  403 
Nuck,  canal  of,  1408 
Nuclei,  832 

of  abducent  nerve,  883 

of  acoustic  nerve,  881 

of  auditory  nerve,  881 

of  brain,  857 

of  cerebellum,  888 

of  cochlear  nerve,  881 

of  facial  nerve,  882 

of  glossopharyngeal  nerve,  880 

of  hypoglossal  nerve,  878 

of  oculomotor  nerve,  901 

olivarii  accessorii,  873 
dorsalis,  873 
medialis,  873  ■ 

of  olive,  873 


Nuclei   radicis   ascendentis    nervi 

trigemini,  883 
of  solitary  tract,  880 
of  spinal  accessory  nerve,  879 

cord,  cervical,  833 
Deiters',  839 
sacral,  833 
of  tegmentum,  897 
of  trigeminal  nerve,  883 
of  trochlear  nerve,  901 
of  vagus  nerve,  880 
of  vestibular  nerve,  881 
Nucleus  arabiguus,  881 
amygdaline,  948 
anterius,  905 

thalami,  905 
arcuatus,  873 
caudate,  937,  946  • 
caudatus,  946 
dentatus,  888 

dorsalis  [Clarkii],  830,  833 
emboliformis,  889 


funiculi  cuneati,  863 

gracilis,  863 

teretis,  873 
globosus,  889 
globulus,  889 
glossopharyngci,  880 
hypoglossi,  1010 
incertus,  876 
intercalatus,  873 
interpeduncular,  898 
lateralis,  873,  905 

thalami,  905 
lenticular,  947 
lentis,  1107 
magnocellularis,  881 
medialis,  905 
mesencepalic  root,  884 
olivarius  inferior,  873 

superior,  876 
olivary,  873 
postremus,  873 
pulposus,  270 
red,  898 
salivatorius,  882 
semilunaris  [Flechsigi],  905 
tegmenti,  898 
tractus  solitarii,  882 
vagi,  880 
Nuel,  space  of,  1147 
Nuhn   and   Blandin,    glands   of, 

1219 
Nutrient  arterv  of  brachial,  643 

of  filjula,  702 

of  tibia,  702 
canal  of  fil:»ula,  237 

of  metacarpal  bones,  201 

of  radius,  191 

of  ulna,  189 
foramen  of  fibula,  237 

of  metacarpal  bones,  201 

of  radius,  191 

of  tibia,  234 

of  ulna,  189 
Nymphae,  1416 


Obelion,  123,  146 
Obex  [ventriguli]  guarti,  867 
Oblique  diameter  of  pelvis,  216 
foramen  of  mandible,  117 
inguinal  hernia,  1315 
ligament,  311 
line  of  clavicle,  169 
of  mandible,  117 
of  radius,  191 
of  tibia,  234 
of  trapezium.  199 
muscles,  ascending,  428 
descending,  424 
external,  424 


INDEX 


1485 


0))li<|ii('  iiiiisclis,  internal,  428 

s:i.'niili;,r   li-allicnt,  290 

siiiii^  of  |ii  rirnrdium,  549 

vein  of  .M:ii>li;i,ll,  550,  709 
■Ohlicpnis  :iiirirul:ii'  muscles,  1121 

inlriior  niusrlc,  415 

siii.crior  niusclo,  415 
Olilongatii,  861 
Obstetric  perineum,  1415 
Obturator  artery,  673 

liur^a,  327 

cimal,  517 

civst.  1213 

pxternus  muscle,  521 

fascia,  44S 

foramen,  213 

groove,  211,  213,  214 

intornus  muscle,  51S 
l^ursa  of,  51S 

ligament,  295 

membrane,  517 

nerve,  accessory,  1049 

vein,  744 
Occipital  artery,  595 

bcfne,  70 

articulation    of    atlas    with, 
275 
of  axis  with,  277 

bulb,  939 

crest,  external,  70,  132 
internal,  72,  128 

diploic  vein,  719 

fissure,  918 

fossa,  inferior,  128 

groove,  82,  131 

lobe,  924 

fissures  of,  924 

gray  substance  of,  953 

lymph  nodes,  774 

nerves,  1017,  1020 

point  of  skull,  146 

protuberance,  70,  72,  132 

sinus,  723 

triangle,  388,  605 

vein,  713 
Occipitalis  muscle,  363 
Occipito-atlantal  ligaments,  275 
Occipito-axial  ligament,  277 
Occ'iiiitofn>iit;iIis  muscle,  363 
Occi|ntiJiiir,iiitt'phalic  tract,  957 
Ocri|>itoi,:nii'lal  suture,  121 
Occipitupuiitile  tracts,  950 
Oculomotor  uerve,  976 
Odontoblasts,  1212,  1215 
Odontoid  ligaments,  277,  278 
CEsophageal  arteries,  629,  654 

glands,  1239 

groove,  421 

opening  of  diaphragm,  421 

plexus  of  nerves,  1005 
(Esophagus,  1236 

applied  anatomy  of,  1239 

arteries  of,  1239 

Ixmiina  macularis  mucosae,  1239 

lymphatic     vessels     of,     802, 
1239 

nerves  of,  1239 

pars  abdotninalis,  1237 
ceroicalis,  1237 
thoracalis,  1237 

relations  of,  1237 

tela  submucosa,  1239 

tunica  mucosa,  1239 
mu^cularis,  1238 

veins  of,  735,  1239 
Olecranon,  185 

bursa,  .308 

fossa,  182 
Olfactory  areas  of  brain,  960 

bulb,  927 

gray  substance  of,  953 

fissure,  920 

foramina,  138 

gyre,  928 

lobe,  926 


Olfactory  nerve,  973 

applied  anatomy  of,  974 

pathways,  958 

tract,  927 

tubercle,  928,  973 
Oliva,  863 
Olivary  body,  863 

eminence,  90 

fasciculus,  900 

nucleus,  accessory,  873 
inferior,  873 
superior,  876 

process,  126 
Olive  of  medulla  oblongata,  863 
Olivocerebellar  fibers,  873 
Olivospinal  tract  of  Helweg,  839 
Omental  band,  1310 

tuberosity  of  liver,  1321 
Omentum,      gastrocolic,      1254, 
1260 

gastrohepatic,  1254,  1260 

gastrosplenic,  1261 

greater,  1251,  1261 

lesser,  1253,  1260 

niajus,  1261 

viiiius,  1260 
Omohyoid  muscle,  388 

surface  form  of,  403 
Opcrcuhim,  917 
Ophryon,  146 
Ophthalmic  artery,  610 

ganglion,  982 

nerve,  979 

veins,  725 
Opisthion,  132,  146 
Opisthotic   portion   of   temporal 

bone,  88 
Opponens  minimi  digiti  muscle, 
foot,  541 
hand,  493 

poUicis  muscles,  490 
Optic-acoustic  reflex  path,  898 
Optic  axis,  1088 

chiasm,  910,  974 

cup,  1101 

disk,  1100 

foramen,  90,  126 

groove,  90,  126 

nerves,  974 

papilla,  1101 

radiation,  905 

tract  and  its  central  connec- 
tions, 909 

vesicles,  852 
Oraserrata,  1100,  1104 
Oral  cavity,  1199 
Orbicular  ligament,  310 

muscle,  358 
Orbicularis  oris  muscle,  374 

palpebrarum  muscle,  366 
surface  form  of,  380 
Orbiculus  ciliaris,  1094 
Orbit,  136 

fascia  of,  371 

margin  of,  101 
Orbita,  136 
Orbital  artery,  598 

fascia,  371 

fossa,  138 

index  of  skull,  146 

muscle,  371 
sheaths  of,  371 

nerve,  983 

•operculum,  917 

plates,  79 

portion  of  frontal  bone,  79 

process  of  malar  bone,  108 
of  palate  bone,  112 

region,  muscles  of,  368 

applied  anatomv  of,  371 

septum,  368,  1112 

sinus,  112 

veins,  712 

wings  of  sphenoid  bone,  93 
Orbitofrontal  fissures,  919 


OrbitoiKil|,i'l,nil  sulcus,  1112 
Orbitos|,lMii,,i,|s,  'J.-, 
Organ  •  ,f  '  niii.   nil 

of  digusUuu,  ll'J'J 

of  Girald(3s,  1384 

of  Golgi,  817 

reproductive,  female,  1397 
male,  1371 

of  respiration,  1163 

of  Rosenmiiller,  1401 

of  taste,  1148 

of  touch,  1150 

urinary,  1343 

urogenit.al,  1343 

of  voice,  1163 
Organa  genitalia  muliebria,  1397 
virilia,  1371 

oculi  nrcrssnnV,,  1112 

■pamx/i/iiiHillnlirn,  1450 

Oraanon  n'lrliliis,  1119 
(Justus,  1148 
olfactm,  1079 
spirale  [Cortii],  1144 
tactus,  1150 
vomeronasale,  1083 
Orifice  of  canal  for  nasal  duct, 

141 
of  maxillary  atrium,  141 
mitral,  560 
tricuspid,  556 
Orificium  externum  uteri,  1406 
labium  anterius,  1406 
posterius,  1406 
internum  uteri,  1408 
ureteris,  1356 

urethrae  externum,  1366,  1369, 
1417 

internum,  1365,  1366 
Os  acetabuli,  213,  214 
calcis,  239 
capitatum,  199 
centrale,  206 
coceygis,  61 
cordis,  562 
coxae,  207 
cuboideum,  245 
cuneiforme  primum,  247 

secundum,  248 

tertium,  248 
external,  1406 
frontale,  76 
hamatum,  200 
hyoideum,  153 
ilium,  207 
incae,  74 
incisivum,  105 
innominatum,  207 
internal,  1405 
ischii,  210 
lacrimale,  106 
magnum,  199 
metacarpale,  I,  202 

//,  202 

III,  202 

IV,  203 

V,  203 
metatarsale,  I,  250 

//,  251 

III,  251 

IV,  251 
y,  252 

multanguluni  majus,  198 

mitnis,   199 
7\avicidirc  manus,  196 

pedis,  246 
occipitale,  70 
palatinurn,  109 
parietalc,  74 
pisiforme,  198 
planum,  98 
pidns,  212 
sacrum,  58 
sphenoidale,  89 
temporale,  80 


1486 


INDEX 


Os  trigonuni,  245 

triquetrum,  197 

uteri,  1406 
Osborn,  supracommissure  of,  906 
Ossa  carpi,  95 

faciei,  99 

metacarpalia,  201 

metatarsalia,  249 

nasalia,  99 

sesamoidea,  257 

tarsi,  2.39 

triquetra,  144 

unguis,  106 
Ossein,  42 
Osseous  labyrinth  of  ear,  1136 

tissue  of  bone,  38 
Ossicles  of  tympanum,  1131 
articulations  of,  1133 
movements  of,  1134 
Ossicula  auditus,  1131 
Ossification  of  bone,  42 
centre  of,  44 
intracartilaginous,  42 
intramenibranous,  42 
Osteoblasts,  39,  40,  44 
Osteogenetic  fibers,  42 
Osteology,  definition  of,  34 
Ostium  ahdominale  tubae  uterinae, 
1401 

arteriosum,  560 
•pulmonis,  558 

pharyngeum    tubae    auditivae, 
1229 

primum  of  Born,  759 

secundum  of  Born,  759 

uterinum  tubae,  1401 

venosum  dextriim,  556 
ventriculi  dextri,  557 
sinistri,  559,  560 
Otic  ganglion,  989 

vesicles,  141 
Otoconia,  1143 
Otoliths,  1141,  1143 

membrane,  1143 
Outlet  of  pelvis,  217 
Oval  bundle  of  Flechsig,  836 
Ovaria,  1397 

discus  proligerus,  1400 

liquor  folliculi,  1399 

theca  folliculi,  1399 

tunica  albuginea,  1399 

zona  granulosa,  1399 
pellucida,  1400 
radiata,  1400 
Ovarian  plexus  of  nerves,  1076 
Ovaries,  1397 

applied  anatomy  of,  1401 

arteries  of,  665,  1401 

cortex  of,  1399 

descent  of,  1398 

at  different  ages,  1399 

fimbrise  of,  1401 

hilum  of,  1400 

lymphatic  vessels  of,  797,  1401 

medulla  of,  1400 

nerves  of,  1401 

suspensory  ligament  of,  1398 

veins  of,  751,  1401 
Ovarium,  139S 
Oviduct,  1401 

Ovoid  depression  of  femur,  221 
Ovulation,  1400 
Ovules  of  Naboth,  1410 
Owen,  osteodentin  of,  1212 
Oxyntic  cells,  1276 

glands,  1276 


Pacchionian  bodies  of  brain,  970 

depressions,  74 
Pacinian  corpuscles,  816 
Pad,  sucking,  376 
Palatal  aponeurosis,  397 


Palatal  process  of  maxilloe,  102, 
104 
region,  muscles  of,  397 

applied  anatomy  of,  399 
Palate,  1202 
arteries,  1204 
bone,  109 
cleft,  151 
Palatine  artery,  597 
ascending,  593 
descending,  602 

applied  anatomy  of,  602 
canal,  anterior,  138,  139  , 
posterior,  102,  110,  111,  134 
accessory,  110,  128 
foramen,  posterior,  128 
fossa,  anterior,  128 
glands,  1202 
nerves,  986 
ruga;,  1202 
spine,  110 
Palatoglossus  muscle,  398 
Palatomaxillary  canal,  102 
Palatopharyngeus  muscle,  398 
Palatum,  1202 
durum,  1202 
'  molle,  1202 
Pallidum,  948 
Palmar  arch,  deep,  645 
superficial,  652 

applied  anatomy  of,  652 
surface  marking  of,  652 
cutaneous   nerve,    1036,    1037, 

1039 
fascia,  488 

interossei  muscles,  494 
interosseous  arteries,  648 
plexus  of  veins,  729 
region,  muscles  of,  493 
veins,  731 
Palmaris  brevis  muscle,  492 
surface  form  of,  497 
longus  muscle,  474 

surface  form  of,  496 
Palpebrae,  1112 
Palpebral  arteries,  610,  612 
nerves,  984 
region,  muscles  of,  366 
Pancreas,  1336 

applied  anatomy  of,  1341 
arteries  of,  662,  1341 
fades  anterior,  1338 
inferior,  13.38 
posterior,  1338 
lymphatic  vessels  of,  796,  1341 
margo  anterior,  1338 
inferior,   1338 
superior,  1338 
nerves  of,  1341 
surface  form  of,  1341 
veins  of,  753,  1341 
Pancreatic  duct,  1340 
juice,  1341 
magna,  662 
plexus  of  nerves,  1076 
Pancreaticoduodenal        arteries, 
661,  663 
lymph  nodes,  793 
plexus  of  nerves,  1076 
veins,  753 
Panniculus  adiposus,  360,  1154 
Papilla,  bile,  1287 

duodeni  [Santorini],  1287 
incisiva,  1202 
lacrimal,  1113 
mammae,  1428 
pili,  1159 
renal,  1349 
Papillae  filiformes,  1218 
fungiformes,  1218 
lacrimalis,  1116 
of  tongue,  1218 
mllatae,  1218 
Papillary  layer  of  skin,  1153 
muscles,  558 


Paracardial  lymph  nodes,  700 
Paracentral  fissure,  920 

gyre,  921 
Parachordal  cartilages,  141 
Paradidymis,  1384 
Paraduodenal  fossa,  1266 
Paramesal  fissures,  919 
Parametrium,  1406,  1407 
Paranucleus,  1341 
Paraoccipital  fissure,  923 
Paraplexus,  940,  971 
Pararectal  fossa,  1256 
Parasinoidal  spaces,  721 
Parasympathetic  bodies,  1450 
Parathyroid  glands,  1439 

applied  anatomy  of,  1440- 
development  of,  1440 
Paravesical  fossa,  1361 
Paraxones,  811 
Parenchyma  of  kidneys,  1349 
of  lungs,  1195 
of  .spleen,  1445 
of  testes,  1380 
Parenchymatous  cells,  1437 
Parietal  artery,  ascending,  817 
bone,  74 
cells,  1276^ 
eminence,  74 
foramen,  74 
fissure,  923 
lobe,  922 

fissures  of,  922 
gyres  of,  923 
lymph  nodes,  787,  798 
peritoneum,  1244 
veins,  development  of,  764 
Parietocolic  fold,  1267 
Parietotemporal  artery,  617 
Parolfactory  area,  928 
sulcus,  anterior,  928 
Paroophoron,  1401 
Parotid  duct,  1200 
fascia,  377 
glands,  1223 

arteries  of,  1225 
duct  of,  1225 
lymphatics  of,  1225 
nerves  of,  1225 
veins  of,  1225 
lymph-nodes,  774,  1225 
nerves,  988 
Parovarium,  1401 
Parrot's  nodes,  151 
Pars  basilaris,  71 
pontis,  874 
calcaneocuboid ea   ligamenti   bi- 

furcati,  348 
ca  Icaneonavicularis      ligamenti 

bifurcati,  348 
ciliaris  retinae,  1100 
diaphragmatica  fasciae   pelvis, 

454 
dorsalis  pontis,  864 

fiber  tracts  in.  876 
iridica     retinae,     1098,     1099, 

1100 
lacrimalis  musculus  orbicularis 

oculi,  367 
Tnetencephalica     [tnedullae    ob~ 

longatae],  864 
orbitalis    musculus    orbicularis 

oculi,  366 
palpebralis  musculus  orbicula- 
ris oculi,  366 
tympanica,  87 
Partes   genitales    externae   mulie- 
bres,  1415 
petrosa  et  mastoidea,  81 
Parumbilical  veins,  754 
Parvidural  artery,  600 
Patella,  230 

applied  anatomy  of,  231 
ligaments  of,  331 
surface  form  of,  231 
Patellar  bursa,  512 


INDEX 


1487 


Patellar  plexus  of  nerves,  1051 
Pavilion  of  Fallopian  tube,  1401 
Peetineus  muscle,  513 
Pectoral  fascia,  456 
lymph  nodes,  782 
region,  dissection  of,  455 
Pectoralis  major  muscle,  456 
surface  form  of,  495 
minor  muscle,  460 

surface  form  of,  495 
muscles,  dissection  of,  459 
Peculiar  ribs,  163 

thoracic  vertebra,  54 
Peduncle  of  cerebellum,  889 

of  corpus  callosum,  928 
Peduncular    sulcus    of    cerebel- 
lum, 885 
Pedunculated  hydatid,  1379 
Pelvic  colon,  1306 

curve  of  vertebral  column,  66 
fascia,  448 

ligament,  transverse,  446 
outlet,  fascice  of,  440, 

muscles  of,  440 
plexuses  of  nerves,  1077 
viscera,  lymphatic  vessels   of, 
792 
Pelvis,  215 

applied  anatomy  of,  220 
articulations  of,  290 

vertebral  column  with,  289 
axes  of,  218 
brim  of,  215 
cavity  of,  216 
axis  of,  218 
circumference  of,  215,  217 
diameters  of,  215,  217 
diaphragm  of,  1240 
difference   between  male   and 

female,  218 
false,  216 
in  fetus,  219 
inlet  of,  215 
axis  of,  218 
plane  of,  218 
lymphatics  of,  787,  789,  790 
major,  215 
minor,  215 
outlet  of,  217 
axis  of,  218 
position  of,  217 
surface  form  of,  219 
true,  215 

of  ureter,  1349,  1356 
uretericus  s.  renalis,  1349 
veins  of,  739 
white  line  of,  449 
Penis,  1386 

applied  anatomy  of,  1390 
arteries  of,  1389 

dorsal,  676 
dorsum  of,  1388 
frenulum  of,  1389 
lymphatics  of,  1390 
nerves  of,  1390 
dorsal,  1061 
prepuce  of,  1388 
suspensory  ligament  of,  1388 
tunica  albuginea,  1386 
urethral  surface  of,  1388 
veins  of,  1390 
dorsal,  746 
Penniform  muscle,  358 
Peptic  glands,  1276 
Perforated  space,  anterior,  928 

posterior,  898 
Perforating  arteries  of  foot,  704 
of  thigh,  690 
cutaneous  nerve,  1060 
Pericardium,  54S 

applied  anatomv  of,  550 
arteries  of,  550,  632,  654 
fibrous,  548 
nerves  of,  550 
serous,  549 


Pericardium,  sinus  of,  550 

vestigial  fold  of,  550 
Pericecal  fossa,  1266 
Pericellular  lymph  spaces,  767 
Perichondrium,  44,  259 
Perichoroidal  space,  1090 
Periclaustral  lamina,  948 
Pericranial  nerves,  980 
Peridental  membrane,  1212 
Perilymph,  1136 

space,  1136 
Perimedullary  lamella  of  bone,  39 
Perimetrium,  1409 
Perimysium,  355 
Perineal  arteries,  675 

body,  1309 

fascia,  446 

muscle,  superficial  transverse, 
442,  445 

nerves,  1061 

cutaneous,  1055 
Perineum,      central      tendinous 
point  of,  442 

in  female,  muscles  of,  445 

lymphatic  vessels  of,  790 

in  male,  muscles  of,  442 
Perineural  lymph  spaces,  767 
Perineurium,  812 
Periosteal  lamella  of  bone,  39 
Periosteum  alveolare,  1205 

of  bone,  38,  44 

cranial,  364 
Peripheral  axone  of  an  afferent 
neurone,  807 

fibrilL-E,  816 

lamella  of  bone,  39 

nerve  beginnings,  815 
Perirenal  arteries,  665 

fat,  1348 
Periscleral  lymph  spaces,  1086 
Peritoneal  cavity,  1244 
Peritoneum,  1244 

apphed  anatomy  of,  1268 

development  of,  1245 

mesenteric,  1249 

parietal,  1244 

rectovesical  fold  of,  1361 
pouch  of,  1361 

uterovesical  pouch  of,  1361 

visceral,  1244 
Peritracheobronchial  lymph 

nodes,  1179 
Perivascular  Ivmph  spaces,  707, 

767 
Perivitelline  space,  1400 
Peroneal  arteries,  701,  702 

groove,  246 

nerve,  1059 

spine,  242 
Peroneus  brevis  muscle,  535 
surface  form  of,  544 

longus  muscle,  534 

surface  form  of,  544 

tertius  muscle,  527 

surface  form  of,  544 
Perpendicular    plate    of    palate 
bone,  110 

portions  of  mandible,  117 
Pes  anserinus,  996 

hippocampi,  942 

leonis,  942 

of  midbrain,  900 
Petrolus  epiglottidis,  1167 
Petromastoid    portion    of    tem- 
poral bone,  82 
Petro-occipital   suture,   73,    122, 

127 
Petrosal  artery,  600 

nerves,  985 
deep,  1066 
superficial,  989,  996 

process,  90 

sinus,  715,  726 
Petrosphenoidal  fissure,  122 

suture,  131 


Petrosquamous  sinus,  723 

suture,  84 
Petrotympanic  fissure,  88,  1126 
Petrous  ganglion,  1002 

portion  of  temporal  bone,  83 
Peyer's  patches,  1293 
Phalanges  digilorum  manus,  204 
pedis,  252 
of  foot,  252 

applied  anatomj*  of,  256 
articulations  of,  354 
surface  form  of,  354 
,    of  hand,  204 

applied  anatomy  of,  206 
articulations  of,  321 
development  of,  207 
surface  form  of,  205 
ungual,  205 
Phalanx  prima  digilorum  pedis, 
252 
secuTida  digitoruni  pedis,  253 
ieriia  digilorum-  pedis,  253 
Pharyngeal  aponeurosis,  395 
artery,  ascending,  597 
nerve,  986,  1003,  1006,  1068 
plexus  of  nerves,  1003,  1006 

of  veins,  715 
region,  muscles  of,  394 
ring,  lymphatic,  1234 
spine,  71,  131 
tonsil,  1230 
veins,  715 
Pharyngoepiglottic  fold,  1233 
Pharynx,  1229 

applied  anatomy  of,  1235 
development  of,  1234 
isthmus  of,  1230 
pars  laryngea,  1233 
nasalis,  1229 
omlis,  1230 
tunica  rmicosa,  1233 
Philtrum,  375 
Phrenic  arteries,  658 
ganglion,  1074 
nerve,  1024 

applied  anatomy  of,  1025 
plexus  of  nerves,  1074 
veins,  734,  751 
Phrenicocostal  sinus,  1346 
Phrenocolic  ligament,  1305 
Pia  of  brain,  971 
arteries  of,  972 
nerves  of,  972 
veins  of,  972 
mater  encephali,  971 
spinalis^  845 
of  spinal  cord,  845 

applied  anatomy  of,  846 
arteries  of,  846 
Pigmentation  of  skin,  1155 
Pili,  1159 
Pillars    of    external    al^dominal 

ring,  427 
Pineal  body,  906 
Pinna  of  ear,  1119 
arteries  of,  1121 
cartilage  of,  1120 
integument  of,  1120 
ligaments  of,  1121 
lymphatics  of,  777,  1122 
muscles  of,  1121 
veins  of,  1121 
Pisiform  bone,  198 
Pisometacarpal  ligament.  316 
Piso-uncinate  ligament,  316 
Pit  of  stomach,  166 
Pituitary  body,  909 
Pivot-joint,  264,  265 
Placental  circulation,  755 
Planes  of  body.  34 
Plantar  arch,  704 
arteries,  703 
surface  marking  of.  704 
metatarsal  veins,  741 
nerves,  1057,  1058 


1488 


INDEX 


Plantar  region,  fascia  of,  537 

muscles  of,  538 
veins,  741 
Plantaris  muscle,  530 
Planum  popUteum,  224 

sternale,  159 
Plate,  cribriform,  of  ethmoid,  96 
horizontal,  of  palate  bone,  109 
perpendicular,  of  palate  bone, 

110 
pterygoid,  94 
tympanic,  131 
vertical,  of  ethmoid,  97 

of  palate  bone,  110 
Platysma  muscle,  381 

surface  form  of,  402 
Pleura  costalis,  1183 
diaphragmatica,  1183 
Tnediastinalis,  1183 
parietalis,  1181 
pulmonalis,  1181 
Pleuras,  1181 

applied  anatomy  of,  1185 
arteries  of,  1185 
cavity  of,  1181 
cervical,  1183 
costal,  1183 
diaphragmatic,  1183 
lymphatic  vessels  of,  802,  1185 
mediastinal,  1183 
nerves  of,  1185 
reflections  of,  1183 
veins  of,  1185 
Plexus  of  arteries,  subpleural  me- 
diastinal, 632  ^ 
choroid,   of    fourth    ventricle, 
867 

of  lateral  ventricles,  940 

of  third  ventricle,  940 
of   nerves,    abdominal    aortic, 
1076 

brachial,  1026 

cardiac,  1072 

carotid,  1066 

cavernous,  1066 

cer-sdcal,  1018,  1020 

coccygeal,   1062 

cceliac,  1008,  1073 

colic,  1076 

coronary,  1073,  1076 

cystic,  1076 

gastric,  1076 

gastroduodenal,  1076 

gastroepiploic,  1076 

hemorrhoidal,   1077 

hepatic,  1008,  1076 

hypogastric,  1077 

ileocolic,  1076 

infraorbital,  984,  998 

intestinal,  1076 

lumbar,  1044 

lumbosacral,  1044 

mesenteric,  1074 

03sophageal,  1005, 1007, 1073 

ovarian,  1076 

pancreatic,  1076 

pancreaticoduodenal,    1076 

patellar,  1051 

pelvic,  1077 

pharyngeal,  1003,  1006 

phrenic,  1074 

prostatic,  1077 

pudendal,  1060 

p»lmonarv,  1073 

posterior,  1005,  1007 

pyloric,  1076 

renal,  106S,  1075 

sacral,  1053 

sigmoid,  1076 

solar,  1076 

spermatic,  1076 

splenic,  1008,  1076 

suprarenal.  1074 

thjToid.  1069 

tympanic,  1002 


Plexus  of  nerves,  uterine,  1077 

vaginal,  1077 

vesical,  1077 
of  veins  of  foot,  739 

of  hand,  729 

hemorrhoidal,  745 

palmar,  729 

pampiniformis,  750 

pharyngeal,  715 

pterygoid,  712 

spermatic,  750 

on  thyroid  body,  734 

uterine,  747 

vaginal,  747 

vertebral,  737 

vesical,  745 

vesicoprostatic,  745 
Plexus  aorticus  ahdominalis,  1072, 

1076 
arteriae  ovaricae,  1076 
basilaris,  727 
brachialis,  1026 

fasciculus  lateralis,  1028 
medialis,  102S 
posterior,  1028 

pars  infraclavicularis,  1028 
supraclavicularis,  1027 

rami  musculares,  1028 
cardiacus,  1072 
caroticus  externus,  1069 

internus,  1066 
cavernosus,  1066 

concharum,  1084 
cervicalis,  1020 
■    chorioideus  ventriculi  lateralis, 
971 
quarti,  972 
tertii,  971 
coccygeus,  1062 
coeliacus,  1073 
coronarius  anterior,  1073 

posterior,  1073 
dentalis  inferior,  989 

superior,  984 
gastricus  superior,  1076 
gulae,  1004,  1238 
haeynorrhoidalis  inferior,  1077 
hepaticus,  1076 
hypogastricus,  1072,  1077 
lienalis,  1076 
lumhalis,  1044 
lujnbosacralis,  1044 

rami  anterior es,  1044 
mesentericus  inferior,  1076 

superior,  1076 
oesophageus,  1238 
pampiniformis,  750 
pharyngeus,  1006  '      ' 

phrenicus,  1074 
prosiaiicus,  1077 
pudendus,  1060 
pulmonalis  anterior,  1007 

posterior.  1004,  1005,  1007 

ra??ii    bronchiales   anteriores, 
1007 
posteriores,  1007 
,  1075 
sacralis,  1053 
spermaticiis,  1076 
suprarenalis,  1074  ' 

sympathici,  1063 
thyroideus,  1069 
tynipanicus,  1002 

[Jacobsoni],  1135 
uterovaginalis,  1077 
venosi  pampiniformis,  1377 

pterygoideus,  712 

thyreoideus  impar,  734 

vertebrales,  717 
anteriores,  737 
externi,  737 
interni,  738,  843 
posteriores,  737 
venosus  caroticus  internus,  714, 

727 


Plexus  verlebralis,   1069 

vesiculis,  1077 
Plica  aryepiglottica,  1166 

duodenojejunalis,   1266 

duodenomesocolica,  1265 

fimhriata,  1217 

ileocecalis,  1267 

lacrimalis  [Hasneri],  1177 

longiiudinalis  duodeni,   1287 
-    nervi  laryngei,  1233 

pharyngoepiglotlica ,  1233 

salpingopalatina,  1230 

salpingopharyngea,  1230 

semilunaris  conjunctivae,  1115 

sublingualis,  1201,  1226 

synovialis  patellaris,  336 

triangularis,  1231 

umhilicalis,  1361 
lateralis,  1361,  1363 
rnedia,  1361,  1362 

vesicalis  transversa,  1256,  1359 
Plicae  alares,  336 

palatinae  transversae,  1202 

palmatae,  1408,  1410 

rectouterinae,  1407 

rectovesicales,  1255,  1362 

semilunares  coli,  1298,  1310 

uretericae,  1365 

ventriculares,  1170 

vesicouterinae,   1362 

vocales,   1170 
Pneumogastric  nerve,  1003 
Polus  anterior  lentis,  1107 

posterior  lentis,  1107 
Polyaxonic  neurones,  810 
Polymazia,  1430 
Polymorphous  cells,  952 
Polynuclear  cells,  40 
Polythelia,  1430 
Pomum  Adami,  1164 
Pons,  864 

basilar  surface  of,  864 

tegmental  part  of,  876 

tract,  inter-radicular,  864 

varolii,  864 

veins  of,  720 
Ponticulus  of  Arnold,  863 
Pontile  arteries,  622 

flexure  of  brain,  855 
Pophteal  artery,  691 

applied  anatomy  of,  693 
surface  marking  of,  693 

groove,  226 

lymph  nodes,  784 

nerves,  1055,  1059 

notch,  233 

space,  691 

boundaries  of,  692 
contents  of,  692 
position  of  contained  parts, 
692 

vein,  742 
Popliteus  muscle,  531 
Porta,  853 

hepatis,  1323 
Portal  vein,  751 

applied  anatomy  of,  754 
development  of,  764 
Porus  lactiferus,  1431 

opticus,  1090,  1100 

sudorifervs,  1162 
Postbrachium,  895 
Postcalcarine  fissure,  919 
Postcapillary  veins,  706 
Postcardiual  veins,  764 
Posteava,  748 
Postcentral  fissures,  923 

gyre,  923 
Postcisterna,  969 
Postcornu,  939 
Postdural  artery,  597 
Postfemoral     cutaneous     nerve, 

1054 
Postforceps,  933 
Postgemina,  897 


INDEX 


1489 


Postgenieulum,  895 
Postglenoid  process,  81 
Posthypophysis,  909 
Postinsula,  925 

Postoblongata  of  Wilder,  861 
Postoperouluin,  917 
Postorbital  linil.us,  922 
PosdKirii'lnl  u-vrr,  923 
Pos(prdiuiculii>,  SS9 
Postperfoiatuiii,  817,  898. 
Postpontile  recess,  862 
Postramus  of  cerebellum,  888 
Postrhinal  fissure,  925 
Postvermis,  885 
Poupart's  ligament,  426,  427 
Praeputium,  1388 

diioridis,  1416,  1420 
Preaortic  lymph  nodes,  789 
Preauricular  lymph  nodes,  775 
Prebrachium,  895 
Precapillary  arteriole,  573 
Precardinal  veins,  764 
Precava,  735 
Precentral  fissures,  '919 

gyre,  921 
Precommissure,  946 
Precornu,  936 
Precuneal  fissures,  923 
Precuneus,  924 
Preforceps,  933 
Pregemina,  894,  897 
Pregeniculum,  904 
Prehypophysis,  909 
Preinsula,  925 

fissure,  925 
Preinsular  gyres,  926 
Prelaryngeal  lymph  nodes,  779 
Premaxillary  bones,  105 

centre,  106 
Preoblongata,  864 
Preoccipital  notch,  914 
Preoperculum,  917 
Prepatellar  bursa,  336,  512 
Prepedunculi,  891 
Preperforatum,  847,  928 
Prepuce  of  clitoris,  1416 

of  penis,  1388 
Prepyramidal  tract  of  cord,  839 
Preramus  of  cerebellum,  888 
Presternal  notch,  157,  166,  171 
Presternum,  157 
Presylvian  ramus,  917 
Pretracheal  fascia,  384 

lymph  nodes,  779 
Prevermis,  885 
Prevertebral  artery,  597 

fascia,  384 
Primitive    sheath    of    Schwann, 

811 
Princeps  hallucis  artery,  700 

poUicis  artery,  647 
Prismata  adamantina,  1210 
Process  or  Processes,  acromion, 
175 

alveolar,  of  maxillEe,  104 

angular,  77,  78,  135 

of  atlas,  51 

of  axis,  52 

axis  cylinder,  807 
mediillated,  811 
nonmeduUated,  812 

basilar,  71 

of  calcaneus,  242 

ciharv,  1094 

chnoid,  90,  94,  126 

cochleariform,  1127 

condyloid,  of  mandilile,  118 

coracoid,  176 

coronoid,  of  mandible,  118 

costal,  50 

ethmoidal,  114 

falciform,  508 

frontal,  of  malar,  108 

funicular,  1379 

94 


Process   or   Processes,    hamular, 

94,  107,  130 
intrajugular,  73 
jugular,  71,  131 
lacrimal,  114 
malar,  101,  104 
mastoid,  of  temporal  bone,  82, 

133 
maxillary.  111,  114 
mental,  116,  135 
nasal,  of  maxiUse,  104 
olivary,  126 
orbital,  of  malar,  108 

of  palate  bone,  112 
palatal,  of  maxillae,  102,  104 
petrosal,  99 
postglenoid,  81 
pterygoid,   of   sphenoid   bone, 

94 
sphenoidal,  1080 

of  palate  bone,  112 

turbinated,  91,  95 
spinous,  of  ilium,  210 
stylohyal,  89 
styloid,  88,  131 

of  fibula,  236 

of  radius,  192 

of  ulna,  189 
supracondylar,  181  (note) 
.    transverse,  71 

turbinated,  middle,  98,   139 

sphenoidal,   138 

superior,  98 
tympanohyal,  88 
unciform,  200 

of  ethmoid,  98 
vaginal,  of  sphenoid,  92,  94,  95 
zygomatic,  of  malar,  109 

of  temporal  bone,  81 
Processus  accessorius,  57 
aheolaris,  104 
articularis  inferior,  49 

superior,  49 
caudatus,  1324 
ciliares,  1094 
clinoidei  medii,  90 

posterior,  90 
clinoirieus  anterior,  94 
condyloideus,  118 
coracoideus,  176 
coronoideus,  118,  185 
costarius,  57 

durae  matris  encephali,  966 
ethmoidalis  concha  nasalis  in- 
ferior, 114 
falciformis  ligamentum  sacrotu- 

berosum,  291 
frontalis,  104 
frontosphenoidalis,  108 
inferior  tegm-enti  tympani,  88 
intrajugularis,  71,  73 
jugularis,  71 

lacrimalis    concha    nasalis    in- 
ferior, 114 
lateralis  tuberis  calcanei,  242 
mammillaris,  57 
mastoideus,  82 
maxilla? is.  111 

concha  nasalis  inferior,  114 
medialis  tuberis  calcanei,  242 
orbitalis,  112 
palatinus,  102,  104 
papillaris,  1324 
posterior  tali,  245 
pterygoidei,  94 
pyramidalis,  111 
sphenoidalis,  112 

septi  cartilaginei,  1080 
spinosus,  49 
slyloideus,  189,  192 

OS  metacarpale  III,  203 
temporalis,  109 
trochlearis,  242 
tubarius,  94,  1138 
U7icinatus,  98,  1337 


Processus     vaginalis    '  peritonaei, 
1379 
processus  pterygoidei,  95 

vermiformis,  1298 

xiphoideus,  157 

zygomaticus,  104 
Profunda  arteries,  642,  643,  651, 

689 
Prominentia      canalis      facialis, 
1126 

laryngea,  1164 

spiralis,  1144 

styloideae,  1125 
Promontorium,  58,  1126 
Promontory  of  sacrum,  58 

of  temporal  bone,  85 

of  tympanum,  1126 
Pronator  quadratus  muscle,  478 

teres,  472 

aiDplied  anatomy  of,  473 
surface  form  of,  496 
Pronephric  duct,  1420 

tubules,  1420 
Pronephros,  1420 
Pro-otic     portion     of     temporal 

bone,  88 
Prosencephalon,  902 
Prtfsiaia,  1391 

fades  anterior,  1393 
posterior,  1391 
Prostate  gland,  1391 

applied  anatomy  of,  1395 
arteries  of,  1395 
development  of,  1426 
lymphatics  of,  796,  1395 
nerves  of,  1395 
veins  of,  1395 
Prostatic  ducts,  orifice  of,  1367 

plexus  of  nerves,  1077 

sinus,  1367 
Pcosthion,  146 
Proton  of  cerebellum,  855 
Protuberance,   occipital,   70,   72, 

131 
Protuberantia  nientalis,  116 

occipitalis  externa,  70 
interna.,  72 
Prussak,  pouch  of,  1134 
Psalterium,  944 
Pseudocele,  934,  945 
Psoas  magnus  muscle,  504 

applied  anatomy  of,  505 

parvus  muscle    504 
Pterion,  76,  133,  146 

ossicle,  80,  144 
Pteriotic    portion    of    temporal 

bone,  88 
Pterygoid  artery,  601 

canal,  130 

depression,  118 

fossa,  94,  109 

muscles,  379,  380 

nerves,  987,  988 

notch,  94 

plates,  94 

plexus  of  veins,  712 

processes  of  sphenoid  bone,  94 

ridge,  92,  132 

tubercle,  95 
Pterygomandibular  ligament,  376 

region,  muscles  of.  379 
Pterygomaxillary   fissure,    134 
Pterygopalatine  artery,  602 

canal,  92,  1.30,  134 

groove,  110,  111 

nerve,  986 
Pterygospinous  foramen,  383 

hgament,  382 
Pubes,  1159 
Pubic  arch,  217 

artery,  681 

bones,  articulation  of,  294 

ligaments,  294 

vein,  743 
Pubis,  212 


1490 


INDEX 


Pubis,  angle  of,  212 
body  of,  212 
crest  of,  212 
ramus  of,  213,  214 
spine  of,  212 
Pubococcygeus  muscles,  452 
Pubofemoral  ligament,  323 
Puboprostatic  ligament,  450 
Puborectalis  muscles,  452 
Pubovesical    space    of    Retzius, 

1360 
Pudendal  nerve,  inferior,  1055 

plexus  of  nerves,  1060 
Pudendum  muliebre,  1415 
Pudic  artery,  accessory,  675 
external,  6S9 
internal,  674,  676 
nerves,  1061 
veins,  internal,  744 
Pulmonary  artery,  574 

applied  anatomy  of,  575 
left,  575 
opening  of,  557 
right,  575 
circulation,  548 
heart,  553 
nerves,  1007 
plexus  of  nerves,   1005,   1007, 

1073 
sinuses  of  Valsalva,  559,  561 
valve,  559 
veins,  559,  707 

applied  anatomy  of,  708 
Pulmones,  1188 
fades  costalis,  1189 

mediasiinalis,  1189 
lobiis  inferior,  1192 
medium,  1192 
superior,   1192 
marge  anterior,  1190 
inferior,  1190 
posterior,  1190 
Pulp  cavity,  1212 
chamber,  1212 
Palpa  dentis,  1212 

lienis,  1445 
Pulvinar,  904,  910 
Puv^ta  lacrimalia,  1116 
Punctum  lacrimale,  1113,  1116 
Pupil  of  eve,  1096 
Pupilla,  1096 
Pupillary  margin,  1097 
Purldnje  fibers,  357,  565 
Purkinjean  cells,  892 
Putamen,  948 
Pyloric  artery,  661 

applied  anatomy  of,  662 
canal,  1272 
glands,  1278 
ligaments,  1274 
orifice,  1271 
plexus  of  nerves,  1076 
sphincter,  1273 
valve,  1273 
vein,  754 
vestibule,  1272 
Pj'ramid  of  medulla  oblongata, 
863 
of  vestibule  of  ear,  1137 
Pyramidal  cells,  952 
lobes,  887 
tract  of  brain,  900 
of  cord,  crossed,  S3S 
direct,  839 
PjTamidalis  muscle,  435 
nasi  muscle,  372 

surface  form  of,  380 
Pyramides  [medullae  oblongatae], 
863 
renales  [Malpighii],  1350 
Pyramido-olivary  groove,  863 
Pyramis  veslibuli,  1137 
Pyriformis  muscle,  517 
bursa  of,  517 
fascia  of,  448 


Q 

Quadrate  lobes  of  brain,  886 

of  liver,  1324 
Quadratus  femoris  muscle,  520 
bursa  of,  521 
lumborum  muscle,  439 

fascia  covering,  439 
menti  muscle,  374 
tubercle  of,  224  (note) 
Quadriceps  extensor  muscle,  509 
applied  anatomy  of,  512 
surface  form  of,  543 
tendons  of,  512 
Quadrigeminal  bodies,  894,  897 
Quadrilateral  muscles,  358 
Quiet  respiration,  423 


R 

Radial  artery,  644 

applied  anatomy  of,  646 
surface  marking  of,  646 
carpal  arteries.  647 
fossa,  182 
nerve,  1038 
recurrent  artery,  646 
region,  muscles  of,  479,  489 
veins,  730 
Radialis  indicis  artery,  647 
Radiate  fissures,  920 
Radiatio  callosi,  933 
Radii  lentis,  1107 
Radiocarpal  articulation,  314 
Radioulnar  articulation,  310 
inferior,  312 
middle,  311 
superior,  310 

applied  anatomj'  of,  311 
surface  form  of,  311 
surface  form  of,  314 
synovial  membrane  of,  313 
ligaments,  312 

region,    anterior,    muscles    of, 
472 
applied  anatomj'  of,  478 
posterior,  muscles  of,  480 
applied  anatomy  of,  485 
Radius,  190 

applied  anatomy  of,  192 
oblique  line  of,  191 
shaft  of,  191 
sigmoid  cavity  of,  192    , 
surface  form  of,  192 
Radix  arcus  vertebrae,  48 
dentis,  1204 
linguae,  1217 
mesenterii,  1263 
nasi,  1079 
penis,  1388 
pili,  1159 
puhnonis,  1193 
unguis,  1156 
Rami  calcanei  mediales,  703 
perforantes      anteriores      [arcus 
plantaris],  704 
posteriores  [arcus  plantaris], 

704 
[venae  mammariae  internae], 
734 
sternales  [venae  mammariae  in- 
ternae, 734 
Ramus    carpens  dorsalis  [arteria 
radialis],  647 
of  cerebellum,  888 
communieans   [arteria   nulricia 

tibiae],  703 
episyhdan,  917 
hjTJOsylvian,  917 
inferior  ossis  ischii,  212 

pubis,  213 
of  ischium,  212 
of  mandible,  117 
plantaris  profundus,  700 


Ramus,  presylvian,  917 

of  pubis,  212,  213 

subsylvian,  917 

superficialis    [arteria    plantaris 
medialis],  703 

superior  ossis  pubis,  212 
Ranine  artery,  591 

vein,  715 
Ranvier,  constrictions  of,  811 

nodes  of,  811 
Raphe,  872 

palati,  1202 

palpebralis  lateralis,  367,  1114 

■pterygomandihularis,  376 

scroti,  1372 
Receptaculum  chyli,  771,  772 
Recess,  elliptical,  1137 

epitympanic,  1125 

spheno-ethmoidal,  140 

spherical,  1137 
Recessus  duodenojejunalis,  1266 

epitympanicus,  1125 

ileocecalis  inferior,  1267 
superior,  1266 

intersigmoideus,  1267 

lienalis,  1259 

membranae    iympani    anterior, 
1134 
posterior,  1134 
superior,  1134 

nasopalaiinus,  1083 

pharyngeals,  1230 

pinealis,  906 

pyriformis,  1163,  1233 

retrocecalis,  1267 

sacciformis,  308,  313 

sphenoethmoidalis,  140,  1082 

suprapinealis,  908 

utriculi,  1140 
Rectal  valves,  1310 
Recti  muscles,  370 
Rectococcygeal  muscles,  1310 
Rectouterinus  muscle,  1408 
Rectovaginal  fold,  1407 

pouch,  1256,  1362,  1407 
Rectovesical  fascia,  1361 

fold  of  peritoneum,  1256,  1361 

muscle,  1362 

pouch    of    peiitoneum,    1255, 
1361,  1362 
Rectum,  1306 

ampulla  of,  1308 

lymphatic  vessels  of,  794 

relations  of,  1308 
Rectus  abdominis  muscle,  "433 
surface  form  of,  439 

capitis  anticus  major  muscle, 
400 
minor  muscle,  400 
lateralis  muscle,  400 
posticus  major  muscle,  414 
minor  muscle,  414 

femoris  muscle,  510 

applied  anatomy  of,  512 
surface  form  of,  543 

sheath,  434 
Recurrent  artery,  radial,  646 
tibial,  698  ' 
ulnar,  650 
Red  nucleus,  898 
Reil,  island  of,  925 
Reissner,  membrane  of,  1144 
Remak's  fibers,  812 
Renal  arteries,  665 

columns,   1349 

corpuscles,   1350 

fascia,  1348 

impression  of  liver,   1321 

papillse,  1349 

plexus  of  nerves,  1008,  1075 

sinus,  1349 

veins,  751 

zone  of  Hyrtl,  exsanguinated, 
665,  1353 
Renes,  1343 


INDEX 


H'Jl 


Rcncs  cxtrcmilnx  inferior,  Ki-18 

.s»;j..r/-»-,  Ki-lS 
fiinrs  aiilrrinr,   lS4:i 

/loslrriur.    V.Ur:, 
iiiiprr.sKni  iiiiixi-ularis,    1347 
n,nni„  lnl.n,l,s.   1347 

nn,r„lli.-:.    I.MS 

/»/Kta  ,/;6njsa,  1349 
Reproductive      organs,     female, 
1397 
male,  1371 
Kesiiiration,  forced,  423 
mechanism  of,  422 
organs  of,  1163 
quiet,  423 
Respiratory  bronchiole?,  1195 
cpitheUum,  1195 
nerves  of  Bell,  1024,  1029 
Restir,,rm  IhhIv,  S73 
;fr,sY/x,  S(iL'.  MU 

Rch'  artf  rinsiini  rutaiiciiin,  1156 
siihpapiUarr,   1156 
vcnoswn,  1156 
canalis  hypofjlossi,  727 
carpi  dorsalc  [ay-teria  radialis], 
647 
[arteria  ulnaris],  651 
volar e  [arteria  radialis],  647 
foraminis  ovalis,  727 
testis,  1380 

venosum.  dorsale  ijianus,  729 
pedis  cutaneum,  739 
plantare  cutaneum,  739 
Retia  mirabilia,  573 
Reticular    formation    of    spinal 
cord,  830 
laver  of  skin,  1154 
Retina,  1100 

applied  anatomy  of,  1111 
central  artery  of,  613 
layers  of,  1101 
nerve  fibers  of,  1101 
supporting  framework  of,  1104 
yellow  spot  of,  1100 
Relinneula  cutis.  1150,  1430 
Retinaculum    of    capsular    liga- 
ment of  hip,  322 
musculi   peronaeorum  inferius, 
537 
superius,  537 
patellae  laterale,  331,  510 
mediate,,  331,  511 
Retrahens  aurem  muscle,  366 
Retroaortic  lymph  nodes,  789 
Retrocecal  fo^sa,  1267 
Retroduodonal  fossa,  1266 
Retroperitoneal  fossae,  1265 
Retropharyngeal    lymph    nodes, 
776 
space,  384,  1229 
Retrorectal  space,  1308 
Retzius,  brown  stria  of,  1210 
fundiform  ligament  of,  536 
pubovesical  space  of,  1360 
Rliinencephalon.  926 
Rhodopsin,  1100 
Rhombencephalon,  861 
Rhomboid  impression,  171 

ligament,  296 
Rhomboidal  fossa,  865 
Rhomboideus  major  muscle,  407 
surface  form  of,  416 
minor  muscle,  407 

surface  form  of,  416 
Ribs,  161 

applied  anatomy  of,  167 
articulations  of,  with  vertebras, 

282 
cer'\'ical,  53,  64,  167 
common  characters  of,  162 
false,  161 
floating,  161 
peculiar,  163 
true,  161 
tubercle  of,  162 


Ribs,  verd'hral,  161 

veil.hn.rl Iial,   161 

vri1,l.rn^l,rn;,l,    161 
Ridel',  lol.r  (,l  liver,  1320 
Rider's  hone,  229 
Ridge,  crucial,  71 

gluteal,  224 

mylohyoid,  117 

pterygoid,  92,  132 

superciliary,  77,  79,  134 

supracondylar,   180 

supraorbital,  135 

temporal,  of  frontal  bone,  78 
of  parietal  boue,  74 

trapezoid,  109 
Rima  ijlottidis,  1171 

pars  inlercartilaginea,  1171 
interniemhranacea,   1171 

oris.  1199 

palprebranwi,  1112 

pudcndi,  1415 
Ring  muscle  of  Mi'iller,  1090 
Ripa,  903 

Risorius  muscle,  377 
Rivinus,  duct  of,  1220 

notch  of,  1130 
Rivus  lacrinialis,  1113 
Rods  of  Corti,  1145 
Rolaudic  angle,  918 
Rolando,  fissure  of,  918 
Rosenmiiller,  fossa  of,  1229 

lymph  nodes  of,  780 

organ  of,  1401 
Rostral  fissure,  920 
Rostrum  corporis  callosi,  934 

of  corpus  callosum,  934 

of  sphenoid,  92 

spheiioidalis,  92 
Rotary  joint,  205 
Rotation  in  joints,  267 
Rotatores  spinae  muscle,  413 
Rubrospinal  tract  of  cord,  839 
Rubrum,  898 
Rudiniontal     third     trochanter, 

224 
Rudimcntum  processus  vaginalis, 

1379 
Rugae  vaginales,  1414 
Ruysch,  membrane  of,  1093 


Sac,  lacrimal,  1116 
Saccule,  1141 

laryngeal,  1171 

of  lungs,  1195 
Sacculi,  1310 
Sacculus,  1141 
Saccus  lacrimalis,  1116 
Sacral  arteries,  669,  678 

canal,  61 

cornua,  59 

foramina,  59 

groove,  60 

Ivmph  nodes,  788 

nerves,  1019 

divisions  of,  1019,  1051 

nucleus  of  spinal  cord,  833 

plexus  of  ner\-es,  1053 

veins,  744,  748 

vertebra,  58 
Sacrococcygeal  ligaments,  293 
Sacrogenital  folds,  1257 
Sacroiliac  artieidation,  290 
surface  form  of,  290 

ligaments,  290 
Sacrosciatic  foramen,  292 
great,  211 
lesser,  211 

ligaments,  291,  292 

notch,  210,  211 
Sacrouterine  ligaments,  1407 
Sacrovertebral  angle,  58 
Sacrum,  58 


Sacrum,  .-dii  of,  01 

articiiliilionsof,  01,  290.  292 

dilTirii between    mule   unci 

rcmale,  01 

promontory  of,  58 

variations  in,  01 
Saddle-joint,  204,  265 
Sagittal  axis,  108H 

planes  of  body,  34 

sinus,  74,  124,  721 

sulcus,  72,  78 

.suture,  121 
Salivary  glands,  1223 

applied  anatomy  of,  1229 
artcrie-s  of,  1227 
developnwnl  of,  1227 
nerves  „f,  1227 
surface  form  of,  1227 
veins  of,  1227 
Salpingopalatine  fold,  12.30 
Salpingopharyngeal  fold,  1230 
Sal|)ingopharyngeus  muscle,  399 
.Sanlorini,  cartilage  of,  1100 

caruncula  of,  1287 

duct  of,  1340 

fissures  of,  1122 
Saphenous  nerves,  1050,  1057 

opening,  .TOS 

veins.  740,  741 
Sarcolemma,  356 
Sarcomere,  ."^56 
Sarcoplasm,  356 
Sarcostj'le,  356 

Sarcous  elements  of  muscle,  350 
Sartorius  muscle,  508 

surface  form  of,  543 
Scala  tympani,  1140 

vcstibuH,  1140 
Scalenus  anticus  nuiscle,  401 

mcdius  niiisclr,    101 

posticus  ITlU^clr.   402 

Scalp,  l\'nij»hatic  \'eesels  of,  776 

skin  of,  363 
Scapha,  1120 

Scaphoid,  articulation  of  astraga- 
lus with,  340 
of  ealcanre-  and,  348 
witli  cuLoid,  350 
with  cuneiform,  349 
bone  of  foot,  240 

of  hand,  196 
fossa,  94,  130,  1120 
Scapula,  172 

applied  anatomy  of,  178 
head  of,  176 
ligaments  of,  299 
neck  of,  176 

anatomical,  178 
siu'gical,  17<S 
spine  of,  174 
surface  form  of,  177 
Scapular  artery,  posterior,  030 
nerve,  posterior,  1029 
region,    muscles    of,    anterior, 
463 
posterior,  464 
Scapuloclavicular      articulation, 

297 
Scopus  pili,  1161 
Scarf  skin,  1151 
Scarpa,  fascia  of,  424 
foramina  of.  105,  128 
givnglion  of,  1000.  1147 
triangle  of,  509,  085 
Schachowa.  spiral  tube  of.  1351 
Sehindvlesis,  264 
Schlcmm.  canal  of.  1092 

ligament  of,  302 
Schmidt-Lantcrmanii,     incisures 

of,  811 
Sehneiderian  membrane.  1083 
Schreger.  concentric  lines  of.  1211 
Schultze.  comma  tract  of,  835 
Schwann,  .sheaths  of,  Sll 
Sciatic  artery,  677 


1492 


INDEX 


Sciatic  nerves,  1054 

veins,  744 
Sclera,  1090 

applied  anatomy  of,  1110 
Scleral  sulcus,  lOSS 
Scrobiculus  cordis,  166 
Scrotal  nerve,  1055 
Scrotum,  1372 

applied  anatomy  of,  1382 

dartos  of,  1373 

integument  of,  1373 

septum  of,  1373 
Sebaceous  glands,  1113,  1161 
Second  nerve,  974 
Sella  turcica,  90,  126 
Semen,  1381 

Semicanalis     niiisculus     iensoris 
tympani,  1127 

tubae  audiiivae,  1127 
Semicircular  canals,  bony,  1137 

membranous,  1142 
Semilunar  bone,  197 

fibrocartilages,  334,  335 

fold  of  Douglas,  430 

ganglion,  978,  1073 

hiatus,  730 

lobe,  inferior,  887 
Semimembranosus  muscle,  524 

surface  form  of,  544 
Seminal  duct,  1383 

vesicles,  1384 

applied  anatomy  of,  1385 
arteries  of,  1385 
lymphatics  of,  797,  1385 
nerves  of,  1385 
veins  of,  1385 
Semispinalis  colli  muscle,  413 

dorsi  muscle,  413 
Semitendinous  muscle,  524 

surface  form  of,  543 
Sensor  area  of  l^rain,  960 

neurones,  804 

root  of  spinal  cord,  823 
Septa  of  lungs,  1195 
Septomarginal  tract  of  cord,  837 
Septum,  aortic,  759,  760 

dorsal,  fenestrated,  845 

interauricular,  559 

interventricular,  557,  561 

lingual,  393 

of  nasal  sinus,  139 

nasi  osseum,  139 

of  nose,  138 
artery  of,  602 

orbital,"  368,  1112 

pectiniforme,  1386 

of  scrotum,  1373 

secundimi,  759 

spurium.  758 

ventricular,  759 
Septum  atriorum,  559 

canalis  muscidotvbarii,  1127 

corporum  caveniosorum,  1418 

femorale  [Cloqucti],  504 

inferius,  759 

intermedium,  759 

iniermusculare  laterale,  508 
mediale,  508 

linguae,  393 

lucidum,  934,  945 

menibranaceum    ventriculorum, 
561 

mobile  nasi.  1079 

musculare  ventriculorum,   561 

orbitale,  1112 

pelluciduin,  913,  945 

penis,  1386 

prlmum,  759 

scroti,  1373 

sinuum  frontalium,  79 
sphenoidalium,  91 

ventriculorum.  557,  561 
Serous  membranes  of  diaphragm, 
421 

pericardium,  549 


Serratus  magnus  muscle,  461 

applied  anatomy  of,  461 
surface  form  of,  495 

posticus  muscles,  408 
surface  form  of,  416 
Sertoh,  columns  of,  1380 
Sesamoid  bones.  257 

cartilage,  lOSO 
Sessile  hydatid,  1378 
Seventh  nerve,  994 
Sharpey's  fibers,  38 
Sheath,  axillary,  636 

crural,  683 

femoral,  683 

of  Henle,  812 

myelin,  811 

of  nerves,  812 

of  orhiital  muscle,  371 

rectus,  434 

of  Schwann,  811 
Sliin  bone,  231 
Shoulder  blade,  172 

fascia  of,  461 

girdle,  169 

-joint,  articulations  of,  301 
applied  anatomy  of,  304 
arteries  of,  303 
bursae  of,  303 
muscles  of,  303 
nerves  of,  303 
surface  form  of,  304 
synovial  membrane  of,  303 

muscles  of,  461 
Shrapnell,  membrana  flaccida  of, 

1130 
Sibson's  fascia,  1183 
Sigmoid  arteries,  667 

cavity  of  radius,  192 
of  ulna,  187 

flexure,  1297 

fossa,  82 

mesocolon,  1264 

notch,  118 

plexus  of  nerves,  1076 

sinus,  723 
Sinus  or  Sinuses,  707 

of  aorta,  great,  576 

basilar,  727 

cavernous,  723 

circular,  726 

confluence  of,  723 

coronary,  555,  708 

costomediastinal,  1184 

costophrenic,  1184 

definition  of,  77  (note) 

of  dura,  721 

epididymis,  1378 

ethmoidal,  99 

facialis,  721 

frontal  air,  79 

intercavernous,  726 

of  internal  jugular  vein,  714 

jugular,  713 

laryngeal,  1170 

lateral,  722 

lymph,  768 

maxillary,  101,  103 

of  Morgagni.  395 

occipital,  723 

orbital,  112 

of  pericardium,  550 

petrosal,  715,  726 

petrosquamous,  723 

phrenicocostal,  1346 

prostatic,  1367 

pvriformis,  1233 

renal,  1349 

sagittal,  inferior,  721 
superior.  74,  124,  721 

sigmoid.  723 

sphenoidal.  91,  139 

sphenoparietal,  725 

straiglit,  722 

tentorial.  722 

terminaUs,  831 


Sinus  or  Sinuses,  of  Valsalva,  576 

pulmonary,  559,  561 
venosus,  554,  757 
venous,  707 
Sinus  or  Sinuses,  cavernosus,  724 
circularis,  726 
coronarius,  55.5,  708 
cost07nediastinalis,   1184 
durae  m.atris,  721 
epididymidis,  1378 
frontalis,  79 
intercavernosus  anterior,  726 

posterior,  726 
lactiferans,  1431 
maxillaris,  103 
occipitalis,  723 
petrosus  inferior,  726 

superior,  726,  966 
phrenicocostalis,  1184 
pocularis,  1367 
rectales,  1310 
rectus,  722,  966 
renalis,  1349 
sagittalis  inferior,  721,  966 

superior,  721,  966 
sphenoidales,  91 
spkenoparietalis,  725 
tarsi,  239 
tentorii,  722 

transversus,  722,  727,  966 
.   pericardii,  550 
venarum,   554 
venosus  sclerae,  1092 
vcrtebrales  longitttdinales,  738 
Sinusoids,  573,  751,  763 
Sixth  nerve,  993 
Skeletal  muscles,  355 
Skin,  1149 

appendages  of,  1156 
arteries  of,  1156 
of  auditory  canal,  1123 
bloodvessels  of,  1161 
coriimi  of,  1153 
cuticle  of,  1151 
folds  of,  1150 
furrows,  1150 
lymphatics  of,  1156 
nerves  of,  1156,  1161 
pigmentation  of,  1155 
ridges,  1150 
of  scalp,  363 
scarf,  1151 
true,  1153 
veins  of,  1156 
SkuU,  anterior  region  of,  134 
applied  anatomy  of,  149 
base  of,  123 
bones  of.  69 
brachyfacial,  146 
chemoprosope,  146 
development  of,  141 
differences  in,  due  to  age,  143 

to  sex,  144 
dolichofacial,  146 
fossa  of,  anterior,  123 

condylar,  131 

digastric,  131 

floccular,  128 

glenoid,  131 

inferior  occipital,  128 

middle,  125' 

posterior,  127 

scaphoid,  130 

sphenomaxillary,  134 

temporal,   132 

zygomatic,  130,  133 
index  of,  146,  147 
lateral  regions  of,  132 
leptoprosope,  146 
measurements  of,  146 
megacephalic,  145 
mesal  plane  of,  146 
mesocephalic,  145 
microcephalic,  145 
surface  form  of,  147 


INDEX 


\\\r.i 


Skull,  sutures  of,  121 
obliteration  of,  144 
tables  of,  36 
vertex  of,  123 
Smegma  praepulii,  1389 
Socia  parotidis,  1224 
Soft  palate,  1202 

aponeurosis  of,  1203 
mucous  membrane  of,  1203 
muscles  of,  1203 
piUars  of,  1203 
Solar  plexus  of  nerves,  1073 
Sole  plate,  357 
Soleus  muscle,  529 

surface  foi-m  of,  544 
Solit:.n-  r'.llirl,.^  1292 
SoiiKil.M>l-niv,   1245 

Soiiii -iiiL',  ■jaii!J:Uon  of,  896 

Space,  cijidural,  843 
of  Fontana,  1097 
intercostal,  155 
intornvdintc,  of  ilium,  210 

illlrv|.lrur:il,    1185 
lli.Uir,iip:il,    202 

of  Xu.'l,  U  17 
perilymph,  1136 
popliteal,  691 
retropharyngeal,  384 
semilunar,  of  Traube,  1280 
subarachnoid,  845 
subdural,  845 
suprasternal,  383 
Spaiia   arwuli  iridis  [Fonlanae], 
1092,  1097 
interolobtilares,  1211 
interossea  metacarpi,  202 
zonularia,  1106 
Spatium  intercostale,  i^o 
perichoroideale,  1090 
suprasternale,  383 
Speech  tract,  emissary,  957 
Spermatic  arteries,  665,  1376 
canal,  437,  1375 
cord,  437,  1375 
arteries  of,  1376 
lymphatics  of,  1377 
nerves  of,  1377 
veins  of,  1377 
fascia,  external,  427, 1374 

internal.  437 
nerve,  1047 
plexus  of  nerves,  1076 

of  veins,  750 
veins,  750 
Spermatocytes,  1381 
Spermatogonia,  1380 
Spermatozoa,  1381 
Spermia,  1381 

Sphenoetlimoidal  recess,  140 
Sphenofrontal  suture,  122 
Sphenoid  bone,  89 

rostrum  of,  92,  130 
Sphenoidal  fissure,  93,  126,  134 
foramen,  structures  transmit- 
ted by,  126 
nerves,  990 
process,  1080 

of  palate  bone,  112 
sinuses,  91,  139 
spine,  92 

turbinated   processes,    91,    95, 
138 
Sphenomaxillary     fissure,      109, 
134,  137 
fossa,  109,  134 
Sphenopalatine     foramen,     112, 
134,  138,  139 
ganglion,  982,  984,  986 
nerve,  983 
notch,  112 
Sphenoparietal  sinuses,  725 

suture,  122 
Spherical  recess,  1137 
Sphincter  ani  muscles,  453,  454 
muscle,  35S 


Sphincter,  ii.\l<irii',  1273 

linihrn,    ill.  nihiflitacCaC,  448 

vaKinai'  iiui.s.-lc,  445 
Spigelian  loljc  of  liver,  1324 

recess,  1256 
Spina  annularis,  92 
bifida,  68 
helicis,  1120 

iliaca  anterior  inferior,  210 
superior,  210 
posterior  inferior,  210 
superior,  210 
ischiadica,  211 
nasalis  anterior,  105 

posterior,   110 
scapiilnc,  174 
vestibuli  of  His,  758 
Spinae  inentalcs,  117 
Spinal  accessory  nerve,  1009 
nucleus  of,  879 
arteries,  620,  621 
Ijulh,  8G1 
column.  48 
cord,  820 

applied  anatomy  of,  842 

arachnoid  of,  844 

axones  of,  myelinization  of, 

840 
central  canal  of,  831 

ligament  of,  845 
columns  of,  826 

dorsal,  ground  bundle  of, 

837 
lateral,  ground  bundle  of, 

839 
ventral,  ground  bundle  of, 
840 
commissure  of,  gray,  831 

white,  834 
conus,  823 
cornua  of,  8.30 
development  of,  827 
dura  of,  843 
enlargements  of,  823 
filum,  825 
fissures,  825 
grooves  of,  825 
horns  of,  8.30 
membranes  of,  842 
morphology  of,  822,  829 
nerve  cells  of,  832 

fibers  of,  832,  834 
nucleus  of,  834 
pia  of,  845 
reticula  of.  830 
roots  of,  823 
substance  of,  gray,  829,  840 

■whjte,  833,  841 
tracts  of,_834 
veins  of,  739 
weight  of,  821 
foramen,  49 
ganglia,  1013 
nerves,  1012 

connections  of  sympathetic 

with,  1064 

divisions  of,  1014,  1019 

points  of  emergence  of,  1014 

roots  of,  1013 

veins,  external,  845 

Spinalis  colh  muscle,  412 

dor.si  muscle,  412 
Spindles,  muscle,  of  Kiihne,  817 
neuromuscular,  817 
neurotendinous,  817 
Spine,  48 

ethmoidal,  90,  125 
of  helix  of  car,  1120 
of  Henle,  81 
of  ischium,  211 
nasal,  79 

anterior,  105,  135,  139 
posterior.  129,  139 
palatine,  110 


Spine,  peroneal,  242 

pharyiigeul,  71,  131 

of  pubis,  212 

of  Bcajiula,  174 

sphenoidal,  92 

of  tibia.  233 
Spinoglenoid  ligament,  301 
Wpinome.sencephalic  tract  of  cord, 

838 
Spinothalamic  tract  of  cord,  838 
Si)inous  processes  of  ilium,  210 
Spiral  ganglion,  1000 

line  of  fenuir,  224 

tube  of  Schacliowa,  1351 
Splanchnic  ncr\'es,  1071 
Splanchnology,  definition  of,  34 
Splanchnopleure,  1245 
Spleen,  1442 

applied  anatomy  of,  1447 

arteries  of,  1446,  1449 

lymphatic  vessels  of,  706, 1446, 
1449 

mobility  of,  1444 

nerves  of,  1446,  1449 

parenchyma  of,  1445 

relations  of,  1444 

supports  of,  1444 

surface  form  of,  1446 

trabecuUe  of,  1445 

veins  of,  752,  1446,  1449 
Splenial  crntrc,  119 
Splenic  arterv,  661 

cells,  1445 

corpuscles,  1445 

lymph  nodes,  790 

plexus  of  nerves,  1008,  1076 

pulp,  1445 
Splcnium  corporis  cnllosi,  934 

of  corpus  callosum,  934 
Splenius  capitis  muscle,  409 

colli  muscle,  409 

surface  form  of,  416 

dorsi  muscle,  surface  form  of, 
416 
Spongioblasts,  806 
Squamoparietal  suture,  122 
Sciuamosphenoidal   suture,   122 
Squamous   portion   of   temporal 
bone,  80 

temporalis,  SO 
Stahr,  middle  lymph  node  of,  778 
Stapedius  muscles,  1 134 
Stapes,  1133 

crura  of,  1133 

cms  anterins,  1133 
posferiu-s,  1133 

head  of,  1133 

ligament  of,  1133 

neck  of,  1133 
Statoliths,  1143 
Stellate  ligament,  282 

ner\'e  cells,  808  ...^ 

Stenson,  duct  of,  1225 

foramina  of,  105.  128 
Stephanion,  133,  146 
Sternal  arteries,  632 

fissure,  161 

foramen,  1.59,  161 

furrow,  166 

nor\-e,  1022 
Sternoclavicular  articulation,  295 
applied  anatomy  of,  297 
surface  form  of.  297 
syno\-ial  membranes  of.  296 

ligaments.  296 
Sternocostal  ligaiiienl.  2S6 
Sternohyoid  muscle.  3sC 
Sternoniastoid  arter.v,  590,  595 

muscle,  385 

applied  anatomy  of,  386 
surface  form  of.  402 
Sternothyroid  nuiscles,  387 
Sternum,  157 

applied  anatomy  of,  167 

articulations  of,  161,  288 


1494 


INDEX 


Sternum,   ensiforra  appendix  of, 
159 

gladiolus  of,  159 

ligaments  of,  2SS,  289 

manubrium  of,  157 

xiphoid  appendix  of,  159 
Stomach,  1270 

alterations  in  position  of,  1272 

applied  anatomy  of,  12S0 

arteries  of,  1278 

rliamber,  1270 

component  parts  of,  1272 

curvatures  of,  1271 

fundus  of,  1270 

innervation  of,  1280 

interior  of,  1273 

l.\'mphatic  vessels  of,  792,  1279 

movements  of,  1279 

mucous  membrane  of,  1275 

nerves  of,  1279 

openings  of,  1271 

pit  of.  166 

relations  of,  1279 

rugEe,  1273 

surface  form  of,  1280 

surfaces  of,  1271 

teeth,  1207 

veins  of,  1279 
Stomata,  573,  767 
Straight  sinus,  722 
Stratum  cinereum,  897 

lemni-sci,  897 

opticum.  897,  898 

reticulatuni,  904 

zoTialc,  897 
Stria  nuUleolaris,  1130 

medxdlaris,  903,  906 
thnlami,  958 

termiualis,  903 

vascularis,  1144 
Striae  acusticae,  865,  866 

Lancisii,  934 

lougitudinales,  928 

mfdullares,  865 

obliquae,  866 
Striate  veins,  720 
Striated  muscles,  355,  357 

involuntarj'.  ner\'es  of,  357 
structure  of,  355 
Striatothalamie  fibers,  950 
Striped  muscle-.  355 
Stroma  irirlis,  1098 

of  iris,  109S 
Structure  of  arachnoid  of  brain, 

g70 

of  bile  duct,  1334 

of  bladder,  1363 

of  bone,  38 

of  cartilages  of  larj^ns,  1167 

of  cerebellum,  888 

of  cerebral  cortex,  951 

hemispheres,  912,  931 
of  choroid,  1093 
of  ciliarj'  processes,  1095 
of  clavicle,  171 
of  coccygeal  gland,  1450 
of  coccv-x,  63 
of  cornea,  1091 
of  Cowper's  glands,  1397 
of  crystalline  lens.  1106         ' 
of  duodenum.  1289 
of  dura  of  brain,  967 

of  spinal  cord,  844 
of  ejaculatory  ducts,  1386 
of  epidid%Tnis.  1379 
of  eyelids,  1113 
of  Fallopian  tube,  1402 
of  female  urethra,  1370 
of  femur.  226 
of  forebrain,  902 
of  frontal  bone.  SO 
of  gall-bladder,  1332 
of  heart,  562 
of  hindbrain,  S61 
of  humerus,  182 


Structure     of    invertebral    sub- 
stance, 270 

iris,  1098 

kidneys,  1349 

lacrimal  gland,  1116 

sac,  1117 

large  intestine,  1309 

liver,  1328 

lungs,  1194 

lymphatics,  769 

male  urethra,  1369 

mammary  gland,  1430 

medulla  oblongata,  867 

Meibomian  glands,  1114 

membrana  tjTnpani,  1130 
membranous      labjTinth, 

1142 

midbrain,  894,  896 

mouth,  1201 

mucous  membrane  of  nasal 

fossa!,  1084 

muscle  fiber,  356 

nerve  system,  807 

nerves,  812 

nipple,  1430 

nose,  1079 

occipital  bone,  73 

oesophagus,  1238 

OS  innominatum,  214 

ovaries,  1399 

pancreas,  1340 

parath^Toid  glands,  1440 

parotid  gland,  1225 

pars  dorsalis  pontis,  874 

patella,  231 

penis,  1389 

pharjTix,  1231 

pineal  body,  906 

pinna  of  ear.  1120 

pituitary  body,  909 

pleura,  1185 

pons,  874 

prostate  gland,  1393 

radius,  192 

retina,  1101 

ribs,  165 

sacrum,  63 

salivarj-  glands,  1226 

scapula,  176 

sclera,  1090 

seminal  vesicles,  1385 

small  intestine,  1289 

spermatic  cord,  1376 

spinal  arachnoid,  845 

cord,  822.  829 

ners-es,  1014 

pia.  846 
of  spleen,  1444 
of  sternum.  159 
of  stomach.  1274 
of  striated  muscle.  355 
of  stiprarenal  glands.  1448 
of  tarsal  glands,  1114 
of  teeth,  1209 
of  temporal  bone,  88 
of  testes,  1380 
of  thalamus.  905 
of  thoracic  duct.  773 
of  th'VTnus  dand,  1441 
of  th^Toid  gland,  1436 
of  tibia,  235 
of  tongue,  1217 
of  tonsils.  1231 
of  trachea.  1177 
of  ulna.  190 

of  uriniferous  tubules,  1351 
of  uterus,  1409 
of  vagina.  1414 
of  vas  deferens.  1384 
of  vermiform  appendix,  1300 
of  vertebrae.  62 

of  villi  of  small  intestine,  1291 
Styloglossus  muscle,  392 
St.vlohyal  process,  89 
Stylohyoid  ligament,  389 


Stylohyoid  muscle,  389 

ners-e,  998 
Styloid  process  of  fibula,  236 
of  radius,  192 
of  ulna,  189 
Stylomandibular  Ugament,   280 

382 
Stylomastoid  artery,  596 

foramen,  87,  131 
Stylopharyngeus  muscle,  396 
!  Subacromial  bursa,  303 
Subanconeus  muscle,  471 
Subarachnoid  cisterna,  969 

space,  845,  969 

tissue,  845 
Subarachnoidean  areolar  tissue, 

968 
Subarcuate  fossa,  86 
Subcalcarine  gyve,  925 
Subcapsrdar  Ijinph  sinus,  768 
Subcardinal  veins,  765 
Subcecal  fossa,  1267 
Subcentral  fissures,  923 
Subcerebellar  veins,  720 
Subclainan  arterj',  623 

applied  anatomj-  of,  627 

left,  625 

right,  623 

surface  marking  of,  626 

groove,  171 

hrniph  nodes.  783 

triangle,  388,  605 

vein,  732 
Subcla^-ius  muscle,  460 
SuljcoUateral  gj-re,  925 
Subcoracoid  centre,  177 
Subcostal  angle,  156 

groove,  463 
Subcutaneous     acromial     bursa, 
303 

areolar  tissue,  1154 

malae  ner\'e,  983 

svno^-ial  bursae,  262 

tibial  bursa,  336 

trochanteric  bursa,  327 
Subdeltoid  bursa,  303,  462 
Subdural  space,  845 
Subendothelial    fibroelastic    tis- 
sue, 573 
Subfrontal  fissures,  919 

gj^e,  921 
Sublingual  artery,  591 

fossa,  117 

gland,  1226 
Sublobular  veins,  751 
Submaxillary  artery,  593 

fossa,  117 

ganglion.  990 

gland,  1225 

arteries  of,  1226 
duct  of,  1226 
Ij-mphatics  of,  1226 
neries  of.  1226 
veins  of,  1226 

hTiiph  nodes,  778 

triangle,  604 
Submental  artery,  593 

l^■mph  nodes,  779 
Subnasal  point  of  skull,  146 
Suboccipital  triangle,  415,  620 
Suboperculum,  917    . 
Subparotid  IjTnph  nodes,  776 
Subpleural    mediastinal    plexus, 

632 
Subpubic  ligament,  294 
Subpyloric  Ij-mph  nodes,  790 
Subrostral  fissure,  920 
Subscapular  angle,  172 

artery,  630,  639 

bursa,  303 

fascia,  463 

fossa,  172 

Kmiph  nodes,  783 

nerv'e,  1030 
Subscapularis  muscle,  464 


INDEX 


1495 


Sitlisliuilin  ndinnnnlina,  1210 
nll.n  ,„,,l,i/l„  spinuUs,  81'J,  S33 


inh,    mil 
,un,,a.    IL'II 


,/,/-, //„„x„   |/,'„/„«f/,-|,  829 
Uns.a   rnilnilis,   N-'.l 

i,„,l„ll„  ,.,„„„/, .s,   819 
),H,/„llnri«  pill,    11111 
nidra,  S97 
ossea,  1212 

perforata  posterior,  847 
reticularis  alba,  925 
spongiosa,  3S 
Substernomastoid  lymph  nodes, 

779 
Subsylvian  ramus,  917 
Subtemporal  fissure,  924 

gyre,  925 
Subtendinous  iliac  bursa,  327 

synovial  bursse,  262 
Sulxirethral  glands,  1420 
Sucldng  pad,  376 
Sudoriferous  glands,  1161 
Sulci  cutis,  1150 
longitudinales,  553 
orbilales,  921 
Sulcomarginal  tract  of  cord,  840 
Sulcus,  intraparietal,  of  Turner, 
922 
lacrimal,  107 
lunatus,  924 
of  Monro,  908 
orbitopalpebral,  1112 
parolfactory,  928 
peduncular,  of  cerebellum,  885 
sagittal,  72,  78 
scleral,  1088 

tympanic,  87,  1122,  1130 
Sulcus     antihclicus     transversus, 
1121 
arteria  occipitalis,  82 
arteriae  vertebralis,  51 
basilaris  [pontis],  864 
bulbi,  1387 
calcanei,  239 
caroticus,  91 
centralis  [Rolandi],  918 
chiasmatis,  90 
circularis  [Reili\,  917 
coronarius    553 
costae,  163 
frontalis  inferior,  919 

superior,  919 
horizontalis  cerebelli,  885 
infraorbitalis,  102 
intermedius   anterior  [medullae 
spinalis],  826 
posterior  [medullae  spinalis], 
826 
interparietalis,  922 
intertubercularis,  180 
lacrimalis,  107 

lateralis  anterior  [medullae  ob~ 
longatae],  862 
mesencephali,  894 
posterior        [medullae        ob- 
longatae],  862 
[medidlae  spinalis],  825 
limitans    [fossae    rhomboideac], 

866 
longitudinalis  anterior,  553 
m.  flexoris  halluds  longi,  245 
m.  peronei  longi,  246 
malleolaris,  235,  238 
matricis  unguis,  1156 
mediaretts  linguae,  1217 

posterior  [medullae  spinalis], 
825 
■mylohyoideus,  117 
meri'i  oculomotorii,  894,  897 
radialis,  180 
ulnaris,  182 


Sulcus     obturatorius,     213,     214, 

1)20 
piiriilfaclorius  anterior,  928 

posterior,  928 
praci'cntralis,  919 

superior,  91!) 
pminontorii,  1126 
pliruiiopnlnlinuH,  92,  95,  110 
T<1riiiiliiiidiil(irix.    1388 
sdipllnliy.,  IJ.,  78 
sc/rrac,  11188 
spiralis,  1144 

e.rternus,  1144 

iutcmus,  1144 
sutniamae,  163 
/«;/,  245 
tiinporulis  inferior,  924 

vicdius,  924 

superior,  924 
terminalis,  554 

rt?fw  (/f.r/ci,  554 


(,-'   ■     -  '  ,   1128 

/v, ,       ,  .  -7,  1122,  1130 

Sui.uivLiiUal  li.-,.,urcs,  919 
Supcrcilia,  1112,  1159 
Superciliary  ridge,  77,  79,  134 
Superfrontal  fissures,  919 

gyre,  921 
Supernumerary  bones,  144 
Supinator  [brevis]  muscle,  482 

longus  muscle,  479 
Supra-acromial  artery,  6.30 
Supracardinal  veins,  765 
Supraclavicular     lymph     nodes, 
779 

nerve,  1022 
Supracommissure     of      Osborn, 

906 
Supracondvlar  process,  181  (note) 

ridge,  180 
Supracondyloid     foramen,     181 

(note) 
Suprahyoid  aponeurosis,  389 

artery,  591 

lymph  nodes,  779 

region,  muscles  of,  388 

triangle,  605 
-'upramastoid  crest,  81 
.■^uprameatal    triangle    of    Mac- 

Ewan,  81,  151 
Supraorbital  arch,  77 

artery,  610 

foramen,  135 

nerve,  980 

notch,  77,  135 

ridge,  135 

vein,  710 
Suprapatellar  bursa,  336 
Suprarenal  artery,  662 

glands,  1446 
accessory,  1448 
hilum  of,  1447 
lymphatic  vessels  of,  796 

impression  of  liver,  1322 

plexus  of  nerves,  1074 

veins,  751 
Suprascapular  artery,  629 

ligament,  300 

nerve,  1029 

notch,  175 
Suprascleral  lymph  spaces,  1086 
Supraspinales  muscle,  414 
Supraspinatus  fascia,  464 

muscle,  464 
Supraspinous  fossa,  172 

ligament,  272 
Suprasternal  artery,  629 

notch,  403 

space,  3 S3 
Supratonsillar  fossa,  1231 
Supratrochlear  foramen,   182 

lymph  nodes,  782 

nervp,  980 
Sural  artery,  694 


Sural  veins,  742 

Surface  form  of  abductor  huIluciH 
muscle,  544 

minimi  diKiti  muscle,  544 
of  ueromiocluvicular  articu- 
lation, 299 
of  adductor  longus  muscle, 
543 

maitnus  muscle,  M'.i 

transversus  liollicis  mus- 
cle, 497 
of  anconeus  muscle,  490 
of  ankle-joint,  340 
of    articulations    of    elbow- 
joint,  309 

of  hip-joint,  329 

of  phalanges  of  foot.  3.54 

of  shoulder-joint,  304 
of    biceps    fcmoris    muscle, 
543 

muscle,  495 
of  bladder,  1365 
of  bones  of  foot,  255 
of  lirachialis  anticus  muscle, 

4UU 
of     IjrachioradiaUs    muscle, 

496 
of  carpal  bones,  205 
of  clavicle,  171 
of   coracobrachialis   muscle, 

495 
of  crureus  muscle,  543 
of  deltoid  muscle,  495 
of  digastric  muscle,  403 
of    erector    spinae    muscle, 

416 
of  extensor  brevis  digitorum 
muscle,  544 

longus  digitorum  muscle, 
544 

proprius  hallucis  muscle, 
544 
of  external  oblique  muscle, 

439 
of  eyeUds,  1117 
of  femur,  228 
of  fibula,  238 

of    flexor    brevis    digitorum 
muscle,  .544 

carpi  radialis  muscle,  496 
ulnaris  muscle,  496 

sublimis  digitorum   mus- 
cle, 496 
of  foot,  255 
of     gastrocnemius     muscle, 

544 
of  gluteus  maximus  muscle, 
543 

medius  muscle,  543 
of  gracilis  muscle,  543 
of  heart,  567 
of  humerus,  184 
of  hyoid  bone,  154 
of  interossei  muscle,  497 
of  intestines,  1313 
of  kidneys,  1354 
of  knee-joint,  338 
of   latissimus  ■  dorsi   nnisclc, 

416 
of   levator   anguli   scapulae 

nuisclc.  416 
of  lumbricalcs  muscle.  497 
of  lungs,  1196 
of  niassetcr  muscle,  380 
of  metacarpal  bonci.  20,5 
of  metacarpophalanceal  ar- 
ticulations. 321 
of  muscles  of  face,  380 

of  head,  380 

of  lower  extremity,  543 

of  neck,  402 

of  upper  extremity,  495 
of  omohyoid  muscle,  403 
of   orliicularis   palpebrarum 

muscle,  380 


14!)(j 


INDEX 


Surface  form  of  piilinaris  hrevis 
muscle,  497 
longus  niusclc.  49G 
'  pancreas,  1341 

patella,  231 

pcetoralis  muscles,  405 

pelvis,  219 

peroneus  nmscles,  544 

phalanges,  205 
'  platysma  nmsele,  402 

pronator     teres    muscle, 
496 

pyramidalis  nasi  muscle, 
380 

ciuadriceps  extensor  mus- 
cle, 543 

radioulnar    articulation, 
314 

radius,  192 

rectus  alidorainis  muscle, 

439 
femoris  muscle,  543 

rhomboideus  muscles,  416 
sacroiliac  articulation,  290 

salivary  glands,  1227 

sartorius  muscle,  543 

scapula,  177 

semimembranous  muscle, 
544 

semitendinous     muscle, 
543 

serratus  magnus  muscle, 

495 
posticus  muscles,  416 

skull,  147 

soleus  muscle,  544 

spleen,  1446 

splenius  colli  muscle,  416 
dorsi  muscle,  416 

sternocalvicular    articu- 
lation, 297 

steruomastoid     muscle, 
402 

stomach,  1281 

subcrureus  muscle,  543 

superior  radioulnar  artic- 
ulation, 311 

temporal  muscle,  380 
temporomandibular    ar- 
ticulation, 281 

tensor    fasciae    femori? 
muscle,  543 

teres  major  muscle,  495 

thorax,  166 

tibia,  236 

tibialis  muscles,  544 

trachea,  1179 

trachelomastoid    muscle, 
416 

trapezius  muscle,  416 

triceps  muscle,  496 

ulna,  190 

vastus   externus   muscle, 
.    543 
internus  muscle,  543 

vertebral  column,  67 

wrist-joint,  315 

:ing  of  abdominal   aorta, 
657 

anterior  tibial  artery,  697 

axillary  artery,  637 

brachial  artery,  641 

common   carotid    artery, 

586 
iliac  arteries,  669 

dorsalis  pedis  artery,  699 

external   carotid   artery, 
588 
iliac  artery,  680 

femoral  artf>r\-.  fiS7 

intpriiiil  iliiir  aiir-rv,  679 

plantar  -M^^-rv-..  704 

popliteal  artery,  693 

posterior  tibial  artery,  701 

radial  artery,  646 


Surface   marking  of    subclavian 
artery,  626 

of  superficial   palmar   arch, 
652 

of  trigeminal  nerve,  990 

of  ulnar  artery,  649 
relations  of  liver,  1.334 
Surf-line  of  aorta,  580 
Surgical  anatomy.     See  Applied 

anatomy, 
neck  of  humerus,  178 
Suspensory   ligament   of     axilla, 
456 

of  chtoris,  1418 

of  Cooper,  456 

of  eye,  1087 

of  lens,  1106 

of  liver,  1325 

of  malleus,  1133 

of  mamma,  456 

of  ovaries,  1398 

of  penis,  138.8 

of  Treitz,  1285 
muscle  of  duodenum,  1285 
Sustentaculmn  lienis,  1264 

tali,  242 
Sutura,  263 
coronalis,  121 
dentata,  264 
frontalis,  121 
frontoethmoidalis,  122 
frontolacrinialis,  122 
frontomaxillaris,  122 
hxirmonia,  264 
intermaxillaris,  135 
internasalis,  135 
lambdoidea,  121 
limbosa,  264 
nasofrontalis,  122 
nasoniaxillaris,  135 
occipito7nastoid-ea,  122 
parietomastoidea,   122 
sagitlalis,  121 
serrata,  264 
sphenofrontalis,  121 
spherwparietalis,  122 
sphenosquamosa,  122 
squamosa,  264 
vera,  264 

zygomaticofrontalis,  121 
Sutural  bones,  144 
ligament,  121,  259 
membrane,  263 
Sutures,  121 
basilar,  122 
coronal,  76,  121 
false,  264 
frontal,  121 
fronto-ethmoidal,   122 
frontolacrimal,  122 
frontomalar,  121 
frontomaxillary,  122 
frontoparietal,  121 
frontosphonoidal,   121 
intermaxillary-,  135 
internasal,  135 
interparietal,  121 
lambdoid,  73,  76,  121 
lateral,  121 

mastn-neeipiliil,    73,    122 


nasotronlal.   122 
nasomaxillar.i,-.  135 
neuroeentrali  63 
obliteration  of,  144 
occipitoparietal,  121 
petro-occipital.  73 
petrosphenoidal,  131 
petrosquamous,  S4 
sagittal,  76,  121 
sphenofrontal,  122 
sphenoparietal,  122 
squamoparietal,  122 
squamosphenoidal,   122 


Sutures,  transverse,  122,  139 
facial,  121 
true,  264 

zygomaticofrontal,   122 
Sweat  glands,  1161 
Sylvian  fissure  and  its  rami,  916 
development  of,  917 
veins,  720 
Sympathetic  nerve  sy.stem,  1063 
Symphysis  of  mandible,  115 
ossiuni  pubis,  294 
sacrococcygea,  292 
Synarthrosis,  263,  266 
Synchondrosis,  264 
sphenooccipitalls,  122 
sternalis,  157 
Syndesmology,  definition  of,  34 
Syndesmosis  tibiofihularis,  341 
Syndosmo-odontoid  joint,  274 
Synergic  muscles,  359 
Synovia,  261 

Synovial    burss,    subcutaneous, 
262 
subtendinous,  262 
thecal,  262 
ligaments,  262 
membrane,  259,  261 

of   acromioclavicular  articu- 
lation, 298 
of  ankle-joint,  345 
articular,  261 

of   articulations    of    carpus, 
317 
of  elbow-joint,  308 
of  shoulder-joint,  303 
bursal,  262 
of    calcaneo-astragaloid    ar- 

ticul.ation,  347 
of   calcaneocuboid   articula- 
tion, 348 
of  carpometacarpal  articula- 
tions, 318 
of  costocentral  articulations, 

283 
of  costosternal  articulations, 

288 
of  flexor  tendons  at  wrist, 

486 
of  hip-joint,  326 
of  inferior  tibiofibular  artic- 
ulation, 342 
of  knee-joint,  336 
in  metatarsal  joint,  353 
of   radioulnar   articulations, 

313 
of  sternoclavicular  articula- 
tion, 296 
of  superior  tibiofibular  artic- 
ulation, 341 
in  tarsal  joint,  353 
of  tarsometatarsal  articula- 
tion, 352 
of    temporomandibular    ar- 
ticulation, 280 
vaginal,  262 
pads,  262 
.sheath,  262 
villi,  262 
Systemic  circulation,  548 

veins,  708 
Systole,  auricular,  565 
ventricular,  565 


TABLE.S  of  skull,  36 
Tactile  corpuscles,  816 
Taenia  coli,  1310 

libera,  1310 

mesocolica,  1310 

omentalis,  1310 

pontis,  895 

semicircularis,  937,  938 

thalami,  903 


INDEX 


1497 


Taeniae  cnli,  1296 

Talus,  244 

Tapetum    of    corpus    callosum, 

933,  938 
Tarsal  arch,  inferior,  612 
superior,  612 
artery,  699 

articulations,    syno^^al    mem- 
brane in,  353 
transverse,  349 
bones,  development  of,  254 
glands,  1114 
ligaments,  366 
muscles,  369,  370 
nerve,  1059 
plates,  1113 
Tarsometatarsal       articulations, 
351 
synovial  membrane  of,  352 
Tarsus,  239 

articulations  of,  347 
Taste  buds,  1149 
nerves  of,  1149 
organs  of,  1148 
Tawara,  node  of,  564 
Tectospinal  tract,  900 
Teeth,  1204 
auditory,  1144 
bicuspid,  1207 
calcification  of,  1216 
canine,  1206 
cementum  of,  1212 
chemical  composition  of,  1210 
deciduous,  1205 
dentin  of,  1211 
development  of,  1212 
eruption  of,  1216 
enamel  of,  1210 
ivory  of,  1211 
milk,  1205 
molar,  1207 
permanent,  1206 
premolar,  1207 
stomach,  1207 
structure  of,  1209 
temporary,  1205 
Tegvien  tyynpani,  84,  1125 
Tegmental  part  of  pons,  876 

tract,  900 
Tennunliim,  S96,  897 
of  midbrain,  897 

fiber  tracts  in,  898 
nucleus  of,  898 
Tela  choroidea,  867,  971 
superior,  940 

ventriculi    quarli,    865,    867, 
972 
tertii,  971 
subcutanea,  1154 
Telencephalon,  902 
pars  optica  hypothalami  of, 
908 
Telodendria,  811,  815 
Temporal  arteries,  597,  598,  600, 
601,  617 
bone,  80 
crest,  74 

diploic  veins,  718 
fascia,  378 
fossa,  92,  132 
lobe,  924 

fissures  of,  924 
gyres  of,  924 
muscle,  378 

surface  form  of,  380 
nerve  from  facial,  998 

from  internal  maxillary,  987 
from  superior  maxillary,  983 
ridge  of  frontal  bone,  78 

of  parietal  bone,  74 
veins,  712 

wings  of  sphenoid,  92 
Temporofacial  nerve,  996 
Temporomalar  filaments,  109 
foramen,  109 


Temporomalar  nerve,  983 
Temporomandibular       articula- 
tion, 133,  279 
applied  anatomy  of,  281 
surface  form  of,  281 
synovial  membrane  of,  280 
region,  muscles  of,  377 
Tempbromaxiilary  vein,  712 
Tcmporopontile  tract,  900,  950, 

957 
Tcmh,  360 
Achillis,  530 

l^ursa  of,  530 
crilcancua  [ArhilKs],  530 
ocuh,  366,  367 
Tendons,  360 

of  diaphragm,  419 
flexor,  fibrous  sheaths  of,  539 
at     wrist,     synovial     mem- 
branes of,  486 
of  Lockwood,  370 
of  quadriceps  extensor  muscle, 

512 
of  triceps  muscle,  470 
of  Zinn,  370 
Tenon's  capsule,  371 
Tensor   fasciae   femoris   muscle, 
508 
surface  form  of,  543 
palati  muscle,  397 
tarsi  muscle,  367 
tympani,  canal  for,  1127 
Tenth  nerve,  1003 

thoracic  verteljra,  54 
Tentorial  liiatus,  847 

sinus,  732 
Tentorium  cerebelli,  966 
Teres  major  muscle,  466 

surface  form  of,  495 
minor  muscle,  466 
Terma,  847,  908,  909 
Terminal  arteries,  573,  618 

fibrilla;,  816 
Testes,     1371,     1377.     ,See    also 
Testicle, 
applied  anatomy  of,  1383 
descent  of,  1424 
efferent  ducts  of,  1380 
extremiius  inferior,  1378 

superior,  1378 
fades  lateralis,  1378 

Tnedialis,  1378 
lymphatic  vessels  of,  796 
margo  anterior,  1378 

posterior,  1378 
parenchyma  of,  1380 
structure  of,  1380 
tunica  albiiginea,  1380 
dartos,  1373 
fibrosa,  13S0 

vaginalis  communis,  1374 
propria,  1374,  1379 
lamina  parietalis,  1379 
visceralis,  1379 
vascvlosa,  1380 
Testicle,  1371 

coverings  of,  1372 
tunics  of,  1379 
Thalamencephalon,  902 
Thalami,  902 

Thalaraofrontal  fibers,  950 
Thalamostriate  fibers,  950 
Thebesius,  valve  of,  555,  70S 

veins  of,  709 
Theca  folliculi,  1399 
Thecal  synovial  bursa,  262 
Thenar  eminence,  486 
Thigh,  fascia  of.  505 

muscles  of,  505 
Third  nerve,  976 

occipital  nerve,  1017 
ventricle,  907 
Thoracic  aorta.  653 

applied  anatomy  of,  654 
arteries,  638,  639 


Thoracic  cardiac  ner\'C  1007 
curve  of  vertcl)rul  co!\itnii,  flO 

duct,  771 

applied  anatomy  of,  771 
tributaries  of,  772 
nerve,  1018 
anterior,  1030 
divi.sions  of,  lOlK,  10 10 
long,  1029 
posterior,  1029 
portion     of    gangliatcd     cord, 

1070 
region,  fasciie  of,  455 

muscles  of,  455,  401 
vein,  long,  732 
vertebra.',  53 
\-i3ccra,   lymphatic  vessels  of, 

802 
wall,     lymphatic     vessels    of, 
798 
Thoracicoepigastric  vein,  732 
Thoracicolunibar  nerves,  1043 
Thoracoabdominal       intercostal 

nerves,  1043 
Thorax,  154 

applied  anatomy  of,  167 
fascia;  of,  416 
inlet  of,  155 
l.vmph  nodes  of,  798 
muscles  of,  416 
surface  form  of,  166 
veins  of,  727 
Thymic  artery,  582,  1442 
Thymus  gland,  1440 

applied  anatomy  of,  1442 
arteries  of,  1442 
lymphatic    vessels    of,    S02, 

1442 
nerves  of,  1442 
veins  of,  1442 
Thyroarytenoid  ligaments,  1170 

muscles,  1173 
Thyroepiglottic  ligaments,  1167, 

1169 
ThjToepiglotticus  muscle,  1173 
Thvroglossal  duct,  1219 
Thyrohyals,  154 
Thyrohyoid  ligaments,  1167 
membrane,  1164,  1167 
muscle,  387 
nerve,  1011 
Thyroid  artery,  inferior,  629 
.superior,  589 
axis,  628 
body,  1435 

plexus  of  veins  on.  734 
cartilage,  11G3 
foramen,  213 
gland,  1435 
acces.sory,  1436 
applied  anatomy  of,  1438 
arteries  of,  1437 
lymphatics  of,  1438 
nerves  of,  1438 
structure  of,  1436 
veins  of,  1438 
nerve,  1069 

plexus  of,  1069 
vein,  inferior,  734 
middle,  716 
superior,  715 
ThjToidea  ima  artcr.v,  582 

vein.  735 
Tibia,  231 
crest  of,  234 

internal  malleolus  of.  235 
nutrient  artery  of,  702 

foranu'U  of,  234 
obliriue  line  of,  234 
poi>litcal  notch  of.  233 
spine  of,  233 
structure  of,  235 
surface  form  of,  236 
tubercle  of,  233 
Tibial  artery,  anterior,  696 


1-1!)8 


INDEX 


itcry,   anterior,   applied 
;iii!ifoniy  of,  697 
■.■iirn-iit,   BOS 
irfarr  ni:ii-kiu«of,  097 


:i|.|'li'-ii  :ii]:itoniy  of,  701 

ri'ciirrciit,  69S 

surface  marking  of,  701 

bursa,  subcutaneous,  330 

Ivnipb  tir.'Ic.  7S4 

M,-n.-,   111,-1,-,.  lll.-,7,  1059 
TibLili-  :inii-u-  muscle,  526 
\,m>-A  ..r.  520 
surface  form  of,  544 

Ijosticus  muscle,  533 

surface  form  of,  544 
Tibiofibular    articulations,    340, 
3U 

rejriou,  nmscles  of,  525,  528 
Tiliiotarsal  articulation,  342 

ligaments,  343 
Tifiroid  bodies,  809 
Tissue,      fibroelastic,      subendo- 
thelial,  573 

spaces,  767 

subarachnoid,  845 
Todd    and    Bowman,    trachealis 

muscle  of,  1178 
Tomes,  graniilar  layer  of,  1211 

socondarv  dentin  of,  1212 
Tongue,  1217 

applied  anatomy  of,  1222 

arteries  of,  1219 

■development  of,  1221 

lymphatic  vessels  of,  777,  1220 

mucous  membrane  of,  1217 

muscles  of,  393 

nerves  of,  1221 

papilla'  of,  1218 

veins  of,  1219 
Tonsilla,  887 

ccrehelli,  887 

intestinalis,  1292 

linfliudls,  1219 

palatina,  1230 

pharyiiffea,  1230 
Tonsillar  artery,  593 

nerve,  1003 
Tonsils.   1230 

applied  anatomy  of,  1233 

arteries  of,  1231 

development  of,  1232 

lingual,  1219 

lymphatics  of,  1231 

nerves  of,  1231 

pharyngeal,  1230 

tubal,  1128 

veins  of,  1231 
Topographic     anatomy,     defini- 
tion of,  33 
Topographv,  craniocerebral,  962 
Torculnr,  72,  12S 

Hrn.phili,  7_'-l 
Tvru:i   i,il,nir<l,rinis,   1365 

tiilmriiix.  lL'2il 

utcrinus,  1257 
Touch  .  corpuscles    of    Meissner 
and  Wagner,  816 

organ  of,  11,50 
Triihecidrie  carneae,  558 

corporum  cavernosutn,  1389 

nrmii,  141 

lirnis,  1445 

of  spleen,  1445 
Trails  cerebri.  933 
Trachea,  1175 

applied  anatomy  of,  1180 

arteries  of,  629,  1179 

cartilages  of,  1177 

glands  of.  1178 

lynipli  nodes  of,  1179 

mucous  menjlirane  of,  1178 

relations  of,  1175 

surface  form  of,  1179 

veins  of,  735,  1179 


Tracheal  lymph  nodes,  1179 
Trachealis  nmscle  of  Todd  and 

Bowman,   1178 
Trafhcluniastoid  muscle,  412 

surface  form  of,  416 
Trarheubronchial   lymph   nodes, 

801 
Trachoma  glands,  1115 
Tract,  ascending,  957 

cells  of  spinal  cord,  841 

corticopontile,  900 

descending,  956 

frontopontile,  900,  951,  957 

geniculate,  9.50 

nerve,  cerebrospinal,  838 
Lowenthal's,  840 

ventral  cerebrospinal,  840 
Marchi's,  839 
Monakow's,  839 
prepyramidal,  839 

occipitomesencephalic,    957 

occipitopontile,  950 

olfactory,  927 

pyramidal,  900 

solitary,  nucleus  of,  880 

speech,  emissary,  957 

of  spinal  cord,  834 

tectospinal,  900 

tegmental,  900 

temporopontile,  900,  950,  957 
Tractus  cervicolumbalis,  836 

iliotibialis  [Maissiati],  507 

olfaciorius,  927 

peduncularis  transversus,   895 

poniocerebellares,  890  > 

rubrospinalis,  898 

solitarius,  880 

spinotectalis,  838 

spiralis  foraminosus,  85,  1139 

thalamicus,  838 

tectospinalis,  840 
Tragi,  1159 

Tragicus  muscles,  1121 
Tragus,  1120 
Transinsula  fissure,  925 
Transorbital  fissure,  921 
Transparietal  fissure,  924 
Transprecentral  fissures,  920 
Transtemporal  fissure,  924 

gyre,  924 

gray  substance  of,  953 
Transversalis     capitis     muscles, 
412 

cervicis  muscle,  412 

fascia,  436 

muscle,  432 
Transverse  aorta,  579 

colon,  1303 

mesocolon,  1264,  1304 
Transversus    auriculae   muscles, 
1121 

perinei  profundus,  448 

sulcus  antihelicis,  1121 
Trapezium,  876 

bone,  198 
Trapezius  muscle,  404 

surface  form  of,  416 
Trapezoid  bone,  199 

ligament,  298 

ridge,  169 
Treitz,  fossse  of,  1265 

suspensory  ligament  of,  1285 
Triangle,  carotid,  388,  603,  604 

of  election,  604 

He.sselbach's,  437 

Lessor's,  591,  1012 

of  necessitv,  603 

of  neck,  386,  602,  603,  605 

occipital,  388,  605 

Petit,  407,  426 

Scarpa's,  509,  685 

subclavian,  388,  605 

submaxillary,  604 

suboccipital,  415,  620 

suprahyoid,  605 


Triangle,  suprameatal,  81 
Triangular  articular  disk,  312 
fascia,  425,  428 
ligament  in  female,  446, 

in  male,  446 
muscles,  358 
Triangularis  sterni  muscle,  417 
Triceps  extensor  cubiti  muscle, 
470 
muscle,  470 

applied  anatomy  of,  471 
surface  form  of,  496 
tendon  of,  470 
Tricuspid  orifice,  557 

valve,  558 
Trifacial  nerve,  978 
Trigeminal  depression,  84 
nerve,  978 

applied  anatomy  of,  991 
nucleus  of,  883 
surface  marking  of,  990 
Trigone  of  bladder,  1367 
Trigonum  collatcrale,  938 
feniorale,  685 
fihrosuyn,  562 
habenulae,  903,  906 
hypoglossi,  866 
lumbale,  426 
olfactorium,  928,  973 
vagi,  866 
ventriculi,  938 
vesicae,  1365 
Trineural  fasciculus,  880 
Trochanter,  greater,  222 
bursa  of,  327 
lesser,  223 
major,  222 
minor,  223 

rudimental  third,  224 
tertius,  224 
Trochanteric  bursa,  327 

fossa,  223 
Trochlea,  182 
of  femur,  225 
humeri,  182 
phalangis,  205 

of  superior  oblique  muscle,  370 
tali,  245 
Trochlear  fossa,  79 
nerve,  977 
nucleus,  901 
Trochoid,  264,  265 
Troeltsch,  recesses  of,  1134 
Trolard,  anastomotic  vein  of,  720 
True  pelvis,  215 
skin,  1153 
suture,  264 
Trunci  lumbales,  772,  789 
Truncus  corporis  callosi,  933 
costocervicalis,  633 
intestinalis,  772,  789 
jugularis,  780 
lumbosacralis,  1044 
subclavius,  783 
sympatheticus,  1066 
pars  cepholica,  1066 
cervicalif-,    1066 
sympathici,  1066 
thyreocervicalis,  628 
Trunk,  arteries  of,  653 
articulations  of,  268 
fasciae  of,  403 
muscles  of,  403 
Tuba  audiliva  [Eustachii],  1127 
pars  cartilaginea,  1127 
ossea,   1127 
interna  [Fallopii],  1401 
stratwn  circulare,  1402 

longitudinale,   1402 
t^mica  mucosa,^  1402 

plicae  ampullares,  1402 
isthmicae,  1402 
tubariae,  1402 
muscularis,  1402 
serosa,  1402 


INDEX 


\V.)\) 


TuImI  tonsil,  1128 
Tube,  Eustacliian,  1127 
Tuber  caicunci,  243 

cinereum,  847,  908 

frontale,  76 

ischiacHcum,  211 

innxUhir,.    102 

o,t„„i,il,.  \:;-l\,  1338 


l>" 


:,l„h 


TuhL:riil  luljfs,  887 
Tubercle,  adductor,  225 

amygdaloid,  939,  948 

of  calcaneus,  242 

Chassaignae's,  68 

conoid,  169 

of  Darwin,  1120 

deltoid,  169 

distobuccal,  1207 

distolingual,  1207 

of  femur,  224 

genial,  117 

of  ilium,  210 

infraglenoid,  175 

jugular,  73 

lacrimal,  104 

of  Lower,  557 

mental,  116 

olfactory,  928,  973 

pterygoid,  95 

of  quadratus,  224  (note) 

supraglenoid,  176 

of  tibia,  233 

of  ulna,  187 

zygomatic,  81 
Tubercula  menlalia,  116 
Tuberculum  ncusticum,  866,  881 

anteriuf!,  50,  904 
Ihalai,,;.   904 

,n,r,r:il,n    {Dnrwini],   1120 

,;//,./>.(„/,  Mil 

costac,  102 
epiglotticum,  1167 
inlercondyloideum  lateralc,  233 

Ttiediale,  233 
iniervenosum  [Loioeri],  557 
jugulare,  73 
ma  jus,  180 
minus,  180 
obturatorium  anterius,  214 

posterius,  214 
ossis  multanouli  majoris,  199 

navicidaris,  196 
papillare,  1322 
phanjii'jcnm,  71 
posterius,  51 
pubicum,  212 
scaleni,  163 
sellae,  90 
ihyroideum  inferius,  1164 

superius,  1164 
vestibularis,  866 
Tuberositas  coracoidea,  169 
costae  II,  165 
costalis,  171 
deltoidea,  181 
glutaea,  224 
iliaca,  210 
infraglenoidalis,  175 

ossis  cuboidei,  246 
metaiarsalis  I,  251 

F,  252^ 
navicularis,  247 

radii,  191 

sabralis,  60 

supraglenoidalis,  176 

iiftiac,  233 

ulnae,  187 

unguiculnris,  205 
Tuberosity,  bicipital,  191 

of  femur,  226 

of  humerus,  180 

of  ischium,  211 

maxillary,  102 

of  palate  bone.  111,  128 

of  ribs,  162 


Tuberosity  of  scaphoid  bono  of 
foot,  247 
of  tibia,  233 
Tuhuirs,  pinncphric,  1420 
Tu/.k//  ,-..7,,  i:;mi 


,■/.//,.•. 


///..,■//,    IUSO 


Tui.i,':!  all.iiL'iiir:!.  i:;mi 

l„,ti„l,n,r,n„.    lilt 


(il.l 


IMS 


Uncinate  (jvre,  925 
C/ncu.f,  929 

Ungual  phalanKcs,  205 
Ungues,  1150 
margo  latcritlis,  1 1 50 
lihcr.   1150 


^//>>, 


1 1: 


SOK 


357 


.„■»/,,   Ul.s'.l 
intima,  573 
mucosa  lympani,  1134 
p/ica  incudis,  1134 

malleolaris         anterior 
1134 
posterior,  1134 
stapedis,  1134 
serosa,  1244 

/cia  sufescrasrt,  1244 

vaginalis,  1379 

vasculosa,  1380 

ocuK,  1092 

Tunics  of  eye,  1089 

of  testicle,  1379 
Turbinated  bone,  113 
crests,  102,  104,  110 
process,  middle,  98,  139 
sphenoidal,  91,  95,  139 
superior,  98 
Tiirck's  bundle,  957 
Turner,   intraparietal  sulcus  of, 

922 
Twelfth  nerve,  1010 

thoracic  vertebrte,  55 
Tympanic  arteries,  597,  600,  609 
cavity,  1125 
membrane,  87,  1128 
nerve  from  facial,  997 

from  glossopharyngeal,  1002 
plate,  131 

plexus  of  nerves,  1002 
portion  of  temporal  bone,  87 
sulcus,  87,  1122,  1130 
TjTiipanohyal  process,  88 
Tympanum,  1124 

appHed  anatomy  of,  1135 
arteries  of,  1135 
floor  of,  1125 

mucous  membrane  of,  1134 
muscles  of,  1134 
nerves  of,  1135 
ossicles  of,  1131 
promontory  of,  1126 
roof  of,  1125 
veins  of,  1135 
wall  of,  anterior,  1127 
inner,  1126 
outer,  1125 
posterior,  1126 


Ulna,  185 

applied  anatomy  of,  192 

surface  form  of,  192 
Ulnar  artery,  648 

carpal  arteries,  651 

groove,  182 

nerve,  1036 

recurrent  arteries,  650 

region,  muscles  of,  492 

veins,  729 
Umbilical  arteries,  570 

circulation,  756 

ligament,  1361 

vein,  764 
Umbilicus,  435 
Umbo  membranae  hjmpanae,  lldU 
Unciform  hone,  200 

process,  200 
of  ethmoid,  98 
I  Uncinate  fasciculus,  955 


Ul. n,  -     , 

Uli-lri I   n.ii 

UnslriiH.I    mil         , 
Urachns,   1301) 
Ureteral  folds,  1365 

orifice,  1305 
Ureters,  1356 

applied  anatomy  of,  1358 

arteries  of,  1358 

calices  of,  1356 
■    infundibula  of,  1356 

lymphatic  vessels  of,  796 

muscles  of,  1363 

nerves  of,  1358 

pars  ahdomiiudis,  1356 
petvina,  1356 

pelvis  of.  1349,  1356 

rclalinii.^  ..f.   i:'..")(j 

sirnlu,,,  ,xh  .„„,„.  1358 


tunicii  adrcnlilia,  1358 
mucosa,   1358 
muscularis,   1358 
Urethra,  arteries  of,  676 
development  of,  1426 
female,  1370 
lymphatic  vessels  of,  796 
male,  1366 

applied  ana'tomy  of,  1369 
bulbous  portion,  1369 
membranous  portion,  1367 
penile  portion.  1368 
prostatic  portion,  1366 
spongy  portion,.  1368 
muliebris,  1370 

stralum  circulare,  1370 

lo7igitudinale,  1370 
tunica  mucosa,  1370 
muscularis,  1370 
orifice  of,  1369 
virilis,  1366 

pars  cavernosa,  1368 
metnbranacca,  1367 
prostatica,  1366 
stratum  circidarc,  1369 

longitudinale,  1369 
tunica  fibrosa,  1369 
Urethral  bulb,  1386 
Urinary  bladder,  1358 
meatus,  1417 
organs,  1343 

development  of,  1420 
Ivmphatic  vessels  of,  796 
Uriniferous  tubules,  structure  of, 

1.351 
Urinogenital  organs,  1343 
Uterine  arbor  vitae,  14(28 
plexus  of  nerves,  1077 
plrxu-^rs  nf  veins.  747 
Uten«i.r;-I  liu:,iiients.  1107 
Utonivi-iriil   fi.lil.   1407 

pourh,  IJ.Ml.  1:502.  1  104.  1407 
Uterus,  1402  _ 

abnormalities  of,  1408 
applied  anatomy  of.  1411 
arteries  of.  672,  1410 
bieornate,  1408 
changes      in,      at     menstrual 
period,  1408 
by  pregnancy,  1409 
at  different  ages,  140S 
folds  of,  1406 
ligaments  of.  1406 
l,\-mphatic  vessels  of,  797.  Mil 
masculinus ,  1367 
mucous  membrane  of,  1410 
nerves  of,  1411 
Irmica  viucosa,  1410 


1500 

uterus  lunica  muscularis,  1409 
stratum  mucosum,  1409 
subserosum,  1409 
supravasculare,    1409 
vasculare,  1409 
serosa,  1409 
veins  of,  747,  141 1 
Utricle,  1140 
Utricular  nerve,  1000 
Utriculoampullar  nerves,  1000 
Utriculus,  1140 

prostat'icus,  1367 
Uvea,  1098 
UviUa,  1203 
palatina,  1203 
vermis,  887 
vesieae,  1365 
Uvular  lobes,  887 


Vagina,  1413 

arteries  of,  672,  1415 

applied  anatomy  of,  673 
lymphatic  vessels  of,  797,  1415 
mucosa  intertubercularis,  303 

tendinis,  262 
mucous  membrane  of,  1414 
musculus  recti  abdominis,  434 
nerves  of,  1415 
'paries  anterior,  1413 

posterior,  1413 
relations  of,  1414 
rugous  columns  of,  1414 
tunica  mucosa,  1414 

muscularis,  1414 
veins  of,  747,  1415 
vestibule  of,  1416 
Vaginal  bulb,  1420 

arteries  of,  1420 

nerves  of,  1420 
plexus  of  nerves,  1077 

of  veins,  747 
process  of  sphenoid,  92,  94 
syno'i'ial  membrane,  262 
Vagus  nerve,  1003 

applied  anatomy  of,  1008 

nucleus,  880 
Valentin,  ganglion  of,  984 
Vallecula,  884,  1167 

syhdi,  917 
Valleculae,  1167 
Vallum  unguis,  1156 
Valsalva,  sinuses  of,  576 

pulmonary,  559,  561 
Valve,  anal,  1310 
aortic,  561 
bicuspid,  561 
coronary,  555,  708 
Eustachian,  555 
of  Gerlach,  1299 
of  Guerin,  1369 
of  Hasner,  1117 
of  heart,  action  of,  565 

development  of,  760 
Houston's,  1310 
ileocecal,  1.301 
of  Kerkring.   1289 
mitral,  561 
of  Morgagni,  1310 
pulmonary,  559 
pyloric,  1273 
rectal,  1310 
of  Thebesius,  555,  708 
tricuspid,  558 
venous,  758 
of  Vieussens,  891 
Valvula,  884,  891 
bicuspidalis,  561 

cuspis  anterior,  561 
posterior,  561 
pylori,  1273 
spiralis  [Heisteri],  1333 
tricuspidalis,  558 

cuspis  anterior,  558 


iNi>i:x 

Valvula  tricuspidalis  cuspis  medi- 
alis,  558 
posterior,  558 
venae    cavae    inferioris    [Eu^- 
tachii],  556 
Valvulae  conniventes,  1289 
fossa  navicularis,  1369 
semilunares  aortae,  561 

arteria  pulmonalis,  559 
sinus  coronarii  [Thehesii],  556 
Valvuli  coli,  1301 

labium  inferius,  1301 
superius,  1301 
Vas  deferens,  1383 
ampulla  of,  1383 
arteries  of,  671 
lymphatic  vessels  of,  797 
efferens,  768 
Vasa  aberrantia,  641 
afferentia,  768 
brevia  arteries,  662 
intestini  tenuis,  663,  1293 
Vascular  papillse,  1154 

system,  changes  in,  at  birth,  571 
in  fetus,  peculiarities  of,  568 
Vascularization  of  bone,  45 
Vasomotor  nerve  fibers,  813 
Vastus  externus  muscle,  510 
surface  form  of,  543 
internus  muscle,  510 

surface  form  of,  543 
Vater,  ampulla  of,  1334 

corpuscles  of,  816 
Vegetative  muscle,  355 
Vein  or  Veins,  705 
of  abdomen,  739 
accessory  cephalic,  731 
adventitia  of,  706 
anastomosis  of,  706 

between     portal     and     sys- 
temic, 754 
anastomotic,  posterior,  720 

of  Trolard,  720 
angular,  710 
of  auditory  canal,  1123 
auricular,  712 
axillary,  731 
azygos,  736 
basilar,  720 
I      basilic,  730 

of  bile  ducts,  1334 

of  bladder,  1365 

of  bodies  of  vertebrte,  738 

brachial,  731 

brachiocephalic,  733 

bronchial,  737 

cardiac,  708 

anterior,  556 
of  cecum,  1300 
cephalic,  730,  731 
cerebellar,  720 
cerebral,  719 
cervical,  717 
choroid,  720 
companion,  731 
coronary,  709 
costoaxillarj',  732 
cystic,  754 
definition  of,  548 
development  of,  763 
digital,  728,  739,  741 
of  diploe,  718 
dorsal,  of  penis,  746 
of  dura  of  brain,  967 
dural,  719 
emissary,  727 
epigastric,  742 
extravertebral,  737 
of  face,  exterior  of,  710 
facial,  710,  712 
of  Fallopian  tube,  1402 
femoral,  742 

of  fingers,  superficial,  728 
of  foot,  739,  741 
frontal,  710 


Vein  or  Veins,  of  Galen,  720,  942 
of  gall-bladder,  1334 
gastric,  753 
gastroepiploic,  753 
of  globe  of  eye,  1109 
gluteal,  743 
of  hand,  728 
of  head,  710 
of  heart,  565 
hemorrhoidal,  744 
hepatic,  751 
histology  of,  706 
iliac,  742,  743,  747 
iliolumbar,  748 
innominate,  733 
intercostal,  735,  736 
interdigital,  739 
interosseous,  731,  739 
intervertebral,  738 
intima  of,  706 
intralobular,  751 
intravertebral,  738 
jugular,  713,  714 
of  kidneys,  1354 
of  large  intestine,  1312 
laryngeal,  735 
of  larynx,  1174 
of  left  ventricle,  709 
lingual,  715 
of  Uver,  1328 

of  lower  extremity,  739,  741 
lumbar,  749 

ascending,  736,  749 
of  mammary  gland,  734,  1432: 
marginal,  709 
maxillary,  712 
media  of,  706 
median,  721,  730 
of  medulla  oblongata, -721 
membrana  tympani,  1131 
meningeal,  719 
meningorachidian,  843 
mesenteric,  753 
metatarsal,  741 
nasal  arch  of,  710 
.    fossa;,  1085 
nasofrontal,  725 
of  neck,  710,  713 
of  nose,  1081 

oblique,  of  Marshall,  550,  709' 
obturator,  744 
occipital,  713 
oesophageal,  735,  1239 
ophthalmic,  725 
orbital,  712 
ovarian,  751,  1401 
palmar,  731 
pancreatic,  753,  1341 
pancreaticoduodenal,  753 
parietal,  development  of,  764 
of  parotid  gland,  1225 
parumbilical,   754 
of  pelvis,  739 
of  penis,  1390 
pharyngeal,  715 
phrenic,  734,  751 
of  pia  of  brain,  972 
of  pinna  of  ear,  1121 
plantar,  741 
of  pleura,  1185 
plexus  of,  of  toot,  739 

of  hand,  729 

hemorrhoidal,  745 

palmar,  729 

pharj'ngeal,  715 

pterygoid,  712 

spermatic,  750 

on  thyroid  body,  734 

uterine,  747 

vaginal,  747 

vesical,  745 

vesicoprostatic,  745 

vertebral,  737 
of  pons,  720 
popliteal,  742 


INDEX 


loOl 


II  •  r  ^'-ins,  portal,  751 

.„    -    ,  ;    i   llhlVV,    706 

,..-  .   i.linni.  764 
po-.;'-.a,  74S 
prtCLirdinal,  764 
pronava,  735 
of  prostate  gland,  1395 
puliie,  743 
I)iulic,  744 
piJnionary,  559,  707 
pyloric,  754 
radial,  730,  731 
ranine,  715 
renal,  751 
sacral,  744,  748 
of  salivary  glands,  1227 
saphenous,  740,  741 
sciatic,  744 

of  seminal  vesicles,  1385 
of  skin,  11.56 
of  small  intestine,  1295 
spermatic,  750 
■spinal,  external,  845 
of  spinal  cord,  739 
splenic,  752,  1446,  1449 
of  stomach,  1279 
striate,  inferior,_720 
subcardinal,  765 
suV'cerebellar,  720 
subclavian,  732 
sul'lobular,  751 
of  submaxillary  gland,  1226 
supracardinal,^  765 
supraorbital,  710 
suprarenal,  751 
sural,  742 
sylvian,  720 
systemic,  708 
temporal,  712 
temporomaxillary,  712 
of  Thebesius,  709 
thoracic,  long,  732 
thoracicocpigastric,  732 
of  thorax,  727 
of  thymus  gland,  1442 
thyroid  accessory,  717 
inferior.  734 
gland,  1438  ,  ! 

middle,  716  _ 
superior,  715 
thvroidea  ima,  735 
tibial,  742 
of  tongue,  1220 
of  tonsil,  1231 
tracheal,  735,  1179_ 
of  tvmpanum,  1135 
ulnar,  729 
umbilical,  752,  764 
of  upper  extremity,  727,  728, 

731 
uterine,  747,  1411 
vaginal,  747,  1415  _ 
vena  capitis  lateralis,  766 
cava,  inferior,  748 

applied  anatomy  of,  748 
development  of,  765  ^ 
opening     for,     in     dia- 
phragm, 421 
superior,  735 
of  vermiform  appendix,  1300 
vertebral,  717,  737 
of  voluntary  muscles,  357 
Vdlecula  nrehelli,  884 
Vnlum,  884 

inlerposilum,     884,     903,    934, 

940,  971 
medullare  anterius,  865 

postcrius,  866,  888 
pnlatinum.  1203 
Vena  anonyma  dexfra,  733 
simstm,  734 
amformis.  1354 
widitivae  iniernae,   1148 
aurioularis  posterior,  712 
axillaris,  731 


Vena  nzyoos,  736 


.■,7;< 


o/;»7(.v  lalrnili',,  766   ^ 
cava  inferior,  555,  748 
sinistra,  550 
superior,  555,  735 
cephalica,  730 

acc-ess&ria,  731 
cerebri  magna,  720 
cervicalis  profunda,  713,  718 
choroidea,  720 

circumflexa  ilium  profunda,  742 
colica  dextrae,  753 

media,  753 
cordis  magna,  709 
media,  709 
parva,  709 
coronaria  ventriculi,  753 
corporis  striati,  720 
cystica,  754 
dipl-  id  frontalis,  718 
OLyipitulis,  719 
temporalis  anterior,  718 
posterior,  718,  719 
epigastrica  inferior,  742 
facialis  anterior,  710 
communis,  710 
posterior,  712 
femoralis,  742 
frontalis,  710 
gastroepiplmca  dextra,  753 

sinistra,  753 
hemiazygos,  736 
accessoria,  737 
hcmorrhoidalis  media,  744 

superior,  753 
hypogastrica,  743 
iliaca  communis  dextra,  748 
sinistra,  748 
externa,  742 
intercostalis     suprema     dextra, 
735 
sinister,  7.35 
jugularis  anterior,  713 
externa,  713 
internxt,  714 
posterior,  713 
laryngea  inferior,  735 
linealis,  752 
lumbalis  ascendens,   736,   737, 

749 
magna  Galeni,  720 
maxillaris  interna,^  712 
mediana  basilica,  730 
cephalica,  730 
cubiti,  730 
mesenterica  inferior,  753 

superior,  753 
nasofrontalis,  710,  725 
obliqua  atriisinistri  [Marshallil 

550,  709 
obturatoria,  744 
occipitalis,  713 
ophthalmica  inferior,  726 

superior,  725 
popliiea,  742 

portae,  751  .    .      .     - 

posterior  ventriculi  simstri,  709 
profunda  femoris,  742 
radialis,  730 
renalis,  1354 
sacrdlis  media,  748 
saphena  magna,  740 

parva,  741 
subclavia,  732 
supraorbitalis,  710 
thoracalis  lateralis,  732 
thoracoepigastrica,  732 
thyreoidea  ima,  735 

superioris,  715 
vertebralis,  717 
Fenac  anonymac,  733 
auditivae  internae,  723,  72b 
to^st'Ziis  [iJoscntAaZi],  720 


Venae  basis  vertebrae,  48 
brachiales,  731 
bronehiales  anteriores,  737 

postcriares,  737 
cerebelli  inferiores,  720 

supcriores,  720 
cerebri,  719 

inferiores,  720 

internae,  720 

media,  720 

superiores,  719 
comites,  697,  707,  731 
cordis,  708 

anteriores,  709 

minimae,  709 
costoaxillares,  732 
digiiales  communes  pedis,  739 

dorsales  propriae,  728 

pedis  dorsalis,  739 

plantares,  741 

volares  propriae,  729 
gastricae  breves,  753 
glutaeae  inferiores,  744 

superiores,  743 
hemorrhoidales  inferiores,  744 
hepaticae,  751 
iliolutnbales,  748 
intercapitulares,  729,  739 
intercostalis,  736 
intervertebrales,  737,  738 
iniestinales,  753 
lingu/xles,  715 
lumbales,  749 
mammariae  internae,  734 
rami  perforanles,  734 
sternales,  734 
meningeae,  719 
metacarpeae  dorsales,  729 
metqtarseae  dorsales  pedis,  741    • 

plantares,  7il 
minimae  cordis,  555,  559 
oesophageae,  735 
ovariacae,  751 
pancreaticae,  753 
pancreaticoduodenales,  753 
parumbilicales,  754 

pharyngeae,  715 

phrenicae  inferiores,  751 

pulmonales,  707 

rectae,  1354 

renales,  751 

revehentes,  764 

sacrales  laterales,  744 

saphena  parva,  1054 

sifimoideae,  753 

spermaticae,  750 

spinales,  739 
extemne,  845 

suprarenales,  751  ^ 

thyreoideae  inferiores,  734 

tibialis  anteriores,  742 
posteriores,  742 

tracheales,  735 

uterinae,  747 

rorticosae,  725,  1090,  1093 
Venous  arches  of  fingers,  728 

mesocardium,  549 

valves,  758 
yenfer  anterior  7nuscidus  digas- 
tricu^,  389 

inferior  musculus  omohyoideus, 

388  ,       J.      ,  . 

posterior  musculus  d^gastncus, 
388  ,      . , 

superior    musculus    omohyoid- 
eus, 388 
Ventral  aorta,  761 

cerebrospinal  tract._840 
column  of  cord,  827 

ground  bundle  of,  840 
fissure  of  medulla  oblongata, 
861 
of  spinal  cord.  825 
horn  of  spinal  cord,  834 
lamina  of  brain,  855 


1502 

Ventral  root  of  spinal  cord,  823 

spinal  artery,  621 
Ventrales     Hinderstrangsbundel 

[Striimpell],  837 
Ventricle  of  brain,  Bfth,  934,  945 
fourth,  864 

choroid  plexus  of,  867 
floor  of,  865^ 
furrows  of,  866 
roof  of,  866 
of  heart,  fibers  of,  563 
left,  560 
right,  557 
of  larynx,  1170 
lateral,  936 
left,  vein  of,  709 
primitive,  757 
third,  907 
Ventricular  diastole,  565 
septum,  759 
systole,  565 
VentriciXlus,  1270 
dexter,  557 

larynqis  [Morrjagnii],  1170 
lateralis,  936 

cornu  anterius,  936 

inferius,  938 

pars  centralis,  936 

fronioparietalis,  937 

paries  posterior,  1272 

plicae  mucosae,  1275 

villosae,  1275 
quartus,  S64 
sinister,  560 
tela  suhmucosa,  1275 
tertius,  907 
tunica  mucosa,  1275 
muscularis,  1274 

fibrae  ohliquae,  1275 
stratum  circulare,  1274 
longitudinale,  1274 
serosa,  1274 
Ventrolateral  fissure  of  medulla 

oblongata,  862 
Ventromedian  fissure  of  medulla 

oblongata,  861 
Ventroparamedian      fissure       of 

spinal  cord,  826 
Venules,  547,  706 
Verga's  ventricle,  944 
Vermiform  appendix,  1298 
applied  anatomy  of,  1302 
arteries  of,  1300 
canal  of,  1299 
lymphatics  of,  1300 
mesentery  of,  1265 
veins  of,  1300 
Vermis,  885 

Verrucae  gyri  hippocampi,  925 
Verumontanum,  1367 
Vertebra,  48 
cervical,  49 
atlas  of,  50 
axis  of,  52 
seventh,  53 
lumbar,  56 
structure  of,  62 
thoracic,  53 
Vertebrae  cervicales,  49 
coccyjeae,  61 
lumbales,  56 
prominens,  50,  53,  67 
thoracales,  53 
Vertebral  aponeurosis,  404,  408 
artery,  619,  628 

applied  anatomy  of,  620 
bodies,  ligaments  of,  268 
canal,  49,  67 
column,  48 

applied  anatomy  of,  68 
articulations  of,  268 

applied  anatomy  of,  278 
"with  cranium,  275 
with  pelvis,  289 
with  ribs,  282 


Vertebral  column,  movements  of, 
272 
surface  form  of,  67 
as  a  whole,  66 
foramen,  49 
groove,  67 

region,  muscles  of,  400 
ribs,  161  ^ 

veins,  737  . 

Vertebrarterial  foramen,  .30 
Vertebrochondral  ribs,  161 
Vertebrosternal  ribs,  161 
Vertex  of  skull,  123 

vesicae,  1361 
Vesica  fellea,  1332 

tunica  mucosa,  1333 
muscularis,  1332 
serosa,  1332 
urimiria,  1358 

stratum  externum,  1363 
internum,  1363 
mciKun,  1363 
tunica  fibrosa,  1363 
mucosa,  1363 
tnuscularis,  1363 
Vesical  arteries,  671,  672 
plexus  of  nerves,  1077 
of  veins,  745 
Vesicles,  auditory,  141 
optic,  852 
otic,  141 
Vesicoprostatic  plexus  of  veins, 

745 
Vesiculae  seminales,  1384 
tunica  adventitia,  1385 
vfiucpsa,  1385 
Tnuscularis,  1385 
Vestibular  ganglion,  1000 
nerve,  1000 
nuclei,  881 
Vestibule  of  ear,  1136 

of  vagina,  1416 
Vestibulospinal    tracts    of    cord, 

839,  840 
Vestibulum,  1136 
macula  crihrosa  inferior,  1138 
media,  1137 
superior,   1137 
nasi,  1082 
oris,  1200 
recessus  cochlearis,  1137 

ellipticus,  1137 
sphaericus,  1137 
vaginae,  1416 
Vestigial  fold  of  Marshall,  550 
Vibrissae,  1159 
Vicq  d'  Azvr,  bundle  of,  905 
Vidian  artery,  602,  609 
canal,  93,  130,  134 
nerve,  985,  1066 
Vieussens,  valve  of,  891 
Villi  intestinales,  1291 

of  small  intestine,  1291 
Vincula  accessoria  tendinum,  476 
lingulae  cerebclli,  886 
iendineae,  476 
Visceral  lymph  nodes,  790,  799 
peritoneum,  1244 
veins,  763 
Visual  axis,  1088 

purple,  1100 
Vitelline  circulation,  755 
membrane,  1400 
veins,  763 
Vitellus,  755 
Vitreous  body,  1105 
humor,  1105 
table  of  skull,  36 
Vocal  cords,  1170 
Voice,  organs  of,  1163 
Volar  interosseous  nerve,  1036 

hgament,  319 
Volkmann's  canals,  39 
Voluntary  muscles   355 
Vomer,  114 


Vomer,  alae  of,  114,  13s 
Vomerine  cartilage,  108  ) 
Vou  Ebner,  glands  of,  1219 
^^ortices  pilorum,  1159 
Vulvovaginal  glands,  1420     ■ 

W 

Wedge  bones,  247 

Weight  of  brain,  849 
of  spinal  cord,  821 

Wernekink's  commissuc,  899 

Wliarton's  duct,  1225 

White  blood  cells,  40 

commissure  of  spinal  cord,  834 
line  of  pelvis,  449  .'    ■ 

substance  of  spinal  cord,  833, 
841 

Wilder,  postoblongata  of,  SOI- 

Willis,  circle  of,  617,  61s 

Winslow,  foramen  of,  1258 
1" .striiiir  liu'ament  of.  332 

Wirsuii".  .im-il  of,  1.339  . 

Wol.ttiun  I  i"lv,  1421 

Womb,  14U2 

Worm  of  cerebellum,  885 

Wormian  bones,  144 

Wrisberg,    cardiac    gariL'ii'.n     "' 
1072 
cartilage  of,  1166 
ligament  of,  336  , 

nerves  of,  1034  _     I 

pars  intermedia  of,  995 

Wrist,  articulations  of,  314  i 
applied  anatomy  of,  31a| 
bursse  of,  487  v 

flexor    tendons    at,    synqviai 

men"il>ranes  of,  4S6         > 
-joint,  arteries  of,  315         ^ 
nerves  of,  315 
surface  form  of,  315 
syno\ial  membrane  of,  315 
ligaments  of,  314  .      >  ■ 


Xiphoid  appendix,  159 


Y-LIGAMENT,  324 

Yellow  elastic  tissue,  2t.l 
spot  of  retina,  1100 


ZiNN,  ligament  of,  370  ' 

zonule  of,  1106  i 

Zona  arcuata,  1144  J 

fasciculata,  1449  .     J 

glomerulosa,  1449        •     : 

granulosa,  1399 

orbicularis,  322 

pectinata,   1144 

pellucida,  1400 

radiata,  1400 

reticularis,  1449 

tecta,  1144 
Zone  of  brain,  855 

cornu    commissurale    [Mariel^ 
837  _  . 

exsanguinated  renal,  <><  Wyrtt 
665 
Zonula  ciliaris,  1106 
Zonule  of  Zinn,  1106 
Zygapophyses,  49 
Zygoma,  80 

Zygomatic  fossa,   92,    1^       >.l  . 
133 

process  of  malar  bone,  lO'.i 
of  temporal  bone,  80 

tubercle,  81  j 

Zygomaticofrontal  sutui|B,  "'22. 
Zygomaticus  muscles.  37|( 
Zymogen  granules,  1340  J 


COLUMBIA   UNIVERSITY 

This   book  is  due  on  the  date  indicated  below,  or  uL  the 
expiration  of  a  definite  period  after  the  date  of  borrowing, 
as  provided  by  the  rules  of  the  Library  or  by  special  ar- 
rangement with  the  Librarian  in  charge. 

• 

DATE  BORROWED 

DATE  DUE 

DATE  BORROWED 

DATE  DUE 

m  ■-    .^■. 

'APR  1 J 

1944 

H^'ir         :  '40 

4AN  3  1  1i 

m 

OCT  1  2  19^ 

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ywyj  y  o 

Oa;-'  "2  0  W 

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^AY  2      194' 

MAY  2  9  IS 

41 

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1954 

